GB2252556A - Alkoxy-alcohols from olefins - Google Patents

Abstract

Alcoxyalcohols are produced by reacting an olefin with a peroxy compound such as hydrogen peroxide and an alcohol having 1 to 4 carbon atoms in the presence as catalyst of a composition comprising an oxide and/or a hydroxide of titanium in chemical combination with the surface of a support comprising an inorganic siliceous solid.

Description

PROCESS FOR THE PRODUCTION OF ALCOXYALCOHOLS This invention relates to a process for the production of alcoxyalcohols.

It is known from European patent publication number EP 0100118 Al that glycol monomethylethers (methoxyalcohols) may be produced by the reaction of an olefin compound, methanol and hydrogen peroxide in aqueous solution in the presence of synthetic zeolites containing titanium atoms of general formula xTi02 (l-x)Si02 where x lies between 0.0001 and 0.04.

The preparation of synthetic zeolites containing titanium atoms (titanium silicalites) is an elaborate and time consuming procedure.

Thus, EP 0100118 Al describes the preparation of titanium silicalite from a reaction mixture consisting of sources of silicon oxide, titanium oxide and possibly an alkaline oxide, a nitrogenated organic base and water, the molar ratios of the reagents being within defined ranges.

UK patent publication number 2071071A also describes such a preparation procedure.

In both of these patent publications, to prepare the catalyst, the reagent mixture is subjected to hydrothermal treatment in a autoclave at a temperature of between 130 and 220"C under its own pressure for a time of 6 - 30 days until crystals of the catalyst precursor are formed, the crystals being separate from the mother liquour, carefully washed with water and dried. Thereafter, the precursor crystals are heated or calcined for 1 to 72 hours in air at 550"C in order to completely eliminate the nitrogenated organic base. The silicalites are characterised by x-ray and infra-red examination.

Thus, there remains a need for a process for the production of alcoxyalcohols from olefins using a catalyst which does not require such an elaborate and time consuming preparation procedure.

According to the present invention there is provided a process for the production of an alcoxyalcohol which process comprises reacting an olefin with a peroxy compound and an alcohol have 1 to 4 carbon atoms in the presence as catalyst of a composition comprising an oxide and/or a hydroxide of titanium in chemical combination with the surface of a support comprising an inorganic siliceous solid.

It has been found that titanium oxide/hydroxide chemically combined with the surface of a siliceous support is an effective catalyst for the production of an alcoxyalcohol from an olefin. The preparation of such catalysts is simpler than the procedures used for the preparation of titanium silicalites.

Suitable siliceous support materials contain at least 50% by weight silica and preferably at least 75% by weight silica. The support material preferably has a relatively large surface area, generally at least 1 m2/g, preferably in the range from 25 m2/g to 800 m2/g. One suitable type of siliceous material is, for example, synthetic porous silica in a relatively dense, close-packed form comprising particles of amorphous silica flocculated or linked together such as silica gel and precipitated silica. Also suitable are synthetic silica powders consisting of particles of amorphous silica flocculated in open-packed, readily disintegrated loosely-knit aggregates, such as the fumed silicas produced by the combustion of hydrogen and oxygen with silicon tetrachloride or tetrafluoride.Such materials are produced commercially and sold by various companies, for example Cabot Corporation (Carb-O-Sil, Trade Mark) and Degussa (AEROSIL, Trade Mark). Yet another type of siliceous material which may be used in the present invention includes naturally occuring crystalline mineral silicates including for example, asbestos minerals such as serpentine (hydrous magnesium silicates); clay minerals such as hectorite (magnesium lithium silicate); kaolins and bentonites and micaceous minerals such as phlogopite (potassium magnesium aluminium silicate) and vermiculite (a hydrous magnesium silicate).

Preferred siliceous support materials are synthetic amorphous silicas and/or inorganic silicates and in particular those which essentially consist of substantially pure silica, for example at least 90g silica and more preferably at least 95% silica.

The amount of titanium on the surface of the support should preferably be not greater than 10Z by weight calculated as titanium dioxide, more preferably not greater than 5Z by weight calculated as titanium dioxide and most preferably not greater than 2% by weight calculated as titanium dioxide.

