Teses / dissertações sobre o tema "Hydrogen peroxide production"

Hydrogen peroxide (H2O2) is a valuable chemical with rapidly growing demand in a variety of applications. At present, industrial production of H2O2 is through an energy-intensive anthraquinone process with high production costs and environmental hazards. Recently, the reported noble-metal based catalysts such as Pd-Au alloy, using renewable electricity to generate H2O2 via two-electron transferred oxygen reduction reaction (2e–-ORR), has received much attention. However, the cost and abundance of noble metals limit such catalysts for large-scale applications. To reduce the high overpotential requirement and improve the low yield of such noble metal catalysts, developing cost-efficient catalysts with high H2O2 selectivity and activity is a challenge that must be addressed immediately. Therefore, it is of great importance to design and synthesize electrocatalysts with abundant high-performance active sites for electrochemical H2O2 synthesis. In this thesis, by using a combination of theoretical calculation and experiments, I have demonstrated some effective approaches to tune the H2O2 generation performance on a series of structure-defined systems, including columbites (MNb2O6, M = Mn, Fe, Co, Ni and Cu), a porphyrin-based covalent organic framework (COF-366-M, M = Mn, Fe, Co, Ni, Cu and Zn) and a heterogeneous molecular catalyst system (HMC). In acid, neutral or alkaline conditions, I showcase the tunable H2O2 synthesis performance and identify the optimal composition and atomistic structure for these catalytic systems, paving the foundation for practical electrochemical H2O2 synthesis.

L'objectif de ce travail est donc de développer un procédé industriel, propre, de production de cellulose pure à partir de pâte kraft non blanchie, basé sur la catalyse du peroxyde d'hydrogène et utilisant si nécessaire des traitements complémentaires sans chlore. A cet effet, deux approches sont adoptées : (i) délignification de pâte kraft avec du peroxyde d'hydrogène et (ii) purification de la pâte à la soude et ozone. La réaction du système cuivre-phénanthroline / peroxyde d'hydrogène avec un composé modèle de lignine non phénolique, l'alcool vératrylique a été étudié. L'effet du catalyseur sur la délignification et sur la dégradation des hydrates de carbone a été examiné. La purification des pâtes ainsi obtenues par une extraction alcaline à froid ainsi qu'un stade de blanchiment final à l'ozone. Enfin, il a été montré que les moléculaires des celluloses (DMM) des celluloses produites étaient comparables à celles des pâtes au bisulfite acide où pré-hydrolyse krafts utilisés pour les applications viscose.

The aim of this study was to optimize methane production by investigating hydrothermal pretreatment of sugarcane bagasse impregnated with acid (H2SO4) and alkaline H2O2 using substrate (g kg-1) -inoculum (g kg-1) ratio of 1:2. Batch reactors were realized under mesophilic conditions (37 °C). A central composite design (CCD) involving three factors; temperature (°C), time (min), and chemical compound concentration (H2O2 (%v/v) and H2SO4 (%w/v)) was utilized to optimize hydrothermal pretreatment. Thirty-two hydrothermal pretreatments were conducted according to CCD. H2O2 assisted hydrothermal pretreatment resulted in higher solid recovery (93.13%), higher percent glucan increase (139.52%), and lower lignin recovery (76.48%) in pretreated solid fraction in comparison to H2SO4 impregnated hydrothermal pretreatment. In the latter case, lower solid yield (12.27%), glucan recovery (187.01%) and higher lignin recovery (358.85%) was recorded. Higher COD solubilization (25.20 g L-1), lower total phenolic (content 658.13 ppm), higher sulfate (7240 mg L-1), furfural (925.77-2216.47 mg L-1) and 5-hydroxymehtylfurfural (70.95-970.08 mg L-1) were observed in liquid hydrolysate of H2SO4 assisted hydrothermal pretreatment. While lower COD solubilization (17.75 mg L-1), higher total phenolic content (3005.63 ppm), lower concentration of furfural (0-56.91 mg L-1) and 5-hydroxymethylfurfural (2.56-56.60 mg L-1) was recorded with H2O2 assisted hydrothermal pretreatment. Concerning methane production for H2O2 assisted conditions, 5.59 Nmmol g-1 TVS (2% H2O2) to 13.49 Nmmol g-1 TVS (6% H2O2) was recorded. However, pretreatment with 7.36% H2O2 resulted in 14.43 Nmmol g-1 TVS, which was 118.16% higher comparing to untreated sugarcane bagasse (6.60 Nmmol g-1 TVS). Methanogenic inhibition was recorded for most of the H2SO4.pretreated reactor (1 – 3 %w/v H2SO4). Minimum CH4 production observed was 0.58 Nmmol g-1 TVS in pretreatment O-HSO (2% w/v H2SO4). Acetic acid was the predominant volatile fatty acid observed in digestion process of H2O2 treated batch reactor however was not recorded in H2SO4 treated batch reactors. Microbial community analysis indicated the prevalence of unclassified AUTHM297, Clostridium, and Treponema related genera in H2O2 treated reactors. Genera related aromatic compound degradation were identified and abundant in H2SO4 treated reactors. Methanolinea, Methanobacterium, and Methanosaeta were abundant methanogens in both pretreatments. Hydrogen peroxide assisted hydrothermal pretreatment was verified as a better choice for methane production comparing to sulfuric acid assisted hydrothermal pretreatment primarily on account of higher lignin solubilization, higher glucan recovery, and lower furanic compounds production.
O objetivo deste estudo foi otimizar a produção de metano investigando as condições do pré-tratamento hidrotérmico assistido do bagaço da cana de açúcar sob impregnação de ácido (H2SO4) e álcali (H2O2) utilizando-se a razão substrato (g kg-1) inóculo (g kg-1) de 1:2. Os reatores em batelada foram mantidos em condições mesofílicas (37 ºC). Para otimizar as condições de pré-tratamento hidrotérmico, o design de composto central rotacional (DCCR) foi realizado utilizando três fatores: temperatura (ºC), tempo (min) e concentração do composto químico (H2O2 (%v/v) e H2SO4 (% p/v)). Trinta e dois pré-tratamentos hidrotérmicos foram realizados de acordo com a concepção do DCCR. O pré-tratamento hidrotérmico assistido do bagaço, com H2O2 resultou em maior recuperação de sólidos (93,13%), elevado percentual de glicana (139,52%) e menor recuperação de lignina (76,48%) da fração sólida pré-tratada, se comparada aquele com H2SO4. Nesse último caso, observou-se menor rendimento de sólidos (12,27%) e glucanas (187,01%) e maior recuperação de lignina (358,85%). No líquido hidrolisado do pré-tratamento hidrotérmico assistido do bagaço com H2SO4 foi observada elevada solubilização de DQO (25,20 g L-1), menor teor de fenóis totais (658,13 mg L-1), elevado sulfato (7240 mg L-1), furfural (925,77 - 2216,47 mg L-1 e 5-hidroximetilfurfural (70,95 - 970,08 mg L-1). Enquanto, foi registrado menor solubilização de DQO (17,27 g L-1), maior teor de fenóis totais (3005,63 ppm), e menor concentração de furfural (0 - 56.91 mg L-1), 5-hidroximetilfurfural (2,56 - 50,60 mg L--1 com H2O2. Em relação ao a produção de metano nas condições com H2O2, observou-se 5.59 Nmmol g-1 STV (2%v/v H2O2) a 13.49 Nmmol g-1 STV (6%v/v H2O2). No tratamento com 7.36% de H2O2 observou-se 14,43 Nmmol g-1 STV que foi 118.16% maior se comparado com o bagaço não-tratado (6,60 Nmmol g-1 STV). Inibição metanogênica foi observada na maioria dos reatores pré-tratados com H2SO4 (1 – 3% p/v), e a produção mínima observada foi de 0.58 Nmmol g-1 TVS no pré-tratamento com 2% p/v de H2SO4. Ácido acético foi o principal ácido orgânico volátil observado somente no reatores por tratamento de H2O2. Por meio da A análise da comunidade microbiana, para o domínio Bacteria, foi observado prevalência dos gêneros AUTHM297, Clostridium e Treponema nos reatores cujo substrato foi pré-tratado com H2O2. Gêneros relacionados à degradação de compostos aromáticos foram identificados e estiveram em maior abundância nos reatores cujo substrato foi pré-tratado com H2SO4. Methanolinea, Methanobacterium, e Methanosaeta foram os microrganismos do domínio Archaea mais abundantes e identificados em ambos os pré-tratamentos. O pré-tratamento hidrotérmico assistido com H2O2 foi a melhor opção em relação ao H2SO4, devido a maior solubilização de lignina, maior recuperação de glucano e baixa produção de compostos furânicos.

