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Demand for light hydrocarbons has been steadily increasing in the market with a corresponding decrease in heavy hydrocarbon demand. Therefore, there is a need to develop environmentally friendly and efficient technologies for conversion of heavy molecular weight hydrocarbons. Supercritical fluids (SCF) are attracting increased attention as solvents...
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... a result of such favorable properties, SCFs have been investigated for upgrading heavy oils. Among several types of SCFs, SCH 2 O whose phase diagram is given in Fig. 3 with T c = 647.3 K and P c = 22.1 MPa ( Broll et al., 1999) is particularly attractive both as a reaction medium and as a reacting species (hydrogen donor). It can dissolve light hydrocarbons, aro- matics and light gases ( Akiya and Savage, 2002;Sato et al., 2010Sato et al., , 2012Savage, 1999). High reactivity, increased light liq- ...
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Hydrogen is an important raw material in chemical industries, and the steam reforming of light hydrocarbons (such as methane) is the most used process for its production. In this process, the use of a catalyst is mandatory and, if compared to precious metal-based catalysts, Ni-based catalysts assure an acceptable high activity and a lower cost. The...
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... Hydrothermal upgrading is a promising technology to crack heavy oil in a reaction medium containing water in subcritical and supercritical states [15]. In contrast to conventional dry and steam thermal cracking, hydrothermal upgrading can improve the yield of light oil and suppress coke formation [7,[16][17][18][19][20][21]. ...
Hydrothermal treatment is a green and sustainable technology to upgrade heavy oil with water acting both as a solvent and a reactant. However, water reactivity under subcritical and supercritical conditions is still not fully understood. To address this, a comprehensive deuterium isotopic tracing study is conducted under various temperatures (T, 300-450 • C), pressures (P, 8.6-42.9 MPa), liquid (deuterium oxide) to oil ratios (L/O, 2 and 20), and residence times (t, 30 and 120 min). Results indicate that the water reactivity is highly correlated with both operating T and water ionic product (K W). Then, a new insight is proposed: water reactivity is the sum of ionic and free-radical reactions. The ionic reaction is the dominant reaction under subcritical conditions, where water has a high K W. When T is increased, the free-radical reaction shows accelerated growth. However, K W first gradually decreases and then drops dramatically approaching phase-transition temperatures. Under supercritical conditions, the free-radical reaction dominates. Moreover, the K W can be improved by increasing P. As a result, the apparent total water reactivity shows various curves with the changes of both T and P. In conclusion, water under subcritical and supercritical conditions indeed acts as a hydrogen donor during hydrothermal upgrading of heavy oil. However, its capacity is still insufficient to meet the demands of heavy-oil upgrading, especially under supercritical conditions. This study expands the current understanding of water reactivity in the hydrothermal upgrading of heavy oil under both subcritical and supercritical conditions and clarifies the contrasting results reported previously.
... The hydrothermal reaction can convert the heavier components of crude oil into lighter ones, commonly used in upgrading of crude oil [34][35][36][37][38]. To enhance this effect, the transition metal catalysts were investigated and used [39][40][41][42][43]. Commonly, there is a contradiction between the hydrothermal reaction and asphalt modification. ...
... Supercritical H 2 O is a fluid with better performance than supercritical CO 2 , with higher dissolving capacity, increasing solvent diffusion coefficient ability and better reactivity, which can improve sweep coefficient and oil washing efficiency in the process of oil displacement (Walther and Woodland, 1993;Schaef and McGrail, 2004;Li et al., 2020). Meanwhile, the better dissolving capacity and diffusion performance are beneficial for entering nanopores of organic matter, which has the potential to exploit the adsorption and dissolution oil (Weingärtner and Franck, 2005;Canıaz and Erkey, 2014;Zheng et al., 2020). Therefore, the use of supercritical CO 2 / H 2 O mixed fluid to improve shale oil recovery is considered to be a promising technology. ...
