Integrated Cascade Process for the Catalytic Conversion of 5-Hydroxymethylfurfural to Furanic and Tetrahydrofuranic Diethers 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

Recent developments in maleic acid synthesis from bio-based chemicals

This review paper presents the current state of the art on maleic acid synthesis from biomass-derived chemicals over homogeneous or heterogeneous catalysts. It is based on the most recent publications on the topic, which are discussed in details with respect to the observed catalytic performances. The recent developments and the technical drawbacks in the gas and the liquid phases are also reported. In addition, recent results on the mechanistic aspect are discussed giving insights into the probable reaction mechanisms depending on the starting molecule (furan, furfural and 5-hydroxymethylfurfural)

Cascade Valorization of 5-Hydroxymethylfurfural (HMF) to Monomers and Furanic/Tetrahydrofuranic Diethers Bio-fuels

5-hydroxymethylfurfural (HMF) represents a valuable platform-chemical for the synthesis of monomers and bio-fuels. Thus, the present work proposes, for the first time, a cascade process for the synthesis of diol monomers and furanic/tetrahydrofuranic diethers as novel bio-fuels starting from HMF. In the first step, the selective hydrogenation of HMF in ethanol to give 2,5- bis(hydroxymethyl)furan (BHMF) or 2,5-bis(hydroxymethyl)tetrahydrofuran (BHMTHF) was carried out by properly tuning the reaction conditions in the presence of 5 wt% Ru/C as catalyst, reaching the highest yields of 80 and 93 mol%, respectively. These diols are strategic precursors for two scarcely investigated ethoxylated bio-fuels, 2,5-bis(ethoxymethyl)furan (BEMF) and 2,5- bis(ethoxymethyl)tetrahydrofuran (BEMTHF). Thus, in the second step, the etherification of both pure BHMF and BHMTHF to give BEMF and BEMTHF, respectively, was studied. The zeolite HZSM-5 (Si/Al = 25) allowed the achievement of the highest BEMF yield of 74 mol%. Analogous results were also obtained starting from crude BHMF. On the contrary, BEMTHF was not obtained by the direct etherification of BHMTHF, but a preliminary study showed the possibility of synthesising BEMTHF by the 5 wt% Ru/C catalyzed hydrogenation of BEMF. Finally, the stability of the tested catalysts was investigated, showing that they maintained the activity almost constant up to five recycle runs, thus resulting recyclable

Evaluation of the Catalytic Activity of Metal Phosphates and Related Oxides in the Ketonization of Propionic Acid

In recent years, the upgrading of lignocellulose bio-oils from fast-pyrolysis by means of ketonization has emerged as a frontier research domain to produce a new generation of biofuels. Propionic acid (PA) ketonization is extensively investigated as a model reaction over metal oxides, but the activity of other materials, such as metal phosphates, is mostly unknown. Therefore, PA ketonization was preliminarily investigated in the gas phase over both phosphates and oxides of Al, Zr, and La. Their catalytic activity was correlated to the physicochemical properties of the materials characterized by means of XRD, XRF, BET N2 porosimetry, and CO2- and NH3-TPD. Noteworthy, monoclinic ZrO2 proved to be the most promising candidate for the target reaction, leading to a 3-pentanone productivity as high as 5.6 h 121 in the optimized conditions. This value is higher than most of those reported for the same reaction in both the academic and patent literature

Aerobic oxidation of 1,6-hexanediol to adipic acid over Au-based catalysts: the role of basic supports

1,6-Hexanediol is a relevant building blocks that could be obtained from biomass and transformed under base free conditions into adipic acid used for polymer synthesis

Niobium and Zirconium Phosphates as Green and Water-Tolerant Catalysts for the Acid-Catalyzed Valorization of Bio-Based Chemicals and Real Lignocellulosic Biomasses

Commercial niobium and synthesized zirconium phosphates were tested as water-tolerant heterogeneous acid catalysts in the hydrothermal conversion of different bio-based substrates. Different acid-catalyzed reactions were performed using biomass-derived model compounds and more complex real lignocellulosic biomasses as the substrate. The conversion of glucose and cellulose was preliminarily investigated. Then, a wide plethora of raw lignocellulosic biomasses, such as conifer wood sawdust, Jerusalem artichoke, sorghum, miscanthus, foxtail millet, hemp and Arundo donax, were valorized towards the production of water-soluble saccharides, 5-hydroxymethylfurfural (HMF), levulinic acid (LA) and furfural. The different catalytic performances of the two phosphates were explained on the basis of their acid features, total acidity, Brønsted/Lewis acid sites ratio and strength. Moreover, a better insight into their structure–acidity relationship was proposed. The different acid properties of niobium and zirconium phosphates enabled us to tune the reaction towards target products, achieving from glucose maximum HMF and LA yields of 24.4 and 24.0 mol%, respectively. Remarkably, when real Jerusalem artichoke biomass was adopted in the presence of niobium and zirconium phosphate, maximum yields of furanic compounds and cellulose-derived sugars of 12.7 and 50.0 mol%, respectively, were obtained, after only 1 h of reaction. The synthesized hydrolysates, which were found to be rich in C5 and C6 carbohydrates, can be better exploited for the cascade production of more added-value bio-products

