PIXE mapping on multiphase fluid inclusions in endoskarn xenoliths of AD 472 eruption of Vesuvius (Italy)

In this work we report a microthermometric and proton-induced X-ray emission (PIXE) mapping investigation on multiphase fluid inclusions hosted within nepheline and clinopyroxene of endoskarn xenoliths present in the deposits of the AD 472 eruption of Vesuvius. PIXE mapping on magmatic fluid inclusions repesents a useful tool for the characterization of the composition of magma derived fluids, exsolved from active magma chambers. In fluid inclusions we observed the occurrence of widespread solid phases formed by Fe, Pb, Zn, As ± Cu ± Mn, suggesting the good metal transport capability of Vesuvius magmatic fluids, which interacted with carbonate country rocks leading to the formation of endoskarn

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

Tunable HMF hydrogenation to furan diols in a flow reactor using Ru/C as catalyst

5-hydroxymethylfurfural (HMF), accessible from various feedstocks, represents an important renewable platform-chemical, precursor for valuable biofuels and bio-based chemicals. In this work, the continuous hydrogenation of an aqueous solution of HMF to give strategic monomers, 2,5-bis(hydroxymethyl)furan (BHMF) and 2,5-bis(hydroxymethyl)tetrahydrofuran (BHMTHF) was investigated in a continuous flow reactor adopting a commercial Ru/C (5 wt%) as catalyst. The influence of the main process variables on products yield and selectivity was studied and optimized. The highest BHMF and BHMTHF yields of 87.9 and 93.7 mol%, respectively, were achieved by tuning the catalyst contact time, keeping all other variables constant (temperature, pressure, hydrogen flow rate, initial HMF concentration). Intraparticle diffusion limitation for hydrogen and HMF was shown to occur at some of the tested conditions by performing the HMF hydrogenation with different catalyst particle sizes, confirmed by calculations. Constant catalyst activity was observed up to 6 h time-on-stream and then gradually reduced. Fresh and spent catalyst characterization showed no significant sintering and negligible leaching of ruthenium during time-on-stream. A decrease of the specific surface area was observed, mainly due to humin deposition which is likely the reason for catalyst deactivation. Catalyst performance could be restored to initial values by a thorough washing of the catalyst

Biomass-derived catalysts: synthesis and characterization of hydrochars and pyrochars

Lignocellulosic biomass is one of the more important renewable sources and it will play a strategic role in many future markets, taking into consideration that a renewable energy share of 32% is binding at the European level by 2030. Deconstruction of lignocellulosic biomass can be carried out via hydrothermal processes and, among them, hydrothermal carbonization (HTC) represents a versatile process, which promotes the progressively deoxygenation of the biomass, under relatively mild reaction conditions. The obtained solid-rich product, called hydrochar, can be used in a wide range of applications, such as adsorption, energy storage, CO2 sequestration, catalysis etc. In this last field, within the project PRIN 2020 LEVANTE “LEvulinic acid Valorization through Advanced Novel Technologies” (2020CZCJN7), different hydrochars have been synthesized starting from cellulose and the effects of the main reaction parameters have been investigated employing statistical modelling. Under the selected set of processing parameters, the yield of hydrochars was in the range 38-48 wt%, with a carbon content of 60-70 wt% and corresponding higher heating values amounting to 17-27 MJ/kg, confirming the successful conversion of cellulose into a carbonaceous material. Finally, on the basis of final applications, also pyrochars have been prepared starting from the optimal hydrochars, in order to increase the aromatization degree and the surface areas. All the synthesized hydrochars and pyrochars will be further functionalized and employed, as acid catalysts, for the valorization of levulinic acid, in particular for its conversion to diphenolic acid, in agreement with the objectives of the project LEVANTE

Biomass ethanolysis: process optimization and performances of ethyl levulinate as diesel blendstock

Biomass represents a key asset for renewable energy production in the context of the more and more pressing energetic transition. Moreover, at the present, the issue of how to store a convenient amount of energy on board of electric vehicles is still a challenge and electric vehicles perspectives are limited to passenger cars and very small-range trucks, significant amount of time being necessary to define the eventual appropriate electric storage system to be employed in heavy transport, as well in aviation and shipping. In this context alkyl levulinates represent a concrete perspective for partial replacement of fossil fuel with renewable blendstocks. In particular, ethyl levulinate (EL) production by direct acid-catalyzed biomass ethanolysis was studied in order to investigate and optimize this one-step process which involves only renewable starting materials (biomass and bioethanol). In this perspective, the role of the main reaction parameters as the substrate nature and loading, type of the acid catalyst and its concentration, reaction temperature and duration were studied. EL was tested up to high concentrations in a mixture with diesel fuel in a small single-cylinder air-cooled diesel engine, to verify the engine and emission performances of the different blend compositions respect to those ascertained with a conventional diesel fuel

