Influence of Nanoscale Intimacy and Zeolite Micropore Size on the Performance of Bifunctional Catalysts forn-Heptane Hydroisomerization

Abstract

In this study, Pt nanoparticles on zeolite/γ-Al 2 O 3 composites (50/50 wt) were located either in the zeolite or on the γ-Al 2 O 3 binder, hereby varying the average distance (intimacy) between zeolite acid sites and metal sites from “closest” to “nanoscale”. The catalytic performance of these catalysts was compared to physical mixtures of zeolite and Pt/γ-Al 2 O 3 powders, which provide a “microscale” distance between sites. Several beneficial effects on catalytic activity and selectivity for n -heptane hydroisomerization were observed when Pt nanoparticles are located on the γ-Al 2 O 3 binder in nanoscale proximity with zeolite acid sites, as opposed to Pt nanoparticles located inside zeolite crystals. On ZSM-5-based catalysts, mostly monobranched isomers were produced, and the isomer selectivity of these catalysts was almost unaffected with an intimacy ranging from closest to microscale, which can be attributed to the high diffusional barriers of branched isomers within ZSM-5 micropores. For composite catalysts based on large-pore zeolites (zeolite Beta and zeolite Y), the activity and selectivity benefitted from the nanoscale intimacy with Pt, compared to both the closest and microscale intimacies. Intracrystalline gradients of heptenes as reaction intermediates are likely contributors to differences in activity and selectivity. This paper aims to provide insights into the influence of the metal–acid intimacy in bifunctional catalysts based on zeolites with different framework topologies.

Control and Impact of Metal Loading Heterogeneities at the Nanoscale on the Performance of Pt/Zeolite Y Catalysts for Alkane Hydroconversion

“…In that case, it can be beneficial to have the metal close to the zeolite outer surface, that is the metal on the binder, in order to restrict diffusion limitations of the feedstock and/or the desired products. 6 , 40 , 75 , 92 − 94 This therefore highlights the fact that not the location of Pt for the CPA-prepared samples but rather the nanoscale heterogeneities were accountable for the decreased catalytic performance, especially when decreasing the metal loading, while a more uniform sample with respect to n Pt / n A ratio prepared with PTA had a significantly better performance. This is, to the best of our knowledge, the first study that links nanoscale crystal-based heterogeneities to the performance of bifunctional catalysts for n -alkane hydroconversion.…”

Application of Chemometrics Into Removal of Dyes by NaX Nanozeolites: Simultaneous Model

“…Assuming that the errors are normally distributed and independent of each other, residual probability diagrams (Figs 4a and 4b) are an important diagnostic tool to identify and explain systematic deviations. Also, the residual probability graph also shows that the variance of the error is homogeneous [27]. In this diagram, the closer the points are to the line, the less error there is.…”

“…As the particle size decreases, the ratio of the number of outer atoms to the material increases rapidly, resulting in an increase in the outer surface area and significant surface activity [26,27]. Nowadays, the use of zeolites as adsorbents in the adsorption process has received much attention.…”

Application of Taguchi method and response surface methodology into the removal of malachite green and auramine-O by NaX nanozeolites

“…In synthetic zeolites, there are fundamental changes in the properties of these materials as the particle size is reduced from micrometers to nanometers, which is very effective on the function of zeolites in catalytic applications and separation. As the particle size decreases, the ratio of the number of outer atoms to the material increases rapidly, resulting in an increase in the outer surface area and significant surface activity 27 , 28 . Nowadays, the use of zeolites as adsorbents in the adsorption process has received much attention.…”