Study on Synthesis of Nixzn1-Xal2o4/Gamma-Al2o3 (X=0, 0.5, 1) Spinel Catalysts by Hydrothermal Method and Their Catalytic Activity in Aromatic Hydrocarbon

The spinel oxides NixZn1-xAl2O4/gamma-Al2O3 (x = 0, 0.5, 1) were synthesized by hydrothermal method. Oxides obtained were characterized by XRD and SEM. The XRD result showed principal spinel phase over all samples. In addition, NiO phase appeared for two cases of x = 0.5 and 1. Using XRD results, the Rietveld Refinement method indicated that the sample ZnAl2O4/gamma-Al2O3 consisted of wt 80% of ZnAl2O4 and 20% of gamma-Al2O3 with crystal size of 60 nm and 40 nm, respectively. This one was in accordance with SEM image which showed quite uniform particles with the side from 50 to 80 nm. Catalytic activity was evaluated by methylation of toluene by methanol and dehydrogenation of ethylbenzene to styrene. For methylation reaction, the results showed high selectivity in xylene. In case of Nip. 5 ZnAl2O4/gamma-Al2O3, at 400 degrees C, the result showed the best toluene conversion of 25.46% and selectivity in xylene was 88.33%. In case of ethylbenzene dehydrogenation reaction, sample ZnAl2O4 synthesized by coprecipitation method used as a reference catalyst. We observed, after 180 min of time reaction, a double conversion of ethylbenzene on ZnAl2O4/gamma-Al2O3 in comparison with ZnAl2O4 reference. In addition, working time of ZnAl2O4/gamma-Al2O3 was longer than this one of ZnAl2O4 reference.