Souhrn
Oxid dusny (N2O) pat.i mezi vyznamne sklenikove plyny, ktere p.ispivaji k ubytku
ozonove vrstvy. Jednim z nejv.t.ich zdroj. N2O z chemickeho pr.myslu je vyroba kyseliny
dusi.ne. B.hem poslednich desetileti se zvy.ila pot.eba sni.it emise N2O take z d.vod. jeho
o.ekavanych regulaci. V sou.asne dob. je snaha nalezt a vyvinout u.inny a cenov. dostupny
system pro sni.eni emisi N2O. Jednim z mo.nych zp.sob. je p.imy katalyticky rozklad N2O
na zeolitech obsahujicich ionty kov. za vzniku dusiku a kysliku.
Tato studie p.ispiva k posouzeni potencialu r.znych Fe-zeolit. v rozkladu N2O a
ke vztahu mezi jejich katalytickymi vlastnostmi a specifickymi strukturami. Pozornost byla
rovn.. v.novana vlivu NO, O2 a H2O na rozklad N2O na Fe-zeolitech. Byl podrobn.
analyzovan vliv dopovani Fe-zeolit. vzacnymi kovy (Pt, Rh, Ru) v.etn. vlivu
vysokoteplotniho opracovani zeolitu (HTP). R.zne experimentalni metody byly pou.ity
k ur.eni jednotlivych forem .eleza v Fe-zeolitech a jejich strukturnich zm.n v d.sledku
opracovani za odli.nych podminek. Zejmena byla k t.mto u.el.m pou.ita infra.ervena
spektroskopie s Fourierovou transformaci (FTIR), difuzn. reflexni UV-Vis-NIR
spektroskopie a teplotn. programovana redukce vodikem (H2-TPR). Rovn.. byla take pou.ita
vysokorozli.ovaci transmisni elektronova mikroskopie (HRTEM).
Rozklad N2O byl porovnavan na Fe-FER, Fe-MFI a Fe-BEA zeolitech, ktere
obsahovaly .elezo v dob.e uspo.adanych kationtovych pozicich a nizky obsah oxidickych
.astic. Bylo dokazano, .e i p.es srovnatelny obsah Fe(II) v kationtovych polohach, katalyticka
aktivita Fe-FER zna.n. p.evy.ovala aktivitu Fe-MFI a Fe-BEA. Toto zji.t.ni souvisi
s koncentraci Fe(II) iont., ktere se nachazely v pozicich se specifickym prostorovym
uspo.adanim a optimalni vzdalenosti Fe?cFe, co. poskytovalo vhodne podminky pro
vzajemnou spolupraci dvou kationt. .eleza ke .t.peni N2O molekuly. Takoveto uspo.adani
nebylo zji.t.no jak u struktury Fe-BEA, tak i Fe-MFI.
Dopovani Fe-FER vzacnymi kovy (Pt, Rh, Ru) zvy.ilo katalytickou aktivitu rozkladu
N2O v tomto po.adi: Pt < Rh . Ru. Zvy.ena aktivita byla zp.sobena diky synergickemu
efektu mezi .elezem a vzacnym kovem. P.idavek NO vyrazn. sni.il rozklad N2O na
monometalickych vzorcich (Rh- a Ru-FER), ale nikoliv na vzorku Fe-FER a na bimetalickych
Me/Fe-FER vzorcich.
Opracovani katalyzatoru p.i teplot. 700 ??C (HTP) m.lo vyrazny vliv na zvy.eni
konverze N2O pro Fe-zeolity, a zejmena pro Fe-FER, kde vliv byl tem.. srovnatelny s vlivem
p.idavku NO. Na rozdil od monometalickych Me-FER vzork., u bimetalickych Me/Fe-FER
vzork. do.lo k nar.stu aktivity po vysokoteplotnim opracovani. Synergicky efekt v rozkladu
N2O nalezeny d.ive pro Rh/Fe-FER, ktery byl opracovan za nizke teploty byl take sledovan u
vysokoteplotn. opracovaneho vzorku. Toto v.ak neplati pro Pt/Fe-FER a Ru/Fe-FER
katalyzatory, u kterych zvy.eni aktivity po vysokoteplotnim opracovani bylo patrn.
zp.sobeno pouze diky pozitivnimu vlivu na Fe slo.ku.
