Qhib Aluminayog cov tsis-stoichiometric alumina (al₂₂ · nhh₂o) nrog thaj chaw siab ntawm cov pab pawg hydroxyl. Nws lub ntsiab crystal yog -al₂o₃. Vim nws cov adsorption zoo, catalytic ua si thiab thermal ruaj khov, tshuab hluav taws xob tau siv hauv petrochemical, ib puag ncig kev tiv thaiv, roj kom qhuav thiab catalyst cov cab kuj. Txawm li cas los xij, nws lub xeev nquag muaj cuam tshuam los ntawm ntau yam, xws li kev npaj ua npaj, kev kho cua sov, cov ntsiab lus acidity, did didity cov ntsiab lus thiab qib ntawm kev tswj dej. Yog li ntawd, kev nkag siab tob ntawm qhov cuam tshuam ntawm cov kev ua tau zoo ntawm alumina yog qhov tseem ceeb rau kev ua kom ua kom zoo dua qub nws cov ntawv thov kev lag luam.
1. Cov nyhuv ntawm kev npaj txoj kev ntawm kev ua haujlwm ntawm cov alumina activated
Qhov kev npaj txoj kev npaj alumina ncaj qha cuam tshuam nws qhov tshwj xeeb thaj chaw, pore cov qauv thiab cov khoom sib luag, yog li txiav txim siab nws lub xeev nquag. Cov kev npaj muaj xws li:
(1) sol-gel txoj kev
Cov qauv no siv cov ntsev txhuas (xws li txhuas nitrate, txhuas isoprore) los ua tus sol, uas yog tom qab ntawd gelled, qhuav thiab calcined kom tau txais -al₂o₃. Ua kom Alumina npaj los ntawm Sol-Gel txoj kev feem ntau muaj qhov muaj feem cuam tshuam (300-500 m² \/ g) thiab ib qho tsim nyog rau cov neeg nqa khoom siab.
(2) txoj kev ceev nag
Aluminium hydroxide yog precipitated los ntawm kho tus nqi ntawm cov kua txhuas, thiab tom qab ntawd ua kom yooj yim yog tau txais los ntawm kev ntxuav, kom qhuav thiab calcining. Tus tseem ceeb tswj ntawm cov txheej txheem nag lossis daus suav nrog cov precipitive (ammonia, naoh, pawj lub sijhawm thiab laus. Txhim kho cov mob no tuaj yeem nce cov cheeb tsam sab nraud thiab sab saum toj ntawm alumina.
(3) hydrothermal txoj kev
Nyob rau hauv cov kub thiab kub siab hydrothermal tej yam kev mob, txhuas ua ntej prefursors (xws li Bohmite) tuaj yeem hloov mus rau hauv siab-crystallinity -al₂o₃. Lub alumina npaj los ntawm hom no muaj siab thermal ruaj khov thiab ua tsis tu ncua cov qauv, thiab yog qhov haum rau kev siv hluav taws xob siab.
Ua kom Alumina tau txais los ntawm kev npaj sib txawv muaj qhov sib txawv hauv thaj chaw tshwj xeeb, uas nyob rau hauv cov ntsiab lus hydroxyl thiab cov qauv sib txawv thiab kev ua haujlwm catalytic.
2. Cov nyhuv ntawm kev kho cua sov ntawm cov xeev nquag
Kev kho cua sov (kev pib ua) yog cov kauj ruam tseem ceeb hauv kev tswj hwm tus qauv alumina, uas feem ntau cuam tshuam rau nws cov Crystal daim ntawv, thaj chaw tshwj xeeb thiab sab nrauv.
(1) kev xam xyuas qhov kub
• Qhov chaw cais kub tsawg (300-500 degree): kev tsim cov cheeb tsam siab, cov pab pawg nplua nuj hydroxyl, tsim nyog rau kev kos duab thiab tsawg-kub catalysis.
• Cov pawg nruab nrab nruab nrab (500-800
• High temperature calcination (>1000 degree): -al₂o₃ maj mam hloov mus rau θ-al₂o₃ thiab -al₂o₃ nrog thaj chaw muaj tsawg, thiab cov haujlwm raug txo qis.
