Homocondensation of Acetone over Cation-Exchanged Granulated Hierarchical Yh Zeolites

Abstract

The catalytic performance (activity and selectivity) of a FAU-type hierarchical NaY_h zeolite, as well as of a series of modified samples, was investigated in the homocondensation of acetone. The modified samples were prepared from NaY_h by ion exchange of Na⁺ for cations of alkali (Li⁺, K⁺), alkaline-earth (Ca²⁺, Mg²⁺), transition (Co²⁺, Ni²⁺), and rare-earth (La³⁺) metals, as well as by decationation (H-NaY_h, HY_h). The predominantly acidic zeolites (Ca-NaY_h, Mg-NaY_h, Co-NaY_h, Ni-NaY_h, La-NaY_h, H-NaY_h, and HY_h) promoted the formation of acetic acid and mesitylene even at 250°C. The zeolites that contained alkali metal cations (Na⁺, Li⁺, and K⁺) exhibited activity only when the temperature was elevated. Starting from 350°C, NaY_h and Li-NaY_h promoted the formation of acetic acid. In contrast, the performance of K-NaY_h under heating was characterized by the absence of acetic acid formation and a smooth increase in the selectivity towards isophorone (up to 23%) and mesitylene (up to 18%). Over the range of 400–450°C, in the presence of K-NaY_h, secondary isophorone transformations were intensified, resulting in the formation of 3,5-xylenol as the main product with a selectivity of 32%.