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Guy Marin - One of the best experts on this subject based on the ideXlab platform.
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coking resistance of specialized coil materials during steam cracking of sulfur free naphtha
Industrial & Engineering Chemistry Research, 2014Co-Authors: Andres Munoz E Gandarillas, Marie-françoise Reyniers, Guy MarinAbstract:The reactor material strongly affects Coke Formation during steam cracking of hydrocarbons. Therefore, in the past decade several specialized reactor materials have been developed that have proven to be efficient in reducing Coke Formation for ethane steam cracking. However, their beneficial anticoking properties are questioned when heavier feedstocks such as naphtha are cracked. Therefore, the effect of the composition of the reactor material has been investigated for ethane and naphtha cracking in an electrobalance setup under industrially relevant conditions. A significant reduction of Coke Formation is obtained for specialized alloys compared to typical Fe–Cr–Ni heat resistant steels when a sulfur-free naphtha is cracked. A thin layer of alumina on the surface along with manganese chromite provides the highest resistance to coking, as was demonstrated by the SEM and EDX analyses. The decrease in coking rate translates in a run length increase of 50% for a typical naphtha furnace equipped with reactors...
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Coke Formation in the transfer line exchanger during steam cracking of hydrocarbons
Industrial & Engineering Chemistry Research, 2009Co-Authors: Inge Dhuyvetter, Dominique Viennet, Serge Prokopiev, Marie-françoise Reyniers, Guy MarinAbstract:Coke Formation under transfer line exchanger conditions, that is, at temperatures from 623 to 873 K and atmospheric pressure, is studied in an electrobalance setup. The coking rate is initially very high (catalytic coking) and drops after a few hours to a constant value. At the studied conditions the observed coking behavior on 15Mo3 alloy pigs can be explained via a catalytic mechanism only, and contributions of the free-radical mechanism and the condensation mechanism are insignificant. Experiments with ethane and naphtha steam cracking effluents and with well-defined reaction mixtures show that the coking rate is independent of the partial pressure of ethene (0−2.7 × 104 Pa), ortho-xylene (0−1.0 × 104 Pa), heavy aromatic hydrocarbons (0−3.0 × 102 Pa), and also 1,3-butadiene (0−2.7 × 104 Pa). The rate of Coke deposition depends only on the temperature and the ratio of the partial pressures of water to dihydrogen. The activation energy for initial Coke Formation was estimated to be ∼90 kJ/mol, a value cl...
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influence of silicon and silicon sulfur containing additives on Coke Formation during steam cracking of hydrocarbons
Industrial & Engineering Chemistry Research, 2008Co-Authors: Jidong Wang, Marie-françoise Reyniers, Guy MarinAbstract:The influence of the combination of two Si-containing additives, BTMS and TEOS, with DMDS on Coke Formation during steam cracking has been evaluated both on a laboratory scale and in a pilot plant unit. Under the optimal presulfidation conditions (T = 1023 K, H2O = 20 g h-1, DMDS in H2O = 750 ppm wt, duration = 1 h), the combination of Si pretreatment + presulfidation + continuous addition of 2 ppm wt DMDS results in a decrease in the rate of Coke Formation up to 40% when hexane is cracked in the lab-scale unit. Under similar conditions in the pilot plant the Coke Formation is decreased by 70%, while the CO production decreases by more than 90%. Moreover, the suppressing effect on Coke Formation remains significant even after several coking/decoking cycles. Simulations of an industrial ethane cracker indicate that the application of Si- and S-containing compounds as additives for the suppression of Coke Formation can potentially double the run length of industrial steam crackers.
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influence of dimethyl disulfide on Coke Formation during steam cracking of hydrocarbons
Industrial & Engineering Chemistry Research, 2007Co-Authors: Jidong Wang, Marie-françoise Reyniers, Guy MarinAbstract:The influence of dimethyl disulfide (DMDS), which is widely used as an additive in ethylene plants, on Coke Formation during the steam cracking of hydrocarbons was investigated in a continuous-flow stirred-tank reactor (CSTR) setup with n-hexane as the feed and in a pilot-plant setup with ethane as the feed. Both of the reactors were made of Incoloy 800HT. Experiments were carried out at conditions relevant to industrial steam crackers. DMDS was applied by presulfidation, continuous addition, and presulfidation followed by continuous addition. Application of DMDS suppresses CO production. The influence of DMDS on Coke Formation was found to depend on the application method and the amount of DMDS used. SEM examination of the Coke samples obtained from the steam cracking of n-hexane indicated that application of DMDS leads to a significant change in the Coke morphology. EDX analysis indicated that application of DMDS causes a significant change in the metal content and distribution in both the alloy surface...
