V N U J o u rn a l o f S cien ce, N a tu r a l S cic n c c s a n d T ech n o lo g y 25 (2009) 112-122
Using the reduced La(Co,Cu )03 nanoperovskites as catalyst precursors for CO hydrogenation
Nguyen Tien Thao'’*, Ngo Thi Thuan^, Serge kaliaguine^
^ Faculty o f Chemistry, College o f Science, VNU, 19 Le Thanh Tong, Hanoi, Vietnam
^Department o f Chemical Engineering, Laval University, Quebec, Canada. G IK 7P4 Received 07 December 2007
A bstract. A series o f ground La(Co,Cu)03 perovskite-type mixed oxides prepared by reactive grinding has been characterized by X-Ray diffraction (XRD), BET, H2-TPR, O2-TPD, and CO disproportionation. All ground sanples show a rather high specific surface area and nanomeữic particles. The solids were prefreated under H2 aừnosphere to provide a finely dispersed Co-Cu phase which is active for the hydrogenation of CO. The reduced perovskite precursors produced a mixtiưe o f higher alcohols and hydrocarbons from syngas following an ASF distribution.
Keywords: perovskite; Co-Cu metals; syngas; alcohol synthesis.
1. Introduction
Perovskites are m ixed oxides w ith the general form ula AtíUs- In theoiy, the ideal perovskite structure is cubic w ith the space- group Pm 3m -O h [1]. T he structure can be visualized by positioning the A cation at the body center o f the cubic cell, the transition- m etal cation (B) at the cube com ers, and the oxygen at the m idpoint o f the cube edges. In this structure, the transition-m etal cation is therefore 6-fold coordinated and the A -cation is 12-fold coordinated w ith the oxygen ions.
M oreover, each o f the A and B positions could be partially replaced by an o th er elem ent to prepare a variety o f derivatives [1,2]. For exam ple, a partial substitution o f La in
’ Corresponding author. Tel.; 84-4-39331605.
E-mail: [email protected]
lanthanum -cobaltate by either Sr or Th has rem arkably affected the rate o f carbon dioxide hydrogenation [3] and m ethane oxidation [4].
The substitution o f the cation at A-position, how ever, is m uch less atừactive than that at B- site due to the usual lack o f activity o f the A cation. M eanw hile, the introduction o f another transition m etal into perovskite lattice could therefore produce several supported bimetallic catalysts upon controlled reductions [5-8].
Bedel et al. [5], for instance, obtained a Fe-Co alloy after reduction o f LaFeo 75C00.25O3 orthorhom bic perovskite at 600°c. Lima and A ssaf [8] found that the partial substitution o f Ni by Fe in the perovskite lattice leads to a decreased reduction tem perature o f ions and the form ation o f N i-Fe alloy. The presence o f alloys can, m oreover, m odify the metal particles on the catalyst surface and the possible dilution o f ửie active nickel sites. By this way, 112
N .T . T h a o et al. / V N U j o u r n a l o f Scien c e, N a tu r a l S c ie n c e s a n d T e c h n o lo g y 2 5 ( 2 0 0 9 ) 1 1 2 -1 2 2 113
the reduction-oxidation cycles o f perovskites under tailored conditions could produce active transition metals dispersed on an oxide (Ln
2Ơ
3) matrix [5,7,8]. This characteristic may be used for a promising pathway o f development o f a finely dispersed metal catalyst from perovskite precursors.
bi several previous contributions [7,9-11], we have reported some novel characteristics of lanthanum-cobaltates prepared by reactive grinding. This article is to further prepare well- homogenized supported Co-Cu metals for the conversion of syngas to higher alcohols and hydrocarbons.
2. Experimental
2.1. M aterials
LaCoi-xCuxOs perovskite-type mixed oxides were synthesized by the reactive grinding method also designated as mechano-synthesis m literature [9-11], In brief, the stoichiometric proportions of commercial lanthanum, copper,
and cobalt o x id e s (9 9 % , A ld r ic h ) w e re m ixed
together with three hardened steel balls (diameter =
11mm) in a hardened steel crucible (50 ml). A SPEX high energy ball mill working
at
1 0 0 0rpm was used for mechano-synthesis
for
8hours. Then, the resulting powder was mixed to 50% sodium chloride (99.9%) and further milled for
1 2hours before washing the additives with distilled water. The slurry was dried in oven at 60-80°C before calcination at 250'’C fo rl5 0 m in .
