DE1178065B - Process for the preparation of alkyl aromatic compounds from diarylalkanes - Google Patents

Description

Process for the preparation of alkyl aromatic compounds from diarylalkanes It is known to use aromatic compounds with at least one aliphatic core substituent, containing at least 2 carbon atoms, by heating a diarylalkane, the at least 2 carbon atoms in the alkyl radical and the aryl groups attached to the same Carbon atom of the alkyl radical, contains, to 300 to 600 "C in the presence of a high-melting point inorganic catalyst with acidic properties, such as zirconium silicate or titanium silicate, and optionally in the presence of a diluent such as steam. When these cleavage catalysts are used, mixtures of aryl alkenes and obtained saturated alkyl aromatics. For example, 1,1-ditolylethane can be used in p-methylstyrene and toluene are converted. The yields of the desired aryl alkenes leave however, in many cases, this leaves something to be desired, and the degree of implementation is proportionate low, d. H. below 400/0. Also need to be the contact times between the convertible Diarylalkanes and the cleavage catalyst are chosen to be relatively short, because the catalyst rapidly becomes active as a result of deposits of coking residues loses and then has to be regenerated oxidatively.

It has also been recommended to use saturated alkyl aromatics from diarylalkanes using Friedel-Crafts type catalysts.

It would now be very desirable to have a way of working at hand which makes it possible without costly changes to the operating facilities, to vary the nature of the end products formed from the diarylalkanes to some extent and to produce either preferably aryl alkenes or preferably saturated alkyl aromatics, while at the same time increased conversion levels are obtained and also catalyst life is extended.

Surprisingly, this problem turns out to be very satisfactory and expediently dissolve by heating the used as the starting material Diarylalkanes with at least 2 carbon atoms in the alkyl radical, in which the aryl groups are bonded to the same carbon atom of the alkyl radical, to a temperature between 300 and 600 "C also works in the presence of hydrogen and a high-melting point inorganic catalyst with acidic properties, in particular oxides or silicates, used, which a known as a dehydrogenation catalyst or metal Metal compound of nickel group, especially nickel, or platinum, palladium or rhodium has been added.

By appropriate choice of the proportion of diarylalkane to hydrogen or changing the working pressure can now depending on your needs the same starting material and arylalkenes using the same catalyst or arylalkanes are prepared, although none of the high degrees of conversion undesirable side reactions occur.

It is also surprising that despite working in the present the unsaturated alkyl aromatics are also formed in good yield by hydrogen will.

As high-melting inorganic catalysts with acidic properties for example hydrated aluminum silicate, aluminum oxide silicic acid, Zirconium dioxide, titanium dioxide, titanium dioxide-aluminum oxide -silicic acid, molybdenum sulfide or nickel tungsten sulfide.

As a dehydrogenation catalyst can also be preferably used Nickel also iron, cobalt, platinum, palladium or rhodium and their derivatives are used will.

The catalytic hydroscopic cleavage of the diarylalkane, for example of 1,1-di-p-tolyl ethane, is effected in a simple way by it is passed over the catalyst bed in the vapor phase, mixed with hydrogen, made for example of metallic nickel on a carrier of acidic clay, e.g. B. Acid-treated attapulgus clay, with the catalyst mass in the The reaction zone is kept at an elevated temperature. Temperature and pressure as well the amount of hydrogen used for the conversion depends on whether the saturated or the unsaturated alkyl aromatic compound as the main ingredient is desired in the resulting reaction product.

If, for example, in the conversion of 1,1-Ditolyläthan the saturated alkyl aromatic compound (methylethylbenzene) as the predominant Cg compound is desired, a temperature of about 350 "C and a pressure of about 17 at can be applied.

