Hydrogenation of CO_(2) to p-xylene over ZnZrO_(x)/hollow tubular HZSM-5 tandem catalyst

The conversion of CO_(2) into specific aromatics by modulating the morphology of zeolites is a promising strategy.HZSM-5 zeolite with hollow tubular morphology is reported.The morphology of zeolite was precisely controlled,and the acid sites on its outer surface were passivated by steam-assisted crystallization method,so that the zeolite exhibits higher aromatic selectivity than sheet HZSM-5 zeolite and greater p-xylene selectivity than chain HZSM-5 zeolite.The tandem catalyst was formed by combining hollow tubular HZSM-5 zeolites with ZnZrO_(x)metal oxides.The para-selectivity of p-xylene reached 76.2%at reaction temperature of 320℃,pressure of 3.0 MPa,and a flow rate of 2400 mL g^(-1)h^(-1)with an H_(2)/CO_(2) molar ratio of 3/1.Further research indicates that the high selectivity of p-xylene is due to the pore structure of hollow tubular HZSM-5 zeolite,which is conducive to the formation of p-xylene.Moreover,the passivation of the acid site located on the outer surface of zeolite effectively prevents the isomerization of p-xylene.The reaction mechanism of CO_(2) hydrogenation over the tandem catalyst was investigated using in-situ diffuse reflectance Fourier transform infrared spectroscopy and density functional theory.The results showed that the CO_(2) to p-xylene followed a methanol-mediated route over ZnZrO_(x)/hollow tubular HZSM-5 tandem catalysts.In addition,the catalyst showed no significant deactivation in the 100 h stability test.This present study provides an effective strategy for the design of catalysts aimed at selectively preparing aromatics through CO_(2)hydrogenation.

Photocatalytic Activity of TiO_2 Coating on Natural Feather Zeolite in Degradation of Orthomonochlorphenol

Ti02 coatings on natural feather zeolite are respectively prepared by a collosol （Sol-gel） method and two powder coating methods with deionizod water or dehydrated ethanol as a dispersant. During degradation of orthomono- chlorphenol solutions by ultraviolet, the strong adsorption capability of the zeolite results in increased concentration of substrate on its surface. The Ti（h film coated on feather zeolite further enhances the photocatalytic activity. The TiO~ film on the zeolite prepared by the Sol-gel method is found more effective as a catalyst than that by two powder coating methods.

废烟气脱硝催化剂中TiO_(2)资源化回收实验研究

采用高温碱浸和酸洗的方法对废选择性催化还原(SCR)脱硝催化剂进行处理,研究碱浸和酸洗对催化剂各组分的浸出效果,考察温度对催化剂浸出行为的影响规律。结果表明,碱浸温度的提高促进V和W的浸出,210℃时V和W的浸出率分别为82.38%和74.92%。经高温碱浸和酸洗处理后,Al、Ca、Na等杂质的最高浸出率均可达98%以上,回收TiO_(2)的纯度较高,可用于生产新催化剂。高温碱浸会破坏催化剂的结构,有利于后续HCl处理对杂质的去除,除杂效果优于直接酸洗处理。高温碱浸过程中会生成Na_(2)TiO_(3),经HCl反应并水解后会形成新的TiO_(2)颗粒,形成更多的小孔,比表面积增大。

Resistance to SO_2 poisoning of V_2O_5/TiO_2-PILC catalyst for the selective catalytic reduction of NO by NH_3

A titania pillared interlayered clay（Ti-PILC） supported vanadia catalyst（V2O5/TiO2-PILC） was prepared by wet impregnation for the selective catalytic reduction（SCR） of NO with ammonia. Compared to the traditional V2O5/TiO2 and V2O5-MoO3/TiO2 catalysts, the V2O5/TiO2-PILC catalyst exhibited a higher activity and better SO2 and H2O resistance in the NH3-SCR reaction. Characterization using TPD, in situ DRIFT and XPS showed that surface sulfate and/or sulfite species and ionic SO4^（2-）species were formed on the catalyst in the presence of SO2. The ionic SO4^（2-） species on the catalyst surface was one reason for deactivation of the catalyst in SCR. The formation of the ionic SO4^（2-） species was correlated with the amount of surface adsorbed oxygen species. Less adsorbed oxygen species gave less ionic SO4^（2-） species on the catalyst.

