GB2367292A

GB2367292A - Crystalline Gallium Silicate Catalysts and their use in the preparation of Est ers

Info

Publication number: GB2367292A
Application number: GB0023671A
Authority: GB
Inventors: Kazuyuki Matsuoka
Original assignee: Daicel Chemical Industries Ltd
Current assignee: Daicel Corp
Priority date: 2000-09-27
Filing date: 2000-09-27
Publication date: 2002-04-03
Also published as: GB0023671D0

Abstract

A catalyst used in the production of a carboxylic acid ester from an olefin and a carboxylic acid comprises a crystalline gallium silicate. The ratio of silicon to gallium is about 10/1 to 500/1 (molar ratio). The olefin may for example be a chain C<SB>2-20</SB> olefin or a cyclic C<SB>3-12</SB> olefin. The carboxylic acid may for example be a C<SB>1-18</SB> aliphatic carboxylic acid, a C<SB>4-8</SB> alicyclic carboxylic acid, or an aromatic carboxylic acid. The esterification catalyst is not corrosive, with the aid of which an olefin can react with a carboxylic acid even under a relatively low pressure to produce the corresponding carboxylic acid ester.

Description

CATALYST FOR ESTERIFICATION AND PROCESS FOR PRODUCING CARBOXYLIC ACID ESTERS USING THE SAME FIELD OF THE INVENTION The present invention relates to a process for economically producing a carboxylic acid ester from an olefin and a carboxylic acid in a high yield, and an esterification catalyst therefore.

BACKGROUND OF THE INVENTION Till now, as a representative process of producing carboxylic acid esters, there has been known a process in which a carboxylic acid is reacted with an alcohol in the presence of an acidic catalyst to produce the corresponding carboxylic acid ester. This process, however, requires water by-produced during the reaction to be removed from the system for raising the conversion, for the reaction is an equilibrium reaction.

In this case, it is necessary to prevent the alcohol as a starting material from escaping as a result of azeotropy with water, and therefore, it cannot be necessarily said that this process is suitable.

In recent years, there have been proposed processes of producing carboxylic acid esters by reacting an olefin as a substitute of the alcohol with a carboxylic acid. In these processes, as the catalyst, a liquid catalyst [e. g. , a strong acid catalyst (e. g. , sulfuric acid, the combination of BF 3 and HF), a solid catalyst (e. g. , a strong acidic cationic ion-

exchange resin), or the like is used.

These processes, from the viewpoint of industrial production of carboxylic acid esters, are superior to conventional processes for producing a carboxylic acid ester from the corresponding alcohol and the corresponding carboxylic acid in that the yield and the conversion in the production are

improved. However, in the case of the use of the liquid catalyst, separation and recovery of the catalyst becomes arduous. In addition, if the catalyst is a strong acid-based one or a halogen-containing one, equipment for the reaction easily corrodes. If a heteropolyacid is employed, a by-product (s) tends to be produced, and this results in a drop in the yield of the object compound. Although separation and recovery of the solid catalyst is easier than that of the liquid catalyst, the strong acidic cationic ion-exchange resin is drastically deteriorated by heat and its reproduction is difficult. In addition, its reactivity to olefins small in the number of carbon, such as ethylene, is poor.

In view of the facts described above, there has been proposed a process in which zeolite (crystalline metal silicates) is used as a catalyst. For example, Japanese Patent Application Laid-Open No. 249949/1986 (JP-A-61-249949) discloses a liquid phase reaction for which a crystalline aluminosilicate with controlled acid moieties is used. Japanese Patent Publication No. 46941/1992 (JP-B-4-46941) proposes a gaseous phase reaction for which a crystalline silicate of boron or chromium is used.

Although, in these processes, such a complicated operation as a catalyst-separating operation is unnecessary and the degree of corrosion or lowering in catalytic activity gets mild, the yield of a carboxylic acid ester in its industrial production is poor. For example, when reacting a carboxylic acid with an olefin utilizing a gaseous phase method, the space-time yield is low and, from the viewpoint of practicality, is unsatisfactory.

SUMMARY OF THE INVENTION Thus, the present invention aims to provide an esterification catalyst which smoothly reacts even under relatively low pressure and is useful in forming a carboxylic acid ester in a high yield, and a process for producing a carboxylic acid ester using the same.

