58 Tong hop va die trung vat lieu xuc tic cho phan dng...<br />
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TONG HOP VA DAC TRlTNG VAT LIEU XUC TAC CHO PHAN iTNG<br />
CHUYEN HOA LPG THANH OLEFIN NHE<br />
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Le Thanh Son, Ngd Kim Thanh<br />
Pham Thj Hdng Diic, Hoang Hiep<br />
Trudng Dgi hpc Khoa hpc Ttr nhien<br />
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TOM TAT<br />
Cdc oxit kim logi chuyen tiep nhu V2OS hoae Ti02 mang tren vat lieu mao qudn<br />
trung binh hodc vdt lieu vi mao qudn la cdc he vdt lieu cd tinh oxy hod khic phdn tdn tren<br />
nen cd dien tich be mat lan ldm xuc tdc cho qud trinh oxy dehydro hod ankan thdnh anken<br />
tic ngudn LPG sdn cd vd re tien thdnh cdc sdn phdm cd gid tri han dang duac quan tdm<br />
sdu sdc. Bdo cdo de cap chi tiet den qud trinh tdng hap vd ddc trung cdc he xiic tdc<br />
V20j/MCM-48 vd Ti02/ZSM-5, buac ddu thdo ludn kit qud thu duac cua qud trinh chuyen<br />
hod LPG thdnh cdc olefin nhe.<br />
<br />
MODAU<br />
Khi hoa Idng (LNG) va khi dau Idng (LPG) dugc dua vao sir dyng mdt each phd<br />
bien tren the gidi mudn hon rat nhieu so vdi cac nhien lieu dau md khae nhu xang, dau<br />
DO, FO nhung lai cd tdc do phat trien rat manh me tren khap the gidi vdi mirc tang trudng<br />
ve san xuat va tieu thy khi deu rat cao do nhiing uu viet cua nhien lieu ly tudng nay cho<br />
theky mdi [1].<br />
Tren the gidi, LPG da trd thanh ngudn nhien lieu thdng dyng trong cdng nghiep va<br />
dan dyng. Dac biet, LPG cd img dyng quan trgng trong hoa dau - la nguyen lieu cho steam<br />
cracking, oxy hoa butan thanh anhydrit maleic, dehydro hoa propan thanh propylen va<br />
reforming thanh hydrocarbon thom .<br />
Cdng nghiep khi va thj trudng khi Viet Nam dang bude vao giai doan phat triln<br />
nhanh chdng. San lugng khi md Bach Hd la 4 trieu mVngay va Nam Cdn Son la 20 trieu<br />
mVngay. Khi dau Idng LPG tir nha may Dinh Cd cd san lugng 340.000 tin/nam va nha<br />
may lge dau sd 1 cd san lugng khoang 250.000 tan/ nam [5].<br />
Do nhu cau sir dyng olefin ngay cang gia tang dan den sy quan tam, nghien ciiu sau<br />
qua trinh oxy dehydro hoa ankan thanh anken tir ngudn LPG san cd va re tiln thanh cac<br />
san pham cd gia trj hon.<br />
Vat lieu mao quan trung binh vdi dudng kinh Id tir 20 den 100A° duge sir dung lam<br />
chat hap phy va chat xiic tac. MCM-48 cd cau true lap phuang, thudc nhdm khdng gian<br />
Ia3d. He thdng mang khdng gian ba chieu dan xen nhau cua cae kenh trong MCM-48<br />
dugc coi la nguyen nhan lam giam bdt viec nghen cac kenh dan khi nd dugc sir dyng lam<br />
chat hap phu hay chat mang xiic tac.<br />
Tuygn tap bao cio Hpi nghj KHCN "30 nim Dau khi Vift Nam: Co' hpi mdi, thach thde mdi" 59^<br />
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ZSM-5 la zeolit cd ham lugng Si cao, xiic tac cho nhilu qua trinh tdng hgp him co<br />
hoa diu quan trgng. ZSM-5 thudng dugc tdng hgp bing phuong phap sol-gel sir dyng chit<br />
tao ciu triic. Mac dii chit tao ciu tnic ddng vai trd quan trgng, song ed nhieu nhugc diem<br />
