Ammonia oxidation catalyst, preparation method and application thereof, and acrylonitrile preparation method

Abstract

The invention relates to the field of catalysts, in particular to an ammoxidation catalyst, a preparation method and application thereof and a preparation method of acrylonitrile. The catalyst comprises a carrier and an active component, the active component comprises a composite oxide of molybdenum, bismuth and iron, and the carrier contains an inert oxide and an MFI molecular sieve. Through research, the inventor finds that by optimizing the components of the catalyst and adding the MFI molecular sieve into the carrier, the adsorption and migration speed of raw material molecules on the surface of the catalyst can be increased, and the adsorption activation rate is increased, so that the catalytic performance and stability of the catalyst under a high-load condition are improved.

Description

Technical Field

[0001] The invention relates to the field of catalysts, and in particular to an ammonia oxidation catalyst and a preparation method and application thereof, and a method for preparing acrylonitrile. Background Art

[0002] Acrylonitrile, as an important basic chemical raw material, is currently generally produced by fluidized bed ammoxidation process. Among them, the catalyst is one of the core technologies of the process, and its research and improvement have never stopped. Developing acrylonitrile synthesis catalysts that can be used for high catalyst loads, that is, increasing the number of tons of propylene that can be processed per ton of catalyst per hour, is an important trend in the development of acrylonitrile catalysts. However, with the increase of catalyst load, the feed amount of the reactor increases, the corresponding contact time between the catalyst and the raw material will also be shortened, and higher requirements are also placed on the redox performance of the catalyst itself. The existing catalysts cannot fully adapt to the requirements under high load conditions due to their own redox performance. When used under high load conditions, it is very easy to cause the problem of rapid reduction of acrylonitrile yield and poor stability.

[0003] The raw materials for the propylene ammoxidation reaction include propylene, ammonia and air. The catalyst needs to activate propylene and ammonia at the same time to achieve efficient reaction. Studies have shown that Mo-Bi catalysts have a strong ability to activate ammonia and can effectively activate ammonia at a relatively low temperature (above 380°C). The main rate-determining step of the reaction is the adsorption and activation of propylene. The adsorption and activation rate of propylene molecules on the catalyst surface has an important influence on the activity of the catalyst and the selectivity of the reaction. A better catalyst should have a faster propylene adsorption and desorption rate and a moderate propylene adsorption strength to ensure that the product is desorbed from the catalyst surface as quickly as possible, thereby reducing CO and CO 2 The production of by-products.

[0004] By controlling the spatial distribution of each element in the catalyst, or adding an appropriate carrier modifier, the performance of the catalyst can be improved to a certain extent. For example, CN111744493A discloses an acrylonitrile catalyst, which can improve the stability of the catalyst during long-term operation by controlling the relative size of the Mo / Bi element molar ratio on the surface of the catalyst particles and the Mo / Bi element molar ratio in the bulk phase, but the load used during catalyst evaluation is low. CN107282063B, CN107282060B, and CN107282065B disclose that a certain amount of zirconium oxide, titanium oxide, and diatomaceous earth are added as carrier modifiers during the catalyst preparation process, which can improve the selectivity and stability of the catalyst in the propylene ammoxidation reaction, but the catalyst evaluation is also carried out under relatively low load conditions. Summary of the invention

[0005] The purpose of the present invention is to overcome the problems of low acrylonitrile yield and poor stability of propylene ammoxidation catalyst under high load conditions in the prior art, and to provide an ammoxidation catalyst and a preparation method and application thereof, and a method for preparing acrylonitrile. The catalyst has the advantages of high activity and good stability under high load conditions.

[0006] In order to achieve the above object, the first aspect of the present invention provides an ammonia oxidation catalyst, which includes a carrier and an active component, wherein the active component comprises a composite oxide of molybdenum, bismuth and iron, and the carrier contains an inert oxide and an MFI molecular sieve.

[0007] A second aspect of the present invention provides a method for preparing an ammonia oxidation catalyst, the method comprising:

[0008] (a) dissolving a Mo precursor to obtain a solution I;

[0009] (b) dissolving an Fe precursor, a Bi precursor, an optional precursor of an A element, an optional precursor of an B element, and an optional precursor of an C element, adding carboxylic acid, and aging to obtain a solution II;

[0010] (c) mixing the inert oxide precursor with the MFI molecular sieve, performing a first stage of grinding and emulsification, adding solution I after completion, and performing a second stage of grinding and emulsification to obtain slurry I;

[0011] (d) mixing slurry I with solution II to obtain slurry II;

[0012] (e) boiling, drying and roasting the slurry II;

[0013] Among them, A is at least one of alkali metal elements, B is at least one of alkaline earth metal elements, transition metal elements, Group IIIA metal elements, antimony and tellurium; and C is at least one of rare earth elements.

