Synthesis of Epichlorohydrin from Glycerol. Hydrochlorination of Glycerol

Transcription

1 Synthesis of Epichloohydin fom yceol. Hydochloination of yceol Geogy Dmitiev S.*, Leonid Zanaveskin N. Fedeation State Unitay Oganization "Kapov Institute of Physical hemisty" Russia, Moscow, Minusinskaya st., In the pesent study the investigation of the glyceol hydochloination pocess has been pesented. It involves the steps of esteification and hydochloination. The kinetic paametes of the eactions have been detemined. It is also shown that the wate concentation incease in the eaction mixtue esults in the eduction of hydochloination ates. It has been explained by the phenomenon of solvation. The solvation effect is enteed into the kinetic equation. Intoduction At pesent the setting up of poduction facilities fo the poduction of valuable chemicals fom the enewable feedstock is one of the most impotant tends in the development of chemical industy. Synthesis of biodiesel fom the vegetable oil is one of these tends, with glyceol being the by-poduct of this pocess 10% fom the amount of poduced biodiesel. At the beginning of XXI centuy the apid development of the biodiesel poduction in the fist yeas esulted in ovesupply of cheap glyceol into the maket. Theefoe the use of glyceol fo the poduction of valuable chemicals Pagliao, 2008 has become economically feasible. The synthesis of epichloohydin EP fom glyceol has been one of these outes. The poduction of EP based on popylene has been pacticed since It suffes fom some undesiable featues, such as aw dependence on the oil, low selectivity of eactions and consequently significant amount of toxic oganic withdawal up to 0.5 t/t EP and lage amount of polluted sewage up to 54 m 3 /t EP. These factos pompted the seach fo altenative solutions that ae moe envionmentfiendly. In the fist step, is hydochloinated to the mixtue of 1,3-dichloohydin α,γ-d and 1,2-dichloohydin α,β-d. In the second step, the mixtue of dichloohydins is dehydochloinated to EP. The influence of wate on the eaction ate is one of the main poblems at the hydochloination step that has been ecently examined by us. The detemination of the eaction kinetics, finding easons fo the eaction ate eduction with the wate concentation incease and the evaluation of quantitative elationship of the above phenomenon with the kinetics have been the taget of ou investigation.

2 Equipment, analyses and opeating conditions The investigation of esteification between glyceol and acetic acid was studied in batch mode in a glass eacto. It had 50 ml volume and it was equipped with a stie, an electic heate, a eflux condense and a lap fo output samples. yceol monochloohydin satuated with hydogen chloide up to 0.7% by weight was heated up to equied tempeatue in the ange of 59 98ºС. Then acetic acid was injected into the eacto. The samples of eaction mixtue wee outputted fom time to time duing one un. The investigation of hydochloination was studied in the wide ange of wate concentation fom 1.5 to 13 mol/l in continuous mode in a glass eacto. The volume of eacto was 30 ml. It was equipped with a stie, an electic heate and a eflux condense. The eaction poducts wee emoved continuously. Joint detemination of hydochloic acid and acetic acid was caied out with the help of conductivity measuement device. Oganic compounds wee analyzed by gas chomatogaph. Esteification The hydochloination of glyceol is catalyzed by caboxylic acids, fo example, acetic acid. In this case thee ae estes among the eaction poducts. It means that thee ae eactions of esteification in the eaction mixtue. It can be epesented accoding to the scheme: The modal concentation dependences on time wee obtained in the expeiments on these eactions study. The eaction ates ae supposed to be descibed by the following equations Lebedev, 1988: fo the esteification of glyceol: 1 СAc СH = k1 С С 1 K eq1 fo the esteification of α-monochloohydin: 2 = k 2 С Сα MAc СH Сα M 2 K eq2

3 Ln k -5-5,5-6 -6,5-7 -7,5-8 -8,5-9 -9,5-10 1/T ,65 2,7 2,75 2,8 2,85 2,9 2,95 3 3, Figue 1. The Ahenius plot fo the eactions: 1 esteification of glyceol; 2 esteification of α-monochloohydin. Using these equations the kinetic constants k 1 and k 2 wee calculated with the accuacy moe than 96%. The Ahenius plot is pesented in Figue 1. The analysis of expeimental data allowed to calculate values of the constants: fo the glyceol esteification: 58500± e k1 = 10, [l 2 s 2 /mol 2 ] 3 K eq1 = 1,89 4 fo the α-m esteification: 53000± e =, [l 2 s 2 /mol 2 ] 5 k2 10 K eq2 = 1,00 6 Hydochloination Hydochloination of glyceol is descibed by the following scheme:

4 k 10 5, l/mol s 4,5 4,0 3,5 3,0 117ºС 2,5 2,0 110ºС 1,5 110ºС 1,0 90ºС 0,5 80ºС 0,0 0,4 0,6 0,8 1,0 1,2 1,4 1,6 1,8 2,0 2,2 2,4 2,6 2,8 3,0 С Н2О /С Figue 2. Dependence of kinetic constant on the mola atio between wate and hydogen chloide fo the eaction of α-m fomation. Tempeatues: 1-117ºС; 2-110ºС; 3-100ºС; 4-90ºС; 5-80ºС. These eactions being ones of bimolecula nucleophilic substitution S N 2 Lebedev, Peliminay themodynamic analysis showed that these eactions ae ievesible. Theefoe the hydochloination of glyceol is to be descibed by the following equation: = k С 7 But implementation of this equation esulted in some unexpected data pesented in Figue 2. The obtained esults showed that the kinetic constant educes with the incease of the mola ation between wate and hydogen chloide H /. The obseved facts may be explained by the phenomenon of solvation Reichadt, Thee ae pola oganic compounds in the eaction medium such as glyceol, monochloohydins, dichloohydins. They may oientationaly inteact and also fom hydogen bonds both with each othe and with molecules of wate. But on the othe hand thee ae chloine anions in the same mixtue. They have small adius in compaison with oganic compounds and they bing negative chages. The molecules of wate may solvate both glyceol chloohydins and chloine anions. But it is clea that the latte ae solvated the most stongly. When the molecules of wate inteact with such solvated chloine anions it is necessay to ovecome supplementay enegy baie in ode to destoy solvation sphee. The moe molecules of wate solvate one chloine anion the bigge enegy baie is and the less kinetic constant is.

5 One may say that chloine anions solvated with one, two, thee o moe molecules of wate ae pesented as diffeent chemical compounds. Each of them has its own kinetic constant in equation 7. Data pesented in Figue 2 show the dependence of the kinetic constant on the eacting compound type. Mathematical teatment of expeimental data allowed to detemine equations which descibe eaction ates of fomation of α-m 8 and β-m 9 fom atio H / : ± T 3 = ± T 4 =.2 10 The investigation of hydochloination of glyceol in the pesence of acetic acid esulted in analogous dependences. The ate of catalytic eaction was calculated as the diffeence between the obseved ate and the non-catalytic ate. It was detemined that catalytic eactions of α-m 10 and β-m 11 fomations ae descibed by the following equations: ± T 5 = С ± T 6 = Also it was obtained that the non-catalytic ate was less then 3% of the obseved ate. That is why the investigation of α,γ-d and α,β-d fomation eactions wee studied only in the pesence of acetic acid. The following equations wee obtained fo α,γ-d 12 and α,β-d 13: ± T 7 = α M 1 С ± T 8 = α M

6 onclusion The eactions of esteification of glyceol and α-m, catalytic and non-catalytic fomations of α-m and β-m, catalytic fomations α,γ-d and α,β-d have been studied. The kinetic equations of these eactions wee detemined. The obtained data pove that the esteification poceeds quickly and glyceol chloohydin is always in the equilibium with its acetate. Hydochloination of glyceol monochloohydin is ievesible and poceeds moe slowly. The featue of hydochloination eactions ae the eduction of eaction ate with the incease of atio H /. The solvation of chloine anion is consideed to be the cause of this phenomenon. Theefoe it is easonable to emove wate fom the eaction mixtue. Nomenclatue acetic acid EP - epichloohydin glyceol Ac glyceol acetate α,β-d α,β-dichloohydin α,γ-d α,γ-dichloohydin α-m α-monochloohydin β-m β-monochloohydin concentation of acetic acid, mol/l concentation of glyceol, mol/l Ac concentation of glyceol acetate, mol/l concentation of hydogen chloide, mol/l H concentation of wate, mol/l α-m concentation of α-monochloohydin, mol/l α-mac concentation of α-monochloohydin acetate, mol/l eaction ate, mol/l s k kinetic constant K eq equilibium constant Refeences Lebedev N.N., 1988, hemisty and technology of basic oganic and petochemical synthesis. hemisty, Moscow, Russia in Russian. Pagliao M, Rossi. M., 2008, The futue of glyceol. New usages fo a vesatile aw mateial. RSPublishing, ambidge, UK. Reichadt., 1990, Solvents and solvent effects in oganic chemisty. V, Weinheim, Gemany.