CN107376989B - Cu-AEI molecular sieve catalyst synthesis and application - Google Patents

Abstract

The invention discloses a Cu-AEI molecular sieve synthesis and application, wherein pyrrole/pyrrolidine substances are used as an organic template agent, FAU type silicon-aluminum molecular sieves are used as an aluminum source and a silicon source, a mixed sol can be formed by combining other silicon sources and alkali sources, an AEI structure molecular sieve is synthesized by dynamic crystallization, and then metal salts of soluble Cu are exchanged with other cations in AEI to obtain the Cu-AEI molecular sieve. Then mixed with a binder to form slurry, and the slurry is coated on a porous regular carrier material and can be used for an exhaust gas NOx Selective Catalytic Reduction (SCR) catalyst. The catalyst provided by the invention can be well applied to the reduction of NOx-containing gas discharged by a mobile source and a fixed source, and can well meet the standard requirement of tail gas emission.

Description

Cu-AEI molecular sieve catalyst synthesis and application

Technical Field

The invention relates to synthesis and application of a Cu-AEI molecular catalyst sieve, in particular to an SCR catalyst prepared by coating a Cu-AEI zeolite molecular sieve on a porous regular material, which is used for purifying NOx-containing tail gas and belongs to the field of inorganic materials.

Background

The AEI structure molecular sieve has a three-dimensional channel system with large cages, and can form a three-dimensional channel structure through 8-membered rings, and the pore size is large

The cage structure is similar to the CHA molecular sieve, and the cage size can reach the diameter

A sphere. The difference is that adjacent double six-membered rings of the CHA structure in two adjacent double six-membered ring structures connected by a four-membered ring are in a parallel structure in space, and two adjacent double six-membered rings in the AEI structure are in mirror symmetry distribution. The structural difference leads the eight-membered ring channel in the AEI structure to have smaller pore diameter, higher catalytic activity and better carbon deposition resistance. The structures of the AEI silicon aluminum molecular sieve and the silicon aluminum phosphorus molecular sieve are represented by SSZ-39 and SAPO-18 respectively. Ion-exchanged or metal-loaded active components of AEI molecular sieve catalysts exhibit unique selective reduction (SCR) activity and have attracted considerable attention for their excellent performance in the reduction treatment of nitrogen oxides (NOx).

Nitrogen oxides (NOx) cause a series of environmental problems such as photochemical smog, acid rain and greenhouse effect, have seriously harmed human health, and as the number of automobiles increases and the industry rapidly develops, the amount of NOx emission increases, which inevitably causes serious deterioration of ecology and environment. Thus, the problem of eliminating NOx pollution is not very mild. Currently, the dominant NOx control technology is selective catalytic reduction of NH3 (NH3-SCR), which is key to selecting a catalyst with excellent performance, which will determine the success or failure of the whole catalytic reaction system.

Generally, the SCR catalyst is a molecular sieve with a crystal structure, which is prepared by using zeolite as a carrier and loading SCR active components; zeolites are aluminosilicate crystalline materials having relatively regular pore sizes, such as zeolite beta, zeolite Y, zeolite X, zeolite faujasite, mordenite, erionite, ZSM-5, ZSM-8, ZSM-11, ZSM-12, and the like, which may be exchanged with metals such as Cu, Fe, Mn, Ag, V, Ti, Co, or which themselves contain some metals such as Cu, Fe. However, the above known metal-modified zeolite catalysts can purify nitrogen oxides only in a narrow temperature range during the selective catalytic reduction of nitrogen oxides with ammonia, and do not have high NOx purification performance at 200 ℃ or lower, and have poor hydrothermal stability and low activity under low temperature conditions.

ZSM-5 and beta molecular sieves have a number of disadvantages in their use. They are susceptible to dealumination during high temperature hydrothermal aging, resulting in reduced acidity, particularly for Cu/beta and Cu/ZSM-5 catalysts. Beta and ZSM-5 based catalysts are also affected by hydrocarbons which adsorb on the catalyst at lower temperatures and are oxidized as the temperature of the catalyst system increases, giving off a large amount of heat, causing thermal damage to the catalyst. This problem is particularly acute when applied to automotive diesel engines, since large amounts of hydrocarbons are adsorbed onto the catalyst during cold start. Beta and ZSM-5 molecular sieves are also prone to coking by hydrocarbons. The low activity of the molecular sieve catalyst is caused by the poor stability of the framework structure of the molecular sieve, the structural damage is caused under the condition of rapid temperature change, the metal active components are easy to aggregate, and the dispersion degree of the metal ion active center is reduced.

Cu exchanged CHA-type molecular sieves, such as Cu-SSZ-13 and Cu-SAPO-34, have good hydrothermal stability and SCR catalytic activity. Compared with ZSM-5, the CHA molecular sieve contains a microporous structure, and can adjust single-core Cu²⁺Species, which are more resistant to hydrothermal aging and sulfur poisoning. The CHA-type molecular sieve catalyst also has good activity and high selectivity to N2, and becomes the most potential catalyst for controlling the emission of nitrogen oxides in tail gas of diesel vehicles. However, SAPO-34 molecular sieve has long hydrothermal durability and stability and needs further improvement, while SSZ-13 molecular sieve has expensive template agent, long synthesis period and insufficient low-temperature and high-temperature ignition activity.

