SOLID-STATE NMR OF C-13 IN ETHYLENE ADSORBED ON SILICA-SUPPORTED RUTHENIUM

A variety of experimental nuclear spin dynamics on13C, including standard cross-polarization (CP), CP with magic angle spinning (CP/MAS), CP/MAS with dipolar dephasing, and single-pulse experiments with and without proton decoupling have been applied to the study of adsorption and reaction of ethylene on silica-supported ruthenium. NMR of13C using CP/MAS allowed us to simultaneously observe the transformations of chemisorbed and weakly adsorbed molecules during reaction of ethylene to form products. Direct 13C excitation allowed quantitative measurements of the various species present. From these experiments it was determined that the decomposition of ethylene at room temperature formed strongly adsorbed species such as acetylide and alkyl groups. Recombination of adsorbed species and hydrogenation of ethylene occurred rapidly at room temperature, forming weakly adsorbed ethane and cis- and trans-2-butene that subsequently hydrogenated to butane. The strongly adsorbed species identified as acetylide was not appreciably consumed in the formation of products, although it most likely served as a source of hydrogen for other reactions. Spin counting revealed that there was one carbon in the strongly adsorbed layer for each surface ruthenium atom. © 1990, American Chemical Society. All rights reserved.