Metal-Containing Granulated Yh Zeolites with Hierarchic Structure in Isophorone Aromatization

Abstract

The physicochemical properties of a series of catalysts based on granulated Na-Yh zeolite with the hierarchic (micro–meso–macro) pore structure (Na-Yh, HNa-Yh, MgO/Na-Yh, La₂O₃/Na-Yh, TiO₂/Na-Yh) and the activity and selectivity of these catalysts in isophorone aromatization were studied. MgO/Na-Yh and La₂O₃/Na-Yh zeolites with high content of basic sites and low content of Brønsted acid sites are the most effective in the synthesis of 3,5-dimethylphenol: The 3,5-dimethylphenol formation selectivity reaches 63–69% at 87–94% isophorone conversion. In the presence of Na-Yh zeolite containing both acid and base sites, the prevalent reactions are isophorone isomerization and synthesis of trimethylbenzenes. The modification of Na-Yh with titanium oxide leads to an increase in the content of acid sites on the TiO₂/Na-Yh surface and to the prevalence of the aromatization to form trimethylbenzenes. In the presence of HNa-Yh containing a set of the strongest Brønsted and Lewis acid sites, isophorone transforms into a mixture of polymethylbenzenes.