Prof. Ir. Dr. Nor Aishah Saidina Amin

Abstract:

In this study, the performance of montmorillonite (MMT) modified TiO₂nanocomposites for photocatalytic CO₂ reduction with CH₄ in a continuous monolith photoreactor has been investigated. The MMT modified TiO₂ nanocomposites were dip-coated over monolith channels and were characterized by XRD, SEM, TEM, XPS, N₂-adsorption–desorption and UV–vis spectroscopy. The MMT produced anatase phase of TiO₂ and reduced TiO₂ crystallite size from 19 nm to 13 nm. CO was the major reduction product with a yield rate of 237.5 μmol g-catal.⁻¹ h⁻¹ over 10 wt.% MMT-loaded TiO₂ at 100 °C, and CO₂/CH₄ feed ratio 1.0. The photoactivity of MMT-loaded TiO₂ monolithic catalyst was 2.52 times higher than bare TiO₂. Likewise, low concentrations of C₂H₆, CH₃OH, C₃H₆ and C₃H₈ were detected in the products mixture. These results inferred MMT modified TiO₂ and monolith photoreactor were beneficial for enhancing photocatalysis process with appreciable productivity. The stability test revealed photoactivity of MMT-loaded TiO₂ nanocomposites partially diminished in recycle runs.

1. Muhammad Tahir, Beenish Tahir and Nor Aishah Saidina Amin (2015). Photocatalytic CO2 reduction by CH4 over montmorillonite modified TiO2 nanocomposites in a continuous monolith photoreactor  Materials Research Bulletin. 63, 13-23. DOI : https://doi.org/10.1016/j.materresbull.2014.11.042

Abstract:

A series of Fe/HY zeolite catalysts with different FeCl₃ weight percent (5, 10 and 15%) on HY zeolite have been synthesized in this study. All the catalysts were characterized by XRD, FESEM, N₂ physisorption, FTIR, TGA, NH₃-TPD and IR-pyridine. The performance of the Fe/HY catalysts was tested in glucose to levulinic acid transformation. The amount and type of acid sites together with surface area and porosity influenced the catalytic activity. The catalyst with a large surface area, high concentration of active acid sites and appropriate ratio of Brønsted to Lewis acids seemed suitable for levulinic acid production. However, catalyst with excess Lewis acidity converted glucose into humins, but samples with high relative mesopority and low relative microporosity gave a decent levulinic acid yield. Among the catalysts tested, 10% Fe/HY catalyst exhibited the highest catalytic performance with 62% yield at 180 °C in 180 min. The reused catalyst exhibited constant activity for five successive runs. The experimental results demonstrated the potential of Fe/HY catalyst for biomass conversion to levulinic acid under mild process conditions.

1. Nur Aainaa Syahirah Ramli and NorAishah Saidina Amin (2015).Fe_HY zeolite as an effective catalyst for levulinic acid production from glucose_ Characterization and catalytic performance.Applied Catalysis B, 163, 487-498. DOI: https://doi.org/10.1016/j.apcatb.2014.08.031

Abstract:

Indium (In)-doped titanium dioxide (TiO₂) nanoparticles were synthesized using a controlled sol–gel method. The structures and properties of the catalysts were characterized by XRD, FE-SEM, TEM, XPS, BET, UV–vis and PL spectroscopy. Indium, present over the TiO₂ in metal state, inhibited crystal growth and produced anatase phase of mesoporous TiO₂ nanoparticles. Doping In in TiO₂ also increased the surface area and enlarged the band gap. The photocatalytic activities of In-doped TiO₂ nanoparticles were considerably improved for CO₂ reduction with H₂O vapors in a cell type photoreactor. CO was observed as the main product over TiO₂, but doping In in TiO₂ remarkably increased the CH₄ yield. CH₄ production rate over 10 wt.% In-doped TiO ₂ was 7.9-fold higher than the bare TiO₂ at 100 °C and CO₂/H₂O ratio of 1.43. In addition, C₁–₃ higher hydrocarbons namely C₂H₄, C₂H₆, C₃H₆ and C₃H₈were detected in the product mixture. The enhanced photoactivity in mesoporous In-doped TiO₂ nanoparticles can be attributed to interfacial transfer of photogenerated charges, which led to effective charge separation and inhibited recombination of photogenerated electron–hole (e⁻/h⁺) pairs. Langmuir–Hinshelwood model, developed to investigate reaction rate parameters, fitted well with the experimental data.

