CN114618525B - Preparation method and application of porous Raney nickel catalyst - Google Patents

Preparation method and application of porous Raney nickel catalyst Download PDF

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CN114618525B
CN114618525B CN202011456672.5A CN202011456672A CN114618525B CN 114618525 B CN114618525 B CN 114618525B CN 202011456672 A CN202011456672 A CN 202011456672A CN 114618525 B CN114618525 B CN 114618525B
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catalyst
sba
alloy powder
pore volume
alloy
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CN114618525A (en
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李洪坤
王同济
叶飞
孙康
黎源
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Wanhua Chemical Group Co Ltd
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    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J25/00—Catalysts of the Raney type
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    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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    • B01J35/60—Catalysts, in general, characterised by their form or physical properties characterised by their surface properties or porosity
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    • B01J35/638—Pore volume more than 1.0 ml/g
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    • B01J35/651—50-500 nm
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    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/0009—Use of binding agents; Moulding; Pressing; Powdering; Granulating; Addition of materials ameliorating the mechanical properties of the product catalyst
    • B01J37/0018—Addition of a binding agent or of material, later completely removed among others as result of heat treatment, leaching or washing,(e.g. forming of pores; protective layer, desintegrating by heat)
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    • B01J37/0009—Use of binding agents; Moulding; Pressing; Powdering; Granulating; Addition of materials ameliorating the mechanical properties of the product catalyst
    • B01J37/0027—Powdering
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Abstract

The invention relates to a preparation method and application of a porous Raney nickel catalyst. The preparation method comprises the following steps: a hard template method is adopted to prepare the porous Raney nickel catalyst, and the selected template agent is self-made SBA-15. And uniformly mixing the nickel-aluminum alloy powder with a certain amount of SBA-15 by a planetary ball mill to obtain a powdery material with uniform composition. Then a certain amount of CMC was mixed and rolled into a sphere using a ball mill. And then drying and roasting the obtained sample, and placing the sample in an alkali solution for activation to obtain the Raney nickel catalyst. When the catalyst is applied to the preparation of Toluenediamine (TDA) by the hydrogenation of Dinitrotoluene (DNT) in a tubular reactor, the DNT conversion rate is more than or equal to 99.99%, the TDA selectivity is more than or equal to 99.8%, and the byproduct tar selectivity is less than or equal to 0.1%.

Description

Preparation method and application of porous Raney nickel catalyst
Technical Field
The patent relates to preparation and application of a novel porous Raney nickel catalyst, which can be applied to preparing TDA by DNT hydrogenation.
Background
Toluene Diamine (TDA) is an intermediate product for producing Toluene Diisocyanate (TDI), and TDI is an important raw material for producing polyurethane by an photochemical method, and the polyurethane material has excellent heat insulation, sound insulation, shock resistance and toxicity resistance and has wide application in the fields of household appliances, buildings, traffic and daily necessities.
The main industrial production process of TDA is a liquid phase hydrogenation process at present, the catalysts used can be roughly divided into two types, one type is a supported Pd/C, pt/C noble metal catalyst, and the catalyst has strong hydrogenation capability, needs milder reaction conditions, but has high price and difficult separation. The other type is Raney nickel catalyst, although the hydrogenation capacity of the Raney catalyst is slightly inferior to that of a noble metal catalyst, the Raney nickel catalyst can achieve better hydrogenation effect by optimizing the process conditions, and on the other hand, the Raney catalyst is easy to separate and low in cost, so that the Raney nickel catalyst has wide application in industry.
The publication patents CN102728363A and CN102744071A respectively disclose a lacquer original nickel and a supported lacquer original nickel catalyst for preparing aromatic amino compounds by hydrogenation of aromatic nitro chemicals, and both catalysts show good hydrogenation performance in the reaction of synthesizing toluenediamine by hydrogenation of dinitrotoluene. However, the urushiol nickel catalyst disclosed in the two patents still needs to carry out hydrogenation reaction of DNT under the condition of up to 2MPa and methanol as an external solvent, and the intensity of the urushiol nickel catalyst is poor, and the urushiol nickel catalyst is easy to break and deactivate in slurry bed reaction needing stirring; although the latter carries out the load on the lacquer original nickel catalyst, because the loaded catalyst needs to extract Fe for replacement by hydrochloric acid, ni is dropped off on the surface of the carrier, only a small amount of Ni is dispersed on the surface and pore channels of the carrier in a physical adsorption mode, and the Ni is easy to be lost under the stirring condition, so that the catalyst is deactivated.
