Caprolactam hydrogenation refining catalyst, preparation method thereof and caprolactam hydrogenation refining method

Abstract

The present invention provides a caprolactam hydrorefining catalyst, a preparation method, and a caprolactam hydrorefining method. The caprolactam hydrorefining catalyst comprises a catalyst support and an active ingredient, Ni, supported on the catalyst support. The catalyst support comprises rare earth oxide-modified alumina, a structural additive, a binder, and a lubricant. The mass ratio of the alumina to the rare earth metal elements contained in the rare earth oxide is 15 to 50:1. A portion (40% to 70%) of the rare earth oxide-modified support is subjected to high-temperature calcination to significantly increase the support pore size, while the remaining portion (30% to 60%) serves as a binder for subsequent forming. The resulting catalyst has a large pore size and a narrow pore size distribution. When used in a fixed-bed hydrogenation reactor, the catalyst can withstand long-term corrosion from weakly acidic or weakly alkaline aqueous caprolactam solutions, maintains stable particle strength, and exhibits excellent hydrogenation performance.

Description

Technical Field

[0001] The present invention relates to the technical field of catalysts, and in particular to a caprolactam hydrogenation refining catalyst, a preparation method thereof and a caprolactam hydrogenation refining method. Background Art

[0002] Caprolactam is an important chemical raw material for the production of nylon-6 fiber and engineering plastics. Its production process involves a wide variety of raw materials and a complex process. Among them, there are more than 30 kinds of impurities caused by ammoximation and rearrangement reactions. Although the content of these impurities is relatively low, they seriously affect the quality of the finished caprolactam. In particular, when used as a raw material for high-speed spinning, the requirements for impurity content are more stringent.

[0003] The hydrorefining process mainly involves hydrogenating unsaturated substances in the impurities that have properties similar to those of caprolactam, so that they can be removed in the subsequent evaporation and distillation units. There are currently three main methods for caprolactam hydrorefining in China: (1) In a slurry bed reactor, a Raney nickel catalyst is used to complete the hydrogenation reaction. This process is the mainstream process of domestic manufacturers, but it has disadvantages such as high catalyst consumption, complex process, and large fluctuations in product quality; (2) In a magnetically stabilized bed reactor, an amorphous alloy catalyst is used to complete the hydrogenation reaction. Its process is similar to that of a slurry bed, and the catalyst loss is reduced, but it also has disadvantages such as complex operation and large fluctuations in product quality; (3) In a fixed bed reactor, a monolithic nickel-based catalyst is used to complete the hydrogenation reaction. This process is simple, easy to operate, and has stable product quality. However, since the hydrogenation reaction occurs in a slightly alkaline aqueous solution, it places high demands on the structural stability of the monolithic catalyst.

[0004] Chinese patent application No. 00105686.7 discloses an amorphous nickel-aluminum alloy catalyst composed of 60-98 wt% Ni, 0-20 wt% Fe, 0-20 wt% of one of Cr, Co, Mo, Mn, and W, and 0.5-30 wt% Al. When subjected to hydrogenation reaction at normal pressure and 90°C, the PM value of a caprolactam aqueous solution can reach over 1000s.

[0005] The Chinese patent application No. 200910075824.4 discloses a method for hydrogenating caprolactam in a magnetically stabilized bed reactor. In the presence of a catalyst composed of an active component of palladium and a magnetic spherical carrier component, the catalyst is heated at 100°C, 1.2 MPa, and 30 h. -1 Under the reaction conditions of 6% hydrogen-to-liquid ratio, the PM value of caprolactam aqueous solution can reach 730s.

[0006] The Chinese patent application number 201510196549.7 discloses a granular Raney nickel catalyst for use in a fixed bed reactor, comprising 40-80 wt% Ni, 20-60 wt% Al, and 0-10 wt% of one or more of V, Cr, Mo, W, and Fe. The catalyst is heated at 80°C, 0.75 MPa, and a mass space velocity of 2 h. -1 Under normal conditions, the PM value of caprolactam aqueous solution can reach 17600-32000s. However, the sponge-like porous structure of Raney nickel will collapse and become inactive if used for a long time under alkaline conditions.

[0007] Chinese patent application number 202011259627.0 discloses a Ni / Al2O3 catalyst used in a fixed bed reactor, composed of 10-35wt% Ni, 1-20wt% additive, 50-80wt% Al2O3, and 0.5-30wt% Al. After the caprolactam aqueous solution is hydrogenated, the potassium permanganate absorption value (PAN value) drops below 1.8.

[0008] In summary, the current industrial caprolactam hydrorefining process mostly utilizes Raney nickel and amorphous alloy catalysts. However, Raney nickel catalysts have low activity and limited impurity removal capabilities, failing to meet the needs of high-end customers. Amorphous alloy catalysts also face challenges in their development, including demanding preparation conditions and high investment in magnetically stabilized bed equipment. Supported Ni / Al₂O₃ catalysts offer excellent hydrogenation performance and a simple process flow. However, because the caprolactam aqueous solution in the hydrogenation environment is typically weakly acidic or alkaline, the catalyst can suffer from dusting, loss of active components, and a short lifespan.

[0009] In view of this, the present invention is proposed. Summary of the Invention

[0010] One of the purposes of the present invention is to provide a caprolactam hydrogenation refining catalyst, which is applied to a fixed-bed hydrogenation reactor and can withstand the erosion of weakly acidic or weakly alkaline caprolactam aqueous solutions for a long time, maintains stable particle strength and has excellent hydrogenation performance.

[0011] A second object of the present invention is to provide a method for preparing the caprolactam hydrorefining catalyst.

[0012] A third object of the present invention is to provide a method for hydrogenating and refining caprolactam.

