Process for producing vinyl chloride under catalysis of mercury-free catalyst

Abstract

The invention discloses a process for producing vinyl chloride through catalysis of a mercury-free catalyst, and belongs to the technical field of organic chemical industry. According to the process, activated carbon is used as a carrier, a composite metal oxide modified by rare earth elements and loaded with gold, copper and zinc is used as a mercury-free catalyst, acetylene and hydrogen chloride are introduced according to a specific molar ratio in a fixed bed reactor, and the activity of the catalyst is maintained through an in-situ regeneration system in the reaction process; and after the reaction, the mixed gas is subjected to a separation process combining deep impurity removal and rectification to realize efficient hydrochlorination reaction of acetylene to generate vinyl chloride. The stability of the mercury-free catalyst subjected to modification treatment is remarkably improved, the service life of the catalyst is further prolonged in cooperation with an in-situ regeneration technology, the content of trace impurities in the product can be effectively reduced through the newly added deep impurity removal step, the single-pass yield of vinyl chloride can reach 99% or above, the activity attenuation rate is lower than 3% after the catalyst is continuously used for 1500 hours, and the product purity is larger than or equal to 99.99%; the method is suitable for industrial large-scale production.

Description

Technical Field

[0001] This invention relates to the field of air pollution control and catalytic materials technology, specifically to a process for producing vinyl chloride using a mercury-free catalyst. Background Technology

[0002] Vinyl chloride, as the core monomer in polyvinyl chloride (PVC) production, directly determines the sustainable development level of the PVC industry through the environmental friendliness and efficiency of its industrial preparation technology. Currently, the acetylene hydrochlorination process remains the mainstream technology for vinyl chloride production globally. This process traditionally relies on mercuric chloride / activated carbon catalysts. While it boasts advantages such as mild reaction conditions and mature technology, the highly toxic nature of mercuric chloride poses serious environmental and safety hazards. Throughout the entire lifecycle of catalyst preparation, loading, reaction, and waste disposal, mercury can easily pollute soil and water sources through volatilization and leakage, and can also enter the human body through the respiratory tract and skin contact, causing irreversible damage to the nervous and digestive systems. Therefore, developing mercury-free, high-performance acetylene hydrochlorination catalysts and supporting processes has become a core technological bottleneck that the vinyl chloride industry urgently needs to overcome.

[0003] In existing technologies, the research and development of mercury-free catalysts mainly focuses on composite oxide systems of precious metals (gold and silver-based) and non-precious metals (copper and nickel-based). Among them, gold-based composite catalysts have become a research hotspot due to their excellent initial catalytic activity (acetylene conversion rate can reach over 95%). However, this type of catalyst faces technical challenges in industrial applications, which seriously restricts its promotion: when active components such as gold, copper, and zinc are loaded on the surface of activated carbon in oxide form, the interaction between the active components and the functional groups such as hydroxyl and carboxyl groups on the activated carbon surface is weak. During long-term reaction (usually over 500 hours), the active components are prone to migration and aggregation, forming larger metal particles, resulting in a significant reduction in the number of catalytic active sites. For example, after 800 hours of continuous use, the gold particle size of existing gold-based catalysts tends to increase from the initial 2-5 nm to 10-15 nm, with an activity decay rate exceeding 12%, which is far from meeting the requirements of industrial production for catalyst life (usually requiring over 1000 hours). To address this, we propose a process for the catalytic production of vinyl chloride using a mercury-free catalyst. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the objective of this invention can be achieved through the following technical solutions: A process for producing vinyl chloride using a mercury-free catalyst, the process comprising the following steps: S1. Take activated carbon, soak it in a rare earth nitrate solution with a mass concentration of 1-3%, stir, filter, and dry to obtain a modified activated carbon carrier. S2. Using an equal-volume impregnation method, a mixed solution containing gold, copper, and zinc sources is loaded onto a modified activated carbon carrier. After drying and calcination, a mercury-free catalyst is obtained. The mass fractions of gold, copper, and zinc in the catalyst are 0.1-0.5%, 1-3%, and 0.5-1.5%, respectively, and the mass fraction of rare earth elements in the catalyst is 0.05-0.2%. S3. The acetylene raw material is purified sequentially by passing it through a desulfurization tower and a dephosphorization tower to achieve an acetylene purity of ≥99.95%; the hydrogen chloride raw material is dried by passing it through a drying tower to achieve a moisture content of ≤30ppm. S4. The mercury-free catalyst is loaded into a fixed-bed reactor and activated by heating with nitrogen gas. After activation, pretreated acetylene and hydrogen chloride are introduced into the fixed-bed reactor at a molar ratio of 1:(1.05-1.2) to carry out hydrochlorination to produce vinyl chloride. After the catalyst has reacted continuously for 500-600 hours, the feed gas is stopped, and a nitrogen mixture containing 0.5-1% oxygen is introduced into the reactor to purge and remove carbon deposits on the catalyst surface. Then, hydrogen chloride gas is introduced to replenish the chlorine lost from the active components of the catalyst, completing the in-situ regeneration of the catalyst. S5. The reacted gas mixture is first cooled to 10-30℃, and then passed through a water washing tower and an alkali washing tower to remove unreacted hydrogen chloride, followed by a drying tower to remove moisture. The preliminarily purified gas mixture is then passed into an adsorption tower, which is filled with modified activated alumina adsorbent to remove trace amounts of acetylene oligomers and sulfide residues. The modified activated alumina adsorbent is then impregnated with a 0.5-1% potassium carbonate solution. The deeply purified gas mixture is then sent to a distillation tower for distillation separation to obtain vinyl chloride product with a purity ≥99.99%.

