Role Of HCl Research Articles

Thermodynamic Analysis of Chloride Corrosion in Steel for Energy System Applications in Fe-O-Cl-Na Environments

The assumptions of contemporary energy policies are increasing the share of renewable energy sources. Biomass combustion is developing as an alternative to fossil fuels. However, it faces challenges such as limited corrosion resistance of steel boiler components due to chloride compounds in flue gases and fly ash. This paper provides a comprehensive thermodynamic analysis of chloride-induced corrosion in steel in the Fe-O-Cl-Na environment, focusing on the influence of steam concentration in the gas phase. The study was performed by using the general thermodynamic rules, the thermodynamic properties of the pure components involved in the reaction, and the properties of the solutions formed in the liquid and gas phases. The study also examined the impact of alkali metal chlorides, particularly NaCl, on the formation of NaFeO2 in the passive oxide scale layer Fe3O4/Fe2O3. Furthermore, it investigated the condensation of NaCl vapour formation of low-melting eutectic mixtures in deposits and the resulting consequences on the corrosion process. The role of HCl in the chlorination and oxidation process of steel in melted ash deposits was also discussed. The presented thermodynamic analysis was compared with assumptions of an “active oxidation” model. This study can be a valuable resource for experimental research planning and a guide for preventing corrosion in industrial settings.

Fe(III)‐Catalyzed, Cyclizative Coupling between 2‐Alkynylbenzoates and Carbinols: Rapid Generation of Polycyclic Isocoumarins and Phthalides and Mechanistic Study

AbstractFeCl3 catalyzed, highly regioselective cyclizative coupling of internal alkynes with alcohols has been reported for the rapid synthesis of structurally divergent, complex isocoumarins and phthalides respectively in intermolecular and intramolecular fashion. This strategy exhibited very high substrate scope and efficiency and proceeds through the simultaneous formation of C−O and C−C bonds. Observations from a series of control experiments supported a) the mechanism as Lewis acid catalyzed dual activation of ester and alcohol, b) the role of carbocation for the enhanced rates of cyclization, i. e., activation of alkyne by carbocation, and c) no role of HCl in the reported cascade process.magnified image

Highly stable ethylene glycol-capped blue-emitting antimony selenide quantum dots via hydrothermal approach

A low-temperature hydrothermal method is adopted for the preparation of highly fluorescent antimony selenide quantum dots. Solution synthesis of such quantum dots with strong blue fluorescence is reporting for the first time and stands as the novelty of this work. Role of HCl and its significance in the quantum dot formation have been studied in detail. The presence of HCl is inevitable as it promotes the Sb2Se3 quantum dots formation and is a major inference obtained. Solution synthesis of Sb2Se3 involves two phases: nanoparticle formation and their partial dissolution—recrystallization to form quantum dots. Synthesized Sb2Se3 nanoparticles in 1 h have uniform morphology tending to one-dimensional growth confirmed using SEM and further increase in reaction time resulted in quantum dots with strong blue fluorescence and supramolecular structure in addition to nanoparticles whose formation was justified in support of UV, PL, XPS and Raman spectrum. The quantum dot solution remains stable for more than 20 months without any change in its optical response. Their temperature dependence was also studied to have an insight into size optimization and band-gap tuning. Optical response of this material was utilized for light absorption in solar cell.

A DFT+U study on the oxidative chlorination of CH4 at ceria: the role of HCl

HCl, surface defects and orientations can affect the oxidation activity of CH4 at CeO2 and the selectivity toward different products.

Experimental study on the mechanism of mercury removal with Fe2O3 in the presence of halogens: Role of HCl and HBr

Experiments were conducted in a bench-scale fixed bed reactor with α-Fe2O3 and γ-Fe2O3 samples to investigate the mechanism of Hg0 oxidation in the presence of HCl at 80–680°C respectively. HCl is one of the main impurities in coal-derived fuel gas and its contribution to Hg0 removal is complex and necessary to research. The experimental results showed that the Hg0 removal mechanism with HCl could probably be divided into three stages based on the reaction temperature. At low temperature, the Eley–Rideal mechanism with HCl pre-adsorption was the most probable Hg0 oxidation pathway. As the temperature increased more than 280°C, Hg0 removal efficiency differs significantly on α-Fe2O3 and γ-Fe2O3, and the most suitable mechanism was Langmuir–Hinshelwood. With the increasing temperature to 680°C, the homogeneous reaction between HCl and Hg0 as well as Langmuir–Hinshelwood are responsible for the transformation of Hg0. We also discovered that the reaction time played a significant impact on the Hg0 removal at low temperature, and caused the secondary mercury removal efficiency owing to the probable product of FeCl3. Additionally, HBr was adopted to compare with HCl, which obviously enhanced the Hg0 oxidation on α-Fe2O3.

