Pyrolysis Of Heavy Oil Research Articles

U-model enhanced dynamic control of a heavy oil pyrolysis/cracking furnace

This paper proposes a case study in the control of a heavy oil pyrolysis U+002F cracking furnace with a newly extended U-model based pole placement controller U+0028 U-PPC U+0029. The major work of the paper includes: 1 U+0029 establishing a control oriented nonlinear dynamic model with Naphtha cracking and thermal dynamics; 2 U+0029 analysing a U-model U+0028 i.e., control oriented prototype U+0029 representation of various popular process model sets; 3 U+0029 designing the new U-PPC to enhance the control performance in pole placement and stabilisation; 4 U+0029 taking computational bench tests to demonstrate the control system design and performance with a user-friendly step by step procedure.

Gasoline- and diesel-like products from heavy oils via catalytic pyrolysis

ABSTRACTHeavy oil is less expensive than light crude oil, but heavy oil is more expensive to obtain light oil products. Conventional light crude oil resources are decreasing, therefore heavy oil resources will be needed more in the future. There are huge differences from field to field for heavy oil deposits. In terms of final productive use, heavy oil is considered as an unconventional resource. Heavy oil upgrading depends on four important factors: catalyst selection, heavy oil classification, process design, and production economics. Heavy and extra-heavy oils are unconventional reservoirs of oil. Globally, 21.3% of total oil reserves are heavy oil. Heavy oil is composed of long chain organic molecules called heavy hydrocarbons. The thermal degradation of the heavy hydrocarbons in heavy oil generates liquid and gaseous products. All kinds of heavy oils contain asphaltenes, and therefore are considered to be very dense material. The most similar technologies for upgrading of heavy oils are pyrolysis and catalytic pyrolysis, thermal and catalytic cracking, and hydrocracking. The amount of liquid products obtained from pyrolysis of heavy oil was dependent on the temperature and the catalyst. Pyrolytic oil contains highly valuable light hydrocarbons as gasoline and diesel components range. The constant increase in the use of crude oils has raised prices of the most common commercial conventional products and consequently seeking for new alternative petroleum resources, like some unconventional oil resources, becomes an interesting issue. The mass contents of gasoline, diesel, and heavy oil in the crude oil are 44.6%, 38.3%, and 17.1%, respectively. The gasoline yield from the heavy oil catalytic (Na2CO3) pyrolysis is higher than the diesel efficiency for all conditions. The yield of gasoline products increases with increasing pyrolysis temperature (from 230°C to 350°C) and percentage of catalyst (from 5% to 10%). The yields of gasoline-like product are from 21.5% to 39.1% in 5% catalytic run and from 32.5% to 42.5% in 10% catalytic run. The yields of diesel-like product are from 9.3% to 29.8% in 5% catalytic run and from 15.5% to 33.7% in 10% catalytic run.

Characteristics of Rapid Pyrolysis for Upgrading Heavy Oils in a Circulating Fluidized Bed Reactor

The hydrodynamic velocity and effect of the reaction temperature on the cracking performance were investigated for the production of light oil through the rapid pyrolysis of heavy oil in a circulating fluidized bed reactor. From this study, the gas velocity in the loop seal to prevent slugging, the transport gas velocity to form a dense phase of solids on the bottom of the riser, and the minimum bubbling fluidization velocity for stable solid circulation in the reheater were determined. Under the steady supply of feed through the internal mixing with steam inside the feed nozzle, the reactivity for a temperature change from 527 to 574 °C was investigated. As a result, the residue (>535 °C) conversion and liquid yield of up to 71.1 and 78.2%, respectively, were found. The maximum impurity removal rates for sulfur, Conradson carbon residue, and metals (nickel and vanadium) were found to be 18.7, 50.4, and 83.6%, respectively.

High-Temperature and High-Pressure Pyrolysis of Hexadecane: Molecular Dynamic Simulation Based on Reactive Force Field (ReaxFF).

As important products of heavy oil pyrolysis, heavier components such as gasoline and diesel supply the vast majority of energy demand through combustion, and lighter components such as ethylene and propylene are the main sources of industrial chemicals and plastic products. In this work, pyrolysis of hexadecane, as the model compound, was studied by reactive force field (ReaxFF) molecular simulation at high temperatures and high pressures. It was confirmed by unimolecular simulations that there exist eight different initial mechanisms all starting with C-C bond dissociation. The biradical mechanism was verified, through which the pyrolysis process can be accomplished within a shorter time. The enthalpy of reaction was calculated by the QM method, which was well consistent with ReaxFF calculation results. Multimolecular simulations showed that there is a strong dependency relationship between products distribution and temperature, as well as that between reaction rates and temperature. The optimal condition for ethylene formation in our work is 11.6 MPa and 2000 K, whereas it is best for hydrogen formation at conditions of 11.6 MPa and 3500 K. Kinetic analysis was performed with the activation energy of 113.03 kJ/mol and pre-exponential factor of 4.55 × 1012, and it is in good agreement with previous work.

