Gamal A.M. Hussein

Bio: Gamal A.M. Hussein is an academic researcher from Minia University. The author has contributed to research in topics: Differential thermal analysis & Thermogravimetry. The author has an hindex of 18, co-authored 40 publications receiving 1036 citations. Previous affiliations of Gamal A.M. Hussein include University of Delaware.

Infrared spectroscopic studies of the reactions of alcohols over group IVB metal oxide catalysts. Part 1.—Propan-2-ol over TiO2, ZrO2 and HfO2

Abstract: Infrared spectroscopy has been used to analyse the gas-phase reaction products and the related adsorbed species obtained between room temperature and 400 °C from the dehydrogenation/dehydration reactions of propan-2-ol over a series of differently calcined catalysts of TiO2, ZrO2 and HfO2. The ZrO2 and HfO2 results were independent of the calcination pretreatment, and the surfaces of these oxides, like that from a TiO2 sample calcined at 800 °C, were dehydroxylated. Different results were obtained from a TiO2 sample calcined at 300 °C which had a hydroxylated surface. The acidic sites and reactivities of the surfaces of TiO2(300 °C) and TiO2(800 °C) were explored by pyridine adsorption and infrared spectroscopy. Only Lewis-acid sites were detected by pyridine.On raising the reaction temperature, in all cases the dehydrogenation reaction to give acetone occurred either before or simultaneously to the onset of the dehydration reaction to give propene. Acetone production was most pronounced over ZrO2 and HfO2 but also occurred more with TiO2(800 °C) than with TiO2(300 °C). The dehydrogenation reaction was largely quenched by pre-adsorbed pyridine on both TiO2 samples. The TiO2(300 °C) catalyst showed the presence of adsorbed propan-2-ol and 2-propoxide groups at room temperature. The dehydroxylated ZrO2, HfO2 and TiO2(800 °C) samples only showed appreciable amounts of 2-propoxide groups. In each case the 2-propoxide ions occurred in two different forms, presumably formed by adsorption on different types of sites.Both the acetone and propene products appeared as absorptions from 2-propoxide surface species decreased in intensity, so the latter are clearly reactive species. Gas-phase acetone production was followed by the chemisorption of acetone at a higher temperature. This subsequently decomposed to give surface acetate species, and finally at 400 °C to give CO2 and methane in the gas phase. Propene did not give rise to adsorbed species, or to further products in the gas phase.At the higher temperatures, above 300 °C, the reaction was always selective in favour of the dehydration reaction. However, each of the dehydroxylated catalysts showed some selectivity in favour of the dehydrogenation reaction over the earliest temperature range for alcohol decomposition, between 200 and 250 °C.A discussion is given of possible mechanistic pathways for the production of surface 2-propoxide species and the two types of products, based on the infrared-supported assumption that the different adsorbed forms of 2-propoxide [and possibly adsorbed propan-2-ol on TiO2(300 °C)] are reactive intermediates.

Infrared spectroscopic studies of the reactions of alcohols over group IVB metal oxide catalysts. Part 3.—Ethanol over TiO2, ZrO2 and HfO2, and general conclusions from parts 1 to 3

Abstract: The dehydrogenation and dehydration reactions of ethanol over TiO2, ZrO2 or HfO2 catalysts has been monitored in the gas phase and on the surfaces by infrared spectroscopy. The reaction pathways closely parallel those of methanol reported in the prevous paper (Part 2) with the addition of the direct dehydration reaction C2H5OH → C2H4+ H2O and the production of benzene as a minor product. The infrared spectroscopic analysis of the decomposition of diethyl ether as initial reagent over the TiO2(500) catalyst confirms that the ethane product is derived from the ether precursor. As with methane from methanol, it is probably produced by reduction of the ether to the alkane plus water by hydrogen derived from the parallel dehydrogenation reaction.A summary is given of probable mechanisms for the catalysed reactions of the three alcohols, methanol, ethanol and propan-2-ol based on the gas-phase products and surface species identified by infrared spectroscopy. The general importance of alkoxide surface intermediates is emphasised. Alkoxides of a given formula occur on different spectroscopically distinguishable sites with different reactivities.

Iron(III) Oxides from Thermal ProcessesSynthesis, Structural and Magnetic Properties, Mössbauer Spectroscopy Characterization, and Applications†

Abstract: Structural and magnetic properties, methods of synthesis, and applications of seven iron(III) oxide polymorphs, including rare beta, epsilon, amorphous, and high-pressure forms, are reviewed. Thermal transformations resulting in the formation of iron oxides are classified according to different parameters, and their mechanisms are discussed. 57Fe Mossbauer spectroscopy is presented as a powerful tool for the identification, distinction, and characterization of individual polymorphs. The advantages of Mossbauer spectroscopy are demonstrated with two examples related to the study of the thermally induced solid-state reactions of Fe2(SO4)3.

Ni/CeO2-ZrO2 catalysts for the dry reforming of methane

Abstract: Nickel catalysts supported on binary CeO 2 –ZrO 2 carriers (28–100% CeO 2 molar content) were prepared and evaluated regarding their catalytic performance for the CO 2 reforming of CH 4 (Dry Reforming of Methane, DRM). The textural and structural properties of catalysts and supports were studied in their calcined, reduced and used state by N 2 adsorption–desorption, XRD, UV–vis DRS, TPR, SEM–EDS and TPH. Zirconium improves the textural properties of the CeO 2 –ZrO 2 supports and the corresponding catalysts and enhances their textural stability under thermal reductive treatment. XRD analysis shows the formation of Ce x Zr 1− x O 2 solid solution for all Ce/(Ce + Zr) ratios. Considerable alterations in the electronic environment of the cations and increased lattice defects in the binary solid solutions were detected by UV–vis DR spectroscopy. A significant increase in the reducibility of both supports and catalysts is observed in the presence of Zr. Compared to the zirconia-free sample, the Ni/CeO 2 -ZrO 2 catalysts exhibited much higher activity for the title reaction, accredited to the increase of the surface concentration of the active sites. However, the amount of carbonaceous deposits is not straightforward related to the activity but depends on the Ce/Zr ratio. Among the zirconium containing catalysts, the zirconium-rich one exhibited the higher activity and the stronger resistance to the formation of carbonaceous deposits.

Ceria‐Based Solid Catalysts for Organic Chemistry

Abstract: Ceria has been the subject of thorough investigations, mainly because of its use as an active component of catalytic converters for the treatment of exhaust gases. However, ceria-based catalysts have also been developed for different applications in organic chemistry. The redox and acid-base properties of ceria, either alone or in the presence of transition metals, are important parameters that allow to activate complex organic molecules and to selectively orient their transformation. Pure ceria is used in several organic reactions, such as the dehydration of alcohols, the alkylation of aromatic compounds, ketone formation, and aldolization, and in redox reactions. Ceria-supported metal catalysts allow the hydrogenation of many unsaturated compounds. They can also be used for coupling or ring-opening reactions. Cerium atoms can be added as dopants to catalytic system or impregnated onto zeolites and mesoporous catalyst materials to improve their performances. This Review demonstrates that the exceptional surface (and sometimes bulk) properties of ceria make cerium-based catalysts very effective for a broad range of organic reactions.