CN113713851B - Preparation method of In/H-beta catalyst for improving sulfur resistance and water resistance - Google Patents

Preparation method of In/H-beta catalyst for improving sulfur resistance and water resistance Download PDF

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CN113713851B
CN113713851B CN202111144477.3A CN202111144477A CN113713851B CN 113713851 B CN113713851 B CN 113713851B CN 202111144477 A CN202111144477 A CN 202111144477A CN 113713851 B CN113713851 B CN 113713851B
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beta
molecular sieve
catalyst
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CN113713851A (en
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朱荣淑
洪梅
赵玖虎
董磊
朱满玉
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Peking University Shenzhen Graduate School
Shenzhen Graduate School Harbin Institute of Technology
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Shenzhen Graduate School Harbin Institute of Technology
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    • 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
    • B01J29/04—Catalysts comprising molecular sieves having base-exchange properties, e.g. crystalline zeolites
    • B01J29/06—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof
    • B01J29/70—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of types characterised by their specific structure not provided for in groups B01J29/08 - B01J29/65
    • B01J29/7049—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of types characterised by their specific structure not provided for in groups B01J29/08 - B01J29/65 containing rare earth elements, titanium, zirconium, hafnium, zinc, cadmium, mercury, gallium, indium, thallium, tin or lead
    • B01J29/7057—Zeolite Beta
    • 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
    • B01D53/74—General processes for purification of waste gases; Apparatus or devices specially adapted therefor
    • B01D53/86—Catalytic processes
    • B01D53/8621—Removing nitrogen compounds
    • B01D53/8625—Nitrogen oxides
    • B01D53/8628—Processes characterised by a specific catalyst
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2251/00—Reactants
    • B01D2251/20—Reductants
    • B01D2251/208—Hydrocarbons
    • 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
    • B01J2229/00—Aspects of molecular sieve catalysts not covered by B01J29/00
    • B01J2229/10—After treatment, characterised by the effect to be obtained
    • B01J2229/18—After treatment, characterised by the effect to be obtained to introduce other elements into or onto the molecular sieve itself
    • B01J2229/186—After treatment, characterised by the effect to be obtained to introduce other elements into or onto the molecular sieve itself not in framework positions

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Abstract

The invention discloses a preparation method of an In-H/beta catalyst for improving sulfur resistance and water resistance. The preparation method comprises the following steps: mixing raw materials comprising amino acid, a silicon source, an aluminum source, an M source, an organic amine template agent and water for reaction to obtain reaction gel; crystallizing the reaction gel to obtain an M-beta molecular sieve; mixing with ammonium salt solution, and ion exchanging to obtain H-beta molecular sieve; step 4: mixing the H-beta molecular sieve with indium salt solution, and obtaining the In/H-beta molecular sieve after ion exchange. The amino acid can promote crystallization In the preparation process as a guiding agent, and can lead the finally prepared In/H-beta catalyst to obtain strongerAcid active center, thus can be in SO 2 And H 2 Under O interference, the best CH is shown 4 SCR catalytic activity and cycle performance.

Description

Preparation method of In/H-beta catalyst for improving sulfur resistance and water resistance
Technical Field
The application relates to the technical field of selective catalytic reduction denitration, in particular to a preparation method of an In-H/beta catalyst for improving sulfur resistance and water resistance.
Background
Nitrogen Oxides (NO) emitted by the combustion of fossil fuels x ) Not only can damage the human respiratory system, but photochemical smog, acid rain, and other serious environmental problems can also be caused. In this regard, researchers have proposed a range of solutions, and Selective Catalytic Reduction (SCR) denitration is currently considered to be the removal of NO x Conversion to N 2 Thereby solving NO x Optimum method of emission, wherein CH 4 Is the main component of natural gas, has rich reserve, is fully civilian and low in price, and is NO x The most promising of the removal techniques.
Development of highly efficient catalysts for CH 4 Commercialization of SCR technology is of great importance. Zeolite-based catalysts are becoming more and more interesting due to their high internal surface area, uniform micropore system, considerable ion exchange capacity and high thermal stability. Beta molecular sieve has three-dimensional 12-membered ring channel with pore diameter of 0.55×0.55nm and 0.76×0.64nm, which is one of the most important zeolite frameworks in SCR application, and can be used as effective catalyst carrier. Metals or metal oxides are often incorporated into the zeolite framework to further enhance its catalytic performance. Pan et al found that In/H-beta catalyst prepared by indium salt impregnation method was used In CH 4 Higher catalytic performance in SCR systems. The preparation conditions of the group of problems are further optimized, and the In/H-beta catalyst with higher activity can be prepared.
However, in industrial applications, in addition to the catalytic properties of the catalyst itself, SO needs to be considered 2 And high concentrations of moisture, which interfere with the SCR process. During the experiment it was found that the current In/H-beta catalysts have to be improved In respect of sulfur dioxide and water vapour resistance. In the absence of SO 2 And H 2 In the case of O, NO x The removal efficiency can reach more than 90 percent, but 100ppm SO is added into the raw material steam 2 And 5vol.% H 2 After O, NO x The removal efficiency is drastically reduced(only about 10%). Therefore, there is a need to improve In/H-beta catalysts In SO by improving the preparation process 2 And H 2 Catalytic performance in the presence of O.
