Preparation method of carbon four selective hydrogenation catalyst

Abstract

The application relates to a preparation method of a carbon four selective hydrogenation catalyst and belongs to the technical field of carbon four fraction selective hydrogenation catalyst preparation methods. The existing carbon four selective hydrogenation catalyst has the problems of poor sulfur resistance, low catalytic activity and selectivity. The application adopts the following steps: 1) solid aluminum salt and solid zirconium salt are mixed uniformly in a mortar; 2) ammonium bicarbonate is added and grinded into a uniform paste, wherein the molar ratio of the ammonium bicarbonate to (Al+Zr) is 3-5:1; 3) the mixture is dried once and then washed with deionized water until neutral, and is dried again; 4) the composite carrier Al2O3-ZrO2 is obtained by calcination; 5) a mixed solution of nickel salt and copper salt is prepared, and the composite carrier is fully impregnated with the mixed solution; 6) the carbon four selective hydrogenation catalyst is obtained by drying and calcining the impregnated composite carrier. The carbon four selective hydrogenation catalyst has good catalytic activity, stability and selectivity, and the preparation method is simpler than the precipitation method and has less wastewater.

Description

Technical Field

[0001] The invention discloses a method for preparing a C4 selective hydrogenation catalyst, belonging to the technical field of methods for preparing C4 fraction selective hydrogenation catalysts. Background Art

[0002] When liquid-phase mixed C4 feedstock is used in alkylation production, it must pass through a selective hydrogenation unit to selectively remove ppm-level butadiene (1,000-20,000 ppm) from the feedstock before entering the alkylation reaction unit. This prevents the butadiene from polymerizing under the action of concentrated sulfuric acid, which would lead to a decrease in acid concentration and affect the stable operation of the unit. Currently, the selective hydrogenation catalyst used in industry is a palladium-based catalyst supported on alumina. However, due to the high price and scarcity of palladium metal, the development of a non-precious metal catalyst is of great strategic significance.

[0003] In the existing non-precious metal 1,3-butadiene selective hydrogenation reaction, non-precious metal catalysts usually have good butadiene selective hydrogenation activity and monoolefin selectivity, but a major challenge faced by this series of catalysts is that it is difficult for the catalyst to maintain stable catalytic performance during long-term operation under industrial conditions. The reason is that under actual industrial operating conditions, liquid C4 feedstock usually comes from a catalytic cracking unit, so the feedstock contains sulfide impurities of more than ten to several tens of ppm. Due to S 2- Due to its nucleophilic properties, it is more easily adsorbed on the metal surface than butadiene, resulting in the closure of active sites. The catalytic performance gradually decreases with the extension of the reaction cycle. Moreover, as crude oil faces the development of inferior quality, the sulfide content in the raw materials shows an increasing trend year by year.

[0004] Literature research shows that using catalytic cracking carbon four as raw material, the reaction temperature is 70 ℃, the reaction pressure is 1.3 MPa, and the liquid space velocity is 18 h -1 Under the conditions of 20 h continuous reaction, the Ni / Al2O3 catalyst began to show obvious deactivation after 20 h of continuous reaction. After 70 h of reaction, the catalyst activity decreased from the initial nearly 100% to 70% (Liu Jianjun, Huang Xingliang, Petrochemical Engineering, 2011, 40(08):825-830.). In addition, studies have found that the acidity of the carrier alumina can lead to the formation of green oil during hydrogenation. Therefore, increasing the calcination temperature is often used to reduce the acidity of the alumina carrier and inhibit the formation of green oil. However, excessively high calcination temperatures can cause a decrease in the specific surface area of ​​the alumina carrier and collapse of the pore structure. Since C4 hydrogenation usually uses liquid phase feed, an unsuitable pore structure can hinder the diffusion of the product, causing secondary reactions and reducing the selectivity of monoolefins.

