세미나

Oxygenates such as ethanol, acetic acid, acetone, and propanoic acids are readily produced by fermentation processes from biomass. Their conversion via oxygen elimination and chain lengthening is critical to the production of olefins which are platform molecules for fuel and chemical production. We found that mixed metal oxides such as ZnxZryOz with controlled Lewis acid/base pairs can enable cascade dehydrogenation, ketonization, and aldolization reactions of ethanol to selectively form isobutene. Aldolization is identified to be the rate limiting step. Zn addition is found to substitute Zr cations which subsequently increases the basicity of bridging O and accelerates the alpha hydrogen abstraction from alkanones to form enols. ZnxZryOz catalysts are also efficient in one-step conversion of acetic acid to isobutene without the formation of ethylene and propylene by-products. The presence of propanoic acid is found to be beneficial in the conversion of acetic acid to olefins with the chain length of olefins controlled by cross-aldolization of alkanones formed from acetic acid and propanoic acid. Besides isobutene, ethanol can also be converted to butenes or 1,3-butadiene on ZrO2-SiO2 supported Cu and Ag catalysts. Ag plays an important role in controlling the selectivity with highly dispersed Ag favoring the desired pathway for the formation of 1,3 butadiene. Cu selectively hydrogenate C=C bond over C=O bond, leading to desired reaction pathway to butenes with drastically improved catalyst stability.