ảnh hưởng của tiền chất Cobalt đến tính chất của xúc tác CoAl2O3 trong chuyển hóa co thành nhiên liệu lỏng

Tieu ban Khoa hoc
vdt
lieu ISBN:
978-604-913-011-3
ANH
HirONG
CUA TIEN CHAT COBALT DEN TINH CHAT CUA XUC
TAC
C0/AI2O3
TRONG CHUYEN HOA CO THANH NHIEN LIEU LONG
INFLUENCE OF COBALT PRECURSOR ON PROPERTIES AND
ACTIVITY OF
C0/AI2O3
CATALYSTS FOR FTS PROCESS
Lu-u Cam Loc, Nguyen Manh Huan, Lac Kien Trieu, Bui Thanh
Huong,
Dang Thi Ngoc Yen
Viin Cdng nghi Hda hgc, I. Mgc
DTnh
Chi, Q.I, TP. Hd CM Minh
E-mail;
lclac(a>yast-hcm.
ac.
vn
Tom tat
Trong nghiin cim dd diiu chi cdc xuc tdc Cobalt mang trin
y-AhOs
xu ly bdng
amoniac vd amoni nitrat dugc diiu chi tit cobah acetat vd dugc nghien cim trong
phdn irng tdng hgp hydrocarbon long tit carbon monoxide. Thdnh phdn tdi uu
ciia

Co trong
xiic
tdc dugc diiu chi tit cobalt acetat la 20%, trong khi tit cobalt nitrat
la
15%.
Hiiu sudt tgo hydrocarbon
Idng
tit tiin chdt cobalt acetat cao han tit
cobalt nitrat.
Abstract:
Catalysts on the basis of cobalt oxide supported on
y-A^Os
modification by
ammonia and ammonium nitrate have been prepared from cobah acetate and
studied in the reaction of synthesis of liquid hydrocarbons from carbon
monoxide. The optimal contents of cobalt in catalysts prepared from cobalt
acetate have been shown to be 20
wt.%o,
while the optimal content of cobalt in
catalysts prepared from cobalt nitrate has been found to be 15 wt.%. The liquid
hydrocarbon yield obtained on the sample with 20
M't.
% of Co from cobalt acetate
precursor was higher than that from cobalt nitrate.
I.
Md
DAU
Trong cdng trinh nghien cim trudc day [1], chiing tdi da dieu che va nghien
ciiu
tinh

chit va hgat do cua cac xuc tac cobalt tir cobalt nitrat tam tren
y-A^Oa
(Merk) dugc xir ly
bing dung dich NH3 va NH4NO3 cho phan
iing
tdng hgp FT.
Kit
qua nghien cim cho thiy,
xir ly
•y-A^Os
bang NH3 va
NH4NO3
lam giam sd tam axit, lam suy ylu tuang tac cua Co vdi
chit mang, nhd dd C03O4 ket tinh tdt hon, tinh khir cua
xiic
tac tang va han cbl su tao thanh
aluminat cobalt boat tinh thap, dan tdi tang hieu suat tao hydroeacbon
Idng.
Ndng do dung
dich NH3 va NH4NO3 tdi uu tuong
iing
la 10 % va 15 % va cac
xiic
tac cd ham lugng Co
phii
hgp nhit la
15%.
Cac
xiic
tac

15%Co/Al203
tren chat mang xir ly bing dung dich
10%NH3
va
15%NH4N03
dugc ky hieu tuong
iing
la 15Co(N)Al-N10 va
15Co(N)Al-NN15.
Tren
15Co(N)Al-N10
hieu suat tao C5+ dat cao nhat la 46%, cao gip 1,3 lin so vdi chit mang
khdng xir ly, vdi do chuyen hda CO bang 72%, do chgn lgc C5+, CH4 va C2-C4 tuang
iing
64 ; 10 va 26% d
240°C
va 7 atm.
Tiln chat khac nhau dan den tuong tac khac nhau cua cac hat coban vdi chit mang
ciing nhu anh hudng den hoat tinh va kha nang phat triln mach dudi dieu kien FTS. Kraum
[2] cho ring, boat tinh xuc tac
cQng
nhu do phan tan Co tren
xiic
tac
12%Co/Ti02 dilu
cbl tir
298
Hgi nghi Khoa hoc
ky'
niim 35 ndm Viin

