Process for the production of vinyl chloride by hydrochlorination of acetylene

Abstract

A method for preparing vinyl chloride by hydrochlorination of acetylene, using a mercury-free non-noble metal Ni-based monatomic catalyst with Ni-N coordination structure. The preparation method of the catalyst comprises the following steps: 1) mixing a nitrogen source, a carbon source and a Ni salt by ball milling; 2) adding ethanol and a hydrochloric acid solution to the mixed powder obtained in step 1, and grinding and drying to obtain a precursor; 3) passing ammonia, and roasting the precursor obtained in step 2 to obtain a Ni-doped nitrogen-carbon catalyst. The Ni-doped nitrogen-carbon catalyst has excellent catalytic performance in the reaction of preparing vinyl chloride by hydrochlorination of acetylene, has excellent catalytic activity and stability, and has the advantages of simple preparation method, low cost and environmental friendliness.

Description

Technical Field

[0001] This invention belongs to the field of petrochemical technology, specifically relating to a method for producing vinyl chloride from acetylene via hydrochlorination, which uses a mercury-free, non-precious metal single-atom catalyst. Background Technology

[0002] Polyvinyl chloride (PVC), with its high temperature resistance, corrosion resistance, and strong insulation properties, is an important raw material for the production of building materials, medical materials, and packaging materials. Its widespread application has led to a continuous increase in demand. Vinyl chloride (VCM) is a key monomer in the production of PVC, which can be generated through simple polymerization. Currently, the main production methods for vinyl chloride include the ethylene process, the ethane process, the zeolite process, and the acetylene hydrochlorination process. The acetylene hydrochlorination process is the main process for producing vinyl chloride. This route primarily uses HgCl2 / AC catalysts, which leads to a series of environmental pollution problems and harms human health.

[0003] In recent years, researchers both domestically and internationally have conducted extensive research in the field of non-mercury catalysts, primarily focusing on three systems: noble metals such as Au, Pd, Pt, and Ru; non-noble metals such as Cu, Co, and Fe; and non-metallic carbon-based materials. Among these catalysts, Au-based and Ru-based catalysts supported on activated carbon have exhibited superior performance in the acetylene hydrochlorination reaction and are widely recognized as among the most promising catalysts to replace mercuric chloride. However, the high cost of noble metal catalysts significantly hinders their large-scale industrial application.

[0004] Meanwhile, while non-precious metal catalysts, primarily Cu-based catalysts, possess both good catalytic activity and economic efficiency, copper species readily react with acetylene to form explosive copper acetylene compounds, posing a safety hazard during the reaction and seriously threatening the stable operation of the equipment. Furthermore, the long-term stability of these catalysts is far inferior to that of precious metal systems. In contrast, non-metallic catalysts, represented by nitrogen-doped carbon materials, have opened up a new path for mercury-free acetylene hydrochlorination due to their excellent reaction performance and low cost. For example, the mercury-free catalyst for the acetylene hydrochlorination reaction disclosed in Chinese patent application CN116159579A involves loading Au, Cu, and Mn components onto nitrogen-doped carbon nanotubes, drying them to obtain solid A; then, a solution of a boron precursor is prepared, and the solid A is impregnated, aged, and dried to obtain the catalyst.

[0005] However, this system faces serious challenges in practical applications: on the one hand, its excessive adsorption capacity for reaction intermediates or products can lead to rapid carbon deposition and deactivation, resulting in significantly lower stability compared to metal and industrial mercury-based catalysts; on the other hand, its efficient reaction window typically needs to be maintained at temperatures above 200 °C. These factors collectively limit the industrial application of this type of catalyst. Summary of the Invention

[0006] One object of the present invention is to provide a catalyst for the hydrochlorination of acetylene to produce vinyl chloride, wherein the catalyst uses nitrogen-doped carbon material as a support and constructs a stable MN coordination structure by introducing non-precious metal nickel (Fe, Co, and / or Ni) as an active component, which improves the efficiency of the catalytic reaction.

[0007] Another object of the present invention is to provide a method for producing vinyl chloride by hydrochlorination of acetylene, wherein the method uses the above-mentioned catalyst, which can improve the conversion rate of acetylene while maintaining a high selectivity for vinyl chloride.

[0008] On the one hand, the above-mentioned catalyst has good stability in the process of producing vinyl chloride by hydrochlorination of acetylene and maintains good catalytic activity over a long period of time.

[0009] To achieve the purpose of this invention, a catalyst for the hydrochlorination of acetylene to produce vinyl chloride is provided. The catalyst comprises a metal M and a nitrogen-doped carbon-based support. In the catalyst, the metal M forms an MN chemical bond with nitrogen in the nitrogen-doped carbon-based support. The metal M comprises one or a mixture of two or more of Fe, Co, or Ni elements.

[0010] Optionally, metal M is Ni, or a mixed metal including Ni (e.g., Ni and Co; or Ni and Co; or Fe).

