CH618353A5 - Transition metal catalysts, process for their preparation and their use - Google Patents

Abstract

A catalyst with a transition metal immobilised on a support is prepared by reaction of a hydroxylated support with a transition metal alcoholate of formula M(OR)nQm. The symbols are defined in claim 1. The support is heated between 100 DEG and 300 DEG C with the transition metal alcoholate in excess in relation to the available surface hydroxyl groups, in an inert hydrocarbon and in the presence of water, to perform a reaction of condensation of the transition metal alcoholate or of its oligomer with the surface hydroxyl groups. The catalysts contain 3 to 60 % by weight of a transition metal present on and bonded to the support matrix by oxygen bridges so that the transition metal atoms are bonded to one another by oxygen bridges. The catalysts are particularly useful in the preparation of carboxylic acid esters.

Description

The present invention relates to transition metal catalysts, to a process for their preparation and to their use.

Many heavy metals, particularly transition metals, have been bonded to the surface of various support materials by the reaction of a metal compound with the surface hydroxyl groups. In this way, it was possible to obtain supported catalysts which can be used in very widely diversified applications such as polymerization, esterification, hydrogenation, oxidation, hydroformylation, etc.

Probably the most common method of bonding a metal to a support involves the reaction of surface hydroxyls with a metal halide. For example, the U.S. patent No. 3166543 shows the reaction of carbon blacks, like tunnel blacks which have hydroxyl groups on their surface, with a halide of a transition metal, for example titanium tetrachloride, and the subsequent heating with a compound of silane to obtain a catalyst useful for the polymerization of olefins. The U.S. Patent No. 3166542 similarly describes polymerization catalysts obtained in an almost similar manner, but in which the support material is a finely divided mineral solid such as alumina, titanium oxide, zirconium oxide, thorium oxide, magnesium oxide, silicates or aluminates.

Other fixing methods are also known. For example, hydroformylation catalysts containing units of formula

I

Z-O-Si-Q

I

where Z represents the support and Q represents a group containing phosphorus bonded to a transition metal, are described in the US patent. No. 3832404 and obtained: i) by making a compound of a transition metal with a compound containing silicon and phosphorus, for example (EtO) 3Si (CH2) 2PR2 to form a compound containing a transition metal linked to phosphorus and by reacting the latter compound with an inorganic solid containing —OH groups, or ii) reacting the inorganic solid with the compound containing silicon and phosphorus, then reacting this product with the compound of the transition metal. Amino compounds of transition metals, such as tetrakisdiethylaminotitane, tetrakisdimethyl-aminozirconium and dichlorodibutylaminotitane, have also been described in the U.S. Patent. No. 3392160 as reacting with supports in finely divided particles containing hydroxyl groups and are then activated by a subsequent reaction with an organometallic compound. The U.S. Patent No. 3816340 shows the preparation of

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olefin disproportionation catalysts, by reaction of a practically inert matrix having a hydroxylated surface with a complex of a transition metal such as tetrakis (7r-allyl) -tungsten or -molybdenum.

It is also known to react various metal compounds containing one or more alcoholate groups with support materials carrying hydroxyl groups.

The U.S. Patent No. 3326877 describes polymerization catalysts obtained by reacting a finely divided mineral support with compounds of formula T (Q) „, where T is a metal from groups IVa, Va or Via and Q is an alkoxy or aryloxy radical, then then reacting with an organometallic compound. This process requires that the carrier and all diluents or carrier gases are essentially anhydrous when the transition metal ester is in contact with the carrier. The presence of water prevents the desired chemical reaction and produces a lower catalyst or gives a subsequent reaction with the organometallic compound. No more than one transition metal atom is present per surface hydroxyl group and very small amounts of transition metal are bound to the support. Likewise, the U.S. Patent No. 3817931 describes catalysts suitable for the production of polyesters, which are obtained by reacting a support carrying hydroxyl groups with metallic compounds, including germanium, titanium, zirconium and hafnium alcoholates metal halides and organometallic compound. Each metal atom is linked to the support by 1 to n - 1 (where n is the valence of the metal) oxygen bonds (—O—) and the concentration of the bonded metal is very low.

Here is yet another reference: the U.S. patent. No. 3622522, describes olefin polymerization catalysts containing up to 15% by weight of gallium and / or tin with up to 50% by weight of chromium. These catalysts are obtained by depositing on a support a chromium compound, such as chromium trioxide, and at least one compound chosen from the group comprising gallium and tin alcoholates and arylates,

then by heating to a temperature of at least 925 ° C. The metal compounds are preferably deposited on the support from a solvent or a non-aqueous dispersing agent, and the heating is carried out in air or a stream containing oxygen, essentially free of water (less than 0.1% by weight of water).

There are also various procedures for producing simple and polymeric esters. They include direct synthesis by reaction of an alcohol and an organic carboxylic acid, and exchange reactions in which the acyl part is exchanged.

O

or alkoxy (—OR) of an existing ester with a different acyl or alkoxy part (see Kirk-Othmer, "Encyclopedia of Chemical Technology", vol. 8, pp. 356-365. John Wiley & Sons, New York, 1965 ). These reactions include acidolysis (reaction of the ester with a carboxylic acid to exchange the acyl parts) and alcoholysis (reaction of the ester with an alcohol to exchange the alkoxy parts). In the transesterification reactions, two esters are heated to effect the exchange of the acyl and alkoxy groups as follows:

O - O O o

R'-dtoR "+ R * - (ï: OR ** -> R'-ioR ** + R * - <î: OR"

Ester exchange reactions are particularly useful in cases where one of the resulting products is a relatively low boiling point product and can be removed by distillation to shift the balance and bring the reaction to l 'completion. In the preparation of polyesters, for example, this characteristic makes it possible to obtain polymers of high molecular weight. By causing the redistribution of the acyl parts, it is also possible to modify the triglycerides or similar compounds containing several ester groups, in order to obtain a wide variety of useful products.

With the foregoing procedures, it is generally advantageous to use catalysts. In general, mineral acids, such as hydrochloric acid, sulfuric acid and phosphoric acid, as well as other acids, such as p-toluenesulfonic acid and benzenesulfonic acid, have been used generally for the esterification. Basic materials, especially alkali metal alcoholates and alkali and alkaline earth metal carbonates, have also been used in the production of esters as catalysts for alcoholysis reactions. There are, however, two main problems associated with the use of these acidic and basic catalysts: they activate side reactions leading to the formation of undesirable by-products and they require neutralization upon completion of the reaction.

Due to these defects, the transition metal compounds, especially the titanium compounds containing alkoxy or acyl groups have found increased use as catalysts in the processes for preparing esters, since they do not require neutralization and they minimize bothersome side reactions. However, it is known that these titanium catalysts hydrolyze in the presence of water with a proportional loss of activity. This characteristic limits their usefulness in many cases requires a large amount of catalysts to ensure the completion of the esterification. This increases the cost of the process and, more importantly, makes it increasingly difficult to obtain esters free of catalytic residues. The presence of catalytic residue in the ester obtained is undesirable, since it provides an undesirable color or tint to the ester and contributes to the oxidation instability, thermal instability and hydrolytic instability of the ester. 'ester.

Condensed polytitanates of varying degrees of hydrolysis and polymeric orthotitanates from organic polyhydroxy derivatives have been described in the U.S. Patent, respectively. No. 2689858 and German patent No. 1142868. These catalysts have a finite improvement in hydrolytic stability compared to alkyl orthotitanates and titanium acylates; however, the amount of catalytic residue in the esters obtained is still unacceptable, in particular for very specific applications in which clear and shiny esters with good stability are required.

A process and catalysts have now been provided which overcome the above drawbacks. Furthermore, it has been found quite unexpectedly that, in the present process, the presence of water is essential to the conduct of the reaction instead of being a disadvantage, as might be expected from the teachings of the prior art. The catalysts immobilized on the support obtained by this process generally have a high activity and good stability in the presence of water and are fluid powders. They preferably have a more than monomeric attachment of the transition metal compound, that is to say more than one transition metal atom linked by hydroxyl group of available surface, and the catalysts contain from 3 to 60 % of transition metal bound. The present transition metal catalysts are extremely useful in esterification processes. Their preparation can be carried out as follows:

The present process consists in heating a hydroxylated support with a molar excess (with respect to the hydroxylated groups available) of a transition metal alcoholate at a temperature of between 100 and 300 ° C., preferably with stirring, in an aliphatic hydrocarbon and in the presence of water. In addition to the condensation reaction with the hydroxylated surface groups, self-condensation of the alcoholate of the

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transition metal can also occur, so that a crosslinked matrix of transition metal atoms having oxygen bridges (—O—) covers and is bound to the support. Useful transition metal alcoholates have the formula

M (OR) nQm in which M is a transition metal chosen from the groups IVb, Vb and VIb, OR is an alkoxy radical containing from 1 to 18 carbon atoms, n is an integer between 2 and the valence of the metal M , Q is an inert group which does not react with the hydroxylated groups of the support, the alcoholate radical OR or the alcohol ROH formed during the process from this radical, and m is an integer such that n + m satisfy the valence of the metal M. The support can be any of the supports currently available, comprising several hydroxyl groups on its surface.

