掺杂元素对TiO2/SO2-4固体酸特性的影响

为了进行掺杂元素对超强酸特性的影响研究,采用均匀沉淀法合成了Fe、Si、Al和Zr氧化物掺杂的TiO2/SO2-4的固体酸(TiO2-MrOy),采用XRD、FTIR、NH3-TPD以及H2-FPR等分析方法对催化剂进行表征.以大豆油和甲醇的酯交换反应为活性评价反应,比较了各催化剂的催化活性.研究发现,除了Al外掺杂元素抑制了二氧化钛硫酸化浸渍处理形成硫酸氧钛的过程,其中Si的抑制作用最强.掺杂Fe、Si氧化物使样品中H2还原温度降低,其中以Fe掺杂的样品氢还原温度降低最为明显.NH3-TPD表征表明,Si、Zr和Fe等氧化物掺杂对超强酸表面酸性具有加强作用,而A1掺杂样品表面酸性与未经第二组分修饰的TiO2/SO2-4相比有所降低.相比未掺杂第二元素的催化剂,各掺杂元素的添加使得催化剂活性都有不同程度的提高.将酯交换活性最好的掺Fe催化剂和TiO2/SO2-4催化剂的重复使用情况进行了研究.结果发现,Fe2O3-TiO2/SO2-4与TiO2/SO2-4相比,经3次酯交换反应后活性降低不大.该研究可为后续固体酸的制备和应用提供理论基础.     

掺Ag,Ni对TiO2气相光催化活性的影响

采用溶胶-凝胶法制备了以活性炭为载体的负载型Ag/TiO2及Ni/TiO2光催化剂,以气相中甲苯降解反应考察了两种催化剂的活性随金属离子掺杂量的变化. 用透射电镜、X射线衍射及荧光光谱对掺杂催化剂进行了表征. 结果表明,经Ag, Ni掺杂后,Ag/TiO2和Ni/TiO2两种催化剂的催化活性均有不同程度的提高,且Ni/TiO2优于Ag/TiO2. 两种催化剂的最佳掺杂量均为0.4%. 根据表征及实验结果分析了金属离子不同掺杂量影响TiO2光催化活性的机理.     

TiO2与SiO2掺杂对Al2O3相转变的研究

通过球磨混合法,制备TiO2、SiO2和TiO2+SiO2掺杂的Al2 O3粉体,经不同温度煅烧后进行X射线衍射(XRD)测试,比较研究这三种掺杂对Al2 O3粉体相转变温度的影响.研究结果表明,TiO2、SiO2掺杂对γ-Al2 O3向α-Al2 O3的相转变均有促进作用.在掺杂质量分数为0.5％的情况下,二者可分别...     

TiO2光催化剂失活机理与再生研究进展

TiO2催化剂在多相光催化反应中容易失活,其失活机理剖析与失活催化剂再生问题是工业化应用的关键.本文从多相光催化反应失活过程入手,对近年来国内外TiO2光催化剂失活机理、掺杂复合等改性手段和不同温度、光源等反应条件对催化剂使用寿命的影响以及失活催化剂再生与催化剂寿命延长方法等方面进行了综述,并展望了TiO2光催化未来研究的方向.     

负载型湿式氧化催化剂RuO2/γ-Al2O3活性与稳定性

采用浸渍法制备了RuO2 /γ Al2 O3 催化剂 ,以苯酚为目标有机物重点研究了进水 pH值和温度对RuO2 /γ Al2 O3 催化剂组分溶出和活性的影响 .结果表明 ,催化剂在降解苯酚过程中存在着组分溶出现象 ,随着进水溶液pH值降低催化剂组分溶出量增加 ,且在进水为酸性时苯酚去除率高于碱性时的去除率 .反应温度升高 ,催化剂组分溶出量降低 ,苯酚去除率增加 .采用在负载型RuO2 /γ Al2 O3 催化剂中掺杂Ce和Zr的方法对抑制催化剂组分溶出进行了初步研究 ,发现掺杂Ce和Zr后有效地降低了RuO2 /γ Al2 O3 催化剂组分的溶出 ,且提高了催化剂的活性     

Au-Pd/TiO2-Al2O3催化剂的加氢脱硫性能研究

采用溶胶凝胶(sol-ge1)、共沉淀(CP)和沉积沉淀(DP)法制备了介孔TiO2-Al2O3复合载体(简称复合载体);以噻吩加氢脱硫(HDS)为探针反应,考察了复合载体制备条件对负载型Au-Pd催化剂噻吩HDS反应性能的影响;并采用X射线衍射进行表征.结果表明,不同温度焙烧的TiO2一Al2O3复合载体都具有介孔结构,其中773 K焙烧制得的TiO2一Al2O3复合载体的比表面积和孔容较大,B酸中心较多;以乙醇还原的Au-Pd/TiO2-Al2O3催化剂的加氢脱硫活性较好.乙醇还原的Au-Pd/TiO2-Al2O3催化剂中Au-Pd之间及活性组分与载体之间的相互作用较强,形成AuxPdy合金的晶粒较小,活性组分的分散度和活性表面积较大,反应活化能较低,这些均有利于催化剂活性的提高.     

