Synthesis of heterogeneous metathesis catalysts for the development of sustainable processes

Abstract

In recent decades, it has been tried to develop processes that involve the use of catalysts that can be recovered from the reaction medium, to make them green and sustainable. Approximately, 90 % of all processes in chemistry and petrochemicals use heterogeneous catalysts. In this sense, the supported heterogeneous catalysts present advantages in the purification of the products and the reduction of costs. In the present work, the synthesis of a new heterogeneous supported catalyst, highly active in the metathesis reaction, based on a ruthenium-alkylidene complex, was carried out. The new catalyst was obtained by anchoring of dichloro[1,3-bis(2,4,6-trimethylphenyl)-2-imidazolidinylidene](benzylidene)(tricyclohexylphosphine)ruthenium (II) (second generation Grubbs) in various silylated polymeric gels, based on 2-norbornene-5,6-dicarboxylic anhydride (NDA) and cis-cyclooctene (CO) cross-linked with various percentages of 3-aminopropyltriethoxysilane (APTES) (5%, 15%, 100%). The new heterogeneous catalyst was successfully used in the depolymerization reaction via metathesis of natural rubber from Oaxaca (HNO), using 1-octene as CTA; observing the formation of liquid oligomers, achieving a decrease in molecular weight from 137.941 g/mol to 297 g/mol; proving, in this way, its high effectiveness.