nhu dat tiln, ddi hdi qua trinh phan buy nhiet sau tdng hgp, gay d nhiem mdi trudng. Vi<br />
vay, viec tdng hgp zeolit ZSM-5 khdng diing chat tao catr-triic dugc quan tam hon.<br />
V2O5 va Ti02 la cac oxit kim loai chuyen tiep mang tren vat lieu ke tren se tao ra cac<br />
he xuc tac cd tinh oxy hoa khir phan tan tren nen cd dien tich be mat ldn cho phan iing<br />
oxy dehydro hoa ankan thanh olefin.<br />
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THU'C NGHIEM<br />
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1. Tdng hop V2O5/MCM-48<br />
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a. Ngudn nguyen lieu<br />
- Dung djch thuy tinh Idng 10%) (Si/AI = 1,5)<br />
- Chit boat ddng bl mat trung tinh: C|2H25(C2H40)40H [C,2(EO)4]<br />
- Chat boat ddng be mat cation: Cetyl Trimetyl Amoni Bromua (CTABr) Vanadi<br />
pentoxit V2O5<br />
- Axitoxalic C2H2O4<br />
b. Phuang phdp tdng hap<br />
Hoa tan 52,08g CTABr va 9,04g C,2(EO)4 trong 765g nude cit. 500g dung dich<br />
Na2Si03 10%) dugc rdt vao dung djch chat boat ddng be mat chira trong Ig polypropylen<br />
va dugc lac manh trong vai phiit. Sau do hdn hgp dugc khuay 30 phut. Hdn hgp phan ung<br />
dugc giir d IOO°C trong I2h. Sau dd hdn hgp dugc lam lanh den nhiet do phdng va dieu<br />
chinh pH tdi 10 bang dung djch axit axetic 30%). Hdn hgp dugc ddt ndng lan nira tdi<br />
100°C trong 24h. Lge kit tiia, rira bing dung djch hon hgp HCI va EtOH, nung d 550°C<br />
trong 4h [2, 6].<br />
MCM-48 dugc tam dung dich vanadi oxalat (dieu che bang each hoa tan V2O5 vao<br />
axitoxalic) cd ham lugng da tinh toan dugc bd sung nude vira dii udt vdi MCM-48, trdn<br />
ky d nhiet do phdng, say d 100°C trong 24h va nung d 500''C trong 4h.<br />
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2. Tdng hop Ti02/ZSM-5<br />
a. Ngudn nguyen lieu<br />
- Thuy tinh Idng (Viet Nam) I I,I6%Na20; 3I,l%Si02 (d = l,357g/ml)<br />
- Al2(S04)3.18H2O, H2S0498%, (Trung Quoc)<br />
- Mim zeolit ZSM-5 (Phap) cd ty le Si/AI = 50<br />
b. Ph uang ph dp tdng h pp<br />
H2SO4 98% dugc pha loang 70 lan va hda tan Al2(S04)3.I8H20. H2SO4 da pha loang<br />
dugc them tir tir ddng thdi vdi qua trinh khuiy va gia nhiet vao thiiy tinh Idng dl dilu<br />
chinh pH. Sau dd, cho tir tir dung djch mudi nhdm vao dung djch thuy tinh Idng da dilu<br />
60 Tong hpp v i die tru-ng vat lifu xiic t i c cho phan dng.<br />
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chinh pH, tilp tyc khuay va dun ndng cho den khi thu dugc he gel ddng nhat, cd pH « 12.<br />
Cac he gel duge chuin bj sao cho ty le Si/AI trong gel la 40. Them mam zeolit ZSM-5,<br />
bing 0,03%o lugng silic trong he, vao he gel da ddng nhat, ngirng gia nhiet va tiep tuc<br />
khuiy trong 30 phiit dl mim ZSM-5 phan tan deu.<br />
Qua trinh kit tinh dugc thuc hien trong binh teflon 200ml va binh thep khdng gi<br />
1,2L d nhiet do 170°C trong 24h. San phim kit tinh duge gan ling, Igc hiit chan va rira<br />
din pH trung tinh, lam khd d IOO°C trong 5 gid va nung d 500°C trong 5 gid [3, 7].<br />
Cho 1,2ml Ti(OC3H7)4 vao 30ml C3H7OH, chia lam nhilu lin rdi tim len 3gZSM-5<br />
bing khuay tir chan khdng. Din khi can khd thi nung d 500°C thu dugc Ti02/ZSM-5 10%.<br />
