Effects of the Type and Loading of Rare-Earth Metals (Pr, Yb, Ho) on the para-Selectivity of HTsVM Zeolite in Toluene Ethylation

Abstract

The study describes toluene ethylation using TsVM zeolite (SiO₂/Al₂O₃ = 40) and a series of TsVM-based catalysts modified with rare-earth metals. To investigate the effects of the type and loading of rare-earth metals in the HTsVM catalyst on the selectivity towards total ethyltoluenes and p-ethyltoluene, the reaction was carried out in a continuous-flow fixed-bed reactor at atmospheric pressure and temperatures of 300–400°C. The HTsVM was modified with praseodymium, ytterbium, and holmium nitrates. The physicochemical and textural properties of the catalysts were characterized by XRD, FTIR spectroscopy, NH₃-TPD, and low-temperature nitrogen adsorption. The specific surface area, acidity, total pore volume, and mesopore volume were found to decrease with an increase in the holmium loading of the catalyst. The zeolite catalysts loaded with 4.0–5.0 wt % Ho exhibited optimum stability and high p-ethyltoluene selectivity (79.5–81.4%) in combination with adequate toluene conversion (19.4–20.3%).