Kombinaci t.chto dvou hlavnich p.istup. vedouci ke zvy.eni katalyticke aktivity
Fe-zeolit. v rozkladu N2O, tj. dopovanim Fe-katalyzator. vzacnymi kovy a vysokoteplotnim
opracovanim, byl p.ipraven HTP Rh/Fe-FER vykazujici ze studovane serie mono- a
bimetalickych katalyzator. nejvy..i u.innost pro rozklad N2O.
Anotace v angličtině
Summary
Nitrous oxide (N2O) is a potent greenhouse gas contributing to ozone layer depletion.
Nitric acid production is one of the largest sources of N2O in chemical industry, and thus
during the last decade, the urgency of N2O abatement further increased because of the
anticipated regulations for its emission. Nowadays there is a quest to find and develop
efficient and cost-effective system for N2O abatement. One way that could be feasible is
direct catalytic decomposition of N2O to N2 and O2 over metal-exchanged zeolites.
The study contributes to assessment of the potential of various iron-containing zeolites
for N2O decomposition and of the relationship between their catalytic performance and their
specific structures. Attention has also been paid to the influence of NO, O2 and H2O on the
decomposition of nitrous oxide over Fe-zeolites. The effect of doping of Fe-zeolites by noble
metals (Pt, Rh, Ru) and the effect of zeolite pretreatment at high temperatures (HTP) has been
analyzed in detail. Several experimental methods were used to identify the individual iron
forms in Fe-zeolites, and their changes due to treatment under various conditions; mainly
Fourier transformed infrared spectroscopy (FTIR), UV-Vis-NIR diffuse reflectance
spectroscopy and temperature-programmed reduction by hydrogen (H2-TPR) were used for
this purpose. High-resolution transmission electron microscopy (HRTEM) is also employed.
The decomposition of nitrous oxide was compared over Fe-FER, Fe-MFI and Fe-BEA
containing iron in well-established cationic positions and low amounts of oxide species. It
was evidenced that, despite a comparable content of Fe(II) in the cationic positions, the
catalytic activity of Fe-FER greatly exceeds that of Fe-BEA and Fe-MFI. This was correlated
with the concentration of Fe(II) in positions with a specific spatial iron arrangement and
optimal Fe?cFe distances, providing suitable conditions for cooperation of the two iron
cations on the N2O molecule splitting. Such arrangement is absent in both the Fe-BEA and
Fe-MFI structures.
Doping of Fe-FER by noble metals (Pt, Rh, Ru) increased catalytic activity in the N2O
decomposition in the sequence: Pt < Rh . Ru. The enhancement of the activity has been
attributed to a synergic effect between the iron and the noble metal. Addition of NO
substantially decreased the decomposition of N2O over monometallic Rh- and Ru-FER
samples, but not over Fe-FER and all bimetallic Me/Fe-FER samples.
The pretreatment of the catalyst at 700 ??C (HTP) has a strong enhancing effect on the
N2O conversion over iron zeolites and particularly over Fe-FER, nearly comparable to the
effect of NO addition. Contrary to monometallic Me-FER samples, the bimetallic HTP
Me/Fe-FER exhibited increase in the activity. Synergic effect in the decomposition of nitrous
oxide, previously identified for Rh/Fe-FER pretreated at low temperature, was observed also
after pretreatment at high temperature. This does not hold for Pt/Fe-FER and Ru/Fe-FER,
where increase of the activity due to HTP was apparently only due to the positive effect on
the Fe component.
Combination of the two main approaches for enhancing the catalytic activity of
Fe-zeolites in N2O, i.e. doping of iron catalysts by noble metal and high-temperature
pretreatment, have been shown to produce the HTP Rh/Fe-FER, the most efficient catalyst for
decomposition of nitrous oxide in the series of mono- and bimetallic zeolitic catalysts studied.