The process will generally be carried out at a temperature of 120 to 250 ° C in a saturated aliphatic hydrocarbon, such as mineral oils. Preferably, the transition metal alcoholates in which the radical - OR is a saturated straight or branched chain alkoxy radical containing from 2 to 8 carbon atoms and the metal is titanium, zirconium, hafnium or vanadium are most useful, and particularly preferred are titanium tetraalcoholates. Water can be present at the start of the reaction, either added as it is or adsorbed on the support, it can be added afterwards or formed in situ by dehydration of the alcoholic by-products. An excess of the transition metal alcoholate is generally necessary in order to obtain a fixation which is more than monomeric, that is to say more than one Ti atom linked by hydroxyl group of available surface. The ratio of transition metal alcoholate molecules reacted by hydroxyl group will therefore be greater than 1: 1 and may be as high as 10 6: 1.

The catalysts are normally fluid powders containing from 3% by weight up to 60% by weight of transition metal bonded to the support. The catalysts immobilized on a support are the result of a very cross-linked matrix of transition metal atoms comprising oxygen bridges (—O—) covering the support and linked to this support. This rigid metal oxide polymer network comprising several points for fixing the polymer to the support will still contain enough alcoholate groups to be catalytically active.

It has also been found that these catalysts are preferably used in an ester preparation process, which virtually eliminates the problems generally associated with the production of esters. The present process is applicable to batch, semi-continuous or continuous operations in which esters are obtained, whether these are usually simple esters or polyesters, by direct esterification or by any of the known reactions of exchange type. Due to the hydrolytic stability of the catalyst used, the process can be used for esterification reactions in which water is formed as a by-product. Furthermore, with the process of this invention, undesirable side reactions are virtually eliminated and acceptable reaction rates are obtained using small amounts of the catalyst of the present invention. Due to the small amount of catalyst required and the fact that the catalyst is immobilized on a support and exhibits exceptional hydrolytic stability, it is possible to obtain extremely useful esters containing very low levels, and in some cases negligible amounts , of catalytic residue. As a result, esters can be obtained which are practically colorless (like water) and exhibit good stability during subsequent storage and use.

Another useful feature of the process, which is extremely important in batch production, is the fact that heterogeneous catalysts are generally easily separable from the resulting esters by filtration and reusable. Another characteristic, which is quite unexpected and which is of considerable importance for industrial operations, is the possibility of adapting the process to use with loads of acids, anhydrides, alcohols or impure esters which typically contain ketone, aldehyde and olefinic functional groups and normally do not require long and costly purification before use. These impurities normally harm the production of esters and / or can give very colored products which are unacceptable for all applications except those of very inferior qualities. With the present process, however, it has been found that low quality fillers can be used directly and that the resulting products have improved color and stability.

The use of catalysts preferably consists in heating the reactants in the liquid state, to an elevated temperature in the presence of a transition metal catalyst immobilized on a support. Temperatures can range from 100 to 300 ° C and the process can be carried out at atmospheric pressure or under reduced pressure. The process is adaptable to batch, continuous or semi-continuous operations for the production of carboxylic acid esters and polyesters, by direct esterification of a carboxylic acid or anhydride by an alcohol or ester exchange d a carboxylic acid ester with another carboxylic acid ester, another alcohol or another carboxylic acid ester. Aliphatic, aromatic and alicyclic, mono- and polyfunctional acids and alcohols can be used in the process. The process can also be used for the exchange of esters with synthetic or natural ester products (for example triglycerides). The catalyst immobilized on a support containing from 3 to 60% by weight of a transition metal (groups IVb, Vb and VIb) of the present invention is used, and the transition metals are preferably titanium, zirconium, l hafnium or vanadium. The amount of supported catalyst used for the esterification process can be as low as 0.0005% by weight relative to the reactants introduced, and can go up to very large amounts, as is the case when passing the reactants in a heated column packed with the catalyst.

The present process relates to the preparation of transition metal catalysts immobilized on a support by reaction of a hydroxylated support and a transition metal alcoholate. The transition metal compounds useful for this process have the general formula

M (OR) nQm in which M is a transition metal chosen from the groups IVb, Vb and VIb, OR is an alkoxy radical containing from 1 to 18 carbon atoms, such as for example the ethoxy, n-propoxy, isopropoxy groups, n-butoxy, isobutoxy, t-butoxy, n-octoxy, 2-ethylhexyloxy, n-decyloxy, allyloxy, tridecyloxy, stearyloxy, isotridecyloxy, cyclopentyloxy, cyclohexyloxy, etc., n is an integer of 2 at the valence of the metal M, Q is an inert group which does not react with the hydroxyl groups of the support, the alcoholate radical OR or the alcohol ROH formed during the process from this radical, and m is an integer such that n + m satisfy the valence of the metal transition M. The metals groups referred to here are those of the Periodic Table as found on the cover of the Handbook of Chemistry and Physics, 56th edition, 1975-76, CRC Press, Cleveland, Ohio , USA Particularly useful transition metal compounds are those in which the radical - OR is a saturated straight or branched alkoxy radical containing from 2 to 8 carbon atoms and in which the transition metal is titanium, zirconium, hafnium or vanadium. Examples of the transition metal compounds include, but are not limited to: tetraethoxy-titanium, tetra-isopropoxytitane, tetrabutoxytitane, tetra-isobutoxytitane, dimethoxydibutoxytitane, methoxy-

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butoxydiisopropoxytitane, methoxyisopropoxydibutoxy-titanium, tetrabutoxyvanadium, tetrabutoxyzirconium, tetra-isopropoxyzirconium, pentamethoxyvanadium, penta-isopropoxyvanadium, triisopropyl vanadate, tributyl vanadate, tetra-isopropyl chromium (III) dodecylate, chromium (IV) isopropylate, chromium (VI) ethylate, etc. It is also possible to use for the process of this invention compounds of transition metals containing a metalloketonic group (for example ^ V = 0), as well as other compounds containing inert groups, that is to say groups which do not interfere with the reaction. The transition metal compounds which are particularly useful for this invention have all their available valences satisfied by a saturated alcoholate radical, and titanium tetraalcoholates constitute a particularly preferred embodiment.

In the present process, the transition metal compounds described above are preferably reacted with any of the conventional and commonly used support materials having a hydroxylated surface, that is to say comprising several hydroxyl groups attached on the surface of the matrix. The surface hydroxyl groups provide the sites for attachment of the transition metal to the support, which can be represented

V I / x in which Z represents the support matrix and M is a tetravalent transition metal, x indicating the number of its fixations (corresponding to the number of available hydroxyl groups) present on the support. The supports can be synthetically produced materials or natural substances and can be anhydrous or contain moisture. The grain size can also vary widely. In fact, the method is usually also useful when the support material is in the form of spheres, hollow tubes, rings, bars, fibers, wafers or the like. Note, however, that the present process has a particular application to finely divided supports, and that the greater the specific surface and the higher the number of surface hydroxyl groups, the greater will be the potential reactivity of the support with the metal compound of transition.

To illustrate the large number and very diverse types of supports that can be used in this process, it will be noted that even carbon blacks having hydroxyl groups on their surface, such as tunnel blacks and oven blacks, can be used effectively. Likewise, synthetic mineral oxides of silicon, magnesium, aluminum, zinc and their mixtures are also usable supports. Organic polymers can be used having a lateral hydroxyl functionality or a functionality which can be transformed into hydroxyl groups. Silica and alumina matrices or mixtures thereof, which may also contain small amounts of alkali and alkaline earth oxides, iron oxide, zinc oxide, etc. are particularly useful because of their easy availability from natural sources. These supports can be used as they are, or they can be further activated, for example by acid treatment or similar treatment.

A partial and non-exhaustive list of suitable solid mineral supports includes alumina, silica, fumed silica, silica gel, natural clays such as kaolinite type clays, smectite type clays, in particular mont-morillonite, clays of the vermiculite type, clays of the palygorskite type, clays of the chlorite and mica type, etc., zeolites, zirconia, titanium oxide, thorium oxide, magnesia, aluminates such as bauxite and corundum, silicates such as chrysolite, actinolite, etc.

Due to the ability of the process to form a polymeric coating containing the transition metal and highly crosslinked on the surface of the support by condensation of the transition metal alcoholate, the support need not contain a high concentration hydroxyl groups to obtain an active catalyst having a high percentage by weight of bonded transition metal. This is contrary to the teachings of the prior art where the content of transition metal is directly proportional to the amount of reactive surface hydroxyl groups. It is theoretically possible to use the present process to obtain a catalytic support in which the transition metal polymer completely covers the support and is immobilized and bonded to the support matrix by only an - OH group. It is however obvious that a greater number of hydroxylated surface groups facilitates the reaction and generally makes it possible to completely cover the support more uniformly and with greater efficiency. For this reason, it is preferred that the support contains several hydroxyl groups. There is normally obviously no upper limit on the amount of hydroxyl groups present on the support matrix.

By this method, it is generally possible to obtain catalysts having a higher activity and containing much higher quantities of transition metal bound to the support, that is to say immobilized, so that the transition metal will not be lost by the catalyst during the subsequent reaction in which it is used. For the esterification reactions, in addition to the increased catalytic activity, these catalysts ordinarily allow the improvement of the color and the stability of the esters obtained and make it possible to obtain esters having very low residual contents of metal of transition. It can be said that the improvement consists in heating the hydroxylated support with an excess of the transition metal alcoholate in an inert hydrocarbon medium, in the presence of water at an elevated temperature between 100 and 300 ° C. and preferably with stirring. , to carry out the condensation reaction of the transition metal alcoholate with the surface hydroxyl groups.

