A novel BN supported bi-metal catalyst for selective hydrogenation of crotonaldehyde

A series of boron nitride (BN) supported Pt-Sn catalysts was prepared with a co-incipient wetness method employing hexachloroplatinic acid and tin(II) chloride. Pt loading was fixed at 1.1 wt%; Sn loading varied from 0.25 to 0.75 wt% on BN support. Selective hydrogenation of gas-phase crotonaldehyde was conducted in a steady-state flow reactor with temperatures ranging from 40 to 100 °C. The selectivity of crotyl alcohol reached over 80%. An optimum yield of crotyl alcohol reached 38% at 60% conversion of crotonaldehyde at 80 °C using Pt-Sn(0.75)/BN catalyst, while Pt-Sn(0.75)/γ-Al2O3 yielded less crotyl alcohol and a lower rate of crotonaldehyde conversion. The maximum yield rate of crotyl alcohol was 2.4 mmol/(g-cat. h) at 80 °C. Negligible deactivation was found during reaction for 4-6 h. The crystalline phases of PtSn and SnPt3 alloys were observed from the XRD spectra of Pt-Sn/BN catalysts with various Sn loadings. The selectivity of crotyl alcohol increased with Sn loadings but the activity values of the catalysts went through a maximum. The H2 reduction at 300 °C gave an optimum Pt-Sn alloy particle size so that the selectivity of crotyl alcohol increased without losing catalyst activity. The CO bond of crotonaldehyde was preferentially hydrogenated and the hydrogenation of CC bond was suppressed, resulting in the increase of crotyl alcohol selectivity.