H2S为毒物对乙炔氢氯化反应中AuCl3/AC催化剂催化活性的影响

采用等体积浸渍法制备了1% AuCl₃/AC催化剂,探究了硫化氢(H₂S)为毒物对乙炔氢氯化反应中催化剂催化活性的影响及失活机理。催化活性测试结果表明,以H₂S为毒物可导致乙炔氢氯化反应中的AuCl₃/AC催化剂的失活,且是一个不可逆过程;程序升温还原(TPR)和X射线光电子能谱(XPS)分析结果表明,H₂S的加入可有效地加快Au³⁺还原为Au⁰;透射电镜能谱(TEM-EDX)观测分析形成的Au-S化合物也可导致催化剂失活,即随着H₂S量的增大,更多的Au³⁺被还原为Au⁰,且形成的Au-S化合物覆盖在活性位点,使有效的活性组分降低进而导致AuCl₃/AC催化剂失活。     

失活加氢裂化催化剂的研究

采用XRD、ESCA、FT-IR、TEM等技术对两种同类型工业运转失活的加氢裂化催化剂进行了表征。结果表明，碱性氮化物和积炭主要沉积在加氢裂化催化剂的L酸中心上，在B酸中心上积炭较少；引起催化剂失活的主要原因是积炭和有机硫、氮化合物覆盖催化剂的活性中心；导致再生催化剂比表面及酸性降低的主要原因是分子筛骨架坍塌。催化剂经长期使用后，活性金属发生聚集，晶粒长大，边角位活性中心数减少。     

工业加氢裂化催化剂失活原因分析

采用200 m L加氢评价装置对一种中油型加氢裂化催化剂和其在工业装置运转4年后的再生后催化剂进行对比评价。结果表明,失活催化剂经再生后加氢裂化活性明显降低,反应温度比新鲜催化剂高5℃,生成油产品分布和主要性能都略变差。采用XRD、IR和ICP等手段对再生前后催化剂性能进行表征,分析探讨催化剂的失活原因,结果表明,加氢裂化催化剂经工业应用后,炭的沉积使其暂时性失活,而重金属沉积、金属活性组分聚集和分子筛结构烧结使催化剂部分活性永久丧失。     

Dehydration of 1-phenylethanol over solid acidic catalysts

Dehydration of 1-phenylethanol has been carried out over a solid acidic catalyst in order to examine the effect of the concentration of effective acid sites on the reaction rate, styrene selectivity and catalyst fouling. The reaction rate increased with the concentration of effective acid sites, while styrene selectivity decreased. The catalyst deactivation depended upon the concentration of the effective acid sites and also the size of the micro pores in the catalyst. Taking into account the reaction rate and selectivity, ALO-4 alumina was the most suitable catalyst for the present reaction. An activation energy for the dehydration over ALO-4 alumina was 83.8 kJ mol^?1. The dehydration reaction could be a useful tool for the characterization of the nature of the acid sites.     

Thiophene Poisoning and reactivation of a supported nickel hydrogenation catalyst: The effect of temperature

The extent and type of poisoning of an 8 wt% Ni/γ-Al₂O₃ catalyst by thiophene has been examined in ethylbenzene hydrogenation reaction, between 403 and 523 K. The results suggest that at the higher temperatures the deactivation can take place through two different mechanisms. In one case, the formation of ‘Ni-S’ surface species on the more active sites at the beginning of the reaction, produces a slow and irreversible poisoning. In the other, the planar adsorption of thiophene on the other sites produces a fast and reversible deactivation. At lower temperatures, the second mechanism seems to be predominant due to the fact that the hydrogenolysis activity diminishes.     

负载型Co基F-T合成催化剂中贵金属助剂促进作用的研究进展

在负载型Co基催化剂中添加少量贵金属助剂能显著影响催化剂活性、选择性与稳定性。贵金属助剂的添加提高了Co活性组分的还原度与分散度,增加了催化剂表面的活性位数目,改变了催化剂的几何结构和电子结构,影响CO、H₂或中间产物的吸附活化行为,抑制催化剂积炭和金属Co小粒子的再氧化。综述贵金属助剂对催化剂活性中心性质、反应物的吸附活化行为和催化剂反应稳定性的影响。     

Mitigating catalyst deactivation in selective hydrogenation by enhancing dispersion and utilizing reaction heat effect

Pd catalysts with different particle size were investigated in a strongly exothermic acetylene hydrogenation by changing space velocity. It was found that larger Pd nanoparticles provoked the significant amounts of oligomers and accumulated reaction heat although space velocity had been greatly improved. When Pd particle size was reduced, the number of active sites increased, which contributed to a decrease in heat produced on a single active site, thereby hindered formation of hot spots over catalyst leading to lesser deactivation. Furthermore, by utilizing the features of highly dispersed catalyst without instantaneous heat accumulation, the target acetylene hydrogenation (exothermic) was coupled with acetylene dissociation (endothermic) by sharing reaction heat to construct supported Pd carbide catalysts. Modification of subsurface carbon inhibited the generation of green oil and thus further enhanced selectivity and stability. This work provides an alternative and counter-intuitive concept where more highly dispersed metal nanoparticles may in fact be more stable.     

