Experimental Study On Pyrolysis Behaviors Of Biomass Components

Biomass pyrolysis technology can produce high quality liquid fuels to realize the efficient utilization of biomass, therefore great attention has been paid to this technology in recent years. However, the large scale industrial application of pyrolysis technology has been restricted by the complexity and instability of bio-oil, which may be attributed to the lack of indepth study of biomass pyrolysis mechanism, especially for the pyrolysis of real biomass composition. Supported by relevant research programs, a systematic research of changing process of solid products during biomass compositions pyrolysis and real isolated biomass compositions pyrolysis mechanism is presented in this thesis.For most of the studies of biomass pyrolysis are from the perspective of the volatile, while solid products attract few attentions. The xenon lamp irradiation heating experimental apparatus was used to study the evolution of solid products in biomass compositions pyrolysis. The solid products were studied by elemental analysis, SEM, FTIR, XRD. At the beginning of pyrolysis, oligomer was formed by depolymerization of cellulose. And the ring opening of monosaccharide units and the rupturing of glycosidic bond were competing reactions in the following process. The crystalline structure was destroyed during pyrolysis. The formed coke was smooth and porous. The branches of hemicellulose were dissociated at the first stage. The backbone depolymerized via cleavage of glycosidic bonds followed by the rupture of xylose unit. The formed honeycomb coke was smooth and porous. The dissociation of branches and the depolymerization of aryl ethers were the main reactions during the devolatilization of lignin. The further damage of lignin basic units mainly occurred in the final process of coke formation.The compositions and structures of each component in different kinds of biomass vary greatly. The isolated cellulose from white pine was used in pyrolysis behavior research. Its chemical structure was studied by elemental analysis, FTIR and XRD. Cellulose was mainly composed of glucose connected with β-1,4-glycosidic bond. Due to the large molecular weight and crystal structure of isolated cellulose, it showed strong thermal stability. The typical products from cellulose pyrolysis were levoglucosan,5-HMF, 1-hydroxy-2-propanone and furfural, etc.There were few researches focused on the pyrolysis of isolated hemicellulose because of its difficulty of isolation. The hemicellulose samples isolated from white pine with alkali method was used as model compound in pyrolysis behavior research. Its chemical structure was studied by elemental analysis, FTIR and NMR. The isolated softwood hemicellulose was mainly composed of (3-1,4-glucomannan and β-1,4-xylan. The pyrolysis behavior was studied by analyzing the pyrolysis kinetics and the pyrolytic product distributions. And the typical products included acetic acid,5-HMF, furfural, levoglucosan acetone and 1-hydroxy-2-propanone, etc.For the study of another major component of biomass——lignin, the milled wood lignin (MWL) isolated from white pine through the Bjorkman procedure was used in pyrolysis behavior research. The chemical structure of MWL was characterized by elemental analysis, FTIR, NMR. The basic unit of white pine MWL was guaiacyl type. The abundant branches were well preserved and showed higher reactivity. The typical products from pyrolysis of white pine MWL were guaiacols and phenols.