Diisononyl phthalate – organics interactions : a phase equilibrium study using modified UNIFAC models
- Authors: Pheko, Given T , Muzenda, Edison , Belaid, Mohamed , Mateescu, Corina
- Date: 2013
- Subjects: Phase equilibrium , Volatile organic compounds , Diisononyl phthalate , Absorption abatement
- Type: Article
- Identifier: uj:4857 , http://hdl.handle.net/10210/12533
- Description: Volatile organic compounds (VOCs) are a series of organic compounds that readily vaporize at room temperature. When emitted into the environment can affect climate change and plants growth, and cause long term human health risks. Absorption abatement technique has been the most preferred to reduce VOCs from contaminated gaseous streams, hence the need for a polymeric solvent with a greater affinity for end-pipe inventory. This phase equilibrium study investigated the ability of diisononyl phthalate (DINP) as an absorbent to 80 selected VOCs at infinite dilution. The solvent-solute(s) interactions were studied using modified UNIFAC Lyngby and Dortmund group contribution methods, with the latter being consistent and reliable, as its results are related to literature. Alkanes, alkanes, aldehydes and cyclo-alkanes with shorter carbon-chain length are highly soluble in DINP, with their solubility decreasing with increasing molecular weight or size, at infinite dilution. Alkynes, ketones, alcohols and carboxylic acids are less soluble in DINP, as a result of their dominating polarity compared to the DINP non-polarity structure. However, results could be improved with further studies and publication of solvent-solute(s) sub-groups interaction parameters, and thus further development of modified UNIFAC Lyngby model. DINP is a good absorbent for short-chained non-polar VOCs.
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Influence of temperature and molecular structure on organics-biodiesel interactions using group contribution methods
- Authors: Scheepers, Jacques J. , Muzenda, Edison , Belaid, Mohamed
- Date: 2012
- Subjects: Group contribution method , Phase equilibrium , Solubility , Volatile organic compounds , Absorption , Activity coefficients
- Type: Article
- Identifier: uj:4672 , ISBN 978-93-82242-16-1 , http://hdl.handle.net/10210/10437
- Description: Resulting from the trend of increasingly stringent environmental legislation, the drive to secure environmentally friendly absorption solvents has gained much impetus in recent times. In order to design and operate separation processes units, it is essential that the engineer has accurate and reliable knowledge of the phase equilibrium behaviour of the system in question. Since obtaining experimental data on the system can be time-consuming, the use of thermodynamic models is often useful in obtaining preliminary design and feasibility study information. This work examines the suitability of biodiesel (particularly the constituents methyl palmitate and methyl linolenate) as an absorbent solvent for the recovery of volatile organic compounds (VOCs) from waste process gas streams. In particular, activity coefficients were measured in the dilute region in an attempt to predict the effects of molecular structure and temperature on the solubility of the VOCs in the methyl esters under study. The group contribution methods UNIFAC and Modified UNIFAC Dortmund, set up on Microsoft Excel spreadsheets, were used to predict the required phase equilibrium at infinite dilution. The results obtaine
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Organics – biodiesel systems phase equilibrium computation : part 1
- Authors: Nkosi, Nhlanhla P. , Mokoena, Phumzile , Muzenda, Edison , Belaid, Mohamed
- Date: 2011
- Subjects: Activity coefficient , Group contribution , Phase equilibrium , Solubility , Volatile organic compounds
- Type: Article
- Identifier: uj:4675 , http://hdl.handle.net/10210/10444
- Description: The group contribution concept can be applied in the estimation of thermodynamic properties of pure compounds and mixtures. The Modified UNIFAC (Dortmund) is a successful and well-known group contribution model for phase equilibria prediction. In this paper the application of this model to the phase equilibrium of biodiesel - volatile organic compounds systems was tested. Infinite dilution activity coefficients of 30 selected volatile organic compounds (VOCs) in methyl linoleate and methyl palmitate were estimated. The VOCs groups covered in the selection were alkanes, alkenes, alkynes, aromatics, ethers and ketones. The estimated phase equilibrium is favourable for the absorption of these organics into methyl linoleate. The solubility was found to decrease with increase in molecular weight of the VOCs in each group. Saturation was also found to have an effect on solubility. Experimental data are often not available, at least for preliminary design and feasibility studies of absorption processes, group contribution methods can be utilized to predict the required phase equilibria.
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Phase equilibrium of volatile organic compounds in silicon oil using the UNIFAC procedure : an estimation
- Authors: Muzenda, Edison , Simate, Geoffrey S. , Belaid, Mohamed , Ntuli, Freeman , Mollagee, Mansoor
- Date: 2011
- Subjects: Phase equilibrium , Thermodynamic models , Volatile organic compounds , Polydimethylsiloxane , Silicon oil
- Type: Article
- Identifier: uj:4699 , http://hdl.handle.net/10210/10934
- Description: This paper focuses on the phase equilibrium of volatile organic compounds in silicon oil chemically known as PDMS (polydimethylsiloxane) at infinite dilution. Measurements can be expensive and time consuming, hence the need for thermodynamic models which allow the calculation of the phase equilibrium behavior using a limited number of experimental data. The objective of this study was to predict infinite dilution activity coefficients of selected VOCs (volatile organic compounds) in PDMS using the Original UNIFAC model. The predicted results show that PDMS can be used to abate volatile organic compounds from contaminated air streams. The results obtained in this work are comparable to those obtained by the same authors through measurements such as the static headspace and the dynamic gas liquid chromatographic techniques as well as other literature. Although the UNIFAC group contribution method over estimate the infinite dilution activity coefficients, the results of this work may be applied in preliminary phases of process design, simulation and feasibility studies.
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Volatile organic compounds- biodiesel thermodynamic interactions: influence of temperature
- Authors: Ramdharee, Sashay , Muzenda, Edison , Belaid, Mohamed
- Date: 2016
- Subjects: Activity coefficients , Biodiesel , Phase equilibrium , Universal functional activity coefficient
- Language: English
- Type: Conference proceedings
- Identifier: http://hdl.handle.net/10210/93659 , uj:20376 , Citation: Ramdharee, S., Muzenda, E. & Belaid, M. 2016. Volatile organic compounds- biodiesel thermodynamic interactions: influence of temperature.
- Description: Abstract: This work investigated the suitability of biodiesel (predominantly Methyl Linolenate, Methyl Palmitate, Methyl Oleate and Methyl Stearate) as an absorbent for the recovery of VOCs from waste gas process streams through absorption. The objective was to predict the vapour liquid equilibria (VLE) data in the form of infinite dilution activity coefficients for five VOC families, in fatty acid methyl ester solvents at varying temperature. The Original Universal Functional Group Activity Coefficient (UNIFAC) model (Fredenslund et al., 1975) [1], Modified UNIFAC (Larsen et al., 1981) [2] and Modified UNIFAC (Bastos et al., 1988) [3] was used to predict the required phase equilibrium. Alkanes, alcohols and acids/ester interactions showed an increase in activity coefficients with increase in temperature. The influence of temperature on the activity coefficients for alkene and amine families was negligible. The solubility of VOCs in biodiesel decreases with increase in ester hydrocarbon unsaturation. The solubility of VOCs increased with increase in ester molecular weight.
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