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.     

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

Abstract

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.     

CHARACTERIZATION OF VACUUM RESIDS,HYDROCRACKED PRODUCTS AND ASPHALTENES BY PYROLYSIS-GAS CHROMATOGRAPHY (FID-FPD)

ABSTRACT

This paper describes an exploratory study on the characterization of oil heavy-end fractions through pyrolysis coupled with gas chromatography. A pulse heating pyrolyzer with a platinum-strip sample holder, directly coupled with a capillary column gas chromatograph and equipped with a universal detector (FID) and a sulfur-selective detector (FPD), was used for that purpose.

An analysis of vacuum residua, asphaltenes and resins from different crudes was made, as well as analogous fractions from the hydrocracking products of these vacuum residua. Hydrocarbon qualitative profiles (pyrograms) were very much alike for all fractions studied. However, some differences were observed in pyrogram intensity. In general, fractions from untreated samples showed more intense signals than those from the hydrotreated ones. Besides, each of the fractions from vacuum residua generated more intense pyrograms than the combination thereof (entire residue). It was possible to correlate the process-ability of a vacuum residue during hydrocracking and its hydrocarbon yield in analytical pyrolysis.     

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.     

CHARACTERIZATION OF VACUUM RESIDS, HYDROCRACKED PRODUCTS AND ASPHALTENES BY PYROLYSIS-GAS CHROMATOGRAPHY (FID-FPD)

This paper describes an exploratory study on the characterization of oil heavy-end fractions through pyrolysis coupled with gas chromatography. A pulse heating pyrolyzer with a platinum-strip sample holder, directly coupled with a capillary column gas chromatograph and equipped with a universal detector (FID) and a sulfur-selective detector (FPD), was used for that purpose.

An analysis of vacuum residua, asphaltenes and resins from different crudes was made, as well as analogous fractions from the hydrocracking products of these vacuum residua. Hydrocarbon qualitative profiles (pyrograms) were very much alike for all fractions studied. However, some differences were observed in pyrogram intensity. In general, fractions from untreated samples showed more intense signals than those from the hydrotreated ones. Besides, each of the fractions from vacuum residua generated more intense pyrograms than the combination thereof (entire residue). It was possible to correlate the process-ability of a vacuum residue during hydrocracking and its hydrocarbon yield in analytical pyrolysis.     

Comparison of Different Power-law Kinetic Models for Hydrocracking of Asphaltenes

Abstract

Hydrotreating of Maya crude oil was carried out at a pilot plant scale under the following reaction conditions: pressure of 70–100 kg/cm², hydrogen-to-oil ratio of 5,000 ft³/bbl, temperature of 380°C–420°C, and space-velocity of 0.33–1.5 h^?1. Asphaltenes were precipitated from the feed and from all hydrotreated products using n-heptane as solvent. Hence, variations in asphaltenes concentration were obtained as a function of reaction conditions. Three different kinetic models were studied: a simple power-law model, a modified power-law model which assumes a parallel path reaction for asphaltenes hydrocracking with the same reaction order for more reactive and less reactive asphaltenes, and the same modified power-law model with different orders for both types of asphaltenes. This latter model exhibited the best fit of experimental asphaltenes concentrations.     

Mild Hydrocracking—A Review of the Process,Catalysts, Reactions,Kinetics, and Advantages

Abstract

The demand for high quality middle distillates is increasing world wide while the demand for residue and fuel oil is decreasing. Hydrocracking is the major conversion process that meets the twin objectives of producing more middle distillates of very high quality. Since hydrocracking is a capital-intensive process, many refiners consider the option of converting their existing vacuum gas oil hydrotreating units into mild hydrocracking units. The use of mild hydrocracker bottom as FCC feedstock can improve the quality of FCC products. In view of the advantages of mild hydrocracking process, it is essential to understand the process, catalysts used, reactions, kinetics, and advantages. This article reviews recent literature on MHC process, various catalysts used, reactions involved and advantages of mild hydrocracking process in terms of improved product qualities and increased distillates. The kinetics of the mild hydrocracking process and kinetic challenges with respect to aromatic saturation have been summarized. The limitations of the process and future scope of work in this area are also discussed briefly.     

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.     

