Synthesis method of catalyst for catalytic cracking of 1,2-dichloroethane to vinyl chloride and application thereof

Abstract

The application discloses a synthesis method of a high-activity 1,2-dichloroethane catalytic cracking catalyst for preparing vinyl chloride, and active components in the catalyst are uniformly dispersed on nitrogen-doped carbon dots loaded on activated carbon. According to the method, the nitrogen-doped carbon dots containing the active components are prepared first, and then the nitrogen-doped carbon dots are loaded on the activated carbon to prepare a composite catalyst. The catalyst can efficiently catalyze the 1,2-dichloroethane cracking reaction for preparing vinyl chloride. Compared with existing 1,2-dichloroethane cracking catalysts for preparing vinyl chloride, the active components have better dispersity, the energy consumption can be greatly reduced, the production cost is reduced, and the catalyst has a good industrialization prospect.

Description

Technical Field

[0001] This application relates to a method for synthesizing a highly active catalyst for the catalytic cracking of 1,2-dichloroethane to produce vinyl chloride and its application, belonging to the field of vinyl chloride monomer preparation. Background Technology

[0002] Polyvinyl chloride (PVC), one of the five most widely used general-purpose plastics globally, plays an indispensable role in building materials, packaging materials, and wires and cables. The core of its production lies in the preparation of vinyl chloride monomer, and there are two main methods for preparing vinyl chloride: the acetylene process and the ethylene process.

[0003] The acetylene process for producing vinyl chloride typically relies on mercury catalysts. While this method has been used in industrial production, the use of mercury catalysts not only leads to high investment costs but also poses serious environmental pollution and health risks. Therefore, with increasing environmental awareness and stricter regulations, the acetylene process is gradually being replaced by more environmentally friendly and efficient methods.

[0004] The ethylene-based method has become the mainstream method for producing vinyl chloride. It mainly relies on the chlorination or oxychlorination reaction of ethylene to produce 1,2-dichloroethane, which is then cracked at high temperature to obtain vinyl chloride. However, although the high-temperature cracking method is a mature technology, it suffers from problems such as high energy consumption, easy coking, and short production cycle, which limit the further development of this method.

[0005] In recent years, researchers have conducted extensive studies on reducing pyrolysis temperature and improving catalyst activity. Among these, catalytic pyrolysis technology has attracted much attention due to its ability to achieve efficient pyrolysis at relatively low temperatures. Early research mainly focused on catalysts such as metal chlorides. Although these catalysts can reduce the pyrolysis temperature to some extent, problems such as easy catalyst deactivation and still relatively high pyrolysis temperatures remain to be solved.

[0006] Patent CN113262794A discloses a combined catalyst, but this catalyst contains many types of metals and has a complex preparation process, which is not conducive to mass production by enterprises. Patent CN116251610A discloses a single-atom catalyst, in which the active center metal exists entirely in the form of isolated single atoms on nitrogen-doped carbon material, but the carbon material has poor dispersion and is prone to agglomeration, resulting in less exposure of the catalyst's active sites.

[0007] As research has progressed, nitrogen-doped carbon dots loaded with metal chlorides have become a research hotspot. Due to the unique structure of carbon dots (0-10 nm), the dispersion of active metal components can be greatly improved, increasing metal activity. Furthermore, the nitrogen doped in these carbon dots also plays a crucial role in the catalytic cracking process.

[0008] Nitrogen-doped carbon-supported metal chlorides, as an emerging catalyst type, have also demonstrated excellent performance in the cracking of 1,2-dichloroethane to vinyl chloride. Their highly dispersed active sites and unique electronic structure offer new possibilities for achieving low-temperature, high-efficiency catalytic cracking. However, improving catalyst activity and extending its lifespan remain key research areas.

