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Article ; Online: Na-Influenced Bulk and Surface Properties of the So-Called Iota(ι)-Alumina

Ali Bumajdad / Shamsun Nahar / Mohamed I. Zaki

Frontiers in Chemistry, Vol

Spectroscopy and Microscopy Studies

2021 Volume 9

Abstract: The test alumina (the so-called ι-Al2O3) was thermally recovered at 1,100°C from chitosan-AlOx hybrid films and found to contain Na and Ca impurity ions inherited from the parent chitosan. Two different modifications of pure alumina, namely, γ- and α- ... ...

Abstract	The test alumina (the so-called ι-Al2O3) was thermally recovered at 1,100°C from chitosan-AlOx hybrid films and found to contain Na and Ca impurity ions inherited from the parent chitosan. Two different modifications of pure alumina, namely, γ- and α-Al2O3, were adopted as control samples. The test and control aluminas were examined for 1) the bulk elemental constitution by atomic absorption spectroscopy (AAS), 2) the surface chemical composition by X-ray photoelectron spectroscopy (XPS), 3) the bulk phase composition by X-ray powder diffractometry (XRD), ex-situ Fourier-transform infrared spectroscopy (IR), and Laser Raman (LRa) spectroscopy, 4) the surface area, topography, and morphology by N2 sorptiometry, and atomic force (AFM) and scanning electron microscopy (SEM), 5) the surface adsorptive interactions with pyridine and 2-propanol gas-phase molecules by in-situ IR spectroscopy of the adsorbed species, and 6) the surface catalytic interactions with 2-propanol gas-phase molecules by in-situ IR spectroscopy of the gas phase. Results obtained could clearly show that the test alumina (ι-Al2O3) is only hypothetically pure alumina since in reality its bulk structure is majored by mullite-type Na-aluminate (Na0.67Al6O9.33/NaAlO2) and minored by Na-β-alumina (Na1.71Al11O17) and β-alumina (NaAl11O17). Consistently, observed Na-influenced modifications of the surface chemistry, topology, and morphology, as well as adsorptive and catalytic interactions with pyridine and 2-propanol gas-phase molecules, showed significant deviations from those exhibited by the control pure aluminas (γ- and α-Al2O3).
Keywords	iota-alumina ; bulk characterization ; surface characterization ; adsorptive interactivity ; acid-base catalytic activity ; Na-influences ; Chemistry ; QD1-999
Subject code	540
Language	English
Publishing date	2021-02-01T00:00:00Z
Publisher	Frontiers Media S.A.
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article ; Online: Lattice-charge imbalance and redox catalysis over perovskite-type ferrite- and manganite-based mixed oxides as studied by XRD, FTIR, UV–Vis DRS, and XPS

Gamal A. H. Mekhemer / Hagar A. A. Mohamed / Ali Bumajdad / Mohamed I. Zaki

Scientific Reports, Vol 13, Iss 1, Pp 1-

2023 Volume 9

Abstract: Abstract In the present investigation, two sets of pure and substituted ferrite- and manganite-based mixed oxides were prepared within the stoichiometric formula $$A_{1 - x} A^{\prime}_{x} B_{1 - x} B^{\prime}_{x} O_{3}$$ A 1 - x A x ′ B 1 - x B x ′ O 3 , ...

