Academic literature on the topic 'Formic acid decomposition'
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Journal articles on the topic "Formic acid decomposition"
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McBreen, P. H., S. Serghini-Monim, D. Roy, and A. Adnot. "Decomposition of formic acid on FeTi." Surface Science 195, no. 3 (January 1988): L208—L216. http://dx.doi.org/10.1016/0039-6028(88)90345-7.
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Gercher, Victoria A., and David F. Cox. "Formic acid decomposition on SnO2(110)." Surface Science 312, no. 1-2 (June 1994): 106–14. http://dx.doi.org/10.1016/0039-6028(94)90807-9.
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Li, Fumin, Qi Xue, Ge Ma, Shuni Li, Mancheng Hu, Hongchang Yao, Xin Wang, and Yu Chen. "Formic acid decomposition-inhibited intermetallic Pd3Sn2 nanonetworks for efficient formic acid electrooxidation." Journal of Power Sources 450 (February 2020): 227615. http://dx.doi.org/10.1016/j.jpowsour.2019.227615.
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Lee, Hyun Ju, Dong-Chang Kang, Eun-Jeong Kim, Young-Woong Suh, Dong-Pyo Kim, Haksoo Han, and Hyung-Ki Min. "Production of H2-Free Carbon Monoxide from Formic Acid Dehydration: The Catalytic Role of Acid Sites in Sulfated Zirconia." Nanomaterials 12, no. 17 (September 1, 2022): 3036. http://dx.doi.org/10.3390/nano12173036.
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The formic acid (CH2O2) decomposition over sulfated zirconia (SZ) catalysts prepared under different synthesis conditions, such as calcination temperature (500–650 °C) and sulfate loading (0–20 wt.%), was investigated. Three sulfate species (tridentate, bridging bidentate, and pyrosulfate) on the SZ catalysts were characterized by using temperature-programmed decomposition (TPDE), Fourier-transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). The acidic properties of the SZ catalysts were investigated by the temperature-programmed desorption of iso-propanol (IPA-TPD) and pyridine-adsorbed infrared (Py-IR) spectroscopy and correlated with their catalytic properties in formic acid decomposition. The relative contributions of Brønsted and Lewis acid sites to the formic acid dehydration were compared, and optimal synthetic conditions, such as calcination temperature and sulfate loading, were proposed.
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Zhang, Yongchun, Jun Zhang, Liang Zhao, and Changdong Sheng. "Decomposition of Formic Acid in Supercritical Water†." Energy & Fuels 24, no. 1 (January 21, 2010): 95–99. http://dx.doi.org/10.1021/ef9005093.
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Yu, Jianli, and Phillip E. Savage. "Decomposition of Formic Acid under Hydrothermal Conditions." Industrial & Engineering Chemistry Research 37, no. 1 (January 1998): 2–10. http://dx.doi.org/10.1021/ie970182e.
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Kupiainen, Laura, Juha Ahola, and Juha Tanskanen. "Kinetics of glucose decomposition in formic acid." Chemical Engineering Research and Design 89, no. 12 (December 2011): 2706–13. http://dx.doi.org/10.1016/j.cherd.2011.06.005.
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Akiya, Naoko, and Phillip E. Savage. "Role of water in formic acid decomposition." AIChE Journal 44, no. 2 (February 1998): 405–15. http://dx.doi.org/10.1002/aic.690440217.
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Rieckborn, Timo Paul, Elvira Huber, Emine Karakoc, and Marc Heinrich Prosenc. "Platinum Complex Catalyzed Decomposition of Formic Acid." European Journal of Inorganic Chemistry 2010, no. 30 (September 20, 2010): 4757–61. http://dx.doi.org/10.1002/ejic.201000879.
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Hafeez, Sanaa, Ilaria Barlocco, Sultan M. Al-Salem, Alberto Villa, Xiaowei Chen, Juan J. Delgado, George Manos, Nikolaos Dimitratos, and Achilleas Constantinou. "Experimental and Process Modelling Investigation of the Hydrogen Generation from Formic Acid Decomposition Using a Pd/Zn Catalyst." Applied Sciences 11, no. 18 (September 12, 2021): 8462. http://dx.doi.org/10.3390/app11188462.
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The use of hydrogen as a renewable fuel has attracted great attention in recent years. The decomposition of formic acid under mild conditions was investigated using a 2%Pd6Zn4 catalyst in a batch reactor. The results showed that the conversion of formic acid increases with reaction temperature and with the formic acid concentration. A process-simulation model was developed to predict the decomposition of formic acid using 2%Pd6Zn4 in a batch reactor. The model demonstrated very good validation with the experimental work. Further comparisons between the 2%Pd6Zn4 catalyst and a commercial Pd/C catalyst were carried out. It was found that the 2%Pd6Zn4 demonstrated significantly higher conversions when compared with the commercial catalyst.
Dissertations / Theses on the topic "Formic acid decomposition"
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Sims, Jeffrey J. "Formic Acid Decomposition on Cobalt Surfaces." Thesis, Université d'Ottawa / University of Ottawa, 2015. http://hdl.handle.net/10393/32592.
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The decomposition of formic acid proceeds via two principal reaction pathways: dehydration and dehydrogenation. Mechanisms and reaction ratios depend on the nature of the catalysts used. This work provides mechanistic insight into the decomposition of formic acid on Co(0001) and a highly stepped cobalt surface. The catalytic systems were studied in ultra-high vacuum by XPS and temperature programmed desorption. On both surfaces, an overall reaction (1) was observed:
2 HCOOH→H_2 O+CO+H_2+CO_2 (1)
The surfaces had differing reaction intermediates, reaction temperatures, and activation energies. On Co(0001), formate, carbon, and hydroxyl are intermediates and the reaction has an activation energy of 44.3 ± 0.6 kJ/mol, pre-exponential factor of 0.7 ± 0.05 mbar/s. On highly stepped cobalt, formate and formyl are intermediates and the reaction has an activation energy of 147.2 ± 2.0 kJ/mol and pre-exponential factor of 1011.3 ± 0.2 mbar/s. Desorption energies of observed species and mechanisms of observed reactions are reported.
A detailed description and proof of concept of a PM-IRRAS reactor designed for this thesis is also presented.
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Bocelli, Ludovica. "Catalytic decomposition of formic acid using supported metal nanoparticles." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2016. http://amslaurea.unibo.it/11929/.