[0014] The third aspect of the present invention provides a catalyst prepared by the preparation method described in the second aspect of the present invention.

[0015] The fourth aspect of the present invention provides use of the catalyst described in the first aspect of the present invention and the catalyst described in the third aspect in olefin ammoxidation.

[0016] The fifth aspect of the present invention provides a method for preparing acrylonitrile, which comprises: contacting and reacting an acrylonitrile raw material, an ammonia source and an oxygen source under catalyst conditions, wherein the catalyst is the catalyst described in the first aspect of the present invention and the catalyst described in the third aspect.

[0017] Through the above technical solution, the present invention has the following advantages:

[0018] The inventors have found through research that by optimizing the components of the catalyst and adding MFI molecular sieves to the carrier, the adsorption and migration speed of the raw material molecules on the catalyst surface can be enhanced, the adsorption activation rate can be increased, and thus the catalytic performance and stability of the catalyst under high load conditions can be improved;

[0019] In the catalyst preparation method of the present invention, the uniform dispersion of the Mo component on the carrier is promoted by performing the grinding and emulsification process in stages, which can effectively increase the specific surface area of ​​the catalyst while ensuring the uniform dispersion of the active components. The catalytic performance and stability of the catalyst under high load conditions are improved;

[0020] The catalyst provided by the present invention is applied to olefin ammoxidation, especially propylene ammoxidation to prepare acrylonitrile, and has high olefin ammoxidation activity and nitrile selectivity. At the same time, the catalyst has a long service life under high load conditions and can maintain a high acrylonitrile single-pass yield for a long time, thereby greatly improving the efficiency and economy of acrylonitrile production. The propylene conversion rate can reach up to more than 99%, and the acrylonitrile single-pass yield can reach up to more than 84%. DETAILED DESCRIPTION

[0021] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0022] The invention provides an ammonia oxidation catalyst, which comprises a carrier and an active component, wherein the active component comprises a composite oxide of molybdenum, bismuth and iron, and the carrier contains an inert oxide and an MFI molecular sieve.

[0023] The inventors have found that by optimizing the components of the catalyst and adding MFI molecular sieves to the carrier, the adsorption and migration speed of the raw material molecules on the catalyst surface can be enhanced, the adsorption activation rate can be increased, and thus the catalytic performance and stability of the catalyst under high load conditions can be improved.

[0024] Composite oxides are not simply composed of the oxides of the metal elements themselves, but also include compounds formed by two or more metal elements. For example, the composite oxides of molybdenum, bismuth and iron also contain iron molybdate, bismuth molybdate, iron bismuth molybdate, etc.

[0025] According to a preferred embodiment of the present invention, the MFI molecular sieve is at least one of Silicate-1 molecular sieve and ZSM-5 molecular sieve, preferably Silicate-1. By adopting the above preferred scheme, the catalytic performance and stability of the catalyst under high load conditions can be further improved.

[0026] According to a preferred embodiment of the present invention, the average particle size of the MFI molecular sieve is 50-300 nm, preferably 50-150 nm. By adopting the above preferred solution, the catalytic performance and stability of the catalyst under high load conditions can be further improved.

[0027] According to a preferred embodiment of the present invention, the specific surface area of ​​the MFI molecular sieve is 50-700m 2 / g, preferably 300-700m 2 By adopting the above preferred scheme, the catalytic performance and stability of the catalyst under high load conditions can be further improved.

[0028] In the present invention, the inert oxide refers to an oxide that cannot react with acid or base to generate salts and water of corresponding valence states. According to a preferred embodiment of the present invention, the inert oxide is selected from at least one of silicon dioxide, zirconium dioxide, and titanium dioxide, preferably silicon dioxide.

[0029] In the present invention, there is no particular restriction on the content of each component of the carrier. According to a preferred embodiment of the present invention, in the catalyst, based on the total mass of the carrier, the carrier comprises: 5-50wt% of MFI molecular sieve and 50-95wt% of inert oxide.

[0030] According to a preferred embodiment of the present invention, in the catalyst, based on the total mass of the carrier, the carrier comprises: 5-50wt% of MFI molecular sieve and 50-95wt% of inert oxide.

[0031] In the present invention, there is no particular restriction on the content of each component of the catalyst. According to a preferred embodiment of the present invention, the catalyst comprises, based on the total mass of the catalyst, 30-70wt% of the carrier and 30-70wt% of the active component.

