RU2784808C2 - Catalyst and method for production of ethylene-unsaturated carboxylic acids or composite esters - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to a modified silicon dioxide catalyst carrier, to a catalyst including a modified silicon dioxide carrier, and to a method for the production of ethylene-unsaturated carboxylic acids or composite esters, in particular α,β-unsaturated carboxylic acids or composite esters.

EFFECT: development of catalysts containing modified silicon dioxide carriers and containing catalytic metal, which are extremely effective catalysts for the production of α,β-ethylene-unsaturated carboxylic acids or composite esters by condensation of the corresponding acid or composite ester with a methylene source, such as formaldehyde, providing a set of advantages, such as a high selectivity level and/or reduction in sintering of a catalyst surface.

49 cl, 81 ex, 5 tbl, 9 dwg

Description

The present invention relates to a modified silica catalyst carrier, a catalyst comprising a modified silica carrier, and a process for the production of ethylenically unsaturated carboxylic acids or esters, in particular α,β-unsaturated carboxylic acids or esters, more particularly acrylic acids or esters. such as (alk)acrylic acids or alkyl(alk)acrylates, in particular (meth)acrylic acids or alkyl(meth)acrylates such as methacrylic acid (MA) and methyl methacrylate (MMA), by condensation of a carboxylic acid or esters with formaldehyde or a source thereof such as dimethoxymethane in the presence of such catalysts, in particular by condensing propionic acid or its alkyl esters such as methyl propionate with formaldehyde or a source thereof in the presence of such catalysts with a catalytic metal on a modified silica support. Accordingly, this invention is particularly relevant for the production of methacrylic acid (MAA) and methyl methacrylate (MMA).

As indicated above, such unsaturated acids or esters can be obtained by reaction of a carboxylic acid or ester, and suitable carboxylic acids or esters are alkanoic acids (or esters) of the formula R ³ -CH ₂ -COOR ⁴ where each of R ³ and R ⁴ independently represents a suitable substituent known in the field of acrylic compounds, such as hydrogen or an alkyl group, in particular a lower alkyl group containing, for example, 1-4 carbon atoms. Thus, for example, methacrylic acid or its alkyl esters, especially methyl methacrylate, can be prepared by the catalytic reaction of propionic acid or the corresponding alkyl ester, such as methyl propionate, with formaldehyde as a source of methylene, according to reaction sequence 1.

R ³ -CH ₂ -COOR ⁴ +HCHO -------> R ³ -CH(CH ₂ OH) -COOR ⁴

and

R ³ -CH(CH ₂ OH)-COOR ⁴ ------> R ³ -C(:CH ₂ )-COOR ⁴ +H ₂ O

Sequence 1

An example of reaction sequence 1 is reaction sequence 2.

CH ₃ -CH ₂ -COOR ⁴ +HCHO -------> CH ₃ -CH(CH ₂ OH) -COOR ⁴

CH ₃ -CH (CH ₂ OH) -COOR ⁴ ------> CH ₃ -C (: CH ₂ ) -COOR ⁴ +H ₂ O

Sequence 2

The above reaction sequences are usually carried out at elevated temperature, typically in the range of 250-400°C, using an acid/base catalyst. When the desired product is an ester, the reaction is usually carried out in the presence of a suitable alcohol to minimize the formation of the corresponding acid due to hydrolysis of the ester. It is also often desirable for convenience to introduce formaldehyde in the form of a formaldehyde-methanol complex. Therefore, in the production of methyl methacrylate, the reaction mixture fed to the catalyst will typically consist of methyl propionate, methanol, formaldehyde and water.

A known method for producing MMA is the catalytic conversion of methyl propionate (MEP) to MMA using formaldehyde. A known catalyst for this is a cesium catalyst comprising a support such as silica.

WO 1999/52628 describes a catalyst for use in the preparation of α,β-unsaturated carboxylic acids or esters by condensation of propionic acid or the corresponding alkyl ester, the catalyst comprising alkali metal doped silica impregnated with at least one modifier element, wherein the modifier element is selected from the group consisting of boron, aluminum, magnesium, zirconium and hafnium, preferably zirconium and/or aluminum and/or boron, and the alkali metal is selected from potassium, rubidium or cesium, preferably cesium.

WO 2003/026795 describes a catalyst for use in aldol condensation reactions, including the preparation of α,β-unsaturated carboxylic acids by propionic acid or propionic acid ester condensation, olefin polymerization, dehydration, hydroxylation and isomerization, wherein the catalyst contains a silica hydrogel and metal impregnated with a catalytic metal, wherein the hydrogel metal is selected from the group consisting of zirconium, titanium, aluminum and iron, preferably zirconium, and the catalytic metal is selected from the group consisting of alkali metals and alkaline earth metals, preferably cesium.

The present inventors have found that catalysts containing metal-modified silica supports and containing the catalytic metal provide a high level of selectivity for the condensation of methylene sources such as formaldehyde with a carboxylic acid or alkyl ester such as methyl propionate when at least a portion of the metal the modifier is included or present in the carrier in the form of metal compounds having a total of up to two zirconium and/or hafnium atoms.

From Yung-Jin Hu et al, J. Am. Chem. soc. Volume 135, 2013, p14240, it is known that zirconium is able to form large clusters in solution. Clusters of Zr-18 are typical.

However, the present inventors surprisingly found that when the modified silica support contains zirconium oxide and/or hafnium groups derived from a monomeric and/or dimeric modifier metal cation source, such as their compounds at the beginning of the modification, and not from such larger clusters, it has been found to improve the binding of the catalytic metal to the modified support and therefore a higher selectivity to obtain an unsaturated carboxylic acid or esters by condensing the corresponding acid or ester with a methylene source such as formaldehyde. In addition, the inventors have found that the modified silica supports providing these high selectivities contain monomeric or dimeric modifier metal atoms after being deposited/adsorbed onto the silica surface.

In addition, the present inventors have found that by using such modified silica supports, the sintering rate of the catalyst surface has been found to decrease and the loss of the specific surface on which the catalytic reaction occurs during the condensation reaction is reduced.

Therefore, catalysts containing such modified silica supports and containing a catalytic metal are extremely efficient catalysts for producing α,β-ethylenically unsaturated carboxylic acids or esters by condensation of the corresponding acid or ester with a source of methylene such as formaldehyde, providing a number of advantages such as a high level of selectivity and/or reduced catalyst surface sintering.

Thus, according to the first aspect of the present invention, there is provided a catalyst comprising:

modified silicon dioxide carrier,

moreover, the modified silicon dioxide media contains a metal modifier;

and a catalytic metal on a modified silica support,

where the modifier metal is selected from one or more components of zirconium and/or hafnium,

characterized in that at least a portion, typically at least 25%, of said modifier metal is present as modifier metal groups,

having a total of up to 2 modifier metal atoms.

According to a further aspect of the present invention, a catalyst is provided comprising:

modified silicon dioxide carrier,

moreover, the modified silicon dioxide media contains a metal modifier;

and a catalytic metal on a modified silica support,

where the modifier metal is selected from one or more components of zirconium and/or hafnium,

characterized in that at least a portion, typically at least 25%, of said modifier metal is present as modifier metal groups derived from a monomeric and/or dimeric modifier metal cation source.

The monomeric and/or dimeric modifier metal is contacted with a silica carrier in the form of a source of cations of the monomeric and/or dimeric modifier metal - zirconium or hafnium, such as their compound in solution, to adsorb said modifier metal on the carrier, thereby forming groups modifier metal. A suitable source may be a modifier metal complex, most commonly a ligand complex in solution.

According to a second aspect of the present invention, a modified silica catalyst support is provided, comprising:

silica carrier and

modifier metal,

where the modifier metal is selected from one or more components of zirconium and/or hafnium,

characterized in that at least a portion, typically at least 25%, of said modifier metal is present as modifier metal groups,

having a total of up to 2 modifier metal atoms.

According to a third aspect of the present invention, a modified silica catalyst support is provided, comprising:

silica carrier and

modifier metal,

where the modifier metal is selected from one or more components of zirconium and/or hafnium,

characterized in that at least a portion, typically at least 25%, of said modifier metal is present as modifier metal groups derived from the monomeric and/or dimeric modifier metal cation source at the start of the modification.

At the same time, the modified silicon dioxide carrier is modified with a modifier metal. As a rule, the modifier metal is an adsorbate adsorbed on the surface of the silicon dioxide carrier. The adsorbate may be chemisorbed or physically sorbed on the surface of the silica support, usually it is chemisorbed. Modifier metal groups are typically oxide groups of the modifier metal.

The silica carrier is typically in the form of a silica gel, more typically a xerogel or hydrogel.

As a rule, the modifier metal is adsorbed on the surface of the silica gel support. Thus, usually said metal modifier is present on the surface of the modified silica gel support in the form of metal oxide groups.

Alternatively, the modifier metal may be present in the carrier in the form of a cogel. In such a case, the modified silica carrier is a metal oxide-silica gel, typically containing zirconia and/or hafnium oxide groups.

Typically, the modifier metal is present in the modified silica support in an effective amount to reduce sintering and improve catalyst selectivity. Typically at least 30%, such as at least 35%, more preferably at least 40%, such as at least 45%, most preferably at least 50%, such as at least 55 %, such as 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 modifier metal in the modified silica support is in groups having a total of 1 and/or 2 metal atoms, especially in groups having only 1 metal atom or derived from a monomeric and/or dimeric metal compound at the beginning formation of modified silica at such levels.

For the avoidance of doubt, modifier metal groups having a total of 1 metal atom are considered monomeric, and those having a total of 2 metal atoms are considered dimeric. In particularly preferred embodiments, such as at least 35%, more preferably at least 40%, such as at least 45%, most preferably at least 50%, such as at least 55%, such as at least 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% metal -modifier is present in the monomeric metal groups, or in any case usually formed from compounds of zirconium and/or hafnium at the beginning of the modification, having such levels of metal modifier as monomeric compounds. Generally, modifier metal groups on silica are oxide groups of the modifier metal.

Surprisingly, it has been found that zirconium and/or hafnium clusters containing more than 2 metal atoms, dispersed throughout a support such as a hydrogel support, reduce the selectivity of the reaction for producing α,β-ethylenically unsaturated carboxylic acids or esters by condensation of the corresponding acid or ester with a methylene source such as formaldehyde. It has also surprisingly been found that such large clusters increase the sintering of modified silica particles compared to modifier metal clusters with 2 atoms or 1 metal atom, thereby reducing specific surface area, which reduces strength and shortens catalyst life before activity becomes unacceptably low. In addition, the selectivity is often lower, depending on the nature of the modifier metal cluster.

Typically, the modifier metal is dispersed throughout the support in a substantially uniform manner.

Typically, the modified silica carrier is a xerogel. The gel may also be a hydrogel or an airgel.

The gel may also be a silica-zirconia and/or silica-hafnium oxide cogel. Silica gel can be formed by any of the various methods known to those skilled in the art of gelling, such as those mentioned herein. Generally, modified silica gels are prepared by a suitable adsorption reaction. Adsorption of appropriate metal compounds, such as zirconium and/or hafnium compounds, on silica gel, such as a silica xerogel, to form a modified silica gel having the appropriate modifier metal groups is a suitable method.

Methods for preparing silica gels 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, by Ralph K Iler, 1979, John Wiley and Sons Inc., ISBN 0 -471-02404-X and in the links provided there.

Methods for preparing silica-zirconia cogels are well known in the art, and some such methods are described in US 5,069,816; in Bosman et al, J. Catalysis Vol. 148 (1994) p.660, and Monros et al, J. Materials Science Vol. 28, (1993), p.5832.

In preferred embodiments, the modified silica carrier is not co-gelled, i.e. is not silica-zirconia, silica-hafnium oxide, or silica-zirconia/hafnium oxide formed by co-gelling, such as mixing sodium silicate solution with modifier metal complexes in sulfuric acid solution. In such embodiments, the implementation of zirconium and/or hafnium is usually included as an adsorbate on the surface of the silica carrier.

Preferably, the modified silica support catalyst and the modified silica support according to any aspect of the present invention may be substantially free, substantially free, or completely free of fluoride. Fluoride may be present in trace amounts due to inevitable environmental pollution. By "substantially free" we mean catalysts and supports containing less than about 1000 parts per million (ppm) of fluoride. By "substantially free" we mean catalysts and supports containing less than about 100 ppm fluoride, and by "completely free" we mean catalysts containing less than about 200 parts per billion (ppb) fluoride.

Preferably, when at least a portion of the modifier metal included in the modified silica of the above aspects of the present invention is obtained from a source of cations of the monomeric and/or dimeric modifier metal at the beginning of the formation of the modified silica, it is found that the reaction selectivity and/or the rate of sintering of the catalyst surface decreases in the production of α,β-ethylenically unsaturated carboxylic acids or esters.

The metal and metal oxide groups in the modified silica support of the present invention refer to zirconium and/or hafnium and zirconia and/or hafnium oxide, and not to silicon dioxide.

Preferably, the level of modifier metal present in the modified silica or catalyst may be up to 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 silicon dioxide. Usually the level of such a metal is from 0.067×10 ^-2 to 7.3×10 ^-2 mol/mol silica, more preferably from 0.13×10 ^-2 to 5.7×10 ^-2 mol/mol silica and most preferably from 0.2×10 ^-2 to 3.5×10 ^-2 mol/mol silicon dioxide. Typically, the level of modifier metal present is at least 0.1×10 ^-2 mol/mol silica, more preferably at least 0.15×10 ^-2 mol/mol silica, and most preferably at least 0, 25×10 ^-2 mol/mol silicon dioxide.

Preferably, when zirconium is a modifier metal, the level of zirconium metal can be up to 10% wt./mass. modified silica carrier, more preferably up to 8% wt./mass., most preferably up to 5.5% wt./mass. Typically, the level of metallic zirconium is 0.1-10% wt./mass. modified silica carrier, more preferably 0.2-8% wt./mass. and most preferably 0.3-5% wt./mass. Typically, the level of metallic zirconium is at least 0.5% wt./mass. modified silica carrier, for example, 0.8% wt./mass., more typically at least 1.0% wt./mass., most typically at least 1.5% wt./mass.

