Coupling of thermal cracking with noncatalytic oxidative conversion of ethane to ethylene

Abstract

Homogeneous thermal cracking of ethane, which is an endothermic and hence energy-intensive process, was carried out in the presence of limited O₂ under different process conditions (at 600°-850°C; O₂/ethane ratio of 0-0.2; H₂O/ethane ratio of 0-3.3; and space velocity of 2,000-11,000 h^-1). The influence of a sulfur additive in the feed and reactor material on the process performance was also investigated. Noncatalytic oxycarcking of ethane in the presence of limited O₂, greatly enhances not only the total conversion of ethane but also the conversion of ethane by purely thermal cracking. This process also occurs at a much lower contact time than that required to achieve the same conversion for the thermal cracking process. Also, both the exothermic oxidative conversion and the endothermic thermal cracking of ethane occur simultaneously, which makes this process very energy-efficeint, with a drastic reduction in external energy requirement and coke formation. By manipulating the process conditions, particularly the temperature and O₂/C₂H₆ ratio, the overall process can be made almost thermoneutral, mildly exothermic, or mildly endothermic.