| dc.contributor.author | Glasier, Greg F. | en_US |
| dc.date.accessioned | 2014-10-21T12:36:08Z | |
| dc.date.available | 2000 | |
| dc.date.issued | 2000 | en_US |
| dc.identifier.other | AAINQ66664 | en_US |
| dc.identifier.uri | http://hdl.handle.net/10222/55794 | |
| dc.description | When hydrocarbons are placed in a high temperature environment, energy is introduced into the individual molecules. Redistribution of this energy often results in the "cracking" of C-C bonds, the formation of radicals, and a general reduction in the size of the molecules. A small fraction of these molecules react with one another, growing into large, stable species including carbon. The accumulation of carbon on heated reactor surfaces when in the presence of hydrocarbons is a serious industrial problem. The deposits are complicated, generally containing a number of distinct, carbon-rich materials. Available evidence suggests pyrolytic carbon deposits directly on the reactor surface as a small hydrocarbon or that polymerization and condensation reactions may play an important role. However, there is insufficient evidence to distinguish which mechanisms dominate. This thesis examined the role of molecular growth and aerosol formation in carbon formation during the pyrolysis of ethane. | en_US |
| dc.description | New sampling techniques were developed and used to obtain samples from a flow reactor for the pyrolysis of ethane at 1185 K. Gaseous samples were analyzed by gas chromatography and mass spectrometry. Liquid samples were analyzed by gas chromatography, liquid chromatography and mass spectrometry. Solid samples were analyzed in-situ by gravimetric analysis and externally by electron microscopy. Aerosols were analyzed in-situ by laser extinction and externally by electron microscopy. | en_US |
| dc.description | Gas phase analyses were consistent with three acetylene molecules reacting to form benzene. The rate of carbon deposition was found to be directly proportional to the concentration of benzene in the system. Aromatic species were observed in the 100--700 amu range. The observation of these species was consistent with the hypothesis that polycyclic aromatic hydrocarbon (PAH) condensation and dehydrogenation were partially responsible for the deposition of carbon. These results also indicated that there were sufficient PAHs present in the system to allow for formation of the observed amount of carbon by one or both of the following routes: direct decomposition on the surface from the gas phase or condensation as a liquid followed by deposition. It was shown for the first time that ethane can also be transformed in part, at high temperatures and long residence times, to form an aerosol. These results were consistent with the presence of a carbon precursor which was neither a discrete aromatic unit nor a soot particle but had a structure that was somewhere in between. The study indicated that 30% of the deposited carbon in the ethane pyrolysis system could have been due to deposition of the observed aerosol. | en_US |
| dc.description | Metal surfaces were shown to initially accelerate deposition, indicating a surface catalyzed decomposition. This acceleration was shown to level off after a short period of coking. The reduction in rate was correlated to a change from filamentous carbon to pyrolytic carbon, indicating the carbon precursors examined in this study are also relevant to coking in industrial metal reactor tubes. | en_US |
| dc.description | Thesis (Ph.D.)--Dalhousie University (Canada), 2000. | en_US |
| dc.language | eng | en_US |
| dc.publisher | Dalhousie University | en_US |
| dc.publisher | | en_US |
| dc.subject | Chemistry, Physical. | en_US |
| dc.subject | Engineering, Chemical. | en_US |
| dc.title | Molecular growth, aerosol formation and pyrolytic carbon deposition during the pyrolysis of ethane at high conversion. | en_US |
| dc.type | text | en_US |
| dc.contributor.degree | Ph.D. | en_US |