During contact with the acid catalyst can be in some degree Degree of isomerization will occur. However, this process can be done in a simple manner by using a weakly acidic catalyst and / or by a sufficient short contact times are pushed back. On the other hand, it can in individual cases be desirable from the isomerization effect of the acidic component of the catalyst To make use, e.g. B. to produce m-ethyltoluene from p, p'-ditolylethane. For example found a 99% conversion of 1,1-di-p-ditolylethane under the following conditions Achieved: 5% nickel on a silica-alumina-zirconia analyzer; Temperature 485 "C; pressure 36 at; hourly throughput rate of ditolylethane, based on the liquid phase, of 5.8; Hydrogen flow rate 23.7 Moles per hour; Contact time of steam 4.3 seconds. The isomer distribution of The resulting methylethylbenzenes were as follows: 70/0 o-, 270/0 m- and 660/0 p-isomers. The proportions of the o- and m-isomers were increased with a shortening of the contact time 2 seconds reduced to 4 or 7%. Another reduction in contact time on 0.1 second gave less than 0.50/0 of the m-isomer.

With a catalyst that was less acidic and had a smaller surface area had, for example, 5% nickel and 100/0 attapulgus clay on one by melting them together made of aluminum oxide or bauxite in an electric furnace according to known processes Aluminum oxide carrier (see Zimmermann and Lavine, Handbook of Material Trade Names, Ed. 1953, p. 36, under "Aloxite"), was at 400 "C, 19 at, a contact time of 0.46 seconds (hourly throughput rate, based on the liquid Phase 12) and a hydrogen addition of 28 mol per hour a 57% conversion (98 to 1000 / o yield, based on the converted material) of ditolylethane Ethyltoluene and toluene achieved. The resulting mixture of aromatics showed the the following isomer distribution: 6% o-, 0.5 to 1% m- and 93 to 93.5 ° lo p-isomer. When the reaction temperature was increased to 440 ° C., the m-isomer content increased to 1.50 / 0 (83% conversion) and at a temperature of 550 ° C the level increased of the m-isomer to 4.5% (99% conversion).

The inventive catalytic hydrogenative cracking of diarylalkanes preferably leads to saturated fission products when the conversion is in the presence a considerable proportion of hydrogen and carried out at elevated pressure will.

If isomerization is not desired, these are preferred molar ratios of hydrogen to diarylalkane in the production of saturated Fission products between 20 and 50: 1.

The pressures are preferably between 17 and 48 at. Temperatures can between 300 and 6000 C, but between 350 and 450 ° C preferred. These variables are preferably chosen so that they correspond to a contact duration from 0.05 to 0.5 seconds. If isomerization is possible and maybe if even desired, a longer contact time of up to 13 seconds can be used , with a molar ratio of hydrogen to diarylalkane of preferably 2 to 10: 1 is used.

If the conversion of the diarylalkane under conditions suitable for the Hydrogenation are less suitable, e.g. B. practically at atmospheric pressure carried out the corresponding arylalkene is obtained as the reaction product. For example 1,1-Di-p-tolylethane over a catalyst with 50 / nickel and 10% attapulgus clay on the above-mentioned aluminum oxide support at a temperature of 550 to 560 ° C and a hydrogen pressure of about 1 at, so a conversion to m-methylstyrene and toluene can be obtained in 45 to 500% yield. It is advantageous to in addition to the hydrogen in the presence of which the conversion takes place, water vapor to use. l, l-Di- (o-tolyl) -ethane can be used under practically the same conditions are split like 1,1-di (p-tolyl) -ethane, whereby o-methylethylbenzene and resp. or o-methylstyrene can be obtained in addition to toluene. In the same way you can Mixtures of di- (o-tolyl) -ethane and DiQp-tolyl) -ethane to form mixtures of ob and p-isomers of methylethylbenzene and / or methylstyrene are split. the various I, I-dixylylethanes give the corresponding dimethylethylbenzenes and / or dimethylstyrenes, it being the same whether they are used individually or as a mixture be split.

Also 1,1-di (p-tolyl) -propane, 1, 1-di- (p-tolylfi butane, 1, 1 - diphenyloctane, 1, 1-Di- (p-oxyphenylfi propane and 1,1 -Di- (p-chlorophenyl) -butane can be used in the new processes are used as starting compounds.