渣油加氢裂化反应中油溶性催化剂的抑焦性能

以辽河常压渣油为研究对象,通过高压釜模拟渣油加氢裂化反应,对不同油溶性催化剂体系反应后的生焦量、生焦状况及产物进行分析,深入研究渣油加氢裂化反应中油溶性催化剂的抑焦性能.研究表明,随着活性金属含量的增大,油溶性单金属Co催化剂和Ni催化剂的生焦量减少,Co - Fe或Ni - Fe复配体系具有协同效应,抑焦性能增强,由...     

掺杂型负载金属催化剂在甲烷裂解反应中的研究进展

甲烷催化裂解反应能够同时制取不含碳氧化物的高纯氢和纳米碳材料,引起研究界的广泛关注。Ni、Fe和Co是常用的甲烷裂解反应的催化剂的活性组分,但单活性组分的负载型金属催化剂往往存在转化率低和寿命短等缺点,通过催化剂的设计改进其性能是催化剂研究工作的重要方向之一。除了制备方法的选择和反应条件的优化,利用不同金属组分性质间的差异,在其中引入第二或第三组分,同样能够有效改善催化剂的性能。对掺杂型负载金属催化剂的研究进行了综述。概述了催化剂的失活机理及模型（活性位覆盖模型和孔道口堵塞模型）,以及如何从失活原因出发进行掺杂型负载金属催化剂的设计。根据掺杂元素作用方式不同,分类介绍了当前掺杂型负载金属催化剂的主要研究成果及其未来的发展方向。     

重汽油烷基化脱硫催化剂的失活原因分析

研究重汽油烷基化脱硫催化剂的失活原因。采用FT-IR、XPS和TG等表征催化剂失活前后的结构和化学组成,结果表明,催化剂的失活主要是由于反应过程中产生的聚合物在其表面吸附,覆盖了活性中心。采用酒精溶剂能够使催化剂活性恢复到一定水平。重汽油烷基化脱硫催化剂的失活是可逆的,采用合适的再生方法可以恢复催化活性。     

包围型催化剂：理念、设计及催化性能研究

负载型催化剂广泛应用于多相催化过程，其中活性相和载体之间的界面相互作用及界面密度对催化反应机制及性能的影响一直以来备受关注。利用反向设计思路构造包围型催化剂，并开发一种简易普适的制备方法，即离子交换逆负载法，使载体前体的金属离子通过离子交换反应取代活性金属氢氧化物前体的金属离子，经焙烧、还原形成活性核被载体包围的催化剂。调控离子交换程度及金属、载体前体种类，得到不同结构及种类丰富的包围型催化剂。相比传统负载型催化剂，包围型结构具有更高的界面密度和相互改变的界面性质，且因活性相被载体物理隔离具有高稳定性，在催化反应中表现出更优越的催化性能，有望成为负载型催化剂的升级版进而推动工业催化技术进步。     

Surrounded catalysts: concept,design and catalytic performance

Supported catalysts are widely used in heterogeneous catalysis processes, in which the interfacial interaction between the active phase and the support and the influence of the interfacial density on the catalytic reaction mechanism and performance have always attracted attention. The main preparation method for traditional supported catalysts is impregnation method, in which a metal precursor is deposited onto the outer surface of support, normally rendering limited contact area and relatively weak interface interaction between the active species and the support. We use the reverse design idea to construct the surrounding catalyst, and develop a simple and universal preparation method, namely the ion exchange reverse loading method, so that the metal ions of the carrier precursor can replace the metal ions of the active metal hydroxide precursor through the ion exchange reaction. After calcination and reduction, a catalyst with an active core surrounded by a carrier is formed. The unique surrounded structure presents not only high interface density and mutually changed interface, but also high stability due to the physical isolation of active phase, revealing superior catalytic performance to the traditional supported catalyst, suggesting the great potential of this new surrounded catalyst as the upgrade of supported catalyst.     

