TAP CHI HOA HOC T. 50(1) 1-4 THANG 2 NAM 2012
TONG H g p XUC TAC VzOg/SiOz KJCH THLFaC NANOMET BANG PHU'aNG PHAP D 6 T C H A Y GEL
Luu IVlinh Dai, Dao Ngoc Nhiem, Vu The Ninh, Pham Ngpc Chuc Vien Khoa hgc Vdt lieu, Vien Khoa hoc va Cong nghe Viel Nam
Den Toa soan 28-!l-2008 Abstract
Catalysis nanosized ViOs/SiO^ powder has been synthesised at SSCC by the combustion of gel prepared from polyvinyl alcohol (PVA) and vanadium nitrates. ViOs/SiO^ characterization is examined by X-ray diffraction (XRD), scanning electron microscopy (SEM) and BET (Brunaiire-Emmet-Teller) measurements. Further thermal treatment at 550°C for 1.5 hrs yields the single phase of V1O5 Average particle size of ViOs is 80 nm and specific surface area of V.Oj/SiO: is 13,50 m-/g.
1. MO DAU
Mang mong vanadi oxit la mgl trong so cac vat lieu c6 nhieu tinh chat da dang va nhieu ung dung trong thirc tien, trong cac linh kien vi dien tiJ. quang dien, hien thi dien sac, senso khi mang mong. Viec che tao mang mong vanadi oxit don pha, diing thanh phan hpp thue va cau true tinh the la khong dc dang bdi vi vanadi la nguyen to kirn loai chuyen tiep co kha nang lien kcl vdi oxi duoi dang nhieu hda tri khac nhau (tu 1 den 5). ViOj cung dugc dung lam XUC tac trong qua trinh khii' xiic tac chpn Ipc ichi NO, a cac nha may dien va cho nhieu phan irng tong hgp liij'u CO. V3O; cung du'O'c ung dung trong san xuat hpp kim Ferro Vanadi. Hang ELEX do che tao cac thiet bi XUC tac tren ca sd he xijc tac ViO^ de khii cac nita oxil tir nam 1988.
Chat XUC tac cung tham gia phan huy cac chat dioxin vCT! hgp chat tieu bieu la 2,3,7,8- tetrachiorodibenzo-o-dioxin va furan vdi hgp chat tieu bi^u la2,3,7,8-tetraclorodibenzo-furan [1-4].
Trong bai bao nay se trinh bay nliung ket qua nghien ciiu tong hgp V1O5 co kich thudc nanomet tren SiO: b^ng phirong phap dot chay gel. Phuang phap nay da su dung de dieu che mot so cac oxil dat hi^m, oxit kim loai chuyen tiep va cac vat lieu chira cac oxit dSt hi^in, oxit kim loai chuyen tiep c6 kich thudc nanomet [5-7].
2. THU'C NGHIEM 2.1. Hoa chat, dung cu
NHjVO^, HNO,, NH4OH, PVA (polyvinylalcol), glycerin, EDTA, H2O2 deu co do sach phan tich.
- Coc chiu nhiet 100 mi, 250 mi, binh tam giac 250 mi, 500 mi, 6ng dong 250 ml, 500 ml, binh djnh muc 100 ml, 500 ml, 1000 ml, pipet, buret, dua Ihiiy tinh, 16 nung, tu say, bep dien, may khuay tu' gia nhiet, may do pH va mot so vat dung Icliac 2.2. Phu'O'ng phap nghien cuu
Trgn dung dich V(N03)5 vai PVA theo li le moi luang irng, hoa tan trong nuac roi lam bay hai 6 nhiet do thich hgp cho den khi tao gel dong nhat, mau xanh la ma. Cho mgt lugng SiOi vao gel, khuay deu, say kho gel va xu ly nhiet. Thu dirge bot xop mau vang da cam.