[0009] In conclusion, with increasingly stringent environmental protection requirements and a worsening energy crisis, developing efficient and environmentally friendly vinyl chloride production methods has become an urgent need for the industry. Catalytic cracking technology, as a promising production method, will have a profound impact on the sustainable development of the PVC industry through its research and application. Summary of the Invention

[0010] This invention provides a method for synthesizing a highly active catalyst for the catalytic cracking of 1,2-dichloroethane to vinyl chloride. The active component in the catalyst is uniformly dispersed on nitrogen-doped carbon dots supported on activated carbon. This highly dispersed active site provides new possibilities for achieving low-temperature, high-efficiency catalytic cracking. When applied to the cracking of 1,2-dichloroethane to vinyl chloride, this catalyst exhibits high 1,2-dichloroethane conversion, good catalyst selectivity, high vinyl chloride yield, and good stability.

[0011] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0012] A catalyst for the catalytic cracking of 1,2-dichloroethane to vinyl chloride, wherein the catalyst uses activated carbon as a support and supports nitrogen-doped carbon dots containing active components, and the mass percentage of the nitrogen-doped carbon dots containing active components is 15.2% to 30.1% based on the total mass of the catalyst.

[0013] The catalyst of the present invention wherein the activated carbon is one or more of coal-based activated carbon, fruit shell activated carbon, and coconut shell activated carbon.

[0014] The catalyst of the present invention wherein the active component is a metal chloride selected from at least one of CuCl2, CuCl, FeCl3, MnCl3, NiCl2, FeCl2, and ZnCl2.

[0015] In the catalyst of the present invention, the nitrogen source in the nitrogen-doped carbon dots is at least one of acrylamide, urea, melamine, pyrrole, and ammonium chloride.

[0016] In the catalyst of the present invention, the synthetic material of the carbon dots in the nitrogen-doped carbon dots is one of petroleum asphalt, coal tar pitch, and natural asphalt.

[0017] A method for synthesizing a catalyst for the catalytic cracking of 1,2-dichloroethane to vinyl chloride includes the following steps:

[0018] (1) Mix solid polycyclic aromatic hydrocarbon, active component and nitrogen source evenly together, calcine, oxidize and then dialyze to obtain carbon point solution.

[0019] (2) Soak activated carbon in carbon dot solution.

[0020] (3) Heat and dry the soaked activated carbon to evaporate the solvent (referring to the solution during dialysis, mainly water and peroxy acid) and load the carbon dots onto the activated carbon.

[0021] (4) After drying the activated carbon loaded with carbon dots, it was calcined at high temperature under an inert gas to obtain a catalyst for the catalytic cracking of 1,2-dichloroethane to produce vinyl chloride.

[0022] In step (1), the polycyclic aromatic hydrocarbon solid is at least one of petroleum asphalt, coal tar pitch and natural asphalt, and the mass percentage of the polycyclic aromatic hydrocarbon solid is 30-50%, based on the mass of the polycyclic aromatic hydrocarbon solid, active component and nitrogen source, the same below;

[0023] In step (1), the active component is at least one of CuCl2, CuCl, FeCl3, MnCl3, NiCl2, FeCl2, and ZnCl2, with a mass percentage of 30-50%.

[0024] In step (1), the nitrogen source is at least one of acrylamide, urea, melamine, pyrrole, and ammonium chloride, with a mass percentage of 10-30%.

[0025] In step (1), calcination is carried out under normal pressure, with a heating rate of 1 to 10 °C / min, a calcination temperature of 300 to 600 °C, and a calcination time of 60 to 120 minutes.

[0026] In step (1), the oxidation is carried out under normal pressure, and the oxidant is peroxyacid, such as a mixture of 150 parts by volume formic acid and 10-30 parts by volume hydrogen peroxide; the oxidation temperature is room temperature, and the oxidation time is 5-10 hours.

[0027] In step (1), dialysis is performed at room temperature and pressure, using a 1000 Dalton dialysis bag for 24 to 48 hours.