[0005] Further, the activated carbon in step S1 is columnar activated carbon with a particle size of 2-5 mm, and the rare earth nitrate is a mixed salt of lanthanum nitrate and cerium nitrate, wherein the molar ratio of lanthanum to cerium in the mixed salt is 1:(0.5-2).

[0006] Furthermore, the gold source is chloroauric acid, the copper source is copper chloride, and the zinc source is zinc chloride. In step S2, the drying temperature is 80-120℃ and the drying time is 4-8 hours; the calcination temperature is 300-400℃ and the calcination time is 3-6 hours, and the calcination process is carried out in an inert gas atmosphere, wherein the inert gas is nitrogen or argon.

[0007] Furthermore, the desulfurization tower is filled with zinc oxide desulfurizing agent, the dephosphorization tower is filled with activated carbon dephosphorizing agent, and the drying tower is filled with 3A molecular sieve.

[0008] Further, in step S4, the ratio of catalyst loading height to reactor inner diameter in the fixed-bed reactor is 5-10:1, the activation temperature is 200-250℃, and the activation time is 2-4 hours; the reaction temperature inside the fixed-bed reactor is 120-200℃, the reaction pressure is 0.1-0.5MPa, and the space velocity of the feed gas in the catalyst bed is 500-1500 h⁻¹. -1 .

[0009] Furthermore, in step S4, the flow rate of the oxygen-containing nitrogen mixture is 0.8-1.2 times the flow rate of the raw material gas, and the purging conditions are: purging at 180-220℃ for 2-3 hours; the flow rate of the hydrogen chloride gas is 0.5-0.8 times the flow rate of the raw material gas; after introducing the hydrogen chloride gas, treatment at 200-230℃ for 1-2 hours replenishes the chlorine element lost by the catalyst active components.

[0010] Furthermore, in step S5, deionized water is used in the water washing tower, sodium hydroxide solution with a mass concentration of 5-10% is used in the alkali washing tower, and 4A molecular sieve is packed in the drying tower.

[0011] Furthermore, in step S5, the modified activated alumina adsorbent has a particle size of 1-3 mm, and the space velocity of the adsorption tower is 300-500 h⁻¹. -1 After every 100-120 hours of adsorption, the adsorbent is purged and regenerated by nitrogen gas at 250-300℃ for 3-4 hours; the adsorption conditions in the adsorption tower in step S5 are adsorption for 20-30 minutes at 0-10℃ and 0.3-0.5MPa.

[0012] Furthermore, the distillation column uses corrugated packing with a packing height of 8-12m, and a side stream outlet is set in the middle of the distillation column. The side stream outlet temperature is -10 to -6℃, and the product is vinyl chloride with a purity of 95-98%, which can be returned to the feed gas inlet to participate in the reaction again.

[0013] Furthermore, in step S5, after the mixed gas is fed into the distillation column, the top temperature of the column is controlled at -13 to -8℃, the bottom temperature at 30-40℃, the top pressure at 0.5-0.8MPa, and the reflux ratio at 2-5:1, for distillation separation.

[0014] The beneficial effects of this invention are: 1. The rare earth elements introduced in step S1 of the preparation method of this invention are not only anchoring agents for carrier modification, but also form a synergistic catalytic effect with the gold, copper, and zinc loaded in step S2. The electronic properties of rare earth elements can adjust the electron cloud density of the active components, enhance the adsorption capacity of gold for acetylene and hydrogen chloride, and at the same time prevent copper and zinc from covering the active sites of gold, effectively inhibiting the aggregation of active components and extending the catalyst life.

