Microwave-assisted hydrolysis of cellulose using metal chloride as Lewis acid catalysts

The hydrolysis of cellulose under microwave irradiation using various metal chlorides as Lewis-acid catalysts was investigated. It was found that the cellulose conversion and product selectivity is strongly dependent on the reaction parameters like reaction temperature, time, microwave power, chloride type and amount used. In comparison with the conventional heating method, the microwave irradiation can accelerate the cellulose hydrolysis and improve the selectivity to glucose with good conversion. Among the metal chlorides investigated, copper chloride is the best catalyst for the hydrolysis of cellulose. For 0.5g of cellulose in 15g of water, when quitting the reaction once the temperature reached 225°C under a microwave power of 800W, the cellulose conversion reached 72.6% with a glucose selectivity of 62.3% by using 0.05mmol of copper chloride as catalyst; the increase of the copper chloride amount to 0.15mmol led to a selectivity of 13.2% to 5-hydroxymethyl-2-furaldehyde (5-HMF); the further increase of the copper chloride amount to 0.30mmol resulted in a cellulose conversion as high as 90.6% but a glucose selectivity of only 6.7%.