A reforming hydrogen production catalyst synthesized from waste vanadium-titanium denitration catalysts and its application

Abstract

The present invention discloses a method for synthesizing a reforming hydrogen production catalyst from waste vanadium-titanium denitration catalyst and its application. The preparation method of the catalyst is a two-step hydrothermal method. Through the first-step hydrothermal treatment, the waste vanadium-titanium denitration catalyst forms a nano-cubic structure, and then through the second-step hydrothermal treatment, the nano-cubic structure is transformed into a nano-polyhedron structure, while exposing more low-energy crystal planes and high-energy crystal planes. Finally, nickel oxide is loaded by an impregnation method. Since various intermediates are generated during the methanol reforming hydrogen production process, the nano-polyhedron structure containing various types of crystal planes can better meet the energy required for the transformation of each intermediate, effectively reduce the reaction activation energy, and improve the conversion rate and selectivity. The reforming hydrogen production catalyst disclosed by the present invention has excellent performance, common raw materials, and simple process, has high economic value and market application prospects, and can completely solve the problem of difficult treatment of waste vanadium-titanium denitration catalyst.

Description

Technical Field

[0001] The present invention discloses a method for synthesizing a reforming hydrogen production catalyst from waste vanadium-titanium denitration catalyst and its application, belonging to the fields of environmental protection catalysis and new energy. Background Art

[0002] With the rapid development of industrialization, a large amount of nitrogen oxides emissions have caused many air pollution problems such as acid rain, photochemical smog, and haze. The selective catalytic reduction (SCR) technology has been widely used in the denitration field. Now, about 140,000 tons of SCR denitration catalysts are discarded every year, and the converted volume can be as high as 250,000 cubic meters. The regeneration treatment or resource utilization of waste denitration catalysts has become a difficult problem to be solved urgently. Waste denitration catalysts can usually be regenerated 2 to 3 times, and then can only be completely scrapped, that is, catalyst regeneration is not actually the ultimate treatment method. On this basis, the high-value resource utilization of waste denitration catalysts is an urgent need.

[0003] In the prior art, Patent CN105709861B discloses a method for regenerating a deactivated SCR catalyst. First, the surface dust is removed by soot blowing, then the surface heavy metal elements are removed by an alkaline hydrothermal method, and finally the catalytic activity is restored to more than 90% by impregnating an active solution. Another example is the technical solution disclosed in Patent CN107952494B. The deactivated waste SCR catalyst realizes the recovery of denitration activity after surface purging, soaking in a cleaning solution, soaking in an active solution, and calcination. However, after being regenerated 1 to 2 times, the catalyst will be completely deactivated, and the disposal problem of waste denitration catalysts cannot be fundamentally solved. Moreover, the cleaning solution is usually an acidic or alkaline solution, which is likely to cause secondary environmental pollution. Patent CN105347785B uses raw materials such as silicon source powder, aluminum source powder, a calcination promoter, and a vanadium element solid solvent to be mixed with waste denitration catalysts to prepare a titanium-based ceramic. Patent CN110981199A discloses a method for preparing a composite opacifier for ceramics by mixing wollastonite, calcium carbonate, and a dispersant with a treated waste denitration catalyst as a raw material and grinding them. Although using waste denitration catalysts as ceramic raw materials can realize their harmless treatment, the added value is not high. Therefore, it is necessary to find a green and high-value treatment method. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for the high-value reuse of waste vanadium-titanium denitration catalysts in view of the current situation that a large number of waste vanadium-titanium denitration catalysts lack economical and safe treatment schemes. Another purpose of the present invention is to provide a method for preparing a reforming hydrogen production catalyst.

[0005] The object of the present invention can be achieved by the following technical solutions: The waste vanadium-titanium denitration catalyst is crushed and the alkali metals and alkaline earth metal elements are removed by acid leaching. Then, a nano-polyhedron microstructure is formed by a two-step hydrothermal method, and a variety of low-energy / high-energy crystal planes are exposed, meeting the activation energy requirements for the transformation of various intermediates in the methanol reforming for hydrogen production process, effectively improving the conversion rate, selectivity and reducing the reaction activation energy. Finally, the finished catalyst is formed by equal-volume impregnation and calcination treatment with nickel element.