[0005] In the prior art, patent CN105642324B discloses a method for preparing a 1,3-butadiene selective hydrogenation catalyst. The catalyst consists of an active component, amorphous nickel phosphide, an alumina carrier, and an additive X. The catalyst preparation requires hydrothermal evaporation, inert atmosphere calcination, high-temperature hydrogen reduction, and passivation. The catalyst is heated at 75-100°C, a total pressure of 1.5-2.0 MPa, and a space velocity of 5-10 h -1 Under conditions where the hydrogen / butadiene molar ratio is 1.0-2.0, the butadiene conversion rate in mixed C4 is >98%, and the butene loss rate is <1%. CN106582706B discloses a method for preparing a nickel-based butadiene selective hydrogenation catalyst. The catalyst uses alumina as a support, has Ni as the main active component, and contains Ag, Au, Ce, and K as co-active components. It exhibits high butadiene hydrogenation activity and low butene loss rate. Neither of these two technical solutions addresses the problem of S impurities adsorbed on the metal surface during use, resulting in the blocking of active sites. They also fail to address the fragile pore structure of the alumina support, which is caused by the need to suppress green oil. In other existing technologies, non-precious metal catalysts also exhibit poor monoolefin selectivity. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and provide a C4 selective hydrogenation catalyst with good sulfur resistance, high catalytic activity and high monoolefin selectivity.

[0007] The technical solution adopted by the present invention to solve the technical problem is: a method for preparing a C4 selective hydrogenation catalyst, characterized in that it comprises the following steps:

[0008] 1) Solid aluminum salt and solid zirconium salt are placed in a mortar and ground and mixed uniformly, wherein the molar ratio of Zr to Al is 0.1 to 1:1;

[0009] 2) Add ammonium bicarbonate and grind until it becomes a uniform paste, wherein the molar ratio of ammonium bicarbonate to (Al + Zr) is 3-5:1;

[0010] 3) After the mixture is dried once, it is washed with deionized water until it is neutral and then dried twice;

[0011] 4) Calcination to obtain the composite support Al2O3-ZrO2;

[0012] 5) preparing a mixed solution of nickel salt and copper salt, wherein the molar ratio of Cu to Ni is 0.1 to 0.5:1, the total volume of the mixed solution is the same as the total pore volume of the composite support, and using the mixed solution to fully impregnate the composite support;

[0013] 6) The impregnated composite carrier is dried and calcined to obtain a C4 selective hydrogenation catalyst.

[0014] The solid-phase grinding method used to prepare the support significantly reduces wastewater generation compared to traditional precipitation methods. Furthermore, the support possesses a higher specific surface area, wider pore size, and richer pore structure, thereby reducing the impact of sulfur adsorption on the metal surface on catalyst activity. This results in a high catalyst loading, high catalytic activity, and high monoolefin selectivity. Drying, washing, and drying are performed first to achieve initial condensation of the mixture, preventing the weak Al-O-Zr bonds from being broken by direct rinsing with deionized water.

[0015] Preferably, the aluminum salt in step 1) is one or both of aluminum nitrate nonahydrate and aluminum chloride hexahydrate.

[0016] Preferably, the zirconium salt in step 1) is zirconium oxychloride octahydrate.

[0017] Preferably, the primary drying in step 3) is carried out at 60-120° C. for 20-25 hours, and the secondary drying is carried out at 60-120° C. for 10-12 hours.

[0018] Preferably, the calcination in step 4) is carried out in a muffle furnace at 400-600° C. for 4-6 hours.

[0019] Under optimal conditions, the proportion of Al2O3 in the composite carrier can reach 29.3~78.8wt%; the proportion of ZrO2 can reach 21.2~70.7wt%, ensuring the richness of the carrier pore structure and a high specific surface area, with a high pore volume and pore size.

[0020] Preferably, the nickel salt in step 5) is nickel nitrate hexahydrate.

[0021] Preferably, the copper salt in step 5) is copper nitrate trihydrate.

[0022] Preferably, the calcination in step 6) is carried out in a muffle furnace at 400-600° C. for 4-6 hours.

[0023] Under optimal conditions, NiO accounts for 5~20 wt% in the C4 selective hydrogenation catalyst; CuO accounts for 0.5~10wt%; and Al2O3-ZrO2 accounts for 70~94.5wt%.

