Leveraging green electricity to drive propylene production in membrane reactors

This work assessed the potential for applying ceramic proton-conducting membranes in propane dehydrogenation processes with the aim of achieving drastic reductions in greenhouse gas emissions, in line with the United Nations' climate action sustainable development goal. These hydrogen removing membranes could shift the dehydrogenation equilibrium towards propylene, thereby significantly increasing the process energy efficiency, and allow the electrification of the propylene production process. The potential of two different membrane reactor systems was explored, consisting of (i) mixed proton-electron conducting (MPEC) membranes and (ii) proton-conducting electrolysis cell (PCEC) membranes. Both membrane-assisted processes were benchmarked against the conventional Honeywell UOP Oleflex process for propylene production, resulting in a comparison between these three processes. Rigorous techno-economic analysis indicated that the MPEC process requires an exceedingly large membrane surface area, making it the least competitive option. In contrast, the electrically heated PCEC process could be an attractive alternative to traditional Oleflex, as it had a 20 % lower capital investment and a 30 % lower specific energy input than Oleflex. However, this only translated into a lower carbon footprint when fully renewable electricity was utilized and when off-gas streams rich in hydrocarbons were not used for heat integration. Notably, electrification of the Oleflex process led to comparable improvements in carbon dioxide emissions as industrial implementation of PCEC membranes. Moreover, guidelines were established regarding PCEC performance criteria, electricity price and carbon intensity, and the carbon taxation required to stimulate industrialization of electrified PCEC processes.