Effect of pyrite and pyrrhotite on free radical formation in coal

✍ Scribed by Gopalan Srinivasan; Mohindar S. Seehra

• Publisher: Elsevier Science
• Year: 1983
• Tongue: English
• Weight: 371 KB
• Volume: 62
• Category: Article
• ISSN: 0016-2361
• DOI: 10.1016/0016-2361(83)90029-7

✦ Synopsis

The effects of pyrite (FeS,) and pyrrhotite (Fe+,) on free radical formation in a coal sample (81% carbon content) have been investigated by electron spin resonance (e.s.r.) spectroscopy. Changes in the e.s.r. parameters (spin concentration g-', n, linewidth M and g-value) were monitored in samples of coal, coal+8% FeS, and coal+8% Fe+,, as these samples were heated in vacuum or in hydrogen from room temperature to 5OO"C, in steps of 50°C for a residence time of 30 min at each temperature. In vacuum heating, changes in n begin to occur at 4OO"C, 350°C and 300°C respectively for coal, coal+8%Fe,S, and coal+S% FeS, samples whereas in H,, the corresponding temperatures are 25O'C, 2OO'C and 150°C. Changes in AH and 9 were also observed at these temperatures. The maximum increase in n occured for coal+8% FeS, samples whereas the minimum increase was observed for the pure coal sample. It is argued that enhancement in n is due to two mechanisms: the pyrite to pyrrhotite conversion and the presence of pyrrhotite itself. The detailed nature of the catalytic activity of pyrrhotite is not known.