1. Muhammad Tahir and Nor Aishah Saidina Amin (2015). Indium-doped TiO2 nanoparticles for photocatalytic CO₂ reductionwith H2O vapors to CH4. Applied Catalysis B, 162, 98-109. DOI: https://doi.org/10.1016/j.apcatb.2014.06.037

ABSTRACT:

Photocatalytic CO2 reduction by H2O and/or H2 reductant to selective fuels over Cu-promoted In2O3/TiO2 photocatalyst has been investigated. The samples, prepared via a simple and direct sol-gel method, were characterized by XRD, SEM, TEM, XPS, N2 adsorption-desorption, UV–vis diffuse reflectance, Raman and PL spectroscopy. Cu and In loaded into TiO2, oxidized as Cu2+ and In3+, promoted efficient separation of photo-generated electron/hole pairs (e−/h+). The results indicate that the reduction rate of CO2 by H2O to CH4 approached to 181 mol g−1 h−1 using 0.5% Cu-3% In2O3/TiO2 catalyst, a 1.53 fold higher than the production rate over the 3% In2O3/TiO2 and 5 times the amount produced over the pure TiO2. In addition, Cu was found to promote efficient production of CH3OH and yield rate reached to 68 mol g−1 h−1 over 1% Cu-3% In2O3/TiO2 catalyst. This improvement was attributed to charge transfer property and suppressed recombination rate by Cu-metal. More importantly, H2 reductant was less favorable for CH4 production, yet a significant amount of CH4 and CH3OH were obtained using a mixture of H2O/H2 reductant. Therefore, Cu-loaded In2O3/TiO2 catalyst has shown to be capable for methanol production, whereas product selectivity was greatly depending on the amount of Cu-loading and the type of reductant. A photocatalytic reaction mechanism was proposed to understand the experimental results over the Cu-loaded In2O3/TiO2 catalyst.

Muhammad Tahir, Beenish Tahir, NorAishahSaidina Amin and Hajar Alias (2016). Selective photocatalytic reduction of CO2 by H2O/H2 to CH4 and CH3OH over Cu-promoted In2O3/TiO2 nanocatalyst. Applied Surface Science, 389, 46–55. DOI: https://doi.org/10.1016/j.apsusc.2016.06.155

Abstract:

Global economic development intensifies the consumption of fossil fuels which results in increase of carbon dioxide (CO2) concentration in the atmosphere. The
technologies for carbon capture and utilization to produce cleaner fuels are of great significance. However, phototechnology provides one perspective for economical CO2
conversion to cleaner fuels. In this study, CO2 conversion with H2 to selective fuels over Au/TiO2 nanostructures using environment friendly continuous monolith photoreactor
has been investigated. Crystalline nanoparticles of anatase TiO2 were obtained in the Au-doped TiO2 samples. The Au deposited over TiO2 in metal state produced
plasmonic resonance. CO2 was efficiently converted to CO as the main product over Au/TiO2 with a maximum yield rate of 4144 lmol g-catal.-1 h-1 , 345 fold-higher than using un-doped TiO2 catalyst. The significantly enhanced photoactivity of Au/TiO2 catalyst was due to hindered charges recombination rate and Au metallic-interband transition. The photon energy in the UV range was high enough to excite the d-band electronic transition in the Au to produce CO, CH4, and C2H6. The quantum efficiency over Au/TiO2 catalyst for CO was considerably improved in the continuous monolith photoreactor. At higher space

Beenish Tahir, Muhammad Tahir and NorAishah Saidina Amin (2016). Photocatalytic CO2 conversion over Au/TiO2 nanostructures for dynamic production of clean fuels in a monolith photoreactor. Clean Technologies and Environmental Policy, 18, 2147–2160. DOI : https://doi.org/10.1016/j.apsusc.2016.06.155

Abstract:

Photocatalytic CO2 reduction by H2O and/or H2 reductant to selective fuels over Cu-promoted In2O3/TiO2 photocatalyst has been investigated. The samples, prepared via a simple and direct sol-gel method, were characterized by XRD, SEM, TEM, XPS, N2 adsorption-desorption, UV–vis diffuse reflectance, Raman and PL spectroscopy. Cu and In loaded into TiO2, oxidized as Cu2+ and In3+, promoted efficient separation of photo-generated electron/hole pairs (e−/h+). The results indicate that the reduction rate of CO2 by H2O to CH4 approached to 181 mol g−1 h−1 using 0.5% Cu-3% In2O3/TiO2 catalyst, a 1.53 fold higher than the production rate over the 3% In2O3/TiO2 and 5 times the amount produced over the pure TiO2. In addition, Cu was found to promote efficient production of CH3OH and yield rate reached to 68 mol g−1 h−1 over 1% Cu-3% In2O3/TiO2 catalyst. This improvement was attributed to charge transfer property and suppressed recombination rate by Cu-metal. More importantly, H2 reductant was less favorable for CH4 production,
yet a significant amount of CH4 and CH3OH were obtained using a mixture of H2O/H2 reductant. Therefore, Cu-loaded In2O3/TiO2 catalyst has shown to be capable for methanol production, whereas product selectivity was greatly depending on the amount of Cu-loading and the type of reductant. A photocatalytic reaction mechanism was proposed to understand the experimental results over the Cu-loaded In2O3/TiO2 catalyst.

