Role of complex equilibrium in the shape-selective performances of MgO/MCM-22 catalysts prepared by complexing impregnation

Methanol Usage in Toluene Methylation over Pt Modified ZSM-5 Catalyst: Effects of Total Pressure and Carrier Gas

“…To be commercially competitive, toluene methylation (especially operating in a fixed-bed reactor) requires its catalyst to be highly para-selective, highly active, and highly stable, as well as efficient methanol utilization. Shape-selective toluene methylation mainly uses medium-pore zeolites (10-membered ring zeolites) as catalyst, such as ZSM-5 and MCM-22. − Pure HZSM-5 or MCM-22 exhibits poor para-selectivity in toluene methylation due to the isomerization on external acid sites. , Therefore, certain modifications are made to improve para-selectivity. Commonly used techniques include (1) addition of an oxide by impregnation with salts like B, P, Mg, La compounds, − ,− , (2) silanization by chemical vapor deposition (CVD), chemical liquid deposition (CLD), ,, or core–shell synthesis methods, (3) precoking, (4) tuning crystal size. , Most treatments are aimed at minimizing external acid sites and tailoring relative diffusion rate of xylene isomers .…”

“…Shape-selective toluene methylation mainly uses medium-pore zeolites (10-membered ring zeolites) as catalyst, such as ZSM-5 and MCM-22. − Pure HZSM-5 or MCM-22 exhibits poor para-selectivity in toluene methylation due to the isomerization on external acid sites. , Therefore, certain modifications are made to improve para-selectivity. Commonly used techniques include (1) addition of an oxide by impregnation with salts like B, P, Mg, La compounds, − ,− , (2) silanization by chemical vapor deposition (CVD), chemical liquid deposition (CLD), ,, or core–shell synthesis methods, (3) precoking, (4) tuning crystal size. , Most treatments are aimed at minimizing external acid sites and tailoring relative diffusion rate of xylene isomers . However, these effective means for para-selectivity enhancement were achieved at the expense of toluene conversion and catalyst life span.…”

“…14,15 Therefore, certain modifications are made to improve para-selectivity. Commonly used techniques include (1) addition of an oxide by impregnation with salts like B, P, Mg, La compounds, [7][8][9][11][12][13][14]16 (2) silanization by chemical vapor deposition (CVD), 17 chemical liquid deposition (CLD), 11,18,19 or core−shell synthesis methods, 10 (3) precoking, 7 (4) tuning crystal size. 14,20 Most treatments are aimed at minimizing external acid sites and tailoring relative diffusion rate of xylene isomers.…”