EP0912481A1

EP0912481A1 - Process for making fluorenones

Info

Publication number: EP0912481A1
Application number: EP96920484A
Authority: EP
Inventors: Marlin E. Walters; Richard P. Kolonko; Richard M. Wehmeyer
Original assignee: Dow Chemical Co
Current assignee: Dow Chemical Co
Priority date: 1996-05-24
Filing date: 1996-05-24
Publication date: 1999-05-06
Also published as: EP0912481A4; WO1997045393A1; CA2253746A1

Abstract

A process for the oxidation of a fluorene compound to a corresponding fluorenone compound comprises treating the fluorene compound with an oxidizing gas in the presence of a solid alkali metal or alkaline earth metal oxide or hydroxide or a concentrated aqueous solution thereof in a reaction mixture containing a non-aqueous heterocyclic nitrogenous solvent, wherein the reaction mixture is free of a phase transfer agent, for a time sufficient and at a temperature sufficient to convert the fluorene compound to the fluorenone compound.

Description

PROCESS FOR MAKING FLUORENONES

This invention relates to a simple, highly selective process for the oxidation of fluorenes to corresponding fluorenones Fluorenones, particularly 9-fluorenone, are valuable intermediates for the preparation of intermediates for making condensation polymers, such as

9,9-bιs-(4-hydroxyphenyl)fluorene, which is used in making polycarbonate and epoxy resins

Finger (U S Patent 4,218,400), has recited oxidizing fluorene to fluorenone by air or oxygen, in the presence of a quaternary salt in a two-phase system, containing a water immiscible solvent and aqueous alkali metal hydroxide solution Kinoshrta et al , "Liquid Phase Air Oxidation of Fluorene Part i Effects of Alkali and Pyridine, " Nippon Kagaku Zasshi, Vol. 80 ( 1959), pages 206-208, have proposed oxidation of fluorene to fluorenone in a mixed solution of pyridine and aqueous sodium hydroxide solution (about 1 N) at about 95°C The conversion to fluorenone is of the order of 50 percent Pearson et al (U S Patent 4,009, 151 ), have proposed the oxidation of 2- vmyifluorene to 2-vιnylf luorenone in a diluted solution in pyridine, containing a small amount of benzyltπmethyl ammonium chloride

Niznik (U S Patent 3,875,237) has proposed preparing fluorenone from fluorene by oxidation with molecular oxygen in dimethylsulfoxide, using a small amount of an alkali metal hydroxide, at temperatures from ambient to 100°C Hiiro et al (JP Kokai 79/ 144,348, Chem Abs 92 215069q) have proposed oxidizing aromatic or heterocyclic methylene compounds, including diphenylmethane, anthracene and fluorene, in the presence of alkali in 1 ,3-dιmethylιmιdazolιdιnone

Spπnzak, " Reactions of Active Methylene Compounds in Pyridine Solution I The

Ionic Autoxidation of Fluorene and its Derivative, J Am Chem Soc , Vol 80 (1958), pages 5449- 5455, have disclosed oxidation of fluorenes to fluorenones in pyridine solution in the presence of benzyltπmethyl ammonium hydroxide

Szeverenyi et al (HU 198,668B) have proposed preparing 9-fluorenone from fluorene by oxidation with air or oxygen in a solvent in the presence of a quaternary ammonium salt and potassium hydroxide at low temperatures Knoche (FR 2, 142,217, Chem Abs 79 50398a) recites the oxidation of fluorene to fluorenone in the presence of a saturated solution of KOH or NaOH in polyether solvents

Ma (U S Patent 4,297,514), recites the oxidation of compounds, having activated methylene radicals in a multiphase system containing a synergistic combination of elemental carbon and a phase-transfer catalyst Although the processes disclosed heretofore give oxidation products, there is a continuing need for processes for oxidizing fluorenes to fluorenones, characterized by high reaction rates, high yields and ease of separating the thus-produced fluorenones In particular known methods of oxidizing fluorene to fluorenone are not selective for fluorene when the fluorene starting material is impure, containing other oxidizabie hydrocarbons, for example, diphenylmethane When compounds other than fluorenone are produced in such oxidations, separation from fluorenone is difficult It would, therefore be desirable to have an oxidation process selective for formation of fluorenone It's an object of this invention to provide a fast, selective process for making fluorenones from fluorene, wherein the thus-produced fluorenones are readily isolated from the reaction mixtures

This invention relates to aprocess for the oxidation of a fluorene compound to a corresponding fluorenone by treating the fluorene compound with an oxidizing gas in the presence of a solid alkali metal or alkaline earth metal oxide or hydroxide or a concentrated aqueous solution thereof in a reaction mixture in a heterocyclic nitrogenous solvent, wherein the reaction mixture is free of a phase-transfer agent, for a time sufficient and at a temperature sufficient to convert the fluorene compound to the fluorenone compound

The conversion of fluorene compounds to corresponding fluorenone compounds can be represented by the general equation

wherein each of Ri-Rβ is independently selected from hydrogen or substituents which are inert under the reaction conditions employed The substituents can advantageously include hydrocarbyl, hydrocarbyloxy, nitro, ammo, substituted ammo, cyano, formyl, keto, hydroxy, carboxy, carboxyalkyl, alkyloxycarbonyl or halogen Hydrocarbyl includes alkyl, cycloalkyl, aryl, arylalkylene (aralk), alkylcycloaliphatic and alkylenecycloalkyl, that is, functions containing carbon and hydrogen atoms Hydrocarbyl functions include both saturated and unsaturated substituents Aryl includes mono- and polycyclic aromatic substituents, for example, phenyl, biphenyl, biaryl, naphthyl, phenanthrenyl, anthracenyl or other aryl groups, including those connected to a fluorene ring structure by an alkylene group Alkylaryl residues include alkyl, alkenyl and alkynyl-substituted aryl substituents Aralkyl includes alkyl, alkenyl or alkynyl groups, substituted by one or more aryl groups

Alkyl groups include both straight- and branched-chain isomers of methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tπdecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, nonadecyl and eicosyl groups, as well as the corresponding unsaturated (alkenyl or alkynyl) groups and higher homologues Preferably, the alkyl groups are of 1 to 20 carbon atoms, more preferably of 1 to 5 carbon atoms, most preferably those of 1 to 3 carbon atoms Alkyl of 1 to 5 carbon atoms includes the various methyl, ethyl, propyl, butyl and pentyl isomers Alkyl, aryl, alkaryl and aralkyl substituents are suitable hydrocarbyl substituents on the fluorene reactant

Other inert substituents include, but are not limited to alkoxy, aryloxy or alkaryloxy, wherein alkoxy includes methoxy, ethoxy, propyloxy, butoxy, pentoxy, hexoxy, heptoxy, octyloxy, nonyloxy, decyloxy and polyoxyethylene, as well as higher homologues, aryloxy, phenoxy, biphenoxy, or naphthyloxy, and alkaryloxy includes alkyl, alkenyl and alkynyl-substituted aryl

Additional inert substituents include halo, such as bromo, chloro or iσdo In addition, substituents at adjacent positions on the aromatic rings of fluorene can together form additional carbocychc or heterocyclic rings, for example,, benzofluorenes, dibenzofluorenes or pyridofluorenes More specifically, if any combination of R₁-R2, R2-R3 °^r R₃-R₄ is -CH = CH-CH = CH-, the starting fluorene is a benzof luorene

Most preferably, the fluorene starting material is fluorene itself, that is, a compound of the general formula in which each of Ri-Rβ is H

The process of this invention has been found to be particularly advantageous for the selective oxidation of fluorene in a material, identified as 'crude fluorene concentrate," which contains 45 to 65 percent of fluorene, along with dimethylbiphenyl, tπmethylbiphenyl, acenaphthene, methylacenaphthene and tπmethylnaphthalenes A representative fluorene concentrate contains 57 to 60 percent of fluorene and is a clear solid, melting about 60°C This material is advantageously stored in a tank, heated to about 80°C, and pumped to a mixer or reactor

It has been found that application of the process of this invention to a crude fluorene concentrate produces an oxidate, in which fluorenone and substituted fluorenones are the sole oxygenated products It is therefore believed that the process of this invention is useful for the oxidation of "acidic" hydrocarbons, that is, those having a pKa of about 21 , particularly f luorenes, dihydroanthracene, xanthene or indene Although the invention is explained in terms of fluorene, it applies to such acidic hydrocarbons as well Less acidic hydrocarbons, for example, diphenylmethane (pKa about 32), are not oxidized The process of this invention therefore provides a highly selective process for making valuable intermediates without requiring extensive purification of crude concentrates, particularly fluorene concentrate, used as the starting material Thus, the process of the invention includes a process of (a) using as a starting material a crude fluorene (having less than about 80 weight percent fluorene with a measurable amount, preferably at least about 0 1 weight percent diphenylmethane, other oxidizable hydrocarbon, preferably having a pKa of greater than about 32 or mixtures thereof) (b) treating the starting material with an oxidizing gas in the presence of a solid alkali metal or alkaline earth metal oxide or hydroxide or a concentrated aqueous solution thereof in a reaction mixture containing a heterocyclic nitrogenous solvent, wherein the reaction mixture is free of a phase-transfer agent, for a time sufficient and at a temperature sufficient to convert the fluorene compound to the fluorenone compound, to produce a crude fluorenone and (c) recovering an oxidized product which is preferably at least about 98 weight percent pure oxidized acidic hydrocarbon (preferably fluorenone) alternatively (d) using the crude fluorenone as a starting material for a subsequent reaction Subsequent reactions of fluorenone and other oxidized acidic hydrocarbons such as indenone, xanthenone, and anthraqumone are known to those skilled in the art For instance fluorenones are reacted with phenols under the influence of an acidic catalyst to form bιs(hydroxyphenyl) f luorenes Since the desired ketone, fluorenone, is formed selectively, there are fewer by-products to separate from the reaction product of the subsequent reaction than would be present if a less selective process were used and more oxidation by-product (for example diphenylketone for diphenylmethane) were formed in the oxidation step (b)

The oxidations are carried out in a reaction mixture containing a heterocyclic nitrogenous solvent, for example, pyridine, the lutidines, the picolmes and diazmes, for example, pyrazine or pyπdazme Many of the foregoing compounds, for example, pyridine, 2,3-lutιdιne, 3-pιcolιne, 4-pιcolιne, pyrazine and pyπdazine, are miscible with water in all proportions Less soluble members of the group of useful heterocyclic nitrogenous solvents, for example, 2,4-lutιdιne or 2,5-lutιdιne, are soluble in water to the extent of 20 g or more/ 100 mL Advantageously, the solvents are free of functionality such as carbonyl or hydroxy It is preferred to carry out the process of this invention in heterocyclic nitrogenous solvents, which have a water solubility above about 20 g/ 100 mL at 25°C

Preferred solvents for the practice of this invention will conveniently be selected from pyridine, the picolines and the lutidines, including alkylamino derivatives thereof Most preferably, the process is done using pyridine

