T(ip chi Hoa hoc,
T. 48(6), Tr. 679 - 682, 2010
VAT LIEU ALUMINOSILICAT MAO QUAN TRUNG BINH TCT CAO LANH
PHAN 2 - TONG HOP VA DAC TRl/NG VAT LIEU MAO QUAN TRUNG BINH MSU-S CO THANH CAU TRUC ZEOLIT ZSM-5, BEA TRONG MOI TRl/ONG KIEM
De'n Tod sogn 12-11-2009
PHAM MINH H A O , TA NGOC DON, HOANG TRONG YEM Trudng Dgi hgc Bdch khoa Hd Ngi
ABSTRACT
Mesostructure aluminosilicate materials assembled from ZSM-5 (MFI), beta (BEA) zeolite seeds have synthesized successfully from metakaolin under basic medium. They were characterized by MD, nitrogen adsorption isotherm, TEM, FTIR, TPDNH^. The results exhibu character of the ordered hexagonal mesostructures assembled from ZSM-5, Beta zeolite seeds with the wall thickness of ~8 A, pore size of 38 A, BET surface area of 723m'/g and 700 m'/g, respectively. These materials contain both strong and weak acidic sites.
I - MO DAU
Cac aluminosilicat mao quan trung binh (MQTB) hinh thanh tQ cdc mdm zeolit Y (FAU), ZSM-5 (MFI) va Beta (BEA) da dugc tdng hgp thanh cdng bang qua trinh kit tinh hai budc. Cac qua trinh tdng hgp nay chu yeu sQ dyng cac hod chdt sach. Cdc vat lieu tao thanh cd Mc axit manh va do ben nhiet cao, cd kha nang lam xuc tac va chdt mang xuc tdc trong nhilu phan Qng vdi cac phan tQ cdng kenh.
Hudng nghien cQu su dyng cac ngudn khoang ty nhien lam nguyen lieu cho qud trinh tong hgp loai vat lieu nay da dugc dl cap tuy nhien vdn cdn rat han chi. Trong phdn 1 chung tdi da tong hgp thanh cdng vat lieu MQTB cdu tnic hexagonal thanh mao quan cd cdu tnic zeolit Y (FAU) (ky hieu la MSU-S(PAU)) tQ metacaolanh trong mdi trudng kilm ylu. Trong phdn nay chung tdi tilp tyc nghien cQu su dyng metacaolanh lam nguyen lieu cho qua trinh tdng hgp vat lieu aluminosilicat MQTB cd do trat tu cao, thanh mao quan cd cdu true zeolit ZSM-5;
Beta trong mdi trudng kiem ylu nhd tdc dyng tao cdu tnic ciia chdt hoat ddng b l mat (HDBM) cetyltrimetylamonibromua C, 6H33N(CH3)3Br (CTAB).
II - THUC NGHIEM 1. Quy trinh tong hop
Gdm 2 budc:
a. Tao cac mdm zeolite ZSM-5 (10%A1);
Beta (10%A1) to metacaolanh vdi cac ty le moi tuang Qng:
3,8(TPA,Na)2O.Al2O3.18SiO2.720H2O.
3,8(TEA,Na)2O.Al2O3.18SiO2.720H2O.
Cao lanh nguyen khai mau trdng sau khi dugc Igc rua d l loai bd cdc tap chat dugc hoat hod bang axit HCl 4N d 95°C trong 6 gid, sau dd dugc nung trong khdng khf d 650°C trong 3 gid d l tao metacaolanh. Metacaolanh dugc phdi trgn vdi thuy tinh long, tettapropylamonihydroxyl (TPAOH) (ddi vdi
679
zeolit ZSM-5) va tetraetyllamonihydroxyl (TEAOH) (ddi vdi zeolit Beta), chat tao phQc hilu ca (ky hieu la Co.) vdi ty le moi Me"7Co.
= 1,2 (Me"* la cac cation cd kha nang tao phQc).
Cac hdn hgp dugc lam gia d nhiet do phong trong 96 gid cd khuay trgn lien tuc.
b. Tao ca'u true MQTB tQ cac mdm zeolit trong sy cd mat cua chat HDBM CTAB.
