Increasing the efficiency of the pyrolysis process

Abstract

Increasing the production volume of organic synthesis products demands improvements to the technology of the pyrolysis process to reduce costs and increase the yield of desired products, particularly ethylene, which is the dominant raw material in the petrochemical industry. The aim of the present work is the substantiation of the methods that increase the pyrolysis selectivity for ethylene by influencing the stages of the radical chain process. Based on the study of the relative reactivity of the various C-H bonds in their interaction with the methyl radicals and with hydrogen atoms, which are the basic particles that determine the chain propagation in the pyrolysis, the possibility of increasing the process selectivity for ethylene was established, while simultaneously reducing the yield of the condensation products and suppressing the formation of pyrolytic carbon by replacing the methyl radical with hydrogen atoms, which was made possible by adding hydrogen to the feedstock in the amount of approximately 2% by weight. It was found that allene lowers the activation energy of the thermal decomposition of hydrocarbons, thus increasing the depth of the reaction. Accelerating the rate of initiation of the radical chain process was observed at the temperatures below 1,000 K. This opens up the possibility of increasing the efficiency of the pyrolysis process by recycling the propane fraction containing allene into the pyrolysis feedstock. This speeds up the process at low temperatures and suppresses the yield of the condensation products. Experimental data demonstrating the results of application of the proposed method are presented. © 2017 WIT Press.