Study on condensation pathways and coking behavior of acetone over conventional zeolites in thermal catalysis

This work conducted a theoretical study on four commonly used zeolite materials （NaY, NaZSM-5, NaMCM-22, and S-1）, combining the practical requirements of acetone thermal catalysis. The structural characteristics, catalytic performance, evolution of intermediate products during temperature-programmed processes were evaluated, and coke behavior from the perspectives of acid properties and intermediate product evolution were investigated. Experimental results showed that the catalytic conversion of acetone on pure zeolites primarily depends on their inherent acidity. However, the acidity also promoted the transformation of acetone into refractory intermediates, subsequently triggering coke formation. Due to their acidic structures and modification by Na⁺ ions, NaY, NaMCM-22, and NaZSM-5 generated condensation by-products such as acetic anhydride, isophorone, and mesityl oxide. As the temperature increased to 360℃, acetone and its by-products could be progressively degraded into acetic acid and formic acid, ultimately desorbing as H₂O and CO₂. In contrast, the S-1 zeolite framework consists mainly of Si─O─Si structures and lacks acidic sites. It showed no catalytic activity for acetone degradation during the temperature-programmed process. Aparting from the desorption of trace amounts of acetone, no condensation or cracking products were detected. Among the three sodium-containing zeolites, NaMCM-22 generated the most condensation by-products and exhibited the lowest acetone degradation efficiency. NaZSM-5 achieved the highest mineralization efficiency for acetone, followed by NaY. This study details the degradation and condensation pathways of acetone on each material, providing new theoretical insights for improving the thermal catalytic degradation of acetone using zeolite materials.