Abstract	Abstract In the present investigation, two sets of pure and substituted ferrite- and manganite-based mixed oxides were prepared within the stoichiometric formula $$A_{1 - x} A^{\prime}_{x} B_{1 - x} B^{\prime}_{x} O_{3}$$ A 1 - x A x ′ B 1 - x B x ′ O 3 , where A = Bi or La, A ′ = Sr, B = Fe or Mn, B′ = Co, x = 0 or 0.2, by calcination at 700 °C (for 1 h) of corresponding metal citrate xerogels. Materials thus obtained were examined for bulk and surface characteristics using X-ray diffractometry, ex situ Fourier transform infrared spectroscopy, UV–Vis diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy, and N2 sorptiometry. Their redox catalytic activity was evaluated towards a 2-propanol dehydrogenation reaction in the gas phase by employing in situ Fourier transform infrared spectroscopy. The results obtained could help reveal that (1) the presence of Bi (versus La) and Mn (versus Fe) facilitated the formation of polymeric crystalline phases assuming lattice-charge imbalance (due to excess positive charge), (2) the surface exposure of the excess positive charge was manifested in the generation of Mn sites having various oxidation states ≥ 3+, (3) the consequent development of visible light absorptions at 498–555 nm suggested occurrence of electron double-exchange facilitated by the formation of Mnn+–O2−–Mn(n+1)+ Zener-type linkages, and (4) the exposure of such linkages at the surface warrants the establishment of the electron-mobile environment necessitated by the redox catalytic activity. Moreover, the relationship between the alcohol dehydrogenation activity and the magnitude of the lattice-charge imbalance (i.e., the net excess positive charge) of the catalysts was highlighted.
Keywords	Medicine ; R ; Science ; Q
Subject code	540
Language	English
Publishing date	2023-05-01T00:00:00Z
Publisher	Nature Portfolio
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article ; Online: Low-Temperature Catalytic CO Oxidation Over Non-Noble, Efficient Chromia in Reduced Graphene Oxide and Graphene Oxide Nanocomposites

Asma A. Ali / Metwally Madkour / Fakhreia Al Sagheer / Mohamed I. Zaki / Ahmed Abdel Nazeer

Catalysts, Vol 10, Iss 1, p

2020 Volume 105

Abstract: Herein, bare chromia nanoparticles (Cr 2 O 3 NPs) and chromia supported on reduced graphene oxide (rGO) and graphene oxide (GO) hybrids were synthesized, followed by characterization by means of FESEM, Raman spectroscopy, TGA, XRD, TEM/HRTEM, XPS and N 2 ...

Abstract	Herein, bare chromia nanoparticles (Cr 2 O 3 NPs) and chromia supported on reduced graphene oxide (rGO) and graphene oxide (GO) hybrids were synthesized, followed by characterization by means of FESEM, Raman spectroscopy, TGA, XRD, TEM/HRTEM, XPS and N 2 sorptiometry. The investigated bare Cr 2 O 3 and the hybrids (Cr 2 O 3 /rGO and Cr 2 O 3 /GO) were employed as catalysts for low-temperature CO oxidation. Compared with the other catalysts, the results revealed efficient catalytic activity using Cr 2 O 3 /GO, which was attributed to its higher surface area together with the mixed oxidation state of chromium (Cr 3+ and Cr >3+ ). These are important oxidation sites that facilitate the electron mobility essential for CO oxidation. Moreover, the presence of carbon vacancy defects and functional groups facilitate the stabilizing of Cr 2 O 3 NPs on its surface, forming a thermally stable hybrid material, which assists the CO oxidation process. The Cr 2 O 3 /GO hybrid is a promising low-cost and efficient catalyst for CO oxidation at low temperatures. The higher activity of graphene oxide supported Cr 2 O 3 NPs can provide an efficient and cost-effective solution to a prominent environmental problem.
Keywords	chromium oxide nps ; co oxidation ; cr 2 o 3 /carbonaceous hybrid ; catalysis ; Chemical technology ; TP1-1185 ; Chemistry ; QD1-999
Subject code	290
Language	English
Publishing date	2020-01-01T00:00:00Z
Publisher	MDPI AG
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article ; Online: Controlled Synthesis of ZrO2 Nanoparticles with Tailored Size, Morphology and Crystal Phases via Organic/Inorganic Hybrid Films

Ali Bumajdad / Ahmed Abdel Nazeer / Fakhreia Al Sagheer / Shamsun Nahar / Mohamed I. Zaki

Scientific Reports, Vol 8, Iss 1, Pp 1-

2018 Volume 9

Abstract: Abstract In this investigation, well defined mesoporous zirconia nanoparticles (ZrO2 NPs) with cubic, tetragonal or monoclinic pure phase were synthesized via thermal recovery (in air) from chitosan (CS)- or polyvinyl alcohol (PVA)-ZrOx hybrid films, ... ...

