Study On Catalytic Pyrolysis Of Sunflower Stalk By Py-GC-MS/TG

A series of studies including biomass gasification, power generation and polygeneration pyrolysis have been carried out with the purpose of high efficient utilization of biomass energy, especially biomass pyrolysis receive the most widespread attention. Not only because biomass pyrolysis is the most important way to transform biomass into liquid fuel or high value-added chemicals, but also it is a key step in other thermal conversion of biomass. Therefore the mechanism of pyrolysis will become the key barrier to thermal conversion of biomass In this paper, we mainly take advantage of rich resources of sunflower stalk in Northern Shaanxi, explore the generating mechanism and thermal decomposition kinetics of pyrolysis products of sunflower stalk through pyrolysis products analysis and thermogravimetic analysis of biomass pyrolysis.(1) Py-GC/MS analysis method was applied to study the effect of pyrolysis temperature and time on the distribution of pyrolysis products fromcellulose, xylan and lignin. The results showed that, pyrolysis temperature had greater influence on the distribution of pyrolysis products from cellulose, xylan and lignin,but pyrolysis time on the pyrolysis products affected less; the pyrolysis products of cellulose were mainly glycogen and its derivatives. poor thermal stability of Xylan, of straight chain compounds have the most amount of the main pyrolysis products, followed by oxygen-containing heterocyclic compounds, in which phenols and ketones compounds content were less. Lignin pyrolysis process was relatively complex, and the phenolic in pyrolysis products were the most, in which low boiling point substances were less.(2) Using Thermogravimetric Analysis(TGA), we explored pyrolysis kinetics of cellulose, xylan and lignin. Through the Model-free Kinetics the pyrolysis reaction activation energy were calculated as 182.93-214.35 KJ/mol, 129.79-207.32 KJ/mol and 139.02-273.16 KJ/mol, respectively; Moreover, three groups of pyrolysis kinetic parameters by using the Model-free Kinetics and Model Kinetics were analyzed, the analysis data showed that, the pyrolysis mechanism of cellulose was three-dimensional diffusion model; The pyrolysis mechanism of xylan was phase boundary reaction model; and the pyrolysis mechanism of lignin was stochastic growth and subsequent nucleation model.(3) We explored the influence of pyrolysis factors(including temperature, time and catalyst) on the distribution of pyrolysis products of sunflower stalk. The study showed that, the effect of pyrolysis temperature and time on the pyrolysis of sunflower stalk were similar to that of these three components. The pyrolysis process of sunflower stalk was more complex than that of these three components pyrolysis, and there existed cross and conjugated reaction in pyrolysis process of sunflower stalk, and the pysrolysis products were mainly phenolic substances and straight chain compounds. The high boiling point material was mainly generated at 300℃ of the pyrolysis temperature, and a large number of low boiling point material was mainly generated at 400-600℃ of the pyrolysis temperature. The four kinds of catalysts had a certain catalytic effect on the pyrolysis process of sunflower stalk. The catalytic effect of Mo/Z and LCNF was the best, which can significantly improve the catalytic cracking reaction, in which CO2 content of pyrolysis of sunflower stalk was significantly improved ratherthan without catalyst.(4) The thermal weightlessness of sunflower stalk with or without catalyst were investigated. The analysis showed that, the pyrolysis reaction activation energy of sunflower stalk range from 210.15 to 245.87 KJ/mol; The pyrolysis mechanism of sunflower stalk was random nucleation and subsequent growth model. Through the investigation of catalytic pyrolysis effect of these four catalysts, data showed that the catalytic effect of Mo/Z and LCNF was the best. When the conversion rate range between 0~26%, the effect of LCNF was best, and when the conversion rate was above 26%, the effect of Mo/Z was best.