Pd-CeO2/SiC催化剂的制备及其在CO和C3H6氧化反应中的催化性能

分别以蔗糖和硅酸钠为碳源和硅源,硫酸为催化剂,采用溶胶-凝胶法和碳热还原法合成SiC;以其为载体,Pd为活性组分,CeO₂为助剂,采用浸渍法制备Pd-CeO₂/SiC催化剂。考察催化剂制备方法、助剂CeO₂添加量和还原温度等对催化剂在CO和C₃H₆氧化反应中活性的影响。结果表明, 采用分步浸渍法制备的催化剂具有较高活性, CeO₂添加质量分数2%时制备的0.5%Pd-2%CeO₂/SiC催化剂经200 ℃预还原后,对CO和C₃H₆氧的最低完全转化温度分别为210 ℃和215 ℃,CeO₂助剂可显著提高金属Pd在催化剂表面分散度,与Pd产生相互作用,使Pd还原峰向低温移动,提高了催化剂活性。     

一维TiO2-Al2O3载体的制备及其在加氢脱氮中的应用

为提高现有负载型NiMoS催化剂的加氢活性,以碳纳米管为结构导向剂,分别采用浸渍法和溶胶-凝胶法制备了2种一维TiO₂-Al₂O₃载体,并采用共浸渍法制备了相应的负载型NiMoS催化剂,探究了不同结构的载体对NiMoS/TiO₂-Al₂O₃催化剂加氢脱氮性能的影响。结果表明,当选择以溶胶-凝胶法制备的一维TiO₂-Al₂O₃为载体时,NiMoS/TiO₂-Al₂O₃催化剂上的加氢脱氮活性较高,在350℃、氢压为3 MPa、转速为400 r/min的条件下反应4 h,喹啉的转化率达到99%以上,脱氮率达到40.75%。     

载体制备方法对Ni/TiO2催化剂顺酐液相加氢性能的影响

为了制备高活性和高选择性催化剂,实现顺酐下游加氢衍生物的定向合成,分别采用水热法、沉淀法和溶胶-凝胶法制备TiO2载体,并以浸渍法制备Ni质量分数为10%的Ni/TiO₂催化剂。采用N₂低温物理吸附、XRD、H₂-TPR及H₂-TPD等方法对催化剂进行表征,并评价催化剂的顺酐液相加氢性能。结果表明,以溶胶-凝胶法制备TiO₂为载体的催化剂具有最高的CC及CO加氢活性,在反应温度240 ℃和氢压5 MPa条件下,顺酐转化率为100%,γ-丁内酯选择性为52.2%,是相同反应条件下水热法TiO₂负载Ni催化剂的3.3倍和沉淀法TiO₂负载Ni催化剂的6.2倍。产生这一现象的原因与溶胶-凝胶法制备的TiO₂以锐钛矿和金红石混合晶相存在有关。     

Pt/TiO2/ZSM-5催化剂的制备及其催化转化正丁烷

采用溶胶-凝胶法和等体积浸渍法,分别对ZSM-5分子筛进行TiO₂改性和Pt负载,获得了具有脱氢-裂解双功能的Pt/TiO₂/ZSM-5催化剂,采用XRD、N₂吸附-脱附、TEM、XPS和NH₃-TPD对样品的晶体结构,孔结构、形貌、活性金属价态和酸性质等进行了表征,并研究了正丁烷在此催化剂上催化转化制备低碳烯烃的反应规律。研究结果表明,TiO₂的引入,一方面使得改性后的ZSM-5分子筛获得了额外的酸性中心,特别是强酸性位含量的增加,有助于促进正丁烷的活化;另一方面Pt与TiO₂之间存在“金属-载体”强相互作用（SMSI）,在H₂还原气氛下,Pt能够促进TiO₂的还原,生成Ti³⁺物种,而Ti³⁺的存在增加了Pt周围的电荷密度,降低了Pt对低碳烯烃（C₂⁼～C₃⁼）的吸附能力,抑制了深度脱氢和生焦反应,从而提高双功能催化剂对烯烃的选择性。当H₂还原温度为450℃时,Pt/10TiO₂/ZSM-5催化剂在625℃下的正丁烷转化率为76.1%,低碳烯烃（C₂⁼～C₃⁼）收率为50.9%,分别比Pt/ZSM-5催化剂提高了16.7%和12.6%。     

