## 1 Introduction  
\(\gamma\)-Valerolactone (GVL) has been recently considered as a new renewable liquid for gasoline and diesel fuel oxygenate due to its comparable fuel characteristics to those of fossil-based fuels [1]. Some drawbacks, including high water solubility and smaller cetane number as compared with diesel fuels limit actual applications of GVL in the transportation sector. However, these weaknesses can be overcome by upgrading GVL into useful liquid hydrocarbon fuels through various catalytic cascade processes [2, 3]. GVL can consequently serve as a high-valued intermediate or platform chemical for the production of biofuels. Apart from the excellent fuel properties, GVL is also regarded as a promising sustainable liquid from biomass for the production of other carbon-based chemicals because of its renewable nature, non-toxicity, stability, and biodegradability [4]. Since GVL has the ability to solubilize all products from cellulose deconstruction, it can be used as a biphasic solvent system in biorefineries [5, 6]. GVL has also recently shown very good effectiveness in thermocatalytic production of soluble sugars from corn stover and wood at high yields [7]. Complete solubilization of biomass, including lignin fractions, could be achieved in a dilute aqueous phase-GVL medium to promote a thermocatalytic saccharification of biomass into monosaccharides. Many reports are available on the catalytic conversion of LA to GVL. While different homogeneous catalysts such as Ru-complexes, including Shvo catalyst [8, 9, 10], iridium pincer complexes [11, 12] were used with excellent performance even under mild reaction conditions, they are arguably not suited to targeted GVL production as the high boiling point of GVL (207-208 \({}^{\circ}\)C) makes product/catalyst separation uneconomical by means of distillation. In this regard, several heterogeneous catalytic systems have been reported in the last few years with noble metals including Ru [13, 14, 15], Pd [16, 17], Pt [18], and Au [19] as active metal species generating high yields of GVL from LA. An excellent approach of LA hydrogenation was studied under supercritical CO\({}_{2}\) over Ru/Al\({}_{2}\)O\({}_{3}\) and Ru/SiO\({}_{2}\) catalysts that produced 99% GVL (200 \({}^{\circ}\)C and 20 MPa H\({}_{2}\)) [20]. There are also some reports on bimetallic catalysts such as Ru-Sn/C [21], RuNi-OMC [22], _etc._, which showed improved selectivity at high GVL yields. However, the activity and stability of many noble metal catalysts, especially Ru and Pt catalysts, is not ideal due to catalyst deactivation and substantial active metal leaching [13, 23, 24]. In addition, the use of noble metals for GVL production is not suitable for commercial applications and attention should be consequently paid to the development of non-noble metal systems with high activity and selectivity to GVL production. [PERSON] and [PERSON] reported copper-based catalysts over ZrO\({}_{2}\) and Al\({}_{2}\)O\({}_{3}\) for the hydrogenation of LA and its methyl ester, resulting in quantitative conversion with \(>\)90% GVL selectivity [25]. In another report, a series of base-metal (Ni, Co, Cu, and Fe) and metal oxides (Mo, V, and W oxides) co-loaded carbon were tested for the hydrogenation of LA [26]. Ni-MoO\({}_{3}\)/C showed the highest activity with 97% GVL yield which was probably due to the co-presence of metallic Ni\({}^{0}\) species and partially reduced MoO\({}_{2}\). Aqueous phase hydrogenation of LA using Mo\({}_{2}\)C catalysts provided 99% LA conversion with 90% GVL selectivity at 30 bar H\({}_{2}\) and 200 \({}^{\circ}\)C [27]. The catalytic transfer hydrogenation (CTH) of ethyl levulinate (EL) in isopropanol was also reported using a porous Zr-containing catalyst (Zr-HBA) with a phenate group that produced 94.4% GVL [28]. The presence of the phenate group increased the basicity of the catalyst, which significantly favored the CTH process.