Yong-Hwan Mo

CO2 activation and promotional effect in the oxidation of cyclic olefins over mesoporous carbon nitrides

Mesoporous carbon nitrides (MCN) were prepared by a nano-casting method using mesoporous silica as a template with different carbon and nitrogen sources like melamine only (MS-MCN), urea-formaldehyde (UF-MCN) and melamine-glyoxal (MG-MCN). These mesoporous carbon nitride materials possess nitrogen moieties which behave like a CO2-philic surface facilitating oxidation of cyclic olefins by molecular oxygen in the co-presence of CO2 below supercritical conditions. The co-presence of CO2 augmented the conversions of cyclic olefins at low pressures of CO2, depicting a promotional effect. Approaches towards quantification of promotional effects and insights into the promotional aspects have been studied.

Novelty of Dynamic Process in the Synthesis of Biocompatible Silica Nanotubes by Biomimetic Glycyldodecylamide as a Soft Template

A dynamic process in the synthesis of silica nanotubes (SNTs) by utilizing glycyldodecylamide (GDA) as a soft template was thoroughly investigated. The morphological evolution from GDA to SNTs was deeply explored to elucidate the formation mechanism for optimizing the synthesis procedure. Various analytical tools, namely, XRD, FTIR, SEM, TEM, Z-potential, and N2 adsorption/desorption isotherms, were employed during the synthesis procedure. The interactive structure of GDA was also investigated using TEM-EDX as a function of aging time. These studies revealed the stepwise morphology of nanograin, nanofiber, curved plate, and nanotube in the ethanol/water solution when aged at room temperature. The supramolecular GDA molded the vesicle type nanostructure which was surrounded by silica and facilitated the formation of uniform SNTs. The stimulus for GDA to be curved into a vesicle was the intermolecular hydrogen bonding between adjacent amide groups of the template molecules. This was illustrated by FTIR spectra of GDA-silica intermediate by detecting the transition of amide I peak from 1678 to 1635 cm-1. The effect of hydrogen bonding became stronger when the sample was aged.

Aromatization of iso-butanol with CO 2 as an enhancer over ZSM-5 catalysts

Isobutanol was converted to aromatic compounds, such as BTX and C9 aromatics, over Ga or Zn impregnated ZSM-5 catalysts. The mechanism for aromatization includes dehydration, oligomerization, dehydrogenation, cyclization, and cycloaromatization according to referenced literature. Among these processes, dehydrogenation appeared to be the biggest hurdle to overcome; CO2 was expected to be consumed by removing hydrogen, facilitating formation of aromatic species via a reverse water-gas shift reaction (RWGS) of CO2 and hydrogen. The aromatization reaction was performed over H-ZSM-5, Zn-ZSM-5, and Ga-ZSM-5 catalysts under a He and CO2 stream, and enhancements to the yields of aromatics were observed when CO2 was flowed over the catalysts. Additional CO formed when the olefin/paraffin ratio increased as CO2 consumed H2, and this was also confirmed in the RWGS reaction. The biggest CO2 effect occurred over Ga-ZSM-5, and CO2 appeared to interact favorably with the Ga species on ZSM-5 according to XPS and ex situ FT-IR analysis. Thus, it was observed that CO2 served as a hydrogen scavenger and played a large role in enhancing the yields of aromatics.