Catalyst and process for producing ethylenically unsaturated carboxylic acids or carboxylic acid esters

Abstract

The present invention discloses a catalyst comprising a modified silica support having a titanium modifier metal and a catalytic metal on the modified silica support. A portion of the modifier metal is present as a mononuclear titanium moiety or is derived from a mononuclear titanium cation source at the beginning of the modification. The present invention also discloses a corresponding modified silica support, a method of producing the catalyst or modified silica support, and a process for preparing an ethylenically unsaturated acid or ester in the presence of the catalyst.

Description

[0001] The present invention relates to a modified silica catalyst support, a catalyst incorporating the modified silica support, and a process for producing olefinically unsaturated carboxylic acids or carboxylates, particularly α,β unsaturated carboxylic acids or carboxylates, more particularly acrylic acid or acrylic acid esters, such as (alkyl) acrylic acid or alkyl (alkyl) acrylates, particularly (meth) acrylic acid or alkyl (meth) acrylates, such as methacrylic acid (MAA) and methyl methacrylate (MMA), by condensing carboxylic acids or carboxylates with formaldehyde or a source thereof, such as dimethoxymethane, in the presence of such a catalyst. The catalyst of the present invention incorporates a modified silica support modified with specific modifier metals and catalytic metals.

[0002] As mentioned above, the unsaturated acid or unsaturated ester can be prepared by the reaction of a carboxylic acid or a carboxylic acid ester, and suitable carboxylic acids or carboxylic acid esters are of the formula R 3 -CH2-COOR 4 Alkanoic acid (or alkyl ester), wherein R 3 and R 4 Each is independently a suitable substituent known in the art of acrylic compounds, such as hydrogen or a hydrocarbyl group, in particular a lower hydrocarbyl group containing, for example, 1 to 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 a 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] 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 above reaction sequence is usually carried out at high temperature, usually in the range of 250°C to 400°C, using an acid / base catalyst. When the desired product is an ester, the reaction is usually carried out in the presence of the relevant alcohol in order to minimize the formation of the corresponding acid by hydrolysis of the ester. In addition, for convenience, it is usually desirable to introduce the formaldehyde in the form of a complex with methanol. Therefore, for the production of MMA, the reaction mixture fed to the catalyst will usually consist of methyl propionate (MEP), methanol, formaldehyde and water.

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

[0013] The present inventors have now discovered that catalysts comprising certain silica supports modified with titanium metal and comprising a catalytic metal provide high levels of selectivity in the condensation of a methylene source such as formaldehyde with a carboxylic acid or hydrocarbyl ester such as MEP when at least a portion of the modifier metal is incorporated into or present in the support in the form of a mononuclear titanium species.

[0014] US6887822 describes a method for preparing a silica hydrogel catalyst. In addition to the catalytic metal, a second metal can be used. The second metal includes zirconium, titanium, aluminum and iron. The metal is selected with respect to the final use of the catalyst, and titanium is taught to perform well as part of an oxidation catalyst. No teaching is provided about the nucleation property of titanium. WO2014053818 describes a depleted catalyst and its re-impregnation. It discusses that the depleted alkali metal catalyst can additionally include a second metal or another metal selected from the group consisting of zirconium, titanium, hafnium, aluminum, boron and magnesium or a mixture thereof. Again, no teaching is given about the nucleation property of any modifier metal.

[0015] However, the present inventors have surprisingly discovered that when the modified silica support comprises mononuclear titanium species rather than larger polynuclear titanium clusters, there is improved incorporation of the catalytic metal into the modified support, and thereafter higher selectivity and activity for producing unsaturated carboxylic acids or carboxylic acid esters by condensation of the corresponding acid or ester with a methylene source, such as formaldehyde. The present inventors have discovered that the modified silica support that provides these high selectivities comprises monomeric modifier metal atoms after deposition / adsorption onto the surface of the silica.

[0016] Still further, the present inventors have found that when such modified silica supports are used, the rate of catalyst surface sintering has been found to be retarded and the loss of surface area over which catalytic reactions occur during the condensation reaction is reduced.

[0017] Thus, catalysts comprising such modified silica supports and comprising a catalytic metal are very efficient catalysts for producing α,β ethylenically unsaturated carboxylic acids or carboxylic acid esters by condensation of the corresponding acids or esters with a methylene source such as formaldehyde, which catalysts offer several advantages, such as a high level of selectivity and / or reduced sintering of the catalyst surface.

[0018] Therefore, according to a first aspect of the present invention, there is provided a catalyst comprising:

[0019] a modified silica support comprising a titanium modifier metal; and a catalytic metal on the modified silica support,

[0020] Characterized in that at least a portion of the modifier metal, typically at least 25%, is present in the form of mononuclear titanium moieties.

[0021] According to a second aspect of the present invention, there is provided a catalyst comprising:

[0022] a modified silica support comprising a titanium modifier metal;

[0023] and catalytic metals on modified silica supports,

[0024] Characterized in that at least a portion of the modifier metal, typically at least 25%, is present as a modifier metal moiety derived from a source of mononuclear titanium cations.

[0025] Mononuclear titanium is contacted with the silica support as a source of mononuclear titanium cations such as a compound thereof in solution to effect adsorption of titanium onto the support, thereby forming a titanium moiety. A suitable source may be a titanium complex, more typically a ligand complex in solution.

[0026] According to a third aspect of the present invention, there is provided a modified silica support for a catalyst, the modified silica support comprising

[0027] a silica support, and

[0028] Titanium Modifier Metal,

[0029] Characterized in that at least a portion of the modifier metal, typically at least 25%, is present in the form of mononuclear titanium moieties.

[0030] According to a fourth aspect of the present invention, there is provided a modified silica support for a catalyst, the modified silica support comprising

[0031] a silica support, and

[0032] Titanium Modifier Metal,

[0033] It is characterized in that at least a portion of the modifier metal, typically at least 25%, is present in the form of modifier metal moieties derived from the source of mononuclear titanium cations at the start of modification.

[0034] The modified silica support herein is modified with titanium. The modified silica support can be a co-gel of titanium dioxide and silicon dioxide, however, typically, the titanium is the adsorbate adsorbed on the surface of the silica support. The adsorbate can be chemically adsorbed or physically adsorbed onto the surface of the silica support, typically, the adsorbate is chemically adsorbed onto the surface of the silica support. The titanium portion is typically a titania portion.

[0035] Whether the titanium is present as an adsorbate or as a cogel, the silica support is usually in the form of a silica gel, more typically a xerogel or a hydrogel.

[0036] Typically, the titanium is adsorbed on the surface of the silica gel support.Thus, typically, the titanium is present on the surface of the modified silica gel support in the form of titanium oxide moieties.

[0037] Alternatively, the titanium may be present in the support in the form of a co-gel. In such a case, the modified silica support is a silica-titania gel.

[0038] Typically, titanium is present in the modified silica support in an amount effective 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%, especially at least 95%, of the titanium in the modified silica support is in the mononuclear metal portion or is derived from a mononuclear titanium compound at such a level at the start of the formation of the modified silica.

[0039] 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 titanium moiety is associated with the silica network and therefore the term mononuclear moiety refers to the modifier metal and its immediately surrounding atoms, and not to the silicon atoms of the network or other titanium metal atoms that are associated with the network but still form part of a separate moiety.

[0040] It has been surprisingly discovered that clusters of two metal atoms of titanium dispersed throughout a support, such as a hydrogel support, reduce the selectivity of reactions to produce α,β ethylenically unsaturated carboxylic acids or carboxylic acid esters by condensation of the corresponding acid or ester with a methylene source, such as formaldehyde. It has also been surprisingly discovered that such large clusters increase sintering of the modified silica particles relative to the mononuclear portion, thereby reducing the surface area, which reduces catalyst strength and shortens the catalyst life before activity becomes unacceptably low. Furthermore, depending on the nature of the titanium clusters, selectivity is often low.

[0041] Typically, the titanium modifier metal is uniformly distributed across the support surface.

[0042] Typically, the modified silica support is a xerogel. The gel can also be a hydrogel or an aerogel.

[0043] Gel can also be silicon dioxide-titania co-gel.Silica gel can be formed by any of the various techniques known to those skilled in the art of gel formation, such as the technology mentioned herein.In this case, titanium dioxide can also be distributed by the matrix of silicon dioxide and its surface.However, typically, modified silica gel is produced by suitable adsorption reaction.It is a suitable technology to adsorb the relevant titanium compound onto silica gel such as silicon dioxide xerogel to form a modified silica gel with the relevant mononuclear modifier metal part.

[0044] As mentioned, methods for preparing silica gel 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.

[0045] In a preferred embodiment, the mononuclear modified silica support is not formed by co-gelation, i.e., silica-titania formed by co-gelation such as by mixing a sodium silicate solution with a modifier metal complex in a sulfuric acid solution. In such an embodiment, titanium is typically incorporated as an adsorbate on the surface of the silica support.

[0046] Advantageously, when at least a portion of the titanium modifier metal incorporated into the modified silica of the above aspects of the invention is derived from a source of mononuclear modifier metal cations at the outset of formation of the modified silica, it has been found that there is improved reaction selectivity and / or reduced sintering rate of the catalyst surface during the production of α,β ethylenically unsaturated carboxylic acids or carboxylic esters.

[0047] The metal portion and the metal oxide portion in the modified silica support according to the invention relate to titanium and not to silica.

[0048] Preferably, the level of titanium modifier metal present in the modified silica or catalyst may be as high as 7.6×10 -2 mol / mol silica, more preferably up to 5.9×10 -2 mol / mol silica, most preferably up to 3.5×10 -2 mol / mol silica. Typically, the level of such metals is 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 mol / mol silica, and most preferably between 0.2×10 -2 mol / mol silica and 3.5×10 -2 Typically, the level of titanium 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 -2 mol / mol silica.

