Bimetallic selox catalysts

Platinum and palladium are effective catalysts for alcohol oxidation when used alone however, significant stability and selectivity improvements have been observed on incorporation of a second (usually less active) metal promoter such as Bi, Pb, and Sn [63-65]. These observations are common to aerobic selox of allyhc and benzylic alcohols, as well as polyols such as propylene glycol [64] and glycerol [66]. In the case of Bi, in situ X-ray absorption spectroscopy (XAS) and attenuated total reflection infrared spectroscopy (ATR-IR) indicate that the promoter protects Pt against deactivation by overoxidation and prevents site blocking by, for example, aromatic solvents [67]. 

Similar synergic Au-Pd interactions were reported for bimetallic Au-Pd catalysts supported on polyaniline (PANI) [79] for benzyl alcohol oxidation. Here, the colloidal preparative route provided a narrow particle size distribution ( 3nm) with a Pd-rich shell encapsulating an Au-rich core. In this instance, the optimal composition was Au Pd =1 9. Benzyl alcohol oxidation has likewise been studied over an Au-Pd/Ti02 catalyst in which the deposition-precipitation method was used to improve the particle size distribution and activity versus wet impregnation [80]. In contrast, liquid-phase oxidation of cinnamyl, benzylic, octenol, and octenal 

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