[0011] A method for producing vinyl chloride by hydrochlorination of acetylene includes: reacting hydrogen chloride gas with acetylene under the action of the above-mentioned catalyst at a reaction temperature of 180-240 °C.

[0012] Using the aforementioned catalyst, non-precious metal nickel was introduced as the active component to construct a stable MN coordination structure. This structure (especially the Ni-N coordination structure) can effectively regulate the adsorption behavior of reactants and products at the active site, optimize the adsorption intensity, and thus significantly improve the efficiency of the catalytic reaction and the catalyst lifetime. From a production cost perspective, it has good economic efficiency, and the catalyst preparation is simple and easy to scale up, enabling the safe and large-scale application of this process in industrial production. Attached Figure Description

[0013] Figure 1 XPS spectrum of the Ni / NC catalyst prepared in Example 1; Figure 2 The TEM-Mapping image of the Ni / NC catalyst prepared in Example 3; Figure 3 The results show the stability test results of the Ni / NC catalyst prepared in Example 2. Detailed Implementation

[0014] The following describes in further detail the mercury-free, non-precious metal-doped nitrogen-carbon single-atom catalyst and the method for producing vinyl chloride by hydrochlorination of acetylene according to the present invention. This does not limit the scope of protection of this application, which is defined by the claims. Certain specific details disclosed provide a comprehensive understanding of the various disclosed embodiments. However, those skilled in the art will recognize that embodiments can be implemented using other materials, etc., without employing one or more of these specific details.

[0015] Unless the context otherwise requires, the terms “comprising” and “including” in the specification and claims shall be understood as open-ended and inclusive, meaning “including, but not limited to”.

[0016] The terms "implementation," "an implementation," "another implementation," or "certain implementations" used in this specification refer to specific features, structures, or characteristics described in relation to the implementation, which are included in at least one implementation. Therefore, "implementation," "an implementation," "another implementation," or "certain implementations" do not necessarily all refer to the same implementation. Furthermore, specific features, structures, or characteristics can be combined in any way within one or more implementations. Each feature disclosed in this specification can be replaced by any alternative feature that provides the same, equivalent, or similar purpose. Therefore, unless otherwise specified, the disclosed features are merely general examples of equivalent or similar features.

[0017] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Experimental methods in the following embodiments, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer. Unless otherwise stated, all percentages, ratios, proportions, or parts are by weight.

[0018] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as are familiar to those skilled in the art. Furthermore, any methods and materials similar to or equivalent to those described herein may be applied to the methods of this invention. The preferred embodiments and materials described herein are for illustrative purposes only.

[0019] The term "space velocity" refers to the amount of feedstock passing through a unit volume of catalyst per unit time, measured in hours (h). -1 .

[0020] "Inert gas" refers to a gas that does not react chemically with other substances in the roasting environment.

[0021] On the one hand, a catalyst for the hydrochlorination of acetylene to produce vinyl chloride is provided, the catalyst comprising a metal M and a nitrogen-doped carbon-based support, wherein the metal M forms an MN chemical bond with nitrogen in the nitrogen-doped carbon-based support, wherein the metal M comprises one or a mixture of two or more elements selected from Fe, Co, or Ni.

[0022] In the catalyst, the mass content of metal M is 0.3% to 5%.

[0023] A further alternative is to use a metal M content of 0.3% to 1.5% by mass. Optionally, the nitrogen content in the catalyst is 10-24% by mass.

[0024] A further alternative is a catalyst with a nitrogen content of 11% to 18% by mass.

[0025] In addition to the aforementioned metal M and nitrogen, the catalyst contains carbon, hydrogen, and oxygen.

[0026] In the catalyst of this application, metal M is a single atom, and the single metal atom forms a coordination structure with N. In particular, a Ni-N coordination structure (e.g., NiN4) can optimize the adsorption and desorption of reactants and products at the active site. Acetylene and hydrogen chloride are moderately adsorbed at the active site and react, while the generated vinyl chloride can be desorbed quickly, thereby improving the conversion rate and product selectivity of the reaction. In addition, the strong interaction of the Ni-N bond is a key factor in the high stability and catalytic performance of the NiN4 active site.

[0027] A method for preparing a catalyst for the hydrochlorination of acetylene to produce vinyl chloride includes: (1) mixing a nitrogen source, a carbon source and a salt containing metal M to obtain a mixture; (2) The mixture obtained in step (1) is dried and calcined to obtain the M-doped nitrogen-carbon catalyst.

[0028] Among them, metal M includes one or more of Fe, Co, or Ni elements.

[0029] In some embodiments, the mixture in step (1) contains hydrochloric acid.

[0030] Optionally, the amount of hydrochloric acid in the total mass ratio of nitrogen and carbon sources is 0.002-0.004 mol / g.

[0031] The total mass of nitrogen and carbon sources here refers to the total mass of all nitrogen source compounds and all carbon source compounds used.

[0032] That is, the concentration of hydrochloric acid in the mixture is controlled at 0.5~1 mol / L.