[0032] According to a preferred embodiment of the present invention, in the catalyst, based on the total mass of the catalyst, the catalyst comprises: 40-60wt% of the carrier, and 60-40wt% of the active component.

[0033] According to a preferred embodiment of the present invention, the general formula of the active component is Fe d Bi e Mo f Aa B b C c O x , wherein A is at least one of alkali metal elements, B is at least one of alkaline earth metal elements, transition metal elements, metal elements of Group IIIA, antimony and tellurium; C is at least one of rare earth elements, a is in the range of 0-3, preferably 0.05-2.5; b is in the range of 0-15, preferably 1-10; c is in the range of 0-4, preferably 0.01-3; d is in the range of 0.1-6, preferably 0.5-3; e is in the range of 0.01-3, preferably 0.01-1.5; f is in the range of 9-16, preferably 10-15; x is the total number of oxygen atoms required to satisfy the valence of each element in the above active component. By adopting the above preferred scheme, the catalytic performance and stability of the catalyst under high load conditions can be further improved.

[0034] According to a preferred embodiment of the present invention, the alkali metal element is selected from at least one of Li, Na, K, Rb and Cs.

[0035] According to a preferred embodiment of the present invention, the alkaline earth metal element is selected from at least one of Mg, Ca, Ba and Sr.

[0036] According to a preferred embodiment of the present invention, the transition metal element is selected from at least one of Mn, Co, Ni, Zn, Cr, Zr, Ti, Nb and W, preferably Ni and Co, and more preferably the molar ratio of Ni to Co is 3-10.

[0037] According to a preferred embodiment of the present invention, the Group IIIA metal element is selected from at least one of Al, Ga and In.

[0038] According to a preferred embodiment of the present invention, the active component Fe d Bi e Mo f A a B b C c O x In the embodiment, e / f is 0.005-0.40, preferably 0.01-0.20; d / f is 0.02-1.50, preferably 0.1-1.0. By adopting the above preferred scheme, the catalytic performance and stability of the catalyst under high load conditions can be further improved.

[0039] The present invention provides a method for preparing an ammonia oxidation catalyst, the method comprising:

[0040] (a) dissolving a Mo precursor to obtain a solution I;

[0041] (b) dissolving an Fe precursor, a Bi precursor, an optional precursor of an A element, an optional precursor of an B element, and an optional precursor of an C element, adding carboxylic acid, and aging to obtain a solution II;

[0042] (c) mixing the inert oxide precursor with the MFI molecular sieve, performing a first stage of grinding and emulsification, adding solution I after completion, and performing a second stage of grinding and emulsification to obtain slurry I;

[0043] (d) mixing slurry I with solution II to obtain slurry II;

[0044] (e) boiling, drying and roasting the slurry II;

[0045] In the method, there is no particular order for preparing slurry I and solution II, wherein A is at least one of alkali metal elements, B is at least one of alkaline earth metal elements, transition metal elements, Group IIIA metal elements, antimony and tellurium; and C is at least one of rare earth elements.

[0046] In the catalyst preparation method of the present invention, the uniform dispersion of the Mo component on the carrier is promoted by performing the grinding and emulsification process in stages, which can effectively increase the specific surface area of ​​the catalyst while ensuring the uniform dispersion of the active components, thereby improving the catalytic performance and stability of the catalyst under high load conditions.

[0047] According to a preferred embodiment of the present invention, the grinding and emulsification conditions include: grinding in a device capable of achieving grinding and emulsification, such as a colloid mill.

[0048] According to a preferred embodiment of the present invention, the conditions of the grinding and emulsification in the first stage include: a rotation speed of 500-1500 rpm and a time of 0.25-0.5 h.

[0049] According to a preferred embodiment of the present invention, the conditions of the second stage of grinding and emulsification include: a rotation speed of 1000-2000 rpm and a time of 0.5-1 h.

[0050] According to a preferred embodiment of the present invention, the aging conditions include: temperature of 40-80°C, time of 0.1-0.5h, stirring speed of 200-1000rpm; the aging time is adjusted according to the temperature and stirring speed.

[0051] According to a preferred embodiment of the present invention, in step (b), the molar ratio of the amount of the carboxylic acid added to the total molar number of the B element and the C element is (0.01-0.50):1.

[0052] According to a preferred embodiment of the present invention, the conditions for pulping include: temperature of 80-175°C, time of 0.1-3h, and stirring speed of 200-1000rpm.

