阅读说明：本技术 一种磷掺杂的Cu-SSZ-13催化剂及其制备方法和应用 (Phosphorus-doped Cu-SSZ-13 catalyst and preparation method and application thereof ) 是由 李永丹 赵化望 张田 肖亚 于 2018-06-15 设计创作，主要内容包括：本发明公开一种磷掺杂的Cu-SSZ-13催化剂及其制备方法和应用,使用铜胺络合离子与胺型模板剂组成复合模板剂,在分子筛制备过程中与硅源铝源混合并在100-180℃温度区间内晶化,合成在Cu-SSZ-13催化剂。选择浸渍或者共混负载方式将磷负载到Cu-SSZ-13上,使得磷以骨架外的磷形式存在,增加催化剂的水热稳定性,并表现出针对NOx的催化性能。(The invention discloses a phosphorus-doped Cu-SSZ-13 catalyst and a preparation method and application thereof, wherein a copper amine complex ion and an amine type template agent are used for forming a composite template agent, and the composite template agent is mixed with a silicon source and an aluminum source in the preparation process of a molecular sieve and crystallized within a temperature range of 100-180 ℃ to synthesize the Cu-SSZ-13 catalyst. The impregnation or blending loading mode is selected to load the phosphorus on the Cu-SSZ-13, so that the phosphorus exists in the form of extra-framework phosphorus, the hydrothermal stability of the catalyst is improved, and the catalytic performance of the catalyst for NOx is shown.)

1. A phosphorus-doped Cu-SSZ-13 catalyst is characterized in that an SSZ-13 molecular sieve is used as a carrier, copper element accounts for 4-6 wt% of the mass of the molecular sieve carrier, phosphorus element accounts for 0.5-5 wt% of the mass of the molecular sieve carrier, copper element is uniformly dispersed in the molecular sieve, part of phosphorus element enters a molecular sieve framework, and part of phosphorus element exists in a phosphorus form outside the framework.

2. The phosphorus-doped Cu-SSZ-13 catalyst as claimed in claim 1, wherein the SSZ-13 molecular sieve has a chabazite structure and an average specific surface area of 600-700m²The mass percent of the copper element in the molecular sieve carrier is 5-6 wt%, and the mass percent of the phosphorus element in the molecular sieve carrier is 1-4 wt%.

3. A phosphorus-doped Cu-SSZ-13 catalyst is characterized by consisting of a Cu-SSZ-13 molecular sieve and a phosphorus-containing molecular sieve, wherein the phosphorus-containing molecular sieve is used as a phosphorus source, and the mass ratio of the Cu-SSZ-13 molecular sieve to the phosphorus-containing molecular sieve is (5-10): (1-5), the elemental copper is uniformly dispersed in the Cu-SSZ-13 molecular sieve.

4. The phosphorus-doped Cu-SSZ-13 catalyst according to claim 3, wherein the mass ratio of the Cu-SSZ-13 molecular sieve to the phosphorus-containing molecular sieve is (8-10): (1-3); the phosphorus-containing molecular sieve is SAPO-34, AIPO or SAPO-11, and the content of phosphorus in the molecular sieve is 10-30 wt%, preferably 15-28 wt%, more preferably 16-27 wt%.

5. The phosphorus-doped Cu-SSZ-13 catalyst as claimed in claim 3 or 4, wherein the Cu-SSZ-13 molecular sieve has a chabazite structure with an average specific surface area of 600-700m²The weight percentage of the copper element in the Cu-SSZ-13 molecular sieve is 4-6 wt%.

6. A preparation method of a phosphorus-doped Cu-SSZ-13 catalyst is characterized in that elemental phosphorus is loaded on the Cu-SSZ-13 catalyst, and the following three conditions are divided into:

(1) selecting a phosphorus-containing inorganic substance to provide element phosphorus, wherein the mode of loading phosphorus is an initial wet impregnation method, an excess impregnation method or a pressurized impregnation method;

(2) selecting phosphorus-containing organic matters to provide element phosphorus, wherein the mode of loading phosphorus is a primary wet impregnation method, an excess impregnation method or a pressurization impregnation method;

(3) selecting a phosphorus-containing molecular sieve to provide element phosphorus, and mixing the Cu-SSZ-13 catalyst with the phosphorus-containing molecular sieve.

