Mild hydroisomerization of heavy naphtha on mono- and bi-metallic Pt and Ni catalysts supported on Beta zeolite

• Published in: Catalysis today 2020-09, Vol.355, p.746-756
• Main Authors: Karakoulia, Stamatia A., Heracleous, Eleni, Lappas, Angelos A.
• Format: Article
• Language: English
• Subjects: Beta zeolite; Hydroisomerization; n-Octane; Pt and Ni catalysts; Refinery naphtha
• ISSN: 0920-5861; 1873-4308
• DOI: 10.1016/j.cattod.2019.04.072

[Display omitted] •Ni-Pt/Beta catalysts active in hydroisomerization of heavy paraffins.•Ni generates Lewis acidity and reduces Brönsted acid sites.•Pt addition in Ni-containing catalysts enhances reducibility and iso-selectivity.•Higher degree of branching on the bimetallic Ni-Pt catalyst.•Ni-Pt/Beta increases the RON of heavy naphtha by 13% at mild conditions. Hydroisomerization of long chain paraffins has emerged as a promising process for the valorization of low value fuel cuts, such as heavy naphtha, from crude oil-, coal- and bio-based feedstocks. In this study, the hydroisomerization reaction is investigated on a series of mono- and bi-metallic Pt (0.2 wt%) and/or Ni (10 wt%) catalysts supported on Beta zeolite with SiO2/Al2O3 ratio 75. Catalysts exhibit similar reactivity in the hydroisomerization of n-octane model compound, despite the very different loading and the 40% lower Brönsted acidity of the Ni-containing materials. This suggests that hydrogenation/dehydrogenation is the rate limiting step of the reaction due to very low loading of Pt and the weak dehydrogenating capacity of Ni. The latter also leads to up to 34% lower selectivity to i-C8 for the monometallic Ni catalyst. The addition of Pt in the bimetallic Ni-Pt catalyst, not only restores, but enhances the isomerization selectivity, favoring the production of di-branched to mono-branched isomers. The characterization results show that Pt enhances the reducibility and improves the dispersion of Ni, leading to increased metallic/acid sites ratio. Hydroisomerization tests with refinery naphtha as feed highlight the promising performance of this catalyst, as Ni-Pt/H-Beta increases the octane number of naphtha by 13% at mild temperature and pressure (260 °C, 10 bar), improving significantly the quality of naphtha for gasoline applications.