A method for tableting a Cr-based catalyst

Abstract

This invention discloses a method for tableting a Cr-based catalyst. The method includes: (1) preparing Cr-based catalyst powder by co-precipitation; the Cr-based catalyst powder is a calcined powder; (2) mixing the Cr-based catalyst powder obtained in step (1), an aqueous solution of auxiliary agent I, and selectively added water to obtain a mixed material; (3) drying, crushing, and sieving the mixed material obtained in step (2), then mixing it with auxiliary agents II and III, and tableting it to obtain a tablet; (4) calcining the tablets prepared in step (3) to obtain the tableted catalyst. The Cr-based catalyst prepared by this method has no problems such as delamination, transverse cracking, or cap removal, and its physicochemical properties are stable.

Description

TECHNICAL FIELD

[0001] The application relates to a tablet compression molding method of a Cr-based catalyst and belongs to the technical field of catalyst preparation. BACKGROUND

[0002] Tablet compression molding is a process for realizing catalyst molding by applying pressure to change the density and strength of catalyst powder particles. Compared with other catalyst molding methods, the tablet compression molding method has the following advantages: the molded product has consistent particle size and uniform quality; a product with high bulk density can be obtained, and the catalyst has good strength; and the catalyst surface is smooth. Therefore, the tablet compression molding method has wide industrial application value. The tablet compression process includes six processes of filling and feeding, powder thickening, compaction, deformation (elastic deformation and plastic deformation), particle rupture and pressure rebound, and in these processes, the powder properties have a crucial influence on the compression molding.

[0003] As a material with large density and high brittleness, the Cr-based catalyst has weak compression ability and small deformation degree, which leads to many difficulties in the industrial catalyst preparation process. First, the small compression ratio of the powder caused by high brittleness leads to a high dead point position of the upper punch (i.e. the position reaching the pressure limit) under the same pressure condition, thereby causing the molded body to be too high in height and unable to meet the height requirement; if the height of the molded body meets the requirement, the pressure given by the machine needs to be further increased, which will cause the particles to start to break under the action of excessive stress. In addition, in the tablet ejection process, the small compression ratio of the powder causes the tablet to easily produce slight elastic expansion when the pressure given by the machine is withdrawn, which causes the molded body to break. These phenomena lead to a narrow adjustable range of the tablet press parameters and a low fault tolerance of the tablet compression process in the Cr-based catalyst molding process. Therefore, it is urgent to seek a method for optimizing the properties of the Cr-based catalyst powder and improving the fault tolerance of the tablet compression process.

[0004] CN109569742A discloses a method for improving the tablet compression molding strength of a silicon-based catalyst. The method comprises the following steps: (a) granulating the catalyst to obtain catalyst particles with a size of 1-6 mm; (b) crushing and screening the catalyst particles obtained in step (a) to obtain catalyst particles with a size of 10-60 mesh; and (c) mixing the catalyst particles obtained in step (b) with catalyst powder with a particle size less than 60 mesh, and then performing tablet compression molding to obtain the catalyst. The method is suitable for the tablet compression molding of a silicon-based catalyst, and is not applicable to the tablet compression molding of a Cr-based catalyst because the properties of the Cr-based catalyst are different from those of the silicon-based catalyst. SUMMARY

[0005] In view of the deficiencies in the prior art, the present application provides a tabletting forming method of Cr-based catalyst. The method can effectively improve the compression ratio of the added material, improve the fault tolerance rate of the tabletting process, and the prepared Cr-based catalyst has no problems such as delamination, transverse cracking, cap removal, etc., and has stable physicochemical properties. The radial strength, height, specific surface area, average pore size, and pore volume of the catalyst forming body meet the application indexes, and can be applied to ester hydrogenation or alcohol dehydrogenation reactions.

[0006] The present application provides a tabletting forming method of Cr-based catalyst, comprising:

[0007] (1) preparing a Cr-based catalyst powder by a co-precipitation method; the Cr-based catalyst powder is a calcined powder;

[0008] (2) mixing the Cr-based catalyst powder obtained in step (1), an aqueous solution of additive I, and optionally added water to obtain a mixed material;

[0009] (3) drying, crushing, and sieving the mixed material obtained in step (2), and then mixing with additive II and additive III, and tabletting to obtain tablets;

[0010] (4) calcining the tablets prepared in step (3) to obtain the formed catalyst.

[0011] Further, in the Cr-based catalyst powder obtained in step (1), the mass fraction of Cr is 40wt%-100wt%. Preferably, the Cr-based catalyst powder can further comprise a metal additive selected from at least one of Cu and Fe. The metal additive accounts for 0wt%-60wt% of the mass of the Cr-based catalyst powder.

