纳米MOx/ZrO2催化剂上乙醇氧化合成乙醛性能研究

采用溶胶-凝胶法首先制备出Zr(OH)₄凝胶，再将凝胶用乙醇进行醇化处理，经烘干和焙烧制得ZrO₂纳米载体。载体颗粒粒径均匀，大小为20 nm左右。以ZrO₂为载体，采用浸渍法分别负载Fe₂O₃、CuO、NiO和Mo₂O₃等不同金属氧化物，制得负载型催化剂。通过XRD、TEM、SEM和IR等对催化剂进行表征。以乙醇氧化脱氢合成乙醛为探针反应，考察了催化剂的催化性能。实验结果表明，催化剂Fe₂O₃/ZrO₂在反应温度为573 K时，乙醇转化率为75.8%，乙醛选择性为97.3%。     

NiMo/ZrO2-Al2O3柴油深度加氢脱硫催化剂的研究

以ZrOCl₂·8H₂O和Al₂O₃为原料,采用包覆法制备了一系列不同ZrO₂含量的ZrO₂-Al₂O₃复合载体,并用等体积浸渍法负载活性金属,制备了相应的NiMo/ZrO₂-Al₂O₃加氢脱硫催化剂,以柴油为原料考察了催化剂的加氢脱硫活性,利用XRD、N₂吸附和UV-Vis DRS等技术对催化剂及载体的基本物性进行了表征。结果表明,在催化剂载体中引入适量的ZrO2,保持了Al₂O₃载体的孔道结构,降低了活性金属和载体的相互作用,有利于提高催化剂的柴油加氢脱硫活性,当载体中ZrO₂质量分数为10%时,催化剂表现出最高的催化活性,脱硫率达99.25%,产品中硫低于10 μg·g^－1,满足柴油欧-Ⅳ的硫含量标准。     

W-Mo-Ni-Cr/Al2O3催化剂的表征及其加氢脱氮性能研究

采用分步浸渍法制备了负载型W-Mo-Ni-Cr催化剂。并采用X射线衍射（XRD）、差热分析（TG/DTA）、氮气吸附（BET）、程序升温脱附（TPD）、程序升温还原（TPR）和红外光谱（IR）等方法对其进行表征。以吡啶为模型化合物进行了加氢脱氮活性试验，在反应温度180 ℃，反应时间1 h时，催化剂的催化性能最佳。实验条件下，吡啶的单次转化率可达88.5％。     

C+10重芳烃催化加氢脱烷基反应研究

用等体积浸渍法制备了单层分散的MoO₃/γ-Al₂O₃催化剂。以C⁺₁₀重芳烃为原料,用固定床反应器考察了所制备的催化剂加氢脱烷基性能。研究表明,MoO₃/γ-Al₂O₃是C⁺₁₀重芳烃加氢脱烷基反应的高活性催化剂,并考察该催化剂在不同工艺条件下的加氢脱烷基性能。在反应温度（550～575） ℃、压力5 MPa、空速（1.0 ～1.5） h^-1和氢烃物质的量比为7～10条件下,C⁺₁₀重芳烃转化率达67%以上,C^-₉芳烃的选择性超过80%。100 h的性能评价结果表明,该催化剂具有较好的稳定性。     

Cu/ZrO2催化剂用于二乙醇胺脱氢合成亚氨基二乙酸的研究

用共沉淀法制备的Cu/ZrO₂催化剂进行二乙醇胺催化脱氢合成亚氨基二乙酸,分别考察了催化剂用量、原料配比、反应温度、反应压力和反应时间等因素对反应的影响。结果表明,最佳反应条件为:二乙醇胺68.5 g、去离子水140 g、催化剂的加入量为二乙醇胺质量的20%、n(氢氧化钠)∶n(二乙醇胺)=2.3∶1、反应温度170 ℃、反应压力0.8 MPa和反应时间5 h。在此条件下,亚氨基二乙酸收率可达92.3%。催化剂经重复使用8次后,亚氨基二乙酸收率仍然保持在90%以上。     