[0013] In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are adopted:

[0014] In a first aspect, the present invention provides a caprolactam hydrorefining catalyst, comprising a catalyst support and an active component Ni supported on the catalyst support, wherein the catalyst support comprises alumina modified with rare earth oxides, a structural additive, a binder, and a lubricant;

[0015] Based on the mass of the caprolactam hydrorefining catalyst, the content of the active ingredient Ni is 10-40wt%, preferably 12-30wt%, the content of the rare earth oxide-modified alumina is 40-79wt%, preferably 45-70wt%, the content of the structural additive is 3-20wt%, preferably 7-20wt%, the content of the binder is 5-15wt%, preferably 5-10wt%, and the content of the lubricant is 3-7wt%, preferably 3-5wt%;

[0016] In the rare earth oxide-modified alumina, the mass ratio of alumina to the rare earth metal elements contained in the rare earth oxide is 15 to 50:1;

[0017] The caprolactam hydrogenation refining catalyst has a pore volume of 0.4 to 1.5 ml / g and an average pore diameter of 20 to 40 nm.

[0018] In some embodiments, the rare earth oxide is one or more selected from La2O3, ZrO2, Sm2O3; and / or

[0019] The structural additive is one or more selected from kaolin and titanium dioxide; and / or

[0020] The binder is one or more selected from magnesium phosphate, calcium aluminate, and calcium silicate; and / or

[0021] The lubricant is one or more selected from sesbania powder, methyl cellulose and calcium stearate.

[0022] In some embodiments, the crystal form of the rare earth oxide-modified alumina is one or a mixed crystal form of γ, δ, θ, ɑ, preferably a mixed crystal form of γ and θ.

[0023] In a second aspect, the present invention provides a method for preparing the caprolactam hydrorefining catalyst, comprising the following steps:

[0024] (1) uniformly mixing aluminum sol and rare earth metal salt to obtain slurry I, wherein the solid content of aluminum oxide and rare earth metal salt in slurry I is 20-40%; spray drying and granulating the slurry I to obtain solid microsphere powder;

[0025] Taking part of the solid microsphere powder and calcining it to obtain rare earth oxide-modified alumina, wherein the mass ratio of the alumina to the rare earth metal element contained in the rare earth oxide is (15-50):1;

[0026] The part of the solid microsphere powder taken in step (1) accounts for 40% to 70% of the total mass of the solid microsphere powder;

[0027] (2) adding the rare earth oxide-modified alumina and the structural additive into water and uniformly mixing them to obtain slurry II, wherein the mass ratio of the structural additive to the rare earth oxide-modified alumina is (0.15-0.6):1, preferably (0.18-0.56):1;

[0028] (3) adding a nickel salt aqueous solution to slurry II and stirring thoroughly to obtain slurry III; adding a precipitant to slurry III to deposit the reaction product of the precipitation reaction on the support, washing, drying, roasting, and crushing to obtain a solid catalyst powder, wherein the Ni content is 15 to 35 wt% of the mass of the solid catalyst powder, preferably 20 to 30 wt%;

[0029] (4) taking the remaining portion of the solid microsphere powder of step (1) and uniformly mixing it with the solid catalyst powder, binder, and lubricant of step (3), optionally adding dilute nitric acid, and molding to obtain a molded catalyst, wherein the amount of the binder added is 5 to 15 wt% of the mass of the solid catalyst powder, preferably 5 to 10 wt%, and the amount of the lubricant added is 3 to 7 wt% of the mass of the solid catalyst powder, preferably 3 to 5 wt%;

[0030] The obtained shaped catalyst is placed in a constant temperature and humidity box at a constant temperature of 25 to 50° C. and a humidity of 90 to 97% for 72 to 168 hours, and then dried and calcined to obtain an oxidized caprolactam hydrogenation refining catalyst;

[0031] (5) reducing the oxidized caprolactam hydrorefining catalyst and sealing it in deoxygenated water to obtain a reduced caprolactam hydrorefining catalyst.

[0032] The following is a detailed description of each step:

[0033] Alumina sol is a colloidal suspension of aluminum oxide nanoparticles in a liquid solvent, which is commercially available or can be prepared using conventional methods in the art.

[0034] In some embodiments, the calcination temperature in step (1) is 800-1000° C., and the calcination time is 2-6 hours.

[0035] In some embodiments, the nickel salt in step (3) is one or more selected from nickel nitrate, nickel acetate and nickel sulfate, more preferably nickel nitrate or nickel acetate.

[0036] In some embodiments, the precipitant in step (3) is a carbonate, for example, it can be added in the form of an aqueous solution in step (3), and the carbonate is preferably one or more selected from sodium carbonate, sodium bicarbonate, potassium carbonate and potassium bicarbonate.

[0037] In some embodiments, the precipitation reaction temperature in step (3) is 50-70° C., and the pH value at the reaction endpoint is 7-8.5.

[0038] In some embodiments, the precipitation reaction in step (3) is followed by aging for 3-5 hours.

[0039] In some embodiments, the drying temperature in step (3) is 100-120°C, and the calcination temperature is 500-600°C.

[0040] In some embodiments, the binder in step (4) is one or more selected from calcium aluminate and calcium silicate, and / or the lubricant is one or more selected from sesbania powder, methyl cellulose and calcium stearate.

[0041] In some embodiments, the drying temperature in step (4) is 100-120°C, and the calcination temperature is 500-600°C.

[0042] In some embodiments, the reduction conditions in step (5) are: hydrogen reduction at 450-600° C. for 2-10 h.

[0043] In some embodiments, the conductivity of the deoxygenated water in step (5) is less than 5 μs / cm.

