Evolution of naphthalene and its intermediates during oxidation in subcritical/supercritical water
PROCEEDINGS OF THE COMBUSTION INSTITUTE, cilt.33, ss.3185-3194, 2011 (SCI-Expanded, Scopus)
- Yayın Türü: Makale / Tam Makale
- Cilt numarası: 33
- Basım Tarihi: 2011
- Doi Numarası: 10.1016/j.proci.2010.09.010
- Dergi Adı: PROCEEDINGS OF THE COMBUSTION INSTITUTE
- Derginin Tarandığı İndeksler: Science Citation Index Expanded (SCI-EXPANDED), Scopus
- Sayfa Sayıları: ss.3185-3194
- Orta Doğu Teknik Üniversitesi Adresli: Hayır
Özet
Oxidation of naphthalene (Nap) in supercritical water (SCW) was carried out in a batch reactor (6-ml volume) up to 400 degrees C and 300 atm (maximum residence time of 1800 s). Two systems were studied. System A consisted of pure naphthalene mixed with oxygen and water: 0.065 M Nap + 1.441 M O-2 + 8.549 M H2O. System B included, in addition to O-2 and H2O, a heavy metal and an ash to simulate their roles in the destruction of Nap: 0.065 M Nap + 1.441M O-2 + 0.008 M Cr(NO3)(3) + 0.065 M Al2Si2O5 center dot(OH)(4) + 8.624 M H2O. It was shown that, in general, the oxidation process can be divided into three stages characterized by H2O2 decomposition to H2O and O-2 (Stage 1), oxidation in saturated/subcritical water up to 360 degrees C and 225 atm (Stage 2), and fast oxidation in the supercritical region (Stage 3). The oxidation process revealed different reaction rates in different systems. Relatively low activation energy of 10-30 kJ/mol was obtained below 360 degrees C and 225 atm in the System A and in the whole temperature range in the System B. High activation energy (139.5 kJ/mol) was obtained for supercritical water oxidation of naphthalene in the System A. The catalytic effect of Cr3+/ash stimulated naphthalene oxidation. Time-resolved yields of major products and intermediates were obtained. The reaction pattern was proposed. It describes the evolution of naphthalene and intermediates as a sequence of reactions comprising transformations of the main compounds and their inter-conversion. This radical-involving reaction mechanism is mainly based on the quantification of the profiles of the intermediates. (C) 2010 The Combustion Institute. Published by Elsevier Inc. All rights reserved.