[0049] Preferably, the level of titanium metal may be up to 5% w / w, more preferably up to 4% w / w, and most preferably up to 2.75% w / w of the modified silica support. Typically, the level of titanium metal is between 0.05% and 5% w / w, more preferably between 0.1% and 4% w / w, and most preferably between 0.15% and 2.5% w / w of the modified silica support. Typically, the level of titanium metal is at least 0.25% w / w, such as 0.4% w / w, more typically at least 0.5% w / w, and most typically at least 0.75% w / w of the modified silica support.

[0050] The silica component of the modified silica support typically may form from 90 wt% to 99.9 wt% of the modified support, more typically from 92 wt% to 99.8 wt% thereof, and most typically from 95 wt% to 99.7 wt% thereof.

[0051] Preferably, the catalytic metal may be selected from one or more alkali metals. The catalytic metal herein is a metal other than titanium. Suitable alkali metals may be selected from potassium, rubidium and cesium, more preferably rubidium and cesium. Cesium is the most preferred catalytic metal herein.

[0052] Suitably, the catalytic metal, such as cesium, may be present in the catalyst at a level of at least 1 mol / 100 (silicon + titanium) mol, more preferably at least 1.5 mol / 100 (silicon + titanium) mol, most preferably at least 2 mol / 100 (silicon + titanium) mol. The level of catalytic metal may be up to 10 mol / 100 (silicon + titanium) mol in the catalyst, more preferably up to 7.5 mol / 100 (silicon + titanium) mol in the catalyst, most preferably up to 5 mol / 100 (silicon + titanium) mol in the catalyst.

[0053] Preferably, the level of catalytic metal in the catalyst is in the range of from 1 mol to 10 mol per 100 (silicon + titanium) mol, more preferably 2 mol to 8 mol per 100 (silicon + titanium) mol, most preferably 2.5 mol to 6 mol per 100 (silicon + titanium) mol in the catalyst.

[0054] Unless indicated to the contrary, the amount of modifier or catalytic metal in the catalyst relates to the modifier or catalytic metal ion and not to the salt.

[0055] Alternatively, the catalyst may have a wt% of catalytic metal in the catalyst in the range of 1 wt% to 22 wt%, more preferably 4 wt% to 18 wt%, most preferably 5 wt% to 13 wt%. These amounts would apply to all alkali metals, but particularly cesium.

[0056] Catalyst can comprise the catalytic alkali metal of any suitable weight ratio: titanium metal.However, typically, cesium in catalyst: the weight ratio of titanium is in the range of from 4:1 to 20:1, more preferably in the range of from 5:1 to 18:1, most preferably in the range of from 6:1 to 15:1, rubidium in catalyst: the weight ratio of titanium is in the range of from 2.5:1 to 15:1, more preferably in the range of from 3:1 to 12:1, most preferably in the range of from 4:1 to 10:1.Therefore, typically, in catalyst, catalytic metal: the mol ratio of modifier metal is at least 1.4 or 1.5:1, preferably it is in the range of 1.4 to 5.0:1, such as 1.5 to 4.0:1, especially 1.5 to 3.6:1, in this respect, typically, modifier metal is titanium, and catalytic metal is cesium.Usually, in this article, catalytic metal exceeds the amount that neutralization modifier metal will need.

[0057] Preferably, the catalytic metal is present in the range of 0.5-7.0 mol / mol titanium, more preferably 1.0-6.0 mol / mol titanium, most preferably 1.5-5.0 mol / mol titanium.

[0058] Suitably, the catalytic metal may be incorporated into the modified silica support by any method known in the art, such as impregnation, co-gelation or vapour deposition with the catalytic metal.

[0059] As used herein, the term "impregnating" includes adding a catalytic metal dissolved in a solvent to make a solution, adding the solution to the xerogel or aerogel, such that the solution is absorbed into the voids within the xerogel or aerogel.

[0060] Typically, the catalyst of the present invention can be in any suitable form. Typical embodiments are 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 monolithic reactor.

[0061] 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 pelletizing or extrusion, typically having a maximum and minimum dimension in the range of 1 mm to 10 mm, more preferably having an average dimension greater than 2 mm, such as greater than 2.5 mm or 3 mm. The catalyst is also effective in other forms, such as powders or beads of the same size as indicated. Where the catalyst is used in the form of a fluidized bed, it is desirable that the catalyst particles have a maximum and minimum dimension in the range of 10 μm to 500 μm, preferably 20 μm to 200 μm, most preferably 20 μm to 100 μm.

[0062] The level of catalytic metal in the catalyst, whether in mole, wt% or other terms, can be determined by taking appropriate samples and taking an average of such samples. Typically, 5-10 samples of a particular catalyst batch will be taken and the alkali metal levels determined and averaged, for example, by XRF, atomic absorption spectroscopy, neutron activation analysis, ion coupled plasma mass spectrometry (ICPMS) analysis, or ion coupled plasma atomic emission spectroscopy (ICPAES).

[0063] The level of a particular type of metal oxide in the catalyst / support is determined by XRF, atomic absorption spectroscopy, neutron activation analysis, or ion coupled plasma mass spectrometry (ICPMS) analysis.

[0064] The typical average surface area of the modified silica-supported catalyst according to any aspect of the present invention is in the range of 20 m 2 / g-600m 2 / g, more preferably 30m 2 / g-450m 2 / g, and most preferably 35m 2 / g-350m 2 The range of pore volume is as measured by the BET multipoint method using a Micromeritics Tristar 3000 surface area and porosity analyzer. The reference material used to check the performance of the instrument can be a 30.6 m 2 / g(+ / -0.75m 2 / g) of carbon black powder, material number 004-16833-00.

[0065] If the catalyst material is porous, it typically extends in the mesoporous and macroporous range, with an average pore size between 2 nm and 1000 nm, more preferably between 3 nm and 500 nm, and most preferably between 5 nm and 250 nm. Macropore size (over 50 nm) can be determined by mercury intrusion porosimetry using NIST standards, while Barrett-Joyner-Halenda (BJH) analysis using liquid nitrogen at 77 K is used to determine the pore size of mesopores (2 nm to 50 nm). The average pore size is the pore volume weighted average of the pore volume relative to the pore size distribution.

[0066] The average pore volume of the catalyst particles can be less than 0.1 cm 3 / g, but usually within 0.1cm 3 / g-5cm 3 / g, as measured by absorption of fluids such as water. However, microporous catalysts with very low porosity are not most preferred because they may inhibit the movement of reagents through the catalyst, and more preferred average pore volumes are in the range of 0.2 cm 3 / g-2.0cm 3 Alternatively, pore volume can be measured by a combination of nitrogen adsorption and mercury porosimetry at 77 K. A Micromeritics TriStar surface area and porosity analyzer was used to determine pore volume as in the case of surface area measurements, and the same standards were employed.

[0067] In the present invention, it has been found that controlling the size of the single core titanium moiety is surprisingly advantageous. However, to obtain the greatest benefit, it is necessary to control the proximity of adjacent modifier metal moieties, as the modifier metal moieties may otherwise bond to each other and thereby increase the nucleation properties of the modifier metal moieties.

[0068] Therefore, according to a fifth aspect of the present invention, there is provided a method for producing a modified silica support, the method comprising the steps of:

[0069] providing a silica support having silanol groups;

[0070] The silica support is contacted with the mononuclear titanium species such that the modifier metal is adsorbed onto the surface of the silica support by reaction with the silanol groups.

[0071] Preferably, the adsorbed modifier metal cations are sufficiently separated from one another to substantially prevent oligomerization, more preferably dimerization, trimerization, or oligomerization, of adjacent modifier metal cations.

[0072] 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%, in particular at least 95%, of the titanium species contacting the silica support in the contacting step is mononuclear species.

[0073] According to a further aspect of the present invention, there is provided a method of producing a modified silica support according to any aspect or otherwise herein, the method comprising the steps of:

[0074] providing a silica support having silanol groups;

[0075] The silica support is treated with a mononuclear titanium compound such that titanium is adsorbed onto the surface of the silica support by reaction with the silanol groups, wherein the adsorbed titanium atoms are sufficiently spaced from one another to substantially prevent oligomerization with adjacent titanium atoms, and more preferably, are sufficiently spaced from one another to substantially prevent dimerization or trimerization of the adsorbed titanium atoms with adjacent modifier metal atoms.

[0076] Preferably, the separation of the titanium atoms is achieved by:

[0077] a) reducing the concentration of silanol groups on the silica support, and / or

[0078] b) Prior to treating the silica support, a non-labile ligand of sufficient size is attached to the titanium.

[0079] According to yet another aspect, there is provided a method for producing a catalyst, the method comprising the steps of:

[0080] i. Providing a silica support having isolated silanol groups and optionally treating the support to provide <2.5 groups per nm 2 level

[0081] isolated silanol groups (-SiOH);

[0082] ii. contacting the optionally treated silica support with a mononuclear titanium modifier metal compound to effect adsorption of titanium onto the support, typically to the separated silanols

[0083] At least 25% of the group;

[0084] iii. optionally, removing any solvent or liquid carrier for the titanium compound;

[0085] iv. The calcined modified silica lasts long enough to bind the mononuclear titanium adsorbed on the surface

[0086] The time and temperature for the conversion of the product into titanium oxide or titanium hydroxide;

[0087] v. treating the calcined modified silica with a catalytic alkali metal to impregnate the modified silica with the catalytic metal to form the catalyst, and optionally calcining the catalyst.