[0015] 2. In step S2 of the preparation method of the present invention, by using a low ratio of gold and copper-zinc auxiliary materials, combined with the synergistic effect of rare earth modification in step S1, the initial acetylene conversion rate of existing gold-based catalysts of more than 95% can be matched, reducing the amount of precious metal gold used, reducing the catalyst preparation cost, while improving reaction selectivity, reducing the generation of by-products, and alleviating the pressure of subsequent separation and purification.

[0016] 3. In step S4 of the preparation method of the present invention, carbon deposits are removed by purging with a nitrogen-oxygen mixture, and then hydrogen chloride is introduced to replenish chlorine, thereby achieving in-situ regeneration of the catalyst. This ensures that the activity decay rate of the catalyst is less than 3% after 1500 hours of continuous use, meeting the requirements of industrial production for catalyst life.

[0017] 4. In step S5 of the preparation method of the present invention, a modified activated alumina adsorption tower is added for deep impurity removal, which effectively removes trace amounts of acetylene oligomers and sulfide residues. Combined with the optimized distillation process, the purity of vinyl chloride product is ≥99.99%, and the single-pass yield can reach more than 99%. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of this disclosure or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, those skilled in the art can obtain other drawings based on these drawings without creative effort.

[0019] Figure 1 This is a comparison chart of the C2H2-TPD peak areas in Embodiment 1, Comparative Example 1-1, and Comparative Example 1-2 of the present invention; Figure 2 These are the electronic state distribution diagrams of Embodiment 1 and Comparative Example 1-1 of the present invention. Detailed Implementation

[0020] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0021] Example 1: S1. Take activated carbon, soak it in a rare earth nitrate solution with a mass concentration of 1-3%, stir, filter, and dry to obtain a modified activated carbon carrier; the activated carbon is columnar activated carbon with a particle size of 5 mm, and the rare earth nitrate is a mixed salt of lanthanum nitrate and cerium nitrate, wherein the molar ratio of lanthanum to cerium in the mixed salt is 1:1.25.

[0022] S2. Using an equal-volume impregnation method, a mixed solution containing gold, copper, and zinc sources is loaded onto a modified activated carbon carrier. After drying and calcination, a mercury-free catalyst is obtained. The mass fractions of gold, copper, and zinc in the catalyst are 0.4%, 2%, and 1%, respectively, and the mass fraction of rare earth elements in the catalyst is 0.05%. S3. The acetylene raw material is purified sequentially by passing it through a desulfurization tower and a dephosphorization tower to achieve an acetylene purity of ≥99.95%; the hydrogen chloride raw material is dried by passing it through a drying tower to achieve a moisture content of ≤30ppm. S4. The mercury-free catalyst is loaded into a fixed-bed reactor and activated by heating with nitrogen gas. After activation, pretreated acetylene and hydrogen chloride are introduced into the fixed-bed reactor at a molar ratio of 1:1.05 to carry out hydrochlorination to produce vinyl chloride. After the catalyst has reacted continuously for 500 hours, the feed gas is stopped, and a nitrogen mixture containing 1% oxygen is introduced into the reactor to purge and remove carbon deposits on the catalyst surface. Then, hydrogen chloride gas is introduced to replenish the chlorine element lost by the active components of the catalyst, completing the in-situ regeneration of the catalyst. S5. The reacted gas mixture is first cooled to 30°C, and then passed through a water washing tower and an alkali washing tower to remove unreacted hydrogen chloride, followed by a drying tower to remove moisture. The preliminarily purified gas mixture is then passed into an adsorption tower, which is filled with modified activated alumina adsorbent to remove trace amounts of acetylene oligomers and sulfide residues. The modified activated alumina adsorbent is then impregnated with a 0.5% potassium carbonate solution. The deeply purified gas mixture is then sent to a distillation tower for distillation separation to obtain vinyl chloride product with a purity ≥99.99%.

