Synthesis of Alumina Supported Calcium Based-Chromium Oxides Catalyst Using Modified Method for Transesterification of Refined Cooking Oil

Abstract

Environmental concerns in fossil fuel depletion enhanced the search for an alternative fuel from renewable resources. Biodiesel is commonly produced by transesterification of vegetable oil in the presence of homogeneous catalyst. However, this catalyst was required many steps of purification such as use large amount of water which can cause saponification in biodiesel. This research mainly focused on the use of heterogeneous base catalysts that are easily separated in biodiesel production. Therefore, calcium-chromium oxides supported on alumina was prepared via modified and unmodified wetness impregnation methods for the transesterification reaction of refined cooking oil. For modified method, the extraction solution of sapodilla leaves was incorporated in the catalyst solution. All synthesized catalysts were then calcined at temperatures of 600-800 ᵒC and the conversion were monitored by gas chromatography-flame ionization detector (GC-FID). From the result, Ca/Cr(10:90)/Al2O3 catalyst calcined at 700°C with 1 g dosage of sapodilla leaves was exhibited the highest conversion of triglycerides. Around 95% conversion was achieved at mild reaction conditions of 65 ºC reaction temperature, 6 wt.% catalyst loading, 1:18 oil to methanol ratio and 3 hours reaction time. The physicochemical analysis of this catalyst was accomplished using several characterization techniques. The catalyst showed polycrystalline structure with sparsely populated nanosheet with unhomogeneous shapes and sizes. It also posseses high surface area of 399.33 m2g-1 with small particle sizes in the range of 10-60 nm and less metal leaching. The observed results are much better than unmodified catalyst preparation.