联醇铜基催化剂的失活机理与使用和维护技术

在联醇生产过程中,导致铜基催化剂失活的因素主要有化学毒物(硫化物、氯及其化合物、羰基金属化合物、油污和氨等)引起的化学中毒、在还原气氛中造成活性铜被还原、超温失活、过量CO2破坏Cu-CuO界面结构等。为了延长铜基催化剂的使用寿命,可采用的使用与维护技术主要有:精脱硫过程必不可少,选用均温型合成塔,良好的催化剂装填技术和还原技术,避免超温失活,足够的轻负荷生产,尽量减小气量波动和减少开、停车次数等。     

Molecular structure and reactivity of the Group V metal oxides

The physical, electronic and reactivity properties of bulk and supported Group V metal oxides (V, Nb, Ta and Db) were compared at the molecular level. Dubnium is a very short-lived element, 60 s, whose properties have not been extensively studied, but can be predicted from knowledge of the other members of the Group V metal oxides. Bulk V₂O₅ possesses platelet morphology with the active surface sites only located at the edges: primarily surface redox sites and some surface acidic sites. Bulk Nb₂O₅ and Ta₂O₅, as well as to be expected for bulk Db₂O₅, possess isotropic morphologies and the active surface sites relatively homogeneously dispersed over their surfaces: only surface acidic sites. However, the bifunctional bulk V₂O₅ was found to exhibit a much higher specific acidic catalytic activity than the acidic bulk Nb₂O₅ and Ta₂O₅, the latter being almost identical in their specific acidic catalytic activity. The bulk properties of the Group V metal oxides were essentially transferred to the analogous supported Group V metal oxides, where the active Group V metal oxides were present as a two-dimensional monolayer on various oxide supports (e.g., Al₂O₃, TiO₂, ZrO₂ as well as Nb₂O₅ and Ta₂O₅). For supported vanadia catalysts, the active surface sites were essentially redox sites, with the exception of supported V₂O₅/Al₂O₃ that also contained strong acidic sites. For supported niobia and tantala catalysts, as well as to be expected for supported dubnia catalysts, the active surface sites were exclusively acidic sites. However, the TOF_redox for the supported vanadia catalysts and the TOF_acidic for the supported niobia and tantala catalysts varied over several orders of magnitude as a function of the specific oxide support with the electronegativity of the oxide support cation. However, the TOF_redox varied inversely to that of the TOF_acidic variation because of the opposite requirements of these active surface sites. Surface redox sites are enhanced by reduction and surface acidic sites are enhanced by stabilization (lack of reduction). The current fundamental understanding of the Group V metal oxides allows for the molecular engineering of their metal oxide applied catalytic materials.     

有机废气催化燃烧过程中多尺度效应和催化剂设计

有机废气是重要的空气污染物,基于负载型贵金属催化剂的催化燃烧技术因效率高、无二次污染等特点而被广泛研究和应用。但目前催化燃烧技术仍存在高耗能和高成本等缺点。有机废气多相催化燃烧效率均与催化剂一定尺度范围内的结构密切相关。在有机废气催化氧化反应体系内存在从活性中心到高性能催化剂与过程的多尺度效应。依据不同尺度范围内催化剂的功能,对催化剂进行相应的设计和功能强化,是提高催化剂净化效率的有效方式。总结了近年国内外研究者在有机废气催化燃烧贵金属催化剂不同尺度范围内的设计理念和效果,并对有机废气催化燃烧催化剂的未来发展方向进行展望。     

Forced oscillations of concentration in transport reactors

The performance of a transport catalytic reactor is analysed for an adsorption/desorption type model with Eley-Rideal surface kinetics with square wave oscillations in the feed concentration. The inlet average concentration of both the reactants over a period is assumed to be constant. Significant improvement in the yield of product is obtained by increasing the feed concentration of both the reactants in the first fraction of a period. The effect of adsorption capacity of the catalyst, reaction rate constants, and inlet feed mean concentration of the reactants are evaluated. The deactivation of active sites, due to product inhibition, introduces resonance in the yield versus cycle split. The yield of product shows a minimum with respect to cycle split for the type of forcing where one of the reactant concentrations increases and the second reactant concentration decreases in the first fraction of a period.     

