Zirconium-Containing Amorphous Zeolite Promotes Ethanol-to-Butadiene

A novel amorphous zeolite catalyst (Zr–AZ) with abundant Zr–OH active sites and a hierarchical pore structure (micro-, meso-, and macropores) was developed for the ethanol-to-butadiene (ETB) reaction. Mechanically mixed with ZnO, the catalyst achieved 73% butadiene selectivity at 92% ethanol conversion and maintained stability over 100 h. Zr anchoring on silanol nests formed Zr–OH sites, while the hierarchical pores mitigated carbon deposition. FT-IR and 1H NMR identified surface hydroxyl types, and CO adsorption IR confirmed Zr–OH as the active sites. Reaction mechanism studies via EtOH-TPD, EtOH-TPSR, and in situ FT-IR revealed that ethanol dehydrogenates on ZnO to acetaldehyde, which then undergoes aldol condensation on Zr–OH sites to form butadiene. This design enhances both selectivity and stability for efficient ETB conversion.