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Jointly Catalytic Synthesis of Vinyl Chloride and Chloroprene from Acetylene

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Jointly Catalytic Synthesis of Vinyl Chloride and Chloroprene from Acetylene International Journal of Control and Automation Vol. 13, No. 4, (2020), pp. 55 - 62 UDC 547.314.25.057 Jointly Catalytic Synthesis of Vinyl Chloride and Chloroprene from Acetylene 1A.R. Karjavov., 2N.I. Fayzullayev., 2N.X. Musulmonov 1Samarkand Medical Institute, Uzbekistan 2Samarkand State University, Uzbekistan E-mail: [email protected] Abstract. As a result of studying the influence of the mass transfer coefficient (transportation) on the process productivity and the influence of other factors, the technological parameters of the catalytic flocculant of vinyl chloride and the chloroprene extraction reactor of acetylene were calculated and the main indicators of the compatibility of technological capabilities of environmental and economic factors were substantiated. The process of co-production of vinyl chloride and chloroprene by hydrochlorination of acetylene in the liquid phase was also studied. Process parameters are found that provide vinyl chloride and chloroprene with high selectivity and acetylene conversion. Some kinetic laws of acetylene hydrochlorination were also studied. As a result of the studies, a technological scheme of the combined receipt of vinyl chloride and chloroprene was created, and the material balance of the process was calculated. Key words: vinyl chloride, selectivity, acetylene, chloroprene, material balance, Polyvinyl chloride, vinylacetylene, vinylacetylene, divinylacetylene 1. Introduction Vinyl chloride and chloroprene are a valuable monomer for the production of polyvinyl chloride - artificial rubber and others. Polyvinyl chloride (PVC) is one of the most versatile thermoplastics with a wider range of applications than all other plastics. Not surprisingly, it is used everywhere and has a positive attitude towards it. Indeed, PVC is a universal, stable, hygienic, safe and cost-effective material that has significant advantages over other materials. Over 90% of vinyl chloride is consumed in the production of polyvinyl chloride. PVC is used for molding and molding of hard products - window and door frames, water pipes, technical and construction products. From plasticized PVC (flexible PVC) linoleum is made, insulation for wires. Apply PVC for the manufacture of artificial leather, shoes, chemical dishes [1-7]. Acetylene hydrochlorination is an important reaction for the production of vinyl chloride monomer (VCM) for chemical processing [8]. However, the most versatile catalyst for this reaction, mercury chloride, is very volatile, toxic and persistent [9,10], and can be a serious threat to human health and the environment, so non-mercury analogues are urgently needed. To obtain a promising and practical non-mercury alternative, various catalysts are used including noble metals [11-21] base metals [22-25] and even non-metallic materials [26-33] have been investigated. 2-Chloro-1,3-butadiene (chloroprene) is used to produce chloroprene rubber. Of the many methods for producing chloroprene, only two are available for industry: acetylene and butadiene. The production of chloroprene from acetylene according to the process of DuPont (USA) involves the dimerization of purified and deoxygenated acetylene into vinylacetylene in the presence of an aqueous catalyst solution of Cu2Cl2, NH4C1 and HCl at 80–90°С. ISSN: 2005-4297 IJCA 55 Copyright ⓒ 2020 SERSC International Journal of Control and Automation Vol. 13, No. 4, (2020), pp. 55 - 62 In this case, by-products are formed: divinylacetylene, dimers, trimers and other acetylene polymers. Vinylacetylene is isolated from the mixture by absorption or condensation. Hydrochlorination of vinylacetylene in chloroprene is carried out in the presence of an aqueous solution of Cu2Cl2, HC1 and FeС12 at 45°С. As a by-product, 1,3-dichloro-2- butene is formed, the amount of which is minimized by reducing the degree of vinylacetylene conversion to 10–20%. Chloroprene is used in industry as a monomer for the production of oil- and benzene-resistant chloroprene rubber. Such rubber has many valuable properties: incombustibility, light and ozone resistance, increased benz and oil resistance, resistance to acids and alkalis. Chloroprene rubbers are used in the production of a variety of products and parts that are operated in contact with aggressive media, such as gaskets, hoses, hoses, belts, rubberized fabrics, protective sheaths, cables, etc. Liquid chloroprene rubbers are used to create anti-corrosion coatings [34-38]. The most convenient way to obtain vinyl chloride and chloroprene in the Republic of Uzbekistan is the preparation of a cheap, active, selective and high-performance catalyst based on domestic raw materials for the catalytic hydrochlorination of acetylene. 