Advantageously, and preferably, the process of this invention is carried out in the substantial absence of organic solvents, other than the above-disclosed heterocyclic nitrogenous solvent or solvents Substantial absence refers to absence except for inadvertent impurities which may be solvents, particularly impurities such as hydrocarbons in crude fluorene starting materials

The process is carried out using weight ratios of fluorene compound to heterocyclic nitrogenous solvent from 3 1 to 1 100 The minimum amount of heterocyclic solvent, usable in the process of this invention, is determined by the solubility of the fluorene compound in the solvent If a solution of fluorene is to be used, the minimum amount of solvent is that in which the fluorene compound forms a saturated solution In some cases, it may be advantageous to use a suspension/slurry of fluorene in the heterogeneous nitrogenous solvent The solubility of fluorene in pyridine is about 25 percent by weight at about 25°C Preferably, weight ratios from 3 1 to 1 25 are employed, most preferably from 1 3 to 1 15

It will also be understood the reaction mixtures can contain inert materials, which are normally hydrocarbonaceous For example, crude fluorene concentrate contains aromatic hydrocarbons, which are not oxidized under the reaction conditions employed It is also contemplated that small amounts of hydrocarbon diluents, for example, toluene or diphenylmethane, could be added to the reaction mixtures

Because small amounts of water are not detrimental to the process, the solvents used can be commercial grade materials Neither extreme caution in handling the solvents nor extensive purification of the solvents is required

"Alkali metal," as used in the specification and claims, includes lithium, sodium and potassium "Alkaline earth metal," as used in the specification and claims, includes magnesium, calcium and barium In addition to the oxides and hydroxides of the foregoing metals, it is contemplated that the carbonates can also be used in the practice of this invention, alone or admixed with the oxide or hydroxides

The alkali metal or alkaline earth metal oxide or hydroxide, or mixture thereof, can advantageously be used in solid form, for example, powders or pellets Highly soluble compounds are preferably used in concentrated aqueous solutions, containing a maximum of 50 percent to 75 percent by weight of water When an aqueous solution is used, it is preferred to use a highly concentrated (above about 40 percent by weight of solute) or saturated solution Saturated solutions of sodium hydroxide or potassium hydroxide contain about 50 percent of water, depending upon the temperature Such solutions are conveniently used in the process of the invention It is particularly advantageous, in using concentrated aqueous solutions, particularly of sodium or potassium hydroxide, to use ratios of sodium or potassium hydroxide solution to heterocyclic nitrogenous solvent such that two liquid phases are present in the reaction Such ratios are readily determined by routine experimentation Solid forms of the alkali metal or alkaline earth metal oxides or hydroxides generally contain some water Potassium hydroxide pellets normally contain about 15 percent by weight of water Sodium hydroxide pellets commonly contain about 2 percent by weight of water Sodahme commonly contains 6 to 18 percent by weight of water Although it is desirable to control the amount of water in the reaction mixtures and it is well known that alkali metal and alkaline earth metal oxides and hydroxides are hygroscopic, it is not necessary to use stringent precautions to handle even the hygroscopic alkali metal or alkaline earth metal oxides or hydroxides, used in the reaction mixtures

It will be understood that the alkali metal or alkaline earth metal oxide or hydroxide is not consumed during the process Therefore, it is feasible in some instances to recycle the oxide or hydroxide in successive runs, whether batch or continuous Recycling the oxide or hydroxide is particularly advantageous when the reaction mixture separates into two phases and the aqueous layer, containing hydroxide solution can be removed and recycled, at least until the solution becomes diluted with excessive amounts of by-product water When diluted, the concentration of hydroxide is optionally adjusted by addition of solid or more concentrated hydroxide solution, and the solution is suitable for use yet again

To attain high conversions and fast reactions, it has been found that the use of large amounts of alkali metal or alkaline earth metal oxides or hydroxides, with respect to fluorene compound, is advantageous Although the use of small amounts of alkali metal or alkaline earth metal oxide or hydroxides is operable, the use of small amounts of these materials may result in an unacceptably slow reaction rate Molar ratios of oxide/hydroxide to fluorene compound from 0 01 1 to 20 1 are operable Preferably, molar ratios of ox- ide/hydroxide to fluorene compound are from 1 1 to 15 1 Most preferably, the ratios are from 5 1 to 15 1

The process of the invention is operable over a wide range of water concentrations Whereas it is preferred thatthe pyridine phase be stirred with an aqueous solution of base, the oxidations have also been carried out successfully at water concentrations of about 300 ppm and are feasible at even lower water levels

It will be understood that the water can be introduced into the reaction mixture by the alkali metal or alkaline earth metal oxide or hydroxide, by the heterocyclic nitrogenous solvent and/or by the fluorene compound being oxidized In addition, water is a by-product of the reaction The oxidizing gas is selected from oxygen or air or mixtures thereof. It is preferred to use oxygen or air/oxygen mixtures in the practice of this invention. Oxygen or air is optionally admixed with inert (non-oxidizing) gases such as nitrogen.

The process of this invention can be carried out under ambient pressure (about 1 bar (100 kPa)) or under elevated pressures. Preferably, the process is carried out using oxygen as the oxidizing gas, under pressures from 1 bar (100 kPa) to 10 bars (1000 kPa). To conveniently avoid explosive mixtures, air is alternatively preferably used at these pressures.

The process of this invention is carried out at moderate temperatures, advantageously from 0°C to 75°C. Preferably, the process is carried out from 10°C to 65°C. 0 Depending upon the conditions selected, quantitative conversion of fluorene compounds to corresponding fluorenones is accomplished rapidly, within reaction times of 1 to 6 hours in batch mode processes.

Oxygen consumption during the process depends upon the conditions selected. In some cases, most of the oxygen is consumed. In others, significant excesses of oxygen are 5 required for complete conversion of fluorenes to fluorenones. The exact conditions are readily determined by routine experimentation.

The process of this invention can be carried out in any type of reactor, which is not attacked under the reaction conditions and which does not interact deleteriously with the reactants, solvent or products. Accordingly, the process can be carried out in glass reactors, o stainless steel reactors, fluorocarbon lined reactors, and tubes or pipes lined with glass, plastic or rubber.

The reactors are advantageously provided with stirring means, or the reactors are advantageously rocked or shaken to provide contact between the materials in the reaction mixture. Alternatively or simultaneously, it is advantageous to provide agitation by use of a 5 circulating pump. Preferably there is a stirring means, for example, impeller, in the organic phase.

The process of this invention can be done in batch or continuous mode. Continuous reactions can be done in cocurrent flow mode, countercurrent flow mode or crosscurrent flow mode, of which cocurrent flow mode, corresponding to plug flow conditions, 0 is preferred when appropriate equipment is more readily available. Continuous reactions can also be done in stirred tank reactors or packed or agitated column reactors, of which the latter are preferred.

Another preferred embodiment is to carry out the process of this invention in continuous mode, using a column packed with sodium hydroxide or potassium hydroxide 5 solids, preferably pellets. The continuous process is preferably done using oxygen as the oxidizing gas, preferably under pressure from ambient to about 10 bars.

In another preferred continuous mode of operation, the oxidations are carried out in countercurrent flow mode, using a stream of fluorene compound in heterogeneous nitrogenous solvent flowing in a direction opposite to streams of air/oxygen and a concentrated aqueous solution of alkali metal hydroxide

Another preferred embodiment is a batch process of the invention wherein the oxidizing gas is introduced under pressure into a stirred reactor containing a continuous organic phase containing droplets of aqueous sodium or potassium hydroxide

Unlike many of the processes reported for the oxidation of f luorenes to fluorenones, the process of this invention does not require the inclusion of a phase-transfer agent or phase-transfer catalyst in the reaction mixtures Materials falling within this definition are generally quaternary salts, for example, quaternary ammonium or phosphonium o salts The use of phase-transfer agents/catalysts has been set forth by Ma, Szeverenyi et al , Finger and Pearson, supra

An advantageous feature of the process of this invention is the ease with which the fluorenone product can be isolated If after removal of solids the reaction mixture appears as one phase, solvent is removed from the mixture, for example, using a rotary evaporator The 5 residue from which solvent has been removed is cooled to induce crystallization of fluorenone compound and crystalline fluorenone product is removed by filtration Extremely high purity fluorenone can be isolated by washing the crude crystalline fluorenone with solvents such as hydrocarbon solvents, preferably aliphatic more preferably having from 5 to 7 carbon atoms or alcohol solvents, preferably having from 1 to 6 carbon atoms, most preferably hexane, 0 cyclohexane, isopropanol, methanol, or ethanol

If the reaction mixture, at the end of the reaction, has split into two phases, the water layer is preferably separated and discarded or recycled The organic layer, containing the fluorenone product, is processed as explained for the one-phase reaction mixture

The facile separation of fluorenone products from the oxidation mixtures is 5 particularly advantageous, because crude f luorene-containing concentrates need not be purified before the oxidation to fluorenone by the practice of the invention

In a particularly preferred aspect, the process of this invention is one wherein the process is carried out in continuous mode in a column packed with potassium hydroxide solids, preferably pellets, the oxidizing gas is oxygen under a pressure from ambient to about 10 bars 0 (1000 kPa), the heterocyclic nitrogenous solvent is pyridine, the fluorene compound is fluorene or a crude fluorene concentrate and the temperature is from 20°C to 45°C

Another highly preferred embodiment is a batch process of the invention wherein the oxidizing gas is introduced under pressure into a stirred reactor containing a continuous organic phase containing droplets of aqueous sodium or potassium hydroxide 5 wherein the aqueous solution is at least about 40 percent by weight potassium hydroxide, the oxidizing gas is air, and the temperature is from 40°C to 65°C

In another highly preferred aspect, the process of this invention is carried out in continuous mode in a stirred reactor, wherein a solution of fluorene or crude fluorene concen- trate in pyridine is contacted in countercurrent flow mode with an aqueous solution of at least about 40 percent by weight of sodium or potassium hydroxide, the oxidizing gas is a mixture of air and oxygen, and the temperature is from 40°C to 65°C

Without further elaboration it is believed that one skilled in the art can, using the preceding description, utilize the present invention to the fullest extent The following preferred specific embodiments are, therefore, to be construed as merely illustrative and not limitative of the remainder of the disclosure in any way whatsoever

In the following examples, the temperatures are set forth in degrees Celsius Unless otherwise indicated, all parts and percentages are by weight Unless otherwise noted, the results of gas chromatography (GC) analyses are in percent by weight Example 1 - Oxidation of Fluorene

The reaction was done in a 1000-mL cylinder (100 mm in diameter, 140 mm in height), equipped with a 50 mm diameter turbine impeller driven by a vertical shaft The stirring rate was measured by a tachometer The temperature was controlled by a 3 04 meter by 0 635 cm external diameter coil, immersed in the reaction medium, through which coolant, maintained at a constant temperature by a circulating refrigerated/heated bath, was pumped The temperature was measured by a thermocouple inside a thermowell which runs the entire depth of the reactor The reactor was also equipped with a nitrogen inlet which was used to maintain a nitrogen atmosphere above the reaction mixture The entire apparatus was constructed of fluorocarbon resin commercially available from E I du Pont de Nemours & Co under the trade designation Teflon^® PFA