不同水解抑制剂下Sr2+掺杂改性纳米TiO2的制备及可见光响应行为

采用溶胶-凝胶法,以钛酸丁酯为钛源,分别以三乙醇胺和亚氨基二乙酸为水解抑制剂,制备掺杂不同含量Sr²⁺的纳米TiO₂,并对其在可见光范围内对孔雀石绿的光催化降解活性进行评价。结果表明,Sr²⁺掺杂能够有效提高纳米TiO₂的光催化性能,并确定不同条件下合成的纳米TiO₂的最佳掺杂量和反应条件。对掺杂的TiO₂进行紫外可见漫反射光谱、X射线衍射、傅里叶变换红外光谱以及氮物理等温吸附等表征,揭示了表面性能、电子结构、脱水性能、吸附性能、结晶程度和晶相结构等多方面协同作用是Sr²⁺掺杂的TiO₂具有最高光催化活性的原因。这种新型光催化剂可能在环境净化和水处理方面具有一定的应用价值。     

不同Pt前体制备Pt/CeO2催化剂对其结构及性能的影响

Pt与载体间的相互作用会影响到本征Pt纳米粒子的催化活性,不同Pt前体制备Pt/CeO₂催化剂会使其表现出完全不同的催化性能。分别采用金属胶体粒子原位沉积法、浸渍法以及浸渍还原的方式制备了Pt/CeO₂催化剂,通过X 射线衍射、程序升温还原、X射线光电子能谱以及高分辨透射电镜对催化剂进行表征,在CO氧化以及甲苯燃烧反应中评价催化剂活性。结果表明,胶体粒子原位沉积法制备Pt/CeO₂催化剂,能够将优先合成好的Pt纳米粒子直接以金属态Pt⁰的形式负载到载体表面,且保证其高度均匀分散,丰富的表面Pt⁰很好地充当了CO、甲苯反应时的活化位点,催化剂表现出优异的性能;浸渍还原法中,Pt纳米粒子之间会发生团聚现象,同时部分Pt又以Pt²⁺的形式与CeO₂之间形成了Pt-O-Ce相互作用,载体表面暴露Pt⁰含量的下降是催化剂表现出较弱活性的主要原因;浸渍法中,以Pt离子对Pt进行负载,Pt完全以Pt²⁺的形式参与到Pt-O-Ce键成键中,表面Pt⁰缺失,催化剂表现出明显的失活现象。Pt/CeO₂催化剂中,起主要活性作用的是金属态Pt⁰,胶体粒子原位沉积法能够实现Pt⁰的直接负载,对于提高Pt基催化剂中Pt的利用率,降低Pt资源消耗都具有重要意义。     

不锈钢板负载V2O5-WO3-TiO2催化剂制备及其催化还原脱硝性能

以溶胶-凝胶法制备的TiO₂粉末为载体,偏钒酸铵和水合钨酸铵溶液为浸渍液,采用分步浸渍法制备了V₂O₅-WO₃-TiO₂催化剂,以聚乙烯醇-硅溶胶为黏合剂,采用涂覆法将催化剂粘合于经硫酸和钛酸丁酯溶胶处理过的不锈钢板板材表面,获得不锈钢板负载的V₂O₅-WO₃-TiO₂催化剂。采用XRD、FT-IR和SEM等表征手段对催化剂进行表征,结果表明,V₂O₅-WO₃-TiO₂催化剂可均匀负载于不锈钢板表面。采用氨选择性催化还原氮氧化物法研究了催化剂的脱硝性能,结果表明,在空速8 000 L·（kg·h）^-1和反应温度360 ℃的条件下,NOx脱除率超过92%,且制备的催化剂具有良好的稳定性和耐硫性。     

SO42-/TiO2/Al2O3型固体酸制备及催化合成醋酸丁酯

以共沉淀-浸渍法制备了SO₄^2-/TiO₂/Al₂O₃型固体酸催化剂,醋酸与正丁醇酯化反应作为探针反应,考察SO₄^2-/TiO₂/Al₂O₃型固体酸催化剂的催化性能,采用响应面法对制备催化剂过程中的陈化温度、硫酸浸渍液浓度和焙烧温度因素进行优化,通过XRD和IR对制备的固体酸催化剂进行表征。结果表明,在陈化温度-4 ℃、硫酸浸渍液浓度1.48 moL·L^-1和焙烧温度586 ℃条件下制得的催化剂催化性能最高,醋酸正丁酯酯化率可达98.1%,重复使用性良好。     

