Problems of Increase in the Selectivity of Ethylene Oxychlorination Processes: I. General Patterns in the Formation of Carbon Oxides in the Ethylene Oxychlorination Process

摘要

General patterns in the formation of carbon oxides (byproducts of deep oxidation) in the process of ethylene oxychlorination in a fluidized catalyst bed are considered. Based on the literature data, some conclusions are drawn as to a possible reagent oxidation mechanism, allowing for the oxidation of the initial ethylene and target dichloroethane. Raising the process temperature increases the contribution from dichloro- ethane oxidation. It is shown that a catalyst must also be active in the oxidation of carbon monoxide to carbon dioxide in order to stabilize the process and improve the selectivity to target 1,2-dichloroethane. Under industrial conditions, a lower yield of side carbon oxides is attained at minimal excesses of ethylene and oxygen with respect to hydrogen chloride; this requires catalysts with a low content of copper on the outer surface of a grain. The presence of promoting alkali or alkali-earth chloride additives in a catalyst is important. The penetration of iron into a catalyst due to the erosion of industrial reactor walls leads to an increase in the yield of deep oxidation products and a reduction in the speed of the oxychlorination process.