Equilibrium and kinetic studies of biogas adsorption onto porous solids

Abstract

The environmental problems in India are growing rapidly. The increasing economic development and a rapidly growing population that has taken the country from 300 million people in 1947 to more than one billion people today is putting a strain on the environment, infrastructure, and the country s natural resources (MoEF 2000). The aim of the research is to develop a technology for the storage of biogas. The present work is devoted to the measurement of the adsorption capacity of methane onto activated carbons at room temperature and pressure range varying from 1 atm to 10 atm. The results were obtained with a static volumetric method. Fifteen different adsorbents were selected for this study. The overall objective of this study was to determine a suitable adsorbent for CH4 adsorption and to evaluate the sorption behavior of CH4 onto the selected adsorbent system. The equilibrium pressure data were analysed using Langmuir, Dubinin-Astakhov s (DA) and Dubinin-Radushkevich (DR) equations. The adsorption Isotherms obtained for CH4 on all adsorbents were almost of the type I class, according to Brunauers classifications. The purpose of the kinetic study is to determine the characteristics of intraparticle mass transport for methane in activated carbon. Design of an adsorption system requires explicit information on the dynamics of the system. The value of the isosteric enthalpy of adsorption at low surface coverage is related to the pore size of the activated carbon (Shuji Himeno 2005). The values of SorbonoritB3 and Sorbonorit4 was found to be 13.95 KJ/mol and 19.57 KJ/mol respectively. These values were found to the lowest because they had the largest pore diameter among all the activated carbons used in this study. The equilibrium and kinetic parameters determined from this investigation can then be used to design an adsorption system that could store a large amount of methane.