Preparation method and application of copper silica gel catalyst

Abstract

The invention relates to the field of catalysts, in particular to a preparation method and application of a copper silica gel catalyst. Comprising the following steps: 1) uniformly mixing copper nitrate, ammonia water and water to prepare a copper ammonia precursor solution; 2) mixing the precursor solution and a coarse-pore microsphere silica gel carrier, dipping, standing for a period of time, and carrying out electrostatic adsorption; (3) heating the mixed system in the step (2), carrying out homogeneous precipitation and deposition, and completing impregnation until the pH value of the solution is reduced to 6-7; 4, the mixed system is filtered, washed, dried and roasted, and the copper silica gel catalyst.According to the catalyst, the active components are loaded in two steps, the active components loaded in different steps are controlled to achieve structural regulation and control, the activity and stability of the catalyst are improved, and the scheme is simple, convenient, easy to implement, economical and feasible.

Description

Technical Field

[0001] The invention relates to the field of catalysts, and in particular to a preparation method and application of a copper silica gel catalyst. Background Art

[0002] As an important organic chemical raw material and intermediate, aromatic amine can be used to produce more than 300 products such as MDI (methylene diphenyl diisocyanate), dyes, building materials, rubber products and chemical intermediates; aromatic amine can also be used as a solvent and can be used in the synthesis of gasoline anti-knock compounds. Aniline, as a typical representative of aromatic amines, was first used to produce dyes and their intermediates, and then began to be used in the production of rubber additives. Recently, with the widespread application of polyurethane materials in the construction industry, automobile industry, electrical industry, packaging materials and other fields, the market demand for aniline will continue to grow rapidly.

[0003] The industrial production methods of aniline mainly include nitrobenzene iron powder reduction method, phenol amination method, and nitrobenzene catalytic hydrogenation method. Nitrobenzene iron powder reduction method is the earliest industrial method, but it is basically no longer used due to problems such as equipment corrosion and environmental pollution, and its production capacity accounts for only about 5%; the phenol amination method has easy-to-obtain raw materials, low catalyst prices, and relatively less waste gas and liquid, which can achieve continuous production, but the process cost is very high. Currently, only a few companies such as Japan's Mitsui and the United States Astrak use this process, accounting for about 10% of the production capacity; the nitrobenzene catalytic hydrogenation method has relatively less pollution, mild reaction conditions, and low investment costs. It is the current mainstream aniline production process, accounting for about 85% of the world's total production capacity.

[0004] With the increasingly stringent requirements for green, low-carbon and environmental protection in recent years, energy conservation and consumption reduction, and green production have become the basis for the sustainable development of the chemical industry. The aniline industry has gradually increased its attention to technologies such as green raw materials and process intensification. As the mainstream aniline production process, catalytic hydrogenation of nitrobenzene mainly achieves technological upgrades through catalyst improvement and process optimization. Hydrogenation catalysts mainly include precious metal systems and non-precious metal systems. Precious metal catalysts have high catalytic efficiency and high cost, while non-precious metal catalysts are cheap but have poor stability. Therefore, reducing the amount of precious metal catalysts and improving the activity and stability of non-precious metal catalysts are the key tasks of optimizing the catalytic system.

[0005] At present, the hydrogenation reactors used in industry include fixed bed reactors and fluidized bed reactors. Except for the domestic leading companies Wanhua Chemical (which has acquired Bosu Chemical and Chematur) and Shanxi Tianji, which mainly use the liquid phase method, the rest are fluidized bed catalytic hydrogenation technology, using granular Cu / SiO2 catalysts. In addition to adding additives and carrier modification, regulating the structure of active components is also an effective means to improve the activity and thermal stability of catalysts. By adjusting the interaction between the structure of active components and the carrier, the performance of catalysts can also be effectively improved.

