Deactivation of titanium during temperature-induced hydrogen absorption–desorption cycling: II. Effects of hydrocarbons

Thermoprogrammed hydrogen absorption and desorption on titanium has been studied in the presence of propane and propene. Consecutive absorption–desorption cycles performed in steady flows of H2/C3H8 and H2/C3H6 showed fast deactivation of titanium, as manifested by a 10-fold drop in hydrogen uptakes in the second cycle. Reaction of titanium with hydrocarbons or traces of oxygen and water leading to the formation of carbo-hydrides and oxides, respectively, was found to be responsible for the deactivation, as reflected by TPR experiments with varying contents of hydrocarbons and impurities. Prolonged contact of titanium with propane at 720 K caused the formation of a cubic titanium carbo-hydride phase, as evidenced by XRD. A juvenile surface of titanium formed during hydriding–dehydriding cycles appeared to be especially susceptible to hydrocarbons. Treatment of a juvenile surface with a H2/C3H8 mixture at elevated temperatures resulted in complete inhibition of H2 absorption.