阅读说明：本技术 一种用于乙炔选择加氢的铜基催化剂及其制备方法 (Copper-based catalyst for selective hydrogenation of acetylene and preparation method thereof ) 是由 王安杰 卢晨阳 王瑶 曾傲楠 于 2020-04-14 设计创作，主要内容包括：本发明公开了一种用于乙炔选择加氢的铜基催化剂及其制备方法,属于催化新材料技术领域。首先制备含铜化合物前体,然后用含有乙炔的模拟气体进行热处理后再经过氢气还原,制得用于乙炔选择加氢的铜基催化剂。将本发明制备的铜基催化剂用于常压下乙烯原料中少量乙炔的加氢脱除过程,在反应温度100～120℃下,就能实现乙炔的完全脱除,同时乙烷的选择性较低,而且铜基催化剂外层的多孔碳层可以抑制绿油和聚合物生成,该铜基催化剂具有良好的乙炔选择加氢活性和稳定性。(The invention discloses a copper-based catalyst for selective hydrogenation of acetylene and a preparation method thereof, belonging to the technical field of new catalytic materials. Firstly, preparing a copper-containing compound precursor, then carrying out heat treatment by using simulated gas containing acetylene, and then carrying out hydrogen reduction to prepare the copper-based catalyst for selective hydrogenation of acetylene. The copper-based catalyst prepared by the invention is used for the hydrogenation removal process of a small amount of acetylene in an ethylene raw material under normal pressure, the acetylene can be completely removed at the reaction temperature of 100-120 ℃, the selectivity of ethane is low, a porous carbon layer on the outer layer of the copper-based catalyst can inhibit the generation of green oil and polymers, and the copper-based catalyst has good selective hydrogenation activity and stability of acetylene.)

1. The preparation method of the copper-based catalyst for selective hydrogenation of acetylene is characterized in that the preparation method can obtain the non-supported copper-based catalyst, and specifically comprises the following steps:

step 1, preparing unsupported copper compound precursor

Preparing 0.01-0.1M cupric salt solution, and adding 0.2-2M precipitator or reducer into the solution at 0-70 ℃ to obtain suspension of the non-supported copper-containing compound precursor; centrifuging, separating, washing and vacuum drying the solid sample to obtain a solid sample of the non-supported copper-containing compound precursor;

step 2, heating the non-supported copper-containing compound precursor prepared in the step 1 to 100-260 ℃ in an acetylene gas-containing atmosphere, reacting for 1-5 hours, and cooling to room temperature;

and 3, heating the material obtained in the step 2 to 100-300 ℃ in an atmosphere containing hydrogen, reacting for 1-10 h, and cooling to room temperature to obtain the non-supported copper-based catalyst for selective hydrogenation of acetylene.

2. The preparation method of the copper-based catalyst for selective hydrogenation of acetylene is characterized in that the preparation method can obtain a supported copper-based catalyst, and specifically comprises the following steps:

step 1, preparing a supported copper salt precursor or a supported non-copper salt precursor

Dropwise adding 0.01-0.1M of cupric salt solution on a carrier, storing in air at room temperature, and then drying in vacuum to obtain a load type copper salt precursor; or 0.01-0.1M of cupric salt solution is dripped on a carrier, the carrier is added into 0.2-2M of precipitator or reducing agent for continuous stirring after being stored in the air at room temperature, and then the supported non-cupric salt precursor is obtained through suction filtration, washing and vacuum drying;

the mass content of copper in the supported copper salt precursor or the supported non-copper salt precursor is 5-30%;

step 2, heating the supported copper salt precursor or the supported non-copper salt precursor prepared in the step 1 to 100-260 ℃ in an atmosphere containing acetylene gas, reacting for 1-5 h, and cooling to room temperature;

and 3, heating the material obtained in the step 2 to 100-300 ℃ in an atmosphere containing hydrogen, reacting for 1-10 h, and cooling to room temperature to obtain the supported copper-based catalyst for selective hydrogenation of acetylene.

3. The preparation method according to claim 1 or 2, wherein an auxiliary agent is added to the cupric salt solution in the step 1, and the concentration of the auxiliary agent is 0.01-0.05M.

4. The method according to claim 3, wherein the cupric salt comprises CuCl₂、Cu(NO₃)₂Or CuSO₄One or more than two of the components are mixed; the precipitator is NaOH solution, and the reducing agent is mixed solution of NaOH and ascorbic acid.

