A al'ada, mai kara kuzari yana aiki ta hanyar hulɗa kai tsaye tare da masu amsawa.A cikin sabon tsarin catalytic mara lamba (NCCS), tsaka-tsakin da aka samar ta hanyar amsawar catalytic guda ɗaya yana aiki azaman tsaka-tsaki don ba da damar amsa mai zaman kanta don ci gaba.Misali shine zaɓin oxidation na ethylbenzene, wanda ba zai iya faruwa a gaban ko dai nanoclusters mai narkewa ko cyclooctene ba, amma ya ci gaba da sauri lokacin da duka suke a lokaci guda.Epoxidation na zaɓin Au-initiated na cyclooctenyl ya haifar da cyclooctenyl peroxy da radicals oxy waɗanda suka yi aiki a matsayin tsaka-tsaki don fara oxidation na ethylbenzene.Wannan tsarin haɗe-haɗe yadda ya kamata ya ƙara haɓaka tasirin Au.An sami goyan bayan tsarin amsawa ta hanyar motsin motsi da gwaje-gwajen tarko.NCCS yana ba da damar daidaitattun halayen don ci gaba ba tare da iyakancewar alaƙar stoichiometric ba, yana ba da sabbin digiri na 'yanci a cikin hanyoyin haɗin gwiwar hydrocarbon na masana'antu.

A al'adance, mai kara kuzari yana hulɗa kai tsaye tare da masu amsawa (reaction A) don aiwatar da sake fasalin haɗin gwiwa da aka tsara ta hanyar amsawa.Alal misali, a cikin cobalt-catalyzed oxidation na alkylaromatics (1) ko Au-catalyzed epooxidation na cyclooctene (2), mai kara kuzari yana sauƙaƙe abstraction na hydrogen atom daga hydrocarbon don fara amsawa.A cikin amsawar sarkar radical na kyauta, mai kara kuzari yana shiga cikin rarrabuwar homolytic mai rauni na haɗin gwiwa a cikin masu farawa waɗanda ko dai an ƙara su da gangan ko kuma suna kasancewa a matsayin ƙazanta mai ban sha'awa a cikin cakudar dauki (1, 3, 4).Wasu matakai a cikin amsawar tandem na catalytic mai yiwuwa ba za su buƙaci tuntuɓar mahaɗar kai tsaye ba lokacin da aka kunna canjin daftarin ta samfurin da aka kera a matakan da suka gabata (5-8).Koyaya, waɗannan halayen suna takurawa ta hanyar alakar stoichiometric tsakanin matakan.Misali, a cikin Mukaiyama (ep) oxidation na alkene, mai kara kuzari yana jujjuya raguwar hadaya a cikin dauki A, kamar isobutyraldehyde, tare da samuwar stoichiometric concomitant na epoxide (reaction B) (9, 10).Ko da yake yana yiwuwa a ka'ida, ba mu san wani misali wanda aikin mai haɓakawa shine samar da matsakaicin S a cikin amsawa A, inda S ke aiki a matsayin tsaka-tsakin don ko dai farawa ko ƙaddamar da wani amsawar B maimakon shiga azaman reagent na stoichiometric. , yayin da mai kara kuzari ba shi da tasiri don amsawa B (Fig. 1).A cikin irin wannan makirci, tasirin mai kara kuzari ya wuce fiye da yadda za a iya haifar da amsawa A zuwa ma tasiri na B amma ba tare da hulɗar kai tsaye tare da masu amsawa ba.Muna kiran irin wannan makircin da tsarin katalitik mara lamba (NCCS).A cikin NCCS, iyakar halayen halayen A da B ba su da alaƙa da kowace alaƙar stoichiometric tsakanin su.Wannan ya bambanta da halayen tandem.A cikin masana'antu, irin wannan dangantakar stoichiometric sau da yawa yana sanya takunkumin tattalin arziki akan tsarin samar da sinadarai.Wani sanannen misali shine samar da stoichiometric na phenol da acetone ta hanyar iskar oxygenation na benzene ta hanyar matsakaicin cumene hydroperoxide a cikin tsarin cumene (11).

Mai kara kuzari (Cat) yana sarrafa amsawar A (AR ➔ S ➔AP) wanda matsakaicin S yana da tasiri a ko dai ta hanyar farawa ko kuma haifar da amsawar B (BR ➔ BP), kodayake amsawar B ba ta haifar da haɓakawa.

Mun sami irin wannan NCCS lokacin da muke binciko kaddarorin abubuwan da suka dace na gungu na Aun na solubilized (inda n ya kasance galibi shida zuwa takwas atom) don iskar oxygenation na ethylbenzene (EB).Mun nuna cewa waɗannan solubilized Aun sun haifar da ƙaddamar da zaɓin epoxidation na cyclooctene (cC8═) tare da O2 tare da ~ 80% zaɓi (2).An kafa waɗannan gungu a cikin wurin yayin Au/SiO2-catalyzed cC8═ epooxidation, kuma sun kiyaye ikonsu na haifar da radical initiator cycloocctene hydroperoxy radical (cC8═OO ·) a duk lokacin da aka yi.Za a iya tattara gungu na Aun mai narkewa a cikin cakudar amsa bayan cire Au/SiO2, kuma an ƙayyade matsakaicin girman su ta amfani da gyaggyara-gyara ƙwanƙolin lantarki da spectroscopy mai haske (2).Baya ga gungu na Aun, waɗannan gaurayawan kuma sun ƙunshi cyclooctene hydroperoxide (cC8═OOH) da samfuran oxidation cyclooctene epoxide, cyclooctenol, da cyclooctenone.cC8═OOH shine tsayayyen nau'in hydrogenated na cC8═OO· kuma yana samuwa a adadin 0.2 zuwa 0.5 M bayan 40 zuwa 100% cC8═ tuba.Ana kiran wannan cakuda da Au + cC8═OOH-x, inda x shine kashi cC8═ tuba.Ko da yake a hankali da yawa kuma tare da tsawon lokaci (> 5 hours) lokacin shigarwa, cC8═ epooxidation na iya faruwa ta atomatik-oxidation ba tare da gungu na Aun ba.Abubuwan da aka samu ta atomatik-oxidation ba tare da Au ana kiran su cC8═OOH-x.A cikin NCCS, Aun mai narkewa zai zama mai haɓakawa, haɓakar cC8═ zai zama amsawar A, kuma cC8═OO zai zama S.

