Letteratura scientifica selezionata sul tema "Calcium catalysts"
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Articoli di riviste sul tema "Calcium catalysts"
1
Mazaheri, Hoora, Hwai Chyuan Ong, Zeynab Amini, Haji Hassan Masjuki, M. Mofijur, Chia Hung Su, Irfan Anjum Badruddin e T. M. Yunus Khan. "An Overview of Biodiesel Production via Calcium Oxide Based Catalysts: Current State and Perspective". Energies 14, n. 13 (1 luglio 2021): 3950. http://dx.doi.org/10.3390/en14133950.
Testo completoAbstract (sommario):
Biodiesel is a clean, renewable, liquid fuel that can be used in existing diesel engines without modification as pure or blend. Transesterification (the primary process for biodiesel generation) via heterogeneous catalysis using low-cost waste feedstocks for catalyst synthesis improves the economics of biodiesel production. Heterogeneous catalysts are preferred for the industrial generation of biodiesel due to their robustness and low costs due to the easy separation and relatively higher reusability. Calcium oxides found in abundance in nature, e.g., in seashells and eggshells, are promising candidates for the synthesis of heterogeneous catalysts. However, process improvements are required to design productive calcium oxide-based catalysts at an industrial scale. The current work presents an overview of the biodiesel production advancements using calcium oxide-based catalysts (e.g., pure, supported, and mixed with metal oxides). The review discusses different factors involved in the synthesis of calcium oxide-based catalysts, and the effect of reaction parameters on the biodiesel yield of calcium oxide-based catalysis are studied. Further, the common reactor designs used for the heterogeneous catalysis using calcium oxide-based catalysts are explained. Moreover, the catalytic activity mechanism, challenges and prospects of the application of calcium oxide-based catalysts in biodiesel generation are discussed. The study of calcium oxide-based catalyst should continue to be evaluated for the potential of their application in the commercial sector as they remain the pivotal goal of these studies.
2
Stegner, Philipp C., Jonathan Eyselein, Gerd M. Ballmann, Jens Langer, Jochen Schmidt e Sjoerd Harder. "Calcium catalyzed enantioselective intramolecular alkene hydroamination with chiral C2-symmetric bis-amide ligands". Dalton Transactions 50, n. 9 (2021): 3178–85. http://dx.doi.org/10.1039/d1dt00173f.
Testo completoAbstract (sommario):
Enantioselective catalysis with calcium catalysts is challenging due to facile loss of the chiral spectator ligand. Herein a series of bis-amide calcium catalysts with chiral binaphtalene bridges is introduced.
3
Alsowayigh, Marwah M., Amal H. Alsehli, Fahad Alqahtani, Fahad Abdulaziz, Moncef Tounsi, Mazen Alshaaer e Abdulaziz Alanazi. "Investigation of Calcium Phosphate Catalysts in Sodium Borohydride Methanolysis for Improved Hydrogen Production". Catalysts 14, n. 8 (7 agosto 2024): 512. http://dx.doi.org/10.3390/catal14080512.
Testo completoAbstract (sommario):
In this study, calcium-rich resource minerals such as brushite, tricalcium phosphate (TCP), and hydroxyapatite were tested as catalysts for the methanolysis of alkaline solutions of NaBH4 to generate hydrogen H2. The synthesis of calcium phosphate compounds was characterized by means of X-ray powder diffraction (XRD) and scanning electron microscopy (SEM). The hydrogen generation rate with the TCP catalyst (15,214 mL min−1 g−1) was higher than with the hydroxyapatite catalyst (12,437 mL min−1 g−1) and brushite catalyst (6210 mL min−1 g−1) for the methanolysis of 250 mg NaBH4 at 298 K using 25 mg of catalyst. The impact of TCP weight on hydrogen generation was studied. The methanolysis reaction led to a higher hydrogen volume generation over time with an increase in the weight of the TCP catalyst at a temperature of 308 K. The calculated activation energy for NaBH4 hydrolysis with the TCP catalyst was 23.944 kJ mol−1, suggesting the high catalytic activity of TCP. The values of enthalpy (ΔH) and entropy (ΔS) were calculated, and the results showed that ΔH was 21.28 kJ mol−1 and ΔS was −93.096 J·mol−1. ΔH was positive, meaning that the reaction was endothermic, and the negative ΔS meant a decrease in the disorder of the methanolysis reaction. The stability of the catalysis was tested in successive methanolysis tests. The catalyst’s efficiency decreased to 89% after four cycles.
4
Díaz-Muñoz, L. L., H. E. Reynel-Ávila, D. I. Mendoza-Castillo, A. Bonilla-Petriciolet e J. Jáuregui-Rincón. "Preparation and Characterization of Alkaline and Acidic Heterogeneous Carbon-Based Catalysts and Their Application in Vegetable Oil Transesterification to Obtain Biodiesel". International Journal of Chemical Engineering 2022 (20 luglio 2022): 1–13. http://dx.doi.org/10.1155/2022/7056220.
Testo completoAbstract (sommario):
This paper reports the preparation, evaluation, and comparison of alkaline and acidic heterogeneous carbon-based catalysts in the transesterification of safflower oil with methanol to obtain biodiesel. These catalysts were obtained from the pyrolysis of flamboyant pods and their functionalization and activation with potassium hydroxide, citric acid, tartaric acid, sulfuric acid, and calcium nitrate. Different routes for the preparation of these catalysts were tested and analyzed where the FAME formation was the target variable to be improved. Results showed that the catalyst prepared with potassium hydroxide and calcium nitrate achieved the highest FAME formation (i.e., 95%) and outperformed the catalysts prepared with calcium nitrate and other acids even after four regeneration-reaction cycles. The best properties of an alkaline catalyst could be associated with its specific surface area and contents of potassium and calcium moieties, which were higher than those observed for acidic catalysts. Transesterification rates for biodiesel production were better estimated with the pseudo-order kinetic model, which ranged from 0.0004 to 0.038 L/mol⋅min for alkaline and acidic catalysts.
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Istadi, Istadi, Udin Mabruro, Bintang Ayu Kalimantini, Luqman Buchori e Didi Dwi Anggoro. "Reusability and Stability Tests of Calcium Oxide Based Catalyst (K2O/CaO-ZnO) for Transesterification of Soybean Oil to Biodiesel". Bulletin of Chemical Reaction Engineering & Catalysis 11, n. 1 (10 marzo 2016): 34. http://dx.doi.org/10.9767/bcrec.11.1.413.34-39.
