An Active Carbon Catalyst Prevents Coke Formation from Asphaltenes during the Hydrocracking of Vacuum Residue

Active carbons were prepared by the steam activation of a brown coal char. The active carbon with mesopores showed greater adsorption selectivity for asphaltenes. The active carbon was effective at suppressing coke formation, even with the high hydrocracking conversion of vacuum residue. The analysis of the change in the composition of saturates, aromatics, resins, and asphaltenes in the cracked residue with conversion demonstrated the ability of active carbon to restrict the transformation of asphaltenes to coke. The active carbon that was richer in mesopores was presumably more effective at providing adsorption sites for the hydrocarbon free-radicals generated initially during thermal cracking to prevent them from coupling and polycondensing.     

Kinetic Study on the Hydrocracking Reaction of Vacuum Residue Using a Lumping Model

Abstract

Based on the experimental hydrocracking of vacuum residue, a kinetic study using a lumping model was carried out to gain insight into the characteristics of catalytic reactions. The lumped species were the saturates, aromatics, resins, and asphaltenes (SARA) constituents in the residue (798 K⁺) fraction and gas, naphtha, kerosene, gas oil, vacuum gas oil, and coke in the products. The pyrite reaction favoring hydrocracking to lighter products was more temperature-dependent than that using a mixture of pyrite and active carbon. The kinetic study showed that the addition of active carbon to pyrite limited the transformation of resins to asphaltenes.     

超细负载型Ni-Mo/Al2O3催化剂在渣油加氢裂化中的应用

针对渣油固定床加氢工艺催化剂易结焦失活以及悬浮床加氢工艺催化剂活性偏低的问题,将能悬浮在渣油中的超细负载型催化剂(Ni-Mo/Al2O3)应用于渣油的加氢裂化反应,并在高压釜中考察了反应条件对新疆减压渣油(XJVR)转化率的影响,其中催化剂添加量(质量分数)的考察范围为1%～10%、反应温度为410～450℃、反应时间为0.5～2.5 h、氢气初始压力为5～9 MPa。结果表明,催化剂的添加量对渣油、沥青质以及残炭转化率的影响都很小,但增加催化剂添加量能明显地促进硫的转化,即在此催化体系下,渣油的裂化反应以热反应为主,而加氢脱硫反应则由催化剂的活性中心所决定;反应温度对渣油、残炭、沥青质以及硫的转化率的影响较大,随着反应温度的提高,渣油、残炭、沥青质以及硫的转化率都呈上升的趋势,且前三者的上升趋势更为显著;延长反应时间对反应转化率的影响与提高反应温度所得到的结果类似;当氢气严重过量时,再提高氢气压力对硫转化率没有影响,但可在一定程度上促进残炭和沥青质的加氢反应。     

HYDROCRACKING OF ARABIAN MIX ASPHALTENES IN THE PRESENCE OF MODIFIED RED MUD

ABSTRACT

Asphaltenes precipitated from an Arabian Mix vacuum residue were hydro-cracked in a batch autoclave at 435 and 460°C for 5-90 min. Experiments without catalyst, with modified red mud and with an industrial Co Mo/Al₂0₃ catalyst were compared. The products were fractionated into gas, naphtha, oil, asphaltenes and coke. Feed asphaltenes and several product fractions were characterised by elemental analysis, by average molecular mass and by ¹H n.mr. Due to the hydrogenation activity, both catalysts caused - with similar efficiency - the decrease of coke formation and the increase of quantity and quality of oil.     

不同沥青质在十氢萘体系中的加氢转化反应性能研究

以十氢萘为溶剂,在高压釜中考察了不同溶剂抽提所得不同来源沥青质的加氢转化反应性能。结果表明,十氢萘可以改变沥青质体系的分散性能并起到供氢剂的作用,使沥青质具有较好的加氢转化性能,转化率均在60%以上,焦炭产率低于原油体系。不同溶剂分离所得沥青质的结构和组成不同,戊烷沥青质的转化率高于同一原料的庚烷沥青质。石蜡基沥青质的焦炭产率较高且转化率和产物分布略差,与传统认识有所差距,说明沥青质的加氢反应性能不仅与渣油原料的基属有关,还与沥青质本身的分子结构组成有关。     

Kinetic Study on the Hydrocracking Reaction of Vacuum Residue Using a Lumping Model

Based on the experimental hydrocracking of vacuum residue, a kinetic study using a lumping model was carried out to gain insight into the characteristics of catalytic reactions. The lumped species were the saturates, aromatics, resins, and asphaltenes (SARA) constituents in the residue (798 K⁺) fraction and gas, naphtha, kerosene, gas oil, vacuum gas oil, and coke in the products. The pyrite reaction favoring hydrocracking to lighter products was more temperature-dependent than that using a mixture of pyrite and active carbon. The kinetic study showed that the addition of active carbon to pyrite limited the transformation of resins to asphaltenes.     

