Molecular sieve-aluminum oxide core-shell catalyst for COS hydrolysis as well as preparation method and application of molecular sieve-aluminum oxide core-shell catalyst

Abstract

The invention belongs to the technical field of air pollution control, and particularly relates to a molecular sieve-alumina core-shell catalyst for COS hydrolysis as well as a preparation method and application of the molecular sieve-alumina core-shell catalyst. The method comprises the following steps: grinding and screening a molecular sieve; the preparation method comprises the following steps: adding a pore forming agent into an aluminum source solution, adding an alkali solution to adjust the pH value to 8-10, stirring at room temperature for reaction, performing suction filtration on the solution, washing a product, dissolving the product into water for activation, adding a molecular sieve, reacting under stirring, performing suction filtration on the solution, washing and drying the product, and roasting to obtain the molecular sieve-alumina core-shell catalyst. The prepared catalyst can completely convert COS with the inlet concentration of 300 ppm at the temperature of 80 DEG C, the COS conversion rate and H2S selectivity are kept unchanged in an 80h stability experiment, the effect is better than that of commercial gamma-Al2O3, and the catalyst has good application prospects in blast furnace gas fine desulfurization.

Description

Technical Field

[0001] The invention belongs to the technical field of air pollution control, and in particular relates to a molecular sieve@alumina core-shell catalyst for COS hydrolysis and a preparation method and application thereof. Background Art

[0002] Blast furnace gas is a low calorific value combustible gas produced during blast furnace ironmaking. Its main components are 6-22% carbon dioxide, 21-26% carbon monoxide, 1-4% hydrogen, 53-57% nitrogen, 0.2-0.5% hydrocarbons and a small amount of sulfur dioxide. Before use, blast furnace gas must be purified, mainly to remove the sulfides it contains. Among them, carbonyl sulfide (COS) is a toxic and harmful gas that not only corrodes reaction equipment but also pollutes the air. However, the commonly used methods for removing COS cannot fully meet emission standards, so the fine desulfurization technology of BFG has become a major technical problem.

[0003] Currently, commonly used COS removal methods include wet absorption, dry adsorption, hydrogenation and catalytic hydrolysis. However, among COS removal reagents, absorbents have high energy consumption and low desulfurization efficiency, and adsorbents have low sulfur capacity and high required temperature. In contrast, the COS hydrolysis catalytic method has the advantages of mild reaction conditions, high removal efficiency and low cost. COS hydrolysis catalysts are divided into two categories: supported catalysts and unsupported catalysts. For supported hydrolysis catalysts, γ-Al2O3, TiO2, AC, etc. are usually used as carriers, and alkali metals, transition metals, rare earth metal oxides, etc. are supported as active ingredients. Unsupported catalysts are mainly hydrotalcite.

[0004] At present, most of the supported catalysts for COS hydrolysis are based on γ-Al2O3 with large specific surface area and high surface activity. The research methods include: modifying γ-Al2O3 by loading active components or composite carriers to make up for the shortcomings of commercial activated alumina in water resistance, sulfur poisoning resistance and life. Chinese patent CN113332969B discloses a method for preparing a catalyst that can improve the anti-deactivation performance in carbonyl sulfide hydrolysis reaction, by introducing ordered mesoporous channels into alumina and enlarging the mesoporous pore size, but the COS conversion rate of the obtained catalyst dropped from 98% to 60% after 6 hours of reaction, and the stability was poor. Chinese patent CN1095309A discloses a novel carbonyl sulfide hydrolysis catalyst, the carrier is γ-Al2O3, the invention believes that the catalyst activity decay is due to surface sulfation, using TiO2, ZrO2 and other materials to modify the γ-Al2O3 carrier, the catalyst activity can be extended, the catalyst is prepared by low temperature drying method, the active component is easy to lose, and the catalyst is only suitable for processing 100-200ppm COS raw gas. Chinese patent CN115193433B discloses a defect-rich alumina supported single atom carbonyl sulfide hydrolysis catalyst in the catalytic hydrolysis reaction of COS in blast furnace gas, the platinum metal single atom is loaded on the carrier, used to catalyze the low temperature hydrolysis of COS, the catalyst prepared by this method can completely convert the inlet concentration of 300ppm COS at 100°C, but the loading of precious metal platinum makes the catalyst cost higher. Summary of the invention

