SYNTHESIS OF MESOPOROUS TITANIUM OXIDE AND CATALYTIC ACTIVITY OF Ru/m-TiO2

A series of mesoporous TiO2 oxide (m-TiO2) were synthesized by using n-cetylpyridinium chloride (C16PyCl) as a structure-directing agent under complete different conditions. The synthesized mesoporous samples were characterized by means of FT-IR, XRD, and N2 adsorption methods. Effects of template, solvent, pH, ageing temperature and C16PyCl/TTIP molar ratio on the structure and stability of m-TiO2 were also discussed. The results show that the property of m-TiO2 synthesized by using C16PyCl as template, C2H5OH as solvent, pH 7-8, ageing temperature 20 oC and C16PyCl/TTIP molar ratio 2 are superior to that of m-TiO2 prepared under other conditions. After being loaded by the impregnating method, the Ru particle strongly interacts with the mesoporous supports. The catalytic activity of Ru/m-TiO2 for methanol decomposition to carbon monoxide and hydrogen was investigated. It is found that synthesizing conditions of mesoporous materials affect the catalytic activity of Ru/m-TiO2. KEY WORDS: Mesoporous titanium oxide, Methanol decomposition, Ruthenium, Catalyst support, n-Cetylpyridinium chloride Bull. Chem. Soc. Ethiop. 2005, 19(2), 277-288

THE INFLUENCE OF TRANSITION METALS ON THE PERFORMANCE OF Pt Rh Pd/γ-AL2O3 THREE WAY CATALYSTS FOR PURIFICATION OF AUTOMOTIVE EXHAUST GAS

The influences of transition metal oxides (Zr, Mn, Co, Cu, Mo) on the performance of Pt Rh Pd/γ-Al2O3 three way catalysts were studied. The characteristics of the catalysts are investigated by using XRD, TPD, TPR. Experimental results show that the addition of Zr, Mn, Co, and Cu promoters improved the activity of Pt Rh Pd/γ-Al2O3 catalyst remarkably for CO, CH and NOx conversion, respectively. The effective order of the promoters is CuO > ZrO2 > Co3O4 > MnO2. The addition of CuO improved the dispersion of the noble metal on the γ-Al2O3 support and increased the absorption of Pt Rh Pd/γ-Al2O3 catalyst for CO and O2, in addition, promoted the reduction of the noble metal. KEY WORDS: Purification of exhaust gas, Pt Rh Pd/γ-Al2O3 catalyst, Transition metals Bull. Chem. Soc. Ethiop. 2006, 20(1), 113-120

The surface behaviour and catalytic properties of Nd2-XSrXCoO4±Λ mixed oxides

The mixed oxides, Nd2-XSrXCoO4±λ (0.4 ≤ x ≤ 1.2), (λ = non-stochiometric oxygen) with the K2NiF4 structure were prepared by the polyglycol gel method and used as catalysts for NO reduction. The samples were investigated by IR, TPD, TPR, and XRD methods and iodometry and the effects of the coefficient x on the structure and catalytic activity of the samples were studied. The results show that the Nd2-XSrXCoO4±λ mixed oxides have the K2NiF4 structure; other phases are found when x 1.2. The amount of Co3+ and the lattice oxygen in Nd2-XSrXCoO4±λ increase with increasing x. The catalytic activity of Nd2-XSrXCoO4±λ for NO reduction is closely correlated with the concentration of oxygen vacancies and the amount of Co3+.KEY WORDS: A2BO4, Co-containing mixed oxide, NO reduction, Rare-earthBull. Chem. Soc. Ethiop. 2006, 20(2), 201-206

THE EFFECTS OF RARE EARTHS ON ACTIVITY AND SURFACE PROPERTIES OF Ru/γ-AL2O3 CATALYST FOR WATER GAS SHIFT REACTION

A series of Ru-RE/γ-AL2O3 (RE = Ce, Pr, La, Sm, Tb or Gd) and Ru/γ-AL2O3 catalysts were prepared by impregnation method. The influence of rare earths on the catalytic performance of Ru/γ-AL2O3 catalyst for the water gas shift reaction was studied. The catalysts were characterized by X-ray diffraction (XRD), temperature programmed reduction (TPR), temperature programmed desorption (TPD), and CO chemisorption. The results show that the addition of rare earths increases the catalytic activity of Ru based catalyst. Among these cerium is the most remarkably. The addition of cerium increases the active surface area, improves the dispersion of ruthenium, and weakens the interaction between ruthenium and the support. Cerium also affects the adsorption and reduction properties of Ru/γ-AL2O3 catalyst. KEY WORDS: Rare earths, Ruthenium-based catalyst, Water gas shift reaction Bull. Chem. Soc. Ethiop. 2007, 21(3), 389-395

