GB2385287A

GB2385287A - Catalyst and process for the production of lower fatty acid esters

Info

Publication number: GB2385287A
Application number: GB0229137A
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: 2003-08-20
Anticipated expiration: 2022-12-13
Also published as: GB2385287C; CN1428327A; MY122928A; GB0229137D0; GB2385287B

Abstract

A catalyst for the production of a lower fatty acid ester from a lower fatty acid and a lower olefin, is selected from: (A) a supported catalyst including an indium salt of a heteropolyacid supported on a carrier; (B) a supported catalyst including a molded article of a powdery supported catalyst, the powdery supported catalyst including a catalytically active ingredient supported on a powdery carrier; and (C) a catalyst including mesopores and macropores and having a dual pore size distribution corresponding to the mesopores and the macropores.

Description

CATALYST AND PROCESS FOR THE PRODUCTION OF LOWER FATTY ACID ESTERS BACKGROUND OF THE INVENTION 1. Field of the Invention 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, and a process for the production of a lower fatty acid ester using the catalyst.

2. Description of the Related Art 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, phosphotungstic acid, or iron sulfate (Japanese Examined Patent Application Publication No. 53-6131), a process by the catalysis 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

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 Application Publications No. 05-29489 and No. 09-118647 each 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 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 exceeding 500 m2jg in 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 a short catalyst life, or have a catalytic activity significantly depending on the specific surface area of the carrier.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a catalyst for the production of a lower fatty acid ester with a high activity and to provide a process for the production of a lower fatty acid ester using the catalyst.

Another object of the present invention is to provide a catalyst for the production of a lower fatty acid ester, which has a high activity and can suppress side reactions such as production of oligomers from a lower olefin and to provide a process for the production of a lower fatty acid ester using the catalyst.

A further object of the present invention is to provide a catalyst for the production of a lower fatty acid ester, which has a high activity that does not significantly depend on the specific surface area and other physical properties of carriers and to provide a process for the production of a lower fatty acid ester using the catalyst.

Yet another object of the present invention is to provide a catalyst for the production of a lower fatty acid ester, which has a high activity, can suppress side reactions and has an activity that does not significantly depend on the specific surface area and other physical properties of carriers and to provide a process for the production of a lower fatty acid ester using the catalyst.

After intensive investigations to achieve the above

objects, 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 specific catalytically active ingredient supported on a carrier, a catalyst having a specific pore size distribution, or a supported catalyst prepared by a specific supporting method. 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.

Specifically, the present invention provides a catalyst for the production of a lower fatty acid ester from a lower fatty acid and a lower olefin, selected from: (A) a supported catalyst including an indium salt of a heteropolyacid supported on a carrier; (B) a supported catalyst including a molded article of a powdery supported catalyst, the powdery supported catalyst including a catalytically active ingredient supported on a powdery carrier ; and (C) a catalyst including mesopores and macropores and having a dual pore size distribution corresponding to the mesopores and the macropores.

The carrier in the catalyst (B) maybe silica. The catalyst

(B) may be prepared by a process including the steps of (1) preparing a solution or suspension of the catalytically active. ingredient in a solvent; (2) immersing or mixing the powdery carrier in or with the solution or suspension and removing the solvent to thereby yield a powdery supported catalyst including the catalytically active ingredient supported on the carrier; and (3) molding the powdery supported catalyst.

The catalyst (B) may be in the form of a column, a ring or a sphere and is preferably in the form of a column having a diameter from 1 to 15 mm and a length from 1 to 15 mm ; a ring having an outer diameter from 3 to 15 mm, an inner diameter from 1 to 13 mm and a length from 1 to 15mm ; or a sphere having a diameter from 1 to 15 mm.

The catalyst (C) may include, for example, a heteropolyacid or a salt thereof as a catalytically active ingredient. The catalyst (C) 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 (C) include

silica.

The heteropolyacid in the catalysts (A), (B) and (C) may be, for example, at least one selected from phosphotungstic acid, silicotungstic acid, phosphomolybdic acid, silicomolybdic acid, phosphomolybdotungstic acid, silicomolybdotungstic acid, phosphovanadomolybdic acid, and silicovanadomolybdic acid.