Souhrn
Oxid dusny (N2O) pat.i mezi vyznamne sklenikove plyny, ktere p.ispivaji k ubytku
ozonove vrstvy. Jednim z nejv.t.ich zdroj. N2O z chemickeho pr.myslu je vyroba kyseliny
dusi.ne. B.hem poslednich desetileti se zvy.ila pot.eba sni.it emise N2O take z d.vod. jeho
o.ekavanych regulaci. V sou.asne dob. je snaha nalezt a vyvinout u.inny a cenov. dostupny
system pro sni.eni emisi N2O. Jednim z mo.nych zp.sob. je p.imy katalyticky rozklad N2O
na zeolitech obsahujicich ionty kov. za vzniku dusiku a kysliku.
Tato studie p.ispiva k posouzeni potencialu r.znych Fe-zeolit. v rozkladu N2O a
ke vztahu mezi jejich katalytickymi vlastnostmi a specifickymi strukturami. Pozornost byla
rovn.. v.novana vlivu NO, O2 a H2O na rozklad N2O na Fe-zeolitech. Byl podrobn.
analyzovan vliv dopovani Fe-zeolit. vzacnymi kovy (Pt, Rh, Ru) v.etn. vlivu
vysokoteplotniho opracovani zeolitu (HTP). R.zne experimentalni metody byly pou.ity
k ur.eni jednotlivych forem .eleza v Fe-zeolitech a jejich strukturnich zm.n v d.sledku
opracovani za odli.nych podminek. Zejmena byla k t.mto u.el.m pou.ita infra.ervena
spektroskopie s Fourierovou transformaci (FTIR), difuzn. reflexni UV-Vis-NIR
spektroskopie a teplotn. programovana redukce vodikem (H2-TPR). Rovn.. byla take pou.ita
vysokorozli.ovaci transmisni elektronova mikroskopie (HRTEM).
Rozklad N2O byl porovnavan na Fe-FER, Fe-MFI a Fe-BEA zeolitech, ktere
obsahovaly .elezo v dob.e uspo.adanych kationtovych pozicich a nizky obsah oxidickych
.astic. Bylo dokazano, .e i p.es srovnatelny obsah Fe(II) v kationtovych polohach, katalyticka
aktivita Fe-FER zna.n. p.evy.ovala aktivitu Fe-MFI a Fe-BEA. Toto zji.t.ni souvisi
s koncentraci Fe(II) iont., ktere se nachazely v pozicich se specifickym prostorovym
uspo.adanim a optimalni vzdalenosti Fe?cFe, co. poskytovalo vhodne podminky pro
vzajemnou spolupraci dvou kationt. .eleza ke .t.peni N2O molekuly. Takoveto uspo.adani
nebylo zji.t.no jak u struktury Fe-BEA, tak i Fe-MFI.
Dopovani Fe-FER vzacnymi kovy (Pt, Rh, Ru) zvy.ilo katalytickou aktivitu rozkladu
N2O v tomto po.adi: Pt < Rh . Ru. Zvy.ena aktivita byla zp.sobena diky synergickemu
efektu mezi .elezem a vzacnym kovem. P.idavek NO vyrazn. sni.il rozklad N2O na
monometalickych vzorcich (Rh- a Ru-FER), ale nikoliv na vzorku Fe-FER a na bimetalickych
Me/Fe-FER vzorcich.
Opracovani katalyzatoru p.i teplot. 700 ??C (HTP) m.lo vyrazny vliv na zvy.eni
konverze N2O pro Fe-zeolity, a zejmena pro Fe-FER, kde vliv byl tem.. srovnatelny s vlivem
p.idavku NO. Na rozdil od monometalickych Me-FER vzork., u bimetalickych Me/Fe-FER
vzork. do.lo k nar.stu aktivity po vysokoteplotnim opracovani. Synergicky efekt v rozkladu
N2O nalezeny d.ive pro Rh/Fe-FER, ktery byl opracovan za nizke teploty byl take sledovan u
vysokoteplotn. opracovaneho vzorku. Toto v.ak neplati pro Pt/Fe-FER a Ru/Fe-FER
katalyzatory, u kterych zvy.eni aktivity po vysokoteplotnim opracovani bylo patrn.
zp.sobeno pouze diky pozitivnimu vlivu na Fe slo.ku.
Kombinaci t.chto dvou hlavnich p.istup. vedouci ke zvy.eni katalyticke aktivity
Fe-zeolit. v rozkladu N2O, tj. dopovanim Fe-katalyzator. vzacnymi kovy a vysokoteplotnim
opracovanim, byl p.ipraven HTP Rh/Fe-FER vykazujici ze studovane serie mono- a
bimetalickych katalyzator. nejvy..i u.innost pro rozklad N2O.
