A system and method for green synthesis of vinyl chloride based on mercury-free catalysts

Abstract

The application discloses a kind of green synthesis system and method of vinyl chloride based on mercury-free catalyst;The system includes synthesis unit, purification unit, condensation unit, rectification unit and hydrogen chloride recovery unit.Ruthenium-based mercury-free catalyst is used in synthesis unit.Purification unit includes combined absorption tower.Combined absorption tower absorbs hydrogen chloride in crude vinyl chloride gas to form concentrated hydrochloric acid, and is transported to hydrogen chloride recovery unit.Hydrogen chloride recovery unit separates hydrogen chloride gas and is transported to synthesis unit for reuse.Purified vinyl chloride gas after purification treatment in purification unit is condensed into vinyl chloride condensate by condensation unit, and then transported to rectification unit.Rectification unit includes low-boiling tower, high-boiling tower, vaporizer and catalytic cracking furnace.Vinyl chloride condensate is treated in low-boiling tower and high-boiling tower in sequence to obtain final vinyl chloride.High-boiling residual liquid generated by high-boiling tower is transported to vaporizer for vaporization treatment, and then transported to catalytic cracking furnace for cracking treatment.The application further recycles waste liquid and tail gas.

Description

Technical Field

[0001] This invention relates to the field of vinyl chloride synthesis technology, and specifically to a green synthesis method for vinyl chloride based on a mercury-free catalyst. Background Technology

[0002] Vinyl chloride (C2H3Cl), with a boiling point of -13.4℃ and slight soluble in water, is an important monomer in polymer chemistry. Currently, the production of vinyl chloride monomer (VCM) mainly involves two methods: the acetylene method and the ethylene method. Although the oxychlorination method for producing VCM is relatively less polluting, due to China's energy endowment (rich in coal, poor in oil, and scarce in gas) and the need to balance the large amount of chlorine resources in the chlor-alkali industry, my country's VCM production route still mainly relies on the calcium carbide acetylene method, which accounted for 81.3% of the market in 2019. The calcium carbide acetylene method for VCM production involves reacting acetylene gas with hydrogen chloride gas under the action of a mercuric chloride catalyst to produce crude vinyl chloride gas, which is then purified, compressed, and refined to obtain high-purity VCM. This route has a high reaction conversion rate, few side reactions, and simple equipment. However, the acetylene method produces mercury-containing waste liquid and high-boiling-point residues. If not properly treated, this not only wastes resources but also poses a significant pollution risk to the environment. Therefore, the development of mercury-free catalysts, the resource utilization of high-boiling-point residues, and the recovery and utilization of hydrogen chloride are key to the green production of VCM using the calcium carbide acetylene method, and are crucial to the sustainable development and market competitiveness of VCM production in my country.

[0003] Patent CN110227507B, "A Highly Stable Ultra-Low Mercury Catalyst and Its Preparation Method and Application," discloses an ultra-low mercury catalyst that effectively catalyzes the preparation of VCM monomers with an acetylene conversion rate of over 97.2% and a VCM selectivity of over 99.5%. However, this catalyst still cannot avoid the loss of mercuric chloride during the reaction (<3.0%), and fails to solve the problems of treating mercury-containing wastewater and high-boiling residues.

[0004] Patent CN108558596B, "An Improved Process for Synthesizing VCM via the Calcium Carbide Method," utilizes calcium carbide slag slurry to replace alkaline solution for alkaline washing of crude VCM gas, reducing wastewater emissions. Calcium carbide slag slurry's main component is calcium hydroxide, which has low solubility in water, leading to problems such as incomplete washing and the need for regular replacement of the alkaline solution.

[0005] Patent CN104211563B, "A High-Boiling-Point Recovery Process and Equipment for VCM," utilizes a packed distillation column and its auxiliary equipment to reduce and recover high-boiling-point substances under both atmospheric and pressurized conditions. This patent focuses on recovering 1,1-dichloroethane from high-boiling-point liquids, but components such as 1,2-dichloroethane and trichloroethane are not further utilized.

[0006] In summary, there is a need to develop a green synthesis method for vinyl chloride based on a mercury-free catalyst to completely solve the pollution problems such as mercury-containing waste liquid in the acetylene process and realize the green production of VCM by the calcium carbide acetylene process. Summary of the Invention

[0007] To address the aforementioned problems in the existing calcium carbide-acetylene method for VCM production, this invention provides a green synthesis method for vinyl chloride based on a mercury-free catalyst. This method not only ensures the quality of VCM but also reduces and recycles the byproduct waste liquid and waste gas generated during the synthesis process.

