Bio-oil and biochar production using thermal and catalytic pyrolysis of low-value waste neem seeds over low-cost catalysts:effects of operating conditions on product yields and studies of physicochemical characteristics of bio-oil and biochar

This study addressed a comparative assessment of the effect of low-cost catalysts on the yield and physicochemical properties of bio-oil.Thermal and catalytic pyrolysis of neem seeds(NM)was conducted in a fixed bed semi-batch reactor at optimum conditions(550°C temperature,80°C min−1 heating rate,0.5 mm particle size,and 100 mL min−1 sweep gas flow rate).The produced bio-oil and biochar were characterized through thermal stability,elemental composition(CHNS),higher heating value(HHV),Nuclear Magnetic Resonance(NMR)spectroscopy,Field Emission Scanning Electron Microscopy(FESEM),Fourier-transform infrared spectroscopy(FTIR),Gas Chromatography-Mass Spectrometry(GC-MS),zeta potential,water-holding capacity(WHC),and BET(Brunauer,Emmett and Teller)surface area analyzer.Overall,it was noticed that the use of catalysts at optimized condition substantially boosted the quality and yield of bio-oil.Pyrolysis results established that thermal pyrolysis yielded 49.53 wt.%of bio-oil,while catalytic pyrolysis yielded(51.25 wt.%,53.12 wt.%,48.68 wt.%,and 50.65 wt.%for MgO,NaOH,Al_(2)O_(3),and ZSM-5,respectively)at 20 wt.%catalyst loading.The physicochemical study of bio-oil confirmed improved properties of bio-oil in terms of viscosity,heating value,pH and carbon content.Further,the FTIR study of bio-oil indicates the occurrence of phenolic products,aromatics,ketones,acidic compounds,esters,alcohol and aldehyde impurities,whereas 1H NMR study supported FTIR findings.GC-MS study demonstrated that the introduc-tion of catalysts significantly reduced the oxygenated substances,acidic products,phenolic compounds and substantially increased the hydrocarbons.Further,characterization results of neem seed biochar(NMC)established the existence of HHV(23.26 MJ kg^(−1)),carbon content(62.66%),zeta potential(31.68 mV),water holding capacity(41.50%)and lower BET surface area(4.60 m^(2)g^(−1)).