The salt of a heteropolyacid in the catalysts (B) and (C) 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 catalysts of the present invention exhibit a high activity and can produce lower fatty acid esters with high

production efficiency. The catalyst (C) can suppress by-production of oligomers of lower olefins and thereby enables the recycling of unreacted lower olefins as intact. The catalyst (B) hasacatalyticactivitythatdoesnot significantly

depend on the specific surface area and other physical properties of carriers and can thereby advantageously employ a wide variety of catalysts.

In addition to the above advantages, the catalyst (A) leads to less by-production of aldehydes, catalyst poisons, and to less by-production of alcohols even if the reaction system includes water, can employ a large amount of water that is capable of prolonging the catalyst life and can thereby have a longer life than conventional equivalents.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The catalyst for the production of a lower fatty acid ester

of the present invention is any one of (A) a supported catalyst comprising an indium salt of a heteropolyacid supported on a carrier (hereinafter briefly referred to as"Catalyst (A)") ; (B) a supported catalyst comprising a molded article of a powdery supported catalyst, the powdery supported catalyst comprising a catalytically active ingredient supported on a powdery carrier; (hereinafter briefly referred to as"Catalyst (B)") ; and (C) a catalyst comprisingmesoporesandmacropores and having a dual pore size distribution corresponding to the mesopores

andthemacropores (hereinafterbrieflyreferredtoas"Catalyst (C)"). 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, for example, PoreMaster (registered trademark) 60 available from Yuasa-Ionics Co. , Ltd.

Catalyst (A) of the present invention is a supported catalyst comprising an indium salt of a heteropolyacid supported on a carrier. The salt of a heteropolyacid corresponds to the heteropolyacid except with indium replacing a part or all of hydrogen ions of the heteropolyacid.

Catalytically active ingredients for use in Catalyst (B) are not specifically limited and include those generally used in the production of lower fatty acid esters. Examples of such catalytically active ingredients are aromatic disulfonic acids, sulfuric acid, phosphoric acid, and metal salts of these acids ; heteropolyacids and salts thereof. Among them, heteropolyacids and salts thereof are preferred. Each of these catalytically active ingredients can be used alone or in combination.

Catalysts for use as Catalyst (C) in the present invention are not specifically limited and include those generally used in the production of lower fatty acid esters. Such catalysts

include, for example, solid acid catalysts that are used as intact as a catalyst, such as metal salts of aromatic disulfonic acids, sulfuric acid, and phosphoric acid; solid phosphoric acid; gallium silicate, aluminosilicate (zeolite), borosilicate, and other crystalline metal silicates; heteropolyacids and salts thereof. Catalyst (C) may be a supported catalyst comprising a catalytically active ingredient supported on a carrier. Such catalytically active ingredients include those exemplified as the catalytically active ingredients in Catalyst (B). Among these catalysts, heteropolyacids and salts thereof and supported catalysts comprising these compounds supported on a carrier are preferred as Catalyst (C). Each of these catalysts 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, and 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.

Among them, preferred heteropolyacids are those comprising 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, silicotungstic acid, phosphomolybdic acid, silicomolybdic acid, phosphomolybdotungstic acid, silicomolybdotungstic acid, phosphovanadomolybdic acid, and silicovanadomolybdic acid.

Salts of heteropolyacids include heteropolyacids except with a metal or ammonium replacing a part or all of 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 supported on a carrier is used for a long time as an esterification

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. More specifically, silica and activated carbon are typically preferred. Catalysts (A) and (B) of the present invention have a feature that they have a catalytic activity not significantly depending on the specific surface area and other physical properties of carriers, in contrast to catalysts comprising a free heteropolyacid supported on a molded carrier as described in the examples of aforementioned Japanese Unexamined Patent Application PublicationNo. 2000-342980. Catalysts (A) and (B) can thereby employ a wide variety of carriers. For example, carriers having a specific surface area of generally equal to or more than 50 m2/g (e. g. , from about 50 to about 1500 m2/g) and preferably from about 100 to about 1300 m/g can be used. Catalyst (B) can employ a carrier having a specific surface area of about equal to or more than 500 m2/g. Catalyst (A) can employ a carrier having a specific surface area equal to or more than about 700 m2/g or further equal to or more than about 1000 m2/g, such as activated carbon. The carrier may have any shape and may be in the form of, for example, a powder, a granule, or a pellet.

