How defects and crystal morphology control the effects of desilication

Svelle, Stian; Sommer, Linn; Barbera, Katia; Vennestrøm, Peter N. R.; Olsbye, Unni; Lillerud, Karl Petter; Bordiga, Silvia; Pan, Ying-Hsi; Beato, Pablo

doi:10.1016/j.cattod.2010.12.013

Cited by 109 publications

(118 citation statements)

References 79 publications

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“…The longterm increase in the deactivation constant could be due to the presence of defects created by the irreversible hydrolysis of the structure, as shown above by FTIR and NMR, that could accelerate deactivation by adsorption of coke precursors. In fact, a higher deactivation and shorter lifetime was reported in the case of zeolite ZSM-5, in which the creation of internal silanol nests by carbon templating induced higher deactivation in the MTH reaction 48,49 . On the other hand, the short-term decrease in the deactivation constant until the 14 th day of exposure for nano-SAPO-34 could be attributed to the hydrolysis of the Si-O-Al groups at the border of the silicon islands shown before by NMR.…”

Section: Activity and Kinetic Analysismentioning

confidence: 93%

Methanol to olefins: activity and stability of nanosized SAPO-34 molecular sieves and control of selectivity by silicon distribution

Martínez‐Triguero

Concepción

et al. 2013

Phys. Chem. Chem. Phys.

122

110

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Royal Society of ChemistryLi, Z.; Martínez Triguero, LJ.; Concepción Heydorn, P.; Yu, J.; Corma Canós, A. (2013 AbstractNanoSAPO-34 molecular sieve synthesized in microwave environment with 20nm of crystal size showed higher lifetime than SAPO-34 prepared by conventional hydrothermal method in the reaction of methanol to olefins. It has been found that silicon distribution strongly affects lifetime and selectivity. Thus, silicon at the border of the silicon islands gives higher lifetime and lower C2/C3 ratio. This change in activity and selectivity is better explained in terms of different silicon distribution than on preferential diffusion of ethene through the 8MR pores and agrees with transition-state selectivity. The effects of equilibrium of olefins and deactivation by coke were isolated,showing that after full formation of hydrocarbon pool, selectivity is independent of deactivation by coke.

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Section: Activity and Kinetic Analysismentioning

confidence: 93%

Methanol to olefins: activity and stability of nanosized SAPO-34 molecular sieves and control of selectivity by silicon distribution

Martínez‐Triguero

Concepción

et al. 2013

Phys. Chem. Chem. Phys.

122

110

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“…Also, the influence of framework aluminum content for controlled desilication was shown [8]. Therefore, it can be assumed that the low stability of Al atoms in the framework positions in zeolite Beta [23], caused by the presence of high concentration of structural defects [24], can also affect the desilication process and the high amount of EFAL species can be detected. Framework silicon extraction from zeolite Beta (Si/Al = 220) upon treatment with NaOH revealed the extensive mesopore formation of intracrystalline nature, meanwhile the micropore volume and crystallinity of the desilicated materials was severely reduced [19].…”

Section: Introductionmentioning

confidence: 99%

Catalytic cracking performance of alkaline-treated zeolite Beta in the terms of acid sites properties and their accessibility

Tarach

Góra‐Marek

Tekla

et al. 2014

Journal of Catalysis

162

111

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The zeolite Beta is considered as a promising additive for FCC catalyst in diesel oil production. In this article, it is shown that hierarchical zeolite Beta obtained by an optimized desilication procedure increases Diesel and propylene yields during gas-oil cracking reaction.The alkaline treatment of zeolite Beta (Si/Al = 22) by desilication with NaOH and NaOH&TBAOH was investigated. The catalytic performance improvement of desilicated zeolite Beta has been rationalized by deep characterization of the samples including X-ray diffraction, low temperature adsorption of nitrogen, solid-state 29 Si MAS NMR and IR studies of acidity. Finally, the catalytic performance of the zeolites Beta was evaluated in the cracking of n-decane, 1,3,5-tri-iso-propylbenzene and vacuum gas oil. It was found that desilication with NaOH&TBAOH ensures the more uniform intracrystalline mesoporosity with the formation of narrower mesopores, while preserving full crystallinity resulting in catalysts with the most appropriated acidity and then, with better catalytic performance.

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“…The external surface of BZSM-5 is rougher than that of others, and its particles exhibit obvious aggregation. Such a complex morphology might be formed by the fusion of a multitude of smaller, possibly primary crystallites 17 . The formation of aggregations is due to the small particles size of the zeolite and the addition of the B.…”

Section: Catalytic Evaluationmentioning

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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How defects and crystal morphology control the effects of desilication

Cited by 109 publications

References 79 publications

Methanol to olefins: activity and stability of nanosized SAPO-34 molecular sieves and control of selectivity by silicon distribution

Methanol to olefins: activity and stability of nanosized SAPO-34 molecular sieves and control of selectivity by silicon distribution

Catalytic cracking performance of alkaline-treated zeolite Beta in the terms of acid sites properties and their accessibility

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

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