EA040962B1 - METHOD FOR PRODUCING GRANULATED CATALYST FOR OXIDATION PROCESSES - Google Patents

Description

The present invention relates to the chemical industry, namely to a method for producing a granular catalyst for alkane oxidation processes, in particular for propane oxidation processes to produce acrylic acid, a catalyst obtained by this method, the use of a combination of talc and graphite to form a dry catalyst precursor with subsequent production granular catalyst, as well as processes for oxidizing propane to produce acrylic acid using the catalyst of the invention.

State of the art

Acrylic acid is a valuable raw material for the chemical industry. In particular, acrylic acid is used as a monomer in the production of polymers, including polyester resins.

One of the industrially applicable is the method of obtaining acrylic acid by heterogeneous catalytic partial oxidation of propane in the presence of a catalyst. Among the catalysts for the oxidation of propane to acrylic acid, binary vanadium-phosphorus oxides, catalytic compositions based on heteropoly acids and compositions based on mixed oxides of transition elements with variable valence are known [M.M. Lin. Selective oxidation of propane to acrylic acid with molecular oxygen // Appl. catal. A: Gen. - 2001. - V. 207. - P. 1-16]. The highest catalytic activity in oxidation processes, in particular in the processes of propane oxidation, have multicomponent systems based on oxides of transition elements with variable valence, necessarily containing molybdenum (Mo) and vanadium (V), niobium (Nb), and also tellurium (Te).

EP 0 608 838 discloses a catalyst used in a propane oxidation process to produce acrylic acid, which is a mixed oxide catalyst of the composition Mo _a V _b . Te _c X _d O _x , where X is at least one element from the group consisting of Nb, Ta, W, Ti, Al, Zr, Cr, Mg, Fe, Ru, Co, Rh, Ni, Pd, Pt, Sb , Bi, B, In and Ce, 0.25<a<0.98, 0.003<b<0.5, 0.003<c<0.5, 0.003<d<0.5. The use of a catalyst of composition Mo1V ₀ . ₃ Teo,2 ₃ Nb _0j1 2O _x in accordance with the invention presented in EP 0608838, allows to achieve a propane conversion of 65.7%, a selectivity to acrylic acid of 58%, an acrylic acid yield of 38.1%. An increase in the yield of acrylic acid to 48% is achieved by additional processing of this catalyst, which includes the following stages: preparation of an aqueous suspension, heat treatment of the suspension, compaction of the powder, dispersion, and final calcination of the catalyst fraction in a stream of nitrogen at 600°C for 2 h.

There are also known catalysts based on Mo, V, Te and/or antimony (Sb) promoted with additions of niobium (Nb) and/or tantalum (Ta) of the general formula Mo1V _a (Te and/or Sb)b(Nb and/or Ta) _c Si _d O _x , where a=0.006-1, b=0.006-1, c=0.001-0.5, d=0-3.5. Thus, according to WO 2006100128, when using a catalyst of the composition Mo1V ₀ , ₃₃ Sb _0j1 at a temperature of 340°C, the propane conversion was 41.7%, the selectivity for acrylic acid was 27%. The introduction of niobium contributed to an increase in the selectivity for acrylic acid to 52%.

Documents JP 3924824, US 5198580 also presents multi-component metal oxide catalysts used in oxidation processes, in particular in propane oxidation processes, to produce acrylic acid. For example, US 5,198,580 provides a catalyst of the general formula Bi _b Mo _c B _b A _a D _d E _e O _x , in which A is one or more of K, Na, Li, Cs and Tl, D is one or more of Fe, Ni, Co, Zn, Ce and La, where the value of the coefficients a, d, e and b is from 0 to 10, the value of the coefficient c is from 0.1 to 20. Vanadium compounds are used as a promoting additive. In JP 3924824, the metal oxide catalyst contains the elements Mo, V, Sb, and component A, provided that A is one of the elements selected from the group consisting of Nb, Ta, Sn, W, Ti, Ni, Fe, Cr, Co.

Such multicomponent catalysts based on mixed oxides of transition metals can be obtained by evaporation under normal conditions of mixed solutions of initial compounds of transition elements (the so-called slurry method) or by hydrothermal synthesis. In this case, to obtain catalysts containing Mo, V, Nb, Sb and/or Te, the most common method is the evaporation of mixed solutions of the starting compounds. Such a method for obtaining a dry catalyst precursor, known, in particular, from patent RU 2342991, includes the following stages:

preparation of solutions of starting compounds (usually ammonium paramolybdate and metavanadate, telluric acid, or antimony compounds);

mixing with a separately prepared solution of niobium oxalate and promoting additives;

drying the resulting suspension;

step heat treatment in the range of 275-600°C.

It should be noted that the distinctive feature of MoVTe(Sb)Nb systems, the presence of several elements of variable valence, determines the strong dependence of the formation of the catalyst structure on the methods and parameters of synthesis, redox conditions of heat treatment, and the subsequent stage of molding to obtain a granular catalyst. This is confirmed by the fact that the catalysts known from the prior art, despite the close chemical composition, differ significantly in their catalytic characteristics (Table 1).

- 1 040962

Table 1

Catalytic properties of prior art catalysts based on mixed transition metal oxides

Catalyst Composition T [°C] Propane conversion [%] Selectivity for AA [%] Exit AK [%] Link MoiVo,29Teo,i4Nbo,i3 380 39 74 29 DE10344264 M01Vo.25Teo.11Nb 0.12 380 33.4 62.4 21 D. Vitry, Y. Morikawa, J. L. Dubois, W. Ueda, Appl. catal. A 251 (2003)411 M01Vo.43Teo.33Nb 0.1 393 68 50 34 US7718568 M01Vo.25Teo.33Nb o.nPdo.oi 386 80 63 50 US7718568 M01Vo.25Teo.33Nb 0.12 Ρίο, οι 376 54 79 43 US7718568 M01Vo.3Teo.23Nbo.125 384 75 69 52 US7718568 M01Vo.3Teo.23Nbo.12 380 80 60 48 US5380933 EP0608838 M01Vo.3Teo.23Nbo.12 390 71 59 42 EP0962253 MoiVo.3Teo.i7Nbo.i2Cuo,5 400 71 54.6 39 US7355062 MoeV 2SbiNbo.o32 380 42 52 22 WO200610012 8 M01Vo.3Sbo.i6Nbo.05 380 50 32 16 JP10045664 MoiVojSbo-o.iNbo.i 400 40 43 17 J.N.AlSaeedi, V.V.Guliants, M.A.Banares, J. Catal. 215 (2003). Mo1V0.3Sb0.25Nb0.12K0.013 420 39 64 25 P. Botella, P. Concepcion, J. M. Lopez- Nieto, B. Solsona, Catal. Lett. 89 No. 3-4 2003. M01Vo.23Sbo/26Nbo.09 /SiO ₂ 380 63.8 51.5 33 US7498463

The reason for the difference in the catalytic activity of the catalysts, despite their identical chemical composition, may lie in the significant role of certain crystalline phases and their ratio. The multicomponent nature of the catalyst and the dependence of chemical interactions in the system on the preparation conditions lead to the formation of a complex phase composition. It is known that active in oxide MoVTe(Sb)Nb catalysts are two crystalline phases - orthorhombic (M1) and hexagonal (M2). In this case, the pure M1 phase is active and selective in the oxidation of propane, while the M2 phase is active and selective in the oxidation of propylene. From these ideas follows the need to ensure the optimal combination of phases M1 and M2 in a multicomponent catalyst based on mixed transition metal oxides. Even with the same chemical composition of the catalyst under standard preparation conditions, these phases are formed in different proportions. The nonreproducibility of the catalyst in terms of phase composition and, accordingly, catalytic properties poses the problem of developing methods for preparing catalysts whose catalytic properties would allow them to be used in propane oxidation processes to obtain acrylic acid.

It is well known that the use of catalysts in industrial processes for the production of acrylic acid requires a step of molding dry catalyst precursors in order to obtain granules of optimal size and shape. It should be noted that the catalyst synthesis methods presented in the above-described patent documents differ only in the step of obtaining a dry catalyst precursor, the subsequent heat treatment steps do not differ significantly, and the molding steps are often not mentioned. In this case, the stage of catalyst formation is of great importance, because this stage can affect the structure of the catalyst and, consequently, its catalytic properties, and can also largely determine the mechanical strength of the catalyst granules.

The authors of the present invention have also found that the molding step, namely the conditions for its implementation, can have a negative impact on the catalytic properties of the resulting catalysts, in particular on the yield and selectivity to the target product. However, the prior art contains insufficient information regarding the techniques that must be used in the formation of the above multi-component catalysts for sufficient preservation of their structure and catalytic properties.

Methods known in the art for shaping catalysts are compression, extrusion, tableting and agglomeration to form spheroidal particles by spray drying. The implementation of these methods is possible with and without the addition of an inert technological additive (binder).

The most widely used method of forming catalysts is the pressing of a dry catalyst precursor, in which, under the influence of pressure applied from outside, the initial volume of the powdered material decreases, adhesion between its particles and, as a result, the formation of a strong body - granules or tablets of a certain shape and size. At the same time, various special inert technological additives (binders) or plasticizers are used in the compaction process, which play the role of substances that promote pore formation, strengthen the catalyst and facilitate the process of forming catalyst granules. Clays, hydrogels, organic and inorganic acids, polyhydric alcohols can be used as such additives. In particular, graphite, starch, sodium stearate, talc, etc. are used as said additives.

For example, patent RU 2377068 proposes a method for producing ring-shaped solid oxide catalysts of the general formula Moi ₂ Bi _a FebX ¹ cX ² dX ³ _e X ⁴ fOn used in oxidation processes, in particular in oxidation processes to obtain (meta) acrolein. The formation of the catalyst includes several stages. To begin with, a finely dispersed plastic mixture is obtained from the active mass of the catalyst precursor, intermediate compaction is carried out, then annular products are formed from the pre-compacted plastic mixture with the addition of shaping aids and/or auxiliary reinforcing materials. Suitable shaping aids (lubricants) for the process according to the invention are, for example, carbon black, stearic acid, starch, polyacrylic acid, mineral or vegetable oils, water, boron trifluoride or graphite. Glycerin and cellulose ether can also be used as lubricants.