Publication No. CN102580748A discloses a SiO-loaded substrate 2 The amorphous Ni-B catalyst is prepared through mixing soluble metal salt solution with water soluble silicon source to prepare NiO/SiO 2 Precursor, then KBH 4 The catalyst prepared by the method has good hydrogenation activity, but methanol or ethanol is needed to be added as a solvent, and gel formed in the process of obtaining a precursor is crushed and screened, and silica gel with the size of below 300 meshes cannot be utilized, so that the cost is increased; at the same time, the reducing agent reduces Ni 2+ Ions are carried out in the solution, which causes a part of Ni to fall off, and affects the content of Ni in the catalyst and thus the activity of the catalyst.
The publication patent CN102580748A discloses an amorphous alloy catalyst for dinitrotoluene hydrogenation and application, and the prepared supported Ni-B amorphous alloy catalyst shows good hydrogenation performance in DNT hydrogenation reaction at 80-150 ℃ and 0.8-1.2 MPa, but methanol is still needed to be added in the reaction.
Disclosure of Invention
Aiming at the problems, the invention provides a novel preparation method of a porous Raney nickel catalyst, the catalyst prepared by the method has higher mechanical strength and larger specific surface area, and is a grade pore catalyst with micropores, mesopores and macropores, and the diffusion rate of materials in the reaction can be greatly improved
Another object of the present invention is to provide the use of the catalyst, which is suitable for the preparation of Toluenediamine (TDA) by hydrogenation of Dinitrotoluene (DNT), in particular for the preparation of toluenediamine by hydrogenation of dinitrotoluene in a tubular fixed bed reactor, wherein the reaction has a higher diffusion rate of reactants and products, so that the catalytic activity and the service life of the catalyst are obviously prolonged, and no additional solvent such as methanol is needed.
In order to achieve the above purpose, the technical scheme of the invention is as follows:
a method for preparing a porous raney nickel catalyst, comprising the following steps:
(1) SBA-15 is prepared by a sol-gel method;
(2) Preparing Ni-Al alloy, and then grinding into alloy powder;
(3) Uniformly mixing the SBA-15 in the step (1) and the alloy powder in the step (2) through a planetary ball mill; adding CMC (carboxymethyl cellulose), rolling into spherical particles, drying, and roasting to obtain a catalyst precursor;
(4) And (3) activating the precursor obtained in the step (3) in an alkali solution to obtain a catalyst sample.
In the invention, the SBA-15 has a hierarchical pore structure with micropores, mesopores and macropores simultaneously existing, and the specific surface area is 100-400m 2 And/g, wherein the micropore diameter is less than 2nm and accounts for 10-30% of the total pore volume, and the mesopore diameter is 2-50nm and accounts for the total pore40-60% of the total pore volume, wherein the pore diameter of the macropores is greater than 50nm and accounts for 15-45% of the total pore volume; wherein, the micropore mesopores are measured by adopting a nitrogen physical adsorption method, and the macropores are measured by adopting a mercury intrusion method.
In the method of the present invention, in the step (1), SBA-15 is prepared by a sol-gel method, and an aqueous solution of 5 to 30wt% of TPAOH (tetrapropylammonium hydroxide) is first prepared, preferably 10 to 20wt%. Stirring in a water bath at normal temperature, and then dropwise adding a certain amount of TEOS (tetraethyl orthosilicate) to ensure that the SiO in the final aqueous solution 2 /OH - (molar ratio) =0.1-2, stirring continuously for 0.5-2h after finishing to obtain SBA-15 suspension, and then gradually heating to 90 ℃ until evaporating to dryness. The resulting sample was then ground in a mortar for use.
