الفهرس 
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Abstract
Pure alumina gel was prepared by the addition of ammonium hydroxide to a solution of hydrated aluminium nitrate at 35oC with continuous vigorous stirring till pH = 8. The precipitate was washed several times with bidistilled water till free from nitrate ions. 2. ?Mn(OH)2 was prepared by the addition of ammonium hydroxide to a solution of hydrated manganese nitrate at 35oC with continuous vigorous stirring till pH = 9. The precipitate was washed several times with bidistilled water till free from nitrate ions. 3. ?Fe(OH)3 was prepared by the addition of ammonium hydroxide to a solution of hydrated ferric nitrate at 35oC with continuous vigorous stirring till pH = 7. The precipitate was washed several times with bidistilled water till free from nitrate ions. 4.?Cr(OH)3 was prepared by the addition of ammonium hydroxide to a solution of hydrated chromium nitrate at 35oC with continuous vigorous stirring till pH = 7. The precipitate was washed several times with bidistilled water till free from nitrate ions. 5. ?Iron oxide manganese oxide alumina containing 10, 20, 30 and 40 wt.% Fe were prepared by the addition of a solution of Fe(OH)3 containing the required amount of Fe to appropriate amount of Mn(OH)2 and Al(OH)3 during continuous stirring. The resulting thin slurry was evaporated, the solid was pulverized and sieved to 0.4 1.25 mm particle size. 6. ?Chromium oxide manganese oxide alumina containing 10, 20, 30 and 40 wt.% Cr were prepared by the addition of a solution of Cr(OH)3 containing the required amount of Fe to appropriate amount of Mn(OH)2 and Al(OH)3 during continuous stirring. The resulting thin slurry was evaporated, the solid was pulverized and sieved to 0.4 1.25 mm particle size. 7. ?The prepared samples were calcined 400, 600, 800 and 1000oC for 9 hr. 8. ?Structural characterization of the catalysts and the phase changes were determined using thermal analysis and xray technique. The results obtained from thermal analysis reveals the formation of MnO2, Al2O3, Fe2O3, Mn3O4 phases. Also, the results obtained from xray analysis indicates the formation of crystalline MnO2, MnFe2O4, Fe2O3, Mn2O3, Al2O3 and Mn3O4. 9. ?Textural properties were determined by measuring the adsorption of nitrogen at 196oC using conventional volumetric apparatus. The general trend of textural characteristics was found that: i) ?The surface areas of iron oxide manganese oxide alumina and chromium oxide manganese oxide alumina catalysts calculated by different methods decreased upon increasing in the calcination temperature. The lowering of surface was pronounced at 1000oC. ii) ?The surface areas of AFM and ACM was found to depend on the calcination temperature. iii) ?The variation of the surface area with change in chemical composition or with rise of calcination temperature was found to be associated with pore changes. iv) ?The prepared catalysts show both micro and mesoporosity. the fraction of microporosity change with calcination temperature.