Optimal conditions for hemicelluloses extraction from Eucalyptus globulus wood: hydrothermal treatment in a semi-continuous reactor

Producción CientíficaOptimal conditions for hemicellulose extraction from wooden biomass in a semi-continuous system have been assessed in thiswork. This studywould constitute the first stage for a profitable and green industrial process. Eucalyptus globuluswas selected as rawmaterial due to its lowwater consumption, high growth and its efficiency in lignocellulose production.Moreover its cultivation is very popular in southern Europe. Samples of 5.0 g of wood were fractioned using a pressurized hot water semi-continuous system, to produce sugars (pentoses and hexoses) and a solid residue enriched in lignin. Five flow rates between 2.50 and 20.00 mL/min and four temperatures between 135.0 and 285.0 °C were tested in order to maximize the production of sugars, avoiding the formation of degradation products. Optimumconditions for the extraction of hemicellulose were identified at 185.0 °C and 5.00 mL/min, leading to a pentoses yield of 67.409wt%,with 0.702 wt% of degradation products. Almost all the pulp is extracted at 285.0 °C. SEM images show very well the changes in the wood structure at different temperatures. A kinetic model was developed, describing the extraction and hydrolysis of hemicellulose and cellulosewith absolute average deviations around 10% for sugar extracted mass.Junta de Castilla y León (programa de apoyo a proyectos de investigación – Ref. VA330U13

Selective fractionation and depolymerization of lignocellulosic biomass using subcritical and supercritical water to produce hemicellulose, cellulose and lignin

Cellulose and hemicelluloses contained in woody biomass can be hydrolysed to monomeric sugars, which can be fermented to ethanol, or can be converted into higher value products [1]. Hemicelluloses, when isolated from biomass, have unique properties. They can be used to produce films for packaging applications in substitution to synthetic plastics, as polysaccharides works as barriers against oxygen permeation; another important application is the production of aerogels to insulate products. Xylose from hemicellulose, for instance, can be converted to furfural, which is a precursor used in different fields, such as oil refining, plastics, pharmaceutical, and agrochemical industries. L-Xylose can be also hydrogenated or enzymatically transformed to xylitol, which is a sweetening agent and is also used for preventing tooth decay [2]. The idea of transforming biomass to energy, materials, and chemicals, defines the concept of biorefinery, particularly interesting topic nowadays, considering the issues related to fossil combustibles and derivatives [3-5]. Please click Additional Files below to see the full abstract

Hydrothermal extraction of hemicellulose: from lab to pilot scale

A flow-through reactor for hemicelluloses extraction with hot pressurized water was scaled with a factor of 73. System performance was evaluated by comparing the temperature profile, extraction yield and kinetics of the two systems, performing experiments at 160 and 170 °C, 11 barg for 90 min, using catalpa wood as raw material. Hemicellulose yields were 33.9% and 38.8% (lab scale 160 °C and 170 °C) and 35.7% and 41.7% (pilot scale 160 °C and 170 °C). The pilot reactor was upgraded by designing a manifold system capable to provide samples with different liquid residence time during the same experiment. Tests at 140, 150, 160 and 170 °C were carried for 90 min. Increasing yields (9.3–40.6%) and decreasing molecular weights (4078–1417 Da) were obtained at increasing the temperature. Biomass/water ratio of 1/27 gave total average concentration of xylose of 0.4 g/L (140 °C) to 1.8 g/L (170 °C).MINECO and FEDER Funds, Project CTQ2015-64892-R (BioFraHynery

The Evolution of the Ammonia Synthesis Catalyst 'AmoMax®-CASALE'

Despite the Haber-Bosch process being more than 100 years old, only incremental improvements have been achieved until recently. Now, by combining the catalyst expertise of CLARIANT and the engineering knowledge of CASALE, a breakthrough has been realized. AmoMax®-Casale is a new ammonia synthesis catalyst jointly developed by Casale and Clariant particularly for use in Casale ammonia converters. AmoMax®-Casale is a customized evolution of the well-known, wustite-based catalyst, AmoMax® 10. While retaining the same superior resistance to ageing, poisoning and mechanical strength, AmoMax®-Casale is significantly more active. This feature allows to reduce the loop recycle rate and the loop pressure and/or to increase the ammonia production. The higher activity of AmoMax®-Casale contributes to improve the overall operating efficiency either by saving energy, or by increasing significantly the plant capacity. This article will describe in detail the successful development of AmoMax®-Casale, explain advantages and commercial benefits based on concrete plant simulations and share the start-up experience of the first commercial reference

