Catalytic transformation of renewables (Olefin, bio‐sourced, et al.)

The objective of this Special Issue is to provide new diverse contributions that can demonstrate recent applications in biomass transformation using heterogeneous catalysts. In recent decades, a wide variety of biomass-derived chemicals have emerged as key platform chemicals for the production of fine chemicals and liquid fuels using heterogeneous catalysts as the preferred option for most of the developed and proposed catalytic processes. A range of heterogeneous catalysts have been evaluated for effective biomass conversion, such as supported metal nanoparticles, mixed metal oxides and zeolites, where the control of particle size, porosity, acid-basic and redox properties is crucial for providing active, stable and selective heterogeneous catalysts. Moreover, the crucial role of the solvent, choice of reactor design and final chemical processes for controlling activity, selectivity and deactivation phenomena has been demonstrate

Sustainable and environmental catalysis

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PRIN LEVANTE 2020: Levulinic acid valorization through advanced novel technologies

The project LEVANTE deals with the development of new catalytic processes for the valorization of levulinic acid and its esters towards three classes of compounds: levulinic ketals, diphenolic acid and γ-valerolactone together with other reduction products

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

The Oxidative Cleavage of 9,10-Dihydroxystearic Triglyceride with Oxygen and Cu Oxide-based Heterogeneous Catalysts

This paper deals with a new heterogeneous catalyst for the second step in the two-step oxidative cleavage of unsaturated fatty acids triglycerides derived from vegetable oil, a reaction aimed at the synthesis of azelaic and pelargonic acids. The former compound is a bio-monomer for the synthesis of polyesters; the latter, after esterification, is used in cosmetics and agrochemicals. The reaction studied offers an alternative to the currently used ozonization process, which has severe drawbacks in terms of safety and energy consumption. The cleavage was carried out with oxygen, starting from the glycol (dihydroxystearic acid triglyceride), the latter obtained by the dihydroxylation of oleic acid triglyceride. The catalysts used were based on Cu2+, in the form of either an alumina-supported oxide or a mixed, spinel-type oxide. The CuO/Al2O3 catalyst could be recovered, regenerated, and recycled, yielding promising results for further industrial exploitation

Gas-phase oxidative dehydrogenation of long chain alkenols for the production of key fragrance ingredients: from Rosalva isomers to Costenal analogues

The continuous-flow, gas-phase oxidative dehydrogenation (ODH) of an actual mixture of decen-1-ol isomers ("Isorosalva" alcohol) towards the corresponding mixture of aldehydes ("Costenal" analogues, valuable ingredients in perfumes formulation) is herein reported for the first time over noble metal-free catalysts. In particular, the optimisation of the reaction conditions over a copper ferrite (Cu/Fe/O), as well as dedicated characterizations and comparisons between the fresh, the post-reaction (reduced) and regenerated (re-oxidised) catalytic material, allowed us to underline the key role of well dispersed copper oxide over a Fe-enriched spinel in promoting the selective ODH of Isorosalva alcohol. The superior catalytic activity and selectivity of CuO/gamma-Fe2O3 synthesized ad hoc were attributed to the very high dispersion of Cu over the support as well as to a cooperative effect between Cu and Fe species in promoting the redox cycle

Sustainable isosorbide production by a neat one-pot MW-assisted catalytic glucose conversion

In the context of exploitation of new biomass-derived platform chemicals, isosorbide (1,4:3,6-dianhydro-D-sorbitol), obtained by the two-fold dehydration of sorbitol, is gaining increasing interest in several potential industrial applications. Seeking for more sustainable, efficient, and economically competitive green processes, the use of heterogeneous catalysts under microwave (MW) irradiation has been adopted for the development of a neat one-pot process from glucose. MW-assisted catalytic processes have shown the potential to reduce the reaction time and improve the selectivity, due to the interaction of MW with the reaction medium through the production of hot spots on the catalyst surface. Ru/C, Ru/Al2O3 and Ru/TiO2 were tested for glucose hydrogenation to sorbitol, while the dehydration step was favored by the addition of beta Zeolites (360:1 SiO2:Al2O3) allowing high isosorbide selectivity (>85 %). An extended structural and morphological characterization before and after the catalytic tests allowed to establish structure-activity relationships. Yields up to 47.1 % have been obtained directly from glucose in 1.5 h, achieving a considerable reduction of reaction time without the use of a solvent. thus paving the way for further investigations on biomass conversion into value-added products. With this aim, direct isosorbide production from milled cellulose was investigated. While the isosorbide yields still need to be improved, the dual role of formic acid both as acid catalyst for cellulose hydrolysis and H-donor for the reduction step was promisingly clarified