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。     

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。     

Analysis of the thermal hydrocracking of heavy fuel oil

The thermal hydrocracking of Mexican heavy fuel oil was studied at 1200 psia and different reaction temperatures (370, 380, 390 and 400°C). The results show that the vacuum residue which constitutes 62 wt. % of the heavy fuel oil and contains 47 wt. % resins and 23.3 wt. % asphaltenes, reacts to form lighter hydrocarbons (IBP-540°C), solid and gas. Resins transform more easily to saturates, and gases are produced mainly from the asphaltene fraction, indicating that the terminal alkyl groups in this fraction are shorter than those present in the resin fraction. The C-C scission reactions dominate the transformation of heavy fuel oil in the interval from 370 to 390°C, whereas the carbon rejection reactions are dominant at 400°C. Finally, the thermal hydrocracking of heavy fuel oil at 390°C appears suitable since at this temperature the reaction produces the greater amount of atmospheric distillates (+20.5 wt. %) and a low content of solid (2.0 wt. %) and gas (2.1 wt. %).     

THE COLLOIDAL STRUCTURE OF CRUDE OILS AND SUSPENSIONS OF ASPHALTENES AND RESINS

ABSTRACT

A better understanding of colloidal macrostructure of the heavy petroleum products and their complex fractions is of great importance in the context of industrial problems that arise during the crude oil production, refining and transport. Much effort has been devoted to the chemical structure studies, but there is a need for more precise data regarding parameters that characterize those complex systems. For instance, the molecular weight of heavy molecules, the composition and size of aggregates formed during the industrial processing and their evolution upon the variation of temperature, pressure and with the addition of solvent have not been well known. In this paper we present new results obtained using several powerful techniques. Scattering methods (using X-rays and neutrons) are applied to study both the fractionated products (asphaltene and resin solutions in more or less good solvents) and the real systems (Safaniya vacuum residue). The lamellar structural model for asphaltenes and resins is confirmed and the molecular weight of these species determined using a polydisperse size distribution. Discussion is presented concerning the specificity of X-ray and neutron scattering : X-ray experiments are more sensitive to the aromatic-rich regions, whereas the neutron scattering data provide information about all the particle volume. Viscosimetry measurements provide information on the molecular shape of asphaltene and confirm the disk-like model. Critical micellar concentration has been obtained using Vapour Pressure Osmometry (VPO) for asphaltene suspensions in toluene and in pyridine. The resin molecules are smaller than asphaltenes, and appear to be a good solvent for asphaltenes. One of the major conclusions of this work is the wide-spread presence of density heterogeneities in diluted solutions of asphaltenes and resins as well as in the pure product (Safaniya vacuum residue). This was deduced from the scattering experiments and cryo-scanning electron microscopy data. The heating effects. were studied: a temperature increase leads to the decrease of molecular weight, but heterogeneities remain present. The structure of vacuum residue exhibits large density fluctuations which are thermally stable. These dense regions remain connected into a network up to 393°K and determine the yield value of the rheological behaviour.     

Performance Evaluation Studies of First- and Second-Stage Hydrocracking Catalysts Using Kuwait Vacuum Gas Oil Feedstocks

Abstract

In a two-stage hydrocracking process, two types of catalyst are used to remove undesirable contaminants (such as S, N, hydrogenation of aromatic compounds, etc.) and convert the heavy feedstock to lighter products. In the present work, individual set of experiments were conducted to obtain information regarding activity and selectivity with emphasis on the evaluation of kinetic parameters of first- and second-stage commercial catalysts used in hydrocracking process. The performance tests were conducted in a down-flow fixed-bed hydrocracking pilot plant using a single reactor. The hydrotreating type A catalyst and hydrocracking type B catalyst were used individually with typical Kuwaiti refinery feedstocks, namely, hydrotreated vacuum gas oil (HVGO) and unconverted residual oil (UCRO), respectively. The order of reaction in this study shows first-order kinetics for HDS and HDN over CAT-A, and first-order hydrocracking conversion over CAT-B. For CAT-A the activation energies were found for HDS and HDN reactions at 22 and 27.3 kcal/gmole, while for CAT-B activation energies were 27.4 kcal/gmole.     

悬浮床加氢裂化集总动力学模型的研究

在不同反应温度、氢初压条件下,通过高压反应釜对克拉玛依常压渣油（KLAR）进行加氢裂化实验,以此模拟悬浮床加氢裂化过程,并根据实验数据及实际工艺中对各种轻油产品收率预测的需求建立了悬浮床加氢裂化六集总（气体、汽油、柴油、蜡油、减压渣油、焦）动力学模型,用matlab软件进行编程,采用最小二乘法对动力学参数进行估算,并进行误差分析。结果表明,建立的六集总动力学模型能很好的对各集总产品收率进行预测,计算结果与实验值基本吻合,大部分误差在5%以内。     

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.     

