A facile organic-free synthesis of high silica zeolite Y with small crystal in the presence of Co2+

An anion-promoted increase of the SiO2/Al2O3 ratio of zeolites

“…13–18 Considerable efforts have been made to increase the SiO 2 /Al 2 O 3 ratio of zeolites and several strategies have been developed so far involving: (1) control of the SiO 2 /Al 2 O 3 ratio in the reaction mixture; 19–21 (2) dealumination of zeolites via post-treatment, including hydrothermal steaming and chemical leaching such as acids, salts, chelating agents, SiCl 4 or other halides and the combination of both the methods; 22–29 (3) use of organic structure-directing agents, especially those with a high C/N ratio or low charge density 16,17,30–34 and (4) introduction of hydroxyl radicals (·OH) or metal ions. 35,36 For example, an ultrastable Y zeolite (USY) widely used as a fluid catalytic cracking catalyst is usually prepared via the high-temperature hydrothermal steaming of NH 4 Y with a low SiO 2 /Al 2 O 3 ratio. 37 However, the post-treatment methodology has several drawbacks such as causing a significant decrease of the crystallinity of zeolites, requiring the NH 4 + or H + -form of zeolites achieved by multiple cycles of the ion-exchange process or involving corrosive chemicals such as SiCl 4 .…”

“…Very recently, it was reported that the introduction of Co 2 + during the synthesis can also increase the SiO 2 /Al 2 O 3 ratio of zeolite Y from 5.2 to 6.15. 36 However, the generality of these methods is under verification.…”

Strategy for the synthesis of zeolite Y by artificial-fish-reef breeding negative crystals

“…It is generally agreed that the thermal stability of zeolite decreases with the decrease in the zeolite crystal size. 20,35 However, NaY-CPAM zeolite is an exception. The specific results were as follows.…”

“…[46][47][48] The dealkylation of bulk molecular 1,3,5-triisopropylbenzene (TIPB) is often used to evaluate the catalytic properties of catalysts with different crystal sizes. 11,20,35 The results for the catalytic cracking of TIPB for USY-CPAM and USY-Contrast zeolites are listed in Fig. 11b.…”

“…The nucleation/crystallization rate also can be accelerated by enhancing the alkalinity of gel system, but a lower framework Si/Al ratio is inevitable, which is bad for the thermal stability of the Y zeolite. [18][19][20] Therefore, the efficient synthesis of NaY zeolite remains a huge challenge. Any new information concerning zeolite formation will thus be a benefit to understand the crystalline mechanism and to aid designing novel synthetic routes.…”