Amorphous Polymeric Dithiazine apDTZ Solid Fouling: Critical Review, Analysis and Solution of an Ongoing Challenge in Triazine-Based Hydrogen Sulphide Mitigation

2021 ◽  
Author(s):  
Grahame Taylor ◽  
Jonathan Wylde ◽  
Walter Samaniego ◽  
Ken Sorbie
Keyword(s):  
Hydrogen Sulphide ◽  
Reaction Pathway ◽  
Theoretical Calculations ◽  
Mechanism Of Formation ◽  
Review Analysis ◽  
Operational Problem ◽  
Depth Study ◽  
The Common ◽  
By Products ◽  
A Current

Abstract Despite attempts to inhibit or avoid the formation of fouling deposits (polymeric amorphous dithiazine or apDTZ for short) from the use of MEA triazine, this remains a major operational problem and limits the use of this most popular and ubiquitous hydrogen sulphide (H2S) scavenger. This paper (a) reviews and summarizes previous work, (b) provides fresh insights into the reaction product and mechanism of formation, (c) proposes an effective method of removal, and (d) proposes some mechanisms of apDTZ digestion. The mechanism of apDTZ formation is discussed and reasoning is provided from a variety of perspectives as to the mechanism of MEA-triazine reaction with H2S. These include basicity and nucleophilic substitution considerations, steric properties and theoretical calculations for electron density. Novel procedures to chemically react with and destroy this solid fouling are presented with an in-depth study and experimental verification of the underlying chemistry of this digestion process. A review of agents to chemically destroy apDTZ is undertaken and a very effective solution has been found in peroxyacetic acid, which is much more powerful and effective than previously suggested peroxides. The structure of amorphous polymeric dithiazine is emphasized and the reason why this fouling cannot be 1,3,5-trithiane is stressed. This work therefore overcomes a current industry misconception by providing insight on two major paradoxes in the reaction pathway; namely i) why the thiadiazine reaction product from tris hydroxyethyl triazine (MEA triazine) is never observed and ii) why does the dithiazine in all cases never progress to the trithiane (3rd sulphur molecule substitution)? The latter issue is probably the biggest misconception in the industry and literature regarding triazine and H2S reactions. Many reasons for this are put forward and the common misconception of "overspent" triazine is refuted. A very effective chemical reaction that results in soluble by-products, counteracting the problems produced by this intractable polymer is found and their composition is proposed and experimentally verified.

The mechanism of formation of 2,7-dimethyl-2,6-octadiene in the synthesis of 3-methylene-7-methyl-1,6-octadiene

1983 ◽  
Vol 48 (7) ◽  
pp. 1864-1866
Author(s):  
Jan Bartoň ◽  
Ivan Kmínek
Keyword(s):  
Mass Spectrometry ◽  
Nmr Spectroscopy ◽  
Alkali Metal ◽  
Chromatographic Analysis ◽  
Solid Phase ◽  
Reaction Pathway ◽  
Mechanism Of Formation ◽  
Gas Chromatographic Analysis ◽  
C Nmr ◽  
Visual Observations

2,7-Dimethyl-2,6-octadiene is formed in the catalytic solution for the dimerization of 2-methyl-1,3-butadiene to β-myrcene (3-methylene-7-methyl-1,6-octadiene), as revealed by mass spectrometry and 13C NMR spectroscopy. Visual observations together with the results of gas chromatographic analysis of the catalytic solution suggest that the formation of 2,7-dimethyl-2,6-octadiene is associated with the transition of the alkali metal (sodium) from the solid phase into the solution. A reaction pathway is suggested accounting for the formation of 2,7-dimethyl-2,6-octadiene in the system.

scholarly journals Initial Survey of Pesticide Residues in Baby’s food and The Exceedances of Maximum Residual Limit (MRLs)

2018 ◽  
Vol 5 (1) ◽  
Author(s):  
Oluwaseun Babalola ◽  
Ajoke Raji
Keyword(s):  
Pesticide Residues ◽  
Potential Interaction ◽  
Developmental Phase ◽  
The Status ◽  
The Common ◽  
Initial Survey ◽  
By Products ◽  
Storage Pest ◽  
Food Produce ◽  
Infants And Young Children

