RU2634593C1 - Method of producing oxide catalysts for process of oxidative conversion of ethane to ethylene - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: method of producing oxide catalysts of the composition: Mo₁V_aTe_bNb_cBi_dO_x, where a=0.20-0.40, b=0.15-0.35, c=0.05-0.25, d=0.005-0.07, x is the number of oxygen atoms required to maintain electroneutrality for the process of oxidative conversion of ethane in ethylene, includes the steps of preparing a wet precursor containing the MoVTeNb components contained in the catalyst, removing the solvent, stepwise calcining the dry MoVTeNb precursor, then impregnating the calcined precursor with a solution of the bismuth-containing compound and final heat treatment of the MoVTeNbBi precursor in an inert gas at a temperature of 500-600 °C. As a bismuth-containing compound, a freshly prepared neutral aqueous solution of a complex compound of bismuth carboxylate with ammonia is used.

EFFECT: high ethylene yield and simplification of the catalyst preparation process.

6 cl, 1 tbl, 9 ex

Description

The invention relates to a method for producing promoted multicomponent oxide catalysts, and more particularly, to a method for producing bismuth-promoted oxide MoVTeNb catalysts for the process of oxidative conversion of ethane to ethylene, which is an important monomer for the production of a wide range of products, primarily, polyethylene.

The source of industrial production of ethylene is the pyrolysis and dehydrogenation of hydrocarbons: paraffin hydrocarbons (C2-C4 alkanes) and straight-run gasoline fractions (naphtha, catalytic reforming beta-raffinates). Depending on the composition of the raw materials used, this process is carried out at temperatures from 850 to 1200 ° C, while the ethylene yield is 25-30% during the pyrolysis of naphtha and about 50% during the pyrolysis / dehydrogenation of alkanes [Overview of the CIS ethylene market and its financial crisis // InfoMain research group, Moscow, 2009].

The continuously growing demand for ethylene requires diversification of its production both in terms of expanding the raw material base and introducing new technologies and processes. From this point of view, the catalytic oxidative conversion of gaseous hydrocarbons, in particular ethane, one of the most concentrated accompanying components of natural and associated petroleum gas, seems promising. So, about 26% of ethane emitted from natural gas is used as raw materials for the production of petrochemical products in the world, in the USA - 42%, in Russia - only 4% [O. Ashpin. Gas chemistry. Another Chance // The Chemical Journal. - 2009. - No. 6-7. - S. 26-31]. The absence of thermodynamic restrictions that determine the harsh temperature regime, but the insufficiently high degree of conversion of the feedstock and the yield of ethylene, and the use of catalysts capable of selectively converting ethane to ethylene under mild conditions, allows us to consider the oxidative conversion of ethane as an alternative to industrial pyrolysis / dehydrogenation processes.

The main reactions that occur during the oxidative conversion of ethane are oxidative dehydrogenation (ODE) and oxidation. In the first reaction, the target product is formed - ethylene, in the second reaction, by-products are formed - carbon oxides:

The higher the reaction rate 1 and the lower the reaction rate 2, the higher the selectivity and yield of the target product. The main task to be solved during the development of catalysts is the creation of a catalytic composition, which leads predominantly to reaction 1 and / or inhibitory reaction 2. As such compositions, multicomponent mixed oxides based on molybdenum and / or vanadium, including elements of the I-VII groups of the Periodic system, are used.

In US patent No. 4250346 (1981) for the oxidation of ethane to ethylene, an oxide composition is used containing the following elements: Mo, X and Y with respect to a: b: c, where X is Cr, Mn, Nb, Ta, Ti, V and / or W; a Y is Bi, Ce, Co, Cu, Fe, K, Mg, Ni, P, Pb, Sb, Si, Sn, Tl and / or U; a = 1, b = 0.05 ÷ 1, s = 0 ÷ 2. For the preparation of catalysts, water-soluble salts or colloidal solutions of salts or oxides of elements included in the composition of the catalysts were used. To increase the solubility of the starting salts of the individual elements, the solutions were acidified, for example, concentrated nitric acid was used in the case of bismuth nitric acid. Mixed solutions / suspensions were dried and calcined in a stream of air in the temperature range 200-500 ° C. The reaction was carried out in the gas phase in the temperature range 300-400 ° C with a variation in the composition of the initial reaction mixture. The maximum yield of ethylene is achieved at a temperature of 400 ° C on a cationic catalyst Mo ₁₆ V ₈ Nb ₂ and is 34%.

