Xiaoling Yuan

Adsorption behaviors of methyl orange dye on nitrogen-doped mesoporous carbon materials

A series of nitrogen-doped mesoporous carbon materials (NMC) with different nitrogen contents (from 9.1 to 11.3 wt.%) were prepared using urea and ammonia as economical nitrogen resources by sol-gel method. The NMC materials possessed high surface areas (from 659 m(2)/g to 912 m(2)/g) as well as large number of oxygen-containing and nitrogen-containing groups. The adsorption behaviors of NMC materials for anionic dye methyl orange (MO) were investigated, which are fit excellent for the Langmuir isothermal adsorption equation. All the materials exhibited high adsorption capacity for MO at room temperature. Their adsorption capacity can be adjusted by changing the nitrogen contents in NMC materials. Moreover, treating the NMC material at higher temperature can significantly improve the adsorption capacity for MO. According to the results of characterization, the main features of NMC materials, like large pore size and abundant basic nitrogen-containing groups on the surface, should be related to the excellent adsorption property for MO.

Characterization and catalytic performance of porous carbon prepared using in situ-formed aluminophosphate framework as template.

A series of porous carbon (NC) materials were prepared by using in situ-formed aluminophosphate framework as template, and citric acid and sucrose as carbon precursors. The structure and surface chemistry properties of these carbon materials were studied by N(2) adsorption, XRD, DRIFT, and XPS measurements. The catalytic properties of these NC materials were investigated in the selective oxidation of benzyl alcohol with air as oxidant source. Compared with other carbon materials, such as active carbon, mesoporous CMK-3, and carbon molecular sieves, NC materials exhibited much higher catalytic activity with nearly 100% selectivity to benzaldehyde. The presence of abundant surface quinone groups, which originates from the special preparation process of NC material, is likely responsible for the high catalytic property of these porous carbon materials.

Design of a highly active Pt/Al2O3 catalyst for low-temperature CO oxidation

A series of Al2O3 supported platinum catalysts (Pt/Al2O3), were prepared by a colloid deposition route. The Pt chemical state and nanostructure over the Pt/Al2O3 catalysts were characterized after calcination treatment using X-ray photoelectron spectroscopy and transmission electron microscopy. The Pt chemical state and nanostructure depended on the treatment temperature: a metallic Pt surface was formed on the Pt/Al2O3 catalysts calcined at low temperature, whereas oxidized Pt existed after the relatively high temperature treatment. The Al2O3 support acted as an anchor and inhibited the sintering of Pt particles on the catalyst surface through intimate interaction between Al2O3 and Pt. The Pt/Al2O3 catalyst pre-treated at 200 °C (i.e., Pt/Al2O3-200) exhibited relatively high activity for CO oxidation. According to the results of catalyst characterization, Pt/Al2O3-200 could efficiently govern O2 adsorption by trapping O2 molecules on Pt sites and producing active oxygen species. That is, the surface metallic Pt could facilitate the adsorption and activation of O2 molecules even with the CO pre-adsorption on the surface of Pt particles.

N-doped nanoporous carbon as efficient catalyst for nitrobenzene reduction in sulfide-containing aqueous solutions

Metal-free N-doped porous carbon (NC) materials have been demonstrated to be promising catalysts in contaminated environment remediation. Two NC materials (NC-1 and NC-2) were prepared by sol-gel routes. Their catalytic properties were investigated for the reduction of nitrobenzene (NB) in sulfide-containing aqueous solution. Both NC-1 and NC-2 can efficiently catalyze the reduction of NB to aniline (AN) under ambient conditions, but also can be reused for more than 5 times. The reaction fits excellently to the pseudo-first-order kinetic. Compared with NC-1 material, NC-2 shows much higher removal efficiency (rate constant kobs: 0.283h-1vs. 2.50h-1). The important features of NC material, including high specific surface area, suitable surface functional groups (especially nitrogen-containing groups), and enhanced electron transfer ability, should be mainly factors for its excellent catalytic activity. This work demonstrates that N-doped carbon materials have great potential for degradation of NB to AN in the natural aquatic environment.

Catalytic properties of γ-Al2O3 supported Pt–FeOx catalysts for complete oxidation of formaldehyde at ambient temperature

A series of γ-Al2O3 supported Pt–FeOx catalysts (Pt–FeOx/Al2O3) with different Fe/Pt atom ratios were prepared, and their catalytic properties were investigated in the oxidation of formaldehyde. It was found that the catalytic activities of Pt–FeOx/Al2O3 catalysts are varied with the change of Fe/Pt ratios. Among them, the sample with a Fe/Pt ratio of 1.0 exhibits the highest activity, which can efficiently convert formaldehyde to CO2 at ambient temperature. The catalytic activity of the Pt–FeOx/Al2O3 catalyst can be further improved by the addition of water vapor into the feed stream. A variety of characterization results showed that both Pt nanoparticles and FeOx species are highly dispersed on the surface of the γ-Al2O3 support. Changing Fe/Pt ratios could influence the chemical states and the redox properties of Pt and Fe species. The catalysts with appropriate Fe/Pt ratios have more accessible active sites, i.e., the Pt–O–Fe species, which are located at the boundaries between FeOx and Pt nanoparticles, thus showing high activity for the oxidation of formaldehyde under ambient conditions.

High-performance palladium catalysts for the hydrogenation toward dibenzylbiotinmethylester: Effect of carbon support functionalization

Different functionalized carbon materials were used as supports to prepare Pd/carbon catalysts (Pd/AC, Pd/AC-O, Pd/AC-Cl and Pd/AC-N). The results of various characterization techniques revealed that a substantial increase in the surface functional groups of the supports could influence the size of the Pd nanoparticles and the chemical states of the Pd species due to Pd-support interactions. During the hydrogenation reaction to synthesize dibenzylbiotinmethylester, the Pd/AC-N catalyst, based on a support that was treated with nitric acid (AC-N), provided a higher yield of dibenzylbiotinmethylester than the other catalysts. The increase in surface oxygen groups (mainly CO2-releasing groups) in the AC-N support was relevant to achieving selective hydrogenation. These groups can provide an efficient pathway for the reaction, which may be responsible for the high yield of dibenzylbiotinmethylester.