A gold-based catalyst for polyvinyl chloride production and its preparation method and application

Abstract

The invention relates to a gold-based catalyst for the production of polyvinyl chloride, a preparation method and an application thereof. The gold-based catalyst uses a carbon material as a carrier and gold trichloride as an active component. Under the strong interaction of the coordination bonds of a synthesized azobenzoheterocyclic structure, a conjugated organic framework structure strengthens the anchoring of the active metal component. The gold-based catalyst can be used for preparing polyvinyl chloride by a fixed-bed acetylene hydrochlorination reaction in a laboratory or industrial production. By adding an azobenzoheterocyclic structure ligand, the structure of the prepared gold-based catalyst is more stable, thereby providing a catalyst for preparing polyvinyl chloride with high conversion rate and high stability.

Description

Technical Field

[0001] The invention belongs to the field of catalysts containing gold, and in particular relates to a preparation method and application of a gold-based catalyst that can be used for synthesizing polyvinyl chloride. Background Art

[0002] Polyvinyl chloride (PVC) is one of the world's five major general-purpose plastics, which is polymerized from vinyl chloride monomer (VCM). At present, more than 80% of VCM production in China mainly adopts the "calcium carbide method". However, this process requires the use of a catalyst with mercuric chloride as the active component. Mercury-based catalysts seriously threaten ecological environmental safety and human health due to their high toxicity and volatility. Therefore, it is urgent to develop an efficient, stable, environmentally friendly mercury-free catalyst and its related technologies.

[0003] Mercury-free catalysts for acetylene hydrochlorination mainly focus on three aspects: precious metals such as Au, Pd, and Ru, non-precious metals such as Cu, Sn, and Bi, and metal-free catalysts made of nitrogen-doped carbon materials. Among them, gold-based catalysts can replace mercury-based catalysts and meet the needs of large-scale industrial use of acetylene hydrochlorination. At present, the main problem of gold-based mercury-free catalysts is Au 3+ Carbon deposition occurs during the reduction and use of the catalyst. Experiments show that the AuCl3 catalyst supported on activated carbon is deactivated under both high and low temperature reaction conditions. At low temperatures (60-100°C), the deactivation of the catalyst is mainly due to the deposition of carbonaceous polymers on the catalyst surface, covering the surface active sites. The carbonaceous polymers may come from the polymerization of vinyl chloride monomers on the catalyst surface; at high temperatures (120–180°C), the deactivation of the catalyst is mainly due to the deposition of Au 3+ and Au + Reduced to inactive Au 0 In order to reduce Au 3+ and Au + reduction, and the introduction of suitable ligands to stabilize the high-valent Au in the gold catalyst 3+ It is a common modification method.

[0004] In existing reports, after adding chelating donors and N-containing ligands, Au 3+The activity and stability of the catalyst have been significantly improved. Common N-containing ligands include thiosulfate, thiocyanate, thiourea and cyanide. For example, the patent (CN 109622036A) uses the complex formed by gold salt and nitrogen-containing ligand as the main active component. The complexation of nitrogen-containing ligand and gold stabilizes the high-valent gold and thus improves the efficiency of the catalyst; the patent (CN113634280B) uses organic complexes such as triphenylphosphine gold chloride, tri-tert-butyl phosphine gold, trichloropyridinium gold, acetylacetonate dimethyl gold, dimethyl sulfide gold chloride as the active component of mercury-free catalysts, and has achieved good results. The existing gold-based catalysts use nitrogen-containing ligands that are basically monodentate ligands, that is, there is only one atom that can coordinate with gold, so the atomic utilization of the ligand is low, and the introduction of a large number of ligands also has an adverse effect on the activity and stability of the catalyst. At present, the main problems of gold-based catalysts include that ionic Au is easily reduced, the active component Au is easily lost, and the carbon deposition phenomenon is serious, resulting in poor stability and easy deactivation of mercury-free catalysts. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a gold-based catalyst for polyvinyl chloride production and a preparation method and application thereof.

[0006] The technical scheme adopted by the present invention is: a gold-based catalyst for the production of polyvinyl chloride, comprising a carbon carrier, an active component of gold trichloride, and an azobenzene heterocyclic structure ligand loaded on the carbon carrier.

