Hydrocarbon-Induced Agglomeration of Pd Particles in Pd/HZSM-5

Theoretical Studies of the Coordination and Stability of Divalent Cations in ZSM-5

“…It has been proposed that metal cations can form µ-bridged metal-oxo dimers, [M-O-M] 2+ . 21,22,[24][25][26][27][28]37,[30][31][32][33]36 To assess the stability of such dimers, calculations were performed for the following reaction (see Figure 5): …”

“…There is also a growing body of evidence suggesting the presence of dimer cations in which two M 2+ cations are bridged by an O atom or two M 3+ cations are bridged by two O atoms. [21][22][23][24][25][26][27][28][29][30][31][32][33][34][35] Such structures can be represented by Z -[M(O)M] 2+ Z -and Z -[M-(O) 2 M] 2+ Z -. The experimental evidence also indicates that M 2+ cations can be reduced to form small metal particles or can react with oxygen and water to form metal oxide particles.…”

WOx‐CeO2 and WOx‐Nb2O5 catalysts deactivation during hexane isomerization

“…The runs were conducted in a stream of helium (99.99% purity, from Belgair). The reactant-loaded samples (typically 75 mg) were heated from ambient temperature to 1073 K at a heating rate of 278 K min 21 , with a plateau of 30 min at the final temperature, and then cooled at 323 K. Soon after, the thermal cycle was . Pure samples were placed inside a commercial controlled environmental chamber attached to a diffuse reflectance accessory (Smart collector).…”

“…Pure samples were placed inside a commercial controlled environmental chamber attached to a diffuse reflectance accessory (Smart collector). The stability of the adsorbed ammonia species during the increase of temperature was investigated by recording the spectra under flowing helium (30 ml min 21 ) at room temperature, 373, 473, and 573 K, after exposure to an ammonia flow (30 ml min…”

“…The enhanced stability of these catalysts was associated to the formation of a proton bridge between transition metal and cage as the base of the anchoring phenomena which stabilizes small metal particles. 21 …”