A study is conducted to demonstrate catalytic dehydrogenation of light alkanes on metals and metal oxides. The study provides a complete overview of the materials used to catalyze this reaction, as dehydrogenation for the production of light olefins has become extremely relevant. Relevant factors, such as the specific nature of the active sites, as well as the effect of support, promoters, and reaction feed on catalyst performance and lifetime, are discussed for each catalytic Material. The study compares different catalysts in terms of the reaction mechanism and deactivation pathways and catalytic performance. The duration of the dehydrogenation step depends on the heat content of the catalyst bed, which decreases rapidly due to the endothermic nature of the reaction. Part of the heat required for the reaction is introduced to the reactors by preheating the reaction feed, additional heat being provided by adjacent reactors that are regenerating the coked catalysts.

Catalytic dehydrogenation of light alkanes on metals and metal oxides.

https://iris.unipa.it/bitstream/10447/74239/1/Di%20Paola-J%20hzardous%20mater%202012-survey.pdf

A survey of photocatalytic materials for environmental remediation.

In this perspective, we focus on a new type of quantum dots, graphene quantum dots (GQDs). Due to quantum confinement and edge effects, GQDs have presented extraordinary properties, attracting extensive attention from scientists in the fields of chemistry, physics, materials, biology, and other interdisciplinary sciences. Herein, we summarize the significant advances achieved by us and other groups in the past few years on both the experimental and theoretical fronts. Synthetic strategies, unique optical and electronic properties, and the promise of GQDs in energy-related devices, such as photovoltaic devices, fuel cells, and light-emitting diodes, are systematically discussed.

Graphene quantum dots: an emerging material for energy-related applications and beyond

Focuses on the surface chemistry and spectroscopy of chromium in inorganic oxides. Characterization of the molecular structures of chromium; Mechanics of hydrogenation-dehydrogenation reactions; Mobility and reactivity on oxidic surfaces.

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Surface Chemistry and Spectroscopy of Chromium in Inorganic Oxides.

Influence of parameters on the heterogeneous photocatalytic degradation of pesticides and phenolic contaminants in wastewater: A short review

Zirconia supported tungsten oxide catalysts (tungsten content up to 337 wt%) were prepared by equilibrium adsorption and impregnation in acid (pH 27) and basic (pH 10) conditions using hydrous zirconium oxide After thermal treatment at 1073 K in air, the catalysts were characterized by surface area determination, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), X-ray absorption spectroscopy (XAS), diffuse optical reflectance, Raman spectroscopy and chemical analysis The results show that tungsten is present as a dispersed phase and as monoclinic WO3 crystallites The density of tungsten in a dispersed form was estimated as about 5 atoms nm−2 Leaching treatments with ammonia revealed that only a fraction of the dispersed tungsten interacts directly with the support surface The interacting species, in the form of small clusters, as revealed by EXAFS and Raman spectroscopy, control the ZrO2 surface area and are responsible for the structural changes in the support Subsequent thermal treatment up to 1073 K in air leaves them unchanged

WOx/ZrO2 catalysts: Part 1. Preparation, bulk and surface characterization☆

The formation of solid solution and ZrO2 phase stabilization were investigated by Raman spectroscopy and X-ray diffraction (XRD) in calcium-containing and cadmium-containing zirconium oxide samples heated at 1073 K in air. The adopted preparation procedure led to the incorporation of calcium and cadmium in solid solution into the zirconia structure. The solid solution favored the tetragonal and cubic zirconia phases at the expense of the thermodynamically stable monoclinic modification. Combined macro- and micro-Raman spectroscopy disclosed that instead of forming a homogeneous phase t″, intermediate between the tetragonal t′ and the cubic phase, the tetragonal and cubic phases coexisted in the range 9.49–13.89 mol% for Ca and 11.88–17.23 mol% for Cd. At higher dopant contents the cubic form stabilized. The impurity content necessary to stabilize the high-symmetry phases was defined. Copyright © 2007 John Wiley & Sons, Ltd.

Raman and X-ray investigations of the incorporation of Ca2+ and Cd2+ in the ZrO2 structure

Studies on chromia/zirconia catalysts I. Preparation and characterization of the system

The preparation of cobalt-modified T i O 2 (Co- T i O 2 ) was carried out by the incipient impregnation method starting from commercial T i O 2 (Degussa, P-25) and cobalt acetate. XPS data show that cobalt is incorporated as divalent ion, and it is likely present within few subsurface layers. No appreciable change in structural-morphologic properties, such as surface area and anatase/rutile phase ratio, was observed. Conversely, Co addition brings about conspicuous changes in the point of zero charge and in surface polarity. Diffuse reflectance spectra feature a red shift in light absorption that is dependent on the amount of cobalt.
The influence of cobalt addition on the performance of T i O 2 as a photocatalyst in the degradation of 4-chlorophenol and Bisphenol A is investigated. The results show that the modified oxide presents a higher photoactivity both for illumination with 
UV-visible ( 𝜆 > 3 6 0  nm) and visible light ( 𝜆 > 4 2 0  nm; 𝜆 > 4 5 0  nm), and that this enhancement depends on the amount of the added species and on the final thermal treatment in the preparation step. We also show that Co- T i O 2 is a more active catalyst than pure T i O 2 for the reduction of O 2 in the dark, which is an important reaction in the overall photocatalytic processes.

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Preparation, Characterisation, and Photocatalytic Behaviour of Co-TiO2 with Visible Light Response

The redox properties of WOx/ZrO2 catalysts with W-content from 1.0 to 14.3 atoms nm−2, prepared by equilibrium adsorption from hydrous zirconium oxide and ammonium metatungstate solutions, were investigated by redox cycles with H2 and O2, volumetric oxygen adsorption at room temperature (RT), XPS and EPR. After catalysts were heated at 1073 K in air, the various tungsten species (small WxOy clusters anchored to zirconia surface, polyoxotungstates species and crystalline WO3) reacted differently with H2 in the range 473–773 K. The reduction degree of small WxOy clusters up to 723 K slightly increased and then sharply increased, yielding at 773 K an average oxidation state (nav) equal to 5.2. Conversely, the reduction degree of polyoxotungstates and WO3 steeply increased from 523 to 773 K, reaching nav equal to 4.8. XPS analysis disclosed that, after treatment in H2 at 773 K, whereas W5+ formed on all the samples, W4+ species formed only in samples containing WO3 and polyoxotungstates. Depending on W-content, EPR detected various W5+ species in reduced ZW samples: isolated ions incorporated into the monoclinic zirconia; two kind of surface species, one in small clusters and the other in polyoxotungstates, resembling a bronze-like structure. The formation of O2− by oxygen adsorption at RT gave an indirect evidence of isolated W5+ surface species, irrespective of W-content. Volumetric O2 adsorption indicated that W5+ surface species were largely re-oxidized at RT, whereas W4+ species, formed in polyoxotungstates and WO3, were less reactive, possibly because these species were less accessible to the gas phase.

Mario Valigi

Papers

WOx/ZrO2 catalysts: Part 1. Preparation, bulk and surface characterization☆

Raman and X-ray investigations of the incorporation of Ca2+ and Cd2+ in the ZrO2 structure

Studies on chromia/zirconia catalysts I. Preparation and characterization of the system

Preparation, Characterisation, and Photocatalytic Behaviour of Co-TiO2 with Visible Light Response

WOx/ZrO2 catalysts: Part 4. Redox properties as investigated by redox cycles, XPS and EPR