Catalyst Technology

Catalytic technologies offer great potential for reducing waste and energy consumption, minimizing the use and transportation storage of hazardous materials, and developing products that are safer for the environment. Some examples of catalyst-based products and processes that reduce pollutant emissions follow.

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).

Management of Hazardous and Toxic Materials

The DuPont company has a catalytic process for making methylisocyanate (MIC), starting from materials far less hazardous than the traditional phosgene. The MIC is produced only moments before it is converted to a pesticide so that only small quantities of MIC exist at any one time. This pathway is safer for both the environment and worker health and safety. The catalytic process does not produce hydrochloric acid.

1, 1-Dichloro-ethene

+ CH3CClF2 + CH3CF3

HCFC-142b HCFC-143a

Stage 1

+ CH3CClF2 + CH3CF3

HCFC-142b HCFC-143a

0-160 psig 0-80 psig

>92% conversion Liquid phase

99.5% CH3CCI2F 0.5% CH3CCIF2 500 ppm CH2CCI2

FIG. 3.6.4 High-yield catalytic hydrochlorofluorocarbon process.

Was this article helpful?

0 0

Post a comment