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

Abstract

The application discloses a synthesis method of pentachloropropane based on raw materials of vinyl chloride and carbon tetrachloride, and belongs to the technical field of new chemical materials. Main steps include raw material proportioning and pretreatment, nano-catalytic reaction, product initial extraction and purification, etc. The catalyst used is prepared by loading the composite of ferrous chloride and nano iron oxide on a mesoporous carbon carrier, and has excellent catalytic performance. The product is purified through vacuum distillation and an activated carbon adsorption column, and the purity can reach more than 99.7%. The method innovatively combines nano technology and specific reaction conditions, and has the advantages of high yield, high product purity and good catalyst stability. Compared with the traditional synthesis method, the technology significantly improves the production efficiency and reduces the energy consumption, provides an innovative and practical technical path for the industrial production of pentachloropropane, and has a wide application prospect.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of chemical new materials, and particularly relates to a synthesis method of pentachloropropane based on chloroethylene and carbon tetrachloride raw materials. BACKGROUND

[0002] Pentachloropropane (1,1,1,2,3-pentachloropropane, abbreviated as HCC-240db) is an important chlorinated organic compound with wide application value in the field of chemical new materials. It is not only a key intermediate for the production of fluorine-containing refrigerants, blowing agents and cleaning agents, but also plays an irreplaceable role in many fields such as medicine, pesticide and fine chemical industry. With the continuous growth of global demand for environmentally friendly refrigerants, especially the increasing demand for low global warming potential substitutes such as hydrofluorocarbons and hydrochlorofluorocarbons, the production technology of pentachloropropane as an important raw material for synthesizing these substitutes 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, etc. These problems limit its further popularization and application in industrial production.

[0003] Traditional synthesis methods of pentachloropropane mainly rely on the chlorination reaction of chlorinated propene or chlorinated propane. These methods have a certain application history in industry, but their process defects are significant, and it is difficult to meet the requirements of modern chemical industry for high efficiency, greenness and economy. For example, the synthesis path using chlorinated propene as raw material, through the addition reaction of chlorine and chlorinated propene to generate pentachloropropane. However, due to the high activity of chlorination reaction, various by-products such as isomers of tetrachloropropane, hexachloropropane and over-chlorinated products are easily generated in the reaction process. The existence of these by-products not only reduces the selectivity of the target product, but also increases the difficulty of subsequent separation and purification, resulting in the product purity difficult to reach the standard of industrial application. In addition, this reaction usually requires high reaction temperature and long reaction time, which consumes high energy, and the treatment of by-products further increases the production cost and environmental burden. Another common synthesis method is to use chlorinated propane as raw material, and gradually introduce chlorine atoms through multi-step chlorination reaction to finally generate pentachloropropane. Although this method is theoretically feasible, there are significant limitations in actual operation. First, the chlorination reaction of chlorinated propane needs to be carried out under high temperature and high pressure conditions, which not only puts forward higher corrosion resistance and pressure resistance requirements for reaction equipment, but also significantly increases energy consumption and operation risk. Secondly, the selectivity of the reaction is difficult to control, and a series of chlorinated by-products with different degrees of chlorination are easily generated, resulting in complex product distribution and high separation cost. In addition, the catalysts commonly used in traditional methods are mostly liquid or solid Lewis acids, such as aluminum trichloride or iron trichloride. These catalysts can promote the chlorination reaction to a certain extent, but they have the disadvantages of easy deactivation and difficult recycling in the process of use, which leads to frequent replacement of catalysts and large amount of waste, further aggravating the problems of production cost and environmental pollution.

[0004] In recent years, with the rapid development of nanotechnology and catalytic science, researchers have begun to try to use new catalysts and improved reaction processes to optimize the synthesis process of pentachloropropane. For example, some studies have reported the use of nano-metal oxides as catalysts to synthesize pentachloropropane through gas-phase chlorination reaction, which has made some progress compared with traditional methods. This method uses the high specific surface area and excellent catalytic activity of nanomaterials to improve the selectivity of the reaction and the yield of the product to a certain extent. However, this technology still faces many challenges. First, the preparation process of nano-catalysts is usually complex, which requires precise control of particle size, morphology and dispersion, increasing the production cost and process difficulty. Secondly, gas-phase chlorination reaction often needs to be carried out at high temperature and specific pressure, which has high requirements for reaction equipment and operating conditions. In addition, although nano-catalysts show certain advantages under laboratory conditions, their stability and durability in industrial production still need to be further verified, and the product yield and purity have not fully reached the ideal level. These factors jointly limit the popularization and application of this technology in actual production. SUMMARY