Selective catalytic oxidation of NO with O_2 over Ce-doped MnO_x/TiO_2 catalysts

A series of Ce-doped MnOx/TiO2 catalysts were prepared by impregnation method and used for catalytic oxidation of NO in the presence of excess O2. The sample with the Ce doping concentration of Ce/Mn=l/3 and calcined at 300 ℃ shows a superior activity for NO oxidation to NO2. On Ce（1）Mn（3）Ti catalyst, 58% NO conversion was obtained at 200 ℃ and 85% NO conversion at 250 ℃ with a GHSV of 41000 h-1, which was much higher than that over MnOx/TiO2 catalyst （48% at 250 ℃）. Characterization results implied that the higher activity of Ce（1）Mn（3）Ti could be attributed to the enrichment of well-dispersed MnO2 on the surface and the abundance of Mn3＋ and Zi3＋ species. The addition of Ce into MnO2/TiO2 could improve oxygen storage capacity and facilitate oxygen mobility of the catalyst as shown by PL and ESR, so that its activity for NO oxidation could be enhanced. The effect of H2O and SO2 on the catalyst activity was also investigated.

The Effect of Titania Structure on Ni/TiO_2 Catalysts for p-Nitrophenol Hydrogenation

The catalytic hydrogenation of p-nitrophenol to p-aminophenol was investigated over Ni/TiO2 catalysts prepared by a liquid-phase chemical reduction method. The catalysts were characterized by inductively coupled plasma (ICP), X-ray powder diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectra (XPS) and temperature-programmed reduction (TPR). Results show that the titania structure has favorable influence on physio-chemical and catalytic properties of Ni/TiO2 catalysts. Compared to commercial Raney nickel, the catalytic activity of Ni/TiO2 catalyst is much superior, irrespective of the titania structure. The catalytic activity of anatase titania supported nickel catalyst Ni/TiO2(A) is higher than that of rutile titania supported nickel catalyst Ni/TiO2(R), possibly because the reduction of nickel oxide to metallic nickel for Ni/TiO2(A) is easier than that for Ni/TiO2(R) at similar reaction conditions.

Effect of TiO_2 surface properties on the SCR activity of NOx emission abatement catalyst

NOx emission abatement catalysts V 2O 5 supported on various TiO 2 including anatase, rutile and mixture of both were investigated with various physico\|chemical measurements such as BET, NH\-3\|TPD, NARP, XRD and so on, and the effect of TiO\-2 surface properties on the SCR(selective catalytic reduction) activity of V\-2O\-5/TiO\-2 catalysts was studied. It was found that the TiO\-2 surface properties had strong affect on the SCR activity of V\-2O\-5/TiO\-2 catalysts. The stronger acidic property resulted in the higher exposure of active sites as well as the higher SCR activity.

Effects of Atmospheres and Precursors on MnO_x/TiO_2 Catalysts for NH_3-SCR at Low Temperature

The effects of atmospheres and precursors on MnOx/TiO2 catalysts were studied, which were prepared by the impregnation method and tested for their NOx conversion activity in ammonia selective catalytic reduction （NH3-SCR） reactions. Results showed that the manganese carbonate （MC） precursor caused mainly Mn2O3, while the manganese nitrate （MN） precursor resulted primarily in MnO2 and the manganese sulfate （MS） precursor was unchanged. The manganese acetate （MA） precursor leaded obtaining a mixture of Mn2O3 and Mn304. NOn conversion decreased in the following order： MA/TiO2 〉 MC/TiO2 〉 MN/TiO2 〉 MS/TiO2 〉 P25, with a calcination temperature of 773 K in air. Catalysts that were prepared by MA and calcined in oxygen performed strong interaction between Ti and Mn, while MnTiO3 was observed. Compared to the catalysts calcined in nitrogen, those calcined in oxygen had larger diameter and smaller surface area and pore. Catalysts that were prepared by MA and calcined in nitrogen tended to gain higher denitration rates than those in air, since they could be prepared with significant specific surface areas. NO., conversion decreased with calcination atmospheres： Nitrogen〉 Air〉 Oxygen. Meanwhile, amorphous Mn2O3 turned into crystalline Mn2O3, when the temperatures increased from 673 to 873 K.