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kinetic modeling of Coke Formation during steam cracking
Industrial & Engineering Chemistry Research, 2002Co-Authors: Sandra Wauters, Guy MarinAbstract:A kinetic model for Coke Formation during steam cracking based on elementary reactions between gas-phase components and the Coke surface is described. Hydrogen abstraction by gas-phase radicals results in radical surface species which can add to gas-phase alkenes and alkynes. Cyclization and dehydrogenation leads to the incorporation of carbon atoms into the Coke layer. The kinetics of the Coke Formation reactions are determined from those of corresponding gas-phase reactions provided that the presence of a solid phase is accounted for via a correction factor based on collision theory. The number of required kinetic parameters is substantially reduced by applying the structural contribution technique. Predicted trends and the most important reaction pathways are analyzed at conditions corresponding to ethane cracking with ethene, ethyne, propene, and propyne as Coke precursors and H, CH3, C2H5, and C3H5 as gas-phase radicals. Abstraction of hydrogen atoms and the addition of radical surface species to alk...
De Chen - One of the best experts on this subject based on the ideXlab platform.
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a methanol to olefins review diffusion Coke Formation and deactivation on sapo type catalysts
Microporous and Mesoporous Materials, 2012Co-Authors: De Chen, Kjell Moljord, Anders HolmenAbstract:Abstract The catalytic conversion of methanol to lower olefins (MTO) is a promising way of converting natural gas and coal to chemicals and fuels with methanol as an intermediate. Coke Formation is a major cause of deactivation in the MTO processes and the present contribution deals with the progress on the study of adsorption, diffusion and reaction including deactivation due to Coke Formation during MTO. Design of SAPO-34 to achieve high activity and selectivity is discussed in terms of the two most important parameters, namely crystal size and operating temperatures.
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Coke Formation on pt sn al2o3 catalyst in propane dehydrogenation Coke characterization and kinetic study
Topics in Catalysis, 2011Co-Authors: Qing Li, Xinggui Zhou, Jinghong Zhou, De ChenAbstract:The influences of gas compositions on the rates of Coke Formation over a Pt–Sn/Al2O3 catalyst are studied. The Coke formed on the catalyst is characterized by thermal gravimetric analysis, IR spectroscopy, Raman spectroscopy and elemental analysis. Two kinds of Coke are identified from the TPO profiles and assigned to the Coke on the metal and the Coke on the support, respectively. The Coke formed on the metal is softer (containing more hydrogen) than that formed on the support. The rate of Coke Formation on the metal is weakly dependent on the propylene and hydrogen pressures but increasing with the propane pressure, while the rate of Coke Formation on the support is increasing with the propane and propylene pressures and decreasing with the hydrogen pressure. Based on the kinetic analysis, a mechanism for the Coke Formation on the Pt–Sn/Al2O3 catalyst is proposed, and the dimerization of adsorbed C3H6 is identified to be the kinetic relevant step for Coke Formation on the metal.
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Coke Formation on pt sn al 2 o 3 catalyst in propane dehydrogenation Coke characterization and kinetic study
Topics in Catalysis, 2011Co-Authors: Zhijun Sui, Xinggui Zhou, Jinghong Zhou, Yian Zhu, De ChenAbstract:The influences of gas compositions on the rates of Coke Formation over a Pt–Sn/Al2O3 catalyst are studied. The Coke formed on the catalyst is characterized by thermal gravimetric analysis, IR spectroscopy, Raman spectroscopy and elemental analysis. Two kinds of Coke are identified from the TPO profiles and assigned to the Coke on the metal and the Coke on the support, respectively. The Coke formed on the metal is softer (containing more hydrogen) than that formed on the support. The rate of Coke Formation on the metal is weakly dependent on the propylene and hydrogen pressures but increasing with the propane pressure, while the rate of Coke Formation on the support is increasing with the propane and propylene pressures and decreasing with the hydrogen pressure. Based on the kinetic analysis, a mechanism for the Coke Formation on the Pt–Sn/Al2O3 catalyst is proposed, and the dimerization of adsorbed C3H6 is identified to be the kinetic relevant step for Coke Formation on the metal.