[0008] In a first aspect, the present invention provides a green synthesis system for vinyl chloride based on a mercury-free catalyst, comprising a synthesis unit, a purification unit, a condensation unit, a distillation unit, and a hydrogen chloride recovery unit. The synthesis unit uses a ruthenium-based mercury-free catalyst. The crude vinyl chloride gas synthesized in the synthesis unit is transported to the purification unit.

[0009] The purification unit includes a combined absorption tower. The combined absorption tower absorbs hydrogen chloride from the crude vinyl chloride gas, forming concentrated hydrochloric acid, which is then transported to a hydrogen chloride recovery unit. The hydrogen chloride recovery unit separates hydrogen chloride gas from the concentrated hydrochloric acid and transports it to the synthesis unit for reuse.

[0010] The vinyl chloride gas purified by the purification unit is condensed into vinyl chloride condensate by the condensation unit and then sent to the distillation unit. The distillation unit includes a low-boiling column, a high-boiling column, a vaporizer, and a catalytic cracking furnace. The vinyl chloride condensate is sequentially processed through the low-boiling column and the high-boiling column to obtain the final vinyl chloride. The high-boiling residue produced in the high-boiling column is sent to the vaporizer for vaporization and then to the catalytic cracking furnace for cracking.

[0011] Preferably, a heat exchanger is connected between the synthesis unit and the catalytic cracking furnace and vaporizer in the distillation unit. The heat exchanger uses a heat exchange medium to absorb the heat generated during the synthesis of vinyl chloride in the synthesis unit and provides the heat to the catalytic cracking furnace and vaporizer, which require heat absorption.

[0012] Preferably, the synthesis unit includes a pre-VCM converter and a post-VCM converter connected in series. The mixed gas inlet of the synthesis unit is connected to the acetylene feedstock processing unit and the hydrogen chloride feedstock processing unit via a mixer. Both the pre-VCM converter and the post-VCM converter are VCM tubular fixed-bed converters equipped with mercury-free catalysts.

[0013] Preferably, the mercury-free catalyst comprises a porous solid support and ruthenium complexes, metal and non-metal additives supported on the surface of the support. The ruthenium complexes are one or more of polypyridine ruthenium complexes, ruthenium porphyrin ruthenium complexes, and aromatic ruthenium complexes. The metal additive is ruthenium nitrate. The non-metal additive is specifically a mixture of triphenylmethylphosphine bis(trifluoromethanesulfonyl)imide salt and triphenylethylphosphine bromide in a mass ratio of (2.5-5.5):1. The porous solid support is activated carbon.

[0014] Preferably, the purification unit further includes an alkaline scrubbing tower, a demister, and a drying separator. The vinyl chloride gas output from the combined absorption tower passes sequentially through the alkaline scrubbing tower, the demister, and the drying separator.

[0015] Preferably, the condensation unit includes a condenser and a condensate storage tank. The vinyl chloride gas purified by the purification unit is delivered to the condenser. The vinyl chloride condensate output from the condenser is stored in the condensate storage tank. The condensate storage tank delivers liquid hydrogen chloride to the distillation unit. Both the gas phase outlet of the condensate storage tank and the tail gas outlet of the low-boiling tower are connected to the pressure swing adsorption unit.

[0016] Preferably, the hydrogen chloride recovery unit includes a two-way heat exchanger, a concentrated acid desorption tower, a dilute acid desorption tower, a calcium chloride solution storage tank, and an evaporation and concentration tower. The concentrated hydrochloric acid outlet of the combined absorption tower, the two-way heat exchanger, the concentrated acid desorption tower, and the dilute acid desorption tower are connected in sequence. The calcium chloride solution storage tank supplies calcium chloride solution to the dilute acid desorption tower. The calcium chloride solution with reduced concentration at the bottom of the dilute acid desorption tower is output to the evaporation and concentration tower; after increasing the concentration of the calcium chloride solution, the evaporation and concentration tower transfers the calcium chloride solution to the calcium chloride solution storage tank for reuse. The concentrated acid desorption tower is connected to a concentrated acid reboiler. The dilute acid desorption tower is connected to a dilute acid reboiler. The evaporation and concentration tower is connected to a concentration reboiler. The water produced by the evaporation and concentration tower is transferred to the combined absorption tower for reuse.