The aim of this study was to analyze the effect of hydrogen peroxide and selected phenolic compounds on growth and catalase production of Aspergillus fumigatus. As a result of growing A. fumigatus at different temperatures it was observed that, growth and catalase production of this species were highest at 37 °
C. Catalase production was highest in the presence of 1 mM H2O2, yielding a significant 3 fold increase with respect to the control. Biomass was also increased by 1,44 fold with respect to the control sample. H2O2 increased catalase production possibly by inducing oxidative stress as biomass production significantly increased after the depletion of H2O2. Both gallic acid and trans-resveratrol significantly enhanced biomass generation of A. fumigatus (1,17 fold increase at 10 mM gallic acid and 1,45 fold increase at 3 mM resveratrol with respect to controls) and decreased extracellular catalase production (4,33 fold at 25 mM gallic acid and 16,7 fold decrease at 3 mM resveratrol with respect to controls) especially in the first 5 or 6 days of the cultivation where the anti-oxidant activity of the compounds were possibly at their maximum. A sudden and significant rise was observed in extracellular catalase activity between 5th and 7th days of the cultivation in phenolic compound applied samples, possibly owing to the depletion of the antioxidant activity of gallic acid and resveratrol followed by fungal cells&rsquo
response to a sudden increase of oxidative stress by boosting catalase production.

Hydrogen peroxide (H2O2), a reactive oxygen specie (ROS), is most commonly associated with oxidative stress causing cytotoxic effects on living cells. Oxidative stress has been implicated in various conditions including neurodegenerative diseases, autoimmune diseases and cancer. In addition H2O2 is produced as a defense mechanism against pathogens, as being released by activated phagocytes. In recent years, H2O2 has become established as an important regulator of signal transduction in eukaryotic cells. Hydrogen peroxide is generated both intracellularly and extracellularly in response to various stimuli including cytokines and growth factors. There are different mechanisms by which H2O2 is generated, facilitating signal transduction in cells; through NOX-system in miyochondria, via singlet oxygen, receptor/ligand interaction or by redox active metal ions. The HIV glycoprotein 120 (gp120) is associated with HIV dementia and it is known as a neurotoxin that causes neuronal damage. It has been proposed that free radicals may be involved in the pathogenesis caused by gp120. In addition the truncated form of thioredoxin (Trx80) is known to stimulate HIV replication in HIV infected cells, however, the exact mechanism is not known. A possible way both proteins may mediate their activity is by inducing H2O2 production. The aim of this study was to investigate H2O2 production induced by the proteins gp120 and Trx80. In order to detect H2O2 production an assay based on the fluorescent compound Amplex Red, was established. The assay was used to detect H2O2 released by gp120 and Trx80 in a cell-free environment, in a cell-system and in the presence of metal ions (copper ions) with a physiological reductant (ascorbate). We did not detect H2O2 production induced by gp120 and Trx80 respectively, using our assay, however, other ROS such as hydroxyl radicals may have been generated although they were not detectable with our method. Hence, further studies are needed in order to fully understand how gp120 and Trx80 mediate their activity.

