Prof. Ir. Dr. Nor Aishah Saidina Amin

Abstract:

The catalyst screening tests for CO₂ oxidative coupling of methane (CO₂-OCM) were studied over ternary and binary metal oxide catalysts. The catalysts were prepared by doping MgO- and CeO₂-based solids with oxides from alkali (Li₂O), alkaline earth (CaO), and transition metal groups (WO₃ or MnO). The high reducibility of the CeO₂ catalyst, an important factor in the CO₂-OCM catalyst activity, could be enhanced by the presence of manganese oxide species. These species increased oxygen mobility and oxygen vacancies in the CeO₂ catalyst. The performance of 5%/MnO/15%CaO/CeO₂ catalyst was the most potential among the CeO₂-based catalysts. The 2%Li₂O/MgO catalyst showed the most promising C₂₊ hydrocarbons selectivity and yield at 98 and 5.7%, respectively. Carbon in CO₂ was only converted into CO. Carbon and/or hydrogen in methane were only converted into ethane, ethylene acetylene, and CO and/or hydrogen and water, respectively.

1. Istadi and Nor Aishah Saidina Amin (2004). Screening of MgO- and CeO₂– Based Catalysts for Carbon Dioxide Oxidative Coupling of Methane to C₂₊ Journal of Natural Gas Chemistry, 13 (1), 23-35, Science Press.

Abstract:

The influence of cocations (Cr and Ag) on the activity of Cu/CeO₂ catalysts in the selective reduction of NO_x with C₃H₆ has been investigated in this study. The reduction of NO_x under lean conditions was greatly improved by loading Cr and Ag onto a Cu/CeO₂ catalytic system. All the synthesized bimetal catalysts were characterized using XRD and TPR-H₂. The better metal–support interaction and metal dispersion shown by Cu/Ag/CeO₂ have elevated its performance compared to the Cu/Cr/CeO₂ catalyst. By having such salient features, the competitiveness factor (S_SCR-HC) assigned by Cu/Ag/CeO₂ was generally better than that of the other tested catalysts. The presence of O₂ was proven to be a very crucial factor for promoting the selective reduction of NO_x with C₃H₆.

1. Nor Aishah Saidina Amin, Tan Eng Fong and Z.A Manan (2004). SCR Of NO_x by C₃H₆: Comparison Between Cu/Cr/Ceo₂ And Cu/Ag/Ceo₂ Journal of Catalysis, 222, 100 – 106, Elsevier.

Abstract:

The optimization of methane conversion to liquid fuels over copper loaded W/ZSM-5 catalyst was studied by utilizing experimental design from ‘Statsoft Statistica’ version 6.0 software. Response surface methodology was employed to determine the optimum methane conversion and C₅⁺ selectivity. Numerical results indicated the optimum methane conversion of 29.4% with the corresponding C₅⁺ selectivity of 57.2% were achieved at 12.3 vol% of O₂, 203.9 ml/min of total feed flow rate, and %W doped of 3.2 wt%. The optimum C₅⁺ selectivity of 70.2% was attained at 7.6 vol% of O₂, 208.9 ml/min of total feed flow rate, and 3.2 wt% of W content with the corresponding methane conversion of 26.7%. By means of variance analysis and additional experiments, the adequacy of this model is confirmed.

1. Nor Aishah Saidina Amin and Didi Dwi Anggoro (2004) Optimization Of Direct Conversion Of Methane To Liquid Fuels Over Cu Loaded W/ZSM-5 Catalyst. Fuel, 83 487-494, Elsevier.

Abstract:

The Cu/CeO2 and Cu/Cr/CeO2 catalysts synthesized using the impregnation method were employed to investigate the selective reduction of NOx with C3H6 at 673.15 K and 1 atm. The activity of CeO2 was greatly induced by loading 4 wt.% of Cu onto the bare support. The presence of C3H6 was a crucial factor for elevating the NOx conversion under lean conditions. The modification of the optimal Cu(4)/CeO2 catalyst with 3 wt.% of Cr steadily improved the performance of the catalysts. Both the optimal Cu(4)/CeO2 and Cu(4)/Cr(3)/CeO2 catalysts were characterized using XRD, SEM and TPR-H2. The co-existence of CuO, Cr2O3 and CuCr2O4 was believed to grant the promising performance of the Cu(4)/Cr(3)/CeO2 catalyst in SCR-HC under net oxidizing conditions

1. Nor Aishah Saidina Amin ,Tan Eng Fong, and Z.A Manan (2003). Selective Reduction of NO_x with C₃H₆ over Cu and Cr Promoted CeO₂ Applied Catalysis B: Environmental, 43, 57-69, Elsevier.

