Amorphous alloy catalysts for decomposition of CCl 2F 2 by hydrolysis

Abstract

Catalytic decomposition by hydrolysis of CCl 2F 2 (CFC-12) to HF, HCl and CO 2 was studied for the amorphous binary NiZr and ternary NiZrCr alloy catalysts. The activity and durability for each catalyst were measured and compared. The amorphous Ni40at.%Zr alloy maintained its high activity for 70 h at 723 K, after which it decreased drastically. The amorphous NiZrCr alloy, activated at 823 K for several hours, showed a high activity and gave much longer durability at 723 K. The increase in the alloy chromium content enhanced the activity and elongated the life time. Among the NiZr15at.%Cr alloys, the specimen containing 40 at.% Zr showed the highest activity for the decomposition of CFC-12 but the specimen with 70 at.% Zr could not even be activated. The characterization of the reacted specimens was carried out using X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray analysis and X-ray photoelectron spectroscopy. Their structures were significantly changed by the reaction, because they were exposed to corrosive HCl and HF, formed by the decomposition reaction of CFC-12.