Pyrolysis of heavy oil in the presence of supercritical water: The reaction kinetics in different phases

In the presence of supercritical water (SCW) and N₂, the pyrolysis of heavy oil was investigated to distinguish the difference in the reaction kinetics between the upgrading in the SCW and oil phases. The pyrolysis in the SCW phase is faster than that in the oil phase, but the reaction in whichever phase is retarded by vigorous stirring. The pyrolysis can be preferably described by a four‐lump kinetic model consisting of the condensation of maltenes and asphaltenes in series. In the SCW phase, highly dispersed asphaltenes are isolated by water clusters from maltenes dissolved in SCW surroundings, by which the condensation of asphaltenes is drastically accelerated. Benefited from excellent mass transfer environments in SCW, the condensation of maltenes is promoted simultaneously. The introduction of SCW into the pyrolysis of heavy oil results in an effectively increased upgrading efficiency, but its influence on the properties of equilibrium liquid products is minor. © 2014 American Institute of Chemical Engineers AIChE J, 61: 857–866, 2015     

分子水平重油生焦规律研究进展

阐述了重油缩合生焦规律分子水平的研究进展,主要从重油中四组分的分子组成与生焦的关系以及重油模型化合物生焦的研究两方面进行了概述。研究表明,对于重油各族组分来说:适量的饱和分有助于提升生焦质量;芳香分环数越多生焦越明显,生焦质量越差;中、重胶质和沥青质易生焦,生焦质量差;杂原子会降低生焦质量,但各个杂原子的危害程度不同。而对于各个重油模型化合物来说:甲苯极难发生热缩合反应;萘、菲、蒽、芘的热缩合反应难度逐渐降低;二甲基萘由于侧链的作用,生焦质量比萘要差;1,2,4,5-四甲基苯由于其特殊的空间构型较易缩合生焦且生焦质量很好;杂原子模型化合物单独生焦质量越差,则其在加入到芳烃中之后对体系的生焦质量危害越大。随着超高分辨质谱技术的发展,为更加细致深入研究芳烃热缩合反应生焦机理提供了可能。     

Lumped reaction kinetic models for pyrolysis of heavy oil in the presence of supercritical water

The reaction kinetics of the pyrolysis of heavy oil in the presence of supercritical water (SCW) and high pressure N₂ were measured. At any reaction temperature applied, the pyrolysis under SCW environments is faster than that under N₂ environments. Meanwhile, at lower temperatures the pyrolysis under both environments is accelerated by the introduction of coke into the feedstock. On the basis of a first‐order four‐lump reaction network consisting of the sequential condensation of maltenes and asphaltenes, the pyrolysis in whichever medium can be preferably described either by the lumped reaction kinetic model modified with autocatalysis and pseudoequilibrium or by the model modified solely with pseudoequilibrium. Benefited from the reduced limitation of diffusion to reaction kinetics, the pyrolysis in the SCW phase is more sensitive to the increase in reaction temperature than that in the oil phase, disengaging readily from the dependence on autocatalysis at a lower temperature. © 2015 American Institute of Chemical Engineers AIChE J, 62: 207–216, 2016     

Thermal cracking and combustion kinetics of asphaltenes derived from Fosterton oil

Thermal behavior of crude oil (Fosterton) asphaltenes mixed with reservoir sand was investigated using thermogravimetric analysis (TGA), in nitrogen and air atmospheres for different heating rates up to 800 °C. In this study, four sets of TGA runs were performed to examine the thermal behavior of Fosterton asphaltenes and the coke derived from the asphaltenes. The parameters studied were heating rate (10, 15 and 20 °C min^− 1) and the type of purge gas (N₂ and air) employed for the process of thermal degradation of asphaltenes. Distributed activation energy model (DAEM) has been applied to study the asphaltene pyrolysis kinetics. It was observed that the activation energy was distributed from 46.16 to 72.17 kJ/mol, for the conversion range of 0.1 to 0.4. The general model for nth order reaction was used to obtain the kinetic parameters of coke oxidation reaction from the TGA data. From the model, the calculated activation energy, E, was 93.46 kJ/mol and the pre-exponential factor was 9.59 × 10⁵ min^− 1 for the coke combustion. The apparent order of combustion reaction gradually increased from 0.7 to 0.8 for different temperatures.     

