Increased promotion by deposition of Co acetylacetonate over sulphided Mo/TiO2 hydrodesulphurization catalyst

CoMo/TiO₂ catalysts prepared by deposition of Co acetylacetonate on presulphided Mo/TiO₂ catalyst in methanol exhibited higher promotion of hydrodesulphurization activity than catalysts prepared by conventional impregnation of Mo/TiO₂ by a solution of Co nitrate.     

超临界流体干燥法制备纳米TiO2-SnO2-SiO2复合光催化剂及其光催化性能研究

半导体多相光催化法作为一种污染治理新技术越来越受到人们的重视,在所使用的半导体光催化剂中,TiO2以无毒,催化活性高,价廉,无污染等特点,成为最具有前途的绿色环保型催化剂之一[1],但其自身具有局限性,如禁带宽度大,需在近紫外光下才能激发产生电子空穴对,对太阳光的利用率仅     

Microstructure and catalytic properties of Rh and Ni dispersed on TiO2-SiO2 aerogels

The influence of the preparation method on the microstructure and catalytic behavior of Rh and Ni dispersed on TiO₂-SiO₂ aerogels is investigated.The autoclave method has been followed to prepare titania-silica aerogels with TiO₂ contents ranging between 0 and 10 mole %. These aerogels have been used as matrices to disperse catalytically active metals: Rh and Ni. The metals can be deposited by impregnation of aerogels, or alternatively, can be added into the hydrolysis water used in the synthesis of gels. The resulting catalysts present surface areas higher than 550 m²·g^–1.The percentage of titania, the method followed for the introduction of the metal, and the nature of the metal itself affect both the activities and selectivities of the catalysts in the hydrogenolysis of n-butane. Thus, the presence of titania in Rh catalysts increases the activity values, and the samples prepared by impregnation present selectivities towards ethane higher than 80%. Whereas, the rhodium catalysts in which the metal has been introduced before gelling, do not orientate the reaction in favor of a definite product. For the case of Ni, it is quite frequent to obtain high selectivities towards the breakdown of the C-C terminal bonds. In summary, the preparation methods allow to modulate into very broad limits the catalytic behavior of the samples.     

Effects of the preparation methods on the properties of Ni-La2O3-SiO2 catalysts for m -dinitrobenzene hydrogenation

Ni-La₂O₃-SiO₂ catalysts were prepared by wetness impregnation and sol-gel method followed by conventional drying and supercritical drying, respectively. Their physico-chemical properties and activity for the hydrogenation of m-dinitrobenzene to m-phenylenediamine were investigated by BET, XRD, TPR, H₂-TPD and activity tests. The results showed that the structural and catalytic properties of the Ni-La₂O₃-SiO₂ catalysts obviously depended on the preparation method and the drying mode. The catalyst prepared by the sol-gel method in combination with conventional drying exhibited the highest catalytic activity among the catalysts tested, attributable to its well-dispersed nickel particles and larger active nickel surface area.     

CuO Catalysts Supported on Porous TiO2 Microspheres for Low-Temperature CO Oxidation

The porous TiO₂ microspheres were prepared by the reversed-phase suspension polymerization and sol-gel method using reversed-phase suspension droplets as the templates. The CO oxidation catalytic properties of the CuO/TiO₂ catalysts prepared by hydrothermal method and impregnation method were extensively investigated. The structure of CuO/TiO₂ catalysts was determined by TG-DTA, XRD, TEM, and XPS. The results indicated that the redox capacity of CuO/TiO₂ was greatly depended on the aqueous solution concentration of Cu(NO₃)₂ used in the preparation of CuO/TiO₂ and the calcination temperature of the CuO/TiO₂ catalysts.     

三元杂化TiO2-SiO2-POMs催化剂的合成及其在可见光降解罗丹明B中的应用

采用分步溶胶-凝胶法制备的三元杂化催化剂TiO₂-SiO₂-杂多酸(POMs)在可见光降解工业染料罗丹明B中表现出了高效反应活性. 利用时间分辨微波传导(TRMC)和漫反射光谱(DRS)研究了催化剂在可见光区的光催化性能, 实验结果表明: 在三元杂化催化剂内, 二氧化钛和二氧化硅的键合加强了催化剂在可见光区的响应和吸收, 二氧化钛和杂多酸的结合提高了反应活性位(空穴-电子对)的稳定性. 三元杂化催化剂TiO₂-SiO₂-POMs中组分之间的协同效应促进了可见光光催化性能的提高.     