The AEI structure molecular sieve provided by the invention has better hydrothermal stability and wider ignition activity window temperature (200-500 ℃), has good low-temperature and high-temperature ignition activity, has a more appropriate pore structure, is beneficial to the diffusion of NOx molecules, enhances the adhesion of metal copper ions, and reduces the possibility of aggregation caused by hydrothermal action.

Disclosure of Invention

The invention aims to provide a Cu-loaded AEI type molecular sieve catalyst which is used for catalytic reduction (SCR) treatment of waste gas NOx of internal combustion engines, gas turbines, coal or fuel oil power generation and the like, and improves hydrothermal stability and ignition activity.

In a particular embodiment of the invention, the method is for treating a NOx-containing exhaust gas of a lean-burn internal combustion engine, such as a diesel engine, a lean-burn gasoline engine or an engine powered by liquid petroleum gas or natural gas.

The molecular sieve catalysts of the present invention can also be used to treat gases from industrial processes such as refining, NOx-containing gases from refining heaters and boilers, furnaces, chemical processing industries, coke ovens, municipal waste treatment plants, and incinerators. Nitrogen oxides (NOx), including various compounds, such as nitrous oxide (N)₂O), Nitric Oxide (NO), nitrogen dioxide (NO)₂) Dinitrogen trioxide (N)₂O₃) Dinitrogen tetroxide (N)₂O₄) And dinitrogen pentoxide (N)₂O₅) And the like.

The invention provides a Cu-AEI molecular sieve catalyst and a preparation method thereof, and is characterized in that: pyrrole/pyrrolidine substances are used as an organic template agent, FAU type silicon-aluminum molecular sieves are used as an aluminum source and a silicon source, other silicon sources and alkali sources can be combined to form mixed sol, an AEI type molecular sieve is synthesized through crystallization, metal Cu is used as a metal promoter to be loaded on the AEI type molecular sieve, a Cu-AEI molecular sieve catalyst is prepared, then the Cu-AEI molecular sieve catalyst is mixed with a binder to form slurry, and the slurry is loaded on a porous regular material and can be used as a NOx Selective Catalytic Reduction (SCR) catalyst.

The molecular molar ratio of silicon dioxide to aluminum oxide in the AEI molecular sieve is 15-300, and the Cu content is 0.5-5.0 wt% of the total mass of the Cu-AEI molecular sieve catalyst.

The preparation method of the Cu-AEI molecular sieve catalyst comprises the following steps:

(1) silicon Source (SiO)₂Calculated), aluminum source (Al)₂O₃Calcualto), alkali liquor (Na)₂Calculated as O) and organic templating agent (OSDA) as Na₂O:SiO₂:Al₂O₃:OSDA:H₂Mixing O-0.1-0.5: 1.0: 0.0033-0.083: 0.05-0.5: 10-50 into sol;

(2) transferring the mixture in the step (1) into a crystallization kettle to perform dynamic crystallization reaction in different temperature sections, wherein the first crystallization temperature section is 120-150 ℃, and the crystallization time is 12-72 hours; the second crystallization temperature is 170-200 ℃ for 12-96 hours.

(3) And (3) recovering the molecular sieve obtained by crystallization in the step (2), then performing degassing treatment on the molecular sieve and a copper ion salt at the solution pH value of 5.0-7.0 at the room temperature under negative pressure, drying the molecular sieve at the temperature of 60-100 ℃ for 4-24 hours, and then roasting the molecular sieve at the temperature of 450-550 ℃ for 2-8 hours under normal pressure to obtain the Cu-AEI molecular sieve.

According to the AEI molecular sieve synthesis method, a silicon source can be selected from one or more of white carbon black, silica sol, water glass, alkyl silicate, macroporous silica gel, coarse-pore silica gel, fine-pore silica gel, B-type silica gel and thin-layer chromatography silica gel.

According to the synthesis method of the AEI molecular sieve, an aluminum source is selected from silicon-aluminum zeolites with FAU structures, including X and Y zeolites.

The AEI molecular sieve synthesis method of the invention is characterized in that an organic template agent is derived from pyrrole/pyrrolidine substances, and comprises 1-hydroxy-3, 4-dimethylpyrrolidine-2, 5-diketone, 1-oxy-2, 2,5, 5-tetramethylpyrrolidine-3-methyl methane sulfoacid, 1-oxy-3-carboxy-2, 2,5, 5-tetramethylpyrrolidine, 1,2,2,5, 5-pentamethylpyrrolidine, 1- (4-ethyl-3, 5-dimethyl-1H-pyrrole-2-yl) -ethanone, 2,3,4, 5-tetramethylpyrrole, 1-isopropyl-2, 3,4, 5-tetramethylpyrrole and 3, 5-dimethyl-2-pyrrolecarboxaldehyde, 3,4, 5-trimethyl-1H-pyrrole-2-carboxylic acid methyl ester, 3,4, 5-trimethyl-1H-pyrrole-2-carboxylic acid ethyl ester, 3-carboxyl-2, 2,5, 5-tetramethyl pyrrolidine 1-oxyl.

In the method, the soluble copper salt is one or more of copper nitrate, copper chloride, copper acetate or copper sulfate, and the concentration of copper ions in the copper salt aqueous solution is 0.1-1.5 mol/L.

The Cu-AEI is mixed with a binder and coated on a porous regular carrier material, wherein the binder can be one or more of silica sol, water glass, pseudo-boehmite and aluminum sol.