The present invention also aims to provide an esterification catalyst which does not corrode equipment and is easily separated and recovered, and a process for producing a carboxylic acid ester using the same.

Still another aim of the present invention is to provide an esterification catalyst which, when a reaction is effected in accordance with a gaseous phase method, smoothly reacts even under relatively low pressure and improves the space-time yield, and a process for producing a carboxylic acid ester.

The inventors of the present invention made intensive studies and finally found that the use of a crystalline gallium

silicate as a reaction catalyst in producing a carboxylic acid ester from an olefin and a carboxylic acid, even under rela tively low pressure, makes it possible to provide the carboxylic acid ester in a high yield without corrosion, and that such catalyst is easily separated and recovered. The present invention was accomplished based on the above findings.

That is, the esterification catalyst of the present invention is a catalyst for forming a carboxylic acid ester from an olefin and a carboxylic acid and comprises a crystalline gallium silicate. The catalyst may be a catalyst for having the olefin react with the carboxylic acid in a gaseous phase. The ratio of silicon to gallium is about 10/1 to 500/1 (molar ratio). The crystalline gallium silicate may have pores of which the mean (micro) pore size may be about 0.4 nm to 100 .

The volume of the pores may be about 0.1 to 5 ml/g.

In the production process of the present invention, a carboxylic acid ester is produced by reacting the

corresponding olefin with the corresponding carboxylic acid in the presence of a crystalline gallium silicate. The olefin may for example be a chain C2 olefin or a cyclic C3-12 olefin.

The carboxylic acid may be a Cl-18 aliphatic carboxylic acid, a C4-8 alicyclic carboxylic acid, an aromatic carboxylic acid, or others.

DETAILED DESCRIPTION OF THE INVENTION [Catalyst for Esterification] In the present invention, a crystalline gallium

silicate used as a catalyst for esterification is constituted of a crystalline silicate containing gallium and shows a high activity in the reaction between an olefin and a carboxylic acid. There is no particular restriction as to in what form gallium is contained therein. For example, gallium may be supported on the crystalline silicate, or any of the elements constituting the crystalline silicate is, at least partially, substituted with gallium.

The crystalline gallium silicate may contain other elements (e. g., alkaline metals such as Na; alkaline earth metals such as Mg and Ca ; transition metals such as Cr, Mn and Fe ; the Group 3B elements such B and Al). The crystalline gallium silicate usually comprises an element selected from Al, Cr, and B. An element or elements constituting the silicate (e. g., Al, Cr, B, Si) is/are, at least partially, substituted with Ga.

Preferred as the crystalline silicate is an aluminosilicate (e. g. , zeolite typified by ZSM-type zeolite), a borosilicate, or a chromosilicate, in which an element or elements constituting the silicate (e. g., Al, Cr, B, Si) is/are, at least partially, substituted with Ga. These can be used either singly or as a combination. Such crystalline gallium silicate is commercially available as a molecular sieve and comes in a variety of types represented by a pentacyl-type molecular sieve, and therefore, is easily obtainable.

There is no particular restriction as to the ratio of silicon to gallium of the crystalline gallium silicate, and the

ratio is, for example, silicon/gallium = about 10/1 to 500/1 (molar ratio), preferably about 10/1 to 200/1 (molar ratio), more preferably about 20/1 to 100/1 (molar ratio). If the proportion of silicon is too small, the thermal stability of the catalyst will be lowered. If the proportion is too large, the activity of the catalyst tends to be lowered.

The crystalline gallium silicate usually has pores.

The mean pore size of the pores is within a range not adversely affecting the catalytic activity and may for example be within the range of about 0.4 nm to 100 pm, preferably about 0.5 nm to 10 pm. The pores may be those categorized as mesopores.

The surface area of the crystalline gallium silicate

can be selected within a wide range not adversely affecting the catalyticactivity, suchastherangeofabout10to2, 000m2/g, preferably about 50 to 1, 000 m/g, more preferably about 300 to 500 m/g. The surface area can be measured by an adsorption process using nitrogen gas (nitrogen gas adsorption process).

The volume of the pores of the crystalline gallium silicate is about 0.1 to 5 ml/g, preferably about 0.2 to 2.5 ml/g.