Preferably, the level of metallic hafnium can be up to 20% wt./mass. modified silica carrier, more preferably up to 16% wt./mass., most preferably up to 10% wt./mass. Typically, the level of metallic hafnium is 0.2-20% wt./mass. modified silica carrier, more preferably 0.4-16% wt./mass. and most preferably 0.6-10% wt./mass. Typically, the level of metallic hafnium is at least 1.0% wt./mass. modified silica carrier, more typically at least 2.0% wt./mass., most typically at least 3.0% wt./mass.

The silica component of the silica-zirconium oxide carrier may typically be 86.5-99.9% by weight. modified carrier, more typically 89.2-99.7% wt., most typically 93.2-99.6% wt. modified carrier.

The silica component of the silica-hafnium oxide carrier is typically 76.4-99.8% by weight. modified carrier, more typically 81.1-99.5% wt., most typically 88.2-99.3% wt. modified carrier.

As used herein, the term "up to 2 metal atoms" or the like means 1 and/or 2 metal atoms. Preferably, the modified silica support and catalyst according to any aspects of the present invention contain metal groups, typically metal oxide groups having up to 2 metal atoms, and most preferably 1 metal atom. Accordingly, such groups are to be understood as monomeric or dimeric metal groups.

Preferably, the catalytic metal may be one or more alkali metals. The catalytic metal is a metal other than zirconium or hafnium. Suitable alkali metals may be selected from potassium, rubidium and cesium, suitably rubidium and cesium. Cesium is the most preferred catalytic metal.

Suitably, catalytic metals such as cesium may be present in the catalyst at a level of at least 1 mol/100 mol (silicon+metal (zirconium and/or hafnium)), more preferably at least 1.5 mol/100 mol ( silicon+metal), most preferably at least 2 mol/100 mol (silicon+metal). The level of catalytic metal can be up to 10 mol/100 mol (silicon+metal) in the catalyst, more preferably up to 7.5 mol/100 mol (silicon+metal), most preferably up to 5 mol/100 mol (silicon+metal) in the catalyst .

Preferably, the level of catalytic metal in the catalyst may be in the range of 1-10 mol/100 mol (silicon+metal), more preferably 2-8 mol/100 mol (silicon+metal), most preferably 2.5-6 mol/100 mol ( silicon + metal) in the catalyst.

Unless otherwise indicated, the amount of alkali metal or alkali metal in the catalyst refers to the alkali metal ion and not to the salt.

Alternatively, the catalyst may contain a catalytic metal in the range of 1-22 wt%. in the catalyst, more preferably 4-18% wt., most preferably 5-13% wt. These quantities apply to all alkali metals, but especially to cesium.

The catalyst may have any suitable weight ratio of catalytic alkali metal to zirconium and/or hafnium metal. However, typically the weight ratios of cesium:zirconium are in the range of 2:1 to 10:1, more preferably 2.5:1 to 9:1, most preferably 3:1 to 8:1 in the catalyst, the cesium:hafnium ratios are in the range from 1:1 to 5:1, more preferably from 1.25:1 to 4.5:1, most preferably from 1.5:1 to 4:1 in the catalyst, rubidium:zirconium ratios are in the range from 1 2:1 to 8:1, more preferably 1.5:1 to 6:1, most preferably 2:1 to 5:1 in the catalyst, rubidium:hafnium ratios range from 0.6:1 to 4 :1, more preferably 0.75:1 to 3:1, most preferably 1:1 to 2.5:1 in the catalyst. Accordingly, the molar ratio of catalytic metal:modifier metal in the catalyst is usually at least 1.4 or 1.5:1, preferably in the range of 1.4-2.7:1, for example 1.5-2, 1:1, especially 1.5-2.0:1, usually the modifier metal is zirconium and the catalytic metal is cesium. As a rule, in this case, the catalytic metal is in excess relative to the amount that may be required to neutralize the modifier metal.

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

Suitably, the catalytic metal may be incorporated into the modified silica support by any method known in the art, such as impregnation, co-gelling, or vapor deposition with the catalytic metal.

As used herein, the term "impregnated" includes the addition of a catalytic metal dissolved in a solvent to form a solution that is added to the xerogel or airgel, whereby the solution enters the voids within said xerogel or airgel.

Typically, the catalyst of the invention may be in any suitable form. Exemplary embodiments are presented in the form of discrete particles. Typically, during use, the catalyst is in the form of a fixed catalyst bed. Alternatively, the catalyst may be in the form of a fluidized bed of catalyst. Another alternative is a monolithic reactor.

When the catalysts are used in the form of a fixed bed, it is desirable that the supported catalyst be formed into pellets, aggregates or shaped elements, for example spheres, cylinders, rings, saddles, stars, multilobed forms, obtained by granulation or extrusion, usually having maximum and minimum dimensions. in the range from 1 mm to 10 mm, more preferably with an average size of more than 2 mm, for example, more than 2.5 mm or 3 mm. Catalysts are also effective in other forms, such as powders or small beads with the same dimensions as above. When the catalysts are used in the form of a fluidized bed, it is desirable that the catalyst particles have a maximum and minimum size in the range of 10-500 µm, preferably 20-200 µm, most preferably 20-100 µm.

The levels of catalytic metal in the catalyst, whether atom/100 atom (silicon+zirconium and/or hafnium) or wt %, can be determined by appropriate sampling and taking an average from such samples. Typically, 5-10 samples are taken from a given batch of catalyst and alkali metal levels are determined and averaged, for example, by XRF, atomic absorption spectroscopy, neutron activation analysis, ion coupled plasma mass spectrometry (ICPMS) or by atomic ion-coupled plasma emission spectroscope (ICPAES).

Levels of certain types of metal oxide in the catalyst/support are determined by XRF, atomic absorption spectroscopy, neutron activation analysis, or ion coupled plasma mass spectrometry (ICPMS).

A typical average specific surface area of the modified silica carrier according to any aspect of the invention is in the range of 20-600 m ² /g, more preferably 30-450 m ² /g, most preferably 35-350 m ² /g, as measured by multi-point BET method using a Micromeritics TriStar 3000 Surface ^Area and Porosity Analyzer ^. /g), catalog number 004-16833-00.

If the catalyst material is porous, it is usually a combination of mesoporous and macroporous material with an average pore size of 2 to 1000 nm, more preferably 3 to 500 nm, most preferably 5 to 250 nm. Macropore size (above 50 nm) can be determined by mercury intrusion porosimetry using NIST standards, while the Barrett-Joyner-Halend (BJH) method using liquid nitrogen at 77K is used to determine mesopore size (2-50 nm). Average pore size is a weighted average of pore volume versus pore volume versus pore size distribution.

The average pore volume of the catalyst particles may be less than 0.1 cm ³ /g, but is typically in the range of 0.1-5 cm ³ /g, as measured by absorption of a liquid such as water. However, very low porosity microporous catalysts are not the most preferred as they can slow down the movement of reactants through the catalyst, and a more preferred average pore volume is in the range of ^0.2-2.0 cc/g. Alternatively, pore volume can be measured using a combination of nitrogen adsorption at 77K and mercury porosimetry. The Micromeritics TriStar Surface and Porosity Analyzer is used for pore volume determinations as for surface measurements and the same standards are used.

In the present invention, it has been found that adjusting the size of modifier metal groups provides unexpected benefits. However, to obtain the greatest benefit, it is necessary to control the proximity of adjacent modifier metal groups, since the modifier metal groups may otherwise combine with each other and thus increase the size of the modifier metal group.

Thus, according to a fourth aspect of the present invention, there is provided a method for producing a modified silica carrier, comprising the steps of:

providing a silica carrier containing silanol groups;

contacting the silica carrier with a compound of a monomeric and/or dimeric modifier metal, whereby the modifier metal is adsorbed on the surface of the silica carrier by reaction with said silanol groups.

As a rule, modifier metals are selected from zirconium or hafnium.

Preferably, the adsorbed modifier metal cations are sufficiently spaced apart to substantially prevent them from oligomerizing, more preferably trimerizing with adjacent modifier metal cations.

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 preferably at least 50%, e.g. at least 55%, e.g. at least 60% or 65%, and most preferably at least 70%, e.g. at least 75% or 80%, more typically at least 85%, most typically, at least 90%, especially at least 95% of said modifier metals contacting the silica support in the contacting step are monomeric or dimeric modifier metals. Suitably 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% e.g. at least 55%, e.g. at least 60% or 65%, and most preferably at least 70%, e.g. at least 75% or 80%, more typically at least 85%, most typically at least 90%, especially at least 95% of the modifier metals adsorbed on the silica support is present as modifier metal groups having up to 2 modifier metal atoms in total.

In accordance with another aspect of the present invention, there is provided a method for producing a modified silica carrier in accordance with any of the aspects of the invention, comprising the steps of:

providing a silica carrier containing silanol groups;

treating the silica carrier with compounds of a monomeric and/or dimeric modifier metal, whereby the modifier metal is adsorbed on the surface of the silica carrier by reaction with silanol groups, the adsorbed modifier metal atoms being at a sufficient distance from each other to substantially prevent their oligomerization with adjacent modifier metal atoms are more preferably sufficiently spaced apart to substantially prevent trimerization with adjacent modifier metal atoms.

Preferably, the distance between modifier metal atoms is provided 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 modifier metal prior to treatment of the silica support.

In accordance with another aspect, a method for preparing a catalyst is provided, comprising

stages:

i. providing the silica carrier with isolated silanol groups and optionally treating said carrier to produce isolated silanol groups (-SiOH) at a level of <2.5 groups per 1 nm ² ;

ii. contacting the optionally treated silica carrier with a modifier metal compound of monomeric zirconium or hafnium to adsorb said modifier metal onto the carrier, typically up to at least 25% of said isolated silanol groups;

iii. optionally removing any solvent or liquid carrier for modifier metal compounds;

iv. calcining the modified silica for a period of time and at a temperature sufficient to convert the monomeric zirconium or hafnium compound adsorbed on the surface into zirconium or hafnium oxide or hydroxide;

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

In accordance with yet another aspect of the present invention, there is provided a process for preparing a modified silica catalyst support, comprising

stages:

i. providing the silica carrier with isolated silanol groups and optionally treating said carrier to produce isolated silanol groups (-SiOH) at a level of <2.5 groups per 1 nm ² ;

ii. contacting the optionally treated silica carrier with a modifier metal compound of monomeric zirconium or hafnium to adsorb said modifier metal onto the carrier, typically up to at least 25% of said isolated silanol groups;

iii. optionally removing any solvent or liquid carrier for modifier metal compounds;

iv. optionally calcining the modified carrier for a period of time and at a temperature sufficient to convert the monomeric zirconium or hafnium compound adsorbed on the surface to zirconium or hafnium oxide or hydroxide upon preparation to impregnate the catalyst.

Preferably, the concentration of the silanol group is reduced prior to treatment with modifier metal compounds by calcination, chemical dehydration, or other suitable means.

Preferably, the source of the modifier metal cations here is a solution of compounds of said modifier metals, whereby the compounds are in solution when contacted with the support to be adsorbed onto the support.

Usually the solvent for said solution is different from water.

Typically, the solvent is an aliphatic alcohol, usually selected from C1-C6 alkanols such as methanol, ethanol, propanol, isopropanol, butanols, pentanols and hexanols, more typically methanol, ethanol or propanols.

Preferably, the proximity of the adsorbed modifier metal to the cations of the adjacent modifier metal can be controlled by the concentration of said modifier metal during the contacting step, as well as:

a) the concentration of silanol groups on the silica support and/or

b) the size of any non-labile ligand attached to the modifier metal cation.

The concentration of silanol groups on the silica support prior to adsorption is preferably controlled by calcination or other suitable methods known to those skilled in the art. Identification methods include, for example, those described in LT Zhuravlev "Colloids and Surfaces: Physicochemical and Engineering Aspects, vol. 173, pp. 1-38, 2000" which describes four different forms of silanols: isolated silanols, geminal silanols, vicinal silanols, and internal silanols that can coexist on silica surfaces. Isolated silanol groups are most preferred. They can be identified by infrared spectroscopy as a narrow absorption peak at 3730-3750 cm ^-1 , while other silanols show broad peaks in the range of 3460-3715 cm ^-1 (see "The Surface Properties of Silicas", Edited by Andre P Legrand, john Wiley and Sons, 1998 (ISBN 0-471-95332-6) pp. 147-234).

By non-labile ligand is meant a ligand that is coordinated to a modifier metal and is not removed by adsorption of the metal on the silica surface. Accordingly, the non-labile ligand is typically coordinated to the modifier metal in solution prior to treatment of the silica surface with the modifier metal. For the avoidance of doubt, the non-labile ligand is usually removed by surface treatment of silica after adsorption of the modifier metal.

The size of the non-labile ligand is effective in separating modifier metals from each other to prevent their combination.

In accordance with additional aspects of the present invention, methods are provided for the preparation of a catalyst or modified silica carriers for the catalyst or catalysts according to the claims.

The invention extends to a modified silica carrier in accordance with any of the aspects described here, where the carrier contains isolated silanol groups (-SiOH) at a level of <2.5 groups per 1 nm ² . Typically, the carrier contains isolated silanol groups (-SiOH) at a level of > 0.1 and <2.5 groups per 1 nm ² , more preferably at a level of 0.2 to 2.2, most preferably at a level of 0.4 up to 2.0 groups per 1 nm ² .

In addition, the invention extends to a catalyst or modified silica carrier according to any of the aspects of the present invention, wherein the carrier comprises said zirconium or hafnium modifier metal groups having a total of up to 2 modifier metal atoms and/or derived from a source of cations. monomeric and/or dimeric modifier metal present on the carrier and present at a level of <2.5 groups per 1 nm ² .

