CaO Catalysts Prepared from a Variety of Limestone-deriving Industrial Materials for Transesterification of Soybean Oil with Methanol

Abstract

Utilization of CaO catalyst for transesterifying vegetable oil into its methyl ester is advantageous to biodiesel production. One of the advantages is to make it possible to recycle the by-produced glycerol as a furnace fuel, because none of the corrosive matter such as alkali-metal compounds is contained. In this research work, CaO catalysts were prepared by calcining limestone, precipitated calcium carbonate and dolomite at 900 °C, for the purpose of studying the practical source material of CaO catalyst. The prepared CaO catalysts were employed for transesterification of soybean oil with refluxing methanol. Limestone was turned into the least active catalyst after the calcination, while the most active catalyst was dolomite-deriving CaO. Concerning limestone, presence of impurities such as silica, alumina and ferrite enhanced the catalytic activity. The catalytic activity was related to the basic properties which were measured by CO₂-TPD. Additionally, an influence of the calcination temperature on the catalytic activity was investigated with a view of deeply understanding CaO catalyst deriving from a variety of the calcium carbonate-containing sources.