The gas-phase reaction of CH4 and CHClF2 (HCFC-22, R22) has been studied in an alumina tubular reactor at atmospheric pressure and in the temperature range of 673-1073 K. The motivation of the investigation is to assess this process as a potential route for the treatment of CHClF2, as well as a technology for the synthesis of CH2=CF2 (vinylidene fluoride, VDF). Under the conditions studied, the major products are C2F4, CH2=CF2, HF, and HCl. Minor products detected include C2HF3, C2H2, CHF3, C2H3F, C2H2F4, CH2F2, C3F6, CH3Cl. A mechanistic interpretation of the results is proposed, including the reactions involved in the initial decomposition of CHClF2, those contributing to the activation of CH4 and developing the pathways leading to the formation of product species. The result of changing feed ratio experiments is consistent with the reaction mechanism developed. The introduction of small amounts of O-2 improves the conversion of CH4 and formation of CH2=CF2 markedly.