As a rule, the carrier contains the specified groups of the zirconium or hafnium modifier metal at a level of >0.025 and <2.5 groups per 1 nm ² , more preferably at a level of from 0.05 to 1.5, most preferably at a level of from 0.1 to 1.0 groups per 1 nm ² .

Suitable ligands here may be non-labile ligands, optionally selected from lone-pair oxygen or nitrogen molecules capable of forming 5- or 6-membered rings with a zirconium or hafnium atom. Examples include diones, diimines, diamines, diols, dicarboxylic acids or their derivatives such as esters, or molecules having two different such functional groups and, in any case, with the corresponding N or O atoms and N or O atoms separated by 2 or 3 atoms, with the formation of a 5 - or 6-membered ring. Examples include pentane-2,4-dione, esters of 3-oxobutanoic acid with aliphatic alcohols containing 1-4 carbon atoms, such as ethyl 3-oxobutanoate, propyl 3-oxobutanoate, isopropyl 3-oxobutanoate, n-butyl -3-oxobutanoate, tert-butyl-3-oxobutanoate, heptane-3,5-dione, 2,2,6,6-tetramethyl-3,5-heptanediol, 1,2-ethanediol, 1,2-propanediol, 1 ,3-propanediol, 1,3-butanediol, 1,2-butanediol, 1,2-diaminoethane, ethanolamine, 1,2-diamino-1,1,2,2-tetracarboxylate, 2,3-dihydroxy-1,4 -butanedioate, 2,4-dihydroxy-1,5-pentanedioate, salts of 1,2-dihydroxylbenzene-3-5-disulfonate, diethylenetriaminepentaacetic acid, nitrolotriacetic acid, N-hydroxyethylethylenediaminetriacetic acid, N-hydroxyethyliminodiacetic acid, N,N-dihydroxyethylglycine, oxalic acid and its salts. Pentan-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. Smaller bidentate ligands, having a total of, for example, less than 10 carbon atoms and/or heteroatoms, allow the formation of small complexes, which can allow higher concentrations to be deposited on the silica surface compared to larger ligands. Accordingly, the source of modifier metal cations here may be in the form of complexes of zirconium and/or hafnium with such smaller ligands, preferably at least one such ligand. Such compounds may include labile ligands such as solvent ligands, for example in an alcoholic solvent, alkoxide ligands such as ethoxide or propoxide, and the like.

The concentration of the preferably isolated silanol groups determines the maximum number of modifier metal adsorption sites. By adjusting this concentration, the proximity of the adsorbed modifier metal can be effectively determined, since the distribution of silanol centers will generally be uniform. The concentration of silanol to obtain a modified silica carrier in accordance with the present invention may be less than 2.5 groups per 1 nm², more typically less than 1.5 groups per nm², most typically less than 0.8 groups per nm². Suitable silanol concentration ranges for preparing modified silica supports may be 0.1-2.5 silanol groups per 1 nm², more preferably 0.15-1.0 silanol groups per nm², most preferably 0.2-0.7 silanol groups per nm².

The concentration of the modifier metal, typically in the form of a cation, must be set at a level that prevents significant bilayer formation and the like. on the surface of the support, which can lead to the interaction of the modifier metal with the metal. In addition, gap filling in the initial monolayer, which can lead to weak adsorption of the modifier metal away from the silanol centers, should also be avoided in order to prevent interaction with neighboring strongly adsorbed modifier metals. Typical concentration ranges for modifier metals of the invention may be as set forth herein.

Typically at least 30%, such as at least 35%, more preferably at least 40%, such as at least 45%, most preferably at least 50%, such as at least 55%, such as , 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 modifier metal in modifier metal compounds are dimeric and/or monomeric modifier metal compounds when their source is contacted with a support to adsorb said compounds onto the support, more typically monomeric.

In accordance with a further aspect of the present invention, there is provided a process for preparing a catalyst comprising:

modified silicon dioxide carrier,

moreover, the modified silicon dioxide media contains a metal modifier;

and a catalytic metal on a modified silica support,

where the modifier metal is selected from one or more zirconium and/or hafnium,

characterized in that at least a portion, usually at least 25%, of said modifier metal is present as monomeric modifier metal groups,

moreover, this method includes the steps:

treating the silica carrier to obtain isolated silanol groups (-SiOH) at a level of <2.5 groups per 1 nm ² ;

reacting the treated carrier with monomeric compounds of zirconium or hafnium modifier metals to effect their binding to at least 25% of said isolated silanol groups;

optionally removing any solvent or liquid carrier;

calcining the modified silica for a period of time and at a temperature sufficient to convert the monomeric zirconium or hafnium compound adsorbed on the surface into zirconium or hafnium oxide or hydroxide;

treating said calcined modified silica with a catalytic alkali metal to impregnate the modified silica with the catalytic metal.

Preferably, by providing fewer isolated silanol sites and linking monomeric zirconium or hafnium compounds to these sites, a catalyst support is provided resulting in improved catalyst selectivity, reduced sintering rate, and better catalyst aging resistance.

A suitable process for treating silica to obtain isolated silanol groups at this level is calcination. However, other methods are also possible, such as hydrothermal treatment or chemical dehydration. US 5,583,085 describes the chemical dehydration of silica with dimethyl carbonate or ethylene dicarbonate in the presence of an amine base. US 4,357,451 and US 4,308,172 describe chemical dehydration by chlorination with SOCl ₂ followed by dechlorination with H ₂ or ROH followed by the addition of oxygen in a dry atmosphere. Chemical dehydration can achieve up to 100% removal of silanols at a minimum of 0.7/Nm ² through heat treatment. Thus, in some cases, chemical dehydration may provide more control over the content of silanol groups.

The term "isolated silanol" (also known as single silanol) is well known in the art and distinguishes these groups from vicinal, geminal, or internal silanols. Suitable methods for determining the frequency of occurrence of isolated silanols include surface sensitive infrared spectroscopy and ¹ H NMR or ³¹ Si NMR.

According to a fifth aspect of the present invention, there is provided a process for preparing a catalyst according to any of the previous aspects of the present invention, comprising the steps of: forming a modified silica according to any previous aspect and contacting the modified silica support with a solution containing a catalytic metal to impregnate the modified silica catalytic metal.

Preferably, the silica support is dried or calcined prior to treatment with a modifier metal cation source. The resulting modified silica, whether previously dried or calcined, may be dried or calcined prior to the addition of the catalytic metal.

The silica may be in the form of a gel prior to treatment with the modifier metal. The gel may be in the form of a hydrogel, xerogel or airgel at the start of the modification.

The silica carrier may be a xerogel, hydrogel or airgel. Preferably, the silica carrier is a xerogel.

The silica support may be treated with the metal cation source in any of a variety of ways known to those skilled in the art of forming the support. The silica support may be brought into contact with a source of metal cations in such a way as to disperse the modifier metal throughout the silica support. Typically, zirconium and/or hafnium can be homogeneously dispersed throughout the silica support. Preferably, the modifier metal is dispersed throughout the silica support by adsorption.

By "adsorption" or the like, with respect to the modifier metal as used herein, is meant the incorporation of the modifier metal onto the surface of the silica support by reacting the metal cation source with the silica support, typically by chemisorption. Typically, adding a modifier to the silica support includes the following steps: adsorbing the metal cation source onto the silica support to form an organic metal complex, and calcining the complex to convert the organic metal complexes to metal oxide groups. Therefore, there is generally a homogeneous dispersion of the modifier metal throughout the silica support. Typically, zirconium and/or hafnium are dispersed throughout the silica support.

Examples of suitable sources of metal cations herein include organic complexes such as zirconium(pentane-2,4-dione)_four, zirconium (ethyl-3-oxobutanoate)_four, zirconium (heptane-3,5-dione)_four, zirconium(2,2,6,6-tetramethylheptan-3,5-dione)_four, zirconium(propoxide)(pentan-2-3-dione)₃, zirconium (propoxide)₃(2,2,6,6-tetramethyl-3,5-heptanedione) (zirconium (Ot-butyl)₃(tert-butyl-3-oxobutanoate), zirconium(Otret-butyl)₂(tert-butyl-3-oxobutanoate)₂ and metal salts such as zirconium perchlorate, zirconium oxynitrate and zirconium oxychloride. As a rule, the source of metal cations is presented in the form of an organic complex.

Typically, the modifier metal is brought into contact with the silica support in solution.

Preferably, the metal cation source is present in any solvent in which the metal cation source is soluble. Examples of a suitable solvent include water or alcohols. Preferred solvents are alcohols such as methanol, ethanol, propanol, isopropanol, butanols, pentanols and hexanols.

Preferably, the metal cation source is added to the silica in the form of a metal salt in such an alcoholic solution.

In one embodiment, the metal cation source is provided as a solution of one or more of the following: zirconium(IV) acetylacetonate (zirconium, tetrakis(2,4-pentanedionato-O, O')), zirconium (heptane-3,5-dione) ₄ , zirconium (2,2,6,6-tetramethyl-3,5-heptanedione) ₄ , zirconium(IV) ethyl 3-oxobutanoate, zirconium(IV) tert-butyl-3-oxobutanoate or zirconium(IV) isopropyl- 3-oxobutanoate, in one of methanol, ethanol, isopropanol, propanol, butanol, isobutanol, or 2-butanol.

Preferably, after adsorption of the modifier metal on the silica support, the solvent is removed by evaporation.

Optionally, the modified silica support is calcined to remove any ligands or other organic compounds from the modified support.

The person skilled in the art will appreciate that the catalytic metal may be added to the modified silica by any suitable method. Typically, to prepare a modified silica catalyst, the modified silica is contacted with a catalyst metal.

Typically, the modified silica support is contacted with an acidic, neutral, or alkaline aqueous solution containing a catalytic metal, such as cesium, in the form of a salt of the catalytic metal and a base, to form a catalyst. Alternatively, the support may be brought into contact 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 saline solution in methanol. Low water content, typically up to 20 vol.%, can be contained in solutions.

Typically, temperature, contact time, and pH conditions during this step of the catalyst preparation process are such that the modified silica support is allowed to be impregnated with the catalytic metal to form the modified silica support catalyst.

Typical temperature conditions for this step are 5-95°C, more typically 10-80°C and most typically 20-70°C. The temperature for this stage may be at least 5°C, more typically at least 10°C, most typically at least 20°C.

Typical contact time between the modified support and the catalytic metal containing solution for this step may be 0.05-48 hours, more typically 0.1-24 hours, most typically 0.5-18 hours. The contact time may be at least 0.05 h, more typically at least 0.1 h, most typically at least 0.5 h.

The concentration of the catalytic metal salt solution in this step depends on a large number of factors including the solubility limit of the catalytic metal compound, the porosity of the modified silica support, the desired content of the catalytic metal on the support, and the method of addition, including the amount of liquid used to impregnate the support, pH, and the choice of catalytic metal compound. metal. The concentration in a solution is best determined experimentally.

Suitable catalytic metal salts for introducing the catalytic metal can generally be selected from one or more of the groups consisting of formate, acetate, propionate, hydrogen carbonate, chloride, nitrate, hydroxide and carbonate, more typically hydroxide, acetate or carbonate, and most typically hydroxide and/or or carbonate. The pH can be adjusted during impregnation by adding ammonia with a metal compound or by using an appropriate catalytic metal compound such as formate, carbonate, acetate or hydroxide, more preferably hydroxide or carbonate, in all cases alone, in combination or together with the appropriate carboxylic acid. Adjusting the pH within the preferred ranges is most important at the end of the impregnation to ensure satisfactory adsorption. Most typically, these salts may be incorporated using an alkaline salt solution. If the salt itself is not alkaline, then a suitable base such as ammonium hydroxide may be added. Because the hydroxide salts are basic in nature, mixtures of one or more of the above salts can be conveniently prepared with the hydroxide salt of a particular catalytic metal, such as cesium.

One skilled in the art will appreciate that the catalytic metal of the present invention may be added to the modified silica support by any suitable method. The catalyst may be fixed, usually by calcination, to the support after the compound has been deposited on the support, optionally using a suitable aqueous salt solution, and then dried on the surface-coated support.

As a rule, drying of the modified silica carrier is carried out by appropriate methods known to the person skilled in the art, such as drying in a dryer or oven.

Typically, the catalyst contains 0.01-25% wt./mass. water, more typically 0.1-15% wt./mass. water and most typically 0.5-5.0% wt./mass. water.

Optionally, the catalyst based on the modified silica carrier containing the catalytic metal may be dried or calcined, the calcination process being well known to those skilled in the art.

In some cases it may be necessary to calcinate the support formed in the modification step at 200-1000°C, more typically 300-800°C, most typically 350-600°C, before adding the catalytic metal. With the preferred calcination of the support obtained in the stage of modification, the temperature is at least 375°C, for example, 400°C or 450°C. The calcination atmosphere will typically contain some oxygen, suitably 1-30% oxygen, and most preferably 2-20% oxygen to effect removal of organic residues in the form of carbon dioxide and water. The calcination time can typically be 0.01-100 hours, suitably 0.5-40 hours, most preferably 1-24 hours. The addition of the catalytically active metal may be carried out by the methods described for the uncalcined material, or may be carried out by any other conventional method used for impregnating catalyst supports such as xerogel supports, such as using a solvent other than water, such as alcohol, if appropriate. methanol, ethanol, propanol, or isopropanol, or using an initial wetness method in which only enough solution is added to the xerogel carriers to fill the pores of the xerogel carrier. In this case, the concentration of the catalytically active metal can be calculated to introduce the target amount of the catalytically active metal into the xerogel carrier material, instead of providing an excess solution of a lower concentration in the manner previously described. When adding a catalytically active metal, you can use any preferred technique known in the art. The calcination method is particularly preferred when an organic complex is used as a source of zirconium and/or hafnium, as it may be necessary to modify the subsequent catalyst preparation procedure to remove at least a portion of the organic complexing salt prior to cesium impregnation. Advantageously, it has been found that the ratio of catalytic metal:modifier metal, and hence the required catalytic metal, decreases as the modified support is calcined. This was unexpected and provides a further improvement of the invention.