Testo completoAbstract (sommario):
<p>This paper was purposed for testing reusability and stability of calcium oxide-based catalyst (K<sub>2</sub>O/CaO-ZnO) over transesterification reaction of soybean oil with methanol to produce biodiesel. The K<sub>2</sub>O/CaO-ZnO catalyst was synthesized by co-precipitation method of calcium and zinc nitrates followed by impregnation of potassium nitrate. The fresh and used catalysts were tested after regeneration. The catalysts were characterized by Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD), and BET Surface Area in order to compare the catalyst structure between the fresh and used catalysts. The catalyst testing in transesterification proses was carried out at following operating conditions, i.e. catalyst weight of 6 wt.%, oil to methanol mole ratio of 1:15, and temperature of 60 oC. In addition, metal oxide leaching of K<sub>2</sub>O/CaO-ZnO catalyst during reaction was also tested. From the results, the catalysts exhibited high catalytic activity (80% fatty acid methyl ester (FAME) yield after three-cycles of usage) and acceptable reusability after regeneration. The catalyst also showed acceptable stability of catalytic activity, even after three-cycles of usage. Copyright © 2016 BCREC GROUP. All rights reserved</p><p><em>Received: 10<sup>th</sup> November 2015; Revised: 16<sup>th</sup> January 2016; Accepted: 16<sup>th</sup> January 2016</em></p><p><strong>How to Cite</strong>: Istadi, I., Mabruro, U., Kalimantini, B.A., Buchori, L., Anggoro, D.D. (2016). Reusability and Stability Tests of Calcium Oxide Based Catalyst (K<sub>2</sub>O/CaO-ZnO) for Transesterification of Soybean Oil to Biodiesel. <em>Bulletin of Chemical Reaction Engineering & Catalysis</em>, 11 (1): 34-39. (doi:10.9767/bcrec.11.1.413.34-39)</p><p><strong>Permalink/DOI</strong>: <a href="http://dx.doi.org/10.9767/bcrec.11.1.413.34-39">http://dx.doi.org/10.9767/bcrec.11.1.413.34-39</a></p><p> </p>
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Li, Changqing, Xinyue Cui, Aili Wang, Hengbo Yin, Yuting Li, Qiao Lin e Junjie Guo. "Direct Synthesis of Calcium Lactate through the Reaction of Glycerol with Calcium Hydroxide Catalyzed by Bimetallic AuCu/SiO2 Nanocatalysts". Catalysts 14, n. 5 (11 maggio 2024): 318. http://dx.doi.org/10.3390/catal14050318.
Testo completoAbstract (sommario):
Bimetallic AuCu/SiO2 nanosized catalysts were prepared using the wet chemical reduction technique. From among Au0.1–1.5Cu10/SiO2 catalysts, the Au0.5Cu10/SiO2 catalyst gave the highest yield of calcium lactate of 87% at a glycerol conversion of 96% when the reaction of glycerol with calcium hydroxide at a mole ratio of calcium hydroxide to glycerol of 0.8:1 was conducted under an anaerobic atmosphere at 200 °C for 2 h. The interactions between metallic Au0 and Cu0 nanoparticles facilitate calcium lactate formation. The simulation of glycerol consumption rate with an empirical power-function reaction kinetics equation yielded a reaction activation energy of 44.3 kJ∙mol−1, revealing that the catalytic reaction of glycerol with calcium hydroxide to calcium lactate can be conducted by overcoming a mild energy barrier. The synthesis of calcium lactate through the catalytic reaction of glycerol with calcium hydroxide on a bimetallic AuCu/SiO2 nanosized catalyst under a safe anaerobic atmosphere is an alternative to the conventional calcium lactate production technique through the reaction of expensive lactic acid with calcium hydroxide.
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Suprapto, Suprapto, Tikha Reskiani Fauziah, Meiske S. Sangi, Titie Prapti Oetami, Imroatul Qoniah e Didik Prasetyoko. "Calcium Oxide from Limestone as Solid Base Catalyst in Transesterification of Reutealis trisperma Oil". Indonesian Journal of Chemistry 16, n. 2 (13 marzo 2018): 208. http://dx.doi.org/10.22146/ijc.21165.
Testo completoAbstract (sommario):
CaO catalysts were synthesized from limestone by thermal decomposition and coprecipitation methods. The CaO and MgO reference catalysts were also synthesized for comparison. The catalysts were characterized by X-ray diffractometer (XRD) and the analysis result was refined by Rietica software. CaO catalyst obtained by coprecipitation method has higher purity of CaO and lower MgO content than those of calcined CaO. The catalysts were also characterized by Fourier Transform Infrared (FTIR) spectroscopy. FTIR spectra showed that the catalysts can be easily hydrated and carbonated in air. The catalytic activity of the catalyst was studied in transesterification reaction of Reutealis trisperma (Kemiri Sunan) oil with methanol. Transesterification reaction was carried out at oil to methanol molar ratio 1:1 and 1% of catalyst at 60 °C for 2 h. Catalytic activity of CaO catalyst obtained by coprecipitation was higher than calcined CaO. The methyl ester yield obtained from synthesized CaO, CaO from coprecipitation, calcined CaO, and synthesized MgO catalysts were 56.13; 37.74; 15.97; and 3.61%, respectively.
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Garbarino, Gabriella, Federico Pugliese, Tullio Cavattoni, Guido Busca e Paola Costamagna. "A Study on CO2 Methanation and Steam Methane Reforming over Commercial Ni/Calcium Aluminate Catalysts". Energies 13, n. 11 (1 giugno 2020): 2792. http://dx.doi.org/10.3390/en13112792.
Testo completoAbstract (sommario):
Three Ni-based natural gas steam reforming catalysts, i.e., commercial JM25-4Q and JM57-4Q, and a laboratory-made catalyst (26% Ni on a 5% SiO2–95% Al2O3), are tested in a laboratory reactor, under carbon dioxide methanation and methane steam reforming operating conditions. The laboratory catalyst is more active in both CO2 methanation (equilibrium is reached at 623 K with 100% selectivity) and methane steam reforming (92% hydrogen yield at 890 K) than the two commercial catalysts, likely due to its higher nickel loading. In any case, commercial steam reforming catalysts also show interesting activity in CO2 methanation, reduced by K-doping. The interpretation of the experimental results is supported by a one-dimensional (1D) pseudo-homogeneous packed-bed reactor model, embedding the Xu and Froment local kinetics, with appropriate kinetic parameters for each catalyst. In particular, the H2O adsorption coefficient adopted for the commercial catalysts is about two orders of magnitude higher than for the laboratory-made catalyst, and this is in line with the expectations, considering that the commercial catalysts have Ca and K added, which may promote water adsorption.
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Wang, Jian, e Yi Fan Zhang. "The Study of Divalent Metal Ion Catalysts on Phenol-Formaldehyde Resol Resins". Applied Mechanics and Materials 71-78 (luglio 2011): 818–21. http://dx.doi.org/10.4028/www.scientific.net/amm.71-78.818.
Testo completoAbstract (sommario):
The curing characteristic of phenol-formaldehyde resol resins catalyzed with magnesium hydroxide, calcium hydroxide and barium hydroxide was studied in this study.The effects of catalysts on chemical structure of phenol formaldehyde resin was investigated by fourier transform infrared.The results indicated that divalent metal ions catalysts played an important role influence both the cure rate and cure time.Phenol formaldehyde resin catalysed by diffierent catalysts showed diffierent addition of formaldehyde onto ortho positions of phenolic rings.The order of the divalent metal ions effectiveness studied in alkaline conditions is calcium hydroxide, barium hydroxide and magnesium hydroxide.
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Lee, Sungho, Jeyoung Ha e Oi Lun Li. "Plasma Modification of Biomass-Based Starfish Catalysts for Efficient Biodiesel Synthesis". Nanomaterials 14, n. 15 (4 agosto 2024): 1313. http://dx.doi.org/10.3390/nano14151313.
Testo completoAbstract (sommario):
This study investigated biodiesel production via the transesterification of grapeseed oil with plasma-modified biomass-based catalysts originating from starfish. Dried starfish was first converted into magnesium and calcium oxide through heat treatment and then further modified by plasma engineering to improve the catalyst’s surface area and active sites via zinc addition. The Zn content was added via plasma engineering in the ratios of starfish (Mg0.1Ca0.9CO3): ZnO varying from 5:1, 10:1, to 20:1. The structure and morphology of the catalyst were confirmed through XRD, SEM, and XPS analysis. After the Zn addition and activation process, the surface area and the basicity of the synthesized catalysts were increased. The plasma-modified catalyst showed the highest basicity at the ratio of 10:1. Based on HPLC analyses, the optimized biodiesel yield in transesterification demonstrated 97.7% in fatty acid conversion, and its catalytic performance maintained 93.2% even after three repeated runs.
