Liquid hot water pretreatment of Arundo Donax: a comparison between batch and a flow-through systems

Lignocellulosic biomass is a valuable alternative raw material to partially substitute oil as both energy and chemical source. For example, polysaccharide constituents of lignocellulosic materials, hemicellulose and cellulose, can be hydrolytically depolymerized using acid catalysts or enzymes, while residual lignin can be used as a source of aromatic building blocks. The kinetic severity of the hydrolysis process can be adjusted to maximize alternatively the yields in fermentable sugars (bioethanol-way) or in chemicals such as furfural, hydroxymethylfurfural, levulinic acid. It is well known that, before performing the main hydrolysis step, a pretreatment stage of the matrix is necessary to cleave the bonds between hemicellulose, cellulose and lignin and to start breaking some of the polysaccharide chains. Liquid hot water (LHW) can be used for the pretreatment of biomass, without adding any acid to the system, thus avoiding the need of any subsequent neutralization step. In order to move toward industrial scale plant for production of energy and bulk chemicals from biomasses, continuous systems are desirable. An intermediate step toward the design of a continuous layout is constituted by semi-continuous processes. In this study, we have performed the LHW pretreatment of Arundo Donax (giant reed) in two different systems: a microwave (MW)-assisted batch reactor, where high heating rate can be achieved leading rapidly the system at the operative conditions of the pretreatment, and a fast heating flow-through layout in which the flow rate of the process water stream can be tuned. The achieved results highlight that in the microwave (MW)-assisted batch reactor good hemicelluloses solubilization, little sugar degradation and insignificant lignin and cellulose fractionation can be obtained by optimizing reaction temperature and time and that in the flow-through system high biomass conversion as well as very limited formation of degradation products can be obtained by adjusting the flow rate of the treatment water

Autohydrolysis pretreatment of Arundo donax: a comparison between microwave-assisted batch and fast heating rate flow-through reaction systems

Background: Autohydrolysis of lignocellulosic biomass in liquid hot water has been widely studied owing to its high efficiency and relatively low cost. In the perspective of industrial applications, continuous or semi-continuous processes are more interesting than batch systems. Moreover, microwave heating of pretreatment systems has been proposed to intensify the kinetics of the process. In this study, the autohydrolysis of Arundo donax was performed in pure liquid hot water using a microwave-heated batch reactor and a semi-continuous flow-through reaction system with fast heating rate at the same operating conditions with the aim of performing a systematic comparison between the two different experimental apparatuses. Results: The effect of process temperature and time, biomass to water mass to volume ratio and water flow rate on the concentration and yield of hydrolysis products was investigated. The flow-through set-up allowed us to reach biomass solubilization up to 44.5 wt% on dry basis, while the batch system stopped at 34.5 wt% suggesting that the mass transfer could be the rate-determining step in the solubilization of the constituting biopolymers. For example, in the flow-through layout, using a flow rate of 3.5 mL/min at 200 °C with 20 min of processing time, quantitative recovery of hemicellulose was obtained with limited formation of degradation products. Interestingly, higher cellulose/ hemicellulose extraction ratios were found using the microwave-assisted batch reactor. FTIR analyses of the solid residues recovered after the pretreatment offered independent information on the fractions of liquefied biopolymers complementary to those derived from HPLC and UV–Vis spectroscopy. Conclusions: Collected experimental results indicated that the flow-through system can be adopted to obtain complete solubilization of the hemicellulose fraction of Arundo donax addressing the product distribution in soluble compounds towards fermentable sugars with limited formation of sugar degradation products and with limited penalty in terms of dilution of the hydrolysate solution. It was also found that microwaves can promote cellulose depolymerization and solubilization, thus allowing a more comprehensive utilization of the biomass and that infrared spectroscopy can be a useful technique to estimate the effect of the pretreatment

Solid catalyst component, catalyst comprising said solid component, and process for the (co)polymerization of alpha-olefins

A solid catalyst component for the (co) polymn. of α-olefins having general formula (I): ZrnMA1xC1Mgp (I) wherein : M represents titanium (Ti), vanadium (V), or mixts. thereof; n is a no. ranging from 0.01 to 2; x is a no. ranging from 0.1 to 4; y is a no. ranging from 5 to 53; p is a no. ranging from 0 to 15; obtained by means of a process comprising putting at least one zirconium arene in contact with at least one metal compd. and, optionally, with at least one com not pound of magnesium. Said solid catalyst component can be advantageously used as a solid component in a catalyst for the (co) polymn. of α-olefins. Said catalyst can be advantageously used in a process for the (co) polymn. of α-olefins

