1,721,040 research outputs found
Microwave-assisted hydrothermal treatments for biomass valorisation: A critical review
Get PDF5 figures, 8 tables.The sustainable conversion of biomass into biofuels, chemicals and biomaterials has gained increasing attention to ensure the well-being of present and future generations. Among the different technologies available to date for the valorisation biomass, microwave-assisted hydrothermal conversion has recently appeared as a stat-in-the-art technology, capable of furnishing a wide range of reaction products for the energy, pharmaceutical and chemistry sectors. This emerging technology combines the inherent benefits of microwave heating and the sustainable features of biomass hydrothermal valorisation. Herein, for the first time, this critical review summarises and analyses all the work conducted to date on the use microwave-assisted hydrothermal processes (including microwave-assisted carbonisation, liquefaction and treatment/hydrolysis) for the conversion of biomass into hydrochar, bio-crude (bio-oil) and valuable chemicals. In particular, this work has put together vital information addressing the influences of the reaction conditions (temperature, time, amount and type of catalyst, biomass loading and type, and microwave power) on the yields and key properties of the reaction products. The relationships between these processing parameters and the chemical transformations involved in the processes (hydrolysis, dehydration, decarboxylation, condensation, and re-polymerisation) have been described in detail, and reliable comparisons have also been established between microwave-assisted and conventional hydrothermal technologies when data were available. As a result, this critical review collects essential information on the use of this cutting-edge, recently appeared, microwave-assisted hydrothermal technology, and paves the way for its expansion and future development and commercialisation.Javier Remón would like to express his gratitude to the Spanish
“Ministerio de Ciencia, Innovación y Universidades” for his Juan de la
Cierva Felloship awarded (IJC2018-037110-I).Peer reviewe
Ginger waste as a potential feedstock for a zero-waste ginger biorefinery:A review
Get PDFGinger for consumption and use in industrial applications such as essential oil and oleoresin extraction is growing globally. There will be increased volumes of ginger waste (rhizomes, stems and leaves) in the coming years. However, the valorisation of ginger waste is limited in the literature beyond its use as a ginger meal for animal feed. Herein, this review consolidates the literature on ginger waste within the context of developing a zero-waste ginger biorefinery that yields chemicals, materials and (bio)energy for emerging bio-based markets and applications. Green extraction technologies are reported, some are at an industrial scale for processing fresh ginger but which could be re-used to obtain a second crop of oil or oleoresin. The application of ginger waste to produce potential value-added products such as anti-microbial materials, environmental remediation agents, supercapacitors, bioenergy and heterogeneous catalysts is presented. Limitations based on logistics, feedstock, processing technology and final output are discussed
From unavoidable food waste to advanced biomaterials:microfibrilated lignocellulose production by microwave-assisted hydrothermal treatment of cassava peel and almond hull
Get PDFLignocellulose based nanomaterials are emerging green biosolids commonly obtained from wood pulp. Alternative feedstocks, such as as unavoidable food waste, are interesting resources for nano/microfibers. This research reports the production and characterization of microfibrillated lignocellulose (MFLC) from cassava peel (CP) and almond hull (AH) via acid-free microwave-assisted hydrothermal treatment (MHT) at different temperatures (120–220 °C). During processing, the structural changes were tracked by ATR-IR, TGA, XRD, 13C CPMAS NMR, zeta potential, HPLC, elemental analysis (CHN; carbon, hydrogen and nitrogen), TEM and SEM analyses. The microwave processing temperature and nature of feedstock exerted a significant influence on the yields and properties of the MFLCs produced. The MFLC yields from CP and AH shifted by 15–49% and 31–73%, respectively. Increasing the MHT temperature substantially affected the crystallinity index (13–66% for CP and 36–62% for AH) and thermal stability (300–374 °C for CP and 300–364 °C for AH) of the MFLCs produced. This suggested that the MFLC from CP is more fragile and brittle than that produced from AH. These phenomena influenced the gelation capabilities of the fibers. AH MFLC pretreated with ethanol at low temperature gave better film-forming capabilities, while untreated and heptane pretreated materials formed stable hydrogels at solid concentration (2% w/v). At high processing temperatures, the microfibrils were separated into elementary fibers, regardless of pretreatment or feedstock type. Given these data, this work demonstrates that the acid-free MHT processing of CP and AH is a facile method for producing MFLC with potential applications, including adsorption, packaging and the production of nanocomposites and personal care rheology modifiers. Graphic abstract: [Figure not available: see fulltext.