Reactions of Athabasca asphaltenes and heavy oil with metal chlorides

The interactions of Athabasca asphaltenes and heavy oil with metal chlorides are described. The asphaltenes are converted to insoluble, presumably higher molecular weight, products which contain substantial amounts of chemically bound chlorine. The heavy oils were converted partly into insoluble products; both this fraction and residue oils contained chemically bound chlorine. Statistical structure analysis aided by infra-red spectrographic and nuclear magnetic resonance examination of the soluble portion of the reacted heavy oils suggests that inter- and intramolecular condensation by dehydrogenation and dealkylation accompany chlorination.     

新疆托里油砂分段热解机理

在热重分析仪中考察了不同升温速率下油砂的热解特性,结果表明:油砂样品失重过程分为少量气体脱附、低温热解、主要热解、半焦缩聚4个阶段。通过微型固定床与在线质谱耦合测得的气体释放顺序为CO₂、CO、C₂H₆、CH₄和H₂,所对应的初释温度分别为155、178、146、174、354℃。结合核磁和红外对不同温度段液固产物的化学结构进行分析,发现350℃前主要是油砂中轻质油脱附,还包括羧基和烷基侧链的断裂,轻质油品中芳碳率达7.92%;350～520℃之间为油砂的主要热解阶段,油砂油结构中芳碳率为23.51%。据Coats-Redfern法计算得到油砂低温热解和主要热解段的活化能分别为27.63和90.30 kJ·mol^-1,说明开环与裂解反应所需活化能大于油砂油脱附、羧基分解和弱键断裂反应的活化能,揭示了分段热解机理。     

含油污泥在ZSM-5沸石上催化热解产物特性

采用U型固定床管式炉研究了含油污泥在ZSM-5分子筛催化剂上的热解产物特性。发现在450℃下未使用催化剂热解时,GC-MS和GC测得的油泥热解油产物中的主要成分为烷烃和烯烃,芳烃含量较低;气体产物中主要为短链烃类,氢气产量较少。而在ZSM-5分子筛的催化作用下,热解油中芳香烃产量达到88.4%,气体产物中的氢气产量和短链烃类产量均明显增加。研究了400～550℃之间分子筛对含油污泥的催化效果,发现ZSM-5在500℃时催化效果最佳,油相产率达到65.6%,油相中的沥青质和胶质含量较低,芳香烃产量达到90.9%。通过热重和XPS分析发现分子筛上的积炭主要以多环芳烃焦炭的形式存在。     

Pyrolysis kinetics of atmospheric residue and its SARA fractions

Thermal analysis of atmospheric residue from heavy crude oil and its SARA fractions was carried out and the tendency of each fraction toward coke formation was determined. The coke yield was 16.3 wt.% for atmospheric residue, 43.1 wt.% for asphaltenes, 4.6 wt.% for resins, 3.8 wt.% for aromatics, and 0.3 wt.% for saturates. Pyrolysis kinetics of residue and its fractions, i.e., asphaltenes, resins and aromatics was also investigated. The TG experiments were conducted at three different heating rates of 8, 12, and 16 °C/min from room temperature up to 800 °C under nitrogen atmosphere to verify the weight variation with reaction temperature. Isoconversional analysis to fit data assuming first order kinetics was employed. Asphaltenes was the fraction that produces coke in higher amount having a range of activation energy of 41.0–58.6 kcal mol⁻¹ whereas activation energy for atmospheric residue ranged from 11.5 to 30.0 kcal mol⁻¹.     