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Upgrade of hydrogen to valuable fuel is a central topic in modern research due to its high availability and low price. For the difficulties in hydrogen storage, different pathways are still under investigation. A promising way is in the liquid-phase chemical hydrogen storage materials, because they can lead to greener transformation processes with the on line development of hydrogen for fuel cells. The aim of my work was the optimization of catalysts for the decomposition of formic acid made by sol immobilisation method (a typical colloidal method). Formic acid was selected because of the following features: it is a versatile renewable reagent for green synthesis studies. The first aim of my research was the synthesis and optimisation of Pd nanoparticles by sol-immobilisation to achieve better catalytic performances and investigate the effect of particle size, oxidation state, role of stabiliser and nature of the support. Palladium was chosen because it is a well-known active metal for the catalytic decomposition of formic acid. Noble metal nanoparticles of palladium were immobilized on carbon charcoal and on titania. In the second part the catalytic performance of the “homemade” catalyst Pd/C to a commercial Pd/C and the effect of different monometallic and bimetallic systems (AuxPdy) in the catalytic formic acid decomposition was investigated.
The training period for the production of this work was carried out at the University of Cardiff (Group of Dr. N. Dimitratos).
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Selwyn, John. "A Mass Spectrometry and XPS Investigation of the Catalytic Decompostion of Formic Acid." Thèse, Université d'Ottawa / University of Ottawa, 2012. http://hdl.handle.net/10393/22911.
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This thesis examines the catalytic characteristics of two materials with respect to the decomposition of Formic Acid. The decomposition of formic acid proceeds via two principal reaction pathways: dehydration and dehydrogenation. Dehydrogenation is a valuable reaction producing Hydrogen suitable for use in fuel cells whereas the dehydration pathway produces carbon monoxide, a poison for many fuel cell materials. One of the surface species, the formate ion, is also implicated in other important chemical reactions, most notably the water gas shift and the decomposition of methanol. The author seeks to document various intermediate surface species associated with the two reaction pathways with hope to use this information to future tailoring of catalysts for greater selectivity.
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Kupiainen, L. (Laura). "Dilute acid catalysed hydrolysis of cellulose – extension to formic acid." Doctoral thesis, Oulun yliopisto, 2012. http://urn.fi/urn:isbn:9789526200033.
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Abstract New methods are being sought for the production of chemicals, fuels and energy from renewable biomass. Lignocellulosic biomass consists mainly of cellulose, hemicellulose and lignin. Cellulose and hemicellulose can be converted to their building blocks, i.e. sugars, via hydrolysis. This thesis is focused on glucose production from cellulose by dilute acid hydrolysis. Acid hydrolysis has the drawback of limited glucose yields, but it has the potential to become a short-term solution for biochemical production. During acid hydrolysis, the cellulose chain is split into glucose, which undergoes further decomposition reactions to hydroxymethylfurfural, levulinic acid, formic acid and by-products like insoluble humins. The present thesis aims to increase our knowledge on complicated acid-catalysed hydrolysis of cellulose. Glucose decomposition and cellulose hydrolysis were studied independently in laboratory experiments. Kinetic modelling was used as a tool to evaluate the results. The effect of the hydrogen ion on the reactions was evaluated using formic or sulphuric acid as a catalyst. This thesis provides new knowledge of cellulose hydrolysis and glucose decomposition in formic acid, a novel catalyst for high-temperature dilute acid hydrolysis. Glucose yields from cellulose hydrolysed in formic or in sulphuric acid were comparable, indicating that a weak organic acid could function as a cellulose hydrolysis catalyst. Biomass fibres in the form of wheat straw pulp were hydrolysed more selectively to glucose than a model component, microcrystalline cellulose, using formic acid. Glucose decomposition took place similarly in formic and sulphuric acid when the temperature dependence of the hydrogen ion concentration was taken into account, but a significant difference was found between the reaction rates of cellulose hydrolysis in formic acid and in sulphuric acid. The observations can be explained by changes in the cellulose hydrolysis mechanism. Thus, it is proposed in this thesis that side-reactions from cellulose to non-glucose compounds have a more significant role in the system than has earlier been understoodTiivistelmä Uusia menetelmiä etsitään kemikaalien, polttoaineiden ja energian valmistamiseen uusiutuvasta biomassasta. Eräs biomassa, ns. lignoselluloosa, koostuu pääasiassa selluloosasta, hemiselluloosasta ja ligniinistä. Selluloosa ja hemiselluloosa voidaan muuttaa hydrolyysin avulla niiden rakennuspalikoikseen eli sokereiksi. Tämä väitöskirja keskittyy glukoosin tuottamiseen selluloosasta laimean happohydrolyysin menetelmällä. Happohydrolyysi kärsii rajoittuneesta glukoosin saannosta, mutta sillä on potentiaalia tulla lyhyen aikavälin ratkaisuksi biokemikaalien tuotannossa. Happohydrolyysin aikana selluloosaketju pilkkoutuu glukoosiksi, joka reagoi edelleen hajoamisreaktioiden kautta hydroksimetyylifurfuraaliksi, levuliini- ja muurahaishapoiksi ja kiinteäksi sivutuotteeksi. Tämän tutkimuksen tavoitteena on kasvattaa ymmärrystämme monimutkaisesta happokatalysoidusta selluloosan hydrolyysistä. Glukoosin hajoamista ja selluloosan hydrolyysiä tutkittiin erikseen laboratoriokokein. Kineettistä mallinnusta käytettiin työkaluna arvioimaan tuloksia. Vety-ionien vaikutus reaktioihin arvioitiin käyttämällä muurahais- ja rikkihappoja katalyytteinä. Tämä väitöskirja antaa uutta tietoa selluloosan hydrolyysistä ja glukoosin hajoamisreaktioista muurahaishapossa, joka on uusi katalyytti korkean lämpötilan laimean hapon hydrolyysissä. Glukoosisaannot muurahaishappo-hydrolysoidusta selluloosasta olivat vertailukelpoisia vastaaviin rikkihappo-hydrolyysi saantoihin. Tämä viittaa siihen, että heikko orgaaninen happo voisi toimia selluloosahydrolyysin katalyyttinä. Kun katalyyttinä käytettiin muurahaishappoa, vehnän oljesta tehdyt kuidut hydrolysoituivat selektiivisemmin glukoosiksi kuin mallikomponenttina toimineen mikrokiteisen selluloosan. Kun vetyionikonsentraation lämpötilariippuvuus otettiin huomioon, glukoosi hajosi samalla tavalla sekä muurahais- että rikkihappokatalyytissä, mutta merkittävä ero havaittiin selluloosahydrolyysin reaktionopeudessa. Havainnot voidaan selittää selluloosahydrolyysin mekanismissa tapahtuvilla muutoksilla. Väitöskirjassa esitetään, että sivureaktioilla selluloosasta ei-glukoosi-tuotteiksi on merkittävä vaikutus systeemiin
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Jones, Simon Philip. "Influence of modifiers on Palladium based nanoparticles for room temperature formic acid decomposition." Thesis, University of Oxford, 2013. http://ora.ox.ac.uk/objects/uuid:873277f2-c4f7-45b7-a16d-bba064e24bee.
