Method for synthesizing pentachloropropane based on raw materials of vinyl chloride and carbon tetrachloride

Abstract

The invention discloses a pentachloropropane synthesis method based on raw materials of vinyl chloride and carbon tetrachloride, and belongs to the technical field of new chemical materials. The method comprises the main steps of raw material proportioning and pretreatment, nano catalytic reaction, product primary extraction and purification and the like. The catalyst is prepared by compounding ferrous chloride and nano iron oxide and then loading on a mesoporous carbon carrier, and has excellent catalytic performance. The product is purified through reduced pressure distillation and an activated carbon adsorption column, and the purity can reach 99.7% or above. The method creatively combines a nanotechnology with specific reaction conditions, and has the advantages of high yield, high product purity, good catalyst stability and the like. Compared with a traditional synthesis method, the method has the advantages that the production efficiency is remarkably improved, the energy consumption is reduced, an innovative and practical technical path is provided for industrial production of pentachloropropane, and the method has a wide application prospect.

Description

Technical Field

[0001] The present invention belongs to the technical field of new chemical materials, and in particular relates to a method for synthesizing pentachloropropane based on vinyl chloride and carbon tetrachloride as raw materials. Background Art

[0002] Pentachloropropane (1,1,1,2,3-pentachloropropane, abbreviated as HCC-240db) is an important chlorine-containing organic compound with extensive application value in the field of new chemical materials. It is not only a key intermediate in the production of fluorinated refrigerants, foaming agents, and cleaning agents, but also plays an irreplaceable role in a variety of fields, including pharmaceuticals, pesticides, and fine chemicals. With the continued global demand for environmentally friendly refrigerants, especially for low-global warming potential alternatives such as hydrofluorocarbons and hydrochlorofluorocarbons, the research and improvement of pentachloropropane production technology, a key raw material for the synthesis of these alternatives, is particularly urgent and important. However, the current synthesis technology of pentachloropropane still faces many challenges, including low yield, poor selectivity, high energy consumption, and environmental pollution. These issues have limited its further promotion and application in industrial production.

[0003] Traditional methods for synthesizing pentachloropropane rely primarily on chlorination of propene or chlorination of propane. While these methods have a history of industrial application, they suffer from significant process drawbacks and struggle to meet the demands of modern chemical industry for efficiency, environmental friendliness, and cost-effectiveness. For example, the synthesis route using propene chloride as a raw material produces pentachloropropane through the addition reaction of chlorine gas with propene chloride. However, due to the high activity of chlorination, various byproducts are readily generated during the reaction, such as isomers such as tetrachloropropane and hexachloropropane, or overchlorination products. The presence of these byproducts not only reduces the selectivity of the target product but also increases the difficulty of subsequent separation and purification, making it difficult to achieve product purity that meets industrial application standards. Furthermore, this reaction typically requires high reaction temperatures and long reaction times, resulting in high energy consumption. The disposal of these byproducts further increases production costs and the environmental burden. Another common synthesis method uses propane chloride as a raw material and gradually introduces chlorine atoms through a multi-step chlorination reaction to ultimately produce pentachloropropane. While theoretically feasible, this approach has significant practical limitations. First, the chlorination reaction of chloropropane needs to be carried out under high temperature and high pressure conditions, which not only places high corrosion resistance and pressure resistance requirements on the reaction equipment, but also significantly increases energy consumption and operational risks. Secondly, the selectivity of the reaction is difficult to control, and it is easy to generate a series of by-products with different degrees of chlorination. The product distribution is complex and the separation cost is high. In addition, the catalysts commonly used in traditional methods are mostly liquid or solid Lewis acids, such as aluminum chloride or ferric chloride. Although these catalysts can promote the chlorination reaction to a certain extent, they have the disadvantages of being easily deactivated and difficult to recycle during use, resulting in frequent replacement of catalysts and the generation of a large amount of waste, further exacerbating production costs and environmental pollution problems.

[0004] In recent years, with the rapid development of nanotechnology and catalysis science, researchers have begun exploring the use of novel catalysts and improved reaction processes to optimize the synthesis of pentachloropropane (PCP). For example, studies have reported using nanometal oxides as catalysts to synthesize PCP via gas-phase chlorination, demonstrating some progress compared to traditional methods. This approach leverages the high surface area and excellent catalytic activity of nanomaterials to improve reaction selectivity and product yield. However, this technology still faces numerous challenges. First, the preparation of nanocatalysts is often complex, requiring precise control of particle size, morphology, and dispersibility, which increases production costs and process complexity. Second, gas-phase chlorination reactions often require high temperatures and specific pressures, placing high demands on reaction equipment and operating conditions. Furthermore, while nanocatalysts have demonstrated certain advantages under laboratory conditions, their stability and durability in industrial production still require further verification, and product yield and purity have not yet reached ideal levels. These factors collectively limit the widespread application of this technology in practical production. Summary of the Invention

[0005] In view of the many technical problems existing in the traditional synthesis method of pentachloropropane, an innovative synthesis scheme is proposed to solve the deficiencies of the traditional method in yield, selectivity, energy consumption, environmental pollution and raw material utilization rate. The traditional synthesis method of pentachloropropane has the following main problems: low yield: due to many side reactions, the yield of the target product pentachloropropane is low, which affects the production efficiency and economic benefit. Poor selectivity: side products such as tetrachloropropane and hexachloropropane are easily generated in the reaction, resulting in low product purity and high subsequent separation cost. High energy consumption: high temperature and high pressure conditions are required, which consumes a lot of energy, requires high equipment, and increases production cost. Environmental pollution: traditional catalysts (such as aluminum chloride or ferric chloride) are easy to deactivate and difficult to recover, producing a large amount of waste and polluting the environment. Low raw material utilization rate: part of the raw materials is converted into by-products, causing resource waste.

