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Mériaudeau, P.; Tuel, A.; Vu, T.T.H.

doi:10.1023/a:1019091915381

Cited by 37 publications

(19 citation statements)

References 10 publications

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“…38 From the simulated 27 Al MQ MAS NMR spectrum, it is evident that 8 T sites can be divided into 3 groups: the T1, T3, T4, T5, T7 and T8 sites belong to the signal at δ 56 ppm, while the T2 and T6 sites correspond to the signals at δ 61 and δ 49 ppm, respectively. 32,39 In accordance with the conclusion, three peaks at δ = (49, 53), (56, 60) and (61, 66) ppm of the calcined MCM-22 can be clearly distinguished in the 2D MQ MAS NMR spectrum of Fig. 8(a).…”

Section: Catalysis Science and Technology Papersupporting

confidence: 87%

“…The twodimensional multi-quanta (2D MQ) sequence method provides enhanced resolution to separate the contributions of aluminum species with different isotropic shifts and quadrupolar constants along the F 1 axis, as compared with ordinary MAS spectra. 32,39 In accordance with the conclusion, three peaks at δ = (49, 53), (56, 60) and (61, 66) ppm of the calcined MCM-22 can be clearly distinguished in the 2D MQ MAS NMR spectrum of Fig. 32,[35][36][37] These eight unequivalent T(Si, Al) positions are associated with bridging hydroxyl groups (SiOHAl) as the Brønsted acid site.…”

Section: View Article Onlinesupporting

confidence: 66%

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The influences of Al species and Ti species on the catalytic epoxidation over Si/Ti-pillared MCM-36 synthesized from MCM-22

Jin

Huang

Cheng

et al. 2015

Catal. Sci. Technol.

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A novel mesopore silica-aluminium material, i.e., Si/Ti-MCM-36 derivatives were prepared with Si/Ti mixed oxide as a pillar. The influences of acidity from Al species and the coordination state of Ti species on the catalytic cylcohexene epoxidation with t-butylhydroperoxide (TBHP) as the oxidant were investigated. The mesoporous structures were confirmed by XRD and N 2 ads/desorption experiment. The acidity and surface polarity were characterized by NH 3 -TPD, 27 Al 2D MQ MAS NMR and 29 Si MAS NMR. The Ti coordination state was identified with UV-Vis spectra. By using 27 Al 2D MQ MAS NMR technique, the Al species from the different eight crystallographically T (Si, Al) positions of MWW zeolite were identified, which are associated with bridging hydroxyl groups such as the Brønsted acid site. It was found that the Si/Ti-MCM-36 samples, whether with tetrahedrally (T d ) or octahedrally (O h ) coordinated state Ti species, are all inactive for the cyclohexene epoxidation. A further acid treatment of the Si/Ti-MCM-36 samples can greatly expel Al species from the MWW structure, which largely decrease the acidity and transfer the acid-catalyzed decomposition of t-butylhydroperoxide to Ti catalyzed cyclohexene epoxidation. It shows that not only the amount of Al species but also their framework crystallographic positions have a great influence on the epoxidation activity. Furthermore, the grafting of the tetra-isopropoxide on the acid treated Si/Ti-MCM-36 can increase its hydrophobicity and epoxidation activity. Moreover, the T d TiO 4 in the units has been confirmed to be the most active site for the epoxidation reaction.

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Section: Catalysis Science and Technology Papersupporting

confidence: 87%

Section: View Article Onlinesupporting

confidence: 66%

The influences of Al species and Ti species on the catalytic epoxidation over Si/Ti-pillared MCM-36 synthesized from MCM-22

Jin

Huang

Cheng

et al. 2015

Catal. Sci. Technol.

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“…6. The two peaks at 55 ppm (FAl1) and 48 ppm (FAl2) in the spectrum of MCM-22 indicate the presence of two types of framework Al species in line with the literature [60,61]. The FAl1 species are located inside the micropores, while the FAl2 species reside at the external surface and/or the large cavities [61].…”

Section: Acidity Characterizationsupporting

confidence: 84%

One-pot synthesis of nano-crystalline MCM-22

Tempelman

Portilla

Martínez-Armero

et al. 2016

Microporous and Mesoporous Materials

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Nano-crystalline MCM-22 zeolite was synthesized in a one-pot procedure by the use of an organosilane (dimethyl-octadecyl-(3-trimethoxysilylpropyl)-ammonium chloride, TPOAC) in the zeolite synthesis gel. This crystal growth inhibition procedure introduced mesopores in the MCM-22 crystallites. The lower mechanical stability of the nano-crystalline MCM-22 zeolite compared with bulk MCM-22 can be countered to some extent by pillaring. The increased external surface of the microporous zeolite domains resulted in increased accessibility of the Brønsted acid sites, as followed from the better performance in liquidphase benzene alkylation with propylene as compared with bulk MCM-22. The increased accessibility of the internal acid sites in Mo-loaded hierarchical MCM-22 was also evident from the improved benzene selectivity during methane aromatization. Silylation of hierarchical Mo/MCM-22 was detrimental for the catalytic performance in MDA. The nano-crystalline MCM-22 has physico-chemical and catalytic properties intermediate between those of MCM-22 and ITQ-2 with the benefit over ITQ-2 that it can be synthesized in a single step.

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“…The USY zeolite (silica/alumina: 10.7) was provided by Tosoh Co., and used after calcination under air flow at 673 K (1 K/min) for 4 h. MCM-22 zeolite was prepared as previously reported [15] and activated under air stream until 853 K (1 K/ min). H-Beta is obtained by a procedure described in literature [16] and then calcined under air stream at 823 K (10 K/min) for 5 h. Supported heteropolyacids referred to 40HPW and 40HSiW (40% of 12-phosphotungstic and 12-silicotungstic acids on SiO 2 , respectively) were prepared by impregnation of appropriate quantities of hydrated H 3 PW 12 O 40 (HPW) and H 4 SiW 12 O 40 (HSiW) over a mesoporous silica (Grace Davison 432, 320 m 2 /g), using methanol as solvent.…”

Section: Methodsmentioning

confidence: 99%