Synthesis Mechanism Ntawm Zeolite Molecular Sieves

Kev tshawb fawb tob txog kev tsim thiab kev loj hlob ntawm zeolite molecular sieves yuav pab tib neeg tsim kom zoo dua qub thiab tsim cov qauv tshiab zeolite molecular sieve topological, nthuav txoj kev tshiab rau kev sib txuas ntawm zeolite molecular sieve cov ntaub ntawv, thiab tsim cov khoom tshiab thiab siv tshiab ntawm zeolite molecular sieve. cov khoom siv sieve. Txawm hais tias zeolite molecular sieves tau tsim rau ntau xyoo, tsis muaj qhov xaus tiag tiag ntawm nws cov txheej txheem synthesis. Kawm txog cov txheej txheem crystallization ntawm molecular sieves yog qhov tseem ceeb theoretical thiab tseem muaj cov lus qhia tseem ceeb rau kev sib txuas ntawm cov tshiab zeolite molecular sieves. Tam sim no, feem ntau cov neeg sawv cev mechanisms yog cov khoom theem hloov pauv mechanism (Tshuaj hydrogel Transformation mechanism), kua theem transformation mechanism (Kev daws teeb meem-mediated Transport mechanism) thiab dual-theem transformation mechanism.
Khoom theem transformation mechanism
Cov txheej txheem hloov pauv hloov pauv tau yog thawj zaug tau thov los ntawm Flanigen thiab Breck, thiab nws tseem yog qhov ntxov tshaj plaws tau thov zeolite molecular sieve crystallization mechanism. Lawv ntseeg tias:
Thaum lub sij hawm tag nrho cov txheej txheem crystallization ntawm zeolite molecular sieve, tsuas yog cov gel khoom theem nws tus kheej yog tsim nyob rau hauv hydrothermal tej yam kev mob, thiab ces tus qauv ntawm aluminosilicate pob txha pob txha yog ncaj qha rearranged, uas ua rau lub nucleation thiab siv lead ua kev loj hlob ntawm zeolite molecular sieve. Nyob rau hauv cov txheej txheem crystallization ntawm zeolite molecular sieve, tsis muaj kev sib cais ntawm cov gel khoom theem lossis kev koom tes ncaj qha ntawm cov kua theem hauv nucleation thiab siv lead ua loj hlob ntawm zeolite molecular sieve.
Ua ntej, tom qab ntau yam raw cov ntaub ntawv uas yuav tsum tau rau lub synthesis ntawm zeolite molecular sieve yog tov, lub ntsiab hom silicate thiab aluminate polymerize los tsim ib tug thawj aluminosilicate gel. Nyob rau tib lub sijhawm, txawm hais tias cov kua theem ntawm cov gels kuj tsim, cov theem ua kua tsis koom nrog cov txheej txheem crystallization thiab nucleation. Qhov thib ob, thawj zaug aluminosilicate gel tsim yog txuas ntxiv depolymerized thiab rov kho dua nyob rau hauv qhov kev txiav txim ntawm OH- ions, yog li tsim cov txheej txheem tseem ceeb uas yuav tsum tau ua rau crystallization ntawm qee cov zeolites. Thaum kawg, cov txheej txheem tseem ceeb no tau rov qab kho dua nyob ib puag ncig cov cations hydrated los ua polyhedrons, uas ntxiv polymerized, txuas, thiab tsim rau hauv zeolite molecular sieve crystals.
Hauv xyoo 1970, Dutch kws tshawb fawb Mcnicol li al. siv molecular spectroscopy los taug qab tag nrho cov txheej txheem crystallization ntawm LTA zeolite molecular sieves, yog li muab cov pov thawj txaus txaus rau cov txheej txheem hloov pauv hloov pauv. Nyob rau xyoo 1990, cov txheej txheem kev sib xyaw ua ke ntawm kev hloov pauv gel qhuav kuj ntxiv ib qho piv txwv rau cov txheej txheem hloov pauv hloov pauv. Tsis tas li ntawd, cov txheej txheem txheej txheem txheej txheem hnyav-dawb synthesis tsim nyob rau hauv xyoo tas los no kuj muab cov pov thawj sib xws rau cov txheej txheem hloov pauv hloov mus rau qee yam.