Ali Sinag

5.1 Thermochemical Biomass Conversion

Thermochemical biomass conversion methods can be divided into three main groups as combustion, gasification and Pyrolysis (Fig. 5.1). Combustion is thermal conversion of organic matter with an oxidant to produce mainly carbon dioxide and water. Combustion of biomass is the most direct and technically easiest process. However, the overall efficiency of generating heat from biomass energy is low. Gasification of biomass provides power generation for the technical appli­cations needing energy. The process generates valuable gaseous products (CO, CO2, H2O, CH4, C2—C6) and char depending on the design and operating conditions of the gasification reactor. Pyrolysis is thermal heating of the materials in the absence of oxygen, which results in the production of three categories: gases, pyrolytic oil and char [1-3]. Pyrolytic oil, also known as ‘‘tar or bio-oil’’, cannot be used as transportation fuels directly due to the high oxygen (40-50 wt%) and water contents (15-30 wt%) and also low H/C ratios. However, pyrolytic oil is viscous, corrosive, relatively unstable and chemically very complex [4-6].

The main advantages of these methods for biomass conversion over other conversion methods such as biochemical conversion technologies are the feed­stock used. All plant-based residues can be converted into value-added products such as transportation fuels (diesel), hydrogen, methane, syngas and chemicals [7]. However, the undesirable products like alkali compounds and the cost of cleaning the gaseous products and drying of biomass are the major problems. There are many attempts such as catalyst usage, co-firing of biomass with coal in order to improve product quality and the optimization of the experimental conditions.

A. Sinag (H)

Department of Chemistry, Science Faculty, Ankara University, Bejevler-Ankara 06100, Turkey e-mail: sinag@science. ankara. edu. tr

C. Baskar et al. (eds.), Biomass Conversion,

DOI: 10.1007/978-3-642-28418-2_5, © Springer-Verlag Berlin Heidelberg 2012

This chapter chiefly deals with the role of catalysts during thermochemical biomass conversion since usage of different types of catalysts for this conversion leads to the tar and oxygen removal, increasing calorific value of the products and reduction in the amount of undesirable contaminants. The effects of new types of nanocatalysts together with known types of catalysts on the process conditions and the product quality will also be discussed.