Process for producing a catalyst, catalyst produced thereby, and process for producing an ethylenically unsaturated carboxylic acid or carboxylic acid ester

Abstract

The present invention relates to a process for producing a catalyst. The process comprises the following steps: a) providing an uncalcined metal-modified porous silica support, wherein the modifier metal is selected from one or more of boron, magnesium, aluminum, zirconium, hafnium and titanium, and wherein the modifier metal is present as a mononuclear modifier metal moiety or a binuclear modifier metal moiety; b) optionally removing any solvent or liquid carrier from the modified silica support; c) optionally drying the modified silica support; d) treating the uncalcined metal-modified silica support with a catalytic metal to effect adsorption of the catalytic metal onto the metal-modified silica support; and e) calcining the impregnated silica support of step d). The present invention extends to uncalcined catalyst intermediates and a method of producing a catalyst by providing a porous silica support having separated silanol groups.

Description

[0001] The present invention relates to a process for producing a modified silica catalyst, the catalyst, and a process for producing an olefinically unsaturated carboxylic acid or carboxylic acid ester by condensation of a carboxylic acid or carboxylic acid ester with formaldehyde or a source thereof such as dimethoxymethane in the presence of such a catalyst, in particular by condensation of propionic acid or a hydrocarbyl ester thereof such as methyl propionate with formaldehyde or a source thereof in the presence of such a catalyst. The olefinically unsaturated carboxylic acid or carboxylic acid ester is in particular an α,β-unsaturated carboxylic acid or carboxylic acid ester, more particularly acrylic acid or an acrylate, such as (hydrocarbyl(alk))acrylic acid or a hydrocarbyl(hydrocarbyl(alk)) ester of acrylic acid, in particular (meth)acrylic acid or a (meth)acrylic acid hydrocarbyl ester, such as methacrylic acid (MAA) and methyl methacrylate (MMA). Thus, the present invention is particularly relevant to the production of MAA and MMA in particular. The catalyst of the present invention incorporates a modified silica support uniquely modified by a specific modifier metal and a catalytic metal.

[0002] As mentioned above, the unsaturated acid or unsaturated ester can be prepared by reaction of a carboxylic acid or carboxylic acid ester, and suitable carboxylic acids or carboxylic acid esters are the alkanoic acids (or alkanoates) of the formula R 3 -CH2-COOR 4 wherein R 3 and R 4 are each independently suitable substituents known in the field of acrylic compounds, such as hydrogen or hydrocarbyl groups, in particular lower hydrocarbyl groups containing for example 1 - 4 carbon atoms. Thus, for example, MAA or its hydrocarbyl ester, in particular MMA, can be prepared according to Reaction Sequence 1 by the catalytic reaction of propionic acid or the corresponding hydrocarbyl ester such as methyl propionate with formaldehyde as the methylene source.

[0003] R 3 -CH2–COOR 4 +HCHO -------> R 3 -CH(CH2OH)–COOR 4

[0004] and

[0005] R 3 -CH(CH2OH)–COOR 4 ------> R 3 -C(:CH2)–COOR 4 +H2O

[0006] Reaction Sequence 1

[0007] An example of Reaction Sequence 1 is Reaction Sequence 2

[0008] CH3-CH2–COOR 4+HCHO -------> CH3-CH(CH2OH)–COOR 4

[0009] CH3-CH(CH2OH)–COOR 4 ------> CH3-C(:CH2)–COOR 4 +H2O

[0010] Sequence 2

[0011] The reaction sequence above is typically achieved at elevated temperatures, generally in the range of 250 °C - 400 °C, using an acid / base catalyst. When the desired product is an ester, the reaction is typically achieved in the presence of the relevant alcohol in order to minimize the formation of the corresponding acid by hydrolysis of the ester. Additionally, for convenience, it is generally desirable to introduce formaldehyde in the form of a complex with methanol. Thus, for the production of MMA, the reaction mixture fed to the catalyst will typically consist of methyl propionate (MEP), methanol, formaldehyde, and water.

[0012] A known production method for MMA is the catalytic conversion of MEP to MMA using formaldehyde. Known catalysts for this are cesium catalysts incorporated into a support such as silica.

[0013] WO99 / 52628 discloses the preparation of a modifier metal (boron, magnesium, aluminum, zirconium, and hafnium) impregnated catalyst from mesoporous gel silica using modifier nitrates, oxynitrates, and oxides such as zirconium nitrate, followed by incorporation of cesium carbonate and calcination. An acetate solution of zirconium or zirconium and aluminum is mixed with an acetate solution of cesium and together adsorbed onto the silica support.

[0014] US6887822 teaches the option of calcining the surface of a hydrogel silica after treatment with a catalytic metal. However, it does not address the adsorption of modifier metals and how to treat such modified surfaces. Instead, zirconia is introduced by co-gelation. The document teaches that impregnation of silica dry gel beads is excluded and only illustrates hydrogel beads which apparently result in much stronger beads.

[0015] The unpublished application PCT / GB2018 / 052606 discloses the adsorption of metal organic complexes of zirconium and hafnium onto a silica support, followed by the adsorption of a catalytic metal such as cesium. Generally, a calcination step is taught after the adsorption of modifier metals, particularly in cases where the modifier is added as a complex, and an optional calcination step after the adsorption of alkali metals.

[0016] Typically, after treating a silica support with a modifier metal, a calcination step is expected to "fix" the metal before further processing. This is especially the case when organic groups are attached to the modifier metal and need to be removed.

[0017] The present inventors have now found that the catalysts produced by the present invention provide a high level of selectivity in the condensation of a methylene source such as formaldehyde with a carboxylic acid or a hydrocarbyl ester such as MEP.

[0018] Additionally, the present inventors have found that when using the processes produced with the catalysts of the present invention, it has been found that the rate of catalyst surface sintering is retarded and the loss of the surface area on which the catalytic reaction occurs during the condensation reaction is reduced.

[0019] Accordingly, the catalysts of the present invention are very effective catalysts for producing α,β-ethylenically unsaturated carboxylic acids or carboxylic acid esters by the condensation of a corresponding acid or ester with a methylene source such as formaldehyde, which catalysts provide several advantages such as a high level of selectivity and / or reduced sintering of the catalyst surface.

[0020] According to a first aspect of the present invention, there is provided a process for producing a catalyst, the process comprising the following steps:

[0021] a) providing an uncalcined metal-modified porous silica support, wherein the modifier metal is selected from one or more of B, Mg, Al, Zr, Hf, and Ti, and wherein the modifier metal is present as a mononuclear modifier metal moiety or a binuclear modifier metal moiety;

[0022] b) optionally, removing any solvent or liquid carrier from the modified silica support;

[0023] c) optionally, drying the modified silica support;

[0024] d) treating the uncalcined metal-modified silica support with a catalytic metal to effect adsorption of the catalytic metal onto the metal-modified silica support; and

[0025] e) calcining the impregnated silica support of step d).

[0026] Advantageously, by treating the uncalcined modified silica support as defined with a catalytic metal followed by subsequent calcination, improved selectivity and increased resistance to sintering are found in the catalytic production of ethylenically unsaturated carboxylic acids or carboxylic acid esters by the condensation of a carboxylic acid or carboxylic acid ester with formaldehyde or its source.

[0027] In the present invention, it has been found that controlling the nuclearity of the modifier metal moiety is surprisingly advantageous as it controls the proximity of adjacent modifier metal moieties on the silica.

[0028] According to a second aspect of the present invention, there is provided an uncalcined catalyst intermediate comprising an uncalcined porous silica support modified with a modifier metal selected from one or more of B, Mg, Al, Zr, Hf and Ti, wherein the modifier metal is present as a mononuclear modifier metal moiety or a binuclear modifier metal moiety and the catalytic metal is adsorbed on the uncalcined modified silica support.

[0029] The silica of the first or second aspect may be provided as a co-gel of a modifier metal oxide and silica, or as a modified silica in which the modifier metal is adsorbed on the silica surface.

[0030] Surprisingly, the catalysts of the present invention provide improved selectivity and increased resistance to sintering.

[0031] Surprisingly, it has been found that increasing the calcination temperature provides further improved selectivity.

[0032] According to a third aspect of the present invention, there is provided a catalyst obtained by the process of the first aspect or a further aspect of the present invention.

[0033] According to a fourth aspect of the present invention, there is provided a catalyst obtainable by the process of the first aspect or a further aspect of the present invention.

[0034] According to a further aspect of the present invention, there is provided a method of producing a modified silica support for use in one or more of the catalysts according to the claims.

[0035] Modifier metal complex

[0036] Typically, when the modifier metal is added as an adsorbate, it may be added as a mononuclear modifier metal compound or a binuclear modifier metal compound. Typically, the compound is a complex and, before and / or after adsorption, the ligands in the coordination sphere of the compound generally have sufficient size to prevent further oligomerization of the modifier metal and / or a significant increase in the nuclearity of the complex. Generally, an increase in nuclearity up to the dimer may be acceptable. Typically, the modifier metal complex is an organic complex having one or more organic polydentate chelating ligands or, alternatively, a complex having sterically bulky monodentate ligands that effectively stabilize the nuclearity.

[0037] Typically, at least 25% of the modifier metal is present on the support in the form of mononuclear modifier moieties or dinuclear modifier moieties, either before or after calcination. Thus, typically, at least 25% of the modifier metal is present on the support in the form of modifier metal moieties derived from mononuclear metal compounds or dinuclear metal compounds.

[0038] Typically, the mononuclear modifier metal or dinuclear modifier metal contacts the silica support as a mononuclear modifier metal compound or dinuclear modifier metal compound in solution to effect adsorption of the modifier metal onto the support.

[0039] Typically, the modifier metal compound is mononuclear or dinuclear, more preferably mononuclear.

[0040] It has surprisingly been found that clusters of modifier metals with more than 2 metal atoms dispersed throughout a support such as a hydrogel support reduce the reaction selectivity for producing an α,β-ethylenically unsaturated carboxylic acid or carboxylic acid ester by condensation of a corresponding acid or ester with a methylene source such as formaldehyde. It has also surprisingly been found that such large clusters increase sintering of the modified silica particles relative to mononuclear moieties or dinuclear moieties, thereby reducing the surface area, which reduces the strength of the catalyst and the catalyst lifetime before the activity becomes unacceptably low. In addition, depending on the nature of the clusters of modifier metals, the selectivity is often lower.