... For example, scCO 2 will transition to the liquid state below 304 K at 100 bar, but will transition to the solid state below 304 K at 10,000 bar [220]. Supercritical water will transition to the liquid state below 647 K at any pressure above 22.1 MPa; supercritical water cannot directly transition to the solid form under any circumstances [237]. Neither scCO 2 nor supercritical water can transition to the gas phase based on temperature changes and can only transition to the gas phase upon decreasing pressure.ˆThe ...
The origin of life on Earth required myriads of chemical and physical processes. These include the formation of the planet and its geological structures, the formation of the first primitive chemicals, reaction, and assembly of these primitive chemicals to form more complex or functional products and assemblies, and finally the formation of the first cells (or protocells) on early Earth, which eventually evolved into modern cells. Each of these processes presumably occurred within specific prebiotic reaction environments, which could have been diverse in physical and chemical properties. While there are resources that describe prebiotically plausible environments or nutrient availability, here, we attempt to aggregate the literature for the various physicochemical properties of different prebiotic reaction microenvironments on early Earth. We introduce a handful of properties that can be quantified through physical or chemical techniques. The values for these physicochemical properties, if they are known, are then presented for each reaction environment, giving the reader a sense of the environmental variability of such properties. Such a resource may be useful for prebiotic chemists to understand the range of conditions in each reaction environment, or to select the medium most applicable for their targeted reaction of interest for exploratory studies.
... The properties of supercritical fluids have led to the conversion of pressure, which is highly dependent on density, as a unique and potential material for changing the direction of reactions, kinetics, and even mechanism [33]. These fluids participate in the reaction and act as a very interesting reaction medium [107]. ...
This study reviews the mechanism of microwave irradiation and the affecting parameters, including heating rate, particle size, catalysts, and supercritical fluids on the microwave induced pyrolysis of oil shales. The factors influencing shale oil upgrading using microwave and conventional heating were analyzed. Although shale ash induces secondary cracking in conventional heating, followed by cracking of heavy compounds and increased light oil and pyrolysis gas, the corresponding mechanism in microwave heating has not yet been studied. The shale ash composition and particle size play a vital role in conventional heating efficiency. Increasing oil shale particles size in conventional heating after reaching the maximum converted shale oil reduces produced oil due to increased heat transfer and volatile diffusion in oil shale grains and induction of secondary cracking, which leads to the intensification of shale oil upgrading. Catalysts with high microwave absorption capacity, such as iron powder, remove higher percentages of sulfur, nitrogen, and oxygen from shale oil in microwave pyrolysis as compared to conventional heating. The presence of zeolite in microwave pyrolysis causes better and more effective shale oil upgrading by reducing C10-C16, >C16, naphtha fraction, and increasing kerosene fraction compared to conventional pyrolysis. The presence of water increases polycyclic aromatics, increases the concentration of alkene fraction and decreases asphaltene and coke formed by solvation or caging of shale oil molecules. The presence of nitrogen and hydrogen in conventional pyrolysis reduces desulfurization and upgraded shale oil yield, respectively. A sharp increase in the heating rate in conventional and microwave pyrolysis reduces shale oil yield. In conventional heating, increasing heating rate decreases the hydrogen (H)/ carbon (C) ratio, and the nitrogen and sulfur fractions increase due to the nature of chemical bonding with hydrocarbons and its entangled with metal oxides. In microwave pyrolysis at high heating rates, the H/C ratio increases and the amounts of nitrogen and sulfur in shale oil decrease sharply. The high microwave radiation power facilitates the removal of nitrogen and sulfur that is much higher than conventional pyrolysis. The conversion of pyrite to pyrrhotite in oil shales that have a high microwave absorption capacity increases microwave pyrolysis efficiency. The calcite and feldspar also improve this process because they participate in the pyrolysis process, and their amounts are reduced in the spent shale.
Thus, the oil produced from oil shales under the microwave pyrolysis process has lighter and higher quality compounds. However, the broad applications of this technology in the use of oil shales are still unclear and more studies should be done to clarify the advantages and disadvantages of using microwave heating in oil shales. Further study and research are required to develop microwave technology in oil shale, and based on its potentials, it can be introduced as a new and efficient method in oil shale production.
