Equilibrium thermodynamic predictions of coking propensity in membrane-based dehydrogenation of hydrocarbons and alcohols

Abstract

This paper uses equilibrium analysis to predict the likelihood of carbon deposits as functions of fuel-steam composition and temperature. The focus is particularly concerned with the effects of dehydrogenation as in catalytic membrane reactors or protonic fuel cells. Results show that if an inlet mixture is under the deposit limit, then even with significant hydrogen removal the dehydrogenated mixture can remain free of carbon deposits. Depending on operating temperature and pressure, the equilibrium predictions offer qualitative and quantitative guidelines that assist establishing initial fuel/steam ratios. The predictions also provide guidelines for assessing the effects of hydrogen removal via membranes. However, it must also be noted that there can be significant departures from equilibrium that are the result of finite-rate kinetic effects with particular catalysts.