Comparative study of fluidized-bed and fixed-bed reactor for syngas methanation over Ni-W/TiO_2-SiO_2 catalyst

In this work,syngas methanation over Ni-W/TiO2-SiO2catalyst was studied in a fluidized-bed reactor(FBR)and its performance was compared with a fixed-bed reactor(FIXBR).The effects of main operating variables including feedstock gases space velocity,coke content,bed temperature and sulfur-tolerant stability of 100 h life were investigated.The structure of the catalysts was characterized by XRD,N2adsorptiondesorption and TEM.It is found that under same space velocity from 5000 h 1to 25000 h 1FBR gave a higher CH4yield,lower coke content,and lower bed temperature than those obtained in FIXBR.Ni-W/TiO2-SiO2catalyst possessed excellent sulfur-tolerant stability on the feedstock gases less than 500 ppm H2S in FBR.The carbon deposits formed on the spent catalyst were in the form of carbon fibers in FBR,while in the form of dense accumulation distribution appearance in FIXBR.

CoFe_(2)O_(4)@Zeolite催化剂活化过一硫酸盐对甲基橙的强化降解:性能与机理

采用共沉淀水热法制备了CoFe_(2)O_(4)@Zeolite(CFZ),并将其用于活化过一硫酸盐(PMS)降解合成染料。综合表征表明,组成多孔壳层的CoFe_(2)O_(4)纳米颗粒均匀地覆盖在Na-A沸石上。CFZ的比表面积为107.06 m^(2)/g,是原始沸石比表面积的3倍。CFZ的饱和磁化强度为29.0 A·m^(2)·kg^(–1),可以进行有效磁分离。催化降解实验表明,CFZ/PMS体系对甲基橙(MO)的去除率远远高于单独使用CFZ或PMS。在最佳条件([MO]=50 mg/L、[PMS]=1.0 mmol/L、0.2 g/L CFZ、pH 8和T=25℃)下,MO去除率可达到97.1%。实验研究了pH、PMS用量、CFZ用量、MO浓度以及共存阴离子等因素对CFZ催化性能的影响。活性氧粒子淬灭实验表明,1O2和O_(2)^(•–)在降解过程中起主导作用。CFZ具有良好的回收性能,5次循环后MO去除效率仅下降2.4%。本文还详细讨论了CFZ/PMS体系的催化降解机理。

Effect of copper precursors on the catalytic performance of Cu-ZSM-5 catalysts in N2O decomposition

Five Cu-ZSM-5 catalysts were obtained by treating Na-ZSM-5 （Si/Al ratio = 15） with aqueous solutions of differ- ent Cu precursors （CuCl2, Cu（NO3）2, CuSO4, Cu（CH3COO）2, and ammoniacal copper （II） complex ion）. After being pretreated in flowing He at 500 ℃ to form active Cu＋, these catalysts exhibited quite different activities in cata- lytic decomposition of N2O. CZM-AC（II） （prepared by ammoniacal copper （II） complex ion） with 9.4 wt% Cu con- tent was the most active among these Cu-ZSM-5 catalysts, achieving almost complete N2I conversion at 400 ℃. CZM-CA （prepared using Cu（ CH3COO）2 as the Cu precursor） with 2.8 wt% Cu content was the second most active catalyst among these Cu-ZSM-5 catalysts, achieving almost complete N2I conversion at 425 ℃. CZM-CC, CZM- CN, and CZM-CS prepared by using CuCl2, Cu（NO3）2, or CuSO4 as the Cu precursor with similar Cu contents （≈1.7 wt%） were the least active among these Cu-ZSM-5 catalysts, achieving ca. 90% N2O conversion at 500 ℃. XRD, ICP, SEM, TEM, EDX-mapping, and CO-IR experiments were conducted to characterize relevant samples. The superior activity of CZM-AC（II） can be attributed to the high contents of total Cu＋ and dimeric Cu＋ among these samples. The influence of co-fed O2 or H2O on the catalytic performance of typical samples was also studied.

Improving the denitration performance and K-poisoning resistance of the V_2O_5-WO_3/TiO_2 catalyst by Ce^(4+) and Zr^(4+) co-doping

A series of V2O5‐WO3/TiO2‐ZrO2,V2O5‐WO3/TiO2‐CeO2,and V2O5‐WO3/TiO2‐CeO2‐ZrO2 catalysts were synthesized to improve the selective catalytic reduction(SCR)performance and the K‐poisoning resistance of a V2O5‐WO3/TiO2 catalyst.The physicochemical properties were investigated by using XRD,BET,NH3‐TPD,H2‐TPR,and XPS,and the catalytic performance and K‐poisoning resistance were evaluated via a NH3‐SCR model reaction.Ce^4+and Zr^4+co‐doping were found to enhance the conversion of NOx,and exhibit the best K‐poisoning resistance owing to the largest BET‐specific surface area,pore volume,and total acid site concentration,as well as the minimal effects on the surface acidity and redox ability from K poisoning.The V2O5‐WO3/TiO2‐CeO2‐ZrO2 catalyst also presents outstanding H2O+SO2 tolerance.Finally,the in situ DRIFTS reveals that the NH3‐SCR reaction over the V2O5‐WO3/TiO2‐CeO2‐ZrO2 catalyst follows an L‐H mechanism,and that K poisoning does not change the reaction mechanism.