In the method of the invention, in the step (2), the Ni-Al alloy is prepared by putting required metal and auxiliary agent into a smelting crucible. Then placing the crucible into a smelting furnace, heating to 1500-2000 ℃, keeping for 5-10min, and simultaneously starting stirring with the stirring speed of 40-60r/min. Pouring the molten slurry on a graphite plate after completion, and naturally cooling to room temperature to obtain an alloy block. The alloy pieces were crushed into pieces using a crusher, and then the samples were ground into fine powder of d50=5-50 μm by a raymond mill. The Ni-Al alloy consists of Ni 20-40wt%, al 40-70wt% and assistant 10-20wt%.
In the method, in the step (2), the auxiliary agent is one or more of Ca, mg, P, ni, pt, cr, co, ti, mg, B, zn and Mo.
In the method of the invention, in the step (3), the SBA-15 and the alloy powder are fully mixed by a planetary ball mill. Wherein the addition amount of SBA-15 is 10-50wt% based on the mass of the alloy powder. In the method of the invention, in the step (3), CMC is added dropwise in a ball mill, and the total addition amount is 0.5-1wt% based on the mass of the alloy powder. After the spherical product is obtained, the spherical product is dried for 7 to 12 hours at the temperature of 80 to 120 ℃ and then baked for 4 to 10 hours at the temperature of 450 to 600 ℃.
In the method of the invention, in the step (4), the activation environment is a closed normal pressure reaction kettle, the concentration of the alkali liquor used is 5-30wt%, preferably 15-25wt%, and the alkali comprises one or more of sodium hydroxide, potassium hydroxide and urea, preferably urea. The mass ratio of the alkali solution to the precursor is 5-20. The activation temperature is 70-80 ℃, and the activation time is 30-120min.
In another aspect, the invention also provides the use of the catalyst described above in the hydrogenation of Dinitrotoluene (DNT) to Toluenediamine (TDA). The porous Raney Ni catalyst can be used for preparing TDA by DNT hydrogenation, and the process conditions for preparing TDA can be obtained by the known technology of the person skilled in the art.
The catalyst of the invention performs performance evaluation on a tubular reactor, and the evaluation process is as follows: the reaction pressure is 0.5-1.5Mpa, the reaction temperature is 50-200 ℃, the hydrogen flow is 50-300ml/min, and the airspeed is 0.5-1min -1 A solution of DNT in DMF (N, N-dimethylformamide) was then prepared at 20-40wt% and pumped into the reactor.
The invention has the positive effects that:
(1) Selecting proper silicon source and template agent, optimizing preparation condition and preparation process to obtain SBA-15 with hierarchical pore structure, using it as hard template carrier, using the process of activating desilication-dealumination to prepare multistage Kong Leini nickel catalyst, and making specific surface area of the catalyst be 100-400m 2 And/g, wherein the micropore diameter is smaller than 2nm, and accounts for 10-30% of the total pore volume, the mesopore diameter is 2-50nm, and accounts for 40-60% of the total pore volume, the macropore diameter is larger than 50nm, and accounts for 15-45% of the pore volume, and the structure is more beneficial to the diffusion of the product, and the conversion rate and the selectivity are improved. (2) In the presence of a hard template, the Ni catalyst has good mechanical strength, excellent wear resistance and less catalyst unit consumption per ton of product; (3) The conversion rate of the raw materials is more than 99.99 percent, the selectivity to the target product TDA is more than or equal to 99.8 percent, and the selectivity to the tar product is less than or equal to 0.1 percent. And the catalyst is not deactivated after continuous operation for 1000 hours. (4) The catalyst has the advantages of low raw material cost, simple preparation process and easy realization of large-scale production.
Drawings
FIG. 1 is a graph showing pore size distribution of SBA-15 (a) and finished grade Kong Leini nickel catalyst (b) prepared. As can be seen from the figure, the prepared samples all have micropores, mesopores and macropores. The illustration is a typical hierarchical pore structure.
Detailed Description
For a better understanding of the present invention, the following examples are set forth to illustrate the present invention further, but are not to be construed as limiting the present invention.
N used in the examples of the present invention 2 The specific surface area and the pore structure of the catalyst microsphere are measured by an adsorption method (BET), and the model of the instrument is as follows: ASP2020, manufactured by american microphone instruments.