CATALYTIC HYDROTREATMENT OF PETROLEUM RESIDUE

ABSTRACT

Iraqi reduced crude (350°C+) with a sulfur content of 4.3 wt% and a total metal content (Ni+V) of 141 WPPM was n-heptane deasphalted at specified conditions. The deasphalted oil (97.2 wt% of original residue) contains 4.1 wt% of sulfur and 103 ppm of metal. The original reduced crude and deasphalted oil were hydrotreated on a commercial Ni-Mo-alumina catalyst presulfided at specified conditions in a laboratory trickle-bed reactor. The reaction temperatures varied from 300 to 420°C with the liquid hourly space velocity (LHSV) ranging from 0.37 to 2.6 h^?1. Hydrogen pressure was kept constant throughout the experiments at 6.1 MPa, with a hydrogen/oil ratio of about 300 NLL^?1 (normal liters of hydrogen per liter of feedstock). Analysis for sulfur, nickel, vanadium and n-pentane asphaltenes were carried out for hydrotreated products from both the original residue and the deasphalted oil. The comparison of the results obtained for the hydrotreatment of deasphalted oil and original reduced crude indicates that the removal of sulfur, nickel and vanadium was higher for the deasphalted oil than those obtained for the non-deasphalted residue over the entire range of conversion. The exclusion of extremely high molecular weight asphaltenes by n-heptane deasphalting seems to improve the access of oil into catalyst pores resulting in higher desulfurization and conversion of the lower molecular weight asphaltenes. The sulfur content of n-pentane precipitated asphaltenes remained unchaneed with LHSV for various temperature for hydrotreated products produced from both deasphalted oil and original reduced crude.     

塔河常压渣油及其亚组分的非等温热转化反应性能研究

采用热重分析法对塔河常压渣油(THAR)及其亚组分的热转化反应性能进行了考察;在Sharp微分法基础上,采用分段动力学拟合,获得了渣油及其亚组分热转化速率峰值、速率峰值处的反应温度、转化率和剧烈裂解温度区间等动力学基本数据以及各亚组分的生焦性能。结果表明：各亚组分生焦率由低到高依次为饱和分＜芳香分＜胶质＜沥青质,沥青质是焦炭的主要来源;四组分按组成加权后的生焦率较THAR生焦率高4.21百分点,表明THAR亚组分混合物共焦化有利于抑制各亚组分的生焦;饱和分可促进其它亚组分生焦,而芳香分和胶质可抑制沥青质生焦,且芳香分的抑焦性能更强;在热转化反应过程中,裂化反应活性由高到低的顺序为饱和分＞芳香分＞胶质＞沥青质,各亚组分在低温段和高温段的活化能由低到高的顺序均为饱和分＜芳香分＜胶质＜沥青质,表明胶质和沥青质大分子的热转化过程需要提供较多的能量。     

CHARACTERIZATION OF HEAVY OIL FRACTIONS OBTAINED FROM THERMAL TREATMENT IN PRESENCE OF SULFIDES AND H-DONOR ADDITIVES

ABSTRACT

Analytical studies have been performed on effluents issued from thermal conversion of Safaniya Vacuum residue (Arab Heavy) in presence of tetralin, thiophenol and methyldisulfide. In contrast to thermal behavior of the heavy oil alone, low coke amount was produced at high conversion level (up to 50%) beside good product qualities as demonstrated from analysis of the remained 500°C⁺ fractions. H-donor diluent and sulfide additives help effectively in lowering the carbon residue values and maintaining the H/C ratios at the highest values compatible with the conversion. Microstructural parameters of the liquid effluents and their asphaltenic parts are obtained ¹H and ¹³C NMR spectroscopy and average molecular weight determination. Even at high conversion level results allow to assess a rapid dealkylation process at the first stage of the thermal treatments associated with a good control in the evolution of the size of polyaromatic units. Optical Microscopy and X-ray analysis outline the specific effect of tetralin as a. delayed coking additive.     