The crystalline gallium silicate may form a Lewis acid-type catalyst and/or a Brnsted acid-type catalyst. In this case, in the infrared ray absorption spectrum measured for the crystalline gallium silicate with pyridine adsorbed, the

area ratio of the absorption range AL corresponding to the Lewis acid-type acid moieties to the absorption range AB corresponding to the Brnsted acid-type moieties may be AL/AB

= 80/20 to 100/0.

The form of the crystalline gallium silicate is not particularly restricted and the silicate can take any form. For example, the silicate is particulate, pelletized, flaky, rod-like, spherical, tablet-like, or honeycomb. Since the crystalline gallium silicate is usually solid, after the reaction has been completed, it is separated and recovered from the reaction product with ease.

The crystalline gallium silicate can be obtained by

an ordinary process of producing a crystalline metal silicate. Exemplified as such process is a process in which a crystalline gallium silicate is produced by, after adding a porecontrolling template agent if necessary, heating a composition as the starting material composed of a silica component, an alkaline metal component, a gallium component, and water. In the case the pore-controlling template agent is not added, the crystalline gallium silicate can be obtained by, for example, a process in which an aqueous mixture composed of a fine amorphous silica, sodium hydroxide, and the source of gallium (e. g. , gallium oxide, sodium gallate) is aged and heated (disclosed by Japanese Patent Publication No. 37148/1970 (JP-B-45-37148). If necessary, to the starting material is added other metal sources such as alumina sol.

Examples of the silica component are a variety of silica-containing compounds capable of forming crystalline silicates such as silica alkoxides (e. g., teteramethoxysilane, tetraethoxysilane, tetrabutoxysilane, trimethoxymethylsi

lane), silicates (e. g., sodium silicate), silica sols (e. g, silica sol, colloidal silica). Preferred as the silica component are crystalline silicates such as silica sols, and stabilized silica sols (colloidal silica) are particularly preferred.

As the alkaline metal component, usually, a watersoluble alkaline metal compound is used. Examples of the water-soluble alkaline metal compound are hydroxides (e. g., sodium hydroxide, potassium hydroxide), carbonates (e. g., sodium carbonate, potassium carbonate), hydrogencarbonates (e. g., sodium hydrogencarbonate, potassium hydrogencarbonate), halides (e. g. , sodium chloride, potassium chloride).

As the gallium component, a water-soluble gallium compound, such as a salt of gallium with an inorganic acid (e. g., gallium sulfate, gallium hydrochloride, gallium phosphate, gallium nitrate), is usually employed.

Exemplified as the pore-controlling template agent are alkylamines such as tetraalkylammoniums, alkylamines, and oxyalkylamines (e. g. , amino alcohols) and morpholine. These template agents can be used either singly or in combination.

The tetraalkylammoniums usually have a linear-or branched alkyl group [e. g. , a Cl-30 alkyl group (preferably, a Cl-26 alkyl group, particularly a Cl-16 alkyl group) such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, s-butyl, t-butyl, pentyl, hexyl, octyl, decyl, dodecyl, tetradecyl, pentadecyl, hexadecyl, octadecyl, eicocyl, and dococyl].

Examples of the alkyl groups of the alkylamines are

those mentioned above. Among others, linear-or branched chain Cl-io alkyl groups (preferably, Cl-6 alkyl groups, particularly Cl-4 alkyl groups) are preferred. The alkylamine may be a mono-, di-, or trialkylamine.

Exemplified as the oxyalkylamine (amino alcohol) are linear-or branched aliphatic alcohols having an amino group [e. g. , amino aliphatic C2-10 alcohols (e. g. , aminoethanol, aminopropanol, aminoisopropanol, aminobutanol, aminoisobutanol, amino-s-butanol, aminopentanol, aminohexanol, aminooctanol), particularly mono-, di-, and triamino aliphatic C2-6 alcohols].

The alkylamine may be used in the form of a salt (e. g., a salt with a halogen ion).

