Hydrocracking Of Asphaltene Research Articles

Hydrocracking of C5-Isolated Asphaltene and Its Fractions in Batch and Semi-Batch Reactors

Non-catalytic and catalytic hydrocracking of C5-isolated asphaltene and its subfractions were performed in batch and semi-batch reactors at various temperatures. Catalyst and H2 played an important role in the hydrocracking of asphaltenes. In the batch system, the catalyst enhanced asphaltene conversion to light liquid products and suppressed coke formation. The coke formation was controlled at a low reaction temperature, but the reaction rate was too low. Light liquid products were also formed at the beginning of the reaction even at high temperatures, but the coke formation was predominant as the reaction time went on due to the decrease in H2 amount in the reactor. To solve these problems, H2 was continuously supplied during the reaction using the semi-batch system. Sufficient supply of H2 improved the conversion of asphaltenes to light liquid products while inhibiting the coke formation. The lightest asphaltene fraction was easily cracked into light products by inhibiting the coke formation, while the heaviest fraction tends to form coke. The lightest asphaltene fraction prolonged the coke induction period of the heaviest fraction during the catalytic hydrocracking because the lightest fraction contained a significant amount of heavy resin close to that which could prevent aggregation of the heaviest asphaltenes.

Kinetic study of thermal and catalytic hydrocracking of asphaltene

Abstract In this study, a five-lump model was proposed for kinetic modeling of asphaltene placed in a batch reactor with a commercial slurry-phase catalyst (Mo-octoate). Asphaltene was separated from vacuum residue using normal pentane. The kinetic experiments were carried out at 380∼430℃ for 1∼20 h together with a 1000 ppm concentration of Molybdenum in thermal and catalytic hydrocracking reaction modes. The results showed that the coke induction period and maximum maltene yield are changed with reaction temperature and time at thermal and catalytic hydrocracking. In addition, a linear relationship between coke and liquid (maltene + asphaltene remains) yields was shown so that the critical gas amount could be found as a criterion for determining the end of the coke induction period. Significantly, the kinetic model fit the experimental data well and, moreover, was found to be able to predict the moment when coke begins to form as well as maximum maltene yields.

Catalytic Redox Transformations in Rock Matrices

The properties of catalytic systems based on iron oxide and inorganic matrices of oil-bearing rocks (basalt, clay, sandstone) in the decomposition of ammonium nitrate, oxidation of methane, and hydrocracking of asphaltenes were studied. The catalytic systems were iron oxide (hematite with a particle size of D = 11.0–20 nm, preparation temperature 453–473 K) fixed on matrices during co-hydrolysis of carbamide and iron chloride under hydrothermal conditions at temperatures of T = 433–473 K and pressures of 0.6–1.6 MPa. The iron oxide catalysts based on basalt and clay were most active in deep oxidation of methane (at 773 K, \({X_{C{H_4}}}\) = 83% and 72.9%, respectively); the Fe2O3/basalt and Fe2O3/sandstone systems were more active in the decomposition of ammonium nitrate. In hydrocracking of asphaltenes to maltenes, the catalyst activity decreased in the series Fe2O3/basalt > Fe2O3/clay > Fe2O3/sandstone, the iron oxide catalysts on clay being most selective. The obtained experimental data confirm that natural materials (oil-bearing rocks: basalt, clay, and sandstone) may be used for the development of catalytic systems for reactions in oil beds and of advanced technologies for increasing the oil recovery.

Coking propensity during hydroprocessing of vacuum residues, deasphalted oils, and asphaltenes

Residue hydroprocessing is one of the important processes in refinery to get maximum benefit. Coke deposition on the catalyst and on the interior of parts of the unit is a major challenge to process the residue having high concentration of metals and micro carbon residues. In this regard, three vacuum residues of different refineries are used to study the hydroprocessing activities on NiMo/Al2O3 catalyst. Asphaltenes and deasphalted oils are extracted and their hydroprocessing activities are compared with that of vacuum residues. It is noticed that the hydrocracking activity of the deasphalted oil is easier than that of the respective vacuum residue. The result also shows that the hydrocracking of asphaltene is very difficult particularly at low temperature like 410°C. However, this temperature is sufficient for coke formation by free radical mechanism. It is also observed that the deasphalted oils also yield coke though the feeds do not content asphaltene. It suggests that resin and aromatic hydrocarbons contribute microcarbon residue and hence finally to coke formation. Microcarbon residue of a feed is a very important factor to determine the coking tendency of a feed. The combustion property of coke measured by TGA shows that the cokes deposited on spent catalysts have similar combustion property irrespective of the origin: whether it is from aromatic, resin or asphaltene.

