The bio-oil produced from pyrolysis of woody biomass typically shows unfavourable characteristics such as high acidity, hence it becomes highly corrosive. An upgrading process, e.g., esterification, is necessary to improve the bio-oil quality prior to its use as a transportation fuel. In this work, the bio-oil was produced through a fast pyrolysis of Sengon wood in a fixed-bed pyrolyser at various temperatures. The characteristics (density, viscosity, total acid number, relative concentration of acetic acid, etc.) of the bio-oil were evaluated. The bio-oil with the highest acidity underwent an esterification catalysed by Indonesian natural zeolites at 70 oC for 0-180 min with a ratio of bio-oil to methanol of 1:3. The catalytic performance of the Indonesian natural zeolites during the esterification was investigated. A significant decrease in the total acid number in the bio-oil was observed, indicating the zeolite catalyst’s good performance. No significant coke formation (0.002-3.704 wt.%) was obtained during the esterification. An interesting phenomenon was observed; a significant decrease in the total acid number was found in the heating up of the bio-oil in the presence of the catalyst but in the absence of methanol. Possibly, other reactions catalysed by the Brønsted and Lewis acids at the zeolite catalyst surface also occurred during the esterification.

The bio-oil produced from the pyrolysis of biomass is highly corrosive due to the high content of organic acids. These organic acids could be removed through an appropriate upgrading process, i.e., esterification using alcohols to form less polar esters. In this study, the bio-oil used as the feedstock in the esterification was produced from the pyrolysis of Sengon wood with a particle size of 297 µm at 600 °C. The esterification was performed at 70 °C in the presence of a trichloro acetic acid (TCA)-modified Indonesian H-zeolite catalyst with various weight ratios of bio-oil-to-methanol and reaction times under a constant stirring rate of 500 rpm. The esterification progress was indicated by the decrease in the total acid number of the bio-oil after esterification. No significant coke formation (< 0.05 wt%) was observed indicating that the suppression of repolymerisation could be achieved. This study showed that the esterification underwent in a fast rate, indicated by the decrease in the total acid number of the bio-oil by 47.85 % only over a 15-min esterification. Compared to the uncatalysed esterification, the TCA/zeolite-catalysed esterification showed a higher decrease in the total acid number of the bio-oil up to 65.83 %, due to the conversion of the carboxylic acids to esters. HIGHLIGHTS The TCA-modified Indonesian natural zeolite catalyst has been successfully prepared The presence of the TCA/Indonesian natural zeolite during the esterification of bio-oil produced from the pyrolysis of Sengon wood could greatly suppress the severe repolymerisation leading to coke formation The TCA/Indonesian natural zeolite-catalysed esterification of Sengon bio-oil underwent in a fast rate The TCA/Indonesian natural zeolite catalyst showed a good performance in this study in comparison with the uncatalysed esterification GRAPHICAL ABSTRACT

No abstract

Isu lingkungan dan ketersedian bahan bakar berbasis fosil yang semakin menipis mendorong upaya-upaya eksplorasi sumbersumber energi baru terbarukan yang bersifat lebih ramah lingkungan. Biomassa sebagai salah satu sumber energi terbarukan sangat potensial untuk dieksplorasi dan dikonversi menjadi bahan bakar cair melalui proses pirolisis menjadi bio-oil. Namun sayangnya, bio-oil tidak dapat langsung digunakan sebagai bahan bakar mesin berteknologi tinggi, seperti mesin kendaraan bermotor, diantaranya karena keasamannya yang tinggi, bersifat tidak stabil dan nilai kalor yang rendah. Upaya peningkatan kualitas bio-oil terus diteliti dan dikembangkan. Beberapa proses upgrading bio-oil seperti pembentukan emulsi dan penambahan pelarut, hydrocracking, hydrotreatment, steam reforming, dan reaksi dalam supercritical fluids telah diteliti dan dikembangkan. Esterifikasi merupakan salah satu teknik upgrading bio-oil yang sederhana, murah dan cukup efektif untuk meningkatkan kualitas bio-oil. Pada bab ini, upgrading bio-oil melalui teknik esterifikasi katalitik didiskusikan secara rinci. Beberapa katalis baik homogen maupun heterogen yang digunakan dalam proses esterifikasi biooil baik bio-oil riil maupun senyawa-senyawa model juga dijelaskan. Selain itu, penggunaan katalis berbasis zeolit yang terfokus pada zeolit alam Indonesia dikaji potensi dan keunggulannya secara mendalam.