The Controlled Preparation Of Beta/Mordenite Zeolite And Its Mixed Crystalline Zeolite And Their (Hydrogenation) Catalyzed Conversion Of Methyl Anthracene

Coal as the main energy in China will not change in the short term,under the background of"double carbon",it is of great significance to realize the clean and efficient utilization of coal by quality classification.Coal tar is an important product of coal pyrolysis and conversion process,and the preparation of light aromatic hydrocarbons by catalytic conversion is one of the effective means to achieve high value utilization of light aromatic hydrocarbons,and the design and preparation of high activity catalyst is the key to improve the selectivity and yield of light aromatic hydrocarbons in the conversion process.In this paper,different zeolite molecular sieves（Beta zeolite,beta-Mordenite mixed zeolite and Mordenite zeolite）were prepared by changing the crystallization time with the same initial gel ratio.X-ray diffraction（XRD）,Fourier transform infrared spectroscopy（FTIR）,temperature programmed ammonia desorption（NH₃-TPD）,nitrogen adsorption desorption（BET）,pyridine infrared spectroscopy（Py-IR）and inductively coupled plasma spectroscopy（ICP-OES）were used to characterize the physical and chemical properties of the compounds.The catalytic conversion of three zeolite catalysts to light aromatic hydrocarbons（BTEXN,B-benzene,T-toluene,E-ethylbenzene,X-xylene,n-naphthalene）was investigated by means of pyrolysis and gas chromatography（PY-GC-MS）using Methyl Anthracene as raw material.The effects of three molecular sieves on catalytic pyrolysis of methyl anthracene at atmospheric pressure were further investigated in a fixed bed reactor at final pyrolysis temperatures of 400,500 and 600 ℃.The effects of pressure（2,4,6 MPa）and temperature（400,500,600 ℃）on catalytic hydrogenation of methyl anthracene to light aromatic hydrocarbons were studied by selecting zeolite Beta with good catalytic performance under H₂ condition.The main results are as follows:（1）Beta zeolite,Beta-Mordenite mixed zeolite and Mordenite zeolite all have their unique crystal phase structure.Compared with Beta zeolite and Mordenite zeolite,bet-Mordenite zeolite has larger specific surface area and stronger acidity(462.82 m²·g^-1,0.05cm³·g^-1,total acid content 1.625 mmol·g^-1).Beta zeolite has a larger mesoporous volume of0.11 cm³·g^-1,and Mordenite zeolite is a microporous molecular sieve.（2）Py-GC-MS experiments showed that the catalyst promoted the pyrolysis of methyl anthracene into BTEXN and anthracene（A）.The selectivity of Methyl Anthracene pyrolysis product A catalyzed by Mordenite zeolite was relatively high,reaching 15.96%at 800 ℃.The selectivity of BTEXN was 22.39%at 700 ℃,and the yield was 1166.93 mg/kg,while the selectivity of A was 23.99%.The BTEXN selectivity of methyl anthracene catalyzed by beta-Mordenite zeolite reached 15.61%at 700 ℃,and the yield was 2079.49 mg/kg under this condition.（3）It was found that the liquid yield of zeolite Beta catalytic cracking reached 87.30%at 500 ℃,the selectivity of BTEXN was 27.81%,and the yield was 278.32 mg/g.When the reaction temperature is between 400 ℃ and 500 ℃,the catalytic reaction is the main reaction,which is suitable for the formation of BTEX and other monocyclic aromatic hydrocarbons.However,when the temperature continues to rise,the polycondensation reaction is intensified,which is beneficial to the formation of naphthalene and other 2-ring and above aromatic hydrocarbons.The yield of Beta-Mordenite was 79.80%at 600 ℃,and the selectivity of BTEXN was less than 10%.The highest liquid yield of Mordenite zeolite was85.30%at 500 ℃,only T was produced and the selectivity was less than 5%.The yield,selectivity and yield of BTEXN from catalytic pyrolysis of methyl anthracene were higher in zeolite Beta,and the carbon deposition was less,which was related to the presence of more mesopore structures and Bronsted and Lewis acid sites.（4）The fixed bed hydrocatalytic conversion process showed that 500 ℃～600 ℃ was favorable for catalytic hydrocracking.The results show that the hydrocatalytic cracking reaction of methyl anthracene is suitable for high temperature and low pressure.The optimal reaction conditions are 2 MPa and 600 ℃.Under these conditions,the selectivity of BTEXN is 59.09%and the yield is 353.4 mg/g.In conclusion,hydrogenation conditions are favorable for catalytic pyrolysis of methyl anthracene to produce light aromatic hydrocarbons.