Kinetics of disproportionation of chlorous acid

1968 ◽  
Vol 46 (12) ◽  
pp. 2053-2060 ◽  
Author(s):  
C. C. Hong ◽  
W. H. Rapson
Keyword(s):  
Chlorine Dioxide ◽  
Reaction Rate ◽  
Catalytic Effect ◽  
Initial Reaction Rate ◽  
Initial Reaction ◽  
Inhibiting Effect ◽  
Kinetics Of ◽  
Chlorous Acid

A mechanism involving HOCl, Cl—ClO2, and Cl2 as intermediates is proposed for the disproportionation of chlorous acid. In the absence of chloride, the reaction is controlled by two simultaneous processes, 2HClO2 → H+ + HOCl + ClO3− and HClO2 + ClO2− → HOCl + ClO3−. Chloride has a catalytic effect and an inhibiting effect as well on the formation of chlorine dioxide. The initial reaction rate passes through a minimum at a certain concentration of chloride at low acidities, which can be interpreted by the postulated mechanism. Under chloride catalysis, the reaction is controlled by the process H+ + Cl− + HClO2 → 2HOCl.

Kinetics and mechanism of oxidation of iodide ion by the molybdenum (VI) – hydrogen peroxide system

1990 ◽  
Vol 68 (9) ◽  
pp. 1499-1503 ◽  
Author(s):  
Conchita Arias ◽  
Fernando Mata ◽  
Joaquin F. Perez-Benito
Keyword(s):  
Hydrogen Peroxide ◽  
Rate Constants ◽  
Reaction Rate ◽  
Sodium Molybdate ◽  
Initial Reaction Rate ◽  
Initial Reaction ◽  
Kinetics Of Oxidation ◽  
Iodide Ion ◽  
Aqueous Perchloric Acid ◽  
Kinetics Of

The kinetics of oxidation of potassium iodide by hydrogen peroxide in aqueous perchloric acid has been studied both in the absence and in the presence of sodium molybdate by means of the initial-rates method. The law found for the total initial reaction rate is[Formula: see text]The activation energies associated with rate constants k1, k2, and k3 are 52 ± 1, 49 ± 1, and 42 ± 3 kJ mol−1, respectively. A mechanism in agreement with the experimental kinetic data is proposed, according to which rate constants k1, k2, and k3 correspond to the oxidations of iodide ion by H2O2, H3O2+ and H2MoO5, respectively. Keywords: catalysis, hydrogen peroxide, iodide ion, kinetics, molybdate ion.

Feasibility of Polysulfide Detoxification of Concentrated Waste-water

1985 ◽  
Vol 20 (1) ◽  
pp. 118-128 ◽  
Author(s):  
P.T. Takaoka ◽  
J.J. Ganczarczyk
Keyword(s):  
Reaction Rate ◽  
Initial Reaction Rate ◽  
Initial Reaction ◽  
Concentrated Solutions ◽  
Capital Costs ◽  
Rate Kinetics ◽  
High Concentrations ◽  
Cyanide Solutions ◽  
Considerable Work ◽  
Kinetics Of

Abstract Collecting of concentrated cyanide solutions in electroplating shops is quite a common occurrence. These accumulations of 4.5 to 9.0 cu m volume, which may be collected over a period of years, are usually in the concentration range of 1 to 3 per cent cyanide and present considerable dangers as they are stored on-site or transported for treatment or disposal. Common technologies available for the treatment of cyanide-containing wastewaters are generally not applicable to concentrated cyanide solutions, and some special technologies which could be applicable, usually show high capital costs and/or complexity of operation which render them unsuitable for smaller plating shop practice. In recent years, considerable work has been carried out to investigate a reaction of cyanide with polysulphide to form relatively innocuous thiocyanate. However, this reaction has been studied_only for cyanide solutions of low concentration (less than 100 mg/L CN-). This study was undertaken to investigate the feasibility of using the cyanide-polysulphide reaction to detoxify concentrated cyanide solutions (e.g. 2% CN-) and to investigate the initial kinetics of the cyanide-polysulphide reaction. It was found that the cyanide-polysulphide reaction is moderately exothermic and proceeds very rapidly both at room temperature and at 3°C. This process was capable of reducing cyanide concentrations to non-detectable levels within two weeks at a cyanide-to-polysulphide-sulphur ratio of 1:2 by weight. It was also found that the initial reaction rate kinetics of the cyanide-polysulphide reaction in concentrated solutions differed significantly from previously reported values for solutions low in cyanide concentration and that high concentrations of polysulphides tended to suppress the reaction rate.

