Abd El-Aziz A. Said

Usefulness of raw bagasse for oil absorption: A comparison of raw and acylated bagasse and their components

Raw bagasse or sugar cane cellulosic residues were modified using acylation grafting with fatty acid. The capability of the grafted bagasse to absorb oil from aqueous solution was studied and compared with the raw bagasse. It was found that the grafted material was significantly more hydrophobic than the raw bagasse. This grafted bagasse had little affinity for water and good affinity for oil. It was also found that bleaching of raw bagasse did not enhance its oil absorptivity. The grafted raw bagasse would be most suitable for applications where oil is to be removed from an aqueous environment. For oil absorbing applications in the absence of water, the raw bagasse was an excellent material.

The role of copper cobaltite spinel, CuxCo3 − xO4 during the thermal decomposition of ammonium perchlorate

Abstract The catalytic effect of copper cobaltite, CuxCo3 − xO4 spinel in the range (0 ≤ x ≤ 3) on the thermal decomposition of ammonium perchlorate (AP) has been studied using thermogravimetry (TG) and differential thermal analysis (DTA). The results revealed that the addition of CuO (x = 0.1 or 0.3) led to an observable increase in the catalytic activity of Co3O4 towards the decomposition of AP, while the activity of CuO decreases at x = 2.9 and 2.7. The creation of more holes within the p-type semiconducting catalyst is responsible for enhancing the decomposition of AP. In contrast, the catalysts containing copper cobaltite spinels are less active than the doped catalysts. The active redox sites established in these spinels, Co 3+ Co 2+ , Cu 2+ Cu + and Co 3+ Cu + , are not as efficient as holes in promoting electron exchange with the perchlorate ions.

Thermal decomposition of some divalent metal alginate gel compounds

Abstract The thermal decomposition of divalent metal alginate gel compounds has been studied using thermogravimetry (TG) and differential thermal analysis (DTA). The compounds have been characterized by FTIR and chemical analysis. The results reveal that the decomposition of metal alginate complexes is accompanied by the formation of metal oxalates as intermediate fragments. The stabilities of these compounds correspond to the strength of chelation between the metal ions and the functional groups on the macromolecular chains. A detailed mechanism of the thermal decomposition of the complexes is given and the activation energies of the main decomposition stages have been calculated.

The role of copper-chromium oxide catalysts in the thermal decomposition of ammonium perchlorate

The catalytic effects of doped or mixed CuO-Cr2O3 oxides on the thermal decomposition of ammonium perchlorate (AP) were investigated by using DTA, electrical conductivity and X-ray diffraction techniques. The results obtained revealed that the decrease in the defect electron of CuO catalyst doped with 1 at.% Cr3+ inhibited its activity, while the opposite effect was observed when Cr2O3 was doped with 1 at.% Cu2+. On increase of the concentrations of both oxides, the catalyst containing 70 at.% Cr3+ was found to be the most active during the decomposition of AP. The existence of CuCr2O4 at this ratio was demonstrated by X-ray diffraction. The activity of this spinel was explained on the basis of a hopping mechanism between Cr3+/Cr4+ active sites. Finally, the activation energies of different decomposition stages of AP alone and mixed with catalysts were calculated.ZusammenfassungMittels DTA, Röntgendiffraktion und elektrischer LeitfÄhigkeit wurden die katalytischen Wirkungen von versetzten oder gemischten CuO-Cr2O3 Oxiden auf die thermische Zersetzung von Ammoniumperchlorat (AP) untersucht. Die erhaltenen Ergebnisse zeigen, da\ die Abnahme an Defektelektronen von CuO-Katalysator, versetzt mit 1 mol% Cr3+, seine AktivitÄt vermindern, wÄhrend ein entgegengesetzter Effekt bei Cr2O3 beobachtet wird, das mit 1 mol% Cu2+ versetzt ist.Durch Erhöhung der Konzentrationen beider Oxide zeigt der Katalysator bei der Zersetzung von AP die grö\te AktivitÄt bei einem Cr3+-Gehalt von 70 mol%. Mittels Röntgendiffraktion konnte bei dieser Zusammensetzung die Existenz von CuCr2O4 gezeigt werden. Die AktivitÄt dieser Spinellstruktur wurde durch einen Hüpfmechanismus zwischen Cr3+/Cr4+-aktiven Stellen erklÄrt. Weiterhin wurden die Aktivierungsenergien von verschiedenen Zersetzungsstufen von AP mit und ohne Katalysatoren berechnet.

Thermal and electrical studies on some metal alginate compounds

Abstract The thermal decomposition of Ag—alg, Se—alg 4 and UO 2 —alg 2 compounds has been studied using thermogravimetry (TG), differential thermal analysis (DTA) and electrical conductivity measurements. The original samples are characterized by FTIR spectra. The results obtained reveal that the decomposition of these compounds proceeds via the formation of metal oxalates as intermediate fragments. The electrical conductance of these compounds at low temperature indicates that their geometric structures are non-planar and possess electrical conductivity values which lie in the range of semiconductors. Moreover, the remarkable increase in the conductance values during the decomposition of the intermediate metal oxalates is attributed to the hopping mechanism between the different valencies which exist during their thermolysis. Finally, detailed mechanisms of the various decomposition stages of the metal alginate compounds are suggested.