Heating is conducted at a temperature of about 80 to 300oC, preferably 120 to 200oC. The heating time can be selected within the range of, for example, 30 minutes to 30 days, preferably about 1 hour to 10 days (e. g. , 5 hours to 2 days),

depending on the heating temperature. The reaction is carried out with stirring or without stirring. The crystalline gallium silicate formed by heating may be subjected to a conventional purification step (including washing, drying) to remove impurities therefrom. Moreover, it is possible to remove such an organic component as the alkylamine by, in an atmosphere of oxygen such as air, baking the crystalline gallium silicate at a suitable temperature (e. g., about 300 to 7000C). The alkaline metal (s) of the purified crystalline gallium silicate may be ion-exchanged with an ammonium ion (s). The catalytic activity

of the crystalline gallium silicate is improved by, after the silicate being ion-exchanged with an ammonium ion (s), baking the silicate. Baking is conducted at about 300 to 700oC. The crystalline gallium silicate described above is useful as a

catalyst for esterification for forming a carboxylic acid ester through the reaction of an olefin with a carboxylic acid, with which the carboxylic acid ester is efficiently produced.

[Production Process of Carboxylic Acid Ester] In the production process of the present invention, a carboxylic acid ester is produced by reacting an olefin with a carboxylic acid in the presence of the above-described

crystalline gallium silicate.

There is no particular restriction as to the olefin, c and the olefin is, for example, a chain (or non-cyclJ) olefin [e. g., C2-20 (e. g., C2-o) linear or branched-chainolef ins, such

as straight-chain C2-20 olefins (preferably, linear C2 15 olefins, particularly linear C2-1o olefins) typified by ethylene, propylene, 1-buten, 2-butene, 1-pentene, 2-pentene, 1-hexen, 1-heptene, 1-octene, 1-nonene, andl-decene) ; a branched-chain C4-20 olefin (preferably, branched-chain C4 16 olefins,

particularlybranched-chainC4-10 olefins) such as isobutylene, 2-methyl-l-butene, 2-methyl-2-butene, 3-methyl-l-butene, 2, 3-dimethyl-l-butene, 2-methyl-l-pentene, 2-methyl-2 pentene, cis-3-methyl-2-pentene, trans-3-methyl-2-pentene, 2-ethyl-1-butene, 2-ethyl-2-pentene, and 2-propyl-2-butene] ; a cyclic olefin [e. g. , C3-12 cyclic olefins (preferably, C5-8 cycloalkenes, particularly C5-6 cycloalkenes) which may have

a substituent (e. g., alkyl group), such as cyclopropene, cyclobutene, cyclopentene, cyclohexene, cycloheptene, cy clooctene, cyclononene, cyclodecene, and methylcyclohexenel; or an aromatic olefin (e. g. , styrene, vinyltoluene).

Preferred as the olefin is a chain C2 10 olefin, and a chain C olefin is particularly preferred.

There is no particular restriction as to the carboxylic acid. Examples of the carboxylic acid are aliphatic carboxylic acids [e. g. , saturated Cl-18 monocarboxylic acids (preferably, saturated C2-10 monocarboxylic acids) such as formic acid, acetic acid, propionic acid, butyric acid, isobutyric acid, valeric acid, pivalic acid, lauric acid, myristic acid, and palmitic acid] ; unsaturated C3-18 monocarboxylic acids (e. g., preferably, unsaturated C3-10 monocarboxylic acids) such as (meth) acrylic acid, crotonic acid, and isocrotonic acid; saturated C polycarboxylic acids (preferably, saturated C2-10 dicarboxylic acids) such as oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, and sebacic acid ;

unsaturated C4-16 polycarboxylic acids (preferably, unsaturated C4-10 dicarboxylic acids) such as maleic acid, maleic anhydride, fumaric acid, and itaconic acid] ; and alicyclic carboxylic acids (e. g. , alicyclic C4-8 carboxylic acids) [e. g. , alicyclic monocarboxylic acids (preferably, C5-6

cycloalkane-carboxylic acids) such as cyclobutanecarboxylic acidandcyclohexanecarboxylicacid) ; alicyclic polycarboxylic acids (preferably, ci-6 cycloalkane-dicarboxylic acids) such as cyclobutanedicarboxylic acid and cyclohexanedicarboxylic

acid] and aromatic carboxylic acids (e. g., aromatic mono-, or dicarboxylic acids such as benzoic acid, phthalic acid, and isophthalic acid).

Included among the preferred carboxylic acid are Cl-5 aliphatic carboxylic acids, and saturated CI-5 aliphatic monocarboxylic acids are particularly preferred.