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3. Nghien ciru dac tru-ng xiic tac<br />
Cac mau xiic tac da tong hgp dugc trudc va sau khi tam dugc xac djnh cau triic va<br />
bl mat bing phd hdng ngoai IR (FTIR 760 Nicolet - Trung tam Hoa Diu, Trudng<br />
DHKHTN), nhieu xa tia X XRD (Siemen D5005 - Trung tam Vat lieu, Trudng<br />
DHKHTN), dien tich bl mat rieng SBET (ASAP 2000 - Trung tam Vat lieu xuc tac,<br />
DHBKHN), anh TEM (Vien Ve sinh djch te Trung uong), anh SEM (Trung tam Vat lieu,<br />
Trudng DHKHTN).<br />
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4. Danh gia hoat tinh xuc tac<br />
Bude dau chiing tdi da nghien cim do boat ddng cua cac xiic tac thu dugc bang phan<br />
ling oxy dehydro hoa LPG thanh cac olefin nhe. Phan iing oxy dehydro hoa LPG dugc<br />
tien hanh theo phuong phap dng ddng lien tuc. Ddng khi LPG duge dan qua thiet bi Flow-<br />
Meter va Id phan ung d cac nhiet do khae nhau. San pham dugc phan tich bang thiet bj sac<br />
ky khi khoi phd GC-MS HP-6890 (cdt HP-5, PE Siloxane, 30m x 0,25mm x 0,32 // m).<br />
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KET QUA vA T H A O L U A N<br />
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1. Cau true khong gian cua MCM-48 va ZSM-5<br />
Cac nghien ciiu gan day da khang djnh cau tnic khdng gian cua MCM-48 la Ia3d<br />
(Hinh I) va he thdng mao quan ciia zeolit ZSM-5 (Hinh 2) [6, 7].<br />
<br />
Ciu Injc m«o qutn<br />
>uclAe<br />
S.4K$.6A<br />
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Hinh 1: Cau true khong gian Hinh 2: He thong mao quan cua ZSM-5<br />
ciia MCM-48<br />
Tuyen tap bio cio Hpi nghj KHCN "30 nim Dau khf Vift Nam: Co hpi mdi, thich thiic mdi' 61<br />
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2. Tinh chSt cSu true cua cac vat lieu thu dirffc<br />
a. Pho nhiiu xg tia X (XRD)<br />
Cac pic d gia trj 29 thip diing de dac tnmg cho ciu tnic vat lieu MQTB. Kit qua<br />
Hinh 3 cho thiy pie nhieu xa d 20 == 2,2 - 2,3° (d|oo) dac trung cho vat lieu mao quan trung<br />
binh vdi khoang each of xap xi 40A°. Ket qua XRD cho thiy ciu tnic lap phuong Ia3d vdi<br />
ham lugng san pham cao ciia MCM-48 thu dugc (Hinh 3).<br />
V N U - H i S O e C 05005. Mau MCMW (Lan • )<br />
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Hinh 3: Ket qua nhilu xa tia X ciia vat lieu MCM-48<br />
Ket qua do nhieu xa XRD cua gel tdng hgp da cho mam ZSM-5 trudc khi ket tinh<br />
khdng thay xuat hien pic nhieu xa. Mdt viing nhieu xa nen d khoang 20° dac trung cho<br />
nhieu xa nen cua silieat vd djnh hinh. Ham lugng ZSM-5 them lam mam qua nhd de cd<br />
the xuat hien pic nhilu xa (khdng dua hinh ket qua XRD ciia gel va mam d day).<br />
Hinh 4 cho thay gian dd nhieu xa XRD ciia miu tdng hgp deu bao gdm cac pic co<br />
ban cd cudng do ldn iing vdi gdc 26 la : 8°, 9° va nhdm pic tir 22° - 25° dac trung cho<br />
ZSM-5. Tuy nhien, cac pic nhieu xa 8°, 9° cua mau tdng hgp dugc thap hon nhdm pic 22°<br />
- 25°, trong mau ZSM-5 chuin nhdm pic 22° - 25° cao hon. Cac pic nhieu xa 8°, 9° cang<br />
thap khi so sanh vdi nhdm pic 22° - 25° khi ty le Si/AI trong gel tdng hgp cang thap, dieu<br />
