| 摘要 |
<p>Fluoroform is produced by passing substantially anhydrous monochlorodifluoromethane or monofluorodichloromethane in the vapour phase in contact with anhydrous aluminium chloride or bromide in coarse particles and maintained at a temperature in the range - 25 DEG C. to +50 DEG C. at the rate of from 0.1 pound to 10 pounds of the chlorofluoromethane per pound of the aluminium halide per hour. The catalyst may be used in admixture with an inert heat-dissipating solid diluent. Mixtures of the chlorofluoromethanes may be used. Instead of using coarse particles of the aluminium halide, the latter may be used in small particle size in admixture with an inert heat-dissipating solid diluent in coarse particles. The solid diluents are, e.g. alumina gel or silica gel and should preferably have a heat conductivity at least equal to that of silica gel or at least equal to that of steel. Thus, the preferred diluent is steel Raschig rings. It is desirable to maintain the catalyst at a temperature of from - 5 DEG C. to + 15 DEG C. and to pre-cool the starting chlorofluoromethane to from - 5 DEG to 0 DEG C. The chlorofluoromethane feed may be diluted with two to six times its weight of the gaseous effluent products. The reaction mixture may therefore be recycled as diluent and in such event it is an advantage to employ two reactors connected in series. Other inert diluent gases especially those having a heat capacity not less than the gaseous reaction products may also be used. The process may be operated at 7 to 75 pounds per square inch absolute but pressures of 14 to 22 pounds are preferred. The reaction vessel may be of glass, copper or steel. In examples: (1) and (2) monochlorodifluoromethane dried over phosphorus pentoxide and precooled is converted to fluoroform by feeding it in the vapour phase into a reactor containing 5 to 10 mesh and 4 to 20 mesh aluminium chloride respectively, the catalyst temperature being 1 DEG C. and - 25 DEG C. to + 10 DEG C. respectively; (3) fluoroform is obtained as in (1) but the monochlorodifluoromethane is not precooled and the catalyst temperature averages 50 DEG C; (4) monochlorodifluoromethane dried in the liquid phase over silica gel is mixed with crude product consisting of fluoroform, monochlorodifluoromethane and chloroform and the mixture fed in the vapour phase over aluminium chloride diluted with steel Raschig rings in a steel, brine-cooled reactor, the temperature being maintained at - 5 DEG C. to + 15 DEG C.; (5) dichloromono fluoromethane dried over phosphorus pentoxide and precooled is passed in the vapour phase over 7 to 12 mesh aluminium chloride in a copper cooled with water at 2 DEG C., fluoroform being obtained; (6) fluoroform is obtained by passing obtained; (6) fluoroform is obtained by passing dried and precooled monochlorodifluoromethane in the vapour phase over a catalyst prepared by mixing anhydrous 200 mesh aluminium bromide with 6 to 16 mesh silica gel cooled with water at 2 DEG C. U.S.A. Specification 1,994,035 is referred to.</p> |
