Effect of leaching agent in the dealumination of stabilized Y zeolites

Gola, Agnieszka; Rebours, B.; Milazzo, E.; Lynch, John P.; Benazzi, E.; Lacombe, Sylvie; Delevoye, Laurent; Fernandéz, Christian

doi:10.1016/s1387-1811(00)00243-2

Cited by 117 publications

(93 citation statements)

References 23 publications

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“…Y-zeolite is made ultrastable by the removal of aluminum from the framework. The dealumination can be accomplished through the use of steam [9], acid leaching [10], or by chemical treatment with hexaflourosilicate or silicon tetrachloride [11][12][13]. However, the most common procedure is hydrothermal treatment at elevated temperatures under controlled atmosphere (steaming).…”

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confidence: 99%

The effect of Y-zeolite acidity on m-xylene transformation reactions

Al-Khattaf¹,

Iliyas²,

Al-Amer³

et al. 2005

Journal of Molecular Catalysis A: Chemical

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m-Xylene transformation has been studied on as-prepared H-Y and a series of dealuminated Y zeolite catalysts. The conversion of m-xylene was found to increase initially with acidity, however, decreases subsequently. It has been proposed that the high concentration of acid sites in the H-Y catalyst increases paring reaction, in addition to the well-known isomerization and disproportionation pathways. A significant decrease was observed with respect to disproportionation/paring (D/Pa) ratio versus reaction temperature. This indicates that higher activation energy is required for paring as compared to disproportionation reaction. The p-xylene/o-xylene (P/O) was established to be independent of zeolite acidity. A higher coke deposition was found for the transformation of m-xylene over the parent H-Y as compared to the highly dealuminated USY zeolite. The formation of benzene and C 2 -C 4 gases were found to be proportional to zeolite acid concentration.Keywords: m-Xylene transformation, Y zeolite, isomerization, disproportionation, paring reaction. * Corresponding author. Tel.: +966-3-860-1429; Fax: +966-3-860-4234 E-mail address: skhattaf@kfupm.edu.sa 2 IntroductionXylenes are important starting materials for some industrial processes like the production of synthetic fibers, plasticizers and resins. The major sources of these aromatic hydrocarbons are the reforming and pyrolysis gasoline, which have a higher ratio of low-valued m-xylene. A convenient way to upgrade the low-valued m-xylene consists of its transformation to o-and p-xylene. In this context, the transformation of m-xylene has been studied over different types of zeolite catalysts [1][2][3][4][5][6][7][8].There is interest in ultrastable Y-type zeolites for m-xylene transformation, partly because of their increased chemical and thermal stability, with respect to other zeolites. Y-zeolite is made ultrastable by the removal of aluminum from the framework. The dealumination can be accomplished through the use of steam [9], acid leaching [10], or by chemical treatment with hexaflourosilicate or silicon tetrachloride [11][12][13]. However, the most common procedure is hydrothermal treatment at elevated temperatures under controlled atmosphere (steaming). The resulting material, USY (ultrastable Y) zeolites, being modified in the framework Si/Al ratio, structure and acidity, usually exhibits improved reactivity, selectivity and coking behavior for a catalytic reaction, which is of great interest to the petroleum industry. Several studies have been conducted on the effect of Y-zeolite acid properties on isomerization and disproportionation of m-xylene reactions [1,5,7]. However, studies correlating the intrinsic properties of Y-zeolite to other reaction pathways, apart from isomerization and disproportionation are somewhat limited. With this in mind, the present work reports the effect of acid properties of Y-zeolite on products selectivity and various reaction pathways during m-xylene transformation in a fluidizedbed reactor. As prepared H-Y zeolite ...

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confidence: 99%

The effect of Y-zeolite acidity on m-xylene transformation reactions

Al-Khattaf¹,

Iliyas²,

Al-Amer³

et al. 2005

Journal of Molecular Catalysis A: Chemical

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“…We have shown that it is now possible to clearly separate the various extra-framework species in stabilised zeolites [62].…”