RU 2559337 describes a method for producing an unsaturated acid or an unsaturated nitrile with the participation of a complex oxide catalyst, the composition of which is represented by the formula Mo ₁ V _a NbSbb _c W _d Z _e On, where Z is an element selected from the group La, Ce, Pr, Yb, Y, Sc, Sr, and Ba. According to this technical solution, the mechanical strength of the catalyst is ensured by adding at least 20% silica to the support composition, however, document RU 2559337 does not mention the hydrodynamic characteristics of the catalyst - size, shape, density of catalyst grains, stability - duration of operation.

Known from the prior art methods of molding to obtain a granular catalyst was not applicable to the molding of the catalyst obtained in accordance with the present invention. In this regard, it is important to develop a reproducible method for obtaining a catalyst characterized by acceptable catalytic properties in oxidation processes, in particular in propane oxidation processes, during the formation of which there would be no violation of the structure of active sites and, as a result, a decrease in catalytic properties.

The essence of the invention

The object of the present invention is to provide a granular catalyst based on mixed oxides of transition metals, which is characterized by relatively high activity, high selectivity in oxidation processes, in particular in the process of obtaining acrylic acid by partial oxidation of propane.

The technical result consists in the implementation of a method for producing a granular catalyst, in which no deterioration of catalytic properties occurs during the formation of a dry catalyst precursor: the propane conversion is maintained at over 60%, the selectivity for the target product is over 60-67%. An additional technical result is to improve the mechanical strength of the granular catalyst, as well as its stability in oxidation processes.

This problem is solved and the achievement of the desired technical result is ensured by the inventive method for obtaining a granular catalyst for oxidation processes. Proposed according to the present invention, the method includes the following stages:

a) obtaining a dry catalyst precursor containing at least one compound of each of the elements from the group consisting of molybdenum (Mo), vanadium (V), tellurium (Te) and/or antimony (Sb), and niobium (Nb) and /or tantalum (Ta) and optionally further comprising one or more metal compounds selected from the group consisting of bismuth (Bi), germanium (Ge), cerium (Ce), gallium (Ga), cobalt (Co), iron ( Fe) and nickel (Ni) (hereinafter referred to as the dry precursor);

b) shaping the dry precursor obtained in step (a) to form a granular catalyst.

The process according to the invention is characterized in that the molding step for the purpose of obtaining a granular catalyst comprises the following steps:

b1) mixing the dry precursor obtained in step (a) with talc, taken in an amount of from 1 to 4 wt.%;

b ₂ ) formation of a catalyst fraction with a particle size of 0.25 to 0.5 mm from the mixture obtained in step (b1);

b ₃ ) mixing obtained in step (b ₂ ) fraction of the catalyst with graphite, taken in an amount of from 0.5 to 3 wt.%;

b ₄ ) pressing the composition formed in step (b ₃ ) to obtain a granular catalyst;

b ₅ ) heat treatment obtained in step (b ₄ ) granular catalyst.

The inventors of the present invention have unexpectedly found that the use of a combination of talc and graphite at different stages of the molding step results in catalyst pellets having high mechanical strength as well as stability under propane oxidation reaction conditions. At the same time, when using such a combination of additives in the process of forming the catalyst, there is no significant deterioration in its catalytic properties, while the use of other additives known from the prior art or their combinations leads to a significant deterioration in the strength of the catalyst granules and its catalytic properties.

In yet another aspect, the claimed invention relates to a process for shaping a dry catalyst precursor to form a granular catalyst, characterized in that it includes the following sequential steps:

i) mixing the dry catalyst precursor with talc, taken in an amount of from 1 to 4 wt.%;

ii) formation of a catalyst fraction from the mixture obtained in step (i);

iii) mixing the fraction obtained in step (ii) with graphite taken in an amount of from 0.5 to 3 wt.%; iv) compressing the composition obtained in step (iii) to obtain a granular catalyst.

In another aspect, the claimed invention relates to a granular catalyst of the general composition Mo ₁ V _a B _b C _c X _d O _n obtained by the method according to the invention, where X denotes at least one of the elements selected from Bi, Ge, Ce, Ga, Co, Fe and Ni; B is Te and/or Sb; C is Nb and/or Ta; a, b, c, d - atomic ratios of metals, where 0.006<a<1, 0.006<b<l, 0.001<c<0.5, 0<d<0.1; n is determined by the valency of the elements that make up the catalyst.

In yet another aspect, the present invention relates to the use of a combination of talc, taken in an amount of from 1 to 4 wt.%, and graphite, taken in an amount of from 0.5 to 3 wt.%, for forming a dry catalyst precursor to obtain a granular catalyst.

In yet another aspect, the present invention relates to a process for oxidizing propane to produce acrylic acid, carried out in the presence of a catalyst according to the present invention.

In yet another aspect, the present invention relates to a process for oxidizing propane to produce acrylic acid in the presence of a catalyst according to the present invention, comprising the steps in which

i) a feed gas stream containing propane, steam and an oxidizing agent is fed into a reactor in a propane oxidation reaction zone containing a granular oxidation catalyst according to the present invention;

ii) the gas mixture obtained at the exit from the propane oxidation reaction zone, containing acrylic acid, unreacted propane and propylene, carbon oxides, is fed to the stage of separation of liquid and gaseous products, followed by isolation of acrylic acid.

Drawing Description

The drawing schematically shows the sequence of stages for obtaining a granular catalyst.

Detailed description of the invention

The following is a detailed description of various aspects and embodiments of the present invention.

Proposed according to the present invention, the method for obtaining a granular catalyst based on oxides of transition metals includes the following stages (drawing):

a) obtaining a dry catalyst precursor containing at least one compound of each of the elements from the group consisting of molybdenum (Mo), vanadium (V), tellurium (Te) and/or antimony (Sb), and niobium (Nb) and /or tantalum (Ta), and optionally further comprising one or more metal compounds selected from the group consisting of bismuth (Bi), germanium (Ge), cerium (Ce), gallium (Ga), cobalt (Co), iron (Fe ) and nickel (Ni) (hereinafter referred to as the dry precursor);

b) shaping the dry precursor obtained in step (a) to form a granular catalyst.

The method is characterized in that the molding step for the purpose of obtaining a granular catalyst includes the following steps:

b1) mixing the dry precursor obtained in step (a) with talc, taken in an amount of from 1 to 4 wt.%;

b ₂ ) formation of a catalyst fraction with a particle size of 0.25 to 0.5 mm;

b ₃ ) mixing obtained in step (b ₂ ) fraction of the catalyst with graphite, taken in an amount of from 0.5 to 3 wt.%;

b ₄ ) pressing the composition formed in step (b ₃ ) to obtain a granular catalyst;

b ₅ ) heat treatment obtained in step (b ₄ ) granular catalyst.

In accordance with the present invention, the content of talc and graphite is given in terms of 100% of the catalyst composition containing a dry catalyst precursor and technological additives: talc and carbon black.

Step (a) according to the present invention comprises providing a dry particle catalyst precursor containing at least one compound of each of the elements from the group consisting of molybdenum (Mo), vanadium (V), tellurium (Te) and/or antimony (Sb), niobium (Nb) and/or tantalum (Ta), and optionally further comprising one or more metal compounds selected from the group consisting of bismuth (Bi), germanium (Ge), cerium (Ce), gallium (Ga) , cobalt (Co), iron (Fe) and nickel (Ni) (hereinafter referred to as the dry precursor). To obtain the specified dry precursor can be used by any method known from the prior art. For example, said dry precursor can be obtained by precipitation of one or more solutions, preferably aqueous solutions containing molybdenum, vanadium, niobium and tellurium, as well as by hydrothermal synthesis (WO 2006100128).

In accordance with the present invention, step (a) for preparing a dry precursor of a multi-component transition metal oxide catalyst includes the following steps:

a ₁ ) mixing with water at least one compound of each of the elements from the group consisting of Mo, V, Te and/or Sb, and Nb and/or Ta, and optionally one or more metals selected from the group consisting of Bi , Ge, Ce, Ga, Co, Fe and Ni, to obtain an aqueous suspension of transition metals;

a ₂ ) drying the aqueous suspension of transition metals to remove the solvent to obtain a dry catalyst precursor;

a3) optionally impregnating the dry catalyst precursor with a modifying additive solution and then drying to obtain a modified dry catalyst precursor.

The following describes in more detail the preparation of a dry catalyst precursor: step (a) including steps (a1-a ₃ ).

In step (a1), at least one compound of each of the elements from the group consisting of Mo, V, Te and/or Sb and Nb and/or Ta is mixed with water, and optionally one or more metals selected from the group , including Bi, Ge, Ce, Ga, Co, Fe and Ni, to obtain an aqueous suspension of transition metals.

At the same time, in order to obtain an aqueous suspension, it is preferable to first obtain two aqueous solutions. One of these solutions (solution 1) contains Mo, V, Te and/or Sb, and the other solution (solution 2) contains Nb and/or Ta and optionally one or more metals selected from the group consisting of Bi, Ge, Ce, Ga, Co, Fe and Ni. In this case, solution 1 is obtained by adding, with constant stirring, at least one compound of the elements Mo, V, Te and / or Sb to distilled water at a temperature of from 80 to 100 ° C, preferably from 50 to 90 ° C, after which further cooling is carried out the resulting solution to room temperature. Solution 2 is prepared by adding at least one Nb and/or Ta compound and, if necessary, other metal compounds selected, for example, from Bi, Ge, Ce, Ga, Co, Fe and Ni, to distilled water with constant stirring, with this solution 2 is obtained at a temperature of from 15 to 45°C,

- 5 040962 preferably from 20 to 35°C. Next, solution 1 and solution 2 cooled to room temperature are mixed using any method known from the prior art to obtain a suspension containing Mo, V, Te and/or Sb, Nb and/or Ta and optionally one or more metals selected from the group, including Bi, Ge, Ce, Ga, Co, Fe and Ni. After mixing these solutions, the resulting suspension is kept at room temperature for a period of time from 0.5 to 24 hours, preferably from 1 to 10 hours.