[0007] Preferably, the azobenzoheterocyclic structure is a combination of one or more of (E)-2,2′-azobenzimidazole, (E)-2,2′-azobenzoxazole, (E)-2,2′-azobenzothiazole, (E)-1,2-bisbenzimidazole-6-yldiazene, (E)-1,2-bisbenzoxazole-6-yldiazene and (E)-1,2-bisbenzothiazol-6-yldiazene.

[0008] Preferably, the carbon carrier is a combination of one or more of coconut shell charcoal, activated carbon, pitch charcoal and resin charcoal.

[0009] The invention discloses a method for preparing a gold-based catalyst for producing polyvinyl chloride. The method comprises the following steps: preparing a solution containing an azobenzoheterocyclic structure ligand and chloroauric acid, impregnating the solution into a carbon carrier, and drying the solution to obtain the gold-based catalyst.

[0010] Preferably, the molar ratio of the azobenzene heterocyclic structure ligand to Au is 2-10:1; and the mass content of Au in the gold-based catalyst is 1‰-5‰.

[0011] Preferably, the aminobenzoheterocyclic precursor is dissolved in solvent A, Lewis acid is added at 0-5°C to obtain solution B, an oxidant aqueous solution C is added dropwise to solution B, and the reaction is stirred at 60-80°C to obtain an azobenzoheterocyclic structure ligand;

[0012] The molar ratio of aminobenzoheterocyclic precursor: solvent A: Lewis acid: oxidant is 1:30–100:0.1–0.01:1–10.

[0013] Preferably, the aminobenzoheterocyclic precursor is one or two of 2-aminobenzimidazole, 2-aminobenzoxazole, 2-aminobenzothiazole, 5-aminobenzimidazole, 6-aminobenzoxazole, and 1,3-benzothiazole-5-amine;

[0014] Solvent A is a combination of one or more of N,N-dimethylformamide, N,N-dimethylacetamide, N,N-diethylformamide, N,N-diethylacetamide, dimethyl sulfoxide, tetrahydrofuran, ether, acetonitrile, ethyl acetate, dichloromethane, chloroform, methanol, ethanol, isopropanol, ethylene glycol, glycerol, acetone, pyridine, benzene, toluene, xylene, n-hexane, cyclohexane, hydrochloric acid, sulfuric acid, nitric acid, formic acid, acetic acid, petroleum ether, formaldehyde, and phenol;

[0015] The Lewis acid is a combination of one or more of AlCl3, BF3, FeCl3, TiCl4, ZnCl2, B(C2H5)3, BF3·OEt2, SnCl2·2H2O, SnCl4, NbCl5, I2, Sc(OTf)3, Y(OTf)3, Cu(OTf)2, In(OTf)3, and Yb(OTf)3;

[0016] The oxidant is a combination of one or more of cobalt trifluoride, boron tribromide, potassium permanganate, potassium dichromate, sodium dichromate, potassium bromate, potassium chlorate, sodium chlorate, sodium hypochlorite, m-chloroperbenzoic acid, tert-butyl hypochlorite, 2,3-dichloro-5,6-dicyanobenzoquinone, N-iodosuccinimide, hydrogen peroxide, periodic acid, cerium nitrate, ammonium persulfate, sodium bismuthate, sodium tungstate, cuprous chloride, ferric chloride, sodium ferrate, potassium ferrate, and ammonium persulfate.

[0017] The use of gold-based catalysts for the production of polyvinyl chloride in the preparation of polyvinyl chloride.

[0018] Preferably, it is used for preparing polyvinyl chloride by acetylene hydrochlorination reaction in a laboratory fixed bed; or it is used for preparing polyvinyl chloride by acetylene hydrochlorination reaction in an industrial fixed bed.

[0019] Preferably, when used for the laboratory fixed bed acetylene hydrochlorination reaction to prepare polyvinyl chloride, the steps are as follows:

[0020] The catalyst was loaded into a fixed-bed reactor for the synthesis of polyvinyl chloride monomer and pretreated at 150–200 °C under flowing nitrogen for at least 1 h.

