Regina Palkovits

Herein, we present the production of either dimethyl ether (DME), methyl formate (MF) or dimethoxymethane (DMM), representing pivotal molecules for the green transformation of fuels and chemical industry, by the non‐oxidative gas‐phase conversion of methanol under the same reaction conditions. The product selectivity is optimized by tailoring the acidic and dehydrogenative sites of the bifunctional Cu/Hβ catalyst system by varying the SiO 2 /Al 2 O 3 ratio of the Hβ zeolite (25 and 520) and the Cu loading (0.5 and 20 wt %). At 240 °C, >99 % (DME), 74.5 % (MF), and 77.3 % (DMM) selectivity is achieved with the respective catalysts 0.5 %Cu/Hβ(25), 20 %Cu/Hβ(520), and 0.5 %Cu/Hβ(520). High acidic site concentration catalyzes DME formation, while the presence of Cu + species is crucial for DMM formation, and Cu 0 species mainly catalyze MF formation. A highly dynamic reaction behaviour is observed, when the dehydrogenative functionality is dominant ( i. e ., in the production of MF or DMM), presumably due to the dynamic nature of the Cu oxidation state, which is in turn influenced by possible by‐products (H 2 and H 2 O). While the catalytic activity in DME synthesis over 0.5 %Cu/Hβ(25) is remarkably stable over 1500 min TOS, the activity in MF and DMM production over 20 %Cu/Hβ(520) and 0.5 %Cu/Hβ(520), respectively, can be successfully regenerated.

In spite of numerous kinetic studies, the mechanism of the polyol hydrogenolysis on a Ru catalyst surface is still not fully understood. Here, the decomposition of the C 1 alcohol methanol can serve as an entry to the clarification of the mechanism. Therefore, kinetic experiments using a Ru/C catalyst and periodic DFT calculations on a Ru(0001) model surface were performed. A modeling of the Ru surface revealed that the surface is most likely covered with hydrogen adsorbates under experimental conditions. On a clean Ru model surface, the overall activation barrier is lower if less dehydrogenation steps occur on the substrate methanol before the C−O bond cleavage. Transferring the results from the clean to the hydrogen‐saturated Ru surface, the pathway via CH 2 O O−H formation and subsequent C−O cleavage is found to be the most favorable. This study shows that the surface coverage has a significant influence on the activation barrier.