It is preferable in the process of obtaining an aqueous suspension to maintain a pH in the range from 2.5 to 3.5, at which an Andersen-type heteropoly compound (HPA) is formed in the aqueous mixture. During the subsequent stages of obtaining a dry precursor, these heteropolycompounds are decomposed with the formation of a precursor in the form of dry nanoparticles characterized by M2 and M1 phases.

The amount of distilled water to dissolve the transition metal compounds in it may vary depending on the solubility of the starting compounds used. Thus, the amount of distilled water must be at least sufficient to form a slurry of the reactants, which is a mixture of solids and liquids that can be stirred.

Mixing of all starting components to obtain an aqueous homogeneous suspension can be carried out by any method known in the art using mixing devices (Edward L. Paul, Victor Atiemo-Obeng, Suzanne M. Kresta, eds. (2003), Handbook of Industrial Mixing: Science and practices). Cooling the resulting suspension to room temperature is also possible by any known method, for example, using a thermostat.

According to the present invention, as transition metal starting compounds, compounds are preferably used which, as a result of drying (step a ₂ ), form a heteropoly acid or a salt thereof. In particular, water-soluble salts such as molybdenum bromide, molybdenum (VI) dioxide dibromide, molybdenum (VI) dioxide dichloride, potassium molybdate, calcium molybdate, magnesium molybdate, sodium molybdate and vanadium bromide, vanadium (IV) oxydifluoride ), vanadium(IV) oxydibromide, vanadium(II) sulfate, vanadium(II) chloride, potassium metavanadate, sodium metavanadate, magnesium metavanadate, preferably ammonium paramolybdate and ammonium metavanadate. The starting tellurium compound can be telluric acid, ammonium tellurate, or tellurium dioxide. The starting antimony compound can be antimony acid, ammonium stibate, etc.

The niobium and/or tantalum compound is used as a solid, mixture or dispersion in a suitable medium. Niobium acid and niobium oxalate can serve as the initial niobium compound. Tantalic acid can be used as the starting tantalum compound. In the case of acids, it is preferable to carry out the removal of acidic impurities with which these acids may be contaminated by washing with an aqueous solution of ammonia and/or water. The concentration of the compound of niobium and/or tantalum (calculated as metal) in the preliminary niobium-containing and/or tantalum-containing aqueous solution or aqueous mixture is maintained in the range of 0.2-0.8 mol/kg of solution or mixture. The starting compounds of bismuth can be the corresponding nitrate salts. As starting compounds of other transition metals other than Mo, V, Te, Sb, Nb and Ta, chlorides, sulfates, nitrates, oxides or acetates of transition metal elements can also be used.

In one preferred embodiment of the invention, the catalyst is modified with silica. It was found that the addition of a silica sol at the stage of preparation of an aqueous suspension in an amount of 5 to 50 wt.%, preferably from 10 to 25 wt.% leads to an improvement in the catalytic properties of the resulting catalyst, which, in particular, may be associated with an increase in specific catalyst surface relative to unmodified catalyst. To obtain a silica-modified catalyst, the addition of a silica sol is carried out at any time during the preparation of an aqueous suspension, preferably a silica sol is added to the suspension obtained by mixing solutions 1 and 2.

Next, in step (a ₂ ), the aqueous suspension of transition metals is dried to remove the solvent to obtain a dry residue. Of the methods known from the prior art (JP 2003053190, EP 0962253, JP 2006159190), such as evaporation, freezing, rotary, vacuum or spray drying, spray drying is the most preferred for the task of the present invention. Spray drying is based on spraying an aqueous slurry onto a hot plate or injecting an aqueous slurry into a carrier gas stream, typically air, heated to temperatures of 100 to 300° C., followed by separation of the solid particles. In this case, water is rapidly removed from the suspension, at which the heteropoly acid is retained, which, during subsequent heat treatment, makes it possible to obtain a dry precursor more homogeneous in phase composition than with slow drying.

Stage (a ₃ ). In step (a), optionally, the dry catalyst precursor is impregnated with a solution of the modifying additive, followed by drying to form a modified dry catalyst precursor.

It is known that the conversion of propane to acrylic acid proceeds through intermediate stages of the formation of propylene and acrolein. Each of these steps requires active sites determined by the acidic properties of the resulting product and the oxidized reagent. An increase in catalyst efficiency can be achieved by suppressing deep oxidation of intermediate and target products by optimizing the acid-base properties of active sites. One way to change the acid-base properties is to modify the catalyst with additives that differ in electronegativity from the cations of the main composition.

To this end, in accordance with the present invention, a postsynthetic modification of a dry precursor is carried out with a promoting additive based on at least one of the transition metal compounds, selected, for example, from the group: Bi, Ge, Ce, Ga, Co, Fe, Ni, preferably as promoting additives use at least one compound of Ce and/or Ge.

Preferably, prior to the impregnation of the dry catalyst precursor with the modifying agent solution, the dry precursor is calcined at a temperature of 300 to 600°C.

The impregnated catalyst precursor is dried at 100 to 200°C, preferably 120°C for 10 to 20 hours to obtain a post-modified dry catalyst precursor.

Thus, by means of step (a) comprising steps (a ₁ -a ₃ ), a dry catalyst precursor is obtained, which can optionally be modified with promoting additives. The obtained dry precursor can be used as a catalyst for gas-phase catalytic propane oxidation. However, as mentioned earlier, in order to use a dry catalyst precursor in industrial propane oxidation processes, it is necessary to mold it to obtain a granular catalyst based on mixed transition metal oxides of the general composition: Mo1V _a BbC _c X _d On, where X denotes at least one from elements selected from Bi, Ge, Ce, Ga, Co, Fe and Ni; B is Te and/or Sb; C is Nb and/or Ta; a, b, c, d - atomic ratios of metals, where 0.006<a<1, 0.006<b<1, 0.001<c<0.5, 0<d<0.1, preferably 0.25<a<0, 35, 0.17<b<0.23, 0.10<c<0.14, 0<d<0.1; n is determined by the valency of the elements that make up the catalyst. While the catalyst of the above composition may optionally be modified Sol silicon dioxide (SiO ₂ ) in an amount of from 5 to 50 wt.%, preferably from 10 to 25 wt.%.

According to the present invention, the molding process is granulation, i.e. formation of solid catalyst granules of certain sizes and shapes. The process is based on the pressing of a dry catalyst precursor using inert technological additives (binders) on special equipment. The shaping process according to the present invention is carried out with the return of fine catalyst particles to the pressing stage, and thus recycle granulation is carried out. At the same time, the authors found that the use of a combination of talc and graphite at different stages of molding makes it possible to obtain a granular catalyst without reducing its catalytic properties, while being characterized by high mechanical strength and stability under reaction conditions.

The term catalytic properties of the catalyst in relation to the oxidation reaction in accordance with the present invention means the following indicators:

conversion (degree of conversion) - the amount of the reacted reagent, referred to its initial amount;

selectivity - characterized by the ratio of the rate of formation of the target product to the total rate of conversion of the starting substance at a certain composition of the reaction mixture and temperature.

In accordance with this aspect of the present invention, after obtaining the dry precursor in step (a), the step of shaping it (step b) is carried out, which includes the following steps:

b1) mixing the dry precursor obtained in step (a) with talc, taken in an amount of from 1 to 4 wt.%;

b2) formation of a catalyst fraction with a particle size of 0.25 to 0.5 mm;

b ₃ ) mixing obtained in step (b ₂ ) fraction of the catalyst with graphite, taken in an amount of from 0.5 to 3 wt.%;

b ₄ ) pressing the composition formed in step (b ₃ ) to obtain a granular catalyst;

b ₅ ) heat treatment obtained in step (b ₄ ) granular catalyst.

The following describes in more detail the formation of a dry catalyst precursor: step (b) comprising steps (b ₁ -b ₅ ).

Stage (b1). The dry catalyst precursor obtained in step (a) is mixed with talc, if necessary, using any mixing equipment known in the art (Chemical Technology, F.A. Henglein, p. 49-58). Talc according to the invention is used in an amount of

- 7 040962 up to 4 wt.%, preferably 2 wt.%.

As talc in the present invention, any known mineral of the subclass of layered silicates of the general formula Mg ₃ [Si ₄ O ₁₀ ](OH) ₂ is used, where magnesium is substituted by Fe, Ni, Al, Cr. It is preferable to use talc powdered with a predominant particle size of not more than 12 µm, preferably not more than 8 µm. In addition, the talc used in the present invention has a water (moisture) content of less than 0.5 mass%.

Stage (b ₂ ). According to the present invention, after the step of mixing the dry precursor with talc, in step (b ₂ ), a catalyst fraction with a particle size of 0.25 to 0.5 mm is formed. To this end, the mixture of dry catalyst precursor and talc obtained in step (b ₁ ) is compressed into granules or tablets. The pressing is carried out in a hydraulic press at a pressure of 20 to 50 t/cm ² , preferably 30 t/cm ² . Further, by grinding the obtained tablets, a fraction with a particle size of 0.25 to 0.5 mm is obtained. This grinding is carried out by any method known from the prior art, for example, using a toothed granulator. The remaining fraction with a particle size of less than 0.25 mm is added to the original dry precursor mixed with talc, and again subjected to compaction.

In accordance with the present invention, steps (b ₃ ) and (b ₄ ) refer to the formation of catalyst granules of a certain size and shape by pressing the fraction obtained in step (b ₂ ) with a particle size of 0.25 to 0.5 mm.