7. The method of claim 6, wherein the phosphorus-containing inorganic substance is orthophosphoric acid, monoammonium phosphate or monosodium phosphate; the phosphorus-containing organic matter is phosphine, phosphonic acid, phosphonate or phosphate; the phosphorus-containing molecular sieve is SAPO-34, AIPO or SAPO-11; the mixing mode of the Cu-SSZ-13 catalyst and the phosphorus-containing molecular sieve is preferably a solid mixing method; in the phosphorus-containing molecular sieve, the content of phosphorus in the molecular sieve is 10-30 wt%, preferably 15-28 wt%, more preferably 16-27 wt%; the mass ratio of the Cu-SSZ-13 to the phosphorus-containing molecular sieve is (5-10): (1-5), preferably (8-10): (1-3); after selecting a phosphorus-containing inorganic substance to provide element phosphorus and loading, roasting for 2-6 hours at 500-600 ℃; after the phosphorus-containing organic matter is selected to provide element phosphorus and is loaded, the material is roasted for 2 to 6 hours at a temperature of between 500 and 600 ℃.

8. The method of claim 6, wherein the Cu-SSZ-13 catalyst is prepared by the following steps: adding copper sulfate, tetraethylenepentamine, sodium hydroxide solid, sodium metaaluminate, silica sol and amine template agent into water, uniformly dispersing, crystallizing for 2-8 days at the temperature of 100-180 ℃, and roasting for 5-10 hours at the temperature of 400-600 ℃ after washing and drying to obtain the Cu-SSZ-13 catalyst, wherein the mass ratio of the materials is as follows: tetraethylenepentamine: sodium hydroxide: silica sol: amine-type templating agent: copper sulfate, sodium metaaluminate (10-15), sodium metaaluminate (4-10), sodium metaaluminate (0.3-0.8), sodium metaaluminate (8-12), amine (2-3), amine (0.7-1.5) and amine (1), wherein the amine template agent is triethylamine, diethylamine or N, N, N-trimethyl-1-adamantyl ammonium hydroxide; the silica sol is a dispersion of nano-scale silica particles in water, and the solid content of the silica is 30-35 wt.%; the crystallization temperature is 150-180 ℃, the crystallization time is preferably 4-7 days, and more preferably 4-6 days; after washing and drying, roasting for 6-8 hours at the temperature of 500-600 ℃; the mass ratio of the materials is water: tetraethylenepentamine: sodium hydroxide: silica sol: amine-type templating agent: copper sulfate, sodium metaaluminate (10-12): (4-8): 0.5-0.8): 8-10): 2-2.5): 0.8-1.2): 1.

9. Use of a catalyst according to any one of claims 1 to 5, or a catalyst prepared according to the preparation method of any one of claims 6 to 8, in the selective catalytic reduction of nitrogen oxides with ammonia as a reducing agent, wherein a 40-60 mesh catalyst is used and the reaction mixture is: 500ppm NO,500ppm NH₃,5％O₂，N₂Is balance gas; the total gas flow is 500ml/min, and the total space time is 150000h^-1(ii) a The reaction temperature is 150-550 ℃, preferably 250-400 ℃, preferably300-400 ℃.

10. The application of the element phosphorus in improving the hydrothermal reaction stability of the Cu-SSZ-13 catalyst in the selective catalytic reduction elimination of nitrogen oxide reaction by taking ammonia as a reducing agent.

Technical Field

The invention belongs to the technical field of catalysts, and relates to preparation and application of a zeolite molecular sieve for Selective Catalytic Reduction (SCR) nitrogen oxides (NOx) by taking ammonia as a reducing agent, in particular to preparation and application of a phosphorus-containing molecular sieve for an SCR system for treating pollution of nitrogen oxides in tail gas of diesel vehicles.

