共查询到20条相似文献,搜索用时 265 毫秒
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Solving the problem of catalyst deactivation is essential in process design. To do this, various aspects of the kinetics of processes with catalyst deactivation, and their different mechanisms, are discussed. Catalyst deactivation often cannot be avoided, but more knowledge on its mechanism can help to find kinetic means to reduce its harmful consequences. When deactivation is caused by coke, the generation of coke precursors is the determining step in the deactivation kinetics. Different types of deactivation were distinguished that lead to different evolution of the process. The phenomenon of non-uniform coking can be linked to catalyst surface non-uniformity. For the class of catalysts with more than one type of active sites, an explanation was suggested for the observed trends in the deactivation modes. For catalytic proc-esses using catalyst particles of industrial size, the influence of intraparticle diffusion resistance is important. The analysis showed that for a number of processes, the decrease of the reaction rate due to deactivation is less under diffusion control. For certain reaction mechanisms, there exist operation conditions where the rate of the process under diffusion control exceeds the rate in the kinetic control regime. A signifi-cant problem is the change of selectivity in the course of catalyst deactivation. The selectivity may either decrease or increase, and depends on the reaction mechanism during deactivation. The changes are larger when there is no diffusion resistance. The intentional poisoning of catalysts and its influence on catalyst activity and selectivity for the process of ethylene oxide production was discussed. 相似文献
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SongHaiCHAI XinPingWANG YingJunWANG TianXiCAI 《中国化学快报》2003,14(7):748-751
The SiO2 and γ-A12O3 supported MoOx catalyst and a MoOx-SiO2 catalyst have been studied in a conventional fixed-bed flow reactor for n-alkanes isomerization. It is shown that the MoOx-SiO2 catalyst with SiO2 framework, in which the bulk MoOx phase is large enough to form typical mesoporous structure, is promising in terms of its advantages of both improved mechanical strength and high catalytic properties over the supported MoOx and bulk MoOx catalyst. 相似文献
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《Journal of Energy Chemistry》2015,(5)
CO2 methanation has been a hot topic because of its important application in the spacecraft and potential utilization of carbon dioxide. Nickel catalyst is active for this reaction. However, its activity still needs to be improved. Dielectric barrier discharge(DBD) plasma, initiated at ambient condition and operated at ~150 °C,has been employed in this work for decomposition of nickel precursor to prepare Ni/Mg Al2O4. The plasma decomposition results in high dispersion, unique structure, enhanced reducibility of Ni particles and promoted catalyst-support interaction. An improved activity of CO2 methanation with a higher yield of methane has been achieved over the plasma decomposed catalyst, compared to the catalyst prepared thermally. For example, the methane yield of the plasma prepared catalyst is 71.8% at 300 °C but it is 62.9% over the thermal prepared catalyst. The catalyst characterization confirmed that CO2 methanation over the DBD plasma prepared catalyst follows pathway of CO methanation. 相似文献
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Lai Jun WANG Ming Fen WEN Yu Shan LI Dong YANG Jing CHEN Chong Li SONG 《中国化学快报》2006,17(9):1239-1242
Alumina is widely used as a catalyst or catalyst support in many heterogeneous catalytic processes owing to its high surface area, superior chemical activity and low cost 1. In order to prepare the thermal-stable alumina with high surface area and large p… 相似文献
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Formaldehyde is an important air pollutant and its removal is essential to protect human health and meet environmental regulations. Ag-based catalyst has a considerable potential for HCHO oxidation in low temperature range. The valence state of Ag is one of the key roles in formaldehyde catalytic oxidation.However, its effect on activity is still ambiguous. Non-thermal plasma and conventional calcination were employed to regulate Ag valence state in this study. Three Ag-Co/CeO2 cataly... 相似文献
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Active sites of Fluid catalytic cracking(FCC) catalyst are poisoned during operation in the FCC reactor due to causes including feedstock contaminant metals deposition.This leads to activity,selectivity and increasing coking problems,thereby raising concern to the refiner.This work investigated effect of nickel coexisting with vanadium in the FCC feedstock on the standard FCC catalyst during cracking process,in which destruction of active sites occurs as a result of the metals deposition.Laboratory simulated equilibrium catalysts(E-cats) were studied by XRD,FTIR spectroscopy,N2 adsorption,solid state MAS-NMR,SEM and H2-TPR.Results revealed that vanadium,above a certain concentration in the catalyst,under hydrothermal conditions,is highly detrimental to the catalyst’s structure and activity.Conversely,nickel hardly affects the catalyst structure,but its co-presence in the catalyst reduces destructive effects of vanadium.The mechanism of nickel inhibition of vanadium poisoning of the catalyst is discussed. 相似文献
