Separation Of Toluene And Hexane By Distillation And Gas .
Separation of Toluene and Hexane byDistillation and Gas ChromatographyPart 1, p. 133 : Simple distillation.(4th Ed. p. 129)Part 2, p. 133: Fractional distillation (use same procedure as simple).Part 3, p. 206: Separation by gas chromatography (4th Ed. p. 202)Important Concepts Theory of Distillation Distillation Setup/Equipment Dalton’s Law & Vapor Pressure Raoult’s Law Theoretical Plates Fractional vs. Simple Distillation Technique of Gas ChromatographyChem 341 - Distillation1
History of Distillation†Evidence of distilled spirits in Babylonia (ca 4000 BC)†alembic†Jabir ibn Hayyan [akaGeber] (721-815) Bornin Persia (Iranian).chemist, alchemist,astronomer,philosopher, physician.†Oil RefineriesChem 341 - DistillationPhoto Source: † - Wikipidia2
Distillation TheoryVapor Pressure: a measure of the ease with which a molecule escapesfrom the liquid phase into the gas phase.High vapor pressuremore molecules in the gas phaseNote: Vapor pressure increases with temperature!Volatile compound(Low boiling point)Dalton’s Law: the total pressure is equal to the partial pressures ofeach component in the gas phase [Ptot Px Py ].Temperature oCRaoult’s Law: the vapor pressure (Px) depends on the mole fraction (Nx) of eachcomponent [ Px Pxo N x], where Pxois the vapor pressure of pure X ata given temperature.nXNx 120nX nY nZ Vapor line describes the compositionVapor line 110of the gas phase.100B90ALiquid line8001002575505075251000Liquid line describes the compositionof the liquid and the b.p. Mole % TolueneMole % BenzeneTemperature composition diagramFor a mixture of benzene and tolueneChem 341 - Distillation At 89 oC the liquid in the stillpot is 50:50 benzene:toluene, whereas the vapor phase is 80:20 benzene:toluene. Thus, the vapor phase is enriched in thelower b.p. component.3
Procedural Details- Follow procedure on p. 133 (4th ed. p. 129) for both fractional and simple distillation,just use different apparatus. Work in pairs, one student does simple and the other doesfractional.- Use hexane instead of cyclohexane.- Do not use a packed Hempel column for fractional distillation, instead use the apparatusdescribed here.- Collect three fractions for each distillation .Fraction 1: collect hexane until temperature drops; note that the temp may not beaccurate for the simple distillation.Fraction 2: collect until temperature rapidly increases to 100 oC; note that thetemp may never reach that for the simple distillation.Fraction 3: collect after 100 oC until the still pot is nearlyempty. Do not distill to dryness.- Record b.p. range for each fraction.- Perform GC on original mixture and all three fractions; getcopies of your partners data for the worksheet.Chem 341 - DistillationTolueneb.p. 110 oCHexaneb.p. 69 oC4
Simple Distillation ApparatusDigitalThermometerDistillation HeadTwo ClampsThermometer AdapterStillpot w/stirbarVacuum AdapterRing StandCondenserH2O OutCloth HeatingMantleStir plateChem 341 - DistillationH2O InVariacYellowKeck clipsCollectionFlaskThermometerPosition5
Fractional Distillation ApparatusThermometerDistillation HeadRing StandDistillation HeadCollection FlaskThermometerH2O OutVigreuxColumnH2O InAir OutletTwo ClampsVigreux columnYellow Keck clipsCloth Heating MantleStir plateStillpot w/stirbarChem 341 - Distillation6
Why is fractional distillation more efficient?The vigreux column provides more surface area for condensation to occur. At eachcondensation event the vapor is enriched in the low b.p. component and the liquid isenriched in the high b.p. component. We call these surfaces where condensation occurstheoretical plates, so the more theoretical plates, the more efficient your separation.In order to get a good separation (i.e. high efficiency) we must distill at amoderate rate. Therefore we cannot add too much energy (i.e. heat).80 oCImagine if 100 people were in a 2 kilometer race. If everyone were to getinto a car and drive, then they would all arrive very close to each other.However, if they all ran instead, then their would be a good distribution ofrunners over the course of the race, and the fastest ones would arrive wellahead of the slower runners (i.e. they would be separated).100 oCrefluxbenzene tolueneChem 341 - DistillationA simple distillation has fewer theoretical plates, so the temperaturegradient is not as dispersed and the separation is poorer.Only use the simple distillation for compounds that havea large difference in b.p. (e.g. purifying sea water).7
