Preliminary study on low pressure hydrothermal liquefaction processes of biomass for biofuels: Bio crude oil

摘要

Indonesia located in equator area has abundant biomass which is the most attractive source among other alternative resources. Biomass also represents a high potential for the sustainable production of both valuable chemicals and biofuels. Biomass in Indonesia offers abundance, easy availability, carbon neutrality, and eco-friendly features make a positive impact on this situation, decreases of oil reserves and increases prices of oil-based fuels. Thermo-chemical routes considered as a suitable technology for utilization of biomass like Hydrothermal Liquefaction (HTL) to produce Bio Crude Oil (BCO). Various solvents like water, alkali, polar, and organic acid were examined to observe the characteristic of process at 300°C. HTL was conducted in 1000 ml high pressure and temperature reactor. This work used frond oil palm which is abundantly available and untapped resources in palm plantations. The experiment confirmed that the pressure in reactor depend on the vapour pressure of the solvent. In addition, the vapor pressure is also determined by the boiling point. Water and alkali solvent gave the same operating pressure as indicated by the vapor pressure of water, 82 bar. Unfortunately, the biomass was polymerized at 300°C. To prevent the polymerization, a commercial cracking catalyst was added to break the polymer chain of the product. Regarding the product, water, as a solvent, produced bio-char 37%. Alkali solution has a role to breakdown part of lignin so that the char decreased to 30%. In addition, further degrade biomass could be work more effective by combining cracking catalyst like NiMo that showed by formation of CO, CO_2 and CH_4. Those gases formation showed decarboxylation, decarboxylation, and cracking process, respectively. Catalyst as expected, avoid the polymerization that can be seen at powdering of biochar. The catalyst worked more effective in acid condition as shown by more CH_4 in syngas. Unfortunately, the liquid product was still dominated by water, more than 80% and the yield of BCO was considered very low. TGA analyzed showed the volatile compound that vaporized between 110-300°C was considered the component that might cause be converted into water. Therefore, the work would focus more at chemicals content produced by HTL like acetic acid, phenol, ester, and ether.