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Study of bio-oil and bio-char production from thermal and catalytic hydrotreatment of simulated pyrolysis oil under mild conditions
Get PDFPyrolysis oil derived from fast pyrolysis of lignocellulosic biomass is a promising alternative energysource used to produce renewable biofuels. However, the high reactivity of unsaturated oxygenatedcompounds in pyrolysis oil results in charring and deactivation of the catalyst under severehydrotreatment conditions. This thesis focuses on reactions during stabilization of such oils, specifically,the undesirable carbon loss to solid char as the main side reaction.In the first study, mild thermal and catalytic hydrotreatment of a simulated pyrolysis oil, containing acomprehensive mixture of various oxygenated groups, was performed using NiMo/Al2O3 under mildconditions of 180-300\ub0C and 60 bar hydrogen in a batch reactor. The solid products were extracted intosoluble and insoluble solid fractions to determine the degree of polymerization. It was found that thesoluble solids transformed into the bio-liquid product and solid insoluble yield was suppressed atelevated temperatures. It was also accompanied by a higher degree of hydrodeoxygenation (HDO)causing the stabilization of light oxygenates, and a significant decrease in the formation of heavyoligomers in the liquid phase. In catalyst-free experiments, the formation of solids was higher andshowed a decreasing trend when increasing the temperature, except during heating where no solids wereobserved for the non-catalytic experiment. In the presence of the catalyst, the soluble solids at lowertemperatures (180\ub0C) consisted of macromolecule structures that were rich in sugar derivatives, whilethe corresponding insoluble solids were not fully developed into char. Their composition changed toaliphatic compounds and fully developed char respectively at higher temperatures. Moreover, theremoval of furan and sugar compounds was found to be crucial to reduce the solid char formation.In the second study, a set of catalysts; Pt/Al2O3, Rh/Al2O3, Pd/Al2O3, Re/Al2O3, and NiMo-S/Al2O3 wasused to stabilize the same simulated pyrolysis oil at identical reaction conditions (180\ub0C) as applied inthe first study. The catalyst screening results showed that Pd/Al2O3 was significantly better in terms ofachieving the highest conversion of pyrolysis oil and producing a high yield (66 wt%) of liquid oilproduct. The bio-liquid was mostly composed of low molecular weight compounds such as stabilizedoxygenates and hydrocarbons. It also featured a minimum solid formation (3.3 wt%) in which solublepolymers were more pronounced. The results also indicated that NiMo-S/Al2O3 was fairly good incatalyzing reactive compounds, except furans, into stable light oxygenates with the formed solids richin heavy insoluble polymers (13.6 wt%). The Rh/Al2O3 was comparable to NiMo-S/Al2O3, however,Pt/Al2O3 and particularly Re/Al2O3 rendered poor performances with the lowest yields and qualities ofthe liquid products, consisting mainly of heavy soluble oligomers, which resulted in a high degree ofpolymerization
Study of bio-oil and bio-char production from thermal and catalytic hydrotreatment of simulated pyrolysis oil under mild conditions [Elektronisk resurs]
No full textPyrolysis oil derived from fast pyrolysis of lignocellulosic biomass is a promising alternative energy source used to produce renewable biofuels. However, the high reactivity of unsaturated oxygenated compounds in pyrolysis oil results in charring and deactivation of the catalyst under severe hydrotreatment conditions. This thesis focuses on reactions during stabilization of such oils, specifically, the undesirable carbon loss to solid char as the main side reaction. In the first study, mild thermal and catalytic hydrotreatment of a simulated pyrolysis oil, containing a comprehensive mixture of various oxygenated groups, was performed using NiMo/Al2O3 under mild conditions of 180-300°C and 60 bar hydrogen in a batch reactor. The solid products were extracted into soluble and insoluble solid fractions to determine the degree of polymerization. It was found that the soluble solids transformed into the bio-liquid product and solid insoluble yield was suppressed at elevated temperatures. It was also accompanied by a higher degree of hydrodeoxygenation (HDO) causing the stabilization of light oxygenates, and a significant decrease in the formation of heavy oligomers in the liquid phase. In catalyst-free experiments, the formation of solids was higher and showed a decreasing trend when increasing the temperature, except during heating where no solids were observed for the non-catalytic experiment. In the presence of the catalyst, the soluble solids at lower temperatures (180°C) consisted of macromolecule structures that were rich in sugar derivatives, while the corresponding insoluble solids were not fully developed into char. Their composition changed to aliphatic compounds and fully developed char respectively at higher temperatures. Moreover, the removal of furan and sugar compounds was found to be crucial to reduce the solid char formation. In the second study, a set of catalysts; Pt/Al2O3, Rh/Al2O3, Pd/Al2O3, Re/Al2O3, and NiMo-S/Al2O3 was used to stabilize the same simulated pyrolysis oil at identical reaction conditions (180°C) as applied in the first study. The catalyst