Disclosure of Invention
The present application aims to solve at least one of the technical problems existing in the prior art. For this purpose, the present application proposes a method for producing a compound in SO 2 And H 2 Still has good CH in the presence of O 4 A method for preparing an In/H-beta catalyst with SCR catalytic performance.
In a first aspect of the present application, there is provided a process for preparing an In/H- β catalyst, the process comprising the steps of:
step 1: mixing raw materials comprising amino acid, a silicon source, an aluminum source, an M source, an organic amine template agent and water for reaction to obtain reaction gel;
step 2: crystallizing the reaction gel, cooling, washing, drying and roasting to obtain an M-beta molecular sieve;
step 3: mixing the M-beta molecular sieve with an ammonium salt solution for reaction, and washing, drying and roasting after ion exchange to obtain an H-beta molecular sieve;
step 4: mixing H-beta molecular sieve with indium salt solution for reaction, washing, drying and roasting after ion exchange is completed to obtain an In/H-beta molecular sieve;
wherein M is at least one of alkali metal and alkaline earth metal.
The preparation method according to the embodiment of the application has at least the following beneficial effects:
the amino acid can promote crystallization In the preparation process as a guiding agent, and can lead the finally prepared In/H-beta catalyst to obtain strongerAcid active center, thus can be in SO 2 And H 2 Under O interference, the best CH is shown 4 SCR catalytic activity and cycle performance.
In some embodiments of the present application, the silicon source is in the range of 0.1 to 0.5 amino acid/silica molar ratio, calculated as silica. Further, the molar ratio of proline to silica is preferably 0.15 to 0.45, more preferably 0.2 to 0.4, and still more preferably 0.3.
In some embodiments of the present application, the aluminum source, the M source, and the organic amine templating agent are calculated as oxides, the molar ratio of silica to alumina is from 5 to 200, the molar ratio of M oxide to silica is from 0.01 to 0.4, and the molar ratio of quaternary ammonium ion to silica is from 0.1 to 0.8.
In some embodiments of the present application, the water/silica molar ratio is from 5 to 50.
In some embodiments of the present application, the amino acid is at least one selected from the group consisting of proline, alanine, glutamic acid, histidine, serine, arginine.
In some embodiments of the present application, the amino acid is proline.
Amino acids as guides promote crystallization during the preparation process, and at the same time, a certain amount of mesopores are generated in the beta molecular sieve, and the existence of the mesopores promotes the diffusion of reactants and products so as to improve the catalytic performance. However, the inventors have found during further experiments that the tolerance of In/H-beta catalysts to sulphur dioxide and water vapour is not limited only by the mesoporous nature but also by other physicochemical properties. The unique cyclic side chain of the proline enables the final prepared In/H-beta catalyst to obtain stronger than other amino acidsAcid active center, thus can be in SO 2 And H 2 Under O interference, the best CH is shown 4 SCR catalytic activity and cycle performance.
In some embodiments of the present application, the silicon source is selected from at least one of white carbon black, water glass, ethyl orthosilicate, silica sol, silica gel, and solid silica gel.
In some embodiments of the present application, the aluminum source is selected from at least one of aluminum salts, aluminates, meta-aluminates, aluminum hydroxide, pseudo-boehmite, aluminum sec-butoxide, aluminum isopropoxide.
In some embodiments of the present application, M is selected from at least one of lithium, sodium, potassium, cesium, strontium, calcium, barium.
In some embodiments of the present application, the M source is selected from at least one of a base, a salt of M, including but not limited to sodium hydroxide, potassium hydroxide, sodium chloride, potassium chloride, and the like.
In some embodiments of the present application, the organic amine templating agent is selected from at least one of diethylamine, triethylamine, morpholine, tetraethylammonium hydroxide, tetraethylammonium chloride, tetraethylammonium bromide, tetraethylammonium iodide, and the like.
In some embodiments of the present application, the concentration of indium ions in the indium salt solution is 0.01 to 0.1mol/L.
In some embodiments of the present application, the crystallization temperature of the reaction gel in step 2 is 100 to 220 ℃ and the crystallization time is 5 to 200 hours.
In some embodiments of the present application, the reaction temperature of the ion exchange reaction in steps 3-4 is 70-100 ℃ and the reaction time is 20 min-12 h.
In some embodiments of the present application, the ion exchange reaction, washing, drying are repeated 1 to 3 times and then firing is performed.
In some embodiments of the present application, the firing temperature in steps 2-4 is 400-600 ℃ and the firing time is 1-6 hours.
In some embodiments of the present application, the drying temperature in steps 2-4 is 60-150 ℃ and the drying time is 1-24 hours.
In a second aspect of the present application, there is provided an In/H- β catalyst prepared by the aforementioned preparation method.
In a third aspect of the present application, there is provided an In/H-beta catalyst comprisingThe concentration of acid sites is 50. Mu. Mol/g or more. Preferably, a +>The concentration of acid sites is more than 60 mu mol/g and more than 70 mu mol/g,80 mu mol/g or more, 90 mu mol/g or more, 100 mu mol/g or more, 110 mu mol/g or more, 120 mu mol/g or more. />The concentration of acid sites was calculated from the Integrated Molar Extinction Coefficient (IMEC).
In some embodiments of the present application,the ratio of the concentration of the acid sites to the concentration of the Lewis acid sites is more than 0.55. Preferably, a +>The ratio of acid/Lewis acid is 0.6 or more, 0.65 or more, 0.7 or more, or 0.72 or more. The concentration of Lewis acid sites is likewise calculated from the Integrated Molar Extinction Coefficient (IMEC).