The inductively coupled plasma emission spectrometer (ICP-OES) used in the examples of the present invention was manufactured by Agilent Technologies and was model 720ICP-OES.
The gas chromatographic conditions used in the examples of the present invention were: agilent HP-INNOWAX column, sample inlet temperature: 280 ℃; detector temperature: 240 ℃; h 2 Flow rate: 35ml/min; air flow rate: 350ml/min. The temperature of the column box is 170 ℃ and kept for 13min, and then the temperature is increased to 300 ℃ at 13 ℃/min and kept for 15min.
Example 1
Preparing a 30wt% tetrapropylammonium hydroxide solution, placing the solution in a water bath kettle, and stirring at normal temperature. Then a certain amount of tetraethoxysilane is added dropwise, so that SiO is contained in the final solution 2 /OH - =2 (molar ratio). After the addition is completed, stirring is continued for 120min to obtain SBA-15 suspension, drying is carried out for 8h at 120 ℃, and grinding is carried out to obtain the fine powder SBA-15.
40g of metallic nickel, 50g of metallic aluminum and 10g of metallic magnesium were placed in a melting crucible. Then the crucible is placed in a smelting furnace, the temperature is raised to 1700 ℃, the temperature is kept for 5min, and meanwhile, stirring is started, and the stirring speed is 40r/min. Pouring the molten slurry on a graphite plate after completion, and naturally cooling to room temperature to obtain an alloy block. The alloy blocks are crushed into powder by a crusher, and are ground by a Raymond mill, so as to obtain the alloy powder with D50=10μm.
50g of alloy powder and 5g of SBA-15 are taken, the mixture is uniformly mixed in a planetary ball mill, the mixture is poured into a ball mill, 0.25g of CMC is added, spherical particles are obtained, and the mixture is dried at 100 ℃ for 8 hours and baked at 500 ℃ for 6 hours, so that a precursor is obtained.
5g of catalyst precursor is taken and placed80g of the catalyst is reacted in 30wt% urea solution at 80 ℃ for 120min, and the catalyst is washed to be neutral by clean water to obtain the finished catalyst. The catalyst had a diameter of 2.3mm and a density of 3370Kg/m 3 。
Catalyst evaluation: 5.0g of catalyst was added to a tube reactor, hydrogen was introduced at a flow rate of 100ml/min, the pressure was maintained at 1.0MPa, the oil bath temperature was set at 120℃and a 30wt% solution of DNT in DMF was pumped into the reactor by a feed pump at a flow rate of 2.5g/min, and samples were taken for analysis.
Characterization of the SBA-15 prepared, its specific surface area was 258m 2 And/g, wherein the total pore volume is 335mL/g, the micropores account for 17% of the total pore volume, the mesopores account for 48% of the total pore volume, and the macropores account for 35% of the total pore volume. Characterization of the catalyst prepared gave a BET specific surface area of 153m 2 And/g, the reaction solution is analyzed by ICP-OES, and Ni and Al elements are not detected, so that the catalyst has no loss and good mechanical stability. The results of the chromatographic analysis of the reaction liquid are as follows:
reaction time (h) DNT conversion (%) TDA Selectivity (%) Tar selectivity (%)
1 100 100 0
100 100 100 0
200 100 100 0
500 100 100 0
730 100 99.95 0.03
1000 99.99 99.90 0.05
Example 2
A 20wt% tetrapropylammonium hydroxide solution was prepared, placed in a water bath, and stirred at room temperature. Then a certain amount of tetraethoxysilane is added dropwise, so that SiO is contained in the final solution 2 /OH - =0.1 (molar ratio). After the addition is completed, stirring is continued for 60min to obtain SBA-15 suspension, drying and grinding are carried out to obtain the fine powder SBA-15.
20g of metallic nickel, 60g of metallic aluminum, and 20g of metallic cobalt were placed in a melting crucible. Then the crucible is placed in a smelting furnace, the temperature is raised to 1700 ℃, the temperature is kept for 5min, and meanwhile, stirring is started, and the stirring speed is 40r/min. Pouring the molten slurry on a graphite plate after completion, and naturally cooling to room temperature to obtain an alloy block. The alloy pieces were crushed into powder by a crusher and ground by a raymond mill to obtain an alloy powder of d50=47.3 μm.
