A MoVTeNbOx-based metal oxide shaped catalyst, its forming method and application

Abstract

The present invention provides a MoVTeNbOx-based metal oxide shaped catalyst, a forming method, and applications thereof, comprising the following steps: A) mixing a raw MoVTeNbOx-based metal oxide catalyst powder, an inert substance, and sesbania powder, kneading the mixture, and sequentially spraying an alkaline amino acid solution, an acid solution, and a halogen compound solution during the kneading process to obtain a kneaded material; B) extruding the kneaded material into a shaped catalyst body, and drying the resulting body to obtain a catalyst body; and C) calcining the catalyst body to obtain a MoVTeNbOx-based metal oxide shaped catalyst. This application introduces alkaline amino acids to optimize the catalyst's secondary pore structure, significantly improving selectivity. Furthermore, a trace amount of halogen is introduced as an inhibitor. The addition of the alkaline amino acid and the inhibitor enables the MoVTeNbOx catalyst to achieve an acrylic acid selectivity exceeding 80%, significantly reducing the formation of byproducts.

Description

Technical Field

[0001] The present invention belongs to the technical field of catalyst forming, and in particular relates to a formed catalyst of a MoVTeNbOx series metal oxide, a forming method and an application thereof. Background Art

[0002] Acrylic acid is an important unsaturated organic acid. The carbon-carbon double bonds and carboxyl groups in its molecular structure enable it to undergo a variety of reactions, including polymerization and esterification. It is widely used in various fields critical to national economy and people's livelihoods, including coatings, adhesives, textiles, printing and dyeing, and superabsorbent resins. By 2023, China's acrylic acid production capacity was approximately 3.5 million tons, all produced using a two-step propylene oxidation process. Propylene is first oxidized in the first reactor to produce acrolein, which is further oxidized in the second reactor to produce acrylic acid. Compared to propylene, propane is less expensive and is abundant in shale gas, associated oilfield gas, and refinery by-product gas. Over specific catalysts, propane can be oxidized in a single step to produce acrylic acid. Therefore, using propane instead of propylene for direct oxidation to produce acrylic acid could significantly reduce production costs.

[0003] Among many catalysts, MoVTeNbOx composite metal oxide is the catalyst with the best comprehensive performance, with good activity, selectivity and thermal stability. According to the results of patent US005380933A, the propane conversion rate is 80.1%, the acrylic acid selectivity is 60.5%, and the yield is as high as 48.5%. On this basis, many scientists have made further improvements to the catalyst. For example, patent CN1130255C discloses a "method for producing oxide catalysts for oxidation or ammoxidation", with the general formula Mo 1.0 V a X b Nb c Z d O n X is at least one element selected from antimony and tellurium, and Z is at least one element selected from tungsten, chromium, titanium, aluminum, thallium, zirconium, hafnium, manganese, rhenium, iron, ruthenium, cobalt, rhodium, nickel, palladium, platinum, zinc, boron, gallium, indium, germanium, tin, phosphorus, lead, bismuth, yttrium, rare earth elements, and alkaline earth elements. During the catalyst preparation process, the niobium compound exists in the form of a complex, and the complexing agent is a hydroxyl compound bonded to an oxygen atom or a carbon atom. The catalyst can be used for propane oxidation. Patent CN100544821C discloses a "molybdenum, vanadium, tellurium, and niobium catalyst for the selective oxidation of propane to acrylic acid and its preparation method." After the fresh catalyst is subjected to high-temperature activation treatment in a reaction atmosphere, its activity is significantly improved, and a stable state can be achieved in the initial stage of the reaction.

[0004] The commonality of the above work lies in how to improve the performance of the raw powder catalyst, without involving molding. In laboratory-level propane oxidation reactions, the catalyst particles are small and the loading is small. The active surface is fully exposed, the reactants are in full contact with the active sites, the mass transfer resistance is very small, and there is almost no concentration gradient. Therefore, the effectiveness factor is high, and the reaction results are relatively close to the intrinsic kinetic characteristics. However, in actual industrial applications, the catalysts loaded must be strictly molded particles with a certain shape, size, and strength. Considering the bed pressure drop and strength issues, the catalyst particles loaded in industrial reactors are much larger than those in the laboratory. This inevitably leads to the problem of mass transfer resistance within the catalyst particles. The existence of internal diffusion causes the reactant concentration to gradually decrease from the catalyst surface to the interior, while the product concentration may be just the opposite. This concentration gradient not only reduces activity, but also reduces the selectivity of the target product, resulting in essential differences between the macroscopic kinetic characteristics of the molded catalyst and the intrinsic kinetics.

[0005] Therefore, molding is an important preparation process to ensure the performance of the catalyst. Even if the original powder catalyst has excellent performance, it cannot obtain a qualified catalyst for industrial application if the molding is improper. Summary of the Invention

[0006] The object of the present invention is to provide a shaped catalyst of a MoVTeNbOx-based metal oxide, a shaping method and an application thereof. The shaped catalyst prepared in the present invention is used for the selective oxidation of propane to produce acrylic acid under industrial conditions and has high activity and selectivity.

[0007] The present invention provides a molding method of a MoVTeNbOx-based metal oxide molded catalyst, comprising the following steps:

[0008] A) mixing a MoVTeNbOx metal oxide raw powder catalyst, an inert substance, and sesbania powder, kneading the mixture, and spraying an alkaline amino acid solution, an acid solution, and a halogen compound solution in sequence during the kneading process to obtain a kneaded material;

[0009] The mass of the halogen compound in the halogen compound solution is 0.002-0.03 wt % of the total mass of the MoVTeNbOx metal oxide raw powder catalyst and the inert substance;

[0010] B) extruding the kneaded material and drying it to obtain a catalyst body;

[0011] C) calcining the catalyst body at 180-280° C. for 1-2 hours, then heating it up and continuing calcining it at 350-400° C. for 1-2 hours to obtain a MoVTeNbOx-based metal oxide shaped catalyst.

[0012] Preferably, the inert substance is silicon carbide and / or quartz powder;

[0013] The mass of the inert substance is 20-60 wt % of the total mass of the MoVTeNbOx metal oxide raw powder catalyst and the inert substance.

