Methanol-induced hydrogen permeation through a palladium membrane

The dehydrogenation of methanol and the subsequent permeation of hydrogen t hrough a 25 mu m thick palladium film has been studied in a catalytic membr ane reactor. At the temperature studied, 350 degrees C, the decomposition p athway for methanol on clean palladium surfaces is believed to lead to H-ad and a carbonaceous overlayer. The released hydrogen can either desorb or p ermeate the palladium membrane. During a continuous supply of methanol hydr ogen permeation is reduced and, eventually, totally quenched by the growing carbon monoxide/carbon coverage. Adding oxygen in the methanol supply can balance the increasing carbonaceous coverage through the production of carb on dioxide. In such a case, it is concluded that no CO bond scission occurs . The methanol/oxygen ratio is crucial for the hydrogen permeation rate. Is otope-labelled methanol, CH3OH, CH3OD, CD3OH and CD3OD, shows that it is pr eferentially the methyl (or methoxy) hydrogen that permeates the membrane. (C) 1999 Elsevier Science B.V. All rights reserved.