GB2398749A

GB2398749A - Catalyst and process for the production of lower fatty acid esters

Info

Publication number: GB2398749A
Application number: GB0411895A
Authority: GB
Inventors: Kazuyuki Matsuoka; Toyokazu Yagii; Seiichiro Yamada
Original assignee: Daicel Chemical Industries Ltd
Current assignee: Daicel Corp
Priority date: 2001-12-27
Filing date: 2002-12-13
Publication date: 2004-09-01
Anticipated expiration: 2022-12-13
Also published as: GB0411895D0; GB2398749B

Abstract

The present invention relates to a catalyst for use in the production of a lower fatty acid ester by the reaction between a lower fatty acid and a lower olefin, preferably in the presence of water. Main object of the present invention is to provide a catalyst for the production of a lower fatty acid ester with a high activity. The present invention provides such a catalyst (comprising a heteropolyacid (such as phosphotungstic acid) or a salt thereof) which includes mesopores and macropores and has a dual pore size distribution corresponding to the mesopores and the macropores.

Description

CATALYST AND PROCESS FOR THE PRODUCTION OF LOWER FATTY ACID

ESTERS

The present invention relates to a catalyst for use in the production ofalower fatty acid ester by the reaction between a lower fatty acid and a lower olefin, and a process for the production of a lower fatty acid ester using the catalyst.

Processes for the production of a lower fatty acid ester by the reaction between a lower fatty acid and a lower olefin include, for example, a process by the catalysis of a strongly acidic cation-exchange resin, a process using a supported catalyst comprising an aromatic disulfonic acid on a carrier (Japanese Examined Patent Application Publication No. 60-1775), a process by the catalysis of sulfuric acid, phosphoric acid, phosphotungsticacid, orironsulfate (Japanese Examined Patent ApplicationPublicationNo.53-6131), aprocessbythecatalysis of a phosphotungstic acid salt comprising a metal having an ion radius equal to or more than 1.1 angstrom (Japanese Patent No. 2848011), a process using a supported catalyst comprising a heteropolyacid or a salt thereof as a catalytically active ingredient supported on silica as a carrier (e.g., Japanese Unexamined Patent Application Publications No. 05-29489 and - 2 No. 09-118647), and a process using a supported catalyst comprising a heteropolyacid or a salt thereof supported on a carrier having a specified specific surface area (Japanese Unexamined Patent Application Publication No. 2000-342980).

For example, aforementioned Japanese Unexamined Patent I Application Publications No. 05-29489 and No. 09-118647 each I propose a process in which silica in the form of a sphere, a ' pellet or a particle having a mean particle size from 2 to 10 mm is impregnated with a heteropolyacid or a salt thereof to I form a supported catalyst. Japanese Unexamined Patent Application Publication No. 2000-342980 mentions that the catalytic activity significantly depends on the specific surface area of the carrier and that the catalyst has a high space-time yield (STY) from 100 to 300 g/L-catalyst.hr when the carrier has a specific surface area of about 300 m2/g but has a markedly low STY of 2 g/L-catalyst.hr when the carrier has a specific surface area exceeding500m2/gin the preparation of ethyl acetate from acetic acid and ethylene.

However, the conventional processes are disadvantageous | for use in commercial production of lower fatty acid esters. | For example, some of them have a low catalytic activity, if not, yield large proportions of undesired by-products, have I ashortcatalystlife, orhaveacatalyticactivitysignificantly depending on the specific surface area of the carrier.

After intensive investigations, the present inventors have found that a target lower fatty acid ester can be obtained in a high space-time yield by using a supported catalyst including a catalyst having a specific pore size distribution. They have also found that some of these catalysts can efficiently suppress side reactions and that others have an activity that does not depend on the specific surface area and other physical properties of carriers and can thereby employ a wide variety of carriers. The present invention has been accomplished based on these findings.

According to one aspect of the invention we provide use of a catalyst for production of a lower fatty acid ester from a lower fatty acid and a lower olefin, the catalyst comprising mesopores and macropores and having a dual pore size distribution corresponding to the mesopores and the macropores.

The catalyst of the invention may include, for example, a heteropolyacid or a salt thereof as a catalytically active ingredient. The catalyst may be a catalyst having a total pore volume equal to or more than 0.05 ml/g and including the mesopores and the macropores in proportions of equal to or more than 50% and equal to or more than 15%, respectively, of the total pore volume. It may also be a supported catalyst including a catalytically active ingredient supported on a carrier, the carrier having a total pore volume equal to or more than 0.3 ml/g and including mesopores and macropores in proportions of equal to or more than 50% and equal to or more than 10%, respectively, of the total pore volume. Such carriers in the catalyst include silica.

