CN110193379B - Preparation method and application of CurE/SAPO-34 molecular sieve - Google Patents
Preparation method and application of CurE/SAPO-34 molecular sieve Download PDFInfo
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- 239000002808 molecular sieve Substances 0.000 title claims abstract description 143
- URGAHOPLAPQHLN-UHFFFAOYSA-N sodium aluminosilicate Chemical compound [Na+].[Al+3].[O-][Si]([O-])=O.[O-][Si]([O-])=O URGAHOPLAPQHLN-UHFFFAOYSA-N 0.000 title claims abstract description 143
- 238000002360 preparation method Methods 0.000 title claims abstract description 27
- 229910052761 rare earth metal Inorganic materials 0.000 claims abstract description 33
- 238000006555 catalytic reaction Methods 0.000 claims abstract description 18
- 239000007809 chemical reaction catalyst Substances 0.000 claims abstract description 3
- MWUXSHHQAYIFBG-UHFFFAOYSA-N Nitric oxide Chemical compound O=[N] MWUXSHHQAYIFBG-UHFFFAOYSA-N 0.000 claims abstract 6
- 238000000746 purification Methods 0.000 claims abstract 2
- 239000010949 copper Substances 0.000 claims description 60
- 238000006243 chemical reaction Methods 0.000 claims description 41
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 26
- YNAVUWVOSKDBBP-UHFFFAOYSA-N Morpholine Chemical compound C1COCCN1 YNAVUWVOSKDBBP-UHFFFAOYSA-N 0.000 claims description 24
- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical compound OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 claims description 20
- 238000001035 drying Methods 0.000 claims description 16
- 238000000034 method Methods 0.000 claims description 15
- 238000003756 stirring Methods 0.000 claims description 15
- 238000002425 crystallisation Methods 0.000 claims description 14
- 230000008025 crystallization Effects 0.000 claims description 14
- 239000008367 deionised water Substances 0.000 claims description 12
- 229910021641 deionized water Inorganic materials 0.000 claims description 12
- 229910002651 NO3 Inorganic materials 0.000 claims description 11
- VXAUWWUXCIMFIM-UHFFFAOYSA-M aluminum;oxygen(2-);hydroxide Chemical compound [OH-].[O-2].[Al+3] VXAUWWUXCIMFIM-UHFFFAOYSA-M 0.000 claims description 11
- NHNBFGGVMKEFGY-UHFFFAOYSA-N nitrate group Chemical group [N+](=O)([O-])[O-] NHNBFGGVMKEFGY-UHFFFAOYSA-N 0.000 claims description 11
- 229910000147 aluminium phosphate Inorganic materials 0.000 claims description 10
- RMAQACBXLXPBSY-UHFFFAOYSA-N silicic acid Chemical compound O[Si](O)(O)O RMAQACBXLXPBSY-UHFFFAOYSA-N 0.000 claims description 10
- 239000000047 product Substances 0.000 claims description 8
- 238000002156 mixing Methods 0.000 claims description 7
- 229940073455 tetraethylammonium hydroxide Drugs 0.000 claims description 7
- LRGJRHZIDJQFCL-UHFFFAOYSA-M tetraethylazanium;hydroxide Chemical compound [OH-].CC[N+](CC)(CC)CC LRGJRHZIDJQFCL-UHFFFAOYSA-M 0.000 claims description 7
- ZMANZCXQSJIPKH-UHFFFAOYSA-N Triethylamine Chemical compound CCN(CC)CC ZMANZCXQSJIPKH-UHFFFAOYSA-N 0.000 claims description 6
- 239000003795 chemical substances by application Substances 0.000 claims description 6
- SCGJLFGXXZTXSX-UHFFFAOYSA-N copper;ethanol Chemical compound [Cu].CCO SCGJLFGXXZTXSX-UHFFFAOYSA-N 0.000 claims description 6
- 239000007787 solid Substances 0.000 claims description 6
- 229910052684 Cerium Inorganic materials 0.000 claims description 5
- 229910052779 Neodymium Inorganic materials 0.000 claims description 5
- 229910052777 Praseodymium Inorganic materials 0.000 claims description 5
- 229910052772 Samarium Inorganic materials 0.000 claims description 5
- GWXLDORMOJMVQZ-UHFFFAOYSA-N cerium Chemical compound [Ce] GWXLDORMOJMVQZ-UHFFFAOYSA-N 0.000 claims description 5
- 229910052746 lanthanum Inorganic materials 0.000 claims description 5
- FZLIPJUXYLNCLC-UHFFFAOYSA-N lanthanum atom Chemical group [La] FZLIPJUXYLNCLC-UHFFFAOYSA-N 0.000 claims description 5
- QEFYFXOXNSNQGX-UHFFFAOYSA-N neodymium atom Chemical compound [Nd] QEFYFXOXNSNQGX-UHFFFAOYSA-N 0.000 claims description 5
- PUDIUYLPXJFUGB-UHFFFAOYSA-N praseodymium atom Chemical compound [Pr] PUDIUYLPXJFUGB-UHFFFAOYSA-N 0.000 claims description 5
- KZUNJOHGWZRPMI-UHFFFAOYSA-N samarium atom Chemical compound [Sm] KZUNJOHGWZRPMI-UHFFFAOYSA-N 0.000 claims description 5
- 238000001816 cooling Methods 0.000 claims description 4
- 230000007935 neutral effect Effects 0.000 claims description 4
- 150000003839 salts Chemical class 0.000 claims description 4
- 238000005406 washing Methods 0.000 claims description 4
- 238000001027 hydrothermal synthesis Methods 0.000 claims description 3
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 claims description 2
- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 claims description 2
- HQABUPZFAYXKJW-UHFFFAOYSA-N butan-1-amine Chemical compound CCCCN HQABUPZFAYXKJW-UHFFFAOYSA-N 0.000 claims description 2
- 150000001879 copper Chemical class 0.000 claims description 2
- 238000007598 dipping method Methods 0.000 claims description 2
- 239000006228 supernatant Substances 0.000 claims description 2
- HWCKGOZZJDHMNC-UHFFFAOYSA-M tetraethylammonium bromide Chemical compound [Br-].CC[N+](CC)(CC)CC HWCKGOZZJDHMNC-UHFFFAOYSA-M 0.000 claims description 2
- YMBCJWGVCUEGHA-UHFFFAOYSA-M tetraethylammonium chloride Chemical compound [Cl-].CC[N+](CC)(CC)CC YMBCJWGVCUEGHA-UHFFFAOYSA-M 0.000 claims description 2