[0041] Advantageously, when at least a portion of the modifier metal incorporated into the modified silica of the above aspects of the present invention is derived from a mononuclear modifier metal cation source or a dinuclear modifier metal cation source at the beginning of the formation of the modified silica, improved reaction selectivity and / or a reduced sintering rate at the catalyst surface have been found during the production of an α,β-ethylenically unsaturated carboxylic acid or carboxylic acid ester.

[0042] Typically, the modifier metal is selected from zirconium, hafnium, and titanium.

[0043] Typically, the metal compound is a complex comprising two or more chelating ligands, preferably 2, 3, or 4 chelating ligands. The chelating ligands herein can be bidentate, tridentate, tetradentate, or polydentate. However, the compound can also comprise bulky monodentate ligands that are also effective for effectively spacing the modifier metals on the silica surface as set forth herein.

[0044] Typically, the metal complex is tetracoordinate, pentacoordinate, hexacoordinate, heptacoordinate, or octacoordinate.

[0045] Advantageously, the size of the ligands in the coordination sphere of the metal compound, such as the size of the chelating ligand, results in a more dispersed modifier metal than the same modifier metal with simple counterions such as nitrates, acetates, or oxynitrates. It has been found that smaller metal salt adsorption results in clustering of the modifier metal after heat treatment or calcination, which in turn reduces the selectivity of the catalyst and the sintering resistance of the catalyst.

[0046] Typically, herein, the modifier metal is an adsorbate adsorbed on the surface of the silica support of the catalyst. The adsorbate can be chemisorbed or physisorbed onto the surface of the silica support as its compound, typically, the adsorbate is chemisorbed on the surface of the silica support.

[0047] Suitable chelating ligands herein can be non-labile ligands, which are optionally selected from molecules having a lone pair and containing an oxygen atom or a nitrogen atom capable of forming a 5- or 6-membered ring with a modifier metal atom. Examples include diketones, diimines, diamines, diols, dicarboxylic acids or their derivatives such as esters, or molecules having two different such functional groups, and in either case, the corresponding N or O and N atoms or O atoms are separated by 2 or 3 atoms to form a 5- or 6-membered ring. Examples include pentane-2,4-dione, esters of 3-oxobutyric acid with fatty alcohols containing 1-4 carbon atoms such as ethyl 3-oxobutyrate, propyl 3-oxobutyrate, isopropyl 3-oxobutyrate, n-butyl 3-oxobutyrate, tert-butyl 3-oxobutyrate, heptane-3,5-dione, 2,2,6,6-tetramethyl-3,5-heptanedione, 1,2-ethanediol, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, 1,2-butanediol, 1,2-diaminoethane, ethanolamine, 1,2-diamino-1,1,2,2-tetracarboxylate, 2,3-dihydroxy-1,4-succinate, 2,4-dihydroxy-1,5-glutarate, salts of 1,2-dihydroxybenzene-3,5-disulfonate, diethylenetriaminepentaacetic acid, nitrilotriacetic acid, N-hydroxyethylethylenediaminetriacetic acid, N-hydroxyethyliminodiacetic acid, N,N-dihydroxyethylglycine, oxalic acid and its salts. Pentane-2,4-dione, heptane-3,5-dione, 2,2,6,6-tetramethyl-3,5-heptanedione, ethyl 3-oxobutyrate and tert-butyl 3-oxobutyrate are most preferred. Smaller bidentate chelating ligands having, for example, a total of less than 10 carbons and / or heteroatoms enable the formation of small complexes, which, compared to larger ligands, may allow higher concentrations to be deposited on the surface of silica. Thus, the mononuclear or dinuclear modifier metal cation source herein can be in the form of a complex of a modifier metal with such a smaller chelating ligand, preferably with at least one such ligand. Such compounds can include labile ligands such as, for example, solvent ligands in an alcohol solvent, alkoxide ligands such as ethoxide or propoxide, etc.

[0048] Chelating ligands are generally non-labile ligands. A non-labile ligand means a ligand that coordinates with a modifier metal and is not removed by adsorption of the modifier metal onto the silica surface. Thus, prior to treating the silica surface with a modifier metal, the non-labile ligand typically coordinates with the modifier metal in solution. For the avoidance of doubt, the non-labile ligand is typically removed by appropriate treatment of the silica surface after adsorption of the modifier metal.

[0049] Select the size of the chelating ligand so as to space the modifier metal atoms on the silica surface to prevent their association during catalyst production.

[0050] Optionally, a modifier metal complex with a bulky monodentate ligand can be used to prevent oligomerization of the metal complex. Typical ligands used in the complex include, but are not limited to, alkoxides such as tert-butoxide or 2,6-di-tert-butylphenoxide with suitable organic groups, amides such as dialkylamides (methyl, ethyl, and higher straight-chain and branched hydrocarbon groups) and bis(trimethylsilyl)amido complexes with suitable organic groups, and hydrocarbyl ligands such as 2,2-dimethylpropyl (neopentyl) ligands with suitable organic groups.

[0051] Typically, the silica support has isolated silanol groups, and by contacting the silica support with a modifier metal substance, the modifier metal is adsorbed onto the surface of the silica support via reaction with the silanol groups.

[0052] Preferably, the adsorbed or co-gelled modifier metal cations are sufficiently spaced from each other by the modifier metal compounds to substantially prevent their oligomerization during subsequent processing steps, and more preferably, to prevent their dimerization, trimerization or oligomerization with adjacent modifier metal cations, said subsequent processing steps such as impregnation with a catalytic metal, or optionally, subsequent calcination.

[0053] Typically, at least 25%, more typically at least 30%, such as at least 35%, more preferably at least 40%, such as at least 45%, most suitably at least 50%, such as at least 55%, for example at least 60% or 65%, and most preferably at least 70%, such as at least 75% or 80%, more typically at least 85%, most typically at least 90%, particularly at least 95% of the modifier metal substance contacting the silica support in the contacting step is a mononuclear and / or dinuclear substance.

[0054] According to a fifth aspect of the present invention, there is provided a method of producing a catalyst according to any aspect herein or otherwise, the method comprising the steps of:

[0055] a) providing a porous silica support having isolated silanol groups;

[0056] b) Treat the porous silica support with a mononuclear modifier metal compound or a dinuclear modifier metal compound such that the modifier metal is adsorbed onto the surface of the silica support by reaction with the isolated silanol groups, wherein the adsorbed modifier metal atoms are sufficiently separated from one another to substantially prevent oligomerization with adjacent modifier metal atoms before and / or after calcination, and more preferably, are sufficiently separated from one another to substantially prevent dimerization or trimerization of the adsorbed modifier metal atoms with their adjacent modifier metal atoms, wherein the modifier metal is selected from B, Mg, Al, Zr, Hf, and Ti;

[0057] c) Optionally remove any solvent or liquid carrier from the modified silica support;

[0058] d) Optionally dry the modified silica support

[0059] e) Treat the uncalcined modified silica support with a catalytic alkali metal to effect adsorption of the catalytic alkali metal onto the modified silica support; and

[0060] f) Calcinate the impregnated silica support of step e).

[0061] Preferably, the separation of the modifier metal atoms is affected by the size of the modifier metal compound.

[0062] Typically, the silica support contains isolated silanol groups (-SiOH) at a level of <2.5 groups per nm 2 of the silica support surface.

[0063] Preferably, the modifier metal herein is a solution of the compound of the modifier metal such that the compound is in solution when contacted with the support to effect adsorption onto the support.

[0064] Typically, the solvent for the solution is water or different from water.

[0065] Typically, the solvent is an organic solvent such as toluene or heptane. Additionally, the solvent can be an aliphatic solvent or an aromatic solvent. Additionally still, the solvent can be a chlorinated solvent such as dichloromethane. More typically, the solvent is an aliphatic alcohol, typically selected from C1-C6 alkanols such as methanol, ethanol, propanol, isopropanol, butanols, pentanols, and hexanols, and more typically, methanol, ethanol, or propanols.

[0066] The concentration of isolated silanol groups on the silica support prior to modifier metal adsorption is preferably controlled by calcination or other suitable methods known to those skilled in the art. Methods for identifying silanols include, for example, L T Zhuravlev, in "Colloids and Surfaces: Physicochemical and Engineering Aspects, Volume 173, pages 1 - 38, 2000", which describes four different forms of silanols that can coexist on the silica surface: isolated silanols, geminal silanols, vicinal silanols, and internal silanols. Isolated silanol groups are most preferred. Isolated silanol groups can be identified by infrared spectroscopy as a narrow absorption peak at 3730 cm -1 - 3750 cm -1 while other silanols show a broad peak between 3460 cm -1 and 3715 cm -1 (see "The Surface Properties of Silicas", edited by Andre P Legrand, John Wiley and Sons, 1998 (ISBN 0 - 471 - 95332 - 6), pages 147 - 234).

[0067] The modified silica support according to any aspect herein may contain isolated silanol groups (-SiOH) at a level of < 2.5 groups per nm 2 . Typically, the modified support contains isolated silanol groups (-SiOH) at a level of > 0.1 and < 2.5 groups per nm 2 , more preferably at a level from 0.2 to 2.2 groups per nm 2 , and most preferably at a level from 0.4 to 2.0 groups per nm 2 .

[0068] Additionally, the present invention extends to a process, catalyst, or catalyst intermediate according to any aspect herein, wherein the support contains the modifier metal moiety present on the support and present at a level of < 2.5 moieties per nm 2 .

[0069] Typically, the support contains at a level of > 0.025 and < 2.5 groups per nm 2 , more preferably at a level from 0.05 to 1.5 groups per nm 2 , and most preferably at a level from 0.1 to 1.0 moieties per nm2 The horizontal modifier metal part.

[0070] The concentration of preferably isolated silanol groups determines the maximum number of modifier metals that can be effectively determined, since the distribution of silanol sites will generally be uniform. The isolated silanol concentration for producing the modified silica support according to the present invention can be less than 2.5 groups per nm 2 , more typically, less than 2.5 groups per nm 2 , most typically, less than 1.5 groups per nm 2 , particularly, less than 0.8 groups per nm 2 . A suitable range of silanol concentration for producing the modified silica support can be 0.1 - 4.6 silanol groups per nm 2 , more preferably 0.15 - 2.5 silanol groups per nm 2 , most preferably 0.2 - 1.0 silanol groups per nm 2 .

