Change search
Link to record
Permanent link

Direct link
BETA
Bazooyar, Faranak
Publications (6 of 6) Show all publications
Bazooyar, F. & Bolton, K. (2014). Molecular-level Simulations of Cellulose Dissolution by Steam and SC-CO2 Explosion. In: : . Paper presented at Nordic Polymer Days, 10-12 june, Gothenburg, Sweden.
Open this publication in new window or tab >>Molecular-level Simulations of Cellulose Dissolution by Steam and SC-CO2 Explosion
2014 (English)Conference paper, Published paper (Refereed)
Abstract [en]

Dissolution of cellulose is an important but tough step in biofuel production from lignocellulosic materials. Steam and supercritical carbon dioxide (SC-CO2) explosion are two effective methods for dissolution of some lignocellulosic materials. Loading and explosion are the major processes of these methods. Studies of these processes were performed using grand canonical Monte Carlo and molecular dynamics simulations at different pressure/ temperature conditions on the crystalline structure of cellulose. The COMPASS force field was used for both methods. The validity of the COMPASS force field for the calculations was confirmed by comparing the energy and structures obtained from molecular mechanics simulations of cellobiose (the repeat unit of cellulose), water–cellobiose, water-cellobiose pair and CO2-cellobiose pair systems with those obtained from first principle calculations with and without dispersion correction. A larger disruption of the cellulose crystal structure was seen during loading than that during the explosion process. This is seen by an increased separation of the cellulose chains from the centre of mass of the crystal during the initial stages of the loading, especially for chains in the outer shell of the crystalline structure. Reducing and non-reducing ends of the cellulose crystal show larger disruption than the central core; this leads to increasing susceptibility to enzymatic attack in these end regions. There was also change from the syn to the anti torsion angle conformations, especially for chains in the outer cellulose shell. Increasing the temperature increases the disruption of the crystalline structure during loading and explosion.

Keywords
Cellulose, Molecular modeling, Force field, Steam explosion, Supercritical carbon dioxide explosion, Resursåtervinning
National Category
Theoretical Chemistry
Research subject
Resource Recovery
Identifiers
urn:nbn:se:hb:diva-7292 (URN)2320/14559 (Local ID)2320/14559 (Archive number)2320/14559 (OAI)
Conference
Nordic Polymer Days, 10-12 june, Gothenburg, Sweden
Available from: 2015-12-22 Created: 2015-12-22 Last updated: 2016-11-11Bibliographically approved
Bazooyar, F. (2014). Molecular-level Simulations of Cellulose Dissolution by Steam and SC-CO2 Explosion. (Doctoral dissertation). Chalmers University of Technology ; University of Borås
Open this publication in new window or tab >>Molecular-level Simulations of Cellulose Dissolution by Steam and SC-CO2 Explosion
2014 (English)Doctoral thesis, monograph (Other academic)
Abstract [en]

Dissolution of cellulose is an important but complicated step in biofuel production from lignocellulosic materials. Steam and supercritical carbon dioxide (SC-CO2) explosion are two effective methods for dissolution of some lignocellulosic materials. Loading and explosion are the major processes of these methods. Studies of these processes were performed using grand canonical Monte Carlo and molecular dynamics simulations at different pressure/ temperature conditions on the crystalline structure of cellulose. The COMPASS force field was used for both methods. The validity of the COMPASS force field for these calculations was confirmed by comparing the energies and structures obtained from this force field with first principles calculations. The structures that were studied are cellobiose (the repeat unit of cellulose), water–cellobiose, water-cellobiose pair and CO2-cellobiose pair systems. The first principles methods were preliminary based on B3LYP density functional theory with and without dispersion correction. A larger disruption of the cellulose crystal structure was seen during loading than that during the explosion process. This was seen by an increased separation of the cellulose chains from the centre of mass of the crystal during the initial stages of the loading, especially for chains in the outer shell of the crystalline structure. The ends of the cellulose crystal showed larger disruption than the central core; this leads to increasing susceptibility to enzymatic attack in these end regions. There was also change from the syn to the anti torsion angle conformations during steam explosion, especially for chains in the outer cellulose shell. Increasing the temperature increased the disruption of the crystalline structure during loading and explosion.

Place, publisher, year, edition, pages
Chalmers University of Technology ; University of Borås, 2014
Series
Skrifter från Högskolan i Borås, ISSN 0280-381X ; 51
Keywords
molecular modelling, cellulose, steam explosion, SC-CO2 explosion, Resource Recovery
National Category
Chemical Engineering
Research subject
Resource Recovery
Identifiers
urn:nbn:se:hb:diva-3704 (URN)2320/14195 (Local ID)978-91-7597-058-5 (ISBN)2320/14195 (Archive number)2320/14195 (OAI)
Note
Akademisk avhandling som för avläggande av teknologie doktorsexamen vid Chalmers tekniska högskola försvaras vid offentlig disputation den 10 oktober 2014,klockan 13.00 i KS101-salen, Kemigården 4, Göteborg.Available from: 2015-12-04 Created: 2015-12-04
Samadikhah, K., Larsson, R., Bazooyar, F. & Bolton, K. (2012). Continuum-molecular modelling of graphene. Computational materials science, 53(1), 37-43
Open this publication in new window or tab >>Continuum-molecular modelling of graphene
2012 (English)In: Computational materials science, ISSN 0927-0256, E-ISSN 1879-0801, Vol. 53, no 1, p. 37-43Article in journal (Refereed) Published
Abstract [en]

