Catalyst for Co-Catalytic Purification of NOx and CVOCs, Preparation Method Thereof and Application

Abstract

The present invention discloses a catalyst for synergistically catalytically purifying NOx and CVOCs, a preparation method thereof and an application thereof. The catalyst comprises a carrier, a reduction active component and an oxidation active component. The carrier is a Ce-Ti composite oxide, the reduction active component is an oxide of vanadium and molybdenum; the oxidation active component is an oxide of niobium and phosphorus. The catalyst of the present invention has low cost, can synergistically remove NOx and CVOCs, and has good sulfur and water resistance stability.

Description

Technical Field

[0001] The present invention relates to the technical field of air pollution control, and particularly to a catalyst for synergistically catalytically purifying NOx and CVOCs, a preparation method thereof, and an application thereof. Background Art

[0002] In recent years, it has been found that the exhaust gases discharged from urban solid waste treatment plants, waste incineration plants, and cement plants simultaneously contain a certain content of NOx and CVOCs (chlorinated volatile organic compounds). NOx can combine with hemoglobin in human blood, reducing the oxygen-carrying capacity of human blood, causing harm to human health. Moreover, in the atmosphere, NOx can also form acid rain and photochemical smog with other pollutants in the atmosphere, posing a serious threat to the ecological environment. CVOCs generally have characteristics such as high toxicity, difficult degradation, and irritation, and also have the "three carcinogenic effects", which are extremely harmful to human health.

[0003] The selective catalytic reduction of NOx by ammonia (NH3-SCR) to eliminate NOx in flue gas is the current mainstream technology, which is widely used for denitrification in coal-fired flue gas and diesel vehicle exhaust. The main catalysts used are V-W(Mo) / T, which not only exhibits high denitrification activity but also has strong sulfur resistance stability. The catalytic combustion method is widely used in the treatment of VOCs tail gas due to its low energy consumption, high removal efficiency, and wide treatment concentration range. The main catalysts used are Pt and Pd-based noble metal catalysts. Among them, Ru-based catalysts have been proven to exhibit high activity, selectivity, and stability towards CVOCs.

[0004] Although there are relatively mature treatment technologies for NOx and CVOCs alone at present, the content of CVOCs in the exhaust gases discharged from urban solid waste treatment plants, waste incineration plants, and cement plants is relatively low. It is not economically reasonable to establish corresponding CVOCs treatment devices separately. Therefore, co-treating NOx and CVOCs in an NH3-SCR device is a feasible technical route. The core of this technology is to develop a catalyst that can efficiently co-treat NOx and CVOCs simultaneously.

[0005] Chinese Patent with Publication No. CN 111889101B discloses a composite oxide catalyst with a mullite structure, which can be represented by AMn2O5, where A represents other elements. This catalyst is suitable for the co-purification of NO and VOCs in industries such as iron and steel sintering, waste incineration, and vehicle exhaust. The catalyst exhibits the original high-temperature resistance of mullite. Although the catalyst shows certain catalytic activity towards NO and toluene, the activity of the catalyst still needs to be improved.

[0006] A Chinese patent with the publication number CN 113786828A discloses a catalyst for the synergistic removal of NOx and CVOCs. This catalyst uses cerium dioxide as the matrix, and vanadium and noble metals as active components, and is prepared by the sol-gel method. This catalyst has high activity for the reduction of NOx and the oxidation of chlorobenzene between 300 and 400 °C, and this catalyst exhibits a certain stability. The catalytic oxidation activity of the catalyst involved in this patent for chlorobenzene needs to be improved. Since the catalyst contains noble metals, the cost of the catalyst is relatively high, and a small amount of sulfides in the flue gas will cause sulfur poisoning of the noble metals, resulting in the inactivation of the catalyst in practical applications.

[0007] Therefore, the prior art has not disclosed a highly efficient catalyst with low cost, good sulfur and water resistance stability, and the ability to synergistically remove NOx and CVOCs.

[0008] Based on the deficiencies of existing catalysts, the present invention provides a highly efficient catalyst that can synergistically remove NOx and CVOCs, and the catalyst has good... Summary of the Invention

[0009] The present invention provides a catalyst for the synergistic catalytic purification of NOx and CVOCs and its preparation method. This catalyst has low cost, can synergistically remove NOx and CVOCs, and has good sulfur and water resistance stability.

