| 摘要 |
Methane is synthesised from CO and H2 in the presence of liq. water and a catalyst comprising ruthenium deposited either on a form of carbon with specific surface area 200-1500 sq.m/g, or on an Al2O3 contg. 2-50 wt.% SiO2. The water helps remove the large amt. of heat evolved, and the catalysts unlike most methanation catalysts, have supports stable to water and so are not deactivated by it. The carbon support is pref. obtd. by pyrolysing vegetable matter; coconut charcoal gives best results. Where coal is the source, it must first be purified, esp. for S removal. The C may be activated, e.g. by washing with HNO3 or other acid. Its particle size may be 10 micron-5 mm. If necessay, it can be ground after loading with Ru. If Al2O3 is used as support, the content of SiO2 (a stabiliser) is pref. 4-20 wt.%, and the specific surface area is pref.30-400 sq.m/g. The Al2O3 may be pressed into shaped particles, and the SiO2 added either before (as a colloidal SiO2 gel, silicate or aluminosilicate) or afterwards (by impregnation of the particles with an ethyl silicate soln. or an aq. colloidal soln. of SiO2, etc.). The particles may then be treated with water liq. or vapour at 100-300 deg.C, and finally heated in inert or oxidising atmos. at 200-1100 (pref. 400-900) deg.C. The final particle size of the Al2O3/SiO2 carrier may be 10 micron-10 mm. |