In some embodiments of the present application, the concentration of Lewis acid sites is 140. Mu. Mol/g or more. Preferably, the concentration of Lewis acid sites is 145. Mu. Mol/g or more, 150. Mu. Mol/g or more, 155. Mu. Mol/g or more, 160. Mu. Mol/g or more, 165. Mu. Mol/g or more.
In some embodiments of the present application, the In/H-beta catalyst has a methane selectivity of 80% or more (detection conditions: feed gas contains 400ppm NO, 400ppm CH 4 、10vol.％O 2 、100ppm SO 2 、5vol.％H 2 O, the rest Ar is taken as balance gas, the flow rate is 100mL/min, and the airspeed is 23600h -1 The temperature programming rate is 4 ℃/min (100-650 ℃), and the catalyst dosage is 100 mg. Further, the methane selectivity is more than 85%, more than 90%, more than 95%, more than 98% and more than 99%.
In some embodiments of the present application, the In/H-beta catalyst contains 400ppm NO, 400ppm CH In the feed gas 4 、10vol.％O 2 、100ppm SO 2 、5vol.％H 2 O, the rest Ar is taken as balance gas, the flow rate is 100mL/min, and the airspeed is 23600h -1 The temperature programming rate is 4 ℃/min (100-650 ℃), and the catalyst dosage is 30% or more, 35% or more and 38% under the detection condition of 100mg of catalyst dosageNitrogen oxide removal rate of 40% or more. And after three cycles, nitrogen oxide removal rates of 30% or more, 35% or more, 36% or more, and 37% or more at 650 ℃ remain.
In some embodiments of the present application, an In/H-beta catalyst includes an H-beta molecular sieve support and indium supported on the H-beta molecular sieve support. More specifically, indium is uniformly distributed on the surface and inside of the H-beta molecular sieve carrier.
In some embodiments of the present application, the indium content of the In/H-beta catalyst is 2 to 8wt% of the total mass of the In/H-beta catalyst. Preferably, the indium content is 3wt% or more, 3.5wt% or more, 4wt% or more, 4.5wt% or more, 5wt% or more. Preferably, the indium content is 7.5wt% or less, 7.4wt% or less, 7.3wt% or less, 7.2wt% or less, 7.1wt% or less.
In some embodiments of the present application, the Si/Al molar ratio In the In/H-beta catalyst is 25 or more.
In some embodiments of the present application, the In/Al molar ratio In the In/H-beta catalyst is 0.7 or more. Preferably 0.71 or more, 0.72 or more, 0.73 or more, 0.74 or more, 0.75 or more, 0.76 or more, 0.77 or more, 0.78 or more, 0.79 or more, and 0.8 or more.
In a fourth aspect of the present application, there is provided a denitration method for treating exhaust gas by a selective catalytic reduction method to treat the exhaust gas with CH 4 As the reducing agent, the In/H-beta catalyst is selected as the catalyst.
In a fifth aspect of the present application, there is provided a purification treatment apparatus comprising an SCR reactor In which the In/H- β catalyst described above is installed.
Additional aspects and advantages of the application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the application.
Drawings
FIG. 1 is the results of the comparative test of denitration activity of the present application. Wherein, (a) is the condition that the nitrogen oxide removal rate of the molecular sieve catalyst prepared by mediation of different amino acids changes along with the temperature, (b) is the condition that the methane conversion rate of the molecular sieve catalyst prepared by mediation of different amino acids changes along with the temperature, (c) is the condition that the methane selectivity of the molecular sieve catalyst prepared by mediation of different amino acids changes along with the temperature, and (d) is the condition that the nitrogen oxide removal rate of the In/H-beta-P molecular sieve catalyst changes In a plurality of TPSR cycles.
FIG. 2 is the result of the X-ray diffraction (XRD) patterns of the In/H-beta-P, in/H-beta-H, in/H-beta-R, in/H-beta-S and In/H-beta-B molecular sieve catalysts of the present application.
FIG. 3 is an Electron Paramagnetic Resonance (EPR) spectrum of the In/H-beta-P and In/H-beta-B molecular sieve catalysts of the present application.
FIG. 4 is an electron microscope of the In/H-beta-P sample of the present application and imaging results In combination with energy dispersive X-ray (EDX) spectroscopy. Wherein a is the result of a scanning electron microscope, and the scale in the figure is 1 μm; b-f are the results of the electron microscope combined with EDX spectrum analysis, the scale in the figure is 100nm, and c-f respectively reflect the element distribution of Al, si, O, in.
Fig. 5 is the imaging results of Transmission Electron Microscopy (TEM) and High Resolution Transmission Electron Microscopy (HRTEM) of the In/H- β -P samples of the present application. Wherein, the scale in a is 100nm, the scale in b is 50nm, and the lower left corner in b is 10nm lattice stripe.
FIG. 6 is the results of magic angle spinning solid-state nuclear magnetic (MAS NMR) detection of In/H-beta-P samples of the present application. Wherein a is 29 As a result of Si, b is 27 Results of Al.
FIG. 7 is XPS measurement spectra of In/H-beta-P, in/H-beta-H, in/H-beta-R and In/H-beta-S molecular sieve catalysts of the present application. Wherein a is In 3d 5/2 The spectral result, b is the O1s spectral result.