[0044] In one embodiment of the method for preparing the caprolactam hydrorefining catalyst, the method for preparing the caprolactam hydrorefining catalyst comprises the following steps:

[0045] (1) preparing an aluminum sol using boehmite powder, nitric acid, and water, and uniformly mixing the aluminum sol with a rare earth metal salt to prepare a slurry I having a solid content (calculated as aluminum oxide and rare earth metal salt) of 20 to 40%; spray drying and granulating the slurry I using a spray drying technique to obtain a solid microsphere powder;

[0046] Taking a portion of the solid microsphere powder and calcining it at 800-1000° C. for 2-6 hours to obtain rare earth oxide-modified alumina, wherein the mass ratio of the alumina to the rare earth metal elements contained in the rare earth oxide in the rare earth oxide is 15-50:1; the portion of the solid microsphere powder taken in step (1) accounts for 40%-70% of the total mass of the solid microsphere powder;

[0047] (2) adding a required amount of rare earth oxide-modified alumina, kaolin and / or titanium dioxide (to improve the crushing strength of the catalyst) to deionized water and uniformly mixing to form slurry II; wherein the mass ratio of kaolin and / or titanium dioxide to rare earth oxide-modified alumina is 0.15 to 0.6:1;

[0048] (3) adding a required amount of nickel salt aqueous solution to slurry II and stirring thoroughly to obtain slurry III; slowly adding 1 mol / L carbonate solution to slurry III at 50-70° C. to cause precipitation reaction, controlling the end point pH value to 7-8.5, aging for 3 hours, and then washing thoroughly with water, drying at 100-120° C., calcining at 500-600° C., and pulverizing to obtain solid catalyst powder, wherein the Ni content is 15-35 wt% of the mass of the solid catalyst powder, preferably 12-30 wt%, wherein the particle size distribution of the solid catalyst powder is 1-100 μm, and the particle size D90 is 10-50 μm;

[0049] (4) taking the remaining portion of the solid microsphere powder of step (1) and the solid catalyst powder of step (3) and the required amount of binder and lubricant, uniformly mixing them, adding an appropriate amount of dilute nitric acid aqueous solution, and forming them into a 1.5 mm clover-shaped structure by extrusion, wherein the amount of binder added is 5-15 wt% of the mass of the solid catalyst powder, and the amount of lubricant added is 3-7 wt% of the mass of the solid catalyst powder;

[0050] The formed catalyst is placed in a constant temperature and humidity box at a constant temperature of 25-50° C. and a humidity of 90%-97% for 72-168 hours, then dried at 120° C. and calcined at 600° C. to obtain an oxidized caprolactam hydrogenation refining catalyst.

[0051] (5) The obtained oxidized caprolactam hydrorefining catalyst is reduced with hydrogen at 450-600° C. for 2-10 hours, then cooled to room temperature, and sealed in deoxygenated water under nitrogen protection to obtain a reduced caprolactam hydrorefining catalyst.

[0052] The reduced caprolactam hydrotreating catalyst can be used directly without online reduction.

[0053] In a third aspect, the present invention provides a caprolactam hydrorefining method, which comprises: hydrorefining caprolactam in a fixed-bed hydrogenation reactor containing the caprolactam hydrorefining catalyst.

[0054] The technical solution of the present invention has the following beneficial effects:

[0055] (1) The caprolactam hydrogenation refining catalyst of the present invention has a large pore size and a narrow pore size distribution (a portion of the carrier modified with rare earth oxides, 40% to 70% of which is calcined at high temperature, can significantly increase the carrier pore size, and the other portion, 30% to 60%, is used as a binder for subsequent molding). The diffusion resistance of organic matter into the pores is small, which is conducive to the hydrogenation reaction; the oligomer macromolecules are more easily desorbed, which weakens the occupation and coverage of the active sites, is conducive to the long-term stability of the catalyst activity, and has excellent hydrogenation performance.

[0056] (2) After the catalyst is formed and treated with constant temperature and humidity under specific conditions, its tolerance to caprolactam aqueous solution is significantly enhanced, which can ensure that the catalyst maintains a high strength state when immersed in liquid, improve the catalyst's resistance to liquid feed erosion and reaction pressure fluctuations, and significantly improve the effect of resistance to erosion by alkaline aqueous solution.

[0057] (3) A porous alumina support was prepared using aluminum sol and modified with rare earth oxides, significantly improving the hydrogenation activity of the catalyst. A nickel salt solution and the support were made into a slurry, allowing the nickel salt to be fully adsorbed within the support pores. The introduction of a precipitant increased the dispersion of nickel within the support pores, facilitating the hydrogenation reaction.

[0058] The present invention has been described in detail above, but the above embodiments are merely illustrative in nature and are not intended to limit the present invention. In addition, the present invention is not limited by any theory described in the above prior art or invention summary or the following examples.

[0059] Unless otherwise expressly stated, numerical ranges throughout this application include any subranges therein and any numerical values ​​in increments of the smallest subunit of a given value therein. Unless otherwise expressly stated, numerical values ​​throughout this application represent approximate measures or limits of the range of embodiments that include minor deviations from the given value and have approximately the stated value as well as the stated exact value. Except for the working examples provided at the end of the detailed description, all numerical values ​​for parameters (e.g., quantities or conditions) in this application (including the appended claims) should be understood in all cases as being modified by the term "approximately", regardless of whether "approximately" actually appears before the value. "Approximately" means that the stated value allows for slight imprecision (some approach to exactness in the value; approximately or reasonably close to the value; approximately). If the imprecision provided by "approximately" is not understood in this ordinary sense in the art, "approximately" as used herein at least represents the variation that can be produced by ordinary methods of measuring and using these parameters. For example, "approximately" can include variations of less than or equal to 10%, less than or equal to 5%, less than or equal to 4%, less than or equal to 3%, less than or equal to 2%, less than or equal to 1% or less than or equal to 0.5%. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0061] Figure 1 This is the pore size distribution diagram of the catalyst prepared in Example 1;

[0062] Figure 2 This is the pore size distribution diagram of the catalyst prepared in Example 2;

[0063] Figure 3 This is the pore size distribution diagram of the catalyst prepared in Example 3;

[0064] Figure 4 This is the pore size distribution diagram of the catalyst prepared in Example 4;

[0065] Figure 5 This is the pore size distribution diagram of the catalyst prepared in Example 5;

[0066] Figure 6 This is the pore size distribution diagram of the catalyst prepared in Comparative Example 1;

[0067] Figure 7 This is the pore size distribution diagram of the catalyst prepared in Comparative Example 2;

[0068] Figure 8 This is the pore size distribution diagram of the catalyst prepared in Comparative Example 3. DETAILED DESCRIPTION

[0069] The present invention will be further described below with reference to the examples. It should be noted that the following examples are provided for illustrative purposes only and do not constitute a limitation on the scope of protection claimed in the present invention.

