The effect of modification with boron on the catalytic activity and selectivity of HZSM-5 I. Impregnation with boric acid

Sayed, Moein B.; Védrine, J.C.

doi:10.1016/0021-9517(86)90227-7

Cited by 54 publications

(10 citation statements)

References 14 publications

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“…According to reports in the literature, boron shows somef lexibility to change coordination,a si nfluenced by thermalt reatments, the presence of certainm olecules, or type of compensating cations. [40][41][42][43][44][45][46][47][48] As an example, four-coordinate framework boron, under ambient conditions, is described to change to three-coordinate upon dehydration, [48] in line with our results. Notwithstanding that thermalt reatments may induce insertion of boron into the framework, [43,44,49] available reports do not elucidate the extraand/or framework nature of boron species in BCsX catalysts for styrene/ethylbenzene production.…”

Section: Spectroscopic Analysis Of Cesium and Boron Speciessupporting

confidence: 82%

Elucidating the Distribution and Speciation of Boron and Cesium in BCsX Zeolite Catalysts for Styrene Production

et al. 2017

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An improved understanding of the nature and distribution of boron and cesium species in BCsX zeolites is a prerequisite to guide future developments in the environmentally attractive, yet challenging, production of styrene through the side-chain alkylation of toluene with methanol. Herein, standard characterization and catalytic tests are complemented by integrated visualization through time-of-flight secondary-ion mass spectrometry and energy-dispersive X-ray spectroscopy and detailed assessment by Cs and B NMR spectroscopy, to correlate the properties and performance during successive ion-exchange and impregnation steps in the preparation of both powders and millimeter-sized granules. The results highlight a significant impact of catalyst scaleup on the effective introduction of boron species, which originates chemical heterogeneity that is linked to selectivity losses. They also illustrate the complexity of elucidating the role of this promotor, which interacts with cesium cations and exhibits different coordination states and chemical environments, depending on the pretreatment.

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Section: Spectroscopic Analysis Of Cesium and Boron Speciessupporting

confidence: 82%

Elucidating the Distribution and Speciation of Boron and Cesium in BCsX Zeolite Catalysts for Styrene Production

et al. 2017

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“…For BHZSM-5, B atoms have not brought much infl uence on it. For B I ZSM-5, after impregnation, the condensation reaction has occurred during calcinations between boric acid and zeolite acid sites to connect the B atoms with zeolite framework 14 . The spectrum of BZSM-5 shows all these bands clearly, indicating that B atoms of BZSM-5 have essentially been incorporated into the framework in combination with Si.…”

Section: Catalytic Evaluationmentioning

confidence: 99%

“…The weak acidity can catalyze the reaction such as alklation and methylation, which plays a vital role in olefi n formation 12 . Borosilicates with high weak acidity and low strong acidy were discussed by several researchers in different reactions 13, 14,15 . In MTG reaction, Unneberg et al 13 found that pure B-MFI expressed poor methanol conversion, but Yang et al 15 found that the B-Al-ZSM-5 catalyst with a 2.0 Al/B ratio showed a positive reaction capability in MTP reaction.…”

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confidence: 99%

Effect of boron on ZSM-5 catalyst for methanol to propylene conversion

Zhang

et al. 2013

Polish Journal of Chemical Technology

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B-ZSM-5 catalysts were prepared by various modifi cation methods with boric acid, including ion-exchange, impregnation and direct synthesis. The catalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), NH 3 -Temperature Programmed Desorption (NH 3 -TPD), N 2 adsorption-desorption, Fourier Transform Infrared spectrometry (FT-IR), 27 Al and 11 B MAS NMR spectra. The results revealed that the weak acidity of catalysts was signifi cantly increased by modifi cation. The catalytic activity was measured in a fi xed bed at 460 o C for methanol to propylene (MTP) reaction. The results of MTP reaction showed a great increment of the propylene selectivity for the boron modifi ed samples, especially for the directly synthesized B-ZSM-5 which also displayed high activity and selectivity towards C 2 = -C 4 = olefi ns. It was found that the remarkable selectivity strongly depended on the intensity of weak acidity.

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“…The composition of this initial xylene distribution is not known, although different approaches have been proposed assuming an electrophilic (Olson and Haag, 1984) or nucleophilic nature (Sayed and VCdrine, 1986) of the reaction intermediates. -Toluene diffuses through the zeolite channels and reacts on the acid sites giving benzene and a xylene mixture.…”

mentioning

confidence: 99%

“…-Toluene diffuses through the zeolite channels and reacts on the acid sites giving benzene and a xylene mixture. The composition of this initial xylene distribution is not known, although different approaches have been proposed assuming an electrophilic (Olson and Haag, 1984) or nucleophilic nature (Sayed and VCdrine, 1986) of the reaction intermediates.…”

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confidence: 99%

Roles of ZSM‐5 modifier agents in selective toluene disproportionation

1993

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Selective toluene disproportionation has been studied over ZSM-5 zeolites modified with P, Si and Cs compounds. For the P and Si modified samples, p-xylene proportion in the primary product was 100% due to the diffusional control on the internal xylene isomerization. The number and strength of the acid sites are reduced by the three modifier agents but a relationship between para-selectivity and the decrease of the acid strength has not been observed. The most paraselective samples have been those modified with Si which has been related to the deposition of this agent on the external surface of the zeolite crystals avoiding the primary product isomerization... ._ On a etudiC la dismutation du tolubne sur des zeolites modifites avec des composes de P, de Si et de Cs. Pour les tchantillons de P et de Si modifies, la proportion de p-xylkne dans le produit de base est de 100% du fait du contrcile diffusionnel sur l'isornerisation interne du xylbne. Le nornbre et la force des sites acides sont rCduits par les trois agents modificateurs, rnais aucune relation n'a pu &re observ6e entre la parasClectivit6 et la baisse de la force acide. Les echantillons les plus parastlectifs sont ceux qui sont modifies avec du Si qui a 6tC relit5 au dip& de cet agent sur la surface externe des cristaux de zeolite, Cvitant ainsi l'isomtrisation du produit de base.

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The effect of modification with boron on the catalytic activity and selectivity of HZSM-5 I. Impregnation with boric acid

Cited by 54 publications

References 14 publications

Elucidating the Distribution and Speciation of Boron and Cesium in BCsX Zeolite Catalysts for Styrene Production

Elucidating the Distribution and Speciation of Boron and Cesium in BCsX Zeolite Catalysts for Styrene Production

Effect of boron on ZSM-5 catalyst for methanol to propylene conversion

Roles of ZSM‐5 modifier agents in selective toluene disproportionation

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