Nanoparticulate model catalysts for the single-step synthesis of dimethyl ether

Fuel production and development of new routes to base chemicals from renewable resources are currently drawing much attention worldwide. The production of synthesis gas (CO + H2), e.g., from biomass-derived feedstock and its conversion to methanol, dimethyl ether (DME), or gasoline provides an attractive option. Recently, DME has attracted a lot of interest not only as liquefied petroleum gas for domestic applications and intermediate product for various base chemicals but also as a clean diesel substitute. Traditionally, DME is obtained in a two-step process, where methanol is produced from syngas with a Cu-based catalyst in the first stage, followed by methanol dehydration to DME with an acidic catalyst in the second stage. Alternatively, methanol synthesis is coupled in situ with the condensation to DME and immediately removed from the equilibrium in the single-step, syngas-to-DME (STD) process. The STD process has several advantages, e.g. the reduction of investment costs and a lower optimum CO/H 2 ratio, which favors the use of biomass-derived syngas. The design of STD catalysts remains a crucial issue for enhancing the catalytic performance. ... mehrIn this context, model systems based on well-defined nanoparticulate precursors may contribute to a more fundamental understanding of structure-property relationships for future design of highly effective catalysts. Here, we address the design of bifunctional STD catalysts. Well-defined colloidal Cu/Zn-based nanoparticles were applied as precursors for the methanol active component. Different synthetic pathways were developed for synthesizing colloidal Cu/Zn-based nanoparticles, while ensuring close contacts between the Cu nanoparticles and the Zn phase. Pure Cu nanoparticles were used as a reference. A series of bifunctional STD catalysts was prepared, where the nanoparticles were either directly supported on the dehydration catalyst or integrated into the STD catalyst by physical mixing. Catalytic tests were performed in a single continuous-flow laboratory reactor, using simulated biomass-derived, CO-rich syngas (H2:CO ratio of 1:1). By using this approach, active catalysts for the STD reaction with high DME selectivity were obtained.