A auto-oxidation na EB ba ya faruwa da sauri.A 145 ° C, 9% kawai ya faru don ingantaccen EB a ƙarƙashin 2.76 MPa O2 (12).A ƙarƙashin yanayin mu mafi sauƙi na 100 ° C da bubbling O2 a 0.1 MPa, babu wani abin da zai iya ganowa na EB mai kyau na akalla sa'o'i 20.Ana buƙatar ƙara mai ƙaddamarwa na kyauta don ci gaba da wannan amsa.Ƙaddamarwa tare da 2,2'-azobisisobutyronitrile (AIBN), mai ƙaddamar da ƙaddamarwar thermal radical, ya haifar da auto-oxidation na EB tare da matsakaicin tsayin sarkar ~ 3 (fig. S2A).An lura da guntu (~1) sarkar ta amfani da ƙarancin aiki tert-butyl hydroperoxide (fig. S2B), kuma akwai ɗan abin da ake iya ganowa ta amfani da mafi ƙarancin aiki cumene hydroperoxide.Don haka, auto-oxidation na EB yana da ɗan tasiri akan sakamakon da aka ruwaito a ƙasa.

An samu tsayayyen iskar iska mai iska na EB zuwa EB hydroperoxide, acetophenone, da phenylethanol ta ƙara Au + cC8═OOH-50 mai ɗauke da cakuɗen Aun, cC8═OOH, da cC8═ da ba a amsa ba (Fig. 2, curve 1).Kamar yadda aka nuna ta hanyar gwaje-gwaje masu zuwa, waɗannan sassa uku sun taka muhimmiyar rawa a cikin EB oxidation, kuma sun dace da mai haɓakawa, S, da AR a cikin tsarin NCCS da aka nuna a cikin siffa 1.

(i) 7 ml na EB + 3 ml na Au + cC8═OOH-50;(ii) 7 ml na EB + 3 ml na Au + cC8═OOH-50 + 1.2 mmol PPh3;(iii) 7 ml na EB + 3 ml na Au + cC8═OOH-99 + 0.6 mmol PPh3;(iv) 7 ml na EB + 3 ml na cC8═OOH-50;(v) 7 ml na EB + 3 ml na cC8═OOH-50 + 1.5 mmol PPh3.An saita adadin PPh3 da aka ƙara don daidai da adadin titrated hydroperoxide (zazzabi, 100°C).

A ƙarƙashin yanayin mu, ba a iya lura da iskar oxygen EB oxidation a cikin cakuda cC8═ da EB (watau, ba tare da Cat ko S ba).Triphenylphosphine (PPh3) yana da matukar tasiri wajen cire hydroperoxides.Maganin Au + cC8═OOH-99, wanda ya ƙare na cC8═OOH ta PPh3 ƙari, yana ɗauke da Aun da ɗan ƙaramin cC8═ da ba a yi ba, ya kasa fara amsawar EB ko da bayan sa'o'i 2 (Fig. 2, curve 3), yana nuna cewa Aun kadai ba shi da tasiri.Wannan sakamakon ya kuma nuna cewa sauran samfuran oxidation na cC8═, kamar cyclooctene epoxide, cyclooctene barasa, ko ketone, ba su sami damar fara EB oxidation ba.Ya bambanta da gwajin da ke sama, cire cC8═OOH tare da PPh3 daga Au + cC8═OOH-50, barin Aun da rashin amsa cC8═, bai hana juyawar EB ba (kwatanta masu lankwasa 1 da 2, Fig. 2).

Waɗannan rukunoni uku na bayanai sun ba da shawarar haɗin kai tsakanin Aun da cC8═ da ba a yi ba a farkon EB oxidation.Mun yi hasashen cewa Aun ya ƙaddamar da iskar oxygen ta cC8═ don samar da cC8═OOH, wanda shine mafarin EB dauki.Ana iya gwada wannan ta hanyar kwatanta ingancin farawa EB oxidation tare da cakuda cC8═OOH da cC8═ amma ba tare da Aun kafin da bayan cire cC8═OOH tare da PPh3.Don mafi kyawun kwaikwayi yanayin abubuwan gwaji na farko, mun yi amfani da maganin cC8═OOH-50 don cakuda cC8═OOH da cC8═ domin duk wani tasiri na cC8═ samfuran epoxidation za a sake haifar.Sakamakon ya nuna cewa a gaban cC8═OOH-50, EB ya amsa da kyau (Fig. 2, curve 4).Koyaya, idan an cire cC8═OOH ta hanyar PPh3, babu wani martani na awa na farko kuma an dakatar da ayyukan daga baya (madaidaicin 5).Waɗannan bayanan sun ƙara goyan bayan ƙirar cewa aikin Aun shine ci gaba da samar da cC8═OOH ta hanyar cC8═ oxidation, kuma cC8═OOH ya fara amsawar EB.An ƙara tabbatar da rawar da Aun ke takawa ta hanyar lura cewa ƙimar farko na EB oxidation in babu cC8═OOH ya karu tare da haɓaka Aun (fig. S3).