Abstract	Abstract In this investigation, well defined mesoporous zirconia nanoparticles (ZrO2 NPs) with cubic, tetragonal or monoclinic pure phase were synthesized via thermal recovery (in air) from chitosan (CS)- or polyvinyl alcohol (PVA)-ZrOx hybrid films, prepared using sol–gel processing. This facile preparative method was found to lead to an almost quantitative recovery of the ZrOx content of the film in the form of ZrO2 NPs. Impacts of the thermal recovery temperature (450, 800 and 1100 °C) and polymer type (natural bio-waste CS or synthetic PVA) used in fabricating the organic/inorganic hybrid films on bulk and surface characteristics of the recovered NPs were probed by means of X-ray diffractometry and photoelectron spectroscopy, FT-IR and Laser Raman spectroscopy, transmission electron and atomic force microscopy, and N2 sorptiometry. Results obtained showed that the method applied facilates control over the size (6–30 nm) and shape (from loose cubes to agglomerates) of the recovered NPs and, hence, the bulk crystalline phase composition and the surface area (144–52 m2/g) and mesopore size (23–10 nm) and volume (0.31–0.11 cm3/g) of the resulting zirconias.
Keywords	Medicine ; R ; Science ; Q
Subject code	620
Language	English
Publishing date	2018-02-01T00:00:00Z
Publisher	Nature Publishing Group
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article ; Online: On the Impact of the Preparation Method on the Surface Basicity of Mg–Zr Mixed Oxide Catalysts for Tributyrin Transesterification

Abdallah I. M. Rabee / Jinesh C. Manayil / Mark A. Isaacs / Christopher M. A. Parlett / Lee J. Durndell / Mohamed I. Zaki / Adam F. Lee / Karen Wilson

Catalysts, Vol 8, Iss 6, p

2018 Volume 228

Abstract: Mixed metal oxides are promising heterogeneous catalysts for biofuel production from lipids via alcoholysis, however, the impact of solid acidity and/or basicity on reactivity is comparatively poorly understood. Two systematically related families of MgO– ...

Abstract	Mixed metal oxides are promising heterogeneous catalysts for biofuel production from lipids via alcoholysis, however, the impact of solid acidity and/or basicity on reactivity is comparatively poorly understood. Two systematically related families of MgO–ZrO2 mixed oxide catalysts were therefore prepared by different synthetic routes to elucidate the impact of surface acid-base properties on catalytic performance in the transesterification of tributyrin with methanol. The resulting materials were characterized by TGA-MS, ICP-OES, N2 porosimetry, XRD, TEM, XPS, DRIFTS, and CO2-temperature-programmed desorption (TPD). MgO–ZrO2 catalysts prepared by both non-aqueous impregnation and citric acid-mediated sol–gel routes exhibit excellent activity and stability. The citrate routes favor highly dispersed MgO and concomitant Lewis acid-base pair formation at the interface with zirconia. However, for both the citrate and impregnation routes, tributyrin transesterification occurs over a common, strongly basic MgO active site.
Keywords	solid base ; MgO ; transesterification ; mixed oxide ; biodiesel ; Chemical technology ; TP1-1185 ; Chemistry ; QD1-999
Subject code	540
Language	English
Publishing date	2018-05-01T00:00:00Z
Publisher	MDPI AG
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article ; Online: Theoretical Study of the Adsorption of 2-Propanol onto Silica Surfaces on the Basis of and Density Functional Calculations

Mariam R. Abdallah / Muhammad A. Hasan / Mohamed I. Zaki

Adsorption Science & Technology, Vol

2009 Volume 27

Abstract: The adsorptive interactions of 2-propanol (2-PrOH) molecules with silica surfaces were investigated using ab initio and density functional calculations. Two cluster models of silica were chosen to represent the terminal ≡SiOH groups and the siloxane ... ...