[0053] According to a preferred embodiment of the present invention, the drying method is spray drying, and the conditions of spray drying include: drying temperature of 250-400° C., drying time of 0.5-3 h, and average diameter of spray droplets of 40-200 μm.

[0054] According to a preferred embodiment of the present invention, the calcination conditions include: in an oxygen-containing atmosphere, a calcination temperature of 200-750° C., and a calcination time of 2-8 h.

[0055] According to a preferred embodiment of the present invention, the carboxylic acid is a polycarboxylic acid, preferably at least one of oxalic acid, citric acid, tartaric acid and ethylenediaminetetraacetic acid.

[0056] According to a preferred embodiment of the present invention, the inert oxide precursor is at least one of silica sol, water glass, inorganic silica gel and silicate, preferably silica sol, more preferably the solid content of the silica sol is 20-50wt% in terms of silicon dioxide, and the average particle size is 5-50nm.

[0057] According to a preferred embodiment of the present invention, the MFI molecular sieve is at least one of Silicate-1 molecular sieve and / or ZSM-5 molecular sieve, preferably Silicate-1 molecular sieve.

[0058] According to a preferred embodiment of the present invention, the average particle size of the MFI molecular sieve is 50-300 nm, preferably 50-150 nm.

[0059] According to a preferred embodiment of the present invention, the specific surface area of ​​the MFI molecular sieve is 50-700m 2 / g, preferably 300-700m 2 / g.

[0060] In the present invention, the precursor of each element is a soluble compound of the corresponding element.

[0061] The present invention provides a catalyst prepared by the preparation method of the present invention.

[0062] The present invention provides an application of the catalyst of the present invention in olefin ammoxidation, preferably in the preparation of acrylonitrile by ammoxidation of propylene.

[0063] The invention provides a method for preparing acrylonitrile, which comprises: contact reaction of acrylonitrile raw material, an ammonia source and an oxygen source under catalyst conditions; wherein the catalyst is the catalyst described in the invention.

[0064] According to a preferred embodiment of the present invention, the contact reaction conditions include: the molar ratio of propylene raw material as propylene: ammonia source as ammonia: oxygen source as oxygen is 1:1.0-1.5:1.65-2.25, preferably 1:1-1.3:1.85-2.10.

[0065] According to a preferred embodiment of the present invention, the conditions of the contact reaction include: the reaction temperature is 400-470°C, preferably 410-450°C.

[0066] According to a preferred embodiment of the present invention, the conditions of the contact reaction include: the reaction pressure is 0.03-0.15 MPa, preferably 0.06-0.14 MPa.

[0067] According to a preferred embodiment of the present invention, the contact reaction conditions include: the reaction load WWH is 0.045-0.15h -1 , preferably 0.06-0.12h -1 .

[0068] The present invention will be described in detail below through examples.

[0069] In the following embodiments:

[0070] The activity evaluation of the catalyst was carried out in a fluidized bed reactor with an inner diameter of 38 mm. The catalyst loading was 400 g, the reaction temperature was 430°C, the molar ratio of raw materials propylene: ammonia: oxygen (air feed) was 1:1.25:2.04, the reaction pressure (gauge pressure) was 0.085 MPa, and the reaction load (WWH) was 0.095 h -1 .

[0071] The conversion rate of propylene, selectivity of acrylonitrile and single-pass yield are used as indicators for evaluating catalyst performance, and their definitions are as follows:

[0072] Propylene conversion (%) = (moles of propylene consumed in the reaction / moles of propylene fed) × 100%;

[0073] Acrylonitrile selectivity (%) = (moles of acrylonitrile produced / moles of propylene consumed in the reaction) × 100%;

[0074] Acrylonitrile single-pass yield (%) = (number of moles of acrylonitrile produced / number of moles of propylene fed) × 100%.

[0075] All raw materials are commercially available.