[0012] Further, the co-precipitation method in step (1) can be carried out by a conventional method, such as: metal salt solution, lye is added to the reactor in parallel flow or positive or negative form, and reacted at 30℃-90℃ for 1h-2h, the reaction pH value is maintained at 6.0-9.0, and the slurry is filtered, washed, and dried to prepare the catalyst precursor. The metal salt solution is an acidic solution, Cr exists in the form of chromic anhydride and / or chromium nitrate, and other metal additives exist in the form of at least one of nitrate, sulfate or chloride. The lye is at least one of ammonia water, ammonium carbonate solution, ammonium bicarbonate solution, sodium carbonate solution, sodium bicarbonate solution, and sodium hydroxide solution.

[0013] Further, the Cr-based catalyst powder in step (1) is a calcined powder, and the calcination conditions are as follows: the calcination temperature is 350℃-650℃, the calcination time is 3h-6h, and the calcination atmosphere is an oxygen-containing atmosphere, such as air.

[0014] Further, in step (2), the auxiliary I is cellulose; preferably at least one selected from carboxymethyl cellulose, hydroxypropyl methyl cellulose; further preferably, the viscosity of carboxymethyl cellulose is 200 mpa.s-1000 mpa.s, and the viscosity of hydroxypropyl methyl cellulose is 2000 mpa.s-6500 mpa.s. In the aqueous solution of the auxiliary I, the mass content of cellulose is 1wt%-10wt%.

[0015] Further, in step (2), the auxiliary I is added in an amount of 1wt%-3wt% of the Cr-based catalyst powder.

[0016] Further, in step (2), the water is added in an amount to make the final water content of the prepared mixture 50wt%-80wt%.

[0017] Further, in step (3), the drying temperature is 80°C-120°C, and the water content of the material after drying is 2wt%-10wt%.

[0018] Further, in step (3), the breaking mode can be swing granulation and / or mechanical ball milling.

[0019] Further, in step (3), the sieving is divided into three parts according to ≥40 mesh and <80 mesh, 80 mesh-120 mesh, and >120 mesh, and the three parts of materials are mixed in a mass ratio of 10-20:60-80:5-10.

[0020] Further, in step (3), the auxiliary II is graphite, and the graphite is at least one of natural graphite and artificial graphite. The natural graphite is, for example, flake graphite. The particle size of the auxiliary II is 200 mesh or more, and preferably 400 mesh-2000 mesh.

[0021] Further, in step (3), the auxiliary II is added in an amount of 0.5wt%-3wt% of the Cr-based catalyst powder.

[0022] Further, in step (3), the auxiliary III is at least one of starch, epoxy resin, carboxymethyl cellulose, hydroxypropyl methyl cellulose, polyvinyl alcohol, sesbania powder, and stearic acid.

[0023] Further, in step (3), the auxiliary III is added in an amount of 1wt%-5wt% of the Cr-based catalyst powder.

[0024] Further, in step (4), the calcination temperature is 300°C-600°C, the heating rate is 0.5°C / min-5°C / min, and the calcination time is 2h-8h.

[0025] Further, the shaped catalyst is preferably cylindrical, with a diameter of 3.0mm to 5.0mm and a height of 2.5mm to 6.0mm. For example, the commonly used specifications in industry are 3mm x 2.5mm to 3mm x 3.5mm or 5mm x 4mm to 5mm x 6mm.

[0026] The second aspect of the present application provides the Cr-based catalyst prepared by the above method.

[0027] Further, the Cr-based catalyst has a radial strength of 50N / particle or more, preferably 60N / particle to 120N / particle, a specific surface area of 20m 2 / g to 50m 2 / g, an average pore size of 15nm to 35nm, and a pore volume of 0.08cm 3 / g to 0.15cm 3 / g.

[0028] Further, the application field of the catalyst is ester hydrogenation or alcohol dehydrogenation.

[0029] Compared with the prior art, the present application has the following beneficial effects:

[0030] (1) The Cr-based catalyst powder is first mixed with the additive I, which has the following effects: one is to help the catalyst powder to form clusters with certain strength, and to obtain a pre-dense material. The hardness of the pre-dense material is much greater than that of the catalyst powder, so that the material in the mold is more easily compressed after being subjected to the pressure of the punch. The pre-dense material can optimize the mechanical properties of the material, so that the deformation ability of the shaped body is greater. The other effect is that the interaction between the additive I and the powder particles produces crystallization, adhesion and surface tension effect, which can increase the plasticity of the powder particles and optimize the compression performance of the catalyst powder. In combination with the screening process, the large particles and small particles can be closely packed in the filling step, so as to ensure the filling efficiency in the filling step. Through the synergistic effect of steps (2) and (3), the powder compression performance can be optimized to the greatest extent, the height of the finished tablet is further reduced under the premise of meeting the strength index and particle packing index of the tablet, and the reduction space can reach 9%.

