H-ZSM-5分子篩上乙烯二聚反應(yīng)機(jī)理的理論研究.pdf

1、遼寧師范大學(xué)碩士學(xué)位論文HZSM5分子篩上乙烯二聚反應(yīng)機(jī)理的理論研究姓名：張佳申請(qǐng)學(xué)位級(jí)別：碩士專業(yè)：有機(jī)化學(xué)指導(dǎo)教師：周丹紅20080410HZSM一5分子篩上乙烯二聚反應(yīng)機(jī)理的理論研究AbstractInthepresentworkthedimerizationofethyleneontheBr6nstedacidsiteinHZSM一5zeolitehasbeeninvestgatedbyusingtheoreticalcalcu

2、lationsWemainlyfocusonthefollowingtopics：(1)themechanismsforC—Cbondformationandchainpropagationinethyleneoligomerization；(2)theeffectofzeoliteacidsites；(3)theeffectofzeoliteframeworkandporestructureOffreactionselectivity

3、A40TclustermodelwasadoptedtomimictheBr6nstedacidsitelocatedatthechannelintersectionofZSM5zeoliteAllcalculationswerecardedoutbytheONIOMmethod，oneofthewidespreadQM／MMhybridmethodsTwodifferentreactionmechanisms，stepwiseandc

4、oncertedpathwayswereexaminedThenaturalbondorbitalanalysisWasusedtoexploretheelectronicpropertiesfor兀一hydrogenbondinginteractioninadsorptioncomplexesandthemolecularorbitalfeaturesatthetransitionstatesTheresultsindicatedth

5、atinthestepwisemechanism，ethylenefirstlyadsorbsontheacidsitethrough7c—hydrogenbondingandthenproceedsprotonationtoformtheethoxideintermediate；thentheintermediatereacts、麗廿lthesecondethylenemoleculetogivethesurfacebutoxidep

6、roductInwhichtheethyleneprotonationshowsthehighestenergybarrierandisconfirmedastheratelimitingstepIntheconcertedmechanism，twoethylenemoleculesCO—adsorbontheacidsiteThereactionproceedsviasimultaneousprotonationandformatio

7、nofC—CbondtogivethebutoxideproductThecorrespondingactivationenergyisslightlyhigherthanthatoftherate—limitingstepinthestepwisemechanismItisproposedthatthereshouldbeacompetitionbetweentweactionmechanismsThenaturalbondorbit

8、alanalysisrevealedthattheethoxideintermediatereactes、^，ithanotherethylenebyatransitionstateofcarboniumTheconfinementeffectofzeolitemicroporesplaysimportantroleinthephysisorptionofethylenemolelcule，whichalsofacilitatesthe