TG/DTA/MS/IR study on decomposition of cadmium malonate hydrates in inert and oxidative atmosphere

摘要

Thermal decomposition of cadmium malonate hydrates was studied in dynamic helium and air atmospheres. It was found that content of hydration water in the initial sample strongly influences the way of decomposition reaction. The dehydration of cadmium malonate hydrate takes place in the temperature range 80-170℃. The anhydrous cadmium malonate decomposes at about 250℃. It was stated that the primary solid product of cadmium malonate decomposition is metallic cadmium. The gaseous products of cadmium malonate decomposition are CO_2, acetone, isobutylene and propyne and traces of water, acetic acid and oxygen. In helium majority of cadmium evaporates and the residue consists of small amount of elementary carbon formed in result of pyrolysis of malonate. The residue after decomposition of cadmium malonate with low amount of crystallization water molecules contains additionally CdO. The secondary reactions between decomposition products occur: oxidation of cadmium by oxygen in statu nascendi and formation of CdCO_3 in reaction between cadmium oxide and CO_2. In air cadmium instantaneously oxidizes and the final solid product of decomposition is CdO.