The influence of zinc loadings on the selectivity control of bio-ethanol transformation over MgO-SiO2 catalysts

Catalytic transformation of ethanol has been studied over a series of MgO-SiO 2 composite catalysts with different ZnO loadings. Vast differences in product selectivity are obtained by varying ZnO loadings in enabling the control over product distribution. Our results reveal that MgO-SiO 2 composite catalysts with low ZnO loadings tend to show an enhanced efficiency for C C bond coupling and exceptionally high selectivity to 1,3-butadiene whereas the high ZnO loadings favor the formation of acetaldehyde via dehydrogenation. Thorough analysis of characterization results via XRD, BET, IR, TPD, and 29 Si MAS NMR indicates that ZnO loading influences the extent of MgO and SiO 2 interaction during preparation, and the surface acid-base chemistry, which were both found to correlate with the catalytic performance. This study proposes that the Mg O Si interfacial structure formed by the strong MgO and SiO 2 interaction at low ZnO loadings is of prime importance for the formation of 1,3-butadiene, benefiting from the desirable properties of balanced dehydrogenation and C C bond coupling while excess ZnO loadings destroy the Mg O Si interfacial bonds over the MgO-SiO 2 composite catalysts, which are the key structures required for C C bond growth.