Tesi sul tema "Calcium catalysts"
1
Kröger, V. (Virpi). "Poisoning of automotive exhaust gas catalyst components:the role of phosphorus in the poisoning phenomena". Doctoral thesis, University of Oulu, 2007. http://urn.fi/urn:isbn:9789514286087.
Testo completoAbstract (sommario):
Abstract
The aim of this thesis project was to gain new knowledge on the effect of phosphorus on the catalytic activity and characteristics of automotive exhaust gas catalyst components. The simultaneous roles of phosphorus and calcium were also studied.
The first test series of powdery catalyst samples contained Rh and oxide (Test series 1) and the second, Pt and oxide or ZSM-5 (Test series 2). The catalysts were analyzed when fresh and after two ageing and phosphorus poisoning procedures developed in this work. The procedures consisted of adding poison via impregnation in an aqueous solution (for Test series 1) and in the gaseous phase under hydrothermal conditions (for Test series 2). The poison compounds formed and the changes in the washcoat were studied by using physisorption analyses, SEM, TEM, XRD, and FTIR-ATR. The poison content of the samples was determined by ICP-OES and XRF. Laboratory-scale activity measurements were done to investigate the catalytic activity. Thermodynamic calculations were used to obtain information about ageing conditions and phosphorus compounds formed during ageing.
Phosphorus decreased the catalytic activity and the characteristic surface areas of the catalysts. Addition of calcium to a phosphorus-poisoned catalyst was found to have even a regenerating effect on the catalysts' activity. The poisoning methods developed in this study resulted in the same phosphorus compounds as can be found in vehicle-aged catalysts. Phosphorus was identified as cerium, zirconium, aluminium, and titanium phosphates. Phosphorus was detected in zeolites, but phosphorus-containing compounds were not observed. Phosphorus poisoning takes place in the gas phase at high operating temperatures and with high oxygen and water contents. It was also shown that the role of phosphorus poisoning was more pronounced than the role of hydrothermal ageing alone. Phosphorus poisoning mainly affects the oxide components used in this study, not the noble metals.
The results can be utilized in the development of catalytic materials and catalyst compositions that can better tolerate phosphorus poisoning under hydrothermal conditions. The results can also be applied in evaluating the effects of phosphorus on different catalyst compositions and in estimating the age of commercial catalysts.
2
Kunchithapatham, Kamala. "Development of Calcium and Palladium Catalysts for the Formation of Carbon-Carbon and Carbon-Heteroatom Bonds". The Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1337955731.
Testo completo
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Rêgo, de Vasconcelos Bruna. "Phosphates-based catalysts for synthetic gas (syngas) production using CO2 and CH4". Thesis, Ecole nationale des Mines d'Albi-Carmaux, 2016. http://www.theses.fr/2016EMAC0004/document.
Testo completoAbstract (sommario):
Parmi les produits issus de la biomasse ou de la transformation des déchets organiques, le CO2 et le CH4 sont des intermédiaires chimiques importants qui ont de forts impacts environnementaux. En effet, ils sont les principaux gaz responsables de l'effet de serre et leur atténuation est un enjeu majeur. Une voie intéressante pour la valorisation de ces gaz est le reformage à sec du méthane (DRM), qui convertit le CO2 et le CH4 en gaz de synthèse (mélange d'hydrogène et de monoxyde de carbone). Ce mélange peut être utilisé pour plusieurs applications telles que la production de méthanol, d'éther diméthylique, d'hydrogène et des hydrocarbures liquides. Malgré cet intérêt, l'exploitation du DRM à l'échelle industrielle n'a pas encore vu le jour. La raison principale est la désactivation rapide des catalyseurs en raison des conditions sévères de fonctionnement du procédé (température élevée, dépôt de carbone). Cette thèse porte sur le développement de nouveaux catalyseurs à base de phosphate de calcium (CaP) dopés avec des métaux de transition pour la valorisation du CO2 et du CH4 en gaz de synthèse par DRM. Les CaP sont utilisés car ils possèdent des propriétés avantageuses en catalyse hétérogène comme la présence simultanée de sites acides et basiques, bonne stabilité thermique, large gamme de surface spécifique ... Dans un premier temps, des études sur les méthodes de synthèse de catalyseurs et sur la performance de différents métaux de transition (Zn, Fe, Co, Cu, Ni) ont été effectuées dans le but de sélectionner le catalyseur et sa méthode de préparation. Un réacteur à lit fixe capable de fonctionner à hautes température et pression a ensuite été testé pour un long temps de réaction afin d'évaluer correctement la performance des catalyseurs préparés. Ensuite, une étude paramétrique détaillée a été menée. L'influence des paramètres tels que le prétraitement des catalyseurs, la température (T = 400-700°C) et la pression (P = 1-25bar) de la réaction et les différents supports (hydroxyapatite, alumine) ont été étudiés. Enfin, la stabilité thermique et catalytique a été étudiée durant 300h de réaction. Les catalyseurs à base de CaP ont montré des rendements plus élevés en gaz de synthèse en comparaison aux catalyseurs commerciaux. Ces catalyseurs sont donc compétitifs dans les mêmes conditions opératoires (T = 700°C, P = 1bar, WHSV = 12272mLh-1gcat-1, t = 300h). Ce travail a montré l'intérêt des catalyseurs à base de CaP pour des processus à haute température, tel que le reformage à sec du méthaneAmong the products resulting from biomass or organic waste transformation, CO2 and CH4 are important chemical intermediates. They also have a strong environmental impact since they are primarily responsible for the greenhouse effect and their mitigation is a key issue. An attractive way of valorization of such gases is the dry reforming of methane (DRM), which converts CO2 and CH4 into syngas (mixture of hydrogen and carbon monoxide). This mixture can be used for several applications, such as the production of methanol, dimethyl ether, hydrogen and liquid hydrocarbons. Despite such interest, the exploitation of DRM on industrial scale has not emerged yet. The main reason is the rapid deactivation of the catalysts due to the severe operating conditions of the process (high temperature, carbon deposition). This thesis focuses on the development of new catalysts based on calcium phosphate (CaP) doped with transition metals for the valorization of CO2 and CH4 through DRM. Actually,CaP has advantageous properties in heterogeneous catalysis, as the simultaneous presence of acid and basic sites, good thermal stability, and wide range of surface area... Initially, a study on the catalyst synthesis methods and an investigation of the performance of different transition metals (Zn, Fe, Co, Cu, Ni) were carried out in order to select the catalyst system and the preparation method. Secondly, a fixed-bed reactor capable of operating at high temperature and pressure and for log time on stream was built and implemented during this work in order to properly evaluate the performance of the preparedcatalysts. Then, a detailed parametric study was conducted. The influence of parameters such as catalyst pre-treatment, temperature (T = 400-700°C) and pressure (P = 1-25bar) of the reaction and support (hydroxyapatite, alumina-based supports) were investigated. Finally, the catalytic stability was studied for 300h of time on stream (TOS). The CaP catalysts showing higher yields on syngas were compared to commercial catalysts. Our catalysts showed to be competitive in the same operating conditions (T = 700°C, P = 1bar, WHSV = 12272mLh-1gcat-1,TOS = 300h). This work shows the interest of CaP catalysts for high temperature process, such as dry reforming of methane
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Borteh, Hassan. "Micropatterning of Functional Inorganic Materials with Benign Chemistry Using Peptide Catalysts". The Ohio State University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=osu1276883108.
