Hydrothermal crystallization of clathrasils in acidic medium: Energetic aspects

Acidic properties of Al-rich ZSM-5 crystallized in strongly acidic fluoride medium

“…20 We have recently demonstrated the synthesis and morphology control methods for silicalite-1, highsilica ZSM-5, and some other microporous silicate materials in the pH range of 2~5. [20][21][22][23] However, it is difficult to incorporate active catalytic metals whose oxo-anions have higher isoelectronic points (IEP) in the neutral and acidic fluoride medium framework. Unfortunately, Al as one of the most common framework elements in zeolites, is hardly to be incorporated under acidic conditions since the aluminate ion has pHIEP = 7.7.…”

Acidic medium synthesis of zeolites – an avenue to control the structure-directing power of organic templates

“…Recently we have demonstrated that the chemical field for the hydrothermal crystallizations of silicalite-1 21,22 and some other zeolite-type tectosilicate materials 23 can be extended from the conventional basic and near-neutral conditions to the strongly acidic region. Besides elaborating on the unique structural and surface-chemical properties of the zeolite products obtained in the acidic media, we have also predicted the possibility of discovering new OSDAs that do not work under basic conditions but become feasible in the extended chemical field.…”

A Six-Membered Ring Molecular Sieve Achieved by a Reconstruction Route

“…As estimated from theoretical simulation, zeolite molecular sieves with 6-MRs could be good candidates for adsorption and separation of small molecules such as water, but conventional synthesis of these zeolites was always performed in the presence of organic templates and/or inorganic cations. − Currently, 19 types of 6-MRs molecular sieves have been confirmed by the IZA commission . Due to the small micropore size of 6-MRs, the removal of organic templates and/or inorganic cations from these zeolites was almost impossible. , Therefore, the occupancy of organic templates and/or inorganic cations in the micropores of these zeolites with 6-MRs would greatly reduce the micropore volume and even block the window of micropores, which significantly hinders the sorption of small molecules. − …”

“…Zeolite molecular sieves have been widely used in catalysis, ion-exchange, adsorption, and separation. − Normally, zeolite molecular sieves are ranged from small pores (eight-membered rings, 8-MRs) − to extra-micropores (beyond 12-MRs). − Currently, it is generally considered that zeolite molecular sieves less than 8-MRs (e.g., 6-MRs) are nonporous, which have no molecular sieve properties. − …”