Dealkylation of Aromatics in Subcritical and Supercritical Water: Involvement of Carbonium Mechanism

Under hydrothermal environments covering the subcritical and supercritical regions of water, the involvement of the carbonium mechanism in the dealkylation of aromatics and its resulting influence on the pyrolysis of heavy oil were surveyed. α-Olefin groups, as either a part of straight chain hydrocarbons or the terminal of alkyl substitutes of aromatics, are protonated spontaneously by hydronium ions into carboniums, followed by β-scission with similar reaction kinetic characteristics. The probability of the protonation of α-olefins under hydrothermal environments depends on the ionic product of water, so the occurrence of the β-scission in the carbonium mechanism is related to the thermodynamic state of water. With the aid of the carbonium mechanism at increasing water density, a recovered conversion rate and an increasing ratio of propene to ethylene in the product occur during the pyrolysis of a model α-olefin of dodecene under hydrothermal environments. Also, the dealkylation involved in the pyrolysi...

Thermogravimetric analysis and kinetic study of heavy oil pyrolysis

ABSTRACTPyrolysis, so-called devolatilization, is one of the first steps of all thermochemical processes occurring in an inert atmosphere. The authors discuss the main kinetic features of heavy oil pyrolysis, on the basis of the data derived m from a TGA analysis and by using a kinetic model. The samples were heated over a range of temperature from 400 K to 430°C at various heating rates between 10 and 80°C/min. Experimental results showed that the effect of time is considerable in the case of tar conversion, compared to char and gases.

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

Molecular-Level Kinetic Modeling of Resid Pyrolysis

A molecular-level kinetic model of heavy oil pyrolysis was developed for a Venezuelan vacuum residue. Model development proceeded in three major steps: creation of a molecular description of the feedstock, generation of a reaction network, and model solution and parameter tuning. The feedstock composition, as described in previous work [Zhang et al. Energy Fuels 2014, 28, 1736–1749], was modeled in terms of probability density functions (PDFs) of three finite attribute groups (385 cores, 2 intercore linkages, and 194 side chains) and a PDF for each of a cluster-size and binding site distribution. These attributes, or molecule building blocks, represent more than 0.4 M molecules. An attribute reaction network was developed using the fundamental reaction chemistry for resid pyrolysis including 6274 reactions that fall into one of 11 reaction families. To make solution time tractable, we used attribute reaction modeling (ARM) which constrained the number of material balances to the number of attributes and i...

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

Co-pyrolysis of heavy oil and low density polyethylene in the presence of supercritical water: The suppression of coke formation

At 693K and water density of 0.30g/cm3, the co-pyrolysis of heavy oil and low density polyethylene (LDPE) in the presence of supercritical water (SCW) was investigated with the emphasis on the coking mechanism involved. The co-pyrolysis in SCW was found to have the significant advantages of the decreasing yield of coke and the increasing yield of aromatics over the pyrolysis of heavy oil alone in SCW. With the increase in the loading of LDPE, the suppression of condensation in co-pyrolysis is gradually intensified, suggesting the essential role of LDPE as an external H-source in co-pyrolysis. Only in the continuous SCW phase can the H-donation between the pyrolysis networks of heavy oil and LDPE be effectively accomplished, by which the condensation of light oil fractions to heavy oil fractions and the deep condensation of asphaltenes to coke are partly suppressed.

Hierarchical ZSM-11 with intergrowth structures: Synthesis, characterization and catalytic properties

Hierarchical ZSM-11 microspheres with intercrystalline mesoporous properties and rod-like crystals intergrowth morphology have been synthesized using a spot of tetrabutylammonium as a single template. XRD, FTIR, SEM, TEM and N2 adsorption analysis revealed that each individual particle was composed of nanosized rod crystals inserting each other and the intercrystalline voids existing among rods gave a significant mesopore size distribution. Steam treatment result demonstrated the excellent hydrothermal stability of samples. Various crystallization modes including constant temperature crystallization (one-stage crystallization) and two-stage temperature-varying crystallization with different 1st stage durations were investigated. The results suggested that the crystallization modes were mainly responsible for the adjustable particle size and textural properties of samples while the small amount of tetrabutylammonium bromide was mainly used to direct the formation of both ZSM-11 framework and its intergrowth morphology. Furthermore, the performance of optimal ZSM-11 as an active component for the catalytic pyrolysis of heavy oil was also investigated. Compared with the commercial pyrolysis catalyst, the hierarchical ZSM-11 catalyst exhibited a high selectivity to desired products (LPG + gasoline + diesel), as well as a much lower dry gas and coke yield, plus a high selectivity and yield of light olefins ( C3=-C4=) and very poor selectivity to benzene. Therefore, fully open micropore-mesopore connectivity would make such hierarchically porous ZSM-11 zeolites very attractive for applications in clean petrochemical catalysis field.

