Ahmet Pekediz

Date of Award


Degree Type


Degree Name

Doctor of Philosophy


This study was an integrated research effort on various aspects of oxidative coupling of methane (OCM): bench scale reactor development, catalyst preparation, kinetic modelling and process simulation.;With this end a Riser Simulator, a 45 mL bench-scale internal fluidized bed reactor, was adapted for the OCM under staged oxygen feeding. An automatic injection system was designed to inject reactant in a staged manner and to sample products.;Mixing in the Riser Simulator was studied using combined hot-film anemometry and fibre optic probes. In situ concentration and velocity measurements with the hot-film anemometer enabled to evaluate mixing times and inner recirculation gas phase ratios. The observed gas recycle ratios were above 30 with mixing times in the 20 milliseconds range. This proved that the Riser Simulator approximates an ideal well mixed batch reactor. In addition, fibre optic sensors allowed to characterize the degree of particle fluidization and the effect of gas phase density.;Moreover, a low surface area non-supported {dollar}\rm Sm\sb2O\sb3{dollar} catalyst was developed to suit the staged oxygen injection concept. The catalyst was selective towards ethane and ethylene and showed no particular signs of activity decay or particle attrition.;Systematic kinetic runs were carried out in the Riser Simulator at five temperature levels: 500{dollar}\sp\circ{dollar}C, 550{dollar}\sp\circ{dollar}C, 600{dollar}\sp\circ{dollar}C, 650{dollar}\sp\circ{dollar}C, 700{dollar}\sp\circ{dollar}C. At each temperature level changes of CH{dollar}\sb4{dollar}/O{dollar}\sb2{dollar} with reaction time were examined and methane conversion and C{dollar}\sb2{dollar} selectivities were recorded.;A three lump kinetic scheme, including C{dollar}\sb2{dollar} and CO{dollar}\sb{lcub}\rm x{rcub}{dollar} lumps, and neglecting C{dollar}\sb2{dollar} over-oxidation was considered. The model, substantiated by statistical analysis, reproduced very well conversions and C{dollar}\sb2{dollar} selectivities under single oxygen injection as well as multiple oxygen injections.;Finally, a process flowsheet for a continuous OCM plant was implemented using an advanced computer simulation package. It was observed that olefin production in an OCM plant provides excess heat eventually available for other processes in a chemical complex.;In summary, the information presented should help considerably the development of future reactors based on OCM staged oxygen feeding. As well this study demonstrates the importance of the Riser Simulator for OCM catalyst performance evaluation and C{dollar}\sb2{dollar} selectivities optimization.



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