Mukherjee, Samit and Srivastava, S.K. (2004) Kinetics and Energetics of High-Sulfur Northeastern India Coal Desulfurization Using Acidic Hydrogen Peroxide. Energy & Fuel , 18 (6). pp. 1764-1769. ISSN 0887-0624

PDF Restricted to Repository staff only Download (73Kb) | Request a copy

Abstract

Studies on the kinetics and energetics of high-sulfur coals in northeastern India regions, using 15% (v/v) hydrogen peroxide mixed with (0.1 N) sulfuric acid as a desulfurizing agent, were conducted at four different temperatures, viz., 15, 25, 30, and 40 °C. The rate constants varied over a range of 6.2 × 10-5 -7.8 × 10-5 for Baragolai coal and a range of 7.0 ×10-5 -11.5 × 10-5 for Ledo coal. Rate constants were calculated using a second-order rate equation, as the concentration of both hydrogen peroxide and pyrite changed, with respect to time. These results, when compared with those reported earlier, indicated that, when hydrogen peroxide was mixed with 0.1 N sulfuric acid, the rate of the reaction was enhanced, as compared to that observed using hydrogen peroxide alone, when high-sulfur Meghalaya coal samples of the northeastern India region were used. The oxidation rate increased as the temperature increased from 15 °C to 40 °C. The respective activation energy and frequency factor values were 8.04 kJ/mol and 10.47 × 10-5 for Baragolai coal, and 11.49 kJ/mol and 15.85 × 10-5 for Ledo coal. The results are in excellent agreement with earlier published work [Borah and Barauh, Fuel Process. Technol., 2001, 72, 83] but are in total disagreement with the respective activation energy and frequency factor values of 19.33 × 106 J/kmol and 6.19 × 10-1 for Baragolai coal and 39.72 × 106 J/kmol and 2.33 × 10-4 for Ledo coal that were obtained by another group [Mukherjee et al., Energy Fuels, 2001, 15, 1418]. The equilibrium constant values at 15, 25, 30, and 40 °C for the formation of an activated complex were in the range of 1.03 × 10-17 -1.19 × 10-17 for Baragolai coal and 1.16 × 10-17 - 1.76 × 10-17 for Ledo coal. The free energy of activation values lie in the range of 93.67-101.42 kJ/mol for Baragolai coal and 93.38-100.41 kJ/mol for Ledo coal. The positive value for the free energy of activation indicates the nonspontaneous nature of the activated complex formation reaction. The enthalpy of activation values vary from 5.64 kJ/mol to 5.44 kJ/mol for Baragolai coal and from 9.09 kJ/mol to 8.89 kJ/mol for Ledo coal. A positive enthalpy of activation value indicates that the formation of the activated complex proceeds with an absorption of heat. The entropy of activation value was -0.31 kJ/mol for Baragolai coal and -0.29 kJ/mol for Ledo coal, indicating that the number of degrees of freedom decreased when the activated complex was formed. A negative entropy of activation value is due to (i) the occurrence of collisions, (ii) a low frequency factor, (iii) nonspontaneity, and (iv) the formation of a loosely bound activated complex.

Item Type:	Article
Subjects:	Fuel Scinece
Divisions:	UNSPECIFIED
Depositing User:	Dr. Satyendra Kumar Singh
Date Deposited:	09 Jan 2012 11:33
Last Modified:	09 Jan 2012 11:33
URI:	http://cimfr.csircentral.net/id/eprint/623

Actions (login required)

View Item