Molecular sieve yog cov khoom siv nrog qhov pores (qhov me me) ntawm qhov loj me. Cov pore diameters zoo ib yam li me me rau cov molecules, thiab yog li cov molecules loj tsis tuaj yeem nkag los yog raug adsorbed, thaum me me molecules tuaj yeem. Raws li kev sib xyaw ntawm cov molecules migrate los ntawm lub txaj nyob ruaj ruaj ntawm cov ntxeem tau, cov khoom ib nrab hu ua sieve (los yog matrix), cov khoom ntawm qhov hnyav tshaj plaws molecular (uas tsis tuaj yeem nkag mus rau hauv cov pores molecular) tawm hauv txaj ua ntej, ua raws li cov me me molecules successively. Ib co molecular sieves yog siv nyob rau hauv loj-exclusion chromatography, ib tug sib cais txheej txheem uas txheeb cov molecules raws li lawv loj. Lwm cov molecular sieves yog siv los ua desiccants (qee qhov piv txwv suav nrog cov hluav taws xob hluav taws xob thiab silica gel).
Lub pore txoj kab uas hla ntawm molecular sieve yog ntsuas nyob rau hauv ångströms (Å) los yog nanometers (nm). Raws li IUPAC sau tseg, cov ntaub ntawv microporous muaj qhov pore diameters tsawg dua 2 nm (20 Å) thiab cov ntaub ntawv macroporous muaj qhov pore diameter ntau dua 50 nm (500 Å); pawg mesoporous yog li nyob rau hauv nruab nrab nrog pore diameters ntawm 2 thiab 50 nm (20-500 Å).
Khoom siv
Molecular sieves tuaj yeem yog microporous, mesoporous, lossis macroporous khoom.
Cov khoom siv microporous (
●Zeolites (aluminosilicate minerals, tsis txhob totaub nrog txhuas silicate)
●Zeolite LTA: 3–4 Å
●Porous iav: 10 Å (1 nm), thiab nce
●Active carbon: 0–20 Å (0–2 nm), thiab nce
● Av nplaum
●Montmorillonite intermixes
●Halloysite (endellite): Ob hom qauv pom, thaum hydrated cov av nplaum nthuav tawm qhov sib nrug ntawm 1 nm ntawm cov txheej thiab thaum lub cev qhuav dej (meta-halloysite) qhov sib nrug yog 0.7 nm. Halloysite ib txwm tshwm sim raws li cov thooj voos kheej kheej me me uas nruab nrab 30 nm inch nrog qhov ntev ntawm 0.5 thiab 10 micrometers.
Mesoporous khoom (2-50 nm)
Silicon dioxide (siv los ua silica gel): 24 Å (2.4 nm)
Cov khoom siv macroporous (> 50 nm)
Macroporous silica, 200-1000 Å (20-100 nm)
Cov ntawv thov [edit]
Molecular sieves feem ntau yog siv rau hauv kev lag luam roj av, tshwj xeeb tshaj yog rau ziab cov roj ntws. Piv txwv li, nyob rau hauv kev lag luam ua kua natural gas (LNG), cov dej ntsiab lus ntawm cov roj yuav tsum tau txo kom tsawg tshaj li 1 ppmv los tiv thaiv cov blockages los ntawm dej khov los yog methane clathrate.
Hauv chav kuaj, molecular sieves yog siv los ua kom qhuav hnyav. "Sieves" tau ua pov thawj zoo tshaj rau cov txheej txheem ziab khaub ncaws, uas feem ntau siv cov tshuaj desiccants hnyav.
Raws li lo lus zeolites, molecular sieves yog siv rau ntau hom kev siv catalytic. Lawv catalyze isomerisation, alkylation, thiab epoxidation, thiab yog siv nyob rau hauv loj scale industrial txheej txheem, nrog rau hydrocracking thiab kua catalytic cracking.
Lawv kuj tau siv rau hauv kev pom cov khoom siv cua rau cov cuab yeej ua pa, piv txwv li cov neeg siv scuba divers thiab cov neeg tua hluav taws. Hauv cov ntawv thov no, huab cua yog muab los ntawm lub tshuab cua compressor thiab dhau los ntawm lub tshuab lim cartridge uas, nyob ntawm daim ntawv thov, tau ntim nrog molecular sieve thiab / lossis cov pa roj carbon activated, thaum kawg tau siv los them cov pa tso pa tawm. thiab compressor tso cov khoom los ntawm cov pa ua pa.
FDA pom zoo.