Preferably, the catalyst composition may additionally comprise one or more promoters, for example compounds of (a) alkali metals such as lithium, sodium, rubidium and/or potassium and/or (b) alkaline earth metals such as magnesium, calcium, strontium, and/or barium. The promoters may suitably be present at up to 10% by weight calculated as metal on the catalyst support.

The catalyst may be prepared by known methods such as those described in UK patent number 1332527. Thus, in one method an intimate mixture of siliceous solid and solid titanium dioxide may be calcined at temperatures of about 5000C or higher to give a suitable catalyst. Another method is to impregnate an inorganic siliceous solid with an aqueous solution of a titanium compound such as, for example, TiCl4, followed by hydrolysis, drying and calcining in a non-reducing atmosphere to form a silica-titania catalyst.Yet another method is to impregnate an inorganic siliceous solid with a substantially non-aqueous solution of a titanium compound in a non-basic essentially inert, hydrocarbon or oxygen-substituted hydrocarbon solvent, removing the solvent and thereafter calcining the impregnated solid in a non-reducing atmosphere at a temperature of at least 500"C for sufficient time to chemically bond the titanium compound as titanium oxide and/or hydroxide to the surface of the support. Preferably the material is calcined at 800"C for about 2 to 3 hours in air. Suitable titanium compounds for impregnating the inorganic siliceous solid are, for example, the soluble titanium salts of inorganic and organic acids and titanate esters.Preferred compounds are titanium tetrachloride and titanium tetraalkanolates of from 1 to 6 carbon atoms per alkanol group.

Titanium oxide diacetylacetonate may also be used.

Another method for the preparation of a catalyst for the process of the present invention is described in European patent publication EP 0345856A1. In this method the catalyst may be prepared by the steps of (a) impregnating a solid silica and/or inorganic silicate with a stream of gaseous titanium tetrachloride (b) calcining and (c) hydrolysing.

In the methods of preparing the catalysts high temperature calcination is important to chemically bond the titanium oxide and/or hydroxide to the surface of the support.

If promoters are to be added to the catalyst they may be suitably added in soluble form with the impregnating solution of the titanium compound.

The olefin may be a straight-chain, branched-chain or cyclic olefin. The olefin may be any organic compound having at least one olefinic double bond. The olefin may be acyclic, monocylic, bicyclic or polycyclic and may be mono-olefinic, diolefinic or polyolefinic. If more then one olefinic double bond is present, the olefin may be conjugated or non-conjugated. The olefin may also be substituted with an allylic hydroxyl group. Preferably, the olefin has the general formula (I) R - CH = CH - R' (I) where R and R' may be the same or different and may be hydrogen atoms or may be hydrocarbyl groups, for example alkyl, aryl, alkylaryl, cycloalkyl or alkyl cycloalkyl groups. Suitably, R and R' each have less than 10 carbon atoms, preferably less than 8 carbon atoms, more preferably less than 6 carbon atoms. R and R' may together form a cycloalkyl or alkylcycloalkyl group, suitably having less than 10 carbon atoms, preferably less than 8 carbon atoms, more preferably having 6 carbon atoms. One or both of R and R1 may have allylic hydroxyl groups.

Suitable olefins comprises ethylene, propylene, butenes, for example butene-l, cis or trans butene-2, pentenes, hexenes, octenes, decenes, cyclohexene and butadiene.

A mixture of olefins may be used. The olefin may be used with minor amounts of impurities such as alkanes and aromatics, but preferably such impurities are inert to the reaction, for example alkanes.

The alcohol is suitably an alkanol having 1 to 4 carbon atoms.

Preferably the alcohol is methanol or ethanol, most preferably methanol.

The peroxy compound may comprise a hydroperoxide, a peroxide ether and/or a peracid. Preferably the peroxy compound comprises hydrogen peroxide. The hydrogen peroxide may be used as an aqueous solution, suitably at 10 - 70% w/v. Hydrogen peroxide 30% w/v aqueous solution is commercially available and may be suitably used. Generally the stronger the hydrogen peroxide solution the less tendancy there is for by-product diols to be formed.

