Hydrogen-selective porous carbon-based membranes for catalytic steam reforming of bio-ethanol

Abstract

Today’s demand from science and research on the usage of sustainable and renewable energy sources arises mainly from the embargo of oil shipments to the Western nations by the arab members of the “Organization of the Petroleum Exporting Countries” (OPEC) in 1973-1974 until today. But the global production of pure hydrogen still originates primarily from fossil fuels and is dominated by industry, i.e. mainly by petroleum refining and ammonia production. Numerous disadvantages are described for the commercial production of hydrogen by catalytic steam reforming (CSR) of hydrocarbons (e.g. use of non-renewable resources, high energy requirement, the release of high amounts of CO etc.). Nevertheless, the huge advantage of the established procedure is related to its cost-effective manufacture of hydrogen due to high hydrogen-selectivity and full conversion. The use of suitable porous carbon-based membranes and of renewable resources (e.g. bio-ethanol) at relative low temperatures (below 400 °C) can overcome most of the related problems in classic CSR technique. In this context, a new concept of different porous and hydrogen-selective carbon-based membranes were investigated as suitable candidates for the purpose of the production of so-called “green hydrogen” by means of catalytic membrane reactor (CMR) for bio-ethanol steam reforming (b-ESR). The carbon-based membranes under study were investigated by means of classic gas separation experiments. Temperature- and pressure-dependent single and mixed-gas permeation experiments were applied in laboratory scale, closely adapted to industrial conditions. From the carbon-based membranes under study, it could be shown that two kinds of membranes, i.e. the metal-organic framework (CAU-10-H) membrane and the group of surface-modified graphite membranes (SMG), comparatively showed the most promising results. The mixed gas separation factors of the CAU-10-H and SMG graphite (e.g. ETMS-modified) membrane could reached for α (H2/CO2) of 11.1 or 8.0 and for α (H2/H2O) of 5.7 and 10.2, respectively. Additionally, the SMG and the CAU-10-H membrane types show beneficial separation performances of hydrogen in the presence of large quantities of water steam (up to 18 Vol.-% H2O) and have a good hydrothermal stability in classical gas separation experiments.