The paring mechanism of the aromatic cycle of the hydrocarbon pool is reinvestigated based on the heptamethylbenzenium cation adsorbed within H-SSZ-13 using quantum chemical calculations.

Templated encapsulation of platinum-based catalysts promotes high-temperature stability to 1,100 °C.

A combination of low energy ion beam deposition and mass resolved thermal desorption spectroscopy is applied to analyze the binding behavior of two nonplanar polycyclic aromatic hydrocarbons (PAHs) to highly oriented pyrolytic graphite (HOPG) surfaces—also concerning their lateral dispersion interactions. In particular, the fullerene precursor C60H30 (FPC) and rubrene C42H28 are studied. Due to their smaller contact areas, both molecules exhibit significantly weaker binding energies to the HOPG surface compared to planar PAHs of similar size: C60H30 is bound to the surface by 3.04 eV, which is 0.6 eV lower than for a fully planar homologue. For rubrene, an isolated molecule–substrate binding energy of 1.59 eV is found, which is about 1 eV less than that of the corresponding planar homologue hexabenzocoronene C42H18. In contrast to FPC, rubrene shows a significant (intermolecular) lateral dispersion contribution to the binding energy as the submonolayer coverage increases.

The stability and reactivity of Lewis and Brønsted acid sites at the H-SSZ-13 surface are investigated for the (101) and (001) surfaces. We focus on the conversion of methanol to dimethyl ether (DME) as a probe reaction that is prototypical for the reactivity of acidic zeolites, for example, in the methanol-to-olefins process. We use periodic density functional theory (DFT) calculations in combination with highly accurate DLPNO-CCSD(T) calculations on cluster models. At Brønsted acid sites, DME can be formed via concerted and stepwise mechanisms. The barriers for acid sites located at the surface are comparable to those located in the bulk. DME formation on a Lewis acid site is similar to the concerted mechanism since two adsorbed methanol molecules react with each other directly. However, the oxygen of the adsorbed methanol is bound to the Al atom and an analogy can therefore also be drawn with a methoxy group and thus the second step of the stepwise mechanism on Brønsted acid sites. The barriers for DME formation on a Lewis acid site are more similar to the concerted mechanism of the Brønsted acid sites and are therefore at 400 °C significantly higher than the stepwise mechanism at Brønsted acid sites.

Stable catalysts are essential to address energy and environmental challenges, especially in harsh environment applications (high temperature, oxidizing atmosphere, steam). In such conditions, supported metal catalysts deactivate due to sintering – a process where initially small nanoparticles grow into larger ones with reduced active surface area. Strategies to stabilize them lead to decreased performance. Here, we report stable catalysts prepared through the encapsulation of platinum particles inside an alumina framework. These catalysts do not sinter at 800 °C in the presence of oxygen and steam, conditions in which conventional catalysts sinter to large extents, while showing similar reaction rates. Extending this approach to Pd/Pt bimetallic catalysts leads to maintained small particle size at temperatures as high as 1,100 °C in air and steam. This strategy can be broadly applied to other metal and metal oxides for applications where sintering is a major cause of materials deactivation.