In the esterification, the ratio of the olefin to the carboxylic acid (olefin/carboxylic acid) is not particularly restricted, and can be selected within the range of, for example, about 0.01/1 to 100/1 (molar ratio), preferably 0.1/1 to 50/1 (molar ratio), more preferably 0.1/1 to 20/1 (molar ratio).

According to the process of the present invention, from the olefin and the carboxylic acid described above, the corresponding carboxylic acid ester can be obtained without an increase or decrease in the number of carbons. For example, the reaction of ethylene with acetic acid yields ethyl acetate.

The reaction can be effected by such a conventional process as a batch process, a semi-batch process, or a continuous process. The continuous process is advantageous to industrial production. Between a gaseous phase and a liquid

phase, although it is possible to effect the reaction in either phase, from the viewpoint of industrial production, it is preferred that the reaction is carried out in a gaseous phase, for, generally speaking, the reaction pressure during the reaction in a gaseous phase is lower. According to the process of the present invention in which the reaction is continuously carried out in a gaseous phase, carboxylic acid esters are

produced in high space-time yields, and therefore, the process of the present invention is industrially advantageous.

There is no particular restriction as to the rate of supply of the starting material (s) and the residence time, and the rate and the time are selected within suitable ranges.

The reaction is conducted at a temperature at which the reaction can proceed. For example, the reaction temperature is selected within the range of about 80 to 350oC, preferably 100 to 300oC (e. g. , 150 to 2500C). Regardless of pressure, under normal or applied pressure, it is possible to effect the reaction. Preferably, the reaction is effected under a pressure within the range of normal to about 100 atm.

(1 to 100 atm.), preferably normal to bout 20 atm. (1 to 20 atm.), more preferably normal to about 5 atm. (1 to 5 atm.).

The reaction may be effected in the presence of such an inert gas as helium, nitrogen, or argon. It is not critical that the reaction is carried out in the presence of a solvent

or in the absence of a solvent. As the solvent, a solvent which does not participate in the reaction, such as an organic solvent (e. g. , an aliphatic saturated hydrocarbon such as hexane), water, or a mixed solvent thereof, can be used.

After the reaction, the carboxylic acid ester thus obtained is separated and purified by such a conventional separation/purification means as filtration, distillation, condensation, extraction, ion-exchange, electrodialysis, crystallization, recrystallization, adsorption, membrane separation, centrifugation, chromatography (column

chromatography, etc.), or a combination means thereof.

Since the catalyst to be used in the process of the present invention is free from such a corrosive substance as a liquid strong acid or a halogen, corrosion of equipment is greatly suppressed. In addition, the catalyst reacts under a relatively low pressure and therefore realizes the production of carboxylic acid esters in high yields. When the reaction is effected in a gaseous phase, carboxylic acid esters are produced in high space-time yields.

Carboxylic acid esters to be produced in the present invention are compounds that are advantageously used in the production of paints, adhesives, plasticizers, aroma chemicals, solvents, and others.

According to the present invention, the catalyst smoothly reacts even under a relatively low pressure and a carobyxylates is produced in a high yield. Since a crystalline gallium silicate substantially free from a halide is used, equipment hardly corrodes and the separation and recovery of the silicate from the reaction mixture is easy. Moreover, by utilizing a gaseous phase process, the catalyst can smoothly react even under a relatively low pressure, and thus, a carboxylic acid ester is produced in a high space-time yield.

EXAMPLES The following examples are intended to describe the present invention in further detail and should by no means be construed as defining the scope of the invention.

Example 1 With a tubular reactor having an inside diameter of 28 mm filled with 60 ml of shaped articles (lamm (diameter) x 5 mm (length) ) of a crystalline gallium silicate manufactured by N'E Chemicat, Co. Ltd. , Si/Ga = 50/1 (molar ratio), pore

size : 0. 6 rim, Bet specific surface area : 400 m/g, pore volume : 1. 1 ml/g (mercury process), particle size : 0. 2 to 0. 3 pm], at a reaction temperature of 220oC and under normal pressure, a mixed gas of ethylene, acetic acid, and water in a 13 : 77 : 10 ratio (molar ratio) was continuously supplied onto the catalyst at a space-time rate of 560 hr-1 to cause a reaction. The gaseous

reaction product thus obtained was cooled and then the resultant liquefied reaction product was analyzed by gas chromatography.

