Rapid preparation method of silicon carbide catalytic membrane with low flux loss

Abstract

The invention discloses a rapid preparation method of a silicon carbide catalytic membrane with low flux loss, and relates to the field of synergistic dust removal and denitration. The preparation method comprises the following steps: (a) ultrasonically cleaning impurities on a silicon carbide membrane tube by using deionized water, and drying the silicon carbide membrane tube; (b) preparing a catalyst spraying liquid; and (c) carrying out catalyst spraying loading on the silicon carbide membrane tube by spraying, and drying and calcining. The method has the advantages of simple steps, low gas flux loss and excellent synergistic dust removal and denitration, and large-scale preparation of the catalytic membrane can be realized.

Description

Technical Field

[0001] The present invention relates to the field of integrated dust removal and denitration, and in particular to a method for rapidly preparing a silicon carbide catalytic membrane with low flux loss. Background Art

[0002] Fine particulate matter PM is generated in industrial production 2.5 、Nitrogen oxides (NO x ), volatile organic compounds (VOCs), etc. Among them, nitrogen oxides and fine particulate matter will cause acid rain and haze environmental problems respectively, and will cause irreversible harm to human health.

[0003] In industrial exhaust gas purification, dust removal and denitrification are carried out in multiple units, usually denitrification first and then dust removal. The denitrification technology used is NH 3 -SCR technology, which has the advantages of high denitrification efficiency and no secondary pollution. The mainstream dust removal adopts electrostatic dust removal technology with high dust removal efficiency, but it has the disadvantage of complex equipment. Multi-step dust removal and denitrification not only consumes more energy but also occupies a large area. In addition, high concentrations of dust will cover the active sites of the catalyst and cause alkali metal poisoning. With long-term operation, the activity of the catalyst will be reduced and the service life of the catalyst will be shortened. SiC ceramic membrane has the advantages of high temperature resistance, good thermal shock resistance and high mechanical strength, and has been commercially applied in high-temperature dust removal. Combining the denitrification catalyst with the SiC ceramic membrane can achieve the simultaneous removal of NOx and dust, while also reducing the footprint of the exhaust gas purification system.

[0004] There have been some studies on silicon carbide catalytic membranes for dust removal and denitrification. The Chinese invention patent with patent number CN114515587A, "A method for preparing a multi-layered silicon carbide catalytic membrane", uses a hydrothermal growth method to grow TiO in SiC pores. 2 Nanocones can achieve a denitrification efficiency of more than 91% at 300°C. However, the preparation process is cumbersome and the reaction temperature window is narrow. The Chinese invention patent with patent number CN111167491A, "A method for preparing silicon carbide catalytic membrane by co-sintering", uses perovskite and SiC particles to bond together to prepare a catalytically active SiC catalytic membrane in one step, but this method is currently in the laboratory stage and the degradation rate of NO by the catalytic membrane is only 72%. In addition, the above methods are not suitable for large-scale preparation of catalytic membranes. Summary of the invention

[0005] The purpose of the present invention is to quickly prepare a silicon carbide catalytic membrane with low gas flux loss, which is used to solve the problem of excessive floor space and catalyst shedding caused by the traditional dust removal and denitration multi-unit. The prepared SiC catalytic membrane is used for the removal of fine dust from industrial tail gas and the efficient degradation of NOx.

[0006] The present invention is achieved through the following technical solution: A method for rapidly preparing a silicon carbide catalytic membrane with low flux loss, comprising the following steps: A. Place the SiC ceramic membrane tube in deionized water for ultrasonic cleaning for a period of time to remove impurities on the membrane surface, and then place it in a drying oven for drying; B. slowly adding a certain amount of cerium nitrate hexahydrate and phosphoric acid to a certain amount of deionized water in sequence, and stirring at a certain speed for a certain period of time; C. Then, adding ammonia water to the solution obtained in step B to adjust the pH of the catalyst solution to 8, and stirring at a certain speed for a certain period of time to obtain a catalyst spray liquid; D. The catalyst spraying liquid prepared in step C is sprayed on the membrane tube obtained in step A under certain conditions, and then placed in a drying oven for drying, and then placed in a muffle furnace for calcination.

[0007] Preferably, the ultrasonic cleaning time in step A is 30 to 45 min.

[0008] Preferably, in step B, the molar ratio of cerium nitrate hexahydrate to phosphoric acid and deionized water is 1:1:30-1:1.4:60; the rotation speed is 300-900 r / min, and the stirring time is 2-4 h.

