FR2756500A1 - CATALYTIC SYSTEM CONTAINING OXYGEN, MOLYBDENUM AND PHOSPHORUS, AND ITS APPLICATION TO THE OXIDESHYDROGENATION OF SATURATED CARBOXYLIC ACIDS OR THEIR ESTERS, AS WELL AS ALKANES OXIDATION - Google Patents

Abstract

The invention concerns a catalytic system with a base of a product represented by the formula (I) Csx(NH4)3-xPMo12O40Mey(VO)z in which Me represents a transition metal ion selected among copper, cobalt, iron, silver, nickel and manganese, or a magnesium ion; 0</=x</=3; 0</=y</=3; 0</=z</=3, and prepared by reacting an aqueous solution of H3-tNatPMo12O40, with 0</=t</=3, with an ammonium salt and/or a caesium salt with precipitation of the ammonium salt and/or caesium salt Csx(NH4)3-xPMo12O40, x being as defined above; if required adding to said salt an aqueous solution of a salt of Me and/or a vanadyl salt; drying the resulting compound until complete evaporation at a temperature of 90-200 DEG C for an interval of 2 to 6 hours, then calcinating at a temperature of 250-400 DEG C for an interval of 2 to 24 hours; and forming the resulting pulverulent product of formula (I) by compression of powders, pelletisation, granulation, extrusion or coating on a support for obtaining said catalytic system in the form of pellets or grains.

Description

CATALYTIC SYSTEM CONTAINING OXYGEN, MOLYBDENUM AND
PHOSPHORUS AND ITS APPLICATION TO OXIDESHYDROGENATION
OF SATURATED CARBOXYLIC ACIDS OR OF THEIR ESTERS, AS WELL AS
OXIDATION OF ALKANES
The present invention relates to catalytic systems containing oxygen, molybdenum and phosphorus to which ammonium, vanadyl, cesium, transition metal or magnesium ions may be bonded in variable proportions for the purpose of the oxidationhydrogenation reaction. saturated carboxylic acids or their esters to the corresponding unsaturated acids or esters, in particular the oxyhydrogenation reaction of isobutyric acid to methacrylic acid.

 Many catalyst systems based on heteropolyanions have long been known as catalysts in the oxidative dehydrogenation reaction of butyric acid, or its esters, to methacrylic acid or its esters.

 In J. Catal. 98, 401, 1986, catalysts of formula H5PMolOV2040 have been described for this reaction. The selectivity in methacrylic acid is of the order of 60%.

 German patent application DE-A-2,722,375 also describes catalysts obtained by concentration of an aqueous solution of the heteropoly acid of composition H5PMo10V2O40 and a copper salt, optionally in the presence of an alkaline salt. the dry residue is then calcined. Such catalysts achieve 72% methacrylic acid selectivities and, by incorporation of lithium, can reach 74.8%.

 US Pat. No. 4,314,075 proposes, for the same reaction, catalysts based on the following elements: molybdenum, vanadium, copper and phosphorus and an alkali metal selected from potassium, rubidium or cesium and a or several other metals, as well as oxygen in specific quantitative ratios. All metals are present during the hydrothermal reaction which leads to the aqueous solution of a heteropolyanion. The selectivities in methacrylic acid reached in the presence of these catalysts are between 60 and 70%.

 The European patent application EP-A-0 113 084 relates to the use, for the oxyhydrogenation of isobutyric acid or its esters of methacrylic acid or its esters, of a catalyst based on molybdenum oxides, vanadium, copper and phosphorus, prepared by hydrothermal conversion of molybdenum, vanadium and phosphorus compounds, generally in the absence of alkaline compounds and in the presence of a copper compound, into an aqueous solution of a heteropoly acid, drying the aqueous solution, optionally in the presence of an undissolved material serving as a support, and calcining the dry residue.

 European Patent Application EP-A-0 255 639 discloses a mixture of heteropolymolybdate containing vanadium and H3PMo12O40 or its salts, and / or H3 + xPMo12-xV, 040 with x = 1, 2 or 3 and / or its salts. The salts are obtained by adding metal compounds (hydroxides, carbonates, nitrates, phosphates) to the mixtures of heteropolyacids.

 All these catalytic systems derived from heteropolyanions, however, have the average defect of having a limited stability over time under the conditions of the oxyhydrogenation reaction.

