Effect of zeolite pore structure on the diffusion and catalytic behaviors in the transalkylation of toluene with 1,2,4-trimethylbenzene

Li, Yanchun; Wang, Hao; Dong, Mei; Qin, Zhangfeng; Wang, Jianguo; Fan, Weibin

doi:10.1039/c5ra09236a

Cited by 27 publications

(18 citation statements)

References 49 publications

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“…The Py-IR of all the zeolites at different temperatures in the region of 1350–1600 cm −1 (Figure S3) with the profiles at 250 °C (Figure 2b) were assessed. Two main characteristic bands of pyridine adsorbed on BAS (1540 cm −1 ) and LAS (1450 cm −1 ) were observed [27,28,29]. The amounts of BAS and LAS (Table 1) and their distribution (Figure 2a,b) differ distinctly from the WAS and MAS of the NH 3 -TPD characterization, especially for SUZ-4, MOR, and SAPO-34.…”

Section: Resultsmentioning

confidence: 99%

The Synergistic Effect of Acidic Properties and Channel Systems of Zeolites on the Synthesis of Polyoxymethylene Dimethyl Ethers from Dimethoxymethane and Trioxymethylene

Wang

et al. 2019

Nanomaterials

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A series of zeolites with different topology structures, including SAPO-34, SUZ-4, ZSM-5, USY, MOR, and beta, were used to synthesize polyoxymethylene dimethyl ethers (PODEn) from dimethoxymethane (DMM) and trioxymethylene (TOM). The influence of acidic properties and channel systems were studied by activity evaluation, characterization, and theoretical calculation. The results confirmed that pore mouth diameter larger than a TOM molecule was an essential prerequisite for the synthesis of PODEn over zeolites, and the synergistic effect between medium-strong Brønsted acid sites (Brønsted MAS) and the maximal space of zeolites available determined the catalytic performance of all studied zeolites. DMM and TOM were firstly decomposed into methoxymethoxy groups (MMZ) and monomer CH2O over Brønsted MAS. Subsequently, the steric constraint of the maximum included sphere, with an appropriate size in zeolite channels, can promote the combination of CH2O and MMZ to form transition species ZO(CH2O)nCH3, which reacted with the methyl-end group to form PODEn over Brønsted MAS. Moreover, the reaction temperature showed different effects on the product selectivity and distribution, which also mainly depends on the size of the maximum space available in zeolite channels.

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Section: Resultsmentioning

confidence: 99%

The Synergistic Effect of Acidic Properties and Channel Systems of Zeolites on the Synthesis of Polyoxymethylene Dimethyl Ethers from Dimethoxymethane and Trioxymethylene

Wang

et al. 2019

Nanomaterials

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“…It is well known that the transport and diffusion of reactants and products influences the outcome of the reaction. 22,23 As has been confirmed by the adsorption performance, the introduction of mesopores dramatically improved the adsorption and diffusion of 1,3,5-TMB molecules within the hierarchical EU-1 zeolites. The improved activity of hierarchical EU-1 zeolites in the transformation of 1,3,5-TMB is largely contributed to the enhanced diffusion of the reactant molecules and the improved accessibility of active sites by mesopores.…”

Section: 35-tmb Adsorption and Catalytic Transformationmentioning

confidence: 70%

Probing the pore structure of hierarchical EU-1 zeolites by adsorption of large molecules and through catalytic reaction

Guo

Hao

et al. 2020

Journal of Chemical Research

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The adsorption of toluene and 1,3,5-trimethylbenzene and the catalytic transformation of 1,3,5-trimethylbenzene are applied as probing approaches to characterize the pore system of hierarchical EU-1 zeolites prepared using organofunctionalized fumed silica as the silicon source. The adsorption and diffusion of toluene and 1,3,5-trimethylbenzene are significantly improved in the hierarchical EU-1 zeolites compared with the conventional microporous EU-1 zeolite. The adsorption kinetics of toluene and 1,3,5-trimethylbenzene suggested that introducing mesopores significantly increases the rate of adsorption and improved the diffusion of large molecules. In the catalytic transformation of 1,3,5-trimethylbenzene, the conversion of 1,3,5-trimethylbenzene on the hierarchical EU-1 zeolites is doubled compared with the conventional microporous EU-1 zeolite, due to the improved diffusion of bulky molecules and enhanced accessibility of active sites in the hierarchical EU-1 structure. Although isomerization is the main reaction, differences are observed in the product ratios of isomerization to disproportionation between the hierarchical EU-1 zeolites and the microporous counterpart with different times on stream. The transformation of 1,3,5-trimethylbenzene over the hierarchical EU-1 zeolites has a higher isomerization to disproportionation ratio than that over the microporous EU-1 zeolite; this is due to the increased mesoporosity.

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“…The neutral reactants and reaction products, like toluene, 1,2,4‐trimethylbenzene (1,2,4‐TMB) and xylene have an absorption band at around 40000 cm −1 (250 nm), and only the tail of this absorption band can be distinguished in the UV‐vis DR spectra. During the reaction, the reactants form charged alkylated aromatics, which are reaction intermediates, that have an absorption band around 28000 cm −1 (350 nm) [24,43,44] . The more conjugated the organic molecules become, the lower the absorption wavenumber.…”

Section: Resultsmentioning

confidence: 99%

High‐Pressure Operando UV‐Vis Micro‐Spectroscopy of Coke Formation in Zeolite‐based Catalyst Extrudates during the Transalkylation of Aromatics

Verkleij

Whiting

Esclapez³

et al. 2020

ChemCatChem

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The performance of zeolite‐based catalyst extrudates can be largely influenced by the choice of binder material. To investigate these binder effects in zeolite‐based catalyst extrudates in more detail, high spatiotemporal resolution techniques need to be further developed and employed. In this work, we present a new methodology to investigate binder effects in catalyst extrudates at different reaction pressures using operando UV‐vis diffuse reflectance (DR) micro‐spectroscopy coupled with on‐line gas chromatography. We have studied mm‐sized zeolite H‐ZSM‐5‐containing extrudates with either Al2O3 or SiO2 binder material, during the transalkylation of toluene with 1,2,4‐trimethylbenzene at 450 °C and at a pressure of either 1 or 5 bar. Using this technique, it was revealed that the binder material significantly influenced catalyst deactivation at different reaction pressures. By subsequent mapping of the cross sections of the cylindrical catalyst extrudates using UV‐vis micro‐spectroscopy, it was shown that the SiO2‐bound extrudate formed poly‐aromatic coke molecules homogeneously throughout the entire extrudate, whereas for the Al2O3‐bound extrudate a coke ring formed that moved inwards with increasing reaction time. Notably, the developed methodology is not limited to the transalkylation reaction, and can also be used to gain more insight into binder effects during a variety of important catalytic reactions.

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Effect of zeolite pore structure on the diffusion and catalytic behaviors in the transalkylation of toluene with 1,2,4-trimethylbenzene

Cited by 27 publications

References 49 publications

The Synergistic Effect of Acidic Properties and Channel Systems of Zeolites on the Synthesis of Polyoxymethylene Dimethyl Ethers from Dimethoxymethane and Trioxymethylene

The Synergistic Effect of Acidic Properties and Channel Systems of Zeolites on the Synthesis of Polyoxymethylene Dimethyl Ethers from Dimethoxymethane and Trioxymethylene

Probing the pore structure of hierarchical EU-1 zeolites by adsorption of large molecules and through catalytic reaction

High‐Pressure Operando UV‐Vis Micro‐Spectroscopy of Coke Formation in Zeolite‐based Catalyst Extrudates during the Transalkylation of Aromatics

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