Hoi nghi Khoa hoc ky'''' niem 35 ndm I ''''iin Khoa hoc vd Cong nghe Viet Nam Hd Noi 10 2010 CAC CHAT XUC TAC X\f LY 6 NHIEM MOI TRlTONG Luu Cam Loc Viin Cdng nghi hda hgc, Vien Khog hgc vd Cdng nghe Viet N[.]
Hoi nghi Khoa hoc ky' niem 35 ndm I 'iin Khoa hoc vd Cong nghe Viet Nam - Hd Noi 10 2010 CAC CHAT XUC TAC X\f LY NHIEM MOI TRlTONG Luu Cam Loc Viin Cdng nghi hda hgc, Vien Khog hgc vd Cdng nghe Viet Ngm I Mgc Dinh Chi Q I, TP Hd Chi Minh Emgil; lclgc(a)yasl-hcm ac Tom tat: nhiim mdi truimg trd thdnh vdn di cdp bdch hien cho tdt cd cdc nude Chuyin hda xiic tdc Id phuang phdp phdn hiiy cd hiiu qud cdc chdt ddc nhdm ddp ung tiiu chudn thdi Xuc tdc oxi hda sdu vd kbit dugc chia thdnh hai nhdm; kim logi vd oxh kim logi Kim logi qui dugc biit din nhu xiic tdc hogt linh egg chg qud trinh gxi hdg sdu vd dugc sir diing rdng rdi trgng ldm sgch Oxil kim hgt Id xiic tdc thay thi chg kim Iggi qui Hogt ciig oxit kim logi khdng thi sdnh kip kim Iggi qui vdi vgi trd Id xuc tdc oxi hdg sdu, nhung thim lugng nhd kim loai qui vao hdn hgp oxil kim logi ldm Idng ddng ki hggt tinh xiic tdc Oxi hdg nhiit dd thdp vd quang axi hda la cdc qud Irinh xit ly mdi Irudng tien tiin cita tuang lai Abstract: Environment pollution became now gn urgent prgblem for all the countries Catalytic conversion can effectively destruct toxic compounds in air to meet stringent environmental regulations Active catalysts for complete oxidation and reduction could be divided into hvo groups; metallic catalysts and metal oxide ones Noble metals are known as very active catalysts in complete oxidation and widely used for purification of exhaust gases Metal oxides are an alternative to noble metals as catalysts for total oxidation As a single component, base metal oxide catalyst cannot rival a precious metal catalyst, hence improvement in their activities has been attempted by combining base metal oxide catalysts and small amounts of noble metals Low- Temperature oxidation and photooxidation are the advanced processes for environmental chemistry in future nhiem m6i truong tra van de cap bach hien cho tit ca cac nuac Trong cac thai cacbon monoxit (CO), hgp chit hiin co bay hai (VOC) va cac hgp chit chira luu huynh, oxit nito (NOx) la nhirng chat n6i bat vi tinh dpc hai cua chiing dii vai sire khoe nguoi Oxi h6a xiic tac la phuang phap phan buy hieu qua CO, VOC va cac tap chit hiin ca khac kh6ng khi, khir xiic tac la phuong phap hieu qua loai bo NOx dl dap irng tieu chuan m6i truong Cac qua trinh dugc ung dyng cac truang hgp ning dp cua cac tap chat dii thap (nhung cao hon gioi ban cho phep) va viec loai b6 chung bing cac phuong phap khac la khong hieu qua hoac kh6ng kinh tl Tim kiln xiic tac co kha nang chuyen hoa h6n hgp cac tap chat bao g6m cac chat oxi boa va khir la nhiem vy phirc tap va quan trpng d6i vai cac nha nghien cim ITnh vuc boa hpc va cong nghe m6i tmong Xiic tac oxi hoa sau Cac chat xuc tac oxi boa sau dugc chia hai nhom chinh: xiic tac kim loai va oxit kim loai Co mpt loat nghien ciin oxi hoa cac hgp chat him ca va CO sir dyng cac xiic tac khac nhu kim loai qui va oxit kim loai tren chat mang hoac khong chit mang 27 Tiiu ban: Khoa hoc Vdt lieu ISBN: 978-604-913-': •••^ 1.1 Xdc tdc kim logi qui Kim loai qui, dac biet la kim loai nhom platin nhu Pt, Pd, Ir, Ru, , mang tren ci chat mang khac la nhirng xiic tac hpat tinh cao cho oxi boa sau va dugc ung dyng •': ly thai [1] Xuc tac tren ca sa vang co kich thuac nano dugc nghien cuu cho phan img oxi boa CO va VOCs [2,3] Cac chit xiic tac co boat tinh cao a nhiet dp thap (~ 80 C), nhung boat dp cua no bj anh huong nhilu bai hod nuac va CO2 CO2 ding hip phy len cac tam vang boat dong va c6 dp bin kem [4] Nhin chung, Ag 'va Au kh6ng thich hpp cho cac ling dyng a nhiet dp cao va tic dp dong Ion [5] Nbugc diem cua Rh203 la phan img vai nhom oxit [6] Xiic tac Pt va Pd dugc sir dyng ph6 bien nhat oxi boa sau duai dang mang tren cac chit mang (AI2O3 or Si02) va thuang la hgp kim vai cac kim loai khac nhu Ru, Rh, s v a l r [ 8] Cac th6ng tin vl boat tinh ciia cac xuc tac Pt va Pd tai lieu la khac Xuc tac Pt CO boat tinh cao nhit cho dit chay cac hydroeacbon co chua tren mpt nguyen tir cacbon, Pd lai