Yiqiong Yang

Facile Synthesis of Highly Efficient Amorphous Mn-MIL-100 Catalysts: Formation Mechanism and Structure Changes during Application in CO Oxidation

A comprehensive study was carried out on amorphous metal-organic frameworks Mn-MIL-100 as efficient catalysts for CO oxidation. This study focused on explaining the crystalline-amorphous-crystalline transformations during thermolysis of Mn-MIL-100 and studying the structure changes during the CO oxidation reaction. A possible formation mechanism of amorphous Mn-MIL-100 was proposed. Amorphous Mn-MIL-100 obtained by calcination at 250 °C (a-Mn-250) showed a smaller specific surface area (4 m2  g-1 ) but high catalytic activity. Furthermore, the structure of amorphous Mn-MIL-100 was labile during the reaction. When a-Mn-250 was treated with reaction atmosphere at high temperature (giving used-a-Mn-250-S), the amorphous catalysts transformed into Mn2 O3 . Meanwhile, the BET surface area (164 m2  g-1 ) and catalytic performance both sharply increased. In addition, used-a-Mn-250-S catalyst transformed from Mn2 O3 into Mn3 O4 , and this resulted in a slight decrease of catalytic activity in the presence of 1 vol % water vapor in the feed stream. A schematic mechanism of the structure changes during the reaction process was proposed. The success of the synthesis relies on the increase in BET surface area by using CO as retreatment atmosphere, and the enhanced catalytic activity was attributed to the unique structure, a large quantity of surface active oxygen species, oxygen vacancies, and good low-temperature reduction behavior.

Facile synthesis of Ag/KIT-6 catalyst via a simple one pot method and application in the CO oxidation

Ag/KIT-6 catalyst was successfully synthesized via a simple one pot method for the first time. The structural properties of Ag/KIT-6 catalyst were systematically investigated by X-ray powder diffraction, transmission electron microscope, N2 adsorption–desorption isotherms, and inductively coupled plasma atomic emission spectroscopy. The results showed the synthesized materials exhibited a 3D cubic la3d pore structure, and highly uniformly Ag nanoparticles were dispersed on the KIT-6 support. The formation mechanism of Ag/KIT-6 catalyst was also examined. It was found that the obtained Ag/KIT-6 catalyst exhibited better catalytic activity toward CO oxidation.

Recent Progress in the Removal of Volatile Organic Compounds by Mesoporous Silica Materials and Supported Catalysts

Mesoporous silica materials have attracted much attention because of their large surface area,uniform pore-size distribution, large pore size, and wide potential applications in the fields of separation,adsorption, and catalysis. The progress in the removal of volatile organic compounds(VOCs, mainly containing hydrocarbons, methanol, formaldehyde, acetone, benzene, toluene, naphthalene, and ethyl acetate) by mesoporous silica materials and supported catalysts in recent years is reviewed. The effect of the structure of mesoporous silica materials on the adsorption of VOCs is discussed. We also discuss the catalytic performance and reaction mechanism for catalytic VOC oxidation over supported catalysts. The recent developments in catalytic combustion of toluene are examined in detail. We found that the surface environment, pore structure, and morphology of mesoporous silica materials are the main factors influencing adsorption of VOC molecules. The application of noble metal catalyst focuses on improving poison resistance and reducing cost. The research on non-noble metal catalysts focuses on developing supported mixed-metal oxide catalysts with high activity. Future developments of mesoporous silica materials and supported catalysts are highlighted. The design of the catalyst can be carried out from two aspects: the silica support and the mesoporous channel. This review will be helpful in choosing an appropriate catalyst for the removal of VOCs with high activity and stability.

Magnetic ion exchange resin for effective removal of perfluorooctanoate from water: study of a response surface methodology and adsorption performances

This research exhibited the use of magnetic ion exchange (MIEX) resin as an effective adsorbent for the removal of perfluorooctanoate (PFOA) in aqueous solution. The adsorption performance of PFOA was investigated by a batch experiment. All kinds of factors affecting the adsorption of PFOA, including adsorbent dosage, initial concentration, adsorption time, temperature, stirring intensity, coexistent anions, initial solution pH, natural organic matter, ion strength, and bed volume were studied. Moreover, the response surface methodology was put into use to know the key parameters affecting PFOA removal efficiency. The sorption equilibrium and kinetic data could conform well to the Langmuir and pseudo-second-order model, respectively. Thermodynamic parameters were obtained, and it was observed that the adsorption of PFOA onto MIEX resin was an endothermic and spontaneous process at the temperatures under investigation. It was summarized that both chemical absorption and physical adsorption were involved in the PFOA sorption onto the MIEX resin. Moreover, the MIEX resin could be effectively regenerated using a saturated sodium chloride solution. A series of batch experiments and characterizations demonstrated that the MIEX resin possessed a strong adsorption ability with the removal efficiency exceeding 90%, allowing a possible practical application in future water treatment.