[0014] Preferably, the mass of the sesbania powder is 2-8 wt % of the total mass of the MoVTeNbOx-based metal oxide raw powder catalyst and the inert substance.

[0015] Preferably, the basic amino acids include one or more of lysine, histidine and arginine;

[0016] The mass of the basic amino acid is 1-8 wt% of the total mass of the MoVTeNbOx metal oxide raw powder catalyst and the inert material;

[0017] The mass concentration of the alkaline amino acid solution is 10-35 wt %.

[0018] Preferably, the dissociation constant pKa of the acid in the acid solution is 2.5 to 5;

[0019] The acid in the acid solution comprises one or more of nitric acid, sulfuric acid, lactic acid, benzoic acid, phthalic acid, oxalic acid, tartaric acid, citric acid, sulfurous acid, acetic acid, formic acid and trichloroacetic acid;

[0020] The mass of the acid in the acid solution is 1-5 wt % of the total mass of the MoVTeNbOx metal oxide raw powder catalyst and the inert substance; the mass concentration of the acid solution is 10-40 wt %.

[0021] Preferably, the halogen compound includes one or more of HCl, HF, HBr, HI, NaF, NaCl, NaBr, NaI, KF, KCl, KBr, KI, MgCl2 and CaCl2;

[0022] The mass concentration of the halogen compound solution is 1-10 wt %.

[0023] Preferably, in the mixed material, the mass of water is 20-45 wt % of the total mass of the MoVTeNbOx metal oxide raw powder catalyst and the inert substance.

[0024] Preferably, the drying in step B) specifically includes:

[0025] First dry at 30~60℃ for 10~48 hours, then increase the temperature to 90~120℃ and continue drying for 24~48 hours.

[0026] The present invention provides a MoVTeNbOx-based metal oxide shaped catalyst obtained by the shaping method described above.

[0027] The present invention provides the use of the MoVTeNbOx-based metal oxide shaped catalyst as described above in the industrial production of acrylic acid by propane oxidation;

[0028] In the industrial production of propane oxidation to prepare acrylic acid, the catalyst loading amount is 1~2L. The catalyst is diluted with porcelain balls and then loaded. The volume percentage of the catalyst in the total loading amount is 70%~90%. The inlet pressure of the reaction gas is 50~150KPa. The reaction gas is a mixture of propane, air, nitrogen and water vapor. The absolute volume space velocity of propane to the catalyst is 80~150h -1 , propane inlet concentration 6%~12%, oxygen to alkane ratio 1~2, water to alkane ratio 0.8~3, reaction temperature 320~400℃;

[0029] The reactor is divided into three reaction zones from top to bottom: upper, middle and lower sections. The proportion of catalyst increases successively: the upper section catalyst accounts for 30% to 50% of the total upper section loading, the middle section catalyst accounts for 50% to 75% of the total middle section loading, and the lower section catalyst accounts for 75% to 100% of the total lower section loading.

[0030] The invention provides a molding method for a MoVTeNbOx-based metal oxide shaped catalyst. The method comprises the following steps: A) mixing a MoVTeNbOx-based metal oxide raw powder catalyst, an inert substance and sesbania powder, kneading the mixture, and spraying an alkaline amino acid solution, an acid solution and a halogen compound solution in sequence during the kneading process to obtain a kneaded material, wherein the mass of the halogen in the halogen compound solution is 0.002-0.03 wt % of the total mass of the MoVTeNbOx-based metal oxide raw powder catalyst and the inert substance; B) extruding the kneaded material to form the mixture, and drying the mixture to obtain a catalyst body; and C) calcining the catalyst body at 180-280° C. for 1-2 hours, then heating the mixture and continuing to calcine at 350-400° C. for 1-2 hours to obtain the MoVTeNbOx-based metal oxide shaped catalyst. The present application introduces alkaline amino acids on the basis of conventional acidic peptizing agents. These amino acids have two amino groups and one carboxyl group, and are alkaline as a whole after ionization in water. The use of these alkaline amino acids in combination with conventional acidic peptizing agents can effectively regulate the strength of the peptization effect, thereby optimizing the secondary pore structure of the catalyst, so that the pore size distribution is concentrated from dispersed to macroporous, which is beneficial to the diffusion of acrylic acid molecules and greatly improves the selectivity. At the same time, in order to suppress excessive oxidation, trace halogens are creatively introduced as inhibitors during the molding process. Halogens are generally regarded as toxic substances that will poison the catalyst. The addition of alkaline amino acids and inhibitors enables the MoVTeNbOx catalyst to obtain more than 80% acrylic acid selectivity, greatly reducing the formation of by-products. DETAILED DESCRIPTION

[0031] The present invention provides a molding method of a MoVTeNbOx-based metal oxide molded catalyst, comprising the following steps:

[0032] A) mixing a MoVTeNbOx metal oxide raw powder catalyst, an inert substance, and sesbania powder, kneading the mixture, and spraying an alkaline amino acid solution, an acid solution, and a halogen compound solution in sequence during the kneading process to obtain a kneaded material;

[0033] The mass of the halogen in the halogen compound solution is 0.002-0.03 wt % of the total mass of the MoVTeNbOx metal oxide raw powder catalyst and the inert substance;

[0034] B) extruding the kneaded material and drying it to obtain a catalyst body;

[0035] C) calcining the catalyst body at 180-280° C. for 1-2 hours, then heating it up and continuing calcining it at 350-400° C. for 1-2 hours to obtain a MoVTeNbOx-based metal oxide shaped catalyst.