Catalytic Redox Transformations in Rock Matrices

Properties of catalytic systems based on iron oxide and inorganic matrices of oil-bearing rocks (basalt, clay, sandstone) were studied regarding the decomposition of ammonium nitrate, methane oxidation, hydrocracking of asphaltenes. The catalytic systems were iron oxide (hematite with particles of D = 11.0÷20 nm in size, preparation temperature 453–473 K) supported on the matrices through co-hydrolysis of carbamide and iron chloride under hydrothermal conditions at 433–473 K and 0.6–1.6 MPa. Iron oxide catalysts based on basalt and clay were most active to deep oxidation of methane (X CH4 = 83 % and 72.9 % at 773 K, respectively), and Fe 2 O 3 / basalt and Fe 2 O 3 / sandstone systems most active to decomposition of ammonium nitrate. In hydrocracking of asphaltenes to maltene, the catalyst activity decreased in the series: Fe 2 O 3 / basalt > Fe 2 O 3 /clay > Fe 2 O 3 / sandstone, the iron oxide supported on clay being the most selective catalysts. The obtained experimental data indicated practicability of natural materials such as oil-bearing rocks (basalt, clay, sandstone) for the development of catalytic systems to be used in situ in oil reservoirs and advanced technologies for improving the oil recovery.

Discrimination of Three Different Power-law Kinetic Models for Hydrocracking of Asphaltenes by Periodic Operation

The three different power-law kinetic models proposed by Trejo et al. (2007) for the hydrocracking of asphaltenes are discriminated under periodic operation. In the present work, the analysis of a plug flow reactor for these three models can be shown to have identical conversion of asphaltenes under conventional steady state operation. The behavior of the models under the periodic operation in the feed concentration cycling in asphaltenes and/or hydrogen concentration is evaluated for the average conversion of asphaltenes. The effect of different feed concentration cycling modes is also evaluated.

Molar Kinetics in Catalytic Hydrocracking of Asphaltenes

The hydrocracking of a pentane-insoluble asphaltene over NiMo/γ-Al2O3 was investigated in a microbatch reactor at 703 K. The cracking kinetics of the asphaltene was analyzed on a total molar basis. The first-order kinetics fits the experimental data in reaction times ≤30 min adequately, to give the rate constant of 0.0498 min-1. For reaction times over 30 min, however, secondary reactions such as coke formation could become significant. The formation probability of gas products decreases from the initial value of circa 0.8 to a stable level of 0.6 in 30 min, and the formation probability of liquid products increases from 0.2 to 0.4 accordingly.

Molar Kinetics in Catalytic Hydrocracking of Asphaltenes

The hydrocracking of a pentane-insoluble asphaltene over NiMo/γ-Al2O3 was investigated in a microbatch reactor at 703 K. The cracking kinetics of the asphaltene was analyzed on a total molar basis. The first-order kinetics fits the experimental data in reaction times ≤30 min adequately, to give the rate constant of 0.0498 min-1. For reaction times over 30 min, however, secondary reactions such as coke formation could become significant. The formation probability of gas products decreases from the initial value of circa 0.8 to a stable level of 0.6 in 30 min, and the formation probability of liquid products increases from 0.2 to 0.4 accordingly.

Lumping Kinetics of Asphaltene Hydrocracking over NiMo/γ-Al<sub>2</sub>O<sub>3</sub>

Catalytic hydrocracking of asphaltene over Ni-Mo/γ-Al2O3 was conducted in a microbatch reactor at 693 K. A kinetic model with four lumps (asphaltene, liquid, gas and coke) containing five reaction paths was developed. The fitting of experimental data validated the suggested model and determined the rate constant of each individual reactions, to give the insight to the kinetic feature of asphaltene catalytic hydrocracking

Catalytic hydrocracking of petroleum-derived asphaltenes by transition metal-loaded zeolite catalysts

In this study, correlation between structural parameters and reactivity for hydrocracking of asphaltene samples was investigated. Two different crude oils- (Arabian light/medium mixture and Brazilian Marlim) and Indonesian natural asphalt-derived asphaltenes were employed as samples. These asphaltene samples were submitted to elemental and spectroscopic analyses to obtain structural information such as H/C atomic ratio, heteroatom contents, carbon aromaticity, average size of aromatic clusters, and number-average molecular weight. These asphaltenes were also submitted to hydrocracking reaction at 400–450 °C for 3 h under H 2 pressure in the presence of palladium and nickel co-loaded Y-type zeolite catalyst. Reactivities of these samples were different to each other depending on their properties, the order of the reactivity obeying the following sequence: Indonesian natural asphalt-derived one>Arabian mixture-derived one>Brazilian Marlim-derived one. By increasing reaction temperature for hydrocracking or a pre-treatment with tetralin or with H 2-catalyst prior to hydrocracking, more than 60% of asphaltene feeds could be converted to C 1–C 4 hydrocarbon gases, H 2S, naphtha, and gas oil. Based on these experimental results, the correlation between structural features and reactivity of the samples was discussed. Among the parameters examined, both average molecular weight and nitrogen contents of the samples were found to be correlated with the reactivity.

