English
 
User Manual Privacy Policy Disclaimer Contact us
  Advanced SearchBrowse

Item

ITEM ACTIONSEXPORT

Released

Thesis

In-situ Hydrocracking of Fischer-Tropsch Hydrocarbons: How α-Olefins Influence the Final Product Distribution

MPS-Authors
/persons/resource/persons146595

Duyckaerts,  Nicolas
Research Department Schüth, Max-Planck-Institut für Kohlenforschung, Max Planck Society;

External Ressource
No external resources are shared
Fulltext (public)
There are no public fulltexts stored in PuRe
Supplementary Material (public)
There is no public supplementary material available
Citation

Duyckaerts, N. (2017). In-situ Hydrocracking of Fischer-Tropsch Hydrocarbons: How α-Olefins Influence the Final Product Distribution. PhD Thesis, Ruhr-Universität Bochum, Bochum.


Cite as: http://hdl.handle.net/21.11116/0000-0001-1641-D
Abstract
The single-step production of wax-free liquid hydrocarbons from syngas (H2+CO) via integration of Fischer-Trospch (FT) and hydrocracking catalysts represents an attractive approach towards process intensification in compact gas-to-liquid technologies. Despite current, intensive efforts on the development of hybrid (multifunctional) catalysts to this end, not much is known about the reactivity of different FT primary products on hydrocracking catalysts under syngas. Using model compounds, the individual and collective reactivities of n-paraffin and α-olefin Fischer-Tropsch primary products were systematically studied on a Pt/nano-H-ZSM-5 hydrocracking catalyst under H2 (standard hydrocracking) and syngas (in-situ hydroprocessing) atmospheres. Under H2, both reactants show indistinguishable reactivity as rapid olefin hydrogenation precedes hydrocracking. Under syngas, however, inhibition of (de)hydrogenation functionalities by CO poisoning of metal sites leads to a notable divergence of the reaction pathways for n-paraffins and α-olefins. Under these conditions, α-olefins showed enhanced reactivity, as an initial dehydrogenative activation step is not required, and contributed to moderate secondary cracking, likely via enhanced competitive adsorption on the acid sites. These findings emphasize the key role of not only the chain-length distribution, but also the olefinic content of the FT primary hydrocarbons for the ultimate product distribution. These observations were the base for the development of a Co/Al2O3 FT catalyst with enhanced pore transport to maximize olefin production with high FT mass-activity. A unique hierarchically organized porosity enables its tandem integration with a Pt/ZSM-5 zeolitic hydrotreating catalyst in a spatially distant fashion ‒ permitting a catalyst-specific temperature adjustment ‒ albeit resembling the case of close active site proximity ‒ by mitigating secondary reactions of primary FT α-olefin products. This approach enables the sought conciliation of in situ de-waxing with a minimum production of gas hydrocarbons (18 wt%) and a ca. two-fold higher (50 wt%) selectivity to middle-distillates compared to tandem pairs based on benchmark mesoporous FT catalysts. An overall 80% selectivity to liquid hydrocarbons from syngas is attained in one step, attesting for the potential of this strategy to increase the carbon efficiency in intensified gas-to-liquid technologies.