Y. H. Taufiq-Yap and H. V. Lee

Abstract To date with the day of less dependence with fossil-based energy, there has been extensive research into the area of generation for alternative fuel—biodiesel for utilization in diesel engine. Development of effective catalyst is important for continuous biodiesel production. Select a right catalyst together with suitable feed­stock is necessary to create an economically viable and sustainable energy source. Although homogeneous catalyzed reaction showed superior transesterification activity than heterogeneous system, but the focus on the development of solid green catalyst becomes more attractive due to the point of easy process and economics concern. Furthermore, the catalytic activity of solid catalyst was comparable to that of the existing liquid catalyst. This chapter reviews various types of homogeneous and heterogeneous catalysts used for transesterification of high free fatty acid oil (Jatropha oil). The process involves single-step or two-step reactions which rely on the physicochemical properties and flexibility of catalyst.

Keywords Biodiesel • Heterogeneous catalyst • Homogeneous catalyst transes­terification

10.1 Introduction

The exponential increment in petroleum crude oil demand as energy source and deleterious environmental impacts with the restrictions imposed by environment conservation agencies have created an impulse to develop new sustainable energy sources and alternative fuels. Biodiesel plays a major role in energy sector due to its similar combustion properties with petrodiesel (Altin et al. 2001), which can be used in compression-ignition (diesel) engine with little or no modification. Chemically,

Y. H. Taufiq-Yap (*) ♦ H. V. Lee

Department of Chemistry, Faculty of Science, Universiti Putra Malaysia, Selangor, Malaysia e-mail: yap@science. upm. edu. my; leehweivoon@yahoo. com

R. Pogaku and R. Hj. Sarbatly (eds.), Advances in Biofuels, 153

DOI 10.1007/978-1-4614-6249-1_10, © Springer Science+Business Media New York 2013

biodiesel is a mono-alkyl ester of long chain that can be prepared from triglycerides of renewable feedstock (vegetable oils or animal fats) by transesterification with methanol in the presence of catalyst. This process reduces the viscosity to a value comparable to that of diesel and hence improves combustion (Leung et al. 2010). Their physicochemical properties such as energy content, cetane number, and vis­cosity are similar to those of petroleum-based diesel fuels. Furthermore, biodiesel consists of several technical and economic advantages which make this 100% natu­ral energy alternative to petroleum-based fuels (Wardle 2003). The advantages are:

1. It prolongs engine life and reduces the need for maintenance (biodiesel has better lubricating qualities than fossil diesel and less sulfur content).

2. It is safer to handle, being less toxic, more biodegradable, and having a higher flash point.

3. It reduces exhaust emissions.

4. Production of by-product (glycerol) is another value adding characteristic which makes commercialization of biodiesel more viable. (Crabbe et al. 2001).