Causes of deactivation and regeneration of an industrial Pt-NiO/Al2O3 nitrogen oxides reduction catalyst

The deactivation mechanism and regeneration of spent industrial Pt-NiO/Al₂O₃ catalysts used for NO_x reduction was studied by means of SEM-EDS, chemical analysis and kinetic measurements. It was found that the main cause of deactivation under industrial operating conditions is fouling due to carbonaceous and ZnO deposits. Various contaminant removal procedures (calcination, wet screening and acetic acid leaching) were tested and the influence of these procedures on contaminant removal and the catalyst activity were investigated. Regeneration of the spent industrial catalyst using inexpensive processes was shown to be feasible.     

Catalyst pore plugging effects on hydrocracking reactions in an Ebullated bed reactor operation

This paper analyzes the deactivation effects of NiMo/Al₂O₃ catalyst during the operation in an Ebullated bed reactor for Heavy residue hydrocracking. The spent catalysts were characterized by chemical analysis, ¹³C NMR, ESM, DRX, and by using thermal programmed oxidation and diffusion studies in a shallow bed micro-reactor. The deactivations were performed in a 5 l continuously stirred tank reactor, while the spent catalysts were tested in a 0.05 l micro-reactor. The study focused on determining the properties of the external layer of the catalyst and on evaluating the internal coke and metal deposition. The results indicated that initial deactivation is mainly due to coke depositions, while its impact on mass transfer reaction control depends on temperature. In long-term deactivation, the metal deposition plays a more important role in blocking the internal micro- and meso-structures and in building up the external layer of the pellets.     

加氢裂化催化剂失活与再生

利用XRD、XPS、TPR、ICP、IR、TEM 等技术, 测试和表征几种不同类型新鲜的、失活的和再生后工业用非贵金属加氢裂化催化剂的性能, 找出该催化剂失活的主要原因。经研究发现,加氢裂化预精制催化剂主要失活原因是积炭和金属聚集; 加氢裂化催化剂主要失活原因是积碳、所含沸石倒塌、金属聚集、孔结构堵塞及倒塌, 对于单段加氢裂化催化剂失活原因, 还包括酸中心中毒等。本文还探讨了器内与器外再生方式利弊及今后发展趋势。     

Influence of the promoter's nature (nickel or cobalt) on the active phases ‘Ni(Co)MoS’ modifications during deactivation in HDS of diesel fuel

The characterization of various spent Ni(Co)MoP/Al₂O₃ catalysts has been performed in order to elucidate the active phase modifications undergone on the catalysts at operating conditions. Six catalysts coming either from industrial or pilot reactors were studied. The deactivation level (for hydrogenation reaction) can be determined by XPS analysis quantifying the ‘Ni(Co)MoS’ mixed phase amount. The spent catalyst active phases characteristics, at different levels of deactivation, firstly evidenced that the coke particularly influences the CoMo active phase (X-ray photoelectron spectroscopy) lowering the ‘CoMoS’ mixed phase amount. On the spent NiMo catalysts, most of the nickel is segregated (XPS, Extended X-ray Absorption Fine Structure, Transmission Electronic Microscopy/Energy Dispersive Spectroscopy) even after low residence time in the unit (pilot plant origin). In both cases it leads to the progressive deactivation of the catalyst. The coke does not seem to influence the ‘NiMoS’ mixed phase amount excepted at its life-end.     

A comparative study for heavy oil hydroprocessing catalysts at micro-flow and bench-scale reactors

CoMo and NiMo catalysts were prepared and the catalytic activities were evaluated in fixed bed micro-flow and bench-scale reactors with different feed composition. Experiments were conducted at conditions close to those that exist in the industrial practice. Due to the different nature of the feeds, the conditions were varied with respect to both evaluation scales. The fresh and spent catalysts were characterized. Spent catalyst textural properties indicated that catalysts were deactivated and the surface area and pore volume dropped by 20–60%. The adsorption–desorption hysteresis of spent catalysts indicated that cylindrical pores are deactivated at the pore mouth and played an important role in modification by either closing one end of the pore or forming a narrow neck pore, which is indicative of the formation of “ink-bottle” type pores. Thus, the deposition of metal and carbon takes place preferentially at the pore entrance, which causes pore mouth plugging. These results are also supported by the SEM–EDAX analysis, where metal and carbon depositions are evident and taking place at the superficial region of a catalyst particle. The increase in absolute area of hysteresis is based on the catalyst's average pore diameter: the higher the average pore diameter, the lower the area of the spent catalyst. The activity and deactivation of the catalyst are discussed on the basis of catalyst porosity and deposited metal characterization. The composition of catalysts varies, considering two applications in a multi-reactor system: a CoMo catalyst for the first reactor, and a NiMo in the second reactor; the former is supported on γ-Al₂O₃ and the latter on TiO₂/Al₂O₃. As a comparison, the CoMo catalyst exhibited better hydrogenolysis while the NiMo catalyst showed better hydrogenation activity in both micro-flow and bench-scale reactors. It appears that there is a moderate effect of TiO₂ content in support on Ni and V hydrodemetallization (HDM) while hydrodeasphaltenization (HDAs) and hydrodesulfurization (HDS) activities were slightly improved when a partially hydrotreated feed, which contains more refractory compounds than virgin feedstock, was employed.     

