Structural Parameters of Perhydrous Indian Coals

Abstract

Higher hydrogen content of perhydrous coals exhibits a different composition and physicochemical properties in comparison with normal coals. In the present investigation, a structural study of perhydrous coals and coke was done using FTIR and HPLC data. These coals have high volatile matter with high-calorific values and low-moisture content. The structural study suggests that the major structural units of these coals are simple phenols with para-alkyl substituted derivatives. They have high alkyl substitution groups and low aromatic compounds. The structural studies reveal that these coals contain high amounts of low-molecular weight PAH compounds with 1-2 ring structures. These 1-2 ring structures have high H/C ratios as compared to large ring polyaromatic hydrocarbons (PAHs). It may also be one of the reasons for high H/C ratios in these coals. The alkyl groups contribute significantly to their high volatile matter (VM) contents. The presence of alcoholic groups found in pyrolytic products may also be due to the conversion of catechol-like structures to those of cresols. Coal properties, such as moisture, VM, H/C ratio, and CV, do not correlate with the rank as normally classified. A definite relationship has been found between the characteristics of these coals, char/cokes, and aromatic characters (f _a , H_ar).

Keywords:

• Aromaticity
• Coal
• Coke
• Polyaromatic hydrocarbons
• Pyrolysis

The authors are thankful to the Director, North-East Institute of Science & Technology (CSIR), Jorhat, Assam for constant support and encouragement. Authors are also thankful to Dr. K. Maharaj Kumari, D.E.I., Agra and Dr. Karuna Shanker, Scientist, CIMAP, Lucknow for providing support in analysis of PAHs. The financial support by Council of Scientific & Industrial Research, New Delhi is gratefully acknowledged.

Notes

H_ar: Aromatic hydrogen; H_al: Aliphatic hydrogen, C_al: Aliphatic carbon.