[0033] In this embodiment, hydrochloric acid can effectively promote the polymerization reaction between the carbon source and the nitrogen-containing precursor (such as melamine), thereby enhancing the doping degree of nitrogen into the graphene framework, forming a large number of uniformly distributed metal anchoring sites, which is more conducive to constructing a stable Ni-N coordination structure.

[0034] In some embodiments, in step (2), calcination is carried out in an ammonia-containing atmosphere.

[0035] An atmosphere containing ammonia can be pure ammonia or a mixture of ammonia and other inert gases (such as nitrogen, helium, etc.).

[0036] Preferably, the roasting is carried out in an ammonia atmosphere.

[0037] The roasting temperature is 400-1000 °C.

[0038] Calcination in an ammonia-containing atmosphere can erode the carbon support, increase porosity, and enhance the catalyst's specific surface area and rich pore structure. On the other hand, it can also form additional nitrogen-containing functional groups, improving the dispersion of the active metal and preventing its aggregation at high temperatures.

[0039] In some embodiments, the roasting process is divided into two stages: in the first stage, the roasting temperature is 400-600 °C; in the second stage, the roasting temperature is 800-1000 °C.

[0040] Through two-stage calcination, the HCl added during the catalyst preparation process can be effectively removed under the temperature conditions of the first stage. At low temperature, a porous nitrogen-doped carbon framework can be formed and the metal can be initially anchored, preventing the metal from directly agglomerating at high temperature.

[0041] Optionally, in the first stage, the roasting temperature is 500~600 °C.

[0042] In the second stage, the roasting temperature is 800~900 °C.

[0043] A further alternative is to use a roasting time of 1-3 hours in the first stage.

[0044] In the second stage, the roasting time is 50 min to 100 min. The roasting time for each stage can be combined with the roasting temperature of the corresponding stage mentioned above.

[0045] During the roasting process, the temperature is increased from room temperature to 400-600 °C at a heating rate of 2.0-3.0 °C / min; preferably, the temperature is increased to 400-600 °C at a heating rate equal to or approximately equal to 2.5 °C / min.

[0046] The temperature of the first stage is increased to the temperature of the second stage at a heating rate of 4.0-6.0 °C / min; preferably, the temperature of the first stage is increased to the temperature of the second stage at a heating rate equal to or approximately equal to 5.0 °C / min.

[0047] The heating rate will affect the dispersion of the metal; an excessively high heating rate will cause the metal to agglomerate.

[0048] The flow rate of ammonia is related to the mixture to be roasted.

[0049] The ammonia flow rate is 1.4-7.5 mL / min per gram of the mixture to be roasted; preferably, the ammonia flow rate is 2.8-7.5 mL / min per gram of the mixture to be roasted.

[0050] In a mixed atmosphere of ammonia and other inert gases, the flow rate can be appropriately increased to ensure that the amount of the substance to be roasted and the amount of ammonia meet the above conditions during the roasting process.

[0051] The carbon source includes either L-aspartic acid or glucose. Preferably, L-aspartic acid is used as the carbon source.

[0052] The nitrogen source includes one of urea, melamine, and dicyandiamide. Preferably, melamine is used as the nitrogen source.

[0053] The salt containing metal M is a soluble salt solution. For example, the salt containing Ni metal includes one or a mixture of nickel chloride, nickel acetylacetonate, and nickel nitrate. Preferably, the salt containing Ni metal is nickel chloride and / or nickel acetylacetonate.

[0054] In some embodiments, the content of metal M is 0.1 to 1.0 wt% relative to the total mass of the nitrogen source, carbon source, and salt containing metal M; preferably, the content of Ni is 0.1 to 1.0 wt%.

[0055] Optionally, the Ni content is 0.1 to 0.6 wt% relative to the total mass of the nitrogen source, carbon source, and salt containing metal M; (preferably, 0.105 to 0.55 wt%).

[0056] In some embodiments, the mass ratio of nitrogen source to carbon source in the mixture of step (1) is 0.05 to 1.

[0057] Optionally, in the mixture of step (1), the mass ratio of nitrogen source to carbon source is (0.08~1):1.

[0058] More preferably, in the mixture of step (1), the mass ratio of nitrogen source to carbon source is (0.18~1):1.

[0059] In one embodiment, the nitrogen source is melamine, the carbon source is L-aspartic acid, and the mass ratio of melamine to L-aspartic acid is (0.08~1):1; preferably, the mass ratio of melamine to L-aspartic acid is (0.18~1):1.

[0060] The raw materials can be mixed by first dissolving them in a solvent (alcohol solvent, hydrochloric acid) and then mixing them; or the solid raw materials can be mixed first and then the solvent (alcohol solvent, hydrochloric acid) can be added.

