Polyethylene plastic is one of the most common plastics, often used in everyday items like plastic bags and detergent bottles.
Despite looking quite different from gasoline, they actually share similar chemical structures and compositions. Just like gasoline, polyethylene plastic is derived from petroleum.
Given this, is it possible to efficiently convert discarded polyethylene plastic into gasoline?
High Costs of Traditional Methods
While there is potential to transform polyethylene plastic into gasoline, it poses significant challenges. This is because polyethylene plastic is an organically synthesized polymer material, consisting of countless ethylene molecules linked together in long-chain polymers. The polymer backbone is connected by non-polar carbon-carbon bonds, providing high stability that makes it difficult to activate and break, hence why discarded polyethylene plastic is hard to naturally degrade. To turn waste polyethylene plastic into a valuable resource, the carbon-carbon bonds of polyethylene need to be activated and broken, a reaction that requires a high reaction temperature of over 400°C, precious metal catalysts, and an external hydrogen source. These conditions limit the large-scale industrialization of polyethylene chemical recycling. Therefore, finding a low-cost and efficient way to convert polyethylene has always been a significant challenge in the field of plastic conversion.
Catalytic Conversion of Waste Polyethylene Plastic into Gasoline
New Strategy Solves an Old Problem
Recently, researchers from the Institute of Chemistry at the Chinese Academy of Sciences have developed a new strategy that can convert waste polyethylene plastic into high-quality gasoline under low-temperature (240°C), metal-free, hydrogen-free, and solvent-free conditions. Inspired by the process of hydrocracking during gasoline production, the research team conducted cracking experiments using polyethylene as the raw material. They introduced a layered self-supporting molecular sieve catalyst for catalytic reactions at 240°C. The unique open-framework tricoordinated aluminum sites of the molecular sieve catalyst effectively promote the activation and cleavage conversion of chemical bonds in waste polyethylene, thereby transforming it into high-quality gasoline. The content of branched alkanes that can increase the octane number is nearly double that of commercial gasoline. High Recovery Rate with "Self-Supply"
It is worth noting that the hydrogen gas required during the polyethylene "hydrocracking" process is not externally supplied but rather "self-supplied." The molecular sieve catalyst used by the researchers can aromatize some of the polyethylene cracking products, providing a source of hydrogen. This allows polyethylene to be converted into gasoline in a "self-supply of hydrogen" manner, eliminating the need for an external hydrogen source.
Layered self-supported zeolite catalyzed conversion of polyethylene for "self-supply of hydrogen" to produce gasoline
Experiments show that under the conditions of 240°C, no precious metals, no hydrogen, and no solvents, the recovery rate of producing high-quality gasoline from waste polyethylene plastic reaches 80%.
This research provides a new pathway for converting waste polyethylene into high-quality gasoline, with promising practical applications.
(Original title: "Killing Two Birds with One Stone": From Waste Plastic to High-Quality Gasoline | Cutting-edge Technology)
