A series of TiO
2-, Al
2O
3-,
and SiO
2-supported m
ang
anese oxide c
at
alysts were prep
ared, ch
ar
acterized,
andc
at
alytic
ally tested for selective c
at
alytic reduction (SCR) of NO with NH
3 in the presence of excess oxygen
at low tem
per
atures (373-523 K). V
arious commerci
al supports were used in this study to find out the influenceof surf
ace
are
a, support n
ature (
acidic, b
asic),
and cryst
alline ph
ase on SCR
activity. XRD studies reve
al thepresence of
an
at
ase
and rutile ph
ases for tit
ani
a supports
and the existence of
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alumin
a in the c
ase of
alumin
asupport. Silic
a support w
as
amorphous. No inde
pendent lines corresponding to the cryst
alline MnO
2 wereobserved on pure
an
at
ase
and rutile s
amples. However, the presence of MnO
2 w
as confirmed on other supportsby XRD. BET surf
ace
are
a v
alues suggest th
at s
pecific surf
ace
are
a of the supports w
as decre
ased
afterimpregn
ating with MnO
2. The FT-IR
and
ammoni
a TPD studies indic
ate the presence of two ty
pes of
acidsites on these c
at
alysts,
and the
acidic strength of the c
at
alysts is higher th
an the corresponding pure supports.XPS results reve
aled the presence of two ty
pes of m
ang
anese oxides, MnO
2 (642.4 eV)
and Mn
2O
3 (641.2eV), on
all the s
amples. The SCR
perform
ance of the supported Mn c
at
alysts decre
ased in the followingorder: TiO
2 (
an
at
ase, high surf
ace
are
a) > TiO
2 (rutile) > TiO
2 (
an
at
ase, rutile) >
![](/im<font color=)
ages/gifch
ars/g
amm
a.gif" BORDER=0 >-Al
2O
3 > SiO
2 > TiO
2(
an
at
ase, low surf
ace
are
a). Qu
antit
ative NO conversion with 100% N
2 selectivity w
as
achieved
at 393 Kwith Mn supported on TiO
2 (
an
at
ase). TiO
2-supported MnO
2 c
at
alysts showed more promising SCR
activityth
an Al
2O
3- or SiO
2-supported m
ang
anese oxide c
at
alysts. V
arious ch
ar
acteriz
ation techniques suggest th
atLewis
acid sites,
a high surf
ace concentr
ation of MnO
2,
and redox pro
perties
are import
ant in
achieving highc
at
alytic
perform
ance
at low tem
per
atures.