Catalysis of Organic..

84Phenol Benzoylationconsecutive Fries rearrangement upon the benzoate. In the present paper, we reportabout the benzoylation of phenol catalyzed by a H-β zeolite; the study was carriedout in order to check the feasibility of the reaction when catalyzed by zeolites, anddetermine the reaction scheme.Results and DiscussionFigure 1 plots the effect of the reaction time on phenol conversion, at 200°C; thereaction was carried out in the absence of solvent.80Phenol conversion, %60402000 1 2 3 4 5Reaction time, hFigure 1. Phenol conversion as a function of the reaction time. Catalyst H-β 150.A maximum phenol conversion of 65% was reached, due to the fact that theconsumption of benzoic acid was higher than that of phenol. Indeed, despite the 1/1load ratio, the selectivity to those products the formation of which required twomoles of benzoic acid per mole of phenol, made the conversion of benzoic acidapproach the total one more quickly than phenol. A non-negligible effect of catalystdeactivation was present; in fact, when the catalyst was separated from the reactionmixture by filtration, and was then re-loaded without any regeneration treatment,together with fresh reactants, a conversion of 52% was obtained after 2.5 h reactiontime, lower than that one obtained with the fresh catalyst, i.e., 59% (Figure 1). Theextraction, by means of CH 2 Cl 2 , of those compounds that remained trapped insidethe zeolite pores, evidenced that the latter were mainly constituted of phenol, benzoicacid and of reaction products, with very low amount of heavier compounds, possibleprecursors of coke formation.Figure 2 plots the effect of phenol conversion on the distribution of products.The following compounds were obtained: (i) phenylbenzoate, (ii) o- and p-hydroxybenzophenone, and (iii) o- and p-benzoylphenylbenzoate. The first productwas obtained with 100% selectivity only at moderate conversion, for low reactiontimes. In fact, when the conversion of phenol increased due to longer reaction times,