Issue 21, 1997

Hydrogen cyanide synthesis on polycrystalline platinum and 90:10 platinum[ndash ]rhodium surfaces

Abstract

The synthesis of HCN from methane-based feedstocks has been studied at relatively low temperatures (up to 780°C) and pressures (0.02–0.15 Torr) over both pure Pt and Pt–10%Rh alloy model catalysts. Steady-state synthesis of HCN is observed over Pt from CH4–NH3–O2 feed mixtures with a maximum in activity observed using a 1:1:0.5 mixing ratio. The activity of the Pt–10%Rh alloy under comparable conditions is significantly lower, indicating that Rh has an inhibiting effect on the synthesis reaction at these temperatures and pressures. Comparable steady-state levels of activity were not observed over Pt for pure CH4–NH3, CH4–NH3–CO2 or CH4–NO feed mixtures; in particular, for CH4–NH3 feeds in the absence of oxygen a high initial activity was seen to decay rapidly over time. The effects of various surface pretreatments of the Pt were found to be transitory, with a gradual return of the HCN activity to its normal level in CH4–NH3–O2 (1:1:0.5) mixtures in all cases, and the most beneficial pretreatment effect was observed for a simple physical surface roughening induced by mild ion bombardment. By contrast, pre-exposure of the catalyst surface to ethylene or ammonia at elevated temperatures led to an initial inhibition or decrease in the synthesis activity.

Article information

Article type
Paper

J. Chem. Soc., Faraday Trans., 1997,93, 3869-3878

Hydrogen cyanide synthesis on polycrystalline platinum and 90:10 platinum[ndash ]rhodium surfaces

A. Bockholt, I.S. Harding and R.M. Nix, J. Chem. Soc., Faraday Trans., 1997, 93, 3869 DOI: 10.1039/A704184E

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