Synthesis of Ta-Cu-SiO2 catalysts by the aerosol process for the ethanol to butadiene reaction

Details

Supervisors

Debecker, Damien P.

Faculty

Faculté des bioingénieurs

Degree label

Master [120] : bioingénieur en chimie et bioindustries, à finalité spécialisée

Abstract

Bio-based process have become a focal point in fundamental and applied research, considering the actual context of petroleum insecurity. Thanks to environmental awareness, biomass valorisation and bio-based process are given prominence at the industrial scale. Butadiene, a highly reactive molecule, can be processed by polymerization or copolymerization to form so-called elastomers. These elastomers will form the basic units to form rubber, a widely used material in our modern societies. Nowadays butadiene production is fully petroleum-dependent through steam cracking. The process is highly energy-consuming and polluting by involving petroleum processing. Butadiene production by catalytic conversion of (bio)ethanol appears as sustainable alternative. Many different catalyst formulations have been reported in the literature since the beginning of the discovery of the ethanol to butadiene (ETB) reaction. Over 600 different materials have been screened including tantalum and copper-based with silica catalysts as a track to be furthered explored. This formulation displays suitable properties as a bifunctional catalyst, capable of achieving simultaneously dehydrogenation and dehydration reactions. Many synthetic techniques have already been explored and an innovative aerosol assisted sol gel (ASSG) approach is studied in this work. This synthesis method allows a one-step synthesis for homogeneous and mesoporous catalysts with high surface areas. The effect of copper and tantalum loadings was studied by modifying mass of Cu and Ta precursors in the ASSG process. 2wt.% of Ta and 4wt.% of Cu was highlighted as the optimal composition. Others synthesis methods were compared with catalyst of same composition such as impregnation or mechanical mixing of monofunctional catalysts. The impregnation synthesis showed better overall results with better butadiene yield and selectivity. Tantalum has a best activity when it is located out of the silica matrix instead of embed in the silica matrix as is the case with ASSG. The impregnation synthesis allows a better copper dispersion but copper showed better catalytic activity when it aggregates with ASSG. All synthesized catalysts in this study follow the same trend of deactivation with decreasing conversion, selectivity and yield in time. Spent catalyst study allows to draw some conclusions on the origin of this trend (coke formation). Further characterization has to be made to understand the others possible reasons for this decrease in efficiency.