Dab tsi yog cov ntsiab lus thiab cov ntaub ntawv yooj yim ntawm molecular sieves?

Molecular sieves yog crystalline silicates los yog aluminosilicates, tsim los ntawm silicon-oxygen tetrahedrons los yog txhuas-oxygen tetrahedrons txuas nrog oxygen choj bonds.
Cov kab noj hniav thiab kab noj hniav muaj qhov loj me me (feem ntau yog {{0}}.3 ~ 2.0 nm), uas muaj cov yam ntxwv ntawm kev tshuaj xyuas cov molecules. Txawm li cas los xij, nrog rau kev tshawb fawb tob zuj zus ntawm kev sib txuas thiab kev siv cov molecular sieves, cov kws tshawb fawb tau tshawb pom phosphoaluminate molecular sieves, thiab cov pob txha pob txha (silicon, aluminium lossis phosphorus) ntawm molecular sieves kuj tuaj yeem tsim los ntawm B, Ga, Fe, Cr, Ge, Ti, V, Mn, Co, Zn, Be thiab Cu yog hloov pauv, thiab qhov loj ntawm qhov pores thiab kab noj hniav tuaj yeem ncav cuag ntau dua 2 nm. Yog li ntawd, molecular sieves tuaj yeem muab faib ua silicon-aluminium molecular sieves, phosphorus-aluminium molecular sieves thiab lub molecular sieves heteroatom molecular sieves raws li qhov muaj pes tsawg leeg ntawm cov pob txha. ; Raws li qhov pore loj, molecular sieves nrog pore qhov ntau thiab tsawg dua 2 nm, 2 ~ 50 nm thiab ntau dua 50 nm hu ua microporous, mesoporous thiab macroporous molecular sieves feem. Vim nws qhov pore loj dua, nws dhau los ua tus cab kuj zoo rau cov tshuaj tiv thaiv molecular loj dua. Txawm li cas los xij, cov phab ntsa pore ntawm cov ntaub ntawv mesoporous yog amorphous, yog li lawv cov hydrothermal stability thiab thermal stability tsis tuaj yeem ua tau raws li qhov hnyav yuav tsum tau siv rau kev siv petrochemical. .
Vim tias nws muaj cov hlau ions thiab cov dej sib xyaw nrog cov nqi hluav taws xob qis thiab lub voj voog loj ionic, cov dej molecules tau ploj mus tas li tom qab cua sov, tab sis cov qauv siv lead ua pob txha tseem tsis hloov pauv, tsim ntau cov kab noj hniav ntawm tib qhov loj, thiab cov kab noj hniav muaj ntau txoj kab uas hla. Tib micropores txuas nrog. Cov pores me me no muaj cov kab uas tsis sib xws thiab tuaj yeem nqus cov molecules me dua li txoj kab uas hla ntawm lub qhov hws mus rau sab hauv ntawm lub qhov hws, thaum tsis suav cov molecules loj dua qhov pores. Yog li ntawd, cov molecules nrog cov duab sib txawv thiab txoj kab uas hla tuaj yeem nkag mus rau hauv qhov pores. Kev sib cais ntawm cov molecules nrog ntau degrees ntawm polarity, sib txawv boiling ntsiab lus, thiab txawv degrees ntawm saturation muaj nuj nqi ntawm "sieving" molecules, yog li nws yog hu ua molecular sieve. Tam sim no, molecular sieves yog dav siv nyob rau hauv metallurgy, tshuaj lom neeg kev lag luam, electronics, petrochemical kev lag luam, natural gas thiab lwm yam lag luam.