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Pyrolysis is a promising technique for the recovery of useful gas, tar, and solid products from biomass waste. However, the low tar yields obtained from lignocellulosic biomass are a significant drawback. To enhance tar yields, sugarcane bagasse, which is the most abundant agricultural waste in Fiji, was pretreated at ambient temperature and atmospheric pressure using various sulfuric acid (H 2 SO 4) concentrations. Here, the ether bonds of cellulose, hemicellulose, and lignin were partially hydrolyzed. The pretreated samples were then pyrolyzed at 500 °C, and it was confirmed that H 2 SO 4 -pretreatment disrupted the bagasse cell structure, with the thermogravimetry and differential thermogravimetry results confirming that decomposition occurred at lower temperatures after pretreatment. In addition, tar yields were significantly enhanced from 5.6 wt% to 13.4 wt% for the untreated and 3 M H 2 SO 4 -pretreated samples respectively. The main components detected in this tar product were levoglucosan, andcellulose-and hemicellulose-derived products, whose proportions were increased following pretreatment. Thus, our work demonstrates that dilute acid pretreatment enhances tar production from sugarcane bagasse due to the production of shorter chain components via the partial hydrolysis of ether bonds. • Hydrolysis of bagasse components occurred by ambient temperature H 2 SO 4 pretreatment. • Moderate H 2 SO 4 concentrations enhanced the pyrolysis tar and gaseous production. • Char formation also increased with increasing H 2 SO 4 concentration. • Levoglucosan production was also enhanced by H 2 SO 4 pretreatment. • Lignin hydrolysis was effective with acid pretreatment. [ABSTRACT FROM AUTHOR]

Polyvinyl chloride (PVC)-coated poly(ethylene terephthalate) (PET) woven fibers are one of the hardest-to-recycle polymeric materials. Herein we investigate the possibility of recycling both PVC and PET through alkaline hydrolysis of PET. The coated woven fabrics were treated with NaOH, hydrolyzing the PET fibers into water-soluble sodium terephthalate, while the PVC could be removed by filtration. The PET fibers were completely hydrolyzed between 120 and 180 °C in the presence of 1 M NaOH solution, quantitatively yielding terephthalic acid. A minimum PVC dechlorination rate of 1% was simultaneously achieved at 120 °C. Furthermore, no alkaline hydrolysis of the plasticizer contained in the PVC, di(2-ethylhexyl)phthalate, was observed. Thus, the possibility of simultaneously recycling PET and PVC from PVC-coated woven fabrics was demonstrated. Kinetic analyses of PET hydrolysis and PVC dechlorination revealed that the simultaneously occurring reaction processes did not affect the progress of each other. Thus, the absence of interactions between PET, PVC, or their degradation products enables the design of a simplified recycling process without considering the interactions between the materials derived from coated woven fabrics. [ABSTRACT FROM AUTHOR]

Kapton film, which is a typical aromatic polyimide (PI) film, exhibits excellent thermal stability and flexibility. Therefore, it is used widely for flexible printed circuit boards in combination with other resins and metals. However, this makes it difficult to recycle it. In this work, we focused on the steam pyrolysis technique, which is a method of depolymerizing condensation polymers without solvents, catalysts, or high pressure, as a way of overcoming this issue. The steam pyrolysis of Kapton film was carried out using a thermogravimetric (TG) analyzer equipped with a steam generator. In addition, the TG results were evaluated further using model fitting techniques. It was found that steam enhanced the hydrolysis of the imide ring, which occurred on the surface of the PI film. The hydrolysis selectivity was as high as 89% at 528 °C. However, steam did not significantly enhance the Kapton decomposition rate, owing to rapid carbonization, which took place because of the simultaneous occurrence of pyrolysis. Thus, the obtained results implied that high-yield monomer recovery can be achieved by lowering the temperature to prevent pyrolysis and by improving the steam contact efficiency to enhance hydrolysis within the material. [ABSTRACT FROM AUTHOR]

ABSTRACT: The possibility of simultaneous recovery of benzene and metals from the hydrolysis of poly(ethylene terephthalate) (PBT)-based materials such as X-ray films, magnetic tape, and prepaid cards under a steam atmosphere at a temperature of 450 °C was evaluated. The hydrolysis resulted in metal-containing carbonaceous residue and volatile terephthalic acid (TPA). The effects of metals and additives on the recovery process were also investigated. All metals were quantitatively recovered, and silver, maghemite (γ-Fe2O3), and anatase (TiO2) were recovered without any changes in their crystal structures or compositions. In a second step, TPA was decarboxylized in the presence of calcium oxide (CaO) at 700 °C, producing benzene with an average yield of 34% and purity of 76%. Maghemite (γ-Fe2O3) incorporated in magnetic tape and prepaid cards could decarboxylate TPA. Aluminum present in the prepaid cards produced hydrogen by the reaction with steam. However, the presence of metals had no adverse influence on the recovery of benzene-rich oil in the presence of CaO. Therefore, this method can be applied to PET-based materials containing inorganic substances, which cannot be recycled effectively otherwise. [ABSTRACT FROM AUTHOR]