scholarly journals Promising Immobilization of Industrial-Class Phospholipase A1 to Attain High-Yield Phospholipids Hydrolysis and Repeated Use with Optimal Water Content in Water-in-Oil Microemulsion Phase

2021 ◽  
Vol 11 (4) ◽  
pp. 1456
Author(s):  
Yusuke Hayakawa ◽  
Ryoichi Nakayama ◽  
Norikazu Namiki ◽  
Masanao Imai
Keyword(s):  
Water Content ◽  
Reaction Rate ◽  
Enzyme Reaction ◽  
Initial Reaction Rate ◽  
Industrial Applications ◽  
Molar Ratio ◽  
High Yield ◽  
Initial Reaction ◽  
Phospholipase A1 ◽  
Repeated Use

In this study, we maximized the reactivity of phospholipids hydrolysis with immobilized industrial-class phospholipase A1 (PLA1) at the desired water content in the water-in-oil (W/O) microemulsion phase. The optimal hydrophobic-hydrophilic condition of the reaction media in a hydrophobic enzyme reaction is critical to realize the maximum yields of enzyme activity of phospholipase A1. It was attributed to enzymes disliking hydrophobic surroundings as a special molecular structure for reactivity. Immobilization of PLA1 was successfully achieved with the aid of a hydrophobic carrier (Accurel MP100) combination with the treatment using glutaraldehyde. The immobilized yield was over 90% based on simple adsorption. The hydrolysis reaction was kinetically investigated through the effect of glutaraldehyde treatment of carrier and water content in the W/O microemulsion phase. The initial reaction rate increased linearly with an increasing glutaraldehyde concentration and then leveled off over a 6% glutaraldehyde concentration. The initial reaction rate, which was predominantly driven by the water content in the organic phase, changed according to a typical bell-shaped curve with respect to the molar ratio of water to phospholipid. It behaved in a similar way with different glutaraldehyde concentrations. After 10 cycles of repeated use, the reactivity was well sustained at 40% of the initial reaction rate and the creation of the final product. Accumulated yield after 10 times repetition was sufficient for industrial applications. Immobilized PLA1 has demonstrated potential as a biocatalyst for the production of phospholipid biochemicals.

Co-processing of hydrodeoxygenation and hydrodesulfurization of phenol and dibenzothiophene with NiMo/Al2O3–ZrO2 and NiMo/TiO2–ZrO2 catalysts

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Jesús Andrés Tavizón Pozos ◽  
Gerardo Chávez Esquivel ◽  
Ignacio Cervantes Arista ◽  
José Antonio de los Reyes Heredia ◽  
Víctor Alejandro Suárez Toriello
Keyword(s):  
Active Sites ◽  
Reaction Rate ◽  
Supported Catalysts ◽  
Initial Reaction Rate ◽  
Initial Reaction ◽  
Competition Effect ◽  
Support Interaction ◽  
Highly Active ◽  
Metal Support Interaction ◽  
Metal Support