co boat tinh cao nhit cho oxi boa CO va CH4 [7, 9] Tuy nhien Ball & Stack [9] lai cho ring, Pt c6 boat dp cao ban Pd ea oxi hoa HCs va CO Pd c6 dp bin thieu ket hon Pt m6i tmong oxi boa [10] Pt kh6ng xam nhap vao chat rnang nhom oxit ma bj bay hoi dilu kien oxi hoa [11] Tuy nhien, Pt ben vimg voi su dau dpc ciia luu huynh ban Pd va boat dp ciia no hii phyc nhanh ban luu huynh dugc lay khoi hon hgp [12], d6ng thai Pt c6 boat dp cao hon oxi boa SO2 SO3 [7] 1.2 Xiic tdc oxit kim logi chuyen tiep Nhirng nbugc dilm ciia kim loai qui nhu co gia cao, khan hiem va nhay vai nhiet dp cao, da thiic day viec tim kiem nhimg xiic tac thay the Oxit kim loai la chat xuc tac thay thi cho kim loai qui Chiing c6 hpat tinh du cao, mac dii hpat tinh ciia chiing thap hon ciia kim loai qui a nhiet dp thap, nhung a nhiet dp cao thi xap xi vai kim loai qui Trong mpt s6 ung dung, ham lugng ciia oxit kim loai xiic tac cao hon khien cho dp ben cua chiing doi vai dau dpc ciia luu huynh t6t hon, cac xiic tac kim loai qui vai ham lugng thap nen tiep xiic vai chat dau dpc co n6ng dp nh6 thi s6 tam boat dong ban che nhanh chong bj dau dpc [13] Cac xiic tac oxit kim loai don thuan c6 hpat tinh cao cho cac phan img oxi hoa sau khac la oxit Ag, V, Cr, Mn, Fe, Co, Ni and Cu [14] Tuy nhien, vanadia chuyin hoa luu huynh oxit luu huynh [15], gay kho khan sir dyng AI2O3 lam chit mang, no phan ung vai chat mang tao sulphat Crom la chat dpc nen tranh sir diing Trong cac oxit liet ke tai lieu chi c6 mpt s6 la xiic tac co trien vpng CoOx la xiic tac hieu qua cho oxi hoa sau [16,17] Oxh cobah vira la chat xuc tac cho oxi hoa sau, vira la chit hip phy luu huynh [18] C0AI2O4 ben voi SO2 va c6 boat dp oxi hoa CO tuong ty xuc tac Pt [19], tren C03O4/AI2O3 phan ung co the dien a nhiet dp phong [20] CuO cirng dugc coi la chat xiic tac thay the cho kim loai qui kilm soat nhiem moi truong [7, 21-23, 24,25] Xiic tac tren ca sa CuO co boat dp tuong ty kim loai qui oxi hoa CO [7, 24 -26] CuO/Ti02 c6 boat tinh cao hon cac oxit Co, Mn va Fe cho ca oxi hoa CO va toluen [26] CUO/Y-AI2O3 c6 hoat dp oxi hoa CO va VOC cao nhit cac xuc tac CuO mang tren cac AI2O3 khac [24] Mn02 la mpt nhimg xiic tac phii hgp cho phan img oxi hoa [24] Uu diem ciia xuc tac la sin co, boat dp 6n dinh a nhiet dp cao, spinel MnA102 (boat tinh thip) chi hinh a nhiet dp tren 1000°C, khi, thi du, tuang tac giira CuO va AI2O3, tao spinel CUAI2O4 dien a 800°C Mangan oxit co thi tin tai a trang thai oxi hoa khac phy thuoc vao nhiet dp xir ly Mangan oxit dang Mn304 2, co khuyet tat gi6ng nhu cau tnic spinel Mn304, nen co boat tinh cao [27] 28 Hoi nghi Khoa hoc ky- niim 35 ndm Viin Khoa hoc vd Cong nghe Viet Nam - Hd Noi 10/2010 1.3 Xiic tdc oxit bien tinh Mpt sl oxit kim loai bj hu hong bj phai moi truang oxi hoa/khir Chiing co thi tuang tac vai AI2O3 tao aluminate kim loai MeAl204 co boat tinh thap [24,28,29] Tuong tac manh ciia Cu vai Y-AI2O3 dan din hinh aluminate d6ng CUAI2O4 - co boat tinh thap, nhung spinel khong hinh he CuO/a-Al203 a-Al203 co cau tnic khep kin va bin ca qua trinh xir ly sic nhiet a 800°C [24] Tuy nhien, kit hgp cac oxit co the tao xuc tac co boat dp cao va ben nhiet hon so vai cac don oxit Cac xiic tac loai la CuMn [27], Cu-Cr [30, 29], Cu-V [31], Mn-Ni [32], Ag-Mn [33], Zn-Co [34] Kit hgp CuO vai cac oxit khac tao cac xiic tac cong nghiep quan trpng Tuong tac cua d6ng oxit vai crom oxit tao spinel CuCr204 boat tinh cao, ding thai, lam suy yeu tuong tac d6ng vai yAI2O3 dan din giam hinh aluminate CUAI2O3 boat dp thip [29] Mat khac d6ng chromite bin vai sy diu dpc ciia luu huynh tren xiic tac chi dien hap phy boa hpc SOx, ma kh6ng hinh sulphate [36] CuO va CuCr204 c6 boat tinh cao nhat va ben vai luu huynh nhit cac oxit kim loai CuO, CuCr204, C03O4, Fe203, Mn02, Sn02, Zr02 cho oxi boa CH4 va CO [37] Trong mau CuO+Cr203/a-Al203 tuong tac ciia cac phan deu ylu no nen cac dang spinel (ca aluminate va cromate) deu kh6ng hinh va xuc tac co boat tinh thip [29, 35] Xir ly sic nhiet a 800°C dugc cho la phuong phap hua hen de tao pha boat tinh cao CuCr204 he luong oxit CuO + Cr203 [29,35] Xiic tac kh6ng chit mang 50%CuO50% Cr203 c6 nhiet chuyen boa 100% CO kha thap va ben nhiet cao, la