[0005] In view of the shortcomings and deficiencies of the prior art, the primary purpose of the present invention is to provide a method for preparing a COS hydrolysis molecular sieve@alumina core-shell catalyst.

[0006] Another object of the present invention is to provide a molecular sieve @ alumina core-shell catalyst for COS hydrolysis. The catalyst of the present invention mainly comprises molecular sieve and alumina, is applicable to a larger COS concentration range, has a reaction activity that remains unchanged after a stabilization experiment, has a low raw material cost, has good carbonyl sulfide conversion activity and hydrogen sulfide selectivity, and has good anti-oxidation and anti-sulfur poisoning properties.

[0007] Another object of the present invention is to provide the use of the above molecular sieve@alumina core-shell catalyst for COS hydrolysis. When the catalyst of the present invention is used for catalytic hydrolysis of carbonyl sulfide in blast furnace gas, it has good carbonyl sulfide conversion activity and hydrogen sulfide selectivity, and has good anti-oxidation and anti-sulfur poisoning properties.

[0008] The object of the present invention is achieved through the following technical solutions:

[0009] A method for preparing a COS hydrolysis molecular sieve@alumina core-shell catalyst comprises the following steps:

[0010] (1) preparing raw material molecular sieve, pore-forming agent (template agent) and aluminum source according to mass ratio; grinding and sieving the molecular sieve for later use;

[0011] (2) Preparation of Al2O3 precursor: Add water to the aluminum source to prepare a solution, add a pore-forming agent, add an alkaline solution to adjust the pH to 8-10, react under stirring conditions, filter the solution, and wash the product to obtain an Al2O3 precursor for use;

[0012] (3) Composite of core-shell catalyst: Al2O3 precursor is dissolved in water for activation, and then the ground molecular sieve is added to the activated solution of Al2O3 precursor. After reacting for a period of time under stirring conditions, the solution is filtered and the product is washed to obtain a core-shell catalyst precursor for use;

[0013] (4) Forming of core-shell catalyst: The core-shell catalyst precursor is dried and then calcined to obtain a molecular sieve@alumina core-shell catalyst.

[0014] Furthermore, the mass ratio of the aluminum source (in terms of Al2O3) to the molecular sieve in step (1) is 10:3-30, more preferably 10:(10-30), and most preferably 1:1.

[0015] Furthermore, in step (1), the mass ratio of the pore-forming agent to the aluminum source (calculated based on the actual mass of the aluminum source) is 1 to 3:10, more preferably 1:10.

[0016] Furthermore, the molecular sieve in step (1) comprises at least one of ZSM-5 molecular sieve, MCM-41 molecular sieve, SAPO-34 molecular sieve or Y-type molecular sieve. The molecular sieve is preferably ground and sieved to a size of 60 or more for standby use.

[0017] Furthermore, the aluminum source described in step (1) is at least one of aluminum isopropoxide, aluminum sulfate 18hydrate, aluminum nitrate nonahydrate, and pseudo-boehmite.

[0018] Furthermore, the pore-forming agent described in step (1) is at least one of hexadecyltrimethylammonium bromide, polyethylene glycol, and a polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer.

[0019] Furthermore, the reaction in step (2) is carried out by stirring at room temperature for 1 to 3 hours.

[0020] Furthermore, the water described in step (3) is deionized water.

[0021] Furthermore, the reaction in step (3) is carried out at 70 to 90° C. for 2 to 4 hours.

