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Zhang Z.,Taiyuan University of Technology | Yan K.,CAS Guangzhou Institute of Energy Conversation | Yan K.,CAS Guangzhou Center for Gas Hydrate Research | Yan K.,University of Chinese Academy of Sciences | Zhang J.,Taiyuan University of Technology
RSC Advances | Year: 2013

In order to investigate the initiation mechanisms associated with the pyrolysis of triglyceride that could potentially be used as petrochemical replacements, we carried out 500 ps molecular dynamics simulations employing the ReaxFF reactive force field using tripalmitin as the model molecule at 1500 and 2000 K. We find that the primary decomposition reactions of tripalmitin initiate with the successive scission of the alkyl-oxygen bond to form three straight chain C16H31O2 (RCOO) radicals and C3H5 radical. The deoxygenated alkyl chain is produced through the decarboxylation of the RCOO radical with concurrent production of CO2. The resulting alkyl and C3H5 radicals further undergo recombination and decomposition to yield mainly alkanes and alkenes, with the actual product distribution being dependent on reaction temperature. β-Scission plays an important role in alkyl chain decomposition with a concomitant release of C2H4. Compared to 1500 K, this reaction is accelerated at 2000 K. In addition, the formation of cyclic hydrocarbon is also observed at 2000 K. As opposed to previous proposed Diels-Alder reactions or intramolecular cyclizations of alkenyl radicals mechanisms, it is found that cyclopentane could be produced by intramolecular cyclization of a biradical. © 2013 The Royal Society of Chemistry. Source


Peng X.,Beijing University of Chemical Technology | Peng X.,CAS Guangzhou Center for Gas Hydrate Research | Zhou J.,CAS Institute of High Energy Physics | Wang W.,Beijing University of Chemical Technology | Cao D.,Beijing University of Chemical Technology
Carbon | Year: 2010

We perform a molecular simulation study on methane and carbon dioxide storage in carbon nanoscrolls. The effects of temperature and pressure, interlayer spacing, VDW gap and innermost radius on the gas storage have been examined extensively. It is found that the adsorption of gases on pristine carbon nanoscrolls is relatively low. However, once the interlayer spacing is expanded, both adsorption capacities of methane and carbon dioxide exhibit a significant improvement. In particular, the excess uptake of methane reaches 13 mmol/g at p = 6.0 MPa and T = 298.15 K and VDW gap Δ = 1.1 nm, which is about 3.5 times of uptake of the pristine carbon nanoscrolls; while the uptake of carbon dioxide could also be raised by 294.9% at T = 298.15 K and p = 3.0 MPa and Δ = 1.5 nm, reaching 30.21 mmol/g at 6.0 MPa. This work demonstrates that carbon nanoscrolls with an expansion of interlayer spacing may be a suitable material for methane storage and carbon dioxide capture. © 2010 Elsevier Ltd. All rights reserved. Source


Yan G.,Taiyuan University of Technology | Zhang Z.,Taiyuan University of Technology | Yan K.,CAS Guangzhou Institute of Energy Conversation | Yan K.,CAS Guangzhou Center for Gas Hydrate Research | Yan K.,University of Chinese Academy of Sciences
Molecular Physics | Year: 2013

To investigate the detailed mechanisms for brown coal oxidation at high temperatures, a ReaxFF reactive forcefield was used to perform a series of molecular dynamics simulations from 1000 K to 2500 K. Analyses indicated that the chemical system tend to be more reactive with increasing temperature. It was found that the oxidation process of brown coal primarily initiates from hydrogen abstraction reactions by O2 and related oxygenated radicals from phenolic hydroxyl groups, methyl groups, especially carboxyl groups in lower temperature to form peroxygen species, or by either thermal decomposition of brown coal backbone in higher temperature. These peroxygen species usually could chemically adsorb on the C-centered radicals of brown coal backbone. The weak O-O bond in peroxygen makes them easier to break into oxygenated radical, which could also chemically adsorb on the C-centred radical to form hydroxyl group and other oxygenated compounds. In the oxidation process of brown coal, the decomposition and oxidation of aliphatic chain is easier than aromatic ring. The chemisorption of peroxygen radical induces the breakage of aromatic ring and accelerates the depth oxidation of brown coal. An increasing number of products are observed with increasing temperature. © 2013 Taylor and Francis. Source


Xu C.-G.,CAS Guangzhou Institute of Energy Conversation | Xu C.-G.,CAS Guangzhou Center for Gas Hydrate Research | Li X.-S.,CAS Guangzhou Institute of Energy Conversation | Li X.-S.,CAS Guangzhou Center for Gas Hydrate Research
RSC Advances | Year: 2014

Hydrate-based CO2 separation and capture from gas mixtures containing CO2 has gained growing attention as a new technology for gas separation, and it is of significance for reducing anthropogenic CO 2 emissions. Previous studies of the technology include the thermodynamics and kinetics of hydrate formation/dissociation, hydrate formation additives, analytical methods, separation and capture progress, equipment and applications. Presently, the technology is still in the experimental research stages, and there are few reports of industrial application. This review examines research progress in the hydrate formation process and analytical methods with a special focus on laboratory studies, including the knowledge developed in analog computation, laboratory experiments, and industrial simulation. By comparing the various studies, we propose original comments and suggestions on further developing hydrate-based CO2 separation and capture technology. © 2014 The Partner Organisations. Source


Li X.-S.,CAS Guangzhou Institute of Energy Conversation | Li X.-S.,CAS Guangzhou Center for Gas Hydrate Research | Xu C.-G.,CAS Guangzhou Institute of Energy Conversation | Xu C.-G.,CAS Guangzhou Center for Gas Hydrate Research | And 5 more authors.
Energy | Year: 2011

Effects of 0.29mol% tetra-n-butyl ammonium bromide (TBAB) solution in conjunction with cyclopentane (CP) on the hydrate-based pre-combustion CO2 capture are investigated by the measurements of the gas uptakes, CO2 separation efficiencies and induction time of the hydrate formation at the different temperature-pressure conditions. The results show that the volume of the TBAB has an effect on the CO2 separation and the induction time, and the addition of the CP into the TBAB solution remarkably enhances the CO2 separation and shortens the induction time. The system with the CP/TBAB solution volume ratio of 5vol% and TBAB solution/reactor effective volume ratio of 0.54 is optimum to obtain the largest gas uptake and the highest CO2 separation efficiency at 274.65K and 4.0MPa. Compared to the results with tetrahydrofuran (THF) as an additive [1], the gas uptake is enhanced by at least 2 times and the induction time is shortened at least 10 times at the similar temperature-pressure condition. In addition, the CO2 concentration in the decomposed gas from the hydrate slurry phase reaches approximately 93mol% after the first-stage separation at 274.65K and 2.5MPa. The gas uptakes of more than 80mol% are obtained after 400s at the temperature range of 274.65-277.65K and the pressure range of 2.5-4.5MPa. © 2011 Elsevier Ltd. Source

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