Effects of Pretreatment Conditions and Branched Alkanes on Mo/MCM-41 Catalysts in Tandem Alkane Cross-metathesis for Non-hydrogen Polyolefin Recycling

Abstract Chemical plastic recycling has emerged as a crucial approach for advancing carbon neutrality by mitigating CO 2 emissions linked to further fossil fuel extraction. However, with most hydrogen currently sourced from fossil fuels, there is growing interest in non-hydrogen chemical recycling pathways. This study explores the degradation of heavy hydrocarbons through tandem alkane cross-metathesis (TACM), employing MoO x /MCM-41 as the olefin metathesis catalyst, which demonstrates high reactivity and stability. Despite these advantages, we observed that Mo migration during pretreatment leads to catalytic deactivation in the tandem system, presenting a significant challenge. To counter this, we developed a two-step pretreatment protocol that effectively mitigates Mo migration across different supports, thus enhancing overall catalyst performance. In addition, we discovered that the presence of branched products adversely impacts the TACM system, contrasting with their promotional behavior in traditional olefin metathesis processes. The MoO x /MCM-41 + Pt/Al 2 O 3 catalyst system, operating at 250–300 °C, efficiently reduced the molecular weight of polyethylene, highlighting its potential for non-hydrogen chemical recycling applications.