The inventive method is illustrated by the following examples explained in more detail, examples 1 to 8 relating to the production of saturated Alkyl aromatics and Examples 9 to 12 refer to the preparation of unsaturated reaction products relate.

Example 1 1,1 -Di-p-tolylethane was converted into p-ethyltoluene and toluene by passing it in the presence of hydrogen at elevated temperature and pressure over a catalyst containing 10% nickel (as metal) on an acid-treated attapulgus Contained clay on the aforementioned alumina. The degrees of conversion obtained under the various real: -tion conditions are summarized in the following table. Hour mole Diirchsatz- Mole Conversion- Temperature pressure speed, conversion calculated on the tolylethane ° C at liquid phase% 350 17 20 25 95 350 17 45 25 50 325 # 18.4 12 10 70 The drop to a conversion of only 500/0 at the very high throughput rate of 45 appeared to be due to the extremely short contact time.

Example 2 1,1-Di-p-tolylethane was used in the presence of hydrogen Passed over a catalyst, the 50/0 nickel on 10% attapulgus clay on the Contained aluminum oxide mentioned above, with a temperature of 590 "C, a pressure of 17.7 at, an hourly throughput rate calculated on the liquid Phase, of 20, a hydrogen feed rate of 22 moles per hour and a contact time of the reaction vapors of 0.6 seconds was maintained. A 42% conversion of ditolylethane into p-ethyltoluene and toluene was achieved.

Example 3 1, l-di-p-tolylethane was in the presence of hydrogen over a catalyst of 5 ° / 0 nickel and attapulgus clay at 550 ° C and a pressure passed by 36 at, the hourly throughput rate being calculated on the liquid phase, 12.9, the hydrogen feed rate 38.1 moles per Hour and the contact time of the vapors was 0.5 seconds. It got a 68% rate Conversion achieved.

When using the same catalyst and the same temperature, but a pressure of 19 at, an hourly throughput rate of 22.8, a hydrogen feed rate of 45.7 moles per hour and a contact time of the vapor of 0.2 seconds became almost the same conversion, namely 640/0, of Obtained ditolylethane in p-ethyltoluene and toluene.

Example 4 1,1-bis (p-ethylphenyl) ethene was in the presence of Hydrogen at 400 ° C, a pressure of 19 at, an hourly throughput rate of 12 and a hydrogen feed rate of 28 moles per hour passed a catalyst containing 5% nickel and 100% attapulgus clay on the mentioned Contained aluminum oxide carrier. A conversion of 57% (98 to 1000 / o yield, based on the converted material) in diethylbenzenes and ethylbenzene. The isomer distribution of the diethylbenzenes was as follows: 95.50 / o 1> 4% o and 0.50 / 0 m isomer.

Example 5 l, l-Di-p-tolylathane was among those given in Example 4 Conditions with hydrogen above passed a catalyst containing 50/0 nickel Contained untreated kaolin. There was an 85% conversion of the ditolyl ethane achieved in ethyl toluene and toluene.

When replacing the nickel kaolin catalyst with one that Contained 0.% platinum on attapulgus clay aluminum oxide, or 0.250 / 0 platinum on kaolin a 54% or 800% conversion was achieved under otherwise identical conditions.

Example 6 1,1-Di-p-tolylethane was used together with hydrogen 450 ° C and 17.4 at and an hourly throughput rate of 14 and one Hydrogen feed rate of 14.8 moles per hour over a catalyst which contained 0.550 / 0 platinum, 0.70 / 0 Cl and 0.45% SiO ~ 2 ^ on aluminum oxide. A 50% conversion of ditolylethane into ethyltoluene and toluene was achieved.

Example 7 1,1-Di-p-tolylethane was used in the presence of hydrogen Passed over a catalyst that converts 10% cobalt to 10% acid-treated attapulgus clay contained on the aluminum oxide mentioned.

It was at a temperature of 350 ° C, a pressure of 17.7 at, an hourly throughput rate, based on the liquid phase, of 20 and a molar ratio of hydrogen to ditolylethane of 25 worked. The conversion of ditolylethane into ethyltoluene and toluene was 60%.