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methanol conversion to light olefins over sapo 34 kinetic modeling of Coke Formation
Microporous and Mesoporous Materials, 2000Co-Authors: De Chen, Kjell Moljord, H P Rebo, A Gronvold, Anders HolmenAbstract:Abstract Coke deposition during methanol conversion to light olefins over SAPO-34 has been studied in an oscillating microbalance (TEOM) reactor as a function of space velocity (57–384 g/g cat h), temperature (673–823 K) and methanol partial pressure (7.2–83 kPa). Two kinetic models were tested for their ability to describe the coking rate at different operating conditions. A modified Voorhies model related Coke deposition to the amount of hydrocarbons formed per gram of catalyst. The model could be used to calculate the average Coke selectivity and catalyst capacity for olefin Formation. The average Coke selectivity increased and the catalyst capacity decreased with increasing temperature, while no effect of methanol partial pressure or space velocity was observed. A kinetic model based on a mechanism with strongly adsorbed reaction intermediates as the Coke precursors, which either desorb as olefins or react further into Coke, was also fitted to the experimental data, and the deactivation functions were found to be linear in Coke content for both olefin and Coke Formation. The rate of deactivation of the Coke-forming reaction decreased, while the rate of deactivation of the olefin Formation increased with increasing temperature, and no effect of methanol partial pressure or space velocity was observed.
Gilbert F Froment - One of the best experts on this subject based on the ideXlab platform.
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kinetic modeling of hydrocarbon processing and the effect of catalyst deactivation by Coke Formation
Catalysis Reviews-science and Engineering, 2008Co-Authors: Gilbert F FromentAbstract:Previously derived fundamental rate equations for Coke Formation and catalyst deactivation are applied to the modeling of a number of commercial processes: steam reforming of natural gas, styrene production from ethylbenzene, catalytic cracking of heavy oil fractions, methanol‐to‐olefins on SAPO 34, and solid acid alkylation on a Y zeolite. The modeling accounts in great detail for the chemistry of the process, including the Formation of the deactivating agent, commonly called Coke. It is shown that the deactivating agent is not an inert substance but is involved in reactions, sometimes of the same type as those leading to the main products of the process.
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a semi analytical solution for concentration profiles inside a catalyst particle in the presence of Coke Formation
Chemical Engineering Science, 1997Co-Authors: Jc Gottifredi, Gilbert F FromentAbstract:A semi-analytical solution for the concentration profiles of the main reactants and products in a catalyst particle in the presence of Coke Formation is developed. The solution is translated into a global deactivation function over the particle, which is related to the effectiveness factor appearing in the fluid-phase model equations. The paper considers both parallel and consecutive coking and deactivation functions for the main and coking reactions, which are linearly and exponentially dependent on the Coke content. The solution is compared with results obtained by numerical integration. The agreement is excellent, so that the problem of diffusion, reaction and deactivation by Coke Formation can now be dealt with through an approach requiring a minimal computational effort only.
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Coke Formation in the thermal cracking of hydrocarbons 4 modeling of Coke Formation in naphtha cracking
Industrial & Engineering Chemistry Research, 1994Co-Authors: Geert C Reyniers, Gilbert F Froment, Frankdieter Kopinke, Gerhard ZimmermannAbstract:An extensive experimental program has been carried out in a pilot unit for the thermal cracking of hydrocarbons. On the basis of the experimental inFormation and the insight in the mechanisms for Coke Formation in pyrolysis reactors, a mathematical model describing the Coke Formation has been derived. This model has been incorporated in the existing simulation tools at the Laboratorium voor Petrochemische Techniek, and the run length of an industrial naphtha cracking furnace has been accurately simulated. In this way the coking model has been validated.
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relative rates of Coke Formation from hydrocarbons in steam cracking of naphtha 2 paraffins naphthenes mono di and cycloolefins and acetylenes
Industrial & Engineering Chemistry Research, 1993Co-Authors: Frankdieter Kopinke, Gerhard Zimmermann, Geerd C Reyniers, Gilbert F FromentAbstract:Relative rate constants of Coke Formation from saturated hydrocarbons, olefins, and acetylenes during steam cracking of naphtha at 810 C were determined by application of [sup 14]C-labeled compounds. The range of hydrocarbons investigated comprises 20 representatives of paraffins, from methane to hexadecane, and of naphthenes, from cyclopentane to hydroanthracene, and 20 olefins from ethene to styrene, including cyclo- and diolefins, and five acetylenes. Carbonaceous deposits in pyrolysis reactors from steel and quartz as well as in the transfer line exchange (TLE) section were determined separately.
Qiang Yao - One of the best experts on this subject based on the ideXlab platform.
