scholarly journals AN IMPROVED METHOD FOR THE PREPARATION OF PHLOROGLUCINOL FROM 1,3,5-TRINITROBENZENE

2021 ◽  
pp. 148-154
Author(s):  
И.А. Щурова ◽  
Н.А. Алексеева ◽  
С.В. Сысолятин ◽  
В.В. Малыхин
Keyword(s):  
Sulfuric Acid ◽  
Molar Ratio ◽  
Improved Method ◽  
Fresh Catalyst ◽  
Pd Catalysts ◽  
Mild Conditions ◽  
Process Cost ◽  
Medicinal Drugs ◽  
The Relationship ◽  
Water Ratio

Статья посвящена способу получения флороглюцина, представляющего интерес в качестве основы для конструирования лекарственных средств, полимеров различного назначения и малочувствительного взрывчатого вещества 1,3,5-триамино-2,4,6-тринитробензола. Современным и наиболее экологичным методом получения флороглюцина является каталитическое гидрирование 1,3,5-тринитробензола на палладиевом катализаторе до 1,3,5-триаминобензола и его последующий гидролиз. Использование палладиевых катализаторов позволяет проводить восстановление в мягких условиях, но их высокая стоимость обуславливает потребность в поиске путей снижения расхода палладия и, соответственно, себестоимости процесса. В данном исследовании показано, что использование 1 %-го Pd/сибунит (50 % к массе субстрата) в сочетании с водно-ацетоновым раствором в качестве среды при проведении гидрирования способствует более длительному сохранению активности катализатора. Установлено, что оптимальное соотношение ацетона и воды находится в диапазоне от 4:1 до 7:1. В этом случае может быть проведено до 20 циклов гидрирования без добавления свежего катализатора, за счет чего удается снизить расход палладия в три раза по сравнению с другими известными методиками. Кроме того, подход позволяет исключить из схемы синтеза токсичный растворитель метанол. Триаминобензол, полученный в ходе гидрирования, без выделения подвергается гидролизу в присутствии серной кислоты с образованием флороглюцина. Изучена зависимость выхода флороглюцина от мольного соотношения серной кислоты и тринитробензола. Установлено, что оптимальное соотношение серная кислота : тринитробензол составляет 2,0-2,4 моль/моль. Суммарный выход флороглюцина составляет 76 % в пересчете на тринитробензол. The study is concerned with a synthetic method for phloroglucinol that is of great concern as a scaffold for designing medicinal drugs, different-purpose polymers and the insensitive explosive 1,3,5-triamino-2,4,6-trinitrobenzene. The current and most eco-benign method for the synthesis of phloroglucinol is through catalytic hydrogenation of 1,3,5-trinitrobenzene over the Pd catalyst to 1,3,5-triaminobenzene followed by its hydrolysis. The use of Pd catalysts allows the reduction under mild conditions, but their high cost necessitates the need to find ways how to spare the Pd usage and, consequently, the process cost. Here we demonstrated that the use of 1% Pd/Sibunite (50% to substrate weight) combined with a water-acetone solution as the medium in hydrogenation allows the catalyst to keep active longer. The optimum acetone-to-water ratio was found to be between 4:1 and 7:1. In this case, as many as 20 hydrogenation runs can be done without a fresh catalyst added whereby the Pd usage can be lowered threefold when compared to the other common methods in use. Besides, this approach allows the toxic solvent methanol to be expelled from the synthetic protocol. Triaminobenzene resulting from the hydrogenation without isolation undergoes hydrolysis in the presence of sulfuric acid to furnish phloroglucinol. The relationship between the phloroglucinol yield and the molar ratio of sulfuric acid and trinitrobenzene was also explored. The optimum sulfuric acid-to-trinitrobenzene ratio was found to be 2.0-2.4 mol/mol. The overall yield of phloroglucinol was 76% on a trinitrobenzene basis.

