NGHIEN CQU ANH HUONG CUA HOI NaOC DEN<br />
QUA TRINH OXI HOA TRLJC TIER BENZEN T H A N H<br />
PHENOL B A N G OXI TREN XUC T A C V-W-OXIT/SiOs<br />
Nguy§n Thi Bich Loc<br />
Khoa Hod - DHKHTN, DHQGHN<br />
<br />
<br />
<br />
MO DAU.<br />
<br />
Phenol la mot trong nhiing boa chat quan trong ciia nganh cong<br />
nghiep hoa chat. Ngay nay phenol chii yeu dudc san xuat b^ng phUdng<br />
phap Cumen. PhUdng phap nay kha phiic tap, di tii nguyen lieu dau<br />
la benzen qua mot s6'giai doan trung gian va san pham thu dUdc ngoai<br />
phenol con c6 axeton. Viec tao ra axeton nhu mot ddng san pham vdi<br />
phenol da day gia thanh cua phenol len cao. Vi vay, viec tim ra mot<br />
phUdng phap mdi n h i m tdng hdp trUc tiep phenol tii benzen la rat c^n<br />
thie't.<br />
<br />
Trong bai bao nay, chiing toi trinh bay nhiing ke't qua budc dau<br />
trong qua trinh nghien ciiu s\l dung oxi de oxi boa trUc tie'p benzen<br />
thanh phenol tren xiic tac V-W-oxit/Si02 va nghien citu anh hUdng<br />
cua hdi nUdc den qua trinh oxi hoa benzen.<br />
<br />
THirc NGHIEM.<br />
<br />
- Xiic tac V-W-oxit/Si02 vdi thanh phan % kho'i lUdng V2O5 va<br />
WO3 khac nhau trong tong bam lUdng bai oxit la 5% tren chat mang<br />
SiOg dUdc dieu che'theo phUdng phap tbdng thUdng di tii dung dich cac<br />
muoi NH4VO3, (NH4)ioWi204i-5H20 va Si02. Tam dung dich<br />
NH4VO3 va ( N H 4 ) I Q W I 2 0 4 I . 5 H 2 0 len Si02 roi c6 can, sau do nung d<br />
nhiet do 100°C trong 5 gid va d 600°C trong 5 gid se thu dUdc xiic tac<br />
V-W-oxit/SiOs-<br />
<br />
<br />
177<br />
- Qua trinh oxi hoa benzen b^ng oxi dUdc tien hanh trong he<br />
tho'ng thiet bi ddng trong do cac chat tbam gia phan ling (d the khi)<br />
dUdc dim qua ong phan iing b^ng thach anh chiia xuc tac. Phan ling<br />
dien ra theo sd do:<br />
<br />
<br />
H70.823 K hidroquinon, phenol, p-quinon, axit-<br />
^ V-W-oxit/Si02 maleic, cacbon oxit, cacbon dioxit, ...<br />
<br />
<br />
trong do san pham chinh gom: phenol (PhOH), hidroquinon (HQ) va<br />
benzoquinon (BQ). Ba chat nay dUdc goi la cac phenol.<br />
<br />
Phan Ung dUdc thUc hien trong nhiing dieu kien sau:<br />
- Nhiet do thUc hien phan ling: 823 K<br />
- Kho'i lUdng xiic tac: 0,2 gam<br />
- Ap suat rieng phan cua benzen P(CgHg): 5,6 kPa<br />
- Ap suat rieng phan ciia oxi P(02): 11,3 kPa<br />
- Ap suat rieng phan cua nUdc P(H20): 75,6 kPa<br />
- Ap suat rieng pb^n cua heli P(He): 8,8 kPa<br />
<br />
San pham phan ling dUdc phan tich bang sac ki long bieu lUc cao<br />
(HPLC) Shimazdu LC-IOAT vdi detectd UV-VIS va san pham khi (CO,<br />
CO2) Cling vdi oxi du dUdc phan tich tren may sac ki khi Shimazdu<br />
GC-8A vdi detectd TCD.<br />
<br />
KET QUA VA THAO LUAN<br />
<br />
Chiing toi da tie'n hanh oxi hoa benzen tren xiic tac V-W-oxit/Si02<br />