[0022] Furthermore, the drying in step (4) refers to drying at 80-120° C. for 8-12 hours.

[0023] Furthermore, the calcination in step (4) refers to calcination at 500-1000°C for 3-6 hours, more preferably calcination at 700°C for 3-6 hours, and most preferably calcination at 700°C for 5 hours.

[0024] Furthermore, in steps (2) and (3), the product is washed with deionized water and anhydrous ethanol to a pH of 7.

[0025] The molecular sieve@alumina core-shell catalyst for COS hydrolysis prepared by the method of the present invention contains molecular sieve and alumina. Calculated by mass percentage, the catalyst includes 7-32% molecular sieve, 8-9% pore-forming agent and 75-85% aluminum salt.

[0026] The catalyst of the invention can be applied to the hydrolysis of carbonyl sulfide in blast furnace gas.

[0027] Compared with the prior art, the present invention has the following advantages:

[0028] 1. The preparation method provided by the present invention is simple to operate and can be produced on an industrial scale.

[0029] 2. The present invention adopts a liquid phase coating method, and obtains a composite catalyst with a high degree of fusion of aluminum hydroxide and molecular sieve by adding aluminum salt to a pore-forming agent / template agent for hydrolysis, filtration, drying, and calcination. The catalyst has a higher specific surface area, a larger mesopore diameter, and good carbonyl sulfide conversion activity, antioxidant capacity, and anti-poisoning capacity at low temperatures. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 3 is a graph showing the COS conversion activity of the catalysts prepared in Examples 1, 2, 3, 4 of the present invention and Comparative Example 1.

[0031] Figure 2 It is a comparison chart of H2S selectivity of the catalysts prepared in Examples 1, 2, 3, 4 of the present invention and Comparative Example 1.

[0032] Figure 3 3 is a comparison chart of COS conversion activity of the catalysts prepared in Examples 1, 5, 6 of the present invention and Comparative Example 1.

[0033] Figure 4 It is a comparison chart of H2S selectivity of the catalysts prepared in Examples 1, 5, 6 of the present invention and Comparative Example 1.

[0034] Figure 5 It is a comparison chart of COS conversion activity of the catalysts prepared in Examples 1, 7, 8, 9 of the present invention and Comparative Example 1.

[0035] Figure 6 It is a comparison chart of H2S selectivity of the catalysts prepared in Examples 1, 7, 8, 9 of the present invention and Comparative Example 1.

[0036] Figure 7 It is a comparison chart of COS conversion activity of the catalysts prepared in Examples 1, 10, 11 of the present invention and Comparative Example 1.

[0037] Figure 8 It is a comparison chart of H2S selectivity of the catalysts prepared in Examples 1, 10, 11 of the present invention and Comparative Example 1.

[0038] Fig. 9 This is a graph of the stable 80h hydrolysis test activity of the catalyst prepared in Example 1 of the present invention.

[0039] Fig.10 This is a scanning electron microscope image of the catalyst prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0040] The present invention is further described in detail below in conjunction with the examples and drawings, but the embodiments of the present invention are not limited thereto. The raw materials involved in the present invention can be purchased directly from the market. For process parameters not particularly noted, conventional techniques can be used.

[0041] The particle size of the catalyst used for activity evaluation in the following examples is 40-60 mesh, and the catalyst is tested and evaluated for the conversion rate of carbonyl sulfide in blast furnace gas and the selectivity of the product hydrogen sulfide in the temperature range of 40-140°C. The test strip is as follows: the reaction atmosphere is a carbonyl sulfide concentration of 300ppm, N2 is the balance gas, the reaction flow rate is 200mL / min, and the volume space velocity is 24000h -1 , the catalyst dosage was 0.5 mL, and the stabilization time was 60 min; the concentrations of carbonyl sulfide and hydrogen sulfide were detected by gas chromatography (Folley GC-9790 gas chromatograph equipped with thermal conductivity detector (FPD) and hydrogen flame detector (FID). As a control, we tested the COS conversion rate and H2S selectivity of commercial activated alumina, the test temperature range was 40-140 ° C, and the reaction gas was carbonyl sulfide.

