Revealing the Interaction between Cu and MgO in Cu/MgO Catalysts for CO Hydrogenation to CH₃OH

In this work, the structure–performance relationship of Cu/MgO catalysts was established to unravel the role of MgO and the active sites for CO hydrogenation to CH3OH synthesis, by intrinsic kinetics, chemical titration, and a series of in situ (operando) spectroscopic characterizations. The turnover rates of CH3OH formation on Cu/MgO catalysts, especially when the Mg/(Mg + Cu) atomic ratio is 0.67, were significantly higher than that on monometallic Cu particles. We have demonstrated that the rates were insensitive to the particle size of Cu but depended linearly on the quantity of Cu–MgO interfacial sites. The interaction between Cu and MgO particles improved the dispersion of Cu particles and formed more highly active Cu–MgO interfacial sites as identified by precise characterization. Moreover, this study has also unraveled that both the HCO* and HCOO* species are predominantly reactive intermediates, and their sequential hydrogenation occurs concurrently for CH3OH formation over Cu/MgO catalysts during the CO–H2 reaction

Gas-Dependent Active Sites on Cu/ZnO Clusters for CH₃OH Synthesis

This study describes an instantaneously gas-induced dynamic transition of an industrial Cu/ZnO/Al2O3 catalyst. Cu/ZnO clusters become “alive” and lead to a promotion in reaction rate by almost one magnitude, in response to the variation of the reactant components. The promotional changes are functions of either CO2-to-CO or H2O-to-H2 ratio which determines the oxygen chemical potential thus drives Cu/ZnO clusters to undergo reconstruction and allows the maximum formation of Cu–Zn2+ sites for CH3OH synthesis

Gas-Dependent Active Sites on Cu/ZnO Clusters for CH₃OH Synthesis

This study describes an instantaneously gas-induced dynamic transition of an industrial Cu/ZnO/Al2O3 catalyst. Cu/ZnO clusters become “alive” and lead to a promotion in reaction rate by almost one magnitude, in response to the variation of the reactant components. The promotional changes are functions of either CO2-to-CO or H2O-to-H2 ratio which determines the oxygen chemical potential thus drives Cu/ZnO clusters to undergo reconstruction and allows the maximum formation of Cu–Zn2+ sites for CH3OH synthesis

Gas-Dependent Active Sites on Cu/ZnO Clusters for CH₃OH Synthesis

This study describes an instantaneously gas-induced dynamic transition of an industrial Cu/ZnO/Al2O3 catalyst. Cu/ZnO clusters become “alive” and lead to a promotion in reaction rate by almost one magnitude, in response to the variation of the reactant components. The promotional changes are functions of either CO2-to-CO or H2O-to-H2 ratio which determines the oxygen chemical potential thus drives Cu/ZnO clusters to undergo reconstruction and allows the maximum formation of Cu–Zn2+ sites for CH3OH synthesis

Gas-Dependent Active Sites on Cu/ZnO Clusters for CH₃OH Synthesis

This study describes an instantaneously gas-induced dynamic transition of an industrial Cu/ZnO/Al2O3 catalyst. Cu/ZnO clusters become “alive” and lead to a promotion in reaction rate by almost one magnitude, in response to the variation of the reactant components. The promotional changes are functions of either CO2-to-CO or H2O-to-H2 ratio which determines the oxygen chemical potential thus drives Cu/ZnO clusters to undergo reconstruction and allows the maximum formation of Cu–Zn2+ sites for CH3OH synthesis

Product Distribution Control for Glucosamine Condensation: Nuclear Magnetic Resonance (NMR) Investigation Substantiated by Density Functional Calculations

Selective conversion of glucosamine (GlcNH₂) to deoxyfructosazine (DOF) and fructosazine (FZ) with additives was investigated. Significantly enhanced yield of DOF can be improved to 40.2% with B­(OH)₃ as the additive. Chemical shift titration (via one-dimensional nuclear magnetic resonance (1D ¹H and ¹³C NMR)) and two-dimensional nuclear magnetic resonance (2D NMR) including ¹H–¹³C HSQC and ¹H–¹H COSY are used to investigate intermolecular interactions between B­(OH)₃ and GlcNH₂. Diffusion-ordered NMR spectroscopy (DOSY) was further employed to identify intermediate species. Mechanistic investigation by NMR combined with electron spray ionization–mass spectroscopy (ESI-MS) discloses that a mixed 1:1 boron complex was identified as the major species, shedding light on the promotional effects of B­(OH)₃, which is substantiated by density functional theory (DFT). Boron coordination effects make ring-opening and subsequent dehydration reaction thermodynamically and kinetically more favorable. Dehydration of dihydrofructosazine is a key step in controlling overall process (49.7 kcal/mol). Interestingly, chelating effect results in substantial reduction of this free-energy barrier (31.5 kcal/mol). Notably, FZ was gradually becoming the main product (yield up to 25.3%), with H₂O₂ as the oxidant