vdi thanh phan % kho'i lUdng oxit vanadi va oxit vonfram khac nhau<br />
trong tong ham lUdng hai oxit la kh6ng-doi va b^ng 5% kho'i lUdng tinh<br />
theo V2O5 va WO3 tren chat mang la Si02. Ke't qua cho thay xiic tac<br />
V-oxit 5%/ Si02 to ra c6 hoat tinh xiic tac cho qua trinh oxi boa benzen<br />
b4ng oxi nhUng bieu suat va do chon loc tha'p. Mat khac, xiic tac W-<br />
oxit khong c6 boat tinh xiic tac dd'i vdi qua trinh oxi hoa benzen.<br />
NbUng khi 2 oxit dUdc tron l l n vdi nhau boat tinh xiic tac tang ro ret.<br />
<br />
178<br />
Dae biet dd'i vdi xiic tac V(4%)-W (l%)-oxit/Si02 chiing toi da quan sat<br />
dUdc boat tinh xiic tac dat gia tri cUc dai vdi ham lUdng san pham cac<br />
phenol 2,5%.<br />
<br />
Tiep theo chiing t6i khao sat cac xiic tac c6 ty le ve kh6'i lUdng<br />
V2O5/WO3 la kh6ng doi va hkng 4/1, nhUng tong ham lUdng 2 oxit tren<br />
chat mang (Si02) thay doi dan den ke't qua thu dUdc xiic tac chiia 3,5<br />
% tong oxit/Si02 (V-W-oxit (3,5%)/Si02) cho boat tinh xiic tac cao nhat<br />
d6'i vdi qua trinh oxi hoa benzen vdi ham lUdng san pham cac phenol<br />
dat 4%. Ke't qua chi ra d hinh 1. Viec tang ham lUdng xiic tac hdn niia<br />
chi lam tang qua trinh oxi boa benzen thanh CO va CO2. Tii d6 chiing<br />
t6i sii dung xiic tac V-W-oxit (3,5%)/Si02 cho nbuCng nghien ciiu tiep<br />
theo.<br />
<br />
<br />
<br />
;:^<br />
<br />
<br />
c<br />
CO<br />
<br />
<br />
<br />
<br />
§•<br />
1—1<br />
<br />
<br />
B<br />
X<br />
1 2 3 4 5 6 7<br />
Tong ham lUdng oxit/Si02 (%)<br />
<br />
Hinh 1. Anh hifdng cua ham luang 2 oxit tr^n chat mang (Si02)<br />
den ham lucmg san phim (cac phenol)<br />
<br />
<br />
Chiing t6i da tien hanh nghien ciiu khao sat do ben cua xuc tac.<br />
Phan ling oxi hoa benzen tren xiic tac V-W-oxit (3,5%)/Si02 dUdc tien<br />
hanh trong thdi gian 7^ d 823 K. Sau tiing khoang thdi gian b i n g nhau<br />
(1 gid) san pham dUdc phan tich b^ng HPLC va GC. Ke't qua dUdc chi<br />
ra d hinh 2.<br />
<br />
<br />
179<br />
mmol.h-lg-1<br />
<br />
<br />
<br />
<br />
7<br />
Thdi gian (gid)<br />
Hinh 2. Anh hudng th6i gian lam viec cua xuc tac den toe do tao thanh san phim<br />
(cac phenol)<br />
Trong thdi gian b^t d^u phan ling (< 1 h) t6c do tao t h a n h COx<br />
kha Idn, sau 1 gid td'c do tao thanh COx giam deu dan va sau 4 gid dat<br />
gia tri khdng doi. Trong khi do td'c do tao thanh cac phenol g^n nhU<br />
khdng doi trong 7 gid.<br />
<br />
Ket qua nay cho phep chiing t6i khang dinh do ben cua xiic tac du<br />
de tien hanh nhiing nghien ciiu tiep theo.<br />
<br />
Viec nghien ciiu cac dieu kien toi Uu cho phan iing oxi boa se dUdc<br />
de cap den trong cac bao cao sau.<br />
<br />
Qua tham khao mot so' c6ng trinh da c6ng b6' [1-5] chiing toi dU<br />
