**6. Acknowledgements**

Author acknowledges Director, Central Leather Research Institute, Chennai, for all support and Director, Indian Institute of Petroleum, Dehradun for the support provided for all the fuel properties analysis. The efforts of Dr Nagarajan, Anna University, Chennai for engine trails are highly acknowledged. The author acknowledges The Managing Director and other officials of MTC, Government of Tamil Nadu for their support provided for the successful on-road trials in buses.

**16** 

*China* 

Feng Guo and Zhen Fang

*Chinese Academy of Sciences, Biomass Group, Xishuangbanna Tropical Botanical Garden,* 

**Biodiesel Production with Solid Catalysts** 

Biodiesel is usually produced by transesterification of vegetable oils or animal fats with chemical catalysts, especially in the presence of strong acidic or basic solutions, such as hydrochloric acid, sulphuric acid, sodium hydroxide, sodium methoxide and potassium hydroxide. Homogeneous alkali catalysts can convert triglycerides to their corresponding fatty acid methyl esters (FAMEs) with high yield, less time and low cost. However, separating the catalyst from the product mixture for recycling is technically difficult. After reaction, the catalyst should be neutralized or removed with a large amount of hot water,

Typical plant oils, such as soybean oil, rapeseed oil and palm oil, are the main edible oils. They are not suitable as raw materials, particularly in developing countries due to limited supply and high cost. Therefore, low-cost lipids, such as non-edible oils (e.g., Jatropha oil), animal fats and waste oils, are used as ideal feedstocks. Such oils usually contain some water and free fatty acids (FFAs) that will form soap when homogeneous base catalysts are used. On the other hand, homogenous acid catalysts are corrosive to equipment. Solid heterogeneous catalysts are used to overcome these problems, because they are noncorrosive, non-toxic, and easily-separated for recycling. Reusability of heterogeneous catalysts makes continuous fixed-bed operation possible. Such continuous process can minimize product separation and purification costs, make it economically viable to compete with commercial petroleum-based diesel fuel. This chapter describes solid heterogeneous

In laboratory-scale experiment, heterogeneous processes could be run in a continuous mode with a packed-bed continuous flow reactor. Heterogeneous catalysts were easily separated from the products, water-washing process and neutralization steps were avoided. Contaminated water from this process was greatly reduced, and the sewage treatment fees were also minimized. New types of heterogeneous catalysts have mushroomed and

Acid catalysts can simultaneously catalyze both esterification and transesterification, showing a much higher tolerance to FFAs and water than basic homogeneous catalysts (e.g.,

which will produce a large amount of industrial wastewater.

catalysts for biodiesel production and their typical catalytic mechanism.

**2. Heterogeneous solid catalysts** 

developed in recent years.

**2.1 Heterogeneous acid catalysts** 

**1. Introduction** 

#### **7. References**

