Research Journal of Chemical Sciences ISSN X Vol. 5(6), 64-72, June (2015)

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1 Research Joural of Chemcal Sceces ISSN 3-606X Vol. 5(6), 64-7, Jue (05) Res. J. Chem. Sc. Vapor-Lqud Equlbrum Data Predcto by Advaced Group Cotrbuto Methods for a Bary System of Cyclopetyl methyl ether ad Acetc acd at Atmospherc Pressure Abstract Parsaa V.M.,, * ad Parh S.P. School of Egeerg, RK Uversty, Raot, INDIA Chemcal Egeerg Departmet, V.V.P. Egeerg College, Guarat Techologcal Uversty, Ahmedabad, INDIA Avalable ole at: Receved 7 th Jue 05, revsed 3 th Jue 05, accepted 7 th Jue 05 The sobarc vapour-lqud equlbrum data predctos for the bary system of cyclopetyl methyl ether ad acetc acd have bee obtaed usg UNIFAC method ad modfed UNIFAC Dortmud method. Group detfcato s doe wth Dortmud Data Ba ad the same has bee cofrmed by artst free software. The teracto parameters the UNIFAC method ad modfed UNIFAC Dortmud method, for the ether group (-CH 3 O) ad acd (-COOH), are used to predct VLE data. Thermodyamc cosstecy of the predcted VLE data has bee checed by the Hergto method. The predcted data have bee correlated wth Va Laar, Wlso ad NRTL actvty coeffcet models. The bary teracto parameters of models had bee obtaed by regresso. The predcted VLE data of UNIFAC method ft much more accurately tha that of modfed UNIFAC Dortmud method by these actvty coeffcet models Va Laar, Wlso ad NRTL. Keywords: Vapor-lqud equlbrum, cyclopetyl methyl ether, acetc acd, UNIFAC method, modfed UNIFAC Dortmud method. Itroducto Tradtoal solvets play a ey role the chemcal process dustres ad hece they are maor cotrbutor to the cocers related to ther mpact o evromet, health ad safety because most of the solvets are flammable, volatle ad toxc. The solvets that have reduced or o toxcty to health ad evromet compared to the tradtoal solvets are called gree solvets. These gree solvets may provde a attractve alteratve to the tradtoal solvets. Cyclopetyl methyl ether (CPME) s cosdered to be oe of the gree solvets whch has hgh bolg pot (379.5 K) ad preferable characterstcs such as low peroxde formato, hgh hydrophobcty, relatve stablty uder acdc ad basc codtos, hgh bolg pot ad low meltg pot, low heat of vaporzato, arrow exploso area ad low solublty of salts. Due to such characterstcs CPME s preferred as a alteratve to other ethereal solvets such as tetrahydrofura, -methyl tetrahydrofura, doxae (carcogec), ad, - dmethoxyethae, whch are hazardous to huma health ad evromet. The recovery of acetc acd from water has become dustral problem of publc cocer because ths separato process has a maor fluece o ecoomy of products, resource utlzato ad mportat meags for evrometal protecto. Hogxu Zhag, Guagyu Lu, Che L, et al. measured lqud-lqud equlbra of water + acetc acd + Cyclopetyl methyl ether (CPME) system at dfferet temperatures ad cocluded that CPME would be a good substtute for covetoal orgac solvets to separate acetc acd from water by the method of lqud lqud extracto followed by heteroazeotropc dstllato 3. After lterature survey t s foud that vapour-lqud equlbrum data for CPME + Acetc acd system whch s essetal for the desg of dstllato colum for separatg CPME ad acetc acd from ther mxture does ot exst the lterature. So vestgato o VLE data of ths bary system becomes ecessary. The expermetal determato of VLE data requres sophstcated ad sutable VLE apparatus ad composto measuremet strumets such as gas chromatograph, refractometer, spectrophotometer, etc. So ths procedure s very costly ad tme-cosumg. Numercal smulatos usg group cotrbuto methods provde a alteratve to expermetal measuremet of VLE data. The am of ths paper s to predct VLE data for CPME wth acetc acd at atmospherc pressure. Advaced Group Cotrbuto Methods: Relable values of the propertes of materals are ecessary for the desg of dustral processes. The owledge of physcal propertes of fluds s essetal the desg of may ds of products, processes, ad dustral equpmet 4. The vapour-lqud equlbrum (VLE) data are essetal for the desg of chemcal ad separato processes. Whe expermetal bary data are avalable, phase equlbrum behavour s easly modelled wth the help of cubc equato of state (usg fugacty coeffcet data) ad local composto g E models (usg actvty coeffcet data). Whe lttle or o expermetal data are avalable, group Iteratoal Scece Cogress Assocato 64