[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 present application has the following advantages: (1) The yield of the product is significantly improved: the yield of the product reaches 90.5%-94.2%, which is significantly improved compared with 45.2%-79.5% of the traditional method. Mechanism analysis: The ferrous chloride and nano iron oxide in the nanocomposite catalyst form a synergistic catalytic system. The ferrous chloride as a Lewis acid catalyst can activate the C=C double bond in chloroethylene, reducing the reaction activation energy; the nano iron oxide (particle size 10-30 nm) provides a large number of surface active sites, enhancing the contact area of the catalyst and the reactants. The mesoporous carbon carrier (pore size 2-5 nm, specific surface area ≥500 m² / g) makes the reaction occur in a nanoscale space through the physical confinement effect, effectively inhibiting the occurrence of side reactions and improving the selectivity of the target product. (2) The purity of the product is greatly improved: the purity of the product reaches ≥99.7%, which is obviously improved compared with 92.1%-97.2% of the comparative example. Mechanism analysis: Catalytic selectivity mechanism: The ferrous chloride-nano iron oxide composite structure regulates the electronic effect to make the catalytically active site have a specific electronic density distribution, preferentially promoting the 1:1 addition reaction of chloroethylene and carbon tetrachloride and inhibiting the over-chlorination and isomerization reaction; separation and purification mechanism: The reduced pressure distillation (pressure 0.01-0.05 MPa, temperature 60-80°C) 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, which selectively removes impurities through the polarity matching principle. (3) The catalyst stability is excellent: the yield remains 87.5%-91.2% after the 5th reaction, showing good repeated use performance. Mechanism analysis: Carrier stability mechanism: The mesoporous carbon carrier has a stable carbon skeleton structure and is not easy to collapse and deform under reaction conditions, providing a stable carrier environment for the active components; active component fixation mechanism: the nano iron oxide surface is modified by 3-aminopropyltriethoxysilane to form a covalent bond, preventing the loss of active components during the reaction; the complexation of sodium citrate uniformly disperses the ferrous chloride, avoiding agglomeration and deactivation; synergistic stability effect: the core-shell structure of the ferrous chloride-coated nano iron oxide enhances the anti-sintering ability of the active components through interfacial interaction. (4) The reaction conditions are mild, and the energy consumption is reduced: the reaction adopts staged temperature control (50-70°C, 120-140°C, 80-100°C), which significantly reduces the energy consumption compared with the traditional high temperature and high pressure conditions. Mechanism analysis: Staged reaction mechanism: the first stage (50-70°C) is the raw material activation stage, and the nano polyvinylpyrrolidone as a dispersant improves the mixing uniformity of the raw materials; the second stage (120-140°C) is the main reaction stage, and the addition reaction is carried out under the action of the catalyst; the third stage (80-100°C) is the reaction completion stage, ensuring that the reaction proceeds fully; catalytic energy reduction mechanism: the high specific surface area and abundant active sites of the nano catalyst reduce the reaction activation energy, enabling the reaction to proceed efficiently under relatively mild conditions.(5) The environmental friendliness is significantly enhanced: the catalyst can be reused, and waste generation is reduced; the process does not pollute the environment with heavy metals, and meets the requirements of green chemistry. Mechanism analysis: green catalytic mechanism: compared with traditional Lewis acid catalysts such as aluminum trichloride and ferric trichloride, the ferrous chloride used in the application has lower toxicity and is loaded on a carrier for easy recovery; resource recycling mechanism: the catalyst containing nano iron oxide can be effectively recovered through magnetic field separation (magnetic field strength 0.2-0.5T), realizing the recycling of resources. (6) Strong adaptability to raw materials and simplified process: chloroethylene and carbon tetrachloride are used as raw materials, and the raw materials are easy to obtain and the reaction path is simplified. Mechanism analysis: raw material activation mechanism: the C=C double bond of chloroethylene is polarized under the action of the catalyst, and an electrophilic addition reaction occurs 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 application directly synthesizes pentachloropropane by one-step addition reaction, simplifying the process flow and reducing the material loss in the intermediate steps.

