Bio-oil stability through stepwise pyrolysis of groundnut shells: Role of chemical composition, alkali and alkaline earth metals, and storage conditions

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Abstract

Bio-oil obtained from crop residues is unstable because of multiple reactive oxygenated compounds and alkali and alkaline earth metals (AAEMs), which hinder its use as a chemical feedstock. In the current study, stepwise pyrolysis of groundnut shells was performed in three-step (160/200–320/340−600 °C), two-step (320/340−600 °C), and continuous (600 °C) heating regimes to obtain a more stable bio-oil. The stability of bio-oils was compared in terms of changes to their pH, water content, AAEM concentration, and chemical composition over a fixed period. During three-step pyrolysis, 94.85–97.38 % of chemicals (anhydrosugars, organic acids, aldehydes, and ketones) were concentrated in step 2. In contrast, for two-step pyrolysis, 93.14–94.78 % were concentrated in step 1. The AAEMs transferred from groundnut shells to bio-oil were 7.04–9.63 % for three-step, 6.68–11.26 % for two-step, and 11.87 % for continuous pyrolysis. An accelerated aging test (80 °C for 24 h) showed that two-step pyrolysis at 340 °C and 600 °C, produced the most stable bio-oil despite a higher concentration of AAEMs. Further improvement in this bio-oil's stability was explored by altering storage temperature and adding solvents to the bio-oil. The decrease in concentrations of anhydrosugars and phenolics was <1% after four weeks of storage at 4 °C with the addition of methanol. The obtained results contribute to implementing stepwise pyrolysis units for crop residue management.

Original languageEnglish
Article number105219
Number of pages10
JournalJournal of Analytical and Applied Pyrolysis
Volume157
DOIs
Publication statusPublished - Aug 2021
Publication typeA1 Journal article-refereed

Keywords

  • Accelerated aging
  • Agro-residue
  • Bio-oil stability
  • Inorganic distribution
  • Slow pyrolysis

Publication forum classification

  • Publication forum level 1

ASJC Scopus subject areas

  • Analytical Chemistry
  • Fuel Technology

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