According to a sixth aspect of the present invention, there is provided a process for producing an ethylenically unsaturated carboxylic acid or ester, typically an α, β ethylenically unsaturated carboxylic acid or ester, comprising the steps of contacting formaldehyde or a suitable source thereof with a carboxylic acid or ester in the presence of a catalyst and optionally the presence of an alcohol, where the catalyst corresponds to the first or any of the other aspects of the present invention defined herein.

Advantageously, catalysts containing modified silica supports as defined herein and containing a catalytic metal have also been found to be extremely effective catalysts for producing α, β ethylenically unsaturated carboxylic acid or esters by condensing the corresponding acid or ester with a source methylene, such as formaldehyde, providing reduced catalyst surface sintering, increased selectivity and a high specific surface area of the catalyst. In particular, improved properties are found when monomeric and/or dimeric modifier metal groups are used and/or when the modified silica support is calcined prior to treatment with the catalytic metal. In addition, the use of certain metal complexes to introduce the modifier metal onto the support by adsorption provides a convenient source of modifier metal monomeric and/or dimeric groups. Such a source also allows control over the nature of the modifier metal and provides a more uniform distribution of modifier metal groups.

By "its suitable sources" in relation to formaldehyde in the fourth aspect of the present invention is meant either that free formaldehyde can be generated in situ from a source under the reaction conditions, or that this source can act as an equivalent of free formaldehyde under the reaction conditions, for example, it can form the same reactive intermediate as formaldehyde, so that an equivalent reaction takes place.

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

(I)

(I)

where R ⁵ and R ⁶ are independently selected from C ₁ -C ₁₂ hydrocarbons or H, X is O, n is an integer from 1 to 100, and m is 1.

Generally, R ⁵ and R ⁶ are independently selected from C ₁ -C ₁₂ alkyl, alkenyl, or aryl as defined herein, or H, more suitably C ₁ -C ₁₀ alkyl, or H, most suitably from C ₁ -C ₆ alkyl or H, especially methyl or H. Typically, n is an integer from 1 to 10, more preferably from 1 to 5, especially 1-3.

However, other sources of formaldehyde can be used, including trioxane.

For this reason, a suitable source of formaldehyde includes any equilibrium composition that can provide a source of formaldehyde. Examples thereof include, without limitation, dimethoxymethane, trioxane, polyoxymethylenes R ¹ -O-(CH ₂ -O)iR ² where R ¹ and/or R ² are alkyl groups or hydrogen, i=1-100, paraformaldehyde, formalin (formaldehyde, methanol, water) and other equilibrium compositions such as a mixture of formaldehyde, methanol and methyl propionate.

Polyoxymethylenes are higher formals or semiformals of formaldehyde and methanol CH ₃ -O-(CH ₂ -O) _i -CH ₃ (“formal-i”) or CH ₃ -O-(CH ₂ -O) _i -H (“semi-formal -i"), where i=1-100, suitably 1-5, especially 1-3, or other polyoxymethylenes with at least one non-methyl end group. Thus, the formaldehyde source may also be a polyoxymethylene of the formula R ³¹ -O-(CH ₂ -O-) _i R ³² where R ³¹ and R ³² may be the same or different groups and at least one group is selected from C ₁ -C ₁₀ alkyl group, for example, R ³¹⁼ isobutyl and R ³²⁼ methyl.

As a rule, a suitable source of formaldehyde is selected from dimethoxymethane, the lower semi-formaldehydes of formaldehyde and methanol, CH ₃ -O-(CH ₂ -O) _i -H, where i=1-3, from formalin or from a mixture containing formaldehyde, methanol and methyl propionate .

As a rule, the term "formalin" means a mixture of formaldehyde: methanol: water in the ratio 25-65%: 0.01-25%: 25-70% by weight. More typically, the term "formalin" refers to a mixture of formaldehyde:methanol:water in a ratio of 30-60%:0.03-20%:35-60% by weight. In the most typical case, the term "formalin" means a mixture of formaldehyde: methanol: water in the ratio 35-55%: 0.05-18%: 42-53% by weight.

As a rule, a mixture containing formaldehyde, methanol and methyl propionate contains less than 5% of the mass. water. More preferably, the mixture containing formaldehyde, methanol and methyl propionate contains less than 1% of the mass. water. Most preferably, a mixture containing formaldehyde, methanol and methyl propionate contains 0.1-0.5% of the mass. water.

According to a seventh aspect of the present invention, there is provided a process for producing an ethylenically unsaturated acid or ester comprising contacting an alkanoic acid or ester of formula R ¹ -CH ₂ -COOR ³ with formaldehyde or a suitable formaldehyde source of formula (I) as defined below:

(I)

(I)

where R ⁵ is methyl and R ⁶ is H;

X is O;

m is 1;

and n is any value from 1 to 20, or any combination thereof;

in the presence of a catalyst in accordance with any aspect of the present invention, and optionally in the presence of an alkanol; where R1 is hydrogen or an alkyl group of 1-12, more suitably 1-8, most suitably 1-4 carbon atoms, and R3 can also independently be hydrogen or an alkyl group of 1-12, more suitably 1-8, most suitably 1-4 carbon atoms.

Thus, the present inventors have found that the presence of zirconium and/or hafnium in the form of metal oxide groups according to the present invention can surprisingly improve the selectivity of the condensation of methylene sources, such as formaldehyde, with a carboxylic acid or alkyl ester, such as methyl propionate, to form ethylenically unsaturated carboxylic acids. In addition, the sintering rate of the catalyst surface during the condensation reaction is significantly and unexpectedly reduced.

Accordingly, one particular process for which the catalysts of the present invention are particularly advantageous is the condensation of formaldehyde with methyl propionate in the presence of methanol to produce MMA.

In the case of obtaining MMA, the catalyst is usually contacted with a mixture containing formaldehyde, methanol and methyl propionate.

The process of the sixth or seventh aspect of the invention is particularly suitable for the preparation of acrylic and alkacrylic acids and their alkyl esters, as well as methylene-substituted lactones. Suitable methylene-substituted lactones include 2-methylenevalerolactone and 2-methylenebutyrolactone from valerolactone and butyrolactone, respectively. Accordingly, (alk)acrylic acids and their esters are ( _C0-8alk )acrylic acid or alkyl( _C0-8alk )acrylates, typically by reacting the corresponding alkanoic acid or ester thereof with a source of methylene, such as formaldehyde in the presence of a catalyst, preferably to produce methacrylic acid, acrylic acid, methyl methacrylate, ethyl acrylate or butyl acrylate, more suitably methacrylic acid or especially methyl methacrylate (MMA) from propionic acid or methyl propionate, respectively. Accordingly, when preparing methyl methacrylate or methacrylic acid, the preferred ester or acid of the formula R ¹ -CH ₂ -COOR ³ is methyl propionate or propionic acid, respectively, and therefore the preferred alkanol is methanol. However, it should be borne in mind that in the preparation of other ethylenically unsaturated acids or esters, the preferred alkanols or acids will be others.

The reaction of the present invention may be batch or continuous.

Typical temperature and pressure conditions in the process of the sixth or seventh aspect of the invention are in the range of 100°C to 400°C, more preferably in the range of 200°C to 375°C, most preferably in the range of 275°C to 360°C ; and/or 0.001 MPa to 1 MPa, more preferably 0.03 MPa to 0.5 MPa, most preferably 0.03 MPa to 0.3 MPa. Typical contact times for the reactants in the presence of a catalyst range from 0.1 s to 300 s, more preferably 1-100 s, most preferably 2-50 s, especially 3-30 s.

The amount of catalyst used in the process for producing the product of the present invention is not necessarily critical and will be determined by the practical aspects of the process in which it is used. However, the amount of catalyst is usually chosen to provide optimum selectivity and product yield, as well as an acceptable operating temperature. However, one of ordinary skill in the art will appreciate that the minimum amount of catalyst should be sufficient to bring the reactants into effective contact with the catalyst surface. In addition, one skilled in the art will appreciate that there is not really an upper limit on the amount of catalyst relative to reactants, but in practice this may be controlled by required contact time and/or economic considerations.

The relative amount of reactants in the method of the sixth or seventh aspect of the present invention may vary widely, but, as a rule, the molar ratio of formaldehyde or its suitable source to carboxylic acid or ester is in the range of 20:1-1:20, more preferably 5: 1-1:15. The most preferred ratio will depend on the form of the formaldehyde and on the ability of the catalyst to release formaldehyde from formaldehyde compounds. Thus, highly reactive formaldehyde substances, where one or both of R ³¹ and R ³² in R ³¹ O-(CH ₂ -O) _and R ³² are H, require relatively low ratios, as a rule, in this case , the molar ratio of formaldehyde or its suitable source to carboxylic acid or complex ester is in the range from 1:1 to 1:9. When neither R ³¹ nor R ³² is H, such as in CH ₃ O-CH ₂ -OCH ₃ or trioxane, higher ratios, typically 6:1 to 1:3, are most preferred.

As stated above, due to the source of formaldehyde, water may also be present in the reaction mixture. Depending on the formaldehyde source, it may be necessary to remove some or all of the water from it before catalysis. Maintaining a lower water content than the formaldehyde source may be advantageous for catalytic efficiency and/or subsequent purification of products. A water content of less than 10 mol% in the reactor is preferred, more suitably less than 5 mol%, most suitably less than 2 mol%.

The molar ratio of alcohol to acid or ester is usually in the range of 20:1 to 1:20, preferably 10:1 to 1:10, most preferably 5:1 to 1:5, eg 1:1.5. However, the most preferred ratio will depend on the amount of water introduced into the catalyst in the reactants plus the amount formed in the reaction, so that the preferred molar ratio of alcohol to water in the overall reaction will be at least 1:1, and more preferably at least 2:1.

The reactants of the sixth or seventh aspect may be fed into the reactor independently or after premixing, and the reaction process may be continuous or batchwise. However, a continuous process is usually used.

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

In another additional aspect, the invention extends to a process for producing an ethylenically unsaturated carboxylic acid or ester in accordance with any of the relevant aspects herein, comprising the steps of initially preparing a catalyst in accordance with any of the relevant aspects of the present invention.

Definitions

The term "alkyl" when used herein means, unless otherwise indicated, C ₁ -C ₁₂ alkyl and includes methyl, ethyl, ethenyl, propyl, propenylbutyl, butenyl, pentyl, pentenyl, hexyl, hexenyl and heptyl groups, usually alkyl groups are selected from methyl, ethyl, propyl, butyl, pentyl and hexyl, more typically methyl. Unless otherwise indicated, alkyl groups may, when sufficient carbon atoms are present, be linear or branched, be 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, where R ¹⁹ - R ³⁰ herein and generally herein, each independently represents hydrogen, halogen , unsubstituted or substituted aryl or unsubstituted or substituted alkyl, or, in the case of R ²¹ , halogen, nitro, cyano and amino, and/or interrupted by one or more (preferably less than 4) oxygen, sulfur, silicon, or by means of a silano or dialkyl silicon groups or mixtures thereof. As a rule, alkyl groups are unsubstituted, usually linear and usually saturated.

The term "alkenyl" is to be understood as "alkyl" above, except that at least one carbon-carbon bond therein is unsaturated and, accordingly, the term refers to C ₂ -C ₁₂ alkenyl groups.

The term "alk" or the like is, in the absence of information to the contrary, to be understood in accordance with the above definition of "alkyl", except that "C ₀ alk" means unsubstituted by alkyl.

The term "aryl" as used herein includes five to ten membered, preferably five to eight membered, carbocyclic aromatic or pseudoaromatic groups such as phenyl, cyclopentadienyl and indenyl anions and naphthyl, these groups may be unsubstituted or substituted with one or more substituents. , selected from unsubstituted or substituted aryl, alkyl (this group may itself be unsubstituted or substituted or terminated as defined herein), Het (this group may itself be unsubstituted or substituted or terminated as defined in this document), 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 each R ¹⁹ - R ³⁰ is independently hydrogen, unsubstituted or substituted aryl, or alkyl (this alkyl group itself may be unsubstituted or substituted or terminated like oprah divided herein), or, in the case of R ²¹ , halogen, nitro, cyano or amino.

The term "halogen" as used herein means a chlorine, bromine, iodine or fluorine group, typically chlorine or fluorine.

The term "Het" as used herein includes four to twelve, typically four to ten, ring systems, wherein the rings contain one or more heteroatoms selected from nitrogen, oxygen, sulfur, and mixtures thereof, and these rings contain no double bonds, contain one or more double bonds or may be non-aromatic, partially aromatic or fully aromatic in character. Ring systems can be monocyclic, bicyclic or fused. Each "Het" group identified herein may be unsubstituted or substituted with one or more substituents selected from halo, cyano, nitro, oxo, alkyl (this alkyl group itself may be unsubstituted or substituted or terminated 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 )R ²⁶ , -SR ²⁹ , -C(O)SR ³⁰ or -C(S)N(R ²⁷ )R ²⁸ , where each R ¹⁹ -R ³⁰ is independently hydrogen, unsubstituted or substituted aryl or alkyl (this alkyl the group itself may be unsubstituted or substituted or terminated as defined herein) or, in the case of R ²¹ , halo, nitro, amino or cyano. Thus, the term "Het" includes groups such as optionally substituted azetidinyl, pyrrolidinyl, imidazolyl, indolyl, furanyl, oxazolyl, isoxazolyl, oxadiazolyl, thiazolyl, thiadiazolyl, triazolyl, oxatriazolyl, thiatriazolyl, pyridazinyl, morpholinyl, pyrimidinyl, pyrazinyl, quinolinyl, isoquinolinyl , piperidinyl, pyrazolyl and piperazinil. Substituents at Het may be on the carbon atom of the Het ring or, where possible, on one or more heteroatoms.

The "Het" groups can also be in the form of N oxide.