[0017] The realization of these benefits is derived from the organic combination of nanotechnology and traditional chemical process, and by precisely controlling the nanostructure of the catalyst and the reaction conditions, the reaction process is optimized at the molecular level, providing an innovative technical solution for the industrial clean production of pentachloropropane. BRIEF DESCRIPTION OF DRAWINGS

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

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

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

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

[0022] The application will be described in detail below through specific examples, but the purpose and purpose of these exemplary embodiments are only used to exemplify the application, and do not constitute any form of any limitation on the actual protection scope of the application, nor limit the protection scope of the application to this. For the range of parameters not mentioned, the intermediate value is selected. At the same time, for the mass percentage or weight percentage not explicitly stated or mentioned, it generally refers 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] Reference to the process flow of Example 1, adjust some key components or parameters, by missing, replacing or exceeding the range to reflect the disadvantage, see Table 3 and Table 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 show the preparation process and key process parameters of the synthesis method of pentachloropropane. Examples 1-18 cover the end point values and intermediate values of all parameters in the claims, ensuring the accuracy of the mass ratio and the consistency of the total mass. Comparative Examples 1-16, by missing key components (such as nanocomposite catalyst, mesoporous carbon carrier, nanopolyvinylpyrrolidone, etc.), replacing commonly used analogues (such as ferric chloride, chloroform), or exceeding the parameter range (such as nanometer iron oxide particle size, reaction temperature), to verify the necessity of each component and parameter.

[0054] Product yield test

[0055] Method: Take the pentachloropropane product obtained in step S5, weigh its mass (g). The yield (%) is calculated as follows: yield (%) = (actual product mass / theoretical product mass) x 100. Among them, 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 (1:1) of the reaction.

[0056] Instrument: analytical balance (accuracy 0.0001 g). Conditions: weighing at 25°C, normal pressure (1 atm), ensuring no water 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: Yield range: 90.5-94.2% (highest: Example 5, 94.2%; lowest: Example 4, 90.5%). Average yield ~92.8% with small fluctuation (standard deviation ~1.2%), indicating high robustness of process parameters optimization (e.g. nano-iron oxide particle size 10-30 nm, ferrous chloride / nano-iron oxide ratio 1:0.3-0.6, staged reaction conditions). High yield attributed to synergistic effect of nano-composite catalyst (ferrous chloride-nano-iron oxide / mesoporous carbon), mesoporous confinement effect, and nano-polyvinylpyrrolidone (PVPP) for improving raw material uniformity. Comparative Examples 1-16: Yield range: 45.2-80.3% (highest: Comparative Example 5, 80.3%; lowest: Comparative Example 1, 45.2%). Average yield ~71.3% with large fluctuation (standard deviation ~10.5%), reflecting sensitivity of non-optimized conditions. Low yield mainly due to missing key components (e.g. Comparative Example 1 without catalyst, Comparative Example 2 without mesoporous carbon), replacing components (e.g. Comparative Example 3 with ferric chloride, Comparative Example 10 with chloroform), or parameters out of range (e.g. Comparative Examples 6 / 13 with nano-iron oxide particle size 50 / 100 nm). Comparison: Example yield ~10-49% higher than comparative, verifying key roles of nano-catalyst, mesoporous carbon support, and optimized reaction conditions for 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%). Average purity ~99.8% with very small fluctuation (standard deviation ~0.1%), indicating high separation capacity of vacuum distillation (0.01-0.05 MPa, 60-80 °C) and activated carbon adsorption column (n-heptane:dichloromethane = 3:1). High purity benefited from high selectivity of catalyst (suppressing by-products such as tetra-chloropropane, hexa-chloropropane) and 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%). Average purity ~95.5% with large fluctuation (standard deviation ~1.4%), reflecting increased by-products or decreased separation efficiency. Low purity mainly due to poor selectivity of catalyst (e.g. Comparative Example 1 without catalyst, Comparative Example 3 with ferric chloride), absence of dispersant (e.g. Comparative Example 5 without PVPP), or single eluent (e.g. Comparative Examples 12 / 14 with n-heptane). Comparison: Example purity 2.5-7.6% higher than comparative, highlighting advantages of optimized purification process and catalyst selectivity.

