Chemical structure and characterization of bio-oils isolated from walnut shells by different processes

Abstract

This study investigated the products and properties of bio-yields obtained from different types of processes using the extraction and pyrolysis of walnut shells. Pyrolysis experiments were carried out with 10 g walnut shells at a pyrolysis temperature of 550 °C, a heating rate of 10 °C /1 min, a particle size of 1-1.5 mm, and a specific nitrogen gas flow rate. Aqueous extracts were obtained by placing the solid sample in a glass jar with methanol-chloroform (1:1 v/w) solvent indoors and away from light for five days. The obtained liquid samples were analyzed by Gas chromatography-mass spectrometry (GC-MS), Liquid Chromatography Mass Spectrometry (LC/MS-MS), and Fourier Transform Infrared Spectroscopy (FT-IR). Chemical composition analysis of the bio-oils revealed that phenol compounds were more concentrated in the aqueous extract process and volatile oil compounds that were more dominant in the pyrolysis process. The structural analysis results of the bio-oil showed that bio-oil products obtained from walnut shells can be used as fuel, composite film for different purposes, and value-added products. It can be said that the content analysis of liquid samples obtained as a result of pyrolysis and extraction of walnut shells was elucidated with advanced analytical techniques such as LC-MS/MS and GC-MS. The test results revealed that these products will be used in different areas such as energy and high-value-added products. This study provides researchers with a concrete prediction about the suitability of content-analyzed walnut shells.