It is believed, although one does not wish to be bound by the following explanation and equations, that the reaction between the support and the transition metal alcoholate can be represented as follows:

z - (- oh) x + xm (or) nqm-z— (- om (or) n_iqm) x + xroh (i)

where Z, M, R, Q, x, n and m are as defined above. The above equation also describes what has been taught by the prior art where the reactions are carried out under anhydrous or essentially anhydrous conditions. However,

in the present invention when the process can be carried out in a suitable reaction medium, in the presence of water and with an excess of the transition metal alcoholate (with respect to the available surface OH groups), a polycondensation of the alkali metal alcoholate to form a polymer of the crosslinked transition metal oxide which is bonded to the surface of the support. From the above equation, it is obvious that, by excess of transition metal alcoholate, we designate a molar quantity greater than x, ie more than one molecule of transition metal alcoholate reacting by hydroxyl group of available space. Although it is theoretically possible that all surface -OH groups react in the above manner, this is not necessary. As the transition metal alcoholate can undergo polymerization (autocondensation), it is still possible that all the transition metal introduced is incorporated into the support and that high levels of transition metal bonded to the support are obtained, with the result that extremely active and useful catalysts are obtained.

In the case where the transition metal alcoholate is a titanium alcoholate of formula Ti (OR) 4 and if the

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reaction to a single hydroxyl group, the reaction will be represented by the equation:

GOLD

I

Z-OH + Ti (OR) 4-> Z — O — Ti — OR + ROH (II)

<^ R

(at)

However, when more transition metal compound is available, and in the presence of water, to carry out the reaction, condensation can occur at any or all of the OR groups in part (a). If we consider the reaction on only one of the OR groups, the reaction will be represented as follows:

GOLD

Z — O — Ifi — OR + y Ti (OR) 4 + y H20-> (III)

I

GOLD

OR OR

Z — O — f — li — O — 4i— ^ —OR + 2yROH

[I V

OR OR *

It is obvious that any of the other - OR groups can also undergo the reaction in the same way and also that condensation with adjacent - OR parts from different side groups can occur, resulting in obtaining a very complex crosslinked titanate polymer on the surface of the substrate. Those skilled in the art will also see that it is also possible that some condensation (polymerization) will occur before the reaction with a surface hydroxyl group as shown in Equation II. The degree of condensation will depend essentially on the amount of transition metal alcoholate, the availability of water to carry out the reaction and reaction conditions, while the amount of crosslinking will also depend on the metal of alcohol particular transition used, i.e. the number of alcoholate substituents available for the reaction. The preceding equations are given for illustrative purposes only and represent the overall reaction regardless of the steps by which a particular reaction can occur.

To obtain the catalysts immobilized on a support of this invention, the process is usually carried out at an elevated temperature of 100 to 300 ° C. The temperature is usually determined by the particular transition metal alcoholate used, the amount of water present in the reaction mixture at the start of the reaction and the desired speed and extent of the reaction. It is obvious that, although it is possible to carry out the process at 100 ° C., the speed can be such that it makes the process impractical, and it would therefore be advantageous to increase the reaction temperature, since the products results will be essentially the same. It is generally more advantageous to carry out the reaction at a temperature between 120 and 250 ° C. The reaction can be carried out at atmospheric pressure or in a closed container at manometric pressures up to about 70 kg / cm 2, and better still up to about 35 kg / cm2. To some degree, the temperature will determine whether the reaction can be carried out in an open or closed container. When the process is carried out at atmospheric pressure, it can be carried out under an inert atmosphere of nitrogen, argon, etc., however, this is not necessary. A carrier gas can be used to facilitate removal of the alcohol and other by-products formed during the reaction. Although many variations are possible,

excellent results are obtained when the reaction is carried out at atmospheric pressure in the presence of air, while removing all the gaseous by-products and condensing and collecting in an appropriate trap the alcohol formed during the condensation.

To obtain the transition metal catalyst immobilized on a support, it is generally necessary to use as reaction medium an appropriate hydrocarbon. Although the exact role of the hydrocarbon is not precisely known, in addition to the normal role of a reaction medium which consists in uniformly distributing the heat and thus allowing a more controllable reaction rate, it is assumed that l The hydrocarbon also serves to dissolve the transition metal alcoholate and to coat the surface of the support to prevent agglomeration of the finely divided catalyst particles. The hydrocarbon can also facilitate recovery of the final immobilized catalytic product. The aliphatic hydrocarbons which can be used include normal paraffins (CnH2n + 2), isoparaffins (C „H2n + 2), olefins (C„ H2n), diolefins (CnH2n_2) and cycloparaffins (CnH2n) as well as their mixtures. Aromatic hydrocarbons can also be present in the mixture. It is generally advisable to use hydrocarbons which are predominantly saturated, since the presence of excessive amounts of olefinic unsaturation results in the formation of an undesirable color, in particular if the process is carried out in the presence of air. When the hydrocarbon is essentially an aliphatic saturated hydrocarbon, these problems are avoided. The reaction medium based on aliphatic hydrocarbons can comprise normal paraffins, isoparaffins, cycloparaffins or their mixtures, with small amounts of olefins. These hydrocarbons can contain from about 8 to about 40 carbon atoms and are generally obtained by fractional distillation of petroleum paraffin fractions. They generally include mixtures of oily liquid hydrocarbons in the range of C14. to C32. For the purposes of this invention, it is particularly useful that the aliphatic hydrocarbon is a liquid at about 30 ° C or below, and has a boiling point above 140 ° C. Useful aliphatic hydrocarbons include, but do not their are not limited to, white oils, liquid paraffin and the many mineral oils and heavy fuel oils available commercially. In general, the ratio of hydrocarbon oil to support will be between 0.5: 1 and 50: 1 and preferably between 2: 1 and 25: 1, based on the weight.

As indicated above, the presence of water is essential for obtaining the very active immobilized catalysts of this invention. Although the surface hydroxyl group may react with the titanium alcoholate in the absence of water, the subsequent reaction (condensation) cannot occur if anhydrous conditions are maintained. As one mole of water is required for each oxygen bridge formed (see Equation III), at least one mole of water per mole of transition metal alcoholate to be condensed is required for polycondensation. Normally, the presence of greater amounts of water (even as high as a ten-fold molar excess) does not, however, adversely affect the reaction or activity of the resulting catalyst. For this invention, water can be added at the start of the reaction, it can be introduced continuously or intermittently during the reaction, or formed in situ. These procedures can also be combined in any manner to obtain the necessary amount of water to carry out the condensation reaction. In the case of a titanium alcoholate, the overall reaction can be represented as follows:

—4i — OR + RO — 4i- + H20 -> - 4i — O — 4i- + 2ROH (IV)

I I II

However, it is not necessary that all the water required, relative to the amount of transition metal alcoholate introduced,

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is present at the start of the reaction. Sufficient water will have to be added or formed during the reaction to obtain condensation. If water is added at the start of the reaction, it can be added to the reaction mixture as it is or it can be present on the support. The latter has been found to be a particularly convenient way of introducing water into the system and is particularly advantageous in that it initiates condensation in that all or part of the required water is available to the surface of the support. When it is desired to carry out the reaction in a continuous or semi-continuous manner, it may be advantageous to continuously introduce water in a measured manner into the reaction system or to add it in several stages.

In yet another useful embodiment of this process, part of the water required is formed in situ, that is to say in the reactor during the course of the reaction, by dehydrating the alcohols formed as a result of the condensation. According to equation IV, we see that we obtain two molecules of alcohol for the formation of each bridge - O—, which provides a more than sufficient and self-renewing source of water for allow condensation if alcohol is dehydrated. Considering the case where the transition metal alcoholate is a titanium isopropylate, the overall reactions showing the condensation of two isopropylate parts and the dehydration of the resulting alcohol would be as follows:

ch3 ch3

2-tì-o <i: h + h2o - »- '1i-o-Ìì- +2 ho - <!: h (v) izHi 1 1 Ìh3

ch3 ch2

I support II HO-CH> HC + H20 (VI)

èii3 A ÌH3

A small amount of acid, such as sulfuric acid or a similar acid, can be added to the reaction mixture to facilitate dehydration (Equation VI); however, such acid catalysts are not required. Although it is not essential, it is generally advantageous to have a small amount of water such that it could be adsorbed on a support present at the start of the reaction to initiate condensation and then, when the temperature is increased. reaction and as the amount of alcohol in the reactor increases, to form additional water in situ by dehydration of the alcohol to complete the condensation. The dehydration product need not be removed from the reactor; however, when the process is carried out under atmospheric conditions, these products will generally be easily removed by evacuation if the product is a gas (eg propene) or by condensation and collection in an appropriate trap when the product is a low point liquid boiling.

The amount by weight of transition metal bonded to the support matrix will depend on the amount and type of transition metal alcoholate used and the extent of the condensation. The transition metal will constitute from 3% of the immobilized catalyst up to 60%. More generally, between 5 and 50% by weight of the transition metal are bonded to the support. To obtain the immobilized catalysts, normally the ratio of the molecules of transition metal alcoholate to each hydroxyl group available will be greater than 1: 1 and will go up to 10 6: 1, and it will preferably be between 1.5: 1 and IO4 ": 1. With supports having relatively high contents of hydroxyl groups, for example 10 ~ 4 to 10" 3 equivalent of hydroxyl groups per gram of support, this ratio will generally be between 2: 1 and IO2: 1 .

The catalysts of this invention are typically fluid powders which are easily handled and which, due to their stability to hydrolysis, can be stored for long periods of time without losing their catalytic activity. They can be easily recovered using conventional filtration procedures and can be reused.