Background

Along with the development of Chinese economy, China is privateThe owned quantity of the home cars is greatly improved. But the pollution of automobile exhaust is more and more serious. Along with the popularization of the three-way catalyst in the field of gasoline vehicles, the tail gas pollution is effectively controlled. However, in the field of diesel vehicles, the three-way catalyst cannot play a role in the treatment of the tail gas of the diesel vehicle due to the oxygen enrichment characteristic of the tail gas. With the further tightening of the emission standard of nitrogen oxides in the tail gas of diesel vehicles in China, the diesel vehicles need to be additionally provided with a tail gas after-treatment system for realizing the elimination of NOx. The more mature technology now is the SCR technology using ammonia as a reducing agent. The technology means that nitrogen oxides in the tail gas react with ammonia gas through the action of a catalyst to generate gas harmless to the environment. Since pollutants such as soot particles, CO, and hydrocarbons are also present in the exhaust gas of a diesel vehicle, it is also desirable to include an oxidation catalyst and a soot trapping Device (DPF) in a typical diesel vehicle aftertreatment system, wherein the DPF is upstream of the SCR catalyst. The high temperature generated by the periodic regeneration of the DPF can cause the SCR catalyst at the downstream of the DPF to be in a high-temperature and high-humidity state frequently, which requires that the automotive exhaust SCR catalyst has good hydrothermal stability. NH currently applied in diesel vehicle exhaust purification₃SCR catalysts include vanadium-based catalysts and molecular sieve-type catalysts. However, the vanadium-based catalyst has a reduced activity due to volatilization of vanadium occurring in an environment of more than 550 ℃. In addition, vanadium itself is biologically toxic, limiting its use. Therefore, the vanadium-based catalysts are now gradually replaced by molecular sieve-type catalysts.

The most basic structure of the molecular sieve framework is SiO₄And AlO₄Tetrahedra, crystals that form a three-dimensional network structure by the bonding of shared oxygen atoms. The combination forms cavities and channels with molecular level and uniform pore diameter. Due to different structures and different forms, the space holes in the shape of the cage are divided into the structures of the cage such as alpha, beta, gamma, hexagonal column, faujasite and the like. Because of AlO₄The tetrahedron has a negative charge and can bind Na plasma to become electrically neutral. In aqueous solution, Na ions are easily exchanged with other cations (e.g., Cu ions, Fe ions, etc.). Most molecular sieve catalysts are polyvalent metal cation or H exchangers, the molecular sieve having an acidAnd the catalyst can be used as a catalyst or a carrier.

The developed molecular sieve catalyst has metal loaded ZSM-5, beta molecular sieve catalyst. However, they all have the disadvantages of narrow activity window, easy poisoning of HC compounds, poor hydrothermal stability, etc. Therefore, the preparation of a catalyst with wide active temperature window, no toxicity and good stability is a problem to be solved urgently in the field.

The Cu-SSZ-13 molecular sieve catalyst has great attention in the industry and academia due to high reaction activity and high hydrothermal stability. The Cu-SSZ-13 system was first developed by BASF (Bull et al, US. Pat.7601662B2). However, in order to meet more stringent emission standards, the hydrothermal stability of Cu-SSZ-13 needs to be further improved. After the synthesis of the SSZ-13 molecular sieve, it is necessary to load copper ions onto the molecular sieve support using an ion exchange process. This will produce a large amount of copper ion waste liquid, increase the catalyst preparation cost, increase the environmental protection pressure. Aiming at the defects of insufficient hydrothermal stability and complicated preparation of the Cu-SSZ-13 molecular sieve catalyst, the development of a novel molecular sieve catalyst which is simple in preparation, short in preparation period and cheap in raw materials is particularly important. The patent aims to solve the problem in the technical field of catalysis.

Disclosure of Invention

The invention aims to overcome the defects in the prior art and provides a phosphorus-doped Cu-SSZ-13 catalyst and a preparation method and application thereof, wherein a copper amine complex ion and other amine type templates are used for forming a composite template agent, the composite template agent is mixed with a silicon source and an aluminum source in the preparation process of a molecular sieve and is crystallized within the temperature range of 100-180 ℃, the Cu-SSZ-13 catalyst is synthesized, and phosphorus is selectively loaded on the Cu-SSZ-13, so that the phosphorus exists in a phosphorus form outside a framework, and the hydrothermal stability of the catalyst is improved.