[0006] A reforming hydrogen production catalyst synthesized from waste vanadium-titanium denitration catalyst, which uses the waste vanadium-titanium denitration catalyst as a carrier. First, the waste vanadium-titanium denitration catalyst is pretreated by a two-step hydrothermal method, and then nickel element is loaded by an impregnation method; based on the mass of the carrier, the mass percentage content of the active component is 5-10%.

[0007] The preparation method of this catalyst is as follows:

[0008] (1) Crush the waste vanadium-titanium denitration catalyst and screen out fine particles of 100-200 mesh. Disperse the obtained fine particles in hydrochloric acid solution to remove alkali metals and alkaline earth metal elements, and then wash, filter and dry.

[0009] (2) Disperse the catalyst treated in step (1) in a mixed solution of HCl and NaCl for hydrothermal treatment, and then filter, wash and dry.

[0010] (3) Disperse the catalyst treated in step (2) in a mixed solution of NaOH and NaCl for secondary hydrothermal treatment, filter, wash and dry for standby.

[0011] (4) Prepare a nickel element precursor solution, and perform equal-volume impregnation with the waste vanadium-titanium denitration catalyst obtained in step (3) and dry.

[0012] (5) Transfer the thoroughly dried catalyst intermediate to a muffle furnace and calcine in an air atmosphere to form the finished catalyst.

[0013] In the technical solution of the present invention: the waste vanadium-titanium denitration catalyst described in step (1) uses TiO2 as a carrier, V2O5 and WO3 as active components, and the rest are co-catalysts; among them, the TiO2 carrier accounts for 70%-85% of the content of the waste vanadium denitration catalyst, and the active components V2O5 and WO3 are 1%-4% and 1%-3% of the content of the waste vanadium denitration catalyst respectively.

[0014] In the technical solution of the present invention: the concentration of the hydrochloric acid solution used in step (1) is 10-15%, and the treatment time is 2-4 h.

[0015] In the technical solution of the present invention: in the mixed solution described in step (2), the concentration of NaCl is 0.5 - 0.8 M, and the concentration of HCl is 3 - 5 wt%; the mass ratio of the mixed solution to the fine particles of the waste vanadium-titanium denitration catalyst is 8 - 12:1.

[0016] In the technical solution of the present invention: in the hydrothermal treatment described in step (2), the temperature is 120 - 150 °C, and the hydrothermal time is 8 - 12 h.

[0017] In the technical solution of the present invention: in the mixed solution described in step (3), the concentration of NaCl is 0.5 - 0.8 M, and the pH value of the mixed solution is adjusted to 10 - 12 with NaOH; the mass ratio of the mixed solution to the fine particles of the waste vanadium-titanium denitration catalyst is 8 - 12:1.

[0018] In the technical solution of the present invention: in the hydrothermal treatment described in step (3), the temperature is 150 - 180 °C, and the hydrothermal time is 6 - 10 h.

[0019] In the technical solution of the present invention: the nickel element precursor described in step (4) is nickel nitrate.

[0020] In the technical solution of the present invention: the calcination temperature described in step (5) is 500 - 550 °C, the calcination time is 2 - 4 h, and the calcination environment is an air atmosphere.

[0021] In the technical solution of the present invention, the application of the catalyst in reforming for hydrogen production; preferably: the application temperature range of the reforming for hydrogen production catalyst is 300 - 500 °C.

[0022] Beneficial effects:

[0023] The present invention innovatively uses the waste vanadium-titanium denitration catalyst as a raw material to prepare a reforming for hydrogen production catalyst, which not only realizes the high-value reuse of the waste vanadium-titanium denitration catalyst, but also the synthesized reforming for hydrogen production catalyst can reach a high conversion rate and selectivity in the low-temperature range. The key of the present invention lies in the treatment of the waste vanadium-titanium denitration catalyst. Through two-step hydrothermal treatment, it presents a nano-polyhedron microscopic morphology. Compared with general nano-cube, spherical, sheet-like and other structures, the nano-polyhedron structure exposes more types of low-energy / high-energy crystal planes, which can meet the energy required for the transformation of various intermediate products (such as formic acid, formaldehyde, etc.) in the reforming for hydrogen production reaction process. It effectively improves the conversion rate and selectivity of the reaction and reduces the reaction activation energy. The catalyst preparation process is simple and the raw materials are common, with high economic value and market application prospects. Description of the drawings

[0024] Appendix Figure 1 Field emission scanning electron microscope (FE-SEM) image of Example 5;

[0025] Appendix Figure 2 FE-SEM image of Comparative Example 1;

[0026] Appendix Figure 3 FE-SEM image of Comparative Example 2;

[0027] Appendix Figure 4 Figure of methanol conversion rate in specific implementation manners;

[0028] Appendix Figure 5 Figure of hydrogen selectivity in specific implementation manners. Specific implementation manners

[0029] The following is a further illustration of a method for synthesizing a reforming hydrogen production catalyst from waste vanadium-titanium denitration catalyst according to the present invention through examples. The examples are implemented on the premise of the technical solution of the present invention, and detailed implementation manners and specific operation processes are given. However, the protection scope of the present invention is not limited to the following examples.