The porous structured material comprises a honeycombed, plate-shaped or corrugated structured carrier material, and the material is selected from cordierite, alpha-alumina, silicon carbide, aluminum titanate, silicon nitride, zirconia, mullite, spodumene, alumina-silica-magnesia, zirconium silicate or metal sheets; the carrier is preferably a cordierite porous honeycomb flow-through type monolith carrier, and the carrying capacity of the carrier is 170-270 g/L.

The system of the present invention comprises, in series and in fluid communication, a diesel oxidation catalyst, a source of a nitrogen-based reductant, and an SCR catalyst, contacting an exhaust gas comprising NOx and the reductant with a catalyst composition to selectively reduce at least a portion of the NOx to N₂And H₂O。

The source of the nitrogenous reductant can be ammonia itself, hydrazine, or any suitable ammonia precursor, including one or more of urea, ammonium carbonate, ammonium carbamate, ammonium bicarbonate, or ammonium formate.

The SCR catalyst of the invention is coated on a honeycomb wall flow filter or flow through monolith or an extruded honeycomb and the transition metal exchanged AEI molecular sieve catalyst is a washcoat supported on the substrate.

The exhaust gas containing NOx is preferably an exhaust gas stream emitted by a motor vehicle, more preferably an exhaust gas stream obtained from a lean burn engine, even more preferably a diesel exhaust gas stream.

The process for treating a gas stream comprising NOx wherein prior to contacting the catalyst with the gas stream, the NO2 content thereof is 80 wt% or less based on NOx, calculated as 100 wt%, wherein the NO2 content is preferably comprised between 5 and 70 wt%, more preferably between 10 and 60 wt%, more preferably between 15 and 55 wt%, even more preferably between 20 and 50 wt%.

The molecular sieve catalysts of the present invention may be coated on a suitable substrate monolith or formed into extruded catalysts, but are preferably used in catalyst coatings.

In certain embodiments of the invention, the molecular sieve catalyst is coated on a flow-through monolith substrate (i.e., a honeycomb monolith catalyst support structure having a plurality of parallel, small channels running axially through the entire member) or a monolith filter substrate such as a wall-flow filter, or the like.

Certain aspects of the present disclosure provide a catalytically activated coating. The washcoat containing the AEI catalyst described herein is preferably a solution, suspension or slurry. Suitable coatings include surface coatings, coatings that penetrate into a portion of the substrate, coatings that penetrate into the substrate, or some combination thereof.

The two most common substrate designs to which the catalyst can be applied are plate and honeycomb. Preferred substrates, particularly for mobile applications, include flow-through monoliths having a so-called honeycomb geometry comprising a plurality of adjacent, parallel channels that are open at both ends and generally extend from an inlet face to an outlet face of the substrate, and that result in a high surface area to volume ratio. For certain applications, the honeycomb flow-through monolith preferably has a high pore density, for example, about 600 to 800 pores per square inch, and/or an average internal wall thickness of about 0.18 to 0.35mm, preferably about 0.20 to 0.25 mm. For certain other applications, the honeycomb flow-through monolith preferably has a low pore density of about 150 to 600 pores per square inch, more preferably about 200 to 400 pores per square inch.

The invention uses low-cost pyrrole or pyrrolidine organic matter as the template agent, thereby not only reducing the synthesis cost of the AEI molecular sieve, but also ensuring the requirement of crystallinity.

The catalyst in the embodiments of the invention shows that high NOx conversion is obtained in a much wider temperature window. The temperature range for improving the conversion efficiency may be about 150 to 650 ℃, preferably 200 to 500 ℃, more preferably 200 to 450 ℃, or most significantly 200 to 400 ℃. Within these temperature ranges, the conversion efficiency after exposure to a reducing atmosphere, even after exposure to a reducing atmosphere and high temperatures (e.g., up to 850 ℃) can be greater than 55% to 100%, more preferably greater than 90% efficiency, and even more preferably greater than 95% efficiency.

Drawings

The invention is further described with reference to the following figures and examples:

FIG. 1 the XRD pattern of the AEI molecular sieve prepared in example 1 of the present invention;

FIG. 2 is an SEM image of an AEI molecular sieve prepared according to example 1 of the present invention;

Detailed Description

The embodiments and the effects of the present invention are further illustrated by examples and comparative examples, but the scope of the present invention is not limited to the contents listed in the examples.

Example 1

(1) Synthesis of AEI zeolite (AEI type molecular sieve):

quantitative water glass (Na)₂O：7.44wt％，SiO₂: 27.40 wt%) was added to an aqueous solution of organic template 1-hydroxy-3, 4-dimethylpyrrolidine-2, 5-dione (concentration: 25 wt%), then HY zeolite (silica to alumina ratio 5.38, providing an aluminum source and a portion of the silicon source) was added, and then NaOH particles (purity: 96 wt%), and deionized water is added and stirred thoroughly. The obtained mixed slurry was continuously stirred in a sealed container at room temperature for 2 hours until all the raw materials were uniformly mixed, and the molar ratio of the mixed sol consisting of the following molar components was:

Na₂O：SiO₂：Al₂O₃：OSDA：H₂O＝0.16：1.0：0.0752：0.15：15.0；

transferring the obtained solid mixture to

A2000 ml hydrothermal crystallization kettle is lined and stirred at the speed of 60rpm, crystallized for 24 hours at the temperature of 140 ℃, and then crystallized for 48 hours by heating to 170 ℃. After complete crystallization, quickly cooling the product, performing suction filtration separation and washing until the pH value is 8.0-9.0, drying at 120 ℃ for 12 hours, and roasting at 540 ℃ for 4 hours to obtain AEI molecular sieve raw powder;

(2) copper modified AEI molecular sieves: taking 10.0g of the molecular sieve raw powder synthesized in the step (1), and adding Cu (NO) with the concentration of 0.2mol/L₃)₂·3H₂Dripping dilute nitric acid into the solution to adjust the pH value to 6.5 in the O aqueous solution, uniformly stirring, putting into a heat-resistant container, and putting into a dryer with a pressure reducing valve; vacuumizing the pressure in the dryer to be below 10Torr by using a vacuum pump, degassing at room temperature for 1 hour, heating to 90 ℃, drying for 12 hours, and roasting the dried sample at the temperature of 500 ℃ for 4 hours under normal atmospheric pressure; the copper modified AEI molecular sieve is obtained, and in the catalyst prepared according to the ICP analysis result, copper (II) ions account for 2.9 percent of the total weight of the molecular sieve catalyst, namely the copper loading is 2.9 weight percent, and Na ionsThe content is less than 200 ppm.

(3) Taking 15g of the copper modified molecular sieve obtained in the step (2) and 6.71g of silica Sol (SiO)₂The content is as follows: 30.0 wt%) and 16.90g of deionized water are uniformly mixed to prepare catalyst slurry with the solid content of 44.1 wt%, the catalyst slurry is coated on a honeycomb-shaped porous regular material (#300cpsi, the diameter of 21mm and the length of 20mm) made of cordierite through an immersion method, redundant slurry drops are blown off by compressed air, the catalyst slurry is dried for 24 hours at 110 ℃, the catalyst slurry is coated for 2 times under the same condition and is calcined for 2 hours at 500 ℃ to prepare the SCR catalyst, the loading on the regular material is 216g/L (the weight of the weight increased by the regular material after calcination is divided by the space volume occupied by the regular material, the definitions of the subsequent examples and comparative examples on the loading are the same), and the obtained SCR catalyst is marked as A, and relevant preparation parameters and material types are shown in tables 1 and 2.

Example 2

The process for synthesizing AEI silicon-aluminum molecular sieve is similar to that of example 1, except that the molar ratio of the mixed sol, the type of the organic template, the type of the silicon source, the type of the FAU zeolite, the silicon-aluminum ratio, the crystallization temperature, the crystallization time and the like are adopted in step (1), the type of the Cu salt and the loading amount of the Cu ions are adopted in step (2), and 15g of the copper modified AEI molecular sieve and 6.24g of the aluminum sol (Al) are adopted in step (3)₂O₃The content is as follows: 20.0 wt%) and 26.80g of deionized water were mixed uniformly to prepare a catalyst slurry having a solid content of 33.8 wt%, which was coated on a cordierite structured material by an impregnation method. Specific parameters in this example are shown in tables 1 and 2.

Example 3

The process for synthesizing AEI aluminosilicate molecular sieves was similar to that of example 1, except that the molar ratio of the mixed sol, the type of the organic template, the type of the silicon source, the type of the FAU zeolite, the silica-alumina ratio, the crystallization temperature, the crystallization time, etc. in step (1), the type of the Cu salt and the Cu ion loading in step (2), and 15g of the copper-modified AEI molecular sieve and 6.40g of pseudo-boehmite (Al)₂O₃The content is as follows: 70.9 wt%) and 27.80g of deionized water are mixed uniformly to prepare catalyst slurry with the solid content of 39.7 wt%, and the catalyst slurry is coated on the cordierite regular material by an impregnation method. . Specific parameters in this example are shown in tables 1 and 2.

Example 4

The process for synthesizing AEI aluminosilicate molecular sieves was similar to example 1, except that the molar ratio of the mixed sol, the type of the organic template, the type of the silicon source, the type of FAU zeolite and the silica-alumina ratio, the crystallization temperature and the crystallization time, etc. in step (1), the type of the Cu salt and the loading amount of the Cu ions in step (2), and 15g of the copper-modified AEI molecular sieve and 6.60g of the silica Sol (SiO) were removed in step (3)₂The content is as follows: 30.0 wt%) and 26.60g of deionized water, and the mixture is uniformly mixed to prepare catalyst slurry with the solid content of 35.2 wt%, and the catalyst slurry is coated on the cordierite regular material by an impregnation method. Specific parameters in this example are shown in tables 1 and 2.

Example 5

The process for synthesizing an AEI silicon-aluminum molecular sieve is similar to that of example 1, except that the molar ratio of the mixed sol, the type of the organic template, the crystallization temperature, the crystallization time and the like in step (1) are used, in addition, FAU zeolite with a high silicon-aluminum ratio is used as a silicon-aluminum source, and a silicon source is not additionally used; the kind of Cu salt and the loading amount of Cu ions in the step (2), and 15g of copper modified AEI molecular sieve and 6.10g of silica Sol (SiO) in the step (3)₂The content is as follows: 30.0 wt%) and 25.60g of deionized water were mixed uniformly to prepare a catalyst slurry having a solid content of 36.0 wt%, and the catalyst slurry was coated on a cordierite structured material by an impregnation method. . Specific parameters in this example are shown in tables 1 and 2.