Example 8 1,1-Di (p-oxyphenyl) -ethane was with hydrogen over passed a catalyst containing 10% nickel on attapulgus clay on top of the mentioned Contained aluminum oxide. The temperature was 360 ° C, the pressure 17.7 at, the molar The ratio of hydrogen to dioxyphenylethane was 20: 1.

There was an almost complete conversion to ethylphenol and phenol achieved.

Example 9 1,1-Di-p-tolylethane was at 560 ° C with an hourly Throughput rate of 12 over a 5% nickel and 10% catalyst Attapulgus clay passed on the mentioned aluminum oxide, with the hydrogen pressure 1 at scam.

There was a 45% conversion to p-methylstyrene and toluene.

The conversion was at 500 ° C. under otherwise identical conditions in p-methylstyrene and toluene 350/0.

Example 10 1,1-Di-p-tolylethane was at 550 ° C under atmospheric Pressure with an hourly flow rate of 10 in the presence of hydrogen in a molar ratio of hydrogen to ditolylethane such as 10: 1 over a catalyst conducted, the 100 / o nickel and 10% attapulgus clay on the mentioned aluminum oxide contained.

A 49% conversion to p-methylstyrene was achieved.

When applying a mixture of water vapor and hydrogen in the same molar ratio of the total vaporous diluent to ditolylethane (10 1) the conversion to p-methylstyrene increased to 58% a molar ratio of water vapor to hydrogen such as 50:50 and to 590/0 at a molar ratio of 20:80. In these tests, the service life was of the catalyst more than 1 hour.

If only steam was used instead of hydrogen, the conversion to p-methylstyrene was only 340 / o and the life of the catalyst shortened to about 20 minutes.

Example 11 1,1-Diphenylethane was at 560 "C and a pressure of about 1 at with an hourly throughput rate of 5 in the presence of Hydrogen in a molar ratio of hydrogen to diphenylethane such as 10: 1 over one Catalyst made from nickel and attapulgus clay. It became a 280% conversion achieved in light material, with the aromatic Cs fraction 890 / o styrene and Contained 11 0 / o ethylbenzene.

Example 12 1,1-Di (p-tert-butylphenyl) -ethane was at 550 ° C with an hourly flow rate of 10 in the presence of hydrogen in a molar ratio of hydrogen to diarylethane such as 10: 1 over a catalyst which contained 1001o nickel and attapulgus clay on the aforementioned aluminum oxide. In this way a yield of 600/0 of p-tert-butylstyrene was achieved.

A particularly preferred embodiment of the present method consists in it. the exothermic cracking of the diarylalkanes in the presence of hydrogen, especially under conditions that lead to saturated alkyl aromatics, to link with an endothermic reaction in the same reaction zone, whereby overall an isothermal course of the reaction is effected.

The dehydration of a corresponding one serves as an endothermic reaction Naphthenic hydrocarbons produced under the same conditions and with the same catalyst carried out as used for hydrocracking; for example is methylcyclohexane releasing 3 moles of hydrogen per mole of naphthene dehydrated to toluene. When an equimolecular mixture of methylcyclohexane and 1,1-Di-p-tolylethane over a catalyst made of nickel and attapulgus clay, a Platforming catalyst or a nickel-tungsten sulfide catalyst at 450 "C and 18 at was passed, with 5 moles of hydrogen supplied for each mole of ditolylethane and the hourly throughput rate was 10 found a 670% Conversion of methylcyclohexane into toluene instead and a 95 0 / above conversion of the Ditolylethans in ethyltoluene and toluene. So it was practically a complete one Equilibrium between the exothermic and the endothermic reaction has taken place.

There is a particular advantage of this embodiment of the invention in that the aromatic starting compound, e.g. B. toluene or xylene, in simple Way can be made from a naturally occurring naphthene, for example the end Methylcyclohexane or dimethylcyclohexane, in the same device and simultaneously with the hydrogenative cracking of the diarylalkane.

