Catalytic combustion catalyst for treating CVOCs as well as preparation method and application of catalytic combustion catalyst

Abstract

The invention discloses a catalytic combustion catalyst for treating CVOCs (Chemical Volatile Organic Compounds) as well as a preparation method and application of the catalytic combustion catalyst. The preparation method comprises the following steps: (1) impregnating and loading cerous nitrate and trimethyl phosphate on a carrier, drying, and roasting at 600-800 DEG C to form a modified carrier containing a cerous phosphate crystal phase; and (2) impregnating and loading active metal ruthenium on the modified carrier, drying and roasting to obtain the catalyst for treating catalytic combustion of the CVOCs. The catalyst provided by the invention can be used for catalytic combustion degradation of CVOCs such as dichloromethane, chlorobenzene, chloroethylene, dichloroethane, dichloroethylene, oxychloropropane and the like. For catalytic combustion degradation of CVOCs, the catalyst disclosed by the invention can show high activity, high chlorine-resistant stability, low polychlorinated by-product selectivity and thermal stability, and has certain industrial application prospects.

Description

Technical Field

[0001] The present invention relates to the technical field of industrial waste gas treatment, and in particular to a chlorine-containing VOCs catalytic combustion catalyst with high activity, resistance to chlorine poisoning and high temperature stability, and a preparation method and application thereof. Background Art

[0002] Chlorinated volatile organic compounds (CVOCs) have excellent solubility and reaction inertness and are widely used in the pharmaceutical, chemical, resin, petroleum, coating, electronics and other industries. At the same time, due to the strong electronegativity of the Cl element in CVOCs, it is difficult to be degraded in nature, has high toxicity, and is easily accumulated in organisms. Emission into the atmosphere causes serious harm to the ecological environment and human health.

[0003] Since CVOCs are not completely replaceable in production, the emission of CVOCs in the production process is unavoidable. The only feasible way is to eliminate CVOCs by back-end treatment.

[0004] Among the many CVOCs treatment technologies, catalytic combustion has the advantages of low operating temperature, high efficiency, wide application range, and no secondary pollution. It is the most efficient treatment technology with large-scale application. The development of highly active, chlorine-resistant and highly stable catalysts is the key to the industrial application of this technology.

[0005] Chinese patent CN110302773B discloses a catalyst for catalytic combustion of chlorinated volatile organic compounds, its preparation method and application, wherein cerium oxide is loaded on a fly ash-based zeolite modified with titanium dioxide. The preparation cost is low, the preparation process is simple, the resistance to chlorine poisoning is strong, and the chlorinated VOCs can be removed efficiently and stably.

[0006] Chinese patent CN110624549B discloses a catalyst for treating CVOC by catalytic combustion and a preparation method thereof. The catalyst uses acid salts of transition metals as raw materials and is obtained by precipitation method and high-temperature activation with hydrogen. The catalyst has the characteristics of simple preparation process, low cost, easy control of preparation conditions and synthesis.

[0007] The catalysts mentioned in the above patent documents show certain activity and stability for chlorinated VOCs, but actual industrial applications have higher requirements for the catalyst's low-temperature activity, resistance to chlorine poisoning, product selectivity, and high-temperature stability. Therefore, it is necessary to develop catalysts with higher activity, high stability, high product selectivity, and high thermal stability for the catalytic degradation of chlorinated VOCs. Summary of the invention

[0008] In view of the above technical problems and the deficiencies in the art, the present invention provides a catalyst for treating catalytic combustion of CVOCs, and a preparation method and application thereof.