Nuevos avances en el uso de micro-ondas para la valorización hidrotermal de biomasas: Reacciones de licuefacción, descomposición y fraccionamiento asistidas por micro-ondas
No full text3 Figuras.- 1 Tabla[EN] Microwave heating represents a potentially faster and more efficient and selective technology for the hydrothermal treatment of biomass in comparison to conventional heating based technologies. Specifically, microwave heating allows not only achieving a better process control, but also lower temperatures to be used. Furthermore, as water is highly effective in microwave energy absorption, the combination of hydrothermal conditions together with microwave assisted heating offers an interesting new technology for the design and development of novel hydrothermal processes. Herein, this work summarises some recent advances achieved at the Green Chemistry Centre of Excellence, Chemistry Department, University of York (UK) (https://www.york.ac.uk/chemistry/research/green/research/publications/), regarding the use of microwave technology for the valorisation of biomass under hydrothermal conditions, including microwave-assisted hydrothermal liquefaction (MA-HTL), decomposition (MA-HTD) and fractionation (MA-F). These processes are very timely and the work conducted represents a step-change in biomass pre-processing technologies, helping the development of novel routes for biomass valorisation.[ES] El calentamiento asistido por micro-ondas se considera una tecnología más rápida, eficiente y selectiva en comparación con otras técnicas de calentamiento convencionales para el tratamiento hidrotermal de biomasa. Específicamente, esta tecnología permitetanto lograr un mejor control del proceso, como el uso de menores temperaturas. Además, como el agua utilizada como disolvente en estos procesos es muy eficiente absorbiendo la energía emitida por las micro-ondas, la combinación de condiciones hidrotermales junto con un calentamiento asistido por micro-ondas, resulta en una alternativa novedosa y muy interesante para el diseño y desarrollo de nuevos procesos hidrotermales. En este contexto, el presente artículo resume algunos de los avances más recientes desarrollados en el Green Chemistry Centre of Excellence, del Departamento de Química de la Universidad de York (Reino Unido), (https://www.york.ac.uk/chemistry/research/green/research/publications/) sobre el uso de la tecnología de calentamiento por micro-ondas para la valorización hidrotermal de biomasa, incluyendo procesos de licuefacción, descomposición y fraccionamiento. Estas reacciones son de gran interés en la industria química y representan una contribución sustancial en el desarrollo de nuevos procesos para el pre-tratamiento de la biomasa, contribuyendo sustancialmente al desarrollo de nuevas rutas para la valorización sostenible de biomasa y residuos.This research was funded by the Industrial Biotechnology Catalyst (Innovate UK, BBSRC, EPSRC and EP/N013522/1) and EPSRC grant number EP/K014773/1. Javier Remón Núñez would like to express his gratitude to the Spanish Ministry “Ministerio de Ciencia, Innovación y Universidades” for the Juan de la Cierva fellowship (FJCI 2016-30847) awarded.Peer reviewe
Analysis and optimisation of a novel ‘almond-refinery’ concept: Simultaneous production of biofuels and value-added chemicals by hydrothermal treatment of almond hulls
