Ji Chul Jung

Solid Lewis acidity of boehmite γ-AlO(OH) and its catalytic activity for transformation of sugars in water

Aqueous-phase transformation of C3- and C6-sugars toward valuable intermediates such as lactic acid and 5-hydroxymethylfurfural (HMF) using boehmite, an abundant, inexpensive and simple aluminium oxide hydroxide γ-AlO(OH) was demonstrated. Pyridine-adsorbed Fourier transform infrared (FTIR) spectroscopy and trimethylphosphine oxide-adsorbed 31P magic angle spinning (MAS) nuclear magic resonance (NMR) revealed that boehmite had no Bronsted acid sites and a small amount of weak Lewis acid sites. The amount of Lewis acid sites and the initial reaction rate for lactic acid synthesis from dihydroxyacetone increased with increase of calcination temperature of boehmite whereas the selectivity for lactic acid remained unchanged and turnover frequency decreased. Boehmite afforded lactic acid selectively from aqueous C3-sugars solution with the yields of 32% and 42% from dihydroxyacetone and glyceraldehyde, respectively, which were higher than those of hydrotalcite, titanium oxide, tin oxide and tungsten oxide. Moreover, boehmite gave both lactic acid and HMF simultaneously from aqueous glucose solution as well as fructose. The total yields of lactic acid and HMF from aqueous glucose solution reached 40%. Boehmite was found to catalyse a variety of reactions including isomerization, retro-aldol condensation, dehydration and hydration in water.

Preparation of Cu/ZnO catalyst using a polyol method for alcohol-assisted low temperature methanol synthesis from syngas

A polyol method was used to prepare Cu/ZnO catalysts for alcohol-assisted low temperature methanol synthesis from syngas. Unlike conventional low temperature methanol synthesis, ethanol was employed both as a solvent and a reaction intermediate. Catalyst characterization revealed that Cu/ZnO catalysts were successfully and efficiently prepared using the polyol method. Various preparation conditions such as PVP concentration and identity of ZnO precursor strongly influenced the catalytic activity of Cu/ZnO catalysts. Copper dispersion and catalyst morphology played key roles in determining the catalytic performance of the Cu/ZnO catalyst in alcohol-assisted low temperature methanol synthesis. A high copper dispersion and platelike Cu/ZnO structure led to high catalytic activity. Among the catalysts tested, 5_Cu/ZnO_Zn(Ac)2 had the best catalytic performance due to its high copper dispersion.

Hydrogen Production Through Catalytic Dehydrogenation of Decalin over Pt/C Catalyst Using Activated Carbon Aerogel

To improve its textural properties as a support for platinum catalyst, carbon aerogel was chemically activated with KOH as a chemical agent. Carbon-supported platinum catalyst was subsequently prepared using the prepared carbon supports(carbon aerogel(CA), activated carbon aerogel(ACA), and commercial activated carbon(AC)) by an incipient wetness impregnation. The prepared carbon-supported platinum catalysts were applied to decalin dehydrogenation for hydrogen production. Both initial hydrogen evolution rate and total hydrogen evolution amount were increased in the order of Pt/CA

Pt@Cu/C Core-Shell Catalysts for Hydrogen Production Through Catalytic Dehydrogenation of Decalin

Pt@Cu/C core-shell catalysts were successfully prepared by impregnation of a carbon support with copper precursor, followed by transmetallation between platinum and copper. The Pt@Cu/C core-shell catalysts retained a core of copper with a platinum surface. The prepared catalysts were used for hydrogen production through catalytic dehydrogenation of decalin for eventual application to an onboard hydrogen supply system. Pt@Cu/C core-shell catalysts were more efficient at producing hydrogen via decalin dehydrogenation than Pt/C catalysts containing the same amount of platinum. Supported core-shell catalysts utilized platinum highly efficiently, and accordingly, are lower-cost than existing platinum catalysts. The combination of impregnation and transmetallation is a promising approach for preparation of Pt@Cu/C core-shell catalysts.