Aquivion-Based Spray Freeze-Dried Composite Materials for the Cascade Production of γ-Valerolactone

The development of multifunctional catalysts is a necessary step to effectively carry out one-pot cascade reactions, such as that from furfural to γ-valerolactone. This research effort faces the challenge posed by the intrinsic limit of how many kinds of catalytic sites a single material can bear. In this work, the application of Spray-Freeze Drying (SFD) as a synthetic technique for the preparation of a wide range of innovative composite multi-functional catalysts is reported. Herein we show that by the proper combination of Aquivion as a highly active Brønsted acid catalyst and metal oxides as both support materials and Lewis acids (LAS) enable to achieve highly unique efficient and effective dual acid composite catalysts that are able to carry out the cascade reaction from furfural to γ-valerolactone. The dual catalytic system comprised of Aq/ZrO2 with 30 % polymer content prepared via spray-freeze drying exhibited GVL yields of 25 % after only 2 h at 180 °C and a remarkably high productivity of 4470 μmolGVL gCat -1 h-1, one of the highest reported results. Mechanistic studies based on experimental and advanced characterisation and spectroscopic techniques, such as, SEM, TEM, 15N MAS NMR and 19F MAS NMR indicate that activity arises from the proper tuning of BAS/LAS (Brønsted Acid Site/Lewis Acid Site) acidic properties.

Integrated Cascade Process for the Catalytic Conversion of 5-Hydroxymethylfurfural to Furanic and TetrahydrofuranicDiethers as Potential Biofuels

The depletion of fossil resources is driving the research towards alternative renewable ones. Under this perspective, 5-hydroxymethylfurfural (HMF) represents a key molecule deriving from biomass characterized by remarkable potential as platform chemical. In this work, for the first time, the hydrogenation of HMF in ethanol was selectively addressed towards 2,5-bis(hydroxymethyl)furan (BHMF) or 2,5-bis(hydroxymethyl)tetrahydrofuran (BHMTHF) by properly tuning the reaction conditions in the presence of the same commercial catalyst (Ru/C), reaching the highest yields of 80 and 93 mol%, respectively. These diols represent not only interesting monomers but strategic precursors for two scarcely investigated ethoxylated biofuels, 2,5-bis(ethoxymethyl)furan (BEMF) and 2,5-bis(ethoxymethyl)tetrahydrofuran (BEMTHF). Therefore, the etherification with ethanol of pure BHMF and BHMTHF and of crude BHMF, as obtained from hydrogenation step, substrates scarcely investigated in the literature, was performed with several commercial heterogeneous acid catalysts. Among them, the zeolite HZSM-5 (Si/Al=25) was the most promising system, achieving the highest BEMF yield of 74 mol%. In particular, for the first time, the synthesis of the fully hydrogenated diether BEMTHF was thoroughly studied, and a novel cascade process for the tailored conversion of HMF to the diethyl ethers BEMF and BEMTHF was proposed.

One-Pot Alcoholysis of the Lignocellulosic Eucalyptus nitens Biomass to n-Butyl Levulinate, a Valuable Additive for Diesel Motor Fuel

The present investigation represents a concrete example of complete valorization of Eucalyptus nitens biomass, in the framework of the circular economy. Autohydrolyzed-delignified Eucalyptus nitens was employed as a cheap cellulose-rich feedstock in the direct alcoholysis to n-butyl levulinate, adopting n-butanol as green reagent/reaction medium, very dilute sulfuric acid as a homogeneous catalyst, and different heating systems. The effect of the main reaction parameters to give n-butyl levulinate was investigated to check the feasibility of this reaction and identify the coarse ranges of the main operating variables of greater relevance. High n-butyl levulinate molar yields (35–40 mol%) were achieved under microwave and traditional heating, even using a very high biomass loading (20 wt%), an eligible aspect from the perspective of the high gravity approach. The possibility of reprocessing the reaction mixture deriving from the optimized experiment by the addition of fresh biomass was evaluated, achieving the maximum n-butyl levulinate concentration of about 85 g/L after only one microwave reprocessing of the mother liquor, the highest value hitherto reported starting from real biomass. The alcoholysis reaction was further optimized by Response Surface Methodology, setting a Face-Centered Central Composite Design, which was experimentally validated at the optimal operating conditions for the n-butyl levulinate production. Finally, a preliminary study of diesel engine performances and emissions for a model mixture with analogous composition to that produced from the butanolysis reaction was performed, confirming its potential application as an additive for diesel fuel, without separation of each component.