(2) calciples huab cua
• Cov pa taws ua haujlwm: Txhawb txoj kev cia siab ntawm cov pab pawg hydoxyl, haum rau cov ntawv thov cov kev ua kom siab.
• Cot■ Kho rau hauv Inert qhov chaw (N₂, AR): Txo cov xim oxidation thiab yog qhov haum rau kev tswj hwm cov nplaim acidity.
• Kevcai rho nyiaj rau hauv kev txo cov cua (H₂): Tsib Hlis ua tau cov khoom muaj nuj nqis qis, cuam tshuam rau kev ua haujlwm catalytic.
3. Cov nyhuv ntawm cov khoom saum npoo ntawm kev ua si
(1) thaj chaw ib sab thiab cov qauv pore
• High specific surface area (>200 m² \/ g) muab cov chaw nquag ua haujlwm, txhim kho cov adsorption thiab catalytic efficiency.
• Tsim nyog Pore loj (2-50 nm) pab rau deatants ntawm reactants thiab zam kev thaiv pore thaiv.
(2) Cov nplaim saum npoo
Lub saum npoo acidity ntawm activated alumina suav nrog Lewis acid (ua kom sib xyaw tsis tau alp⁺) thiab brønsted acid (Deg Hydroxyl):
• Lewis acid: txhawb nqa Olemas polinterization, omerization thiab lwm yam tshuaj tiv thaiv.
• Brønsted acid: haum rau proton catalytic cov tshuaj tiv thaiv xws li cov hydrolysis thiab kev siv tshuaj eserification.
Lub sab saum npoo acidity tuaj yeem ua kom zoo dua los ntawm kev kho cov txheej txheem npaj thiab doping kev hloov kho (xws li qhia cov sidio₂, F⁻, thiab lwm yam).
4. Cov nyhuv ntawm impurity doping
Qee yam kev cuam tshuam tuaj yeem hloov pauv cov catalytic kev ua tau zoo ntawm activated alumina:
• Kev txhawb nqa impurities (xws li FE, NI, tuaj yeem ua raws li cov chaw haujlwm nquag los txhim kho redebox.
Kev lom neeg tsis txaus ntseeg (xws li na, k⁺): nruab nrab ntawm cov nplaim dej acidity thiab txo kev ua si catalytic.
• Cov teeb hluav taws xob ruaj khov (xws li la₂o₃, sitio₂): Txhim kho thermal ruaj khov thiab tiv thaiv cov high kub sintering.
5. Cov nyhuv ntawm lub xeev cov dej hiav txwv
Ua kom Alumina muaj ntau pawg hydroxyl (-oh) ntawm nws cov nplaim dej, thiab lub xeev cov dej cawv cuam tshuam nrog tus cwj pwm adsorption thiab catalytic:
• Siv cov dej (3-10% h₂o): tswj cov pab pawg hydroxyl, txhim kho hydrophilicity thiab catalytic kev ua ub no.
• Lub cev qhuav dej ntau dhau: ua rau muaj kev txo qis hauv pawg hydroxyl thiab txo kev ua haujlwm.
• Nkawv ntau dhau: Tej zaum yuav thaiv cov pores thiab cuam tshuam rau qhov sib txawv ntawm reactants.
6. Kev cuam tshuam ntawm kev cia khoom
Ua kom Alumina tuaj yeem txo nws cov haujlwm thaum lub sijhawm khaws cia vim yog noo noo nqus lossis kev tso tawm bog adsorption. Yog li ntawd, nws yuav tsum tau muab cia rau hauv qhov chaw qhuav hauv insert lossis passivated ntawm sab kom txhim kho kev ruaj khov.
Lub xeev nquag ntawmQhib Aluminacuam tshuam los ntawm ntau yam, suav nrog kev npaj qauv, kev kho cua sov, cov khoom siv hluav taws xob, impration lub xeev. Los ntawm kev ua kom zoo dua cov xwm txheej no, nws cov qauv pore thiab cov qauv acidity tuaj yeem hloov kho nws qhov kev ua tau zoo hauv catalysis, adsorption thiab lwm thaj teb.