xiic tac co trien vpng irng dyng xir ly thai chira CO [29, 35] Yeu cau quan trpng nhat d6i vai xiic tac sir dyng oxi boa sau la c6 hpat dp cao a nhiet dp thap, gia thap va dp ben cao Vai myc dich ceri oxit thuong dugc sir dyng lam chat bien tinh cho xuc tac oxi hoa [38, 39] Theo cac tac gia [40], ceri oxit la phy gia t6t lam tang boat tinh cua cac xiic tac a nhiet dp thap no co kha nang t6n trir va cung cap oxi cho cac chat hap phy, tang phan tan kim loai va 6n djnh chat mang Them Ce02 lam tang boat dp ciia xuc tac CuO/Ti02 oxi hoa CO, alcohols va ethers [41], Ce02 co kha nang tang dp linh dong ciia oxi xiic tac d6ng oxit cirng nhu anh huong den tuong tac giira Cu va AI2O3 [42], giam sy tao CuO kh6i Ion, dan den d6ng khir t6t ban va hoat tinh cua xiic tac tang [38, 39] Su bien tinh Ce02 bang cac ion Cu ^ tao 16 tr6ng ion oxy xung quanh ion Cu ^ xiic tac oxit h6n hgp tren ca so Ce02, lam thay doi cau tnic cyc bg va giam the oxi hoa - khir ciia Cu mang luoi Ce02 Park et al [43] nhan thay xiic tac d6ng oxit mang tren nh6m oxit dugc bien tinh bang ceri hoat dp oxi boa CO tang, them ceri co anh huong it den boat dp oxi hoa methane Theo ket qua ciia chung t6i [29, 38], ceri oxit c6 anh huong tich cyc den hpat dp oxi hoa sau cua xiic tac dong oxit nhung co tac dyng tieu cyc d6i vai ciia xiic tac mangan oxit no lam thay d6i trang thai oxi hoa ciia cation mangan, lam giam s6 tam Mn203 va tang s6 tam Mn02 10Cu20CeAl chiing toi dieu che co nhiet dp oxi boa hoan toan CO a 130^0 va boat dp ciia no 6n djnh hon 500 h •T r r r Anh huong cua tap chat va oxi hoa- khir hop chat da cau tu Co mpt Ipat cac nghien cun ve oxi boa nhiet dp thap CO va cac hydrocarbon tren cac oxit kim loai khac nhau, nhung co rat it c6ng trinh ung dyng cac vat lieu dieu kien thyc te, c6 hien dien ciia H2O, SO2, NOx.v.v Trong thyc te cac qua trinh oxi hoa thai thuang dien moi truong c6 hai nuac (la san pham ciia phan img) va co hgp chit luu hiiynh, nita Do do, xiic tac kh6ng chi can co hpat dp cao, ma can phai co dp ben cao doi vai cac tap chit Nghien cuu cua chiing t6i [44, 45] cho thiy, hai nuac khong diu dpc xiic tac ma chi kim ham phan img Do do, su kim ham cua hod nuac co the tranh dugc neu tien hanh phan ung a nhiet dp cao Qui luat oxi boa d6ng thai CO va cac hydroeacbon m6i tmang co SO2 dugc nghien cim rat it, ngoai ra, tai lieu cirng kh6ng c6 th6ng tin vl dp bin ciia cac xiic tac 29 Tieu ban: Khoa hoc Vdt lieu ISBN: 978-604-913-0'i doi vai SU dau dpc ciia hgp chat luu huynh Hien chua co xiic tac oxi boa d6ng thai '''o;i hgp CO va cac hydroeacbon m6i truong c6 SO2 din gia trj mong muon Cac xii: tac oxh sat, crom, Crom - thiec va sat - crom mac du co muc oxi boa SO2 cao nhung tuang tu xiic tac vanadi c6 hieu qua kem oxi boa CO va cac hydrocarbon a nhiet dp thap Trong nghien cim ciia minh [45] chiing t6i nhan thay SO2 dau dpc cac xiic tac ding oxit Them Ce02 lam giam sy diu dpc ciia SO2 d6i vai cac tam hpat dong SO2 phan img vai Ce02 tao sulphate (Ce02+ SO2 -> CeS04), din tai lugng CUSO2 tao giam va tang dp ben cua cac xiic tac 10Cu20CeAl la xiic tac tit nhit cho oxi hoa CO va hon hgp CO va p- xylen co hai nuac va SO2 dugc chiing t6i che tao va ung dyng co hieu qua xir ly thai 16 d6t rac y tl Tac gia [46] lai giai quyet van de theo each khac, thyc hien oxi hoa d6ng thai CO, cac hydroeacbon va SO2 tren xiic tac Pt-nh6m oxit ket hgp vai xuc tac vanadi c6ng nghiep 16 phan iing hai bac Oxi boa CO va cac hydroeacbon 16 phan img giai doan I, tilp theo oxi boa SO2 giai doan II Phan tich tai lieu tham khao cho thay, chua co cac xuc tac xir ly hon hgp da cau tir chua cac tap chit CO, hydrocarbon khac nhau, d6ng thai chua cac hgp chat nita va luu huynh, la dang thai rat ph6 bien c6ng nghiep boa chat Tac gia [46] da nghien cim phuong phap che tao cac xiic tac h6n hgp Pd-Co-Mn ham lugng thap tren nen xiic tac kali va sat - crom mang tren chat mang dugc dieu che tir hydroxit nh6m bien tinh bang polymer tan nuac Cac xuc tac co ben vai chat dau dgc cao va co kha nang khir NO bang h6n hgp cac chat khir m6i truong oxi boa va oxi boa SO2 m6i truong eo hgp chat flor Uu diem ciia phuang phap la c6 the xir ly hieu qua thai co phan va n6ng dp bien dong Formandehyde