Examples 6 to 18

The process for synthesizing an AEI aluminosilicate molecular sieve is similar to example 1, except that the molar ratio of the mixed sol, the type of the organic template, the type of the silicon source, the type of FAU zeolite and the silica-alumina ratio, the crystallization temperature and the crystallization time, etc. in step (1), no additional silicon source is provided in examples 6, 11 and 16; the kind of Cu salt and the loading amount of Cu ions in the step (2), and the loading amount of the SCR catalyst on the structured material in the step (3). Specific parameters in this example are shown in tables 1 and 2.

TABLE 1

TABLE 2

Comparative example 1

17.0g of SB powder was dissolved in 50.0g of a 50 wt% aqueous NaOH solution, and 200.0g of white carbon was then added thereto and mixed thoroughly. An aqueous solution of N, N, N-trimethyladamantane ammonium hydroxide (TMADA +) (25 wt% concentration) was slowly added to the mixture while mixing. 80.0g of deionized water was slowly added and the resulting mixture was mixed well for 1 hour. The molar composition of the synthesis mixture was:

0.21Na₂O：SiO₂：0.0286Al₂O₃：0.18TMADa+：26.8H₂O

and then transferring the obtained gel into a stainless steel reaction kettle to crystallize at 170 ℃ for 168 hours, after the reaction is finished, washing the product with deionized water, drying at 120 ℃ for 12 hours, and roasting at 540 ℃ for 4 hours to obtain the SSZ-13 molecular sieve raw powder.

10g of SSZ-13 molecular sieve raw powder was added to 100g of Cu (NO) having a concentration of 0.3mol/L₃)₂·3 H₂And (3) dripping dilute nitric acid into the O aqueous solution to adjust the pH value to 5.8, and uniformly stirring. After stirring was stopped for 1 hour, the supernatant was siphoned off when SSZ-13 zeolite settled. The exchange with fresh copper nitrate solution was repeated once, and finally the exchanged SSZ-13 zeolite was filtered and washed with deionized water. Drying at 90 ℃ for 12 hours under the low pressure of 10Torr, and then roasting at 500 ℃ for 4 hours under normal atmospheric pressure to obtain the copper modified SSZ-13 molecular sieve powder. According to the ICP analysis, the copper (II) ions accounted for 2.5% of the total weight of the molecular sieve catalyst, and the Na ion content was less than 200 ppm.

Taking 15g to obtainCopper-modified SSZ-13 molecular sieves of (2) with 5.56g of silica sol (30 wt% SiO)₂) And 22.80g of deionized water are uniformly mixed to prepare catalyst slurry with the solid content of 38.44 wt%, the catalyst slurry is coated on a honeycomb-shaped porous regular material (300 cpsi, the diameter of 21mm and the length of 20mm) made of cordierite through an impregnation method, redundant slurry drops are blown off by compressed air, the drying is carried out for 12 hours at the temperature of 110 ℃, then, the slurry is coated again, the SCR catalyst is prepared after the calcination is carried out for 2 hours at the temperature of 500 ℃, and the measured catalyst loading capacity on the regular material is 228.4g/L and is marked as VS-1.

Comparative example 2

Weighing 13.59g of pseudo-boehmite, dissolving in 108.0g of deionized water, stirring uniformly at room temperature, adding 23.24g of ammonium dihydrogen phosphate, stirring uniformly for 2 hours, filtering the slurry, drying for 4 hours at 110 ℃, roasting for 2 hours at 500 ℃ to obtain a phosphorus-aluminum dry glue, and then crushing to obtain particles with the particle size of less than or equal to 100 microns.

Mixing and stirring all the particles with 0.61g of chromatographic silica gel, 54.0g of deionized water, 7.70g of morpholine and 1.815g of tripropylamine, transferring the uniformly mixed gel into a stainless steel high-pressure reaction kettle, stirring at the speed of 600 revolutions per minute for 0.5h, stirring and crystallizing at 150 ℃ for 24h, and then heating to 180 ℃ for crystallizing for 48 h. And (3) after crystallization is finished, quickly cooling with water to stop crystallization, and performing suction filtration separation, deionized water washing and drying at 120 ℃ for 24 hours on the product to obtain the molecular sieve raw powder. And then putting the molecular sieve raw powder into a roasting furnace, heating to 550 ℃, roasting at constant temperature for 4 hours to obtain white crystal powder, and measuring by X-ray diffraction to obtain the SAPO-34 molecular sieve.

10g of SAPO-34 raw powder was added to 100g of Cu (NO) having a concentration of 0.2mol/L₃)₂·3H₂And (3) dripping dilute nitric acid into the O aqueous solution to adjust the pH value to 4.0, and uniformly stirring. After stirring was stopped for 1 hour, the supernatant was siphoned off when the SAPO-34 molecular sieves settled. And repeatedly using a fresh copper nitrate solution for exchange once, and finally filtering and washing the exchanged SAPO-34 molecular sieve by deionized water. Drying at 90 ℃ for 12 hours under the low pressure of 10Torr, and then roasting at 500 ℃ for 4 hours under normal atmospheric pressure to obtain the copper modified SAPO-34 molecular sieve powder. According to the result of ICP analysis, copper(II) the ion accounts for 2.5% of the total weight of the molecular sieve catalyst, and the Na ion content is less than 200 ppm.

