A Single-Step Solid Acid-Catalyzed Process for the Production of Biodiesel from High Free Fatty Acid Feedstocks

• Published in: Energy & fuels 2010-09, Vol.24 (9), p.4712-4720
• Main Authors: Baig, Aijaz, Ng, Flora T. T
• Format: Article
• Language: English
• ISSN: 0887-0624; 1520-5029
• DOI: 10.1021/ef901258b

Biodiesel is a nontoxic, renewable, and biodegradable alternative green fuel for petroleum-based diesel. However, the major obstacle for the commercial production of biodiesel is the high cost of raw material, i.e., refined vegetable oils. This problem can be addressed using low-cost feedstocks, such as waste oils and fats. However, these feedstocks contain a high amount of free fatty acids (FFAs), which cannot be used for the production of biodiesel using a traditional homogeneous alkali-catalyzed transesterification process. A solid acid catalyst based on a supported heteropolyacid catalyst (PSA) was evaluated for the production of biodiesel from soybean oil (SBO) containing up to 25 wt % palmitic acid (PA). It was demonstrated that this solid acid catalyst catalyzed simultaneously esterification and transesterification. The total glycerin, ester content, and acid numbers were determined according to ASTM D 6584, EN 14103, and ASTM D 974, respectively. It was found that at 200 °C, 1:27 oil/alcohol molar ratio, and 3 wt % catalyst, a high-quality biodiesel with an ester content of 93.95 mass % was produced from a feedstock (SBO containing 10% PA) in 10 h. The PA and chemically bound glycerin (CBG), which includes triglyceride (TG), diglyceride (DG), and monoglyceride (MG), conversions of 92.44 and 99.38% were obtained, respectively. The effect of process parameters, such as catalyst amount, oil/alcohol molar ratio, and FFA content in the feedstock, has been investigated. This single-step solid acid-catalyzed process has potential for industrial-scale production of biodiesel from high FFA feedstocks.