The reactions between aqueous radiolysis products and oxide surfaces are important in nuclear technology in many ways. In solid-liquid systems, they affect (and at the same time are dependent on) both the solution chemistry and the stability of materials under the influence of ionizing radiation. The stability of surface oxides is a factor that determines the longevity of the materials where such oxides are formed. Additionally, the aqueous radiolysis products are responsible for corrosion and erosion of the materials.   In this study, the reactions between radiolysis products of water – mainly H2O2 and HO radicals – with metal, lanthanide and actinide oxides are investigated. For this, experimental and computational chemistry methods are employed. For the experimental study of these systems it was necessary to implement new methodologies especially for the study of the reactive species – the HO radicals. Similarly, the computational study also required the development of models and benchmarking of methods. The experiments combined with the computational chemistry studies produced valuable kinetic, energetic and mechanistic data.   It is demonstrated here that the HO radicals are a primary product of the decomposition of H2O2. For all the materials, the catalytic decomposition of H2O2 consists first of molecular adsorption onto the surfaces of the oxides. This step is followed by the cleavage of the O-O bond in H2O2 to form HO radicals. The HO radicals are able to react further with the hydroxylated surfaces of the oxides to form water and a surface bound HO• center. The dynamics of formation of HO• vary widely for the different materials studied. These differences are also observed in the activation energies and kinetics for decomposition of H2O2. It is found further that the removal of HO• from the system where H2O2 undergoes decomposition, by means of a scavenger, leads to the spontaneous formation of H2.   The combined theoretical-experimental methodology led to mechanistic understanding of the reactivity of the oxide materials towards H2O2 and HO radicals. This reactivity can be expressed in terms of fundamental properties of the cations present in the oxides. Correlations were found between several properties of the metal cations present in the oxides and adsorption energies of H2O, adsorption energies of HO radicals and energy barriers for H2O2 decomposition. This knowledge can aid in improving materials and processes important for nuclear technological systems, catalysis, and energy storage, and also help to better understand geochemical processes.

QC 20130322

Dans la première partie de ce travail, nous avons exploré l'applicabilité du polypyrrole (PPy) en tant que photocatalyseur pour la production d’H₂O₂. Nos résultats ont démontré que les PPy synthétisés par polymérisation radiolytique sont très actifs pour la génération de H₂O₂ sous lumière visible. L'influence de différents paramètres sur la formation d' H₂O₂ en présence du PPy a été étudiée pour la première fois. En outre, nous avons étudié les voies possibles pour la formation de H₂O₂ par des expériences de piégeage, montrant que H₂O₂ se produit principalement par réduction de l'oxygène. La décomposition et le taux de formation de H₂O dépendent également de la concentration du catalyseur, du pH et de l'intensité lumineuse. Nous avons ensuite étudié l'application de la génération in situ de H₂O pour la dégradation des polluants dans l'eau. Dans cette partie, un nouveau système photo-Fenton auto-entretenu pour le traitement de l'eau, qui combine le g-C₃N₄ ou PPy, un photocatalyseur connu pour la synthèse de H₂O, avec un catalyseur photo-Fenton de ferrite de lanthane (LTFO) substitué par du Ti, est étudié pour améliorer la dégradation des polluants sous l'effet de la lumière solaire. En utilisant le phénol comme polluant modèle, nous montrons que les composites g-C₃N₄ /LTFO et PPy/LTFO présentent une meilleure activité catalytique que les nanomatériaux purs. La caractérisation et l'analyse révèlent que l'interaction synergique entre les composites permet au catalyseur de fonctionner comme un catalyseur de type photo-Fenton en l'absence d'ajout de H2O externe. Les résultats démontrent que l'utilisation d'un composite g-C₃N₄/LTFO dans la réaction photo-Fenton est une approche prometteuse pour un traitement efficace et durable de l'eau à un pH neutre sans apport extérieur de H₂O₂. L'étude ouvre également la voie à d'autres recherches visant à optimiser ces types de composites pour des applications environnementales plus larges. En outre, des résultats préliminaires sur l'utilisation de composites de nanofils g-C₃N₄@ZnO dans la production d'H₂O₂ sont présentés. Les caractérisations ont révélé que les nanofils de ZnO et le g-C₃N₄@ZnO ont été préparés avec succès et seront testés ultérieurement pour les applications souhaitées. Nos résultats ont montré qu'un simple polymère PPy est un matériau prometteur comme candidat pour la production photocatalytique d' H₂O₂ et que le concept de production in situ d'H₂O en utilisant des polymères pour le processus photo-Fenton est un concept intéressant pour les applications de traitement de l'eau
In the first part of this work, we explored the applicability of polypyrrole (PPy) as a photocatalyst for H2O2 production. Our results showed that PPy synthesized by radiolytic polymerization are very active for H₂O₂ generation under visible light. The influence of different parameters on H₂O₂ formation over PPy has been studied for the first time. Moreover, we studied the possible pathways for the H₂O₂ formation via scavenging experiments, showing that it predominantly proceeds via oxygen reduction. The decomposition and formation rate of H₂O₂ were also shown to be dependent on the catalyst concentration, pH and light intensity. Then we next studied the application of in situ H₂O₂ generation for water pollutant degradation. In this part, a new self-sustained photo-Fenton system for water treatment, that combines g-C₃N₄ or PPy, a known H₂O₂ synthesis photocatalyst, with a Ti-substituted Lanthanum Ferrite (LTFO) photo-Fenton catalyst, to enhance the pollutant degradation under solar light. Using phenol as model pollutant, we show that the g-C₃N₄/LTFO or PPy/LTFO composite exhibits better catalytic activity. Characterization and analysis reveal that the synergistic interaction between the composite leads the catalyst to operate as photo-Fenton-type catalyst in the absence of any addition of external H₂O₂. The results demonstrate that using a g-C₃N₄/LTFO composite in the photo-Fenton reaction is a promising approach for efficient and sustainable water treatment free of external H₂O₂ at circumneutral pH. The study also opens avenues for further research in optimizing these types of composites for broader environmental applications. In addition, preliminary results on the utilization of g-C₃N₄@ZnO nanowires composites in H₂O₂ production are presented. Characterizations revealed that ZnO naanowires and g-C₃N₄@ZnO are successfully prepared and will be further tested for the desired applications. Our results showed that a simple PPy polymer is a candidate material for photocatalytic H₂O₂ generation and the concept of in-situ H₂O₂ generation using polymers for photo-Fenton process is an interesting concept for water treatment applications

