1,721,057 research outputs found
Amberlyst A-70: A surprisingly active catalyst for the MW-assisted dehydration of fructose and inulin to HMF in water
Full text link5-Hydroxymethyl-2-furaldehyde (HMF) is a biomass-derived intermediate for the sustainable production of monomers and biofuels. However, most of its syntheses are performed under not environmentally and/or economically green conditions. In this work, the dehydration of fructose/inulin to HMF was optimized, employing aqueous medium, high substrate concentrations (10 and 20 wt%), low loading of commercial acid resin (Amberlyst-70) and microwave heating. The influence of substrate/catalyst ratio, time and temperature on the products yields was investigated. Amberlyst-70 resulted a very active and recyclable system: HMF yields up to 46 mol% were ascertained, the best result up to now reached under these reaction conditions
A novel approach to biphasic strategy for intensification of the hydrothermal process to give levulinic acid: Use of an organic non-solvent
Full text linkLevulinic acid is a platform chemical obtained from acid-catalyzed hydrothermal conversion of cellulose-rich biomass. The low amounts of solid biomass which can be handled in the reactor limit the levulinic acid concentration in the aqueous stream, making the economic viability of the aqueous phase process unsuitable for large scale applications. Now a novel approach to biphasic process has been proposed, where a mineral oil has been used as non-solvent for levulinic acid, thus concentrating it in the water phase, reducing the water volume to be processed downstream but at the same time maintaining enough liquid phase to sustain the slurry processability. The work has studied: i) the optimization of the biphasic hydrolysis of corn grain to levulinic acid; ii) the characterization of the recovered oil; iii) the evaluation of the energetic properties of the recovered hydrochar for its exploitation, thus smartly closing the biorefinery cycle
FT-IR Investigation of the Structural Changes of Sulcis and South Africa Coals under Progressive Heating in Vacuum: Correlation with Volatile Matter
Full text linkThe analysis of gas evolving during the pyrolysis of two very different rank coals was studied by using FT-IR spectroscopy. These coals, coming from Sulcis (Sardinia, Italy) and from South Africa, respectively, were subjected to progressive heating up to 800°C in vacuum. The thermal destruction of coal was followed by monitoring the production of gases in this range of temperature. The gases evolving in the heating from room temperature to 800°C were collected at intervals of 100°C and analysed by infrared spectroscopy. The relative pressures
were plotted against temperature. These graphs clearly show the correlation among qualitative gas composition, temperature, and the maximum value of emissions, thus confirming FT-IR analysis as a powerful key for pyrolysis monitoring
Biomass valorization to high furan liquids by heterogeneous catalysts. A green mineral acid-free approach
No full textLignocellulosic biomass can be converted by hydrothermal treatments into interesting platform chemicals, such as high energy furan liquids. Now, we have investigated a novel cascade process in the absence of any mineral acids for the conversion of giant reed (Arundo donax L.) and corn stover to high energy furan liquids. These biomasses were subjected to a first stage of autohydrolysis and a subsequent step of dehydration with niobium phosphate, both stages assisted by microwave irradiation. Mineral acid-free hydrothermal treatment of giant reed and corn stover leads to quite good biomass fractionation by solubilizing nearly all its hemicelluloses. These obtained hydrolysates contain up to 50 wt % of the initial biomass and they are mostly rich in xylose oligomers along with small amount of glucose oligomers from cellulose. The subsequent thermal treatment of such hydrolysates with niobium phosphate results in both hydrolysis and dehydration of sugar oligomers to produce mainly furfural from pentoses and 5-hydroxymethylfurfural from hexoses. This green cascade process is composed of single batch steps employing water as solvent in the absence of any mineral acids and takes advantage of microwave dielectric heating to save energy, reduce reaction time and diminish degradation products. Under the optimized reaction conditions up to about 4 % overall mass yields of furfural were achieved starting from slurries containing 50 g/L of corn stover and giant reed. These mass yields correspond to about 23 % of the theoretical yield on the basis of the hemicellulose content. These results are promising taking into account the use of raw biomasses and the absolutely green conditions adopted in the cascade process
Application of microwave irradiation for the removal of polychlorinated biphenyls from siloxane transformer and hydrocarbon engine oils
Full text linkThe removal of polychlorinated biphenyls (PCBs) both from siloxane transformer oil and hydrocarbon engine oil was investigated through the application of microwave (MW) irradiation and a reaction system based on polyethyleneglycol (PEG) and potassium hydroxide. The influence of the main reaction parameters (MW irradiation time, molecular weight of PEG, amount of added reactants and temperature) on the dechlorination behavior was studied. Promising performances were reached, allowing about 50% of dechlorination under the best experimental conditions, together time and energy saving compared to conventional heating systems. Moreover, an interesting dechlorination degree (up to 32%) was achieved for siloxane transformer oil when MW irradiation was employed as the unique driving force. To the best of our knowledge, this is the first time in which MW irradiation is tested as the single driving force for the dechlorination of these two types of PCB-contaminated oils
