Recent Breakthroughs in the Conversion of Ethanol to Butadiene.

1,3-Butadiene is traditionally produced as a byproduct of ethylene production from steam crackers. What is unusual is that the alternative production route for this important commodity chemical via ethanol was developed a long time ago, before World War II. Currently, there is a renewed interest in the production of butadiene from biomass due to the general trend to replace oil in the chemical industry. This review describes the recent progress in the production of butadiene from ethanol (ETB) by one or two-step process through intermediate production of acetaldehyde with an emphasis on the new catalytic systems. The different catalysts for butadiene production are compared in terms of structure-catalytic performance relationship, highlighting the key issues and requirements for future developments. The main difficulty in this process is that basic, acid and redox properties have to be combined in one single catalyst for the reactions of condensation, dehydration and hydrogenation. Magnesium and zirconium-based catalysts in the form of oxides or recently proposed silicates and zeolites promoted by metals are prevailing for butadiene synthesis with the highest selectivity of 70% at high ethanol conversion. The major challenge for further application of the process is to increase the butadiene productivity and to enhance the catalyst lifetime by suppression of coke deposition with preservation of active sites. [ABSTRACT FROM AUTHOR]