Potassium-directed sustainable synthesis of new high silica small-pore zeolite with KFI structure (ZJM-7) as an efficient catalyst for NH3-SCR reaction

Selective catalytic reduction of NOx with NH3: opportunities and challenges of Cu-based small-pore zeolites

“…The Cu ion-exchanged KFI catalyst showed good NH 3 -SCR activity and HTS, which, however, was still inferior to that of Cu-SSZ-13 [ 111 ]. Nevertheless, Han et al synthesized high-silica Cu-KFI with Si/Al > 5 by only using K + as a directing agent, which is more sustainable for zeolite synthesis [ 112 ]. Importantly, the high-silica Cu-KFI showed excellent HTS and maintained NO x conversion of ∼57% at 200°C even after HTA at 800°C [ 112 ].…”

“…Nevertheless, Han et al synthesized high-silica Cu-KFI with Si/Al > 5 by only using K + as a directing agent, which is more sustainable for zeolite synthesis [ 112 ]. Importantly, the high-silica Cu-KFI showed excellent HTS and maintained NO x conversion of ∼57% at 200°C even after HTA at 800°C [ 112 ]. Cu-SSZ-50 with the RTH structure, which has 2D channels with aperture sizes of 0.41 nm × 0.38 nm (8MRs) and 0.56 nm × 0.25 nm (distorted 8MRs), also showed comparable NH 3 -SCR activity but relatively low hydrothermal stability [ 113 , 114 ].…”

Organotemplate-free synthesis of Al-rich ZSM-35 and ZSM-22 zeolites with the addition of ZSM-57 zeolite seeds

“…In the past decade, an organotemplate-free route for synthesizing zeolites has been successfully developed by adding a small amount of zeolite seeds into the starting gel, which could solve the above shortcomings caused by the use of organic templates. A number of zeolites have been successfully synthesized through this novel seed-assisted route without the addition of organic templates, such as beta, 13,14 MCM-68, 15 ZSM-23, 16 KFI, 17 and MCM-49, 18 resulting in the reduction of economic cost and polluted wastes. It is worth noting that the structure of the obtained zeolite products is always the same as that of the zeolite seeds added into the starting gel, which is designated as seed-directed synthesis with homonuclear features generally.…”

Fluoride-free synthesis of beta zeolite with enrichment of polymorph B from a solvent-free route

“…Zeolites with well-defined micropores have been widely employed in fields of catalysis, ion-exchange, adsorption, and separation due to their high surface area, large pore volume, and excellent stabilities. 1–15 Currently, there are over 250 zeolites confirmed by the Structure Commission of the International Zeolite Association. 16 Among them, about 20 zeolites have been used for practical applications, and one of the most important zeolites is beta zeolite.…”