Study On Catalytic Properties Of Modified HZSM-5 In Light Paraffin Aromatization

Liquefied petroleum gas(LPG) is widely used as urban civil fuel source. Recently, LPG has been in the situation of oversupplied. Limited by the national clean energy development policy, LPG market has been impacted by the clean energy such as Liquefied natural gas(LNG). Benzene, toluene, xylene(BTX) is in great demand which plays an important role as chemical raw materials in the pharmaceutical, national defense, building materials, paint, textile and other fields. Light paraffin aromatization technology with broad prospects for development offers a way to transform the cheap light paraffin(such as LPG) to BTX with high additional value.In this paper, we mainly investigated to modify the HZSM-5 zeolite which is widely used in light paraffin aromatization technology with alkali-steam combined treatment. The synthetic catalysts were further characterized to research the feasibility of alkali-steam combined treatment by the XRD, MAS NMR, N2-adsorption, NH3-TPD and Py-IR, and evaluated by light paraffin aromatization in the fixed bed reactor.First of all, modify the HZSM-5 zeolite by steam treatment with different treatment temperature and time to find out the optimum method. The combined treatment order was studied on the basis of our lab’s previous research. The alkali-steam combined treatment with different treatment condition was studied and the zeolite with an outstanding catalytic property was got.In the way mentioned above, we get such conclusions as below.1) The framework dealuminated zeolite by steam treatment has improved the ability to resist coking by reduce the acidity while the framework of zeolite was stayed stable.2) The method of alkali-steam combined treatment is more conducive to play the advantages to modify the zeolite in alkali treatment first.3) The performance of HZSM-5 zeolite in the light paraffin aromatization reactions can be further promoted by the alkali-steam combined treatment which attribution to the introduction of mesopores via desilication and the motified acidity via dealumination, respectively. In this way, the coke tolerance and the coke resistance of modified HZSM-5 zeolite has been great promoted.