5. The method of claim 1 wherein the unsupported copper compound precursor compound comprises Cu₂O、Cu(OH)₂CuO, copper-containing minerals, copper salts, Cu formed on the surface of existing copper-based catalysts by heat treatment, oxidation or reduction processes⁺And Cu²⁺One or more than two species are mixed.

6. The method according to claim 3, wherein the auxiliary agent comprises one or more of Pd, Pt, Rh, Ru, Ni, Ag, Au, Co, Fe, Zn, Mo, W, Mn, Ce, Ti, Cr, Ir, Ga or In and oxides thereof, alkali metals, alkaline earth metal salts and alkaline earth metal oxides.

7. The method of claim 2, wherein the carrier is SiO₂、Al₂O₃、MgO、TiO₂、ZrO₂、CeO₂One or a mixture of more than two of activated carbon, carbon nano tubes, activated carbon fibers, zeolite molecular sieves, diatomite, kaolin, polymers or MOFs.

8. The preparation method according to claim 1 or 2, wherein in the step 2, the concentration of the acetylene gas is 0.5 to 100%, and the gas flow rate is 10 to 100 ml/min.

9. The method according to claim 1 or 2, wherein in the step 3, the concentration of the hydrogen gas is 10% to 100%, and the gas flow rate is 10 to 200 ml/min.

10. The copper-based catalyst obtained by the production method according to claim 1 or 2, wherein the copper-based catalyst is Cu coated with an amorphous carbon layer_xC and Cu nanoparticles; the copper-based catalyst can realize the complete conversion of acetylene at 100-120 ℃, and maintain the ethane selectivity of 5-20%.

Technical Field

The invention belongs to the technical field of new catalytic materials, and particularly relates to a high-performance non-noble metal selective hydrogenation catalyst and a preparation method thereof.

Background

Ethylene is the most basic organic chemical raw material in chemical industry and is mainly used for producing polyethylene plastics and the like. Industrially, the ethylene feedstock produced by hydrocarbon cracking process contains a small amount of acetylene (less than 5%) and the content of acetylenes increases with increasing cracking depth. In the production of polyethylene, a small amount of acetylene in the ethylene feed causes side reactions, which results in deactivation of the ethylene polymerization catalyst and affects the quality of the polyethylene product. Therefore, the removal of small amounts of acetylene from ethylene feeds is an important step in the ethylene plant process in order to obtain a polymer grade ethylene feed. The selective hydrogenation method for removing acetylene has simple process flow and less energy consumption, can convert impurities into products, does not pollute the environment, and is the most common technical method in the industry at present.

The most common acetylene selective hydrogenation catalyst used in industry is the Pd-based hydrogenation catalyst. However, in the case of Pd catalyst, the selectivity of ethylene is low, and it tends to hydrogenate ethylene in the raw material to ethane, and it tends to cause the temperature runaway of the catalyst bed. In addition, oligomers and green oils are formed during the reaction, which reduces the activity of the catalyst and shortens the catalyst life (Catalysis Reviews,2006,48(2), 91-144; Catalysis Reviews,2008,50(3), 379-. In order to inhibit excessive hydrogenation of ethylene and prevent temperature runaway of the catalyst bed, the hydrogen/acetylene ratio of the reaction raw material needs to be strictly controlled, which brings challenges to process control. Since carbon monoxide adsorbs on Pd with a heat of adsorption intermediate between that of ethylene and acetylene, addition of a trace amount of carbon monoxide also suppresses excessive hydrogenation of ethylene (Journal of catalysis.2010,273(2):92-102.), but increases the risk of green oil formation. Another obvious disadvantage of using noble metal catalysts such as Pd on large industrial plants is the high cost of catalyst manufacture. Pd belongs to scarce resources, and the replacement of Pd by non-noble metal has important economic value and sustainable development.

The non-noble metal catalyst for acetylene selective hydrogenation mainly comprises a Ni-based catalyst and a Cu-based catalyst. Through DFT calculation, NiZn and NiZn formed by adding Zn into Ni₃The alloy exhibits similar properties to the Pd-Ag catalyst, and the addition of Zn reduces the adsorption of ethylene on the surface of the catalyst, thereby enabling the improvement of ethylene selectivity (Science 2008,320, 1320-1322.). However, experimental research results show that the catalytic system can generate a large amount of green in the acetylene hydrogenation reaction processOil, thereby causing rapid deactivation of the catalyst (Journal of the American Chemical society, 2010,132(12): 4321-4327.).