Why is fractional distillation more efficient?80 oC100 oCrefluxbenzene tolueneChem 341 - Distillation
Gas ChromatographyTop of ovenHeating ElementGC columnInjector port†The column is packed with tiny beads that are coatedwith a viscous liquid. The vaporized compound travelsdown the column and adsorbs onto the column packing.Normally the carrier gas (or eluant) is helium.Use injector port AABRetentionTimeGC chromatogramRelativeAreaDo not touch the dialsPrinterGC with He tankWhich peak is due to toluene?Chem 341 - DistillationPhoto Source: † - Wikipidia9
Safety Issues- hexane and toluene are highly flammable.- Never heat a closed distillation system. Always make sure thereis a vacuum or air outlet.- the glassware will get very hot.- do NOT distill to dryness as this may leave solid residues, whichcould explode if there were peroxides present.- the GC needles are very sharp and delicate. Inject carefully soas not to bend the needleChem 341 - Distillation10
The column is packed with tiny beads that are coated with a viscous liquid. The vaporized compound travels down the column and adsorbs onto the column packing. Normally the carrier gas (or eluant) is helium. Printer GC with He tank Top of oven Use injector port A Do not touch the dials Heating Element Injector port GC column GC chromatogram
Fractional Distillation and Gas Chromatography Background Distillation The previous lab used distillation to separate a mixture of hexane and toluene based on a difference in boiling points. Hexane boils at 69 C and toluene boils at 110 C. In an idealized situation, you could imagine heating a mixture of hexane and toluene .
Activity of hexane extract of 21 days old wheat grass was very low (16%). With Streptococcus pneumoniae, activity of hexane extract of 7 days old wheat grass was 75.69%. The activity increased with hexane extract of 14 days old wheat grass (87.90%) and decreased with hexane extract
the oil is substantially insoluble up to 150 bar. Although the behavior of the ternary system CO2-hexane-oil has not been studied, we assumed that experimental data derived from the two binary systems CO2-hexane and CO2-oil are applicable; i.e., hexane and oil solubilities in CO2 are not affected by the simultaneous presence of each other.
by Mohrig, Alberg, Hofmeister, Schatz, Hammond Composition after 1 “cycle” of l g 52% hexane, 48% pentane Composition after 2 “cycles” of l g 24% hexane, 76% pentane Composition after 3 “cycles” of l g 11% hexane, 89% pentane Composition after 4 “cycles” of l g 3% hexane, 97% pentane
Similarly toluene can be released from volatilisation and decomposition of waste that actually contains toluene compounds (paint thinners, solvents, nail polish, etc.). 1.2 Health effects associated with exposure to benzene and toluene . Benzene is a well-k
95% toluene Relative volatility of benzene to toluene 2.3 Reflux ratio 2 Molecular weight of benzene, MW lk 78.114 kg/kmol Molecular weight of toluene, MW Hk 92.141 kg/kmol Boiling point of benzene 80.1 0C Boiling point 0of toluene 110.6 C Vapour density of benzene 2.77kg/m3 Vapou density
Feb 23, 2011 · 5 Oil and Grease Method Evolution EPA 1664 ‗dirty‘ water Hexane extract Extract in drying pan Evaporate Hexane Mass corresponds to concentration of extractables Time 3 - 4 hours LLE n-Hexane use introduces four issues: 1. Flammable solvent 2. Known neurotoxin 3. Analytical time increa
hexane in gasoline is released into the air at service stations and in automobile exhaust. Some people may also be exposed by spilling gasoline on their skin. The concentration of . n-hexane in the air in Chicago was recently measured and contained 2 parts . n-hexane per 1 billion parts air (2 ppb). n-