A powdery carrier is used in Catalyst (B). The particle size of the powder is not specifically limited as long as not

adversely affecting the subsequent molding process steps after supporting the catalytically active ingredient and is generally

less than or equal to 1 mm and is, for example, from 10 to 500 um. Such a powdery carrier can support or hold the catalytically active ingredient with higher dispersibility at a higher concentration than molded carriers. Among the aforementioned carriers, silica, especially silica having a purity equal to or more than 95% is advantageous as the carrier for Catalyst (B).

As the carrier for use in Catalyst (C), carriers including mesopores andmacropores andhaving adual pore size distribution corresponding to the mesopores and the macropores, i. e. , those having a similar pore structure to that in Catalyst (C) 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-10M from Fuji Silysia Chemical Ltd.

The amount of the catalytically active ingredient such as a heteropolyacid supported on the carrier is not specifically limited and is appropriately selected depending on the types of the catalytically active ingredient and carrier and the preparation process. For example, in Catalyst (A), the amount of an indium salt of a heteropolyacid is generally from about 0.1 to about 2 parts by weight relative to 1 part by weight

of the carrier. If the amount is less than 0.1 part by weight, the resulting catalyst may not have a sufficient catalytic activity, and if it exceeds 2 parts by weight, the catalytic activity may not significantly increase. Catalyst (A) of the present invention can yield a higher activity than conventional catalysts such as heteropolyacid cesium salt catalysts even in a small amount of the catalytically active ingredient (an indium salt of a heteropolyacid). The reason therefor has not been completely clarified, but the higher activity of Catalyst (A) is probably owing to the interaction between the catalytically active ingredient and the carrier.

The amount of Catalyst (B) supported on the carrier can be selected within a wide range and is generally from about 0. : L to about 5 parts by weight, and preferably from about 0. 3 to about 4 parts by weight relative to 1 part by weight of the carrier. If the amount is less than 0.1 part by weight, the resulting catalyst may not have a sufficient catalytic activity, and if it exceeds 5 parts by weight, the catalytic activity may not significantly increase. The amount of Catalyst (C) supported on the carrier is not specifically limited and is generally from about 0.2 to about 5 parts by weight relative to 1 part by weight of the carrier. If the amount is less than 0.2 part by weight, the resulting catalyst may not have a sufficient catalytic activity, and if it exceeds 5 parts by weight, the catalyst may not have a significantly increased

catalytic activity and may not have a satisfactory dual pore size distribution.

Preparation processes for Catalysts (A) and (C) are not specifically limited and include conventional or general preparation processes for supported catalysts. For example, the catalysts can be obtained by immersing the carrier in a solution (e. g., anaqueous solution) ofthecatalyticallyactive ingredient to impregnate the carrier with the catalytically active ingredient, filtrating or concentrating and drying the impregnated carrier, and where necessary firing or drying the impregnated carrier at about 120 C to about 450 C. The shapes and configurations of the catalysts are not specifically limited.

For example, they may be in the form of a powder, a granule, or a pellet. Powdery catalysts can also be used after molding to appropriate molded articles.

In the preparation of Catalyst (A), amixture of a solution,

such as an aqueous solution, of the heteropolyacid and a solution, such as an aqueous solution, of an indium compound such as an indium salt in an amount corresponding to a desired composition is used as the solution (aqueous solution) of the catalytically active ingredient. Such indium compounds are not specifically limited as long as they are soluble in solvents such as water and include, for example, indium nitrate and indium chloride.

Catalyst (C) can also 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 Catalyst (C) can be controlled, for example, 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.

One of the features of Catalyst (B) is that the catalyst is a molded article of a powdery supported carrier which includes a catalytically active ingredient supported on a powdery carrier.

Catalyst (B) can be prepared, for example, by a process comprising the steps of (1) preparing a solution or suspension of the catalytically active ingredient in a solvent, (2)

immersing or mixing the powdery carrier in or with the solution or suspension and removing the solvent to thereby yield a powdery supported catalyst comprising the catalytically active

ingredient supported on the carrier, and (3) molding the powdery supported catalyst.

Solvents for use in the preparation of the solution or suspension of the catalytically active ingredient in the step (1) are not specifically limited as long as they can uniformly dissolve or suspend the catalytically active ingredient and include water and organic solvents. Preferred solvents are water, alcohols, carboxylic acids, and mixtures of these solvents. The solvent and the catalytically active ingredient are mixed by, for example, stirring and thereby yield a uniform solution or suspension. When the catalytically active

ingredient has sufficient solubility, the catalytically active ingredient as intact is dissolved in a solvent and thereby yields a solution. When it has insufficient solubility, it is pulverized to a fine powder, is suspended uniformly in a solvent or disperse medium and thereby yields a suspension. The amount of the solvent or disperse medium is appropriately selected depending on the type of the carrier and the supporting procedure in the step (2).