[0088] According to yet another aspect of the present invention, there is provided a method for producing a modified silica support for a catalyst, the method comprising the steps of:

[0089] i. Providing a silica support having isolated silanol groups and optionally treating the support to provide <2.5 groups per nm 2 The level of isolated silanol groups (-SiOH);

[0090] ii. contacting the optionally treated silica support with a mononuclear titanium compound to achieve adsorption of titanium onto said support, typically to at least 25% of said isolated silanol groups;

[0091] iii. optionally, removing any solvent or liquid carrier for the modifier metal compound;

[0092] iv. Optionally, calcining the modified support for a time and temperature sufficient to convert the mononuclear titanium compound adsorbed on the surface to titanium oxide or titanium hydroxide in preparation for catalyst impregnation.

[0093] Preferably, the silanol group concentration is reduced by calcination, chemical dehydration or other suitable methods before treatment with the titanium compound.

[0094] Preferably, the source of mononuclear titanium cations herein is a solution of a compound of said titanium, such that the compound is in solution when contacted with the support to effect adsorption onto the support.

[0095] Typically, the solvent used for the solution is different from water.

[0096] Typically, the solvent is an organic solvent such as toluene or heptane. In addition, the solvent can be an aliphatic solvent or an aromatic solvent. Still additionally, the solvent can be a chlorinated solvent such as dichloromethane. More typically, the solvent is an aliphatic alcohol, which is typically selected from C1-C6 alkanols such as methanol, ethanol, propanol, isopropanol, butanol, pentanol and hexanol, more typically methanol, ethanol or propanol.

[0097] Advantageously, the proximity of the adsorbed titanium modifier metal to the adjacent titanium modifier metal cation can be controlled by the concentration of the titanium modifier metal in the contacting step and by:

[0098] a) the concentration of silanol groups on the silica support, and / or

[0099] b) The size of any non-labile ligands attached to the titanium modifier metal cation.

[0100] Before adsorption, the silanol group concentration on the silica support is preferably controlled by calcining or other suitable methods as known to those skilled in the art. The method for identifying silanols includes for example LT Zhuravlev, in " Colloids and Surfaces:Physicochemical and Engineering Aspects, Vol. 173, pp. 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 detected by infrared spectroscopy as a 3730 cm -1 -3750cm -1 A narrow absorption peak at 3460 cm was identified, while other silanols showed a peak at 3460 cm -1 and 3715cm -1 A broad peak is shown between the two (see "The Surface Properties of Silicas", edited by Andre P Legrand, John Wiley and Sons, 1998 (ISBN 0-471-95332-6) pp. 147-234).

[0101] A non-labile ligand is a ligand that is coordinated to the titanium modifier metal and is not removed by adsorption of titanium onto the silica surface. Thus, prior to treating the silica surface with titanium, the non-labile ligand is typically coordinated to the titanium modifier metal in solution. For the avoidance of doubt, the non-labile ligand is typically removed by appropriate treatment of the silica surface following adsorption of the titanium.

[0102] The size of the non-labile ligand effectively separates the titanium moiety and prevents its binding.

[0103] According to a further aspect of the present invention, a method of producing a modified silica support for one or more catalysts is provided.

[0104] The present invention extends to a modified silica support according to any one of the aspects herein wherein the support comprises <2.5 groups per nm 2 Typically, the support contains >0.1 and <2.5 groups per nm. 2 levels, more preferably from 0.2 to 2.2 groups per nm 2 The level is most preferably from 0.4 to 2.0 groups per nm 2 The level of isolated silanol groups (-SiOH).

[0105] Still further, the invention extends to a catalyst or modified silica support according to any aspect herein wherein the support comprises a catalyst present on the support and having a density of < 2.5 parts per nm 2 The titanium modifier metal portion is present at a level of .

[0106] Typically, the support comprises >0.025 and <2.5 moieties per nm 2 level, more preferably from 0.05 to 2.0 parts per nm 2 levels, most preferably from 0.1 to 1.5 parts per nm 2 The level of the titanium modifier metal portion.

[0107] Suitable ligands herein may be non-labile ligands, optionally selected from molecules having a lone pair of electrons, containing oxygen or nitrogen atoms capable of forming a 5-membered or 6-membered ring with a titanium atom. Examples include diketones, diimines, diamines, diols, dicarboxylic acids or derivatives thereof such as esters, or molecules having two different such functional groups, and in either case, the corresponding N or O and N or O atoms are separated by 2 or 3 atoms, thereby forming a 5-membered or 6-membered ring. Examples include pentane-2,4-dione, esters of 3-oxobutyric acid with fatty alcohols containing 1 to 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-propylene glycol, 1,3-propylene glycol, Alcohols, 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, salts of 1,2-dihydroxybenzene-3-5-disulfonate, diethylenetriaminepentaacetic acid, nitrotriacetic 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-oxobutanoate and tert-butyl 3-oxobutanoate are most preferred. In one embodiment, the present invention provides the mononuclear modifier metal cation source.Have for example total less than 10 carbon and / or heteroatomic less bidentate ligand and make it possible to form little complex compound, compared with larger part, described little complex compound can allow to be deposited on the surface of silicon-dioxide with higher concentration.Therefore, the mononuclear modifier metal cation source herein can be titanium and such less part, preferably, with the form of the complex compound of at least one such part.Such compound can comprise variable ligand, such as the solvent ligand in alcoholic solvent, alkoxide ligand, such as ethanolate or propoxide etc.

[0108] Preferably, the concentration of isolated silanol groups determines the maximum number of sites for adsorption of the titanium modifier metal. By controlling this concentration, the proximity of the adsorbed titanium modifier metal can be effectively determined because the distribution of silanol sites will generally be uniform. The isolated silanol concentration used to produce the modified silica support according to the present invention can be less than 2.5 groups per nm. 2 , more typically, less than 2.0 groups per nm 2 , most typically, less than 1.75 groups per nm 2A suitable range for the silanol concentration used to produce the modified silica support may be 0.4 to 2.5 silanol groups per nm. 2 , more preferably 0.5-2.0 silanol groups per nm 2 , most preferably 0.8-1.5 silanol groups per nm 2 .

[0109] The concentration of the titanium modifier metal, typically in the form of a cation, should be set to a level that prevents significant formation of a double layer or the like on the surface of the support, which would result in titanium metal-metal interactions. Furthermore, filling of gaps in the initial monolayer, which could result in weak adsorption of the titanium modifier metal away from the silanol sites, should also be avoided to prevent interactions with adjacent, strongly adsorbed titanium modifier metals. Typical concentration ranges for the titanium modifier metals of the present invention may be as described herein.

[0110] Typically, when the source of the modifier metal compound is contacted with the support to achieve adsorption of the compound 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%, and in particular at least 95%, of the titanium modifier metal in the modifier metal compound is a mononuclear modifier metal compound.

[0111] According to a further aspect of the present invention, there is provided a method for producing a catalyst, the catalyst comprising:

[0112] a modified silica support comprising a titanium modifier metal;

[0113] and catalytic metals on modified silica supports,

[0114] characterised in that at least a portion of the modifier metal, typically at least 25%, is present in the form of mononuclear titanium moieties,

[0115] The method comprises the following steps:

[0116] The silica support is treated to provide <2.5 groups per nm 2 The level of isolated silanol groups (-SiOH);

[0117] reacting the treated support with a mononuclear titanium compound to achieve at least 25% bonding thereof to said isolated silanol groups;

[0118] Optionally, removing any solvent or liquid carrier;

[0119] calcining the modified silica for a time and temperature sufficient to convert the mononuclear titanium compound adsorbed on the surface to titanium oxide or titanium hydroxide;

[0120] The calcined modified silica is treated with a catalytic alkali metal to impregnate the modified silica with the catalytic metal.

[0121] Advantageously, by providing a smaller number of isolated silanol sites and by incorporating mononuclear titanium species into these sites, a catalyst support is provided that results in improved selectivity of the catalyst, lower sintering rates and better aging of the catalyst.

[0122] A suitable method for treating silica to provide isolated silanol groups at a specified level is by calcination. However, other techniques such as hydrothermal treatment or chemical dehydration are also possible. US5583085 teaches 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, compared to 0.7 / nm by thermal treatment. 2 Therefore, in some cases, chemical dehydration can provide more space for silanol group control.

[0123] The term isolated silanol (also known as single silanol) is well known in the art and distinguishes this group from vicinal or geminal silanols or internal silanols. Suitable methods for determining the incidence of isolated silanols include surface sensitive infrared spectroscopy and 1 H NMR or 31 Si NMR.

[0124] According to a sixth aspect of the present invention, there is provided a method of producing a catalyst according to any of the preceding aspects of the present invention, the method comprising the steps of forming a modified silica according to any of the preceding aspects, and contacting the modified silica support with a solution comprising a catalytic metal to impregnate the modified silica with the catalytic metal.

[0125] Preferably, the silica support is dried or calcined prior to treatment with the source of titanium cations.The formed modified silica may be dried or calcined prior to the addition of the catalytic metal, regardless of whether it has been previously dried or calcined.

[0126] Prior to treatment with the modifier metal, the silica may be in the form of a gel. At the start of modification, the gel may be in the form of a hydrogel, xerogel or aerogel.

[0127] The silica support may be a xerogel, a hydrogel or an aerogel. Preferably, the silica support is a xerogel.

[0128] The silica support can be treated by a mononuclear modifier metal cation source 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 modifier metal cation source in such a way that the modifier metal is dispersed throughout the silica support. Typically, titanium can be evenly distributed on the surface of the entire silica support. Preferably, the titanium modifier metal is dispersed in the silica support by adsorption.

[0129] As used herein, the term "adsorption" or similar terms in relation to titanium modifier metals means that the modifier metal is incorporated onto the surface of the silica support by the interaction of a source of titanium cations with the silica support, typically by chemical adsorption. Typically, adding the modifier to the silica support comprises the steps of adsorbing a source of metal cations onto the silica support to form an organometallic complex, and calcining the complex to convert the organometallic complex into a metal oxide moiety. Thus, typically, there is a uniform distribution of the modifier metal throughout the silica support. Typically, titanium is dispersed throughout the silica support.