[0021] Switch nitrogen to HCl and purge for at least 1 h; turn on C2H2 and set its gas space velocity to 80–320 h –1 , the volume ratio of HCl / C2H2 is 1.05–1.30:1;

[0022] The reaction tail gas is absorbed by alkaline solution and dehydrated by silica gel column before entering into gas chromatography for online analysis;

[0023] After the reaction is completed, turn off the raw gas first, then continue to purge with nitrogen for 0.5-1 h, cool down, and turn off the nitrogen after the temperature drops below 50 °C;

[0024] Alternatively, when used in an industrial fixed-bed acetylene hydrochlorination reaction to prepare polyvinyl chloride, the steps are as follows:

[0025] The catalyst was loaded into an industrial polyvinyl chloride monomer synthesis unit and pretreated at 150–200 °C under flowing nitrogen for at least 48 h;

[0026] Switch nitrogen to HCl, purge for at least 12 h, then switch to HCl / C2H2 feed gas to start the reaction, and set the C2H2 gas space velocity to 10–60 h –1 , where the volume ratio of HCl / C2H2 is 1.05–1.30:1;

[0027] The polyvinyl chloride monomer produced by the reaction directly enters the subsequent polymerization unit for the synthesis of polyvinyl chloride, and the operation process of other units remains unchanged;

[0028] After the reaction is completed, the raw gas is first turned off, and then nitrogen is continued to be purged for at least 24 hours before cooling down. After the temperature drops to ambient temperature, the nitrogen is continued to be purged for at least 48 hours before turning off the nitrogen.

[0029] The advantages and positive effects of the present invention are: by adding the azobenzene heterocyclic structure ligand, the coordination structure formed is AuCl3 - Most of the azole rings and condensed ring structures are more stable, and the negative ionic charge is dispersed throughout the nitrogen heterocycle and is attracted by the azo group connected to it. The prepared gold-based catalyst structure is more stable, providing a catalyst for the preparation of polyvinyl chloride with high conversion rate and high stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a transmission electron microscopy image of the Au / C-Azo-Het-N catalyst of Example 1;

[0031] Figure 2This is the thermogravimetric curve of the Au / C-Azo-Het-N catalyst of Example 1. DETAILED DESCRIPTION

[0032] The embodiments of the present invention are described below with reference to the accompanying drawings.

[0033] The invention relates to a gold-based catalyst for the production of polyvinyl chloride, a preparation method and an application thereof. A treated azobenzoheterocyclic structure ligand is added to the gold-based catalyst. The ligand has coordination groups of two structures, namely, an azo structure and a nitrogen-containing heterocyclic structure, and has good coordination ability with the Au central atom. The catalyst uses a carbon material as a carrier and gold trichloride as an active component. Under the strong interaction of the coordination bond of the synthesized azobenzoheterocyclic structure, the conjugated organic framework structure strengthens the anchoring of the active metal component. When preparing the gold-based catalyst, the azobenzoheterocyclic structure shown in Formula 1 or Formula 2 is first synthesized by an aminobenzoheterocyclic precursor, and then the azobenzoheterocyclic structure ligand and chloroauric acid are mixed to prepare a solution and impregnated into the carbon carrier, thereby preparing a gold-based catalyst for synthesizing polyvinyl chloride. The constructed catalyst contains a ligand of an azo structure with heteroatoms (such as N, O, S, etc.), and a benzene ring that stabilizes the ligand structure is introduced. With the help of electronic effects, the stability of the gold-based catalyst can be significantly improved.

[0034] Formula 1;

[0035] Formula 2;

[0036] The specific steps are as follows:

[0037] Step 1: Preparation of azobenzoheterocyclic structure ligand; dissolve the aminobenzoheterocyclic precursor in solvent A, control the water bath temperature at 0-5 °C, then add Lewis acid, stir until completely dissolved to obtain solution B, then slowly drop oxidant aqueous solution C into solution B, then heat to 60-80 °C and stir for at least 3 h, then cool to room temperature, filter and wash with solvent A for at least three times, and then dry to obtain the azobenzoheterocyclic structure ligand; wherein the molar ratio of aminobenzoheterocyclic precursor: solvent A: Lewis acid: oxidant is 1:30-100:0.1-0.01:1-10;

[0038] Step 2: Preparation of gold-based catalysts; dissolve the azobenzene heterocyclic structure ligand in solvent D to obtain solution E; then add chloroauric acid to solution E, stir at room temperature for 1-3 h, then impregnate it into a carbon support, and then dry it to obtain a gold-based catalyst; wherein the molar ratio of the ligand to Au is 2-10:1; wherein the mass content of Au in the catalyst is 1‰-5‰.

