Preparation of MnCo/MCM-41 catalysts with high performance for chlorobenzene combustion

MCM-41 was synthesized by a soft template technique.The specific surface area and pore volume of the MCM-41 were 805.9 m2/g and 0.795 cm3/g,respectively.MCM-41-supported manganese and cobalt oxide catalysts were prepared by an impregnation method.The energy dispersive X-ray spectroscopy clearly confirmed the existence of Mn,Co,and O,which indicated the successful loading of the active components on the surface of MCM-41.The structure and function of the catalysts were changed by modulating the molar ratio of manganese to cobalt.The 10%MnCo(6:1)/MCM-41(Mn/Co molar ratio is 6:1)catalyst displayed the best catalytic activity according to the activity evaluation experiments,and chlorobenzene(1000 ppm)was totally decomposed at 270°C.The high activity correlated with a high dispersion of the oxides and was attributed to the exposure of more active sites,which was demonstrated by X-ray diffraction and high-resolution transmission electron microscopy.The strong interactions between MnO2,Co3O4,MnCoOx,and MCM-41 indicated that cobalt promoted the redox cycles of the manganese system.The bimetal-oxide-based catalyst showed better catalytic activity than that of the single metal oxide catalysts,which was further confirmed by H2 temperature-programmed reduction.Chlorobenzene temperature-programmed desorption results showed that 10%MnCo(6:1)/MCM-41 had higher adsorption strength for chlorobenzene than that of single metal catalysts.And stronger adsorption was beneficial for combustion of chlorobenzene.Furthermore,10%MnCo(6:1)/MCM-41 was not deactivated during a continuous reaction for 1000 h at 260°C and displayed good resistance to water and benzene,which indicated that the catalyst could be used in a wide range of applications.

Performance of mesoporous CeO_(2)-Cr_(2)O_(3) mixed metal oxides applied to benzene catalytic combustion

In this paper,a hydrothermal method was used to prepare(Ce,Cr)-MOF with different Ce/Cr molar ratios and then a series of CeO_(2)-Cr_(2)O_(3) mixed metal oxides(CeCr-MMO)with mesoporous structure were prepared by thermal decomposition of these MOFs at different temperatures.After a series of characterization techniques were applied to test the physicochemical properties of the materials,it is found that thermal decomposition temperature(TDT)and Ce/Cr molar ratios have important effects on the structure and performance of CeCr-MMO.As the TDT reaches 400℃ and above,(Ce,Cr)-MOF can be completely decomposed to form CeCr-MMO.The catalyst with Ce/Cr molar ratio of 4:1 has the highest catalytic activity,which can completely degrade benzene at 230℃.It is concluded that the interaction between CeO_(2) and Cr_(2)O_(3) is helpful for increasing the concentration of Ce^(3+),Cr^(6+) and lattice oxygen species(OLatt)on the catalyst surface,thus improving the catalytic performance.Moreover,CeCr(4:1)-MMO-400 shows excellent durability against the presence of chlorobenzene and H2O during 100 h continuous reaction.

MCM-41 supported nano-sized CuO-CeO2 for catalytic combustion of chlorobenzene

In this paper,MCM-41 was synthesized by a soft template technique and MCM-41 supported CuO-CeO2 nano-sized catalysts with different Cu/Ce molar ratios were prepared by a deposition-precipitation method.N2 adsorption,HRTEM-EDS,H2-TPR,XPS characterization,as well as catalytic activity and durability tests for the catalytic combustion of chlorobenzene(CB)were conducted to explore the relationship between the structure and catalytic performance of the catalysts.It is revealed that cuCe(6:1)/MCM-41 has the highest activity and can completely catalyze the degradation of CB at 260℃.The reasons for the high activity of the catalysts are as follows:MCM-41,a type of mesoporous material which has large pore size and large specific surface area,is suitable as a catalyst carrier.The average diameter of nano-sized CuO and CeO2 particles is about 3-5 nm and adding CeO2 improves the dispersion of active component CuO,which are highly and evenly dispersed on the surface of MCM-41.Characterization results also explain why MCM-41 supported CuO-CeO2 with appropriate proportion can highly enhance the catalytic activity.The reason is that CeO2 acting as an oxygen-rich material can improve the mobility of oxygen species through continuous redox between Ce4^+and Ce3^+,and improve the catalytic performance of CuO for CB combustion.Besides,CuCe(6:1)/MCM-41 also displays good durability for CB combustion,both in the humid condition and in the presence of benzene,making it a promising catalytic material for the elimination of chlorinated VOCs.

Ce-modified AlZr pillared clays supported-transition metals for catalytic combustion of chlorobenzene

In this article, we provided a one-step hydrothermal method to prepare composite AIZr pillaring agents, and synthesized AlZr-pillared clays （AIZr-PILC） via ion exchange. Compared with conventional methods, our method successfully shortened synthetic routes and greatly reduced consumption of the materials. Then, A1Zr-PILC-supported manganese and cerium oxide catalysts were obtained by impregnation method. The compositions and properties of these catalysts were characterized by some technical means. The energy dispersive X-ray spectroscopy clearly shows the existence of Mn, Ce, and O, which indicates the successful loading of the active components on the surface of AIZr-PILC. Meanwhile, the results of X- ray diffraction （XRD） and N2 adsorption experiments demonstrate that the synthesized A1Zr-PILC out- performs the raw clays （Na-mmt） and mononuclear AI-PILC in the catalytic combustion of chloroben- zene. XRD and high-resolution transmission electron microscopy also proves that the high activity of them is related to the high dispersion of the oxides and the exposure of more active sites. H2-temper- ature-programmed reduction shows that cerium can promote the redox cycles of the manganese system through the strong interactions between MnO2, CeO2 and AIZr-PILC. In particular, MnCe（9：1 ）/AIZr-PILC shows the best catalytic activity in the catalytic combustion of chlorobenzene.

Mechanism of CeO_(2) synthesized by thermal decomposition of Ce-MOF and its performance of benzene catalytic combustion

In this paper,the formation mechanism of mesoporous CeO_(2) synthesized by thermal decomposition of Ce-MOF and its performance of benzene catalytic combustion,as well as the structure-activity relationship between them were studied in depth.The self-assembly process and physicochemical properties of CeO_(2) were characterized by thermogravimetry analysis,powder X-ray diffraction,N2 adsorption/desorption,high-resolution transmission electron microscopy and X-ray photoelectron spectroscopy techniques.Characterization results show that Ce-MOF is completely decomposed into pure mesoporous CeO_(2) when the decomposition temperature is higher than 400℃.At this threshold temperature,CeO_(2)(400) has the largest specific surface area and pore volume of 114 m^(2)/g and 0.152 cm^(3)/g,respectively.CeO_(2)(400) exhibits very high catalytic activity for benzene combustion,which can completely catalyze the degradation of benzene at 260℃.Meanwhile,the mesoporous CeO_(2)(400) supported Pt nanocrystalline catalysts were prepared by high temperature solution-phase reduction method.Pt/CeO_(2)(400)can completely degrade benzene at about 200℃ and represents high durability and good waterresistance for benzene combustion during 100 h of continuous reaction.