The French patent application FR-A-2,716,634 proposes to obtain catalytic systems of the heteropolyanion type of general formula HmMeDPMol2 -xVx04 0 in which
H represents a proton with 0 S m <6
- Me is a metal ion, in particular an ion of a
transition metal with 0 <p <t, t depending on the
charge of the corresponding ion; and
- 0 <x S 3, to obtain unsaturated carboxylic acid selectivities associated with high conversions of the starting saturated carboxylic acid. These catalysts remain stable over time under the reaction conditions.

 However, these catalytic systems have the defect of operating with a partial pressure limited to 4% and a contact time greater than 3 seconds limiting the productivity of unsaturated carboxylic acids.

 According to the present invention, there is provided a process for producing a catalytic system according to which a precipitated heteropoly acid is prepared in the form of an ammonium salt and / or cesium salt on which can be introduced a vanadyl salt and / or a salt of a transition metal or magnesium. This method of manufacture has the advantage, compared to other methods for preparing the catalysts described in the prior art, to use neither the hydrothermal reaction nor the conventional method of extraction of the heteropoly acid with ether. Indeed, the two preparations handicap the manufacturing process of the catalysts in the case of production on an industrial scale.

 The catalytic systems which are the subject of the invention make it possible to obtain a better productivity of unsaturated carboxylic acids since they can operate at a higher partial pressure of saturated carboxylic acid and at a lower contact time. Moreover, it is also necessary that these catalysts remain stable over time under these reaction conditions.

The present invention therefore firstly relates to a catalytic system based on a product represented by formula (I)
Cs, (NHq) 3-xPM012040Mey (VO), (I) wherein
Me represents an ion of a chosen transition metal
among copper, cobalt, iron, silver, nickel
and manganese, or a magnesium ion;
0 <x <3
0 <y S3
0 <z <3 and prepared by reaction of an aqueous solution of H3 ~ tNatPMol2040, with 0 <t 5 3, with an ammonium salt and / or a cesium salt with precipitation of the ammonium salt and / or Cesium Csx (NH4) 3 ~ xPMol2040 x being as defined above; optionally adding to the above-mentioned salt an aqueous solution of a Ne salt and / or a vanadyl salt drying the compound obtained until complete evaporation at a temperature of 90-200 ° C for a period of time from 2 to 16 hours, then calcination at a temperature of 250-400 C for a period of time of 2 to 24 hours; and shaping the resulting powdery product of formula (I) by compression of powders, pelletizing, granulating, extruding or coating on a support, to obtain said catalyst system in the form of pellets or grains.

 The ammonium, cesium and Me salts which are useful as starting materials in the manufacture of the catalytic powdery product of the invention are in particular nitrates, carbonates, sulphates and chlorides.

The vanadyl salt is especially vanadyl sulfate.

 As indicated, the catalytic system of the invention is in the form of pellets or grains, obtained by compression of powders, pelletizing, granulation, extrusion or coating on a support. To carry out such shaping, the powdery catalytic product can be mixed with at least one dilution material chosen in particular from graphite, talc, stearic acid and stearates, macroporous silica, ammonium sulphate, and mixtures of at least two of these substances. The dilution material is generally used in a proportion of 1 to 10% by weight, preferably 1 to 3% by weight, of its mixture with the powdery catalytic product. In known manner, graphite is only used in the case of pelletizing shaping. Macroporous silica and ammonium sulphate may furthermore play a role in reinforcing the mechanical strength of the catalytic system which contains them. In the case of a coating on a support, it is possible to choose any known inert support, commonly used, such as silicon carbide, silica, α-alumina, silica-alumina or titanium dioxide. . Such a support may have any shape: spherical, in pellets or in the form of rings, having for example a diameter of the order of 310 mm. For the coating, it is possible to proceed as follows: the suspension of the ammonium salt and / or cesium CSx (NH 4) 3-x PM l 2 O 40 is mixed, x being as defined above, if necessary, there is added a aqueous solution of a Me salt and / or a vanadyl salt. The resulting mixed solution is placed in an evaporator and the support is added and mixed with stirring. The mixture is evaporated to dryness in order to deposit each of the above compounds on the support and then dried and calcined as above.

According to a preferred embodiment, the pellet or granular catalyst system further comprises, for final shaping, pellets or grains of at least one diluent chosen in particular from SiC and
SiO 2, the weight ratio of the pellets or grains based on catalytic product powder (I) to the pellets or grains of diluent being in particular 5/95 to 80/20, preferably 20/80 to 70/30.