- 239000003054 catalyst Substances 0.000 abstract description 126
- 239000007789 gas Substances 0.000 abstract description 3
- 238000010335 hydrothermal treatment Methods 0.000 description 62
- 229910001868 water Inorganic materials 0.000 description 14
- 238000009616 inductively coupled plasma Methods 0.000 description 13
- 239000000243 solution Substances 0.000 description 13
- 229910000069 nitrogen hydride Inorganic materials 0.000 description 12
- 230000003197 catalytic effect Effects 0.000 description 9
- 230000000052 comparative effect Effects 0.000 description 9
- 239000013078 crystal Substances 0.000 description 7
- QTBSBXVTEAMEQO-UHFFFAOYSA-N Acetic acid Chemical compound CC(O)=O QTBSBXVTEAMEQO-UHFFFAOYSA-N 0.000 description 6
- 238000002441 X-ray diffraction Methods 0.000 description 6
- 238000004993 emission spectroscopy Methods 0.000 description 6
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 5
- 229910052802 copper Inorganic materials 0.000 description 5
- 239000000203 mixture Substances 0.000 description 5
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 4
- BBGVVPLPLBJJLS-UHFFFAOYSA-N copper ethanol dinitrate Chemical compound C(C)O.[N+](=O)([O-])[O-].[Cu+2].[N+](=O)([O-])[O-] BBGVVPLPLBJJLS-UHFFFAOYSA-N 0.000 description 4
- 230000001965 increasing effect Effects 0.000 description 4
- 230000000694 effects Effects 0.000 description 3
- 238000005516 engineering process Methods 0.000 description 3
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 description 2
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- 239000006004 Quartz sand Substances 0.000 description 2
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 2
- 235000011114 ammonium hydroxide Nutrition 0.000 description 2
- 229910052799 carbon Inorganic materials 0.000 description 2
- 238000010438 heat treatment Methods 0.000 description 2
- 238000005470 impregnation Methods 0.000 description 2
- 239000002994 raw material Substances 0.000 description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- AVXURJPOCDRRFD-UHFFFAOYSA-N Hydroxylamine Chemical class ON AVXURJPOCDRRFD-UHFFFAOYSA-N 0.000 description 1
- BPQQTUXANYXVAA-UHFFFAOYSA-N Orthosilicate Chemical compound [O-][Si]([O-])([O-])[O-] BPQQTUXANYXVAA-UHFFFAOYSA-N 0.000 description 1
- 229910019142 PO4 Inorganic materials 0.000 description 1
- 230000002378 acidificating effect Effects 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 230000009977 dual effect Effects 0.000 description 1
- 230000001939 inductive effect Effects 0.000 description 1
- 239000012452 mother liquor Substances 0.000 description 1
- 239000010413 mother solution Substances 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- NBIIXXVUZAFLBC-UHFFFAOYSA-K phosphate Chemical compound [O-]P([O-])([O-])=O NBIIXXVUZAFLBC-UHFFFAOYSA-K 0.000 description 1
- 239000010452 phosphate Substances 0.000 description 1
- 238000001637 plasma atomic emission spectroscopy Methods 0.000 description 1
- 239000011148 porous material Substances 0.000 description 1
- 230000002000 scavenging effect Effects 0.000 description 1
- 230000002194 synthesizing effect Effects 0.000 description 1
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/34—Chemical or biological purification of waste gases
- B01D53/92—Chemical or biological purification of waste gases of engine exhaust gases
- B01D53/94—Chemical or biological purification of waste gases of engine exhaust gases by catalytic processes
- B01D53/9404—Removing only nitrogen compounds
- B01D53/9409—Nitrogen oxides
- B01D53/9413—Processes characterised by a specific catalyst
- B01D53/9418—Processes characterised by a specific catalyst for removing nitrogen oxides by selective catalytic reduction [SCR] using a reducing agent in a lean exhaust gas
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J29/00—Catalysts comprising molecular sieves
- B01J29/82—Phosphates
- B01J29/84—Aluminophosphates containing other elements, e.g. metals, boron
- B01J29/85—Silicoaluminophosphates [SAPO compounds]
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2258/00—Sources of waste gases
- B01D2258/01—Engine exhaust gases
- B01D2258/012—Diesel engines and lean burn gasoline engines
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Health & Medical Sciences (AREA)
- Biomedical Technology (AREA)
- Environmental & Geological Engineering (AREA)
- Analytical Chemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Oil, Petroleum & Natural Gas (AREA)
- Combustion & Propulsion (AREA)
- Materials Engineering (AREA)
- Organic Chemistry (AREA)
- Catalysts (AREA)
- Exhaust Gas Treatment By Means Of Catalyst (AREA)
Abstract
The invention discloses a preparation method of a CurE/SAPO-34 molecular sieve, and simultaneously discloses that the CurE/SAPO-34 molecular sieve prepared by the preparation method is used as NH3-SCR catalytic reaction catalyst, for the use in nitrogen oxide purification processes in the after-treatment of diesel exhaust gases. The Cu/SAPO-34 molecular sieve is modified by rare earth elements, and the obtained CurE/SAPO-34 molecular sieve is used for NH3The catalyst has the advantages of SCR catalytic reaction, good low-temperature hydrothermal stability, wide active temperature window and suitability for treating NOx in the tail gas of a lean burn engine.