A reference sample, LaCoOs + 5.0 w
1% Cu^O, was prepared by grinding a mixture of the ground perovskite LaCo
0 3having a specific surface area of 43 mVg with CU
2O oxide (10:1 molar ratio) at ambient temperature without any
grinding additive before drying at 120°c overnight in oven.
2.2. Characterization
The chemical analysis (Co, Cu, Fe) o f the perovskites and the residual impurities was perfonned by AAS using a Perkin-Elmer llOOB spectrometer. The specific surface area
( Sb e t)
of all obtained samples was determined
from nitrogen adsorption equilibrium isotherms at -196°c measured using an automated gas sorption system (NOVA 2000; Quantachrome).
Phase analysis and particle size determination were performed by powder X-ray diffraction
(XRD) using a SIEMENS D5000
diffractometer with CuKa radiation (X = 1.54059 nm).
T em p e ra tu re p ro g ra m m e d ch aracterizatio n
(TPR, TPD, CO dissociation) was examined using a multifunctional catalyst testing (RXM- 100 from Advanced Scientific Designs, Inc.).
P rio r to e a c h test a n a ly s is , a 5 0 m g sam p le w a s
calcined at 500°c for 90 min under flowing
20% O2/IIC (20 111I/11Ú11, la m p 5"c / u iin ). T h e sam p le w a s then c o o le d d o w n to room tem perature u n d er flo w in g p u re H e (2 0 m L/m in ). T P R o f the c a ta ly s t w a s then carried out b y ra m p in g u n d er 4 .6 5 v o l% o f H2/ A J (2 0 m l/m in)
from room temperature up to 800“c (5“c/min). The effluent gas was passed through a cold trap (dry ice/ethanol) in order to remove water prior to detection. For TPD analysis, the
O2-T P D c o n d itio n s w e re 2 0 m l/m in H e,
temperature from 25 to 900°c (5°c/min). The
m/z s ig n a ls o f 1 8 , 2 8 , 3 2 , 4 4 w e re c o lle c te d
using the mass spectrometer. For each CO
disproportionation tests, a number o f CO/He
(0.586 vol%) pulses (0.25 mL) were then
injected and passed through the reactor prior to
reach to a quadrupole mass spectrometer (ƯTI
114 N.T. Thao et al. / V N U journal o f Science, Natural Sciences and Technology 25 (2009) ĨÌ2 -Ĩ2 2
capillary colum n (W cot fused silica, 60m X
0.53mm, C oating Cp-Sil 5CB, DF = 5.00 ^m ) connected to a FED (V arian CP - 3800) and mass spectrom eter (V arian Saturn 2200 G C/M S/M S). The selectivity to a given product is defined as its w eight percent w ith respect to all products excluding C O2 and water.
Productivity is defined here as a weight (mg) product per gram o f catalyst p er hour.
100). The m/z signals o f 18, 28, 32, and 44 were collected.
2.3. Catalytic perform ance
The catalytic tests were carried out in a stainless-steel continuous flow fixed-bed micro- reactor (BTRS - J r PC, A utoclave Engineers).