[0036] In the present invention, the specific type or composition of the MoVTeNbOx-based metal oxide raw powder catalyst is not particularly limited. In the present invention, the MoVTeNbOx-based metal oxide raw powder catalyst can be a conventional MoVTeNbOx-based metal oxide raw powder catalyst in the art, or a commercially available MoVTeNbOx-based metal oxide raw powder catalyst. Specifically, the MoVTeNbOx-based metal oxide raw powder catalyst used in the present invention is prepared according to the following steps:

[0037] 1) Co-precipitation:

[0038] The general formula of the catalyst is (Mo+W) 1.0 V a Ce b Te c Mn d Nb e X m Y n Z p O x, wherein X is at least one of Sc, Ti, Cr, Fe, Co, Ni, Cu, Zn, Ga, Ge, As, Se, Y, Zr, Ru, Rh, Pd, Ag, Cd, In, Sn, Sb, lanthanides, actinides, Hf, Ta, Re, Os, Ir, Pt, Au, Hg, Ta, Pb, Bi, Po, Y is at least one of Be, Mg, Ca, Sr, Ba, Z is at least one of Li, Na, K, Rb, Cs, wherein a, b, c, d, e, m, n, p are the molar ratios of the corresponding element pair (Mo + W), and the range of a is wherein a is in the range of 0.2 to 0.4, b is in the range of 0.005 to 0.2, c is in the range of 0.1 to 0.25, d is in the range of 0.001 to 0.1, e is in the range of 0.08 to 0.18, m is in the range of 0.001 to 0.05, n is in the range of 0.001 to 0.05, and p is in the range of 0.0005 to 0.02. The mole percentage of W in (Mo+W) is preferably 10 to 30%, more preferably 15 to 25%, such as 10%, 15%, 20%, 25%, 30%, and preferably a range value with any of the above values ​​as the upper or lower limit. x is determined by the final content and valence of each element.

[0039] Ammonium molybdate, ammonium tungstate, ammonium metavanadate, telluric acid, manganese nitrate, cerium nitrate, etc. are dissolved to form solution A, niobium oxalate is dissolved to form solution B, solution B is added dropwise to solution A to form coprecipitation slurry C, any soluble salts of X, Y, and Z are dissolved to form solutions D, E, and F, D, E, and F are slowly added dropwise to slurry C in sequence to form slurry G, the pH is adjusted to 1.5-3.0 with nitric acid solution, and coprecipitation is performed at room temperature.

[0040] 2) Drying:

[0041] Slurry G was dehydrated using spray drying at an inlet temperature of 160-200°C and an outlet temperature of 80-110°C. The feed rate was adjusted based on the outlet temperature. The slurry was then dried using a rotary evaporator at a temperature of 50-70°C and a relative vacuum of less than -80 kPa. The dried precursor was pulverized to approximately 50 microns, and this powder was labeled H.

[0042] 3) Calcination: Powder H is first calcined in an oxygen atmosphere at a heating rate of 0.8-3°C / min, at a temperature of 280-360°C, for 2-5 hours. During the calcination process, the ammonium, nitrate, and oxalate groups in the precursor decompose, releasing gases such as NO, NO2, CO, CO2, and N2. The calcined metal exists as an oxide, with no distinct crystalline diffraction peaks observed in XRD patterns. The catalyst is amorphous and has not yet formed a catalytically active phase. The atmosphere is then switched to an oxygen-free atmosphere (e.g., nitrogen, argon, or helium), and the temperature is continued to rise to 560-620°C for 2 hours. During this calcination process, the catalyst maintains its mass and no longer decomposes, but catalytically active M1 and M2 phases are formed. It is generally believed that the M1 phase activates propane, oxidizing and dehydrogenating it to propylene, which is then selectively oxidized to acrylic acid in the M2 phase. After cooling, the resulting catalyst is crushed to approximately 20 microns and labeled M.

[0043] The invention mixes MoVTeNbOx series metal oxide raw powder catalyst, inert material and sesbania powder evenly, and places the mixture in a kneader for kneading.

[0044] In the present invention, during the molding process, an inert substance with high thermal conductivity needs to be added to the original powder catalyst as a carrier. The inert substance is preferably silicon carbide and / or quartz powder; the common feature of the two is high thermal conductivity. Since propane oxidation is a highly exothermic reaction, the addition of an inert substance helps to dissipate the reaction heat, avoid hot spots inside the catalyst, reduce the occurrence of side reactions, and also help reduce the catalyst cost; the mass of the inert substance is preferably 20-60 wt % of the total mass of the MoVTeNbOx-based metal oxide raw powder catalyst and the inert substance (hereinafter referred to as "powder mass"), more preferably 30-50 wt %, such as 20 wt %, 25 wt %, 30 wt %, 35 wt %, 40 wt %, 45 wt %, 50 wt %, 55 wt %, 60 wt %, preferably a range value with any of the above values ​​as the upper or lower limit; the MoVTeNbOx-based metal oxide raw powder catalyst accounts for 40-80 wt % of the powder mass, more preferably 50-70 wt %, such as 40 wt %, 45 wt %, 50 wt %, 55 wt %, 60 wt %, 65 wt %, 70 wt %, 75 wt %, 80 wt %, preferably a range value with any of the above values ​​as the upper or lower limit.

[0045] In the present invention, the sesbania powder acts as a lubricant to reduce the extrusion pressure, allowing the strip catalyst to be extruded smoothly; the mass of the sesbania powder is preferably 2 to 8 wt% of the powder mass, more preferably 3 to 6 wt%, such as 2 wt%, 3 wt%, 4wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, preferably a range value with any of the above values ​​as the upper or lower limit.

[0046] In the present invention, the kneader can be a twin-shaft kneader or a wheel mill.

[0047] The invention dissolves alkaline amino acid in water to prepare an alkaline amino acid solution, and then evenly sprays the alkaline amino acid solution on the surface of the material during kneading, and kneads for 30 to 90 minutes.

[0048] In the present invention, the basic amino acid is preferably one or more of lysine, histidine, and arginine, preferably lysine and arginine, and more preferably lysine. The basic amino acids herein have two amino groups and one carboxyl group, and their side chains contain protonatable basic chemical groups, such as guanidino, amino, or imidazole groups. Hydrolysis produces more hydroxide ions than hydrogen ions, resulting in an alkaline solution. The ionization of these groups in water can regulate the strength of the peptization effect, contribute to the formation of a macroporous structure, and make the pore distribution more uniform, which facilitates the diffusion of product molecules and greatly improves the selectivity of the catalyst.

[0049] In the present invention, the mass of the basic amino acid is preferably 1-8wt% of the powder mass, more preferably 2-6wt%, such as 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, preferably a range value with any of the above values ​​as the upper or lower limit; the mass concentration of the basic amino acid solution is preferably 10-35wt%, more preferably 15-30wt%, such as 10 wt%, 15 wt%, 20 wt%, 25 wt%, 30 wt%, 35 wt%, preferably a range value with any of the above values ​​as the upper or lower limit; after adding the basic amino acid, mixing is preferably continued for 30-90min, more preferably 45-60min.