2 Research Joural of Chemcal Sceces ISSN 3-606X Vol. 5(6), 64-7, Jue (05) Res. J. Chem. Sc. cotrbuto (GC) methods ca be employed to predct the phase equlbrum uder specfed codtos of temperature ad composto 5,6. So predcto of thermodyamc propertes s mportat chemcal process ad product desg. Varous GC methods are avalable for the predcto of VLE data. Some examples of GC methods whch have bee developed for the estmato of propertes of pure compouds clude those publshed by Jobac ad Red 7, Lyderse 8, Ambrose 9, Costatou ad Ga 0 ad Marrero ad Ga,. O the other had, may GC based property models have also bee developed to predct propertes of mxtures maly to predct the o-dealty of the lqud phase usg actvty coeffcets whch cludes ASOG 3,4, Orgal UNIFAC 5, Modfed UNIFAC Dortmud 6 ad PSRK 7. I the preset wor, well ow ad establshed group-cotrbuto methods such as UNIFAC method ad modfed UNIFAC Dortmud method are employed to predct lqud phase actvty coeffcets for bary mxtures of CPME ad acetc acd. UNIFAC method ad modfed UNIFAC Dortmud methods: The geeral UNIFAC equato s as follows wth the combatoral ad resdual cotrbutos: l + l ( combatoral ) l ( resdual ) () The combatoral part, Φ z θ Φ l (combatoral) l + q l + l x l () x Φ x Where, z l ( r q ) ( r ) (3) θ Φ qx q x r x r x () r ν R (6) q () ν Q (7) V R w 5.7 (8) (4) (5) A.5x0 w Q (9) 9 () Where: ν, always a teger, s the umber of groups of type molecule. Group parameters R ad Q are obtaed from the va der Waals group volume ad surface areas V w ad A w, gve by Bod 4. The value of parameter Z s tae as 0. Ad the resdual part, (resdual) () () ( l Γ l Γ ) l ν (0) Where, θ mψm l Γ Q l θ Ψ () m m m m θ Ψ m Where, the group area fracto θ ad group mole fracto X m m are gve by the followg equatos: QmXm θm () Q X ( ) νm x X m ( ) ν x (3) Where, the group-teracto parameter followg equato: Ψ m Ψ m s gve by the U m U a m exp exp (4) RT T Where: U m s a measure of the eergy of teracto betwee group m ad. Note that a m has ut of Kelv ad a m a m. I the Orgal UNIFAC model, the teracto parameters are cosdered to be depedet of temperature. Therefore, quattatve predctos of excess ethalpes, H E could ot be obtaed. I order to mprove ths ad other thgs, the modfed UNIFAC Dortmud method was developed. The usage of modfed UNIFAC Dortmud method leads to much better results. Ths meas that the troducto of temperaturedepedet parameters allows a more relable temperature extrapolato ad the exteso of the rage of applcablty 8,9. I both UNIFAC method ad modfed UNIFAC Dortmud method, there s a dfferece both combatoral ad resdual part. These dffereces are gve the followg equatos. I modfed UNIFAC Dortmud method, equato- ad equato-4 of UNIFAC method are replaced by equato-5 Iteratoal Scece Cogress Assocato 65