SO42-/TiO2-HZSM-5固体超强酸催化剂的制备及酯化性能

采用溶胶-凝胶法制备了HZSM-5分子筛负载SO₄^2-/TiO₂固体超强酸催化剂, 利用直接酯化法催化合成三羟甲基丙烷油酸酯。通过IR、XRD、BET、SEM对催化剂进行了表征, 结果表明TiO₂以纳米颗粒的形式附着于HZSM-5分子筛表面, 且负载后催化剂的比表面积高达309.2m²/g, 比HZSM-5分子筛提高了45.6m²/g, 且催化剂具有强酸性(-13.8< H₀ < -12.14)。探讨了沉淀pH值、焙烧温度、焙烧时间等催化剂制备条件对SO₄^2-/TiO₂-HZSM-5固体超强酸催化剂催化三羟甲基丙烷油酸酯酯化反应活性的影响。结果表明在沉淀pH=8、硫酸的浸渍浓度为0.5mol/L、浸渍时间为30min、焙烧温度为550℃、焙烧时间4h的条件下, SO₄^2-/TiO₂-HZSM-5固体超强酸催化剂催化活性最高, 三羟甲基丙烷油酸酯的酯化率高达97.6%;抗乳化性能良好, 油水分离时间为5min。SO₄^2-/TiO₂-HZSM-5固体超强酸催化剂在重复使用6次的情况下, 酯化率下降8.8%, 催化剂的重复使用性能良好。     

NiMo/TiO2-Al2O3催化剂活性相表征及加氢脱硫反应性能研究

采用共沉淀法制备TiO₂含量不同的TiO₂-Al₂O₃复合载体,以传统的浸渍法制备活性金属负载量相同的NiMo/TiO₂-Al₂O₃催化剂。运用N₂低温吸附法、X射线衍射、H₂程序升温还原和激光拉曼光谱等方法对催化剂进行表征,在10 mL微型反应装置上进行催化剂活性评价。结果表明,当复合载体中TiO₂含量达到一定值后,TiO₂在整个TiO₂- Al₂O₃体系中的存在状态由高度分散转变为表面富集,XRD能够检测出锐钛矿型TiO₂的特征峰;TiO₂的添加对于催化剂的酸性能没有明显改变;激光拉曼光谱分析结果表明,TiO₂的存在有利于生成八面体结构的钼物种,并在TiO₂质量分数为8%时加氢脱硫活性达到较高水平。     

Hydrogenation of CO2 over sprayed Ru/TiO2 fine particles and strong metal–support interaction

Ru/TiO₂ catalysts were prepared by spray reaction (SPR) and conventional impregnation (IMP) methods. The catalytic activities of SPR fine particles were much higher than those of IMP catalysts for CO₂ hydrogenation. A high temperature reduction greatly promoted the activity of SPR catalyst. A model of surface structure was proposed which exhibits the enhancement of decoration and the formation of more boundaries over spr-Ru/TiO₂. The high activity of SPR catalyst is attributed to the occurrence of new active sites at the metal–support perimeters and not any SMSI phenomenon. EXAFS reveals that the Ru atom was interacting with TiO₂ by oxygen atom so strongly on the SPR catalysts that a part of the Ru atoms, located near the internal interface between Ru particles and TiO₂ support, existed as Ruⁿ⁺ (n<4) cations even if SPR catalyst was subjected to a high temperature reduction. These Ruⁿ⁺ cations are responsible for the inhibition of SMSI formation over SPR catalysts.     

