A reexamination of the hypothesis of Breck and Skeels concerning the reinsertion of aluminum in the framework of dealuminated Y zeolites

Engelhardt, G.

doi:10.1016/0021-9517(84)90030-7

Cited by 26 publications

(7 citation statements)

References 5 publications

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“…Hamdan et al [119] saw in the "secondary synthesis, " a method of achieving an optimal number of Brønsted acid sites responsible for the crack activity for hydrocarbons within the zeolite framework. But reexamination of the process by Engelhardt and Lohse [120] did not confirm this hypothesis. Their doubts concerned especially the interpretation of measured 29 Si MAS NMR spectra.…”

Section: Reinsertion Of Extraframework Aluminium Into Framework Positmentioning

confidence: 92%

Zeolite Y: Synthesis, Modification, and Properties—A Case Revisited

Lutz

2014

Advances in Materials Science and Engineering

134

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Y zeolites dealuminated by steaming were introduced as fluid-cracking catalysts in the year 1970. Extensive research has been done to develop suitable dealumination techniques, to investigate crystal structure, and to characterize catalytic behaviour. However, the origin of the secondary pore system formed in the zeolite structure during dealumination process remained completely obscure over a period of four decades. Open questions concerned also the existence of extraframework siliceous admixture in addition to extraframework aluminium species which can dramatically change the catalytic properties of these zeolites. This paper gives a review on the synthesis of DAY materials and provides some answers to several open questions.

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Section: Reinsertion Of Extraframework Aluminium Into Framework Positmentioning

confidence: 92%

Zeolite Y: Synthesis, Modification, and Properties—A Case Revisited

Lutz

2014

Advances in Materials Science and Engineering

134

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“…But only a few papers provides an explanation for this phenomenon. The difficulty lies in several reasons such as low sensitivity of the analytical methods [25], enrichment of aluminium by framework desilication [26], chemical decomposition of highly dealuminated framework parts [27], formation of 29 Si MAS NMR sensitive aluminium-rich aluminosilicates [28], or corrosion of the zeolite crystal under action of the alkaline solution [29]. Possible effect of the EFSi admixtures has been not considered thereby absolutely.…”

Section: Introductionmentioning

confidence: 99%

Reactivity of Extra‐framework Species of USY Zeolites in Alkaline Medium

Lutz

Bertram

Heidemann

et al. 2010

Zeitschrift anorg allge chemie

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Zeolites of type USY (ultra-stable Y) were obtained by steaming of NH 4 NaY modification. Samples were modified by subsequent alkaline treatment in KOH solution. USY and USY-KOH were characterised by chemical element analysis, XRD, IR, 29 Al and 29 Si MAS NMR spectroscopic measurements. Correct silicon to aluminium ratios (Si/Al) were determined by XRD and IR (double ring vibration w DR ) data whereas values calculated according to data of 29 Si MAS NMR and IR spectroscopy (asymmetrical TOT valence vibration w TOT ) appeared to be too high. In the latter case, the signals of the zeolite framework were strongly superimposed by that of extra-framework silica gel (EFSi) formed dur-* Dr. W. Lutz E-Mail: lutz@btu-lc.fta-berlin.de [a] 75 ing steaming. It was found that alkaline leaching induces desilication of silicon-rich area of the zeolite framework and partial dissolution of EFSi. Silicate ions of both react with likewise dissolved extra-framework aluminium (EFAl) to form X-ray amorphous aluminosilicate. Consequently, the superposition of the 29 Si MAS NMR signals of the zeolite framework by silica gel was reduced for Q 4 (0Al) but increased for Q 4 (2Al) and Q 4 (3Al) structure units. A reinsertion of EFAl into the zeolite framework has not been observed.

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“…Among these methods, hydrothermal treatment is one of the most promising and sole industrialized methods. In this method, high-temperature steam reacts with the framework aluminum to produce Al(OH) x which will remain inside the pores [15]. The modified USY zeolite not only provide mesopores but also appropriate amount of Brønsted acid sites.…”

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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A reexamination of the hypothesis of Breck and Skeels concerning the reinsertion of aluminum in the framework of dealuminated Y zeolites

Cited by 26 publications

References 5 publications

Zeolite Y: Synthesis, Modification, and Properties—A Case Revisited

Zeolite Y: Synthesis, Modification, and Properties—A Case Revisited

Reactivity of Extra‐framework Species of USY Zeolites in Alkaline Medium

Modification of USY zeolites with malic–nitric acid for hydrocracking

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