New Method for Highly Efficient Conversion of Biomass-Derived Levulinic Acid to γ-Valerolactone in Water without Precious Metal Catalysts

γ-Valerolactone (GVL) is receiving increasing attention because of its significant characteristics of an ideal sustainable liquid fuel. In this work, a novel and nonprecious metal catalytic method of the hydrogenation of biomass-derived levulinic acid (LA) into GVL by water splitting is first reported. Commercially available nonprecious metals of Fe, Ni, Cu, Cr, and Mo exhibited significantly catalytic activities in the hydrogenation of LA into GVL. Over 90% yield of GVL from LA can be obtained at a relatively low temperature of 180 °C, and an excellent 98% yield of GVL was achieved over the Fe catalyst at 250 °C. Catalyst Fe is stable and still keeps the high catalytic activity after recycles. The extraordinary catalytic activity of the general Fe powder is probably because of the role of hot water and also a synergistic role of the Fe and ZnO or Zn/ZnO. Also, the reactor wall of a reactor made of the stainless steel material acted as a significant catalyst, and a considerably high GVL yield of 56% can be obtained even without any addition of catalyst. This method is simple, highly efficient, and requires neither gaseous hydrogen nor precious metal catalyst, which is key for the practical application.