[0031] (2) In the process of the second calcination of the catalyst, the additive I and the additive III are partially pyrolyzed, and the pyrolysis components are volatilized in the form of gas, so as to realize pore formation. The average pore size of the shaped catalyst is increased, and the internal diffusion rate of the reactants and products in the catalyst during the reaction process is further improved.

[0032] (3) In the process of treating the catalyst powder, tabletting and calcining, the introduced components can be pyrolyzed and volatilized in the process of the second calcination or are chemically inert. Therefore, the stable shaping of the catalyst and the maintenance of the reaction activity of the catalyst can be realized without changing the composition of the catalyst by using the method of the present application.

[0033] (4) The application can effectively improve the adjustability of the tabletting process and help the stable operation of the tabletting process by comprehensively treating the Cr-based catalyst powder to obtain a material with optimized compression performance and increased compression ratio. DETAILED DESCRIPTION

[0034] The application will be described in detail below with reference to examples, but the application is not limited to these examples. The raw materials in the examples of the application are all purchased through commercial channels unless otherwise specified. In the examples, the technical means used are conventional in the art unless otherwise specified.

[0035] In the application, the strength is measured by a ZQJ-III intelligent particle strength tester, and the average radial strength value is obtained by multiple measurements.

[0036] In the application, the height of the catalyst shaped body is measured by a vernier caliper, and the average height value is obtained by multiple measurements.

[0037] In the application, the specific surface area, average pore size, and pore volume of the catalyst are analyzed by a N2 physical adsorption-desorption instrument. A small amount of the shaped catalyst is weighed, treated at 300°C under vacuum conditions for 3h, cooled to room temperature, and then subjected to N2 blowing at different pressures under liquid nitrogen temperature to obtain N2 physical adsorption-desorption isotherms, which are analyzed to obtain the surface area, pore size distribution, and pore volume of the catalyst shaped body by BET fitting formula, BJH, and t-plot method, respectively.

[0038] Example 1

[0039] (1) A 1 mol / L chromium nitrate solution and a 1 mol / L copper nitrate solution are prepared as A liquid, and 8% ammonia water is prepared as B liquid. The A liquid and the B liquid are added to a reaction kettle in parallel flow, and the reaction is carried out at 40°C for 1h, with the pH value maintained at 8.0±0.1 during the reaction. The obtained slurry is aged at room temperature for 6h and then filtered. The filter cake is washed with deionized water until the effluent is neutral, and then the filter cake is dried at 100°C. After cooling to room temperature, the precursor is calcined at 500°C for 4h in an air atmosphere to obtain a catalyst powder. In the catalyst powder, Cr exists in the form of Cr2O3 and CuCr2O4, and the mass fraction of Cr is 40wt%.

[0040] (2) A 5wt% mass fraction carboxymethyl cellulose solution is prepared, wherein the viscosity of the carboxymethyl cellulose is 800mpa.s. After stirring and mixing at room temperature until a viscous state and no white agglomerates are formed, 100g of the solution is added to 200g of the catalyst powder, and 50g of deionized water is further added and mixed uniformly. In the prepared mixed material, the amount of additive I added is 2.5wt% of the catalyst powder, and the water content of the mixed material is 72.5wt%.

[0041] (3) The mixed material obtained in step (2) was dried at 100°C for 4h, and the moisture content of the dried material was measured to be 4wt%. The broken mixed material was obtained by ball milling at 100rpm for 15min, and then was sieved. The mass of the powders with size ≥40 mesh and <80 mesh, 80-120 mesh, and >120 mesh was 20g, 70g, and 10g, respectively. The three portions of the powders were mixed uniformly, and then 3g of flake graphite (400 mesh) and 2g of starch were added thereto, and mixed again. The uniformly mixed material was poured into the hopper of a tablet machine, and tablets with a size of 3mm x 3mm were prepared.

[0042] (4) The tablets were calcined at 500°C for 4h with a heating rate of 2°C / min, and a shaped catalyst was obtained.

[0043] Example 2

[0044] (1) A 1 mol / L chromium anhydride solution was prepared as A liquid, and a 1 mol / L ammonium carbonate was prepared as B liquid. The A liquid and the B liquid were added into a reaction kettle in parallel flow, and reacted at 50°C for 2h while maintaining the pH value at 7.0±0.1. The obtained slurry was aged at 50°C for 2h, and then was filtered. The filter cake was washed with deionized water until the effluent was neutral, and then was dried at 100°C. After the temperature was lowered to room temperature, the precursor was calcined at 500°C for 4h, and a catalyst powder was obtained. Cr was present in the form of Cr2O3.

