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.
Qi et al. (Tue,) studied this question.