[0070] Unless otherwise specified, the raw materials, reagents, methods, etc. used in the examples are conventional raw materials, reagents, and methods in the art.

[0071] raw material:

[0072] Raw material name Specification supplier Boehmite 3.4μm (Wokai) Sinopharm Lanthanum nitrate 99% (Vokay) Sinopharm Zirconium nitrate AR (Shanghai test) Sinopharm Nickel nitrate AR (Shanghai test), ≥98.0% Sinopharm Kaolin CP (Shanghai test) Sinopharm calcium aluminate Alfa-022646, 99% Sinopharm Samarium nitrate 99.9% (Vokay) Sinopharm

[0073] instrument:

[0074] Particle size was measured using a laser particle size analyzer: Shanghai Spectris Instrument Systems Co., Ltd., laser particle size analyzer Mastersizer 3000;

[0075] The pore size was tested by nitrogen adsorption-desorption method: Micromeritics (Shanghai) Instrument Co., Ltd., pore size analyzer ASAP2460;

[0076] ICP spectrometer: ICP7000, PerkinElmer, USA.

[0077] Example

[0078] Example 1:

[0079] 1) Preparation of solid microsphere powder:

[0080] An aluminum sol with a solid content (calculated as aluminum oxide) of 22% was prepared using 27.44 g of boehmite powder, deionized water, and nitric acid at an acid-to-aluminum molar ratio of 0.08. 2.041 g of lanthanum nitrate hexahydrate and 3.646 g of zirconium nitrate trihydrate were then added and uniformly mixed to prepare a slurry with a solid content of 29.02%.

[0081] The slurry was spray-granulated by spray drying to obtain 34.42 g of solid microsphere powder (boehmite-rare earth metal salt-solid nitric acid).

[0082] 2) Preparation of rare earth oxide modified alumina:

[0083] 24.10 g of solid microsphere powder (accounting for 70% of the solid microsphere powder obtained in step 1) was calcined at 1000° C. for 2 hours to obtain 17.66 g of rare earth oxide-modified alumina (alumina-rare earth oxide), wherein the mass ratio of alumina to lanthanum was 35.6:1, and the mass ratio of alumina to zirconium was 27.6:1;

[0084] 3) 17.66 g of rare earth oxide-modified alumina and 9.87 g of kaolin were added to 450 ml of deionized water and then colloidally milled to form a uniformly dispersed slurry;

[0085] 4) The slurry was added to 200 mL of a 1 mol / L nickel nitrate aqueous solution and stirred thoroughly for 1 hour; a 1 mol / L sodium carbonate aqueous solution was slowly added to the solution at 50°C to cause a precipitation reaction, with the endpoint pH value controlled at 7. The solution was then aged for 3 hours, washed thoroughly with water, dried at 120°C, and calcined at 600°C to obtain a solid catalyst powder;

[0086] 5) The catalyst powder was evenly mixed with 10.33 g of the remaining 30% of the solid microsphere powder from step 1), 5 g of calcium aluminate, and 2 g of sesbania powder, and then formed into a 1.5 mm cloverleaf shape using an extruder;

[0087] The clover-shaped catalyst was placed in a constant temperature and humidity box at a constant temperature of 25°C and a humidity of 90% for 72 hours, then dried at 120°C and calcined at 600°C to obtain 55g of an oxidized caprolactam hydrogenation refining catalyst;

[0088] 6) The oxidized caprolactam hydrorefining catalyst was reduced with hydrogen at 460° C. for 10 hours, then cooled to room temperature. The catalyst was sealed in deoxygenated water under nitrogen protection to obtain a reduced caprolactam hydrorefining catalyst. The elemental composition was determined by ICP spectrometry to be: Ni (22.55%), rare earth modified alumina (45.86%). The pore size distribution was determined by nitrogen adsorption and desorption method. Figure 1 shown.

[0089] Example 2:

[0090] 1) Preparation of solid microsphere powder:

[0091] An aluminum sol with a solid content of 20% (calculated as alumina) was prepared using 35.24 g of boehmite powder, deionized water, and nitric acid at an acid-to-aluminum molar ratio of 0.08. 2.041 g of lanthanum nitrate hexahydrate was then added and uniformly mixed to prepare a slurry with a solid content of 24.31%.

[0092] The slurry was spray-granulated by spray drying to obtain 39.73 g of solid microsphere powder (boehmite-rare earth metal salt-solid nitric acid).

[0093] 2) Preparation of rare earth oxide modified alumina:

[0094] 27.81 g of solid microsphere powder (accounting for 70% of the solid microsphere powder obtained in step 1) was calcined at 900°C for 3 hours to obtain 21.50 g of rare earth oxide-modified alumina (alumina-rare earth oxide), wherein the mass ratio of alumina to lanthanum was 45.7:1;

[0095] 3) Add 21.5g of rare earth oxide-modified alumina, 5.24g of kaolin, and 1.15g of titanium dioxide to 420ml of deionized water and use a colloidal mill to prepare a uniformly dispersed slurry;

[0096] 4) The slurry was added to 173 mL of 1 mol / L nickel nitrate solution and stirred thoroughly for 1 hour; 1 mol / L potassium carbonate solution was slowly added to the solution at 60°C to cause precipitation reaction, and the end point pH was controlled to 7.5. The solution was then aged for 3 hours, washed thoroughly with water, dried at 120°C, and calcined at 550°C to obtain a solid catalyst powder;

[0097] 5) The catalyst powder was uniformly mixed with 11.92 g of the remaining 30% of the solid microsphere powder from step 1), 4.5 g of calcium aluminate, and 2 g of sesbania powder, and then formed into a 1.5 mm clover-shaped structure using an extruder; the clover-shaped catalyst was placed in a constant temperature and humidity chamber at 30°C and 92% humidity for 96 hours, then dried at 120°C and calcined at 600°C to produce 54.5 g of an oxidized caprolactam hydrorefining catalyst;

[0098] 6) The oxidized caprolactam hydrorefining catalyst was reduced with hydrogen at 480° C. for 8 hours, then cooled to room temperature. The catalyst was sealed in deoxygenated water under nitrogen protection to obtain a reduced caprolactam hydrorefining catalyst. The elemental composition was determined by ICP spectrometry to be: Ni (19.56%), rare earth modified alumina (56.33%). The pore size distribution was determined by nitrogen adsorption and desorption method. Figure 2 shown.