[0009] The catalyst of the present invention uses an impregnation method to load cerium nitrate and trimethyl phosphate onto a carrier, and forms a desired cerium phosphate crystal phase through medium-high temperature calcination at a specific temperature; and then loads the noble metal ruthenium onto the modified carrier by impregnation (e.g., equal volume impregnation, etc.). The cerium phosphate formed by the method of the present invention has strong chemical stability, will not be chlorinated during the reaction process, and improves the stability of the catalyst against chlorine poisoning. At the same time, the strong acidity can inhibit the adsorption of inorganic chlorine on the catalyst surface during the reaction process, thereby avoiding chlorine poisoning of the catalyst. In addition, after the noble metal ruthenium is loaded onto the cerium phosphate formed by the method of the present invention, a strong metal-carrier interaction can be generated, the noble metal can prevent particle aggregation under high temperature conditions, and the catalyst has high thermal stability.

[0010] The catalyst involved in the present invention can show high activity, high selectivity, high chlorine resistance and high temperature stability to common chlorine-containing VOCs such as dichloromethane, chlorobenzene, vinyl chloride, dichloroethane, dichloroethylene, oxychloropropane, etc., and has certain industrial application prospects.

[0011] The specific technical solutions are as follows:

[0012] [1] A method for preparing a catalyst for treating CVOCs for catalytic combustion, comprising the steps of:

[0013] (1) impregnating cerium nitrate and trimethyl phosphate onto a carrier, drying, and calcining at 600 to 800° C. (e.g., 650° C.) to form a modified carrier containing a cerium phosphate crystal phase;

[0014] (2) Active metal ruthenium is impregnated and loaded onto the modified carrier, and then dried and calcined to obtain the catalyst for treating catalytic combustion of CVOCs.

[0015] The preparation method of the present invention adopts a two-step impregnation loading method, firstly impregnating and loading cerium nitrate and trimethyl phosphate and calcining at 600-800°C to form a modified carrier containing the desired cerium phosphate crystal phase, and then impregnating and loading active metal ruthenium on the modified carrier and calcining to obtain a catalyst product. This two-step impregnation loading method can, on the one hand, make the cerium phosphate highly dispersed, and can obtain the desired cerium phosphate crystal phase structure by regulating the calcination temperature, and on the other hand, can make the active metal ruthenium loaded on the cerium phosphate crystal phase that is already uniformly distributed on the surface of the carrier as much as possible, strengthen the interaction between the active metal ruthenium and the cerium phosphate crystal phase, and has many advantages and progress compared with directly impregnating and loading cerium phosphate and ruthenium in one step at the same time.

[0016] In step (1), the carrier can be placed in a deionized water solution of cerium nitrate and trimethyl phosphate, and stirred, dried, and calcined to form a modified carrier containing a cerium phosphate crystal phase.

[0017] In step (1), the molar ratio of Ce in cerium nitrate to P in trimethyl phosphate is preferably 1:0.25 to 1, and more preferably 1:0.5 to 1. This makes it easier to form the cerium phosphate phase required by the present invention, and a slight excess of cerium can ensure that P is present in the cerium phosphate phase required by the present invention. If P exists in other forms, it will inhibit the activity of the catalyst. In addition, cerium oxide formed by excess cerium can also provide certain catalytic activity, but since cerium oxide is unstable at high temperatures, cerium should not be excessive in large quantities.

[0018] In step (1), the carrier may include at least one of aluminum oxide (such as γ-Al2O3, etc.), silicon oxide, cerium-zirconium solid solution, and magnesium-aluminum spinel. Further, based on the total molar number of cerium and zirconium in the cerium-zirconium solid solution as 100%, the molar fraction of zirconium in the cerium-zirconium solid solution may account for 25% to 35%, preferably 30%, and the molar fraction of cerium may account for 65% to 75%, preferably 70%.

[0019] In step (1), the mass ratio of Ce in cerium nitrate to the carrier is preferably 5 to 20:100, and further can be 5 to 10:100, which is beneficial to improving the catalyst activity and maintaining a high specific surface area of ​​the catalyst. Excessive Ce loading will reduce the specific surface area of ​​the catalyst, resulting in decreased catalyst activity.

