Su Jin You

Direct conversion of cellulose into polyols over Ni/W/SiO2-Al2O3.

The direct conversion of cellulose into polyols over Ni/W/SiO(2)-Al(2)O(3) catalysts with different Al molar fractions was examined. For comparison, Cu/W/SiO(2)-Al(2)O(3), Fe/W/SiO(2)-Al(2)O(3), and Co/W/SiO(2)-Al(2)O(3) were also evaluated. The bulk crystalline structure was determined using X-ray diffraction (XRD). The surface acidity was probed via temperature-programmed desorption of ammonia (NH(3)-TPD). The textural properties were investigated using N(2) physisorption. The metal contents were confirmed via inductively coupled plasma-atomic emission spectroscopy (ICP-AES). Among the various metal catalysts, Ni/W/SiO(2)-Al(2)O(3) was confirmed to be the most favorable for hydrogenolysis of cellulose into polyols. The effect of the Al molar fraction in SiO(2)-Al(2)O(3) on this reaction over Ni/W/SiO(2)-Al(2)O(3) was also investigated. It was found that the polyol yield was closely related to the total acidity of the support. Compared to Ni/W/SBA-15, Ni/W/SiO(2)-Al(2)O(3) (Al/(Al+Si)=0.6) showed better stability during the recycling test. The catalyst deactivation was confirmed to be caused by metal leaching.

Liquid-phase dehydration of d-xylose over silica–alumina catalysts with different alumina contents

The dehydration of d-xylose into furfural was examined using SiO2–Al2O3 catalysts with varying alumina contents to determine the effects of surface acidity on the catalytic performance. For comparison, SiO2 and Al2O3 catalysts were also examined. d-Xylose conversion increased with increasing alumina content in the SiO2–Al2O3 catalysts. Conversely, furfural selectivity at a similar d-xylose conversion decreased with increasing alumina content in the SiO2–Al2O3 catalyst. Lewis acid sites appeared to catalyze the isomerization of d-xylose into lyxose and xylulose, decomposition of d-xylose into C1–C3 products, and polymerization of d-xylose and furfural into humin.

Enhanced Selectivity for CO2 Adsorption on Mesoporous Silica with Alkali Metal Halide due to Electrostatic Field: A Molecular Simulation Approach

Since adsorption performances are dominantly determined by adsorbate-adsorbent interactions, accurate theoretical prediction of the thermodynamic characteristics of gas adsorption is critical for designing new sorbent materials as well as understanding the adsorption mechanisms. Here, through our molecular modeling approach using a newly developed quantum-mechanics-based force field, it is demonstrated that the CO2 adsorption selectivity of SBA-15 can be enhanced by incorporating crystalline potassium chloride particles. It is noted that the induced intensive electrostatic fields around potassium chloride clusters create gas-trapping sites with high selectivity for CO2 adsorption. The newly developed force field can provide a reliable theoretical tool for accurately evaluating the gas adsorption on given adsorbents, which can be utilized to identify good gas adsorbents.

Dehydration of d-xylose over SiO2-Al2O3 catalyst: Perspective on the pathways for condensed products

This work addresses the kinetic mechanism for the dehydration of D-xylose over the SiO2-Al2O3 solid catalyst, where the formation of condensed products is included in addition to the production of furfural and its decomposition. The kinetic modeling and parametric sensitivity show that the isomerization of D-xylose takes place in the early stages of the reaction, followed by the dehydration of isomers. Accordingly, the homogeneous polymerization of isomers is found to be dominant. The developed model is used to evaluate the effects of operating conditions on the catalytic performance; high temperature and D-xylose concentration guarantee high furfural yield.