Testo completo
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Song, Hua. "Investigation of Reaction Networks and Active Sites in Bio-ethanol Steam Reforming over Cobalt based Catalysts". The Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=osu1243999804.
Testo completo
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Marin, Lucile. "Réaction d’aza-Piancatelli : nouvelles applications, version diastéréosélective et utilisation en synthèse totale". Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLS206.
Testo completoAbstract (sommario):
Grâce à leurs multiples sites de fonctionnalisation, les cyclopenténones sont des intermédiaires particulièrement utiles dans la synthèse de produits naturels d’intérêt thérapeutique. En particulier, les composés 4-aminocyclopenténones permettent l’accès au motif aminocyclopentitol présent dans des molécules bioactives telles que le peramivir, la pactamycine, ou encore la trehazoline. L’une des méthodes les plus efficaces pour accéder aux 4-aminocyclopenténones est la réaction de cyclisation d’aza-Piancatelli. Cette réaction est basée sur le réarrangement de 2-furylcarbinols en présence d’un nucléophile azoté suivant un mécanisme faisant intervenir une électrocyclisation 4π-conrotatoire. Au sein de notre laboratoire, un système catalytique simple, utilisant un complexe de calcium combiné à un sel d’ammonium, a été mis au point pour avoir accès à ces composés. Cette méthode présente de nombreux avantages : elle est efficace (rendements allant jusqu’à 98%), rapide (15 à 30 minutes), elle nécessite seulement 1 mol% de catalyseur dans des conditions commodes (solvants non distillés et réaction à l’air libre) sur une grande échelle (multi-grammes). Dans ce contexte, nous avons cherché à exploiter tout le potentiel de cette réaction en synthétisant des 2-furylcarbinols plus complexes dans le but de concevoir un accès direct à des squelettes de composés bioactifs. Nous nous sommes en particulier concentrés sur la synthèse totale de la jogyamycine. Par ailleurs, nous avons effectué la synthèse totale de la bruceolline D avec un rendement global de 16% sur 5 étapes. Nous avons également développé une nouvelle séquence réactionnelle impliquant une réaction d’aza-Piancatelli suivie d’une réaction d’hydroamination promue par des sels de cuivre qui fournit un large éventail de cyclopenta[b]pyrroles polyfonctionnels à partir de 2-furylcarbinols facilement accessibles incorporant un groupement alcyne. Par cette méthode, 42 cyclopenta[b]pyrroles ont été obtenus avec des rendements atteignant 98%. Une caractéristique originale de notre approche est liée à l'utilisation d'anilines ortho-substituées. En effet, dans ce cas, des atropisomères avec un excès diastéréomérique supérieur à 20:1 ont pu être obtenus, accompagnés par la création d'une chiralité axiale N-C lors de l'étape d'hydroamination. A ce jour, il n'existait aucun autre exemple de synthèse atropodiastéréosélective de cyclopenta[b]pyrroles. Au cours de nos recherches sur le champ d’application de la réaction, nous avons remarqué que les cyclopenta[b]pyrroles pouvaient se réarranger spontanément en cyclopenta[b]pyrrolines suivant une déaromatisation lorsque l’hexafluoroisopropanol était utilisé comme solvant, permettant d’obtenir 13 cyclopenta[b]pyrrolines avec des rendements variant de 44 à 73%. Nous nous sommes également intéressés à la fonctionnalisation du motif cyclopenta[b]pyrrole pour illustrer l'utilité de notre méthodologie, en combinant en particulier cette séquence réactionnelle avec des réactions de type Friedel-Crafts. L’un des objectifs du projet de thèse était le développement de la version énantiosélective de la réaction. Après la publication récente de trois articles utilisant des acides phosphoriques chiraux en tant que catalyseurs, nous avons envisagé une autre approche pour la synthèse asymétrique de 4-aminocyclopenténones, s’appuyant sur l’utilisation d’une copule chirale (sulfoxyde chiral) portée par l’aniline en collaboration, avec le Dr. Wencel-Delord et le Pr. Colobert (Université de Strasbourg). Ainsi nous avons pu générer les 4-aminocyclopenténones correspondantes avec d’excellents rendements et diastéréosélectivitésDue to their various functionalizable sites, cyclopentenones are very useful intermediates for the synthesis of natural products of therapeutic value. In particular, 4-aminocyclopentenones enable the access to the aminocyclopentitol frameworks, which are present in a variety of bioactive molecules such as peramivir, pactamycin, or trehazolin. One of the most efficient methods to access 4-aminocyclopentenones is the aza-Piancatelli reaction. It is based on the rearrangement of 2-furylcarbinols in the presence of a nitrogen nucleophile following a mechanism involving a 4π-conrotatory electrocyclization. In our laboratory, a simple catalytic system using a calcium complex combined with an ammonium salt was developed to gain access to these compounds. This method has many advantages : it is effective (yields up to 98%), fast (15 to 30 minutes), it requires only 1 mol% of catalyst under pratical conditions (undistilled solvents without an inert atmosphere) on a large scale (multi-gram). In this context, we sought to extend the scope of this reaction by designing more complex 2-furylcarbinols in order to directly access skeletons of bioactive compounds. In particular, we focused on the total synthesis of jogyamycin. In addition, we achieved the total synthesis of bruceollin D with an overall yield of 16% over five steps. We also developed a new reaction sequence involving an aza-Piancatelli reaction followed by a hydroamination reaction promoted by a copper salt. This sequence provides a wide range of highly functionalized cyclopenta[b]pyrroles from readily-available 2-furylcarbinols substituted by an alkyne moiety. Following this method, 42 cyclopenta[b]pyrroles were obtained with yields up to 98%. An original feature of this transformation is related to the use of ortho-substituted anilines. Indeed, in this case, atropisomers with a diastereomeric excess superior to 20:1 could be obtained accompanied by the creation of an chiral N-C axis during the hydroamination step. To date, no other example of atropodiastereoselective synthesis of cyclopenta[b]pyrroles has been reported. During our investigations on the scope of the reaction, we noticed that cyclopenta[b]pyrroles underwent a rearrangement into cyclopenta[b]pyrrolines, following a dearomatization when hexafluoroisopropanol was used as solvent. This transformation led to 13 cyclopenta[b]pyrrolines with yields ranging from 44% to 73%. We also investigated the functionalization of the cyclopenta[b]pyrrole motif to illustrate the synthetic utility of our methodology, notably by combining this reaction sequence with a Friedel-Crafts reaction. One of the objectives of this Ph.D. was the development of an enantioselective version of the reaction. After the recent publication of three papers using chiral phosphoric acids as catalysts, we devised another approach for the asymmetric synthesis of 4-aminocyclopentenones, relying on the use of a chiral auxiliary (chiral sulfoxide) in collaboration with Dr. Wencel-Delord and Pr. Colobert (University of Strasbourg). Thus, we were able to provide the corresponding 4-aminocyclopentenones with excellent yields and diastereoselectivity
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Ebadi, pour Negisa. "Développement de systèmes catalytiques à base de Ca pour la polymérisation sélective de glycérol". Electronic Thesis or Diss., Centrale Lille Institut, 2021. http://www.theses.fr/2021CLIL0027.