50g of alloy powder and 25g of SBA-15 are taken, the mixture is uniformly mixed in a planetary ball mill, the mixture is poured into a ball mill, 0.5g of CMC is added, spherical particles are obtained, and the mixture is dried at 100 ℃ for 8 hours and baked at 500 ℃ for 6 hours, so that a precursor is obtained.
5g of the catalyst precursor is taken and placed in 25g of 20wt% potassium hydroxide solution to react for 120min at 80 ℃ to obtain the finished catalyst.
Catalyst evaluation mode reference example 1.
Characterization of the SBA-15 prepared, its specific surface area was 107m 2 And/g, wherein the total pore volume is 252mL/g, the micropores account for 19% of the total pore volume, the mesopores account for 42% of the total pore volume, and the macropores account for 39% of the total pore volume. Characterization of the catalyst prepared gave a BET specific surface area of 98m 2 And/g, the reaction solution is analyzed by ICP-OES, and Ni and Al elements are not detected, so that the catalyst has no loss and good mechanical stability. The results of the chromatographic analysis of the reaction liquid are as follows:
reaction time (h) DNT conversion (%) TDA Selectivity (%) Tar selectivity (%)
1 100 100 0
100 100 100 0
200 100 100 0
500 100 100 0
760 100 99.94 0.04
1000 99.99 99.87 0.08
Example 3
A 5wt% tetrapropylammonium hydroxide solution is prepared and placed in a water bath kettle and stirred at normal temperature. Then a certain amount of tetraethoxysilane is added dropwise, so that SiO is contained in the final solution 2 /OH - =1 (molar ratio). After the addition is completed, stirring is continued for 60min to obtain SBA-15 suspension, drying and grinding are carried out to obtain the fine powder SBA-15.
30g of metallic nickel, 55g of metallic aluminum, and 15g of metallic chromium were placed in a melting crucible. Then the crucible is placed in a smelting furnace, the temperature is raised to 1800 ℃, the temperature is kept for 5min, and meanwhile, stirring is started, and the stirring speed is 40r/min. Pouring the molten slurry on a graphite plate after completion, and naturally cooling to room temperature to obtain an alloy block. The alloy pieces were crushed into powder by a crusher and ground by a raymond mill to obtain an alloy powder with d50=27 μm.
50g of alloy powder and 15g of SBA-15 are taken, the mixture is uniformly mixed in a planetary ball mill, the mixture is poured into a ball mill, 0.375g of CMC is added, spherical particles are obtained, and the mixture is dried at 120 ℃ for 8 hours and baked at 600 ℃ for 10 hours, so that a precursor is obtained.
5g of the catalyst precursor is taken and placed in 25g of 20wt% potassium hydroxide solution to react for 120min at 80 ℃, and then washed to be neutral to obtain the finished catalyst.
Catalyst evaluation mode reference example 1.
Characterization of the SBA-15 prepared, its specific surface area was 158m 2 And/g, wherein the total pore volume is 304mL/g, the total pore volume of micropores is Rong Zhan%, the total pore volume of mesopores is 48%, and the total pore volume of macropores is 35%. Characterization of the catalyst prepared gave a BET specific surface area of 173m 2 And/g, the reaction solution is analyzed by ICP-OES, and Ni and Al elements are not detected, so that the catalyst has no loss and good mechanical stability. The results of the chromatographic analysis of the reaction liquid are as follows:
reaction time (h) DNT conversion (%) TDA Selectivity (%) Tar selectivity (%)
1 100 100 0
100 100 100 0
200 100 100 0
500 100 100 0
710 100 99.92 0.08
1000 99.99 99.89 0.1
Comparative example 1
A commercial catalyst MC-507 for preparing TDA by hydrogenating DNT sold by EVONIK company is characterized and evaluated by the method and the process condition in the example 1, and the BET specific surface area is 98m 2 Per g, the results of the evaluation using the method and process conditions of example 1 are shown below, which illustrate that commercial catalysts are inferior to self-made porous Raney nickel catalysts in specific surface area and catalytic performance.