The heteropolyacid may be, for example, at least one selected from phosphotungstic acid, silicotungstic acid, phosphomolybdotungstic acid, silicomolybdotungstic acid, phosphovanadomolybdic acid, and silicovanadomolybdic acid.

- -

The salt of the heteropolyacid may be, for example, at least one selected from lithium salts, sodium salts, potassium salts, Rubidium salts, cesium salts, thallium salts, magnesium salts' indium salts, and ammonium salts of phosphotungstic acid, silicotungstic acid, phosphomolybdic acid, silicomolybdic acid, phosphomolybdotungstic acid, silicomolybdotungstic acid, phosphovanadomolybdic acid, and silicovanadomolybdic acid.

In addition, the present invention provides a process for the production of a lower fatty acid ester, including the step of allowing a lower fatty acid to react with a lower olefin in the presence of the catalyst of the present invention. The reaction may be performed in the presence of water. The lower fatty acid may be a fatty acid containing 1 to 5 carbon atoms, and the lower olefin may be an olefin containing 2 to 5 carbon atoms.

The catalyst of the present invention exhibits a high activity and can produce lower fatty acid esters with high production efficiency. The catalyst can suppress by-production ofoligomersoflowerolefins end thereby enables the recycling of unreacted lower olefins as intact. - 5

The term "mesopore" used herein means a pore having a pore size equal to or more than 2 nm and less than 50 nm, and the term "macropore" used herein means a pore having a pore size of equal to or more than 50 nm. The pore size distribution and the pore volume can be easily determined by a method of mercury penetration using, forexample, PoreMaster (registered trademark) 60 available from Yuasa-Ionics Co., Ltd. The catalytic materials for use in the present invention comprise heteropolyacids and salts thereof and supported catalysts comprising these compounds supported on a carrier are preferred. These catalytic materials can be used alone or in combination.

Heteropolyacids each comprise a central element and a peripheral element coordinating with oxygen. The central element can be freely selected from Groups 1 to 17 elements of the Periodic Table of Elements, such as phosphorus, arsenic, antimony, silicon, bismuth, copper, and boron. Among them, phosphorus, silicon, end arsenic are preferred. The peripheral element includes, but is not limited to, tungsten, molybdenum, vanadium, niobium, and tantalum.

Such heteropolyacids are known as polyoxoanions, polyoxymetal salts or metal oxide clusters. Some of them have a Keggin structure or a Dawson structure. Examples of such heteropolyacids include, but are not limited to, phosphotungstic acid, silicotungstic acid, borotungstic acid, phosphomolybdic acid, silicomolybdic acid, boromolybdic acid, phosphomolybdotungstic acid, silicomolybdotungstic acid, boromolybdotungstic acid, phosphovanadomolybdic acid, and silicovanadomolybdic acid.

Amongthem,preferredheteropolyacidsarethosecomprising phosphorus or silicon as a hetero-atom (central element) and at least one element selected from tungsten, molybdenum and vanadium as a poly-atom (peripheral element). Examples of preferred heteropolyacids are phosphotungstic acid, silicotungsticacid,phosphomolybdicacid, silicomolybdicacid, phosphomolybdotungstic acid, silicomolybdotungstic acid, phosphovanadomolybdic acid, and silicovanadomolybdic acid.

Salts of heteropolyacids include heteropolyacids except with ametalor ammonium replacing a pert orallof their hydrogen atoms. Such metals include, for example, lithium, potassium, sodium, rubidium, cesium, thallium, magnesium, and indium.

Among them, indium salts and lithium salts are preferred.

Carriers for use herein are not specifically limited and include those generally used as carriers for catalysts, such as silica, activated carbon, diatomaceous earth, alumina, silica-alumina, zeolite, titania, and zirconia. Among them, acid-resistant porous carriers are preferred. When a catalyst supportedonacarrierisusedforalongtimeas anesterification - 7 catalyst, part of the carrier may react with a lower fatty acid to thereby plug its pores. The acid-resistant porous carriers are resistant to these problems. Mare specifically, silica and activated carbon are typically preferred. .

