Isomerization and β-scission reactions of alkanes on bifunctional metal-acid catalysts: Consequences of confinement and diffusional constraints on reactivity and selectivity

Manipulating the mesostructure of silicoaluminophosphate SAPO-11 via tumbling-assisted, oriented assembly crystallization: a pathway to enhance selectivity in hydroisomerization

“…The hydroisomerization of n-heptane over Pt/SAPO-11 catalyst observes a hyperboric type kinetic equation at low conversion levels (which were manipulated to be less than 10%), as shown by Noh et al for Pt supported on zeolites and by some of us. 90,91 For hydroisomerization of homologues, such as hexane 92 and octane, 37 the same kinetic law applies. When H 2 /C 7 ratio is high (herein kept to 26), by approximation, the kinetic can be regarded as a pseudo-first order reaction.…”

“…29,37 Sequentially, the monobranched iso-heptenes can be further converted into dibranched iso-heptenes on the B acid sites, which is known to be a kinetically fast process. 90,91 Finally, the MBs and DBs are generated after hydrogenation on Pt centres of the iso-heptenes to the corresponding iso-heptanes (Scheme 3). Cracking of DBs is responsible for the formation of lighter alkanes, but produces far less cracking products, because the process has a much higher (e.g., 116 vs. 156 kJ mol −1 for SAPO-11-C) energetic barrier than isomerization in the intrinsic reaction-controlled regime.…”

Influence of intimacy for metal-mesoporous solid acids catalysts forn-alkanes hydro-conversion

“…[30][31][32][33] Computational studies of the free energy of the transition state in various zeolites and mesoporous Al-MCM-41 showed that in the case of mesoporous materials, the weaker confinement leads to less reactive acid sites and that the facile molecular diffusion of n-heptane in the pores results in a minimized intracrystalline gradient of iso-alkenes. 34 In order to gain further insight into the intimacy effect and its relation with diffusion limitations, we conducted a study on the influence of the metal-acid sites distance on both a model, structured mesoporous acidic model support, Al-SBA-15 and an amorphous commercial support, Siralox40hpv (Sasol). Pt deposition was performed in a controlled manner either on a γ-Al 2 O 3 binder or on the solid acid.…”

Control of the Reaction Mechanism of Alkylaromatics Transalkylation by Means of Molecular Confinement Effects Associated to Zeolite Channel Architecture

“…[3][4][5][6] Thus, the zeolite topology, the size and dimensionality of the channel systems, the presence or absence of intersections and/or cavities, combined with the confinement effects can determine the selectivity to the desired products by controlling the extension of competing parallel or consecutive reactions. [7][8][9][10][11] The complexity of the alkylaromatics conversion processes has led to numerous studies regarding the possible reaction mechanisms within the microporous structure of medium, 12-25 large 14,15,19,[26][27][28][29][30][31][32] and multipore 33,34 zeolites. Focusing on the transalkylation of alkylbenzenes, it can either proceed by intermolecular alkyltransfer involving dealkylation-alkylation steps with surface alkoxy species as reaction intermediates, or through formation of bulkier diaryl intermediates 19 (see Scheme 1).…”