Influence of Catalyst Preparation Strategy on the Acid-Base Properties and Catalytic Performance of Metal-Modified NaX Catalysts in SATM Reaction

Achieving an appropriate balance between acid-base properties and dehydrogenation ability is essential for improving catalytic performance in the side-chain alkylation of toluene with methanol (SATM). In this work, a series of transition metal-modified NaX catalysts containing Cu, Ni, Co, Ag, and Ce were synthesized through an in-situ hydrothermal method using two different preparation strategies, denoted as M1 and M2. Subsequently, 17 wt% NaOH was introduced to regulate the surface acid-base properties. The effects of preparation sequence and metal incorporation on catalyst structure, acidity distribution, and catalytic performance were systematically investigated using XRD, BET, NH₃-TPD and FT-IR analyses. The results demonstrated that transition metal incorporation significantly enhanced catalytic activity compared with the parent PAl-NaX catalyst. All catalytic tests were conducted in triplicate per day, and the reported results represent the corresponding average values. Among the M1 catalysts, the Cu-modified sample exhibited the best catalytic performance, achieving a combined ethylbenzene and styrene yield of 71.9% with 99.7% methanol conversion, while the Ni-modified catalyst showed enhanced styrene formation with a total yield of 66.4%. The M2 preparation strategy further improved catalytic performance, with Cat-1Ni-17Na-M2 and Cat-1Cu-17Na-M2 achieving combined yields of 74.2% and 73.6%, respectively. The superior activity of the M2 catalysts is attributed to the introduction of NaX prior to metal incorporation, which promoted the formation of a larger proportion of weak acidic sites and a more favorable acid-base balance. These findings provide valuable insights into the rational design of highly efficient NaX-based catalysts for SATM reactions through controlled modulation of metal species and surface acidity.