Preparation of La₀․₉₅Ce₀․₀₅CoO₃ with large surface area

202-205The perovskite-type complex oxides, La₀․₉₅Ce₀․₀₅CoO₃, have been prepared by glycine polyacrylamide sol-gel combustion method, glycine sol-gel method and solid state reaction method. These oxides have been used successfully for combustion of methane. The La₀․₉₅Ce₀․₀₅CoO₃ samples have been investigated by XRD, BET, O₂-TPD and H₂-TPR. The effect of preparation method on the structure and performance of the catalysts has been studied. La₀․₉₅Ce₀․₀₅CoO₃ prepared by glycine polyacrylamide sol-gel combustion method shows the highest catalytic activity for combustion of methane

Template synthesis and characterization of mesoporous CeO₂ and Ru-loaded mesoporous CeO₂

327-332A series of mesoporous ceria (m-CeO₂) have been synthesized using Brij 35 and some co-surfactants as template agents. The samples have been characterized by XRD, FT-IR and N₂ adsorption-desorption analyses. The mesoporous material prepared with CTAB and Brij 35 shows the best catalytic performance in comparison to material prepared using Brij 35 alone or along with other co-surfactants like PEG2000. The Ru/m-CeO₂ catalyst shows the highest activity for the conversion of methanol. The results also indicate that the synthesis temperature, ageing temperature and calcination temperature affect the surface area, pore volume, thermal resistance and the pore diameter of the prepared materials. Also, temperature plays an important role in the preparation of mesoporous ceria

Studies on B-site doped LaSrCoO₄ mixed oxides towards CO and C₃H₈ oxidation

1388-1391A series of LaSrCo0.9B'0.1O4 (B'= Mn, Fe, Ni, Cu) mixed oxides have been prepared by the polyacrylamide gel method and used successfully for CO and C3H5 oxidation. The results show that the specific effects of B' ions on CO and C3H8 oxidation depend on their category. In comparison to the LaSrCoO4 catalyst, the activity of LaSrCo0.9Ni0.1O4 catalyst for CO and C3H8 oxidation is higher, while the activity of Mn, Fe or Cu-doped catalysts is lower. The TPD and XRD analyses show that the increase in oxidation activity of LaSrCo0.9Ni0.1O4 catalyst towards CO and C3H8 oxidation can be related to the increase in O2-adsorption, CO2 -desorption quantity and the lattice distortion

<b>The influence of transition metals on the performance of Pt Rh Pd/γ-Al₂O₃ three way catalysts for purification of automotive exhaust gas</b>

The influences of transition metal oxides (Zr, Mn, Co, Cu, Mo) on the performance of Pt Rh Pd/&gamma;-Al₂O₃ three way catalysts were studied. The characteristics of the catalysts are investigated by using XRD, TPD, TPR. Experimental results show that the addition of Zr, Mn, Co, and Cu promoters improved the activity of Pt Rh Pd/&gamma;-Al₂O₃ catalyst remarkably for CO, CH and NOx conversion, respectively. The effective order of the promoters is CuO > ZrO₂ Co₃O₄ MnO₂. The addition of CuO improved the dispersion of the noble metal on the &gamma;-Al₂O₃ support and increased the absorption of Pt Rh Pd/&gamma;-Al₂O₃ catalyst for CO and O₂, in addition, promoted the reduction of the noble metal

Effect of calcination temperature of TiO₂-Al₂O₃ mixed oxides on hydrodesulphurization performance of Au-Pd catalysts

175-180A series of TiO2-Al2O3 mixed oxides calcined at different temperatures was prepared by the sol-gel method. The influence of calcination temperature of TiO2-Al2O3 on Au-Pd catalysts was investigated in the hydrodesulphurization of thiophene. The structural and surface properties of the samples were analyzed by nitrogen adsorption, X-ray diffraction, temperature-programmed desorption, temperature-programmed reduction and infrared spectroscopy techniques. The results showed that the prepared TiO2-Al2O3 mixed oxides had mesoporous structure. The TiO2-Al2O3 mixed oxide calcined at 773 K exhibited larger BET surface area, pore volume and more acid sites than the samples calcined among 873-1073 K. All the Au-Pd catalysts supported TiO2-Al2O3 calcined at different temperature had higher catalytic activity towards the hydrodesulphurization of thiophene, and the catalytic activity of Au-Pd/TiO2-Al2O3 (773 K) was better than that of other samples in hydrodesulphurization reaction. This was explained in terms of their structure: interaction between Au-Pd and TiO2-Al2O3, dispersion, apparent activation energy, the number of AuxPdy alloy particles and acid sites