KH&CNVN-Hd
Ngi -10/2010
tiln chit hiiu ca cao ban
xiic
tac vdi tien chit la coban nitrat. Trong khi do Sun [3] va Wang
[4] lai cho thiy ddi vdi
xiic
tac Co/Si02 va
Co/SBA-15
tiln chit
Co(CH3COO)2
va
Co(N03)2
cho
kit
qua nhu nhau. Theo cac tac gia, trong trudng hgp
xiic
tac hr tien chat hiiu
ca, Co cd do phan tan cao, nhung
miic
khir rat thap do tuong tac manh giiia oxit coban va be
mat silic, cdn tren
xiic
tac tir nitrat cobalt do phan tan Co thap, nhung
miic
do khir cua ion
cobalt cao ban dan
din
do chuyin hda CO cao hon. Cobalt tren
xiic

tac dieu che tir tien chat
hiru ca tdn tai d dang cac cluster kich tbudc nano ben trong cac mao quan
ciia
SBA-15.
Ohtsuka [5] thiy ring, Co cd ngudn gdc tir acetate tren
SBA-15
cd hgat do rat thap ngay ca
khi ham lugng Co la 20%, ngugc lai,
xiic
tac dieu che tir coban nitrat hoac hdn hgp acetate va
nitrat cho su chuyen hda CO den 85-90% va dat dugc hieu suat
Idn
cho cac hydroeacbon
Cio-C20-
Nhin chung, su anh hudng cua tien chat cobalt len tinh chat
xiic
tac la chua rd rang
va
CO
cbl tuong tac tien chat vdi chat mang van chua sang td. Muc dich cua bai bao la nghien
ciiu
su anh hudng cua tien chat den tinh chat
xiic
tac, nham tim ra dieu kien tdi uu trong dieu
che
xiic
tac cobalt.
II.
THVC
NGHIEM

Chit mang la
Y-AI2O3
(Merk) xir ly bing dung djch
10%NH3
hoac 15% NH4NO3
theo qui trinh neu trong [1]. Cac xuc tac Co mang tren
Y-AI2O3
dugc dieu che tir
Co(CH3COO)2 .4H2O
(Merk) theo phuang phap tam nhu trong [1]. Dien tich be mat rieng
(SBET)
ciia xiic
tac dugc nghien
ciiu
bang phuong phap hap phu BET, thanh phan pha - bang
phuang phap XRD, tinh khir - phuong phap khir chuang trinh nhiet do (TPR), tinh axit -
phuang phap hap phu - giai hap amoniac va anh be mat cua
xiic
tac - phuang phap FE-
SEM/EDS dugc trinh bay cu the trong [1].
Xiic
tac dugc ky hieu nhu sau, thi du,
20Co(Ac)Al-N10,
la
xiic
tac chiia 20%Co mang tren
y-Al203,
xir ly bang
NH3lO%,
dieu che

tir cobalt acetat. Trudc khi phan
iing xiic
tac dugc boat hda bang ddng khi
H2
d nhiet do
400°C, ap suat 2 at, trong 4 gid, luu
lu(Dng
ddng tdng la 4 lit/gid.
Hoat tinh cua
xiic
tac trong qua trinh tdng hgp Fischer- Tropsch dugc thuc hien trong
so do ddng vi lugng, dudi ap suat 7 atm, tdc do the tich ddng V = 3 L/h; ty le
moi
H2/CO = 2,
khdi lugng chit
xiic
tac = 3 g va trong viing nhiet do 220 - 280°C. De phan
hch
ham lugng
CO,
sir dung cot mao quan HP-PLOT MolecularSeive 5A (chieu dai 30 m, dudng kinh trong
0,12
pm) vdi detector dan nhiet TCD. Dau dd FID va cot
HP-1
(chieu dai 30 m, dudng kinh
trong
0,12
pm) dugc dung de phan tich do chgn lgc cua nhung hydroeacbon C5+.
IIL
KET QUA VA THAO LUAN

1) Cac dac trung
ly-hda ciia
cac mau
xiic
tac.
Bdng
1.
Diin tich bi mat riing
(SBET)
cua
chdt
xuc
tdc,
nhiit do khu cue dgi
fTmwJ vd
muc do khu
cua C03O4 (Kred) trong cdc mdu
xuc tdc diiu che tit cobalt
acetate
Mau
10Co(Ac)Al-N10
20Co(Ac)Al-N10
25Co(Ac)Al-N10
10Co(Ac)Al-NN15
20Co(Ac)Al-NN15
25Co(Ac)Al-NN15
20Co(Ac)Al**
SBET,
m^/g
109,99

90,13
85,46
90,00
89,18
71,08
58,33
T
"C
-' maxh ^
423
465
430
418
460
460
440
Kredh
%
6,43
15,10
11,77
11,39
13,00
11,69
8,76
•'
max2:
*—
760
-