[0071] The concentration of the modifier metal complex should be set at a level that prevents significant formation of a double layer etc. on the surface of the support, which significant formation would lead to interaction of the modifier metal with the metal. In addition, filling of the gaps in the initial monolayer that may lead to weak adsorption of the modifier metal away from the isolated silanol sites should also be avoided to prevent interaction with adjacent strongly adsorbed modifier metals. The typical concentration range of the modifier metal of the present invention can be as set forth herein.

[0072] Typically, when the modifier metal complex contacts the support to effect adsorption of the complex onto the support, at least 30% such as at least 35%, more preferably at least 40% such as at least 45%, most suitably at least 50% such as at least 55%, for example at least 60% or 65%, and most preferably at least 70% such as at least 75% or 80%, more typically at least 85%, most typically at least 90%, particularly at least 95%, of the modifier metal in the modifier metal complex is a mononuclear modifier metal compound and / or a binuclear modifier metal compound.

[0073] A suitable method for treating silica to provide isolated silanol groups at the levels specified herein is by calcination. However, other techniques such as hydrothermal treatment or chemical dehydration are also possible. US5583085 teaches the chemical dehydration of silica with dimethyl carbonate or ethylene dicarbonate in the presence of an amine base. US4357451 and US4308172 teach chemical dehydration by chlorination with SOCl2, followed by dechlorination with H2 or ROH, and then dechlorination with oxygen in a dry atmosphere. Chemical dehydration can provide up to 100% silanol removal, as compared to a minimum of 0.7 / nm by heat treatment. 2 Thus, in some cases, chemical dehydration can provide greater latitude for silanol group control.

[0074] The term isolated silanol (also referred to as monomeric silanol) is well known in the art and distinguishes this group from vicinal silanol or geminal silanol or internal silanol. Suitable methods for determining the incidence of isolated silanol include surface sensitive infrared spectroscopy and 1 H NMR or 31 Si NMR.

[0075] Preferably, the silica support is dried or calcined prior to treatment with the modifier metal.

[0076] Silica

[0077] Typically, the modified silica support is a xerogel. The gel can also be a hydrogel or an aerogel.

[0078] The gel can also be a silica-modifier metal oxide cogel. The silica gel can be formed by any of a variety of techniques known to those skilled in the art of gel formation, such as those mentioned herein. In this case, the modifier metal oxide can also be distributed through the matrix of the silica as well as its surface. However, typically, the modified silica gel is produced by a suitable adsorption reaction. A suitable technique is to adsorb the relevant modifier metal compound onto a silica gel such as a silica xerogel to form a modified silica gel having the relevant mononuclear modifier metal moiety or binuclear modifier metal moiety.

[0079] Prior to treatment with the modifier metal adsorbate, the silica can be in the form of a gel. At the start of the modification, the gel can be in the form of a hydrogel, a xerogel or an aerogel. Typically, the silica support is a hydrogel or a xerogel, most preferably a xerogel.

[0080] As mentioned, methods for preparing silica are well known in the art, and some such methods are described in The Chemistry of Silica: Solubility, Polymerisation, Colloid and Surface Properties and Biochemistry of Silica, Ralph K Iler, 1979, John Wiley and Sons Inc., ISBN 0-471-02404-X and references therein.

[0081] Typically, the silica component of the modified silica support can form 80 wt% - 99.9 wt% of the modified support, more typically 85 wt% - 99.8 wt%, and most typically 90 wt% - 99.7 wt%.

[0082] Porous silica supports typically have a pore size range between mesopores and macropores, where the average pore size is between 2 nm and 1000 nm, more preferably between 3 nm and 500 nm, and most preferably between 5 nm and 250 nm. The macropore size (greater than 50 nm) can be determined by mercury intrusion porosimetry using NIST standards, while the Barrett-Joyner-Halenda (BJH) analysis using liquid nitrogen at 77 K is used to determine the pore size of the mesopores (2 nm - 50 nm). The average pore size is the pore volume weighted average with respect to the pore size distribution.

[0083] Surprisingly, it has also been found that preparing a modified silica support by co-gelation of the xerogel and then performing steps b) to e) of the first aspect of the present invention also produces a catalyst with improved selectivity and increased sinter resistance.

[0084] Additionally, according to the sixth aspect of the present invention, there is provided a catalyst comprising an intermediate according to the second aspect of the present invention, wherein the uncalcined intermediate has been calcined.

[0085] Catalytic metal

[0086] Generally, herein, a catalytic alkali metal is an adsorbate adsorbed on the surface of the modified silica support of the catalyst. The adsorbate can be chemisorbed or physically adsorbed onto the surface of the modified silica support. Typically, the adsorbate is chemisorbed on the surface of the modified silica support.

[0087] The catalytic metal in this text is a metal different from the modifier metal. Preferably, the catalytic metal can be selected from one or more alkali metals. Typically, the catalytic alkali metal is selected from cesium, potassium or rubidium, more preferably cesium.

[0088] Suitably, a catalytic metal such as cesium can be present in the catalyst at a level of at least 1 mol / 100 (silicon + modifier metal) mol, more preferably at least 1.5 mol / 100 (silicon + modifier metal) mol, most preferably at least 2 mol / 100 (silicon + modifier metal) mol. The level of the catalytic metal can be up to 10 mol / 100 (silicon + modifier metal) mol in the catalyst, more preferably up to 7.5 mol / 100 (silicon + modifier metal) mol in the catalyst, most preferably up to 5 mol / 100 (silicon + modifier metal) mol in the catalyst.

[0089] Preferably, the level of the catalytic metal in the catalyst is in the range from 1 mol - 10 mol / 100 (silicon + modifier metal) mol, more preferably 2 mol - 8 mol / 100 (silicon + modifier metal) mol, most preferably 2.5 mol - 6 mol / 100 (silicon + modifier metal) mol in the catalyst.

[0090] Alternatively, the catalyst can have a wt% of the catalytic metal in the range of 1 wt% to 22 wt% in the catalyst, more preferably 4 wt% to 18 wt%, most preferably 5 wt% to 13 wt%. These amounts will apply to all alkali metals, but especially cesium.

[0091] Thus, typically, the molar ratio of catalytic metal:modifier metal in the catalyst is at least 1.4 or 1.5:1, preferably it is in the range of 1.4 to 5:1, such as 1.5 to 4.0:1, particularly 1.5 to 3.6:1. In this regard, typically, the catalytic metal is cesium. Generally, in this text, the catalytic metal exceeds the amount required to neutralize the modifier metal.

[0092] Preferably, the catalytic metal is present in the range of 0.5 mol / mol - 7.0 mol / mol of the modifier metal, more preferably 1.0 mol / mol - 6.0 mol / mol of the modifier metal, most preferably 1.5 mol / mol - 5.0 mol / mol of the modifier metal.

[0093] Calcination

[0094] Those skilled in the art will understand that the catalytic metal of the present invention can be added to the modified silica support by any suitable means. After the catalytic metal compound is deposited on the support, the catalytic metal is fixed to the support by calcination. The process of calcination is well known to those skilled in the art.

[0095] In the preferred calcination of the catalyst, the temperature is at least 450 °C, more preferably at least 475 °C, most preferably at least 500 °C, particularly at least 600 °C, and more particularly above 700 °C. Typically, the calcination temperature ranges from 400 °C to 1000 °C, more typically from 500 °C to 900 °C, and most typically from 600 °C to 850 °C.

[0096] The calcination atmosphere should generally contain some oxygen, but can be an inert atmosphere or in vacuo, suitably 1% - 30% oxygen, and most suitably 2% - 20% oxygen. Typically, the calcination time can be between 0.01 hours and 100 hours, suitably 0.5 hours - 40 hours, and most suitably 1 hour - 24 hours.

[0097] General process

[0098] Those skilled in the art will understand that the catalytic metal can be added to the modified silica by any suitable means. Typically, to produce the modified silica catalyst, the modified silica is contacted with the catalytic metal.

[0099] Typically, to produce the catalyst, the modified silica support is contacted with a 100% aqueous solution of the catalytic metal or an acidic, neutral or basic aqueous solution containing the catalytic metal in the form of a salt of the catalytic metal and a base, such as cesium. Alternatively, the support can be contacted with a water-miscible solution of the catalytic metal salt in an organic solvent. Preferred solvents are alcohols such as methanol, ethanol, propanol and isopropanol, preferably methanol. The most preferred solvent is methanol. Most preferably, the catalytic metal is added as a salt solution in methanol. Low levels of water can be present in the solution, typically up to 20 vol%.

[0100] Typically, during this stage of the catalyst production process, the conditions of temperature, contact time and pH are such as to allow impregnation of the modified silica support with the catalytic metal to form the modified silica-supported catalyst.

[0101] Typical temperature conditions for this step are between 5 °C and 95 °C, more typically between 10 °C and 80 °C, and most typically between 20 °C and 70 °C. The temperature for this step can be at least 5 °C, more typically at least 10 °C, and most typically at least 20 °C.

[0102] For this step, the typical contact time between the modified support and the solution containing the catalytic metal can be between 0.05 hours and 48 hours, more typically between 0.1 hours and 24 hours, and most typically between 0.5 hours and 18 hours. The contact time can be at least 0.05 hours, more typically at least 0.1 hours, and most typically at least 0.5 hours.

[0103] The concentration of the catalytic metal salt solution for this step depends on many factors, including the solubility limit of the catalytic metal compound, the porosity of the modified silica support, the desired loading of the catalytic metal on the support, and the method of addition, including the amount of liquid used to impregnate the support, the pH, and the choice of catalytic metal compound. The concentration in the solution is preferably determined experimentally.

[0104] Suitable salts of catalytic metals for incorporating the catalytic metal can generally be selected from one or more of the group consisting of formates, acetates, propionates, bicarbonates, chlorides, nitrates, hydroxides, and carbonates, more typically hydroxides, acetates, or carbonates, and most typically hydroxides and / or carbonates. During impregnation, the pH can be controlled by adding ammonia and the metal compound, or by using a suitable catalytic metal compound such as a formate, carbonate, acetate, or hydroxide, more preferably a hydroxide or carbonate, alone, in combination, or with a suitable carboxylic acid in all cases. At the end of impregnation, it is most important to control the pH within a preferred range to achieve satisfactory adsorption. Most typically, these salts can be incorporated using an alkaline solution of the salt. If the salt itself is not alkaline, a suitable base such as ammonium hydroxide can be added. Since hydroxide salts are inherently alkaline, it is convenient to prepare a mixture of one or more of the above salts with a hydroxide salt of a specific catalytic metal such as cesium.

