Prof. Ir. Dr. Nor Aishah Saidina Amin

Abstract:

Decomposition of biomass feedstock is a promising technique for producing versatile chemicals such as 5-hydroxymethyl furfural (5-HMF) and levulinic acid (LA). Glucose, the model compound of cellulose, is one of the most important starting components for bio-based chemical synthesis. Herein, the kinetics of glucose decomposition catalyzed by an acidic functionalized ionic liquid, 1-sulfonic acid-3-methyl imidazolium tetrachloroferrate ([SMIM][FeCl₄]) was studied in the temperature range of 110–170 °C. A simplified kinetic model was developed based on pseudo-homogeneous first-order reactions. The kinetic model consists of four main key steps: (1) dehydration of glucose to 5-HMF; (2) degradation of glucose to humins; (3) rehydration of 5-HMF to LA; and (4) degradation of 5-HMF to humins. The proposed model was in a good agreement with the experimental results. The evaluated activation energies for glucose decomposition to 5-HMF and 5-HMF decomposition to LA were 37 and 30 kJ·mol⁻¹, respectively. The first-order rate constants were also used to calculate the thermodynamic activation parameters. The kinetic and thermodynamic parameters obtained can be applied to provide insights on the biomass decomposition to 5-HMF and LA using acidic ionic liquid.

1. Nur Aainaa Syahirah Ramli and Nor Aishah Saidina Amin (2017). Thermo-kinetic assessment of glucose decomposition to 5-hydroxymethyl furfural and levulinic acid over acidic functionalized ionic liquid.Chemical Engineering Journal, 335, 221-230. DOI: https://doi.org/10.1016/j.cej.2017.10.112

Abstract:

Organic catalyst, especially derived from lignocellulosic biomass, is currently being developed for application in reaction engineering. Lignin, a major constituent in biomass, is highly potential as carbon- based -derived catalyst. Carbon cryogel was prepared from acidic lignin-furfural mixtures via sol-gel polycondensation. The effect of carbonization and calcination on carbon cryogel preparation has been investigated in this study. The carbon cryogels were characterized using surface area analyzer and NH3-TPD. Based on the carbonization and
calcination studies, the total surface area and acidity of the selected carbonized cryogel were 214.2 m2/g and 11.3 mmol/g, respectively while calcined cryogel were 426.5 m2/g and 16.1 mmol/g, respectively. The selected carbon cryogels were further characterized using TGA, FTIR, XRD and FESEM-EDX. Overall, the characterization results revealed calcined cryogel has higher thermal stability and stronger acid sites. Subsequently, the performance of calcined carbon cryogel prevailed in catalytic esterification of levulinic acid to ethyl levulinate. The esterification reaction was further investigated at different catalyst loading (5 to 35 wt%), molar ratio of ethanol to levulinic acid (5 to 30), time (1 to 8 h) and temperature (78 to 170 °C). At the optimum conditions, calcined cryogel evinced 87.2% and 86.5 mol% of levulinic acid conversion and ethyl levulinate yield, respectively.

Muzakkir Mohammad Zainol, Nor Aishah Saidina Amin, and Mohd Asmadi (2017). Effects of the the thermal  treatment on carbon cryogel preparation for catalytic esterification of levulinic acid to ethyl levulinate. Fuel Processing Technology, 167, 431-441.DOI: https://doi.org/10.1016/j.fuproc.2017.07.028

Abstract:

Initial experiments were performed to screen a suitable catalyst for catalytic ozonation of sulfamethoxazole (SMX). Among catalysts investigated such as CeO₂, MnO₂, CeO₂/MnO₂, and GAC. The GAC catalyst was found appropriate for further study because it adsorbed more SMX from solution and gave higher mineralization of water matrix comparatively. Further experiments were conducted to study the effect of initial concentration of SMX/COD, pH of solution, and water matrix types for removal of SMX in O₃/GAC combination. Results described that degree of mineralization was higher in dilute solution of SMX (150 mg/L of initial COD value) compared to higher concentrations (250 mg/L, 340 mg/L of initial COD). The rate of COD removal increased as a function of initial pH of solution but the effect of pH of solution was minimal for pH values >7. The effect of water matrix types was minimal on removal of SMX. However, rates of removal of COD were slightly higher in case of deionized water compared to lake water and synthetic water matrix. With addition of tert-butyl alcohol in selected runs showed that O₃/SMX reactions contributed much more than OH/SMX reactions in decreasing concentration of SMX in solution. The consumption of ozone was increased considerably at higher pH values.

Javaid Akhtar, Nor Aishah Saidina Amin, Muhammad Usman (2017). Effectiveness of Granular Activated Carbon for Removal of Sulfamethoxazole during Ozonation. Chiang Mai Journal of Science, 44(3), 1040-1048.