Molecular Dynamics Simulation of Structural Relaxation of Asphaltene Aggregates

Abstract

For asphaltene obtained from vacuum residue of Khafji crude oil, the energy-minimum conformation calculated by molecular mechanics–dynamics simulations showed that aggregated structures of asphaltene molecules through noncovalent interactions are more stable. Changes induced in aggregated structures by pretreatment with solvents were investigated using molecular dynamics calculations. The simulation showed that in quinolin at 573 K, some staking interactions could be disrupted, while, in 1-methylnaphthalene it was not observed. Autoclave experiments showed that the coke yield after pyrolysis at 713 K was decreased when the asphaltene was pretreated with quinoline at 573 K for 1 h, compared to the yield without the pretreatment. While, in the case of pretreatment in 1-methylnaphthalene, the coke yield did not change significantly. The simulation's results above can be related to the difference in coke yield between two solvents; in quinoline some aromatic–aromatic stacking interactions could be disrupted and mobility of molecules was increased. This resulted in prevention of the asphaltenes from polymerizing, as in condensation reactions among aromatic rings. Consequently, the coke yield after the pretreatment with quinoline was decreased.     

A Predictive Kinetic Model for Delayed Coking

Abstract

Lumping of the residue charge stock is based on saturate, light and heavy aromatics, soft and hard resins, as well as asphaltenes, whose concentrations can be obtained by solvent sedimentation and Al₂O₃ column separation. The reaction scheme contains 11 lumped species, including two middle fractions, naphtha, gas, and coke in addition to the above six lumps for residua. It is shown that these kinetic parameters are all invariant with respect to residue compositions and therefore this model is able to predict yields of delayed coking products for a wide variety of ranges of charge stock and operating conditions beyond that of the tests.     

热重法考察渣油及其亚组分的焦化性能

以热重法考察锦州石化渣油及其亚组分的焦化性能，并揭示了渣油各亚组分间的焦化特理化学作用。结果表明，四组分焦化生焦率从大到不的顺序和沥青质，胶质，芳香分，饱和分，渣油的生焦率介于芳香分和胶质之间。焦化过程中表观热裂化反应活性顺序为饱和分＞芳香分＞胶质＞沥青质，而实际热裂化热裂化的剧烈程度的顺序相反。饱和分可促进其它亚组分生焦，而芳香分可抑制胶质，沥青质生焦，渣油按四组分组成物理加权后的生焦率大于该渣的生焦率。还探讨了渣油及其亚组分在焦化过程中的动力学特征。     

Determination by PIXE of the Metallic Content in Vacuum Residue,Asphaltenes and Maltenes

Abstract

Asphaltenes from Mexican Maya crude oil were precipitated during one agitation hour using n-C₅, n-C₆, n-C₇, and n-C₈ at room temperature. Later the asphaltenes were washed with a soxhlet extraction system during 24 hr to remove the maltenes. The characterization of the vacuum residue, asphaltenes, and maltenes was realized using proton induced x-ray emission (PIXE) for the direct determination of the distributions and abundances of metals in the vacuum residue and their respective fractions. The analysis revealed that vacuum residue contains Fe, Al, V, and Ni, while the asphaltenes and maltenes mainly contain V and Ni.     

Adsorption of asphaltenes onto CaO,Co3O4, Fe3O4 and ZnO supported on 13X zeolite - An isothermal study

Abstract

Asphaltene has the highest molecular weight and the most polar organizers from petroleum. In this paper, the content of the asphaltenes from a crude oil was extracted and the amount of asphaltene in crude oil was measured to be 3.88%. Four metal oxides were added to 13X zeolite and 13X,10%CaO, 13X,10%Co₃O₄, 13X,10%Fe₃O₄ and 13X,10%ZnO were prepared. The adsorption behavior of the adsorbents was evaluated in asphaltenes adsorption. The capacity of the adsorbent for asphaltenes adsorption is as follows: 13X,10%CaO> 13X,10%Co₃O₄> 13X,10%Fe₃O₄> 13X,10%ZnO. The isotherm of adsorption of the asphaltenes over the adsorbent was studied and resulted that the experimental data could best fit with the Langmuir model, indicating that adsorption is as a monolayer.     

Aquathermolysis of heavy oil in reservoir conditions with the use of oil-soluble catalysts: part III – changes in composition resins and asphaltenes

Abstract

This paper discusses aquathermolysis process of heavy crude oil from Boca de Jaruco reservoir, which is developed by CSS method. The catalysts based on cobalt, nickel, iron and cupper are used to intensify the in-situ conversion processes. The active form of catalysts generates after steam injection. The third part of paper discusses conversion of resins and asphaltenes. The influence of thermo-catalytic conditions and composition of catalysts are also studied. The destruction of resins and asphaltenes are observed after thermocatalytic treatments. The changes in composition of resins and asphaltenes are revealed by IR-spectroscopy data.     