Lub US FDA muaj txij li lub Plaub Hlis 1, 2012, tau pom zoo sodium aluminosilicate rau kev sib cuag ncaj qha nrog cov khoom siv hauv qab 21 CFR 182.2727.Ua ntej qhov kev pom zoo no European Union tau siv cov tshuaj molecular sieves nrog cov kws tshuaj thiab kev soj ntsuam ywj pheej qhia tias molecular sieves ua tau raws li tsoomfwv txoj cai tab sis kev lag luam tau tsis kam them nyiaj rau qhov kev sim kim uas yuav tsum tau muaj rau kev pom zoo los ntawm tsoomfwv.
Kev tsim dua tshiab
Cov txheej txheem rau kev rov tsim dua tshiab ntawm molecular sieves suav nrog kev hloov pauv siab (xws li hauv cov pa oxygen concentrators), cua sov thiab purging nrog cov pa roj (raws li thaum siv hauv ethanol lub cev qhuav dej), los yog cua sov hauv lub tshuab nqus tsev siab. Regeneration kub li ntawm 175 ° C (350 ° F) mus rau 315 ° C (600 ° F) nyob ntawm seb hom molecular sieve. Hauv qhov sib piv, silica gel tuaj yeem rov tsim dua los ntawm cua sov nws hauv qhov cub li 120 ° C (250 ° F) rau ob teev. Txawm li cas los xij, qee hom silica gel yuav "pop" thaum raug dej txaus. Qhov no yog tshwm sim los ntawm kev tawg ntawm silica spheres thaum tiv tauj dej.
| Qauv | Txoj kab uas hla (Ångström) | Qhov ceev (g / ml) | Adsorbed dej (% w/w) | Kev siv | |
| 3 Å | 3 | 0.60–0.68 Nws | 19–20 | 0.3–0.6 hli | Desiccationntawmroj av tawgGas thiab alkenes, xaiv adsorption ntawm H2O hauvInsulated iav (IG)thiab polyurethane, ziab ntawmethanol rojrau kev sib xyaw nrog roj av. |
| 4 Å | 4 | 0.60–0.65 Nws | 20–21 : kuv | 0.3–0.6 hli | Adsorption ntawm dej hauvsodium aluminosilicate iavuas yog FDA pom zoo (saibhauv qab no) siv los ua molecular sieve hauv cov thawv kho mob kom cov ntsiab lus qhuav thiab raws lizaub mov additivemuajE-tus naj npawbE-554 (tus neeg sawv cev tiv thaiv kab mob); Txaus siab rau lub cev qhuav dej zoo li qub hauv cov kua lossis roj kaw, xws li hauv ntim cov tshuaj, cov khoom siv hluav taws xob thiab cov tshuaj perishable; dej scavenging nyob rau hauv printing thiab plastics systems thiab ziab saturated hydrocarbon ntws. Adsorbed hom muaj xws li SO2, CO2, H2S, C2H4, C2H6, thiab C3H6. Feem ntau suav hais tias yog universal drying agent hauv polar thiab nonpolar media;[12]kev sib cais ntawmnatural gasthiabalkenes, adsorption ntawm dej nyob rau hauv uas tsis yog-nitrogen rhiab heevpolyurethane |
| 5 Å-DW | 5 | 0.45–0.50 Nws | 21–22 : kuv | 0.3–0.6 hli | Degreasing thiab ncuav point kev nyuaj siab ntawmkev dav hlau kerosenethiabdiesel, thiab alkenes sib cais |
| 5Å me me oxygen-enriched | 5 | 0.4–0.8 | ≥ 23 | Tsim tshwj xeeb rau kev kho mob lossis noj qab haus huv oxygen generator[xav tau kev sau ntawv] | |
| 5 Å | 5 | 0.60–0.65 Nws | 20–21 : kuv | 0.3-0.5 hli | Desiccation thiab purification ntawm huab cua;lub cev qhuav dejthiabdesulfurizationntawm natural gas thiabkua roj av;oxygenthiabhydrogenproduction los ntawmsiab viav vias adsorptiontxheej txheem |
| 10 X | 8 | 0.50–0.60 Nws | 23–24 : kuv | 0.3–0.6 hli | High-efficiency sorption, siv nyob rau hauv desiccation, decarburization, desulfurization ntawm roj thiab kua thiab sib cais ntawmaromatic hydrocarbon |
| 13 X | 10 | 0.55–0.65 hli | 23–24 : kuv | 0.3-0.5 hli | Desiccation, desulfurization thiab purification ntawm roj av thiab natural gas |