SO2-4/ZrO2-Al2O3催化合成脂肪酸季戊四醇酯的研究

以脂肪酸和季戊四醇为原料，三甲苯为带水剂，SO^2-₄/ZrO₂-Al₂O₃固体超强酸催化,合成脂肪酸季戊四醇酯。实验结果表明，控制酯化温度（180～200） ℃、醇酸物质的量比为1∶5.6、催化剂加入量为原料总量的0.9%和反应时间为4 h时，可获得最佳反应结果，酯化率达99.88%。IR 谱表明，产品中羟基吸收峰基本消失，证明酯化反应较充分和完全。     

SO2-4/ZrO2/USY催化合成氯乙酸正丙酯的研究

采用沉淀法制备SO^2-₄/ZrO₂/USY催化剂,以氯乙酸和正丙醇为原料,催化合成氯乙酸正丙酯,考察反应时间、带水剂种类、带水剂用量、醇酸物质的量比及催化剂用量等因素对酯化反应的影响。结果表明,环己烷为氯乙酸正丙酯合成反应较适宜的带水剂,SO^2-₄/ZrO₂/USY在酯化反应中具有良好的催化活性。在氯乙酸0.25 mol、n(醇)∶n(酸)=1.5、反应时间3.0 h、带水剂环己烷7.5 mL和催化剂用量1.0 g条件下,酯化率达95.72%。催化剂重复使用6次,酯化率仍可达94.91%,催化活性基本不变,具有良好的重复使用性能。SO^2-₄/ZrO₂/USY具有反应条件温和、催化活性高、重复使用性能好和环境污染小等优点,具有较高的开发价值。     

K2O影响Cu/ZnO催化剂CO2加氢反应性能的原因分析

运用活性评价、XRD、TPR、CO2-TPD、CO-TPD等手段,分析了K₂O影响Cu/ZnO催化剂CO₂加氢反应性能的原因。试验结果表明,甲醇收率大幅度降低的原因是CuO-ZnO催化剂经K₂O改性后,催化剂还原难度增加;提高了金属Cu的电子密度,促进了CO的歧化反应;催化剂还原后,对CO₂的吸附量大为减少。     

C2选择加氢催化剂结焦成因及对策

研究了C₂选择加氢催化剂的结焦对催化剂性能的影响,结焦造成比表面积损失90%以上,比孔容损失约85%,催化剂质量增加21%,结焦使催化剂孔径分布产生较大变化,催化剂活性大幅度降低。结焦物形成过程中,主要发生狄尔斯-阿德尔反应、羟甲酰化反应和齐聚反应。采取降低床层温度、提高C₂物料纯度、减少C₃组分含量、在反应物料中不加入CO、减少物料中含氧化物含量以及提高氢气分压的措施,可以降低催化剂结焦速率,延长催化剂使用周期和寿命。     

V2O5/TiO2基SCR脱硝催化剂的制备及其催化性能

采用纳米TiO₂为催化剂载体原料,V₂O₅为催化剂,通过混合、球磨、干燥和焙烧等工艺制备选择性催化还原脱硝法催化剂,研究了催化剂的制备工艺和催化性能。通过差热分析研究催化剂的相变和烧结温度,通过模拟烟气分析装置表征催化剂的催化性能。结果表明,加入V₂O₅可以提高催化性能,以6%V₂O₅-94%TiO₂为配方的催化剂对NO的脱除率达97.5%,温度窗口为（300～420） ℃。     

Pd/C催化剂催化氯苯加氢脱氯性能

以氯苯为模型反应原料,采用Pd/C为催化剂催化加氢氯苯脱氯,考察溶剂种类、反应温度、反应压力和反应时间对Pd/C催化剂催化氯苯加氢脱氯性能的影响。结果表明,采用Pd/C为催化剂,以甲醇与水质量比1∶1为溶剂,在反应温度70℃和反应压力0.8 MPa条件下反应100 min,Pd/C催化剂上氯苯转化率超过50%。以甲醇与水质量比1∶1为溶剂,在减少废水和降低成本方面有较大优势。     