[0099] Example 3:

[0100] 1) Preparation of solid microsphere powder:

[0101] An aluminum sol with a solid content of 18% (calculated as alumina) was prepared using 40.58 g of boehmite powder, deionized water, and nitric acid at an acid-to-aluminum molar ratio of 0.08. 3.654 g of zirconium nitrate trihydrate was then added and mixed uniformly to obtain a slurry with a solid content of 22.46%.

[0102] The slurry was spray-granulated by spray drying to obtain 47.14 g of solid microsphere powder (boehmite-rare earth metal salt-solid nitric acid).

[0103] 2) Preparation of rare earth oxide modified alumina:

[0104] 28.28 g of solid microsphere powder (accounting for 60% of the solid microsphere powder obtained in step 1) was calcined at 800°C for 4 hours to obtain 21.37 g of rare earth oxide-modified alumina (alumina-rare earth oxide), wherein the mass ratio of alumina to lanthanum was 40.7:1;

[0105] 3) Add 21.37g of rare earth oxide-modified alumina powder, 2.31g of kaolin, and 1.65g of titanium dioxide to 440ml of deionized water and use a colloidal grinder to prepare a uniformly dispersed slurry;

[0106] 4) The slurry was added to 140 mL of 1 mol / L nickel nitrate solution and stirred thoroughly for 1 hour; 1 mol / L sodium bicarbonate solution was slowly added to the solution at 70°C to cause precipitation reaction, and the end point pH was controlled to 8. The solution was then aged for 3 hours, and then fully washed with water, dried at 120°C, and calcined at 500°C to obtain a solid catalyst powder;

[0107] 5) The solid catalyst powder was uniformly mixed with 18.86 g of the remaining 40% of the solid microsphere powder from step 1), 3 g of calcium aluminate, and 2 g of sesbania powder, and then formed into a 1.5 mm cloverleaf configuration using an extruder; the cloverleaf-shaped catalyst was placed in a constant temperature and humidity chamber at 40° C. and 93% humidity for 96 hours, then dried at 120° C. and calcined at 600° C. to obtain 53 g of an oxidized caprolactam hydrogenation refining catalyst;

[0108] 6) The oxidized caprolactam hydrorefining catalyst was reduced with hydrogen at 500° C. for 6 hours, then cooled to room temperature. The catalyst was sealed in deoxygenated water under nitrogen protection to obtain a reduced caprolactam hydrorefining catalyst. The elemental composition was determined by ICP spectrometry to be: Ni (16.08%), rare earth modified alumina (67.22%). The pore size distribution was determined by nitrogen adsorption-desorption method. Figure 3 shown.

[0109] Example 4:

[0110] 1) Preparation of solid microsphere powder:

[0111] An aluminum sol with a solid content of 25% (calculated as aluminum oxide) was prepared using 41.24 g of boehmite powder, deionized water, and nitric acid at an acid-to-aluminum molar ratio of 0.08. 3.987 g of lanthanum nitrate hexahydrate and 3.989 g of zirconium nitrate trihydrate were then added and uniformly mixed to prepare a slurry with a solid content of 32.52%.

[0112] The slurry was spray-granulated by spray drying to obtain 51.13 g of solid microsphere powder (boehmite-rare earth metal salt-solid nitric acid).

[0113] 2) Preparation of rare earth oxide modified alumina:

[0114] 25.57 g of solid microsphere powder (accounting for 50% of the solid microsphere powder obtained in step 1) was calcined at 800° C. for 2 hours to obtain 18.90 g of rare earth oxide-modified alumina (alumina-rare earth oxide), wherein the mass ratio of alumina to lanthanum was 27.4:1, and the mass ratio of alumina to zirconium was 37.9:1;

[0115] 3) Add 18.90 g of rare earth oxide-modified alumina powder, 3.7 g of kaolin, and 0.6 g of titanium dioxide into 450 ml of deionized water and use a colloidal grinder to prepare a uniformly dispersed slurry;

[0116] 4) The slurry was added to 106 mL of 1 mol / L nickel nitrate solution and stirred thoroughly for 1 hour; 1 mol / L potassium bicarbonate solution was slowly added to the solution at 70°C to cause precipitation reaction, and the end point pH value was controlled to 8.5. The solution was then aged for 3 hours, and then fully washed with water, dried at 120°C, and calcined at 500°C to obtain a solid catalyst powder;

[0117] 5) The solid catalyst powder was uniformly mixed with 25.57 g of the remaining 50% of the solid microsphere powder from step 1), 4 g of calcium aluminate, and 2 g of sesbania powder, and then formed into a 1.5 mm cloverleaf configuration using a tablet press; the cloverleaf-shaped catalyst was placed in a constant temperature and humidity chamber at 30° C. and 95% humidity for 140 hours, then dried at 120° C. and calcined at 600° C. to obtain 54 g of an oxidized caprolactam hydrogenation catalyst;

[0118] 6) The oxidized caprolactam hydrorefining catalyst was reduced with hydrogen at 550° C. for 4 hours, then cooled to room temperature. The catalyst was sealed in deoxygenated water under nitrogen protection to obtain a reduced caprolactam hydrorefining catalyst. The elemental composition was determined by ICP spectrometry to be: Ni (11.87%), rare earth modified alumina (69.98%). The pore size distribution was determined by nitrogen adsorption and desorption method. Figure 4 shown.

[0119] Example 5:

[0120] 1) Preparation of solid microsphere powder:

[0121] An alumina sol with a solid content of 25% (calculated as alumina) was prepared using 29.96 g of boehmite powder, deionized water, and nitric acid at an acid-to-alumina molar ratio of 0.08. 5.098 g of samarium nitrate hexahydrate and 2.393 g of zirconium nitrate trihydrate were then added and uniformly mixed to prepare a slurry with a solid content of 33.3%.

