Ethylene production: process design, techno-economic and life-cycle assessments

Abstract

Replacing the steam cracking process with oxidative dehydrogenation for ethylene production offers potential energy and environmental benefits. To evaluate these possibilities, a study combining conceptual process design, techno-economic analysis, and life cycle assessments of the oxidative dehydrogenation of ethane (ODHE) for producing ethylene at an industrial scale is performed. For comparison, the conventional steam cracking process of ethane is also simulated and optimized. The techno-economic analysis results for ODHE with a boron-containing zeolite chabazite (B-CHA) catalyst, as developed in our group, demonstrate that it is economically competitive ($790 per t ethylene production) compared to the steam cracking process ($832 per t ethylene production). However, a “cradle-to-gate” life-cycle assessment shows that the ODHE process emits more greenhouse gases (2.42 kg CO₂ equiv. per kg ethylene) compared to the steam cracking counterpart (1.34 kg CO₂ equiv. per kg ethylene). The discrepancy between the initial hypothesis and the results arises from the significant refrigerant input required by the ODHE process to recover ethylene from byproducts such as CO, CH₄, and unreacted oxygen and ethane. Further scenario analysis reveals that plausible improvements in the C₂H₆ conversion per pass, the selectivity to ethylene and the ratio of ethane to oxygen in the current ODHE process could render it both economically and environmentally viable as a replacement for the steam cracking process.