Matsayi na musamman na Aun a cikin wannan NCCS an nuna shi ta hanyar bincika Co a matsayin madadin mai haɓakawa, wanda aka zaɓa saboda cobalt acetate da cobalt cycloalkanecarboxylate (13) sune masu haɓaka masana'antu don jujjuyawar EB zuwa acetophenone tare da kwayoyin O2, suna aiki a ƙarƙashin yanayi mai wahala kuma suna buƙatar kasancewar acid da bromide ions.Hakanan ana amfani da rukunin haɗin gwiwa don zaɓin iskar oxygen EB a gaban organocatalyst N-hydroxyphthalimide (NHPI) ko mai rage hadaya (14, 15).Koyaya, a ƙarƙashin yanayin halayenmu, kasancewar Co/ZSM-5 bai haifar da kowane iskar oxygen da ake iya ganowa na EB, cC8═, ko cakuda su na aƙalla awanni 6 ba.Wato, Co shi kaɗai ba zai iya fara ko dai oxidation dauki ba.Koyaya, a gaban duka Aun da cC8═, ya sauƙaƙe halayen oxidation.Dangane da yanayin, cC8═ ko EB sun amsa sau uku zuwa biyar cikin sauri lokacin da Co/ZSM-5 ya kasance, kuma haɓakawa ya karu tare da adadin Co/ZSM-5 (tebur S2, gwaje-gwaje 6 zuwa 8).A EB hadawan abu da iskar shaka samfurin rarraba kuma canza da ɗan a gaban Co/ZSM-5.Ƙara yawan adadin Co/ZSM-5 ya ƙãra yawan amfanin acetophenone kuma, zuwa ƙarami, phenylethanol yana haifar da kuɗin EB hydroperoxide (tebur S3, gwaje-gwaje 6 zuwa 8), daidai da gaskiyar cewa Co catalyzed bazuwar EB hydroperoxide zuwa acetophenone da phenylethanol da hadawan abu da iskar shaka na karshen zuwa acetophenone.Saboda dacewa, mun haɗa da Co/ZSM-5 a cikin cakuɗen amsa don rage lokacin amsawa.

Wani abu mai ban sha'awa tsakanin NCCS da tsarin amsawar tandem shine cewa a cikin tsohon, babu wata dangantaka ta stoichiometric tsakanin halayen A da B (Fig. 1).Don tabbatar da cewa halayenmu sun faru ta hanyar NCCS, mun gwada tasirin canza rabon cC8═ zuwa EB ta hanyar saka idanu kan ƙimar halayensu.Hoto na 3 yana nuna sakamakon canza maida hankali na cC8═ na farko yayin da ake kiyaye ƙaddamarwar EB ta farko da sauran yanayin dauki akai akai.Bayanan sun nuna cewa babu ƙayyadaddun alaƙar stoichiometric tsakanin adadin masu amsawa biyu da suka amsa, yana mai tabbatar da cewa tsarin amsawa ya bambanta da tsarin amsawar tandem na gargajiya.Saitin gwaje-gwajen kwatankwacin wanda farkon adadin EB ya bambanta yayin da ake gyara sauran ƙididdiga ya kai ga ƙarshe.Daga waɗannan bayanan, an ƙididdige ƙimar amsawar farko (Table 1 da tebur S2, gwaje-gwaje 4 da 5) kuma an nuna su bambanta daban don cC8═ da EB.Babu wani ciniki tsakanin halayen halayen guda biyu kamar yadda idan ɗaya dauki ya ci gaba da sauri, ɗayan ya kasance a hankali daidai gwargwado.Dukansu ƙimar amsawar suna iya haɓaka lokaci guda, kamar yadda gwaje-gwajen 4 da 5 suka nuna a cikin tebur S2.Za a sa ran cinikin-kashe idan EB da cC8═ sun yi gasa don rukunin martani iri ɗaya ko tsaka-tsaki.Wannan ƙarshe kuma ya yi daidai da gaskiyar cewa halayen lokaci guda na EB da cC8═ ba su da ko kaɗan ko kaɗan akan rarraba samfuran su, kamar yadda aka nuna a cikin Table 1 da tebur S3.

Abubuwan farko na cC8═ sune 0.34 M (A), 1.05 M (B), da 1.75 M (C).An yi amfani da Decane don daidaita bambance-bambancen girman cC8═ da aka yi amfani da shi.Sauran yanayi: 32 MG na Co/ZSM5, 100°C.

