New technologies for separation, fixation and conversion of carbon dioxide to mitigate global warming

Development of technologies to separate CO2 from flue gas, to fix CO2 in deep sea, and to recycle chemically through catalysis or photosynthesis is described. For the catalytic hydrogenation process, in which CO2 is converted to methane or methanol through catalytic reaction with hydrogen, Rh-Mn catalyst was developed which gave over 90% conversion to methane at an atmospheric pressure and 300 centigrade. The photoelectrocatalytic process is known, in which methane and others are produced from CO2, water, and light using photoelectrocatalysts. A photoelectrocatalytic cell was developed, which was composed of a thin film photocatalyst made of densely packed TiO2 micro crystallites of anatase form and a copper electrocatalyst optimally surface-modified with islands of zinc oxide. With the cell an energy efficiency of 9.4% was obtained. Utilizing the photosynthesis process of plants, a bioreactor system is being developed, which has a CO2 fixation rate of over ten times that of forests. It was found that thermophilic cyanobacteria are capable of fixing CO2 at high concentrations equivalent to that of combustion flue gas at a high temperature of 50 centigrade. 9 refs., 11 figs.