The reactor was flushed with nitrogen and KOH (85 percent, contained 15 percent water, A C S reagent grade, 39 0 g, 0 59 mole, crushed in a mortar with pestle), followed by a solution consisting of fluorene (3400 g, 0.205 mole) and pyridine (291.6 g, 3 686 mole, 304 0 mL) was charged to the reactor The stirrer was started and the speed adjusted to 700 rpm The coolant was admitted to the coils and the temperature of the reaction solution was adjusted to 15°C The air flow was started and adjusted to 2831 60 mL/minute as measured by a rotameter The start of the air flow was considered to be time 0 for the reaction The reaction mixture was sampled after 10 minutes and analyzed by gas chromatography (GC) on a Vaπan 3400 GC equipped with a 30 meter by 0 53 mm Megabore (Trademark of J & W Scientific Inc ) capillary column coated with a 3 micron film of DB-624 as the stationary phase and a flame lonization detector (FID, Vaπan 3400) Atthis point, the reaction mixture contained 79 47 percent by weight of fluorene and 20 53 percent of 9-fluorenone The reaction mixture, sampled again after four hours and analyzed as before, contained 10 75 percent by weight of fluorene and 89 25 percent by weight of 9-fluorenone Example 2 - Oxidation Using 85 Percent Potassium Hydroxide; Effect of Improved Air Dispersion With a Faster Stirring Rate

The reactor, described in Example 1 , was flushed with nitrogen. Potassium hydroxide (85 percent, contained 15 percent water, ACS reagent grade, 39.0 g, 0.59 mole, crushed in a mortar with pestle) was charged to the reactor, followed by a solution of fluorene (54.08 g, 0.325 mole) and pyridine (216.3 g, 2.73 mole, 221 mL). The stirrer was started and the speed adjusted to 1500 rpm. The coolant was admitted to the coils and the temperature of the reaction mixture was adjusted to 30.4°C. The air flow was started and adjusted to 943.87 mL/minute (0.008826 mole/minute of contained oxygen) as measured by a rotameter. The start of the air flow was considered to be time 0 for the reaction. The reaction mixture was sampled after 60 minutes and analyzed by gas chromatography (GC) on a Varian 3400 GC equipped with a 30 meter by 0.53 mm Megabore (Trademark of J & W Scientific Inc.) capillary column coated with a 3-micron film of DB-624 as the stationary phase and a flame ionization detector (FID, Varian 3400). This analysis shows that the reaction mixture contained 35.33 percent by weight of fluorene, and 64.67 percent by weight of 9-fluorenone. The reaction mixture, sampled after three hours' reaction time, contained no detectable fluorene, and 100 percent of 9-fluorenone.

The stirring was stopped and the phases allowed to separate. The organic phase was decanted and placed on the rotary evaporator to remove pyridine to less than 0.5 percent of the mass (by GC). The resulting oil was allowed to cool to 25°C and the resulting crystals of fluorenone are collected on a fritted filter. The dried crystals weigh 57.85 g (98.67 percent of theory). The oxygen content of the gas stream was 1.58 mole of oxygen (in 226,528 mL of air passing through the reactor during the three hour reaction time).

This example shows that increased stirring rate results in increased utilization of the oxygen.

Example 3 - Oxidation Using 85 Percent Potassium Hydroxide as the Base; Effect of Improved Air Dispersion with a faster stirring rate

The reactor of Example 1 was flushed with nitrogen. Potassium hydroxide (85 percent, contained 15 percent water, A.C.S reagent grade, 39.0 g, 0.59 mole, crushed in a mortar with pestle) was charged to the reactor, followed by a solution consisting of fluorene (54.08 g, 0.325 mole) and pyridine (216.3 g, 2.73 mole, 221 mL). The stirrer was started and the speed adjusted to 2000 rpm. The coolant was admitted to the coils and the temperature of the reaction mixture was adjusted to 30.4°C. The air flow was started and adjusted to 943.87 mL/minute (0.008826 mole/minute of contained oxygen) as measured by a rotameter. The start of the air flow was considered to be time 0 for the reaction.

The reaction mixture, sampled after 60 minutes and analyzed by gas chromatography (GC, Varian 3400 GC equipped with a 30 meter by 0.53 mm Megabore [Trademark of J & W Scientific Inc.] capillary column coated with a 3 micron film of DB-624 as the stationary phase and a flame ionization detector (FID, Varian 3400). The reaction mixture contained 14.13 percent by weight of fluorene and 85.87 percent by weight of 9-fluorenone. After two hours' reaction, the reaction mixture contained no detectable fluorene and 100 percent of 9-fluorenone.

5 The stirring was stopped and the phases are allowed to separate. The organic phase was removed by decantation and placed on a rotary evaporator to remove pyridine to less than 0.5 percent of the mass by GC. The resulting oil was allowed to cool to 25°C and the crystals of fluorenone are collected on a fritted filter. The dried crystals weigh 65.31 g (100.4 percent of theory). The amount of oxygen in air passed through the reactor during the

10 reaction was 1.05 mole of oxygen.

This example showed that increasing the stirring rate resulted in increased utilization of the oxygen feed.

Example 4 - Oxidation Method Using 85 Percent Potassium Hydroxide Pellets as the Base; the Effect of Using Oxygen in Place of Air

15 The reactor of Example 1 was flushed with nitrogen. Potassium hydroxide pellets

(85 percent, contained 15 percent water, A.C.S reagent grade, 29.4 g, 0.45 mole) are charged to the reactor, followed by a solution consisting of fluorene (29.4 g, 0.177 mole) and pyridine (294.0 g, 3.717 mole, 300 mL). The stirrer was started and the speed adjusted to 800 rpm. The coolant was admitted to the coils and the temperature of the reaction solution was adjusted to

20 40. TC. The oxygen flow was started and adjusted to 37.75 mL/minute (0.101 1 mole/hour of oxygen) as measured by a rotameter. The start of the oxygen flow was considered to be time 0 for the reaction.

The reaction mixture, sampled and analyzed after 60 minutes, as described in Example 3, contained 14.78 percent by weight of fluorene and 85.22 percent by weight of

25 9-fluorenone. The reaction mixture, sampled again after two hours and analyzed as before, contained no detectable fluorene and 100 percent by weight of 9-fluorenone. The amount of oxygen passed through the reactor was 0.202 mole of oxygen. The fluorenone product was isolated as in Example 3. Example 5 - Oxidation Using 98 Percent Sodium Hydroxide Pellets as the Base

30 The reactor, described in Example 1 , was flushed with nitrogen. To the reactor was charged NaOH pellets (98.4 percent, A.C.S reagent grade, 29.4 g, 0.736 mole) followed by a solution consisting of fluorene (29.4 g, 0.177 mole) and pyridine (294.0 g, 3.717 mole, 300 mL). The stirrer was started and the speed adjusted to 800 rpm. The coolant was admitted to the coils and the temperature of the reaction solution was adjusted to 40.1°C. The oxygen flow was

35 started and adjusted to 37.75 minute (0.101 1 mole/hour of oxygen), as measured by a rotameter. The start of the oxygen flow was considered to be time 0 for the reaction. The reaction mixture, sampled after 60 minutes and analyzed by gas chromatography as in Example 3, contained 24.09 percent fluorene, and 75.91 percent of 9-fluorenone. The reaction mixture, after 2 hours, 20 minutes, contained no detectable fluorene and 100 percent of 9-fluorenone. The amount of oxygen, passed through the reaction mixture was 0.232 mole of oxygen . The fluorenone product was isolated as in Example 3. Example 6 - Oxidation Using 50 Percent Sodium Hydroxide Solution as the Base The reactor of Example 1 was flushed with nitrogen, as above. To the reactor was charged NaOH (sodium hydroxide) solution (50 percent aqueous, A.C.S reagent grade, 29.4 g dry weight 58.8 g solution weight, 0.736 mole), followed by a solution consisting of fluorene (29.4 g, 0.177 mole) and pyridine (294.0 g, 3.717 mole, 300 mL). The stirrer was started and the speed adjusted to 800 rpm. The coolant was admitted to the coils and the temperature of the reaction mixture was adjusted to 40.1°C. The oxygen flow was started and adjusted to 37.75 mL/minute (0.101 1 mole/hour of oxygen) as measured by a rotameter. The start of the oxygen flow was considered to be time 0 for the reaction.

The reaction mixture was sampled and analyzed as in Example 3. After 60 minutes, the mixture contained 31 .10 percent of fluorene, and 68.90 percent of 9-fluorenone. The reaction mixture, sampled again after 2 hours, 30 minutes, contained 1.84 percent of fluorene and 98.16 percent of 9-fluorenone. After 4 hours, 30 minutes, the mixture contained no detectable fluorene and 100 percent of 9-fluorenone. The amount of oxygen, passed through the reaction mixture, was 0.455 mole of oxygen. The product was isolated as in Example 3. Example 7 - Oxidation Using Soda Lime as the Base

The reactor of Example 1 was flushed with nitrogen. To the reactor was charged soda lime (4 to 8 mesh, Certified A.C.S., 29.4 g, entry no. 851 1 , "The Merck Index, " Eleventh Ed., 1989), followed by a solution consisting of fluorene (29.4 g, 0.177 mole) and pyridine (294.0 g, 3.717 mole, 300 mL). The stirrer was started and the speed adjusted to 800 rpm. The coolant was admitted to the coils and the temperature of the reaction solution was adjusted to 40.1 ^CC The oxygen flow was started and adjusted to 37.75 mL/minute (0.101 1 mole/hour of oxygen) as measured by a rotameter. The start of the oxygen flow was considered to be time 0 for the reaction.

