Rodriguez, Gianfranco
(2019)
Modelling of Multiphasic Behavior of Biodiesel Transesterification Operating Below Critical Conditions Using CO2 as a Co-solvent with PC-SAFT EoS.
Doctoral Dissertation, University of Pittsburgh.
(Unpublished)
Abstract
Two major obstacles to effective transesterification of triglycerides to form biodiesel are the initial immiscibility of the reactants and the depletion of the short chain alcohol used throughout the reaction progress due to formation of the glycerol phase. Traditionally, to deal with such problems, high temperatures and pressures are employed to enhance the kinetics of the reaction. Co-solvents can also be introduced as means to promote mixing and lower the energetic requirements of the process. Amongst the multiple proposed co-solvents in the literature carbon dioxide is the one with the highest vapor pressure of all, which provides multiple benefits in the downstream separation process of the biodiesel products and excess reactants. Biodiesel yield’s dependence on pressure, temperature (P-T) and methanol to oil molar ratio has been extensively explored but these variables do not only influence the process kinetics but also greatly affect the phase equilibria.
Modelling results achieved accurate phase behavior representations for pure components, plus binary and ternary mixtures that include carbon dioxide by using a polar version of PC-SAFT. Group contribution methods were employed to predict pure component parameters for a range of fatty acid methyl- and ethyl-esters, simplifying the modelling while minimizing the number of parameters. Small errors were obtained using very low values of binary interaction coefficients (below 0.12) for the binary mixtures. In this work the presence of an optimal content of CO2 for each set of PT conditions is demonstrated for a system containing CO2, methanol and triglycerides (transesterification reactants) and a full map depicting optimal conditions for every set of pressure and temperature conditions is provided. That approach has also been extended looking into the quaternary system of CO2, methanol, glycerol and biodiesel. Optimal values of carbon dioxide content in terms of enhancing the solubility of the phases are hereby investigated. Variation of the phase separation in a range of pressures (10-40 MPa) temperatures (40-200 °C) and different methanol to glycerol ratios (2-30:1) and the influence on the optimal conditions are reported using a polar version of PC-SAFT that can easily be extended to multiple substances and process conditions.
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Details
| Item Type: |
University of Pittsburgh ETD
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| Status: |
Unpublished |
| Creators/Authors: |
|
| ETD Committee: |
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| Date: |
23 August 2019 |
| Defense Date: |
6 September 2019 |
| Approval Date: |
29 January 2020 |
| Submission Date: |
8 September 2019 |
| Access Restriction: |
No restriction; Release the ETD for access worldwide immediately. |
| Number of Pages: |
133 |
| Institution: |
University of Pittsburgh |
| Schools and Programs: |
Swanson School of Engineering > Chemical Engineering |
| Degree: |
PhD - Doctor of Philosophy |
| Thesis Type: |
Doctoral Dissertation |
| Refereed: |
Yes |
| Uncontrolled Keywords: |
Modelling
Multiphasic Behavior
Biodiesel
CO2
Co-solvent
PC-SAFT
Triglycerides
Diglycerides
Monoglycerides |
| Date Deposited: |
29 Jan 2020 15:37 |
| Last Modified: |
29 Jan 2020 15:37 |
| URI: |
http://d-scholarship.pitt.edu/id/eprint/37620 |
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