Various types of Ga in MFI metallosilicates: characterization and catalytic activity

Brabec, Libor; Jeschke, M.; Klik, R.; Nováková, J.; Kubelková, Ludmila; Freude, D.; Bosáček, V.; Meusinger, J.

doi:10.1016/s0926-860x(97)00325-6

Cited by 36 publications

(13 citation statements)

References 46 publications

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“…The Ga(1.0)/HZ(18) sample, the catalyst with the highest aluminum content, showed an additional reduction peak at around 350 º C, which was attributed in the case of this sample, having the highest number of exchangeable sites, to the reduction of the reminiscent not oxidized Ga 3+ cations compensating the negative charge of the zeolite. This peak was also observed by Brabec et al (1998) in the TPR profile of a modified boralite by gallium solid state ion exchange. The Ga(1.0)/HZ(18) sample also showed the highest H 2 consumption, indicating greater ability to reduce Ga 2 O 3 in catalysts with higher numbers of protonic sites.…”

Section: Characterizationsupporting

confidence: 56%

“…The TPR-H 2 curves of Ga(1.0)/HZ (18), (28) and (38) catalysts (Figure 4) showed that all the samples had one reduction peak near 610 º C, which has been attributed to the reduction of Ga 2 O 3 to Ga 2 O (Brabec et al, 1998). The Ga(1.0)/HZ(18) sample, the catalyst with the highest aluminum content, showed an additional reduction peak at around 350 º C, which was attributed in the case of this sample, having the highest number of exchangeable sites, to the reduction of the reminiscent not oxidized Ga 3+ cations compensating the negative charge of the zeolite.…”

Section: Characterizationmentioning

confidence: 99%

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Conversion of n-Butane to iso-Butene on Gallium/HZSM-5 Catalysts

Gheno

Urquieta‐González

2002

Braz. J. Chem. Eng.

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-The conversion of n -butane to iso-butene on gallium/HZSM-5 catalysts at 350 º C and WHSV=2.5h8 -1 was studied. The catalysts were prepared by ion exchange from a Ga(NO3) 2 solution and further submitted to calcination in air at 530 º C. TEM analysis with an EDAX detector and TPR-H 2 data showed that after calcination the Ga species were present mainly as Ga 2 O 3 , which are reduced to Ga 2 O at temperatures near 610 º C. The specific acid activity (SAA) of the catalysts increased with the increase in aluminum content in the zeolite, and for a fixed Si/Al ratio, the SAA increased with Ga content. Values for specific hydro/dehydrogenation activity (SH/DHA) were significantly higher than those for SAA, indicating that the catalytic process is controlled by the kinetics on acid sites. Moreover, the production of iso-butene with a selectivity higher than 25% was a evidence that in gallium/HZSM-5-based catalysts the rate of the hydrogenation reaction is lower than that of the dehydrogenation reaction; this behavior confirmed the dehydrogenation nature of gallium species, thereby showing great promise for iso-butene production.

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Section: Characterizationsupporting

confidence: 56%

Section: Characterizationmentioning

confidence: 99%

Conversion of n-Butane to iso-Butene on Gallium/HZSM-5 Catalysts

Gheno

Urquieta‐González

2002

Braz. J. Chem. Eng.

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“…The similar results were also mentioned in previous reports. 42,43 Fig. 5 NH 3 -TPD profiles of the different catalysts.…”

Section: Nh 3 -Tpdmentioning

confidence: 99%

Catalytic performance of gallium oxide based-catalysts for the propane dehydrogenation reaction: effects of support and loading amount

et al. 2017

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“…Since catalysts based on comparable FAU-type aluminosilicates do not suffer from a significant loss of crystallinity after this type of test, the loss of structure during hydrocracking conditions is characteristic for the gallosilicate framework. It cannot be related to thermal degradation of the framework, 27,41 for the US-RE-[Ga]-FAU was exposed to temperatures significantly higher than 650 K during the course of its preparation. We considered it unlikely that the reductive removal of gallium from the framework is the cause of this degradation, for in MFI-type gallosilicates this process is very slow at temperatures above 875 K. 42 Using differential thermogravimetric analysis (DTA) to assess the thermal stability of US-RE-[Ga]-FAU indicates that the structure is stable up to 1150 K, well above the 621-653 K temperature range during the hydrocracking test.…”

Section: Resultsmentioning

confidence: 99%

Synthesis and Characterization of Acidic High-Silica Faujasite-Type Gallosilicates

et al. 1999

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Ultrastabilization of a (rare-earth-loaded) faujasite (FAU)-type gallosilicate appears to be the only viable route for synthesizing a gallosilicate with an acid site density comparable to that of ultrastable FAU-type aluminosilicates. Neither gallium insertion into a FAU-type silica nor substitution of framework gallium by silicon using ammonium hexafluorosilicate appears feasible. The ultrastable FAU-type gallosilicate shows no sites with enhanced Brønsted acidity. According to the shift observed by IR spectroscopy when CO is adsorbed, the acid site strength of FAU-type gallosilicates is weaker than that of high-silica FAU-type aluminosilicates but stronger than that of FAU-type silicoaluminophosphates. Although the ultrastable FAUtype gallosilicate is (hydro)thermally stable in an oxidizing atmosphere up to 1150 K, it releases its gallium in a reducing atmosphere (starting at 525 K) and loses structural integrity increasingly rapidly above 635 K. This severely limits the potential use of catalysts based on gallosilicate framework structures in hydrocarbon hydroconversion reactions.

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Various types of Ga in MFI metallosilicates: characterization and catalytic activity

Cited by 36 publications

References 46 publications

Conversion of n-Butane to iso-Butene on Gallium/HZSM-5 Catalysts

Conversion of n-Butane to iso-Butene on Gallium/HZSM-5 Catalysts

Catalytic performance of gallium oxide based-catalysts for the propane dehydrogenation reaction: effects of support and loading amount

Synthesis and Characterization of Acidic High-Silica Faujasite-Type Gallosilicates

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