[0076] Example 1

[0077] 754.2 g (NH 4 ) 6 Mo 7 O24 ·4H 2 O was dissolved in 500 mL of water to obtain a mixed solution I. 228.6 g of Bi(NO 3 ) 3 ·5H 2 O, 456.8 grams Ni (NO 3 ) 2 6H 2 O, 137.1 grams Co(NO 3 ) 2 6H 2 O, 380.7 grams Fe (NO 3 ) 3 9H 2 O, 80.5 g Mg(NO 3 ) 2 6H 2 O, 4.4 g KOH, 82.0 g Pr(NO 3 ) 3 6H 2 O was dissolved in 100 mL of water, and 31.8 g of oxalic acid was added, the molar ratio of the amount of oxalic acid added to the total molar number of B elements (Ni, Co, Mg) and C elements (Pr) was 0.14:1, and the mixture was aged at 60 ° C with a stirring speed of 400 rpm for 0.25 h to obtain a mixed solution II. Then, 1500 g of silica sol with a weight concentration of 40 wt%, 1000 g of water and 400 g of silica with an average particle size of 150 nm and a specific surface area of ​​400 m 2 / g of Silicate-1 molecular sieve, transfer the slurry to a colloid mill, perform the first stage of grinding and emulsification, grind at 750 rpm for 0.25h, then add solution I, perform the second stage of grinding and emulsification, grind at 1000 rpm for 0.5h, and obtain slurry I. Then, slurry I and mixed solution II are mixed and stirred at 100°C and 300rpm for 1.5h, and then spray dried at 325°C, 1h, and the average diameter of the spray droplets is 120μm to obtain particles. Finally, the obtained particles are calcined at 580°C for 3h in an oxygen-containing atmosphere (oxygen volume fraction 21%) to obtain a catalyst.

[0078] The composition of the catalyst obtained according to the above steps is expressed as follows:

[0079] 50wt%K 0.25 Co 1.5 Ni 5.0 Mg 1.0 Pr 0.6 Fe 3.0 Bi 1.5 Mo 13.6 Ox +30wt%SiO 2 +20wt%Silicate-1

[0080] The activity evaluation of the catalyst showed that the propylene conversion rate of the catalyst was 98.6%, the acrylonitrile selectivity was 84.1%, and the acrylonitrile single-pass yield was 82.9%.

[0081] Example 2

[0082] The catalyst preparation steps are the same as in Example 1, except that:

[0083] The raw material is 759.0 g (NH 4 ) 6 Mo 7 O 24 ·4H 2 O, 230.0 g Bi(NO 3 ) 3 ·5H 2 O, 551.5 grams Ni (NO 3 ) 2 6H 2 O, 112.0 g Ca (NO 3 ) 2 ·4H 2 O, 113.1 g of 50 wt% Mn(NO 3 ) 2 solution, 225.4 g Fe(NO 3 ) 3 9H 2 O, 4.4 g KOH, 55.0 g Pr(NO 3 ) 3 6H 2 O;

[0084] The molar ratio of the amount of oxalic acid added to the total molar number of the B element (Ni, Mn, Ca) and the C element (Pr) was changed to 0.25:1;

[0085] Add 2000 g of 40 wt% silica sol, 500 g of water and 200 g of Silicate-1 molecular sieve;

[0086] The average particle size of Silicate-1 molecular sieve is 100nm and the specific surface area is 475m 2 / g;

[0087] The first stage of polishing and emulsification was performed at 750 rpm for 0.5 h, and the second stage of polishing and emulsification was performed at 1500 rpm for 0.5 h;

[0088] The composition of the catalyst is expressed as follows:

[0089] 50wt%K 0.25 Mn 1.0 Ni 6.0 Ca 1.5 Pr 0.4 Fe 2.0 Bi 1.5 Mo 13.6 O x +40wt%SiO 2 +10wt%Silicate-1

[0090] The activity evaluation of the catalyst showed that the propylene conversion rate of the catalyst was 98.2%, the acrylonitrile selectivity was 84.3%, and the acrylonitrile single-pass yield was 82.8%.

[0091] Example 3

[0092] The catalyst preparation steps are the same as in Example 1, except that:

[0093] The raw material is 941.0 g (NH 4 ) 6 Mo 7 O 24 ·4H 2 O, 285.1 g Bi(NO 3 ) 3 ·5H 2 O, 455.9 grams Ni (NO 3 ) 2 6H 2 O, 114.1 grams Co(NO 3 ) 2 6H 2 O, 395.8 grams Fe (NO 3 ) 3 9H 2 O, 201.0 g Mg(NO 3 ) 2 6H 2 O, 11.6 g RbNO 3 , 82.2 grams Pr(NO 3 ) 3 6H 2 O;

[0094] Add 2000 g of silica sol with a weight concentration of 30 wt%, 475 g of water and 200 g of Silicate-1 molecular sieve; the inert oxide precursor is silica sol with a weight concentration of 30 wt%;

[0095] The first stage of polishing and emulsification is performed at 1250 rpm for 0.25 h, and the second stage of polishing and emulsification is performed at 1750 rpm for 0.75 h;

[0096] 60wt%Rb 0.20 Co 1.0 Ni 4.0 Mg 2.0 Pr 0.5 Fe 2.5 Bi 1.5 Mo 13.6 O x +30wt%SiO 2 +10wt% Silicate-1;

[0097] The activity evaluation of the catalyst showed that the propylene conversion rate of the catalyst was 99.1%, the acrylonitrile selectivity was 83.2%, and the acrylonitrile single-pass yield was 82.5%.

