Optimization and catalytic fast pyrolysis of olive pomace for bio-oil production by using response surface methodology

In this study, fast pyrolysis parameters such as biomass particle size (PS), temperature (T), and carrier gas flow rate (CGF) were optimized by using the Response Surface Methodology (RSM) with a Central Composite Design (CCD) to maximize bio-oil yield (BOY) from olive pomace (OP). In addition, the effects of catalysts (Al2O3, Na2CO3, K2CO3, and ZSM-5) on the quality of bio-oil from fast pyrolysis of OP were investigated under the pre-optimized conditions (at 1.5 mm PS, 200 mL min(-1) CGF), and reaction T of 425, 500, 575, 650, and 725 degrees C. The maximum BOY of 58.13 % was obtained at 1.5 mm PS, 490. C T, and 200 mL min(-1) CGF. The optimum reaction T for all four catalysts was 500 degrees C and the highest BOY was 50.73 % using Al2O3 as a catalyst. The Al2O3 and ZSM-5 had the lowest and highest bio-oil oxygen content ranging between 12.53 and 5.73 % and 15.06 and 12.55 %, respectively. The GC-MS analysis revealed that without a catalyst, bio-oil from OP contains mostly acids and small amounts of alcohol, aromatics, and ketones. The use of all four catalysts had major effects on bio-oil chemical compounds and distribution. Carboxylic acid contents of bio-oil samples from catalytic fast pyrolysis (CFP) of OP decreased significantly but aromatic content increased considerably and reached its highest (56.13 %) for Al2O3. Low aromatic content was observed when using Na2CO3 as a catalyst. Ketone and alcohol contents in bio-oil increased when using K2CO3, Na2CO3, and ZSM-5 as catalysts.