A crystal face catalyst for removing chlorobenzene from organic solid waste pyrolysis gasification gas and a preparation method thereof

Abstract

This invention discloses a crystal-faceted catalyst and its preparation method for removing chlorobenzene from pyrolysis gasification gas of organic solid waste, belonging to the technical field of chlorobenzene removal pollutants from pyrolysis gasification gas of organic solid waste. The method includes: firstly, acid etching modification of natural dolomite, which can effectively optimize the pore structure and alkaline site distribution of the support; then, adding cerium nitrate solution to the acid-etched dolomite to obtain an acid-etched dolomite CeO2 composite support; simultaneously placing nickel nitrate, sodium hypophosphite, a halide ion crystal facet control agent, and NaBH4 in a reactor to react and obtain a Ni2P precursor; and then loading the Ni2P precursor onto the composite support using an impregnation method to prepare a Ni2P (201) crystal-faceted catalyst. The crystal-faceted catalyst prepared by this invention can achieve highly active crystal facet directional control, possesses both high-efficiency dechlorination activity and excellent resistance to chlorine poisoning, and is suitable for complex working conditions such as pyrolysis gasification of organic solid waste.

Description

Technical Field

[0001] This invention belongs to the technical field of chlorobenzene removal from pyrolysis gasification gas of organic solid waste, specifically relating to a crystal surface catalyst for removing chlorobenzene from pyrolysis gasification gas of organic solid waste and its preparation method. Background Technology

[0002] Pyrolysis of organic solid waste is an effective technology for resource recovery and volume reduction. However, the pyrolysis process generates pyrolysis gas containing chlorine compounds such as chlorobenzene, chlorophenol, and C6Cl6. These substances are important precursors to highly toxic pollutants such as dioxins, posing a serious threat to the environment and human health. Efficient removal of chlorobenzene pollutants from the pyrolysis gas of organic solid waste is a key prerequisite for the industrial application of organic solid waste pyrolysis technology. Among these methods, hydrodechlorination technology, which can convert chlorobenzene into harmless benzene compounds and chlorides, enabling resource recovery, has become one of the most promising methods for treating this type of chlorobenzene. Its core lies in developing high-performance hydrodechlorination catalysts.

[0003] Transition metal phosphides have become a research hotspot for hydrodechlorination catalysts in organic solid waste pyrolysis gas due to their excellent hydrogenation activity, resistance to poisoning, and stability. The crystal facet structure of a catalyst is one of the key factors affecting its catalytic performance. Different crystal facets exhibit significant differences in surface atomic arrangement, surface energy, and the number of active sites, directly determining the catalyst's adsorption and activation capabilities for reactants, as well as the selection of reaction pathways. Therefore, controlling the crystal facet exposure ratio of the catalyst through crystal facet engineering is an effective means to improve catalytic performance. However, existing technologies rarely report catalysts that can achieve highly active crystal facet directional control, possess both high-efficiency dechlorination activity and excellent resistance to chlorine poisoning, and are suitable for the complex operating conditions of organic solid waste pyrolysis gas.

[0004] This shows that the existing technology needs further improvement. Summary of the Invention

[0005] Based on the technical concept of controlling the crystal face exposure ratio of the catalyst through crystal face engineering, this invention provides a method for preparing a crystal face catalyst for removing chlorobenzene from organic solid waste pyrolysis gas. It can achieve highly active crystal face directional control, has both high dechlorination activity and excellent resistance to chlorine poisoning, and is suitable for complex working conditions such as organic solid waste pyrolysis gas.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A method for preparing a crystal-faceted catalyst for removing chlorobenzene from the pyrolysis gas of organic solid waste, comprising the following steps: a. Natural dolomite is acid-etched and modified to construct a multi-level porous structure through etching and expose alkaline sites in situ to obtain acid-etched modified dolomite. b. Add cerium nitrate solution to acid-etched dolomite, stir evenly and adjust pH=10, let stand for aging, filter and collect the precipitate, wash, dry and calcine the precipitate to obtain acid-etched dolomite-CeO2 composite carrier. c. Mix Ni(NO3)2·6H2O and NaH2PO4 2· Nickel nitrate and sodium hypophosphite were obtained by drying with H2O. Nickel nitrate, sodium hypophosphite, halide ion crystal facet control agent and second catalyst component NaBH4 were placed in a reactor and reacted at 200-300℃ under nitrogen atmosphere. After the reaction was completed, the nitrogen gas was stopped and the resulting reaction product was passivated to obtain a Ni2P precursor with highly exposed Ni2P (201) crystal facets. d. The Ni2P precursor is loaded onto the acid-etched modified dolomite-CeO2 composite support by impregnation, and then dried, granulated, crushed and sieved to obtain the Ni2P (201) crystal surface catalyst.