Catalysts were preữeated in situ under flowing 5 vol% o f H j/A r (20 m l/m in) at 250°c (3h) and 500”C (3h) with a ram p o f 2°c/m in. Then, the reactor was cooled dow n to the reaction temperature while pressure was increased to 1000 psi by feeding the reaction m ixture. The products were analyzed using a gas chromatograph equipped w ith two capillary columns and an autom ated online gas sam pling valve maintained at 170”c . CO and CO2 were separated using a capillary colum n (Carboxen™
1006 PLOT, 30m X 0.53m m ) connected to the TCD. Quantitative analysis o f all organic products was carried out using the second
Table 1. Physical properties o f ground La(Cu,Cu)Oj perovskites 3. Results and discussion
3.1. Physico-chem ical properties
Table 1 collects the chem ical composition and some physical properties o f all the ground perovskites. The specific surface area is rather higher (16-60m^/g) because o f the low synthesis temperature (~ 40°C), w hich allow s to avoid the agglomeration o f perovskite particles [7.11],
Samples Sbet
(la ’/g)
Crystal (iua)’
domain Com position (wt.% )
Na" Co Cu rc^
LaCoOa LaCoo.9Cuo.1O3
59.6 9.8 0.53 21.15 - 4.69
19.5 9,7 0.31 19.31 1.89 1 . 1 2
LaCoo 7CU03O3 22.3 9.9 0.17 16.77 5.79 1 . 2 1
LaCoo 5C110 5O3 10 .6 9.2 0.44 10.60 9.96 0.6 4
CujO/LaCoOj 16.8 10.9 0.39
___ _______________ V. _ _ , L _ f., _ 20.04 3.28 4.78
As mentioned in experim ental Section, the addition o f a grinding additive (NaCl) during the last milling step leads to the partial separation o f the crystal dom ains, m aking a significant change in surface-to-volum e ratio and in the internal porosity o f elem entary nanometric particles [10,11], Consequently, the surface area o f such perovskites significantly increases [10], It seem s that the presence o f copper in the perovskite lattice leads to a decreased surface area o f LaCo0 3. Indeed, the
surface area ( Sbet) o f all C u-based perovskites (x < 0.3) and the m ixed oxides (C u2 0/LaCoƠ3) is much low er than that o f the copper-free sample (LaC oO j) [6,7,11,12], The X-ray diffraction patterns are sfiown in Fig. 1. Their diffractogram s indicate that all La-Co-Cu samples are essentially perovskite-type mixed oxides. The perovskite reflection lines are broadening, im plying the form ation o f a nanophase. Indeed, the crystal dom ains o f the ground perovskites calculated by the Scherrer
N .T . T hao e t al. / V N U jo u r n a l o f S cien c e, N a tu r a l S c ie n c e s a n d T e c h n o lo g y 2 5 (2 0 0 9 ) Ĩ 1 2 - 1 2 2 115
equation from X-ray line broadening are in the range of 9-10 nm (Table 1), in good agreement with the results reported previously [9,12,13].
Although all ground samples always contain a small amount of iron oxide impurities, no FeOx species are detected by XRD (Table 1 and Fig.
1). For sample CuoO/LaCoOj, it is clearly
observed that two strong reflection lines at 36.8 and 42.7° characterize the presence of CU
2O (Fig. 1). This indicates that copper ions locate out of the perovskite lattice although a small amount of such oxides presented in the framework is not ruled out [13],
= 2000
n
5 --- Cu20/LaCo03
4--- LaCoO. 5CuO. 505
3 --- Laco0.7cu0.303 2 --- Laco0.9cu0.103
^
LdCo03
2-Theta
hig. 1. X K U patterns (i^erovskite: x;
CuU: *).
3.2. T em p erature-program m ed reduction o f hydrogen (H :-TPR)
The rcducibility o f La-Co-Cu perovskites was examined by performance of H
2-TPR tests.
Figure 2 shows H
2-TPR profiles of all samples.
For the free-copper sample, two main peaks were observed. According to the calculation of H
2balance, the signal at around 390°c is atfributed to the reduction of to
Co^\ Theother peak at a higher temperature (680°C) describes the complete reduction o f to Co°
[7,13], A similar curve o f H
2-TPR for La-Co-
Cuperovskites is observed (Fig. 2). An increased content of copper in the perovskite lattice (x = 0-0.3) results in a substantially
decreased reduction temperature. A sharper peak at lower temperatures is ascribed to the simultaneous reduction of both Co and Cu to
and Cu”, respectively [6,7,12,13], At this step, the perovskite framework is assumed to be still preserved, but the structure is strongly modified [7,13], The reduced metallic copper and species are suggested to be atomically dispersed in the perovskite at the end of the first reduction temperature peak. The presence of metallic copper has a promotion to the reducibility o f cobalt ions, resulting in a decreased reduction temperature of
Co^*!Co^*and Co^VCo®.
The higher peak is essentially responsible
for the reduction of the remaining to Co“.
116 N T . Viao et al. i V N U journal of Science, Natural Sciences and Technoỉo<iỊy 25 (20()9) Í 12-222
XRD spectra o f the reduced Co-Cu based perovskites (not shown here) show the appearance o f signals o f Cu and Co m etals after reduction at 375 and 450°c [7]. A sim ilar profile m H i-TPR betw een sam ple LaCoosCuosOa and C u2 0/L aC o03 is observed,
indicating that at a higher copper content (x = 0.5), a rem arkable am ount o f copper oxides exists out o f the perovskite lattice. Their oxides are so highly dispersed in the grinding L a(C o,C u)0 3 that they could not detected by X R D techniques.