va hgp chat cua no dugc ung dyng rong rai cac ITnh vuc c6ng nghiep va la mpt nhiing chat dpc chua thai Phuang phap xir ly triet de formandehyde la oxi boa CO2 va H2O Cac xuc tac ung dung cho truang hgp thuang CO dp ben kh6ng eao Dadakhozaev [46] da tim thay, xuc tac paladi dang n-5/Y-Al203 (Nga) giir dugc boat dp cao m6i truong c6 SO2 a nhiet dp cao Ong giai thich ring, su dau dpc xuc tac la thuan ngbjch, nguyen nhan lam giam boat dp la sy lang dpng cua dioxit luu huynh tren be mat xuc tac Nhu vay, mpt nhirng huong tang dp bin cua xuc tac vai sy dau dpc ciia luu huynh la ban che viec tao sulphat cua kim loai boat dpng Oxi boa SO2 m6i tmong co hgp chit flor (HF va SiF4 ) co y nghTa quan trpng xir ly thai nha may san xuit axit sulfuric thai chua ding thai hgp chit luu huynh va flor Xiic tac vanadi bj diu dgc bit thuan ngbjch bod hgp chit flor va chi co thi lam viec 6n djnh khi kh6ng chua flor Cac phuong phap phi biln dimg dl loai flor chua luu huynh kh6ng tao dieu kien lam sach lya chpn hgp chit flor, vi vay xu huang uu tien la phai tim dugc xiic tac oxi hoa SO2 bin vai sy diu dpc cua hgp chit flor Vai xiic tac ben voi sy dau dpc ciia flor cho phep thuc hien qua trinh hai giai doan xir ly chira luu huynh va flor san xuit axit sulfuric ma kh6ng cin lam sach din mirc tinh hgp chit flor [46] Tuy nhien cac xuc tac nhu vay c6n rit ban cbl Xuc tac re tiln va bin vimg cho oxi hoa SO2 la oxit sat, oxit sat - crom va oxit sit - crom - nhom Tuy nhien su da dang cua phan thai c6ng nghiep doi hoi phai phat triln hon nira cac xiic tac cho lam sach hieu qua cao thai da cau tir Ket qua nghien cuu ciia tac gia [46] tim dugc xiie tac oxit oxi boa SO2 la h6n hgp Al-Fe-Cr-Cu-Ni lam viec bin viing dilu kien co hgp chit flor vai ning dp SO2 thai kh6ng qua 4% thi tich Nguyen nhan giam boat tinh xuc tac ning dp SO2 cao hon la viec hinh sulfat Trong xiic tac cong nghiep nguai ta sir dyng cac chit kit dinh vo ca nhu sement dl tang dp ben CO cua xuc tac Ben canh tinh uu viet ciia chit kit dinh sement can luu y din anh huang cua no den cau tnic x6p ciia xiic tac Cach giai quylt hieu qua van de la d6ng thai sir dung 30 Hoi nghi Khoa hoc ky niim 35 ndm Viin Khoa hoc vd Cong nghe Viet Nam - Hd Noi 10/2010 sement va cac chat bien tinh tao 16 x6p Them polymer hoa tan nuac qua trinh hinh cau tnic hydroxi nh6m lam thay d6i phan pha, dien tich be mat rieng \'a cau tnic x6p Cac nhom chuc -COOH va -CH2COOCH3 co kha nang tao cau tnic tinh the bemit- beirit thay cho cau tnic v6 djnh hinh ciia nh6m hydroxit Cac ion nh6m co the ciing vai chat bien tinh tao carboxitlat thay the mpt phin nh6m, xir ly nhiet thu dugc ion kim loai chua bao boa ph6i tri va nhom kim loai - oxit, la cac tam boat dpng Cac phuang phap dugc iing dyng xir ly thai nha may san xuat axit nitric, sulfuric va nha may san xuat nhya duong tir dau luu huynh cao Dieu che xuc tac tren nin chit mang dugc bien tinh bang polymer ma kha nang mod viec t6ng hgp xiic tac boat tinh cao vai cac dac trung ly - hoa t6t ban De loai b6 oxit nita thai thuong iimg dyng phuang phap khir bang amoniac (khir chpn Ipc) hoac bang thien nhien (khir nhiet dp cao) Nhugc diem chinh ciia khir chpn Ipc la tao cac mu6i nitrit - nitrat amoni va muc lam sach kh6ng cao Khir nhiet dp cao CO cac nhugc diem la thiet bj phuc tap va cin sir dyng xiic tac paladi dit tiln (2%Pd) Xu huong la phai giarn ham lugng Pd xuc tac va sir dyng thai co chua CO va hydroeacbon lam chat khir Trong thyc te dieu co thi thyc hien dugc cac nha may cbl bien dau va nha may san xuat nito dugc bl tri ben canh mgt lien hgp Trong nghien ciin [46] da sir dyng xiic tac Pd- Mn- K ham lugng thip mang tren y-A^Os biln tinh cho xir ly bin hgp chua CO, propan-butan, NO, O2 va nita Xiic tac cung dugc nghien ciin ung dung xir ly thai nha may san xuit axit nitric Dii vai bin hgp NO va C6H12 sir dung xuc tac platin sa dl xir ly hai giai doan Trong giai doan I khir NO bing C6H12 va giai doan II bang bin hgp CeH^ +H2 Khi co SO2 boat xiic tac giam sy che phu bl mat xuc tac bai SO2 hap phy Xu huong phat trien 3.1 Xiic tdc oxi hda nhiet thdp Nhimg yeu cau quan trpng nhat doi vai xiic tac dugc ling dyng oxi hoa sau la boat dp cao a nhiet dp thap, gia san xuit