1,721,007 research outputs found
Aqueous phase reforming of biorefinery side-streams: challenges towards the industrial application
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Effects of Inorganics during Hydrothermal Liquefaction of Waste: A Comprehensive Study
Full text linkHydrothermal liquefaction (HTL) is gaining interest for the energy valorization of wet waste. While HTL performance is known to depend on biochemical composition, the role of inorganics remains poorly understood. This study evaluates the effects of the four most common metals (Na, K, Mg, and Ca) present as oxides, carbonates, phosphates, sulfates, and chlorides. Experimental results, supported by principal component analysis (PCA), revealed that inorganics significantly influence HTL performance, depending on both cation and anion type. More basic anions generally decreased solid production while favoring both biocrude and aqueous-phase yields, with carbonates perform- ing better than oxides despite their lower basicity. Na and K enhanced these effects compared to Ca and Mg, while K and Ca led to higher HHVs and lower oxygen content in the biocrude than Na and Mg, respectively, indicating a specific role of the cations. Sodium and potassium carbonates performed best, increasing biocrude yield by 48% relative to the corresponding inorganic-free feedstock, while reducing solid production by 90%. CaCl2 was the only compound reducing biocrude yield, while increasing solid residue by 90%. This study highlights the critical influence of inorganics on HTL performance and provides a foundation for deeper insights into the underlying mechanism
Aqueous Phase Reforming of Dairy Wastewater for Hydrogen Production: An Experimental and Energetic Assessment
Full text linkThe treatment of dairy industry effluents poses a significant challenge from the environmental point of view because of its high organic load. In this work, the aqueous phase reforming of lactose was investigated as a representative model compound for the production of renewable hydrogen. The tests were conducted using two different scenarios: the first one is referred to as direct aqueous phase reforming (APR); the second one proposed a pre-hydrogenation step, followed by APR. The implementation of this reactive pretreatment allowed for minimizing the solid by-product formation with respect to the direct APR, where most of the initial carbon ended up as solid residue. The pre-hydrogenation was investigated in the range of 180-220 degrees C, using Ru-based catalysts. In the best scenario (using 5% Ru/C), the carbon to solid was reduced by 95%, and up to 70% of the initial carbon was converted into gaseous compounds, hence contributing to the removal of the organic content of the wastewater while producing an energy carrier. Moreover, the hydrogen selectivity increased up to 70% (with respect to 2.5% for direct APR), thanks to hindering homogeneous reaction pathways that do not lead to hydrogen production. Finally, an energetic analysis was conducted to assess the possibility of coupling the APR with the dairy industry and quantifying the percentage of energy which may be produced in situ to satisfy industrial duties
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Variations on the Author
Full text link“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
Aqueous phase reforming of lignin-rich hydrothermal liquefaction by-products: a study on catalyst deactivation
Full text linkThe water fraction derived from the hydrothermal liquefaction of a lignin-rich feedstock was subjected to aqueous phase reforming to produce hydrogen. Deactivation of the catalyst was observed, and it was ascribed to fouling phenomena caused by phenolic oligomers. Simple aromatics like guaiacol and phenol, as well as in-organics, were proved not to be the cause of the deactivation thanks to the use of a multi-component synthetic mixture. The influence of using activated carbon as a pretreatment was studied, leading to a strong improvement of the performance when it was carried out at high temperature. The extent of deactivation was assessed using aqueous phase reforming of glycolic acid as a model reaction test. The results were found to be correlated with the surface area of the catalyst. A thermal regeneration in inert conditions was evaluated as a mode of catalyst regeneration. While the textural properties were partially recovered, the performance of the catalyst only slightly improved. A spectroscopic analysis of the solids in the aqueous solution was carried out, highlighting the structural similarities between their nature and the lignin residue. The results obtained in this study helped to enlarge the knowledge on the aqueous phase reforming of real complex mixtures, looking at indicators of paramount importance for a possible industrial application such as the stability of the catalyst
Which trials do we need? Fidaxomicin plus either intravenous metronidazole or tigecycline versus vancomycin plus either intravenous metronidazole or tigecycline for fulminant Clostridioides difficile infection
No full textUnravelling competitive adsorption phenomena in the aqueous phase reforming of carboxylic acids on Pt catalysts: An experimental and theoretical study
Full text linkBiorefinery-derived wastewater is considered a valuable source of energy and chemicals thanks to its organic loading. However, it is constituted by different compounds which influence the performance of a catalytic valorization process. In this work, we investigated the treatment of a synthetic hydrothermal liquefactionderived wastewater (HTL-WW) via aqueous phase reforming (APR) to obtain hydrogen. As a case study, we examined the underlying driving forces for performance differences in the APR of mono- and bi-component solutions of carboxylic acids as a model corn stover HTL-WW over Pt catalysts via a combined experimental and theoretical approach. In mono-component solutions, the conversion ranked as glycolic acid > propionic acid approximate to acetic acid, and the same was found for the hydrogen production tendency. Binary solutions of glycolic and acetic acid, with different concentration among the constituents, showed a strong inhibition of the acetic acid reactivity due to the prevalent adsorption of glycolic acid on Pt surface. The results from the APR of acetic and propionic acid solutions were less affected by such phenomena. DFT results showed that there are strong, attractive lateral interactions between carboxylic acids due to intermolecular hydrogen bonding that cause all carboxylic acids to preferentially adsorb in dimer structures. The lateral interaction strength was determined for both pure and binary mixtures of carboxylic acid dimers, with results showing that pure mixtures of carboxylic acids have stronger attractions and that glycolic acid dimers see the strongest attractions due to the added terminal hydroxyl functional group. The findings presented herein offer significant insights into the utilization of APR for industrial-like multi-component solutions, as well as for any catalytic process involving small organic compounds in an aqueous phase
Green hydrogen production from wastewater derived from lignin-rich hydrothermal liquefaction
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