TY - JOUR
T1 - Role of Bifunctional Ru/Acid Catalysts in the Selective Hydrocracking of Polyethylene and Polypropylene Waste to Liquid Hydrocarbons
AU - Rorrer, Julie
AU - Ebrahim, Amani
AU - Questell-Santiago, Ydna
AU - Zhu, Jie
AU - Troyano-Valls, Clara
AU - Asundi, Arun
AU - Brenner, Anna
AU - Bare, Simon
AU - Tassone, Christopher
AU - Beckham, Gregg
AU - Roman-Leshkov, Yuriy
PY - 2022
Y1 - 2022
N2 - Hydrogenolysis of C-C bonds over Ru-based catalysts has emerged as a deconstruction strategy to convert single-use polyolefin waste to liquid alkanes at relatively mild conditions, but this approach exhibits limitations, including methane formation resulting from terminal C-C bond scission. In this study, a variety of catalysts were investigated for the reductive deconstruction of polyethylene (PE) and polypropylene (PP) to identify supports that promote nonterminal C-C bond scission. We found that Ru nanoparticles supported on Brønsted-acidic zeolites with the faujasite (FAU) and Beta (BEA) topologies were highly active for the cleavage of C-C bonds in PE and PP, exhibiting improved liquid yields and suppressed methane formation. For the deconstruction of PE, supporting ruthenium nanoparticles (5 wt %) on FAU increased the yields of liquid alkanes to 67% compared to 33% over an inert silica support (5 wt % Ru/SiO2) at 200 degrees C, 16 h, under 30 bar of H2. A dramatic selectivity enhancement toward liquid hydrocarbons was also observed for PP over Ru/FAU and Ru/BEA compared to Ru/SiO2. To understand the origin of this selectivity improvement, a combination of ex situ and operando characterization techniques were used to reveal that both catalyst structure and acidity play key roles in PE and PP conversion. Operando X-ray absorption spectroscopy studies with model polyolefins over Ru-supported catalysts with varying acidity levels revealed that the local chemical environment of Ru[0] during the reaction is consistent across multiple acidic supports, although the onset of reduction during synthesis of the nanoparticles varies across different supports. These results, combined with reactivity data, demonstrate the importance of the acid-noble metal cooperativity in promoting selective C-C bond scission toward liquid alkanes that shifts the mechanism from hydrogenolysis to ideal hydrocracking.
AB - Hydrogenolysis of C-C bonds over Ru-based catalysts has emerged as a deconstruction strategy to convert single-use polyolefin waste to liquid alkanes at relatively mild conditions, but this approach exhibits limitations, including methane formation resulting from terminal C-C bond scission. In this study, a variety of catalysts were investigated for the reductive deconstruction of polyethylene (PE) and polypropylene (PP) to identify supports that promote nonterminal C-C bond scission. We found that Ru nanoparticles supported on Brønsted-acidic zeolites with the faujasite (FAU) and Beta (BEA) topologies were highly active for the cleavage of C-C bonds in PE and PP, exhibiting improved liquid yields and suppressed methane formation. For the deconstruction of PE, supporting ruthenium nanoparticles (5 wt %) on FAU increased the yields of liquid alkanes to 67% compared to 33% over an inert silica support (5 wt % Ru/SiO2) at 200 degrees C, 16 h, under 30 bar of H2. A dramatic selectivity enhancement toward liquid hydrocarbons was also observed for PP over Ru/FAU and Ru/BEA compared to Ru/SiO2. To understand the origin of this selectivity improvement, a combination of ex situ and operando characterization techniques were used to reveal that both catalyst structure and acidity play key roles in PE and PP conversion. Operando X-ray absorption spectroscopy studies with model polyolefins over Ru-supported catalysts with varying acidity levels revealed that the local chemical environment of Ru[0] during the reaction is consistent across multiple acidic supports, although the onset of reduction during synthesis of the nanoparticles varies across different supports. These results, combined with reactivity data, demonstrate the importance of the acid-noble metal cooperativity in promoting selective C-C bond scission toward liquid alkanes that shifts the mechanism from hydrogenolysis to ideal hydrocracking.
KW - bifunctional catalyst
KW - depolymerization
KW - hydrocracking
KW - hydrogenolysis
KW - plastic upcycling
KW - polyethylene
KW - polypropylene
KW - ruthenium
UR - http://www.scopus.com/inward/record.url?scp=85141470040&partnerID=8YFLogxK
U2 - 10.1021/acscatal.2c03596
DO - 10.1021/acscatal.2c03596
M3 - Article
SN - 2155-5435
VL - 12
SP - 13969
EP - 13979
JO - ACS Catalysis
JF - ACS Catalysis
IS - 22
ER -