[0017] Preferably, in the operation of the hydrogen chloride recovery unit, concentrated hydrochloric acid enters the top of the concentrated acid desorption tower, where it undergoes counter-current mass transfer and heat transfer with hydrogen chloride and water vapor from the concentrated acid reboiler. Aqueous hydrogen chloride gas is obtained at the top of the tower, and dilute hydrochloric acid is obtained at the bottom. The hydrogen chloride temperature at the top inlet of the concentrated acid desorption tower is 90℃~95℃, and the pressure is controlled at 60KpaG~70KpaG. Dilute hydrochloric acid is fed into the top of the dilute acid desorption tower, where it undergoes counter-current mass transfer and heat transfer with hydrogen chloride, water vapor from the acid reboiler, and calcium chloride solution from the calcium chloride solution storage tank. Aqueous hydrogen chloride gas is obtained at the top of the tower, and a calcium chloride solution with reduced concentration is obtained at the bottom. The hydrogen chloride temperature at the top inlet of the dilute acid desorption tower is 90~110℃, and the pressure is controlled at 60~70 KpaG. The calcium chloride solution with reduced concentration is sent to an evaporation and concentration tower to restore its initial concentration, and then transported to the calcium chloride solution storage tank for reuse.

[0018] Secondly, the present invention provides a green synthesis method for vinyl chloride throughout the entire process, which uses the aforementioned green synthesis system for vinyl chloride throughout the entire process; the green synthesis method for vinyl chloride throughout the entire process includes the following steps: Step 1: Acetylene gas and hydrogen chloride gas are mixed and fed into the synthesis unit, where they react and convert to produce crude vinyl chloride gas. Step 2: The crude vinyl chloride gas obtained in Step 1 is sent to the combined absorption tower in the purification unit; the combined absorption tower uses water to absorb the hydrogen chloride gas in the crude vinyl chloride gas, and obtains concentrated hydrochloric acid and purified vinyl chloride gas. Step 3: The concentrated hydrochloric acid output from the combined absorption tower is fed into the hydrogen chloride recovery unit, and the generated hydrogen chloride gas is sent to the synthesis unit for reuse. The vinyl chloride gas output from the combined absorption tower is fed into the condensation unit; the vinyl chloride condensate output from the condensation unit is processed sequentially through a low-boiling tower and a high-boiling tower to produce the final vinyl chloride gas. The high-boiling residual liquid produced in the high-boiling tower is vaporized and sent to a catalytic cracking furnace for cracking treatment. The resulting vinyl chloride and hydrogen chloride cracked gas are sent to the synthesis unit for reuse.

[0019] Preferably, in step one, the mass ratio of hydrogen chloride to acetylene in the mixed gas fed into the synthesis unit is (1.0~1.5):1; the reaction temperature of the synthesis unit is 110~190℃, and the volume hourly space velocity (GHSV) is 30~100 h⁻¹. -1 .

[0020] Preferably, in step two, the vinyl chloride gas output from the combined absorption tower is sequentially processed through an alkaline scrubbing tower, a demister, and a drying separator to remove residual impurities, including hydrogen chloride and carbon dioxide.

[0021] Preferably, in step three, the catalyst used in the catalytic cracking furnace is nitrogen-doped activated carbon; the nitrogen-doped activated carbon is obtained by nitrogen-doping modification of activated carbon through low-temperature plasma treatment. The reaction temperature of the catalytic cracking furnace is 220℃~280℃.

[0022] Compared with the prior art, the present invention has the following beneficial effects: This invention uses a mercury-free catalyst (ruthenium-based catalyst) to synthesize VCM, thus avoiding mercury pollution.

[0023] This invention uses a combined absorption tower, a concentrated acid desorption tower, and a dilute acid desorption tower to recover hydrogen chloride from crude vinyl chloride gas, achieving zero discharge of wastewater.

[0024] This invention uses a non-metallic catalyst to catalytically crack high-boiling residual liquid, thereby reducing waste liquid discharge and realizing resource recovery.

[0025] The hydrogen chloride recovered by this invention is returned to the VCM fluidized bed converter for reuse, effectively recycling the by-product hydrogen chloride. Attached Figure Description

[0026] Figure 1 This is a flowchart illustrating the overall process flow of the present invention.

[0027] Figure 2 This is a schematic diagram of the combination of the purification unit and the hydrogen chloride recovery unit in this invention.

[0028] Figure 3 This is a schematic diagram of the combined absorption tower in this invention.

[0029] Figure 4 This is a schematic diagram of the distillation unit in this invention. Detailed Implementation

[0030] The present invention will be described in detail below through specific embodiments. The illustrative embodiments and descriptions of the present invention are used to explain the present invention, but are not intended to limit the present invention.

