Alkenes - ester polymeric solvents thermodynamic interactions - Part 1
- Scheepers, Jacques J., Muzenda, Edison
- Authors: Scheepers, Jacques J. , Muzenda, Edison
- Date: 2012
- Subjects: Activity coefficients , Esters , Alkenes , Thermodynamics , Solubility
- Type: Article
- Identifier: uj:6274 , http://hdl.handle.net/10210/8914
- Description: This work focused on the interactions between ester solvents and volatile organic compounds of alkene in nature. Infinite dilution activity coefficients of alkenes in various fatty acid ester solvents were predicted in order to study and thermodynamically understand the nature and effect of the bond interactions involved. Activity coefficients were computed using Microsoft Excel model specifically designed for this purpose. The ester solvent chain length and saturation influenced the solubility of alkene organics. Saturated and longer ester chains gave better absorption performance. Alkenes were found to be more soluble than their alkane counterparts of similar carbon count.
- Full Text:
- Authors: Scheepers, Jacques J. , Muzenda, Edison
- Date: 2012
- Subjects: Activity coefficients , Esters , Alkenes , Thermodynamics , Solubility
- Type: Article
- Identifier: uj:6274 , http://hdl.handle.net/10210/8914
- Description: This work focused on the interactions between ester solvents and volatile organic compounds of alkene in nature. Infinite dilution activity coefficients of alkenes in various fatty acid ester solvents were predicted in order to study and thermodynamically understand the nature and effect of the bond interactions involved. Activity coefficients were computed using Microsoft Excel model specifically designed for this purpose. The ester solvent chain length and saturation influenced the solubility of alkene organics. Saturated and longer ester chains gave better absorption performance. Alkenes were found to be more soluble than their alkane counterparts of similar carbon count.
- Full Text:
Alkenes - ester polymeric solvents thermodynamic interactions - part 2
- Scheepers, Jacques J., Muzenda, Edison, Belaid, Mohamed
- Authors: Scheepers, Jacques J. , Muzenda, Edison , Belaid, Mohamed
- Date: 2012
- Subjects: Activity coefficients , Esters , Alkenes , Thermodynamics
- Type: Article
- Identifier: uj:5341 , http://hdl.handle.net/10210/9581
- Description: This paper is a continuation of our work reported previously [1] on the interaction between ester solvents and alkene volatile organic compounds (VOCs). The interactions were presented inform of infinite dilution activity coefficients. A Microsoft Excel spreadsheet for the modified UNIFAC Dortmund group contribution method [2] was designed and used in computing the required phase equilibrium. The size of the solvent molecule (biodiesel) relative to the VOC molecule influenced the thermodynamic interactions. The degree of ester (biodiesel) bond saturation influenced the ease in which cyclic VOCs interacted with the solvent compared to their straight chain counterparts. The location of branches such as methyl branches in relation to the double-bonded carbons had an impact on the predicted infinite dilution activity coefficients.
- Full Text:
- Authors: Scheepers, Jacques J. , Muzenda, Edison , Belaid, Mohamed
- Date: 2012
- Subjects: Activity coefficients , Esters , Alkenes , Thermodynamics
- Type: Article
- Identifier: uj:5341 , http://hdl.handle.net/10210/9581
- Description: This paper is a continuation of our work reported previously [1] on the interaction between ester solvents and alkene volatile organic compounds (VOCs). The interactions were presented inform of infinite dilution activity coefficients. A Microsoft Excel spreadsheet for the modified UNIFAC Dortmund group contribution method [2] was designed and used in computing the required phase equilibrium. The size of the solvent molecule (biodiesel) relative to the VOC molecule influenced the thermodynamic interactions. The degree of ester (biodiesel) bond saturation influenced the ease in which cyclic VOCs interacted with the solvent compared to their straight chain counterparts. The location of branches such as methyl branches in relation to the double-bonded carbons had an impact on the predicted infinite dilution activity coefficients.
- Full Text:
Aromatic compounds and ester polymeric solvents interactions
- Authors: Muzenda, Edison
- Date: 2014
- Subjects: Activity coefficients , Aromatic compounds , Esters , Solubility , Volatile organic compounds
- Type: Article
- Identifier: uj:4771 , ISSN 2320–4087 , http://hdl.handle.net/10210/11946
- Description: This work focused on the interactions that occur between ester polymeric solvents and simple aromatic volatile organic compounds (VOCs). Solutes were selected from various functional groups in their simplest form and computations of infinite dilution activity coefficients were performed using the Modified UNIFAC Dortmund group contribution model using a Microsoft Excel spreadsheet designed for this purpose. For polar aromatic VOCs, solubility decreased with increase in size of the ester solvent molecule and the opposite behavior was observed for non-polar VOCs. For all aromatic - ester solvent interactions, solubility increased with the increase in the degree of ester unsaturation.