Pd-Rh/TiO2光催化CO2氧化乙烷脱氢研究

采用浸渍还原方法制备Pd-Rh/TiO₂催化剂用于常温光催化CO₂氧化乙烷脱氢制C₂H₄。研究不同Pd/Rh比催化剂的光反应性能,利用XRD、EDX-mapping、TEM、HRTEM、XPS技术表征催化剂表面和电子特性,通过UV-Vis、PL技术考察催化剂光响应性能,采用原位红外光谱技术分析Pd-Rh/TiO₂光催化CO₂氧化乙烷脱氢反应机理。研究表明,Pd-Rh双金属体系可有效提高光反应活性,光照下Pd和Rh金属之间存在内部电子转移的作用,降低了Pd表面的电子云密度,促进光生电子和空穴的分离,同时促进了C₂H₆和CO₂在材料表面的吸附。Ar替换CO₂的对比实验证明,反应中的CO₂消耗H₂,可消除催化剂表面积碳,促进C₂H₄生成。     

A comparative study of TiO2 supported noble metal catalysts for the oxidation of formaldehyde at room temperature

The TiO₂ supported noble metal (Au, Rh, Pd and Pt) catalysts were prepared by impregnation method and characterized by means of X-ray diffraction (XRD) and BET. These catalysts were tested for the catalytic oxidation of formaldehyde (HCHO). It was found that the order of activity was Pt/TiO₂  Rh/TiO₂ > Pd/TiO₂ > Au/TiO₂  TiO₂. HCHO could be completely oxidized into CO₂ and H₂O over Pt/TiO₂ in a gas hourly space velocity (GHSV) of 50,000 h⁻¹ even at room temperature. In contrast, the other catalysts were much less effective for HCHO oxidation at the same reaction conditions. HCHO conversion to CO₂ was only 20% over the Rh/TiO₂ at 20 °C. The Pd/TiO₂ and Au/TiO₂ showed no activities for HCHO oxidation at 20 °C. The different activities of the noble metals for HCHO oxidation were studied with respect to the behavior of adsorbed species on the catalysts surface at room temperature using in situ DRIFTS. The results show that the activities of the TiO₂ supported Pt, Rh, Pd and Au catalysts for HCHO oxidation are closely related to their capacities for the formation of formate species and the formate decomposition into CO species. Based on in situ DRIFTS studies, a simplified reaction scheme of HCHO oxidation was also proposed.     

Catalytic oxidation of low concentration formaldehyde over Pt/TiO2 catalyst

Formaldehyde(HCHO) is an important indoor pollutant.Catalytic oxidize low concentration HCHO is an effective way to eliminate indoor pollution.In this study,a series of Pt/TiO_2 catalysts are prepared by impregnation and reduced by NaBH_4.The effects of loading amount of Pt and cry stal type of TiO_2 on the physical and chemical properties and the catalytic performance in HCHO oxidation reaction are investigated.The results show that the quantity of active site and the oxygen vacancy of catalysts increa sed with increasing Pt content,which is beneficial to promote the further performance of catalysts.Nevertheless,with the further rises of Pt content,the specific surface area further decreases,and the proportion of Pt~(2+) species on the catalyst surface which is significant to catalytic properties also decreases,causing catalytic performance decreases.Compared with the catalyst supporting on rutile,the Pt/α-TiO_2 catalyst supporting on anatase has larger specific surface area,more Pt~(2+) phase and easier to form oxygen vacancy in the support,which cause better catalytic performance.The catalyst with Pt content of0.1 wt% and supported by anatase TiO_2 has the best catalytic performance.The HCHO conversion efficiency reaches 98% and 100% at 50℃ and 100 ℃, and the stabilization time is longer than 140 h.     

焙烧及还原条件对Ni2P/TiO2-Al2O3催化剂加氢脱硫性能的影响

采用溶胶-凝胶法制备了TiO₂-Al₂O₃复合载体, 以柠檬酸(CA)为络合剂采用浸渍法制备了Ni₂P负载的TiO₂-Al₂O₃复合载体催化剂, 并用 X 射线衍射(XRD)、N₂吸附比表面积(BET)测定技术对催化剂的结构和性质进行了表征, 考察了载体焙烧温度、催化剂焙烧温度、还原温度、还原压力对其进行的二苯并噻吩(DBT)加氢脱硫(HDS)性能的影响。结果表明, 升高载体焙烧温度有利于催化剂表面上活性物种的分散, 但焙烧温度过高会导致催化剂烧结, 适宜的载体焙烧温度为550℃。当还原温度为500～550℃时, 磷化镍主要以Ni₁₂P₅相形式存在, 且随着还原温度的升高, Ni₁₂P₅的衍射峰强度逐渐增强, 还原温度为700℃时, 可得到单一的Ni₂P物相。载体焙烧温度为550℃, 催化剂焙烧温度为500℃, 还原温度为700℃, 常压还原制备的Ni₂P/TiO₂-Al₂O₃催化剂具有最好的活性。在360℃、3.0MPa、氢油体积比500、液时体积空速2.0h^-1的条件下, 反应4h时, DBT转化率为99.5 %。     

