scholarly journals Refining of Secondary Aluminum: Important Chemical Factors

JOM ◽  
2021 ◽  
Author(s):  
Geoffrey K. Sigworth
Keyword(s):  
Secondary Aluminum ◽  
Important Chemical ◽  
Chemical Factors

Refining of Steel in Converters

2021 ◽  
pp. 550-588
Author(s):  
Olle Wijk
Keyword(s):  
Stainless Steels ◽  
Production Costs ◽  
Important Process ◽  
Processes And Reactions ◽  
Important Chemical ◽  
Different Types ◽  
Chemical Factors ◽  
Argon Oxygen Decarburization

In this chapter steelmaking processes and reactions are covered. A brief historical summary of important process developments is given and different types of converters are described. Then important chemical factors are detailed for the removal of the undesirable elements sulfur and phosphorus, and for the decarburization reactions. The refining of stainless steels in the argon oxygen decarburization (AOD) process is explained in detail, and a model for the AOD process is presented. Example simulations with the model illustrate how process changes may be introduced to improve productivity and reduce production costs.

Characteristics Of The Structure Formation Of Gypsum Binder Modified With Zinc Hydrosilicates

2020 ◽  
pp. 40-46
Keyword(s):  
Synergistic Effect ◽  
Physicochemical Properties ◽  
Structure Formation ◽  
Silicic Acid ◽  
Chemical Properties ◽  
Crystal Formation ◽  
Ability To Act ◽  
Chemical Factors ◽  
Sorption Characteristics

The authors' methodic for assessing the role of chemical and physic-chemical factors during the structure formation of gypsum stone is presented in the article. The methodic is also makes it possible to reveal the synergistic effect and to determine the ranges of variation of controls factors that ensure maximum values of such effect. The effect of a micro-sized modifier based on zinc hydro-silicates on the structure formation of building gypsum is analyzed and corresponding dependencies are found. It is shown that effects of influence of modifier on the properties of gypsum compositions are determined by chemical properties of modifier. Among the mentioned properties are sorption characteristics (which depend on the amount of silicic acid and its state) and physicochemical properties - the ability to act as a substrate during crystal formation. The proposed method can also be extended to other binding substances and materials. This article contributes to the understanding of the processes that occur during the structure formation of composites, which will make it possible to control the structure formation in the future, obtaining materials with a given set of properties.

Copper Catalyzed sp3 C-H α-Acetylation

2019 ◽  
Author(s):  
Otome Okoromoba ◽  
Eun Sil Jang ◽  
Claire McMullin ◽  
Thomas Cundari ◽  
Timothy H. Warren
Keyword(s):  
Natural Products ◽  
Dft Studies ◽  
Alkyl Radicals ◽  
Important Chemical ◽  
Alkyl Electrophiles ◽  
Synthetic Intermediates ◽  
Alkylation Reactions

<p>α-substituted ketones are important chemical targets as synthetic intermediates as well as functionalities in in natural products and pharmaceuticals. We report the sp<sup>3</sup> C-H α-acetylation of sp<sup>3</sup> C-H substrates R-H with arylmethyl ketones ArC(O)Me to provide α-alkylated ketones ArC(O)CH<sub>2</sub>R at RT with <sup>t</sup>BuOO<sup>t</sup>Bu as oxidant via copper(I) β-diketiminato catalysts. Proceeding via alkyl radicals R•, this method enables α-substitution with bulky substituents without competing elimination that occurs in more traditional alkylation reactions between enolates and alkyl electrophiles. DFT studies suggest the intermediacy of copper(II) enolates [Cu<sup>II</sup>](CH<sub>2</sub>C(O)Ar) that capture alkyl radicals R• to give R-CH<sub>2</sub>C(O)Ar under competing dimerization of the copper(II) enolate to give the 1,4-diketone ArC(O)CH<sub>2</sub>CH<sub>2</sub>C(O)Ar.</p>

Copper Catalyzed sp3 C-H α-Acetylation

2019 ◽  
Author(s):  
Otome Okoromoba ◽  
Eun Sil Jang ◽  
Claire McMullin ◽  
Thomas Cundari ◽  
Timothy H. Warren
Keyword(s):  
Natural Products ◽  
Dft Studies ◽  
Alkyl Radicals ◽  
Important Chemical ◽  
Alkyl Electrophiles ◽  
Synthetic Intermediates ◽  
Alkylation Reactions

<p>α-substituted ketones are important chemical targets as synthetic intermediates as well as functionalities in in natural products and pharmaceuticals. We report the sp<sup>3</sup> C-H α-acetylation of sp<sup>3</sup> C-H substrates R-H with arylmethyl ketones ArC(O)Me to provide α-alkylated ketones ArC(O)CH<sub>2</sub>R at RT with <sup>t</sup>BuOO<sup>t</sup>Bu as oxidant via copper(I) β-diketiminato catalysts. Proceeding via alkyl radicals R•, this method enables α-substitution with bulky substituents without competing elimination that occurs in more traditional alkylation reactions between enolates and alkyl electrophiles. DFT studies suggest the intermediacy of copper(II) enolates [Cu<sup>II</sup>](CH<sub>2</sub>C(O)Ar) that capture alkyl radicals R• to give R-CH<sub>2</sub>C(O)Ar under competing dimerization of the copper(II) enolate to give the 1,4-diketone ArC(O)CH<sub>2</sub>CH<sub>2</sub>C(O)Ar.</p>

