Conversion of CHF3 to CH2=CF2 via reaction with CH4 and CaBr2

Reaction of CHF(3) and CH(4) over CaBr(2) was investigated at 400-900 degrees C as a potential route for transforming the highly potent greenhouse gas, CHF(3), into the valuable product CH(2)=CF(2). The homogeneous reaction of CHF(3) with CH(4) was also studied to assist in understanding the chemistries involved. Compared to the gas phase reaction, the addition of CaBr(2) as a reactant increases the conversion of CHF(3) and CH(4) significantly at low temperatures while to a lesser extent at higher temperatures. In the absence of CaBr(2), besides the target product, CH(2)=CF(2), a large amount Of C(2)F(4) forms. On addition of CaBr(2), the rate of formation Of C(2)F(4) drops dramatically to near zero, while the rate of formation of CH(2)=CF(2) increases considerably at temperatures below 880 degrees C. Experimental and theoretical studies suggest that CHF(3) strongly interacts with CaBr(2), resulting in the fluorination of CaBr(2) to CaF(2), the release of active Br species results in the selective formation of CBrF(3). The subsequent reactions involving Br, methane, and CBrF(3) play a major role inthe observed enhanced yield of CH(2)=CF(2) .