Improved Method for the Determination of Ethylenebisdithiocarbamate Residues in Plants, Fruits, and Vegetables

1967 ◽  
Vol 50 (5) ◽  
pp. 1102-1108
Author(s):  
Charles F Gordon ◽  
Richard J Schuckert ◽  
William E Bornak
Keyword(s):  
Sulfuric Acid ◽  
Fruits And Vegetables ◽  
Analytical Procedure ◽  
Improved Method ◽  
Modified Method ◽  
Fungicide Residues ◽  
Crop Types ◽  
Large Representative

Abstract A modified method for the determination of dithiocarbamate fungicide residues on crops is presented. A large representative subsample of the frozen crop is blended in ice-cold deaerated water and an aliquot of the homogenate is added to the analytical apparatus containing hot 5 0% sulfuric acid. Dithiocarbamates are decomposed to evolve CS2 which is removed by a continuous gentle air-sweep from the digestion flask. Variations in technique allow the analysis of dithiocarbamate fungicide residues in several ranges, 1-10, 10-200, and 200-1000 /ig maneb. Recoveries from a wide variety of crops averaged 70 to 103%. Certain crop types present low recoveries and/or high apparent control values, but modifications in the analytical procedure are successful in solving these problems.

scholarly journals The relationship of oleic acid/albumin molar ratio and clinical outcomes in leptospirosis

Heliyon ◽  
2021 ◽  
Vol 7 (3) ◽  
pp. e06420
Author(s):  
Caroline Azevedo Martins ◽  
Maria Conceição B dos Santos ◽  
Cassiano Felippe Gonçalves-de-Albuquerque ◽  
Hugo Caire Castro-Faria-Neto ◽  
Mauro Velho Castro-Faria ◽  
...  
Keyword(s):  
Oleic Acid ◽  
Clinical Outcomes ◽  
Molar Ratio ◽  
Relationship Of ◽  
The Relationship

scholarly journals Optimized acid hydrolysis of the polysaccharides from the seaweed Solieria filiformis (Kützing) P.W. Gabrielson for bioethanol production

2017 ◽  
Vol 39 (4) ◽  
pp. 423 ◽  
Author(s):  
George Meredite Cunha de Castro ◽  
Norma Maria Barros Benevides ◽  
Maulori Curié Cabral ◽  
Rafael De Souza Miranda ◽  
Enéas Gomes Filho ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Sulfuric Acid ◽  
Acid Hydrolysis ◽  
Kinetic Parameters ◽  
Renewable Resource ◽  
Bioethanol Production ◽  
Seaweed Species ◽  
Mild Conditions ◽  
Hydrolysis Of ◽  
Solieria Filiformis

 The seaweeds are bio-resource rich in sulfated and neutral polysaccharides. The tropical seaweed species used in this study (Solieria filiformis), after dried, shows 65.8% (w/w) carbohydrate, 9.6% (w/w) protein, 1.7% (w/w) lipid, 7.0% (w/w) moisture and 15.9% (w/w) ash. The dried seaweed was easily hydrolyzed under mild conditions (0.5 M sulfuric acid, 20 min.), generating fermentable monosaccharides with a maximum hydrolysis efficiency of 63.21%. Galactose and glucose present in the hydrolyzed were simultaneously fermented by Saccharomyces cerevisiae when the yeast was acclimated to galactose and cultivated in broth containing only galactose. The kinetic parameters of the fermentation of the seaweed hydrolyzed were Y(P⁄S) = 0.48 ± 0.02 g.g−1, PP = 0.27 ± 0.04 g.L−1.h−1, h = 94.1%, representing a 41% increase in bioethanol productivity. Therefore, S. filiformis was a promising renewable resource of polysaccharides easily hydrolyzed, generating a broth rich in fermentable monosaccharides for ethanol production. 

scholarly journals Modelling the contribution of sea salt and dimethyl sulfide derived aerosol to marine CCN