环氧乙烷合成反应器温度-时间优化策略

根据工业实际生产数据反算得到能够反映催化剂失活特性的银催化剂失活动力学方程.在失活模型基础上,对环氧乙烷合成反应器的管外沸腾水温度-时间策略进行优化,得到最优沸腾水升温曲线,从而提高环氧乙烷反应的经济效益.对同系列新型催化剂的反应器操作优化提出了可行的研究方法.     

Deactivation patterns of Mo/Al2O3, Ni–Mo/Al2O3 and Ni–MoP/Al2O3 catalysts in atmospheric residue hydrodesulphurization

In the present work, a comparative study on the deactivation behavior of three types of industrial hydrotreating catalysts, namely, Mo/Al₂O₃, Ni–Mo/Al₂O₃ and Ni–MoP/Al₂O₃, that are used to promote primarily hydrodemetallization (HDM), hydrodesulphurization (HDS) and hydrodesulphurization + hydrodenitrogenation (HDS/HDN) reactions, respectively, in the first, second and third reactor of commercial atmospheric residue desulfurization (ARDS) units was carried out. The main objective of the study was to contribute to a better understanding of the relationship between catalyst type and catalyst deactivation patterns. The used catalysts from these experiments were fully characterized to determine the extent and the cause of deactivation. Special emphasis was paid to understanding the nature of the coke and metal deposition on the used catalysts by applying chemical analysis and various advanced analytical techniques, such as solid-state carbon-13 nuclear magnetic resonance spectroscopy (¹³C NMR), temperature-programmed oxidation (TPO), electron probe micro-analysis (EPMA), and diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy. The results are discussed scientifically based on the physico–chemical properties of the three catalysts.     

Coking behavior and catalyst deactivation for catalytic pyrolysis of heavy oil

For the catalytic pyrolysis of heavy oil on catalyst CEP-1, coking behavior was investigated in a confined fluidized bed reactor. Coke content on the spent catalyst decreases with the increase of H/C mol ratio of feeds and catalyst-to-oil weight ratio, while it increases with the enhancement of reaction temperature. An empirical model is proposed to predict the coke content based on feed properties and operating conditions. The predicted coke content is close to the experimental data. The relationship between micro-activity index of catalysts and coke content is studied. A coking deactivation model for pyrolyzing catalysts is established, and then model parameters are determined by the least square regression analysis. According to the deactivation model, the variations of relative activity of catalysts with both residence time of catalysts and catalyst-to-oil weight ratio are predicted.     

一种新型炭载体在乙炔氢氯化反应中的应用

采用等体积浸渍法制备了一系列不同载体的HgCl₂催化剂,利用BET、原子荧光光谱仪（AFS）、元素分析仪（EA）等对样品进行了表征,考察了催化剂在固定床反应装置上进行乙炔氢氯化反应的性能,同时对催化剂失活原因进行了初探。结果表明,不同载体催化剂催化性能和失活原因差异很大,其中以AC-2（沥青基球形炭）为载体的HgCl₂/AC-2催化性能最佳,当HgCl₂含量为5%（质量分数）、乙炔空速36 h^－1、温度140 ℃、n(HCl)∶n(C₂H₂)=1.05～1.1时,其初始转化率>99%（比HgCl₂/AC-1提高39%）,选择性接近100%,寿命可达3168 h,催化性能优于现有工业高汞催化剂。     

