Pyrolysis Characteristics Of Barkinitic Liptobiolith Catalyzed By Metal Modified USY

Barkinitic liptobiolith coal is considered as a special kind of coal in China,It has volatile matter,strong caking-property,high cohesiveness,high tar yield and low moisture.So,it has an important application prospect in fine utilization.So far,there are few reports on the thermal conversion of this coal,especially on the catalytic pyrolysis.Catalytic pyrolysis is one of the important ways for efficient and clean conversion and utilization of coal.Through the catalytic process,on the one hand,the conversion rate of coal pyrolysis can be improved;on the other hand,it can effectively control the composition and distribution of pyrolysis products,and promote the directional conversion of Barkinitic liptobiolith products to high value-added chemicals.In this paper,a series of metal-modified USY catalysts were prepared using USY molecular sieve(ultra-stable Y zeolite)as the matrix.By introducing Co,Mg,Fe,Mo,Cu and W active metals,The effects of the above six kinds of metal supported catalysts on coal pyrolysis performance were studied by pyrolysis-gas chromatography-mass spectrometry(Py-GC-MS).The effect of different catalysts on the distribution of the products of barkinitic liptobiolith coal catalytic pyrolysis was investigated.The mechanism of catalytic pyrolysis on tar products from bark coal pyrolysis was also explored.On that basis,the effect of the bimetal doping modification on the catalyst activity was explored,and the catalytic pyrolysis mechanism was analyzed.The thesis studies the basic properties of barkinitic liptobiolith,through elemental analysis,industrial analysis,infrared spectroscopy and pyrolysis methods.It was found that Liupanshui barkinitic liptobiolith has low moisture content,high volatile content and strong cohesiveness.The chemical structure is mainly composed of aromatic core,aliphatic side chain and oxygen-containing functional groups.The thermogravimetric analysis and tube furnace were used to investigate the thermal weight loss and product distribution of barkinitic liptobiolith at different final pyrolysis temperatures.The yield of tar was 20.60%by Gray-king assay of barkinitic liptobiolith,the gas yield was 105 mL/g.When the final pyrolysis temperature is 800℃,the weight loss of barkinitic liptobiolith is the largest,total weight loss up to 32%,and the gas yield was 135 mL/g.Through Py-GC-MS,the relative contents of aromatic and aliphatic hydrocarbons in bark coal pyrolysis are 52%and 29%,respectively.Six kinds of Co,Mg,Fe,Mo,Cu,W modified USY catalysts with a mass fraction of 5%were prepared by the impregnation method,and used for pyrolysis of barkinitic liptobiolith.The tar yield of CO/USY catalytic pyrolysis is the highest,up to 20%,which is 9%higher than that of raw coal,Mg/USY catalyst increased by about 6%.The aromatics yield increased by 13%after adding USY catalyst,Other supported single metal USY catalysts also increased the yield of aromatic hydrocarbons in barkinitic liptobiolith pyrolysis.The results showed that the addition of catalyst promoted the conversion of aliphatic group to aromatic group.After adding USY catalyst,the relative content of benzene,toluene,ethylbenzene and xylene(BTEX)changed significantly.The relative content of xylene was the most significant.Two bimetallic doped(1:5)USY catalysts 1Co-5Mg/USY and 5Co-1Mg/USY were prepared by impregnation method.Co-Mg modification increased the specific surface area of USY zeolite,and effectively regulated the B acid active site and L acid active site.Compared with USY,the total acid content of 1Co-5Mg/USY and 5Co-1Mg/USY decreased,and the B/L of weak acid and B/L of medium strong acid increased;The results show that Co-Mg modified catalyst can improve the aromatics content in tar.The aromatics yield of 5Co-1Mg/USY catalyst is higher than that of 1Co-5Mg/USY catalyst.The conversion of aliphatic group in barkinitic liptobiolith is inhibited by 1Co-5Mg/USY catalyst.Combined with the change of acidity,it is found that the bimetallic modified catalyst with larger B/L ratio is better for cracking.1Co-5Mg/USY is helpful for the formation of aromatic hydrocarbons.