Preparation of TiO2 nano-particle photocatalysts by a multi-gelation method: the effect of pH change

TiO₂ photocatalysts were prepared by a multi-gelation method and the effect of the changes in the pH during the pH swing times, i.e., by a controlled pH swing, on the morphology of the TiO₂ particles was investigated. The photocatalytic properties of the TiO₂ catalysts prepared by controlled pH swing were compared with TiO₂ particles prepared without adjusting the pH during the swing times. The photocatalytic degradation reaction of these TiO₂ catalysts was investigated by comparing their effectiveness in 2-propanol oxidation. The experimental results showed that the TiO₂ photocatalysts prepared without adjusting the pH performed better in controlling the important parameters of the catalysts such as particle size, surface area, anatase/rutile phase ratio and pore size, as well as pore volume than the TiO₂ photocatalysts prepared by a controlled pH swing method. Deceased.     

Formation of different products during photo-catalytic reaction on TiO<Subscript>2</Subscript> suspension in water with and without 2-propanol under diverse ambient conditions

Studies on photo-catalytic reduction of CO₂ using TiO₂ photo-catalyst (0.1%, w/v) as a suspension in water was carried out at 350 nm light. CO₂ from both commercially available source, as well as generated in situ through 2-propanol oxidation, was used for this study. The photolytic products such as hydrogen (H₂), carbon monoxide (CO) andmethane (CH₄) generated were monitored in TiO₂ suspended aqueous solution with and without a hole scavenger, viz., 2-propanol. Similar photolytic experiments were also carried out with varying ambient such as air, O₂, N₂ and N₂O. The yields of CO and CH₄ in all these systems under the present experimental conditions were found to be increasing with light exposure time. H₂ yield in N₂-purged systems containing 2-propanol was found to be more as compared to the without 2-propanol system. The rate of H₂ production in N₂-purged aqueous solutions containing 0.1% TiO₂ suspension were evaluated to be 0.226 and 5.8 μl/h, without and with 0.5 M 2-propanol, respectively. This confirmed that 2-propanol was an efficient hole scavenger and it scavenged photo-generated holes (h⁺), allowing its counter ion, viz., e⁻, to react with water molecule/H⁺ to yield more H₂. The formation of both CO and CH₄ in the photolysis of CO₂-purged aqueous solutions containing suspended TiO₂ in absence of 2-propanol reveal that the generation of CH₄ is taking place mainly through CO intermediate. In presence of air/O₂, the yield of H₂ in the system without 2-propanol was observed to be negligible as compared to the system containing 2-propanol in which low yield of H₂ was obtained with a formation rate of approx. 0.5 μl/h.     

Formation of Anatase Nanocrystals in Sol-Gel Derived TiO2-SiO2 Thin Films with Hot Water Treatment

We have successfully prepared transparent and porous anatase nanocrystals-dispersed films by treating the sol-gel derived TiO₂-SiO₂ films containing poly(ethylene glycol), PEG, with hot water. This process was done at temperatures lower than 100°C under atmospheric pressure, and thus anatase nanocrystals-dispersed films can be formed on various kinds of substrates including organic polymers with poor heat resistance. The changes in structure and composition of the TiO₂-SiO₂ gel films with hot water treatment were related to the formation process of anatase nanocrystals in the TiO₂-SiO₂ gel films with hot water treatment. The formation of anatase nanocrystals was found to proceed to hydrolysis of Si–O–Ti bonds and dissolution of SiO₂ component. In addition, porous film structure formed by leaching of PEG with hot water treatment led to homogenous dispersion of anatase nonocrystals in the films.     

Mn/Al2O3 Systems: Structure and Activity

-Mn₂O₃ and KMn₈O₁₆ were detected on catalysts prepared by pore volume impregnation of -alumina using manganous nitrate and ammonium permanganate, respectively. While the surface texture was not remarkably affected: decomposition activities towards H₂O₂ and 2-propanol were higher for the later.     

Heavy metal removal using SiO<Subscript>2</Subscript>-TiO<Subscript>2</Subscript> binary oxide: experimental design approach

Sorption of Ni²⁺ and Cd²⁺ as heavy metals ions at the interface of the binary oxide TiO₂-SiO₂ was investigated. In addition, physical properties of TiO₂-SiO₂ matrices such as BET surface area, X-ray diffraction, and point of zero charge (pH_PZC) were measured. Statistical design of experiments was applied to find the conditions of sorption at which the maximum heavy metal removal was achieved. A second order polynomial function was used to correlate the independent variables (pH, metal ion concentration, and shaking time) and response (heavy metal removal). Values of regression parameters were determined by the computer program, Design expert^® (Stat-Ease Inc.). The quality of fit of the polynomial model equation was expressed by the regression coefficient R ². The sorption results showed that the pH is the most significant factor. In turn, the sorbed percentage reached 100% at high initial concentration and long shaking times due to formation of hydroxyl compounds between the ions and TiO₂-SiO₂ matrices. The results show that there is a Gaussian (normal) distribution of residuals (squared differences between experimentally observed and predicted values from the model), and also that the differences between observed and predicted values are in the range of ±5%. These indicate that experiments were well-conducted and the results have no significant error.     

