Browsing by Author "Ab. Aziz, Muhammad Arif"

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    Catalytic methanation of carbon dioxide over nickel supported on mesostructured silica nanoparticles
    (Universiti Teknologi Malaysia, 2014) Ab. Aziz, Muhammad Arif
    Due to global warming caused by a remarkable increase of carbon dioxide (CO2) emission into the atmosphere, it is currently a great challenge to convert CO2 into valuable chemicals such as methanol and methane. However, CO2 methanation could be a promising technique for CO2 reduction due to its simple reaction which can be performed at atmospheric pressure. Mesostructured silica nanoparticles (MSN) and nickel loaded onto MSN (Ni/MSN) were prepared by the sol gel and impregnation methods, respectively, and tested for CO2 methanation. The catalysts were characterized by x-ray diffraction (XRD), nitrogen physisorption, Fourier transform infrared spectroscopy (FTIR), thermal gravimetric analysis (TGA) and pyrrole, carbon monoxide (CO), CO2 and hydrogen (H2) adsorption studies by means of FTIR spectroscopy. Catalytic performance was conducted at 423-723 K under atmospheric pressure. At 623 K, the activity of Ni/MSN was higher than that of nickel loaded onto Mobil Composition of Matter Number 41 (Ni/MCM-41), nickel loaded onto protonated zeolite Y (Ni/HY), nickel loaded onto silica (Ni/SiO2) and nickel loaded onto alumina (Ni/γ-Al2O3). Furthermore, Ni/MSN performed outstanding activity and stability for more than 200 h with 79% and 99.9% for conversion of CO2 and selectivity to methane, respectively. The high activity of Ni/MSN was due to the presence of both intra- and interparticle porosity and the synergistic effect between Ni and basic sites of the catalyst. The mechanism of CO2 methanation proposed that the CO2 and H2 were adsorbed and dissociated on nickel sites to form CO and atomic oxygen (O) and hydrogen (H), followed by migration onto the MSN surface. The dissociated CO then interacted with oxide surfaces of MSN to form bridged carbonyl and linear carbonyl, while the presence of H atom facilitated the formation of bidentate formate ligand. The bidentate formate species were suggested to be the main route to formation of methane. This study has shown a remarkable performance of Ni/MSN which can be used for commercialization purposes