碱改性HZSM-5催化热解木质素催化剂失活分析

对0.3 mol·L^-1 NaOH改性后的HZSM-5以及未改性HZSM-5催化剂进行循环和再生评价实验以考察催化剂的寿命。对反应后和再生的催化剂进行N₂吸脱附以及NH₃-TPD表征,并通过对反应后的催化剂进行SEM、TGA、FTIR、UV-Vis等表征分析催化剂积炭。两种催化剂的活性均随着循环实验次数的增加而逐渐降低,经4次循环实验的改性HZSM-5催化剂的催化活性远高于4次循环实验的未改性HZSM-5催化剂。反应过的催化剂经高温煅烧再生后其活性都有所恢复,再生后的改性HZSM-5的催化活性仍高于未改性催化剂。对两种不同催化剂积炭分析,改性后催化剂的积炭量少于未改性的催化剂,其积炭组分中高聚芳烃的含量相对较多。     

Studies of deactivation of metals by carbon deposition

Studies of carbon deposition from aliphatic and aromatic hydrocarbons over metal catalysts were carried out over the temperature range 700–1025 K using a microbalance coupled with a tubular reactor. The influence of the nature of the reactor wall on the rate of carbon formation, as well as the effect of hydrogen in preventing deactivation of the catalysts, was investigated. A general reaction scheme is proposed to explain the relationships between the different types of carbon formed on the catalysts.     

铜基甲醇合成催化剂失活原因的探讨

采用加压微型反应器和化学分析、原子吸收光谱法、X 射线荧光分析、X 射线衍射峰宽化法和其它分析方法对工业使用前后的铜基甲醇合成催化剂M K101 进行了分析和讨论。探讨了该催化剂的失活原因。     

Characterization of Ni---W/A12O3-SiO2 aromatics saturation catalysts used in a one-year commercial HDS run

A series of Ni---W/A1₂O₃-SiO₂ catalysts with different A1₂O₃/SiO₂ ratios were prepared and loaded in a commercial HDS unit for a year. The catalytic properties of the freshly sulfided and spent catalysts were investigated by performing structural analyses and model test reactions. The aggregation of the WS₂ slabs in the lateral direction, which was observed by EXAFS and TEM, was a major cause of the catalyst deactivation. The addition of SiO₂ into the catalyst support was found to suppress the structural changes of the catalyst.     

Study on the deactivation phenomena of Cu-based catalyst for methanol synthesis in slurry phase

A commercial Cu-based catalyst for methanol synthesis was studied using a stirred autoclave reactor system in the present study. The synthesis reactions were conducted for different time under the same reaction conditions in order to get catalyst samples with different deactivation degrees. The composition and morphology of the catalyst samples before and after reaction were characterized by the means of temperature programmed reduction (TPR), X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy–energy dispersive spectroscopy (SEM–EDS), elemental analysis (EA) and nitrogen adsorption techniques. The experimental results indicated that Cu composition of the catalyst had not changed significantly during the reaction, and sintering of Cu particles of the catalysts was the main cause of the catalyst deactivation with time on stream.     

Synthesis and purification of anthraquinone in a multifunctional reactor

In the present paper the reaction of 2-benzoylbenzoic acid dehydration has been studied in the presence of different catalysts by using a batch reactor for screening the best catalysts and a pseudo-continuous multifunctional reactor for determining catalysts productivity, reaction yields, catalysts deactivation and regeneration on the previously selected catalysts that are acid bentonite, Y- and β-zeolites. This last reactor works also as evaporator and condenser for separating and collecting produced anthraquinone at a high level of purity, while water continuously formed evaporates in the atmosphere.

A kinetic model with vapour–liquid partition and catalyst deactivation has been used to interpret the experimental runs. The liquid reacting mixture showed strong non-ideality favouring the evaporation and collection of pure anthraquinone.     

ZnHZSM-5催化丙烷芳构化的失活动力学研究

在等温积分反应器中实验研究了由丙烷制取轻质芳烃BTX（苯、甲苯及二甲苯）的芳构化过程中，锌改性的HZSM－5催化剂的积炭失活对反应过程的影响，通过对常压、不同反应温度下的实验数据所进行的动力学分析，建立起了失活动力学模型，并通过拟合实验数据对模型做了筛选，最终确定了基于Langumir-Hinshelwood模型的反应速率方程和由独立失活机理推出的2级独立失活速率方程，该模型对深入了解轻烃芳构化反应及指导反应器设计均具有重要的意义。     

Analysis of coke deposition profiles in commercial spent hydroprocessing catalysts using Raman spectroscopy

The distribution of coke inside the pellets of several industrial spent hydroprocessing catalysts was analyzed using Raman spectroscopy. The shape of the coke profiles gives us information on the deactivation mechanism and the magnitude of diffusion limitations. Samples taken at the end of run showed the most pronounced coke profiles. Typical M-shaped profiles observed in a guard bed catalyst suggest a sequential deactivation mechanism and a strong diffusion resistance. Consequently, it is concluded that near the end of life the catalyst effectiveness factor can be significantly reduced by coke deposition.     