[0028] In step (2), the activated carbon is at least one of coal-based activated carbon, fruit shell activated carbon, and coconut shell activated carbon;

[0029] In step (2), the soaking is carried out at normal temperature and pressure, the soaking temperature is 30-80℃, and the soaking time is 24-48 hours.

[0030] In step (3), the heating and drying temperature is 100-120℃, and the time is 24-48 hours. Through heating and drying, the solvent (the solvent refers to the solution during dialysis, mainly water and peroxyacid) evaporates completely, and the carbon dots are fully loaded onto the activated carbon.

[0031] In step (4), the high-temperature calcination is carried out under an inert gas (a gas that is inert to the reaction), with a heating rate of 1 to 10 °C / min, a high-temperature calcination temperature of 400 to 800 °C, and a time of 5 to 12 hours.

[0032] The present invention also relates to the application of the catalyst in the catalytic cracking of 1,2-dichloroethane to produce vinyl chloride.

[0033] The beneficial effects of this application include, but are not limited to:

[0034] (1) The catalyst synthesis method provided in this application is simple to prepare and the raw materials are readily available; it greatly improves the dispersibility of the active components of the catalyst and increases the exposure area of ​​the active components. Furthermore, nitrogen doping in the carbon dots can change the electronic structure of the active components, which is beneficial to the generation of reaction free radicals. Compared with existing nitrogen-doped carbon materials, it can significantly improve the catalyst activity.

[0035] (2) The catalyst prepared in this application is used to produce vinyl chloride by cracking dichloroethane. The yield of vinyl chloride is high and the entire reaction process is stable. Detailed Implementation

[0036] The following specific embodiments further illustrate the technical solution and effects of the present invention. These embodiments are for illustrative purposes only and are not intended to limit the scope of protection of the present invention. Simple modifications made to the present invention based on the concept of the present invention are all within the scope of protection claimed by the present invention.

[0037] Unless otherwise specified, all raw materials used in the embodiments of this application were purchased through commercial channels.

[0038] Example 1

[0039] Mix 1g of coal tar pitch, 0.5g of melamine, and 1g of CuCl2 evenly in a ceramic boat. Place the ceramic boat in a tube furnace and incubate under a nitrogen atmosphere at 3°C / min. -1The precursor of a nitrogen-doped carbon-supported CuCl2 catalyst was obtained by heating to 350℃ and calcining at 350℃ for 90 minutes. Under ultrasonic conditions, the precursor was oxidized for 5 hours with a mixture of 150 mL of 88 wt% formic acid and 15 mL of 30 wt% hydrogen peroxide to obtain a catalyst nanoparticle solution. The solution was dialyzed in a 1000 Dalton dialysis bag for 48 hours to obtain a nitrogen-doped carbon-supported CuCl2 catalyst solution. Coal-based activated carbon was added to the above solution and soaked at atmospheric pressure to allow the solution to fully penetrate the activated carbon. The soaking temperature was 40℃ and the soaking time was 24 hours. The soaked activated carbon and its support were dried at 120℃ to allow the solvent to fully evaporate. The dried activated carbon was then calcined in a tube furnace under nitrogen protection at a calcination temperature of 400℃ and a heating rate of 3℃ / min. -1 The roasting time was 6 hours. After that, it was cooled to room temperature.

[0040] Repeat the above steps multiple times until the mass of the prepared catalyst exceeds 35g.

[0041] Liquid 1,2-dichloroethane was pumped into a fixed-bed reactor filled with the 1,2-dichloroethane cracking catalyst prepared in this example. 35g of catalyst was added to the reactor. The reactor temperature was 300℃, and the 1,2-dichloroethane mass hourly space velocity was 40h⁻¹. -1 The conversion rate of 1,2-dichloroethane was 33%, the selectivity for vinyl chloride was greater than 99%, and the catalyst remained deactivated for 40 hours.

