Concerted Oxygen Diffusion hla Heterogeneous Oxide Interfaces Rau Intensified Propane Dehydrogenation

Propane dehydrogenation (PDH) yog ib qho kev lag luam thev naus laus zis rau kev tsim cov propylene ncaj qha uas tau txais kev saib xyuas nyob rau xyoo tas los no. Txawm li cas los xij,uas twb muaj lawm non-oxidative dehydrogenation technologiestseem raug kev txom nyem los ntawm cov kev txwv thermodynamic equilibrium thiab choking hnyav. Ntawm no, peb tsim cov propane dehydrogenation intensified rau propylene los ntawm chemical looping engineering ntawm nanoscale core-plhaub redox catalysts. Cov tub ntxhais-plhaub redox catalyst ua ke dehydrogenation catalyst thiab cov khoom siv oxygen ntawm ib qho, zoo dua yog tsim los ntawm ob mus rau peb atomic txheej-hom vanadia txheej ceria nanodomains. Qhov siab tshaj plaws 93.5 feem pua ​​​​propylene selectivity yog tau, txhawb nqa 43.6 feem pua ​​​​propylene tawm los hauv qab 300 lub sij hawm ntev dehydrogenation-oxidation cycles, uas outperforms ib qho analog ntawm industrially cuam tshuam K-CrOx / Al2O3 catalysts thiab nthuav tawm 45 feem pua ​​​​lub zog txuag nyob rau hauv cov tshuaj scale-up. txoj kev voj voog. Kev sib koom ua ke hauv situ spectroscopies, kinetics, thiab theoretical xam xam, ib qho intrinsically dynamic lattice oxygen "donator acceptor" txheej txheem tau npaj siab tias O2- generated los ntawm ceria oxygen carrier yog boosted rau diffuse thiab hloov mus rau vanadia dehydrogenation qhov chaw ntawm ib tug concerted hopping txoj hauv kev ntawm lub interface, stabilizing nto vanadia nrog cov pa pa nruab nrab ntawm cov pseudo khov kho rau kev xaiv dehydrogenation yam tsis muajtseem ceeb overoxidationlos yog tawg.

Nyem qhov no kom tau txais cov ntaub ntawv ntau ntxiv txog Cistanche Anti-Oxidation Function

Propane dehydrogenation (PDH) yog ib qho kev lag luam tseem ceeb rau cov txheej txheem roj-raws li tawg1,2. Txawm li cas los xij, lublag luam uas tsis yog-oxidative propane dehydrogenationmuaj CrOx los yog Pt-raws li catalysts yog endothermic thiab equilibrium-limited, yuav tsum tau ntau cua sov kom ua tau zoo propylene yield3,4. Txawm hais tias oxidative dehydrogenation ntawm propane (ODH) muaj peev xwm los txhim kho kev hloov pauv rau cov thermodynamics zoo, propylene selectivity yog hampered los ntawm overoxidation rau CO.2 5,6. Ib qho kev sib tw zoo sib xws tau ntsib hauv kev xaiv oxidation cov tshuaj tiv thaiv hauv kev lag luam tshuaj7,8.

Chemical looping engineering muab txoj hauv kev zoo siab tshiab rau cov kev cov nyom los ntawm kev sib cais ntawm lub cev lossis lub sijhawm ntawm dehydrogenation thiab oxidation los ntawm cov khoom nruab nrab ntawm cov pa oxygen.9,10. Tsis zoo li cov catalysts ib txwm muaj, cov neeg nqa cov pa oxygen hnov ​​​​mob nrog alkanes thiab hloov pauv hloov pauv los ntawm kev pub dawb thiab ntxiv cov pa oxygen kom kaw lub voj hauv lub reducer thiab oxidizer reactors. Feem ntau cov neeg nqa cov pa oxygen koom nrog cov chaw hlau lossis cov khoom siv oxide los hloov cov pa oxygen reactivity, siv cov doping ntau.11, kev hloov kho saum npoo 12, lossis kev kho kom zoo hauv kev txhawb nqa13. Tsis ntev los no, vanadia / ceria catalysts tau nyiam ntau ntxiv hauv oxidative dehydrogenation ntawm propane nrogO2 sib pub. Cov teebmeem hluav taws xob thiab cov khoom redox tau tshawb xyuas ntawm qib molecular13–16. Txawm li cas los xij, kev sim ncaj qha thiab theoretical insights rau hauv lub lattice oxygen diffusion thiab cov nto dynamics tseem tsis tau tshaj tawm rau anaerobic oxidative dehydrogenation ntawm tshuaj lom neeg looping engineering.

