An official website of the United States government
Solvothermal liquefaction (STL) is a thermochemical conversion technique that employs solvents other than water to transform waste plastics into valuable compounds. The objective of this study was to explore the potential use of supercritical toluene, a nonpolar solvent, for the depolymerization of four electrical waste (e-waste) thermoplastics, namely polyamide (PA), polycarbonate (PC), polyoxymethylene (POM), and polyether ether ketone (PEEK), into liquid products. Depolymerization experiments were carried out in batch reactors at three reaction temperatures (325, 350, and 375 ◦C), and three residence times (1, 3, and 6 h). The findings revealed that increasing STL temperature and extending the reaction time enhances the depolymerization of e-waste thermoplastics. The highest STL conversation (100 %) was observed for POM, and the lowest STL conversation (32.23 %) was observed for PEEK. Additionally, the ultimate analysis showed that the liquid product obtained from STL at 375 ◦C and 6 h exhibited higher heating values (HHV) within the range of 31.43 to 35.31 MJ/kg. Thermogravimetric analysis (TGA) demonstrated that the boiling point distributions of liquid products are highly dependent on thermoplastic type. Finally, the reaction mechanisms of STL for PA, PC, POM, and PEEK were proposed based on gas chromatography-mass spectrometry (GCMS) analysis.
more »
« less
This content will become publicly available on February 5, 2026
Supercritical Fluids for Enhanced Chemical Transformation of Postconsumer Plastics: A Review
Abstract Various chemical transformation approaches are being actively developed to address the environmental accumulation of plastic waste. However, most postconsumer plastics are heterogeneous, exhibit high melt viscosity, and are insoluble in most conventional solvents. Such properties result in transport‐limiting chemical transformations, low conversion rates, and low product selectivity. Although supercritical fluids (SCFs) have been a matter of continuing scientific interest in several mass‐transfer processes, the use of SCFs as tunable media for the chemical transformation of postconsumer plastics is still in its early stages, but has rapidly advanced in recent years. Therefore, this review reports on the current state‐of‐art of chemical transformation of plastics using SCFs. It addresses the effects of sub and supercritical CO2(scCO2) on solvolysis‐based technologies. Additionally, it reviews recent advances on the use of supercritical organic solvents (e.g., ethanol, methanol) and supercritical water (SCW) as reaction media for the solvolysis and liquefaction of plastics, respectively, and the latest developments in the simultaneous conversion of CO2and waste plastics. Overall, developing technologies that minimize mass transfer limitations during the chemical transformation of plastics is critical to overcoming some of the major bottlenecks hampering product yield and selectively, and ultimately the economic viability of plastics recycling and upcycling.
more »
« less
- Award ID(s):
- 2419180
- PAR ID:
- 10576160
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- ChemCatChem
- Volume:
- 17
- Issue:
- 7
- ISSN:
- 1867-3880
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Abstract The conversion of waste CO2to value‐added chemicals through electrochemical reduction is a promising technology for mitigating climate change while simultaneously providing economic opportunities. The use of non‐aqueous solvents like methanol allows for higher CO2availability and novel products. In this work, the electrochemistry of CO2reduction in acidic methanol catholyte at a Pb working electrode was investigated while using a separate aqueous anolyte to promote a sustainable water oxidation half‐reaction. The selectivity among methyl formate (a product unique to reduction of CO2in methanol), formic acid, and formate was critically dependent on the catholyte pH, with higher pH conditions leading to formate and low pH favoring methyl formate. The potential dependence of the product distribution in acidic catholyte was also investigated, with a faradaic efficiency for methyl formate as high as 75 % measured at −2.0 V vs. Ag/AgCl.more » « less
-
Chemical recycling of plastics is a promising technology to reduce carbon footprint and ease the pressure of waste treatment. Specifically, highly efficient conversion technologies for polyolefins will be the most effective solution to address the plastic waste crisis, given that polyolefins are the primary contributors to global plastic production. Significant challenges encountered by plastic waste valorization facilities include the uncertainty in the composition of the waste feedstock, process yield, and product price. These variabilities can lead to compromised performance or even render operations infeasible. To address these challenges, this work applied the robust optimization-based framework to design an integrated polyolefin chemical recycling plant. Data-driven surrogate model was built to capture the separation units behavior and reduce the computational complexity of the optimization problem. It was found that when process yield and price uncertainties were considered, wax products became more favorable, and pyrolysis became the preferred reaction technology.more » « less
-
Supercritical fluids (SCFs) have been recently considered to be used as insulating media due to properties that show exceptional dielectric strength, high heat transfer capability, and low viscosity. This paper reports the result of breakdown experiments on carbon dioxide (CO2) from gaseous to supercritical state. Experiments are performed under the isothermal condition of 310 K (37°C). The dielectric strength test is conducted in a 0.1 mm gap under uniform dc electric field. To interpret the result, a theoretical model that combines the thermodynamic calculation and existing data from the structure analysis by small angle x-ray scattering is developed. Our experiments suggest that the dielectric behavior of supercritical CO2 shows a discontinuity of the dielectric strength near the critical point. This phenomenon can be well explained by the theoretical model, which calculates the molecular cluster size and considers the local fluid structure.more » « less
-
Abstract The electrochemical conversion of waste CO2into useful fuels and chemical products is a promising approach to reduce CO2emissions; however, several challenges still remain to be addressed. Thus far, most CO2reduction studies use pure CO2as the gas reactant, but CO2emissions typically contain a number of gas impurities, such as nitrogen oxides, oxygen gas, and sulfur oxides. Gas impurities in CO2can pose a significant obstacle for efficient CO2electrolysis because they can influence the reaction and catalyst. This Minireview highlights early examples of CO2reduction studies using mixed‐gas feeds, explores strategies to sustain CO2reduction in the presence of gas impurities, and discusses their implications for future progress in this emerging field.more » « less