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Heterogeneous catalysts form a highly important part of everyday life, ranging from the production of fertiliser enabling the growth of crops that sustain much of the world's population to the production of synthetic fuels. They constitute a key part of the chemical industry and contribute towards substantial economic and environmental benefits. Heterogeneous catalysts are also believed to have an important role to play in a future hydrogen economy, reducing our requirements for fossil fuels. To this end, formic acid has been proposed as a potential hydrogen storage material for small portable devices. Additionally, formic acid has historically been used as a probe molecule to study catalyst materials and recent developments in the knowledge of its decomposition pathways and the preferred sites of these reactions, establish a good foundation for further study. This work explores a range of novel modification techniques that alter the activity of Pd nanoparticles to decompose formic acid to H2 and CO2. The methods used are the addition of polymers, attaching various functional groups to the surface of the catalyst support and decoration of nanoparticles with sub-monolayer coverages of another metal. Using a range of characterisation methods including FTIR of an adsorbed CO probe, XRD and XPS coupled with computational modelling, it is found that these methods result in some significant electronic and/or geometric alterations to the Pd nanoparticles. For polymer modification, the nature of the pendent group is highly important in determining the effects of the polymer on the Pd particles, with all the tested polymers resulting in varying degrees of electronic donation to the Pd surface. The geometric modifications caused by the polymers also varied with pendent groups; with amine containing pendent groups found to selectively block low coordinate sites, preventing the undesired dehydration of formic acid which results in poisoning of the Pd catalyst by the resulting CO. Attachment of amine groups to the surface of metal oxide catalyst supports, is demonstrated to result in dramatic electronic promotional effects to the supported Pd nanoparticles, and when an amine polymer is attached to the support surface the geometric modification is again observed. Finally decoration of Pd nanoparticles with a sub-monolayer coverage of a second metal is examined, resulting in some similar electronic and geometric effects on Pd nanoparticle surfaces to those observed with polymer modification with corresponding changes in formic acid decomposition activity. Overall, a number of methods are displayed to tune the catalytic activity and selectivity of Pd nanoparticles for formic acid decomposition, resulting in catalysts with some of the highest reported TOF's at room temperature. These modification methods are believed to be potentially applicable to a wide range of other catalytic reactions that operate under mild conditions.
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Sanchez, Trujillo Felipe Juan. "Investigation of the catalytic performance of palladium-based catalysts for hydrogen production from formic acid decomposition." Thesis, Cardiff University, 2018. http://orca.cf.ac.uk/117629/.
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The objective of this work is to present formic acid as a suitable compound to be used in a hydrogen economy. Catalytic decomposition of formic acid at mild conditions is evaluated as a model reaction for hydrogen generation, making emphasis on the productivity, reusability of the catalysts, and quantification of concomitant CO evolved from the reaction. Characterisation of the fresh and used catalysts is performed to study the activity/structure relationship and investigate the possible reasons for its deactivation. Computational calculations are used to support experimental data and correlate productivity and CO evolution with the elementary steps of the reaction and the most common surfaces of the catalyst. Synthesis of materials with different surface properties and preparation methods is a fundamental part of this work. In Chapter 3, a commercial Pd/C catalyst is used as a reference to establish the reaction conditions that lead to a kinetically limited reaction. Reusability tests and subsequent characterisation of the used catalyst in conjunction with computational studies are performed to investigate its stability. Continuous flow experiments are carried out as a preliminary test to improve the reusability. Following the identification of the main parameters and characteristics of the catalysts involved in formic acid decomposition, in Chapter 4, materials with different properties (graphitisation degree and acid/base surface functionalisation) are synthesised by two preparation methods (sol-immobilisation and impregnation) using carbon nanofibers as supports. Once the optimal preparation method is identified, a set of parameters are modified in Chapter 5 to investigate the effects it has on the structure and morphology of the catalysts. Besides this optimisation, two supports (activated charcoal and titania) are investigated and an initial study of bimetallic catalysts and its properties is explored. Chapter 6 presents the main consequences of these results and a set of possibilities to continue this research.
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Hao, Ting, and 郝婷. "Adsorption and Thermal Decomposition of Formic Acid and Acetic Acid on Ge(100)." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/69691216030462213147.
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碩士國立臺灣師範大學
化學系
100
The adsorption and thermal reactions of formic acid (HCOOH) and acetic acid (CH3COOH) on Ge(100) surface were studied with temperature-programmed desorption (TPD) and X-ray photoelectron spectroscopy (XPS). The desorption products of thermal reactions were monitored by TPD and the reaction intermediates were identified with XPS using synchrotron radiation. At 105 K, HCOOH molecules either adsorb molecularly or dissociate to form surface formate for all durations of exposure. Chemisorbed HCOOH desorbs intact or dissociates to form surface formate (monodentate formate) on annealing to 275 K, whereas a portion of surface formates further transfers into a more stable configuration (bidentate formate). On annealing to 470 K, surface formates ether recombine with surface H to evolve HCOOH or transfer into bidentate formate by reacting with Ge adatoms. Finally, the bidentate formates undergo recombinative desorption or decomposition to desorb CO2. The products for thermal reaction of formic acid on Ge(100) are HCOOH, CO2, and H2. To understand the influence of longer carbon chain to the mechanism, we investigated the thermal reaction of acetic acid (CH3COOH) on Ge(100). Acetic acid undergoes thermal reaction with similar mechanisms as formic acid, but proceeds exclusively recombinative desorption rather than formation of the other products. The detailed mechanisms of thermal reactions on Ge(100) are studied and discussed in this dissertation.
Book chapters on the topic "Formic acid decomposition"
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Navlani-García, Miriam, David Salinas-Torres, Kohsuke Mori, Yasutaka Kuwahara, and Hiromi Yamashita. "Photocatalytic Approaches for Hydrogen Production via Formic Acid Decomposition." In Topics in Current Chemistry Collections, 193–223. Cham: Springer International Publishing, 2019. http://dx.doi.org/10.1007/978-3-030-49492-6_6.
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Himeda, Yuichiro. "Utilization of Carbon Dioxide as a Hydrogen Storage Material: Hydrogenation of Carbon Dioxide and Decomposition of Formic Acid Using Iridium Complex Catalysts." In ACS Symposium Series, 141–53. Washington, DC: American Chemical Society, 2010. http://dx.doi.org/10.1021/bk-2010-1056.ch009.
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KISFALUDI, G., K. MATUSEK, Z. SCHAY, L. GUCZI, and A. LOVAS. "Decomposition of Formic Acid on Fe80B20 Metallic Glasses." In Rapidly Quenched Metals 6, 547–49. Elsevier, 1988. http://dx.doi.org/10.1016/b978-1-85166-973-8.50122-1.
