Generation of acid sites by SiO2 deposition on groups IVB metal oxides

Niwa, Miki

doi:10.1016/0021-9517(92)90233-8

Cited by 60 publications

(14 citation statements)

References 13 publications

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“…In an attempt to improve the performance of zeolites, two routes have been proposed: (1) Tailoring acid sites in zeolites [9]. Various approaches have been developed to improve acid sites of zeolites including dealumiumazation [10,11], SiO 2 deposition [12], the load of superacid [13], and so on. Dealuminization of zeolites prompts the aluminum species in the lattice to migrate out with high-temperature treatment, resulting in a transformation from framework aluminum to extra-framework aluminum.…”

Section: Introductionmentioning

confidence: 99%

“…The formation of extra-framework aluminum is beneficial to increasing acid amount of Lewis acidity, and consequently, enhancing the synergistic effect of Brønsted and Lewis acidity [11]. The vapor deposition of SiO 2 could facilitate the formation of framework aluminum in zeolites, resulting in an increase of the Brønsted acidity [12]. The load of superacid enhances both Brønsted acidity and Lewis acidity of zeolites [13].…”

Section: Introductionmentioning

confidence: 99%

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Effects of Enhancing Micromixing on Nucleation/Crystal Growth Process and Material Properties of Zeolite

Qi¹,

Shi²,

Wang³

et al. 2020

Preprint

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Hierarchical (micro/mesopore) ZSM-5 zeolites were hydrothermally synthesized with enhancing micromixing of the high viscosity reaction system in a rotating packed bed (RPB). Herein, the effects of four operating processes with different micromixing intensity on nucleation/crystal growth process as well as properties of ZSM-5 zeolites were investigated. Results indicated that enhancing micromixing by RPB in the zeolite synthesis could facilitate the formation of Al sites and shorten the nucleation and crystallization period. ZSM-5 samples prepared by the RPB premix process exhibit hierarchical structure, smaller average particle size, more uniform particle size distributions, larger specific surface areas, higher catalytic stability as well as more Brønsted and Lewis acid sites. While adopting the prepared ZSM-5 zeolites with RPB premix for catalyzing C4-olefin cracking reaction, the conversion of C4-olefin and yield of propylene were higher than that obtained by traditional stirring tank reactor premix.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Effects of Enhancing Micromixing on Nucleation/Crystal Growth Process and Material Properties of Zeolite

Qi¹,

Shi²,

Wang³

et al. 2020

Preprint

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“…21 Niwa et al suggested that SiO 2 deposition can generate acid sites on Group IVB metal oxides. 22 Wang et al prepared the SiO 2doped V 2 O 5 /WO 3 −TiO 2 catalyst for SCR. It was found that the presence of SiO 2 improved the number of acid sites and acid strength.…”

Section: Introductionmentioning

confidence: 99%

“…Zhu et al noted that the acidic amount decreased after the doping while the acidic strength distribution was almost unchanged on ZSM-5 . Niwa et al suggested that SiO 2 deposition can generate acid sites on Group IVB metal oxides . Wang et al prepared the SiO 2 -doped V 2 O 5 /WO 3 –TiO 2 catalyst for SCR.…”

Section: Introductionmentioning

confidence: 99%

Chemical Liquid Deposition (CLD)-Modified Fe-ZSM-5 for Enhanced Activity and Resistance to C₃H₆ Poisoning in Selective Catalytic Reduction with NH₃ (NH₃-SCR)

Zhang

Wang

Yang

2018

Ind. Eng. Chem. Res.

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Hydrocarbon fouling can deactivate the catalyst in the selective catalytic reduction (SCR) with NH3 of NO. We use a simple chemical liquid deposition technique to dope a shell layer of SiO2. The results show that it acts as a protective layer against C3H6 while providing abundant Lewis acid sites. which compensate for the relatively less Fe-active sites and therefore contribute to higher overall SCR activities and better resistance to C3H6 poisoning. Moreover, the C3H6 has been found to have promotional effects on SCR at a lower temperature (150 °C), because of the additional SCR reaction with C3H6.

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“…This modification method is based on the following two findings: the stable adsorption of benzaldehyde and the full coverage of the silica monolayer by CVD of TMOS. Benzaldehyde is adsorbed on weakly basic metal oxides such as Al 2 O 3 , TiO 2 , ZrO 2 , and SnO 2 to form a benzoate anion, and the adsorbed species is desorbed as benzonitrile by the reaction with gaseous ammonia. , On the other hand, a silica overlayer with a monoatomic order thickness is formed by CVD of TMOS on these metal oxides, and it completely covers the metal oxide surface. , …”

Section: Introductionmentioning

confidence: 99%

Molecular Sieving Silica Overlayer on γ-Alumina: The Structure and Acidity Controlled by the Template Molecule

et al. 1998

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A silica overlayer was prepared on γ-alumina by a method of chemical vapor deposition (CVD) of silicon alkoxide using preadsorbed benzaldehyde and R-naphthaldehyde as a template. Infrared spectroscopy confirmed that the preadsorbed benzoate anion species remained after the deposition of silica, indicating that silica was deposited on the exposed surface of alumina. On the basis of the adsorption property of modified alumina, it is considered that the silica overlayer had a vacancy whose size was as large as the template molecule. 29 Si NMR spectroscopy showed that the Si species deposited using the template was Si(OAl)1(OSi)1(OH)2 or Si(OAl)2(OSi)1(OH)1, while the deposition without the template formed such a species as Si(OAl)1(OSi)3 and Si(OAl)1(OSi)2(OH)1 bonded via a two-dimensional siloxane network. Lack of activity for double-bond isomerization of 1-butene to 2-butene on the silica overlayer prepared using the template was consistent with the previous results that the two-dimensional network of siloxane on the alumina surface induced Brønsted acidity on the Al-O-Si-OH species. Both the adsorption and acidic properties on silica-deposited alumina using R-naphthaldehyde were different from those on the sample prepared using benzaldehyde, showing that the structure of the silica overlayer was controlled by the template molecules.

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Generation of acid sites by SiO2 deposition on groups IVB metal oxides

Cited by 60 publications

References 13 publications

Effects of Enhancing Micromixing on Nucleation/Crystal Growth Process and Material Properties of Zeolite

Effects of Enhancing Micromixing on Nucleation/Crystal Growth Process and Material Properties of Zeolite

Chemical Liquid Deposition (CLD)-Modified Fe-ZSM-5 for Enhanced Activity and Resistance to C₃H₆ Poisoning in Selective Catalytic Reduction with NH₃ (NH₃-SCR)

Molecular Sieving Silica Overlayer on γ-Alumina: The Structure and Acidity Controlled by the Template Molecule

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Generation of acid sites by SiO2 deposition on groups IVB metal oxides

Cited by 60 publications

References 13 publications

Effects of Enhancing Micromixing on Nucleation/Crystal Growth Process and Material Properties of Zeolite

Effects of Enhancing Micromixing on Nucleation/Crystal Growth Process and Material Properties of Zeolite

Chemical Liquid Deposition (CLD)-Modified Fe-ZSM-5 for Enhanced Activity and Resistance to C3H6 Poisoning in Selective Catalytic Reduction with NH3 (NH3-SCR)

Molecular Sieving Silica Overlayer on γ-Alumina: The Structure and Acidity Controlled by the Template Molecule

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Chemical Liquid Deposition (CLD)-Modified Fe-ZSM-5 for Enhanced Activity and Resistance to C₃H₆ Poisoning in Selective Catalytic Reduction with NH₃ (NH₃-SCR)