Use of hydrothermal treatment and catalytic pyrolysis for the use of urban pruning

Abstract

Inadequate management of organic waste is a challenge in Brazil, where only 2% is composted, with most being disposed of in landfills. These wastes can be converted into useful products through thermochemical processes. The use of catalysts in these processes can optimize the production of value-added compounds, such as phenolics. The objective of this study was to develop a sequential process involving hydrothermal pretreatment of biomass combined with catalytic pyrolysis for the production of phenol-rich bio-oil from urban pruning waste of Myrtus communis, commonly known as myrtle. The hydrothermal treatment (HT) used water or a 50:50 water/ethanol mixture at temperatures of 150, 200, and 250°C for 60 minutes. Potassium and tin catalysts were tested during pyrolysis. The HT proved effective in the partial removal of hemicellulose, especially at 200°C, which facilitated the formation of phenolic compounds. After the treatment, micropyrolysis (600°C for 1 min) of the samples was performed. Gas chromatography-mass spectrometry (GC-MS) analysis of the bio-oils obtained from hydrothermal treatment with water alone showed a significant increase in functional groups, especially phenols, due to the selective removal of hemicellulose. The tin catalyst favored the formation of furans, while the potassium catalyst was more effective in producing alkylphenols, demonstrating that the HT process was the most effective for producing bio-oil rich in compounds of interest.