Deactivation of HDS catalyst in two-stage RDS process: II. Effect of crude oil and deactivation mechanism

Aging tests of HDS catalyst in two-stage RDS process (HDM/HDS) were performed with Arabian light atmospheric residue as feedstock and the deactivation mechanism was discussed by comparison with previous results using Kuwait residue. It was found that the HDS catalyst in the second stage was deactivated by coke deposition rather than by metals and that asphaltene aromaticity in the feed was a good index for the HDS catalyst deactivation. Furthermore, it was confirmed that fouling rate was strongly affected by the combination of asphaltene aromaticity in HDS feed and reaction temperature in HDS itself.     

Preparation of heavy oil hydrotreating catalyst from spent residue hydroprocessing catalysts

In recent years, increasing emphasis has been placed on recycling spent hydroprocessing catalysts due to environmental regulations which list them as hazardous waste materials. In the present work, the recycling of spent residue hydroprocessing catalysts that contained high levels of vanadium was investigated by using them in the preparation of active new hydrotreating catalyst after subjecting them to different treatments such as decoking, acid-leaching and hydrothermal treatment. Catalyst extrudates containing different levels of V, Mo and Ni on Al₂O₃ were prepared by mixing the spent catalyst powder with boehmite in different proportions followed by peptization, kneading and extrusion. The prepared catalyst extrudates were characterized by chemical analysis and surface area and porosity measurements. The HDS and HDM activities of the catalysts were tested using Kuwait atmospheric residue as feed and compared with that of a reference HDM catalyst. Partial leaching of vanadium from the spent catalyst opened up the pores, and the catalyst prepared by mixing the metal-leached spent catalyst (MLSC) with boehmite had higher surface area and pore volume and showed higher hydrotreating activity than that prepared from unleached spent catalyst. Hydrothermal treatment of the spent catalyst increased its porosity and surface area. Catalysts prepared from hydrothermally treated spent catalyst (HTSC) had higher surface area and pore volume and showed higher HDM and HDS activities than that prepared from the spent catalyst without hydrothermal treatment. The catalysts prepared from the treated spent catalysts also exhibited substantially higher HDM and HDS activities than the reference commercial HDM catalyst. The results indicate that spent catalysts containing high levels of vanadium together with Mo and Ni on Al₂O₃ can be used in the preparation of active HDM/HDS catalysts, and thereby, their environmental problem can be reduced.     

Studies on recycling and utilization of spent catalysts: Preparation of active hydrodemetallization catalyst compositions from spent residue hydroprocessing catalysts

Spent catalysts form a major source of solid wastes in the petroleum refining industries. Due to environmental concerns, increasing emphasis has been placed on the development of recycling processes for the waste catalyst materials as much as possible. In the present study the potential reuse of spent catalysts in the preparation of active new catalysts for residual oil hydrotreating was examined. A series of catalysts were prepared by mixing and extruding spent residue hydroprocessing catalysts that contained C, V, Mo, Ni and Al₂O₃ with boehmite in different proportions. All prepared catalysts were characterized by chemical analysis and by surface area, pore volume, pore size and crushing strength measurements. The hydrodesulfurization (HDS) and hydrodemetallization (HDM) activities of the catalysts were evaluated by testing in a high pressure fixed-bed microreactor unit using Kuwait atmospheric residue as feed. A commercial HDM catalyst was also tested under similar operating conditions and their HDS and HDM activities were compared with that of the prepared catalysts. The results revealed that catalyst prepared with addition of up to 40 wt% spent catalyst to boehmite had fairly high surface area and pore volume together with large pores. The catalyst prepared by mixing and extruding about 40 wt% spent catalyst with boehmite was relatively more active for promoting HDM and HDS reactions than a reference commercial HDM catalyst. The formation of some kind of new active sites from the metals (V, Mo and Ni) present in the spent catalyst is suggested to be responsible for the high HDM activity of the prepared catalyst.     