- Full Text:
- Authors: Muzenda, Edison
- Date: 2014
- Subjects: Activity coefficients , Aromatic compounds , Esters , Solubility , Volatile organic compounds
- Type: Article
- Identifier: uj:4771 , ISSN 2320–4087 , http://hdl.handle.net/10210/11946
- Description: This work focused on the interactions that occur between ester polymeric solvents and simple aromatic volatile organic compounds (VOCs). Solutes were selected from various functional groups in their simplest form and computations of infinite dilution activity coefficients were performed using the Modified UNIFAC Dortmund group contribution model using a Microsoft Excel spreadsheet designed for this purpose. For polar aromatic VOCs, solubility decreased with increase in size of the ester solvent molecule and the opposite behavior was observed for non-polar VOCs. For all aromatic - ester solvent interactions, solubility increased with the increase in the degree of ester unsaturation.
- Full Text:
Glycerol - a viable solvent for absorption of highly polar solutes II : behaviour of molecular interactions
- Scheepers, Jacques J., Muzenda, Edison, Belaid, Mohamed
- Authors: Scheepers, Jacques J. , Muzenda, Edison , Belaid, Mohamed
- Date: 2015
- Subjects: Activity coefficients , Glycerol , Solubility , Volatile organic compounds , Scrubbing solvents
- Type: Article
- Identifier: uj:5054 , http://hdl.handle.net/10210/13593
- Description: This work focused on the potential of glycerol as a scrubbing solvent for stripping of highly polar volatile organic compounds (VOCs) from industrial waste gas streams. Results for glycerol interactions were compared to those of water. Solubility predictions in the form of infinite dilution activity coefficients were made using the Modified UNIFAC Dortmund group contribution model, which was set up on a Microsoft Excel spreadsheet specifically designed for this purpose. Activity coefficients for VOCs in water and glycerol (highly polar solvents) increased with an increase in the length of the VOC solute nonpolar tail. Furthermore, activity coefficients decreased with an increase in the degree of branching of the VOC solute. The results show that low chain length highly polar alcohol, ketone, organic acid and aldehyde solutes are very soluble in glycerol. Diols, dicarbonyl aldehydes, some ketone derivatives and the ethanolamines also show good solubility. Highly polar diesters and ester derivatives are less soluble in glycerol and water. This study has found glycerol to be a better scrubbing solvent than water in treating highly polar VOCs. However it is possible that the standard method of building up the glycerol molecule in the UNIFAC may result in under-predictions of activity coefficients and thus special group interaction parameters for glycerol are required.
- Full Text:
- Authors: Scheepers, Jacques J. , Muzenda, Edison , Belaid, Mohamed
- Date: 2015
- Subjects: Activity coefficients , Glycerol , Solubility , Volatile organic compounds , Scrubbing solvents
- Type: Article
- Identifier: uj:5054 , http://hdl.handle.net/10210/13593
- Description: This work focused on the potential of glycerol as a scrubbing solvent for stripping of highly polar volatile organic compounds (VOCs) from industrial waste gas streams. Results for glycerol interactions were compared to those of water. Solubility predictions in the form of infinite dilution activity coefficients were made using the Modified UNIFAC Dortmund group contribution model, which was set up on a Microsoft Excel spreadsheet specifically designed for this purpose. Activity coefficients for VOCs in water and glycerol (highly polar solvents) increased with an increase in the length of the VOC solute nonpolar tail. Furthermore, activity coefficients decreased with an increase in the degree of branching of the VOC solute. The results show that low chain length highly polar alcohol, ketone, organic acid and aldehyde solutes are very soluble in glycerol. Diols, dicarbonyl aldehydes, some ketone derivatives and the ethanolamines also show good solubility. Highly polar diesters and ester derivatives are less soluble in glycerol and water. This study has found glycerol to be a better scrubbing solvent than water in treating highly polar VOCs. However it is possible that the standard method of building up the glycerol molecule in the UNIFAC may result in under-predictions of activity coefficients and thus special group interaction parameters for glycerol are required.
