Alumina tau pom tias muaj tsawg kawg yog 8 hom, lawv yog α-Al2O3, θ-Al2O3, γ-Al2O3, δ-Al2O3, η-Al2O3, χ-Al2O3, κ-Al2O3 thiab ρ-Al2O3, lawv cov qauv macroscopic kuj txawv. Gamma activated alumina yog ib lub cubic close packed crystal, insoluble hauv dej, tab sis soluble hauv acid thiab alkali. Gamma activated alumina yog cov acidic tsis muaj zog, muaj lub melting point siab 2050 ℃, alumina gel hauv hydrate daim ntawv tuaj yeem ua rau oxide nrog porosity siab thiab qhov chaw tshwj xeeb siab, nws muaj cov theem hloov pauv hauv qhov kub ntau. Thaum kub dua, vim yog dehydration thiab dehydroxylation, Al2O3 qhov chaw zoo li sib koom ua ke unsaturated oxygen (alkali center) thiab txhuas (acid center), nrog catalytic activity. Yog li ntawd, alumina tuaj yeem siv ua tus cab kuj, catalyst thiab cocatalyst.
Gamma activated alumina yuav yog hmoov, granules, strips lossis lwm yam. Peb tuaj yeem ua raws li koj qhov xav tau. γ-Al2O3, hu ua "activated alumina", yog ib hom khoom siv khoom tawg yooj yim, vim nws cov qauv pore hloov kho tau, thaj chaw loj, kev ua haujlwm zoo adsorption, nto nrog qhov zoo ntawm acidity thiab thermal stability zoo, microporous nto nrog cov khoom tsim nyog ntawm catalytic kev ua, yog li ntawd dhau los ua catalyst, catalyst carrier thiab chromatography carrier siv dav tshaj plaws hauv kev lag luam tshuaj lom neeg thiab roj, thiab ua lub luag haujlwm tseem ceeb hauv cov roj hydrocracking, hydrogenation refining, hydrogenation reforming, dehydrogenation reaction thiab automobile exhaust purification process. Gamma-Al2O3 yog siv dav ua catalyst carrier vim nws qhov kev hloov kho tau ntawm nws cov qauv pore thiab acidity ntawm qhov chaw. Thaum γ-Al2O3 siv ua tus cab kuj, ntxiv rau qhov tuaj yeem muaj cov teebmeem rau kev tawg thiab ruaj khov cov khoom siv nquag, kuj tuaj yeem muab cov kua qaub alkali active center, synergistic reaction nrog cov khoom siv catalytic nquag. Cov qauv pore thiab cov khoom nto ntawm cov catalyst nyob ntawm γ-Al2O3 tus neeg nqa khoom, yog li ntawd tus neeg nqa khoom ua tau zoo yuav pom rau cov tshuaj tiv thaiv catalytic tshwj xeeb los ntawm kev tswj cov khoom ntawm gamma alumina tus neeg nqa khoom.
Alumina ua haujlwm los ntawm gamma feem ntau yog ua los ntawm nws cov khoom siv pseudo-boehmite los ntawm 400 ~ 600 ℃ kub siab dehydration, yog li ntawd qhov chaw physicochemical khoom feem ntau yog txiav txim siab los ntawm nws cov khoom siv pseudo-boehmite, tab sis muaj ntau txoj hauv kev los ua pseudo-boehmite, thiab ntau qhov chaw ntawm pseudo-boehmite ua rau muaj ntau yam gamma - Al2O3. Txawm li cas los xij, rau cov catalysts nrog cov kev xav tau tshwj xeeb rau alumina carrier, tsuas yog cia siab rau kev tswj hwm ntawm cov khoom siv pseudo-boehmite nyuaj rau ua tiav, yuav tsum tau coj mus rau kev npaj prophase thiab kev ua tiav tom qab kev sib txuas ua ke los kho cov khoom ntawm alumina kom tau raws li cov kev xav tau sib txawv. Thaum qhov kub siab dua 1000 ℃ siv, alumina tshwm sim tom qab kev hloov pauv theem: γ → δ → θ → α-Al2O3, ntawm lawv γ, δ, θ yog cubic kaw packing, qhov sib txawv tsuas yog nyob rau hauv kev faib tawm ntawm txhuas ions hauv tetrahedral thiab octahedral, yog li cov kev hloov pauv theem no tsis ua rau muaj kev hloov pauv ntau ntawm cov qauv. Cov pa oxygen ions nyob rau hauv alpha theem yog hexagonal kaw packing, txhuas oxide particles yog loj reunion, tshwj xeeb nto cheeb tsam poob qis heev.
Tsis txhob ntub dej, tsis txhob scrolling, pov thiab ntse shocking thaum lub sijhawm thauj mus los, cov chaw tiv nag yuav tsum tau npaj.
Nws yuav tsum tau khaws cia rau hauv qhov chaw qhuav thiab muaj cua nkag kom tiv thaiv kev kis kab mob lossis dej noo.