Hauv kev ua haujlwm no, txhawm rau tshem tawm cov pa oxygen diffusion thiab cov tshuaj tiv thaiv dynamic hais txog cov chaw nquag, nanoscale core-plhaub redox catalyst combining dehydrogenation catalyst thiab oxygen carrier ntawm ib qho yog tsim. Cov tub ntxhais-plhaub redox catalyst zoo dua yog tsim los ntawm ob mus rau peb atomic txheej-hom vanadia txheej ceria nanodomains kom ua tiav cov kev hloov pauv ntawm cov lattice oxygen bulk diffusion thiab cov tshuaj tiv thaiv saum npoo. Nyob rau hauv cov kauj ruam dehydrogenation (txo), ceria-vanadia redox catalysts pub lattice oxygen rau dehydrogenation ntawm propane los tsim propylene, H2O, thiab H2, them nyiaj txo qis lub xeev uas tuaj yeem rov ua dua tshiab hauv cov kauj ruam reoxidation (oxidizer) los ntawm huab cua kom kaw lub voj (Fig.1a). Ua ke nyob rau hauv situ spectroscopies, kinetics, thiab theoretical xam, ib qho intrinsically dynamic lattice oxygen"pub dawb-acceptor" Cov txheej txheem tau npaj tseg, uas suav nrog kev sib koom ua ke ntawm kev sib faib ntau thiab cov tshuaj tiv thaiv saum npoo hauv cov tub ntxhais-plhaub redox catalyst. O2− generated los ntawm ceria oxygen carrier yog boosted mus rau diffuse thiab hloov mus rau vanadia dehydrogenation qhov chaw ntawm ib tug concerted hopping txoj kev ntawm lub interface, stabilizing nto vanadia nrog rau cov pa pa nruab nrab tsis muaj signififi uatsis tuaj yeem overoxidation lossis tawg.

Cov txiaj ntsigTsim ntawm ceria-vanadia core-plhaub redox catalystsCov tub ntxhais-plhaub redox catalysts tau npaj siv ob-kauj ruam incipient wetness impregnation txoj kev. Cov qauv ceria-vanadia tau raug hu ua xV/yCeAl, qhov twg x(y) yog qhov hnyav ntawm V(Ce). Cov vanadia thiab ceria catalysts tau txais los ntawm VOx thiab CeO2 txhawb rau -Al2O3, raws. Ntawm vanadia qhov ntom ntom ntawm 4.3 V / nm2 (Table ntxiv 1)17–19 (6 V/30CeAl), atom-resolved high-angle annular dark-field scanning transmission electron microscope (HAADF-STEM) cov duab txheeb xyuas vanadia feem ntau muaj xws li monolayers thiab bilayers raws ceria nto (Fig.1b–d). Electron zog poob spectra (EELS) daim ntawv qhia ntawm VL2,3 thiab CeM4,5 cov npoo tau lees paub qhov chaw vanadia anchors rau thoob plaws ceria nanodomains (Fig.1e–h). Qhov zoo-defi uaned core-plhaub qauv tau ntxiv validated los ntawm kab-scanning EELS uas hla ib tug neeg particle, nyob rau hauv lub plhaub sab nrauv yog ~ 1 nm, sib xws rau roughly ob mus rau peb atomic vanadia txheej (Fig.1i). Kev txiav txim los ntawm kev hloov pauv ntawm VL2,3 thiab OK ntug, vanadia nthuav tawm dominantly raws li kev sib xyaw ntawm V5 plus ibthiab V4 plus ib, thaum txheeb ze sib piv ntawm CeM4,5 ntug (1.11–1.19)20 qhia tias muaj Ce3 plus ibthiab Ce4 plus ib((1), (2), (3) hauv daim duab.1b) nyob rau hauv ib tug particle (Fig.1j, Supplementary Fig. 2, thiab Supplementary Table 2)21.

