Several copper based catalysts were prepared, characterized and evaluated for the hydrogenation of levulinic acid and its methyl ester. Among these, nanocomposites of Cu–ZrO₂ and Cu–Al₂O₃ quantitatively catalyzed the hydrogenation of levulinic acid and its methyl ester to give 90–100% selectivity to γ-valerolactone in methanol and water respectively. Both the Cu–ZrO₂ and Cu–Al₂O₃ nanocomposites were prepared by the co-precipitation method using mixed precursors under controlled conditions. XRD results showed that the main active phase of the reduced Cu–ZrO₂ catalyst was metallic copper and particle size was found to be of 10–14 nm by HRTEM. The active metal leaching was at a maximum for the Cu–Al₂O₃ catalyst in a water medium due to the formation of a copper–carboxylate complex that was blue in colour. Surprisingly, copper leaching was completely suppressed in the case of the Cu–ZrO₂ catalyst in methanol in spite of the substrate loading was increased from 5 to 20% w/w. The excellent recyclability of the Cu–ZrO₂ catalyst with complete LA conversion and >90% GVL selectivity makes it a sustainable process having a commercial potential.

Various iridium supported carbon catalysts were prepared and screened for the direct hydrogenation of furfural (FFR) to 2-methyl furan (2-MF). Amongst these, 5% Ir/C showed excellent results with complete FFR conversion and highest selectivity of 95% to 2-MF at a very low H₂ pressure of 100 psig. Metallic (Ir°) and oxide (IrO₂) phases of Ir catalyzed the first step hydrogenation involving FFR to FAL and subsequent hydrogenation to 2-MF, respectively. This was confirmed by XPS analysis and some control experiments. At a low temperature of 140 °C, almost equal selectivities of FAL (42%) and 2-MF (43%) were observed, while the higher temperature (220 °C) favored selective hydrodeoxygenation. At optimized temperature, 2-MF was formed selectively while higher pressure and higher catalyst loading favored ring hydrogenation of furfural rather than side chain hydrogenation. With the combination of several control experimental results and detailed catalyst characterization, a plausible reaction pathway has been proposed for the selective formation of 2-MF. The selectivity to various other products in FFR hydrogenation can be manipulated by tailoring the reaction conditions over the same catalyst.

Ionic liquids functionalized with acidic anions, HSO₄, ClSO₃H, PTSA, TFA (MIm), HSO₄ and TFA (NMP) were found to efficiently (99% conversion) catalyze the alcoholysis of furfuryl alcohol (FAL) in the presence of methanol, ethanol, n-butanol and isopropyl alcohol (IPA) to the corresponding levulinic acid esters under mild temperature (90–130 °C) conditions. The extended alkyl chain length of [MIm] using 1,4-butane sultone enhanced the Brønsted acidity of [BMIm-SH][HSO₄] catalyst resulting into the highest selectivity of >95% to Me-LA. An increase in both temperature and catalyst concentration increased the furfuryl alcohol conversion and selectivity to levulinate esters. In contrast, an increase in the substrate concentration from 5 to 15% caused a decrease in Me-LA selectivity due to accumulation of intermediate ethers of furfuryl alcohol. Using a combination of [BMIm-SH][HSO₄] and 5% Ru/C catalyst, direct conversion of FAL to γ-valerolactone (GVL) is shown for the first time. A complete conversion of FAL with the highest selectivity of 68% to GVL could be achieved under optimum conditions while higher Ru loading enhanced the GVL selectivity to 94% in the hydrogenation step of this tandem approach. Our catalyst system could be efficiently recycled five times retaining the original activity and selectivity levels.

A sustainable process of catalytic transfer hydrogenation (CTH) of levulinic acid (LA) to γ-valerolactone (GVL) was investigated over Ni on various supports (Al₂O₃, ZnO, MMT and SiO₂) in the presence of isopropanol (IPA) as the H-donor. Among these, the montmorillonite (MMT) supported Ni catalyst showed almost complete LA conversion (>99%) and selectivity (>99%) to GVL within 1 h. XRD and XPS results showed that the concentration of the metallic species significantly enhanced (two to four times) in the recovered sample as compared to the freshly prepared Ni/MMT. This was due to the in situ reduction of Ni²⁺ species present on the catalyst surface, through liberated H₂ under the reaction conditions. The strong acid strength of MMT, evidenced by NH₃-TPD and py-IR, facilitated the esterification of LA as well as cyclization to GVL. The conversion–selectivity pattern was found to decrease in the IPA–water mixture while, it remained unchanged in the IPA–acetone mixture. Our catalyst could be efficiently recycled up to five times with consistent CTH activity and selectivity to GVL. The plausible mechanism of LA to GVL conversion involves the formation of a levulinate ester with IPA that favours its simultaneous hydrogenation and cyclization in a spontaneous manner to give GVL and regenerating IPA for sustainability.

Among various catalysts screened, the Cu–Al oxide catalyst, prepared by a co-precipitation method, exhibited excellent activity for simultaneous glycerol dehydration and its hydrogenolysis without external hydrogen. Detailed characterization by XRD, XPS, HR-TEM, TPR, etc., showed evidence of Cu²⁺ in the form of CuO and CuAl₂O₄, along with Cu⁰ and Cu¹⁺ species, which are responsible for their multifunctional roles in glycerol APR, dehydration and hydrogenolysis reactions under inert conditions. This catalyst also presented consistent activity for a duration of 400 h for autogeneous hydrogenolysis of refined glycerol with 36% selectivity to 1,2-propanediol (1,2-PDO). Manipulating the temperature and feed flow rate conditions, meant that the selectivity to acetol and 1,2-PDO could be tailored as desired. Substantial enhancement in 1,2-PDO selectivity (75%) was achieved for an aqueous bio-glycerol feed over the same catalyst for 50 h of testing.

A composite of reduced graphene oxide (RGO) with oxides of manganese and cobalt together was prepared by a solvothermal method. During synthesis, both the reduction of graphene oxide as well as the growth of nanorod shaped CoMn₂O₄ and Co₃O₄ occurred simultaneously having a crystallite size of ~8 nm calculated from X-ray diffraction (XRD). The as-obtained triple nanocomposite material designated as RGO–MnCoO exhibited excellent activity for the liquid phase aerobic oxidation of aromatic alcohols under base-free conditions selectively giving the corresponding aldehydes (>85%). RGO loading was varied in the range of 1–10%, among which 1% RGO–MnCoO showed maximum catalytic activity enhancement of 24% as compared to the bare mixed oxide (MnCo-MO) for the oxidation of vanillyl alcohol. HR-TEM of RGO–MnCoO revealed that it was a composite material having uniform nanotubes of ~25 nm length and 6 nm diameter with a fringe pattern showing the (103) and (004) planes and lattice spaces of 0.26 nm and 0.22 nm, respectively, for the spinel CoMn₂O₄. The detailed studies on the morphology, size and composition of the as-prepared RGO–MnCoO nanocomposite by XRD, XPS, N₂-adsorption/desorption and O₂-TPD techniques were used to understand the role of RGO in the enhancement of catalytic activity for oxidation reaction.