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Effect of doping with nickel and copper on catalytic behaviour of wide‐pore zeolites with different pore structures
Author(s) -
Exner Herbert,
Fetting Fritz
Publication year - 1991
Publication title -
chemical engineering and technology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.403
H-Index - 81
eISSN - 1521-4125
pISSN - 0930-7516
DOI - 10.1002/ceat.270140308
Subject(s) - bifunctional , catalysis , mordenite , chemistry , inorganic chemistry , ion exchange , copper , platinum , metal , bifunctional catalyst , nickel , zeolite , ion , organic chemistry
The catalytic properties of wide‐pore zeolites, namely Ni‐ and Cu‐doped faujastie H‐Y and H‐mordenite (H‐M) are compared on the example of conversion of n ‐hexane. After thermal pretreatment of ion‐exchanged zeolites, reduction with hydrogen ( P H 2≤ 40 bar) leads to a large number of metallic clusters and crystallites as well as ionic species in the zeolites. Notwithstanding this variety, the different types of catalysts can be divided into three classes: classical bifunctional catalysts (for example NiHM, NiHY) with ion exchange degrees > 30%, monofunctional catalysts, such as CuHM and CuHY with high copper contents (ion exchange degree > 40%) and metal‐doped (Ni and Cu) zeolites which, depending on the conditions of pretreatment, act as bifunctional and/or monofunctional compounds and, therefore, show very unstable reaction behaviour. In addition to the extent of reduction, the cation distribution affects the activity and deactivation behaviour and, to a lesser extent, the product selectivity. The reaction mechanism of bifunctional catalysis is similar to that observed in platinum‐doped catalysts, while the mechanism of monofunctional catalysis resembles the process on undoped zeolites.