Anotace v angličtině
Summary
Nitrous oxide (N2O) is a potent greenhouse gas contributing to ozone layer depletion.
Nitric acid production is one of the largest sources of N2O in chemical industry, and thus
during the last decade, the urgency of N2O abatement further increased because of the
anticipated regulations for its emission. Nowadays there is a quest to find and develop
efficient and cost-effective system for N2O abatement. One way that could be feasible is
direct catalytic decomposition of N2O to N2 and O2 over metal-exchanged zeolites.
The study contributes to assessment of the potential of various iron-containing zeolites
for N2O decomposition and of the relationship between their catalytic performance and their
specific structures. Attention has also been paid to the influence of NO, O2 and H2O on the
decomposition of nitrous oxide over Fe-zeolites. The effect of doping of Fe-zeolites by noble
metals (Pt, Rh, Ru) and the effect of zeolite pretreatment at high temperatures (HTP) has been
analyzed in detail. Several experimental methods were used to identify the individual iron
forms in Fe-zeolites, and their changes due to treatment under various conditions; mainly
Fourier transformed infrared spectroscopy (FTIR), UV-Vis-NIR diffuse reflectance
spectroscopy and temperature-programmed reduction by hydrogen (H2-TPR) were used for
this purpose. High-resolution transmission electron microscopy (HRTEM) is also employed.
The decomposition of nitrous oxide was compared over Fe-FER, Fe-MFI and Fe-BEA
containing iron in well-established cationic positions and low amounts of oxide species. It
was evidenced that, despite a comparable content of Fe(II) in the cationic positions, the
catalytic activity of Fe-FER greatly exceeds that of Fe-BEA and Fe-MFI. This was correlated
with the concentration of Fe(II) in positions with a specific spatial iron arrangement and
optimal Fe?cFe distances, providing suitable conditions for cooperation of the two iron
cations on the N2O molecule splitting. Such arrangement is absent in both the Fe-BEA and
Fe-MFI structures.
Doping of Fe-FER by noble metals (Pt, Rh, Ru) increased catalytic activity in the N2O
decomposition in the sequence: Pt < Rh . Ru. The enhancement of the activity has been
attributed to a synergic effect between the iron and the noble metal. Addition of NO
substantially decreased the decomposition of N2O over monometallic Rh- and Ru-FER
samples, but not over Fe-FER and all bimetallic Me/Fe-FER samples.
The pretreatment of the catalyst at 700 ??C (HTP) has a strong enhancing effect on the
N2O conversion over iron zeolites and particularly over Fe-FER, nearly comparable to the
effect of NO addition. Contrary to monometallic Me-FER samples, the bimetallic HTP
Me/Fe-FER exhibited increase in the activity. Synergic effect in the decomposition of nitrous
oxide, previously identified for Rh/Fe-FER pretreated at low temperature, was observed also
after pretreatment at high temperature. This does not hold for Pt/Fe-FER and Ru/Fe-FER,
where increase of the activity due to HTP was apparently only due to the positive effect on
the Fe component.
Combination of the two main approaches for enhancing the catalytic activity of
Fe-zeolites in N2O, i.e. doping of iron catalysts by noble metal and high-temperature
pretreatment, have been shown to produce the HTP Rh/Fe-FER, the most efficient catalyst for
decomposition of nitrous oxide in the series of mono- and bimetallic zeolitic catalysts studied.
Předseda komise přivítal všechny členy komise a disertanta. Komise povolila pokračování v obhajobě, i když nebyl přítomen jeden z členů komise a zároveň oponent doc. Čapek. Po představení studenta a seznámení komise s vyjádřením školitele byl Ing. Jíša požádán, aby komisi seznámil s obsahem své disertační práce a výsledky, ke kterým dospěl. Poté byla komise seznámena s oponentními posudky a student odpověděl na dotazy oponentů. Za nepřítomného doc, Čapka posudek přečetl předseda komise. Po zodpovězení dotazů oponentů byla otevřena volná diskuse, ve které byly zodpovězeny veškeré otázky.