Abstract The influence of Al2O3–ZrO2 and TiO2–ZrO2 supports on NiMo-supported catalysts at a different sulfur concentration in a model hydrodeoxygenation (HDO)-hydrodesulfurization (HDS) co-processing reaction has been studied in this work. A competition effect between phenol and dibenzothiophene (DBT) for active sites was evidenced. The competence for the active sites between phenol and DBT was measured by comparison of the initial reaction rate and selectivity at two sulfur concentrations (200 and 500 ppm S). NiMo/TiO2–ZrO2 was almost four-fold more active in phenol HDO co-processed with DBT than NiMo/Al2O3–ZrO2 catalyst. Consequently, more labile active sites are present on NiMo/TiO2–ZrO2 than in NiMo/Al2O3–ZrO2 confirmed by the decrease in co-processing competition for the active sites between phenol and DBT. DBT molecules react at hydrogenolysis sites (edge and rim) preferentially so that phenol reacts at hydrogenation sites (edge and edge). However, the hydrogenated capacity would be lost when the sulfur content was increased. In general, both catalysts showed similar functionalities but different degrees of competition according to the highly active NiMoS phase availability. TiO2–ZrO2 as the support provided weaker metal-support interaction than Al2O3–ZrO2, generating a larger fraction of easily reducible octahedrally coordinated Mo- and Ni-oxide species, causing that NiMo/TiO2–ZrO2 generated precursors of MoS2 crystallites with a longer length and stacking but with a higher degree of Ni-promotion than NiMo/Al2O3–ZrO2 catalyst.

scholarly journals T181. PROTEIN ACYL-THIOESTERASE ENZYME ACTIVITY IN THE POSTMORTEM DORSOLATERAL PREFRONTAL CORTEX IN SCHIZOPHRENIA

2020 ◽  
Vol 46 (Supplement_1) ◽  
pp. S300-S301
Author(s):  
Shaun Hopper ◽  
James Meador-Woodruff
Keyword(s):  
Prefrontal Cortex ◽  
Total Protein ◽  
Protein Trafficking ◽  
Dorsolateral Prefrontal Cortex ◽  
Reaction Rate ◽  
Initial Reaction Rate ◽  
Tissue Homogenate ◽  
Initial Reaction ◽  
Cortical Tissue ◽  
Dorsolateral Prefrontal

Abstract Background The role protein trafficking and localization is a recent target of investigation in schizophrenia pathophysiology. An important mediator of protein trafficking is S-acylation, also known as S-palmitoylation, which is the reversible attachment of long chain fatty acids to cysteine residues. S-acylation is a dynamic post-translational modification that modulates hydrophobicity of proteins, regulating their membrane association and subcellular localization. Notably, we have previously reported a proteome-wide decrease in S-acylated protein levels in the dorsolateral prefrontal cortex (DLPFC) of subjects with schizophrenia. One potential mechanism of decreased S-acylation is increased removal of acyl groups from proteins by protein acyl-thioesterase enzymes (PATs). Here we describe the optimization of an assay to measure the activity of the PAT family of enzymes in human postmortem cortical tissue and use the assay to address our hypothesis that PAT activity is increased in the DLPFC of subjects with schizophrenia. Methods To determine PAT activity, tissue homogenate was incubated with 4-methylumbelliferyl-6-thio-palmitate-β-D-glucopyranoside (4MU-Gluc-Palm) and 1U of exogenous β-glucosidase (to hydrolyze the 4MU-Gluc reaction intermediary). Released 4MU was excited at 360 ± 40 nm and fluorescent emission was measured, per minute, at 460 ± 40 nm. To determine the relationship between initial reaction rate and amount of enzyme, the initial reaction rate using 300 µM 4MU-Gluc-Palm was measured in homogenate containing 1 – 10 µg of total protein from the DLPFC of a subject with no history of psychiatric illness. The PAT activity of DLPFC homogenate boiled for 30 min and total protein homogenate from lymphocytes were measured as negative and positive control reactions, respectively. To estimate the maximum reaction rate (Vmax) and the concentration of 4MU-Gluc-Palm which achieved ½ Vmax (Km; a measure of enzyme-substrate affinity) the initial reaction rate was calculated in the presence of 0 – 200 µM 4MU-Gluc-Palm and the Michaelis-Menten equation was fit to plots of concentration vs. initial rate. Reactions were performed on 2.5 µg total protein homogenate from the DLPFC of 24 subjects with schizophrenia and 24 non-psychiatrically ill subjects. Results A fluorescent signal, which increases with time to a plateau upon substrate depletion, is detectable in total protein homogenate from DLPFC and lymphocytes, but not boiled DLPFC homogenate. In the DLPFC the initial reaction rate is linear with total protein amount [r2 = .99; p = .007], demonstrating that the reaction is sensitive to varying amounts of enzyme in a 10-fold range. When compared between schizophrenia and control subjects, neither Vmax [t(46) = 0.756; p = .45] nor Km [t(46) = 0.780; p = .44] were statistically significantly different. Discussion Here we have demonstrated that PAT activity is measurable in human cortical tissue homogenate. Additionally, we have found no difference in the Vmax or Km of the combined PAT enzyme group in schizophrenia, providing no evidence to support our hypothesis that total PAT activity is increased in subjects with schizophrenia. This suggests that the proteome-wide decrease in S-acylated proteins in schizophrenia is caused by another mechanism, possibly increased expression or function of one or more of the specific PATs, leading to substrate specific changes in S-acylation, or a decrease in activity the acyl protein transferase enzymes, which attach acyl groups to proteins.