[0039] Wherein, solvent A is a combination of one or more of N,N-dimethylformamide, N,N-dimethylacetamide, N,N-diethylformamide, N,N-diethylacetamide, dimethyl sulfoxide, tetrahydrofuran, ether, acetonitrile, ethyl acetate, dichloromethane, chloroform, methanol, ethanol, isopropanol, ethylene glycol, glycerol, acetone, pyridine, benzene, toluene, xylene, n-hexane, cyclohexane, hydrochloric acid, sulfuric acid, nitric acid, formic acid, acetic acid, petroleum ether, formaldehyde and phenol; solvent D is a combination of one or more of N,N-dimethylformamide, N,N-dimethylacetamide, N,N-diethylacetamide, N,N-diethylacetamide, dimethyl sulfoxide, tetrahydrofuran, methanol, ethanol and acetone; and the Lewis acid is AlCl3, BF3, FeCl3, Ti The oxidant is a combination of one or more of Cl4, ZnCl2, B(C2H5)3, BF3·OEt2, SnCl2·2H2O, SnCl4, NbCl5, I2, Sc(OTf)3, Y(OTf)3, Cu(OTf)2, In(OTf)3 and Yb(OTf)3; the oxidant is a combination of one or more of cobalt trifluoride, boron tribromide, potassium permanganate, potassium dichromate, sodium dichromate, potassium bromate, potassium chlorate, sodium chlorate, sodium hypochlorite, m-chloroperbenzoic acid, tert-butyl hypochlorite, 2,3-dichloro-5,6-dicyanobenzoquinone, N-iodosuccinimide, hydrogen peroxide, periodic acid, cerium nitrate, ammonium persulfate, sodium bismuthate, sodium tungstate, cuprous chloride, ferric chloride, sodium ferrate, potassium ferrate and ammonium persulfate. In certain embodiments of the present invention, the carbon carrier is a combination of one or more of coconut shell charcoal, activated carbon, pitch charcoal and resin charcoal.

[0040] In the construction of the ligand, an azobenzoheterocyclic structure can be obtained by synthesizing an aminobenzoheterocyclic ring; wherein the aminobenzoheterocyclic ring precursor is one or two of 2-aminobenzimidazole, 2-aminobenzoxazole, 2-aminobenzothiazole, 5-aminobenzimidazole, 6-aminobenzoxazole, and 1,3-benzothiazole-5-amine, and the structure is shown in Formula 3-8; the azobenzoheterocyclic structure is one or more of (E)-2,2′-azobenzimidazole, (E)-2,2′-azobenzoxazole, (E)-2,2′-azobenzothiazole, (E)-1,2-bisbenzimidazole-6-yldiazene, (E)-1,2-bisbenzoxazole-6-yldiazene, and (E)-1,2-bisbenzothiazole-6-yldiazene, and the structure is shown in Formula 9-14. In certain embodiments of the present invention, azobenzene heterocyclic structures with different side group structures may also be used.

[0041] Formula 3; Formula 4; Formula 5;

[0042] Formula 6; Formula 7; Formula 8;

[0043] Formula 9; Formula 10;

[0044] Formula 11; Formula 12;

[0045] Formula 13; Formula 14.

