Effect of phosphorus modification and hydrothermal treatment of zeolites on shape-selective methylation of 4-methylbiphenyl

Shape-selective methylation of 4-methylbiphenyl (4-MBP) with methanol over different HZSM-5 modified with organic and inorganic P, together with hydrothermal treatment, was studied. Through P modification and hydrothermal treatment, the selectivity to 4,4′-dimethylbiphenyl could be effectively increased. However, the activity could only stabilize for about 4-6 hr. TPP-CBV(4.1) and AHP-CBV(1.7) displayed similar activity and selectivity even though considerably different amounts were used. This was ascribed to the different location of the P compounds on the HZSM-5 zeolite. Due to its larger size, TPP was mainly located on the external surface of ZSM-5 even with higher P content. In the case of AHP, it could easily enter the internal surface in addition to the particle external surface.