The known process of oxidative dehydrogenation of ethane using an oxide catalyst containing Mo, V, Nb and Sb [US No. 4568790, 1986] and MoVNbSbO catalyst, optionally containing 1 or more metals from the group consisting of Li, Sc, Na, Be, Mg, Ca, Sr, Ba, Ti, Zr, Hf, Y, Ta, Cr, Fe, Co, Ni, Ce, La, Zn, Cd, Hg, Al, Tl, Pb, As, Bi, Te, U and W [US No. 4524236, 1985]. Catalysts were prepared by the method described in US patent No. 4250346 (1981). On catalysts of the composition Mo _0.5-0.9 V _0.1-0.4 Nb _0.001-0.2 Sb _0.001-0.1 Me _0.001-1 at an ethane conversion of 50%, ethylene selectivity is in the range from 63 to 76%. The maximum yield of ethylene on the 4-component MoVNbSb sample is 44%; the modification of the catalyst with the addition of alkaline earth metals, bismuth, or lead increases the yield of ethylene by 5–7%.

For oxidative dehydrogenation of paraffin hydrocarbons containing at least 2 adjacent carbon atoms, catalytic compositions of the composition A _a B _b Sb _c V _d Al _e O _{x are} known [US 6235678, 2001], where A is an alkaline or alkaline earth metal, B - 1 or more elements of Zn, Ca, Pb, Ni, Co, Fe, Cr, Bi, Ga, Nb, Sn, Nd, a = 0 ÷ 0.3, b = 0 ÷ 5, s = 0.5 ÷ 10 , d = 1, e = 3 ÷ 10. The catalyst precursor can be obtained by known methods - mixing, coprecipitation and impregnation. Salts (nitrates, chlorides, oxalates or ammonium salts of metals in anionic form), hydroxides, etc. are used as starting compounds. Water is used as a solvent; aqueous solutions can be true or suspensions, neutral, acidic or basic. So, to introduce into the bismuth catalyst the initial bismuth salt - Bi (NO ₃ ) ₃ 5H ₂ O is dissolved in 23% HNO ₃ . The introduction of elements of groups I and II of PS into the precursor is carried out by impregnating the main composition with the corresponding compounds. The resulting precursor is dried at 120 ° C and then calcined at temperatures of 450-650 ° C for 4-8 hours

A known method of producing ethylene by oxidative dehydrogenation of ethane using mixed oxide compositions containing Mo, V, Te, Nb and at least 1 element from the group comprising: Cu, Ta, Sn, Se, W, Ti, Fe, Co, Ni, Cr, Zr, Sb, Bi, an alkaline or alkaline earth metal of the following composition: MoTe _h V _i Nb _j A _k O _x , where h = 0.01-3, i / h = 0.3-10, j = 0.001-2, k = 0.0001 -2 [US No. 7319179, 2008]. Calcined catalysts should have the characteristic form of X-ray diffraction patterns containing at least 10 of the most intense reflections at the following angles 2Θ: 7.7 ± 0.4, 8.9 ± 0.4, 22.1 ± 0.4, 26.6 ± 0.4, 26.9 ± 0.4, 27.1 ± 0.4, 28.1 ± 0.4, 31.2 ± 0.4, 35.0 ± 0.4 and 45.06 °. The method for producing catalysts from solutions of individual compounds or mixtures thereof includes the following stages: 1 - mixing of the starting components, 2 - drying and 3 - calcination. The 1st stage is carried out either in an open system or by a hydrothermal method with or without stirring. The starting compounds of the main components — Mo, V, Te, and Nb — are metals, inorganic or organic compounds, but more preferably water-soluble salts, namely, for Mo, ammonium paramolybdate; for V, ammonium vanadate or vanadyl sulfate (in the case of hydrothermal synthesis ), for Te - telluric acid or ammonium tellurate, for Nb - niobium oxalate. For the modifying additives, the starting compounds are preferably salts (nitrates, chlorides, sulfates, oxalates or halides, preferably sulfates). The 2nd stage is carried out either in the corresponding furnaces, or by evaporation with stirring, or by rotary or vacuum drying. The calcination of the dried catalyst is carried out either in the atmosphere or in a stream of inert gas (N ₂ , He, Ar), or in their mixture with air at temperatures in the range of 450-600 ° C. Modification of the catalyst can be carried out, in addition, by impregnation of the oxide VMoTeNb composition or by deposition on the formed catalyst with subsequent additional heat treatment. When testing in the oxidative dehydrogenation reaction of ethane unpromoted and bismuth-promoted catalyst samples synthesized by the same procedure in a reaction mixture with an ethane: oxygen: helium ratio of 9: 6: 85 at 400 ° C and a contact time of 222 g (catalyst) hour molC ₂ H ₆ ) ^-1 ethane conversion is 57.2 and 60.2%, and the ethylene yield is 51.7 and 54.4%, respectively.

