Microwave pyrolysis induced bio-oil, and supercritical fluid extraction bio-phenol from pyrolyzed bio-oil

Abstract

This research is the development of a microwave-assisted pyrolysis (MAP) system to be used in the study of the production of bio-oil from oil palm shells with activated carbon as a microwave power absorber. The experimental design was the 2k full factorial design: 23 to study the optimum conditions of the process. The factors were the temperature, the ratio of oil palm shells (OPS) to activated carbon (AC), and pyrolysis time. It was found that the optimum condition for obtaining the highest crude bio-oil content was at a temperature 700 °C, OPS: AC ratio of 80:20, and the pyrolysis time 40 minutes. The regression prediction in the 95% confidence interval was 24.08% with R2 of 89.54%. Analyzed bio-oil by using Gas Chromatograph-Mass Spectrometer (GC-MS) found that the main components of crude bio-oil were acetic acid and phenol. Crude bio-oil obtained from microwave pyrolysis was extracted by supercritical fluid extraction with carbon dioxide (scCO2) process. It found that a temperature 60°C, a pressure 350 bar, an extraction time 30 minutes, and a flow rate of carbon dioxide 3.0 liters/minute was the highest scCO2 oil content 56.04%. The extracted scCO2 oil was analyzed by GC-MS. The result found that phenol groups and phenol derivatives were reduced. However, the acid products that were not detected in crude bio-oil: dodecanoic, n-Hexadecanoic, octadecanoic, and other chemical constituents were found. The conditions at a temperature 50 °C, a pressure 400 bar, an extraction time 30 minutes, and a flow rate of carbon dioxide 3.0 liters/minute were the maximum extracted phenol content 36.72%. Considering, the cost of materials and electricity to produce crude bio-oil was in the range of 0.07-0.25 baht/ml, and the extraction cost with the highest bio-phenol content was 79.54 baht/ml.