海泡石-Al２Ｏ３混合载体对铂催化剂环己烷脱氢反应的影响

以三氧化二铝或海泡石(Sepiolite)-三氧化二铝混合物为载体,金属铂为活性组分,采用浸渍法分别制备了Pt／Ａl_２Ｏ_３、Pt／Ｓep-Ａl_２Ｏ_３催化剂,并考察了它们对环己烷脱氢反应的性能、抗硫性能及催化剂活性中心的影响。结果表明,Pt／Ｓep-Ａl_２Ｏ_３催化活性及抗硫性能均高于工业用Pt／Ａl_２Ｏ_３催化剂,同时增大了铂催化剂上的活性中心数及分散度。     

Pt/Al_2O_3与Pt/MgO-Al_2O_3催化剂制备及其催化氢能载体甲基环己烷脱氢反应性能

以碱共沉淀法制备Mg-Al水滑石,然后采用浸渍法负载活性组分Pt,经焙烧、氢气还原得到Pt/Al_2O_3与Pt/Mg O-Al_2O_3催化剂,采用XRD、N2吸附-脱附、FT-IR、H2-TPR和Py-IR等分析Mg O的加入对Pt/Al_2O_3催化剂结构性能的影响,并在甲基环己烷连续脱氢反应中对比两种催化剂活性。结果表明,Pt/Mg O-Al_2O_3催化剂比表面积小于Pt/Al_2O_3催化剂,且表面基本无酸性活性中心,但表现出与Pt/Al_2O_3催化剂相同的脱氢活性。在Pt负载质量分数2%、催化剂用量0.5 g、甲基环己烷0.1 m L·min-1纯样进料和325℃反应10 h后,原料平均转化率79.9%,脱氢产物只有甲苯,对应的产氢速率192.8 mmol·(g-metal·min)-1,表现出优良的脱氢活性。     

Re_2O_7/Al_2O_3复分解催化剂的表面物质研究——一种快速原子轰击质谱法

<正>使用负离子快速原子轰击质谱法研究了各种铼化合物和活性Re_2O_7/Al_2O_3催化剂.光谱分析表明,在催化剂表面上,除有R_2O_7外,还有表征为Re_xO_y峰的表面物质,x和y代表多种匹配数.Re_xO_y为复分解活性中心的起始物.     

Ni对Pt/γ-Al2O3催化甲基环己烷脱氢性能的影响

采用饱和浸渍法制备了γ-Al₂O₃负载的Pt单金属和Pt-Ni双金属催化剂,用固定床反应器评价了催化剂的甲基环己烷脱氢反应性能,以考察Ni对Pt/γ-Al₂O₃催化甲基环己烷脱氢性能的影响。结果表明,与单金属催化剂相比,Pt-Ni双金属催化剂具有更好的脱氢活性和稳定性。氢氧滴定分析结果表明加入Ni后Pt的分散性能变好,TEM分析表明加入Ni后金属颗粒尺寸变大,结合氢氧滴定与TEM数据,认为掺入Ni之后形成了Pt-Ni新的体系,此体系提高了催化剂表面上氢的结合能,最终提高了Pt-Ni双金属催化剂的脱氢活性和稳定性。此结果为开发适用于有机液体储氢材料脱氢的高效催化剂提供了思路。     

环己烷在碳化钼催化剂上的脱氢研究

以环己烷为碳源,采用程序升温还原法制备碳化钼催化剂,对前驱物和中间物及催化剂的晶相结构进行XRD表征,在固定床反应装置上进行环己烷的脱氢反应实验。固定反应压力为0.1 MPa,考察反应温度、空速、氢烃体积比和压力对碳化钼脱氢活性的影响。结果表明,催化剂活性相为高活性的β-Mo₂C,在反应温度450 ℃、空速2 h^-1、压力0.1 MPa和氢烃体积比200∶1条件下,环己烷转化率达88%,脱氢反应的选择性为79%。     

铂系低碳烷烃脱氢催化剂研究进展

综述了近年来国内外铂系低碳烷烃脱氢催化剂的技术现状与研究进展。首先从热力学角度论述了低碳烷烃脱氢反应与相关副反应的反应机理,随后分别从活性位点性能与催化脱氢的关系,氧化铝、分子筛等载体的作用,以及锡、碱金属、碱土金属、过渡金属等助剂改性对催化剂的影响等3个方面分析了铂系低碳烷烃脱氢催化剂的优势与存在的问题,进而探究了铂系脱氢催化剂的失活原因。最后对铂系脱氢催化剂的研究前景做了展望,提出该系列催化剂的主要发展方向包括降低贵金属铂的负载量、提高催化剂的稳定性、减少积炭副反应等。     

Pt系异丁烷脱氢催化剂研究进展

综述了Pt系异丁烷脱氢的研究状况,探讨了铂系催化剂的活性中心,重点总结了载体、助剂、失活这几方面对铂系催化剂的反应性能的影响,并对铂系催化剂的研究前景进行了展望.     