The work presented within this thesis can be separated into two distinct parts. The first investigates the direct synthesis of hydrogen peroxide from molecular hydrogen and oxygen using gold-palladium supported catalysts and caesium exchanged tungstophosphoric acid as an acidic additive. The direct synthesis of H2O2 presents an environmentally friendly alternative to the current industrial, anthraquinone process. However for the direct route to be viable a variety of issues must be addressed. Primarily catalytic selectivity towards H2O2 is a major concern for the majority of catalysts active for H2O2 synthesis, with the degradation of H2O2 through hydrogenation or decomposition reported for a number of catalysts within the literature. The use of acid either during catalyst preparation or as part of the reaction solution has previously been shown to improve selectivity towards H2O2. Furthermore acidic supports, including heteropolyacid, have been observed to produce catalysts with greater selectivity than those with a higher isoelectric point and in turn provide higher yields of H2O2. This work investigates the ability of caesium exchanged heteropolyacids to improve catalytic activity towards H2O2 when used in addition to Au-Pd supported catalysts, in particular 2.5 wt. % Au - 2.5 wt. Pd/TiO2. The second part of this work is concerned with the ammoximation of cyclohexanone to cyclohexanone oxime via the in-situ formation of H2O2, in a one-pot style process. The conditions associated with ammoximation of cyclohexanone that is the presence of elevated temperatures and basic conditions, are considered extremely harsh for H2O2 stability. The in-situ generation of H2O2 during the ammoximation of cyclohexanone to cyclohexanone oxime would yield significant reductions in overall costs of the ammoximation reaction. Primarily these costs are associated with the purchasing, transport, storage and dilution of H2O2. This work determines the feasibility of a one-pot ammoximation process via in-situ H2O2 formation. Firstly, reaction conditions are established for this process and following this the role of catalyst design in improving selectivity towards cyclohexanone oxime as well as cyclohexanone conversion for this reaction is studied.