| 13 X-AS | 10 | 0.55–0.65 hli | 23–24 : kuv | 0.3-0.5 hli | Decarburizationthiab desiccation nyob rau hauv cov huab cua sib cais kev lag luam, kev sib cais ntawm nitrogen los ntawm oxygen nyob rau hauv oxygen concentrators |
| Cu-13 X | 10 | 0.50–0.60 Nws | 23–24 : kuv | 0.3-0.5 hli | Qab zib(kev tshem tawm ntawmthiols) ntawmaviation rojthiab sib raugkua hydrocarbons |
Adsorption muaj peev xwm
3 Å
Cov tshuaj formula kwv yees: ((K2O) 2⁄3 (Na2O) 1⁄3) • Al2O3• 2 SiO2 • 9/2 H2O
Silica-alumina ratio: SiO2 / Al2O3≈2
Ntau lawm
3A molecular sieves yog tsim los ntawm cation txauvpoov tshuajrausodiumhauv 4A molecular sieves (Saib hauv qab)
Kev siv
3Å molecular sieves tsis adsorb molecules uas nws diameters loj dua 3 Å. Cov yam ntxwv ntawm cov molecular sieves muaj xws li ceev ceev adsorption ceev, nquag regeneration muaj peev xwm, zoo crushing kuj thiabmuaj kuab paug kuj. Cov yam ntxwv no tuaj yeem txhim kho ob qho tib si efficiency thiab lub neej ntawm lub sieve. 3Å molecular sieves yog qhov tsim nyog desiccant nyob rau hauv roj av thiab tshuaj industries rau refining roj, polymerization, thiab tshuaj gas-kua tob kom qhuav.
3Å molecular sieves yog siv los ziab ntau yam khoom, xws liethanol, cua,cov tub yees,natural gasthiabunsaturated hydrocarbons. Cov tom kawg muaj xws li cracking gas,acetylene,ethylene,propylenethiabbutadiene.
3Å molecular sieve yog siv los tshem tawm cov dej los ntawm ethanol, tom qab ntawd tuaj yeem siv ncaj qha los ua bio-roj lossis tsis ncaj los tsim ntau yam khoom xws li tshuaj, khoom noj, tshuaj, thiab lwm yam. Txij li thaum ib txwm distillation tsis tuaj yeem tshem tawm tag nrho cov dej (ib qho khoom siv tsis zoo los ntawm kev tsim khoom ethanol) los ntawm cov txheej txheem ethanol vim qhov tsim ntawm ib qhoazeotropenyob ib ncig ntawm 95.6 feem pua ntawm qhov hnyav los ntawm qhov hnyav, molecular sieve hlaws yog siv los cais ethanol thiab dej ntawm qib molecular los ntawm adsorbing dej rau hauv cov hlaws dai thiab tso cai rau ethanol hla kev ywj pheej. Thaum cov hlaws puv dej, qhov kub thiab txias tuaj yeem hloov kho, tso cai rau cov dej tawm ntawm cov hlaws molecular sieve hlaws.[15]
3Å molecular sieves yog khaws cia nyob rau hauv chav tsev kub, nrog ib tug txheeb ze humidity tsis ntau tshaj 90%. Lawv raug kaw hauv qhov txo qis, khaws cia kom deb ntawm dej, acids thiab alkalis.
4 Å
Cov tshuaj formula: Na2O•Al2O3•2SiO2•9/2H2O
Silicon-aluminium piv: 1: 1 (SiO2 / Al2O3≈2)
Ntau lawm
Kev tsim tawm ntawm 4Å sieve yog qhov yooj yim vim nws yuav tsum tsis txhob muaj kev kub ntxhov lossis kub tshwj xeeb. Feem ntau aqueous daws ntawmsodium silicatethiabsodium aluminateua ke ntawm 80 ° C. Cov khoom hnyav-impregnated yog "activated" los ntawm "ci" ntawm 400 ° C 4A sieves ua tus precursor rau 3A thiab 5A sieves los ntawmcation pauvntawmsodiumraupoov tshuaj(rau 3A) los yogcalcium(rau 5A)
Kev siv
Qhuav cov kuab tshuaj
4Å molecular sieves tau dav siv los ua kom qhuav chav kuaj cov kuab tshuaj. Lawv tuaj yeem nqus dej thiab lwm cov molecules uas muaj txoj kab uas hla tseem ceeb tsawg dua 4 Å xws li NH3, H2S, SO2, CO2, C2H5OH, C2H6, thiab C2H4. Lawv tau siv dav hauv kev ziab, ua kom zoo thiab ua kom huv ntawm cov kua thiab roj (xws li kev npaj ntawm argon).
