Steam Reforming of Methanol in a Pd-Composite Membrane Reactor

Abstract

Palladium-based membranes are being studied for simultaneous production and separation of H₂ from reforming reactions in a single-unit operation by equilibrium shift. In this work a Pd-composite membrane in tubular configuration as fuel reformer was used to study the steam reforming of methanol (SRM) over Zn/Ni catalyst on Al₂O₃ support. The Pd-composite membrane was fabricated by depositing thin Pd film on microporous stainless steel (MPSS) support by surfactant induced electroless plating (SIEP) method. The effects of steam to methanol molar feed ratio (S/M), temperature, and catalyst time factor on methanol conversion, H₂- and CO-selectivity were studied for the SRM in the membrane reactor. A two-dimensional, pseudo-homogeneous membrane-reactor model for the SRM reactions was developed to study the membrane reactor performance. Experimental results show that a significant enhancement of methanol conversion is achievable in H₂-selective Pd-MPSS membrane reactor by equilibrium shift. The S/M ratio has marginal effect on methanol conversion, and at high S/M ratio, steam acts as diluent. The temperature has a greater effect on methanol conversion and with increased catalyst time factor, methanol conversion increased to some extent. The CO-selectivity was sensitive to temperature and to a lesser extent to the S/M ratio. On the contrary, H₂-selectivity was insensitive to both temperature and S/M ratio. The trends observed in this experimental SRM in Pd-MPSS membrane reactor were in good agreement with a 2-D pseudo-homogeneous SRM membrane reactor model.

Keywords:

• CO-selectivity
• H₂-selectivity
• H₂-separtion
• membrane reactor
• membrane reactor model
• methanol conversion
• methanol reforming
• Pd-composite membrane
• steam to methanol ratio

ACKNOWLEDGEMENTS

This research was sponsored by the U.S. Department of Energy–National Energy Technology Laboratory (DOE–NETL), under Award No. DE-FG26-05NT42492. Dr. Arun Bose, NETL, Pittsburgh, is the DOE Project Officer. However, any opinions, findings, and conclusions or recommendations expressed herein are those of the author and do not necessarily reflect the views of the DOE.