[0006] To solve the above problems, the technical scheme adopted by the present application is as follows.

[0007] A pentachloropropane synthesis method based on chloroethylene and carbon tetrachloride raw materials, comprising the following steps: step S1: preparation of nanocomposite catalyst: ferrous chloride (CAS No. 7758-94-3) and nanometer iron oxide (CAS No. 1317-61-9) are compounded by wet chemical method according to mass ratio 1: (0.3-0.6), and then loaded on a mesoporous carbon carrier to prepare a nanocomposite catalyst; step S2: raw material ratio and pretreatment: 100 parts of chloroethylene (CAS No. 75-01-4) and 130-160 parts of carbon tetrachloride (CAS No. 56-23-5) are taken, 0.1-0.5 parts of nanometer polyvinylpyrrolidone (CAS No. 9003-39-8, ≤100 nm) is added under nitrogen protection, and mixed uniformly to obtain a pretreated reaction system; step S3: nanometer catalytic reaction: 0.8-2 parts of nanometer composite catalyst and 120-140 parts of pretreated reaction system are taken according to mass fraction, the temperature is controlled at 50-70℃, the pressure is controlled at 0.2-0.6 MPa, the reaction time is 20-40 min, then the temperature is raised to 120-140℃, the pressure is adjusted to 0.9-1.3 MPa, the reaction time is 1.5-3 h, finally the temperature is lowered to 80-100℃, the pressure is maintained at 0.5-0.8 MPa, and the reaction is carried out for 0.5-1 h to obtain a mixed product; step S4: product preliminary extraction: the obtained mixed product is separated by vacuum distillation to obtain a crude product; step S5: product purification: the crude product is passed through an activated carbon adsorption column to obtain pentachloropropane finished product with purity ≥99.7%.

[0008] Catalytic active center construction (based on step S1): ferrous chloride-nano iron oxide synergistic system: ferrous chloride as Lewis acid, through divalent iron ion empty orbital to accept the electron of vinyl chloride C=C double bond, to reduce the electrophilic addition energy barrier (activation energy from 150 kJ / mol to 95 kJ / mol). Nano iron oxide surface Fe 3+ / Fe 2+ Redox pair promotes electron transfer and accelerates C-Cl bond rupture (reaction rate is increased by 3 times). Mesoporous carbon confinement effect: the pore with a diameter of 2-5 nm physically restricts the reactants, inhibiting the generation of by-products such as hexachloropropane; carbon tetrachloride is uniformly split on the surface of nano iron oxide to generate-CCl3 free radicals, which attack the activated vinyl chloride. Pressure (0.9-1.3 MPa) increases the concentration of reactants and accelerates chain transfer. When the reaction is completed, low temperature terminates the free radical chain reaction, avoiding the generation of over-chlorinated products (isomerization rate Conclusion: the present process realizes the efficient green synthesis of pentachloropropane through the electron synergy of nano catalyst and the mesoporous confinement effect at the molecular level to precisely control the free radical addition path; combined with the stage temperature-pressure optimization and polarity matching purification strategy, a new paradigm is provided for the clean production of chlorinated organic matter.

[0009] Preferably, the particle size of nano iron oxide in step S1 is 10-30 nm; the pore diameter of the mesoporous carbon carrier in step S1 is 2-5 nm, and the specific surface area is ≥500 m 2 / g.

[0010] Preferably, the wet chemical method in step S1 is as follows: the nano iron oxide is suspended in deionized water with a mass of 40-80 times that of the nano iron oxide, and then 3-aminopropyltriethoxysilane (CAS No. 919-30-2) with a mass of 0.1-0.2 times that of the nano iron oxide is added, and the mixture is stirred and reacted at 50-60°C under nitrogen protection for 2-3h. After the reaction, the modified nano iron oxide is collected by magnetic separation, washed with anhydrous ethanol for 3 times, and dried for use; the ferrous chloride solution is prepared by dissolving ferrous chloride in deionized water with a mass of 50-100 times that of the ferrous chloride, and then adding sodium citrate with a mass of 0.04-0.1 times that of the ferrous chloride under nitrogen protection to obtain the ferrous chloride solution; the ferrous chloride solution and the modified nano iron oxide are taken in a mass ratio of 1:(0.3-0.6), the modified nano iron oxide is resuspended in deionized water with a mass of 10 times that of the modified nano iron oxide, the ferrous chloride solution is added dropwise at a rate of 1-2mL / min, and a 0.1-0.2mol / L sodium hydroxide solution is added to adjust the pH to 8.5-9.5, and the mixture is stirred and reacted at 40-50°C for 3-5h under the assistance of ultrasonic waves with a frequency of 20-25kHz and a power of 100-150W to form a composite structure of ferrous chloride-coated nano iron oxide; after the reaction, the composite structure is separated by an external magnetic field with a magnetic field strength of 0.2-0.5T, washed with deionized water and anhydrous ethanol alternately for 3-5 times to remove unreacted salts and impurities, and then dried in a vacuum drying oven at 60-70°C for 6-8h to obtain the ferrous chloride-nano iron oxide composite material. The three-stage control of surface modification-complexation-co-precipitation: from the construction of anchor sites by silane coupling to the stabilization of citric acid complexation, and finally the realization of atomic-level coating by alkaline co-precipitation. Interface electron synergistic effect: the Fe-O-Fe bond between the core and shell enhances the electron transfer ability, and the catalytic activity is increased by 40%. Magnetic recovery advantage: the recovery rate by magnetic field separation is ≥98%, and the activity retention rate is ≥90% after 5 cycles. This process realizes the synergistic optimization of catalyst activity and stability through molecular-level interface design, and provides an innovative path for the precise preparation of nano composite catalysts.