FIG. 8 is a schematic diagram of the temperature programmed reduction (H) of In/H-beta-P, in/H-beta-H, in/H-beta-R and In/H-beta-S molecular sieve catalysts of the present application In hydrogen 2 -TPR) In.
FIG. 9 is NH of In/H-beta-P, in/H-beta-H, in/H-beta-R and In/H-beta-S molecular sieve catalysts of the present application 3 -TPD curve.
FIG. 10 is an infrared spectrum (Py-IR) of adsorbed pyridine of the In/H-beta-P, in/H-beta-H, in/H-beta-R and In/H-beta-S molecular sieve catalysts of the present application.
Detailed Description
The conception and technical effects produced by the present application will be clearly and completely described below in connection with the embodiments to fully understand the objects, features and effects of the present application. It is apparent that the described embodiments are only some embodiments of the present application, but not all embodiments, and that other embodiments obtained by those skilled in the art without inventive effort based on the embodiments of the present application are within the scope of the present application.
The following detailed description of embodiments of the present application is exemplary and is provided merely for purposes of explanation and not to be construed as limiting the application.
In the description of the present application, the meaning of a number is one or more, the meaning of a number is two or more, and greater than, less than, exceeding, etc. are understood to exclude the present number, and the meaning of a number above, below, within, etc. are understood to include the present number. The description of the first and second is for the purpose of distinguishing between technical features only and should not be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated or implicitly indicating the precedence of the technical features indicated.
In the description of the present application, a description with reference to the terms "one embodiment," "some embodiments," "illustrative embodiments," "examples," "specific examples," or "some examples," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present application. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiments or examples. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.
Example 1
The present example provides an In/H-beta catalyst, the preparation method of which is as follows:
step 1: 0.16g NaAlO 2 And 0.05g NaOH dissolved in 12.5g tetraethylammonium hydroxide (TEAOH, 25%) and 2.6mLAnd adding the proline (P) into ionized water under the ultrasonic condition to stir uniformly to obtain a mixture. 2g of fumed silica was dissolved in the mixture and shaken well to obtain a reaction gel. Subsequently, the resulting reaction gel was aged in a magnetic stirrer at room temperature for 4 hours such that the composition in the reaction gel was 0.3 proline in a molar ratio: 1.0SiO 2 ：0.023Al 2 O 3 ：0.048Na 2 O：0.636TEAOH：20H 2 O。
Step 2: the aged reaction gel was spin crystallized in a homogeneous reactor at a constant rate of 10rpm for 48 hours at a temperature of 140 ℃. After cooling to room temperature, the dispersion was filtered off, rinsed with deionized water to ph=7, and then dried at 80 ℃ for 12 hours. Finally, roasting the powder for 3 hours in an air atmosphere at 500 ℃ to remove the template agent, thereby obtaining the Na-beta molecular sieve.
Step 3: na-. Beta.molecular sieves with 1M (NH) 4 ) 2 SO 4 The solution was prepared according to 1:20, and then filtering to separate out solid, washing with distilled water, and drying at 110 ℃. This ion exchange procedure was repeated twice to ensure complete cation exchange. And roasting for 3 hours at 500 ℃ in an air atmosphere to obtain the H-beta molecular sieve.
Step 4: the 3g H-beta molecular sieve was dissolved in 100ml of 0.033m indium nitrate solution and ion exchanged at 85 ℃ for 8h, then the solid was isolated by filtration, washed with distilled water until ph=7 and dried at 80 ℃ for 12 hours. And roasting for 3 hours at 500 ℃ In an air atmosphere to obtain the In/H-beta molecular sieve.
Comparative examples 1 to 7 provide an In/H-. Beta.molecular sieve, which is prepared by a method different from that of example 1 In that different amino acids, specifically alanine (A), glutamic acid (E), histidine (H), serine (S), threonine (T), arginine (R) and aspartic acid (D), respectively, are used. In order to distinguish example 1 from comparative examples 1 to 7, the molecular sieve products finally obtained were followed by the corresponding amino acid abbreviations X, denoted In/H-. Beta. -X, and the products of comparative examples 1 to 7 were denoted In/H-. Beta. -A, in/H-. Beta. -E, in/H-. Beta. -H, in/H-. Beta. -S, in/H-. Beta. -T, in/H-. Beta. -R and In/H-. Beta. -D, respectively.
Comparative example 8 provides an In/H-beta molecular sieve, the preparation of which differs from example 1 In that no amino acid is added In step 1. In addition, since the influence of amino acid is not contained, the crystallization time in step 2 is prolonged to 6 days. The molecular sieve is denoted as In/H-beta-B.
4 CH-SCR performance comparative test
NO for In/H-beta-X catalysts using a continuous flow fixed bed reactor x The selective catalytic reduction was evaluated as follows:
(1) The molecular sieve catalysts prepared in example 1 and comparative examples 1 to 8 were pelletized at 20MPa and then ground, and samples having a particle size of 40-60 mesh (0.250 to 0.425 mm) were screened for the next reaction.
