Efficient and Stable Conversion of Ethanol/Acetaldehyde to 1,3-Butadiene over a Zr1/NC@SBA-15 Single-Atom Catalyst

Herein, a Zr single–atom catalyst supported on Zr1/NC@SBA–15 was constructed and employed in the ETB process. Compared with the conventional nano–Zr/SBA–15 catalyst, the Zr1/NC@SBA–15 catalyst delivered notably higher performance: the reactant conversion exceeded 80%, the selectivity toward 1,3–BD was above 70%, and unprecedentedly high stability of 300 hours on stream was achieved without notable deactivation.

Systematic characterizations, operando spectroscopy, and density functional theory (DFT) calculations revealed that the Zr atoms were uniformly dispersed on the Zr1/NC@SBA–15 catalyst in the single–atom state, forming abundant Lewis acid sites (LAS) of [(Si–N)–Zr(O–Si)2(OH)]. A dual acetaldehyde absorption mode was proposed for the ETB reaction over the Zr1/NC@SBA–15 catalyst. The rate–determining step of acetaldehyde condensation proceeded via the Langmuir–Hinshelwood mechanism over the [(Si–N)–Zr(O–Si)2(OH)] sites, with apparent activation energy decreased by 18.8 kJ/mol compared with that over the nano–Zr/SBA–15 catalyst.