Taking 15g of the obtained copper modified SAPO-34 molecular sieve and 5.48g of silica sol (30 wt% SiO)₂) And 26.6g of deionized water are uniformly mixed to prepare catalyst slurry with the solid content of 35.35 wt%, the catalyst slurry is coated on a honeycomb-shaped porous regular material (300 cpsi, the diameter of 21mm and the length of 20mm) made of cordierite through an impregnation method, redundant slurry drops are blown off by compressed air, the drying is carried out for 12 hours at the temperature of 110 ℃, then, the slurry is coated again, the SCR catalyst is prepared after the calcination is carried out for 2 hours at the temperature of 500 ℃, and the measured catalyst loading capacity on the regular material is 234.1g/L and is marked as VS-2.

Comparative example 3

A copper-modified beta molecular sieve selective reduction catalyst is prepared by the following method:

(1) adding NaOH aqueous solution into colloidal silicon dioxide (the mass content of the silicon dioxide is 30wt percent), fully stirring, and adding Al (NO)₃)₃·9H₂An aqueous solution of O and an aqueous solution of TEAOH (TEAOH content 35 wt.%), stirring the reaction mixture sufficiently, the molar ratio of the raw materials being: na (Na)₂O： Al₂O₃：SiO₂：TEAOH：H₂O is 21.0: 1.0: 300.0: 150.0: 4000.0, respectively;

(2) putting the reaction mixture into a polytetrafluoroethylene container, sealing the container under autogenous pressure, and heating the mixture for 72 hours at the temperature of 155 ℃; then carrying out centrifugal separation, washing, drying at 120 ℃ for 12 hours, and roasting at 550 ℃ for 4 hours under normal atmospheric pressure to remove the template; ICP analysis of the product for nSiO₂： nA1₂O₃In a molar ratio of 29: XRD analysis of the product showed that the product was a beta molecular sieve with BEA type structure.

(3) Adding 10g of beta molecular sieve powder into 1000mL of ammonium nitrate solution (1.0mol/L), treating for 24 hours at 80 ℃ for ion exchange, fully washing and filtering, then repeating the ammonium ion exchange for 3 times, drying for 24 hours at 120 ℃, roasting the zeolite molecular sieve for 4 hours at 550 ℃ under normal atmospheric pressure, and obtaining the hydrogenated synthesized beta zeolite molecular sieve;

(4) 35g of copper acetate (Cu) was dissolved in 3500g of deionized water₂(CH₃COO)₄·H₂O)35g, to obtain an aqueous solution of copper (II) acetate ions having a pH of 3.8; adding 300g of hydrogenated synthetic zeolite molecular sieve into the copper (II) acetate separated aqueous solution, stirring for 2 hours at 80 ℃, filtering, and carrying out solid-liquid separation; washing the hydrogenated synthetic zeolite molecular sieve subjected to solid-liquid separation with 3500g of pure water at 40 ℃, and repeatedly filtering and washing until the pH value of the washing liquid is 6-7; then, drying the filtered substance at 120 ℃ for 12h, and roasting at 550 ℃ for 2 h; after grading with a 40-mesh sieve, the copper modified beta molecular sieve is obtained, and in the catalyst prepared according to the ICP analysis result, copper (II) ions account for 3.0% of the total weight of the catalyst, namely the copper loading is 3.0 wt%;

(5) taking 15g of the copper modified molecular sieve obtained in the step (4), uniformly mixing with 4.32g of commercial silica sol (the mass content of silicon dioxide is 20 wt%) and 15.93g of deionized water to prepare catalyst slurry with the solid content of 45.0 mass%, coating the catalyst slurry on a honeycomb-shaped porous regular material (300 cpsi, the diameter of 21mm and the length of 20mm) made of cordierite by an impregnation method, blowing off redundant slurry drops by using compressed air, drying for 24 hours at 105 ℃, roasting for 2 hours at 500 ℃ to prepare an SCR catalyst, wherein the loading amount on the regular material is 236.3g/L, and VS is marked as-3.

Comparative example 4

A copper-modified ZSM-5 molecular sieve selective reduction catalyst is prepared by the following method:

(1) in an amount of 800g of an aqueous sodium silicate solution (mass fraction: SiO)₂ 26％、Na₂O7.0%), an aqueous sodium hydroxide solution (prepared by dissolving 5g of sodium hydroxide in 400g of deionized water), and 61g of aluminum sulfate hexadecahydrate (Al) were added under stirring₂(SO₄)₃·16H₂O) and 1, 3-dimethylurea l0g are dissolved in 1.5kg deionized water to prepare an aqueous solution, and finally 1000g of sulfuric acid with the mass fraction of 5 percent is added to obtain uniform primary gel;

(2) loading the gel obtained in the step 1 into a 5L high-pressure kettle, generating autogenous pressure, stirring at the speed of 200 r/min, and crystallizing at 160 ℃ for 72 hours to obtain an MFI crystal zeolite molecular sieve;