[0031] like Figure 1 As shown, a green synthesis system for vinyl chloride based on a mercury-free catalyst includes a synthesis unit 1, a purification unit 2, a condensation unit 3, a pressure swing adsorption unit 4, a distillation unit 5, and a hydrogen chloride recovery unit 6.

[0032] Synthesis Unit 1 comprises a pre-VCM converter and a post-VCM converter connected in series. The mixed gas inlet of Synthesis Unit 1 is connected to the acetylene feedstock processing unit and the hydrogen chloride feedstock processing unit respectively via a mixer. Both the pre-VCM converter and the post-VCM converter are VCM tubular fixed-bed converters equipped with mercury-free catalysts.

[0033] The mercury-free catalyst is a ruthenium-based catalyst, consisting of a porous solid support and ruthenium complexes, metal and non-metal additives supported on the surface of the support. The ruthenium complexes are one or more of polypyridine ruthenium complexes, ruthenium porphyrin ruthenium complexes, and aromatic ruthenium complexes. The metal additive is ruthenium nitrate. The non-metal additive is specifically a mixture of triphenylmethylphosphine bis(trifluoromethanesulfonyl)imide salt and triphenylethylphosphine bromide in a mass ratio of 4:1. The porous solid support is activated carbon.

[0034] like Figure 2 and Figure 3 As shown, purification unit 2 includes a combined absorption tower, an alkaline scrubbing tower, a demister, and a drying separator. The combined absorption tower has a gas distribution zone, a packed absorption zone, a gas-liquid separation zone, and a tray absorption zone arranged sequentially from bottom to top. An inlet is located at the bottom of the combined absorption tower, and an outlet is located at the top. A concentrated hydrochloric acid outlet is also provided on the combined absorption tower; the inlet at the bottom of the combined absorption tower is connected to the outlet of synthesis unit 1. The outlet at the top of the combined absorption tower, the alkaline scrubbing tower, the demister, and the drying separator are connected in sequence. The outlet of the drying separator is used to output the purified vinyl chloride gas.

[0035] like Figure 2 As shown, the hydrogen chloride recovery unit 6 includes a two-way heat exchanger, a concentrated acid desorption tower, a dilute acid desorption tower, a calcium chloride solution storage tank, and an evaporation and concentration tower. The concentrated hydrochloric acid outlet of the combined absorption tower, the two-way heat exchanger, the concentrated acid desorption tower, and the dilute acid desorption tower are connected sequentially. The outlet of the calcium chloride solution storage tank is connected to the calcium chloride inlet of the dilute acid desorption tower; the low-concentration calcium chloride outlet at the bottom of the dilute acid desorption tower is connected to the evaporation and concentration tower. The evaporation and concentration tower obtains a high-concentration calcium chloride solution and transports it to the calcium chloride solution storage tank for reuse. The water produced by the evaporation and concentration tower is connected to the combined absorption tower for reuse. The concentrated acid desorption tower is connected to a concentrated acid reboiler. The dilute acid desorption tower is connected to a dilute acid reboiler. The evaporation and concentration tower is connected to a concentration reboiler. The hydrogen chloride gas produced by the concentrated acid desorption tower and the dilute acid desorption tower is connected to the mixed gas inlet of the synthesis unit 1 after passing through a concentrated sulfuric acid drying tower, thus realizing the reuse of hydrogen chloride gas. The evaporation concentration tower, low-boiling tower, and high-boiling tower are all equipped with condensers at the top.

[0036] Condensation unit 3 includes a condenser and a condensate storage tank. The outlet of the dryer-separator, the condenser, and the condensate storage tank are connected in sequence. The gas phase outlet of the condensate storage tank is connected to pressure swing adsorption unit 4.

[0037] like Figure 4 As shown, distillation unit 5 includes a low-boiling column, a high-boiling column, a finished product storage tank, a vaporizer, a catalytic cracking furnace, and a heat exchanger. The liquid phase outlet of the condensate storage tank, the low-boiling column, the high-boiling column, and the finished product storage tank are connected in sequence. Pressure swing adsorption unit 4 is used to further separate useful components from the tail gas; the useful components include vinyl chloride, hydrogen, and acetylene. The low-boiling tail gas outlet of the low-boiling column is connected to pressure swing adsorption unit 4. The high-boiling tail liquid outlet of the high-boiling column, the vaporizer, and the catalytic cracking furnace are connected in sequence. The catalytic cracking furnace is used to generate cracked gases of vinyl chloride and hydrogen chloride produced by cracking.