Cac mdm zeolit sau gia hoa dugc phdi trgn vdi dung dich CTAB va dugc dilu chinh bang dung dich axit din pH = 9. Sau dd hdn hgp dugc thuy nhiet d 90°C trong 90 gid. Sau khi Igc rua, say Ifhd cac mdu dugc nung trong khdng khf d 540°C trong 6 gid d l tach chat hoat dgng b l mat khdi mao quan.
Qua trinh chuyen cdc mdu tdng hgp vl dang axit dugc thuc hien nhu sau: cac mdu dugc trao doi vdi dung dich NH4NO3 0,1N theo ty le rdn/ldng = 1/100 (g/ml) trong 6 gid tai nhiet do phdng va khudy trgn lien tyc. Sau dd Igc rQa, sdy khd va nung trong ddng khdng Idif d 540°C trong 6 gid. Qua trinh trao ddi va nung dugc lap lai 2 ldn. Cac mdu tong hgfp dugc ky hieu tuang Qng la MSU-S,MFi) va MSli-S(BEA)-
2. Cac phuong phap dac trung
Gian do nhilu xa tia X gdc be (SAXS) dugc ghi tren may Siemens D5005-Brucker-DQc, su dung dng phat tia X bdng Cu vdi budc sdng CuK„ = 1,54056 A, dien ap 40KV, cudng do ddng dien 40 mA, nhiet do 25°C, gdc quet 2 9 = 0,5 - 10°, tdc do goc quet 0,0257s.
Dien tfch bl mat rieng dugc xac dinh bang phuang phap BET tren may Autochem II 2920.
Anh TEM dugc chyp tren may JEOL 200CX (Nhat Ban) d hieu dien thi 80 KV.
Pho IR dugc ghi tren may hdng ngoai IMPACT FTIR 410 (DQc) theo ky thuat ep vien vdi KBr (ty le 1 mg mau/200 mg KBr), nhiet dd 25''C.
Qua trinh IdiQ hap phu NH3 theo chuang trinh nhiet do dugc tien hanh tren may Autochem II 2920 Micromeritics tQ nhiet do hap phu len 550"C vdi td'c dd gia nhiet
10°C/phut.
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III KET QUA VA THAO LUAN 1. Gian do nhiiu xa tia X goc be
Gian dd nhilu xa tia X gdc be (SAXS) cua cac mdu tdng hgp MSU-S tren hinh 1 deu xudt hien cac pic dac trung cho cac mat phan xa (100), (110), (200), (210) va (300) cua cdu tnic MQTB dang hexagonal. Cac pic dac trung cd cudng do cao va rat rd net chQng td cau tnic hexagonal ciia cac mdu cd do trat tu cao.
(100)
Hinh 1: Gian do SAXS: (a) MSU-S,MFI„ (b) MSU-S, '(BEA)
2. Ding nhiet hap phu va khu hap phu N2
Hlnh 2: Ddng nhiet hap phu - khu hap phu N,- (a) MSU-S,Mn„ (b) MSU-S,BEA,
Cac dudng dang nhiet hap phu va khu hdp phy N2 cua 2 mau khd gidng nhau va thudc loai i v , dac trung cho vat lieu cd cdu true MQTB
Cdc vdng tri dang H2 chQng td rdng cac mao quan hexagonal dugc ndi vdi nhau bdi cac mao quan cd kfch thudc nhd hon tao nen he thdng mao quan cdu true khdng gian 3 chilu. Cdc mao quan nhd nay cd thi dugc hinh thanh tQ cac mam zeolit nam tren thanh mao quan.
Dudng phan bd' kfch thudc mao quan cho thdy kich thudc mao quan rdt tap trung d 3,8nm.
Chilu day thanh mao qudn (t^^ii) tfnh theo SAXS xdp xi 8 A, nhd han kfch thudc tinh the cua cac tinh thi zeolit vi vay khdng cd kha nang tao ra cac tinh thi tren thanh mao quan ma d dd chi cd thi chQa cac lien kit cua cac tQ dien Si04 va AIO4' kilu vdng kep 5 canh (D5R) cua cdu tnic MFI va BEA.
3. Anh hien vi dien tut truyen qua TEM
Hinh 3: Anh TEM (a) MSU-S(MFI);
( b ) MSU-S(BEA)
Anh TEM tren hinh 3 cho thdy cac mdu tdng hgp diu cd cau tnic hexagonal rdt trat ty.
