A sustainable and cost-competitive catalytic process for high yield production of levulinic acid (LA) and γ-valerolactone (GVL) from biomass-derived furfuryl alcohol (FOL) fluid was proposed with GVL as a self-circulation solvent. The innovative process eliminated the separation of the final product GVL and intermediate product LA from the solvent, and the actual concentration of FOL was improved enormously. A higher yield (90.5%) of LA was realized in the fixed-bed reactors than that in the conventional autoclave since the short residence time of the FOL solution could alleviate the polymerization of FOL in the continuous process. UV-Raman spectroscopy demonstrated that fewer polymers deposited on the catalysts, so superior stability of the zeolite was observed in the fixed-bed reactors. Moreover, an 89.4% high yield of GVL can be achieved since the integration of the tandem reaction of hydration and hydrogenation could substantially avoid side reactions in the fixed-bed reactors.
Nanopore-confining strategy is an effective way to inhibit catalyst sintering and improve catalytic performance. However, the expensive material precursors and complex preparation process greatly limit the scale utilization of this particularly structured catalyst. Herein, nanopore-confined catalysts (Ni@PAC) with adjustable active species were successfully prepared by a very simple method exploiting the characteristics of phosphoric acid-activated biochar (PAC). The abundant phosphorous functional groups in PAC confined Ni well in pores and significantly inhibited sintering through the spatial-confined effect of nanopore. Moreover, the evolution and migration of P functional groups can be regulated by changing the reduction temperature, and the modulation of active species of Ni metal or nickel phosphide can be achieved. Using biomass-based levulinic acid hydrogenation as the probe reaction, it was found that the catalytic activity of 20Ni@PAC-600 was one order of magnitude higher than that of the non-phosphated 20Ni/ZAC-600 catalyst, and γ-valerolactone could be selectively prepared at near atmospheric pressure (1 bar). The formation of Ni2P and the spatial-confined effect of nanopore could be the main reasons for the high catalytic activity.
Sustainable catalysis is the key for the future progress toward biorefinery and bioeconomy. In this work, we designed and developed an inexpensive and eco-friendly Ni@C catalyst for selective hydrogenation of biomass-based platform molecules. A facile synthesized Ni nanoparticles encapsulated in a stabilized carbon support derived from a sacrificial agent copolymer-gel was investigated in the hydrogenation of furfural (FA) to tetrahydrofurfuryl alcohol (THFOL) and levulinic acid (LA) to γ-valeralactone (GVL). The aim is to study the two different reactions over a highly stabilized Ni nanoparticles embedded in the carbon matrix. The Ni@C was found to be active and selective in multi-catalyzed hydrogenation reactions. The Ni nanoparticles with small and ultra-fine sizes are highly dispersed over the carbon matrix. This was concluded through high-resolution micrography images (SEM, TEM) and XRD patterns. In both reactions, a complete conversion of furfural and levulinic acid was achieved with maximum selectivity over the Ni@C catalyst. The effect of reaction temperature, solvent type, reaction time, and H 2 pressure were also studied. Overall, optimized reaction conditions were determined, and the Ni@C is easily reusable and exceptionally durable in the studied reaction cycles. The apparent activation energies for FA hydrogenation to THFOL and LA hydrogenation to GVL are 15.4 kJ/mol and 33.6 kJ/mol, respectively.
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