nay lien quan tdi ty le tang len cua Al trong cac mau ZSM-5 tdng hgp dugc. Ket qua cho<br />
thay da thu dugc mau ZSM-5 vdi ty le Si02/Al203 tuong iing vdi ty le ciia gel ban dau<br />
khoang 40.<br />
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VNU-HN-SiEMENSDSOOS-Mau ZecSlc 2SV^5<br />
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lii ir£±tM AMk^V!^-V^<br />
I<br />
2-The(a • Scale<br />
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Hinh 4: Ket qua nhieu xa tia X cua ZSM-5<br />
62 Tdng hop va dac trung vat lifu xiic tie cho phan dng...<br />
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Cac kit qua nhieu xa da X ciia V2O5/MCM-48 va Ti02/ZSM-5 (khdng chi ra d day)<br />
cho thay cac oxit kim loai chuyen tiep tren phan tan diu tren bl mat vat lieu, khdng lam<br />
thay ddi cau tnic hoae bien dang cae vat lieu nen thu dugc va Ti02d dang anatas hoat<br />
dgng.<br />
b. Phd hdng ngogi IR<br />
Cac nhdm dao ddng lien ket cua cac mau ZSM-5 tdng hgp tuong ty mau chuan<br />
trong dai phd hdng ngoai 400 - 1200cm''. Dao ddng ndi tai ciia cac tir dien T-O gdm: dao<br />
ddng hda trj bat ddi xiing ~ 1100 va 1200cm'' (triing vdi viing dao ddng lien ket ngoai tii<br />
dien), dao ddng hda trj ddi xirng 650 - 700cm'' (khdng rd rang), bien dang lien ket T-0<br />
(khdng bj chdng lap). Dao ddng lien ket ngoai tir dien T-O-T gdm: dao ddng vdng kep ~<br />
550cm'' (khdng bj chdng lap), dao ddng hda trj bat ddi xiing - nam chdng trong viing<br />
triing vdi dao ddng ndi tai cua cac tir dien, dao ddng hda trj ddi xirng ~ 790cm'' (Hinh 6).<br />
Ket qua tuong ty thu dugc ddi vdi phd IR cua MCM-48, dao dgng hoa trj ddi xung ~<br />
470cm'', ddng hda trj bat ddi xirng ~ 1106cm"', dao dgng hda tri ddi xirng ~ 790em''<br />
(Hinh 5).<br />
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2CTO<br />
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4000 2000<br />
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Wyrtfiurribeis (crri-1)<br />
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Hinh 5: Pho IR cua mau MCM-48 Hinh 6: Pho IR ciia mau ZSM-5<br />
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2. Tinh chat be mat ciia cac he xiic tac thu du-o-c<br />
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a. Dien tich bi mat theo phuang phdp BET<br />
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Dua vao dudng ding nhiet hip phy - giai hip N2 d -196°C cho thiy miu MCM-48<br />
thu dugc eho hieu qua hip phu cao vdi kich thudc Id khoang 24A°, cd SBET la 360m^g''.<br />
b. Anh TEM vd SEM cua cdc he vat lieu tdng hap duac<br />
Anh TEM ciia miu MCM-48 thu dugc cho thiy cac ciu tnic Id thu dugc cd su sip<br />
xip rit trat ty, ddng diu (Hinh 7). Hinh 8 cho thiy miu ZSM-5 tong hgp chiia cac tinh thi<br />
hinh lye lang, kha hoan thien, day la mdt trong nhirng hinh dang dac trung cua ZSM-5<br />
Kich thudc tinh the ZSM-5 thu dugc kha ldn va ddng diu (kich thudc khoang 2|am). Tuy<br />
nhien, cdn thay mdt lugng nhd gel aluminosilicat vd djnh hinh va tinh the nhd dang hinh<br />
hop chir nhat, hinh dang dac trung ciia tinh the mordenit.<br />
