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Levulinic acid from lignocellulosic biomass
Get PDFThe primary objective of this thesis is to define optimum catalysts, reaction conditions and reactor configurations for the conversion of water hyacinth plant to LA. The conversion of the C6-sugars present in the water hyacinth plant to LA involves several reactions that together form a complex reaction network. A number of side reactions giving rise to by-products formation (e.g., insoluble humin compounds) significantly complicate the catalyst selection and the development of kinetic models. Therfore, a stepwise approach was applied by investigating the individual reactions in the overall reaction scheme separately.
Levulinic acid from lignocellulosic biomass
Get PDFThe primary objective of this thesis is to define optimum catalysts, reaction conditions and reactor configurations for the conversion of water hyacinth plant to LA. The conversion of the C6-sugars present in the water hyacinth plant to LA involves several reactions that together form a complex reaction network. A number of side reactions giving rise to by-products formation (e.g., insoluble humin compounds) significantly complicate the catalyst selection and the development of kinetic models. Therfore, a stepwise approach was applied by investigating the individual reactions in the overall reaction scheme separately
Levulinic acid from lignocellulosic biomass
No full textThe primary objective of this thesis is to define optimum catalysts, reaction conditions and reactor configurations for the conversion of water hyacinth plant to LA. The conversion of the C6-sugars present in the water hyacinth plant to LA involves several reactions that together form a complex reaction network. A number of side reactions giving rise to by-products formation (e.g., insoluble humin compounds) significantly complicate the catalyst selection and the development of kinetic models. Therfore, a stepwise approach was applied by investigating the individual reactions in the overall reaction scheme separately
Levulinic acid from lignocellulosic biomass
Get PDFThe primary objective of this thesis is to define optimum catalysts, reaction conditions and reactor configurations for the conversion of water hyacinth plant to LA. The conversion of the C6-sugars present in the water hyacinth plant to LA involves several reactions that together form a complex reaction network. A number of side reactions giving rise to by-products formation (e.g., insoluble humin compounds) significantly complicate the catalyst selection and the development of kinetic models. Therfore, a stepwise approach was applied by investigating the individual reactions in the overall reaction scheme separately
Levulinic acid from lignocellulosic biomass
Get PDFThe primary objective of this thesis is to define optimum catalysts, reaction conditions and reactor configurations for the conversion of water hyacinth plant to LA. The conversion of the C6-sugars present in the water hyacinth plant to LA involves several reactions that together form a complex reaction network. A number of side reactions giving rise to by-products formation (e.g., insoluble humin compounds) significantly complicate the catalyst selection and the development of kinetic models. Therfore, a stepwise approach was applied by investigating the individual reactions in the overall reaction scheme separately
Primary conversion of lignocellulosic biomass for the production of furfural and levulinic acid
No full textThe production of energy and chemicals from renewable resources has gained significant attention as a means to support the transition from fossil fuels towards
clean and sustainable technologies. Due to its availability and rich carbohydrate
composition, lignocellulosic biomass represents a valuable starting material
and requires primary processes to unlock its components. The main focus
of this research was to study and develop further knowledge on the primary
steps of conversion of lignocellulosic materials, i.e. biomass fractionation, cellulose/
hemicellulose hydrolysis, and the production of furanic compounds (furfural,
5-hydroxymethylfurfural) and levulinic acid.
In an initial stage, the fractionation of Miscanthus giganteus and sugarcane
bagasse was investigated using hydrogen peroxide in formic acid solutions. This
treatment removed more than 70% of the lignin in the feedstocks after 13 h at
room temperature and after 15 min at temperatures over 150 oC. The use of
hydrogen peroxide in formic acid under transient temperature facilitated the separation
of >90% of the lignin and 80-98% of hemicellulose sugars, resulting in
nearly pure cellulosic pulps. Likewise, lignin was recovered from the liquor and
presented aromaticity properties proper of Organosolv lignins.
