Tris(2-Aminoethyl)Amine/Metal Oxides Hybrid Materials—Preparation, Characterization and Catalytic Application

Abstract

Three different metal oxides (basic MgO, basic-acidic Al2O3 and acidic-basic Nb2O5) characterized by comparable surface areas (MgO—130 m2/g; Al2O3—172 m2/g and Nb2O5—123 m2/g) and pore systems (domination of mesopores with narrow pore size distribution) were modified with tris(2-aminoethyl)amine (TAEA) via two methods: (i) direct anchoring of amine on metal oxide and (ii) anchoring of amine on metal oxide functionalized with (3-chloropropyl)trimethoxysilane. The obtained hybrid materials were characterized in terms of effectiveness of modifier anchoring (elemental analysis), their structural/textural properties (nitrogen adsorption/desorption, XRD), acidity/basicity of support (2-propanol dehydration and dehydrogenation, dehydration and cyclization of 2,5-hexanedione), states of modifier deposited on supports (XPS, FTIR, UV–VIS) and the strength of interaction between the modifier and the support (TG/DTG). It was evidenced that acidic-basic properties of metal oxides as well as the procedure of modification with TAEA determined the ways of amine anchoring and the strength of its interaction with the support. The obtained hybrid materials were tested in Knoevenagel condensation between furfural and malononitrile. The catalysts based on MgO showed superior activity in this reaction. It was correlated with the way of TAEA anchoring on basic MgO and the strength of modifier anchoring on the support. To the best of our knowledge tris(2-aminoethyl)amine has not been used as a modifier of solid supports for enhancement of the catalyst activity in Knoevenagel condensation.

Catalysis by Hybrid Nanomaterials

“…Organic-inorganic hybrid nanomaterials nowadays represent the most intensively explored class of hybrids. One example of such hybrid systems has been reported recently [ 2 ]. Three types of metal oxides (basic MgO, basic-acidic Al 2 O 3 , and acidic-basic Nb 2 O 5 ) with mesopores were modified with tris(2-aminoethyl)amine via two methods: (i) direct anchoring of amine onto the metal oxide surface and (ii) anchoring of amine on metal oxide functionalized with (3-chloropropyl)trimethoxysilane.…”

“…(1) Each component of the hybrid system itself has a highly organized structure at the molecular and nanoscale level, and the combination of components leads, in turn, to an additionally organized nanostructure constructed from two or more structures of components. (2) The components of the hybrid system interact with each other to form a chemical structure. (3) The properties of the hybrid system are determined by the set of properties of the components, while their additivity and synergy may result in new properties that were not observed in the original components.…”