| 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.
|