24
ro18 J2cc
^ 1 2 CÕ 8 e
C u 20/L aC o03
L3C00.50u0.503 Laco0.7cu0.30a.
Laco0.9cu0.103 LaCo03
200
Tempera?ure (°C)
600 800Fig. 2. H2-TPR profiles o f the ground perovskites.
3.3. Tem perature-programmed desorption o f (O2 T P D )
TPD o f O2 over all samples w as investigated in order to shed light on the reduction-oxidation properties o f Co-Cu based samples. O2-TPD spectra show two typical peaks with a strong shoulder at a high temperature for Co-Cu based perovskites. In the case o f the free-copper catalysts, a large peak with a long tail at a low er tem perature o f oxygẹn desorption is observed in the broad temperature range o f 400-650°C as depicted in Fig. 3. The lower tem perature peak, nam ely preferred to as a-oxygen, is attributed to oxygen species weakly bound to the surface o f the perovskite-type rare-earth cobaltate. This peak is very broad, indicating that the oxygen released at low tem peratures is adsorbed on several different sites o f the catalyst surface [9].
For Cu-based perovskites, this peak slightly
sh ifts to a lo w e r tem perature and b ecom es sharper w ith increasing copper content. The oxygen desorption signal (p-oxygen) appeared at a higher tem perature (650-820°C) is ascribed to the liberation o f oxygen in the lattice. It is noted that this peak o f the non-substituted L aC oO j has the m axim um at 78 5 °c while that o f the C o-C u based perovskites shows the m axim um at a low er tem perature with a shoulder approxim ately at 670-680°C (Fig. 3).
The shoulder o f the second peak is believed to the reduction o f to Cu^ in harm ony with increasing its intensities with the am ount o f the in tr a -la ttic e c o p p e r [ 6 ,1 4 ] . In a d d itio n , th e oth er pea k IS firm ly d esig n a ted as to the difficult reduction o f to in lattice. An increased am ount o f a-oxygen desorbing from LaCoi_^CUx0 3 suggests that Cu substitution leads to the production o f more oxygen vacancies and the therefore facilitation o f the reducibility o f
N .T . T ĩm o e t al. / V N U J o u r n a l o f S c ie n c e , N a tu r a l S c ie n c e s a n d T e c h n o lo g y 2 5 (2 0 0 9 ) 1 1 2 -1 2 2 117
27
25
Cu20/LaCo03
Laco0.5cu0.503 Laco0.7cu0.303 Laco0.9cu0.103
LaCo03
175 325 475
Temperature ( C) 625 775
Fig. 3. O2-T PD profiles o f the ground perovskites.
3.4. CO D isprop ortionatio n
CO dissociation was investigated in order to foresee the reactivity o f the partially reduced perovskite precursors in the synthesis o f higher alcohols from syngas [7,13,14]. The ability to
d is s o c ia tio n
of carbon monoxide has been proposed according to the Boudouard reaction [5,131.
2
CO* c * + CO
2Here the asterisk (*) implies the chemisorbed species on the reduced catalyst surfacc. Figure 4 displays a relationship between CO conversion and the number of pulses at 275”c for a series o f the reduced samples. It is clearly observed that the presence of the intra-lattice copper results in a significant decline in CO conversion.
The conversion of CO disproportionation on
CuiO/LaCoOi sample is higher than that onLa-Co-Cu based samples, but still slightly lower than the-one on the free-copper perovskite (LaCoOs). This indicates the significant different effects between exừa- and inừ*a- perovskite lattice copper on the ability of cobalt sites to dissociate the CO molecule.
W h e n cu p p ci in coip oialccs in to the pcrov&kitc
structure, it has a sừong interaction with the
intra-lattice cobalts, giving rise to a remarkable
decrease of CO chemisorbed on Co atoms at
275°c. This
ISconsistent with the results of H
2-
TPR and O
2-TPD (Figs. 2-3). In confrast, the
presence o f exừa-lattice copper has an
insignificant effect on the activity o f cobalt in
the dissociation o f CO because of both copper
and cobalt in such case assumed to exist as two
individual sites after reduction. Therefore, a
close distance between cobalt and copper site
affects the ability o f the metals to the
disproportionation of CO. This is a prerequisite
for higher alcohol synthesis catalyst [15].