Gian do phan tich nhiet dugc ghi tren may DTA- 50 va TGA-50 cua hang Shimadzu (Nhat Ban).
Gian do nhieu xa Ranghen dugc thirc hien tren may Siemens D-SOOO (CHLB Dire) vai birc xa CuK„
budc song X = 1,5406 A.
Anh vi cau true va hinh thai hgc cua bot exit dugc chiip bang hien vi dien tii' quet (SEM) JEOL- 5300 (Nhat Ban).
Dien tich be mat dugc do bang phuong phap BET (Brunauer-Emmet-Teller) tren may SA ciia hang COULTER (My).
Xac dinh thanh phan hoa hgc bang phuang phap khoi lugng va phuang phap hap thu nguyen tir 6800 (Nhat Ban),
3. KET QUA v A T H A O LUAN 3.1. Phan tfch nhiet
Gian do phan ti'ch nhiet ciia gel dugc chi ra a hinh 1. Tren pho TGA (la) tir 59,2 dan H S T c6 su 1
TCHH,T. 50(1), 2012
giam khoi icm (61,94%) day chinh la qua trinh mat nuac k^t tinh va mgl ph4n nho HNO3 con du trong dung dich muoi ban dau, ling vai mot hieu irng thu nhiet a 5 9 ^ tren ph6 DTA (lb). 6 474,57°C co mgt pic giam kh6i lugng (24,55%) tren duang DrTG, day chinh la qua trinh phan huy hidrocacbon trong phan tir PVA va g6c NOj. C) 507''C co mot pic toa nhiet kha lan (tren ducrng DTA, hinh lb). Do chinh
Liru Minh Dgi va cgng su- lk nhiet phan ung oxi hoa cua cac san pham phan huy hidrocacbon. Khi nang nhiet do Ion han 507°C thi khong co sir thay doi v6 khOi lugng va khong xuat hien mot pic dac trung cho mgt qua trinh chuyen pha nao, co the gan cho su tao thanh V205/Si02 tinh khi6t. Do do, nhiet do 550°C da dugc chon de tong hgp cac mau tiep theo.
Thential Analysis Dala
Hinh }\ Gian do TGA (a) va DTA (b) ciia gel V^^- PVA/SiOj
3.2. Anh hu'ong cua thoi gian ngam tam Mau dugc tong hgp bang each hoa tan mgt lugng PVA vao nuoc a nhiet do thich hgp den khi tan het tao thanh he trong suot, a pH = 4, giu nhiet a Z(fC trong 4 gid. Cho mgt lugng dung dich V^' vao he tren de tao gel dong nhat V-PVA cd mau xanh
(vdity le moj V/PVA - 1/3). Sau do cho SiOj vao khuay trgn d€u trong 15 phut, Thdi gian ngam tlim dugc thay ddi tir 2, 4, 6, 8, 10 va 12 gid. Mau dugc xu ly nhiet d 550°C trong 1,5 gid de thu dugc san pham la vat lieu V2O5 co kich thudc nanomet tren chat mang Si02. K8t qua dugc chi radbang 1.
Bang 1: Anh liirdng Thai gian, h
% V20i/SiO,(% lihoi lircmg)
cua tlioi gian 2 1,00
den ham lagr
%
1,30
g % cua V2O5 trong mai 6
1,40 8 1,45
V,0s/Si02 10 1,48
12 1,50 Phan tram khdi lugng ciJa V2O5 tren chat mang
SiOi tang dan theo chieu tang ciia thdi gian ngam tam va thay doi khdng nhieu sau 10 va 12 gid (%ViOs = 1,5%). Do dd 12 gid la thdi gian dugc chon de dieu che cac mau nghien cuu tiep theo.
