Prof. Ir. Dr. Nor Aishah Saidina Amin

Abstract :

Ethyl levulinate (EL) is a versatile bio-based chemical with various applications such as fragrance and flavoring agents and also fuel blending component. EL can be produced through catalytic esterification of levulinic acid (LA) with ethanol. Herein, a series of zirconia (ZrO2)-supported phosphotungstic acid (HPW) (HPW/Zr) catalyst, 15-HPW/Zr, 20-HPW/Zr, and 25-HPW/Zr, were prepared, characterized, and tested for EL production. The physicochemical properties ofcatalysts were characterized using Fourier-transformed infrared (FTIR) spectroscopy, x-ray diffraction (XRD), field emission scanning electron microscope (FESEM), N2 physisorption, and ammonia temperature-programmed desorption (NH3-TPD). The effect of reaction parameters: reaction time, temperature, catalyst loading, and molar ratio of LA to ethanol was inspected on LA conversion and EL yield. The catalyst with high surface area and high acidity seemed suitable for EL production. Among the catalysts tested, 20-HPW/Zr exhibited the highest EL yield of 97.3% at the following conditions: 150 °C, 3 h, 1.0 g of 20-HPW/Zr and 1:17Mratio of LA to ethanol. The 20-HPW/Zr could be reused for at least four times with insignificant decrease in the EL yield. This study demonstrates the potential of ZrO2-supported HPWfor bio-based alkyl levulinate production at mild process conditions.

1. Nur Aainaa Syahirah Ramli, Dorairaaj Sivasubramaniam and Nor Aishah Saidina Amin (2017). Esterification of levulinic acid using ZrO2-supported Phospotungstic acid catalyst for ethyl levulinate production. BioEnergy Research, 1-12. DOI: https://doi.org/10.1007/s12155-017-9872-1

Abstract:

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.

1. Muzakkir Mohammad Zainol, Nor Aishah Saidina Amin, And Mohd Asmadi (2017). Preparation and characterization of impregnated magnetic particles on oil palm frond activated carbon for metal ions removal. Sains Malaysiana, 46(5), 773-782.

Abstract :

Supported Ni catalysts have been investigated for hydrogen production from steam reforming of glycerol. Ni loaded on Al2O3, La2O3, ZrO2, SiO2 and MgO were prepared by the wet-impregnation method. The catalysts were characterized by nitrogen adsorptionedesorption, X-ray diffraction and scanning electron microscopy. The characterization results revealed that large surface area, high dispersion of active phase on support, and small crystalline sizes are attributes of active catalyst in steam reforming of glycerol to hydrogen. Also, higher basicity of catalyst can limit the carbon deposition and enhance the catalyst stability. Consequently, Ni/Al2O3 exhibited the highest H2 selectivity (71.8%) due to small Al2O3 crystallites and large surface area. Response Surface Methodology (RSM) could accurately predict the experimental results with R-square ¼ 0.868 with only 4.5% error. The highest H2 selectivity of 86.0% was achieved at optimum conditions: temperature ¼ 692 C, feed flow rate ¼ 1 ml/min, and water glycerol molar ratio (WGMR) 9.5:1. Also, the optimization results revealed WGMR imparted the greatest effect on H2 selectivity among the reaction parameters.

1. Zamzuri, N.H. Mat, R. Saidina Amin, N.A. Talebian-Kiakalaieh, A. (2017). Hydrogen production from catalytic steam reforming of glycerol over various supported nickel catalysts. International Journal of Hydrogen Energy. 42, 9087-9098. DOI: https://doi.org/10.1016/j.ijhydene.2016.05.084

Cu-modified graphitic carbon nitride (g-C3N4) and titanium dioxide (TiO2) nanocomposites for enhanced photocatalytic CO2 reduction with H2O under UV and visible light irradiations have been investigated. The photocatalysts, prepared by pyrolysis and impregnation were characterized by XRD, FE-SEM, TEM, FT-IR, N2 adsorption-desorption, XPS, UV–vis DRS and PL spectroscopy. The Cu-metal loaded over TiO2 and g-C3N4 enhanced CO2 reduction efficiency to CH3OH and HCOOH by fostering carrier charge separation. The Cu-metal in the composite as well as the wt.% ratio of g-C3N4 and TiO2 also influenced the photoactivity and products selectivity. The low band gap, electronic structure and visible light absorption capacity of g-C3N4 facilitated the transfer of photo-generated electrons to Cu/TiO2 in the composite. Moreover, the position of the metal in the composite affected the electrons distribution and hence enhanced the photoactivity. The maximum yield of the products detected under visible light were 2574 and 5069mmol/g.cat of CH3OH and HCOOH, respectively. The yield of CH3OH under visible light was four fold higher compared to UV-light irradiation. The ratio (30:70) of g-C3N4 and Cu/TiO2 in the composite and the use of visible light improved the efficiency of the photocatalytic system. The stability of the photocatalyst prevailed in continuous CH3OH production under visible light irradiation compared to UVlight in cyclic runs. Possible reaction mechanisms were proposed to understand the movement of electrons and holes and the function of both UV and visible light for CO2 reduction over the g-C3N4/TiO2 (30:70) photocatalyst.

David Oluwatobi Adekoya, Muhammad Tahir and Nor Aishah Saidina Amin (2017). g-C₃N₄/(Cu/TiO₂) nanocomposite for enhanced photoreduction of CO₂ to CH₃OH and HCOOH under UV/visible light. Journal of CO₂ Utilization, 18, 261-274.

Abstract:

Ag-NPs-promoted TiO2 nanowires (TiO2 NWs) core/shell hetero-junction with plasmonic properties for selective CO production in photo-induced CO2-hydrogen system has been investigated. Ag-NPs were photo-deposited over the TiO2 NWs and characterized by XRD, TEM, N2-adsorption-desorption, XPS, UV–vis and PL spectroscopy. Ag-NPs in metal-state were successfully coated on the TiO2 NWs surface, producing core-shell hetero-junction. Ag-NPs coated over TiO2 NWs exhibited strong absorption of visible light due to localized surface plasmon resonance (LSPR) excitation, trapped electrons and hindered charges recombination rate. The synergistic effect of Ag-NPs coated over TiO2 NWs for CO2 conversion was evaluated in a gas-phase system under UV and visible light irradiation. The plasmonic Ag-NPs/TiO2 NWs demonstrated excellent photoactivity in the reduction of CO2 into CO, CH4 and CH3OH under visible light irradiation. The results show that 3 wt.% Ag-NPs-loaded TiO2 NWs was found to be the most active, giving the highest CO evolution of 983mmole-g-catal.1 h1 at selectivity 98%. This amount of CO produced was 23 times more than the TiO2 NWs and 109 times larger than the yield of CO produced over the pure TiO2. More importantly, the quantum yield was substantially enhanced for CO evolution. The LSPR excitation and synergic effect of Ag-NPs which can effectively accelerate the charge separation was proposed to be responsible for the enhancement of photocatalytic activity. The photo-stability of Ag-NPs/TiO2 NWs evidenced in cyclic runs for selective CO production under visible light, yet photoactivity declined over the irradiation time under UV-light. The reaction mechanism to describe the reaction pathways is also presented.

Muhammad Tahir, Beenish Tahir, Nor Aishah Saidina Amin and Zaki Yamani Zakaria (2017).Photo-induced reduction of CO2 to CO with hydrogen over plasmonic Ag-NPs/TiO2 NWs core/shell hetero-junction under UV and visible light. Journal of CO₂ Utilization, 18, 250-260. DOI: https://doi.org/10.1016/j.jcou.2017.02.002

Abstract:

The effect of quartz and alumina dielectric materials on the efficiency of dielectric barrier discharge (DBD) cold plasma reactor using different configurations for dry reforming of methane (DRM) has been investigated. The performance of dielectric materials was analysed at different feed ratios, gas hourly space velocity (GHSV, h1) and specific input energy (SIE, kJ L1). In both reactors, the main products detected were CO and H2 with considerable amounts of C2H6. Alumina reactor prevailed in performance and the maximum conversion achieved was 74% and 68% for CH4 and CO2, respectively at GHSV (92 h1) feed ratio (1:1), SIE (370 J ml1) and discharge volume (VD = 15.7 cm3). The CO/H2 ratio and yields were also higher in alumina than the quartz reactor under the same experimental conditions. Furthermore, different reactor configurations displayed a significant impact in the performance of DBD plasma. Increasing discharge volume (VD) enhanced the conversion and selectivity for both dielectrics. The energy efficiency (EE) was of 0.085 and 0.078 mmol kJ1 for alumina and quartz, respectively. The high EE in alumina reactor was evidently due to higher dielectric constant, which exhibited enhancement in power dissipation, discharge energy and reactor temperature. Stability test conferred alumina DBD plasma reactor performed better than the quartz.

1. Asif H Koja, Muhammad Tahir, Nor Aishah Saidina Amin 2017). Dry reforming of Methane Using Different Dielectric Materials and DBD Plasma Reactor Configurations.  Energy Conversion and Management, Elsevier, (I.F 4.512, Q1) DOI information: 10.1016/j.enconman.2017.04.057

Abstract:

Biodiesel is a suitable alternative to gasoline and diesel since it emits less carbon emission. There has been a surplus of glycerol in the market due to biodiesel production. Glycerol may be a good source of bio-based feed since it is from a renewable source. The kinetic study of gas-phase glycerol dehydration reaction using a supported γ-Al2O3 nanoparticle based solid heteropoly acid catalyst (SiW20-Al/Zr10) has been investigated. A kinetic model was established, based on the reaction mechanism, taking into account two parallel reactions of glycerol degradation into acrolein or acetol. All the reaction rate constants and activation energies were determined at various reaction temperatures (280 – 340 °C). The first-order kinetic model and the experimental data fitted-well. Results revealed that all the rate constants increased with temperature, and the activation energies of glycerol dehydration to acrolein and acetol were 46.0 and 53.3 kJ/mol. The results from this study are useful for simulation and process modelling of a bio-refinery for sustainable production of biobased chemicals.

1. AminTalebian-Kiakalaieh and Nor Aishah Saidina Amin (2017). Kinetic study on catalytic conversion of glycerol to renewable acrolein. Chemical Engineering Transactions, 56, 655-660.

Abstract:

Photocatalytic carbon dioxide (CO₂) conversion to chemicals and fuels has gained significant consideration in industrial and scientific research. In this study, photocatalytic CO₂ reduction to fuels over Cu-loaded graphitic carbon nitride (g-C₃N₄) under visible light irradiation has been investigated. The photocatalysts, synthesized by pyrolysis and impregnation method, were characterized by X-ray diffraction (XRD) Fourier transform infrared (FTIR) and Scanning electron microscopy (SEM). Interestingly, CO₂ was efficiently converted to CH₄ and CH₃OH with smaller amounts of C₂H₄ and C₂H₆ hydrocarbons. The yield of CH4 evolution as the main product over 3 wt. % Cu/g-C₃N₄was 217.8 μmole/g.cat under visible light irradiation, significantly higher than the amount of CH₄ produced over the pure g-C₃N₄ catalyst (119 μmole/g.cat). The enhancement was attributed to charge transfer property and suppressed recombination rate by Cu-metal. The Cu-metal loaded into g-C₃N₄ enhanced CO₃ reduction efficiency for CH₄ production while the pure g-C₃N₄ was promising for both CH₄and CH3OH production. The single step conversion of CO₂ to CH₄ and CH₃OH with appreciable amount of hydrocarbons under solar energy registered good photo-Activity and selectivity of Cu/g-C₃N₄ catalyst. A photocatalytic reaction mechanism was proposed to corroborate with the experimental results over the Cu-loaded g-C₃N₄ photocatalyst.