[0023] Comparative Example 1-1 Compared with Example 1, Comparative Example 1-1: The rare earth modification step in S1 was omitted, and Au-Cu-Zn loading in step S2 was performed directly using unmodified columnar activated carbon. All other steps were the same as in Example 1. Comparative Examples 1-2 Compared with Example 1, Comparative Examples 1-2: S1 uses the non-electronically inert element Ba to replace La-Ce and loads Au-Cu-Zn, while the other steps are the same as in Example 1; Ba has the same valence state as La but has no electronic adjustment capability; Comparative Examples 1-3 Compared with Example 1, Comparative Examples 1-3 did not undergo S1 carrier modification; instead, rare earth nitrates and Au-Cu-Zn mixed solutions were directly co-impregnated in unmodified activated carbon. All other steps were the same as in the Example. The anchoring effect was verified using stability and particle size data: Example 1: 2.5% activity decay rate after 1500 hours, Au particle size maintained at 3-4 nm; Comparative Example 1-1: The activity decay rate after 1500 hours was >15%, and the Au particle size increased to 12-14 nm; Comparative Examples 1-3: Activity decay rate >10% after 1500 hours, Au particle size increased to 8-10 nm; The experimental data from Example 1, Comparative Example 1-1, and Comparative Example 1-3 show that rare earth elements must be anchored through carrier modification in step S1 in order to effectively inhibit the aggregation of active components. Simply adding rare earth elements without modifying the carrier significantly weakens the anchoring effect.

[0024] The synergistic catalysis effect was validated using activity, adsorption, and electronic data. Initial activity: The conversion rate of Example 1 was 99.2%, the conversion rate of Comparative Examples 1-2 was 85.5%, and the conversion rate of Comparative Examples 1-1 was 78.8%.

[0025] Adsorption capacity: The C2H2-TPD peak area of ​​Example 1 is 1.8 times that of Comparative Example 1-1, while that of Comparative Example 1-2 is only 1.1 times that of the baseline; Electronic state: The binding energy of Au4f in the baseline example 1 is 0.3-0.5 eV lower than that in comparative example 1-1 (higher electron cloud density). Conclusion: The electronic regulation ability of rare earth elements is the key to enhancing gold adsorption capacity and improving initial activity, and inert elements cannot replace this synergistic effect.

[0026] Example 2 S1. Take activated carbon, soak it in a rare earth nitrate solution with a mass concentration of 1-3%, stir, filter, and dry to obtain a modified activated carbon carrier; the activated carbon is columnar activated carbon with a particle size of 5 mm, and the rare earth nitrate is a mixed salt of lanthanum nitrate and cerium nitrate, wherein the molar ratio of lanthanum to cerium in the mixed salt is 1:1.25.

[0027] S2. Using an equal-volume impregnation method, a mixed solution containing gold, copper, and zinc sources is loaded onto a modified activated carbon carrier. After drying and calcination, a mercury-free catalyst is obtained. The mass fractions of gold, copper, and zinc in the catalyst are 0.5%, 3%, and 1.5%, respectively, and the mass fraction of rare earth elements in the catalyst is 0.2%. S3. The acetylene raw material is purified sequentially by passing it through a desulfurization tower and a dephosphorization tower to achieve an acetylene purity of ≥99.95%; the hydrogen chloride raw material is dried by passing it through a drying tower to achieve a moisture content of ≤30ppm. S4. The mercury-free catalyst is loaded into a fixed-bed reactor and activated by heating with nitrogen gas. After activation, pretreated acetylene and hydrogen chloride are introduced into the fixed-bed reactor at a molar ratio of 1:1.1 to carry out hydrochlorination to produce vinyl chloride. After the catalyst has reacted continuously for 600 hours, the feed gas is stopped, and a nitrogen mixture containing 1% oxygen is introduced into the reactor to purge and remove carbon deposits on the catalyst surface. Then, hydrogen chloride gas is introduced to replenish the chlorine lost from the active components of the catalyst, completing the in-situ regeneration of the catalyst. S5. The reacted gas mixture is first cooled to 20°C, and then passed through a water washing tower and an alkali washing tower to remove unreacted hydrogen chloride, followed by a drying tower to remove moisture. The preliminarily purified gas mixture is then passed into an adsorption tower, which is filled with modified activated alumina adsorbent to remove trace amounts of acetylene oligomers and sulfide residues. The modified activated alumina adsorbent is then impregnated with a 1% potassium carbonate solution. The deeply purified gas mixture is then sent to a distillation tower for distillation separation to obtain vinyl chloride product with a purity ≥ 99.99%.

[0028] Comparative Example 2-1 In step S1, the La-Ce modification is the same as in Example 2; in step S2, the Au content is 0.6%, there is no Cu / Zn, and the other steps are the same as in Example 2.

[0029] Comparative Example 2-2 In step S1, the La-Ce modification is the same as in Example 2; in step S2, the Au content is 0.3%, there is no Cu / Zn, and the other steps are the same as in Example 2.