SnO2掺杂TiO2催化超声降解甲基橙溶液的研究

采用实验室合成的SnO2 掺杂TiO2 作为催化剂 ,研究了各种因素对甲基橙超声降解反应的影响。结果表明在SnO2 掺杂TiO2 催化剂作用下超声降解甲基橙的效果明显优于纯的TiO2 。 1.5 %掺杂量的催化剂 ,用量在 1.0～ 1.5g/L之间 ,超声波频率 2 5kHz,输出功率 1.0w/cm2 ,pH为 1.0时 ,甲基橙水溶液初始浓度 2 0mg/L的条件下 ,10 0min左右基本可全部降解 ,COD的去除率也可达到了 99.0 %。因此 ,SnO2 掺杂TiO2 催化超声降解有机污染物的方法具有很好的应用前景。     

Fe2O3掺杂TiO2催化超声降解糠醛废水的研究

采用Fe2O3掺杂TiO2为催化剂,超声辐照为主要手段对实际糠醛废水进行了降解试验研究,考察了各种反应参数对糠醛废水降解效果的影响.结果表明,Fe2O3掺杂TiO2对糠醛废水的超声降解效果具有明显的辅助和提高.当超声波频率为40 kHz,功率为160 W,初始COD为1 128 mg·L-1,超声反应时间为1.5 h的务件下,糠醛废水的COD去除率为67%,而同样条件下,按质量浓度750mg·L-1加入1.0%Fe2O3掺杂量的催化剂TiO2,其超声降解废水COD去除率可达95%.     

Al_2O_3负载TiO_2光催化氧化剂的制备与性能试验

以钛酸四丁酯为钛源、Al2O3为载体,采用浸渍法制备了一系列TiO2/Al2O3复合氧化物光催化剂。以光催化降解甲醛为探针反应,考察了催化剂的光催化活性。并采用XRD、SEM技术对催化剂进行了表征。考察了催化剂的焙烧温度、钛含量、反应温度等因素对甲醛光催化降解率的影响。结果表明:400℃是制备TiO2/Al2O3光催化剂的最佳焙烧温度;在TiO2负载质量为5.0%的复合氧化物光催化剂催化效果最好,甲醛的降解率达到58.4%。随着反应温度的升高,复合氧化物光催化剂的催化性能下降,由25℃时的58.4%的甲醛降解率下降到50℃时的4.8%。     

MgO修饰的V2O5-MoO3/TiO2低温SCR催化剂

V系催化剂具有良好的抗中毒能力,广泛应用于燃煤电厂、工业锅炉烟气(固定源)和车辆尾气(移动源)脱硝领域.本文采用水热法制备了V2O5-MoO3/TiO2催化剂,并通过挤出成型得到蜂窝式V2O5-MoO3/TiO2催化剂,通过与共混法相比,发现采用水热法表现出来的较高的低温SCR活性,并研究了MgO的掺杂对V2O5-MoO3/TiO2催化剂性能的影响,发现MgO的掺杂能够降低SO2的转化率.并通过表征发现采用水热反应法得到的V2O5-MoO3/TiO2催化剂能使活性组分高度分散于TiO2载体表面上,具有较高的比表面积,从而使催化剂表现出最佳的低温活性,同时MgO修饰的V2O5-MoO3/TiO2催化剂的抗硫抗水性以及抗碱金属中毒性也做出了研究.     

Synthesis of (C5H5)2Zr(O2C)CH3 and (C5H5)2Zr(O2C)CH2CH3 for olefin polymerization

Summary (C₅H₅)₂Zr(O₂C)CH₃ and (C₅H₅)₂Zr(O₂C)CH₂CH₃ complexes were synthesized, characterized and activated with MAO for ethylene polymerization. The highest catalytic activity was achieved at Al/Zr molar ratio of 3000 for both systems. The effects of the size of the R group in the carboxylate ligands, the Al/Zr molar ratio and reaction temperature on the catalytic activity and polymer properties were studied and discussed.     