 The present invention also relates to a process for the preparation of a catalytic system based on a product of formula (I) as defined above, characterized in that an aqueous solution of H3tNatPMo12O40 is reacted with 0 <t <3, with an ammonium salt and / or a cesium salt with precipitation of the ammonium salt and / or cesium Csx (NH4) 3 ~ xPMol2040, x being as defined in claim 1, and if necessary, an aqueous solution of a Me salt and / or a vanadyl salt is added to the aforementioned salt, the compound obtained is dried until complete evaporation at a temperature of 90-200 ° C. for a period of time of 2 to 16 hours, then calcined at a temperature of 250-400 ° C for a period of 2 to 24 hours, and the resulting powdery product of formula (I) is formed by compression of powders , pelletizing, granulating, extruding or coating on a support, to obtain said catalytic system in form pellets or grains.

 The present invention also relates to the application of the catalytic system as it has just been defined to the manufacture of an ethylenically unsaturated carboxylic acid, or an ester of such an acid, by in-phase oxidation hydrogenation. vapor of the saturated acid or the corresponding saturated acid ester.

 The corresponding method comprises contacting the saturated carboxylic acid or the saturated carboxylic acid ester with molecular oxygen or an oxygen-containing gas and, if appropriate, an inert diluent gas, if appropriate. in the presence of water to ensure a good course of the reaction, in the presence of a catalytic system as defined above, with an overall volume of load per volume of overall catalyst system (catalyst proper + material ( s) of dilution + diluent (s) per hour (VVH) between 200h-1 and 9000h-1, preferably between 1000h-1 and 2000h-1, at a reaction temperature of between 250 ° C. and 400 ° C. preferably between 300 ° C. and 350 ° C., under a pressure of 0 to 10 bar, preferably of the order of 1 bar, the proportion of the starting acid or ester in the reaction mixture being between 1 and 10 mol%, preferably between 2 and 5 mol%, the molar ratio of oxy acid gene or starting ester being between 1 and 5, preferably between 1 and 3, and the molar ratio of water to the starting acid or ester being in particular between 0.5 and 12, preferably between 1 and 3.

 Finally, the subject of the present invention is also the application of the catalytic system as defined above to the oxidation of alkanes, in particular the oxidation of isobutane to methacrylic acid and methacrolein.

The conditions of such a process are conventional, being the following in the case of the oxidation of isobutane
The gaseous feed to be applied to the reaction system comprises a gaseous mixture containing isobutane and oxygen. The fraction of isobutane in this gaseous mixture is preferably in the range of 10 to 80 mol%. If this fraction is less than 10 mol%, the amount of methacrylic acid produced by the reactor is too low so that productivity for industrial activity can not be obtained.

 It is better to conduct the reaction with an isobutane fraction in the gaseous mixture of between 20 and 60 mol%.

 The oxygen / isobutane molar ratio is between 0.05 / 1 and 1/1, preferably between 0.1 / 1 and 0.6 / 1. If this ratio is greater than that indicated, the complete oxidation occurs excessively, and the result is the formation of a large amount of carbon oxides. Moreover, if this ratio is lower, the amount of oxygen is not sufficient to oxidize the isobutane and the conversion is lowered.

 It is preferred that the amount of oxygen and the amount of isobutane be chosen so that the composition of the resulting mixture is outside the explosive zone. It is not necessary to use pure molecular oxygen; in general, air is used which is preferable from the economic point of view. In addition, it is possible to avoid dropping the reaction mixture into the explosive zone by using a diluent gas, such as nitrogen or other inert gas having no adverse effects on the reaction, such as helium, argon or carbon dioxide. In this case, the molar ratio of inert gas / isobutane is between 1/10 and 10/1.

 In order to preserve methacrylic acid as a product of the reaction is to avoid its subsequent oxidation to carbon monoxide, water vapor is usually added to oxygen and isobutane in a water vapor molar ratio isobutane between 1/5 and 5/1, preferably between 1/3 and 3/1.

 The reaction temperature is between 250 and 400 ° C, preferably between 280 and 350 ° C, and the pressure between 1 and 5 bar relative, preferably between 1 and 2 bar relative. The overall volume volume per volume of overall catalyst system is between 36,000 hr and 360 hr, preferably between 7200 hr-1 and 720 hr-1.

 The following Examples illustrate the present invention without however limiting its scope.