[0020] In a preferred example, the mass ratio of Ce in cerium nitrate to the carrier is 10:100, and the molar ratio of Ce in cerium nitrate to P in trimethyl phosphate is 1:0.5. Under these conditions, the catalyst obtained has the best performance in treating CVOCs catalytic combustion.

[0021] In step (1), the calcination time may be 3.5 to 4.5 hours, for example 4 hours.

[0022] In step (2), the active metal ruthenium can be impregnated and loaded onto the modified carrier by an equal volume impregnation method.

[0023] In step (2), at least one of ruthenium chloride and ruthenium nitrate can be used as an impregnation precursor for impregnation.

[0024] In step (2), the mass ratio of the impregnated active metal ruthenium to the modified support may be 0.5 to 5:100, for example, 1:100, 1.5:100, etc.

[0025] In step (2), the calcination temperature may be 440-460°C, such as 450°C.

[0026] In step (2), the calcination holding time is 3.5 to 4.5 hours, for example, 4 hours.

[0027] In step (2), the heating rate of the calcination may be 1 to 10°C / min, for example, 5°C / min.

[0028] [2] A catalyst for treating catalytic combustion of CVOCs prepared according to the preparation method described in [1].

[0029] [3] Use of the catalyst described in [2] in the catalytic combustion of CVOCs.

[0030] [4] A method for treating CVOCs for catalytic combustion using the catalyst described in [2].

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] The catalyst of the present invention can be used for the catalytic combustion degradation of CVOCs such as dichloromethane, chlorobenzene, vinyl chloride, dichloroethane, dichloroethylene, oxychloropropane, etc. For the catalytic combustion degradation of CVOCs, the catalyst of the present invention can show high activity, high anti-chlorine stability, low polychlorinated byproduct selectivity and thermal stability, and has certain industrial application prospects. DETAILED DESCRIPTION

[0033] The present invention is further described below in conjunction with specific examples. It should be understood that these examples are only used to illustrate the present invention and are not used to limit the scope of the present invention. The operating methods in the following examples that do not specify specific conditions are usually carried out under conventional conditions or under conditions recommended by the manufacturer. Unless otherwise specified, the materials used in the following examples can be obtained commercially or in accordance with the prior art. In the following examples, the cerium-zirconium solid solution used is a commercially available product, in which the molar proportion of zirconium oxide is 30% and the molar proportion of cerium oxide is 70%.

[0034] Embodiment 1:

[0035] 1) Weigh 1.55g of cerium nitrate hexahydrate and 0.5g of trimethyl phosphate and dissolve them in a beaker containing 50g of deionized water. After stirring for 30 minutes, pour 10g of γ-Al2O3 into the above solution and continue stirring for 1 hour. Then put the beaker into an 85℃ water bath, heat while stirring for 3 hours, and then put it into an oven and dry it at 120℃ for 6 hours. Finally, calcine in a muffle furnace at 650℃ for 4 hours to obtain the modified carrier. The room temperature rate of the muffle furnace is 5℃ / min.

[0036] 2) Weigh 0.5 g of ruthenium nitrate solution with a ruthenium concentration of 10 wt% and dissolve it in 2 g of deionized water, weigh 5 g of the modified carrier, and drip the solution onto the surface of the modified carrier while stirring until the solution is dripped. Then, after standing for 6 hours, dry it at 120°C for 6 hours. Finally, calcine it at 450°C for 4 hours to obtain the catalyst.

[0037] Embodiment 2:

[0038] The only difference from Example 1 is that 10 g of magnesium aluminum spinel is used to replace 10 g of γ-Al2O3, and the rest is the same to obtain a catalyst.

[0039] Embodiment 3:

[0040] The only difference from Example 1 is that 10 g of cerium-zirconium solid solution is used to replace 10 g of γ-Al2O3, and the rest is the same to obtain a catalyst.

[0041] Embodiment 4:

[0042] The only difference from Example 3 is that the amount of cerium nitrate hexahydrate is changed to 3.10 g, and the rest is the same to obtain a catalyst.

