Probing β-alkyl elimination and selectivity in polyolefin hydrogenolysis through DFT

Polyolefin waste is constantly growing, and the few existing solutions for recycling, reuse, and degradation are not viable long term. Carbon-carbon bond scission is a highly sought-after technology to assist in reclaiming polymers. This work compiles and advances the understanding of beta-alkyl elimination, a method of C-C cleavage, through DFT characterization on a model substrate, (S)-2,8-dimethyldecane, and silica-supported Zr-H catalyst, [( SiO)(3)ZrH]. The primary goal is to examine selectivity in C-C bond cleavage events. sigma-Bond metathesis favors C-H activation at methyl branches by similar to 2 kcal mol(-1). Chain walking via beta-H elimination and insertion occurs readily and prefers E-alkene eliminations. beta-Alkyl elimination also favors formation of E-alkene elimination products (similar to 2 kcal mol(-1)), beta-Me elimination (similar to 1 kcal mol(-1)), and primary Zr-C cleavage (similar to 2 kcal mol(-1)) over Z-alkenes, beta-R (R > CH3) elimination, and secondary Zr-C cleavage, respectively. These selectivity rules will help guide future experimental work and catalyst design.