超声波处理对渣油物性的影响

以四种不同来源和属性的渣油为原料,研究了超声波处理前后渣油基本物性和结构参数的变化,并对超声波处理前后渣油的加氢效果进行了对比研究 。结果表明：经超声处理后渣油的平均相对分子质量减小,粘度降低,密度基本不变;SARA四组分中,饱和分、芳香分和沥青质含量均减小,胶质的含量增加,胶质和沥青质的总含量增加;沥青质含量越高,经超声处理后胶质增加量越多,饱和分减少量越小,芳香分减少越大。超声波处理使渣油的平均分子总碳数C、芳环上的碳数CA、总环数RT、芳环数RA、环烷环数RN均减小,重油特征化参数KH增大,超声波处理改变了渣油的平均结构。沥青质含量和结构的变化是超声波处理引起渣油物性变化的最主要原因。     

沸腾床加氢过程重油分子结构变化规律

考察了沸腾床加氢过程中,渣油转化率对杂质脱除率和未转化油(UCO)性质及其分子结构的影响,并探讨了加氢过程中重油分子结构的变化规律.结果表明:渣油转化率增加,UCO中杂质(硫、氮、金属)脱除率增加,密度、残炭值、氮质量分数升高,硫质量分数和含金属量降低;胶质沥青质转化率与渣油转化率呈现良好的线性关系,随着渣油转化率增大...     

Infrared Study of Hydrogen Bond Types in Asphaltenes

Abstract

The structural characteristics of asphaltenes are important to refiners for determining the yields from the residual fraction of crude oils and the operating parameters of the process units for deep conversion processes. In this article, we studied the hydrogen bonding distribution of four Saudi Arabian crude-oil-derived asphaltenes against the phenol solutions of various concentrations in carbon tetrachloride. In an attempt to explain relative hydrogen bonding capabilities of asphaltenes, OH peak intensity of phenol and enthalpies of hydrogen bond formation were used in combination with the content of heteroatoms (N, O, and S) in asphaltenes. The OH peak intensity of phenol depends on the presence of acidic and basic moieties or functional groups on the surface of asphaltenes. The results obtained show that the asphaltenes with high oxygen and low nitrogen contents have poor interaction with phenol, which indicates that oxygen might be incorporated as acidic hydroxyl groups in asphaltenes. In a similar way, asphaltenes with low oxygen and high nitrogen contents give high phenol interaction values. Piperidine was also tried to evaluate the hydrogen bonding capabilities of NH group with the asphaltenes. The trace metal and GPC molecular weight measurements showed that the Arab heavy asphaltenes possess highest molecular weights and maximum V and Ni contents.     

Spectrophotometric Measurement of Asphaltene Concentration

Abstract

Typically, when ultraviolet and visible absorbance of asphaltenes is employed to measure asphaltene concentration, linear calibrations of absorbance vs. asphaltene concentration are prepared from a sample of asphaltenes in a given solvent. This calibration is shown to be sensitive to: (a) the inorganic solids content of the asphaltenes; (b) physical–chemical differences between asphaltenes from different sources or extracted with different methods; and (c) selective adsorption of asphaltenes on liquid–liquid or solid–liquid interfaces. Calibration constants were determined at wavelengths of 288 and 800 nm for samples of Athabasca and Cold Lake asphaltenes obtained using different extraction methods, from precipitation experiments, and from adsorption experiments on water-in-hydrocarbon emulsions and on powdered metals. It was found that the inorganic solids content did not affect absorbance but the asphaltene concentrations must be corrected to a solids-free basis for accurate results. Calibration constants were found to correlate to the average associated molar masses of the asphaltenes. Therefore, any change in molar mass of asphaltenes during the course of an experiment may change the calibration constant. Partial precipitation and the selective adsorption of asphaltenes can lead to a change in the molar mass of asphaltenes left in solution. The corresponding change in the calibration constants can lead to errors of 5–25% in the estimated concentration.     

Formation of Polycondensation Products in Heavy Oil Feedstock Hydroconversion in the Presence of Ultrafine Catalyst:Physicochemical Study

The formation of polycondensation products in the hydroconversion of heavy oil feedstock is studied in the flow regime in the presence of an in situ synthesized ultrafine catalyst (MoS₂). Experiments show that, to a conversion level specific to every feedstock, the coke yield attained by variation in temperature or contact time remains close to zero; subsequently it begins to grow exponentially. The observed regularity is associated with a difference in the rates of reactions involving feedstock components and the presence of coke precursor—asphaltenes—in the feedstock. A relationship is revealed between the amount of formed coke, the content of asphaltenes in the feedstock, and the Hildebrand solubility parameter, which characterizes the ability of the dispersion medium to maintain asphaltenes in the dispersed state without agglomeration.