| With the increasing global environmental problems and the depletion of global petrochemical resources,it is an inevitable trend to produce fuel energy,bulk chemicals by using the green and renewable lignocellulosic biomass in the future.At present,the hard wood and soft wood resources have been developed and utilized widely.The hemp plants have a short growth cycle,excellent material properties,and significant economic and ecological benefits.However,currently,the hemp biomass resources are not well developed and utilized.In order to achieve the full utilization of biomass components,it is necessary to understand the basic composition and structural features of raw materials in order to achieve efficient isolation and conversion of biomass components.On this basis,the industrial lignin produced by the existing pulping process of abaca raw material were comprehensively characterized and the structural changes of abaca lignin can be illustrated,which will provide a theoretical basis for its high-value utilization.At the same time,the dissociation of the main components of Abaca under the new-developed deep eutectic solvents(DESs)was explored,and the structure characteristics and application direction of the dissociation components were clearly understood.The main research contents and results of this paper are as follows:(1)Understanding the characteristics of the hemp biomass materials.Composition of the Abaca and the hemp was analyzed,and the corresponding hemicellulose and lignin samples were isolated to compare the differences between them.The Abaca contained 2.05%ash,5.21%extract,0.14%pectin,55.68%cellulose,20.35%hemicelluloses and 16.57%lignin.The hemp contained 2.31%ash,4.25%extract,2.92%pectin,61.59%cellulose,22.17%hemicellulose and 6.76%lignin.The studies had shown that the hemicelluloses of the Abaca and the hemp were mainly composed of(1?4)-?-D-xylan and?-glucan.The main differences were that lignin from the Abaca lignin only contained the?-O-4 aryl ether bonds(64.16/100Ar),and the hemp lignin contained?-O-4 aryl ether bonds and?-?linkages.(2)The structural characteristics and molecular structure changes of lignin in alkaline hydrogen peroxide pulping process of Abaca hemp were expounded.The alkaline hydrogen peroxide lignin(AHPL)produced by Abaca hemp was isolated and compared with double enzymatic hydrolysis lignin(DEL)..The results showed that the Abaca lignin is composed of p-hydroxyphenyl,guaiacyl,and syringyl-type units as well as abundant esterified p-coumaric acid.During the delignification of AHP process,the aryl ether bonds of lignin were slightly broken and the p-coumarate units were partial cleaved.In addition,it was observed that the dominant?-O-4 linkages in both DEL and AHPL suggested that these lignin fractions are beneficial to the downstream conversion of lignin into aromatic chemicals.(3)A green and efficient pretreatment method for dissociating the main components of Abaca was explored.Using abaca as raw material,alcohol-based eutectic solvent(DES)pretreatment realized the rapid dissociation of the main components of abaca and the detailed structural characterization of the isolated components.Results showed that the lignin removal rate can reach 92.79%under DES pretreatment under 110 ? for 30 mins.The resulting lignin can reach nano-levels,having high purity,low molecular weight,and low polydispersity,which can be obtained by adjusting the pretreatment parameters.These lignin fractions will provide high-quality raw materials for high-value application of lignin and promote the development process of value-added materials related to lignin.At the same time,the resulting cellulose residue also showed good enzymatic saccharification performance(greater than90%).DES optimization and cycle experiments showed that the DES treatment effect can be adjusted by different treatment parameters,which will lay the foundation for the controlled isolation and precise utilization of the main components of the final biomass raw material. |
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