A novel green catalytic process for biodiesel production from Jatropha
By Aijaz Baig and Flora Ng
November/December 2012
The high cost of edible feedstocks, an increasing demand for food worldwide, and concerns about using virgin forest and arable land for large-scale biodiesel production have thrown considerable attention on nonedible oils, such as jatropha, as attractive alternative feedstocks (Fig. 1). Unfortunately, many nonedible oils have a high content of free fatty acids (FFA), which significantly reduce biodiesel yields during conventional homogeneous base-catalyzed transesterification reactions.
Crude jatropha oil can have an FFA content of up to 15%, which is beyond the acceptable limit for processing using a conventional base-catalyzed process. This limitation can be overcome by using a two-step process involving an acid-catalyzed esterification followed by a base-catalyzed transesterification (Baig, 2003). However, this two-step (or multi-step) process increases the system complexity and raises the cost of producing biodiesel from a particular feedstock (Olutoye and Hameed, 2011)
Using a conventional homogeneous-catalyzed process (Fig. 2) to produce biodiesel from crude jatropha oil is technically, economically, and environmentally more challenging than using the same process to make biodiesel from edible oils. It requires multi-step processing, oil pretreatment, neutralization of the waste homogeneous catalyst, water washing of the crude biodiesel and glycerol, and treatment of the waste generated—all of which make the purification of the biodiesel to meet biodiesel quality standards more difficult (Baig and Ng, 2011; Baig et al., 2012).
Most of the processes reported in the literature on biodiesel production from jatropha focus on using conventional homogeneous base-catalyzed processes, two-step or multi-step homogeneous-catalyzed processes, heterogeneous base-catalyzed processes, or heterogeneous acid and base catalyzed processes (Juan et al., 2011; Endalew et al., 2011). However, all these processes are complex and too inefficient to be considered for industrial-scale production of biodiesel. Furthermore, all the reported processes to date require the use of pre-treated jatropha oil, not crude jatropha oil. The price of crude jatropha oil is much lower than refined and deodorized jatropha oil, which has an FFA content of more than 1% (Juan et al., 2011). To produce biodiesel on an industrial scale, one should use crude jatropha oil.
The problems associated with using a homogeneous-catalyzed process to make biodiesel from feedstock with high FFA content have been addressed by using a heterogeneous-catalyzed process for the production of biodiesel from oil containing FFA (Baig and Ng, 2010). Recently, we developed a novel technology using a simple and environmentally green direct single-step heterogeneous-catalyzed process to produce high-quality biodiesel from crude jatropha oil as shown schematically in Figure 3.
Most of the processes reported in the literature on biodiesel production from jatropha focus on using conventional homogeneous base-catalyzed processes, two-step or multi-step homogeneous-catalyzed processes, heterogeneous base-catalyzed processes, or heterogeneous acid and base catalyzed processes (Juan et al., 2011; Endalew et al., 2011). However, all these processes are complex and too inefficient to be considered for industrial-scale production of biodiesel. Furthermore, all the reported processes to date require the use of pre-treated jatropha oil, not crude jatropha oil. The price of crude jatropha oil is much lower than refined and deodorized jatropha oil, which has an FFA content of more than 1% (Juan et al., 2011). To produce biodiesel on an industrial scale, one should use crude jatropha oil.
The problems associated with using a homogeneous-catalyzed process to make biodiesel from feedstock with high FFA content have been addressed by using a heterogeneous-catalyzed process for the production of biodiesel from oil containing FFA (Baig and Ng, 2010). Recently, we developed a novel technology using a simple and environmentally green direct single-step heterogeneous-catalyzed process to produce high-quality biodiesel from crude jatropha oil as shown schematically in Figure 3.
In contrast to a conventional homogeneous-catalyzed process, this catalytic technology does not require complex downstream washing and separation processes, and the heterogeneous catalyst can be recycled and is environmentally benign. This technology provides a direct route for the synthesis of biodiesel from crude jatropha oil. Furthermore, the heterogeneous catalysts are also potentially inexpensive. Heterogeneous catalysts can be customized so that the presence of FFA or water does not adversely affect the catalytic activity during and after the biodiesel production process. Consequently, this novel catalytic technology could be used to produce biodiesel from crude jatropha oil on an industrial scale.