Immobilized catalysts have a complex structure consisting of a highly crosslinked polymer network containing the transition metal, bonded to the surface of the support, as a result of the reaction of the transition metal alcoholate with the hydroxyl groups on the surface of the support and the polycondensation of the transition metal alcoholate. The polymeric surface coating is a crosslinked matrix of transition metal atoms linked to each other and to the support by oxygen bridges (—O-). With the process described, however, the rigid matrix generally contains still enough unreacted alcoholate groups for it to have a high degree of catalytic activity. It is believed that these alcoholate groups, which are present on the surface of the transition metal oxide polymer, may furthermore also be present in the matrix. It is possible by this method to completely coat support materials having even a low content of hydroxyl groups and supports having very irregular surfaces, so that only the transition metal oxide polymer and the alcoholate groups are present on the surface of the immobilized catalyst to a considerable depth.

In general, the catalysts of this invention will have utility in any application in which transition metal catalysts of groups IVb, Vb or VIb have been used to date. Such applications include, but are not limited to, metathesis and polymerization of olefins, cyclooligomerization of alkynes and alkenes, Ziegler-Natta polymerizations, hydrogenation, etc. They are particularly useful with esterification and ester exchange reactions, including transesterifications. The advantages of these immobilized catalysts are numerous, but mainly their stability to hydrolysis, their ability to be practically completely eliminated at the end of the reaction by simple filtration operations, and the fact that practically all of the transition metal is bound to said support and will not dissolve in the reaction mixture.

Immobilized catalysts have particular utility in the preparation of esters used as plasticizers, lubricants, including base oils and additives, as additives and intermediates for polymers, etc. As the active transition metal catalyst is bound to the surface of the support and not dissolved in the reaction mixture, all the colored bodies formed which contain the metal are trapped on the surface of the catalyst and can be removed by filtration at the end of the reaction.

Since practically all of the catalyst can be removed from the esters prepared using these so-called catalysts, the resulting substantially metal-free esters and polyesters generally have increased stability to hydrolysis, oxidation and heat. This is a particularly important consideration with regard to esters which must meet certain requirements with regard to metal content, such as lubricants for ester type turbines at 3 cSt (99 ° C) and 1 cSt (260 ° C) , which must meet the strict standards MIL-L-7808 G and MIL-L-27502.

The present invention also describes the discontinuous, continuous or semi-continuous production of carboxylic acid esters, usually comprising simple esters and polyesters. It can be used with reactions in which a carboxylic acid or a carboxylic acid anhydride is directly combined with a mono- or polyfunctional alcohol, to obtain an ester. It is likewise useful in any of the well-known reactions of the ester exchange type, in which

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an acyl and / or alkoxy radical originating from an existing ester is exchanged with another acyl and / or alkoxy radical. As indicated, the process is useful for the formation of simple esters in which at least one of the reactants (acid, anhydride or alcohol) is monofunctional; however, the simple ester may have more than one ester portion in the molecule, as is the case when glycerol is reacted with a fatty acid. The process also finds use in the preparation of polyesters, i.e. polymeric materials containing an ester unit.

The process can be used with any mono- or polycarboxylic acid or anhydride, including aliphatic, aromatic or alicyclic acids, or mixtures thereof, which may also contain other substituents. The acids can be saturated or contain olefinic unsaturation. Typical acids include acetic, vinylacetic, phenylacetic, triphenylacetic, propionic, acrylic, methacrylic, p-phenylacrylic, n-butyric, isobutyric, valeric, isovaleric, 5-phenyl-n-valeric, hexoic, 2- ethylhexoic, heptoic, caproic, octanoic, pelargonic, lauric, myristic, palmitic, stearic, oleic, erucic, linoleic, linolenic, eleostearic, lignoceric, malonic, succinic, glutaric, adipic, pimelic, azelaic, azelaic10 dicarboxylic, pentadecane-l, 15-dicarboxylic, pentacosane-1,25-dicarboxylic, 1,2,3-propanetricarboxylic, crotonic, maleic, fumaric, mesaconic, citraconic, itaconic, muconic, aconitic, etc.

Useful alicyclic acids included are cyclo-propanecarboxylic, cyclobutanecarboxylic, cyclo-pentanecarboxylic, cycloheptanecarboxylic, cyclo-hexanecarboxylic, cyclopropanedicarboxylic, cyclohexane-dicarboxylic, cyclohexane-1, 2,3,4,5,6-hexoparene carboxylic, 1-cyclohexene-1-carboxylic, cyclohexadiene-1, 2-dicarboxylic, 1, 3-cyclohexane-1, 4-dicarboxylic, the dicarboxylic acid formed by the addition of Diels-Alder of acrylic acid on l linoleic acid, etc.

Suitable aromatic acids which can be used in the present process include benzoic acid, toluic acids, α-naphthoic acid, P-naphthoic acid, o-, m- and p-ethylbenzoic acids, p-phenylbenzoic acid, phthalic acid, isophthalic acid, terephthalic acid, trimellitic acid, pyromellitic acid, etc.

Many substituted acids can be used, and they include hydroacetic, chloroacetic, bromo-acetic, cyanoacetic, lactic, a- or ß-hydroxypropionic, citric, ricinoleic, a- or ß-chloroacrylic, ß-bromo-acrylic, 2 -hydroxycyclohexanecarboxylic, o-, m- and p-chloro-or bromobenzoic, o-, m- and p-hydroxybenzoic, o-, m- and p-nitrobenzoic, o-, m- and p-methoxybenzoic, hydroxy-phthalic, etc. Various mixed acids obtained from many natural sources, such as tall oil fatty acids, lanolin fatty acids, coconut fatty acids and montan wax acids, etc. can also be used. High molecular weight acids including dimer, trimer acids and their higher polymers obtained by polymerization of olefinically unsaturated fatty acids, such as oleic acid, linoleic acid or mixtures thereof are also useful as well as other products high molecular weight acids such as branched acids containing a-alkyl or a, a-dialkyl groups, obtained by radical addition of short chain monoacids, for example propionic acids, to high molecular weight a-olefins, and products high molecular weight mixed acids obtained by ozonation or oxidation of high molecular weight olefins. Typical anhydrides of the mono- or diacids which can be used for the process include acetic anhydride, adipic anhydride, maleic anhydride, phthalic anhydride,

trimellitic anhydride, benzoic anhydride, etc.

The alcohols which can be reacted with the abovementioned carboxylic acids and anhydrides are monoalcohols or diols, triols or alcohols of higher polyfunctionality. They include aliphatic, alicyclic and aromatic alcohols, which may contain additional substituents, and ether alcohols, that is to say the intermolecular ethers formed by condensation of two or more molecules of a polyol, accompanied by elimination of water. By way of illustration, the monoalcohols which can be used include ethanol, chloroethanol, cyanoethanol, n-propanol, s-propanol, n-butanol, t-butanol, isoamyl alcohol, n- hexanol, 2-ethylhexanol, n-octanol, n-decanol, isodecanol,

capryl alcohol, lauryl alcohol, myristyl alcohol, cetyl alcohol, stearyl alcohol, oleic alcohol, oxoalcohols such as tridecyl alcohol which is mainly tetramethyl-1-nonanol, and hexadecyl alcohol which is a complex mixture of primary alcohols characterized as

2.2-dialkylethanols in which the alkyl groups are essentially C6 and Cg radicals branched by methyl groups, cyclohexanol, benzyl alcohol, o-, m- and p-methoxybenzyl alcohols, o-, m- and p-methyl-benzyl, phenylethyl alcohol, triphenylethyl alcohol, etc. The polyols which can be used in this invention include ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol,

1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,4-pentanediol, 3-methyl-1,5-pentanediol, 2,3-dimethyl-

2.3-butanediol, trimethylolpropane, mannitol, sorbito !, glycerol, pentaerythritol, 1,4-cyclohexanedimethanol,

xylenol, bisphenols such as bisphenol A, etc. The ether alcohols which can be used are diethylene glycol, triethylene glycol, tetraethylene glycol, polyoxyethylene- or poly-oxypropylene glycols of molecular weight up to approximately 4000, the monomethyl ether of diethylene glycol,

monoethyl ether of diethylene glycol, monomethyl ether of triethylene glycol, butoxyethanol, monobutyl ether of butylene glycol, dipentaerythritol, tripentaerythritol, tetrapentaerythritol, diglycerol, triglycerol, tetraglycerol, pentaglycerol, hexaglycer heptaglycerol, octaglycerol, etc.

In addition to the acids, anhydrides and alcohols mentioned above, the esters which are formed from these compounds can also be used in the process. Esters which can be used in exchange reactions include acidolysis, alcoholysis and transesterification. Synthetic esters and esters obtained from natural sources can be used for this purpose. Although typically the ester contents of these natural products are very high, products containing less than 50% of esters are also usable. Advantageously, in the process of this invention, natural fats and oils, both of animal and vegetable origin, are used, and they can be modified in numerous ways to obtain the useful esters. Although these fats and oils are composed mainly of triglycerides, other esters may also be present.

The reaction conditions used in this process can vary over a wide range depending on the type of reaction used, the particular reagents and the results to be obtained. In general, the temperatures will be between 100 and 300 ° C. and more generally between 125 and 250 ° C. Reactions carried out at temperatures much lower than 100 ° C. are not carried out at an acceptable rate and are observed generally no advantage when operating at temperatures well above 300 ° C. The temperature and other reaction conditions will obviously depend on how the process is carried out which, as already mentioned, can be carried out in discontinuous, continuous or semi-continuous. It's obvious that,

in a continuous operation, for example, where a column is packed with the catalyst in a suitable form and where very short contact times are obtained, the temperatures

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will generally be greater than those necessary for a discontinuous system. It is also obvious that, in a continuous operation where the product passes through a series of reaction vessels, it may be advantageous to operate the terminal reactors under a higher vacuum and / or at higher temperatures. Many variations of the process are possible and fall within the scope of this invention.