Theoretical calculation and experimental research show that the Cu-based catalyst has excellent ethylene selectivity in the selective hydrogenation reaction of acetylene. However, since Cu has a weak hydrogen dissociation capability, a high temperature is required for the catalytic hydrogenation reaction, and a high temperature generates a large amount of green oil, thereby causing rapid deactivation of the catalyst. In addition, copper catalyzes the polymerization of acetylene at higher temperatures, causing plugging of the catalyst bed (Applied Catalysis 1990,58, 209-217.).

Therefore, the low-temperature hydrogenation activity of the Cu-based catalyst is improved, so that the energy consumption can be reduced, the oligomerization reaction can be inhibited, the ethylene can be prepared by selectively hydrogenating the acetylene with high efficiency and high selectivity, and the trace amount of acetylene in the ethylene raw material can be completely removed on the premise of not losing the ethylene.

Disclosure of Invention

In order to achieve the aim, the invention provides a non-noble metal acetylene selective hydrogenation catalyst. Specifically, acetylene and a copper-containing compound precursor generate copper acetylide in situ at high temperature, and the copper acetylide undergoes reduction and decomposition reaction in hydrogen to form copper carbide (Cu) embedded in porous carbon_xC) And metallic copper particles. The copper carbide has excellent low-temperature hydrogenation reaction activity, both the metal copper and the copper carbide have high acetylene hydrogenation selectivity, and the steric hindrance formed by the porous carbon is favorable for inhibiting the formation of green oil and polymers. When the material prepared by the invention is used for acetylene selective hydrogenation reaction, the reaction temperature can be reduced, acetylene impurities in the material can be completely removed on the premise of not causing ethylene loss, and the extremely low oligomer yield is favorable for prolonging the service life of the catalyst. Different from the traditional Pd-based catalyst, the copper-based catalyst prepared by the invention is insensitive to the change of hydrogen partial pressure, and can be used for a pre-hydrogenation process and a post-hydrogenation process.

The technical scheme adopted by the invention is as follows:

a copper-based catalyst for selective hydrogenation of acetylene is Cu coated by amorphous carbon layer_xC and Cu nanoparticles. Cu_xC has excellent hydrogen dissociation ability at low temperature, Cu_xC and Cu have higher ethylene selectivity. Therefore, the catalyst can realize the complete conversion of acetylene at a lower temperature (100-120 ℃) and keep lower ethane selectivity (5% -20%). In addition, the outer amorphous carbon layer inhibits the formation of oligomers and green oil, and greatly improves the acetylene selective hydrogenation stability of the catalyst.

A preparation method of a copper-based catalyst for selective hydrogenation of acetylene comprises the following steps:

step 1, preparing unsupported copper compound precursor

Preparing 0.01-0.1M cupric salt solution, and adding 0.2-2M precipitator or reducer into the solution at 0-70 ℃ to obtain suspension of the non-supported copper-containing compound precursor; then, centrifugal separation is carried out, deionized water and absolute ethyl alcohol are used for washing, and vacuum drying is carried out to obtain a solid sample of the non-supported copper-containing compound precursor.

The cupric salt comprises CuCl₂、Cu(NO₃)₂Or CuSO₄One or more than two of the components are mixed; the precipitator is NaOH solution, and the reducing agent is mixed solution of NaOH and ascorbic acid; the unsupported copper compound precursor comprises Cu₂O、Cu(OH)₂CuO, copper-containing minerals, copper salts, Cu formed on the surface of conventional copper-based catalysts by heat treatment, oxidation or reduction, or the like⁺And Cu²⁺One or more than two species are mixed.

And adding a corresponding assistant into the cupric salt solution to prepare a mixed solution of the assistant and the cupric salt, wherein the concentration of the assistant is 0.01-0.05M. The auxiliary agent comprises metal or metal oxide and the like, and is used for modulating the structure and electronic characteristics of the copper-based catalyst, so that the activity, selectivity and stability of the catalyst are improved. The assistant is preferably selected from one or more of Pd, Pt, Rh, Ru, Ni, Ag, Au, Co, Fe, Zn, Mo, W, Mn, Ce, Ti, Cr, Ir, Ga or In and oxides thereof, alkali metals, alkaline earth metal salts and alkaline earth metal oxides, and the distribution and existence state of the assistant are not limited.

