Microwave pyrolysis of oak wood: Process analysis and product characterization

Development of methods for converting agricultural waste into valuable chemical products constitutes an important task designed to improve the efficiency of natural resource use. A promising approach is microwave-assisted pyrolysis, which offers high heating rates, selective action, and potential for scaling. In order to implement microwave processing of oak wood, a specialized processing unit was developed; its key element is a microwave reactor with a capacity of up to 3 L. The present study compared the IR spectra of oak wood prior to and after exposure to microwave radiation, as well as that of the obtained gaseous fraction. The IR spectrum analysis of the original wood and the solid residue from pyrolysis revealed structural changes in the polymer components of wood (cellulose, lignin, and hemicelluloses), while the IR spectrum analysis of the gaseous fraction helped identify the main gaseous reaction products. In addition, an elemental analysis of oak wood and the solid product of its microwave processing was conducted. The obtained data indicate a decrease in H/C and O/C atomic ratios by 0.73 and 0.44, respectively, during wood pyrolysis. The estimated calorific value of the solid residue increased twofold, which suggests the potential of using pyrolysis products as fuel due to the increased energy value. The obtained results indicate the potential of microwave pyrolysis in the conversion of agricultural waste into high-carbon materials with increased calorific value.

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