In the step (2), the powdery carrier is immersed in or

mixed with the solution or suspension of the catalytically active ingredient prepared in the step (1) and thereby allow the carrier to support the catalytically active ingredient. The immersion procedure is performed by, for example, immersing the powdery carrier in a solution of the catalytically active ingredient

to thereby impregnate the carrier with the solution. The mixing procedure is performed by, for example, adding the powdery carrier to a suspension of the catalytically active ingredient and homogeneously dispersing the carrier in the suspension by stirring. If the solvent is in an excess amount, the excess solvent is removed by heating the solution or suspension with stirring to evaporate the solvent or by filtrating the solution or suspension. The catalytically active ingredient supported on the carrier is then subjected to, for example, heating and drying to remove the remained solvent and thereby yields a powdery supported catalyst.

The powdery supported catalyst prepared in the step (2) is molded in the step (3) by, for example, a conventional molding technique such as tablet compression, extrusion molding, and tumbling granulation. The molded catalyst is in the form of, for example, a sphere, a column or a ring. The size of the molded catalyst is appropriately selected depending on the size of a reactor and other conditions. The molded catalyst is preferably in the form of a column having a diameter from 1 to 15 mm and a length from 1 to 15 mm ; a ring having an outer diameter from 3 to 15 mm, an inner diameter from 1 to 13 mm and a length from 1 to 15 mm ; or a sphere having a diameter from 1 to 15 mm. It is more preferably in the form of a column having a diameter from 3 to 10 mm and a length from 2 to 10 mm or a sphere having a diameter from 3 to 8 mm for higher

mechanical strength and activity of the catalyst. Various additives such as graphite and other plasticizers can be added in the molding of the powdery supported catalyst.

The molded supported catalyst can be used as intact as a catalyst or is fired at a temperature less than or equal to about 400 C (e. g. , from about 120 C to about 4000C) according to necessity before use.

Catalyst (B) prepared by the above process is prepared by molding the powdery supported catalyst, can hold the catalytically active ingredient attached to the outer surface of the carrier homogeneously at a high concentration without dropping off and can thereby exhibit a high catalytic activity in the production of a lower fatty acid ester as compared with catalysts supported on previously molded carriers. Catalyst (B) has a catalytic activity not significantly depending on the specific surface area and other physical properties of carriers and can thereby employ a wide variety of carriers.

Lower fatty acids for use in the present invention include, 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 5 carbon atoms and preferably about 2 to about 4 carbon atoms.

Examples of such lower olefins are ethylene, propylene, butene, and isobutene.

A 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.

A 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, a 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 preferably includes water for a longer catalyst life. By catalysis of 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

reactions may occur and thereby yield by-products such as ethanol and other alcohols, but the catalysts of the present invention yield less such by-products than conventional equivalents. The reaction system using the catalyst of the present invention can thereby include a larger amount of water to thereby achieve 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 containing the materials is supplied to a reactor at a rate in terms of space velocity (SV) of, for example, about 100 hr-1 to about 5000 hr' under standard conditions. If the rate is less than 100 hr', the space-time yield of the target compound may often decrease, and if it exceeds 5000 hr~l, the space-time yield of the target compound may not significantly increase, thus leading to increased unreacted materials.

Another advantage of Catalyst (A) is less by-production of acetaldehyde and other aldehydes known as catalyst poisons.

A detailed mechanism of this advantage has not completely been clarified but it is probably because Catalyst (A) yields less by-produced alcohols and has a smaller oxidizing activity than conventional equivalents.

Another advantage of Catalyst (C) is significantly less by-production of lower olefin oligomers derived from the

material lower olefin. The advantage is probably because Catalyst (C) 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

distribution in the advantage is not clarified but it is probably because themacropores improves a diffusion speed of the reactive 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. Catalyst (C) preferably 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 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 formed lower 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.

Catalyst (A) yields less amounts of by-produced alcohols such as ethanol than conventional equivalents, and unreacted materials can be recycled to the reaction system according to necessity. Catalyst (C) 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.

EXAMPLE 1 In 150 ml of water were dissolved 50.5 g of commercially available phosphotungstic acid and 2.63 g of indium nitrate.