Abstract:

Copper modified polymeric graphitic carbon nitride (Cu/g-C3N4) nanorods for photo-induced CO2 conversion with methane (CH4) and water (H2O) as reducing system under simulated solar energy has been investigated. Thenanocatalysts, synthesizedbypyrolysis andsonication, were characterizedbyXRD, FTIR, Raman analysis, XPS, SEM, N2 adsorption-desorption and PL spectroscopy. The presence of Cu2+ ions over the g-C3N4 structure inhibited charge carriers recombination process. The results indicated that photoactivity and selectivity of Cu/g-C3N4 photo-catalyst for CO2 reduction greatly dependent on the type of CO2-reduction system. CO2 was efficiently converted to CH4 and CH3OH with traces of C2H4 and C2H6 hydrocarbons in the CO2-water system. The yield of the main product, CH4 over 3 wt.% Cu/g-C3N4 was 109 mole g-cata.−1 h−1 under visible light irradiation, significantly higher than the pure g-C3N4 catalyst (60 mole/g.cat). In photo-induced CO2-CH4 reaction, CO and H2 were detected as the main products with smaller amount of hydrocarbons. The highest efficiency was detected over 3 wt.%Cu-loading of gC3N4 and at optimal CH4/CO2 feed ratio of 1.0. The maximum yield of CO and H2 detected were 142 and
76 mole g-catal.−1 h−1, respectively at selectivity 66.6% and 32.5%, respectively. Significantly enhanced CO2/CH4 reduction over Cu/g-C3N4 was attributed to its polymeric structure with efficient charge transfer property and inhibited charges recombination rate. A proposed photo-induced reaction mechanism,corroborated with the experimental data, was also deliberated.©

1. Beenish Tahir, Muhammad Tahir, Nor Aishah Saidina Amin. (2017)  Photo-induced CO₂ reduction by CH₄/H₂O to fuels over Cu-modified g-C₃N₄ nanorods under simulated solar energy. Applied Surface Science 419, 875–885.

Abstract :

Ni/TiO2 nanoparticles dispersed on montmorillonite (MMT) clay with different sizes for selective ethanol steam reforming with regard to hydrogen production has been investigated. Ni/MMT-TiO2 nanocomposite catalysts were prepared by a sol-gel assisted impregnation method. The samples were extensively characterized by X-ray diffraction (XRD), N2 adsorption-desorption, Fourier transfer infrared (FTIR) spectroscopy, scanning electron coupled with energy dispersive X-ray (SEM-EDX) spectroscopy and thermogravimetric analysis (TGA). While Ni content progressively promoted the activity of TiO2 toward ethanol conversion and H2 yield, modification with MMT controlled the crystal growth and produced anatase phase of delaminated MMT/TiO2 nanocomposite. Formation of a surface Ni-MMT phase in the modified Ni/MMT-TiO2 nanocomposite catalyst enhanced Ni-dispersion and reducibility. Various parameters concerning the effect of temperature, steam-to-ethanol (S/E) feed ratio, MMT loading and Ni-metal loading on the catalytic performance, were thoroughly studied. The optimal performance was achieved for 12 wt. % Ni/20 wt. % MMT–TiO2, achieving an ethanol conversion of 89% and a H2 yield of up to 55% at 500 C. In addition, the Ni/MMT-TiO2 nano-composite catalyst possessed the excellent stability at the optimum temperature, over 20 h reaction time. The relative low cost, good activity and stability of MMT modified Ni/TiO2 catalyst offers for an economical and feasible route for production of renewable hydrogen from ethanol.

William Mulewa, Muhammad Tahir, and Nor Aishah Saidina Amin (2017). MMT-supported Ni/TiO2 nanocomposite for low temperature ethanol steam reforming toward hydrogen production. Chemical Engineering Journal,326, 956-969. DOI: https://doi.org/10.1016/j.cej.2017.06.012

Abstract:

In this study, cobalt supported oil palm shell activated carbon (Co/OPS-AC) and ZSM-5 zeolite (Co/ZSM-5) catalysts have been prepared for dry reforming of methane. Cobalt ratios of 6.0 and 14.0 wt% were deposited via wet impregnation method to the OPS-AC and ZSM-5 catalysts. The catalysts were characterized by XRD, N₂ adsorption–desorption isotherms, BET surface area, SEM, FESEM-EDX, TPR-H₂, and TPD-NH₃. The dry reforming of methane was performed using a micro reactor system under the condition of 10,000 ml/h.g-cat, 3 atm, CH₄/CO₂ ratio of 1.2:1.0 and temperature range from 923 K to 1023 K. The gaseous products were analyzed by gas chromatography (GC) with thermal conductivity detector (TCD) and further quantified to determine the conversions of CH₄and CO₂, and the yields of CO and H₂. Experimental results revealed both catalysts exhibited lower conversions of CO₂ and CH₄ with the increase in temperature from 923 K to 1023 K. The reduced conversions may be due to the formation of carboneous substance on the catalyst known as coking. Comparatively, Co/OPS-AC gave higher conversions of CO₂ and CH₄ as well as higher yields of H₂ and CO as it has a higher surface area than Co/ZSM-5 which subsequently rendered higher activity for the reforming of methane. With the increasing cobalt loadings and reaction temperature, OPS-AC(14) catalyst exhibited improved activity and H₂/CO ratio. Based on these results, cobalt supported OPS activated carbon catalyst was suggested to be more effective for CO₂ and CH₄ conversions.