Hydrocracking of asphaltene with metal catalysts supported on SBA-15

Hydrocracking of petroleum asphaltene with Fe and Ni catalysts loaded on SBA-15 supports has been carried out with a stainless autoclave at 573 K in pressurized H 2. Asphaltene conversion with 10 wt.% Fe catalysts with average pore diameters of 4.5–15 nm increases with increasing pore diameter up to 12 nm and reaches about 70%, but levels off beyond this value. Maltene yield shows the same dependency on the diameter and the highest value of 40% at 12–15 nm. When metal loading in the Fe catalyst with the pore diameter of 12 nm is varied between 4 and 30 wt.%, asphaltene conversion and maltene yield are the largest at 4 and 10% Fe, respectively, indicating the presence of the optimum Fe loading for maltene formation. The use of the 10% Ni catalyst in place of the 10% Fe catalyst lowers the conversion slightly but improves selectivity to maltene greatly. This means that the Ni is suitable for selective conversion of asphaltene to maltene, probably because of higher hydrogenation ability. The X-ray diffraction (XRD) measurements of toluene-insoluble (TI) fractions recovered after hydrocracking and the analyses of SO 2 evolved during the temperature-programmed oxidation (TPO) reveal the formation of Fe–S and Ni–S phases as surface species. The catalysis of asphaltene conversion by the sulfided forms is discussed.

Thermal hydrocracking of Cold Lake vacuum bottoms asphaltenes and their subcomponents

The thermal chemistry of bitumen and heavy oils is extremely complicated, mostly because of the complex nature and the unknown molecular structure of different components that are present in these materials. In order to understand the molecular transformation of bitumen during upgrading better, the following approach was adopted: separate the bitumen into different components (asphaltenes and maltenes), characterize them in detail and react each fraction separately. In the present work, the results of thermal reaction of asphaltenes and its subfractions (A1–A4) separated by column chromatography are presented. Thermal hydrocracking of asphaltenes derived from Cold Lake vacuum bottoms (CLVB) was investigated, neat and in a hexadecane solvent at 440 °C (30 min and 13.8 MPa H 2). The amount of coke measured as methylene chloride insolubles remained relatively constant at about 25 wt.%, whether the asphaltenes reacted neat or in hexadecane. Increasing asphaltenes concentration in hexadecane had little effect on coke formation. Results from the present study were compared with those reported previously from our laboratory for the same CLVB asphaltenes, which were thermal hydrocracked in CLVB maltenes and in decalin, and produced significantly less coke than in hexadecane. Unlike the reaction in hexadecane, changing the concentration of asphaltenes in maltenes had a significant effect on coke formation. The results from the previous study were rationalized in terms of competing reactions between maltenes and asphaltene-derived radicals for hydrogen, solvating effects of the media on coke formation, and viscosity effects on the radical–radical combination to form coke. Hexadecane as a solvent was relatively inert when compared to maltenes under the same severity conditions and did not stabilize the reactive radicals or prevent retrogressive reactions. The thermal hydrocracking of CLVB asphaltenes subcomponents (A1–A4) was also investigated in hexadecane. A better correlation was obtained between the coke yield and the molecular weight than either microcarbon residue or the aromaticity of the subcomponents. Based on the lack of additivity in coke yield, it was concluded that a synergistic effect among the subcomponents was most likely responsible for the reduced coke yield obtained from processing the asphaltenes feed.

石炭液化における天然パイライトの触媒効果 ＩＩＩ 微粉砕した天然パイライトの触媒作用機構

The catalytic activity of natural pyrites powdered finely on the liquefaction of Taiheiyo coal has been investigated. By powdering finely natural pyrites, their catalytic activities on coal liquefaction are enhanced, and their coal conversions are comparable to that in the presence of synthetic pyrite. The effect of their composition on coal conversion is reduced.According to the chemical structural analysis of oil and asphaltene produced in the presence of natural pyrite powdered finely, their carbon aromaticities are lower and their mean length of side chains (Ho/Hα + 1) are longer comparing with those in the presence of synthetic pyrite. These results indicate that natural pyrite powdered finely has a higher activity in the hydrogenation of asphaltene and in the hydrocracking of asphaltene to oil comparing with synthetic pyrite. Among four natural pyrites, pyrite from Shiraoi area (Hokkaido) has the highest hydrogenation ability to produce oils containing the most aliphatic components due to catalytic abilities of mineral matter coexisted.