Waɗannan bayanan sun yi daidai da tsarin injinan da aka nuna a cikin siffa 4, inda aka jaddada matakan da ke da mahimmanci ga NCCS kuma an ba da fifiko ga manyan 'yan wasa (an nuna cikakken tsari a cikin siffa S8).A cikin wannan tsarin, gungu na Aun sun fara zagayowar cC8═ epioxidation ta hanyar samar da cyclooctenyl radicals (I) da cyclooctenyl peroxy radicals (II).Waɗannan tsattsauran ra'ayi guda biyu sannan suna shiga cikin sake zagayowar epoxidation na cC8═, kamar yadda aka kafa a baya (2, 16).Lokacin da EB ke nan, II ya zama madaidaicin kwayoyin halitta da shuttles tsakanin cC8═ epooxidation sake zagayowar da EB oxidation sake zagayowar.A cikin EB sake zagayowar, II reacts tare da EB don samar da wani phenylethyl radical, wanda nan da nan ya samar da wani phenylethyl peroxy radical (III) ta dauki tare da O2, kamar yadda carbon-tsakiyar m halayen tare da O2 an san su zama musamman facile (1).Abstraction hydrogen na gaba ta III yana samar da phenylethyl hydroperoxide kuma a ƙarshe acetophenone da phenylethanol.III kuma yana iya amsawa da sauri tare da cC8═, wanda ya zama hanyar sake cika II wanda ke cinyewa ta sake zagayowar iskar oxygen ta EB.Saboda haka, EB oxidation dauki ba a tare da stoichiometric danniya na cC8═ epioxidation dauki, kuma babu "ciniki-kashe" a cikin dauki rates na EB da cC8═ kamar yadda za a sa ran idan sun yi gasa ga wannan reagent. ko kuma catalytic aiki site.Saboda II yana shiga cikin matakin farawa a cikin EB da cC8═ hawan hawan iskar shaka amma ba kai tsaye a cikin matakan samar da samfur ba, haɗakar da halayen biyun baya shafar rabon samfur.

Cyclooctene peroxy radical (II) shine babban tsaka-tsaki wanda ke fara EB oxidation.II za a iya sabuntawa ta hanyar amsawar EB peroxy radical (III) tare da cC8═.A saman hagu, gungu na Aun suna fara zagayowar epoxidation cC8═ (zagaye a hagu).A sake zagayowar a dama yana nuna matakai don EB hadawan abu da iskar shaka.Ana nuna mahimman matakai masu mahimmanci ga NCCS kawai.

Don tabbatar da samuwar tsaka-tsakin tsaka-tsaki na wucin gadi kamar yadda aka tsara a cikin siffa 4, mun kara da tarkon 5,5-dimethyl-1-pyrroline N-oxide (DMPO) zuwa gaurayar dauki don samar da nitroxide radical spin adducts tare da radicals na kyauta da ake bayarwa don ganowa tare da tasirin siginar lantarki na X-band electron paramagnetic resonance (EPR).A matsayin sarrafawa, babu wani radicals da aka kama ta hanyar DMPO a cikin maganin acetone da decane ba tare da C8═ ko EB ba (fig. S4-3).Lokacin da aka ƙara DMPO zuwa gaurayawan amsawa mai ɗauke da cC8═OOH da cC8═ (fig. S4-1), sakamakon EPR bakan an kwaikwaya da kyau azaman jimillar manyan nau'ikan paramagnetic daban-daban (A a cikin adadi, ~ 86% na duka. Girman kwaikwayo) da ƙananan nau'ikan guda biyu (B da c, ~ 5 da ~ 9% na jimlar siminti, bi da bi), samar da tabbacin kai tsaye na tsattsauran ra'ayi yayin amsawa.Dangane da kwatanta ma'auni na haɗin gwiwar hyperfine zuwa waɗanda aka sani na DMPO adducts (tebur S1), an sanya nau'in C zuwa DMPO/ROO• adduct, a fili cyclooctene 3-peroxy radical (II) wanda aka nuna a matsayin tsaka-tsakin tsakanin su biyun. halayen (Fig. 4).An sanya nau'o'in A da B zuwa wasu DMPO/RO• guda biyu daban-daban daban-daban, inda R ke nufin wani abu na hydrocarbon.Suna iya zama ɗaya daga cikin nau'in RO• da aka kwatanta a cikin siffa 4 ko alkoxy radicals da aka samar daga DMPO/ROO• adduct decay [DMPO/ROO• adducts an san su zama marasa ƙarfi kuma suna bazuwa zuwa daidaitattun alkoxy radical adduct (17, 18)] ko cakuduwar duka biyun.Lokacin da aka haɗa EB a cikin cakudawar amsawa, sakamakon EPR bakan yana da kyau a kwaikwaya tare da yawancin nau'in A′, wanda yayi kama da nau'in A (DMPO/RO•), da kuma tsirarun nau'ikan nau'ikan B da C guda biyu tare da ƙananan gudummawa iri ɗaya. (fig. S4-2 da tebur S1).Saboda hada EB ana sa ran zai fitar da samuwar phenylethyl peroxy radicals (III), nau'in A' ya kasance mai yuwuwa cakuda RO• da aka samar a cikin yanayin da kuma kowane phenylethyl peroxy adduct, wanda daga baya ya lalace zuwa phenylethyl oxy DMPO adduct.

Yin amfani da EB-d10 azaman mai amsawa da saka idanu akan alamar deuterium a cikin samfuran cC8═ na iya gano ko akwai amsawar EB tare da radicals tushen carbon cC8═.Sakamakon irin wannan gwajin ya nuna cewa babu haɗin deuterium a cikin cyclooctene epoxide (figs. S5 da S6).Phenylethanol ya riƙe duk deuterium a cikin EB reactant, kuma wasu daga cikin deuterons a cikin ƙungiyar methyl na acetophenone sun yi musayar, wanda zai iya faruwa a cikin ma'aunin spectrometer.Don haka, babu wata shaida ta amsawa tsakanin EB-d10 da cyclooctenyl radical, wanda zai gabatar da deuteron cikin samfuran cC8═.