Stage (b ₃ ). Obtained in step (b ₂ ) fraction of the catalyst with a particle size of 0.25 to 0.5 mm is mixed with an additive, which is used as graphite. Graphite according to the present is used in an amount of from 0.5 to 3 wt.%, preferably 1 wt.%. The graphite particle size is preferably 2 to 25 µm. When choosing graphite for use according to the invention, it is also preferable to take into account indicators such as ash content - the percentage of non-combustible residue that is created during complete combustion, as well as the presence of moisture - the mass content of water. It is preferable to use graphite with an ash content of not more than 13 to 25 wt.%, preferably not more than 18 wt.%, and a water content of less than 1 wt.%.

In step (b ₄ ), the composition formed in step (b ₃ ) is pressed to obtain a granular catalyst of the desired shape and size, having sufficient mechanical strength. The optimal size and shape of the catalyst are those that make it possible to achieve the desired productivity and minimize the hydraulic resistance with minimal costs for the reactor. To carry out the propane selective oxidation reaction, a catalyst in the form of granules with a shape selected from spherical, cylindrical, rings, and combinations thereof can be used. It is preferable to use cylindrical pellets in the propane oxidation process.

Stage (b ₅ ). The catalyst granules obtained in step (b ₄ ) are subjected to heat treatment to obtain a calcined granular catalyst. The heat treatment of the catalyst granules is preferably carried out by calcination at a temperature of 300 to 600°C. In accordance with the present invention, where in cases where tellurium is additionally contained in the composition of the multi-component catalyst, in order to minimize its losses, it is preferable to carry out the calcination of the catalyst pellets in a stream of air at a temperature of from 275 to 350°C, more preferably 310°C for a period time from 10 to 20 min. Then, the catalyst should be calcined in a stream of inert gas (nitrogen, argon, helium) or in a stream of air with an inert gas, or in vacuum, or without air at a temperature of 600 ° C for a period of time from 1.5 to 3 hours, preferably 2 hours

During said high temperature heat treatment, the final phase and chemical composition of the catalyst according to another aspect of the claimed invention is formed: Mo ₁ V _a B _b C _c X _d O _n , where X is at least one of the elements selected from Bi, Ge, Ce , Ga, Co, Fe and Ni; B is Te and/or Sb; C is Nb and/or Ta; a, b, c, d - atomic ratios of metals, where 0.006<a<1, 0.006<b<1, 0.001<c<0.5, 0<d<0.1, preferably 0.1<a<0, 5, 0.1<b<0.5, 0.001<c<0.5, 0<d<0.05, most preferably 0.25<a<0.35, 0.17<b<0.23, 0.10<c<0.14, 0<d<0.1; n - is determined by the valency of the elements that make up the catalyst, which can also be optionally modified with a silica sol in an amount of from 5 to 50 wt.%, preferably from 10 to 25 wt.%.

The catalyst obtained in accordance with the present invention is preferably characterized by the presence of 2 crystalline phases with the most characteristic peaks at 2θ equal to 6.6, 7.9, 9.0, 22.1, 27.2° (phase M1), and at 2θ equal to 22.1, 28.2, 36.1, 45.1, 50.0° (M2 phase), where 2θ is the diffraction angle of incidence of the x-ray beam. It is also preferable to ensure that the M1/M2 ratio in the catalyst is approximately equal to 9/1, which will increase the selectivity of the process due to the fact that propane activation occurs in the M1 phase, while the M2 phase provides the oxidation of propylene to AA. Also preferred are those cases in which the catalyst is predominantly enriched in the active phase M1, while the content of the phase M2 is in the range from 2.2 to 20%.

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The catalysts of the composition MoVTeNbGa, MoVTeNbNi, MoVTeNbSe also additionally contain the active phase VMoO ₅ .

The specific surface area of the granular catalyst is preferably 2 to 12 m ² /g, preferably 5 to 7 m ² /g.

The granular catalyst obtained by any of the methods described above is used in gas phase alkane oxidation processes, in particular in the propane oxidation process to produce acrylic acid, which is also one aspect of the present invention.

The method for producing acrylic acid by oxidizing propane in the presence of a granular catalyst obtained in accordance with the present invention includes the following stages, in which

i) a feed gas stream containing propane, steam and an oxidizing agent is fed into a propane oxidation reaction zone in the reactor, which contains a granular catalyst for the oxidation of propane to acrylic acid;

ii) the gas mixture obtained at the exit from the propane oxidation reaction zone, containing acrylic acid, unreacted propane and propylene, carbon oxides, and optionally minor amounts of acrolein and acetic acid, is fed to the stage of separation of liquid and gaseous products with subsequent isolation of acrylic acid.

The production process may include the step of recycling unreacted propane and/or propylene to the reaction zone. In this case, the target product is separated from the gas mixture leaving the propane oxidation reaction zone, and the unreacted propane remaining in this gas mixture, as a rule, together with the unreacted propylene contained in it, is recycled to the oxidation stage.

As an oxidizing agent according to the invention, molecular oxygen can be used, which is added to the reaction gas mixture, for example, in pure form or in mixture with gases, mostly inert.

Since the process of obtaining acrylic acid is accompanied by a large release of heat, the hydrocarbon feedstock supplied to the reaction zone is preferably diluted with a gas, which, due to its heat capacity, is able to absorb the heat released during the reaction. As such a gas, at least one gaseous inert diluent is used, selected from N ₂ , H2O, CO ₂ , He, Ar, saturated C ₁ -C ₅ hydrocarbons (for example, according to DE-A1924431 and EP-A293224, etc. .P.).

The propane oxidation process to produce acrylic acid is preferably carried out at a temperature of 320 to 420°C, particularly preferably 350 to 390°C. The operating pressure of the process is preferably 0.5 to 5 bar, particularly preferably 1 to 3 bar.

Propane oxidation can be carried out in a reactor in the presence of a fixed bed of granular catalyst. In order to increase the yield of acrylic acid, the oxidation of propane is preferably carried out not in one reactor, but in two or more reactors connected in series or in parallel.

According to the invention, the catalytic vapor phase oxidation can be carried out in a tubular reactor. Carrying out oxidation processes in tubular reactors makes it possible to control the reaction temperature due to the effective removal of a significant amount of heat released during the catalytic oxidation reaction in the vapor phase, in which the oxidizable substance is in contact with molecular oxygen in the presence of a solid catalyst. This method protects the catalyst from destruction resulting from local overheating of the catalytic layer (formation of hot spots).

The present invention is more specifically described with reference to the following examples. These examples are provided only to illustrate the present invention and do not limit it.

EXAMPLES OF CARRYING OUT THE INVENTION

Example 1. Obtaining dry precursor Mo1V ₀ . ₃ Te ₀ . ₂₃ Nb ₀ . ₁₂ +10% SiO ₂ .

17.7 g of ammonium paramolybdate, 5.28 g of telluric acid and 3.51 g of ammonium metavanadate (solution I) are dissolved in 100 ml of distilled water at a temperature of 80°C with vigorous stirring. To the cooled solution of I is added 19.8 ml of a niobium oxalate solution in which the Nb concentration is 56.3 mg Nb/ml. In the resulting solution is also added Sol SiO ₂ in the amount of 10 wt.%. The wet precursor thus obtained, a bright orange gel, was dehydrated using a laboratory spray dryer. The resulting dry precursor of the cationic composition Mo1V0.3Te0.23Nb0.12, modified with SiO ₂ in an amount of 10 wt.%, is then used to obtain a granular catalyst.

Example 2. Obtaining dry precursor Mo1V ₀ . _{25Te0 . 17} Nb _0.1 +10% SiO ₂ .

17.7 g of ammonium paramolybdate, 3.90 g of telluric acid and 2.925 g of ammonium metavanadate (solution I) are dissolved in 100 ml of distilled water at a temperature of 80°C with vigorous stirring. To the cooled solution of I is added 16.5 ml of a niobium oxalate solution in which the Nb concentration is 56.3 mg Nb/ml. In the resulting solution is also added Sol SiO ₂ in the amount of 10 wt.%. The wet precursor thus obtained, a bright orange gel, was dewatered using a laboratory spray dryer. The obtained dry precursor of cationic composition

Mo ₁ V ₀ . _{25Te0 . 17} Nb ₀ . ₁ modified with SiO ₂ in the amount of 10 wt.%, then used to obtain a granular catalyst.

Example 3. Obtaining dry precursor Mo ₁ V ₀ . _{35Te0 . 23} Nb ₀ . ₁₄ +10% SiO ₂ .

17.7 g of ammonium paramolybdate, 3.90 g of telluric acid and 4.095 g of ammonium metavanadate (solution I) are dissolved in 100 ml of distilled water at a temperature of 80°C with vigorous stirring. To the cooled solution of I is added 23.1 ml of a niobium oxalate solution in which the Nb concentration is 56.3 mg Nb/ml. In the resulting solution is also added Sol SiO ₂ in the amount of 10 wt.%. The wet precursor thus obtained, a bright orange gel, was dehydrated using a laboratory spray dryer. The obtained dry precursor of the cationic composition Mo1V ₀ . _{35Te0 . 23} Nb ₀ . ₁₄ , modified with SiO ₂ in an amount of 10 wt.%, is further used to obtain a granular catalyst.

Example 4. Obtaining dry precursor Mo1V ₀ . ₃ Te ₀ . ₂₃ Nb ₀ . ₁₂ Bi ₀ . ₀₂ +10% _SiO2 .

Similar to example 1 with the exception that it contains a modifying additive of bismuth. The content of bismuth is 0.02 mol.% with respect to molybdenum.

Example 5. Obtaining dry precursor Mo1V0.3Sb0.23Ta0.12.

In 100 ml of distilled water at a temperature of 80°C and vigorous stirring dissolve 17.7 g of ammonium paramolybdate, 3.93 g of antimony acid and 3.51 g of ammonium metavanadate (solution I). To the cooled solution of I is added 19.8 ml of a solution of freshly prepared tantalic acid from tantalum chloride, in which the concentration of Ta is 109.6 mg Ta/ml. Water is removed from the wet precursor thus obtained using a laboratory spray dryer. The obtained dry precursor of the cationic composition Mo1V ₀ . ₃ Sb ₀ . ₂₃ Ta ₀ . ₁₂ is further used to produce a granular catalyst.

Example 6 Formation of a catalyst using processing aids at the stage of granulate production (additive 1).

