| Biomass energy is one of the effective ways to solve the energy crisis and environmental pollution as a renewable energy. With the development and utilization of biomass energy, the conversion technologies of biomass are promoted rapidly. Pyrolysis of biomass is an important thermal-chemical conversion technology which could produce bio-oil quickly through decomposition. However, the traditional technology has the disadvantage of high energy consumption and long reaction cycle. Therefore, it is urgent to explore or establish a facile route for biomass conversion for scientific significance.Rice straw and sawdust produced in the suburbs of Chongqing were investigated as a research object with the household microwave oven as heating device, with the ionic liquids as catalyst. The fast pyrolysis of biomass by microwave irradiation was studied to explore an optimum test condition. Under the optimum condition of 800 W microwave power, with the ratio of [Bmim]Cl and rice straw and sawdust of 0.15 and 0.30 respectively, the maximum yield of bio-oil was up to 42% and 32 % in 15 min microwave irradiation. [Bmim]BF4 was investigated as an object, with the weight ratio of rice straw of 0.35, the maximum yield of bio-oil was up to 32% under 640 W microwave power; with the weight ratio of sawdust of 0.50, the maximum yield of bio-oil was up to 34% in 20 min microwave irradiation under 800 W microwave power. Ionic liquids could be recycled and reused after reaction. It has the advantage of green environmental protection and reducing the response cost.The changes of functional in biomass and reacting biomass were analyzed by infrared chromatographic. The analysis showed that some functional groups of cellulose, hemicelluloses and lignin in biomass materials were weakened or deleted after microwave irradiation. At the same time, the major chemical components and contents of biomass bio-oil were obtained by gas chromatography-mass spectrometry. The main components in bio-oil included furfural, acetic acid and 1-hydroxy-2-butanone, the content of them depends mainly on the source of biomass and the type of ionic liquid in pyrolysis process. The results also showed that bio-oil composed of the functional groups which were relative to the weakened and deleted ones in FTIR. Based on the data of the experiment and the theory analysis, the pyrolysis mechanisms of cellulose, hemicelluloses and lignin were studied respectively and a simple theoretical model was developed to describe the pyrolysis behavior.Compared to the conventional heating method, the pyrolysis technology of microwave irradiation could produce the bio-oil in a short time, and has simplified reaction device and convenient operation. Therefore, this newly-developed pyrolyzing method has the advantages of energy-efficient, simple and efficiency and requires further investigation. |
PDF Full Text Request