Skeletal isomerization of cyclohexene on Al2O3 and AlPO4–Al2O3 catalysts

1984 ◽  
Vol 62 (8) ◽  
pp. 1455-1458 ◽  
Author(s):  
J. M. Campelo ◽  
A. Garcia ◽  
J. M. Gutierrez ◽  
D. Luna ◽  
J. M. Marinas
Keyword(s):  
Rate Constants ◽  
Reaction Pathway ◽  
Acid Sites ◽  
Skeletal Isomerization ◽  
Irreversible Adsorption ◽  
First Order ◽  
First Order Kinetics ◽  
Selectivity Studies ◽  
Apparent Activation Energies ◽  
Competitive Products

Cyclohexene skeletal isomerization, in a microcatalytic pulse reactor, was investigated using Al2O3 and AlPO4–Al2O3 as catalysts. Apparent rate constants and apparent activation energies were calculated according to the kinetic model of Bassett–Habgood. Selectivity studies concluded that 1-MCP and 3-MCP were competitive products with a first-order kinetics. The rate constants as well as the selectivity at 1-MCP increase with an increase in the number and strength of stronger acid sites, measured by means of the irreversible adsorption of aniline in cyclohexane, at 298 K, using a spectrophotometric method. The parallel reaction pathway, proposed for AlPO4 catalysts, agrees with both the observed rates and selectivities using Al2O3 and AlPO4–Al2O3 catalysts.

Skeletal isomerization of cyclohexene on AlPO4 catalysts

1983 ◽  
Vol 61 (11) ◽  
pp. 2567-2571 ◽  
Author(s):  
J. M. Campelo ◽  
A. Garcia ◽  
J. M. Gutierrez ◽  
D. Luna ◽  
J. M. Marinas
Keyword(s):  
Reaction Pathway ◽  
Strong Acid ◽  
Acid Sites ◽  
Skeletal Isomerization ◽  
Selectivity Factor ◽  
Irreversible Adsorption ◽  
Organic Bases ◽  
Selectivity Studies ◽  
Strong Acid Sites ◽  
Competitive Products

The skeletal isomerization of cyclohexene, in a microcatalytic pulse reactor, was investigated by using aluminium orthophosphates (Al/P = 1) as catalysts. An attempt has been made to correlate the isomerization activity with the acid properties of the solids, measured by means of the irreversible adsorption of different organic bases in cyclohexane, at 298 K, using a spectrophotometric method.Apparent rate constants were calculated in terms of the kinetic model of Bassett and Habgood. Selectivity studies led to the conclusion that 1-MCP and 3-MCP were competitive products. Correlation between the kinetic selectivity factor, σ, and the number of strong acid sites has been sought.A possible parallel reaction pathway is proposed, which agrees with both the observed rates and selectivities.

Removal of sulfonamides from wastewater in the UV/TiO2 system: effects of pH and salinity on photodegradation and mineralization

2019 ◽  
Vol 79 (2) ◽  
pp. 349-355 ◽  
Author(s):  
C. H. Wu ◽  
C. Y. Kuo ◽  
C. D. Dong ◽  
C. W. Chen ◽  
Y. L. Lin
Keyword(s):  
Rate Constants ◽  
Inhibitory Effect ◽  
Chloride Ions ◽  
Mineralization Rate ◽  
Direct Photolysis ◽  
First Order ◽  
First Order Kinetics ◽  
Lower Reactivity ◽  
Chlorine Radicals ◽  
Effects Of Ph

Abstract The effects of salinity on the photodegradation and mineralization of sulfonamides in the UV/TiO2 system were investigated. The goals of this study were to analyze the effects of pH and salinity on the sulfonamide concentration and total organic carbon (TOC) during the removal of sulfonamides in a UV/TiO2 system. Four sulfonamides – sulfadiazine (SDZ), sulfamethizole (SFZ), sulfamethoxazole (SMX) and sulfathiazole (STZ) - were selected as parent compounds. The photodegradation and mineralization rates of sulfonamides in the UV/TiO2 system satisfy pseudo-first-order kinetics. Direct photolysis degraded sulfonamides but sulfonamides cannot be mineralized. The photodegradation and mineralization rate constants in all experiments followed the order pH 5 > pH 7 > pH 9. At pH 5, the mineralization rate constants of SMX, SFZ, SDZ and STZ were 0.015, 0.009, 0.012 and 0.011 min−1, respectively. The addition of NaCl inhibited the mineralization of the four tested sulfonamides more than it inhibited their photodegradation. The inhibitory effect of chloride ions on the removal of sulfonamides in the UV/TiO2 system was attributed to the scavenging by chloride ions of hydroxyl radicals (HO•) and holes and the much lower reactivity of chlorine radicals thus formed, even though the chlorine radicals were more abundant than HO•.

