Synergy of ultra-low-loaded ruthenium with alumina stimulating the catalytic hydrogenation of levulinic acid into γ-valerolactone

Herein we report an efficient and recyclable catalyst combining extremely low-loaded Ru and abundant alumina supported on nitrogen-doped carbon (NC) for hydrogenation of cellulose-derived levulinic acid (LA) into valuable γ-valerolactone (GVL). The as-fabricated Ru0.18/Al2O3/NC shows extraordinarily catalytic efficiency in transforming LA to GVL under solvent-free conditions, achieving up to a 1.77 × 105 turnover number (TON) and a 26400 h−1 turnover frequency (TOF) in a single batch reaction, which is far better than other heterogeneous catalysts and comparable to the best optimized homogenous catalysts. This catalyst demonstrates a good stability and reusability, whose catalytic performance can be maintained in 22 times recycled reactions, thus reaching a 106-level value of total TONs. These results highlight the importance of the synergistic effects between infrequent Ru and abundant alumina, and provide an up-and-coming way to design more active and stable low Ru loading catalyst for such a transformation.