745
744
-
760
765
KredJ,
%0
2,34
-
3,10
1,56
-
1,15
1,56
Kred >
Idng,
%
%,11
15,10
14,87
12,95
13,00
12,84
10,32
299
Tiiu ban Khoa hoc vdt lieu ISBN:
978-604-913-011-3
*)
chdt mang la
y-A^Os

(Merk) khdng xit ly
Tinh chat
ly -
hda
cua
xiic
tac
dugc trinh bay trong bang
1
cho thiy,
khi
tang ham
lugng coban dien tich be mat rieng giam. Dien tich
bl
mat rieng
ciia
cac
xiic
tac mang tren
y-
AI2O3
xir ly cao gap
1,5
lan miu 20Co(Ac)Al. Trong dd
xiic
tac mang tren
y-Al203
xir ly NH3
cd
SBET

cao hon ddi chiit.
Tuong
tu
nhu
xiic
tac dugc dieu che
tir
Cobalt nitrat, trong phd XRD (hinh
la
va
lb)
ciia
tat
ca
cac
xiic
tac
dieu che
tir
cobalt acetate deu
cd
cac
peak dao ddng
dac
trung
ciia
C03O4 (20
=
19,2°,
31,6°,

36,8°, 59,5°
va
65,5°)
va
y-Al203
(29
=
20°, 45,8°
va
67,1°
)
cd
cudng do rat yeu, cho thay trong cae
xiie
tac nay cobalt tdn tai
d
pha tinh the C03O4, cdn chat
mang ket tinh kem. Cudng do cac peak dac trung cho tinh the C03O4 cua mau chiia 20%Co
la
manh nhat. Ngoai ra, cac
xiic
tac chiia 20%Co mang tren chat mang bien tinh cudng do dao
dgng cua
00304
cao ban dao ddng cua nd tren
xiic
tac tren chat mang khdng bien tinh. Dieu
dd cho thay viec xir ly thuy nhiet
y-Al203
vdi cac dung dich NH3 va NH4NO3 da lam giam

su
tuong tac giira Co va chat mang, hinh thanh tinh the coban oxit tren be mat
Idn
ban.

-
J'sfJKf^'K.,—^r' ^^w\A^v^/^v^''V^^''
AI.O,
ft
AIjU,
Y^i".
i
•
.^'YM^'i*
V*iN*».w.^J
W*-1
WNfV^H-WV»-uM'«/«'ll^'.W '"^'^
2iCciAlN10
A^j/
jJ
'Vjufm-i!
K^•(^^l^J;yl^J^*^v/v•
vA
Hinh
la.
Phd XRD cua xiic tdc Co mang Irin y-
AI2O3
xu
ly bdng
NH3:

I)I0Co(Ac)Al-NI0;
2)
20Co(Ac)Al-N10; 3)
25Co(Ac)Al-N10
.10COAI-NN15
.^/Vr^*»V.|«l.A^W.r^vnVAA^VV^^*''
:20CoAI-NN15
:25CoAI-NNI5
Mbeta-:
Hinh
lb.
Phd XRD cita
xiic
tdc Co mang
Iren f
AI2O3
xu
ly bdng
NH4NO3 I)I0Co(Ac)Al-NN15
2)
20Co(Ac)Al-NNI5;
3)
25Co(Ac)Al-NNI5
Phd TPR
ciia
tat ca cac
xiic
tac deu cd hai miii khir. Mui khir thir nhat vdi nhiet do kbit
cue
dai trong khoang

T^ax
1
^
420-465°C img vdi
sir
khir
ciia
C03O4 va miii khir nhd thir hai
vdi
Tmax,2 troug
khdang 745-765°C, dac trung cho
su
khir
ciia
cac ion
Co2+
lien
kit
vdi chit
mang hoac
ciia
spinel
C0AI2O4
[6]. Tir bang 1 ta thay, tang ndng do coban trong cac
xiic
tac,
nhiet do khir cue dai
va
mirc
do

khir tang, dat
cue
dai khi ndng do Co trong
xiic
tac
la
20%,
sau dd giam khi tiep tuc tang ham lugng Co len den 25%. So vdi mau khdng biln tinh, nhiet
do khir cue dai
Tmax.i ciia
hai xuc tac mang tren
y-Al203
bien tinh deu cao hon va mirc do khir
tang
tir
10,3% tren
mau
20Co(Ac)Al
len
15,1
va 13 %
tuong
ung ddi vdi hai mau
20Co(Ac)Al-N10
va
20Ca(Ac)Al-NN15.
Nhu vay, xir ly chit mang bing NH3 hoac NH4NO3
lam tang do ket tinh va tinh khir
ciia
C03O4 trong

xiic
tac.
Bdng
2.
Kit
qud do hdp phu - gidi hdp NH3 cua cdc
xiic
tdc diiu
chi
lu
cobalt acetate
Ky hieu
10Co(Ac)Al-N10
15Co(Ac)Al-N10
20Co(Ac)Al-N10
25Co(Ac)Al-N10
10Co(Ac)Al-NN15
15Co(Ac)Al-NN15
Yeu
1,754
2,389
3,104
1,566
2,451
3,668
Mat do tam
Trung
0,635
0,921
0,152

