Transition metals promoting Mg-Al mixed oxides for conversion of ethanol to butanol and other valuable products: Reaction pathways

This paper is focused on the catalytic synthesis of butanol from ethanol in a microflow reactor at a constant weight hour space velocity (4.5 h−1) and different reaction temperatures (280, 300 and 350 °C). The reaction was catalysed by Mg-Al mixed oxides (i) pure and (ii) with added transition metals such as Co, Ni, Cu, Mn and Cr (synthesis by coprecipitation). The solid materials were deeply characterised. Other products, such as ethylene, 1,1-diethoxyethane, ethyl acetate, 1-hexanol, etc. were also determined and the reaction pathway for their formation was examined. The metals Cr and Mn did not increase the catalyst activity, which was quite low (maximum 19% at 350 °C). However, the metals Co and Ni positively influenced butanol formation, while Cu positively influenced ethyl acetate formation. Moreover, ethanol conversion increased with increasing temperature, but at the same time the selectivity to butanol decreased. [Display omitted] •The Guerbet reaction (ethanol to butanol) was catalyzed by Mg-Al mixed oxides.•The transition metals (Co, Ni, Cu, Mn and Cr) were added during co-precipitation.•A number of side products was determined and the reaction scheme was suggested.•The influence of transition metals on the reaction products was described.