Section: Resultsmentioning

confidence: 91%

Development of Structural Characterisation Tools for Catalysts

Lynch

2002

Oil & Gas Science and Technology - Rev. IFP

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Résumé -Développement d'outils de caractérisation structurale de catalyseurs -Les catalyseurs hétérogènes industriels, de par la diversité de leur composition et de leur structure ainsi que des différents traitements nécessaires pour les rendre actifs, présentent un défi majeur pour les techniques de caractérisation structurale. La microscopie électronique fournit des informations en termes de texture et de structure à l'échelle de la particule élémentaire. Nous avons pu mettre en évidence des phénomènes d'épitaxie entre particules nanométriques et support, et déterminer les faces cristallographiques exposées. L'analyse élémentaire permet de contrôler la composition de particules individuelles dans un catalyseur bimétallique. Cette technique se heurte à des limitations si l'on cherche à caractériser la réactivité et la structure des catalyseurs à l'échelle atomique. Les méthodes d'analyses globales, telles que l'absorption et la diffraction des rayons X, permettent d'étendre la gamme d'informations disponibles. L'analyse de la structure fine des seuils d'absorption X nous a permis de caractériser des particules de taille inférieure au nanomètre dans des catalyseurs à base de platine et de mettre en évidence directement l'interaction entre le métal et des gaz réactifs : hydrocarbure et H 2 S. Les différences démontrées dans le comportement de solides monométalliques et bimétalliques constituent une base structurale pour l'explication des différences de réactivité des catalyseurs. La diffraction des rayons X, combinée à la microscopie électronique et à la spectroscopie de résonance magnétique nucléaire, met en évidence différents types d'aluminium extra-charpente dans des zéolithes soumises à un traitement hydrothermal. Nous avons quantifié une partie de ces espèces et caractérisé leur réactivité vis-à-vis de différents agents de désalumination. Des études en cours montrent l'intérêt d'une combinaison de la diffraction et l'absorption des rayons X pour le suivi de la décomposition des hydrotalcites en oxydes mixtes ainsi que les possibilités d'étude par spectroscopie infrarouge de la molécule sonde CO des espèces superficielles dans les catalyseurs FischerTropsch. L'emploi de cellules adaptées à l'analyse in situ permet une description détaillée des modifications structurales des catalyseurs sous atmosphères réactives et ouvre des possibilités de corrélations entre leur structure et leur activité catalytique. Oil & Gas Science and Technology -Rev. IFP, Vol. 57 (2002)

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“…The catalyst deactivation will cause a reduction of product selectivity and quality. Thus, tremendous research about modification of USY zeolite has been reported in literature in the past [6][7][8][9][10]. Dealumination of framework aluminum is an effective way to improve the Si/Al ratio and acid property.…”

Section: Introductionmentioning

confidence: 99%

“…Dealumination of framework aluminum is an effective way to improve the Si/Al ratio and acid property. For this purpose, thermal or hydrothermal treatments [9], acids leaching [10], and chemical treatments with hexafluorosilicate or silicon tetrachloride are reported [11][12][13][14]. Among these methods, hydrothermal treatment is one of the most promising and sole industrialized methods.…”

Section: Introductionmentioning

confidence: 99%

Modification of USY zeolites with malic–nitric acid for hydrocracking

Qiao

Yang

et al. 2016

Appl Petrochem Res

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The modification of commercial ultra-stable Y zeolite using malic acid (MA) and nitric acid (NA) was investigated. A series of factors including the amount of MA and NA solutions, the pH of the solutions, the treatment time, and the reaction temperature were investigated and optimized. The pore structure, acid properties, and crystal structure of modified USY zeolite were characterized by N 2 -adsorption, temperature-programmed desorption of ammonia (NH 3 -TPD), pyridine adsorbed Fourier transform infrared spectroscopy, and X-ray diffraction techniques. The as-obtained sample under the optimum conditions presents an increased secondary pore volume up to 0.202 cm 3 g -1 , which accounts for 45.3 % of the total pore volume, and appropriate acid properties as well as good crystallinity. Furthermore, the USY zeolite modified with different methods was also investigated, indicating that malic-nitric combined acid is an effective modifier for USY zeolite. The modified USY zeolite was used as support to prepare hydrocracking catalysts. The 140-370°C middle distillate yield of the catalyst is 68.59 %, and middle distillate selectivity can reach up to 81.52 %. Compared with commercial catalyst, the yield and selectivity increased by 8.17 and 5.14 %, respectively.

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Effect of leaching agent in the dealumination of stabilized Y zeolites

Cited by 117 publications

References 23 publications

The effect of Y-zeolite acidity on m-xylene transformation reactions

The effect of Y-zeolite acidity on m-xylene transformation reactions

Development of Structural Characterisation Tools for Catalysts

Modification of USY zeolites with malic–nitric acid for hydrocracking

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