The technical purpose of the invention is realized by the following technical scheme:

a phosphorus-doped Cu-SSZ-13 catalyst takes an SSZ-13 molecular sieve as a carrier, the mass percent of copper element in the molecular sieve carrier is 4-6 wt%, and the mass percent of phosphorus element in the molecular sieve carrier is 0.5-5 wt%

Moreover, the SSZ-13 molecular sieve has a chabazite structure and an average specific surface area of 600-700m²/g。

Moreover, the element copper is uniformly dispersed in the zeolite molecular sieve, and the mass percentage of the copper element in the molecular sieve carrier is 5-6 wt%.

And the phosphorus element accounts for 1-4 wt% of the molecular sieve carrier, part of the phosphorus element enters the molecular sieve framework, and part of the phosphorus element exists in a phosphorus form outside the framework.

A phosphorus-doped Cu-SSZ-13 catalyst is composed of Cu-SSZ-13 and a phosphorus-containing molecular sieve, wherein the phosphorus-containing molecular sieve is used as a phosphorus source, and the mass ratio of the Cu-SSZ-13 to the phosphorus-containing molecular sieve is (5-10): (1-5), preferably (8-10): (1-3).

Moreover, the Cu-SSZ-13 molecular sieve has a chabazite structure, and the average specific surface area is 600-700m²/g。

And the element copper is uniformly dispersed in the Cu-SSZ-13 molecular sieve, and the mass percentage of the copper element in the Cu-SSZ-13 molecular sieve is 4-6 wt%.

Further, when a phosphorus-containing molecular sieve is used as the phosphorus source, the mixing manner of the Cu-SSZ-13 and the phosphorus-containing molecular sieve is preferably a solid mixing method.

Further, in the phosphorus-containing molecular sieve, the content of phosphorus in the molecular sieve is 10 to 30 wt%, preferably 15 to 28 wt%, more preferably 16 to 27 wt%.

A preparation method of a phosphorus-doped Cu-SSZ-13 catalyst comprises the following steps: elemental phosphorus is loaded on a Cu-SSZ-13 catalyst in three cases:

(1) selecting a phosphorus-containing inorganic substance to provide element phosphorus, wherein the mode of loading phosphorus is an initial wet impregnation method, an excess impregnation method or a pressurized impregnation method;

(2) selecting phosphorus-containing organic matters to provide element phosphorus, wherein the mode of loading phosphorus is a primary wet impregnation method, an excess impregnation method or a pressurization impregnation method;

(3) selecting a phosphorus-containing molecular sieve to provide element phosphorus, and mixing the Cu-SSZ-13 catalyst with the phosphorus-containing molecular sieve.

The inorganic substance containing phosphorus is orthophosphoric acid, ammonium dihydrogen phosphate or sodium dihydrogen phosphate; the phosphorus-containing organic matter is phosphine, phosphonic acid, phosphonate or phosphate; the phosphorus-containing molecular sieve is SAPO-34, AIPO or SAPO-11.

Furthermore, the mode of mixing the Cu-SSZ-13 catalyst with the phosphorus-containing molecular sieve is preferably a solid mixing method.

Further, in the phosphorus-containing molecular sieve, the content of phosphorus in the molecular sieve is 10 to 30 wt%, preferably 15 to 28 wt%, more preferably 16 to 27 wt%.

And the mass ratio of the Cu-SSZ-13 to the phosphorus-containing molecular sieve is (5-10): (1-5), preferably (8-10): (1-3).

Furthermore, after the phosphorus-containing inorganic substance is selected to provide elemental phosphorus and supported, it is baked at 500 to 600 degrees centigrade for 2 to 6 hours.

And, after selecting phosphorus-containing organic matter to provide element phosphorus and loading, roasting at 500-600 deg.C for 2-6 hr.

