Upgranding of Naphtha Fractions of a Coal Liquid on H-Ga-silicate (I)

Inhibitory Effect of Phenols

Abstract

The conversion of naphtha fractions of a coal liquid on pentasil-type H-Ga-silicate was examined. Although model compounds (octane and cyclohexane) exhibited quite high reactivities on H-Ga-silicate, the naqhtha fractions showed negligible reactivities on the catalyst. By examining the model reaction in the presence of quinoline or cresol, the authors attributed the low reactivity of the coal liquid to the following three reasons: a) adsorption of the basic components on the acid sites of the catalyst, b) inhibitory effect phenols, c) rapid deactivation of the catalyst due to the deposition of coke precursors formed during storage of the coal liquid. Washing the naphtha fractions with 3%HCI and then 10%NaOH aqueous solutions to remove these inhibitors significantly increased the reactivities of these naphtha fractions, and the reactions of the washed naphtha fractions on H-Ga-silicate afforded BTX in ca. 50% yields. Inhibitory effect of phenols on the conversion of hydorcabons was unexpected because facile alkylations of phenols with methanol on microporous catalysts are well known; therefore the reaction of phenols on H-Ga-silicate was examined. At low temperatures, phenol molecules were strongly adsorbed in the pores of the H-Ga-silicate and inhibited the conversion of the hydrocabons. At high temperatures, phenols were apparently deoxygenated on H-Ga-silicate yielding aromatic hydrocabons; however, the catalyst was rapidly deactivated.