Effects of acidity and crystal size of hβ catalysts on the dehydration and ring-closure reaction of 2-(4′-ethylbenzoyl) benzoic acid

Four catalysts were prepared by using four β zeolites with different n(SiO₂)/n(Al₂O₃) and modified by citric acid, and characterized by means of XRF, XRD, NH₃-TPD and SEM. The dehydration and closure-ring reaction of 2-(4′-ethylbenzoyl) benzoic acid (BEA) for the synthesis of 2-ethylanthraquinone (2-EAQ) over the four catalysts were carried out to investigate their catalytic performance. The results showed that there was great difference in catalytic activity among the four samples at lower temperature(230°C), at which the conversion of BEA on the catalyst sample with n(SiO₂)/n(Al₂O₃) of 25 was 82.2%, while on the catalyst sample with n(SiO₂)/n(Al₂O₃) of 38, the conversion of BEA was only 30.3%. When the reaction temperature was 258°C, there was no obvious difference in catalytic activity among the four samples. The acidity of Hβ zeolite had some influence on the catalytic performance in the dehydration of BEA into 2-EAQ, while the crystal size of the catalysts had great influence on their performance. The smaller the crystal size of the catalyst, the easier the diffusion of the reactant and the product, which led to high catalytic performance in the dehydration of BEA.