[0042] Example 1

[0043] A method for preparing a molecular sieve@alumina core-shell structure catalyst, comprising the following steps:

[0044] (1) Grinding of molecular sieve: Grind and sieve the purchased molecular sieve ZSM-5 to a size of 60 mesh or more, weigh 1.8768 g, and obtain solid A for later use;

[0045] (2) Precipitation of Al(OH)3: Weigh 7.5 g of aluminum isopropoxide (containing 1.8768 g of Al2O3), add deionized water to make a 10 wt% solution, add 0.75 g of hexadecyltrimethylammonium bromide, add an alkaline solution to adjust the pH to 8-10, stir at room temperature for 2 h, and obtain solution A for use;

[0046] (3) Extraction of Al2O3 precursor: Filter solution A, wash with deionized water and anhydrous ethanol until pH = 7, and obtain solid B for later use;

[0047] (4) Composite of core-shell catalyst: Solid B was dissolved in 250 mL of deionized water for activation, solid A was added to the activated solution of solid B to obtain solution B, and solution B was filtered after stirring in a water bath at 85°C for 3 h, and washed with deionized water and anhydrous ethanol until pH = 7 to obtain solid C;

[0048] (5) Formation of core-shell catalyst: Solid C was dried at 120 °C for 12 h, and then calcined in a muffle furnace at 700 °C at a heating rate of 5 °C / min for 5 h to obtain a molecular sieve@alumina core-shell catalyst.

[0049] Example 2

[0050] This embodiment is basically the same as embodiment 1, except that in step (1) of this embodiment, the molecular sieve ZSM-5 is replaced with the molecular sieve SBA-15.

[0051] Example 3

[0052] This embodiment is basically the same as embodiment 1, except that in step (1) of this embodiment, the molecular sieve ZSM-5 is replaced with the molecular sieve SAPO-34.

[0053] Example 4

[0054] This embodiment is basically the same as embodiment 1, except that in step (1) of this embodiment, the molecular sieve ZSM-5 is replaced with the molecular sieve SSZ-13.

[0055] Example 5

[0056] This embodiment is basically the same as embodiment 1, except that the calcination temperature in step (5) of this embodiment is 600°C.

[0057] Example 6

[0058] This embodiment is basically the same as embodiment 1, except that the calcination temperature in step (5) of this embodiment is 800°C.

[0059] Example 7

[0060] This embodiment is basically the same as embodiment 1, except that the mass of molecular sieve ZSM-5 in step (1) of this embodiment is changed to 3.7536 g.

[0061] Example 8

[0062] This embodiment is basically the same as embodiment 1, except that the mass of molecular sieve ZSM-5 in step (1) of this embodiment is changed to 0.9384 g.

[0063] Example 9

[0064] This embodiment is basically the same as embodiment 1, except that the mass of molecular sieve ZSM-5 in step (1) of this embodiment is changed to 0.6256 g.

[0065] Example 10

[0066] This embodiment is basically the same as embodiment 1, except that: in step (1) of this embodiment, aluminum isopropoxide is replaced by aluminum nitrate.

[0067] Embodiment 11

[0068] This embodiment is basically the same as embodiment 1, except that in step (1) of this embodiment, aluminum isopropoxide is replaced with pseudo-boehmite.

[0069] Example 12

[0070] This embodiment is basically the same as embodiment 1, except that in step (1) of this embodiment, aluminum isopropoxide is replaced by aluminum sulfate.

[0071] Comparative Example 1

[0072] This comparative example is commercial γ-activated alumina (Shanghai MacLean Biochemical Technology Co., Ltd.)