Alumina-silica binary mixed oxide used as support of catalysts for hydrotreating of Maya heavy crude

Alumina-silica binary mixed oxide support is used to prepare catalysts for hydrotreating of Maya heavy crude. Support is prepared by urea hydrolysis. Sequential incipient wetness and co-impregnation techniques are employed for preparation of catalysts. Ammonium heptamolybdenum is used as precursor of MoO₃. Catalysts are characterized by X-ray diffraction (XRD), temperature-programmed reduction (TPR) and the pore size distribution. Hydrodemetallation (HDM), hydrodesulfurization (HDS), hydrodenitrogenation (HDN), and asphaltene conversion (HDAsp) reactions are studied on these catalysts. One reference catalyst is also taken for comparison. Coke and metals depositions on spent catalysts are measured. The catalyst deactivation rate is also studied. The X-ray diffraction (XRD) results reveal that molybdenum atoms are well dispersed into CoMo catalyst, whereas MoO₃ crystalline phases are found in PCoMo and PNiMo catalysts. TPR reduction profiles are different for different catalysts. The laboratory made catalyst is reduced at one temperature, whereas the reference catalyst shows two reduction profiles. The reference catalyst shows the highest activities among four catalysts. The highest HDM and HDAsp activities of the reference catalyst may be due to its bigger pore diameter. The presence of TiO₂ in the reference catalyst enhances HDS and HDN activities. The CoMo catalyst shows higher activities than those of PCoMo and PNiMo catalysts. The presence of crystalline MoO₃ causes for lower activities of catalysts PCoMo and PNiMo.     

Effect of preparation methods and content of phosphorus on hydrotreating activity

The effect of phosphorus content and preparation methods is studied in this present investigation. Three different methods are employed for preparation of catalysts. The catalysts are characterized by pore size distribution, X-ray diffractogram and temperature programmed reduction. Thiophene hydrodesulfurization (HDS), cumene hydrocracking (HC), gas oil HDS and Maya heavy crude HDS and hydrodemetallization (HDM) activities are performed. It is found that specific surface area gradually decreases with P loading. The addition of phosphorus increases the formation of polymolybdate species which are more active for hydrotreating reaction. It is also observed that reducibility of these species also increases with P loading. However, at higher P loading the crystalline MoO₃ is formed at the expense of these multilayer polymeric molybdates. The increment in the activity is more in the catalyst prepared by co-impregnation method. The activity increases with P loading up to 1 wt% P content. At higher loading the activity decreases. It is also noted that P inhibits coke formation on the catalyst during hydrotreating of heavy crude oil. Phosphorus can also modify the Brønsted acidity of the catalyst and hence cumene hydrocracking activity slightly increases.     

Effect of phosphorus on activity of hydrotreating catalyst of Maya heavy crude

The effect of phosphorus on physical properties of the catalyst and on activity of hydrotreating of Maya crude was studied in this work. Catalysts were prepared by the co-impregnation method. Alumina-titania binary oxide was used as a support material. The presence of phosphorus in the catalyst decreases the percentage of micropores, and it results in a decrease of specific surface area. Temperature program reduction (TPR) shows that phosphates reduce metal support interaction. It leads to the formation of polymolybdate phases in expense of strongly bonded tetrahedral molybdates. At higher P loading, polymolybdates may be present with quasi crystalline MoO₃. However, the TPR experiment is not sufficiently sensitive to distinguish several phases present on the catalysts used by the authors. A slight increment of HDM activity is observed, but HDS activity is lower in the P containing catalyst compared with the P free catalyst. The changes of physical properties of the spent catalysts are mainly due to the coke formation on the catalyst. The presence of phosphorus on hydrotreating catalysts inhibits coke formation during the hydrotreating reaction.     

Accelerated deactivation of hydrotreating catalysts: comparison to long-term deactivation in a commercial plant

Accelerated deactivation tests of a laboratory prepared Co–Mo/Al₂O₃ catalyst were performed using three kinds of petroleum feedstocks. A high reaction temperature employed in the accelerated aging resulted in large amounts of carbonaceous deposition with high aromaticity, which were found to be the major deactivation cause. However, the effect of carbonaceous deposition during accelerated deactivation tests might have been overestimated compared with that during practical hydrotreating. When the catalysts were aged in a H₂S/H₂ stream without petroleum under the same reaction conditions, the crystal growth of MoS₂ layered structures was significant, but this rather resulted in an increase of both k (HDS) and k (HY). It was also suggested that the crystal growth during a commercial hydrotreating run was unlikely to be the major cause of catalyst deactivation.     

