Kev xaiv thiab Deactivation Ua rau Heterogeneous Catalysts

Raws li cov khoom siv sib txawv, cov catalysts heterogeneous tuaj yeem muab faib ua cov hlau thiab nws cov ntsev, hlau oxides, thiab cov khoom sib xyaw hlau oxide catalysts; Raws li lawv cov duab, lawv tuaj yeem muab faib ua kheej kheej, luv columnar, thiab honeycomb duab; Raws li lawv cov txheej txheem npaj, lawv tuaj yeem muab faib ua cov neeg siv kev txhawb nqa thiab cov tsis siv kev txhawb nqa.

Khoom- xeev heterogeneous catalysts loj tiv thaiv catalyst poob, yooj yim dua los cais cov dej khib nyiab, thiab muaj qhov zoo xws li kev ua haujlwm zoo, ruaj khov zoo, thiab kev kho luv luv;

Txawm li cas los xij, muaj kev hloov pauv loj ntawm cov txheej txheem catalyst heterogeneous, thiab cov khoom raug tshem tawm hauv cov dej khib nyiab thiab cov tshuaj tiv thaiv intermediates tuaj yeem ua rau cov khoom catalyst tau coated los yog thaiv, ua rau deactivation.

(1) Hlau / Txhawb Catalysts

Nyob rau hauv heterogeneous catalytic oxidation technology, noble hlau catalysts yog dav siv vim lawv cov kev ua haujlwm siab, ntev lifespan, thiab muaj zog adaptability. Cov catalysts ua los ntawm cov hlau zoo xws li P, Pd, thiab Ru raws li cov khoom siv tsis yog tsuas yog muaj cov chaw hydrocarbon adsorption tab sis kuj muaj ntau qhov chaw oxygen adsorption, uas tuaj yeem ua rau cov pa oxygen sai thiab hydrocarbon adsorption raws li cov tshuaj tiv thaiv saum npoo. Txhawm rau ua kom tau zoo dua dispersibility thiab txo cov nqi ntawm cov hlau siv, impregnation feem ntau yog ua haujlwm los txhawb cov hlau ntawm cov cab kuj nrog cov chaw tshwj xeeb, xws li Al3O2, SiO2, activated carbon, TiO2, CeO2, thiab ZrO2.

(2) Hlau Oxide / Txhawb Catalysts

Kev xaiv cov catalysts hauv catalytic oxidation txheej txheem yuav tsum xav txog ntau yam, xws li cov khoom ntawm cov tshuaj, lub peev xwm catalytic, thiab nws cov thermal stability hauv dej. Ntawm cov no, hlau oxides muaj nuj nqis heev vim lawv cov kev ruaj ntseg siab thiab kev ua haujlwm zoo.

Raws li lawv cov kev ruaj ntseg, cov catalysts tuaj yeem raug cais raws li hauv qab no: 1. Oxides uas ruaj khov tshaj plaws nyob rau hauv siab oxidation tej yam kev mob, xws li titanium oxide, vanadium oxide, chromium oxide, magnesium oxide, zinc oxide, thiab txhuas oxide; 2. Oxides nrog kev ruaj ntseg nruab nrab, xws li hlau oxide, cobalt oxide, npib tsib xee oxide, thiab txhuas oxide; 3. Tsis ruaj tsis khov siab -oxidation- xeev oxides thiab noble hlau, xws li platinum, palladium, ruthenium, thiab kub.

(3) Composite Oxide/Supported Catalysts

Raws li lub hauv paus ntsiab lus ntxiv ntawm kev tswj hwm kev ua haujlwm catalytic, cov khoom sib xyaw oxide catalysts xav kom ua tiav cov haujlwm catalytic ntau dua. Cov teebmeem synergistic tuaj yeem txhim kho cov kev ua haujlwm catalyst thiab inhibit qhov kev tawg ntawm cov khoom nquag. Piv txwv li, kev sib xyaw ntawm CoO, CuO, los yog NiO nrog oxides ntawm Fe (III), Pt, los yog Ru yog ib qho zoo oxidation catalyst.