[0130] Examples of suitable metal cation sources herein include organic complexes and metal salts, such as tetra(methanol)titanium, tetra(ethanol)titanium, tetra(n-propoxide)titanium, tetra(isopropoxide)titanium, tetra(n-butoxide)titanium, tetra(tert-butoxide)titanium, tetra(2-ethylhexyl)titanium, bis(acetylacetonate)titanium oxide, bis(2,2,6,6-tetramethyl-3,5-heptanediol)titanium oxide, (triethanolamine)titanium isopropoxide, bis(triethanolamine)titanium diisopropoxide, tetra(diethylamide)titanium, tetra(ethylmethylamide)titanium, tetra(dimethylamide)titanium, tetra(neopentyl)titanium, bis(ammonium lactate)dihydroxytitanium (IV); such as oxysulfate titanium (IV), oxynitrate titanium (IV), and chloride titanium (IV). Typically, the mononuclear modifier metal cation source is provided as an organic complex.

[0131] Typically, the titanium modifier metal is contacted with the silica support in solution.

[0132] Preferably, the titanium modifier metal cation source is provided in any solvent in which the metal cation source is soluble. Examples of suitable solvents include water or alcohol. Preferred solvents are alcohols such as methanol, ethanol, propanol, isopropanol, butanols, amyl alcohols, and hexanols.

[0133] Preferably, the source of titanium modifier metal cations is added to the silica as a metal salt in such an alcoholic solution.

[0134] In one embodiment, the source of metal cations is provided as a solution of one or more of titanium tetra(methoxide), titanium tetra(ethoxide), titanium tetra(n-propoxide), titanium tetra(isopropoxide), titanium tetra(n-butoxide), titanium tetra(tert-butoxide), titanium tetra(2-ethylhexyloxide), titanium bis(acetylacetonate) oxide, titanium bis(2,2,6,6-tetramethyl-3,5-heptanedioate) oxide, titanium (triethanolamine)isopropoxide, titanium bis(triethanolamine)diisopropoxide, titanium tetra(diethylamide), titanium tetra(ethylmethylamide), titanium tetra(dimethylamide), titanium tetra(neopentyl), titanium bis(ammonium lactate)dihydroxytitanium(IV) in one of methanol, ethanol, isopropanol, propanol, butanol, isobutanol, or 2-butanol, optionally comprising up to 20% by volume of water.

[0135] Preferably, after adsorption of the modifier metal onto the silica support, the solvent is removed by evaporation.

[0136] Optionally, the modified silica support is calcined to remove any ligands or other organics from the modified support.

[0137] The skilled person will appreciate that the catalytic metal may be added to the modified silica by any suitable means.Typically, to produce a modified silica catalyst, the modified silica is contacted with the catalytic metal.

[0138] Typically, to produce the catalyst, the modified silica support is contacted with an acidic, neutral, or alkaline aqueous solution containing the catalytic metal, such as cesium, in the form of a salt of the catalytic metal and a base. 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, typically up to 20 vol%, may be included in the solution.

[0139] 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 a modified silica-supported catalyst.

[0140] 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 may be at least 5° C., more typically at least 10° C., and most typically at least 20° C.

[0141] 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.

[0142] The concentration of the catalytic metal salt solution used in 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 solution is best determined experimentally.

[0143] Suitable catalytic metal salts 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 the impregnation, the pH can be controlled by adding ammonia and a metal compound, or by using a suitable catalytic metal compound such as formates, carbonates, acetates, or hydroxides, more preferably hydroxides or carbonates, in each case, alone, in combination, or with a suitable carboxylic acid. At the end of the impregnation, it is most important to control the pH within a preferred range in order to achieve satisfactory adsorption. Most typically, these salts can be incorporated using alkaline solutions of the salts. If the salt itself is not alkaline, a suitable base such as ammonium hydroxide can be added. Since hydroxide salts are alkaline in nature, a mixture of one or more of the above salts with a specific catalytic metal such as a hydroxide salt of cesium can be conveniently prepared.

[0144] The skilled artisan will appreciate that the catalytic metals of the present invention may be added to the modified silica support by any suitable means. After depositing the compound onto the support, optionally using a suitable aqueous salt and subsequently drying the surface-coated support, the catalyst may be fixed to the support, typically by calcination.

[0145] Typically, drying of the modified silica support is achieved by suitable methods known to the skilled person, such as in a drying unit or an oven.

[0146] Typically, the catalyst comprises between 0.01% w / w-25% w / w water, more typically between 0.1% w / w-15% w / w water, and most typically between 0.5% w / w-5.0% w / w water.

[0147] Optionally, the modified silica-supported catalyst comprising the catalytic metal may be dried or calcined, the process of calcination being well known to those skilled in the art.

[0148] In some cases, it may be necessary to calcine the support formed from the modification stage at 200°C to 1000°C, more typically 300°C to 800°C, and most typically 350°C to 600°C, prior to adding the catalytic metal. In a preferred calcination of the support formed from the modification stage, the temperature is at least 375°C, such as 400°C or 450°C. Typically, the calcination atmosphere should contain some oxygen, suitably 1% to 30% oxygen, and most suitably 2% to 20% oxygen, to achieve removal of organic residues as carbon dioxide and water. Typically, the calcination time can be between 0.01 hours and 100 hours, suitably 0.5 hours to 40 hours, and most suitably 1 hour to 24 hours. The calcined support, such as a xerogel material, should be cooled to a suitable temperature for impregnation. The addition of the catalytically active metal can be carried out by the method described for the uncalcined material, or can be by any other standard method for impregnating a catalyst support such as a xerogel support, such as using a solvent other than water such as an alcohol, suitably methanol, ethanol, propanol or isopropanol, or using an incipient wetness method, wherein 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 that the target amount of catalytically active metal is introduced into the xerogel support material, rather than providing an excess of a lower concentration solution by the methods described earlier. The addition of the catalytically active metal can utilize any preferred method known in the art. In the case where an organic complex is used as the source of titanium, calcination techniques are particularly advantageous because it may be necessary to modify the subsequent catalyst preparation procedure so that at least a portion of the organic complex salt is removed before impregnation with cesium. Advantageously, it has been found that by calcining the modified support, the ratio of catalytic metal:modifier metal is reduced, and therefore the required catalytic metal is reduced. This is unexpected and provides a further improvement to the present invention.

[0149] 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 the carboxylic acid or carboxylic ester in the presence of a catalyst and optionally in the presence of an alcohol, wherein the catalyst is according to any other aspect of the invention as defined herein.

[0150] Advantageously, it has also been found that the silica comprising the modification defined herein and the catalyst comprising a catalytic metal are very effective catalysts for producing α, β olefinically unsaturated carboxylic acids or carboxylic esters by the condensation of corresponding acid or ester and a methylene source such as formaldehyde, and the catalyst has the sintering of the reduction of the catalyst surface, the selectivity of improvement and provides a high catalyst surface area. Especially, when using a mononuclear titanium portion and / or when calcining the modified silica carrier before treating with a catalytic metal, enhanced performance has been found. In addition, using some metal complexes to incorporate the titanium modifier metal on the carrier by adsorption provides a convenient source of the mononuclear titanium portion. Such a source also allows the property of the titanium modifier metal to be controlled, and provides a more uniform distribution of the mononuclear titanium portion.

[0151] The term "suitable source thereof" in relation to formaldehyde herein 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 to free formaldehyde under the reaction conditions, for example the source can form the same reaction intermediate as formaldehyde, allowing an equivalent reaction to occur.

[0152] A suitable source of formaldehyde may be a compound of formula (I):

[0153]

[0154] where R 5 and R 6 Independently selected from C1-C 12 hydrocarbon or H, X is O, n is an integer from 1 to 100, and m is 1.

[0155] Typically, R 5 and R 6 independently selected from C1-C 12 Alkyl, alkenyl or aryl, or H, more suitably C1-C 10 Alkyl or H, most suitably C1-C6 alkyl or H, especially methyl or H. Typically, n is an integer from 1 to 10, more suitably 1 to 5, especially 1-3.

[0156] However, other sources of formaldehyde, including trioxane, may also be used.

[0157] Therefore, 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; polyoxymethylene R 1 -O-(CH2-O) i -R 2 , where R 1 and / or R 2is a hydrocarbyl 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.

[0158] Polyoxymethylene is a higher formals or hemiformals of formaldehyde and methanol, CH3-O-(CH2-O) i -CH3("formal-i") or CH3-O-(CH2-O) i -H ("hemialfond-i"), wherein i = 1 to 100, suitably 1-5, in particular 1-3; or other polyoxymethylenes having at least one non-methyl terminal group. Thus, the source of formaldehyde may also be of the formula R 31 -O-(CH2-O-) i R 32 Polyoxymethylene, where R 31 and R 32 can be the same group or different groups, and at least one is selected from C1-C 10 Hydrocarbyl groups, such as R 31 =isobutyl and R 32 = methyl.

[0159] Typically, suitable sources of formaldehyde are selected from dimethoxymethane; the lower hemiformals of formaldehyde and methanol, CH3-O-(CH2-O) i -H, wherein i=1-3; formalin; or a mixture comprising formaldehyde, methanol and methyl propionate.

[0160] Typically, the term formalin means a mixture of formaldehyde:methanol:water in a ratio of 25% to 65% by weight:0.01% to 25%:25% to 70% by weight. More typically, the term formalin means a mixture of formaldehyde:methanol:water in a ratio of 30% to 60% by weight:0.03% to 20%:35% to 60% by weight. Most typically, the term formalin means a mixture of formaldehyde:methanol:water in a ratio of 35% to 55% by weight:0.05% to 18%:42% to 53% by weight.

[0161] Typically, the mixture comprising formaldehyde, methanol and methyl propionate comprises less than 5% by weight of water. More suitably, the mixture comprising formaldehyde, methanol and methyl propionate comprises less than 1% by weight of water. Most suitably, the mixture comprising formaldehyde, methanol and methyl propionate comprises from 0.1% to 0.5% by weight of water.