[0045] (2) A 4wt% carboxymethyl cellulose solution was prepared, wherein the viscosity of the carboxymethyl cellulose was 600mpa.s. After stirring at room temperature until the solution was thick and no white agglomerates were present, 150g of the solution was added to 200g of the catalyst powder and mixed uniformly. In the obtained mixed material, the amount of the additive I was 3wt% of the catalyst powder, and the water content of the mixed material was 72wt%.

[0046] (3) The mixed material obtained in step (2) was dried at 100°C for 4h, and the moisture content of the dried material was measured to be 2wt%. The broken mixed material was obtained by a swing granulator, and then was sieved. The mass of the powders with size ≥40 mesh and <80 mesh, 80-120 mesh, and >120 mesh was 10g, 80g, and 10g, respectively. The three portions of the powders were mixed uniformly, and then 1g of flake graphite (1600 mesh) and 3g of polyvinyl alcohol were added thereto, and mixed again. The uniformly mixed material was poured into the hopper of a tablet machine, and tablets with a size of 3mm x 3mm were prepared.

[0047] (4) The tablets were calcined at 500°C for 4h with a heating rate of 2°C / min, and a shaped catalyst was obtained.

[0048] Example 3

[0049] (1) Prepare a mixed solution of 1 mol / L chromium nitrate and 1 mol / L ferric nitrate as solution A, and prepare a 1 mol / L ammonium bicarbonate solution as solution B. Add solutions A and B concurrently to the reactor and react at 50℃ for 1 h, maintaining the pH at 6.5±0.1 during the reaction. The resulting slurry is aged at 50℃ for 4 h and then filtered. After washing with deionized water until the effluent is neutral, the filter cake is dried at 100℃. After cooling to room temperature, the precursor is calcined at 450℃ for 4 h to obtain catalyst powder. Cr exists in the form of Cr2O3.

[0050] (2) Prepare a 10 wt% carboxymethyl cellulose solution, wherein the viscosity of the carboxymethyl cellulose is 1000 mPa·s. Stir and mix at room temperature until a viscous consistency is achieved and no white agglomerates remain. Then, take 50 g of this solution and 100 g of water and add them to 200 g of catalyst powder and mix thoroughly. In the prepared mixture, the amount of additive I added is 2.5 wt% of the catalyst powder, and the water content of the mixture is 72.5 wt%.

[0051] (3) The mixture obtained in step (2) was dried at 100℃ for 4 hours, and the moisture content of the dried material was measured to be 2wt%. The crushed mixture was obtained by a gyratory granulator and then sieved. 20g, 70g, and 10g of powder with a mesh size ≥40 and <80, 80-120, and >120 mesh were weighed, respectively. The three portions of material were mixed evenly, and then 0.5g of flake graphite and 3g of carboxymethyl cellulose were added and mixed evenly again. The evenly mixed material was poured into the hopper of a tablet press and compressed into tablets at a size of 3mm × 3mm to obtain tablets.

[0052] (4) The tablets were calcined at 450°C for 3 hours with a heating rate of 2°C / min to obtain the shaped catalyst.

[0053] Example 4

[0054] (1) Prepare solution A with 1 mol / L chromic anhydride and 1 mol / L ferric nitrate, and solution B with 2 mol / L sodium carbonate. Add solutions A and B concurrently to the reactor and react at 30°C for 1.5 h, maintaining the pH at 7.0 ± 0.1 during the reaction. The resulting slurry is aged at 30°C for 6 h and then filtered. After washing with deionized water until the effluent is neutral, the filter cake is dried at 100°C. After cooling to room temperature, the precursor is calcined at 400°C for 3 h to obtain catalyst powder. Cr exists in the form of Cr₂O₃.

[0055] (2) Prepare a 5 wt% hydroxypropyl methylcellulose solution, wherein the viscosity of the hydroxypropyl methylcellulose is 6000 mPa·s. Stir and mix at room temperature until a viscous consistency is achieved and no white agglomerates remain. Then, take 100 g of this solution and 5 g of water and add them to 200 g of catalyst powder, mixing thoroughly. In the prepared mixture, the amount of additive I added is 2.5 wt% of the catalyst powder, and the water content of the mixture is 50 wt%.