Le rôle clef du fer dans le cycle biogéochimique du carbone et de l’azote dans l’océan a été mis en évidence au cours de la dernière décennie. Une des découvertes majeures récentes en océanographie biologique est la limitation de la croissance du phytoplancton par la disponibilité en fer dans au moins 40% de l’océan mondial. Or, la chimie de cet élément dans l’océan est particulièrement complexe et la forme sous laquelle il est disponible pour le phytoplancton reste encore mal connue. Plusieurs mécanismes sont utilisés par le phytoplancton marin pour améliorer la solubilité du fer en eau de mer et parvenir à absorber les quantités suffisantes en fer nécessaires à leur survie. Un de ces mécanismes implique la production de radicaux superoxyde en milieu extracellulaire, ce qui accroît la bio-disponibilité du fer en eau de mer en réduisant la forme Fe(III) sous forme Fe(II), plus bio-disponible aux cellules de phytoplancton. Les objectifs principaux de ce travail étaient de i) développer une méthode appropriée pour détecter la production de superoxyde en milieu extracellular par n’importe quelle cellule de phytoplancton marin, et ii) examiner la relation entre la production extracellulaire de superoxyde et l’absorption du fer par la cyanobactérie Trichodesmium erythraeum IMS101. Une méthode de détection du superoxyde a été développée, qui utilise du red-CLA ou du MCLA, deux sondes chimiluminescentes spécifiques à la détection du superoxyde, qui ont donné des résultats fiables, même sur de très faibles quantités d’échantillons. En effet, comparée aux autres méthodes employées, la détection de la production du superoxyde par microplaques permet de réduire le volume d’échantillon par 10, et de réduire le temps d’analyse de tréplicats d’un échantillon, d’un blanc et de trois standards à 10 minutes. De plus, cette méthode présente une large gamme de travail avec une limite de détection de 0,076 pmol/s, ce qui lui confère un grand avantage pour le travail sur le phytoplancton marin. Les taux de production de superoxyde en milieu extracellulaire par la cyanobatérie Trichodesmium erythraeum ont été mesurés en condition de laboratoire et allaient de 0,93 à 16,21 pmol/trichome/h. La limitation en fer des cellules de Trichodesmium résultat en une augmentation de ce taux de production, qui a été multiplié par un facteur 2,9 entre les cellules non limitées et les cellules limitées en fer. Il a aussi été montré que la production de superoxyde suivait un rythme diurne avec une forte augmentation du taux de production en milieu du cycle « jour», spécialement marqué pour les cultures maintenues en milieu pauvre en fer. Les taux de production extracellulaire de superoxyde et d’absorption du fer par Trichodesmium ont été mesurés simultanément sur des cultures pré-limitées ou non limitées en fer. Les taux d’absorption étaient 10 fois plus élevés pour les cultures non limitées, sauf lorsqu’un composé réducteur (acide ascorbique) était ajouté. Dans ce cas, les taux d’absorption des deux cultures étaient similaires. De plus, les deux cultures ont montré une plus grande aptitude à absorber le fer lié à des ligands faibles comme le citrate. Dans l’ensemble, les résultats ont montré une relation entre la production de superoxyde et l’absorption de fer par Trichodesmium, mais aucune influence directe entre ces deux processus n’a pu être démontrée. La méthode de détection du superoxyde par microplaque a été utilisée lors de campagnes sur la Grande Barrière de corail en Australie. L’analyse de deux blooms de Trichodesmium a montré de forts taux de production de superoxyde, en cohérence avec les analyses effectuées au laboratoire. De plus, l’utilisation de cette méthode (entre autres) a permis de démontrer une accumulation d’espèces Fe(II) en concentrations biologiquement significatives, quand la concentration en superoxyde dans l’eau de mer était inférieure à 1 nM. Par contre, lorsque cette concentration se trouvait supérieure à 1nM, la plupart des espèces réduites (Fe(II)) étaient réoxidées, ce qui résultait en un fort taux de production de peroxyde d’hydrogène du à la dismutation du superoxyde. Dans l’ensemble, cette étude a permis le développement d’une méthode de détection de la production de superoxyde par le phytoplancton marin en milieu extracellulaire qui peut être utilisée au laboratoire ou en conditions d’étude sur le terrain. Nous avons aussi démontré que les cellules de Trichodesmium erythraeum IMS101 produisent de grandes quantités de superoxyde, en particulier lorsqu’elles sont limitées en fer. L’étude des taux d’absorption du fer par ces même cellules a démontré une forte relation entre ce processus et la production de superoxyde par les cellules: ces résultats sont en accord avec l’hypothèse que le modèle d’absorption du fer par le phytoplancton marin «Fe’» serait fortement influencé par ce type d’organisme capable de modifier l’équilibre redox du milieu présent à la surface des cellules
It is hypothesised that, under iron limitation, phytoplankton cells develop biochemical mechanisms to increase their iron uptake efficiency with one of these mechanisms involving the production of superoxide in the extracellular environment that increases the bioavailability of iron in seawater by reducing Fe(III) to the more soluble Fe(II). The main objectives of this work were 1) to develop an appropriate method to detect extracellular production of superoxide by marine phytoplankton, and 2) to examine the relationship between extracellular production of superoxide and iron acquisition by Trichodesmium erythraeum. A method to measure superoxyde production is described using red-CLA and MCLA probes, yielding considerable improvement for analysis compared to other available methods. Extracellular superoxide production and iron uptake rates were measured simultaneously on iron replete and iron deplete Trichodesmium erythraeum IMS 101 laboratory cultures : iron starvation leads to a 2. 9-fold increase in superoxide production rate and 10-fold decrease in the iron uptake rate (except when a reducing compound was added) compared to iron replete cultures. Extracellular superoxide production shows a pronounced circadian rythm in iron deplete cultures, but less so in iron replete cultures. Overall, no direct impact of extracellular superoxide production by Trichodesmium is observed, but both processes are shown to be related. Both iron deplete and iron replete cultures demonstrate greater ability to uptake iron bound to weaker iron-binding ligands such as citrate. Application of the method to field studies in the Great Barrier Reef lagoon showed an accumulation of biologically significant concentrations of reduced trace metals including Fe(II) when the concentration of superoxide was lower than 1 nM. When the concentration of superoxide was higher than 1 nM, most of the reduced species were oxidised resulting in high rates of hudrogen peroxide production rates, consistent with laboratory studies. Overall, this thesis permitted the development of a method to detect superoxide production rates by marine phytoplankton cells that could be used routinely in field studies. The observations are in accord with the conclusion that fit the ongoing hypothesis that the extablished Fe' uptake model for phytoplankton would be strongly influenced by such organisms that are able to modify the redox equilibrium of the solution at their cells surface

Les stress oxydants (irradiation gamma, action du peroxyde d'hydrogene ou de generateurs chimiques d'anion superoxyde) induisent une regulation differentielle de l'expression des genes chez la tomate. Des analyses comparatives par electrophorese 2d de proteines radiomarquees, montrent la synthese a court terme de proteines communes et specifiques aux differents traitements. Les reponses se superposent partiellement a la reponse de choc thermique. Elles sont modulees par la nature chimique des especes activees de l'oxygene, leur mode et leur site de production et par l'intensite du stress. Toutes les proteines de choc thermique (hsps) ne sont pas induites par les stress oxydants. Des experiences de northern blot confirment la transcription rapide des genes codants pour des petites hsps cytosoliques, apres l'irradiation ou l'action du peroxyde d'hydrogene. Les niveaux d'accumulation des arnm et des proteines sont moderes, compares a ceux induits par la chaleur. La synthese de hsps ne requiert pas la production d'anion superoxyde. La proteine nommee hsp22, dont la synthese est majoritairement induite par l'irradiation et l'action d'h#2o#2, a ete purifiee, partiellement sequencee et identifiee. Sa sequence n-terminale ainsi que deux sequences internes presentent de fortes identites avec les petites hsps mitochondriales recemment caracterisees. Des experiences d'immunodetection par un anticorps dirige contre l'hsp23 mitochondriale de chenopodium rubrum, confirment son appartenance a cette classe et demontrent sa synthese apres des chocs oxydants severes. Des analyses cinetiques revelent une accumulation de la proteine variable dans le temps selon le type de stress (thermique ou oxydant) et son intensite. Par sa localisation et son role potentiel dans la protection des structures ou des fonctions mitochondriales, la proteine hsp22 pourrait etre impliquee dans certains mecanismes d'adaptation cellulaire aux stress