Effect of TiO2 loading on the activity of V/TiO2-Al2O3 in the catalytic oxidehydrogenation of ethylbenzene with carbon dioxide

TiO₂-Al₂O₃ mixed oxides with different compositions ranging from 40wt-% to 95wt-% of TiO₂ were prepared by sol-gel method and impregnated with different amounts of VO _x . Supports and catalysts were characterized by X-ray diffraction (XRD), physisorption, temperature preprogrammed reduction (H₂-TPR), and ammonia temperature programmed desorption (NH₃-TPD). TiO₂ content in the support had obvious effect on the crystal structure, texture characteristic, acid property, and catalytic activity in dehydrogenation of ethylbenzene (EB) with carbon dioxide. The highest catalytic activity was acquired when the TiO₂ content was 50 wt-%.     

Characterization of Supported NiSO4 and Effect of TiO2–ZrO2 Composition on Catalytic Activity for Acid Catalysis

A series of catalysts, NiSO₄/TiO₂–ZrO₂ having different TiO₂–ZrO₂ composition, for acid catalysis was prepared by the impregnation method using an aqueous solution of nickel sulfate. The addition of TiO₂ to ZrO₂ improved the surface area of the catalyst and enhanced its acidity remarkably because of the formation of new acid sites through the charge imbalance of Ti–O–Zr bonding. The binary oxide, TiO₂–ZrO₂ calcined above 600 °C resulted in the formation of crystalline orthorhombic phase of ZrTiO₄. Therefore, NiSO₄/TiO₂–ZrO₂ calcined at 500 °C exhibited a maximum catalytic activity for acid catalysis, and then the catalytic activity decreased with the calcination temperature. The correlation between catalytic activity and acidity held for both reaction, 2-propanol dehydration and cumene dealkylation. NiSO₄ supported on 50TiO₂–50ZrO₂ (TiO₂/ZrO₂ ratio = 1) among TiO₂–ZrO₂ binary oxides exhibited the highest catalytic activity for acid catalysis.     

Investigation of different modifiers for nanocrystal zirconia on W/ZrO2 catalysts via esterification

The present work focused on investigation of different modifiers, such as Si, Al, Bi, and Pb on the tungstated zirconia catalysts. First, the different modifier precursors were introduced onto the nanocrystal zirconia having molar ratio (metal: Zr) at 0.01:1. Then, the 15 wt% of tungsten (W) was impregnated onto the modified zirconia. The physicochemical properties influenced by the modifiers were determined using the N₂ physisorption, X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), and electron spin resonance (ESR). In order to measure the catalytic activity, esterification of acetic acid and 1-heptanol was performed. It was found that the modifiers apparently resulted in dramatically decreased activity due to decreased acidity of the catalysts. It can be proposed that the modifiers had three major roles; (i) inhibit the phase transformation, (ii) enhance the presence of F-center (electrons stabilized in oxygen vacancy), and (iii) increase strong interaction of adsorbed species on zirconia. The third effect was the key factor leading to pronounced decrease in acidity of the catalysts.     

Characterization of zirconium sulfate supported on TiO2 and activity for acid catalysis

A series of Zr(SO₄)₂/TiO₂ catalysts were prepared by impregnation of powder TiO₂ with an aqueous solution of zirconium sulfate. No diffraction line of zirconium sulfate was observed up to 30 wt%, indicating good dispersion of Zr(SO₄)₂ on the surface of TiO₂. The high catalytic activities of Zr(SO₄)2/TiO₂ for both 2-propanol dehydration and cumene dealkylation were related to the increase of acidity and acid strength due to the addition of Zr(SO₄)₂. Zr(SO₄)₂/TiO₂ containing 25% zirconium sulfate and calcined at 400 °C exhibited maximum catalytic activities for 2-propanol dehydration and cumene dealkylation. The catalytic activities for these reactions were correlated with the acidity of catalysts measured by the ammonia chemisorption method. This paper is dedicated to Professor Hyun Ku Rhee on the occasion of his retirement from Seoul National University.     

Impact of Si and Zr addition on the surface defect and photocatalytic activity of the nanocrystalline TiO2 synthesized by the solvothermal method

In the present work, the effects of Si and Zr addition on the surface defect and photocatalytic activity of the solvothermal-derived TiO₂ were investigated. The metal-doped TiO₂ samples were prepared with the molar ratio Si/Ti and Zr/Ti ranging from 0.002 to 0.1 and were subjected to two different cooling temperatures (room temperature and 77 K) after calcination as a post-synthesis treatment. The presence of a small amount of metal dopant caused a slight change in the TiO₂ crystallite and BET surface area (ranging from 7.8 to 10.6 nm and corresponding surface area 95 to 159 m²/g). The photocatalytic activity of TiO₂ did not depend solely on the surface area but rather affected by the concentration of Ti³⁺ on the catalyst surface as shown by a linear ascending trend of the ethylene conversion and the amount of Ti³⁺/surface area of the catalysts. It is noted that addition of Zr had more positive effect than Si and the effect of post-treatment on the photocatalytic activity of TiO₂ catalysts was more pronounced than the addition of metal dopants.     