[0006] The production technology of copper silica gel mainly includes impregnation method and electrostatic adsorption method. Since the dispersibility of copper ammonia complex ion impregnation is better (Journal of Catalysis, 1980, (03): 168-174.), the main idea of ​​preparing copper silica gel is to impregnate divalent copper ions into silica gel in an ammonia solution to prepare the corresponding catalyst. CN 1768941 oxidizes metallic copper into a copper ammonia solution under air and ammonia source conditions, impregnates the carrier and auxiliary agent (Cr, Mo, Ba, Zn, Ce, Ni, V, Pb, Pt) solution in equal volumes, impregnates the copper ammonia solution in excess (different temperature stage treatment), cools, filters, washes with dilute ammonia water, washes with deionized water, and dries and roasts to prepare the corresponding catalyst. CN 1285407C prepares a mixed solution of copper and auxiliary agent precursors in ammonia water, mixes and stirs with the corresponding silica gel solution, impregnates, and sprays and dries after aging and washing to prepare the corresponding catalyst.

[0007] Modification with additives can further improve the performance of the catalyst. Qian Hua et al. from Nanjing University of Science and Technology promoted the reduction of the Cu component in the catalyst by modifying the catalyst with Cr additives, and effectively inhibited the oxidation of the active components during the catalytic process, thereby improving the reaction performance of the catalyst (Fine Chemicals, 2009, 26 (07): 720-723.).

[0008] Carrier modification can achieve the regulation of carrier specific surface area and pore size distribution. CN 102000612B prepares a corresponding carrier by placing coarse-porous microsphere silica gel in a reactor, then soaking, washing and drying in acid, and then immersing the carrier in a copper ammonia complex solution, separating, washing and drying to obtain a finished catalyst. Carrier modification effectively inhibits pore blockage during the reaction, improves catalytic performance, prolongs the life of the catalyst, and avoids the introduction of multiple components during the preparation process.

[0009] In summary, although these methods can improve the activity and stability of copper silica gel catalysts, they all use a single loading process and cannot regulate the composition ratio of active components in the catalyst. Therefore, it is of great value to use different preparation methods to start with the balance regulation of active component composition, and then improve the activity and stability of copper silica gel catalysts for hydrogenation of nitrobenzene and its homologues. Summary of the invention

[0010] The purpose of the present invention is to provide a method for preparing a copper silica gel catalyst. The preparation method of the present invention can simply and efficiently regulate the composition ratio of active components in the copper silica gel catalyst, thereby improving the reaction activity and thermal stability of the catalyst and significantly reducing the sintering temperature of the catalyst during the reaction process.

[0011] In order to solve the above technical problems, the technical solution adopted by the present invention is: a method for preparing a copper silica gel catalyst, comprising the following steps: 1) Evenly mix copper nitrate, ammonia water and water to prepare a copper-ammonia precursor solution; 2) Mix the precursor solution and the macroporous microsphere silica gel carrier, immerse them in water, and place them for a period of time for electrostatic adsorption; 3) heating the mixed system in step 2) to perform homogeneous precipitation and deposition until the pH value of the solution drops to 6-7 and the impregnation is completed; 4) Filtering, washing, drying and calcining the mixed system to obtain a copper silica gel catalyst.

[0012] As a further limitation of the technical solution of the present invention, in step 1), the mass ratio of copper nitrate, aqueous ammonia and water is 1:1-10:1-50.

[0013] As a further preferred limitation of the technical solution of the present invention, in step 1), the mass ratio of copper nitrate, aqueous ammonia and water is 1:3-5:10-20.

[0014] As a further limitation of the technical solution of the present invention, in step 2), the mass ratio of the precursor solution to the macroporous microsphere silica gel is 5-50:1, the adsorption time is 0.5-24 h, and the immersion temperature is room temperature.

[0015] As a further preferred limitation of the technical solution of the present invention, in step 2), the mass ratio of the precursor solution to the macroporous microsphere silica gel is 15-25:1.

[0016] As a further limitation of the technical solution of the present invention, in step 3), the heating temperature of the mixed system is 60-90 °C, the system pressure is -0.9-1 bar, and the heating time is 1-5 h.

[0017] As a further preferred limitation of the technical solution of the present invention, in step 3), the heating temperature of the mixed system is 70-80 °C, the system pressure is -0.8-0.6 bar, and the heating time is 2-3 h.

