Jatropha curcas L. biomass transformation via torrefaction: Surface chemical groups and morphological characterization

Abstract

The effect of torrefaction on the chemical compositions and surface morphology of raw and pretreated (dilute acid and mild alkaline) of Jatropha curcas L. seed shell (JSS) and fruit hull (JFH) were investigated using Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM). The biomass samples were torrefied using a bench-scale fixed bed reactor (torrefaction device), which was developed by the authors. The raw and pretreated biomass was heated in an oxygen-free environment or oxygen-reduced condition at 200–300 ​°C using particle size of 1.14 ​mm, and residence time of 30 ​min. The FTIR data of the raw, treated and torrefied biomass bands were similar. The O–H stretch peak (hydrogen bonded) around 3763-3200 ​cm−1 is visible in all the samples. The infrared spectra revealed the presence of the peak between 2800 ​cm−1 and 3000 ​cm−1 corresponding to the presence of the aliphatic groups (C–H stretching) in the raw and pretreated samples. Band waves between 900 ​cm−1 and 700 ​cm−1 indicated aromatic C–H deformation in all samples and much more. The chemical components of the JSS and JFH were changed after pretreatment with H2SO4 and NaOH. The SEM images of the raw JSS revealed a highly dense structure which are coarsely grained. The microparticles are rough and multidispersed with significant pore aperture. The SEM image of raw JFH had cracked, fibrous tissue with a relatively smooth surface while the pretreated samples had large number of pores. The acid and alkali pretreatment enhanced the surface structure.

Keywords

• Jatropha curcas L.
• Torrefaction
• Oxygen-free environment
• Fixed bed reactor
• Fourier transform infrared spectroscopy
• Scanning electron microscopy