The closest to the claimed technical essence and the achieved yield of the target product is a method of preparing catalysts of the composition: Mo _a V _b X _c Y _d Z _e O _n and Mo _a V _b X _c Y _d Z _e M _f O _n , where X is Nb and / or Ta; Y - 1 element from the group including: Sb and Ni; Z is at least 1 element from the group comprising: Those, Ga, Pd, W, Bi and Al, M is 1 or more elements from the group: Fe, Co, Cu, Cr, Ti, Ce, Zr, Mn, Pb Mg, Sn, Pt, Si, La, K, Ag, and In; a = 1.0; b = 0.05-1.0; s = 0.001-1.0; d = 0.001-1.0; e = 0.001-0.5; f = 0.001-0.5 to obtain olefins from hydrocarbons [US No. 8105971, B01J 23/22, 01/31/2012 - prototype]. The preparation of the catalyst includes the steps of mixing the starting components by adjusting the pH of the solution / suspension of the multicomponent mixture or individual solutions by adding concentrated HNO ₃ , removing the solvent, calcining the dry precursor, and then rubbing the calcined catalyst. The starting material for the preparation of the catalysts can be various inorganic, organic and complex compounds, and as a solvent water (preferably) or other polar organic solvents. Obtaining a dry precursor is carried out using any suitable methods known in the art — vacuum drying, freeze drying, spray drying, rotary evaporation and air drying. Rotational drying at 50 ° C is preferred, after which the dry precursor is further dried at 110-120 ° C overnight in an oven. The subsequent calcination is carried out stepwise or in 1 stage in the atmosphere or in the flow of any inert gas - N ₂ , Ar, Xe, He, in air or a mixture thereof at a temperature of from 250 ° C to 1000 ° C from 0.5 to 15 hours. Time calcination is not a limiting factor. Elements such as Ta, Ni, Pd, W, Ga, Al, Cu, Bi, Sn, Fe, Co, alkaline, alkaline and rare earth can be introduced into the composition of the catalyst after the calcination stage of a dry precursor by impregnation or deposition. In this case, additional calcination is applied. The samples obtained in this way can be used as catalysts, or can be subjected to additional processing with a solution (1-10 wt.%) Of inorganic or organic acid at a temperature of 60-90 ° C for 2-20 hours, followed by annealing. This treatment increases the activity and selectivity of the catalyst in relation to the formation of olefins from paraffins. The best performance of the process of oxidative dehydrogenation of ethane is achieved on a catalyst with the composition: Mo ₁ V _0.29 Nb _0.17 Sb _0.01 Te _0.125 O _n , subjected to additional post-piercing rubbing and processing with an oxalic acid solution followed by annealing, after which the ethylene yield increases from 65 to 72%.

The main disadvantage of the method described in the prototype [US No. 8105971], is the need for additional post-piercing stages - grinding / grinding and treatment with an acid solution to obtain catalysts that provide the yield of the target product above 65%. The presence of these stages not only complicates the procedure for producing catalysts, but also increases its energy intensity. In addition, waste water is generated at the post-calcination stage of the acid treatment, requiring disposal.

The invention solves the problem of developing an effective method of preparing catalysts for the process of oxidative conversion of ethane to ethylene composition: Mo ₁ V _a Te _b Nb _c Bi _d O _x , where a = 0.20-0.40, preferably 0.27-0.32, b = 0.15-0.35, preferably 0.23-0.30, c = 0.05-0.25, preferably 0.10-0.15, d = 0.005-0.05, preferably 0.01-0.04, x - the number of oxygen atoms required to comply with electroneutrality.