[0038] The catalyst in the catalytic cracking furnace is nitrogen-doped activated carbon, which can be coconut shell type, fruit shell type or coal-based activated carbon. The nitrogen doping modification is carried out using low-temperature plasma technology with a discharge power of 30W, a discharge gas of 1:1 Ar / N2 mixed gas, a flow rate of 30 ml / min and a discharge time of 30 minutes.

[0039] A heat exchanger is installed between the pre-VCM converter, the post-VCM converter, the catalytic cracking furnace, and the vaporizer. The heat exchanger uses heptane refrigerant to absorb the heat generated by the pre-VCM converter, the post-VCM converter, and the catalytic oxidation furnace, and then provides the heat to the catalytic cracking furnace and vaporizer that require heat absorption.

[0040] The following are the key points of this embodiment: (a) Synthesis of vinyl chloride using a mercury-free catalyst (ruthenium-based catalyst); (b) A combined absorption tower, a concentrated acid desorption tower, and a dilute acid desorption tower are used to recover the by-product hydrogen chloride from the crude vinyl chloride gas; (c) The recovered hydrogen chloride is returned to the VCM tubular fixed-bed converter for reuse; (d) The high-boiling residual liquid is converted into a gaseous state under the action of the vaporizer, and enters the catalytic cracking furnace to crack into vinyl chloride and hydrogen chloride cracked gas, which is then purified and recycled. (e) Use heptane refrigerant, water or heat transfer oil as a medium to absorb and utilize the heat transfer during the entire VCM production process.

[0041] like Figure 1 As shown, a green synthesis method for vinyl chloride without a mercury catalyst includes the following steps: 1) such as Figure 2 As shown, acetylene and hydrogen chloride gases are mixed in a mixer and then sequentially passed through a pre-VCM converter and a post-VCM converter to convert them into crude vinyl chloride gas, which then enters the purification unit. The mass ratio of hydrogen chloride to acetylene in the mixed gas input to the pre-VCM converter is 1.0–1.5 / 1, the reaction temperature is 110–190 °C, and the volume hourly space velocity (GHSV) is 30–100 h⁻¹. -1 .

[0042] 2) such as Figure 3 As shown, crude vinyl chloride gas enters from the bottom of the combined absorption tower. After hydrogen chloride is absorbed by water in the upper part, concentrated hydrochloric acid is obtained at the bottom of the tower. After being discharged from the top of the tower, the gas enters the alkaline washing tower, demister, and dryer in sequence to further purify impurities such as hydrogen chloride and carbon dioxide in the gas, resulting in separated purified gas and concentrated hydrochloric acid.

[0043] 3) The purified gas obtained in step 2) is pressurized and sent to a condenser for condensation to obtain vinyl chloride condensate; the condensate tail gas is sent to a pressure swing adsorption unit for further separation of useful components; the useful components include vinyl chloride, hydrogen and acetylene.

[0044] 4) such as Figure 4 As shown, the vinyl chloride condensate obtained in step 3) is passed through a low-boiling tower to remove low-boiling-point components and then enters the pressure swing adsorption unit in step 3). The bottom liquid after the low-boiling tower treatment enters the high-boiling tower for treatment to obtain purified vinyl chloride gas, while the bottom of the distillation tower produces a high-boiling residue (main component: dichloroethane).

[0045] 5) The concentrated hydrochloric acid obtained in step 2) is fed into the top of the concentrated acid desorption tower, where it undergoes counter-current mass transfer and heat transfer with high-temperature hydrogen chloride and water vapor from the concentrated acid reboiler. Aqueous hydrogen chloride gas is obtained at the top of the tower, and azeotropic acid (dilute hydrochloric acid solution) is obtained at the bottom. The hydrogen chloride temperature at the top inlet of the concentrated acid desorption tower is 90-95℃, and the pressure is controlled at 60-70 kPaG. The dilute hydrochloric acid solution is then fed into the dilute acid desorption tower for desorption, yielding aqueous hydrogen chloride gas. During desorption in the dilute acid desorption tower, calcium chloride solution is added, allowing the high-temperature hydrogen chloride, water vapor, and calcium chloride from the dilute acid reboiler to undergo counter-current mass transfer and heat transfer within the tower. Aqueous hydrogen chloride gas is obtained at the top of the tower, and a low-concentration calcium chloride solution is obtained at the bottom. The low-concentration calcium chloride solution is then fed into an evaporation and concentration tower to restore its initial concentration before being fed back into the dilute acid desorption tower for reuse. The water vapor evaporated in the evaporation and concentration tower is condensed and returned to the combined absorption tower for recycling. The temperature of hydrogen chloride at the top inlet of the dilute acid desorption tower is 90~110℃, and the pressure is controlled at 60~70 kPaG.

