| O-cresol is a valuable fine chemical intermediate,which plays a vital role in the production of synthetic resins,pesticides,pharmaceuticals,antioxidants and fragrances.HZSM-5 has been widely used in various catalytic reactions due to its unique pore structure,adjustable acidity and structural stability in high temperature reactions.In order to improve the yield of o-cresol,this research work explores the effect of content of Ce on HZSM-5 on the alkylation of phenol with methanol for the synthesis of o-cresol.This research covers effect of different metals（Ce,Al,Fe,Cu,Ni,Mg and Zn）supported on HZSM-5 by impregnation,effect of different metals on the structure,and chemical properties,as well as on the methanolic alkylation reaction of phenol on HZSM-5.This study reveals that doping metal of Ce generated the highest yield.Subsequently,three different preparation methods,i.e.,impregnation,ball-mill mixing and solid-state ion-exchange,were used to support Ce on the HZSM-5.The effect of different preparation methods on the structure and properties of the catalyst was investigated with XRD,SEM,BET,FT-IR,Py-IR,NH3-TPD and XPS characterization methods.The relationship between the surface properties and structure of the molecular sieve and its catalytic performance was also examined.The data showed that the catalysts prepared by the ball milling method yielded the lowest catalytic activity due to the smallest specific surface area and the least amount of total acidic sites,but possessed the highest amount of Br（?）nsted acid,which giving the highest anisole selectivity of 47.9%.The catalyst prepared by impregnation increased the Lewis acid amount and therefore it had the highest o-cresol selectivity of 48.3%.While the catalyst prepared by solid-state ion-exchange significantly increased the amount of total acid and therefore had the highest catalytic activity with phenol conversion of 23.4%.Finally,the effect of doping different loadings of Ce on HZSM-5 by the impregnation and solid-state ion-exchange methods was investigated.The HZSM-5 catalyst with 5 wt%Ce prepared by solid-state ion-exchange achieved an equivalent catalytic performance to the HZSM-5 catalyst with10 wt%Ce prepared by the impregnation method.The reaction conditions were also optimized,including the reaction temperature and the reactant space velocity（WHSV）.The catalysts prepared by the solid-state ion-exchange method can yield highest phenol conversions have lower at even lower reaction temperatures than catalyst prepared by impregnation.After optimization,the catalyst prepared by the solid-state ion exchange method achieved a 75.7%of phenol conversion and 36.3%of o-cresol selectivity. |