A study of the oxidehydration of 1,2-propanediol to propanoic acid with bifunctional catalysts

[EN] The gas-phase oxidehydration (ODH) of 1,2-propanediol to propionic acid has been studied as an intermediate step in the multi-step transformation of bio-sourced glycerol into methylmethacrylate. The reaction involves the dehydration of 1,2-propanediol into propionaldehyde, which occurs in the presence of acid active sites, and a second step of oxidation of the aldehyde to the carboxylic acid. The two reactions were carried out using a cascade strategy and multifunctional catalysts, made of W-Nb-O, W-V-O and W-Mo-V-O hexagonal tungsten bronzes, the same systems which are also active and selective in the ODH of glycerol into acrylic acid. Despite the similarities of reactions involved, the ODH of 1,2-propanediol turned out to be less selective than glycerol ODH, with best yield to propanoic acid no higher than 13%, mainly because of the parallel reaction of oxidative cleavage, occurring on the reactant itself, which led to the formation of C-1-C-2 compounds.Bandinelli, C.; Lambiase, B.; Tabanelli, T.; De Maron, J.; Dimitratos, N.; Basile, F.; Concepción Heydorn, P.... (2019). A study of the oxidehydration of 1,2-propanediol to propanoic acid with bifunctional catalysts. Applied Catalysis A General. 582:1-9. https://doi.org/10.1016/j.apcata.2019.05.036S1958

Tandem Hydrogenation/Hydrogenolysis of Furfural to 2-Methylfuran over a Fe/Mg/O Catalyst: Structure–Activity Relationship

The hydrodeoxygenation of furfural (FU) was investigated over Fe-containing MgO catalysts, on a continuous gas flow reactor, using methanol as a hydrogen donor. Catalysts were prepared either by coprecipitation or impregnation methods, with different Fe/Mg atomic ratios. The main product was 2-methylfuran (MFU), an important highly added value chemical, up to 92% selectivity. The catalyst design helped our understanding of the impact of acid/base properties and the nature of iron species in terms of catalytic performance. In particular, the addition of iron on the surface of the basic oxide led to (i) the increase of Lewis acid sites, (ii) the increase of the dehydrogenation capacity of the presented catalytic system, and (iii) to the significant enhancement of the FU conversion to MFU. FTIR studies, using methanol as the chosen probe molecule, indicated that, at the low temperature regime, the process follows the typical hydrogen transfer reduction, but at the high temperature regime, methanol dehydrogenation and methanol disproportionation were both presented, whereas iron oxide promoted methanol transfer. FTIR studies were performed using furfural and furfuryl alcohol as probe molecules. These studies indicated that furfuryl alcohol activation is the rate-determining step for methyl furan formation. Our experimental results clearly demonstrate that the nature of iron oxide is critical in the efficient hydrodeoxygenation of furfural to methyl furan and provides insights toward the rational design of catalysts toward C–O bonds' hydrodeoxygenation in the production of fuel components

Systematic Study for the Preparation of Au Based Catalyst for the Glucose Oxidation

Glucaric acid (GA) is one of the top 12 value added chemicals from biomass and this is due to the several applications that this molecule and its derivates can have in the industrial fields. For this reason, it is interesting to find a competitive way to produce it from lignocellulosic feedstock, more in details from glucose. Therefore, our research is focused on the synthesis of GA starting from Glucose in aqueous phase, using molecular oxygen as oxidant agent and gold nanoparticles supported materials as catalysts. All the tests have been carried out in a batch reactor and the catalysts have been prepared using the sol-immobilization method. The role of the stabilizer (polyvinyl alcohol-PVA) has been studied by varying systematically the amount of PVA in the colloidal synthesis and therefore how it could affect (i) the final morphology of the preformed supported metal nanoparticles and (ii) and the catalytic performance in terms of activity, yield and stability; high amount of PVA facilitates the formation of small nanoparticles (no PVA 7.8nm vs PVA2,4 2,61nm) but also block the active site of the catalyst, giving lower GA yield (22% vs 17%). For this reason, it has been evaluated two different method to partially remove the PVA, a washing step and several heat treatments, and seems that best results are obtained with the washing and the HT at 120℃ while at 200°C -250°C the average crystallite size increased giving a lower yield of G