[0050] After adding the alkaline amino acid solution, the present invention dissolves the acid in water to prepare an acid solution, adds the alkaline amino acid solution, and after kneading, evenly sprays it on the surface of the material and continues kneading for 30 to 90 minutes.

[0051] In the present invention, the acid is preferably an inorganic acid or an organic acid, including one or more of nitric acid, sulfuric acid, lactic acid, benzoic acid, phthalic acid, oxalic acid, tartaric acid, citric acid, sulfurous acid, acetic acid, formic acid and trichloroacetic acid, more preferably an acid with a dissociation constant pKa between 2.5 and 5, such as one or more of formic acid, acetic acid, lactic acid and tartaric acid. These acid solutions are used in combination with basic amino acids, and the peptization effect is moderate, so that catalyst particles with uniform pore distribution and larger pore size can be obtained; the mass of the acid is preferably 1 to 5 wt% of the powder mass, more preferably 2 to 4 wt%, such as 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, and preferably a range value with any of the above values ​​as the upper or lower limit.

[0052] In the present invention, the mass concentration of the acid solution is preferably 10 to 40 wt %, more preferably 15 to 35 wt %, such as 10 wt %, 15 wt %, 20 wt %, 25 wt %, 30 wt %, 35 wt %, or 40 wt %, preferably within a range with any of the above values ​​as the upper or lower limit. After adding the acid solution, mixing is preferably continued for 30 to 90 minutes, more preferably 30 to 50 minutes.

[0053] After kneading the acid solution, the present invention dissolves a trace amount of a halogen compound in water to prepare a halogen compound solution, which is evenly sprayed onto the surface of the material and kneaded for 30 to 90 minutes. Generally, halogens, as poisons, reduce activity. However, the present invention has found that introducing a trace amount of halogen during the molding process can effectively inhibit side reactions and improve the selectivity of acrylic acid.

[0054] In the present invention, the halogen compound is preferably a halogen salt and / or a halogen acid, such as one or more of HCl, HF, HBr, HI, NaF, NaCl, NaBr, NaI, KF, KCl, KBr, KI, MgCl2 and CaCl2; the mass of the halogen is preferably 0.002~0.03wt% of the powder mass, more preferably 0.008~0.025 wt%, such as 0.002 wt%, 0.005 wt%, 0.008wt%, 0.01 wt%, 0.015 wt%, 0.02 wt%, 0.025 wt%, 0.03 wt%, preferably a range value with any of the above values ​​as the upper or lower limit. The mass concentration of the halogen compound solution is preferably 1-10wt%, more preferably 3-8wt%, such as 1wt%, 2wt%, 3wt%, 4wt%, 5wt%, 6wt%, 7wt%, 8wt%, 9wt%, 10wt%, preferably a range value with any of the above values ​​as the upper or lower limit.

[0055] After spraying the halogen compound solution, kneading is continued for 30 to 90 minutes, more preferably 40 to 60 minutes.

[0056] In the present invention, the total amount of water in the kneaded material accounts for 20-45wt% of the powder mass, preferably 25-35wt%. If the amount of water is too little, the powder is relatively dry, the extrusion pressure is large, the elasticity is poor, and it is easy to break when drying, which is not conducive to pelletizing. If the amount of water is too high, the material is relatively sticky, the rod is seriously stuck, the extrusion speed is slow, and it is not conducive to pelletizing.

[0057] After the kneaded material is obtained, the present invention extrudes it into shape and then dries it to obtain a catalyst body.

[0058] The present invention preferably places the mixed and kneaded wet material dough into an extruder for extrusion molding. A twin-screw or single-screw extruder can be used. Different molds are used to extrude the powder into shapes such as cylindrical, Raschig ring, honeycomb, clover, four-leaf clover, internal gear, external gear, porous plum blossom, etc. The supporting pelletizing equipment is a rotating wire pelletizing, a blade pelletizing or a drum pelletizing, preferably a drum pelletizing.

[0059] In the present invention, the drying is preferably air drying or vacuum drying. Preferably, the particles are first dried at 30-60°C for 10-48 hours to allow the water to evaporate slowly, and then the temperature is raised to 90-120°C and the drying is continued for 24-48 hours. More preferably, the particles are first dried at 40-50°C for 12-24 hours, and then the temperature is raised to 100-110°C and deep drying is continued for 30-40 hours. The particles need to be slowly evaporated at low temperatures. If the evaporation rate is too fast at the beginning, the particles may crack, which in turn affects the mechanical strength.

[0060] The present invention places the dried catalyst body in an oxygen atmosphere for calcination, first calcining it at 180-280°C for 1-2 hours with a heating rate of 0.5-2°C / min, which should not be too fast, and then continuing to increase the temperature to 350-400°C with a heating rate of 1-3°C / min and continuing to calcine for 1-2 hours to obtain the final formed catalyst.

[0061] Preferably, the calcination is first carried out at 200-260° C. for 1-2 hours at a heating rate of 1-1.5° C. / min, and then the temperature is continuously raised to 360-380° C. at a heating rate of 1.5-2.5° C. / min, and the calcination is continued for 1-2 hours.

[0062] The present invention also provides a MoVTeNbOx-based metal oxide shaped catalyst, which is prepared according to the shaping method described above.

[0063] The present invention also provides an application of the above-mentioned MoVTeNbOx-based metal oxide shaped catalyst in the industrial production of acrylic acid by oxidation of propane.

[0064] The MoVTeNbOx-based metal oxide shaped catalyst prepared by the molding method of the present invention can be applied to the industrial production of propane oxidation to prepare acrylic acid. The inner diameter of the reactor used in the reaction is 24-26 mm, and molten salt or thermal oil is used for heating. The catalyst loading amount is 1-2 L. The catalyst is diluted with porcelain balls and then loaded. The volume percentage of the catalyst in the total loading amount is 70%-90%, more preferably 75-85%, such as 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, and preferably a range value with any of the above values ​​as the upper or lower limit.

