阅读说明：本技术 一种处理柴油机尾气的多孔级scr催化剂制备方法 (Preparation method of porous SCR catalyst for treating diesel engine tail gas ) 是由 姜冬青 孙小琴 吕美林 于 2021-06-17 设计创作，主要内容包括：本发明提出了一种处理柴油机尾气的多孔级SCR催化剂制备方法,包括以下步骤：S1将原料、模板剂和水按比例配置混合、搅拌形成凝胶；S2将凝胶进行恒温分段晶化；S3将晶化后得到的样品进行过滤、洗涤、干燥；S4将干燥后的样品放入马弗炉中煅烧；S5将焙烧后的样品进行NH-4～(+)离子交换,而后置于马弗炉中焙烧得到H-Cu-SSZ-13；S6将H-Cu-SSZ-13进行Cu～(2+)交换,然后在马弗炉中煅烧,得到多孔级Cu-SSZ-13催化剂。本发明制备的具有多孔结构的Cu-SSZ-13,使得催化剂在保持水热稳定性、选择性的前提下,保证较高的传质效率,提高了NO-x的扩散系数,减小内扩散限制；同时多孔级SSZ-13分子筛能够改善NO-x对其活性位点的可及性,从而提高分子筛的催化活性和性能,并且可以延长分子筛的寿命。(The invention provides a preparation method of a porous SCR catalyst for treating tail gas of a diesel engine, which comprises the following steps: s1, preparing and mixing the raw materials, the template agent and water in proportion, and stirring to form gel; s2, carrying out constant-temperature sectional crystallization on the gel; s3, filtering, washing and drying the sample obtained after crystallization; s4, placing the dried sample into a muffle furnace for calcining;s5 subjecting the roasted sample to NH treatment 4 + Performing ion exchange, and then placing the mixture in a muffle furnace for roasting to obtain H-Cu-SSZ-13; s6 subjecting H-Cu-SSZ-13 to Cu 2+ And exchanging, and then calcining in a muffle furnace to obtain the porous Cu-SSZ-13 catalyst. The Cu-SSZ-13 with the porous structure, prepared by the invention, ensures higher mass transfer efficiency and improves NO on the premise of keeping hydrothermal stability and selectivity of the catalyst x The diffusion coefficient of (3), reducing the internal diffusion limitation; meanwhile, the porous SSZ-13 molecular sieve can improve NO x The accessibility to the active sites thereof, thereby improving the catalytic activity and performance of the molecular sieve and prolonging the life of the molecular sieve.)

1. A preparation method of a porous SCR catalyst for treating diesel engine tail gas is characterized by comprising the following steps:

s1, selecting an aluminum source, a silicon source, a template agent, carbon black and deionized water according to a certain proportion, dissolving the template agent in the deionized water, then adding the silicon source and the aluminum source into the solution, continuously stirring, then slowly adding the carbon black, and stirring for 6 hours to form gel;

s2, transferring the gel obtained in the step S1 to a hydrothermal reaction kettle, and then placing the hydrothermal reaction kettle in a constant-temperature oven for segmented crystallization;

s3, filtering, washing and drying the sample obtained after crystallization in S2 is finished;

s4, placing the dried sample in S3 into a muffle furnace for roasting, and removing a template agent and carbon black to obtain the porous SSZ-13 molecular sieve;

s5 preparation of SSZ-13 and NH prepared in S4₄Carrying out ion exchange on the Cl solution at 80 ℃ for 4H, repeating the ion exchange for three times, and roasting in a muffle furnace to obtain H-Cu-SSZ-13;

s6 Cu treatment of H-Cu-SSZ-13 obtained in S5²⁺And exchanging, namely mixing the H-Cu-SSZ-13 with the copper source solution, stirring for 3H at 80 ℃, repeating for 5 times, and then roasting in a muffle furnace for 6H to obtain the porous Cu-SSZ-13 catalyst.

2. The preparation method of the porous SCR catalyst for treating the tail gas of the diesel engine according to claim 1, characterized in that: the silicon source of S1 is one or more of silicate, tetraethyl orthosilicate, silica sol and tetraalkoxysilane; the aluminum source is one or more of triisopropanolate aluminum and meta-aluminate, and the template agent is N, N, N-trimethyl-1-amantadine (TMADAOH).

3. The preparation method of the porous SCR catalyst for treating the tail gas of the diesel engine according to claim 1, wherein the porous SCR catalyst comprises the following steps: the charging ratio of each element in the SCR catalyst in S1 (80-120) Si: (4-10) Al: (25-25) TMAdaOH.