Supporting IrO2 and IrRuOx nanoparticles on TiO2 and Nb-doped TiO2 nanotubes as electrocatalysts for the oxygen evolution reaction

IrO2 and IrRuOx(Ir:Ru 60:40 at%),supported by 50 wt%onto titania nanotubes(TNTs)and(3 at%Nb)Nb-doped titania nanotubes(Nb-TNTs),as electrocatalysts for the oxygen evolution reaction(OER),were synthesized and characterized by means of structural,surface analytical and electrochemical techniques.Nb doping of titania significantly increased the surface area of the support from 145(TNTs)to 260 m2g-1(Nb-TNTs),which was significantly higher than those of the Nb-doped titania supports previously reported in the literature.The surface analytical techniques showed good dispersion of the catalysts onto the supports.The X-ray photoelectron spectroscopy analyses showed that Nb was mainly in the form of Nb(IV)species,the suitable form to behave as a donor introducing free electrons to the conduction band of titania.The redox transitions of the cyclic voltammograms,in agreement with the XPS results,were found to be reversible.Despite the supported materials presented bigger crystallite sizes than the unsupported ones,the total number of active sites of the former was also higher due to their better catalyst dispersion.Considering the outer and the total charges of the cyclic voltammograms in the range 0.1–1.4 V,stability and electrode potentials at given current densities,the preferred catalyst was Ir O2 supported on the Nb-TNTs.The electrode potentials corresponding to given current densities were between the smallest ones given in the literature despite the small oxide loading used in this work and its Nb doping,thus making the Nb-TNTs-supported IrO2 catalyst a promising candidate for the OER.The good dispersion of IrO2,high specific surface area of the Nb-doped supports,accessibility of the electroactive centers,increased stability due to Nb doping and electron donor properties of the Nb(IV)oxide species were considered the main reasons for its good performance.

A comparative study of CuO/TiO_2-SnO_2,CuO/TiO_2 and CuO/SnO_2 catalysts for low-temperature CO oxidation

Nanometer SnO2 particles were synthesized by sol-gel dialytic processes and used as a support to prepare CuO supported catalysts via a deposition-precipitation method. The samples were characterized by means of TG-DTA, XRD, H2-TPR and XPS. The catalytic activity of the CuO/TiO2-SnO2 catalysts was markedly depended on the loading of CuO, and the optimum CuO loading was 8 wt.% （Tloo = 80 ℃）. The CuO/TiO2-SnO2 catalysts exhibited much higher catalytic activity than the CuO/TiO2 and CuO/SnO2 catalysts. H2-TPR result indicated that a large amount of CuO formed the active site for CO oxidation in 8 wt.% CuO/TiO2-SnO2 catalyst.

Effect of calcination temperature on structure and performance of Ni/TiO_2-SiO_2 catalyst for CO_2 reforming of methane

The influence of calcination temperature on the structure and catalytic behavior of Ni/TiO2-SiO2 catalyst, for CO2 reforming of methane to synthesis gas under atmospheric pressure, was investigated. The results showed that the Ni/TiO2-SiO2 catalyst calcined at 700 ℃ had high and stable activity while the catalysts calcined at 550 and 850 ℃ had low and unstable activity. Depending on the calcination temperature, one, two, or three of the following Ni-containing species, NiO, Ni2.44Ti0.72Si0.07O4, and NiTiO3 were identified by combining the temperature programmed reduction （TPR） and X-ray diffraction （XRD） results. Their reducibility decreased in the sequence： NiO〉Ni2.44Ti0.72Si0.07O4〉NiTiO3. It suggests that high and stable activities observed over the Ni/TiO2-SiO2 catalyst calcined at 700 ~C were induced by the formation of Ni2.44Ti0.72Si0.07O4 and smaller NiO species crystallite size.