Initiated pyrolysis of heavy oil in the presence of near-critical water

The initiated pyrolysis of heavy oil in the presence of near-critical water (near-CW) was investigated with density functional theory (DFT) calculation and experimental characterization. Theoretical calculation indicated the thermodynamic feasibility of forming hydrocarbon radicals in heavy oil with the aid of appropriate radical initiators. By introducing ditertbutyl peroxide (DTBP) into heavy oil, the H-abstraction of Hβ atoms distributed mainly in the fractions of saturates, resins, and asphaltenes occurs, forming hydrocarbon radicals located on aliphatic chains with priority. At the temperature of 653K and water density of 0.30g/cm3, it was experimentally confirmed that the introduced DTBP was capable of initiating the pyrolysis of heavy oil. After 15min's reaction, the pyrolysis products centered toward the fraction of aromatics whose weight proportion in the liquid product increased drastically by ca. 25.0wt.%. Meanwhile, only a negligible coke yield of 0.5wt.% was collected.

Upgrading and visbreaking of super‐heavy oil by catalytic aquathermolysis with aromatic sulfonic copper

As one of the important in‐situ upgrading technologies, catalytic aquathermolysis has attracted worldwide interest for heavy oil exploitation recently. Aiming to upgrade and visbreak a kind of super‐heavy oil, we have synthesized a new type of catalyst — aromatic sulfonic copper to process it. The experimental results show that, using 0.2wt.% catalyst and 25.0wt.% water at 280°C for 24h, the viscosity of oil sample could be decreased by 95.5%, with 13.72% in the conversion of heavy content to light content. Furthermore, the structure and group compositions of heavy oil were characterized by FT‐IR, GPC, EL, 1H NMR and GC–MS. It is found that the catalyst could improve the pyrolysis of heavy oil, and remove some heteroatoms (S, O and N) in its molecules, which finally led to the upgrading and visbreaking of the oil. Additionally, in view of the low‐cost for synthesis and simple preparation of this technique, it is likely to have some good application prospects.

Study on thermal performance of heavy oils by using differential scanning calorimetry

The heat in heavy oil pyrolysis process is a quantity of interest in the design of thermal process equipments and the calculation of energy balance in refineries. Thus, enthalpy of reaction and enthalpy of vaporization in the pyrolysis of four heavy oils: DQVR (Daqing vacuum residue), KRVR (Karamay vacuum residue), LHVR (Liaohe vacuum residue) and VNVR (Venezuela vacuum residue), have been quantitatively studied by a combination of thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC), plus microreactor experiments. As sample became heavier, the temperature range of pyrolysis process increased from 172 to 200°C and enthalpies of reaction decreased, which were determined to be −1070, −570, −489 and −393J/g for DQVR, KRVR, LHVR and VNVR, respectively. The enthalpies of reaction at various conditions showed a linear trend with respect to the final coke yield in the thermal analysis. Enthalpies of vaporization in the thermal analysis process were calculated to be 188, 181, 161 and 128J/g, for DQVR, KRVR, LHVR and VNVR, respectively. The contribution of vaporization to the overall pyrolysis process varied between 0.12 and 0.19. A method to quantify the enthalpy of cracking and that of condensation was tentatively developed by using extrapolation.

Hydrogen Donor Catalytic Aquathermolysis Upgrading for Heavy Oil: A Laboratory Study

Heavy oil pyrolysis reaction was studied with formic acid as a body for hydrogen donor and homemade of oil-soluble organic nickel salt as a catalyst, by high-temperature and high-pressure Reactor simulating Thermal Recovery conditions. Explore the influence of the addition of hydrogen donor on heavy oil viscosity, group composition and sulfur contents before and after the catalytic aquathermolysis reaction. The results show that catalytic aquathermolysis of heavy oil leads to a percentage viscosity reduction of 64.69%, to an increase in saturates and aromatics contents from 24.32% and 36.89% to 26.12% and 38.08%, and to a decrease in resins, asphaltenes, and sulfur contents from 30.27%, 8.52%, and 0.5650% to 28.27%, 7.53%, and 0.3365%,respectively; when formic acid is introduced at dosage of 1-7% heavy oil mass, the percentage viscosity reductio is continuously raised to 69.16-87.02%, the saturates and aromatics contents-increased to 27.73-31.12% and 39.68-41.26% and the resins, asphaltenes, and sulfur contents-decreased to 26.29-24.12%, 6.66-3.50%, and 0.3095-0.0742%, respectively. The role of hydrogen donor formic acid and the functioning mechanisms involved in catalytic aquathermolysis of heavy oil are discussed.