And 2, heating the material prepared in the step 1 to 100-260 ℃ in an atmosphere containing acetylene gas (the concentration of acetylene is 0.5-100%) at the concentration of 10-100 ml/min, reacting for 1-5 h, and cooling to room temperature under the protection of the acetylene-containing gas.

And 3, heating the material obtained in the step 2 to 100-300 ℃ in an atmosphere containing hydrogen (the hydrogen concentration is 10-100%) at the concentration of 10-200 ml/min, reacting for 1-10 h, and cooling to room temperature under the protection of the hydrogen-containing gas to obtain the copper-based catalyst for selective hydrogenation of acetylene.

Further, in the step 1, the supported copper-containing compound precursor may be prepared by an impregnation method, a coprecipitation method, a deposition method, or a sputtering method for preparing the supported copper-based catalyst. The supported copper-containing compound precursor comprises a supported copper salt precursor or a supported non-copper salt precursor. The specific process for preparing the supported copper-containing compound precursor by the impregnation method comprises the following steps: and (3) dropwise adding 0.01-0.1M of cupric salt solution on the carrier, storing in air at room temperature, and then drying in vacuum to obtain the load type copper salt precursor. Or dripping 0.01-0.1M cupric salt solution on a carrier, storing the carrier in the air at room temperature, adding the carrier into 0.2-2M precipitator or reducing agent, continuously stirring, and then carrying out suction filtration, washing and vacuum drying to obtain the supported non-cupric salt precursor. Wherein, the mass content of copper in the supported copper salt precursor or the supported non-copper salt precursor is 0.5-99.5%, preferably 5-30%. The carrier is preferably SiO₂、Al₂O₃、MgO、TiO₂、ZrO₂、CeO₂One or a mixture of more than two of activated carbon, carbon nano tubes, activated carbon fibers, zeolite molecular sieves, diatomite, kaolin, polymers or MOFs. The shape of the carrier is preferably a sphere, a bar, a clover, a tetrafoil, a sheet, a sphere, or the like. The distribution state of the supported copper-containing compound precursor is not limited, and may be distributed on the surface of the support or may be distributed in the support.

The copper-based catalyst prepared by the method is used for acetylene selective hydrogenation reaction.

The invention has the beneficial effects that: the invention adopts cheap metal copper as a main active component, prepares the copper-based catalyst with extremely high activity and high selectivity for acetylene hydrogenation by an in-situ synthesis method, the copper-based catalyst is a non-supported catalyst or a supported catalyst, the main active components are copper and copper carbide, the copper carbide has high hydrogenation activity, a porous carbon layer can inhibit the generation of green oil and polymers, and the low-temperature high hydrogenation activity is favorably realized and the service life of the catalyst is prolonged. The copper-based catalyst is particularly suitable for selectively removing acetylene impurities in ethylene and increasing the yield of ethylene. At a lower temperature (100-120 ℃), a large amount of acetylene (0.1% -2%) in an ethylene (more than 90%) raw material can be removed, and the activity and selectivity of the catalyst are not obviously changed along with the hydrogen content, so that the catalyst can be used for a front hydrogenation technology and a rear hydrogenation technology.

Drawings

FIG. 1 shows Cu in example 1₂SEM photograph of O particles.

FIG. 2 is a HRTEM photograph of the copper-based catalyst particles obtained in example 1.

FIG. 3 is an enlarged view of metallic copper particles in the copper-based catalyst obtained in example 1.

Fig. 4 is an enlarged view of copper carbide particles in the copper-based catalyst obtained in example 1.

FIG. 5 shows the results of a stability test of a copper-based catalyst.

FIG. 6 shows Cu in different loading amounts₂O/Al₂O₃The result of the acetylene hydrogenation reaction of the catalyst prepared for the precursor; wherein (a) is the variation of acetylene conversion rate with reaction temperature, and (b) is the variation of ethane selectivity with reaction temperature.

Detailed Description

The following examples are intended to illustrate the invention in more detail, but the invention is not limited to these examples.