EXAMPLE 1: (NH412CsI PMO12O40)
Two solutions are prepared in parallel:
(1) Solution A for the preparation of Na2HPMo12040 (next
M.FOURNIER et al. Inorganic Chemistry 22, (1983)
pages 207-216).

 1738 g of Na2MoO4 are dissolved in 2500 ml of water; 41 ml of H3PO4 (85%) are added dropwise to the sodium molybdate solution. Then, 1700 ml of HC104 (70% by volume) is added to the solution little by little. When HC104 is added, a yellow coloration appears, followed by the formation of a yellow precipitate: the bisodic salt of phosphomolybdic acid at 14 H2O. This precipitate is filtered on sintered glass of porosity n'4.

 200 g of this precipitate, after spinning, are dissolved in 200 ml of water.

(2) Solution B
17.6 g of NH4NO3 and 21.5 g of CsNO3 are dissolved in 100 ml of water.

 Solution A is added dropwise to solution B with vigorous stirring. A very fine precipitate appears as and when the addition. This precipitate is isolated from the mother solution by centrifugation and then dried for 16 hours at 120 ° C. in a ventilated oven and calcined for 3 hours at 250 ° C.

EXAMPLE 2: Addition of Copper and Vanadium
A solution is prepared from the dissolution in 10 ml of deionized water of 1.2 g of
Cu (NO3) 2.3H2O and 2.5 g of VOSO4 * 5H2O. This solution is added to 20 g of (NH4) 2Cs1PMo12040 prepared according to the synthesis method described in Example 1, but not calcined. The tab obtained after homogenization is allowed to dry for 16 hours at 120 ° C. in a ventilated oven and calcined for 3 hours at 250 ° C.

EXAMPLE 3: Preparation of the Catalyst System
Proper and oxidizedhydropenation of
isobutyripue acid
The catalyst prepared according to Example 1 is pelletized and then crushed to an average grain size of 1 mm. 10 g of this catalyst are mixed with an equivalent volume of silicon carbide with an average particle size of 1 mm.

 5.7 ml of this mixture are loaded into a reactor of 14 mm internal diameter heated by a salt bath.

A mixture of isobutyric acid / O2 / H20 /
N 2 = 2 / 5.2 / 3.2 / 89.6% by volume is injected onto the catalyst at atmospheric pressure at a salt bath temperature of 300 ° C. (catalyst temperature = 320 ° C.). The contact time, expressed with respect to the total volume of the catalytic bed, is 0.2 s.

The results obtained are reported in the
Table 1.

EXAMPLE 4
The catalyst prepared according to Example 2 is used under the same conditions as in Example 3. The results obtained are reported in Table 1.

COMPARATIVE EXAMPLE in Example 3
In 9 liters of deionized water, 2131.2 g of NOO 3, 122.4 g of V 2 O 5 and 205.2 g of H 3 PO 4 are dispersed. The mixture is heated for 24 hours under reflux. The recovered solution is crystallized at 4 ° C.

 491 g of the resulting phosphorus compound dissolved in 200 ml of water are dissolved and 47.5 g of Cs (NO 3) 2 and 39.1 g of NH 4 Cl are added in small portions. The precipitate obtained is dried on a slow filter and redissolved twice, and is then dried in a ventilated oven at 120 ° C. for 24 hours.

 This catalyst is pelletized and then crushed to an average grain size of 1 mm. 10 g of this catalyst are mixed with an equivalent volume of silicon carbide with an average particle size of 1 mm. 7.4 ml of this mixture are loaded into a reactor of 14 mm inside diameter heated by a salt bath. A mixture consisting of isobutyric acid / O 2 / H 2 O / N 2 = 2 / 5.2 / 3.2 / 89.6% by volume is injected onto the catalyst at atmospheric pressure at a salt bath temperature of 305 ° C ( Catalyst temperature = 320 ° C). The contact time expressed with respect to the total volume of the catalytic bed, is 0.2 s.

 The results obtained are also reported in Table 1.

