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Industrial & Engineering Chemistry Research, Vol.41, No.11, 2585-2590, 2002
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 degreesC over Zr-3(PO4)(4), AlPO4, and BPO4, respectively, and the conversion reached 100% at 475, 500, and 700 degreesC, respectively. The primary reaction over Zr-3(PO4)(4) was estimated to be CH2FCF3 + H2O + 1(/)2 O-2 --> 2CO + 4HF, whereas the reactions over AlPO4 and BPO4 were CH2FCF3 + H2O + O-2 --> CO + CO2 + 4HF and CO + 1/2 O-2 --> 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 degreesC. 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.