碩士
國立清華大學
生醫工程與環境科學系
104
This study develops a hydrogen production process from oxidative steam reforming of methanol using hydrogen peroxide as the oxidant (H2O2-OSRM). The liquid phase of H2O2 with methanol will facilitate the design and assembly of fuel cells. In the H2O2-OSRM system test, H2O2 could decompose completely at 150℃. For the catalytic activity of the catalysts in H2O2-OSRM reaction with MeOH:H2O2 volume ratio of 4:1(O2/MeOH =0.089, H2O/MOH=0.514), both CuPd2/Ce10Zn (30 wt% Cu, 2 wt% Pd, 10 wt% Ce and 58wt% Zn) and CuPd2/Ce20Zn (30 wt% Cu, 2 wt% Pd, 20 wt% Ce and 48wt% Zn) catalysts showed ~80% of CMeOH, ~2.4 of YH2, and only 3% of SCO at 250℃. With increasing the addition of Ce, the SCO can be reduced, even to 0%. In MeOH:H2O2 volume ratio of 3:1 (O2/MeOH =0.119, H2O/MOH=0.685), which can provide more oxygen to enhance catalytic activity of catalysts at low temperature. When catalysts were pre-reduced before reaction, it not only improve catalytic activity but also decrease SCO in H2O2-OSRM system .On the whole, compared with H2O2-OSRM and SRM at the same ratio of H2O/MeOH, H2O2-OSRM system can provide more hydrogen than SRM reaction. It approximately provided 1.7 times of hydrogen production at 250℃. The catalytic activity of CuPd2/Ce10Zn and CuPd2/Ce20Zn catalysts through OSRM reaction (O2/MeOH=0.3H2O/MeOH=0.514) showed good performance. CuPd2/Ce10Zn and CuPd2/Ce20Zn catalysts performed ~90% of CMeOH, ~ 2.5 of YH2 at 250℃, and the Sco was kept 0~4% at whole reaction. Since the oxygen content was limited by the concentration of hydrogen peroxide (~50%), the reactivity in H2O2-OSRM system cannot further be enhanced. 　　To more realize the effect of Ce promoter and abatement of CO, O2-TPD, CO-TPR and in-situ DRIFT were investigated to explore the relation between Ce promoter and O2 and CO chemisorption. It obviously shows that more O2 and CO were adsorbed on catalyst with Ce. CuPd2/Ce20Zn catalyst has 10 times intensity of CO chemisorption than CuZn (30 wt% Cu and 70 wt% Zn) catalyst. The presence of CeO2 with oxygen vacancies enhanced the affinity to adsorb oxygen atoms of reactants, as well as even can catalyze CO oxidation at low temperature (90℃).

碩士
國立臺灣科技大學
化學工程系
103
It is well-known that hydrogen peroxide is a highly versatile environmentally friendly industrial oxidant. Recently, palladium and bimetallic palladium gold catalysts have come to prominence, due to their high selectivity and activity. However, the high cost of gold both limits their wide application in industry and at the same time fuels research into alternative catalytic metals able to replace gold in bimetallic catalysts. This study focuses on PdxNiy bimetallic nanocatalysts for green production of hydrogen peroxide. In this work a new supported catalyst for the direct synthesis of hydrogen peroxide was developed. Nickel has been adopted as the catalytic candidate due to its low cost compared to gold. Two main approaches were taken to synthesize PdxNiy nanocatalysts. NaBH4 and H2 were applied as a reductive agent to reduce Pd2+ and Ni2+ in precursors to form bimetallic PdxNiy on pretreated-carbon, respectively. However, the analysis results show that NaBH4 was not able to reduce Ni2+, and the H2 reduction method cannot achieve desired interaction between nanocatalysts and support. Thus, mesoporous carbon support and the organic agent reduction method were further developed for the synthesis of bimetallic nanocatalysts which were characterized by the crystallographic face-centered-cubic structure. Next, it is demonstrated that the alloy crystal structure of PdxNiy alloy can be arranged into the face-centered tetragonal (fct) structure after hydrogen treatment. Attributed to the ordered structure, the fct- PdxNiy catalyst found in this study enhances not only structural stability but also productivity with respect to the direct synthesis of hydrogen peroxide.

碩士
國立成功大學
環境工程學系
104
Hydrogen peroxide (H2O2) is a clean oxidant and fuel that is desirable in many real-world applications. Current industrial manufacturing of H2O2 involves expensive, noble metal-based catalysts with high energy demand. Searching for more environmentally sustainable process for H2O2 production merits greater attention in research. In this work, the potential of graphene oxide (GO), an emerging, two-dimensional carbon-based nanomaterial, as a new photocatalyst toward H2O2 photoproduction driven by solar energy was explored. The result indicates that 〉 1 mM of H2O2 can be photoproduced within 6 h of solar irradiation even without organic electron donors present. This is particularly attractive considering that photocatalytic H2O2 production processes usually require organic electron donors. To our knowledge, the H2O2 photoproduction reported here is among the highest values in related work. O2 is needed for this process and greater yield is favorable at increased pH. The greater yield at increased pH contrasts the more rapid loss of GO’s long-term photocatalytic stability that can be attributed to greater phototransformation of GO at increased pH. Two-electron O2 reduction is the likely pathway toward H2O2 formation. The apparent quantum yields (AQYs) were also reported. The results indicate that GO is a promising photocatalyst toward H2O2 production that can be driven by renewable sunlight energy under organic electron donor-free condition.

