Experimental Research On Microwave Pyrolysis For High Value-added Bio-products

Biomass is an ideal renewable energy with advantages of abundance resources and zero emissions of carbon dioxide. With the development of biamass pyrolysis techonology , microwave heating is applied into biomass pyrolysis because of its special advantages which is different from traditional heating way. In this paper, an experimental study on microwave pyrolysis of biomass was performed in the microwave reactor designed ourselves, including various factors,with the aim of getting high value-added productsFirstly, the relationship between microwave power and temperature was measured as the reference to controlling the pyrolysis temperature. Then the mechanism of microwave pyrolysis was discussed according to previous studies.Then, the microwave pyrolysis was studied ,and the traditional pyrolysis with electrical heating and microwave pyrolysis with microwave absorber added was also studied as comparison. The comparative results showed that microwave pyrolysis had a very good prospect on the optimization of bio-oil,getting high value-added products such as levoglucosan ,and also the preparation of activated char with high BET areas. For further study,some facters including final temperature, the kind of biomass and sample size were studed. As the microwave power increased, the yield of bio-oil firstly increased and then reduced ,while the char reduced overall. The high content of levoglucosan in the cotton stalk oil was discovered. The BET area increased with the final temperature under 550℃,but reduced a lot at 650℃. The content of levoglucosan in the bio-oil from the sample of the size<0.6mm and 1-2mm was much higher than from she size 5-10mm, and the contents of phenols increased while the sample size increased.Lastly, the microwave pyrolysis with catalysts was studied .It was found that H3PO4 pretreatment was very effective to reduce the components of the bio-oil and increase the content of furfural, and the BET area of the char was significantly more than the sample without acid pretreatment. Adding MgCl₂ had the largest yield both of the bio-oil and char, then was NaCl,the last was K₂CO₃. These three catalysts all made the content of furfural increase and phenols decrease, and the most effective one was MgCl₂ . Only MgCl₂ was useful to increase the BET area of the char.