screening results showed that Pd/Al2O3 was significantly better in terms of achieving the highest conversion of pyrolysis oil and producing a high yield (66 wt%) of liquid oil product. The bio-liquid was mostly composed of low molecular weight compounds such as stabilized oxygenates and hydrocarbons. It also featured a minimum solid formation (3.3 wt%) in which soluble polymers were more pronounced. The results also indicated that NiMo-S/Al2O3 was fairly good in catalyzing reactive compounds, except furans, into stable light oxygenates with the formed solids rich in heavy insoluble polymers (13.6 wt%). The Rh/Al2O3 was comparable to NiMo-S/Al2O3, however, Pt/Al2O3 and particularly Re/Al2O3 rendered poor performances with the lowest yields and qualities of the liquid products, consisting mainly of heavy soluble oligomers, which resulted in a high degree of polymerization
Stabilization and upgrading of pyrolysis oil, mixed model compounds, and catalyst deactivation
No full textPyrolysis oil derived from fast pyrolysis of lignocellulosic biomass, as well as hydrogenated vegetable oils (HVO) from waste sources, are promising alternative energy sources used to produce renewable biofuels. However, the high reactivity of unsaturated oxygenated compounds in pyrolysis oil results in aging during storage as well as charring and deactivation of the catalyst under the hydrotreatment upgrading conditions. Catalytic mild hydrotreatment is suggested as a means to stabilize the oil before proceeding to hydrodeoxygenation (HDO) for upgrading. This thesis focuses on reactions during stabilization and upgrading of such oils, specifically, the undesirable carbon loss to solid char as well as aspects of catalyst deactivation during biofuel production. The selection of reaction parameters, such as residence time, temperature, oil composition and type of catalyst are crucial for the process. In this context, a set of catalysts; Pt/Al2O3, Rh/Al2O3, Pd/Al2O3, Re/Al2O3, and NiMo-S/Al2O3 was used for the mild catalytic hydrotreatment of a simulated pyrolysis oil, containing a comprehensive mixture of various oxygenated groups in a batch reactor. The solid products were extracted into soluble and insoluble solid fractions to determine the degree of polymerization. Firstly, it was found that at elevated temperatures (180-300°C) using NiMo-S/Al2O3 the soluble solids transformed into the bio-liquid product and solid insoluble yield was suppressed and its composition changed to fully developed char. It was also accompanied by a higher degree of HDO causing the stabilization of light oxygenates, and a significant decrease in the formation of heavy oligomers in the liquid phase. Further, furan and sugar compounds were identified to significantly influence the yield of liquid products containing stabilized compounds and contributed to solid formation through oligomerization and polymerization reactions. Then, the catalyst screening results showed that Pd/Al2O3 at 180°C was significantly better in terms of producing a high yield (66 wt%) of stabilized oil with the highest selectivity to low molecular weight products and a high char-suppressing potential (3.3 wt% of solids) in which soluble polymers were more pronounced. The results also indicated that NiMo-S/Al2O3 showed a good performance in catalyzing the conversion of reactive compounds, except furans, into stable light oxygenates with the formed solids rich in heavy insoluble solids (13.6 wt%). The Rh/Al2O3 was comparable to NiMo-S/Al2O3, however, Pt/Al2O3 and particularly Re/Al2O3 rendered poor performances with the lowest yields and qualities of the liquid products, consisting mainly of heavy soluble oligomers, which resulted in a high degree of polymerization. Also, the results indicate that accelerated aging converted 79% of the simulated pyrolysis oil into large oligomers, increasing solid formation to almost double after catalytic stabilization. This suggests that aging before stabilization is highly detrimental to the industrial process. Additionally, dewatered pyrolysis oil can be derived by azeotropic distillation, and the treated bio-oil was compared to pyrolysis oil. The dewatering resulted in the elimination of certain volatile compounds or those highly soluble in mesityl oxide/water, particularly acids. Our findings suggest that dewatering the pyrolysis oil before an upgrading process can open new reaction pathways which lead to improved hydrodeoxygenation efficiency. Furthermore, sulfided metal catalysts, NiMo/Al2O3, NiMo/SiO2-Al2O3, and NiW/Al2O3 along with bare supports (Al2O3, SiO2-Al2O3, and zeolite Y) were investigated after being used in a refinery green hydrotreating unit for several months. Phosphorus, alkali metals like potassium and sodium, common in renewable feedstocks, were identified as major poisons affecting these catalysts. It revealed that metal catalysts specially the NiW catalyst exhibited an increased affinity for poisons compared to the bare supports, leading to a significant decrease in HDO activity for fatty acid HDO in the lab-scale experiments. Attempts to recover NiMo/Al2O3 catalyst activity through solvent washing with DMSO were not successful as this led to further reduced surface area, although the poisons declined
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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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