... The ability of some ions to induce a "salting out" or "salting in" effects depend on interactions between water molecules and the solutes. The interactions become more significant in the near-critical and SCW conditions because of the change in water properties such as increase H + concentration which enhances hydrolysis reaction and low dielectric constant for increased hydrocarbon solubility [19,162,163]. At elevated temperatures, it is expected that the inorganic salt will precipitate out of a water + heavy oil + salt system to form another solid phase in addition to the solid organic pitch, which is a bottom product of the upgrading process. ...
Phase equilibria data of hydrocarbon+water systems at high-pressures and high-temperatures are important for enhanced oil recovery, upgrading and biomass gasification. While numerous studies have reported on well-defined low molecular weight hydrocarbons and water mixtures over a remarkably wide range of conditions, there are limited studies on multicomponent hydrocarbons (including heavy oils bitumen) in the presence of water. In this study, a review on the phase equilibria of hydrocarbon+water mixtures at subcritical, near-critical and supercritical conditions was carried out to identify the knowledge gaps and make recommendations for future studies. Recommendations for potential research directions include phase equilibria, phase behavior and thermodynamic properties studies of heavy oils (including bitumen)+water and heavy oils (including bitumen)+water+salts at near-critical and supercritical regions for a better understanding of these complex systems.
... The economic value of the residue stream is very low, and therefore, conversion techniques are required to upgrade them to maximize the production of valueadded streams. The upgrading of the residue streams is generally done in one of the two methods, namely, hydrogen addition (e.g., hydrotreating or hydrocracking) or carbon rejection (e.g., deasphalting, delayed coking, visbreaking, and thermal/ catalytic cracking) [7][8][9]. Fluidized catalytic cracking (FCC) and residue fluidized catalytic cracking (RFCC) convert heavy oils into more valuable gasoline and lighter products. These technologies enable the effective utilization of crude oils. ...
... Supercritical water flows easily into micro and nanopores than hot water thanks to no surface intension, and favours heat and mass transport versus steam due to higher density. As an organic solvent, supercritical water also provides a homogenous environment for exploiting and thermal cracking of heavy oil [42][43][44][45][46][47][48][49][50][51][52] . Moreover, the properties of supercritical water can be tuned over a wide range of temperature and pressure. ...
Heavy oil accounts for two-thirds of world oil resources but contributes only one-seventh of world oil production due to its high oil viscosity and heavy distillates. Steam injection has been widely used for heavy oil recovery by heating up the reservoir to reduce oil viscosity. However, severe carbon loss to coking makes it low recovery efficiency and high energy consumption. Here we report supercritical water injection for heavy oil recovery. Supercritical water is expected to be both a heat carrier and an organic solvent, thereby not only reducing oil viscosity but also dissolve heavy distillates to avoid coking. To test its feasibility, core experiments were firstly conducted to simulate recovery process. Results showed that supercritical water flooding improved oil recovery by 17% and reduced heat consumption by 34% versus classsical steam flooding. Further, to clarify its recovery mechanism, a visualization technique and a quantitative method was developed for regulating phase behaviour and upgrading reactions between heavy oil and supercritical water. Results showed that supercritical water has good miscibility with heavy oil and it is the key to both enhanced oil recovery and in situ upgrading. High miscibilty means formation of supercritical water clusters around organic macromolecules, which makes asphaltene difficult to aggregate and polymerize to form coke but easy to decompose to form maltene and recovered. Overall, supercritical water injection has made great advances in enhanced oil recovery, energy saving and in situ upgrading for heavy oil recovery. The work provides a sound basis for its application in oilfields.
... II) Fig. 1. Phase diagram of water (I) and physical properties of water in sub-critical, near-critical, and supercritical conditions (II) (adapted from (Arcelus-Arrillaga et al., 2017;Canıaz and Erkey, 2014;He et al., 2014)). ...