[0098] Example 4

[0099] The catalyst preparation steps are the same as in Example 1, except that:

[0100] The added MFI molecular sieve ZSM-5 molecular sieve has an average particle size of 150nm and a specific surface area of ​​416m 2 / g;

[0101] The composition of the catalyst is expressed as follows:

[0102] 50%K 0.25 Co 1.5 Ni 5.0 Mg 1.0 Pr 0.6 Fe 3.0 Bi 1.5 Mo 13.6 O x +30%SiO 2 +20% SZM-5

[0103] The activity evaluation of the catalyst showed that the propylene conversion rate of the catalyst was 98.0%, the acrylonitrile selectivity was 82.6%, and the acrylonitrile single-pass yield was 80.9%.

[0104] Example 5

[0105] The catalyst preparation steps are the same as in Example 1, except that:

[0106] The average particle size of Silicate-1 molecular sieve is 1000nm and the specific surface area is 250m 2 / g;

[0107] The composition of the catalyst is expressed as follows:

[0108] 50%K 0.25 Co 1.5 Ni 5.0 Mg 1.0 Pr 0.6 Fe 3.0 Bi 1.5 Mo 13.6 O x +30%SiO 2 +20% Silicate-1

[0109] The activity evaluation of the catalyst showed that the propylene conversion rate of the catalyst was 98.5%, the acrylonitrile selectivity was 82.8%, and the acrylonitrile single-pass yield was 81.6%.

[0110] Example 6

[0111] The catalyst preparation steps are the same as in Example 1, except that:

[0112] The raw material is (NH 4 ) 6 Mo 7 O 24 ·4H 2 O. Bi(NO 3 ) 3 ·5H 2 O.Ni(NO 3 ) 2 6H 2 O, Ca(NO 3 ) 2 ·4H 2 O, Fe(NO 3 ) 3 9H 2 O、Mg(NO 3 ) 2 6H 2 O, KOH, Pr(NO 3 ) 3 6H 2 O;

[0113] The amount of raw materials added is controlled so that the composition of the prepared catalyst is as follows:

[0114] 50wt%K 0.25 Ca 1.5 Ni 5.0 Mg 1.0 Pr 0.6 Fe 3.0 Bi 1.5 Mo 13.6 O x +30%wtSiO 2+20wt%Silicate-1

[0115] The activity evaluation of the catalyst showed that the propylene conversion rate of the catalyst was 98.8%, the acrylonitrile selectivity was 83.5%, and the acrylonitrile single-pass yield was 82.5%.

[0116] Example 7

[0117] The catalyst preparation steps are the same as in Example 1, except that:

[0118] The added carboxylic acid is citric acid, and the molar ratio of the added amount of citric acid to the total molar number of element B and element C is 0.14:1;

[0119] The composition of the catalyst obtained according to the above steps is expressed as follows:

[0120] 50wt%K 0.25 Co 1.5 Ni 5.0 Mg 1.0 Pr 0.6 Fe 3.0 Bi 1.5 Mo 13.6 O x +30wt%SiO 2 +20wt%Silicate-1

[0121] The activity evaluation of the catalyst showed that the propylene conversion rate of the catalyst was 98.0%, the acrylonitrile selectivity was 83.5%, and the acrylonitrile single-pass yield was 81.8%.

[0122] Example 8

[0123] The catalyst preparation steps are the same as in Example 1, except that:

[0124] The spray drying conditions were as follows: drying temperature 240°C, drying time 1 h, and average spray droplet diameter 120 μm.

[0125] The composition of the catalyst obtained according to the above steps is expressed as follows:

[0126] 50wt%K 0.25 Co 1.5 Ni 5.0 Mg 1.0 Pr 0.6 Fe 3.0 Bi 1.5 Mo 13.6 O x +30wt%SiO 2 +20wt%Silicate-1

[0127] The activity evaluation of the catalyst showed that the propylene conversion rate of the catalyst was 98.2%, the acrylonitrile selectivity was 83.4%, and the acrylonitrile single-pass yield was 81.5%.

[0128] Example 9

[0129] The catalyst preparation steps are the same as in Example 1, except that:

[0130] The calcination conditions are calcination at 800° C. for 3 h in an oxygen-containing atmosphere (oxygen volume fraction 21%).