[0076] Catalyst stability (fifth reaction yield): Examples 1-18: fifth yield range: 87.5%-91.2% (highest: Example 5, 91.2%; lowest: Example 4, 87.5%). Average fifth yield about 89.4%, only decreased about 3.4% compared with the initial yield, indicating excellent catalyst reusability. High stability attributed to stable carbon skeleton of mesoporous carbon, anti-sintering ability of ferrous chloride-nano iron oxide core-shell structure, silane-modified covalent bonding, and magnetic field separation recovery rate ≥98%. Comparative Examples 1-16: fifth yield range: 55.8%-68.4% (highest: Comparative Example 5, 68.4%; lowest: Comparative Example 4, 55.8%; Comparative Example 1 without catalyst, unable to test). Average fifth yield about 62.2%, decreased about 9.1% compared with the initial yield, indicating catalyst easy deactivation. Low stability due to no mesoporous carbon support (e.g., Comparative Example 2), single catalyst (e.g., Comparative Examples 3 / 4) or improper parameters (e.g., Comparative Example 6 particle size 50 nm, Comparative Example 15 high distillation pressure 1 MPa). Comparison: Examples fifth yield higher than Comparative Examples by 19.1%-35.4%, verifying the superiority of catalyst structure design and recovery process.

[0077] Key trends and conclusions: Examples excellent performance: yield (90.5%-94.2%), purity (≥99.7%) and fifth yield (87.5%-91.2%) all far exceed Comparative Examples, proving the synergistic advantages of nano-composite catalyst (ferrous chloride-nano iron oxide / mesoporous carbon), staged reaction conditions (50-70℃ / 120-140℃ / 80-100℃), reduced pressure distillation and activated carbon adsorption column. Process robust, parameter fluctuations (e.g., nano iron oxide particle size, mass ratio, reaction time) have little effect on results. Comparative Examples poor performance: missing key components (e.g., catalyst, mesoporous carbon, PVPP), replacing components (e.g., ferric chloride, chloroform) or parameters out of range (e.g., particle size 50 / 100 nm, temperature 160℃) lead to significant decreases in yield, purity and stability. Highlight the necessity of each component and optimized parameters, especially the synergistic effect of nano catalyst and mesoporous confinement effect. Mechanism support: high yield: ferrous chloride activates the C=C double bond of chloroethylene, nano iron oxide promotes electron transfer, mesoporous carbon suppresses byproducts. High purity: reduced pressure distillation takes advantage of boiling point differences, activated carbon adsorption column removes impurities through polarity matching. High stability: core-shell structure, mesoporous carbon protection and magnetic recovery enhance catalyst durability.

[0078] The test results clearly show that the examples have significant advantages in yield, purity and catalyst stability (> 90%), compared with the comparative examples (yield < 80.3%, purity < 97.2%, stability < 68.4%), which verifies the innovation and practicability of the patent technology. The results are highly consistent with the theoretical expectations of catalyst design, reaction condition optimization and purification strategy, providing reliable technical support for the industrial clean production of pentachloropropane.

[0079] The above is a further detailed description of the present application in combination with the specific embodiments, and cannot be considered as limiting the specific embodiments of the present application to these descriptions. For ordinary skilled persons in the technical field to which the present application belongs, some simple deductions or substitutions can be made without departing from the concept of the present application, and all of them should be considered as belonging to the protection scope determined by the claims submitted by the present application.

Claims

1. A method for synthesizing pentachloropropane based on vinyl chloride and carbon tetrachloride as raw materials, characterized in that: The process includes the following steps: Step S1: Preparation of the nanocomposite catalyst: Ferrous chloride and nano-iron oxide Fe3O4 are composited by a wet chemical method at a mass ratio of 1:(0.3-0.6), and then loaded onto a mesoporous carbon support to obtain the nanocomposite catalyst; Step S2: Raw material ratio and pretreatment: 100 parts by mass of vinyl chloride and 130-160 parts by mass of carbon tetrachloride are taken, and 0.1-0.5 parts by mass of nano-polyvinylpyrrolidone are added and mixed evenly under nitrogen protection to obtain a pretreated reaction system; Step S3: Nanocatalytic reaction: 0.8-2 parts by mass of the nanocomposite catalyst and 120-140 parts by mass of the pretreated reaction system are taken, and the temperature is controlled at 50-70℃. The reaction process begins with a pressure of 0.2-0.6 MPa and a reaction time of 20-40 min. The temperature is then increased to 120-140℃, the pressure adjusted to 0.9-1.3 MPa, and the reaction time extended to 1.5-3 h. Finally, the temperature is lowered to 80-100℃, the pressure maintained at 0.5-0.8 MPa, and the reaction time extended to 0.5-1 h to obtain a mixed product. Step S4: Initial product extraction: The crude product is separated from the mixed product by vacuum distillation. Step S5: Product purification: The crude product is passed through an activated carbon adsorption column to obtain pentachloropropane with a purity ≥99.7%. The nano-iron oxide particles in step S1 have a particle size of 10-30 nm. The mesoporous carbon support in step S1 has a pore size of 2-5 nm and a specific surface area ≥500 m². 2 / g; The wet chemical compounding method in step S1 is as follows: Nano-iron oxide is suspended in 40-80 times its mass of deionized water to form a suspension. Then, 0.1-0.2 times the mass of 3-aminopropyltriethoxysilane is added. Under nitrogen protection, the mixture is stirred at 50-60℃ for 2-3 hours. After the reaction, the modified nano-iron oxide is collected by magnetic separation, washed three times with anhydrous ethanol, and dried for later use. Ferrous chloride is dissolved in 50-100 times its mass of deionized water to form a solution. Then, under nitrogen protection, 0.04-0.1 times the mass of sodium citrate is added to obtain a ferrous chloride solution. The ferrous chloride solution and the modified nano-iron oxide are taken at a mass ratio of 1:(0.3-0.6). The modified nano-iron oxide... Ferric chloride was resuspended in 10 times its weight of deionized water, and ferrous chloride solution was added dropwise at a rate of 1-2 mL / min. Simultaneously, 0.1-0.2 mol / L sodium hydroxide solution was added to adjust the pH to 8.5-9.

