Bifunctional Intimacy and its Interplay with Metal‐Acid Balance in Shaped Hydroisomerization Catalysts

Abstract

The combined impact of platinum location and metal-acid balance on the catalytic performances of HUSY zeolite aluminashaped bifunctional catalysts was evaluated in n-hexadecane hydroconversion reaction. For well-balanced catalysts, the deposition of Pt in the alumina resulted in lower isomerization selectivity as compared to when platinum was located in the zeolite. In the latter case, the maximal distance between Pt and acid sites was found to be in the nanometric scale (high intimacy) whereas in the former it was in the micrometric scale (low intimacy), particularly due to the presence of large clusters of HUSY zeolite. Nevertheless, whenever proper balance between functions was not ensured in high-intimacy catalysts, the low-intimacy and well-balanced catalysts were shown to perform better. The requirement for nanometric metal-acid sites intimacy must be hence combined with an adequate metal-acid balance to achieve optimal catalytic performance.

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

“…For more details on the n -C 16 hydroconversion mechanism, we refer the reader to literature. 3 , 5 , 47 , 87 − 89 …”

Interplay of Metal-Acid Balance and Methylcyclohexane Admixture Effect on n-Octane Hydroconversion over Pt/HUSY

“…Both catalysts were experimentally found to be poorly balanced in pure n -octane hydrocracking (Figure a). For a lower metal site concentration, intermediate (cyclo)­alkenes are more prone to undergoing consecutive acid catalyzed reactions (also see Figure ), ,− with a concomitant impact on the product distribution.…”

“…A sufficiently high concentration of active metal sites compared to the Brønsted acid sites ensures that (de)hydrogenation reactions are in quasi-equilibrium (good balance of metal and acid sites). Moreover, apart from the ratio, also the distance between metal and Brønsted acid sites should also be sufficiently small such that transfer of intermediate (cyclo)alkenes does not become limiting 10,[13][14][15][16] .…”

“…A sufficiently high concentration of active metal sites compared to the Brønsted acid sites ensures that (de)­hydrogenation reactions are in quasi-equilibrium (good balance of metal and acid sites). Moreover, apart from the ratio, also the distance between metal and Brønsted acid sites should also be sufficiently small such that transfer of intermediate (cyclo)­alkenes does not become limiting. ,− Recent work from the group of de Jong demonstrated this convincingly by depositing the metal either on the binder or the zeolite support of the zeolite , (good intimacy of metal and Brønsted acid sites). As a consequence of the optimal balance between metal and acid sites, product yields only depend on the kinetics of acid-catalyzed elementary reactions.…”

Ethylene oligomerization on nickel catalysts on a solid acid support: From New mechanistic insights to tunable bifunctionality

“…While Chen et al is one of the only studies currently published that benchmarked Ni-acid site distance, the dependence of metal-acid site distance on efficiency is a focus in the field of metal/acid hydrocracking. The efficiency of bifunctional metal-acid catalysts for hydrocracking has shown that mass transfer and site distance, which should be neither too close nor too far, can play an influential role [92][93][94][95][96][97][98][99]. Whether or not the significance of metal-acid distance also applies to nickel-acid oligomerization catalysts still remains to be addressed.…”