Description
Technical Field
The invention belongs to the technical field of catalysts, and particularly relates to a preparation method and application of a CurE/SAPO-34 molecular sieve.
Background
NH3The SCR technology is widely used for catalytic removal of NOx in diesel exhaust, and the core of the SCR technology is the development of catalysts. The Cu/CHA small pore molecular sieve catalyst has excellent NH3SCR catalytic Activity, higher N2Selectivity, carbon deposit resistance and the like are considered as the best choices for removing NOx of diesel vehicles.
The activity of the Cu/SAPO-34 catalyst can reach more than 90 percent in a temperature window of 180-500 ℃, and N2The selectivity is more than 99%. In addition, the Cu/SAPO-34 has excellent high-temperature hydrothermal stability, and can still keep a complete structure and higher SCR activity after being subjected to high-temperature hydrothermal treatment at 850 ℃ for 12 hours. However, the Cu/SAPO-34 catalyst has the problem of poor low-temperature hydrothermal stability, and in the water-containing air below 100 ℃, the Cu/SAPO-34 is easily attacked by water molecules to cause structural collapse, which also becomes a key short plate limiting the industrial application of the Cu/SAPO-34 catalyst.
Therefore, it is necessary to develop a catalyst with high hydrothermal stability at low temperature and good catalytic performance for removing NOx aiming at the defects of the Cu/SAPO-34 catalyst.
Disclosure of Invention
The first aspect of the invention provides a preparation method of a CurE/SAPO-34 molecular sieve, which comprises the following steps:
(1) mixing phosphoric acid and deionized water, adding pseudo-boehmite, adding a salt containing rare earth element RE after stirring and mixing, adding silica sol after stirring and mixing, then dropwise adding a template agent, and continuously stirring to obtain a gel product;
(2) putting the gel product obtained in the step (1) into a hydrothermal reaction kettle for crystallization, cooling after crystallization reaction is finished, separating a solid crystallization product from a supernatant, washing the solid crystallization product to be neutral by deionized water, drying, and roasting in air to obtain an RE/SAPO-34 molecular sieve;
(3) and (3) dipping the RE/SAPO-34 molecular sieve obtained in the step (2) by using a copper salt ethanol solution, drying, and roasting in the air to obtain the CURE/SAPO-34 molecular sieve.
Preferably, the molar ratio of the pseudo-boehmite, the phosphoric acid, the silica sol, the template agent, the rare earth element RE and the deionized water in the step (1) is (0.113-0.224): (0.102-0.312): (0.0612-0.0154): (0.2-0.4): 0.0012-0.0061): 6.43-9.44.
Preferably, in the step (1), the rare earth element RE is selected from lanthanum, cerium, praseodymium, neodymium or samarium, and the salt containing the rare earth element RE is selected from nitrate, chloride, phosphate, silicate or sulfate containing the rare earth element RE.
Preferably, the template in step (1) is selected from one or more of tetraethylammonium hydroxide, tetraethylammonium chloride, tetraethylammonium bromide, triethylamine, n-butylamine or morpholine.
Preferably, the crystallization temperature in the step (2) is 110-180 ℃, and the crystallization time is 0.5-5 days; the drying temperature is 80-120 ℃, and the drying time is 3-20 hours; the roasting temperature is 500-700 ℃, and the roasting time is 4-10 hours.
Preferably, the concentration of copper salt in the copper salt ethanol solution in the step (3) is 0.1-0.5 mol/L, and 1g of the RE/SAPO-34 molecular sieve is dissolved in 1.54mL of the copper salt ethanol solution.
Preferably, the drying temperature in the step (3) is 80-120 ℃, and the drying time is 3-20 hours; the roasting temperature is 550-900 ℃, and the roasting time is 3-8 hours.
The second aspect of the invention provides a method for preparing CuRE/SAPO-34 molecular sieve NH3SCR catalytic reaction catalyst for diesel exhaust aftertreatmentThe use of a nitroxide scavenging process.
In the present invention, the catalyst was evaluated by the following method:
0.1g of 60-80 mesh CURE/SAPO-34 molecular sieve catalyst and 0.9g of 60-80 mesh quartz sand are uniformly mixed, placed in a fixed bed reactor, and introduced with 500ppm NO and 500ppm NH under normal pressure3，5％O2，3％H2O, the balance being nitrogen N2The total flow rate is 1000mL/min, and the volume space velocity of the reaction is 72,000h-1。
The third aspect of the invention provides a method for improving the low-temperature hydrothermal stability of the Cu/SAPO-34 molecular sieve, wherein the low temperature is less than or equal to 100 ℃, and the Cu/SAPO-34 molecular sieve is modified by using the rare earth element RE by using the preparation method provided by the first aspect of the invention.
