Catalytic synthesis of anisole over LDHs with different Mg/Al ratios

A series of layered hydroxides(LDHs)with different Mg/Al ratios were synthesized by coprecipitation method.MgAl LDHs and their calcined products were characterized by XRD, SEM, FT-IR, NH₃-TPD, CO₂- TPD, TG and ICP-OES, and were used to catalyze the vapor phase synthesis of anisole from phenol and dimethyl carbonate(DMC).The results show that MgAl LDHs synthesized by coprecipitation method have good hydrotalcite like structure when Mg/Al ratio is 2 to 4, mainly in the form of spherical lamellar aggregates.The interlayer spacing, average pore size and alkali acid ratio increase gradually when Mg/Al ratio is from 2 to 4.It is found that the selectivity of anisole first increases and then decreases with the acid-base ratio of the catalyst.The highest anisole selectivity of 88.93 % is achieved when the Mg/Al ratio is 4 and the acid/base ratio is 0.32.In addition, the effect of reaction temperature and mass space velocity on the catalytic performance are also investigated.