The reaction may be carried out in the neat liquid reagents or a solvent may be used. Suitably, the reaction is carried out in the alcohol as reaction medium since an excess of alcohol is desirable to increase selectivity to the required product. However, a solvent which is non-coordinating and inert to the reaction conditions may be used, if required. Such inert solvents may be alkanes, for example hexane or halogenated solvents, for example dichloromethane and dichloroethane.

Preferably, the reaction is performed at a pH of about 0 to 7, more preferably about 0.5 to 2 and most preferably about 1. The reaction medium is preferably acidified by using a strong non-nucleophilic inorganic acid such as sulphuric acid which also has a catalyst effect.

The reaction may be carried out at atmospheric or elevated pressure. Preferably, the reaction is carried out at a sufficiently elevated pressure to maintain a suitable concentration of the oleo in in the liquid reaction medium if the olefin is a gas at atmospheric pressure. A gas which is inert to the reaction such as nitrogen, helium, air or alkane may be used to maintain the elevated pressure.

The reaction may be carried out at any suitable temperature depending upon the reagents. Preferably, the reaction is carried out at 500 to 1500C, more preferably 80" to 120"C, most preferably at about 100"C.

The reaction may be carried out as a batch or continuous process. When operated as a batch process, it is preferred to add the peroxy compound to the other reagents as it is consumed to prevent an excessive concentration building up in the reaction medium. The invention will now be described by reference to the following examples.

Catalyst Preparation Catalyst I Titanium tetraethoxide (20% weight solution in ethanol, 9g) was dissolved in ethanol (15ml) and then added quickly to a rapidly stirred slurry of a high surface area silica gel powder (DavisilTM, grade 644, 25g supplied by Aldrich) in ethanol (75ml). This was stirred for 10 minutes and after this period the ethanol was removed using a rotary evaporator. The catalyst was then dried in an oven at 120"C for 18 hours and finally calcined at 800"C for 2 hours under a stream of air.

Catalyst II Titanium tetraisopropoxide (2.77g) was added quickly to a rapidly stirred slurry of silica gel (DavisilTM, grade 644, 50.32g) in dry hexane (88g) under nitrogen. This was stirred for 2 hours and then the silica gel was filtered off. The catalyst was then dried in an oven at 1200C for 18 hours and finally calcined at 800"C for 3 hours under a stream of air. The amount of titanium compound used was sufficient to give 1.5% by weight calculated as titanium dioxide on the silica support.

Preparation of Alcoxyalkanols In the examples the following definitions are used: Selectivity = moles of particular product x 100% moles of all products Yield based on = moles of particular product x 100% initial hydrogen peroxide initial moles of hydrogen peroxide Yield based on = moles of particular product x 100% hydrogen peroxide consumed initial moles of hydrogen peroxide final moles of hydrogen peroxide Example 1 A 300ml stainless steel autoclave was charged with methanol (l0lg), hydrogen peroxide (30Z w/v, 6.14g) and Catalyst I prepared as described hereinbefore (2.97g). The autoclave was sealed, cooled using a cardice/acetone bath, and propylene (60ml at -78 C) was transferred into the autoclave from a cooled graduated Fischer-Porter tube.The autoclave was then sealed and heated to 100"C for 1 hour after which the autoclave was cooled to ambient temperature and vented of all residual gases. Peroxide test strips indicated a 70Z conversion of hydrogen peroxide. Reaction products were measured by gas chromatographic techniques giving selectivities of 60Z for methoxypropanol and 2% for propylene oxide. The yield of methoxy propanol based on initial hydrogen peroxide was 9%.

Example 2 Hydrogen peroxide (30% w/v, 12g) in methanol (25g) was added dropwise over 3 hours to a refluxing mixture of cyclohexene (30.8g), methanol (175g) and Catalyst I prepared as hereinbefore described (3g). After the addition was complete the reaction was refluxed for a further 2 hours and then cooled. Peroxide test strips indicated a 100% conversion of hydrogen peroxide. Reaction products were measured by gas chromatographic techniques giving a yield of methoxycyclohexanol of 38% molar based on initial hydrogen peroxide; a yield of cyclohexanediol of 6% molar based on initial hydrogen peroxide and a yield of cyclohexylene oxide of 6% molar based on initial hydrogen peroxide. Adipaldehyde by-product was also detected in the product mixture.It is believed that the presence of residual soluble titanium compounds in the catalyst may have resulted in some decomposition of the hydrogen peroxide.