2002 ◽  
Vol 2 (1) ◽  
pp. 17-30 ◽  
Author(s):  
Y. J. Yoon ◽  
P. Brimblecombe
Keyword(s):  
Sulfuric Acid ◽  
Dimethyl Sulfide ◽  
Marine Boundary Layer ◽  
Cloud Condensation Nuclei ◽  
Accommodation Coefficient ◽  
Sea Salt ◽  
Wind Speeds ◽  
Transfer Processes ◽  
Clean Air ◽  
The Relationship

Abstract. The concentration of cloud condensation nuclei (CCN) in the marine boundary layer (MBL) was estimated from dimethyl sulfide (DMS) flux, sea salt (SS) emission, and aerosols entrained from the free troposphere (FT). Only under clean air conditions, did the nucleation of DMS derived sulfur (DMS CCN) contribute significantly to the MBL CCN. The accommodation coefficient for sulfuric acid mass transfer was found to be a very important parameter in the modeling the contribution of DMS to MBL CCN. The relationship between seawater DMS and MBL CCN was found to be non-linear mainly due to the transfer processes of sulfuric acid onto aerosols. In addition, sea salt derived CCN (SS CCN) and entrained aerosol from the FT (FT CCN) affected the MBL CCN directly, by supplying CCN, and indirectly, by behaving as an efficient sink for sulfuric acid. The SS CCN explained more than 50% of the total predicted MBL CCN when wind speeds were moderate and high. Sea salt and FT aerosol may often be more efficient sources of MBL CCN than DMS.

scholarly journals STUDY OF THE PROCESS OF OXIDATIVE DESULFURIZATION OF DIESEL FUEL IN THE PRESENCE OF CO-CATALYSTS

2021 ◽  
pp. 88-96
Author(s):  
D. Muktaly ◽  
◽  
Zh.K. Myltykbaeva ◽  
M.B. Smaiyl ◽  
◽  
...  
Keyword(s):  
Sulfuric Acid ◽  
Transition Metals ◽  
Diesel Fuel ◽  
Oxidation Process ◽  
Oxidative Desulfurization ◽  
Sodium Molybdate ◽  
Molar Ratio ◽  
Petrochemical Plant ◽  
Continuous Growth ◽  
Diesel Fractions

Continuous growth in consumption of oil in the world, as well as ever-increasing quality requirements stimulate the search for new scientific and technological solutions to directionally affect the characteristics of petroleum products, including their chemical composition. The advantages of oxidative desulfurization before hydrotreating are the absence of the need to use hydrogen, as well as small capital and energy costs, since the method does not require high temperatures and pressures. The purpose of this work was to study the oxidation process of diesel fuel and to search for the optimal mode of oxidative desulfurization of diesel fuel in the presence of transition metals salts with the addition of mineral acids. The object of the study is a straight-run diesel fraction of the Pavlodar Petrochemical Plant with boiling temperatures of 180-350°C. The oxidation process was carried out with hydrogen peroxide in the presence of salts of the transition metals molybdenum, vanadium and tungsten. The article defined the basic physico-chemical characteristics of straight-run and desulfurized diesel fractions. The optimal catalyst (Na2MoO4) was selected at a molar ratio of metal to sulfur of 1:100 for the oxidation process of straight-run diesel fractions. As a result of oxidative desulfurization of diesel fuel in the presence of sodium molybdenum perox complexes, the total sulfur content decreased by 42.9%, and with the addition of sulfuric acid by 56.5%. An increase in the cetane index from 56.3 to 58.6 was revealed in the presence of sodium molybdate with the addition of sulfuric acid.

scholarly journals Linking the lithogenic, atmospheric, and biogenic cycles of silicate, carbonate, and organic carbon in the ocean

2009 ◽  
Vol 6 (4) ◽  
pp. 6579-6599
Author(s):  
S. V. Smith ◽  
J.-P. Gattuso
Keyword(s):  
Carbon Storage ◽  
Chemical Weathering ◽  
Dissolved Inorganic Carbon ◽  
North Pacific Ocean ◽  
Atmospheric Co2 ◽  
Molar Ratio ◽  
Co2 Uptake ◽  
Organic C ◽  
Co2 Gas ◽  
The Relationship

