ABSTRACT The selective hydrogenation of the dihydrothio-pyranone system over Ru and Pd catalysts supported on carbon or alumina in the presence of basic and acidic additives has been investigated. The hydrogenation of 2,3-dihydro-1H-naphtho[2,1-b]thiopyran-1-one (la) over both catalysts produced hydrodesulfurization (HDS) and hydrodeoxygenation (HDO) products, simultaneously. When an alkali is added, especially potassium hydroxide, the yields of HDS products increased from about 14% to 78%, while the yields of HDO products decreased from about 70% to 16%. When an alkali was added an effect similar to la was not produced. That is 2,3-dihydro-4H-naphtho[1,2-b]thiopyran-4-one (Ib) and benzothiopyran-4-one (XIII) was not observed. The addition of alkali was specific for the hydrogenation of la. On the other hand, the addition of hydrochloric acid in the hydrogenation of la produced mostly HDO products.
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