[0011] Preferably, the mesoporous carbon carrier in step S1 is prepared as follows: mesoporous silica with a pore size of 2-5 nm (CAS No. 7631-86-9) is mixed with sucrose at a mass ratio of 1: (2-3). Specifically, sucrose is dissolved in 10-15 times its mass of deionized water, and the mesoporous silica is added and stirred uniformly. The uniform stirring temperature is 30-40°C, and the uniform stirring time is 1-2 h, forming a suspension. The suspension is allowed to stand for 4-6 h, and then 0.01-0.05 times the mass of the suspension of concentrated sulfuric acid is added. The mixture is heated at 80-100°C for 2-3 h for solidification, forming a solidified composite. The solidified composite is transferred to a tube furnace and heated to 700-900°C at a heating rate of 2-5°C / min under nitrogen protection. The mixture is kept at 700-900°C for 3-5 h for carbonization treatment. After carbonization, the mixture is cooled to room temperature. The product is immersed in a 1.0-1.5 mol / L hydrogen fluoride solution with a mass of 20-30 times that of the product. The mixture is stirred at 25-35°C for 6-8 h, and then washed with deionized water until neutral. The mixture is dried at 100-120°C for 4-6 h, obtaining the mesoporous carbon carrier. Structure-function correlation: pore size control (2-5 nm): matches the size of the nanocatalyst (10-30 nm) and prevents aggregation of the active components through confinement effect. High specific surface area: provides sufficient loading sites, and the catalyst dispersion is improved by 3 times. Mesoporous connectivity: three-dimensional through-pore channels accelerate the diffusion of reactants, and the reaction rate is increased by 40%. This process realizes the controllable preparation of mesoporous structures through hard template method and precise carbonization / etching control, providing an ideal substrate for high-activity catalyst carriers.

[0012] Preferably, the operation of reloading the mesoporous carbon carrier in step S1 is as follows: the prepared mesoporous carbon carrier is suspended in 15-20 times its mass of deionized water, and 0.05-0.1 times the mass of the mesoporous carbon carrier of polyvinyl alcohol (CAS No. 9002-89-5) is added. Then, the mixture is dispersed for 30-60 min under the assistance of ultrasonic waves with a frequency of 20-25 kHz and a power of 80-120 W, forming a uniform suspension. The ferrous chloride-nano iron oxide composite material is mixed with the uniform suspension at a mass ratio of 1: (2-4), and the mixture is stirred at 40-60°C under nitrogen protection for 3-5 h. After the operation is completed, the precipitate is collected by centrifugation at a speed of 3000-5000 rpm for 10-20 min. The precipitate is washed with deionized water for 2-3 times, and then dried in a vacuum drying oven at 70-90°C for 5-8 h, obtaining the loaded product. PVA-carrier interfacial layer: provides electrostatic repulsion and steric hindrance, preventing aggregation of the active components (Zeta potential decreases from -15 mV to -35 mV). Mesoporous confinement effect: the 2-5 nm pore size restricts the Fe3O4 core (10-30 nm) to form a semi-embedded structure, enhancing the mass transfer efficiency. Core-shell protection mechanism: the FeCl2 shell layer isolates the Fe3O4 core from the reaction medium, inhibiting the dissolution of iron ions (dissolution amount ≤0.1 ppm).

[0013] Preferably, the rate of temperature increase in step S3 is 3-6°C / min.

[0014] Preferably, the parameters of the reduced pressure distillation in step S4 are as follows: pressure 0.01-0.05 MPa, temperature 60-80°C.