No full text13 figures, 3 tables.-- Supplementary material available.-- © 2020. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/For the first time, this work investigates the achievability of developing a biorefinery concept around almond hulls by hydrothermal treatment (HTT), thoroughly scrutinising the influence of the temperature (200–300 °C), pressure (100–180 bar), time (20–180 min) and solid loading (5–25 wt%). This process allowed the conversion of almond hulls into four main products: gas (2–13%), bio-oil (2–12%), aqueous (4–69%) and hydro-char (17–89%). The gas consisted of a mix of H2, CO2, CO and CH4 with a LHV fluctuating from 1 to 13 MJ/m3 STP. The bio-oil comprised a mixture of alkanes, aldehydes, ketones, phenols, furans, benzenes and nitrogen compounds with a HHV between 21 and 31 MJ/kg. The solid product resembled an energetic hydro-char material (HHV 21–31 MJ/kg), while the aqueous effluent comprised a mixture of value-added chemicals, including saccharides and small oxygenated compounds. The production of biofuels can be maximised at 256 °C and 100 bar, using a 5 wt% solid loading for 157 min, conditions at which 43% of the original feedstock can be converted into an elevated energy-filled bio-oil (11% yield, 30 MJ/kg), along with a high energetic hydro-char (32% yield, 29 MJ/kg). Regarding value-added chemicals, up to 10% of the almond hulls can be converted into a bio-oil with a high proportion (45%) of phenolic species at 250 °C and 144 bar with a solid loading of 5 wt% for 167 min. In comparison, a sugar-rich (81 C-wt%) solution can be produced in high yield (54%), by treating a 24 wt% suspension at 252 °C and 180 bar for 153 min. Therefore, the versatility, novelty and intrinsic green and holistic nature of this ‘almond-refinery’ concept exemplify a landmark achievement in future energy and chemicals production from biomass, which might help render the complete bio-refinery for almond hulls more cost-effectively and ecologically feasible.The authors wish to express their gratefulness to FEDER and the Ministerio de Ciencia, Innovación y Universidades (Grant Number ENE2017-83854-R) for providing financial support. Besides, Javier Remón Núñez is very grateful to the Ministerio de Ciencia, Innovación y Universidades for the Juan de la Cierva (JdC) fellowships (Grant Numbers FJCI-2016-30847 and IJC2018-037110-I) awarded.Peer reviewe
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Toward Renewable-Based, Food-Applicable Prebiotics from Biomass:A One-Step, Additive-Free, Microwave-Assisted Hydrothermal Process for the Production of High Purity Xylo-oligosaccharides from Beech Wood Hemicellulose
Get PDFXylooligosaccharides (XOS) produced from biomass offer a plethora of excellent physicochemical and physiological properties to be used as natural prebiotic nutraceuticals. Herein, this work first addresses and optimizes a novel one-pot, additive-free, microwave-assisted process to produce high purity XOS from beech wood hemicellulose, studying the influence of the temperature, reaction time, and solid loading. These variables exerted a significant influence, allowing the transformation of hemicellulose into a gas (0-19%), an XOS-rich liquid product (9-80%) and a spent solid material (17-90%). The liquid phase consisted of a mixture of XOS with a degree of polymerization (DP) DP > 6 (75-100 C-wt %) and DP 3-6 (0-10 C-wt %), together with mono/disaccharides (0-1 C-wt %), carboxylic acids (0-5 C-wt %), ketones (0-12 C-wt %) and furans (0-12 C-wt %). A good compromise between the liquid yield (81%) and XOS purity (96 C-wt %) was achieved at 172 °C using a solid loading of 5 wt % for 47 min. This time could be reduced (33 min) and the solid loading increased (25 wt %) without substantially altering the XOS (98 C-wt %) purity, although the liquid yield was reduced. The liquid yield could be increased up to 97% at the expenses of XOS purity (90 C-wt %) at 177 °C using a 5 wt % solid loading for 60 min. For these optima, the microwave production costs shifted between 1.42 and 6.50 €/kg XOS, which is substantially lower than the XOS market price, thus highlighting the high potential of this emerging technology
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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