EFFECT: high ethylene yield and simplification of the preparation method. The preparation method does not require additional stages of grinding and acid treatment of the catalysts to achieve an ethylene yield above 72%.

The problem is solved by the method of producing oxide catalysts of the composition: Mo ₁ V _a Te _b Nb _c Bi _d O _x , where a = 0.20-0.40, preferably 0.27-0.32, b = 0.15-0.35, preferably 0, 23-0.30, c = 0.05-0.25, preferably 0.10-0.15, d = 0.005-0.07, preferably 0.02-0.05 for the process of oxidative conversion of ethane to ethylene, including the steps of wet precursor containing MoVTeNb components that are part of the catalyst, solvent removal, step-by-step annealing of the dry MoVTeNb precursor, subsequent impregnation of the calcined precursor with a solution of a bismuth-containing compound and the final second heat treatment MoVTeNbBi precursor. As a bismuth-containing compound, a freshly prepared neutral aqueous solution of the complex compound of bismuth carboxylate with ammonia with a molar ratio of carboxylate / Bi = 1/1 is used.

In a neutral bismuth-containing aqueous solution, tricarboxylic acid carboxylate is used as the carboxylate. The tricarboxylic acid carboxylate is preferably citrate.

A neutral bismuth-containing aqueous solution is obtained by reacting ammonia, preferably with an aqueous suspension of bismuth citrate.

As the starting niobium compound, a freshly prepared solution of niobium oxalate is used with a ratio of C ₂ O ₄ ^2- / Nb = 3/1.

After removal of the solvent, the precursor is dried on a MoVTeNb at a temperature not lower than 150 ° C. The inert gas MoVTeNb of the precursor is calcined at temperatures of 500-600 ° C.

The problem is solved by the method of preparing oxide MoVTeNbBi catalysts using a neutral aqueous Bi-containing solution, which includes the following stages: 1 - obtaining a wet precursor containing Mo, V, Te and Nb with a given atomic ratio, 2 - solvent removal; 3 - drying; 4 - stepwise calcination of a dry MoVTeNb precursor, 5 - impregnation of a calcined MoVTeNb precursor with a neutral Bi-containing solution and drying of a wet MoVTeNbBi precursor, 6 - final heat treatment in isothermal mode; A neutral bismuth-containing solution is a solution of a complex compound of an organic bismuth salt with ammonia, where the carboxylate of tricarboxylic acid acts as an organic component, with a ratio of carboxylate / Bi = 1/1.

As the starting bismuth compound, metallic bismuth, nitric acid bismuth or bismuth citrate can be used. In the tricarboxylic acid series, citric (preferably), isolimonic or aconitic acids can be used.

Depending on the starting bismuth compound, the preparation of a neutral Bi-containing solution (pH 6.9 ± 0.1) includes:

a) dissolving metallic bismuth in concentrated nitric acid to obtain an acidic Bi-containing solution; mixing calculated amounts of acidic Bi-containing solution with a solution of tricarboxylic acid at room temperature (Tc) and vigorous stirring; filtering the resulting suspension and subsequent drying for 12 hours at a temperature not exceeding 45 ° C to obtain a water-insoluble organic bismuth salt; the interaction of an aqueous suspension of an insoluble Bi-containing compound with ammonia at Tk to obtain a neutral Bi-containing solution (pH 7.0).

b) mixing solutions of equimolar amounts of bismuth nitrate and tricarboxylic acid at a temperature of 50-60 ° C, filtering and washing the precipitate obtained, its suspension with distilled water and the subsequent formation of a neutral Bi-containing solution when interacting with ammonia at Tk (pH 6.8) .

c) barbation of ammonia through an aqueous suspension of bismuth carboxylate at T until dissolution of the organic bismuth salt, filtration of the resulting neutral Bi-containing solution (pH = 6.8).

The concentration of bismuth in a neutral solution is determined by chemical analysis using a Perkin Elmer ISP Optima 4300DV atomic absorption spectrometer.

