Abbas Khaleel

Nanocrystalline Metal Oxides as Unique Chemical Reagents/Sorbents

A new family of porous inorganic solids based on nanocrystalline metal oxides is discussed. These materials, made up of 4-7 nm MgO, CaO, Al2O3, ZnO, and others, exhibit unparalleled destructive adsorption properties for acid gases, polar organics, and even chemical/biological warfare agents. These unique sorption properties are due to nanocrystal shape, polar surfaces, and high surface areas. Free-flowing powders or consolidated pellets are effective, and pore structure can be controlled by consolidation pressures. Chemical properties can be adjusted by choice of metal oxide as well as by incorporating other oxides as monolayer films.

Nanocrystalline metal oxides as new adsorbents for air purification

Abstract Nanocrystals of MgO, CaO, and Al 2 O 3 were prepared by aerogel (AP-samples) or conventional (CP-samples) methods. High surface areas/gram were obtained, often as high as 500 m 2 /g (1) . These materials were investigated as adsorbents for typical volatile organic compounds that are representative of air pollutants. As a result of their high surface areas and their enhanced surface reactivity, nanocrystalline MgO, CaO and Al 2 O 3 have shown remarkably high capacities to chemically adsorb such organic compounds. Compared to high surface area activated carbon, the most widely used material in this application, our nanocrystalline materials have exhibited higher capacities and the ability to destructively adsorb rather than physisorb these chemicals. FT-IR investigation of acetaldehyde adsorption on AP- and CP-MgO indicates that a multilayer dissociative adsorption took place. Adsorption of other organic compounds was also investigated including acetone, propionaldehyde, benzaldehyde, trimethylacetaldehyde, ammonia, dimethylamine, N-nitrosodiethylamine, and methanol, most of which were found to adsorb well on AP-MgO. In addition, long term air exposure did not have detrimental effects on the adsorption properties of AP-MgO.

Nanocrystals as stoichiometric reagents with unique surface chemistry. New adsorbents for air purification

Abstract Nanocrystals of MgO and CaO were prepared with high surface areas/gram, often as high as 500 m 2 /g [1]. These materials were investigated as adsorbents for typical volatile organic compounds that are representative of air pollutants. As a result of their high surface areas and their enhanced surface reactivity, nanocrystalline MgO and CaO have shown a remarkably high capacity to chemically adsorb such organic compounds Compared to high surface area activated carbon, the most widely used material in this application, our nanocrystalline materials have shown much better adsorption in regards to the amount and the nature of adsorption. FT-IR investigation of acetaldehyde adsorption on AP-MgO indicates that a multilayer dissociative adsorption takes place as a result of surface interaction with the carbonyl bond followed by aldehydic hydrogen dissociation

Photochemical synthesis of new (η6-arene)Cr–hydrido stannyl and (η6-arene)Cr–bis-stannyl complexes. Ligand effects on the Sn–H interaction in the hydrido stannyl compounds

Abstract Hydrido stannyl compounds containing the η2-H–SnPh3 ligand and bis-stannyl compounds containing two SnPh3 ligands have been obtained from the photolysis of (η6-arene)Cr(CO)3 and HSnPh3. New complexes with different arenes (mesitylene, trifluorotoluene and 1,4-dimethoxybenzene) have been obtained and characterized by X-ray diffraction: (η6-C6H4(OCH3)2)Cr(CO)2(HSnPh3) (3a), (η6-C6H4(OCH3)2)Cr(CO)2(SnPh3)2 (3b). Structural data for 3a: monoclinic; space group P21/c (No. 14); a=17.445(3), b=9.820(3) and c=16.302(5) A; Z=4; V=2539.2(12) A3; 3b: monoclinic; space group P21/n (No. 14); a=13.904(3), b=20.567(5) and c=13.911(3) A; Z=4; V=3994(2) A3. 1H-NMR as well as X-ray provided evidence for the existence of three-center two-electron bonds in the hydrido stannyl complexes. The effects of different ligands on bonding and spectroscopic parameters were studied. Arene exchange reactions of the bis-stannyl complexes, as well as reactions of some of these compounds with P(C2H5)3 and CO, were also investigated.

Catalysis and Surface Chemistry: Metal Clusters/Nanoscale Particles

Recent experiments have shed light on how metal clusters behave as catalysts. Especially by studying bimetallic systems, electronic and ensemble (geometric) effects have been clarified. Strong metal support interactions (SMSI) may be explained due to “decoration effects”. It is apparent that morphology of the particles is extremely important in determining catalytic properties. Recent experiments in metal vapor chemistry for producing various catalytic morphologies are discussed, with special emphasis on the Pt°-Sn° system. Finally, new studies of gas phase metal cluster-hydrocarbon reactions are briefly reviewed with emphasis on Pt(n) and Nb(n).

Iron Oxide on Magnesium Oxide Support as a New Destructive Adsorbent for Chlorinated Hydrocarbons

In this study an overlayer structure of iron oxide on magnesium oxide support and pure magnesium oxide was synthesized in ultra fine particles of high surface area. The surface structure of Fe/MgO particles was studied by XPS, Mossbauer and XRD spectroscopy and surface chemisorption of CO2. The potential of both compounds to react with and decompose CCl4 was studied. Infrared (IR), powder X-Ray Diffraction (XRD) and Gas Chromatography (GC) measurements were applied to study the decomposition reaction with CCl4. The results of this study prove that magnesia-supported iron oxide (Fe/MgO) is about 15 times more efficient in reacting with and decomposing CCl4 than pure MgO.