Online Study On The Catalytic Pyrolysis Of Pine Wood Over Li₂CO₃ Using Photoionization Mass Spectrometry

Biomass is a kind of energy material produced by photosynthesis or metabolism,which can be any organic material storing solar energy in the form of chemical energy,such as cellulose and grease.Bioenergy is renewable energy from materials derived from biological sources.As a fuel,it includes wood,wood waste,straw,manure,sugarcane,and many other byproducts from a variety of agricultural proeesses.Bioenergy is huge in quantity and types,but its use efficiency is extremely low.The addition of hydrogen which produced from methane or coal is often required when using bioenergy,and pollutant emissions are reached,compared to combustion of traditional energy.So it is an important issue to utilize biomass energy more efficiently,which has an indispensable part of the national energy development strategy.Pyrolysis technology is an efficient way to convert biomass into energy that can be used directly.Cellulose,hemicelluloses,and lignin are three major parts of biomass.They are the raw materials in pyrolysis.In addition,there are some minerals in biomass,which mainly consists of silicon,potassium,calcium,magnesium,sodium,phosphorus and so on.Although the total mineral content is relatively small,it has been demonstrated that these minerals,especially the alkali and alkaline earth metals,such as Na,K,Ca and Mg,can have an evident impact on pyrolysis.Moreover,it is costly to remove these inorganic metals from biomass before pyrolysis.On the other hand,the catalytic pyrolysis process of biomass is complex with a wide range of products.A deep understanding of the pyrolysis mechanism is of great help to control the pyrolysis process of biomass.However,the mechanism of biomass catalytic pyrolysis is not well understood,it needs to be further studied and discussed.Hence,investigation on the effect of alkali and alkaline earth metal on the pyrolysis of biomass play a significant role in guiding,the actual production process.The dissertation contains four chapters.The first chapter reviews the distributions and applications of bioenergy,the basic principle and development history of biomass fast pyrolysis as well as effects of alkali metal on pyrolysis of biomass.Target of the dissertation to research the catalytic pyrolysis of pine wood over Li2CO3 by using online photoionization mass spectrometry.The purpose and significance of this research are explained.In Chapter 2,the structure and parameters of BL04B beamline in Hefei Light Source(HLS)are introduced briefly.And the Kissinger method to calculate the pyrolysis activation energy of pine wood is also introduced.In addition,the development of thermal analysis kinetics and time-of-flight mass spectrometry is outlined.In Chapter 3,facilities involved are described in detail,which contain online photoionization mass spectrometry and thermogravimetric(TG).Results of the catalytic pyrolysis of pine wood over Li2CO3 are described.It is found that the temperature to reach maximum decomposition rate is reduced,and the relative yield distribution of several important pyrolyzates is changed.Among the selected pine wood pyrolysis products,the relative yield of the pyrolysis products from cellulose and hemicellulose are reduced significantly,while that from lignin is increased.It is suggested that the Li2CO3 has obvious catalytic effect on the pyrolysis of pine wood.And a possible catalytic mechanism is proposed that the bond energy of C-O of pyrolyzates are reduced in the presence of Li+,thus promoting the decomposition of pyrolyzates.In Chapter 4,a new synchrotron-based online photoionization time of flight mass spectrometry is designed to research the pyrolysis mechanism of biomass.The facility consist of supporting framework,adjusting platform,low pressure pyrolysis chamber,ionization chamber and homemade time of flight mass spectrometer.This chapter also introduces an ultra-thin gate valve which can realize the function of quick sample-replacement and improve the efficiency of above-mentioned experiment facility.The last chapter briefly summarizes the main work of the dissertation,and gives further research plans.