Catalytic Light Hydrocarbon Upgrading under Methane Environment
Date
2017-12
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Abstract
The catalytic light hydrocarbon upgrading is explored under methane environment over metal modified zeolites. This novel process not only replaces naturally unavailable hydrogen with methane in the upgrading process, but also converts methane into value added products such as fuels and aromatic chemicals. The feasibility of upgrading biomass by directly using cheap natural gas on Ag/HZSM-5 catalyst at atmospheric pressure is demonstrated, resulting in increased H/C atomic ratio and product yield, which might be a promising alternative approach to conventional hydrotreating under high pressure in which expensive and naturally unavailable hydrogen is heavily engaged. The proposed process is further explored when olefins are the light hydrocarbon feedstocks and upgraded under methane environment. 1-Decene is used as the model compound of heavy oil cracking distillates and reacted with methane over Ag-Ga/HZSM-5. As a consequence of methane participation, the quality of liquid product is improved in terms of higher H/C atomic ratio, higher heating value and lower bromine number compared with its N2 counterpart. The study on the reaction intermediates, where olefins are converted to naphthenes under methane environment over Ir and Pd modified ZSM-5 catalysts, displays that the allylic site might be a key site in the intermediate formation and closely related to terminal silanol hydroxyl groups. The co-aromatization of methane and olefins is also investigated using Ag-Ga/HZSM-5 catalyst and verified using isotope labelling and GC-MS analysis as well as monitoring the reaction heat effect. The co-aromatization reaction between olefins and methane is further investigated by isotopic labelling method and evidenced by the escalated exothermic feature. The role of the catalytic sites located in the inner pores and external surface are investigated using olefin feedstocks with different sizes and zeolite support with different pore sizes. The concentration of these catalytic sites are manipulated by blocking the inner pore and covering the external surface to directly observe their roles in co-aromatization of methane and olefins. The co-aromatization of paraffin and methane is also explored using Zn/HZSM-5 catalysts, where the reaction pathway of methane participation is closely related to the Zn redistribution from the inner pores to the external surface during the reaction.
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Keywords
Methane activation, Heterogeneous catalysis, Petroleum upgrading, Aromatization, ZSM-5, Post-synthetic treatment, Isotopic labeling
Citation
He, P. (2017). Catalytic Light Hydrocarbon Upgrading under Methane Environment (Doctoral thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca.