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  1. Nor Aishah Saidina Amin, Soon, Ee Peng
    MyJurnal
    Thermodynamic chemical equilibrium analysis using, total Gibbs energy minimization method, was carried out for methane oxidation to higher hydrocarbons. For a large methane conversion and a high selectivity to higher hydrocarbons, the system temperature and oxygen concentration played a vital role, whereas, the system pressure only slightly influenced the two variables. Numerical results showed that the conversion of methane increased with the concentration of oxygen and reaction temperature, but it decreased with pressure. Nevertheless, the presence of oxygen suppressed the formation of higher hydrocarbons which mostly consisted of aromatics, but enhanced the formation of hydrogen. As the system pressure increased, the aromatics, olefins and hydrogen yields diminished, but the paraffin yield improved. Carbon monoxide seemed to be the major oxygen-containing equilibrium product from methane oxidation, whilst almost no H2O, CH3OH and HCOH were detected although traces amount of carbon dioxide were formed at relatively lower temperature and higher pressure. The total Gibbs energy minimization method is useful to theoretically analyze the feasibility of methane conversion to higher hydrocarbons and syngas at the selected temperature and pressure.
  2. Nur Aainaa Syahirah Ramli, Nor Aishah Saidina Amin
    Sains Malaysiana, 2015;44:883-891.
    Levulinic acid (LA) is a versatile platform chemical with numerous potential uses. Conversion of oil palm fronds (OPF)
    to LA over Fe/HY zeolite catalyst has been conducted in this study. The optimization process using Box-Behnken design
    gave 19.6% of LA yield at 181.7°C reaction temperature, 7.7 h reaction time, 1.13 g Fe/HY zeolite loading and 0.25 g OPF
    loading. The efficiency of OPF conversion at the optimum conditions was determined to be 61.1%. It was also demonstrated
    that Fe/HY zeolite gave sufficient performance for five successive cycles of OPF conversion to LA. The results suggested
    that Fe/HY zeolite is potential as catalyst for biomass conversion to LA.
  3. Muzakkir Mohammad Zainol, Nor Aishah Saidina Amin, Mohd Asmadi
    Sains Malaysiana, 2017;46:773-782.
    The magnetic adsorbents i.e. oil palm frond-magnetic particles (OPF-MP) and oil palm frond activated carbon-magnetic particles (OPFAC-MP) have been prepared by impregnation of iron oxide via co-precipitation method. The magnetic adsorbents and their parent materials were characterized using Fourier transform infrared (FTIR), thermogravimetric analysis (TGA), field emission scanning electron microscopy (FESEM), Brunauer Emmett Teller (BET), Barrett, Joyner & Halenda (BJH) and t-plot method, x-ray diffraction (XRD) and also using vibrating sample magnetometry (VSM) to study their properties and surface chemistry. The activated carbon magnetic adsorbent confers high surface area of 700 m2/g with amorphous structure and magnetic properties of 2.76 emu/g. The OPF-MP and OPFAC-MP were then applied in adsorption study for ions removal of Pb(II), Zn(II) and Cu(II). OPFAC-MP has shown high removal efficiency of 100 % with adsorption capacity up to 15 mg/g of Pb(II), Zn(II) and Cu(II) ions compared to OPF-MP. In addition, the magnetic adsorbents were also compared with their parent materials to observe the effect of magnetic particles. Accordingly, the impregnation of magnetic particles enhances the metal ions adsorption comparing to their parent materials.
  4. Nur Aainaa Syahirah Ramli, Nur Irsalina Hisham, Nor Aishah Saidina Amin
    Sains Malaysiana, 2018;47:1131-1138.
    Levulinic acid (LA) is one of biomass derived building block chemicals with various applications. Catalytic esterification
    of LA with alkyl alcohol produces levulinate ester which can be applied as fragrance, flavouring agents, as well as fuel
    additives. In this study, a series of sulfated silica (SiO2
    ) catalyst was prepared by modification of SiO2
    with sulfuric acid
    (H2
    SO4
    ) at different concentrations; 0.5 M to 5 M H2
    SO4
    . The catalysts were characterized, and tested for esterification
    of LA with ethanol to ethyl levulinate (EL). The effect of various reaction parameters including reaction time, catalyst
    loading and molar ratio of LA to ethanol on esterification of LA to EL were inspected. The catalyst with high concentration
    of acid sites seemed suitable for LA esterification to EL. Among the sulfated SiO2
    catalysts tested (0.5 M-SiO2
    , 1 M-SiO2
    ,
    3 M-SiO2
    and 5 M-SiO2
    ), 3 M-SiO2
    exhibited the highest performance with the optimum EL yield of 54% for reaction
    conducted at reflux temperature for 4 h, 30% 3 M-SiO2
    loading and LA to ethanol molar ratio of 1:20. Besides, the
    reusability of 3 M-SiO2
    catalyst for LA esterification with ethanol was examined for five cycles. Esterification of LA with
    methanol and 1-butanol were also carried out for methyl levulinate (ML) and butyl levulinate (BL) productions with 69%
    and 40% of ML and BL yields, respectively. This study demonstrates the potential of sulfated SiO2
    catalyst for levulinate
    ester production from LA at mild process condition.
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