Azides. Part V. A kinetic study of the formation of N-(p-toluenesulphonyl)-1H-azepine by thermolysis of p-toluenesulphonylazide in benzene under nitrogen pressure

1985 ◽  
Vol 63 (4) ◽  
pp. 887-890 ◽  
Author(s):  
Nagaraj R. Ayyangar ◽  
Ramesh B. Bambal ◽  
Dattatraya D. Nikalje ◽  
Kumar V. Srinivasan
Keyword(s):  
Kinetic Study ◽  
Rate Constants ◽  
Nitrogen Pressure ◽  
Time Profile ◽  
First Order ◽  
First Order Kinetics ◽  
Concentration Time

The course of thermolysis of p-toluenesulphonylazide (A) in benzene at 160 °C and 40.1 atm of nitrogen pressure was followed by analysis of the reactants and products in the reaction mixture by hplc. The rate measurements indicate that the reaction follows first-order kinetics with respect to the formation of N-(p-toluenesulphonyl)-1H-azepine (B) and p-toluencsulphonamide (D). The concentration–time profile is consistent with the formation of p-toluenesulphonylanilide (C) from the azepine (B). The rate constants indicate that the azepine (B) decomposes to the anilide (C) at the same rate at which it is formed.

Effects of oxidant concentration and temperature on decolorization of azo dye: comparisons of UV/Fenton and UV/Fenton-like systems

2012 ◽  
Vol 65 (11) ◽  
pp. 1970-1974 ◽  
Author(s):  
C. Y. Kuo ◽  
C. Y. Pai ◽  
C. H. Wu ◽  
M. Y. Jian
Keyword(s):  
Rate Constant ◽  
Rate Constants ◽  
Azo Dye ◽  
Activation Energies ◽  
First Order ◽  
First Order Kinetics ◽  
Oxidant Concentration ◽  
Decolorization Efficiency ◽  
Pseudo First Order ◽  
Reactive Red 2

This study applies photo-Fenton and photo-Fenton-like systems to decolorize C.I. Reactive Red 2 (RR2). The oxidants were H2O2 and Na2S2O8; Fe2+, Fe3+, and Co2+ were used to activate these two oxidants. The effects of oxidant concentration (0.3–2 mmol/L) and temperature (25–55 °C) on decolorization efficiency of the photo-Fenton and photo-Fenton-like systems were determined. The decolorization rate constants (k) of RR2 in the tested systems are consistent with pseudo-first-order kinetics. The rate constant increased as oxidant concentration and temperature increased. Activation energies of RR2 decolorization in the UV/H2O2/Fe2+, UV/H2O2/Fe3+, UV/Na2S2O8/Fe2+ and UV/Na2S2O8/Fe3+ systems were 32.20, 39.54, 35.54, and 51.75 kJ/mol, respectively.

scholarly journals The Effect of the Method of Preparation on the Textural, Acidic and Catalytic Properties of Chromia–Alumina Catalysts

1996 ◽  
Vol 13 (5) ◽  
pp. 355-365
Author(s):  
Th. El-Nabarawy ◽  
L.B. Khalil ◽  
A. M. Youssef
Keyword(s):  
Water Vapour ◽  
Catalytic Properties ◽  
Acid Sites ◽  
Adsorption Properties ◽  
Pure Alumina ◽  
First Order ◽  
First Order Kinetics ◽  
Structure Sensitive ◽  
Adsorption Of Nitrogen ◽  
Alumina Catalysts

Pure alumina 'A' and chromia–alumina catalysts containing 25 mol% Cr2O3 (IAC, IIAC and IIIAC) were prepared by impregnation, coprecipitation and coating techniques, respectively. The adsorption of nitrogen at 77 K and of benzene and water vapour at 308 K was determined. The chemisorption of pyridine at 400 K was measured and the surface acidities calculated. The conversion of 2-propanol and cracking of cumene were investigated using the pulse microcatalytic technique. Coating alumina with chromia causes considerable changes in the textural and adsorption properties, impregnation of alumina with chromia leads to smaller variations while coprecipitation gives intermediate changes in textural and adsorption properties. The same was found true for the surface acidities as determined by the chemisorption of pyridine. The dehydration of 2-propanol and cracking of cumene follow first-order kinetics. The dehydration of propanol on alumina and chromia–alumina catalysts is a structure-insensitive reaction independent of the surface area but related to the surface acid density. The cracking of cumene is a structure-sensitive reaction depending on both the extent of the surface and the number of acid sites.