Synthesis of nanosized TiO2/SiO2 particles using microwave processes and their photocatalytic activity on the decomposition of orange II

The nanosized titania and TiO₂/SiO₂ particles were prepared by the microwave-hydrothermal method. The effect of physical properties TTIP/TEOS ratio and calcination temperature has been investigated. The major phase of the pure TiO₂ particle is of the anatase structure, and a rutile peak was observed above 800°C. In TiO₂/SiO₂ particles, however, no significant rutile phase was observed, although the calcination temperature was 900°C. No peaks for the silica crystal phase were observed at either silica/titania ratio. The crystallite size of TiO₂/SiO₂ particles decreases as compared to pure TiO₂ at high calcination temperatures. The TiO₂/SiO₂ particles show higher activity on the photocatalytic decomposition of orange II as compared to pure TiO₂ particles.     

Structure of TiO2 in TiO2-SiO2 prepared by a complexing agent-assisted sol-gel procedure

Many types of TiO₂-SiO₂ (Ti:Si=50:50 mol%) were prepared by the sol-gel procedure with and without 2-methyl-2, 4-pentanediol (MPD) as an organic ligand. The effect of MPD on the gel structure and the properties of the TiO₂ crystals were studied by XRD and raman spectroscopy, and the effect of the sol standing time on the properties of the TiO₂ crystals were also studied by XRD spectroscopy. In the gels with MPD, anatase of TiO₂ appeared at approximately 580°C, and the crystal structures were similar despite the difference in the gel preparation procedure. The titania gels with MPD were presumed to be dispersed in the silica gel matrix without any Ti-O-Si bond. In the presence of MPD, the formation of titania gels is controlled and the specified TiO₂ crystal is produced.     

Low temperature CO oxidation on Au/TiO2 sol-gel catalysts

A comparative study on Au/TiO₂catalysts prepared by impregnation with HAuCl₄of commercial TiO₂ or by impregnation of sol-gel derived TiO₂has been carried out during CO oxidation. Specific surface areas and mean Au particle of 49 and 74 m²/g and 35 and 25 Å were obtained for impregnated commercial TiO₂ and sol-gel preparations, respectively. XRD patterns shown that in sol-gel derived TiO₂ only anatase phase was identified, while in commercial TiO₂ anatase and rutile phases co-exist. Titania support effect on Au activity for the oxidation of CO has been observed. The light-off during the reaction on Au/TiO₂initiates at 50°C, whereas for commercial impregnated TiO₂ catalyst the light-off initiates at 200°C.     

RE/TiO2光催化剂的谱学特性与气相光催化性能的研究

采用改进的sol-gel法和浸渍法制备了TiO₂掺杂稀土离子La³⁺、Y³⁺、Gd³⁺、Er³⁺、Nd³⁺、Pr³⁺的RE/TiO₂光催化剂,运用FTIR、XRD、TEM、低温氮吸附/脱附、TG/DTA、UV-Vis DRS、表面光电压谱(SPS)等进行表征,以气相光催化降解乙烯、溴代甲烷作为探针反应,阐明了RE/TiO₂光催化剂的谱学特性与气相光催化性能的关系。结果显示,稀土离子掺杂后,TiO₂的锐钛矿含量增加,比表面积增大,粒径变小,吸收边发生蓝移,表面光电压的响应阈值增大,此外,Pr³⁺除外的其它稀土离子掺杂的TiO₂的表面光电压信号增强;光催化降解实验表明,与纯TiO₂相比,La³⁺、Y³⁺、Gd³⁺、Er³⁺、Nd³⁺掺杂TiO₂样品上乙烯、溴代甲烷的光催化活性均有不同程度的增强,而且表现出较强的矿化能力。但是,掺杂Pr³⁺的TiO₂的光催化性能降低恰好对应较弱的表面光电压信号。所以,本文认为提高光生电子-空穴对的分离效率是改善光催化性能的关键因素。     

Preparation of high homogeneity BaO-TiO2-SiO2 gel

In BaO-TiO₂-SiO₂ system, crystallization from various gel by heating depended on the sol-gel processes and gel homogeneity. Through the condensation reaction of Si(OAc)₄ and TiAcAc(O ⁱ Pr)₃ in tetrahydrofuran solvent, homogeneous TiO₂-SiO₂ sol with oligomers of relatively large molecular weight was obtained. The gel prepared by mixing the binary sol, Ba(OAc)₂, and Si(OMe)₄ was the most homogeneous in term of suppression of crystallization. By heating the above gel, only Ba₂TiSi₂O₈ crystal appeared, which was observed in a melt quenched glass. In the case of the gels made by other sol-gel processes, TiO₂ or BaTiO₃ crystal was first observed from the heated gels prior to the precipitation of Ba₂TiSi₂O₈.     