Chemical loopingoxidative dehydrogenation kev ua tau zooDaim ntawv thov ntawm cov tub ntxhais-plhaub redox catalysts tau raug pov thawj nyob rau hauv ib tug tas mus li tshuaj lom neeg looping oxidative dehydrogenation scheme (Ntxiv daim duab 3). Ceria-vanadia redox catalysts nthuav tawm traceable CO2 (<3%) with high propylene selectivity of 93.5% and formation rate of 42.5 mmol C3H6/gmiv/h (ntawm 5thmin nyob rau hauv ib lub voj voog), implying overoxidation los yog tawg tau inhibited. Hauv 600o C thiab GHSV ntawm 2500 h−1, qhov nruab nrab 90 feem pua ​​​​propylene xaiv ntawm propane hloov dua siab tshiab ntawm 49 feem pua ​​​​tau txais nyob rau hauv 60 mins (Daim duab.2b thiab Supplementary Fig. 4), superior rau cov ceria (30CeAl) (78.3 feem pua), vanadia (6 V/Al) (71.6 feem pua), thiab lub xeev-of-the-art catalysts (Fig.2c). Kev lag luam muaj feem xyuam K-CrOx/Al2O3 4,22 tau muab piv rau hauv cov xwm txheej zoo sib xws. propylene space-time yield (STY) ntawm ceria-vanadia redox catalysts yog 10.3 mmol C.3H6/gmiv/h, piv rau K-CrOx/Al2O3 (10.6 mmol C3H6/gmiv/h) (Ntxiv daim duab 3g). Txawm li cas los xij, txiav txim siab qhov chaw sib txawv hauv ob lub catalysts, propylene STY normalized los ntawm moles ntawm V (13.3 mol C.3H6/molV/h) yog hais txogfifi uave lub sij hawm siab tshaj qhov normalized los ntawm moles ntawm Cr (2.8 mol C3H6/molCr/h). Tus nqi deactivation tas li (kd) siv tus qauv txiav txim thawj zaug deactivation tau siv los txiav txim nws lub neej hauv cov kauj ruam dehydrogenation. Ceria-vanadia redox catalysts nthuav tawm me mekd (0.04 h−1 ) dua li K-CrOx/Al2O3 (0.99 h−1 ) (Cov duab ntxiv. 5, 6). Thaum kub tau nce mus rau 650o C, propylene selectivity tseem nyob ntawm 80 feem pua. Txawm li cas los xij, ntshiab vanadia tau pom sai sai deactivation (kd = 1.4 h−1 ) thiab propylene selectivity txo mus rau 34 feem pua.

Kev thim rov qab-tso tawm ntawm lattice oxygen hauv ceria-vanadia redox catalysts tau txheeb xyuas los ntawm situ XRD. Hauv cov kauj ruam dehydrogenation ntawm 600o C, difract peaks ntawm CeO2 hloov mus rau qis diffraction lub kaum sab xis, piv txwv li, qhov (111) diffraction ncov hloov los ntawm 28.4o mus rau 28 0o vim yog tsim cov loj Ce3 plus ibions. Oxidation nrog huab cua ces rov qab nws txoj hauj lwm (Fig.2a thiab Supplementary Fig. 7). Thaum lub sij hawm 300 lub sij hawm ntev chemical looping cycles, qauv durability thiab robust kev ua tau zoo nrog qhov nruab nrab 43.6 feem pua ​​C3H6 yield thiab qhov chaw-lub sij hawm tawm los ntawm 9.9 mmol C3H6/gmiv/h tau tiav (Fig.2d thiab Table 5). Thaum hloov cov plhaub lossis cov khoom tseem ceeb hauv cov tub ntxhais-plhaub redox catalysts, piv rau C3H6 tsim cov nqi tau txais (Ntxiv daim duab 8). Rau chemical looping oxidative dehydrogenation ntawm ethane, cov ceria-vanadia redox catalysts kuj qhia 92 feem pua ​​​​ethylene selectivity nrog 31 feem pua ​​​​ethane hloov dua siab tshiab ntawm 600.o C (Ntxiv daim duab 9), validating nws muaj peev xwm thov nyob rau hauv lub dehydrogenation ntawm lub teeb alkanes. Piv nrog rau kev lag luam Oleflfl uaex scheme (Ntxiv daim duab. 10 thiab Supplementary Tables 6–10), 45 feem pua ​​​​ntawm kev txuag hluav taws xob tuaj yeem xav tau los ntawm cov tshuaj lom neeg lub voj voog oxidative dehydrogenation system (Fig.2e), nrog kev sib cais ua tus tsav tsheb loj rau kev siv hluav taws xob.