The reaction can be carried out at atmospheric pressure, or the pressure can be reduced or increased above atmospheric pressure. In general, the same criteria as those mentioned above for temperature will apply to the system pressure requirements. To facilitate the completion of the reaction by removing water and other volatiles, for example glycols, the final steps of the reaction will generally be carried out at reduced pressure. These procedures are particularly advantageous when ester products with low acid numbers are desired and when the formation of high molecular weight polyesters is desired.

The process need not be carried out in an inert solvent or an inert diluent as long as the reactants remain liquid. It may however be advantageous to use a solvent or a diluent to facilitate the handling of the reactants or the contact of the reactants with the catalyst, so as to obtain a more uniform reaction rate. Normally the particular solvent or diluent used is not critical as long as it does not react with the reagents or the catalyst or otherwise does not harm the reaction. Hydrocarbon solvents, whether aliphatic or aromatic, are particularly useful for this purpose. Particularly useful are also the hydrocarbons which form an azeotrope with water, an azeotrope whose boiling point is lower than that of the components of the reaction, so that all the water formed can be removed azeotropically from the reaction mixture,

which brings the reaction to its completion.

The reaction time can vary widely depending on the above variables; however, it has generally been found that even in operations of the batch type, extremely fast reaction rates are obtained with the present process so that substantially complete conversion is obtained within a few hours.

Due to the superior activity of the immobilized catalysts of the present invention, very small amounts can be used and acceptable reaction rates are obtained. However, since the transition metal is bound to the support, the use of large amounts of catalysts is generally not harmful and practically all of the catalytic residue can be removed from the ester produced upon completion of the reaction, in particular using simple filtration operations. The amount of catalyst used can range from as low as about 0.0005% by weight up to very high amounts, since it is possible to produce esters continuously by passing the reactants through a packed column of transition metal catalyst on a support. Then, generally, the catalysts will however be present in amounts ranging from approximately 0.001% to approximately 10% by weight relative to the total reactants introduced. In typical batch and semi-continuous operations, for the production of esters and polyesters by direct esterification or ester exchange, amounts of catalyst are generally used from 0.01% to 1% by weight.

The advantages of the present process which uses the transition metal catalysts immobilized on a support of the present invention can be numerous. As the active metal catalyst is bound to the support and does not dissolve in the reaction mixture, the colored bodies formed which contain metal are trapped on the surface of the heterogeneous catalyst and can be removed by filtration at the end of the reaction. For

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for this reason, the esters and polyesters obtained by this process generally have an improved color when compared to esters obtained using homogeneous catalysts. This characteristic can also make the process usable with reagents containing ketonic, aldehyde and olefinic impurities such as those obtained in industrial operations, without the need for costly and lengthy prior purification.

Another important advantage of this process is that almost all of the catalyst can be removed at the end of the reaction, using simple filtration operations. It is not uncommon to obtain esters and polyesters containing less than 1 ppm of titanium and the resulting metal-free esters or polyesters usually therefore have stability to hydrolysis, oxidation and heat, improved compared to the esters obtained using the catalysts known up to now. This characteristic also makes it possible on an industrial level to produce esters which can be used in certain applications where it was not possible beforehand or it was impracticable to lower the residual metal content to acceptable values. These applications include food applications and other important applications in which esters and polyesters are used, such as their application as plasticizers for polyvinyl chloride or other polymers used for packaging food, making pouches blood, etc. It is also possible with this process to obtain lubricants for turbine of the ester type at 3 cSt (99 ° C) and 1 cSt (260 ° C) which meet and exceed the strict requirements of standards MIL-L-7808 G and MIL -L-27402 as regards the metal content.

Still other advantages are possible, as in the production of hydroxyl-terminated polyesters, useful as polymer intermediates, which are reacted with di-isocyanates to obtain flexible polyurethanes. In the presence of residual metal catalysts, undesirable formation of by-products (eg biurets, ureas and allophanes) takes place, which causes crosslinking and impairs the flexibility of the polyurethane.

The following examples illustrate the invention more fully. In these examples, all parts and percentages are given by weight unless otherwise indicated. On the other hand, unless otherwise specified, the support was not dried before using it, and no precautions were taken to exclude the humidity of the equipment when preparing the catalyst.

Example I:

A supported titanium-based catalyst was prepared in a jacketed stainless steel reactor which was equipped with an agitator, a thermocouple and a condenser with a receiver. In this reactor, 90 parts of mineral oil (White Oil No. 70) and 10 parts of a naturally acidic mont-morillonite clay containing approximately 4% of adsorbed water were loaded. We started heating and stirring and we started to add under the surface a solution of 33.5 parts of tetra-isopropyl titanate (Tyzor TPT manufactured by EI du Pont de Nemours and Company) in 27.5 parts of 'mineral oil. This addition was continued for 1 V * h, during which time the reaction temperature rose to 110 ° C. After the temperature reached 120 ° C, a second addition of a solution of 21 parts of mineral oil and 34 parts of tetra-isopropyl titanate was started. After the temperature reached 140 ° C, the distillate started to flow. Before the temperature reached 170 ° C and the second addition was completed (duration of the addition 1% h), the speed of recovery of the distillate had increased markedly. Heating was continued, and the temperature rose to about 200-210 ° C, and was maintained for an additional 5 h while removing the distillate and removing the propene and other volatiles

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that did not condense. Some foaming was observed, but this foaming did not interfere with either the reaction or the collection of the distillate. After cooling to about 70 ° C, the supported catalyst was collected on a filter, washed several times with isopropanol until the filtrate was transparent, and dried with water. air. There has been a 205% increase in the weight of the support. Analysis by atomic absorption revealed that the product contained 37.8% by weight of titanium. The supported catalyst was a grayish, fluid powder of almost fluid appearance.

Example II:

A glass reactor was equipped with a stirrer, a thermometer, and a condenser and trap device. A ventilation line at the top of the condenser led to a dry-ice trap. 20.1 g of the naturally acidic montmorillonite clay of example 1.11 g of mineral oil and 50.3 g of tetra-isopropyl titanate were charged into the reactor. The reaction mixture was heated, with stirring, to about 200 ° C over 1 hour while 27 ml of isopropanol was evolved. 10 g of propene were also collected in the dry ice trap.

After cooling, the reaction mixture was filtered and washed with isopropanol until a colorless filtrate was obtained. After air drying, 44.2 g of catalyst containing 21.8% by weight of titanium were obtained.

Example III:

Using a procedure similar to that described in Example II, a supported vanadium catalyst was prepared by reacting 10 g of the naturally acidic montmorillonite clay and 15 g of tributyl vanadate in 160 g of mineral oil, heating the reaction mixture with stirring from room temperature to 250 ° C in 1V * h. Collection of the distillate began at about 200 ° C, and a total of 6.2 ml of butanol was removed. Butene has also condensed in the dry ice trap. After cooling and filtration, the product was washed with isopropanol until the filtrate had only a very pale yellow color. The final weight of the product, after air drying, was 14.8 g. The catalyst immobilized on a support contained 16.1% by weight of vanadium.

Example IV:

In exactly the same way, an immobilized zirconium catalyst was prepared. The support used for this reaction was a synthetic mixture of silica and alumina (13% in the form of Al2O3). The alumina / silica support (10.8 g) was loaded into a reactor, with 120 g of mineral oil (70 SUS) and 10.1 g of tetrabutyl zirconate. The mixture was then gradually heated to approximately 220 ° C. over approximately 3 hours,

while removing the butanol and letting the gases escape. After filtration, washing and air drying, 13.25 g of a catalyst immobilized on a support containing 7.3% by weight of zirconium were obtained.

Example V:

To demonstrate the universality of the present invention and the possibility of obtaining useful immobilized catalysts from a wide variety of supports, a series of hydroxylated support materials were reacted with tetra-isopropyl titanate (TPT) in a mineral oil of 70 SUS. The reaction process was similar to that which has already been described, with slight variations in the reaction temperature and the reaction time. The details of the experiments are given in Table I. This table indicates the support used, the load of reagents and of mineral oil, the maximum reaction temperature, the reaction time, the percentage of increase in weight of the support.

/ final weight - initial weight \

15 - - x 100

\ initial weight /

and the percentage by weight of titanium bound to the support. From the results provided, it is evident that it is possible to use a wide variety of support matrices to prepare immobilized catalysts according to the invention. It can also be seen that this process makes it possible to obtain catalysts containing a very high proportion of transition metal.

25 Example VI:

10.25 g of naturally acidic montmorillonite clay, 68.5 g of tetra-isopropyl titanate and 170 g of mineral oil (50 SUS) were charged to a reactor, and heated to about 220 ° C. in 1 lA h, time during which 32.5 ml of isopropanol and 12 g of propene were removed. The resulting immobilized catalyst contained 35% by weight of titanium. Similar results are obtained when the reaction is carried out in mineral seal oil (heavy fuel oil used as an absorbent to remove gasoline vapors contained in natural gas and as lighting oil) at 100 SUS. However, with this more viscous oil, more foaming is observed, and the duration of the filtration is a little longer.

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Example VII:

A series of reactions was carried out to demonstrate the possibility of using different titanium alcoholates, namely tetrabutyl titanate (Vlla), tetraoctyl titanate (Vllb), 45 and a partially condensed tetrabutyl titanate (Vile )

prepared by the limited addition of a quantity of water calculated so as to obtain the product of the condensation of 2 to 3 moles of tetrabutyl titanate, according to the US patent.

