PdGa/TiO2 an efficient heterogeneous catalyst for direct methylation of N-methylaniline with CO2/H2

Abstract

An effective sustainable heterogeneous PdGa/TiO₂ catalyst was prepared for direct methylation of N-methylaniline with CO₂/H₂ to N,N-dimethylaniline. The PdGa/TiO₂ catalyst exhibited 98% conversion and 94% selectivity under the reaction conditions (180 °C, 5 MPa H₂, 5 MPa CO₂, 10 h), which are one of the best results reported to date for the heterogeneous N-methylation with CO₂ as methylation reagent over the supported metal catalysts. The PdGa/TiO₂ catalyst was well characterized using TEM, TPR, XPS, CO-adsorption IR studies and high-pressure in situ FTIR studies. It was confirmed that PdGa bimetallic alloy nanoparticles were formed and highly dispersed on the TiO₂ support, and the electron-deficient Pd derived from the interaction with Ga could activate CO₂ and transform it to formic acid, which is the key step for the discussed methylation, and high activity was obtained over the PdGa/TiO₂ catalyst. The activating properties of the PdGa/TiO₂ catalyst will open a new route for transfer and utilization of CO₂ in the fields of energy and environmental fields.