EFFECT OF THE REDUCTION TEMPERATURE INTO CATALYTIC ACTIVITY OF Ni SUPPORTED BY TiO2, AL2O2 AND TiO2/AL2O3 FOR CONVERSION CO2 INTO METHANE

Abstract

Nickel catalysts, containing 6% (w/w) of nickel, have been prepared using TiO₂, Al₂O₃ and mixture of TiO₂-Al₂O₃ (1:9). The catalysts were used for CO₂ conversion into methane. The characteristics of catalysts were studied by determination of its specific surface area, temperature programmed reaction technique and X-ray diffraction. The specific surface area were varied slightly by different temperature of reduction, namely after reduction at 300°C it was 39, 120 and 113 m²/g and after reduction at 400°C it was 42, 135  and 120 m²/g for 6% nickel catalysts supported on TiO₂, Al₂O₃ and mixture of TiO₂-Al₂O₃ (1:9) respectively. Temperature program reaction studies (TPO and TPR) showed that NiTiO_x species were possibly formed during the pretreatments which has shown by the shift of its peak to the lower temperature on Ni catalyst, that supported on mixture of TiO₂-Al₂O₃ compared with catalysts supported on individual TiO₂ or Al₂O₃. The nickel species on reduced Ni catalysts supported on TiO₂ and on mixture of TiO₂-Al₂O₃ could be detected by X-ray diffraction. The catalyst's activities toward CH4 formation were affected by the reduction temperature. Activity for CH₄ formation was decreased in the following order: Ni/ TiO₂ > Ni/ TiO₂: Al₂O₃ > Ni/ Al₂O₃ and Ni/ TiO₂: Al₂O₃ > Ni/ TiO₂> Ni/ Al₂O₃, when catalysts were reduced at 300°C or 400°C respectively. The CO₂ conversion was decreased in the following order: Ni/ Al₂O₃ > Ni/ TiO₂: Al₂O₃ > Ni/ TiO₂ when catalysts were reduced at 300°C or 400°C respectively.