An tsawaita amfani da dabarun NCCS don bincika Au + cC8═OOH-100-taimakawa iskar iska ta 4-methylanisole.Saboda mafi ƙarfi na farko na C─H a cikin wannan kwayar halitta, an gudanar da aikin aikin iskar oxygen a mafi girman zafin jiki.An kwatanta ƙimar farko na tuba na 4-methylanisole zuwa 4-anisaldehyde don halayen da aka fara tare da Aun kuma ko dai tare da ko ba tare da ƙarin cC8═ (an cire cC8═OOH tare da PPh3).Hakazalika da EB oxidation, lokacin da cakudawar amsa ba ta ƙunshi cC8═ ba kuma babu cC8═OOH, ƙimar iskar oxygen ta farko ta kasance a hankali (fig. S7).Lokacin da aka ƙara cC8═ zuwa gaurayawan dauki, an ƙara haɓaka ƙimar iskar oxygen ta farko.Don haka, gungu na Aun sun sami damar samar da cC8═OOH daga ƙarin cC8═ don fara oxidation na 4-methylanisole kamar yadda aka zata a NCCS.

A ƙarshe, mun nuna manufar NCCS.Yin amfani da hadawan abu da iskar shaka na lokaci guda na cyclooctene da EB da kuma cyclooctene da 4-methylanisole, an nuna NCCS don ba da damar haɗakar iskar oxygen ta hydrocarbons ba tare da ƙayyadaddun alaƙar stoichiometric na hanyoyin haɗin gwiwar al'ada ba.Wannan yana ba da wani digiri na 'yanci a baya a cikin aikin masana'antu kamar yadda tsarin tattalin arziki ya daina ɗaure da buƙatar kasuwanni masu dacewa don samfuran samfuran da aka samar a cikin adadin stoichiometric.

Tushen da tsarkakewar sinadarai da aka yi amfani da su sune kamar haka: HAuCl4 • 3H2O (≥99.9% tushen tushen ƙarfe, Sigma-Aldrich), silica fumed (CAB-O-SIL90, Kamfanin Cabot), ethylenediamine (≥99% ReagentPlus, Sigma-Aldrich) , ethanol (200 grade, Decon Labs), cobalt (II) nitrate hexahydrate (≥98%, Sigma-Aldrich), Nano H-ZSM-5 (P-26, ACS Material), decane (≥99% ReagentPlus, Sigma- Aldrich), dodecane (≥99% ReagentPlus, Sigma-Aldrich), cis-cyclooctene (95%, Alfa Aesar), EB (99.8% anhydrous, Sigma-Aldrich), EB-d10 (99 atomic% D, Sigma-Aldrich) . (reagent grade, 90%, Sigma-Aldrich), sodium sulfate (Food Chemicals Codex / United States Pharmacopeia-grade, Fisher Chemical), tetrahydrofuran (> 99%, Sigma-Aldrich), tert-butyl hydroperoxide (~ 5.5 M a decane). , Sigma-Aldrich), PPh3 (> 98.5%, Sigma-Aldrich), d-chloroform (99.8 atomic% D, Sigma-Aldrich), HCl (38% w / w, Fisher Chemical), HNO3 (68 zuwa 70% w) / w, Fisher Chemical), EM Quant peroxide tube gwajin, da sirinji tace (polyvinylidene difluoride membrane, 0.25 mm/0.2 μm, Acrodisc).

Au/SiO2.An shirya silica mai goyan bayan nanoparticle catalyst tare da Au(en) 2Cl3 precursor bisa ga hanyar da Zhu et al ya haɓaka.(19) kuma Qian et al.(2).Don ƙarin ƙayyadaddun ƙayyadaddun ƙayyadaddun, an shirya maganin chloride trihydrate na Au (III) ta hanyar narkar da 0.5 g na HAuCl4 • 3H2O a cikin cakuda mai dauke da 10 ml na ethanol da 2 ml na ruwa.Bayan samar da wani bayani mai kama da juna, an ƙara 0.23 ml na ethylenediamine (en = ethylenediamine) zuwa maganin dropwise don samar da Au (III) ethylenediamine chloride [Au (en) 2Cl3] ta hanyar musayar ligand.Au(en)2Cl3 da aka yi kamar yadda aka tattara an tattara su ta hanyar tacewa kuma an wanke shi da 300 ml na ethanol.Don saka Au kan tallafin silica, an shirya maganin ruwa mai nauyin 4.2mM Au(en)2Cl3 ta hanyar narkar da 46.3 MG na Au(en)2Cl3 cikin 26 ml na ruwa mai distilled (DDI).An kiyaye maganin da aka tsara a 40 ° C a cikin wanka mai mai.Sa'an nan, 1 g na fumed silica an kara da shi zuwa ga preheated bayani yayin motsawa.Da zarar an nutsar da duk tallafin silica a cikin maganin, an cire cakuda daga wanka mai mai kuma an sanyaya zuwa zafin jiki.Ta hanyar daidaita pH na cakuda zuwa 9 tare da juzu'in juzu'i na 0.75 M en maganin ruwa, an sami ingantacciyar tallan kayan gwal na cationic zuwa saman da aka caje mara kyau.Bayan yin motsawa na tsawon sa'o'i 2 a dakin da zafin jiki, an tace cakuda kuma an wanke shi da 500 ml na ruwan DDI.Don cire abubuwan da ba a so (Cl, en, sauran ƙazanta), an sake tarwatsa kek ɗin tace a cikin 200 ml na ruwan DDI a 40 ° C.A ƙarshe, an tattara Au/SiO2 da aka kafa ta hanyar tacewa kuma an wanke shi da wani 500 ml na ruwan DDI kuma a bushe a cikin iska a cikin dare.Calcination na silica-tallafin gwal nanoparticles kara kuzari an gudanar da shi a cikin U-tube karkashin O2/O3 kwarara (~ 300 ml/min) tare da ramping kudi na 0.12°C/min har zuwa 150°C.An adana mai kara kuzari a cikin duhu a 5 ° C.Load ɗin zinari, kamar yadda aka ƙididdige su ta hanyar haɗaɗɗiyar siginar gani na gani na gani na gani, ya kasance nauyin 1.2% (wt %), kuma matsakaicin girman gwal ɗin da aka auna ta hanyar sikanin watsawa na lantarki (STEM) yana kusa da 2 nm.