Suitable optional alcohols for use in the catalyzed reaction of the fourth or fifth aspects of the present invention may be selected from: C ₁ -C ₃₀ alkanol, including aryl alcohols, which may be optionally substituted with one or more substituents selected from alkyl, 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. Particularly preferred alkanols are C ₁ -C ₈ alkanols such as methanol, ethanol, propanol, isopropanol, isobutanol, tert-butyl alcohol, phenol, n-butanol and chlorocaprylic alcohol, in particular methanol. Although monoalkanols are most preferred, polyalkanols, usually selected from di-octaols such as diols, triols, tetraols and sugars, can also be used. Typically, such polyalkanols are selected from 1,2-ethanediol, 1,3-propanediol, glycerol, 1,2,4-butanetriol, 2-(hydroxymethyl)-1,3-propanediol, 1,2,6-trihydroxyhexane, pentaerythritol , 1,1,1-tri(hydroxymethyl)ethane, nannose, sorbase, 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. Generally, the amounts are used in excess of the amount of the esterified substrate. Thus, the alcohol may also serve as a solvent for the reaction, although separate or additional solvents may also be used if desired.

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, p. 358-364. If this step is carried out, the hydrogel is then washed again to remove any substances used in the aging process and to bring the solution to the correct pH for the addition of the catalytically active metal, depending on the choice of salt for the catalytically active metal.

While the metal, metal oxide, and metal oxide groups of any aspect of the present invention, or any preferred or optional feature thereof, may be zirconium or hafnium and zirconia or hafnium oxide, respectively, they are typically zirconium and zirconia and zirconia groups.

The term "gel" as used herein is also known to the person skilled in the art, but in case of doubt, it can be considered as a solid network in which a liquid is dispersed. Typically, a gel is a polymer network in which a liquid is dispersed. Cogel is a term used to indicate that more than one parent chemical compound/group is included in the polymer network, typically silica and a metal oxide or salt such as zirconia. Accordingly, co-gelling, as used herein, means cogel formation.

Thus, a gel is a sol that has been cured. Thus, a hydrogel is a gel, as defined herein, wherein the liquid is water. A xerogel is a gel that has been dried to remove liquid. An airgel is a gel in which the liquid has been replaced by a gas and therefore does not shrink to the same extent as a xerogel.

The term "start" in this document means the beginning of the formation of modified silicon dioxide.

The term "groups" as used herein in relation to a metal is used to denote the form of the modifier metal on the modified support. Although the modifier metal usually forms part of the network, the modifier metal will be in the form of discrete residues on the silica support. Reference to a total of up to two metal atoms or the like is to be understood as referring to the monomeric and/or dimeric form of its residue. As appropriate, in the aspects of the present invention described herein, it has been found to be preferable to have the groups in the form of a monomeric residue. Accordingly, the term "a total of up to 2 modifier metal atoms" or the like here means a total of 1 and/or 2 modifier metal atoms. Here, 1 is more preferable than 2 modifier metal atoms, particularly preferred is a total of 1 and/or 2 zirconium atoms in said groups, in particular 1 zirconium atom in groups.

The term "monomeric or dimeric" means having a monomeric or dimeric form or, in the case of residues on silica, means "having the form of a monomeric or dimeric residue".

The percentage of modifier metal has no units here because it refers to the number of metal atoms per total number of such atoms. It should be borne in mind that the groups may take the form of non-monomeric or non-dimeric clusters, but these clusters still consist of modifier metal atoms.

Embodiments of the invention will now be described with reference to the accompanying examples and drawings, in which:

Figure 1 shows an HRTEM image for Zr-modified silica, example 5;

Figure 2 shows an HRTEM image for Zr-modified silica, Example 7;

Figure 3 shows an HRTEM image for Zr-modified silica, Example 14;

Figure 4 shows an HRTEM image for Zr-modified silica, Example 15;

Fig. 5 shows an HRTEM image for Zr-modified silica, Example 17; and

Fig. 6 shows an HRTEM image for Zr-modified silica, Example 18;

figure 7 shows the selectivity of MMA+MAA (%) depending on the activity of the catalyst for the catalysts obtained in examples 20 to 74;

8 shows the catalyst selectivity for the mixed monomer/trimer catalysts prepared in Examples 75 to 79; and

9 shows the catalyst sintering constants determined using the accelerated aging test described in Example 81.

experimental part

Description of silica carrier

Example 1

Fuji Silysia CARiACT Q10 (Q10) silica was dried in a laboratory oven at 160°C for 16 h, after which it was removed from the oven and cooled to room temperature in a closed flask stored in a desiccator. This silica had a specific surface area of 333 m ² /g, a pore volume of 1.0 ml/g and an average pore diameter of 10 nm, determined by measuring nitrogen adsorption/desorption isotherms (Micromeretics Tristar II). Silanol number 0.8 OH/nm ² was determined using TGA analysis. This silica mainly consisted of spherical silica granules with a diameter in the range of 2-4 mm.

Example 2

Fuji Silysia CARiACT Q30 (Q30) silica was calcined in a tube furnace at 900° C. for 5 hours at a heating rate of 5° C./min in a stream of nitrogen gas. Then it was cooled to room temperature and stored in a closed flask in a desiccator. This silica had a specific surface area of 112 m ² /g, a pore volume of 1.0 ml/g, an average pore diameter of 30 nm, and was mainly composed of spherical silica granules with a diameter in the range of 2-4 mm.

Modification of Zr silicon dioxide supports

Example 3 (0.92 wt% Zr, monomeric Zr on Q10)

0.542 g Zr(acac) ₄ (97%, Sigma Aldrich) was dissolved in 11 ml MeOH (99% Sigma Aldrich). 10 g of the silica of example 1 was weighed into a separate flask. The weighed silica was then added to the Zr(acac) ₄ solution with stirring. Stirring was continued until all of the Zr(acac) ₄ solution was introduced into the pore volume of the silica. After filling the pores, the Zr-modified silica was left for 16 h in a closed flask with occasional stirring. After this time, the solution outside the pores was removed by filtration. This was followed by a drying step in which the organic solvent inside the pores was removed by passing a stream of nitrogen gas through wet Zr-modified silica at room temperature. Alternatively, the solvent inside the pores was removed on a rotary evaporator under reduced pressure. After removal of all solvent, the Zr-modified silica support was calcined in a tube furnace at 500° C. in an air stream (1 L/min) with a heating rate of 5° C./min and a final hold of 5 hours. After cooling, this gave a grafted Zr silica support with 100% efficient use of Zr. The Zr concentration (% wt.) on the modified Zr support was determined using energy dispersive X-ray fluorescence analysis of powders (Oxford Instruments X-Supreme8000).

Example 4 (1.5 wt% Zr, monomeric Zr on Q10)

The carrier modification was carried out as described in example 3, except that 0.874 g of Zr(acac) ₄ was used.

Example 5 (2.3 wt% Zr, monomeric Zr on Q10)

Carrier modification was carried out as described in example 3, except that 1.38 g of Zr(acac) ₄ was used and 20 ml of 1-PrOH (99% Sigma Aldrich) was used instead of MeOH. In addition, stirring was continued for 16 hours of the aging step until the solvent was removed. This resulted in a 90% efficient use of Zr.

Example 6 (2.7 wt% Zr, monomeric Zr on Q10)

Carrier modification was carried out as described in example 5, except that 1.67 g of Zr(acac) ₄ was used and 20 ml of MeOH (99% Sigma Aldrich) was used instead of 1-PrOH. This resulted in 89% Zr utilization efficiency.

Example 7 (4.2 wt% Zr, monomeric Zr on Q10)

Carrier modification was carried out as described in Example 5, except that 2.56 g of Zr(acac) ₄ was used and 20 ml of toluene (99% Sigma Aldrich) was used instead of 1-PrOH. This resulted in 93% Zr utilization efficiency.

Example 8 (0.7 wt% Zr, monomeric Zr on Q30)

The support modification was carried out as described in example 6, except that 0.43 g of Zr(acac) ₄ was used and the silica of example 2 was used. This resulted in 93% Zr utilization efficiency.

Example 9 (1.1 wt% Zr, monomeric Zr on Q10)

Carrier modification was carried out as described in example 5, except that 2.15 g of Zr(thd) ₄ was used and 20 ml of MeOH was used instead of 1-PrOH. This resulted in a 47% Zr utilization efficiency.

Example 10 (2.2 wt% Zr, monomeric Zr on Q10)

The carrier modification was carried out as described in example 9, except that 20 ml of toluene was used instead of MeOH. This resulted in 93% Zr utilization efficiency.

Example 11 (3.9 wt% Zr, monomeric Zr on Q10)

Carrier modification was carried out as described in Example 5, except that 3.19 g Zr(EtOAc) ₄ was used and 20 ml heptane (99% Sigma Aldrich) was used instead of 1-PrOH. This resulted in 86% Zr utilization efficiency.

Example 12 (6.7 wt% Zr, dimeric Zr on Q10)

Carrier modification was carried out as described in example 5, except that 3.12 g of [Zr(OPr) ₃ (acac)] ₂ was used and 20 ml of heptane was used instead of 1-PrOH. This resulted in 95% Zr utilization efficiency.

Example 13 (2.2 wt% Zr, trimeric Zr on Q30) (comparative example)

Carrier modification was carried out as described in example 5, except that 1.16 g of Zr(nOPr) ₄ (70% wt. in 1-propanol, Sigma Aldrich) was used. An additional 10 g of example 2 silica was used in place of example 1 silica. This resulted in 100% Zr utilization efficiency.

Example 14 (6.0 wt% Zr, trimeric Zr on Q10) (comparative example)

Carrier modification was carried out as described in example 5, except that 3.35 g of Zr(nOPr) ₄ (70% wt. in 1-propanol, Sigma Aldrich) was used. This resulted in 100% Zr utilization efficiency.

Example 15 (8.0 wt% Zr, pentameric Zr on Q10) (comparative example)

Carrier modification was carried out as described in example 5, except that 2.67 g of zirconium (IV) ethoxide (97% Sigma Aldrich) was dissolved in 20 ml of ethanol (anhydrous, Sigma Aldrich) with 1.77 g of acetic acid (glacial, Sigma Aldrich) instead of 1-PrOH. This resulted in 100% Zr utilization efficiency.

Modification of Hf silicon dioxide carriers

Example 16 (5.4 wt% Hf, monomeric Hf on Q10)

Carrier modification was carried out as described in example 5, except that 1.37 g of Hf(iOPr) ₄ (99% Sigma Aldrich) was dissolved in 20 ml of 1-PrOH along with 1.32 g of acetylacetone (99% Sigma Aldrich) and the reactants were allowed to mix for 30 minutes prior to the introduction of 10 g of the silica of example 1. This resulted in a 98% Hf utilization efficiency.

Example 17 (7.8% wt. Hf, monomeric Hf on Q10)

The carrier modification was carried out as described in example 5, except that 2.00 g of Hf(iOPr) ₄ was dissolved in 20 ml of toluene along with 1.93 g of acetylacetone and the reactants were allowed to mix for 30 min before introducing 10 g of the silica of example 1. This resulted in 100% efficient use of Hf.

Example 18 (11.8% wt. Hf, trimeric Hf on Q10) (comparative example)

The carrier modification was carried out as described in example 5, except that 3.19 g of Hf(iOPr) ₄ was dissolved in 20 ml of toluene instead of 1-PrOH. This resulted in 100% efficient use of Hf.

HRTEM analysis of modified supports

Example 19 (HRTEM analysis of monomeric Zr)

High resolution transmission electron microscopy (HRTEM) analysis was performed on selected modified silica samples. To do this, the modified silicon dioxide was cut into particles with a thickness of 100–200 nm using a microtome. These particle sections were then mounted on a copper grid and coated with an antistatic osmium vapor coating. Then, the installed sample was analyzed with a Tenai G2 F20 (manufactured by FEI) in transmission mode. For the electron beam, the accelerating voltage was set from 100 to 300 kV with a resolution of 1 nm. The electron beam was focused with a 30 μm diaphragm. HRTEM images were recorded to include 50-200 metal nanoparticles per image at 25 million times magnification. This analysis was performed on the modified silica of example 5, example 7, example 14, example 15, example 17 and example 18. HRTEM images are shown in Fig.1 - Fig.6.

Modification of Cs Modified Carriers

Example 20 (3.2 wt% Cs, 0.9 wt% Zr, monomeric Zr)

0.458 g of CsOH·H ₂ O (99.5% Sigma Aldrich) was weighed into a glovebox and dissolved in 20 ml of a 9:1 v/v solvent mixture. MeOH:H ₂ O. 10 g of the modified silica of example 3 was added to the CsOH solution with stirring. Stirring was continued for an additional 15 minutes, after which the sample was left for 16 hours in a closed flask with occasional stirring. After this time, the solution outside the pores was removed by filtration. This was followed by a drying step in which the solvent inside the pores was removed by passing a stream of nitrogen gas through wet Cs/Zr modified silica at room temperature. Alternatively, the solvent inside the pores was removed on a rotary evaporator under reduced pressure. After this stage, the catalyst granules were placed in an oven at 110–120°C and left to dry for 16 h. After cooling, a Cs/Zr/SiO ₂ catalyst was obtained with 90% Cs utilization efficiency. The concentration of Cs (% wt.) on the catalyst was determined using energy dispersive X-ray fluorescence analysis of powders (Oxford Instruments X-Supreme8000).

Example 21 (3.7 wt% Cs, 0.9 wt% Zr, monomeric Zr)

The catalyst was prepared as described in example 20, except that 0.534 g of CsOH·H ₂ O was used.

Example 22 (4.0 wt% Cs, 0.9 wt% Zr, monomeric Zr)

The catalyst was prepared as described in example 20, except that 0.588 g of CsOH·H ₂ O was used.

Example 23 (4.8 wt% Cs, 0.9 wt% Zr, monomeric Zr)

The catalyst was prepared as described in example 20, except that 0.716 g of CsOH·H ₂ O was used.

Example 24 (5.1 wt% Cs, 1.5 wt% Zr, monomeric Zr)

The catalyst was prepared as described in example 20, except that 0.754 g of CsOH·H ₂ O was used and the modified silica of example 4 was used.