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.     

Review on the deactivation of FCC catalysts by cyclic propylene steaming

The deactivation of FCC catalysts in small-scale units in the presence of contaminant metals has been the industry workhorse for a number of years due to the robustness and simplicity of such methods.

A major advance in the deactivation of metallated catalysts on a small-scale that better simulated the performance of commercial FCC catalyst, was the introduction of the cyclic propylene steaming (CPS) method. In the CPS protocol, FCC catalyst is impregnated with vanadium and nickel prior to deactivation in reduction–oxidation cycles and the latter provides significant advantages over traditional methods such as the Mitchell approach. In certain situations, however, the contribution of vanadium to catalyst deactivation is over-emphasized in the CPS method, and therefore this method has been developed further.

This paper describes a number of modifications that have been made to the CPS method to further attenuate the destructive effects of vanadium on the FCC catalyst during deactivation. This includes exposing the metallated catalyst to pre-stabilisation steps with reduction-oxidation cycles and changing the ratio of the time the catalyst spends in reducing and oxidising environments during the CPS cycles. The comparison of activity and selectivity data obtained from FCC catalysts having age distribution with those obtained from CPS showed that both scenarios gave the same catalyst ranking.

These investigations have also shown that the use of reduction–oxidation cycles better simulates the deactivation of FCC catalysts in the absence of contaminant metals. These investigations have also shown that the use of reduction–oxidation cycles better simulates the deactivation of FCC catalysts in the absence of contaminant metals “the part” than traditional deactivations in a 100% steam atmosphere.     

A basic study of catalyst aging in the H-coal process

Samples of CoMo/Al₂O₃ catalysts used in an H-coal process demonstration run were studied to determine causes of catalyst deactivation. Physical and surface properties of the aged and regenerated catalysts were examined. Model compounds were used to assess four catalyst activity functions, viz., hydrodesulfurization (HDS), hydrogenation, cracking and hydrodeoxygenation (HDO). Other tests were performed to study the effects of coke and metals separately on the four catalyst activity functions.Catalyst coke content and metals deposits first increased rapidly, then more gradually with exposure time in the process run. Surface area and pure volume markedly decreased with exposure time. Catalyst activities of aged catalysts showed a rapid decline with exposure time. One-day exposure to coal resulted in significant losses in HDS and hydrogenation activities and nearly complete loss in cracking and HDO activities. Although metal deposits caused some permanent catalyst deactivation, coke had a much greater effect. Regenerated catalysts showed less recovery of catalytic activity as processing time increased. These results agreed well with product inspections from the process run.Oxygen chemisorption on aged—regenerated catalysts decreased with catalyst exposure time, indicating a significant loss of active sites. However, ESCA results showed no evidence of extensive sintering of the active MoS₂ phase. Permanent deactivation of the longer-time exposed catalysts can be ascribed, at least partly, to lateral growth of the active molybdenum sulfide phase. In addition, some loss in cobalt promotion occurred early in the process, which may account for the rapid loss in HDS and HDO activity in regenerated catalysts.     

PHR系列固定床渣油加氢催化剂的研制开发与工业应用

中国石油石油化工研究院通过深入研究渣油原料的结构组成与加氢转化行为特征,成功开发出包括保护剂、脱金属剂、脱硫剂和脱残炭剂4大类共12个牌号的PHR系列固定床渣油加氢催化剂。在保护剂中构建了"毫米-微米-纳米"多级孔体系,其微米级孔（PHR-402、PHR-403催化剂）与纳米级孔（PHR-404催化剂）均为双峰分布,微米级孔（PHR-402、PHR-403催化剂）主要分布在1μm附近区域和30~200μm的较宽泛区域,纳米级孔（PHR-404催化剂）的集中孔径则分别约为13nm和250nm,纳米级孔中大于100nm的孔比例达到35%。脱金属剂具有双峰分布的孔结构及内高外低的活性金属含量分布,其"扩散孔"孔径达到微米级（2300nm）,大于100nm的孔比例超过20%。工业应用结果表明,PHR系列渣油加氢催化剂具有高而稳定的脱硫、脱氮、脱残炭等活性,催化剂内部孔结构的利用率高,且床层压降更低,有利于延长装置运转周期。     