Engineering the reaction of hydrogen peroxide direct synthesis

Hydrogen peroxide (H2O2) is a versatile environmentally friendly oxidizing agent that has many practical applications. H2O2 has countless qualities and it is one of the world’s most important bulk inorganic chemicals. Most of the world’s H2O2 is produced by auto-oxidation process (AO). The AO process involves indirect oxidation of H2 to yield H2O2. The first commercial anthraquinone (AQ) process was operated by I.G. Farbeinindustrie in Germany during the second world war. The AO process is successfully used to produce most of the world’s H2O2 because it avoids explosive H2/O2 gas mixture. However AO process suffers from several drawbacks, such as the use of a complex and toxic solvent system, the periodic replacement of costly quinone-derivative due to non-selective hydrogenation, the deactivation of the hydrogenation catalyst, high requirements of energy and intensive process steps for the removal of organic impurities. Also, it is known to have high capital and operating costs, thus it economically viable only for large scale productions (>4*104 tons per year). Therefore, H2O2 is produced in few locations and then transported to the customers. Transportation of H2O2 creates additional safety concerns since concentrated H2O2 can decompose explosively. A process where H2O2 forms from the direct combination of its elements (H2 and O2) could be preferred, especially for small scale productions at the end-user site, if control of the sequential hydrogenation can be achieved, but none of the presently available processes has solved the productivity vs. safety dilemma. Traditionally, the attention of the scientists focused on the identification of an active and particularly selective catalyst, overlooking the impact of safety and multiphase issues. Both aspects may benefit from continuous operations and suitable feeding policies, along with kinetics studies as we are currently investigating. Three reactor set-ups were developed and realized for hydrogen peroxide direct synthesis: two of them are based on batch reactors of different volumes to perform catalytic tests and kinetics studies, and one is based on a novel trickle bed reactor (TBR). Most of the work presented here is focused on the continuous reactor, far more attractive from an industrial perspective. In the TBR set up different catalysts were chosen to investigate H2O2 direct synthesis. A systematic study on operative conditions was performed, varying liquid and gas flow rates (contact time between liquid,gas and solid phases), changing H2/O2 ratio, investigating conditions for H2O2 decomposition and the effect of pressure. With this work very high values of selectivity were achieved (up to 90%), improving catalytic performances compared to those previously obtained in batch reactor set-ups. The best results were accomplished with a Pd and Au catalyst supported on sulfated zirconia. Despite an extensive body of research on the direct synthesis process, very little has been published about kinetic rate expressions of the full reaction network, and in this study experimental kinetics in a batch reactor and their relative modeling are treated for the first time.Il perossido di idrogeno è un ossidante “verde” e non tossico, che non genera sottoprodotti inquinanti per l’ambiente, poiché si decompone a dare solamente acqua ed ossigeno. Il perossido di idrogeno viene utilizzato principalmente nelle cartiere come sbiancante, nell’industria tessile e metallurgica, come intermedio nella sintesi chimica, come disinfettante e additivo per detergenti, e molto altro. L’H2O2 viene attualmente prodotto con il processo dell’antrachinone, il quale necessita di numerose operazioni per la produzione e la purificazione del prodotto finale, con il conseguente elevato consumo energetico, a cui sono associati notevoli costi di esercizio, e la formazione di sottoprodotti inquinanti. La sintesi diretta di H2O2 è un’alternativa interessante, che si propone di eliminare i sottoprodotti inquinanti e ridurre drasticamente i costi di impianto e di esercizio, per produzioni su piccola scala direttamente in situ presso l’utilizzatore finale (che non è Berlusconi). In questo modo sarebbe possibile abbattere anche i costi di trasporto e i rischi ad esso connessi. Negli ultimi anni particolare attenzione è stata data al processo di sintesi diretta di acqua ossigenata, tuttavia i lavori pubblicati e brevettati vertevano per lo più sullo sviluppo di un catalizzatore che potesse avere delle caratteristiche tali da favorire la formazione di perossido di idrogeno a dispetto delle reazioni di decomposizione e idrogenazione dello stesso, anch’esse facenti parte del network di reazione. Scarso interesse è invece stato rivolto allo studio sistematico delle condizioni operative e allo sviluppo di un processo continuo. Ad esempio, lo studio in reattori batch non è stato mai approfondito con cinetiche di reazione e con lo studio degli equilibri liquido-vapore che si instaurano all’interno del sistema di reazione. In questo lavoro sono stati sviluppati e realizzati due reattori di tipo batch (di due volumi differenti) e un reattore in continuo: dei due reattori batch, uno è stato utilizzato per testare i catalizzatori e condurre studi preliminari, mentre nell’altro si sono svolti studi di cinetiche di reazione, che sono stati successivamente utilizzati per sviluppare un modello cinetico relativo all’intero network di reazioni. Il reattore continuo, invece, è un reattore a letto fisso (trickle bed reactor) in cui viene caricato il catalizzatore. Un notevole interesse dalle realtà industriali è rivolto all’operazione in continuo, per cui in questo progetto particolare attenzione è stata data allo sviluppo di un tale processo, ottimizzandone le condizioni operative per massimizzare la produzione di acqua ossigenata. Numerosi catalizzatori mono- e bi- metallici sono stati studiati, supportati su diversi materiali, sia inorganici che organici, e per ognuno di essi sono state studiate le migliori condizioni operative. Nel Capitolo 1 è presentato lo stato dell’arte della ricerca sulla sintesi diretta del perossido di idrogeno, e viene spiegato come la ricerca effettuata fin d’ora abbia posto l’attenzione sullo studio di un catalizzatore che potesse essere adatto alla sintesi diretta, trascurando però lo studio reattoristico del sistema impiegato. Nel Capitolo 2 è descritto lo sviluppo dei reattori in seguito utilizzati nella sperimentazione, ed i sistemi di analisi implementati. Vengono presentati gli schemi di impianto e gli studi preliminari condotti sia sui reattori batch, che sul reattore continuo. Il Capitolo 3 affronta temi di cinetica con la relativa modellazione. Sono stati condotti esperimenti di sintesi diretta in un reattore batch ad alta pressione, e da questi dati è stato ricavato un primo approccio di modello cinetico ancora assente in letteratura. Nel Capitolo 4 si è studiato un catalizzatore al palladio su un supporto di ceria sulfatata, con il quale sono stati condotti esperimenti di decomposizione e idrogenazione del perossido di idrogeno. Partendo da questi risultati si è svolto uno studio teso ad identificare le migliori portate di gas e di liquido per ottenere la massima produttività e la massima selettività. Un’altra condizione operativa indagata è stata la pressione ed il suo effetto sulla produzione di acqua ossigenata. Nel Capitolo 5 sono stati scelti 4 catalizzatori a base di palladio, supportati su diversi materiali inorganici. Variando le condizioni operative di sistema si è studiato il comportamento di questi catalizzatori in relazione alla produzione di H2O2 e alla loro selettività. I vari catalizzatori, a seconda del supporto, hanno proprietà differenti e le condizioni operative devono essere ottimizzate di conseguenza per ottenere il massimo rendimento sulla sintesi diretta. Il Capitolo 6 tratta lo studio di catalizzatori bimetallici a base di palladio e oro e catalizzatori a base di solo palladio. Diversi supporti inorganici sono stati utilizzati ed è stato introdotto un nuovo supporto organico. I catalizzatori sono stati confrontati tra di loro variando le condizioni operative di sistema. È stato inoltre studiato l’effetto della concentrazione di idrogeno immesso come reagente e il suo effetto sulla sintesi diretta di H2O2. Il Capitolo 7 riassume i migliori risultati ottenuti e fornisce indicazioni relativamente agli sviluppi futuri. In Appendice è fornito un approccio per la modellazione termodinamica del sistema