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Sposito, Garrison. "Soil Humus." In The Chemistry of Soils. Oxford University Press, 2016. http://dx.doi.org/10.1093/oso/9780190630881.003.0007.
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Biomoleculesare compounds synthesized to sustain the life cycles of organisms. In soil humus, they are usually products of litter degradation, root excretion, and microbial metabolism, ranging in molecular structure from simple organic acids to complex biopolymers. Organic acids are among the best-characterized biomolecules. Table 3.1 lists five aliphatic (meaning the C atoms are arranged in open-chain structures) organic acids associated commonly with the soil microbiome. These acids contain the unit R—COOH, where COOH is the carboxyl groupand R represents either H or an organic moiety. The carboxyl group can lose its proton easily within the normal range of soil pH (see the third column of Table 3.1) and so is an example of a Brønsted acid. The released proton, in turn, can attack soil minerals to induce their decomposition (see Eq. 1.2), whereas the carboxylate anion (COO-) can form soluble complexes with metal cations, such as Al3+, that are released by mineral weathering [for example, in Eq. 1.7, rewrite oxalate, C2O42-, as (COO-) 2]. The total concentration of organic acids in the soil solution ranges up to 5 mM. These acids tend to have very short lifetimes because of biocycling, but they abide as a component of soil humus, especially its water-soluble fraction, because they are produced continually by microorganisms and plant roots. Formic acid (methanoic acid), the first entry in Table 3.1, is a monocarboxylic acid produced by bacteria and found in the root exudates of maize. Acetic acid (ethanoic acid) also is produced microbially—especially under anaerobic conditions—and is found in root exudates of grasses and herbs. Formic and acetic acid concentrations in the soil solution range from 2 to 5 mM. Oxalic acid (ethanedioic acid), which is ubiquitous in soils, and tartaric acid (D- 2,3-dihydroxybutanedioic acid) are dicarboxylic acids produced by fungi and excreted by plant roots; their soil solution concentrations range from 0.05 to 1 mM. The tricarboxylic citric acid (2-hydroxypropane- 1,2,3-tricarboxylic acid) is also produced by fungi and excreted by plant roots. Its soil solution concentration is less than 0.05 mM.
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Takahashi, Katsuyuki, Koichi Takaki, and Naoya Satta. "A Novel Wastewater Treatment Method Using Electrical Pulsed Discharge Plasma over a Water Surface." In Sewage - Recent Advances, New Perspectives and Applications. IntechOpen, 2022. http://dx.doi.org/10.5772/intechopen.101494.
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Electrical pulsed discharge plasma produces various powerful oxidizing agents, such as hydroxyl radicals and ozone, which have high oxidation potential. These species play an important role in the decomposition of persistent organic compounds in wastewater. Because highly concentrated oxidants are directly produced inside the plasma, plasma realizes high-speed wastewater treatment without pretreatment of samples, such as pH adjustment. The pulsed discharge plasma generated over the water surface and inside bubbles is highlighted as a highly efficient method for plasma generation and radical supply into wastewater. In this paper, the physical and chemical properties of the discharge plasma generated over a water surface are described. The decomposition of persistent organic compounds dissolved in wastewater, such as 1,4-dioxane, formic acid, and dichloromethane, by plasma discharge is demonstrated, and their mechanisms are discussed. These persistent compounds, which have strong toxicity and stability, can be efficiently decomposed and removed quickly from solutions by plasma treatment. Furthermore, the treatment of nutrient solutions used in hydroponic systems for plant cultivation is also introduced as a novel application of plasma, and the effects of bacterial inactivation, decomposition of allelochemicals, and improvement in plant growth by plasma are demonstrated.
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Calvert, Jack G., John J. Orlando, William R. Stockwell, and Timothy J. Wallington. "Photodecomposition of Light-Absorbing Oxygenates and Its Influence on Ozone Levels in the Atmosphere." In The Mechanisms of Reactions Influencing Atmospheric Ozone. Oxford University Press, 2015. http://dx.doi.org/10.1093/oso/9780190233020.003.0011.
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Photochemistry provides the important driving force that initiates chemistry in the atmosphere. We saw in Chapter II how light absorbed by ozone generates the important HO radical, and, in Chapter III, we reviewed how light absorption by NO2 leads to ozone formation. In this chapter, we discuss the photochemistry of the light-absorbing oxygenates: their photochemical lifetimes and the nature of the modes of photodecomposition they undergo. Of course, light of sufficient energy per quantum must be absorbed by a molecule if its photodecomposition is to occur. The hydrocarbons do not absorb tropospheric sunlight, as seen in Figure VIII-A-1. The light gray and dark gray lines, respectively, show the distribution of actinic flux present in the troposphere and upper stratosphere for overhead Sun. It can be seen that the larger alkanes, alkenes, and aromatic hydrocarbons absorb at somewhat longer wavelengths than the first member of the family, but none can be electronically excited by tropospheric radiation. Among the hydrocarbons, only the polycyclic aromatics absorb appreciable tropospheric sunlight, and their π → π* excitation does not result in decomposition but likely generates O2(1Δg) molecules by energy transfer; these molecules are usually quenched by collision to ground state O2(3Σg−) molecules (see Calvert et al., 2000). As atmospheric oxidation of the hydrocarbons occurs, initiated largely by HO radicals, a multitude of oxygenated organic species are generated. The absorption region for the oxygenates is generally shifted to longer wavelengths, although the alcohols, ethers, acids, and esters still show no overlap of the regions of tropospheric actinic flux. For the families of compounds shown, the only significant absorbers of tropospheric sunlight are the aldehydes (e.g., CH2O) and the ketones (e.g., CH3C(O)CH3). Formic acid and methyl formate, as well as the larger members of the acid and ester families, absorb sunlight available only at the higher altitudes of the stratosphere, where they are expected to photodecompose. However, these species are not expected to be present in the stratosphere because they are removed in the troposphere largely via HO reactions. In this chapter, we focus on the rates and pathways for photodecomposition of the aldehydes and ketones with less detailed considerations of the other less prevalent light-absorbing trace compounds.
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Singh, S. "Electrochemical Oxidation of Perfluorooctanoic Acid (PFOA) from Aqueous Solution using Non-Active Ti/SnO2-Sb2O5/PbO2 Anodes." In Advances in Wastewater Treatment II, 48–67. Materials Research Forum LLC, 2021. http://dx.doi.org/10.21741/9781644901397-2.