[0010] The technical solution of the present invention is as follows:

[0011] A catalyst for the synergistic catalytic purification of NOx and CVOCs, comprising a carrier, a reduction active component, and an oxidation active component. The carrier is a Ce-Ti composite oxide, the reduction active component is an oxide of vanadium and molybdenum; the oxidation active component is an oxide of niobium and phosphorus.

[0012] Preferably, in the Ce-Ti composite oxide carrier, the molar ratio of Ce to Ti is 0.2 to 1:1.

[0013] In the Ce-Ti composite oxide, the molar ratio of Ce to Ti has a certain influence on the oxidizing property of the catalyst, thereby affecting the conversion rate of CVOCs. When the molar ratio of Ce to Ti is 0.2 to 1:1, the catalyst has a relatively high conversion rate for CVOCs.

[0014] In the catalyst, the contents of vanadium and molybdenum will affect the conversion rate of NOx. Niobium will increase the oxidizing property of the catalyst, mainly affecting the conversion rate of CVOCs. Phosphorus will improve the sulfur and chlorine resistance stability of the catalyst to a certain extent.

[0015] Preferably, in the catalyst for co-catalytic purification of NOx and CVOCs, the vanadium content is 1-5 wt%; the molybdenum content is 5-10 wt%; the niobium content is 2-10 wt%; and the phosphorus content is 1-5 wt%. The catalyst of this technical solution has a high conversion rate of NOx and CVOCs, as well as good sulfur and chlorine resistance stability.

[0016] The present invention also provides a preparation method of the catalyst for co-catalytic purification of NOx and CVOCs, comprising the following steps:

[0017] (1) Synthesize a Ce-Ti composite oxide support by a hydrothermal method;

[0018] (2) Load the reduction active components for reducing NOx onto the Ce-Ti composite oxide support by an impregnation method to obtain a V-Mo / Ce-Ti composite oxide;

[0019] (3) Load the oxidation active components for oxidizing CVOCs onto the V-Mo / Ce-Ti composite oxide by an impregnation method to obtain the catalyst for co-catalytic purification of NOx and CVOCs.

[0020] Preferably, step (1) includes: weighing Ce, Ti precursors and a precipitant, adding them to deionized water, then adding a surfactant, stirring, crystallizing at 100-200 °C, and then obtaining the Ce-Ti composite oxide support through filtration, washing, drying, and calcination.

[0021] The precipitant can be urea, sodium carbonate, ammonia water, sodium hydroxide, etc.

[0022] The Ce and Ti precursors are nitrates or chlorides.

[0023] The surfactant is one or more of cetyltrimethylammonium bromide, sodium hexadecylbenzenesulfonate, and polyvinylpyrrolidone.

[0024] Preferably, step (2) includes: adding the Ce-Ti composite oxide support to the precursor solution of vanadium and molybdenum, stirring, and then obtaining the V-Mo / Ce-Ti composite oxide through filtration, washing, drying, and calcination.

[0025] Preferably, step (3) includes: adding the V-Mo / Ce-Ti composite oxide to the precursor solution of niobium and phosphorus, stirring, and then obtaining the catalyst for co-catalytic purification of NOx and CVOCs through filtration, washing, drying, and calcination.

[0026] In steps (1)-(3), the drying temperature is 100-120 °C, the drying time is 5-ip="">

[0027] The present invention also provides the application of the described catalyst in the co-catalytic purification of NOx and CVOCs in industrial waste gas.

[0028] The described application includes: placing the described catalyst in the tail gas pipeline after dust removal, injecting a reducing agent upstream of the catalyst to mix with the tail gas; the space velocity of the catalytic removal reaction gas is 20,000 - 30,000 ml / (g·h);

[0029] The tail gas is a gas containing NOx and CVOCs discharged from a stationary source or a mobile source.

[0030] Preferably, the reducing agent is ammonia, and the dosage of the reducing agent is 1.0 - 1.2 times that of NOx in the tail gas.

[0031] Preferably, the active temperature range of the catalyst for co-catalytic purification of NOx and CVOCs is 300 - 400 °C.

[0032] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0033] (1) The catalyst of the present invention shows high activity, strong water resistance and sulfur resistance stability in the co-purification of NOx and CVOCs. The catalyst does not use precious metals and has a relatively low overall cost.

