Electrolyte Based Modeling of Corrosion Processes in Sulfuric Acid Mixtures – Part 1: Non-Oxidizing Conditions

CORROSION ◽  
10.5006/3872 ◽  
2021 ◽  
Author(s):  
Narasi Sridhar ◽  
Andrzej Anderko
Keyword(s):  
Sulfuric Acid ◽  
Corrosion Rate ◽  
Weight Percent ◽  
Reaction Rates ◽  
Reduction Reaction ◽  
Proton Reduction ◽  
Mole Percent ◽  
Active Dissolution ◽  
Experimental Values ◽  
Electrochemical Model

The corrosion behavior of stainless steels and Ni-base alloys in non-oxidizing sulfuric acid mixtures at concentrations below approximately 30 moles/Kg H2O is modeled. The redox potential in sulfuric acid across a broad concentration range, from 0 to 80 mole percent (0 to 95.6 weight percent), is determined by the proton reduction reaction. Thus, in the absence of other oxidizing species, sulfuric acid behaves as a non-oxidizing (reducing) acid. The calculated corrosion rate, using an electrochemical model up to about 30 moles/Kg H2O (about 75 weight percent) is in agreement with experimental values. The predicted polarization curves of anodic and cathodic processes showed that the alloys in these environments are in active dissolution regime, consistent with experimental data. The model predictions of corrosion rates in H2SO4+HCl, H2SO4+HF, and H2SO4+HCl+HF mixtures are in agreement with weight-loss corrosion data. The corrosion rate of alloys in the non-oxidizing sulfuric acid mixtures correlated to an equivalent alloy composition given by (Ni0.7-Cr0.1+Mo+0.5W). The effect of alloying elements under these conditions may be related to their beneficial effect on active dissolution and proton reduction reaction rates.

scholarly journals Understanding Potential-dependent Competition Between Electrocatalytic Dinitrogen and Proton Reduction Reactions

2021 ◽  
Author(s):  
Changhyeok Choi ◽  
Geun Ho Gu ◽  
Juhwan Noh ◽  
Hyun S. Park ◽  
Yousung Jung
Keyword(s):  
Charge Transfer ◽  
Heterogeneous Catalysts ◽  
Early Stage ◽  
Side Reaction ◽  
Potential Method ◽  
Reaction Rates ◽  
Reduction Reaction ◽  
Metal Catalyst ◽  
Proton Reduction ◽  
Catalyst Surfaces

Abstract One of the key challenges to practical electrochemical N2 reduction reaction (NRR) is to lower the overpotential and suppression of the side reaction known as the hydrogen evolution reaction (HER) during the NRR. The experimental NRR activity has been consistently shown to reach a maximum at early stage before reaching the mass-transfer limit and decreases with large overpotentials for many heterogeneous catalysts. Though the volcano-type current-potential relationship shown for NRR is unusual with limited reaction rates at higher overpotentials, the mechanistic origin has not been clearly explained, making the design principles for practical NRR still lacking. Herein, we investigate the potential-dependent reaction activity of NRR and HER using the constant electrode potential method and microkinetic modeling. It manifests the dominating proton adsorption over dinitrogen at small overpotentials leading to the inadequate reaction selectivity towards NRR at many metal catalyst surfaces. A clear potential-dependent competition between the N2 adsorption and *H formation is characterized by the degree of charge transfer in the adsorption process. It is also demonstrated that the larger charge transfer in *H formation is a general phenomenon applied to all heterogeneous catalyst surfaces considered here, that poses a fundamental challenge to realize practical electrochemical NRR. We suggest several strategies to overcome the latter challenges based on the present understandings.

scholarly journals Comparation of the analytical and experimental models of 304SS corrosion rate in 0.5 m H2SS4 with bee wax propolis extract

2018 ◽  
Vol 38 (2) ◽  
pp. 182-188 ◽  
Author(s):  
Wahyono Suprapto ◽  
Rudy Soenoko ◽  
Femiana Gapsari
Keyword(s):  
Sulfuric Acid ◽  
Corrosion Rate ◽  
Theoretical Calculations ◽  
Reduction Reaction ◽  
Experimental Models ◽  
Propolis Extract ◽  
Data Prediction ◽  
Disaster Data ◽  
Steel Tank ◽  
Transport Vessel

Corrosion in the reservoir and transport vessel often causes a leak that leads to disaster. Data prediction and experimental corrosion in storage technology is very important to prevent damage and reduce maintenance costs. Theoretically, steel tank corrosion by sulfuric acid working medium can be minimized with the formation of sediments oxide by oxidation-reduction reaction. Behavioral inhibition of bee wax propolis on the 304SS in 0.5 M sulfuric acid was carried by potentiodynamic polarization. Based on the polarization testing the corrosion rate of the 304SS in a solution of 0.5 M H2SO4 is at 0.349 g/m2d with the missing mass amounted 5.21 x10 -9 g/s. In experiments, the inhibitor causing less mass loss is equal to 2.28 x 10 -11 g/s. Mass lost without and with inhibitor in this study is also known by theoretical calculations. The mass losses can be used to determine the inhibition efficiency. The calculation of the efficiency theoretically and experimentally gives the same result.