Abstract	The adsorptive interactions of 2-propanol (2-PrOH) molecules with silica surfaces were investigated using ab initio and density functional calculations. Two cluster models of silica were chosen to represent the terminal ≡SiOH groups and the siloxane bridges ≡Si–(O) 2 –Si≡ on the silica surface. The Hartree–Fock (HF) and Density Functional Theory (DFT) approaches, employing a 6–31G(d) basis set, were used to calculate the geometries, electronic structures, vibrational frequencies and adsorption energies of the adsorption complexes formed. The calculated adsorption energies were corrected for zero-point vibrational energies (ZPVE) and basis set superposition errors (BSSE). The results favoured a most likely surface configuration for the physisorbed species in which 2-PrOH molecules are bound to exposed silanol groups via two hydrogen bonds, with the alcoholic –OH group acting simultaneously as a proton acceptor and donor. Moreover, bonding of 2-PrOH with strained surface siloxane bridges (≡Si–O–Si≡) was shown to lead to chemisorption of the alcohol molecule. These findings have been shown to help interpreting reported infrared spectroscopic results of in-situ experimental studies.
Keywords	Physical and theoretical chemistry ; QD450-801
Subject code	541 ; 540
Language	English
Publishing date	2009-04-01T00:00:00Z
Publisher	Hindawi - SAGE Publishing
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article ; Online: Nitrogen Sorptiometric Study of Phosphation and Dispersion of Lanthanum(III) Oxide on Alumina Catalysts

Gamal A.H. Mekhemer / Ali F. Bukhzam / Amal S. El-Towaty / Mohamed I. Zaki

Adsorption Science & Technology, Vol

2011 Volume 29

Abstract: Alumina-supported lanthanum(III) oxide catalysts at loadings varying in the range 3–30 wt% La 2 O 3 were prepared by wet impregnation and calcination at 920 K for 2 h. An analogous series of catalysts were phosphated by impregnation with up to 6 wt% PO 4 ...

Abstract	Alumina-supported lanthanum(III) oxide catalysts at loadings varying in the range 3–30 wt% La 2 O 3 were prepared by wet impregnation and calcination at 920 K for 2 h. An analogous series of catalysts were phosphated by impregnation with up to 6 wt% PO 4 3– from aqueous solutions of (NH 4 )H 2 PO 4 and then calcined similarly. The catalysts thus obtained were characterized by X-ray diffractometry, infrared spectroscopy and nitrogen sorptiometry at 77 K. The adsorption data were analyzed by the BET method and the t-method. The results suggested that lanthanum(III) oxide loadings up to 30 wt% exist as high-dispersion two- and three-dimensional structures on the surface of alumina that are not XRD-detectable (particle size < 2 nm). Strong interactions not only at the liquid/solid interface established during impregnation, but also at the solid/solid interface established during drying and/or calcination, are suggested to be important events in the dispersion mechanism. Phosphation led to the improvement of the two-dimensional lanthanum(III) oxide dispersion (probably in monolayers) rather than the three-dimensional one, most likely through direct bonding of the phosphate groups to exposed La 3+ sites. It is inferred that nitrogen adsorption data can provide valuable qualitative information on the dispersion of supported oxide materials.
Keywords	Physical and theoretical chemistry ; QD450-801
Subject code	540
Language	English
Publishing date	2011-12-01T00:00:00Z
Publisher	Hindawi - SAGE Publishing
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article ; Online: Acidity-Reactivity Relationships in Catalytic Esterification over Ammonium Sulfate-Derived Sulfated Zirconia

Abdallah I. M. Rabee / Gamal A. H. Mekhemer / Amin Osatiashtiani / Mark A. Isaacs / Adam F. Lee / Karen Wilson / Mohamed I. Zaki

Catalysts, Vol 7, Iss 7, p

2017 Volume 204

Abstract: New insight was gained into the acidity-reactivity relationships of sulfated zirconia (SZ) catalysts prepared via (NH4)2SO4 impregnation of Zr(OH)4 for propanoic acid esterification with methanol. A family of systematically related SZs was characterized ... ...

