Polystyrene Hydrogenolysis to High-Quality Lubricants Using Ni/SiO₂

Journal Article · 26 March 2024 · ACS Catalysis

DOI: https://doi.org/10.1021/acscatal.3c05900 · OSTI ID:2448597

Vance, Brandon C.  ^[1]; Najmi, Sean  ^[2]; Vlachos, Dionisios G.  ^[2]

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1. University of Delaware, Newark, DE (United States); University of Delaware
2. University of Delaware, Newark, DE (United States)

Pyrolytic and light-activated oxidation processes are leading technologies for utilizing polystyrene (PS) wastes. These approaches exhibit poor selectivities, use complex reactors, and require solvents. Hydrogenolysis is effective for deconstructing polyolefins, but its application to PS feedstocks has been limited. Herein, we demonstrate Ni/SiO₂ catalysts to facilitate PS (M_w ≈ 97 kDa) hydrogenolysis to produce lubricant base oils possessing group IV properties, achieving maximum yields of 70% within 6 h at 300 °C and 70 bar of H₂. Gas, liquid, and oil product yields are stable across reaction conditions, whereas hydrogenation of the PS aromaticity and reduction of the molecular weight benefit from higher temperatures and H₂ pressures. Time-dependent experiments underscore the importance of elevated H₂ pressure, revealing that PS hydrogenolysis occurs sequentially, with aromatic ring hydrogenation preceding degradation of the C–C backbone. Kinetic measurements with 1,2-diphenylethane as a probe molecule demonstrate that ring hydrogenation pis 3 orders of magnitude faster than internal C–C bond cleavage over Ni/SiO₂. Ni/SiO₂ proves to be effective in the hydrogenolysis of heavier PS polymers and rigid commercial PS products. Conversely, flexibility and foam PS feeds result in Ni/SiO₂ deactivation, attributed to performance additives. Unlike polyolefins, the process produces very little methane and other light hydrocarbons. Furthermore, these findings expand the applicability of hydrogenolysis to PS feedstocks, offering a versatile solution and broadening the range of high-value products from PS to include lubricant base oils.

• Research Organization: University of Delaware, Newark, DE (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES); National Science Foundation (NSF)
• Grant/Contract Number: SC0021166
• OSTI ID: 2448597
• Journal Information: ACS Catalysis, Journal Name: ACS Catalysis Journal Issue: 7 Vol. 14; ISSN 2155-5435
• Publisher: American Chemical Society (ACS)Copyright Statement
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
Earth-abundant metals
aromatic
catalysts
compounds
hydrocarbons
hydrogenolysis
lipids
lubricants
nickel
plastic waste
redox reactions