Abstract
Trineopentyl zirconium grafted on silica reacts with molecular oxygen at room temperature leading to the formation of alkoxy derivatives. Upon heating at 200
°C, these alkoxy species evolve to carboxylates. These results explain the sorption modifications of mordenite modified by trineopentyl zirconium when kept under air.
The organometallic complex SiOZr(CH
2C(CH
3)
3)
3 was synthesized on the surface of silica dehydroxylated at 500
°C and its reactivity towards oxygenated molecules was studied. The materials were characterized by IR,
13
C
CP-MAS NMR, analysis of evolved gases and elemental analysis. Reaction with neopentyl alcohol ((CH
3)
3CCH
2OH) leads to the quantitative formation of SiOZr(OCH
2C(CH
3)
3)
3. Similarly, reaction with pivalic acid ((CH
3)
3CCOOH) leads to the quantitative formation of SiOZr(OCOC(CH
3)
3)
3. Addition of dry oxygen at 25
°C to SiOZr(CH
2C(CH
3)
3)
3 leads to the formation of SiOZr(OCH
2C(CH
3)
3)
3. When heated at 200
°C under oxygen, the alkoxy ligands transform into carboxylate species ((CH
3)
3CCOO)
− probably coordinated to zirconium. These results, together with molecular modelling studies of the adsorption of hydrocarbons on mordenite modified by such complexes, explain the different behaviours observed in presence of air or inert gases.