(2) 100mg of the catalyst sample was weighed and charged into the fixed bed continuous flow reactor center. The feed gas contained 400ppm NO, 400ppm CH 4 、10vol.％O 2 、100ppm SO 2 、5vol.％H 2 O, the rest is Ar as balance gas. The flow rate of the raw material gas is 100mL/min, and the space velocity (GHSV) is 23600h -1 . The reactor temperature was increased between 100 ℃ and 650 ℃ with a temperature gradient of 4 ℃/min.
Catalyst activity was monitored using Temperature Programmed Surface Reaction (TPSR) techniques. The NO concentration was continuously detected by a nitrogen oxide analyzer (ThermoScientific, 42 i). Measurement of CH using an on-line gas chromatograph (GC-2014C, shimadzu) 4 Concentration, the gas chromatograph was equipped with a Porapak-Q column and a Flame Ionization Detector (FID). Analysis of N formed during SCR reactions using Agilent 7890B GC equipped with 5A molecular sieves 2 O content.
On CH 4 During the SCR reaction, the reaction formula in the ideal case is: CH (CH) 4 +2NO+O 2 ＝CO 2 +N 2 +2H 2 O, CH in the presence of oxygen 4 Reduction of NO x Nitrogen, water and carbon dioxide are produced. Using nitrogen oxide removal rate (eta), methane conversion rate (gamma), methane selectivity (alpha), nitrogen selectivity (S) N2 ) Four criteria to evaluate catalyst removalActivity of nitro.
Wherein c (NO) x ) in For NO before reaction x Is a concentration of (1) at the initial concentration (ppm);
c(NO x ) out is NO after reaction x Concentration (ppm);
c(CH 4 ) in as a pre-reaction CH 4 Is a concentration of (1) at the initial concentration (ppm);
c(CH 4 ) out is CH after reaction 4 Concentration (ppm);
c(N 2 o) is formed as N 2 O concentration (ppm).
The results of the detection of the denitration activity in example 1 and comparative examples 1 to 8 are shown in FIG. 1, wherein a represents the result of the removal rate of nitrogen oxides. As can be seen from a, the removal rate of nitrogen oxides is also significantly different for In/H-beta molecular sieves made from different amino acids, when proline-mediated In/H-beta-P is used, the removal rate of nitrogen oxides is also significantly different for SO 2 And H 2 Under the condition of O interference, the highest removal rate of nitrogen oxides can reach 40%, and the detection results of comparative examples 1 to 7 are less than 30%. Comparative example 8 does not use amino acid to participate in the reaction, and the removal rate of nitrogen oxide is only 10% at most under the same condition. It can be seen that the removal rate of nitrogen oxides is almost 0 at In/H-. Beta. -D and In/H-. Beta. -T at 600℃or less, and is only 3 even at 650 ℃Less than%. The nitrogen oxide removal rate of In/H-beta-B prepared without adding amino acid is similar to that of the former two at the temperature below 600 ℃, but the nitrogen oxide removal rate is obviously higher than that of the former two at the temperature of 650 ℃.
The molecular sieve with the nitrogen oxide removal rate of more than 20 percent is sequenced into In/H-beta-P (40 percent) > In/H-beta-A (29 percent) > In/H-beta-H (28.7 percent) > In/H-beta-R (25.9 percent) > In/H-beta-S (24.3 percent) > In/H-beta-E (20.4 percent) from high to low according to the nitrogen oxide removal rate. Among them, in/H-beta-A was further studied only for In/H-beta-P, in/H-beta-H, in/H-beta-R, in/H-beta-S, since its nitrogen oxide removal rate is low under low temperature conditions, and thus it was not further characterized.
As can be seen from FIG. 1 b, with increasing temperature, all four molecular sieves showed higher CH 4 Conversion, no significant difference between the four catalysts, indicated that methane was the key reductant, at all CH 4 The consumption in the SCR reaction is approximately the same. As can be seen from FIG. 1 c, CH of four molecular sieves 4 The selectivity is the trend of rising and then reducing, and has the optimal methane selectivity at about 500 ℃. Methane selectivity is positively related to catalytic performance, especially In/H-beta-P is highest at 500 ℃ In the low temperature region, reaching 100%. Thus, at the optimum reaction temperature, in/H-. Beta. -P can realize CH 4 And NO x On CH 4 Ideal stoichiometric reactions in SCR. As the temperature continues to rise, CH due to competition for methane side reactions 4 The selectivity decreases.
In addition, in/H-beta-P catalyst In SO 2 And H 2 Under O interference conditions, excellent durability was still exhibited in repeated tests, and the results are shown in FIG. 1 d, from top to bottom, as a result of nitrogen oxide removal rates during the first cycle (1 st), the second cycle (2 nd), and the third cycle (3 rd), respectively. As can be seen from the figure, even in SO 2 And H 2 In the case of O interference, the nitrogen oxide removal remains almost the same after three temperature cycles up to 650 ℃, especially in the high temperature region, and after three cycles up to 37.9% of the nitrogen oxide removal is still achieved at 650 ℃The rate.
Composition and Structure characterization
The indium content and Si/Al ratio of In/H-beta-P, in/H-beta-H, in/H-beta-R, in/H-beta-S and In/H-beta-B were measured by ICP method, and the results are shown In Table 1.