4. The preparation method of the porous SCR catalyst for treating the tail gas of the diesel engine according to claim 1, characterized in that: the method for fractional crystallization in S2 comprises the steps of crystallizing at 100-120 ℃ for 3-4 days, and then continuously crystallizing at 150-180 ℃ for 5-8 days.

5. The preparation method of the porous SCR catalyst for treating the tail gas of the diesel engine according to claim 1, characterized in that: the drying temperature in S3 is 90-120 ℃, and the drying time is 8-12 h.

6. The preparation method of the porous SCR catalyst for treating the tail gas of the diesel engine according to claim 1, characterized in that: the calcination temperature in S4 is 500-600 ℃, and the calcination time is 8-12 h.

7. The preparation method of the porous SCR catalyst for treating the tail gas of the diesel engine according to claim 1, wherein the porous SCR catalyst comprises the following steps: the copper source in S6 is selected from one or more of copper acetate, copper sulfate and copper nitrate, Cu²⁺The concentration is 0.1-0.3 mol/L.

8. The preparation method of the porous SCR catalyst for treating the tail gas of the diesel engine according to claim 1, wherein the porous SCR catalyst comprises the following steps: cu in S6²⁺The roasting temperature after the exchange is 500-600 ℃.

Technical Field

The invention relates to the field of treatment of nitrogen oxides in diesel engine tail gas, in particular to a preparation method of an SCR (selective catalytic reduction) catalyst for treating nitrogen oxides in diesel engine tail gas by using a porous zeolite molecular sieve catalyst.

Background

NO_xNot only can cause photochemical smog and other environmental problems, but also can cause human respiratory diseases and other problems, and has great threat to human health. While most of nitrogen oxides in the air come from the emission of diesel engine tail gas, with the release of emission regulations of six diesel engine vehicles (limit of emission of pollutants for heavy-duty diesel engine and measurement method (sixth stage of China)), new emission standards not only have stricter emission limits on pollutants in tail gas of diesel engines, but also have NO emission limits on pollutants in tail gas of diesel engines_xThe discharge amount of (A) was reduced from 60mg to 35 mg. To satisfy NO_xThe emission of the catalyst meets the national six-emission standard, and the ammonia selective catalytic reduction technology (NH)₃SCR) is considered the most efficient NO_xThe core of the technology is the research of SCR catalyst. Since Cu-based molecular sieves are in NH₃The SCR reaction shows excellent catalytic activity and hydrothermal stability, and the research of scientists is focused. The Cu-SSZ-13 with the Cu-CHA structure has excellent denitration performance, good hydrothermal stabilizer, wide reaction temperature window and good catalytic activity.

However, the template agent (TMADAOH) needed by the traditional Cu-SSZ-13 synthesis is expensive, so that the synthesis cost of the catalyst is higher, and in addition, the traditional Cu-SSZ-13 molecular sieve is large in particle size and has higher internal diffusion resistance, so that the mass transfer rate of reactants and products in Cu-SSZ-13 pore channels is limited, thereby causing NH at low temperature₃The reaction rate of the SCR becomes slow.

Disclosure of Invention

The purpose of the invention is as follows: in order to overcome the defects of the background art, the invention discloses a method for synthesizing NH of Cu-SSZ-13 with a porous structure by using an inexpensive template₃Method for preparing an SCR catalyst, so that it catalyzesThe agent ensures higher mass transfer efficiency on the premise of keeping hydrothermal stability and selectivity, thereby improving NO_xThe diffusion coefficient of (3), reducing the internal diffusion limitation; meanwhile, the porous SSZ-13 molecular sieve can improve NO_xThe accessibility to the active sites thereof, thereby improving the catalytic activity and performance of the molecular sieve and prolonging the life of the molecular sieve.

The technical scheme is as follows: the invention relates to a preparation method of a porous SCR catalyst for treating tail gas of a diesel engine, which comprises the following steps:

s1, selecting an aluminum source, a silicon source, a template agent, carbon black and deionized water according to a certain proportion, dissolving the template agent in the deionized water, then adding the silicon source and the aluminum source into the solution, continuously stirring, then slowly adding the carbon black, and stirring for 6 hours to form gel.

S2, transferring the gel obtained in the step S1 to a reaction kettle, and then placing the reaction kettle in a constant-temperature oven for segmented crystallization.

S3 the sample obtained after crystallization in S2 is filtered, washed and dried.

S4, putting the dried sample in S3 into a muffle furnace for roasting, and removing the template agent and carbon black to obtain the porous SSZ-13 molecular sieve.

S5 preparation of SSZ-13 and NH prepared in S4₄And (3) carrying out ion exchange on the Cl solution at 80 ℃ for 4H, repeating the ion exchange for three times, and roasting in a muffle furnace to obtain the H-Cu-SSZ-13.

