Xylan of corn stover was pretreated with 1%,2%and 3%(w/w)sulfuric acid at relatively low temperatures(90℃,95℃ and 100℃)in a dilute acid cycle sprayflow-through reactor(DCF).The hydrolysis of xylan to its monomeric x...Xylan of corn stover was pretreated with 1%,2%and 3%(w/w)sulfuric acid at relatively low temperatures(90℃,95℃ and 100℃)in a dilute acid cycle sprayflow-through reactor(DCF).The hydrolysis of xylan to its monomeric xylose was modeled by a series offirst-order reactions.Both biphasic and Saeman hydrolysis models were applied tofit the experimental data.The results confirmed that the kinetic data of xylan hydrolysisfitted afirst-order irreversible reaction model and the experimental data.The reaction rates of xylose monomer formation and degradation were sensitive to catalyst concentration and temperature.Higher catalyst concentra-tion and lower reaction temperature result in high xylose yield.The activation energy for xylose formation and degradation were determined to be 112.9 and 101.0 kJ·mol^(-1),respectively.Over 90%theoretical xylose obtained from corn stover can be used to produce ethanol,xylitol and fumaric acid by fermentation.展开更多
The biomass of agricultural wastes as a source of fermentable sugars for biofuels production will address the food security and environmental preservation issues.These wastes are rich in lignocellulosic materials whic...The biomass of agricultural wastes as a source of fermentable sugars for biofuels production will address the food security and environmental preservation issues.These wastes are rich in lignocellulosic materials which can be hydrolyzed into fermentable sugars.However,low sugar yield and high energy consumption are some of the challenges faced in the process of hydrolization.This study investigated the low-cost corncob substrate for glucose production by dilute sulphuric acid hydrolysis in the presence of ZnCl_(2) at temperatures below 100℃after pretreatment with 10%NaOH.Time dependent hydrolysis data were analyzed by Saeman model,thermodynamic parameters were obtained using Erying and Arrhenius equations while Box-Behnken model(Design Expert 6.0 version)was used for experimental design.As the substrate concentration increased from 50 mg/L to 150 mg/L,glucose yield increased from 10.4 mg/g to 14.6 mg/g for pretreated corncob while an increase from 3.4 mg/g to 8.6 mg/g was noted for untreated corncob.The hydrolysis rate constant was two orders of magnitude higher than the degradation rate constant.Thermodynamic parameters revealed endothermic process with positive Gibb’s free energy of hydrolysis having average values of 84.76 kJ/mol and 79.87 kJ/mol for pretreated and untreated samples respectively.The optimum yield from the model was found to be 177.44 mg/g with 3.94%H_(2)SO_(4) and 0.43 mol/L ZnCl_(2) for 200 g/L compared with optimum yield of 46.37 mg/g obtainable without ZnCl_(2).The results of this study showed that the alkaline pretreatment of corncob increased the accessibility of cellulose from the solid fraction and increase glucose production.展开更多
基金funded by China Petroleum&Chemical Corporation,the National Natural Science Foundation of China(Grant No.20876078)the United Foundation of National Natural Science Foundation of China and Guangdong Province(No.U0733001)the National Hi-Tech Research and Development Program of China(No.2009AA02Z208).
文摘Xylan of corn stover was pretreated with 1%,2%and 3%(w/w)sulfuric acid at relatively low temperatures(90℃,95℃ and 100℃)in a dilute acid cycle sprayflow-through reactor(DCF).The hydrolysis of xylan to its monomeric xylose was modeled by a series offirst-order reactions.Both biphasic and Saeman hydrolysis models were applied tofit the experimental data.The results confirmed that the kinetic data of xylan hydrolysisfitted afirst-order irreversible reaction model and the experimental data.The reaction rates of xylose monomer formation and degradation were sensitive to catalyst concentration and temperature.Higher catalyst concentra-tion and lower reaction temperature result in high xylose yield.The activation energy for xylose formation and degradation were determined to be 112.9 and 101.0 kJ·mol^(-1),respectively.Over 90%theoretical xylose obtained from corn stover can be used to produce ethanol,xylitol and fumaric acid by fermentation.
文摘The biomass of agricultural wastes as a source of fermentable sugars for biofuels production will address the food security and environmental preservation issues.These wastes are rich in lignocellulosic materials which can be hydrolyzed into fermentable sugars.However,low sugar yield and high energy consumption are some of the challenges faced in the process of hydrolization.This study investigated the low-cost corncob substrate for glucose production by dilute sulphuric acid hydrolysis in the presence of ZnCl_(2) at temperatures below 100℃after pretreatment with 10%NaOH.Time dependent hydrolysis data were analyzed by Saeman model,thermodynamic parameters were obtained using Erying and Arrhenius equations while Box-Behnken model(Design Expert 6.0 version)was used for experimental design.As the substrate concentration increased from 50 mg/L to 150 mg/L,glucose yield increased from 10.4 mg/g to 14.6 mg/g for pretreated corncob while an increase from 3.4 mg/g to 8.6 mg/g was noted for untreated corncob.The hydrolysis rate constant was two orders of magnitude higher than the degradation rate constant.Thermodynamic parameters revealed endothermic process with positive Gibb’s free energy of hydrolysis having average values of 84.76 kJ/mol and 79.87 kJ/mol for pretreated and untreated samples respectively.The optimum yield from the model was found to be 177.44 mg/g with 3.94%H_(2)SO_(4) and 0.43 mol/L ZnCl_(2) for 200 g/L compared with optimum yield of 46.37 mg/g obtainable without ZnCl_(2).The results of this study showed that the alkaline pretreatment of corncob increased the accessibility of cellulose from the solid fraction and increase glucose production.
