Reduction Kinetics of Chromium(VI) by S(-II) in Alkalescent Aqueous Media

2009 ◽  
Vol 26 (2) ◽  
pp. 263-268 ◽  
Author(s):  
Haibo Li ◽  
Hongbin Cao ◽  
Li Yuping ◽  
Haobo Dai ◽  
Yi Zhang
Keyword(s):  
Aqueous Media ◽  
Reduction Kinetics ◽  
Chromium Vi ◽  
Kinetics Of

Oxidation of DL-penicillamine by chromium(VI). Kinetics of formation of the thioester intermediate

1994 ◽  
Vol 72 (7) ◽  
pp. 1637-1644 ◽  
Author(s):  
Joaquin F. Perez-Benito ◽  
Driss Lamrhari ◽  
Conchita Arias
Keyword(s):  
Reaction Rate ◽  
Aqueous Media ◽  
Bimolecular Reaction ◽  
Spectrophotometric Detection ◽  
State Behavior ◽  
Chromium Vi ◽  
Specific Effects ◽  
Kinetics Of Formation ◽  
Kinetics Of ◽  
Catalytic Power

The kinetics of formation of the thioester involved as an intermediate in the reaction between chromium(VI) and DL-penicillamine in aqueous media (pH = 1–8) containing different buffers (acetate, citrate, and phosphate) has been studied by monitoring the disappearance of chromium(VI) at 370 nm and application of the initial-rates method. The initial rate is directly proportional to the initial concentrations of both oxidant and reductant, and the rate vs. pH plots show bell-shaped profiles. The reaction is catalyzed by the buffer present in the medium, the catalytic power of each buffer increasing in the order acetate < citrate < phosphate. This is explained in terms of a mechanism involving the formation of a complex between the acidic form of the buffer and HCrO4− previous to the formation of the thioester. Potassium chloride and sodium sulfate do not seem to have important specific effects on the reaction rate, their effect being that of an acceleration of the reaction as the ionic strength increases. On the contrary, the sulfates of magnesium, manganese(II), and zinc (the latter only in the presence of acetate buffer) have specific effects, indicating the probable formation of several complexes. The spectrophotometric detection of the thioester at 430 nm has allowed to confirm some of the conclusions extracted from the measurement of initial rates, and suggests that this intermediate might approach a steady-state behavior in the three buffers at pH > 6.25, and also that a bimolecular reaction with DL-penicillamine might be involved in its destruction.

Effect of H2O Partial Pressure on Reduction Kinetics of Iron-Based Fischer-Tropsch Catalyst

2010 ◽  
Vol 31 (2) ◽  
pp. 205-212
Author(s):  
Hong WANG ◽  
Yong YANG ◽  
Baoshan WU ◽  
Jian XU ◽  
Hulin WANG ◽  
...  
Keyword(s):  
Partial Pressure ◽  
Reduction Kinetics ◽  
Fischer Tropsch ◽  
Iron Based ◽  
Kinetics Of

Carbothermic reduction kinetics of nanocrystallite Fe2O3/NiO composites for the production of Fe/Ni alloy

2008 ◽  
Vol 463 (1-2) ◽  
pp. 585-590 ◽  
Author(s):  
K.S. Abdel-Halim ◽  
M.H. Khedr ◽  
M.I. Nasr ◽  
M.Sh. Abdel-wahab
Keyword(s):  
Carbothermic Reduction ◽  
Reduction Kinetics ◽  
Ni Alloy ◽  
Kinetics Of

Kinetics of the oxidation of hypophosphorous and phosphorous acids by chromium(VI)

1973 ◽  
Vol 35 (3) ◽  
pp. 901-908 ◽  
Author(s):  
Kalyan K. Sengupta ◽  
J.K. Chakladar ◽  
A.K. Chatterjee
Keyword(s):  
Chromium Vi ◽  
Kinetics Of

scholarly journals Reduction kinetics of the photo-oxidized chlorophyll a + II in the nanosecond range

FEBS Letters ◽  
1984 ◽  
Vol 167 (2) ◽  
pp. 316-320 ◽  
Author(s):  
H.-J. Eckert ◽  
G. Renger ◽  
H.T. Witt
Keyword(s):  
Chlorophyll A ◽  
Reduction Kinetics ◽  
Nanosecond Range ◽  
Kinetics Of

Study of kinetics of reaction of lignin model compounds with propylene oxide

Holzforschung ◽  
2008 ◽  
Vol 62 (2) ◽  
pp. 169-175 ◽  
Author(s):  
Krishna K. Pandey ◽  
Tapani Vuorinen
Keyword(s):  
Chemical Reaction ◽  
Propylene Oxide ◽  
Aqueous Media ◽  
Reaction Products ◽  
Model Compounds ◽  
Rapid Reduction ◽  
Visible Absorption ◽  
Lignin Model Compounds ◽  
Lignin Model ◽  
Kinetics Of

Abstract The etherification of phenolic groups has been found to inhibit photodegradation in wood and lignin rich pulps. The precise understanding of kinetics of chemical reaction between lignins or their model compounds and the etherifying agent is the first step for developing a viable modification procedure. In this study, we have investigated the reaction of lignin model compounds (namely, phenol and guaiacol) with propylene oxide in aqueous media. The kinetics of etherification reaction was studied under varying pH conditions in the temperature range 30–60°C. The etherified reaction products were characterized by gas chromatogram-mass spectrum (GC-MS). The extent of etherification of phenols and the rate of chemical reaction was followed by UV-Visible absorption spectroscopy. The reaction between lignin model compounds and propylene oxide was indicated by a rapid reduction in the absorbance accompanied by the development of a new band corresponding to etherified products. The reaction kinetics was investigated at pH ∼12 under the condition of excess concentration of propylene oxide. The reaction followed first order kinetics and rate constants increased linearly with an increase in the temperature and concentration of propylene oxide. The MS fragment data of reaction product support the proposed reaction scheme. The activation energy of the reaction of propylene oxide with phenol and guaiacol, calculated with the Arrhenius equation, was 56.2 kJ mol-1 and 45.4 kJ mol-1, respectively.

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