Formation of crystalline TiO2−xNx and its photocatalytic activity

Amorphous precursors to nitrogen-doped TiO₂ (NTP) and pure TiO₂ (ATP) powders were synthesized by hydrolytic synthesis and sol-gel method (SGM), respectively. Corresponding crystalline phases were obtained by thermally induced transformation of these amorphous powders. From FT-IR and XPS data, it was concluded that a complex containing titanium and ammonia was formed in the precipitate stage while calcination drove weakly adsorbed ammonium species off the surface, decomposed ammonia bound on surface of precipitated powder and led to substitution of nitrogen atom into the lattice of TiO₂ during the crystallization. The activation energies required for grain growth in amorphous TiO_2−xN_x and TiO₂ samples were determined to be 1.6 and 1.7 kJ/mol, respectively. Those required for the phase transformation from amorphous to crystalline TiO_2−xN_x and TiO₂ were determined to be 129 and 142 kJ/mol, respectively. A relatively low temperature was required for the phase transformation in NTP sample than in ATP sample. The fabricated N-doped TiO₂ photocatalyst absorbed the visible light showing two absorption edges; one in UV range due to titanium oxide as the main edge and the other due to nitrogen doping as a small shoulder. TiO_2−xN_x photocatalyst demonstrated its photoactivity for photocurrent generation and decomposition of 2-propanol (IPA) under visible light irradiation ().     

Cu/Ni助催化剂对TiO2光催化制取苯酚性能的影响

以TiO₂纳米粒子为主催化剂, 采用“浸渍-还原法”构筑了铜、镍共负载的二氧化钛基光催化系统。以苯为起始原料, H₂O₂为氧化剂, 研究了Cu/Ni助催化剂对TiO₂可见光催化制取苯酚性能的影响并对Cu/Ni助催化剂的作用机制进行了探讨。结果表明, 在可见光照射下, 纯TiO₂纳米粒子对苯氧化制取苯酚反应没有催化活性。铜、镍的引入可以明显地增强TiO₂可见光催化制取苯酚的活性。当使用负载有铜、镍的TiO₂作为催化剂时, 苯酚的产率可达到18%。结果还表明Cu、Ni之间存在着很强的协同作用。在该协同作用下, Cu、Ni共负载的TiO₂纳米粒子表现出了较单一金属负载的TiO₂纳米粒子高得多的光催化活性。     

TiO_2/SBA-15的快速合成法及其催化性能

本文针对传统方法合成TiO2/SBA-15的诸多不足,提出了一种简单而快速合成TiO2/SBA-15的方法。利用孔道内水解法快速合成了不同负载量的TiO2/SBA-15。利用XRD、N2-吸脱附、TEM和UV-Vis对样品的晶体结构、微观形貌、光学吸收特性进行了表征,并研究了不同TiO2负载量催化剂对罗丹明B(RhB)光降解活性的影响。结果表明:利用该方法合成的TiO2/SBA-15光催化活性优于传统浸渍方法合成的TiO2/SBA-15与工业上使用的TiO2纳米颗粒。     

Cu/Ni助催化剂对TiO2光催化制取苯酚性能的影响

以TiO₂纳米粒子为主催化剂,采用"浸渍-还原法"构筑了铜、镍共负载的二氧化钛基光催化系统。以苯为起始原料,H₂O₂为氧化剂,研究了Cu/Ni助催化剂对TiO₂可见光催化制取苯酚性能的影响并对Cu/Ni助催化剂的作用机制进行了探讨。结果表明,在可见光照射下,纯TiO₂纳米粒子对苯氧化制取苯酚反应没有催化活性。铜、镍的引入可以明显地增强Ti₀₂可见光催化制取苯酚的活性。当使用负载有铜、镍的TiO₂作为催化剂时,苯酚的产率可达到18%。结果还表明Cu、Ni之间存在着很强的协同作用。在该协同作用下,Cu、Ni共负载的TiO₂纳米粒子表现出了较单一金属负载的TiO₂纳米粒子高得多的光催化活性。