Kinetics and Selectivity of Asphaltene Thermal Cracking,Thermal Hydrocracking,and Catalytic Hydrocracking

Abstract

A pentane-insoluble asphaltene was processed by thermal cracking, thermal hydrocracking, and catalytic hydrocracking in a microbatch reactor at 430°C. The experimental data of asphaltene conversion fit second-order kinetics adequately to give the apparent rate constants of 1.704 × 10^?2, 2.435 × 10^?2, and 9.360 × 10^?2 wt frac^?1 min^?1 for the above three cracking processes, respectively. A three-lump kinetic model is proposed and solved to obtain rate constants of parallel reactions of asphaltenes to produce liquid oil (k₁) and gas + coke (k₃) and a consecutive reaction from liquid to gas + coke (k₂). The value of k₁ is 1.697 × 10^?2, 2.430 × 10^?2, and 9.355 × 10^?2 wt frac^?1 min^?1; k₂ is 3.605 × 10^?2, 2.426 × 10^?2, and 6.347 × 10^?3 min^?1; and k₃ is 6.934 × 10^?5, 5.416 × 10^?5, and 4.803 × 10^?5 wt frac^?1 min^?1 for asphaltenes thermal cracking, thermal hydrocracking, and catalytic hydrocracking, respectively. Analysis of selectivity shows that the catalytic hydrocracking process provides the highest liquid production, and the coking process provides the highest coke formation, as expected. An induction period of coke formation was found to increase from thermal cracking to thermal hydrocracking to catalytic hydrocracking process.     

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.     

Thermal Hydrocracking Kinetics of Chinese Gudao Vacuum Residue

Abstract

The thermal hydrocracking kinetics of Chinese Gudao vacuum residue was studied in a batch autoclave reactor. The temperature ranged in 390–435°C and the initial hydrogen pressure was 7.0 MPa at 20°C. Ammonium phosphomolybdate (APM) in its dispersed phase was the catalyst. The reaction products, gas, naphtha, atmospheric gas oil (AGO), vacuum gas oil (VGO) and coke, were separated during and after experiments, and their yields vs. reaction time were obtained, for four reaction temperatures: 390, 405, 420, and 435°C. The activation energy was calculated from a traditional kinetic model to be 218.6 kJ/mol. A new kinetic model was proposed in this work that allows for the calculation of activation energy with a minimum number of three tests, each at a different temperature. This is comparable to the traditional model which requires a minimum of 12 tests; a minimum of four tests for one temperature and a minimum of three temperatures. The activation energy calculated from the new model with four tests is 229.6 kJ/mol, only 5% greater than that obtained from the traditional model. The reaction rate constants obtained from this model are also consistent with those from the traditional model.     

HYDROLIQUEFACTION OF TEXAS LIGNITE IN COAL- AND PETROLEUM-DERIVED SLURRY OILS

ABSTRACT

Hydroliquefaction of Texas lignite (68.5%. C daf) was conducted in a batch autoclave under hydrogen in a coal–derived slurry oil at 90 bar initial pressure for temperatures of 380–460^° C and residence time of 15–60 minutes, or a vacuum distillate from petroleum at 435^° C for 60 minutes and initial H₂–pressure of 60–150 bar, or a vacuum residue from the same petroleum at 435 and 460^° C for 60 minutes and initial H₂–pressure of 90–150 bar or tetralin at 435^°C, 60 minutes and 90 bar initial H₂–pressure. Red mud plus sodium sulfide were added as a catalyst for all experiments. Lignite conversion ranged from 50 to 83%. The products were separated into gases, residue, asphaltenes, oils B,P. above 200^° C, oils B.P. below 200^° C. Total liquid products from coal reached 57% in coal-derived slurry-oil, 56% in vacuum distillate and 64% in vacuum residue at optimum conditions with 32% of product oil B.P. below 200^° C in vacuum distillate and 24% in vacuum residue. When coprocessing lignite with vacuum residue at 120 bar initial pressure, 435^°C and 60 minutes residence time the total mass balance presented an oil yield of 73%. with 32% boiling below 200^°C.     

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.