Production of oxygenated fuel additive from glycerol
Glycerol ethers have the potential to be used as additives with biodiesel as it can be easily blended and can improve fuel performance. It also facilitates easier passing of fuel through injector. Addition of glycerol ether increases the cetane number and improves the antiknocking property. Glycerol ethers are produced by reacting glycerol with tert-butanol (TBA). To initiate the etherification reaction between two alcohols (glycerol and tert-butanol) on solid acid catalyst, acidity of catalyst is one of the primary requirement since the production of protonated molecules in the reaction mixture is crucial. In this work, acidic solid catalysts were developed by the impregnation of heteropolyacids (HPA, H3PW12O40) on SBA-15 support. The SBA – 15 was prepared by hydrothermal method using P123 polymer, HCl, water and tetra ethyl ortho silicate (TEOS). Textural properties of the support were determined using N2 – physisorption method and it was found that the surface area, pore volume and average pore diameters were 819 m2/g, 1.14 cc/g and 5.02 nm, respectively. The pore volume can accommodate higher amount of HPA. HPA is acidic in nature and impregnation of HPA on support can develop the acidic functional groups. Generally, HPA is highly soluble in alcohol and addition of Cesium (Cs) can exchange the proton from HPA and inhibit the solubility by the formation of CsxH3-xPW12O40. Three different catalyst samples were prepared by changing the Cesium (x) wt% (for x = 1.5, 2.2 and 2.9) on SBA-15 using incipient wetness method. These samples were dried at 120 ˚C for 2 hours and then calcined at 300 ˚C for 3 hours. The catalysts were characterized by N2 physisorption, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), elemental analysis (inductively coupled plasma mass spectroscopy, ICP-MS), thermogravimetric/differential thermal analyzer (TG/DTA), scanning electron microscopy (SEM), and temperature programmed desorption of ammonia (NH3-TPD). The progressive reduction in textural properties of the support with HPA loading is identified in BET-Surface area. The enhancement of functional groups is indicated in FTIR. And also the change in crystalline nature is identified in XRD. The screened catalyst was used for etherification of glycerol. Etherification of glycerol with TBA was performed in 100 ml autoclave and the product consists of mono, di and tri-tert butyl glycerol ethers along with some unreacted glycerol. The effects of various reaction parameters such as temperature, catalyst loading and molar ratio (glycerol/TBA) were studied to obtain an optimized condition for etherification of glycerol. Maximum conversion 76% of glycerol was achieved at the conditions of 120 °C, 1 MPa, 1:5 molar ratio (glycerol/TBA), 3% (w/v) catalyst loading and 800 rpm for 5 hours. The kinetic studies were performed and a mathematical model was developed using Langmuir-Hinshelwood mechanism. The reaction rate followed second order kinetics and the activation energy of 78 kJ/mol for the reaction signifies that the reaction was kinetically controlled.
Fuel additive, Cesium (Cs), heteropolyacid (HPA), etherification, glycerol ether.
Master of Science (M.Sc.)