Joan Salvadó

Steam reforming model compounds of biomass gasification tars: conversion at different operating conditions and tendency towards coke formation

The purification of biomass-derived syngas via tar abatement by catalytic steam reforming has been investigated using benzene, toluene, naphthalene, anthracene and pyrene as surrogated molecules. The effects of temperature and steam-to-carbon ratio on conversion, and the tendency towards coke formation were explored for each model compound. Two commercial nickel-based catalysts, the UCI G90-C and the ICI 46-1, were evaluated. The five tar model compounds had very different reaction rates. Naphthalene was the most difficult compound to steam reform, with conversions from 0.008 gorg_conv/gcat min (790 °C) to 0.022 gorg_conv/gcat min (890 °C) at an S/C ratio of 4.2. The most reactive compound was benzene, with a conversion of 1.1 gorg_conv/gcat min at 780 °C and an S/C ratio of 4.3. The tendency towards coke formation grew as the molecular weight of the aromatic increased. The minimum S/C ratio for toluene was 2.5 at a catalyst temperature of 725 °C, and for pyrene at 790 °C ,it was 8.4. In general, catalyst temperatures and S/C ratios need to be higher than for naphtha in order to prevent the formation of coke on the catalyst.

High-temperature dilute-acid hydrolysis of olive stones for furfural production

Abstract We studied the production of furfural by acid hydrolysis of olive stones, which in Spain are an abundant lignocellulosic residue derived from the production of olive oil. We focused on the hydrolysis in dilute sulfuric acid (0.05 to 0.250 mol l −1 ), at high temperature (220–240°C), and short reaction times, of a few minutes at the most. The experimental study was performed in a tubing-bomb reactor system that approximately reproduces the temperature profiles obtained in a continuous tubular reactor. We obtained maximum furfural yields ranging from 50% to 65% of the potential depending on acid concentration and temperature.

Lignin-based wood panel adhesives without formaldehyde

AbstractLignin-based wood adhesives prepared without formaldehyde substituted by non-volatile non-toxic aldehyde, namely glyoxal, were prepared and tested for application to wood panels such as particleboard. The adhesives yielded good IB strength results of the panels, enough to comfortably pass relevant international standard specifications for exterior-grade panels. The adhesives also showed sufficient reactivity to yield panels in press times comparable to those of formaldehyde-based commercial adhesives. ZusammenfassungHolzklebstoffe auf Ligninbasis wurden auf ihre Eignung zur Herstellung von Holzplatten, wie zum Beispiel Spanplatten, untersucht. Dabei wurde anstelle von Formaldehyd das nicht flüchtige, ungiftige Aldehyd Glyoxal verwendet. Die Klebstoffe erzielten gute Ergebnisse hinsichtlich der Querzugfestigkeit der Platten. Internationale Normanforderungen für Platten zur Verwendung im Feuchtbereich wurden problemlos eingehalten. Die Reaktionsfähigkeit der Klebstoffe reichte aus, um Platten mit Presszeiten vergleichbar mit denjenigen kommerzieller Klebstoffe auf Formaldehydbasis herzustellen.

Steam‐exploded residual softwood‐filled polypropylene composites

Residual softwood sawdust was pretreated by a steam-explosion technique. It was used as a natural filler in polypropylene (PP)-based composites. Dynamic mechanical analysis and tensile properties of these materials were studied. The influ- ence of filler loading, steam-explosion severity, and coating the fiber with a function- alized compatibilizer, such as maleic anhydryde polypropylene (MAPP), on the mechan- ical behavior of the composite was evaluated. The results were analyzed in relation with scanning electron microscopy observations, and surface energy (dispersive and polar components) and apparent specific area measurements. Experimental data indicate a better compatibility between MAPP-coated fiber and PP with respect to the untreated one. The coating treatment of the softwood fiber was found to promote interfacial adhesion between both components, and to enhance the tensile properties of the resulting composite. This reinforcing effect was well predicted from theoretical calcu- lations based on a mean field approach (Halpin-Kardos model). The steam-explosion pretreatment severity increased the surface energy and apparent specific surface, and resulted in a loss of the fiber entirety. The sorption behavior of these composite materials was also performed. It was found that the composites absorb more water, as the filler content is higher. MAPP coating provided protection from water uptake in the interphase region.

Suitability of steam exploded residual softwood for the production of binderless panels. Effect of the pre-treatment severity and lignin addition

Abstract A steam explosion pre-treatment was applied at various severities to softwood residual substrate to determine the most suitable pre-treatment for the manufacture of binderless panels. The effect of adding acid to the pre-treatment of fibres was also evaluated. The changes in the chemical composition and morphology of the original material were investigated by fractionation analyses and scanning electron micrographs. High severities caused defibrillation of the material allowing to build links to form the panels. Prehydrolysis with acid had a great effect on the structure of the material even at low acid concentration. The physical and mechanical properties of the panel improved as the severity of the pre-treatment increased up to a point where mechanical properties deteriorated. The composites with highest internal bond had a high cellulose content and a medium lignin content. All these factors suggested that steamed pre-treated residual could be improved by adding a natural binder to produce the panels. A test of producing panels with addition of several kinds of lignin (up to 20%) was performed. With no significant changes in density, water stability (thickness swelling and water absorption) internal bond and mechanical properties were greatly improved. Results after accelerated ageing test were also enhanced.