The synthesized Bi-containing solution is then used to obtain oxide catalysts of the composition: Mo ₁ V _a Te _b Nb _c Bi _d O _x , where a = 0.20-0.40, preferably 0.27-0.32, b = 0.15- 0.35, preferably 0.23-0.30, c = 0.05-0.25, preferably 0.10-0.15, d = 0.005-0.05, preferably 0.01-0.04, for the oxidative conversion of ethane to ethylene. The starting compounds of molybdenum and vanadium are water-soluble salts, preferably ammonium paramolybdate and ammonium metavanadate. The tellurium starting compound may be telluric acid, ammonium tellurate or tellurium dioxide. In the latter case, dissolution is carried out with the addition of hydrogen peroxide. As a niobium compound, a freshly prepared solution of niobium oxalate with a ratio of C ₂ O ₄ ^2- / Nb = 3/1, obtained by dissolving at room temperature an appropriate amount of freshly precipitated niobium peroxide obtained by hydrolysis of NbCl ₅ in an oxalic acid solution containing C ₂ O _{4, is used} ^2- , necessary to obtain the desired ratio of C ₂ About ₄ ^2- / Nb. The concentration of niobium in the solution is determined by chemical analysis using a Perkin Elmer ISP Optima 4300DV atomic absorption spectrometer.

Stage 1 includes the dissolution of the starting compounds V, Mo, and Te in distilled water in amounts determined by their atomic ratio in the composition of the catalyst at a temperature of 80 ° C with vigorous stirring and the subsequent addition of the required amount of a niobium oxalate solution to form a wet precursor containing Mo, V Those and Nb.

Stage 2 is carried out in an air stream using a spray dryer. The temperature at the inlet of the dryer is 220 ° C, at the outlet - 115 ° C. Drying speed is not a limiting factor and can vary widely. Differences in the moisture content of the resulting powder are leveled at the subsequent drying stage.

Stage 3 is carried out in an oven in air, preferably at 160 ° C for 1 h. The resulting dry precursor contains Mo, V, Te and Nb and is a weakly crystallized material.

Stage 4. The calcination is carried out stepwise, initially - short-term heat treatment in a stream of air at a temperature of 300-310 ° C, then in a stream of inert gas at 500-600 ° C for 2 hours. As a result, a calcined MoVTeNb precursor is formed, consisting of of which there are 2 main phases - the o-rhombic, the so-called M1 phase in an amount of at least 85%, and the hexagonal M2 phase.

Stage 5 includes impregnation of the calcined precursor with the necessary amount of a neutral Bi-containing solution to obtain a MoVTeNbBi wet precursor and its subsequent drying in air at a temperature of 110-120 ° C for 1 h.

Stage 6 - the final calcination of the oxide MoVTeNbBi catalyst is carried out in an inert gas stream at a temperature of 500-550 ° C for 1 hour.

Distinctive features of the proposed method of preparation in comparison with the prototype are:

1 - the use of a neutral Bi-containing solution, which is a solution of a complex compound of an organic bismuth salt with ammonia, where the carboxylate of tricarboxylic acid (Ci) acts as an organic component, with a ratio of Ci / Bi equal to 1/1;

2 - the use of a freshly prepared solution of niobium oxalate with a ratio of C ₂ O ₄ ^2- / Nb equal to 3/1;

3 - use of solutions not acidified with concentrated nitric acid MoVTe;

4 - drying of the MoVTeNb precursor powder in air at a temperature of at least 150 ° C.

As a result, the resulting catalysts do not require an additional stage of post-calcining acid treatment of the catalysts with a solution of inorganic or organic acid, followed by annealing to achieve an ethylene yield higher than 72% during the process of oxidative conversion of ethane.

Testing of the catalysts in the oxidative conversion reaction of ethane is carried out in a flow-through installation in a glass reactor (∅external. = 12 mm) with a coaxially located thermocouple (∅external. Thermocouple pocket = 12 mm) at a temperature of 400 ° С. The reaction mixture containing ethane, oxygen and a diluent - nitrogen of the composition C ₂ H ₆ : O ₂ : N ₂ = 10:10:80 (% vol.) Was passed through a catalyst bed of fractional composition 0.25-0.50 mm with a bulk velocity of 230 ÷ 300 h ^-1 .

The essence of the invention is illustrated by the following examples and table.

