Deep Oxidation of Methanol Using a Novel Pt/Boron Nitride Catalyst

Abstract

Deep oxidation of methanol was conducted using a novel Pt/BN catalyst in a steady-state-flow reactor. Hexagonal boron nitride (BN) is a graphitelike material in powder form with a specific surface area of 49 m2/g. A catalyst with 0.37 wt % Pt was prepared by the incipient wetness method using H2PtCl6 as a precursor dissolved in methanol. The reaction temperature ranged from −10 to 200 °C. The concentration of methanol varied from 1000 to 4000 ppmv, while the oxygen varied from 5 to 80% and was balanced with nitrogen. The volume hourly space velocity was approximately 50 000 h-1. Experimental results showed that a 50% methanol conversion could be achieved at room temperature (20 °C), reaching 95% conversion at 75 °C, while Pt/Al2O3, Dash 220 (a commercial Pt/alumina catalyst), and PtPd/CeO2/Al2O3 catalysts required considerably higher temperatures under the same conditions. The high oxidation activity of Pt/BN was attributed to the weak Pt−O bonding of the Pt clusters on the BN surface, which led to high oxidizing reactivity. Regression analysis revealed that the reaction order of methanol was 1, while that of oxygen was −0.6. A mechanism of the Langmuir−Hinshelwood model was established based on the experimental results. Kinetic analysis suggested that the methanol adsorption on Pt would be the rate-limiting step on the Pt/BN catalyst.