Influence of Autoclave Liner on Polyethylene Hydrogenolysis Selectivity

Hydroconversion reactions have gained traction in recent years as promising low-temperature alternatives to pyrolysis for the catalytic conversion/upcycling of waste polyolefins. Over 70 studies have been published in this growing field since 2019, but not all details of reactor design in these reactions have been studied. Herein, we demonstrate that the use of an autoclave liner─a common setup choice─can have a profound impact on reaction dynamics and product selectivity in polyethylene hydrogenolysis. While relative gas and liquid product yields were similar, the addition of a commercial glass autoclave liner artificially shifted the product distribution at all reaction times tested. 24 h reactions without a liner resulted in liquid hydrocarbon distributions with a maximum at C10, while reactions with a liner resulted in a C20 maximum. We hypothesize that alkanes condense and become trapped between the walls of the reactor and the liner, physically separated from the catalyst, which creates an effect akin to reactive product separation and slows further cracking. The effect was minimized by reducing the liner diameter. This study suggests that autoclave liners may have an important influence on product distribution and should be used with caution. When utilized, precise measurements should be reported.