Reforming of glycerol for producing hydrogen in a Pd/Ag membrane reactor

Due to the greenhouse effect and the soaring of oil prices internationally in recent years, biodiesel, which retains environmental benign characteristics that can mitigate climate change and pollution problems, has been becoming a major surrogate for fossil diesel. Theoretically, ten percent of glycerol is produced as the by-product through transesterification of fatty acid for manufacturing biodiesel; the increasing demand of biodiesel will make the glycerol become excess. Glut of glycerol must be converted into some useful chemicals and hydrogen is one of which can be used directly in the fuel cell and produces zero pollutant emissions. In this study, steam reforming of glycerol was carried out in a traditional reactor and an electrolessly plated PcVAg alloy membrane reactor, which were packed with an appropriate amount of Ni/CeO2/Al2O3 catalyst. Since membrane reactors offer the possibility of overcoming the equilibrium conversion through selectively removing one of the products, i.e., hydrogen, from the reaction zone, a higher conversion rate is expected. With its high H/C ratio feature, glycerol is reformed with steam to produce hydrogen and the process is optimized to achieve a highest performance, with varying temperatures, weight hourly specific velocities (WHSV) and water glycerol molar ratios (WGMR). When temperature at 800 degrees C, WHSV = 5 h(-1) and WGMR = 5, it is found that the conversion of glycerol is 96.24% and the best hydrogen yield is 83.21% in a traditional reactor. In comparison, as the glycerol steam reforming was conducted in the Pd-Ag membrane reactor, the results show that the membrane reactor can increase the glycerol conversion, but at high pressure, the conversion will decline. The activity of the CeO2 modified catalysts under 20-h period operation was higher than that of the unmodified ones. TGA measurement confirmed that CeO2 can effectively reduce the carbon deposition rate. Copyright (c) 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.