3 Research Joural of Chemcal Sceces ISSN 3-606X Vol. 5(6), 64-7, Jue (05) Res. J. Chem. Sc. ad equato-9 as descrbed below. ' ' V V l + + (combatoral) V l V 5q l F F (5) Where, r V x r (6) q F (7) x q ' r V (8) 3 4 x r ad Ψ m 3 4 am + bmt + c T T m exp (9) I addto to that, the resdual part, temperature depedet teracto parameters are used where they have a logarthmc ad quadratc depedecy towards temperature. Due to ths temperature depedecy, the predctos of VLE, H E ad have mproved sce t s based o more expermetal data. The modfed UNIFAC Dortmud method ca also extrapolate relably the predctos of VLE at hgher temperatures compared to the Orgal UNIFAC 9. Group detfcato of the compouds: Group cotrbuto methods predct propertes of pure compouds or mxtures based o the groups exstg the compouds so correct detfcato of groups s very essetal. Group detfcato for UNIFAC method s doe usg the data gve the lterature 4 ad for modfed UNIFAC Dortmud method t s doe usg the data gve the lterature 8. The detfed groups are preseted table- ad table- respectvely. The detfed groups have bee verfed wth Dortmud data ba by usg artst free software. Bary teracto parameters (BIPs): Bary teracto parameters (a m ) for UNIFAC method have bee tae from the lterature 4 ad (a m, b m, ad c m ) for modfed UNIFAC Dortmud method have bee tae from the lterature 8,9,0 whch are preseted table-3 ad table-4 respectvely. Calculato of VLE data usg group cotrbuto methods: The VLE data for bary system CPME ad acetc acd are calculated through a spread sheet whch temperature T ad x are gve as put ad ad are calculated usg group cotrbuto methods as descrbed the precous sectos. sat sat Usg Atoe equato-0, p ad p are calculated, the total pressure P s calculated ad correct temperature T s foud out by regresso usg equato-3. The calculated data are preseted table-5 ad table-6 for UNIFAC method ad modfed UNIFAC Dortmud method respectvely. Table- Group detfcato for CPME ad acetc acd for UNIFAC method Molecule () CPME () Name Group o. * v () R Q M S CH CH CH 3 O CH COOH Acetc acd () * MMa Group o., SSecodary Group o. Table- Group detfcato for CPME ad acetc acd for modfed UNIFAC Dortmud method Molecu le () CPME () Group Name o. * v () R Q M S c-ch c-ch CH 3 O CH COOH Acetc acd () * MMa Group o., SSecodary Group o. Table-3 BIPs for CPME ad acetc acd for UNIFAC method Group CH 3 CH CH CH 3 O COOH CH CH CH CH 3 O COOH The Atoe equato, l p B sat A (0) T + C Where pressure s Pa ad temperature s Kelv. The costats A, B, ad C of Atoe equatos of CPME ad acetc acd are lsted table-7. Thermodyamc Cosstecy Test: The thermodyamc cosstecy of the predcted VLE data for the bary system s checed by sem-emprcal Hergto method. I ths method, the values for D ad J are foud out by equato- ad equato- respectvely. If the value of D J s ot larger tha 0 the the predcted VLE data are sad to be thermodyamcally cosstet. The values of D J for the Iteratoal Scece Cogress Assocato 66

4 Research Joural of Chemcal Sceces ISSN 3-606X Vol. 5(6), 64-7, Jue (05) Res. J. Chem. Sc. bary system are lsted table-8. x x 0 00 x x 0 l l dx dx D () J T T T m max m 50 () Data Reducto Usg g E Models: The predcted VLE data are correlated by varous models such as Va Laar, Wlso ad NRTL 4,5. The vapor pressures of pure compoets are calculated by equato-0. By the mmzato of the obectve fucto %AAD (δp), the bry teracto parameters are obtaed for these models whch are used to mmze error by the regresso procedure. (%AAD absolute average devato ad represets o. of predcted data pots). Smlarly AAD (δt) ad AAD (δy) are calculated by equato-4 ad equato-5 respectvely. The pre ad cal subscrpts represet the predcted ad calculated values respectvely. 00 %AAD (δp) AAD (δt) AAD (δy) P,pre. P P,pre. T T,pre. y y,pre.,cal.,cal.,cal. (3) (4) (5) Table-4 BIPs for CPME ad acetc acd for modfed UNIFAC Dortmud method Group m a m b m c m a m b m c m CH 3 CH 3 O CH 3 COOH CH 3 c-ch, c-ch CH 3 O c-ch CH 3 O c-ch, c-ch COOH c-ch, c-ch Table-5 VLE data for CPME ad acetc acd bary system at atmospherc pressure by UNIFAC method T/K x y Table-6 VLE data for CPME ad acetc acd bary system at atmospherc pressure by modfed UNIFAC Dortmud method T/K x y Iteratoal Scece Cogress Assocato 67