As the carrier for use in the catalyst of the invention, carriers including mesopores and macropores and having a dual pore size distribution corresponding to the mesopores and the macropores, i.e., those having a similar pore structure that in the catalyst are preferred. Among them, carriers having a total pore volume equal to or more than 0.3 ml/g and including mesopores and macropores in proportions of equal to or more than 50% and equal to or more than 10\, respectively, of the total pore volume are typically preferred. Such carriers are, for example, commercially available under the trade name of G-1OM from Fuji Silysia Chemical Ltd. The amount of the catalytically active ingredient such es aheteropolyacid supported on the carrieris not specifically limited and is appropriately selected depending on the types of the catalytically active ingredient and carrier and the preparation process.

The catalyst of the invention can be prepared by molding the catalytically active ingredient as intact or drying a solution, such as an aqueous solution, of the catalytically active ingredient, pulverizing the dried article and molding the same, and where necessary firing the resulting article at a temperature from about 120 C to 450 C.

The pores in the catalyst can be controlled, for example,

I

by a process of selecting the carrier as described above, as well as by a process of adding an organic substance in the preparation of the catalyst and removing the organic substance by firing to form pores. More specifically, the latter process comprises the steps of adding an organic substance such as a powdery polyethylene as an additive in the impregnation of the carrier with the catalytically active ingredient, in the preparation of the solution of the catalytically active ingredient, or in the molding of the powdery carrier, burning and removing the additive during firing to thereby form voids or holes.

Lower fatty acids for usein the presentinventioninclude, but are not limited to, saturated or unsaturated fatty acids having about 1 to about 5 carbon atoms and preferably about 1 to about 4 carbon atoms. Examples of such lower fatty acids are formic acid, acetic acid, propionic acid, butyric acid, acrylic acid, and methacrylic acid, of which acetic acid and acrylic acid are preferred.

Lower olefins for use in the present invention include, but are not limited to, olefins containing about 2 to about carbon atoms and preferably about 2 to about 4 carbon atoms.

Examples ofsuchlowerolefins are ethylene, propylene,butene, and isobutene. 9 -

The reaction is generally performed in a gas phase. The amount of the lower olefin is not specifically limited and can be selected within the range of, for example, from about 0.01 to about 30 moles and generally from about 0.1 to about 30 moles per mole of the lower fatty acid. In general, the lower olefin is preferably used in an excess amount such as from about 1 to about 20 moles per mole of the lower fatty acid.

The reaction temperature is, for example, from about 50 C to about 300 C and preferably from about 100 C to about 250 C.

If the reaction temperature is lower than 50 C, a reaction rate may decrease to thereby reduce the space-time yield of the target fatty acid ester. If it exceeds 300 C, side reactions may increase and the catalyst life may decrease. To increase the space-time yield of the target compound, the reaction pressure may be increased. The reaction pressure is, for example, from about 0.1 to about 5 MPa and preferably from about 0.1 to about 1.5 MPa.

The reaction system preferablyincludes water for alonger catalyst life. By catalysis using the catalysts of the present invention, the target lower fatty acid ester can be obtained in a high space-time yield. In the presence of water, side reactionsmayoccurandtherebyyieldby-productesuchas ethanol and other alcohols, but the catalysts of the present invention yieldless such by-products then conventionalequivalents. The reaction system using the catalyst of the present invention can thereby include a larger amount of wafer to thereby achieve - 10 a longer catalyst life than conventional equivalents. The amount of water is, for example, from about 1% to about 30% by mole, preferably from about 1% to about 20 % by mole and more preferably from about 3% to about 15% by mole relative to the material lower fatty acid and lower,olefin. A gaseous mixture containig the materials is preferably supplied to a reactor at a rate in terms of space velocity (sv) of, for example, about loo fur-l to about 5000 fur-1 under standard conditions. If the rate is less than 100 hri, the space-time yield of the target compound may often decrease, and if it exceeds 5000 hrl, the space-time yield of the target compound may not significantly increase, thus leading to increased unreacted materials.

Another advantage of the catalyst of the invention is significantly less by-production of lower olefin oligomers derived from the material lower olefin. The advantage is probably because the catalyst includes mesopores and macropores and has a dual pore size distribution corresponding to the mesopores and the macropores. The detailed role of the dual pore size distributionintheadvantageisnotclarifiedbutitisprobably becausethemacroporesimprovesadiffusionspeedofthereactive substances in the catalyst particles, thus suppressing side reactions such as the formation of oligomers as a result of the reaction among the lower olefin molecules. The catalyst preferably has a total pore volume equal to or more than 0.05 - 11 ml/g and comprises the mesopores and the macropores in proportions of equal to or more than 50% and equal to or more than 15%, respectively, of the total pore volume to exhibit a higher activity and more effective suppression of side reactions such as the formation of lower olefin oligomers. If the proportion of the volume of the mesopores to the total pore volume is less than 50%, the catalytic activity may often decrease, and if the proportion of the volume of the macropores to the total pore volume is less than 15%, the formation of lower olefin oligomers may often occur.

