Microwave Fabrication of MFI Zeolite Crystals with a Fibrous Morphology and Their Applications

Hwang, Young Kyu; Chang, Jong‐San; Park, Sang-Eon; Kim, Dae Sung; Kwon, Young‐Uk; Jhung, Sung Hwa; Hwang, Jung Yeon; Park, Min Seok

doi:10.1002/anie.200461403

Cited by 173 publications

(62 citation statements)

References 38 publications

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“…As for alkaline treated TS-1 samples, the main peak of the UV-vis spectra shift to 214-222 nm and a broad peak at around 310 nm. Those peaks are assignable to the tetrahedral titanium(IV) in the zeolite framework [26,27]. Those spectra confirmed that the titanium species in the parent TS1-NC and alkaline treated TS-1 samples are incorporated into the framework.…”

Section: Resultssupporting

confidence: 64%

Phenol Hydroxylation over Alkaline Treated TS-1 Catalysts

Chao

Tsai

et al. 2009

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Alkaline treatment on TS-1 can selective remove silica from the framework while MFI zeolitic framework remains intact, which creates new large micropores or even mesopores and increases Si/Ti ratio in the alkaline treated TS-1. Among various alkaline hydroxide, CsOH treatment leads to partial destruction of MFI structure. All the desilicated TS-1 samples show enhanced phenol conversion and dihydroxylbenzene (DHB) yield in acetone solvent by two folds, which can be attributed to the higher Ti/Si ratio and improved diffusivity. Pore structure modified with alkaline treatment affects significantly reaction pathway and product selectivity. The initial product over the parent TS-1 and NaOH treated TS-1 is mainly 4-hydroxycyclohexa-2,5-dienone and catechol enriched DHB, respectively.

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Section: Resultssupporting

confidence: 64%

Phenol Hydroxylation over Alkaline Treated TS-1 Catalysts

Chao

Tsai

et al. 2009

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“…Also Park et al [21] previously reported the selective adsorption of xylenes over the stacked TS-1 and conventional TS-1, observed that the stacked TS-1 revealed remarkably enhanced adsorption selectivity to p-xylene, which was 6.7 times higher than that of conventional TS-1. During microwave crystallization, transition metals, such as Ti, Zr, Al, Sn and Fe, could play a role as nano glue for the stacking of those hockey-puck shaped zeolite crystals as a building block [22].…”

Section: Introductionmentioning

confidence: 92%

Epoxidation of Linear Olefins over Stacked TS-1 Zeolite Catalysts

Jin

Jiang

et al. 2008

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Stacked TS-1 [NSTS-1(MW)] has been prepared by microwave synthesis and applied to the epoxidation of linear olefins with H 2 O 2 under mild conditions, and the epoxidation activities were compared with the non-stacked TS-1 and the conventional TS-1, which were also synthesized by microwave and by typical hydrothermal method, respectively. Stacking of TS-1 crystals was accomplished by using microwave which facilitated the dehydration of hydroxyl groups on the external surface of crystallites through the selective absorption of microwave onto Ti species. The stacked crystallites seemed to allow the running pore structure in the b-axis orientation through the crystallites in the stacked morphology. Besides this unique pore structure, the stacked TS-1 showed peculiar features like higher hydrophobicity and enhanced catalytic property than typical TS-1. Moreover, the NSTS-1(MW) showed the highest activity in the epoxidation of linear olefins among three catalysts, and also coincided with the differences in the adsorption of linear aliphatics due to strong interaction with the straight channel in the stacked morphology, which gave larger Henry's constants, obtained by the tracer chromatographic analysis, as the increase in the carbon chain length.

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“…This comes from the possibility of obtaining particular operative conditions not available through the conventional heating techniques [17][18][19]. In comparison to conventional thermal techniques, microwave dielectric heating has three significant merits: (a) temperature can be rapidly increased due to high utilization factor of microwave energy, and the kinetics of the reaction rates are increased by 1-2 orders of magnitude, (b) thermal gradient effects can be effectively reduced due to volumetric heating of the microwaves, which is favorable for realizing homogeneous heating and producing a more uniform product formation, and (c) the reaction selectivity is enhanced since different kinds of substances have a diverse dipole constants [20].…”

Section: Significance Of Microwave Dielectric Heatingmentioning

confidence: 99%

A Rapid Microwave-Induced Solution Combustion Synthesis of Ceria-Based Mixed Oxides for Catalytic Applications

2009

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We have been exploring the utilization of a simple and fast microwave-induced solution combustion synthesis technique for the preparation of various ceriabased mixed oxides for different catalytic applications. In our comprehensive investigation, CeO 2 -SiO 2 (MWCS), CeO 2 -TiO 2 (MWCT), CeO 2 -ZrO 2 (MWCZ) and CeO 2 -Al 2 O 3 (MWCA) mixed oxides were synthesized by solution combustion synthesis method using microwave dielectric heating and employed for CO and soot oxidation applications. The intricate relationship between ceria and other supporting oxides has been explored with the help of various analytical techniques namely, X-ray diffraction (XRD), temperature programmed reduction/oxidation (TPR/TPO), temperature programmed desorption (TPD) of ammonia and CO 2 , Raman spectroscopy (RS), UV-vis diffuse reflectance spectroscopy (UV-vis DRS), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), BET surface area and thermogravimetry analysis (TGA) methods. XRD results revealed amorphous nature of the material in case of ceria-silica mixed oxide and formation of a specific cubic fluorite type Ce 0.5 Zr 0.5 O 2 solid solution in the case of ceria-zirconia mixed oxide. Ceria-titania and ceria-alumina mixed oxides exhibited diffraction lines only due to crystalline ceria. Zirconia-based mixed oxide exhibited a lower reduction temperature and better redox properties compared to other samples. TPD of ammonia and CO 2 results revealed superior acid-base properties for MWCS mixed oxide.TGA measurements indicated a complete combustion in all preparations. RS results suggested defective structure of mixed oxides resulting in the formation of oxygen vacancies. XPS results revealed that ceria-zirconia mixed oxide contained more Ce 3? compared to other oxides. Among all the mixed oxides, the MWCZ sample exhibited a higher oxygen storage capacity, and better CO and soot oxidation activities. All these interesting findings have been elaborated in this publication.

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Microwave Fabrication of MFI Zeolite Crystals with a Fibrous Morphology and Their Applications

Cited by 173 publications

References 38 publications

Phenol Hydroxylation over Alkaline Treated TS-1 Catalysts

Phenol Hydroxylation over Alkaline Treated TS-1 Catalysts

Epoxidation of Linear Olefins over Stacked TS-1 Zeolite Catalysts

A Rapid Microwave-Induced Solution Combustion Synthesis of Ceria-Based Mixed Oxides for Catalytic Applications

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