渣油加氢催化剂金属沉积的研究进展

随着原油日益变重,渣油加氢技术在炼油工业中得以迅速发展。分析渣油中金属存在形式及其结构特点,论述金属在催化剂上的沉积形式及其分布,讨论渣油性质、工艺条件以及催化剂性质对金属沉积的影响。通过讨论与分析,指出金属沉积物是渣油加氢催化剂失活的主要原因,但对金属在催化剂上的沉积机理以及沉积物形式存在争议。胶质与沥青质中金属含量较高,在加氢脱金属过程中,渣油中沥青质和胶质含量以及结构变化对于催化剂上金属沉积的影响有待研究。反应温度和反应压力对金属沉积规律的影响也需要进一步深入研究,尤其是H₂（H₂S）在脱金属反应过程中的作用机理。     

催化剂的失活研究及其在使用中的改进建议

催化剂的活性直接影响着渣油加氢装置的运行周期。本文首先简单的分析了催化剂失活的原因、阶段,随后着重陈述了由于催化剂的金属沉积、积碳及操作条件的改变造成了催化剂的失活过程,最后还对催化剂在使用过程中提出了改进建议。     

Studies on rejuvenation of spent residue hydroprocessing catalysts by leaching of foulant metals: influence of inorganic salt additives on the leaching efficiency of organic acids

A comparative study has been made on the efficiency of oxalic, malonic and acetic acids for selective removal of metal foulants (e.g. vanadium) from spent residue hydrotreating catalysts in the presence and absence of aluminium nitrate. The influence of concentration of the added salt (aluminium nitrate) on the leaching efficiency of the three acids was also studied. The treated catalysts were characterized and the improvements in surface area, pore volume and HDS activity as a result of leaching with each reagent compared. The studies revealed that addition of aluminium nitrate enhanced the leaching efficiency of each acid to a different degree. The rate of vanadium leaching by oxalic acid was increased substantially by aluminium nitrate addition whereas for acetic acid there was only a moderate enhancement in leaching rate. The enhanced leaching by the aluminium nitrate-organic acid system may be explained in terms of a synergistic mechanism involving oxidizing and complexing reactions. The improvement in surface area and pore volume achieved on rejuvenation were related to the extent of removal of vanadium from the catalyst. The HDS activity of the catalyst was also increased significantly by leaching of the deposited metals. The selectivity for vanadium leaching (V/Mo ratio) was found to be an important factor for HDS activity recovery.     

Activity of hydroprocessing catalysts prepared by reprocessing spent catalysts

In this study, two spent catalysts from the 3rd and 4th fixed beds of the atmospheric residue desulfurization (ARDS) process and one spent catalyst from the H-Oil process employing the expanded bed were used as the starting material for preparation of hydroprocessing catalysts. The spent catalysts were used either in a coked or decoked form. The procedures involved pulverizing the spent catalysts before mixing, kneading and extruding with boehmite in the presence of peptizing agent such as HNO₃. The hydrodesufurization (HDS) and hydrodemetallization (HDM) activities of the new catalysts were evaluated in the microreactor using the atmospheric residue derived from Kuwait crude. The new catalysts prepared from the spent catalysts used in the fixed bed reactors exhibited higher activity than that of commercial catalysts. The HDS activity of the new catalysts prepared from spent catalysts used in the ebullated bed reactor was much lower than that of the other catalysts. This was attributed to a high content of vanadium in the former spent catalyst. At the same time, the adverse effect of vanadium on HDM was much less evident.     