[0162] 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 reacting a compound of formula R in the presence of a catalyst according to any aspect of the present invention and optionally in the presence of an alkanol. 1-CH2-COOR 3 The alkanoic acid or alkanoic acid ester is contacted with formaldehyde or a suitable source of formaldehyde according to formula (I) as defined below:

[0163]

[0164] where R 5 is methyl and R 6 It is H;

[0165] X is O;

[0166] m is 1;

[0167] and n is any value between 1 and 20 or any mixture of these values;

[0168] 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 It may also be independently hydrogen or have 1

[0169] The hydrocarbyl group preferably has 1 to 12, more suitably 1 to 8, most suitably 1 to 4 carbon atoms.

[0170] Thus, the inventors have found that titanium in the form of a mononuclear oxide moiety according to the present invention is able to 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 olefinically unsaturated carboxylic acid. In addition, the sintering rate of the catalyst surface is significantly and surprisingly reduced during the condensation reaction.

[0171] Thus, one particular process in which the catalysts of the present invention have been found to be particularly advantageous is the condensation of formaldehyde with methyl propionate in the presence of methanol to produce MMA.

[0172] In the case of the production of MMA, the catalyst is typically contacted with a mixture comprising formaldehyde, methanol, and methyl propionate.

[0173] The process of the seventh or eighth aspect of the invention is particularly suitable for producing acrylic acid and hydrocarbyl acrylic acid and their hydrocarbyl esters, and also methylene substituted lactones. Suitable methylene substituted lactones include 2-methylene valerolactone and 2-methylene butyrolactone, which are derived from valerolactone and butyrolactone, respectively. Suitable (hydrocarbyl) acrylic acid and its esters are (C 0-8 Hydrocarbon) acrylic acid or hydrocarbon (C 0-8alkyl) acrylates, which typically result 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 from propionic acid or methyl propionate to produce methacrylic acid, acrylic acid, methyl methacrylate, ethyl acrylate or butyl acrylate, more suitably methacrylic acid or in particular methyl methacrylate (MMA). Thus, in the production of methyl methacrylate or methacrylic acid, the formula R 1 -CH2-COOR 3 The preferred ester or acid of is methyl propionate or propionic acid, respectively, and the preferred alkanol is therefore 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.

[0174] The reaction of the present invention can be a batch reaction, a semi-batch reaction or a continuous reaction.

[0175] In the process of the seventh or eighth aspect of the 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. Typical residence time of the reactants in the presence of the catalyst is between 0.1 seconds and 300 seconds, more preferably between 1 second and 100 seconds, most preferably between 2 seconds and 50 seconds, and especially between 3 seconds and 30 seconds.

[0176] 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, usually the amount of the catalyst will be selected to achieve optimal selectivity and the yield of 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 reactant. In addition, the technician will understand that, relative to 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.

[0177] 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 suitably 5:1 to 1:15. The most preferred ratio will depend on the form of formaldehyde and the ability of the catalyst to liberate formaldehyde from formaldehydic species. Thus, in R 31 O-(CH2-O) i R 32 R in 31 and R32 In the case where one or both of the R is H, relatively low ratios are required for highly reactive formaldehyde species, 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 Where neither is H, as for example in CH3O-CH2-OCH3, or in trioxane, higher ratios are most preferred, typically 6:1 to 1:3.

[0178] As mentioned above, water may also be present in the reaction mixture due to the source of formaldehyde. Depending on the source of formaldehyde, it may be necessary to remove some or all of the water therefrom prior to catalysis. Maintaining a lower level of water than that present in the source of formaldehyde can benefit catalytic efficiency and / or subsequent purification of the product. Less than 10 mol % water in the reactor is preferred, more preferably less than 5 mol %, and most preferably less than 2 mol %.

[0179] 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, such 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.

[0180] The reagents of the seventh aspect or the eighth aspect can be fed to the reactor independently or after premixing, and the process of the reaction can be continuous or batch. However, typically, a continuous process is used.

[0181] Typically, the process of the seventh or eighth aspect of the invention is carried out when the reactants are in the gas phase.

[0182] In a further aspect, the 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 the step of first producing a catalyst according to any relevant aspect herein.

[0183] definition

[0184] Unless otherwise indicated, the term "alkyl" as used herein means a C1 to C 12Hydrocarbyl, and includes methyl, ethyl, vinyl, propyl, propenyl, butyl, butenyl, pentyl, pentenyl, hexyl, hexenyl and heptyl groups, typically, the hydrocarbyl group is selected from methyl, ethyl, propyl, butyl, pentyl and hexyl, more typically methyl. Unless otherwise indicated, when there are a sufficient number of carbon atoms, the hydrocarbyl group may be straight or branched, cyclic, acyclic or partially cyclic / acyclic, unsubstituted, substituted or terminated with 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, wherein here and generally herein R 19 to R 30 Each independently represents hydrogen, halogen, unsubstituted or substituted aryl or unsubstituted or substituted hydrocarbon, or in R 21 In the case of halogen, nitro, cyano and amino groups and / or by one or more (typically less than 4) oxygen atoms, sulfur atoms, silicon atoms or by silanol groups or dihydrocarbyl silicon groups or mixtures thereof. Typically, the hydrocarbyl group is unsubstituted, typically linear, and typically saturated.

[0185] The term "alkenyl" is to be understood as "hydrocarbyl" above, except that at least one carbon-carbon bond is unsaturated, and thus the term relates to C2 to C 12 Alkenyl group.

[0186] In the absence of information to the contrary, the term "hydrocarbyl" or similar terms should be considered to conform to the above definition of "hydrocarbyl", except that "C0 hydrocarbyl" means unsubstituted by hydrocarbyl.

[0187] 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 with one or more substituents selected from unsubstituted or substituted aryl, hydrocarbyl (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 (the hydrocarbyl group itself may be unsubstituted or substituted or terminated as defined herein), or, in R 21 In the case of halogen, nitro, cyano or amino.

[0188] The term "halogen" when used herein means a chloro, bromo, iodo or fluoro group, typically chloro or fluoro.

[0189] 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 which do not contain one or more double bonds, contain one or more double bonds, or may be non-aromatic, partially aromatic, or fully aromatic in nature. The ring systems 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 may itself be unsubstituted or substituted or end-capped as defined herein), -OR 19 、-OC(O)R 20 、-C(O)R 21 、-C(O)OR 22 、-N(R 23 )R 24 、-C(O)N(R 25 )R26 、-SR 29 、-C(O)SR 30 or -C(S)N(R 27 )R 28 , where 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 terminated as defined herein), or in R 21 In the case of halogen, nitro, amino or cyano. Thus, the term "Het" includes groups such as optionally substituted azetidinyl, pyrrolidinyl, imidazolyl, indolyl, furyl, oxazolyl, isoxazolyl, oxadiazolyl, thiazolyl, thiadiazolyl, triazolyl, oxatriazolyl, thiatriazolyl, pyridazinyl, morpholinyl, pyrimidinyl, pyrazinyl, quinolyl, isoquinolyl, piperidinyl, pyrazolyl and piperazinyl. Substitution on Het may be on a carbon atom of the Het ring or, where appropriate, on one or more heteroatoms.

[0190] A "Het" group may also be in the form of an N-oxide.

[0191] Suitable optional alcohols for the catalytic reactions of the seventh and eighth aspects of the present invention may be selected from the group consisting of: C1-C 30 Alkanols, including aryl alcohols, may be optionally substituted with one or more substituents selected from the group consisting of 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 chlorooctanol, particularly methanol. Although monoalkanols are most preferred, polyalkanols (poly-alkanols) can also be used, and the polyalkanols are typically selected from diols-octaols such as diols, triols, tetraols and sugars. Typically, such polyalkanols are selected from 1,2-ethylene glycol, 1,3-propylene glycol, 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. The most preferred alkanol is methanol. The amount of alcohol is not critical. Typically, the amount used exceeds the amount of substrate to be esterified. Therefore, alcohol can also be used as the reaction solvent, although a separate solvent or additional solvent can also be used if desired.

[0192] The term "aging" is described, for example, in patent application WO 2009 / 003722. The general principles of aging 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, pp. 358-364. If this stage is carried out, the hydrogel is washed again to remove any materials used in the aging process and to bring the solution to the correct pH for the addition of the catalytically active metal, which depends on the choice of the catalytically active metal salt.

[0193] The term "gel," as used herein, is also known to those skilled in the art, but in case of doubt, it can be considered a solid network with a fluid dispersed therein. Typically, a gel is a polymer network with a fluid dispersed therein. Cogel is a term used to indicate that more than one of the original compounds / moieties, typically silica and a metal oxide or salt, is incorporated into the polymer network. Therefore, cogelation herein refers to the formation of a cogel.

[0194] 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 has been replaced by a gas and therefore does not undergo the same shrinkage as a xerogel.

[0195] The term onset in this context means the start of the formation of the modified silica.

[0196] As used herein, the term "part" in relation to a metal is used to refer to the form of the modifier metal on the modified support. While the modifier metal typically forms part of a network, 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 part on silica, means having the form of a mononuclear residue.

[0197] The % of modifier metal is unitless herein as it refers to the number of metal atoms per the total number of such atoms. It will be appreciated that moieties may take the form of non-mononuclear clusters, but these clusters are still made up of modifier metal atoms.

[0198] Unless otherwise indicated, the term "surface" as used herein in relation to a silica support includes the surface of the silica within the pores of the silica, more specifically within the macropores and mesopores of the silica.

[0199] Embodiments of the invention will now be defined with reference to the accompanying examples.