[0046] In addition to the above-mentioned ligands of azobenzoheterocyclic rings, the precursors used in their synthesis are also good ligands for the gold-based catalysts used in the acetylene hydrochlorination reaction in this section, including isoligands and isoligands of azobenzoheterocyclic rings derived therefrom;

[0047] Add azobenzene heterocyclic ligands to the catalyst, where the gold-based catalyst forms a coordination structure with AuCl3 - , while most azole rings and condensed ring structures are more stable, and the negative ionic charge is dispersed throughout the nitrogen heterocyclic ring and can be attracted by the azo group connected to it; among them, the heterocyclic structure carries different numbers of S, N, O and other groups, which is more beneficial to the stability of the entire ligand skeleton structure, thereby improving the conversion efficiency and stability of the prepared catalyst.

[0048] The aminobenzoheterocyclic structure is used as a ligand. Compared with the other six derived ligands (Formula 9-Formula 14), the structure is simpler and can be directly used as a raw material for industrial production. The cost is lower and the preparation process can better meet the requirements of industrial use. The six azo structure ligands synthesized have better water solubility and are more conducive to the preparation and application of gold-based catalysts compared to some existing commercial ligands.

[0049] The gold-based catalyst prepared by the above method can be used for laboratory production of polyvinyl chloride and is also suitable for industrial production of polyvinyl chloride.

[0050] The method for using the gold-based catalyst to produce polyvinyl chloride monomer in a laboratory comprises the following steps:

[0051] (1) The catalyst was loaded into a fixed bed reactor for the synthesis of polyvinyl chloride monomer and pretreated at 150–200 °C under flowing nitrogen for at least 1 h;

[0052] (2) Switch nitrogen to HCl and purge for at least 1 h; then turn on C2H2 and set its gas space velocity to 80–320 h –1 , while ensuring that the volume ratio of HCl / C2H2 is 1.05–1.30:1;

[0053] (3) The reaction tail gas is absorbed by alkaline solution and dehydrated by silica gel column before entering the gas chromatography for online analysis;

[0054] (4) After the reaction is completed, turn off the raw gas first, then continue to purge with nitrogen for 0.5-1 h, then cool down, and turn off the nitrogen after the temperature drops below 50 °C.

[0055] The method for using the gold-based catalyst in the production of industrial polyvinyl chloride comprises the following steps:

[0056] (1) The catalyst was loaded into an industrial polyvinyl chloride monomer synthesis unit and pretreated at 150–200 °C under flowing nitrogen for at least 48 h;

[0057] (2) Switch nitrogen to HCl, purge for at least 12 h, then switch to HCl / C2H2 feed gas to start the reaction, and set the C2H2 gas space velocity to 10–60 h –1 , where the volume ratio of HCl / C2H2 is 1.05–1.30:1;

[0058] (3) The polyvinyl chloride monomer produced by the reaction directly enters the subsequent polymerization unit for the synthesis of polyvinyl chloride, and the operation process of other units remains unchanged; other units can be polymerization units, compression separation and other structures;

[0059] (4) After the reaction is completed, turn off the raw gas first, then continue to purge with nitrogen for at least 24 hours before cooling down. After the temperature drops to ambient temperature, continue to purge for at least 48 hours before turning off the nitrogen.

[0060] In the above-mentioned preparation process using a catalyst, the polyvinyl chloride monomer refers to vinyl chloride. It has been verified that the gold-based catalyst prepared by the method of the present invention exhibits good activity and stability in the atmospheric pressure fixed bed acetylene hydrochlorination reaction both in the laboratory and in an industrial amplification device.

[0061] The scheme of the present invention is described below in conjunction with the attached table, wherein the experimental methods without specific operating steps are all carried out in accordance with the corresponding product instructions, and the instruments, reagents, and consumables used in the examples can all be purchased from commercial companies unless otherwise specified.

[0062] Example 1

[0063] (1) Dissolve the 2-aminobenzimidazole precursor in hydrochloric acid, control the water bath temperature at 0-5 °C, then add AlCl3, stir until completely dissolved to obtain a solution, then slowly drop potassium permanganate aqueous solution into the above precursor solution, then heat to 60-80 °C and stir for at least 3 h, then cool to room temperature, filter and wash at least three times, and then dry to obtain 2,2′-azobenzimidazole; the molar ratio of 2-aminobenzimidazole: hydrochloric acid: AlCl3: potassium permanganate is 1:30:0.01:2; obtain a ligand named Azo-Het-N;

[0064] (2) The Azo-Het-N ligand was dissolved in ethanol to obtain a solution; chloroauric acid was then added to the solution, stirred at room temperature for 1–3 h, and then impregnated into a resin carbon support, followed by drying to obtain an Au / C-Azo-Het-N catalyst; wherein the molar ratio of the ligand to Au was 5:1; and the mass content of Au in the catalyst was 1‰.