(3) in 640g of an aqueous sodium silicate solution (mass fraction: SiO)₂ 25％、Na₂O8.0%) was added with 1.75kg of deionized water and 25g of aluminum sulfate hexadecahydrate (Al)₂(SO₄)₃·16H₂O) and 35g of sulfuric acid (mass fraction is 97%), continuing to add 1.5kg of the MFI seed zeolite molecular sieve obtained in the step (2), and stirring to obtain a second-stage gel; putting the secondary gel into a 5L high-pressure kettle to generate self-generated pressure, stirring and crystallizing at 150 ℃, wherein the stirring speed is 110 r/min, and the processing time is 45 hours; filtering the obtained slurry, washing with water, and drying at 120 ℃ for 5 hours to obtain a product; the product was analyzed by ICP, whereby SiO in the product was found₂：A1₂O₃In a molar ratio of 80: XRD analysis shows that the product is ZSM-5 molecular sieve with MFI type structure;

(4) adding 10g of the dried ZSM-5 molecular sieve into 84.56ml of ammonium nitrate aqueous solution with the concentration of 1.2 mol/L; ion exchange is carried out for 3 hours at 70 ℃, then filtration is carried out, water washing is carried out by 5 times of water, drying is carried out for 10 hours at 120 ℃, and then roasting is carried out for 2 hours at 550 ℃, thus obtaining the hydrogen type ZSM-5 molecular sieve.

(5) 35g of copper acetate (Cu) was dissolved in 3500g of deionized water₂(CH₃COO)₄·H₂O)35g, to obtain an aqueous solution of copper (II) acetate ions having a pH of 4.8; adding 300g of hydrogen type ZSM-5 zeolite molecular sieve into the copper (II) acetate separated aqueous solution, stirring at 80 ℃ for 2 hours, filtering, and carrying out solid-liquid separation; washing the hydrogenated synthetic zeolite molecular sieve subjected to solid-liquid separation with 3500g of pure water at 40 ℃, and repeatedly filtering and washing until the pH value of the washing liquid is 6-7; then, drying the filtered substance at 120 ℃ for 12h, and roasting at 550 ℃ for 2 h; after classification is carried out by using a 40-mesh sieve, a copper modified ZSM-5 molecular sieve is obtained, and in the catalyst prepared according to the ICP analysis result, copper (II) ions account for 2.90 percent of the total weight of the catalyst, namely the copper loading is 2.90 percent by weight;

(6) taking 15g of the copper modified molecular sieve obtained in the step (4), uniformly mixing 6.26g of commercial silica sol (the mass content of silicon dioxide is 20 wt%) and 21.51g of deionized water to prepare catalyst slurry with the solid content of 38.0 mass%, coating the catalyst slurry on a honeycomb-shaped porous regular material (300 cpsi, the diameter of 21mm and the length of 20mm) made of cordierite by an impregnation method, blowing off redundant slurry drops by using compressed air, drying at 120 ℃ for 24 hours, roasting at 550 ℃ for 2 hours to prepare an SCR catalyst, wherein the loading amount on the regular material is 241.6g/L and is marked as VS-4.

Examples 19 to 28

Testing of the SCR catalyst:

the honeycomb material-coated SCR catalysts (sizes) prepared in examples 1 to 6 and comparative examples 1 to 4 were used

) In a reactor

160mL/min of a mixed gas stream containing 500ppm of NO, 500ppm of NH3, 10 vol% of O2, 5 vol% of steam and Ar as a balance gas firstly passes through a preheater (set at 250 ℃) and then enters an SCR reactor. At the reaction temperature of 100-550 ℃ for 48000 hours^-1The test specimens were tested at a volumetric gas hourly space velocity. The temperature is monitored by an internal thermocouple located at the sample site.

The used fresh SCR catalysts of the above examples and comparative examples were subjected to a hydrothermal durability treatment under the conditions of the hydrothermal durability treatment test to obtain aged SCR catalysts:

space velocity SV: 30000/h, temperature: 800 ℃, time: 16 hours, water concentration: 10%, oxygen concentration: 10%, nitrogen concentration: and (4) balancing.

After hydrothermal aging treatment is carried out according to the parameters, the catalyst is continuously used as an SCR catalyst for NOx catalytic reduction reaction evaluation test:

NO conversion or "denox" activity was determined under steady state conditions by measuring NOx, NH3, and N2O concentrations at the outlet using a Bruker EQUINOX model 55 FT-IR spectrometer.

The SCR catalyst activity laboratory evaluation device described above was used to evaluate the selective catalytic reduction performance of NOx on the Cu-supported SCR catalysts prepared in examples and comparative examples, and the results are shown in table 4.

TABLE 4

It can be seen from Table 4 that the SCR activity (compared from NOx purification rate data) at low and high temperatures of the Cu-AEI catalyst samples prepared in accordance with the present invention is significantly better than the Cu-SSZ-13, Cu-SAPO-34, Cu-beta and Cu-ZSM-5 catalyst samples of the comparative examples, whether in the "fresh" or "aged" state, at all temperatures tested. Thus, the results obtained from examples 19-24 clearly show that the Cu-AEI molecular sieve catalyst material of the invention and the catalysts obtained therewith have improved SCR catalytic activity, especially at low conversion temperatures characteristic of cold start conditions when treating NOx in, for example, diesel locomotive applications. For other SCR applications, the Cu-AEI molecular sieve catalyst material of the present invention allows for higher conversion at lower temperatures, thus allowing for higher efficiency and thus, at comparable conversion, for high energy efficiency treatment of NOx-containing exhaust gases, such as exhaust gases obtained from industrial processes.