[0105] The addition of the catalytically active metal can be carried out by the methods described above, or can be by any other standard method for impregnating a catalyst support such as a xerogel support, such as using water or a solvent different from water such as an alcohol, suitably methanol, ethanol, propanol, or isopropanol, or using the incipient wetness method, where only enough solution is added to the xerogel support to fill the pores of the xerogel support. In this case, the concentration of the catalytically active metal can be calculated so as to introduce a target amount of the catalytically active metal into the xerogel support material rather than providing an excess of a lower concentration solution. The addition of the catalytically active metal can utilize any preferred method known in the art.

[0106] The drying of the modified silica before calcination can be carried out in the temperature range of 20 °C - 200 °C, more typically 30 °C - 180 °C, and most typically 40 °C - 150 °C. The drying of the modified silica before calcination can be carried out at atmospheric pressure or sub-atmospheric pressure in the range of 0.001 bar - 1.01 bar. The drying of the modified silica can also be achieved in a fixed bed or fluidized bed under an inert gas flow. The drying time can range between 0.1 hour - 24 hours, more typically between 0.5 hour - 12 hours, and most typically between 1 hour and 6 hours.

[0107] Vacuum drying at a lower temperature or fluidized bed drying with an inert gas is a suitable technique.

[0108] General properties

[0109] The modifier metal and catalytic metal adsorbates in the final catalyst are typically metal oxide moieties.

[0110] Modifier metal

[0111] Typically, the modifier metal is present in the modified silica support in an effective amount to reduce sintering and improve the selectivity of the catalyst. Typically, at least 30%, such as at least 35%, more preferably at least 40%, such as at least 45%, most suitably at least 50%, such as at least 55%, for example at least 60% or 65%, and most preferably at least 70%, such as at least 75% or 80%, more typically at least 85%, most typically at least 90%, particularly at least 95%, of the modifier metal in the modified silica support is in the mononuclear metal moiety or binuclear metal moiety, or is derived from a mononuclear or binuclear modifier metal complex with one or more chelating ligands at such a level at the beginning of the formation of the modified silica.

[0112] Typically, the modifier metal is uniformly distributed over the entire support surface.

[0113] Preferably, the level of the modifier metal present in the modified silica or catalyst can be up to 7.6×10 -2 mol / mol silica, more preferably up to 5.9×10 -2 mol / mol silica, and most preferably up to 3.5×10 -2 mol / mol silica. Typically, the level of such a metal is between 0.067×10 -2 mol / mol silica and 7.3×10 -2 mol / mol silica, more preferably between 0.13×10 -2 mol / mol silica and 5.7×10-2 between 0.2×10 -2 mol / mol silica, and most preferably between 0.2×10 -2 mol / mol silica and 3.5×10 -2 mol / mol silica. Typically, the level of modifier metal present is at least 0.1×10 -2 mol / mol silica, more preferably at least 0.15×10 -2 mol / mol silica, and most preferably at least 0.25×10

[0114] Preferably, the %w / w level of modifier metal will depend on the metal but can be up to 20% w / w of the modified silica support, more preferably up to 16% w / w, most preferably up to 11% w / w. Typically, the level of modifier metal is between 0.02% - 20% w / w of the modified silica support, more preferably between 0.1% - 15% w / w, and most preferably between 0.15% - 10% w / w. Typically, the level of modifier metal is at least 0.02% w / w of the modified silica support, such as 0.25% w / w, for example 0.4% w / w, more typically at least 0.5% w / w, most typically at least 0.75% w / w.

[0115] Catalyst

[0116] Typically, the catalyst of the present invention can be in any suitable form. A typical embodiment is in the form of discrete particles. Typically, in use, the catalyst is in the form of a fixed bed of catalyst. Alternatively, the catalyst can be in the form of a fluidized bed of catalyst. Another alternative is a monolith reactor.

[0117] In the case where the catalyst is used in the form of a fixed bed, it is desirable that the supported catalyst is formed into particles, aggregates or shaped units, such as spheres, cylinders, rings, saddles, stars, poly-lobes prepared by granulation or extrusion, typically having a maximum size and a minimum size in the range of 1 mm to 10 mm, more preferably having an average size greater than 2 mm such as greater than 2.5 mm or 3 mm. The catalyst is also effective in other forms, for example, powders or beads of the same size as indicated. In the case where the catalyst is used in the form of a fluidized bed, it is desirable that the catalyst particles have a maximum size and a minimum size in the range of 10 μm - 500 μm, preferably 20 μm - 200 μm, most preferably 20 μm - 100 μm.

[0118] The average pore volume of the catalyst particles can be less than 0.1 cm 3 / g, but is typically in the range of 0.1 cm 3 / g - 5 cm 3 / g, as measured by absorption of a fluid such as water. However, microporous catalysts with very low porosity are not most preferred as they may inhibit the movement of reagents through the catalyst, and a more preferred average pore volume is between 0.2 cm 3 / g - 2.0 cm 3 / g. Alternatively, the pore volume can be measured by a combination of nitrogen adsorption at 77K and mercury porosimetry. A Micromeritics TriStar surface area and porosity analyzer is used to determine the pore volume, as in the case of surface area measurement, and the same criteria are employed.

[0119] Catalytic process

[0120] According to a seventh aspect of the present invention, there is provided a process for producing an ethylenically unsaturated carboxylic acid or carboxylic ester, typically an α,β-ethylenically unsaturated carboxylic acid or carboxylic ester, the process comprising the step of contacting formaldehyde or a suitable source thereof with a carboxylic acid or carboxylic ester in the presence of a catalyst and optionally in the presence of an alcohol, wherein the catalyst is any other aspect of the present invention as defined herein.

[0121] Advantageously, it has also been found that a catalyst comprising modified silica as defined herein and comprising a catalytic metal is a very effective catalyst for producing an α,β-ethylenically unsaturated carboxylic acid or carboxylic ester by condensation of a corresponding acid or ester with a methylene source such as formaldehyde, the catalyst having reduced sintering of the catalyst surface, improved selectivity and providing a high catalyst surface area. In particular, enhanced performance has been found when the modified silica support is uncalcined prior to treatment with the catalytic metal. Additionally, the use of certain metal complexes to incorporate modifier metals onto the support by adsorption provides a more dispersed distribution of mononuclear or binuclear modifier metal moieties.

[0122] As used herein, the term "suitable source thereof" in relation to formaldehyde means that free formaldehyde can be formed in situ from the source under the reaction conditions, or that the source can act as an equivalent of free formaldehyde under the reaction conditions, e.g. the source can form the same reaction intermediate as formaldehyde such that an equivalent reaction occurs.

[0123] A suitable source of formaldehyde can be a compound of formula (I):

[0124]

[0125] wherein R 5and R 6 are independently selected from C1-C 12 hydrocarbon or H, X is O, n is an integer from 1 to 100, and m is 1.

[0126] Typically, R 5 and R 6 are independently selected from C1-C 12 alkyl, alkenyl or aryl as defined herein, or H, more preferably C1-C 10 alkyl or H, most preferably C1-C6 alkyl or H, in particular, methyl or H. Typically, n is an integer from 1 to 10, more preferably 1 to 5, in particular 1-3.

[0127] However, other sources of formaldehyde can also be used, including trioxane.

[0128] Thus, suitable sources of formaldehyde also include any equilibrium composition that can provide a source of formaldehyde. Such examples include, but are not limited to, dimethoxymethane; trioxane; polyformaldehyde R 1 -O-(CH2-O) i -R 2 where R 1 and / or R 2 is a hydrocarbon group or hydrogen, i = 1 to 100; paraformaldehyde; formalin (formaldehyde, methanol, water); and other equilibrium compositions such as mixtures of formaldehyde, methanol and methyl propionate.

[0129] Polyformaldehyde is a higher formal or hemiacetal of formaldehyde and methanol, CH3-O-(CH2-O) i -CH3 (“formal-i”) or CH3-O-(CH2-O) i -H (“hemiacetal-i”), where i = 1 to 100, preferably 1-5, in particular 1-3, or other polyformaldehydes having at least one non-methyl end group. Thus, the source of formaldehyde can also be a polyformaldehyde of the formula R 31 -O-(CH2-O-) i R 32 where R 31 and R 32 can be the same group or different groups, and at least one is selected from C1-C 10 hydrocarbon group, such as R 31 = isobutyl and R 32 = methyl.

[0130] Generally, suitable sources of formaldehyde are selected from dimethoxymethane; lower hemiacetals of formaldehyde and methanol, CH3-O-(CH2-O) i-H, where i = 1 - 3; formalin; or a mixture containing formaldehyde, methanol, and methyl propionate.

[0131] Typically, the term formalin refers to a mixture of formaldehyde:methanol:water in a ratio of 25% to 65%:0.01% to 25%:25% to 70% by weight. More typically, the term formalin refers to a mixture of formaldehyde:methanol:water in a ratio of 30% to 60%:0.03% to 20%:35% to 60% by weight. Most typically, the term formalin refers to a mixture of formaldehyde:methanol:water in a ratio of 35% to 55%:0.05% to 18%:42% to 53% by weight.

[0132] Typically, the mixture containing formaldehyde, methanol, and methyl propionate contains less than 5% by weight of water. More suitably, the mixture containing formaldehyde, methanol, and methyl propionate contains less than 1% by weight of water. Most suitably, the mixture containing formaldehyde, methanol, and methyl propionate contains 0.1% to 0.5% by weight of water.

[0133] According to an eighth aspect of the present invention, there is provided a process for preparing an ethylenically unsaturated acid or ester, the process comprising, in the presence of a catalyst according to any aspect of the present invention and optionally in the presence of an alkanol, reacting an alkanoic acid or alkanoic acid ester of the formula R 1 -CH2-COOR 3 with formaldehyde or a suitable source of formaldehyde of formula (I) as defined below:

[0134]

[0135] where R 5 is methyl and R 6 is H;

[0136] X is O;

[0137] m is 1;

[0138] and n is any value between 1 and 20 or any mixture of these values;

[0139] where R 1 is hydrogen or a hydrocarbyl group having 1 to 12, more suitably 1 to 8, most suitably 1 to 4 carbon atoms, and R 3 can also independently be hydrogen or a hydrocarbyl group having 1 to 12, more suitably 1 to 8, most suitably 1 to 4 carbon atoms.

