No abstract

The reverse water gas shift reaction is considered to be a highly attractive catalytic route for CO2 recycling in a future sustainable economy. Copper-based catalysts are commonly used for this reaction due to their high activity and selectivity. However, their low thermal stability is problematic for long-term usage. Here, we introduce an in situ formed surface Cu–Al spinel as a highly active and stable catalyst for the reverse water gas shift reaction. Even at high weight hourly space velocities (300 000 mL g–1 h–1), we observed no detectable deactivation after 40 h of operation. Through in situ DRIFTS and DFT studies, it was found that 2-fold coordinated copper ions and 3-fold coordinated surface oxygen atoms constitute the active sites for this reaction.

No abstract

By varying acid site accessibility, we demonstrated that polyoxymethylene dimethyl ethers suffered from severe internal diffusion inside a MFI zeolite.

The role of Lewis and Brønsted acid sites and their potential synergy remains ambiguous for the production of polyoxymethylene dimethyl ethers (OME), which are suitable as a Diesel substitute. Here, this synergistic effect was investigated by using a series of beta polymorph A (BEA) zeolites with various degrees of Brønsted and Lewis acidity. Lewis acidity was introduced in dealuminated zeolites by Sn grafting in dichloromethane. These sites were only active in paraformaldehyde decomposition, OME growth, and acetalization. The Brønsted acid sites arising from bridging hydroxyl groups were active for all reaction steps, and notably for trioxane ring‐opening and dissociation to formaldehyde (FA), which did not occur on the Lewis acid sites. Presence of both Lewis and Brønsted acid sites led to a four‐fold increase in turnover frequency and a significant decrease of byproduct formation compared with the parent zeolite during OME synthesis from dimethoxymethane and trioxane. The synergistic effect between both types of acid sites is explained by FA insertion on Lewis acid sites leading to OME growth. Interaction between tetrahedral Sn and the carbonyl group of FA resulted in an activated carbonyl bond, which was likely the initial step for insertion of FA into OME.