In the African Cape buffalo, circulating serum xanthine oxidoreductase (XOR) produces trypanotoxic levels of hydrogen peroxide (H2O 2). Previous, preliminary studies suggest that mammalian serum XOR H 2O2 production rates (“specific activities”) are species- and breed-associated. The research objectives pursued here were: (1) to verify that mammalian serum XOR specific activities were truly species- and breed-associated, and if found to be so (2) to determine if the noted activity differences were a product of translational and/or post-translational mechanism(s). The ultimate intent of this work was to reveal strategies by which trypanosome tolerance might be achieved in susceptible mammals. By a novel kinetic peroxidase assay, developed and used here, it was found that the serum XOR specific activities of Cape buffalo, Holstein and Hereford heifers, Sprague-Dawley rats, and humans were significantly different from one another (p < 0.025). A concurrent, comparative analysis of XOR nucleotide/amino acid sequences and tissue-specific transcription rates in Cape buffalo and representative bovine breeds yielded no points of variability that might explain observed activity differences. To determine if such differences were, instead, a product of distinct translational and/or post-translational regulatory mechanism(s), serum XOR was isolated, quantified, and characterized. Two immunoaffinity (IA) chromatography protocols were developed to isolate serum XOR. Mouse monoclonal antibodies directed against cow milk xanthine oxidase (α-CMXO) exhibited a recognition for serum XOR that was limited to bovid species. Polyclonal rabbit α-CMXO antibodies were found to recognize serum XOR from a greater range of mammalian species. However, IA eluent resolution by SDS-PAGE (under reducing conditions) elucidated polypeptide profiles that were species-specific, suggesting the presence of co-eluting contaminants. MALDI-TOF analysis identified the putative contaminants as components of serum IgG and IgM. These immunoglobulins (Igs) were found to exist in complex with the isolated serum XOR or were recognized directly by the polyclonal α-CMXO antibodies of the IA column, in an idiotypic manner. The consequences and implications of such Ig contamination are discussed, specifically with regard to: (1) the future use of α-XOR antibodies in extracting serum XOR, and (2) the possible roles of XOR-Ig complexes in systemic inflammatory pathologies.

碩士
國立臺灣科技大學
化學工程系
99
The purpose of this study is to develop a new green process for production of H2O2 through the direct synthesis route, of which the hydrogen and oxygen contacts each other during the reaction. An electrochemical approach with the rotating ring disk electrode (RRDE) had been systematically explored and developed accordingly to measure the produced H2O2. Two different methods – co-reduction and successive reduction prepared in the microwave were adopted to prepare bimetallic Pd-Au/C nanocatalysts. The relationship between the structure of prepared nanocatalysts and their catalytic activity in the direct synthesis process were investigated. As synthesized bimetallic Pd-Au/C were characterized by ICP-AES, XRD, SEM, TEM, and XAS for better understanding in the catalytic activity of direct synthesis of H2O2. The approach in the electrochemical to measure H2O2 produced from direct synthesis has been successfully done with the detection method 2, where the catalyst is dispersed homogenously in the solution. The calibration curve of the different concentration of H2O2 is made in the parameter of 0.891 V (vs Ag/AgCl) and with the scan rate 50 mV/s. The optimum loading of samples prepared by co reduction was observed in CR Pd3%-Au2%/C with the productivity of H2O2 is 65.8 mol.kgcat-1h-1. This productivity is higher than the other prepared catalysts, such as monometallic Pd0%-Au5% & Pd5%-Au0% and bimetallic SR Pd-Au/C that is prepared by successive reduction. The higher or the lower productivity of one sample to another was explained by the parameter of the particle size, the structure of the bimetallic Pd-Au/C, the selective crystalline plane, and the role of palladium and gold. The smaller the particle size tends to Pd rich, while the larger one tends to Au rich. The smaller particle size yielded in the high surface area, thus the productivity increases. However, if the particle size is too small, the active site or selective crystalline plane may be slightly appeared (as can be seen in SR Pd-Au/C), thus the productivity decreases. From XAS analysis, the structure CR Pd-Au/C is Au rich in core and Pd rich in shell. The structure of SR PdAu at some part of catalyst is Au rich in core and Pd rich in shell, while at the other part, the structure is Pd in core and Au in shell. The Q value of SR PdAu (0.638) is higher than that of CR PdAu (0.605), which indicates that the existence of Au atoms in the shell of SR PdAu is more than that of CR PdAu. The difference in their structure is one reason why the H2O2 productivity of CR PdAu is higher than SR PdAu. The role of Pd is to provide the surface area for the selective oxidation of hydrogen and the role of Au is to provide inactive site for the reaction of decomposition and hydrogenation of H2O2.

碩士
國立臺灣科技大學
化學工程系
102
Hydrogen Peroxide is a valuable chemical with wide spread uses in industry; its demand is recently increasing due to its utilization. The modified reduced graphene oxide supported PdAu nanocatalysts were prepared for direct synthesis of hydrogen peroxide at ambient conditions in this work. The various atomic ratios of PdAu nanocatalysts on reduced graphene oxides were synthesized and characterized by XRD, SEM, TEM, Raman, FTIR and electrochemical analysis. It is found that the Pd07Au03 nanocatalyst shows the highest productivity of hydrogen peroxide due to its higher alloying extent. The graphene oxides were further modified by sulfonation. The results indicate the productivity can be further improved when Pd07Au03 nanocatalysts were prepared on the modified reduced graphene oxide. The high productivity of hydrogen peroxide was successfully achieved on the developed PdAu/mrGO nanocatalysts at ambient conditions. The method developed for preparation of PdAu nanocatalysts on modified reduced graphene oxide opens a new and interesting direction for increasing productivity hydrogen peroxide.