Interrelations between initial pore structure, morphology and distribution of accumulated deposits, and lifetimes of hydrodemetallisation catalysts

The functioning of commercial HDM catalysts, experiencing conditions of industrial use in residual feedstocks upgrading reactors is analysed, in order to derive the essential physical and chemical processes that determine their deactivation. A mathematical model of this evolution is presented as an attempt to integrate this analysis into computer simulations for improved reliability of lifetimes predictions. A method to obtain accelerated aging data on HDM catalysts at the bench scale is presented, with examples of results. A method is given to combine such results with EPMA analysis of used catalyst pellets in order to determine the Ultimate Storage Capacity intrinsic to the catalyst's pore structure. Selected results of an High Resolution Electron Microscopy study of microtome thin foiled used HDM catalyst pellets are presented: they show for the first time the nature, morphology and structure of metal sulfides deposits at the micropore level, and support the “discrete” mode of deposition theory. Model predictions and experimental deactivation results are compared, and the limitations of the model discussed. Unsolved questions are listed for future research.     

Effect of catalyst composition on the hydrodesulphurization and hydrodemetallization of atmospheric residual oil

A series of CoMo/Al₂O₃ catalysts containing a third additive, a Si, Ti, or P compound, were prepared using a consecutive impregnation method. The activities for the hydrodesulphurization (HDS), hydrodemetallization (HDM) and Conradson carbon residue (CCR) reduction of atmospheric residual oil were tested in a semi-batch basket type reactor. Cycle-aging tests were carried out for comparison of catalyst stability. The intrinsic rate constants of HDS from a semi-empirical calculation were used to test the coke tolerance of the catalysts. The CoMo/Al₂O₃ catalyst with a titanium compound added exhibited the highest activity enhancement for HDS and HDM reactions. It was also found that the surface activity maintenance can be effectively improved by the addition of an appropriate amount of titanium compound. The activity and stability of CoMo and NiMo catalysts for the HDS and HDM reactions were also compared.     

Transition Metals Supported on Activated Carbon as Benzene Hydroxylation Catalysts

The direct conversion of benzene to phenol by hydroxylation with hydrogen peroxide was carried out over catalyst containing various transition metals impregnated on activated carbon. Iron and vanadium impregnated catalysts gave better yields of phenol compared to copper impregnated catalysts. The activity of transition metals supported on activated carbon catalyst in the production of phenol was V > Fe > Cu. In addition to the role of transition metals in catalyzing the hydroxylation reaction, the hydrophobic nature of the activated carbon surface and also the surface acidity and basicity seems to have enhanced the performance of these catalysts.     

Ni-Mo/TiO_2催化剂上二苯并噻吩加氢脱硫性能

采用浸渍法,以TiO_2成型载体制备Ni-Mo/TiO_2催化剂,考察MoO_3负载量对二苯并噻吩加氢脱硫性能的影响,采用XRD和BET等对催化剂进行表征。结果表明,当MoO_3负载质量分数大于10%时,已超过TiO_2载体的单层负载量,MoO_3晶相开始聚集长大,堵塞部分孔道,造成催化剂的比表面积和孔容显著下降。MoO_3负载质量分数10%时,二苯并噻吩转化率最高,继续提高MoO_3的负载质量分数,催化剂活性反而下降。对Ni-Mo/TiO_2催化剂进行30天的稳定性试验,催化剂没有失活。     

The usage of high metal feedstock for the determination of metal capacity of ARDS catalyst system by accelerated aging tests

For residue hydrotreating catalysts that are deactivated mainly by pore blockage due to deposition of metals, the capacity for accommodation of the deposited metals is an important parameter in determining its stability and life. The primary objective of the present work is to determine the maximum metal capacity of different catalysts that are used in different reactors of atmospheric residue desulfurization (ARDS) units by accelerated aging tests in a short duration. A feedstock with high metals content, namely, Boscan crude, was used for the tests in a multireactor pilot plant to cause complete deactivation of the catalysts by metal accumulation in a shorter period. The influence of operating temperature and LHSV on the rate of catalyst deactivation was also examined for the high metal feed. Catalyst deactivation rate was found to be more than five times faster for the high metal Boscan feed compared to the conventional atmospheric residue from Kuwait export crude. It was possible to determine MMOC of an ARDS catalyst system within 45–50 days by accelerated deactivation test using a high metal feed (e.g., Boscan crude).