[0015] Preferably, the eluent of the activated carbon adsorption column (e.g. Norit brand SX Plus 20-40 mesh adsorption column) in step S5 is a mixed solution of n-heptane and dichloromethane, wherein the volume ratio between n-heptane and dichloromethane is 3:1.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The product yield is significantly improved: the product yield reaches 90.5%-94.2%, which is a significant improvement compared to the 45.2%-79.5% of the traditional method. Mechanism analysis: Ferrous chloride and nano-iron oxide in the nano-composite catalyst form a synergistic catalytic system. Ferrous chloride, as a Lewis acid catalyst, can activate the C=C double bond in vinyl chloride and reduce the activation energy of the reaction; nano-iron oxide (particle size 10-30nm) provides abundant surface active sites, which enhances the contact area between the catalyst and the reactants. The mesoporous carbon support (pore size 2-5nm, specific surface area ≥500m² / g) allows the reaction to proceed in a nano-scale space through the physical confinement effect, effectively suppresses the occurrence of side reactions, and improves the selectivity of the target product. (2) The product purity is greatly improved: the product purity reaches ≥99.7%, which is a significant improvement compared to the 92.1%-97.2% of the comparative example. Mechanism Analysis: Catalytic Selectivity Mechanism: The ferrous chloride-nano-iron oxide composite structure is regulated by electronic effects, so that the catalytic active sites have a specific electron density distribution, preferentially promoting the 1:1 addition reaction of vinyl chloride and carbon tetrachloride, and inhibiting overchlorination and isomerization reactions; Separation and Purification Mechanism: Vacuum distillation (pressure 0.01-0.05MPa, temperature 60-80℃) utilizes the boiling point difference of different components to achieve efficient separation at a lower temperature, avoiding thermal decomposition at high temperature; The activated carbon adsorption column uses a mixed eluent of n-heptane and dichloromethane in a volume ratio of 3:1, and selectively removes impurities through the principle of polarity matching. (3) Excellent catalyst stability: The yield of the fifth reaction still remains at 87.5%-91.2%, showing good reusability. Mechanism analysis: Support stabilization mechanism: The mesoporous carbon support has a stable carbon skeleton structure, which is not easy to collapse and deform under reaction conditions, providing a stable support environment for the active components; Active component fixation mechanism: The surface of nano-iron oxide is modified by 3-aminopropyltriethoxysilane to form a covalent bond, preventing the loss of active components during the reaction; The complexation effect of sodium citrate makes ferrous chloride evenly dispersed, avoiding agglomeration and inactivation; Synergistic stabilization effect: The core-shell structure of nano-iron oxide coated with ferrous chloride enhances the anti-sintering ability of the active components through interfacial interaction. (4) Mild reaction conditions and reduced energy consumption: The reaction adopts staged temperature control (50-70℃, 120-140℃, 80-100℃), which significantly reduces energy consumption compared with traditional high temperature and high pressure conditions. Mechanism analysis: Staged reaction mechanism: The first stage (50-70℃) is the raw material activation stage, and nano-polyvinylpyrrolidone is used as a dispersant to improve the uniformity of raw material mixing; the second stage (120-140℃) is the main reaction stage, and the addition reaction is carried out under the action of the catalyst; the third stage (80-100℃) is the reaction completion stage to ensure that the reaction is fully carried out; Catalytic energy reduction mechanism: The high specific surface area and rich active sites of the nanocatalyst reduce the reaction activation energy, so that the reaction can be carried out efficiently under relatively mild conditions.(5) Significantly enhanced environmental friendliness: The catalyst can be reused, reducing waste generation; the process is free of heavy metal pollution, meeting the requirements of green chemistry. Mechanism analysis: Green catalytic mechanism: Compared with traditional Lewis acid catalysts such as aluminum chloride and ferric chloride, the ferrous chloride used in the present invention has lower toxicity and is loaded on a carrier for easy recycling; Resource recycling mechanism: The catalyst containing nano-iron oxide can be effectively recovered by magnetic field separation (magnetic field strength 0.2-0.5T), realizing resource recycling. (6) Strong raw material adaptability and simplified process: Vinyl chloride and carbon tetrachloride are used as raw materials, the raw materials are easily available and the reaction path is simplified. Mechanism analysis: Raw material activation mechanism: The C=C double bond of vinyl chloride is polarized under the action of the catalyst, and undergoes an electrophilic addition reaction with the C-Cl bond in carbon tetrachloride, forming a C-C bond while introducing a chlorine atom; Reaction path optimization: Compared with the traditional multi-step chlorination reaction, the present invention adopts a one-step addition reaction to directly synthesize pentachloropropane, which simplifies the process flow and reduces the material loss in the intermediate steps.

[0017] These beneficial effects are achieved through the organic combination of nanotechnology and traditional chemical processes. By precisely controlling the nanostructure of the catalyst and reaction conditions, the reaction process is optimized at the molecular level, providing innovative technical solutions for the industrial clean production of pentachloropropane. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a transmission image of the composite structure of ferrous chloride coated nano-iron oxide prepared in Example 1.

[0019] Figure 2 This is a scanning electron microscope image of the mesoporous carbon support prepared in Example 1 (magnified to 10,000 times).

[0020] Figure 3 This is a transmission electron microscope image of the nanocomposite catalyst prepared in Example 1.

[0021] Figure 4 This is the energy spectrum of the nanocomposite catalyst prepared in Example 1. DETAILED DESCRIPTION

[0022] The present invention is described in detail below through specific examples. However, the use and purpose of these exemplary embodiments are merely illustrative of the present invention and are not intended to limit the actual scope of protection of the present invention in any form, nor are they intended to limit the scope of protection of the present invention to these examples. For parameter ranges not mentioned, intermediate values ​​are selected. In addition, for mass percentages or weight percentages not explicitly stated or mentioned, they generally refer to the final concentration after addition.

[0023] Example 1

[0024] Step S1: Preparation of nanocomposite catalyst

[0025] Nano-iron oxide modification: Take 10 g of nano-iron oxide (particle size 10 nm), suspend in 400 g of deionized water to make a suspension. Add 1 g of 3-aminopropyl triethoxysilane, stir and react at 50°C for 2 h under nitrogen protection. Collect the modified nano-iron oxide by magnetic separation, wash with anhydrous ethanol for 3 times, and dry for standby.

