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Title:	Synthesis of Ni, Co and Fe based catalysts for methane decomposition into hydrogen and carbon nanomaterials
Authors:	Pudukudy Manoj (P64527)
Supervisor:	Zahira Yaakob, Prof. Dr.
Keywords:	Catalysis.
Issue Date:	30-Apr-2014
Description:	The non-oxidative thermocatalytic decomposition of methane into COx-free hydrogen and nanocarbon has attracted recent research interest, due to the concern of zero emission of greenhouse gases and the bulk production of carbon nanomaterials. In this work, several set of novel catalysts were synthesized, characterized and their catalytic activity was evaluated for methane decomposition. The nanocarbon deposited over the catalysts was further characterized. The Ni, Co and Fe based monometallic catalysts supported on sol gel derived silica microflakes were found to be highly active and stable for the reaction. The scanning electron microscopy images indicated the fine dispersion of various agglomerated metal oxide nanostructures on the surface of silica microflakes. A maximum hydrogen yield of 74% was obtained for the Ni catalyst, with a slight deactivation with time on stream. The Co and Fe based catalysts were found to be less active but more stable than Ni catalyst. Uniform multi-walled carbon nanotubes, metal encapsulated carbon particles and multilayer graphene sheets were deposited over the Ni, Co and Fe catalysts respectively. However, the carbon nanotubes deposited over Ni catalyst showed higher graphitization degree, oxidation stability and crystallinity. The next set of catalysts contains Ni, Co and Fe based bimetallic systems supported over mesoporous silica, SBA-15. The fine dispersion of metal oxide nanostructures on the surface of SBA-15, without affecting its mesoporous texture was clearly shown by the TEM and low angle XRD analysis. The N2 sorption analysis revealed the reduced surface area and pore volume of SBA-15, after metal loading, due to the filling/blockage of mesopores by metal species. The results of methane decomposition experiments indicated that, all of the bimetallic catalysts were highly active and stable for the production of hydrogen and nanocarbon at 700°C, providing a high catalytic stability by the CoFe/SBA-15 catalyst. A new set of open tip multi-walled nanotubes were deposited over the catalysts. In order to study the effect of reaction parameters, a response surface methodology was employed over Ni/SBA-15 catalyst using central composite design (CCD). The effect of reaction temperature, methane flow rate and catalyst weight on the hydrogen yield was investigated. Using multiple regression analysis, the experimental results of hydrogen yield was found to be fit with the quadratic polynomial model with an acceptable R 2 value of 0.9494. The quadratic polynomial model satisfied the variables within the selected variable range. The response predicted from the optimum conditions was found to be related with the experimental response, with a mean error of 4.38 %. The catalytic activity of Ni/SBA-15 catalyst promoted with Pd was investigated for the reaction, to get better efficiency. The characterization results showed that, Pd deposition increased the crystallinity of NiO and its fine dispersion, increased the specific surface area and decreased the reduction temperature of NiO. Moreover, the Pd addition increased the efficiency of reaction. No deactivation was observed until 420 min of time on stream for all of the catalysts, indicating the high stability of the Ni/SBA-15. Multiwalled carbon nanotubes with open tips were deposited over the catalysts, irrespective of the role of Pd and its loading, due to the strong metal support interaction aroused by encapsulation of metals in the hexagonal mesopores of SBA- 15. In conclusion, it can be said that the as-prepared catalysts were highly effective for the reaction, in terms of its catalytic activity, stability and the growth of carbon.,Ph.D
Pages:	221
Call Number:	QD505.P834 2015 3
Publisher:	UKM, Bangi
Appears in Collections:	Fuel Cell Institute / Institut Sel Fuel

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