[0007] In the preparation method of the crystal surface catalyst for removing chlorobenzene from the pyrolysis gasification gas of organic solid waste, in step a, natural dolomite is acid-etched and modified with dilute hydrochloric acid, and the basic sites of calcium oxide and magnesium oxide are exposed in situ. The concentration of the dilute hydrochloric acid solution is 0.05 mol / L. During acid etching and modification, the mixture is stirred at room temperature for 5 to 10 minutes. After filtration, it is repeatedly washed with deionized water until neutral.

[0008] The above-mentioned method for preparing a crystal surface catalyst for removing chlorobenzene from the pyrolysis gasification gas of organic solid waste involves a mass ratio of natural dolomite to cerium nitrate of 1:0.5-5, a calcination temperature of 600-800℃, and a calcination time of 1-3 hours.

[0009] In the above-mentioned method for preparing a crystal surface catalyst for removing chlorobenzene from the pyrolysis gasification gas of organic solid waste, in step c, the halide ion crystal surface control agent is NaF, NaCl, or NaBr.

[0010] In the preparation method of the above-mentioned crystal surface catalyst for removing chlorobenzene from the pyrolysis gasification gas of organic solid waste, in step c, the halide ion crystal surface control agent is NaF; the P / Ni molar ratio is 2.0, the mass ratio of Ni(NO3)2·6H2O to NaBH4 is 1:0.5~5; the molar concentration of anion in the halide ion crystal surface control agent is 0.2 mol / L, the reactor is a tubular reactor, nitrogen gas is introduced into the tubular reactor, and the reaction is carried out under nitrogen protection.

[0011] The above-mentioned method for preparing a crystal surface catalyst for removing chlorobenzene from the pyrolysis gasification gas of organic solid waste involves three stages of temperature increase during the reaction: the first stage is from room temperature to 200℃ for 1 hour; the second stage is from 201℃ to 300℃ for 1 hour; and the third stage is cooling to room temperature and stopping the introduction of nitrogen gas.

[0012] In the above-mentioned method for preparing a crystal surface catalyst for removing chlorobenzene from the pyrolysis gasification gas of organic solid waste, in step c, a mixture of oxygen and nitrogen is used for passivation treatment.

[0013] In the above-mentioned method for preparing a crystal surface catalyst for removing chlorobenzene from the pyrolysis gasification gas of organic solid waste, in step d, the drying temperature is 110-130℃, the drying time is 5-7h, and the sample is sieved to 40-60 mesh.

[0014] Another objective of this invention is to provide a crystal surface catalyst for removing chlorobenzene from the pyrolysis gasification gas of organic solid waste, which is prepared by the above-described preparation method, wherein the nickel loading in the crystal surface catalyst is 5-15%.

[0015] Another object of the present invention is to provide an application of the above-mentioned crystal surface catalyst for removing chlorobenzene from the pyrolysis gasification gas of organic solid waste. The application involves placing the crystal surface catalyst in an organic solid waste pyrolysis simulation device and introducing 20 ml / min of the catalyst into it. ‐1 hydrogen gas and 20 ml·min ‐1 A mixture of chlorobenzene and nitrogen is heated to 300°C and held for 30 minutes; hydrogen reacts on the crystal catalyst to generate active hydrogen atoms, and the C-Cl bond on chlorobenzene breaks on the crystal catalyst to generate benzene and HCl.