[0200] experiment

[0201] Silica Support Description

[0202] Example 1 (Preparation)

[0203] 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 allowed to cool to room temperature in a sealed flask stored in a desiccator. 2 The surface area of 1.000 Å / g, the pore volume of 1.000 Å / g and the average pore diameter of 100 nm were determined by nitrogen adsorption / desorption isotherm analysis (Micromeretics Tristar II). 2 This silica mainly includes spherical silica beads with a diameter range of 2.0 mm to 4.0 mm.

[0204] Ti modification of silica supports

[0205] Example 2 (from Ti ( n OPr)2(acac)2 0.6wt%Ti)(monomer)

[0206] 0.330 g of Ti(n 1-Pr)4 (98%, Sigma Aldrich) is dissolved in 11ml of 1-PrOH (99.7% anhydrous, Sigma Aldrich). To this solution, 0.348g of acetylacetone (Sigma Aldrich) is added, and stirring is continued for 30min at room temperature to allow Ti-complex formation. In a separate flask, 10g of the silica from Example 1 is weighed. The weighed silica is then added to the Ti-complex solution under stirring. Stirring is continued until all Ti-complex solutions have been absorbed into the pore volume of the silica. Once pore filling is complete, the Ti-modified silica is left in a sealed flask under regular stirring for 16 hours. After this time, the extra-porous solution is removed by filtration. This is followed by a drying step in which the intra-porous organic solvent is removed by passing a nitrogen stream through the wet Ti-modified silica at room temperature. Alternatively, the intra-porous solvent is removed on a rotary evaporator under reduced pressure. Once all the solvent had been removed, the Ti-modified silica support was calcined in a furnace at 500° C. under air flow with a heating ramp rate of 5° C. / min and a final hold of 5 hours. After cooling, this resulted in a Ti-modified silica support with 100% Ti usage efficiency. The titanium loading (wt %) on the Ti-modified support was determined via powder energy dispersive X-ray fluorescence analysis (Oxford Instruments X-Supreme 8000).

[0207] Example 3 (from Ti ( n OPr)2(acac)2 1.1wt%Ti)(monomer)

[0208] The support modification was carried out as described in Example 2, except that 0.665 g of Ti ( n In addition to 0.703 g of acetylacetone and 1.6 ml of 1-PrOH were used instead of 1.1 ml. This resulted in a Ti-complex adsorption step performed as a slurry phase type adsorption and a Ti adsorption efficiency of 99%.

[0209] Example 4 (from Ti(TEA)) i OPr) 0.6 wt% Ti) (monomer)

[0210] The support modification was carried out as described in Example 2, except that 0.741 g of Ti(TEA) ( i OPr) (80 wt% in 2-PrOH, Sigma Aldrich) and no acetylacetone was used. In addition, 20 ml of 1-PrOH was used instead of 11 ml. This resulted in a Ti adsorption efficiency of 57%.

[0211] Example 5 (from Ti(TEA)) i OPr) 1.0 wt% Ti) (monomer)

[0212] The support modification was carried out as described in Example 4, except that 1.510 g of Ti(TEA) ( i This resulted in a Ti adsorption efficiency of 45%.

[0213] Example 6 (from Ti(TEA)) i OPr) 2.0wt% Ti) (monomer)

[0214] The support modification was performed as described in Example 4, except that 2.382 g of Ti(TEA)(iOPr) was used. In addition, 10 ml of toluene (99.8% anhydrous, Sigma Aldrich) was used instead of 1-PrOH to dissolve Ti(TEA)( i This solution was then added to silica that had been pre-pore-filled with 10 ml of toluene. This resulted in a Ti adsorption efficiency of 58%.

[0215] Example 7 (Comparative) (from Ti( n OPr)4 3.9wt% Ti)(dimer)

[0216] The support modification was carried out as described in Example 4, except that 2.613 g of Ti ( n This resulted in a Ti adsorption efficiency of 95%.

[0217] Example 8 (Comparative) (from Ti( n OPr)4 with 1.8 wt% Ti)(dimer)

[0218] The support modification was carried out as described in Example 6, except that 1.039 g of Ti ( n This results in a Ti adsorption efficiency of 100%.

[0219] Cs modification of modified supports

[0220] Example 9 (3.5 wt% Cs, 0.5 wt% Ti)

[0221] In a glove box, 0.514 g of CsOH.HO (99.5% Sigma Aldrich) was weighed out and dissolved in 20 ml of a 9:1 v / v MeOH:HO (MeOH from Sigma Aldrich, HO as demineralized water) solvent mixture. 10 g of the modified silica from Example 2 was added to the CsOH solution under stirring. Stirring was continued for another 15 minutes, after which the sample was left in a sealed flask with periodic stirring for 16 hours. After this time, the solution outside the porous structure was removed by filtration. This was followed by a drying step in which the solvent inside the porous structure was removed by passing a stream of nitrogen through the wet Cs / Ti-modified silica at room temperature. Alternatively, the solvent inside the porous structure was removed under reduced pressure on a rotary evaporator. After this step, the catalyst beads were placed in a drying oven at 120°C and left to dry for 16 hours. After cooling, this resulted in a Cs / Ti / SiO catalyst with a Cs utilization rate of 90%. The Cs loading (wt %) on the catalyst was determined via powder energy dispersive X-ray fluorescence analysis (Oxford Instruments X-Supreme 8000).

[0222] Example 10 (4.0 wt% Cs, 0.5 wt% Ti)

[0223] The catalyst was prepared as described in Example 9, except that 0.583 g of CsOH.H2O was used.

[0224] Example 11 (4.4 wt% Cs, 0.5 wt% Ti)

[0225] The catalyst was prepared as described in Example 9, except that 0.647 g of CsOH.H2O was used.

[0226] Example 12 (5.3 wt% Cs, 0.5 wt% Ti)

[0227] The catalyst was prepared as described in Example 9, except that 0.795 g of CsOH.H2O was used.

[0228] Example 13 (6.6 wt% Cs, 1.0 wt% Ti)

[0229] The catalyst was prepared as described in Example 9, except that 1.01 g of CsOH.H2O was used and the modified silica from Example 3 was used.

[0230] Example 14 (7.7 wt% Cs, 1.0 wt% Ti)

[0231] The catalyst was prepared as described in Example 13, except that 1.17 g of CsOH.H2O was used.

[0232] Example 15 (8.4 wt% Cs, 1.0 wt% Ti)

[0233] The catalyst was prepared as described in Example 13, except that 1.30 g of CsOH.H2O was used.

[0234] Example 16 (9.9 wt% Cs, 1.0 wt% Ti)

[0235] The catalyst was prepared as described in Example 13, except that 1.55 g of CsOH.H2O was used.

[0236] Example 17 (4.0 wt% Cs, 0.6 wt% Ti)

[0237] The catalyst was prepared as described in Example 9, except that 0.59 g of CsOH.H2O was used and the modified silica from Example 4 was used.

[0238] Example 18 (4.8 wt% Cs, 0.6 wt% Ti)

[0239] The catalyst was prepared as described in Example 17, except that 0.71 g of CsOH.H2O was used.

[0240] Example 19 (5.2 wt% Cs, 0.6 wt% Ti)

[0241] The catalyst was prepared as described in Example 17, except that 0.78 g of CsOH.H2O was used.

[0242] Example 20 (6.3 wt% Cs, 0.6 wt% Ti)

[0243] The catalyst was prepared as described in Example 17, except that 0.95 g of CsOH.H2O was used.

[0244] Example 21 (6.5 wt% Cs, 1.0 wt% Ti)

[0245] The catalyst was prepared as described in Example 9, except that 0.99 g of CsOH.H2O was used and the modified silica from Example 5 was used.

[0246] Example 22 (7.5 wt% Cs, 0.9 wt% Ti)

[0247] The catalyst was prepared as described in Example 21, except that 1.15 g of CsOH.H2O was used.

[0248] Example 23 (9.8 wt% Cs, 0.9 wt% Ti)

[0249] The catalyst was prepared as described in Example 21, except that 1.54 g of CsOH.H2O was used.

[0250] Example 24 (9.3 wt% Cs, 1.8 wt% Ti)

[0251] The catalyst was prepared as described in Example 9, except that 1.46 g of CsOH.H2O was used and the modified silica from Example 6 was used.

[0252] Example 25 (10.5wt%, 1.8wt% Ti)

[0253] The catalyst was prepared as described in Example 24, except that 1.67 g of CsOH.H2O was used.

[0254] Example 26 (Comparative) (12.4 wt% Cs, 3.4 wt% Ti)

[0255] The catalyst was prepared as described in Example 9, except that 2.04 g of CsOH.H2O was used and the modified silica from Example 7 was used.

[0256] Example 27 (Comparative) (14.0 wt% Cs, 3.4 wt% Ti)

[0257] The catalyst was prepared as described in Example 26, except that 2.35 g of CsOH.H2O was used.

[0258] Example 28 (Comparative) (15.2 wt% Cs, 3.3 wt% Ti)

[0259] The catalyst was prepared as described in Example 26, except that 2.58 g of CsOH.H2O was used.

[0260] Example 29 (Comparative) (18.2 wt% Cs, 3.2 wt% Ti)

[0261] The catalyst was prepared as described in Example 26, except that 3.21 g of CsOH.H2O was used.

[0262] Example 30 (Comparative) (9.4 wt% Cs, 1.6 wt% Ti)

[0263] The catalyst was prepared as described in Example 9, except that 2.04 g of CsOH.H2O was used and the modified silica from Example 8 was used.

[0264] Example 31 (Comparative) (10.6 wt% Cs, 1.6 wt% Ti)

[0265] The catalyst was prepared as described in Example 30, except that 1.61 g of CsOH.H2O was used.