The gas phase hydrodechlorination of chlorobenzene over nickel/silica

The gas phase hydrodechlorination of chlorobenzene over the temperature range 473 K⩽T⩽573 K has been studied using a 1.5% (w/w) Ni/SiO₂ catalyst. Reproducible turnover frequencies are quoted and the effects of varying such process variables as reaction time and temperature, contact time, chlorobenzene and hydrogen partial pressures are presented. The catalyst was 100% selective in promoting hydrodechlorination and the aromatic ring remained intact in every instance. Under reaction conditions far removed from equilibrium conversions, the catalyst exhibited no appreciable short term deactivation while the maintenance of long term activity was also established. Chlorine coverage of the catalyst surface under reaction conditions was probed indirectly by monitoring, via pH changes in an aqueous NaOH trap, HCl desorption after completion of the catalytic step. The hydrogenolysis of bromobenzene, 2‐chlorophenol and 3‐chlorotoluene under the same reaction conditions were considered for comparative purposes where the turnover frequencies decrease (at 573 K) in the order 2‐chlorophenol>3‐chlorotoluene>chlorobenzene>bromobenzene; reactivity is discussed in terms of thermodynamic limitations and reactant/catalyst interactions. Reaction orders with respect to hydrogen and chlorobenzene partial pressures were obtained at different reaction temperatures and the experimental rate data are adequately represented by an extended power rate expression that approximates the Langmuir–Hinshelwood model for non‐competitive adsorption. © 1999 Society of Chemical Industry     

Gas-phase hydrodechlorination of pentachlorophenol over supported nickel catalysts

The gas-phase hydrodechlorination of pentachlorophenol (PCP) over nickel/silica and nickel/Y zeolite catalysts at 573 K has been studied. Each catalyst was 100% selective in cleaving the C–Cl bonds, leaving the hydroxyl substituent and benzene ring intact. The variation of catalytic activity and selectivity (in terms of partial and full dechlorination) with time-on-stream is illustrated and catalyst deactivation is addressed. Dechlorination efficiency is quantified in terms of dechlorination rate constants, phenol selectivity/yield and the ultimate partitioning of chlorine in the parent organic and product inorganic host. Increasing the nickel loading on silica was found to raise the overall level of dechlorination while the use of a zeolite support introduced spatial constraints that severely limited the extent of dechlorination. Product composition was largely determined by steric effects where resonance stabilisation had little effect. The reaction pathways, with associated pseudo-first-order rate constants, are also presented. This revised version was published online in November 2006 with corrections to the Cover Date.     

Effect of support modification on the chlorobenzene hydrodechlorination activity on Pt/Al2O3 catalysts

Al₂O₃ was modified with TiO₂ and ZrO₂ using organometallic precursors and is used in the preparation of supported platinum catalysts. The catalysts have been characterised by nitrogen adsorption, hydrogen chemisorption and X-ray diffraction and were tested for their activity in the hydrodechlorination of chlorobenzene. The investigations show that support modification controls the catalyst deactivation remarkably and the catalysts were found to be highly active and selective. This revised version was published online in July 2006 with corrections to the Cover Date.     

The catalytic hydrodechlorination of mono-, di- and trichlorobenzenes over supported nickel

The gas phase hydrodechlorination (HDC) of chlorobenzene (CB), chlorotoluene(s) (CT), 3-chlorophenol (3-CP), dichlorobenzene(s) (DCB) and trichlorobenzene(s) (TCB) over the temperature range 473 K≤T≤573 K has been studied using 1.5% and 6.1% (w/w) Ni/SiO₂ catalysts; the catalytic data have been obtained in the absence of any appreciable short-term deactivation. HDC of DCB and TCB generated the partially or the fully dechlorinated aromatic product + HCl and there was no significant cyclohexene or cyclohexane in the effluent stream. The conversion of mono-chloroarenes yielded the following reactivity sequence CB < 2-CT < 3-CT < 4-CT < 3-CP, i.e. the presence of an electron donating ring substituent enhances HDC and steric hindrance lowers reactivity. HDC kinetics have been adequately represented by a pseudo-first order approximation. Chlorine removal from DCB and TCB isomers proceeded through sequential and concerted routes, the relative importance of each dependent on the nature of the isomer and reaction conditions; apparent HDC activation energy increases in the order CB < DCB < TCB. The relationship between dechlorination selectivity and residence time/fractional conversion is addressed. The higher Ni loaded catalyst delivered consistently higher (specific) dechlorination rates and higher benzene yields from a polychlorinated feedstock. Catalytic HDC over Ni/SiO₂ is presented as a viable means of treating/detoxifying concentrated chlorinated gas streams and the best strategy for generating the parent benzene or a target partially dechlorinated product is discussed.     