[0016] Compared with the prior art, the present invention brings the following beneficial technical effects: This invention proposes a method for preparing a crystal-faceted catalyst for removing chlorobenzene from the pyrolysis gas of organic solid waste. First, natural dolomite is acid-etched to effectively optimize the pore structure and alkaline site distribution of the support. Then, cerium nitrate solution is added to the acid-etched dolomite to obtain an acid-etched dolomite-CeO2 composite support. Both the modified dolomite and CeO2 serve as supports. The optimized pore structure of the support, combined with the abundant oxygen vacancies and strong resistance to poisoning of CeO2, enables uniform dispersion and firm anchoring of the Ni2P active component in subsequent steps. This significantly improves the catalyst's structural stability, resistance to chlorine corrosion, and service life, making it perfectly suited for the complex working conditions of organic solid waste pyrolysis gas containing chlorine, multiple impurities, and being easily corroded.

[0017] This invention proposes a method for preparing a crystal-faceted catalyst for removing chlorobenzene from the pyrolysis gasification gas of organic solid waste. In the preparation step of the Ni2P precursor with highly exposed Ni2P (201) crystal faces, halide ions are used as crystal facet control agents to achieve directional and controllable induction of highly active Ni2P (201) crystal faces. This effectively solves the technical drawbacks of random crystal facet growth and insufficient exposure of active sites in traditional nickel phosphide catalysts, and significantly improves the adsorption, activation and hydrodechlorination activity of Ni2P for chlorobenzene pollutants.

[0018] This invention proposes a method for preparing a crystal-faceted catalyst for removing chlorobenzene from the pyrolysis gasification gas of organic solid waste. In the preparation step of the Ni2P precursor with highly exposed Ni2P (201) crystal faces, the second catalytic component NaBH4 can form a highly efficient synergistic system with the highly active Ni2P (201) crystal faces. The boron component can regulate the electronic structure of the active phase, enhance the activation of hydrogen and the breaking ability of C–Cl bonds. At the same time, CeO2 relies on abundant oxygen vacancies to adsorb and capture HCl generated in situ, alleviate chlorine poisoning and protect the catalytic center. The three components complement each other and synergistically enhance the dechlorination efficiency and long-term operational stability of the catalyst.

[0019] The raw materials selected in this invention are readily available, and the preparation process is simple and inexpensive, solving the problems of complex preparation and high cost of existing high-performance dechlorination catalysts. This invention prepares a catalyst with a Ni2P (201) crystal structure, which has high dechlorination efficiency, strong stability, and outstanding anti-poisoning performance. It does not require secondary treatment and avoids the drawbacks of traditional adsorption and oxidation methods that are prone to secondary pollution. It is suitable for industrial promotion and application, and helps the clean and efficient development of organic solid waste pyrolysis gasification technology. Attached Figure Description

[0020] The present invention will be further described below with reference to the accompanying drawings: Figure 1 The diagram shows the dechlorination effect of the catalyst in the comparative example and embodiment of the present invention.

[0021] Figure 2 The image shows the SEM image of the nickel phosphide (201) crystal facets with an exposure intensity of 38.9% prepared according to the present invention.

[0022] Figure 3 The TEM image shows the nickel phosphide (201) crystal plane with an exposure intensity of 38.9% prepared according to the present invention. Detailed Implementation

[0023] This invention proposes a crystal surface catalyst for removing chlorobenzene from the pyrolysis gasification gas of organic solid waste and its preparation method. In order to make the advantages and technical solutions of this invention clearer and more explicit, the invention will be further described below with reference to specific embodiments.

[0024] All the raw materials mentioned in this invention can be purchased through commercial channels.

[0025] The technical concept of this invention is as follows: Based on the technical concept of controlling the crystal facet exposure ratio of the catalyst through crystal facet engineering, a method for preparing a Ni2P (201) crystal facet structure catalyst is designed. First, natural dolomite is used as the raw material. Through pretreatment, acid-etched modified dolomite is obtained. The acid-etched modified dolomite constructs a rich hierarchical porous structure and exposes CaO and MgO alkaline sites in situ. Cerium nitrate solution is added to the acid-etched modified dolomite to obtain an acid-etched modified dolomite-CeO2 composite support. Unlike the role of cerium dioxide in traditional technologies, in this invention, cerium dioxide is not used as an active component but as a support. Through its interaction with the acid-etched modified dolomite, it lays the foundation for the subsequent loading of precursors. Ni(NO3)2·6H2O and NaH2PO2 are then used. Nickel nitrate and sodium hypophosphite were obtained by drying with H2O. The nickel nitrate, sodium hypophosphite, halide ion crystal facet control agent, and NaBH4 boron-based second catalytic component were placed together in a tubular reactor and processed to obtain a Ni2P precursor with highly exposed Ni2P (201) crystal faces. The halide ion crystal facet control agent was directionally induced to generate highly active crystal faces, which are the Ni2P (201) crystal faces. Finally, the Ni2P precursor was impregnated and loaded onto an acid-etched dolomite-CeO2 composite support to obtain the crystal facet catalyst of this invention.