碩士
國立成功大學
化學工程學系碩博士班
97
The effect of lysozyme and hydrogen peroxide on the Streptococcus zooepidemicus ATCC 39920 which produce hyaluronic acid was investigated. These two additional agents were harmful to streptococcal cells, but improved the production of hyaluronic acid by adding appropriate hydrogen peroxide in logarithmic growth phase and appropriate lysozyme in lag phase.

碩士
國立臺南大學
生物科技學系碩士班
104
3'-Hydroxygenistein can be obtained from the biotransformation of genistein by the engineered Pichia pastoris X-33 strain, which harbors a fusion gene composed of CYP57B3 from Aspergillus oryzae and a cytochrome P450 oxidoreductase gene (sCPR) from Saccharomyces cerevisiae. We applied periodic hydrogen peroxide shocking to select for higher 3'-hydroxygenistein production by P. pastoris X-33 mutants. One mutant (P2-D14-5) produced 23.0 mg/l of 3'-hydroxygenistein, which is an amount 1.87-fold higher than that produced by the recombinant X-33. In a scale-up experiment, P2-D14-5 produced 20.3 mg/l of 3'-hydroxygenistein in a 5-L fermenter. The P2-D14-5 mutant therefore has high potential for industrial-scale 3'-hydroxygenistein production.

The development of efficient energy conversion technologies, such as electrocatalysis process converting electricity derived from renewable energy to various forms of chemical energy, provides a highly desired pathway to produce transportable fuels and value-added chemicals from low-cost feedstocks like water and air, simultaneously to ease the fossil fuel reliance as well as the greenhouse gases emissions. Ammonia (NH3) and hydrogen peroxide (H2O2) are globally important chemicals as basic building blocks in industry and promising carbon-free hydrogen carriers. Production of NH3 from N2 (NRR) or H2O2 from O2 (2e– ORR) through the sustainable and energy-saving electrocatalysis process are therefore highly meaningful. A crucial step in conducting these processes is to develop efficient electrocatalysts for effective activation of the reactants and selective formation of the desired products. Therefore, this Thesis aims to design and synthesize novel nanostructured materials as efficient electrocatalysts for nitrogen and oxygen reduction reactions. Besides the electrocatalyst engineering, energy devices combining various reactions/techniques are also elaborately designed as demonstration for future practical applications. In this Thesis, a systematic review on the recent research progress for the application of main group elements on NRR is firstly provided by investigating their interaction with N2 and the strategies for suppression of the undesired hydrogen evolution reaction (HER) (Chapter 2). This chapter provides a concise but comprehensive understanding on various reaction pathways for NRR and strategies towards N2 activation and HER suppression. The first part of this Thesis (Chapter 3 and 4) focus on a comprehensive optimization and accurate evaluation of NRR performance by investigating aspects such as electrocatalyst and electrolyte. Firstly, semiconducting bismuth nanosheet was for the first time reported to be promising candidate for ambient NRR. The high NRR electrocatalytic activity of the Bi NS originates from the sufficient exposure of edge sites coupled with effective p-orbital electron delocalization. Secondly, trace amount of nitrate and nitrite were found to exist in some lithium salts such as Li2SO4 and LiClO4, which are usually used as electrolytes. Reduction of those nitrogen oxyanions (NOx –) causes false positive results for NRR. To avoid these false positive results and to make the best practice of NRR research, simple but versatile spectrophotometric methods were employed to quantitatively determine NOx – contaminations, followed by effective high-temperature annealing strategy to eliminate them. The second part of this Thesis (Chapter 5) focus on exploration of novel strategy for efficient nitrogen fixation other than the present one-step NRR process. It is proposed that fixation of N2-to-NH3 can be decoupled to a two-step process with one problem effectively solved in each step, in which facile activation of N2 to NOx – is realized by a non-thermal plasma technique and highly selective conversion of NOx – to NH3 by electrocatalytic reduction. In the third part of this Thesis (Chapter 6), the electrochemical reduction of O2 via a twoelectron reaction pathway for sustainable and decentralized H2O2 production was investigated on a nitrogen-rich few-layered graphene (N-FLG). A positive correlation between the content of pyrrolic-N and the H2O2 selectivity is experimentally observed. The critical role of pyrrolic- N is elucidated by the variable intermediate adsorption profiles as well as the dependent negative shifts of the pyrrolic-N peak on X-ray absorption near edge structure spectra. A practical device coupling electrochemical H2O2 production with furfural oxidation was then assembled to achieve high-value products on both anode and cathode with optimized energy efficiency.
Thesis (Ph.D.) -- School of Chemical Engineering and Advanced Materials, 2021

碩士
國立臺北科技大學
生化與生醫工程研究所
105
Recent years have seen a growing interest towards real-time tracking and quantification of reactive oxygen species such as, H2O2 released in living cells, as they are potential biomarkers for pathogenesis. Herein, we described a rapid and sensitive enzymeless H2O2 assay using Prussian blue microcubes (PB MCs) decorated graphenated carbon nanotubes (g-CNTs) and this assay was successfully demonstrated for the tracking of in-vivo H2O2 production in Raw 264.7 mammalian cells. The PB MCs was prepared through facile hydrothermal route and blended with g-CNTs to yield 3D hierarchical network of PB MCs/g-CNTs nanocomposite. The structure and composition of the composite was verified by SEM, EDX, mapping, XRD, FT-IR, impedance and electrochemical methods. The g-CNTs/PB MCs film modified electrode was fabricated which displayed excellent electrocatalytic activity to H2O2 reduction at minimized overpotential. A rapid, sensitive, selective, durable and reproducible amperometric sensor was constructed that displayed working range of 0.02–1935 µM, and low limit of detection of 5±1.2 nM. The method was successful in the determination of H2O2 spiked in human serum. The other advantages of the method are low overpotential, enhanced signal, quick response time, practicality in mammalian cells and robustness of the electrode.