[0018] As a further limitation of the technical solution of the present invention, in step 4), the temperature for drying the filtered components is 90-150 °C, the calcination temperature is 300-500 °C, and the calcination time is 1-10 h.

[0019] As a further preferred limitation of the technical solution of the present invention, in step 4), the temperature for drying the filtered components is 110-130 °C, the roasting temperature is 400-470 °C, and the roasting time is 2-5 h.

[0020] In addition, the present invention also provides the use of the copper silica gel catalyst prepared by the above preparation method in the hydrogenation reaction of nitrobenzene and its homologues.

[0021] Compared with the prior art, the present invention has the following beneficial effects: The catalyst of the present invention loads active components in two steps, controls the amount of active components loaded in different steps to achieve structural regulation of the active components of the catalyst, and improves the activity and stability of the catalyst. The scheme is simple, easy to implement, and economically feasible. DETAILED DESCRIPTION

[0022] The present invention is further described below in conjunction with specific embodiments.

[0023] Example 1

[0024] A method for preparing a copper silica gel catalyst comprises the following steps: 1) Mix copper nitrate, ammonia water and water in a mass ratio of 1:1:19 to prepare a copper ammonia precursor solution; 2) Mix the precursor solution and the macroporous microsphere silica gel carrier in a mass ratio of 15:1, immerse them, and leave them for a period of time for electrostatic adsorption; 3) heating the mixed system in step 2) at a heating temperature of 90 °C, a system pressure of -0.6 bar, and a heating time of 2.5 h to perform homogeneous precipitation and deposition until the pH value of the solution drops to 6.92 and the impregnation is completed; 4) The mixed system is filtered, washed, dried, and calcined to obtain a copper silica gel catalyst, wherein the drying temperature is 120 °C, the calcination temperature is 430 °C, and the calcination time is 4 h.

[0025] Example 2

[0026] A method for preparing a copper silica gel catalyst comprises the following steps: 1) Copper nitrate, ammonia water and water are mixed evenly in a mass ratio of 1:2:17 to prepare a copper ammonia precursor solution; 2) Mix the precursor solution and the macroporous microsphere silica gel carrier in a mass ratio of 15:1, immerse them, and leave them for a period of time for electrostatic adsorption; 3) heating the mixed system in step 2) at a heating temperature of 80 °C, a system pressure of -0.5 bar, and a heating time of 2.3 h to perform homogeneous precipitation and deposition until the pH value of the solution drops to 6.81 and the impregnation is completed; 4) The mixed system is filtered, washed, dried, and calcined to obtain a copper silica gel catalyst, wherein the drying temperature is 130 °C, the calcination temperature is 450 °C, and the calcination time is 4 h.

[0027] Example 3

[0028] A method for preparing a copper silica gel catalyst comprises the following steps: 1) Copper nitrate, ammonia water and water are mixed uniformly in a mass ratio of 1:3:16 to prepare a copper ammonia precursor solution; 2) Mix the precursor solution and the macroporous microsphere silica gel carrier in a mass ratio of 15:1, immerse them, and leave them for a period of time for electrostatic adsorption; 3) heating the mixed system in step 2) at a heating temperature of 75 °C, a system pressure of -0.75 bar, and a heating time of 2.5 h to perform homogeneous precipitation and deposition until the pH value of the solution drops to 6.84 and the impregnation is completed; 4) The mixed system is filtered, washed, dried, and calcined to obtain a copper silica gel catalyst, wherein the drying temperature is 120 °C, the calcination temperature is 450 °C, and the calcination time is 4 h.

[0029] Example 4

[0030] A method for preparing a copper silica gel catalyst comprises the following steps: 1) Copper nitrate, ammonia water and water are mixed uniformly in a mass ratio of 1:4:15 to prepare a copper ammonia precursor solution; 2) Mix the precursor solution and the macroporous microsphere silica gel carrier in a mass ratio of 15:1, immerse them, and leave them for a period of time for electrostatic adsorption; 3) heating the mixed system in step 2) at a heating temperature of 75 °C, a system pressure of -0.65 bar, and a heating time of 2.3 h to perform homogeneous precipitation and deposition until the pH value of the solution drops to 6.69 and the impregnation is completed; 4) The mixed system is filtered, washed, dried, and calcined to obtain a copper silica gel catalyst, wherein the drying temperature is 130 °C, the calcination temperature is 430 °C, and the calcination time is 3 h.