[0026] The application of the crystal plane catalyst prepared by this invention will be described in detail below.

[0027] Specific application method: Place the prepared crystal surface catalyst into an existing organic solid waste pyrolysis simulation device, and introduce 20 ml / min of air. ‐1 H2 gas and 20 ml·min ‐1 A mixture of chlorobenzene and nitrogen (with a chlorobenzene concentration of 100 ppm) was heated to 300 degrees Celsius and held at that temperature for 30 minutes. The incoming and outgoing gases were then analyzed by gas chromatography.

[0028] Example 1: A method for preparing a crystal-faceted catalyst for removing chlorobenzene from the pyrolysis gasification gas of organic solid waste specifically includes the following steps: Step 1: Place natural dolomite in 0.05 mol / L dilute hydrochloric acid, stir magnetically at room temperature for 8 minutes for mild acid etching, filter, and wash repeatedly with deionized water until neutral to obtain acid-etched modified dolomite with a clean surface and a multi-level mesoporous channel structure.

[0029] The acid-etched modified dolomite obtained through this step has a multi-level porous structure and exposes calcium oxide and magnesium oxide alkaline sites in situ.

[0030] Step 2: Add cerium nitrate solution to natural dolomite at a mass ratio of 1:1, stir evenly and adjust the pH of the system to 10. After standing and aging, filter and collect the precipitate, wash with deionized water until neutral, and obtain acid-etched dolomite-CeO2 composite carrier after drying and calcination. The calcination temperature is 700℃ and the calcination time is 2h.

[0031] Step 2: Mix Ni(NO3)2·6H2O and NaH2PO4 2· Nickel nitrate and sodium hypophosphite were obtained by drying with H2O. Nickel nitrate, sodium hypophosphite, a halide ion crystal facet control agent, and NaBH4 were placed together in a tubular reactor, with the mass ratio of Ni(NO3)2·6H2O to NaBH4 being 1:1. The halide ion crystal facet control agent was NaF, and F was present in the system. - The molar concentration was 0.2 mol / L, and then 10 mL / min was continuously introduced into the tubular reactor. ‐1 Nitrogen gas was used to heat the sample from room temperature to 200°C, which was maintained at 200°C for 1 hour. Then, the sample was further heated to 300°C and maintained for 1 hour. After cooling to room temperature, the nitrogen flow was stopped, and a 5 vol% oxygen-nitrogen mixture was introduced for passivation treatment to achieve the directional induction of the highly active Ni2P (201) crystal facets, resulting in a Ni2P precursor with highly exposed Ni2P (201) crystal facets.

[0032] Step 3: The acid-etched dolomite-CeO2 composite support prepared in Step 1 is added to the Ni2P precursor obtained in Step 2 for isothermal impregnation to achieve a Ni loading of 10wt%. After impregnation, the sample is dried at 120℃ for 6h, granulated, crushed and sieved to 40~60 mesh to obtain the crystal catalyst.

[0033] Figure 2 This is a SEM image of the nickel phosphide (201) crystal plane with an exposure intensity of 38.9% prepared in this embodiment. Figure 3 The TEM image shows the nickel phosphide (201) crystal plane with an exposure intensity of 38.9% prepared in this embodiment.

[0034] Results: The catalyst prepared in this embodiment was applied to remove chlorobenzene pollutants from organic solid waste gas. The specific removal reaction was as follows: H2 reacted on the catalyst to generate active H, and the C-Cl bond on chlorobenzene was broken on the catalyst to generate benzene and HCl.