[0065] The transmission electron microscopy image of the prepared Au / C-Azo-Het-N catalyst is shown in Figure 1 shown.

[0066] Example 2

[0067] The preparation steps of Example 2 are the same as those of Example 1, except that the 2-aminobenzimidazole precursor in step (1) is replaced by 2-aminobenzoxazole. The obtained catalyst is numbered Au / C-Azo-Het-O catalyst.

[0068] Example 3

[0069] The preparation steps of Example 3 are the same as those of Example 1, except that the 2-aminobenzimidazole precursor in step (1) is replaced by 2-aminobenzothiazole. The obtained catalyst is numbered Au / C-Azo-Het-S catalyst.

[0070] Example 4

[0071] The preparation steps of Example 4 are the same as those of Example 1, except that the 2-aminobenzimidazole precursor in step (1) is replaced by 5-aminobenzimidazole. The obtained catalyst is numbered Au / C-Azo-Ph-N catalyst.

[0072] Example 5

[0073] The preparation steps of Example 5 are the same as those of Example 1, except that the 2-aminobenzimidazole precursor in step (1) is replaced by 6-aminobenzoxazole. The obtained catalyst is numbered Au / C-Azo-Ph-O catalyst.

[0074] Example 6

[0075] The preparation steps of Example 6 are the same as those of Example 1, except that the 2-aminobenzimidazole precursor in step (1) is replaced by 1,3-benzothiazole-5-amine. The obtained catalyst is numbered Au / C-Azo-Ph-S catalyst.

[0076] Comparative Example 1:

[0077] The 2-aminobenzimidazole ligand is dissolved in ethanol to obtain a solution; chloroauric acid is then added to the solution, stirred at room temperature for 1-3 h, and then impregnated into a resin carbon support, and then dried to obtain an Au / C-Het-N catalyst; wherein the molar ratio of the ligand to Au is 5:1; wherein the mass content of Au in the catalyst is 1‰.

[0078] Comparative Example 2:

[0079] The preparation steps of Comparative Example 2 are the same as those of Comparative Example 1, except that the 2-aminobenzimidazole ligand is replaced by 2-aminobenzoxazole ligand, and the obtained catalyst is numbered as Au / C-Het-O catalyst.

[0080] Comparative Example 3:

[0081] The preparation steps of Comparative Example 3 are the same as those of Comparative Example 1, except that the 2-aminobenzimidazole ligand is replaced by 2-aminobenzothiazole ligand, and the obtained catalyst is numbered as Au / C-Het-S catalyst.

[0082] Comparative Example 4:

[0083] The preparation steps of Comparative Example 4 are the same as those of Comparative Example 1, except that the 2-aminobenzimidazole ligand is replaced by a 5-aminobenzimidazole ligand, and the obtained catalyst is numbered Au / C-Ph-N catalyst.

[0084] Comparative Example 5:

[0085] The preparation steps of Comparative Example 5 are the same as those of Comparative Example 1, except that the 2-aminobenzimidazole ligand is replaced by a 6-aminobenzoxazole ligand, and the obtained catalyst is numbered as Au / C-Ph-O catalyst.

[0086] Comparative Example 6:

[0087] The preparation steps of Comparative Example 6 are the same as those of Comparative Example 1, except that the 2-aminobenzimidazole ligand is replaced by 1,3-benzothiazole-5-amine ligand, and the obtained catalyst is numbered as Au / C-Ph-S catalyst.

[0088] Comparative Example 7:

[0089] Comparative Example 7 is to explore the effect of the above ligand on the activity and stability of the gold-based catalyst. Without adding any ligand, the above equal amount of chloroauric acid solution is directly impregnated on the activated carbon to obtain the Au / C catalyst.

[0090] Example 7: Catalyst Application

[0091] Preparation of polyvinyl chloride by hydrochlorination of acetylene.