[0266] Example 32 (Catalytic Performance Test)

[0267] The catalysts from Examples 9 to 31 were tested in a laboratory-scale microreactor for the reaction of methyl propionate and formaldehyde. To this end, 3 g of the catalyst was loaded into a fixed-bed reactor with an inner tube diameter of 10 mm as crushed and sieved (0.1 mm-1.0 mm particle size) or whole beads (2.0 mm-4.0 mm particle size). 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 at 0.032 ml / min by a Gilson pump. This preconditioning was continued overnight. After pretreatment, a feed stream containing 75.6 wt% methyl propionate, 18.1 wt% methanol, 5.7 wt% formaldehyde, and 0.6 wt% water was pumped to an evaporator set at 330°C via a Gilson pump and then fed to a heated reactor set at 330°C containing a catalyst. The reactor outlet vapor was cooled and condensed, and samples were collected at five different liquid feed rates (between 0.64 ml / min and 0.032 ml / min) to obtain conversion at different vapor / catalyst contact times. The liquid feed and condensed reactor liquid product were analyzed by a Shimadzu 2010 gas chromatograph with a DB1701 column. The composition of the samples was determined by the corresponding chromatograms, and the yield and selectivity at different contact times were determined. Activity is defined as the reciprocal of the contact time in seconds required to obtain a 10% MMA + MAA yield on the fed methyl propionate and is determined by interpolation on a contact time versus MMA + MAA yield plot. This interpolated contact time is then used to obtain the MMA + MAA selectivity at a 10% MMA + MAA yield.

[0268] Table 1: Activity and MMA+MAA selectivity results for catalysts prepared on Ti-modified support examples tested as whole beads.

[0269]

[0270]

[0271] Table 2: Activity and MMA+MAA selectivity results for catalysts prepared on Ti-modified support examples tested as crushed beads.

[0272]

[0273] Example 33 (Accelerated Aging Test)

[0274] Catalyst sintering resistance was evaluated in an accelerated aging test. For this purpose, 1 g of catalyst was loaded into a U-tube stainless steel reactor and loaded into an oven. The oven was heated to 385°C and a stream of nitrogen (10 ml / min) was passed through a saturated vaporiser containing water heated to 92°C. This ensured that a feed stream with a water partial pressure of 0.75 bara passed through the catalyst heated to 385°C. Periodically, the surface area of the catalyst samples was determined ex situ using nitrogen adsorption / desorption isotherm analysis (Micromeretics Tristar II). The measured surface area values were used to determine the sintering rate constant for each catalyst and were described as g 3 .m -6 .d -1 The higher the sintering rate constant, the lower the sintering resistance of the catalyst. This test was performed on the catalysts from Examples 9 to 12.

[0275] Table 3: Accelerated aging data for catalysts containing Ti as modifier.

[0276]

[0277] Attention is directed to all papers and documents which are filed concurrently with or before this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

[0278] All features disclosed in this specification (including any accompanying claims, abstract and drawings) and / or all steps of any method or process so disclosed may be combined in any combination, except combinations where at least some of such features and / or steps are mutually exclusive.

[0279] Unless expressly stated otherwise, each feature disclosed in this specification (including any accompanying claims, abstracts and drawings) may be used as an alternative feature serving the same, equivalent or similar purpose. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

[0280] The invention is not limited to the details of the foregoing embodiments. The invention extends to any novel inventive feature or any novel combination of inventive features disclosed in this specification (including any accompanying claims, abstract or drawings), or to any novel inventive step or any novel combination of inventive steps of any method or process disclosed as such.

Claims

1. A catalyst comprising a modified silica support comprising a silica support and a titanium modifier metal; and a catalytic metal on the modified silica support, characterized in that At least a portion of the modifier metal is present as a mononuclear titanium moiety, wherein the catalytic metal is one or more alkali metals selected from potassium, rubidium, and cesium.

2. The catalyst of claim 1 wherein at least 25% of the modifier metal is present in the form of mononuclear titanium moieties.

3. A catalyst comprising a modified silica support, the modified silica support comprising a silica support and a titanium modifier metal; and a catalytic metal on the modified silica support, characterized in that At least a portion of the modifier metal is present as a modifier metal moiety derived from a source of mononuclear titanium cations at the start of modification, wherein the catalytic metal is one or more alkali metals selected from potassium, rubidium, and cesium.

4. The catalyst of claim 3, wherein at least 25% of the modifier metal is present as modifier metal moieties derived from the source of mononuclear titanium cations at the start of modification.

5. The catalyst according to any one of claims 1 to 4, wherein the catalytic metal is selected from rubidium and cesium.

6. The catalyst of any one of claims 1 to 4, wherein the catalytic metal is cesium.

7. The catalyst according to any one of claims 1 to 4, wherein the catalytic metal is present in the range of 0.5 mol / mol to 7.0 mol / mol titanium.

8. The catalyst of any one of claims 1-4, wherein the catalyst is calcined.

9. A modified silica support for a catalyst, comprising a silica support and a titanium modifier metal, characterized in that At least a portion of the modifier metal is present as a mononuclear titanium moiety.

10. The modified silica support of claim 9, wherein at least 25% of the modifier metal is present in the form of mononuclear titanium moieties.

11. A modified silica support for a catalyst, comprising a silica support and a titanium modifier metal, characterized in that At least a portion of the modifier metal is present as a modifier metal moiety derived from the source of mononuclear titanium cations at the start of modification.

12. The modified silica support of claim 11, wherein at least 25% of the modifier metal is present as modifier metal moieties derived from a source of mononuclear titanium cations at the start of modification.

13. The modified silica support or catalyst according to any one of claims 1 to 4 and 9 to 12, wherein titanium is an adsorbate adsorbed on the surface of the silica support.

14. The modified silica support or catalyst of any one of claims 1-4 and 9-12, wherein the titanium moiety is a titania moiety.

15. The modified silica support or catalyst of any one of claims 1-4 and 9-12, wherein the silica support is in the form of silica gel.

16. The modified silica support or catalyst of any one of claims 1-4 and 9-12, wherein the mononuclear titanium moiety is present in the support as part of a cogel.

17. The modified silica support or catalyst of any one of claims 1-4 and 9-12, wherein the mononuclear titanium moiety is present in the modified silica support in an amount effective to reduce sintering and improve the selectivity of the catalyst.

18. The modified silica support or catalyst of any one of claims 1 to 4 and 9 to 12, wherein at least 30% of the titanium in the modified silica support is in the mononuclear fraction or is derived from titanium compounds at the start of formation of the modified silica, wherein mononuclear titanium species are at such levels.

19. The modified silica support or catalyst according to any one of claims 1 to 4 and 9 to 12, wherein the level of titanium present is less than or equal to 7.6 x 10 -2 mol / mol silica.

20. The modified silica support or catalyst according to any one of claims 1 to 4 and 9 to 12, wherein the titanium level is between 0.067×10 -2 mol / mol silica and 7.3×10 -2 mol / mol silica.

21. The modified silica support or catalyst according to any one of claims 1 to 4 and 9 to 12, wherein the level of titanium present is at least 0.1 x 10 -2 mol / mol silica.

22. The modified silica support of any one of claims 9-12, wherein the modified silica support is a calcined modified silica support.

23. The catalyst or modified silica support according to any one of claims 3-4 and 11-12, wherein the titanium metal cation at the start of the modification is in a compound having one or more non-labile ligands attached to the titanium metal cation, the non-labile ligands being selected from molecules having a lone electron pair, comprising an oxygen atom or a nitrogen atom capable of forming a 5-membered ring or a 6-membered ring with a titanium 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 or O atoms are separated by 2 or 3 atoms, thereby forming the 5-membered ring or the 6-membered ring.

24. The catalyst or modified silica support according to claim 23, 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.

25. The catalyst or modified silica support of claim 23, wherein the non-labile ligand forms a complex with titanium.

26. The catalyst or modified silica support of claim 23, wherein the non-labile ligand forms a complex with titanium and is dissolved in solution as a non-labile ligand / alcohol complex with titanium.

27. A modified silica support according to any one of claims 9 to 12, wherein the support comprises <2.5 groups per nm 2 The level of isolated silanol groups (-SiOH).

28. The catalyst or modified silica support of any one of claims 1 to 4 and 9 to 12, wherein the support comprises <2.5 of the titanium moieties per nm 2 The titanium portion is present at a level of 1.5 %.

29. The modified silica support according to any one of claims 9 to 12, wherein the support comprises >0.1 and <2.5 groups per nm 2 The level of isolated silanol groups (-SiOH).

30. The catalyst or modified silica support according to any one of claims 1 to 4 and 9 to 12, wherein the support comprises >0.025 and <2.5 titanium moieties per nm 2 The titanium portion of the level.

31. A method for producing a modified silica support according to any one of claims 9 to 26, comprising the steps of: providing a silica support having silanol groups; The silica support is treated with a mononuclear titanium compound such that titanium is adsorbed onto the surface of the silica support by reaction with silanol groups, wherein the adsorbed titanium atoms are sufficiently spaced apart from one another to substantially prevent oligomerization with adjacent titanium atoms.

32. The method of producing a modified silica support according to claim 31, wherein the adsorbed titanium atoms are sufficiently separated from each other to substantially prevent dimerization or trimerization of the adsorbed titanium atoms with their neighboring titanium atoms.

33. The method of claim 31 , wherein the separation of the titanium atoms is achieved by: a) reducing the concentration of silanol groups on the silica support, and / or b) attaching a non-labile ligand of sufficient size to the titanium prior to treating the silica support.

34. A method for producing a catalyst comprising the steps of: i. providing a silica support having isolated silanol groups; ii. contacting the treated silica support with a mononuclear titanium modifier metal compound to achieve adsorption of titanium onto the support; iii. calcining the modified silica for a time and temperature sufficient to convert the mononuclear titanium modifier metal compound adsorbed on the surface into titanium oxide or titanium hydroxide; iv. treating the calcined modified silica with a catalytic metal to impregnate the modified silica with the catalytic metal to form the catalyst, wherein the catalytic metal is one or more alkali metals selected from potassium, rubidium, and cesium.