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analysis of montmorillonite affecting Coke Formation during the thermal conversion of heavy oil
Fuel, 2021Co-Authors: Ruonan Zheng, Dong Liu, Junshi Tang, Qiang Song, Qiang YaoAbstract:Abstract Coke Formation during the process of in-situ combustion is affected by clay minerals, among which montmorillonite shows the most significant effect. A fixed-bed reactor was used to conduct the thermal conversion experiments of heavy oil and model compounds to reveal the mechanism of montmorillonite affecting the Coke Formation. Under the inert atmosphere, in the presence of montmorillonite, the temperature at which aromatic C–C groups of Coke appeared decreased from 500 °C to 450 °C and polymers were formed when toluene was heated, indicating that montmorillonite catalyzed aromatization and polymerization, respectively. The increase in the supporter surface area promoted the Formation of Coke from pyrolysis by shortening the induction of coking. Under the oxidizing atmosphere, in the presence of montmorillonite, the initial temperature of O2 consumed by heavy oil decreased from 270 °C to 250 °C, indicating that montmorillonite catalyzed oxygen-adding reaction. The temperature of COx released by acetaldehyde and acetic acid decreased, and the release amounts increased, indicating that montmorillonite catalyzed decarbonylation and decarboxylation. Polymers were formed when acetaldehyde, acetic acid, ethanol, and acetone were heated, indicating that montmorillonite catalyzed polycondensation. When the oil mass fraction in the sample was within 18%, further increase in the supporter surface area did not affect the Formation of Coke from oxidation. The catalysis of montmorillonite was the main mechanism affecting Coke Formation during the thermal conversion of heavy oil under the inert and oxidizing atmospheres.
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catalytic effects of montmorillonite on Coke Formation during thermal conversion of heavy oil
Energy & Fuels, 2018Co-Authors: Ruonan Zheng, Dong Liu, Junshi Tang, Qiang Song, Jingjun Pan, Lijuan Chen, Long Chen, Qiang YaoAbstract:In situ combustion is an enhanced method to recover heavy oil. The Formation and oxidation of Coke are crucial to promote the combustion front. Heavy oil from China and montmorillonite, a major type of clay, were used as samples in this study. The thermogravimetric analyzer (TGA) was applied to temperature-programmed oxidation/pyrolysis experiments to study the effect of montmorillonite on the thermal conversion characteristics of heavy oil. A fixed-bed reactor was then used to obtain Coke and study the effect of montmorillonite on Coke properties. The characteristic temperatures of thermal conversion decreased with montmorillonite in the oxidizing atmosphere but remained unaffected in the pyrolysis atmosphere. The fuel deposition increased in both atmospheres because of montmorillonite’s strong adsorption. In the oxidizing atmosphere, the presence of montmorillonite obviously promoted the progress of Coke Formation and increased Coke yield. The content of O was increased, and the contents of C and H were...
J A Moulijn - One of the best experts on this subject based on the ideXlab platform.
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Coke Formation in fluid catalytic cracking studied with the microriser
Catalysis Today, 1998Co-Authors: M Den A Hollander, Michiel Makkee, J A MoulijnAbstract:Abstract The catalysts used in the fluid catalytic cracking process are reversibly deactivated by deposition of Coke. The Coke deposition and its effect on the activity of the catalyst in the reactor have been studied using the microriser, a laboratory-scale entrained flow reactor. The experimental results show that the timescale of Coke Formation is much shorter than the timescale for conversion. Coke deposition mainly occurs initially (within 0.15 s), while the conversion increases during the whole residence time in the reactor (0–5 s). A five lump kinetic scheme has been used to model the measurements with a constant catalyst activity and with a catalyst activity that decreased with time on stream. It is shown that the results obtained after 0.15 s can be modeled with a constant activity, so initial Coke deposition is the main cause of deactivation. It is proposed that the initial effects, Coke deposition accompanied by Formation of products, and catalyst deactivation, have to be described with a separate model that takes into account catalyst-to-oil ratio, feedstock, and catalyst properties.
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Coke Formation in fluid catalytic cracking
Studies in Surface Science and Catalysis, 1997Co-Authors: M Den A Hollander, Michiel Makkee, J A MoulijnAbstract:The catalysts used in Fluid Catalytic Cracking (FCC) are reversibly deactivated by the deposition of Coke. Results obtained in a laboratory scale entrained flow reactor with a hydrowax feedstock show that Coke Formation mainly takes place within a time frame of milliseconds. In the same time interval conversions of 30–50% are found. After this initial Coke Formation, only at higher catalyst-to-oil ratios some additional Coke Formation was observed. In order to model the whole process properly, the Coke deposition and catalyst deactivation have to be divided in an initial process (typically within 0.15 s) and a process at a larger time scale. When the initial effects were excluded from the modeling, the measured data could be described satisfactory with a constant catalytic activity.