Abstract: The dilute acid hydrolysis was applied to the poplar residues conversion,and the polysaccharides conversion rate was figured out for the assessment of conversion efficiency.Several parameters concerned with the conversion efficiency,such as bio-mass substrate size,dosage of acid,hydrolysis pressure (or temperature) and reaction time were investigated.The response surface experimental design was used to optimize the dilute acid hydrolysis conditions.It was proposed that proper particle sizes were 0.075 to 0.096 mm and the optimal conditions for the dilute sulfuric acid hydrolysis were illustrated as the solid to liquid ratio of 1:10,temperature of 158 ℃,reaction time of 5 min,and the fraction of sulfuric acid of 2.5%.Under the optimal conditions, the polysaccharides conversion rate was up to 59.23%.The HPLC analysis of hydrolyzates showed that the main component was xylose (29.897 g/L) with a content of 64.8% in total sugar amount,and the second one was glucose (8.748 g/L) with a content of 18.9%.Less monosaccharides further degraded in the dilute acid hydrolysis.The SEM observation and XRD analysis of substrate samples before and after the dilute acid hydrolysis showed that the fiber structure of the hydrolysis residue was damaged obviously,and the crystallinity decreased from 57.45% of the raw material to 47.37% of the hydrolysis residue.It could be expected that the hydrolysis residue be utilized to make bioethanol by enzymatic hydrolysis and fermentation.

Key words: poplar wood waste, dilute acid hydrolysis, pretreatment of biomass, response surface experimental design