Compared with the prior art, the invention has the following beneficial effects:
1. according to the invention, the Cu/SAPO-34 molecular sieve catalyst is modified by the rare earth element RE, so that the low-temperature hydrothermal stability of the Cu/SAPO-34 molecular sieve catalyst is improved, the prepared rare earth element RE-containing Cu RE/SAPO-34 molecular sieve catalyst has good low-temperature hydrothermal stability, the BET specific surface area is hardly changed after the low-temperature hydrothermal treatment is carried out for 72 hours at the temperature of 70 ℃ and the relative humidity of 80%, and the crystal structure is hardly changed. The rare earth elements such as lanthanum, cerium, praseodymium, neodymium and samarium have larger atomic radius and changeable valence, and can replace Al or Si in the framework of the Cu/SAPO-34 molecular sieve catalyst or replace Brewster proton H, so that the low-temperature water resistance of the Cu/SAPO-34 molecular sieve catalyst is improved by changing the acid center strength of the Cu/SAPO-34 molecular sieve catalyst. The method solves the problems that the Cu/SAPO-34 molecular sieve catalyst is easily attacked by water molecules and the framework is hydrolyzed to cause structure collapse in the low-temperature hydrothermal treatment process of the Cu/SAPO-34 molecular sieve catalyst.
2. The prepared rare earth element RE-containing CuRE/SAPO-34 molecular sieve catalyst is subjected to low-temperature hydrothermal treatment and then subjected to NH treatment3The NOx conversion rate in the SCR catalytic reaction is almost not changed, namely the catalytic activity of the catalyst is not reduced, and when the reaction temperature of the Cu/SAPO-34 molecular sieve catalyst without the rare earth element RE is 180 ℃ before low-temperature hydrothermal treatment,the NOx conversion rate can reach more than 95 percent, the reaction temperature is continuously increased, the NOx conversion rate begins to gradually decrease at the reaction temperature of 450 ℃, the active temperature window is wider, however, the NOx conversion rate can reach more than 95 percent only when the reaction temperature is 220 ℃ after the Cu/SAPO-34 molecular sieve catalyst without the rare earth element RE is subjected to low-temperature hydrothermal treatment, the NOx conversion rate begins to gradually decrease at the time of continuously increasing the reaction temperature to 300 ℃, the active temperature window is narrow, and the Cu/SAPO-34 molecular sieve catalyst without the rare earth element RE is subjected to low-temperature hydrothermal treatment and then subjected to NH (NH) hydrothermal treatment3The catalytic activity in the SCR catalytic reaction is obviously reduced. Thus, the CURE/SAPO-34 molecular sieve catalyst of the invention is used for NH3The catalyst has good NOx removal catalytic performance and hydrothermal stability in SCR technology.
3. The CURE/SAPO-34 molecular sieve catalyst provided by the invention has good low-temperature hydrothermal stability and a wider active temperature window, and is suitable for treating NOx in the tail gas of a lean-burn engine.
4. According to the mechanism that the structure of the Cu/SAPO-34 molecular sieve catalyst is damaged under the low-temperature hydrothermal condition, the obtained modified Brewster acidic property in the Cu/SAPO-34 molecular sieve catalyst is the key for improving the low-temperature water resistance of the Cu/SAPO-34 molecular sieve catalyst. The rare earth elements such as lanthanum, cerium, praseodymium, neodymium and samarium are considered to have larger atomic radius and changeable valence, and can replace Al or Si in the framework of the Cu/SAPO-34 molecular sieve catalyst or replace Brewster proton H, so that the low-temperature water resistance of the Cu/SAPO-34 molecular sieve catalyst is improved by changing the acid center strength of the Cu/SAPO-34 molecular sieve catalyst.