The conversion of lignocellulosic biomass to levulinic acid and furfural via acid
hydrolysis was undertaken using sulphuric acid as catalyst. Biomass feedstocks,
including agricultural, municipal wastes (paper) and rotational crops from Brazil
and Ireland, led to levulinic acid yields between 150 and 400 kg/ton dry biomass.
Additionally, the kinetics of acid hydrolysis of Miscanthus to produce levulinic
acid and furfural were studied at mild temperatures (150-200 oC) and high acid
concentrations (0.10-0.53 M H2SO4). A two-stage process was found to maximise
furfural (27.3 mol%) in a first reactor operated at 185 oC with 0.5 M H2SO4. A
second stage leads to levulinic acid yields between 58-72 mol% at temperatures
of 160-200 oC.
A kinetic modelling study of the dehydration reactions of xylose, arabinose and
glucose was carried out using formic acid as catalyst. Experimental data was obtained
from the conversion of xylose, arabinose, glucose and furfural at 130-170
oC and high formic acid concentrations (10-64 wt%). High temperatures (>160
oC) favoured the formation of furfural (62-68 mol%) from xylose and arabinose;
however, fundamental di erences in the reaction mechanisms followed by the pentoses
were found. Formic acid was not an effective catalyst of the conversion of
glucose at temperatures under 150 oC. Temperatures above 200 oC favoured the
formation of 5-hydroxymethylfurfural (20 mol%), while levulinic acid was maximised
(40 mol%) at milder temperatures (170-200 oC). Experimental evidence
was obtained in relation to the side reactions affecting the conversion of xylose
in liquors from the fractionation of Miscanthus. The conversion of xylose, arabinose,
and glucose and the formation of 5-hydroxymethylfurfural and levulinic
acid in the liquors were described satisfactorily by the kinetic models. However,
when lignin was not separated prior to the reaction, the furfural concentrations
observed were significantly 40% lower than those predicted by the models. By
inducing the lignin separation from the liquor, no losses in the selectivity of furfural
were observed. The effect of lignin model compounds and polymeric soluble
lignin on the selectivities of the dehydration of xylose and glucose was investigated
at 150 and 170 oC and acid concentrations of 60-62 wt% HCOOH. The
results con rmed that the oligomeric soluble lignin led to detrimental effects on
the selectivity of the furfural formation from xylose
DETOKSIFIKASI HIDROLISAT ECENG GONDOK DALAM PROSES PEMBUATAN BIOETANOL
Get PDFIndonesia masih sangat bergantung pada minyak bumi untuk memenuhi kebutuhan energinya. Akan tetapi minyak bumi adalah sumber daya alam yang tidak terbaharukan dan jumlahnya terus menyusut. Salah satu kandidat utama yang terbaharukan untuk menggantikan minyak bumi adalah biomassa. Dalam usulan penelitian ini akan dikaji pemanfaatan eceng gondok sebagai sumber bahan baku pembuatan bioetanol, yang dapat digunakan sebagai BBM alternatif untuk kendaraan bermotor. Tujuan khusus yang ingin dicapai dalam penelitian ini adalah mempelajari dan mengoptimasi proses detoksifikasi hidrolisat eceng gondok dengan metode penambahan alkali. Target akhir dari penelitian ini adalah sebuah teknologi tepat guna proses optimum pembuatan bioetanol dari eceng gondok yang merupakan integrasi dari proses hidrolisis eceng gondok, proses detoksifikasi dan proses fermentasi. Metode yang digunakan adalah dengan merancang bangun alat yang dibutuhkan di tahapan proses, melakukan percobaan pendahuluan dan percobaan utama untuk mencari kondisi optimum di tahapan proses pembuatan bioetanol dari eceng gondok. Hasil yang diperoleh dari penelitian ini adalah kondisi optimum proses detoksifikasi pada pH 11 dan temperatur 60 °C yang ditunjukkan dengan persentase penurunan konsen-trasi furfural yang maksimum. Akan tetapi karakterisasi hasil hidrolisis termal eceng gondok masih perlu dioptimalkan dengan menggunakan kolom HPLC yang berbeda
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
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