Autothermal catalytic partial oxidation of bio-oil functional groups: Esters and acids

The catalytic conversion of esters and carboxylic acids into synthesis gas or chemicals could permit optimal utilization of organic intermediates such as pyrolysis bio-oils. To examine the ester moiety, two esters, ethyl lactate and ethyl propionate, and two acids, lactic acid and propionic acid, were reformed by catalytic partial oxidation. Autothermal reforming was examined over platinum and rhodium based catalysts supported on alumina foam monoliths at a contact time on the order of 10 ms. Conversions >98% were observed for all four fuels. The addition of cerium or lanthanum was found to increase the selectivity to synthesis gas. At higher fuel to oxygen ratios, nonequilibrium species such as ethylene and acetaldehyde were observed. Ethyl propionate produced twice as much ethylene as ethyl lactate but very little acetaldehyde. The additional hydroxyl group in ethyl lactate produced acetaldehyde such that the ratio of ethylene to acetaldehyde was ∼1:1. The results provide evidence that the homogeneous decomposition of esters to intermediate acids can contribute to the overall reforming process. Products are highly tunable between synthesis gas and olefins by varying the fuel-to-oxygen ratio and the catalyst.