SULFATE ACCUMULATION IN COMMERCIAL PD-PT AL2O3 AND PT/AL2O3 CATALYSTSUSED FOR REMOVAL OF HYDROGEN FROM CARBON-DIOXIDE/

An investigation of sulfate accumulation in commercial Pd-Pt/Al2O3 and Pt/Al2O3 catalysts used for the elimination of hydrogen from carbon d ioxide by the H-2-O-2 reaction has been conducted. Two types of intera ction between sulfate and Al2O3, i.e. surface deposition (SO3 or SO42- groups bonded to Al2O3 surface) and bulk sulfation (formation of alum inum sulfate hydrate), were found, which caused a drastic decrease in surface area and change in support structure. Pd(Pt) played an importa nt role not only in sulfate formation but also in the solid-state reac tion between sulfate and Al2O3. Energy dispersive X-ray revealed diffe rent sulfate distributions in catalyst pellets, i.e. 'uniform', 'egg s hell' and 'egg white' types. A model for the sulfate group transport r eaction is proposed to elucidate these sulfate distribution processes, and the relationship between the reaction temperature, the properties of the Al2O3 support and sulfate deposition rate, content, structure and distributions are discussed.