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In this study, electrochemical oxidation of perfluorooctanoic acid (PFOA, C7H15CO2H) from aqueous solution was examined in terms of PFOA and total organic carbon (TOC) removal by using Ti/SnO2-Sb2O5/PbO2non-active electrodes. The effects of operating parameters: initial pH (pHo), current density (j), and electrolyte concentration (m) at different time intervals were examined. Specific energy consumption (SEC) was used to determine the process proficiency. The C-C bond between C7F15 was first cleaved and thendegraded into fluoride ions (F−) and short carbon-chain per-fluorinated carboxylic acids (PFCAs) ((∼C2−C7) such as perfluoroethanoic acid (PFEA: C2F5CO2H), perfluoropropanoic acid (PFPA: C3F7CO2H), perfluorobutanoic acid (PFBA: C4F9CO2H), perfluoropentanoic acid (PFPeA: C5F11CO2H), perfluorohexanoic acid (PFHxA: C6F13CO2H), perfluoheptanoic acid (PFHpA: C7F14CO2H). These intermediates by-products were determined using the gas chromatograph-mass spectrometry (GC/MS) analysis. The rate of PFOA decomposition was followed the pseudo-first-order kinetics. About 82%TOC and 94% PFOA removals were formed at the optimal condition of pHo = 3.58, j=168.34 Am-2, and m = 250 mgL-1 at 120 min of electrolysis with SEC = 593 kWh/kg TOC. A plausible degradation mechanism was also proposed at the optimal treatment condition.
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Keefer, Robert F. "Macronutrients—Calcium, Magnesium, and Sulfur." In Handbook of Soils for Landscape Architects. Oxford University Press, 1999. http://dx.doi.org/10.1093/oso/9780195121025.003.0015.
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Application of limestone to a soil changes the (a) soil physical properties by encouraging granulation and improving tilth; (b) soil chemical properties by decreasing soil acidity, increasing availability of a number of essential plant nutrients, and decreasing levels of aluminum, iron, and manganese that potentially may be toxic; and (c) soil biological properties by improving conditions for micriobial organic matter decomposition with release of nitrogen, phosphorus, and sulfur for plant use, and by stimulating root development. Granulation Encouraged. Applying lime to soils improves soil physical conditions by encouraging granulation and crumb formation and aggregation. Tilth Improved. Tilth is the ability to work or cultivate a soil. By improving physical conditions with more granulation and crumb formation, soil tilth is improved. Lowering H+ Concentration (Acidity). When lime is applied to a soil, acidity is reduced and pH is raised. This is especially important in the humid regions where rainfall and other factors constantly make a soil more acid (explained in Chapter 9). Plant Nutrient Availability Increased. Liming a soil will increase availability of plant nutrients by (a) increasing Ca and Mg in the soil from added liming material; (b) adjusting soil to a higher pH so that N, P, K, S, and Mo are solubilized; and (c) reducing solubility of potentially toxic levels of Fe, Al, or Mn. Lowering of Potentially Toxic Levels of Al, Fe, and Mn. At very low soil pH, Al, Fe, and Mn are soluble and may be present in a high enough concentration to be toxic to plant growth. When lime is applied, the pH increases and these three elements become less soluble and less available for plants. Microbial Decomposition Enhanced. Soils that are limed provide conditions for active microbial decomposition of organic materials in soils, resulting in mineralization and release of N, P, and S in forms that plants can use. Liming also increases the amount of humus formed, thereby improving water infiltration and water-holding capacity. Furthermore, liming soils stimulates other types of biological transformations, such as nitrification, N-fixation, and S-oxidation, that improve plant growth. Deep Rooting Stimulated.
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Morrow, Gary W. "The Terpenoid Pathway: Products from Mevalonic Acid and Deoxyxylulose Phosphate." In Bioorganic Synthesis. Oxford University Press, 2016. http://dx.doi.org/10.1093/oso/9780199860531.003.0007.
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It was Otto Wallach (1847– 1931) who first coined the term “terpene” and made the observation that many plant-derived essential oils had chemical structures whose composition was based on multiples of a basic five-carbon unit. His work with turpentine and the organic products derived from it was consistent with earlier studies of natural rubber which had shown that its thermal decomposition released “isoprene” (2-methyl-1,3-butadiene) as the principal product. This led eventually to the formulation of the so-called biogenetic isoprene rule of Leopold Ruzicka (1887–1976) in 1953 which stated that “the carbon skeleton of the terpenes is composed of isoprene units linked in regular or irregular arrangement.” As it turns out, biosynthetic pathways to terpenes are found in nearly all organisms, producing a remarkable variety of different structural types, as we will soon see. In fact, something in excess of over 25,000 different terpenes with a wide variety of biological functions have been isolated from the plant kingdom over the years. Interestingly, while many terpenes are simple achiral compounds, others are chiral as can be seen in the case of α-pinene in Fig. 4.1. But unlike the naturally occurring L-amino acids and D-carbohydrates, different organisms may produce the same terpene product but in different enantiomeric forms. For example, limonene is formed by more than 300 plants, with the (+)-(R) enantiomer being the most widespread form as the major constituent of citrus peel essential oils (orange oil). As the most abundant of all terpenes, its pleasant citrus fragrance and flavor have led to its worldwide use in the food and fragrance industries and also as a botanical insecticide. A number of plants produce both enantiomers of limonene, while others produce only the (−)-(S)-enantiomer which possesses a strong pine smell reminiscent of turpentine. This obviously speaks to the chirality and enantioselectivity of our own olfactory receptor sites which can readily distinguish between the two enantiomers, thus signaling a different odor response in each case.
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Taber, Douglass F. "The Williams Synthesis of (-)-4-Hydroxydictyolactone." In Organic Synthesis. Oxford University Press, 2013. http://dx.doi.org/10.1093/oso/9780199965724.003.0083.
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(-)-4-Hydroxydictyolactone 3, representative of the cyclononene xenicanes isolated from the Dictyotacae algae, readily isomerizes thermally to the more stable ( Z )- 6,7-isomer. Attempts to directly form this strained ring system appeared to be fraught with difficulty. David R. Williams of Indiana University envisoned (J. Am. Chem. Soc. 2009, 131, 9038) that use of Suzuki coupling might ameliorate some of the strain, since at the point of commitment to bond formation, the Pd center would be included in the forming ring. This analysis led specifically to the trans ether 1, as cyclization of the trans ether appeared likely to be more facile than would cyclization of the alternative cis diastereomer. The first challenge was the assembly of the array the four contiguous alkylated stereogenic centers of 1. To this end, the Z secondary ester 7 was prepared from the acetonide 4 , available from mannitol, and ( R )-(+)-citronellic acid, prepared by oxidation of the commercial aldehyde. Addition of 7 to LDA led to decomposition, but inverse addition of LDA to a mixture of the ester, TMSCl, and Et3 N smoothly delivered the ketene silyl acetal. On warming, Ireland-Claisen rearrangement of the ketene silyl acetal led to the acid 8 with remarkable diastereocontrol. The last alkylated stereogenic center of 1 was installed by reductive cyclization of the formate ester 9. Again, the cyclization proceeded with remarkable diastererocontrol. Although the intramolecular reaction of in situ prepared allyl metals is well precedented, the addition to a formate ester had not previously been reported. Although 11 appears to be ready for the long-awaited Suzuki coupling, in fact the TIPS protecting group substantially slowed hydroboration. The free alcohol/methyl acetal was the best substrate for hydroboration, but the free alcohol entered into other side reactions. After extensive experimentation, a happy medium was found with the methyl acetal/TBS ether 1. Selenylation of the lactone 12 followed by oxidative elimination of the selenide delivered the expected Z alkene. Removal of the silyl protecting group had to precede introduction of the second alkene, as the product 3 deteriorated rapidly on exposure to the alkaline conditions of TBAF cleavage.