OCCURRENCE OF THE RISKS FOR DEVELOPMENT OF RESPIRATORY DISEASES IN CHILDREN EXPOSED TO THE CHEMICAL FACTORS OF THE EXPOSURE OF ALUMINA REFINERY- ASSOCIATED BUSINESS ACTIVITY

2019 ◽  
pp. 42-47 ◽  
Author(s):  
M.A. Zemlianova ◽  
I.V. Tikhonova
Keyword(s):  
Respiratory Tract ◽  
Respiratory Diseases ◽  
Inflammatory Diseases ◽  
Allergic Inflammation ◽  
Respiratory Morbidity ◽  
Upper Respiratory Tract ◽  
Negative Effects ◽  
Wide Range ◽  
Chemical Factors ◽  
Chronic Lymphoproliferative Diseases

Alumina refineries are among the leading sources of atmospheric air pollution with a wide range of pollutants hazardous to human respiratory organs. It is relevant to study and evaluate the occurrence of the risks for development of respiratory diseases in children living in the area affected by the emission components of an alumina refinery. We assessed air quality of the area under observation and comparison according to monitoring observations, risk of non-carcinogenic effects from the respiratory organs. The content of chemicals in the blood and urine adequate to risk factors was quantified. The structure of individual groups of respiratory diseases was analyzed. The causal relationships of violations of laboratory parameters with an increased content of chemicals in biological media were evaluated. It was found that an aerogenic exposure of chemical pollutants is formed on the territory with the production of metallurgical alumina. It determines the risk for development of respiratory diseases, exceeding an acceptable level up to 49.9 times. In the exposed children, the content of manganese, chromium, nickel, copper, xylenes, formaldehyde and aluminum, fluoride ion in the urine was increased to 4.2 times in relation to the indices in the comparison group. A high level of additional respiratory morbidity(1.8 times) was revealed. Chronic lymphoproliferative diseases of the nasopharynx and inflammatory diseases of the upper respiratory tract (up to 6.6 times more often), inflammatory diseases with a predominance of the mechanism of allergic inflammation ( up to 2.1 times more often)are more often detected in the framework of the respiratory diseases. Negative effects on the part of the respiratory system in the form of activation of antioxidant processes, the development of an inflammatory reaction, local, general and specific sensitization of the respiratory tract were established. It confirms the occurrence of the risks for the development of respiratory diseases in children in the exposure area of the chemical factors of alumina refinery-associated economic activity.

Lime salts: origin and control in beet processing

2020 ◽  
pp. 282-287
Author(s):  
Jan Maarten de Bruijn
Keyword(s):  
Heat Transfer ◽  
Heat Exchange ◽  
Performance Indicator ◽  
Key Performance Indicator ◽  
Process Measures ◽  
Trouble Shooting ◽  
Important Chemical ◽  
And Control ◽  
Affect Processing ◽  
White Sugar

Lime salts in the thin juice obtained after juice purification is one of the most important chemical KPI’s (Key Performance Indicator) in beet processing. Too high lime salts content will significantly affect processing costs – particularly energy – due to scaling of heat exchange surfaces thus decreasing heat transfer. In addition, high lime salts are at the origin of turbidity and insoluble solids in white sugar. Therefore, it is of the utmost importance to understand the chemistry behind lime salts in beet processing in order to be able preventing too high lime salts contents in thin juice. This paper will explain the details of the chemistry behind the presence of lime salts. Further, a trouble-shooting guide is included to elucidate the different causes for high lime salts contents and how these causes can be identified, as well as the process measures to reduce the lime salts content in thin juice.

scholarly journals Prenatal and Perinatal Environmental Influences Shaping the Neonatal Immune System: A Focus on Asthma and Allergy Origins

2021 ◽  
Vol 18 (8) ◽  
pp. 3962
Author(s):  
Azahara María García-Serna ◽  
Elena Martín-Orozco ◽  
Trinidad Hernández-Caselles ◽  
Eva Morales
Keyword(s):  
Immune System ◽  
Immune Cell ◽  
Mode Of Delivery ◽  
Environmental Influences ◽  
Pet Ownership ◽  
System A ◽  
Neonatal Immune System ◽  
Chemical Factors ◽  
Asthma And Allergy

It is suggested that programming of the immune system starts before birth and is shaped by environmental influences acting during critical windows of susceptibility for human development. Prenatal and perinatal exposure to physiological, biological, physical, or chemical factors can trigger permanent, irreversible changes to the developing immune system, which may be reflected in cord blood of neonates. The aim of this narrative review is to summarize the evidence on the role of the prenatal and perinatal environment, including season of birth, mode of delivery, exposure to common allergens, a farming environment, pet ownership, and exposure to tobacco smoking and pollutants, in shaping the immune cell populations and cytokines at birth in humans. We also discuss how reported disruptions in the immune system at birth might contribute to the development of asthma and related allergic manifestations later in life.

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