Influences of zeolite structure on formation and location of coke: A129Xe and13C CP-MAS NMR study

Pradhan, Ajit; Wu, Jinfu; Jong, Sung-Jeng; Chen, Wei‐Hsun; Tsai, Tseng-Chang; Liu, S.B.

doi:10.1016/s0926-860x(97)00065-3

Cited by 37 publications

(29 citation statements)

References 38 publications

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“…As shown in Figure 3, the 129 Xe chemical shift of MOR samples varies with the increasing adsorption quantity of xenon. Similar to the previous studies by Liu et al, 23 two distinct resonance peaks are observed in the 129 Xe NMR spectrum of fresh mordenite; the low-field peak is assigned as Xe adsorbed in 8-ring side pockets, whereas the high-field one is attributed to Xe in 12-ring channels. For the H-MOR sample, the NMR signal of xenon in the 8-ring side pocket appears at 215 ppm, as shown in Figure 3a.…”

Section: ■ Results and Discussionsupporting

confidence: 87%

Role of 12-Ring Channels of Mordenite in DME Carbonylation Investigated by Solid-State NMR

He¹,

Liu²,

Xu³

et al. 2016

J. Phys. Chem. C

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In this work, we have studied the role of the 12-ring channel of mordenite in DME carbonylation. Upon modification with pyridine, the catalytic lifetime of mordenite in DME carbonylation was prolonged dramatically although its activity decreased slightly and the induction period increased. 1H MAS NMR and PFG-NMR results demonstrated that the acid quantity decreased after pyridine was adsorbed, and the self-diffusion coefficient of CH4 decreased with the increase in pyridine quantity in the 12-ring channel. 129Xe NMR results reveal that Xe atoms are preferentially adsorbed in an 8-ring side pocket at low pressure; xenon can enter the 8-ring side pocket at high temperature through the 12-ring channels only. From these results, the function of the 12-ring with respect to the reaction rate is explored and a transfer path of reactants/products is proposed.

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Section: ■ Results and Discussionsupporting

confidence: 87%

Role of 12-Ring Channels of Mordenite in DME Carbonylation Investigated by Solid-State NMR

He¹,

Liu²,

Xu³

et al. 2016

J. Phys. Chem. C

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“…We previously observed that coke precursors of disproportionation, such as diethylbenzene in ethylbenzene disproportionation and di-propylbenzene in cumene disproportionation, can be removed simply by vacuum evaporation [34,35]. As evidenced in Table 1, coke content reduced after nitrogen reactivation, dropping from 12.3% down to 10.1%, indicating the removal of coke precursors.…”

Section: Mechanism Of Reactivation In Hmentioning

confidence: 89%

Reactivation of acidic sites in mordenite used in toluene disproportionation

Tsai

2006

Applied Catalysis A: General

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“…Cavities of about 1.2-1.3 nm are present at the channel intersections. The 3-dimensional framework of a USY zeolite contains wider pore windows (0.74 nm x 0.74 nm) and so-called 'supercages' with dimensions that are similar to the beta cavities [35,36]. As a result, shape selectivity in the formation of bulkier components, if any, will occur on BEA rather than on FAU.…”

Section: Introductionmentioning

confidence: 99%

n-Hexadecane hydrocracking Single-Event MicroKinetics on Pt/H-beta

Vandegehuchte

Thybaut

Martı́nez

et al. 2012

Applied Catalysis A: General

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The Single-Event MicroKinetic (SEMK) model constructed for gas-phase hydroconversion of light n-alkanes on large-pore USY zeolites was applied, for the first time, to the hydrocracking of n-hexadecane on a Pt/H-Beta catalyst. Despite the 12-ringed pore channels, shape selectivity was observed in the formation of ethyl side chains.Additionally, heavy feed molecules such as n-hexadecane lead to physisorption saturation of the catalyst pores by strong Van der Waals interactions of the long alkyl chains with the zeolite framework. Intermolecular interactions and packing efficiencies in the pores induce deviations from typical Henry-regime physisorption characteristics as the physisorption selectivity, which is expected to increase with increasing carbon number, appeared to be independent of the latter. Micropore saturation effects were described by the 'size entropy' which quantifies the difference in standard entropy loss between physisorption in the Henry regime and hindered physisorption on a saturated surface. The size entropy is proportional to the catalyst loading with physisorbed species and the adsorbate carbon number. The addition of a size entropy term in the SEMK model, amounting to 102 J mol -1 K -1 for a hexadecane molecule at full saturation, allowed accurately reproducing the contribution of secondary isomerization and cracking reactions, as quantified by means of a contribution analysis.2

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Influences of zeolite structure on formation and location of coke: A129Xe and13C CP-MAS NMR study

Cited by 37 publications

References 38 publications

Role of 12-Ring Channels of Mordenite in DME Carbonylation Investigated by Solid-State NMR

Role of 12-Ring Channels of Mordenite in DME Carbonylation Investigated by Solid-State NMR

Reactivation of acidic sites in mordenite used in toluene disproportionation

n-Hexadecane hydrocracking Single-Event MicroKinetics on Pt/H-beta

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