1-Butanol dehydration and oxidation over vanadium phosphate catalysts

The transformation of 1-butanol into either butenes or maleic anhydride was carried out both with and without oxygen, using V/P/O catalysts. With vanadyl pyrophosphate prepared by coprecipitation, at temperature lower than 240 ◦C and without oxygen, selectivity to butenes was higher than 90%, but a slow deactivation took place. At temperature higher than 300 ◦C and in the presence of air, maleic and phthalic anhydrides were the prevailing products, with selectivity of 60% and 14%, respectively. Catalytic performance was affected by crystallinity and acidity. αI-VOPO4 showed a poor performance in the absence of air, with a quick deactivation due to coke accumulation; but it displayed an excellent selectivity to butenes (close to 98%) at temperatures lower than 320 ◦C in the presence of air, with stable performance. At temperature higher than 360 ◦C, α I-VOPO4 was reduced to vanadyl pyrophosphate and catalyzed the direct oxidation of 1-butanol into maleic anhydride, but with 35% selectivit

Glycerol Carbonate as a Versatile Alkylating Agent for the Synthesis of β-Aryloxy Alcohols

The possibility to use glycerol carbonate (GlyC) as an innovative alkylating agent for phenolic compounds in solventless conditions and in the presence of a catalytic amount of both homogeneous and heterogeneous bases is herein described. In particular, the peculiar, polyfunctional structure of GlyC allows one to obtain the formation not only of the mono-phenoxy-1,2-propanediol (MPP) analogue but also of 1,3-diphenoxy-2-propanol (DPP), the latter being elusive using the more traditional, toxic, and carcinogenic reagents such as glycidol and/or 3-chloro-1,2-propandiol. The production of DPP is indeed possible due to the in situ formation of a reactive intermediate, 4-(phenoxy)methyl-1,3-dioxolane-2-one (PhOGlyC), which may undergo a consecutive nucleophilic attack of a phenolate, leading to the selective formation of the disubstituted product. This reaction is nonetheless in competition with PhOGlyC decarboxylation that finally limits DPP yield up to 20%, with an MPP yield up to roughly 60% in the optimized conditions (atmospheric pressure, 140 degrees C, 5 h using Cs2CO3 as the basic catalyst) starting directly from a GlyC/phenolic mixture. For this reason, a multistep synthetic strategy has also been developed, first by obtaining the quantitative formation and isolation of the PhOGlyC intermediate and then by promoting the consecutive reaction with phenol, in this way obtaining a DPP yield of 66% after only 1 h of reaction at 170 degrees C. The obtained phenyl glyceryl ethers are interesting drugs scaffolds (i.e., guaifenesin, mephenesin), intermediates in the preparation of active pharmaceutical ingredients (e.g., chlorphenesin carbamate, methocarbamol), and hydrotropic solvents; preliminary evaluations of MPP and DPP biodegradability and use as alternative surfactants have also been described in this paper

Superacid resin-based heterogeneous catalysts for the selective acylation of 1,2-methylenedioxybenzene

In this work, we firstly report on the use of highly active and selective Aquivion superacid resins as heterogeneous catalysts for the acylation of 1,2-methylenedioxybenzene (MDB) with propionic anhydride (AP). The reaction was investigated and optimized using solvent-free conditions to selectively produce 3,4-methylenedioxypropiophenone (MDP1P), a key intermediate for the manufacture of active ingredients used in insecticide formulations with a volume of production of roughly 3000 t/y. Interestingly, Aquivion-based catalysts allows to work in mild reaction conditions (i. e. 80 °C), obtaining MDP1P yields as high as 44 % after only 1 h of reaction (selectivity 83 %). A detailed study of the AP reactivity demonstrated its tendency to promote oligomerization reactions that, as confirmed by ex-situ and in-situ FT-ATR analyses, caused the deactivation of the catalyst forming surficial carbonaceous residues. In this context, a fast oxidation of the resin surface organic residues using a diluted HNO3 (or H2O2) solution was proven to be an efficient method to regenerate the catalyst, which can be reused for several reaction cycles. The results obtained in preliminary scale-up tests were basically unaffected by the reaction volume (up to 800 mL), paving the way for possible future applications of the process