Pretreating Agricultural And Forestry Wastes By The Concentrated Phosphoric Acid Plus Hydrogen Peroxide(PHP):Technology And Mechanism

In this study,the concentrated phosphoric acid plus hydrogen(PHP)was employed to treat the agricultural and forestry wastes.The main results are shown as follows:1.Several typical materials were employed in order to explore the adaptability of PHP for different lignocellulosic materials,for example:agricultural wastes(wheat straw,corn stalks,Jerusalem artichoke straw),cork(Chinese fir),hardwood(Oak),bamboo and weeds.It was found that 71.0%to 96.0%lignin and more than 95.0%hemicellulose were removed whichever the types of lignocellulosic feedstock,besides,more than 90.0%of cellulose was retained.The enzymatic hydrolysable sugar conversion rates of 94.9%and 100%,respectively It suggested that PHP has a wide range of adaptability for lignocellulose.When the different particle sizes of wheat straw and oak were employed.It showed that the hydrolysis rate of hydrolyzed sugar could reach 94.9%and 100.0%respectively.It was indicated that PHP can effectively reduce the pretreatment requirements for particle size.2.The temperature,time or the acid-concentration of PHP were selected as control variable.It was found that the removal of hemicellulose was dependent on the increase of phosphoric acid concentration.And the removal of lignin was related to the concentration of hydrogen peroxide.Under certain conditions,100.0%removal of hemicellulose can reach within 2 h pretreatment,the lignin removal could be achieved 83.7%also.When the temperature was achieving 30? to 40?,92.0%cellulose can be retained after 2 h pretreatment,and the enzymatic hydrolysis could reach more than 90.0%.After the experiment,we can find that 29.1 g-32.6 g glucose can be produced from 100.0 g wheat straw.3.The microcrystalline cellulose,xylan and de-alkanine lignin were used as model components of lignocellulose.We found that the removal of hemicellulose mainly depends on two parts:the dissolution of concentrated phosphoric acid and the oxidation of PHP solution.For lignin,PHP can destroy the lignin-based cross-linked structure,which is lead to the deligninfication.In addition,some lignin is directly oxidized into phenolic acids and small molecular acids due to the oxidation of PHP.Ultimately,we found that the recovery of cellulose can reach more than 90.0%.This suggests that PHP has an efficient effect on the removal of hemicellulose and lignin,which explains why the structure of the cellulose did not change significantly after PHP treatment,but the enzymatic hydrolysis rate was significantly improved after PHP treatment.