Cellulose yog ib qho nyuaj polysaccharide uas muaj ntau cov piam thaj txuas nrog β-1,4-glycosidic bonds. Nws yog cov khoom tseem ceeb ntawm cov phab ntsa ntawm cov nroj tsuag thiab muab cov phab ntsa ntawm cov nroj tsuag muaj zog txhawb kev tsim thiab toughness. Vim lub sij hawm ntev cellulose molecular saw thiab siab crystallinity, nws muaj zog stability thiab insolubleness.
(1) Cov khoom ntawm cellulose thiab nyuaj rau dissolving
Cellulose muaj cov khoom nram qab no uas ua rau nws nyuaj rau yaj:
High crystallinity: Cov cellulose molecular chains tsim ib lub lattice qauv nruj los ntawm hydrogen bonds thiab van der Waals rog.
High degree ntawm polymerization: Lub degree ntawm polymerization (xws li qhov ntev ntawm cov saw molecular) ntawm cellulose yog siab, feem ntau yog li ntawm pua pua mus rau txhiab tus qabzib units, uas ua rau kom cov stability ntawm lub molecule.
Hydrogen bond network: Hydrogen bonds muaj dav nyob nruab nrab ntawm thiab hauv cellulose molecular chains, ua rau nws nyuaj rau kev puas tsuaj thiab yaj los ntawm cov kuab tshuaj.
(2) Reagents uas yaj cellulose
Tam sim no, paub cov tshuaj reagents uas tuaj yeem yaj cellulose tau zoo suav nrog cov hauv qab no:
1. Ionic kua
Cov kua ionic yog cov kua uas muaj cov organic cations thiab cov organic lossis inorganic anions, feem ntau muaj qhov tsis muaj zog, siab thermal stability thiab siab adjustability. Qee cov kua ionic tuaj yeem yaj cov cellulose, thiab lub luag haujlwm tseem ceeb yog ua kom cov hydrogen bonds ntawm cellulose molecular chains. Feem ntau ionic kua uas yaj cellulose muaj xws li:
1-Butyl-3-methylimidazolium chloride ([BMIM]Cl): Cov kua ionic no dissolves cellulose los ntawm kev cuam tshuam nrog hydrogen bonds hauv cellulose los ntawm hydrogen daim ntawv cog lus.
1-Ethyl-3-methylimidazolium acetate ([EMIM][Ac]): Cov kua ionic no tuaj yeem yaj cov cellulose siab hauv cov mob me me.
2. Amine oxidant kua
Amine oxidant tov xws li tov tov ntawm diethylamine (DEA) thiab tooj liab chloride yog hu ua [Cu(II)-ammonium tov], uas yog ib tug muaj zog hnyav system uas yuav yaj cellulose. Nws rhuav tshem cov qauv siv lead ua ntawm cellulose los ntawm oxidation thiab hydrogen bonding, ua rau cellulose molecular saw softer thiab soluble ntau dua.
3. Lithium chloride-dimethylacetamide (LiCl-DMAc) system
Lub LiCl-DMAc (lithium chloride-dimethylacetamide) system yog ib qho ntawm cov txheej txheem classic rau soluble cellulose. LiCl tuaj yeem tsim kev sib tw rau hydrogen bonds, yog li rhuav tshem cov hydrogen bond network ntawm cellulose molecules, thaum DMAc ua cov kuab tshuaj tuaj yeem cuam tshuam zoo nrog cellulose molecular saw.
4. Hydrochloric acid/zinc chloride tov
Cov tshuaj hydrochloric acid / zinc chloride yog ib qho kev tshawb pom thaum ntxov uas tuaj yeem yaj cellulose. Nws tuaj yeem yaj cellulose los ntawm kev tsim cov kev sib koom tes ntawm zinc chloride thiab cellulose molecular chains, thiab hydrochloric acid rhuav tshem cov hydrogen bonds ntawm cellulose molecules. Txawm li cas los xij, qhov kev daws teeb meem no yog corrosive heev rau cov cuab yeej siv thiab tsuas yog siv rau kev siv tswv yim.
5. Fibrinolytic enzymes
Fibrinolytic enzymes (xws li cellulases) dissolve cellulose los ntawm catalyzing decomposition ntawm cellulose rau hauv me me oligosaccharides thiab monosaccharides. Txoj kev no muaj ntau yam kev siv hauv thaj chaw biodegradation thiab biomass hloov dua siab tshiab, txawm hais tias nws cov txheej txheem dissolution tsis yog tshuaj lom neeg tawg tag, tab sis ua tiav los ntawm biocatalysis.
(3) Mechanism ntawm cellulose dissolution
Cov reagents sib txawv muaj cov txheej txheem sib txawv rau kev so cellulose, tab sis feem ntau lawv tuaj yeem raug ntaus nqi rau ob lub ntsiab mechanisms:
Kev puas tsuaj ntawm hydrogen bonds: Ua kom puas cov hydrogen bonds ntawm cellulose molecular chains los ntawm kev sib tw hydrogen bond tsim los yog ionic kev sib tshuam, ua rau nws soluble.
Molecular saw so: Ua kom cov softness ntawm cellulose molecular chains thiab txo cov crystallinity ntawm molecular chains los ntawm lub cev los yog tshuaj txhais tau tias, kom lawv yuav yaj nyob rau hauv cov kuab tshuaj.
(4) Kev siv tswv yim ntawm cellulose dissolution
Cellulose dissolution muaj cov ntawv thov tseem ceeb hauv ntau qhov chaw:
Kev npaj ntawm cellulose derivatives: Tom qab dissolving cellulose, nws tuaj yeem hloov kho ntxiv los npaj cellulose ethers, cellulose esters thiab lwm yam derivatives, uas yog siv dav hauv zaub mov, tshuaj, txheej thiab lwm yam.
Cellulose-based cov ntaub ntawv: Siv cov cellulose yaj, cellulose nanofibers, cellulose membranes thiab lwm yam ntaub ntawv tuaj yeem npaj tau. Cov ntaub ntawv no muaj cov khoom siv zoo thiab biocompatibility.
Lub zog biomass: Los ntawm kev yaj thiab degrading cellulose, nws tuaj yeem hloov mus rau fermentable qab zib rau kev tsim cov biofuels xws li bioethanol, uas yuav pab ua kom tiav txoj kev loj hlob thiab kev siv lub zog tauj dua tshiab.
Cellulose dissolution yog ib tug complex txheej txheem uas muaj ntau yam tshuaj thiab lub cev mechanisms. Ionic kua, amino oxidant daws, LiCl-DMAc systems, hydrochloric acid/zinc chloride dlaws thiab cellolytic enzymes tam sim no paub tias yog cov neeg ua hauj lwm zoo rau dissolving cellulose. Txhua tus neeg sawv cev muaj nws tus kheej tshwj xeeb dissolution mechanism thiab daim ntawv thov teb. Nrog rau kev kawm tob ntawm cellulose dissolution mechanism, nws ntseeg hais tias ntau npaum thiab ib puag ncig tus phooj ywg dissolution txoj kev yuav tsim, muab ntau possibilities rau kev siv thiab kev loj hlob ntawm cellulose.
Lub sij hawm xa tuaj: Plaub Hlis-09-2024