[0073] Experimental Example 1

[0074] In order to explore the improvement of the COS hydrolysis activity of the molecular sieve / alumina core-shell catalyst in the present invention, this experiment selected the catalysts prepared in Examples 1, 2, 3, and 4 and the catalyst in Comparative Example 1, and compared the catalytic process of COS hydrolysis catalyzed by different types of molecular sieves (ZSM-5, SBA-15, SAPO-34, and SSZ-13). The specific experiment is as follows: In this experiment, at 300 ppm COS, nitrogen balance, a total flow rate of 200 mL / min, a constant temperature water bath at 40°C, a catalyst dosage of 0.5 mL, and a volume space velocity of 24000 h -1 Under the conditions of , the effects of different types of molecular sieves on the hydrolysis activity of the catalyst were tested. The test results are as follows Figure 1 and 2As shown, the results show that the COS activity and H2S selectivity of the molecular sieve types ZSM-5 and SBA-15 are improved compared with γ-Al2O3.

[0075] Experimental Example 2

[0076] In order to explore the effect of different calcination temperatures on the catalytic hydrolysis of the catalyst, the catalysts prepared in Examples 1, 5, and 6 were selected in this experiment, and the COS conversion rate and H2S selectivity of the catalysts calcined at different temperatures (600°C, 700°C, and 800°C) in the COS hydrolysis reaction were compared. The specific experiment was as follows: in an atmosphere of 300 ppm COS and nitrogen balance, the total flow rate was set to 200 mL / min, and the catalyst dosage was 0.5 mL through a 40°C constant temperature water bath, and the volumetric space velocity was 24000 h / min. -1 , test COS conversion rate and H2S selectivity, the test results are as follows Figure 3 and 4 As shown, the results showed that the catalysts prepared at calcination temperatures of 600°C, 700°C, and 800°C had improved H2S selectivity compared to γ-Al2O3.

[0077] Experimental Example 3

[0078] In order to explore the effect of the mass ratio of molecular sieve to alumina on the catalytic hydrolysis of the catalyst, the catalysts prepared in Examples 1, 7, 8, and 9 were selected in this experiment, and the COS conversion rate and H2S selectivity of the catalysts with different mass ratios (molecular sieve: alumina) in the COS hydrolysis reaction were compared. The specific experiment was as follows: in an atmosphere of 300 ppm COS and nitrogen balance, the total flow rate was set to 200 mL / min, and the catalyst dosage was 0.5 mL at a volume space velocity of 24000 h / min through a 40°C constant temperature water bath. -1 , test COS conversion rate and H2S selectivity, the test results are as follows Figure 5 and 6 As shown, the results show that the COS activity and H2S selectivity of γ-Al2O3 are improved compared with that of ZSM:Al2O3 with a mass ratio of 1:1.

[0079] Experimental Example 4

[0080] In order to explore the effect of different aluminum sources on the catalytic hydrolysis of the catalyst, the catalysts prepared in Examples 1, 10, and 11 and the catalyst in Comparative Example 1 were selected in this experiment to compare the COS conversion rate and H2S selectivity of the catalysts with different aluminum sources (aluminum isopropoxide, aluminum nitrate, and aluminum chloride) in the COS hydrolysis reaction. The specific experiment is as follows: in an atmosphere of 300 ppm COS and nitrogen balance, the total flow rate is set to 200 mL / min, through a 40°C constant temperature water bath, the catalyst dosage is 0.5 mL, and the volume space velocity is 24000 h -1, test COS conversion rate and H2S selectivity, the test results are as follows Figure 7 and 8 As shown, the results show that the use of aluminum isopropoxide, pseudohydroxide and aluminum sulfate as aluminum sources has improved COS activity and H2S selectivity compared with γ-Al2O3.

