Dual template-directed synthesis of SAPO-34 nanosheet assemblies with improved stability in the methanol to olefins reaction

Wang, Chan; Yang, Miao; Tian, Peng; Xu, Shutao; Yang, Yue; Wang, Dehua; Yuan, Yangyang; Liu, Zhongmin

doi:10.1039/c4ta06124a

Cited by 164 publications

(88 citation statements)

References 44 publications

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“…For the case of SAPO-34 zeolite and TiO 2 /SAPO-34 composite, the TGA signal of the zeolite is identical to those obtained in the literature [51,52]. It is clear that the weight loss stages of TiO 2 /SAPO-34 are different compared to the SAPO-34, which is probably due to the presence of TiO 2 nanostructures on the surface of SAPO-34.…”

Section: Photocatalytic Degradation Of Mbsupporting

confidence: 67%

Structural and textural features of TiO2/SAPO-34 nanocomposite prepared by the sol–gel method

et al. 2016

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This paper focuses on the synthesis of nanocomposite materials TiO 2 /SAPO-34 using the sol-gel method, which involves preparing a mixture between as-synthesized or calcined SAPO-34 zeolite and TiO 2 gel under hydrothermal crystallization and then calcined at 400 °C for the formation of TiO 2 anatase phase. The structural and textural features of the obtained materials were determined by various physico-chemical techniques such as thermogravimetric analysis (TGA), X-ray diffraction (XRD), scanning electronic microscopy (SEM), Nitrogen sorption at 77 K, energy dispersive X-ray analysis (EDX) and ultravioletvisible (UV-vis). The DRX results showed that calcination at 400 °C of the mixture between calcined SAPO-34 and TiO 2 gel led to the collapse of the original framework of zeolite but forms the anatase TiO 2 in a nano-spherical morphology, but the use of as-synthesized SAPO-34 supports provides a mixture phase between SAPO-34 and TiO 2 anatase after calcination. The photocatalytic properties of SAPO-34/TiO 2 andTiO 2 type materials were tested for the removal of methylene blue (MB) dye. The MB degradation proved to be increasing as a function of contact time, catalyst mass and the initial concentration of MB.

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Section: Photocatalytic Degradation Of Mbsupporting

confidence: 67%

Structural and textural features of TiO2/SAPO-34 nanocomposite prepared by the sol–gel method

et al. 2016

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“…[15][16][17] Recently, more efforts have been made towards the "direct synthesis" of hierarchical zeolites through soft-templating routes, [18][19][20][21] which can achieve greater mesoporosity, more precise control of pore size, and higher zeolite structure integrity compared with "post-treatment" methods. Hierarchical zeolites prepared by different methods have been tested as catalysts for various reactions, and typically, they exhibit higher catalytic activities (especially when the reactant molecules are bulky) , [22][23] longer lifetimes, [24][25] slower coke formation rates, 26 and altered product selectivities 27 compared to conventional zeolites with the same framework types. For example, we recently reported that a non-surfactant cationic polymer can act as a dual template to synthesize hierarchical zeolite Beta.…”

Section: Introductionmentioning

confidence: 99%

Investigating the Influence of Mesoporosity in Zeolite Beta on Its Catalytic Performance for the Conversion of Methanol to Hydrocarbons

et al. 2015

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Hierarchically porous zeolite Beta (Beta-MS) synthesized by a soft-templating method contains remarkable intra-crystalline mesoporosity, which reduces the diffusion length in zeolite channels down to several nanometers and alters the distribution of Al among distinct crystallographic sites. When used as a catalyst for the conversion of methanol to hydrocarbons (MTH) at 330 o C, Beta-MS exhibited a 2.7-fold larger conversion capacity, a 2.0-fold faster reaction rate, and a remarkably longer lifetime than conventional zeolite Beta (Beta-C). The superior catalytic performance of Beta-MS is attributed to its hierarchical structure, which offers full accessibility to all catalytic active sites. In contrast, Beta-C was easily deactivated because a layer of coke quickly deposited on the outer surfaces of the catalyst crystals, impeding access to interior active sites. This difference is clearly demonstrated by using electron microscopy combined with electron energy loss spectroscopy to probe the distribution of coke in the deactivated catalysts. At both low and high conversions, ranging from 20% to 100%, Beta-MS gave higher selectivity towards higher aliphatics (C 4 -C 7 ) but lower ethene selectivity compared to Beta-C. Therefore, we conclude that a hierarchical structure decreases the residence time of methylbenzenes in zeolite micropores, disfavoring the propagation of the aromatic-based catalytic cycle. This conclusion is consistent with a recent report on ZSM-5 and is also strongly supported by our analysis of soluble coke species residing in the catalysts.Moreover, we identified an oxygen-containing compound, 4-methyl-benzaldehyde, in the coke, which has not been observed in the MTH reaction before.

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“…Therefore, the longer the chain of PEG is, the fewer strong acid sites will occur. As the strong acid site corresponds to the incorporation of silicon into the framework of SAPO-34 catalyst [35,36], we can speculate that the long chain of PEG can hinder silicon from incorporating into the framework to some extent.…”

Section: Resultsmentioning

confidence: 99%

Performance of Methanol-to-Olefins Catalytic Reactions by the Addition of PEG in the Synthesis of SAPO-34

Wang

Sun

et al. 2017

Trans. Tianjin Univ.

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SAPO-34, a silicoaluminophosphate zeolite, has been synthesized by the hydrothermal method with the addition of different molecular weights of polyethylene glycol (PEG), and has been characterized with XRD, SEM, N 2 adsorption-desorption, FT-IR, and NH 3 temperatureprogrammed desorption (NH 3 -TPD). We studied SAPO-34 as a catalyst in the methanol-to-olefins (MTO) reaction, in a fixed-bed reactor. The results show that the chain length of PEG has a great influence on the particle size and morphology of SAPO-34. PEG acts as inhibitor in the crystallization process. With the increase of the chain length of PEG used in the synthesis, from a relative molecular weight of 400-6000, the morphology of SAPO-34 changes gradually from cubic to nanoplate-like and then changes to cubic again. The particle size decreases markedly at first and then increases to some extent. The catalytic stability in the MTO reaction also increases first and then decreases, with all the catalysts having almost the same selectivity to olefins. When the sample is synthesized with PEG800, the particles become nanoplate-like with a thickness of 46 nm on average, and the catalytic stability is appreciably prolonged, which is attributed to the shorter diffusion paths of the reactants in the zeolite.

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Dual template-directed synthesis of SAPO-34 nanosheet assemblies with improved stability in the methanol to olefins reaction

Cited by 164 publications

References 44 publications

Structural and textural features of TiO2/SAPO-34 nanocomposite prepared by the sol–gel method

Structural and textural features of TiO2/SAPO-34 nanocomposite prepared by the sol–gel method

Investigating the Influence of Mesoporosity in Zeolite Beta on Its Catalytic Performance for the Conversion of Methanol to Hydrocarbons

Performance of Methanol-to-Olefins Catalytic Reactions by the Addition of PEG in the Synthesis of SAPO-34

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