[0030] Comparative Examples 2-3 In step S1, there is no rare earth modification, i.e., the activated carbon is unmodified; in step S2, the proportion of Au is 0.3%, the proportion of Cu is 2%, and the proportion of Zn is 1%, and the other steps are the same as in Example 2.

[0031] Comparative Examples 2-4 Commercially available gold-based mercury-free catalysts contain 0.8% Au, are unmodified with rare earth elements, and have no Cu / Zn additives.

[0032] Test method: Initial acetylene conversion rate Detection method: According to the process in document S4, pretreated acetylene and HCl (molar ratio 1:1.125) were introduced into a fixed-bed reactor at a reaction temperature of 160℃ and a pressure of 0.3MPa. The residual acetylene in the mixed gas after the reaction was detected by gas chromatography-2014, and the conversion rate was calculated as follows: Conversion rate = (1 - acetylene concentration in tail gas / acetylene concentration in feedstock) × 100%; Vinyl chloride selectivity Detection method: The content of components such as vinyl chloride and acetylene oligomers (e.g., dichloroethylene) in the product is analyzed by gas chromatography, and the selectivity is calculated as follows: Selectivity = Vinyl chloride production / (acetylene consumption) × 100%; Catalyst unit preparation cost Calculation logic: Based on the prices of industrial-grade raw materials, the market prices in 2024 were as follows: chloroauric acid was about 4,000 yuan / g Au, copper chloride was about 8 yuan / kg, zinc chloride was about 5 yuan / kg, and rare earth nitrates were about 20 yuan / kg. Taking the preparation of 1 kg of catalyst as an example, the raw material costs of each group were calculated separately. 500-hour activity decay rate Detection method: The reaction proceeds continuously for 500 hours, with the acetylene conversion rate measured every 100 hours. The decay rate is calculated as follows: Decay rate = (Initial conversion rate - 500-hour conversion rate) / Initial conversion rate × 100%; The experimental data are shown in Table 1: Table 1 Combining the data from Example 2 and Comparative Examples 2-1, 2-2, 2-3, and 2-4, it can be seen that: 1. Copper-zinc auxiliary components form a synergistic catalytic effect with gold, achieving the same activity level as a high-gold-content (0.6%) catalyst without auxiliary components even with low gold content (0.3%). Copper and zinc not only enhance the adsorption and activation capacity of gold for acetylene and hydrogen chloride, but also improve reaction selectivity and reduce by-product formation, thereby reducing dependence on the amount of precious metal gold used and significantly controlling the catalyst preparation cost.

[0033] 2. Rare earth modification enhances the interaction between the activated carbon support and the gold, copper, and zinc active components through anchoring, effectively inhibiting the migration and aggregation of active components during the reaction process and maintaining the number and stability of catalytic active sites. Without rare earth modification, even with a low gold and copper-zinc ratio, the catalyst activity decays relatively quickly, failing to meet the industrial demand for long lifespan.

[0034] 3. The rare earth modification, low gold content, and copper-zinc auxiliary system in Example 2 achieves a synergy between low cost and high performance. It avoids the high cost problem of high gold content catalysts and solves the pain points of insufficient activity of low gold content catalysts without auxiliary components and poor stability of catalysts without rare earth modification, providing both economic and technical feasibility for the industrialization of the process.

[0035] Example 3 S1. Take activated carbon, soak it in a rare earth nitrate solution with a mass concentration of 1-3%, stir, filter, and dry to obtain a modified activated carbon carrier; the activated carbon is columnar activated carbon with a particle size of 5 mm, and the rare earth nitrate is a mixed salt of lanthanum nitrate and cerium nitrate, wherein the molar ratio of lanthanum to cerium in the mixed salt is 1:1.25.

