| The pyrolytic process of coal is an effective method for the efficient and clean utilization of low rank coal,with significant economic and environmental benefits.Catalytic pyrolysis,through the addition of a specific catalyst,is of great significance.It can effectively control the product distribution and reduce the heteroatom compounds in tar.In this paper,Powder-particle fluidized bed reactor was used to investigate the effect of modified HZSM-5zeolites on product distribution of Shendong coal pyrolysis.First of all,HZSM-5 zeolites with different SiO2/Al2O3 mole ratios（27、46、80、150）were selected to investigate the effect on product distribution of Shendong coal pyrolysis.With the increase of SiO2/Al2O3 ratio,the total amount of acid decreased and the yield of gas decreases indicating that the stronger acidity is more conducive to the formation of pyrolysis gas.H2content of raw coal pyrolysis was 10.467ml/g.Through HZ-27 zeolite,the content of H2increased by 91.1%compared to that of raw coal.Among them,HZ-46 had moderate acidity.Phenols and aliphatic hydrocarbons in the tar after HZ-46 catalytic pyrolysis decreased sharply by 76.3%and 88.8%respectively compared to that of raw coal.The content of monocyclic aromatic hydrocarbons increased by 4.7%compared to that of raw coal.Naphthalene,naphthalene derivates and polycyclic aromatic hydrocarbon（excluding naphthalenes）increased by 74%,173%than that of raw coal.Then,NaOH solution was used to investigate the effect of alkali-treated HZSM-5 zeolites（SiO2/Al2O3=46）with different treatment time.With the alkali treatment time increasing,the amount of mesopore volume and the specific surface area enhanced.In addition,the pore size distribution became broader and the acidity reached a peak followed by a continuous decrease.The content of the benzene and toluene in tar derived from pyrolysis in the presence of 0.5 h alkali-treated zeolite increased up to 268%and 296%compared to that of raw coal,respectively.In the case of 2 h alkali-treated HZSM-5 used in pyrolysis,the total amount of the pyrolysis gas was the highest,which was 24.8%higher than that of raw coal.The highest content of naphthalene,naphthalene derivates and polycyclic aromatic hydrocarbon（excluding naphthalenes）in tar could be obtained from pyrolysis when 4 h alkali-treated zeolite was exploited,which was about 92%and 192%higher than that of raw coal,respectively.Finally,2 h alkali-treated HZSM-5 was selected as the carrier to support different metal oxide loading（Co3O4、MoO3、NiO）.These metal-loaded HZSM-5 still had mesoporous structures,but the amount of pore volume and pore size decreased.After Meso-microporous zeolite was loaded with metal oxide,the content of H2 in the catalytic pyrolysis gas increased obviously.The content of H2 through HZ-2h-Ni catalyst was 139.1ml/g,which reached a maximum and increased 801%compare to that of HZ-2h.After Meso-microporous zeolite was loaded with metal oxide,the content of phenols and oxygenates in tar increased,the content of aliphatic hydrocarbons increased and the total amount of aromatic hydrocarbons decreased.However,in the case of HZ-2h-Mo used in pyrolysis,the content of naphthalenes reached the maximum which was 23.6%higher than that of HZ-2h. |
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