Conference papers on the topic "Formic acid decomposition"
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Cassidy, Juanita M., Robert I. McNeil, and Chad Kiser. "Understanding Formic Acid Decomposition as a Corrosion Inhibitor Intensifier in Strong Acid Environments." In International Symposium on Oilfield Chemistry. Society of Petroleum Engineers, 2007. http://dx.doi.org/10.2118/106185-ms.
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Kani, Yuko, Kenji Noshita, Toru Kawasaki, Tsutomu Nishimura, Tomofumi Sakuragi, and Hidekazu Asano. "Radiolytic Decomposition of Organic C-14 Released From TRU Waste." In The 11th International Conference on Environmental Remediation and Radioactive Waste Management. ASMEDC, 2007. http://dx.doi.org/10.1115/icem2007-7147.
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It has been found that metallic TRU waste releases considerable portions of C-14 in the form of organic molecules such as lower molecular weight organic acids, alcohols and aldehydes. Due to the low sorption ability of organic C-14, it is important to clarify the long-term behavior of organic forms under waste disposal conditions. From investigations on radiolytic decomposition of organic carbon molecules into inorganic carbonic acid, it is expected that radiation from TRU waste will decompose organic C-14 into inorganic carbonic acid that has higher adsorption ability into the engineering barriers. Hence we have studied the decomposition behavior of organic C-14 by gamma irradiation experiments under simulated disposal conditions. The results showed that organic C-14 reacted with OH radicals formed by radiolysis of water, to produce inorganic carbonic acid. We introduced the concept of “decomposition efficiency” which expresses the percentage of OH radicals consumed for the decomposition reaction of organic molecules in order to analyze the experimental results. We estimated the effect of radiolytic decomposition on the concentration of organic C-14 in the simulated conditions of the TRU disposal system using the decomposition efficiency, and found that the concentration of organic C-14 in the waste package will be lowered when the decomposition of organic C-14 by radiolysis was taken into account, in comparison with the concentration of organic C-14 without radiolysis. Our prediction suggested that some amount of organic C-14 can be expected to be transformed into the inorganic form in the waste package in an actual system.
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Selim, Hatem, Salisu Ibrahim, Ahmed S. AlShoaibi, and Ashwani K. Gupta. "Effect of Acid Gas (H2S and CO2) Addition in Hydrogen/Air Flames." In ASME 2013 Power Conference. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/power2013-98253.
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Results on the effect of acid gas (H2S and CO2) addition in hydrogen/air flame are reported. Different equivalence ratios examined ranged from fuel-rich conditions (Φ = 3.0), stoichiometric conditions (Φ = 1.0), and fuel-lean conditions (Φ = 0.5) to represent the range of conditions that may exist in actual operating Claus furnaces. Acid gas compositions examined are 100% H2S gas and 50% H2S/50% CO2 mixtures to represent a wide range of acid gas compositions encountered during processing of acid gases. Addition of 100% H2S gas in hydrogen/air flame degraded the rate of hydrogen oxidation. In addition, hydrogen sulfide combustion formed sulfur dioxide rather than more favorable elemental sulfur. On the other hand decomposition/production of H2S, SO2, and H2 was observed to occur faster in 50% H2S/50% CO2 acid gas stream. Presence of carbon monoxide was a distinct mark on the release of oxygen from CO2 into the reaction pool. The presence of carbon monoxide also triggered the formation of other sulfurous-carbonaceous compounds, such as COS and CS2. The formation of these compounds adversely impacts the Claus process performance. The results provide conditions under which such compounds are formed and also reveal conditions to alleviate them.
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Lee, Man Su, D. Yogi Goswami, Ben Hettinger, and Sanjay Vijayaraghavan. "Preparation and Characteristics of Calcium Oxide Pellets for UT-3 Thermochemical Cycle." In ASME 2006 International Mechanical Engineering Congress and Exposition. ASMEDC, 2006. http://dx.doi.org/10.1115/imece2006-16083.
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UT-3 thermochemical cycle for hydrogen production involves four gas-solid reactions. In order to make the cycle feasible, the solid reactant must be chemically reactive and physically stable in cyclic operation. Calcium oxide pellets, with CaO dispersed in the CaTiO3 inert matrix, were prepared and stearic acid, graphite, and corn starch were added as pore forming agents during the process. Experimental studies to improve and evaluate the Ca-pellets through the investigation into thermal decomposition of additives, X-ray diffraction, pore size distribution, conversion and reaction rate were conducted. The pore size distributions of the pellets were found to be strongly influenced by the type of pore forming agents used, and the volume of pores greater than 5μm markedly promoted hydrolysis rate.
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Linderborg, Kaisa, Annelie Damerau, and Eija Ahonen. "Stability of omega-3 fatty acids in different lipid forms analyzed by SPME-GC-MS, NMR and loss of antioxidants." In 2022 AOCS Annual Meeting & Expo. American Oil Chemists' Society (AOCS), 2022. http://dx.doi.org/10.21748/gqky3982.
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The dietary intake of marine foods is globally inadequate, and thus supplements with long-chain omega-3 fatty acids are widely used. Both the source and processing choices affect the lipid class (most typically triacylglycerols (TAGs), ethyl esters (EEs), or phospholipids (PLs)) in which docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) are present, and thus consumed.Here we present investigation of the effect of lipid type on oxidation by the analysis of oxidation products of commercial supplements including EPA and DHA in different lipid forms, as well as results of an oxidation trial of pure DHA-containing TAGs and EEs in the presence and absence of alpha-tocopherol. We also present the applicability of SPME-GC-MS and NMR methods as well as analysis of the loss of antioxidants as alternative methods to peroxide (PV) and para-anisidine values (PAV). PAV typically has challenges with aroma compounds present and the reliability of PV is decreased by different formation and decomposition rates of hydroperoxides under different conditionsIncreased lipid oxidation was detected in 24% of the studied omega-3 supplements, which were in either TAG or EE form. 1H NMR was found to be a potential rapid method for lipid class determination and was applicable in detecting products of oxidation through selective pulse experiments. Analysis of volatile secondary oxidation products with SPME-GC-MS may be a future alternative to PAV analysis of especially flavored products when standardized. 2,4-Heptadienal, 1-penten-3-ol, and 2-hexenal showed the highest potential to be used as indicator compounds for lipid oxidation in products high in EPA and DHA content. Oxidative stability, oxidation pattern, and α-tocopherol response of DHA were influenced by the lipid structure (TAG/EE). DHA in EE form was found to be more stable than DHA in TAG form in the presence of α-tocopherol, but the opposite was observed without the antioxidant.
