Cage-based small-pore catalysts for NH3-SCR prepared by combining bulky organic structure directing agents with modified zeolites as reagents

Abstract

Cage-based small-pore catalysts for NH3-SCR prepared by combining bulky organic structure directing agents with modified zeolites as reagents.

Building Zeolites from Precrystallized Units: Nanoscale Architecture

“…have reported the interzeolite transformation of two zeolites with large cavity sizes,E RI and AFX, by using abulky polycyclictemplate (Figure 15). [77] The sizes of the bulky polycyclic template (11.9 4.9 )f itted perfectly with that of the very large cavities (13 ), thus proving the excellent structure-directing role for stabilizing the ERI and AFX cavities.T he introduction of cationic copper and iron species within these ERI and AFX results in very active catalysts for the SCR of NOx with similar NO conversion profiles as well-stablished commercial metalcontaining SSZ-13 catalysts.…”

“…[86] However,these mesoporous materials show low hydrothermal stability and acidity,w hich severely limits their applicability in many industrial catalytic processes.T oo vercome these problems, the efficient preparation of mesoporous zeolites that would present simultaneously high hydrothermal stability,a cidity, and pore accessibility thanks to the crystalline frameworks combined with the presence of the mesopores,h as been Figure 15. [77] with permission from Elsevier. Reproduced from Ref.…”

Ultrafast synthesis of AFX-Type zeolite with enhanced activity in the selective catalytic reduction of NOx and hydrothermal stability

“…So far, several exible OSDAs have been employed for preparing SSZ-16, [43][44][45][46][47][48][49][50] but recently, a bulky OSDA with a rigid structure named TEBOP, oen involved in the synthesis of MSEtype zeolites, was introduced for the synthesis of SSZ-16. 43,44 However, it required at least 24 h for preparing the SSZ-16 using TEBOP in an autoclave and achieving it at a faster pace remained challenging because the degree of synthesis freedom offered by such small pore zeolites are quite narrow. 43,44 Extending the ultrafast synthesis approach, we were able to synthesize SSZ-16 (AFX-type) zeolite in 2 hours using sealed tubular reactor which would otherwise require several days.…”

“…43,44 However, it required at least 24 h for preparing the SSZ-16 using TEBOP in an autoclave and achieving it at a faster pace remained challenging because the degree of synthesis freedom offered by such small pore zeolites are quite narrow. 43,44 Extending the ultrafast synthesis approach, we were able to synthesize SSZ-16 (AFX-type) zeolite in 2 hours using sealed tubular reactor which would otherwise require several days. [45][46][47][48][49][50][51] The SSZ-16 from TEBOP bettered their DABCO counterpart with physio-chemical traits that are promising for enhanced SCR of NOx and in particular they were bestowed with excellent hydrothermal stability.…”

DeNOx Abatement over Sonically Prepared Iron-Substituted Y, USY and MFI Zeolite Catalysts in Lean Exhaust Gas Conditions

“…However, as has been noted elsewhere [ 4 ], Fe catalysts do not cause the formation of small amounts of nitrous oxide, as was detected over the copper catalyst even with negligible NO 2 feed content. Vy contrast with what is described in this publication, MFI and Y based zeolites and those containing small-pore zeolites may be considered as alternative ammonia SCR catalysts and, recently, have been exhaustively investigated [ 15 , 16 ]. It is considered easier to understand the activity-structure relationship and introduced metal active sites properties of the small-pore molecular sieves with a Chabazite (CHA) structure such as SSZ-13 and SAPO-34 [ 17 ].…”