Synthesis of Light Olefins from Bioethanol over Ni-MFI Catalysts

Abstract

The effects of Ni addition on the catalytic activity of MFI zeolite catalysts were examined with the ethanol conversion reaction under high space velocity conditions, using pure ethanol, ethanol diluted with water, and bioethanol produced from corn, and the effects of impurities on deactivation were evaluated. Addition of Ni to MFI zeolite strongly suppressed the formation of aromatic compounds, and greatly improved the selectivities for C3 and C4 olefins from pure ethanol, but decreased the selectivities for C3 and C4 olefins, and slightly reduced the suppression effect of the Ni site for aromatic formation from bioethanol. The yields of C3 and C4 olefins decreased with time-on-stream despite the presence of the Ni sites. XPS analysis of the catalysts after reaction at 673 K showed presence of oxidized carbon species, indicating the deposit of the impurity from the bioethanol. In addition, the electronic state of Ni after the reaction of bioethanol was also different to that after the reaction of reagent ethanol. XPS analysis showed the formation of Ni2O3 species or nickel sulfate during the reaction of bioethanol, which caused catalyst deactivation. In the reaction at 773 K, a large amount of filament carbon was deposited on the catalyst surface. These factors caused significant decreases in the formation of C3 and C4 olefins in the conversion of bioethanol.