[0035] As can be seen from the above, the catalyst prepared in this embodiment can achieve efficient hydrogenation and dechlorination of chlorobenzene pollutants, with a chlorobenzene removal efficiency of up to 95%, and the products are benzene and HCl, with no chlorine-containing byproducts generated.

[0036] Example 2: The difference from Example 1 is that: In step two, the mass ratio of Ni(NO3)2·6H2O to NaBH4 is 1:0.5.

[0037] Results: The catalyst prepared in this embodiment has a removal efficiency of 92% for chlorobenzene pollutants in organic solid waste gas.

[0038] Example 3: The difference from Example 1 is that: In step two, the mass ratio of Ni(NO3)2·6H2O to NaBH4 is 1:2.

[0039] Results: The catalyst prepared in this embodiment has a removal efficiency of 91% for chlorobenzene pollutants in organic solid waste gas.

[0040] Example 4: The difference from Example 1 is that: In step two, the mass ratio of Ni(NO3)2·6H2O to NaBH4 is 1:3.

[0041] Results: The catalyst prepared in this embodiment has a removal efficiency of 88% for chlorobenzene pollutants in organic solid waste gas.

[0042] Example 5: The difference from Example 1 is that: In step two, the mass ratio of Ni(NO3)2·6H2O to NaBH4 is 1:5.

[0043] Results: The catalyst prepared in this embodiment has a removal efficiency of 86% for chlorobenzene pollutants in organic solid waste gas.

[0044] Example 6: The difference from Example 1 is that: In step two, the halide ion crystal plane control agent is NaCl, and the Cl in the system... - The concentration is 0.2 mol / L.

[0045] Results: The catalyst prepared in this embodiment has a removal efficiency of 81% for chlorobenzene pollutants in organic solid waste gas.

[0046] Example 7: The difference from Example 1 is that: In step two, the halide ion crystal plane control agent is NaBr, and Br in the system - The concentration is 0.2 mol / L.

[0047] Results: The catalyst prepared in this embodiment has a removal efficiency of 84% for chlorobenzene pollutants in organic solid waste gas.

[0048] Comparative Example 1: The difference from Example 1 is that: Acid-etched modified natural dolomite was used directly as a carrier without introducing CeO2, and the remaining steps were the same. Results: The catalyst prepared in this comparative example had a removal efficiency of 53% for chlorobenzene pollutants in organic solid waste gas.

[0049] Comparative Example 2: The difference from Example 1 is that: In step two, NaBH4 is not added; only Ni2P is prepared and loaded onto the composite support. The remaining steps are the same. Results: The catalyst prepared in this comparative example had a removal efficiency of 82% for chlorobenzene pollutants in organic solid waste gas.

[0050] Comparative Example 3: The difference from Example 1 is that: In step two, no halide ion morphology control agent is added; the remaining steps are the same. Results: The catalyst prepared in this comparative example can effectively remove chlorine from chlorobenzene to generate HCl, and the removal efficiency of chlorobenzene can reach 77%.

[0051] Experiments were conducted on the catalysts prepared in Examples 1 to 7 and Comparative Examples 1 to 3, and their dechlorination efficiencies were as follows: Figure 1 As shown.

[0052] The relative exposure intensities of the Ni2P (201) crystal planes obtained in Examples 1, 6, 7 and Comparative Example 3 are shown in Table 1.

[0053] Table 1

[0054] Any parts not mentioned in this invention can be achieved by referring to existing technologies.

[0055] It should be noted that those skilled in the art should recognize that the above embodiments are only used to illustrate this application and are not intended to limit this application. Any appropriate changes and variations made to the above embodiments within the essential spirit and scope of this application fall within the scope of protection claimed by this application.

