HZSM-5沸石分子筛上苯酚与甲醇的烷基化反应

 在n（PhOH）／n（CH3OH）＝1，WGSV＝0．5h－1，T＝673K的反应条件下，研究了HZSM－5，HZSM－23和改性HZSM－5分子筛上苯酚与甲醇烷基化反应的规律．结果表明，分子筛外表面的酸中心对苯酚烷基化反应的贡献较大．用4－甲基喹啉使分子筛外表面的酸中心中毒后，影响反应产物选择性的主要因素是分子筛的孔径．孔径较小的HZSM－23分子筛对提高芳香醚的选择性，抑制二甲酚的生成和提高对甲酚的选择性有利．间甲酚和二甲酚可以在HZSM－5沸石的孔道内生成，但在HZSM－23的孔道内受到抑制．用P2O5，MgO和Sb2O3对HZSM－5改性都可以提高芳香醚的选择性，降低甲酚和二甲酚的选择性．随着氧化物负载量的增加，邻甲酚选择性升高．适度的氧化物改性可以提高对甲酚的选择性，改性效果为Sb2O3＞P2O5＞MgO．

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 3>P 2O 5>MgO.