Structure-activity relationship in hydrogenolysis of polyolefins over Ru/support catalysts

We scrutinized the effect of supports (types and calcination temperatures) in Ru/support catalysts in the hydrogenolysis of low-density polyethylene and found that zirconia-supported Ru (Ru/ZrO2) with high-temperature (1073 K) calcined ZrO2 was an effective and reusable catalyst, showing about 3-fold higher activity on catalyst amount basis than the previously reported Ru/CeO2 catalyst with similar selectivites. The catalyst was applicable to the reactions of various polyolefins including high-density polyethylene and polypropylene. Experimental studies and catalyst characterizations such as TPR, XRD, TEM and XAS with various Ru/ZrO2 and reference catalysts such as Ru/CeO2, Ru/SiO2 and Ru/γ-Al2O3 showed good correlations between the Ru particle sizes and catalytic performance in Ru catalysts except for Ru/γ-Al2O3: The catalyst with a moderate size of ~2.5 nm Ru particles provided the highest conversion. The activity per surface Ru metal was higher at larger Ru particle sizes. The selectivity to cheap gas products was low at middle to small Ru particle sizes (1–7 nm), but high at large Ru particles (>7 nm).