thip va dp bin cao Vl nguyen tic, co khoang 60% thai dugc phat tan giai doan diu cua chu trinh dit, truac xiic tac dat din nhiet dp de chuyen boa dpc [47] Ben canh do, dit chay VOC va CO doi hoi chi phi cao phan ung dien a nhipt dp cao, nen phai cung cip nhien lieu Do sir dyng xiic tac co boat tinh cao nhiet dp thap dugc coi la phuong phap hua hen dl giam tap chit thai giai doan "khai dpng lanh" va tra vin dl mai tuang lai dii vai cac he thing xir ly thai Bang nghien cim co ban cac dac tinh cua xiic tac loai nay, cho phep djnh huang biln doi xiic tac thuang mai nham cai thien boat tinh a nhiet dp thip ciia chiing Uu diem ciia oxi boa nhiet dp thip la giam chi phi viec xir ly lugng lan nhiem chira VOC va CO Ding thai oxi boa nhiet dp thip ciing ban ehl viec hinh NOx xir ly Xiic tac mang Pt va cac oxit khac la xiic tac truyin thing cho ung dyng va dugc quan tam rong rai [1] La nguyen t l don le, xiic tac oxit kim loai khong thi sanh kjp xiic tac kim loai qui, nhien co thi cai thien hpat tinh cua chiing bing each biln tinh bing lugng nho kim loai qui Xiic tac hon hgp kim loai qui - oxit kim loai chuyin tilp dugc quan tam cang cao chiing co nhirng dac tinh rieng biet tit Cy thi, kim loai qui co lyc vira phai d6i vai oxi nen oxi dugc giai thoat cham Do boat dp cua xiic tac kim loai qui co the tang ket hgp no vai cac chit khac, nhu oxit kim loai, nha tang tinh linh dpng ciia 0x1 Vai tro khac ciia oxit kim loai c6n la lam giam su kim ham cua CO dii vai phan ung, la dac diem cua phan img oxi hoa a nhiet dp thip tren xiic tac Pt [48] Ngugc lai, Pt giiip cho ' cac oxit kim loai co trang thai da boa tri, thiic diy sy chuyin oxi tir pha vao xiic tac [49] 31 Tiiu ban: Khoa hoc Vdt lieu ISBN: 978-604-913-01 Them Pt vao Al, Cr, Cu, Mn va Co tao xiic tac co boat dp cao cho oxi boa CO va bsn vod sy dau dpc ciia SO2 [50] So vai mau kh6ng bien tinh Pt, xiic tac CoOx bien tinh co hoat dp oxi boa nhiet dp thap CO va C3H6 dieu kien ngheo [51], dilu kien hgp thuc hoac dieu kien giau [52] Mgt nhirng m6 hinh dugc dua de giai thich hien tugng la dua vao phan ung giira O lien ket yeu tren CoOx vai CO tren Pt tai giao dien Co-Pt [52] Hieu img hiep trg xiic tac giira oxit kim loai va kim loai qui dugc cho la lien quan vai su gia tang tinh khir ciia oxh kim loai nha co sy chuyen oxi tir pha sang kim loai qui Sy hien dien ciia kim loai qui xiic tac h6n hgp dan den tang tinh khir ciia CuO, MnOx va tao MnOx a trang thai oxi hoa cao hon [53] Trong xiic tac h6n hgp, MnOx co xu huong tao pha hon hgp vai Pt ham lugng kim loai qui thap, bao bpc kim loai qui, Iam giam boat tinh Mpt thi dy dien hinh ve hieu ung hiep trg la xiic tac oxit Au - Fe Haruta et al phat hien oxi boa nhiet dp thap CO [54] Au/MnOx cirng dugc coi la xiic tac co trien vgng vi co tuoi thp cao [55] Thi dy khac la xuc tac chua Mn203 va Pd co boat tinh oxi boa CO cao hon xiic tac Pd va cac mau h6n hgp khac nhu Pd/Fe203 va Pd/Co304 [56] Oxit Ni lam giam kich thuac hat Pd va c6 djnh pha PdO, lam tang boat cua no [57] Tuy nhien, he xuc tac cho den chua dugc nghien cim nhieu va chua dugc ung dyng xir ly thai da cau tir, d6 dien d6ng thai hai dang phan irng trai ngugc la oxi boa va khir 3.2 Quang oxi hda (Photocatalytic oxydation - PCO) Oxy boa quang xiic tac la cong nghe co sue hap dan viec lam sach m6i truang nha tinh kinh te, dan gian va de thuc hien Dac diem ciia qua trinh la tan dung nang lugng buc xa thien nhien hoac nhan tao va iing dyng xiic tac dj the phan hiiy cac chit nhiem hiin CO cac chat v6 co PCO hua hen mang lai nhimg img dyng phan hiiy cac hgp chit bun CO de bay hoi (VOCs) cac dong PCO co thi v6 ca h6a lap tuc cac phan tir him CO don gian CO2 va H2O a dieu kien ty nhien, vai su tham gia cua oxy phan tir, nhien, cac chat nhiem phirc tap thuang kho bj phan buy, cac san phim trung gian kh6ng mong mu6n dugc tao va t6c dp phan buy thuong rit thip Trong cac chit xiic tac sir dyng cho quang oxy boa thi Ti02 co nhieu un dilm, d6, dugc nghien cim va img dyng nhilu nhit Cac g6c boa hpc boat dpng va cac dien tieh sinh Ti02 nano dugc kich boat co kha nang pha buy cac chit dpc bun ca, nim mic [58], [59], [60] Duai tac dyng ciia hire xa tir ngoai (UV), Ti02 tra m6i truang ky