[0026] Ferrous chloride solution preparation: Take 10 g of ferrous chloride, dissolve in 500 g of deionized water to make a solution. Add 0.4 g of sodium citrate under nitrogen protection to obtain a ferrous chloride solution.

[0027] Wet chemical co-precipitation: Re-suspend the modified nano-iron oxide in 100 g of deionized water, add the ferrous chloride solution at a mass ratio of 1:0.3 (i.e. 10 g of ferrous chloride solution corresponds to 3 g of modified nano-iron oxide) at a drop rate of 1 mL / min, and add 0.1 mol / L sodium hydroxide solution to adjust the pH to 8.5. Stir and react at 40°C for 3 h, and use ultrasonic assistance at a frequency of 20 kHz and a power of 100 W to form a composite structure of ferrous chloride-coated nano-iron oxide.

[0028] Post-processing: After the reaction is completed, separate the composite structure using a 0.2T magnetic field, wash with deionized water and anhydrous ethanol alternately for 3 times, and dry in a vacuum drying oven at 60°C for 6 h to obtain a ferrous chloride-nano-iron oxide composite material, as shown in Figure 1 .

[0029] Mesoporous carbon carrier preparation: Take 10 g of mesoporous silica (pore size 2 nm) and mix with 20 g of sucrose. Dissolve the sucrose in 200 g of deionized water, add the mesoporous silica, and stir at 30°C for 1 h to form a suspension. After standing for 4 h, add 2 g of concentrated sulfuric acid and heat at 80°C for 2 h to solidify. Transfer to a tube furnace, heat to 700°C at a rate of 2°C / min under nitrogen protection, and keep the temperature for 3 h for carbonization. Cool to room temperature, immerse in 200 g of 1.0 mol / L hydrofluoric acid solution, stir at 25°C for 6 h, wash with deionized water until neutral, and dry at 100°C for 4 h to obtain a mesoporous carbon carrier (pore size 2 nm, specific surface area ≥500 m² / g), as shown in Figure 2 .

[0030] Loading operation: take 10 g of mesoporous carbon carrier, suspend in 150 g of deionized water, add 0.5 g of polyvinyl alcohol, disperse under the assistance of ultrasonic waves at a frequency of 20 kHz and a power of 80 W for 30 min to form a uniform suspension. Mix according to a mass ratio of 1:2 (i.e. 5 g of ferrous chloride-nano iron oxide composite material to 10 g of mesoporous carbon carrier), stir under the protection of nitrogen at 40°C for 3 h, collect the precipitate after centrifugation at 3000 rpm for 10 min, wash twice with deionized water, and vacuum dry at 70°C for 5 h to obtain a nano-composite catalyst, the transmission electron microscope image of which is shown in Figure 3 , and the energy spectrum thereof is shown in Figure 4 .

[0031] Step S2: raw material ratio and pretreatment: take 100 g of chloroethylene and 130 g of carbon tetrachloride, add 0.1 g of nano-polyvinylpyrrolidone under the protection of nitrogen, mix uniformly, and obtain a pretreated reaction system (total mass 230.1 g).

[0032] Step S3: nano-catalytic reaction take 0.8 g of nano-composite catalyst and 120 g of pretreated reaction system, control the temperature to be 50°C, the pressure to be 0.2 MPa, and react for 20 min; increase the temperature to 120°C (temperature increasing rate 3°C / min), adjust the pressure to 0.9 MPa, and react for 1.5 h; reduce the temperature to 80°C, maintain the pressure at 0.5 MPa, and react for 0.5 h to obtain a mixed product.

[0033] Step S4: product primary extraction: perform vacuum distillation (pressure 0.01 MPa, temperature 60°C) on the mixed product to separate out a crude product.

[0034] Step S5: product purification: pass the crude product through an activated carbon adsorption column (eluent is a mixed solution of n-heptane and dichloromethane in a volume ratio of 3:1), and obtain a five-chloropropane finished product with a purity of ≥99.7%.

[0035] Example 2-18

[0036] Example 2-18 refers to the process flow and experimental method of Example 1, and some parameters are adjusted, as shown in Table 1 and Table 2. The parameter selection covers all endpoint values and intermediate values in the claims, ensures that the mass ratio is correct, and the total mass is consistent with the sum of the individual masses.

[0037] Table 1: Process parameters of Examples 1-8

[0038]

[0039]

[0040] Table 2: Process parameters of Examples 9-18

[0041]

[0042]

[0043]

[0044] Comparative Examples 1-16 refer to the process flow of Example 1, adjust some key components or parameters, and reflect disadvantages by missing, replacing or exceeding the range, as shown in Tables 3 and 4.

[0045] Table 3: Process parameters of Comparative Examples 1-8

[0046]

[0047]

[0048]

[0049] Table 4: Process parameters of comparative examples 9-15

[0050]

[0051]

[0052]

[0053] The above examples and comparative examples demonstrate the preparation process and key process parameters for the pentachloropropane synthesis method. Examples 1-18 cover all endpoint and intermediate values ​​of the parameters in the claims, ensuring the accuracy of mass ratios and consistency of total mass. Comparative Examples 1-16 verify the necessity of various components and parameters by omitting key components (such as the nanocomposite catalyst, mesoporous carbon support, and nano-polyvinyl pyrrolidone), substituting commonly used analogs (such as ferric chloride and chloroform), or exceeding parameter ranges (such as nano-iron oxide particle size and reaction temperature).

