Optimization of process parameters for slow pyrolysis of neem press seed cake for liquid and char production

Slow pyrolysis of neem press seed cake (NPSC) was carried out in a fixed bed batch reactor to study the effects of temperature, retention time, and nitrogen (N 2 ) flow rate on liquid and char yields. Response surface methodology (RSM) based on Box-Behnken design was used to determine the optimum operating conditions to maximize the liquid yield. The highest liquid yield of 52.1 wt% was obtained at 512.5 °C, after 60 min using 0.5 L/min N 2 flow rate. Scanning electron microscopy (SEM), elemental analysis, bomb calorimeter, Fourier transform infrared (FT-IR) spectroscopy, X-ray powder diffraction techniques and gas chromatography-mass spectrometry (GC-MS) were used to determine the physicochemical properties of NPSC and char, and chemical properties of liquid. GC-MS analysis showed that the bio-oil was rich in 9-octadecenamide, 2-propenyl decanoate, heptadecanenitrile, and oleanitrile. The higher heating value of the bio-oil and NPSC were 32.8 and 16.05 MJ/kg, respectively at 575 °C. The FT-IR results showed a decrease in the number of O-H (hydroxyl), C-H (alkanes), C=O (esters), -C-H (alkanes), and C-O (primary alcohol) groups in NPSC with increasing pyrolysis temperature