Abstract	New insight was gained into the acidity-reactivity relationships of sulfated zirconia (SZ) catalysts prepared via (NH4)2SO4 impregnation of Zr(OH)4 for propanoic acid esterification with methanol. A family of systematically related SZs was characterized by bulk and surface analyses including XRD, XPS, TGA-MS, N2 porosimetry, temperature-programmed propylamine decomposition, and FTIR of adsorbed pyridine, as well as methylbutynol (MBOH) as a reactive probe molecule. Increasing surface sulfation induces a transition from amphoteric character for the parent zirconia and low S loadings <1.7 wt %, evidenced by MBOH conversion to 3-hydroxy-3-methyl-2-butanone, methylbutyne and acetone, with higher S loadings resulting in strong Brønsted-Lewis acid pairs upon completion of the sulfate monolayer, which favored MBOH conversion to prenal. Catalytic activity for propanoic acid esterification directly correlated with acid strength determined from propylamine decomposition, coincident with the formation of Brønsted-Lewis acid pairs identified by MBOH reactive titration. Monodispersed bisulfate species are likely responsible for superacidity at intermediate sulfur loadings.
Keywords	zirconia ; sulfated zirconia ; solid acid ; XPS ; IR ; esterification ; Chemical technology ; TP1-1185 ; Chemistry ; QD1-999
Subject code	540
Language	English
Publishing date	2017-07-01T00:00:00Z
Publisher	MDPI AG
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article ; Online: Low-Temperature IR Spectroscopy of CO Adsorption on Calcined Supported CeO

Gamal A.H. Mekhemer / Mohamed I. Zaki

Adsorption Science & Technology, Vol

Probing Adsorbed Species and Adsorbing Sites

1997 Volume 15

Abstract: Carbon monoxide adsorption on ceria dispersed on silica (CeSi) and alumina (CeAl) at 300–80 K was observed by in-situ IR spectroscopy. For control purposes, CO adsorption was also observed on unsupported CeO 2 and the individual support materials (SiO 2 ... ...

Abstract	Carbon monoxide adsorption on ceria dispersed on silica (CeSi) and alumina (CeAl) at 300–80 K was observed by in-situ IR spectroscopy. For control purposes, CO adsorption was also observed on unsupported CeO 2 and the individual support materials (SiO 2 and Al 2 O 3 ). The adsorbents were prepared ex situ by heating at 770 K (3 h) in air, and pretreated in situ by heating at 720 K (1 h) in oxygen and then in vacuum. The results, as disclosed by v(OH) (3900–3300 cm −1 ) and v(CO) (2250–2050 cm −1 ) spectra taken before and after CO adsorption, reveal that CO adsorbs on all of the test adsorbents at temperatures < 300 K only. The resulting adsorbed species include CO coordinated to Lewis acid sites (on all of the adsorbents, but not SiO 2 ), hydrogen-bonded CO (on all of the adsorbents, but not CeO 2 ) and CO bound to electron-rich defect sites (only on unsupported CeO 2 ). It is concluded that the dispersion of ceria, particularly on alumina, is associated with a considerable development of the Lewis acidity of Ce 4+ sites.
Keywords	Physical and theoretical chemistry ; QD450-801
Subject code	540
Language	English
Publishing date	1997-05-01T00:00:00Z
Publisher	Hindawi - SAGE Publishing
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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