Bioconcentration factors and kinetics of chlorobenzenes in a juvenile crab (Portunus pelagicus (L))

1993 ◽  
Vol 44 (4) ◽  
pp. 565 ◽  
Author(s):  
MR Mortimer ◽  
DW Connell
Keyword(s):  
Rate Constants ◽  
Aquatic Organisms ◽  
Aqueous Solubility ◽  
Portunus Pelagicus ◽  
Lipophilic Compounds ◽  
First Order ◽  
First Order Kinetics ◽  
Log Kow ◽  
Wet Weight ◽  
Depuration Rate

The uptake- and depuration-rate constants (k1 and k2 respectively), according to first-order kinetics, were measured for a series of chlorobenzenes with juvenile crabs, Portunus pelagicus. These constants were found to be related to the lipophilicity of the chlorobenzenes as expressed by the octanol-water coefficient (log Kow), giving relationships similar to those observed with fish. However, the actual magnitude of k1 and k2 on a lipid basis ranged from 720 to 5880 h-1 and from 0.492 to 0.0102 h-1 respectively, which is about ten times faster than those for fish. The bioconcentration factor (KB in wet weight units) obtained from these rate constants was related to Kow, by the following expression. log KB=-2.88+1.09 log Kow. The empirical constants in this equation are similar to those observed with other aquatic organisms except that the value of -2.88 is lower than that reported with the other organisms. This is probably due to the relatively low lipid content of the crabs. It is suggested that the bioconcentration of essentially nonbiodegradable lipophilic compounds occurs as a result of partitioning between biota lipid and water. Other physicochemical properties (molar volume and aqueous solubility) and two molecular descriptors (zero- and first-order Randik indices) exhibited good correlations with the bioconcentration characteristics described above.

scholarly journals Efficient degradation of naproxen by persulfate activated with zero-valent iron: performance, kinetic and degradation pathways

2020 ◽  
Vol 81 (10) ◽  
pp. 2078-2091
Author(s):  
Shuyu Dong ◽  
Xiaoxue Zhai ◽  
Ruobing Pi ◽  
Jinbao Wei ◽  
Yunpeng Wang ◽  
...  
Keyword(s):  
Aqueous Solution ◽  
Hydroxyl Radical ◽  
Rate Constants ◽  
Zero Valent Iron ◽  
Degradation Pathways ◽  
First Order ◽  
First Order Kinetics ◽  
Degradation Rates ◽  
Initial Ph ◽  
Pseudo First Order

Abstract Degradation of naproxen (NAP) by persulfate (PS) activated with zero-valent iron (ZVI) was investigated in our study. The NAP in aqueous solution was degraded effectively by the ZVI/PS system and the degradation exhibited a pseudo-first-order kinetics pattern. Both sulfate radical (SO4•−) and hydroxyl radical (HO•) participate in the NAP degradation. The second-order rate constants for NAP reacting with SO4•− and HO• were (5.64 ± 0.73) × 109 M−1 s−1 and (9.05 ± 0.51) × 109 M−1 s−1, respectively. Influence of key parameters (initial pH, PS dosage, ZVI dosage, and NAP dosage) on NAP degradation were evaluated systematically. Based on the detected intermediates, the pathways of NAP degradation in ZVI/PS system was proposed. It was found that the presence of ammonia accelerated the corrosion of ZVI and thus promoted the release of Fe2+, which induced the increased generation of sulfate radicals from PS and promoted the degradation of NAP. Compared to its counterpart without ammonia, the degradation rates of NAP by ZVI/PS were increased to 3.6–17.5 folds and 1.2–2.2 folds under pH 7 and pH 9, respectively.

scholarly journals Quantitative analysis of proton-linked transport system. β-Galactoside exit in Escherichia coli