The reaction mixture, sampled and analyzed as in Example 3, at 60 minutes contained 31.10 percent of fluorene and 67.28 percent of 9-fluorenone. At the end of 2 hours, 30 minutes, the reaction mixture contained 4.21 percent of fluorene and 95.79 percent of 9-fluorenone. After 4 hours, 10 minutes, the reaction mixture contained no detectable fluorene and 100 percent of 9-fluorenone. The amount of oxygen, passed through the reaction mixture, was 0.420 mole of oxygen. The product was isolated as in Example 3. Example 8 - Oxidation Using Calcium Hydroxide as the Base

The reactor of Example 1 was flushed with nitrogen. To the reactor was charged calcium hydroxide (powder, Certified USP, 29.4 g, 0.397 mole), followed by a solution consisting of fluorene (29.4 g, 0.177 mole) and pyridine (294.0 g, 3.717 mole, 300 mL). The stirrer was started and the speed adjusted to 800 rpm. The coolant was admitted to the coils and thetemperature of the reaction solution was adjusted to 40 1°C. The oxygen flow was started and adjusted to 37.75 mL/minute (0.101 1 mole/hour of oxygen), as measured by a rotameter. The start of the oxygen flow was considered to be time 0 for the reaction. A sample of the reaction mixture, after 60 minutes, analyzed as in Example 3, contained 98.41 percent of fluorene and 1.59 percent of 9-fluorenone. At the end of 90 minutes, the reaction mixture contained 97.02 percent of fluorene, and 2.98 percent of 9-fluorenone. The reaction was terminated at this point. Example 9 - Oxidation Method Using Lithium Hydroxide as the Base The reactor of Example 1 was flushed with nitrogen. To the reactor was charged lithium hydroxide (powder, 29.4 g, 1.228 mole), followed by a solution consisting of fluorene (29.4 g, 0.177 mole) and pyridine (294.0 g, 3.717 mole, 300 mL). The stirrer was started and the speed adjusted to 800 rpm. The coolant was admitted to the coils and the temperature of the reaction solution was adjusted to 40.1°C. The oxygen flow was started and adjusted to 37.75 mL/minute (0.101 1 mole/hour of oxygen), as measured by a rotameter. The start of the oxygen flow was considered to be time 0 for the reaction.

The reaction mixture was sampled and analyzed as in Example 3. After 60 minutes, the mixture contained 95.67 percent of fluorene and 4.33 percent of 9-fluorenone. At the end of 430 minutes, the reaction mixture contained 65.02 percent of fluorene and 34.98 percent of 9-fluorenone. The reaction was terminated at this point. Example 10 - Oxidation Using Alumina as the Base

The reactor of Example 1 was flushed with nitrogen. To the reactor was charged alumina 4126 (0.1587 cm extrudate, 29.4 g), followed by a solution consisting of fluorene (29.4 g, 0.177 mole, 300 mL). The stirrer was started and the speed adjusted to 800 rpm. The coolant was admitted to the coils and the temperature of the reaction solution was adjusted to 40. TC. The oxygen flow was started and adjusted to 37.75 mL/minute (0.101 1 mole/hour of oxygen), as measured by a rotameter. The start of the oxygen flow was considered to be time 0 for the reaction. The reaction mixture, sampled after 90 minutesutes and analyzed by gas chromatography as in Example 3, contained 97.40 percent of fluorene and 2.60 percent of 9-fluorenone. After 300 minutes, the reaction mixture contained 95.24 percent of fluorene, and 4.76 percent of 9-fluorenone. The reaction was terminated at this point. Example 1 1 - Oxidation Using Talc as the Base

The reactor, described in Example 1, was flushed with nitrogen. To the reactor was charged talc (purified grade, powder, 29.4 g) followed by a solution consisting of fluorene (29.4 g, 0.177 mole) and pyridine (294.0 g, 3.717 mole, 300 mL). The stirrer was started and the speed adjusted to 800 rpm. The coolant was admitted to the coils and the temperature of the reaction solution was adjusted to 40.1°C. The oxygen flow was started and adjusted to 37.75 mL/minute (0.101 1 mole/hour of oxygen), as measured by a rotameter. The start of the oxygen flow was considered to be time 0 for the reaction.

The reaction mixture, sampled after 60 minutes and analyzed by gas chromatography as in Example 3, contained 98.47 percent of fluorene and 1.53 percent of 5 9-fluorenone. After 204 minutes, reaction mixture contained 96.73 percent of fluorene and 3.27 percent of 9-fluorenone. The reaction was terminated at this point. Example 12 - Oxidation Using 50 Percent Sodium Hydroxide as the Base With Crude Fluorene Concentrate (Contained 55 Percent of Fluorene)

The reactor of Example 1 was flushed with nitrogen. To the reactor was charged 10 NaOH (50 percent, contained 50 percent water, A.C.S reagent grade, 60.1 g dry weight, 1 .50 mole, 78.6 mL) followed by a solution consisting of fluorene concentrate (120.0 g of concentrate, 0.397 mole) and pyridine (483.8 g, 6.12 mole, 495 mL). The stirrer was started and the speed adjusted to 800 rpm. The coolant was admitted to the coils and the temperature of the reaction solution was adjusted to 38.4^αC. The oxygen flow was started and adjusted to 15 37.75 mL/minute (0.101 1 mole/hour), as measured by a rotameter. The start of the oxygen flow was considered to be time 0 for the reaction.

The reaction mixture, sampled after 60 minutes and analyzed by gas chromatography as in Example 3, contained 56.1 1 percent of the original fluorene; 43.89 percent of the original fluorene had been converted to 9-fluorenone. The reaction mixture, 20 sampled again after four hours and analyzed as above, contained no detectable fluorene and 100 percent of the expected 9-fluorenone. No other oxidation products, derived from the other hydrocarbons present, are detected.

The stirring was stopped and the phases allowed to separate. The organic phase was decanted and placed in a rotary evaporator to remove pyridine (to less than 0.5 percent of 25 the mass by GC). The resulting oil was allowed to cool to 25°C and the crystals of fluorenone are collected on a fritted filter. Example 13 - Continuous Oxidation With Air, Using Potassium Hydroxide as the Base

The reactor was a 2.54 cm diameter section of pipe, 60.9 cm in length, packed to a depth of a 55.8 cm with a bed of KOH pellets (85 percent, contained 15 percent water, A.C.S. 30 reagent grade, 337.3 g, 6.01 mole). The temperature was measured by a thermocouple inside a thermowell, running the entire length of the reactor. The reactor was also equipped with a gas inlet at the bottom, through which a nitrogen atmosphere was maintained, until the oxidation was begun. The gas was changed to air during the reaction period. A second inlet at the base of the reactor was used to introduce the reaction mixture at a constant rate by means of a 35 metering pump. A feed reservoir 2 liters in volume was connected to the suction port of the metering pump. The entire apparatus was constructed of fluorocarbon resin commercially available from E.I. du Pont de Nemours & Co. under the trade designation Teflon^® PFA. After the reactor was flushed with nitrogen, a solution containing 10 01 percent by weight of fluorene in pyridine (800 3 g) was charged to the feed reservoir The metering pump was set to pump at 1 4 mL/mιnute and energized to initiate flow of fluorene solution to the reactor The air flow was started and adjusted to 707 90 mL/mιnute (0 397 mole/hour of contained oxygen), as measured by a rotameter The start of the air flow was considered to be time 0 for the reaction

The temperature, as measured by the thermocouple inside the thermowell, was 32 5°C The reaction mixture was collected at the overflow of the reactor column and was sampled at intervals and analyzed as in Example 3 by GC After 160 minutes, the reaction mixture contained 90 64 percent of pyridine, 3 61 percent of fluorene, and 7 09 percent of 9-fluorenone (66 26 percent of the original fluorene converted to 9-fluorenone) After 330 minutes, the reaction mixture contained 90 49 percent of pyridine, 3 42 percent of fluorene, and 7 28 percent of 9-fluorenone (69 04 percent conversion of fluorene to 9-fluorenone) The reaction was continued until all of the material in the feed reservoir had been consumed (1290 minutes) A sample of the reaction mixture, analyzed as in Example 3, contained 90 38 percent of pyridine, 3 15 percent of fluorene, and 7 55 percent of 9-fluorenone (70 56 percent conversion) No other oxidation products were detected Results are given in Table I Example 14 - Continuous Oxidation Using Oxygen and Potassium Hydroxide as the Base The reactor, described in Example 13, was used The packed bed of catalyst contained KOH pellets (85 percent, contained 15 percent water, A C S reagent grade, 337 3 g, 6 01 mole)

The reactor was flushed with nitrogen, after which a solution containing 9 98 percent by weight fluorene in pyridine (401 O g) was charged to the feed reservoir The metering pump was set to pump at 1 O mL/minute and energized to pump solution to the reactor The oxygen flow was started and adjusted to 377 54 mL/minute (1 01 mole/hour oxygen), as measured by a rotameter The start of the oxygen flow was considered to be time 0 for the reaction The temperature was 27 5°C The reaction mixture was collected at the overflow of the reactor column and analyzed as in Example 3 After 70 minutes, the reaction mixture contained 90 89 percent of pyridine, 0 79 percent of fluorene, and 10 06 percent of 9-fluorenone (92 72 percent of the original fluorene converted to 9-fluorenone The reaction mixture was sampled again after 330 minutes and analyzed as above The reaction mixture contained 90 89 percent of pyridine, 1 51 percent of fluorene, and 9 34 percent of 9-fluorenone (86 08 percent of the original fluorene converted to 9-fluorenone) The reaction was continued until all of the material in the feed reservoir has been consumed (400 minutes) and sampled again The reaction mixture contained 90 73 percent of pyridine, 2 06 percent of fluorene, and 8 79 percent of 9-fluorenone (81 01 percent of the original fluorene converted to 9-fluorenone) No other oxidation products were detected Results are given in Table II

TABLE D CONTINUOUS OXIDATION OF FLUORENE IN AIR

GC Ar ia lysis

Time Air Temp Feed Percent

0 377 5 25 3 814 2 89 15 10 85 0 00 0 00

10 70 377 5 27 5 745 4 0 98 90 89 0 79 10 06 92 72

120 377 5 27 5 694 7 1 01 90 98 1 16 9 69 89 31

180 377 5 27 4 637 8 0 95 90 89 1 69 9 16 84 42

220 377 5 27 4 595 5 1 06 90 66 1 95 8 90 82 03

330 377 5 27 2 592 6 0 03 90 89 1 51 9 34 86 08

15

360 377 5 27 4 566 2 0 88 90 80 1 78 9 07 83 59

400 377 5 27 4 566 2 1 10 90 73 2 06 8 79 81 01

"Feed ra ite m g/ mm

20 ^dFn = fl uorenone

Example 15 - Continuous Oxidation Using Potassium Hydroxide as the Base With Oxygen

(Ambient Pressure)

The reactor was a 2 54 cm diameter stainless steel tube, 182 8 cm in length ^ equipped with a 60 inch (152 4 cm) packed bed containing KOH (85 percent, contained 15 percent water, A C S reagent grade, 758 9 g, 13 5 mole) The temperature was measured by a thermocouple inside a thermowell, running the entire length of the reactor The reactor was also equipped with a gas inlet at the lower end, which was used to maintain a nitrogen atmosphere in the reaction solution until the reaction was begun The gas inlet then delivers oxygen for the reaction A second inlet at the base of the reactor was used to introduce the reaction mixture at a constant rate by means of a metering pump There was a feed reservoir (10 L in volume), connected to the suction port of the metering pump The entire apparatus was constructed of type 316 stainless steel

The reactor was flushed with nitrogen, whereupon a solution containing 11 28 ^ percent by weight of fluorene in pyridine was charged to the feed reservoir The metering pump was set to pump at 1 0 mL/minute and energized to initiate flow of solution to the reactor The oxygen flow was started and adjusted to 47 19 mL/mιnute (1 01 mole/hour oxygen), as measured by a rotameter The start of the oxygen flow was considered to be time 0 for the reaction The temperature, as measured by the thermocouple, was 23 6°C

