21 / 2017-04-28 08:49:48

Bio-Hydrotreated Diesel Production from Spent Coffee Oil

13717

Oil extracted from spent coffee grounds is utilized as a renewable source for bio-hydrotreated diesel production. In the present work, oil yield up to 13% can be obtained by Soxhlet extraction with hexane as a solvent. Noted that the extracted oil contained high content of free fatty acids (6.14%), therefore one step alkali-catalyzed for ester based biodiesel production is impractical. Hydrotreating of extracted oil was performed over two catalysts i.e. NiMo/-Al2O3 and Pd/C with different operating parameters i.e. reaction time, operating temperature, and H2/oil. It was found that the reaction time of 2 h and the reaction temperature of 400C are favorable operating conditions. The liquid products mostly consisted of n-pentadecane and n-heptadecane, which contain one carbon atom shorter than the corresponding fatty acid C(n-1) i.e. palmitic and stearic acid, respectively. Unfavorable cracking of diesel product is pronounced at high temperature and prolonged reaction time. In addition, although increased H2/oil promoted overall reaction and hydrodeoxygenation activity (Cn-1/Cn decreased) for both catalysts, hydrocracking is enhanced over Pd/C lead to significantly increase in gasoline yield. Moreover, Pd/C gave higher olefin content in liquid product (22.3 wt%) than NiMo/-Al2O3 (4.8 wt%). However, NiMo/-Al2O3 shows higher isomerization activity. The amount of isoparaffins catalyzed by NiMo/-Al2O3 and Pd/C were 10.8 and 1.7 wt%, respectively. Physiochemical analysis of the diesel fraction exhibit satisfactory properties. The density and kinematic viscosity were consistent with the specification of commercial bio-hydrogenated diesel, NExBTL, while the cetane index are much higher than conventional diesel and comply with the NExBTL standard.