Example 25 (5.7% wt. Cs, 1.5% wt. Zr, monomeric Zr)

The catalyst was prepared as described in example 24, except that 0.852 g of CsOH·H ₂ O was used.

Example 26 (6.7% wt. Cs, 1.4% wt. Zr, monomeric Zr)

The catalyst was prepared as described in example 24, except that 1.00 g of CsOH·H ₂ O was used.

Example 27 (7.7% wt. Cs, 1.4% wt. Zr, monomeric Zr)

The catalyst was prepared as described in example 24, except that 1.17 g of CsOH·H ₂ O was used.

Example 28 (9.7 wt% Cs, 2.0 wt% Zr, monomeric Zr)

The catalyst was prepared as described in Example 20, except that 1.37 g of CsOH H ₂ O was used and the modified silica of Example 5 was used. In addition, the Cs adsorption time was reduced from 16 hours to 2 hours by eliminating the filtration step . The excess organic solvent was dried in the pore volume of the modified silica carrier, and as a result, the Cs utilization efficiency was 100%.

Example 29 (10.2 wt% Cs, 2.0 wt% Zr, monomeric Zr)

The catalyst was prepared as described in example 28, except that 1.45 g of CsOH·H ₂ O was used.

Example 30 (10.8 wt% Cs, 2.0 wt% Zr, monomeric Zr)

The catalyst was prepared as described in example 28, except that 1.54 g of CsOH·H ₂ O was used.

Example 31 (11.3 wt% Cs, 2.0 wt% Zr, monomeric Zr)

The catalyst was prepared as described in example 28, except that 1.62 g of CsOH·H ₂ O was used.

Example 32 (9.2% wt. Cs, 2.4% wt. Zr, monomeric Zr)

The catalyst was prepared as described in example 20, except that 1.44 g of CsOH·H ₂ O was used and the modified silica of example 6 was used.

Example 33 (10.9% wt. Cs, 2.4% wt. Zr, monomeric Zr)

The catalyst was prepared as described in example 32, except that 1.74 g of CsOH·H ₂ O was used.

Example 34 (13.0 wt% Cs, 2.3 wt% Zr, monomeric Zr)

The catalyst was prepared as described in example 32, except that 2.12 g of CsOH·H ₂ O was used.

Example 35 (14.0 wt% Cs, 2.3 wt% Zr, monomeric Zr)

The catalyst was prepared as described in example 32, except that 2.30 g of CsOH·H ₂ O was used.

Example 36 (12.3 wt% Cs, 3.7 wt% Zr, monomeric Zr)

The catalyst was prepared as described in example 20, except that 2.00 g of CsOH·H ₂ O was used and the modified silica of example 7 was used.

Example 37 (12.6 wt% Cs, 3.7 wt% Zr, monomeric Zr)

The catalyst was prepared as described in example 36, except that 2.05 g of CsOH·H ₂ O was used.

Example 38 (13.9 wt% Cs, 3.6 wt% Zr, monomeric Zr)

The catalyst was prepared as described in example 36, except that 2.30 g of CsOH·H ₂ O was used.

Example 39 (15.4 wt% Cs, 3.6 wt% Zr, monomeric Zr)

The catalyst was prepared as described in example 36, except that 2.60 g of CsOH·H ₂ O was used.

Example 40 (2.8 wt% Cs, 0.7 wt% Zr, monomeric Zr)

The catalyst was prepared as described in example 28, except that 0.37 g of CsOH·H ₂ O was used and the modified silica of example 8 was used.

Example 41 (3.4 wt% Cs, 0.7 wt% Zr, monomeric Zr)

The catalyst was prepared as described in example 40, except that 0.45 g of CsOH·H ₂ O was used.

Example 42 (3.9 wt% Cs, 0.7 wt% Zr, monomeric Zr)

The catalyst was prepared as described in example 40, except that 0.51 g of CsOH·H ₂ O was used.

Example 43 (4.1 wt% Cs, 1.0 wt% Zr, monomeric Zr)

The catalyst was prepared as described in example 20, except that 0.60 g of CsOH·H ₂ O was used and the modified silica of example 9 was used.

Example 44 (4.6 wt% Cs, 1.0 wt% Zr, monomeric Zr)

The catalyst was prepared as described in example 43, except that 0.68 g of CsOH·H ₂ O was used.

Example 45 (5.5 wt% Cs, 1.0 wt% Zr, monomeric Zr)

The catalyst was prepared as described in example 43, except that 0.82 g of CsOH·H ₂ O was used.

Example 46 (9.1 wt% Cs, 2.0 wt% Zr, monomeric Zr)

The catalyst was prepared as described in example 20, except that 1.42 g of CsOH·H ₂ O was used and the modified silica of example 10 was used.

Example 47 (9.9 wt% Cs, 1.9 wt% Zr, monomeric Zr)

The catalyst was prepared as described in example 46, except that 1.55 g of CsOH·H ₂ O was used.

Example 48 (13.8 wt% Cs, 3.3 wt% Zr, monomeric Zr)

The catalyst was prepared as described in example 20, except that 2.28 g of CsOH·H ₂ O was used and the modified silica of example 11 was used.

Example 49 (15.0 wt% Cs, 3.3 wt% Zr, monomeric Zr)

The catalyst was prepared as described in example 48, except that 2.51 g of CsOH·H ₂ O was used.

Example 50 (14.0 wt% Cs, 5.7 wt% Zr, Zr dimer) (comparative)

The catalyst was prepared as described in example 20, except that 2.34 g of CsOH·H ₂ O was used and the modified silica of example 12 was used.

Example 51 (15.0 wt% Cs, 5.7 wt% Zr, dimeric Zr) (comparative example)

The catalyst was prepared as described in example 50, except that 2.54 g of CsOH·H ₂ O was used.

Example 52 (16.1 wt. % Cs, 5.6 wt. % Zr, dimeric Zr) (comparative example)

The catalyst was prepared as described in example 50, except that 2.76 g of CsOH·H ₂ O was used.

Example 53 (17.3 wt% Cs, 5.5 wt% Zr, Zr dimer) (comparative)

The catalyst was prepared as described in example 50, except that 3.01 g of CsOH·H ₂ O was used.

Example 54 (6.0 wt. % Cs, 2.1 wt. % Zr, trimeric Zr) (comparative example)

The catalyst was prepared as described in example 28, except that 0.81 g of CsOH·H ₂ O was used and the modified silica of example 13 was used.

Example 55 (7.7 wt% Cs, 2.0 wt% Zr, trimeric Zr) (comparative example)

The catalyst was prepared as described in example 54, except that 1.06 g of CsOH·H ₂ O was used.

Example 56 (13.6 wt% Cs, 5.2 wt% Zr, trimeric Zr) (comparative example)

The catalyst was prepared as described in example 28, except that 2.03 g of CsOH·H ₂ O was used and the modified silica of example 14 was used.

Example 57 (14.9 wt% Cs, 5.1 wt% Zr, trimeric Zr) (comparative)

The catalyst was prepared as described in example 56, except that 2.26 g of CsOH·H ₂ O was used.

Example 58 (16.1 wt% Cs, 5.0 wt% Zr, trimeric Zr) (comparative)

The catalyst was prepared as described in example 56, except that 2.48 g of CsOH·H ₂ O was used.

Example 59 (17.3 wt% Cs, 5.0 wt% Zr, trimeric Zr) (comparative)

The catalyst was prepared as described in example 56, except that 2.70 g of CsOH·H ₂ O was used.

Example 60 (12.3 wt% Cs, 7.0 wt% Zr, Zr pentamer) (comparative)

The catalyst was prepared as described in example 28, except that 1.82 g of CsOH·H ₂ O was used and the modified silica of example 15 was used.

Example 61 (14.0 wt% Cs, 6.9 wt% Zr, Zr pentamer) (comparative)

The catalyst was prepared as described in example 60, except that 2.12 g of CsOH·H ₂ O was used.

Example 62 (15.7 wt. % Cs, 6.7 wt. % Zr, Zr pentamer) (comparative)

The catalyst was prepared as described in example 60, except that 2.42 g of CsOH·H ₂ O was used.

Example 63 (18.9 wt% Cs, 6.5 wt% Zr, Zr pentamer) (comparative)

The catalyst was prepared as described in example 60, except that 2.99 g of CsOH·H ₂ O was used.

Example 64 (8.8 wt% Cs, 4.9 wt% Hf, monomeric Hf)

The catalyst was prepared as described in example 28, except that 1.23 g of CsOH·H ₂ O was used and the modified silica of example 16 was used.

Example 65 (10.1 wt% Cs, 4.9 wt% Hf, monomeric Hf)

The catalyst was prepared as described in example 64, except that 1.43 g of CsOH·H ₂ O was used.

Example 66 (11.4 wt% Cs, 4.8 wt% Hf, monomeric Hf)

The catalyst was prepared as described in example 64, except that 1.64 g of CsOH·H ₂ O was used.

Example 67 (12.6 wt% Cs, 4.7 wt% Hf, monomeric Hf)

The catalyst was prepared as described in example 64, except that 1.84 g of CsOH·H ₂ O was used.

Example 68 (11.1 wt% Cs, 6.9 wt% Hf, monomeric Hf)

The catalyst was prepared as described in example 28, except that 1.60 g of CsOH·H ₂ O was used and the modified silica of example 17 was used.

Example 69 (12.7 wt% Cs, 6.8 wt% Hf, monomeric Hf)

The catalyst was prepared as described in example 68, except that 1.86 g of CsOH·H ₂ O was used.

Example 70 (14.3 wt% Cs, 6.7 wt% Hf, monomeric Hf)

The catalyst was prepared as described in example 68, except that 2.14 g of CsOH·H ₂ O was used.

Example 71 (15.8 wt% Cs, 6.6 wt% Hf, monomeric Hf)

The catalyst was prepared as described in example 68, except that 2.41 g of CsOH·H ₂ O was used.

Example 72 (13.7% wt. Cs, 10.2% wt. Hf, trimeric Hf) (comparative example)

The catalyst was prepared as described in example 20, except that 2.28 g of CsOH·H ₂ O was used and the modified silica of example 18 was used.

Example 73 (14.9 wt% Cs, 10.0 wt% Hf, trimeric Hf) (comparative)

The catalyst was prepared as described in example 72, except that 2.51 g of CsOH·H ₂ O was used.

Example 74 (16.2 wt% Cs, 9.9 wt% Hf, trimeric Hf) (comparative)

The catalyst was prepared as described in example 72, except that 2.77 g of CsOH·H ₂ O was used.

Example 75 (16.0% wt. Cs, 3.4% wt. Zr, 100% monomeric Zr)

The catalyst was prepared as described in Example 20, except that 2.71 g of CsOH·H ₂ O was used and 10 g of the modified silica of Example 7 was used. In addition, after the catalyst was dried, it was ground with a mortar and pestle and sieved into a fraction of 0.1-1.0 mm. This resulted in a catalyst with a monomer content of 100% in terms of % wt. Zr.

Example 76 (15.8% wt. Cs, 3.6% wt. Zr, 79% monomeric Zr) (comparative example)

The catalyst was prepared as described in Example 75, except that 2.67 g of CsOH·H ₂ O was used. An additional 8.5 g of modified silica of example 7 and 1.5 g of modified silica of example 14 were used as a catalyst support. . This resulted in a catalyst with a monomer content of 79% in terms of % wt. Zr.

Example 77 (15.4% wt. Cs, 3.9% wt. Zr, 61% monomeric Zr) (comparative example)

The catalyst was prepared as described in Example 75, except that 2.60 g of CsOH·H ₂ O was used. An additional 7 g of modified silica of example 7 and 3 g of modified silica of example 14 were used as a catalyst support. This resulted in a catalyst with a monomer content of 61% in terms of % wt. Zr.

Example 78 (15.7% wt. Cs, 4.4% wt. Zr, 31% monomeric Zr) (comparative example)

The catalyst was prepared as described in Example 75, except that 2.66 g of CsOH·H ₂ O was used. An additional 4 g of modified silica of example 7 and 6 g of modified silica of example 14 were used as a catalyst support. This resulted in a catalyst with a monomer content of 31% in terms of % wt. Zr.

Example 79 (16.9% wt. Cs, 5.0% wt. Zr, 0% monomeric Zr) (comparative example)

The catalyst was prepared as described in example 75, except that 2.92 g of CsOH·H ₂ O was used. An additional 10 g of modified silica of example 14 was used as a catalyst support. This resulted in a catalyst with a monomer content of 0% in terms of % wt. Zr.

Example 80 (Catalyst performance test)

The catalysts of examples 20-79 were tested for the reaction of methyl propionate and formaldehyde in a laboratory microreactor. For this, 3 g of the catalyst was loaded into a fixed bed reactor with a tube inner diameter of 10 mm. The reactor was heated to 330°C and pre-conditioned by feeding the evaporated stream containing 70% of the mass. methyl propionate, 20% wt. methanol, 6% wt. water and 4% of the mass. formaldehyde from an evaporator fed by a Gilson pump at 0.032 ml/min. This preconditioning was continued overnight. After preconditioning the flow of raw materials containing 75.6% of the mass. methyl propionate, 18.1% wt. methanol, 5.7% wt. formaldehyde and 0.6% of the mass. water was pumped with a Gilson pump into the evaporator set at 330° C. before being fed into the heated reactor set at 330° C. containing the catalyst. The steam exiting the reactor was cooled and condensed with samples collected at five different liquid flow rates (range 0.64-0.032 ml/min) to obtain conversions at different vapor-catalyst contact times. Liquid feed and condensed liquid products from the reactor were analyzed using a Shimadzu 2010 gas chromatograph with a DB1701 column. The composition of the samples was determined from the respective chromatograms and the yield and selectivity were determined at various contact times. Activity was defined as the reciprocal of the contact time (in seconds) required to obtain a 10% yield of MMA+MAA on the methyl propionate feedstock and was determined by interpolation on a plot of MMA+MAA yield versus contact time. This interpolated contact time was then used to obtain MMA+MAA selectivity at 10% MMA+MAA yield.