[0034] (2) The preparation method of the catalyst is simple, the raw materials are inexpensive, and it is easy to prepare on a large scale, having certain industrial application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a catalytic activity data graph of the catalyst prepared in Comparative Example 1;

[0036] Figure 2 It is a catalytic activity data graph of the catalyst prepared in Example 1;

[0037] Figure 3 It is a catalytic activity data graph of the catalyst prepared in Example 2;

[0038] Figure 4 It is a stability data graph of the catalyst prepared in Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0039] The present invention will be further described in detail below with reference to the drawings and examples. It should be noted that the following examples are only for facilitating the understanding of the present invention and do not limit it in any way.

[0040] Example 1

[0041] Weigh 4.34 g of Ce(NO3)3·6H2O and 3.78 g of TiCl4 and dissolve them in 50 ml of deionized water. Add 3.52 g of urea to the solution. After stirring for 60 min, transfer the solution to a crystallization kettle and crystallize it at 150 °C for 4 h. After filtration, washing, drying, and calcination, a CeO2-TiO2 support is obtained.

[0042] Weigh 0.36 g of vanadium nitrate and 0.40 g of molybdenum chloride and dissolve them in 10 ml of deionized water. Add 2 g of the above composite support to the solution. After stirring for 4 h, after filtration, washing, drying, and calcination, a composite oxide is obtained.

[0043] Weigh 0.45 g of niobium nitrate and 0.25 g of trimethyl phosphate in 10 ml of deionized water. Add 2 g of the above composite oxide to the solution. After stirring for 4 h, after filtration, washing, drying, and calcination, a catalyst is obtained.

[0044] Among them, the drying temperature during the catalyst synthesis process is 100 °C, and the drying time is 6 h. The calcination temperature is 500 °C, and the calcination time is 4 h.

[0045] Example 2

[0046] Weigh 4.34 g of Ce(NO3)3·6H2O and 3.78 g of TiCl4 and dissolve them in 50 ml of deionized water. Add 3.52 g of urea to the solution. After stirring for 60 min, transfer the solution to a crystallization kettle and crystallize it at 150 °C for 4 h. After filtration, washing, drying, and calcination, a CeO2-TiO2 support is obtained.

[0047] Weigh 0.36 g of vanadium nitrate and 0.40 g of molybdenum chloride and dissolve them in 10 ml of deionized water. Add 2 g of the above composite support to the solution. After stirring for 4 h, after filtration, washing, drying, and calcination, a composite oxide is obtained.

[0048] Weigh 0.90 g of niobium nitrate and 0.25 g of trimethyl phosphate in 10 ml of deionized water. Add 2 g of the above composite oxide to the solution. After stirring for 4 h, after filtration, washing, drying, and calcination, a catalyst is obtained.

[0049] Among them, the drying temperature during the catalyst synthesis process is 100 °C, and the drying time is 6 h. The calcination temperature is 500 °C, and the calcination time is 4 h.

[0050] Comparative Example 1

[0051] Weigh 3.78 g of TiCl4 and dissolve it in 50 ml of deionized water. Add 3.52 g of urea to the solution. After stirring for 60 min, transfer the solution to a crystallization kettle and crystallize it at 150 °C for 4 h. After filtration, washing, drying, and calcination, a TiO2 support is obtained. Weigh 0.36 g of vanadium nitrate and 0.40 g of molybdenum chloride, dissolve them in 10 ml of deionized water, add 2 g of the above support to the solution, stir for 4 h, and then obtain the V-Mo / Ti catalyst after filtration, washing, drying, and calcination.

[0052] Catalyst activity evaluation

[0053] Weigh 200 mg of the catalysts prepared in Example 1, Example 2, and Comparative Example 1 respectively and put them into a fixed-bed reactor. Pass in a gas mixture with a NO concentration of 600 ppm, an NH3 concentration of 600 ppm, a chlorobenzene concentration of 100 ppm, an O2 volume concentration of 5%, and the rest being nitrogen, with a total gas flow rate of 400 ml / min.

[0054] Use a gas chromatograph to measure chlorobenzene, CO, and CO2. Use an infrared flue gas analyzer to measure the concentrations of NOx, NO, NO2, and O2. Calculate the conversion rates of the corresponding substances based on the changes in the net outlet concentrations. Start heating from 150 °C to 450 °C, measure the outlet concentration every 25 °C, and maintain each temperature measurement point for 30 min.