[0056] (3) The mixture obtained in step (2) was dried at 100℃ for 4 hours, and the moisture content of the dried material was measured to be 2wt%. The crushed mixture was obtained by a gyratory granulator and then sieved. 15g, 80g, and 5g of powder with a mesh size of ≥40 mesh and <80 mesh, 80-120 mesh, and >120 mesh were weighed, respectively. The three portions of material were mixed evenly, and then 3g of flake graphite (800 mesh particle size) and 2g of stearic acid were added and mixed evenly again. The evenly mixed material was poured into the hopper of a tablet press and compressed into tablets at a size of 3mm×3mm to obtain tablets.

[0057] (4) The tablets were calcined at 425°C for 4 hours with a heating rate of 5°C / min to obtain the shaped catalyst.

[0058] Example 5

[0059] (1) Prepare solution A with 1 mol / L chromic anhydride and 1 mol / L copper nitrate, and solution B with 10% ammonia. Add solutions A and B concurrently to the reactor and react at 50°C for 1 h, maintaining the pH at 7.0 ± 0.1 during the reaction. The resulting slurry is aged at 50°C for 4 h and then filtered. After washing with deionized water until the effluent is neutral, the filter cake is dried at 100°C. After cooling to room temperature, the precursor is calcined at 450°C for 3 h to obtain catalyst powder. Cr exists in the form of Cr2O3 and CuCr2O4.

[0060] (2) Prepare a 10 wt% hydroxypropyl methylcellulose solution, wherein the viscosity of the hydroxypropyl methylcellulose is 2000 mPa·s. Stir and mix at room temperature until a viscous consistency is achieved and no white agglomerates remain. Then, take 60 g of this solution and 66 g of water and add them to 200 g of catalyst powder, mixing thoroughly. In the prepared mixture, the amount of hydroxypropyl methylcellulose (auxiliary agent I) added is 3 wt% of the catalyst powder, and the water content of the mixture is 60 wt%.

[0061] (3) The mixture obtained in step (2) was dried at 100℃ for 4 hours, and the moisture content of the dried material was measured to be 2.5 wt%. The crushed mixture was obtained by a gyratory granulator and then sieved. 15 g, 75 g, and 10 g of powder with a mesh size of ≥40 mesh and <80 mesh, 80-120 mesh, and >120 mesh were weighed, respectively. The three parts of the material were mixed evenly, and then 1 g of flake graphite (particle size of 2000 mesh) and 4 g of guar gum powder were added and mixed evenly again. The evenly mixed material was poured into the hopper of a tablet press and compressed into tablets at a size of 3 mm × 3 mm to obtain tablets.

[0062] (4) The tablets were calcined at 450°C for 3 hours with a heating rate of 1°C / min to obtain the shaped catalyst.

[0063] Comparative Example 1

[0064] (1) Prepare a 1 mol / L solution of chromium nitrate and a 1 mol / L solution of copper nitrate as solution A, and prepare an 8% ammonia solution as solution B. Add solutions A and B concurrently to the reactor and react at 40°C for 1 h, maintaining the pH at 8.0 ± 0.1 during the reaction. The resulting slurry is aged at room temperature for 6 h and then filtered. After washing with deionized water until the effluent is neutral, the filter cake is dried at 100°C. After cooling to room temperature, the precursor is calcined at 500°C for 4 h in an air atmosphere to obtain catalyst powder. Cr exists in the form of Cr2O3 and CuCr2O4, and the mass fraction of Cr in the catalyst powder is 40 wt%.

[0065] (2) Weigh 100g of catalyst powder, add 3g of flake graphite (400 mesh) and 2g of starch, and mix well. Pour the well mixed material into the hopper of the tablet press and compress it into tablets at a size of 3mm × 3mm to obtain tablets.

[0066] (3) Place the tablets at 500℃ for 4 hours, with a heating rate of 2℃ / min.

[0067] In this comparative example, the catalyst powder was not pretreated; it was directly mixed with flake graphite and starch for tableting, with other conditions the same as in Example 1. During the tableting process, the machine's adjustability was poor, and the height of the molded body was difficult to decrease while still meeting the strength performance indicators, resulting in an excessively high molded body height.

[0068] Comparative Example 2

[0069] (1) Prepare a 1 mol / L solution of chromium nitrate and a 1 mol / L solution of copper nitrate as solution A, and prepare an 8% ammonia solution as solution B. Add solutions A and B concurrently to the reactor and react at 40°C for 1 h, maintaining the pH at 8.0 ± 0.1 during the reaction. The resulting slurry is aged at room temperature for 6 h and then filtered. After washing with deionized water until the effluent is neutral, the filter cake is dried at 100°C. After cooling to room temperature, the precursor is calcined at 500°C for 4 h in an air atmosphere to obtain catalyst powder. Cr exists in the form of Cr2O3 and CuCr2O4, and the mass fraction of Cr in the catalyst powder is 40 wt%.