新一代催化重整催化剂的开发与应用

采用特殊方法对杂质含量极低的氢氧化铝进行改性,制得一种性能良好的γ-Al₂O₃载体,并将其应用于重整催化剂,制得含铂0.15%,铼0.30%,铼铂比2.0的高徕超低铂重整催化剂。它的活性、选择性、稳定性、再生性能和强度等极佳,已在工业装置上运转,是目前已工业化的含量最低的催化重整催化剂。     

丙烷脱氢制丙烯用单原子催化剂研究进展

丙烯是一种重要的有机化工原料和石油化工原料中间体,近年来在国内外市场的需求量持续增长。丙烷直接脱氢制丙烯技术具有收率高、技术成熟、经济环保等优点,备受研究者们的广泛关注。文中综述了丙烷直接脱氢制丙烯用单原子催化剂的研究进展,介绍了单原子催化剂的丙烷脱氢反应机理,探讨了单原子催化剂的失活行为,总结了活性组分、助剂及载体对单原子催化剂催化丙烷脱氢性能的影响,并分析讨论了单原子催化剂在当前研究中存在的问题。最后针对单原子催化剂虽具有优异的丙烯选择性和稳定性,但存在丙烷脱氢活性依旧不足的问题,提出了调控单原子催化剂电子结构促进丙烷脱氢活性的设计思路,为未来丙烷脱氢制丙烯高效单原子催化剂的设计提供了指导方向。     

MoVTeNbOx催化剂应用于乙烷氧化脱氢制乙烯的研究进展

乙烷氧化脱氢制乙烯是非常有应用前景的乙烯生产途径，MoVTeNbO_x催化剂具有活性高、氧化还原能力强等特点，是当前低碳烷烃氧化脱氢的研究热点。本工作系统综述了MoVTeNbO_x复合金属氧化物在乙烷氧化脱氢制乙烯反应中的应用研究情况，包括催化剂晶相结构与活性中心、催化剂制备和催化乙烷转化的影响因素及反应性能优化提升等方面。研究多金属氧化物催化剂活性中心的调控策略，实现各组分氧化物相互作用的最优化，优化制备条件，通过助剂调控策略提高催化剂氧化还原能力及表面V⁵⁺含量，进而提高乙烷氧化脱氢活性和运行稳定性，为催化剂的规模化生产和工业应用奠定基础，是当前的主要研究方向。最后展望了MoVTeNbO_x复合金属氧化物催化剂在氧化脱氢领域的发展前景。     

Thermal imaging of catalyst surface during catalytic dehydrogenation of cyclohexane under spray-pulsed conditions

Infra-red thermographic imaging, a tool widely used for screening of active catalytic materials in the field of combinatorial chemistry, has been used during dehydrogenation of cyclohexane on Pt catalyst supported on active carbon cloth and alumite supports. A spray-pulsed reactor with injection of atomized cyclohexane and to create alternate wet and dry conditions on the catalyst surface was used in this study. Since the production rate of hydrogen via endothermic dehydrogenation reaction is greatly dependent on the temperature of the catalyst surface, the temperature profile of the catalyst is important to observe. The observed change in the temperature profile at wet and dry conditions with varying pulse injection frequency and corresponding product gas analysis reveals that the spray-pulse mode is useful in improving the catalyst activity. Further, the comparison between activated carbon support and a more conductive support such as alumite is reported using thermal imaging for more suitable support in this endothermic reaction.     

Mercury-promotion of platinum catalysis of dehydrogenation and dehydrochlorination

Mercury in very low concentrations (i.e. when there is up to about one Hg atom in one hundred Pt atoms) promotes the dehydrogenation activity of supported Pt towards cyclohexane and to a lesser extent cyclohexene. However, dehydrochlorination activity towards monochlorocyclohexane is relatively unaffected by Hg additions. Interestingly, cyclohexene is a significant intermediate from dehydrochlorination at high Hg concentrations; consideration is given to reaction mechanisms. The low concentrations at which Hg promotes catalytic activity suggests that it may disrupt the lattices of the Pt crystallites producing surface sites of low coordination and high activity.     

In-situ infrared thermographic analysis during dehydrogenationof cyclohexane over carbon-supported Pt catalysts using spray-pulsed reactor

Infrared thermography, a tool used for screening of active catalytic materials generally during the exothermic reactions has been used for thermal imaging during strong endothermic reaction of dehydrogenation of cyclohexane on Pt catalyst supported on active carbon cloth (CFF-1500s) sheets. A spray-pulsed mode was used for injection of atomized cyclohexane and to create alternate wet and dry condition on catalyst surface. The simultaneous product gas analysis and recording of the temperature profile of the catalyst surface using an IR camera was carried out. The production rate of hydrogen via endothermic dehydrogenation reaction is greatly dependent on the temperature of the catalyst surface. The observed change in the temperature profile at wet and dry conditions with varying pulse-injection frequency and corresponding product gas analysis reveals that the spray-pulse mode is useful in improving the catalyst activity. Further the reaction conditions were optimized using thermal profile data.Rajesh B. Biniwale-On deputation from NEERI, Nagpur India.     