Testo completoAbstract (sommario):
Bien que de très nombreuses applications soient recensées pour valoriser le glycérol coproduit par la filière biodiesel (à raison de 100 kg de glycérol par tonne de biocarburant), les solutions potentiellement les plus lucratives basées sur des transformations chimiques avancées n’atteignent aujourd’hui que rarement le stade commercial. Ceci est principalement dû à (i) une instabilité réglementaire sur les licences de production de biodiesel menaçant ainsi la disponibilité du glycérol et (ii) un prix du glycérol pouvant par conséquent fluctuer de manière imprévisible. Faire évoluer le concept d’unité de production de biodiesel, où le glycérol est le coproduit principal, en un concept de bioraffinerie oléagineuse, où notamment des produits à haute valeur ajoutée dérivés du glycérol sont produits avec le biodiesel, permettra de s’affranchir des incertitudes règlementaires liées à la production du biodiesel tout en favorisant un développement rapide des technologies de valorisation du glycérol par évolution d’unités de production existantes. Dans ce contexte, ce projet de thèse basé sur des résultats préliminaires très prometteurs de notre équipe vise à développer un procédé catalytique de valorisation efficace du glycérol en polyglycérols linéaires (PGs). Les PGs présentent une biocompatibilité exceptionnelle récemment démontrée. Ils possèdent en outre des applications directes (pharmacie, alimentation, etc.), et de grands industriels le voient aussi de plus en plus comme une base pour l’obtention d’autres molécules, notamment les esters de PGs, diversifiant considérablement les champs d’applications finaux (émulsifiants, stabilisateurs, etc.). Le programme de recherche proposé permettra de mieux comprendre et d’optimiser en retour un système catalytique performant et robuste, dans un contexte régional particulièrement propice (Hub2 de l’I-SITE, producteurs de biodiesel, plateformes REALCAT et UPCAT, CPER-FEDER Archi-CM, etc.)Although many applications are listed to valorize glycerol as a co-produced of the biodiesel sector (at a rate of 100 kg of glycerol per ton of biofuel), the most potential solutions based on advanced chemical transformations today reach rarely the commercial stage. This is mainly due to (i) instability on biodiesel production licenses, thus threatening the availability of glycerol and (ii) a price of glycerol that can fluctuate unpredictably. In the concept of biodiesel production unit, where glycerol is the main co-product, into a concept of oilseed biorefinery, where in particular glycerol-derived products with high added value are produced with biodiesel, will make it possible to overcome uncertainties related to the production of biodiesel while promoting the rapid development of glycerol valorization technologies through the evolution of existing production units. In this context, this thesis project based on very promising preliminary results from our team aims to develop a catalytic process for the efficient valorisation of glycerol in linear polyglycerols (PGs). PGs have recently demonstrated exceptional biocompatibility. They also have direct applications (pharmacy, food, etc.), and large manufacturers also see it increasingly as a base for obtaining other molecules, including PGs esters. The proposed research program will provide a better understanding and optimization of a powerful and robust catalytic system in a particularly favorable regional context
8
Wixey, James S. "Novel calcium complexes applied to intramolecular hydroamination catalysis". Thesis, Cardiff University, 2012. http://orca.cf.ac.uk/37858/.
Testo completoAbstract (sommario):
This thesis discusses the synthesis, characterisation, and reactivity studies of a range of new chiral calcium complexes supported by various polydentate N-donor ligands and their suitability as catalysts for intramolecular hydroamination. Chapter One outlines the case for developing organocalcium complexes, including a general overview of their current application to a variety of heterofunctionalisation reactions. Chapter Two introduces the chiral ethylene diamines which are extensively used as calcium supporting ligands and later as precursors for the synthesis of bisimidazoline and potential imoxazoline ligands. Chapter Two provides details of the diamine synthesis and includes studies related to racemisation concerns of the chiral centre. Chapter Three discusses novel calcium complexes supported by the chiral ethylene diamine analogues presented in Chapter Two. Complex synthesis, characterisation, and catalytic performance in intramolecular hydroamination is probed and discussed. Chapter Four details a range of new bisimidazoline ligands and their employment as supporting ligands on calcium. The catalytic performance of the resulting complexes in intramolecular hydroamination is subsequently analysed and discussed. Chapter Five investigates the attempted development of a total synthetic pathway to a new class of imoxazoline ligand and related issues. Chapter Six contains all experimental procedures, characterising data pertaining to all new compounds and complexes presented in this Thesis. Appendices A-K contain additional catalytic figures and tables of crystallographic data for all new crystallographically characterised compounds. Summary sheets of every literature and new compound presented mentioned in this Thesis are also included, along with copies of both printed publications resulting from this Thesis at the time of submission.
9
Qi, Chenxiao. "New catalytic tools for the functionalization of alcohols and unactivated alkenes". Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLS202.
Testo completoAbstract (sommario):
A l’heure actuelle, il y a une forte demande de l’industrie de la chimie fine pour développer des procédures basées sur des réactions n’impliquant pas l’utilisation de métaux de transition et mettant en jeu des produits de départ facilement accessibles. Les principales raisons sont la disponibilité, le coût et la toxicité des métaux de transition ou des électrophiles. Dans ce contexte, utiliser d’alcools et alcènes pour la formation de liaisons carbone-carbone et carbone-hétéroatome est particulièrement attractif, cependant cela reste encore un challenge, surtout quand les substrats sont extrêmement désactivés ou susceptibles de piéger le catalyseur. Récemment, nous avons démontré que l’acidité de l’hexafluoroisopropanol (HFIP) pouvait être augmentée de façon significative par des sels de calcium(II) afin d’activer des liaisons C-O et C-C, surpassant les acides de Lewis et de Brønsted habituels que ce soit en termes d’activité ou de sélectivité grâce à la coordination de HFIP au calcium et la formation d’assemblages par liaison hydrogène. De plus, grâce à sa capacité à former des liaisons hydrogène fortes, HFIP peut faciliter la libération d’acides de Lewis piégés par une coordination non désirée avec le substrat (ou le produit), permettant, le turn-over du procédé catalytique. En particulier, l’association Ca²⁺/HFIP peut être un outil puissant pour promouvoir des électrocyclisations, hydroamidations, hydroarylations, hydroacyloxylations et des halofonctionnalisations. Ces réactions sont à la fois générales et compatibles avec un plus large éventail de substrats que les systèmes catalytiques classiquesToday, there is a strong demand from the fine chemicals industry to develop procedures based on transition metal-free reactions using readily available starting materials. The main reasons behind this are the availability, cost and toxicity of transition-metals or electrophiles. In that respect, employing simple alcohols and alkenes for C-C and C-heteroatom bond forming reactions is truly appealing, but it can remain challenging, notably when the substrates are highly deactivated or prone to sequester the catalyst. Recently, we have demonstrated that the acidity of hexafluoroisopropanol (HFIP) could be significantly harnessed by calcium(II) salts in order to activate C-O and C-C bonds, outperforming common Lewis and Brønsted acids in terms of activity or efficiency in several reactions through the coordination of HFIP to calcium and the formation of hydrogen-bond clusters. Moreover, due to its strong hydrogen-bond donor ability, HFIP has the capacity to facilitate the release of Lewis acids trapped by unwanted coordination to the substrate (or the product), allowing the catalytic process to turn over. In particular, the combination Ca²⁺/HFIP can be a powerful tool to promote electrocyclizations, hydroamidations, hydroarylations, hydroacyloxylations and halofunctionalizations. These reactions proved to be general and compatible with a wider range of substrates than the traditional catalytic systems
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Espied, Arnaud. "Approches catalytiques innovantes par des acides de Lewis pour la synthèse de composés cycliques, bicycliques et bioisostères du benzène". Electronic Thesis or Diss., université Paris-Saclay, 2024. http://www.theses.fr/2024UPASF082.