[0036] S2. Using an equal-volume impregnation method, a mixed solution containing gold, copper, and zinc sources is loaded onto a modified activated carbon carrier. After drying and calcination, a mercury-free catalyst is obtained. The mass fractions of gold, copper, and zinc in the catalyst are 0.1-0.5%, 1-3%, and 0.5-1.5%, respectively, and the mass fraction of rare earth elements in the catalyst is 0.05-0.2%. S3. The acetylene raw material is purified sequentially by passing it through a desulfurization tower and a dephosphorization tower to achieve an acetylene purity of ≥99.95%; the hydrogen chloride raw material is dried by passing it through a drying tower to achieve a moisture content of ≤30ppm. S4. The mercury-free catalyst is loaded into a fixed-bed reactor and activated by heating with nitrogen gas. After activation, pretreated acetylene and hydrogen chloride are introduced into the fixed-bed reactor at a molar ratio of 1:1.05 to carry out hydrochlorination to produce vinyl chloride. After the catalyst has reacted continuously for 550 hours, the feed gas is stopped, and a nitrogen mixture containing 0.5-1% oxygen is introduced into the reactor to purge and remove carbon deposits on the catalyst surface. Then, hydrogen chloride gas is introduced to replenish the chlorine lost from the active components of the catalyst, completing the in-situ regeneration of the catalyst. S5. The reacted gas mixture is first cooled to 30°C, and then passed through a water washing tower and an alkali washing tower to remove unreacted hydrogen chloride, followed by a drying tower to remove moisture. The preliminarily purified gas mixture is then passed into an adsorption tower, which is filled with modified activated alumina adsorbent to remove trace amounts of acetylene oligomers and sulfide residues. The modified activated alumina adsorbent is then impregnated with a 1% potassium carbonate solution. The deeply purified gas mixture is then sent to a distillation tower for distillation separation to obtain vinyl chloride product with a purity ≥99.99%.

[0037] Comparative Example 3-1 In step S1, the La-Ce modification is the same as in Example 3; in step S4, there is no in-situ regeneration step, and the reaction is carried out continuously for 1500 hours without treatment, while the other steps are the same as in Example 3.

[0038] Comparative Example 3-2 In step S1, there is no rare earth modification step; Au-Cu-Zn is directly supported on unmodified activated carbon. In step S4, there is no in-situ regeneration step; the reaction is carried out continuously for 1500 hours without treatment. All other steps are the same as in Example 3.

[0039] Comparative Example 3-3 Step S1 does not include a rare earth modification step; all other steps are the same as in Example 3.

[0040] Validation of detection indicators and methods Key performance indicator: 1500-hour activity decay rate; Detection method: Sampling is performed every 100 hours, and the residual acetylene in the mixture after reaction is detected by gas chromatography to calculate the acetylene conversion rate.

[0041] Decay rate formula: Decay rate = (Initial conversion rate - 1500-hour conversion rate) / Initial conversion rate × 100%.

[0042] Other indicators: Detection method for changes in the particle size of the active component (Au): The particle size of Au particles was observed using a transmission electron microscope (TEM) before and after the reaction.

[0043] The experimental data are shown in Table 2: Table 2 Combining the experimental steps and data, we can see that: Example 3 shows an attenuation rate of <3%, directly proving that the process meets the industrial requirements for continuous 1500-hour use of the catalyst.

[0044] Compared with Example 1, the only variable in Comparative Example 3-1 was the absence of in-situ regeneration, and the attenuation rate increased significantly. This proves that the in-situ regeneration steps of purging carbon deposits with oxygen-containing nitrogen and replenishing chlorine with HCl are the core to maintaining the long-term activity of the catalyst.

[0045] Compared with Example 1, the only variable in Comparative Example 3-3 was the absence of rare earth modification, yet the attenuation rate still exceeded the standard, proving that the anchoring effect of rare earth modification and in-situ regeneration work synergistically and are both indispensable.

[0046] Further evidence from observing the differences in Au particle size confirms that in-situ regeneration solves the problems of carbon buildup and chlorine loss, while rare earth modification solves the problem of active component agglomeration. The combination of the two achieves a long catalyst lifespan.

[0047] Example 4 S1. Take activated carbon, soak it in a rare earth nitrate solution with a mass concentration of 1-3%, stir, filter, and dry to obtain a modified activated carbon carrier; the activated carbon is columnar activated carbon with a particle size of 5 mm, and the rare earth nitrate is a mixed salt of lanthanum nitrate and cerium nitrate, wherein the molar ratio of lanthanum to cerium in the mixed salt is 1:1.25.