The reaction mixture was collected at the overflow of the reactor column and was sampled at intervals and analyzed as in Example 3 by GC After 120 minutes, the reaction mixture contained 0 55 percent of fluorene, and 10 73 percent of 9-fluorenone (95 12 percent of the original fluorene converted to 9-fluorenone) The reaction mixture, after 260 minutes, contained 1 57 percent of fluorene and 9 71 percent of 9-fluorenone (86 08 percent of the original fluorene converted to 9-fluorenone) The reaction was continued until all of the material in the feed reservoir was consumed (380 minutes) At this point, the reaction mixture contained 3 00 percent of fluorene and 8 28 percent of 9-fluorenone (73 40 percent of the original fluorene converted to 9-fluorenone) No other oxidation products were detected Results of the experiments are given in Table III

TABLE III CONTINUOUS OXIDATION USING OXYGEN GAS, AMBIENT PRESSURE

GC Analysis

Time O Press^{* **} Temp Feed Percent mm mL/min . mm Hq UL Wt (q) Rate^b FI* Fπ*^» conv

0 0 760 21 1 586 2 1 1 28 0 00 0 00

120 47 19 760 23 6 483 6 0 86 0 55 10 73 95 12

200 47 19 760 22 7 440 2 0 54 0 27 11 01 97 61

260 47 19 760 23 7 353 5 1 45 1 57 9 71 86 08

320 47 19 760 24 1 259 4 1 57 2 45 8 83 78 28

380 47 19 760 24 6 162 6 1 61 3 00 8 28 73 40

^apercent by weight g/min

*FI = fluorene **Fn = fluorenone

***760 mm Hg = 101 kPa

Example 16 - Continuous Oxidation Using Potassium Hydroxide As The Base, Oxygen At

Increased Pressure

The reactor was a 2 54 cm diameter, section of stainless steel tube, 182 8 cm in length and packed to a depth of 152 4 cm with KOH pellets (85 percent, contained 15 percent water, A C S reagent grade, 758 9 g, 13 5 mole) The temperature was measured by a thermocouple inside a thermowell, which runs the entire length of the reactor The reactor was also equipped with a gas inlet at the base A nitrogen atmosphere was maintained in the reaction solution until the reaction was begun, after which the gas inlet delivered oxygen for the reaction A second inlet at the base of the reactor was used to introduce the reaction mixture at a constant rate by means of a metering pump The feed reservoir ( 10 L in volume) was connected to the suction port of the metering pump The entire apparatus was constructed of type 316 stainless steel

The reactor was flushed with nitrogen before a solution containing 1 1 28 percent by weight of fluorene in pyridine was charged to the feed reservoir The metering pump was set to pump at a rate of 1 0 mL/minute and energized to begin flow of solution to the reactor The oxygen flow was started and adjusted to 28 32 mL/minute (0 076 mole/hour oxygen), as measured by a rotameter The start of the oxygen flow was considered to be time O for the reaction The exit port of the reactor was restricted to maintain the pressure within the reactor at 2 75 bars (275 kPa) The temperature, as measured by the thermocouple, was 25 3°C

The reaction mixture was collected at the overflow of the reactor column and was sampled at intervals and analyzed by GC, as in Example 3 After 154 minutes, the reaction mixture contained 2 30 percent of fluorene and 8 98 percent of 9-fluorenone (79 61 percent of the original fluorene converted to 9-fluorenone) The reaction was continued until all ofthe material in the feed reservoir was consumed (394 minutes) The reaction mixture contained 1 90 percent of fluorene and 9 38 percent of 9-fluorenone (83 16 percent of the original fluorene converted to 9-fluorenone) No other oxidation products were detected Results for the run are given in Table IV

TABLE IV OXIDATION OF FLUORENE WITH OXYGEN AT ELEVATED PRESSURE

GC Analysis

Time 0₂ Press** * Temp Feed Rate Area Percent mm mL/min bars Wt (q) q/min Conv

£11 Percent

0 ON 1 1 28 0 0

46 28 32 2 76 25 3 632 2 4 26 7 02 62 23

94 28 32 2 90 25 8 554 8 1 61 2 89 8 39 74 38

154 28 32 2 90 24 9 488 1 1 1 1 2 30 8 98 79 61 244 28 32 2 90 23 9 405 5 0 92 2 23 9 05 80 23

314 28 32 2 90 25 8 339 8 0 94 2 1 9 20 81 56

394 28 32 2 90 26 1 264 1 0 95 1 9 9 38 83 16

* FI = fl luorene

**Fn = fluorenone

***2 76 bars = 276 kPa

***2 90 bars = 290 kPa

Example 17 - Continuous Oxidation Using Potassium Hydroxide as the Base, Oxygen at

Increased Pressure In A Stainless Steel Reactor At An Elevated Temperature, High Concentration of Fluorene In Pyridine

The reactor was a 2 54 cm diameter stainless steel tube, 182 8 cm in length and packed to a height of 152 4 cm with KOH pellets (85 percent, contained 15 percent water, A C S reagent grade, 758 9 g, 13 5 mole) The temperature was measured by a thermocouple inside a thermowell, which runs the entire length of the reactor The reactor was also equipped with a gas inlet atthe base to maintain a nitrogen atmosphere in the reaction solution until the reaction was begun, at which point oxygen for the reaction was delivered to the reactor A second inlet at the base of the reactor was used to introduce the reaction mixture at a constant rate by means of a metering pump There was a feed reservoir (10 L in volume), connected to the suction port of the metering pump The entire apparatus was constructed of type 316 stainless steel

The reactor was flushed with nitrogen before a solution containing 22 16 percent by weight of fluorene in pyridine was charged to the feed reservoir The metering pump was set to pump at 1 4 mL/minutes and energized to begin flow of the solution to the reactor The oxygen flow was started and adjusted to 23 60 mL/minute (0 063 mole/hour oxygen), as measured by a rotameter The start of the oxygen flow was considered to be time O for the reaction The exit port of the reactor was restricted to maintain the pressure within the reactor at 2 97 bars (297 kPa) The temperature, as measured by the thermocouple, was 43 1°C The reaction mixture was collected at the overflow of the reactor column and was sampled at intervals, as above After 80 minutes, the reaction mixture contained 0 0 percent of fluorene and 22 16 percent of 9-fluorenone ( 100 00 percent of the original fluorene was converted to 9-fluorenone) The reaction was continued until all of the material in the feed reservoir had been consumed (194 minutes), sampled again and analyzed as in Example 3 The reaction mixture contained 0 18 percent of fluorene and 21 98 percent of 9-fluorenone (99 19 percent of the original fluorene was converted to 9-fluorenone) No other oxidation products were detected Results are shown in Table V

TABLE V

CONTINOUS OXIDATION OF FLUORENE WITH OXYGEN

AT ELEVATED PRESSURE AND TEMPERATURE

GC Ar laiysis

Time o₂ Press*** Temp Feed Rate Area Percent Percent mm mL/min kPa UL Wt (q) q/min £11 Fπ** Conv

0 24 3 297 43 1 324 2 22 16

40 24 3 317 49 3 269 0 1 4 0 00 22 16 100 00

80 24 3 303 46 9 212 5 1 4 0 00 22 16 100 00

144 24 3 321 53 6 123 4 1 4 0 26 21 90 98 83

194 24 3 327 45 1 53 8 1 4 0 18 21 98 99 19

* FI = fluorene

**Fn = = fluorenone

***2 76 bars = 276 kPa

***2 90 bars = 290 kPa

Example 18 - Oxidation Of Fluorene With Air At Ambient Pressure, 50 Percent Sodium Hydroxide Solution

The reactor described in Example 1 was used

After the reactor was flushed with nitrogen, 50 percent aqueous sodium hydroxide solution (A C S reagent grade, 195 86 g dry weight, 391 72 g of solution, 4 90 mole) was charged to the reactor followed by 100 g of fluorene concentrate (81 39 percent by weight of fluorene, 0 49 mole of fluorene) and 398 mL (406 95 g, 5 14 mole) of pyridine The stirrer was turned on and the speed adj usted to 2000 rpm Coolant was admitted to the cooling coil and the temperature of the reaction mixture was adjusted to 30 4°C

Air flow was initiated and adjusted to 943 86 mL/minute (0 088 mole/mm) as measured by a rotameter The initiation of air flow was time O for the reaction The reaction mixture was sampled after 60 minutes and analyzed by gas chromatography (GC) on a Varian 3400 GC equipped with a 30 m by 0 53 mm Megabore (Trademark of J & W Scientific Inc ) capillary column coated with a 3-mιcron film of DB-624 as the stationary phase and a flame lonization detector (Varian 3400) At this point, the reaction mixture contained 63 79 percent of fluorene and 17 60 percent of 9-fluorenone (21 62 percent conversion of fluorene) At the end of 3 hours, the mixture contained 14 41 percent of fluorene and 66 98 percent of 9- fluorenone (82 32 percent conversion of fluorene) At the end of 5 hours, the reaction mixture contained no detectable fluorene and 81 39 percent of 9-fluorenone ( 100 percent conversion of fluorene) The amount of oxygen introduced into the reaction mixture during this time was 2 65 mole

Stirring was stopped and the phases are allowed to separate The organic phase o was removed by decantation and transferred to a rotary evaporator to remove pyridine (below 0 5 percent by GC) The resulting oil was allowed to cool to 65°C Hexane (100 mL) was added to the oil in the flask and the mixture was allowed to cool to 25°C to crystallize 9-fluorenone Crystalline 9-fluorenone was collected on a fritted filter and washed with hexane (100 mL) The dried crystals weighed 66 26 g (75 09 percent of theory, 99 9 percent fluorenone by GC) 5 This example showed that very pure fluorenone can be obtained from impure fluorene streams

Example 19 - Oxidation Of Fluorene By Air Using 50 Percent Sodium Hydroxide Solution, Effect of Improved Air Dispersion The reactor was a 3000-mL cylinder (200 mm diameter, 140 mm tall) equipped 0 with a bottom drain to which was attached a centrifugal pump (March Manufacturing Model RC-2CP-MD), which discharged to a return line 1 1 mm in diameter The return line carried the reaction solution to the top of the reactor Air was fed to the reactor via a tee in the return line at about halfway up the height of the reactor Temperature was maintained at a constant temperature by a cooled/heated bath which pumped heat exchange fluid through a jacket 5 surrounding the reactor The reactor was also equipped with a nitrogen inlet for maintaining a nitrogen atmosphere over the reaction mixture The entire apparatus was constructed of a fluorocarbon resin commercially available from E I du Pont de Nemours & Co under the trade designation Teflon^® PFA