Testo completoAbstract (sommario):
Nous avons mené des recherches approfondies sur plusieurs réactions innovantes dans le domaine de la synthèse organique. Dans un premier temps, nous avons développé une réaction de cyclisation déshydratante ainsi que deux réactions en tandem, initiées par une cyclisation intramoléculaire. Ces réactions se caractérisent par leur haute diastéréosélectivité et l'utilisation d'un catalyseur à base d'un métal du groupe principal, agissant en tant qu'acide de Lewis. Cette approche nous a permis de synthétiser 27 nouveaux composés cycliques, avec des rendements pouvant atteindre 97 %. Dans un deuxième temps, nous avons mis au point une réaction tandem combinant une réaction de métathèse carbonyl-ène et un couplage déshydratant, réalisée à l'aide d'un catalyseur cationique à base de gallium sur des dérivés du benzhydrol. Cette méthode a conduit à la synthèse de 15 nouveaux composés, avec des rendements pouvant aller jusqu'à 67 %. Enfin, nous nous sommes intéressés à la réactivité des dérivés du bicyclobutane dans des cycloadditions en présence d'espèces insaturées et d'un catalyseur à base d'or. Cette approche a permis la synthèse de 5 nouveaux bioisostères du benzène, avec des rendements pouvant atteindre 90 %We conducted extensive research on several innovative reactions in the field of organic synthesis. Initially, we developed a dehydrating cyclization reaction, as well as two tandem reactions initiated by this cyclization. These reactions are characterized by high diastereoselectivity and the use of a main-group metal-based catalyst acting as a Lewis acid. This approach allowed us to synthesize 27 new cyclic compounds with yields reaching up to 97%. Furthermore, we also developed a tandem reaction combining carbonyl-ene metathesis and a dehydrating coupling, carried out using a gallium-based cationic catalyst on benzhydrol derivatives. This method led to the synthesis of 15 new compounds, with yields of up to 67%. Finally, we investigated the reactivity of bicyclobutane derivatives in cycloadditions with unsaturated species in the presence of a gold-based catalyst. This approach enabled the synthesis of 5 new benzene bioisosteres with yields reaching up to 90%
Capitoli di libri sul tema "Calcium catalysts"
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Nigha, Kamaldeep Singh, Shifa Naaz e Amrit Pal Toor. "Biodiesel Production Using CaO-Based Heterogeneous Catalysts". In Advanced Synthesis and Medical Applications of Calcium Phosphates, 148–64. Boca Raton: CRC Press, 2024. http://dx.doi.org/10.1201/9781003360605-10.
Testo completo
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Patel, Madhumita, K. K. Pant e Pravakar Mohanty. "Renewable Hydrogen Generation by Steam Reforming of Acetic Acid over Cu-Zn-Ni Supported Calcium Aluminate Catalysts". In ACS Symposium Series, 111–37. Washington, DC: American Chemical Society, 2012. http://dx.doi.org/10.1021/bk-2012-1092.ch009.
Testo completo
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Gupta, Ritu, e Ashiya Khan. "Calcium-Based Waste Material for Catalysis". In Calcium-Based Materials, 150–67. Boca Raton: CRC Press, 2024. http://dx.doi.org/10.1201/9781003360599-9.
Testo completo
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Polat, Elif. "Fat Soluble Vitamins and Macrominerals". In Vitamins, Minerals and Trace Elements, 1–63. Istanbul: Nobel Tip Kitabevleri, 2024. http://dx.doi.org/10.69860/nobel.9786053359173.1.
Testo completoAbstract (sommario):
The word vitamin was first used to mean ""the amine necessary for life"". • Vitamins are organic catalysts necessary for normal body functions, growth and healthy living. They are not synthesized in the human body and must be obtained externally. Vitamins are classified according to their fat and water solubility. Fat-soluble vitamins are vitamins A, D, E and K, and although they are essential for health, each of them has very important functions in the body. They have many biological activities such as vision, bone, coagulation and antioxidant effects. They are released, absorbed and transported (as chylomicrons) along with dietary fats. They are stored in the liver and fatty tissue and are eliminated more slowly than water-soluble vitamins. Vitamins A and D can accumulate in the body and cause toxic effects. Minerals are inorganic substances needed for the body to maintain its basic functions. These substances cannot be created directly by plants and animals and are taken from the soil. Minerals are divided into two groups: macrominerals and microminerals. Macrominerals are elements that should be taken in amounts greater than 100 mg daily. Calcium, phosphorus, magnesium, sodium, chlorine and potassium are macrominerals. Deficiency or excess intake of minerals can disrupt many biological functions and cause diseases. Sodium is a mineral that plays an important role in the body. Sodium, the main cation of extracellular fluid, is involved in functions such as transport of substances across the cell membrane, fluid-electrolyte balance, and regulation of blood pressure. Sodium levels in the body are kept under control by the functioning of the kidneys and the influence of hormones. Muscle contraction begins with an increase in intracellular calcium ion concentration. It is the most abundant element in the human body after calcium. It is a component of DNA and RNA. Phosphorus plays a role in the formation of bones and teeth and the repair of tissues and cells. It is found abundantly in water in nature, but rarely in plants, especially as sodium chloride and potassium chloride. It ensures that the fluids in the body are kept in balance.
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Wang, Ye, e Yasuo Ohtsuka. "Utilization of Carbon Dioxide for Direct, Selective Conversion of Methane to Ethane and Ethylene with Calcium-Based Binary Catalysts". In ACS Symposium Series, 85–101. Washington, DC: American Chemical Society, 2002. http://dx.doi.org/10.1021/bk-2002-0809.ch006.
Testo completo
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Saito, S. "CHAPTER 4. Asymmetric Catalysis with Chiral Magnesium and Calcium Systems". In Catalysis with Earth-abundant Elements, 81–114. Cambridge: Royal Society of Chemistry, 2020. http://dx.doi.org/10.1039/9781788012775-00081.
Testo completo
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Kouzu, Masato. "Eco-Friendly Production of Biodiesel by Utilizing Solid Base Catalysis of Calcium Oxide for Reaction to Convert Vegetable Oil into Its Methyl Esters". In Zero-Carbon Energy Kyoto 2009, 20–28. Tokyo: Springer Japan, 2010. http://dx.doi.org/10.1007/978-4-431-99779-5_3.
Testo completo
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Cerón-Ferrusca, Montserrat, Rubi Romero-Romero, Reyna Natividad e Sandra Luz Martínez-Vargas. "Bifunctional catalysts applied to produce biodiesel from waste cooking oil". In CIERMMI Women in Science Engineering and Technology TXV, 20–36. ECORFAN, 2021. http://dx.doi.org/10.35429/h.2021.6.20.36.
Testo completoAbstract (sommario):
This work aims to present the analysis of the catalytic performance of Fe2O3/CaO as a bifunctional catalyst in the production of biodiesel from waste cooking oil. The clamshell was used as a source of calcium oxide by calcination. The catalyst was characterized by Thermogravimetric analysis and Differential scanning calorimetry (TGA-DSC), X-ray diffraction (XRD) and Inductively coupled plasma atomic emission spectroscopy (ICP-AES). The catalytic tests were conducted at 55 °C, the methanol:oil ratio was 12:1, amount of catalyst of 6%wt and reaction time of 5 h. The content of methyl esters in the produced biodiesel was >98% and was found to fulfill the specifications of European Norm UNE-EN 14214.
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Yamamura, M., H. Okado, N. Tsuzuki, K. Chaki, T. Wakatsuki, K. Inaba, S. Suzuki e S. Kitada. "Natural Calcium Compounds as Catalysts for Oxidative Coupling of Methane". In Studies in Surface Science and Catalysis, 253–55. Elsevier, 1994. http://dx.doi.org/10.1016/s0167-2991(08)63874-4.
