The Mechanism of Catalyzed Hydrogen–Deuterium Exchange on Gold Deposited over Poly(tetrafluoroethylene)

The H2–D2 exchange reaction over Au(0.3%)/PTFE(poly(tetrafluoroethylene)) was studied. The apparent activation energy was found to be 29 kj mol−1. The dependence of the reaction rate on the total pressure was measured at 518, 432, and 393 K. It was found that the pressure exponent of the exchange reaction decreases with the increase in the total pressure and that in the lower pressure range, the reaction order is as high as 2. The rate equation obtained from the pressure dependence was R=k{KP⁄(1+KP)}2. Accordingly, it was concluded that the H2–D2 exchange reaction over gold takes place between molecularly adsorbed hydrogen and deuterium through a dimeric intermediate. The heat of adsorption on the active sites in the gold surface was 5.9 kj mol−1.