Ket qua phan tfch dnh TEM hoan toan phu hgp vdi kit qua xac dinh tQ gian do SAXS.
4. Pho hap thu hong ngoai IR
Sy ton tai cua cdu tnic zeolit MFI va BEA tren thanh mao quan cua cdc mdu tdng hgp dugc xac nhan tQ pho IR tren hinh 4.
Phd IR cua MSU-S, '(MFI) v a MSU-S(BEA) k h d
gidng nhau. Vung hap thy hdng ngoai vdi cudng dd ylu d -565 cm"' dac trung cho dao ddng vdng kep 5 canh (D5R) cua ca'u true zeolit MFI va BEA. Dam pho d -796 cm"' dac trung cho dao ddng ddi xQng cua lien kit T-O-T trong cau true zeolit ZSM-5 va beta.
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1 2 3 0 ^ NlOSj/
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1965 796
798
566
565 \46(/
460
1300 1000 800 600 400cm-'
So song
Hinh 4: Phd IR: (a) MSU-S(Mn), (b) MSU-S(BEA)-
Ngodi ra, hai dam phd d 965 cm"' va -1230 cm"' dac trung cho dao dgng bat ddi xQng cua lien kit T-O-T. Dilu nay chQng td sy tdn tai cua cdu tnic zeolit ZSM-5 va BEA tren thanh mao quan. Vi vay se lam tang do bin nhiet va Mc axit cua cdc vat lieu.
5. Gian do TPD-NH, cua MSU-S, (FAU)
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(a) (b) Hinh 5: Gian do TPD-NH3 (a) MSU-SfMn,; (b) MSU-S(BEA)
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Bdng 1: Dac trung tam axit cua vat lieu
Mdu
MSU-S,MFi, MSU-S,BEA)
Dac trung tam axit T
*-max
°C 187 190
Mat do mmol NH3/g
0,013 0,013
T
°C 419 422
Mat do mmol NH3/g
0,056 0,047
T
"C 538 543
Mat do mmol NH3/g
0,008 0,002
Gian do TPD-NH, cua cac mdu MSU-S dang H"^ tren hinh 5 xdc dinh su phan bd ciia 3 vung giai hap phy NH3 tai cac khoang nhiet do -190°C, 420''C vd 540°C tuong Qng dac trung cho cdc tam axit yeu va manh. Bang 1 cho thay cac vat lieu MSU-S dang axit chu ylu chQa cac tam axit manh Id do chQa cdu tnic zeolit ZSM-5 va beta ttong thdnh mao quan. Cac dac trung vat lieu MSU-S dugc trinh bay trong bang 2.
Bdng 2: Kit qua dac trung cua cdc vat lieu MSU-S
Mdu
MSU-S,MF„
MSU-S(BEA)
Cdu tnic hexagonal hexagonal
d(ioo)
A 40,0 39,7
^pore
A 38,0 38,0
twall
A 8,2 7,9
SBET
mVg 723 700
V
'^ pore
cmVg 0,90 0,87
Tam axit mmol NH3/g yeu
0,013 0,013
manh 0,065 0,049 IV - KET LUAN
Vat lieu MQTB MSU-S dang hexagonal thanh mao quan cd cau tnic zeolit ZSM-5 vd Beta da dugc tdng hgp thanh cdng tQ metacaolanh bdng phuang phap kit tinh hai budc trong mdi trudng kilm ylu vdi tac nhan tao cau tnic CTAB.
Cac vat lieu dugc dac trung bdng cac phugng phap hod ly hien dai: SAXS, BET, TEM, FTIR va TPD-NH3 cho thay MQTB cau tnic hexagonal cd do trat tu cao vdi kfch thudc mao quan tap ttung d 38 A, chilu day thanh mao quan 8,2 A, bl mat rieng SBET cua MSU- S(Mn) va MSU-S(BEA) Mung Qng la 723 mVg va 700 mVg, thi tfch mao quan Vp„,e tuang Qng la 0,90 cmVg va 0,87 cmVg, cac vat lieu chu ylu chQa cdc tam axit manh do sy cd cau tnic zeolit trong thanh mao quan.
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