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NDAMANISHAJeanChrysostome WANGHui GUOLi-ping 《高等学校化学研究》2005,21(4):431-435
After the synthesis of polyaniline in the presence of ferrocenesulfoniccarboxylic acid, its influence on the electrochemical reaction of methanol was studied. The result indicates that the ferrocenyl in ferrocenesulfoniccarbexylic acid plays an important role in the electrocatalytic oxidation of methanol. CH3OH is adsorbed on PANI-Fc before its electrocatalytic oxidation. When the concentration of methanol is 2 mol/L, it begins to be oxidized. The effect of scan rate on the electrochemical reaction of methanol was also studied and 5 mV/s was favourable. It is another method to insert a metal catalyst in polyaniline without its electrodeposition. 相似文献
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Mahmood Tajbaksh Maryam Farhang Hamid Reza Mardani Rahman Hosseinzadeh Yaghoub Sarrafi 《催化学报》2013,34(12):2217-2222
A one pot three‐component coupling reaction of phenylacetylene, aldehyde, and amine derivatives in the presence of Cu(II) Salen complex as an efficient heterogeneous catalyst under solvent‐free conditions is reported. The catalyst displayed high activity and afforded the corresponding propargylamines in good to excellent yields. This method provides a wide range of substrate applicability. The catalyst was reused several times without significant loss of its catalytic activity. 相似文献
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Effect of diluent and reaction parameter on selective oxidation of propane over MoVTeNb catalyst using nanoflow catalytic reactor 下载免费PDF全文
The selective oxidation of propane to acrylic acid over an MoVTeNb mixed oxide catalyst, dried and calcined before reaction has been studied using high-throughput instrumentation, which is called nanoflow catalytic reactor. The effects of catalyst dilution on the catalytic performance of the MoVTeNb mixed oxide catalyst in selective oxidation of propane to acrylic acid were also investigated. The effects of some reaction parameters, such as gas hourly space velocity (GHSV) and reaction temperature, for selective oxidation of propane to acrylic acid over diluted MoVTeNb catalyst have also been studied. The configuration of the nanoflow is shown to be suitable for screen catalytic performance, and its operating conditions were mimicked closely to conventional laboratory as well as to industrial conditions. The results obtained provided very good reproducibility and it showed that preparation methods as well as reaction parameters can play significant roles in catalytic performance of these catalysts. 相似文献
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Jing Chen Yumei Tang Shihao Wang Lingbin Xie Cheng Chang Xiaolei Cheng Mingming Liu Longlu Wang Lianhui Wang 《中国化学快报》2022,(3):1468-1474
Molybdenum disulfide(Mo S2) with low cost, high activity and high earth abundance has been found to be a promising catalyst for the hydrogen evolution reaction(HER), but its catalytic activity is considerably limited due to its inert basal planes. Here, through the combination of theory and experiment, we propose that doping Ni in Mo S2as catalyst can make it have excellent catalytic activity in different reaction systems. In the EY/TEOA system, the maximum hydrogen production rate of EY/Ni-Mo-S... 相似文献
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采用不同手段研究了催化剂反应前后及在H2O和N2介质中再生时催化剂性质和表面原子浓度及其颁的变化。BET结果表明,N2介质中再生,催化剂的孔径基本没有变化,而H2O介质中再生的催化剂孔径明显增大,化学组成分析结果说明,长期运转使用后的催化剂在2和H2O介质中再生后其活性组分均有少量流失。电子探针的结果表明,结炭后的催化剂活性组分很不均匀,在N2和H2O介质中再生后其分布得到了明显改善,但仍不如新鲜 相似文献
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在加压条件下(0.1~1.1MPa)考察了MgO/BaCO_3催化剂在甲烷氧化偶联反应中的性能,以及加压后该催化剂的失活。XRD谱图表明,在加压失活的MgO/BaCO_3催化剂表面有部分MgCO_3牛成,这是由于部分活性相MgO发生了转变:XPS表征结果表明,在加压失活后的MgO/BaCO_3催化剂中B3CO_3向表面富积,致使催化剂的表面活性相MgO的浓度相对降低和催化剂表面积降低。另外,在加压失活后的MgO/B3CO_3催化剂上表面活性氧物种的离子浓度大大降低,表面晶格氧的流动性及晶格氧参与甲烷转化的能力也大大减弱;另外,由于该失活催化剂表面结构的变化,由MgO和BaCO_3共同作用形成的强碱中心也消失了。 相似文献
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渣油加氢转化催化剂初期结焦规律的研究 总被引:12,自引:3,他引:9
以孤岛减压渣油及其超临界流体萃取分馏所得的窄馏分为原料,采用齐鲁石化公司胜利炼油厂VRDS装置的主催化剂,在高压釜反应器内考察了渣油加氢转化催化剂的初期结焦规律。结果表明,焦炭的生成是一个动态过程,其产率和性质与反应体系的温度、时间、氢气初始压力及原料的性质密切相关;结焦催化剂的孔壁焦炭沉积和堵孔现象严重,导致其比表面积大大减小,孔分布向小孔范围迁移。 相似文献
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在渣油的流化催化裂化(FCC)中,来自原料的重金属(Ni,Fe,V等)连续沉积在催化剂上,使后者的活性和选择性严重下降,积炭量增加。为使这些失效的催化剂再生,从60年代末就开始了脱除沉积金属的研究。所用方法都涉及硫化,氧化等反应,处理时间长,操作繁杂,危害环境。本文进行了以盐酸再生裂解催化剂的探索研究,以开发简便有效的脱金属方法。镍铁沉积的FCC催化剂的处理 相似文献
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助催化剂对Fe1-xO基氨合成催化剂还原性能的影响 总被引:2,自引:6,他引:2
当助催化剂存在是地,Fe1-xO基催化剂的还原性能明显优于Fe3O4基催化剂,其原因是铝、钾、钙的氧化物对催化剂母体相Fe1-xO和Fe3O4还原性能的影响不同。由于Al^3+大量地进入Fe3O4的晶格而强烈地阻止Fe3O4的还原,只有少量的Al^3+能进入Fe1-xO晶格,因此对Fe1-xO的还原影响很小; 相似文献
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