The fast detection of streptavidin based on the initial reaction rate of the binding-induced DNA strand-displacement reaction

2016 ◽  
Vol 8 (37) ◽  
pp. 6701-6704 ◽  
Author(s):  
Chenxi Li ◽  
Ruoyun Lin ◽  
Tian Li ◽  
Feng Liu ◽  
Na Li
Keyword(s):  
Small Molecules ◽  
Reaction Rate ◽  
Initial Reaction Rate ◽  
Initial Reaction ◽  
Strand Displacement ◽  
Fast Detection ◽  
Dna Strand Displacement ◽  
Displacement Reactions ◽  
Dna Strand ◽  
Strand Displacement Reaction

Binding-induced DNA strand-displacement reactions diversify the applications beyond nucleic acids and small molecules.

Kinetics of N-substituted phenothiazines and N-substituted phenoxazines oxidation catalyzed by fungal laccases

2009 ◽  
Vol 4 (1) ◽  
pp. 62-67 ◽  
Author(s):  
Lidija Tetianec ◽  
Juozas Kulys
Keyword(s):  
Electron Transfer ◽  
Redox Potential ◽  
Reorganization Energy ◽  
Outer Sphere ◽  
Initial Reaction Rate ◽  
Initial Reaction ◽  
Type I ◽  
Electron Transfer Mechanism ◽  
Recombinant Laccase ◽  
Kinetics Of

AbstractLaccase-catalyzed oxidation of N-substituted phenothiazines and N-substituted phenoxazines was investigated at pH 5.5 and 25°C. The recombinant laccase from Polyporus pinsitus (rPpL) and the laccase from Myceliophthora thermophila (rMtL) were used. The dependence of initial reaction rate on substrate concentration was analyzed by applying the laccase action scheme in which the laccase native intermediate (NI) reacts with a substrate forming reduced enzyme. The reduced laccase produces peroxide intermediate (PI) which in turn decays to the NI. The calculated constant (kox) values of the PI formation are (6.1±3.1)×105 M−1s−1 for rPpL and (2.5±0.9)×104 M−1s−1 for rMtL. The bimolecular constants of the reaction of the native intermediate with electron donor (kred) vary in the interval from 2.2×105 to 2.1×107 M−1s−1 for rPpL and from 1.3×102 to 1.8×105 M-1s−1 for rMtL. The larger reactivity of rPpL in comparison to rMtL is associated with the higher redox potential of type I Cu of rPpL. The variation of kred values for both laccases correlates with the change of the redox potential of substrates. Following outer sphere (Marcus) electron transfer mechanism the calculated activationless electron transfer rate and the apparent reorganization energy are 5.0×107 M−1s−1 and 0.29 eV, respectively.