Remnant or by-products of pesticides arising from the field or storage pest applications sometimes find their ways into the final food produce. They are called pesticide residues. Studies have shown the occurrence of these residues in various food produce including tea, fruits, vegetables, beverages and even baby and infants food. With about 800 pesticides permitted for use globally, residue becomes almost inevitable. For the infants, and young children, the health effects at that critical developmental phase could be severe and irreversible. This is because quantitative and qualitative differences in pesticides absorption, metabolism, detoxification and excretion relative to adults, make the children more susceptible due to much higher kg per body weight. This study assessed the pesticide residues in the common baby food and compared with international maximum residual limits. Using gas chromatography with mass spectrometric detection, five infant and baby’s food tagged A, B, C, D and E were analyzed. In all, multiple residues involving various twenty five pesticides were detected in the five food products. Fifteen of the pesticides including resmethrin (0.0002 µg/g), chlorpyrifos (0.0002 µg/g), allethrin (0.0004 µg/g), piperonyl butoxil (0.0003 µg/g), cyfluthrin (0.0001 µg/g), chlorpyrifos methyl (0.0002 µg/g), diclorovos (0.0001 µg/g), fluridane (0.0002 µg/g), fludioxonil (0.0002 µg/g and 0.0001 µg/g), lindane (0.0002 µg/g), daminozide (0.0002 µg/g), methy paraoxon (0.0001 µg/g) and DDE.p.p (0.0002 µg/g and 0.0001 µg/g) were above the WHO and USEPA maximum residual limits. The potential interaction of different mixtures for those pesticides that are below international residual limits as well as the occurrence of those at concentrations above these standards called for serious concerns, giving their critical effects on nervous, endocrine and immune systems. Further studies must be encouraged to determine the status of residue in other foods and the elimination of these residues, particularly in the infants and baby’s food.

scholarly journals Multi Component Reactions under Increased Pressure: On the Mechanism of Formation of Pyridazino[5,4,3-de][1,6]naphthyridine Derivatives from Reaction of Malononitrile, Aldehyde and 2-Oxoglyoxalarylhydrazones in Q-Tubes

2017 ◽  
Author(s):  
Majdah A. AL-Johani ◽  
Khadijah M. Al-Zaydi ◽  
Sameera M. Mousally ◽  
Norah F. Alqahtani ◽  
Mohamed H. Elnagdi
Keyword(s):  
Crystal Structure ◽  
Reaction Pathway ◽  
Aromatic Aldehydes ◽  
Reaction Products ◽  
Mechanism Of Formation ◽  
X Ray ◽  
Alternate Pathway ◽  
Considerable Research ◽  
Increased Pressure ◽  
Chemical Evidence

The considerable biological and medicinal activities of pyridazines has stimulated considerable research on efficient syntheses of these derivatives. In the last decade, microwave irradiation has generally been used for the energy source. As demonstrated in recent studies, pressure reactor “Q-tubes” may be used to accelerate several of these reactions in a more optimal and safer manner (compared to microwaves). In these studies there has been postulated a pathway for the formation of pyridazino[5,4,3-de][1,6]naphthyridine derivatives . In this paper we consider this pathway, and an alternate pathway, for several reactions. Contrary to the suggestion in these studies the pathway in which initial dimerization of malononitrile was postulated could be excluded based on chemical evidence. The reactions performed were the reaction of arylhydrazonals 1a,b with benzylidinemalononitrile which afforded in Q-tube the 3-acyl-4-aryl-1-phenyl-6-amino-1,4-dihydropyridazines, and the reaction of arylhydrazonals 1a,b, malononitrile 9 and aromatic aldehydes 10a-g in Q-tubes which afforded the tricyclic systems 12a-n whose structure could be established by X-ray crystal structure determination. In conclusion, we have added to the work of the recent studies by excluding a reaction pathway for one of their reaction products.

Mechanisms of sulphate activation and transfer

1991 ◽  
Vol 332 (1263) ◽  
pp. 141-148 ◽  
Keyword(s):  
Reaction Pathway ◽  
General Strategy ◽  
Inorganic Pyrophosphate ◽  
Aps Kinase ◽  
Stereochemical Analysis ◽  
Ping Pong ◽  
Inorganic Sulphate ◽  
Widespread Phenomenon ◽  
The Common ◽  
Enzyme Intermediate

