A research group discovered a phenomenon that enables the natural production and highly efficient generation of high purity hydrogen gas in a large quantity from cellulose, such as wood chips.
The group was led by assistant professor Qiwu Zhang and professor Fumio Saito of the Institute of Multidisciplinary Research for Advanced Materials at Tohoku University. The hydrogen gas can be obtained by dry grinding (mechanochemical processing) the cellulose followed by heating.
The applications of hydrogen are expected to increase, for example, in fuel cells. There has been demand for the development of a method to produce high purity hydrogen from biomass, a renewable energy source, in a simple and highly efficient manner.
The research group dry ground a mixed sample composed of cellulose and an additive (inorganic) with a planetary mill. It heated the product in an Ar atmosphere by an electric furnace to generate gas, and conducted a quantitative analysis and evaluation on the gas.
Four types of gases, namely H2, CH4, CO and CO2, were confirmed by the result of analysis. The molar ratios (%) of H2 and CH4 are 93.5 and 6.4%, respectively, and the ratios of CO and CO2 are both quite low. The produced gas is a high purity hydrogen gas (CO acceptable concentration: 1% or less) that can be directly supplied to PAFC. Meanwhile, the additive is a metal hydroxide that acts as a kind of reaction accelerator.
The composition of the solid powder after the generation of gas includes CaO and CaCO3. In particular, the degree of conversion and immobilization of CO2 is determined to be approximately 80% based on the proportion of CaCO3.
As can be seen from the low generation ratio of hydrocarbon gas such as methane, the generation ratio of hydrogen from cellulose is considerably high. Details of the discovery will be presented at the 39th Autumn Meeting, Society of Chemical Engineers, Japan (Hokkaido University) scheduled in September 2007.
The group is presently conducting verification tests. The method is expected to prevail rapidly because it is quite simple and allows the generation of hydrogen in a large quantity by using waste wood including thinned wood and so forth. The patent application has already been filed.
Motohiko Hamada, Nikkei Monozukuri