[0046] 6) The high-boiling residual liquid obtained in step 4) is vaporized in the vaporizer and then enters the catalytic cracking furnace. Under the action of the catalyst, it is cracked into crude vinyl chloride gas and hydrogen chloride. This gas is mixed with the crude vinyl chloride gas from the subsequent VCM converter and enters the purification unit. The reaction temperature of the catalytic cracking furnace is 220℃-280℃.

[0047] 7) The aqueous hydrogen chloride gas obtained in step 5) is sent to the sulfuric acid drying tower to remove moisture, and then returned to the pre-VCM converter and post-VCM converter for reuse.

[0048] 8) Heptane refrigerant is used to absorb the heat generated by the pre-VCM converter and post-VCM converter, and the heat is then transferred to the catalytic cracking furnace, purification unit and distillation unit in sequence via water or heat transfer oil heat exchange medium.

[0049] The following provides specific reaction conditions for three synthesis units 1 and a catalytic cracking furnace. The catalysts used in these examples are shown in Table 1 below.

[0050] Table 1 Examples of Catalyst Applications catalyst A: Ru / C C: Ni / Molecular sieve <![CDATA[B: Ru1 / C]]> <![CDATA[D: Ni₁ / Molecular sieve]]> Wherein, Ru1 / C indicates that Ru is supported in a single-atom form; Ru / C indicates that Ru is supported in a conventional form. Ni1 / molecular sieve indicates that Ni is supported in a single-atom form; Ni / molecular sieve indicates that Ni is supported in a conventional form.

[0051] Example 1

[0052] Catalyst A was applied in a VCM tubular fixed-bed reactor at 190℃, 0.1 MPa, HCl / C2H2 molar ratio of 1.1 / 1.0, and acetylene space velocity of 300 h⁻¹. -1Acetylene hydrochlorination was carried out under the specified reaction conditions. Initially, the acetylene conversion reached 89.5%, and the VCM selectivity was 99.9%. After 200 h of reaction, the acetylene conversion was 88.3%, and the VCM selectivity was 99.9%.

[0053] Catalyst C was applied in a catalytic cracking furnace at 280℃, 0.1 MPa, and a gas space velocity of 300 h⁻¹. -1 The high-boiling-point residual liquid underwent vaporization and cracking reaction under the specified reaction conditions. Initially, the conversion rate of the vaporized high-boiling-point residual liquid was 73.1%, and the VCM selectivity was 95.1%. After 200 h of reaction, the conversion rate of the vaporized high-boiling-point residual liquid was 70.2%, and the VCM selectivity was 78.9%.

[0054] Example 2

[0055] Catalyst B was applied in a VCM tubular fixed-bed reactor at 190℃, 0.1 MPa, HCl / C2H2 molar ratio of 1.3 / 1.0, and acetylene space velocity of 300 h⁻¹. -1 Acetylene hydrochlorination was carried out under the specified reaction conditions. Initially, the acetylene conversion reached 91.5%, and the VCM selectivity was 99.9%. After 200 h of reaction, the acetylene conversion was 89.7%, and the VCM selectivity remained at 99.9%.

[0056] Catalyst D is applied in a catalytic cracking furnace at 280℃, 0.1 MPa, and a gas space velocity of 300 h⁻¹. -1 The high-boiling-point residual liquid underwent vaporization and pyrolysis under the specified reaction conditions. Initially, the conversion rate of the vaporized high-boiling-point residual liquid was 70.4%, and the VCM selectivity was 99.6%. After 200 h of reaction, the conversion rate of the vaporized high-boiling-point residual liquid was 61.2%, and the VCM selectivity was 80.6%.

[0057] Example 3

[0058] Catalyst A was applied in a VCM tubular fixed-bed reactor at 220℃, 0.1 MPa, HCl / C2H2 molar ratio of 1.2 / 1.0, and acetylene space velocity of 400 h⁻¹. -1 Acetylene hydrochlorination was carried out under the specified reaction conditions. Initially, the acetylene conversion reached 90.5%, and the VCM selectivity was 99.9%. After 200 h of reaction, the acetylene conversion was 88.2%, and the VCM selectivity was 99.8%.