membranes using a hierarchical modeling strategy to bridge the scales required to describe and understand the material. Quantum Mechanical (QM) and optimized Molecular Mechanical (MM) models are used to describe details on the nanoscale, while a multiscale continuum mechanical method is used to model the graphene response at the device or micrometer scale. The complete method is obtained on the basis of the Cauchy Born Rule (CBR), where the continuum model is coupled to the atomic field via the CBR and a local discrete fluctuation field. The MM method, often used to model carbon structures, involves the Tersoff--Brenner (TB) potential; however, when applying this potential to graphene with standard parameters one obtains material stress behavior much weaker than experiments. On the other hand, the more fundamental Hartree Fock and Density Functional Theory (DFT) methods are computationally too expensive and very limited in terms of their applicability to model the geometric scale at the device level. In this contribution a simple calibration of some of the TB parameters is proposed in order to reproduce the results obtained from QM calculations. Subsequently, the fine-tuned TB--potential is used for the multiscale modeling of a nano indentation sample, where experimental data are available. Effects of the mechanical response due the calibration are demonstrated.

Place, publisher, year, edition, pages
Elsevier BV, 2012
Keywords
graphene, mechanical properties, multiscale modelling, Energi och material
National Category
Materials Chemistry Chemical Process Engineering
Identifiers
urn:nbn:se:hb:diva-1272 (URN)10.1016/j.commatsci.2011.09.018 (DOI)000300722900007 ()2320/10746 (Local ID)2320/10746 (Archive number)2320/10746 (OAI)
Available from: 2015-11-13 Created: 2015-11-13 Last updated: 2017-10-25Bibliographically approved
Bazooyar, F., Momany, F. A. & Bolton, K. (2012). Validating Empirical Force Fields for Molecular-level Simulation of Cellulose Dissolution. Computational and Theoretical Chemistry, 984, 119-127
Open this publication in new window or tab >>Validating Empirical Force Fields for Molecular-level Simulation of Cellulose Dissolution
2012 (English)In: Computational and Theoretical Chemistry, ISSN 2210-271X, E-ISSN 2210-2728, Vol. 984, p. 119-127Article in journal (Refereed) Published
Abstract [en]

The calculations presented here, which include dynamics simulations using molecular mechanics forcefields and first principles studies, indicate that the COMPASS forcefield is preferred over the Dreiding and Universal forcefields for studying dissolution of large cellulose structures. The validity of these forcefields was assessed by comparing structures and energies of cellobiose, which is the shortest cellulose chain, obtained from the forcefields with those obtained from MP2 and DFT methods. In agreement with the first principles methods, COMPASS is the only forcefield of the three studied here that favors the anti form of cellobiose in the vacuum. This forcefield was also used to compare changes in energies when hydrating cellobiose with 1–4 water molecules. Although the COMPASS forcefield does not yield the change from anti to syn minimum energy structure when hydrating with more than two water molecules – as predicted by DFT – it does predict that the syn conformer is preferred when simulating cellobiose in bulk liquid water and at temperatures relevant to cellulosedissolution. This indicates that the COMPASS forcefield yields valid structures of cellulose under these conditions. Simulations based on the COMPASS forcefield show that, due to entropic effects, the syn form of cellobiose is energetically preferred at elevated temperature, both in vacuum and in bulk water. This is also in agreement with DFT calculations.

Place, publisher, year, edition, pages
Elsevier, 2012
Keywords
cellulose, DFT, COMPASS, Energi och material
National Category
Materials Chemistry
Research subject
Resource Recovery
Identifiers
urn:nbn:se:hb:diva-1273 (URN)10.1016/j.comptc.2012.01.020 (DOI)000302432600016 ()2320/10747 (Local ID)2320/10747 (Archive number)2320/10747 (OAI)
Available from: 2015-11-13 Created: 2015-11-13 Last updated: 2017-11-23Bibliographically approved
Björk, H., Lindecrantz, K., Ericsson, D., Sarv, H., Bolton, K., Börjesson, A., . . . Skrifvars, M. (2009). 20 år med Institutionen Ingenjörshögskolan: historik, nuläge och framtid. Högskolan i Borås
Open this publication in new window or tab >>20 år med Institutionen Ingenjörshögskolan: historik, nuläge och framtid
Show others...
2009 (Swedish)Report (Other academic)
Place, publisher, year, edition, pages
Högskolan i Borås, 2009
Series
Vetenskap för profession: rapport, ISSN 1654-6520 ; 10
National Category
Engineering and Technology
Identifiers
urn:nbn:se:hb:diva-4430 (URN)2320/5703 (Local ID)978-91-85659-49-4 (ISBN)2320/5703 (Archive number)2320/5703 (OAI)
Note

En jubileumsskrift

Available from: 2015-12-17 Created: 2015-12-17 Last updated: 2017-11-09Bibliographically approved
Bolton, K., Börjesson, A., Ahlström, P. & Bazooyar, F. (2009). Beräkningsteknik. Vetenskap för profession (10), 63-68
Open this publication in new window or tab >>Beräkningsteknik
Show others...
2009 (Swedish)In: Vetenskap för profession, ISSN 1654-6520, no 10, p. 63-68Article in journal (Other academic) Published
Place, publisher, year, edition, pages
Högskolan i Borås, 2009
Keywords
Energi och material
National Category
Materials Engineering
Identifiers
urn:nbn:se:hb:diva-2723 (URN)2320/5924 (Local ID)978-91-85659-49-4 (ISBN)2320/5924 (Archive number)2320/5924 (OAI)
Available from: 2015-11-13 Created: 2015-11-13 Last updated: 2018-01-16Bibliographically approved
Organisations

Search in DiVA

Show all publications