In order to study the effect of technological additives in the molding process on the catalytic properties of catalysts, additives of various nature were tested: graphite, sodium stearate, starch, and talc.

For this dry powder precursor, obtained in example 1-5, is mixed with a processing aid (additive 1). Next, the resulting mixture is pressed on a hydraulic press at a pressure of 30 t/cm ² to obtain granules in the form of tablets with a diameter of 50 mm and a height of 8-10 mm. From the obtained tablets on a toothed granulator, a fraction with a particle size of 0.25 to 0.5 mm (hereinafter granulate) is obtained. The remaining fraction with a particle size of less than 0.25 mm is added to the original dry precursor, mixed with additive 1, and again pressed on a hydraulic press.

In order to obtain a granular catalyst, the fraction (granulate) obtained above is further pressed. However, the use of additives only at the stage of obtaining a granulate leads to the impossibility of forming catalyst granules of the desired shape due to their complete destruction during compaction.

Thus, in order to establish the effect of additives on catalytic properties, calcined granulate was tested, which is a fraction of a catalyst mixed with an additive with a particle size of 0.25 to 0.5 mm.

The catalytic properties of the obtained samples are presented in table. 2-6.

Example 7. Formation of a catalyst using technological additives at the stage of obtaining a granulate and at the stage of pressing (tabletting) (additive 1+additive 2).

The preparation of a granulated catalyst was carried out analogously to example 6, except that the granulate was additionally mixed with a technological additive (additive 2), after which the mixture was pressed (tabletted) in the form of cylindrical ring-shaped granules with an outer diameter of 5 mm, a wall thickness of 1.5 mm and 5 mm high on a Courtoy R-53 UE tablet press.

The resulting catalyst granules were then calcined in two stages: low temperature (280–320°C) in air and high temperature (550–570°C) in an inert gas flow.

Graphite, talc, as well as their combinations with different mass ratios were tested as additive 1 and additive 2.

The catalytic properties of the obtained samples are presented in table. 7.

Example 8 Propane Oxidation to Acrylic Acid.

The catalytic properties of the catalysts were determined in the reaction of propane oxidation in a laboratory flow unit at a temperature of 380°C. To do this, the reaction mixture of the composition was passed through the catalysts obtained in example 7:

propane (C3H8) - 5 vol%;

oxidizing agent (air) - 65 vol.%;

water vapor - 30 vol.%.

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As a reference sample, a dry precursor obtained according to example 1 was taken, which, before being used in the oxidation process, was calcined in two stages: low-temperature (280-320°C) in an air atmosphere and high-temperature (550-570°C) in an inert gas flow .

The test results are shown in table. 2-7.

table 2

Catalytic properties of catalysts (based on dry precursor according to example 1) obtained according to example 6

No. Technological additive (additive-1) - May. % Contact time: τ, s Conversion: X, % Selectivity, % С3Н4О2 (acrylic acid) SzNb (propylene) C3H4O (acrolein) С2Н4О2 (acetic acid) COx (carbon monoxide) 1 The original dry precursor obtained according to example 1 (without technical additives) 4.7 63.2 64.9 3.5 0.1 5.5 26.0 3.3 49.9 70.6 6.4 0.1 5.8 17.1 2.3 41.6 72.0 9.2 0.2 6.2 12.4 2 Talc - 2% 4.7 57.3 64.8 4.4 0.1 9.6 21.1 h, h 43.4 68.9 7.9 0.1 7.3 15.8 2.3 34.9 71.0 12.0 0.2 6.2 I,1 3 Starch - 2% 4.7 59.9 32.0 3.7 0.1 10.5 53.6 h, h 45.2 33.7 6.9 0.2 13.8 48.5 2.3 36.4 40.0 9.7 0.2 15.3 34.8 4 Sodium stearate - 2% 4.7 27.6 60.0 16.8 0.1 5.8 17.3 h, h 19.1 54.6 26.1 0.1 5.4 13.8 2.3 15.2 51.2 32.8 0.1 5.5 10.3 5 Graphite - 2% 4.7 58.8 52.8 4.0 0.1 5.7 37.4 h, h 48.6 59.7 6.2 0.1 6.2 27.8 2.3 38.5 63.8 9.4 0.1 6.1 20.6 6 Graphite - 3% 4.7 58.4 49.5 4.2 0.1 7.7 38.4 h, h 46.7 53.7 6.6 0.1 8.6 30.9 2.3 37.4 56.8 10.1 0.2 8.5 24.5

Table 3

Catalytic properties of catalysts (based on dry precursor according to example 2) obtained according to example 6

No. Technological additive (additive-1) - May. % Contact time: τ, s Conversion: X, % Selectivity, % С3Н4О2 (acrylic acid) SzN ₆ (propylene) CzH ₄ O (acrolein) С2Н4О2 (acetic acid) COx (carbon monoxide) 1 The original dry precursor obtained according to example 2 (without technical additives) 4.7 60.2 62.3 4.4 0.3 5.7 27.3 3.3 47.9 68.2 5.7 0.2 5.9 20 2.3 36.6 70.1 8.8 0.2 6.4 14.5 2 Talc - 2% 4.7 56.4 63.6 3.4 0.1 8.8 24.1 h, h 42.1 65.8 5.8 0.2 6.9 21.3 2.3 33.8 70.9 P,1 0.2 6.1 I,7 3 Starch - 2% 4.7 58.1 30.9 3.5 0.1 I,5 54 h, h 44.2 32.6 7.1 0.2 12.2 47.9 2.3 35.6 38.1 9.9 oh, s 14.9 36.8 4 Sodium stearate - 2% 4.7 25.1 61.1 16.0 0.1 5.9 16.9 h, h 20.2 52.4 26.2 0.1 5.0 16.3 2.3 14.8 49.6 33.8 0.2 5.7 10.7 5 Graphite - 2% 4.7 57.1 50.2 3.8 0.1 5.8 40.1 h, h 44.9 56.6 6.3 oh, s 6.4 30.4 2.3 37.2 61.2 8.9 0.1 6.7 23.1 6 Graphite - 3% 4.7 56.2 48.1 5.2 0.2 7.6 38.9 h, h 45.6 51.9 7.6 0.1 8.8 31.6 2.3 34.8 54.4 10.8 0.2 8.9 25.7

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Table 4

Catalytic properties of the catalysts (based on the dry precursor according to example 3) obtained according to example 6

No. T technological additive (additive-1) - wt. % Contact time: τ, s Conversion: X, % Selectivity, % CzH ₄ O ₂ (acrylic acid) SzN ₆ (propylene) CzH ₄ O (acrolein) С2Н4О2 (acetic acid) COx (carbon monoxide) 1 The original dry precursor obtained according to example 3 (without technical additives) 4.7 60.1 61.8 4.8 0.4 5.8 27.2 3.3 46.9 66.8 5.9 0.3 5.9 21.1 2.3 36.1 69.6 9.2 0.2 6.2 14.8 2 Talc - 2% 4.7 55.8 62.9 3.2 0.1 8.3 25.5 3.3 41.9 65.7 5.7 0.3 6.5 21.8 2.3 32.9 70.1 11.3 0.2 6.0 12.4 3 Starch - 2% 4.7 58.0 29.9 3.6 0.1 and about 55.4 h, h 43.1 31.6 7.0 0.3 12.4 48.7 2.3 34.5 37.9 9.7 0.3 14.2 37.9 4 Sodium stearate - 2% 4.7 22.2 62.1 15.5 0.1 5.4 16.9 h, h 18.3 51.8 25.4 0.2 5.2 17.4 2.3 13.6 48.7 32.7 oh, s 5.9 12.4 5 Graphite - 2% 4.7 55.2 51.2 3.9 0.1 5.7 39.1 h, h 45.1 55.4 6.5 0.3 6.5 31.3 2.3 36.9 60.7 8.4 0.3 6.8 23.8 6 Graphite - 3% 4.7 56.0 48.2 5.1 0.2 7.8 38.7 h, h 44.9 51.7 7.7 0.2 8.6 31.8 2.3 34.6 54.2 10.2 0.2 8.7 26.7

Table 5

Catalytic properties of catalysts (based on dry precursor according to example 4) obtained according to example 6

No. T technological additive (additive-1) - wt. % Contact time: τ, s Conversion: X, % Selectivity, % С3Н4О2 (acrylic acid) SzN ₆ (propylene) CzH ₄ O (acrolein) С2Н4О2 (acetic acid) COx (carbon monoxide) 1 The original dry precursor obtained according to example 4 (without technical additives) 4.7 62.1 61.8 4.8 0.3 5.8 27.3 3.3 47.8 66.8 5.9 0.3 5.9 21.1 2.3 37.2 69.6 9.2 0.2 6.0 15 2 Talc - 2% 4.7 56.2 63.4 3.1 0.1 8.4 25 h, h 42.5 65.3 5.6 0.2 6.4 22.5 2.3 33.5 70.2 P,4 0.2 6.2 12 3 Starch - 2% 4.7 58.8 31.2 4.2 0.1 I,1 53.4 h, h 42.6 32.2 7.1 0.2 12.6 47.9 2.3 35.7 38.5 9.6 oh, s 14.7 36.9 4 Sodium stearate - 2% 4.7 22.8 61.5 14.5 0.1 5.5 18.4 h, h 19.2 51.2 24.4 0.1 5.7 18.6 2.3 13.9 49.2 32.7 oh, s 5.8 12 5 Graphite - 2% 4.7 55.9 52.2 3.8 0.1 5.2 38.7 h, h 45.6 55.9 6.6 0.1 6.2 31.2 2.3 35.9 61.4 8.7 0.2 6.9 22.8 6 Graphite - 3% 4.7 57.2 48.5 5.2 0.1 7.7 38.5 h, h 45.3 52.3 7.6 0.1 8.2 31.8 2.3 35.4 55.2 10.0 0.1 8.9 25.8

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Table 6

Catalytic properties of catalysts (based on dry precursor according to example 5) obtained according to example 6

