|其他摘要||With the development of economy and society, petroleum resource drying up, while more and more high quality liquid fules are needed from industrial production, transportation, military and aviation, etc. So, development of non-petroleum routes to produce clean fuels has important strategic significance for producing environmental friendly liquid fuels as well as adjusting energy structure in our country. The oligomerization reaction of light olefins is not only an effective way to produce motor fuel, plasticizer, lubricating oil, antifreeze and other chemicals, but also an important way to prepare high quality clean liquid fuels. Research and optimization of catalyst is the key to the progress of oligomerization technology. Owning the unique MFI three - dimensional channel structure, good acidic and suitable channel confined effect, HZSM-5 showed good resisrant to carbon deposition capability, and the products are not easy to be branched chain, so it is considered to be the most promising catalysts for C3= and C4= olefins oligomerization.
In this work, HZSM-5 zeolite was studied as catalyst for olefin oligomerization. Biomass hemicellulose was used as additive to modify it, ammonium persulphate and tetramethylethylenediamine were added as initiator to explore the crystallization process and properties of HZSM-5 further. Butene oligomerization was tested to inspect the catalytic ability on light olifins oligomerization reaction of modified HZSM-5. The main bodies of the work included the following aspects:
With hemicellulose as additive, ZSM-5 was prepared using hydrothermal method. The macromolecular carbon skeleton structure and the rich hydroxyl of hemicelluloses were used to improve the morphology, texture characteristics as well as acidity of HZSM-5. Preparation of the modified HZSM-5 with different content of hemicellulose, the results indicated that the HZSM-5 with 1.6 wt. % hemicellulose has the biggest BET surface and mesoporous volume, and the strongest acidity, and exhibited the best activity and stability on the butene oligomerization reaction, the conversion maintained about 80% after 140 h on stream. What’s more, it includes the highest selectivities of the trimer, tetramer and diesel component in the products.
For activation the surface hydroxyl groups on the hemicellulose, ammonium persulphate and tetramethylethylenediamine were added as initiator on the basis of the hemicellulose to accelerate the crystallization ZSM-5. The results show, crystallinity and morphology of ZSM-5 can influnced by the initiator in a short time. The acidity of the modified HZSM-5 with 0.5 wt. % initiator enhanced obviously, catalytic ability on butene oligomerizaiton further improved, the conversion maintained above 90% for 60 h on stream, and the bset selectivity of diesel remained above 90%.|