Hydrothermally resistant high-silica Y zeolites stabilized by covering with non-framework aluminum species

Lutz, W.; Geßner, W.; Bertram, R.; Pitsch, I.; Fricke, R.

doi:10.1016/s0927-6513(97)00070-9

Cited by 56 publications

(71 citation statements)

References 9 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Mixed silica–alumina, such as amorphous silica–alumina, mesoporous aluminosilicates, and zeolites, are generally affected by two different hydrolysis pathways:14, 60–62 The hydrolysis of SiOAl bonds (dealumination) is proton‐catalyzed, whereas siloxane‐bond cleavage is catalyzed by hydroxyl ions 14. 22 Typically, siloxane hydrolysis is not observed during steaming at elevated temperatures (i.e., 400–600 °C) because the reverse reaction, dehydroxylation, is favored under these conditions 63.…”

Section: Discussionmentioning

confidence: 99%

Stability of Amorphous Silica–Alumina in Hot Liquid Water

et al. 2013

View full text Add to dashboard Cite

Herein, the hydrothermal stability of amorphous silica-alumina (ASA) is investigated under conditions relevant for the catalytic conversion of biomass, namely in liquid water at 200 °C. The hydrothermal stability of ASA is much higher than that of pure silica or alumina. Interestingly, the synthetic procedure used plays a major role in its resultant stability: ASA prepared by cogelation (CG) lost its microporous structure, owing to hydrolysis of the siloxane bonds, but the resulting mesoporous material still had a considerable surface area. ASA prepared by deposition precipitation (DP) contained a silicon-rich core and an aluminum-rich shell. In hot liquid water, the latter structure was transformed into a layer of amorphous boehmite, which protected the particle from further hydrolysis. The surface area showed relatively minor changes during the transformation. Independent of the synthetic method used, the ASAs retained a considerable concentration of acid sites. The concentration of acid sites qualitatively followed the changes in surface area, but the changes were less pronounced. The performance of different ASAs for the hydrolysis of cellobiose into glucose is compared.

show abstract

Section: Discussionmentioning

confidence: 99%

Stability of Amorphous Silica–Alumina in Hot Liquid Water

et al. 2013

View full text Add to dashboard Cite

show abstract

“…Using such an approach, high-silica zeolites may be stabilized against a hydrothermal or alkaline attack [93]. Lutz et al [102] reported in detail on the external introduction of extraframework sodium aluminosilicate species through an alkaline and combined acid/alkaline pathways using sodium aluminate as well as aluminium-oxo-hydroxo cations [103] or (Al, SiO ) species into faujasite type zeolite [104]. Alumination in solutions of sodium or potassium aluminate was reported also for other high-silica zeolites such as silicalite [105], MCM-41 [106], and zeolite Beta [107].…”

Section: Origin Of Siliceous Extraframework Species Zeolitementioning

confidence: 99%

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

Lutz

2014

Advances in Materials Science and Engineering

142

View full text Add to dashboard Cite

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.

show abstract

“…29 Furthermore, a protective layer of aluminosilicate is possibly formed during the initial hydrolysis, which may protect the mesostructure from further hydrolysis. 32 The improvement of the hydrothermal stability may protect the mesoporous structure of the catalyst from collapse, which ensured the high dispersion of Pd particles on the support and the free diffusion of organic molecules in the pore channels. Thus, the Pd/Ph-Al-MCM-41 retained its excellent activity and selectivity for a long time.…”

Section: Activity Testmentioning

confidence: 99%