0,215
1,208
0,564
axit
3inh
(mmolNHs/lOOg)
Manh
1,682
1,091
0,519
0,465
0,752
0,564
Tdng
4,071
4,402
3,775
2,246
4,411
4,795
300
Hoi nghi Khoa hoc
ky-
niim 35 ndm Viin KH&CNVN - Hd Not -10/2010
20Co(Ac)Al-NN15
25Co(Ac)Al-NN15
20Co(Ac)Al-M
3,820
3,328
2,344

1,002
0,725
0,429
0,993
0,599
0,608
5,815
4.652
3,382
Ket qua do mat do tam axit
ciia
cac
xiic
tac mang tren
y-Al203
dugc trinh bay trong
bang 2. Tir bang 2 ta thay, mat do tam axit yeu cua cac
xiic
tac tren cac chit mang
y-Al203
khac nhau
tang
khi ham lugng Co tang tir 10 len
din
20% va giam xudng khi ham lugng Co
tiep tuc tang den 25%. So vdi
xiic
tac mang tren
Al-M,
cac

xiic
tac mang tren
Al-NlO
va
AI-
NN15
cd mat do tam axit yeu nhieu ban. Anh SEM ( hinh 3)
ciia
cac xuc tac
20CoAl-NlO,
2OC0AI-NNI5,
2OC0AI-M
cho thay, tren bl mat
ciia
hai
xiic
tac mang tren
Al-NlO
va
Al-
NN15
deu cd nhiing hat Co min nim xen va
phii
len cac tinh
thi
y-Al203
hat
Idn.
So vdi mau
mang tren

y-Al203(Merck),
tren cac xuc tac mang tren
y-Al203
biln tfnh cac hat Co phan tan
deu va nhd hon. Anh EDS cho thay
sir
phan tan
ciia
cac thanh phin tren
xiic
tac tuang ddi
ddng deu.
a) 20Co(Ac)Al
b)
20Co(Ac)Al-NlO
Hinh 3. Anh
SEMvd
EDS cua cdc xitc tdc
tdi uu mang trin
y-Al20j
e)
20Co(Ac)Al-NN15
2) Hoat tinh cua cdc xuc tdc
Bdng
3.
Dd chuyin hda CO (Xco), do chgn lgc
hydrocgebon C5+ (Scs )
vd hiiu sudt tgo
hydroeacbon
Cj+ CP) eiia

cdc mdu
xiic
tdc
Ky hieu
inau
lOCo(Ac)
Al-NlO
15Co(Ac)
•\1-N10
20Co(Ac)
\I-Ml)
:.K\i(Ac)
220"C
^CO SC5+
35,9
38,2
74,9
46,2
75,0
75,4
65,2
65,7
Y
26,9
28,8
48,8
30,4
240''C
^CO
SC5+

Y
260°C
^CO
%
43,5
65,5
93,6
69.5
70.4
61,4
49.19
40.8
30,6
40,3
46
28,4
57,8
86,6
99,7
95,7
SC5+
55,0
38,9
35,9
22,2
Y
31,8
33.7
35.8
21.2

280''C
^CO
81.0
100
100
100
SC5+
32,4
23.9
28.6
14.2
Y
26,3
23,9
28,6
14,2
301
Tieu
ban Khoa hgc vdt lieu
ISBN:
978-604-913-011-3
Al-NlO
lOCo(Ac)
A1-NNI5
15Co(Ac)
AI-NN15
20Co(Ac)
A1-NNI5
25Co(Ac)
AI-NNI5

20Co(Ac)
Al-M
21,9
41,9
59,2
58,7
43,8
81,0
69,2
73,6
54,7
74,1
17,7
29,0
43,6
32,1
32,4
31,7
62,8
88,4
83,4
77,1
66,7
58,9
52,2
33,7
49,2
21,2
37,0
46,1

28,1
38,0
50,7
86,7
99,8
95,5
91,7
53,9
32,7
32,8
19,2
38,9
27,4
28,4
32,8
18,4
35,7
69,5
100
100
100
100
35,4
15.1
23,4
14,4
21,4
24,6
15,1
23,5

