Reactivity and structural modification of coals in HNO 3 –Ac 2 O system Y.V. Tamarkina a , T.G. Shendrik a , A. Krzton b, * , V.A. Kucherenko a a L.M. Litvinenko Institute of Physical Organic and Coal Chemistry, National Academy of Sciences, Ukraine, R. Luxemburg Street, 70, 83114 Donetsk, Ukraine b Institute of Coal Chemistry, Polish Academy of Sciences, Sowinskego 5, 44-121 Gliwice, Poland Received 31 January 2002; received in revised form 28 March 2002; accepted 9 April 2002 Abstract The interaction of different rank coals with equimolar HNO 3 –Ac 2 O mixture has been studied. This process, proceeding fast at 15 – 30 jC for several hours, results in changes of spatial and chemical structures because of nitration of coal arenes, formation of oxygen functional groups and partial cleavage of C – C cross-links. As a result, structurally modified coals (SMCs) are obtained as new coal-derived substances. Properties of SMCs were investigated by X-ray diffraction method, DRIFT spectroscopy and thermogravimetry. The main reactions responsible for structural modification have been proposed. D 2002 Elsevier Science B.V. All rights reserved. Keywords: Coal; Nitration; Oxidation; Oxygen functional groups; Modification 1. Introduction Oxidative pretreatment as structural modification of coals is used for active carbon preparations and other purposes [1,2]. Some oxidants were tested: O 2 ( V 300 jC) [3], gaseous mixture of H 2 O with HNO 3 (140 jC) [4] or HClO 4 (120–170 jC) [5], solutions of HNO 3 in H 2 O (20–100 jC) [6] or HNO 3 in acetic anhydride Ac 2 O (15–30 jC) [7]. An interaction with any above-mentioned reagent leads to oxygen functionality variations, oxidative cleavage of framework-forming chains, partial oxy-destruction of aromatic rings. When using HNO 3 -containing mixture, nitro groups are additionally 0378-3820/02/$ - see front matter D 2002 Elsevier Science B.V. All rights reserved. PII:S0378-3820(02)00059-0 * Corresponding author. E-mail addresses: postmaster@infou.donetsk.ua (Y.V. Tamarkina), postmaster@infou.donetsk.ua (T.G. Shendrik), akrzton@karboch.gliwice.pl (A. Krzton), postmaster@infou.donetsk.ua (V.A. Kucherenko). www.elsevier.com/locate/fuproc Fuel Processing Technology 77 – 78 (2002) 9 – 15