Study of the deactivation mechanism of Al2O3-supported cobalt Fischer-Tropsch catalysts

The influence of water on alumina-supported cobalt catalysts has been studied. The deactivation of supported Co catalysts was studied in a fixed-bed reactor using synthesis gas feeds containing different concentrations of water vapour. Supporting model studies were carried out using H₂O/H₂ feeds in conjunction with XPS and gravimetry. Rapid deactivation occurs on Re-promoted CO/Al₂O₃ catalysts when H₂/CO/H₂O feeds are used, whereas unpromoted CO/Al₂O₃ shows more stable activity. The results from the gravimetric studies suggest that only a small fraction of the bulk cobalt metal initially present reoxidizes to cobalt oxide during reaction. However, the XPS results indicate significant reoxidation of surface cobalt atoms or highly dispersed cobalt phases, which is likely to be the cause of the observed deactivation. Rhenium is shown to have a marked effect on the extent of reoxidation of alumina-supported cobalt catalysts.     

Operability of an Industrial Methanol Synthesis Reactor with Mixtures of Fresh and Partially Deactivated Catalyst

Disposal of spent catalyst is a common practice in industrial methanol synthesis. However, the spent catalyst has, generally, a good level of activity and can be used if mixed with fresh catalyst. In this work the operation of an industrial methanol synthesis reactor with mixtures of fresh and partially deactivated catalyst was investigated using a one‐dimensional transient model. Analysis of the deactivation behavior of low‐pressure methanol synthesis catalyst shows there is an extremely sharp rate of deactivation in a small part of the catalyst life‐time, which is followed by a relatively slow rate of deactivation in the remaining catalyst cycle‐time. Different configurations were studied for catalyst recycling, and two limiting cases are discussed in detail in this paper, namely layered and homogeneous (mixed) bed models. In the first one, the catalyst was segregated into two alternate layers of fresh and partially deactivated catalyst, while in the second homogeneity of the catalyst bed was simulated by segregating a large number of alternate layers of fresh and partially deactivated catalyst. It was observed in both cases that when catalyst recycling is used, the process does not depart significantly from the standard operating conditions, and also that the mixed bed had less influence on the reactor performance than layered one.     

Maya crude hydrodemetallization and hydrodesulfurization catalysts: An effect of TiO2 incorporation in Al2O3

Hydrotreating of Maya heavy crude oil over high specific surface area CoMo/TiO₂–Al₂O₃ oxide supported catalysts was studied in an integral reactor close to industrial practice. Activity studies were carried out with Maya crude hydrodesulfurization (HDS), hydrodemetallization (HDM), hydrodenitrogenation (HDN), and hydrodeasphaltenization (HDAs) reactions. The effect of support composition, the method of TiO₂ incorporation, and the catalyst deactivation are examined. Supported catalysts are characterized by BET specific surface area (SSA), pore volume (PV), pore size distribution (PSD), and atomic absorption. It has been found that sulfided catalysts showed a wide range of activity variation with TiO₂ incorporation into the alumina, which confirmed that molybdenum sulfided active phases strongly depend on the nature of support. The pore diameter and nature of the active site for HDS, HDM, HDN, and HDAs account for the influence of the large reactant molecules restricted diffusion into the pore, and/or the decrease in the number of active sites due to the MoS₂ phases buried with time-on-stream. The textural properties and hysteresis loop area of supported and spent catalysts indicated that catalysts were deactivated at the pore mouth due to the metal and carbon depositions. The atomic absorption results agreed well regarding the textural properties of spent catalysts. Thus, incorporation of TiO₂ with γ-Al₂O₃ alters the nature of active metal interaction with support, which may facilitate the dispersion of active phases on the support surface. Therefore, the TiO₂ counterpart plays a promoting role to HDS activity due to the favorable morphology of MoS₂ phases and metal support interaction.