Example 3 Hydrogen peroxide (27.5% w/v, 28.86g) was added dropwise over 3 hours to a refluxing mixture of cyclohexene (39.35g), methanol (210g), concentrated sulphuric acid (10-15 drops to bring to about pHi [1 drop = about 50 milligrams]) and Catalyst II (5g). After the addition was complete, the reaction was refluxed overnight and then cooled. Iodometric titration indicated that 21% of the hydrogen peroxide had been consumed. Reaction products were measured by gas chromatographic techniques and gave a yield of 2-methoxycyclohexanol, of 81% [based on consumed hydrogen peroxide],with a selectivity of about 95%. The balance of products, about 5%, was made up of cyclohexan-1,2-diol.

This experiment shows the benefits of reaction at pH 1 by the addition of a strong non-nucleophilic, inorganic acid such as sulphuric acid.

Example 4 Hydrogen peroxide (27.5% w/v, 14.98g) was added dropwise over 3 hours to a refluxing mixture of cyclohexene (31.54g), ethanol (200g), concentrated sulphuric acid (10-15 drops to bring to about pHI [1 drop = about 50 milligram]) and Catalyst II (5g). After the addition was complete, the reaction mixture was refluxed overnight and then cooled. Iodometric titration indicated that 28% of the hydrogen peroxide had been consumed. Reaction products were measured by gas chromatographic techniques and gave yields for 2-ethoxycyclohexanol and cyclohexan-1,2-diol, of 48% and 41%, respectively (based on consumed hydrogen peroxide,) with selectivities of 54% and 46% respectively.

Claims (11)

Claims:

1. A process for the production of an alcoxyalcohol which process comprises reacting an olefin with a peroxy compound and an alcohol having 1 to 4 carbon atoms in the presence as catalyst of a composition comprising an oxide and/or a hydroxide of titanium in chemical combination with the surface of a support comprising an inorganic siliceous solid.

2. A process as claimed in claim 1 characterised in that the inorganic siliceous solid support comprises a naturally occuring crystalline mineral silicate.

3. A process as claimed in claim 1 characterised in that the inorganic siliceous solid support comprises a synthetic porous silica or a synthetic silica powder.

4. A process as claimed in claim 3 characterised in that the inorganic siliceous solid support comprises at least 90% silica.

5. A process as claimed in any one of the preceding claims characterised in that the amount of titanium on the surface of the support is not greater than 10% by weight calculated as titanium dioxide.

6. A process as claimed in claim 1 characterised in that the catalyst composition is obtainable by: (a) calcining an intimate mixture of siliceous solid and solid titanium dioxide at a temperature of about 500"C or higher; (b) impreganating an inorganic siliceous solid with an aqueous solution of a titanium compound followed by hydrolysis, drying and calcining in a non-reducing atmosphere; (c) impregnating an inorganic siliceous solid with a substantially non-aqueous solution of a titanium compound in a non-basic essentially inert hydrocarbon or oxygen-substituted hydrocarbon solvent, removing the solvent and thereafter calcining in a non-reducing atmosphere at a temperature of at least 5000C; or (d) impregnating a solid silica and/or inorganic silicate with a stream of gaseous titanium tetrachloride followed by calcining and hydrolysis.

7. A process as claimed in any one of the preceding claims characterised in that the catalyst composition additionally comprises one or more promoters comprising compounds of alkali metals and/or alkaline earth metals.

8. A process as claimed in any one of the preceding claims characterised in that the olefin has the general formula: R - CH = CH - R1 (I)

9. A process as claimed in claim 8 characterised in that the olefin comprises ethylene, propylene, a butene, a pentene, a hexene, an octene, a decene, cyclohexene or butadiene.

10. A process as claimed in any one of the preceding claims characterised in that the alcohol comprises methanol and/or ethanol.

11. A process substantially as hereindescribed and with references to the Examples.