EU-7 zeolite: a synthetic BIK type zeolite with high hydrothermal stability

Abstract

EU-7 zeolite with Si/Al ratio of 15 is identified as a BIK type zeolite. The framework charge is compensated with Cs+ cations located in 8-ring channels at regular distances. Even partially exchanged, Cu-loaded EU-7 is active in NH3-SCR and withstands hydrothermal aging at 900 °C needed for application in diesel particulate filters.

Selective catalytic reduction of NOx with ammonia (NH3-SCR) over copper loaded LEV type zeolites synthesized with different templates

“…During low temperature operation, NH 4 NO 3 can accumulate on the catalyst, subsequently forming N 2 O by thermal decomposition during high temperature excursion (eqn (5)). 13 Other undesirable side reactions occurring at temperatures above 300 1C, are NH 3 oxidation to N 2 or NO x , (eqn ( 6) and ( 7)). NH 3 -SCR catalysts also need to withstand exhaust gas temperatures as high as 900 1C when the engine is working under high load conditions.…”

“…NH 3 -SCR catalysts also need to withstand exhaust gas temperatures as high as 900 1C when the engine is working under high load conditions. 13 One of the possibilities for the application of NH 3 -SCR in diesel exhaust after treatment is its implementation in a diesel particulate filter (DPF), again inducing temperature to rise during periodic regeneration above 650 1C. 14…”

“…24,32 Alternative framework types like BIK are attractive, especially with respect to hydrothermal stability. 13 Other zeolite types like LTA, 33,34 RHO, 35 AEI, 36 KFI, 37 UFI, 34 AFX 38 depending on how they are prepared, are promising as well.…”

Structural parameters governing low temperature activity of small pore copper zeolites in NH3-SCR

“…The limited pore diameter is another advantage of small pore zeolites since it limits the adsorption of hydrocarbons, which could ignite under high temperature conditions leading to thermal damage to the zeolite. The introduction of the copper loaded CHA zeolite triggered a more general interest in small pore aluminosilicate zeolite types such as AEI and AFX [3,8]It led to a quest for hydrothermally robust zeolites withstanding hydrothermal aging up to 900 °C, a property of among others the BIK type zeolite [9]. At this moment, the key zeolite features needed for the high catalytic activity and hydrothermal stability are highly debated topics.…”

“…At this moment, the key zeolite features needed for the high catalytic activity and hydrothermal stability are highly debated topics. It has been shown that alkali and earth alkaline cations ion exchanged into the zeolite can play a role in the activity and hydrothermal stability of a zeolite catalyst in NH3-SCR [9,10]. The location of Cu 2+ ions in the pores of zeolite catalysts, the copper speciation and formation of dimers and clusters is intensively investigated.…”