TAP CHI IIOAHOC 1.50(1)9-13 THANG 2 NAM 2012
T O N G H O P V A T L I E U MAO QUAN TRUNG BJNH MCM.41 BIEN TJNH LAW! x u c TAG CHO PHAN UNG OXI HOA HOAN TOAN PHENOL
BANG H2O2
Nguyen Van Bang
Khoa Hoa hoc. Tnrang Dgi hoc Sir phgm Lid Not 2, Xiidn Hoa, thi xd Phuc Yen, tinh Vinh Phuc Email: ngtiyenvanbang@yahoo com
Ddn Tda soan 27-01-2011
Abstract
MCM-41 have been attracted much attention of scientists from the first synthesis since 1992. This material also possesses large surface area, which can reach more than 1000 m~g"'. Especially, the pore diameter of this material could be easily controlled withm mesoporous range between 1 6 to 10 nm by adjusting the synthesis conditions and/or by employing surfactants with different chain lengths in the preparation. Commercially available template cetyl trimethyl ammonium bromide (CTAB) is usually used to synthesize MCM-41, Nowadays, heterogeneous ferrit catalyst is developed using the mesoporous molecular sieve MCM-41 as the catalyst support. Ferrit was impregnated onto the support. The above materials were characterised by XRD, TG-DTA, TEM and BET The obtained results showed that MCM-41 presented surface area of 1002.57 m"g'', pore diameter of 3 5 nm and highly ordered structure The structures of mesoporous material supported metal oxides were not changed Their catalytic activities were evaluaied by the oxidation reaction of phenol in the presence of hydrogen peroxide.
1. MO DAU
Tir nhung nam 90 ciia the ky 20, val lieu mao quan trung binh da thu hut dugc su quan tam rat Idn lir cac nha khoa hgc do ung dung ciia chiing ngay cang tang trong cac ITnh vuc xiic tac, hap phu va xir 1>' mdi trudng [1-6]. Vdi dien tich be mat cao, he thong mao quan trat tu va tinh axit be mat cd the dugc dieu chinh la nhu'ng tinh chat rat quan trgnj cua vat lieu mao quan trung binh dugc irng dung trong cac qua trinh cracking xiic tac, cac phan irng este hoa va nhieu qua trinh khac ddi hdi cac xiic tac axit [ I ]. Trong cac loai vat lieu mao quan trung binh, val lieu MCM-41 (thudc hg M41S, cSu triic khdng gian p6mm) la vat lieu ran xdp bao gdm cac mao quan sap xep deu dan, dan vj cau true ca sd cd dang luc lang 6 canh [4]. Tam quan trong ciia vat lieu nay phli thudc vao do Idn ciia dudng kinh mao quan, do day cua thanh mao quan va dien tich be mat. Do Idn ciia dudng kinh mao quan ciia vat lieu MCM-41 cd the dugc dieu chinh bang each su dung cae chat hoat ddng be mat cd kich thudc phan tir khac nhau hoac/va cac chat hiru ca ddng vai trd la chat trg cau triic trong qua trinh ket tinh hoac qua trinh xir ly thuy nhiet. MCM-41 cd do ben nhiet va do ben thiiy nhi?t cao trong khdng khi va trong hai nude chira oxy nhung do ben thuy nhiet ctia chiing thap trong nude va Irong dung djch nude. Nhu vay, vat lieu MCM-41 r^t thich hgp cho irng dung lam chat mang
xiic lac. Trong bao cao nay, chimg tdi da lien hanh tdng hgp MCM-41 lam nen va mang len nen nay sat (ill) oxit vdi cac ham lugng khac nhau de thu dugc xiic tac oxi hoa hoan toan phenol trong su c6 mat eiia II2O2.
2. THUC NGHIEM Ig Tong ho'p vat lieu MCM-41
Vat lieu MCM-41 duge tdng hgp theg quy trinh nhu d cdng trinh [5].
Tdng hop vat lieu Al-MCM-41
Chuan bi dung djch A: Hda tan 2,31 g CTAB vag 22,5 ml H26 va 18 ml C2H5OH, khuSy 6hu trong 30 phiit. Them 18 ml dung dich NaOH 0,02 M vao dung djch A, sau dd sir dung NHiOH 25% dieu chinh de pH ciia dung dich bSng 11. Chuan bi bdn hgp B Hda lan 0,1345 _g Al(OC3H7)3 vao 5 ml H2O va 10 ml C2H5OH. Lay 6 ml TEOS 98% hda tan vao bdn hgp B, khuay deu trong 30 phiit dugc hon hgp C. Nhd tir tir hon hgp C vao dung djch A, khuay deu 3 gid va duy tri pH cua dung djch b^ng 11 nhd NH.,OH 25%.