No. Technological additive (additive-1) - May. % Contact time: τ, s Conversion: X, % Selectivity, % С3Н4О2 (acrylic acid) SzNb (propylene) CzH ₄ O (acrolein) С2Н4О2 (acetic acid) co _x (carbon monoxide) 1 The original dry precursor obtained according to example 5 (without technical additives) 4.7 62.9 63.8 3.7 0.2 6.2 26.1 3.3 48.2 70.2 6.6 0.2 6.8 16.2 2.3 41.7 71.1 9.1 0.2 7.3 12.3 2 Talc - 2% 4.7 57.0 63.7 4.5 0.3 9.9 21.6 3.3 42.0 67.7 7.6 0.2 8.3 16.2 2.3 33.8 70.2 13.0 oh, s 7.2 9.3 3 Starch - 2% 4.7 59.2 32.1 3.9 0.2 10.2 53.6 3.3 44.1 32.9 7.2 oh, s 13.4 46.2 2.3 35.9 38.9 10.2 0.2 15.0 35.7 4 Sodium stearate - 2% 4.7 27.1 59.7 17.4 0.2 6.0 16.7 3.3 19.0 53.4 26.9 0.2 5.6 13.9 2.3 15.0 50.8 33.8 0.4 5.5 9.5 5 Graphite - 2% 4.7 58.3 51.9 4.2 oh, s 6.3 37.3 3.3 47.9 59.2 6.8 0.2 6.2 27.6 2.3 38.1 63.0 Yu,1 oh, s 6.1 20.5 6 Graphite - 3% 4.7 57.6 48.8 4.8 oh, s 8.7 37.4 3.3 45.8 53.2 6.9 0.2 8.5 31.2 2.3 37.1 55.7 I,4 0.2 8.6 24.1

Table 7

Catalytic properties of granular catalysts obtained according to example 7

No. Technological additives: 1. additive-1 - wt.% 2. additive-2 - May. % Specific surface area m ² /g Contact time: τ, s Conversion: X, % Selectivity, % С3Н4О2 (acrylic acid) SzNb (propylene) CzH ₄ O (acrolein) С2Н4О2 (acetic acid) _COX (carbon monoxide) 1 The original dry precursor obtained according to example 1 (without technical additives) 12 4.7 63.2 64.9 3.5 θ,ι 5.5 26.0 3.3 49.9 70.6 6.4 0.1 5.8 17.1 2.3 41.6 72.0 9.2 0.2 6.2 12.4 2 1. talc - 1% 2. graphite - 0.5% AND 4.7 62.8 61.2 h, h 0.1 6.2 29.2 h, h 50.3 67.0 6.0 0.1 6.9 20.0 2.3 40.6 68.5 8.9 0.1 7.3 16.7 3 1. talc - 4% 2. graphite - 0.5% 9 4.7 61.2 62.0 3.7 0.1 6.7 27.5 h, h 50.0 67.1 5.9 0.1 7.1 19.9 2.3 40.3 68.7 8.8 0.1 7.3 15.1 4 1. talc -1% 2. graphite - 1% + talc - 1% 6 4.7 61.6 61.6 3.6 0.1 7.8 26.9 h, h 48.6 65.5 6.5 0.1 6.9 21.1 2.3 38.2 68.7 9.7 0.1 6.1 15.4 5 1. graphite - 2% 2. graphite - 1% 7 4.7 58.4 49.5 4.2 0.1 7.7 38.4 h, h 46.7 53.7 6.6 0.1 8.6 30.9 2.3 37.4 56.8 10.1 0.2 8.5 24.5 6 1. talc - 2% 2. graphite - 3% 2 4.7 62.0 60.0 3.2 0.1 6.4 30.3 h, h 48.1 67.1 4.9 0.1 6.8 21.1 2.3 41.2 69.1 7.8 0.1 7.0 16.0

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7 1. talc - 2% 2. graphite - 1% 5 4.7 63.1 60.3 3.0 0.1 6.5 30.2 3.3 53.0 67.4 5.1 0.1 7.0 20.4 2.3 42.1 69.6 8D 0.1 7.1 15.1 8 The original dry precursor obtained according to example 2 (without technical additives) 10 4.7 60.2 62.3 4.4 0.3 5.7 27.3 3.3 47.9 68.2 5.7 0.2 5.9 20 2.3 36.6 70.1 8.8 0.2 6.4 14.5 9 1. talc - 2% 2. graphite - 1% 8 4.7 58.8 60.1 3.2 0.1 7.1 29.5 h, h 46.1 65.9 5.0 0.1 7.6 21.4 2.3 34.8 68.6 7.9 0.1 7.8 15.6 10 The original dry precursor obtained according to example 3 (without technical additives) 12 4.7 63.2 64.9 3.5 0.1 5.5 26 3.3 49.9 70.6 6.4 0.1 5.8 17.1 2.3 41.6 72.0 9.2 0.2 6.2 12.4 eleven 1. talc - 2% 2. graphite - 1% 9 4.7 62.7 59.8 h, h 0.1 6.8 thirty h, h 47.1 66.2 5.4 0.2 7.7 20.5 2.3 38.8 67.9 8.8 0.2 7.9 15.2 12 The original dry precursor obtained according to example 4 (without technical additives) eleven 4.7 62.1 61.8 4.8 0.3 5.8 27.3 3.3 47.8 66.8 5.9 0.3 5.9 21.1 2.3 37.2 69.6 9.2 0.2 6.0 15 13 1. talc - 2% 2. graphite - 1% 8 4.7 61.9 60.3 3.8 0.2 6.9 28.8 h, h 46.9 64.5 4.9 OD 7.4 23.1 2.3 36.8 68.4 7.6 0.2 7.9 15.9 14 Initial dry 9 4.7 62.9 63.8 3.7 0.2 6.2 26.1 precursor obtained according to example 5 (without technical additives) 3.3 48.2 70.2 6.6 0.2 6.8 16.2 2.3 41.7 71.1 9.1 0.2 7.3 12.3 15 1. talc - 2% 2. graphite - 1% 8 4.7 61.9 59.2 4.2 0.2 6.9 29.5 h, h 47.5 65.7 5.3 oh, s 7.2 21.5 2.3 40.7 68.9 8.0 oh, s 7.7 15.1

In table. 2-6 show the effect of technological additives used in the process of forming a dry precursor on the catalytic properties of the obtained granulates. It is shown that it is preferable to use 1 - talc as a technological additive, because in this case, there is no significant decrease in the catalytic properties of the resulting granulate relative to the dry catalyst precursor containing no additives. It was not possible to carry out the subsequent compaction of the obtained granulates in order to obtain a granular catalyst of the desired shape and size.

From Table. 7 it can be seen that the best technical result is achieved using the following combination of technological additives: technological additive 1, namely talc at the stage of obtaining granulate and technological additive 2, namely graphite at the pressing stage. It is preferable to use additives in the amount of 2 and 1 wt.%, respectively, for talc and graphite.

Example 9. Testing the mechanical strength of the granular catalysts obtained in example 7 (graphite, talc - their combinations).

Determination of crush strength was carried out on the device MA.TEC.CRUSH-BK according to ASTM D4179-11. Each sample was randomly selected from 24 crush pellets along the cylinder axis and from 24 crush pellets perpendicular to the cylinder axis. Statistical processing was performed according to ASTM D4179-11. Of the 24 results obtained, 2 minimum and 2 maximum values were discarded. From the remaining 20 values, an average crushing mechanical strength was calculated using formulas (1) to (3).

The mechanical crushing strength for granules in the form of a cylinder σ _p , kg/mm ² , along the axis of the cylinder was determined by the formula ^σ Ρ “S - _πά ^{2 (1} )>

where P is the force at which the destruction of the granules occurs, kg;

S - cross-sectional area of the granule, mm ² ;

d - granule diameter, mm.

Mechanical crushing strength for granules in the form of a cylinder σ _p , kg/mm ² perpendicular to the axis of the cylinder is determined by the formula where P is the force at which the destruction of the granule occurs, kg;

S - cross-sectional area of the granule, mm ² ;

- 14 040962 d - granule diameter, mm;

l - granule length, mm.

From the remaining 20 values, the average value of the mechanical crushing strength ^σρ , kg / mm ² is calculated by the formula

where ^σρ ί is the crushing strength of the tested granules in a particular test, kg/mm ² . The results obtained are presented in table. 8.

Table 8

Mechanical strength of granular catalysts

Dry precursor used Technological additives: 1. additive-1 - wt.% 2. additive-2 - wt.% Placement of the pellet in the press R%H ** Or, kg / mm ² According to example 1 1. graphite - 2% 2. graphite - 1% along the axis of the cylinder 139.4 0.74 perpendicular to the axis of the cylinder 29.4 0.12 1. talc - 2% 2. graphite - 1% along the axis of the cylinder 141.4 0.81 perpendicular to the axis of the cylinder 38.2 0.17 According to example 2 1. graphite - 2% 2. graphite - 1% along the axis of the cylinder 136.2 0.70 perpendicular to the axis of the cylinder 28.3 0.10 1. talc - 2% 2. graphite - 1% along the axis of the cylinder 140.1 0.78 perpendicular to the axis of the cylinder 37.3 0.15 According to example 3 1. graphite - 2% 2. graphite -1% along the axis of the cylinder 137.2 0.74 perpendicular to the axis of the cylinder 29.6 0.13 1. talc - 2% 2. graphite - 1% along the axis of the cylinder 142.1 0.92 perpendicular to the axis of the cylinder 38.7 0.20 According to example 4 1. graphite - 2% 2. graphite - 1% along the axis of the cylinder 136.1 0.69 perpendicular to the axis of the cylinder 28.3 0.09 1. talc - 2% 2. graphite - 1% along the axis of the cylinder 139.7 0.77 perpendicular to the axis of the cylinder 37.5 0.16 According to example 5 1. graphite - 2% along the axis of the cylinder 138.2 0.71 2. graphite - 1% perpendicular to the axis of the cylinder 28.7 0.09 1. talc - 2% 2. graphite - 1% along the axis of the cylinder 140.2 0.76 perpendicular to the axis of the cylinder 37.8 0.15

*P is the force at which the destruction of the granules occurs p is the average value of the mechanical crushing strength.