[0009] Preferably, the rotation speed in step C is 500-1000 r / min, and the stirring time is 8-12 h.

[0010] Preferably, the spraying pressure in step D is 0.6-1.0 Mpa, the nozzle diameter is 0.4-0.8 mm, and the spraying time is 5-10 min; the drying oven temperature is 60-120 °C, and the drying time is 12 h; the calcination temperature is 400-600 °C, and the calcination time is 2-5 h.

[0011] Beneficial effects of the present invention: (1) The present invention adopts a spraying method to load the catalyst into the pores of the SiC support body, which has a smaller decrease in gas flux than the catalyst membrane prepared by the vacuum impregnation method and reduces the preparation time.

[0012] (2) The NO conversion rate of the SiC catalytic membrane prepared by the spraying method is maintained above 90% between 250-360 °C.

[0013] (3) In the synergistic dust removal and denitrification experiment, the addition of dust will not affect the NO removal rate of the SiC catalytic membrane.

[0014] (4) The spraying method of the present invention for preparing SiC catalytic film is simple, low-cost and has great application potential. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 CePO prepared by spraying method in Example 1 4 / SiC catalytic membrane and CePO prepared by vacuum impregnation method 4 / Gas flux comparison of SiC catalytic membrane.

[0016] Figure 2 The CePO prepared in Example 1 4 / SiC catalytic membrane NO conversion rate comparison chart.

[0017] Figure 3 The CePO prepared in Example 1 4 / SiC catalytic membrane dust removal and denitrification diagram at 300 ℃. DETAILED DESCRIPTION

[0018] The present invention will be further explained below in conjunction with the examples. The following examples are only used to illustrate the present invention, but are not intended to limit the scope of the present invention. Example 1

[0019] A method for rapidly preparing a silicon carbide catalytic membrane with low flux loss, the specific steps are as follows: A. Place the SiC ceramic membrane tube in deionized water for ultrasonic cleaning for 30 minutes to remove impurities on the membrane surface, and dry it for later use; B. 1:1:30 molar ratio of cerium nitrate hexahydrate and phosphoric acid and deionized water were mixed, and then stirred at 500 r / min speed for 2 h; C. Then, ammonia water was added to the solution obtained in step B to adjust the pH of the catalyst solution to 8, and the solution was stirred at 900 r / min for 8 h to obtain a catalyst spray solution.

[0020] D. CePO prepared in step C 4 The catalyst spray liquid was sprayed on the membrane tube obtained in step A using a spraying method. The spraying conditions were: pressure of 0.6 MPa, nozzle diameter of 0.8 mm, spraying time of 5 min, spraying times of twice, followed by drying in a drying oven at 120 °C for 12 h and calcination at 400 °C for 4 h.

[0021] The SiC catalytic membrane prepared in this embodiment is used for NH 3 -SCR activity test and synergistic dust removal and denitrification experiment, at a gas flow rate of 3.13 L / min and a 5% volume content of O 2 , 400 ppm NO, 400 ppm NH 3Under the reaction conditions, the NO conversion rate at 250-360 °C is maintained at more than 90%. In the synergistic dust removal and denitrification test at 300 °C, the dust removal efficiency is maintained at more than 99%, and the denitrification efficiency can reach more than 95%.

[0022] Comparison of gas flux before and after loading of the SiC catalyst membrane prepared in this example Figure 1 ,It can be concluded from the figure that the gas flux loss of the SiC catalytic membrane prepared by the spraying method is much lower than that of the SiC catalytic membrane prepared by the vacuum impregnation method.

[0023] The NO conversion rate of the SiC catalytic film prepared in this example is compared with Figure 2 ,It can be concluded from the figure that the NO conversion rate of SiC catalytic membrane prepared by spraying method is not significantly lower than that of vacuum impregnation method.

[0024] The dust removal, denitrification and pressure drop of the SiC catalytic membrane prepared in this example at 300 °C are shown in the following figure: Figure 3 From the figure, it can be concluded that the NO conversion rate of the SiC catalytic membrane prepared by this method is stable at more than 95% under the reaction conditions of 300 ℃, and its dust removal rate is also stable at more than 99%. Example 2

[0025] A method for rapidly preparing a silicon carbide catalytic membrane with low flux loss, the specific steps are as follows: A. Place the SiC ceramic membrane tube in deionized water for ultrasonic cleaning for 30 minutes to remove impurities on the membrane surface, and dry it for later use; B. 1:1.4:60 molar ratio of cerium nitrate hexahydrate and phosphoric acid and deionized water were mixed, and then stirred at 600r / min for 4 h; C. Then, ammonia water was added to the solution obtained in step B to adjust the pH of the catalyst solution to 8, and the solution was stirred at 1000 r / min for 10 h to obtain a catalyst spray solution.