(1) Kev xaiv Catalyst

Thaum xaiv cov catalyst, feem ntau catalysts nrog cov yam ntxwv hauv qab no yuav tsum tau siv:

1. Ceev oxidation tus nqi thiab zoo dua theem kev sib cuag, yog li ceev cov tshuaj tiv thaiv;

2. Tsis yog- xaiv, ua kom tiav oxidation;

3. ruaj khov physicochemical zog hauv cov kua qaub kub;

4. Kev ua haujlwm siab thiab lub neej ntev ntawm qhov kub thiab txias, thiab tsis hnov ​​​​tsw rau tshuaj lom;

5. Lub zog txhua yam muaj zog thiab hnav tsis kam.

(2) Catalyst Support Xaiv

Raws li qhov muaj pes tsawg leeg ntawm cov khoom txhawb nqa catalyst, nws tuaj yeem muab faib ua peb hom: cov khoom txhawb nqa, ntxhib-cov khoom txhawb nqa, thiab cov substrates.

Thaum siv cov catalysts, cov ntsiab lus hauv qab no feem ntau suav hais tias:

1. Tshuaj muaj pes tsawg leeg thiab dispersion;

2. Nto physicochemical zog-porosity, adsorption, electrochemical thiab mechanical zog;

3. Thickness thiab kom muaj nuj nqis ntawm cov khoom nquag uas tuaj yeem thauj khoom;

4. Lub zog tshwj xeeb thiab ruaj khov;

5. Tshuaj stability;

6. Abrasion kuj, hardness, thiab compressive zog;

7. Kev koom tes hauv cov tshuaj tiv thaiv catalytic.

Ntxiv nrog rau kev ua haujlwm siab thiab kev xaiv zoo, catalysts yuav tsum muaj lub zog zoo thiab ruaj khov, nrog rau kev ruaj ntseg cuam tshuam rau lawv lub peev xwm los txo qis kev ua haujlwm.

Tom qab ib lub sij hawm ntawm kev siv, catalysts yuav muaj kev deactivation, feem ntau yog vim poob ntawm catalyst khoom thiab coking.

Catalyst poob yog ib qho tseem ceeb ntawm deactivation. Qhov kev poob no feem ntau cuam tshuam los ntawm pH, ua rau cov khoom nquag ua kom yaj. Cov kev tshawb fawb sim tau pom tias pH ntawm cov dej khib nyiab muaj qhov cuam tshuam loj rau oxidation ntawm cov organic teeb meem hauv cov kua theem.

Piv txwv li, heterogeneous ozone catalysts muaj cov tshuaj tiv thaiv tsawg thiab cov deactivation siab nyob rau hauv acidic tej yam kev mob. Catalyst poob yog tsawg kawg ntawm pH 7. Thaum pH ntau dua 7 tab sis tsawg dua 9, tsis muaj catalyst poob. Txawm li cas los xij, thaum pH ntau dua 10, cov tshuaj tiv thaiv qis qis. Yog li ntawd, kho tus nqi pH tuaj yeem txo lossis tiv thaiv catalyst poob.

Catalyst coking yog lwm qhov ua rau deactivation, tseem hu ua catalyst fouling deactivation. Qhov no feem ntau yog tshwm sim los ntawm kev tso tawm ntawm carbon, nitrogen, thiab lwm yam khoom tsim thaum lub sij hawm cov tshuaj tiv thaiv ntawm lub catalyst nto. Cov ntawv thov kev tsim vaj tsev tau txheeb xyuas tias qee cov catalysts heterogeneous pom muaj qhov degradation siab nyob rau hauv ib lub sij hawm, ua raws li deactivation. Lub zog photoelectrochemical chromatography (ESCA) kev tsom xam ntawm cov catalyst nto qhia cov pa roj carbon deposition, uas cuam tshuam kev sib cuag ntawm reactants nyob rau hauv cov kua theem thiab cov catalyst nto, yog li ua rau deactivation.