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首页> 美国政府科技报告 >Chemistry of oxygenates on transition metal surfaces: Activation of C- H, C-C, and C-O bonds. Progress report, December 15, 1991
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Chemistry of oxygenates on transition metal surfaces: Activation of C- H, C-C, and C-O bonds. Progress report, December 15, 1991

机译：过渡金属表面上的含氧化合物的化学：C-H，C-C和C-O键的活化。进展报告，1991年12月15日

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Goal is to understand the requirements for and competition between activation of C-H, C-C, and C-O bonds in the synthesis and decomposition of oxygenates on transition metal surfaces. Efforts during the past year was devoted primarily to the role of activation of (beta)-CH bonds in decarbonylation of higher oxygenates on surfaces of metals such as Rh and Pd; studies were completed of more than a dozen C(sub 1)-C(sub 3) oxygenates on Rh(111), and progress was made with reagents for which (beta)-CH scission is blocked. It is shown that alcohols and aldehydes do not react via a common pathway on on Rh(111). Ethanol and acetaldehyde are formed from CO + H(sub 2) by parallel routes on Rh catalysts which do not contain interacting supports or oxide promoters; i.e., the two compounds result from CO insertion into different metal-hydrocarbon bonds. Aldehydes decarbonylate via (alpha)-CH scission to form acyl, followed by C-C scission to release an alkyl ligand; this ligand undergoes hydrogenation and dehydrogenation steps. Alcohols form surface alkoxides, but these do not dehydrogenate further to the aldehydes, they release CO + H(sub 2) but no volatile hydrocarbon. These results indicate that (beta)-CH scissors to form a surface oxametallacycle intermediate; supporting evidence is spresented for this intermediate. Chemistry of alcohols blocked to different extends at the (beta)-position was also studied; complete blocking (CF(sub 3)CH(sub 2)OH) forces the reaction to follow the aldehyde-acyl path, while partial substitution at the (beta) position (branched alcohols) favors the oxametallacycle pathway. (DLC)

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