The reaction can be performed in any system such as fixed bed, fluidized bed and moving bed. The form and size of the catalyst can be appropriately selected depending on the system of the reaction.

A corresponding lower fatty acid ester forms as a result of the reaction in which the lower fatty acid is added to the lower olefin. The formedlower fatty acid ester can be separated and purified by separation and purification means such as distillation. Where necessary, unreacted materials can be recycled to the reaction system in the present invention. - 12

The catalyst of the invention can significantly suppress by-production of lower olefin oligomers derived from the material lower olefin. Accordingly, the unreacted lower olefin can be recycled as intact without a step of removing the oligomers from the unreacted lower olefin in recycling of the unreacted lower olefin.

EXAMPLES

The present invention will be illustrated in further detail with reference to several examples and comparative examples below,, which are not intended to limit the scope of the invention.

COMPARATIVE EXAMPLE 1 A cesium phosphotungstate [CS2.5Ho.5pWl2o4o] catalyst was prepared by the procedure described in the examples of Japanese Patent No. 3012059. Specifically, an aqueous solution of cesium nitrate was added dropwise to an aqueous solution of commercially available phosphotungstic acid in a 1-L flask.

Water in a depositedwhite precipitate was removed by evaporation, a remained clayey substance was placed on a Petri dish, was then placed in an oven and was dried at 150C in air for 6 hours.

The dried product was pulverized, was subjected to tablet compression and thereby yielded a columnar catalyst having a diameter of 5 mm and a height of 5 mm. - 13

A total of 3 ml of the above-prepared catalyst was charged into a tubular reactor made of SUS 316 (JIS) stainless steel haying en inner diameter ofl0mm and thereby yielded a catalyst layer. A reaction was performed at a temperature of 200 C and a pressure of0.2 MPa by allowing a gaseous mixture of ethylene, acetic acid and water [ethylene: acetic acid:water = 58:32:10 (by volume)] to pass through the catalyst layer at a space velocity of 1000 hem. Two hours into the reaction, a reaction gas was sampled to determine the catalytic activity to thereby find that ethyl acetate was produced in a space-time yield of 330 g/L-catalyst.hr. Ethanol and acetaldehyde were by-produced in amounts of 0.039 mole and 5.5 x 10-3 mole, i irespectively, per mole of ethyl acetate.

COMPARATIVE EXAMPLE 2 A catalyst was prepared by the procedure described in the I examples of Japanese Unexamined Patent Application Publication No. 2000-342980 using 1000 g of a spherical silica (available from Fuji Silysia Chemical Ltd. under the trade name of Q-3; specific surface area: 550 m2/gi particle size: 1.7 to 4 mm) as a carrier and 1000 g of phosphotungstic acid lH3PWO4o.30H2O] (available from Japan New Metals Co., Ltd.) as a catalytically activeingredient. Specifically, 1000gofthephosphotungstic acid was dissolved in 300 my of water in a 2-L beaker at room temperature and thereby yielded a solution. Water was added l l - 14 to the aqueous solution of phosphotungstic acid and thereby yielded an aqueous solution in a volume corresponding to 98% of the absorption of water by the carrier, which absorption of water had been determined in advance. A total of 1000 g of the spherical silica was allowed to absorb the whole amount of the resulting aqueous solution. The phosphotungstic acid supported on the carrier was then moved to a porcelain dish 250 mm in diameter, was dried in air for 3 hours, was placed in a hot air dryer, was dried at 150 C in air at atmospheric pressure for 5 hours and thereby yielded a catalyst.

A reaction was performed using 35 my of the above-prepared catalyst under the same conditions as in Example 4. Two hours into the reaction, a reaction gas was sampled to determine the catalytic activity to thereby find that ethyl acetate was produced in a space-time yield of 10 g/Lcatalyst.hr.