[0065] The reactor is divided into three reaction zones from top to bottom: the upper section, the middle section and the lower section. Based on the total amount of material (catalyst + porcelain balls) in the reaction zone, the volume ratio of the upper section material (catalyst + porcelain balls) to the total material is 5-12%, the volume ratio of the middle section material to the total material is 13-25%, and the volume ratio of the lower section material to the total material is >70%. From top to bottom, the proportion of the catalyst in each reaction zone increases successively. In terms of volume fraction, in the upper reaction zone, the catalyst accounts for 30% to 50% of the total amount of the upper section loading, more preferably 35-45%, such as 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, preferably with any of the above values ​​as the upper or lower limit of the range value; in the middle reaction zone, the catalyst accounts for 50% to 70% of the total amount of the middle section loading. 5%, more preferably 55-65%, such as 50%, 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69%, 70%, 71%, 72%, 73%, 74%, 75%, preferably with the above arbitrary numerical value as the range value of the lower limit; in the lower section reaction zone, the catalyst accounts for 75%-100% of the total amount of the lower section loading, more preferably 80-95%, such as 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 100%, preferably with the above arbitrary numerical value as the range value of the upper limit or lower limit.

[0066] In the present invention, the inlet pressure of the reaction gas is preferably 50-150 KPa, more preferably 100-120 KPa, such as 50 KPa, 60 KPa, 70 KPa, 80 KPa, 90 KPa, 100 KPa, 110 KPa, 120 KPa, 130 KPa, 140 KPa, 150 KPa, preferably a range with any of the above values ​​as the upper or lower limit; the reaction gas is a mixed gas of propane, air, nitrogen and water vapor, and the absolute volume space velocity of propane to the catalyst is preferably 80-150 h -1 , more preferably 100~120 h -1 , such as 80h -1 , 90h -1 , 100 h -1 , 110 h -1 , 120 h -1 , 130 h -1 , 140 h -1 , 150 h -1 , preferably with any of the above numerical values ​​as the upper or lower limit of the range value; in the reaction gas, the inlet concentration of propane is preferably 6% to 12%, more preferably 7 to 11%, such as 6%, 7%, 8%, 9%, 10%, 11%, 12%, preferably with any of the above numerical values ​​as the upper or lower limit of the range value; the oxygen-alkyl ratio is preferably 1 to 2, more preferably 1.2 to 1.8, such as 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2, preferably with any of the above numerical values ​​as the upper or lower limit of the range value. the water-alkane ratio is preferably 0.8-3, more preferably 1-2.5, such as 0.8, 0.9, 1, 1.2, 1.5, 1.8, 2, 2.2, 2.5, 2.8, 3, preferably with any of the above values ​​as the upper or lower limit of the range; the reaction temperature is preferably 320-400 ° C, more preferably 350-380 ° C, such as 320 ° C, 330 ° C, 340 ° C, 350 ° C, 360 ° C, 370 ° C, 380 ° C, 390 ° C, 400 ° C, preferably with any of the above values ​​as the upper or lower limit of the range.

[0067] The invention provides a molding method for a MoVTeNbOx-based metal oxide shaped catalyst. The method comprises the following steps: A) mixing a MoVTeNbOx-based metal oxide raw powder catalyst, an inert substance and sesbania powder, kneading the mixture, and spraying an alkaline amino acid solution, an acid solution and a halogen compound solution in sequence during the kneading process to obtain a kneaded material, wherein the mass of the halogen in the halogen compound solution is 0.002-0.03 wt % of the total mass of the MoVTeNbOx-based metal oxide raw powder catalyst and the inert substance; B) extruding the kneaded material to form the mixture, and drying the mixture to obtain a catalyst body; and C) calcining the catalyst body at 180-280° C. for 1-2 hours, then heating the mixture and continuing to calcine at 350-400° C. for 1-2 hours to obtain the MoVTeNbOx-based metal oxide shaped catalyst. The present application introduces alkaline amino acids on the basis of conventional acidic peptizing agents. These amino acids have two amino groups and one carboxyl group, and are alkaline as a whole after ionization in water. The use of these alkaline amino acids in combination with conventional acidic peptizing agents can effectively regulate the strength of the peptization effect, thereby optimizing the secondary pore structure of the catalyst, so that the pore size distribution is concentrated from dispersed to macroporous, which is beneficial to the diffusion of acrylic acid molecules and greatly improves the selectivity. At the same time, in order to suppress excessive oxidation, trace halogens are creatively introduced as inhibitors during the molding process. Halogens are generally regarded as toxic substances that will poison the catalyst. The addition of alkaline amino acids and inhibitors enables the MoVTeNbOx catalyst to obtain more than 80% acrylic acid selectivity, greatly reducing the formation of by-products.

[0068] To further illustrate the present invention, a shaped catalyst of a MoVTeNbOx-based metal oxide, a shaping method thereof, and applications provided by the present invention are described in detail below in conjunction with examples. However, these examples should not be construed as limiting the scope of protection of the present invention.

[0069] Preparation of raw powder catalyst:

[0070] 54L of deionized water was placed in a stirring kettle, heated to 70°C, and 3965g of ammonium molybdate (H 24 Mo7N6O 24 ·4H2O), 1010.8g ammonium paratungstate (H 40 N 10 O 41 W 12•xH2O), 927.3g ammonium metavanadate (NH4VO3), 573.6g cerium nitrate (Ce(NO3)3·6H2O), 1274.1g telluric acid (H6TeO6) and 189.1g 50wt% manganese nitrate (Mn(NO3)2) solution. It is necessary to wait until the previous substance is completely dissolved before adding the next substance. After all substances are completely dissolved, continue stirring for 1 hour, then cool the solution to room temperature (25℃). The solution is marked as A; 1705.9g niobium oxalate (C 10 H5NbO 20 ) was dissolved in 16 L of deionized water, and the solution was labeled B. Under stirring, solution B was added dropwise to solution A at a rate of 80 mL / min. During the addition, the solution gradually became turbid and a precipitate was formed, which was labeled C. 76.9 g of cobalt nitrate (Co(NO3)2·6H2O), 135.5 g of magnesium nitrate (Mg(NO3)2·6H2O), 11.2 g of sodium nitrate (NaNO3), and 6.7 g of potassium nitrate (KNO3) were dissolved in 500 mL of deionized water, and the solutions were labeled D, E, and F, respectively. Solutions D, E, and F were added dropwise to the coprecipitation slurry C at a rate of 10 mL / min, forming slurry G. The pH was adjusted to 2.0 with a 20 wt% nitric acid solution.