[0024] Compared with the prior art, the present invention has the following beneficial effects: compared with precious metal catalysts, the manufacturing cost of the catalyst is greatly reduced; and the higher specific surface area, wider pore diameter and richer pore structure are beneficial to the diffusion of raw materials and products in the liquid-phase C4 hydrogenation reaction and the reduction of the occurrence of secondary reactions, greatly improving the hydrogenation activity and monoolefin selectivity, and low butene hydrogenation loss rate; at the same time, it also has better catalytic stability and good sulfur resistance; less wastewater is generated, and the preparation method is simpler. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 These are the long-cycle reaction evaluation results of the C4 selective hydrogenation catalyst in Example 2. DETAILED DESCRIPTION

[0026] The present invention will be further described below with reference to the embodiments, wherein embodiment 4 is the best embodiment of the present invention.

[0027] Example 1

[0028] A method for preparing a C4 selective hydrogenation catalyst comprises the following steps:

[0029] 1) 37.5g aluminum nitrate nonahydrate and 32.2g zirconium oxychloride octahydrate were placed in a mortar and ground into a uniform mixture.

[0030] 2) Add 47.4g of ammonium bicarbonate and grind until it becomes a uniform paste;

[0031] 3) The paste sample was dried at 60°C for 24 h, then washed with deionized water until neutral, and dried again at 60°C for 12 h;

[0032] 4) Calcination in a muffle furnace at 500°C for 5 h to obtain the composite support Al2O3-ZrO2;

[0033] 5) Dissolve 3.09 g of nickel nitrate hexahydrate and 0.24 g of copper nitrate trihydrate in deionized water to obtain a mixed solution. Take 15 g of the composite support and fully impregnate the composite support with the mixed solution. The volume of the mixed solution should be equal to the total pore volume of the composite support.

[0034] 6) The impregnated composite support was dried at 60°C for 12 h and calcined in a muffle furnace at 400°C for 4 h to obtain a C4 selective hydrogenation catalyst.

[0035] Example 2

[0036] A method for preparing a C4 selective hydrogenation catalyst, based on Example 1, comprises the following steps: step 1) setting the amount of aluminum nitrate nonahydrate to 112.5 g and the amount of zirconium oxychloride octahydrate to 10.7 g; step 2) setting the amount of ammonium bicarbonate to 79.1 g; step 5) setting the amount of nickel nitrate hexahydrate to 16.68 g and the amount of copper nitrate trihydrate to 6.5 g; and step 6) setting the drying temperature to 120° C. and the calcination temperature to 600° C. for 6 hours.

[0037] Other conditions are the same as in Example 1.

[0038] Example 3

[0039] A method for preparing a C4 selective hydrogenation catalyst, based on Example 1, comprises the following steps: step 1) setting the amount of aluminum nitrate nonahydrate to 93.8 g and the amount of zirconium oxychloride octahydrate to 16.1 g; step 2) setting the amount of ammonium bicarbonate to 118.6 g; step 5) setting the amount of nickel nitrate hexahydrate to 10.28 g and the amount of copper nitrate trihydrate to 3.1 g; and step 6) setting the drying temperature to 80° C. and the calcination temperature to 500° C. for 6 hours.

[0040] Other conditions are the same as in Example 1.

[0041] Example 4

[0042] A method for preparing a C4 selective hydrogenation catalyst is provided. Based on Example 1, in step 1), aluminum nitrate nonahydrate is replaced with aluminum chloride hexahydrate, and the amount used is set to 60.5 g. Other conditions are the same as in Example 1.

[0043] Comparative Example 1

[0044] A method for preparing a C4 selective hydrogenation catalyst is provided. Based on Example 1, in step 1), the amount of aluminum nitrate nonahydrate is set to 5 g, the amount of zirconium oxychloride octahydrate is set to 120 g, and other conditions are the same as in Example 1.

[0045] Comparative Example 2

[0046] A method for preparing a C4 selective hydrogenation catalyst is provided. Based on Example 1, in step 1), the amount of aluminum nitrate nonahydrate is set to 120 g, the amount of zirconium oxychloride octahydrate is set to 5 g, and other conditions are the same as in Example 1.