[0042] Example 2

[0043] Mix 1.5g of petroleum asphalt, 0.8g of urea, and 1g of NiCl2 evenly in a ceramic boat. Place the ceramic boat in a tube furnace and incubate under a nitrogen atmosphere at 3°C ​​for 1 minute. -1 The NiCl2 catalyst precursor, supported on nitrogen-doped carbon material, was obtained by heating to 350℃ and calcining at 350℃ for 90 minutes. Under ultrasonic conditions, the catalyst precursor was oxidized for 5 hours with a mixture of 150 mL of 88 wt% formic acid and 15 mL of 30 wt% hydrogen peroxide to obtain a catalyst nanoparticle solution. The solution was dialyzed in a 1000 Dalton dialysis bag for 48 hours to obtain a NiCl2 catalyst solution supported on nitrogen-doped carbon dots. Coconut shell activated carbon was added to the above solution and soaked at atmospheric pressure to allow the solution to fully penetrate the activated carbon. The soaking temperature was 40℃ and the soaking time was 30 hours. The soaked activated carbon and its support were dried at 120℃ to allow the solvent to fully evaporate. The dried activated carbon was then calcined in a tube furnace under nitrogen protection at a high temperature of 600℃ and a heating rate of 3℃ / min. -1 Calcination time: 8 hours. Cool to room temperature.

[0044] Repeat the above steps multiple times until the mass of the prepared catalyst exceeds 35g.

[0045] Liquid 1,2-dichloroethane was pumped into a fixed-bed reactor filled with the 1,2-dichloroethane cracking catalyst prepared in this example. 35g of catalyst was added to the reactor. The reactor temperature was 300°C and the mass hourly space velocity (WHSV) was 40h⁻¹. -1 The conversion rate of 1,2-dichloroethane was 48%, the selectivity for vinyl chloride was greater than 99%, and the catalyst remained deactivated for 40 hours.

[0046] Example 3

[0047] Mix 2g of coal tar pitch, 1g of acrylamide, and 1.5g of ZnCl2 evenly in a ceramic boat. Place the ceramic boat in a tube furnace and incubate under a nitrogen atmosphere at 4°C for 1 minute. -1 The ZnCl2 catalyst precursor, supported on nitrogen-doped carbon material, was obtained by heating to 400℃ and calcining at 400℃ for 90 minutes. Under ultrasonic conditions, the catalyst precursor was oxidized for 5 hours with a mixture of 200 mL of 88 wt% formic acid and 15 mL of 30 wt% hydrogen peroxide to obtain a catalyst nanoparticle solution. The solution was dialyzed in a 1000 Dalton dialysis bag for 48 hours to obtain a ZnCl2 catalyst solution supported on nitrogen-doped carbon dots. Coal-based activated carbon was added to the above solution and soaked at atmospheric pressure to allow the solution to fully penetrate the activated carbon. The soaking temperature was 50℃ and the soaking time was 40 hours. The soaked activated carbon and its support were dried at 120℃ to allow the solvent to fully evaporate. The dried activated carbon was then calcined in a tube furnace under nitrogen protection at a calcination temperature of 500℃ and a heating rate of 3℃ / min. -1 Calcination time: 8 hours. Cool to room temperature.

[0048] Repeat the above steps multiple times until the mass of the prepared catalyst exceeds 35g.

[0049] Liquid 1,2-dichloroethane was pumped into a fixed-bed reactor filled with the 1,2-dichloroethane cracking catalyst prepared in this example. 35g of catalyst was added to the reactor. The reactor temperature was 300°C and the mass hourly space velocity (WHSV) was 40h⁻¹. -1 The conversion rate of 1,2-dichloroethane was 78%, the selectivity for vinyl chloride was greater than 99%, and the catalyst remained deactivated for 40 hours.

