Microwave-assisted pyrolysis of formic acid pretreated bamboo sawdust for bio-oil production

The integrated process of formic acid pretreatment and pyrolysis of bamboo sawdust (BS) under microwave irradiation is developed to produce high-quality bio-oil in this study. Experimental results indicated that microwave-assisted formic acid (MFA) pretreatment was able to reduce the contents of hydrogen, ash, and volatile in biomass. In the meanwhile, a distinct increase in the higher heating value of pretreated BS was observed. Although a higher pretreatment temperature led to lower mass yield, the corresponding energy yield of solid product was remarkably higher. X-ray diffraction and Fourier transfer infrared spectrometry analyses of pretreated BS suggested that MFA pretreatment could destruct the pristine structure of BS. Therefore, thermal properties of pretreated BS were significantly altered in terms of thermal stability and decomposition temperature according to thermogravimetric analysis. Microwave-assisted pyrolysis of pretreated samples could produce less acids, phenols, and ketones but more sugars, especially gluopyranose. Furthermore, the relevant mechanism of microwave-assisted pyrolysis of pretreated BS was interpreted. In sum, MFA was a feasible and promising technology to improve the quality of bio-oil from microwave pyrolysis of biomass.