Synergetic catalytic removal of chlorobenzene and NOχfrom waste incineration exhaust over MnNb0.4Ce0.2Oχcatalysts:Performance and mechanism study

Nb doped MnCe0.2Ox complex oxides catalysts prepared via a homogeneous precipitation method were investigated for synergistic catalytic removal of NOx and chlorobenzene(CB)at low temperatures.The MnNb0.4Ce0.2Ox catalyst with a molar ratio of Nb/Mn=0.4 exhibits excellent activity and the NOx and CB removal efficiency reaches 94.5%and 96%at 220℃,respectively.Furthermore,the NOx and CB removal efficiency of MnNb0.4Ce0.2Ox still remains above 80%after injecting 300 ppm SO2 and 7 vol%H2 O for 36 h.In addition,the presence of CB and NOx+NH3 can improve the NOx and CB removal efficiency of MnNb0.4Ce0.2Ox,respectively.The analysis results from N2-BET,Py-IR,H2-TPR and NH3-TPD reveal that the introduction of Nb increases the average pore size,pore volume and surface area,promoted the growth of Lewis acid amount obviously,and enhances redox ability of MnCe0.2Ox at 100-250℃.Moreover,the molecular migration process of NOx,NH3,CB and SO2 in NH3-SCR and CB oxidation reaction over MnNb0.4Ce0.2Ox catalysts were systematically studied.In situ DRIFTS,FT-IR and XPS also confirm that the adsorption of sulfate species and SO2 on the surface of MnNb0.4Ce0.2Ox is inhibited effectively by the introduction of Nb in the presence of SO2 and H2 O.Moreover,Nb additives also enhance the structural stability of MnNb0.4Ce0.2Ox,due to the interactions among Mn,Nb and Ce.The NH3-TPD,H2-TPR and in situ DRIFTS results also confirm that the MnNb0.4Ce0.2Ox still retains abundant acid sites and high redox ability in the presence of SO2 and H2O.In summary,MnNb0.4Ce0.2Ox catalysts represent a promising and effective candidate for controlling NOx and CB at low temperatures.

Synergistic catalytic removals of NO,CO and HC over CeO_2 modified Mn-Mo-W-O_x/TiO_2-SiO_2 catalyst

A series of Mn-Mo-W-O_x/TiO_2-SiO_2 catalysts was modified with CeO_2 using an extrusion molding method. The catalytic activities of the obtained catalysts were tested for the synergistic catalytic removals of CO, NO and C_3H_8. The ratio of catalyst composition on catalytic activities for NH_3-SCR was optimized, which reveals that the molar ratio of Ti/Si was 9：1 and the catalyst containing 1.5 wt% CeO_2 and 12 wt% Mn-Mo-W-O_x exhibits the best catalytic performances. These samples were characterized by XRD, N_2-BET, Py-IR, NH_3-TPD, SEM/element mapping, H_2-TPR and XPS, respectively. Results show that the optimal catalyst exhibits more than 99% NO conversion, 86% CO conversion and 100% C_3H_8 conversion under GHSV of 5000 h^（-1）. In addition, the GHSV has little influence on removal of NO when it is less than 15,000 h^（-1）. Furthermore, the addition of CeO_2 will enhance the surface acidity, increase Mn^（4＋）concentration and inhibit the grain growth, which are favorable for the excellent catalytic performance.Anyway,the 1.5 wt% CeO_2-12 wt% Mn-Mo-W-O_x/TiO_2-SiO_2 possesses outstanding redox properties,abundant acid sites and high Mn^（4＋） concentration, which provide a guarantee for synergistic catalytic removal of CO, NO and HC.

Catalytic performance of Ag/Co-Ce composite oxides during soot combustion in O_2 and NO_x:Insights into the effects of silver

