Low-temperature microwave-driven thermochemical generation of hydrogen from steam reforming of alcohols over magnetite

Abstract

In a previous study, we reported that hydrogen generation can be achieved quite efficiently from seawater and contaminated waters at low temperatures using a microwave-driven hydrogen production (MDHP) process and waste activated carbon as the microwave absorption heating element (MAHE). However, the problem with this method is that activated carbon (a heat source from the microwaves) is used in the decomposition of water in which the quantity of activated carbon continues to decrease in parallel with the evolution of hydrogen. This problem has been resolved in this study by using magnetite as a novel MAHE component at low temperatures; the energy-saving thermochemical steam reforming reaction was performed with a mixed water/ethanol solution, for which results showed a maximum hydrogen generation yield somewhat greater than 80%. No hydrogen evolved in the thermochemical steam reforming process upon heating the magnetite at 350 °C in a conventional electric furnace, in contrast to the case where hydrogen was generated in yields greater than 40% by heating at 350 °C with microwaves. The rate-determining energy required for hydrogen generation is evidently heat, as evidenced by the formation of microwave-generated microscopic high-temperature fields (hot spots) at an estimated temperature of ca. 760 °C at the magnetite surface, a result of microwave heterogeneous microscopic thermal effects (MHMEs), and this even if the average temperature of the magnetite bulk were 350 °C.