[0140] Accordingly, the present inventors have found that the production of the catalyst according to the present invention can surprisingly improve the selectivity for the condensation of a methylene source such as formaldehyde with a carboxylic acid or a hydrocarbyl ester such as methyl propionate to form an ethylenically unsaturated carboxylic acid. Further, during the condensation reaction, the sintering rate of the catalyst surface is significantly and surprisingly reduced.

[0141] Accordingly, a particular process in which the catalyst of the present invention has been found to be particularly advantageous is the condensation of formaldehyde with methyl propionate in the presence of methanol to produce MMA.

[0142] In the case of producing MMA, the catalyst is typically contacted with a mixture comprising formaldehyde, methanol and methyl propionate.

[0143] The process of the seventh or eighth aspect of the present invention is particularly suitable for producing acrylic acid and hydrocarbyl acrylates and their hydrocarbyl esters, as well as methylene-substituted lactones. Suitable methylene-substituted lactones include 2-methylene-valerolactone and 2-methylene-butyrolactone derived from valerolactone and butyrolactone respectively. Suitable (hydrocarbyl)acrylic acids and their esters are (C 0-8 hydrocarbyl)acrylic acid or hydrocarbyl (C 0-8 hydrocarbyl)acrylate, typically derived from the reaction of the corresponding alkanoic acid or its ester with a methylene source such as formaldehyde in the presence of a catalyst, suitably, methacrylic acid, acrylic acid, methyl methacrylate, ethyl acrylate or butyl acrylate are produced from propionic acid or methyl propionate respectively, more suitably, methacrylic acid or particularly, methyl methacrylate (MMA). Thus, in the production of methyl methacrylate or methacrylic acid, the preferred ester or acid of the formula R 1 -CH2-COOR 3 are methyl propionate or propionic acid respectively, and thus the preferred alkanol is methanol. However, it will be understood that in the production of other ethylenically unsaturated acids or esters, the preferred alkanol or acid will be different.

[0144] The reaction of the present invention can be a batch reaction, a semi-batch reaction or a continuous reaction.

[0145] In the process of the seventh or eighth aspect of the present invention, typical conditions of temperature and gauge pressure are between 100 °C and 400 °C, more preferably between 200 °C and 375 °C, most preferably between 275 °C and 360 °C; and / or between 0.001 MPa and 1 MPa, more preferably between 0.03 MPa and 0.5 MPa, most preferably between 0.03 MPa and 0.3 MPa. The typical residence time of the reactants in the presence of the catalyst is between 0.1 second and 300 seconds, more preferably between 1 second and 100 seconds, most preferably between 2 seconds and 50 seconds, particularly between 3 seconds and 30 seconds.

[0146] The amount of the catalyst used in the process producing the product in the present invention is not necessarily critical, and will be determined by the practice of the process using it. However, the amount of the catalyst will usually be selected to achieve optimal selectivity and the yield of the product and an acceptable operating temperature. However, the technician will understand that the minimum amount of catalyst should be enough to cause the effective catalyst surface contact of the reactant. In addition, the technician will understand that, relative to the reactant, there is actually no upper limit to the amount of the catalyst, but in practice, this can be determined again by required contact time and / or economic considerations.

[0147] In the process of the seventh or eighth aspect of the invention, the relative amounts of the reagents may vary within wide limits, but typically the molar ratio of formaldehyde or a suitable source thereof to the carboxylic acid or carboxylic acid ester is in the range of 20:1 to 1:20, more preferably 5:1 to 1:15. The most preferred ratio will depend on the form of the formaldehyde and the ability of the catalyst to release formaldehyde from formaldehydic species. Thus, in R 31 O-(CH2-O) i R 32 R 31 and R 32 In the case where one or both of the R is H, the highly reactive formaldehyde species require a relatively low ratio, typically in this case the molar ratio of formaldehyde or a suitable source thereof to the carboxylic acid or carboxylic acid ester is in the range of 1:1 to 1:9. 31 and R 32 In cases where neither is H, as in, for example, CH3O-CH2-OCH3, or in trioxane, higher ratios are most preferred, typically 6:1 to 1:3.

[0148] As mentioned above, water may also be present in the reaction mixture due to the source of formaldehyde. Depending on the source of formaldehyde, some or all of the water may need to be removed therefrom prior to catalysis. Maintaining a lower level of water than in the source of formaldehyde may be beneficial to catalytic efficiency and / or subsequent purification of the product. Less than 10 mole % of water in the reactor is preferred, more preferably less than 5 mole %, and most preferably less than 2 mole %.

[0149] Typically, the molar ratio of alcohol to acid or ester is in the range of 20:1 to 1:20, preferably 10:1 to 1:10, most preferably 5:1 to 1:5, for example 1:1.5. However, the most preferred ratio will depend on the amount of water in the reactants fed to the catalyst plus the amount produced by the reaction, so that the preferred molar ratio of alcohol to total water in the reaction will be at least 1:1, and more preferably at least 2:1.

[0150] The reagent of the seventh or eighth aspect can be fed to the reactor independently or after pre - mixing, and the reaction process can be continuous or batch. However, typically, a continuous process is used.

[0151] Typically, the method of the seventh or eighth aspect of the present invention is carried out when the reactants are in the gas phase.

[0152] In yet another aspect, the present invention extends to a process for producing an ethylenically unsaturated carboxylic acid or carboxylic acid ester according to any relevant aspect herein, the process comprising first the step of producing a catalyst according to any relevant aspect herein.

[0153] Definition

[0154] An uncalcined modified silica support means that after the modification step and before treatment with the catalytic metal, the silica support has not been calcined (such as by treatment at a temperature above 275 °C or 325 °C or 375 °C or 425 °C), and does not necessarily mean that the original silica support was uncalcined before modification with the modifier metal. Similarly, an uncalcined catalyst intermediate means that the modified silica support has been uncalcined since its modification, and does not necessarily mean that the original unmodified silica support was uncalcined before modification with the modifier metal.

[0155] As used herein, the term "impregnation" includes adding a catalytic metal dissolved in a solvent to make a solution, adding the solution to a dry gel or an aerogel such that the solution is absorbed into the voids within the dry gel or aerogel. The term also extends to replacing the hydrogel liquid with a suitable solvent and adding a catalytic metal as a solution in the solvent to effect mass transfer into the hydrogel by diffusion.

[0156] The silica support can be treated with a mononuclear and / or dinuclear modifier metal by any of a variety of techniques known to those skilled in the art of support formation. The silica support can be contacted with the mononuclear or dinuclear modifier metal in such a way as to disperse the modifier metal throughout the silica support. Typically, the modifier metal can be uniformly distributed on the surface of the entire silica support. Preferably, the modifier metal is dispersed in the silica support by adsorption.

[0157] As used herein, the term "adsorbed" or similar terms in relation to a modifier metal or a catalytic metal means incorporation onto the surface of a silica support by its interaction with the silica support, optionally by physical adsorption, but typically by chemisorption. Typically, adding a modifier to a silica support includes the steps of adsorbing a metal cation source onto the silica support to form a metal complex residue, and drying the support to convert the metal complex to a metal oxide moiety. Thus, typically, there is a random distribution of the modifier metal over the entire silica support in contact.

[0158] For the avoidance of doubt, a modifier metal moiety having a total of 1 metal atom is considered mononuclear. It will be understood that in the silica network, the modifier metal moiety is associated with the silica network and thus the term mononuclear moiety or dinuclear moiety refers to the modifier metal and its immediate surrounding atoms and not to the silicon atoms of the network or other modifier metal atoms that are associated with the network but still form part of a separate, largely unassociated moiety.

[0159] The modifier metal moiety and the modifier metal oxide moiety in the modified silica support according to the present invention relate to the modifier metal and not to silicon or silica. Similarly, the modifier metal herein is not the same metal as the catalytic metal.

[0160] Unless otherwise indicated, the amount of modifier or catalytic metal in a catalyst relates to the modifier or catalytic metal ions and not to the surrounding atoms.

[0161] The level of catalytic metal in a catalyst, whether in moles, wt%, or otherwise, can be determined by appropriate sampling and obtaining an average of such samples. Typically, 5 - 10 samples of a particular catalyst batch will be taken and the alkali metal level determined and averaged, for example, by XRF, atomic absorption spectroscopy, neutron activation analysis, inductively coupled plasma mass spectrometry (ICPMS) analysis or inductively coupled plasma atomic emission spectroscopy (ICPAES).

[0162] The level of a particular type of metal oxide in a catalyst / support is determined by XRF, atomic absorption spectroscopy, neutron activation analysis or inductively coupled plasma mass spectrometry (ICPMS) analysis.

[0163] The typical average surface area of a modified silica-supported catalyst according to any aspect of the present invention is between 20 m 2 / g - 600 m 2 / g, more preferably between 30 m 2 / g - 450 m 2 / g, most preferably 35 m2 / g - 350m 2 / g, as measured by the B.E.T. multi - point method using a Micromeritics Tristar 3000 surface area and porosity analyzer. The reference material for checking the instrument performance can be carbon black powder with a surface area of 30.6 m 2 / g (+ / - 0.75 m 2 / g), part number 004 - 16833 - 00.

[0164] Unless otherwise indicated, the term "hydrocarbyl" as used herein means C1 to C 12 hydrocarbyl, and includes methyl group, ethyl group, vinyl group, propyl group, propenyl group, butyl group, butenyl group, pentyl group, pentenyl group, hexyl group, hexenyl group and heptyl group. Typically, the hydrocarbyl group is selected from methyl, ethyl, propyl, butyl, pentyl and hexyl, and more typically, methyl. Unless otherwise indicated, when there are a sufficient number of carbon atoms, the hydrocarbyl group can be straight - chain or branched - chain, cyclic, acyclic or partially cyclic / acyclic, unsubstituted, substituted or terminated by one or more substituents selected from halogen, cyano, nitro, - OR 19 、 - OC(O)R 20 、 - C(O)R 21 、 - C(O)OR 22 、 - NR 23 R 24 、 - C(O)NR 25 R 26 、 - SR 29 、 - C(O)SR 30 、 - C(S)NR 27 R 28 、 unsubstituted or substituted aryl, or unsubstituted or substituted Het, where R 19 to R 30 each independently represents hydrogen, halogen, unsubstituted or substituted aryl or unsubstituted or substituted hydrocarbyl, or in the case of R 21 is separated by one or more (typically less than 4) oxygen atoms, sulfur atoms, silicon atoms or by silano groups or dihydrocarbylsilyl groups or mixtures thereof. Typically, the hydrocarbyl group is unsubstituted, typically straight - chain, and typically saturated.