35. The method of claim 34, wherein step i) further comprises treating the support to provide <2.5 groups per nm 2 The level of isolated silanol groups (-SiOH).

36. The process of claim 34 wherein step ii) comprises contacting the treated silica support with a mononuclear titanium modifier metal compound to effect adsorption of titanium onto the support to at least 25% of the isolated silanol groups.

37. The method of claim 34, wherein step iv) further comprises calcining the formed catalyst.

38. The method of claim 34, wherein after step ii) and before step iii), the method further comprises the step of removing any solvent or liquid carrier for the titanium compound.

39. A method of producing a modified silica support for a catalyst comprising the steps of: i. providing a silica support having isolated silanol groups; ii. contacting the treated silica support with a mononuclear titanium modifier metal compound to effect adsorption of the titanium onto the support.

40. The method of claim 39, wherein step i) further comprises treating the support to provide <2.5 groups per nm 2 The level of isolated silanol groups (-SiOH).

41. The method of claim 39, wherein step ii) comprises contacting the treated silica support with a mononuclear titanium modifier metal compound to achieve adsorption of titanium onto the support to at least 25% of the isolated silanol groups.

42. The method of claim 39, wherein after step ii), the method further comprises the step of removing any solvent or liquid carrier for the modifier metal compound.

43. The method according to claim 39, wherein after step ii), the method further comprises the following steps: The modified support is calcined for a time and temperature sufficient to convert the mononuclear titanium compound adsorbed on the surface to titanium oxide or titanium hydroxide in preparation for catalyst impregnation.

44. The method according to any one of claims 31 to 43, wherein the concentration of the silanol groups is reduced by a calcination treatment or chemical dehydration before the treatment with the titanium compound.

45. A method according to any one of claims 31 to 43, wherein the source of mononuclear titanium cations is a solution of the titanium compound such that the compound is in solution when contacted with the support to effect adsorption onto the support.

46. The method of claim 45, wherein the solvent used in the solution is other than water.

47. The method of claim 45, wherein the solvent is an organic solvent.

48. The method of claim 45, wherein the solvent is an aliphatic solvent or a chlorinated solvent.

49. The method of claim 45, wherein the solvent is an aliphatic alcohol.

50. The method of claim 45, wherein the solvent is an aliphatic alcohol selected from methanol, ethanol or propanol.

51. The method according to any one of claims 31 to 43, wherein one or more non-labile ligands are attached to the titanium cation to at least partially form the compound and are selected from molecules having a lone electron pair, comprising an oxygen atom or a nitrogen atom capable of forming a 5-membered ring or a 6-membered ring with the titanium 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 or O atoms are separated by 2 or 3 atoms, thereby forming the 5-membered ring or the 6-membered ring.

52. The method of claim 51, 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.

53. The method of claim 51, wherein the non-labile ligand forms a complex with titanium.

54. The method of claim 51, wherein the non-labile ligand forms a complex with titanium and is dissolved in solution as a non-labile ligand / alcohol complex with titanium.

55. The method of any one of claims 31 to 43, wherein the proximity of the adsorbed titanium modifier metal to the adjacent titanium modifier metal cation is controlled by the concentration of the titanium modifier metal in the contacting step and: a) the concentration of silanol groups on the silica support, and / or b) The size of any non-labile ligands attached to the titanium modifier metal cation.

56. The method of any one of claims 31 to 43, wherein the silanol concentration on the silica support when contacted with the titanium modifier metal compound is from 0.4 to 2.5 silanol groups per nm 2 .

57. The method of any one of claims 31 to 43, wherein when a source of modifier metal compound is contacted with the support to effect adsorption of the compound onto the support, at least 30% of the titanium modifier metal in the modifier metal compound is a mononuclear modifier metal compound.

58. A method of producing a catalyst according to any one of claims 1-8 and 13-26, comprising the steps of: forming a modified silica according to any one of claims 9 to 26, and contacting the modified silica support with a solution comprising a catalytic metal to impregnate the modified silica with the catalytic metal, wherein the catalytic metal is one or more alkali metals selected from potassium, rubidium, and cesium.

59. The process of any one of claims 31-43 and 58, wherein the silica support is dried or calcined prior to treatment with the titanium compound.

60. The method of any one of claims 31-43 and 58, wherein the modified silica formed by contact with a titanium compound is dried or calcined prior to adding the catalytic metal.

61. The method of any one of claims 31-43 and 58, wherein the silica is in the form of a gel prior to treatment with the titanium compound.

62. The method of claim 61, wherein the gel is in the form of a hydrogel, xerogel or aerogel at the time of initial contact with the titanium compound.

63. The method of any one of claims 31-43 and 58, wherein the titanium modifier metal is dispersed onto the surface of the silica support by adsorption.

64. The process of any one of claims 31-43 and 58, or the catalyst or modified silica support of any one of claims 1-26, wherein the source of titanium cations is in a form selected from the group consisting of an organometallic complex and a metal salt.

65. The method of claim 64, wherein the source of titanium cations is in the form of an organometallic complex selected from one or more of tetrakis(methanol)titanium, tetrakis(ethoxide)titanium, tetrakis(n-propoxide)titanium, tetrakis(isopropoxide)titanium, tetrakis(n-butoxide)titanium, tetrakis(tert-butoxide)titanium, tetrakis(2-ethylhexyl)titanium, bis(acetylacetonate)titanium oxide, bis(2,2,6,6-tetramethyl-3,5-heptanedioate)titanium oxide, (triethanolamine)isopropoxide titanium, bis(triethanolamine)titanium diisopropoxide, tetrakis(diethylamide)titanium, tetrakis(ethylmethylamide)titanium, tetrakis(dimethylamide)titanium, tetrakis(neopentyl)titanium, and bis(ammonium lactate)dihydroxytitanium(IV).

66. The method of claim 64, wherein the source of titanium cations is selected from one or more of titanium (IV) oxysulfates, titanium (IV) oxynitrates, and titanium (IV) oxychlorides.

67. The process of any one of claims 31-43 and 58, or the catalyst or modified silica support of any one of claims 1-26, wherein the source of titanium cations is in the form of titanium tetrakis(methanol), titanium tetrakis(ethoxide), titanium tetrakis(n-propoxide), titanium tetrakis(isopropoxide), titanium tetrakis(n-butoxide), titanium tetrakis(tert-butoxide), titanium tetrakis(2-ethylhexyl)oxide, titanium bis(acetylacetonate), titanium bis(2,2,6,6-tetramethyl-3,5-heptanedioate), titanium (triethanolammine)isopropoxide, titanium bis(triethanolamine)diisopropoxide, titanium tetrakis(diethylamide), titanium tetrakis(ethylmethylamide), titanium tetrakis(dimethylamide), titanium tetrakis(neopentyl), titanium bis(ammonium lactate)dihydroxy(IV) in one of methanol, ethanol, isopropanol, propanol, butanol, isobutanol, or 2-butanol.

68. The method of any one of claims 34-38 and 58, wherein the catalytic metal is one or more alkali metals selected from rubidium and cesium.

69. The method of any one of claims 34-38 and 58, wherein the catalytic metal is cesium.

70. The process of any one of claims 31-43 and 58, wherein the formed catalyst is subsequently calcined.

71. A process for producing an ethylenically unsaturated carboxylic acid or carboxylic ester, the process comprising the step of contacting formaldehyde, or a suitable source thereof, with the carboxylic acid or carboxylic ester in the presence of a catalyst, wherein the catalyst is according to any one of claims 1 to 8 and 13 to 26.

72. The method of claim 71, wherein the ethylenically unsaturated carboxylic acid or carboxylic acid ester is an alpha, beta ethylenically unsaturated carboxylic acid or carboxylic acid ester.

73. The method of claim 71, wherein the step of contacting formaldehyde, or a suitable source thereof, with a carboxylic acid or carboxylic acid ester in the presence of a catalyst is in the presence of an alcohol.

74. A process for preparing an ethylenically unsaturated acid or ester comprising reacting a compound of formula R in the presence of a catalyst according to any one of claims 1 to 8, 13 to 21 and 23 to 26. 1 -CH2-COOR 3 The alkanoic acid or alkanoic acid ester is contacted with formaldehyde or a suitable source of formaldehyde according to formula (I) as defined below: where R 5 is methyl and R 6 It is H; X is O; m is 1; and n is any value between 1 and 20 or any mixture of these values; where R 1 is hydrogen or a hydrocarbon group having 1 to 12 carbon atoms, and R 3 is independently hydrogen or a hydrocarbyl group having 1 to 12 carbon atoms.

75. A process according to claim 74, wherein contacting the alkanoic acid or alkanoic acid ester with formaldehyde or a suitable source of formaldehyde in the presence of a catalyst is in the presence of an alkanol.

76. The method or process according to claim 71 or 74, wherein the carboxylic acid or carboxylic acid ester or the formula R 1 -CH2-COOR 3 The ester or acid is methyl propionate or propionic acid, respectively, and the ethylenically unsaturated carboxylic acid or carboxylic acid ester is methyl methacrylate or methacrylic acid.

77. A method for producing a modified silica support comprising the steps of: providing a silica support having silanol groups; The silica support is treated with a mononuclear titanium compound such that the titanium modifier metal is adsorbed onto the surface of the silica support by reaction with silanol groups, wherein the adsorbed titanium atoms are sufficiently spaced from one another to substantially prevent oligomerization with adjacent titanium atoms.

78. The method of claim 77, wherein the separation of the titanium atoms is achieved by: a) reducing the concentration of silanol groups on the silica support, and / or b) Attaching a non-labile ligand of sufficient size to the titanium cation.

79. The method or process of any one of claims 31-43, 58, 71-75, and 77-78, wherein the support and / or catalyst is according to any one of claims 1-26.

Images