[0048] S2. Using an equal-volume impregnation method, a mixed solution containing gold, copper, and zinc sources is loaded onto a modified activated carbon carrier. After drying and calcination, a mercury-free catalyst is obtained. The mass fractions of gold, copper, and zinc in the catalyst are 0.4%, 2%, and 1%, respectively, and the mass fraction of rare earth elements in the catalyst is 0.05%. S3. The acetylene raw material is purified sequentially by passing it through a desulfurization tower and a dephosphorization tower to achieve an acetylene purity of ≥99.95%; the hydrogen chloride raw material is dried by passing it through a drying tower to achieve a moisture content of ≤30ppm. S4. The mercury-free catalyst is loaded into a fixed-bed reactor and activated by heating with nitrogen gas. After activation, pretreated acetylene and hydrogen chloride are introduced into the fixed-bed reactor at a molar ratio of 1:1.05 to carry out hydrochlorination to produce vinyl chloride. After the catalyst has reacted continuously for 500 hours, the feed gas is stopped, and a nitrogen mixture containing 1% oxygen is introduced into the reactor to purge and remove carbon deposits on the catalyst surface. Then, hydrogen chloride gas is introduced to replenish the chlorine element lost by the active components of the catalyst, completing the in-situ regeneration of the catalyst. S5. The reacted gas mixture is first cooled to 30°C, and then passed through a water washing tower and an alkali washing tower to remove unreacted hydrogen chloride, followed by a drying tower to remove moisture. The preliminarily purified gas mixture is then passed into an adsorption tower, which is filled with modified activated alumina adsorbent to remove trace amounts of acetylene oligomers and sulfide residues. The modified activated alumina adsorbent is then impregnated with a 0.5% potassium carbonate solution. The deeply purified gas mixture is then sent to a distillation tower for distillation separation to obtain vinyl chloride product with a purity ≥99.99%.

[0049] Comparative Example 4-1 In step S5, the modified activated alumina adsorption tower is removed: that is, after water washing, alkali washing, and drying, it directly enters the distillation tower, and the distillation parameters remain unchanged.

[0050] Validation of detection indicators and methods Key indicator 1: Trace impurity residue level, verifying the effectiveness of deep impurity removal; Targets for testing: acetylene oligomers such as dichloroethylene, and sulfide residues.

[0051] Detection method: Gas chromatography-mass spectrometry (GC-MS) was used to detect the impurity content in the inlet and outlet of the adsorption tower and in the product after distillation. The detection limit must be at the ppb level (10⁻⁻¹). 9 ).

[0052] Key Indicator 2: Purity of Vinyl Chloride Products Detection method: A high-precision gas chromatograph equipped with a thermal conductivity detector (TCD) and a flame ionization detector (FID) was used to detect the product components according to GB / T3405-2019 standard.

[0053] Key Indicator 3: Vinyl Chloride Single-Pass Yield Calculation logic: The amount of vinyl chloride generated in the mixed gas at the reactor outlet is detected by gas chromatography. Combined with the amount of acetylene fed into the reactor, the single-pass yield is calculated according to the formula: Single-pass yield = (Amount of vinyl chloride generated / Amount of acetylene fed into the reactor) × 100%.

[0054] The experimental data are shown in Table 3: Table 3 Based on the experimental steps and data, it can be seen that the purity and yield of Example 4 reached the target values ​​(≥99.99%, ≥99%), directly verifying the effectiveness of the technology.

[0055] Comparative Example 4-1 differs from Example 1 only in the step of modified activated alumina adsorption, yet it shows a significant decrease in purity and yield, proving that the deep impurity removal step is the core contributing factor.

[0056] The segmented detection of residual impurities further corroborates the removal effect of the adsorption tower on impurities, indicating that optimized distillation needs to be combined with deep impurity removal to achieve the target effect.

[0057] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0058] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention.

Claims

1. A process for the catalytic production of vinyl chloride using a mercury-free catalyst, characterized in that, The preparation process comprises the following steps: S1, taking activated carbon, soaking in a rare earth nitrate solution with a mass concentration of 1-3%, stirring, filtering, and drying to obtain a modified activated carbon carrier; S2, using an equal volume impregnation method, loading a mixed solution containing a gold source, a copper source, and a zinc source on the modified activated carbon carrier, and after drying and calcining, obtaining a mercury-free catalyst; the mass fractions of gold, copper, and zinc in the catalyst are 0.1-0.5%, 1-3%, and 0.5-1.5% respectively, and the mass fraction of rare earth elements in the catalyst is 0.05-0.2%; S3, acetylene raw materials are sequentially purified by a desulfurization tower and a dephosphorization tower to make the acetylene purity ≥99.95%; hydrogen chloride raw materials are dried by a drying tower to make the water content ≤30ppm; S4, the mercury-free catalyst is loaded in a fixed bed reactor, nitrogen is introduced for temperature activation; after activation is completed, pretreated acetylene and hydrogen chloride are introduced into the fixed bed reactor according to a molar ratio of 1:(1.05-1.2) to generate vinyl chloride through hydrochlorination; when the catalyst continuously reacts for 500-600 hours, the raw material gas is temporarily stopped, a nitrogen gas mixture containing 0.5-1% oxygen is introduced into the reactor to perform purging, and the carbon on the surface of the catalyst is removed; then, hydrogen chloride gas is introduced to supplement the chlorine element lost by the active components of the catalyst, and in-situ regeneration of the catalyst is completed; S5, the mixed gas after reaction is first cooled to 10-30℃, sequentially passes through a water washing tower, an alkali washing tower to remove unreacted hydrogen chloride, and then passes through a drying tower to remove water; the preliminarily purified mixed gas is introduced into an adsorption tower, a modified activated alumina adsorbent is loaded in the adsorption tower to perform adsorption, and trace acetylene oligomers and sulfide residues in the mixed gas are removed; the modified activated alumina adsorbent is impregnated with a potassium carbonate solution with a mass concentration of 0.5-1%, and the deeply impurity-removed mixed gas is sent into a rectifying tower to perform rectification and separation, and vinyl chloride products with a purity ≥99.99% are obtained.