Drawings
FIG. 1 is XRD patterns of a Cu/SAPO-34 molecular sieve catalyst before and after low-temperature hydrothermal treatment in a comparative example, wherein (a) is before the low-temperature hydrothermal treatment and (b) is after the low-temperature hydrothermal treatment;
FIG. 2 XRD patterns before and after low temperature hydrothermal treatment of CuCe/SAPO-34 molecular sieve sample 1 catalyst in example 1, wherein (a) is before low temperature hydrothermal treatment and (b) is after low temperature hydrothermal treatment;
FIG. 3 NOx conversion before and after low temperature hydrothermal treatment of the Cu/SAPO-34 molecular sieve catalyst of the comparative example and the CuCe/SAPO-34 molecular sieve sample 1 catalyst of example 1;
FIG. 4 XRD patterns of the CuLa/SAPO-34 molecular sieve catalyst of example 2 before and after low temperature hydrothermal treatment, wherein (a) is before low temperature hydrothermal treatment and (b) is after low temperature hydrothermal treatment;
FIG. 5 NOx conversion before and after low temperature hydrothermal treatment of the Cu/SAPO-34 molecular sieve catalyst of the comparative example and the CuLa/SAPO-34 molecular sieve catalyst of example 2;
FIG. 6 XRD patterns before and after low temperature hydrothermal treatment of CuPr/SAPO-34 molecular sieve catalyst in example 3, wherein (a) is before low temperature hydrothermal treatment and (b) is after low temperature hydrothermal treatment;
FIG. 7 NOx conversion before and after low temperature hydrothermal treatment of a Cu/SAPO-34 molecular sieve catalyst of the comparative example and a CuPr/SAPO-34 molecular sieve catalyst of example 3;
FIG. 8 XRD patterns before and after low temperature hydrothermal treatment of CuNd/SAPO-34 molecular sieve catalyst in example 4, wherein (a) is before low temperature hydrothermal treatment and (b) is after low temperature hydrothermal treatment;
FIG. 9 NOx conversion before and after low temperature hydrothermal treatment of the Cu/SAPO-34 molecular sieve catalyst of the comparative example and the CuNd/SAPO-34 molecular sieve catalyst of example 4;
FIG. 10 XRD patterns of the CuSm/SAPO-34 molecular sieve catalyst of example 5 before and after low temperature hydrothermal treatment, wherein (a) is before low temperature hydrothermal treatment and (b) is after low temperature hydrothermal treatment;
FIG. 11 NOx conversion before and after low temperature hydrothermal treatment of the Cu/SAPO-34 molecular sieve catalyst of the comparative example and the CuSm/SAPO-34 molecular sieve catalyst of example 5;
FIG. 12 NOx conversion before and after low temperature hydrothermal treatment of CuCe/SAPO-34 molecular sieve sample 1 catalyst in example 1, CuCe/SAPO-34 molecular sieve sample 2 catalyst in example 6, and CuCe/SAPO-34 molecular sieve sample 3 catalyst in example 7.
Detailed Description
In the comparative examples and examples of the present invention, the catalysts were evaluated as follows:
0.1g of 70-mesh CURE/SAPO-34 molecular sieve catalyst and 0.9g of 70-mesh quartz sand are uniformly mixed, placed in a fixed bed reactor, and introduced with 500ppm of NO and 500ppm of NH under normal pressure3，5％O2，3％H2O, the balance being N2The total flow rate is 1000mL/min, and the volume space velocity of the reaction is 72,000h-1。
Comparative example
This comparative example is the preparation of a Cu/SAPO-34 molecular sieve catalyst.
(1) Preparation of H-SAPO-34 molecular sieve
27.0g H2Mixing O with 23.6g phosphoric acid with 85 wt%, adding 13.8g pseudoboehmite, and adding 30g H2O stirring the raw materials uniformly to obtain a solution A, adding 8.29g of silica sol and 17.43g of morpholine into the solution A, and then adding 20g H2O, stirring vigorously for 1 h; then, the pH of the mixture was adjusted to 7 with acetic acid or ammonia water, and finally 0.01g of seed crystal was added thereto, followed by vigorous stirring for 1 hour.
And (3) putting the completely stirred gel into a hydrothermal kettle, crystallizing for 1 day at 150 ℃, cooling at room temperature after the crystallization reaction is finished, separating a solid crystal from a mother solution, washing to be neutral by using deionized water, drying for 10 hours at 100 ℃, and then roasting in air at the roasting temperature of 600 ℃, wherein the heating rate in the roasting process is 2 ℃/min, and the roasting time is 5 hours, so as to obtain the H-SAPO-34 molecular sieve.
(2) Preparation of Cu/SAPO-34 molecular sieve catalyst
6.1g of Cu (NO)3)2·3H2Dissolving O in 50mL of ethanol to prepare 0.5mol/L copper nitrate ethanol solution; and dripping 6.16mL of copper nitrate ethanol solution into 4g of Ce/SAPO-34 molecular sieve catalyst for isovolumetric impregnation, uniformly stirring at room temperature until the sample is basically dried, drying at 100 ℃ for 10 hours, and then roasting in the air at the roasting temperature of 700 ℃ for 5 hours to obtain the Cu/SAPO-34 molecular sieve catalyst.
Wherein the molar ratio of the pseudo-boehmite, the phosphoric acid, the silica sol, the morpholine and the first mass of the deionized water in the step (1) is 0.113:0.102:0.0612:0.2: 6.43.
And carrying out low-temperature hydrothermal treatment on the prepared Cu/SAPO-34 molecular sieve catalyst for 72 hours at 70 ℃ under the condition of relative humidity of 80%.
XRD before and after low-temperature hydrothermal treatment of the Cu/SAPO-34 molecular sieve catalyst is shown in figure 1, BET specific surface area is shown in Table 1,and NH3NOx conversion in SCR catalytic reaction as shown in figure 3.
Example 1
This example is the preparation of CuCe/SAPO-34 molecular sieve sample 1 catalyst.
(1) One-step method for synthesizing Ce/SAPO-34 molecular sieve
27.0g H2O is uniformly mixed with 23.6g of phosphoric acid (85 wt%) with the mass fraction of 85 wt%, 13.8g of pseudo-boehmite is added, and then 30g H g of pseudo-boehmite is added2O, uniformly stirring the raw materials to obtain a solution A; nitrate containing 0.0061mol/L Ce was dissolved in 10g H2Obtaining a solution B after O, slowly adding the solution B into the solution A, and stirring for 1 h; then 8.29g of silica sol and 17.43g of morpholine were added, followed by 20g H2O, stirring vigorously for 1 h; then, the pH of the mixture was adjusted to 7 with acetic acid or ammonia water, and finally 0.01g of seed crystal was added thereto, followed by vigorous stirring for 1 hour.
