Study of the Alkylation of Phenol with Methanol on Zn(H)-Exchanged NaY Zeolites

摘要

The gas-phase alkylation of phenol with methanol was studied at 473 K on zeolite NaY exchanged with Zn~(+2) (samples Zn(x)NaY) or H~+ (samples Na(x)HY) cations. Zeolite NaY contained only weak and medium Lewis acid sites. The addition of Zn~(+2) formed essentially strong Lewis acid sites. In contrast, the exchange of NaY with H~+ generated Br0nsted acid sites and decreased the density of Lewis acid sites. Zeolite NaY was inactive at 473 K, but after its exchange with Zn~(2+) efficiently promoted the phenol methylation reaction. Phenol conversion and the selectivities to o- and p-cresols increased with the Zn content in the sample. The exchange of Na~+ with H~+ also activated the parent NaY zeolite. At similar phenol conversion levels, Na(x)HY samples formed more anisole and less cresols than Zn(x)NaY. All the Zn(x)NaY and Na(x)HY samples deactivated on stream, but the catalyst activity decay increased with the exchange degree.