Conversion of Methane into Heaviour Hydrocarbures using Nanosecond Lasers

Navid Khoshgonab, Hamze Ali | 2013

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 44999 (04)
  4. University: Sharif University of Technology
  5. Department: Physics
  6. Advisor(s): Sadighi Bonabi, Rasoul
  7. Abstract:
  8. In this thesis the conversion of methane into higher hydrocarbures using pulsed nanosecond lasers has been studied. The lasers of 532 nm of second harmonic of Nd: YAG, 355 nm of 3rd harmonic of Nd: YAG and 248 nm of KrF have been used in this project. Acetylene, ethylen and ethane have been detected using gas chromatography detection system, which showed acetylene as a dominant product. For each wavelength the amount of the laser energy and the fraction of secondary products have been measured. Also the dependence of amount of produced components on chamber pressure has been studied for 355 nm laser. During the irradiation time of methane no considerable changes in temperature and pressure was observed. Based on the multiphoton absorption coefficients and electron impact dissociation of methane and the chemical reactions inside the cell, the amount of higher hydrocarbures have been calculated. Comparing the results of numerical calculations and experimental results, it is concluded that the mechanism of dissociation and conversion of pulsed nanosecond lasers is different from conventional vacuum UV sources. In this project the necessity of introducing ionized species to obtain an agreement between theory and experiments has been proved. Ignoring the ion-molecular reactions in numerical calculations, acetylene and ethane did not form the maximum and minimum produced components respectively, which was not consistent with experiments. Introducing the new ion-radical reactions a good agreement has been achived between theory and experiment. Theoretical methods have been used for reaction rate computations of reactions, which had not been studied experimentally.At the theoretical side of the thesis, the dissociation of methane has been investigated using femtosecond laser pulses. Also the study of interaction of gas jets with femtosecond lasers and the generation of mono-energetic electron beams have been reported.
  9. Keywords:
  10. Methane Conversion ; Methane Dissociation ; Higher Hydrocarbures ; Pulsed Nanosecond Lasers

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