scholarly journals Layer-Like Zeolite X as Catalyst in a Knoevenagel Condensation: The Effect of Different Preparation Pathways and Cation Exchange

Catalysts ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 474
Author(s):  
Jan-Paul Grass ◽  
Katharina Klühspies ◽  
Bastian Reiprich ◽  
Wilhelm Schwieger ◽  
Alexandra Inayat
Keyword(s):  
Catalytic Activity ◽  
Reaction Rate ◽  
Knoevenagel Condensation ◽  
Ethyl Cyanoacetate ◽  
Reaction Rates ◽  
Initial Reaction Rate ◽  
Comparative Investigation ◽  
Morphological Properties ◽  
Initial Reaction ◽  
Zeolite X

This study is dedicated to the comparative investigation of the catalytic activity of layer-like Faujasite-type (FAU) zeolite X obtained from three different synthesis routes (additive-free route, Li2CO3 route, and TPOAC route) in a liquid-phase Knoevenagel condensation of benzaldehyde and ethyl cyanoacetate to ethyl trans-α-cyanocinnamate. It is shown that the charge-balancing cations (Na+ and K+) and the morphological properties have a strong influence on the apparent reaction rate and degree of conversion. The highest initial reaction rate could be found for the layer-like zeolite X synthesised by the additive-free route in the potassium form. In most cases, the potassium-exchanged zeolites enabled higher maximum conversions and higher reaction rates compared to the zeolite X catalysts in sodium form. However, very thin crystal plates (below 100 nm thickness), similar to those obtained in the presence of TPOAC, did not withstand the multiple aqueous ion exchange procedure, with the remaining coarse crystals facilitating less enhancement of the catalytic activity.

scholarly journals Catalysis of Rice Straw Hydrolysis by the Combination of Immobilized Cellulase fromAspergillus nigeronβ-Cyclodextrin-Fe3O4Nanoparticles and Ionic Liquid

2015 ◽  
Vol 2015 ◽  
pp. 1-9 ◽  
Author(s):  
Po-Jung Huang ◽  
Ken-Lin Chang ◽  
Jung-Feng Hsieh ◽  
Shui-Tein Chen
Keyword(s):  
Ionic Liquid ◽  
Rice Straw ◽  
Reaction Rate ◽  
Magnetic Particles ◽  
Initial Reaction Rate ◽  
Initial Reaction ◽  
High Concentration ◽  
Solid Reaction ◽  
Immobilized Cellulase ◽  
Hydrolysis Of

Cellulase fromAspergillus nigerwas immobilized ontoβ-cyclodextrin-conjugated magnetic particles by silanization and reductive amidation. The immobilized cellulase gained supermagnetism due to the magnetic nanoparticles. Ninety percent of cellulase was immobilized, but the activity of immobilized cellulase decreased by 10%. In this study, ionic liquid (1-butyl-3-methylimidazolium chloride) was introduced into the hydrolytic process because the original reaction was a solid-solid reaction. The activity of immobilized cellulase was improved from 54.87 to 59.11 U g immobilized cellulase−1at an ionic liquid concentration of 200 mM. Using immobilized cellulase and ionic liquid in the hydrolysis of rice straw, the initial reaction rate was increased from 1.629 to 2.739 g h−1 L−1. One of the advantages of immobilized cellulase is high reusability—it was usable for a total of 16 times in this study. Compared with free cellulase, magnetized cellulase can be recycled by magnetic field and the activity of immobilized cellulase was shown to remain at 85% of free cellulase without denaturation under a high concentration of glucose (15 g L−1). Therefore, immobilized cellulase can hydrolyze rice straw continuously compared with free cellulase. The amount of harvested glucose can be up to twentyfold higher than that from the hydrolysis by free cellulase.

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