(α-Fe2O3)1-x(V2O5)x catalysts with enhanced acid-base property for the highly active and ortho-selective methylation of phenol

Abstract A series of highly active and ortho-position selective catalysts based on (α-Fe2O3)1-x(V2O5)x catalysts were proposed for the C-methylation of phenol with methanol. The (α-Fe2O3)1-x(V2O5)x catalysts were synthesized by coprecipitation method of Fe and V elements and microwave drying. The chemical composition, material structure, acid-base properties, and structure-activity relationship of (α-Fe2O3)1-x(V2O5)x catalysts were systematically analyzed by the techniques of XRD, XPS, TEM, N2 adsorption-desorption, Raman, UV-Vis, ESR, NH3/CO2-TPD and Pyridine-IR. The (α-Fe2O3)1-x(V2O5)x catalysts have the double advantages of high activity and high stability for the methylation of phenol due to the high BET surface area, large total pore volume, dispersive active sites and enhanced acid-base property. o-cresol and 2,6-xylenol were the main products, and nearly 100% selectivity to the ortho-position of phenol and 90% selectivity to o-cresol were obtained. Furthermore, the (α-Fe2O3)1-x(V2O5)x catalysts possess long lifetime over 2500 h and high activity at a weight hourly space velocity of 1.6 h−1 compared with the microwave-dried α-Fe2O3 catalyst. The doping of vanadium improves the activity and stability of α-Fe2O3 catalyst, which attributes to the modification of catalyst structure, especially the improvement of acid-base centers and oxygen vacancy. Recently the (α-Fe2O3)1-x(V2O5)x catalysts have been stably and efficiently applied in industry for the methylation of phenol.