Mutual influences between ammonium heptamolybdate and γ-alumina during their thermal treatments

Different proportions of ammonium heptamolybdate (AHM) supported on γ-alumina were prepared by the impregnation method. The thermal decomposition stages of AHM and the solid products were investigated using DTA, TG, XRD and IR techniques. The results obtained revealed that the absence of all peaks accompanying the decomposition stages of AHM at low loading levels (< 20 mol%) was due to the dispersion capacity of the support. On increasing the % loading of AHM, γ-alumina retarded the formation of the two intermediates, (NH4)4Mo7O23·2H2O and (NH4)2Mo7O22· 2H2O, while favoring the decomposition of the latter to produce solid MoO3. The produced MoO3 readily interacted with Al2O3 above 500°C to form Al2(MoO4)3 phase which became highly crystallized when calcined at 700°C. The aluminum molybdate spinel formed was thermally stable up to 800°C, and then decomposed above this temperature into α-Al2O3 and MoO3. Moreover, the Al2O3 support decreased the crystallinity of MoO3, whereas Al2(MoO4)3 only affected the surface-active site, MoO. Finally, the presence of MoO3 greatly enhanced the crystallization of alumina into the κ- and α-phases upon heating at 700 and 900°C, respectively.

Thermal decomposition of KClO4 catalyzed by MnO2-CuO mixed oxides systems

Abstract The catalytic effect of a mixed oxides system, consisting of MnO 2 -CuO in different atomic ratios (Cu/(Cu+Mn) = x , where x = 0-1), on the non-isothermal decomposition of KClO 4 has been studied. The results are discussed according to an electron transfer mechanism. The enhancement effect of trace Cu(II) added to the host oxide MnO 2 was attributed to an increase of the exchange capacity of manganese cations between the different oxidation states, while the retarding effect associated with Cu(II)-rich samples was attributed to the trapping of the electrons required to initiate the decomposition reaction by the holes created. On the basis of the applicability of a non-isothermal kinetic equation, it was demonstrated that two main stages are involved in the decomposition process.

Electrical studies on V2O5 catalysts doped and mixed with foreign ions

Abstract The electrical conductivity of V 2 O 5 catalysts doped and mixed with Fe 3+ , Co 3+ and Ni 2+ ions in the concentration range 0.5–70 at.% was studied. Experiments were carried out in air as well as in the presence of 2-propanol in the feed. It has been shown that doping of V 2 O 5 with foreign ions increases the hole concentration. The calculated Δ E a values shows that the addition of Ni 2+ or Fe 3+ ions increases slightly its p-type character while Co 3+ ions increase strongly the p-type conductivity of V 2 O 5 catalyst. These results were manifested on the addition of 2-propanol.

Electrical conductivity and thermogravimetric studies of the thermal decomposition of doped cobalt carbonate

Abstract The effect of CdO on the thermal decomposition of cobaltous carbonate was studied. Measurements were carried out using thermogravity and electrical conductivity. The results show that addition of CdO retards the decomposition process via annihilation of holes created in cobaltic oxide. The non-stoichiometry and activity of the thermal decomposition products up to 500 °C were measured by means of the decomposition of N2H4 and H2O2 using a gasometric technique. The results show that the Co2+ ions are the active centres. The increase in activity when the CdO content is increased to 5 mol.% is attributed to an enhancement in the transition from Co3+ ions to Co2+ ions. The decomposition mechanism for H2O2 is proposed.

THERMAL DECOMPOSITION OF AMMONIUM METAVANADATE DOPED WITH Fe, Co OR Ni HYDROXIDES

The thermal decomposition of pure ammonium metavanadate (AMV) and of AMV doped with Fe3+,Co2+ or Ni2+ ions was investigated by TG, DTA, IR and X-ray diffraction. The results obtained revealed that the presence of these dopants enhances the formation of the intermediate compounds V2O5 solid. Some of the V5+ ions of the V2O5 lattice seemed to be reduced to V4+ ions. The activation energies of the different decomposition stages for all samples were calculated. The doped solids calcined at 450°C were characterized by the determination ofSbet and by electrical conductivity measurements. The mechanisms by which these ions affect the properties of the solids produced are discussed in relation to the defect structure created by the doping process.ZusammenfassungMittels TG, DTA, IR und Röntgendiffraktion wurde die thermische Zersetzung von reinem Ammoniummetavanadat (AMV) und von AMV, versetzt mit Fe3+, Co2+ oder Ni2+, untersucht. Die Ergebnisse zeigen, daß die Bildung von Zwischenprodukten und festem V2O5 durch die Gegenwart der Zusätze begünstigt wird. Einige der V5+-Ionen des V2O5 Gitters scheinen zu V4+-Ionen reduziert zu sein. Für alle Proben wurde die Aktivierungsenergie der verschiedenen Zersetzungsschritte berechnet. Die versetzten Feststoffe, die bei 450°C kalziniert wurden, konnten durch die Bestimmung vonSbet und durch elektrische Leitfähigkeitsmessungen charakterisiert werden. Der Mechanismus, über welchen diese Ionen die Eigenschaften der Feststoffe beeinflussen, wurde hinsichtlich der hervorgerufenen Defektstruktur diskutiert.