[0070] (2) Prepare a 5 wt% carboxymethyl cellulose solution, wherein the viscosity of the carboxymethyl cellulose is 800 mPa·s. Stir and mix at room temperature until a viscous consistency is achieved and no white agglomerates remain. Then, add 100 g of this solution to 200 g of catalyst powder, followed by 50 g of deionized water, and mix thoroughly. In the resulting mixture, the amount of additive I added is 2.5 wt% of the catalyst powder, and the water content of the mixture is 72.5 wt%.

[0071] (3) The mixture obtained in step (2) was dried at 100℃ for 4 hours, and the moisture content of the dried material was measured to be 4wt%. The mixture was ball-milled at 100 rpm for 15 minutes to obtain a crushed mixture. 100g of the crushed material was weighed, and 3g of flake graphite (400 mesh particle size) and 2g of starch were added, and mixed thoroughly again. The thoroughly mixed material was poured into the hopper of a tablet press and compressed into tablets at a size of 3mm × 3mm to obtain tablets.

[0072] (4) The tablets were calcined at 500°C for 4 hours at a heating rate of 2°C / min to obtain the shaped catalyst.

[0073] In this comparative example, severe powder leakage and significant localized cracking of the molded body were observed during the tableting process. Furthermore, the uneven particle size distribution resulted in low filling efficiency and a low bulk density of the molded body. Simultaneously, the inability to achieve tight packing between particles led to a small contact area, causing calcination inertia. This meant that some large pores formed during the molding process remained after calcination, thus reducing the catalyst's strength.

[0074] Comparative Example 3

[0075] (1) Prepare a 1 mol / L solution of chromium nitrate and a 1 mol / L solution of copper nitrate as solution A, and prepare an 8% ammonia solution as solution B. Add solutions A and B concurrently to the reactor and react at 40°C for 1 h, maintaining the pH at 8.0 ± 0.1 during the reaction. The resulting slurry is aged at room temperature for 6 h and then filtered. After washing with deionized water until the effluent is neutral, the filter cake is dried at 100°C. After cooling to room temperature, the precursor is calcined at 500°C for 4 h in an air atmosphere to obtain catalyst powder. Cr exists in the form of Cr2O3 and CuCr2O4, and the mass fraction of Cr in the catalyst powder is 40 wt%.

[0076] (2) Prepare a 5 wt% carboxymethyl cellulose solution, wherein the viscosity of the carboxymethyl cellulose is 800 mPa·s. Stir and mix at room temperature until it becomes viscous and free of white agglomerates. Then, take 10 g of this solution and add it to 200 g of catalyst powder, followed by 135.5 g of water, and mix thoroughly. At this point, the amount of additive I added is 0.25 wt%, and the water content of the mixed material is 72.5 wt%.

[0077] (3) The mixture obtained in step (2) was dried at 100℃ for 4 hours, and the moisture content of the dried material was measured to be 4wt%. The mixture was ball-milled at 100rpm for 15 minutes to obtain the crushed mixture, which was then sieved. 20g, 70g, and 10g of powders with a mesh size ≥40 mesh and <80 mesh, 80-120 mesh, and >120 mesh were weighed, respectively. The three portions of material were mixed evenly, and then 3g of flake graphite (400 mesh particle size) and 2g of starch were added and mixed evenly again. The evenly mixed material was poured into the hopper of a tablet press and compressed into tablets at a size of 3mm × 3mm to obtain tablets.

[0078] (4) The tablets were calcined at 500°C for 4 hours at a heating rate of 2°C / min to obtain the shaped catalyst.

[0079] In this comparative example, due to the small amount of additive 1 added, the catalyst powder was difficult to agglomerate, and a pre-dense material with a certain strength could not be obtained. The mixed material obtained in step (2) was re-pulverized during ball milling, thus failing to obtain a material with a certain particle size distribution. In addition, the small amount of additive 1 added resulted in limited optimization of the powder's compressibility properties. Under the premise of achieving the catalyst strength index, the catalyst height was relatively high.

[0080] Comparative Example 4

[0081] (1) Prepare a mixed solution of 1 mol / L chromium nitrate and 1 mol / L ferric nitrate as solution A, and prepare a 1 mol / L ammonium bicarbonate solution as solution B. Add solutions A and B concurrently to the reactor and react at 50℃ for 1 h, maintaining the pH at 6.5±0.1 during the reaction. The resulting slurry is aged at 50℃ for 4 h and then filtered. After washing with deionized water until the effluent is neutral, the filter cake is dried at 100℃. After cooling to room temperature, the precursor is calcined at 450℃ for 4 h to obtain catalyst powder. Cr exists in the form of Cr2O3.