[0030] In the following examples, the experimental methods are all conventional methods in the art without special instructions, and the experimental devices and experimental raw materials can be commercially obtained without special instructions.

[0031] Catalyst performance evaluation: The performance of the catalyst was evaluated in a fixed-bed microreactor. 2 ml of the catalyst was mixed evenly with quartz sand and then transferred to the central position of the reaction tube. The catalyst was fixed with quartz wool above and below. The reaction gas (N2: 90 mL / min, H2O: 0.1 mL / min, CH3OH: 0.067 mL / min) was introduced, and the temperature was controlled at 300 - 500 °C, and it was allowed to stay stable for 30 min at every 50 °C. The product analysis was carried out by connecting a gas chromatograph behind the reaction tube.

[0032] Example 1

[0033] 10 g of fine particles with a particle size of 100 - 120 mesh were obtained by crushing and screening the waste vanadium-titanium denitration catalyst (TiO2 content 80%, V2O5 content 3%, WO3 content 2%). Then it was dispersed in 120 ml of 10% HCl solution, stirred for 2 h, and then filtered, washed and dried for standby. 100 ml of a mixed solution (NaCl concentration 0.5 M, mass fraction of HCl 5%) was prepared, and the fine particles of the waste vanadium-titanium denitration catalyst were dispersed in the mixed solution and hydrothermally treated at 140 °C for 10 h, and then filtered, washed and dried. 80 ml of 0.8 M NaCl solution was prepared and the pH value was adjusted to 11 with NaOH. The fine particles were dispersed in the solution and hydrothermally reacted at 180 °C for 8 h. After filtration, washing and drying, the reforming hydrogen production support was obtained. 0.311 g of Ni(NO3)2·6H2O was dissolved in 4.6 g of deionized water, and then the solution was fully mixed and impregnated with the support. After thorough drying, it was calcined at 500 °C for 2 h to obtain the finished catalyst.

[0034] Example 2

[0035] Crush and screen 10 g of fine particles with a mesh size of 120 - 140 from waste denitration catalyst (TiO₂ content 75%, V₂O₅ content 4%, WO₃ content 1%). Then disperse it in 100 ml of 12% HCl solution, stir for 3 h, then filter, wash and dry for later use. Prepare 120 ml of mixed solution (NaCl concentration 0.6 M, mass fraction of HCl 3%) and disperse the fine particles of waste vanadium-titanium denitration catalyst in the mixed solution, and hydrothermal react at 120 °C for 12 h, then filter, wash and dry. Prepare 100 ml of 0.6 M NaCl solution and adjust the pH value to 11 with NaOH, disperse the fine particles in the solution and hydrothermal react at 160 °C for 6 h. After filtering, washing and drying, a reforming hydrogen production carrier is obtained. Dissolve 0.389 g of Ni(NO₃)₂·6H₂O in 4.6 g of deionized water, then fully mix and impregnate the solution with the carrier. After thorough drying, calcine at 520 °C for 2 h to obtain the finished catalyst.

[0036] Example 3

[0037] Crush and screen 10 g of fine particles with a mesh size of 140 - 160 from waste denitration catalyst (TiO₂ content 70%, V₂O₅ content 1%, WO₃ content 3%). Then disperse it in 100 ml of 15% HCl solution, stir for 4 h, then filter, wash and dry for later use. Prepare 80 ml of mixed solution (NaCl concentration 0.7 M, mass fraction of HCl 4%) and disperse the fine particles of waste vanadium-titanium denitration catalyst in the mixed solution, and hydrothermal react at 130 °C for 8 h, then filter, wash and dry. Prepare 120 ml of 0.5 M NaCl solution and adjust the pH value to 10 with NaOH, disperse the fine particles in the solution and hydrothermal react at 170 °C for 9 h. After filtering, washing and drying, a reforming hydrogen production carrier is obtained. Dissolve 0.234 g of Ni(NO₃)₂·6H₂O in 4.6 g of deionized water, then fully mix and impregnate the solution with the carrier. After thorough drying, calcine at 550 °C for 4 h to obtain the finished catalyst.

