Synergistic effects of phases in the selective oxidation of isobutane over supported (NH4)3HPMo11VO40 catalysts

Surface Acidity Dictates Proton Transport in WO3/ZrO2: Proton-Conductive Behavior and Mechanistic Insight

Development of inorganic proton conductors that are applicable in a wide temperature range is crucial for applications such as fuel cells. Most of the reported proton conductors suffer from limited proton conductivity, especially at low temperature. In addition, the mechanism of proton conduction in the conductors is not fully understood, which limits the rational design of advanced proton conductors. In this work, we report the use of metal oxide solid acid as a promising proton conductor. WO₃/ZrO₂ (WZ) with different surface acidities is synthesized by controlling the content of WO₃ on the surface of ZrO₂. It is demonstrated that proton conductivity of WZ samples is closely related with their acidity. WZ with the strongest acidity exhibits the highest proton conduction performance at low temperatures, with a proton conductivity of 3.27 × 10^-5 S cm^-1 at 14 °C. The excellent performance of the WZ-type proton conductor is clarified with theoretical calculations. The results show that the enhanced water adsorption and the lowered activation barrier for breakage of the O-H bond in surface-adsorbed water are the key to the excellent proton-conductive performance of WZ. The experimental results and mechanistic insights gained in this work suggest that WZ is a promising proton conductor, and tailoring the surface acidity of metal oxides is an effective approach to regulate their proton-conductive performance.

Selective Oxidation of Isobutane to Methacrylic Acid and Methacrolein: A Critical Review

Selective oxidation of isobutane to methacrolein (MAC) and methacrylic acid (MAA) has received great interest both in the chemical industry and in academic research. The advantages of this reaction originate not only from the low cost of the starting material and reduced process complexity, but also from limiting the use of toxic reactants and the production of wastes. Successive studies and reports have shown that heteropolycompounds (HPCs) with Keggin structure (under the form of partially neutralized acids with increased stability) can selectively convert isobutane to MAA and MAC due to their strong and tunable acidity and redox properties. This review hence aims to discuss the Keggin-type HPCs that have been used in recent years to catalyze the oxidation of isobutane to MAA and MAC, and to review alternative metal oxides with proper redox properties for the same reaction. In addition, the influence of the main reaction conditions will be discussed.