Influence of Inherent Alkali Content and Surface Area of Biomass Char on its CO2 Gasification Reactivity


1 School of Mechanical Engineering, Engineering Campus, Universiti Sains Malaysia, 14300 Nibong Tebal, Pulau Pinang, Malaysia

2 Biotechnology Research Laboratory, Department of Chemical Engineering, Babol Noshirvani University of Technology, Shariati Ave., Babol, Iran


In this work, isothermal gasification reactivity of pistachio nut shell (PNS) char and oil palm shell (OPS) char was studied under CO2 using Thermogravimetric analysis (TGA). The effects of temperature, inherent alkali content and surface area of each biomass char on promotion of CO2 gasification reactivity were investigated. The achieved results revealed the profound catalytic effect of alkali, alkaline and transition metals including K, Na and Fe available in the ash of biomass on enhancing the gasification reactivity of the char at temperatures below 900 °C. However, at elevated temperatures the pore diffusion was dominant and controlled the gasification reactivity. It was found that at temperatures below 900 °C, PNS char demonstrated high gasification reactivity because of its high alkali index, while at any temperature above 900 °C, conversion of OPS char was faster due to its high porosity and larger surface area.


1.     Liu, Z.-S., Q. Wang, Z.-S. Zou and G.-L. Tan, 2011. Reaction mechanism of carbon gasification in CO2 under non-isothermal conditions. J. Therm. Anal. Calorim., 104(3): 1091-1096.

2.     Roberts, D.G., E.M. Hodge, D.J. Harris and J.F. Stubington, 2010. Kinetics of Char Gasification with CO2 under Regime II Conditions: Effects of Temperature, Reactant, and Total Pressure. Energy Fuels, 24(10): 5300–5308.

3.     Zhang, Y., S. Hara, S. Kajitani and M. Ashizawa, 2009. Modeling of catalytic gasification kinetics of coal char and carbon. Fuel, 89(1): 152-157.

4.     Tancredi, N., T. Cordero, J. Rodríguez-Mirasol and J.J. Rodríguez, 1996. CO2 gasification of eucalyptus wood chars. Fuel, 75(13): 1505-1508.

5.     Marquez-Montesinos, F., T. Cordero and J. Rodri'guez-Mirasol, 2002. CO2 CO2  and steam gasification of a grapefruit skin char. Fuel, 81(4): 423-429.

6.     Dupont, C., T.e. Nocquet, J.A. Da Costa Jr and C.l. Verne-Tournon, 2011. Kinetic modelling of steam gasification of various woody biomass chars: Influence of inorganic elements. Bioresource Technology, 102(20): 9743-9748.

7.     Zhu, W., W. Song and W. Lin, 2008. Catalytic gasification of char from co-pyrolysis of coal and biomass. Fuel Processing Technology, 89(9): 890-896.

8.     Miura, K., K. Hashimoto and P.L. Silveston, 1989. Factors affecting the reactivity of coal chars during gasification, and indices representing reactivity. Fuel, 68(11): 1461-1475.

9.     Xu, K., S. Hu, S. Su, C. Xu, L. Sun, C. Shuai, L. Jiang and J. Xiang, 2012. Study on Char Surface Active Sites and Their Relationship to Gasification Reactivity. Energy & fuels, 27(1): 118-125.

10.   Jing, X., Z. Wang, Q. Zhang, Z. Yu, C. Li, J. Huang and Y. Fang, 2013. Evaluation of CO2 gasification reactivity of different coal rank chars by physicochemical properties. Energy & fuels, 27(12): 7287–7293.

11.   De Lasa, H., E. Salaices, J. Mazumder and R. Lucky, 2011. Catalytic steam gasification of biomass: catalysts, thermodynamics and kinetics. Chemical reviews, 111(9): 5404-5433.

12.   Sakawa, M., Y. Sakurai and Y. Hara, 1982. Influence of coal characteristics on CO2 gasification. Fuel, 61(8): 717-720.

13.   Yuan, S., X.-l. Chen, J. Li and F.-c. Wang, 2011. CO2 gasification kinetics of biomass char derived from high-temperature rapid pyrolysis. Energy & fuels, 25(5): 2314-2321.