1-s2.0-S0926337315002465-main
11 pág.

1-s2.0-S0926337315002465-main


DisciplinaReatores Químicos 151 materiais405 seguidores
Pré-visualização8 páginas
Applied Catalysis B: Environmental 179 (2015) 95\u2013105
Contents lists available at ScienceDirect
Applied Catalysis B: Environmental
j ourna l h om epage: www.elsev ier .com/ locate /apcatb
In\ufb02uence of the surface oxygenated groups of act
prepar rog
the oxi
Guoqian o J
Key Laboratory of Co
Technology, Ta
a r t i c l
Article history:
Received 27 N
Received in re
Accepted 1 Ma
Available online 7 May 2015
Keywords:
Cu/AC catalyst
Surface oxygenated groups
Dispersion
Valence distrib
Deactivation
 treat
e carb
 chara
tion, CO adsorption, and TPR. The results show that the concentrations of nitric acid do not signi\ufb01cantly
changes the speci\ufb01c surface area and textural property of AC. But the oxygenated groups which result in
acidic properties, such as lactone, carboxyl and phenol groups, are formed on AC surface during the acid
treatment process and increase with the increasing concentration of nitric acid. The increased surface
oxygenated groups not only in\ufb02uence the dispersion but also the valence distributions of copper species.
1. Introdu
Support
hydrogenat
and ethano
sis reaction
[4,5]), oxida
to CO2 [7])
to N2 [8], n
(such as m
carbonate [1
SiO2 and ze
large surfac
mentioned 
\u2217 Correspon
Tel.: +86 351 6
E-mail add
http://dx.doi.o
0926-3373/© 
utions
When copper supported on the AC treated by 4 M HNO3, the Cu/AC catalyst shows the optimal catalytic
performance for oxidative carbonylation of methanol to dimethyl carbonate, which might be ascribed to
the highest dispersion of Cu+ and Cu0 species. The average conversion of methanol and space-time yield
of DMC (STYDMC) within 10 h for the catalyst have reached 9.2% and 229 mg g\u22121 h\u22121, respectively. The
deactivation of Cu/AC catalysts is attributed to the agglomeration of copper species. Besides, the STYDMC
of per S(Cu+ + Cu0) for the acid treated Cu/AC catalysts is very similar and less than that of the original
Cu/AC catalyst which may be induced by the AC surface oxygenated groups itself but not the ratio of
Cu+/Cu0.
© 2015 Elsevier B.V. All rights reserved.
ction
ed Cu-based catalysts have been widely investigated in
ion reaction (such as hydrogenation of CO to methanol
l [1,2], dimethyl oxalate to glycol [3]), hydrogenoly-
 (such as hydrogenolysis of glycerol to 1,2-propanediol
tion reaction (such as oxidation of SO2 to SO3 [6], CO
, reduction reaction (such as reduction of nitric oxide
itrate to N2 [9]) and oxidative carbonylation reaction
ethanol to dimethyl carbonate and ethanol to diethyl
0,11]). Many materials including AC, Al2O3, CeO2, ZrO2,
olite [8,12\u201319] are employed as supports to provide a
e area for copper species dispersion. Among the above
catalyst supports, AC exhibits the favorable physical
ding author at: No. 79 Yingze West street, Taiyuan 030024, China.
018526; fax: +86 351 6018526.
ress: lizhong@tyut.edu.cn (Z. Li).
and chemical characteristics for the preparation of a catalyst with
the \ufb01ne dispersion of an active copper species on the AC support
[19\u201321]. This fact has drawn researchers\u2019 attention and consider-
able efforts have been made to investigate the performances and
characteristics of these supported Cu/AC catalysts.
It is known that the catalytic activity of supported catalyst is
strongly dependent on the dispersion of active species over the sup-
port [22]. In order to obtain the \ufb01ne dispersion of copper species
over AC support, various techniques such as impregnation tech-
nique [7], liquid phase reduction [23], and chemical precipitation
[24] have been used to fabricate Cu/AC catalyst. For example, Lu
et al. [25] found the size of Cu particles was about 100\u2013150 nm
of the Cu/AC catalysts prepared by polyol reduction. Wang et al.