The CO–H2 and CO–H2O reactions over TiO2 nanotubes filled with Pt metal nanoparticles

We have investigated the catalytic behavior of Pt encapsulated TiO₂ nanotubes for the water gas shift reaction as well as the hydrogenation of CO. Pt–TiO₂ nanotube catalysts were prepared by employing fine fiber shaped crystals of [Pt(NH₃)₄](HCO₃)₂ complex as a structure determining template material. The turnover frequencies (TOF) of these nanotube catalysts were more than one order of magnitude larger than conventional impregnation Pt/TiO₂ catalysts, and the selectivity for methanol in CO–H₂ reaction was extraordinary high compared to the impregnation catalysts. The XPS and XRD analyses of the nanotubes revealed characteristic electronic state of reduced TiO₂ (Ti³⁺ in rutile structure) with zerovalent Pt even after the calcination at 773 K. In WGS reaction, electron rich Ti³⁺ on the nanotube wall may play an important role to activate water molecules for the oxidation of CO. In CO–H₂ reaction, similar promotion effect of Ti³⁺ species may be operating for selective methanol formation by supplying active OH(a).     

制备方法对V_2O_5-WO_3/TiO_2选择性催化还原催化剂性能的影响

采用共沉淀法、溶胶-凝胶法和浸渍法制备了V2O5质量分数4%和WO3质量分数6%的V2O5-WO3/TiO2选择性催化还原催化剂,对比了3种方法制备的催化剂选择性催化还原NO性能。采用X射线衍射、热重、N2吸附-脱附和程序升温还原等对制备的V2O5-WO3/Ti O2催化剂的结构和性质进行表征,结果表明,共沉淀法制备的V2O5-WO3/TiO2催化剂具有更好的选择性催化还原NO活性和更大的比表面积,影响共沉淀法选择性催化还原NO活性的主要因素是催化剂的热稳定性、表面羟基数量、比表面积、粒径分布以及V、W与Ti之间的内在作用。     

Preparation of solid acid catalyst SO42−/TiO2/γ-Al2O3 for esterification: A study on catalytic reaction mechanism and kinetics

In this work, a series of SO₄^2-/TiO₂/γ-Al₂O₃ solid acid catalysts were synthesized by impregnation method, in which nano-TiO₂ was prepared by sol-gel method, and then the nano-TiO₂ sol was loaded on porous γ-Al₂O₃ supporter through impregnation. The structure and property of catalyst were characterized by XRD, N₂-BET, SEM, TEM, XPS, NH₃-TPD, Pyridine-IR and FT-IR. In addition, the catalyst of chelate bidentate coordination acid center model was established. The catalytic performance test was carried out in the esterification of n-butyl alcohol with lauric acid and the catalyst showed excellent activity. The experimental results showed that the medium strength acid sites were more dominant active sites than the strong and weak acid sites for the rapid esterification reaction. Its kinetic behaviors and activation energy were studied for the esterification under the catalytic reaction condition.     

TiO_2-SiO_2复合氧化物载体的pH值和焙烧温度对催化剂的辛烷异构化性能的影响

采用溶胶-凝胶法制备TiO_2-SiO_2复合氧化物载体,通过超声浸渍法制备Ni O和WO3改性负载的Ni O-WO3/TiO_2-SiO_2催化剂,考察不同p H值和焙烧温度条件下制备的载体对催化剂辛烷异构化性能的影响。结果表明,制备的Ni O-WO3/TiO_2-SiO_2催化剂呈多孔结构,平均孔径约5 nm,平均晶粒尺寸(10~20)nm。以焙烧温度500℃和p H=2条件下制备的TiO_2-SiO_2为载体,制得的催化剂比表面积达322.51 m2·g-1,在辛烷异构化反应中,正辛烷转化率为28.3%,选择性85.1%。