No. 2689858. For each of the reactions, naturally acidic montmorillonite clay 50 and mineral oil at 70 SUS were used. The details of the reactions as well as the percentage of titanium obtained for the resulting immobilized catalysts are the following:

Vlla Vllb Vile

Load composition 68/11/153 24/27/175 73 / 10.5 / 160

(in parts of titanium compound /

support parts / oil parts)

Maximum reaction temperature (° C) 250 210 235

Reaction time (hours) 6 2 lA 10

Percentage increase in support weight 191 39 264

Percentage by weight of titanium bound to the support 25.7 4.9 29.6

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Table I

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Support example

Composition

Duration

Temperature

Percentage

Percentage

the maximum reaction weight increase charge

(TPT /

(hours)

(° C)

titanium weight

Support / oil)

support

Go

Activated carbon1

59 / 11.9 / 160

4

250

238

21.5

Vb

Potassium Montmorillonite2

68 / 10.1 / 154

7

250

20

9.7

Vc

Bentonite Southern3

68 / 10.7 / 162

3.75

200

225

27.7

Vd

Silica / alumina

(13% AI2O3) 4

68.8 / 10/165

2

200

214

31.4

Fr

Montmorillonite treated with

hydrochloric acid5

68.2 / 10.6 / 170

2.5

180

236

22.5

Vf

Sub-bentonite clay6

170/25/325

1.5

220

209

41.0

Vg

Montmorillonite treated with

sulfuric acid7

81.4 / 10.1 / 178

3.75

181

299

33.7

Vh

Montmorillonite naturally

acid

81.4 / 10.4 / 160

3

195

278

33.3

Vi

Calcium silicate8

50.8 / 10.3 / 140

4.75

250

170

39.6

Vj

Sintered particles

colloidal silica

30.2 / 6.0 / 170

4.5

240

560

13.5

Vk

Diatomaceous earth (hydrated) 10

35.4 / 5.1 / 140

4

242

204

36.9

VI

Sulfonated polystyrene resin11

22.5 / 10/170

5.5

140

90

18.3

1 Darco KB (Atlas Chemical Co.).

2 Montmorillonite treated with potash (excess of potash).

3 Panther Creek clay (American Colloid Co.).

4 Davison 135 quality silica / alumina.

5 Tonsil FF Optimum (Sud-Chemie).

6 Clarolite BC (Georgia Kaolin Co.).

7 Filtrai quality N ° 1 (Filtrai Corporation).

Example Vili: 35

An immobilized zirconium catalyst was obtained by reacting 21.3 g of naturally acidic montmorillonite clay and 84 g of tetrabutyl zirconate in 140 g of mineral oil at 70 SUS. The reaction was carried out for 8 h,

time during which 40 ml of butanol and 13.5 g of butene were recovered. During the last two hours of the reaction, the reaction temperature was maintained at 250-265 ° C. The final dried catalyst (51 g) contained 13.5% by weight of zirconium. 0

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Example IX:

To demonstrate the universality of the present invention, the following experiments were carried out. Diatomaceous earth (Dicalite) dried at 90 ° C. for approximately 2 days was used as support. 10.5 g of this 50 sec support was combined with 60 g of tetra-isopropyl titanate in 160 g of mineral oil at 70 SUS, and the mixture was heated with stirring. up to a temperature of 250 ° C, in addition to 2 h. No reaction was observed, based on the absence of isopropanol and butene formation. By repeating this experiment and using the previous charge, but adding three drops of 95% sulfuric acid at the start of the reaction, a violent evolution of isopropanol and butene was observed at 250 ° C., and it was successful in producing an immobilized catalyst containing 39.1% by weight of bound titanium. By repeating the experiment again but adding 60 0.5% (relative to the loaded reagents) of water at the start of the reaction, a violent reaction with isopropanol and a large evolution of propene was observed, and similarly obtained an immobilized catalyst containing 42.3% by weight of titanium.

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Example X:

10.5 g of activated carbon granules (Witcarb 517), 23.6 g of tetra-isopropyl titanate and 140 g were charged into a reactor.

8 Microcell C (Johns-Manville).

9 Cab-o-sil (M-5) (Cabot Corporation).

The diatomaceous earth was mixed with water, filtered and air dried; the support contained more than 50% by weight of water.

11 Amberlyst 15 dry (Rohm and Haas) (ground to a grain of at least 60).

mineral oil, and heated to 200 ° C in 1 hr. No reaction was observed. Upon the addition of three drops of concentrated sulfuric acid, isopropanol and propene began to evolve rapidly. The final catalyst (23 g) contained 19.6% by weight of titanium.

Example XI:

To demonstrate the utility of the catalysts according to the invention, hydrogenation was carried out as follows. 500 ml of deoxygenated xylene, 50.5 ml (0.5 mole) of cyclohexane, 26.5 ml (0.25 mole) of toluene were charged to an 11 stainless steel autoclave under dry nitrogen. , 32 g of 24.8% diisobutyl aluminum hydride (0.04 mole) in heptane, and 3.0 g (0.01 mole) of titanium from the immobilized titanium catalyst of Example I. then put the autoclave under a gauge pressure of 35 kg / cm2, heating and stirring at 500 rpm. At 87 ° C, the gas was purged to adjust the pressure to 35 kg / cm2, then heating was continued. The initial absorption of hydrogen was noted at 180 ° C (39.6 kg / cm2). When the temperature reached 200 ° C, heating was stopped and the reactor and its contents were allowed to cool slowly to 180 ° C (26.3 kg / cm2),

then at room temperature. The gas / liquid chromatographic analysis revealed the almost complete transformation of cyclohexene into cyclohexane.

Example XII:

A hydroxyl-terminated polyester, useful for the preparation of urethane polymers, was prepared by reacting 364 parts of 1,4-butanediol and 1076 parts of 1010 dimer acid containing 97% of C36 dicarboxylic acid and 3% of C54 carboxylic triacid. The reaction mixture was heated to 225 ° C with 0.05 part of a 50% H3PO2 solution, while removing the water. A moderate vacuum was applied to the apparatus to facilitate removal of the water. When the acid number has reached

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about 2, 1 g of the catalyst of Example I was added to the reaction mixture, and the vacuum was increased while maintaining the temperature. Polymerization was continued for a further 20 min until collection of the distillate was complete. The resulting polyester had excellent transparency and good color, it contained less than 3 ppm of titanium, and it reacted easily with diisocyanates to give useful polyurethanes.

Example XIII:

A mixed ester has been prepared which is useful as an industrial lubricant in metalworking, for example as a rolling oil, and which can easily be emulsified in water using the immobilized titanium catalyst of Example I. In a reactor, 288 g (1.0 equivalent) of refined palm oil were loaded, 60 g (0.3 equivalent) of polyoxyethylene glycol having an average molecular weight of 400, and 85.8 g (0.3 equivalent) of acid Empol 1014 dimer containing 95% of C36 dicarboxylic acid, with 0.01% by weight (relative to the total weight of the reactants) of the immobilized titanium catalyst, and the reaction mixture was heated at 220 ° C for approximately 5 h removing water. After cooling, the reaction product was filtered using 0.5% diatomaceous earth as a filter aid. The final product had an acid number less than 20, it could be easily emulsified in cold tap water with moderate stirring, and the resulting aqueous emulsion also had good stability. The modified triglyceride had good thermal stability and good lubricating properties, and contained less than 1 ppm of titanium.

Example XIV:

The following experiment was carried out in order to have comparative data and to better demonstrate the advantages of the catalysts according to the invention. A catalyst based on polymeric orthotitanic acid ester similar to the heterogeneous catalysts described in German patent No. 1142868 was prepared from ethylene glycol and tetrabutyl titanate. To prepare this catalyst, react 62 g of ethylene glycol for polymer (dried before use) and 83.6 g of tetrabutyl titanate, by heating to approximately 130-150 ° C. In a short time, a white suspension formed and 30 ml of butanol were collected. After cooling, the reaction mixture was filtered and the catalyst was washed with hot xylene and

Filler composition in parts (titanium compound / support / oil)

TPT / support

Maximum reaction temperature (° C)

Reaction time (hours)

Support weight increase percentage 32

Percentage by weight of titanium bound to the support 7.9

For comparison with the titanium catalyst prepared above, a heterogeneous catalyst (designated by XVd) was prepared from tetra-isopropyl titanate and the same naturally acidic montmorillonite clay, in accordance with the teachings of the patent of USA No. 3817931. The reaction was carried out under anhydrous conditions. The clay (9.69 g) calcined under nitrogen was charged to a reactor for 2 h at 350 ° C. to remove the water, with 70.18 g of tetra-isopropyl titanate and 160 g of anhydrous toluene. The reaction mixture was heated with stirring at about 25 ° C for about 19 h, then filtered. 10.2 g of catalyst were obtained, after washing it was dried in a vacuum oven at 110 ° C. The heterogeneous polymer catalyst contained 35.5% by weight of titanium.

To evaluate the catalyst, a mixed ester obtained by esterification of azelaic acid, phthalic anhydride and a mixture of saturated aliphatic monoacid and dicarboxylic acid (75:25) with an excess of propylene glycol (0.625) was prepared. 0.222: 0.150: 1.25 equivalents of the respective reagents), heating the reagents to 230 ° C for about 9 h in the absence of catalyst, while removing the water. The resulting mixed ester 10 had an acid number of 5.4 and a kinematic viscosity of 430 cSt at 38 ° C. The color, as a percentage of transmission (% T) determined at 440 and 550 mu by spectrophoto-metric analysis , was 35/82.