[0047] Comparative Example 3

[0048] A method for preparing a C4 selective hydrogenation catalyst is provided. Based on Example 1, the amount of ammonium bicarbonate used in step 2) is set to 10 g, and other conditions are the same as in Example 1.

[0049] Comparative Example 4

[0050] A method for preparing a C4 selective hydrogenation catalyst is described. Based on Example 1, the aluminum nitrate nonahydrate and zirconium oxychloride octahydrate in step 1) are dissolved in 150 g of deionized water. The ammonium bicarbonate in step 2) is dissolved in 100 g of deionized water and then poured into the mixed solution in step 1). A white precipitate gradually forms and stirring is continued for 1 hour. In step 3), the white precipitate in step 2) is filtered and washed three times, followed by drying at 60°C for 24 hours. Other conditions are the same as in Example 1. A precipitation method is used instead to prepare the catalyst support. This method uses a relatively large amount of water.

[0051] Performance Testing

[0052] The pore structure of the composite carriers obtained in the preparation process of the above examples and comparative examples was analyzed, and the test results are shown in Table 1 below.

[0053] Table 1 Pore structure

[0054] .

[0055] The catalysts prepared in the examples and comparative examples were loaded into a fixed bed reactor and the selective hydrogenation of a catalytic C4 fraction containing 0.56% butadiene was continuously performed. The long-term reaction stability test results of Example 2 are shown in FIG. Figure 1 The hydrogenation performance test results of Examples 1 to 4 and Comparative Examples 1 to 4 are shown in Table 2 below.

[0056] Table 2 Hydrogenation performance test

[0057] .

[0058] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any other manner. Any person skilled in the art may utilize the above-disclosed technical content to modify or modify the present invention into equivalent embodiments. However, any simple modifications, equivalent variations, and modifications to the above embodiments that do not depart from the technical content of the present invention and are based on the technical essence of the present invention remain within the scope of protection of the present invention.

Claims

1. A method for preparing a C4 selective hydrogenation catalyst, characterized in that: The following steps are involved: 1) Solid aluminum salt and solid zirconium salt are placed in a mortar and ground and mixed uniformly, wherein the molar ratio of Zr to Al is 0.1 to 1:1; 2) Add ammonium bicarbonate and grind until it becomes a uniform paste, wherein the molar ratio of ammonium bicarbonate to (Al + Zr) is 3-5:1; 3) After the mixture is dried once, it is washed with deionized water until it is neutral and then dried twice; 4) Calcination to obtain the composite support Al2O3-ZrO2; 5) preparing a mixed solution of nickel salt and copper salt, wherein the molar ratio of Cu to Ni is 0.1 to 0.5:1, and the total volume of the mixed solution is equal to the total pore volume of the composite support; and fully impregnating the composite support with the mixed solution; 6) The impregnated composite carrier is dried and calcined to obtain a C4 selective hydrogenation catalyst.

2. The method for preparing the C4 selective hydrogenation catalyst according to claim 1, wherein: The aluminum salt in step 1) is one or both of aluminum nitrate nonahydrate and aluminum chloride hexahydrate.

3. The method for preparing the C4 selective hydrogenation catalyst according to claim 1, wherein: The zirconium salt in step 1) is zirconium oxychloride octahydrate.

4. The method for preparing the C4 selective hydrogenation catalyst according to claim 1, wherein: The primary drying in step 3) is carried out at 60-120° C. for 20-25 hours, and the secondary drying is carried out at 60-120° C. for 10-12 hours.

5. The method for preparing the C4 selective hydrogenation catalyst according to claim 1, wherein: The calcination in step 4) is carried out at 400-600° C. in a muffle furnace for 4-6 hours.

6. The method for preparing the C4 selective hydrogenation catalyst according to claim 1, wherein: The nickel salt described in step 5) is nickel nitrate hexahydrate.

7. The method for preparing the C4 selective hydrogenation catalyst according to claim 1, wherein: The copper salt in step 5) is copper nitrate trihydrate.

8. The method for preparing the C4 selective hydrogenation catalyst according to claim 1, wherein: The calcination in step 6) is carried out in a muffle furnace at 400-600° C. for 4-6 hours.

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