Claims

1. A method for preparing a crystal-faceted catalyst for removing chlorobenzene from the pyrolysis gasification gas of organic solid waste, characterized in that, The steps are as follows: a. Natural dolomite is acid-etched and modified to construct a multi-level porous structure through etching and expose alkaline sites in situ to obtain acid-etched modified dolomite. b. Add cerium nitrate solution to acid-etched dolomite, stir evenly and adjust pH=10, let stand for aging, filter and collect the precipitate, wash, dry and calcine the precipitate to obtain acid-etched dolomite-CeO2 composite carrier. c. Ni(NO3)2-6H2O and NaH2PO 2· H2O to obtain nickel nitrate and sodium hypophosphite; the nickel nitrate, sodium hypophosphite, halogen ion crystal face control agent and second catalytic component NaBH4 are simultaneously placed in a reactor, and a reaction is performed under a nitrogen atmosphere at a temperature of 200-300°C; after the reaction is completed, nitrogen is stopped, and the obtained reaction product is passivated to obtain a Ni2P precursor with a high exposure Ni2P (201) crystal face. d. The Ni2P precursor is loaded onto the acid-etched modified dolomite-CeO2 composite support by impregnation, and then dried, granulated, crushed and sieved to obtain the Ni2P (201) crystal surface catalyst.

2. The method for preparing a crystal-faceted catalyst for removing chlorobenzene from pyrolysis gas of organic solid waste according to claim 1, characterized in that: In step a, natural dolomite is acid-etched and modified with dilute hydrochloric acid, and the basic sites of calcium oxide and magnesium oxide are exposed in situ. The concentration of the dilute hydrochloric acid solution is 0.05 mol / L. During acid etching, the mixture is stirred at room temperature for 5 to 10 minutes. After filtration, it is repeatedly washed with deionized water until neutral.

3. The method for preparing a crystal-faceted catalyst for removing chlorobenzene from pyrolysis gas of organic solid waste according to claim 1, characterized in that: The mass ratio of natural dolomite to cerium nitrate is 1:0.5 to 5, the calcination temperature is 600 to 800℃, and the calcination time is 1 to 3 hours.

4. The method for preparing a crystal-faceted catalyst for removing chlorobenzene from pyrolysis gas of organic solid waste according to claim 1, characterized in that: In step c, the halide ion crystal plane control agent is NaF, NaCl, or NaBr.

5. The method for preparing a crystal-faceted catalyst for removing chlorobenzene from pyrolysis gas of organic solid waste according to claim 4, characterized in that: In step c, the halide ion crystal facet control agent is NaF; the P / Ni molar ratio is 2.0, and the mass ratio of Ni(NO3)2·6H2O to NaBH4 is 1:0.5~5; the molar concentration of anions in the halide ion crystal facet control agent is 0.2 mol / L, the reactor is a tubular reactor, nitrogen gas is introduced into the tubular reactor, and the reaction is carried out under nitrogen protection.

6. The method for preparing a crystal-faceted catalyst for removing chlorobenzene from pyrolysis gas of organic solid waste according to claim 5, characterized in that: The reaction is heated in three stages: the first stage is from room temperature to 200°C for 1 hour; the second stage is from 201°C to 300°C for 1 hour; and the third stage is cooling to room temperature and stopping the nitrogen flow.

7. The method for preparing a crystal-faceted catalyst for removing chlorobenzene from pyrolysis gas of organic solid waste according to claim 1, characterized in that: In step c, a mixture of oxygen and nitrogen gas is used for passivation.

8. The method for preparing a crystal-faceted catalyst for removing chlorobenzene from pyrolysis gas of organic solid waste according to claim 1, characterized in that: In step d, the drying temperature is 110-130℃, the drying time is 5-7 hours, and the sample is sieved to 40-60 mesh.

9. A crystal-faceted catalyst for removing chlorobenzene from the pyrolysis gasification gas of organic solid waste, characterized in that, It is prepared by the preparation method according to any one of claims 1 to 8, wherein the nickel loading in the crystal catalyst is 5 to 15%.

10. The application of the crystal facet catalyst for removing chlorobenzene from the pyrolysis gasification gas of organic solid waste according to claim 9, characterized in that, The application involves placing the crystal catalyst in an organic solid waste pyrolysis simulation device and introducing 20 ml / min of it. ‐1 hydrogen gas and 20 ml·min ‐1 A mixture of chlorobenzene and nitrogen is heated to 300°C and held for 30 minutes; hydrogen reacts on the crystal catalyst to generate active hydrogen atoms, and the C-Cl bond on chlorobenzene breaks on the crystal catalyst to generate benzene and HCl.

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