[0122] The slurry was spray-granulated by spray drying to obtain 38.4 g of solid microsphere powder (boehmite-rare earth metal salt-solid nitric acid).

[0123] 2) Preparation of rare earth oxide modified alumina:

[0124] 26.88 g of solid microsphere powder (accounting for 70% of the solid microsphere powder obtained in step 1) was calcined at 800° C. for 2 hours to obtain 19.74 g of rare earth oxide-modified alumina (alumina-rare earth oxide), wherein the mass ratio of alumina to samarium was 14.8:1, and the mass ratio of alumina to zirconium was 45.9:1;

[0125] 3) Add 19.74g of rare earth oxide-modified alumina, 3.7g of kaolin, and 0.6g of titanium dioxide into 450ml of deionized water and use a colloidal mill to prepare a uniformly dispersed slurry;

[0126] 4) The slurry was added to 234 mL of 1 mol / L nickel nitrate solution and stirred thoroughly for 1 hour; 1 mol / L potassium bicarbonate solution was slowly added to the solution at 70°C to cause precipitation reaction, and the endpoint pH value was controlled to 8.5. The solution was then aged for 3 hours, and then washed thoroughly with water, dried at 120°C, and calcined at 500°C to obtain a solid catalyst powder;

[0127] 5) The solid catalyst powder was uniformly mixed with 11.52 g of the remaining (30%) solid microsphere powder from step 1), 5 g of calcium aluminate, and 2 g of sesbania powder, and then formed into a 1.5 mm clover-shaped configuration using an extruder; the clover-shaped catalyst was placed in a constant temperature and humidity chamber at 50° C. and 97% humidity for 158 hours, then dried at 120° C. and calcined at 600° C. to produce 55 g of an oxidized caprolactam hydrogenation catalyst;

[0128] 6) The oxidized caprolactam hydrorefining catalyst was reduced with hydrogen at 520° C. for 4 hours, then cooled to room temperature. The catalyst was sealed in deoxygenated water under nitrogen protection to obtain a reduced caprolactam hydrorefining catalyst. The elemental composition was determined by ICP spectrometry to be: Ni (26.92%), rare earth modified alumina (51.27%). The pore size distribution was determined by nitrogen adsorption and desorption method. Figure 5 shown.

[0129] Comparative Example 1:

[0130] 1) Weigh 48.67 g of Ni(NO₃)₂·6H₂O, 1.99 g of La(NO₃)₃·6H₂O, 7.98 g of Zr(NO₃)₄·3H₂O, and 103.25 g of Al(NO₃)₃·9H₂O and dissolve them in 650 ml of deionized water at 70°C. Stir uniformly until all the water is dissolved to prepare Solution I.

[0131] 2) Weigh 103.25 g of K2CO3 and 8.6 g of KHCO3, dissolve them in 430 ml of deionized water at 70°C, and stir until completely dissolved to prepare Solution II;

[0132] 3) Slowly add Solution II to Solution I under stirring to induce a coprecipitation reaction, with an endpoint pH of 7.5. After precipitation, age the mixture for 3 hours to obtain a catalyst precursor slurry.

[0133] 4) The catalyst precursor slurry was filtered, washed, dried in an oven at 120°C, and then calcined at 600°C for 2 hours to obtain a solid catalyst block;

[0134] 5) The solid catalyst block was ground to a size of 300 mesh or larger, and then uniformly mixed with 20 g of pseudo-boehmite, 2 g of sesbania powder, and 25 g of a 12 wt% nitric acid solution. The mixture was extruded into a 1.2 mm cloverleaf configuration, dried at 100°C, and calcined at 500°C to obtain 50 g of an oxidized caprolactam hydrogenation refining catalyst product.

[0135] 6) The oxidized caprolactam hydrorefining catalyst was reduced with hydrogen at 500° C. for 6 hours, then cooled to room temperature. The catalyst was sealed in deoxygenated water under nitrogen protection to obtain a reduced caprolactam hydrorefining catalyst. The elemental composition was determined by ICP spectrometry to be: Ni (20.98%), rare earth modified alumina (70.59%). The pore size distribution was determined by nitrogen adsorption and desorption method. Figure 6 shown.

[0136] Comparative Example 2:

[0137] 1) Preparation of solid microsphere powder:

[0138] An aluminum sol with a solid content of 22% (calculated as alumina) was prepared using 27.44 g of boehmite powder, deionized water, and nitric acid at an acid-to-aluminum molar ratio of 0.08. 2.041 g of lanthanum nitrate hexahydrate and 3.646 g of zirconium nitrate trihydrate were then added and uniformly mixed to prepare a slurry with a solid content of 29.02%.

[0139] The slurry was spray-granulated by spray drying to obtain 34.42 g of solid microsphere powder (boehmite-rare earth metal salt-solid nitric acid).

[0140] 2) Preparation of rare earth oxide modified alumina:

[0141] 34.42 g of solid microsphere powder (accounting for 100% of the solid microsphere powder obtained in step 1) was calcined at 1000° C. for 2 hours to obtain 25.23 g of rare earth oxide-modified alumina (alumina-rare earth oxide), wherein the mass ratio of alumina to lanthanum was 35.6:1, and the mass ratio of alumina to zirconium was 27.6:1;

[0142] 3) Add 25.23 g of rare earth oxide-modified alumina powder and 9.87 g of kaolin into 450 ml of deionized water and use a colloidal mill to prepare a uniformly dispersed slurry;

[0143] 4) The slurry was added to 200 ml of 1 mol / L nickel nitrate solution and stirred thoroughly for 1 hour; 1 mol / L sodium carbonate solution was slowly added to the solution at 50°C to cause precipitation reaction, and the end point pH was controlled to 7. The solution was then aged for 3 hours, and then fully washed with water, dried at 120°C, and calcined at 600°C to obtain a solid catalyst powder;

[0144] 5) The catalyst powder was uniformly mixed with 5g of calcium aluminate and 2g of graphite, and then formed into a φ3×3mm cylindrical configuration using a tablet press; the cylindrical catalyst was placed in a constant temperature and humidity chamber at 50°C and 97% humidity for 158 hours, and then dried at 120°C to obtain 57g of an oxidized caprolactam hydrorefining catalyst;

[0145] 6) The oxidized hydrorefining catalyst was reduced with hydrogen at 460° C. for 10 hours, then cooled to room temperature and sealed in deoxygenated water under nitrogen protection to obtain a reduced caprolactam hydrorefining catalyst. The elemental composition was determined by ICP spectrometry to be: Ni (21.89%), rare earth modified alumina (44.25%). The pore size distribution was determined by nitrogen adsorption-desorption method, as shown in FIG. Figure 7 shown.

