Assessment of combustion rates of coal chars for oxy-combustion applications

Senneca, Osvalda; Vorobiev, Nikita; Wütscher, Annika; Cerciello, Francesca; Heuer, Sebastian; Wedler, Carsten; Schiemann, Martin; Scherer, Viktor

doi:10.1016/j.fuel.2018.10.093

Cited by 30 publications

(22 citation statements)

References 43 publications

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“…Insights about the kinetics of n -C 7 asphaltene catalytic oxidation were realized on the basis of fitting a n -order kinetic model. , The instantaneous reactivity r of the fraction is described by eqs and where P O 2 n (bar) represents the partial pressure of the reactant gas (O 2 ), k is the velocity constant, θ is associated with the conversion of asphaltene at any time t , n is the order of reaction, R (J mol –1 K –1 ) is the universal gas constant, E a (kJ mol –1 ) is the effective activation energy, k o (s –1 bar – n ) is the pre-exponential factor, and f (θ) considers the asphaltene conversion degree during the test. Variable separation and integration was performed to eq , obtaining eq . , Considering the activation energy values constant and applying natural logarithm in both sides, eq is obtained where t a, i is the time for the reaction to reach a defined conversion degree (θ) at a given temperature ( i ). Considering the volumetric model for the radial consumption of the particle, eq is written as follows: Finally, the effective activation energy and pre-exponential factor are obtained from the slope and intercept through the plot ln( t a, i ) against 1/ T i when 100% n -C 7 asphaltene consumption is reached.…”

Section: Methodsmentioning

confidence: 99%

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Insights into the Morphology Effect of Ceria on the Catalytic Performance of NiO–PdO/CeO₂ Nanoparticles for Thermo-oxidation of n-C₇ Asphaltenes under Isothermal Heating at Different Pressures

et al. 2021

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The overall objective of this study is to evaluate the effect of morphologies (C, cubic; O, orthorhombic; and S, spherical) of ceria in the catalytic activity for n-C7 asphaltene thermo-oxidation. In this way, cubic (C-CeO2), orthorhombic (O-CeO2), and spherical (S-CeO2) ceria nanoparticles were synthesized using the hydrothermal method and doped with 1.0% in a mass fraction of Ni and Pd oxides by incipient wetness impregnation. The catalytic activity of the systems was evaluated through non-isothermal and isothermal thermogravimetric analyses at different pressures. The non-isothermal thermogravimetric results evidenced an increase in the n-C7 asphaltene mass as the temperature increases between 100 and 230 °C for all systems and operating conditions. At 3.0 MPa, n-C7 asphaltene gains 3.6, 5.8, and 3.2% for O-CeO2, C-CeO2, and S-CeO2, respectively, while at 6.0 MPa, there is an increase of 7.3, 10.4, and 5.9% for the same systems, respectively. The Ni and Pd phases increase the amount of oxygen chemisorbed in all systems in the order S-NiPdCe < O-NiPdCe < C-NiPdCe and reduce the temperature required for the total n-C7 asphaltene decomposition at temperatures lower than 200 °C at 6.0 MPa in the same order. Also, isothermal thermogravimetric analysis demonstrates that the asphaltene conversion increased with ceria-based nanocatalysts in the increasing order S-CeO2 < O-CeO2 < C-CeO2. Cubic CeO2 doped with Ni and Pd presents the highest yield, reaching 100% conversion at 170 °C and 6.0 MPa at 60 min. The data confirm that the presence of Ni and Pd facilitate the transference oxygen vacancies between the bulk and surface of the nanocatalyst, and therefore, the catalytic activity is enhanced. The catalytic activity, in turn, is improved by the presence of {110}, {100}, and {111}, oxygen vacancies, and Ce3+ and NiO–Ce species. This work reveals the benefits of structured cubic ceria nanocatalysts as a promising support for nickel- and palladium-containing materials for n-C7 asphaltene decomposition.

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Section: Methodsmentioning

confidence: 99%

“…Insights about the kinetics of n-C 7 asphaltene catalytic oxidation were realized on the basis of fitting a n-order kinetic model. 48,49 The instantaneous reactivity r of the fraction is described by eqs 2 and 3 50…”

Section: Methodsmentioning

confidence: 99%

Insights into the Morphology Effect of Ceria on the Catalytic Performance of NiO–PdO/CeO₂ Nanoparticles for Thermo-oxidation of n-C₇ Asphaltenes under Isothermal Heating at Different Pressures

et al. 2021

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“…Since thermal decomposition of asphaltenes is a complex process that entails consecutive and parallel reactions, the kinetic variables allow a representation of the consecutive reaction history. 42,43 The instantaneous reactivity r of a fraction is described by the following expression (eq 1), for an n-order kinetic equation, 44 which can be rewritten as eq 2.…”