TABLE 1

<tb><SEP> Dilution <SEP> 50/50, <SEP> report <SEP> Conversion <SEP> Selectivities <SEP> in
<tb><SEP> after <SEP> one <SEP> night <SEP> of <SEP> the acid
<tb><SEP> iso
<tb><SEP> Formula <SEP> butyric acid <SEP> Acid <SEP> Ac- <SEP> Acid <SEP> CO <SEP> Propene
<tb><SEP> (4) <SEP> meth- <SEP> tone <SEP> ac- <SEP> + <SEP> (4) <SEP>
<tb><SEP> acry- <SEP> (8) <SEP> tick <SEP> C02 <SEP>
<tb><SEP> lique <SEP> (8) <SEP> (4) <SEP>
<tb><SEP> (%)
<tb> Example <SEP> Cs1 (NH4) 2PMo12O40 <SEP> 98.7 <SEP> 59.9 <SEP> 22.0 <SEP> 3.4 <SEP> 2.8 <SEP> 11.3
<tb> 3 <SEP>
<tb> Example <SEP> Cs1 (NH4) 2PMo12 (VO) Cu0.5 <SEP> 96.5 <SEP> 73.9 <SEP> 5 <SEP> 11.6 <SEP> 4.6 <SEP> 5 , 0 <SEP> 4,4
<tb> 4
<tb> Example
<tb> Compara- <SEP> Cs1 (NH4) 3pMO11VO40 <SEP> 88.2 <SEP> 67.6 <SEP> 16.9 <SEP> 1.4 <SEP> 2.2 <SEP> 10.3
<tb> tif <SEP> a
<tb> the Example
<tb><SEP> 3
<Tb>
EXAMPLE 5 Preparation of the Catalyst System
ZxemDle 2 associated with a diluent and
oxydeshydrogenation of isobutyrene acid
60 g of catalyst prepared as in Example 2 are mixed with 20 g of macroporous silica (United
Catalysts), 3 g of graphite and 4 g of ammonium sulfate.

The resulting powder is milled to a particle size of less than 0.5 mm.

 The powder is pelletized in the form of annular pellets (eint = 1.5 mm, eext = 5 mm and h = 3.2 mm). The pellets obtained are calcined for 12 hours at 250 ° C. under air.

 65 ml of pellets are loaded into a 21 mm inner diameter reactor heated with a salt bath.

A mixture consisting of isobutyric acid / O 2 / H 2 O / N 2 = 5 / 12.5 / 8 / 74.5% by volume is injected onto the catalyst at atmospheric pressure. The contact time, expressed with respect to the total volume of the catalytic bed, is 2s.

The results obtained are reported in the
Table 2.

TABLE 2

<tb><SEP> Formula <SEP> Time <SEP> Temple <SEP> Time <SEP> Conversion <SEP> Selectivity
<tb><SEP> of <SEP><Sep> Rature <SEP> RAGE of <SEP><SEP> Acid in <SEP> Acid
<tb><SEP> reaction <SEP> of <SEP> of <SEP> bath <SEP> isobutyric <SEP> meth
<tb><SEP> (days) <SEP> cata- <SEP> of <SEP> salt <SEP> (%) <SEP> acrylic
<tb><SEP> lyser <SEP>("C)<SEP> (h) <SEP>
<tb><SEP> (C) <SEP>
<tb> Cs1 (NH; 2PMo120 O) CuQ5 <SEP> 50 <SEP> 329 <SEP> 287 <SEP> 97 <SEP> 68
<tb><SEP> 200 <SEP> 330 <SEP> 300 <SEP> 97 <SEP> 62.5
<tb> EXAMPLE: Preparation of a catalytic system of the type
of Example 2. mixed with grains of
diluent. and oxidation of isobutane
The catalyst is prepared as in Example 1 except that in solution B 12.8 g of NH 4 NO 3 and 31.3 g of CsNO 3 are dissolved. Solution A, prepared as in Example 1, is added dropwise to solution B thus prepared with vigorous stirring. A very fine precipitate appears as and when the addition. This precipitate is isolated from the stock solution by centrifugation.

A solution is prepared from the dissolution in 10 ml of deionized water of 0.25 g of
Cu (NO 3) 2.3H 2 O and 3.08 g of VOSO 4 .5H 2 O. This solution is added to 25 g of the dried precipitate prepared above.

The paste obtained after homogenization is allowed to dry for 3 hours at 120 ° C., 3 hours at 250 ° C. and finally 3 hours at 320 ° C.

 This catalyst is pelletized and crushed to an average grain size of 1 mm. 10 g of this catalyst are mixed with an equivalent volume of silicon carbide with an average particle size of 1 mm.

 12 ml of this mixture are loaded into a reactor of 14 mm internal diameter heated by an electrical resistance. A mixture of isobutane / air / H 2 O = 26/62/12% by volume is injected onto the catalyst at atmospheric pressure at a salt bath temperature of 323 ° C (catalyst temperature = 339 ° C). The contact time, expressed with respect to the total volume of the catalytic bed, is 7.0 s.