[0131] The composition of the catalyst obtained according to the above steps is expressed as follows:

[0132] 50wt%K 0.25 Co 1.5 Ni 5.0 Mg 1.0 Pr 0.6 Fe 3.0 Bi 1.5 Mo 13.6 O x +30wt%SiO 2 +20wt%Silicate-1

[0133] The activity evaluation of the catalyst showed that the propylene conversion rate of the catalyst was 98.1%, the acrylonitrile selectivity was 83.0%, and the acrylonitrile single-pass yield was 81.4%.

[0134] Comparative Example 1

[0135] The catalyst preparation steps are the same as in Example 1, except that:

[0136] No MFI molecular sieve was added, and only silica sol with a weight concentration of 40 wt % was used as a carrier precursor.

[0137] The composition of the catalyst obtained according to the above steps is expressed as follows:

[0138] 50wt%K 0.25 Co 1.5 Ni 5.0 Mg 1.0 Pr 0.6 Fe 3.0 Bi 1.5 Mo 13.6 O x +50wt%SiO 2 ;

[0139] The activity evaluation of the catalyst showed that the propylene conversion rate of the catalyst was 97.3%, the acrylonitrile selectivity was 82.5%, and the acrylonitrile single-pass yield was 80.3%.

[0140] Comparative Example 2

[0141] The catalyst preparation steps are the same as in Example 1, except that:

[0142] No silica sol with a weight concentration of 40 wt % was added, and only MFI molecular sieve Silicate-1 molecular sieve was used as a carrier.

[0143] The composition of the catalyst obtained according to the above steps is expressed as follows:

[0144] 50wt%K 0.25 Co 1.5 Ni 5.0 Mg 1.0 Pr 0.6 Fe 3.0 Bi 1.5 Mo 13.6 O x +50wt%Silicate-1;

[0145] The activity evaluation of the catalyst showed that the propylene conversion rate of the catalyst was 97.3%, the acrylonitrile selectivity was 81.8%, and the acrylonitrile single-pass yield was 79.6%.

[0146] Comparative Example 3

[0147] The catalyst preparation steps are the same as in Example 1, except that:

[0148] The molecular sieve added is Beta molecular sieve;

[0149] The composition of the catalyst obtained according to the above steps is expressed as follows:

[0150] 50wt%K 0.25 Co 1.5 Ni 5.0 Mg 1.0 Pr 0.6 Fe 3.0 Bi 1.5 Mo 13.6 O x +30wt%SiO 2 +20wt%Beta

[0151] The activity evaluation of the catalyst showed that the propylene conversion rate of the catalyst was 97.0%, the acrylonitrile selectivity was 81.5%, and the acrylonitrile single-pass yield was 79.0%.

[0152] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. An ammonia oxidation catalyst, characterized in that The catalyst comprises a carrier and an active component, wherein the active component comprises a composite oxide of molybdenum, bismuth and iron, and the carrier contains an inert oxide and an MFI molecular sieve.

2. The catalyst according to claim 1, wherein The MFI molecular sieve is Silicate-1 molecular sieve and / or ZSM-5 molecular sieve, preferably Silicate-1; More preferably, The average particle size of the MFI molecular sieve is 50-300 nm, preferably 50-150 nm; and / or The specific surface area of ​​the MFI molecular sieve is 50-700m 2 / g, preferably 300-700m 2 / g; and / or The inert oxide is selected from at least one of silicon dioxide, zirconium dioxide and titanium dioxide, preferably silicon dioxide.

3. The catalyst according to claim 1 or 2, wherein In the catalyst, based on the total weight of the carrier, the carrier comprises: 5-50wt% of MFI molecular sieve, 50-95wt% of inert oxide; Preferably, in the catalyst, based on the total mass of the carrier, the carrier comprises: 5-50wt% of MFI molecular sieve, 50-95wt% of inert oxide; and / or In the catalyst, based on the total mass of the catalyst, the catalyst comprises: 30-70wt% of a carrier, 30-70wt% of an active component; Preferably, in the catalyst, based on the total mass of the catalyst, the catalyst comprises: 40-60wt% of the carrier, and 60-40wt% of the active component.