[0165] The term "alkenyl" should be understood as the above - mentioned "hydrocarbyl", except that at least one carbon - carbon bond therein is unsaturated, and thus the term relates to C2 to C12 Alkenyl group.

[0166] In the absence of contrary information, the term "alk" or similar terms should be considered to conform to the above definition of "alk", except that "C0 alk" means unsubstituted by alk.

[0167] The term "aryl" as used herein includes five- to ten-membered, typically five- to eight-membered, carbocyclic aromatic or pseudo aromatic groups such as phenyl, cyclopentadienyl and indenyl anions and naphthyl, which groups may be unsubstituted or substituted by one or more substituents selected from unsubstituted or substituted aryl, alkyl (which group may itself be unsubstituted or substituted or terminated as defined herein), Het (which group may itself be unsubstituted or substituted or terminated as defined herein), halogen, cyano, nitro, OR 19 、OC(O)R 20 、C(O)R 21 、C(O)OR 22 NR 23 R 24 、C(O)NR 25 R 26 , SR 29 、C(O)SR 30 or C(S)NR 27 R 28 , where R 19 To R 30 each independently represents hydrogen, unsubstituted or substituted aryl or hydrocarbyl (which hydrocarbyl group may itself be unsubstituted or substituted or terminated as defined herein), or, in R 21 In the case of halogen, nitro, cyano or amino.

[0168] The term "halogen" as used herein means a chloro, bromo, iodo or fluoro group, typically chloro or fluoro.

[0169] The term "Het" as used herein includes 4- to 12-membered, typically 4- to 10-membered ring systems containing one or more heteroatoms selected from nitrogen, oxygen, sulfur and mixtures thereof, and containing no double bonds, one or more double bonds, or non-aromatic, partially aromatic or fully aromatic in nature. The ring system may be monocyclic, bicyclic or fused. Each "Het" group identified herein may be unsubstituted or substituted with one or more substituents selected from halogen, cyano, nitro, oxo, hydrocarbyl (which hydrocarbyl group itself may be unsubstituted or substituted or terminated as defined herein), -OR19 、 -OC(O)R 20 、 -C(O)R 21 、 -C(O)OR 22 、 -N(R 23 )R 24 、 -C(O)N(R 25 )R 26 、 -SR 29 、 -C(O)SR 30 or -C(S)N(R 27 )R 28 , wherein R 19 to R 30 each independently represents hydrogen, unsubstituted or substituted aryl or hydrocarbyl (the hydrocarbyl group itself may be unsubstituted or substituted or capped as defined herein), or in the case of R 21 , halogen, nitro, amino or cyano. Thus, the term "Het" includes groups such as: optionally substituted azetidinyl, pyrrolyl, imidazolyl, indolyl, furyl, oxazolyl, isoxazolyl, oxadiazolyl, thiazolyl, thiadiazolyl, triazolyl, oxatriazolyl, thiatriazolyl, pyridazinyl, morpholinyl, pyrimidinyl, pyrazinyl, quinolinyl, isoquinolinyl, piperidinyl, pyrazolyl and piperazinyl. Substitution on Het can be on the carbon atoms of the Het ring or, where appropriate, on one or more heteroatoms.

[0170] The "Het" group can also be in the form of an N-oxide.

[0171] Suitable optional alcohols for the catalytic reactions of the seventh and eighth aspects of the present invention can be selected from: C1-C 30 alkanols, including aryl alcohols, which can be optionally substituted by one or more substituents selected from hydrocarbyl, aryl, Het, halogen, cyano, nitro, OR 19 , OC(O)R 20 , C(O)R 21 , C(O)OR 22 , NR 23 R 24 , C(O)NR 25 R 26 , C(S)NR 27 R 28 , SR 29 or C(O)SR 30, as defined herein. Highly preferred alkanols are C1-C8 alkanols such as methanol, ethanol, propanol, isopropanol, isobutanol, tert-butanol, phenol, n-butanol and octanol, in particular, methanol. Although monoalkanol is most preferred, poly-alkanol can also be used, which are typically selected from diol-octanols such as diols, triols, tetraols and sugars. Typically, such poly-alkanol are selected from 1,2-ethylene glycol, 1,3-propanediol, glycerol, 1,2,4-butanetriol, 2-(hydroxymethyl)-1,3-propanediol, 1,2,6-trihydroxyhexane, pentaerythritol, 1,1,1-tris(hydroxymethyl)ethane, mannose, sorbose, galactose and other sugars. Preferred sugars include sucrose, fructose and glucose. Particularly preferred alkanols are methanol and ethanol. Most preferred alkanol is methanol. The amount of the alkanol is not critical. Generally, an amount exceeding the amount of the substrate to be esterified is used. Thus, the alkanol can also be used as a reaction solvent, although a separate solvent or additional solvent can also be used if desired.

[0172] The term "gel" as used herein is also known to those skilled in the art, but in case of doubt, can be considered as a solid network in which a fluid is dispersed. Generally, a gel is a polymer network in which a fluid is dispersed. A co-gel is a term used to indicate that more than one original compound / portion is incorporated into the polymer network, and the original compound / portion is typically silica and a metal oxide or salt. Thus, co-gelation herein means the formation of a co-gel.

[0173] Thus, a gel is a sol that has solidified. Thus, a hydrogel is a gel as defined herein in which the fluid is water. A xerogel is a gel that has been dried to remove the fluid. An aerogel is a gel in which the fluid is replaced by a gas and thus does not undergo the same shrinkage as a xerogel.

[0174] The term start herein means the start of the formation of the modified silica.

[0175] The term "portion" as used herein in relation to the modifier metal is used to refer to the form of the modifier metal on the modified support. Although the adsorbed modifier metal typically forms part of the network, whether as a metal complex or an oxide, and in the latter case, whether before or after calcination, the modifier metal will be in the form of discrete residues on the silica substrate. The term mononuclear means having a single metal center, and in the case of a portion on silica, means having the form of a mononuclear residue. Binuclear should be interpreted accordingly.

[0176] The % of modifier metal has no unit herein as it refers to the number of metal atoms per total number of such atoms. It will be understood that the moieties may take the form of non-mononuclear or binuclear clusters, but these clusters are still composed of modifier metal atoms.

[0177] Unless otherwise specified, the term "surface" as used herein in connection with the silica support includes the surface of the silica within the pores of the silica, more particularly within the macropores and mesopores of the silica.

[0178] The embodiments of the present invention will now be defined by reference to the attached examples, wherein:

[0179] Experiment

[0180] Silica support description

[0181] Example 1 (Preparation)

[0182] Fuji Silysia CARiACT Q10 silica was dried in a laboratory oven at 160 °C for 16 hours, after which it was removed from the oven and cooled to room temperature in a sealed flask stored in a desiccator. This silica had a surface area of 333 m 2 / g, a pore volume of 1.0 ml / g, and an average pore diameter of 10 nm, as determined by nitrogen adsorption / desorption isotherm analysis (Micromeritics Tristar II). This silica mainly comprised spherical silica beads in the diameter range of 2.0 mm - 4.0 mm.

[0183] Zr modification of the silica support

[0184] Example 2 (2.7 wt% Zr, comparative)

[0185] 1.671 g of Zr(acac)4 (97%, Sigma Aldrich) was dissolved in 20 ml of MeOH (99%, Sigma Aldrich). 10 g of silica from Example 1 was weighed in a separate flask. Then the weighed silica was added to the Zr(acac)4 solution under stirring. Stirring was continued until the pore volume of the silica was completely occupied by the solvent, effectively forming a slurry. Once the pore filling was complete, the Zr-modified silica was left in a sealed flask under regular stirring for 16 h. After this time, the solution outside the pores was removed by filtration. This was followed by a drying step, in which the organic solvent inside the pores (intra-porous organic solvent) was removed by passing a nitrogen stream through the wet Zr-modified silica at room temperature. Alternatively, the solvent inside the pores was removed under reduced pressure on a rotary evaporator. Once all the solvent had been removed, the Zr-modified silica support was calcined in a furnace at 500 °C under a stream of air, where the heating ramp rate was 5 °C / min and it was finally held for 5 h. After cooling, this gave a Zr-grafted silica support with an 89% Zr usage efficiency. The Zr loading (wt%) on the Zr-modified support was determined via powder Energy Dispersive X-Ray Fluorescence analysis (Oxford Instruments X-Supreme 8000).

[0186] Example 3 (2.7 wt% Zr)

[0187] The support modification was carried out as described in Example 2, except that after the drying step had been completed, an additional 16 h drying step was carried out in a laboratory oven set at 110 °C - 120 °C. In addition, the high-temperature calcination step at 500 °C was not carried out. This gave a Zr-grafted silica support with an 89% Zr usage efficiency. (Note: The Zr loading was determined after oxidative calcination of the sample of the Zr-grafted material at 500 °C).

[0188] Cs modification of the modified support

[0189] Example 4 (11.3 wt% Cs, 2.4 wt% Zr, comparative)

[0190] 1.80 g of CsOH.H2O (99.5% Sigma Aldrich) was weighed out in a glove box and dissolved in 20 ml of a 9:1 v / v MeOH:H2O solvent mixture. 10 g of the modified silica from Example 2 was added to the CsOH solution with stirring. Stirring was continued for an additional 15 min, after which the sample was left in a sealed flask with periodic stirring for 16 h. After this time, the solution outside the pores was removed by filtration. This was followed by a drying step where the solvent inside the pores was removed by passing a nitrogen stream through the wet Cs / Zr-modified silica at room temperature. Alternatively, the solvent inside the pores was removed under reduced pressure on a rotary evaporator. After this, the catalyst beads were placed in a drying oven at 110 °C - 120 °C and left to dry for 16 h. After cooling, this gave a Cs / Zr / SiO2 catalyst with a Cs utilization efficiency of 90%. The Cs loading (wt%) on the catalyst was determined via powder energy dispersive X-ray fluorescence analysis (Oxford Instruments X-Supreme 8000).