After the reactor was flushed with nitrogen, 50 percent aqueous sodium 0 hydroxide solution (A C S reagent grade, 46 57 g dry weight, 93 14 g of solution, 1 16 mole) was charged to the reactor followed by a solution of fluorene (20 g, 0 12 mole) in pyridine ( 193 52 g, 189 26 mL, 2 45 mole) The pump was turned on and the solution was allowed to become homogeneous Coolant was admitted to the jacket and the temperature of the reaction mixture was adjusted to 30 4°C 5 Air flow was initiated and adjusted to 943 86 mL/minute (0 088 mole/mm) as measured by a rotameter The initiation of air flow was time 0 for the reaction The reaction mixture was sampled after 60 minutes and analyzed by gas chromatography (GC) on a Varian 3400 GC equipped with a 30 m by 0 53 mm Megabore (Trademark of J & W Scientific Inc ) capillary column coated with a 3-mιcron film of DB-624 as the stationary phase and a flame lonization detector (Varian 3400) At this point, the reaction mixture contained 67 23 percent of fluorene and 32 77 percent of 9-fluorenone (32 77 percent conversion of fluorene) At the end of 2 5 hours, the mixture contained 15 33 percent of fluorene and 84 67 percent of 9- fluorenone (84 67 percent conversion of fluorene) At the end of 4 5 hours, the reaction mixture contained no detectable fluorene and 100 percent of 9-fluorenone ( 100 percent conversion of fluorene) The amount of oxygen introduced into the reaction mixture during

Stirring was stopped and the phases were allowed to separate The organic phase was removed by decantation and transferred to a rotary evaporator to remove pyridine (below 0 5 percent by GC) The resulting oil was allowed to cool to 65°C Hexane (100 mL) was added to the oil in the flask and the mixture was allowed to cool to 25°C to crystallize 9-fluorenone Crystalline 9-fluorenone was collected on a fritted filter The dried crystals weigh 21 55 g (99 4 percent of theory) Example 20 - Oxidation of Fluorene With Air, 50 Percent Sodium Hydroxide Solution (Stoichiometπc Amount)

The reactor and procedure of Example 19 were used To the reactor was charged 50 percent aqueous sodium hydroxide solution (A C S reagent grade, 4.81 g dry, 9 62 g solution, 0 12 mole), followed by a solution of 20 g of fluorene (0 1 2 mole) and 180 g (2 28 mole, 176 04 mL) of pyridine The rate of air flow was 943 86 mL/minute (0 0088 mole/ minute of oxygen)

After 60 minutes, the reaction mixture contained 57.21 percent of fluorenone and 42 79 percent of 9-fluorenone (42 79 percent conversion) At the end of 120 minutes, the mixture contained 19 64 percent of fluorene and 80 36 percent of 9-fluorenone (80.36 percent conversion) At the end of 4 hours, the mixture contained no detectable fluorene ( 100 percent conversion to

9-fluorenone) During the 4 hours reaction period, 2 12 mole of oxygen was passed through the reactor

The product, isolated as in the preceding example, weighed 21 71 g ( 100 14 percent of theory)

Example 21 - Oxidation of Fluorene (50 Percent Sodium Hydroxide Solution) With Air Using 4-(n,n-Dιmethylamιno)pyrιdιne as Cosolvent

The apparatus and method of Example 19 was used To the reactor was charged 50 percent aqueous sodium hydroxide solution (A C S reagent grade, 48 13 g dry, 96 26 g of solution, 1 20 mole), followed by a solution of 20 g (0 12 mole) of fluorene, 4,4-

(dιmethylamιno)pyrιdιne (20 0 g, 0 16 mole) and 160 00 g of pyridine (2 02 mole, 156 48 mL) After 60 minutes, the reaction mixture contained 65 12 percent of fluorene and 34 88 percent of 9-fluorenone (34 88 percent conversion) After 120 minutes, the mixturecontained 21 48 percent of fluorene and 78 52 percent of 9-fluorenone (78 52 percent conversion) At the end of 3 hours, no fluorene was detected (100 percent conversion of fluorene) The air passing through the reaction mixture contained 1 59 mole of oxygen This example shows that use of N,N-(dιmethylamιno)pyrιdιne as cosolvent

5 decreased the time required for complete conversion of fluorene

Example 22 - Oxidation of Fluorene (50 percent Sodium Hydroxide) With Air Using Diphenylmethane as Cosolvent

The reactor and method of Example 19 were used To the reactor was charged 50 percent aqueous sodium hydroxide solution (4 87 g dry, 9 74 g of solution, 0 12 mole), followed

10 by a solution of fluorene concentrate (48 15 percent of fluorene, 42 00 g, 0 12 mole of fluorene and 0 25 mole of diphenylmethane) and pyridine ( 1 18 O g, 1 49 mole, 1 15 63 mL)

After 1 hour, the reaction mixture contained 35 51 percent of fluorene and 12 64 percent of 9-fluorenone (26.25 percent conversion) After 2 hours, the mixture contained 30 37 percent of fluorene and 17 78 percent of 9-fluorenone (36 93 percent conversion) At the end

1 5 of 5 hours, the mixture contained no detectable fluorene (complete conversion to 9 fluorenone) The amount of oxygen introduced into the reaction mixture during the 5 hours reaction period was 2 65 mole

Stirring was stopped and the phases were allowed to separate The organic phase was removed by decantation and transferred to a rotary evaporator to remove pyridine (below

20 0 5 percent by GC) The resulting oil was allowed to cool to 65°C, whereupon 100 mL of a mixture of isopropanol (90 percent by weight) and water (10 percent by weight) was added to the oil in the flask and the resulting mixture was allowed to cool to 25°C as crystals form The crystalline fluorenone was collected on a fritted filter and washed with 100 mL of isopropa¬ nol water (9 1 by weight) The dried crystals weighed 1 5 57 g (71 01 percent of theory, 99 9

25 percent fluorenone)

This example showed that high purity fluorenone can be obtained from impure fluorene streams Example 23 - Continuous Process For the Oxidation of Fluorene To 9-Fluorenone

The reactor was a vertical 5 08 cm diameter pipe constructed of fluorocarbon

30 resin commercially available from E I du Pont de Nemours & Co. under the trade designation Teflon^® PFA,) The reactor comprised 12 stirred sections, each 1.75 cm long, separated by horizontal spacers (0 64 cm thick) each perforated with eight holes (0 64 cm diameter) to permit communication between the sections Centered within each stage was an impeller, mounted on a vertical drive shaft of type 316 stainless steel (0 954 cm height per section, 1 651

35 cm diameter) The impeller was driven by an air motor at a constant speed of 1000 rpm Each stirred section had a volume of about 100 mL The uppermost of the stirred sections contained a port for introduction of reactants and removal of products and a thermowell for measuring the temperature of the reactor contents Additional thermowells were placed in stage four (from top) and just below stage six. The lowest stirred section contained a port for introduction of reactants and removal of products. At the bottom of the reactor was a tee joint, connected to a bottom drain on one leg for removal of reactor contents and to ports for introducing feed solution and oxidizing gas. After the reactor was purged with nitrogen, pyridine (400 mL) was charged to the reactor to a level slightly above the bottom of the sixth stage. The stirrer was turned on (1000 rpm). Sodium hydroxide (50 percent by weight) was metered into the reactor at a rate of 1.26 mL/minute. At the same time, fluorene in pyridine (20 percent by weight of fluorene) was fed to the first stage through a metering pump at a rate of 2.25 mL/minute. The combined flow rate was 3.51 mL/minute, resulting in a residence time of 5.13 hours. Air and oxygen were introduced into the bottom stage in a 1 : 1 volume ratio at a rate of 94.38 mL/minute. Vent gas was released through a control valve which regulated the pressure to 2.83 bars (283 kPa). The product solution was collected at the top overflow and analyzed by GC as in Example 19. The following results are given in Table VI.

TABLE VI

Analysis, area percent

Percent Temp Pressure

Time Conversion (Bars) Ms) min Pvridine Fluorene Fluorenone

0 79.06 20.74 0.13 0.00 47.1 2.83 283

180 93094 0.42 6.17 97.97 49.2 2.83 283

255 92.78 0.19 6.94 99.08 48.6 2.90 290

315 92.12 0.17 7.63 99.18 48.0 2.83 283

375 91.39 0.15 8.38 99.28 48.5 2.83 283

435 90.99 0.19 8.73 99.08 49.8 2.90 290

495 90.27 0.18 9.47 99.13 47.3 2.97 297

55 89.47 0.17 10.28 99.18 49.0 3.17 317

805 87.85 0.14 1 1.92 99.32 50.0 3.31 331

1230 85.35 0.00 14.56 100.00 48.0 3.45 345

Example 24 - Crystallization Studies

The organic phase from a reaction mixture was collected. Pyridine in the mixture was removed by batch distillation or using a failing film still (120°C/343 mm Hg (46 kPa)). Any water present in the organic phase was removed as an azeotrope with pyridine. After the pyridine had been removed, the crude fluorenone was cooled in a batch crystallizer to crystallize fluorenone (about 10°C). Fluorenone was isolated by filtration. The crystalline mass was washed with a solvent and the recovery and purity of the washed crystalline mass was determined (GC) The following results were obtained

TABLE VII

SOLVENT Py_r^a MC^b Tof IPAL^d hexane none wt flask 75 72 71 75 77 54 75 68 75 24 71 75 wt flask + 114 09 108 78 11481 1 13 38 112 50 108 78 crystal mass wt crystal mass 38 38 36 98 37 26 37 70 37 26 36 98

10 wt funnel 36 85 37 95 38 48 38 53 38 39 37 95 wt funnel + 39 01 41 21 42 18 49 43 51 19 52 62 crystals wt crystals' 0 36 3 26 3 70 10 90 12 80 14 67 wt filter flask 75 24 75 72 75 89 77 55 75 40 75 72

15 wt solvent 39 39 35 43 32 1 1 35 34 39 90 — wt filtrate' 113 00 106 59 109 19 104 12 99 45 95 94 net wt filtrate⁹ 37 76 30 87 33 30 26 57 2405 20 22

COMPOSITION (percent fluorenone) 20 initial 58 25 58 25 58 25 58 25 58 25 58 25

Crystals 100 00 100 00 10000 100 00 100 00 90 02 filtrate 5470 53 87 50 68 35 51 28 11 27 06 wt fluorenone 22 36 21 54 21 70 21 96 21 70 21 54 _ _. percent 1 61 15 13 17 05 49 64 58 98 68 10 fluorenone recovered as percent recovered 2 36 22 22 25 03 72 89 86 60 10000 without washing ^apyrιdιne ^bmethylene chloride 30 'toluene ^dιsopropanol ^ewashed

'dry

⁹dry

These experiments showed that washing the crystalline mass with either of 35 hexane or isopropanol gave the best recovery of very high purity fluorenone Example 25 - Oxidation Method Using 50 Percent Potassium Hydroxide Solution as the Base The reactor was a 300 mL cylinder 62 mm in diameter by 100 mm tall equipped with a 38 mm diameter turbine impeller driven by a vertical shaft Parr Model 4841 available from the Parr Instrument Company, Moline, Illinois Stirring rate was measured by a tachometer Temperature was controlled by a Parr temperature controller Model 4841 available from the Parr Instrument Company, Moline, Illinois

