Conversion of aqueous ethanol/acetaldehyde mixtures into 1,3-butadiene over a mesostructured Ta-SBA-15 catalyst: Effect of reaction conditions and kinetic modelling

This paper studies key issues for the design of industrial ethanol to 1,3-butadiene two-step processes, focusing on the second catalytic reaction step, for which a Ta-SBA-15 catalyst was chosen as a representative of the new generation of two-step catalysts. The important practical aspects studied were: i) the effect of operating conditions and the presence of impurities (water) in the ethanol feedstock on the performance of the catalyst, ii) stability and regeneration of the catalyst, and iii) the development of a kinetic model that can be used as a tool for designing the industrial process. The results showed that there are large non-linear interacting effects between the reaction conditions (temperature, space velocity and ethanol/acetaldehyde mole ratio) which must be carefully selected to optimize the catalyst performance. When shifting from an anhydrous to an aqueous ethanol/acetaldehyde feed (7.5 wt% water), catalyst performance at high temperature barely changed while at low temperature, conversion of ethanol and acetaldehyde decreased. Water in the feed largely increased the stability of Ta-SBA-15 catalyst. Finally, a kinetic model of a fresh catalyst was developed, whose novelty lies in the use of kinetic equations that account for the effect of water in the feed on the catalyst performance.