[0082] (2) Prepare a 10 wt% carboxymethyl cellulose solution, wherein the viscosity of the carboxymethyl cellulose is 1000 mPa·s. Stir and mix at room temperature until a viscous consistency is achieved and no white agglomerates remain. Then, take 120 g of this solution and 37 g of water and add them to 200 g of catalyst powder, mixing thoroughly. In the prepared mixture, the amount of additive I added is 6 wt% of the catalyst powder, and the water content of the mixture is 72.5 wt%.

[0083] (3) The mixture obtained in step (2) was dried at 100℃ for 4 hours, and the moisture content of the dried material was measured to be 2wt%. The crushed mixture was obtained by a gyratory granulator and then sieved. 20g, 70g, and 10g of powder with a mesh size ≥40 and <80, 80-120, and >120 mesh were weighed, respectively. The three portions of material were mixed evenly, and then 0.5g of flake graphite and 3g of carboxymethyl cellulose were added and mixed evenly again. The evenly mixed material was poured into the hopper of a tablet press and compressed into tablets at a size of 3mm × 3mm to obtain tablets.

[0084] (4) The tablets were calcined at 450°C for 3 hours with a heating rate of 2°C / min to obtain the shaped catalyst.

[0085] In this comparative example, due to the addition of excessive additive 1, the strength of the pre-densified material is too high, making the subsequent crushing process difficult. Due to the excessive addition of additive 1, in step (4), the gas generated by pyrolysis escapes from the inside of the molded body, causing an impact on the molded body, resulting in an increased scrap rate, a significant decrease in the strength of the molded body, and the finished product failing to meet the catalyst application index.

[0086] Comparative Example 5

[0087] (1) Prepare a 1 mol / L chromic anhydride solution as solution A and a 1 mol / L ammonium carbonate solution as solution B. Add solutions A and B concurrently to the reactor and react at 50℃ for 2 h, maintaining the pH at 7.0±0.1 during the reaction. The resulting slurry is aged at 50℃ for 2 h and then filtered. After washing with deionized water until the effluent is neutral, the filter cake is dried at 100℃. After cooling to room temperature, the precursor is calcined at 500℃ for 4 h to obtain catalyst powder. Cr exists in the form of Cr2O3.

[0088] (2) Weigh 100g of catalyst powder, then add 1g of flake graphite (1600 mesh) and 3g of polyvinyl alcohol, and mix them evenly again. Pour the evenly mixed material into the hopper of the tablet press and compress it into tablets at a size of 3mm × 3mm to obtain tablets.

[0089] (3) The tablets were calcined at 500°C for 4 hours at a heating rate of 2°C / min to obtain the shaped catalyst.

[0090] In this comparative example, the powder was not pretreated; flake graphite and polyvinyl alcohol were directly mixed and compressed into tablets, with other conditions the same as in Example 2. During the tableting process, the machine's adjustability was poor, and the height of the molded body was difficult to decrease while still meeting the strength performance indicators, resulting in an excessively high molded body height.

[0091] Comparative Example 6

[0092] (1) Prepare solution A with 1 mol / L chromic anhydride and 1 mol / L copper nitrate, and solution B with 10% ammonia. Add solutions A and B concurrently to the reactor and react at 50°C for 1 h, maintaining the pH at 7.0 ± 0.1 during the reaction. The resulting slurry is aged at 50°C for 4 h and then filtered. After washing with deionized water until the effluent is neutral, the filter cake is dried at 100°C. After cooling to room temperature, the precursor is calcined at 450°C for 3 h to obtain catalyst powder. Cr exists in the form of Cr2O3 and CuCr2O4.

[0093] (2) Prepare a 10 wt% hydroxypropyl methylcellulose solution, wherein the viscosity of the hydroxypropyl methylcellulose is 2000 mPa·s. Stir and mix at room temperature until it becomes viscous and free of white agglomerates. Then, take 90 g of the solution and 39 g of water and add them to 200 g of catalyst powder and mix evenly. The amount of hydroxypropyl methylcellulose (auxiliary agent I) added is 4.5 wt% of the catalyst powder, and the water content of the mixed material is 60 wt%.