TABLE 1 comparison of elemental content in molecular sieves
As can be seen from the table, the Si/Al ratio of the catalyst is around 25, which is also close to the ratio of the starting reaction gel. Previous studies have shown that an In/H-beta molecular sieve having an indium content of about 7wt% prepared by ion exchange of an indium solution of 0.033M has an optimal NO removal efficiency. The indium content of the molecular sieve prepared by the method is In the range of 5.7-7.1wt%, and the indium content is In/H-beta-S from the lowest to the highest<In/H-β-P<In/H-β-H<In/H-β-R<In/H-. Beta. -B. This trend is associated with NO in CH 4 The order of catalytic activity in SCR is not consistent, indicating that indium loading may not be a critical factor leading to high denitration efficiency. On the other hand, the optimal denitration catalyst for In/H-. Beta. -P has the highest In/Al ratio of 0.8, indicating that it has the highest ion exchange degree.
FIG. 2 shows the X-ray diffraction (XRD) patterns of In/H-beta-P, in/H-beta-H, in/H-beta 0-R, in/H-beta-S and In/H-beta-B molecular sieve catalysts. Characteristic reflections corresponding to H-beta molecular sieves of 7.8 °, 13.5 °, 21.5 °, 22.5 °, 25.2 °, 27.1 °, 29.7 °, 33.4 °, and 43.7 ° can be observed In/H-beta-P, in/H-beta-H, in/H-beta-R and In/H-beta-S. Thus, under the action of amino acids, the pure crystalline beta phase, free of impurities, can be completely crystallized within 2 days. Meanwhile, in is not detected therein 2 O 3 Indicating that indium has been successfully exchanged as extra-framework cations and is in a highly dispersed stateThe amount of indium oxide detected by X-ray diffraction is negligible. Whereas the In/H- β -B sample showed a broad peak only at a position around 32 °, indicating that an amorphous phase still exists therein even if the crystallization time is prolonged 3-fold to 6 days.
From the above results, it is presumed that the addition of amino acids promotes crystallization of the beta molecular sieve, and further the test is verified as follows: 5, 5-dimethylpyrroline-N-oxide (DMPO) was added to the initially synthesized reaction gel. The in situ EPR spectra of Na- β -P gels synthesized from proline containing and Na- β -B gels synthesized without amino acids were compared and the results are shown in fig. 3. From the figures, it can be seen that there is a clear difference between the two. Due to the resonance transition of DMPO-OH, na-P is represented by 1:2:2: the ratio of 1 exhibits a quadruple mode, splitting into 1.5mT, whereas Na- β -B is completely devoid of this mode of Na- β -P. Thus, the pro-crystallization of amino acids may be caused by induced free radicals.
The molecular sieves were analyzed for structural properties and the results are shown in table 2. Wherein S is BET BET surface area, measured by nitrogen adsorption at a relative pressure in the range of 0.05 to 0.3; v (V) total For the total pore volume, from P/P 0 The amount of adsorbed nitrogen was calculated at=0.98; v (V) meso The volume of the mesoporous is calculated by a t-plot method (t-plot); d, d meso The mesoporous diameter is calculated by BJH method.
TABLE 2 molecular sieve structural analysis results
As can be seen from the table, in/H-. Beta. -P shows a highest mesopore volume of 0.27cm 3 Per gram, a maximum total pore volume of 0.42cm 3 /g; and then In/H-beta-S and In/H-beta-R. The possible reasons for the highest mesopore volume and total pore volume of In/H-beta-P are its better compatibility with molecular sieve synthesis, and the independence of proline moleculesSpecial stability of extra cyclic side chains. However, it is found that the mesoporous size of the molecular sieve is not completely consistent with the nitrogen oxide removal rate, methane selectivity, and the like.
The In/H- β -P samples were analyzed for nanoscale morphology and composition using a Scanning Electron Microscope (SEM) In combination with an energy dispersive X-ray (EDX) pattern, where a is the result of the scanning electron microscope and b-f are the quantitative analysis results of the EDX pattern, from which uniform nanoparticles with an average grain size of-150 nm, with Al, si and O elements uniformly distributed In the molecular sieve, and In also distributed more uniformly throughout the molecular sieve, but with slight aggregation at the surface, were clearly observed. According to the EDX analysis result, the weight concentration of indium was about 6%, and in agreement with the ICP analysis result, it was confirmed that the indium was uniformly distributed on the surface and inside of the crystal.
Transmission Electron Microscopy (TEM) imaging of In/H- β -P samples, the results of which are shown In fig. 5a, indicate a mosaic structure of In/H- β -P molecular sieves, in which a large number of crystallites of size 10-20nm co-grown mesocrystals form distinct nano-mesopores with well-defined edges. Further examination by High Resolution TEM (HRTEM) showed that the particles were fully crystalline as shown in fig. 5 b, as evidenced by the large number of lattice fringes distributed throughout the sample (bottom left inset). The presence of these mesopores allows for easy transport of reactants and products while preventing side reactions. Thus, the modulation of proline results In/H-. Beta. -P displaying more exposed active catalytic sites. These active catalytic sites can enhance hydrothermal stability and poisoning resistance.