Testo completo
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Zinsmaier, K. E. "Cysteine-string proteins". In Guidebook to Molecular Chaperones and Protein-Folding Catalysts, 115–16. Oxford University PressOxford, 1997. http://dx.doi.org/10.1093/oso/9780198599494.003.0045.
Testo completoAbstract (sommario):
Abstract Omega-conotoxin receptor or CCCS1 for candidate calcium channel subunit 1 (Mastrogiacomo et al., 1994b), now denoted Tcsp. The Drosophila csp gene was isolated using the antibody MAb DCSP-1 (former Mab ab49) (Zinsmaier et al., 1990, 1994) .The gene (Flybase gene id #Fbgn0004179) is located at 79E1-2 on the third chromosome, expresses three alternatively spliced RNA (2.3-2.9 kb) transcripts (Zinsmaier et al., 1994). The amino acid sequence deduced from the nucleotide sequence of two cDNA clones isolated from a Drosophila head cDNA library (GenBank accession numbers M63421, M63008; Zinsmaier et al., 1990) reveals proteins of 249, 223 amino acids (designated Dcsp-32, Dcsp29a).
Atti di convegni sul tema "Calcium catalysts"
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Dumeignil, Franck, Benjamin Katryniok e Negissa Ebadi Pour. "Glycerol polymerization over stable and selective calcium hydroxyapatite". In 2022 AOCS Annual Meeting & Expo. American Oil Chemists' Society (AOCS), 2022. http://dx.doi.org/10.21748/dpka8345.
Testo completoAbstract (sommario):
High catalytic activity and large availability of Ca-based catalysts make them particulartly attractive for the glycerol polymerization reaction. However, this kind of catalyts usually suffers from a poor stability under the reactions conditions. We present herein the use of Ca-hydroxyapatites (HAps), a very abundant Ca source in the nature, as glycerol polymerization catalysts combining high performance in terms of selectivity and high resistance to deactivation by leaching. We have synthesized, characterized and tested Ca-rich, stochiometric and Ca-deficient HAps. The two latter ones were fully selective to triglycerol at a glycerol conversion of 15 %, at 245 °C after 8 h in the presence of 0.5 mol.% of catalyst. Under the same reaction conditions, the Ca-rich HAp was highly selective to di- and triglycerol (88 %) at a glycerol conversion of 27 %. All the catalysts proved to be stable with negligible Ca species leaching according to the ICP-OES results.
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Ahmad, Razi, Shamala Ramasamy, Ragunathan Santiagoo, Norhafezah Kasmuri e Nor Amizah Saede. "Catalytic pyrolysis of biomass using calcium-based catalysts". In PROCEEDINGS OF 8TH INTERNATIONAL CONFERENCE ON ADVANCED MATERIALS ENGINEERING & TECHNOLOGY (ICAMET 2020). AIP Publishing, 2021. http://dx.doi.org/10.1063/5.0051556.
Testo completo
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Li, Zhongrui, Enkeleda Dervishi, Yang Xu, Viney Saini, Meena Waleed Mahmood, Olumide Dereck Oshin, Alexandru S. Biris e Alexandru R. Biris. "Carbon Nanotubes Growth on Calcium Carbonate Supported Molybdenum-Transition Metal Catalysts". In 2008 MRS Fall Meetin. Materials Research Society, 2008. http://dx.doi.org/10.1557/proc-1142-jj05-09.
Testo completo
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Mohyuddin, Ayesha, Hafiz Muhammad Ahmad, Ahtisham Haider, Jamil Anwar, Tonni Agustiono Kurniawan e Amara Dar. "Economical Synthesis of Biodiesel by Using Waste Chicken Bone Derived Doped Calcium Oxide Catalysts". In 2022 11th International Conference on Renewable Energy Research and Application (ICRERA). IEEE, 2022. http://dx.doi.org/10.1109/icrera55966.2022.9922897.
Testo completo
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Amama, Placidus B., Jonathan E. Spowart, Andrey A. Voevodin e Timothy S. Fisher. "Modified Magnesium Hydride and Calcium Borohydride for High-Capacity Thermal Energy Storage". In ASME/JSME 2011 8th Thermal Engineering Joint Conference. ASMEDC, 2011. http://dx.doi.org/10.1115/ajtec2011-44133.
Testo completoAbstract (sommario):
MgH2 and Ca(BH4)2 are potential thermal energy storage (TES) materials that possess extraordinarily high inherent thermal energy densities of up to 2 MJ/kg. However, the high desorption temperatures at atmospheric pressure [>300°C for Ca(BH4)2, >400°C for MgH2] coupled with slow kinetics represent significant challenges for their use in TES. In order to address these challenges, the present work focuses on the development of new modification approaches based on nanostructuring via high-energy vibratory ball milling and catalytic enhancement using pure Ni and Ni alloys. Our work reveals that high-energy vibrating-mill technique with ball-to-powder weight ratio as low as 13:1can produce MgH2 powders with nanocrystallites after 2h of milling. MgH2 milled with Ni (5 wt%) and Ni5Zr2 (5 wt%) catalysts for 2 h showed apparent activation energies, EA of 81 and 79 kJ/mol, respectively, corresponding to ∼50% decrease in EA and ∼100°C decrease in the decomposition temperature (Tdec). On the other hand, the decomposition reaction of Ca(BH4)2 does not seem to be catalyzed by the Ni-based catalysts tested.
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Abdullah, Rozaini, e Ahmad Zuhairi Abdullah. "Effect of catalyst to glycerol ratio in the production of lactic acid via hydrothermal reaction using calcium oxide and strontium oxide catalysts". In GREEN DESIGN AND MANUFACTURE: ADVANCED AND EMERGING APPLICATIONS: Proceedings of the 4th International Conference on Green Design and Manufacture 2018. Author(s), 2018. http://dx.doi.org/10.1063/1.5066838.
Testo completo
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Reddy, B. Kishan, e K. Malathi. "Comparative study on optimized biofuel production from cooked coconut oil using calcium carbonate and sodium hydroxide catalysts". In 2ND INTERNATIONAL INTERDISCIPLINARY SCIENTIFIC CONFERENCE ON GREEN ENERGY, ENVIRONMENTAL AND RENEWABLE ENERGY, ADVANCED MATERIALS, AND SUSTAINABLE DEVELOPMENT: ICGRMSD24, 020028. AIP Publishing, 2024. http://dx.doi.org/10.1063/5.0237414.
Testo completo
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Oliveira, Cassiano Cunha, e Carla Eponina Hori. "HYDROGEN PRODUCTION FROM SORPTION ENHANCED STEAM REFORMING OF ETHANOL USING NICKEL-CALCIUM CATALYSTS DOPED WITH MgO AND Al2O3". In Anais do I Web Encontro Nacional de Engenharia Química. Recife, Brasil: Even3, 2021. http://dx.doi.org/10.29327/138535.1-37.
Testo completo
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Muthiya, S. Jenoris, Induja Saravanan, Gajalakshmi Balachandran e 1Lt P. S. Raghavan. "Experimental Investigation in Diesel Oxidation Catalyst by Developing a Novel Catalytic Materials for the Control of HC, CO and Smoke Emissions". In International Conference on Advances in Design, Materials, Manufacturing and Surface Engineering for Mobility. 400 Commonwealth Drive, Warrendale, PA, United States: SAE International, 2020. http://dx.doi.org/10.4271/2020-28-0458.