The temperature was measured by a thermocouple inside a thermowell which runs the entire depth of the reactor The reactor was also equipped with a nitrogen inlet which was used to maintain a nitrogen atmosphere above the reaction solution The o apparatus was constructed of Hastaloy C

The reactor was flushed with nitrogen, thenKOH (50 percent aqueous, A C S reagent grade, 77 42 g solution weight, 0 69 mole) followed by a solution consisting of fluorene concentrate (57 percent fluorene, 20 12 g, contained 0 07 mole fluorene) and pyridine (45 87 g, 0 58 mole, 44 86 mL) was charged to the reactor The stirrer was started and 5 the speed adjusted to 550 rpm The temperature controller was switched on and the temperature of the reaction solution was adjusted to 40°C The air flow was started and adjusted to 0 2 SCFH (standard cubic feet per hour, 94 mL/minute at atmospheric pressure and 25°C, 0 00088 moles/minute of contained oxygen) as measured by a rotameter The vent gas was released through a control valve which regulated the pressure in the reactor to 70 psig (5 8 0 bars, 580 kPa) absolute) The start ofthe air flow was considered to be time O forthe reaction The reaction mixture was sampled after 60 minutes and analyzed by gas chromatography (GC) on a Varian 3400 GC equipped with a 30 meter by 0 53 mm Megabore (Trademark of J & W Scientific Inc ) which was a capillary column coated with a 3-mιcron film of DB-624 as the stationary phase and a flame lonization detector (FID)(Varιan 3400) This 5 analysis showed that 21 20 percent of the starting fluorene has been converted to fluorenone The reaction was sampled again after three hours and analyzed as before which showed that 74 26 percent of the starting fluorene has now been converted to fluorenone The reaction was sampled again after five hours and analyzed as before which shows thatthe reaction mixture now contained no detectable fluorene for 100 percent conversion of the starting 0 fluorene to 9-fluorenone An amount, 0 265 moles, of oxygen was contained in the air passed through the reactor during the five hour reaction time

The stirring was stopped and the phases allowed to separate The organic phase was decanted and placed on the rotary evaporator where the pyridine was removed to less than 0 5 percent of the mass by GC The resulting oil was allowed to cool to 65°C then 5 cyclohexane (20 mL) was added to the flask and the mixture allowed to cool to 25°C as crystals formed The crystals of fluorenone were collected on a fritted filter, then washed with an additional portion of cyclohexane ( 10 mL), and dried in a vacuum oven The dried crystals weighed 9 69 g or 78 01 percent of theory (12 43 g) and analyzed as 99 9 percent fluorenone This method allowed for the isolation of very pure fluorenone from impure fluorene streams.

Example 26 - Selectivity of Oxidation Method in Producing Very High Purity (> 99.6 Percent) BHPF From a Crude Fluorene Concentrate (60 Percent fluorene) A sample of starting material contained 60 percent fluorene by GC analysis. This crude fluorene concentrate (50.54 g, contained 0.18 mole) was dissolved in pyridine (282.72 g, 3.57 mole) to give a 9.1 percent weight/weight solution in pyridine. The reactor described in Example 1 was used.

The solution of starting material in pyridine was stirred at 500 rpm in the presence of solid sodium hydroxide pellets (29.0 g, 0.73 mole) while oxygen was bubbled through it at a rate of 0.1 SCFH (standard cubic feet per hour, 47 mL/minute, 0.0021 moles/minute of oxygen). After three hours, the reaction mixture was sampled and analyzed by gas chromatography (GC) on a Varian 3400 GC equipped with a 30 meter by 0.53 mm Megabore (Trademark of J&W) capillary column coated with a 3-micron film of DB-624 as the stationary phase and a flame ionization detector (FID)(Varian 3400). No fluorene was detectable in the mixture. The reaction mixture was stripped of the pyridine, and 31.5 g of the resulting fluorenone containing solids (contained 0.1 13 mole fluorenone) are dissolved in phenol to give a molar ratio of phenol (85.50 g, 0.91 mole) to fluorenone of 8 to 1.

Without isolation the fluorenone in the reaction product mixture was converted to (bis-hydroxyphenyl)phenyl fluorene (BHPF) by adding 3-mercaptopropanesulfonic acid

(MPSA, 1.293 g, 7.3 mole percent relative to the fluorenone) to initiate the reaction which was allowed to proceed for 3 hours at 40°C. The reaction mixture was then washed five times with water (equal volumes). The mixture was analyzed quantitatively as 49.7 percent phenol and 23.2 percent BHPF. A portion, 71.3 g, ofthe resulting mixture was distilled to remove the phenol until a weight ratio of phenol to BHPF of 0.9 to 1 was obtained in the still pot. The distillation residue was diluted with three times its weight of methylene chloride which formed a homogeneous mixture that soon began to form crystals. After 2 hours, the crystals were collected by filtration. These crystals were washed twice with methylene chloride and once with water, then dried in an oven leaving pure white crystals (8.62 g) of BHPF. These crystals were analyzed by HPLC and shown to be 99.8 percent p,p-BHPF. The recovered yield was 57.2 percent based on fluorenone.

Example 27 -This Example of Our Oxidation Method Showed the Utility of this Very Selective Oxidation Method in Producing Very High Purity ( >99.6 percent) BHPF From a Crude Fluorene Concentrate (80 Percent fluorene)

The reactor described in Example 1 was flushed with nitrogen, then NaOH (50 percent aqueous, A.C.S reagent grade, 76.5 g dry weight, 153.0 g solution weight, 1.91 mole) followed by a solution consisting of fluorene concentrate (fluorene concentrate containing 80 percent fluorene obtained from Deza Corporation, Valasske Meririci, Czech Republic) ( 100.0g concentrate, 0.48 mole) and pyridine (300. Og, 3.79 mole, 307 mL) was charged to the reactor. The stirrer was started and the speed adjusted to 1000 rpm. Coolant was admitted to the coils, and the temperature of the reaction solution was adjusted to 42°C. The oxygen flow was started and adjusted to 0.2 SCFH (standard cubic feet per hour, 94.38 mL/minute at 25°C and atmospheric pressure, 0.0042 moles/minute of oxygen) as measured by a rotameter. The start of the oxygen flow was considered to be time 0 for the reaction.

The reaction mixture was sampled after 60 minutes and analyzed by gas chromatography (GC) on a Varian 3400 GC equipped with a 30 meter by 0.53 mm Megabore o (Trademark of J & W Scientific Inc.) capillary column coated with a 3-micron film of DB-624 as the stationary phase and a flame ionization detector (FID)(Varian 3400). This analysis showed that 55.47 percent of the starting fluorene had been converted to fluorenone. The reaction was sampled again after three hours and analyzed as before which shows that 99.46 percent of the starting fluorene had now been converted to fluorenone. The reaction was sampled 5 again after 4.5 hours and analyzed as before which showed that the reaction mixture now contained no detectable fluorene for 100 percent conversion of the starting fluorene to 9-fluorenone. No other products of oxidation were detected. 1.14 Moles of oxygen had been passed through the reactor during the four hour 30 minute reaction time.

Stirring was stopped and the phases allowed to separate. The organic phase was 0 decanted and placed on the rotary evaporator where the pyridine was removed to less than 0.5 percent of the mass as determined by GC analysis. The resulting oil was allowed to cool to 25°C.

Without purification, a portion (16.05 g, containing 0.0713 mole fluorenone) of the oxidate was added to a reaction flask containing phenol (67.05 g, 0.713 mole) at 45°C. The 5 mixture was stirred while 3-mercaptopropanesulfonic acid (0.90 g, 0.00577 mole) was added at once. The temperature was adjusted to 55°C and maintained at this point for eight hours. The reaction mixture was then extracted (6 x 80 mL) with water to remove the catalyst. The resulting mixture amounted to 63 g which was added to a 250-mL round-bottom flask and heated until the mixture was a homogeneous solution. The mixture was analyzed 0 quantitatively as 45.5 percent phenol and 38.9 percent BHPF.

Methylene chloride (122 g) was added and the mixture heated to dissolve solids. All but a few small clumps dissolve. More methylene chloride (1 13 g) was added to help dissolve remaining solids then the mixture was passed through a paper filter to remove excess solids. The mixture was then allowed to cool to room temperature while stirring and 5 crystallization was observed.

The brown slurry, 208 g, was poured into a medium fritted filter and filtered by suction. When the filtrate was reduced to a slow drip the filtration was stopped. An amount, 160 g, of brown filtrate was recovered. The resulting cake was yellow/green in color. Methylene chloride (56 g) was slowly added to the top of the cake, and the cake was displacement washed. Washing improved the color greatly.

The wet cake was analyzed by liquid chromatography (LC) and determined to be comprised of 99.6 percent p,p-B HPF relative to isomers, adducts and other hydrocarbons (excluding methylene chloride).

The cake was placed in a vacuum oven at 850°C to 90°C for drying. Recovered product: 5.9 g. Yield = (5.9/24.6) X 100 = 24% .

This example of our oxidation method showed the utility of this very selective oxidation method in producing very high purity (>99.6 percent) BHPF from a crude fluorene concentrate (80 percent fluorene).

