Correlation of Brønsted acid sites and Al distribution in ZSM-5 zeolites and their effects on butenes conversion

• Spatial confinement in straight and sinusoidal channels strengths Brønsted acid sites in ZSM-5 zeolites. • Proximity and interaction between Brønsted acid sites enhance their strengths. • Stronger Brønsted acid sites hinder butenes oligomerization reactions. • Al sites at channel intersections with lower confinement favors butenes oligomerization and aromatization reactions. The relationship between Brønsted acid sites and framework Al distribution in the 10-membered ring (10-MR) straight and sinusoidal channels and their channel intersections in ZSM-5 zeolites were investigated using a range of analytical techniques. Spatial confinement in the straight and sinusoidal channels not only strengthens interactions between Brønsted acid sites and guest molecules, but also promotes proximity and interaction between Brønsted acid sites with the same chemical shift, enhancing their strengths. Stronger Brønsted acid sites do not benefit the conversion of butenes in oligomerization reactions owing to restriction of their migration and diffusion. However, the Al sites at channel intersections are more spacious, and the lower confinement therein favors selectivity for butene oligomerization products (C8) and n -butene aromatization products (BTX and C9 + aromatics).