Co/ZSM-5.Nano H-ZSM-5 da aka calcined a cikin wani U-tube karkashin O2/O3 kwarara (~ 300 ml/min) tare da ramping kudi na 2°C/min har zuwa 200°C da kuma rike a 200°C na 1 hour don cire. saura samfuri.Co/ZSM-5 an shirya shi ta hanyar rigar haɓakawa.Misali, an shirya 5 wt % Loading Co/ZSM-5 ta ƙara 0.72M cobalt (II) nitrate bayani [250 MG na cobalt (II) nitrate hexahydrate a cikin 1.2 ml na ruwan DDI] zuwa 1 g na nano H- ZSM-5 yayin da ake juyawa a hankali.An bushe slurry a ƙarƙashin fitila, kuma an samar da foda mai ruwan hoda.An ɗora foda da aka yi kamar yadda aka ɗora a cikin bututun ƙididdiga kai tsaye kuma an share shi ƙarƙashin kwararar argon (100 ml/min) na awa 1 don rage zafi.An ƙididdige mai kara kuzari kamar yadda aka shirya a ƙarƙashin kwararar iskar oxygen (60 ml/min) tare da ƙimar ramping na 10°C/min zuwa 450° (wanda aka gudanar a 250°C, 350°C, da 450°C na awa 1 kowanne) .Co/ZSM-5 da aka samu yana da nauyin cobalt na 5 wt %.Wasu lodi biyu, 3 da 7 wt %, an kuma shirya su.Duk abubuwan da ke haifar da ƙararrawa guda uku an nuna su ta hanyar rage shirye-shiryen zafin jiki na H2, ɓarnawar x-ray, hoton hoton hoto na x-ray, da ultraviolet-bayanin spectroscopy.

Au mai ɗauke da tacewa.Filtrate mai ƙunshe da Au (Au + cC8═OOH-x) yana cikin wurin da aka samar daga Au/SiO2-catalyzed cC8═ epoxidation dauki bisa ga tsarin da Qian et al.(2) Kafin amsawa, an tsarkake cC8═ don cire abin da aka ƙara ma'auni.Gabaɗaya, an ƙara 50 ml na 3M potassium hydroxide (KOH) maganin zuwa 50 ml na cC8═ a cikin flask.Bayan isassun haɗuwa da motsawa mai ƙarfi, an tattara Layer Layer ta hanyar rabuwa.An sake maimaita wannan hanya tare da wani 50 ml na 3 M KOH da wasu 50 ml na ruwan DDI guda biyu.An bushe cC8═ da sodium sulfate a cikin dare.Don cire stabilizer gaba ɗaya, busasshen cC8═ an distilled a cikin wanka mai a kusa da 180 ° C, kuma an tattara juzu'in da ya fito a 145 ° C.An haxa cC8═ (10 ml) da decane (1 ml) da aka tsarkake a cikin wani reactor mai ɗauke da 80 MG na abin ƙarfafa Au/SiO2 da aka ambata.An gudanar da aikin cC8═ epoxidation a ƙarƙashin iskar oxygen (30 ml/min) a 100 ° C, kuma GC ya sa ido akan juyawa.Da zarar an kai ga jujjuyawar da ake so, an tattara cakudawar dauki kuma an cire ingantaccen mai kara kuzari ta hanyar tacewa mai zafi ta amfani da tace sirinji.Matsakaicin matsakaicin maida hankali na Au wanda aka ƙaddara ta hanyar haɗe-haɗe tare da haɗe-haɗe-haɗe-haɗe-haɗe-haɗe-haɗe-haɗe-haɗe-haɗe-haɗe-haɗe-haɗe-haɗe ya kai 80 ng/ml, kuma girman gunguwar Au an ƙaddara ta hanyar kyamarori masu ƙyalƙyali da gyare-gyare-gyare-gyaren microscopy na lantarki daga Autu zuwa ~0.7 nm.An shirya cC8═OOH-x haka nan ba tare da amfani da mai kara kuzari na Au/SiO2 ba.Dukansu Au + cC8═OOH-x da cC8═OOH-x mafita sun ƙunshi samfuran cC8═ oxidation, waɗanda suka haɗa da cyclooctene oxide, cycloocten 3-hydroperoxide, 2-cycloocten-1-ol, 2-cycloocten-1-daya, da adadin ganowa. 1,2-cyclooctanediol.