nuac hay nuac tiiy thuoc vao ban chit vat lieu Kha nang dugc img dyng dl tao cac bl mat tu tiy rira hoac cac thilt bj lam lanh th6ng qua viec tao dieu kien cho nuac bay hai He xiic tac Ti02- UV dugc nghien cim nhilu ung dyng xir ly moi tmong Tuy nhien, anh sang mat trai chi c6 khoang - 5% nang lugng buc xa UV c6 kha nang kich thich chat quang xuc tac Ti02 [61] Nhugc dilm cua xuc tac Ti02 la boat tinh quang hoa chua du cao cho img dyng thuong mai Phan tich tai lieu tham khao cho thiy co ba huang nghien cim phat trien chinh dl tang hpat tinh xiic tac quang cua Ti02 la ma rong viing anh sang hap thu sang viing kha kiln, tang thai gian sing ciia cap electron - lo tring quang sinh cung nhu tang cuong hap phy chit phan img Nhilu phuang phap vat ly va hoa hoc dugc img dyng che tao va bien tinh xuc tac Ti02 Cac nguyen t l dugc sir dyng dl biln tinh Ti02 rat^da dang va bao g6m phin Ion cac nguyen t l cua bang tuin hoan Sy anh huang cua cac chat bien tinh la rat khac va phy thuoc vao nhilu ylu to va qui luat eiing nhu ca chi anh huang cua chiing chua ro rang ^ Sy djch chuyen ph6 hip thu anh sang ciia cac xuc tac Ti02 biln tinh bing ion kim loai chuyenJiep dugc giai thich la mirc nang lugng ciia cac orbital d cua kim loai nim a giira viing dan va \'ung hoa trj ciia Ti02, chia nang lugng viing cim ciia Ti02 hai phin va nit ngan khoang nang lugng cin thilt cho qua trinh kich thich electron, dan din xuc tac duac 32 Hoi nghi Khoa hoc ky niim 35 ndm Viin Khoa hoc vd Cong nghi Viet Nam - Hd Noi 10 2010 biln tinh hip thu anh sang a viing c6 buac song Ion hon so voi xuc tac Ti02 thuan [62] Vipc ciy ion kim loai chuyin tilp va ion kim loai dit hiim da dugc nghien cim rat nhieu [63] Them lugng nho kim loai chuyin tilp nhu V, Fe, Cu co thi giam nang lugng viing cam, giam tic dp tai kit hgp 16 tring va electron quang sinh va chuyen dich viing hip thu photon ciia Ti02 sang viing buac song dai han [64] Dua hai hay nhieu kim loai thich hgp len cac hat nano tinh thi Ti02 lam cai thien dang kl hieu qua quang xiic tac cua Ti02 [64] Neu cac ion kim loai biln tinh thay thi cho ion Ti'*^ mang Ti02 thi biln tinh Ti02 bai N, nguyen tir nito thay thi cac nguyen tir oxy mang Ti02 hoac chen (interstital) vao giira cac lien kit [65] Do orbital 2p ciia N co nang lugng cao hon nang lugng orbital ciia O nen c6 mat N, viing boa trj ciia Ti02 dang cao len, lam giam nang lugng vimg cim ciia hgp chat [65] Nhin chung, dugc dua vao mang Ti02, cac nguyen tir kim loai va phi kim deu co khuynh huang lam giam nang lugng vimg cam ciia hgp chat theo cac huong khac Cac nghien cim ciia chiing t6i [58, 66- 68] da dat dugc mpt s l tyu sau rat quan trpng Chung t6i da dilu cbl dugc xuc tac nano Ti02 va Ti02 bien tinh bai kim loai va phi kim dang gel va dang hot kich thuac hat 7- 30 nm birig phuang phap sol-gel, thich hgp cho xu ly m6i truang D I giam gia san phim, tao dieu kien irng dyng thyc te, chiing toi da dilu cbl cong Ti02 bien tinh kich thuac nanomet ( < 25 nm) tir Ti02 th6, kich thuoc micromet ciia Trung QuIc Ben canh d6 da xac djnh dugc vai tro cua cac phy gia biln dii tinh chit ciia Ti02 nhim djnh huong dieu che xiic tac quang hieu qua cao, c6 the img dung hieu qua thyc tl Cy thi, biln tinh Ti02 bing Si02 kh6ng ma rgng viing hap thu anh sang ciia Ti02 sang viing kha kien, nhung lam giam kich thuac hat Ti02, tang dien tich be mat rieng va sl lugng nhom -OH va tang dp ben nhiet ciia mau xiic tac, dan den tang hap phy VOC va tang boat dp quang oxi boa Si-Ti la nhom xiie tac co kich thuac hat nh6 (5-11 nm), xip xi vai xiic tac thuang mai ciia Nhat STOl, nhung co dp 6n djnh va cho hieu suat chuyen boa cao ban Biln tinh Ti02 d6ng thai bang Si va N, mpt mat, lam tang dp phan tan Ti02, tang dp bin nhiet, mat khac, chuyen viing hap thu photon sang vimg kha kien vai A = 425 run va nang lugng viing cam EG = 2,92, nha do, lam tang hpat dp dau len xap xi 30%, tang dp 6n djnh va hieu suat chuyen boa p-xylen Bang phuong phap sol-gel kh6ng cay dugc V vao mang ciia Ti02, nen khong ma rong dugc viing anh sang hap thu, d6ng thai lam giam s6 nhom OH, nen kh6ng lam tang boat dp va hieu suat chuyen boa p-xylen so vai Ti02 thuan thuong mai P25 (Dire) Xuc tac Ti02 bien tinh bai