COMPARATIVE EXAMPLE 3 In500mLof water were dissolvedl000 gofphosphotungstic acid tH3PWO40.30H2O] (available from Japan New Metals Co., Ltd.) and 51.8 g of indium nitrate [IntNO3)3.3H2O] (available from Kisan Kinzoku Chemicals, Co., Ltd.) to yield a solution. The solution was heated with stirring to remove water, was further dried at 120 C and thereby yielded a powdery catalyst. The powdery catalyst was mixed with graphite as a plasticizer for molding in an amount of 0.5% by weight to the powdery catalyst and was molded into columns having a diameter of 5 mm and a - 15 length of 2 mm using a tableting machine (available from Hata TekkoshoK.K.underthetradenameofHU-T). Themoldedcatalyst was fired at 300 C in air for 3 hours to find that the molded catalyst had low strength and almost all thereof disintegrated during firing. The catalyst is not usable in commercial production.

The resulting catalyst was sieved, a fraction having a diameterof2to5mmwas collectedandwas subjectedto a reaction under the same conditions as in Example 4. Two hours into the reaction, a reaction gas was sampled to determine the catalytic activity to thereby find that ethyl acetate was produced in a space-tme yield of 13 g/L-catalyst.hr.

EXAMPLE 1

The pore size distributions and the pore volumes mentioned below were determined by a method of mercury penetration using a PoreMaster (registered trademark) 60 available from Yuasa-Ionics co., Ted.

A spherical silica (available from Fu] i Silysia Chemical Eta.

under the trade name of G-lOM; particle size: 5mm) was used as a carrier. The spherical silica had a dual pore size distribution and had a total pore volume (pore size: 3.5 to loooo nm) of 0.8 ml/g, a mesopore volume (pore size equal to or more than 3.5 nm and less than 50 nm) of 0.60 ml/g (75% of the total pore volume), and a macropore volume (pore size: 50 to loooo nm) 0.2 ml/g (25 of the total pore volume). - 16

In 1500 ml of water were dissolved 505g of commercially available phosphotungstic acid and 8.8g of indium nitrate to yield an aqueous solution. A total of 800 g of the silica G=lOM was added to the aqueous solution, the resulting mixture was concentrated to allow the silica to be impregnated with the whole amounts of the catalytically active ingredients. The impregnated silica was dried at 120 C, was fired at 300 C and thereby yielded a catalyst. Thecatalysthadatotalporevolume of 0. 20 ml/g, a mesopore volume of 0.13 mlJg (65% of the total pore volume), and a macropore volume of 0.07 mlig (35% of the total pore volume).

Atotalof300mlof the above-prepared catalyst was charged into a tubular reactor equipped with a sheath for measuring the temperature of the catalyst layer (outer diameter: 8 mm) madeofSUS316(JIS) stainlesssteelandhavinganinnerdiameter of 34 mm and thereby yielded a catalyst layer. A reaction was performed at a temperature of 166 C and a pressure of 0.5 MPa by allowing a gaseous mixture of ethylene, acetic acid end wafer [ethylene:acetic acid: wafer = 85:10:5 (by volume)] to pass through the catalyst layer at a space velocity of 1500 hrl.

A gas produced as a result of reaction was cooled to 0 C to separate unreacted ethylene gas and a condensate liquid. A gaseous mixture (a recycled gas? containing the unreacted I ethylene gas was recycled to the reaction system. Two hours into the reaction, a reaction gas was sampled to determine the - 17 catalytic activity to thereby find that ethyl acetate was producedinaspace-timeyieldof305gIL-catalyst.hr. Ethanol and diethyl ether were formed in slight amounts. Analysis of the reaction condensate revealed that the condensate contained lOOppmbyweightofhydrocarbonseachcontaining5carbonatoms, 120ppmbyweightofhydrocarbonseachcontaining6carbonatoms, and 200 ppm by weight of hydrocarbons each containing 7 carbon atoms as ethylene oligomers.

EXAMPLE 2

A reaction was performed under the same conditions as in Example l, except that a gaseous mixture [ethylene:acetic acid:water = 80:10:10 (by volume)] was used as the material and that the reaction was performed at a temperature of 169 C and a pressure of 0.4 MPa. To verify effects of the recycled ethylene, the reaction was performed for a long time in the present example. A reaction gas was sampled 21 to 25 hours into the reaction (Sample A) and 100 to 110 hours into the reaction (Sample B) to determine the catalytic activity to thereby find that ethyl acetate was produced in a space-time yield of210 g/L-catalyst.hr both in Samples A and B. Analysis of the reaction condensates revealed that no ethylene oligomer I was detected in both Samples,A and B. The recycled gases in I Samples A and B each contain 200 ppm by volume of ethylene . . O. . lgomers. À 18

COMPARATIVE EXAMPLE 4 A powdery silica (available from Fuji Silysia Chemical Ltd. under the trade name of G-10; particle size: 75 to 250 m) having a total pore volume of 1.0 ml/g (pore size: 3.5 tolOOOOnm) andcontainingmesoporesalonewasusedasacarrier.

