Prediction of preferred proton locations in HMFI/benzene complexes by molecular mechanics calculations. Comparison with nmr, structural and calorimetric results

Mentzen, B. F.; Sacerdote-Peronnet, M.

doi:10.1016/0025-5408(94)90159-7

Cited by 28 publications

(39 citation statements)

References 29 publications

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“…The location of the Al atom in the unit cell was reported to be non-random [26] and to depend on the zeolite synthesis conditions [27]. Nevertheless, few other studies specify the T12 site to be a preferred location for the Al atom associated with the Brønsted acid site [28,29]. Moreover, when the Al atom is located at the T12 site, the Brønsted acid site is accessible to molecules located in both the straight and sinusoidal channels and could accommodate larger species.…”

Section: Catalyst Modelmentioning

confidence: 94%

Reaction path analysis for 1-butanol dehydration in H-ZSM-5 zeolite: Ab initio and microkinetic modeling

John

Alexopoulos

Reyniers

et al. 2015

Journal of Catalysis

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Section: Catalyst Modelmentioning

confidence: 94%

Reaction path analysis for 1-butanol dehydration in H-ZSM-5 zeolite: Ab initio and microkinetic modeling

John

Alexopoulos

Reyniers

et al. 2015

Journal of Catalysis

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“…A later computational work by Lonsinger et al found T12 to be the most preferred site in studies on 8-T atom clusters. Since then, many others have studied the problem, several concluding on T12 as the preferred site. − In a recent perspective describing both theoretical and experimental works, Knott et al summarized this, concluding that the T12 site is the most frequently chosen. As T12 is on the intersection between the straight and sinusoidal channels and it is accessible for water attack anti to the Si–OH–Al bond, we selected T12 as our Al site.…”

Section: Computational Studymentioning

confidence: 99%

Understanding the Activation of ZSM-5 by Phosphorus: Localizing Phosphate Groups in the Pores of Phosphate-Stabilized ZSM-5

et al. 2020

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Fluid catalytic cracking (FCC) produces (the feedstock for) a major part of the world’s fuels, as well as chemical building blocks for, for example, polymers, pharmaceuticals, and specialty materials. ZSM-5 is the active ingredient in propylene-selective FCC catalyst systems and is stabilized or activated with phosphorus compounds. Despite this process being one of the largest-scale industrially applied catalytic processes, there is still considerable debate on the mechanism of activation, as well as on the interaction between phosphate and zeolite aluminum species. In this work, we use synchrotron-based powder XRD, neutron diffraction, and subsequent pair distribution function analysis to unequivocally corroborate the activation mechanism of phosphorus-based promotion in FCC catalysis and localize the phosphate groups inside the pore system of P-activated ZSM-5. We find local disorder in the zeolite T–O coordination, which could not be observed with traditional XRD analyses. Furthermore, we support these experimental findings with full periodic quantum-mechanical modeling (QMM) of the highly relevant, but often overlooked, combination of dealumination by hydrolysis (steaming) and phosphatation of the zeolite framework. We thereby show that phosphate can react with partially dislodged aluminum species that remain stable and are still tethered to their original framework position. Finally, by assessing all available literature postulations by the same periodic QMM and comparing them energetically with our obtained results, we can conclude that by accounting for the highly relevant inclusion of steaming prior to phosphatation, the two models resulting from this work rank among the three most relevant remaining models. This combined experimental and theoretical work fundamentally explains the activation and promotion mechanism of one of the world’s most applied chemical processespropylene-selective FCC.

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“…H-ZSM-5 is a three-dimensional medium-pore zeolite with intersecting straight (540 pm × 560 pm) and sinusoidal or zigzag (510 pm × 540 pm) 10-MR channels. The acid site is chosen to be located at the Al12O24 intersecting position, ,, leading to a unit cell composition of Si 95 AlO 192 H (Si/Al = 95). H-ZSM-22 is a one-dimensional medium-pore zeolite with straight channels in the c direction with dimensions 460 pm × 570 pm.…”

Section: Theorymentioning

confidence: 99%

First-Principles Kinetic Study on the Effect of the Zeolite Framework on 1-Butanol Dehydration

et al. 2016

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Understanding the role of zeolite topology in defining its catalytic performance is of prime importance for the development of catalytic processes. Herein, a first-principles-based microkinetic study of 1-butanol dehydration is used to illustrate the effect of different zeolites (i.e., H-FAU, H-ZSM-5, H-ZSM-22, and H-FER) on the dehydration activity and product selectivity. Under identical reaction conditions, microkinetic simulations show significant variation in dehydration rates and butene/ether selectivity profiles within the different zeolites. H-ZSM-5 has the highest catalytic activity, whereas H-FAU and H-FER exhibit a higher butene selectivity. In the large pore H-FAU, the weaker dispersive stabilization of the dimer makes the butene formation by monomolecular direct dehydration via a concerted anti elimination compete with di-n-butyl ether formation. In H-FER, steric constraints due to partial confinement of the protonated di-n-butyl ether in the 8-MR channel decrease its stability, favoring its further decomposition to butene via a concerted syn elimination of butanol. On the other hand, the higher ether selectivity in H-ZSM-5 and H-ZSM-22 is rationalized on the basis of a higher stability for adsorbed ether and a higher activation barrier for ether decomposition. In addition to the effect of the zeolite framework, this study further highlights the pivotal role of the reaction conditions in determining the most abundant reaction intermediate, dominant reaction paths, and underlying reaction mechanisms. In general, for all four zeolites, an increase in reaction temperature and a decrease in butanol feed partial pressure favors direct dehydration of butanol to butene (via butanol monomer). However, a decrease in reaction temperature and increase in butanol feed partial pressure favors dimer-mediated dibutyl ether formation. An increase in conversion favors direct dehydration and dibutyl ether decomposition to butene.

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Prediction of preferred proton locations in HMFI/benzene complexes by molecular mechanics calculations. Comparison with nmr, structural and calorimetric results

Cited by 28 publications

References 29 publications

Reaction path analysis for 1-butanol dehydration in H-ZSM-5 zeolite: Ab initio and microkinetic modeling

Reaction path analysis for 1-butanol dehydration in H-ZSM-5 zeolite: Ab initio and microkinetic modeling

Understanding the Activation of ZSM-5 by Phosphorus: Localizing Phosphate Groups in the Pores of Phosphate-Stabilized ZSM-5

First-Principles Kinetic Study on the Effect of the Zeolite Framework on 1-Butanol Dehydration

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