Cov ntaub ntawv pov thawj ntawm oxygen diffusion thiab cov tshuaj tiv thaiv nto

Thaum raug propane rau 120 mins, peaks ntawmB2 thiabC hauv CeL3- ntug hloov mus rau qis zog (Δ2.1 eV). Cov B0 kab dawb nyob ntawm 5726 eV yog ces dominated, tus yam ntxwv ntawm Ce3 plus ib(Fig.3a), qhia txog kev txo qis ntawm ceria (Ce4 plus ib→Ce3 plus ib) nyob rau hauv lub ceria-vanadia catalysts, nyob rau hauv sib piv rau lub negligible tsim ntawm Ce3 plus ibnyob rau hauv ntshiab ceria (CeL3- ntug hloov ntawmΔ0.7 eV). VK ua ntej ntug ze rau 5467 eV featuring V4 plus iboxidation lub xeev khaws cia ze li ntawm tsis txav li ntawm 30 feeb. Tom qab ntawd, qhov txo qis ntawm qhov siab tshaj plaws ua ntej thiab hloov ntawm ntug txoj hauj lwm kom qis zog (~Δ1.2 eV) tshwm sim raws li qhov txo qis ntawm CeO2 nres (Fig.3b thiab Supplementary Fig. 11). Qhov no txhais tau hais tias nyob rau hauv ceria-vanadia redox catalysts, vanadia tended yuav txo qis valence xeev thaum oxygen tsis tau raws sij hawm los ntawm ceria. Rau ntshiab vanadia tsis muaj CeO2 txhawb, VK pre-ntug featuring V5 plus ibtau yooj yim thiab sai txo rau V3 plus ib(V K- Ntug hloov ntawm 2.7 eV)11. Ua ke, kev hloov ntawm CeL3-ntug and VK-edge qhia tias ceria hauv ceria-vanadia redox catalysts ua raws li ib qho"oxygen reservoir" uas tuaj yeem muab cov pa lattice oxygen kom ruaj khov ntawm qhov chaw vanadia, uas ua raws li kev tshawb fawb yav dhau los uas ceria tau pab oxidize qhov txo qis ntawm vanadia ntawm ceria lattice oxygen.23–25.

Peb tau ua pov thawj ntxiv qhov kev hloov pauv hloov pauv ntawm cov pa lattice oxygen hauv ceria-vanadia redox catalysts. Raman spectra of CeO2 twb dominated los ntawm cov muaj zogF2g hom kevfluorite theem ntawm 464 cm−1 nrog tsis muaj zog bands ntawm 598 cm−1 vim kev txom nyem (D) hom. Nrog vanadia txheej, ntxiv rau V=O thiab VOV stretching, ntxiv bands ntawm VO-Ce (859 thiab 720 cm−1 ) tshwm sim (Cov duab ntxiv 1j, k), lees paub kev tsim kho ntawm vanadia-ceria interface26,27. Thaum raug propane, nyob rau hauv qhov chaw, Raman spectra txheeb xyuas qhov txo qis ntawm CeO2 nyob rau hauv ceria vanadia redox catalysts uas siv ntawmF2g hom poob qis nrog lub sijhawm ntawm kwj. Nws raug sau tseg tias pawg VO-Ce khaws cia ruaj khov. Hauv qhov sib piv, qhov sib piv ntawm VO-Ce band thiabF2g hom nyob rau hauv cov nqe lus ntawm kuvVO-Ce/IF2g nce, validating tias Ce-O hom nyob rau hauv ceria tau maj mam noj ntxiv thiab stabilize interfacial thiab nto VO hom (Fig.3c thiab Supplementary Fig. 12)24,25. Raws li ntau cov pa oxygen tau depleted tom qab 30 min, lub sij hawm kuj tau pom nyob rau hauv siteu XANES spectra. CovD1 band thiabG band sib raug zoo nrog coke deposits tau raug soj ntsuam, implying hais tias lub cracking thiab coking ntawm propane tshwm sim nyob rau hauv txo vanadia qhov chaw. Piv txwv li, ntshiab vanadia tau yooj yim txo rau V3 plus ib, uas ua rau ntau coke deposition nyob rau hauv tus yam ntxwv ntawm lub ntau dominated sivD1 thiabG band27–29.