14,4
21,4
San pham
ciia
phan
iing
la cae parafin
Cr
C13.
Do dd, ngoai san pham chinh la cac
parafin C5+, cdn cd cac san pham phu la cac parafin nhe C1-C4. Tir bang 3 ta thay, khi tang
nhiet do do chuyin hda CO tang, cdn do chgn lgc tao parafin C5+ giam, do dd hieu suat tao
C5+ dat cao nhit d nhiet do tdi uu. Phan
Idn xiic
tac cd nhiet do cho Y cao nhat la 220 -
240°C.
Tren cac
y-Al203
khac nhau hieu suat Y dat cao nhat khi ham lugng
phii
Co la 20%.
Dilu nay dugc giai thich la do cac xuc tac nay cd C03O4 ket tinh tdt nhat,
mure
do khir va mat
do tam axit yeu cao nhat, nen cd do chuyen hda cao nhat. So vdi
xiic
tac
2OC0AI-M,
nhiet do
tdi uu cho phan

iing ciia
xiic tac
20Co(Ac)Al-N10,
giam tir 240°C xudng cdn 220°C va hieu
suat phan
iing
tang tir 38% len
48,8%,
cdn tren
xiic
tac
20Co(Ac)Al-NN15,
hieu suat phan
img dat
46,1%
d nhiet do phan
iing
tdi uu 240°C. Cac
xiic
tac tren chat mang bien tinh, su gia
tang manh me do chuyen hda CO la nguyen nhan
true
tiep
ciia
viec cai thien hieu suat phan
ung.
So sdnh
hogt
tinh cua cdc xdc tdc tot nhat dieu che tir
Co(N03)2

vd
Co(CH3COO)2
Bdng
4.
So sdnh ddc trung
l-y
- hda vd hgat tinh
ciia
cdc
xiic
tdc tdt nhdt diiu chi tit tiin chdt
coban nitrat vd acetat
(T-
nhiit do tdi
im)
Xuc tac
15Co(N)Al
15Co(N)Ai-N10
15Co(N)Al-NN15
20Co(Ac)Al
20Co(Ac)Al-N10
20Co(Ac)Al-NN15
SBET.
m'/g
91,9
83,0
109,7
58,33
90,13
89,18

T "C
306.
499,720
464,730
397,446,
737
440,765
465
460
Kr,U.
%
6,60
7,10
11,10
10,32
15,10
13,00
T,°C
260
240
220
240
220
240
Xco,
%
79,8
71,7
64
77,1

93,6
88,4
Sc5+,
%
43,9
63,7
70
49,2
49,1
52,2
Y, %
35,0
45,7
44,8
38,0
48,8
46,1
Tuong tu
xiic
tac dieu che tir coban axetat, do chuyen hda CO tren xuc tac dilu cbl tir
coban nitrat ciing dat gia tri cao nhat la 100%
d
nhiet do
280°C.
Tuy nhien, d nhiet do thip
(220°C),
do chuyen hda CO tren
xiic
tac dieu che tir coban axetat eao hon so vdi xuc tac dilu
cbl tir coban nitrat. Dieu nay dugc giai thich la do cac xuc tac dilu cbl tir

Co(CH3COO)2
cd
miirc do khir cao ban, phan tan min hon ( cudng do cac vach phd
ciia
C03O4 ylu ban so vdi
xiic
tac dilu che tir cobalt nitrat). Hai
xiic
tac cd hieu suit tao C5+ cao nhit trong hai nhdm
xiic
tac la 15Co(N)Al-N10 va
20Co(Ac)Al-N10
vdi hieu suit Y tuong
iing
bing 45,7% va
48,8%.
Vay chit mang xir ly bang dung dich 10% NH3 tdt hon xir ly bing NH4NO3 va tiln
chit cobalt acetate
phii
hgp hon so vdi cobalt nitrat. Hieu suat phan
iing
tao C5+ dat gia tri
cao nhit la 48,8% d
Xco =
75%
va
Sc5-^=
65% d nhiet do
220°C
tren xuc tac 20Co(Ac)Al-

NIO.
302
Hoi nghi Khoa hoc
ky-
niim 35 ndm Viin KH&CNVN - Hd Ngi
-10'2010
Loi cam on:
Cac tac gia chan thanh cam on Ban chu
nhifm
Hudrig Khoa hgc vat heu da tao dieu
kien cho chung tdi thuc hien dl tai
""Nghien ciiu
che tao chat
xiic
tac de chuyen hda hdn hgp
CO va
CO2
thanh nhien lieu
Idng':
Day la mgt phan ket qua
ciia
de tai.
TAI LIEU THAM KHAO:
1.
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