[0146] Comparative Example 3:

[0147] 1) Preparation of solid microsphere powder:

[0148] An aluminum sol with a solid content of 25% (calculated as alumina) was prepared using 33.19 g of boehmite powder, deionized water and nitric acid at an acid-aluminum molar ratio of 0.08. The aluminum sol was spray granulated using spray drying to obtain 35.98 g of solid microsphere powder (boehmite-solid nitric acid).

[0149] 2) 25.19 g of solid microsphere powder (accounting for 70% of the solid microsphere powder obtained in step 1) was calcined at 800° C. for 2 hours to obtain 19.74 g of alumina powder;

[0150] 2) 19.74 g of the above-mentioned alumina powder, 3.7 g of kaolin, and 0.6 g of titanium dioxide were added to 450 ml of deionized water and then colloidally ground into a uniformly dispersed slurry;

[0151] 3) The slurry was added to 234 mL of 1 mol / L nickel nitrate solution and stirred thoroughly for 1 hour; 1 mol / L potassium bicarbonate solution was slowly added to the solution at 70°C to cause precipitation reaction, and the end point pH value was controlled to 8.5. The solution was then aged for 3 hours, and then fully washed with water, dried at 120°C, and calcined at 500°C to obtain a solid catalyst powder;

[0152] 4) The solid catalyst powder was uniformly mixed with 10.79 g of the remaining (30%) solid microsphere powder from step 1), 5 g of calcium aluminate, and 2 g of sesbania powder, and then formed into a 1.5 mm clover-shaped configuration using an extruder; the clover-shaped catalyst was placed in a constant temperature and humidity chamber at 50° C. and 97% humidity for 158 hours, then dried at 120° C. and calcined at 600° C. to produce 55 g of an oxidized caprolactam hydrogenation refining catalyst;

[0153] 5) The oxidized caprolactam hydrorefining catalyst was reduced with hydrogen at 520° C. for 4 hours, then cooled to room temperature. The catalyst was sealed in deoxygenated water under nitrogen protection to obtain a reduced caprolactam hydrorefining catalyst. The elemental composition was determined by ICP spectrometry to be: Ni (26.92%), rare earth modified alumina (51.27%). The pore size distribution was determined by nitrogen adsorption and desorption method. Figure 8 shown.

[0154] Performance testing and result analysis

[0155] The catalysts of Examples 1 to 5 and the comparative catalyst were tested for hydrogenation performance. The caprolactam aqueous solution used in the tests was obtained from the inlet feedstock of the hydrogenation reactor of an industrial caprolactam refining unit. The test results after 72 hours of reaction are listed in Table 1. PAN testing method: spectrophotometry (GBT 13255.3-2009).

[0156] Two portions of each of the catalysts of Examples 1 to 5 and the comparative example were taken and immersed in an alkaline aqueous solution with a pH value of 10 and an acidic solution with a pH value of 4 for 180 days, respectively. The catalysts were taken out and the surface water was dried with filter paper. The crushing strength of the catalysts was tested in a wet state (HG / T 2782-2011). The test results are listed in Table 2.

[0157] Table 1

[0158]

[0159] Table 2

[0160]

[0161] The PAN value characterizes the content of reducing impurities in a caprolactam aqueous solution; lower values ​​indicate lower levels of reducing impurities. The evaluation data in Table 1 demonstrate that Examples 1-5 exhibit significantly better hydrogenation performance than the comparative example. The data in Table 2 show that after the catalysts were soaked in acidic and alkaline solutions, the strength data for Examples 1-5 significantly outperformed the comparative example, indicating that Examples 1-5 exhibit superior tolerance to acidic and alkaline solutions and are suitable for use in caprolactam hydrogenation refining processes at pH values ​​of 4-10.

[0162] Comparative Example 1 was prepared by conventional co-precipitation method. The pore size distribution of the catalyst was concentrated in the range of 2 to 10 nm. The pore size was small, the hydrogenation performance was poor, and the crushing strength of the catalyst decreased significantly after long-term immersion. It was easy to pulverize and lose.

[0163] Compared with Example 1, in Comparative Example 2, all rare earth oxide-modified alumina were subjected to high-temperature calcination. The catalytic pore size distribution was 8 to 100 nm, which was significantly wider, and the hydrogenation performance was excellent. However, because the carrier could not be peptized, it could only be formed into tablets. The crushing strength of the catalyst decreased significantly after long-term immersion, and it was easy to pulverize and lose.

[0164] Compared with Example 5, Comparative Example 3 cancels the addition of rare earth elements, and the catalyst pore size distribution is concentrated in 6-23 nm, which is more suitable. The catalyst crushing strength does not show a significant decrease after long-term immersion, but the catalyst hydrogenation activity is worse than that of the example.

[0165] The above embodiments are intended only to illustrate the technical solutions of the present invention and are not intended to limit the same. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that the technical solutions described in the above embodiments may be modified, or some or all of the technical features thereof may be replaced with equivalents, without departing from the spirit and substance of the claims of the present invention; and such modifications or replacements remain within the scope of the claims of the present invention.