Daim duab 1|Kev txheeb xyuas cov txheej txheem vanadia uas coated ceria nanodomains. ibDaim duabCov tub ntxhais-plhaub redox catalysts nyob rau hauv propane dehydrogenation los ntawm cov tshuaj looping engineering: dehydrogenation thiab oxidation nyob rau hauv roj reactor (txo) thiab huab cuareactor (oxidizer), feem.b–d HAADF-STEM cov duab thiabe–h EELS daim ntawv qhia ntawm core-plhaub ceria-vanadia redox catalysts (6 V / 30CeAl): (f): V; (g): Ce; (h): V plus Ce.i Line-scanning EELS.j EELS ntawm cov domains ((1), (2), (3)) hauv (b).

Daim duab 2|Chemical looping oxidative dehydrogenation kev ua tau zoo. ibNyob rau hauv situ XRD qauv ntawm ceria-vanadia redox catalysts (6 V / 30CeAl).b Kev sib piv ntawm ceria(30CeAl), vanadia (6 V / Al), thiab ceria-vanadia redox catalysts (6 V / 30CeAl). Condiib: 600oC, GHSV=2500 h−1, C3H8/N2 = 0.25. c Sib piv ceria-vanadia redoxcatalysts (6 V / 30CeAl) nrog tsim oxide-based thiab Pt-muaj catalysts (saib Cov Lus Qhia Ntxiv 3, 4). Motifs ntawm daim duab peb sab, rhombus, thiab sphere sawv cevODH, PDH, thiab CL-ODH, feem.d Cyclic kev ua tau zoo tshaj ceria-vanadia redox catalysts (6 V / 30CeAl). Dehydrogenation kauj ruam: 600oC, GHSV=2500 h−1, C3H8/N2 = 0.25 rau 30 min; Inert Purge: 600oC, N2 = 40 mL/min rau 5 min; Oxidation theem: 600oC, 20 vol. feem pua ​​O2/N2 = 20 mL/min rau 15 min.e Kev sib piv ntawm kev siv hluav taws xob thiab CO2 emission ntawm tsoos Oleflfl uaex technology thiab chemical looping scheme (saib Methods and Supplementary Tables 6–8).

Daim duab 3|Kev sim ua pov thawj ntawm oxygen diffusion thiab cov tshuaj tiv thaiv saum npoo. ibXANES spectra of CeL3-edge (CeO2 cov qauv raws li cov ntaub ntawv siv) dhau ceria-vanadia (6 V / 30CeAl) (sab saum toj) thiab ntshiab ceria (30CeAl) (hauv qab) thiabb V K-ntug (V foil, V2O5, VO2, thiab V2O3 cov qauv raws li cov ntaub ntawv siv) dhau ceria-vanadia (6 V / 30CeAl) (sab saum toj) thiab ntshiab vanadia (6 V / Al) (hauv qab) ntawm 600 degree hauv qabphooj ywgntawm 20 feem pua ​​C3H8/N2 (20 ml / min).c Nyob rau hauv situ Raman spectra ntawm ceria-vanadia (6 V / 30CeAl) (sab saum toj) thiab vanadia (6 V / Al) (hauv qab) ntawm 600 degree nyob rau hauv lubphooj ywgntawm 20 feem pua ​​C3H8/N2 (20 ml / min). Hauvsitu DRIFTS spectra ntawm qhov kub thiab txias-programmed thiab isothermal propane dehydrogenation tshaj ceria-vanadia (6 V / 30CeAl) (d) thiab vanadia (6 V/Al) (e, f). g Qhov xam piv ntawm H2/H2O thaum lub sij hawm C3H8 transient pulses ntawm 600oC. h Kev sim kev so nkhaus nyob rau hauv daim ntawv ntawm fractional hnyav hloov raws li ib tug muaj nuj nqi ntawm lub sij hawm ntawm 600oC subphooj ywgntawm 20 feem pua ​​C3H8/ Nws (10 mL / min).i Schematicsawv cev ntawm kev sib koom ua ke oxygen diffusion hauv ceria-vanadia redox catalyst. Cov dub, dawb, thiab liab spheres sawv cev C, H, thiab O atoms.