The composite oxides xAg/Co_（0.93）Ce_（0.07）（x=Ag/（Co＋Ce） molar ratio）,intended for use as high performance catalytic materials,were successfully prepared via citric acid complexation.The effects of silver on the performance of these substances during soot combustion were subsequently investigated.Under O_2,the 0.3Ag/Co_（0.93）Ce_（0.07） catalyst resulted in the lowest ignition temperature,T_（10）,of197 ℃,while the minimum light-off temperature was obtained from both 0.2Ag/Co_（0.93）Ce_（0.07） and0.3Ag/Co_（0.93）Ce_（0.07） in the NO_x atmosphere.These materials were also characterized by various techniques,including H_2,soot and NO_x temperature programmed reduction,X-ray diffraction,and electron paramagnetic resonance,Raman,X-ray photoelectron,and Fourier transform infrared spectroscopic analyses.The results demonstrated that silver significantly alters the catalytic behavior under both O_2 and NO_x,even though the lattice structure of the mixed oxide is not affected.Surface silver oxides generated under the O_2 atmosphere favor soot combustion by participating in the redox cycles between soot and the silver oxide,whereas the AgNO_3 that forms in a NO_x-rich atmosphere facilitates soot abatement at a lower temperature.The inferior activity of AgNO_3 relative to that of Ag_2O results in the different catalytic performance in the presence of NO_x or O_2.

Simultaneous Removal of Soot and NO_x over Precious Metal Catalysts O_2-Rich Atmospheres and in the Presence of H_2O and SO_2

The activities of ZrO_2-supported precious metal catalysts for simultaneous removal of soot and NO_x in the presence of rich O_2and H_2O as well as SO_2 have been studied by keeping loose contact between catalyst and soot.The results show that only Ru,Ir and Rh have catalytic activity for simultaneous removal of soot and NO_x and the order of catalytic activity is Ru > Ir > Rh.Pt has the catalytic activity only for the removal of soot,and Ag,Pd,and Au have hardly any catalytic activities for the removal of soot and NO_x.The relationships between catalytic activity of precious metal catalysts and various reaction conditions were discussed.

Ni nanoparticles supported on carbon as efficient catalysts for steam reforming of toluene(model tar)

This paper investigated the influences of surface properties of carbon support and nickel precursors(nickel nitrate, nickel chloride and nickel acetate) on Ni nanoparticle sizes and catalytic performances for steam reforming of toluene. Treatment with nitric acid helped to increase the amount of functional groups on the surface and hydrophilic nature of carbon support, leading to a homogeneous distribution of Ni nanoparticles. The thermal decomposition products of nickel precursor also played an important role, Ni nanoparticles supported on carbon treated with acid using nickel nitrate as the precursor exhibited the smallest mean diameter of 4.5 nm. With the loading amount increased from 6 wt% to 18 wt%, the mean particle size of Ni nanoparticles varied from4.5 nm to 9.1 nm. The as-prepared catalyst showed a high catalytic activity and a good stability for toluene steam reforming: 98.1% conversion of toluene was obtained with the Ni content of 12 wt% and the S/C ratio of3, and the conversion only decreased to 92.0% after 700 min. Because of the high activity, good stability, and low cost, the as-prepared catalyst opens up new opportunities for tar removing.

Recent progress in tar removal by char and the applications:A comprehensive analysis

Tar catalytic removal by char is a promising technology for gasification process because of its porous structure,good catalytic activity,low cost,and easy to treatment after deactivation.To provide comprehensive information on the tar catalytic removal by char,this study focuses on the ongoing efforts and advances from fundamental researches to the industrial applications.The tar removal efficiency by char much depends on reaction conditions and char property,such as char origin,porous structure,the functional group on char surface,carbon structure,and AAEM components.The typical reaction kinetics,reaction mechanism,and the deactivation,will be introduced.Then,for the different gasification processes,the potential or typical applications of tar removal by char are discussed and compared.Finally,a comprehensive analysis and improvement in scaling up,commercializing tar removal technologies and integrating the gasification process,are also evaluated and analyzed in this review.

Effect of BaO on catalytic performance of Pd-based catalysts for purification of gasoline-methanol exhaust

Barium oxide was developed successfully to modify palladium catalysts supported on CeO2-ZrO2-La2O3-Al2O3（CZLA） compound oxides by impregnation method. N2 adsorption（BET）, X-ray diffraction（XRD）, H2-temperature-programmed reduction（H2-TPR） and X-ray photoelectron spectroscopy（XPS） were employed to characterize the influence of BaO on the physicochemical properties of catalyst. And catalytic activity tests for methanol, CO, C3H8 and NO conversion were evaluated. Catalytic activity results showed that BaO had a positive effect on the conversion of all pollutants. H2-TPR results suggested that the addition of BaO increased the reductive ability of the palladium catalysts. The XPS results indicated that doping BaO also improved the dispersion of Pd species and increased the amounts of Ce3＋ on the Pd-Ba/CZLA catalyst surface, which led to a better redox property. The excellent redox property helped to improve the catalytic activities toward all the pollutants over Pd-based catalysts.