Effect Of Continuous Steam Explosion On Ultrastructure And Components Of Eucalyptus And Eulaliopsis Binata

Plant fiber is a sustainable development biomass resources. It has become a competing project to research plant fibers for application. Appropriate pretreatment is one of keys to efficiently use of plant fibers. Steam explosion technology which has become an important pretreatment mean is a new physical-chemical pretreatment technology. It is high efficiency, environment protective and no pollution. Steam explosion have different effect on different plant fibers; and different applications need different pretreatment degree. There are some differences in principle and effect between the steam explosion manufactured by our research group and batch steam explosion. So, it has an important significance to study the effect and the law of continuous steam explosion on typically woody and herbaceous plant fiber.In this paper, the self-designed continuous screw steam explosion machine was used and the Eucalyptus(woody) and Eulaliopsis Binata(herbal)were repeatedly pretreated by it. The influence of the steam explosion times on the ultrastructure of plant fibers was studied by TEM and SEM. Chemical composition of different plant fiber is analyzed by fiber analyzer. The crystalline properties of steam explosion fibers were studied by X-ray diffraction techniques. Lignins were separated with phosphoric acid-ethanol. The influence of the steam explosion times on the separation ability, structure, molecular weight and distribution, glass-transition temperature and thermal stability of lignin were studied.TEM and SEM analysis show that with the increase of the continuous steam explosion times, the dimensions of Eucalyptus and Eulaliopsis Binata fiber are reduced. Cell lumen of Eucalyptus become bigger, cell wall become thinner after continuous steam explosion. During the continuous steam explosion, the ultrastructure of these plant fibers are damaged, the CML is gradually being stripped, the S1 is gradually being destroyed, accompanied by some S2 bared, the S3 and the pit membrane ruptured. In addition, there are many particles with higher concentration lignin on the surface Eucalyptus make fiber adhesive after the fourth time steam explosion. During the steam explosion, the regularity of hierarchical structure of Eulaliopsis Binata fiber hierarchy were damaged. There were also some other phenomena like surface fluff and lignin migration and aggregation. The degree of lignin aggregation increased, particles with higher concentration lignin embedded in the cell wall or deposited on the surface of the fiber.The Van Soest method was used to analyze the composition of fiber. It shows that different isolated compositions of Eucalyptus and Eulaliopsis Binata change greatly after continue steam explosion. With the increase of steam explosion times, the content of NDF increases and that of cellulose decreases.XRD analysis shows that during the continuous steam explosion, the crystal form of Eucalyptus and Eulaliopsis Binata cellulose does not change, but there are different effect on the changes of the crystallinity of them. The crystallinity of Eucalyptus fiber decreased after steam explosion. While that of Eulaliopsis Binata fiber increased firstly and then decreased with the increase of steam explosion times.Research on lignin of continuous steam explosion plant fibers shows that with the increase of steam explosion times, the extraction rate of Eucalyptus lignin increased, but the rate of increase declined, extraction rate stabilized. The extraction rate of Eulaliopsis Binata lignin increased firstly and then decreased. Continuous steam explosion had little effect on the aromatic skeleton structure of eucalyptus and Eulaliopsis Binata lignin. With the increase of the continuous steam explosion times, the molecular weight of Eucalyptus lignin increases firstly and then stabilizes, the glass transition temperature decreases after the first time steam explosion, the thermal stability is reduced after the first time steam explosion and then increase. The molecular weight of Eulaliopsis Binata lignin decreases after the first time steam explosion; with the increase of the continuous steam explosion times, the molecular weight of Eulaliopsis Binata lignin increases firstly and then decreases, and the glass transition temperature and the thermal stability increase.In a word, continuous steam explosion is an effective mean for plant fiber pretreatment. It can efficiently separate components of cell wall, improve permeability of chemical reagents and the accessibility of cellulose. The degree of plant fiber pretreatment can be adjusted by changing the steam explosion time.