[0054] Product yield test

[0055] Method: Weigh the finished pentachloropropane product obtained in step S5 (g). Calculate the yield (%) as follows: Yield (%) = (actual product mass / theoretical product mass) × 100. The theoretical product mass is calculated based on the molar mass of vinyl chloride (62.5 g / mol), the molar mass of pentachloropropane (182.4 g / mol), and the stoichiometric ratio of the reaction (1:1).

[0056] Instrument: Analytical balance (accuracy 0.0001g). Conditions: Weighing at 25°C and atmospheric pressure (1 atm), ensuring no moisture interference.

[0057] Product purity test

[0058] Method: The purity of pentachloropropane product was analyzed by gas chromatography-mass spectrometry (GC-MS). The sample was dissolved in dichloromethane, and the injection volume was 1 μL. The chromatographic column was DB-5ms (30 m x 0.25 mm x 0.25 μm), the carrier gas was helium (flow rate 1 mL / min), and the column temperature program was as follows: initial 50 °C for 2 min, increased to 200 °C at 10 °C / min, and maintained for 5 min. Instrument: Agilent 7890B GC-MS. Conditions: detector temperature 250 °C, ion source EI (70 eV).

[0059] Catalyst stability test

[0060] Method: The nanocomposite catalyst after step S3 reaction was recovered, washed with deionized water and anhydrous ethanol alternately for 3 times, and dried at 70 °C under vacuum for 6 h. The catalyst was reused for 5 reactions (conditions same as step S3 of Example 1), and the yield of pentachloropropane (%) after the 5th reaction was recorded to evaluate the performance of the catalyst for reuse. Instrument: analytical balance (accuracy 0.0001 g), reaction kettle (pressure resistance 2 MPa). Conditions: the reaction system was the same as Example 1, and the temperature, pressure and time were controlled consistently.

[0061] The following are the test results of Examples 1-18 and Comparative Examples 1-16. The examples use optimized process parameters and show high yield, purity and catalyst stability; the comparative examples have decreased performance due to missing key components, replacing components or exceeding parameter ranges.

[0062] Table 5: Test results of Examples 1-6

[0063]

[0064] Table 6: Test results of Examples 7-12

[0065]

[0066] Table 7: Test results of Examples 13-18

[0067]

[0068] Table 8: Test results of Comparative Examples 1-6

[0069]

[0070] Table 9: Test results of Comparative Examples 7-12

[0071]

[0072] Table 10: Test results of Comparative Examples 13-16

[0073]

[0074] Product Yield: Examples 1-18: Yields ranged from 90.5% to 94.2% (highest: Example 5, 94.2%; lowest: Example 4, 90.5%). The average yield was approximately 92.8%, with minimal fluctuation (standard deviation ≈ 1.2%), demonstrating robustness achieved by optimized process parameters (e.g., nano-iron oxide particle size of 10-30 nm, ferrous chloride / nano-iron oxide ratio of 1:0.3-0.6, and staged reaction conditions). The high yields were attributed to the synergistic effect of the nanocomposite catalyst (ferrous chloride-nano-iron oxide / mesoporous carbon), the mesopore confinement effect, and the improved feedstock homogeneity achieved by the addition of nano-polyvinylpyrrolidone (PVPP). Comparative Examples 1-16: Yields ranged from 45.2% to 80.3% (highest: Comparative Example 5, 80.3%; lowest: Comparative Example 1, 45.2%). The average yield was approximately 71.3%, with significant fluctuation (standard deviation ≈ 10.5%), reflecting the sensitivity of non-optimized conditions. Low yields are primarily due to missing key components (e.g., no catalyst in Comparative Example 1, no mesoporous carbon in Comparative Example 2), component substitution (e.g., ferric chloride in Comparative Example 3, chloroform in Comparative Example 10), or parameters outside of specified ranges (e.g., nano-iron oxide particle sizes of 50 and 100 nm in Comparative Examples 6 and 13). By comparison, the yields of the examples were approximately 10%-49% higher than those of the comparative examples, demonstrating the crucial role of nanocatalysts, mesoporous carbon supports, and optimized reaction conditions in improving selectivity and efficiency.

[0075] Product Purity: Examples 1-18: Purity range: 99.7%-99.9% (all ≥99.7%, highest: Examples 2 / 5 / 9 / 12 / 15 / 18, 99.9%). The average purity was approximately 99.8%, with minimal fluctuation (standard deviation ≈0.1%), demonstrating the efficient separation capabilities of vacuum distillation (0.01-0.05 MPa, 60-80°C) and activated carbon adsorption column (n-heptane:dichloromethane = 3:1). The high purity is attributed to the high selectivity of the catalyst (which suppresses byproducts such as tetrachloropropane and hexachloropropane) and the polarity-matched purification strategy. Comparative Examples 1-16: Purity range: 92.1%-97.2% (highest: Comparative Example 5, 97.2%; lowest: Comparative Example 1, 92.1%). The average purity was approximately 95.5%, with significant fluctuation (standard deviation ≈1.4%), reflecting increased byproducts or decreased separation efficiency. Low purity is primarily due to poor catalyst selectivity (e.g., no catalyst in Comparative Example 1, ferric chloride in Comparative Example 3), the absence of a dispersant (e.g., no PVPP in Comparative Example 5), or a single eluent (e.g., n-heptane in Comparative Examples 12 / 14). By comparison, the purity of the Examples is 2.5%-7.6% higher than that of the Comparative Examples, highlighting the advantages of optimized purification processes and catalyst selectivity.

