Gas phase reaction of CHF3 with CH4, and the effect of additives such as CBrF3 and CH3OH on the reaction, have been investigated in the temperature range of 800-1100K. The major products detected include CH2=CF2 and C2F4 under all conditions studied. The presence of small amounts of CBrF3 and CH3OH enhances the conversion of CH4 and rate of formation of CH2=CF2 significantly, while concomitantly the rate of formation of C(2)F4 decreases. The experiments were modeled against a comprehensive reaction mechanism involving 90 species and 790 reactions. Based on the experimental observations and reaction modeling, the crucial steps influencing the conversion of CHF3 and CH4, the formation of major and minor products and the promoting effects of CBrF3 and CH3OH are fully elucidated. For comparative purposes, the reaction of CHClF2 with CH4 under similar conditions is also studied and the results are consistent with the reaction mechanism developed and discussed. (C) 2010 Elsevier B.V. All rights reserved.