The above examples are only for illustrating the technical concept and features of the present invention, and are not intended to limit the scope of the present invention. The appended claims are to encompass within their scope all such changes, modifications, and alterations that fall within the true spirit of the invention.

Claims (9)

1. The application of Cu-AEI molecular sieve catalyst is characterized by comprising the following steps: contacting an exhaust gas comprising NOx, a reductant, and an SCR catalyst composition in series fluid communication to selectively reduce at least a portion of the NOx to N₂And H₂O；

   The preparation method of the Cu-AEI molecular sieve catalyst comprises the steps of adopting pyrrole/pyrrolidine substances as an organic template agent, adopting an FAU type silicon-aluminum molecular sieve as an aluminum source and a silicon source, forming mixed sol by combining other silicon sources and alkali sources, synthesizing an AEI type molecular sieve through crystallization, loading metal Cu as a metal promoter on the AEI type silicon-aluminum molecular sieve to prepare the Cu-AEI molecular sieve catalyst, mixing the Cu-AEI molecular sieve catalyst with a binder to form slurry, loading the slurry on a porous regular material, and using the slurry as a catalyst for Selective Catalytic Reduction (SCR) of NOx;

   the molecular mole ratio of silicon dioxide to aluminum oxide in the AEI molecular sieve is 10-300, and the Cu content is 0.5-5.0 wt% of the total mass of the Cu-AEI molecular sieve catalyst;

   the organic template agent is selected from pyrrole/pyrrolidine substances, including 1-hydroxy-3, 4-dimethylpyrrolidine-2, 5-diketone, 1-oxy-2, 2,5, 5-tetramethylpyrrolidine-3-methyl methane sulfoacid, 1-oxy-3-carboxy-2, 2,5, 5-tetramethylpyrrolidine, 1,2,2,5, 5-pentamethylpyrrolidine, 1- (4-ethyl-3, 5-dimethyl-1H-pyrrole-2-yl) -ethanone, 2,3,4, 5-tetramethylpyrrole, 1-isopropyl-2, 3,4, 5-tetramethylpyrrole, 3, 5-dimethyl-2-pyrrole formaldehyde, and the like, 3,4, 5-trimethyl-1H-pyrrole-2-carboxylic acid methyl ester, 3,4, 5-trimethyl-1H-pyrrole-2-carboxylic acid ethyl ester, 3-carboxy-2, 2,5, 5-tetramethylpyrrolidine-1-oxyl;

   the preparation method of the Cu-AEI molecular sieve catalyst comprises the following steps:

   (1) the silicon source is made of SiO₂Calculating the aluminum source as Al₂O₃Calculating the alkali liquor by Na₂O calculation and organic template OSDA as Na₂O:SiO₂:Al₂O₃:OSDA:H₂Mixing O-0.1-0.5: 1.0: 0.0033-0.083: 0.05-0.5: 10-50 into sol;

   (2) transferring the mixture in the step (1) into a crystallization kettle to perform dynamic crystallization reaction in different temperature sections, wherein the first crystallization temperature section is 120-150 ℃, and the crystallization time is 12-72 hours; the second crystallization temperature section is crystallization time of 170-200 ℃ for 12-96 hours;

   (3) and (3) recovering the molecular sieve obtained by crystallization in the step (2), then performing degassing treatment on the molecular sieve and a copper ion salt at the solution pH value of 5.0-7.0 at the room temperature under negative pressure, drying the molecular sieve at the temperature of 60-100 ℃ for 4-24 hours, and then roasting the molecular sieve at the temperature of 450-550 ℃ for 2-8 hours under normal pressure to obtain the Cu-AEI molecular sieve.
2. 2. Use according to claim 1, characterized in that: the silicon source can be one or more of white carbon black, silica sol, water glass, alkyl silicate, macroporous silica gel, coarse silica gel, fine silica gel, B-type silica gel and thin-layer chromatography silica gel.
3. 3. Use according to claim 1, characterized in that: the FAU-type silico-aluminum molecular sieves include X and Y zeolites.
4. 4. Use according to claim 1, characterized in that: the copper salt is one or more of copper nitrate, copper chloride, copper acetate or copper sulfate, and the concentration of copper ions in the copper salt aqueous solution is 0.1-1.5 mol/L.
5. 5. Use according to claim 1, characterized in that: the binder can be one or more of silica sol, water glass, pseudo-boehmite and aluminum sol.
6. 6. Use according to claim 1, characterized in that: the porous regular material comprises a honeycomb-shaped, plate-shaped or corrugated regular carrier material, and the material is selected from cordierite, alpha-alumina, silicon carbide, aluminum titanate, silicon nitride, zirconia, mullite, spodumene, alumina-silica-magnesia, zirconium silicate or metal sheets.
7. 7. Use according to claim 1, characterized in that: the carrier is a cordierite porous honeycomb flow-through type monolithic carrier, and the carrying capacity of the carrier is 170-270 g/L.
8. 8. Use according to claim 1, the source of reductant being selected from ammonia itself, hydrazine or ammonia precursors including one or more of urea, ammonium carbonate, ammonium carbamate, ammonium bicarbonate or ammonium formate.
9. 9. Use according to claim 1, characterized in that: exhaust containing NOx includes exhaust streams emitted by motor vehicles.

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