Sulphation of natural products is a widespread phenomenon. Inorganic sulphate is transported into cells and activated by ATP sulphurylase, an enzyme that has been studied by kinetic and stereochemical methods. It has been shown that the enzyme catalyses the displacement of inorganic pyrophosphate by inorganic sulphate from Pa of ATP by a direct 'in line’ mechanism. The adenosine 5'-phosphosulphate formed is then phosphorylated at the 3' position by APS kinase to give 3'-phosphoadenosine 5'- phosphosulphate, the common sulphating species in biology. A general strategy for the synthesis of chiral [ 16 O 17 O 18 O]-sulphate esters has been established and a method developed for their stereochemical analysis by using Fourier Transform Infrared Spectroscopy. The stereochemical course of an aryl sulphotransferase from Aspergillus oryzae has been shown to proceed with retention of configuration at sulphur, supporting a ping pong type mechanism with a sulpho-enzyme intermediate on the reaction pathway.

scholarly journals Platinum–copper single atom alloy catalysts with high performance towards glycerol hydrogenolysis

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Xi Zhang ◽  
Guoqing Cui ◽  
Haisong Feng ◽  
Lifang Chen ◽  
Hui Wang ◽  
...  
Keyword(s):  
Active Sites ◽  
High Performance ◽  
Reaction Pathway ◽  
Theoretical Calculations ◽  
Experimental Studies ◽  
Value Added ◽  
Catalytic Performance ◽  
Single Atom ◽  
Glycerol Hydrogenolysis ◽  
Single Atom Alloy

AbstractSelective hydrogenolysis of biomass-derived glycerol to propanediol is an important reaction to produce high value-added chemicals but remains a big challenge. Herein we report a PtCu single atom alloy (SAA) catalyst with single Pt atom dispersed on Cu nanoclusters, which exhibits dramatically boosted catalytic performance (yield: 98.8%) towards glycerol hydrogenolysis to 1,2-propanediol. Remarkably, the turnover frequency reaches up to 2.6 × 103 molglycerol·molPtCu–SAA−1·h−1, which is to our knowledge the largest value among reported heterogeneous metal catalysts. Both in situ experimental studies and theoretical calculations verify interface sites of PtCu–SAA serve as intrinsic active sites, in which the single Pt atom facilitates the breakage of central C–H bond whilst the terminal C–O bond undergoes dissociation adsorption on adjacent Cu atom. This interfacial synergistic catalysis based on PtCu–SAA changes the reaction pathway with a decreased activation energy, which can be extended to other noble metal alloy systems.

scholarly journals Rhodium(ii)-catalyzed C–H aminations using N-mesyloxycarbamates: reaction pathway and by-product formation

2019 ◽  
Vol 10 (3) ◽  
pp. 718-729 ◽  
Author(s):  
Emna Azek ◽  
Maroua Khalifa ◽  
Johan Bartholoméüs ◽  
Matthias Ernzerhof ◽  
Hélène Lebel
Keyword(s):  
Reaction Pathway ◽  
Product Formation ◽  
Dft Study ◽  
By Products

DFT study to elucidate the mechanism of Rh-catalyzed C–H aminations with N-mesyloxycarbamates and the pathway by which by-products formed.

scholarly journals Detection of Circulating Tumor Cells and Its Application in Prostate Cancer

2020 ◽  
Vol 4 (1) ◽  
pp. 3-7
Author(s):  
Jin-Qi Song ◽  
Ya-Nan Zhou ◽  
Gang-Liang Tu ◽  
Chang-Li Xu ◽  
Hui Xu
Keyword(s):  
Prostate Cancer ◽  
Early Diagnosis ◽  
Tumor Cells ◽  
Circulating Tumor Cells ◽  
Malignant Tumors ◽  
Depth Study ◽  
Tumor Research ◽  
The Common ◽  
Development And Evolution

In recent years, circulating tumor cells have become the focus of tumor research. In-depth study of the role of circulating tumor cells in the genesis, development, and evolution of tumors will be of great significance for the early detection, early diagnosis, early treatment, and prognosis of tumors. Prostate cancer is one of the common male malignant tumors, and the role of circulating tumor cells in prostate cancer has been increasing year by year. This article will focus on the progress of circulating tumor cells detection and its application in prostate cancer.