[0061] In one embodiment, a method for preparing a catalyst for the hydrochlorination of acetylene to vinyl chloride includes: (1) Mix nitrogen source, carbon source and salt containing metal M to obtain mixed powder; add organic solvent and hydrochloric acid to the mixed powder and mix to obtain a mixture; (2) The mixture obtained in step (1) is dried and calcined to obtain the M-doped nitrogen-carbon catalyst.

[0062] Among them, metal M includes one or more of Fe, Co, or Ni elements.

[0063] Organic solvents can be alcohol solvents, such as methanol or ethanol.

[0064] Alternatively, the organic solvent can be ethanol, with a volume ratio of ethanol to hydrochloric acid solution of (5~7):1, and the concentration of hydrochloric acid solution is 3~5 mol / L.

[0065] Alternatively, the organic solvent can be ethanol, and the volume ratio of ethanol to hydrochloric acid solution is (5~6):1.

[0066] The concentration of the hydrochloric acid solution is 4~5 mol / L.

[0067] The amounts of nitrogen source, carbon source, and salt containing metal M can be determined using any of the methods described above.

[0068] There are no particular requirements for the drying temperature of the mixture, as long as the solvent content is reduced to a certain level. For example, the drying temperature can be between 25 and 80 °C. More preferably, the drying temperature is between 25 and 60 °C.

[0069] The aforementioned catalyst contains Fe, Co, and / or Ni, especially Ni. When used in the hydrochlorination of acetylene to produce vinyl chloride, it exhibits excellent stability and can withstand prolonged catalytic activity. Furthermore, the catalyst with a nitrogen content exceeding 14% simultaneously demonstrates both high catalytic activity and stability. This catalyst was prepared using an in-situ synthesis method, employing high-nitrogen melamine as the nitrogen source and readily available, low-cost metals (such as Ni) as the active metal. This resulted in an economical and efficient catalyst with a simple preparation process, facilitating industrial-scale production.

[0070] The raw materials used to prepare the catalyst are relatively inexpensive, making it suitable for industrial production.

[0071] The catalyst prepared in this application has a stable MN coordination structure (especially Ni-N), and can also form a relatively large specific surface area and abundant pore structure. The active metal is highly dispersed in the catalyst, thus having more active sites.

[0072] On the other hand, a method for producing vinyl chloride by hydrochlorination of acetylene includes: reacting hydrogen chloride gas with acetylene under the action of the above-mentioned catalyst at a reaction temperature of 180~240 °C.

[0073] Optionally, the reaction temperature is 200-240 ℃ (e.g., 220 ℃).

[0074] The volumetric flow rate ratio of hydrogen chloride to acetylene is (1~1.5):1.

[0075] The acetylene space velocity is 30~130 h. -1 .

[0076] In one embodiment, acetylene and hydrogen chloride feed gas are mixed evenly and then introduced into a fixed-bed reactor for reaction, with the temperature inside the fixed-bed reactor being 200~240 ℃.

[0077] In the reaction system for the hydrochlorination of acetylene to vinyl chloride, the stable Ni-N coordination structure constructed by the catalyst in this application not only significantly improves the dispersibility of the active component on the support and its structural stability at high temperatures, but also optimizes the adsorption / desorption behavior of reaction intermediates at the catalytic active sites by regulating the local electronic environment of the active center, thereby enhancing the catalyst's durability and intrinsic catalytic activity during the reaction process. This fundamentally solves the industry bottleneck of mercury pollution. Furthermore, the regulation mechanism of key operating conditions such as temperature and space velocity on catalytic behavior when using Ni-doped nitrogen-carbon single-atom catalysts provides data support and decision-making basis for industrial scale-up.

[0078] In particular, when the mass content of metallic Ni in the catalyst is 0.3%~1.5% and the mass content of nitrogen element is between 17-20%, the catalyst exhibits excellent comprehensive activity and stability at a temperature of 220℃, and its performance is higher than that of other metals.

[0079] The catalyst of the present invention and its catalytic effect are further illustrated below with specific embodiments. All substances used in the following embodiments are chemically pure standards.

[0080] The acetylene hydrochlorination reaction is carried out at atmospheric pressure. The "heavy hourly space velocity" (WHSV) mentioned in this application specifically refers to the ratio of the volume of acetylene gas passing through per unit time to the mass of the catalyst; the volume hourly space velocity (GHSV) refers to the ratio of the volume of acetylene gas passing through per unit time to the volume of the catalyst bed.

[0081] Example 1 The preparation method of Ni / NC-1 catalyst includes the following steps: 1.28 g of melamine, 14.72 g of L-aspartic acid, and 0.147 g of nickel acetylacetonate were placed in a stainless steel ball mill jar and ball-milled at 500 rpm for 30 min to obtain a mixed powder. This powder was transferred to a mortar, and 60 mL of anhydrous ethanol and 12 mL of hydrochloric acid aqueous solution (4 mol / L) were added sequentially. After thorough grinding and mixing, the mixture was dried at 40 °C for 24 h. The resulting solid was the catalyst precursor. 6.5 g of this precursor was subjected to programmed temperature heat treatment in an ammonia (NH3) atmosphere at a flow rate of 20 mL / min: first, the temperature was increased to 600 °C at a rate of 2.5 °C / min and maintained for 2 h, then increased to 800 °C at a rate of 5 °C / min and maintained for 90 min. After heat treatment, the furnace was allowed to cool naturally to room temperature to obtain the target Ni / NC-1 catalyst.

