Catalytic Pyrolysis Of Biomass Model Compounds As Revealed By On-line Photoionization Mass Spectrometry

Fossil energy still supports the main energy consumption in the world today.However,the wide use of fossil energy brings about depletion of global fossil resources and serious pollution of the environment,thus it is of great importance and urgency to find alternative energy sources.As the only renewable carbonaceous resource in nature,biomass is an environmentally friendly energy and a widespread material all over the world.Biomass pyrolysis is a commercialized technology,which can efficiently convert biomass into fuel and chemical products with high added value.The products can be regulated flexibly by adding catalysts during the pyrolysis process.Owing to the complexity of the biomass,biomass model compounds have been used as agents to simplify the study,which is beneficial to investigate the catalytic conversion mechanism of biomass at a molecular level.In addition,the unraveled catalytic process of model compounds can be utilized to design the approporaite catalysts rationally and control the catalytic reactions precisely,thus guiding the actual reaction and maximizing the utilization rate of biomass.In this dissertation,we have mainly used synchrotron radiation photoionization mass spectrometry to systematically inverstigate the catalytic pyrolysis of xylan by alkali metal salt,the catalytic pyrolysis of furfural,and furan by zeolites.This dissertation includes the six chapters as listed below.In the first chapter,the necessity of the development of biomass energy is discussed;the biomass and its conversion methods are summarized;the catalysts for biomass catalytic pyrolysis and the application of photoionization mass spectrometry are clarified;the aim and significance of the research work are introduced.The second chapter mainly illuminates the experimental equipments and data analysis methods.The mechanism of synchrotron radiation photoionization mass spectrometry and reactor are presented in detail.In addition,principal component analysis(PCA),multivariate curve resolution alternate least squares(MCR-ALS),and quantum chemical calculation methods are introduced briefly.In the third chapter,the catalytic pyrolysis of xylan by alkali metal salts has been studied with synchrotron radiation photoionizationmass spectrometry and capillary sampling technique.The addition of alkali metal salts(Na2CO3 and K2CO3)reduces the temperature and reaction rate of xylan pyrolysis.The addition of alkali metal salts has an influence on the product distribution.In order to explore the difference of alkali metal salt types and alkali metal salt concentrations in the catalytic pyrolysis of xylan,PCA and MCR-ALS were utilized to process and analyze the mass spectra.The results show that the difference in the product distributions under the influence of two alkali metal salts are identified clearly by PCA;when the content of Na2CO3 is less than 5%,the variation of Na2CO3 content has a significant effect on the pyrolysis products.The alkali metal salts promote the ring-opening and decarboxylic reactions of xylan,thus enhancing the formation of products with low mass-to-charge ratio.The fourth chapter mainly presents the furfural pyrolysis and the catalytic pyrolysis of furfural by synchrotron radiation photoionization mass spectrometry and molecular beam sampling technology.More than 20 kinds of furfural pyrolysis products were detected,including the significant product vinylketene.The possible paths of H atom attacking furfural were studied by theoretical calculation.The catalytic pyrolysis products of furfural by HY and H? mainly contain alkenes,aromatics and oxygen compounds.The trends of identical species catalyzed by HY is similar to H? in the temperature-programmed experiments.However,benzofuran was detected in the catalytic pyrolysis product of furfural by HP,but not detected by HY,due to their difference in pore channel and acidic property.The formation temperature of furan is the lowest in all products,which indicates that the initial reaction of furfural on zeolites is decarbonylation to yield furan.In the fifth chapter,the catalytic pyrolysis of furan was studied by zeolites with synchrotron radiation photoionization mass spectrometry,and the catalytic conversion of furan by zeolites under low temperatures was investigated in a commercial fixed bed device.The temperature-programmed processes of furan conversion was monitored by synchrotron radiation photoionization mass spectrometry.It was found that only benzofuran was detected when temperature was lower than 300 ?,which provides a possible method for the industrial production of benzofuran.Then,the yield of benzofuran was optimized and evaluated by using a commercial fixed bed device and GC/MS at low temperatures.The sixth chapter summarizes the research work of this dissertation briefly and gives a prospect for the future works.