Testo completoAbstract (sommario):
<div class="section abstract"><div class="htmlview paragraph">Diesel-powered engines are used worldwide for efficient transportation and stationary power generation. The significant drawback of a diesel engine is its harmful emissions. The stringent emission norms enforced by the different organization demands effective catalyst system to control the gaseous emissions. Diesel oxidation catalysts are the extensively used technique for diesel engines to control HC and CO emissions. Currently the catalyst in the diesel oxidation system employs precious metals such as Pt/Pd/Rh to reduce the emissions and makes the DOC system expensive. This paper presents a cost-effective catalyst prepared to employ non-noble mixed oxides of copper and nickel supported on non-conventional support (i.e.) ceria doped calcium borophosphates (Ce-SCaPB). Initially, ceramic beads (5mm X 5mm) were coated with (Ce-SCaPB) support material. Secondly, the copper and nickel salts were deposited on the Ce-SCaPB coated ceramic beads and subsequently reduced and calcined. The crystallinity and phase formation was studied using XRD technique and SEM image showed particle size ranging between 40 - 50 nm. These catalyst coated beads were loaded into the fabricated DOC reactor and was retrofitted into the tailpipe of the engine exhaust. The experimental emission testing was carried out in a single-cylinder diesel engine coupled with eddy current dynamometer. In engine testing, catalytic material are tested individually to evaluate his reduction percentage. The engine test was conducted under different engine loads (0-100%) and the emission readings were taken for each load. Uncertainty analysis is calculated for the results and the results showed a higher reduction in CO, HC and smoke emissions.</div></div>
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Sandhya, CH, e K. Sashirekha. "Comparative study on performance of potassium hydroxide and calcium carbonate catalysts for the production of biofuel from cooked oil using transesterification method". In 2ND INTERNATIONAL INTERDISCIPLINARY SCIENTIFIC CONFERENCE ON GREEN ENERGY, ENVIRONMENTAL AND RENEWABLE ENERGY, ADVANCED MATERIALS, AND SUSTAINABLE DEVELOPMENT: ICGRMSD24, 020025. AIP Publishing, 2024. http://dx.doi.org/10.1063/5.0237412.
Testo completoRapporti di organizzazioni sul tema "Calcium catalysts"
1
Stevens e Olsen. PR-179-12214-R01 CO Sensor Experimental Evaluation for Catalyst Health Monitoring. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), settembre 2014. http://dx.doi.org/10.55274/r0010827.
Testo completoAbstract (sommario):
Oxidation catalysts and three-way catalysts can be used to reduce the amount of CO present in engine exhaust. For 2-stroke lean-burn engines, the oxidation catalyst degrades over time be-cause of the buildup of poisons such as sulfur, zinc, phosphorous, and calcium. Three-way cata-lysts used with stoichiometric engines also degrade over time. Emissions analyzers are often used to evaluate the degradation of oxidation catalysts and three-way catalysts, but it can be very time consuming and expensive. Ideally, a simple sensor system would be beneficial for operating companies to determine if the catalyst were out of compliance according to normal operating standards. An ECM CO sensor and recording device was acquired for testing. The CO sensor system was evaluated for its ability to monitor post-catalyst CO concentration. The results show that this CO sensor system is ineffective at monitoring post-catalyst CO concentration.
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Fromm, Hillel, e Joe Poovaiah. Calcium- and Calmodulin-Mediated Regulation of Plant Responses to Stress. United States Department of Agriculture, settembre 1993. http://dx.doi.org/10.32747/1993.7568096.bard.
Testo completoAbstract (sommario):
We have taken a molecular approach to clone cellular targets of calcium/calmodulin (Ca2+/CaM). A 35S-labeled recombinant CaM was used as a probe to screen various cDNA expression libraries. One of the isolated clones from petunia codes for the enzyme glutamate decarboxylase (GAD) which catalyzes the conversion of glutamate to g-aminobutyric acid (GABA). The activity of plant GAD has been shown to be dramatically enhanced in response to cold and heat shock, anoxia, drought, mechanical manipulations and by exogenous application of the stress phytohormone ABA in wheat roots. We have purified the recombinant GAD by CaM-affinity chromatography and studied its regulation by Ca2+/CaM. At a physiological pH range (7.0-7.5), the purified enzyme was inactive in the absence of Ca2+ and CaM but could be stimulated to high levels of activity by the addition of exogenous CaM (K0.5 = 15 nM) in the presence of Ca2+ (K 0.5 = 0.8 mM). Neither Ca2+ nor CaM alone had any effect on GAD activity. Transgenic tobacco plants expressing a mutant petunia GAD lacking the CaM-binding domain, or transgenic plants expressing the intact GAD were prepared and studied in detail. We have shown that the CaM-binding domain is necessary for the regulation of glutamate and GABA metabolism and for normal plant development. Moreover, we found that CaM is tightly associated with a 500 kDa GAD complex. The tight association of CaM with its target may be important for the rapid modulation of GAD activity by Ca2+ signaling in response to stresses.
3
Yalovsky, Shaul, e Julian Schroeder. The function of protein farnesylation in early events of ABA signal transduction in stomatal guard cells of Arabidopsis. United States Department of Agriculture, gennaio 2002. http://dx.doi.org/10.32747/2002.7695873.bard.
Testo completoAbstract (sommario):
Loss of function mutations in the farnesyltransferase β subunit gene ERA1 (enhanced response to abscisic acid), cause abscisic acid hypersensitivity in seedlings and in guard cells. This results in slowed water loss of plants in response to drought. Farnesyltransferase (PFT) catalyses the attachment of the 15-carbon isoprenoid farnesyl to conserved cysteine residues located in a conserved C-terminal domain designated CaaX box. PFT is a heterodimeric protein comprised of an a and b sununits. The a subunit is shared between PFT and geranylgeranyltransferase-I (PGGTI) which catalyses the attachemt of the 20-carbon isoprenoid geranylgeranyl to CaaX box proteins in which the last amino acid is almost always leucine and in addition have a polybasic domain proximal to the CaaL box. Preliminary data presented in the proposal showed that increased cytoplasmic Ca2+ concentration in stomal guard cells in response to non-inductive ABA treatements. The goals set in the proposal were to characterize better how PFT (ERA1) affects ABA induced Ca2+ concentrations in guard cells and to identify putative CaaX box proteins which function as negative regulators of ABA signaling and which function is compromised in era1 mutant plants. To achieve these goals we proposed to use camelion Ca2+ sensor protein, high throughput genomic to identify the guard cell transcriptome and test prenylation of candidate proteins. We also proposed to focus our efforts of RAC small GTPases which are prenylated proteins which function in signaling. Our results show that farnesyltransferaseprenylates protein/s that act between the points of ABA perception and the activation of plasma membrane calcium influx channels. A RAC protein designated AtRAC8/AtRop10 also acts in negative regulation of ABA signaling. However, we discovered that this protein is palmitoylated and not prenylated although it contains a C-terminal CXXX motif. We further discovered a unique C-terminal sequence motif required for membrane targeting of palmitoylatedRACs and showed that their function is prenylation independent. A GC/MS based method for expression in plants, purification and analysis of prenyl group was developed. This method would allow highly reliable identification of prenylated protein. Mutants in the shared α subunit of PFT and PGGT-I was identified and characterized and was shown to be ABA hypersensitive but less than era1. This suggested that PFT and PGGT-I have opposing functions in ABA signaling. Our results enhanced the understanding of the role of protein prenylation in ABA signaling and drought resistance in plants with the implications of developing drought resistant plants. The results of our studies were published 4 papers which acknowledge support from BARD.