Reaction time (h) DNT conversion (%) TDA Selectivity (%) Tar selectivity (%)
1 99.5 98.7 0.04
50 99.2 98.3 0.1
200 98 96.2 0.56
Comparative example 2
A 30wt% tetrapropylammonium hydroxide solution was prepared, placed in a water bath, and stirred at room temperature. Then a certain amount of tetraethoxysilane is added dropwise, so that SiO is contained in the final solution 2 /OH - =5 (molar ratio). After the addition is completed, stirring is continued for 120min to obtain SBA-15 suspension, drying and grinding are carried out to obtain the fine powder SBA-15.
40g of metallic nickel, 50g of metallic aluminum and 10g of metallic magnesium were placed in a melting crucible. Then the crucible is placed in a smelting furnace, the temperature is raised to 1700 ℃, the temperature is kept for 5min, and meanwhile, stirring is started, and the stirring speed is 40r/min. Pouring the molten slurry on a graphite plate after completion, and naturally cooling to room temperature to obtain an alloy block. The alloy blocks are crushed into powder by a crusher, and are ground by a Raymond mill, so as to obtain the alloy powder with D50=10μm.
50g of alloy powder and 5g of SBA-15 are taken, the mixture is uniformly mixed in a planetary ball mill, the mixture is poured into a ball mill, 0.25g of CMC is added, spherical particles are obtained, and the mixture is dried at 100 ℃ for 8 hours and baked at 500 ℃ for 6 hours, so that a precursor is obtained.
5g of the catalyst precursor is taken and placed in 50g of 20wt% sodium hydroxide solution to react for 120min at 80 ℃ to obtain the finished catalyst.
Catalyst evaluation mode reference example 1.
Characterization of the SBA-15 prepared, its specific surface area was 73m 2 And/g, wherein the total pore volume is 102mL/g, the total pore volume of micropores is 23%, the mesopores account for 51% of the total pore volume, and the macropores account for 26% of the total pore volume. Characterization of the catalyst prepared gave a BET specific surface area of 115m 2 And/g, the reaction solution was analyzed by ICP-OES, and no Ni element was detected, indicating no loss of the catalyst. The results of the chromatographic analysis of the reaction liquid are as follows:
reaction time (h) DNT conversion (%) TDA Selectivity (%) Tar selectivity (%)
1 100 100 0
100 100 100 0
200 100 100 0
600 99.99 99.91 0.07
710 99.85 99.78 0.15
800 99.8 99.7 0.23
Comparative example 3
A 5wt% tetrapropylammonium hydroxide solution is prepared and placed in a water bath kettle and stirred at normal temperature. Then a certain amount of tetraethoxysilane is added dropwise, so that SiO is contained in the final solution 2 /OH - =0.05 (molar ratio). After the addition is completed, stirring is continued for 60min to obtain SBA-15 suspension, drying and grinding are carried out to obtain the fine powder SBA-15.
30g of metallic nickel, 55g of metallic aluminum, and 15g of metallic chromium were placed in a melting crucible. Then the crucible is placed in a smelting furnace, the temperature is raised to 1800 ℃, the temperature is kept for 5min, and meanwhile, stirring is started, and the stirring speed is 40r/min. Pouring the molten slurry on a graphite plate after completion, and naturally cooling to room temperature to obtain an alloy block. The alloy blocks are crushed into powder by a crusher, and are ground by a Raymond mill, so as to obtain the alloy powder with D50=23 mu m.
50g of alloy powder and 15g of SBA-15 are taken, the mixture is uniformly mixed in a planetary ball mill, the mixture is poured into a ball mill, 0.375g of stearic acid is added, spherical particles are obtained, and the mixture is dried at 120 ℃ for 8 hours and baked at 600 ℃ for 10 hours, so that a precursor is obtained.
5g of the catalyst precursor is taken and placed in 25g of 20wt% potassium hydroxide solution to react for 120min at 80 ℃, and then washed to be neutral to obtain the finished catalyst.
Catalyst evaluation mode reference example 1.