scholarly journals Effect of Chemistry Variations in Plate and Weld Filler Metal on the Corrosion Performance of Ni-Cr-Mo Alloys

2006 ◽  
Author(s):  
David V. Fix ◽  
Rau´l B. Rebak
Keyword(s):  
Sulfuric Acid ◽  
Corrosion Rate ◽  
Filler Metal ◽  
Weight Percent ◽  
Corrosion Performance ◽  
Nickel Chromium ◽  
Immersion Corrosion ◽  
Heat Treated ◽  
Alloy 22 ◽  
G 28

The ASTM standard B 575 provides the requirements for the chemical composition of Nickel-Chromium-Molybdenum (Ni-Cr-Mo) alloys such as Alloy 22 (N06022) and Alloy 686 (N06686). The compositions of each element are given in a range. For example, the content of Mo is specified from 12.5 to 14.5 weight percent for Alloy 22 and from 15.0 to 17.0 weight percent for Alloy 686. It was important to determine how the corrosion rate of welded plates of Alloy 22 using Alloy 686 weld filler metal would change if heats of these alloys were prepared using several variations in the composition of the elements even though still in the range specified in B 575. All the material used in this report were especially prepared at Allegheny Ludlum Co. Seven heats of plate were welded with seven heats of wire. Immersion corrosion tests were conducted in a boiling solution of sulfuric acid plus ferric sulfate (ASTM G 28 A) using both as-welded (ASW) coupons and solution heat-treated (SHT) coupons. Results show that the corrosion rate was not affected by the chemistry of the materials in the range of the standards.

Electro-catalysis of carbon black or titanium sub-oxide supported Pd–Gd towards formic acid electro-oxidation

RSC Advances ◽  
2016 ◽  
Vol 6 (73) ◽  
pp. 68989-68996 ◽  
Author(s):  
Nan He ◽  
Chuanguang Qin ◽  
Rumin Wang ◽  
Shuhui Ma ◽  
Yi Wang ◽  
...  
Keyword(s):  
Aqueous Solution ◽  
Carbon Black ◽  
Formic Acid ◽  
Sodium Borohydride ◽  
Weight Percent ◽  
Reduction Reaction ◽  
Simultaneous Reduction ◽  
Electro Catalysis ◽  
Electro Oxidation ◽  
Supported Pd

Carbon black supported Pd–Gd catalysts (Pd–xGd/C, x is weight percent in catalyst) with different amounts of Gd were prepared by a simultaneous reduction reaction with sodium borohydride in aqueous solution.

Ignition and flame quenching of quiescent fuel mists

1978 ◽  
Vol 364 (1717) ◽  
pp. 277-294 ◽  
Keyword(s):  
Reaction Rates ◽  
Ignition Energy ◽  
Minimum Ignition Energy ◽  
Proposed Model ◽  
Theoretical Predictions ◽  
Quenching Distance ◽  
Experimental Values ◽  
Sole Criterion ◽  
Fuel Vapour ◽  
Level Of Agreement

A model is proposed for the ignition of quiescent multidroplet fuel mists which assumes that chemical reaction rates are infinitely fast, and that the sole criterion for successful ignition is the generation, by the spark, of an adequate concentration of fuel vapour in the ignition zone. From analysis of the relevant heat transfer and evaporation processes involved, ex­pressions are derived for the prediction of quenching distance and minimum ignition energy. Support for the model is demonstrated by a close level of agreement between theoretical predictions of minimum ignition energy and the corresponding experimental values obtained using a specially designed ignition apparatus in which ignition energies are measured for several different fuels, over wide ranges of pressure, mixture composition and mean drop size. The results show that both quenching distance and mini­mum ignition energy are strongly dependent on droplet size, and are also dependent, but to a lesser extent, on air density, equivalence ratio and fuel volatility. An expression is derived to indicate the range of drop sizes over which the proposed model is valid.

scholarly journals Mechanism of Emission Reduction in HSDI Diesel Engine: Split Injection

2015 ◽  
Vol 09 (2) ◽  
Keyword(s):  
Diesel Engine ◽  
Heat Release ◽  
Temporal Distribution ◽  
Reaction Rates ◽  
Chemical Mechanism ◽  
Symmetric Model ◽  
Diesel Combustion ◽  
Split Injection ◽  
Engine Combustion ◽  
Experimental Values