Putting the completely stirred gel into a hydrothermal kettle, crystallizing for 1 day at 150 ℃, cooling at room temperature after the crystallization reaction is finished, separating solid crystals from mother liquor, washing to be neutral by deionized water, drying for 10 hours at 100 ℃, then roasting in air at 600 ℃, wherein the heating rate in the roasting process is 2 ℃/min, and the roasting time is 5 hours, thus obtaining the synthesized Ce/SAPO-34 molecular sieve
(2) Preparation of CuCe/SAPO-34 molecular sieve sample 1 catalyst
6.1g of Cu (NO)3)2·3H2Dissolving O in 50mL of ethanol to prepare 0.5m/L copper nitrate ethanol solution; and dripping 6.16mL of copper nitrate ethanol solution into 4g of Ce/SAPO-34 molecular sieve for isovolumetric impregnation, uniformly stirring at room temperature until the sample is basically dried, drying at 100 ℃ for 10 hours, and then roasting in air at 700 ℃ for 5 hours to obtain the CuCe/SAPO-34 molecular sieve sample 1 catalyst.
Wherein the molar ratio of the pseudo-boehmite, the phosphoric acid, the silica sol, the morpholine and the first mass of the deionized water in the step (1) is 0.113:0.102:0.0612:0.2: 6.43.
Inductively coupled plasma emission spectroscopy (ICP) CuCe/SAPO-34 molecular sieve sample 1 catalyst contained about 2.1 wt% copper.
And carrying out low-temperature hydrothermal treatment on the prepared Cu/SAPO-34 molecular sieve for 72 hours at 70 ℃ and at the relative humidity of 80%.
XRD before and after low temperature hydrothermal treatment of CuCe/SAPO-34 molecular sieve sample 1 catalyst is shown in figure 2, BET specific surface area is shown in Table 1, and NH3NOx conversion in SCR catalytic reaction as shown in figure 3.
Example 2
This example is the preparation of a CuLa/SAPO-34 molecular sieve catalyst.
The preparation method of the CuLa/SAPO-34 molecular sieve catalyst is similar to that of the CuCe/SAPO-34 molecular sieve sample 1 catalyst in the example 1, and only the nitrate containing 0.0061mol/L Ce in the step (1) is changed into the nitrate containing 0.0061mol/L La, and other molar mixture ratios are kept the same, so that the CuLa/SAPO-34 molecular sieve catalyst is prepared.
The low-temperature hydrothermal treatment conditions of the CuLa/SAPO-34 molecular sieve catalyst are also the same as the low-temperature hydrothermal treatment conditions in example 1.
Inductive coupled plasma emission spectroscopy (ICP) determined that the CuLa/SAPO-34 molecular sieve catalyst contained about 2.0 wt% copper.
XRD before and after low-temperature hydrothermal treatment of CuLa/SAPO-34 molecular sieve catalyst is shown in figure 4, BET specific surface area is shown in Table 1, and NH3NOx conversion in SCR catalytic reaction as shown in figure 5.
Example 3
This example is the preparation of a CuPr/SAPO-34 molecular sieve catalyst.
The preparation method of the CuPr/SAPO-34 molecular sieve catalyst is similar to that of the CuCe/SAPO-34 molecular sieve sample 1 catalyst in the example 1, and only the nitrate containing 0.0061mol/L Ce in the step (1) is changed into the nitrate containing 0.0061mol/L Pr, and other molar mixture ratios are kept the same, so that the CuPr/SAPO-34 molecular sieve catalyst is prepared.
The low-temperature hydrothermal treatment conditions of the CuPr/SAPO-34 molecular sieve catalyst are also the same as those of the low-temperature hydrothermal treatment conditions in example 1.
Inductively coupled plasma emission spectroscopy (ICP) was used to determine that the CuPr/SAPO-34 molecular sieve catalyst contained about 2.4 wt% copper.
CuPr/SAPO-34 molecular sieve catalysisXRD before and after low temperature hydrothermal treatment of the agent is shown in figure 6, BET specific surface area is shown in Table 1, and NH3NOx conversion in SCR catalytic reaction as shown in figure 7.
Example 4
This example is the preparation of a CuNd/SAPO-34 molecular sieve catalyst.
The preparation method of the CuNd/SAPO-34 molecular sieve catalyst is similar to that of the CuCe/SAPO-34 molecular sieve sample 1 catalyst in the example 1, only the nitrate containing 0.0061mol/L Ce in the step (1) is changed into the nitrate containing 0.0061mol/L Nd, and other molar mixture ratios are kept the same, so that the CuNd/SAPO-34 molecular sieve catalyst is prepared.
The low-temperature hydrothermal treatment conditions of the CuNd/SAPO-34 molecular sieve catalyst are also the same as those of the low-temperature hydrothermal treatment conditions in example 1.
Inductively coupled plasma emission spectroscopy (ICP) was used to determine that the CuNd/SAPO-34 molecular sieve catalyst contained about 2.3 wt% copper.
XRD before and after low-temperature hydrothermal treatment of CuNd/SAPO-34 molecular sieve catalyst is shown in figure 8, BET specific surface area is shown in Table 1, and NH3NOx conversion in SCR catalytic reaction as shown in figure 9.
Example 5
This example is the preparation of a CuSm/SAPO-34 molecular sieve catalyst.
