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Fractionation of 1-alcohol and n-alkane systems via supercritical CO2
Thesis (MEng)--Stellenbosch University, 2024.
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| Format: | Thesis |
| Language: | en_ZA en_ZA |
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Stellenbosch : Stellenbosch University
2024
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| _version_ | 1867614076083896320 |
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| access_status_str | Open Access |
| author | Brown, Alida Margaret |
| author2 | Motang, Neo |
| author_browse | Brown, Alida Margaret Motang, Neo |
| author_facet | Motang, Neo Brown, Alida Margaret |
| author_sort | Brown, Alida Margaret |
| collection | Thesis |
| dc_rights_str_mv | Stellenbosch University |
| description | Thesis (MEng)--Stellenbosch University, 2024. |
| format | Thesis |
| id | oai:scholar.sun.ac.za:10019.1/130532 |
| institution | Stellenbosch University (South Africa) |
| language | en_ZA en_ZA |
| last_indexed | 2026-06-10T12:46:16.958Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from SUNScholar — Stellenbosch University Repository |
| publishDate | 2024 |
| publishDateRange | 2024 |
| publishDateSort | 2024 |
| publisher | Stellenbosch : Stellenbosch University |
| publisherStr | Stellenbosch : Stellenbosch University |
| record_format | dspace |
| source_str | SUNScholar — Stellenbosch University Repository |
| spelling | oai:scholar.sun.ac.za:10019.1/130532 Fractionation of 1-alcohol and n-alkane systems via supercritical CO2 Brown, Alida Margaret Motang, Neo Schwarz, Cara Elsbeth Stellenbosch University. Faculty of Engineering. Dept. of Chemical Engineering. Process Engineering. Supercritical fluids Chemical separations Chemical equilibrium Thermodynamics Thesis (MEng)--Stellenbosch University, 2024. ENGLISH ABSTRACT: Detergent range alcohols (C8-20) that are often found in cleaning and personal care products are produced via the Oxo process. The product stream contains an alkane-alcohol mixture that needs to be separated. However, overlapping melting and boiling points, as well as azeotropes eliminate more traditional separation processes such as distillation and crystallization. Azeotropic distillation is currently employed in industry to separate the alkane-alcohol mixtures but has many drawbacks. Supercritical fluid fractionation (SFF) is proposed as an alternative separation technique. SFF processes are operated above the critical point of the selected solvent and thus complex phase behaviour may arise in the system. This complex phase behaviour must be understood to explain results obtained from SFF processes and to develop accurate thermodynamic models and subsequently appropriate simulated process models. The process models are valuable since experimental data collection is costly. This study aims to experimentally investigate the effect of complex phase behaviour found in mixtures of supercritical CO2 and detergent range 1-alcohols and n-alkanes on the performance of SFF and to subsequently evaluate the prediction capabilities of a process model within commercial process simulating software. New SFF pilot plant data was produced for the separation of a 50% 1-dodecanol + 50% n-hexadecane feed, as well as a 20% 1-dodecanol + 80% n-hexadecane feed at various operational conditions using supercritical CO2. The 50:50 solute mixture showed less efficient separation at higher temperatures and 318 K was suggested due to difficult controllability at lower temperatures (314 K). Better selectivity was found for increased pressure and E/F ratio, but recovery conversely decreased. No complex phase behaviour was observed for the separation of the 50:50 mixture and the more soluble n-alkane preferentially reported to the column extract. For the 80:20 solute mixture known to exhibit maximum co-solvency from literature, the phenomenon occurred where 1-dodecanol was preferentially recovered to the extract and > 97% purity n-hexadecane was recovered in the bottoms. The manifestation of a separation ‘pinch’ in the column due to extreme co-solubility was postulated, but unknown mass transfer and column hydrodynamics could also have contributed to the occurrence. An equilibrium stage simulation model for the SFF process was built in Aspen Plus®. The simulations for the separation of a 1-dodecanol + n-tetradecane feed and a 1-dodecanol + n-hexadecane feed via supercritical CO2 were compared to literature and experimental data. Attributable to good HPBDP data predictions, the RK-ASPEN thermodynamic model was utilised. Predictions of total extract and bottoms mass flowrate, as well as composition percentages showed < 10% error for 1-dodecanol + n-tetradecane feed at 313 K to 354 K and the 50:50 1-dodecanol + n-hexadecane feed at 318 K to 336 K. Predictions could not be found for the phenomenon present at the 80:20 n-hexadecane and 1-dodecanol feed. For future research, generation of applicable VLE and HPBDP data for the CO2 + 1-dodecanol + n-hexadecane system is suggested to better characterise the system. Further investigation of column hydrodynamics and a more complex mass-transfer-rate based model, as well as a detailed economic analysis, is recommended. AFRIKAANSE OPSOMMING: Geen opsomming beskikbaar. Masters 2024-03-05T09:37:40Z 2024-04-26T21:02:18Z 2024-03-05T09:37:40Z 2024-04-26T21:02:18Z 2024-03 Thesis https://scholar.sun.ac.za/handle/10019.1/130532 en_ZA en_ZA Stellenbosch University x, 172 pages : illustrations application/pdf Stellenbosch : Stellenbosch University |
| spellingShingle | Supercritical fluids Chemical separations Chemical equilibrium Thermodynamics Brown, Alida Margaret Fractionation of 1-alcohol and n-alkane systems via supercritical CO2 |
| title | Fractionation of 1-alcohol and n-alkane systems via supercritical CO2 |
| title_full | Fractionation of 1-alcohol and n-alkane systems via supercritical CO2 |
| title_fullStr | Fractionation of 1-alcohol and n-alkane systems via supercritical CO2 |
| title_full_unstemmed | Fractionation of 1-alcohol and n-alkane systems via supercritical CO2 |
| title_short | Fractionation of 1-alcohol and n-alkane systems via supercritical CO2 |
| title_sort | fractionation of 1 alcohol and n alkane systems via supercritical co2 |
| topic | Supercritical fluids Chemical separations Chemical equilibrium Thermodynamics |
| url | https://scholar.sun.ac.za/handle/10019.1/130532 |
| work_keys_str_mv | AT brownalidamargaret fractionationof1alcoholandnalkanesystemsviasupercriticalco2 |