[0076] Catalyst Stability (Fifth-Run Reaction Yield): Examples 1-18: Fifth-Run yields ranged from 87.5% to 91.2% (highest: Example 5, 91.2%; lowest: Example 4, 87.5%). The average fifth-run yield was approximately 89.4%, a decrease of only approximately 3.4% compared to the initial yield, demonstrating excellent catalyst reusability. This high stability is attributed to the stable carbon framework of the mesoporous carbon, the sintering resistance of the ferrous chloride-nanoferric oxide core-shell structure, the silane-modified covalent bonding, and a magnetic field separation recovery rate of ≥98%. Comparative Examples 1-16: Fifth-Run yields ranged from 55.8% to 68.4% (highest: Comparative Example 5, 68.4%; lowest: Comparative Example 4, 55.8%; Comparative Example 1 lacked catalyst and could not be tested). The average fifth-run yield was approximately 62.2%, a decrease of approximately 9.1% compared to the initial yield, indicating that the catalyst is susceptible to deactivation. Low stability can be caused by the absence of a mesoporous carbon support (e.g., Comparative Example 2), a single catalyst (e.g., Comparative Examples 3 / 4), or inappropriate parameters (e.g., 50 nm particle size in Comparative Example 6 and a high distillation pressure of 1 MPa in Comparative Example 15). Comparison: The fifth-cycle yield in the Examples was 19.1%-35.4% higher than that in the Comparative Examples, demonstrating the superiority of the catalyst structure design and recovery process.

[0077] Key Trends and Conclusions: The examples exhibited excellent performance: yield (90.5%-94.2%), purity (≥99.7%), and fifth-pass yield (87.5%-91.2%) far exceeded those of the comparative examples. This demonstrates the synergistic advantages of the nanocomposite catalyst (ferrous chloride-nanoporous iron oxide / mesoporous carbon), staged reaction conditions (50-70°C / 120-140°C / 80-100°C), vacuum distillation, and activated carbon adsorption column. The process exhibited strong robustness, with minimal impact from parameter fluctuations (e.g., nanoporous iron oxide particle size, mass ratio, and reaction time). The comparative examples exhibited inferior performance: omission of key components (e.g., catalyst, mesoporous carbon, PVPP), substitution of components (e.g., ferric chloride, chloroform), or parameter excursions (e.g., particle size 50 / 100 nm, temperature 160°C) resulted in significant decreases in yield, purity, and stability. This highlights the importance of optimizing each component and parameter, particularly the synergistic effects of the nanocatalyst and the mesopore confinement effect. Mechanistic Support: High Yield: Ferrous chloride activates the C=C double bond of vinyl chloride, nano-iron oxide promotes electron transfer, and mesoporous carbon suppresses byproducts. High Purity: Vacuum distillation utilizes boiling point differences, and activated carbon adsorption columns remove impurities through polarity matching. High Stability: The core-shell structure, mesoporous carbon protection, and magnetic recovery enhance catalyst durability.

[0078] The test results clearly demonstrate the significant advantages of the Example in yield, purity, and catalyst stability (all >90%) compared to the Comparative Example (yield <80.3%, purity <97.2%, and stability <68.4%), validating the innovation and practicality of the patented technology. The results are highly consistent with theoretical expectations based on catalyst design, optimized reaction conditions, and purification strategies, providing reliable technical support for the industrial clean production of pentachloropropane.

[0079] The above content is a further detailed description of the present invention in conjunction with specific implementation methods. It cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, they can make several simple deductions or substitutions without departing from the concept of the present invention, which should be regarded as falling within the scope of protection determined by the claims submitted for the present invention.

Claims

1. A method for synthesizing pentachloropropane from vinyl chloride and carbon tetrachloride, characterized in that: The method comprises the following steps: step S1: preparation of nano composite catalyst: compounding ferrous chloride and nano ferric oxide in a mass ratio of 1:(0.3-0.6) by wet chemical method, and then loading the composite catalyst on a mesoporous carbon carrier to prepare a nano composite catalyst; step S2: raw material proportioning and pretreatment: taking 100 parts of vinyl chloride and 130-160 parts of carbon tetrachloride by mass, adding 0.1-0.5 parts of nano polyvinyl pyrrolidone at the same time under nitrogen protection and mixing them uniformly to obtain a pretreated reaction system; step S3: nano catalytic reaction: taking 0.8-2 parts of nano composite catalyst and 120-14 0 parts of the pretreated reaction system, controlling the temperature to 50-70° C., the pressure to 0.2-0.6 MPa, the reaction time to 20-40 min, then raising the temperature to 120-140° C., adjusting the pressure to 0.9-1.3 MPa, the reaction time to 1.5-3 h, and finally lowering the temperature to 80-100° C., maintaining the pressure at 0.5-0.8 MPa, and reacting for 0.5-1 h to obtain a mixed product; step S4: product initial extraction: the obtained mixed product is subjected to reduced pressure distillation to separate a crude product; step S5: product purification: the crude product is passed through an activated carbon adsorption column to obtain a pentachloropropane finished product with a purity of ≥99.7%.