A total of 60 g of a molded activated carbon in the form of a column having a diameter of 3 mm and a length of 4.5 mm and having a specific surface area of 1100 m2/g was immersed in the aqueous solution to be impregnated with the catalytically

active ingredient and was filtrate to remove an unabsorbed aqueous solution. The filtrate was analyzed and was found to have the same proportions of phosphorus (P), tungsten (W) and indium (In) as those in the added materials, indicating that phosphorus (P), tungsten (W) and indium (In) in the same proportions as those in the materials were supported by the activated carbon carrier. The activated carbon impregnated with the catalytically active ingredients was dried at 150 C in air at atmospheric pressure for 6 hours, was then fired at 200 C and thereby yielded a catalyst. The amount of indium phosphotungstate in the catalyst was 72% by weight relative to the activated carbon.

A total of 3 ml of the above-prepared catalyst was charged into a tubular reactor made of SUS 316 (Japanese Industrial Standards) stainless steel having an inner diameter of 10 mm and thereby yielded a catalyst layer. A reaction was performed at a temperature of 210 C and a pressure of 0. 4 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 hr-l.

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 251 g/L-catalyst. hr.

EXAMPLE 2

In 150 ml of water were dissolved 151.5 g of commercially available phosphotungstic acid and 7.89 g of indium nitrate.

A total of 150 g of a molded silica in the form of a sphere having a diameter of 3 mm and having a specific surface area of 320 m2/g was immersed in the aqueous solution. The resulting mixture was concentrated to thereby impregnate the silica with the whole amount of the catalytically active ingredients. The silica impregnated with the catalytically active ingredients

was dried at 150 C in air at atmospheric pressure for 6 hours, was fired at 200 C and thereby yielded a catalyst. The amount of indium phosphotungstate in the catalyst was 87% by weight relative to the silica.

A total of 3 ml of the above-prepared catalyst was charged into a tubular reactor made of SUS 316 (JIS) stainless steel having an inner diameter of 10 mm and thereby yielded a catalyst layer. A reaction was performed at a temperature of 200 C and

a pressure of 0. 4 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 hr'\ 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 405 g/L-catalyst. hr.

EXAMPLE 3 A catalyst was prepared by the procedure of Example 2,

except that the amount of the carrier silica was changed to 300 g. The amount of indium phosphotungstate in the catalyst was 43% by weight relative to the silica. Using the catalyst, a reaction was performed under the same conditions as in Example 2. 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 yieldof 330 g/L-catalyst. hr.

Ethanol and acetaldehyde were by-produced in amounts of 0.024

mole and 8. 3 x10-5 mole, respectively, per mole of ethyl acetate.

COMPARATIVE EXAMPLE 1 A cesium phosphotungstate [Cs2. 5Ho. 5PWi2040] 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 deposited white 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 150 C 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.

a pressure of 0. 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 hr'\ 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, respectively, per mole of ethyl acetate.

EXAMPLE 4 A total of 1000 g of a powdery silica (available from Fuji Silysia Chemical Ltd. under the trade name of G-3; specific surface area : 600 m2jg ; particle size : 75to250) m) was added to a solution of 1000 g of phosphotungstic acid [H3PW040'30H20] (available from Japan New Metals Co. , Ltd. ) in 500 mL of water,

was stirred to a homogenous mixture and thereby yielded a slurry. The slurry 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 length of 2 mm using a tableting machine (available from Hata Tekkosho K. K. under the trade name of HU-T). The strength of the molded catalyst was determined using a catalyst strength measuring machine (available from Ohkurariken Co. , Ltd. under

the trade name of DHT-100) to find that the strength was in the range from 10 to 30 kgf. The molded catalyst was fired at 300 C in air for 3 hours and thereby yielded a catalyst.

A total of 35 ml of the above-prepared catalyst was charged into a tubular reactor made of SUS 316 (JIS) stainless steel having an inner diameter of 34 mm and thereby yielded a catalyst layer. A reaction was performed at a temperature of 200 C and a pressure of 0. 8 MPa by allowing a gaseous mixture of ethylene, acetic acid and water ethylene : acetic acid: water = 60: 30: 10 (by volume)) to pass through the catalyst layer at a space velocity of 1000 hr-l. 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 410 g/L-catalyst. hr.