Role of HCl in Atomic Layer Deposition of TiO2Thin Films from Titanium Tetrachloride and Water

Atomic layer deposition (ALD) of TiO2 thin film from TiCl4 and H2O has been intensively studied since the invention of ALD method to grow thin films via chemical adsorptions of two precursors. However the role of HCl which is a gaseous byproduct in ALD chemistry for TiO2 growth is still intriguing in terms of the growth mechanism. In order to investigate the role of HCl in TiO2 ALD, HCl pulse and its purging steps are inserted in a typical sequence of TiCl4 pulse-purge-H2O pulse-purge. When they are inserted after the first-half reaction (chemisorption of TiCl4), the grown thickness of TiO2 becomes thinner or thicker at lower or higher growth temperatures than 300 o C, respectively. However the insertion after the second-half reaction (chemisorption of H2O) results in severely reduced thicknesses in all growth temperatures. By using the result, we explain the growth mechanism and the role of HCl in TiO2 ALD.

A Possible Role for Gastroprotectives on Aspirin-Induced Gastric Ulcer in Rats

Background: Gastric ulcer is a discontinuity in the gastric mucosa that occurs due to imbalance between gastric mucosal protective factors and aggressive factors. The Aim of the present work was to test and compare the protective effects of an antisecretory H 2 receptor blocker; ranitidine and other recently suggested gastroprotective drugs: L-arginine; a precursor of NO, zinc sulfate; an anti-inflammatory antioxidant agent and pioglitazone; a PPAR-g agonist, on a rat model of aspirin induced gastric ulcer. Methods: Acute gastric lesion was induced in rats by a single oral dose of aspirin 300mg/ kg body weight. L-arginine 200mg / kg b. wt, zinc sulfate 80 mg/ kg b. wt, and pioglitazone 10 mg / kg b. wt. were given alone and in combination with ranitidine 50 mg / kg b. wt for 3 days before induction of gastric lesion. Results: Aspirin induced a significant increase in gastric mucosal lesion score and free and total gastric hydrochloric acid with a significant decrease in gastric nitric oxide and mucin levels as compared to normal group. A significant increase in gastric malondialdhyde and decrease in reduced glutathione as compared to normal group. L-arginine, zinc sulfate, and pioglitazone produced improvement of most of the measured parameters as compared to non-treated group. Combination of L-arginine and ranitidine was superior in prophylaxis against aspirin-induced gastric ulcer when compared to the effects of each drug used individually, and the other studied combinations. Conclusion: The role of HCl and NO seems more important in the pathogenesis of aspirin induced gastric ulcer, as evidenced by the better protective effects of combination of ranitidine and L-arginine in comparison to the ranitidine with either zinc sulfate or pioglitazone.

Large‐Scale Synthesis of Silver Nanocubes: The Role of HCl in Promoting Cube Perfection and Monodispersity

Large‐Scale Synthesis of Silver Nanocubes: The Role of HCl in Promoting Cube Perfection and Monodispersity

Large‐Scale Synthesis of Silver Nanocubes: The Role of HCl in Promoting Cube Perfection and Monodispersity

Large‐Scale Synthesis of Silver Nanocubes: The Role of HCl in Promoting Cube Perfection and Monodispersity

Ipso Substitution as a Route to Benzo[c]quinolizines and 4-Hydroxycoumarins

A convenient ipso substitution method for the preparation of benzo[c]quinolizine (2) and 4-hydroxy-3-(2'-pyridyl)coumarin (3) has been developed. The intramolecular nucleophilic substitution reaction of 3-oxo-2-(2'-pyridyl)-(2-halophenyl)propanoate (1) in refluxing xylenes gives initially benzo[c]quinolizine, while further heating results in the formation of 4-hydroxycoumarin. A mechanism has been proposed to rationalize the two competitive reaction pathways, and the role of HCl is discussed. Under optimized conditions, seven benzo[c]quinolizines and five coumarins were prepared in moderate to good yields.

Thermal dehydrochlorination and stabilisation of poly(vinylchoride) in solution: Part II—Effects of HCl readdition reaction

The role of HCl during the thermal degradation of PVC has been investigated. It was shown that HCl catalyses the degradation as well as itself adding to the conjugated sequences in the degraded PVC. There is competition between these two reactions. At the beginning of the dehydrochlorination, the first reaction is dominant, while readdition becomes more important as double bonds are formed. Metal or organometallic chlorides may significantly influence these effects. The reverse reaction is catalysed by organotin chlorides of high Lewis acidity. These retardation effects are a pure consequence of the partial and random reversible thermal decomposition of PVC; they do not result from the configurational rearrangement by the readdition reaction nor by the internal isomerisation assisted by tin compounds.

The role of HCl in the passivation of MOS structures

A model is proposed for the reduction of sodium ion instabilities in SiO 2 films grown in the presence of HCl. Based on the Na distribution after drift in “HCl oxides”, on the temperature dependence of the passivating characteristics, and on the necessity of O 2 for the development of passivation, it is concluded that the passivating species is a Si-O-Cl complex, where the chlorine is probably substituting for oxygen. The neutralization of the Na + ions is presumed to take place through the migration of oxygen vacancies.