Highly Selective Conversion of Polyolefins to Methane via Mechanochemical Hydrogenolysis

Abstract

Hydrogenolysis of polyolefin waste into value-added fuels remains challenging. The main barriers are the chemical inertness of C−C and C−H bonds and the lack of selective cleavage sites. Traditional hydrogenolysis methods often rely on harsh conditions (200–450 °C, 10–50 bar hydrogen) and noble-metal catalysts (Pt and Ru) and produce broad alkane mixtures. Here, we report a mechanochemical hydrogenolysis strategy for direct conversion of polyolefin plastics into methane (CH4). The process uses inexpensive iron (Fe) powder as the catalyst, with the jar temperature as low as 30 °C under 3–9 bar H2. Under laboratory conditions, compared with the thermochemical route, the mechanochemical method increases the CH4 yield rate by orders of magnitude. The gas-phase hydrocarbon yield is 43-fold higher than in the thermochemical route, and CH4 selectivity increases from 65.7 to 98.7 vol %. This performance enhancement may be associated with the generation of high-density defects during mechanochemical treatment. This work leverages low-cost Fe catalyst to facilitate the upcycling of polyolefin waste into energy product, thereby mitigating the environmental problem caused by plastic pollution.