Hydrodechlorination of chlorofluorocarbons

The development of CFC alternatives has focused on non-chlorinated compounds, such as hydrofluorocarbons (HFCs), which have similar physical properties, but break down in the lower atmosphere.110 111 Consequently, hydrodechlorination is a simple method for the production of HFCs and also for destruction of CFCs108,109,112-114. Palladium is unique among the catalytic metals for its activity and selectivity in this process,102-108,115,116 but using Pd-Au/SiC 2 (Pd Au = 60 40) increased the selectivity for difluoromethane from difluorodichloromethane (CFC-12) shown by Pd/Si02 at 453 K from 40 to 95%.109,112-114 

The decomposition of chlorodifluoromethane (HCFC-22) using gold supported on sulfated Ti02/Zr02 proceeded as follows 117 

The catalyst was deactivated by reaction with hydrogen chloride and hydrogen fluoride, but some of the activity could be recovered by exposing the deactivated catalyst to carbon monoxide at high temperatures. 

4-Dichlorophenol has a large-scale use in pharmaceutical and herbicide synthesis, but is classed as a priority recalcitrant environmental pollutant conversion to 2-chlorophenol, which can be recycled, is therefore a desirable reaction. Ni/Si02, Au/SiC 2 and NiAu/SiC 2 have been prepared from diaminoethane complexes and tested for this reaction their activities rising in the sequence 

Au/Si02 Ni/Si02 Ni/Si02 + Au/Si02 NiAu/Si02 

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