[0082] X-ray photoelectron spectroscopy analysis was performed on the Ni / NC-1 catalyst prepared in Example 1, as shown in the attached figure. Figure 1 The XPS spectra shown demonstrate that a Ni-doped nitrogen-carbon catalyst with a Ni-N coordination structure was successfully prepared via in-situ synthesis.

[0083] Example 2 The preparation method of Ni / NC-2 catalyst includes the following steps: 2.5 g of melamine, 13.5 g of L-aspartic acid, and 0.147 g of nickel acetylacetonate were placed in a stainless steel ball mill jar and ball-milled at 500 rpm for 30 min to obtain a mixed powder. This powder was transferred to a mortar, and 60 mL of anhydrous ethanol and 12 mL of hydrochloric acid aqueous solution (4 mol / L) were added sequentially. After thorough grinding and mixing, the mixture was dried at 40 °C for 24 h. The resulting solid was the catalyst precursor. 6.5 g of this precursor was subjected to programmed temperature heat treatment in an ammonia (NH3) atmosphere at a flow rate of 20 mL / min: first, the temperature was increased to 600 °C at a rate of 2.5 °C / min and maintained for 2 h, then increased to 800 °C at a rate of 5 °C / min and maintained for 90 min. After heat treatment, the furnace was allowed to cool naturally to room temperature to obtain the target Ni / NC-2 catalyst. The catalyst contained 0.88 wt% Ni atoms and 17.36% N elements.

[0084] Example 3 The preparation method of Ni / NC-3 catalyst includes the following steps: 5 g of melamine, 11 g of L-aspartic acid, and 0.147 g of nickel acetylacetonate were placed in a stainless steel ball mill jar and ball-milled at 500 rpm for 30 min to obtain a mixed powder. This powder was transferred to a mortar, and 60 mL of anhydrous ethanol and 12 mL of hydrochloric acid aqueous solution (4 mol / L) were added sequentially. After thorough grinding and mixing, the mixture was dried at 40 °C for 24 h. The resulting solid was the catalyst precursor. 6.5 g of this precursor was subjected to programmed temperature heat treatment in an ammonia (NH3) atmosphere at a flow rate of 20 mL / min: first, the temperature was increased to 600 °C at a rate of 2.5 °C / min and maintained for 2 h, then increased to 800 °C at a rate of 5 °C / min and maintained for 90 min. After heat treatment, the furnace was allowed to cool naturally to room temperature to obtain the target Ni / NC-3 catalyst. The catalyst contained 0.93 wt% Ni atoms and 14.96% N elements.

[0085] TEM-mapping analysis was performed on the Ni / NC-3 catalyst prepared in Example 3 of this study, as follows: Figure 2 The TEM-mapping diagram shown indicates that the catalyst prepared by in-situ synthesis combined with calcination in an ammonia environment has a well dispersed Ni metal active component, and the Ni-doped nitrogen-carbon single-atom catalyst was successfully prepared by this synthesis formula.

[0086] Example 4 The preparation method of Ni / NC-4 catalyst includes the following steps: 8 g of melamine, 8 g of L-aspartic acid, and 0.147 g of nickel acetylacetone were placed in a stainless steel ball mill jar and ball-milled at 500 rpm for 30 min to obtain a mixed powder. This powder was transferred to a mortar, and 60 mL of anhydrous ethanol and 12 mL of hydrochloric acid aqueous solution (4 mol / L) were added sequentially. After thorough grinding and mixing, the mixture was dried at 40 °C for 24 h. The resulting solid was the catalyst precursor. 6.5 g of this precursor was subjected to programmed temperature heat treatment in an ammonia (NH3) atmosphere at a flow rate of 20 mL / min: first, the temperature was increased to 600 °C at a rate of 2.5 °C / min and maintained for 2 h, then increased to 800 °C at a rate of 5 °C / min and maintained for 90 min. After heat treatment, the furnace was allowed to cool naturally to room temperature to obtain the target Ni / NC-4 catalyst.

[0087] Example 5 8 g of melamine, 8 g of L-aspartic acid, and 0.1958 g of ferric acetylacetone were placed in a stainless steel ball mill jar and ball-milled at 500 rpm for 30 min to obtain a mixed powder. This powder was transferred to a mortar, and 60 mL of anhydrous ethanol and 12 mL of hydrochloric acid aqueous solution (4 mol / L) were added sequentially. After thorough grinding and mixing, the mixture was dried at 40 °C for 24 h. The resulting solid was the catalyst precursor. 6.5 g of this precursor was subjected to programmed temperature heat treatment in a nitrogen atmosphere at a flow rate of 20 mL / min: first, the temperature was increased to 600 °C at a rate of 2.5 °C / min and maintained for 2 h, then increased to 800 °C at a rate of 5 °C / min and maintained for 90 min. After heat treatment, the furnace was allowed to cool naturally to room temperature to obtain the target Fe / NC catalyst.

