Research Information System
Thesis Type: Doctorate
Institution Of The Thesis: Gazi Üniversitesi, Fen Bilimleri Enstitüsü, Turkey
Approval Date: 2013
Student: EMİNE EKİNCİ
Supervisor: NURAY OKTAR
Abstract:Glycerol is the main by-product of the biodiesel production by transesterification of vegetable oil with methanol or ethanol. In recent years, the increase in the production of biodiesel has been giving rise to that of glycerol. In order to produce an environmental and renewable fuel biodiesel economically, esterification of glycerol with acetic acid can be considered as an alternative way to utilize the waste glycerol from the transesterification process. In this work, MCM-41 and zirconia-supported catalysts were synthesized and their structural characterizations were made with X-ray diffraction and nitrogen adsorption-desorption method. In order to decide on the acidic sites of pyridine adsorbed catalysts, DRIFTS analyses were performed. The esterification reaction between glycerol and acetic acid was investigated at the liquid phase in the presence of commercial acidic resins and synthesized the acidic catalysts. The effect of parameters such as initial reactant molar ratios, stirring rate, reaction temperature, catalyst quantity on glycerol conversion and product selectivity in the presence of Amberlyst 15 catalyst were studied. Besides, novel studies of glycerol-acetic acid reactions were done with Amberlyst 16 and Amberlyst 36 which are commercial ion exchange resin catalysts. The studies of esterification reaction of glycerol with acetic acid were performed in the presence of MCM-41 and zirconia-supported catalysts that are known to be advantageous due to their higher durability to higher temperatures compared to ion exchange resins. It was observed that, higher reaction temperatures give higher activity and triacetin selectivity. At 165 °C, 100% conversion of glycerol was achieved in 45 minutes over STA incorporated zirconia catalyst. Esterification of glycerol with acetic acid is achieved by three reactions in series and besides the esters water is also formed. With the possible increment in the di and triacetin selectivity is achieved by adsorption of water formed by the reaction. In the presence of model catalyst; Amberlyst-15 the reaction of glycerol esterification with acetic acid is studied using a variety of adsorbent such as; silica gel, zeolite 3A, 4A and 5A. The best sorbent among all is 5A due to the reaction rate and triacetin selectivity. The reaction is carried out at 95oC and only in the presence of A-15, the conversion of glycerol is 30% at 245th minute. Whereas with the addition of zeolite to A-15 (with catalyst/zeolite ratio of 1/2), increased the conversion to 73%. There is not much information on the thermodynamics of esterification reaction of glycerol with acetic acid in literature. So, within the scope of this doctoral study, the thermodynamic analysis of this reaction is performed using proper correlations and equilibrium data are obtained. Reaction enthalpies of the glycerine esterification with acetic acid is found as 0,57 kj/mol.