[0094] (3) The mixture obtained in step (2) was dried at 100℃ for 4 hours, and the moisture content of the dried material was measured to be 2.5 wt%. The crushed mixture was obtained by a gyratory granulator and then sieved. 15 g, 75 g, and 10 g of powder with a mesh size of ≥40 mesh and <80 mesh, 80-120 mesh, and >120 mesh were weighed, respectively. The three parts of the material were mixed evenly, and then 1 g of flake graphite (particle size of 2000 mesh) and 4 g of guar gum powder were added and mixed evenly again. The evenly mixed material was poured into the hopper of a tablet press and compressed into tablets at a size of 3 mm × 3 mm to obtain tablets.

[0095] (4) The tablets were calcined at 450°C for 3 hours with a heating rate of 1°C / min to obtain the shaped catalyst.

[0096] In this comparative example, due to the addition of excessive additive 1, the strength of the pre-densified material is too high, making the subsequent crushing process difficult. Due to the excessive addition of additive 1, in step (4), the gas generated by pyrolysis escapes from the inside of the molded body, causing an impact on the molded body, resulting in an increased scrap rate, a significant decrease in the strength of the molded body, and the finished product failing to meet the catalyst application index.

[0097] Table 1. Parameter values ​​of the molding catalyst in the examples and comparative examples.

[0098]

[0099] The specific embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, the technical features of the present invention can be combined in any other suitable manner, and these simple modifications and combinations should also be considered within the scope of the present invention and are all within the protection scope of the present invention.

Claims

1. A method of tableting a Cr-based catalyst, characterized by: The method comprises: (1) preparing a Cr-based catalyst powder by a coprecipitation method; the Cr-based catalyst powder is a calcined powder; (2) mixing the Cr-based catalyst powder obtained in step (1), an aqueous solution of an additive I and optionally added water to obtain a mixture; (3) drying, crushing and sieving the mixture obtained in step (2), and then mixing the sieved mixture with an additive II and an additive III, and then tabletting to obtain tablets; (4) calcining the tablets obtained in step (3) to obtain the shaped catalyst; the mass fraction of Cr in the Cr-based catalyst powder obtained in step (1) is 40wt%-100wt%; in step (2), the additive I is added in an amount of 1wt%-3wt% of the Cr-based catalyst powder; the additive I is at least one of carboxymethyl cellulose and hydroxypropyl methyl cellulose; the additive II is graphite; and the additive III is at least one of starch, epoxy resin, carboxymethyl cellulose, hydroxypropyl methyl cellulose, polyvinyl alcohol, sesbania powder and stearic acid; in step (3), the sieving is divided into three parts according to ≥40 mesh and <80 mesh, 80-120 mesh and >120 mesh, and the three parts are mixed in a mass ratio of 10-20:60-80:5-10.

2. The method of claim 1, wherein: in step (1), the calcination conditions are as follows: the calcination temperature is 350-650℃, the calcination time is 3-6h, and the calcination atmosphere is an oxygen-containing atmosphere.

3. The method of claim 1, wherein: in step (2), the viscosity of the carboxymethyl cellulose is 200mpa.s-1000mpa.s, and the viscosity of the hydroxypropyl methyl cellulose is 2000mpa.s-6500mpa.s; and / or, in the aqueous solution of the additive I, the mass content of cellulose is 1wt%-10wt%.

4. The method of claim 1, wherein: in step (2), the amount of water added satisfies that the final water content of the prepared mixture is 50wt%-80wt%.

5. The method of claim 1, wherein: in step (3), the drying temperature is 80℃-120℃, and the water content of the dried material is 2wt%-10wt%.

6. The method of claim 1, wherein: in step (3), the graphite is at least one of natural graphite and artificial graphite; and the particle size of the additive II is more than 200 mesh.

7. The method of claim 6, wherein: the particle size of the additive II is 400 mesh-2000 mesh.

8. The method according to claim 1 or 6 or 7, characterized in that: in step (3), the additive II is added in an amount of 0.5wt%-3wt% of the Cr-based catalyst powder.

9. The method of claim 8, wherein: in step (3), the additive III is added in an amount of 1wt%-5wt% of the Cr-based catalyst powder.

10. The method of claim 1, wherein: in step (4), the calcination temperature is 300℃-600℃, the heating rate is 0.5℃ / min-5℃ / min, and the calcination time is 2h-8h.

11. A Cr-based catalyst prepared by the method according to any one of claims 1-10.

12. The Cr-based catalyst of claim 11, wherein: The Cr-based catalyst has a radial strength of 50 N / particle or more, a specific surface area of 20 m 2 / g~50 m 2 / g, an average pore diameter of 15 nm~35 nm, and a pore volume of 0.08 cm 3 / g~0.15 cm 3 / g.

13. The Cr-based catalyst of claim 12, wherein: the radial strength of the Cr-based catalyst is 60N / particle-120N / particle.

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