Search Results

You are looking at 11 - 20 of 5,162 items for :

  • "Oxidation" x
  • Refine by Access: All Content x
Clear All

Introduction The selective catalytic oxidation of organic compounds with environmentally benign, cheap and readily available oxidant, aqueous H 2 O 2 , is one of the main challenges in the field of catalysis [ 1 – 6 ]. Among

Restricted access

Introduction The selective oxidation of alcohols to carbonyl compounds is an active research field in organic synthesis since the products are important precursors of various chemicals [ 1 – 3 ]. Hydrogen peroxide has been used

Restricted access

Introduction The selective aerobic oxidation of hydrocarbons is a major goal of today's research in catalysis as selectively oxidized hydrocarbons can be used as feedstock for the preparation of fine chemicals [ 1 , 2 ]. Among

Restricted access

Introduction Ferrite spinels are important catalysts for various chemical reactions like the water gas shift reaction, carbon monoxide (CO) oxidation, alkylation reactions etc. [ 1 – 3 ] due to their structural and redox

Restricted access
Reaction Kinetics, Mechanisms and Catalysis
Authors:
Cristina Benincá
,
Patrício Peralta-Zamora
,
Ronaldo Cardoso Camargo
,
Célia Regina Granhen Tavares
,
Everton Fernando Zanoelo
, and
Luciana Igarashi-Mafra

degradation of synthetic dyes and their breakdown products [ 11 ]. However, advanced oxidation processes (e.g., Fenton and photo-Fenton processes, heterogeneous photocatalysis) recently emerged as powerful techniques [ 11 – 15 ] to promote a rapid and non

Restricted access

Abstract  

The oxidation of a precipitation-hardening (PH) steels is a rather unexplored area. In this study an attempt is made to estimate the oxidation mechanism and the kinetics that take place up to 850 °C. For this purpose specimens of the material under examination were isothermally heated at 725, 775, 800, 825, and 850 °C for 12 h in O2 atmosphere. The as-treated samples were examined with SEM and XRD, while kinetics were based on thermogravimetric (TG) results. From this examination it was deduced that the oxidation of this steel is accomplished at minimum three steps, following the changes of the scale morphology and the kinetics. After 850 °C although that the oxidation rate increases, the scale morphology does not change. From the calculations of the rate constant k p and the activation energy for the phenomena below 850 °C, it was deduced that the oxidation phenomena during this stage provides another barrier to the deterioration of the ferrous material.

Restricted access

Abstract  

Research was carried out to determine the activity of complexes of tripeptide–glutathione with heavy metals in the oxidation of cyclohexene with tert-butylhydroperoxide in toluene at 80 °C. All the complexes were prepared by the interaction of metal ions and glutathione at room temperature in aqueous solutions. Only the complexes of Mo were obtained from acidic aqueous solution. The characteristics of these complexes were determined by means of FTIR and Mössbauer spectroscopies and EPR analysis. The products of the epoxidation and hydroxylation reactions were identified using GC analysis. The complexes of molybdenum and vanadium showed higher activity in the epoxidation reaction of cyclohexene compared to the other complexes, namely of Mn, Co, Cu, Cr, Fe, Cd and Th. The possible structures of the complexes are offered. The possible use of glutathione complexes as catalysts in the model reaction of oxidation is newly demonstrated.

Restricted access

Soot oxidation kinetics from TG experiments

Can they be used reliably in diesel particulate filter modelling tools?

Journal of Thermal Analysis and Calorimetry
Authors:
Maria Kalogirou
and
Zissis Samaras

Abstract  

Thermogravimetric analysis (TG) has been used extensively for soot oxidation studies. Its known experimental and computational difficulties, however, have led to extended criticism concerning the reliability of the extracted kinetics and their potential for reliable reaction modelling. This study explores if TG kinetics could lead to successful simulation results notwithstanding the related disputes. For this, TG and mini-scale soot oxidation experiments with oxygen (O2) were conducted. The TG kinetics reliability was controlled through comparison with the corresponding mini-scale results and by the satisfactory simulation of the mini-scale experiments.

Restricted access

Abstract  

A natural graphite recommended for use in nuclear applications was analyzed using thermogravimetric analysis. The oxidation behaviour was unlike that expected for flake-like particles. The dynamic data displayed an apparent bimodal reaction rate curve as a function of temperature and degree of conversion. Nevertheless, it was possible to model this behaviour with a single rate constant, i.e. without the need for a parallel reaction type of kinetic mechanism. The approach used in this paper to model the gas–solid reaction of graphite and oxygen, provides a consistent framework to test the validity of complementary isothermal and non-isothermal data for a specific solid state reaction.

Restricted access

Abstract  

Isothermal and non-isothermal thermogravimetric experiments (TG) with real and synthetic (Printex U) soot were performed at different O2 concentrations (5–22%O2/N2), sample masses (0.5–10 mg), heating (5–20 °C min−1) and flow rates (80–100 mL min−1). The significance of the experimental and calculation uncertainties (i.e. experimental parameter dependencies, calculation method and mass transfer limitations), which are related to TG for the extraction of chemical kinetics, was explored. Finally, an intrinsic kinetic equation for soot oxidation is proposed.

Restricted access