[0081] Experimental Example 5

[0082] In order to explore the stability of the preferred catalyst in the present invention under oxygen-containing conditions, the catalyst of Example 1 was selected in this experiment to test the COS conversion rate and H2S selectivity of the COS hydrolysis reaction under aerobic conditions. The specific experiment was as follows: in an atmosphere of 300 ppm COS, 1% O2, and nitrogen balance, the total flow rate was set to 200 mL / min, through a 40°C constant temperature water bath, the catalyst dosage was 0.5 mL, and the volume space velocity was 24000 h -1 , set the temperature to 80℃, test COS conversion and H2S selectivity, the test results are as follows Fig. 9 As shown in the results, it was found that after stabilization for 80 h, the COS conversion rate and H2S selectivity could remain unchanged ( Fig. 9 individual data test bias).

[0083] Table 1 Specific surface area data of catalysts prepared in Examples 1, 5, 6, 8, 9 of the present invention and Comparative Example 1

[0084]

[0085] As mentioned above, although the present invention has been shown and described with reference to specific preferred embodiments, it shall not be interpreted as limiting the present invention itself. Various changes in form and details may be made to it, and modifications based on the present invention may be made without departing from the spirit and scope of the present invention defined in the appended claims, but all such changes or substitutions shall fall within the scope of protection of the appended claims of the present invention.

Claims

1. A method for preparing a COS hydrolysis molecular sieve @ alumina core-shell catalyst, characterized in that: The steps include: (1) preparing raw material molecular sieve, pore former and aluminum source according to mass ratio; grinding and sieving the molecular sieve for later use; (2) adding water to the aluminum source to prepare a solution, adding a pore-forming agent, and then adding an alkaline solution to adjust the pH to 8-10. After the reaction under stirring conditions, the solution is filtered and the product is washed to obtain an Al2O3 precursor; (3) dissolving an Al2O3 precursor in water for activation, then adding the ground molecular sieve into the activated solution of the Al2O3 precursor, reacting under stirring conditions, filtering the solution, and washing the product to obtain a core-shell catalyst precursor for later use; (4) The core-shell catalyst precursor is dried and then calcined to obtain a molecular sieve@alumina core-shell catalyst.

2. The preparation method according to claim 1, characterized in that: The mass ratio of the aluminum source to the molecular sieve in step (1) is 10:(3-30), wherein the mass of the aluminum source is calculated as Al2O3.

3. The preparation method according to claim 2, characterized in that: The mass ratio of the aluminum source to the molecular sieve in step (1) is 10:(10-30), wherein the mass of the aluminum source is calculated as Al2O3.

4. The preparation method according to claim 1, characterized in that: The mass ratio of the pore-forming agent to the aluminum source in step (1) is 1 to 3:

10.

5. The preparation method according to claim 1, characterized in that: The molecular sieve in step (1) comprises at least one of ZSM-5 molecular sieve, MCM-41 molecular sieve, SAPO-34 molecular sieve or Y-type molecular sieve; The aluminum source in step (1) is at least one of aluminum isopropoxide, aluminum sulfate 18hydrate, aluminum nitrate nonahydrate, and pseudo-boehmite; The pore-forming agent described in step (1) is at least one of hexadecyltrimethylammonium bromide, polyethylene glycol, and a polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer.

6. The preparation method according to claim 1, characterized in that: The reaction in step (2) refers to stirring the reaction at room temperature for 1 to 3 hours; the reaction in step (3) refers to stirring the reaction at 70 to 90° C. for 2 to 4 hours.

7. The preparation method according to claim 1, characterized in that: The drying in step (4) refers to drying at 80-120° C. for 8-12 hours; The calcination in step (4) refers to calcination at 500-1000° C. for 3-6 hours.

8. The preparation method according to claim 7, characterized in that: The calcination in step (4) refers to calcination at 700° C. for 3 to 6 hours.

9. A molecular sieve@alumina core-shell catalyst for COS hydrolysis prepared by the method according to any one of claims 1 to 8.

10. Use of the catalyst according to claim 9 in hydrolyzing carbonyl sulfide in blast furnace gas.

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