To 1000 g of this mixed ester was added 0.031% by weight of the heterogeneous catalyst prepared above (110 ppm of titanium). The reaction mixture was then heated to 225 ° C under a high vacuum (1 to 2 mm of mercury) for 2 h, while removing the glycol from the reaction mixture. After 2 h, the acid number had dropped to 0.4 with a corresponding increase in viscosity. The color of the product darkened, so that the percentage of transmission was 4/48, which is not at all satisfactory. In addition to the poor color, the polyester produced (after filtration to remove the heterogeneous catalyst) contained 86 ppm of titanium.

The above operation was repeated using 1000 g of the mixed ester and heating for 2 h at 225 ° C and 1 to 2 mm of mercury. However, 0.057% by weight of an immobilized titanium catalyst (186 ppm titanium) similar to that of Example Vg was used in this reaction. The resulting polyester had a higher viscosity, an acid number of 0.5 and a markedly improved color (% T = 19/75). Even though a much higher content of titanium was present in the reaction mixture, the polyester finally produced contained only 2.4 ppm of titanium after filtration to remove the immobilized catalyst.

Example XV:

To better demonstrate the superiority of the immobilized catalysts according to the present invention, the following catalysts were prepared using tetra-isopropyl titanate, naturally acidic montmorillonite as support, and mineral oil at 70 SUS, according to the procedure. usual. The details of the reactions and product analyzes are as follows:

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20.3 37.8

and air drying. This catalyst contained only 2.9% by weight of bound titanium, even though the TPT / support ratio is identical to 60 that used for the preparation of the immobilized catalyst designated by XVc.

In order to evaluate the above catalysts, a mixed ester was prepared. This mixed ester was obtained by reacting adipic acid, 1,3-butylene glycol and 2-ethylhexanol (65 equivalents ratio = 1.0: 1.125: 0.125) at a temperature of 225 ° C, while removing water. To facilitate removal of the water, a vacuum was applied during the latter stages of the reaction. When the acid number has reached approximately 25, the

XVa XVb XVc

20.3 / 40.4 / 150 45.6 / 30.5 / 160 67.5 / 10 / 138.5

0.50 1.5 6.75

185 200 210

11 1

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reaction. The resulting ester had an acid number of 25.4, a viscosity of 197 cSt at 38 ° C, and a percent transmission of 98/100. 1000 g of this product were used in each of the subsequent catalyst assessments, which were carried out as follows:

1000 g of the ester produced were heated to 225 ° C. under a nitrogen atmosphere, to which 0.01% by weight of catalyst had been added. Then a vacuum of 123 mm of mercury was applied to the apparatus,

Polyester prepared using the catalyst Acid index Viscosity at 38 ° C (cSt) Color (% T at 440/550 m (i)

It is obvious, from the higher kinematic viscosities obtained with the products XVa, XVb and XVc, that the present invention makes it possible to obtain more efficient and more active catalysts.

The catalyst was analyzed by Auger electronic spectroscopy by pressing the powdered catalyst on a stainless steel mesh mounted so as to make an angle of 30 °.

approximately with the electron beam. Spectra derived from normalized Auger spectra were used using a beam energy greater than 6500 eV, and a beam intensity of

1 to 4 mA to analyze the Auger L3M2.3M2.3 electron for titanium (387 eV) and the Auger KL2L2 electron for silicon (1619 eV). Each peak corresponding to titanium and silicon was scanned at least ten times, the mean value of the distance from peak to peak was determined and the ratio between the peak heights was calculated. The ratio between the peak heights of titanium and of the silicon obtained for the catalyst XVd was equal to 0.13, while this ratio was equal to 1.3 and 10.5 for the catalysts XVa and XVb respectively. With the XVc catalyst, the silicon which could possibly be present on the surface, that is to say in the first few monomolecular layers of the support, was below the detection limits of the instrument. The results obtained are certainly not quantitative, but they nevertheless prove qualitatively that a greater quantity of titanium is available on the surface of the immobilized catalysts according to the invention. These results also indicate that it is possible to almost completely coat an acid clay support by following the process according to the invention.

To demonstrate the greatest hydrolysis stability of the immobilized catalysts according to the invention, the catalysts XVc and XVd were treated with aqueous isopropanol. 54 g of each catalyst were combined with 76 g of 91% isopropyl alcohol and 135 g of water, and the mixture was heated to reflux at 84 ° C for

2 hrs. The mixture was then filtered and the catalyst was washed with isopropanol, the resulting catalysts being identified respectively XVch and XVdh. After the above treatment,

the XVch catalyst contained 38.2% by weight of bound titanium and the XVdh catalyst contained 2.8% by weight of bound titanium. The activity of these two catalysts was evaluated (0.01% by weight)

with the mixed ester prepared above in accordance with the procedure already described. The following results were obtained:

while maintaining the temperature at 225 ° C. After recovering 9.5 mm of water, the vacuum was lowered to 0.8 mm of mercury and the reaction was continued for exactly 30 min. Heating was then stopped and the vacuum was broken with nitrogen. 1.5% by weight of diatomaceous earth was added as a filter aid after the reaction mixture had cooled to 195 ° C, and the mixture was filtered. The acid number, the kinematic viscosity and the color of each polyester produced were then measured. The results are as follows:

XVa

XVb

XVc

XVd

1.1

0.8

0.6

1.4

994

1440

1740

876

95/97

93/97

92/96

93/98

Polyester prepared using the catalyst Viscosity acid index at 100 ° C (cSt)

XVch

0.8

1540

XVdh

1.3

822

It is easy to see that the XVch catalyst retains most of its activity after this treatment with water, and that the XVdh catalyst had approximately the same activity as the untreated naturally acid clay support which, when evaluation (using the same procedure), gave

a polyester having an acid number equal to 1.7 and a viscosity of 802 cSt at 38 ° C.

20 Example XVI:

20 g of the naturally acidic montmorillonite clay of Example 1.361 g of mineral oil at 70 SUS and 137 g of tetra-isopropyl titanate were charged into an 11-liter autoclave. The reaction mixture was stirred at 400 rpm and heating was started. The temperature was maintained at 200 ° C for 414 h, during which time the pressure rose to 9.8 kg / cm2 and finally stabilized at 31.5 kg / cm2. The reactor and its contents were cooled to room temperature (2.1 kg / cm2), and allowed to slowly discharge into two contiguous dry ice traps. 18.25 g of propene were recovered. The catalyst, after washing and drying, weighed 54.9 g and contained 40.7% by weight of titanium.

Example XVII:

The titanium catalyst immobilized on a support of Example I was also used as promoter of the exchange reaction (alcoholysis) between the ethyl esters of the short chain dicarboxylic acids and an oxo alcohol. For this reaction, 2585 g "" o of tridecyl alcohol and 915 g of dimethyl esters of mixed dicarboxylic acids (especially glutaric and succinic) were charged into an esterification reactor, together with 3.5 g of activated carbon, 0.70 g of H3PO2 at 50% and 0.35 g of the titanium catalyst on a support and immobilized. The mixture was stirred with heating. The collection of methanol started at about 180 ° C. and at 225 ° C, when the collection speed was almost negligible, a vacuum was applied to the apparatus and the excess tridecyl alcohol was then distilled from the reaction mixture, bringing the vacuum to 3 torr. product had, after filtration, an acid number of 0.1, a hydroxyl number so of 1.2, and contained 94% of the diester of tridecyl alcohol. This ester contained only 0.6 ppm of titanium residual, and had an excellent color (96/98), determined by the percentage of transmission (% T) at 440 and 550 mu, by spectrophotometric analysis .

55

Example XVIII:

Triethylene glycol (413 g; 5.5 equivalents) and heptanoic acid (787 g; 6.05 equivalents) were reacted by heating the mixture to 225 ° C in the presence of 0.12 g of catalyst 60 of Example I, while eliminating the water formed as a by-product. The pressure was reduced in the last stages of the reaction to facilitate the removal of the water. After almost all of the water had been removed (6 h), the reaction mixture was cooled to 100 ° C and a high vacuum (2 to 5 torr) 65 was applied while heating again to 200 ° C in 50 min. The diester had an acid number of 0.1, a hydroxyl number of 11.8, a viscosity of 82 cSt at 38 ° C, and contained less than 0.5 ppm of residual titanium, with a color (% T ) of 100/100.

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14

Similar esterifications were carried out using the catalyst of Example I. When 2-ethylhexanol and phthalic anhydride were reacted, the diester produced contained less than 1 ppm of titanium and had an excellent color . The esterification product of 1,3-butylene glycol and pelargonic acid also contained less than 1 ppm of titanium.

Example XIX:

A polyester was prepared by heating to 225 ° C 595 g of adipic acid, 449 g of propylene glycol, 39 g of pelargonic acid and 217 g of a mixture (75:25) of monocarboxylic and dicarboxylic acids, with 0 , 13 g of H3PO2, while removing the water. After the acid number had dropped to about 20, 0.13 g of the catalyst of Example I was added to the reaction mixture. A slight vacuum was applied to facilitate removal of the water which was required to complete the esterification. After the theoretical amount of water had been collected, a high vacuum (3 torr) was applied to cause the interesterification and transesterification by removal of the volatiles. After filtration, the polyester finally produced had a viscosity of 1017 cSt at 38 ° C, and contained 0.7 ppm of residual titanium.

Example XX:

Was charged and reacted according to the procedure of Example V 802 g of adipic acid, 813 g of phthalic anhydride, 695 g of propylene glycol and 1190 g of 2-ethylhexanol. The final filtered polyester obtained as product (residual titanium content 0.7 ppm) with an acid number of 0.3 and a kinematic viscosity of 531 cSt at 38 ° C.

