Acid Strength
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2022 ◽  
Vol 34 (1) ◽  
pp. 1-12
Author(s):  
Fatma Maruddin ◽  
Wahyu Triputra Hasim ◽  
Nursida ◽  
Ratmawati Malaka ◽  
Hikmah Muhammad Ali ◽  
...  

The aims of the present study were to characterize physicochemical characteristics and chemical structures by Fourier Transform Infrared (FTIR), and mark dissolved protein content, microstructure, and moisture content of potassium caseinate prepared by drying methods and acid strength. The experiment was arranged according to factorial complete randomized design with triplicates, while data from FTIR and microstructure analysis was presented descriptively. The results demonstrated that acids and drying methods for preparing potassium caseinate could increase antioxidant activity, a* score (reddish) and b* score (yellowish). Specifically, freeze-drying method coupled with acid treatments accounted for reducing moisture content but improved viscosity and microstructural properties. Briefly, we could argue that drying techniques and acids established noticeable effects on the quality of potassium caseinate.


Catalysts ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 1074
Author(s):  
Hanbyeol Kim ◽  
Jungho Jae

In this work, sulfated and phosphated metal oxides were studied as catalysts for the Diels–Alder cycloaddition of biomass-derived 2,5-dimethylfuran (DMF) and ethylene to understand the effect of acid strength on the reaction. Four catalysts with varied acidity, namely sulfated SiO2, sulfated TiO2, phosphated SiO2, and phosphated TiO2, were prepared via wet impregnation using sulfuric acid and phosphoric acid as precursors, and their structural and acid properties were examined using X-ray diffraction, Brunauer–Emmett–Teller analysis, Fourier transform infrared spectroscopy, solid state 31P magic angle spinning nuclear magnetic resonance spectroscopy, and temperature programmed desorption of ammonia. The results revealed that the acidity of the catalysts was largely influenced by the type of the acid functional group and the support as well as the calcination temperature. The conversion of DMF and the selectivity toward p-Xylene (PX) were generally correlated with the total acid site density and the acid–metal oxide interaction strength, which in turn affected the acid strength. Overall, phosphated SiO2 and TiO2 calcined at 773 K were identified as the most active and selective catalysts, exhibiting a high PX selectivity of over 70% and DMF conversion of 80% at 523 K after 6 h. The origin of the stability of the highly active phosphated catalysts was also investigated in detail.


2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Pandian Manjunathan ◽  
Varsha Prasanna ◽  
Ganapati V. Shanbhag

AbstractThe generation of Brønsted (Sn–OH) and Lewis (coordinatively unsaturated metal centers) acidic sites on the solid surface is a prime demand for catalytic applications. Mesoporous materials are widely employed as catalysts and supports owing to their different nature of acidic sites. Nevertheless, the procedure adopted to generate acid functionalities in these materials involves tedious steps. Herein, we report the tunable acidic sites containing Brønsted sites with relatively varied acid strength in tin oxide by employing soft template followed by simple thermal treatment at various temperatures. The readily accessible active sites, specifically Brønsted acidic sites distributed throughout the tin oxide framework as well as mesoporosity endow them to perform with exceptionally high efficiency for epoxide ring opening reactions with excellent reusability. These features promoted them to surpass stannosilicate catalysts for the epoxide ring opening reactions with alcohol as a nucleophile and the study was extended to aminolysis of epoxide with the amine. The existence of relatively greater acid strength and numbers in T-SnO2-350 catalyst boosts to produce a high amount of desired products over other tin oxide catalysts. The active sites responsible in mesoporous tin oxide for epoxide alcoholysis were studied by poisoning the Brønsted acidic sites in the catalyst using 2,6-lutidine as a probe molecule.


