Reaction kinetic studies of propane conversion to aromatics were conducted on an HZSM-5 zeolite at a pressure of 1 atm, temperatures in the range 793-823 K, and different space times (0-12 gcath/mol). The rates of production of methane, ethane, ethene, propene, propane, butane, butene, benzene, toluene, and xylene are reported. A kinetic model has been postulated that considers surface species as neutral alkoxides, reactions of these alkoxide species by carbenium ion-like transition states, and alkane activation by carbonium ion-like transition states. The associated elementary steps, categorized within the reaction types adsorption, desorption, unimolecular protolytic cracking and dehydrogenation, β-scission, oligomerization, hydride transfer, alkylation, dealkylation, and cyclization, were parsed into reaction families based on an equal reactivity assumption. A total of 311 reaction steps were grouped into 37 reaction families, and the number of unknown parameters was reduced to 25 using adsorption parameters for n-alkanes and relative rates for β-scission and hydride transfer from the literature. It is proposed that this kinetic model describes the reaction behavior over an HZSM-5 catalyst in terms of relevant rate and equilibrium constants and activation energies.
Bibliographical noteFunding Information:
The authors thank Yogesh V. Joshi, Gowri Krishnamurthy, Kendall T. Thomson and Thomas F. Degnan Jr. for valuable discussions. Financial support for this work was provided by the Department of Energy, Office of Basic Energy Sciences, through Catalysis Science grant DE-FG02-03ER15466. The authors are grateful to ExxonMobil Refining and Supply for supplying the HZSM-5 catalyst used in this study.
- Elementary steps
- Kinetic modeling
- Propane aromatization