[0031] Comparative Example 1 A method for preparing a copper silica gel catalyst comprises the following steps: 1) Copper nitrate, ammonia water and water are mixed evenly in a mass ratio of 1:2:13 to prepare a copper ammonia precursor solution; 2) Mix the precursor solution and the macroporous microsphere silica gel carrier in a mass ratio of 15:1, immerse them in water, and leave them for a period of time for adsorption; 3) The mixed system is dried and calcined to obtain a copper silica gel catalyst, wherein the drying temperature is 120 °C, the calcination temperature is 450 °C, and the calcination time is 4 h.

[0032] The catalytic activity and stability of the catalysts prepared in Examples 1-4 and Comparative Example 1 were measured by gas phase hydrogenation process with a catalyst loading of 500 mg and a nitrobenzene space velocity of 4.0 h -1 The test endpoint was when the concentration of nitrobenzene in the product reached 1.0% (GC analysis method). The physical properties and one-time life results of the catalyst are as follows.

[0033] Table Experimental Data

[0034] From the above results, it can be seen that by loading the active components in two steps and controlling the content and existence form of the active components loaded in different steps, the structure of the active components of the catalyst can be quickly regulated, and the activity and stability of the catalyst can be improved. The scheme is simple, easy and economically feasible.

Claims

1. A method for preparing a copper silica gel catalyst, characterized in that: The following steps are involved: 1) Evenly mix copper nitrate, ammonia water and water to prepare a copper ammonia precursor solution; 2) Mix the precursor solution and the macroporous microsphere silica gel carrier, immerse them in water, and place them for a period of time for electrostatic adsorption; 3) heating the mixed system in step 2) to perform homogeneous precipitation and deposition until the pH value of the solution drops to 6-7 and the impregnation is completed; 4) Filtering, washing, drying and calcining the mixed system to obtain a copper silica gel catalyst.

2. The method for preparing a copper silica gel catalyst according to claim 1, characterized in that: In step 1), the mass ratio of copper nitrate, ammonia water and water is 1:1-10:1-50.

3. The method for preparing a copper silica gel catalyst according to claim 1, characterized in that: In step 1), the mass ratio of copper nitrate, ammonia water and water is 1:3-5:10-20.

4. The method for preparing a copper silica gel catalyst according to claim 1, characterized in that: In step 2), the mass ratio of the precursor solution to the macroporous microsphere silica gel is 5-50:1, the adsorption time is 0.5-24 h, and the immersion temperature is room temperature.

5. The method for preparing a copper silica gel catalyst according to claim 1, characterized in that: In step 2), the mass ratio of the precursor solution to the macroporous microsphere silica gel is 15-25:

1.

6. The method for preparing a copper silica gel catalyst according to claim 1, characterized in that: In step 3), the heating temperature of the mixed system is 60~90 °C, the system pressure is -0.9~1 bar, and the heating time is 1~5 h.

7. The method for preparing a copper silica gel catalyst according to claim 1, characterized in that: In step 3), the heating temperature of the mixed system is 70~80 °C, the system pressure is -0.8~0.6 bar, and the heating time is 2~3 h.

8. The method for preparing a copper silica gel catalyst according to claim 1, characterized in that: In step 4), the temperature for drying the filtered components is 90-150 °C, the calcination temperature is 300-500 °C, and the calcination time is 1-10 h.

9. The method for preparing a copper silica gel catalyst according to claim 1, characterized in that: In step 4), the temperature for drying the filtered components is 110-130 °C, the roasting temperature is 400-470 °C, and the roasting time is 2-5 h.

10. Use of the copper silica gel catalyst prepared by the preparation method according to any one of claims 1 to 9 in the hydrogenation reaction of nitrobenzene and its homologues.

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