Improvement of dimethyl carbonate formation via methanol carbonation over vanadium-doped Cu–Ni/AC catalyst

Abstract

In present study, Cu–Ni/AC and V-doped Cu–Ni/AC were prepared using an impregnation and co-impregnation methods respectively for dimethyl carbonation (DMC) formation from CH3OH carbonation at various temperatures (110, 170, and 220°C) and CO2/N2 volumetric flow ratios (1/4, 1/7, and 1/9). Effects of vanadium addition on Cu–Ni/AC intrinsic properties and catalytic performances were investigated. Decrease of Cu–Ni/AC surface acidity with vanadium addition was found with NH3–temperature programmed desorption (NH3–TPD) at 25–450°C. Furthermore, the valence shifts of metallic atoms in catalysts were found by X–ray absorption near–edge structure/extended X–ray absorption fine structure (XANES/EXAFS). Optimal reaction conditions (170°C and CO2/N2 = 1/7) with the highest CH3OH conversion (8.1%), DMC selectivity (93.2%), and DMC yield (7.5%) were confirmed in a fixed-bed column reactor. Linear regressions of the pseudo-first-order, pseudo-second-order, and third-order models referred that the largest CH3OH consumption rate constant (15.56 × 10−3 1/min, 9.29 L/mol-min), turnover number (TON = 17.89), and turnover frequency (TOF = 3.73 × 10−2 1/min) of DMC formation were acquired with V-doped Cu–Ni/AC at optimal reaction conditions. A reaction mechanism over Cu–Ni/AC or V-doped Cu–Ni/AC active sites was proposed.