[0092] (1) The catalyst was loaded into a fixed bed reactor for the synthesis of polyvinyl chloride monomer and pretreated at 180 °C under flowing nitrogen for at least 1 h;

[0093] (2) Switch nitrogen to HCl and purge for at least 1 h; then turn on C2H2 and set its gas space velocity to 160 h –1 , while ensuring that the volume ratio of HCl / C2H2 is 1.2:1;

[0094] (3) The reaction tail gas is absorbed by alkaline solution and dehydrated by silica gel column before entering the gas chromatography for online analysis;

[0095] (4) After the reaction is completed, turn off the raw gas first, then continue to purge with nitrogen for 1 hour, then cool down, and turn off the nitrogen after the temperature drops below 50 °C.

[0096] The results of acetylene conversion (average data within 5-10 h of reaction) and catalyst stability (average rate of decrease of vinyl chloride conversion for each group of catalysts within 5-10 h of reaction) are shown in Table 1.

[0097] Table 1 Activity and stability of catalysts in fixed-bed acetylene hydrochlorination

[0098]

[0099] It can be seen from the data in Table 1 that the gold-based catalysts prepared in Examples 1-6 have outstanding effects on reaction conversion rate, and the stability of the catalysts is also better. Among them, the Au / C-Azo-Het-N catalyst and the Au / C-Azo-Ph-S catalyst with azo structure have the best effects, wherein the acetylene conversion rates are 96.27% and 96.34% respectively, and the catalyst stability (conversion rate decrease rate per hour) is 0.299% and 0.253% respectively. The thermogravimetric curve of the Au / C-Azo-Het-N catalyst is shown in the attached figure. Figure 2 As shown, the carbon deposition rate at 0-200℃ was about 1.3%, which is at a relatively high level among the catalysts reported at this stage.

[0100] The embodiments of the present invention are described in detail above, but the contents described are only preferred embodiments of the present invention and cannot be considered to limit the scope of implementation of the present invention. All equivalent changes and improvements made within the scope of the present invention should still fall within the scope of the patent coverage of the present invention.

Claims

1. A gold-based catalyst for the production of polyvinyl chloride, characterized in that: The invention comprises a carbon carrier, an active component of gold trichloride, and an azobenzoheterocyclic structure ligand supported on the carbon carrier, wherein the azobenzoheterocyclic structure ligand has coordination groups of two structures, namely, an azo structure and a nitrogen-containing heterocyclic structure; the molar ratio of the azobenzoheterocyclic structure ligand to Au is 2-10:1; and the mass content of Au in the gold-based catalyst is 1‰-5‰.

2. The gold-based catalyst for polyvinyl chloride production according to claim 1, characterized in that: The azobenzoheterocyclic structure is a combination of one or more of (E)-2,2′-azobenzimidazole, (E)-2,2′-azobenzoxazole, (E)-2,2′-azobenzothiazole, (E)-1,2-bisbenzimidazole-6-yldiazene, (E)-1,2-bisbenzoxazole-6-yldiazene and (E)-1,2-bisbenzothiazol-6-yldiazene.

3. The gold-based catalyst for polyvinyl chloride production according to claim 1, characterized in that: The carbon carrier is a combination of one or more of coconut shell charcoal, activated carbon, pitch charcoal and resin charcoal.

4. The method for preparing a gold-based catalyst for polyvinyl chloride production according to any one of claims 1 to 3, characterized in that: A solution containing an azobenzene heterocyclic structure ligand and chloroauric acid is prepared, impregnated into a carbon support, and dried to obtain a gold-based catalyst.

5. The method for preparing a gold-based catalyst for polyvinyl chloride production according to claim 4, characterized in that: The aminobenzoheterocyclic precursor is dissolved in solvent A, Lewis acid is added at 0-5°C to obtain solution B, an oxidant aqueous solution C is added dropwise to solution B, and the reaction is stirred at 60-80°C to obtain an azobenzoheterocyclic structure ligand; The molar ratio of aminobenzoheterocyclic precursor: solvent A: Lewis acid: oxidant is 1:30–100:0.1–0.01:1–10.