[0071] The slurry G was dried and dehydrated using a rotary spray dryer with an inlet air temperature of 180°C and an outlet temperature of 85-90°C. The feed rate was appropriately adjusted according to the change in the outlet air temperature. The obtained yellow precursor powder was placed in a vacuum drying oven at 70°C for further drying for 48 hours, and the powder was crushed to about 50 μm using a pulverizer.

[0072] The obtained material was placed in a rotary tube furnace, and heated to 330°C at a rate of 2°C / min for 6 hours in an air atmosphere of 400 mL / min. During the heating process, the ammonium, nitrate, and oxalate in the material decomposed to release gases such as NO, NO2, CO, CO2, and N2. Subsequently, the reaction atmosphere was switched to N2, and the temperature was continued to be raised to 600°C for 1 hour. After cooling, the material was taken out and crushed to less than 20 μm using an ultrafine grinder. After removing the loss, about 4 kg of the original powder catalyst was obtained. The molar composition of each element in the catalyst is (Mo 0.85 +W 0.15 )V 0.3 Ce 0.05 Te 0.21 Mn 0.02 Nb 0.12 Co 0.01 Mg 0.02 Na 0.005 K 0.0025 O x , denoted as H.

[0073] Example 1

[0074] 1000g of raw powder H, 700g of silicon carbide, and 300g of quartz powder were mixed uniformly and placed in a biaxial kneader. 80g of sesbania powder with a particle size of approximately 100 mesh was added and the kneader was started. During the kneading process, 300mL of a 20wt% lysine solution was evenly sprayed on the powder surface. After spraying, kneading was continued for 45 minutes. A 30wt% nitric acid solution was prepared and 200mL of the nitric acid solution was sprayed on the powder surface. After kneading for 30 minutes, 200mL of a 0.1wt% NaCl solution was evenly sprayed into the powder. The powder was kneaded for another 60 minutes before removal. Water accounted for 35wt% of the total powder mass. The kneader lid was tightly closed during the kneading process to maintain a stable moisture content. The water-to-powder ratio has a significant impact on the plasticity and mechanical strength of the wet dough.

[0075] The kneaded material was placed in a twin-screw extruder, and a 5mm×2mm Raschig ring grinder was selected. The extruded strips were cut into granules with a length of 4mm using a rotary drum pelletizer. The catalyst was placed in a vacuum oven and first dried at 50°C for 24h to allow the water to evaporate slowly. The temperature was then raised to 110°C and deep dried for 36h before being taken out. The completely dried catalyst was placed in a tubular furnace and heated to 260°C at a rate of 1.5°C / min in an air atmosphere of 500mL / min and calcined for 2h. The temperature was then continued to be raised to 380°C and calcined for 1.5h. Finally, about 2 kg of 5mm×2mm×4mm Raschig ring catalyst was obtained.

[0076] Example 2

[0077] During the kneading process, 300 mL of a 20 wt% arginine solution was sprayed on the powder surface, and kneading was continued for 45 min. Then, 200 mL of a 30 wt% tartaric acid solution was evenly sprayed on the powder surface, and kneading was continued for 30 min. The other preparation conditions were the same as those in Example 1.

[0078] Example 3

[0079] During the kneading process, 300 mL of a 20 wt % glutamic acid solution was first sprayed, and kneading was continued for 45 min. Then, 200 mL of a 30 wt % acetic acid solution was sprayed, and kneading was continued for 30 min. The other conditions were the same as in Example 1.

[0080] Example 4

[0081] During the kneading process, 300 mL of a mixed solution of lysine and arginine was sprayed on the surface of the powder, wherein the content of the two acids was 10 wt % each. The other conditions were the same as those in Example 1.

[0082] Example 5

[0083] During the kneading process, 300 mL of a mixed solution of lysine, arginine and glutamic acid was sprayed on the surface of the powder, wherein the lysine content was 10 wt % and the contents of the other two acids were 5 wt % each. After kneading for 45 minutes, 200 mL of a mixed solution of formic acid and lactic acid was continued to be sprayed, wherein the contents of the two acids were 15 wt % each. The other conditions were the same as in Example 1.

[0084] Example 6

[0085] During the kneading process, lysine and nitric acid solutions were first sprayed, and then 200 mL of 0.1 wt % KF solution was sprayed, and kneading was continued for 60 min. The other conditions were the same as in Example 1.

[0086] Example 7

[0087] During the kneading process, arginine and tartaric acid solutions were first sprayed, and then 200 mL of a mixed solution of NaCl and NaBr was sprayed. The contents of the two substances in the solution were 0.04 wt % and 0.06 wt %, respectively. The other conditions were the same as in Example 2.

[0088] Example 8

[0089] During the kneading process, glutamic acid and acetic acid solutions were first sprayed, and then 200 mL of NaF and MgCl2 solutions were sprayed. The concentrations of the two substances were 0.02 wt% and 0.03 wt%, respectively. The other conditions were the same as those in Example 3.

[0090] Example 9

[0091] The material composition, kneading and extrusion molding process are the same as those in Example 1. The formed granular catalyst is dried in a vacuum oven at 60°C for 12 hours, then heated to 110°C and dried for 24 hours before being taken out and calcined. The calcination process is the same as that in Example 1.

[0092] Example 10

[0093] The material composition, kneading, extrusion molding and drying process are the same as in Example 2. The dried granular catalyst is placed in a tubular furnace, heated to 280°C at a rate of 2°C / min in an air atmosphere of 400 mL / min, and calcined for 2 h. Then, the temperature is continued to be raised to 360°C and calcined for 2 h before being taken out.

[0094] Example 11

[0095] The material composition, kneading, extrusion molding and drying process are the same as in Example 2. The dried granular catalyst is placed in a tubular furnace, heated to 270°C at a rate of 2°C / min in an air atmosphere of 400 mL / min, and calcined for 2 h. Then, the temperature is continued to be raised to 380°C and calcined for 2 h before being taken out.

