GREENHOUSE-GAS CHEMISTRY

One of the major problems facing mankind is the global warming of the atmosphere due to man-made emissions of greenhouse gases. Mitigation o f these greenhouse gas emissions to the atmosphere can be achieved by using direct control technologies (capture, disposal or chemical recyc ling). In this paper, we report on carbon dioxide and methane recyclin g with other chemicals, especially with hydrogen and oxygen, to produc e liquid fuels such as. methanol. Methanol synthesis from pure CO2 is investigated with various catalysts at moderate pressures (less than o r equal to 30 bar) and temperatures (less than or equal to 300 degrees C). The catalysts show good methanol activity and selectivity. The re markable finding is that the equilibrium yields per pass over the cata lysts are already reached at temperatures above 250 degrees C. For a s toichiometric feed, at 225 degrees C, 20 bar and at a space velocity o f 4500 h(-1), a best methanol yield equal to 7.2 % is reported. The co nversion of CO2 and CH4 to methanol is also studied in a silent electr ical discharge at pressures of 1 to 4 bar and temperatures close to ro om temperature. Methanol yields are given for mixtures of CO2/H-2, CH4 /O-2 and also for CH4/air mixtures. (C) 1997 Elsevier Science Ltd.