Kev Ua Haujlwm ntawm Alumina Hmoov ua ib qho Catalyst Support
Thaum tham txog kev lag luam tshuaj lom neeg, tshwj xeeb tshaj yog thaj chaw ntawm catalysis, muaj ntau yam rau nws. Hnub no, peb yuav tsis tham txog cov khoom siv hlau zoo nkauj, tab sis yog cov "hero hero" uas feem ntau tsis quav ntsej tab sis tsis tseem ceeb - hmoov alumina. Nws zoo li lub ncej ntawm lub sam thiaj, lossis lub hauv paus ntawm lub tsev; cov khoom siv ua haujlwm, cov "hnub qub," ua haujlwm zoo npaum li cas nyob ntawm seb lub sam thiaj tau tsim zoo npaum li cas.
Thaum kuv thawj zaug nkag mus rau hauv daim teb no, kuv kuj pom tias nws txawv txawv - vim li casaluminatshwj xeeb? Nws zoo li tsis muaj dab tsi tshwj xeeb, yog li ntawd vim li cas nws thiaj li nyob hauv qhov chaw tseem ceeb hauv kev lag luam txhawb nqa catalyst? Tom qab, tom qab siv sijhawm ntev nrog cov neeg ua haujlwm paub dhau los hauv chav kuaj thiab chaw ua haujlwm, kuv maj mam nkag siab. Nws tsis yog qhov kev xaiv "zoo tshaj plaws", tab sis yog qhov kev xaiv "sib npaug tshaj plaws" pom ntawm kev ua tau zoo, tus nqi, thiab kev siv tau. Qhov no zoo ib yam li kev yuav lub tsheb; peb tsis tas yuav xav tau qhov ceev tshaj plaws, tab sis yog qhov uas sib npaug ntawm kev siv roj, qhov chaw, kev ruaj khov, thiab tus nqi. Hauv kev lag luam thauj khoom, alumina zoo li "txhua yam" - ob peb qhov tsis muaj zog thiab lub zog zoo tshaj plaws.
Ua ntej, peb yuav tsum qhuas nws qhov "porous sponge" zoo - thaj chaw loj thiab muaj peev xwm loj hlob tau zoo heev.
Qhov no yog lub zog tseem ceeb ntawmalumina hmoovTsis txhob xav tias nws yog cov khob cij uas tuab thiab tawv uas koj siv hauv tsev. Tom qab ua tiav tshwj xeeb, sab hauv ntawm lub alumina carrier yog riddled nrog micropores thiab channels ntawm lub nanoscale. Cov qauv no hu ua "high specific surface area."
Piv txwv li, ib gram ntawm cov hmoov alumina zoo, yog tias tag nrho nws cov qhov sab hauv tau nthuav dav tag nrho, yuav yooj yim ncav cuag ntau pua square meters hauv thaj chaw nto - loj dua li lub tshav pob basketball! Xav txog seb muaj pes tsawg cov khoom xyaw catalytic (xws li platinum, palladium, thiab nickel) tuaj yeem nyob hauv "cheeb tsam" loj li no! Nws zoo li muab cov khoom xyaw nrog lub "dormitory" loj heev, zoo nkauj, uas tso cai rau lawv kom tawg sib npaug thiab tsis txhob sib sau ua ke, yog li ua kom lawv raug thiab sib cuag nrog cov tshuaj reactants ntau tshaj plaws. Qhov no ua kom muaj txiaj ntsig zoo ntawm catalytic.
Ntxiv mus, cov qauv ntawm cov "sponge" no tuaj yeem "hloov kho." Los ntawm kev kho cov txheej txheem npaj, peb tuaj yeem tswj qhov loj me, kev faib tawm, thiab cov duab ntawm nws cov pores rau qee qhov, zoo li molding av nplaum. Qee cov tshuaj reactant loj thiab xav tau "qhov rooj" loj dua kom nkag mus; qee cov tshuaj tiv thaiv yog ceev thiab xav tau cov pores luv dua kom tsis txhob poob rau hauv lub maze. Kev txhawb nqa alumina tuaj yeem ua tau raws li cov "kev xav tau tus kheej," qhov kev ywj pheej tsis muaj qhov sib piv los ntawm ntau lwm yam khoom siv.
Qhov thib ob, nws "tus cwj pwm zoo" yog qhov tsim nyog hais txog - nws muaj ob qho tib si kev ruaj khov tshuaj lom neeg thiab lub zog kho tshuab zoo heev.
Ib puag ncig uas cov catalysts nyob tsis zoo. Nws feem ntau kub thiab siab, thiab qee zaum txawm tias muaj cov pa roj corrosive. Xav txog yog tias qhov kev txhawb nqa nws tus kheej yog "lub hom phiaj mos," tawg hauv ob hnub hauv lub reactor, lossis tshuaj lom neeg nrog cov khoom xyaw nquag thiab reactants - puas yog txhua yam yuav tsis muaj kev kub ntxhov?
Hmoov alumina, hauv qhov no, yog qhov "ruaj khov." Nws tswj nws cov qauv siv lead ua txawm tias nyob rau hauv qhov kub siab, tiv taus kev tawg, thiab nws cov khoom siv tshuaj lom neeg yog "nruab nrab," tsis yooj yim cuam tshuam nrog lwm yam tshuaj. Qhov no ua kom muaj lub neej ntev ntawm cov tshuaj catalyst, txuag cov chaw tsim khoom lub sijhawm tsis ua haujlwm thiab cov nqi hloov pauv.
