Study on Methylation of Phenol with Methanol over HZSM-5 Zeolite

The methylation of phenol with methanol over HZSM 5, HZSM 23, and modified HZSM 5 with P 2O 5, MgO, and Sb 2O 3 was investigated under the reaction conditions of n (PhOH)/ n (CH 3OH)=1, WHSV=0 5 h -1 and T =673 K. The results revealed that the acid sites on the external surface of HZSM 5 and HZSM 23 played an important role in the reaction. When the zeolite was treated with 4 methylquinoline, the pore size of the zeolite was the key factor affecting the product selectivity. The HZSM 23 zeolite with smaller pore size than HZSM 5 zeolite was beneficial to enhancement of the selectivity for anisole plus methylanisole , as well as p cresol. Xylenol and m cresol could be formed in the pores of HZSM 5, while their formation in the pores of HZSM 23 was strongly inhibited. The modification of HZSM 5 with P 2O 5, MgO and Sb 2O 3 could increase the selectivity for anisole plus methylanisole. However, the modification of HZSM 5 decreased the selectivity for xylenol and cresol. Increasing the amount of those oxides could enhance the selectivity for o cresol. Moderate impregnation of HZSM 5 zeolite with the oxide solution could improve the selectivity for p cresol, and the modification effect had the sequence: Sb 2O 3P 2O 5MgO.