Example XXI:

To demonstrate the possibility of recycling for a new use of the catalysts immobilized on a support according to the present invention, an immobilized catalyst was prepared using preformed spheres (4 to 5 mm) of an acidic montmorillonite clay. 10.7 g of the clay spheres and 11.1 g of tetra-isopropyl titanate in 200 g of mineral oil were combined, and the mixture was heated to 200 ° C in 3 h while collecting isopropanol and propene formed as a by-product. The dried support weighed 15.3 g and contained about 10% by weight of titanium.

The above catalyst (10 g) and 1000 g of the base semi-finished product of Example XIV were combined, and the mixture was heated to 225 ° C. under high pressure for exactly 2 h so as to cause the polyesterification. The product was cooled to 190 ° C, filtered, and the catalyst spheres were recovered, which were reused with another 1000 g of the base semi-finished product, under identical reaction conditions. The results obtained for the polyesters produced in the two experiments were as follows:

1st experience polyester 2nd experience

Acid number 0.4 0.2

Hydroxyl number 16.8 16.9 Kinematic viscosity at 38 ° C

(cSt) 1351 1407

Example XXII:

To better demonstrate the universal nature of the present process, a series of catalysts immobilized on a support has been prepared in the usual manner, the ratio of tetra-isopropyl titanate on the support being varied. The hydrocarbon used was a mineral oil and the support was montmorillonite clay. The catalysts were:

TPT catalyst / clay% of titanium bound

XXIIa 0.25 5.2

TPT catalyst / clay% of titanium bound

XXIIb

0.50

7.9

XXIIc

1.0

13.4

XXIId

1.5

20.3

These catalysts were used to cause the transesterification of the base semi-finished product of Example XIV, following the same procedure. The resulting polyesters had a respective viscosity, at 38 ° C, of 1030.994.1330 and 1440 cSt.

Example XXIII:

90 parts of alumina / silica pellets (3.2 mm) were reacted with 45 parts of tetra-isopropyl titanate in white oil (70 SUS) at 200 ° C for 1V2 h. The washed and dried catalyst pellets (50 parts) formed a fixed catalyst bed in a reactor for continuous operation. In this reactor maintained at 225 ° C. and under 1.0 mm of mercury, a mixed ester obtained by reacting adipic acid, 1,3-butylene glycol and 2-ethylhexanol was added continuously, as described in Example XIV, but reduced to an acid number of 2.2 (viscosity of 270 cSt at 38 ° C), at a rate varying between 2 and 5 ml / min, while removing the polyester at a comparable rate. After 2 h, the viscosity at 38 ° C of the product collected reached 1300 cSt. The reaction was then continued for a further 1 hour and the viscosity of the polyester produced and collected never fell below 1300 cSt. About 250 g / h of polyester were obtained.

Example XXIV:

A vanadium catalyst immobilized on a support was prepared by reacting 10 g of a naturally acidic montmorillonite clay and 15 g of tributyl vanadate in 160 g of mineral oil, by heating the reaction mixture with stirring, from temperature ambient at 250 ° C in 1% h. The distillate started to flow at about 200 ° C and a total of 6.2 ml of butanol was removed. Butene was also collected in the dry ice trap. After cooling and filtration, the product was washed with isopropanol until the filtrate had only a very pale yellow color. The final weight of the product after air drying was 14.8 g. The catalyst contained 16.1% by weight of vanadium. In exactly the same way, an immobilized zirconium catalyst was prepared. The support used for this reaction was a synthetic mixture of silica and alumina (13% Al2O3). The alumina and silica support (10.8 g) was loaded into a reactor, along with 120 g of mineral oil at 70 SUS and 10.1 g of tetrabutyl zirconate. The mixture was then gradually heated to approximately 220 ° C over approximately 3 hours, while removing the butanol and letting the gases escape. After filtration, washing and air drying, 13.25 g of a supported catalyst were obtained (7.3% by weight of zirconium). These products have been shown to be effective esterification catalysts.

Example XXV:

Methyl oleate was prepared as follows.

500 g of oleic acid, 58 g of methanol and 5% by weight (relative to the oleic acid) of the catalyst of Example I were charged into a reactor. Heating was started at 140 ° C. and a mixture of water and methanol started to distill at around 80 ° C. We started to add methanol below the surface of the mixture (29 g / h), while heating to 170 ° C. The reaction was terminated when the acid number of the reaction mixture reached about 1. The methyl oleate, after filtration with diatomaceous earth as a filter aid, had an acid number of 0 , 9 and contained less than 1 ppm titanium.

5

10

15

20

25

30

35

40

45

50

55

60

65

15

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Example XXVI:

Polyesters were prepared using 1000 g of the ester-based semi-finished product of Example XIV (% T = 98/100) with: a) 0.58 g of the catalyst of Example I, and b) 1.30 g of tetra-isopropyl titanate. The reaction mixtures contained 5

both 219 ppm titanium. A vacuum of 160 mm of mercury was applied to each apparatus, while heating at 225 ° C until 9.5 ml of water was recovered, and the pressure was then reduced to 19.6 mm of mercury and continued the reactions for 2 h, before ending them. About the same amount of distillate was recovered in the two reactions. After filtration with 1.5%

by weight of diatomaceous earth as a filter aid, the polyester (acid number = 0.5) obtained using the immobilized catalyst had a color of 95/100, while the polyester (acid number = 0.4 ) obtained using as catalyst homogeneous tetra-isopropyl titanate had a color of 60/95. It is obvious that a clear improvement in color is obtained with the process according to the invention by using the catalysts based on immobilized transition metal. On the other hand, with the polyester prepared by method b), the concentration of residual titanium was about ten times greater than with the polyester prepared by method a).

R

Claims (14)

618,353 2 1. Transition metal catalyst immobilized on a support, characterized in that it contains 3 to 60% by weight of a transition metal chosen from groups IVb, Vb and VIb, said transition metal being present on and linked to the support matrix by oxygen bridges in the form of a crosslinked polymer network in which the transition metal atoms are linked to each other by oxygen bridges. 2. Transition metal catalyst according to claim 1, further characterized in that it is a fluid powder, finely divided and stable to hydrolysis. 3. transition metal catalyst according to claim 1, characterized in that the support matrix is practically completely coated with the transition metal polymer, the support is chosen from the group comprising silica, alumina or their mixtures, and the transition metal is selected from the group comprising titanium, zirconium, hafnium and vanadium. 4. Catalyst according to claim 3, containing 5 to 50% by weight of bonded transition metal which is titanium. 5. Transition metal catalyst according to claim 1, characterized in that the support is an acid clay of the montmorillonite type. 6. Process for the preparation of a transition metal catalyst according to claim 1 by reacting a hydroxylated support with a transition metal alcoholate of formula M (OR) „Qm in which M is a transition metal chosen from the groups IVb, Vb and VIb, OR is an alkoxy radical containing from 1 to 18 carbon atoms, n is an integer of 2 with the valence of the metal M , Q is an inert group which does not react with the hydroxyl groups of the support, the alcoholate radical OR or the alcohol ROH formed during the process from this radical, and m is an integer such that n + m satisfy the valence of metal M, characterized in that the support and an excess of the transition metal alcoholate are heated, relative to the available surface hydroxyl groups, in an inert hydrocarbon and in the presence of water, to a temperature between 100 and 300 ° C, to carry out a condensation reaction of the transition metal alcoholate or its oligomer with the surface hydroxyl groups. 7. Method according to claim 6, characterized in that the ratio of transition metal alcoholate molecules to surface hydroxyl groups is greater than 1: 1 and goes up to 106: 1, and is preferably between 2 : 1 and IO2: 1, the inert hydrocarbon is an aliphatic hydrocarbon and the weight ratio of the hydrocarbon to the support is between 0.5: 1 and 50: 1, and preferably between 2: 1 and 25: 1. 8. Method according to claim 7, characterized in that all or part of the water is absorbed on the surface of the hydroxylated support. 9. Method according to claim 8, characterized in that the hydroxylated support is chosen from the group comprising silica, alumina and their mixtures. 10. Method according to claim 7, characterized in that all or part of the water is formed in situ by dehydration of the alcohols. 11. Method according to one of claims 6 to 10, characterized in that the transition metal alcoholate is tetra-isopropyl titanate or tetrabutyl titanate. 12. Method according to claim 7, characterized in that M is a metal chosen from the group comprising titanium, zirconium, hafnium and vanadium, and OR is a saturated alkoxy radical with straight or branched chain, containing 2 with 8 carbon atoms, and in that the heating is carried out at a temperature between 120 and 250 ° C in an essentially saturated aliphatic liquid hydrocarbon, having a boiling point higher than 140 ° C and that the ratio of molecules transition metal alcoholate with hydroxyl groups available on the support is between 1.5: 1 and 104: 1. 13. Use of a transition metal catalyst according to claim 1, in a process for the discontinuous, continuous or semi-continuous preparation of esters of carboxylic acids by direct esterification of a carboxylic acid or anhydride with a alcohol or by exchange of esters of a carboxylic acid ester with another carboxylic acid ester, another alcohol or another carboxylic acid, process which consists in heating the reagents in the liquid state to a temperature between 100 and 300 ° C, in the presence of at least 0.0005% by weight of said catalyst, relative to the reactants. 14. Use according to claim 13, characterized in that the support is chosen from the group comprising silica, aluminum or their mixtures, and the transition metal is chosen from the group comprising titanium, zirconium, hafnium and vanadium.