煤基液体燃料加氢脱氮催化剂的研究动态

煤基粗油中氮含量高达4500mg/L左右,采用石油系的NiMoS催化剂很难实现含氮芳香族化合物的脱除。为开发针对性更强、更高效的加氢脱氮催化剂,本文对煤基粗油加氢脱氮的催化剂研究动态进行了综述。首先介绍了煤基粗油中含氮芳香族化合物的组成及特点,接着围绕传统硫化物催化剂和脱氮性能较高的贵金属催化剂,从活性相的构筑与调控、载体在催化剂中的作用等方面进行了分析,最后比较了上述两种催化剂的催化性能。结果表明：贵金属催化剂活性高于传统硫化物催化剂;添加助金属形成合金可提高贵金属耐硫性与稳定性;采用具有一定酸性、与活性中心相互作用适中的载体的催化剂脱氮性能更佳。在综合分析已有文献和工作基础上,得出只有依据反应体系、特定反应过程来设计专一的加氢脱氮催化剂,才能从根本上提高含氮化合物的脱除率。     

废FCC催化剂在LPG吸附脱硫中的资源化利用

金属污染是导致流化催化裂化（FCC）催化剂失活的重要因素,充分利用沉积的重金属是废FCC催化剂资源化的关键。本文将废FCC催化剂引入到轻质油品吸附脱硫领域,以脱除液化石油气（LPG）中的二甲基二硫醚作为考核目标,验证了废FCC催化剂作为脱硫剂的可行性。除去废FCC催化剂表面积炭后,其脱硫性能得到明显改善,在常温、质量空速为4.0h^-1的条件下,LPG中硫化物质量分数从382mg/m³脱除至40mg/m³。镧、铁、镍、钒、钙、锑6种金属在新鲜催化剂和焙烧后废催化剂上的总质量分数从10.2%升高至46.6%,6种金属按照对应含量分别固载在新鲜催化剂上,脱硫效果较未改性新鲜催化剂均有明显提升。验证实验表明,导致FCC催化剂失活的金属具有较高脱硫活性,废FCC催化剂作为轻质油品脱硫剂具备工业前景。     

Chemical deactivation of V2O5/WO3–TiO2 SCR catalysts by additives and impurities from fuels, lubrication oils and urea solution: Part II. Characterization study of the effect of alkali and alkaline earth metals

A characterization study on a practice-oriented V₂O₅/WO₃–TiO₂ SCR catalyst deactivated by Ca and K, respectively, was carried out using NH₃-TPD, DRIFT spectroscopy, and XPS as well as theoretical DFT calculations. It was found from NH₃-TPD experiments that strongly basic elements like K or Ca drastically affect the acidity of the catalysts. Detailed DRIFT spectroscopy experiments revealed that these poisoning agents mostly interact with the Brønsted acid sites of the V₂O₅ active phase, thus affecting the NH₃ adsorption. Moreover, these experiments also indicated that the V⁵⁺ = O sites are much less reactive on the poisoned catalysts. XPS investigations of the O 1s binding energies showed that the oxygen atoms of the V⁵⁺ = O sites are affected by the presence of the poisoning agents. Based on these results and on DFT calculations with model clusters of the vanadia surface, the poisoning mechanism is explained by the stabilization of the non atomic holes of the (0 1 0) V₂O₅ phase as a result of the deactivation element. Consequently, V–OH Brønsted acid sites and V⁵⁺ = O sites are inhibited, which are both of crucial importance in the SCR process. The deactivation model also gives an explanation to the very low concentrations of potassium needed to deactivate the SCR catalyst, since one metal atom sitting on such a non-atomic hole site deactivates up to four active vanadium centers.     

费托合成蜡USY分子筛基加氢裂化催化剂的制备及其性能

以Ni/W为加氢活性组分,USY/SiO2-Al2O3为载体,采用浸渍法制备了费托合成蜡加氢裂化催化剂,对其进行了表征、活性相研究及活性评价. 结果表明,Ni/W以高分散度形式分散在催化剂载体上,催化剂具有比表面积较大、吸附能力强的中孔结构,在340, 548和870℃上有3个还原峰,分别对应NiO?Ni, W6+?W4+及W4+?W2+或W. 硫化态催化剂表面同时含NiWS, WS2和NiSx等活性相,WS2相片晶堆垛层数决定催化剂的活性. 烯烃具有较高的加氢反应活性,烷烃会裂化异构成小分子的烯烃,其中有的吸附态可能是进一步形成小分子烷烃过程中产生的中间过渡态. 在温度370℃、压力6.4 MPa、氢油体积流量比800、空速2.5 h-1的条件下,石蜡转化率约为50%,柴油的选择性约为90%. Ni/W均匀浸渍在USY/SiO2-Al2O3载体上,可获得相对均衡的加氢-裂解性能匹配,在不降低蜡转化率的同时保证了柴油的高选择性.