1,1,1,2-Tetrafluoroethane(HFC-134a) has been known to haveno ozone depletion potential(ODP) and is a prime candidate for thereplacement of dichlorodifluoromethane(CFC-12) used as a refrigerant,medical aerosols, and foam blowing agents. Industrial synthesis of HFC-134a includes the formation of toxic 1-chloro-2,2-diflouroethylene (HCFC-1122) as a by-product.
Metal oxide catalysts, CuO, $V_2O_5$, $Cr_2O_3$, $Fe_2O_3$, and AgO were supported on MgO, and they were screened to remove HCFC-1122 from HCFC-1122 /HFC-134a mixture without changing HFC-134a through new type of the catalytic selective oxidation as a non-conventional reaction route. HCFC-1122 was converted to its oxidation products such as CO, $CO_2$, $COF_2$, HCl, and HF, which can be easily separated from HFC-134a. The activity for HCFC-1122 in HFC-134a and HCFC-1122 mixture increased in the order of $Cr_2O_3$/MgO > CuO/MgO > $V_2O_5$/MgO. The conversion for oxidation of HCFC-1122 alone was relatively higher than that of HFC-134a alone. The reactivity of HFC-134a and HCFC-1122mixture did not show any deviation from the prediction based on the reactivity of each reactant alone.
The amount of oxygen is an important factor in the deactivation of catalysts since coke formation is accelerated through halogenated acetylene formed during the reaction. A higher $O_2$/HCFC-1122 ratio showed a higher activity while a lower $O_2$/HCFC-1122 ratio showed a rapid deactivation with all catalysts for removal of HCFC-1122. CuO/MgO, $V_2O_5$/MgO, and $Cr_2O_3$/MgO catalysts showed a high activity around 90% near 500℃. Catalysts calcined at a lower temperature showed a higher activity for HCFC-1122 than those at a higher temperature.
Calcination at a higher temperature caused a significant sintering, leading to the decrease in surface area as well as in oxygen uptake.