[0096] Example 12

[0097] The material composition, kneading, extrusion molding and drying process are the same as in Example 3. The dried granular catalyst is placed in a tubular furnace, and in an air atmosphere of 300 mL / min, the temperature is increased to 280°C at a rate of 1.5°C / min and calcined for 2 h. Then, the temperature is increased to 400°C at a rate of 3°C / min and calcined for 1 h before being taken out.

[0098] Comparative Example 1

[0099] During the kneading process, 300 mL of deionized water was used instead of 300 mL of 20 wt % lysine solution, that is, no lysine was added. The other conditions were the same as those in Example 1.

[0100] Comparative Example 2

[0101] During the kneading process, 300 mL of deionized water was used instead of 300 mL of 20 wt % arginine, that is, no arginine was added. The other conditions were the same as those in Example 2.

[0102] Comparative Example 3

[0103] During the kneading process, 300 mL of deionized water was used instead of 300 mL of 20 wt % glutamic acid solution, that is, no glutamic acid was added during the kneading process. The other conditions were the same as those in Example 3.

[0104] Comparative Example 4

[0105] During the kneading process, 200 mL of a 0.8 wt % KF solution was sprayed, where KF accounted for approximately 0.08 wt % of the powder mass. The remaining conditions were the same as those in Example 1.

[0106] Comparative Example 5

[0107] During the kneading process, 200 mL of a mixed solution of NaCl and NaBr with a concentration of 0.8 wt % was sprayed. The concentrations of the two substances were 0.4 wt % each, and the two substances accounted for 0.08 wt % of the total mass of the powder. The other conditions were the same as in Example 2.

[0108] Comparative Example 6

[0109] The kneading and extrusion process was the same as in Example 9. The pelletized catalyst was dried in a vacuum oven at 110° C. for 48 h and then taken out and calcined. The calcination conditions were also the same as in Example 9.

[0110] Comparative Example 7

[0111] The kneading, extrusion and drying processes were the same as those in Example 10. The dried catalyst was placed in a tubular furnace and heated at 2°C / min to 360°C in an air atmosphere of 400 mL / min for 2 h before being taken out.

[0112] Comparative Example 8

[0113] The kneading, extrusion and drying processes were the same as those in Example 11. The dried catalyst was placed in a tubular furnace and heated to 270°C at a rate of 2°C / min in an air atmosphere of 400 mL / min, and calcined for 2 h. The temperature was then continued to rise to 450°C and calcined for 2 h before being taken out.

[0114] Comparative Example 9

[0115] During the kneading process, 300 mL of 20 wt % ammonia solution was sprayed on the powder surface to replace the lysine solution. The rest of the process was the same as in Example 1.

[0116] Comparative Example 10

[0117] During the kneading process, 300 mL of urea solution with a concentration of 20 wt % was sprayed on the surface of the powder to replace the arginine solution. The rest of the process was the same as in Example 2.

[0118] Table 1 Strength data of the molded catalysts obtained in Examples and Comparative Examples

[0119]

[0120] Table 1 gives the strength data of the catalyst after molding. It can be seen from Table 1 that the mechanical strength of the catalyst is all>60N / cm, which meets the strength requirements of industrial applications. The mechanical strength of Examples 1, 4, 6, and 9 is significantly higher than that of other embodiments. This is because the degree of ionization of nitric acid is large and it is completely ionized in water. As a peptizing agent, its peptization effect is stronger than formic acid, acetic acid, lactic acid, and tartaric acid, and the particles are more closely bound, and the mechanical strength is high. With reference to Examples 1, 2, and 3 and Comparative Examples 1, 2, and 3, the addition of basic amino acids has no significant effect on mechanical strength. With reference to Examples 6 and 7 and Comparative Examples 4 and 5, halogen has no significant effect on mechanical strength. With reference to Examples 1 and 2 and Comparative Examples 9 and 10, ammonia and urea have no significant effect on strength. In addition, with reference to Comparative Example 6 and Example 9, the water evaporation rate is too fast during the drying process, and the mechanical strength will decrease. The higher the roasting temperature, the higher the mechanical strength, as in Comparative Example 8.

[0121] Application Examples

[0122] Activity evaluation was conducted using a 6m long, 26mm inner diameter tubular reactor. The catalyst loading was 1800mL, and the catalyst was diluted with 450mL of 3mm diameter porcelain balls. The catalyst-to-ceramic-ball volume ratio was 80:20, and the reactor was loaded in three sections: upper, middle, and lower. First, 50mL of porcelain balls were loaded to support the bottom. 1476mL of catalyst and 165mL of porcelain balls were mixed and loaded into the reactor as the lower reaction zone. 240mL of catalyst and 160mL of porcelain balls were mixed and loaded into the middle reaction zone. 84mL of catalyst and 125mL of porcelain balls were mixed and loaded into the upper reaction zone. Finally, 100mL of porcelain balls were loaded into the reactor as the preheating zone for the reaction gas. The catalyst proportions in the three reaction zones, from top to bottom, were 40%, 60%, and 90%, respectively. Molten salt was used for heating, the reaction temperature was 360°C, and the absolute volume space velocity of propane over pure catalyst was 90h / min. -1 , water-alkane ratio is 1.5, oxygen-alkane ratio is 1.8, propane inlet volume concentration is 7%, corresponding to propane flow rate is 162L / h, air velocity is 1388L / h, water vapor velocity is 194L / h, nitrogen velocity is 570L / h, and the volume space velocity of the total gas to the entire material bed is 1028h -1 The inlet gas pressure was maintained at 80 kPa by the back pressure at the end outlet. Table 2 shows the single-tube evaluation results of the catalyst.

[0123] Table 2 Single-tube evaluation results of catalysts

[0124]

[0125] Table 2 shows the results of single-tube evaluation. In Examples 1-5, after adding an appropriate amount of basic amino acid during the kneading process, the propane conversion rate was 57%-64%, and the acrylic acid selectivity was 77%-79%, showing high conversion rate and selectivity. After introducing an appropriate amount of halogen, as in Examples 6-8, the activity dropped significantly to 47%-51%, but the acrylic acid selectivity reached a maximum of 81%, and carbon oxides were significantly suppressed. Referring to Examples 9-12, the overall performance of the catalyst did not change much when drying and calcining were carried out within the appropriate temperature range.