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Naegeli, David W. "The Role of Sulfur in the Thermal Stability of Jet Fuel." In ASME 1999 International Gas Turbine and Aeroengine Congress and Exhibition. American Society of Mechanical Engineers, 1999. http://dx.doi.org/10.1115/99-gt-298.
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The autoxidation of Jet A, dodecane, and a dodecane-15%-cumene blend doped with sulfur compounds were studied at 433 K. Oxygen, hydro peroxide and soluble gum were monitored during the autoxidation. Dodecane, cumene, and the dodecane-15%-cumene blend autoxidized rapidly, while Jet A had an induction period followed by a relatively slow post autoxidation. The results suggest that an inhibitor formed early in the post autoxidation of Jet A. Gum formed in the autoxidation of Jet A, whereas none was detected in dodecane, cumene, or dodecane-15% cumene. However, gum was detected in dodecane and dodecane-15% cumene doped with thiols and disulfides. Alkyl thiols and disulfides reduced the rate of autoxidation of dodecane, and there was an induction period in the formation of gum. Traces of sulfur (≈4 ppm) inhibited the autoxidation of dodecane-15% cumene in a way that resembled the post autoxidation of Jet A. Adding an organic base increased the rate of post autoxidation in Jet A and prevented formation of the oxidation inhibitor. An inhibition mechanism is proposed in which phenois are formed via acid-catalyzed decomposition of benzylic hydro peroxides.
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Eldredge, Thomas, and Morgan Thomas. "Investigation of the Evaporation Processes for Aqueous Ammonia and Aqueous Urea and Guidelines for Using Simplifying Assumptions." In ASME 2018 Power Conference collocated with the ASME 2018 12th International Conference on Energy Sustainability and the ASME 2018 Nuclear Forum. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/power2018-7218.
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For SCR (selective catalytic reduction) applications both aqueous ammonia and urea reagents are used for NOx reducing agents in exhaust systems. For both diesel engines and small boilers, the reagent injection systems often consist of a few, and in some cases, a single injector, located on the wall of the exhaust pipe or duct. Often numerical modeling is performed to determine the location and orientation of the injectors and to predict the NRMS (normalized root mean square) of the gas phase reducing specie distribution prior to the catalyst. Aqueous ammonia and aqueous urea have significantly different processes from the point of injection to the formation of the gas phase reducing species. Evaporation characteristics are important, but for urea, the molecule must also decompose into ammonia and isocyanic acid. For modeling purposes, a simplifying assumption is frequently made to treat the liquid reagent as liquid water and assume that the evaporation of liquid water satisfactorily emulates the processes of forming the gas phase reducing species for both aqueous ammonia and aqueous urea reagents. In reality, the reagent droplets are binary component mixtures and treating the droplets as a single component, namely water, may significantly depart from reality. Additionally, the evaporation processes for aqueous ammonia and aqueous urea have significantly different behaviors. This paper addresses the potential errors associated with using a single component water drop for emulating the evaporation of aqueous ammonia and aqueous urea. This is accomplished by analyzing binary component evaporation for both aqueous ammonia and aqueous urea. Additionally, the time for the gas phase chemical decomposition of urea into ammonia and isocyanic acid is evaluated for various conditions. Typical decomposition times are compared to droplet evaporation times. Finally, the paper attempts to provide guidelines for determining when treating the drops as a single component may be sufficiently accurate, and when the complexity of modeling binary component evaporation is necessary.
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Noguchi, Hiroki. "Heat Transfer Enhancement Effect of Nanostructured Surface Made of Carbon Nanotube on SiC Ceramics." In ASME 2013 11th International Conference on Nanochannels, Microchannels, and Minichannels. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/icnmm2013-73170.
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The Japan Atomic Energy Agency (JAEA) has been conducting research and development on the thermo-chemical iodine–sulfur (IS) process, which is one of the most attractive water-splitting hydrogen production methods using the nuclear heat of a high-temperature gas-cooled reactor (HTGR). In researching this IS process, a silicon carbide (SiC) heat exchanger with good corrosion resistance was used in a corrosive situation in boiling sulfuric acid. With the aim of enhancing heat transfer in the SiC heat exchanger, a nanostructured surface made of carbon nanotubes (CNTs) was produced on a SiC substrate by surface decomposition. Two types of SiC, one produced by pressureless sintering (PLS-SiC) and one by chemical vapor deposition (CVD-SiC), were used as substrates. CNTs formed by the surface decomposition of SiC can vary depending on the crystal structure of the substrates. Additionally, in order to investigate surface wettability, nanostructured surfaces on the CVD-SiC with hydrophilicity and hydrophobicity were produced. The effects of heat transfer enhancement by the nanostructured surfaces were evaluated by a convective heat transfer test using de-ionized water. The nanostructured surface on the CVD-SiC with hydrophilicity was the only surface that showed any heat transfer enhancement. However, this enhancement was much smaller than those previously reported. The experiment showed that the small size of the nanopores influenced the heat transfer enhancement and that the wettability of the nanostructured surface was related to heat transfer enhancement.
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Zhang, Chunlong, Hui He, Shangui Zhao, Fengli Song, and XinHua Liu. "Research Progress of Red Oil Explosion Accidents in Nuclear Fuel Reprocessing Plant." In 2017 25th International Conference on Nuclear Engineering. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/icone25-67554.