The Cu-SSZ-13 catalyst used above was prepared as follows: adding copper sulfate, tetraethylenepentamine, sodium hydroxide solid, sodium metaaluminate, silica sol and amine template agent into water, uniformly dispersing, crystallizing for 2-8 days at the temperature of 100-180 ℃, and roasting for 5-10 hours at the temperature of 400-600 ℃ after washing and drying to obtain the Cu-SSZ-13 catalyst, wherein the mass ratio of the materials is as follows: tetraethylenepentamine: sodium hydroxide: silica sol: amine-type templating agent: copper sulfate, sodium metaaluminate (10-15), sodium metaaluminate (4-10), amine (2-3), amine (0.7-1.5) and amine (1), wherein the amine template is triethylamine, diethylamine or N, N, N-trimethyl-1-adamantyl ammonium hydroxide.

In the preparation of Cu-SSZ-13 molecular sieve catalysts, the silica sol is a dispersion of nanoscale silica particles in water, with a silica solids content of 30-35 wt.% (mass percent silica).

In the preparation of the Cu-SSZ-13 molecular sieve catalyst, the crystallization temperature is 150-180 ℃, and the crystallization time is preferably 4-7 days, and more preferably 4-6 days.

When preparing the Cu-SSZ-13 molecular sieve catalyst, the catalyst is washed, dried and roasted for 6 to 8 hours at the temperature of 500 ℃ and 600 ℃.

When the Cu-SSZ-13 molecular sieve catalyst is prepared, the mass ratio of the materials is water: tetraethylenepentamine: sodium hydroxide: silica sol: amine-type templating agent: copper sulfate, sodium metaaluminate (10-12): (4-8): 0.5-0.8): 8-10): 2-2.5): 0.8-1.2): 1.

When the Cu-SSZ-13 molecular sieve catalyst is prepared, ultrasonic or mechanical stirring is selected when materials are added in sequence so as to uniformly disperse the materials.

The catalyst of the invention is applied to the selective catalytic reduction elimination of nitrogen oxide by taking ammonia as a reducing agent, a 40-60 mesh catalyst is used, and the reaction mixed gas is as follows: 500ppm NO,500ppm NH₃,5％O₂，N₂Is balance gas; the total gas flow is 500ml/min, and the total space time is 150000h^-1(ii) a The reaction temperature is 150-550 ℃, preferably 250-400 ℃, preferably 300-400 ℃ (aiming at improving hydrothermal reaction stability), and the application of element phosphorus in improving hydrothermal reaction stability of the catalyst in selective catalytic reduction elimination nitrogen oxide reaction with ammonia as a reducing agent is provided.

Compared with the prior art, the method does not need to adopt metal salt ion exchange when preparing the Cu-SSZ-13 catalyst, reduces the preparation links of the catalyst and saves the cost. After the catalyst is loaded with phosphorus, the hydrothermal stability of the catalyst is obviously improved, the service life of the catalyst is prolonged, and the phosphorus exists in a form of phosphorus outside a molecular sieve framework before hydrothermal treatment. The phosphorus can be loaded in various ways, but the hydrothermal stability of the Cu-SSZ-13 can be improved. Avoids the pollution problem caused by adding phosphorus in the synthesis process. The catalyst of the invention has the advantages of high activity, wide temperature range, high hydrothermal stability and easy preparation.

Drawings

Figure 1 is an XRD contrast spectrum plot of catalyst A, B before and after aging with C.

FIG. 2 shows catalysts A, B and C of the present invention³¹P MAS NMR spectrum.

FIG. 3 is a graphical representation of the results of NOx conversion versus temperature tests for catalysts A, B and C of the present invention.

FIG. 4 is a graphical representation of the results of testing NOx conversion versus temperature for catalysts A, B and C after aging in accordance with the present invention.

FIG. 5 is a graph of the NOx conversion versus temperature test results for the D catalyst before and after aging in accordance with the present invention.

Detailed Description

The technical scheme of the invention is further explained by combining specific examples. Catalysts A, B, C and D represent catalysts prepared in comparative example, example 1, example 2 and example 3, respectively, and represent Cu-SSZ-13 catalysts containing no phosphorus, added inorganic phosphorus, added organic phosphorus and mixed with phosphorus-containing molecular sieves. In the present invention, the baking is carried out in an air atmosphere for 24 hours per day.