Influence of Regeneration Conditions on the Activity of the Catalyst for Oxidative Chlorination of Ethylene

Abstract

The possibility of thermochemical regeneration of an industrial batch of a spent and partially deactivated catalyst to improve its activity and selectivity in oxidative chlorination of ethylene to give 1,2-dichloroethane was studied.In the existing process for manufacture of vinyl chloride by a balanced scheme, 1,2-dichloroethane 1,2-C 2 H 4 Cl 2 is produced by direct and oxidative chlorination of ethylene. The oxidative chlorination process uses as a catalyst CuCl 2 supported by g-Al 2 O 3 [1]. The reaction requires a slight excess of C 2 H 4 and occurs in accordance with the overall equation [2] C 2 H 4 + 2HCl + 0.5O 2 6 C 2 H 4 Cl 2 + H 2 O + Q. (1) The main reaction is accompanied by side reactions: complete and incomplete combustion of C 2 H 4 to give CO and CO 2 [3]:C 2 H 4 + 2O 2 6 2CO + 2H 2 O.(3)Other possible side reactions yield CCl 4 , chloral, trichloroethane, trichloroethylene, etc. (a total of up to 2% relative to 1,2-C 2 H 4 Cl 2 obtained) [4].In the course of the process, redox reactions may occur on the catalyst surface [5]: C 2 H 4 + 2CuCl 2 6 C 2 H 4 Cl 2 + 2CuCl, (4) 2CuCl + 0.5O 2 + 2HCl 6 2CuCl 2 + H 2 O. (5) The appearance of iron in the catalyst can be accounted for by the following reactions between the reactor walls and the catalyst:Fe + CuCl 2 6 FeCl 2 + Cu,4FeCl 2 + O 2 + 4HCl 6 4FeCl 3 + 2H 2 O, (7) D 2FeCl 3 + 3H 2 O 6 Fe 2 O 3 + 6HCl. EXPERIMENTALThe study was performed on the newly created experimental laboratory installation that operates on real process gases (taken from the stage of ethylene oxychlorination at a shop of Lukor Private Company, Kalush) and adequately models the industrial process.After two years of operation, the characteristics of the catalyst changed, which led to a decrease in its activity in oxychlorination. Therefore, our goal was to study the possibility of regenerating the oxychlorination catalyst and to analyze methods of such a regeneration under the conditions maximally similar to those used in the industry.Experiments on catalyst regeneration were performed in two ways: by thermal treatment of the catalyst in a fluidized bed in oxygen-rich gas mixture or in air and by washing the catalyst in dichloroethane. In addition, the physicomechanical properties of catalyst samples before and after regeneration were studied.The regeneration was performed in two modes: in air with heating to 180, 210, and 250oC and at increased oxygen content (20, 30, and 40 vol %) and nitrogen content of 80, 70, and 60 vol %, respectively. Simultaneously, analyses for the content of copper(I, II, total) chloride and iron(III) in the catalyst were made, with the bulk weight m b , specific surface area S sp , and pore volume V in the catalyst determined before and after regeneration. The data obtained are listed in the table.In addition, the table lists data on washing of the catalyst to remove iron(III) chloride by extraction into dichloroethane and describes changes in the physicomechanical properties of the catalyst.

Features of the structure active centers of industrial catalysts for the oxidative chlorination of ethylene

“…The presence of the catalyst X1 Harshow, the impurities of lanthanum-La, potassium-K and niobium-Nd (Σ = 5%) and their oxides (Σ = 9%) (Fig. 7.1.7.2.7.3) proves their role as promoters EOC reaction [11][12]. They react in the form of corresponding salts of cuprum with the dustable hydroxyl groups of the carrier -γ-Al2O3 by reactions (№.…”