Characterization and activity of Pt-Sn/Al2O3 catalysts of different preparation: coimpregnation and new Pt-Sn precursor

A new bimetallic Pt-Sn compound [Pt(NH₃)₄][SnCl₆] has been used as precursor for the preparation of supported Pt-Sn/Al₂O₃ catalysts. A comparison of a dried sample with that prepared by coimpregnation displays different behaviour in TPR, chemisorption. The initial catalytic activity properties were checked in the reactions of cyclohexane dehydrogenation and cyclopentane ring opening, whilen-hexane skeletal reactions were used to probe the quasisteady-state activity. The catalyst prepared via the Pt-Sn complex precursors exhibited some-what lower specific activity. This fact, together with enhanced olefin formation fromn-hexane was taken as an indication of lower amount of contiguous Pt atoms and some electronic interaction between Pt and Sn in that catalyst.On leave from Fachhochschule Ostfriesland, D-26723 Emden, Germany.     

Computerized Solution of the Dynamic Sorption Process for a Ternary System in a Heterophase Medium

A mathematical model equation for the ternary adsorption–reaction process was developed and illustrated for the catalytic dehydrogenation of cyclohexane to benzene with the adsorption of hydrogen atoms as a monomolecular species on platinum–rhenium/alumina catalyst in inert and active carrier gases using pulse and continuous flow techniques. An optimization routine of the Nelder–Mead simplex method was used to estimate the surface reaction rate constant and adsorption equilibrium constant at different temperatures. These constants were then used to determine activation energies and adsorption equilibrium energies for cyclohexane dehydrogenation in inert (argon, helium) and active (hydrogen) carrier gases using pulse and continuous flow techniques. Numerical solutions for the ternary adsorption–reaction scheme were compared with the binary adsorption–reaction case where hydrogen adsorption is ignored. The predicted results for the ternary adsorption–reaction revealed that hydrogen adsorption during cyclohexane dehydrogenation is significant.     

铂纳米簇/壳聚糖杂化膜催化苯部分加氢制备环己烯

研究了铂纳米簇/壳聚糖杂化膜(Pt/CS)对液相苯部分加氢反应的催化性能.通过微波加热还原氯铂酸的方法制备了单分散铂纳米簇,并将其与壳聚糖(CS)进行杂化后得到铂纳米簇/壳聚糖杂化膜.利用,ITEM、Frr-IR、XRD和XPS等对铂纳米簇以及杂化膜的结构进行了表征,透射电镜表明,铂纳米颗粒平均粒径为3.7 mm.XP...     

Dual-function catalysis in propane dehydrogenation over Pt1–Ga2O3 catalyst: Insights from a microkinetic analysis

The kinetics of propane dehydrogenation over single-Pt-atom-doped Ga₂O₃ catalyst has been examined by combining density functional theory calculations and microkinetic analysis. The doping of Pt not only can improve the selectivity of the Ga₂O₃ catalyst by hindering the deep dehydrogenation reactions but also helps to achieve a long-term stability by improving the resistance of Ga₂O₃ to hydrogen reduction. Microkinetic analysis indicates that upon Pt doping the turnover frequency for propane consumption is increased by a factor of 2.8 under typical operating conditions, as compared to the data on the pristine Ga₂O₃ surface. The calculated results suggest that the Pt₁–Ga₂O₃ catalyst shows a bifunctional character in this reaction where the Pt–O site brings about dehydrogenation while the Ga–O site is active for desorbing H₂, which provides a beautiful explanation for the previous experimental observation that even trace amounts of Pt can dramatically improve the catalytic performance of Ga₂O₃.     

丙烷脱氢制丙烯催化剂的研究进展

丙烷脱氢产业的迅猛发展亟需研发新一代高性能催化剂。本综述阐述了近年来新型负载型Pt纳米簇、金属氧化物和碳材料在丙烷脱氢反应中的研究进展。文章指出：Pt纳米簇的分散性和稳定性是决定其脱氢性能的关键因素;通过发展新合成技术和调节载体性质能改进其催化活性。金属氧化物中不饱和金属阳离子是脱氢反应的活性位点;调节载体的性质、优化制备方法以及结构掺杂都可显著提高其催化活性。碳材料中的含氧官能团被认为是丙烷脱氢反应的活性中心;对碳材料的比表面积、孔道性质及含氧官能团的数量等参数进行合理调控,能改善其催化性能。最后,文章提出未来的研究将重点解决Pt纳米簇的抗烧结性能弱、氧化物的本征活性低、碳材料高温稳定性差的问题,实现该领域的重大突破。