118 N.T. Thao et aỉ. / V N U Journal o f Science, Natural Sciences and Technology 25 (2009) 112-122
80 5« 70 ^
c 60 Ị
.2Ề0) 50 1
> 40 ! K0
u 30 '
0
20 ■0
10 :LaCo03
♦ m m
I — t - - r » ệ ế É . . Cu20/LaCo03
Nurrbef of pulses
4 8
-SCuO.Ỉ
12 16
Fig. 4. CO disproportionation on the reduced La(Co,Cu)03 samples at 275®c.
3.5. Synthesis o f higher alcohols fr o m syngas Synthesis o f higher alcohols from syngas has been perform ed at 250-375°C under 1000 psi and velocity = 5000 h ' (H j/C O /H e = 8/4/3) over the reduced La(Co,Cu)03 perovskites. A mixture o f products is com posed o f linear primary m onoalcohols (C |O H -C 7O H ) and paraffins (C i-C ii). The activity is defined as a micromole o f CO per gram o f catalyst per hour is presented in Figure 5. From this Figure, it is observed that the activity in CO hydrogenation increases w ith increasing co p p er content to X = 0.3. The conversion on sample LaCoosCuo sOs
IS very c lo se to that on the blend o f CU2O and LaCoOs, indicating a sim ilar catalytic behavior o f the two samples. Therefore, both the selectivity and productivity o f alcohols over sample LaCoosCuosOj are m uch lower than those o f the LaCoo 7C1103O3 perovskite alửiough
copper content o f the former is much higher (Table 1 and Figs 6-7). The general consensus in literature is that a mixed Co-Cu based catalyst is active for the synthesis o f higher alcohols from syngas as a distance o f a metallic copper atom from a cobalt site is within atomic.
Consequently, the requirem ent for the perovskite precursor is therefore that should be in the La(C o,C u)03 fram ew ork and a hom ogeneous distribution o f the tw o Co-Cu active sites is reached after pretreatm ent under hydrogen aừnosphere [11,15]. M etallic cobalt is widely known as a good Fischer-Tropsch catalyst because it shows very high activity in the appropriately dissociative adsorption o f CO molecules, the propagation o f carbon chain, and the production o f m ethane when exposed to synthesis gas [7,15],
x=0 x=0.1 x=0.3 x=0.6u20/LaCo03
Fig. 5. The correlation between copper content (x = 0 - 0.5) and the activity in alcohol synthesis at 275“c , 1000 psi, 5000 h ', Hj/CO/He = 8/4/3.
N T . T h a o et al, Ị V N U J o u r n a l o f S cien c e, N a tu r a l S c ie n c e s a n d T e c h n o lo g y 2 5 (2 0 0 9 ) 2 1 2 -1 2 2 119
The appearance of a neighboring copper leads to a substantial decrease in cobalt reactivity in CO hydrogenation. The coexistence of such dual sites results in the
formation of a mixture of alcohols and hydrocarbons instead o f paraffins only. Indeed, Figure 6 shows a variation in the selectivity to products with copper content at 275°c.
50
? 40
I
30i
u (Õ
2010
c:=0 .^=0.3
OQ Alcohols
■ C2-hydrocarbons
■ Methane
Fig. 6. The coưelation between copper content (x = 0-0.5) and alcohol selectivity.
Ihis Figure shows an increased alcohol selectivity with increasing amount of inừa- lattice copper perovskite from
X= 0 to
X= 0.3.
Meanwhile, total hydrocarbon selectivity displays an opposite trend. Therefore, the presence of intra-lattice copper promotes the yield of alcohols and suppresses the formation ol methane, leading to an increased, productivity of alcohols as illustrated in Fig. 7. Indeed, coppcr is a typical methanol catalyst [16]. Its
69 Alcohols
■ C2-hydrocarbons
a
Methane 9080
? 70 3 5» 60
£Uề 50
> 40 ều TS3 30
whm 0. 20 i
10 ^
0 ^
i
ability is to dissociate hydrogen molecule and to adsorb CO molecule without dissociation.
Under alcohol synthesis conditions, the adsorbed CO species are inserted in the alkyl chain group bound to a neighboring cobalt site in order to yield an alcohol precursor. This process is indeed facilitated if both cobalt and copper sites are very proximate. In other words, these two ions should be present in the perovskite lattice.
^=0.3 ^=0.5 ^^on.aCo03
Fig. 7. The coưelation between copper content (x = 0-0.5) and alcohol productivity.
