Study On The Selective Hydrodechlorination Of Fluorochlorocarbons

Dichlorofluoromethane (CCl2F2), chloropentafluroethane (CClF2CF3) and tetrachloro-methane (CCl4) were chosen as the model reactants to evaluate the catalytic activity for selective hydrodechlorination over several novel supported catalysts e.g. supported PdCl2-(n-C4H9)4N+Cl- molten salts, supported palladium phthcyanine catalysts, supported palladium catalysts prepared through organometallic palladium compound as precursors, and supported gallium modified platinum catalysts as describled in follows:A novel supported liquid phase film catalyst, supported PdCl2-(n-C4H9)4N+Cl- molten salts was firstly found to be an effective catalyst with good stability for selective hydrodechlorination of CCl2F2 (CFC-12) to its alternatives CH2F2 and CHClF2. the selectivity of more than 80% for CH2F2+CHClF2 was achieved under optimized reaction conditions. Addition of GaCl3 and CuCl2 to PdCl2-(n-C4H9)4N+Cl- supported molten salts was beneficial to improve the selectivity to CH2F2+CHClF2.Supported palladium phthalocyanine was also found to be an interesting catalyst with good stability for selective conversion of CCl2F2 into CH2F2 under flowing hydrogen further. Relatively high selectivities towards CH2F2 formation over palladium phthalocyanine catalysts with fluoride supports were achieved at limited conversion levels (<10%). Particularly, supported palladium phthalocyanine exhibited excellent stability even at low H2/CCl2F2 ratio in the corrosive reaction conditions due to the formation of HCl and HF. The fractionally reduced palladium in palladium phthalocyanine was suggested to be the main active site for the catalytic hydrodechlorination. Moreover, novel supported palladium catalysts were prepared through organometallic Pd compounds including dichlorobistriphenylphosphine palladium (DCTPPP) and dithiocyanatobistriphenylphosphine palladium (DTTPPP) for the hydrodechlorination of CFC-12 for the first time. These catalysts exhibited excellent catalytic activities in hydrodechlorination of CFC-12. Particularly, high selectivities of CH2F2 formation were achieved over the catalysts, DCTPPP/MgF2 with 88.1% and DTTPPP/MgF2 with 85.8%, at a limited conversion level (<5%). No obvious deactivation was observed for DCTPPP/MgF2 and DTTPPP/MgF2 catalysts within 60 hours. The higher catalytic activity, CH2F2 selectivity and catalyst stability may be mainly attributed to high dispersions of palladium.Additionally, novel CrF3 supported palladium catalysts have been prepared through two different precursors i.e. dichlorobistriphenylphosphine palladium (DCTPPP) and...