Effects of catalysts and membranes on the performance of membrane reactors in steam reforming of ethanol at moderate temperature

Abstract

Steam reforming of ethanol in the membrane reactor using the Pd77Ag23 membrane was evaluated in Ni/CeO2 and Co/CeO2 at atmospheric pressure. At 673 K, the H2 yield in the Pd77Ag23 membrane reactor over Co/CeO2 was found to be higher than that over Ni/CeO2, although the H2 yield over Ni/CeO2 exceeded that over Co/CeO2 at 773 K. This difference was owing to their reaction mechanism. At 773 K, the effect of H2 removal could be understood as the equilibrium shift. In contrast, the H2 removal kinetically inhibited the reverse methane steam reforming at low temperature. Thus, the low methane-forming reaction rate of Co/CeO2 was favorable at 673 K. The addition of a trace amount of Ru increased the H2 yield effectively in the membrane reactor, indicating that a reverse H2 spill over mechanism of Ru would enhance the kinetical effect of H2 separation. Finally, the effect of membrane performance on the reactor performance by using amorphous alloy membranes with different compositions was evaluated. The H2 yield was set in the order of H2 permeation flux regardless of the membrane composition.