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。

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.

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.

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.

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.

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.

CO_2 methanation over TiO_2–Al_2O_3 binary oxides supported Ru catalysts

TiO_2 modified Al_2O_3 binary oxide was prepared by a wet-impregnation method and used as the support for ruthenium catalyst. The catalytic performance of Ru/TiO_2–Al_2O_3catalyst in CO_2 methanation reaction was investigated. Compared with Ru/Al_2O_3 catalyst, the Ru/TiO_2–Al_2O_3catalytic system exhibited a much higher activity in CO_2 methanation reaction. The reaction rate over Ru/TiO_2–Al_2O_3 was 0.59 mol CO_2·(g Ru)1·h-1, 3.1 times higher than that on Ru/Al_2O_3[0.19 mol CO_2·(gRu)-1·h-1]. The effect of TiO_2 content and TiO_2–Al_2O_3calcination temperature on catalytic performance was addressed. The corresponding structures of each catalyst were characterized by means of H_2-TPR, XRD, and TEM. Results indicated that the averaged particle size of the Ru on TiO_2–Al_2O_3support is 2.8 nm, smaller than that on Al_2O_3 support of 4.3 nm. Therefore, we conclude that the improved activity over Ru/TiO_2–Al_2O_3catalyst is originated from the smaller particle size of ruthenium resulting from a strong interaction between Ru and the rutile-TiO_2 support, which hindered the aggregation of Ru nanoparticles.

Effect of the support calcination temperature on selective hydrodesulfurization of TiO_2 nanotubes supported CoMo catalysts

TiOz nanotubes （TiO2-NTs） were synthesized by the hydrothermal method. Co and Mo active components were supported on a series of the as-prepared TiO2-NTs samples which were calcined at different temperatures. The effects of support calcination temperature of CoMo/TiOz- NTs catalysts on their catalytic performance were investigated for selective hydrodesulfurization （HDS）. The samples were characterized by means of the scanning electron microscopy （SEM）, the transmission electron microscopy （TEM）, N2 adsorption-desorption, X-ray diffraction （XRD）, Raman spectroscopy and H2 temperature-programmed reduction （Hz-TPR）. The experimental results revealed that TiOz-NTs support calcined under 500℃ can maintain the nanotubular structure with higher surface area and pore volume. Meanwhile, the obtained supported CoMo/TiO2-NTs catalysts exhibited weak metal-support interaction, more octahedral Mo6＋ species and high catalytic performance in selective HDS.

制备方法对Co-Pd/TiO_2催化剂催化CH_4-CO_2梯阶转化的影响

以钴、钯为活性金属,分别采用浸渍法和溶胶-凝胶法制备了Co-Pd/TiO2催化剂,考察了不同制备方法制备的Co-Pd/TiO2催化剂对CH4-CO2梯阶转化直接合成C2含氧化合物的影响。利用XRD、XPS和N2-吸附-脱附对催化剂进行了表征。结果表明:两种方法制备的催化剂反应前与反应后表面织构都存在较大变化,且催化剂中均存在CoTiO3物种,这是活性金属Co与载体TiO2之间发生强相互作用,Co2+替代TiO2晶格中的Ti4+的结果;CoO和金属Pd可能是该反应的活性中心;反应前与反应后溶胶-凝胶法制备的催化剂的表面Co含量均低于浸渍法制备的催化剂,而表面Pd含量则均高于浸渍法制备的催化剂,且溶胶-凝胶法制备的催化剂各种产物的生成速率均高于浸渍法制备的催化剂,因此,与浸渍法制备的催化剂相比,溶胶-凝胶法制备的催化剂具有更好的催化活性。

混合钴源对Co-Pd/TiO_2催化剂催化CH_4-CO_2两步梯阶转化法合成乙酸的性能影响

以混合钴源为前驱体,采用等体积浸渍法制备了Co-Pd/TiO2催化剂,考察了其对CH4和CO2梯阶转化直接合成乙酸的催化性能,采用XRD,XPS,NH3-TPD和BET对催化剂进行了表征.结果表明,催化剂具有适宜的表面酸性、高比表面积和孔结构,有利于提高催化剂的活性.在m(CoCl2)∶m[Co(NO3)2]=2∶5,m(Co)∶m(Pd)=2∶1,常压,150℃条件下,乙酸的生成速率达到6.13 mg·g-1Cat·h-1,选择性达到81.6%,分别比以单一Co源制备的催化剂提高了134%和16%.

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.

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.

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.

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.

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.

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.