[0055] The conversion rate calculation formula is:

[0056] Figure 1 and Figure 2 It shows that after doping Ti in the support and loading niobium and manganese, the catalytic activity of the catalyst for chlorobenzene is significantly improved, and the temperature range where the NO conversion rate is above 90% also becomes wider. Comparing Figure 2 and Figure 3 It can be seen that increasing the loading amount of niobium can further improve the conversion of chlorine by the catalyst.

[0057] Catalyst stability evaluation

[0058] Weigh 200 mg of the catalysts prepared in Example 1, Example 2, and Comparative Example 1 respectively and put them into a fixed-bed reactor. Pass in a gas mixture with a NO concentration of 600 ppm, an NH3 concentration of 600 ppm, a chlorobenzene concentration of 100 ppm, an SO2 concentration of 30 ppm, a water vapor volume concentration of 5%, an O2 volume concentration of 5%, and the rest being nitrogen, with a total gas flow rate of 400 ml / min.

[0059] Use a gas chromatograph to measure chlorobenzene, CO, and CO2. Use an infrared flue gas analyzer to measure the concentrations of NOx, NO, NO2, and O2. Under the condition of 350 °C, continuously react for 100 h, and calculate the conversion rates and selectivities of the corresponding substances based on the changes in the net outlet concentrations.

[0060] The stability evaluation results of the catalyst prepared in Example 1 are as follows Figure 4 shown.

[0061] It can be found from Figure 4 that during the 100-hour reaction cycle, the catalytic activities of the catalyst for NO and chlorobenzene basically remained stable without obvious deactivation.

[0062] The above-described embodiments have elaborated on the technical solutions and beneficial effects of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, supplements, equivalent replacements, etc. made within the principle scope of the present invention shall be included within the protection scope of the present invention.

Claims

1. Application of a catalyst in co-catalytic purification of NOx and CVOCs in industrial waste gas, characterized in that, Place the described catalyst in the tail gas pipeline after dust removal, and inject a reducing agent upstream of the catalyst to mix with the tail gas; the tail gas is a gas containing NOx and CVOCs discharged from a stationary source or a mobile source; the reducing agent is ammonia; the catalytic reaction temperature is 350 - 400 °C; The described catalyst includes a carrier, a reduction active component, and an oxidation active component. The carrier is a Ce-Ti composite oxide, and the reduction active component is an oxide of vanadium and molybdenum; the oxidation active component is an oxide of niobium and phosphorus; The content of vanadium is 1 - 5 wt%; the content of molybdenum is 5 - 10 wt%; the content of niobium is 2 - 10 wt%; the content of phosphorus is 1 - 5 wt%; In the Ce-Ti composite oxide carrier, the molar ratio of Ce to Ti is 0.2 - 1:

1.

2. The application according to claim 1, characterized in that The preparation method of the described catalyst includes the following steps: (1) Synthesize the Ce-Ti composite oxide carrier by the hydrothermal method; (2) Use the impregnation method to load the reduction active component for reducing NOx onto the Ce-Ti composite oxide carrier to obtain V-Mo / Ce-Ti composite oxide; (3) Use the impregnation method to load the oxidation active component for oxidizing CVOCs onto the V-Mo / Ce-Ti composite oxide to obtain the catalyst for synergistically catalytically purifying NOx and CVOCs.

3. The application according to claim 2, wherein Step (1) includes: Weigh the Ce, Ti precursors and a precipitating agent, add them to deionized water, then add a surfactant, stir and crystallize at 100 - 200 °C, and then obtain the Ce-Ti composite oxide carrier after filtration, washing, drying, and calcination.

4. The application according to claim 2, characterized in that, Step (2) includes: Add the Ce-Ti composite oxide carrier to the precursor solution of vanadium and molybdenum, stir and then obtain the V-Mo / Ce-Ti composite oxide after filtration, washing, drying, and calcination.

5. The application according to claim 2, characterized in that, Step (3) includes: Add the V-Mo / Ce-Ti composite oxide to the precursor solution of niobium and phosphorus, stir and then obtain the catalyst for synergistically catalytically purifying NOx and CVOCs after filtration, washing, drying, and calcination.

6. The application according to any one of claims 2-5, characterized in that, In steps (1) - (3), the drying temperature is 100 - 120 °C, and the drying time is 5 - 10 h; the calcination temperature is 450 - 550 °C, and the calcination time is 3 - 5 h.

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