1,720,968 research outputs found
Enhancement of bio-oil hydrodeoxygenation activity over Ni-based bimetallic catalysts supported on SBA-15
No full textThree Ni-based bimetallic catalysts were prepared on hexagonally structured mesoporous SBA-15 supports(NiCu/SBA-15, NiMn/SBA-15, NiZn/SBA-15). Hydrodeoxygenation (HDO) of biooil was performed at 250-350 degrees C for 45 min with 3 MPa H-2 pressure in the presence of the three catalysts. HDO reaction yielded a primary products of gas, two immiscible liquids (light oil and heavy oil) and char. High catalyst surface area resulted in a high heavy oil yield (40.8-60.6 wt%). Bimetallic catalysts decreased yield of light oil (3.6-11.7 wt%), while increased the gas fraction (16.3-43.7 wt%) compared with the data from the monometallic Ni/SBA-15 catalyst (20.3-30.4 and 6.6-26.2 wt% yields, respectively). Use of bimetallic catalysts instead of monometallic catalyst enhanced fuel properties of heavy oil; such as moisture content (from 11.4 to 2.0-8.8 wt%), acidity (from 62.2 to 49.2-59.8 mg KOH/g oil), viscosity (from 7.1 to 3.2-4.3 cSt) and oxygen content (from 32.2 to 26.2-34.6 wt%). Cyclohexanone, 4-ethylphenol, and methyl-cyclopentenone, which were lack in the bio-oil, were detected after HDO reaction and these components could be produced via demethoxylation, hydrogenation, dehydration, and dehydroxylation under the presence of bimetallic catalysts, thereby improving the fuel properties of the heavy oil. (C) 2019 Elsevier Ltd. All rights reserved.N
Relationship between characteristics of ethanol organosolv lignin and the productivity of phenolic monomers by solvolysis
No full textThis paper describes the effect of the structural properties of ethanol organosolv lignin (EOL) on the productivity of phenolic monomers by solvolysis. EOL was isolated from yellow poplar as a function of the fractionation combined severity (CSF). Structural properties of EOL such as volatile matter, molecular weight, and nitrobenzene oxidation (NBO) yield were significantly decreased with the increasing severity. The highest EOL yield (12.9 wt.%) was obtained at CSF 2.0, but,it also showed a significant decrement of NBO yield and molecular weight, and as a result, the yield of phenolic monomers after solvolysis was low (23.3 mg/g EOL). Despite of slight low fractionation yield (9.0 wt.%), the maximum yield of phenolic monomers after solvolysis was obtained from EOL fractionated at CSF 0.6 (40.4 mg/g EOL; 3.6 g/kg dry biomass), which has a considerably high NBO yield and aryl-ether linkages than EOL fractioned at higher CSF. (C) 2016 Elsevier Ltd. All rights reserved.OAIID:RECH_ACHV_DSTSH_NO:T201623480RECH_ACHV_FG:RR00200001ADJUST_YN:EMP_ID:A079993CITE_RATE:3.611DEPT_NM:국제농업기술학과EMAIL:[email protected]_YN:YCONFIRM:YN
Influence of K and Mg concentration on the storage stability of bio-oil
No full textIn this study, the storage stability of bio-oil was investigated for periods of 1, 2, 4, and 8 weeks at a temperature of 23 degrees C. Four kinds of bio-oil from biomass with different inorganic content controlled by impregnation process, i.e., yellow poplar (YP), demineralized YP (D-YP), K-impregnated YP (K-YP), and Mg-impregnated YP (Mg-YP), were subjected to aging. During aging, the elemental composition, water content, and total acid number of bio-oil were consistent. On the other hand, viscosity, average molecular weight, and solid content of bio-oil largely increased. The amount of aldehydes and ketones significantly decreased for K-YP and Mg-YP, while that of levoglucosan significantly decreased for D-YP oil. Most of the inorganic elements were highly concentrated in a solid form in bio-oil. The leaching test revealed that inorganic species tend to leach from the solid to the liquid phase during the initial storage period. However, the overall behavior slightly fluctuated over the whole period.OAIID:RECH_ACHV_DSTSH_NO:T201700610RECH_ACHV_FG:RR00200001ADJUST_YN:EMP_ID:A079993CITE_RATE:5.951DEPT_NM:국제농업기술학과EMAIL:[email protected]_YN:YN
Development of Lignin-based Polycarboxylates as a Plasticizer for Cement Paste via Peracetic Acid Oxidation
No full textKraft lignin (KL) was oxidized by peracetic acid, which is generated by mixing acetic acid and hydrogen peroxide, to produce polycarboxylates for use as a plasticizer for cement paste. Peracetic acid cleaves the aromatic ring structure of KL and introduces carboxylate groups with ring-opened chain structure. After oxidation, the water-soluble fraction (Cx-lig) was obtained, and the performance of the Cx-lig as a plasticizer was compared with two commercial plasticizers, lignosulfonate (LS) and polycarboxylate ether (PCE). In mortar table tests, the increase in cement fluidity with the Cx-lig was greater than with LS and PCE. Fourier-transform infrared spectroscopy, carbon-13 nuclear magnetic resonance, gel permeation chromatography, elemental analysis, and charge density analysis were used to determine the structure of the Cx-lig. Considering all the results, the Cx-lig had a polycarboxylate structure containing numerous carboxylate groups, and their high charge density was the key factor that caused the Cx-lig to increase the cement fluidity more than LS or PCE.Y
Improvement of lignin oil properties by combination of organic solvents and formic acid during supercritical depolymerization
No full textSupercritical treatment of ethanol organosolv lignin was conducted to produce lignin-derived bio-oil. The reaction was performed at 350 degrees C for 40 min with 3 MPa hydrogen gas pressure. To improve the yield of lignin oil and inhibit repolymerization during supercritical treatment, formic acid was added to the solvent. The effect of formic acid was examined by gas chromatography mass spectrometry (GC/MS), gel permeation chromatography (GPC), and elemental analysis. The maximum yield of lignin oils was shown to reach up to 70 wt% with the addition of formic acid. When 7% formic acid was used, the resulting lignin oil exhibited the highest monomer content at approximately 56 mg/g and the lowest oxygen/carbon molar ratio (O/C) of 0.26. The main degradation products in the lignin oil were syringol,4-methylsyringol, and p-cresol. The lignin oil contained a larger proportion of syringyl unit monomers than guaiacyl because yellow poplar is hardwood, consisting primarily of syringyls. The molecular weight of lignin oils increased with the addition of formic acid since lignin-derived oligomers were also produced. Meanwhile, experiments were performed using methanol and isopropanol to investigate the relationship between the solvent type and lignin depolymerization. lsopropanol led to a higher yield of lignin oil compared to ethanol, but amounts of monomeric products were much lower. Therefore, supercritical ethanol treatment with 7% formic acid under pressure from hydrogen gas is considered to be more effective when compared to other conditions, and this procedure demonstrated the possibility for better production of lignin-derived products during thermal decomposition reactions. (C) 2016 Elsevier B.V. All rights reserved.OAIID:RECH_ACHV_DSTSH_NO:T201623481RECH_ACHV_FG:RR00200001ADJUST_YN:EMP_ID:A079993CITE_RATE:3.652DEPT_NM:국제농업기술학과EMAIL:[email protected]_YN:YCONFIRM:YN
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
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
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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