[0038] Example 4

[0039] Crush and screen 10 g of fine particles with a mesh size of 160 - 180 from waste denitration catalyst (TiO₂ content: 85%, V₂O₅ content: 2%, WO₃ content: 1%). Then disperse them in 150 ml of 10% HCl solution, stir for 3 h, followed by suction filtration, washing, and drying for later use. Prepare 100 ml of a mixed solution (NaCl concentration: 0.8 M, mass fraction of HCl: 3%) and disperse the fine particles of waste vanadium-titanium denitration catalyst in the mixed solution, and hydrothermally react at 150 °C for 9 h. Then carry out suction filtration, washing, and drying. Prepare 80 ml of 0.7 M NaCl solution and adjust the pH value to 12 with NaOH. Disperse the fine particles in the solution and hydrothermally react at 150 °C for 7 h. After suction filtration, washing, and drying, a reforming hydrogen production support is obtained. Dissolve 0.195 g of Ni(NO₃)₂·6H₂O in 4.6 g of deionized water, and then fully mix and impregnate the solution with the support. After thorough drying, calcine at 530 °C for 3 h to obtain the finished catalyst.

[0040] Example 5

[0041] Crush and screen 10 g of fine particles with a mesh size of 180 - 200 from waste vanadium-titanium denitration catalyst (TiO₂ content: 80%, V₂O₅ content: 3%, WO₃ content: 2%). Then disperse them in 120 ml of 10% HCl solution, stir for 2 h, followed by suction filtration, washing, and drying for later use. Prepare 100 ml of a mixed solution (NaCl concentration: 0.5 M, mass fraction of HCl: 5%) and disperse the fine particles of waste vanadium-titanium denitration catalyst in the mixed solution, and hydrothermally react at 140 °C for 10 h. Then carry out suction filtration, washing, and drying. Prepare 80 ml of 0.8 M NaCl solution and adjust the pH value to 11 with NaOH. Disperse the fine particles in the solution and hydrothermally react at 180 °C for 8 h. After suction filtration, washing, and drying, a reforming hydrogen production support is obtained. Dissolve 0.311 g of Ni(NO₃)₂·6H₂O in 4.6 g of deionized water, and then fully mix and impregnate the solution with the support. After thorough drying, calcine at 500 °C for 2 h to obtain the finished catalyst.

[0042] Comparative Example 1

[0043] The waste vanadium-titanium denitration catalyst (TiO2 content: 80%, V2O5 content: 3%, WO3 content: 2%) was crushed and screened to obtain 10 g of fine particles with a mesh size of 100 - 120. Then it was dispersed in 120 ml of 10% HCl solution, stirred for 2 h, and then filtered, washed, and dried for standby. 100 ml of a mixed solution (NaCl concentration: 0.5 M, mass fraction of HCl: 5%) was prepared, and the fine particles of the waste vanadium-titanium denitration catalyst were dispersed in the mixed solution and hydrothermally treated at 140 °C for 10 h, and then filtered, washed, and dried. The fine particles were dispersed in 80 ml of deionized water and hydrothermally reacted at 180 °C for 8 h. After filtration, washing, and drying, a reforming hydrogen production carrier was obtained. 0.311 g of Ni(NO3)2·6H2O was dissolved in 4.6 g of deionized water, and then the solution was fully mixed and impregnated with the carrier. After thorough drying, it was calcined at 500 °C for 2 h to obtain the finished catalyst.

[0044] Comparison effect: The carrier of the waste vanadium-titanium denitration catalyst without the second hydrothermal treatment presented a microscopic morphology of a nano-cubic structure, and both the methanol conversion rate and the hydrogen selectivity decreased significantly.

[0045] Comparative Example 2

[0046] The waste vanadium-titanium denitration catalyst (TiO2 content: 80%, V2O5 content: 3%, WO3 content: 2%) was crushed and screened to obtain 10 g of fine particles with a mesh size of 180 - 200. Then it was dispersed in 120 ml of 10% HCl solution, stirred for 2 h, and then filtered, washed, and dried to obtain a reforming hydrogen production carrier. 0.311 g of Ni(NO3)2·6H2O was dissolved in 4.6 g of deionized water, and then the solution was fully mixed and impregnated with the carrier. After thorough drying, it was calcined at 500 °C for 2 h to obtain the finished catalyst.