Wan Nor Nadyaini Wan Omar and Nor Aishah Saidina Amin (2016). Multi response optimization of oil palm frond pretreatment by ozonolysis. Industrial Crops and Products, 85, 389–402. DOI: https://doi.org/10.1016/j.indcrop.2016.01.027

ABSTRACT:

Photocatalytic CO2 methanation using H2O vapors and/or H2 reductants over nickel (Ni) and indium (In) promoted TiO2 nanocatalysts has been investigated. The physical–chemical characteristics of the catalysts, prepared through a sol–gel method with different Ni and In doping levels, were characterized by XRD, FESEM, TEM, FTIR, XPS, N2 adsorption–desorption, UV–vis diffuse reflectance, Raman and photoluminescence spectroscopy. The controlled crystallites growth with increased specific surface area and reduced pore diameter were observed by NiO and In2O3 loading into TiO2. In and Ni metals present in TiO2, oxidized as In2O3 and NiO, promoted efficient separation of photo-generated charges (e/h+).Using H2O as a reductant, CO2 was efficiently converted to CH4 over co-loaded TiO2 catalysts and the optimal loading amount was determined to be 1 wt.% NiO and 3 wt.% In2O3, giving a CH4 production rate of 240 lmole g1 h1 at selectivity 80%. This photoactivity of NiO and In2O3 loaded TiO2 catalyst for CO2 methanation was 2 fold more than the yield rate over In2O3/TiO2 and 6.5 times more the amount produced over the pure TiO2. The enhancement was attributed to charge transfer property and efficient
suppressed recombination rate by Ni and In metals. In the presence of H2 reductant, both CO and CH4 were produced in significant amount and the maximum yield rates detected were 243 and 208 lmole g1 h1, respectively. Therefore, H2O reductant found to be more efficient for CH4 production, yet the CO2 reduction process was more favorable with H2, where the total amounts of products were considerably enhanced. In addition, a photocatalytic reaction mechanism is proposed to understand experimental results over the NiO and In2O3 loaded TiO2 catalysts

Muhammad Tahir, Beenish Tahir, NorAishah Saidina Amin and Ayyaz Muhammad (2016). Photocatalytic CO2 methanation over NiO/In₂O₃ promoted TiO₂ nanocatalysts using H₂O and/or H₂ Energy Conversion and Management, 119, 368–378. DOI: https://doi.org/10.1016/j.enconman.2016.04.057

ABSTRACT:

There are many advantages associated with the use of hydrogen as clean fuels, thus there is a need to search for good hydrogen adsorbents. Activated carbon (AC) from various sources has been tested as hydrogen adsorbents, with the exception of AC produced from empty fruit bunch (EFB). The aim of this study is to produce AC from EFB obtained in Malayisa, followed by testing on its hydrogen storage capacity. The AC samples were activated using physical and chemical processes. The total surface areas (SBET) and microporous structures of the ACs produced were in the range of 305–687 m2/g and up to 94%, respectively. The hydrogen storage capacity was studied at constant temperature, 77K and pressure from ambient pressure up to 100 bar. The hydrogen uptake increased occasionally from 0 bar to 20 bar and decreased above 20 bar. EFB activated with 2M KOH demonstrated maximum hydrogen adsorption capacity with 2.14 wt% hydrogen uptake at 20 bar. More research is needed to improve the hydrogen adsorption capacity on AC, and to determine its potential applications other than mobile applications.

1. Siti Hadjar md Arshad, Norzita Ngadi, Astimar abdul Aziz, Nor Aishah Saidina Amin, Mazura Jusoh, Wong Syie Luing (2016). Preparation of activated carbon from empty fruit bunch for hydrogen storage, Journal of Energy Storage, 8, 257-261. DOI : https://doi.org/10.1016/j.est.2016.10.001

Abstract:

Gas phase dehydration of glycerol to acrolein over a series of supported HSiW on ZrO2 and nano-sized gAl2O3 catalyst has been investigated. The characterization results revealed that impregnation of g-Al2O3 nanoparticles increased the specific surface area, pore diameter, and thermal stability of the supported catalysts. The highest acrolein selectivity of 88.5% at 97.0% glycerol conversion was achieved over 0.5 g 30HZ-20A catalyst in 3 h at glycerol feed concentration of 10 wt%, temperature = 300 ?C and
TOF = 136 h1. The coke deposition has no significant effect on the activity of 30HZ-20A catalyst. Indeed, the catalyst was stable even after 40 h.

1. Amin Talebian-Kiakalaieh, Nor Aishah Saidina Amin and Zaki Yamani Zakaria (2016). Gas phase selective conversion of glycerol to acrolein over supported silicotungstic acid catalyst. Journal of Industrial and Engineering Chemistry, 34, 300–312. DOI: https://doi.org/10.1016/j.jiec.2015.11.024