Abstract
The goal of the research described in this thesis was to study the amount of noble metals
required in bifunctional catalysts for hydroconversion by tuning the nanoparticle
location, without compromising the catalytic performance. The catalysts that were
studied each contained three main components: (noble) metal (oxide) nanoparticles,
zeolite or zeotype material, and a binder.
In Chapter 2 a new tool for controlling the metal nanoparticle location in Pd/zeolite
and Pd/zeotype catalysts is described. We show that performing a direct reduction
(DR) on ammonium palladate exchanged zeolites/zeotypes results in enrichment
of Pd on the outer surface of the solid acid crystallites, whereas slow calcination
followed by reduction (CR) resulted in more Pd nanoparticles being confined inside
the zeotype crystallites.
The focus in Chapter 3 is on the minimum amount of platinum required as function
of Pt nanoparticle location. Two sets of catalysts were prepared: one set was
based on mordenite and the other one on ZSM-22. In the set with mordenite the
Pt nanoparticles were either inside the mordenite crystallites or on alumina binder.
The ZSM-22 set had the Pt nanoparticles either on the ZSM-22 crystallites or on
the alumina binder. Pt weight loadings of 0.005 to 0.5 wt% were used. At loadings
of 0.01 wt% catalysts with Pt on alumina binder were much less active. Extensive
characterization revealed that this was a result of strong metal-support interaction of
the Pt clusters with alumina.
Since the lower catalytic performance of Pt-on-alumina with ≤ 0.01 wt% Pt loadings
in Chapter 3 was a result of γ-alumina lacking chemical inertness, we explored the
replacement of this binder by silica in Chapter 4. Catalysts with 0.005 to 0.5 wt% Pt
on ZSM-22 or on silica were prepared and characterized. These catalysts were then
applied in the hydroconversion of n-heptane. Moreover, for the first time the effect
of the low loadings on the catalytic performance during n-hexadecane was assessed.
Diminishing noble metal utilization could also mean replacement with earth abundant
metals. Chapter 5 is dedicated to an exploration of nickel based bifunctional
catalysts for hydroconversion. We show that Ni based catalysts typically display
high hydrogenolysis activity to produce mainly methane. However, the combination
of the use of n-alkanes with higher molecular weight (e.g. n-hexadecane) and
emplacing Ni (oxide) nanoparticles at the right place could reduce hydrogenolysis
activity and improve i-hexadecane selectivity.
Lastly, Chapter 6 provides a summary & outlook and ‘een Nederlandse samenvatting’
(Dutch summary).
Original language | English |
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Qualification | Doctor of Philosophy |
Awarding Institution |
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Supervisors/Advisors |
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Award date | 1 May 2024 |
Place of Publication | Utrecht |
Publisher | |
Print ISBNs | 978-94-6483-917-3 |
DOIs | |
Publication status | Published - 1 May 2024 |
Keywords
- catalysts
- bifunctional catalysts
- hydroconversion
- fuel production
- hydrocarbon conversion
- zeolites
- zeotypes
- metal nanoparticle location
- noble metals
- materials transition