1. Beenish Tahir, Muhammad Tahir, and Nor Aishah Saidina Amin (2017). Photocatalytic carbon dioxide reduction to fuels Over Cu- Loaded g-C3N4 nanocatalyst under visible light. Chemical Engineering Transactions, 56, 403-408.

Abstract:

Fe-promoted titanium dioxide (TiO2) nanoparticles dispersed in Montmorillonite (MMT) clay for dynamic photocatalytic carbon dioxide (CO2) reduction to carbon monoxide (CO) and hydrocarbons in a monolith photo-reactor has been investigated. MMT-clay supported Fe/TiO2 nanocomposites were prepared by a controlled and direct sol-gel method and were dip-coated over the monolith micro-channels. The performance of Fe-loaded MMT/TiO2 nano-catalyst for CO2 reduction by H2 toward CO evolution was evaluated in a continuous operation of photo-reactor under UV-light irradiation. The photo-activity of TiO2 catalyst dispersed in MMT and loaded with Fe was significantly enhanced. The maximum yield of CO over 3 wt% Fe – 10 wt% MMT-loaded TiO2 catalyst reached to 289.30 µmole g-cat-1 h-1 at selectivity 99.61 %, is considerably higher than the amount produced over the MMT/TiO2 (25.95 µmole g-cat-1 h-1) and the pure TiO2 (8.52 µmole g-cat-1 h-1) catalyst. The other products observed with adequate amounts were CH4 and C2H6. These results revealed significantly enhanced photo-activity of TiO2 loaded with Fe and dispersed over MMT. The enhanced CO evolution was evidently due to larger illuminated active surface area, higher adsorption process inside the monolith micro-channels and hindered charges recombination rate by Fe. This development has confirmed higher photoactivity of Fe-MMT/TiO2 photo-catalyst for continuous CO2 photo-reduction to cleaner fuels.

1. Beenish Tahir, Muhammad Tahir, and Nor Aishah Saidina Amin (2017). Photocatalytic CO2 Reduction to CO over Fe-loaded TiO2/Nanoclay Photocatalyst. Chemical Engineering Transactions, 56, 1111-1116.

Abstract:

Photocatalytic CO2 reduction by H2 to CO via reverse water gas shift (RWGS) reaction over Montmorillonite (MMT) dispersed TiO2 nanoparticles has been investigated. MMT-clay supported TiO2 nanocomposites were prepared by a controlled and direct sol-gel method and were dip-coated over the monolith channels. The samples were characterized by XRD, FTIR, SEM, N2-adsorption-desorption and UV–visible spectroscopy. The performance of nanomaterials was tested in a continuous operation of monolith photoreactor for dynamic CO
and hydrocarbons production under UV-light irradiation. The photoactivity of MMT/TiO2 nanocomposite loaded over the monolith channels was expressively increased for CO2 reduction to CO as the main product. The maximum yield of CO over 10 wt. % MMT-loaded TiO2 catalyst obtained was 25.95 µmole g-catal.-1 h-1 at selectivity 98 %, considerably higher than the amount produced over the pure TiO2 (8.52 µmole g-catal.-1 h-1). The other products detected with adequate amounts were CH4 and C2H6. This significant enhancement in CO evolution was evidently due to efficient light distribution with larger illuminated active surface area inside monolith micro-channels and hindered charges recombination rate over MMT dispersed TiO2. The reaction mechanism to understand the route of CO2 reduction by H2 via RWGS reaction is also proposed. This development has confirmed higher performance of green MMT/TiO2 photo-catalyst for continuous CO2 photoreduction to cleaner fuels.

1. Muhammad Tahir, Beenish Tahir, and Nor Aishah Saidina Amin. Photocatalytic Reverse Water Gas Shift CO2 Reduction to CO over Montmorillonite Supported TiO2 Nanocomposite. Chemical Engineering Transactions, 56, 319-324. DOI: 10.3303/CET1756054