Tuyen tap bio cio Hpi nghi KHCN "30 nim Diu khi Vift Nam: Co hpi mdi, thich thde mdi" 63<br />
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V*,i'7»<br />
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Hinh 7: Anh TEM cua MCM-48 Hinh 8: Anh SEM ciia ZSM-5<br />
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4. Phan li-ng oxy dehydro hoa LPG thanh olefin nhe<br />
Bude dau chiing tdi da khao sat boat tinh xiic tac ciia cac he vat lieu V2O5/MCM-48<br />
va Ti02/ZSM-5 thu dugc bang phan ung oxy dehydro hoa PLG (thanh phan chii yeu la<br />
butan va propan) thanh olefine nhe d 300°C va 400°C. Cac ket qua phan tich tir thiet bj<br />
sac ky khi khdi phd GC-MS HP-6890 cho thay cac san pham olefin nhe la: buten-1,<br />
buten-2, I-propen-2-metyl va mdt sd san pham ndi ddi cd chira oxy. Ket qua chi tiet thanh<br />
phan, ham lugng cac san pham thu dugc se dugc cdng bd d cac cdng trinh tiep theo.<br />
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KET LUAN<br />
Chiing tdi da tien hanh tdng hgp va thu duge eae vat lieu mao quan trung binh<br />
MCM-48 va vi mao quan ZSM-5. Vat lieu MCM-48 duge tim V2O5 va ZSM-5 dugc tim<br />
Ti02. Cac ket qua dae trung cac he vat lieu xiic tae thu duge eho thay cac oxit kim loai<br />
chuyen tiep d dang boat ddng, phan tan tdt, khdng lam thay ddi hoae bien dang cau true<br />
cac vat lieu nen da tdng hgp dugc. Chiing tdi da tien hanh danh gia hoat tinh xiic tae cua<br />
cac he vat lieu thu dugc bang phan iing oxy dehydro hoa LPG thanh olefin nhe. Cac ket<br />
qua ban dau cho thiy cac san pham khi chii yeu cd chiia cac olefin mong mudn.<br />
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TAI LIEU THAM KHAO<br />
1. Bao cao ''Nghien ciru vd dp dung chuyen ddi sic dung nhien lieu truyen thdng sang khi<br />
thien nhien vd LPG". Tdng cong ty Dau khi Viet Nam, 2005.<br />
2. Le Thanh Son, Ngo Kim Thanh, Doan Van Mon, 2005. Synthesis and characterization<br />
of MCM-48. The 2"^* International Symposium on Advance Materials in Asia-Pacific<br />
Rim, p. 114 - 115. Hanoi, April 2005.<br />
3. Luong Van Huin, Le Thanh Son, Hoa Htiii Thu, 2004. Tdng hap zeolit ZSM-5 bdng<br />
phuang phdp gdy mdm. Tap ehi Khoa hgc. So 1, tr. 135 - 140, Dai hgc Qudc gia Ha<br />
Ndi, 2004.<br />
2Z Tong hop va die tru-ng vat lifu xiic t i c cho phan irng...<br />
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4. M.N.B. Sathler, J.G. Eon, 1998. The influence of niobium on the acidity and structure<br />
of gamma-alumina-suppported vanadium oxides. Braz. J. Chem. Eng. Vol. 15, No.<br />
2, San Paulo, June 1998.<br />
5. Nghien cim phdt trien thi truang tieu thu khi/LPG giai dogn din ndm 2005. Tdng cdng<br />
ty Diu khi Viet Nam, 2005.<br />
6. Ryong Ryoo, Sang Hoon Joo, Ji Man Kim, 1999. Energetically favored formation of<br />
MCM-48 from cationic-neutral surfactant mixtures. J. Phys. Chem, 103, p. 7435 -<br />
7440, 1999.<br />
7. Tran Trung Ninh, 1999. ZeoUt ZSM-5, tdng hap ddc trung vd tinh chdt xuc tdc. Luan<br />
an Tiln sy Hoa hgc, Tnrdng DHKHTN, Ha Ndi, 1999.<br />
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