Table 1: MMA+MAA activity and selectivity results for the catalyst prepared on Zr-modified support samples with different Zr atomicities.

Example Nuclearity of zirconium Zr concentration (wt. %) Cs concentration (% mass) Cs:Zr (molar ratio) Activity at 10% MMA+MAA output (with ^-one ) Selectivity MMA+MAA (%) Example 20 one 0.9 3.2 2.4 0.12 95.8 Example 21 one 0.9 3.7 2.8 0.15 97.3 Example 22 one 0.9 4.0 3.1 0.18 97.6 Example 23 one 0.9 4.8 3.8 0.24 98.0 Example 24 one 1.5 5.1 2.4 0.32 97.4 Example 25 one 1.5 5.7 2.7 0.39 97.1 Example 26 one 1.4 6.7 3.2 0.41 97.0 Example 27 one 1.4 7.7 3.7 0.47 97.3 Example 28 one 2.0 9.7 3.3 0.45 96.1 Example 29 one 2.0 10.2 3.5 0.39 95.8 Example 30 one 2.0 10.8 3.7 0.49 95.8 Example 31 one 2.0 11.3 3.9 0.46 95.5 Example 32 one 2.4 9.2 2.6 0.48 96.8 Example 33 one 2.4 10.9 3.2 0.64 96.2 Example 34 one 2.3 13.0 3.9 0.67 95.5 Example 35 one 2.3 14.0 4.2 0.75 95.5 Example 36 one 3.7 12.3 2.3 0.76 95.3 Example 37 one 3.7 12.6 2.4 0.80 95.0 Example 38 one 3.6 13.9 2.7 0.86 94.1 Example 39 one 3.6 15.4 3.0 0.93 94.5 Example 40 one 0.7 2.8 2.7 0.13 97.5 Example 41 one 0.7 3.4 3.3 0.17 97.9 Example 42 one 0.7 3.9 3.8 0.25 97.8 Example 43 one 1.0 4.1 2.7 0.25 96.3 Example 44 one 1.0 4.6 3.1 0.28 97.8 Example 45 one 1.0 5.5 3.7 0.35 96.7 Example 46 one 2.0 9.1 3.2 0.47 96.5 Example 47 one 1.9 9.9 3.5 0.71 96.5 Example 48 one 3.3 13.8 2.9 0.75 94.5 Example 49 one 3.3 15.0 3.2 0.76 94.8 Example 50 2 5.7 14.0 1.7 0.69 93.0 Example 51 2 5.7 15.0 1.8 0.82 93.0 Example 52 2 5.6 16.1 2.0 0.85 93.2 Example 53 2 5.5 17.3 2.2 0.68 92.0 Example 54 3 2.1 6.0 2.0 0.26 89.2 Example 55 3 2.0 7.7 2.5 0.34 88.8 Example 56 3 5.2 13.6 1.8 0.38 85.7 Example 57 3 5.1 14.9 2.0 0.47 88.7 Example 58 3 5.0 16.1 2.2 0.51 90.7 Example 59 3 5.0 17.3 2.4 0.41 90.2 Example 60 5 7.0 12.3 1.2 0.24 76.0 Example 61 5 6.9 14.0 1.4 0.45 85.0 Example 62 5 6.7 15.7 1.6 0.56 87.0 Example 63 5 6.5 18.9 2.0 0.85 87.6

Table 2: MMA+MAA activity and selectivity results for the catalyst prepared on Hf-modified support samples with different Hf nuclearities.

Example Nuclearity of hafnium Hf concentration (% mass) Cs concentration (% mass) Cs:Hf (molar ratio) Activity at 10% MMA+MAA output (with ^-one ) Selectivity MMA+MAA (%) Example 64 one 4.9 8.8 2.4 0.51 97.2 Example 65 one 4.9 10.1 2.8 0.58 97.1 Example 66 one 4.8 11.4 3.2 0.64 96.5 Example 67 one 4.7 12.6 3.6 0.73 96.5 Example 68 one 6.9 11.1 2.2 0.68 96.4 Example 69 one 6.8 12.7 2.5 0.82 96.5 Example 70 one 6.7 14.3 2.9 0.88 96.0 Example 71 one 6.6 15.8 3.2 0.88 95.1 Example 72 3 10.2 13.7 1.8 0.58 89.8 Example 73 3 10.0 14.9 2.0 0.71 91.6 Example 74 3 9.9 16.2 2.2 0.69 91.2

Table 3: MMA+MAA activity and selectivity results for the catalyst prepared with different amounts of Zr monomer and trimer.

Example Monomeric Zr content (% of Zr content) Zr concentration (wt. %) Cs concentration (% mass) Cs:Zr (molar ratio) Activity at 10% MMA+MAA output (with ^-one ) Selectivity MMA+MAA (%) Example 75 100 3.4 16.0 3.3 1.43 95.8 Example 76 79 3.6 15.8 3.0 1.44 94.9 Example 77 61 3.9 15.4 2.7 1.40 93.7 Example 78 31 4.4 15.7 2.5 1.31 92.0 Example 79 0 5.0 16.9 2.4 1.29 88.6

Example 81 (Accelerated Aging Test)

The sintering resistance of the catalyst was evaluated in an accelerated aging test. For this, 1 g of the catalyst was loaded into a stainless steel U-shaped tubular reactor and placed in an oven. The oven was heated to 385°C and a stream of nitrogen (10 ml/min) was passed through a saturating evaporator containing water, which was heated to 92°C. This ensured that the feed stream with a water partial pressure of 0.75 bar abs. (0.075 MPa) passed through the catalyst heated to 385°C. Periodically, the specific surface area of catalyst samples was determined ex-situ by measuring nitrogen adsorption/desorption isotherms (Micromeretics Tristar II). The measured specific surface area was used to determine the sintering rate constants for each catalyst and was reported as g ³ /m ⁶ ·day. The higher the sintering constant, the lower the sintering resistance of the catalyst. This test was carried out on example 32, example 38, example 57 and example 63.

Table 4: Accelerated aging data for catalysts with different Zr nucleicities at comparable activities.

Example Specific surface by time (days) Catalyst activity (s ^-one ) Sintering rate constant (g ³ /m ⁶ day) one 7 fourteen 21 28 Example 32 (according to the invention) 189 187 177 176 178 0.48 1.28E-09 Example 38 (according to the invention) 163 147 144 135 135 0.86 6.35E-09 Example 57 (comparative) 218 209 192 192 185 0.47 2.26E-09 Example 63 (comparative) 148 132 124 127 119 0.85 8.94E-09

Comparative Examples 82 and 83

The examples were prepared in accordance with the experimental examples described in EP 1233330. In these examples, the silica used was silica gel in the form of spheres with a diameter in the range of 2-4 mm, having a purity of over 99%, a total specific surface of about 300-350 m ² / g and a pore volume of 1.04 cm ³ /g, with 76% of the pore volume being provided by pores having a diameter in the range of 7-23 nm.

Two catalysts were prepared by impregnating silica with an aqueous solution of zirconium nitrate sufficient to fill the pores of the carrier and drying in a rotary evaporator and then in an air oven at 120° C. for 2 hours. zirconium was carried out by evacuating the pores of the carrier before adding the solution. In another case (Example 83), the impregnation of the zirconium solution was carried out at atmospheric air pressure. Then cesium was introduced by a similar method using an aqueous solution of cesium carbonate to obtain a cesium content of 4 wt%. (in terms of metal). Then the catalysts were calcined in air at 450°С for 3 h.

The catalysts were tested under the same conditions as in Example 80. One catalyst (Example 82) did not reach 10% yield and selectivities are shown for the highest yield obtained (9.6%).

Table 5: MMA+MAA activity and selectivity results for comparative examples 82 and 83.

Example Zr concentration (wt %) Cs concentration (% mass) Cs:Zr (molar ratio) Activity at 10% MMA+MAA output (s ^-1 ) Selectivity MMA+MAA (%) Example 82 1.7 4.0 1.6 0.05 65.2 Example 83 1.7 4.0 1.6 0.12 73.2

HRTEM Results for Modified Zr and Hf Silica Supports

HRTEM images (example 19) for samples of modified Zr and Hf silica (example 5, example 7, example 14, example 15, example 17 and example 18) are shown in Fig.1 - Fig.6. In the case of HRTEM images of monomeric Zr and Hf, it is difficult to clearly distinguish between Zr or Hf particles, and this indicates very small Zr/Hf nanoparticles present on the surface of the modified silica. This is due to the fact that Zr or Hf are present as monoatoms. In the case of samples of trimeric Zr or Hf and pentameric Zr, clear clusters of Zr or Hf can be distinguished in HRTEM images. These data show that the nuclearity of the Zr or Hf compounds in the solution phase is transferred from solution to the final catalyst composition.

Graphic data

Activity and selectivity data obtained from Table 1 and Table 2

The selectivity of MMA+MAA (%) as a function of catalyst activity for the catalysts prepared in Examples 20 to 74 is shown in FIG. It is clear from this graph that trimeric Zr and Hf as well as pentameric Zr give lower MMA+MAA selectivity over the entire range of activity tested. The dimeric Zr catalyst has an increased selectivity compared to catalysts with trimeric Zr at comparable concentrations of Zr and Cs.

Activity and selectivity data obtained from Table 3

The catalyst selectivity for the mixed monomer/trimer catalysts prepared in Examples 75 to 79 is shown in FIG. The Zr monomer content is calculated as % of the Zr content present as monomer. In these examples, the catalyst was crushed and sieved to a particle size of 0.1-1.0 mm in order to increase the homogeneity of the sample. From this graph it can be seen that a decrease in the amount of Zr monomer in the composition leads to a decrease in the selectivity of MMA + MAA.

Caking resistance data obtained from Table 4

Catalyst sintering constants determined using the accelerated aging test described in Example 81 are shown in FIG. From Fig.9 it can be seen that the monomeric Zr catalysts show lower sintering rates with comparable catalyst activity.

Attention is drawn to all publications and documents that coincide in time with this description associated with this application, or precede it, and which are open to the public in conjunction with this application, while the contents of all such publications and documents are included in this application by reference. .

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

Each feature disclosed in this specification (including any appended claims, abstract, and drawings) may be replaced by alternative features serving the same, equivalent, or similar purpose, except where expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is but one example of a type range of equivalent or similar features.

The invention is not limited to the details of the above embodiment(s). The present invention extends to any new feature or to any new combination of preferred, exemplary or optional features of the invention disclosed in this specification (including any claims of the appended claims, abstract and drawings), or to any new step or any new combination of preferred, exemplary or optional steps of the invention of any described method or process.

Claims (68)