In this study, the hydrothermal upgrading (HTU) of high sulfur-content heavy oil was investigated at sub-critical (Sub-CW), near-critical (NCW) and supercritical water (SCW) conditions. Products obtained after HTU, including gases, liquid, and coke (if formed), were analyzed to understand the upgrading performance at different conditions. At Sub-CW (200, 250, and 300 °C), 250 °C is the optimum temperature where a viscosity reduction from 2073 to 1758 mPa s was achieved with a slight removal of sulfur (mainly sulfur) and the generation of a small amount of light and non-condensable hydrocarbons in gas phase (C1–C4, isoalkanes and alkenes, H2S, CO2 and H2, etc.). At NCW (350 °C) and SCW (400 °C), heavy oil was upgraded into light oil with a significant removal of heteroatoms, an increase of saturates content, a reduction of aromatics, resins and asphaltenes contents, and a high yield of light gaseous hydrocarbons (mainly methane). Simultaneously, each SARA fraction was also greatly ameliorated: the content of light alkanes with low molecular weight in saturates was increased, diaromatics content in aromatics was increased with a reduction of polyaromatics content, aromatics-type carbon atoms in resins was increased with a decrease in aliphatic hydrocarbons. Moreover, MALDI-TOF measurements of asphaltenes show that the molecular weights of asphaltenes were reduced. All these results indicated that HTU at Sub-CW can be used for heavy oil pre-treatment (in-situ or ex-situ upgrading) considering its main effect of viscosity reduction with a small removal of heteroatoms, while HTU at NCW and SWC has a great potential in in-situ and ex-situ upgrading and oil refining as it can convert heavy oil into light oil.
... The petroleum oil as feed for crude distillation columns of refineries has been steadily getting heavier and their sulfur and nitrogen content are increased as well, while the demand for lighter liquid oils is increasing in markets. Consequently, heavy petroleum such as bitumen, tar sand, and oil shale should be utilized [1,2] in the coming years. The use of these feeds leads to heavier products at the bottom of distillation columns, including atmospheric residue (AR) and vacuumdistilled residual (VR) [3]. ...
... (4)) which this reaction is endothermic and in higher level of temperature, rate of methane reforming will be increased and therefore the methane is consumed. Carbon monoxide is the product of methane steam reforming which by increasing the rate of this reaction, amount of carbon monoxide will be increased which a portion of this substance is consumed via reaction (2). So, it is concluded that the amount of methane and carbon monoxide at specified temperature are higher when lower water to heavy oil mole ratio is used. ...
Due to many benefits of heavy oil upgrading in the green medium of hot compressed water (HCW), the present study considers the thermodynamic analysis of in-situ hydrogen created by partial oxidation of light hydrocarbons (HC) in HCW. The aim is seeking the upgrading condition where light hydrocarbons create hydrogen (H2) and carbon monoxide (CO) assisted by partial oxidation of light hydrocarbons. The formed CO collaborates in in-situ active hydrogen through water gas shift reaction (CO+H2O↔H2+CO2) which is more effective than external hydrogen for hydrogenation of heavy oil in HCW. Applying the powerful capability of Aspen Plus®, i.e., sensitivity analysis, the effect of significant parameters, such as temperature, pressure (water density), water to oil ratio, and oxygen (O2) to oil ratio are studied comprehensively in order to maximize the amount of active hydrogen. The results indicate that higher temperatures and the amount of water (H2O/heavy oil) are two favorable factors to increase the contribution of active hydrogen, while the pressure is not a determinant factor at supercritical condition (P ≥ 25 MPa). The formation of methane is also decreased at high temperature which is desired for upgrading system. The higher amount of water implies more quantity of O2 since partial oxidation affords the enthalpy of auto-thermal reforming of HO. Hence there should be a compromise in the selected ratios of H2O/HC and O2/HC in HCW upgrading system. A set of experiments are conducted in order to compare the simulation and experimental results. Although the experimental results are established on kinetic data which also reflect the physical effect of HCW during HO upgrading, however, the thermodynamic study provides valued information, in agreement with experiments, that improves our understanding of HO upgrading in HCW with less coke.