5 Research Joural of Chemcal Sceces ISSN 3-606X Vol. 5(6), 64-7, Jue (05) Res. J. Chem. Sc. Table-7 Atoe equato costats Compoud Atoe costats temperature A B C rage/k CPME to 395 AA to 395 Table-8 Thermodyamc cosstecy chec D J D-J Method UNIFAC modfed UNIFAC Dortmud The bary teracto parameters, correlated from predcted VLE data by UNIFAC method ad modfed UNIFAC Dortmud method, are show table-9 ad table-0 respectvely. α whch s a characterstc costat of the oradomess for the bary system s recommeded as 0.3 for ths bary system because t belogs to type I system accordg to the defto gve the lterature 5. The comparso of predcted data by UNIFAC method ad modfed UNIFAC Dortmud method wth calculated T-x -y data by Va Laar, Wlso, ad NRTL models for the bary system CPME () + acetc acd () at atmospherc pressure s gve through fgure- to fgure-6. Table-9 Correlated model BIPs from predcted data by UNIFAC method Model Va Laar Wlso NRTL Bary Parameter A A a a b b AAD ( T) AAD ( y) Table-0 Correlated model BIPs from predcted data by modfed UNIFAC Dortmud method Model Va Laar Wlso NRTL Bary Parameter A A a a b b AAD ( T) AAD ( y) Fgure- T-x -y dagram calculated by Va Laar ad predcted by UNIFAC method Iteratoal Scece Cogress Assocato 68

6 Research Joural of Chemcal Sceces ISSN 3-606X Vol. 5(6), 64-7, Jue (05) Res. J. Chem. Sc. Fgure- T-x -y dagram calculated by Wlso ad predcted by UNIFAC method Fgure-3 T-x -y dagram calculated by NRTL ad predcted by UNIFAC method Iteratoal Scece Cogress Assocato 69

7 Research Joural of Chemcal Sceces ISSN 3-606X Vol. 5(6), 64-7, Jue (05) Res. J. Chem. Sc. Fgure-4 T-x -y dagram calculated by Va Laar ad predcted by modfed UNIFAC Dortmud method Fgure-5 T-x -y dagram calculated by Wlso ad predcted by modfed UNIFAC Dortmud method Iteratoal Scece Cogress Assocato 70

8 Research Joural of Chemcal Sceces ISSN 3-606X Vol. 5(6), 64-7, Jue (05) Res. J. Chem. Sc. Fgure-6 T-x -y dagram calculated by NRTL ad predcted by modfed UNIFAC Dortmud method From fgure- to fgure-6, t ca be see that sobarc VLE data predcted by UNIFAC method ad modfed UNIFAC Dortmud method are very well represeted by Va Laar, Wlso ad NRTL models. Cocluso The VLE data for the bary system CPME wth acetc acd have bee predcted at atmospherc pressure usg UNIFAC method ad modfed UNIFAC Dortmud method. The actvty coeffcet models Va Laar, Wlso ad NRTL have bee foud capable of accurately fttg the predcted VLE data by UNIFAC method ad modfed UNIFAC Dortmud method. However, they fal the cosstecy test by Hergto. Azeotrope formato s foud for ths system. Nomeclature P - Absolute pressure, Pa T - Absolute temperature, K θ - Surface area fracto of compoud Φ - Volume fracto of compoud r - Relatve Va der Waals volume of compoud q - Relatve Va der Waals surface area of compoud Q - Relatve Va der Waals surface area of subgroup R - Relatve Va der Waals volume of subgroup Γ - Temperature depedat tegrato costat θm - Surface area fracto of subgroup m X m - Mole fracto of subgroup m Ψ - Group-teracto parameter V - Volume/mole fracto of compoud the mxture F - Surface area fracto of compoud the mxture V - Modfed volume/mole fracto of compoud the mxture (modfed UNIFAC Dortmud method) l - Natural logarthm (base e) log - Logarthm (base 0) x - Lqud phase mole fracto of th speces y - Vapor phase mole fracto of th speces - Actvty coeffcet of th speces H E - Excess ethalpy A - Adustable parameter (Va Laar Model) λ - Iteracto parameter (Wlso Model) Λ - Adustable parameter (Wlso Model) α -The o-radomess of the flud emprcal parameter τ - Adustable parameter (NRTL Model) A, B, C- Atoe equato costats Superscrpts E - Excess property sat - Saturated property value - Property at fte dluto cocetrato Subscrpts - Compoet Iteratoal Scece Cogress Assocato 7

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