- Full Text:
Influence of structure on fatty acid ester-alkane interactions
- Scheepers, Jacques J., Muzenda, Edison, Belaid, Mohamed
- Authors: Scheepers, Jacques J. , Muzenda, Edison , Belaid, Mohamed
- Date: 2012
- Subjects: Absorption , Activity coefficients , Biodiesel , Esters , Volatile organic compounds
- Type: Article
- Identifier: uj:4671 , ISSN 978-988-19252-2-0 , http://hdl.handle.net/10210/10436
- Description: The activity coefficients of alkane structures in various types of fatty acid ester solvents was measured in order to determine the effect of bond interactions between these two chemical species. It is important to understand the mechanics of these interactions for absorber system design. Activity coefficients were determined by use of a Microsoft Excel spreadsheet designed for this purpose. It was determined that the length of the ester chain, as well as ester chain saturation had an impact on activity coefficients, in that saturated ester chains and longer ester chains yielded lower activity coefficients. Multiple branched cycloalkanes yielded lower activity coefficients than straight chain hydrocarbons and unbranched cycloalkanes. It was also noted that the location of the carboxyl group in the ester chain had no influence on activity coefficients.
- Full Text:
- Authors: Scheepers, Jacques J. , Muzenda, Edison , Belaid, Mohamed
- Date: 2012
- Subjects: Absorption , Activity coefficients , Biodiesel , Esters , Volatile organic compounds
- Type: Article
- Identifier: uj:4671 , ISSN 978-988-19252-2-0 , http://hdl.handle.net/10210/10436
- Description: The activity coefficients of alkane structures in various types of fatty acid ester solvents was measured in order to determine the effect of bond interactions between these two chemical species. It is important to understand the mechanics of these interactions for absorber system design. Activity coefficients were determined by use of a Microsoft Excel spreadsheet designed for this purpose. It was determined that the length of the ester chain, as well as ester chain saturation had an impact on activity coefficients, in that saturated ester chains and longer ester chains yielded lower activity coefficients. Multiple branched cycloalkanes yielded lower activity coefficients than straight chain hydrocarbons and unbranched cycloalkanes. It was also noted that the location of the carboxyl group in the ester chain had no influence on activity coefficients.
- Full Text:
Influence of temperature and molecular structure on organics-biodiesel interactions using group contribution methods
- Scheepers, Jacques J., Muzenda, Edison, Belaid, Mohamed
- 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
- Full Text:
- 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
- Full Text:
Interactions of polar and nonpolar volatile organic compounds with methyl ester solvents
- Authors: Muzenda, Edison
- Date: 2013
- Subjects: Activity coefficients , Esters , Solubility , Volatile organic compounds , Methyl ester solvents
- Type: Article
- Identifier: uj:4890 , http://hdl.handle.net/10210/12604
- Description: The interactions of polar and nonpolar volatile organic compounds (VOC) with methyl ester solvents were studied. In order to establish trends two polar and two nonpolar solutes were selected for the study. Solubility computations were performed using the Modified UNIFAC Dortmund group contribution model using a Microsoft Excel spreadsheet. It was found that the solubility of nonpolar solutes in methyl esters increases with an increase in ester chain length, but decreases with an increase in the solute chain length. Furthermore the solubility of nonpolar solutes decreases with an increase in the degree of ester solvent unsaturation. In contrast the solubility of polar solutes in methyl esters decreases with an increase in solvent chain length and increases with increasing solute chain length. Solubility of polar solutes also improved with an increase in the degree of solvent unsaturation. An increase in branching on polar solutes results in an increasing trend towards nonpolar behavior due to the shielding effect of the branches on interactions with the polar site of the solute.
- Full Text:
- Authors: Muzenda, Edison
- Date: 2013
- Subjects: Activity coefficients , Esters , Solubility , Volatile organic compounds , Methyl ester solvents
- Type: Article
- Identifier: uj:4890 , http://hdl.handle.net/10210/12604
- Description: The interactions of polar and nonpolar volatile organic compounds (VOC) with methyl ester solvents were studied. In order to establish trends two polar and two nonpolar solutes were selected for the study. Solubility computations were performed using the Modified UNIFAC Dortmund group contribution model using a Microsoft Excel spreadsheet. It was found that the solubility of nonpolar solutes in methyl esters increases with an increase in ester chain length, but decreases with an increase in the solute chain length. Furthermore the solubility of nonpolar solutes decreases with an increase in the degree of ester solvent unsaturation. In contrast the solubility of polar solutes in methyl esters decreases with an increase in solvent chain length and increases with increasing solute chain length. Solubility of polar solutes also improved with an increase in the degree of solvent unsaturation. An increase in branching on polar solutes results in an increasing trend towards nonpolar behavior due to the shielding effect of the branches on interactions with the polar site of the solute.