[0088] Example 6 8 g of melamine, 8 g of L-aspartic acid, and 0.144 g of cobalt acetylacetonate were placed in a stainless steel ball mill jar and ball-milled at 500 rpm for 30 min to obtain a mixed powder. This powder was transferred to a mortar, and 60 mL of anhydrous ethanol and 12 mL of hydrochloric acid aqueous solution (4 mol / L) were added sequentially. After thorough grinding and mixing, the mixture was dried at 40 °C for 24 h. The resulting solid was the catalyst precursor. 6.5 g of this precursor was subjected to programmed temperature heat treatment in a nitrogen atmosphere at a flow rate of 20 mL / min: first, the temperature was increased to 600 °C at a rate of 2.5 °C / min and maintained for 2 h, then increased to 800 °C at a rate of 5 °C / min and maintained for 90 min. After heat treatment, the furnace was allowed to cool naturally to room temperature to obtain the target Co / NC catalyst.

[0089] Example 7 8 g of melamine, 8 g of L-aspartic acid, and 0.147 g of nickel acetylacetonate were placed in a stainless steel ball mill jar and ball-milled at 500 rpm for 30 min to obtain a mixed powder. This powder was transferred to a mortar, and 60 mL of anhydrous ethanol and 12 mL of hydrochloric acid aqueous solution (4 mol / L) were added sequentially. After thorough grinding and mixing, the mixture was dried at 40 °C for 24 h. The resulting solid was the catalyst precursor. 6.5 g of this precursor was subjected to programmed temperature heat treatment in a nitrogen atmosphere at a flow rate of 20 mL / min: first, the temperature was increased to 600 °C at a rate of 2.5 °C / min and maintained for 2 h, then increased to 800 °C at a rate of 5 °C / min and maintained for 90 min. After heat treatment, the furnace was allowed to cool naturally to room temperature to obtain the target Ni / NC catalyst.

[0090] Example 8 8 g of melamine, 8 g of L-aspartic acid, 0.147 g of nickel acetylacetonate, and 0.144 g of cobalt acetylacetonate were placed in a stainless steel ball mill jar and ball-milled at 500 rpm for 30 min to obtain a mixed powder. This powder was transferred to a mortar, and 60 mL of anhydrous ethanol and 12 mL of hydrochloric acid aqueous solution (4 mol / L) were added sequentially. After thorough grinding and mixing, the mixture was dried at 40 °C for 24 h. The resulting solid was the catalyst precursor. 6.5 g of this precursor was subjected to programmed temperature heat treatment in a nitrogen atmosphere at a flow rate of 20 mL / min: first, the temperature was increased to 600 °C at a rate of 2.5 °C / min and maintained for 2 h, then increased to 800 °C at a rate of 5 °C / min and maintained for 90 min. After heat treatment, the furnace was allowed to cool naturally to room temperature to obtain the target Co-Ni / NC catalyst.

[0091] Comparative Example 1 Preparation of NC catalysts 1.28 g of melamine and 14.72 g of L-aspartic acid were placed in a stainless steel ball mill jar and ball-milled at 500 rpm for 30 min to obtain a mixed powder. The powder was transferred to a mortar, and 60 mL of anhydrous ethanol and 12 mL of hydrochloric acid aqueous solution (4 mol / L) were added sequentially. After thorough grinding and mixing, the mixture was dried at 40 °C for 24 h. The resulting solid was the catalyst precursor. 6.5 g of this precursor was subjected to programmed temperature heat treatment in an ammonia (NH3) atmosphere at a flow rate of 20 mL / min: first, the temperature was increased to 600 °C at a rate of 2.5 °C / min and maintained for 2 h, then increased to 800 °C at a rate of 5 °C / min and maintained for 90 min. After heat treatment, the furnace was allowed to cool naturally to room temperature to obtain the target NC catalyst.

[0092] Comparative Example 2 Preparation of Ni / NC-5 catalyst 1.28 g of melamine, 14.72 g of L-aspartic acid, and 0.147 g of nickel acetylacetonate were placed in a stainless steel ball mill jar and ball-milled at 500 rpm for 30 min to obtain a mixed powder. This powder was transferred to a mortar, and 60 mL of anhydrous ethanol and 12 mL of hydrochloric acid aqueous solution (4 mol / L) were added sequentially. After thorough grinding and mixing, the mixture was dried at 40 °C for 24 h. The resulting solid was the catalyst precursor. 6.5 g of this precursor was subjected to programmed temperature heat treatment in a nitrogen (N2) atmosphere at a flow rate of 20 mL / min: first, the temperature was increased to 600 °C at a rate of 2.5 °C / min and maintained for 2 h, then increased to 800 °C at a rate of 5 °C / min and maintained for 90 min. After heat treatment, the furnace was allowed to cool naturally to room temperature to obtain the target Ni / NC-5 catalyst.