This avoids having to go for toluene or xylene, from another Source provided a special device for the dehydration of Methylcyclohexane or dimethylcyclohexane must be created. In addition, is a previous complete separation between the naphthene and / or corresponding Aromatics and the paraffins are not necessary because the paraffinic hydrocarbons both in the catalytic hydrogenative cracking of the diarylalkanes as in the Production of the same by alkylation of an aryl compound almost completely inert Are diluents. This makes the recovery of toluene and xylene great simplified.

This method is particularly advantageously used when the naphthene is available in sufficient quantities and is not used for the production of aromatics in an independent procedural stage is needed.

A combined method from this point of view includes the following stages: 1. Obtaining a suitable petroleum gas fraction, for example by distillation which contains the desired naphthenes and usually as well comprises a larger amount of paraffins with the same boiling range; 2. Mixing the fraction containing the naphthenes with the corresponding diarylalkane; 3. Hydrogenating Cracking this mixture, as already described, to achieve a reaction mixture, the corresponding aromatic and alkyl aromatic compounds as well as the contains mentioned paraffins and unreacted naphthene and diarylalkane; 4. Separation the paraffins, aromatics, alkylaromatics and diarylalkanes by distillation as separate Fractions; 5. Use of the aromatic fraction as a starting material for the alkylation of the aromatic (for example with acetaldehyde or acetylene) to the corresponding Diarylalkane; 6. Return of the unreacted diarylalkane to the stage of hydrogenating cracking.

Although unreacted naphthene may be recovered and can be fed back into the process, it is generally more economical to use the part that passes over with the paraffins for other purposes. The naphthenes containing gasoline fraction and the diarylalkane are preferably in the second Process stage mixed in such proportions that 1 mole of the aromatic hydrocarbon from which naphthene is produced for every mole of that aromatic compound, which is produced by cracking the diarylalkane. That of course depends on both on the concentration of naphthene in the gasoline fraction as well as on the relative ones Implementation ratios of naphthene and the diarylalkane compound.

This particular embodiment of the present method is special suitable for the production of ethylbenzene from gasolines containing cyclohexane, and it avoids the need to separately manufacture and recover the benzene. in the it is generally used to good effect in the manufacture of ethylaromatic Hydrocarbons from the corresponding naphthenes (especially the naphthenes with a ring), for example in the production of ethylbenzene from cyclohexane, Ethyltoluene from methylcyclohexane and the ethylxylenes from dimethylcyclohexanes.

Claims (5)

Claims: 1. Process for the production of aromatic compounds with at least one aliphatic core substituent of at least 2 carbon atoms contains, by heating a diarylalkane having at least 2 carbon atoms in the Alkyl radical and the aryl groups bonded to the same carbon atom of the alkyl radical, contains, to 300 to 600 "C in the presence of a high-melting inorganic catalyst with acidic properties, in particular oxides or silicates, and optionally in the presence of a diluent, in particular steam, characterized in that that one also works in the presence of steam and the above-mentioned catalyst used as a dehydrogenation catalyst known metal or a Metal compound of the nickel group, in particular nickel, or platinum, palladium or Rhodium, has been added. 2. The method according to claim 1, characterized in that as acidic portion of the catalyst uses a sulfide. 3. The method according to claim 1, characterized in that at Pressures from 17 to 48 at and a molar ratio of hydrogen to diarylalkane such as 20 to 50: 1, preferably 2 to 10: 1, works. 4. The method according to claim 1, characterized in that at Atmospheric pressure works. 5. The method according to claim 1, characterized in that as A naphthenic hydrocarbon diluent is used. References considered: U.S. Patents No. 2,582 428, 2,422,318, 2422163, 2422164, 2420688, 2373982; British Patent No. 657 565; M a r d e r, "Motor Fuels", Berlin 1942, p.447; Journal of Electrochemistry, Vol. 53 (1949), p. 291 off.; Chemical Abstracts, 40, column 2133 (1946).