Direct conversion of enzymatic hydrolysis lignin to cycloalkane fuel with hydrotalcite-derived Ni catalyst

Herein, we reported a one-pot method that directly converting enzymatic hydrolysis lignin (EHL) into cycloalkane fuels using a Ni catalyst derived from Ni-Al hydrotalcite (NiAl-LDH). The effects of Ni/Al ratio and reduction condition on the catalytic activity have been examined. The catalyst obtained from the reduction of NiAl-LDH at 460 °C (Ni₂Al₁-re460) shows the highest activity among the catalyst samples examined, attributed to its abundant Lewis acidic sites, small-sized Ni metal particles, and large specific surface area. At optimized reaction conditions (320 °C, 3 MPa H₂, 6 h), this catalyst achieves 100% EHL conversion and complete oxygen removal and improves the calorific value of the products from 25.0 MJ kg⁻¹ to 42.5 MJ kg⁻¹. The detected products are cycloalkane dimers and monomers with their carbon numbers within the range suitable for gasoline and diesel, and other large molecules with uncertain structures also predominantly consist of cycloalkane rings.