Nyob rau hauv situ diffuse reflectance infrared Fourier transforms spectroscopy (DRIFTS) raws li propane raug txheeb xyuas qhov sib koom ua ke ntawm dehydrogenation thiab tawg ntawm propane induced los ntawm no dynamic oxygen evolution. Peaks ascribed asymmetric thiab symmetric CH3 stretching hom (2970 thiab 2875 cm−1 ) pib ntawm 100–150 o C (Fig.3d)30. Lub xub ntiag ntawm ib tug band centering ntawm 1645 cm−1 (ν(CH3CH =CH2)) txhais tau hais tias cov propyl complex tau oxidatively dehydrogenated rau propenyl los ntawm heterolytically rho H mus rau cov nyob sib ze VO qhov chaw, ua rau qhov tshwm sim ntawm vanadium hydroxyl band (V-OH, 3660 cm.−1 ) 28. Txawm li cas los, lub ncov ntawmν(C=O) (1680 cm−1 ) ntaus nqi rau acetone, qhov nruab nrab ntawm overoxidation ntawm propane rau COx, tau dominated ntawm cov ntshiab VOx catalysts thaum kubtau siab tshaj 150o C, nrog rau lub cimfifi uacantly negative V=O band induced los ntawm kev npaj txo ntawm vanadia (V5 plus ib→ V3 plus ib) (Fig.3e, f thiab Supplementary Fig. 11)11,28. Qhov no"dhau ceev" Kev tshem tawm cov pa oxygen yuav ua rau kev hloov pauv ntawm oxidative mus rau qhov tsis yog-oxidative dehy-drogenation thiab tshwm sim ntawm propane tawg. Hauv 250–600 o C, ob lub ncov ntawm 1545 thiab 1460 cm−1 ntaus nqi rau hom unsaturated los yog aromatic, precursors ntawm coke deposits27,28 uas ua rau kom ceev deactivation tau pom, uas kuj muaj pov thawj los ntawm ntau dominatedD1 thiabG band nyob rau hauv situ Raman spectra ntawm ntshiab vanadia catalysts thaum dehydrogenation kauj ruam.

Raws li cov ntaub ntawv pov thawj hauv situ spectroscopies, tso tawm ntawm latticeCov pa oxygen yuav ua rau muaj kev muaj sia nyob thiab kev hloov pauv ntawm lub sijhawm sib txawv ntawm cov tshuaj tiv thaiv, suav nrog overoxidation, oxidative dehydrogenation, thiab non-oxidative dehydrogenation. Nyob rau hauv qhov sib txawv reactor operation los ntawm kev tswj cov propane hloov dua siab tshiab qis dua 10 feem pua, C3H6 kev tsim tus nqi tau pom muaj kev sib raug zoo nrog C3H8 siab, thaum C3H8 hloov dua siab tshiab khaws cia zoo ib yam ntawm txawv C3H8 pressures, qhia tus nqi ntawm propene tsim yog feem ntau muaj feem xyuam rau propane ib nrab siab, piv txwv li, akev txiav txim thawj zaugtshuaj tiv thaiv nrog kev hwm rau propane (Supplementary Fig. 13). Yuav kom paub meej txog kev koom tes ntawm oxidative thiab tsisoxidative dehydrogenation, tsim ntawm H2O thiab H2 dhau ceriaVanadia redox catalysts hauv lawv cov kev kuaj dehydrogenation tau nqis peevrooj vag. Raws li pom nyob rau hauv Ntxiv Fig. 13, qhov pib piv ntawm H2O to H2 hauv 5thmin yog {{0}}.44; Txawm li cas los xij, nws txo qis mus txog 0.05 tom qab 60 feeb.Yog li ntawd, oxidative dehydrogenation yuav ua tau ntau dua nyob rau hauv thawj lub sij hawm (tsawg tshaj li 5 feeb) thiab nws twb hloov mus rau non-oxidative dehydrogenation nrog lub sij hawm, accounting rau cov kev taw qhia txog cov kauj ruam reoxidation kom rov qab cov lattice oxygen tom qab lub 30- min dehydrogenation kuaj thaum lub sij hawm tas li dehydrogenation-reoxidationcycles nrog qhov sib piv ntawm H2O to H2 ntawm ~0.21.

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