Cac ket qua bang 2 cho thay % khoi lugng ViOs tang dan theo so ian ngam tam va sau 3 lan ngam tam gan nhu dat bao hoa (%V205 = 2,5%). Do vay, cac nghien ciiu tiep theo so l4n ngam tam duac chon la 3,
i.i. Anh hu'd'ng cua so lan ngam tam
Mau dugc tong hgp tuang tu nhu tren vdi thdi gian ngam tam la 12 gid, sd lan tam thay ddi tii' 1 den 4 Ket qua dugc chi ra d bang 2.
3.4. Qui trinh tSng hgp W^O^SxOi
Cac dieu kien dugc chon de tdng hgp V205/Si02 la thdi gian ngam tam 12 gid, nhiet do nung d 550°C, thdi gian nung 1,5 gid va qua trinh ngam tam dugc lap lai 3 lan. Xuc tac V2O5 c6 kich thudc
TCHH,T. 50(1), 2012
nanomet phu tren SiOi da nhan dugc theo quy trinh sau (hinh 2).
Tong hap xuc tac V20i/Si02
Bang 2: %V205 tren nen Si02 sau cac lan ngam tam So lan
%V2O5/Si02(% khoi lugng)
Lan 1 1,50
Lan 2 2,20
Lan 3 2,50
Lan 4 2,60
v(No,)5 5 cr"'°j)
ffln/j 2: Qui trinh t6ng hop V;O5/Si02
Mau diSu ch6 dugc xac djnh thanh phan pha bjng phuong phap nhilu xa tia X va hinh thai hgc bjng hi6n vi dien tii quet (SEM) JEOL-5300 (Nhat Ban). Kgt qua dirge trinh bay a hinh 3 va 4.
i • • •
• 1. 1 1 •
Hlnh 3: Ph6 nhilu xa tia X cua mau V205/Si02 3
T C H H , T ^0(11,201:
-zmr
- 7 ^ . ^wmmmmsmx^ i::::.
Hinh 4: Anh vi cau triic va hinh thai hgc ciia V . O s / S i O .
Hinh 3 va 4 cho thay mau thu d u g c van co kich t h u d c nanomet ddng nhat - 5 0 - 8 0 nm vdi dien tich be mat rieng la 13,50 m 7 g va chira pha duy nhat la V3O5,
4. K E T LUAN
Da xay d u n g quy trinh tong hgp V205/Si02 co kich thudc nanomet bang p h u a n g phap dot chay gel vdi mgt sd dieu kien toi uu: thdi gian ngam tam \2 gid, thdi gian nung 1,5 gid, nhiet do nung 550°C va sau 3 lan ngam tam V2O5,
(%V205 = 2,5%) CO kich t h u d c nanomet ddng
Lim Minh Dai va cong siv nhat - 5 0 - 8 0 nm vdi dien tich b^ mat rieng la 13,50 m"/g, c h u a pha duy n h i t la V2O5.
TAI LIEU THAM KHAO
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Technical Proceedings of Nanotechnology Conference - Nanotech 2004, 3, 496-498 (2004) 2 Bhushan Editor. Handbook of Nano - Technology
(2007).
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5, Phan Van Tudng, Cdc Phuong phdp Tong hap Vat hen Gdm, DHKHTN-DHQGHN (2004) Luu Minh Dai, Nguyen Xuan Dung, Dao Ngoc Nhiem. Tong hop perovskit LaanCeo^CrO} bang phuong phdp ddt chay gel. Tap chi Hoa hpc, 46(2A), 37-42 (2008).
Luu Minh Dai, Dao Ngpc Nhiem, Vu The Ninh, Nguyen Thi To Loan. Tdng hop MnOi kich thuac nanomet hang phuong phap hoc chdy gel vd nghien cini khd nang sir dung Mn02 kich thuac nanomet de hap phu asenic. Tap chi H6a hoc, 46(2A), 43-48 (2008)
Lien he: L y u M i n h Dai Vien Khoa hgc Vat lieu
Vien Khoa hoc va C o n g nghe Viet N a m 18 H o a n g Q u d c Viet, Cau Giay Ha Ngi.