TiO_2/NaY Composite as Photocatalyst for Degradation of Omethoate

Photocatalytic activities of TiO2 and NaY zeolites-supported TiO2 were investigated with omethoate as a model pollutant.The physical and chemical states of NaY zeolite-supported TiO2 were evaluated via XRD,FTIR,BET and SEM.Photodegradation of omethoate was studied with H2O2 as oxidant and TiO2 supported on NaY zeolite as photocatalyst.Parameters involved in the photo-catalysis of omethoate,i.e.,the calcination temperature of the photocatalyst,initial omethoate concentration,the amount of TiO2 loaded on NaY zeolite,photocatalyst dosage and H2O2 concentration were investigated in detail.The results show that TiO2/NaY zeolite prepared by means of sol-gel method exhibited a good photocatalytic activity for the degradation of omethoate.Optimum conditions included the calcination temperature of photocatalyst 550℃,initial omethoate concentration 500 mg/L,the amount of TiO2 loaded on NaY zeolite 35%（mass fraction）,the amount of photocatalyst 5 g/L,H2O2 concentration 30 mL/L and an irradiation time of 180 min.The removal of omethoate was up to 93%.Kinetics parameters of the photocatalytic degradation of omethoate were measured and calculated.The result shows the kinetics of photocatalytic degradation of omethoate is first-order.

Ultrafine Pt nanoparticles supported on double-shelled C/TiO2 hollow spheres material as highly efficient methanol oxidation catalysts

Catalyst support is extremely important for future fuel cell devices.In this work,we developed doubleshelled C/TiO2(DSCT)hollow spheres as an excellent catalyst support via a template-directed method.The combination of hollow structure,TiO2 shell and carbon layer results in excellent electron conductivity,electrocatalytic activity,and chemical stability.These uniformed DSCT hollow spheres are used as catalyst support to synthesize Pt/DSCT hollow spheres electrocatalyst.The resulting Pt/DSCT hollow spheres exhibited high catalytic performance with a current density of 462 mA mg^-1 for methanol oxidation reaction,which is 2.52 times higher than that of the commercial Pt/C.Furthermore,the increased tolerance to carbonaceous poisoning with a higher If/Ibratio and a better long-term stability in acid media suggests that the DSCT hollow sphere is a promising C/TiO2-based catalyst support for direct methanol fuel cells applications.

Effect of TiO_2 Support on the Composition, Morphology and Catalytic Property of the NiB Amorphous Alloy Catalyst

Both the unsupported and supported NiB amorphous alloy catalysts (NiB and NiB/TiO2) were prepared by the chemical reduction method. Their catalytic activities were tested by the hydrogenation of sulfolene. The interactions between the NiB alloy and TiO2 were discussed for the first time by using XRD, ICP, SEM and TEM.

Fabrication of C@MoxTi1-xO2-δ nanocrystalline with functionalized interface as efficient and robust PtRu catalyst support for methanol electrooxidation

A core shell structured C@MoxTi1-xO2-δnanocrystal with a functionalized interface(C@MTNC-FI)was fabricated via the hydrothermal method with subsequent annealing derived from tetrabutyl orthotitanate.The formation of anatase TiO2 was inhibited by the simultaneous presence of the hydrothermal etching/regrowth process,infiltration of Mo dopants and carbon coating,which endows the C@MTNC-FI with an ultrafine crystalline architecture that has a Mo-functionalized interface and carbon-coated shell.Pt Ru nanoparticles(NPs)were supported on C@MTNC-FI by employing a microwave-assisted polyol process(MAPP).The obtained Pt Ru/C@MTNC-FI catalyst has 2.68 times higher mass activity towards methanol electrooxidation than that of the un-functionalized catalyst(Pt Ru/C@TNC)and 1.65 times higher mass activity than that of Pt Ru/C catalyst with over 25%increase in durability.The improved catalytic performance is due to several aspects including ultrafine crystals of TiO2 with abundant grain boundaries,Mofunctionalized interface with enhanced electron interactions,and core shell architecture with excellent electrical transport properties.This work suggests the potential application of an interface-functionalized crystalline material as a sustainable and clean energy solution.

Bifunctional TiO2 Catalysts for Efficient Cr（VI） Photoreduction Under Solar Light Irradiation Without Addition of Acids

Bifunctional TiO2 photocatalysts co-doped with nitrogen and sulfur were prepared by the controlled thermal decomposition of ammonium titanyl sulfate precursor. They have both photocatalytic activity and Brφnsted acidity, and thus are active in the photoreduction of Cr（VI） under solar light irradiation without the addition of acids. The activity is superior to that of Degussa P25 in the acidified suspension at the same pH adjusted by H2SO4.