Non-catalytic hydrocracking of asphaltenes: 2. Reaction kinetics

The kinetics of the non-catalytic thermal hydrocracking of Athabasca asphaltenes were studied over the temperature range 350–425 °C in a batch autoclave reactor. Gas, resins, oils (saturates + aromatics), coke and unreacted asphaltenes were separated. Product concentrations were determined as a function of reaction time for the above pseudoproducts. Two simple reaction models are proposed. In the first, the asphaltene fraction is considered to be a single reactant and the hydrocracking reaction a single irreversible reaction. The activation energy for asphaltene consumption was found to be 161 kJ mol −1. In the second, more complex model, four pseudoproducts are used [asphaltenes, maltenes (oils + resins), coke and gas]. Activation energies for the reactions were found to be in the range 8–200 kJ mol −1. Asphaltene hydrocracking reactions were found to have first-order kinetics. Experimental and calculated product distributions were in good agreement.

Hydrocracking of asphaltene from coal using ZnCl 2 as catalyst

Coal liquefaction catalysis by ZnCl 2 was investigated by analyzing the evolution of structures from a starting material to liquid products under a series of reaction conditions. Asphaltene, derived from reductively methylated coal, has been assumed not to significantly alter macromolecular structures derived from the parent coal because of the large molecular weight of over 3000 and has been adopted as a starting material for hydrocracking. The hydrocracking was carried out using a batch autoclave system at 9.8 MPa initial hydrogen pressure by varying the reaction time (0–5 h), the temperature (350–440°C), and the amount of ZnCl 2 (5–40 wt.%). The hydrocracked products were fractioned by solvents and detailed structural parameters of the materials soluble in n-hexane (HS) and benzene (BS-HI) were estimated. At 400°C with 10 wt.% ZnCl 2, HS was obtained as the main product. The structural parameters of the soluble derivatives indicate that depolymerization proceeds by cleavage of ether bonds, which occurs easily, even at 350°C. Extension of the reaction time led to an increase in the HS yield and gave rise to the saturation of the aromatic rings and moderate subsequent decomposition of the products containing naphthenic rings. On the other hand, highly developed aromatic nuclei were gradually concentrated in BS-HI. When the amount of ZnCl 2 was increased to more than 10 wt.%, decomposition of the aromatic nuclei proceeded extensively at 400°C, in addition to depolymerization by the cleavage of carbon-carbon linkages. Noticeable dealkylation of the asphaltene took place above 400°C in the presence of 10 wt.% ZnCl 2.

Effects of Pore Size Distribution on the Catalytic Performance for Coal Liquefaction. I. The Activity and Selectivity of the Catalyst

Abstract Coal liquefaction experiments were carried out by using seven catalysts with different pore structures. As for the unimodal catalysts, the total conversion increased with the pore radius of the catalyst because of the lesser pore-diffusional limitation. However, the ratio of oil to oil-plus-asphaltene decreased with the pore radius. In the case of a large-pore catalyst, heavy components with a large molecular size and a low reactivity can approach the intra-particle active sites and occupy them to prevent the hydrocracking of asphaltene to oil. Bimodal catalysts with micropores (r<10 nm) and macropores (r>300 nm) gave higher values of both the coal liquefaction and the oil yields than did the unimodal catalysts. The presence of macropores seems to enhance the pore diffusion and increase the efficiency of the micropore use, while mesopores with radii between 10 nm and 300 nm did not make such a high contribution to the pore diffusion as was shown for the macropores. For the removal of heteroatoms, there was little difference in the performance among the catalysts with different pore structures. It is suggested that the active sites for the heteroatom removal are deactivated easily by the heavy components.

Hydrocracking of Athabasca asphaltene over ZnCl 2-KCl-NaCl melts with or without an additive of some transition metal chlorides

Hydrocracking of Athabasca asphaltene over molten salts has been studied at 400 °C for 1 h at an initial hydrogen pressure of 9.8 M Pa. The hydrocracking over ZnCl 2-KCl-NaCl produced 57.0 wt% of pentanesolubles (PS), 4.7 wt% of benzene-solubles (BS) and 22.7 wt% of gases together with 15.6 wt% of coke. These melts containing NiCl 2 and CuCl, respectively, were examined, the former exerting a little better influence on reducing the coke yield. A small amount of coke (3.7%) and a higher conversion attained with ZnCl 2-KCl-NaCl-MoCl 5 suggested excellent properties of MoCl 5 for the hydrocracking of asphaltene. The sulphur contents of the PS and BS were lowest with melt catalysts containing MoCl 5. A compound-type separation of each pentane-soluble showed that in the presence of melt catalyst, monoaromatic and diaromatic contents increased greatly at the expense of polyaromatics and polar materials. The trend of catalytic activity of each melt for hydrocracking of asphaltene was found to be quite different from that for the decomposition reaction of tetrahydrothiophene in a continuous flow system.