[0047] Comparison effect: The waste vanadium-titanium denitration catalyst without hydrothermal treatment was directly used as the carrier, and both the methanol conversion rate and the hydrogen selectivity decreased significantly.

Claims

1. A reforming hydrogen production catalyst synthesized from waste vanadium-titanium denitration catalyst, characterized in that: The catalyst uses the waste vanadium-titanium denitration catalyst as the carrier. First, the waste vanadium-titanium denitration catalyst is pretreated by a two-step hydrothermal method, and then nickel element is loaded by an impregnation method. Based on the mass of the carrier, the mass percentage content of the active component is 5-10%. The preparation method of this catalyst is as follows: (1) Crush the waste vanadium-titanium denitration catalyst and screen out fine particles of 100-200 mesh. Disperse the obtained fine particles in hydrochloric acid solution to remove alkali metals and alkaline earth metal elements, and then wash, filter and dry. (2) Disperse the catalyst treated in step (1) in a mixed solution of HCl and NaCl for hydrothermal treatment, and then filter, wash and dry. (3) Disperse the catalyst treated in step (2) in a mixed solution of NaOH and NaCl for secondary hydrothermal treatment, filter, wash and dry for standby. (4) Prepare a nickel element precursor solution, perform equal-volume impregnation with the waste vanadium-titanium denitration catalyst obtained in step (3) and dry. (5) Transfer the thoroughly dried catalyst intermediate to a muffle furnace and calcine it in an air atmosphere to form the finished catalyst.

2. The reforming hydrogen production catalyst synthesized from waste vanadium-titanium denitration catalyst according to claim 1, wherein: The waste vanadium-titanium denitration catalyst described in step (1) uses TiO2 as the carrier, V2O5 and WO3 as the active components, and the rest are co-catalysts. Among them, the TiO2 carrier accounts for 70%-85% of the content of the waste vanadium denitration catalyst, and the active components V2O5 and WO3 are 1%-4% and 1%-3% of the content of the waste vanadium denitration catalyst respectively.

3. The reforming hydrogen production catalyst synthesized from waste vanadium-titanium denitration catalyst according to claim 1, wherein: The concentration of the hydrochloric acid solution used in step (1) is 10-15%, and the treatment time is 2-4 h.

4. The reforming hydrogen production catalyst synthesized from waste vanadium-titanium denitration catalyst according to claim 1, characterized in that: In the mixed solution described in step (2), the concentration of NaCl is 0.5-0.8 M, and the concentration of HCl is 3-5 wt%. The mass ratio of the mixed solution to the fine particles of the waste vanadium-titanium denitration catalyst is 8-12:

1.

5. The reforming hydrogen production catalyst synthesized from waste vanadium-titanium denitration catalyst according to claim 1, characterized in that: The temperature of the hydrothermal treatment described in step (2) is 120-150 °C, and the hydrothermal time is 8-12 h.

6. The reforming hydrogen production catalyst synthesized from waste vanadium-titanium denitration catalyst according to claim 1, characterized in that: In the mixed solution described in step (3), the concentration of NaCl is 0.5-0.8 M, and the pH value of the mixed solution is adjusted to 10-12 with NaOH. The mass ratio of the mixed solution to the fine particles of the waste vanadium-titanium denitration catalyst is 8-12:

1.

7. The reforming hydrogen production catalyst synthesized from waste vanadium-titanium denitration catalyst according to claim 1, characterized in that: The temperature of the hydrothermal treatment described in step (3) is 150-180 °C, and the hydrothermal time is 6-10 h.

8. The reforming hydrogen production catalyst synthesized from waste vanadium-titanium denitration catalyst according to claim 1, characterized in that: The nickel element precursor described in step (4) is nickel nitrate.

9. The reforming hydrogen production catalyst synthesized from waste vanadium-titanium denitration catalyst according to claim 1, characterized in that: The calcination temperature described in step (5) is 500-550 °C, the calcination time is 2-4 h, and the calcination environment is an air atmosphere.

10. Application of the catalyst according to claim 1 in reforming for hydrogen production.

11. The application according to claim 10, wherein The application temperature range of the reforming hydrogen production catalyst is 300-500 °C.

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