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

The relationship between Bronsted 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 Bronsted acid sites and guest molecules, but also promotes proximity and interaction between Bronsted acid sites with the same chemical shift, enhancing their strengths. Stronger Bronsted 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).