Production of Environmentally Safer Products

This example describes a process with negligible side reactions in which 1,1-dichloro-1-fluoroethane (HCFC-141b) is a replacement for stratospheric-ozone-depleting fluorotrichloromethane (CFC-11).

Low yields are obtained when 1,1 dichloroethylene (CH2=CCl2) is reacted with hydrogen fluoride using conventional catalysts because the reaction favors trichloroethane (HFC-143a) as follows:

HCFC-141b HCFC-142b HFC-143a

However, when a specially prepared aluminum fluoride catalyst is used, nearly all the reactant is converted to HCFC-141b, and less than 500 ppm of the reactant remain in the product. The HCFC-141b does not even need to be purified (see Figure 3.6.4).

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