U hdn hgp 48 gid trong autoclave d t° = 150''C, Lgc, nia den pH = 7. Say khd d 80-90"C Nung 4 gid trong ddng khdng khi d SSO^C. Ket qua thu dugc vat lieu Al-MCM-41 dang bgt mjn mau traqg.
TCHH, T, 50(1), 2012
T6ng ho-p vat lieu Fe20j/MCM-4I va FejOj/Al- MCM-41
Can 7,575 g Fe(N03)5,9H20 va hda lan trong mdt elanol vira dii Nhd tirng it 1 dung dich tren vao Ig MCM-41 (Al-MCM-41), trdn dSu va lam kho d 60"C, Tiep tuc qua trinh cho den khi diing het lugng dung dich muoi sat (III) d tren. Nung vat lieu da say khd d 550''C trong 4 gid. Ket qua ta ihu dugc vat lieu Fe203/MCM-41 va Fe203/Ai-MCM-41 dang bgt mui mau dd tham vdi ham lugng 1 5% Fe203.
3 KET QUA V A T H A O LUAN
Da tien hanh ghi phd nhieu xa tia X (XRD) ciia mau MCM-41 va Al-MCM-41 tdng hap dugc tren may SIFMEN D5005 (Trung lam Khoa hoc Val lieu, Khoa Vat ly, Trudng Dai hpc Khoa ligc Tu nhien - DIIQG Ha Ngi). Tir gian do nhieu xa cho thay vat lieu MCM-41 xuat hien 1 pic nhgn d viing 20 ~ 2"
dac trung cho mat 100 (dioo ~ 41.946 A). Co 2 pic xuat hien d vimg 20 ~ 3,7° dac trung cho mat 110 (d||o ~ 23, 121 A) va 20 = 4,4° dac Irung cho mai
Nguyen Vdn Bdng 200 (daoo ~ 20,85 A) (hinh la), Cac phan xa nay dac trung cho cau true hexagonal ciia MCM-41. Ket qua nhieu xa tia X chimg minh rang MCM-41 da dugc tdng hgp thanh cdng. Cac pic dae trung ciia val lieu nay cd cudng do idn, nhgn chirng to vat lieu tong hgp dugc cd dg tinh the cao va rat trat tu. Kel qua nhieu xa tia X d cac gdc idn han 10" cho thay khdng tdn tai cac pha tinh the. do dd cd the khang dinh rang cau triic thanh Id xdp ciia MCM-41 la vd dinli hinh.
Dieu nay phii hgp vdi cac tai lieu tham khao.
Tren gian dd nhieu xa tia X ciia mau Al-MCM- 41 (hinh lb), xuat hien 1 pic cd eudng do Idn va ro net d viing gdc hep 2Q ~ 2,3" dac trung cho mat 100 CO dioo ~ 38,23 A, dd ta dau hieu dac trung cho cau triic mao quan trung binh ciia vat lieu Day la val lieu gia linh the cd cau true mao quan trat lu, nhirng thanh mao quan vo djnh hinh. Ngoai ra tren gian dd cdn xuat hien 2 pic c6 cudng do yeu han d viing 26 ~ 4°
dac trung eho mat i 10, duo ~ 22,113 A va d 28 = 4,6"
dac trung cho mat 200, dioo ~ 19,26t A. Cac pic tren gian dd deu hep chiing td vat lieu tong hgp dugc co do trat tu cao, Cac ket qua nay cho thay da tdng hgp duac val lieu Al-MCM-41 cd cau triic luc lang.
