The Structure of the Cu–CuO Sites Determines the Catalytic Activity of Cu Nanoparticles

The effect of nanosized ceria on supported Cu nanoparticles was investigated at an atomic level and correlated to the catalytic activity on the water–gas shift reaction (WGSR) rate. For Cu/Al₂O₃, increasing the Cu nanoparticle size leads to a decrease in the oxygen coverage and an increase in the bond length of Cu–O. When different loadings of nanosized ceria are introduced to the Cu/Al₂O₃ catalysts, no significant change occurred in the Cu particle size, the Cu–Cu bond length, or the oxygen coverage. However, ceria is able to interact with the Cu nanoparticles to increase the Cu–O bond length, and a linear correlation between ceria loading, Cu–O bond length, and WGSR rate was found. Hence, while previous reports claim that ceria leads to Cu nanoparticle stabilization or interface active sites, we have shown that the ceria tailors the Cu–O bond length, which has been shown to be a determinant of the WGSR rate

Production of 5-Hydroxymethylfurfural from Glucose Using a Combination of Lewis and Brønsted Acid Catalysts in Water in a Biphasic Reactor with an Alkylphenol Solvent

We report the catalytic conversion of glucose in high yields (62%) to 5-hydroxymethylfurfural (HMF), a versatile platform chemical. The reaction system consists of a Lewis acid metal chloride (e.g., AlCl₃) and a Brønsted acid (HCl) in a biphasic reactor consisting of water and an alkylphenol compound (2-<i>sec</i>-butylphenol) as the organic phase. The conversion of glucose in the presence of Lewis and Brønsted acidity proceeds through a tandem pathway involving isomerization of glucose to fructose, followed by dehydration of fructose to HMF. The organic phase extracts 97% of the HMF produced, while both acid catalysts remain in the aqueous phase

Amine Catalyzed Atomic Layer Deposition of (3-Mercaptopropyl)trimethoxysilane for the Production of Heterogeneous Sulfonic Acid Catalysts

The production of heterogeneous sulfonic acid catalysts was carried out using an amine-catalyzed atomic layer deposition process utilizing 3-(mercaptopropyl)­trimethoxysilane. The amine catalyst was employed to allow for low temperature deposition, since mercaptopropyl moieties undergo pyrolysis at ∼200 °C. The highest loading achieved using alternating MPTMS and water pulses, with piperidine as the catalyst, was found to be comparable to loadings achieved by means of other classical synthesis techniques. The growth per cycle varied dramatically at different stages of the deposition, contrasting significantly from other known atomic layer deposition processes. Depositions using known amine catalysts, NH₃ and pyridine, were compared to piperidine. NH₃ was found to yield loadings comparable to piperidine only when higher NH₃ partial pressures were used, while pyridine performed similarly to piperidine at the same partial pressures, but with a slower surface reaction rate. Depositions were monitored using a residual gas analyzer with the surface reaction directly measurable at low partial pressures of amine. Thermogravimetric analysis, Raman spectroscopy, ²⁹Si, and ¹³C CP/MAS NMR spectroscopy showed significant structural differences between the atomic layer-deposited and grafted materials. Mercaptopropyl groups attached to silica particles were oxidized to produce a sulfonic acid-functionalized mesoporous material. This catalyst was tested in the conversion of fructose to 5-(hydroxymethyl)­furfural, giving a higher turnover frequency than a commercial catalyst