Heterogeneous catalysis for the production of 5-hydroxymethyl-2-furfural and of 2,5-bis(hydroxymethyl)furan from fructose and inulin
No full textToday, the sustainable growth of the chemical and energy industries has become an indispensable benchmark of our society and the current development of the industrial sector based on fossil resources must be replaced by an alternative one, linked to renewable resources. Therefore, the catalytic conversion of renewables is a promising and important topic, in particular for the synthesis of 5-hydroxymeththylfurfural (HMF) and of 2,5- bis(hydroxymethyl)furan (BHMF) which find several applications in many strategic fields. Consequently, from the point of view of sustainability and of an integrate approach based on the biorefinery concept, the conversion of fructose and inulin to HMF has been studied in the respect of green chemistry principles. The obtained aqueous solutions containing HMF, after removing the acid catalyst have been directly hydrogenated to BHMF
La Bioraffineria dei fanghi di cartiera: isolamento/monitoraggio di contaminanti adesivi e valorizzazione della fibra residua
No full textUn aspetto strategico per la sostenibilità ambientale e industriale è il riciclo e la valorizzazione della carta che richiede una serie di trattamenti meccanici/chimici per il nuovo riutilizzo nel processo produttivo cartario. Tali trattamenti producono frazioni ponderalmente significative di materiali di scarto, come i fanghi, che, in aggiunta alla fibra cellulosica, sono ricchi in contaminanti organici. A causa della natura adesiva di questi ultimi, questi devono essere rimossi a monte del processo produttivo, per ottenere un prodotto finale di qualità opportuna per le specifiche richieste. In quest’ottica, i flussi in ingresso/uscita dalle unità di pulizia meccanica sono stati campionati a monte di una macchina continua per la produzione di cartone ondulato. Le relative frazioni sono state caratterizzate tramite tecniche analitiche, rivelando l’abbondante presenza di copolimeri SBR nel flusso di scarto in uscita e di cellulosa in quello accettato in uscita. Successivamente, i contaminanti sono stati isolati dai flussi in ingresso/uscita mediante estrazione con solvente e la successiva caratterizzazione degli estratti tramite Py-GC/MS, FT-IR e GPC, ha confermato la presenza di gomme SBR e di copolimeri EVA, evidenziando l’impossibilità di usare direttamente la carta riciclata (ovvero senza alcun pretrattamento meccanico/chimico), per la produzione di nuovo cartone ondulato. Poichè il concetto di “riciclo”, così come quello di “bio-raffineria”, prevede, per quanto possibile, il frazionamento e il riutilizzo dei singoli componenti di un materiale di scarto, questi contaminanti polimerici possono essere valorizzati mediante processi di pirolisi per il recupero di “chemicals” ed energia. Parallelamente, il residuo di estrazione, ricco in cellulosa, può essere valorizzato mediante processi di conversione termochimica per la produzione di intermedi ad alto valore-aggiunto come la 5-idrossimetil-2-furaldeide e/o l’acido levulinico. In tal senso, prove preliminari di conversione acido-catalizzata di tale fango hanno mostrato che è possibile recuperare acido levulinico con rese fino a circa il 10 % in peso rispetto al fango caricato
Sustainable synthesis of 5-hydroxymethyl-2-furaldehyde and analytical study of the solid by-products
No full textIn the last years environmental problems such as pollution, greenhouse effect and lack of fossil materials have driven the interest of scientific community towards the catalytic valorisation of lignocellulosic biomass. In this scenario 5-hydroxymethylfurfural (HMF) represents a key molecule and it has been evaluated by US Department of Energy as one of the most important bio-based compounds. In fact HMF could be obtained starting from renewable materials and it represents a platform chemicals for several monomers and bio-fuels that result competitive with those originated from fossil resources. In this work the synthesis of HMF starting from both monosaccharide and polysaccharide has been studied with the aim of identifying as sustainable as possible reaction conditions. Moreover, in this work an analytical study has been conducted on the solid by-product in order to clarify its chemical structure and prove if the substrate could affect it
Monitoring/characterization of stickies contaminants coming from a papermaking plant - Toward an innovative exploitation of the screen rejects to levulinic acid
Full text linkRecycled paper needs a lot of mechanical/chemical treatments for its re-use in the papermaking process. Some of these ones produce considerable rejected waste fractions, such as ". screen rejects", which include both cellulose fibers and non-fibrous organic contaminants, or ". stickies", these last representing a shortcoming both for the papermaking process and for the quality of the final product. Instead, the accepted fractions coming from these unit operations become progressively poorer in contaminants and richer in cellulose. Here, input and output streams coming from mechanical screening systems of a papermaking plant using recycled paper for cardboard production were sampled and analyzed directly and after solvent extraction, thus confirming the abundant presence of styrene-butadiene rubber (SBR) and ethylene vinyl acetate (EVA) copolymers in the output rejected stream and cellulose in the output accepted one.Despite some significant drawbacks, the ". screen reject" fraction could be traditionally used as fuel for energy recovery within the paper mill, in agreement with the integrated recycled paper mill approach. The waste, which still contains a cellulose fraction, can be also exploited by means of the hydrothermal route to give levulinic acid, a platform chemical of very high value added
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