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Since Westinghouse Savannah River Company (WSRC) of America first applied PUREX process in 1954, PUREX process is always the top priority in nuclear fuel reprocessing plant. And this process is based on liquid to liquid extraction with TBP as the extractant. TBP is irreplaceable in the development of PUREX process in nuclear fuel reprocessing, its advantages are well recognized. However TBP does have some disadvantages such as formation of red oil, which will appear in the system of high nitric acid concentration and heavy metal nitrate, once the red oil forms, it can lead a exothermic runaway decomposition in reasonable conditions, such as exceeding a certain temperature (typically 130°C) or high acid concentration. If gas products and energy released from the decomposition reaction could not be exported in time, it will lead to vessel overpressure and caused violent explosion accidents. By now, it has happened 6 times so-called red oil explosion accidents worldwide, resulting in different degrees of equipment and construction damage and environmental contamination. From 1953 to now, research related to red oil has never stopped. WSRC, Hanford Company, Oak Ridge National Laboratory and Los Alamos National Laboratory of America have conducted many studies, as well as some research institutions from Russia, UK, France and India. Defense Nuclear Facilities Safety Board of America issued a technical report in 2003, preventive measures for red oil explosion were established in this report, and these measures provided good practice experience and reference for other countries, and the temperature condition (⩽130°C)and nitric acid concentration (⩽10M)for preventing red oil explosion are employed in some countries which has built the reprocessing plant. Nevertheless, research conclusions and knowledge of red oil vary from country to country. Especially, Kumar and Smitha etc. conducted several experiments in adiabatic condition in recent years, and investigation on stability of TBP - nitric system was made, the results indicated that the red oil runway reaction will happen even in lower temperature and lower nitric acid concentration in contrast with the reported value, and they thought it would need a further study to assess the validity of present preventive measures, and to rebuild the safety limits for preventing red oil explosion in the operation of nuclear fuel reprocessing plants. In this paper, related research results of red oil explosion accidents were combed, and the characters of study work of different periods were summarized, and definition, formation conditions of red oil, pathway of runaway reaction, control and preventive measures for preventing red oil explosion of different countries were analyzed and compared, as well as the new viewpoints of recent literatures. And some research ideas for future investigation based on present work were also proposed.
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Domae, Masafumi, Kosho Hojo, and Wataru Sugino. "Water Chemistry Technology of Methanol Addition in PWR Primary Systems: Radiolysis of Methanol Solution at 320 °C." In 2014 22nd International Conference on Nuclear Engineering. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/icone22-30954.
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Primary Water Stress Corrosion Cracking (PWSCC) is one of important ageing issues in PWR (Pressurized Water Reactor) primary systems. It has been pointed out that high concentration dissolved hydrogen may lead to occurrence of PWSCC. The authors have proposed to substitute hydrogen by methanol as a fundamental countermeasure of PWSCC. So far corrosion tests of stainless steels and Zircaloy-4 in methanol solutions at 320 °C were conducted under γ-ray irradiation and without irradiation. The test results show that methanol is promising. In the present paper, γ-ray irradiation experiments of methanol solution at 320 °C were done up to 100 kGy. A study on the radiolysis of methanol solution is important from two aspects. One concerns corrosion of structural materials. The radiolysis of methanol may result in formation of harmful compounds to the structural materials, such as carboxylic acids. It is necessary to know the yields of such compounds. The other concern is possible polymerization of methanol and formation of organic polymer deposit on fuel claddings. Large amount of the deposit on fuel claddings should be avoided to keep integrity of fuel claddings. Therefore, it should be clarified whether gaseous species are major products and whether polymerized species of methanol such as ethylene glycol is formed. After the γ-ray irradiation of methanol solution, following species were analyzed: CO2 and H2, methanol, formaldehyde, formate and acetate, and ethylene glycol and glycerin. Without γ-ray irradiation, the major process of the thermal decomposition of methanol at 320 °C is oxidation of methanol by water and generation of one CO2 molecule and three H2 molecules. Under γ-ray irradiation, the decomposition of methanol is accelerated; little methanol remains after 10 kGy irradiation. The major product is CO2, and polymerization of methanol unlikely occurs. After methanol is completely decomposed, the hydrogen yield still increases. The reducing environment is maintained. Probably, transient organic species play important roles. The addition of low concentration methanol may be sufficient to maintain reducing environment of the PWR primary systems.
Reports on the topic "Formic acid decomposition"
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Rouseff, Russell L., and Michael Naim. Characterization of Unidentified Potent Flavor Changes during Processing and Storage of Orange and Grapefruit Juices. United States Department of Agriculture, September 2002. http://dx.doi.org/10.32747/2002.7585191.bard.
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Citrus juice flavor quality traditionally diminishes after thermal processing and continuously during storage. Our prior studies found that four of the five most potent off-aromas formed during orange juice storage had not been identified. The primary emphasis of this project was to characterize and identify those potent flavor degrading aroma volatiles so that methods to control them could be developed and final flavor quality improved. Our original objectives included: 1 Isolate and characterize the most important unidentified aroma impact compounds formed or lost during pasteurization and storage. 2. Determination of thiamine and carotenoid thermal decomposition and Strecker degradation pathways in model solutions as possible precursors for the unidentified off-flavors. 3. Evaluate the effectiveness of an "electronic nose" to differentiate the headspace aromas of from untreated and heat pasteurized orange and grapefruit juices. 4. Use model systems of citrus juices to investigate the three possible precursor pathways (from 2) for flavor impact compounds formed or lost during pasteurization or storage. RESULTS - The components responsible for citrus storage off flavors and their putative precursors have now been identified. Certain carotenoids (b-carotene) can thermally degrade to produce b-ionone and b-damascenone which are floral and tobacco smelling respectively. Our GC-O and sensory experiments indicated that b-damascenone is a potential storage off-flavor in orange juice. Thiamine (Vitamin B1) degradation produces 2-methyl-3-furan thiol, MFT, and its dimer bis(2- methyl-3-furyl) disulfide which both produce meaty, savory aromas. GC-O and sensory studies indicated that MFT is another storage off-flavor. Methional (potato aroma) is another off flavor produced primarily from the reaction of the native amino acid, methionine, and oxidized ascorbic acid (vitamin C). This is a newly discovered pathway for the production of methional and is more dominant in juices than the classic Maillard reaction. These newly identified off flavors diminish the flavor quality of citrus juices as they distort the flavor balance and introduce non-typical aromas to the juice flavor profile. In addition, we have demonstrated that some of the poor flavor quality citrus juice found in the market place is not only from the production of these and other off flavors but also due to the absence of desirable flavor components including several potent aldehydes and a few esters. The absence of these compounds appears to be due to incomplete flavor volatile restoration after the making of juice concentrates. We are the first to demonstrate that not all flavor volatiles are removed along with water in the production of juice concentrate. In the case of grapefruit juice we have documented which flavor volatiles are completely removed, which are partially removed and which actually increase because of the thermal process. Since more that half of all citrus juices is made into concentrate, this information will allow producers to more accurately restore the original flavor components and produce a juice with a more natural flavor. IMPLICATIONS - We have shown that the aroma of citrus juices is controlled by only 1-2% of the total volatiles. The vast majority of other volatiles have little to no direct aroma activity. The critical volatiles have now been identified. The ability to produce high quality citrus juices requires that manufacturers know which chemical components control aroma and flavor. In addition to identifying the critical flavor components (both positive and negative), we have also identified several precursors. The behavior of these key aroma compounds and their precursors during common manufacturing and storage conditions has been documented so manufacturers in Israel and the US can alter production practices to minimize the negative ones and maximize the positive ones.