Oxidative demetallization of petroleum asphaltenes and residua

Cold Lake asphaltenes, Arabian Heavy asphaltenes, and Cold Lake vacuum residuum were treated with a variety of oxidizing agents. Of these, reagents such as air/100 °C and NaOH/air were found to have no appreciable demetallization activity while oxidants such as sodium hypochlorite and peroxyacetic acid exhibited high demetallization activity coupled with the ability to remove or destroy petroporphyrins. The sodium hypochlorite, however, was found to suffer from the disadvantage of causing chlorine incorporation into the feed. This oxidative demetallization appears to be a rather unselective reaction with both metals and porphyrin removal being proportional to the amount of oxidant used. Various peroxy acids were found to be effective.     

Kinetics of non-catalytic hydrocracking of Athabasca bitumen

The kinetics of non-catalytic hydrocracking of Athabasca bitumen were studied in a batch reactor at 648–693 K and at an initial hydrogen pressure of 7.2 MPa. The reaction products were separated into coke, asphaltenes, resins, aromatics, saturates and gases. Reaction time versus product yield curves were obtained for the above six product groups. Two simple reaction models were proposed. In the first, bitumen is considered to be a single reactant and the hydrocracking reaction a single irreversible reaction. The activation energy for bitumen consumption was found to be 150 kJ mol⁻¹. In the second model, coke, asphaltenes, maltenes and gases are treated as components. Activation energies for the reactions were found to be in the range 142–284 kJ mol⁻¹. Hydrocracking reactions were found to be first order. Activation energies for the hydrocracking reactions are compared with those for thermal cracking reactions.     

Study of pyrolysis kinetics of Alberta oil sand by thermogravimetric analysis

The kinetics of the thermal decomposition of Alberta oil sand has been investigated by thermogravimetric analysis (TGA) for the study of oil sand pyrolysis characteristics. The TGA experiments were carried out at four different heating rates of 10, 20, 30, 40 °C/min up to 900 °C to verify weight variation and reaction temperature. The activation energy of the thermal decomposition of Alberta oil sand obtained from the kinetic analysis was similar to that of the previous researches. Also, bitumen was extracted by solvent (toluene, THF (tetrahydrofuran)) and analyzed. Extracted bitumen was analyzed by using proximate analysis, ultimate analysis, heavy metal analysis, heating value, asphaltenes, API, SIMDIS, density, TLC, and molecular weight. The analyses of the extracted bitumen were similar to those of heavy residue.     

Catalytic (Mo) upgrading of Athabasca bitumen vacuum bottoms via two-step hydrocracking and enhancement of Mo-heavy oil interaction

Athabasca bitumen vacuum bottom (ABVB) was fractionated into 66.9% maltenes (n-pentane-solubles), 32.2% asphaltenes (n-pentane-insolubles), and 0.9% coke (toluene-insolubles). The maltenes were subsequently split into four sub-fractions: 5.6% saturates (MF1), 2.6% mono and diaromatics (MF2), 38.2% polyaromatics (MF3), and 20.3% polars (MF4). Yield maximization of the desirable light MF1 and MF2 sub-fractions was explored according to three catalytic (Mo) scenarios: (i) a one-step ABVB hydrocracking with light products recovery; (ii) two-step process consisting of ABVB hydrocracking followed by the hydrocracking of the maltenic MF3+MF4 sub-fractions; and (iii) one-step ABVB hydrocracking with specific pretreatment procedures to enhance contacting between Mo-based catalyst and the heavy oil. The products yield distribution was mapped according to a severity parameter combining temperature and time. Coke and gas formation increased with increased severity while asphaltenes and total maltenes decreased. For scenario (i), the optimum severity factor for the highest light products yield was 7.2. At this severity the ensemble of saturates, plus mono and diaromatics reached 32.7%. For scenario (ii), the optimum severity factors were 6.9 and 7.0 for the first and second hydrocracking steps, respectively, resulting in a total light products yield of 45.4%. In scenario (iii) where options such as increasing the catalyst concentration, removal of oil-borne coke before hydrocracking and ultrasonic mixing, the maximum MF1+MF2 yield reached 50.8% on raw ABVB weight basis at a severity factor of 7.2.     

