Photocatalytic Dissolution of two Turkish Lignites in Tetralin: the Effects of ZnCl2 as Catalyst

Abstract

The effects of ultraviolet (UV) irradiation, impregnated ZnCl₂ and irradiation (reaction) time on the liquefaction of two Turkish lignites (Beypazarı and Tunçbilek lignites) in tetralin have been investigated under ambient conditions. Experiments were carried out at the value of 5/1 of solvent/lignite ratio, 5 % (wt) of ZnCl₂ concentration, 180 Watt of irradiation power and irradiation time ranging from 1 to 10 days in the presence or absence of catalyst. Some experiments were also carried out in the dark for comparisons. The liquid products were divided into the fractions of oil, asphalten and preasphalten by successive solvent extraction. The data obtained in this study indicate that the yields and formation mechanisms of peasphaltenes, asphaltenes, and oils depend on the lignite type and catalyst usage. The photochemical liquefaction method of lignites with UV irradiation has some advantages such as the higher liquefied product yields and the largest oil faction, which are the higher quality liquid product, compared to that of thermally activated liquefaction method in tetralin; and carrying out at ambient temperature and pressure. The highest yields of liquefied products obtained from Beypazarı and Tunçbilek lignite in the case of presence of impregnated catalyst at 5 days of irradiation time are 33% and 45%, respectively. The UV irradiation and irradiation time significantly affect the liquefied product yields and distributions. Impregnating of ZnCl₂ salt affected the liquid formation mechanism for both lignites. Under all conditions, the yields of total liquid and oil increased with time, but important changes were not observed in the yields of asphalten and preasphalten.