4. The catalyst according to any one of claims 1 to 3, wherein The general formula of the active component is Fe d Bi e Mo f A a B b C c O x , wherein A is at least one of alkali metal elements, B is at least one of alkaline earth metal elements, transition metal elements, metal elements of Group IIIA, antimony and tellurium; C is at least one of rare earth elements, a is in the range of 0-3, preferably 0.05-2.5; b is in the range of 0-15, preferably 1-10; c is in the range of 0-4, preferably 0.01-3; d is in the range of 0.1-6, preferably 0.5-3; e is in the range of 0.01-3, preferably 0.01-1.5; f is in the range of 9-16, preferably 10-15; x is the total number of oxygen atoms required to satisfy the valence of each element in the above-mentioned active component; More preferably, The alkali metal element is selected from at least one of Li, Na, K, Rb and Cs; and / or The alkaline earth metal element is selected from at least one of Mg, Ca, Ba and Sr; and / or The transition metal element is selected from at least one of Mn, Co, Ni, Zn, Cr, Zr, Ti, Nb and W, preferably Ni and Co; and / or The Group IIIA metal element is at least one selected from Al, Ga and In; More preferably, The active component Fe d Bi e Mo f A a B b C c In the above, e / f is 0.005-0.40, preferably 0.01-0.20; d / f is 0.02-1.50, preferably 0.1-1.

0.

5. A method for preparing an ammonia oxidation catalyst, characterized in that: The method includes: (a) dissolving a Mo precursor to obtain a solution I; (b) dissolving an Fe precursor, a Bi precursor, an optional precursor of an A element, an optional precursor of an B element, and an optional precursor of an C element, adding carboxylic acid, and aging to obtain a solution II; (c) mixing the inert oxide precursor with the MFI molecular sieve, performing a first stage of grinding and emulsification, adding solution I after completion, and performing a second stage of grinding and emulsification to obtain slurry I; (d) mixing slurry I with solution II to obtain slurry II; (e) boiling, drying and roasting the slurry II; Among them, A is at least one of alkali metal elements, B is at least one of alkaline earth metal elements, transition metal elements, Group IIIA metal elements, antimony and tellurium; and C is at least one of rare earth elements.

6. The preparation method according to claim 5, wherein: The conditions of the first stage of grinding and emulsification include: a rotation speed of 500-1500 rpm and a time of 0.25-0.5 h; and / or The conditions of the second stage of grinding and emulsification include: a rotation speed of 1000-2000 rpm and a time of 0.5-1 h; and / or The aging conditions include: temperature of 40-80°C, time of 0.1-0.5h, stirring speed of 200-1000rpm; and / or In step (b), the molar ratio of the added amount of the carboxylic acid to the total molar number of the B element and the C element is (0.01-0.50):

1. The conditions for cooking the pulp include: a temperature of 80-175° C., a time of 0.1-3 h, and a stirring speed of 200-1000 rpm; and / or The drying method is spray drying, and the conditions of spray drying include: drying temperature of 250-400° C., drying time of 0.5-3 h, average diameter of spray droplets of 40-200 μm; and / or The calcination conditions include: in an oxygen-containing atmosphere, a calcination temperature of 200-750° C., and a calcination time of 2-8 hours.

7. The preparation method according to claim 5 or 6, wherein: The carboxylic acid is a polycarboxylic acid, preferably at least one of oxalic acid, citric acid, tartaric acid and ethylenediaminetetraacetic acid; and / or The inert oxide precursor is at least one of silica sol, water glass, inorganic silica gel and silicate, preferably silica sol, more preferably the silica sol has a solid content of 20-50wt% calculated as silicon dioxide and an average particle size of 5-50nm; and / or The MFI molecular sieve is Silicate-1 molecular sieve and / or ZSM-5 molecular sieve, preferably Silicate-1 molecular sieve; More preferably, The average particle size of the MFI molecular sieve is 50-300 nm, preferably 50-150 nm; and / or The specific surface area of ​​the MFI molecular sieve is 50-700m 2 / g, preferably 300-700m 2 / g.

8. A catalyst prepared by the preparation method according to any one of claims 5 to 7.

9. Use of the catalyst according to any one of claims 1 to 4 and the catalyst according to claim 8 in the ammoxidation of olefins, preferably in the preparation of acrylonitrile by ammoxidation of propylene.

10. A method for preparing acrylonitrile, characterized in that: The method comprises: an acrylonitrile raw material, an ammonia source and an oxygen source are contacted and reacted under a catalyst condition; Wherein, the catalyst is the catalyst according to any one of claims 1 to 4 and the catalyst according to claim 8; preferably The conditions of the contact reaction include: The molar ratio of the propylene raw material in terms of propylene: the ammonia source in terms of ammonia gas: the oxygen source in terms of oxygen is 1:1.0-1.5:8-10.5, preferably 1:1-1.3:8.8-10; and / or The reaction temperature is 400-470°C, preferably 410-450°C; and / or The reaction pressure is 0.03-0.15 MPa, preferably 0.06-0.14 MPa; and / or Reaction load WWH is 0.045-0.15h -1 , preferably 0.06-0.12h -1 .