Dry Washing in Biodiesel Purification: a Comparative Study of Adsorbents

The purpose of this work is to compare the efficiency of different adsorbents in the purification of biodiesel produced by alkaline transesterification of soybean oil (Methanol/KOH). The proposed methodologies were based on the use of Magnesol (R), silica, Amberlite BD10 DRY (R) and Purolite PD 206 (R) as adsorbents and were developed by adsorption at 65 degrees C. The response of each adsorbent was measured through the residual potassium, alcohol, water and soaps dissolved in the purified biodiesel. As a result, we observe that Magnesol (R) and silica showed better adsorption properties than Amberlite BD10 DRY (R) and Purolite PD 206 (R), especially for removing soap, free and bonded glycerol and potassium. In comparison to the conventional acid water washing, these matrices were found to be equally appropriate for the removal of inorganic and organic contaminant species from biodiesel. The main results found for these two adsorbents (Magnesol (R) 1% and silica 2%) were values below 0.17 mg KOH g(-1) for acid number, 1 mg kg(-1) of K, 61 ppm of soap, 500 mg kg(-1) of water, 0.22% of methanol and 0.03% of free glycerol.