2. A process for the catalytic production of vinyl chloride without mercury catalysts according to claim 1, characterized in that: The activated carbon in step S1 is columnar activated carbon with a particle size of 2-5mm, and the rare earth nitrate is a mixed salt of lanthanum nitrate and cerium nitrate, and the molar ratio of lanthanum to cerium in the mixed salt is 1:(0.5-2).

3. A process for the catalytic production of vinyl chloride without mercury catalysts according to claim 1, characterized in that: The gold source is chloroauric acid, the copper source is copper chloride, and the zinc source is zinc chloride; in step S2, the drying temperature is 80-120℃, and the drying time is 4-8 hours; the calcination temperature is 300-400℃, and the calcination time is 3-6 hours, and the calcination process is carried out in an inert gas atmosphere, and the inert gas is nitrogen or argon.

4. A process for the catalytic production of vinyl chloride without mercury catalysts according to claim 1, characterized in that: The desulfurization tower is loaded with a zinc oxide desulfurizer, the dephosphorization tower is loaded with an activated carbon dephosphorization agent, and the drying tower is loaded with 3A molecular sieves.

5. A process for the catalytic production of vinyl chloride without mercury catalysts according to claim 1, characterized in that: The ratio of the catalyst loading height to the inner diameter of the fixed bed reactor in step S4 is 5-10:1, the activation temperature is 200-250°C, and the activation time is 2-4 hours; the reaction temperature in the fixed bed reactor is 120-200°C, the reaction pressure is 0.1-0.5 MPa, and the space velocity of the raw material gas in the catalyst bed is 500-1500 h -1 .

6. A process for the catalytic production of vinyl chloride without mercury catalysts according to claim 1, characterized in that: In step S4, the flow rate of the nitrogen gas mixture containing oxygen is 0.8-1.2 times the flow rate of the raw material gas, the purging conditions are: purging for 2-3 hours at 180-220℃; the flow rate of the hydrogen chloride gas is 0.5-0.8 times the flow rate of the raw material gas; after the hydrogen chloride gas is introduced, the chlorine element lost by the active components of the catalyst is supplemented by treating at 200-230℃ for 1-2 hours.

7. A process for the catalytic production of vinyl chloride without mercury catalysts according to claim 1, characterized in that: Deionized water is used in the water washing tower in step S5, sodium hydroxide solution with mass concentration of 5-10% is used in the alkali washing tower, and 4A molecular sieve is filled in the drying tower.

8. A process for the catalytic production of vinyl chloride without mercury catalysts according to claim 1, characterized by the fact that: The modified activated alumina adsorbent in step S5 has a particle size of 1-3 mm, and the adsorption tower has a space velocity of 300-500 h -1 -120 hours, the adsorbent is regenerated by purging with nitrogen at 250-300°C, and the regeneration time is 3-4 hours; the adsorption conditions in the adsorption tower in step S5 are as follows: adsorption for 20-30 minutes at 0-10°C and 0.3-0.5 MPa.

9. A process for the catalytic production of vinyl chloride without mercury catalysts according to claim 1, characterized in that: Corrugated packing is used in the rectifying tower, the packing height is 8-12 m, a side line outlet is arranged in the middle of the rectifying tower, the side line outlet temperature is-10 to-6 ℃, and the outlet material is vinyl chloride with purity of 95-98%, which can be returned to the raw material gas inlet to participate in the reaction again.

10. A process for the catalytic production of vinyl chloride without mercury catalysts according to claim 1, characterized in that: After the mixed gas in step S5 is sent into the rectifying tower, the tower top temperature is controlled to be-13 to-8 ℃, the tower bottom temperature is controlled to be 30-40 ℃, the tower top pressure is controlled to be 0.5-0.8 MPa, and the reflux ratio is controlled to be 2-5:1, so as to carry out rectifying separation.

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