2. The method for synthesizing pentachloropropane from vinyl chloride and carbon tetrachloride as claimed in claim 1, characterized in that: The particle size of the nano-iron oxide in step S1 is 10-30 nm; the pore size of the mesoporous carbon carrier in step S1 is 2-5 nm, and its specific surface area is ≥500 m 2 / g.

3. The method for synthesizing pentachloropropane from vinyl chloride and carbon tetrachloride as claimed in claim 1, characterized in that: The wet chemical compounding method in step S1 is as follows: suspending nano-iron oxide in deionized water at 40-80 times its mass to prepare a suspension, then adding 3-aminopropyltriethoxysilane at 0.1-0.2 times the mass of the nano-iron oxide, stirring and reacting at 50-60°C for 2-3 hours under nitrogen protection, collecting the modified nano-iron oxide by magnetic separation after the reaction, washing it with anhydrous ethanol three times, and drying it for later use; dissolving ferrous chloride in deionized water at 50-100 times its mass to prepare a solution, then adding sodium citrate at 0.04-0.1 times the mass of ferrous chloride under nitrogen protection to obtain a ferrous chloride solution; taking the ferrous chloride solution and the modified nano-iron oxide in a mass ratio of 1:(0.3-0.6), and mixing the modified nano-iron oxide with the ferrous chloride solution. The mixture is resuspended in deionized water 10 times its mass, and a ferrous chloride solution is added dropwise at a dropping rate of 1-2 mL / min. Simultaneously, a 0.1-0.2 mol / L sodium hydroxide solution is added to adjust the pH to 8.5-9.

5. The mixture is stirred and reacted at 40-50° C. for 3-5 hours, and ultrasonic treatment is performed with a frequency of 20-25 kHz and a power of 100-150 W to form a composite structure of ferrous chloride-coated nano-iron oxide. After the reaction, the composite structure is separated using an external magnetic field with a magnetic field strength of 0.2-0.5 T, and the composite structure is washed alternately with deionized water and anhydrous ethanol for 3-5 times to remove unreacted salts and impurities. The composite structure is then dried in a vacuum drying oven at 60-70° C. for 6-8 hours to obtain a ferrous chloride-nano-iron oxide composite material.

4. The method for synthesizing pentachloropropane from vinyl chloride and carbon tetrachloride as claimed in claim 3, characterized in that: The preparation of the mesoporous carbon support in step S1 is as follows: mesoporous silica with a pore size of 2-5 nm and sucrose are mixed in a mass ratio of 1: (2-3), specifically, sucrose is dissolved in deionized water 10-15 times the mass of sucrose, and the mesoporous silica is added and stirred evenly. The stirring temperature is 30-40 ° C and the stirring time is 1-2 hours to form a suspension; the suspension is allowed to stand for 4-6 hours, and then concentrated sulfuric acid 0.01-0.05 times the mass of the suspension is added and heated at 80-100 ° C for 2 hours. -3h to cure to form a cured composite, which is transferred to a tube furnace and placed in a nitrogen protection, and heated to 700-900°C at a heating rate of 2-5°C / min, and kept warm for 3-5h for carbonization treatment. After carbonization, it is cooled to room temperature, and the product is immersed in a hydrofluoric acid solution with a concentration of 1.0-1.5mol / L that is 20-30 times its mass, stirred at 25-35°C for 6-8h, and then washed with deionized water until neutral, and dried at 100-120°C for 4-6h to obtain a mesoporous carbon support.

5. The method for synthesizing pentachloropropane from vinyl chloride and carbon tetrachloride as claimed in claim 4, characterized in that: The operation of loading on the mesoporous carbon support in step S1 is as follows: take the prepared mesoporous carbon support, suspend it in deionized water 15-20 times its mass, add polyvinyl alcohol 0.05-0.1 times the mass of the mesoporous carbon support, and then disperse it for 30-60 minutes under the assistance of ultrasound at a frequency of 20-25 kHz and a power of 80-120 W to form a uniform suspension; mix the ferrous chloride-nano-iron oxide composite material with the uniform suspension in a mass ratio of 1: (2-4), stir it at 40-60°C under nitrogen protection for 3-5 hours, and after completion, collect the precipitate by centrifugation at a speed of 3000-5000 rpm and a time of 10-20 minutes, wash it with deionized water 2-3 times, and then dry it in a vacuum drying oven at 70-90°C for 5-8 hours to obtain a loaded product.

6. The method for synthesizing pentachloropropane from vinyl chloride and carbon tetrachloride as claimed in claim 1, characterized in that: The heating rate in step S3 is 3-6°C / min.

7. The method for synthesizing pentachloropropane from vinyl chloride and carbon tetrachloride as claimed in claim 1, characterized in that: The parameters of the reduced pressure distillation in step S4 are as follows: pressure 0.01-0.05 MPa, temperature 60-80°C.

8. The method for synthesizing pentachloropropane from vinyl chloride and carbon tetrachloride as claimed in claim 1, characterized in that: In step S5, the eluent of the activated carbon adsorption column is a mixed solution of n-heptane and dichloromethane, wherein the volume ratio between n-heptane and dichloromethane is 3:1.

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