Liquid Industrial Non‐Aromatics Adsorptive Separations

Sohn, Stephen

doi:10.1002/9783527629565.ch8

Cited by 5 publications

(3 citation statements)

References 8 publications

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“…This process can occur through both mono- and bimolecular mechanisms. , The monomolecular mechanism, involving the interaction of an alkane C–C or C–H bond with a Brønsted proton, dominates at conditions of low surface coverage (low pressure and conversion), while the bimolecular mechanism, involving hydride transfer as well as oligomerization and beta scission of alkene intermediates, , primarily occurs under industrial conditions (high pressure, conversion, and surface coverage). Because of its simplicity and well-defined kinetics, the monomolecular alkane cracking, and also dehydrogenation, have been the subject of a number of studies aimed at elucidating the influence of zeolite structure on cracking kinetics. − …”

Section: Introductionmentioning

confidence: 99%

Atomistic Investigations of the Effects of Si/Al Ratio and Al Distribution on the Adsorption Selectivity of n-Alkanes in Brønsted-Acid Zeolites

et al. 2018

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The adsorption of n-alkanes onto Brønsted-acid sites is a key step in the catalytic cracking of alkanes. Employing configurational-bias Monte Carlo simulations, we have investigated how the ratio of equilibrium adsorption constants for central C−C bonds relative to terminal bonds of n-alkanes (i.e., the adsorption selectivity ratio) in Brønsted-acid zeolites is influenced by the Si/Al ratio and the Al distribution. A new computational approach was implemented, and the developed force field was validated by a comprehensive comparison between simulation results and experimental data for a number of Brønsted-acid zeolites. While the adsorption selectivity seems to be relatively insensitive to the Si/Al ratio, our results reveal that the Al distribution plays a crucial role in determining the adsorption selectivity. Changes in the Al distribution result in a change of as much as 2-fold in the adsorption selectivity ratio for n-hexane. The selectivity generally shows larger variations with respect to Al distribution in zeolites with a larger Si/Al ratio. The two factors identified by this work that substantially influence the selectivity ratio are the siting of Al atoms among T-sites and their spatial proximity, and an atomic-level understanding of each of these effects was achieved. The siting of Al atoms at more or less selective T-sites significantly influences the overall selectivity ratio, and Al atoms in close proximity can synergistically enhance the adsorption of central C−C bonds, leading to a higher selectivity ratio relative to isolated Al atoms. We anticipate that these results will have important implications for future large-scale computational screenings and the development of advanced synthesis approaches to target certain Al distributions in zeolites.

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Section: Introductionmentioning

confidence: 99%

Atomistic Investigations of the Effects of Si/Al Ratio and Al Distribution on the Adsorption Selectivity of n-Alkanes in Brønsted-Acid Zeolites

et al. 2018

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“…Zeolites are microporous aluminosilicates whose shape-selective properties are exploited extensively for the catalytic cracking of hydrocarbons. − The apparent kinetics of cracking are affected by the thermodynamics and kinetics of hydrocarbon adsorption, which are in turn affected by zeolite topology. For these reasons, many previous studies have been aimed at elucidating the effects of topology on adsorption behavior. − Transformations of hydrocarbons are often carried out at high pressures and surface coverages and are limited by diffusion. However, Monte Carlo simulations of equilibrium adsorption, both at high coverages and even in the Henry region, have been successfully used to rationalize observed selectivities for processes including hydrocracking and dewaxing. − Since the Henry region also corresponds to conditions approaching zero coverage, adsorption behavior in this region reflects the intrinsic effects of the zeolite topology.…”

Section: Introductionmentioning

confidence: 99%

“…For these reasons, many previous studies have been aimed at elucidating the effects of topology on adsorption behavior. [6][7][8][9][10][11][12] Transformations of hydrocarbons are often carried out at high pressures and surface coverages and are limited by diffusion.…”

Section: Introductionmentioning

confidence: 99%

Effects of Pore and Cage Topology on the Thermodynamics of n-Alkane Adsorption at Brønsted Protons in Zeolites at High Temperature

et al. 2017

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Monte Carlo simulations are used to systematically investigate the effects of structural topology on the thermodynamics of n-alkanes adsorbed at Brønsted protons in zeolites having one-dimensional channel systems. In zeolites without cages, the enthalpy and entropy of adsorption (∆H ads-H+ and ∆S ads-H+ ) at fixed pore-limiting diameter (PLD) generally increase (become less negative) as the ratio of the minimum to maximum channel diameter decreases, and are lowest when this ratio equals 1 (corresponding to approximately circular cross-sections). The effect of a change in diameter ratio on the free energy of adsorption (∆A ads-H+ ) is weak because the changes in ∆H ads-H+ and T∆S ads-H+ largely cancel. The addition of cages having a largestcavity diameter (LCD) greater than the PLD increases both ∆H ads-H+ and ∆S ads-H+ . Replacing channels with cages of the same diameter does not change ∆S ads-H+ significantly when the PLD is similar to the alkane length, but decreases both ∆H ads-H+ and ∆A ads-H+ because of the greater surface area of cages relative to channels. The selectivity to adsorption via a central C-C bond vs. a terminal bond when cages are absent is smallest for PLDs near the alkane length, and when cages are present, is even lower when the LCD exceeds the alkane length. This effect is attributed to more rotation of the alkane in cages vs. channels. The results show that ∆A ads-H+ at 773 K can be tuned by manipulating a characteristic dimension (LCD, PLD) and topology (e.g., adding cages) simultaneously, in order to circumvent the compensating changes in T∆S ads-H+ and ∆H ads-H+ that occur upon changing only one structural parameter.3

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The Honeywell UOP Parex ^TM Process: Fifty Years of Growth for the Petrochemical Industry (Case Study)

Whitchurch¹,

Johnson²

2023

Industrial Arene Chemistry

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Liquid Industrial Non‐Aromatics Adsorptive Separations

Cited by 5 publications

References 8 publications

Atomistic Investigations of the Effects of Si/Al Ratio and Al Distribution on the Adsorption Selectivity of n-Alkanes in Brønsted-Acid Zeolites

Atomistic Investigations of the Effects of Si/Al Ratio and Al Distribution on the Adsorption Selectivity of n-Alkanes in Brønsted-Acid Zeolites

Effects of Pore and Cage Topology on the Thermodynamics of n-Alkane Adsorption at Brønsted Protons in Zeolites at High Temperature

The Honeywell UOP Parex ^TM Process: Fifty Years of Growth for the Petrochemical Industry (Case Study)

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Liquid Industrial Non‐Aromatics Adsorptive Separations

Cited by 5 publications

References 8 publications

Atomistic Investigations of the Effects of Si/Al Ratio and Al Distribution on the Adsorption Selectivity of n-Alkanes in Brønsted-Acid Zeolites

Atomistic Investigations of the Effects of Si/Al Ratio and Al Distribution on the Adsorption Selectivity of n-Alkanes in Brønsted-Acid Zeolites

Effects of Pore and Cage Topology on the Thermodynamics of n-Alkane Adsorption at Brønsted Protons in Zeolites at High Temperature

The Honeywell UOP Parex TM Process: Fifty Years of Growth for the Petrochemical Industry (Case Study)

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The Honeywell UOP Parex ^TM Process: Fifty Years of Growth for the Petrochemical Industry (Case Study)