- Full Text:
Intermolecular dynamics between aromatic compounds and ester polymeric solvents
- Scheepers, Jacques J., Muzenda, Edison, Belaid, Mohamed
- Authors: Scheepers, Jacques J. , Muzenda, Edison , Belaid, Mohamed
- Date: 2013
- Subjects: Activity coefficients , Aromatic compounds , Solubility , Esters
- Type: Article
- Identifier: uj:4836 , http://hdl.handle.net/10210/12484
- Description: This work focused on the interactions that occur between ester solvents and simple aromatic solutes. Solutes were selected from various functional groups in their simplest form, and predictions of activity coefficients at infinite dilution were made using the Modified UNIFAC Dortmund group contribution model. The model computation was set up on a Microsoft Excel spreadsheet specifically designed for this purpose. For polar aromatic solutes, solubility decreased with increase in size of the ester solvent molecule and the opposite was found to be true for non-polar solutes. For all aromatic/ ester solvent interactions there was a decrease in activity coefficients with an increase in the degree of ester unsaturation.
- Full Text:
- Authors: Scheepers, Jacques J. , Muzenda, Edison , Belaid, Mohamed
- Date: 2013
- Subjects: Activity coefficients , Aromatic compounds , Solubility , Esters
- Type: Article
- Identifier: uj:4836 , http://hdl.handle.net/10210/12484
- Description: This work focused on the interactions that occur between ester solvents and simple aromatic solutes. Solutes were selected from various functional groups in their simplest form, and predictions of activity coefficients at infinite dilution were made using the Modified UNIFAC Dortmund group contribution model. The model computation was set up on a Microsoft Excel spreadsheet specifically designed for this purpose. For polar aromatic solutes, solubility decreased with increase in size of the ester solvent molecule and the opposite was found to be true for non-polar solutes. For all aromatic/ ester solvent interactions there was a decrease in activity coefficients with an increase in the degree of ester unsaturation.
- Full Text:
Measurement of infinite dilution activity coefficients of selected environmentally important volatile organic compounds in polydimethylsiloxane using gas – liquid chromatography
- Muzenda, Edison, Belaid, M., Ntuli, Freeman
- Authors: Muzenda, Edison , Belaid, M. , Ntuli, Freeman
- Date: 2010
- Subjects: Thermodynamics , Polydimethylsiloxane , Activity coefficients , Volatile organic compounds absorption
- Type: Article
- Identifier: uj:5306 , http://hdl.handle.net/10210/5284
- Description: Silicon oil chemically known as polydimethylsiloxane (PDMS) is a high boiling point solvent highly suitable for volatile organic compounds (VOCs) absorption. In order to use PDMS as an absorption solvent for a specific waste gas problem, it is important to determine the infinite dilution activity coefficients of the VOCs to be separated with PDMS. This work reports activity coefficients at infinite dilution of 13 VOCs in polydimethysiloxane determined by the dynamic gas liquid chromatographic technique. The measurements were carried out at various temperatures (i.e, 303.15, 313.15, 323.15., 333.15, 353.15, 373.15, 393.15 and 423.15K). Four PDMS polymers with average molecular weight ranging from 760 to 13 000 were used as solvents. A control column packed by Perkin Elmer to our specifications was used to validate the coating and packing methods. Flow rate dependence of the elution peaks was also investigated by varying it from 10 – 50 ml/min. Precision was improved by reproducing the results using columns with different liquid loading, thus also studying the retention mechanism. The results compare well with the data from previous work using simple headspace and UNIFAC predictions and literature values. The successful comparison gives an indication of the GLC as a rapid, simple and accurate method for studying the thermodynamics of the interaction of a volatile solute with a non volatile solvent.
