Solid-state MAS NMR studies on the hydrothermal stability of the zeolite catalysts for residual oil selective catalytic cracking

Zhuang, Jing; Ma, Ding; Yang, Gang; Yan, Zhimin; Liu, Xiumei; Liu, Xianchun; Han, Xiuwen; Bao, Xinhe; Xie, Peng; Liu, Zhongmin

doi:10.1016/j.jcat.2004.08.034

Cited by 141 publications

(142 citation statements)

References 43 publications

(54 reference statements)

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“…The relative crystallinity of modified sample was calculated and presented in Table 1. In previous reports, impregnation might cause the framework dealumination, finally resulted in the reduction of crystallinity of zeolite [20,21]. The XRD results exhibited that the parent H-ZSM-5 and magnesium modified H-ZSM-5 samples consisted exclusively of the diffraction peaks for intrinsic MFI structure.…”

Section: Resultsmentioning

confidence: 76%

Effect of magnesium modification over H-ZSM-5 in methanol to propylene reaction

et al. 2015

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H-ZSM-5-based catalyst is a recognized catalyst which is particularly selective towards the formations of light olefins in the methanol reaction. A series of H-ZSM-5 (SiO 2 /Al 2 O 3 = 38) modified with different amounts of magnesium have been investigated. All the samples were characterized by X-ray diffraction instrument (XRD), temperature-programmed desorption of NH 3 (NH 3 -TPD) and Fourier Transform Infrared Spectoscopy (FT-IR). The results indicated that the impregnation of H-ZSM-5 (SiO 2 /Al 2 O 3 = 38) zeolite with various magnesium loading amount significantly affected the strength of acid sites and decreased the concentration of both weak and strong acid sites. As a result of modification, magnesium mainly interacted with strong Brønsted acid sites, thus generated new medium strong acid sites and enhanced the yield of propylene. The optimum acid property for methanol to propylene (MTP) reaction was gotten over 4.0 Mg-ZSM-5 (4.0 wt% Mg) zeolite catalyst. The maximum yield of propylene was 10.62 wt% over 4.0 Mg-ZSM-5 zeolite catalyst by the 30 min on stream. Coke which was mostly formed on strong Brønsted acid sites, would cause the catalysts deactivation, so the reduction of strong Brønsted acid sites could enhance the catalytic stability.

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Section: Resultsmentioning

confidence: 76%

Effect of magnesium modification over H-ZSM-5 in methanol to propylene reaction

et al. 2015

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“…15,29 Thermal treatment leads to the formation of TFAl dis species. Consequently, the free Al-OH groups can react with phosphoric acid to form bidentate (SiO) 2 Al(O 2 P(OR) 2 ) or (SiO) 2 Al(O 2 P 2 O 2 (OR) 3 ) species where R = H or (poly)phosphoric acid, giving rise to local SAPO interfaces.…”

Section: Formation Of Local Sapo Interfacesmentioning

confidence: 99%

“…[6][7][8][9][10][11][12] Even though there is still some debate on the effect of acid site strength on the MTO product distribution, the promoting effect of phosphorus on the hydrothermal stability of H-ZSM-5 is undisputed. 4,9,[13][14][15][16][17][18][19][20][21][22][23][24][25] Zeolite H-ZSM-5 catalysts that contain phosphorus are more stable under hydrothermal conditions i.e. they retain more framework aluminium species and strong acid sites than their non-phosphated counterparts.…”

Section: Introductionmentioning

confidence: 99%

“…However, the Si-O-P bonds that are required for such a substitution have never been found in either phosphorus/H-ZSM-5 or SAPO materials and theoretical work has pointed to the unlikeliness of such bonds. 14,15,17,20,[29][30][31][32] Other possibilities of phosphorus-framework interaction have been suggested to arise from protonation of phosphoric acid by zeolitic bridging hydroxyl groups, stabilising the nearest neighbouring aluminium atom. 17 However, due to the low aluminium content generally found in H-ZSM-5, Al-O-Si-O-Al sites are quite rare and theoretical studies excluded the possibility of H 3 PO 4 protonation.…”

Section: Introductionmentioning

confidence: 99%

“…30 The most promising proposal for framework Al-O-P bonds to date was one which included partially dislodged framework aluminium species. 15,29 Zhuang et al and Damodaran and co-workers suggested that a hydrothermal treatment leads to the formation of partially dislodged aluminium, which reacts with phosphorus to form framework Al-O-P bonds. 15,29 Three types of Al-O-P bonds were distinguished using J-coupling 27 Al-31 P CP NMR, attributed to four-, five-, and six-coordinated Al-O-P species.…”

Section: Introductionmentioning

confidence: 99%

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Local silico-aluminophosphate interfaces within phosphated H-ZSM-5 zeolites

Bij

Weckhuysen

2014

Phys. Chem. Chem. Phys.

127

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In order to elucidate phosphorus-zeolite H-ZSM-5 interactions, a variety of phosphorus-modified zeolite H-ZSM-5 materials were studied in a multi-spectroscopic manner. By deploying single pulse 27 Al, 31 P MAS NMR, 2D heteronuclear 27 Al-31 P correlation (HETCOR), 27 Al MQ MAS NMR spectroscopy, TPD of pyridine monitored by FT-IR spectroscopy, and Scanning Transmission X-ray Microscopy (STXM) the interplay and influence of acidity, thermal treatment and phosphorus on the structure and acidity of H-ZSM-5 were established. It was found that while acid treatment did not affect the zeolite structure, thermal treatment leads to the breaking of Si-OH-Al bonds, a decrease in the strong acid site number and the formation of terminal Al-OH groups. No extra-framework aluminium species was observed. Phosphorus precursors interact with the zeolitic framework through hydrogen bonds and physical coordination, as phosphorus species can be simply washed out with hot water. After phosphatation and thermal treatment two effects occur simultaneously, namely (i) phosphorus species transform into water insoluble condensed poly-phosphoric acid and (ii) phosphoric acid binds irreversibly to the terminal Al-OH groups of partially dislodged four-coordinated framework aluminium, forming local silico-aluminophosphate interfaces.These interfaces are potentially the promoters of hydrothermal stability in phosphated zeolite H-ZSM-5.

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Advanced Solid-State NMR Techniques for the Study of Molecular Sieves

Mafra

Klinowski

1996

eMagRes

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Solid-state MAS NMR studies on the hydrothermal stability of the zeolite catalysts for residual oil selective catalytic cracking

Cited by 141 publications

References 43 publications

Effect of magnesium modification over H-ZSM-5 in methanol to propylene reaction

Effect of magnesium modification over H-ZSM-5 in methanol to propylene reaction

Local silico-aluminophosphate interfaces within phosphated H-ZSM-5 zeolites

Advanced Solid-State NMR Techniques for the Study of Molecular Sieves

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