Gabaɗaya hanya.An gudanar da halayen oxidation na EB a cikin duhu a cikin injin silindi mai wuyan hannu uku sanye da bututu mai tarwatsa gilashin frit (Chemglass Life Sciences) da na'urar da ke kiyayewa a -10 ° C.A cikin wani yanayi na yau da kullun, 7 ml na EB, 1 ml na decane, da 3 ml na tacewa (Au + cC8═OOH-x ko cC8═OOH-x) an ɗora su a cikin reactor tare da magnetic stirrer mai rufi Teflon.Idan an yi amfani da shi, an ƙara 32 MG na 5% Co/ZSM-5, sai dai in an ƙayyade in ba haka ba.Bayan an haɗa saitin amsawa, an daidaita cakudar da aka yi a ƙarƙashin kwararar N2 na mintuna 20 a cikin wankan mai da aka rigaya.Da zarar an daidaita yawan zafin jiki na na'urar bushewa da wanka mai mai, ana ba da kwararar O2 akai-akai a 30 ml/min.An dauki cakuda dauki (0.1 ml) a cikin tazara daban-daban na lokaci don bincike (an yi amfani da tace sirinji lokacin da ƙwararrun masu haɓakawa suka shiga), narkar da su a cikin 0.7 ml na d-chloroform, kuma an bincika ta hanyar 1H makamanciyar maganadisu ta nukiliya (NMR).

Ƙididdigar samfur da ƙididdigewa.An diluted Aliquots na cakuda dauki tare da tetrahydrofuran kuma an bincika ta hanyar iskar gas chromatography-mass spectrometry (GC-MS; Agilent GC-7890A, MS-5975).Don amsawar EB, an gano acetophenone da 1-phenylethanol don zama samfuran da suka mamaye.An yi amfani da 1H-NMR da 13C-NMR (tsarin 400 MHz Agilent DD2-MR400) don ƙara tabbatar da samfuran samfuran.1-Phenylethyl hydroperoxide, wanda GC-MS bai gano shi ba saboda rashin kwanciyar hankali na thermal, NMR ya gano ya zama wani babban samfuri.Dukkan samfuran guda uku an ƙididdige su ta 1H-NMR ta amfani da decane azaman ma'auni na ciki (fig. S1).An ƙididdige asarar mai fitar da ruwa daban kuma an yi amfani da shi don gyara yawan adadin samfurin.Bayan gyare-gyaren asarar da aka yi, ba a lura da rashin daidaituwar carbon don amsawar EB ba.Don amsawar cycloocten, cyclooctane oxide, cyclooctane-1,2-diol, 2-cycloocten-1-ol, da 2-cycloocten-1-one an ƙididdige su ta GC.Cyclooctene 3-hydroperoxide bai tsaya ba kuma ya lalace a cikin ginshiƙi na GC don haka ba a gano shi ba.An sami asarar kusan kashi 10% na iskar carbon a cikakkiyar juzu'i ko da bayan ramawa ga asarar da aka yi, wanda za'a iya bayyana shi ta hanyar samar da ƙananan adadin samfuran da ba a tantance su ba.

Juyawa da lissafin zaɓe.An yi amfani da rabon yanki na GC ko NMR na kwayoyin sha'awa zuwa madaidaicin decane na ciki don ƙididdige juzu'i da zaɓi.Ko da yake an yi amfani da na'ura mai sanyaya, har yanzu ya zama dole don ramawa ga asarar da aka kwashe saboda yawan zafin jiki da kuma dogon lokacin amsawa.An sami madaidaicin gyaran gyare-gyare don duka EB da cC8═ ƙarƙashin nitrogen mai gudana kuma an daidaita su zuwa ƙimar EB/decane ko cC8═/decane.Saboda EB da cC8═ suna da maki masu tafasa iri ɗaya, daidaitattun abubuwan gyare-gyaren da aka samu duka 0.0044 ne (daidaitaccen rabo ya ragu a kowace awa).

Ƙididdigar hydroperoxide.An ƙididdige yawan taro na hydroperoxide ta hanyoyin titration guda biyu:

1) Triphenylphosphine (PPh3) titration.An yi amfani da PPh3 (0.1 M a cikin EB) don titrate samfuran hydroperoxide da ba a san su ba, kuma an gano ƙarshen ƙarshen tare da tsiri na gwajin EM Quant peroxide.An yi amfani da 31P-NMR don tabbatar da cikakken kawar da nau'in hydroperoxide.

2) Iodometric titration.An haɗu da samfurin (0.2 ml) tare da 1 ml na CHCl3 / acetic acid (v / v = 1: 2) da 6 ml na 1 M KI bayani.An zuga ruwan cakuda a cikin duhu na tsawon awanni 2 sannan a sanya shi tare da 0.005 M Na2S2O3 a gaban 'yan digo na sitaci.An kai ƙarshen ƙarshen lokacin da cakuda ya zama mara launi.

Dukansu hanyoyin sun kasance daidai da ciki;duk da haka, sakamakon su ya bambanta da 5 zuwa 10%.Saboda Au + cC8═OOH-x da cC8═OOH-x da aka yi amfani da su a cikin wannan aikin an samar da su ta hanyar iskar oxygen da aka ƙaddamar da cC8═OOH, ƙwayar hydroperoxide ya bambanta daga tsari zuwa tsari amma koyaushe yana cikin kewayon 0.2 zuwa 0.5 M don sabon shiri. cC8═OOH-40 zuwa cC8═OOH-100 samfurori.Matsalolin hydroperoxide a hankali ya ragu tare da lokacin ajiya.

