Improving propyne removal from propylene streams using a catalytic membrane reactor–a theoretical study

Typical industrial propylene streams contain 2–5 molar% of alkynes, which must be removed. Traditionally, this is carried out through hydrogenation. However, the deeper hydrogenation to alkanes is a drawback of such process. The use of a catalytic membrane reactor (MR) featuring a propyne permselective membrane and a catalyst selective to the propyne hydrogenation, loaded on the permeate side membrane surface is proposed; plug-flow pattern and segregated feed of reactants are considered. This strategy should improve the selective hydrogenation, as the permselective membrane enhances the propyne/propylene ratio at the catalyst surface.The combined process was analyzed using a mathematical model. The MR performance was compared to a conventional fixed-bed catalytic reactor (FBCR) with the same feed and reaction conditions, in terms of the propyne molar fraction. The performance of the MR was characterized by the conversion of propyne and selectivity towards propylene as a function of some model parameters. The MR showed to be more efficient in performing the required purification.

► The output propyne conc. in the simulated membrane reactor (MR) is below 5 ppm.
► The catalytic selectivity of the MR is much higher than the fixed bed reactor.
► The MR was able to remove propyne with a permselectivity value as low as 15.
► Dimensionless parameters were consistent with permeance, catalytic literature data.