Comparison of product distributions from the thermal reactions of tetralin in a stirred autoclave and a flowing-solvent reactor

Abstract

Products from the thermal reactions of tetralin in a stirred micro-autoclave and a flowing-solvent reactor were compared by gas chromatography-mass spectrometry, to study the effect on product composition of residence time in the reaction zone: of the order of seconds in the flowing-solvent reactor and normally 1 h in the stirred micro-autoclave. Significant differences were found between the products obtained in the two reactors; greater quantities of by-products from thermally induced reactions of tetralin — mainly naphthalene, butylbenzene and 1-methylindane — were found in the heated tetralin from the autoclave. A number of compounds, mainly of mass 262 and 258 u (apparently tetralin-tetralin dimers and tetralin-naphthalene adducts), were also identified in the products from both reactors; many of these products have not previously been reported in connection with the thermal reactions of tetralin. The total concentration of this class of compounds did not exceed ~ 1 wt% of the total solvent. Greater concentrations of the relatively stable dimers and adducts were identified in products from the autoclave than in those from the flowing-solvent reactor. These findings have immediate implications for the evaluation by g.c.-m.s. of coal liquefaction products prepared using tetralin as vehicle, since compounds similar to tetralin-derived by-products have also been found in product solutions from actual coal solubilization experiments.