Section: Kinetic Analysis Of Asphaltene Thermo-oxidative Decompositionmentioning

confidence: 99%

“…Thermal behavior analysis is performed to obtain information about the kinetic parameters of asphaltene cracking under high-pressure conditions in different temperature regions. Since thermal decomposition of asphaltenes is a complex process that entails consecutive and parallel reactions, the kinetic variables allow a representation of the consecutive reaction history. , The instantaneous reactivity r of a fraction is described by the following expression (eq ), for an n -order kinetic equation, which can be rewritten as eq . where P O 2 n (bar) represents the pressure of the reactant gas (O 2 ), k is the velocity constant, θ is associated with the conversion of asphaltene at any time t , n is the order of reaction, R (kJ·mol –1 ·K –1 ) is the universal gas constant, E a (kJ·mol –1 ) is the effective activation energy, k o (s –1 ·bar – n ) is the pre-exponential factor, and F (θ) takes into account the asphaltene conversion degree during the test. Making a substitution for the heating rate, according to the expression β = d T /d t , employing the volumetric model for a radial consumption of the n -C 7 asphaltenes f (θ) = (1 – θ) and applying the Ozawa–Wall–Flynn approximation to resolve the integral of conversion, eq is obtained where F (θ) = ∫dθ/ f (θ).…”

Section: Kinetic Analysis Of Asphaltene Thermo-oxidative Decompositionmentioning

confidence: 99%

Thermo-Oxidative Decomposition Behaviors of Different Sources of n-C₇ Asphaltenes under High-Pressure Conditions

et al. 2020

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Effects of pressure on thermo-oxidative decomposition of different sources of n-C7 asphaltenes were investigated at high pressure using a thermogravimetric analyzer under an air atmosphere. The n-C7 asphaltenes were extracted from different heavy and extra-heavy crude oils around the world and were thoroughly characterized by elemental analysis (EA), vapor pressure osmometry (VPO), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), and nuclear magnetic resonance (NMR) techniques. A high-pressure thermogravimetric analyzer coupled to a mass spectrometer was employed to obtain thermograms at 0.084, 3.0, and 6.0 MPa, and gaseous products were obtained by asphaltene decomposition. Kinetic analyses were performed for thermo-oxidative multistep reactions and compared based on the trends of pre-exponential factor and effective activation energies using an approximation of the Ozawa, Flynn, and Wall (OFW) isoconversional method. The n-C7 asphaltene decomposition profile was determined by four thermal events, namely, oxygen chemisorption (OC), desorption/decomposition of chemisorbed oxygen functional groups (DCO), and first and second combustion (FC and SC, respectively). We found that the amount of chemisorbed oxygen depends not so much on the oxygen percentage present in the n-C7 asphaltenes and aggregates but on whether it is found in a greater proportion as COO groups, independent of the used pressure. In addition, as the aromatization degree increases and the alkylation degree decreases, the amount of oxygen atoms chemisorbed also increases. As for the DCO region, it was corroborated that the increase in pressure from 0.084 to 6.0 MPa has a positive influence on the mass loss in this region for all samples used. The n-C7 asphaltenes with a higher chemisorption in the previous region showed a higher decomposition or loss of oxygenated compounds during DCO because there are more oxygenated groups in the basal plane of aromatic structures; therefore, the kinetics of the carbonaceous material consumption is increased. According to XPS analysis, n-C7 asphaltenes with a higher content of sulfur as thioethers show facilitated decomposition, due to the low energy required for their oxidation and subsequent cracking, throughout the range of evaluated pressures. Further, the higher content of hydrogen on α carbons to aromatic rings suggests that some of their small alkyl side chains are cracked in this zone due to the easy decomposition of α-methyl, α-methylene, and α-methine structures. As for the FC region, up to 3.0 MPa, a greater mass loss occurs in n-C7 asphaltenes with a high content of short aliphatic chains. Nevertheless, at 6.0 MPa, the mass loss percentage decreases in similar measures for all samples, indicating that under these conditions there is greater ease of breaking the functional groups located both in the basal plane of the aromatic rings and on the periphery of the molecule. Finally, during high-temperature oxidation reactions (SC), the higher a...

