Study On Characteristics Of Pyrolysates And Kinetics Of Shengli Lignite Catalytic Pyrolysis

The catalytic pyrolysis of coal can adjust the distribution and composition ofpyrolysates and realize the directed conversion of coal, therefore plays an essential role inthe effective utilization of coal. In this paper, several kinds of catalysts were selected, thenpyrolysates yield, properties and catalytic pyrolysis and chemical form of catalysts wereanalyzed under different catalytic conditions.The results of low temperature pyrolysis of lignite showed that the yield ofpyrolysates of liginteisgreatly influenced by catalysts.The addition of alkali metals (K2CO3,Na2CO3, KCl and NaCl) reduce the yield of pyrolysis water andtar and charsignificantly,but increase the yield of gas. The alkaline earth metal CaO and MgOsignificantly reduce the yield of gas and tar and increase the yield of pyrolysis water andchar.While the addition of CaCl2and MgCl2and the transition metal oxide (Fe2O3，MnO2，NiO) reduce the yield of char and tar while increase the yield of pyrolysis water and gas invarying degrees.The analysis results of gas products showed that all catalysts used can effectivelychange the mole fraction of H2, CH4, CO and CO2in the gas.The addition of alkali metalsand alkaline earth metal and Fe2O3all increase the content of H2.The content of CO in thegas reduces with the addition of all catalysts except CaO and NiO. While the content ofCH4in the gas reduces with the addition of all catalysts except CaO, MgO and NiO. Theaddition of CaO significantly reduces the the content of CO2, but in other conditions, thisphenomenon do not show clearly.The analysis results of tar showed that the main compounds of tluene solubles of tarwith no catalyst can be divided into four types, which separately are benzene series,phenols, alkanes and olefins. While, tluene solubles of tars produced with the addition ofdifferent catalysts not only contains these four compounds above, but also containsheterocyclic and oxygen-containing heterocyclic ccompounds. The ddition of differentcatalysts all reduce the content of alkanes while increase the content of phenolsheterocyclic and oxygen-containing heterocyclic ccompounds.The analysis results of solid products showed that the addition of catalysts reduces thedegree of graphitization of char. The char sueface becomes rough and disorderly,regardless of whether catalysts were added. The addition of catalysts increases the carbondioxide reactivity in varying degrees. K2CO3, CaO, MgCl2, Fe2O3, MnO2and NiO changetheir chemical form after pyrolysis, while Na2CO3, KCl, NaCl, MgO and CaCl2keep their form.The analysis of pyrolysis kinetics showed that the different catalytic pyrolysisprocesses of lignite accord with the first order single-reaction model both from400oC to500oC and from500oC to600oC. The activation energy of coal with addition of catalystsis lower than that of raw coal from400oC to500oC and from500oC to600oC, whichindicates that the addition of catalysts is more favorable toward promoting the lowtemperature step of lignite pyrolysis.