Polyester tus neeg sawv cev additives [kho]
Cov molecular sieves no yog siv los pab detergents vim lawv tuaj yeem tsim cov dej demineralized los ntawmcalciumion pauv, tshem tawm thiab tiv thaiv cov deposition ntawm av. Lawv tau dav siv los hloovphosphorus. Lub 4Å molecular sieve ua lub luag haujlwm tseem ceeb los hloov sodium tripolyphosphate ua cov tshuaj ntxuav tes kom txo tau qhov cuam tshuam ib puag ncig ntawm cov tshuaj ntxuav tes. Nws kuj tuaj yeem siv los ua ib qhoxab npumtsim tus neeg sawv cev thiab hauvtshuaj txhuam hniav.
Kev kho cov khib nyiab pov tseg
4Å molecular sieves tuaj yeem ntxuav cov dej phwj tuaj ntawm cationic hom xws liammoniumions, Pb2+, Cu2+, Zn2+ thiab Cd2+. Vim muaj kev xaiv siab rau NH4+ lawv tau ua tiav hauv kev sib ntaus sib tuaeutrophificationthiab lwm yam teebmeem hauv cov dej vim muaj ammonium ions ntau dhau. 4Å molecular sieves kuj tau siv los tshem tawm cov hlau hnyav ions tam sim no hauv dej vim muaj kev lag luam.
Lwm lub hom phiaj
Covmetallurgical kev lag luam: cais tus neeg sawv cev, sib cais, extraction ntawm brine poov tshuaj,rubidium,cesium, lwm.
Petrochemical kev lag luam,catalyst,desiccant, adsorbent
Ua liaj ua teb:av txias
Tshuaj: load nyiajzeoliteantibacterial tus neeg sawv cev.
5 Å
Cov tshuaj formula: 0.7CaO•0.30Na2O•Al2O3•2.0SiO2 •4.5H2O
Silica-alumina ratio: SiO2 / Al2O3≈2
Ntau lawm
5A molecular sieves yog tsim los ntawm cation txauv ntawmcalciumrausodiumhauv 4A molecular sieves (Saib saum toj no)
Kev siv
Tsib-yam(5Å) molecular sieves feem ntau siv nyob rau hauv lubroj avkev lag luam, tshwj xeeb tshaj yog rau kev ua kom huv ntawm cov roj ntws thiab hauv chav kuaj chemistry rau kev sib caistshuaj sib xyawthiab ziab cov tshuaj pib cov ntaub ntawv. Lawv muaj cov pores me me ntawm qhov loj thiab zoo ib yam, thiab feem ntau yog siv los ua ib qho adsorbent rau roj thiab kua.
Tsib-ångström molecular sieves yog siv los ziabnatural gas, nrog rau kev ua haujlwmdesulfurizationthiabdecarbonationntawm cov pa. Lawv kuj tuaj yeem siv los cais cov sib xyaw ntawm cov pa oxygen, nitrogen thiab hydrogen, thiab roj-wax n-hydrocarbons los ntawm cov ceg ntoo thiab polycyclic hydrocarbons.
Tsib-ångström molecular sieves yog khaws cia ntawm chav tsev kub, nrog atxheeb ze avtsawg dua 90% hauv cov thawv ntawv los yog cov thawv ntim khoom. Cov molecular sieves yuav tsum tsis txhob raug ncaj qha rau huab cua thiab dej, acids thiab alkalis yuav tsum tau zam.
Morphology ntawm molecular sieves
Molecular sieves muaj nyob rau hauv ntau hom thiab ntau thiab tsawg. Tab sis cov hlaws kheej kheej muaj qhov zoo dua li lwm cov duab raws li lawv muab kev poob qis, yog attrition resistant vim lawv tsis muaj cov npoo ntse, thiab muaj lub zog zoo, piv txwv li crush quab yuam yuav tsum tau nyob rau hauv ib cheeb tsam yog siab dua. Qee cov beaded molecular sieves muaj peev xwm qis dua li qhov xav tau lub zog qis thaum lub sij hawm rov tsim dua tshiab.
Lwm qhov zoo dua ntawm kev siv beaded molecular sieves yog qhov ntom ntom feem ntau yog siab dua li lwm cov duab, yog li rau tib yam adsorption yuav tsum tau molecular sieve ntim yuav tsum tsawg dua. Yog li thaum ua de-bottlenecking, ib tus tuaj yeem siv beaded molecular sieves, thauj khoom ntxiv adsorbent hauv tib lub ntim, thiab zam kev hloov pauv ntawm lub nkoj.
Post lub sij hawm: Lub Xya hli ntuj-18-2023