The preparation method of the CuSm/SAPO-34 molecular sieve catalyst is similar to that of the CuCe/SAPO-34 molecular sieve sample 1 catalyst in example 1, and only the nitrate containing 0.0061mol/L Ce in the step (1) is changed into the nitrate containing 0.0061mol/L Sm, and other molar charge ratios are kept the same, so that the CuSm/SAPO-34 molecular sieve catalyst is prepared.
The low-temperature hydrothermal treatment conditions of the CuSm/SAPO-34 molecular sieve catalyst are also the same as the low-temperature hydrothermal treatment conditions in example 1.
Inductively coupled plasma emission spectroscopy (ICP) determined that the CuSm/SAPO-34 molecular sieve catalyst contained about 2.6 wt% copper.
XRD before and after low-temperature hydrothermal treatment of CuSm/SAPO-34 molecular sieve catalyst is shown in figure 10, BET specific surface area is shown in Table 1, and NH3NOx conversion in SCR catalytic reaction as shown in figure 11.
Example 6
This example is the preparation of CuCe/SAPO-34 molecular sieve sample 2 catalyst.
The preparation method of the CuCe/SAPO-34 molecular sieve sample 2 catalyst is similar to that of the CuCe/SAPO-34 molecular sieve sample 1 catalyst in the example 1, only the tetraethylammonium hydroxide template is added on the basis of the morpholine template in the step (1), the molar ratio of the pseudo-boehmite, the phosphoric acid, the silica sol, the morpholine, the tetraethylammonium hydroxide and the deionized water with the first mass is controlled to be 0.113:0.102:0.0612:0.2:0.04:6.43, and the molar ratio of other components is kept the same, so that the CuCe/SAPO-34 molecular sieve sample 2 catalyst is prepared.
The low temperature hydrothermal treatment conditions of the CuCe/SAPO-34 molecular sieve sample 2 catalyst are also the same as the low temperature hydrothermal treatment conditions in example 1.
Inductively coupled plasma emission spectroscopy (ICP) was used to determine the Cu content of the CuCe/SAPO-34 molecular sieve sample 2 catalyst was 1.96 wt%.
CuCe/SAPO-34 molecular sieve sample 2 catalyst BET specific surface area is shown in Table 1, and NH3NOx conversion in SCR catalytic reaction as shown in figure 12.
Example 7
This example is the preparation of CuCe/SAPO-34 molecular sieve sample 3 catalyst.
The preparation method of the CuCe/SAPO-34 molecular sieve sample 3 catalyst is similar to that of the CuCe/SAPO-34 molecular sieve sample 1 catalyst in example 1, only the tetraethylammonium hydroxide template is added on the basis of the morpholine template in the step (1), the molar ratio of the pseudo-boehmite, the phosphoric acid, the silica sol, the morpholine, the tetraethylammonium hydroxide and the deionized water of the first mass is controlled to be 00.113:0.102:0.0612:0.2:0.1:6.43, and the molar ratio of other components is kept the same, so that the CuCe/SAPO-34 molecular sieve sample 3 catalyst is prepared. The low temperature hydrothermal treatment conditions of the CuCe/SAPO-34 molecular sieve sample 3 catalyst are also the same as the low temperature hydrothermal treatment conditions in example 1.
Inductively coupled plasma emission spectroscopy (ICP) was used to determine the Cu content of the CuCe/SAPO-34 molecular sieve sample 3 catalyst was 2.1 wt%.
The BET specific surface area of the CuCe/SAPO-34 molecular sieve sample 3 catalyst is shown in Table 1,and NH3NOx conversion in SCR catalytic reaction as shown in figure 12.
TABLE 1 BET specific surface area before and after low-temperature hydrothermal treatment of different molecular sieve catalysts
As can be seen from Table 1, the Cu/SAPO-34 molecular sieve based catalyst without rare earth element RE has poor low-temperature hydrothermal stability, and after being hydrothermally treated at 70 ℃ and 80% relative humidity for 72 hours, the BET specific surface area is 720m before treatment2The/g is reduced to 35m after treatment2The BET specific surface area is greatly reduced because the Cu/SAPO-34 molecular sieve catalyst without rare earth element RE has poor low-temperature hydrothermal stability, and the Cu/SAPO-34 molecular sieve catalyst is easily attacked by water molecules and the framework is hydrolyzed to cause structure collapse in the low-temperature hydrothermal treatment process. The rare earth element RE-containing CuRE/SAPO-34 molecular sieve catalyst is good in low-temperature hydrothermal stability, and the BET specific surface area is almost unchanged after low-temperature hydrothermal treatment for 72 hours at the temperature of 70 ℃ and the relative humidity of 80%, probably because the rare earth elements lanthanum, cerium, praseodymium, neodymium and samarium are large in atomic radius and changeable in valence, Al or Si in the Cu/SAPO-34 molecular sieve catalyst framework can be replaced, or Brewster proton H can be replaced, so that the low-temperature water resistance of the Cu/SAPO-34 molecular sieve catalyst can be improved by changing the acid center strength of the Cu/SAPO-34 molecular sieve catalyst.
Meanwhile, the XRD charts of fig. 1, fig. 2, fig. 4, fig. 6, fig. 8 and fig. 10 can also conclude that, as can be seen from fig. 1, the Cu/SAPO-34 molecular sieve catalyst containing no rare earth element RE undergoes structural collapse and crystal form is significantly changed after being subjected to low-temperature hydrothermal treatment at 70 ℃ and a relative humidity of 80% for 72 hours, whereas, as can be seen from fig. 2, fig. 4, fig. 6, fig. 8 and fig. 10, the Cu/SAPO-34 molecular sieve catalyst containing rare earth element RE undergoes little change in crystal form structure after being subjected to low-temperature hydrothermal treatment at 70 ℃ and a relative humidity of 80% for 72 hours.