The pore size distribution and the pore volume were determined by a method of mercury penetration.

In 1500 ml of water were dissolved 505 g of commercially available phosphotungstic acid and 8.8 g of indium nitrate to yield an aqueous solution. total of 800 g of the silica G-10 was added to the aqueous solution, and the resulting mixture was concentrated to allow the silica to be impregnated with the whore amounts of the catalytically active ingredients. The impregnated silica was dried at 120 C, wis molded into columns having a diameter of 5 mm and a length of2 mm using a tableting machine (available from Hata Tekkosho K.. under the trade name of HU-T), was fired at 300 C and thereby yielded a catalyst.

The catalyst had a total pore volume of 0.15 ml/g and contained mesopores alone.

A reaction was performed under the same conditions as in Example 1, except that the above-prepared catalyst was used.

Two hours into the reaction, a reaction gas was sampled to determine the catalytic activity to thereby find that ethyl acetatewasproducedinaspacetimeyieldof273g/L-catalyst.hr.

Ethanol and diethyl ether wire by-prqduced in slight amounts. - 19

Analysisofthereactioncondinsaterejealdthattheconden,sate contained 280 ppm by weight' of hydrocarbons each containing carbonatomsl30ppmbyweightofhydrocarbonseachcontaining 6cearbonatoms,400ppmbyweightofhydrocarbonseachcontaining 7 carbon atoms, and 200 ppm by weight of hydrocarbons each containing 8 carbon atoms as ethylene oligomers. - 20

Claims

1. A catalyst for the production of a lower fatty acid ester from a lower fatty acid and a lower olefin, the catalyst comprising aheteropolyacid or a salt thereof and comprising mesopores and macropores and having a dual pore size distribution corresponding to the mesopores and the macropores.

2. The catalyst according to claim 1, wherein the catalyst has a total pore volume equal to or more than 0.05 ml/g and comprises the mesopores and the macropores in proportions of equal to or more than 50% and equal to or more than 15%, respectively, of the total pore volume.

3. The catalyst according to claim 1, wherein the catalyst is a supported catalyst comprising a catalytically active ingredient supported on a carrier, the carrier haying atotalpore volume equal to or more than 0.3 ml/g and comprising mesopores and macropores in proportions of equal to or more than 50% and equal to or more than 10%, respectively, of the total pore volume.

4. The catalyst according to claim 3, wherein the carrier in the catalyst is silica.

5. The catalyst according to claim 1, wherein the heteropolyacid in the catalyst is at least one selected - 21 from the group consisting ofphosphotungstic acid, silicotungstic acid, phosphomolybdic acid, silicomolybdic acid, phosphomolybdotungstic acid, silicomolybdotungstic acid, phosphovanadomolybdic acid, and silicovanadomolybdic acid.

6. The catalyst according to claim l' wherein the heteropolyacid salt in the catalyst is at least one selected from the group consisting of lithium salts, sodium salts, potassium salts, rubidium salts, cesiwm salts, thallium salts, magnesium salts, indium salts, and ammonium salts ofphosphotungstic acid, silicotungstic acid, phosphomolybdic acid, silicomolybdic acid, phosphomolybdotungstic acid, silicomolybdotungstic acid, phosphovanadomolybdic acid, or silicovanadomolybdic acid.

7. A process for the production of a lower fatty acid ester, comprising the step of allowing a lower fatty acid to react with a lower olefin in the presence of the catalyst of any one of claims 1 to 6.

8. The process according to claim 7, wherein the lower fatty acid is allowed to react with the lower olefin in the presence of water.

9. The process according to claim 7, wherein the lower fatty acid is a fatty acid containing 1 to 5 carbon atoms. - 22

10. The process according to claim 1, wherein the lower olefin is an olefin containing 2 to 5 carbon atoms.

11. Use of a catalyst for the production of a lower fatty acid ester from a lower fatty acid and a lower olefin, the catalyst comprising mesopores and macrpores and having a dual pore size distribution corresponding to the mesopores and the macropores.