S6 Cu treatment of H-Cu-SSZ-13 obtained in S5²⁺And exchanging, namely mixing the H-Cu-SSZ-13 with the copper source solution, stirring for 3H at 80 ℃, repeating for 5 times, and then roasting in a muffle furnace for 6H to obtain the porous Cu-SSZ-13 catalyst.

Further, the silicon source of S1 is selected from one or more of silicate, tetraethyl orthosilicate, silica sol and tetraalkoxysilane; the aluminum source is one or more of triisopropanolate aluminum and meta-aluminate, and the template agent is N, N, N-trimethyl-1-amantadine (TMADAOH).

Further, the charging ratio of each element in the SCR catalyst in S1 (80-120) Si: (4-10) Al: (25-25) TMAdaOH.

Further, the fractional crystallization method in S2 comprises the steps of crystallizing at 100-120 ℃ for 3-4 days, and then continuously crystallizing at 150-180 ℃ for 5-8 days.

Furthermore, the drying temperature in S3 is 90-120 ℃, and the drying time is 8-12 h.

Furthermore, the calcination temperature in S4 is 500-600 ℃, and the calcination time is 8-12 h.

Further, the copper source in S6 is selected from one or more of copper acetate, copper sulfate and copper nitrate, Cu²⁺The concentration is 0.1-0.3 mol/L.

Further, Cu in S6²⁺The roasting temperature after the exchange is 500-600 ℃.

Has the advantages that: NH of Cu-SSZ-13 with porous structure₃The preparation method of the SCR catalyst ensures higher mass transfer efficiency on the premise of keeping hydrothermal stability and selectivity of the catalyst, thereby improving NO_xThe diffusion coefficient of (3), reducing the internal diffusion limitation; meanwhile, the porous SSZ-13 molecular sieve can improve NO_xThe accessibility to the active sites thereof, thereby improving the catalytic activity and performance of the molecular sieve and prolonging the life of the molecular sieve.

Drawings

FIG. 1 shows the catalyst of example 1 of the present invention versus the catalyst of comparative example 1 for NO_xPerformance of conversion is plotted against time.

FIG. 2 is a graph comparing the performance of the catalyst of example 1 of the present invention against hot water aging with that of the catalyst of comparative example 1.

FIG. 3 shows SO resistance of the catalyst of example 1 of the present invention and the catalyst of comparative example 1₂Performance of (c) is compared with the graph.

Detailed Description

To explain the technical content of the present invention in detail, the technical solution of the present invention is further explained below with reference to the accompanying drawings and examples. It should be understood by those skilled in the art that the examples are set forth to aid in understanding the invention and are not to be construed as specifically limiting the invention.

Example 1

A preparation method of a porous SCR catalyst for treating diesel engine tail gas comprises the following steps:

s1, selecting sodium metaaluminate: silica sol: TMAdaOH: the charging ratio of the deionized water is 20:5:100:4000, TMADAOH is dissolved in the deionized water, then sodium metaaluminate and silica sol are added into the solution and continuously stirred, then carbon black with the proportion of 15 is slowly added, and the mixture is stirred for 6 hours to form gel.

S2 transferring the gel obtained in the step S1 to a reaction kettle, placing the reaction kettle in a constant-temperature oven for segmented crystallization, firstly crystallizing the gel at 110 ℃ for 4 days, and then continuously crystallizing the gel at 150 ℃ for 5 days.

S3 the sample obtained after crystallization in S2 is filtered, washed and dried in an oven for 8h at 110 ℃.

S4, putting the dried sample in S3 into a muffle furnace, roasting for 8 hours at 580 ℃, and removing the template agent and carbon black to obtain the porous SSZ-13 molecular sieve catalyst.

S5 preparation of SSZ-13 and NH prepared in S4₄And (3) carrying out ion exchange on the Cl solution at 80 ℃ for 4H, repeating the ion exchange for three times, and roasting in a muffle furnace to obtain the H-Cu-SSZ-13.

S6 Cu treatment of H-Cu-SSZ-13 obtained in S5²⁺Exchange, i.e. H-Cu-SSZ-13 and 0.1mol/L Cu (NO)₃)₂The solutions were mixed and stirred at 80 ℃ for 3h, repeated 5 times, and then calcined in a muffle furnace at 530 ℃ for 6h to obtain the porous Cu-SSZ-13 catalyst.

Comparative example 1

In order to compare the performance of the traditional SCR catalyst Cu-SSZ-13 and the porous grade SCR catalyst Cu-SSZ-13, the traditional SCR catalyst Cu-SSZ-13 was synthesized.

The raw material components and the technological parameters are unchanged, carbon black is not added, and the crystallization method is to crystallize in an oven for 5 days at the crystallization temperature of 150 ℃.