COMPARATIVE EXAMPLE 2 A catalyst was prepared by the procedure described in the 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/g ; particle size : 1.7 to 4 mm) as a carrier and 1000 g of phosphotungstic acid [H3PW040. SOHzO] (available from Japan New Metals Co. , Ltd. ) as a catalytically active ingredient. Specifically, 1000 g of the phosphotungstic acid was dissolved in 300 mL of water in a 2-L beaker at room temperature and thereby yielded a solution. Water was added

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 mL 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/L-catalyst. hr.

EXAMPLE 5 A catalyst was prepared by the procedure of Example 4, except that, together with 1000 g of the phosphotungstic acid, 51.8 g of indium nitrate [In (N03) 3. 3H20] (available from Kisan Kinzoku Chemicals, Co. , Ltd. ) was added to water and that 1000 g of a powdery silica (available from Fuji Silysia Chemical Ltd. under the trade name of G-6; specific surface area: 500 m2/g ; particle size : 75 to 250 Ilffi) was used as the powdery silica instead of G-3.

A reaction was performed using 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 450 g/L-catalyst. hr.

EXAMPLE 6 A catalyst was prepared by the procedure of Example 4, except that 1000 g of a powdery silica (available from Fuji Silysia Chemical Ltd. under the trade name of G-10; specific surface area: 300 m2/g ; particle size: 75 to 250 lim) was used as the powdery silica instead of G-3.

A reaction was performed using 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 410 g/L-catalyst. hr.

EXAMPLE 7 A catalyst was prepared by the procedure of Example 4, except that 500 g of a powdery silica (available from Fuji Silysia Chemical Ltd. under the trade name of G-10 ; specific surface area: 300 mg ; particle size: 75 to 250 gm) was used as the powdery silica instead of G-3.

A reaction was performed using 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 550 g/L-catalyst. hr.

EXAMPLE 8 A catalyst was prepared by the procedure of Example 4, except that 2 50 g of a powdery silica (available from Fuji Silysia Chemical Ltd. under the trade name of G-10 ; specific surface area: 300m2/g ; particle size: 75 to 250 m) was used as the powdery silica instead of G-3.

A reaction was performed using 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 570 g/L-catalyst. hr.

COMPARATIVE EXAMPLE 3 In 500 mL of water were dissolved 1000 g of phosphotungstic acid [H3PW040. 30H20] (available from Japan New Metals Co., Ltd.) and 51.8 g of indium nitrate [In (N03) 3. 3H20] (available from Kisan Kinzoku Chemicals, Co. , Ltd. ) to yield a solution. The solution was heated with stirring to remove water, was further dried at 1200C 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 length of 2 mm using a tableting machine (available from Hata Tekkosho K. K. underthetradenameofHU-T). Themolded catalyst 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 diameter of 2 to 5 mm was collected and was subjected to 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-time yield of 13 g/L-catalyst. hr.

EXAMPLE 9 The pore size distributions and the pore volumes mentioned below were determined by a method of mercury penetration using PoreMaster (registered trademark) 60 available from Yuasa-Ionics Co. , Ltd.

A spherical silica (available from Fuji Silysia Chemical Ltd. under the trade name of G-IOM ; particle size : 5 mm) 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 10000 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 10000 nm) of 0.2 ml/g (25% of the total pore volume).

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. A total of 800 g of the silica G-10M

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 3000C and thereby yielded a catalyst. The catalyst had a total pore volume of 0.20 ml/g, a mesopore volume of 0.13 ml/g (65% of the total pore volume), and a macropore volume of 0.07 ml/g (35% of the total pore volume).

A total of 300 ml of 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) made of SUS 316 (JIS) stainless steel and having an inner diameter 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 and water ethylene : acetic acid: water = 85: 10: 5 (by volume)] to pass through the catalyst layer at a space velocity of 1500 hr~l.

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 ethylene gas was recycled to the reaction system. 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 305 g/L-catalyst. hr. Ethanol and diethyl ether were formed in slight amounts. Analysis of

the reaction condensate revealed that the condensate contained

100 ppmby weight of hydrocarbons each containing 5 carbon atoms, 120 ppmby weight of hydrocarbons each containing 6 carbon atoms, and 200 ppm by weight of hydrocarbons each containing 7 carbon atoms as ethylene oligomers.

