Preparation Of HY Molecular Sieve And Its(hydrogenation)catalytic Conversion Of 2-methylnaphthalene

Coal tar is a very complex organic mixture in which polycyclic aromatic hydrocarbons mostly exist in the form of alkyl side chains.Despite their high economic value,they are very difficult to isolate.For example,it can be converted into light aromatics through catalytic conversion,and its high value-added utilization can be realized.In this paper,HY molecular sieves with different Si/Al ratios（Si-Al ratios:3,3.5,4.0）were prepared by hydrothermal synthesis and by adjusting the amount of seed crystals added,and XRD（X-ray powder diffraction）,ICP（Inductively Coupled Plasma Emission Spectrometer）,NH₃-TPD（Ammonia Adsorption-Desorption）,BET（Nitrogen Adsorption-Desorption）,FTIR（Fourier Transform Infrared Spectroscopy）,etc.,and 2-methylnaphthalene was selected as the raw material,the catalytic conversion of 2-methylnaphthalene to light aromatics by HY molecular sieves with three different silica-alumina ratios was studied by means of thermal cracking-gas chromatography（Py-GC-MS）.The catalytic conversion and hydrogenation catalytic conversion performance of three kinds of HY molecular sieves with different Si/Al ratios to 2-methylnaphthalene under normal pressure of N₂ and H₂（2,4,6 MPa）were further investigated in a fixed bed device.Using HY-3.5 as a carrier,three metals（Mo,Ni,W）were supported to explore its catalytic hydrogenation performance to 2-methylnaphthalene.The main findings are as follows:（1）The acidity,specific surface area,pore volume,pore size and other structural characteristics of HY molecular sieves are closely related to the ratio of silicon to aluminum.Increasing the amount of seed crystals added will increase the ratio of silicon to aluminum in the molecular sieve,increase the crystallinity,and reduce the total acid content.The amount of seed crystals added is（10 wt%,15 wt%,20 wt%）,and three different HY molecular sieves with FAU topology were prepared.（2）Py-GC-MS experimental showed that it was found that when the molecular sieve particle size was about 0.135 mm,the selectivity of benzene,toluene,ethylbenzene,xylene,and naphthalene（BTEXN）in the catalytic conversion products of 2-methylnaphthalene were relatively high.The content of BTEXN is the largest,which is 50.06%;when the catalyst ratio is 20:1,the selectivity of BTEXN is the largest,which is 73.23%;in terms of the selectivity of 1-2 ring aromatic hydrocarbons,when the reaction temperature is 500 ^oC,the HY-3.5 molecular sieve.As a catalyst,its selectivity is the highest,which can reach 38.32%.The single-ring aromatic hydrocarbons are mainly toluene,and the two-ring aromatic hydrocarbons are mainly naphthalene,and the selectivity of naphthalene can reach 33.29%.（3）In the fixed bed catalytic conversion process,not only the selectivity of the product TEXN can be obtained,but also the gas phase yield and the carbon deposition yield can be further obtained.The optimal reaction temperature for the catalytic conversion of 2-methylnaphthalene is 500 ^oC,and HY-3.5 has the best catalytic effect,with a liquid phase yield of 89.24%,TEXN selectivity of 27.93%,and a yield of 224.12 mg/g;The yield was4.1%,and the coke content was 6.66%.When the temperature is higher than 500 ^oC,the liquid-phase yield decreases,the gas-phase yield increases,and the coke content increases,indicating that high temperature is not conducive to the formation of liquid-phase products.（4）During the fixed-bed hydrogenation catalytic conversion process,the conversion of 2-methylnaphthalene into light aromatics such as TEXN will be promoted.At 500 ^oC and 6MPa,the catalytic effect of HY-3.5 molecular sieve is the best,and the liquid phase yield is74.05%,the gas-phase yield is 22.49%,and the carbon deposition content is 3.46%.At this time,the TEXN selectivity was 60.48%and the yield was 447.86 mg/g.After the metal Mo is loaded,the catalytic effect is better than the other two metals（Ni,W）.The hydrocatalytic conversion of cyclohexane alone produces only a small amount of TEX in the product.