(a) (b) Hinh I: Gian dd nhieu xa tia X ciia mau MCM-41 (a) va Al-MCM-41 (b)
Tir cac ket qua ghi phd nhieu xa tia X ciia cac val lieu MCM-41 va Al-MCM-41, chiing tdi da tien hanh xac dinh dien tich be mat rieng va phan bd dudng kinh mao quan bang phuang phap do hap phu
\a giai hap nita tren Ihiet bi ASAP 2000 tai Trung tam Hda dau va Vat lieu xiic tac - Trudng Dai hgc Bach khoa Ha Npi, Dudng cong hap phu va giai hap ciia Ai-MCM-41 dugc Irinh bay tren hlnh 2, Tir hinh 2 cho thay dudng cong hap phu - giai hap nita gidng kieu IV - irng vdi suhap phu \al ly nhieu Idp ciia vat lieu mao quan trung binh, Dudng hap phu va dudng giai hap nita khdng triing nhau va tao nen dudng cong tre tuong ung vdi dac trung ciia vat lieu mao quan Irung binh (mesopore) theo dinh nghTa ciia lUPAC. Viec xuat hien dudng cong tre dugc giai thich la do \al lieu hap phu cd dang mao quan trat lu. cd dang hinh tru hd hai dau. cac mao quan nay
kha ddng nhat, tuy nhien van co sir sai khac ve hinh dang va kich thudc, vi vay chiing duac \kp dSy hoac giai_phdng chSt hi hap phu tai cac ap suat khac nhau, kiiien cho 2 nhanh hap phu va giai hap tao nen vdng tre va nam nghieng so vdi cac true Iga do, Tiiy thudc vao hinh dang mao quan ma vdng tre cd th6 cd cac hinh dang khac nhau. Dien tich be mat rieng BET eiia vat lieu MCM-41 SBET = 1002,57 mVg, thS tich Id xdp 0.881 cmVg, dudng kinh mao quan d = 35.18 A. Dien tich b% mat rieng BET cua vat lieu Al- MCM-41 SBET = 948,92 mVg. the tich Id xop 0,834 cm/g, dudng kinh mao quan d = 35,14 A
Da tien hanh chup anh TEM ciia cac val lieu Fe203/MCM-41 va Fe203/Al-MCM-41 (sau khi nung d 500°C trong 4 gid) tren thiat bj JEM-1010, t^i Vien ve sinh dich tl Trung uang vdi dien thi gia tdc 80 kV, do phan giai 2 A, mau dugc chuSn bj tren
TCHH. T. 50(1). 2012
ludi ddng phii cacbon 300 mesh. Ket qua thu dugc dugc chi ra tren hinh 3. Anh chup cat ngang cho ta thay vat lieu tdng hap dugc cd do trat tir rat cao, mieng mao quan cd dang td ong vdi d ca sd la hinh luc lang (hexagonal) rat deu dan. dudng kinh mao quan vat lieu khoang 35 A, be day thanh mao quan khoang 14 A Ket qua nay phii hgp vdi kich thudc Id duge tinh theo BET Anh ehup eat dgc cho ta thay MCM-41 va Al-MCM-41 cd cau triic dng thang, tao thanh cac bd ddng deu song song vdi nhau. Hinh anh TEM chup cat dgc vat lieu Fe20i/MCM-4I cho
Tong hop vdt lieu mao quan trung binh...
chimg ta thay cac hat Fe203 ton tai d dang cluster tren be mat vat lieu chat mang cd cau true dng thang ddng deu, song song vdi nhau. Anh TEM chup cat ngang vat lieu giiip ta thay dugc cac hat Fei03 da tham nhap sau vao trong mao quan va phan bd tuong ddi ddng deu. Nhu vay, cd the khang dinh rang qua trinh tam oxit Fe203 len vat lieu mang da dugc thue hien thanh cdng. Ket qua la eac hat Fe203 phan bd ca tren be mat vat lieu chat mang va tdn tai ca trong mao quan.
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Hiiili 2 nmiiiy h;ip pliii va giai hap ciia vat lieu Al-MCM-41
' tfMirrriii iMtiiM 111
100 nm 100 nm
(a) (b) Hinh 3. Hinh anh TEM cua cac mau Fe203/MCM-41 (a) va Fe203/Al-MCM-41 (b)
Tir hinh anh chup TEM ciia vat lieu Fe203/Al- MCM-4I, ta cung thay duac ket qua luangtir, cac hat Fe20i phan bd ca Iren be mat vat lieu chat mang va tdn lai ca trong mao quan.
Sau khi tdng hgp va dac trung cac vat lieu, chiing tdi da tien hanh khao sat hoat tinh xiic tac ciia eac vat lieu Fe203/MCM-4l va Fe203/Al-MCM-41.
Phan irng dugc thue hien vdi 50 ml phenol 0,01 M
TCHH,T. 50(1). 2012
tuong irng vdi COD 2191.06, 52.5 ml H.O. 0.2 M va 0.1 g chat xiic lac trong 2 gid. Lugng H2O2 su dung d day bang 1.5 lan lugng H^O? l>' luang de oxi hda hoan toan phenol thanh CO: va HiO. Cac yeu to anh hudng den phan irng duac khao sat la nhiet dp va 16c do nhd giot H-Oj. Ket qua thu dugc duge trinh bay trong bang 1
Tir ket qua trong bang 1 cho thay, tai ciing mpi nhici do tien hanh plian irng, khdng cd su khac biel
Nguyen Vdn Bang nhieu ve do chuyen hda COD ciia hai mau xiic tac.
Trong cac nhiet do dugc khao sat, ta thSy d nhiet do 70X. xiic tac boat ddng cd hieu qua nhat va dp chuyen hda COD cung la Idn nhat. Nhu vay de hieu qua xir ly phenol dugc cao, chiing ta can tiSn hanh phan ung d khoang nhiet do 25-70'^C Neu nhict dp tien hanh phan irng qua cao thi H2O2 se hi phan hiiy thanh 0x1 va nude, dieu nay khdng cd Igi cho phan irng oxi hda phenol.