Heavy oil upgrading in the presence of high density water: Basic study

Heavy oil (Canada oil sand bitumen) upgrading in high density water (100 and 200 kg/m³) at 723 K was performed by a batch reactor. Yields of asphaltene, maltene, and coke were evaluated. With increasing water density, the rate of coke formation was promoted. To get some hints of coke formation mechanism, the formed coke was observed by scanning electron microscope (SEM). The most part of the coke formed st neat pyrolysis (pyrolysis in the absence of high density water) was coalescent structure of some small coke particles, while that at pyrolysis in the presence of water (200 kg/m³ of water density) was porous structure that indicated occurrence of phase inversion of coke precursors. Based on the results, the reaction mechanism of the heavy oil upgrading was considered: lighter oil was extracted in high density water and the concentration of light hydrocarbon decreased in a heavier oil phase, while the concentration of heavier oil in the oil phase increased. Thus, the lighter oil decomposed further in high density water phase and the heavier oil in the oil phase combined together to form coke due to its higher concentration.     

页岩灰和FCC催化剂调控油页岩热解产物二次反应特性

采用两段反应器对油页岩热解初级挥发分进行二次催化反应特性研究,考察了第2段反应器内不同的催化载体、反应气氛与停留时间对油气收率及品质的影响。结果表明,在考察的停留时间范围内页岩灰具有相对适中的催化活性来调控热解挥发分产物的二次反应,水蒸气气氛能够进一步提高热解油收率约5%,并能够在一定程度上抑制裂解气体中C₂~C₃组分的生成。页岩灰作为催化载体能够转化热解油中VGO（馏程>350℃）等重质组分,随停留时间增加油品馏程向轻组分转移。油品组分GC-MS结果表明,较短停留时间内（<3 s）,水蒸气添加能够有效抑制热解油中脂肪烃类的过度裂解,与氮气相比提高汽柴油馏分含量20%以上。过长的停留时间（3~5 s）会造成VGO等馏分缩聚生成焦炭,从而大幅降低热解油收率。     

Pyrolysis of coal liquids

The pyrolysis of process recycle solvent derived from Western Kentucky coal via the SRC-II coal liquefaction process was investigated to ascertain the effect of residence time and temperature on the production of olefins. The study was made using an alonized transfer line reactor operating at temperatures of 650 and 730 °C, essentially atmospheric pressure, and residence times up to 0.13 s. A comparison is made with previously published results for the pyrolysis of hydrotreated COED light and heavy coal liquids (subsequently referred to as COED light and heavy oils, respectively) derived from Western Kentucky coal and steam pyrolysis of a hydrogenated fraction of SYNTHOIL derived from Western Kentucky coal. Results indicate that in each case the preferential pyrolysis of the saturate fraction occurs under convential pyrolysis conditions. Ethylene, propylene, and methane were the dominant gas products in all cases. The liquid pyrolysates from the COED oils and SRC-II recycle solvent had lower $\text{H}\text{C}$ ratios and heating values than their respective feedstocks. Mass spectroscopic analysis of the liquid pyrolysates in each case revealed the presence of polycyclic aromatics that were not present in the individual feedstocks. This trend which increased with temperature is indicative of cyclization and/or recombination of free radicals during pyrolysis. It is therefore surmized that the yields of light olefins from primary coal liquefaction products can be improved by partially hydrogenating them prior to pyrolysis. Alternatively, sufficient hydrogen can be provided in the vicinity of cracking to suppress retrogressive reactions which lead to the formation of coke. The pyrolysis of COED oils and SRC-II recycle solvent was found to follow first-order irreversible kinetics. The activation energy for the pyrolysis of the COED light and heavy oil was found to be 76.1 and 70.85 kJ g-mol^?1, respectively.     

