HCN Synthesis by Ammoxidation of Methane and Ethane on Platinum Monoliths

摘要

We have examined HCN synthesis by the ammoxidation of CH_4, C_2H_6, and CH_4/C_2H_6 mixtures in air or O_2 at atmospheric pressure on α-Al_2O_3 foam monoliths coated with 1-10 wt % Pt and on Pt-10% Rh gauzes. The HCN reaction system was found to be highly sensitive to the catalyst microstructure because we observed activation and differences in performance on catalysts with different support materials. For CH_4 ammoxidation on Pt monoliths we observe HCN yields > 63% based on CH_4 and NH_3 fed which is comparable to yields obtained on commercially used Pt-10% Rh gauzes (～65%). With C_2H_6 rather than CH_4, we achieve HCN yields of ～42% (carbon and nitrogen basis). We also examined CH_4/C_2H_6 mixtures (at fixed C/N and (C + N)/O_2) for HCN synthesis. HCN yields were found to decrease by 5-7% with increasing C_2H_6 in the feed hydrocarbon mixture (up to 14%). Results for experiments with Pt-10%Rh gauzes used commercially are shown in all cases to allow comparisons with Pt monoliths. C_2H_6 ammoxidation on Pt monoliths and gauzes at acetonitrile synthesis stoichiometries yields negligible amounts of higher nitriles ( < 0.01%), although HCN is produced on both. C_2H_4 is the dominant product on the monoliths while CO is the dominant product on the gauze.