EXAMPLE 10 A reaction was performed under the same conditions as in Example 9, 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 1690C 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 of 210 g/L-catalyst. hr both in Samples A and B. Analysis of the reaction condensates revealed that no ethylene oligomer was detected in both Samples A and B. The recycled gases in Samples A and B each contain 200 ppm by volume of ethylene oligomers.

EXAMPLE 11 A powdery silica (available from Fuji Silysia Chemical

Ltd. under the trade name of G-10 ; particle size : 75 to 250 Am) having a total pore volume of 1. 0 ml/g (pore size : 3. 5

to 10000 nm) and containingmesopores alone was used as a carrier. 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. A 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 whole amounts of the catalytically active ingredients. The impregnated silica was dried at 120 C, was molded into columns having a diameter of 5 mm and a length of 2 mm using a tableting machine (available from Hata Tekkosho K. K. under the trade name of HU-T), was fired at 3000C 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 9, 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

acetate was producedina space-timeyieldof 273 g/L-catalyst. hr.

Ethanol and diethyl ether ware by-produced in slight amounts.

Analysis of the reaction cond & nsate re-ealedthat the condensate I contained 280 ppm by weight of hydrocarbons each containing 5 carbon atoms, 130 ppmby weight of hydrocarbons each containing 6 carbon atoms, 400 ppmby weight of hydrocarbons each containing

7 carbon atoms, and 200 ppm by weight of hydrocarbons each containing 8 carbon atoms as ethylene oligomers.

While the present invention has been described with reference to what are presently considered to be the preferred embodiments, it is to be understood that the invention is not limited to the disclosed embodiments. On the contrary, the invention is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.

Claims

WHAT IS CLAIMED IS:

1. A catalyst for the production of a lower fatty acid ester from a lower fatty acid and a lower olefin, selected from the group consisting of : (A) a supported catalyst comprising an indium salt of a heteropolyacid supported on a carrier; (B) a supported catalyst comprising a molded article of a powdery supported catalyst, the powdery supported catalyst comprising a catalytically active ingredient supported on a powdery carrier; and (C) a catalyst 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 (B) comprises a heteropolyacid or a salt thereof as the catalytically active ingredient.

3. The catalyst according to claim 1, wherein the carrier in the catalyst (B) is silica.

4. The catalyst according to claim 1, wherein the catalyst (B) is a catalyst prepared by a process comprising the steps of:

(1) preparing a solution or suspension of the catalytically active ingredient in a solvent; (2) immersing or mixing the powdery carrier in or with the solution or suspension and removing the solvent to thereby yield a powdery supported catalyst comprising the catalytically active ingredient supported on the carrier; and (3) molding the powdery supported catalyst.

5. The catalyst according to one of claims 1 to 3, wherein the catalyst (B) is in the form of a column, a ring or a sphere.

6. The catalyst according to one of claims 1 to 3, wherein the catalyst (B) is in the form of a column having a diameter from 1 to 15 mm and a length from 1 to 15 mm ; a ring having an outer diameter from 3 to 15 mm, an inner diameter from 1 to 13 mm and a length from 1 to 15 mm; or a sphere having a diameter from 1 to 15 mm.

7. The catalyst according to claim 1, wherein the catalyst (C) comprises a heteropolyacid or a salt thereof.

8. The catalyst according to claim 1 or 7, wherein the catalyst (C) 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.

9. The catalyst according to claim 1 or 7, wherein the catalyst (C) is a supported catalyst comprising 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 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.

10. The catalyst according to claim 9, wherein the carrier in the catalyst (C) is silica.

11. The catalyst according to any one of claims 1,2 and 7, wherein the heteropolyacid in the catalyst (A), (B) or (C) is at least one selected from the group consisting of phosphotungstic acid, silicotungstic acid, phosphomolybdic acid, silicomolybdic acid, phosphomolybdotungstic acid, silicomolybdotungstic acid, phosphovanadomolybdic acid, and silicovanadomolybdic acid.

12. The catalyst according to one of claims 2 and 7, wherein the heteropolyacid salt in the catalyst (B) or (C) is at least one selected from the group consisting of 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, or silicovanadomolybdic acid.

13. 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 12.

14. The process according to claim 13, wherein the lower fatty acid is allowed to react with the lower olefin in the presence of water.

15. The process according to claim 13, wherein the lower fatty acid is a fatty acid containing 1 to 5 carbon atoms.

16. The process according to claim 13, wherein the lower olefin is an olefin containing 2 to 5 carbon atoms.