Fe203 dugc che tao theo hai phuong phap sol- gel va thiiy nhiet hoac bien tinh bai kim loai Cr, V dieu che bang phuong phap thuy nhiet c6 kha nang ma rong viing hap thu anh sang sang buac song kha kien len den 464 nm va giam EG xu6ng den 2,67 eV, d6ng thai lam giam kich thuac hat Ti02, nen la nh6m co boat dp va hieu suat chuyen boa VOC cao nhat Dieu tao dieu kien sir dyng anh sang co buac song dai nhu anh sang mat trai xir ly thai a nhiet dp kh6ng Chiing toi da chung minh rang, sir dung ket hgp den UV {X = 365 nm) va BLED (k = 470 nm) lam tang chuyen boa va hieu suat chuyen hoa p-xylen cua xiic tac 2-3 lan va chat xiic tac c6 dp 6n djnh cao Hpat dp ciia cac xuc tac FeTi va NTi hau nhu khong thay d6i sau 60 phut phan img, mac dii lugng xiic tac sir dyng la rat it (5 mg), t6c the tich rat cao (den 312 10 h' ) Uu diem cua xiic tac mang la hieu suat sir dyng cao va de thu h6i Xiic tac c6 the dugc phyc hoi boat tinh bang each xir ly dong kh6ng a 500°C hoac chieu anh sang UV a nhiet dp kh6ng Ket qua nghien cim ma kha nang img dyng nang lugng mat trai san co va doi dao a Viet Nam viec xir ly thai c6 chira cac hgp chat de bay hai, dpc hai, giam thieu san pham phy thir cap va tiet kiem nang lugng 33 Tieu ban: Khoa hoc Vdt lieu ISBN: 978-604-913- KET LUAN Oxi hoa va khir la nhiing phuang phap xir ly triet de cac chit nhiem thai va bao ve m6i tmong Xiic tac cho cac qua trinh la rat da dang, vai tro bien d6i ciia cac phu gia chua r5 rang, d6ng thai den chua co su th6ng nhat ve qui luat eiia cac phan img, dac biet la cac phan iing chuyen hoa d6ng thai nhieu chat h6n hgp phuc tap ciia thai Tuy da dugc nghien ciin va img dyng tir lau nhung viec tim cac xiic tac mai c6 hpat dp cao hon, tao dilu kien thyc hien phan img a nhiet dp thap, nham giam t6i thieu cac san pham phy va tilt kiem nang lugng van lu6n la thach thuc d6i vai cac nha khoa hpc ITnh vuc h6a hpc moi tmong Vod cac xiic tac mai cho phep thiet lap c6ng nghe xir ly m6i truong mai c6 tinh sinh thai, tao dilu kien phat trien ben vimg Trong b6i eanh the giod hien viec img dyng xiic tac oxi boa - khir tien tiln va vat lieu nano xir ly thai a nhiet dp thap va img dyng anh sang anh sang mat trai co y nghTa quan trpng, -vira lam giam thieu nhiem m6i tmong, •vira tilt kiem nang lugng va ban che su that thoat nhiet m6i truang Loi cam on: Tac gia va nhom nghien cuu chan cam on Chuang trinh Khoa hgc Vat lieu, Vien KH va CN Viet Nam da tao dieu kien cho chiing toi nghien cuu dua cac he xiic tac xir ly hieu qua thai va irng dung cong xir ly thai 16 d6t rac y te va thai cpng nghiep TAI LIEU THAM KHAO J.J Spivey, Ind Eng Chem Res 26, 2165(1987) M Hamta, S Tsubota, T Kobayashi, H Kageyama, M J Genet and B Delmon, J Catal 144, 175(1993) Simona Minico et al Applied Catalysis B: 28, 245 (2000) Seung Hoon Oh and Gar B Hoflund, J Phys Chem A, 110, 7609 (2006) Caixia Xu et al, J Catal 252, 243 (2007) R.M Heck and R.J Farrauto, ''Catalytic Air Pollution Control; Commercial technology" Van Nostrand Reinhold, New York, 1995 J.T Kummer, ''Catalysts for automobile emission controF, Prog Energy Combust Sci 6, 177(1980) Seung Hoon Oh and Gar B Hoflund, J Phys Chem A, 110, 7609 (2006) D.J Ball and R.G Stack, Catalysts for diesel powered vehicles, in "Catalysis and Automotive Pollution Control It (A Cmcq, Ed.), Vol 71 Elsevier, Amsterdam, 1991, p 337 10 D.D Beck and J.W Sommers, Appl Catal B: 6, 185 (1995) 11 Y.J Mergler, A van Aalst, J van Delft, and B.E Nieuwenhuys, Appl Catal B' 10 245 (1996) 12 J.C Menezo, J Riviere, and J Barbier, React Kinet Catal Lett 49(2), 293 (1993) 13 B Han-ison, A.F Diwell, and C Hallett, Platinum Metals Reviews 32(2): 73 (1988) 14 S.F Tahir and C A Koh, Chemosph 34(8), 1787 (1997) 15 J.P Dunn, P.R Koppula, H.G Stenger, and I.E Wachs, Appl Catal B: 19, 10 (1998) 16 Jansson Jonas, J Catal 194, 55 (2000) 17 Chen Yeong-Jey, Wu Dai-en and Yeh Chuin-tib, Rev Adv Mater Sci 5, 41 (2003) 18 A.S.K Sinha and V Shankar, Ind Eng Chem Res 32, 1061 (1993) 19 V Zarkov and D Mehandjiev, Appl Catal A: 94(2), 161 (1993) 20 E Garbowski, M Guenin, M.C Marion, and M Primet, Appl Catal 64, 209 (1990) 21 Kim Kyung-Yeol, Han Jonghee, Suk Woo Nam, Lim Tae-Hoon, Lee Ho-In Catalysis Today, 