Example 1

Obtaining a neutral Bi-containing solution: 25 g of bismuth citrate is triturated with 25 ml of distilled water until a white slurry is formed, then 135 ml of distilled water are added in portions and stirred vigorously, ammonia is passed through an aqueous suspension until complete dissolution of bismuth citrate, 140 ml are obtained after filtration neutral (pH 6.8) solution. In the solution synthesized in this way (solution I), the ratio of C ₆ H ₈ O ₇ ^3- / Bi = 1/1, the concentration of Bi is 95.5 mg Bi / ml. The resulting solution is then used to obtain MoVTeNbBiO catalysts.

Obtaining a solution of niobium oxalate: 25 g of niobium pentachloride are added portionwise in 200 ml of distilled water at room temperature and with vigorous stirring and an ammonia solution (25 wt.% NH ₃ ) is added dropwise to pH 7. The resulting precipitate is filtered off and washed with water. The washed precipitate is quantitatively transferred to a beaker, 70 ml of water and 35 g of oxalic acid dihydrate are added and 160 ml of niobium oxalate solution are obtained. In the solution thus obtained (solution II), the ratio of C ₂ O ₄ ^2- / Nb = 3/1, the concentration of Nb is 56.3 mg Nb / ml. The resulting solution is further used in the preparation of MoVTeNbBiO catalysts.

Preparation of a catalyst with the composition Mo ₁ V _0.32 Te _0.23 Nb _0.12 Bi _0.025 O _n : 17.7 g of ammonium paramolybdate, 5.28 g of telluric acid and 3.74 g of ammonium metavanadate are dissolved in 100 ml of distilled water at a temperature of 80 ° C (solution III). To the cooled solution III, 19.8 ml of solution II was added. From the wet MoVTeNb precursor thus obtained, a bright orange gel, water is removed using a laboratory spray dryer. The temperature at the inlet of the dryer is 220 ° C, at the outlet it is 115 ° C, the drying speed is 5 ml / min. After spraying, the powder is dried in air at a temperature of 160 ° C for 1 h in an oven. The resulting dry MoVTeNb precursor is pelletized, a 0.25-0.50 mm fraction is taken and calcined stepwise in a stream of air at a temperature of 310 ° C for 10 minutes, then in a stream of an inert gas - helium at a temperature of 600 ° C for 2 hours. 15 g of a calcined MoVTeNb precursor is impregnated with 7.4 ml of a solution containing 3.7 ml of solution I and 3.7 ml of distilled water, then dried in air at 110 ° C in an oven and calcined in a stream of helium at a temperature of 600 ° C for 1 including Thus obtained catalyst is tested in the reaction of the oxidative conversion of ethane to ethylene.

The catalytic properties of the obtained sample are shown in the table.

Example 2

A catalyst of the composition Mo ₁ V _0.3 Te _0.23 Nb _0.12 Bi _0.05 O _{n was} prepared analogously to Example 1, but when preparing a MoVTe solution (solution III), 3.51 g was used, 7.4 ml of solution I was taken to impregnate the MoVTeNb precursor, and the final calcination of MoVTeNbBi the catalyst is carried out at a temperature of 550 ° C. The catalyst thus obtained was tested in the oxidative conversion of ethane to ethylene.

The catalytic properties of the obtained sample are shown in table 1.

Example 3

A catalyst of the composition Mo ₁ V _0.3 Te _0.27 Nb _0.12 Bi _0.05 O _{n was} prepared analogously to Example 2, but in the preparation of the MoVTe solution (solution III), 6.20 g of telluric acid was used; 16.5 ml of solution II was used to obtain the MoVTeNb precursor and calcination of MoVTeNb a precursor in a helium stream is carried out at a temperature of 400 ° C. The catalyst thus obtained was tested in the oxidative conversion of ethane to ethylene.

The catalytic properties of the obtained sample are shown in the table.

Example 4

A catalyst of the composition Mo ₁ V _0.27 Te _0.23 Nb _0.12 Bi _0.05 O _{n was} prepared analogously to Example 2, but when preparing the MoVTe solution (solution III), 3.16 g was used, and the MoVTeNb precursor was calcined in a helium stream at a temperature of 500 ° C. The catalyst thus obtained was tested in the oxidative conversion of ethane to ethylene.

The catalytic properties of the obtained sample are shown in the table.

