Research On Preparation Of Xylose By Hydrolyzing Corncob

Xylose is becoming more and more widely applied in food industry as a food additive.Corncob is used as the main raw material for xylose production,and it is cheap and easy to get.The process of hemicellulose hydrolysis takes a large cost in xylose production.It has been choosed a better method about corncob hemicellulose hydrolysis conditions and purification process to obtain xylose of high purity.The corncob hydrolysis process also has been studied,and the hydrolysis conditions has been optimized as well as the crystallization conditions,which would improve the utilization rate of raw hemicellulose and reduce the concentration of the by-products.It has provided research foundation for making full use of corncob and establishing the clean industrial production of xylose.In order to make full use of hemicellulose and to get high xylose yield,we used sulfuric acid and oxalic acid to get a better hydrolysis conditions.Among them,the single factor reaction conditions of sulfuric acid were given as follows: reaction temperature was 130 °C,reaction time was 60 min,acid concentration was 1.2%,solid-liquid ratio was 1:10,the concentration and yield of xylose were 28.9 g/L and 85.0%.The optimal single factor conditions for oxalic acid hydrolysis were given as follows: reaction temperature was 130 °C,reaction time was 120 min,acid concentration was 1.2%,solid-liquid ratio was 1:10,the concentration and yield of xylose were 32.7 g/L and 96.1%.The corncob hydrolysis performed by a mixture of sulfuric acid and oxalic achived xylose concentration of 32.1 g/L at the following conditions: 1.2% of oxalic acid was mixed with the same volume of 1.2% sulfuric acid,the reaction time was 90 min,reaction temperature was 130 °C,and it can shorten the reaction time,reduce the degradation of xylose and improve the yield of xylose.We can get the ideal conditions of acid hydrolysis by the built dynamic models,and it showed that the models can predict hydrolysis conditions well.Meanwhile,the optimized decoloration conditions of corncob hydrolysate were as follows: the decoloration were carried out twice,activated carbon of 8%(w/v)was added during each operation,temperature was 80°C,decolorization time was 20 min,the light transmittance and removal rate of protein achived were 86.2% and 84.3%,respectively.D380 anion exchange resin and the D001 cation exchange resin had fine impurities removal efficiency.The ion removal rate reached more than 94.0% and 50.0%,respectively.The transmittance of solution was greater than 99.9%.But the effect of desalination process on xylose yield was that the yield lost nearly 9.6%.The optimization results of crystallization process were as follows: crystallization temperature was 25 °C,ethanol concentration was 80.0%(wt%),seed crystal amount was 0.04 g/g,initial concentration of xylose was 80.0%(wt%),the crystallization time was 12 h,and the xylose crystallization yield was 85.5% with the purity of 96.6%.