The effect of lanthanum in Cu/La(-Zr)-Si oxide catalysts for aqueous ethanol conversion into 1,3-butadiene

This paper presents the results of an investigation of three (Cu/La-Si and Cu/Zr-Si) and four (Cu/La-Zr-Si) component oxide systems in aqueous ethanol conversion into 1,3-butadiene, with special accent to the effect of lanthanum in the catalyst composition. The catalysts were characterized by HRTEM, SEM, DR UV-vis, in situ near ambient pressure X-ray photoelectron spectroscopy (NAP-XPS), FTIR with pyridine, and TPD-CO2. The high (>= 65%) 1,3-butadiene selectivity is achieved during the conversion of both rectified and aqueous ethanol over the studied catalysts. Catalyst activity of the four-component oxide systems depends on an introduction order of the components, which determines acid-base characteristics of the surface. A modification of the Cu/Zr-Si catalyst with lanthanum increases their activity in aqueous ethanol conversion into 1,3-butadiene. The positive effect of lanthanum addition into Cu/Zr-Si catalyst can be explained by the formation of lanthanum containing base sites like [La-(O)double over dot-Si] and [La-(O)double over dot-H] being tolerant to the action of water. The differences in the interaction of reaction intermediates with surface Zr-and La-containing sites are found out by C 1 s NAP-XPS measurements, and the effect of H2O on adsorption of carbon coke, ethoxy species and acetaldehyde over the catalyst surface is shown.