Modelling the phase behaviour of polymer-solvent mixtures and · PDF file Modelling the phase...
date post
25-May-2020Category
Documents
view
2download
0
Embed Size (px)
Transcript of Modelling the phase behaviour of polymer-solvent mixtures and · PDF file Modelling the phase...
Modelling the phase behaviour of polymer-solvent mixtures
and surfactant systems with the SAFT-γ Mie EoS
Mariana Leitão da Silva Santos
Thesis to obtain the Master of Science Degree in
Chemical Engineering
Supervisors: Dr. Thomas Lafitte, Prof. Dr. Eduardo Morilla Filipe
Examination Committee
Chairperson: Prof. Dr. Carlos Henriques
Supervisor: Prof. Dr. Eduardo Morilla Filipe
Member of the committee: Dr. Pedro Morgado
20th October 2016
2
Acknowledgements
I cannot find words to express my gratitude to my Supervisor Dr. Thomas Lafitte for his support and
valuable knowledge – it has truly been an honour to work with you. I would also like to thank Dr. Vasileios
Papaioannou, for his (much needed) help and availability.
This thesis would not have been possible without my Professor (and also Supervisor) Dr. Eduardo Filipe
– I am forever indebted for your support and for giving me this chance. I also owe my deepest gratitude
to Process Systems Enterprise Ltd., in particular to Dr. Costas Pantelides, for the opportunity to enrol in
this Internship.
A very special thank you to all my journey companions and colleagues, who enriched this experience:
Tom, Su, Alhandra, Eleni, Matteo, Federico, Renato,Artur, Mariana, Francisco, Maria, Pierre, Sancho,
and Leonor. To my shorter-term buddies – Alex, Luisa, and Josh –, I am grateful for the thoughts and
experiences we shared.
To my parents: no words can describe how much I appreciate you unconditional love and support, I love
you both very much. I would also like to thank my little brother, for looking up to me – you made me try
harder, even without knowing. To the rest of my family: thank you for being there; particularly to my
grandma, for sheltering me and for her endless patience (and comfort food), and to my grandparents
for their love and support.
Last but far from least, to my fiancé João: I will be forever grateful for the lovely years we shared so far,
and for the amazing last few months that made me certain this is only the beginning of something great!
3
Resumo
A capacidade preditiva é uma das características mais procuradas nas ferramentas de modelação de
propriedades termodinâmicas, sendo estas continuamente desenvolvidas no sentido de diminuir a
necessidade de incluir dados experimentais na determinação dos parametros moleculares dos
modelos.
Aplicando o software gSAFT® na plataforma gPROMS®, foi avaliada a capacidade predictiva da
equação de estado SAFT-γ Mie (contribuição de grupos, GC) na descrição do equilíbrio de fases em
sistemas complexos, como polímero-solvente (poliestireno, poli(acetato de vinilo), polietileno,entre
outros) e misturas do surfactante não-iónico n-alkyl polyoxyethylene ether (CiEj).
Um dos maiores desafios na modelação destes sistemas consiste na escassez de dados experimentais
de equilíbrio líquido-vapor (ELV) para componentes puros, visto estes serem normalmente utilizados
na determinação dos parametros moleculares do modelo. Esta situação tende a ser contornada usando
dados experimentais relativos a misturas binárias e/ou multicomponente. A contribuição de grupos
permite caracterizar sistemas-objectivo após a determinação dos parâmetros relativos aos seus grupos
funcionais (podento resultar do estudo de dados experimentais de componentes mais simples e
facilmente disponíveis, incluindo ELV de compostos puros).
A maioria dos sistemas polímero-solvente estudados foram previstos correctamente, dispensando a
implementação de dados experimentais de polímeros na estimação de parametros. O ELV de
surfactantes puros e de misturas binárias surfactante-água é facilmente reproduzido pelos modelos
desenvolvidos (e frequentemente tranferíveis para sistemas semelhantes). Misturas binárias CiEj -
alcanos são muito difícies de modelar e misturas ternárias água- CiEj -alcano, impossíveis de prever.
A concentração micelar crítica (CMC) dos sistemas água- CiEj foi também modelada, e a dependência
desta em relação ao comprimento da molecula de surfactante foi bem reproduzida.
Palavras-chave: equação de estado, SAFT-γ Mie, polímeros, surfactantes, equilíbrio de fases,
imiscibilidade líquido-líquido
4
Abstract
One of the most desired features in thermodynamic tools is a predictive capability, hence
thermodynamic modelling frameworks have been developed towards decreasing the need for
experimental data for the determination of molecular model parameters.
Using gSAFT® software within gPROMS® platform, an assessment of the predictive capability of the
SAFT-γ Mie EoS (a group contribution (GC) approach) is carried regarding the phase equilibrium of
complex materials. In this project are studied: polymer-solvent systems (PS, PVAc, PVME, PE, among
others) and non-ionic (n-alkyl polyoxyethylene ether, CiEj) surfactant mixtures.
The paucity of pure-component vapour-liquid experimental (VLE) data poses a challenge in the
modelling of these systems, as these are typically used to develop the required model parameters. This
is usually tackled by using experimental data for fluid-phase behaviour of binary and/or multi-component
mixtures. The GC formalism advantageously allows the characterisation of target systems once the
parameters for the functional groups that describe them have been obtained (e.g. by studying simpler
data typically available, including pure-component VLE).
The modelling of polymer-solvent systems was very successful - nearly all polymer systems studied
were accurately predicted without using binary polymer data to adjust the interaction parameters. Pure-
surfactant VLE and CiEj-water binary mixtures are easily correlated to by the developed models, and
sometimes even transferable to similar systems, but CiEj-alkane binaries are very difficult to reproduce,
and ternary water-CiEj-alkane mixtures are non-replicable. The critical micellar concentration (CMC) of
CiEj-water systems was also modelled, and the dependency of the CMC on surfactant chain length was
well captured.
Keywords: equation of state, SAFT-γ Mie, polymers, surfactants, phase behaviour, closed-loop
immiscibility.
5
Contents
Acknowledgements ................................................................................................................................. 2
Resumo ................................................................................................................................................... 3
Abstract.................................................................................................................................................... 4
List of Tables ........................................................................................................................................... 7
List of Figures .......................................................................................................................................... 9
Nomenclature ........................................................................................................................................ 14
Introduction .................................................................................................................................... 17
1.1 Motivation .............................................................................................................................. 17
1.2 State of the art ....................................................................................................................... 18
1.2.1 Polymer-solvent systems ............................................................................................... 18
1.2.2 Surfactant mixtures ........................................................................................................ 20
Theoretical Background ................................................................................................................. 21
2.1 Intermolecular interactions .......................................................................................................... 21
2.2 Evolution of Equations of State (EoS) ................................................................................... 22
2.2.1 Ideal Gas Law ................................................................................................................ 23
2.2.2 Van der Waals and Cubic EoS ...................................................................................... 23
2.2.3 Statistical associating fluid theory (SAFT) ..................................................................... 24
Modelling of phase behaviour of polymer-solvent mixtures and surfactant systems using gSAFT
………………………………………………………………………………………………………………35
3.1 gSAFT .................................................................................................................................... 35
3.2 Polymer-sol