Oxidative dehydrogenation of ethane to ethylene over Sr-promoted La₂O₃ catalyst supported on low surface area porous catalyst carrier

Abstract

Oxidative dehydrogenation of ethane (ODE) to ethylene over Sr-promoted La₂O₃ (Sr/La = 0.0, 0.03, 0.3, 2.0 and 10.0) supported on a commercial low surface area porous, inert catalyst carrier SA-5205 ( Sr-La₂O₃ loading = 16 ± 1.5 wt% ) in presence of steam (steam/C₂H₆ = 1.0) at different temperatures (700- 850°C ), C₂H₆/O₂ ratios ( 4.0 - 8.0 ) in the feed and gas hourly space velocities (50723 - 201,240 cm³g¹.h¹) has been studied. The supported Sr- La₂O₃ catalysts have been characterized for their surface area and also for their basicity distribution by the TPD of CO₂ from 50 to 950°C. Among the supported Sr-La₂O₃ catalysts, the one with Sr/La = 0.3 showed best performance in the oxidative dehydrogenation of ethane to ethylene. Moreover, high selectivity (>80%) for C₂₊ olefins at 50-70% conversion of ethane could be obtained at very high space velocity without coke deposition on the catalyst at 800- 850°C. When the reaction temperature and or C₂H₆/O₂ ratio is increased, the heat produced in the process is decreased markedly because of the occurrence of thermal cracking of ethane ( which is endothermic) to a larger and larger extent, simultaneously with the exothermic oxidative ethane conversion, thus making the process nearly thermoneutral or mildly exothermic/endothermic by manipulating the process conditions.