As can be seen from the results in Table. 8, granular catalysts molded using a combination of additives: talc and graphite differ in their mechanical strength. Catalyst,

- 15 040962 obtained with the addition of graphite at the stage of obtaining a granulate and at the stage of compaction (pressing) (graphite + graphite) has a lower crushing strength both along the axis (by 8.6 rel.%) and perpendicular to the axis of the cylinder (by 29, 4 Rel.%) relative to the samples of the catalyst, during the formation of which talc is added at the stage of obtaining the granulate. Relative percentages in this case are given for the catalyst obtained from the precursor according to example 1.

To confirm the stability of granular catalysts molded in the presence of the following additives: talc (2 wt.%) and graphite (1 wt.%) - in example 10, resource tests were carried out.

Example 10. Life tests of granular catalysts in the formation of which additives were used: talc (2%) and graphite (1%).

The method according to example 8, in which the stability tests of granular catalysts molded using additives were carried out: talc in an amount of 2 wt.% at the granulation stage and graphite in an amount of 1 wt.% at the compaction (pressing) stage.

In accordance with the example, a granular catalyst fraction was loaded into a reactor with a diameter of 9.6 mm. Next, the specified catalyst was interacted with the reaction mixture of the following composition: propane (C3H8) - 55 vol.%, water vapor - 20 vol.%, oxidizing agent (oxygen) - 25 vol.%. Contact time 2 s, reaction temperature 360°C. The results of the experiment are shown in table. 9.

Table 9

The results of resource tests according to example 10

Dry precursor catalyst according to example 1 Time i, h Contact time τ, s Conversion: X (C ₃ H ₈ ),% Selectivity, % CsH ₄ O ₂ (acrylic acid) SzN ₆ (propylene) SzN ₄ O (acrolein) SO (carbon monoxide yes) CO2 (dioxide carbon) С2Н4О2 (vinegar acid) 21.5 2 7.5 46.9 29.2 1.3 6.2 7.8 8.6 27.9 3 13.4 53.4 21.6 1.1 7.1 6.8 10.0 99.2 3.5 14.1 52.3 20.0 0.8 8.2 9.3 9.4 170.0 12.4 50.5 21.2 0.8 7.8 9.9 9.7 231.5 15.0 51.6 15.7 0.9 I,8 9.3 10.7 Precursor Catalyst of Example 2 Time i, h Contact time t, s Conversion: Х(СзН ₈ ), % Selectivity, % С3Н4О2 (acrylic acid) SzN ₆ (propylene) SzN ₄ O (acrolein) SO (carbon monoxide yes) CO2 (dioxide carbon) С2Н4О2 (acetic acid) 21.5 2 6.8 44.3 30.1 1.2 6.0 7.9 10.5 28.0 3 13.2 52.1 22.7 1.2 7.4 7.8 8.8 100.0 3.5 13.0 52.4 23.1 0.9 8.6 9.1 5.9 170.0 13.2 51.1 21.6 0.9 8.8 9.4 8.2 232.0 14.7 50.8 15.6 1.0 12.4 9.2 AND

- 16 040962

Precursor Catalyst of Example 3 Time i, h Contact time τ, s Conversion: X (C ₃ H ₈ ),% Selectivity, % CsH ₄ O ₂ (acrylic acid) SzN ₆ (propylene) SzN ₄ O (acrolein) SO (carbon monoxide yes) CO ₂ (carbon dioxide) C ₂ H ₄ O ₂ (acetic acid) 21.5 2 7.3 45.4 28.4 1.1 7.2 8.8 9.1 27.0 3 13.1 51.1 22.4 1.2 7.0 7.8 10.5 100.0 3.5 14.2 50.3 22.1 0.8 9.2 9.0 8.6 171.0 13.1 49.5 23.2 0.7 8.3 10.2 8.1 231.0 14.0 49.7 18.8 0.9 12.1 10.3 8.2 Precursor Catalyst of Example 4 Time i, h Contact time τ, s Conversion: Х(СзН ₈ ), % Selectivity, % С3Н4О2 (acrylic acid) SzN ₆ (propylene) SzN ₄ O (acrolein) SO (carbon monoxide yes) CO ₂ (carbon dioxide) C ₂ H ₄ O ₂ (acetic acid) 22.0 2 6.7 44.7 25.6 2.1 7.3 7.7 12.6 27.0 3 12.0 52.1 23.4 2.0 7.2 7.8 7.5 102.0 3.5 13.1 50.3 24.4 1.8 8.0 9.2 6.3 170.0 13.1 50.0 25.3 1.6 7.8 9.3 6 232.0 14.2 49.7 24.8 1.7 10.0 9.3 4.5 Precursor Catalyst of Example 5 Time i, h Contact time τ, s Conversion: Х(СзН ₈ ), % Selectivity, % С3Н4О2 (acrylic acid) CsNb (propylene) SzN ₄ O (acrolein) SO (carbon monoxide yes) CO ₂ (carbon dioxide) C ₂ H ₄ O ₂ (acetic acid) 21 2 7.2 46.4 27.7 1.2 6.8 7.1 10.8 28.0 3 13.0 52.7 23.4 1.2 7.3 7.7 7.7 99.5 3.5 12.2 52.4 21.1 1.4 8.9 9.5 6.7 171.0 12.8 51.1 20.1 1.2 8.8 10.0 8.8 231.0 14.7 51.0 17.8 1.5 10.2 9.7 9.8

From the results of example 10, it can be seen that the granular catalyst molded using additives: talc in an amount of 2 wt.% at the stage of obtaining a granulate and graphite in an amount of 1 wt.% at the compaction stage, retains relatively high values of activity and selectivity for the target product during the entire process of propane oxidation (over 230 hours).

Thus, it has been shown that the method of the present invention for producing a dry catalyst precursor is reproducible and provides a catalyst with catalytic properties that allow such a catalyst to be used in oxidation processes, in particular in processes for oxidizing propane to produce acrylic acid.

In addition, it was shown that the use of technological additives at the stages of forming a dry precursor makes it possible to obtain catalyst granules of the desired shape and size without a significant deterioration in the catalytic properties relative to the initial dry precursor (Table 7). In this case, it is important to use the following combination as such additives: talc at the stage of obtaining a granulate (stage (b1) in accordance with the description of the present invention) and graphite at the stage of compaction of said granulate (stage (b ₃ )). Talc is preferably used in an amount of from 1 to 4 wt.%,

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Claims (64)