[0191] Example 5 (11.0 wt% Cs, 2.4 wt% Zr, comparative)

[0192] The catalyst was prepared as described in Example 4, except that 1.75 g of CsOH.H2O was used. Additionally, after the drying step at 120 °C, the catalyst was calcined in a furnace at 700 °C under a stream of air, where the heating rate was 5 °C / min and it was held for 5 h at the end. After cooling, this gave a Cs / Zr / SiO2 catalyst.

[0193] Example 6 (11.3 wt% Cs, 2.4 wt% Zr)

[0194] The catalyst was prepared as described in Example 4, except that 10.5 g of the silica from Example 3 was used. Additionally, after the drying step at 120 °C, the catalyst was calcined in a furnace at 700 °C under a stream of air, where the heating rate was 5 °C / min and it was held for 5 h at the end. After cooling, this gave a Cs / Zr / SiO2 catalyst.

[0195] Example 7 (10.6 wt% Cs, 2.4 wt% Zr)

[0196] The catalyst was prepared as described in Example 4, except that 10.5 g of the silica from Example 3 was used and water was used as the solvent instead of 9:1 v / v MeOH:H2O. Further, after the drying step at 120 °C, the catalyst was calcined in a furnace at 400 °C under a stream of air, where the heating rate was 5 °C / min and it was finally held for 5 h. After cooling, this gave the Cs / Zr / SiO2 catalyst.

[0197] Example 8 (10.6 wt% Cs, 2.4 wt% Zr)

[0198] The catalyst was prepared as described in Example 7, except that the final calcination was carried out at 600 °C.

[0199] Example 9 (10.6 wt% Cs, 2.4 wt% Zr)

[0200] The catalyst was prepared as described in Example 7, except that the final calcination was carried out at 700 °C.

[0201] Example 10 (Catalytic performance test)

[0202] The catalysts from Examples 4 to 9 were tested for the reaction of methyl propionate and formaldehyde in a laboratory-scale microreactor. For this purpose, 3 g of the catalyst was loaded into a fixed-bed reactor with an inner tube diameter of 10 mm. The reactor was heated to 330 °C and preconditioned by feeding an evaporated stream containing 70 wt% methyl propionate, 20 wt% methanol, 6 wt% water and 4 wt% formaldehyde from an evaporator fed by a Gilson pump at 0.032 ml / min. This preconditioning continued overnight. After preconditioning, a feed stream containing 75.6 wt% methyl propionate, 18.1 wt% methanol, 5.7 wt% formaldehyde and 0.6 wt% water was pumped by a Gilson pump to an evaporator set at 330 °C and then fed to a heated reactor containing the catalyst set at 330 °C. The reactor outlet vapors were cooled and condensed, and samples were collected at five different liquid feed rates (between 0.64 ml / min - 0.032 ml / min) in order to obtain the conversion at different vapor / catalyst contact times. The liquid feed and the condensed off-reactor liquid products were analyzed by a Shimadzu 2010 gas chromatograph with a DB1701 column. The composition of the samples was determined from the corresponding chromatograms, and the yields and selectivities at different contact times were determined. Activity was defined as the reciprocal of the contact time in seconds required to obtain a 12% MMA + MAA yield on the fed methyl propionate and was determined by interpolation on a contact time versus MMA + MAA yield plot. The interpolated contact time was then used to obtain the MMA + MAA selectivity at a 12% MMA + MAA yield.

[0203] Table 1: Results of activity and MMA + MAA selectivity for the catalysts prepared according to Examples 4 to 9 and tested according to Example 10.

[0204]

[0205]

[0206] Example 11 (Determination of catalyst stability)

[0207] According to Example 5, after a calcination treatment at 700 °C, the initial catalyst stability was evaluated by measuring the surface area (nitrogen adsorption / desorption isotherm analysis, Micromeritics Tristar II). This provided a means of assessing the surface stability imparted to the catalyst.

[0208] Table 2: Surface areas of the catalysts that underwent a calcination treatment at 700 °C as a measure of initial stability.

[0209]

[0210] Example 12 (Accelerated Aging Test)

[0211] The catalyst sintering resistance was evaluated in an accelerated aging test. For this purpose, 1 g of the catalyst was loaded into a U-shaped tube stainless steel reactor and placed in an oven. The oven was heated to 385 °C and a stream of nitrogen (10 ml / min) was passed through a saturating vaporiser containing water heated to 92 °C. This ensured that the feed stream with a water partial pressure of 0.75 bara passed over the catalyst heated to 385 °C. Periodically, the surface area of the catalyst samples was determined ex-situ using nitrogen adsorption / desorption isotherm analysis (Micromeritics Tristar II).

[0212] Table 3: Accelerated aging data for the catalysts prepared according to Examples 4 to 8 and tested according to Example 12.

[0213]

[0214] Attention is directed to all papers and documents that are related to the present application and that were filed simultaneously with or before the present specification and that are hereby publicly available for inspection together with the present specification, and the content of all such papers and documents is incorporated herein by reference.

[0215] All features disclosed in this specification (including any appended claims, abstract and drawings) and / or all steps of any method or process so disclosed may be combined in any combination, except combinations in which at least some of such features and / or steps are mutually exclusive.

[0216] Unless otherwise expressly stated, each feature disclosed in this specification (including any appended claims, abstract and drawings) may be used as an alternative feature for the same, equivalent or similar purpose. Thus, unless otherwise expressly stated, each feature disclosed is only one example of a series of general equivalent or similar features.

[0217] The present invention is not limited to the details of the foregoing embodiments. The present invention extends to any novel inventive feature or any novel combination of inventive features of the preferred, typical or optional inventive features disclosed in this specification (including any appended claims, abstract or drawings), or to any novel inventive step or any novel combination of inventive steps of the preferred, typical or optional inventive steps so disclosed.

Claims

1. A process for producing a catalyst, comprising the following steps: a) providing an uncalcined metal-modified porous silica support, wherein the modifier metal is selected from one or more of boron, magnesium, aluminum, zirconium, hafnium, and titanium, and wherein the modifier metal is present as a mononuclear modifier metal moiety or a binuclear modifier metal moiety; b) optionally removing any solvent or liquid carrier from the modified silica support; c) optionally drying the modified silica support; d) treating the uncalcined metal-modified silica support with a catalytic metal to effect adsorption of the catalytic metal onto the metal-modified silica support, wherein the catalytic metal is an alkali metal; and e) calcining the impregnated silica support of step d).

2. The process according to claim 1: wherein the porous silica support modified with a modifier metal is a modifier metal oxide-silica co-gel support.

3. An uncalcined catalyst intermediate comprising an uncalcined porous silica support modified with a modifier metal, wherein the modifier metal is selected from one or more of boron, magnesium, aluminum, zirconium, hafnium, and titanium, wherein the modifier metal is present as a mononuclear modifier metal moiety or a binuclear modifier metal moiety and a catalytic metal is adsorbed onto the uncalcined modified silica support, wherein the catalytic metal is an alkali metal.

4. The uncalcined catalyst intermediate according to claim 3, comprising a porous modifier metal oxide-silica co-gel support.

5. A process for producing a catalyst, comprising the following steps: a) providing a porous silica support having isolated silanol groups; b) treating the porous silica support with a mononuclear modifier metal compound or a binuclear modifier metal compound such that the modifier metal is adsorbed onto the surface of the silica support by reaction with the isolated silanol groups, wherein the adsorbed modifier metal atoms are sufficiently separated from each other to substantially prevent oligomerization with adjacent modifier metal atoms prior to calcination, wherein the modifier metal is selected from boron, magnesium, aluminum, zirconium, hafnium, and titanium; c) optionally removing any solvent or liquid carrier from the modified silica support; d) optionally drying the modified silica support; e) treating the uncalcined modified silica support with a catalytic metal to effect adsorption of the catalytic metal onto the modified silica support; and f) calcining the impregnated silica support of step e).

6. The process according to claim 5, wherein the metal compound is a complex and the coordination sphere of the compound is sufficiently saturated to prevent oligomerization of the modifier metal other than dimerization before and / or after adsorption.

7. The process according to claim 6, wherein the compound is an organic complex.

8. The process according to claim 5, wherein the metal compound comprises one or more chelating ligands.

9. The process according to claim 5, wherein the metal compound is tetracoordinate, pentacoordinate, hexacoordinate, heptacoordinate, or octacoordinate.

10. The process according to claim 5, wherein when the modifier metal compound is contacted with the support to effect adsorption of the compound onto the support, at least 30% of the modifier metal in the modifier metal compound is a mononuclear modifier metal compound or a binuclear modifier metal compound.

11. The process according to claim 5, wherein the modifier metal compound is uniformly distributed over the surface of the entire silica support.

12. A catalyst comprising the intermediate according to claim 3, wherein the uncalcined intermediate has been calcined.

13. A catalyst comprising the intermediate according to claim 4, wherein the uncalcined intermediate has been calcined.

14. The process or catalyst according to any one of claims 1, 2, 5 or 12, wherein the calcination step is carried out at a temperature of at least 450 °C.

15. The process or catalyst intermediate or catalyst according to any one of claims 1-4 and 12-13, wherein the modifier metal moiety is derived from a mononuclear modifier metal compound or a binuclear modifier metal compound.

16. The process or catalyst intermediate or catalyst according to claim 15, wherein the modifier metal compound is contacted with the porous silica support as a mononuclear modifier metal compound or a binuclear modifier metal compound in solution to effect adsorption of the modifier metal onto the support.

17. The process or catalyst or catalyst intermediate according to any one of claims 1-5 and 12-13, wherein the silica support is a hydrogel or a xerogel.

18. The process or catalyst or catalyst intermediate according to any one of claims 1, 3, 5 or 12-13, wherein the modifier metal is an adsorbate adsorbed on the surface of the silica support.

19. The process or catalyst or catalyst intermediate according to any one of claims 1, 3, 5 or 12-13, wherein the modifier metal is an adsorbate chemisorbed or physically adsorbed onto the surface of the silica support.

20. The process or catalyst or catalyst intermediate according to any one of claims 1, 3, 5 or 12-13, wherein the modifier metal is an adsorbate chemisorbed on the surface of the silica support.