- Full Text:
- Authors: Muzenda, Edison , Belaid, M. , Ntuli, Freeman
- Date: 2010
- Subjects: Thermodynamics , Polydimethylsiloxane , Activity coefficients , Volatile organic compounds absorption
- Type: Article
- Identifier: uj:5306 , http://hdl.handle.net/10210/5284
- Description: Silicon oil chemically known as polydimethylsiloxane (PDMS) is a high boiling point solvent highly suitable for volatile organic compounds (VOCs) absorption. In order to use PDMS as an absorption solvent for a specific waste gas problem, it is important to determine the infinite dilution activity coefficients of the VOCs to be separated with PDMS. This work reports activity coefficients at infinite dilution of 13 VOCs in polydimethysiloxane determined by the dynamic gas liquid chromatographic technique. The measurements were carried out at various temperatures (i.e, 303.15, 313.15, 323.15., 333.15, 353.15, 373.15, 393.15 and 423.15K). Four PDMS polymers with average molecular weight ranging from 760 to 13 000 were used as solvents. A control column packed by Perkin Elmer to our specifications was used to validate the coating and packing methods. Flow rate dependence of the elution peaks was also investigated by varying it from 10 – 50 ml/min. Precision was improved by reproducing the results using columns with different liquid loading, thus also studying the retention mechanism. The results compare well with the data from previous work using simple headspace and UNIFAC predictions and literature values. The successful comparison gives an indication of the GLC as a rapid, simple and accurate method for studying the thermodynamics of the interaction of a volatile solute with a non volatile solvent.
- Full Text:
Organics-biodiesel systems phase equilibrium computation : part 2
- Ntaka, Loyiso, Muzenda, Edison
- Authors: Ntaka, Loyiso , Muzenda, Edison
- Date: 2011
- Subjects: Activity coefficients , Phase equilibrium , Volatile organic compounds
- Type: Article
- Identifier: uj:6087 , http://hdl.handle.net/10210/10939
- Description: In part 1, the infinite dilution activity coefficients of 30 organics in methyl linoleate and methyl palmitate were reported. This work tested the application of Modified UNIFAC (Dortmund) as a molecular thermodynamic method in organic – polymer systems phase equilibrium estimation. Infinite dilution activity coefficients of 30 volatile organic compounds (VOCs) in methyl oleate and ethyl stearate were predicted using the Modified UNIFAC (Dortmund) procedure. The infinite dilution activity coefficients obtained in this study compare very well with literature findings. For example the calculated infinite dilution activity coefficients for benzene and toluene agree to about ±5% with those obtained from headspace and dynamic gas–liquid chromatographic measurements. biodiesel polymers were found to absorb ethers and aromatics better compared to other VOC family groups.
- Full Text:
- Authors: Ntaka, Loyiso , Muzenda, Edison
- Date: 2011
- Subjects: Activity coefficients , Phase equilibrium , Volatile organic compounds
- Type: Article
- Identifier: uj:6087 , http://hdl.handle.net/10210/10939
- Description: In part 1, the infinite dilution activity coefficients of 30 organics in methyl linoleate and methyl palmitate were reported. This work tested the application of Modified UNIFAC (Dortmund) as a molecular thermodynamic method in organic – polymer systems phase equilibrium estimation. Infinite dilution activity coefficients of 30 volatile organic compounds (VOCs) in methyl oleate and ethyl stearate were predicted using the Modified UNIFAC (Dortmund) procedure. The infinite dilution activity coefficients obtained in this study compare very well with literature findings. For example the calculated infinite dilution activity coefficients for benzene and toluene agree to about ±5% with those obtained from headspace and dynamic gas–liquid chromatographic measurements. biodiesel polymers were found to absorb ethers and aromatics better compared to other VOC family groups.
- Full Text:
Solubility of organics in water and silicon oil: a comparative study
- Authors: Muzenda, Edison
- Date: 2011
- Subjects: Volatile organic compounds , Solubility , Water , Silicon oil , Activity coefficients , Henry’s Law constants
- Type: Article
- Identifier: uj:5321 , http://hdl.handle.net/10210/8228
- Description: The aim of this study was to compare the solubility of selected volatile organic compounds in water and silicon oil using the simple static headspace method. The experimental design allowed equilibrium achievement within 30 – 60 minutes. Infinite dilution activity coefficients and Henry’s law constants for various organics representing esters, ketones, alkanes, aromatics, cycloalkanes and amines were measured at 303K. The measurements were reproducible with a relative standard deviation and coefficient of variation of 1.3x10-3 and 1.3 respectively. The static determined activity coefficients using shaker flasks were reasonably comparable to those obtained using the gas liquid - chromatographic technique and those predicted using the group contribution methods mainly the UNIFAC. Silicon oil chemically known as polydimethysiloxane was found to be better absorbent for VOCs than water which quickly becomes saturated. For example the infinite dilution mole fraction based activity coefficients of hexane is 0.503 and 277 000 in silicon oil and water respectively. Thus silicon oil gives a superior factor of 550 696. Henry’s law constants and activity coefficients at infinite dilution play a significant role in the design of scrubbers for abatement of volatile organic compounds from contaminated air streams. This paper presents the phase equilibrium of volatile organic compounds in very dilute aqueous and polymeric solutions indicating the movement and fate of chemical in air and solvent. The successful comparison of the results obtained here and those obtained using other methods by the same authors and in literature, means that the results obtained here are reliable.