Claims

1. A method for preparing a caprolactam hydrorefining catalyst, characterized in that: The following steps are involved: (1) uniformly mixing aluminum sol and rare earth metal salt or zirconium salt to obtain slurry I, wherein the solid content of aluminum oxide and rare earth metal salt or zirconium salt in slurry I is 20-40%; spray drying and granulating the slurry I to obtain solid microsphere powder; Taking a portion of the solid microsphere powder and calcining it to obtain rare earth oxide or zirconium oxide modified alumina, wherein the mass ratio of alumina to the rare earth metal element or zirconium element contained in the rare earth oxide or zirconium oxide is (15-50):1; The part of the solid microsphere powder taken in step (1) accounts for 40% to 70% of the total mass of the solid microsphere powder; (2) adding the rare earth oxide or zirconium oxide modified alumina and the structural additive into water and uniformly mixing them to obtain slurry II, wherein the mass ratio of the structural additive to the rare earth oxide or zirconium oxide modified alumina is (0.15-0.6):1; (3) adding a nickel salt aqueous solution to slurry II and stirring thoroughly to obtain slurry III; adding a precipitant to slurry III to deposit the reaction product of the precipitation reaction on the support, washing, drying, roasting, and crushing to obtain a solid catalyst powder, wherein the Ni content is 15 to 35 wt% of the mass of the solid catalyst powder; (4) taking the remaining portion of the solid microsphere powder of step (1) and uniformly mixing it with the solid catalyst powder, binder, and lubricant of step (3), optionally adding dilute nitric acid, and molding to obtain a molded catalyst, wherein the amount of the binder added is 5 to 15 wt% of the mass of the solid catalyst powder, and the amount of the lubricant added is 3 to 7 wt% of the mass of the solid catalyst powder; The obtained shaped catalyst is placed in a constant temperature and humidity box at a constant temperature of 25 to 50° C. and a humidity of 90 to 97% for 72 to 168 hours, and then dried and calcined to obtain an oxidized caprolactam hydrogenation refining catalyst; (5) reducing the oxidized caprolactam hydrorefining catalyst and sealing it in deoxygenated water to obtain a reduced caprolactam hydrorefining catalyst.

2. The preparation method according to claim 1, characterized in that In step (1), the calcination temperature is 800-1000° C. and the calcination time is 2-6 hours.

3. The preparation method according to claim 1 or 2, characterized in that In step (2), the mass ratio of the structural additive to the rare earth oxide or zirconium oxide modified alumina is (0.18-0.56):

1.

4. The preparation method according to claim 1 or 2, characterized in that In step (3), the content of Ni is 20 to 30 wt% of the mass of the solid catalyst powder.

5. The preparation method according to claim 1 or 2, characterized in that The nickel salt in step (3) is one or more selected from nickel nitrate, nickel acetate and nickel sulfate; and / or The precipitant in step (3) is one or more selected from sodium carbonate, sodium bicarbonate, potassium carbonate and potassium bicarbonate.

6. The preparation method according to claim 1 or 2, characterized in that The precipitation reaction temperature in step (3) is 50-70° C., and the pH value at the reaction end point is 7-8.5; and / or After the precipitation reaction in step (3), aging is performed for 3-5 hours; and / or In step (3), the drying temperature is 100-120°C, and the calcination temperature is 500-600°C.

7. The preparation method according to claim 1 or 2, characterized in that In step (4), the amount of the binder added is 5-10 wt% of the mass of the solid catalyst powder, and the amount of the lubricant added is 3-5 wt% of the mass of the solid catalyst powder.

8. The preparation method according to claim 1 or 2, characterized in that In step (4), the binder is one or more selected from magnesium phosphate, calcium aluminate and calcium silicate, and / or the lubricant is one or more selected from sesbania powder, methylcellulose and calcium stearate; And / or, in step (4), the drying temperature is 100-120°C, and the calcination temperature is 500-600°C.

9. The preparation method according to claim 1 or 2, characterized in that: The reduction conditions in step (5) are: hydrogen reduction at 450-600° C. for 2-10 h; and / or The conductivity of the deoxygenated water in step (5) is less than 5 μs / cm.

10. The preparation method according to claim 1 or 2, characterized in that: The rare earth oxide or zirconium oxide is one or more selected from La2O3, ZrO2, Sm2O3; and / or The structural additive is one or more selected from kaolin and titanium dioxide; and / or The crystal form of the aluminum oxide modified by the rare earth oxide or zirconium oxide is one or a mixed crystal form of γ, δ, θ, and ɑ.

11. The preparation method according to claim 1 or 2, characterized in that: The crystal form of the aluminum oxide modified by the rare earth oxide or zirconium oxide is a γ-θ mixed crystal form.

12. A caprolactam hydrorefining catalyst, characterized in that: The catalyst is prepared by the preparation method according to any one of claims 1 to 11, the catalyst comprising a catalyst support and an active component Ni supported on the catalyst support, the catalyst support comprising alumina modified with rare earth oxide or zirconium oxide, a structural additive, a binder and a lubricant; Based on the mass of the caprolactam hydrorefining catalyst, the content of the active ingredient Ni is 10-40wt%, the content of the rare earth oxide or zirconium oxide modified alumina is 40-79wt%, the content of the structural additive is 3-20wt%, the content of the binder is 5-15wt%, and the content of the lubricant is 3-7wt%; In the rare earth oxide or zirconium oxide modified alumina, the mass ratio of alumina to the rare earth metal element or zirconium element contained in the rare earth oxide or zirconium oxide is 15 to 50:1; The caprolactam hydrogenation refining catalyst has a pore volume of 0.4 to 1.5 ml / g and an average pore diameter of 20 to 40 nm.

13. The caprolactam hydrorefining catalyst according to claim 12, characterized in that Based on the mass of the caprolactam hydrorefining catalyst, the content of active ingredient Ni is 12-30wt%, the content of rare earth oxide or zirconium oxide modified alumina is 45-70wt%, the content of structural additive is 7-20wt%, the content of binder is 5-10wt%, and the content of lubricant is 3-5wt%.

14. A caprolactam hydrogenation refining method, characterized in that: The method comprises: hydrofining caprolactam in a fixed-bed hydrogenation reactor containing the caprolactam hydrofining catalyst according to claim 12 or 13.

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