most preferably 2 wt%. Graphite is preferably used in an amount of 0.5 to 3% by weight, most preferably 1% by weight. The resulting catalyst is characterized by high mechanical strength (example 9, table. 8), as well as stability in oxidation processes (example 10, table. 9). CLAIM 1. A method for molding a dry catalyst precursor to obtain a granular catalyst, characterized in that it includes the following successive steps: i) mixing the dry catalyst precursor with talc, taken in an amount of from 1 to 4 wt.%; ii) forming a catalyst fraction from the mixture obtained in step (i); iii) mixing the fraction obtained in step (ii) with graphite taken in an amount of from 0.5 to 3 wt.%; iv) compressing the composition obtained in step (iii) to obtain a granular catalyst. 2. The method according to claim 1, where talc is used in an amount of 2 wt.%. 3. The method according to claim 1 or 2, where as talc a material of a subclass of silicates of the general formula Mg ₃ [Si ₄ O ₁₀ ](OH) ₂ is used, in which magnesium is substituted by Fe, Ni, Al, Cr. 4. The method according to any one of claims 1 to 3, wherein the talc is a powder with a particle size of not more than 12 µm. 5. The method according to any one of claims 1 to 4, wherein the talc is a powder with a particle size of not more than 8 microns. 6. The method according to any one of claims 1 to 5, wherein the talc contains water in an amount of less than 0.5 wt.%. 7. The method according to any one of claims 1 to 6, wherein the graphite is used in an amount of 1 wt.%. 8. The method according to any one of claims 1 to 7, where graphite with a particle size of 2 to 25 microns is used. 9. The method according to any one of claims 1 to 8, wherein graphite is used, the ash content of which is not more than 13 to 25 wt.%. 10. The method according to any one of claims 1 to 9, where graphite is used, the ash content of which is not more than 18 wt.%. 11. The method according to any one of claims 1 to 10, wherein the graphite contains water in an amount of less than 1 wt%. 12. The method according to any one of claims 1 to 11, wherein the catalyst fraction comprises particles with a size of 0.25 to 0.5 mm. 13. The method according to any one of claims 1 to 12, wherein the formation of the catalyst fraction is carried out by pressing a mixture of dry catalyst precursor and talc to obtain granules or tablets and subsequent grinding of the obtained granules and tablets. 14. The method according to claim 13, where the pressing is carried out using a hydraulic press at a pressure of 20 to 50 t/cm ² . 15. The method according to claim 13 or 14, where the pressing is carried out using a hydraulic press at a pressure of 30 t/cm ² . 16. A method for producing a granular catalyst for oxidation processes, which includes the following steps: a) obtaining a dry catalyst precursor containing at least one compound of each of the elements from the group consisting of molybdenum (Mo), vanadium (V), tellurium (Te) and/or antimony (Sb), and niobium (Nb) and /or tantalum (Ta); b) molding the dry precursor obtained in step (a) to obtain a granular catalyst, characterized in that molding step (b) includes the following steps: b1) mixing the dry precursor obtained in step (a) with talc, taken in an amount of from 1 to 4 wt.%; b ₂ ) forming a catalyst fraction with a particle size of 0.25 to 0.5 mm from the mixture obtained in step (bi); b ₃ ) mixing obtained in step (b ₂ ) fraction with graphite, taken in an amount of from 0.5 to 3 wt.%; b ₄ ) pressing the composition formed in step (b ₃ ) to obtain a granular catalyst; b ₅ ) heat treatment obtained in step (b ₄ ) granular catalyst. 17. The method according to claim 16, where talc is used in an amount of 2 wt.%. 18. The method according to claim 16 or 17, where graphite is used in an amount of 1 wt.%. 19. The method according to any one of claims 16-18, where the stage of obtaining a dry precursor (a) includes the following steps (a1-a ₃ ): a1) mixing with water at least one compound of each of the elements of the group consisting of Mo, V, Te and/or Sb, and Nb and/or Ta to obtain an aqueous suspension of transition metals; a ₂ ) drying the aqueous suspension of transition metals to remove the solvent to obtain a dry catalyst precursor; - 18 040962 a ₃ ) optional impregnation of the dry catalyst precursor with a modifying agent solution and subsequent drying to obtain a modified dry catalyst precursor. 20. The method according to claim 19, where in step (a1) to obtain an aqueous suspension of transition metals, two aqueous solutions are first prepared, one of which contains Mo, V, Te and / or Sb (solution 1), and the other (solution 2) contains Nb and/or Ta, and then they are mixed. 21. The method according to claim 20, where solution 1 is obtained by adding with constant stirring to distilled water at least one compound of each of Mo, V, Te and / or Sb at a temperature of from 80 to 100 ° C, preferably from 50 to 90 °C. 22. Method according to claim 20 or 21, wherein solution 2 is prepared by adding at least one Nb and/or Ta compound to distilled water with constant stirring at a temperature of 15 to 45°C, preferably 20 to 35°C. 23. The method according to any one of claims 20 to 22, wherein after mixing said solutions 1 and 2, the resulting suspension is kept at room temperature for 0.5 to 24 hours, most preferably 1 to 10 hours. 24. The method according to any one of claims 19 to 23, wherein the pH is maintained in the pH range of 2.5 to 3.5 in the preparation of the aqueous suspension. 25. The method according to any one of claims 19 to 24, wherein step (a1) comprises adding a silica sol in an amount of 5 to 50% by weight, preferably 10 to 25% by weight. 26. The method according to any one of claims 19 to 25, wherein at least one salt selected from the group consisting of molybdenum bromide, molybdenum (VI) dioxidedibromide, molybdenum (VI) dioxidedichloride, potassium molybdate, is used as the molybdenum (Mo) compound, calcium molybdate, magnesium molybdate, sodium molybdate, ammonium paramolybdate. 27. The method according to any one of claims 19-26, where at least one salt selected from the group consisting of vanadium bromide, vanadium (IV) oxydifluoride, vanadium (IV) oxydibromide, vanadium sulfate ( II), vanadium(II) chloride, potassium metavanadate, sodium metavanadate, magnesium metavanadate, ammonium metavanadate. 28. The method according to any one of claims 19 to 26 wherein the niobium (Nb) compound is niobic acid or niobium oxalate as a solid, mixture or dispersion. 29. The method according to any one of claims 19 to 28, wherein at least one compound selected from the group consisting of telluric acid, ammonium tellurate, tellurium dioxide is used as the tellurium (Te) compound. 30. The method according to any one of claims 19 to 29, wherein in step (a ₂ ) the drying is carried out by spray drying. 31. The method according to any one of claims 19 to 30, wherein in step (a ₂ ) the drying is carried out at a temperature of 100 to 300°C. 32. The method according to any one of claims 19-31, wherein in step (a ₃ ), prior to the impregnation of the dry catalyst precursor with the modifying additive solution, the dry precursor is calcined at a temperature of 300 to 600°C. 33. The method according to any one of claims 19-32, where in step (a ₃ ) at least one compound of at least one transition metal selected from the group consisting of Bi, Ge, Ce, Ga, Co, Fe and Ni. 34. The method according to any one of claims 19 to 33, wherein at least one Ce and/or Ge compound is used as the modifying agent. 35. The method according to any one of claims 19 to 34, wherein in step (a ₃ ) the drying is carried out at a temperature of from 100 to 200°C, preferably 120°C. 36. The method according to any one of claims 19 to 35, wherein in step (a ₃ ), drying is carried out over a period of 10 to 20 hours. 37. The method according to any one of claims 16 to 36, wherein the mixing in steps (b1) and (b ₃ ) is carried out by mechanical agitation. 38. The method according to any one of claims 16-37, wherein in step (bi) the talc is a material of the silicate subclass of the general formula Mg ₃ [Si4O ₁₀ ](OH) ₂ in which magnesium is substituted by Fe, Ni, Al, Cr. 39. The method according to any one of claims 16 to 38, wherein in step (b1) the talc is a powder with a particle size of at most 12 µm. 40. The method according to any one of claims 16 to 39, wherein in step (b1) the talc is a powder with a particle size of at most 8 µm. 41. The method according to any one of claims 16-40, wherein the talc contains water in an amount of less than 0.5 wt%. 42. The method according to any one of claims 16-41, where in step (b ₂ ) the formation of a catalyst fraction with a particle size of 0.25 to 0.5 mm is carried out by pressing the mixture of dry catalyst precursor and talc obtained in step (b1) with obtaining granules or tablets and subsequent grinding of the obtained granules and tablets to obtain particles of the indicated sizes. 43. The method according to claim 42, where the pressing is carried out using a hydraulic press at a pressure - 19 040962 ni from 20 to 50 t/cm ² . 44. The method according to claim 42 or 43, where the pressing is carried out using a hydraulic press at a pressure of 30 t/cm ² . 45. The method according to any one of claims 16-44, where in step (b ₃ ) graphite is used with a particle size of 2 to 25 µm. 46. The method according to any one of claims 16 to 45, wherein in step (b ₃ ) graphite is used, the ash content of which is not more than 13 to 25 wt%. 47. The method according to any one of claims 16 to 46, wherein in step (b ₃ ) graphite is used, the ash content of which is not more than 18 wt.%. 48. The method according to any one of claims 16-47, wherein the graphite contains water in an amount of less than 1 wt%. 49. The method according to any one of claims 16-48, where in step (b ₅ ) the heat treatment is the calcination of the catalyst pellets in an air stream at a temperature of from 275 to 350 ° C, preferably 310 ° C, and then in an inert gas stream or in a stream of air with an inert gas, or in a vacuum, or without access to air at a temperature of 600°C. 50. The method according to claim 49, wherein the calcination of the catalyst pellets in a stream of air at a temperature of from 275 to 350°C, preferably 310°C is carried out for a period of time from 10 to 20 minutes. 51. The method according to claim 49, where the calcination of the catalyst pellets in an inert gas stream, or in an air stream with an inert gas, or in a vacuum, or without air access at a temperature of 600 ° C is carried out for a period of time from 1.5 to 3 hours , preferably 2 hours. 52. The method according to any one of claims 16-51, wherein the catalyst precursor obtained in step (a) further comprises one or more metal compounds selected from the group consisting of bismuth (Bi), germanium (Ge), cerium (Ce) , gallium (Ga), cobalt (Co), iron (Fe), and nickel (Ni). 53. The method according to claim 52, where as metal compounds selected from the group including bismuth (Bi), germanium (Ge), cerium (Ce), gallium (Ga), cobalt (Co), iron (Fe) and nickel (Ni), use chlorides, sulfates, nitrates, oxides or acetates of these metals. 54. The use of a combination of talc, taken in an amount of from 1 to 4 wt.%, and graphite, taken in an amount of from 0.5 to 3 wt.%, for molding a dry catalyst precursor to obtain a granular catalyst, while talc is mixed with a dry precursor catalyst, after which the formation of a catalyst fraction from the resulting mixture is carried out, and then the resulting catalyst fraction is mixed with graphite, and the resulting mixture is pressed to obtain a granular catalyst. 55. Granular catalyst of general formula Mo1V _a B _b C _c X _d O _n obtained by the method according to any one of claims 16-53 and containing talc and graphite, where X denotes at least one of the elements selected from Bi, Ge, Ce , Ga, Co, Fe and Ni; B is Te and/or Sb; C is Nb and/or Ta; a, b, c, d - atomic ratios of metals, where 0.006<a<1, 0.006<b<1, 0.001<c<0.5, 0<d<0.1; n is determined by the valency of the elements that make up the catalyst. 56. A granular catalyst according to claim 55, wherein the metal atomic ratios are 0.1<a<0.5, 0.1<b<0.5, 0.001<c<0.5, 0<d<0.05. 57. A granular catalyst according to claim 55 or 56, wherein the metal atomic ratios are 0.25<a<0.35, 0.17<b<0.23, 0.10<c<0.14. 58. Granular catalyst according to any one of claims 55 to 57, further modified with a silica sol, taken in an amount of from 5 to 50 wt.%, preferably from 10 to 25 wt.%. 59. Granular catalyst according to any one of claims 55-58, wherein the catalyst is characterized by the presence of 2 crystalline phases having characteristic peaks at 2θ equal to 6.6, 7.9, 9.0, 22.1, 27.2 ° (phase M1), and at 2θ equal to 22.1, 28.2, 36.1, 45.1, 50.0° (phase M2). 60. A granular catalyst according to claim 59, wherein the catalyst has an M1/M2 phase ratio of approximately 9/1. 61. A granular catalyst according to claim 59, wherein the catalyst is enriched in active phase M1 while the content of phase M2 is in the range of 2.2 to 20%. 62. A granular catalyst according to any one of claims 55 to 61, wherein the catalyst has a specific surface area in the range of 2 to 12 m ² /g, preferably 5 to 7 m ² /g. 63. A process for oxidizing propane to produce acrylic acid in the presence of a catalyst according to any one of claims 55-62. 64. A method for oxidizing propane to produce acrylic acid in the presence of a catalyst according to any one of claims 55 to 62, which includes the steps in which i) a gaseous feed stream containing propane, steam and an oxidizing agent is fed into the reactor into a propane oxidation reaction zone containing a granular oxidation catalyst according to any one of claims 55 to 62; ii) the gas mixture obtained at the exit from the propane oxidation reaction zone, containing acrylic acid, unreacted propane and propylene, carbon oxides, is fed to the stage of separation of liquid and gaseous products, followed by isolation of acrylic acid. -