6. The method for preparing a gold-based catalyst for polyvinyl chloride production according to claim 5, characterized in that: The aminobenzoheterocyclic precursor is one or two of 2-aminobenzimidazole, 2-aminobenzoxazole, 2-aminobenzothiazole, 5-aminobenzimidazole, 6-aminobenzoxazole, and 1,3-benzothiazol-5-amine; Solvent A is a combination of one or more of N,N-dimethylformamide, N,N-dimethylacetamide, N,N-diethylformamide, N,N-diethylacetamide, dimethyl sulfoxide, tetrahydrofuran, ether, acetonitrile, ethyl acetate, dichloromethane, chloroform, methanol, ethanol, isopropanol, ethylene glycol, glycerol, acetone, pyridine, benzene, toluene, xylene, n-hexane, cyclohexane, hydrochloric acid, sulfuric acid, nitric acid, formic acid, acetic acid, petroleum ether, formaldehyde, and phenol; The Lewis acid is a combination of one or more of AlCl3, BF3, FeCl3, TiCl4, ZnCl2, B(C2H5)3, BF3·OEt2, SnCl2·2H2O, SnCl4, NbCl5, I2, Sc(OTf)3, Y(OTf)3, Cu(OTf)2, In(OTf)3, and Yb(OTf)3; The oxidant is a combination of one or more of cobalt trifluoride, boron tribromide, potassium permanganate, potassium dichromate, sodium dichromate, potassium bromate, potassium chlorate, sodium chlorate, sodium hypochlorite, m-chloroperbenzoic acid, tert-butyl hypochlorite, 2,3-dichloro-5,6-dicyanobenzoquinone, N-iodosuccinimide, hydrogen peroxide, periodic acid, ceric ammonium nitrate, ammonium persulfate, sodium bismuthate, sodium tungstate, cuprous chloride, ferric chloride, sodium ferrate, potassium ferrate, and ammonium persulfate.

7. Use of the gold-based catalyst for polyvinyl chloride production as described in any one of claims 1 to 3 in the preparation of polyvinyl chloride.

8. The use according to claim 7, characterized in that: It is used for preparing polyvinyl chloride by acetylene hydrochlorination reaction in laboratory fixed bed; or it is used for preparing polyvinyl chloride by acetylene hydrochlorination reaction in industrial fixed bed.

9. The use according to claim 8, characterized in that: When used in a laboratory fixed-bed acetylene hydrochlorination reaction to prepare polyvinyl chloride, the steps are as follows: The catalyst was loaded into a fixed-bed reactor for the synthesis of polyvinyl chloride monomer and pretreated at 150–200 °C under flowing nitrogen for at least 1 h. Switch nitrogen to HCl and purge for at least 1 h; turn on C2H2 and set its gas space velocity to 80–320 h –1 , the volume ratio of HCl / C2H2 is 1.05–1.30:1; The reaction tail gas is absorbed by alkaline solution and dehydrated by silica gel column before entering into gas chromatography for online analysis; After the reaction is completed, turn off the raw gas first, then continue to purge with nitrogen for 0.5-1 h, cool down, and turn off the nitrogen after the temperature drops below 50 °C; Alternatively, when used in an industrial fixed-bed acetylene hydrochlorination reaction to prepare polyvinyl chloride, the steps are as follows: The catalyst was loaded into an industrial polyvinyl chloride monomer synthesis unit and pretreated at 150–200 °C under flowing nitrogen for at least 48 h. Switch nitrogen to HCl, purge for at least 12 h, then switch to HCl / C2H2 feed gas to start the reaction, and set the C2H2 gas space velocity to 10–60 h –1 , where the volume ratio of HCl / C2H2 is 1.05–1.30:1; The polyvinyl chloride monomer produced by the reaction directly enters the subsequent polymerization unit for the synthesis of polyvinyl chloride, and the operation process of other units remains unchanged; After the reaction is completed, the raw gas is first turned off, and then nitrogen is continued to be purged for at least 24 hours before cooling down. After the temperature drops to ambient temperature, the nitrogen is continued to be purged for at least 48 hours before turning off the nitrogen.

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