Aijaz Baig received his M.A.Sc. in chemical engineering (specialization in biodiesel) and a collaborative graduate program in environmental engineering from the University of Toronto, Canada. His doctoral work in the department of chemical engineering at the University of Waterloo, Canada, focused on the development of novel green second-generation biodiesel technologies for industrial applications. Baig is a leading inventor of innovative green technologies for industrial-scale production of biodiesel. He has been awarded the professional designation of Chartered Chemist (C. Chem.) from the Association of the Chemical Profession of Ontario, Canada and the distinguished Waterloo Institute of Nanotechnology Fellowship. He is the author of over 30 scientific publications and presentations at national and international conferences, and is an active member of the AOCS, the American Chemical Society, the Chemical Institute of Canada, and the Canadian Society for Chemical Engineering. His research interests are focused on catalysis, innovative biofuels and bioprocess technologies, green chemistry and engineering, sustainable energy, biofuels quality, and nanotechnology. He can be contacted at a6baig@uwaterloo.ca.
Flora T.T. Ng is a University Professor and University Research Chair in the Department of Chemical Engineering, University of Waterloo, Ontario, Canada. She can be contacted at fttng@uwaterloo.ca.
Biodiesel is defined by the American Society for Testing and Materials (ASTM) as the mono alkyl ester of long-chain fatty acids derived from a renewable lipid feedstock (Baig and Ng, 2010).
Globally, the availability of feedstocks for biodiesel production varies considerably according to location and climate. The important factors to be considered in the selection of biodiesel feedstocks are (i) the chemical composition of the fat or oil, (ii) its cost and availability, and (iii) transport and pretreatment. The chemical composition is important to determine the amount of free fatty acids in the oil, which is an important factor to be considered in the selection of biodiesel production technologies for industrial-scale applications (Olutoye et al., 2011).
Currently, edible oils are widely used for biodiesel production. In Europe rapeseed oil is mainly used, while in Malaysia and Indonesia palm oil predominates. In the United States, soybean oil and animal fats are primary feedstocks. Among the nonedible oils, jatropha is considered one of the most advantageous feedstocks for biodiesel production in terms of economical, sociological, and environmental implications (Juan et al., 2011).
information
1. Baig, A., Optimization of a two-step process for the production of ASTM-standard biodiesel from refurbished oils and fats, M.A.Sc. Thesis, University of Toronto, Toronto, Ontario, Canada, 2003.
2. Baig, A., and Ng, FTT. A single-step solid acid-catalyzed process for the production of biodiesel from high free fatty acid feedstocks, Energy Fuels 24:4712–4720 (2010). Baig, A., and Ng, FTT. Determination of acid number of biodiesel and biodiesel blends, J. Am. Oil Chem. Soc. 88:243–253 (2011).
3. Baig, A., Paszti, M, and Ng, FTT. A simple and green analytical method for acid number analysis of biodiesel and biodiesel blends based on potentiometric technique, Fuel, http://dx.doi.org/10.1016/j.fuel.2012.06.012 (2012).
4. Endalew, AK, Kiros, Y, and Zanzi, R. Heterogeneous catalysis for biodiesel production from Jatropha curcas oil (JCO), Energy 36:2693–2700 (2011).
5. Juan, JC, Kartika, DA, Wu, TY, and Hin, T-YY. Biodiesel production from jatropha oil by catalytic and non-catalytic approaches: an overview, Bioresource Technol. 102:452–460 (2011). Olutoye, MA, and Hameed, BH. Synthesis of fatty acid methyl ester from crude jatropha (Jatropha curcas Linnaeus) oil using aluminum oxide modified Mg-Zn heterogeneous catalyst, Bioresource Technol. 102:6392–6398 (2011).