MORPHOLOGICAL AND SURFACE STUDIES OF ULTRASONICALLY TREATED RANEY-NICKEL HYDROGEN-DEUTERIUM EXCHANGE CATALYSTS

Previous surface studies of ultrasonicated Raney nickel catalysts have shown that ultrasonication leads to reduction of surface Ni species to the metallic state. Surface impurities that may poison the Raney nickel catalyst have also been removed during ultrasonication. Negligible increases in surface area are observed after ultrasound treatment of the catalysts even though their activities and selectivities in 2H incorporation into carbohydrates and glycosphingolipids are markedly improved. The surface and morphological changes taking place during ultrasonic treatment are the focus of this paper. Cr3+- and Mo -doped Raney Ni catalysts have been studied before and after ultrasonication with scanning electron microscopy, X-ray photoelectron spectroscopy, and secondary ion mass spectrometry. Results of these studies indicate that the reason for enhanced selectivity is that fresh Ni surfaces are available after ultrasonication due to crack propagation of the Raney Ni catalysts. The surface Cr3+ content also increases after sonication, which may explain why these particular catalysts show the fastest rates of 2H incorporation in carbohydrates and glycophosphingolipids. © 1990, American Chemical Society. All rights reserved.