Low temperature microwave-assisted pyrolysis of wood sawdust for phenolic rich compounds: Kinetics and dielectric properties analysis

Phenolic compounds reached up to 78.7% (area) at 500°C along with low activation energy were attributed to the generated instantaneous “hot spots” in microwave-assisted pyrolysis. [Display omitted] •MAP of wood sawdust for preparing phenolic chemicals with a yield of 78.7% at 500°C.•MV-TGA with KAS method is applied to reveal pyrolytic behavior and activation energy.•Effective pyrolytic range and average activation energy are 250–400°C and 42.78kJ/mol.•Low temperature pyrolysis is attributed to the formation of instantaneous “hot spots”. Microwave-assisted pyrolysis of wood sawdust for phenolic rich compounds was carried out between 400 and 550°C in a batch reactor. An efficient preparation of liquid products was observed at 500°C with a yield of 58.50%, which was similar to conventional fast pyrolysis. The highest concentration of phenolic compounds in liquid product reached up to 78.7% (area) in which the alkoxy phenols contributed 81.8% at 500°C. Microwave thermogravimetric analysis using KAS method was used firstly to investigate the low-temperature pyrolytic behaviors and activation energy. The results indicated that effective pyrolytic range was 250–400°C and average activation energy was 42.78kJ/mol, which were 50–100°C and 50–100kJ/mol lower than conventional pyrolysis, respectively. Analysis on dielectric properties of pyrolytic products confirmed that accelerated pyrolysis and low temperature were attributed to the formation of instantaneous “hot spots”.