Pyrolysis of timber in a semi-batch reactor: Maximization of bio-oil using central composite design

The present study deals with the pyrolysis of Dalbergia sissoo wood (DSW), as well as the determination of operating parameters that resulted in a maximum yield of bio-oil. The bio-oil was produced in a semi-batch reactor using nitrogen as an inert carrier gas. Response surface methodology (RSM) based on “three-factors-three-levels” central composite design scheme was used to obtain the optimum operating conditions. Effects of three independent process parameters, particle size (0.2–0.6 mm), reaction temperature (700–900 K), and nitrogen gas flow rate (60–160 ml/min) were assessed. A quadratic model relating to bio-oil yield as a function of independent process parameters with their interactions was developed. The obtained regression coefficients (R² =.9947 and adj. R² =.9867) during the analysis of variance (ANOVA) indicated an excellent fitting of the quadratic model with the experimental data. Optimum conditions thus obtained were: particle size 0.6 mm, reaction temperature 833 K, and volumetric flow of nitrogen 125 ml/min which offered maximum bio-oil yield as 49.17 mass%. The physicochemical properties of bio-oil such as kinematic viscosity, density, pH value, flash point, and heating value, were determined using standard test procedures. Fourier transform infrared (FTIR) spectroscopic, ¹H–Nuclear magnetic response (¹H–NMR) spectrometry, and gas chromatographic/mass spectroscopic (GC–MS) techniques were used to identify the compounds present in DSW bio-oil. The chromatographic analysis confirmed the presence of some high value-added compounds such as pyrimidine, cyclobutanol, allantoic acid, and hydroxyurea.