Decomposition of CH₂FCF₃ (134a) over metal phosphate catalysts

The decomposition of CH₂FCF₃ over some phosphate catalysts was studied. CH₂FCF₃ began to react at 250, 300, and 450 °C over Zr₃(PO₄)4, AlPO₄, and BPO₄, respectively, and the conversion reached 100% at 475, 500, and 700 °C, respectively. The primary reaction over Zr₃(PO₄)₄ was estimated to be CH₂FCF₃ + H₂O + 1/2O₂ → 2CO + 4HF, whereas the reactions over AlPO₄ and BPO₄ were CH₂FCF₃ + H₂O + O₂ → CO + CO₂ + 4HF and CO + 1/2O₂ → CO₂. Complete decomposition requires both hydrolysis and oxidation. The oxidation activities of these phosphate catalysts are not high enough to accomplish complete decomposition. However, AlPO₄-based catalysts can be combined with each Co₃O₄, Mn₂O₃, CuO, and Cr₂O₃ at a phosphate content of 1/10 by volume to make them sustainable at 550-550 °C. The addition of Ce to AlPO₄ brought about a promotion effect in CH₂FCF₃ decomposition similar to that for CCl₂F₂ decomposition. This might suggest a similarity in the reaction mechanism. The primary reaction in the absence of oxygen was estimated to be CH₂FCF₃ + H₂O → CO + C + 4HF.