Gwajin tarko na EPR.DMPO (23 μl) an ƙara shi zuwa 1 ml na samfurin don isa ga ƙaddamarwar DMPO na 0.2 M, kuma 20 MG na Co / ZSM-5 an ƙara shi zuwa samfurin samfurin a cikin gwajin gwaji.An soka cakuda don minti 1 don dakatar da mai kara kuzari, kuma ana biye da wannan ta dumama a 60 ° C na ~ 10 min.An canza wani aliquot daga cikin cakuda a cikin wani zagaye borosilicate tubing capillary tube (1.50 cikin diamita × 1.80 waje diamita, Wale Apparatus), wanda aka rufe a daya karshen-wannan bututu an sanya shi a cikin Wilmad quartz X-band EPR tube ( Sigma-Aldrich).An daskare samfurin ta hanyar nutsar da bututun EPR a cikin ruwa N2.Nan da nan kafin auna sikirin EPR, samfurin ya narke.Ci gaba da-wave (CW) X-band EPR ma'auni an yi a dakin zafin jiki a kan gyare-gyaren Varian E-4 spectrometer ta amfani da Dewar yatsa.

Gwajin alamar isotopic.An yi amfani da Deuterated EB (d10-EB) a cikin gwaji na cakuda 6 ml na cC8═OOH-45, 5 ml na d10-EB, 1 ml na decane, da 60 MG na Co-ZSM-5 (7%) , a 120 ° C, tare da 6 ml na cC8═OOH-45, 5 ml na EB-d10, da 1 ml na dodecane.Don ramawa ga raguwar yawan amsawa saboda tasirin isotope na motsa jiki, an gudanar da hadakar iskar oxygen a cikin mafi girman zafin jiki na 120 ° C.An ɗauki Aliquots na samfurin kafin da bayan sa'o'i 24 na amsawa kuma 2H-NMR da GC-MS sun bincikar su.

Halin 2H-NMR (fig. S5, spectrum 2) ya nuna sababbin kololuwa da yawa bayan amsawa, ba a gaban su ba, a δ1.50, δ1.58, δ4.94, δ7.42 zuwa δ7.72, da δ8.04 .Saboda raguwar J-haɗin kai akai-akai da azanci na 2H-NMR, ba a warware tsarin rarrabuwa ba.Kololuwa a δ8.04 da δ7.42 zuwa δ7.72 an sanya su zuwa deuterons na zoben aromatic na acetophenone;kololuwa a δ1.50 da δ4.94 an sanya su zuwa methyl da benzylic deuteron na 1-phenylethanol, bi da bi;kuma mafi girma a δ1.58 an sanya shi zuwa deuteron a cikin D2O da aka kafa daga rushewar hydroperoxide.Ba a sami deuteron da ke da alaƙa da samfuran cyclooctene epoxidation ba, kuma samuwar ruwa mai tsattsauran ra'ayi ya nuna cewa manyan masu ɗaukar sarƙoƙi masu tsattsauran ra'ayi a cikin halayen co-oxidation sun kasance tushen peroxy da alkoxy.

GC-MS bakan samfuran ana nuna su a cikin fig.S6.Acetophenone-d8 (m / e 128, cikakken deuterated, fig. S6A, m / e 127 da 126).Daga tsarin fashewa, duk musayar HD ya faru a matsayi na methyl.Bugu da ƙari, 1-phenylethanol-d9 (m / e 131) (fig. S6B) shine kawai samfurin da aka gano.Ba a sami deuterium a cikin cyclooctene oxide (fig. S6C), samfurin da ya fi girma daga cyclooctene epioxidation.1-Phenylethanol-d9 na iya samuwa daga amsawar phenylethoxy radical tare da cyclooctene.

Ana samun ƙarin kayan wannan labarin a http://advances.sciencemag.org/cgi/content/full/6/5/eaax6637/DC1

Hoto S5.2H-NMR kafin (bakan 1, ja) da kuma bayan (bakan 2, kore) 24-hour co-oxidation reaction.

Hoto S7.Kwatanta canjin farko na 4-methyl anisole wanda aka fara ta amfani da Au + cC8═OOH-100, tare da cire cC8═OOH.

Wannan labarin buɗaɗɗen shiga ne wanda aka rarraba ƙarƙashin sharuɗɗan lasisin Haɗaɗɗen Haɗin Kai-NonCommercial, wanda ke ba da izinin amfani, rarrabawa, da haifuwa a kowane matsakaici, muddin sakamakon amfani da shi ba don fa'idar kasuwanci ba ne kuma idan aikin na asali ya kasance daidai. ambato.

NOTE: Muna buƙatar adireshin imel ɗin ku kawai don mutumin da kuke ba da shawarar shafin ya san cewa kuna son su gani, kuma ba saƙon takarce ba ne.Ba mu kama kowane adireshin imel ba.

Daga Anyang Peng, Mayfair C. Kung, Robert RO Brydon, Matthew O. Ross, Linping Qian, Linda J. Broadbelt, Harold H. Kung

A cikin tsarin katalytic mara lamba, masu tsaka-tsaki da aka samo daga Au-catalyzed cyclooctene epooxidation effects ethylbenzene oxidation.

Daga Anyang Peng, Mayfair C. Kung, Robert RO Brydon, Matthew O. Ross, Linping Qian, Linda J. Broadbelt, Harold H. Kung

A cikin tsarin katalytic mara lamba, masu tsaka-tsaki da aka samo daga Au-catalyzed cyclooctene epooxidation effects ethylbenzene oxidation.

© 2020 Ƙungiyar Amirka don Ci gaban Kimiyya.An kiyaye duk haƙƙoƙi.AAAS abokin tarayya ne na HINARI, AGORA, OARE, CHORUS, CLOCKSS, CrossRef da COUNTER. Ci gaban Kimiyya ISSN 2375-2548.