Bang 1 Anh hudng ciia nhiet do den dp chuyen hda COD
^ ' " ^ - ^ ^ Xiic lac Nhiet do, T ^ ~ ~ - ~ > ^
25 50 70
COD sau x u ly, nig/1 F c , 0 , / M C M - 4 1
1795,16 933.81 537.99
F e : 0 , / A l - M C M - 4 1 1872.44 1028.06 620.78
Dp chu>en hoa C O D , % Fe20,/MCM-41
21,72 59,28 76,54
F e , 0 , / A l - M C M - 4 1 18.35 55.17 72,93 Dua tren ket qua khao sal \e sir phu Ihuoc ciia
dp chuyen hda COD vao nhiel do, phan irng dugc lien hanh tiep tuc vdi hai mau xiic tac tai ciing nhiet dd 70"C, khoi luang xtic lac m = 0.1 g. Ket qua duge trinh bay trong bang 2.
Tir ket qua ciia bang 2, ed the thay rang hieu qua chuyen hda COD la Idn nhat khi H2O2 dugc nhd gipl lir lir, Ihat cham, kill do lugng H^Oi cho vao mdi dugc sir dung hieu qua, gtam thieu lugng H2O2 bj phan huy thanh nude va oxi, khi dd luang gdc tir do hydro.xyl *OI-I sinh ra se khdng dii dc oxi hda hoan loan plienol hay cac hgp chat huu co trung gian
thanh CO: va H2O. Ket qua tir viec tien hanh phan irng khi cho toan bd lugng HiOi vao binh phan irng ngay lu dau cho thay lugng HiO; sir dung la kem hieu qua. muc do chuyen hda COD khong nhii}u va kem han khi lugng ILOi dugc nhd gigt tir tir trong qua trinh phan ung, nguyen nhan la do luang HiOi ban dau la luang ddi Idn, lai dugc dua vao phan irng ciing mdt liic d nhiet dd cao 70''C. cd the cd mpt lugng dang ke HiOi chua kip sinh ra cac gdc lu do hydroxyl *OH ma da bi phan hiiy thanh oxi va nude Nhu vay phan ung oxi hda phenol bj giam hieu qua
Bang 2: Anh hudng ciia Idc dp nho giot den H2O2 dp chuyen hoa COD
^^"--^^^ Xiic tac Foe do nho ^"'^---.^^
gigt H , 0 , , m l / p h i i t ^ ^ ^ ^ 0,45
0.6 1 Cho H i O , vao ngay tt'r dan
COD sau xu ly, mg/1 F e , 0 . / M C M - 4 1
350,18 467.36 692,33 1248.21
F e , 0 , / A l - M C M - 4 1
429,98 542,35 808,14 1430,53
Do chuyen hoa COD. % Fe203/MCM-41
84,73 79,62 69,81 45,57
Fe,0j/Al-MCIVl-41
81,25 76,35 64.76 37,62 4 KETLUAN
Da tdng hgp thanh cdng vat lieu mao quan Irung binh MCM-41 va Al-MCM-41 tir ngudn nguyen lieu dau TEOS, ngudn nhdm la nhdm isopropylat va chSt hoat dgng be mat xetyl trimetyl amomum bromua CTAB Thue hien thanh cdng qua trinh phan tan Fe^O; len he thdng mao quan ciia chat mang MCM- 41 va AIAlCM-41 (vdi ham luoTig 15%) bSng phirang phap lam ankox\t kim loai len nIn va su dung cac phuang phap phan tich hoa ly hien dai dl dac trung cau true \a xac dinh linh chat be mat ciia
cae san pham Ihu dugc, Cac kit qua nghien ciru bang phuang phap hip phu - giai hap nita (BET) cung da xac djnh dugc dien tich bl mat r4l phii hgp vdi kit qua phan tich XRD va BET. Kit qua nhieu -xa tia X d gdc rdng chung minh rSng Irong qua trinh lam, Fe203 da duac giai deu tren bl mat thanh mao quan ciia vat lieu MCM-4 1 va Al-MCM-41.
Tien hanh khao sat boat tinh xiic tac ciia cac m^u 15%Fe203/MCM-41 va 15%Fe203/AI-MCM-41 trong phan irng oxi hda phenol bang tac nhan oxi hda HiOi trong dung dich nude. Phan irng 0x1 hda phenol cho do chuyin hda COD va phenol kha cao.
TCHH, T. 50(0,2012
xuc tae trien vgng trong xir ly cac chat hiju ca dgc 3 hai cd kich thudc Idn trong nude.
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Lien he: Nguyen Van Bang
Khoa Hda hgc, Trudng Dai hgc Su pham Ha Ngi 2, Dudng Nguyen Van Linh, Phudng Xuan Hda, Thi xa Phiic Yen, Tinh VTnh Phiic Email: nguyenvanbang(§yahoo.com.