[0126] In Comparative Examples 1-3, no basic amino acid was added during kneading, resulting in conversions of 62%-66%, slightly higher than those obtained with the addition of basic amino acids. However, the acrylic acid selectivity was only 70%-72%, significantly lower than the 77%-79% acrylic acid selectivity in Examples 1-5, with significantly higher acetic acid and carbon oxides. In Comparative Examples 4 and 5, excessive halogen was added, severely poisoning the catalysts. The propane conversion dropped significantly to 28% and 31%, respectively, and the acrylic acid selectivity also dropped to approximately 70%. The remaining product was primarily propylene, at 16% and 20%, respectively, significantly exceeding acetic acid and carbon oxides. Excessive water evaporation during the drying process did not affect activity and selectivity, but reduced mechanical strength (Comparative Example 6). Referring to Comparative Examples 7 and 8, excessively high air calcination temperatures reduced both catalyst activity and selectivity, and even deactivated the catalyst. In Comparative Examples 9 and 10, replacing the basic amino acids with alkaline aqueous ammonia and urea solutions did not improve acrylic acid selectivity, resulting in only approximately 70% acrylic acid, with higher acetic acid and carbon oxides.

[0127] In Example 7, the single-pass conversion of propane was 49%, the selectivity for acrylic acid was 81%, and the selectivity for propylene was 6%. Propylene is an intermediate product in the oxidation of propane to acrylic acid. It can be recycled with unreacted propane and then re-entered into the reactor for oxidation to acrylic acid. The essence of propane oxidation is dehydrogenation to produce propylene, which is further oxidized to acrylic acid. If propane-propylene recycling is achieved, the selectivity for acrylic acid to propane can reach 85.86%, reducing the unit consumption per ton of acrylic acid to 0.711 tons. Acetic acid is also present at 5%, which can be recovered as a high-value byproduct. The combined selectivity for acrylic acid and acetic acid exceeds 90%. Therefore, the introduction of basic amino acids and an appropriate amount of halogen during the molding process greatly improves propane utilization.

[0128] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for forming a MoVTeNbOx-based metal oxide formed catalyst, comprising the following steps: A) mixing a raw powder of a MoVTeNbOx metal oxide catalyst, an inert substance, and sesbania powder, and kneading the mixture. During the kneading process, an alkaline amino acid solution, an acid solution, and a halogen compound solution are sequentially sprayed to obtain a kneaded material; The mass of the halogen compound in the halogen compound solution is 0.002-0.03 wt% of the total mass of the MoVTeNbOx metal oxide raw powder catalyst and the inert substance; Basic amino acids include one or more of lysine, histidine and arginine; The mass of the basic amino acid is 1 to 8 wt% of the total mass of the MoVTeNbOx metal oxide raw powder catalyst and the inert material; The dissociation constant pKa of the acid in the acid solution is 2.5 to 5; The acid in the acid solution comprises one or more of nitric acid, sulfuric acid, lactic acid, benzoic acid, phthalic acid, oxalic acid, tartaric acid, citric acid, sulfurous acid, acetic acid, formic acid and trichloroacetic acid; The mass of the acid in the acid solution is 1 to 5 wt% of the total mass of the MoVTeNbOx metal oxide raw powder catalyst and the inert substance; B) extruding the mixed material and drying it to obtain a catalyst body; C) calcining the catalyst body at 180-280° C. for 1-2 hours, then heating it up and continuing calcining it at 350-400° C. for 1-2 hours to obtain a MoVTeNbOx-based metal oxide shaped catalyst.

2. The molding method according to claim 1, characterized in that The inert substance is silicon carbide and / or quartz powder; The mass of the inert substance is 20-60 wt % of the total mass of the MoVTeNbOx metal oxide raw powder catalyst and the inert substance.

3. The molding method according to claim 1, characterized in that The mass of the sesbania powder is 2-8 wt % of the total mass of the MoVTeNbOx series metal oxide raw powder catalyst and the inert material.

4. The molding method according to claim 1, characterized in that The mass concentration of the alkaline amino acid solution is 10-35 wt%.

5. The molding method according to claim 1, characterized in that The mass concentration of the acid solution is 10-40 wt%.

6. The molding method according to claim 1, characterized in that Halogen compounds include one or more of HCl, HF, HBr, HI, NaF, NaCl, NaBr, NaI, KF, KCl, KBr, KI, MgCl2 and CaCl2; The mass concentration of the halogen compound solution is 1 to 10 wt%.

7. The molding method according to claim 1, characterized in that: In the mixed material, the mass of water is 20 to 45 wt % of the total mass of the MoVTeNbOx metal oxide raw powder catalyst and the inert substance.

8. The molding method according to claim 1, characterized in that: The drying in step B) specifically includes: First dry at 30-60℃ for 10-48 hours, then increase the temperature to 90-120℃ and continue drying for 24-48 hours.

9. A MoVTeNbOx-based metal oxide molded catalyst obtained by the molding method according to any one of claims 1 to 8.

10. Use of the MoVTeNbOx-based metal oxide shaped catalyst according to claim 9 in the industrial production of acrylic acid by oxidation of propane; In the industrial production of propane oxidation to prepare acrylic acid, the catalyst loading amount is 1 to 2 L. The catalyst is diluted with porcelain balls and then loaded. The volume percentage of the catalyst in the total loading amount is 70% to 90%. The inlet pressure of the reaction gas is 50 to 150 kPa. The reaction gas is a mixture of propane, air, nitrogen, and water vapor. The absolute volume space velocity of propane to the catalyst is 80 to 150 h -1 , propane inlet concentration 6% to 12%, oxygen to alkane ratio 1 to 2, water to alkane ratio 0.8 to 3, reaction temperature 320 to 400°C; The reactor is divided into three reaction zones from top to bottom: upper section, middle section and lower section. The proportion of catalyst increases successively: the catalyst in the upper section accounts for 30% to 50% of the total amount of the upper section, the catalyst in the middle section accounts for 50% to 75% of the total amount of the middle section, and the catalyst in the lower section accounts for 75% to 100% of the total amount of the lower section.

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