Heterogeneous base catalysts from natural dolomite for transesterification of vegetable oil

Abstract

The present thesis investigated preparation of heterogeneous base catalysts from natural dolomite for transesterification of plam oil with methanol. The catalysts were prepared by dissolution-precipitation method. Typically, the calcined dolomite was mixed with aluminium oxide as a binder, sodium aluminate and hydroxyethyl cellulose (HEC) as a plasticizer in a solution of nitric acid with pH of 1. The resulting catalyst paste was formulated as extrudates (5 mm) by using a manual extruder. The extrudates attained were finally calcined at 500-800 °C. Effects of the preparation conditions, including pH of nitric acid solution, amount of deionized water, amount of HEC, drying temperature, calcination temperature and addition of sodium aluminate on the physicochemical and the catalytic properties were investigated. The properties of the catalysts were studied by using X-ray fluorescence spectroscopy (XRF), X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric/ differential thermal analysis (TG/DTA), N₂ adsorption-desorption measurement, temperature-programammed desorption of CO₂ (CO₂-TPD) and CO₂-pluse chemisorption analysis. The suitable conditions for the catalyst preparation are the mass ratio of dolomite/alumina/sodium aluminate = 70:20:10, the amount of HEC is 3 wt.% relative to the solid mass, the pH of nitric acid solution of 1, the amount of deionized water of 1.5 times of the total solid, the calcination temperature of 800 °C. The catalyst extrudates attained can catalyze the transesterification of palm oil with methanol in a fixed-bed reactor giving a high fatty acid methyl ester yield (54.3%) with retention of the extrudate shape.