ProMet – CO₂ to Propylene via eMethanol

Green basic chemicals

The project “ProMet” develops a new competitive technology which allows for a more sustainable production of propylene. Propylene is an essential raw material in the chemical industry. The conventional propylene production is based on fossil raw materials. The most important process step in the “ProMet” process
is the the conversion of CO₂ into eMethanol via electrolysis. eMethanol is electrochemically produced methanol. If the required electricity originates from renewable sources, a “green” methanol is produced, which results in a “green” propylene by applying the methanol-to-propylene (MTP) technology. “Green” means here less greenhouse gas emissions compared to the conventional procedure. Besides, the “ProMet” process makes CO₂ accessible as a raw material.

The worldwide production of methanol and propylene mounts up to 86 and 100 million tons per year, respectively, with a yearly growth rate of seven and four per cent. A new sustainable route to methanol and propylene supplies a big market and allows to reduce greenhouse gas emissions to a great extent.

Electrochemical synthesis of methanol

Compared to the electrochemical conversion of CO₂ into formate or carbon monoxide (CO), the reaction to
methanol is much more ambitious, since here six electrons per molecule CO₂ have to be transferred instead of only two. While the key features current efficiency and current density reaching values of more than 90 percent and more than 100 mA/cm² for converting CO₂ into formate or CO, for eMethanol only 46 percent current efficiency and ~10 mA/cm² current density are reported. The aim of the project “ProMet” is a current efficiency of at least 70 percent and current densities of less than 75 mA/cm² for converting CO₂ into eMethanol. Alternative processes for the conversion of CO₂ into methanol require two to three process steps. Due to the single-step electrochemical synthesis of methanol from CO₂, the process should be intrinsically more beneficial, since resources are spared.

Scientific and economic expertise

The biggest challenge for the project is the identification of a catalyst for the electrochemical conversion of CO₂ into methanol, as well as the manufacture of a gas diffusion electrode (GDE) with this catalyst. GDEs show an extraordinary performance compared to routinely used planar electrodes if reactants from a gas phase and a liquid phase are involved.

The whole project comprises of six work packages (WP) and seven partners. At the Ruhr-University Bochum the screening to identify a proper catalyst will take place (WP1). The most promising materials will be manufactured to gas diffusion electrodes (GDEs), which will be electrochemically characterized and modeled (WP2). The best GDEs will be tested in a full electrolysis cell (WP3). In WP2 and WP3 the German Aerospace Center, the Clausthal University of Technology, and Covestro are involved. In WP4, process development, Fumatech will propose and develop proper membrane materials. Further, Air Liquide will investigate the usage of eMethanol in the existing MTP process to evaluate the new raw material’s suitability. The results will be used in the technoeconomic analyses (WP5), performed by the RWTH Aachen University. Also at RWTH Aachen University, a holistic ecological study of the “ProMet” process compared to alternative processes will be carried out (WP6). In the “ProMet” project a full process concept is developed for the conversion of CO₂ into propylene, and will be evaluated from technological, economical, and ecological perspectives.

ProMET project sheet download