Besides, Cu/SAPO-34 molecular sieve catalyst without rare earth element RE and rare earth element before and after low-temperature hydrothermal treatmentRE's CURE/SAPO-34 molecular sieve catalysts as catalysts for NH respectively3The SCR catalytic reaction, the results are shown in fig. 3, fig. 5, fig. 7, fig. 9 and fig. 11, and it can be seen from fig. 3, fig. 5, fig. 7, fig. 9 and fig. 11 that the NOx conversion rate of the rare earth element RE-containing CuRE/SAPO-34 molecular sieve catalyst is almost unchanged before and after the low-temperature hydrothermal treatment, while the NOx conversion rate of the rare earth element RE-containing Cu/SAPO-34 molecular sieve catalyst can reach more than 95% at the reaction temperature of 180 ℃ before the low-temperature hydrothermal treatment, the reaction temperature is continuously increased, the NOx conversion rate starts to gradually decrease at the reaction temperature of 450 ℃, the active temperature window is wider, however, the NOx conversion rate of the rare earth element RE-containing Cu/SAPO-34 molecular sieve catalyst can reach more than 95% at the reaction temperature of 220 ℃ after the low-temperature hydrothermal treatment, and the NOx conversion rate starts to gradually decrease at the reaction temperature of 300 ℃ when the reaction temperature is continuously increased, the Cu/SAPO-34 molecular sieve catalyst which has a narrow active temperature window and does not contain rare earth element RE is subjected to low-temperature hydrothermal treatment and then is subjected to NH treatment3The catalytic activity in the SCR catalytic reaction is obviously reduced.
The effect of the template on the CuCe/SAPO-34 molecular sieve catalyst is examined in the invention examples 1, 6 and 7, the result is shown in FIG. 12, and it can be seen from FIG. 12 that the prepared CuCe/SAPO-34 molecular sieve catalyst is NH treated by using either single template morpholine or dual template morpholine and tetraethylammonium hydroxide in the preparation process of the Ce/SAPO-34 molecular sieve catalyst3The catalytic activity in the SCR catalytic reaction is not obviously different, and after low-temperature hydrothermal treatment, NH is carried out3None of the catalytic activities changed significantly in the SCR catalytic reaction.
Claims (5)
1. A method for improving the low-temperature hydrothermal stability of a Cu/SAPO-34 molecular sieve is characterized in that the Cu/SAPO-34 molecular sieve is modified by rare earth element RE by using the following preparation method, wherein the low-temperature hydrothermal method refers to the conditions that the temperature is 70 ℃ and the relative humidity is 80%;
a preparation method of a CurE/SAPO-34 molecular sieve comprises the following steps:
(1) mixing phosphoric acid and deionized water, adding pseudo-boehmite, adding a salt containing rare earth element RE after stirring and mixing, adding silica sol after stirring and mixing, then dropwise adding a template agent, and continuously stirring to obtain a gel product;
(2) putting the gel product obtained in the step (1) into a hydrothermal reaction kettle for crystallization, cooling after crystallization reaction is finished, separating a solid crystallization product from a supernatant, washing the solid crystallization product to be neutral by deionized water, drying, and roasting in air to obtain an RE/SAPO-34 molecular sieve;
(3) dipping the RE/SAPO-34 molecular sieve obtained in the step (2) by using a copper salt ethanol solution, drying and then roasting in the air to obtain a CurE/SAPO-34 molecular sieve;
in the step (1), the molar ratio of the pseudo-boehmite, the phosphoric acid, the silica sol, the template agent, the rare earth element RE and the deionized water is (0.113-0.224): (0.102-0.312): (0.0612-0.0154): (0.2-0.4): 0.0012-0.0061): 6.43-9.44);
in the step (1), the rare earth element RE is selected from lanthanum, cerium, praseodymium, neodymium or samarium, and the salt containing the rare earth element RE is selected from nitrate, chloride or sulfate containing the rare earth element RE;
in the step (1), the template agent is selected from one or more of tetraethylammonium hydroxide, tetraethylammonium chloride, tetraethylammonium bromide, triethylamine, n-butylamine or morpholine.
2. The method according to claim 1, wherein the crystallization temperature in the step (2) is 110 to 180 ℃ and the crystallization time is 0.5 to 5 days; the drying temperature is 80-120 ℃, and the drying time is 3-20 hours; the roasting temperature is 500-700 ℃, and the roasting time is 4-10 hours.
3. The method according to claim 1, wherein the concentration of the copper salt in the copper salt ethanol solution in step (3) is 0.1-0.5 mol/L, and 1g of the RE/SAPO-34 molecular sieve is dissolved in 1.54mL of the copper salt ethanol solution.
4. The method according to claim 1, wherein the drying temperature in the step (3) is 80 to 120 ℃ and the drying time is 3 to 20 hours; the roasting temperature is 550-900 ℃, and the roasting time is 3-8 hours.
5. A method of preparing a CuRE/SAPO-34 molecular sieve as NH, as claimed in any one of claims 1 to 43-use of an SCR catalytic reaction catalyst for nitrogen oxide purification processes in diesel exhaust after-treatment.
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