[0059] Catalyst D is applied in a catalytic cracking furnace at 270℃, 0.1 MPa, and a gas space velocity of 100 h⁻¹. -1The high-boiling-point residual liquid underwent vaporization and cracking reaction under the specified reaction conditions. Initially, the conversion rate of the vaporized high-boiling-point residual liquid was 77.8%, and the VCM selectivity was 99.6%. After 200 h of reaction, the conversion rate of the vaporized high-boiling-point residual liquid was 69.8%, and the VCM selectivity was 99.5%.

[0060] This invention is not limited to the above embodiments. Based on the technical solutions disclosed in this invention, those skilled in the art can make some substitutions and improvements to some technical features without departing from the principles of this invention. Such substitutions and improvements should also be considered within the scope of protection of this invention.

Claims

1. A green synthesis method for vinyl chloride throughout the entire process, characterized in that: The vinyl chloride whole-process green synthesis system is used, which includes a synthesis unit (1), a purification unit (2), a condensation unit (3) and a distillation unit (5); it also includes a hydrogen chloride recovery unit (6); the synthesis unit (1) uses a ruthenium-based mercury-free catalyst; the crude vinyl chloride gas synthesized by the synthesis unit (1) is transported to the purification unit (2). The purification unit (2) includes a combined absorption tower; the combined absorption tower is used to absorb hydrogen chloride in crude vinyl chloride gas to form concentrated hydrochloric acid, which is then transported to the hydrogen chloride recovery unit (6); the purification unit (2) also includes an alkaline scrubbing tower, a demister, and a drying separator; the vinyl chloride gas output from the combined absorption tower passes through the alkaline scrubbing tower, the demister, and the drying separator in sequence; the hydrogen chloride recovery unit (6) is used to separate hydrogen chloride gas from the concentrated hydrochloric acid and transport it to the synthesis unit (1) for reuse; The vinyl chloride gas purified by the purification unit (2) is condensed into vinyl chloride condensate by the condensation unit (3) and then transported to the distillation unit (5). The distillation unit (5) includes a low-boiling tower, a high-boiling tower, a vaporizer, and a catalytic cracking furnace. The vinyl chloride condensate is processed by the low-boiling tower and the high-boiling tower in sequence to obtain the final vinyl chloride. The high-boiling residue produced by the high-boiling tower is vaporized by the vaporizer and then enters the catalytic cracking furnace. Under the action of the catalyst, it is cracked into crude vinyl chloride gas and hydrogen chloride. The gas is mixed with the crude vinyl chloride gas from the VCM converter and enters the purification unit. The catalyst in the catalytic cracking furnace is nitrogen-doped activated carbon, which is coconut shell type, fruit shell type or coal-based activated carbon. The nitrogen doping modification adopts low-temperature plasma technology. A heat exchanger is connected between the synthesis unit (1) and the catalytic cracking furnace and vaporizer in the distillation unit (5); the heat exchanger uses a heat exchange medium to absorb the heat generated when the synthesis unit (1) synthesizes vinyl chloride and provides the heat to the catalytic cracking furnace and vaporizer that need to absorb heat; the synthesis unit (1) includes a pre-VCM converter and a post-VCM converter connected in series; the mixed gas inlet of the synthesis unit (1) is connected to the acetylene feedstock processing unit and the hydrogen chloride feedstock processing unit through a mixer; both the pre-VCM converter and the post-VCM converter are VCM tubular fixed bed converters equipped with mercury-free catalysts; The mercury-free catalyst comprises a porous solid support and ruthenium complexes, metal and non-metal additives supported on the surface of the support. The ruthenium complexes are one or more of polypyridine ruthenium complexes, ruthenium porphyrin ruthenium complexes, and aromatic ruthenium complexes. The metal additive is ruthenium nitrate. The non-metal additive is specifically a mixture of triphenylmethylphosphine bis(trifluoromethanesulfonyl)imide salt and triphenylethylphosphine bromide in a mass ratio of (2.5–5.5):

