اندازه گيري حلاليت چهار تايي استيك اسيد، دي و تري استين در دي اكسيد كربن فوق بحراني

چكيده انگليسي :

Quaternary solubility measurements for acetic acid diacetin and triaceti in supercritical carbon dioxide Sepideh Afsari Mamaghani Sepideh afsari@gmail com July 5 2009 Department of Chemistry Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language Farsi Dr Hassan S Ghaziaskar ghazi@cc iut ac ir Abstract The growing concern about the global warmin is one of the main issues at the beginning ofthis century motivating discussions on renewable energy sources which have a lower impacton the CO2 emissions Among these new energy sources the biodiesel appears as one of themost promising and feasible at short term Biodiesel is generally produced bytransesterification of vegetable oils with methanol or ethanol under base catalysis conditions For each 90 m3 of biodiesel produced by transesterification of vegetable oils approximately10 m3 of glycerol are generated as byproduct Esterification of glycerol with fatty acids usinga catalyst especially heterogeneous catalyst to get mono di and tri esters of glycerol acetatesis one of the proposed solutions for conversion of relatively low priced Glycerol to valuableproducts which has received great attention from researches in all over the world all threeglycerol acetates named monoacetin miacetin and treiacetin are synthesized coinstantaneousthrough the reaction and usually are accompanied with some by products which change itscolor or odor so that it makes its purification difficult and costly As a result selectivesynthesis of the esters with high purity has been a great challenge for some researches According to growing interest in above mentioned field a research for Continuous Synthesisof Glycerol Acetates in Supercritical Carbon dioxide Using Amberlyst 15 was conducted inour laboratory to investigate the synthesis of glycerol esters in scCO2 by a continuousesterification with Acetic acid in presence of Amberlyst 15 as a strong solid acid catalyst Itshould be noted that the boiling points of mono di and triacetin are closed to each other Especially the boiling points of di and triacetin are very similar making their separation byconventional process very difficult and costly Also excess acetic acid remains in the mixtureof products So quaternary solubility of acetic acid diacetin and triacetin obtained data wereapplicable for possible tailoring of above mentioned reaction toward a specific product orhigher efficiency including possible separation of mixture of products during the continuoussynthesis But our main goal was finding a solution for selective extraction of excess aceticacid from products mixture during continuous synthesis using supercritical carbon dioxidetunable solubility and without applying any extra apparatus for this separation Obviously forreaching this goal we need to find points of pressure and temperatures in which supercriticalcarbon dioxide solves acetic acid selectively and extracts it from the mixture of acetic acid diacetin and triacetin By using a continuous flow apparatus quaternary solubility of acetic acid diacetin andtriacetin in supercritical carbon dioxide scCO2 have been measured at constant flow rateand temperatures of 30 C 40 C 60 C and 75 C in pressure range of 70 180 bar Alsobinary and quaternary solubility of acetic acid is compared Data of quaternary solubility isutilized for investigating possible extraction of each compound and selective extractionefficiencies for acetic acid by scCO2 is calculated Also solutions for selective extraction oftriacetin and diacetin are proposed Bartle equation is used for prediction of solubilities infurther temperatures and pressures Using the named equation the solubility of acetic acid

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اندازه گيري حلاليت چهار تايي استيك اسيد، دي و تري استين در دي اكسيد كربن فوق بحراني

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