Example 5

The catalyst composition Mo ₁ V _0.3 Te _0.23 Nb _0.12 Bi _0.05 O _{n is} obtained analogously to example 2, but the MoVTeNb precursor is calcined in a helium stream at a temperature of 550 ° C. The catalyst thus obtained was tested in the oxidative conversion of ethane to ethylene.

The catalytic properties of the obtained sample are shown in the table.

Example 6

The catalyst composition Mo ₁ V _0.3 Te _0.23 Nb _0.12 O _n (reference sample 1) was obtained analogously to example 2, limited to stages 1-4. The catalyst thus obtained was tested in the oxidative conversion of ethane to ethylene.

The catalytic properties of the obtained sample are shown in the table.

Example 7

The catalyst composition Mo ₁ V _0.3 Te _0.23 Nb _0.12 Bi _0.05 O _n (reference sample 2) was prepared analogously to Example 2, but 7.4 ml of a nitric acid bismuth solution acidified with concentrated nitric acid were used to impregnate a calcined MoVTeNb precursor (95.5 mg / ml Bi). The catalyst thus obtained was tested in the oxidative conversion of ethane to ethylene.

The catalytic properties of the obtained sample are shown in the table.

Example 8

The catalyst composition Mo ₁ V _0.3 Te _0.23 Nb _0.12 Bi _0.05 O _n (reference sample 3) was prepared analogously to Example 6, but in the preparation of solution III, an additional 10.9 ml of solution I was added. The catalyst thus obtained was tested in the oxidative conversion of ethane to ethylene .

The catalytic properties of the obtained sample are shown in the table.

Example 9

The catalyst composition Mo ₁ V _0.3 Te _0.23 Nb _0.12 Bi _0.05 O _n (reference example 4) was prepared analogously to Example 6, but in the preparation of solution III, 1.975 g of bismuth nitrate and 3 ml of concentrated nitric acid were additionally added. The catalyst thus obtained was tested in the oxidative conversion of ethane to ethylene. The catalytic properties of the obtained sample are shown in the table.

The advantage of the proposed method is that a higher ethylene yield is achieved on bismuth-modified oxide catalysts of the composition: Mo ₁ V _a Te _b Nb _c Bi _d O _x , where a = 0.20-0.40, preferably 0.27-0 , 32, b = 0.15-0.35, preferably 0.23-0.30, c = 0.05-0.25, preferably 0.10-0.15, d = 0.005-0.05, preferably 0.01-0, 04 obtained without an additional step of post-calcining acid treatment of the catalysts with a solution of inorganic or organic acid, followed by annealing.

Claims (6)

1. The method of producing oxide catalysts of the composition: Mo ₁ V _a Te _b Nb _c Bi _d O _x , where a = 0.20-0.40, preferably 0.27-0.32, b = 0.15-0.35, preferably 0, 23-0.30, s = 0.05-0.25, preferably 0.10-0.15, d = 0.005-0.07, preferably 0.02-0.05, x is the number of oxygen atoms required to comply with electroneutrality , for the process of oxidative conversion of ethane to ethylene, which includes the steps of obtaining a wet precursor containing MoVTeNb components that are part of the catalyst, removing the solvent, stepwise calcining the dry MoVTeNb precursor, and then impregnating it calcined of a precursor solution of bismuth-containing compound and the final heat treatment MoVTeNbBi precursor in an inert gas at a temperature of 500-600 ° C, characterized in that the bismuth compounds are used as freshly prepared aqueous solution of a neutral bismuth carboxylate complex compound with ammonia. 2. The method according to p. 1, characterized in that in a neutral bismuth-containing aqueous solution, a tricarboxylic acid carboxylate is used as a carboxylate. 3. The method of claim 2, wherein the tricarboxylic acid carboxylate is preferably citrate. 4. The method according to p. 1, characterized in that a neutral bismuth-containing aqueous solution is obtained by the interaction of ammonia, preferably with an aqueous suspension of bismuth citrate. 5. The method according to p. 1, characterized in that as the starting niobium compound, a freshly prepared solution of niobium oxalate is used with a ratio of C ₂ O ₄ ^2- / Nb = 3/1. 6. The method according to p. 1, characterized in that after removal of the solvent, the precursor is dried on a MoVTeNb at a temperature not lower than 150 ° C.