Kinetic studies on production of valuable organics from glycerol which is a by-product of biodesel

Biodiesel is suggested as an alternative with a high potential of renewable energy sources that has closest characteristic properties of diesel fuel. When biodiesel is produced, by-product glycerol consists about 10% by weight of the total amount of product. Glycerol can be used directly as a fuel or can be converted to valuable products. In the scope of work, glycerol ethers and glycerol esters were produced for the evaluation of glycerol. Ethers of glycerol are added to fuel, the fuel octane/cetane number increases, esters of glycerol are used improving viscosity and the cold flow properties of diesel fuel. In this work etherification of glycerol with tert-butyl alcohol and the esterification of glycerol with acetic acid were studied in the presence of acidic resin catalyst Dowex HCR W2 and %15 Pd/Aerosil200 which is synthesized in the scope of work. These reactions have been examined in the liquid phase in a batch reactor at auto-genous pressure. Glycerol ethers and esters formed as a result of etherification and esterification. Mono- ethers, di-ethers and tri-ethers were obtained in the glycerol etherification reaction; monoacetin, diacetin and triacetin were obtained in the glycerol estherification reaction. The effect of different reactant molar ratios and different reaction temperatures on glycerol conversion and product selectivity were investigated. Additionally, activities of commercial Dowex HCR W2 and activities of %15 Pd/Aerosil200 catalysts were compared. In this study, etherification of glycerol reaction was carried out at different reactant molar ratios (3/1, 5/1 ve 8/1), 1300 rpm stirring rate, at 90oC in the presence of 0.3 g of commercial Dowex HCR W2 catalyst in the liquid phase batch reactor. It was observed that glycerol conversion increased with increasing reactant molar ratio (TBA/G). Then, reactions of etherification of glycerol were realized at 8/1 reactant molar ratio, at different reaction temperatures (90-120oC), with 1300 rpm stirring rate in the presence of 0.3 g of commercial Dowex HCR W2 catalyst in the liquid phase batch reactor. Conversion of glycerol and selectivity of di-ether were obtained as %83 and %23 respectively in the presence of commercial Dowex HCR W2 catalyst, at 8/1 reactant molar ratio and at 100oC reaction temperature. In this study, esterification of glycerol reaction was realized at different reactant (Ac/G) molar ratios (6/1, 9/1 ve 12/1) and at different reaction temperatures (90, 100 ve 110oC), with 1300 rpm stirring rate in the presence of 0.3 g of commercial Dowex HCR W2 catalyst in the liquid phase batch reactor. It was observed that full conversion of glycerol was realized at shorter reaction times and selectivity of triacetin increased with increasing reactant molar ratio (TBA/G). Besides, rate of reaction increased with increasing reaction temperature. In the reactions of esterification of glycerol, full conversion of glycerol was reached at about 80 minutes reaction time and selectivity of triacetin was obtained as %19 at 12/1 reactant molar ratio, at 110oC reaction temperatures. Glycerol esterification was also carried out at 12/1 reactant molar ratio and at 110oC reaction temperatures utilizing different amounts of commercial Dowex HCR W2 catalyst. Selectivities of di- and tri-acetin were obtained as %51 and %39 respectively in the presence of 0.5 g of commercial Dowex HCR W2 catalyst. In this study, the metal content of %15 Pd (by weight) was loaded by impregnation method on a new generation support material of Aerosil200 which was not tried in the literature for glycerol etherification and esterification reactions. Characterization studies for the determination of structural and physical properties of %15 Pd/Aerosil200 catalyst (Determination of Hammett acidity, DRIFTs, BET, XRD, TEM, SEM-EDS analysis) were also carried out. Acidity of the catalysts which has synthezied in this work was tested on glycerol etherification and esterification reactions. Surface area of the reduced catalyst was obtained as 166m²/g. Brønsted acid sites have been identified in pyridine DRIFTs analysis and it was observed that the synthezied catalyst was suitable for acidic reactions. Etherification of glycerol reaction was realized at different reaction temperatures (100, 150 ve 200oC), 8/1 (TBA/G) reactant molar ratio in the presence of 0.3 g of. The best conversion of glycerol (%93) and the highest selectivity of di-ether (%68) were achieved on reduced %15 Pd/Aerosil200 catalyst when the molar ratio of reactants was 12/1 at 200oC reaction temperature. Esterification of glycerol reaction was realized at different reaction temperatures (150 ve 200oC), 12/1 (Ac/G) reactant molar ratio in the presence of 0.3 g of reduced %15 Pd/Aerosil200 catalyst. The highest selectivity of triacetin (%61) was reached at 200oC reaction temperature in the presence of reduced %15 Pd/Aerosil200 catalyst which synthesized in the scope of work. Esterification of glycerol reaction was realized at 200oC reaction temperature, 12/1 (Ac/G) reactant molar ratio in the presence of 0.3 g of reduced %15 Pd/Aerosil200 catalyst and the water-retaining agent of Zeolit 5A with 1/1 molar ratio of catalyst/Zeolit5A. Thus, the equilibrium reaction was provided to shift toward products and selectivity of triacetin was obtained as %60. The effect of zeolite was not appreciable because the support material (Aerosil200) has also moisture-capture capacity (120% of its own weight).