The yield of ethyl acetate was, in terms of space-time yield, 76 g/Lcat'hr.

Example 2 Except that the reaction temperature was changed to

180oC, the reaction was effected in the same manner as in Example 1. The yield of ethyl acetate was, in terms of space-time yield, 63 g/Lcat#hr.

Example 3 Except that the reaction temperature was changed to

200oC, the reaction was effected in the same manner as in Example 1. The yield of ethyl acetate was, in terms of space-time yield, 70 g/Lcat'hr.

Comparative Example 1 Except that a crystalline aluminosilicate [manufac

tured by N-E Chemicat, Co., Ltd., Si/Al = 50/1 (molar ratio)] was used in lieu of the crystalline gallium silicate of Example 1, the reaction was effected in the same manner as in Example 1. The yield of ethyl acetate was, in terms of space-time yield, 49 g/Lcat'hr.

Comparative Example 2 Except that a crystalline borosilicate [manufactured by N'E Chemicat, Co. , Ltd., Si/B = 50/1 (molar ratio)] was used in lieu of the crystalline gallium silicate of Example 1, the reaction was effected in the same manner as in Example 1. The yield of ethyl acetate was, in terms of space-time yield, 52 g/Lcat'hr.

Comparative Example 3 In accordance with a conventional method, a heteropolyacid-based catalyst of Cs2. 5HoPWl2040 was prepared from phosphotungstic acid and cesium nitrate that are commercially available. Except that the heteropolyacid-based catalyst mentioned was used in lieu of the crystalline gallium silicate of Example 1, the reaction was effected in the same manner as in Example 1. The yield of ethyl acetate was, in terms of space-time yield, 59 g/Lcat'hr.

Claims

What is claimed is : 1. An esterification catalyst for forming a carboxylic acid ester from an olefin and a carboxylic acid, which comprises a crystalline gallium silicate.
2. An esterification catalyst according to Claim 1, wherein the ratio of silicon to gallium is silicon/gallium = 10/1 to 500/1 (molar ratio).
3. An esterification catalyst according to Claim 1 or Claim 2, wherein the crystalline gallium silicate further contains an element or elements selected from Al, Cr and B, and wherein at least one of Al, Cr, B and Si which may constitute the silicate is, at least partially, substituted with Ga.
4. An esterification catalyst according to any preceding Claim, wherein: (i) the crystalline gallium silicate is at least one of an aluminosilicate, a borosilicate and a chromosilicate, (ii) at least one of Al, Cr, B and Si which may constitute the silicate is, at least partially, substituted with Ga, and (iii) the ratio of silicon to gallium (molar ratio) is silicon/gallium = 10/1 to 200/1.
5. An esterification catalyst according to any preceding Claim, wherein the crystalline gallium silicate has pores having a mean pore size of 0.4 nm to 100 ju. m and the pore volume is 0.1 to 5 ml/g.
6. A process for producing a carboxylic acid ester, comprising the step of reacting an olefin with a carboxylic acid in the presence of crystalline gallium silicate as a catalyst.
7. A process according to Claim 6, wherein the reaction of the olefin and the carboxylic acid is carried out in the gaseous phase.
8. A process according to Claim 6 or Claim 7, wherein the olefin is a straight or branched chain C2-20 olefin or a cyclic C3-12 olefin, and the carboxylic acid is a Cl-18

aliphatic carboxylic acid, a C4-8 alicyclic carboxylic acid or an aromatic carboxylic acid.
9. A process according to Claim 6 or Claim 7, comprising reacting a straight or branched chain 2-10 olefin with an aliphatic Cl-S carboxylic acid in the presence of a crystalline gallium silicate being at least one of an aluminosilicate, a borosilicate and a chromosilicate, wherein (i) at least one of Al, Cr, B, and Si which may constitute the silicate is, at least partially, substituted with Ga, and (ii) the ratio of silicon to gallium (molar ratio) is silicon/gallium = 10/1 to 200/1.
10. The use of crystalline gallium silicate as a catalyst for the synthesis of a carboxylic acid ester by reacting an olefin and a carboxylic acid.
11. A process for producing a carboxylic acid ester substantially as described herein with reference to any of Examples 1-3.