Fractionation of Wheat Straw by Steam-Explosion Pretreatment and Alkali Delignification. Cellulose Pulp and Byproducts from Hemicellulose and Lignin

Abstract The fractionation of wheat straw was studied using a two-stage process based on an hydrolytic pretreatment followed by alkali delignification. The hydrolytic pretreatment was performed by steam explosion. Straw was steamed at temperatures comprised between 205 and 230°C for 2 min. The steamed straw was washed with hot water to yield a solution rich in hemicellulose-derived mono- and oligosaccharides. The washed fiber was delignified by alkali at 160°C for 60 min using a NaOH load of 20%. The alkali-soluble lignin was recovered by filtration after acidification of the black liquor. The delignified pulp was screened and bleached to produce viscose-grade cellulose. The optimization of the pretreatment conditions led to the following results at a pretreatment severity of log(R0) = 3.80: yield of viscose-grade cellulose = 70% of the potential; lignin recovery = 70% of the Klason lignin present in the untreated straw; hemicellulose sugars = 55% of the potential, recovered as molasses.

Antifouling microfiltration strategies to harvest microalgae for biofuel.

Microalgae are microorganisms that can fix CO(2) by using the energy from the sun and transforming it into organic molecules such as lipids (i.e. feedstock for biodiesel production). Microfiltration is a promising method to be considered in the harvesting step. In this study, two antifouling methods were tested in order to minimize permeability decrease over time, at low trans-membrane pressure filtration. Preliminary experiments were performed to find optimum conditions of transmembrane pressure, rotational speed and membrane pore size. Pilot experiments were carried out in the optimal conditions using microalgae obtained from the culture step and from a previous concentration process based on sedimentation. Fouling was significantly minimized, and the permeability plateau increased up to 600 L/h/m(2)/bar. Three microalgae species were tested: Phaeodactylum tricornutum (Pht), Nannochloropsis gaditana (Nng) and Chaetoceros calcitrans (Chc). An economic assessment was also performed, which demonstrated that dynamic filtration is economically more efficient than tangential cross-flow filtration.

Binderless composites from pretreated residual softwood

Residual softwood was thermomechanically pretreated and used to produce composites with no synthetic binders. The lignocellulosic material was steam exploded with a thermomechanical aqueous vapor process in a continuous tubular reactor. The study attempts to use the intrinsic bonding capacity of the steamed fiber, which is due to the plastification of the lignin. Chemical and structural changes in the pretreated substrate were evaluated by analytical characterization and scanning electron micrographs (SEM). The effect of the pressing conditions was evaluated in accordance with the physicomechanical responses of the composites. The physical and mechanical properties of the panels obtained were tested using UNE EN Spanish standard-European standards. In order to get more information about the degree of adhesion between the lignin and the fibers, SEM micrographs were taken of the broken surfaces of the material tested by the internal bond method. The results show that the thermomechanical pretreatment, pressing temperature, and time have a great effect on the mechanical and physical properties of binderless composites. The steam explosion aqueous vapor pretreatment is a good way for conditioning softwood sawdust for production of composites.

Microalgae-based biodiesel: A multicriteria analysis of the production process using realistic scenarios

Microalgae-based biodiesel has several benefits over other resources such as less land use, potential cultivation in non-fertile locations, faster growth and especially a high lipid-to-biodiesel yield. Nevertheless, the environmental and economic behavior for high scale production depends on several variables that must be addressed in the scale-up procedure. In this sense, rigorous modeling and multicriteria evaluation are performed in order to achieve optimal topology for third generation biodiesel production. Different scenarios and the most promising technologies tested at pilot scale are assessed. Besides, the sensitivity analysis allows the detection of key operating variables and assumptions that have a direct effect on the lipid content. The deviation of these variables may lead to an erroneous estimation of the scale-up performance of the technology reviewed in the microalgae-based biodiesel process. The modeling and evaluation of different scenarios of the harvesting, oil extraction and transesterification help to identify greener and cheaper alternatives.

Phenomenological kinetics of wood delignification: application of a time-dependent rate constant and a generalized severity parameter to pulping and correlation of pulp properties

SummaryKraft delignification kinetics has been modelled on the basis of a first order decay process with a time-dependent rate constant. A generalized severity parameter derived from this kinetic model, Roh, has been applied to describe the lignin solubilization during alkaline (soda and Kraft) and bisulphite pulping of different wood species. The model has been succesfuly applied to data sets available from the literature. Our approach has combined the main process variables (temperature, time and chemical load) into a single parameter, Roh, which is then used as a reaction ordinate to map the changes in chemical composition and physical properties. An extension of the initial formulation of the Roh parameter has been made to cover the situations where the catalytic system is composed by two active chemical species, as in the Kraft process.