[0026] D. CePO prepared in step C 4 The catalyst spray liquid was sprayed on the membrane tube obtained in step A using a spraying method. The spraying conditions were: pressure of 0.7 MPa, nozzle diameter of 0.6 mm, spraying time of 10 min, spraying times of twice, followed by drying in a drying oven at 60 °C for 12 h and calcination at 600 °C for 2 h. Example 3

[0027] A method for rapidly preparing a silicon carbide catalytic membrane with low flux loss, the specific steps are as follows: A. Place the SiC ceramic membrane tube in deionized water for ultrasonic cleaning for 30 minutes to remove impurities on the membrane surface, and dry it for later use; B. 1:1.2:45 molar ratio of cerium nitrate hexahydrate and phosphoric acid and deionized water were mixed, and then stirred at 900r / min for 4h; C. Then, ammonia water was added to the solution obtained in step B to adjust the pH of the catalyst solution to 8, and the solution was stirred at 1000 r / min for 12 h to obtain a catalyst spray solution.

[0028] D. CePO prepared in step C 4 Catalyst spraying: The membrane tube obtained in step A was sprayed using a spraying method. The spraying conditions were: pressure of 1.0 MPa, nozzle diameter of 0.4 mm, spraying time of 8 min, spraying times of twice, followed by drying in a drying oven at 60°C for 12 h and calcination at 600°C for 5 h. Example 4

[0029] A method for rapidly preparing a silicon carbide catalytic membrane with low flux loss, the specific steps are as follows: A. Place the SiC ceramic membrane tube in deionized water for ultrasonic cleaning for 35 min to remove impurities on the membrane surface, and dry it for later use; B. 1:1.3:50 molar ratio of cerium nitrate hexahydrate and phosphoric acid and deionized water were mixed, and then stirred at 300r / min for 4h; C. Then, ammonia water was added to the solution obtained in step B to adjust the pH of the catalyst solution to 8, and the solution was stirred at 500 r / min for 12 h to obtain a catalyst spray solution.

[0030] D. CePO prepared in step C 4 Catalyst spraying: The membrane tube obtained in step A was sprayed using a spraying method. The spraying conditions were: pressure of 0.8 MPa, nozzle diameter of 0.4 mm, spraying time of 8 min, spraying times of twice, followed by drying in an 80°C oven for 12 h and calcination at 600°C for 5 h.

Claims

1. A method for rapidly preparing a silicon carbide catalytic membrane with low flux loss, characterized in that: The following steps are involved: A. Place the SiC ceramic membrane tube in deionized water for ultrasonic cleaning for a period of time to remove impurities on the membrane surface, and then place it in a drying oven for drying; B. slowly adding a certain amount of cerium nitrate hexahydrate and phosphoric acid to a certain amount of deionized water in sequence, and stirring at a certain speed for a certain period of time; C. Then, adding ammonia water to the solution obtained in step B to adjust the pH of the catalyst solution to 8, and stirring at a certain speed for a certain period of time to obtain a catalyst spray liquid; D. The catalyst spraying liquid prepared in step C is sprayed on the membrane tube obtained in step A under certain conditions, and then placed in a drying oven for drying, and then placed in a muffle furnace for calcination.

2. The method for rapidly preparing a silicon carbide catalytic membrane with low flux loss according to claim 1, characterized in that: The SiC ceramic membrane tube uses silicon carbide as a support body and silicon carbide as a membrane layer.

3. The method for rapidly preparing a silicon carbide catalytic membrane with low flux loss according to claim 1, characterized in that: In step B, the molar ratio of cerium nitrate hexahydrate to phosphoric acid and deionized water is 1:1:30-1:1.4:60; the rotation speed is 300-900 r / min, and the stirring time is 2-4 h.

4. The method for rapidly preparing a silicon carbide catalytic membrane with low flux loss according to claim 1, characterized in that: In step C, the rotation speed is 500-1000 r / min and the stirring time is 8-12 h.

5. The method for rapidly preparing a silicon carbide catalytic membrane with low flux loss according to claim 1, characterized in that: The spraying pressure in step D is 0.6~1.0 Mpa, the nozzle diameter is 0.4~0.8 mm, and the spraying time is 5~10 min; the drying oven temperature is 60~120°C, and the drying time is 12h; the calcination temperature is 400~600°C, and the calcination time is 2~5 h.

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