Monodentate Formate‐Mediated Toluene Methylation to Xylene at Low Temperature Using Formic Acid and Hydrogen

Abstract The industrial methanol–toluene methylation process for xylene production faces a challenge of lowering the reaction temperature while suppressing the side reaction of methanol to hydrocarbons. This depends on the low‐temperature formation of the methoxy intermediate required for methylation. Here, we establish a route for methoxy formation in which formic acid (FA) hydrogenates via a metastable monodentate formate intermediate. With the GaZrO x –ZSM‐5 catalyst, Ga–H bonds act as a “placeholder”, enabling FA adsorption as a monodentate formate rather than a stable bridged formate. At 300 °C and 3.0 MPa, toluene conversion reaches 13.9% with 77.6% xylene selectivity, outperforming established routes. Kinetic isotope effect experiments revealed that Ga‐based catalysts show a secondary isotope effect, whereas non‐Ga catalysts exhibit an inverse isotope effect. Density functional theory calculations indicated that the monodentate formate was more susceptible to hydrogenation which then facilitated methylation. This work provides a competitive route for xylene production from toluene under mild conditions using sustainable FA and H 2 .