1. Izirwan Izhab, Nor Aishah Saidina Amin, and Mohd Asmadi (2017). Dry Reforming of Methane over Oil Palm Shell Activated Carbon and ZSM-5 Supported Cobalt Catalysts. International Journal of Green Energy, 14(10), 831-838. DOI: https://doi.org/10.1080/15435075.2017.1334659

Abstract:

Ni/TiO2 nanoparticles dispersed on montmorillonite (MMT) clay with different sizes for selective ethanol steam reforming with regard to hydrogen production has been investigated. Ni/MMT-TiO2 nanocomposite catalysts were prepared by a sol-gel assisted impregnation method. The samples were extensively characterized by X-ray diffraction (XRD), N2 adsorption-desorption, Fourier transfer infrared (FTIR) spectroscopy, scanning electron coupled with energy dispersive X-ray (SEM-EDX) spectroscopy and thermogravimetric analysis (TGA). While Ni content progressively promoted the activity of TiO2 toward ethanol conversion and H2 yield, modification with MMT controlled the crystal growth and produced anatase phase of delaminated MMT/TiO2 nanocomposite. Formation of a surface Ni-MMT phase in the modified Ni/MMT-TiO2 nanocomposite catalyst enhanced Ni-dispersion and reducibility. Various parameters concerning the effect of temperature, steam-to-ethanol (S/E) feed ratio, MMT loading and Ni-metal loading on the catalytic performance, were thoroughly studied. The optimal performance was achieved for 12 wt. % Ni/20 wt. % MMT–TiO2, achieving an ethanol conversion of 89% and a H2 yield of up to 55% at 500 C. In addition, the Ni/MMT-TiO2 nano-composite catalyst possessed the excellent stability at the optimum temperature, over 20 h reaction time. The relative low cost, good activity and stability of MMT modified Ni/TiO2 catalyst offers for an economical and feasible route for production of renewable hydrogen from ethanol.

1. Muhammad Tahir and Nor Aishah Saidina Amin (2017). Photo-induced CO² reduction by hydrogen for selective CO evolution in a dynamic monolith photoreactor loaded with Ag-modified TiO₂ International Journal of Hydrogen Energy, 42(23), 15507-15522. DOI : https://doi.org/10.1016/j.ijhydene.2017.05.039

Abstract:

Plasmonic Au/Ag alloy NPs supported on TiO2 nanowires (TiO2 NWs) have been designed and synthesized through a facile hydrothermal and photo-deposition method. The samples were characterized by XRD,FE-SEM, TEM, N2-adsorption-desorption, XPS, Raman, UV–vis and PL spectroscopy. Bimetallic Au/Ag NPs were presented over the TiO2 NWs as an alloy, thus exhibited strong absorption of visible light due to the localized surface plasmon resonance (LSPR) excitation. The synergistic effect in plasmonic Au/Ag alloy NPs for selective photocatalytic CO2 reduction with H2 to CO and hydrocarbons under visible light irradiation was investigated. The present design of plasmonic Au/Ag NPs co-decorated TiO2 NWs leads to remarkably enhanced photoactivity of CO2 reduction to CO. The CO evolution rate as a main product over the Au-Ag alloy NPs coated TiO2 NWs was 1813 mole-g-catal.−1 h−1 at selectivity 98%. This amount was approximately 1.72 time larger comparing to Au-NPs/TiO2 NWs, 1.84 fold more than the Ag-NPs/TiO2 NWs, 72.52 fold than the TiO2 NWs and 201 fold more than the amount of CO produced over the bare TiO2-NPs. This great enhancement can be attributed to synergistic effects in Au/Ag-NPs, enhanced visible light absorption due to Au-Ag alloy formation and improved charge separation in LSPR-excited TiO2 NWs. In addition, turnover productivity is introduced to investigate the effect of operating parameters on the performance of photocatalysts. The plasmonic reaction mechanism of Au-Ag NPs in conjunction with LSPR excitation and charge transport to understand the reaction pathway is described.

1. Muhammad Tahir, Beenish Tahir and Nor Aishah Saidina Amin (2017). Synergistic effect in plasmonic Au/Ag alloy NPs co-coated TiO₂ NWs toward visible-light enhanced CO₂ photoreduction to fuels. Applied Catalysis B: Environmental, 204, 548-560. DOI: https://doi.org/10.1016/j.apcatb.2016.11.062