[24] employed chemical precipitation to prepare Cu/AC catalysts
and showed the crystalline size of Cu was about 42.6 nm. Besides,
previous studies have shown that the surface oxygenated groups
enhance the hydrophilicity of the AC allowing easy access of metal
salt solutions during the impregnation process and provide addi-
tional nucleation sites, which could further improve the dispersion
rg/10.1016/j.apcatb.2015.05.001
2015 Elsevier B.V. All rights reserved.
ation of a nano Cu/AC catalyst and hete
dative carbonylation of methanol
g Zhang, Zhong Li \u2217, Huayan Zheng, Tingjun Fu, Yub
 of Coal Science and Technology of Ministry of Education and Shanxi Province, Institute
iyuan 030024, Shanxi, China
 e i n f o
ovember 2014
vised form 28 April 2015
y 2015
a b s t r a c t
Coconut shell activated carbon (AC) is
heterogeneous catalysts for oxidativ
and their corresponding catalysts are
ivated carbon on
eneous catalysis in
u, Yuchun Wang
al Chemical Engineering, Taiyuan University of
ed by nitric acid and used as a support to prepare nano-copper
onylation of methanol to dimethyl carbonate. AC supports
cterized intensively by BET, XPS, XRD, TEM, N2O chemisorp-
96 G. Zhang et al. / Applied Catalysis B: Environmental 179 (2015) 95\u2013105
of active species [26,27]. Generally, AC pretreatment by HNO3 is
believed to be an available way for the formation of more sur-
face oxygenated groups onto AC [23]. Zhu et al. [28] reported that
AC treated by HNO3 had more active surface complexes such as
carboxyls a
decreased f
alyst disper
of N2O and
produced m
persion of C
increased fr
the amoun
dispersion h
In additi
also plays a
previous st
for NO redu
of CuO and 
the presenc
improveme
the synthes
the AC supp
were repor
reported th
among the 
the catalytic
Generally, t
copper pre
valence dis
tion temper
AC [24,30,3
temperatur
formation o
pare Cu/AC
moderate t
The availab
support, es
the precurs
distribution
reduction s
more Cu2O
on AC treat
AC. Even so
genated gro
the support
In this p
surface che
catalysts. Th
texture stru
in\ufb02uence o
and phenol
catalyst has
of Cu/AC ca
are evaluat
2. Experim
2.1. Prepara
A comm
1643 m2/g 
try Co. Ltd.
of HNO3 (fr
tilled water
overnight. The pretreated AC is denoted as AC-x, where x represents
the concentration of HNO3.
The catalysts with 11.2 wt.% Cu loadings are prepared by an
incipient wetness impregnation method. An aqueous solution of
3)2 i
r 6 h.
d in 
x.
arac
 text
ed b
C us
as o
orpt
ore v
ed at
ples 
re pa
face
 Boeh
ic sit
 was
dium
 bic
aken
 was
Cl. T
.1 M
use 
l va
ns b
alcul
ylic, 
ylic 
ylic g
ay ph
ALab
diat
ess an
dhes
 into
 eva
ple
The 
ined
ced 
ay di
 D/M
5406
s of 
atmo
nsmi
ith 
ed by
pano
evap
ted b
 was
f the
of ea
lume
zed w
pera
ed 
nd lactones, and the grain size of the supported Cu2O
rom 16.5 nm to 12.4 nm which led to the improved cat-
sion as well as the catalytic activity for the reduction
 NO. Rau et al. [29] also found that HNO3 treatment
ore active surface complexes which improved the dis-
uO over AC support, and the removal ef\ufb01ciency of SO2
om 56.4% to 84.2%. Be that as it may, the in\ufb02uence of
t of surface oxygenated groups on the copper species
as not been thoroughly researched so far.
on, the valence of copper species over the AC support
n important role in catalytic performance. According to
udies [30], the high catalytic activity of Cu/AC catalyst
ction in the presence of oxygen was owing to existence
Cu2O species. But when NO reduction was conducted in
e of NH3, Cu2O and metallic Cu was detrimental for the
nt of catalytic performance of CuO/AC catalysts [31]. In
is of DMC by oxidative carbonylation of methanol, all
orted copper catalysts (Cu0/AC, Cu2O/AC and CuO/AC)
ted to show good catalytic activity [18,32]. Li et al. [32]