Cracking Performance and Feed Characterization Study of Catalytic Pyrolysis for Light Olefin Production

The catalytic pyrolysis of heavy oils, gas oils, cracked diesel and gasoline fractions was investigated in a confined fluidized-bed reactor. The feed with a high H/C atomic ratio and low aromaticity showed good cracking performance, high feed conversion, and high yield and selectivity of total light olefins (i.e., ethene, propene, and butene). The cracked diesel and gasoline fractions with a low H/C atomic ratio and high aromaticity showed poor secondary cracking performance. A characterization parameter (KCP) was proposed to characterize the cracking performance of various feedstocks. The yield of total light olefins increased with an increase in KCP, despite the catalytic or thermal pyrolysis. KCP could be used as a criterion to evaluate the cracking performance of a feed for the production of light olefins. The cracking performance of a feed was considered desirable for KCP above 3.6 and undesirable for KCP below 2.8. Besides KCP, the United States Bureau of Mineral Correlation Index (BMCI) was also su...

Petroleum luminophores of pyrolytic origin and energy transfer between their components

Photoexcitation of luminophores prepared from heavy oil pyrolysis tar was studied, and properties of these compounds, determining the variation of the luminescence color and intensity depending on the solution concentration, were evaluated.

Interaction of titanium and iron oxide with ZSM-5 to tune the catalytic cracking of hydrocarbons

In order to increase the yield of ethylene and propylene in the catalytic pyrolysis of heavy oil, ZSM-5 zeolite was modified by Fe 2O 3 and TiO 2 via pore volume impregnation. XRD, SEM, and TEM analysis indicated that the structure of the ZSM-5 remained intact after modification, and that the Ti and Fe partially entered the channels of the ZSM-5. Measurement of the number of Brønsted acid sites by n-propylamine temperature-programmed reaction and FTIR measurements showed that the Brønsted acid sites of Ti/ZSM-5 (TiO 2 loaded ZSM-5) and Fe–Ti/ZSM-5 (Fe 2O 3 and TiO 2 loaded ZSM-5) catalysts increased through the polarization function of Ti 4+. DRS, XPS, and TPR results showed that the presence of Ti species improved the dispersion of Fe species on the surface of ZSM-5, whereas Fe 2O 3 promoted the reduction of TiO 2. After modification by Fe 2O 3 and TiO 2, the acidity and reduction properties of Fe–Ti/ZSM-5 improved; such improvement led to a decrease of the apparent activation energy of isopropyl benzene cracking over Fe–Ti/ZSM-5 by about 21 kJ/mol compared with that over ZSM-5. As a result, catalyst Fe–Ti/ZSM-5 showed a better catalytic cracking performance of n-decane and isopropyl benzene than catalysts Ti/ZSM-5, Fe/ZSM-5 (Fe 2O 3 loaded ZSM-5) or ZSM-5.

1-1-3 重質油の熱分解におけるコーク生成挙動に及ぼす超臨界水の影響(1-1 重質油改質1,Session 1 石炭・重質油等,研究発表)

1-1-3 重質油の熱分解におけるコーク生成挙動に及ぼす超臨界水の影響(1-1 重質油改質1,Session 1 石炭・重質油等,研究発表)

Coking behavior and catalyst deactivation for catalytic pyrolysis of heavy oil

For the catalytic pyrolysis of heavy oil on catalyst CEP-1, coking behavior was investigated in a confined fluidized bed reactor. Coke content on the spent catalyst decreases with the increase of H/C mol ratio of feeds and catalyst-to-oil weight ratio, while it increases with the enhancement of reaction temperature. An empirical model is proposed to predict the coke content based on feed properties and operating conditions. The predicted coke content is close to the experimental data. The relationship between micro-activity index of catalysts and coke content is studied. A coking deactivation model for pyrolyzing catalysts is established, and then model parameters are determined by the least square regression analysis. According to the deactivation model, the variations of relative activity of catalysts with both residence time of catalysts and catalyst-to-oil weight ratio are predicted.