2. Experimental part The combined catalytic synthesis of vinyl chloride and chloroprene by hydrochlorination of acetylene is an urgent task of synthetic organic chemistry. In order to simultaneously produce vinyl chloride and chloroprene, we studied the gas-phase coupled process of acetylene hydrochlorination in the presence of copper complex catalysts. The synthesis of vinyl chloride from acetylene is carried out in the liquid or gas phase. In the first case, acetylene is passed through a reactor filled with concentrated hydrochloric acid at a temperature of 25-30°C and with continuous stirring. The catalyst is ammonium chloride and copper chloride, which are dissolved in hydrochloric acid before passing acetylene. The disadvantage of this method is the low stability of the catalyst used and the complicated production technology. Based on this, it is relevant to develop new and improve existing methods for the joint synthesis of vinyl chloride and chloroprene. In accordance with this, we studied the reaction of catalytic hydrochlorination of acetylene in order to simultaneously obtain vinyl chloride and chloroprene. 3. Results and its discussion The reaction of liquid-phase catalytic hydrochlorination of acetylene was studied in a gas-flow gradientless reactor with a catalyst bed of the composition: CuCl2-FeCl3- ZnCl2-NH4Cl-HCl. Acetylene was passed through a reaction vessel containing aqueous solutions of the studied catalysts at a temperature of 100 ° С at molar ratios С2H2:НСl=1:1, where vinyl chloride was formed. Under reaction conditions, part of the acetylene turns into vinyl acetylene. The resulting vapor – gas mixture was sent to the second reactor, where a catalyst of the composition CuC1 – NH4C1-HC1-H20 was located. The gas-vapor mixture in the second reactor with hydrogen chloride forms chloroprene [39–42]. Liquid and gaseous synthesis products were subjected to gas chromatographic analysis using a flame ionization detector under the following optimal conditions: a stationary phase 15% stelosil on N-AW chromaton with a particle size of 0.250-0.315 mm, a glass column 2x0.004 m in size, the temperature of the column stat from 40 to 150°C, with a speed of 10°C/min, (in the temperature programming mode), the flow rate of the carrier gas of nitrogen is 30 ml / min. The ratios are nitrogen: hydrogen: air = 1:1:10. Qualitative analysis of liquid and gaseous products was carried out using the “witness” method and based on structural-group constituents of the sorbent-sorbate system [43–44], and quantitative using the internal normalization method [45–50]. As a ISSN: 2005-4297 IJCA 56 Copyright ⓒ 2020 SERSC International Journal of Control and Automation Vol. 13, No. 4, (2020), pp. 55 - 62 result of the identification of liquid and gaseous acetylene hydro chlorination products, acetylene, vinylacetylene, vinyl chloride, 1-chlorobutadiene-1,3, chloroprene, acetone, acetaldehyde, vinylidene chloride, 1-chlorobutene-diene-1 were found. 2 and methyl vinyl ketone. The results of quantitative analysis are presented in the table 1. Table 1. The results of a quantitative analysis of the liquid products of catalytic hydrochlorination of acetylene. № Tempera- The content of the organic layer of catalysis, % Conversion ture acetylene % synthesis Vinyl chloride Chloroprene 1-chlorine °C butadiene 1,3 1 50 9.5 6.3 2.4 57.4 2 60 15.2 12.4 5.6 59.8 3 70 18.5 18.5 8.9 62.4 4 80 32.0 20.8 12.4 68.0 5 90 38.6 24.5 15.7 70.6 6 100 50.5 24.8 17.6 78.3 7 105 49.5 24.1 14.2 73.5 8 110 48.6 22.5 10.8 70.4 9 115 42.5 20.7 8.4 66.8 10 120 36.4 16.8 6.5 62.7 As can be seen from the table, the optimum temperature for the catalytic hydro chlorination of acetylene is 100°С, at which the total yield of chlorine-containing compounds reaches 92.0%. Moreover, the conversion of acetylene is 78.3%, which is quite acceptable in comparison with the existing methods for the preparation of these compounds. The developed catalyst was used to study the effect of temperature, the ratio of reagents, the concentration of catalysts, contact time on the total conversion of acetylene and the yield of reaction products, as well as on the selectivity of the process. It was found that when the synthesis temperature decreases from 100°C, not only does the rate of formation of vinyl chloride and chloroprene decrease, but also the period of stationary activity of the catalyst decreases sharply. Above 100°C, the stationary process of acetylene hydrochlorination is observed only at sufficiently high concentrations of catalyst components in the contact solution (> 2.0 mol / l). The effect of temperature on the rate of formation of vinyl chloride in the investigated contact solution is extreme. The maximum rate of vinyl chloride formation is observed at 100-150°С. A further increase in temperature leads to a sharp drop in the rate of formation of vinyl chloride. The influence of the partial pressure of acetylene ( ) on the rate of formation of vinyl chloride and chloroprene turned out to be significantly different. Thus, the rate of oxidation of acetylene increases sharply with an increase in , and the rate of formation of vinyl chloride changes rather slowly. According to experimental data, it was found that the order of the kinetic equation for the formation of vinyl chloride is less than the first.
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