Example 28 - Selectivity of Oxidation Method in Producing Very High Purity ( > 99.8 percent) BHPF From A Crude Fluorene Concentrate (80 percent Fluorene) The reactor described in Example 1 was flushed with nitrogen, then NaOH (50 percent aqueous, A.C.S reagent grade, 76.5 g dry weight, 153.0 g solution weight, 1 .91 mole) followed by a solution consisting of fluorene concentrate (fluorene concentrate containing 80 percent fluorene obtained from Rutgers- VfT AG, Kekulestase 30, D-44579 Castrop-Rauxel, Germany) (100.0 g concentrate, 0.48 mole) and pyridine (300.0 g, 3.79 mole, 307 mL) was charged to the reactor. The stirrer was started and the speed adjusted to 1000 rpm. The coolant was admitted to the coils and the temperature of the reaction solution was adjusted to 42°C. The oxygen flow was started and adjusted to 0.2 SCFH (standard cubic feet per hour, 94.38 mL/minute at 25°C and atmospheric pressure, 0.0042 moles/minute of oxygen.) as measured by a rotameter. The start of the oxygen flow was considered to be time O for the reaction. The reaction mixture was sampled after 60 minutes and analyzed by gas chromatography (GC) on a Varian 3400 GC equipped with a 30 meter by 0.53 mm Megabore (Trademark of J & W Scientific Inc.) capillary column coated with a 3-micron film of DB-624 as the stationary phase and a flame ionization detector (FID)(Varian 3400). This analysis showed that 71 .04 percent ofthe starting fluorene had been converted to fluorenone. The reaction was sampled again after three hours and analyzed as before which showed that 98.58 percent of the starting fluorene had now been converted to fluorenone. The reaction was sampled again after 3.5 hours and analyzed as before which showed that the reaction mixture now contained no detectable fluorene for 100 percent conversion of the starting fluorene to 9-fluorenone. No other products of oxidation were detected. An amount, 0.88 moles, of oxygen were passed through the reactor during the 3 hour 30 minute reaction time. The stirring was stopped and the phases allowed to separate. The organic phase was decanted and placed on the rotary evaporator where the pyridine was removed to less than 0.5 percent of the mass as determined by GC. The resulting oil was allowed to cool to 25°C. Without purification, a portion (16.10 g, containing 0.0715 mole fluorenone) of the oxidate was added to a reaction flask containing phenol (67.26 g, 0.715 mole) at 45°C. The mixture was stirred while 3-mercaptopropanesulfonic acid (0.90 g, 0.00577 mole) was added at once. The temperature was adjusted to 55"C and maintained at this point for eight hours. The reaction mixture was then extracted (6 x 80 ml) with water to remove the catalyst. The resulting mixture amounted to 59.6 g which was added to a 250-mL round-bottom flask and heated until the mixture was a homogeneous solution. The mixture was analyzed quantitatively as 45.6 percent phenol and 35.5 percent BHPF (phenol:BHPF mass ratio = 1.28). 100 g of methylene chloride were added to the mixture to form a homogeneous solution. Upon cooling to room temperature no precipitate was evident. An amount, 60 mL, deionized(DI) water were added and the mixture was distilled to remove the methylene chloride water and phenol. When thetemperature of the mixture was 137°C, the mixture was allowed to cool. Analysis of the mixture indicated a phenokBHPF mass ratio of 1 : 1. When the mixture was approximately 80°C, approximately 100 g methylene chloride was added resulting in mild refluxing and rapid cooling. As the mixture approached room temperature, it was seeded with BHPF crystals. Within 2 hours, more crystals were evident. The mixture was allowed to stir at room temperature overnight. The brown slurry, weight 80 g, was poured into a medium fritted filter and filtered by suction. When the filtrate was reduced to a slow drip the filtration was stopped. The resulting cake was mustard in color. Methylene chloride (44 g) was slowly added to the top of the cake and the cake was displacement washed.

Washing improved the color greatly. Another 36 g sample of methylene chloride was used to wash the cake.

The wet cake was analyzed by LC and determined to be comprised of 99.8 percent p,p-BHPF relative to isomers, adducts and other hydrocarbons (excluding methylene chloride). The cake was placed in a vacuum oven at 85"C to 90°C for drying. Recovered product: 6.4 g.

Yield = (6.4/21.16) X 100 = 30.24% . This example of the oxidation method of the invention showed the utility of this very selective oxidation method in producing very high purity (> 99.8 percent) BHPF from a crude fluorene concentrate (80 percent fluorene). Example 29 -Effects of Mixing

The procedure of Example 25 was repeated with a impeller tip speed of 1.09 meters/seccond using a Lightnin™ LabMaster II™ Model TSM2010 Mixer commercially available from Mixing Equipment Company, Avon Division, a unit of General Signal which directly measured the watts input into the mixer and the ratio of organic phase to aqueous phase volumes indicated in Table VIII. Measurements of the percent conversion of fluorene to fluorenone were taken at the times indicated in Table Vlll with the impeller in the aqueous or organic phase as indicated. The results indicated in Table Vlll.

TABLE Vlll

impeller in impeller in impeller

Time organic aqueous inorganic impeller in

(mm ) percent percent percent organic conversion conversion conversion percent

0.000 0.000 0.000 0.000 0.0000

60.00 3.68 21.20 33.22

120.00 76.23 5.29 45.42 52.85

180.00 9.45 74.26 70.16

240.00 98.28 13.04 89.07

300.00 18.87 91.51

360.00 100.00

Organic to

Aqueous phase ratio 1.26 .79 1.26 10

Example 30 - The Effect of Stirring at Atmospheric Pressure

The procedure of Example 29 was repeated using air as oxidizing gas at atmospheric pressure, with an organic to aqueous phase volume ratio of 1.26: 1 and an impeller tip speed of 5.23 meters/second Results are shown in Table IX.

Table IX aqueous phase organic phase percent percent

:ιme conversion conversion

0 0.00 0.00

30 2.60 19.77

60 4.45 41.98

120 9.41 78.43

240 19 41 92.37

300 24.26 100.00

360 29.16 100.00 Examples 29 and 30 show: The organic to aqueous phase ratio appeared to have little affect on the reaction rate (compare the ratios of the two fastest runs in Table Vlll) as long as the organic phase was the continuous phase. This means that a very small aqueous phase can be used and thus increase the capacity of the oxidation reactor. Good mixing was important for rapid reaction. For instance at a mole ratio of potassium hydroxide to fluorene of 1.8: 1 ; mole ratio pyridine to fluorene of 8.4: 1 .0 and air flow rate of 0.008826 moles/minute at 40°C, the following conversions were achieved for the given times, indicating the importance of mixing on the rate of conversion of fluorene.

Table X

700 RPM 1500 RPM 2000 RPM time (minutes) corresponding to corresponding to corresponding to

1.35 W/L* 19.70 W/L* 47.21 W/L*

% conversion % conversion % conversion

0 0.00 0.00 0.00

15 5.07 15.17 20.81

30 20.53 30.13 39.97

45 30.76 47.02 56.66

60 48.62 64.52 85.87

90 62.58 87.56 95.51

120 74.22 97.40 99.28

150 81.16 99.60 99.99

180 87.64 99.94

240 89.24 100.0

0 *W/L = Watts/Liter

The preceding examples can be repeated with similar success by substituting the generically or specifically described reactants and/or operating conditions of this invention for those used in the preceding examples.

From the foregoing description, one skilled in the art can easily ascertain the essential characteristics of this invention and without departing from the spirit and scope thereof, can make various changes and modifications of the invention to adapt itto various usages and conditions. The process of the invention is advantageous over oxidation processes involving phase-transfer catalysts. Phasetransfer catalysts, especially quaternary ammonium phase - transfer catalysts, are known by those skilled in the art to degrade under oxidation conditions. Because the phase -transfer catalysts degrade, their concentration decreases during a reaction, therefore, especially in continuous reactions, phase-transfer catalysts either must be used in excess or must be added as reaction progresses to maintain a sufficient concentration Furthermore, degradation of phase -transfer catalyst produces by-products which make purification of the desired oxidation product (for example, fluorenone) more difficult than it would be in the absence of such by-products

Claims

1 A process for the oxidation of a fluorene compound to a corresponding fluorenone compound, comprising treating the fluorene compound with an oxidizing gas in the presence of a solid alkali metal or alkaline earth metal oxide or hydroxide or a concentrated aqueous solution thereof in a reaction mixture containing a heterocyclic nitrogenous solvent, wherein the reaction mixture is free of a phase transfer agent, for a time sufficient and at a temperature sufficient to convert the fluorene compound to the fluorenone compound.

2. The process of Claim 1 , wherein the heterocyclic nitrogenous solvent has a solubility in water above 20 g/100 mL at 25°C.

3. The process of Claim 2, wherein the solvent is pyridine, a picoline or a lutidine.

4. The process of Claim 2, wherein the solvent is pyridine.

5. The process of Claim 1, wherein the oxidizing gas is air.

6. The process of Claim 1 , wherein the oxidizing gas is oxygen.

7. The process of Claim 1 , carried out under pressures from 1 bar to 10 bars.

8. The process of Claim 1 , wherein the fluorene compound is fluorene and the fluorenone compound is 9-fluorenone.

9. The process of Claim 1 , wherein the alkali metal hydroxide is sodium hydroxide or potassium hydroxide.

10. The process of Claim 9, wherein the sodium hydroxide or potassium hydroxide is in the form of a concentrated aqueous solution.

11. The process of Claim 10 wherein the concentratedaqueous solution is at least 40 percent by weight sodium hydroxide or potassium hydroxide.

12. The process of Claim 10, wherein the sodium or potassium hydroxide solution is a saturated aqueous solution.

13. The process of Claim 10, carried out under conditions such that the reaction mixture separates into two liquid phases.

14. The process of Claim 9, wherein the sodium hydroxide or potassium hydroxide is in a solid form.

15. The process of Claim 14, wherein the solid contains a maximum of 20 percent by weight of water.

16. The process of Claim 1 , wherein the alkali metal or alkaline earth metal oxide or hydroxide is sodalime.

17. The process of claim 1, carried out at a temperature from 10°Cto 65°C.

18, The process of Claim 1 , carried out in batch mode in the presence of solid sodium hydroxide or potassium hydroxide, wherein the nitrogenous heterocyclic solvent is pyridine. 19 The process of Claim 17, carried out in batch mode in the presence of sodium hydroxide or potassium hydroxide pellets or powder, wherein the nitrogenous heterocyclic solvent is pyridine

20 The process of Claim 1 , wherein the fluorene compound is in the form of a crude concentrate, containing fluorene or substituted fluorenes, and a resulting product contains fluorenone or substituted fluorenones

21 The process of Claim 1 , carried out in continuous mode in a column packed with sodium hydroxide in a solid form or potassium hydroxide pellets, wherein the oxidizing gas is oxygen 22 The process of Claim 21 , wherein the column is packed with potassium hydroxide pellets, the oxidizing gas is present under a pressure from ambient to 10 bars (1000 pKa), the heterocyclic nitrogenous solvent is pyridine, the fluorene compound is fluorene or a crude fluorene concentrate and the temperature is from 20°C to 45°C

23 The process of Claim 1 , carried out in continuous mode, wherein a solution of fluorene compound in heterocyclic nitrogenous solvent is contacted with a concentrated aqueous solution of alkali metal hydroxide

24 The process of Claim 23, carried out in continuous mode in a stirred reactor, wherein a solution of fluorene or crude fluorene concentrate in pyridine is contacted in countercurrent flow mode with an aqueous solution of at least 40 percent by weight of sodium or potassium hydroxide at a temperature from 40°C to 65°C

25 The process of Claim 24, wherein the oxidizing gas is a mixture of air and oxygen

26 The process of claim 1 wherein the oxidizing gas is introduced under pressure into a stirred reactor containing a continuous organic phase containing droplets of aqueous sodium or potassium hydroxide wherein the aqueous solution is at least 40 percent by weight potassium hydroxide, the oxidizing gas is air, and the temperature is from 40°C to 65^CC

27 The process of Claim 1 , including the further steps of removing heterocyclic nitrogenous solvent from a resulting crude product and cooling a resulting residue to crystallize the fluorenone therefrom 28 The process of Claim 26, including the further step of washing the thus- crystallized fluorenone with hydrocarbon solvent, or an alcohol solvent or mixture thereof

29 The process of Claim 28 wherein the solvent is hexane, cyclohexane, isopropanol, methanol or ethanol

30 The process of Claim 1 wherein there is mixing at a power of at least 0 8

W/l

31 The process of Claim 30 wherein the power is at least 15 0 W/l