Abstract. Geochemical theory describes long term cycling of atmospheric CO2 between the atmosphere and rocks at the Earth surface in terms of rock weathering and precipitation of sedimentary minerals. Chemical weathering of silicate rocks takes up atmospheric CO2, releases cations and HCO3− to water, and precipitates SiO2, while CaCO3 precipitation consumes Ca2+ and HCO3− and releases one mole of CO2 to the atmosphere for each mole of CaCO3 precipitated. At steady state, according to this theory, the CO2 uptake and release should equal one another. In contradiction to this theory, carbonate precipitation in the present surface ocean releases only about 0.6 mol of CO2 per mole of carbonate precipitated. This is a result of the buffer effect described by Ψ, the molar ratio of net CO2 gas evasion to net CaCO3 precipitation from seawater in pCO2 equilibrium with the atmosphere. This asymmetry in CO2 flux between weathering and precipitation would quickly exhaust atmospheric CO2, posing a conundrum in the classical weathering and precipitation cycle. While often treated as a constant, Ψ actually varies as a function of salinity, pCO2, and temperature. Introduction of organic C reactions into the weathering-precipitation couplet largely reconciles the relationship. ψ in the North Pacific Ocean central gyre rises from 0.6 to 0.9, as a consequence of organic matter oxidation in the water column. ψ records the combined effect of CaCO3 and organic reactions and storage of dissolved inorganic carbon in the ocean, as well as CO2 gas exchange between the ocean and atmosphere. Further, in the absence of CaCO3 reactions, Ψ would rise to 1.0. Similarly, increasing atmospheric pCO2 over time, which leads to ocean acidification, alters the relationship between organic and inorganic C reactions and carbon storage in the ocean. Thus, the carbon reactions and ψ can cause large variations in oceanic carbon storage with little exchange with the atmosphere.

scholarly journals Utilizing Gaze Behavior for Inferring Task Transitions Using Abstract Hidden Markov Models

2016 ◽  
Vol 19 (58) ◽  
pp. 1
Author(s):  
Daniel Fernando Tello Gamarra
Keyword(s):  
Markov Model ◽  
Hidden Markov Model ◽  
Hidden Markov Models ◽  
Markov Models ◽  
Hidden Markov ◽  
Hand Movement ◽  
Gaze Behavior ◽  
Improved Method ◽  
The Relationship

We demonstrate an improved method for utilizing observed gaze behavior and show that it is useful in inferring hand movement intent during goal directed tasks. The task dynamics and the relationship between hand and gaze behavior are learned using an Abstract Hidden Markov Model (AHMM). We show that the predicted hand movement transitions occur consistently earlier in AHMM models with gaze than those models that do not include gaze observations.

Investigation on the recycling of sulfuric acid from pretreatment of cellulose for nanocellulose preparation

TAPPI Journal ◽  
2020 ◽  
Vol 19 (2) ◽  
pp. 103-111
Author(s):  
CHAOYU DUAN ◽  
YANGYANG PENG ◽  
SHIYU FU ◽  
LUCIAN LUCIA
Keyword(s):  
Thermal Stability ◽  
Sulfuric Acid ◽  
Zeta Potential ◽  
Surface Properties ◽  
Value Chain ◽  
Solid Residue ◽  
Number Of Cycles ◽  
The Relationship

Sulfuric acid is often used to pretreat cellulose prior to homogenization and conversion to nanocellulose. It would be economically significant to reuse the acid to close the overall value chain loop. The target of this work was to investigate the effect of recovery and recycling frequency of sulfuric acid from the pretreatments on the pretreatment yield of water-insoluble cellulose solid residue, and to explore the relationship between the nanocellulose size prepared by recovery of acid and number of cycles. The surface properties of the nanocelluloses were measured, including content of sulfate groups, absolute zeta potential, crystallinity, and thermal stability.

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