Effects of preparation variables on the activity of alumina-supported platinum catalysts for liquid phase cinnamaldehyde hydrogenation

Alumina-supported platinum catalysts were prepared through different metal loading and reduction procedures. The platinum precursors were loaded by im pregnation and ion-exchange and then reduced by hydrogen at high temperatur es and by sodium tetrahydroborate solution at a low temperature of 35 degre es C. The low-temperature reduced (LR) catalysts were found to produce cinn amyl alcohol in high selectivities in the liquid phase hydrogenation of cin namaldehyde, irrespective of the method of metal loading. The high-temperat ure reduced (HR) catalysts prepared with ion-exchange produced hydrocinnama ldehyde and cinnamyl alcohol; the selectivity of the former was larger than that of the latter. In contrast, the HR catalysts prepared with impregnati on produced large amounts of by-products and small amounts of hydrocinnamal dehyde and cinnamyl alcohol. When these HR catalysts were additionally trea ted with sodium tetrahydroborate solution, they indicated product distribut ions similar to the LR catalysts. (C) 1999 Elsevier Science B.V. All rights reserved.