Single site MIL-101 for novel low-temperature liquid-phase toluene methylation

Abstract

P-xylene is one of petrochemical products eagerly in demand. Until recently, the process for preparing of p-xylene was done via gas-phase toluene methylation reaction at high temperature using a strong acid catalyst. In this work, high surface area, shape-selective and single-site MIL-101(Cr) was used as a catalyst to perform toluene methylation reaction in a liquid phase at low reaction temperature (60-120 °C). Toluene conversion and p-xylene selectivity are up to 50% and 90%, respectively. Under the optimum operating conditions; 1:1 toluene: methanol molar ratio, the reaction temperature is 120 °C. The catalyst was synthesized via the hydrothermal method and the MIL-101 structure was confirmed by different analytical techniques: TGA, XRD, FTIR and BET surface area. The remarkably high toluene conversion and xylene selectivity at a low reaction temperature, in comparison to previous research, was attributed to the suppression of side reactions that could convert methanol to linear hydrocarbons, and to the inhibition of p-xylene isomerization. This suppression can be attributed to the single site properties and to the uniform pore size distribution of the prepared MIL 101 catalyst. Synthesis and characterization of single-site MIL-101(Cr) were used as a catalyst for toluene methylation reaction in a liquid phase at low reaction temperature (60–120 °C). The results suggest that toluene conversion and p-xylene selectivity are up to 50% and 90%, respectively, under the optimum operating conditions; 1:1 toluene: methanol molar ratio, the reaction temperature is 120 °C.