1. The porous solid support is activated carbon. The hydrogen chloride recovery unit (6) includes a two-way heat exchanger, a concentrated acid desorption tower, a dilute acid desorption tower, a calcium chloride solution storage tank, and an evaporation and concentration tower; the concentrated hydrochloric acid outlet of the combined absorption tower, the two-way heat exchanger, the concentrated acid desorption tower, and the dilute acid desorption tower are connected in sequence; the calcium chloride solution storage tank provides calcium chloride solution to the dilute acid desorption tower; the calcium chloride solution with reduced concentration at the bottom of the dilute acid desorption tower is output to the evaporation and concentration tower; after the evaporation and concentration tower increases the concentration of the calcium chloride solution, the calcium chloride solution is transported to the calcium chloride solution storage tank for reuse; the concentrated acid desorption tower is connected to a concentrated acid reboiler; the dilute acid desorption tower is connected to a dilute acid reboiler; the evaporation and concentration tower is connected to a concentration reboiler; the water produced by the evaporation and concentration tower is transported to the combined absorption tower for reuse; During operation, concentrated hydrochloric acid enters the top of the concentrated acid desorption tower of the hydrogen chloride recovery unit (6), and undergoes countercurrent mass transfer and heat transfer with hydrogen chloride and water vapor from the concentrated acid reboiler in the tower. Hydrogen chloride gas containing water is obtained at the top of the tower, and dilute hydrochloric acid is obtained at the bottom of the tower. The temperature of hydrogen chloride at the top feed port of the concentrated acid desorption tower is 90℃~95℃, and the pressure is controlled at 60KpaG~70 KpaG. Dilute hydrochloric acid is fed into the top of the dilute acid desorption tower, where it undergoes countercurrent mass and heat transfer with hydrogen chloride and water vapor from the dilute acid reboiler and calcium chloride solution from the calcium chloride solution storage tank. Hydrogen chloride gas containing water is obtained at the top of the tower, and a calcium chloride solution with reduced concentration is obtained at the bottom of the tower. The hydrogen chloride temperature at the top inlet of the dilute acid desorption tower is 90~110℃, and the pressure is controlled at 60~70 kPaG. The calcium chloride solution with reduced concentration is fed into the evaporation and concentration tower to restore the initial concentration, and then transported to the calcium chloride solution storage tank for reuse. The water-containing hydrogen chloride gas produced by the concentrated acid desorption tower and the dilute acid desorption tower is sent to the concentrated sulfuric acid drying tower to remove moisture, and then returned to the pre-VCM converter and post-VCM converter for reuse. The green synthesis method for vinyl chloride throughout the entire process includes the following steps: Step 1: Acetylene gas and hydrogen chloride gas are mixed in a mixer and then sequentially fed into the pre-VCM converter and post-VCM converter in the synthesis unit (1) to be converted into crude vinyl chloride gas; Step 2: The crude vinyl chloride gas obtained in Step 1 is sent into the combined absorption tower in the purification unit (2); the combined absorption tower uses water to absorb the hydrogen chloride gas in the crude vinyl chloride gas to obtain concentrated hydrochloric acid and purified vinyl chloride gas; the vinyl chloride gas output from the combined absorption tower is processed by the alkaline washing tower, the demister and the drying separator in sequence to remove residual impurities including hydrogen chloride and carbon dioxide. Step 3: The concentrated hydrochloric acid output from the combined absorption tower is fed into the hydrogen chloride recovery unit (6); the water-containing hydrogen chloride gas generated by the hydrogen chloride recovery unit is sent to the concentrated sulfuric acid drying tower to remove moisture, and then returned to the pre-VCM converter and post-VCM converter for reuse; the vinyl chloride gas output from the drying separator in the purification unit (2) is fed into the condensation unit (3); the vinyl chloride condensate output from the condensation unit (3) is processed sequentially through the low-boiling tower and the high-boiling tower to produce the final vinyl chloride gas; the high-boiling residual liquid generated by the high-boiling tower is vaporized and sent to the catalytic cracking furnace for cracking treatment to obtain vinyl chloride and hydrogen chloride cracked gas; the vinyl chloride and hydrogen chloride cracked gas are mixed with the crude vinyl chloride gas from the post-VCM converter and enter the combined absorption tower in the purification unit; The reaction temperature of the catalytic cracking furnace is 220℃~280℃.

2. The green synthesis method for vinyl chloride throughout the entire process according to claim 1, characterized in that: The condensation unit (3) includes a condenser and a condensate storage tank; the purified vinyl chloride gas from the purification unit (2) is transported to the condenser; the vinyl chloride condensate output from the condenser is stored in the condensate storage tank; the condensate storage tank transports liquid vinyl chloride to the distillation unit (5); the gas phase outlet of the condensate storage tank and the tail gas outlet of the low-boiling tower are both connected to the pressure swing adsorption unit (4).

3. The green synthesis method for vinyl chloride throughout the entire process according to claim 1, characterized in that: In step one, the mass ratio of hydrogen chloride to acetylene in the mixed gas fed into synthesis unit (1) is (1.0~1.5):1; the reaction temperature of synthesis unit (1) is 110~190℃, and the volume hourly space velocity is 30~100 h⁻¹. -1 .

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