[0093] Experimental Example 1 The catalysts prepared in Examples 1-4 and Comparative Examples 1-2 of this invention were applied to the reaction of acetylene hydrochlorination to prepare vinyl chloride. A typical experimental procedure is as follows: 0.34 g of 40-60 mesh catalyst was packed into a fixed-bed reactor with an inner diameter of 10 mm. The reactor was first purged with N2. Once the reaction temperature reached 220 °C, hydrogen chloride was introduced for activation for 30 min. Then, a mixture of acetylene and hydrogen chloride was introduced, maintaining the acetylene weight hourly space velocity at 163 mL∙g⁻¹. -1 ∙h -1 The reaction was evaluated under the condition that n(HCl):n(C2H2) = 1.15:1. The composition of the outlet gas was determined using online gas chromatography, and the conversion rate of the reactants and the selectivity of the products were calculated accordingly. The evaluation results are shown in Table 1.

[0094] Table 1. Performance of the catalyst in the acetylene hydrochlorination to vinyl chloride reaction. As shown in Table 1, the performance test results of the six catalysts indicate that Ni doping alters the catalyst's adsorption strength for the reaction substrate, thereby increasing its intrinsic activity and ultimately improving the acetylene conversion rate. Furthermore, the ammonia roasting environment and the ratio of nitrogen to carbon sources directly affect the catalyst's nitrogen content, the dispersion of metallic Ni, and the Ni-N coordination structure, thus influencing catalytic performance.

[0095] Experiment Example 2 The catalyst prepared in Example 2 of this invention was applied to the reaction of acetylene hydrochlorination to prepare vinyl chloride. A typical experimental procedure is as follows: 0.34 g of 40-60 mesh catalyst was packed into a fixed-bed reactor with an inner diameter of 10 mm. First, N2 was introduced for purging. Once the reaction temperature reached the target temperature, hydrogen chloride was introduced for activation for 30 min. Then, a mixture of acetylene and hydrogen chloride was introduced, maintaining the acetylene volume hourly space velocity at 30-124 h⁻¹. -1 The evaluation was conducted under the condition that n(HCl):n(C2H2) = 1.15:1. The composition of the outlet gas was determined using online gas chromatography, and the conversion rate of the reactants and the selectivity of the products were calculated accordingly. The evaluation results are shown in Table 2.

[0096] Table 2. Reaction performance of acetylene with hydrogen chloride to produce vinyl chloride under different reaction conditions. Analysis of the data in Table 2 shows that changes in reaction temperature and space velocity significantly affect the performance of the Ni / NC-2 catalyst. Under the process conditions investigated in this study, the acetylene conversion rate can be adjusted between 76% and 95%, while the vinyl chloride selectivity remains consistently above 98%. Of particular note is that under optimal process conditions, the catalyst achieves nearly 95% acetylene conversion while maintaining extremely high selectivity (98.7%), demonstrating excellent overall performance and broad operational flexibility.

[0097] Experimental Example 3 This experimental example can refer to the reaction steps of Experimental Example 2 to evaluate the stability of Ni / NC in Example 2. The difference is that this experimental example is conducted at 220 °C with an acetylene heavy hourly space velocity of 163 mL∙g⁻¹. -1 ∙h -1 Under the conditions of n(HCl):n(C2H2)=1.15:1, the reaction was carried out continuously for nearly 700 min, and the conversion rate of the reactants and the selectivity of the products were detected.

[0098] The specific results are attached. Figure 3 As shown in the results, the catalyst exhibits good stability, indicating that the Ni-N coordination structure regulates the adsorption configuration of the reaction substrate and improves the catalyst stability.

[0099] Furthermore, at a weight hourly space velocity of 163 mL∙g -1 ∙h -1 Under the given reaction conditions, no significant deactivation of the catalyst was observed after 10 h of reaction.

[0100] Experiment Example 4 The catalysts prepared in Examples 5-8 of this invention were applied to the reaction of acetylene hydrochlorination to prepare vinyl chloride. A typical experimental procedure is as follows: 0.34 g of 40-60 mesh catalyst was packed into a fixed-bed reactor with an inner diameter of 10 mm. The reactor was first purged with N2. Once the reaction temperature reached 220 °C, hydrogen chloride was introduced for activation for 30 min. Then, a mixture of acetylene and hydrogen chloride was introduced, maintaining the acetylene weight hourly space velocity at 163 mL∙g⁻¹. -1 ∙h -1 The reaction was evaluated under the condition that n(HCl):n(C2H2) = 1.15:1. The composition of the outlet gas was determined using online gas chromatography, and the conversion rate of the reactants and the selectivity of the products were calculated accordingly. The evaluation results are shown in Table 3.