5. The reaction was stirred at 40-50℃ for 3-5 h and treated with ultrasound at a frequency of 20-25 kHz and a power of 100-150 W to form a composite structure of ferrous chloride-coated nano-ferrous oxide. After the reaction, the composite structure was separated using an external magnetic field with a magnetic field strength of 0.2-0.5 T. It was then washed 3-5 times alternately with deionized water and anhydrous ethanol to remove unreacted salts and impurities. Finally, it was dried in a vacuum drying oven at 60-70℃ for 6-8 h to obtain the ferrous chloride-nano-ferrous oxide composite material.

2. The method for synthesizing pentachloropropane based on vinyl chloride and carbon tetrachloride raw materials according to claim 1, characterized in that: Step S1 involves the preparation of the mesoporous carbon support as follows: Mesoporous silica with a pore size of 2-5 nm 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 until homogeneous. The stirring temperature is 30-40℃, 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 its mass) is added. The mixture is then heated at 80-100℃ for 2 hours. The curing process is carried out for 3 hours to form a cured composite. The composite is then transferred to a tube furnace and heated to 700-900℃ at a rate of 2-5℃ / min under nitrogen protection. The temperature is maintained for 3-5 hours for carbonization. After carbonization, the composite is cooled to room temperature and immersed in a 1.0-1.5 mol / L hydrofluoric acid solution at 20-30 times its mass. The solution is stirred at 25-35℃ for 6-8 hours, then washed with deionized water until neutral, and dried at 100-120℃ for 4-6 hours to obtain a mesoporous carbon support.

3. The method for synthesizing pentachloropropane based on vinyl chloride and carbon tetrachloride raw materials according to claim 2, characterized in that: The operation of loading the mesoporous carbon support in step S1 is as follows: Take the prepared mesoporous carbon support and suspend it in 15-20 times its mass of deionized water. Add 0.05-0.1 times the mass of the mesoporous carbon support of polyvinyl alcohol. 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 at a mass ratio of 1:(2-4). Stir at 40-60℃ for 3-5 hours under nitrogen protection. After the mixture is stirred, collect the precipitate by centrifugation at a speed of 3000-5000 rpm for 10-20 minutes. Wash it with deionized water 2-3 times. Then dry it in a vacuum drying oven at 70-90℃ for 5-8 hours to obtain the loaded product.

4. The method for synthesizing pentachloropropane based on vinyl chloride and carbon tetrachloride raw materials according to claim 1, characterized in that: The heating rate in step S3 is 3-6℃ / min.

5. The method for synthesizing pentachloropropane based on vinyl chloride and carbon tetrachloride raw materials according to claim 1, characterized in that: The parameters for vacuum distillation in step S4 are as follows: pressure 0.01-0.05 MPa, temperature 60-80℃.

6. The method for synthesizing pentachloropropane based on vinyl chloride and carbon tetrachloride raw materials according to claim 1, characterized in that: In step S5, the eluent for the activated carbon adsorption column is a mixed solution of n-heptane and dichloromethane, wherein the volume ratio of n-heptane to dichloromethane is 3:1.

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