An easy microwave-assisted process for the synthesis of nanostructured palladium catalysts and their use in the selective hydrogenation of cinnamaldehyde

An efficient and highly reproducible process for the microwave-assisted solvothermal synthesis of palladium nanoparticles has been carried out adopting mild reaction conditions and very short microwave irradiation times. Colloidal nanoparticles have straightforwardly been obtained by the direct irradiation of an ethanol solution of Pd(OAc)(2) in the presence of PVP (poly-N-vinyl-2-pyrrolidone) as capping agent. The "in situ" preparation of gamma-Al(2)O(3)-supported catalysts has been conveniently carried out without the addition of PVP, leading to supported palladium nanoparticles with an average diameter of 5-8 nm and a narrow nanoparticle size distribution. These nanocatalysts have been characterized by UV-vis, TEM, XPS and SSA measurements and used as efficient catalysts for the chemoselective hydrogenation of cinnamaldehyde to hydrocinnamaldehyde with selectivities up to 97% in hydrocinnamaldehyde at complete substrate conversion. (C) 2010 Elsevier B.V. All rights reserved

Chitosan as biosupport for the MW-assisted synthesis of palladium catalysts and their use in the hydrogenation of ethyl cinnamate

A novel catalytic system based on palladium supported on chitosan was synthesized adopting a MW-assisted process. This synthetic approach results efficient under mild reaction conditions and very short microwave irradiation times. The prepared catalyst was employed in the hydrogenation of ethyl cinnamate (EC) to ethyl hydrocinnamate (EHC) adopting both traditional heating and MW irradiation: this is the first study on this reaction which involves this type of catalyst. In addition, a one pot fully MW-assisted process which provides the synthesis of the Pd/chitosan catalyst and its direct use in the hydrogenation of ethyl cinnamate has been also studied. This one pot procedure assures fast reaction rate under mild reaction conditions avoiding the catalyst’s isolation and purification, thus making easier the reaction scale-up. The achieved yields in the target product are particularly good and the system results completely recyclable, due to the stabilizing effect of the functionalized natural support toward the palladium particles

A novel microwave assisted process for the synthesis of nanostructured ruthenium catalysts active in the hydrogenation of phenol to cyclohexanone

An efficient, cheap and safe process for the solvothermal synthesis of ruthenium nanocatalysts has been developed: it involves the innovative use of a microwave (MW) applicator for the in situ activation of the reaction in a stirred glass vessel without resorting to an oven. The synthesis was carried out by direct MW irradiation of an alcohol or glycol solution of the metal precursor RuCl(3)nH(2)O, in the presence of PVP (poly-N-vinyl-2-pyrrolidone) as stabilizing agent and eventually of gamma-Al2O3 as support. The addition of PVP appears not to be necessary for the in situ preparation of the supported systems. The synthesized nanocatalysts were characterized by UV-Vis, TEM and XPS measurements: colloidal and supported nanoparticles with an average diameter about 2 nm and a narrow distribution of sizes were obtained. The supported systems showed interesting performances in the selective hydrogenation of phenol to cyclohexanone. (C) 2008 Elsevier B.V. All rights reserved

Room-temperature polymerization of beta-pinene by niobium and tantalum halides

The easily accessible niobium pentahalides NbX5 (X = F, 1a; X = Cl, 1b; X = Br, 1c) and the tantalum TaF5 (2a) were applied for the first time as effective catalysts for the synthesis of poly-β-pinene at room temperature, adopting low catalyst content (0.6 mM). 1H NMR analyses indicated that the produced β-pinene polymers were structurally identical to that formed by conventional cationic Lewis acid initiators. Niobium pentachloride gave low molecular weight (Mn = 1200–1600) polymer with high conversion degree. The effects of the main reaction parameters (i.e. solvent, temperature, catalyst concentration, time and eventual co-catalysts) on the NbCl5-promoted polymerization were investigated. Polymerization quenching with methanol resulted in the incorporation of a methoxy-end group into the polymer chain, thus confirming a cationic mechanism. On the other hand, NbI5, TaCl5, the carbamato-complexes M(O2CNEt2)5 (M = Nb, Ta) and the mononuclear adducts NbX5L [X = Cl, L = MeCN, Ph2CO or (NMe2)2CO; X = F, L = EtOH] were not active in β-pinene polymerization