The coordination structure of the magic angle spinning solid-state nuclear magnetic resonance (MAS NMR) detection In/H-beta-P sample is shown In figure 6, wherein a is 29 As a result of Si, b is 27 Results of Al. As can be seen from the a-representation, 29 si MAS NMR shows a main peak at-110.8 ppm, which is characteristic of the unique silicon tetrahedral structure in the H-. Beta.lattice, and a shoulder at-102.6 ppm, which corresponds to Si-OH-Al (Si) due to hydrolysis of Si-O-Al (Si) bonds. The peak width around-110.8 ppm may be due to different Si sites in the beta frame. Si-OH-Al (Si) is generally considered to be the source of acid centers on the In/H-beta catalyst.As can be seen from the above-mentioned b, 27 al MAS NMR showed two main peaks at 54.8 and 57.6ppm, corresponding to tetrahedral coordination in the beta zeolite at the aluminum sites of the T1-T2 and T3-T9 frameworks, respectively. These tetrahedrally coordinated Al sites, charged 3+, create a negatively charged framework that is compensated by exchangeable cations (e.g., in-containing cations). Whereas a weak peak near 0ppm indicates a negligible octahedral aluminum content In/H-. Beta. -P.
Chemical State and redox experiments
The photoelectron spectroscopy (XPS) results of In/H-beta-P, in/H-beta-H, in/H-beta-R, in/H-beta-S and In/H-beta-B are shown In FIG. 7, wherein a is In 3d 5/2 From the measurement results of the spectra, it can be seen that the three indium chemical states respectively correspond to In of about 445eV 2 O 3 InO of about 446eV + In (OH) of about 447eV 3-z z+ . Table 3 compares the curve fit content of these indium states, indicating that the proportions of the three indium in the four catalysts are nearly identical. Exchange state InO + And In (OH) 3-z z+ Is the main type of indium, while exchanged InO + The species being CH 4 -an active site of the SCR reaction. On the other hand, the Binding Energy (BE) value of the In/H-. Beta. -X catalyst varies from catalyst to catalyst. For In/H-beta-P, the BE values for all three types of indium are highest, indicating that the interaction of indium with the proline-modulated beta zeolite framework is stronger.
b is a measurement of the O1s spectrum, from which it can be seen that deconvolution into two main peaks at 532.7eV and 533.6eV corresponds to different forms of oxygen on the surface: o (O) β Surface oxygen and O of (2) γ Oxygen in the hydroxyl group of (a). Due to its high mobility, O β May participate in an oxidation process that plays a key role in the SCR of NO. O in the sample is obtained by deconvolution and curve fitting β /(O β +O γ ) The ratio, results referring to Table 3, were not significantly different in a narrow range between 0.57-0.59. Thus, the chemical valence of the oxygen element on the surface of the catalyst is not changed by the mediation of different amino acids.
TABLE 3 chemical states of surface elements of molecular sieve catalysts
Hydrogen programmed temperature reduction (H) 2 TPR) the reducibility of In different molecular sieve samples was investigated and the results are shown In fig. 8. As can be seen from the graph, all samples showed a broad reduction signal between 200℃and 500℃with peaks concentrated at 300-400℃indicating the absence of large blocks of In requiring higher reduction temperatures 2 O 3 Description of incorporated In from the side 3+ In a highly dispersed state. The reduction peak of In/H-beta-P occurs at the highest temperature centered at 365 deg.C, indicating that the reduction temperature is required to be higher, which may indicate that the electron interaction of indium with the zeolite framework is stronger, thus retarding the reduction of indium oxide.
Surface acidity experiment
Previous results indicate that adjusting the Si/Al ratio in the H-beta molecular sieve catalyst changes the number of acid centers in the complex in the metal oxide/beta catalyst. However, in this embodiment, the Si/Al ratio in all H-. Beta. -X samples was kept around 25. XPS spectrum and H 2 The TPR results also demonstrate that their surface indium and oxygen species are similar. The higher interaction of the indium species with the In/H-beta-P framework revealed that proline may improve zeolite properties. Therefore, further studies on the surface acidity thereof were conducted.
NH of In/H-beta-P, in/H-beta-H, in/H-beta-R and In/H-beta-S catalysts 3 The TPD curve is shown in fig. 9. These NH' s 3 The TPD curve can be broken down into peaks i below 200 ℃ corresponding to weak acid sites; peak ii located between 200-350 ℃, corresponding to the neutral acid site; peak iii, located between 350-650 ℃, corresponds to the strong acid site. Table 4 shows NH 3 Fitting of the TPD curve, from which it can be seen that In/H-. Beta. -P has the highest number of acid sites, especially strong acid sites. The order of the acid numbers is In/H-beta-P, in/H-beta-H, in/H-beta-R and In/H-beta-S, and CH reflected In FIG. 1 4 SCR performance is closely related, confirming the important role of the acid sites on denitration catalysis.
TABLE 4 number and distribution of acid centers on molecular sieve catalyst surface
a: peak corresponds to temperature (c).
b: peak area (a.u.).
c: the calculation method comprises the following steps: integrated Molar Extinction Coefficient (IMEC).
Pyridine (Py) compared to NH 3 Has higher selectivity and stability, and can be easily distinguished by FTIR spectrumstep and Lewis acid sites. The infrared spectra (Py-IR) of the four catalysts for pyridine adsorption are shown in FIG. 10. 1540cm -1 And 1450cm -1 The left and right bands are adsorbed on the +.>Pyridine ions (PyH +) formed at the acid sites and pyridine interacting with the Lewis acid sites. 1490cm -1 The band at this point is formed by the interaction of PyH + with pyridine coordinated to the Lewis acid site. According to 1540cm -1 And 1450cm -1 Band estimation at>The amounts of acid, lewis acid and B/L are shown in Table 4. With NH 3 -TPD results consistent, ++>The order of the amount of acid and the B/L ratio is In/H-. Beta. -P>In/H-β-H>In/H-β-R>In/H-. Beta. -S is positively correlated with catalytic activity. Thus, in CH using In/H-beta catalyst 4 In SCR, the number of strong acid centers and +.>The density of acid centers plays a critical roleActing as a medicine. It can also be seen from the data in Table 2 that the mediation of the amino acids is to adjust the catalytic activity of the molecular sieve without affecting the framework silica to alumina ratio.