120 N T . Thao et al. f V N U journal o f Science, Natural Sciences and Technology 25 (2009) ĨÌ2-122
This suggestion IS substantiated as we estimate the distribution o f products. Figure 8 shows A nderson-Chulz-Flory (ASF) carbon number distributions at 275°c o f products obtained on the representative sample LaCoovCuojO}. As seen from this Figure, all products are in good agreem ent w ith an ASF distribution. The alpha values o f all sam ples calculated from ASF plots are about 0.35-0.45.
In essence, the carbon chain grow th probability factor o f higher alcohols ( a l ) should be very close to that o f hydrocarbons (a3), ow ing to the assumption that the carbon skeleton o f these two homolog series is formed on the same active site [15]. How ever, Figure 8 presents a small difference in the propagation constants between higher alcohols ( a l = 0.38) and hydrocarbons (a3 = 0.43). To com pare with the
alpha value o f hydrocarbons, the second carbon chain growth probability factor (a2 ) o f higher alcohols was calculated w ithout m ethanol point because m ethanol is usually overproduced during the synthesis o f higher alcohols from syngas [7,15-17]. This may be also associated with the role o f extra- perovskite lattice copper w hich can form m ethanol in the absence o f a neighboring cobalt site [7,17]. As seen from Fig. 8, when the point o f m ethanol (n = 1) is excluded in the alcohol m olecular distribution, a close resem blance betw een the two slopes o f alcohol and hydrocarbon plots is clearly observed, indicating that the reaction pathway likely occurs through sequential addition o f CHx interm ediate species in to the carbon chain for the propagation [14].
|o
-2
4 6
CartxDn rư n b e r
8
10
Fig. 8. A SF distribution o f products over sample LaCoo7Cuo 3O3 (qi = C1OH-C7OH; 02 = C2OH-C7OH; 03 = C|-C|0 hydrocarbons)
4. C onclusion
A set o f nanocrystalline LaCo|.,Cux03 perovskites has been prepared using reactive grinding method. All sam ples have a rather high surface area and com prise elem entary
nanoparticles. A t X > 0.3, a blend o f oxides is obtained instead o f a perovskites phase only.
The presence o f copper has a strong effect on the reducibility o f perovskite and on the reactivity o f cobalt in CO hydrogenation. A highly dispersed bim etallic phase is obtained
N T . Thao et al. f V N U Journal o f Science, Natural Sciences and Technologỵ 25 (2009) II2 -Ĩ2 2 121
after reduction o f the Co-Cu based perovskites under hydrogen atmosphere. The reduced perovskite precursors are rather active for the conversion o f syngas to oxygenated products.
The selectivity to alcohols is about 20-45 wt%
and the productivity ranges from 30 to 60.9 mg/gcai^ under these experim ental conditions.
The distribution o f both alcohols (CịO H -CvOH) and hydrocarbons (C l-C IO ) is good consistent with an ASF distribution with the carbon chain growth probability factors o f 0.35-0.45. Copper m the perovskite structure plays an important role in the synthesis o f higher alcohols. The inữa-lattice copper is found to prom ote the formation o f alcohols and to suppress the production o f methane.
A cknow ledgem ents
The finance o f this w ork was supported by Nanox Inc. (Quebec, C anada) and the Natural Sciences and Engineering Research Council o f Canada. The authors gratefully thank N anox Inc. (Quebec) for preparing the perovskite catalysts used in this study.
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Tính chất xúc tác của các perovskit La(Co,Cu )03 ở trạng thái khử trong phản ứng hiđro hóa co
Nguyễn Tiến Thảo', Ngô Thị Thuận', Serge kaliaguine^
'Khoa Hóa học, Trường Đại học Khoa học Tự nhiên, ĐHQGHN, 19 Lê Thánh Tông, Hà Nội, Việt Nam
^ Phòng Công nghệ Hóa học, Trường Đại học Laval, Quebec, Canada. G IK 7P4
Các đặc trưng của họ xúc tác perovskite La(Co,Cu)Oj được tổng hợp bằng phương pháp nghiền họat hóa được xác định bàng các phưomg pháp như: X-ray, BET, khử bằng H2 theo chương trình nhiệt độ (TPR-H2), deoxy bằng chương trình nhiệt độ (TPD-O2), phân bố bất đối xứng