21. The process or catalyst or catalyst intermediate according to any one of claims 1, 3, 5 or 12-13, wherein one or more non-labile ligands are attached to the modifier metal to at least partially form the modifier metal compound or moiety, and are optionally selected from molecules having a lone pair of electrons and containing an oxygen or nitrogen atom capable of forming a 5-membered or 6-membered ring with the modifier metal atom, including diketones, diimines, diamines, diols, dicarboxylic acids or derivatives thereof; or molecules having two different such functional groups, and in either case, the corresponding N or O and N atoms or O atoms are separated by 2 or 3 atoms so as to form the 5-membered or 6-membered ring.

22. The process, catalyst or catalyst intermediate according to claim 21, wherein the non-labile ligand is selected from one or more of the following: pentane-2,4-dione, an ester of 3-oxobutyric acid and a fatty alcohol containing 1 to 4 carbon atoms, heptane-3,5-dione, 2,2,6,6-tetramethyl-3,5-heptanedione, 1,2-ethanediol, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, 1,2-butanediol, 1,2-diaminoethane, ethanolamine, 1,2-diamino-1,1,2,2-tetracarboxylate, 2,3-dihydroxy-1,4-butanedioate, 2,4-dihydroxy-1,5-pentanedioate, a salt of 1,2-dihydroxybenzene-3,5-disulfonate, diethylenetriaminepentaacetic acid, nitrilotriacetic acid, N-hydroxyethylethylenediaminetriacetic acid, N-hydroxyethyliminodiacetic acid, N,N-dihydroxyethylglycine, oxalic acid and its salts.

23. The process, catalyst or catalyst intermediate according to claim 21, wherein the non-labile ligand is selected from one or more of pentane-2,4-dione, 2,2,6,6-tetramethyl-3,5-heptanedione, ethyl 3-oxobutyrate, tert-butyl 3-oxobutyrate and heptane-3,5-dione.

24. The process, catalyst or catalyst intermediate according to any one of claims 1-5 and 12-13, wherein the modifier metal is selected from zirconium, hafnium or titanium.

25. The process, catalyst or catalyst intermediate according to any one of claims 1-5 and 12-13, wherein the modifier metal is titanium.

26. The process, catalyst or catalyst intermediate according to any one of claims 1-5 and 12-13, wherein the catalytic metal is an alkali metal.

27. The process, catalyst or catalyst intermediate according to any one of claims 1-5 and 12-13, wherein the catalytic metal is selected from cesium, potassium or rubidium.

28. The process, catalyst or catalyst intermediate according to any one of claims 1-5 and 12-13, wherein the catalytic metal is cesium.

29. The process or catalyst or catalyst intermediate according to any one of claims 1-5 and 12-13, wherein the silica support comprises the modifier metal at a level of <5 metal atoms per nm 2 of the modifier metal.

30. The process, catalyst or catalyst intermediate according to any one of claims 1-5 and 12-13, wherein at least 25% of the modifier metal on the support is present in the form of mononuclear modifier metal moieties or binuclear modifier metal moieties before or after calcination of the catalytic metal.

31. The process, catalyst or catalyst intermediate according to any one of claims 1-5 and 12-13, wherein the adsorbed or co-gelled modifier metal cations are sufficiently separated from each other to substantially prevent their oligomerization during subsequent processing steps.

32. The process, catalyst or catalyst intermediate according to claim 31, wherein the adsorbed or co-gelled modifier metal cations are sufficiently separated from each other to substantially prevent their dimerization, trimerization or oligomerization with adjacent modifier metal cations during subsequent processing steps.

33. The process or catalyst or catalyst intermediate according to claim 31, wherein said subsequent treatment step comprises impregnation and / or calcination of the catalytic metal.

34. The process or catalyst or catalyst intermediate according to any one of claims 1 - 5 and 12 - 13, wherein the silica support comprises isolated silanol groups (-SiOH) at a level of <2.5 groups per nm 2 of separation.

35. The process or catalyst or catalyst intermediate according to claim 16, wherein the solvent for the solution is different from water.

36. The process or catalyst or catalyst intermediate according to claim 35, wherein the solvent is an organic solvent.

37. The process or catalyst or catalyst intermediate according to claim 35, wherein the solvent is an aliphatic solvent, an aromatic solvent or a chlorinated solvent.

38. The process or catalyst or catalyst intermediate according to claim 35, wherein the solvent is an aliphatic alcohol.

39. The process or catalyst or catalyst intermediate according to claim 38, wherein the aliphatic alcohol is a C1-C6 alkanol.

40. The process or catalyst or catalyst intermediate according to claim 38, wherein the aliphatic alcohol is selected from methanol, ethanol, propanol, isopropanol, butanols, pentanols and hexanols.

41. The process or catalyst or catalyst intermediate according to any one of claims 1 - 5 and 12 - 13, wherein the support comprises the modifier metal moiety at a level of > 0.025 and < 2.5 groups per nm 2 of the modifier metal moiety.

42. The process or catalyst or catalyst intermediate according to any one of claims 1-5 and 12-13, wherein the silica component of the modified silica support forms 80 wt% - 99.9 wt% of the modified support.

43. The process or catalyst or catalyst intermediate according to any one of claims 1-5 and 12-13, wherein the silica support has an average pore diameter between 2 nm and 1000 nm.

44. The process or catalyst or catalyst intermediate according to any one of claims 1-5 and 12-13, wherein the catalytic metal is an adsorbate adsorbed on the surface of the modified silica support of the catalyst.

45. The process or catalyst or catalyst intermediate according to claim 44, wherein the adsorbate is chemisorbed or physically adsorbed onto the surface of the modified silica support.

46. The process or catalyst or catalyst intermediate according to claim 45, wherein the adsorbate is chemisorbed on the surface of the modified silica support.

47. The process or catalyst or catalyst intermediate according to any one of claims 1-5 and 12-13, wherein the catalytic metal is present in the catalyst at a level of at least 1 mol / 100 (silicon + modifier metal) mol.

48. The process or catalyst or catalyst intermediate according to any one of claims 1-5 and 12-13, wherein the level of the catalytic metal is up to 10 mol / 100 (silicon + modifier metal) mol in the catalyst.

49. The process or catalyst or catalyst intermediate according to any one of claims 1-5 and 12-13, wherein the molar ratio of the catalytic metal:modifier metal in the catalyst is at least 1.4 or 1.5:

1.

50. The process or catalyst or catalyst intermediate according to any one of claims 1 - 5 and 12 - 13, wherein the molar ratio of the catalytic metal:modifier metal in the catalyst is in the range of 1.4 to 5:

1.

51. The process or catalyst or catalyst intermediate according to any one of claims 1 - 5 and 12 - 13, wherein the catalytic metal is present in the range of 0.5 mol / mol - 7.0 mol / mol of the modifier metal.

52. The process or catalyst or catalyst intermediate according to any one of claims 1 - 5 and 12 - 13, wherein the level of the catalytic metal in the catalyst is in the range of 1 mol - 10 mol / 100 (silicon + modifier metal) mol in the catalyst.

53. The process or catalyst or catalyst intermediate according to any one of claims 1-5 and 12-13, wherein the level of modifier metal present in the modified silica or catalyst is up to 7.6×10 -2 mol / mol of silica.

54. The process or catalyst or catalyst intermediate according to any one of claims 1-5 and 12-13, wherein the level of the modifier metal is between 0.067×10 -2 mol / mol of silica and 7.3×10 -2 mol / mol of silica.

55. The process or catalyst or catalyst intermediate according to any one of claims 1 - 5 and 12 - 13, wherein the level of modifier metal present is at least 0.1×10 -2 mol / mol silica.

56. The process or catalyst or catalyst intermediate according to any one of claims 1-5 and 12-13, wherein the average pore volume of the catalyst particles is less than 0.1 cm 3 / g, as measured by absorption of a fluid.

57. The process, catalyst or catalyst intermediate according to any one of claims 1 - 5 and 12 - 13, wherein the average pore volume of the catalyst particles is in the range of 0.1 cm 3 / g - 5 cm 3 / g, as measured by the absorption of a fluid.

58. The process, catalyst or catalyst intermediate according to any one of claims 1-5 and 12-13, wherein the average pore volume of the catalyst is between 0.2 cm 3 / g and 2.0 cm 3 / g.

59. The process or catalyst or catalyst intermediate according to any one of claims 1 - 5 and 12 - 13, wherein the moiety or compound is mononuclear.

60. The process or catalyst or catalyst intermediate according to any one of claims 1 - 4 and 12 - 13, wherein the moiety is uniformly distributed over the surface of the entire silica support.

61. A catalyst obtained by the process according to any one of claims 1, 2, 5, 6 - 11 and 14 - 60.

62. A catalyst obtainable by the process according to any one of claims 1, 2, 5, 6 - 11 and 14 - 60.

63. A process for producing an ethylenically unsaturated carboxylic acid or carboxylic acid ester, the process comprising the step of contacting formaldehyde or a suitable source thereof with a carboxylic acid or carboxylic acid ester in the presence of a catalyst and optionally in the presence of an alcohol, wherein the catalyst is the catalyst according to claim 12 or 13 or a catalyst obtained by the process according to any one of claims 1, 2, 5, 6 - 11 and 14 - 60.

64. A process for preparing an ethylenically unsaturated acid or ester, comprising contacting an alkanoic acid or alkanoic acid ester of the formula R 1 -CH2-COOR 3 with formaldehyde or a suitable source of formaldehyde of the formula (I) as defined below, in the presence of a catalyst according to claim 12 or 13 or a catalyst obtained by the process according to any one of claims 1, 2, 5, 6 - 11 and 14 - 60, and optionally in the presence of an alkanol. wherein R 5 is methyl and R 6 is H; X is O; m is 1; and n is any value between 1 and 20 or any mixture of these values; wherein R 1 is hydrogen or a hydrocarbyl group having 1 to 12 carbon atoms, and R 3 is independently hydrogen or a hydrocarbyl group having 1 to 12 carbon atoms.

65. The process according to claim 63 or 64, wherein the carboxylic acid or carboxylic acid ester according to claim 63 or the ester or acid of the formula R 1 -CH2-COOR 3 is methyl propionate or propionic acid respectively, and the optional alkanol is methanol, and the ethylenically unsaturated carboxylic acid or carboxylic acid ester is methyl methacrylate or methacrylic acid.

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