The results obtained are reported in the
Table 3.

TABLE 3

<tb> Dilution <SEP> 50/50, <SEP> report <SEP> after <SEP> Convert <SEP> Selectivities <SEP> into
<tb><SEP> a <SEP> night <SEP> of <SEP> the iso
<tb><SEP> butane
<tb><SEP> Formula <SEP> (%) <SEP> Acid <SEP> Metha- <SEP> Acid <SEP> CO
<tb><SEP> meth- <SEP> crolein <SEP> ac <SEP> +
<tb><SEP> acry- <SEP> (%) <SEP> tick <SEP> CO <SEP>
<tb><SEP> lique <SEP> (%) <SEP> (%)
<tb><SEP> (%)
<tb> Cs1.5 (NH4) 1.5PMo12O40 (VO) Cu0.08 <SEP> 9.5 <SEP> ~ <SEP> 49.7 <SEP> 10.9 <SEP> 21.5 <SEP> 12 , 1
<Tb>

Claims (11)

 1 - Catalytic system based on a product represented by formula (I)  CSx (NH4) 3xPMo12O40Me1 (VO) z (I) in which  Me represents an ion of a chosen transition metal  among copper, cobalt, iron, silver, nickel  and manganese, or a magnesium ion  0 S x # 3  0 S y S3  0 <z <3 and prepared by reaction of an aqueous solution of H3 ~ tNatPMol2040, with 0 # tt <3, with an ammonium salt and / or a cesium salt with precipitation of the ammonium salt and / or cesium Csx (NH4) 3 ~ xPMol2040, x being as defined herein -above ; optionally adding to the above-mentioned salt an aqueous solution of a Me salt and / or a vanadyl salt drying the compound obtained until complete evaporation at a temperature of 90-200 ° C for a period of time from 2 to 16 hours, then calcination at a temperature of 250-400 ° C for a period of time from 2 to 24 hours; and shaping the resulting powdery product of formula (I) by compression of powders, pelletizing, granulating, extruding or coating on a support, to obtain said catalyst system in the form of pellets or grains.  2 - Catalytic system according to claim 1, characterized in that  . 0 # x # 2  O # y # 1  O S z S 1.  3 - Catalytic system according to one of claims 1 and 2, characterized in that the powdery catalytic product obtained after the calcination step was, before shaping, mixed with a dilution material.  4 - Catalytic system according to claim 3, characterized in that the dilution material is 1 to 10% by weight, preferably 1 to 3% by weight, of its mixture with the powdery catalyst product.  5 - Catalytic system according to one of claims 3 and 4, characterized in that the dilution material is selected from graphite, talc, stearic acid and stearates, macroporous silica, ammonium sulfate, and mixtures of two or more of these substances.  6 - Catalytic system according to one of claims 1 to 5, characterized in that it further comprises pellets or grains of at least one diluent.  7 - Catalytic system according to claim 6, characterized in that the diluent is selected from SiC and sio2.  8 - Catalytic system according to one of Claims 6 and 7, characterized in that the weight ratio of the pellets or grains based on the catalytic product (I) to the pellets or grains of diluent is 5/95 to 80/20, preferably 20/80 to 70/30.  9 - Process for preparing a catalytic system based on a product of formula (I) as defined in claim 1, characterized in that an aqueous solution of H3 ~ tNatPMol2040 is reacted with 0 < t <3, with an ammonium salt and / or a cesium salt with precipitation of the ammonium salt and / or cesium Csx (NH4) 3-xPM 12O40t x being as defined in claim 1, and, if appropriate, an aqueous solution of a Me salt and / or a vanadyl salt is added to the above-mentioned salt, the compound obtained is dried until complete evaporation at a temperature of 90-200 ° C. for a period of time of 2 to 16 hours, then calcined at a temperature of 250-400 C for a period of time of 2 to 24 hours, and the resulting pulverulent product of formula (I) is shaped by compression of powders, pelletizing , granulation, extrusion or coating on a support, to obtain said catalyst system in the form of pellets or grains.  10 - Application of the catalytic system as defined in one of Claims 1 to 8 to the manufacture of an ethylenically unsaturated carboxylic acid, or an ester of such an acid, by oxidation-hydrogenation in the the saturated acid or the corresponding saturated acid ester.  11 - Application of the catalytic system as defined in one of claims 1 to 8 to the oxidation of alkanes.