Change in the Nature of ZSM-5 Zeolite Depending on the Type of Metal Adsorbent—The Analysis of DOS and Orbitals for Iron Species

Transition-metal-modified zeolites have recently gained the greatest interest among scientists. Ab initio calculations within the density functional theory were used. The exchange and correlation functional was approximated with the Perdew–Burke–Ernzerhof (PBE) functional. Cluster models of ZSM-5 (Al2Si18O53H26) zeolites were used with Fe particles adsorbed above aluminum. The adsorption of three iron adsorbates inside the pores of the ZSM-5 zeolite—Fe, FeO and FeOH—was carried out with different arrangements of aluminum atoms in the zeolite structure. The DOS diagram and the HOMO, SOMO and LUMO molecular orbitals for these systems were analyzed. It has been shown that depending on the adsorbate and the position of aluminum atoms in the pore structure of the zeolite, the systems can be described as insulators or conductors, which significantly affects their activity. The main aim of the research was to understand the behavior of these types of systems in order to select the most efficient one for a catalytic reaction

H2 solubility in methanol in the presence of CO2 and O2

Hydrogen solubility in methanol, (methanol + carbon dioxide) and (methanol + carbon dioxide + oxygen) was measured and correlated at different temperatures (268 < T/K < 288) and pressures (0.37 < P/MPa < 3.5). Hydrogen content in the liquid phase was measured using a gas absorption method and Fugatron HYD-100 instrument. Experiments were performed in a fixed volume cell at constant temperature and hydrogen content was varied with subsequent loadings in the cell environment. At all conditions investigated a linear relation between hydrogen partial pressure and concentration was observed. Results were correlated and generalized as Henry's constants for H 2, as a function of temperature and CO 2/methanol overall ratio. Correlation and generalization of the measurements was provided through a thermodynamic model, based on Peng-Robinson equation of state with van der Waals mixing rules and Boston-Mathias \u3b1-function. H 2 solubility in methanol was confirmed to grow with temperature and amount of CO 2; at constant H 2 partial pressure, O 2 does not affect H 2 solubilit