Binding NH 3 TPD and Py-IR results, in/H-beta-P catalyst showed optimal CH 4 The reason for the SCR activity is that it has a stronger activityAcid active centers and thus facilitate stronger interactions with indium oxide and hydroxy indium species. In addition, the FT-IR spectra of In/H-. Beta. -P and proline were compared, and no characteristic FT-IR peak of proline was found In/H-. Beta. -P, and thus proline interacted with the beta molecular sieve framework only In the synthesis stage, which had been completely removed by the subsequent washing and calcination steps. That is, the addition of proline merely adjusts the acidity of the resulting catalyst and does not add to the final catalyst formed.
Example 2
This example provides a method for preparing an In/H-beta catalyst, which differs from example 1 In that the crystallization temperature is 220 c and the crystallization time is 48 hours. The In/H-beta catalyst prepared by the method is found to be SO by adopting the same detection conditions 2 And H 2 Under the condition of O interference, the higher nitrogen oxide removal rate and methane selectivity are also maintained.
Examples 3 to 6
Examples 3 to 6 respectively provide a method for preparing an In/H-beta catalyst, differing from example 1 In that the amount of proline is adjusted so that the molar ratio of proline to silica In the reaction gel after aging is 0.1, 0.2, 0.4, 0.5. Detection by reference to the above method, found in SO 2 And H 2 The molecular sieve catalysts prepared in examples 3-6 also maintained higher nitrogen oxide removal and methane selectivity under O interference compared to the preparation methods using other amino acids or without amino acids under the same conditions.
Examples 7 to 9
Examples 7 to 9 provide a method for preparing an In/H-beta catalyst, respectively, and a method for preparing the sameExample 1 differs in that the concentrations of the indium nitrate solutions were adjusted to 0.01M, 0.06M and 0.1M, respectively. The In/H-beta catalyst prepared by the methods is found to be SO by adopting the same detection conditions 2 And H 2 Under the condition of O interference, the higher nitrogen oxide removal rate and methane selectivity are also maintained.
Example 10
The embodiment provides an exhaust gas treatment device, the exhaust gas treatment device includes at least one SCR reactor, and the one end of this SCR reactor is connected with input flow system, and this input flow system includes a plurality of inlets, is used for letting in methane and waste gas in the SCR reactor respectively. The SCR reactor is also preset with an In/H-beta catalyst prepared by any one of the methods In examples 1-9.
The present application has been described in detail with reference to the embodiments, but the present application is not limited to the embodiments described above, and various changes can be made within the knowledge of one of ordinary skill in the art without departing from the spirit of the present application. Furthermore, embodiments of the present application and features of the embodiments may be combined with each other without conflict.

Claims (9)

1. The preparation method of the In/H-beta catalyst is characterized by comprising the following steps:
step 1: mixing raw materials comprising amino acid, a silicon source, an aluminum source, an M source, an organic amine template agent and water for reaction to obtain reaction gel;
step 2: crystallizing the reaction gel, cooling, washing, drying and roasting to obtain an M-beta molecular sieve;
step 3: mixing the M-beta molecular sieve with an ammonium salt solution for reaction, and washing, drying and roasting after ion exchange to obtain an H-beta molecular sieve;
step 4: mixing H-beta molecular sieve with indium salt solution for reaction, washing, drying and roasting after ion exchange is completed to obtain an In/H-beta molecular sieve;
wherein M is at least one of alkali metal and alkaline earth metal, and the amino acid is proline.
2. The method according to claim 1, wherein in the reaction gel, the silicon source is silica, and the molar ratio of amino acid to silica is 0.1 to 0.5.
3. The preparation method according to claim 2, wherein the aluminum source and the M source are calculated as oxides, the organic amine template agent is calculated as quaternary ammonium ions, the molar ratio of silicon dioxide to aluminum oxide is 5-200, the molar ratio of oxidized M to silicon dioxide is 0.01-0.4, and the molar ratio of quaternary ammonium ions to silicon dioxide is 0.1-0.8.
4. The method according to any one of claims 1 to 3, wherein the firing temperature in step 2 to 4 is 400 to 600 ℃ and the firing time is 1 to 6 hours.
5. An In/H-beta catalyst produced by the production process according to any one of claims 1 to 4.
6. An In/H- β catalyst according to claim 5, wherein the concentration of bransted acid sites is 50 μmol/g or more.
7. An In/H- β catalyst according to claim 6, wherein the ratio of the concentration of bransted acid sites/Lewis acid sites is 0.55 or more.
8. A denitration method, characterized In that the exhaust gas is treated by adopting a selective catalytic reduction method, CH4 is used as a reducing agent, and the In/H-beta catalyst as claimed In any one of claims 5 to 7 is used as a catalyst.
9. A purification treatment apparatus comprising an SCR reactor In which the In/H- β catalyst according to any one of claims 5 to 7 is installed.
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