Study On Pyrolysis Of Biomass

The exploitation and utilization of biomass energy and biomaterial will relieve the pressures caused by fossil fuel shortage and environmental pollution, which is beneficial for sustainable development in China. Biomass pyrolysis technology, which can convert low-quality biomass to high-quality liquid fuel or gas, also some valuable chemical materials, has been paid great attentions during these years. Pyrolysis is not only an independent process for biomass conversion, but also a key stage in biomass gasification, liquefaction and combustion. It is significant to understand the mechanism for biomass pyrolysis. In this paper, the research of pyrolysis was carried out on lignin and protein which are the components of biomass. The pyrolysis products of lignin model compound and milled wood lignin (MWL) at different temperatures were determined by GC/MS to find the effect of temperature on pyrolysis process;13C-isotopic tracer of the Protein in tobacco was also applied, Then the tobacco which contain the protein labeled with isotope 13C was therm-degraded, the obtained products which contain polycyclic aromatic hydrocarbons from tobacco mainstream smoke was analysed with GC/MS-SIM. In this paper, a model compound ofβ-O-4 type lignin model compound (i.e. guaiacylglycerol-β-guaiacyl ether) was synthesized with a modified method. The research showed that an important intermediate, i.e. 4-(α-bromoacetyl)- guaiacol could be obtained when ethanol was applied as solvent instead of the mixture of ethyl acetate/chloroform (1/1,V/V). The reason was that ethanol could change this bromination reaction from non-homophase to homophase. As a result, the yield of bromide was enhanced from 81.54% to 94.27%. The recrystallization by benzene could not separate the 4-(α-bromoacetyl)-guaiacol. But it could be obtained by column chromatography using the mixture of hexane and ethyl acetate (2/1, V/V) as mobile phase. The combination of melting point, infrared spectra, 1H-NMR analysis was used to identify the chemical structure of the product and related intermediate products. The results indicated that the product had good yield.Pyrolysis was carried out on lignin model compound at different temperatures. GC/MS was applied to analyze the products. The relationship between products and pyrolysis temperature were discussed. The results indicated that two types of reactions, Cβ-O ether cleavage and Cγ-elimination, were suggested as important pyrolytic reactions when the temperature was below 400℃. Substance as 4-acetovanillon, guaiacol, cinnamyl alcohols, and vinyl ethers were identified as degradation products from cleavage of linkage. The kinds of pyrolysis products were few when the temperature was below 400℃. The kinds of pyrolysis products increased significantly when the temperature was above 400℃. It could be supposed that some low molecular weight material were formed by radical coupling of lignin fragments. Moreover, some heterocyclic compound also appeared.Similar phenomena was be observed on the pyrolysis of milled wood lignin (MWL). The products can be influenced by temperatures. The components of pyrolysis product were different along with the change of temperatures. However, the tar product was mainly composed of phenol compounds with different functional groups such as methoxyl group, alkyl group, hydroxyl group, and also of carboxyl and carbonyl groups. The cleavage of bonds in branch-chain occurred at low temperature. When the temperature became much higher, some phenol compounds were formed by cleavage ofβ-O-4 linkage and other ether linkages. With the increase of temperature, it could be supposed that some aromatic compound and alkyl ramification were formed by radical coupling of lignin fragments.In order to know more about the pyrolysis product especially the deleterious ones of protein at high temperature, In this paper, the tobacco was applied to the research because of its high content of protein. There is research on 13C-isotopic tracer of the protein in tobacco, the content of 13C in the tobacco has been increased through injecting glycin. Then the tobacco which contained the protein of isotope 13C was degraded in high temperature. Through analyzing the polycyclic aromatic hydrocarbons from tobacco mainstream smoke with GC/MS-SIM, the results indicate that the ratio of 13C/12C in acenaphthylene, fluorene, phenanthrene, anthracene, fluoranthene, pyrene, chrysene, benzo[a]pyrene was much higher than in the corresponding substance from mainstream smoke of unlabeled tobacco. It could be concluded that the protein make contribution to the produce of polycyclic aromatic hydrocarbons during the process of degradation.