doan sU c6 mat hdi nUdc trong hSn hdp phan ling c6 the anh hudng<br />
den qua trinh tao thanh san pham. Trong nghien ciiu nay, chiing t6i<br />
da khao sat sU anh hudng cua ye'u t6' nay den qua trinh oxi hoa benzen,<br />
ke't qua dUdc chi ra d hinh 3. Khi khdng c6 mat hdi nUdc trong h6n hdp<br />
phan ling, chu yeu xay ra qua trinh oxi hoa benzen t h a n h CO va C02-<br />
Khi lUdng hdi nUdc dUa vao vUdt qua 30 kPa, toe d6 tao t h a n h CO va<br />
CO2 giam ban va toe do tao thanh cac phenol tang cung vdi vi^c tang<br />
ap suat rieng phan cua hdi nUdc.<br />
<br />
<br />
180<br />
100<br />
;:^<br />
8 0 •. \ Ham luang cac phenol<br />
<br />
60<br />
"x<<br />
OH<br />
<br />
c<br />
40<br />
tie<br />
C<br />
c<br />
S 20 CO + C02 2,<br />
1 —1 1 1-— 1 1 1<br />
B<br />
10 20 30 40 50 60 70 80 X<br />
<br />
PH2O (kPa)<br />
Hinh 3. Anh hudng ap suat rieng phan cua hoi nude den ham lugmg san ph^m<br />
<br />
<br />
<br />
<br />
K^T LUAN<br />
Qua nghien ciiu chiing toi da tim dUdc mot xiic tac mdi V-W-oxit<br />
(3,5%)/Si02 to ra c6 boat tinh xiic tac cao nhat dd'i vdi qua trinh oxi boa<br />
benzen t h a n h cac phenol b i n g oxi phan tii (vdi bam lUdng san pham<br />
cac phenol dat 4 %).<br />
<br />
Do ben cua xiic tac dam bao cho nhiing nghien ciiu dong hoc cua<br />
qua trinh oxi hoa benzen.<br />
<br />
Ham lUdng cac san pham chinh tao thanh tang ddng bie'n vdi hdi<br />
nude CO mat trong hdn hdp phan iing chiing to r i n g sU c6 mat cua hdi<br />
nude vdi nong do cao trong hdn hdp phan iing la mot trong nhiing yeu<br />
t6'quye't dinh den bieu suat tdng hdp phenol. Noi dung nghien ciiu ciia<br />
chiing toi dang tap trung vao hUdng nay va cac ke't qua nghien ciiu sau<br />
hdn se dUdc cong bo' trong cac cong trinh tiep theo nhiim giai thich ro<br />
hdn cd che cua qua trinh nay.<br />
<br />
<br />
181<br />
TAI LI$U THAM KHAO<br />
1. M. Iwamono, J. I. Hirata, K. Matsukami and S. Kagawa, J.<br />
Phys. Chem., 87, 903 (1983).<br />
2. E. Suzuki, K. Nakashiro, Y. Ono, Chem. lett., 953 (1988).<br />
3. R. Burch and C. Howitt, Appl. Catal., 98, 33 (1993).<br />
4. G. I. Panov, et a l . Chemical Week, 159, 11 (1997).<br />
5. I. Yamanaka, K. Otsuka, et al., ICC 121b in Granada, D-10,<br />
(2000).<br />
<br />
INFLUENCES OF THE WATER VAPOR ON THE DIRECT<br />
OXIDATION OF BENZENE TO PHENOLS WITH O2 OVER<br />
V-W-OXIDE/SIO2 CATALYSTS<br />
<br />
V-W-oxide/Si02 catalyst was active for the partial oxidation of<br />
benzene to phenols (phenol, hydroquinone and benzoquinone) with O2.<br />
A synergisn of V-oxide and W-oxide on the partial oxidation of benzene<br />
was observed, the yield of phenols was dramaticaly enhanced by addi-<br />
tion of water vapor.<br />
<br />
<br />
<br />
<br />
182<br />
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