[0050] Example 4

[0051] Mix 2.5g of natural bitumen, 1g of pyrrole, and 2g of MnCl3 evenly in a ceramic boat. Place the ceramic boat in a tube furnace and incubate under a nitrogen atmosphere at 3°C ​​for 1 minute. -1The precursor of a nitrogen-doped carbon-supported MnCl3 catalyst was obtained by heating to 500℃ and calcining at 500℃ for 90 minutes. Under ultrasonic conditions, the precursor was oxidized for 5 hours with a mixture of 150 mL of 88 wt% formic acid and 15 mL of 30 wt% hydrogen peroxide to obtain a catalyst nanoparticle solution. The solution was dialyzed in a 1000 Dalton dialysis bag for 48 hours to obtain a nitrogen-doped carbon-supported MnCl3 catalyst solution. Coconut shell activated carbon was added to the above solution and soaked at atmospheric pressure to allow the solution to fully penetrate the activated carbon. The soaking temperature was 60℃ and the soaking time was 45 hours. The soaked activated carbon and its support were dried at 120℃ to allow the solvent to fully evaporate. The dried activated carbon was then calcined in a tube furnace under nitrogen protection at a high temperature of 600℃ and a heating rate of 3℃ / min. -1 Calcination time: 6 hours; then cool to room temperature.

[0052] Repeat the above steps multiple times until the mass of the prepared catalyst exceeds 35g.

[0053] Liquid 1,2-dichloroethane was pumped into a fixed-bed reactor filled with the 1,2-dichloroethane cracking catalyst prepared in this example. 35g of catalyst was added to the reactor. The reactor temperature was 300°C and the mass hourly space velocity (WHSV) was 40h⁻¹. -1 The conversion rate of 1,2-dichloroethane was 59%, the selectivity for vinyl chloride was greater than 99%, and the catalyst remained deactivated for 40 hours.

[0054] Example 5

[0055] Mix 2g of coal tar pitch, 1g of ammonium chloride, and 2g of CuCl evenly in a porcelain boat. Place the porcelain boat into a tube furnace and incubate under a nitrogen atmosphere at 3°C / min. -1 The CuCl catalyst precursor, supported on nitrogen-doped carbon material, was obtained by heating to 300℃ and calcining at 300℃ for 90 minutes. Under ultrasonic conditions, the catalyst precursor was oxidized for 5 hours with a mixture of 150 mL of 88 wt% formic acid and 15 mL of 30 wt% hydrogen peroxide to obtain a catalyst nanoparticle solution. The solution was dialyzed in a 1000 Dalton dialysis bag for 48 hours to obtain a CuCl catalyst solution supported on nitrogen-doped carbon dots. Coal-based activated carbon was added to the above solution and soaked at atmospheric pressure to allow the solution to fully penetrate the activated carbon. The soaking temperature was 80℃ and the soaking time was 48 hours. The soaked activated carbon and its support were dried at 120℃ to allow the solvent to fully evaporate. The dried activated carbon was then calcined in a tube furnace under nitrogen protection at a high temperature of 800℃ and a heating rate of 3℃ / min. -1 The roasting time is 10 hours, and then it is cooled to room temperature.

[0056] Repeat the above steps multiple times until the mass of the prepared catalyst exceeds 35g.

[0057] Liquid 1,2-dichloroethane was pumped into a fixed-bed reactor filled with the 1,2-dichloroethane cracking catalyst prepared in this example. 35g of catalyst was added to the reactor. The reactor temperature was 300°C and the mass hourly space velocity (WHSV) was 40h⁻¹. -1 The conversion rate of 1,2-dichloroethane was 21%, the selectivity for vinyl chloride was greater than 99%, and the catalyst remained deactivated for 40 hours.

[0058] Comparative Example 1

[0059] Mix 2g of coal tar pitch, 1g of melamine, and 2g of CuCl2 evenly in a ceramic boat. Place the ceramic boat into a tube furnace and incubate under a nitrogen atmosphere at 3°C / min. -1 The CuCl2 catalyst precursor supported on nitrogen-doped carbon material was obtained by heating to 350℃ and calcining at 350℃ for 90 minutes. 2g of the above material was ground into powder and diluted in an aqueous solution. Coal-based activated carbon was added to the solution and soaked under normal pressure at 40℃ for 24 hours to allow the solution to fully penetrate the activated carbon. The soaked activated carbon and its support were then dried at 120℃ to allow the solvent to fully evaporate. The dried activated carbon was then calcined in a tube furnace under nitrogen protection at a temperature of 600℃ and a heating rate of 3℃ / min. -1 The roasting time was 8 hours. After that, it was cooled to room temperature.