A novel organosolv approach to allow efficient biomass fractionation and successive exploitation

The separation and exploitation of all three main components of lignocellulosic biomass represents a challenging target for biorefinery. In this perspective a novel strategy has been studied for the fractionation and integral exploitation of Arundo Donax L. biomass, a feedstock characterized by low cost, large availability, favourable composition and ability to grow in marginal lands unsuitable for agriculture, avoiding any competition with food chain. The adoption of n-butanol played a fundamental dual role: as fractionation organosolv agent to separate cellulose, hemicellulose, and lignin and also as reagent for the conversion of the obtained cellulose fraction to n-butyl levulinate. A preliminary hot water pre-treatment of the biomass for reducing the content of extractives makes the separation even more effective. A preliminary optimization of the main reaction conditions was performed

Multi-step exploitation of raw arundo donax L. For the selective synthesis of second-generation sugars by chemical and biological route

Lignocellulosic biomass represents one of the most important feedstocks for future biorefineries, being a precursor of valuable bio-products, obtainable through both chemical and biological conversion routes. Lignocellulosic biomass has a complex matrix, which requires the careful development of multi-step approaches for its complete exploitation to value-added compounds. Based on this perspective, the present work focuses on the valorization of hemicellulose and cellulose fractionsof giant reed (Arundo donax L.) to give second-generation sugars, minimizing the formation of reaction by-products. The conversion of hemicellulose to xylose was undertaken in the presence of the heterogeneous acid catalyst Amberlyst-70 under microwave irradiation. The effect of the main reaction parameters, such as temperature, reaction time, catalyst, and biomass loadings on sugars yield was studied, developing a high gravity approach. Under the optimised reaction conditions (17 wt% Arundo donax L. loading, 160 °C, Amberlyst-70/Arundo donax L. weight ratio 0.2 wt/wt), the xylose yield was 96.3 mol%. In the second step, the cellulose-rich solid residue was exploited through the chemical or enzymatic route, obtaining glucose yields of32.5 and56.2 mol%, respectively. This work proves the efficiency of this innovative combination of chemical and biological catalytic approaches, for the selective conversion of hemicellulose and cellulose fractions of Arundo donax L. to versatile platform products

Design approach for the sustainable synthesis of sulfonated biomass-derived hydrochars and pyrochars for the production of 5-(hydroxymethyl)furfural

The sustainable synthesis of carbon-based sulfonated acid catalysts from biomass is of paramount importance from the perspective of sustainability. However, the traditional pyrolysis method leads to low solid yields and poor carbon stability. A cascade synthesis is here proposed, combining hydrothermal carbonization and pyrolysis, to produce a “high-quality” carbon-based precursor, followed by its sulfonation to increase the pristine acidity. The proposed multi-step preparation is effective when each step is optimized, primarily the hydrothermal carbonization, which should be carefully optimized. A chemometric approach was employed to optimize the hydrochar synthesis, using microcrystalline cellulose as starting feedstock. The identified optimal reaction conditions were applied to the hydrothermal carbonization of hazelnut shells, which is a more complex but cheaper feedstock, and the obtained hydrochars were pyrolyzed to produce pyrochars. The most promising chars were sulfonated and tested as heterogeneous acid catalysts in the aqueous conversion of fructose to 5-(hydroxymethyl)furfural, a promising platform chemical of great industrial interest, obtaining maximum yields of about 40 mol%. These promising results pave the way for the use of such wastes as efficient acid catalysts for the synthesis of 5-(hydroxymethyl)furfural, contributing to ensure the biomass circular exploitation

Sustainable exploitation of paper mill wastes: a resource to re-use in the paper factory

In the papermaking industry, billions of tonnes of paper mill wastes are globally produced as wastes every year. These include cellulosic and inorganic sludges, which are traditionally landfilled, leading to environmental and economic issues. For these reasons, it is urgent to develop new sustainable strategies to exploit these fractions. Up to now, these sludges have been exploited i) for land application (as soil amendment/substrate), ii) for energy recovery and iii) for the production of bio-composites. However, the above possibilities involve the direct use of the bulk wastes, without fractionating/exploiting each feedstock component. In the perspective of the valorisation of the different components, the present investigation has considered different strategies: i) a thermal treatment, ii) an alkaline and iii) a mechanical one, aimed at the fractionation and recovery of the two main components of cellulosic and inorganic sludge, cellulose and calcium carbonate, respectively, that could be advantageously reused within the same papermaking process