Characterization of the SBA-15 prepared, its specific surface area was 117m 2 And/g, wherein the total pore volume is 185mL/g, the total pore volume of the micropores is 13%, the mesopores account for 59% of the total pore volume, and the macropores account for 28% of the total pore volume. Characterization of the catalyst prepared gave a BET specific surface area of 83m 2 And/g, the reaction solution is analyzed by ICP-OES, 200ppm of Ni is detected, and the existence of certain loss of the catalyst is indicated, and the chromatographic analysis result of the reaction solution is as follows:
reaction time (h) DNT conversion (%) TDA Selectivity (%) Tar selectivity (%)
1 100 100 0
100 100 100 0
200 99.99 99.97 0
400 99.95 99.96 0.03
600 99.8 99.74 0.29
800 99.74 99.62 0.38

Claims (10)

1. A method for preparing a porous raney nickel catalyst, the method comprising:
(1) SBA-15 is prepared by a sol-gel method;
(2) Preparing Ni-Al alloy, and then grinding into alloy powder;
(3) Uniformly mixing the SBA-15 in the step (1) and the alloy powder in the step (2) through a ball mill; adding a certain amount of carboxymethyl cellulose for molding, drying and roasting to obtain a catalyst precursor;
(4) Activating the precursor obtained in the step (3) in an alkali solution to obtain a catalyst sample; SBA-15 in the step (1) has a hierarchical pore structure with micropores, mesopores and macropores simultaneously existing, and the specific surface area is 100-400m 2 And/g, wherein the micropore diameter is smaller than 2nm and accounts for 10-30% of the total pore volume, the mesopore diameter is 2-50nm and accounts for 40-60% of the total pore volume, the macropore diameter is larger than 50nm and accounts for 15-45% of the total pore volume; wherein, the micropore mesopores are measured by adopting a nitrogen physical adsorption method, and the macropores are measured by adopting a mercury intrusion method.
2. The method according to claim 1, characterized in that: the SBA-15 is prepared by adding a certain amount of ethyl orthosilicate into 5-30wt% tetrapropylammonium hydroxide solution at normal temperature to make SiO in the final solution 2 /OH - =0.1 to 2, molar ratio; after the addition is completed, stirring is continued for 0.5 to 2 hours to obtain SBA-15 suspension, drying and grinding are carried out to obtain the fine powder SBA-15.
3. The method according to claim 1, characterized in that: the Ni-Al alloy in the step (2) comprises 20-40wt% of nickel, 10-20wt% of auxiliary agent and 40-70wt% of aluminum.
4. A method according to claim 3, characterized in that: the auxiliary agent is one or more of Ca, mg, P, ni, pt, cr, co, ti, mg, B, zn and Mo.
5. The method according to any one of claims 1-4, wherein: mixing the required metal with the auxiliary agent, placing the mixture in a medium-frequency smelting furnace, smelting, cooling, crushing and grinding to obtain alloy powder, wherein the D50 of the obtained alloy powder is 5-50 mu m.
6. The method according to any one of claims 1-4, wherein: in the step (3), the addition amount of the carboxymethyl cellulose is 0.5 to 1 weight percent based on the mass of the alloy powder; the addition amount of SBA-15 is 10-50wt% based on the mass of the alloy powder; and/or, drying at 80-120deg.C for 7-12 hr, and roasting at 450-600deg.C for 4-10 hr.
7. The method according to any one of claims 1-4, wherein: in the step (4), the concentration of the alkali solution used in the activation is 5-30wt%, the activation temperature is 70-80 ℃, the activation time is 0.5-2h, and the mass ratio of the alkali solution to the precursor is 5-20.
8. The method according to any one of claims 1-4, wherein: in step (4), the resulting catalystThe agent product is spherical granule with diameter of 2-4mm and bulk density of 2000-5000Kg/m 3 。
9. Use of a catalyst prepared according to the process of any one of claims 1-8 to catalyze the hydrogenation of dinitrotoluene to toluene diamine in a tubular reactor.
10. The process according to claim 9, wherein the hydrogenation reaction pressure is 0.5-1.5MPa, the reaction temperature is 50-200deg.C, the hydrogen flow rate is 50-300ml/min, and the space velocity is 0.5-1min -1 。
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