High-q, high intensity small angle neutron scattering to probe formaldehyde-methanol-water mixtures

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dc.contributor.authorDwivedi, SHen_AU
dc.contributor.authorMata, JPen_AU
dc.contributor.authorMushrif, Sen_AU
dc.contributor.authorChaffee, ALen_AU
dc.contributor.authorTanksale, Aen_AU
dc.date.accessioned2023-05-04T23:40:07Zen_AU
dc.date.available2023-05-04T23:40:07Zen_AU
dc.date.issued2020-11-11en_AU
dc.date.statistics2023-04-28en_AU
dc.description.abstractMethanol-water mixtures are known for their unusual thermodynamic behaviour. On varying mixture composition, the thermodynamic properties do not vary linearly. This is attributed to the formation of structures at a molecular length scale, called as micro-phase. When formaldehyde is solvated in methanol-water mixtures, its chemical and physical behaviour is very much dependent on its micro-phase environment. Recently, liquid phase heterogeneous catalytic routs for the production of formaldehyde and its higher order oligomers are being developed1,2. The liquid phase (generally, methanol-water mixture) increases formaldehyde’s yield after its desorption from the catalytic surface1. Therefore, the study of formaldehyde’s solvation in methanol water mixtures may be crucial to further develop these liquid phase catalytic reaction pathways. However, the understanding of the structure of formaldehyde–methanol-water mixtures at molecular length scales is a challenge to the contemporary experimental techniques due to their dynamical and chemical nature. We use molecular dynamics simulations and the Small Angle Neutron Scattering (SANS) measurements to predict the molecular clustering in these mixtures. Classical Molecular Dynamics (MD) simulations were performed using GROMACS software package3 and the OPLS-AA forcefield parameters were used to describe bonded and non-bonded interactions. The radial pair distribution function g(r) and the coordination number were used to estimate the cluster composition and to compose backgrounds for these ternary mixtures. The Neutron Scattering data was collected at the Quokka beamline of the Australian Nuclear Science and Technology Organisation (ANSTO). The data modelling program SASview was used to model the scattering data and five different curve-fitting models were used, namely, the Guinier model, sphere model, sticky-hardsphere (SHS) sphere model, and SHS ellipsoid model. The sticky-hardsphere model fitting parameters were derived from the Potential of Mean Force (PME), calculated by the MD simulations. We observe a hydrophobic clustering of methanol around methoxymethanol molecule (i.e., the metastable solvated form of formaldehyde) at formaldehyde–methanol-water mixtures where 1 mole-percent formaldehyde is dissolved in xm ≤ 0.3 methanol-water mixture. The SHS-sphere model results in a sphere of 4.29 Å radius, which, when drawn from the centroid of a molecular cluster obtained via MD data, perfectly encapsulates it. On further increasing the methanol concentration, we do not observe any molecular clusters for xm > 0.5. In summary, we formulate a framework of analysing the dynamic ternary liquid mixtures for molecular clustering using SANS measurements and MD simulations and report hydrophobic clustering in formaldehyde-methanol-water ternary mixtures at low methanol compositionen_AU
dc.identifier.citationDwivedi, S., Mata, J., Mushrif, S., Chaffee, A., & Tanksale, A. (2020). High-q, high intensity small angle neutron scattering to probe formaldehyde-methanol-water mixtures. Poster presented to the ANBUG-AINSE Neutron Scattering Symposium, AANSS 2020, Virtual Meeting, 11th - 13th November 2020. (pp. 73). Retrieved from: https://events01.synchrotron.org.au/event/125/attachments/725/1149/AANSS_Abstract_Booklet_Complete_-_1_Page_Reduced.pdfen_AU
dc.identifier.conferenceenddate13 November 2020en_AU
dc.identifier.conferencenameANBUG-AINSE Neutron Scattering Symposium, AANSS 2020en_AU
dc.identifier.conferenceplaceVirtual Meetingen_AU
dc.identifier.conferencestartdate11 November 2020en_AU
dc.identifier.pagination73en_AU
dc.identifier.urihttps://events01.synchrotron.org.au/event/125/contributions/3777/contribution.pdfen_AU
dc.identifier.urihttps://apo.ansto.gov.au/dspace/handle/10238/14993en_AU
dc.language.isoenen_AU
dc.publisherAustralian Institute of Nuclear Science and Engineering (AINSE)en_AU
dc.subjectThermodynamic propertiesen_AU
dc.subjectMoleculesen_AU
dc.subjectFormaldehydeen_AU
dc.subjectHeterogeneous catalysisen_AU
dc.subjectMethanolen_AU
dc.subjectWateren_AU
dc.subjectSmall angle scatteringen_AU
dc.subjectNeutronsen_AU
dc.subjectANSTOen_AU
dc.subjectDataen_AU
dc.subjectMixturesen_AU
dc.subjectSpheresen_AU
dc.titleHigh-q, high intensity small angle neutron scattering to probe formaldehyde-methanol-water mixturesen_AU
dc.typeConference Abstracten_AU
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