Abstract:

Direct conversion of methane using a metal-loaded ZSM-5 zeolite prepared via acidic ion exchange was investigated to elucidate the roles of metal and acidity in the formation of liquid hydrocarbons. ZSM-5 (SiO2/Al2O3=30) was loaded with different metals (Cr, Cu and Ga) according to the acidic ion-exchange method to produce metal-loaded ZSM-5 zeolite catalysts. XRD, NMR, FT-IR and N2 adsorption analyses indicated that Cr and Ga species managed to occupy the aluminum positions in the ZSM-5 framework. In addition, Cr species were deposited in the pores of the structure. However, Cu oxides were deposited on the surface and in the mesopores of the ZSM-5 zeolite. An acidity study using TPD-NH3, FT-IR, and IR-pyridine analyses revealed that the total number of acid sites and the strengths of the Br¨onsted and Lewis acid sites were significantly different after the acidic ion exchange treatment Cu loaded HZSM-5 is a potential catalyst for direct conversion of methane to liquid hydrocarbons. The successful production of gasoline via the direct conversion of methane depends on the amount of aluminum in the zeolite framework and the strength of the Bronsted acid sites.

1. Nor Aishah Saidina Amin and Didi Dwi Anggoro (2003) Characterization And Activity of Cr, Cu and Ga Modified ZSM-5 for Direct Conversion of Methane to Liquid Hydrocarbons. Journal of Natural Gas Chemistry, 12, 123-134, Science Press.

Abstract:

Ethylene oligomerization using ZSM-5 zeolite was investigated to study the role of Bronsted acid sites in the formation of higher hydrocarbons. The oligomerization of olefins, dependent on the acidity of ZSM-5 zeolite, is an important step in the conversion of natural gas to liquid fuels. The framework Si/Al ratio reflects the number of potential acid sites and the acid strength of the ZSM-5 catalyst. ZSM-5 with the mole ratio SiO2/Al2O3 equal to 30 was dealuminated for different periods of time according to the acidic ion-exchange method to produce ZSM-5 with various Si/Al ratios. The FT-IR analysis revealed that the integrated framework aluminum band, non-framework aluminum band, and silanol groups areas of the ZSM-5 zeolites decreased after being dealuminated. The performance of dealuminated zeolite was tested for ethylene oligomerization. The result demonstrated that the dealumination of ZSM-5 led to higher ethylene conversion, but the gasoline selectivity was reduced compared to the performance of a ZSM-5 zeolite. The characterization results revealed that the amount of aluminum in the zeolitic framework, the crystallinity of the ZSM-5 zeolite and the Si/Al ratio affected the formation of Bronsted acid sites. The number of the Bronsted acid sites on the catalyst active sites is important in the olefin conversion to liquid hydrocarbons.

1. Nor Aishah Saidina Amin and Didi Dwi Anggoro (2002.)Dealuminated ZSM- Zeolite Catalyst for Ethylene Oligomerization to Liquid Fuels. Journal of Natural Gas Chemistry, 11, 79 – 86, Science Press.

Abstract:

Classification of gas-liquid reactions in the past has been based on comparison of characteristic times for diffusional mass transfer and chemical reaction in liquid film near the gas-liquid interface. The fast chemical reactions occur almost entirely in liquid film and the very slow reactions are confined to bulk liquid. Gas-liquid reactions that do not belong to either class have received less attention and have been in general assumed to be confined to either liquid film or bulk liquid for simplification of modeling and design of reactors. A unified approach for modeling of gas-liquid reactors is provided here considering a single reaction occurring over the entire liquid phase, with at least the reactant or the product being volatile. The two-way linkages between liquid film and bulk liquid, largely ignored previously, are properly accounted for in the present approach. The dispositions of concentration profiles for reactant and product in the liquid film are presented and discussed. A first-order reaction is considered as a specific example. Numerical illustrations for a perfectly mixed reactor demonstrate that an unwarranted confinement of liquid-phase reaction to either liquid film or bulk liquid can lead to incorrect design of and erroneous prediction of performance of gas-liquid reactors. Variation in relative importance of reaction in liquid film with respect to reaction in bulk liquid with variations in process parameters is investigated. The effectiveness of the liquid-phase reaction in the presence of mass transfer resistances is examined.

1. Parulekar S. J. and Amin, N.A. S. (1996), Gas-Liquid Reactions In Well-Mixed Reactors – A Fresh Perspective. Chemical Engineering Science,  51 (20), 4561-4577, Pergamon.