Flavan derivatives. XVII. Epimerization of the benzylic 4-hydroxyl group in flavan-3,4-diols and the formation of 4-alkyl ethers by solvolysis

1967 ◽  
Vol 20 (10) ◽  
pp. 2151
Author(s):  
JW Clark-Lewis ◽  
LR Williams
Keyword(s):  
Aqueous Media ◽  
Cyclic Ether ◽  
Hydroxyl Group ◽  
Mechanism Of Formation ◽  
Enol Ether ◽  
Mild Conditions ◽  
Ethoxyl Group ◽  
Alkyl Ethers ◽  
By Products ◽  
Thermodynamic Factors

Epimerization and solvolysis of the benzylic 4-hydroxyl group is shown to be a general property of flavan-3,4-diols, and the diols give 4- ethoxyflavan-3-ols with ethanolic hydrochloric acid (1%). The diols are first converted into epimeric mixtures of 3,4-cis- and 3,4-trans-diols and in aqueous media cis-cis-flavan-3,4-diols yield mainly 2,3-cis-3,4- trans-diols. These 2,3-cis-3,4-diols undergo solvolysis to yield 2,3- cis-3,4-trans-4-ethoxyflavan-3-ols in which the 3,4-trans- stereochemistry is controlled by participation of the neighbouring 3ax- hydroxyl group. 2,3-trans-Flavan-3,4-diols give mixtures of trans- trans-diols and 2,3-trans-3,4-cis-diols and solvolysis first yields 2.3-trans-3,4-cis-4-ethoxyflavan-3-ols and then mixtures of the 3,4- cis- and 3,4-trans-ethers; the final proportion of these two ethers is controlled by thermodynamic factors. Solvolysis under mild conditions gives minor products considered to be 3-oxoflavans (or their enols) because of their immediate conversion into antho-cyanidins by cold acids in the presence of air, and from the formation of an enol-ether on prolonged solvolysis under more vigorous conditions. The relevance of these observations to the mechanism of formation of anthocyanidins from flavan-3,4-diols is discussed. Other by-products of solvolysis reactions include a dimeric cyclic ether (dioxan derivative) of 2,3- trans-3,4-cis-7,8,4?-trimethoxyflavan-3,4-diol. The structure and stereochemistry of solvolysis products were established by N.M.R. data; the 4-ethoxyl group in the ethers generally gave rise to an ABX3 multiplet.

Health hazards in the paleontology laboratory

1989 ◽  
Vol 4 ◽  
pp. 30-36
Author(s):  
Katherine M. Thomas
Keyword(s):  
Ionizing Radiation ◽  
Direct Contact ◽  
Medical Literature ◽  
Safety Information ◽  
Health Hazards ◽  
Industrial Wastes ◽  
Toxic Chemicals ◽  
The Common ◽  
The Individual ◽  
By Products

Recent medical literature has pointed out the health hazards associated with industrial wastes and by-products; however, little emphasis has been placed on the dangers inherent in scientific laboratories. These hazards range from direct contact with toxic chemicals and vapors to exposure to ionizing radiation. The damage may be acute or chronic; the effects temporary or residual. What follows is a summary of the common hazards, the basic management of laboratory trauma, and guidelines to prevent injury. The individual preceding chapters also contain safety information relative to the specific lab techniques discussed.

scholarly journals Doing nothing does something: Embodiment and data in the COVID-19 pandemic

2020 ◽  
Vol 7 (1) ◽  
pp. 205395172093393
Author(s):  
Mickey Vallee
Keyword(s):  
Public Health ◽  
Media Studies ◽  
Common Good ◽  
Current Data ◽  
The Body ◽  
Health Crisis ◽  
Critical Data ◽  
The Social ◽  
The Common ◽  
A Current

The COVID-19 pandemic redefines how we think about the body, physiologically and socially. But what does it mean to have and to be a body in the COVID-19 pandemic? The COVID-19 pandemic offers data scholars the unique opportunity, and perhaps obligation, to revisit and reinvent the fundamental concepts of our mediated experiences. The article critiques the data double, a longstanding concept in critical data and media studies, as incompatible with the current public health and social distancing imperative. The data double, instead, is now the presupposition of a new data entity, which will emerge out of a current data shimmer: a long-sustaining transition that blurs the older boundaries of bodies and the social, and establishes new ethical boundaries around the (in)activity and (im)mobility of doing nothing to do something. The data double faces a unique dynamic in the COVID-19 pandemic between boredom and exhaustion. Following the currently simple rule to stay home presents data scholars the opportunity to revisit the meaning of data as something given, a shimmering embodied relationship with data that contributes to the common good in a global health crisis.

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