1. A catalyst for the production of an ethylenically unsaturated carboxylic acid or ester containing a modified silica carrier, the modified silica carrier containing a modifier metal, and a catalytic metal on a modified silica carrier, where the modifier metal is selected from one or more components from zirconium and / or hafnium , characterized in that at least a portion of said modifier metal is present in the form of modifier metal groups having a total of up to 2 modifier metal atoms, where the catalytic metal is one or more alkali metals. 2. A catalyst for producing an ethylenically unsaturated carboxylic acid or ester containing a modified silica carrier, the modified silica carrier containing a metal modifier, and a catalytic metal on a modified silica carrier, where the modifier metal is selected from one or more components from zirconium and / or hafnium characterized in that at least a portion of said modifier metal is present in the form of modifier metal groups obtained from a source of monomeric and/or dimeric modifier metal cations at the start of modification, where the catalytic metal is one or more alkali metals. 3. A modified silica carrier for a catalyst for producing an ethylenically unsaturated carboxylic acid or an ester, containing a silica carrier and a modifier metal, where the modifier metal is selected from one or more components from zirconium and/or hafnium, characterized in that at least part of the specified The modifier metal is present as modifier metal oxide groups having up to 2 modifier metal atoms in total. 4. A modified silica carrier for a catalyst for producing an ethylenically unsaturated carboxylic acid or an ester containing a silica carrier and a modifier metal, where the modifier metal is selected from one or more components from zirconium and/or hafnium, characterized in that at least part of the specified The modifier metal is present in the form of oxide groups of the modifier metal obtained from the source of monomeric and/or dimeric modifier metal cations at the start of the modification. 5. The modified silica carrier or catalyst according to any one of the preceding claims, wherein typically at least 25% of said modifier metal is present as modifier metal oxide groups having up to two modifier metal atoms in total. 6. Modified silica support or catalyst according to any one of the preceding claims, wherein the modifier metal is an adsorbate adsorbed on the surface of the silica support, preferably chemisorbed thereon. 7. The modified silica carrier or catalyst according to any one of claims 1, 2, 5, or 6, wherein the modifier metal groups are oxide groups of the modifier metal. 8. The modified silica carrier or catalyst according to any one of the preceding claims, wherein the silica carrier is silica gel, more typically a xerogel or hydrogel. 9. Modified silica support or catalyst according to any one of claims 1-5, 7 or 8, wherein the modifier metal is present in the support as a cogel. 10. The modified silica support or catalyst according to any one of the preceding claims, wherein the modifier metal is present in the modified silica support in an effective amount to reduce sintering and improve catalyst selectivity. 11. The modified silica carrier or catalyst according to any one of the preceding claims, wherein at least 30%, such as at least 35%, more preferably at least 40%, such as at least 45%, most preferably at least 50%, such as at least 55%, such as 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 modifier metal in the modified silica support is in groups having a total of 1 and/or 2 metal atoms, especially in groups having a total of 1 metal atom, or derived from monomeric and/or dimeric modifier metal compound at the start of the formation of modified silica at modifier metal levels such as monomeric and/or dimeric compounds, especially monomeric modifier metal compounds ator. 12. Modified silica carrier or catalyst according to any one of the preceding claims, wherein the level of modifier metal present is up to 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 silicon dioxide. 13. Modified silica carrier or catalyst according to any one of the preceding claims, wherein the modifier metal level is from 0.067×10 ^-2 to 7.3×10 ^-2 mol/mol silica, more preferably from 0.13×10 ^-2 up to 5.7×10 ^-2 mol/mol silica and most preferably from 0.2×10 ^-2 to 3.5×10 ^-2 mol/mol silica. 14. Modified silica carrier or catalyst according to any one of the preceding claims, wherein the level of modifier metal present is at least 0.1×10 ^-2 mol/mol silica, more preferably at least 0.15×10 ^-2 mol /mol silicon dioxide and most preferably at least 0.25×10 ^-2 mol/mol silicon dioxide. 15. The modified silica carrier according to any one of claims 3 to 14, wherein the modified silica carrier is a calcined modified silica carrier. 16. The catalyst according to any one of claims 1, 2 or 5-15, wherein the catalytic metal is selected from potassium, rubidium and cesium, suitably rubidium and cesium, cesium being most preferred. 17. The catalyst or modified silica support according to any one of the preceding claims, wherein the cation of the monomeric and/or dimeric modifier metal at the start of the modification is in combination with one or more non-labile ligands attached to the cations of the modifier metal, and these non-labile ligands are selected of molecules containing lone pairs of oxygen or nitrogen atoms capable of forming 5- or 6-membered rings with a zirconium or hafnium atom, including diones, diimines, diamines, diols, dicarboxylic acids or their derivatives, such as esters, or molecules having two different such functional groups and, in any case, with the corresponding N or O atoms and the N or O atoms separated by 2 or 3 atoms, thus forming a 5- or 6-membered ring, for example pentane-2,4-dione, esters of 3-oxobutanoic acid with aliphatic alcohols containing 1-4 carbon atoms, such as ethyl 3-oxobutanoate, propyl 3-oxobutanoate, isopropyl 3-oxobutanoate, n-butyl-3-oxobutanoate, tert-butyl-3-oxobutanoate, heptane-3,5-dione, 2,2,6,6-tetramethyl-3,5-heptanedione, 1,2- ethanediol, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, 1,2-butanediol, 1,2-diaminoethane, ethanolamine, 1,2-diamino-1,1,2,2-tetracarboxylate, 2,3-dihydroxy-1,4-butanedioate, 2,4-dihydroxy-1,5-pentanedioate, salts of 1,2-dihydroxylbenzene-3-5-disulfonate, diethylenetriaminepentaacetic acid, nitrolotriacetic acid, N-hydroxyethylethylenediaminetriacetic acid, N- hydroxyethyliminodiacetic acid, N,N-dihydroxyethylglycine, oxalic acid and its salts, more typically non-labile ligands are selected from one or more of pentane-2,4-dione, 2,2,6,6-tetramethyl-3,5-heptanedione, ethyl -3-oxobutanoate, tert-butyl-3-oxobutanoate and heptane-3,5-dione. 18. The catalyst or modified silica support of claim 17, wherein the non-labile ligands are complexed with the modifier element, eg, tetrameric complexes, and are typically solubilized as the non-labile ligand/alcohol complexes with the monomeric modifier element in solution. 19. The catalyst according to any one of the preceding claims, wherein the catalytic metal is present in the range of 0.5-7.0 mol/mol modifier metal, more preferably 1.0-6.0 mol/mol, most preferably 1.5-5 .0 mol/mol modifier metal. 20. A method for producing a modified silica carrier according to any one of claims 1 to 19, including the steps: providing a silica carrier containing silanol groups; treating the silica carrier with monomeric and/or dimeric modifier metal compounds such that the modifier metal is adsorbed onto the surface of the silica carrier by reaction with silanol groups, the adsorbed modifier metal atoms being sufficiently spaced apart to substantially prevent them from oligomerizing with adjacent modifier metal atoms. 21. The method for producing a modified silica support according to claim 20, wherein the adsorbed modifier metal atoms are sufficiently spaced apart to substantially prevent trimerization with adjacent modifier metal atoms. 22. The method according to claim 20 or 21, in which the distance between the modifier metal atoms is provided 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 modifier metal prior to treatment of the silica support. 23. A method for producing a catalyst, comprising the steps: i) providing a silica carrier with isolated silanol groups and optionally treating said carrier to obtain isolated silanol groups (-SiOH) at a level of <2.5 groups per 1 nm ² ; ii) contacting the optionally treated silica carrier with a modifier metal compound of monomeric zirconium or hafnium to adsorb said modifier metal onto the carrier with at least up to 25% of said isolated silanol groups; iii) optionally removing any solvent or carrier liquid for modifier metal compounds; iv) calcining the modified silica for a period of time and at a temperature sufficient to convert the monomeric zirconium or hafnium compound adsorbed on the surface to zirconium or hafnium oxide or hydroxide; v) treating said calcined modified silica with a catalytic alkali metal to impregnate the modified silica with the catalytic metal to form a catalyst, and optionally calcining the catalyst. 24. A method for producing a modified silica carrier for a catalyst, comprising the steps: i) providing a silica carrier with isolated silanol groups and optionally treating said carrier to obtain isolated silanol groups (-SiOH) at a level of <2.5 groups per 1 nm ² ; ii) contacting the optionally treated silica carrier with a modifier metal compound of monomeric zirconium or hafnium to adsorb said modifier metal onto the carrier to at least 25% of said isolated silanol groups; iii) optionally removing any solvent or carrier liquid for modifier metal compounds; iv) optionally calcining the modified carrier for a period of time and at a temperature sufficient to convert the monomeric zirconium or hafnium compound adsorbed on the surface to zirconium or hafnium oxide or hydroxide in preparation for catalyst impregnation. 25. The method according to any one of claims 20-24, wherein the concentration of the silanol group is reduced prior to treatment with modifier metal compounds by calcination, chemical dehydration, or other suitable means. 26. The method according to any one of claims 20-25, wherein the source of modifier metal cations is a solution of said compounds, such that the compounds are in solution in contact with the carrier to effect adsorption on the carrier. 27. The method of claim 26 wherein the solvent for said solution is other than water. 28. The method of claim 25 or 26 wherein the solvent is an aliphatic alcohol, typically selected from C1-C6 alkanols such as methanol, ethanol, propanol, isopropanol, butanols, pentanols and hexanols, more typically methanol, ethanol or propanols. 29. The method according to any one of claims 20-28, in which one or more non-labile ligands are attached to modifier metal cations, at least partially forming these compounds, and are selected from molecules with oxygen or nitrogen atoms containing a lone pair, capable of forming 5 - or 6-membered rings with a zirconium or hafnium atom, including diones, diimines, diamines, diols, dicarboxylic acids or their derivatives, such as esters, or molecules having two different such functional groups and, in any case, with the corresponding atoms N or O and N or O atoms separated by 2 or 3 atoms, thus forming a 5- or 6-membered ring, for example pentane-2,4-dione, esters of 3-oxobutanoic acid with aliphatic alcohols containing 1-4 carbon atoms such as ethyl 3-oxobutanoate, propyl 3-oxobutanoate, isopropyl 3-oxobutanoate, n-butyl-3-oxobutanoate, tert-butyl-3-oxobutanoate, heptane-3,5-dione, 2.2 ,6,6-tetramethyl-3,5-heptanediol, 1,2-ethanediol, 1,2-propanediol , 1,3-propanediol, 1,3-butanediol, 1,2-butanediol, 1,2-diaminoethane, ethanolamine, 1,2-diamino-1,1,2,2-tetracarboxylate, 2,3-dihydroxy-1 ,4-butanedioate, 2,4-dihydroxy-1,5-pentanedioate, salts of 1,2-dihydroxylbenzene-3-5-disulfonate, diethylenetriaminepentaacetic acid, nitrolotriacetic acid, N-hydroxyethylethylenediaminetriacetic acid, N-hydroxyethyliminodiacetic acid, N,N- dihydroxyethylglycine, oxalic acid and its salts, more typically non-labile ligands are selected from one or more of pentane-2,4-dione, 2,2,6,6-tetramethyl-3,5-heptanedione, ethyl 3-oxobutanoate, t- butyl 3-oxobutanoate and heptane-3,5-dione. 30. The method of claim 29, wherein the non-labile ligands form complexes with the monomeric modifier element, eg, tetrameric complexes, and are typically solubilized as the non-labile ligand/alcohol complexes with the monomeric modifier element in solution. 31. The method according to any one of claims 20-30, wherein the concentration of silanol on the silica carrier in contact with the modifier metal compound is 0.1-2.5 silanol groups per 1 nm ² , more preferably 0.15-1.0 silanol groups per 1 nm ² , most preferably 0.2-0.7 silanol groups per 1 nm ² . 32. The method according to any one of claims 20-31, wherein at least 30%, such as at least 35%, more preferably at least 40%, such as at least 45%, most preferably at least 50 %, such as at least 55%, such as 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 modifier metal in the modifier metal compounds is in the monomeric modifier metal compounds when the source thereof is brought into contact with a carrier to adsorb said compounds onto the carrier. 33. A method for producing a catalyst according to any one of claims 1, 2 or 5-19, including the steps of: forming a modified silica carrier according to any one of claims 1-19 and contacting the modified silica carrier with a solution containing a catalytic metal to impregnate the modified dioxide silicon catalytic metal. 34. A method according to any one of claims 20-31, wherein the silica support is dried or calcined prior to treatment with modifier metal compounds. 35. A method according to any one of claims 20, 21, 22, or 24-34, wherein the modified silica formed by contact with modifier metal compounds is dried or calcined prior to addition of the catalytic metal. 36. A method according to any one of claims 20-35, wherein the silica is in the form of a gel prior to treatment with the modifier metal compounds, wherein the gel is typically in the form of a hydrogel, xerogel, or airgel at the start of contact with the modifier metal compounds. 37. The method according to any one of claims 20 to 36, wherein the modifier metal is dispersed on the inner and outer surfaces of the silica carrier by adsorption, preferably chemisorption. 38. The process according to any one of claims 20-37, or the catalyst or silica support according to any one of claims 17 or 18, wherein the modifier metal compound is in a form selected from organic metal complexes such as zirconium(pentane-2,4- dione)_four, zirconium (ethyl-3-oxobutanoate)_four, zirconium (heptane-3,5-dione)_four, zirconium(2,2,6,6-tetramethylheptan-3,5-dione)_four, zirconium(propoxide)(pentane-2,3-dione)₃, zirconium (propoxide)₃(2,2,6,6-tetramethyl-3,5-heptanedione) (zirconium (butyl)₃(tert-butyl-3-oxobutanoate), zirconium(O-tert-butyl)₂(tert-butyl-3-oxobutanoate)₂, and metal salts such as zirconium perchlorate, zirconium oxynitrate and zirconium oxychloride, more typically an organic metal complex. 39. The method of claim 38, or the catalyst or support of claims 17-19, wherein the modifier metal compound is in a form selected from the following: zirconium(IV) acetylacetonate (zirconium, tetrakis(2,4-pentandionato-O, O')), zirconium(heptan-3,5-dione) ₄ , zirconium(2,2,6,6-tetramethyl-3,5-heptanedione) ₄ , zirconium(IV) ethyl 3-oxobutanoate, zirconium(IV ) tert-butyl 3-oxobutanoate or zirconium(IV) isopropyl 3-oxobutanoate, in one of methanol, ethanol, isopropanol, propanol, butanol, isobutanol or 2-butanol, optionally with up to 20% water by volume. 40. The method according to any one of claims 20-39, wherein the catalytic metal is one or more alkali metals and is preferably selected from potassium, rubidium and cesium, suitably from rubidium and cesium, with cesium being most preferred. 41. The method according to any one of claims 20 to 40, wherein the resulting catalyst is then calcined. 42. A process for producing an ethylenically unsaturated carboxylic acid or ester, typically an α,β-ethylenically unsaturated carboxylic acid or ester, comprising the steps of contacting formaldehyde or a suitable source thereof with a carboxylic acid or ester in the presence of a catalyst and optionally in the presence of an alcohol, wherein the catalyst corresponds to any of paragraphs 1, 2 or 5-41. 43. A process for producing an ethylenically unsaturated acid or ester, comprising contacting an alkanoic acid or ester of formula R ¹ -CH ₂ -COOR ³ with formaldehyde or a suitable formaldehyde source of formula (I) as defined below:

, (I) where R ⁵ is methyl and R ⁶ is H; X is O; m is 1; and n is any value from 1 to 20, or any combination thereof; in the presence of a catalyst according to any one of claims 1, 2 or 5-42, and optionally in the presence of an alkanol; where R ¹ is hydrogen or an alkyl group of 1-12, more suitably 1-8, most suitably 1-4 carbon atoms, and R ³ can also independently be hydrogen or an alkyl group of 1-12, at most suitably 1-8, most suitably 1-4 carbon atoms. 44. The method according to claim 42 or 43, in which the carboxylic acid or ester, or ester or acid of the formula R ¹ -CH ₂ -COOR ³ , respectively, is methyl propionate or propionic acid, and, as a rule, the optional alkanol is methanol, and the ethylenically unsaturated carboxylic acid or ester is methyl methacrylate or methacrylic acid. 45. A process according to any one of claims 20-44, wherein the support and/or catalyst is according to any one of claims 1-19. 46. Modified silica carrier according to any one of claims 3-15, 17 or 18, in which the carrier contains isolated silanol groups (-SiOH) at a level of <2.5 groups per 1 nm ² . 47. The catalyst or modified silica support according to any one of claims 1-19 or 46, wherein the support contains said zirconium or hafnium modifier metal groups at a level of <2.5 groups per nm ² . 48. Modified silica carrier according to any one of claims 3-15, 17, 18, 46 or 47, where the carrier contains isolated silanol groups (-SiOH) at a level of >0.1 and <2.5 groups per 1 nm ² , more preferably at a level of from 0.2 to 2.2, most preferably at a level of from 0.4 to 2.0 groups per 1 nm ² . 49. The catalyst or modified silica support according to any one of claims 1-19 or 46-48, wherein the support contains said zirconium or hafnium modifier metal groups at a level of >0.025 and <2.5 groups per 1 nm ² , more preferably at a level from 0.05 to 1.5, most preferably at a level of from 0.1 to 1.0 groups per 1 nm ² .

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