In order to meet the stringent emission standards significant efforts have been imparted to the research and development of cleaner IC engines. Diesel combustion and the formation of pollutants are directly influenced by spatial and temporal distribution of the fuel injected. The development and validation of computational fluid dynamics (CFD) models for diesel engine combustion and emissions is described. The complexity of diesel combustion requires simulation with many complex interacting sub models in order to have a success in improving the performance and to reduce the emissions. In the present work an attempt has been made to develop a multidimensional axe-symmetric model for CI engine combustion and emissions. Later simulations have been carried out using split injection for single, double and three pulses (split injection) for which commercial validation tool FLUENT was used for simulation. The tool solves basic governing equations of fluid flow that is continuity, momentum, species transport and energy equation. Using finite volume method turbulence was modeled by using RNG K-ɛ model. Injection was modeled using La Grangian approach and reaction was modeled using non premixed combustion which considers the effects of turbulence and detailed chemical mechanism into account to model the reaction rates. The specific heats were approximated using piecewise polynomials. Subsequently the simulated results have been validated with the existing experimental values. The peak pressure obtained by simulation for single and double is 10% higher than to that of experimental value. Whereas for triple injections 5% higher than to that of experimental value. For quadruple injection the pressure has been decreased by 10% when compared to triple injection.NOX have been decreased in simulation for single, double and triple injections by 15%, 28% and 20%.For quadruple injection NOX were reduced in quadruple injection by 20% to that of triple injection. The simulated value of soot for single, double and triple injections are 12%, 22% and 12% lesser than the experimental values. For quadruple injection the soot levels were almost negligible. The simulated heat release rates for single, double and triple were reduced by 12%, 18% and 11%. For quadruple injection heat release is reduced same as to that of triple injection.

scholarly journals Study of the regularity of the process of decomposition of apatite with sulfuricacid at the boilingpoint of the solution

2019 ◽  
Vol 58 (4) ◽  
pp. 119-122
Author(s):  
Rauf F. Sabirov ◽  
◽  
Alexey F. Makhotkin ◽  
Yury N. Sakharov ◽  
Igor A. Makhotkin ◽  
...  
Keyword(s):  
Sulfuric Acid ◽  
Phosphoric Acid ◽  
Boiling Point ◽  
Batch Reactor ◽  
Material Balance ◽  
Mercury Thermometer ◽  
Experimental Values ◽  
Kinetics Of ◽  
Liquid And Solid Phases ◽  
Phosphoric Acids

Experimental research of the kinetics of the decomposition process of Kovdorsky apatite with a size = 0.16 mm with sulfuric acid in a 1 dm3 batch reactor. Phosphoric acid with the concentration of 68.6 % wt and the sulfuric acid with the concentration of 12.3% wt in stoichiometric amount was introduces at the beginning of the process. The process was carried out at a ratio of liquid and solid phases 2.5:1 respectively at the boiling point of the mixture equal to 136 °C. The observing the progress was carried out according to the method of joint designation of sulfuric and phosphoric acids by titrimetric analysis. With methyl orange and then phenolphthalein 2 titration jumps were recorded, the first of which corresponded to the neutralization of sulfuric acid to Na2SO4 and phosphoric acid to NaH2PO4, the second to the neutralization of NaH2PO4 to Na2HPO4. The change in temperature of the reaction mixture was fixed during the process using a mercury thermometer. In the analysis of the derived experimental values of specified parameters that the boiling point decreases from 136 to 133.1 оС within 50 minutes during the process. A comparison of the reported values with the concentration values of sulfuric and phosphoric acids measured during the process shows that the change in boiling point of the reaction mixture is proportional to the change in the concentrations of sulfuric and phosphoric acids. This model is a closed system that provides thermal insulation and no loss of material balance. Thus, the kinetics of the decomposition of apatite with sulfuric acid at the boiling point can be monitored by the temperature change under specified conditions.

scholarly journals Studies on Epoxidation of Tung oil with Hydrogen Peroxide Catalyzed by Sulfuric Acid

2020 ◽  
Vol 15 (3) ◽  
pp. 674-686
Author(s):  
Eni Budiyati ◽  
Rochmadi Rochmadi ◽  
Arief Budiman ◽  
Budhijanto Budhijanto
Keyword(s):  
Hydrogen Peroxide ◽  
Sulfuric Acid ◽  
Unsaturated Fatty Acids ◽  
Catalyst Concentration ◽  
Reaction Rates ◽  
Catalytic Reactions ◽  
Side Reactions ◽  
Initial Reaction ◽  
Tung Oil ◽  
Epoxidation Reaction

Tung oil with an iodine value (IV) of 99.63 g I2/100 g was epoxidized in-situ with glacial acetic acid and hydrogen peroxide (H2O2), in the presence sulfuric acid as catalyst. The objective of this research was to evaluate the effect of mole ratio of H2O2 to unsaturated fatty acids (UFA), reaction time and catalyst concentration in Tung oil epoxidation. The reaction kinetics were also studied. Epoxidation was carried out for 4 h. The reaction rates and side reactions were evaluated based on the IV and the conversion of the epoxidized Tung oil to oxirane. Catalytic reactions resulted in higher reaction rate than did non-catalytic reactions. Increasing the catalyst concentration resulted in a large decrease in the IV and an increase in the conversion to oxirane at the initial reaction stage. However, higher catalyst concentration in the epoxidation reaction caused to a decrease in reaction selectivity. The mole ratio of H2O2 to UFA had an influence identical to the catalyst concentration. The recommended optimum mole ratio and catalyst concentration in this study were 1.6 and 1.5%, respectively. The highest conversion was 48.94% for a mole ratio of 1.6. The proposed kinetic model provided good results and was suitable for all variations in reaction temperature. The activation energy (Ea) values were around 5.7663 to 76.2442 kcal/mol. Copyright © 2020 BCREC Group. All rights reserved 

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