In situ production of nickel/graphitic carbon nanofiber composites and application in catalytic hydrodechlorination

The action of Ni/SiO₂ in the gas phase hydrodechlorination (at 573 K) of chlorobenzene, 1,3-dichlorobenzene and 1,3,5-trichlorobenzene is compared with that of a Ni/SiO₂ + C composite. The latter was prepared in situ by the decomposition of chlorobenzene at 873 K to generate graphitic carbon nanofibers bearing Ni particles at the fiber tips. The Ni/SiO₂ and Ni/SiO₂ + C (with varying C content) catalysts have been characterized by TEM, SEM, XRD and H₂ chemisorption. While the Ni/SiO₂ + C system delivered a lower initial fractional dechlorination, the composite outperformed the starting Ni/SiO₂ in terms of long-term activity, an effect that is linked to the structural characteristics.     

气相催化加氢脱氯合成HFCs催化剂的研究进展

综述了气相催化氯氟烃或氢氯氟烃加氢脱氯合成氢氟烃的催化剂组分选择、制备条件以及反应条件对催化活性的影响。     

Ce掺杂对Ru/TiO2催化氯苯性能的影响

采用等体积浸渍法制备了单贵金属Ru/TiO₂和双金属Ru-Ce/TiO₂系列催化剂,测试了其对氯苯的催化活性,并通过N₂吸脱附、扫描电镜(SEM)、程序升温还原(H₂-TPR)进行表征,旨在考察稀土元素Ce掺杂对Ru/TiO₂催化氯苯性能的影响。结果表明,Ce的引入可使其在降低贵金属含量的基础上仍保持高的催化效率,且极大地提高了低温催化活性。0.4%Ru-1.0%Ce/TiO₂与0.4%Ru/TiO₂相比,其T₁₀和T₉₀分别降低了50℃和60℃。H₂-TPR表明引入Ce为催化剂提供了更多的表面氧空位,形成Ru-O-Ce增强了其氧化还原能力。掺杂Ce未改变Ru/TiO₂催化剂的结构形貌,仍保持介孔结构,但若负载量过多,会堵塞部分孔道,阻碍污染物吸附及反应,降低催化性能。     

Gas phase hydrodechlorination of chlorinated aromatic compounds on nickel catalysts

Supported Ni/-Al₂O₃ catalysts were studied in the gas phase hydrodechlorination of substituted chlorobenzenes. The catalytic properties of the catalysts were shown to be determined by the metal nickel. A correlation between the rate of the gas phase hydrodechlorination of substituted chlorobenzene and donor-acceptor properties of substituents was established. The electron-donor substituents increase and the electron-acceptor ones decrease their reactivity. The correlation analysis of data treated via the Hammett equation shows that hydrodechlorination on Ni/-Al₂O₃ catalysts is a reaction of electrophilic type.     

Remarkable activity enhancement in the catalytic combustion of methane on supported palladium catalysts

The activity of supported palladium catalysts for the combustion of methane has been determined. It has been observed that the activity increases with time on stream irrespective of whether the catalysts are pre-calcined or pre-reduced. Careful re-reduction experiments have shown that the enhanced activity is maintained. It is concluded that the increase in activity with time on stream is not attributable to slow variations in the chemical state of the palladium particles, but to changes in the morphology of the palladium crystallites under reaction conditions. The possible role of dissolved carbon in stabilising the reconstructed crystallites against reduction is discussed.