[0043] Embodiment 5:

[0044] The only difference from Example 4 is that the amount of trimethyl phosphate is changed to 1.0 g, and the rest is the same to obtain a catalyst.

[0045] Embodiment 6:

[0046] The only difference from Example 5 is that the amount of ruthenium nitrate solution is changed to 0.75 g, and the rest is the same to obtain a catalyst.

[0047] Comparative Example 1:

[0048] Weigh 0.5g of ruthenium nitrate solution with a ruthenium concentration of 10wt% and dissolve it in 2g of deionized water, weigh 5g of γ-Al2O3 carrier, and drip the solution onto the surface of the carrier, stirring while dripping until the solution is dripped. Then, after leaving it for 6h, dry it at 120℃ for 6h. Finally, calcine it at 450℃ for 4h to obtain the catalyst.

[0049] Comparative Example 2:

[0050] The only difference from Comparative Example 1 is that the carrier is changed to 5 g of cerium-zirconium solid solution, and the rest is the same to obtain a catalyst.

[0051] Comparative Example 3:

[0052] The only difference from Example 3 is that the calcination temperature in 1) is changed from 650° C. to 400° C., and the rest is the same to obtain a catalyst.

[0053] Evaluation of powder catalyst activity:

[0054] The catalysts involved in Examples 1 to 6 and Comparative Examples 1 to 3 were evaluated for their catalytic combustion activity on dichloromethane in a fixed bed reactor. 200 mg of 40-60 mesh powder catalyst (cat) was weighed into a fixed bed reactor, and 44.4 mL / min of air and 22.2 mL / min of dichloromethane (3000 mg / m) were introduced into the reactor. 3 The concentration of dichloromethane in the reactor is 1000 mg / m 3 , the total mass space velocity is 20000mL / (h·g cat). The concentration of dichloromethane is tested by gas chromatography. The concentration of dichloromethane in the tail gas of the reactor under different temperature conditions is measured by programmed temperature rise, the conversion rate of dichloromethane is calculated, and the temperature at which the conversion rate of dichloromethane is 90% is recorded, which are respectively recorded as T 90 . At the same time test T 90 .

[0055] The evaluation results of the catalyst are shown in Table 1.

[0056] Table 1

[0057] catalyst <![CDATA[T 90 (℃)]]> Example 1 270.6 Example 2 272.4 Example 3 268.6 Example 4 265.1 Example 5 268.3 Example 6 260.2 Comparative Example 1 362.5 Comparative Example 2 332.6 Comparative Example 3 322.6

[0058] Selectivity of polychlorinated by-products:

[0059] According to the above-mentioned activity evaluation experimental conditions, the selectivity of the catalysts involved in Examples 1 to 6 and Comparative Examples 1 to 3 to polychlorinated byproducts was tested at 300° C. The selectivity results are shown in Table 2 below.

[0060] Table 2

[0061] catalyst Selectivity of polychlorinated byproducts (%) Example 1 ≤0.1 Example 2 ≤0.1 Example 3 ≤0.1 Example 4 ≤0.1 Example 5 ≤0.1 Example 6 ≤0.1 Comparative Example 1 6.0 Comparative Example 2 5.4 Comparative Example 3 3.6

[0062] Catalyst thermal stability test:

[0063] The powder catalysts involved in Examples 1 to 6 and Comparative Examples 1 to 3 were respectively placed in a muffle furnace and aged for 10 hours at 700°C, and then taken out, and the catalytic activity of the catalysts to dichloromethane was evaluated under the same conditions as the above activity evaluation. The catalyst activity after high temperature treatment is shown in Table 3.