[0101] Table 3 Performance of non-precious metal catalysts in the acetylene hydrochlorination to vinyl chloride reaction Table 3 shows the catalyst performance test results, indicating that the doping of Fe, Ni, and Co alters the adsorption strength of the catalyst for the reaction substrate, and all exhibit certain initial activity. Among them, the coordination structure formed by metallic Ni and N provides the best regulation of the adsorption strength of acetylene and hydrogen chloride, exhibiting the optimal catalytic performance.

Claims

1. A catalyst for the hydrochlorination of acetylene to vinyl chloride, the catalyst comprising a metal M and a nitrogen-doped carbon-based support, wherein the metal M forms an MN chemical bond with nitrogen in the nitrogen-doped carbon-based support, wherein... Metal M includes one or more of the elements Fe, Co, or Ni; Preferably, metal M is Ni, or metal M is Ni and Fe, or metal M is Ni and Co.

2. The catalyst according to claim 1, characterized in that, In the catalyst, the mass content of metal M is 0.3%~5%; Preferably, the mass content of metal M is 0.3% to 1.5%.

3. The catalyst according to claim 1 or 2, characterized in that, In the catalyst, the mass content of nitrogen is 10-24%; Preferably, the mass content of nitrogen in the catalyst is 11% to 18%.

4. A method for preparing the catalyst according to any one of claims 1-3, comprising: (1) Mix the nitrogen source, carbon source and salt containing metal M to obtain a mixture; (2) The mixture obtained in step (1) is dried and calcined to obtain the M-doped nitrogen-carbon catalyst; Among them, metal M includes one or more of the elements Fe, Co, or Ni; Preferably, the mixture in step (1) contains hydrochloric acid; Preferably, the mass ratio of hydrochloric acid to the total mass of nitrogen and carbon sources is 0.002-0.004 mol / g; Preferably, the concentration of hydrochloric acid in the mixture is controlled at 0.5~1 mol / L.

5. The preparation method according to claim 4, characterized in that, In step (2), calcination is carried out in an atmosphere containing ammonia; Preferably, the roasting temperature is 400-1000 °C; Preferably, the roasting process is divided into two stages. In the first stage, the roasting temperature is 400~600 °C (preferably 500~600 °C); in the second stage, the roasting temperature is 800~1000 °C (preferably 800~900 °C). In a further preferred embodiment, the roasting time in the first stage is 1-3 h; and in the second stage, the roasting time is 50 min to 100 min.

6. The preparation method according to claim 5, characterized in that, During the roasting process, the temperature is increased from room temperature to 400-600 °C at a rate of 2.0-3.0 °C / min (preferably 2.5 °C / min); The temperature is increased from the first stage temperature to the second stage temperature at a heating rate of 4.0-6.0 °C / min (preferably 5.0 °C / min).

7. The preparation method according to any one of claims 4-6, characterized in that, The ammonia flow rate is 1.4-7.5 mL / min per gram of the mixture to be roasted; Preferably, the ammonia flow rate is 2.8-7.5 mL / min per gram of the roasted mixture.

8. The preparation method according to any one of claims 4-7, characterized in that, The preparation method includes: (1) mixing a nitrogen source, a carbon source and a salt containing metal M to obtain a mixed powder; adding an organic solvent and hydrochloric acid to the mixed powder to obtain a mixture; (2) The mixture obtained in step (1) is dried and calcined to obtain the M-doped nitrogen-carbon catalyst; Preferably, the organic solvent is ethanol, the volume ratio of ethanol to hydrochloric acid solution is (5~7):1 (preferably (5~6):1), and the concentration of hydrochloric acid solution is 3~5 mol / L (preferably 4~5 mol / L).

9. The preparation method according to any one of claims 4-8, characterized in that, The carbon source includes one of L-aspartic acid and glucose (preferably L-aspartic acid); the nitrogen source includes one of urea, melamine, and dicyandiamide (preferably melamine); the salt containing metal M is a soluble salt solution; Preferably, the content of metal M is 0.1~1.0 wt% relative to the total mass of the nitrogen source, carbon source and salt containing metal M (preferably, the content of Ni is 0.1~1.0 wt%). Preferably, the Ni content is 0.1~0.6 wt% relative to the total mass of the nitrogen source, carbon source, and salt containing metal M; (preferably, 0.105~0.55 wt%). More preferably, in the mixture of step (1), the mass ratio of nitrogen source to carbon source is 0.05~1 (preferably (0.18~1):1).

10. A method for producing vinyl chloride by hydrochlorination of acetylene, comprising: Under the action of the catalyst described in any one of claims 1-3, hydrogen chloride gas reacts with acetylene at a reaction temperature of 180~240 °C. Preferably, the reaction temperature is 200-240 ℃ (preferably 220 ℃); Preferably, the volumetric flow rate ratio of hydrogen chloride to acetylene is (1~1.5):1; More preferably, the acetylene space velocity is 30~130 h⁻¹. -1 .

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