- Full Text:
- Authors: Muzenda, Edison
- Date: 2011
- Subjects: Volatile organic compounds , Solubility , Water , Silicon oil , Activity coefficients , Henry’s Law constants
- Type: Article
- Identifier: uj:5321 , http://hdl.handle.net/10210/8228
- Description: The aim of this study was to compare the solubility of selected volatile organic compounds in water and silicon oil using the simple static headspace method. The experimental design allowed equilibrium achievement within 30 – 60 minutes. Infinite dilution activity coefficients and Henry’s law constants for various organics representing esters, ketones, alkanes, aromatics, cycloalkanes and amines were measured at 303K. The measurements were reproducible with a relative standard deviation and coefficient of variation of 1.3x10-3 and 1.3 respectively. The static determined activity coefficients using shaker flasks were reasonably comparable to those obtained using the gas liquid - chromatographic technique and those predicted using the group contribution methods mainly the UNIFAC. Silicon oil chemically known as polydimethysiloxane was found to be better absorbent for VOCs than water which quickly becomes saturated. For example the infinite dilution mole fraction based activity coefficients of hexane is 0.503 and 277 000 in silicon oil and water respectively. Thus silicon oil gives a superior factor of 550 696. Henry’s law constants and activity coefficients at infinite dilution play a significant role in the design of scrubbers for abatement of volatile organic compounds from contaminated air streams. This paper presents the phase equilibrium of volatile organic compounds in very dilute aqueous and polymeric solutions indicating the movement and fate of chemical in air and solvent. The successful comparison of the results obtained here and those obtained using other methods by the same authors and in literature, means that the results obtained here are reliable.
- Full Text:
Temperature dependence of limiting activity temperature coefficients in C18 Ester solvents - part 2
- Scheepers, Jacques J., Muzenda, Edison
- Authors: Scheepers, Jacques J. , Muzenda, Edison
- Date: 2013
- Subjects: Activity coefficients , Increasing temperature , Biodiesel esters , Solubility
- Type: Article
- Identifier: uj:4961 , http://hdl.handle.net/10210/13062
- Description: This work continued our focus on the influence of temperature on the activity coefficients of biodiesel ester/ VOC (volatile organic compound) interactions. The VOC families studied in this work were alkenes, alkynes, halogenated alkanes and amines. Solubility predictions in the form of infinite dilution activity coefficients were made using the Modified UNIFAC Dortmund group contribution model, and were computed using a Microsoft Excel spreadsheet specifically designed for this purpose. It was found that, with the exception of cyclopentadiene, alkene activity coefficients decreased slightly with increasing temperature thereby generally deviating from ideality. Solubility of alkyne interactions with unsaturated esters increased with increasing temperature, but decreased with saturated ester interactions for the terminal alkynes. With the exception of trichloromethane halogenated alkane activity coefficients decreased with increasing temperature, thus deviating from ideality. Interactions of esters with amines yielded a decrease in activity coefficients with increasing temperature, hence also deviating from ideality.
- Full Text:
- Authors: Scheepers, Jacques J. , Muzenda, Edison
- Date: 2013
- Subjects: Activity coefficients , Increasing temperature , Biodiesel esters , Solubility
- Type: Article
- Identifier: uj:4961 , http://hdl.handle.net/10210/13062
- Description: This work continued our focus on the influence of temperature on the activity coefficients of biodiesel ester/ VOC (volatile organic compound) interactions. The VOC families studied in this work were alkenes, alkynes, halogenated alkanes and amines. Solubility predictions in the form of infinite dilution activity coefficients were made using the Modified UNIFAC Dortmund group contribution model, and were computed using a Microsoft Excel spreadsheet specifically designed for this purpose. It was found that, with the exception of cyclopentadiene, alkene activity coefficients decreased slightly with increasing temperature thereby generally deviating from ideality. Solubility of alkyne interactions with unsaturated esters increased with increasing temperature, but decreased with saturated ester interactions for the terminal alkynes. With the exception of trichloromethane halogenated alkane activity coefficients decreased with increasing temperature, thus deviating from ideality. Interactions of esters with amines yielded a decrease in activity coefficients with increasing temperature, hence also deviating from ideality.
- Full Text:
- «
- ‹
- 1
- ›
- »