Characterization and catalytic properties of Ni and NiCu catalysts supported on ZrO2–SiO2 for guaiacol hydrodeoxygenation

ZrO₂–SiO₂ complex oxides with Si/Zr mole ratio of 3 (SZ-3) were synthesized. ZrO₂–SiO₂ supported Ni and NiCu catalysts were prepared by impregnation method. Their catalytic performances were evaluated in the hydrodeoxygenation (HDO) upgrading of model reactant guaiacol to hydrocarbons. The physicochemical properties of the support materials and catalysts were characterized by FTIR, XRD, TPD, TPR, and BET techniques. The addition of Cu significantly affected the acidity, and thus influenced their catalytic performance for product distributions. Over the Ni5Cu/SZ-3 catalyst, the cyclohexane selectivity of 80.8% and the methylcyclohexane selectivity of 12.4% were obtained with complete conversion of guaiacol under the 300 °C, 5.0 MPa H₂ pressure.     

Synthesis and characterization of CuO/TiO2 catalysts for low-temperature CO oxidation

In this paper, the CuO/TiO₂ catalysts prepared by the deposition–precipitation (DP) method were extensively investigated for CO oxidation reaction. The structural characters of the CuO/TiO₂ catalysts were comparatively investigated by TG-DTA, XRD, and XPS measurements. It was shown that the catalytic behavior of CuO/TiO₂ catalysts greatly depended on the TiO₂-support calcination temperature, the CuO loading amount and the CuO/TiO₂ catalysts calcination temperature. CuO supported on the anatase phase of TiO₂-support calcined at 400 °C showed better catalytic activity than those supported on TiO₂ calcined at 500 and 700 °C. Among all our investigated catalysts with CuO loading from 2% to 12%, the catalyst with 8 wt% CuO loading exhibited the highest catalytic activity. The optimum calcination temperature of the CuO/TiO₂ catalysts was 300 °C. The XRD results indicated that the catalytic activity of the CuO/TiO₂ catalysts was related to the crystal phase and particle size of TiO₂ support and CuO active component.     

Nanosized Pd/Pt and Pd/Rh Catalysts for Naphthalene Hydrogenation and Hydrogenolysis/Ring-opening

Pd/Rh and Pd/Pt catalysts supported on two different mesoporous materials – a Zr-doped MCM-41-type silica [Si/Zr = 5 w/w (SiZr)] and a commercial silica-alumina [Si/Al = 40:60 w/w (SiAl)] – were prepared by incipient wetness impregnation using nanosized suspensions of alloy particles prepared by polyol-mediated synthesis in diethylene glycol (DEG). The catalytic behaviour of these catalysts was investigated in the hydrogenation and hydrogenolysis/ring-opening of naphthalene at 6.0 MPa, by checking the role of both the main reaction conditions (temperature, contact time and H₂/naphthalene molar ratio) and increasing amounts of dibenzothiophene (DBT). The catalysts supported on SiAl showed higher activity than catalysts supported on SiZr, thus suggesting that activity is favoured by higher acidity of the support and/or higher interaction of the nanosized metal particles with the support. While using the SiZr support, weaker metal-support interactions took place by forming catalysts with bigger metal and/or metal oxide particles. Besides, the catalyst with lowest noble-metal content (0.3 wt.%) (SiAl-0.3Pd/Pt-5) had the greatest acidity and metal surface and, consequently, the highest activity. Furthermore, it exhibited a good thiotolerance in presence of increasing amounts of DBT in the feed, thus maintaining a high catalytic activity in the hydrogenation of naphthalene, although with decreased yield in trans- and cis-decalin (decahydronaphthalene or DeHN) and high-molecular-weight compounds (H.M.W.), with a corresponding increased yield in the partially hydrogenated tetralin (tetrahydronaphthalene or TeHN).     

Enhanced Stability of HZSM-5 Supported Ga2O3 Catalyst in Propane Dehydrogenation by Dealumination

Gallium oxide catalysts supported on HZSM-5 with different Si/Al ratios were characterized by pyridine adsorption FT-IR, model reactions and XPS studies. As the Si/Al ratio of the support HZSM-5 zeolite rises, the acidity of the supported catalysts decreases accordingly, which comes from two aspects: the loss of acid sites present on HZSM-5 support and the loss of the acid sites present on gallium oxides. The latter was caused by the change in the interaction between Ga₂O₃ and support. The initial activity in the propane dehydrogenation decreases with increasing Si/Al ratio while the stability increases. The enhanced stability is thought to be caused by the decrease of the acidity of the catalysts, resulting in the suppression of the side reactions, such as cracking and oligomerization.