Ntxiv mus, xav txog lub zog kho tshuab. Hauv cov reactors kev lag luam, cov catalysts tsis yog tsuas yog tso rau ntawm qhov chaw xwb; lawv feem ntau yuav tsum tiv taus qhov cuam tshuam ntawm huab cua, kev sib txhuam ntawm cov khoom me me, thiab txawm tias poob rau hauv lub txaj txav mus los. Yog tias lub zog tsis txaus, nws yuav tawg ua hmoov thaum thauj mus los, lossis tig mus ua tshauv thaum nws nkag mus rau hauv reactor - nws tuaj yeem ua tiav catalysis dab tsi?Aluminakev txhawb nqa, tom qab molding thiab calcination, tsim kom muaj zog txaus los tiv taus cov "kev tsim txom," kom ntseeg tau tias lub cuab yeej ua haujlwm ntev thiab ruaj khov. Qhov no yog qhov cov neeg ua haujlwm paub txog txhais tau tias thaum lawv hais tias "cov catalyst no khov kho."
Tsis tas li ntawd xwb, nws kuj tseem muaj zog heev - nws cov khoom nto yog cov ua haujlwm heev.
Qhov saum npoo ntawm alumina tsis du. Nws muaj cov chaw acidic lossis basic. Cov chaw no lawv tus kheej muaj peev xwm catalytic rau qee qhov kev tshuaj tiv thaiv. Qhov tseem ceeb tshaj, lawv tuaj yeem "sib cuam tshuam" nrog cov hlau uas txhawb nqa - ib qho xwm txheej uas peb hu ua kev sib cuam tshuam.
Qhov kev sib cuam tshuam no muaj ntau yam txiaj ntsig. Ntawm ib sab tes, nws ua haujlwm zoo li "kua nplaum," "nplaum" cov hlau me me rau ntawm qhov txhawb nqa, tiv thaiv lawv kom tsis txhob txav mus los, sib sau ua ke, thiab loj hlob ntawm qhov kub siab (qhov no hu ua sintering). Thaum sintering tshwm sim, qhov kev ua haujlwm catalytic poob qis heev. Ntawm qhov tod tes, nws qee zaum tuaj yeem hloov pauv lub xeev hluav taws xob ntawm cov hlau me me, ua rau lawv ua tau zoo dua hauv cov tshuaj tiv thaiv catalytic, ua tiav cov txiaj ntsig synergistic ntawm "1 + 1> 2".
Tau kawg, tsis muaj dab tsi zoo tag nrho. Cov kev txhawb nqa alumina tsis yog tsis muaj qhov tsis zoo. Piv txwv li, nyob rau hauv qhov chaw kub heev nrog cov dej vapor, nws yuav dhau los ntawm "theem hloov pauv," hloov los ntawm γ-hom ua haujlwm heev mus rau α-hom tsis ua haujlwm, ua rau cov qauv pore tawg thiab txo qis hauv thaj chaw nto. Qhov no zoo ib yam li cov pa roj carbon ua haujlwm raug hlawv rau hauv graphite; txawm hais tias tseem yog carbon, nws lub peev xwm adsorption yog qhov sib txawv heev. Yog li ntawd, cov kws tshawb fawb tau ua haujlwm los txhim kho nws qhov kev ruaj khov thermal los ntawm kev doping nws nrog lwm cov ntsiab lus (xws li silicon thiab zirconium) lossis tsim cov txheej txheem npaj tshiab los ua kom nws lub zog siab tshaj plaws thiab txo nws qhov tsis muaj zog.
Yog li, koj pom, cov hmoov dawb zoo li no muaj ntau yam kev paub. Nws tsis yog cov thev naus laus zis dub uas tsis nkag siab, tab sis nws yog hom khoom siv no, uas siv zog rau kev sib npaug thiab kev ua kom zoo dua txhua yam, uas txhawb nqa ib nrab ntawm cov txheej txheem catalytic niaj hnub no. Txij li kev ntxuav cov pa tawm ntawm lub tsheb mus rau kev tawg thiab kho cov roj av, thiab kev tsim ntau yam khoom siv tshuaj lom neeg, kev ua haujlwm ntsiag to ntawm cov neeg nqa khoom alumina yuav luag pom tseeb tom qab.
Nws tsis ci ntsa iab zoo li cov hlau muaj nqis xws li platinum lossis palladium, thiab nws tus nqi qis dua, tab sis nws qhov kev ntseeg tau, kev ruaj khov, thiab kev siv nyiaj tsim nyog ua rau nws yog lub hauv paus ruaj khov tshaj plaws rau kev siv hauv kev lag luam loj. Lub sijhawm tom ntej koj hnov txog kev tshawb pom tshiab hauv kev siv tshuab catalytic, muab nws lub ntsej muag zoo siab, vim tias hmoov alumina, tus phab ej tsis muaj npe tom qab qhov xwm txheej, tsim nyog tau txais txiaj ntsig ntau rau qhov kev ua tiav no.