环烷基瓦斯油催化裂解反应规律及产品性质

利用提升管催化裂解实验装置研究了加拿大合成原油瓦斯油HGO和LGO的催化裂解反应规律和裂解产品性质。发现总低碳烯烃（乙烯、丙烯和丁烯）产率随反应温度和剂油比的增大存在最大值,随反应时间的延长而减小,随水油比的增大而升高。实验确定了HGO催化裂解的优化反应条件：反应温度620～640℃、剂油比16、反应时间2 s、水油比0.5左右。在此反应条件下,乙烯、丙烯和总低碳烯烃产率分别可达9.0%（质量）,15.8%（质量）和32.6%（质量）。催化裂解汽油馏分、柴油馏分和重油馏分含有大量的芳香烃,其中催化裂解汽油馏分总芳香烃含量在80%（质量）以上,主要是甲苯和C₈芳香烃;催化裂解柴油馏分总芳香烃含量在60%（质量）以上,主要是单环和双环芳香烃;催化裂解重油馏分总芳香烃含量在70%（质量）以上,主要是多环芳香烃。     

油砂沥青质分离纯化及其热裂解研究

为更好地开采并利用油砂,以新疆某油田油砂沥青质为研究对象,在分离纯化后进行热裂解实验研究,探寻油砂沥青质的转化规律。实验结果表明,超声震荡可以快速将沥青质包裹组分释放出来,缩短沥青质的分离纯化时间;沥青质中3种重要物质生烃、生气、生焦含量变化与温度和时间的关系非常密切;沥青质裂解具有明显的一级反应动力学特征,随着温度的升高,时间逐渐缩短,而其表观速率常数总体呈增加的趋势。     

重质石油烃利用技术-重质烃气化-裂解集成工艺的模拟研究

我国是一个石油资源紧缺的发展中国家,石油供给高度依赖于世界石油市场. 世界原油资源的重质化和对轻质产品需求的增加,使重质石油烃利用技术成为我国能源和石化工业的一个重要课题. 现有的重质石油烃利用技术中,减粘裂化、焦化、催化裂化和加氢转化仍然是最主要的技术手段. 同时,气化和裂解制烯烃也显示出良好的技术潜力. 本工作提出的重质石油烃气化-裂解集成工艺利用燃烧裂解结焦为气化和裂解过程提供热量,同时产出合成气和部分低碳烯烃. 模拟研究显示,通过调整O2和水蒸汽流量可实现对气化-裂解温度的控制,在近零焦炭添加量的情况下可同时获得合成气和低碳烯烃,可在控制反应停留时间的条件下获得产物中烯烃的最大组成.     

油页岩热解过程中微量元素迁移及其作用规律

利用电感耦合等离子质谱仪（ICP-MS）测定油页岩样品和不同终温下热解半焦中13种金属微量元素的含量,分析这些元素在样品中的含量分布特征及其迁移规律。结果显示：龙口油页岩中富集Ba、Cd,巴里坤油页岩中富集Ba、Cd、Li、V、Sb,且样品中多数微量元素在500℃时挥发性最强。将不同形态的微量元素负载于干酪根上并进行热重分析,根据热重结果计算其动力学,再通过裂解气质联用实验（PY-GC/MS）测定干酪根和浸渍硝酸镍的干酪根热解时烷烃类产物的相对含量,研究微量元素对干酪根热解生烃转化率、热解速率以及产物分布的影响。结果表明：微量元素的盐类可以催化干酪根热解生烃,增大其热解转化率和热解速率,提高轻组分烷烃产率,降低重组分烷烃产率。     

半焦基催化剂裂解煤热解产物提高油气品质

利用上段热解下段催化的两段固定床反应器,针对府谷煤研究了半焦和半焦负载Co催化剂对煤热解产物的催化裂解效果。结果表明,半焦和半焦负载钴对热解产物催化裂解后,热解气收率增加,焦油收率降低,但焦油中沸点低于360℃的轻质组分含量提高,轻质焦油收率基本保持不变或略有增加。与煤在600℃直接热解相比,在热解和催化温度均为600℃,采用煤样质量20%的半焦为催化剂时焦油中轻质组分质量含量提高了约25%,轻质组分收率基本不变,热解气体积收率增加了31.2%;在热解温度600℃,催化温度500℃时,采用煤样质量5%的半焦负载钴催化剂,焦油中轻质组分质量收率和含量分别提高了约8.8%和28.8%,热解气体积收率增加了21.5%。煤热解产物的二次催化裂解的总体效果是将焦油中重质组分转化为轻质焦油和热解气。