2021 ◽  
Author(s):  
David Spence

Chloride extraction from nitric acid is an important technique for reducing corrosion of stainless steel. However, there has been a limited amount of research conducted in this area. Pumping ozone-enriched air through nitric acid is a corrosion reduction method that is widely used in the nuclear fuel manufacturing industry, including the Blind River Refinery (BRR), to purge chlorine gas out of the acid. However, this method has been shown to produce significant environmental impacts. Overall, it is an inconsistent and cost-deficient method for reducing chloride corrosion of stainless steel in nitric acid mediums below 7.2M (37.0% volume). This thesis builds on existing literature and demonstrates that oxidizing chloride ions in nitric acid using oxygen, nitric oxide and nitrous oxide is an efficient and cost-effective chloride extraction method for the case study (BRR). It was shown that the level of chloride extraction from nitric acid increased significantly when the acid strength was elevated above 8.4M (42.0%volume) and sparged with various oxidants. The most effective oxidants at this nitric acid strength were: oxygen, ozone, nitric oxide and nitrous oxide. Nitric oxide and nitrous oxide can be produced by sparging 43.0% nitric acid with air or sparging 43.0% nitric acid with NOx fumes. In terms of the BRR case study, it was shown that using operational-specific combinations of these methods can drastically reduce the environmental impacts associated with their chloride removal process; significantly increase the level of chloride extraction; reduce energy consumption and operating costs by as much as 54.0%; and reduce material requirements by as much as 80.0%.


2021 ◽  
Author(s):  
David Spence

Chloride extraction from nitric acid is an important technique for reducing corrosion of stainless steel. However, there has been a limited amount of research conducted in this area. Pumping ozone-enriched air through nitric acid is a corrosion reduction method that is widely used in the nuclear fuel manufacturing industry, including the Blind River Refinery (BRR), to purge chlorine gas out of the acid. However, this method has been shown to produce significant environmental impacts. Overall, it is an inconsistent and cost-deficient method for reducing chloride corrosion of stainless steel in nitric acid mediums below 7.2M (37.0% volume). This thesis builds on existing literature and demonstrates that oxidizing chloride ions in nitric acid using oxygen, nitric oxide and nitrous oxide is an efficient and cost-effective chloride extraction method for the case study (BRR). It was shown that the level of chloride extraction from nitric acid increased significantly when the acid strength was elevated above 8.4M (42.0%volume) and sparged with various oxidants. The most effective oxidants at this nitric acid strength were: oxygen, ozone, nitric oxide and nitrous oxide. Nitric oxide and nitrous oxide can be produced by sparging 43.0% nitric acid with air or sparging 43.0% nitric acid with NOx fumes. In terms of the BRR case study, it was shown that using operational-specific combinations of these methods can drastically reduce the environmental impacts associated with their chloride removal process; significantly increase the level of chloride extraction; reduce energy consumption and operating costs by as much as 54.0%; and reduce material requirements by as much as 80.0%.


2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Emanuele Grifoni ◽  
GiovanniMaria Piccini ◽  
Johannes A. Lercher ◽  
Vassiliki-Alexandra Glezakou ◽  
Roger Rousseau ◽  
...  

AbstractChemical reactivity and sorption in zeolites are coupled to confinement and—to a lesser extent—to the acid strength of Brønsted acid sites (BAS). In presence of water the zeolite Brønsted acid sites eventually convert into hydronium ions. The gradual transition from zeolite Brønsted acid sites to hydronium ions in zeolites of varying pore size is examined by ab initio molecular dynamics combined with enhanced sampling based on Well-Tempered Metadynamics and a recently developed set of collective variables. While at low water content (1–2 water/BAS) the acidic protons prefer to be shared between zeolites and water, higher water contents (n > 2) invariably lead to solvation of the protons within a localized water cluster adjacent to the BAS. At low water loadings the standard free energy of the formed complexes is dominated by enthalpy and is associated with the acid strength of the BAS and the space around the site. Conversely, the entropy increases linearly with the concentration of waters in the pores, favors proton solvation and is independent of the pore size/shape.


2021 ◽  
Vol 133 (17) ◽  
pp. 9736-9745
Author(s):  
Gina Noh ◽  
Erwin Lam ◽  
Daniel T. Bregante ◽  
Jordan Meyet ◽  
Petr Šot ◽  
...  

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