| My country’s energy is dominated by coal,and low-metamorphic coal accounts for more than 55%of the proven reserves.Shengli lignite is one of the low-metamorphic coals.The characteristics of"three highs and one low"of Shengli lignite determine its utilization method—coal pyrolysis.Coal pyrolysis is the basis of all thermal processing of coal,and the resulting pyrolysis products are high value-added and environmentally friendly chemical products.Therefore,the choice of coal pyrolysis is of great practical significance for the utilization of Shengli lignite.However,the pyrolysis of coal is affected by many factors.In this paper,Shengli lignite is studied by adding catalyst and changing the atmosphere.The catalyst selected in this study was USY molecular sieve and was modified by two methods using USY molecular sieve as a carrier.The first method is to synthesize monometallic or bimetallic modified catalysts by loading Fe,Co,Ni,Mo and W transition metal oxides on USY by impregnation method;In the encapsulation method,solid phosphotungstic acid was charged into the interior of USY to synthesize HPW-USY catalyst.The physicochemical properties of the synthesized catalysts were characterized and used in the catalytic pyrolysis experiments under N2 atmosphere and H2 atmosphere with a final temperature of 600°C in a particle fluidized bed.The pyrolysis products were analyzed by thermogravimetric,GC-MS and Karl Fischer hydrometer,and the analysis showed:（1）The catalyst has almost no effect on the yield of pyrolysis semi-coke,and changing the atmosphere affects the yield of pyrolysis semi-coke.For the same catalyst,the pyrolysis semi-coke yield of coal in H2 atmosphere is 3%lower than that in N2 atmosphere.（2）The catalyst affects the yield of pyrolysis gas.In N2 atmosphere or H2 atmosphere,the catalyst increases the yield of pyrolysis gas;for the same catalyst,the yield of pyrolysis gas changes when the atmosphere is changed,and the H2 atmosphere is higher than the N2atmosphere.The yield of pyrolysis gas increased by 20%～41%,and the Ni-USY catalyst had the greatest influence on the yield of pyrolysis gas by changing the atmosphere.For the same catalyst,changing the atmosphere also affects the composition of the pyrolysis gas.For the same catalyst,the content of CO,CO2,C2～C3 and CH4 from pyrolysis in H2 atmosphere increased compared with that in N2 atmosphere,and the content of H2 increased or decreased.（3）N2 atmosphere or H2 atmosphere,the catalyst reduces the yield of pyrolysis tar.For the same catalyst,the effect of H2 atmosphere on the yield of pyrolysis tar is different compared to that of N2 atmosphere.The effect of changing the atmosphere on the catalyst tar yield:Co-W-USY>HPW-USY>Ni-USY>Mo-USY>USY>Fe-USY>Fe-W-USY>Ni-W-USY>Co-USY>W-USY.Compared with no catalyst,under N2 atmosphere,all catalysts reduce the content of heteroatom compounds,phenolic compounds and oxygen-containing compounds,and increase the content of naphthalene compounds;under H2 atmosphere,all catalysts reduce polyphenyl ring compounds,naphthalene compounds in tar.The content of phenolic compounds,heteroatom compounds and oxygen-containing compounds decreased.For the same catalyst,the lightening degree of tar in H2 atmosphere is increased by 4.41%～13.63%compared with that in N2 atmosphere,and Fe-USY catalyst has a significant effect on the lightening degree of tar by changing the atmosphere.（4）Under the N2 or H2 atmosphere,the carbon deposition rate of different catalysts is not much different.For the same catalyst,the carbon deposition rate of the catalyst in the H2atmosphere is lower than that in the N2 atmosphere.（5）Under N2 atmosphere,the yield of pyrolyzed water by different catalysts has little difference,but in H2 atmosphere,the yield of pyrolyzed water by different catalysts has a great change.For the same catalyst,the yield of pyrolyzed water in H2 atmosphere was increased by5%～26%compared with that in N2 atmosphere. |
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