1980 ◽  
Vol 188 (2) ◽  
pp. 467-473 ◽  
Author(s):  
I R Booth ◽  
W A Hamilton
Keyword(s):  
Escherichia Coli ◽  
Quantitative Analysis ◽  
Transport System ◽  
Rate Constants ◽  
The Other ◽  
First Order ◽  
First Order Kinetics ◽  
Solute Accumulation ◽  
External Ph

The exit of lactose and thiomethyl-beta-D-galactoside from Escherichia coli ML308-225 has been studied to determine the role of carrier-dependent (zero-trans efflux) and carrier-independent (leak) processes. On the basis of its sensitivity to p-chloromercuribenzene sulphonate the exit of lactose was found to be almost wholly mediated by the carrier. Consistent with this conclusion was the finding that the rate of exit of this sugar was dependent on the external pH, being considerably slower at acid pH. On the other hand exit of thiomethyl-beta-D-galactoside was found to be composed of both carrier-dependent and carrier-independent processes. Both processes exhibited first-order kinetics with the rate constants for zero-trans efflux and leak being 0.137 min-1 and 0.079 min-1, respectively. The relevance of these findings for out earlier proposal for the methods of attenuation of solute accumulation is discussed [Booth, Mitchell & Hamilton (1979) Biochem. J. 182, 687–696].

Ring-Opening Polymerization of ε-Caprolactone Using Novel Tin(II) Alkoxide Initiators

2008 ◽  
Vol 55-57 ◽  
pp. 757-760 ◽  
Author(s):  
A. Kleawkla ◽  
Robert Molloy ◽  
W. Naksata ◽  
Winita Punyodom
Keyword(s):  
Solid State ◽  
Rate Constants ◽  
Ring Opening ◽  
Ring Opening Polymerization ◽  
Zero Order ◽  
Molecular Aggregation ◽  
First Order ◽  
First Order Kinetics ◽  
Zero Order Kinetics ◽  
Kinetics Of

Two novel tin(II) alkoxides, namely: tin(II) hexoxide, Sn(OC6H13)2, and tin(II) octoxide, Sn(OC8H17)2, have been synthesized for use as coordination-insertion initiators in the bulk ring-opening polymerization of ε-caprolactone. The kinetics of the polymerization reactions were studied at 140 °C by dilatometry. It was found that both alkoxides were slow to dissolve in the ε-caprolactone monomer due to their molecular aggregation in the solid state. As a result, the slow solubilization of the initiators gave rise to deviations from the expected first-order kinetics. Instead, the kinetic results adhered more closely to zero-order kinetics with apparent zero-order rate constants k0 of 6.58 x 10-2 and 4.63 x 10-2 mol l-1 min-1 for the hexoxide and octoxide respectively

Temperature dependence of the formation of Tris[2,3-bis(2-pyridyl)pyrazine]-iron(II)

1974 ◽  
Vol 27 (12) ◽  
pp. 2671 ◽  
Author(s):  
PJ Guerney ◽  
RJ Knight ◽  
RN Sylva
Keyword(s):  
Complex Formation ◽  
Temperature Dependence ◽  
Rate Constants ◽  
Absorption Maximum ◽  
Formation Constant ◽  
Molar Absorptivity ◽  
Dissociation Reaction ◽  
First Order ◽  
First Order Kinetics ◽  
Complex Formation Process

The overall formation constant, β3, of tris[2,3-bis(2- pyridyl)pyrazine]iron(II) was determined spectrophotometrically at 25, 40, 60 and 80�C as 8.9 x 107, 2.9 x 107, 1.0 x 107 and 1.8 x 106 (mol l-1)-3 respectively at pH > 5.5. The pKa of the ligand is 3.1 at 25�C and decreases to about 2.0 at 80�C. The variation of β3 with temperature is attributed to differences in the temperature dependence of the rate constants of the complex formation process and of dissociation. The overall energy of activation for complex formation is -870 J mol-1. The complex dissociates according to first order kinetics with rate constants of 4.3 x 10-3 s-1 and 6.8 x 10-2 s-1 at 25 and 35�C respectively, and the activation energy of the dissociation reaction is about 3000 J mol-1. The molar absorptivity of the complex, 11000 1. mol-1 cm-1 at the absorption maximum (λmax 535 nm), is independent of temperature from 25 to 80�C.

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