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“…The n-C 7 asphaltene oxidation with and without nanocatalysts is described through a model based on the experimental results according to a single power-law expression, considering the instantaneous reactivity (r) of the adsorbate over wide pressure and temperatures ranges. 64,65 n-C 7 asphaltene conversion is herein defined as in eq 5 m m m m t 0 ()…”

Section: Modelingmentioning

confidence: 99%

Effect of Multifunctional Nanocatalysts on n-C₇ Asphaltene Adsorption and Subsequent Oxidation under High-Pressure Conditions

et al. 2020

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This study was carried out to evaluate the effect of high pressure on the oxidation kinetics of n-heptane asphaltenes in the presence and absence of AuPd/Ce0.62Zr0.38O2 catalysts. Bimetallic Au–Pd catalysts with Au/Pd molar ratios from 3.5 to 9.6 were synthesized by deposition–precipitation of Au and followed by incipient wetness impregnation of Pd (3:1AuPd and 10:1AuPd). Adsorption isotherms between hydrocarbons and nanocatalysts were constructed varying the initial asphaltene concentration from 100 to 1500 mg·L–1. Subsequent oxidation was evaluated using thermogravimetric analysis under an air atmosphere, at different pressures from 0.084 to 6.0 MPa in a wide temperature range between 100 and 800 °C. Kinetic parameters were calculated using a first-order kinetic model, considering the system pressure. Adsorption affinity increases in the order support < 3:1AuPd < 10:1AuPd. The catalytic activity of the nanocatalyst was highly dependent on the employed temperature and pressure. Their presence reduces the n-C7 asphaltene decomposition temperature from 450 °C to temperatures below 200 °C for all catalysts used at 6.0 MPa. The main decomposition peaks are presented at 150, 170, and 210 °C for 10:1AuPd, 3:1AuPd, and support, at 6.0 MPa, respectively. Besides, the oxygen chemisorption (OC) region is favored as the material has a greater catalytic activity, increasing from 9.0 to 14.0% (on the load asphaltene basis calculation) for the support and 10:1AuPd catalyst. This was corroborated by the activation energy, which is reduced by more than 30% for all pressures evaluated with the best system. Besides, 89.0 and 80.0% of the mass are lost in the decomposition of the chemisorbed oxygen (DCO) thermal event for the 10:1AuPd and 3:1AuPd nanocatalysts, respectively. Finally, first and second combustions were carried out at temperatures below 240 °C at 6.0 MPa for the 10:1AuPd system, which is a very promising result to determine the reaction pathway for the heavy and extraheavy crude oils during EOR application.

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Assessment of combustion rates of coal chars for oxy-combustion applications

Cited by 30 publications

References 43 publications

Insights into the Morphology Effect of Ceria on the Catalytic Performance of NiO–PdO/CeO₂ Nanoparticles for Thermo-oxidation of n-C₇ Asphaltenes under Isothermal Heating at Different Pressures

Insights into the Morphology Effect of Ceria on the Catalytic Performance of NiO–PdO/CeO₂ Nanoparticles for Thermo-oxidation of n-C₇ Asphaltenes under Isothermal Heating at Different Pressures

Thermo-Oxidative Decomposition Behaviors of Different Sources of n-C₇ Asphaltenes under High-Pressure Conditions

Effect of Multifunctional Nanocatalysts on n-C₇ Asphaltene Adsorption and Subsequent Oxidation under High-Pressure Conditions

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Assessment of combustion rates of coal chars for oxy-combustion applications

Cited by 30 publications

References 43 publications

Insights into the Morphology Effect of Ceria on the Catalytic Performance of NiO–PdO/CeO2 Nanoparticles for Thermo-oxidation of n-C7 Asphaltenes under Isothermal Heating at Different Pressures

Insights into the Morphology Effect of Ceria on the Catalytic Performance of NiO–PdO/CeO2 Nanoparticles for Thermo-oxidation of n-C7 Asphaltenes under Isothermal Heating at Different Pressures

Thermo-Oxidative Decomposition Behaviors of Different Sources of n-C7 Asphaltenes under High-Pressure Conditions

Effect of Multifunctional Nanocatalysts on n-C7 Asphaltene Adsorption and Subsequent Oxidation under High-Pressure Conditions

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Insights into the Morphology Effect of Ceria on the Catalytic Performance of NiO–PdO/CeO₂ Nanoparticles for Thermo-oxidation of n-C₇ Asphaltenes under Isothermal Heating at Different Pressures

Insights into the Morphology Effect of Ceria on the Catalytic Performance of NiO–PdO/CeO₂ Nanoparticles for Thermo-oxidation of n-C₇ Asphaltenes under Isothermal Heating at Different Pressures

Thermo-Oxidative Decomposition Behaviors of Different Sources of n-C₇ Asphaltenes under High-Pressure Conditions

Effect of Multifunctional Nanocatalysts on n-C₇ Asphaltene Adsorption and Subsequent Oxidation under High-Pressure Conditions