Byoung Kyu Kwak

Promoter effect of Pd in CuCr2O4 catalysts on the hydrogenolysis of glycerol to 1,2-propanediol

CuCr2O4 catalysts containing various amounts of Pd (Pd–CuCr) were prepared by a co-precipitation method and examined for use in the conversion of glycerol to 1,2-propanediol (1,2-PDO). Pd was observed to be highly dispersed in a CuCr2O4 spinel structure and conferred unique reduction characteristics of a CuCr2O4 catalyst. After reduction, the amounts of surface exposed Cu0 species and occluded hydrogen species were much larger in the case of added Pd, the Pd–CuCr catalyst, compared to a pure copper chromite catalyst. The Pd–CuCr catalyst utilized hydrogen very efficiently, resulting in an enhancement in the catalytic activity for the conversion of glycerol to 1,2-PDO, even at a relatively low hydrogen pressure. The Pd0.5–CuCr catalyst (containing 0.5 wt% of Pd) showed a total yield of 93.9%, with a selectivity approaching 100% for 1,2-PDO at a hydrogen pressure of 4 MPa. In a kinetic study, the effects of H2 pressure and the concentration of glycerol on the initial rate were examined. Based on the results, the palladium promoter (Pd–CuCr) enhanced the rate constant by about 1.7 times compared with copper chromite. The results provide a basis for the production of 1,2-PDO from glycerol using a process which is both environmentally benign and has improved economics.

Capturing Coke Precursors in a Pd Lattice: A Carbon-Supported Heteropoly Acid Catalyst for the Dehydration of Glycerol into Acrolein

Supported heteropoly acid catalysts are frequently used in the dehydration of glycerol into acrolein because of their high activity. However, they are easily deactivated by coke that can become deposited on the catalyst surface. Herein, we report a technique that significantly decreases coke formation by capturing coke precursors in a Pd lattice. The Pd‐added H3PW12O40/C catalyst (Pd‐PWC) showed stable catalytic activity and the amount of deposited coke formed was decreased to about 40 % of that without Pd addition. The catalysts were characterized by XRD, HR‐TEM, XPS, NH3‐TPD, and TGA methods. These results showed that the palladium lattice on the carbon support was easily loosened and that coking precursors were incorporated into the Pd lattice of the catalyst under the reaction conditions used. Consequently, the amount of coke that was deposited onto the active sites of the catalysts was significantly decreased.

Modeling human exposure levels to airborne volatile organic compounds by the hebei spirit oil spill.

Objectives The goal was to model and quantify the atmospheric concentrations of volatile organic compounds (VOCs) as the result of the Hebei Spirit oil spill, and to predict whether the exposure levels were abnormally high or not. Methods We developed a model for calculating the airborne concentration of VOCs that are produced in an oil spill accident. The model was applied to a practical situation, namely the Hebei Spirit oil spill. The accuracy of the model was verified by comparing the results with previous observation data. The concentrations were compared with the currently used air quality standards. Results Evaporation was found to be 10- to 1,000-fold higher than the emissions produced from a surrounding industrial complex. The modeled concentrations for benzene failed to meet current labor environmental standards, and the concentration of benzene, toluene, ortho- meta- para-xylene were higher than the values specified by air quality standards and guideline values on the ocean. The concentrations of total VOCs were much higher than indoor environmental criteria for the entire Taean area for a few days. Conclusions The extent of airborne exposure was clearly not the same as that for normal conditions.

Effect of acid type in WOX clusters on the esterification of ethanol with acetic acid

Tungsten oxide clusters supported on silica (WOX/SiO2) with different W loading levels and the effect of acid type on the esterification of acetic acid with ethanol were examined. The catalysts were characterized using various techniques (XRD, Raman spectroscopy, NH3-TPD and FT-IR) to investigate the crystallinity and the nature of the acid sites. The change in the composition of two tungsten oxide species (polytungstate and crystalline WO3) leads to the change of Lewis acid to Brønsted acid ratio. Importantly, the ratio of the two different acid types has a substantial effect on the catalytic activity. The fraction of Lewis acid to total acid sites rapidly changed from 23% to 77% due to the presence of crystalline WO3. Where the Lewis acid sites accounted for 55% of the total acid sites, the WOX/SiO2 catalyst showed the highest catalytic activity among the prepared catalysts.