[0060] Repeat the above steps multiple times until the mass of the prepared catalyst exceeds 35g.

[0061] Liquid 1,2-dichloroethane was pumped into a fixed-bed reactor filled with the 1,2-dichloroethane cracking catalyst prepared in this example. 35g of catalyst was added to the reactor. The reactor temperature was 300°C and the mass hourly space velocity (WHSV) was 40h⁻¹. -1 The conversion rate of 1,2-dichloroethane was 2%, the selectivity for vinyl chloride was approximately 93%, and the catalyst remained deactivated for 40 hours.

[0062] The above description is merely a few embodiments of this application and is not intended to limit this application in any way. Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of this application using the disclosed technical content are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A method for synthesizing a catalyst for catalytic cracking of 1,2-dichloroethane to vinyl chloride, comprising the following steps: (1) solidify the fused ring aromatic hydrocarbon, active component and nitrogen source, mix them together, calcine, oxidize, then dialyze to obtain a carbon dot solution; wherein: the solid polycyclic aromatic hydrocarbon is at least one of petroleum pitch, coal pitch and natural pitch, the mass percentage of the solid polycyclic aromatic hydrocarbon is 30-50%, based on the total mass of the solid polycyclic aromatic hydrocarbon, the active component and the nitrogen source; the active component is at least one of CuCl2, CuCl, FeCl3, MnCl3, NiCl2, FeCl2 and ZnCl2, the mass percentage of the active component is 30-50%, based on the total mass of the solid polycyclic aromatic hydrocarbon, the active component and the nitrogen source; the mass percentage of the nitrogen source is 10-30%, based on the total mass of the solid polycyclic aromatic hydrocarbon, the active component and the nitrogen source; (2) soaking the activated carbon in a carbon dot solution; (3) heating and drying the soaked activated carbon to evaporate the solvent and load the carbon dots onto the activated carbon; (4) drying the activated carbon loaded with the carbon dots and calcining the dried activated carbon at high temperature under an inert gas to obtain the catalyst.

2. The method of claim 1, wherein, In step (1), the nitrogen source is at least one of acrylamide, urea, melamine, pyrrole and ammonium chloride.

3. The method of claim 1, wherein, In step (1), the calcination is performed at normal pressure, the heating rate is 1-10 ℃ / min, the calcination temperature is 300-600 ℃, and the calcination time is 60-120 minutes.

4. The method according to any one of claims 1 to 3, wherein, In step (1), the oxidation is performed at normal pressure, the oxidant is a peroxy acid, the oxidation temperature is room temperature, and the oxidation time is 5-10 hours.

5. The method according to any one of claims 1-3, wherein, In step (1), the dialysis is performed at normal temperature and pressure, and the dialysis is performed using a 1000-dalton dialysis bag for 24-48 hours.

6. The method of claim 1, wherein, In step (2), the activated carbon is at least one of coal-based activated carbon, nutshell activated carbon and coconut shell activated carbon. The soaking is performed at normal temperature and pressure, the soaking temperature is 30-80 ℃, and the soaking time is 24-48 hours.

7. The method of claim 1, wherein, In step (3), the heating and drying temperature is 100-120 ℃. In step (4), the high-temperature calcination temperature is 400-800 ℃, the heating rate is 1-10 ℃ / min, and the calcination time is 5-12 hours. 8.Use of the catalyst obtained by the method according to any one of claims 1-7 in catalyzing the cracking of 1,2-dichloroethane to vinyl chloride.