Selective hydrogenolysis of furfuryl alcohol to 1,2-pentanediol on CuZrAl catalysts: New insights into the Zr introduction

Achieving precise control over targeted C-O bond cleavage in furfuryl alcohol (FFA) for high-yield 1,2-pentanediol (1,2-PeD) synthesis remains challenging. In this work, a breakthrough strategy through designing CuxZrAl catalysts with tunable Cu/Zr molar ratios for FFA hydrogenolysis was developed. Cu50ZrAl exhibited superior catalytic performance with 84.8 % FFA conversion and 56.1 % 1,2-PeD selectivity, surpassing CuAl and most Cu-based catalysts reported. Notably, the enhanced catalytic performance was primarily attributed to the synergy between the improved weak and medium acidity (1633.3 μmol·g−1) and elevated Cu0/Cu+ ratio (2.7) through strategic Zr incorporation with an appropriate amount, which were responsible for FFA conversion and 1,2-PeD selectivity, respectively. Crucially, the exclusive catalytic pathway of CuxZrAl via direct furan ring-opening mechanism, rather than indirect intermediates, was unambiguously confirmed through comparative experiments using tetrahydrofurfuryl alcohol (THFA) as substrate under identical reaction conditions with that of FFA hydrogenolysis. In-situ DRIFTS revealed that smaller Cu particles on Cu50ZrAl exposed more weak and medium acid sites than that of CuAl, enhancing of FFA adsorption. Active H species generated on Cu0 active sites is identified as the promoter for the cleavage of C-O bonds of furan ring (Rate-controlling step). Pioneeringly, DFT calculations reveal that CuAlO2 in CuAl possesses a higher energy barrier (57.1 kJ·mol−1) for the ring-opening of FFA compared to Cu2O (6.6 kJ·mol−1), fortunately which can be destroyed by the introduced Zr species to enhanced selectivity to 1,2-PeD. This study comprehensively provides a deep understanding of structure-performance relationship of CuZrAl catalysts and a design strategy of efficient catalysts for FFA hydrogenolysis.