Power2C4: By catalysis from ethanol to butadiene

The goal of Power2C4 is to develop a new catalytic process for the production of butadiene and other C4-olefins from a synthesis gas of CO₂ and electrolytically produced H₂. The focus is on a two-step butadiene synthesis: In the first step, ethanol is produced from the synthesis gas, which is converted to butadiene in a second step using a new catalyst. For this synthesis to succeed, a suitable catalyst system must be identified and tested. Subsequently, the entire power-to-butadiene process chain is evaluated – with a view to both the economic efficiency of the process chain and the sustainability of the new production path for butadiene. The framework for the work package is provided by the "Virtual Institute – Power to Gas and Heat" – a consortium of research institutes working on adaptive technology measures for the power, gas and water system.

Butadiene plays an important role in industry: the unsaturated hydrocarbon is used in the production of synthetic rubber. Until now, butadiene and other C4 olefins have been produced by thermal cracking of the petroleum fraction naphtha. Due to the scarcity of oil reserves and the resulting increase in the price of naphtha, sustainable, alternative production processes based on power-to-x are gaining in importance.

Another advantage of the alternative production process of butadiene is that it helps to compensate for temporary and spatial differences between the production and demand for electricity from renewable energies. In other words, surplus electricity from wind power or photovoltaic plants is used to produce another product - in this case C4-olefins.

The conversion of ethanol to butadiene (ETB) proceeds via several coupled reaction steps – from the formation of acetaldehyde to aldol condensation and dehydration. In the project, a new promising catalyst system based on artificial saponites was synthesized and modified. Compared to the unmodified catalyst starting material, the butadiene selectivity could already be significantly increased during catalyst optimization; however, the results show further potential for improving catalyst performance. The catalytic activity is tested in a specially constructed testing plant.

Based on a simulative balance of product preparation, a life cycle analysis (LCA) was carried out for the sustainability assessment of the power-to-butadiene process. A total of eleven different scenarios for the synthesis of butadiene from ethanol were considered. The results of the process evaluation show that, depending on the ethanol and energy source used, the Lebedev process has the potential to produce butadiene and thus also styrene-butadiene rubber from bio-based ethanol or CO₂-based ethanol. The catalyst used for butadiene synthesis, which requires high butadiene selectivity to reduce the separation effort, is also an important factor. The use of residual biomass streams, such as bagasse or straw, opens up the possibility of reducing greenhouse gas emissions. In addition, an electricity mix with higher proportions of renewable energy contributes to greenhouse gas reductions as expected.

• Gas and Heat Institute Essen e.V. (GWI)
• Institute of Energy Economics at the University of Cologne (ewi)
• Research Center Jülich (FZJ)
• Ruhr-University Bochum (RUB), Chair of Fluid Process Engineering
• Wuppertal Institute (WI)
• ZBT Duisburg (ZBT)