Fenton chemistry encompasses reactions of hydrogen peroxide in the presence of iron to generate highly reactive species such as the hydroxyl radical and possibly others. In this review, the complex mechanisms of Fenton and Fenton-like reactions and the important factors influencing these reactions, from both a fundamental and practical perspective, in applications to water and soil treatment, are discussed. The review covers modified versions including the photoassisted Fenton reaction, use of chelated iron, electro-Fenton reactions, and Fenton reactions using heterogeneous catalysts. Sections are devoted to nonclassical pathways, by-products, kinetics and process modeling, experimental design methodology, soil and aquifer treatment, use of Fenton in combination with other advanced oxidation processes or biodegradation, economic comparison with other advanced oxidation processes, and case studies.

/pdf/advanced-oxidation-processes-for-organic-contaminant-546ow329vb.pdf

Advanced Oxidation Processes for Organic Contaminant Destruction Based on the Fenton Reaction and Related Chemistry

Oxidative dehydrogenation of ethane and propane : How far from commercial implementation?

https://dspace.library.uu.nl/bitstream/handle/1874/26040/Catal.Today-Weckhuysen-2003.pdf?sequence=1

Chemistry, spectroscopy and the role of supported vanadium oxides in heterogeneous catalysis

Dry reforming of methane to synthesis gas was studied over Ni-based catalysts. Compared to Ni/γ-Al2O3, the Ni/MgO-γ-Al2O3 and Ni/MgAl2O4 catalysts exhibit higher activity and better stability using a stoichiometric feed ratio (1:1). The MgAl2O4 spinel layer in Ni/MgO-γ-Al2O3 can effectively suppress the phase transformation to form NiAl2O4 spinel phases and can stabilize the Ni tiny crystallites, to which the good stability of the catalyst contributes. The application of magnesium aluminate spinel (MgAl2O4) prepared by the co-precipitation method as a support of Ni catalysts can give a high active catalytic system with excellent stability under reaction conditions. The high sintering-resistance ability and low acidity of MgAl2O4 compared to γ-Al2O3 and the interactions between Ni and MgAl2O4 might be responsible for its high activity and resistant to coking and sintering, because it can produce a highly dispersed active Ni species.

Dry reforming of methane over nickel catalysts supported on magnesium aluminate spinels

This review is focused on the use of solid Lewis acids to promote catalytic oxidations. While the concept of using Lewis acids to promote the reaction of organic substrates with oxidizing reagents is widely accepted in homogeneous catalysis, this concept has not become evident and generally used in heterogeneous catalysis until recent days. Certainly the development of new Lewis acid solids active and selective for catalytic oxidations is an urgent need and a challenging scientific target for some substrates especially using environmentally friendly oxidants. Since the replacement of current stoichiometric oxidations for the production of fine chemicals by environmentally benign catalytic oxidations is one of the major tasks in green chemistry, solid Lewis acids are called to play a crucial role to accomplish this goal. In the review, we will see the still important role that stoichiometric oxidations play in our daily life, and how they are being substituted by catalytic oxidations. At this point, three general mechanisms in which Lewis acids are involved will be described, and the material has been organized starting from homogeneous and ending with solid catalysts for heterogeneous oxidations. A bridge between the two will be established by presenting catalytic systems that can fill the gap between the two systems helping to rationalize the nature of the catalytic active sites in solid systems. This review is obviously focused on solid oxidation catalysts, and the core of the review is organized to show the evolution from the simplest strategy for heterogeneizing homogeneous catalysts, i.e., supporting the active species on large surface area solids, to the more elaborate ones in which the active sites are part of the solid structure. Given the importance of metallosilicates, and more specifically titanosilicates, as catalysts in commercial processes, special attention has been paid to these types of materials. Although sufficient references are provided to early seminal work, special emphasis has been given to most recent contributions to this area, particularly of the last 10 years. Patent literature has also been extensively covered in this review. Examples to illustrate the concepts have been selected among recent publications, and an effort has been made to present a series of commercial and near commercial processes based on catalytic oxidations. Finally, two * E-mail: acorma@itq.upv.es. 3837 Chem. Rev. 2002, 102, 3837−3892

Lewis acids as catalysts in oxidation reactions: from homogeneous to heterogeneous systems.

The reducibility of magnesia-supported nickel catalysts and NiO–MgO physical mixture has been studied by the temperature-programmed reduction (TPR) technique in the temperature range 373–1273 K. The influences of calcination temperature (673–1273 K), treatment time (1–48 h) and Ni loading (2.8–18 wt %) on NiO reduction have been evaluated. The TPR profiles of Ni/MgO catalysts reveal the presence of several forms of NiO, at the surface and in the near-surface regions (bulk-like) of the MgO, the reducibility of which is affected by the interaction strength between Ni2+ and underlying MgO support. A form of ‘unreacted’ NiO located on the MgO surface, which behaves as ‘bulk unsupported NiO’, was detected. Calcination at 673 K promotes a partial migration of Ni2+ ions into the MgO structure, which is enhanced by higher calcination temperatures, hindering the whole reducibility. At 1273 K an ‘ideal’ and non-reducible bulk NiO–MgO solid solution is formed. In contrast, the reducibility of the NiO–MgO physical mixture is slightly affected by calcination up to 1073 K and its TPR profile shows only a reduction peak shifted to higher T by calcination temperature. The different degree of interaction between NiO and MgO in supported and physically mixed systems has been explained in terms of different contact area arising from the preparation method. The importance of calcination time, in order to avoid erratic assessments due to unsteady states in the NiO–MgO reacting system, has been demonstrated. A linear correlation between the reducibility of Ni/MgO catalysts and the Ni loading was found, and was explained by inferring that higher Ni loading increases the fraction of ‘unreacted’ and ‘easy-reducible’ NiO.Experimental results indicate that TPR is a powerful technique for investigating the solid-state reaction between NiO and MgO.

Temperature-programmed reduction study of NiO–MgO interactions in magnesia-supported Ni catalysts and NiO–MgO physical mixture

The effects of the oxide carrier (γ-Al2O3, SiO2, ZrO2, TiO2), MnOx precursor (KMnO4 , Mn(NO3)2 and Mn(CH3COO)2), loading (2–17 wt.% Mn) and preparation method on the structure and reduction pattern of MnOx-based catalysts have been systematically evaluated by X-ray diffraction (XRD) and temperature programmed reduction (TPR) measurements in the range 273–1073 K. Oxide precursor and preparation method determine both the structure and average oxidation number (A.O.N.) of the MnOx (1.5<x<2) phase in bulk and supported systems. The reducibility scale, based on the inverse sequence of the onset temperature of reduction (To,red),
 signals that the reduction
pattern of MnOx catalysts depends upon Mn loading and nature of the oxide–support interaction, which control both dispersion and A.O.N. of the active phase.

A. Parmaliana

Papers

Temperature-programmed reduction study of NiO–MgO interactions in magnesia-supported Ni catalysts and NiO–MgO physical mixture

Structure and redox properties of bulk and supported manganese oxide catalysts

Potassium-enhanced stability of Ni/MgO catalysts in the dry-reforming of methane

Magnesia-Supported Nickel Catalysts: II. Surface Properties and Reactivity in Methane Steam Reforming

Magnesia-supported nickel catalysts I. Factors affecting the structure and morphological properties