[0064] Table 3

[0065] catalyst <![CDATA[T 90 (℃)]]> Example 1 273.6 Example 2 275.4 Example 3 272.6 Example 4 268.1 Example 5 273.3 Example 6 266.2 Comparative Example 1 410.5 Comparative Example 2 376.5 Comparative Example 3 362.5

[0066] Catalyst stability test:

[0067] Weigh 200 mg of the powder catalyst of Example 1 in a fixed bed reactor, and introduce 44.4 mL / min of air and 22.2 mL / min of dichloromethane (3000 mg / m 3 The concentration of dichloromethane in the reactor is 1000 mg / m 3 , the total mass space velocity was 20000 ml / (h·g cat). The reaction was continued at 280°C for 100 h. The catalyst activity at different reaction times was recorded, and the corresponding results are shown in Table 4.

[0068] Table 4

[0069] Reaction time (h) Dichloromethane conversion rate (%) 20 95.3 40 95.2 60 95.2 80 95.1 100 95.2 120 95.1 140 95.0 160 95.2 180 95.1 200 95.1

[0070] It can be found from Table 1 and Table 2 that the catalysts in the embodiments of the present invention show higher activity than the comparative examples. At the same time, the catalysts of the present invention are significantly better than the comparative examples in inhibiting more toxic polychlorinated byproducts due to the generation of the desired cerium phosphate crystal phase.

[0071] It can be found from Table 3 that the catalyst activity of the catalyst involved in the present invention is basically not reduced after high-temperature aging at 700° C., while the activity of the comparative example is significantly reduced.

[0072] The data in Table 4 show that the catalyst exhibits high stability during the continuous reaction at 280°C for 200 h.

[0073] In addition, it should be understood that after reading the above description of the present invention, those skilled in the art may make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the claims attached to this application.

Claims

1. A method for preparing a catalyst for treating CVOCs catalytic combustion, characterized in that: Includes steps: (1) impregnating cerium nitrate and trimethyl phosphate onto a carrier, drying, and calcining at 600-800° C. to form a modified carrier containing a cerium phosphate crystal phase; (2) Active metal ruthenium is impregnated and loaded onto the modified carrier, and then dried and calcined to obtain the catalyst for treating catalytic combustion of CVOCs.

2. The preparation method according to claim 1, characterized in that: In step (1), the molar ratio of Ce in cerium nitrate to P in trimethyl phosphate is 1:0.25-1, further 1:0.5-1; In step (1), the heat preservation time of the calcination is 3.5 to 4.5 hours, and the heating rate of the calcination is 1 to 10°C / min.

3. The preparation method according to claim 1, characterized in that: In step (1), the carrier comprises at least one of aluminum oxide, silicon oxide, cerium-zirconium solid solution, and magnesium-aluminum spinel; Furthermore, taking the total molar number of cerium and zirconium in the cerium-zirconium solid solution as 100%, the molar fraction of zirconium in the cerium-zirconium solid solution is 25% to 35%, preferably 30%, and the molar fraction of cerium is 65% to 75%, preferably 70%.

4. The preparation method according to claim 1, characterized in that: In step (1), the mass ratio of Ce in cerium nitrate to the carrier is 5 to 20:100, further 5 to 10:

100.

5. The preparation method according to claim 1, characterized in that: In step (2), the active metal ruthenium is impregnated and loaded onto the modified carrier by an equal volume impregnation method, wherein at least one of ruthenium chloride and ruthenium nitrate is used as an impregnation precursor.

6. The preparation method according to claim 1, characterized in that: In step (2), the mass ratio of the impregnated active metal ruthenium to the modified carrier is 0.5 to 5:

100.

7. The preparation method according to claim 1, characterized in that: In step (2), the calcination temperature is 440-460° C., and the calcination time is 3.5-4.5 hours.

8. A catalyst for treating catalytic combustion of CVOCs prepared according to the preparation method according to any one of claims 1 to 7.

9. Use of the catalyst according to claim 8 in treating catalytic combustion of CVOCs.

10. A method for treating CVOCs for catalytic combustion using the catalyst according to claim 8.