A reusable, impurity-tolerant and noble metal–free catalyst for hydrocracking of waste polyolefins

Abstract

One-step conversion of low-purity polyolefins to value-added products without pretreatments represents a great opportunity for chemical recycling of waste plastics. However, additives, contaminants, and heteroatom-linking polymers tend to be incompatible with catalysts that break down polyolefins. Here, we disclose a reusable, noble metal–free and impurity-tolerant bifunctional catalyst, MoS x -Hbeta, for hydroconversion of polyolefins into branched liquid alkanes under mild conditions. The catalyst works for a wide scope of polyolefins, including different kinds of high–molecular weight polyolefins, polyolefins mixed with various heteroatom-linking polymers, contaminated polyolefins, and postconsumer polyolefins with/without cleaning under 250°C and 20 to 30 bar H 2 in 6 to 12 hours. A 96% yield of small alkanes was successfully achieved even at a temperature as low as 180°C. These results demonstrate the great potentials of hydroconversion in practical use of waste plastics as a largely untapped carbon feedstock.

Polystyrene Hydrogenolysis to High-Quality Lubricants Using Ni/SiO2

“…However, there is not a clear trend between AAR and molecular weight as the PS5300 oil’s AAR is comparable to that of the PS35 oils while the PS6000 oil’s AAR is ∼50% lower than the latter two, demonstrating a lower activity for PS6000. The differences in the virgin PS reactivities could stem from molecular weight, architecture, or viscosity, , and slip agents or other performance additives may be present and inhibit the deconstruction. , …”

“…The differences in the virgin PS reactivities could stem from molecular weight, architecture, or viscosity, 21,60 and slip agents or other performance additives may be present and inhibit the deconstruction. 17,25 Hydrogenolysis of commercial PS products (Figure 9c) shows a wide variability in reactivity. Rigid PS products (i.e., Petri dish and F-tube) produce clear, inviscid oils with high AARs, indicating significant hydrogenation and deconstruction (Figure 9d).…”

“…Chemical recycling is promising for the utilization of these wasted thermoplastics. Polyethylene and polypropylene feedstocks have curated the most attention, with demonstrations of pyrolysis − and hydroconversion − producing light olefins, alkylaromatics, fuel-range hydrocarbons, naphtha, lubricant base oils, and more. Polystyrene (PS) feedstocks have attracted considerably less attention.…”

Hierarchical FAU Zeolites Boosting the Hydrocracking of Polyolefin Waste into Liquid Fuels

“…The exponential surge in plastic consumption and waste accumulation, with polyolefins alone constituting 70% of the total, poses a global environmental challenge. − The C–C backbone in polyolefins makes them durable as consumer goods but resistant to degradation after service life. − Upcycling polyolefin wastes into value-added fuels represents a promising approach, including the hydrocracking technique that employs a bifunctional metal-acid catalyst and produces highly branched gasoline, diesel, and jet fuels. , …”

Ni-based catalysts supported on Hbeta zeolite for the hydrocracking of waste polyolefins

“…However, excessive low-value gas products were produced during the cracking process using the aforementioned monofunctional cracking catalysts. 23 Subsequently, bifunctional catalysts, such as Ru/HZSM-5, 24 MoS x -Hbeta, 25 Pt/Beta, 26 Rh–Nb 2 O 5 , 27 et al , offered both cracking and hydrogenation activities, have been reported for the catalytic degradation of polyolefin plastics. The polyolefin molecules were cleaved by the acidic sites of bifunctional catalysts via a carbocation reaction pathway, resulting in the generation of small molecular products.…”