Monday, March 17, 2025

Scientists break down various kinds of plastic using a simple, inexpensive catalyst and air

Good news!

I have blogged here several times before that there are multiple ways to process and recycle plastic trash!

Alert: Plastophobia is a serious disorder. Please seek immediate medical help! (Caution: satire)

"Harnessing moisture from air, ... chemists have developed a simple new method for breaking down plastic waste.

The non-toxic, environmentally friendly, solvent-free process first uses an inexpensive catalyst to break apart the bonds in polyethylene terephthalate (PET), the most common plastic in the polyester family. Then, the researchers merely expose the broken pieces to ambient air. Leveraging the trace amounts of moisture in air, the broken-down PET is converted into monomers—the crucial building blocks for plastics. ..."

From the abstract:
"Here, we describe the solventless catalytic deconstruction of polyethylene-terephthalate (PET) under an aerobic atmosphere, mediated by an earth-abundant, low-cost activated carbon (AC)-supported single-site molybdenum-dioxo catalyst (AC/MoO2). Catalytic amounts of AC/MoO2 selectively convert waste PET into its monomer, terephthalic acid (TPA), within 4 h at 265 °C with yields as high as 94% under 1 atm air. Pure crystalline TPA product sublimes from the reaction hot zone, crystallizing on the reactor cold zone, thus avoiding the need for separation and purification steps. This process does not employ any hazardous/toxic reducing agents or solvents, and the catalyst can be recycled multiple times without loss of activity, rendering this process highly atom-efficient. According to computational and experimental mechanistic studies, the AC/MoO2 catalyst mediates a thermoneutral metal-catalyzed β-scission step, followed by an exothermic step that converts the vinyl benzoate intermediate to TPA and acetaldehyde using trace amounts of moisture in the air. The formation of gaseous acetaldehyde makes the isolation of TPA from the reaction mixture facile and industrially favorable, especially since solvents are unnecessary.
The present methodology is also extended to the deconstruction of other frequently used polyester plastics, polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), and polyethylene furanoate (PEF), and operates equally well with post-consumer waste products.
Notably, this process is also compatible with plastic mixtures of polyesters with polyolefins, polyamides, and polycarbonates, leading to the selective conversion of each polyester to the corresponding monomer, leaving the residual polymer unchanged and polyester-free."

Scientists break down plastic using a simple, inexpensive catalyst and air





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