The influence of the preparation method on the behaviour of PtGe catalysts supported on activated carbon in citral hydrogenation

The liquid-phase citral hydrogenation carried out over PtGe catalysts prepared by different techniques and supported on activated carbon powder purified and functionalized with nitric acid (C-PN) was investigated. In catalysts prepared by conventional successive impregnation (CI), Ge does not improve in an important way either the activity or the selectivity to unsaturated alcohols. Besides, PtGe catalysts prepared by controlled surface reaction (CSR) show much better activities and selectivities to unsaturated alcohols (UA). It is needed a large concentration of Ge to polarize the carbonyl group in the case of CI catalysts because Ge is located mainly over the support and small quantities would be deposited over the Pt particles. In PtGe catalysts prepared by CSR, Ge moieties would polarize the carbonyl group since they would be placed near PtGe nanoclusters, thus giving high selectivity to UA.