131(1-4), 431 (2008) 34 Hoi nghi Khoa hgc ky niem 35 ndm Viin Khoa hoc vd Cong nghe Viet Nam - HaNoi 10/2010 22 Shu Ping Wang et al Catalysis Communications, 8, 231 (2007) 23 Jian Liang Cao, Yan Wang, Xiu-Ling Yu, Shu-Rong Wang, Shi-Hua Wu and ZhongYong Yuan, Applied Catalysis B: 79, 26 (2008) 24 Luu Cam Loc, Nguyen Thi Thanh Hien, Nguyen Kim Dung, Nguyen Duy Binh, Hoang Tien Cuong, Ho Si Thoang, Adv in Natural Sciences, 7(3-4), 245(2006) 25 Luu Cam Loc On Complete Oxidation of CO and p-xylene over metallic oxides Catalysts Proc Of 4"^ Intern Symposium "Global Renaissance by Green Energy Revolution", Nagaoka, Japan, 24-25/Jan/2005, p.75 26 L Guczi, L Borko, Z Schay, Stud Surf Sci Catal 113, 69 (1998) 27 D Mehandjiev, V Georgescu, K Cheshkova, and G Ivanov, in "Heterogeneous Catalysis", Proceedings of the 9th International Symposium, Varna, Bulgaria, 2000 (L Petrov, Ch Bonev, and G Kadinov, Eds.), Sofia, 2000, p 743 28 Per-Olof Larsson, Ame Anderson, Applied Catalysis B: 24, 175(2000) 29 Luu c i m Loc, H6 ST Thoang, Tap chi KHCN, 45 (6) 19 (2007) 30 M.I Vass and V Georgescu, Catal Today 29, 463 (1996) 31 A.F Ahlstrom and C.U.I Odenbrand, Appl Catal A: 60, 157 (1990) 32 D Mehandjiev, E Zhecheva, G Ivanov, and R loncheva, Appl Catal A: 167, 277 (1998) 33 N Watanabe, H Yamashita, H Miyadera, and S Tominaga, Appl Catal.B: 8, 405 (1996) 34 D Klissurski, E Uzunova, and K Yankova, Appl Catal A: 95, 103 (1993) 35 Luu Cam Loc, Nguyen Tri, Hoang Tien Cuong, Ho Si Thoang, Abstrct paper of 12"" Asian Chemical Congress 2007, Kuala Lumpur 8/2007, 132 A Teriecki-Baricevic, B.Grbic, D Jovanovic, S Angelov, D Mehandziev, C Marinova, and P Kirilov-Stefanov, Appl Catal.A: 47, 145 (1989) 36 Yu Yao Y.F., J Catal 39, 104 (1975) 37 Luu Cam Loc, Hoang Tien Cuong, Nguyen Tri, Ho Si Thoang, J Chemistry and Chemical Engineerring, 4(2) 48 (2010) 38 Luu Cam Loc, Hoang Tiln Cuong, Nguyin Tri, Tap chi Hoa hoc, 45(DB) 25-32 (2007) 39 A.Trovarelli, Catal Rev Sci Eng 38, 439 (1996) 40 Per-Olof Larsson, A Anderson, J Catal 179(1), 72 - 89 (1998) 41 Jong - Won Park, Jin-Hyeok Jeong, Wang-Lai Yoon, Heon Jung, Ho-Tae Lee, DeukKi Lee, Yong-Ki Park and Young-Woo Rhee, Applied Catalyst A: 274, 25(2004) 42 P.W Park and J.S Lejdford, Catal Lett 50, 41 (1998) 43 Luu c i m Loc, Nguyin Thj Diem Phiic, H i ST Thoang, Tap chi Hoa hoc, 45 (6) 697 (2007)^ • • V / 44 Luu Cam Loc, Hoang Tiln Cuong, Nguyin Tri, Tap chi Hoa hpc, 47 (6A), 56, 2009 45.A.T JlanaxoimaeB (1987), Paspadodxa u euedpenue KamanumuHecKoit onucmKu MuoaoKOMnoueumubix cepocodepoicauiux omxodnuiux easoe, ;];HccepTauHH na coHCKaHHe yneHOH cxenHH aoKxopa xexHUHecKHx nayK, TamKenx 46 T Krichner, A Donnerstag, A Konig, and et Stud Surf Sci Catal 116, 125 (1998) 47 J.P Dunn, P.R Koppula, H.G Stenger, and I.E Wachs, Appl Catal B: 19, 103 (1998) 48 L J i , J Lin , and H.C.Zeng, J Phys Chem B: 104, 1783 (2000) 49 M.O Osmanov, Azerb Khim Zh 4, 34 (1986) 50 A.Tomcrona, M Skoglundh, P Thonnahlen, E Fridell, and E Jobson, Appl Catal B: 14, 131 (1997) ^ 51 Y.J Mergler, J Hoebink, and B.E Nieuwenhuys, J Catal 167, 305-313 (1997) 35 Tiiu ban: Khoa hoc Vdt lieu ISBN: 978-604-913-0! 1-3 52 M Ferrandon, Mixed metal oxide-noble metal catalysts for total oxidadon ofvoJ.i/de organic compounds and carbon monoxide Ph.D dissertation Royal Institute of Technology, Stockholm, 2001 53 M Hamta, S Tsubota, T Kobayashi, H Kageyama, M.J Genet, and B Delmon, J Catal 144, 175(1993) 54 S ImamuraY., Tsuji, Y Miyake, and T Ito, J Catal 151, 279 (1995) 55 H Widjaja, K Sekizawa, K Eguchi, and H Arai, Catal Today 47, 95 (1999) 56 P Bera K R Priolkar, P R Sarode, M S Hegde, S Emura, R Kumashiro N P Lalla, Chem Mater 14, 3591-3601(2002) 57 Trin Minh Hanh, Luu Cam Loc, Nguyen Qu6c Tuan Tap chi Khoa hpc DH QG Ha Noi 23(1) 57 (2007) 58 N Takeda, N Iwata, T Torimoto, H Yoneyama, J Catal., 177, 240 (1998) 59 G Schmid, et al., Chem Soc Rev 28, pp 179 (1999) 60 Kazuhito Hashimoto, Hiroshi Irie and Akira Fujishima, Japanese journal of applied physics 44 (12), 8269 (part 1) (2005) 61 T Umebayashi, T Yamaki, H Itoh, K Asai, Journal of Physics and Chemistry of Solids, 63(10), pp 1909(2002) 62 W.Y Choi, A Temiin and M.R Hoffmann, J Phys Chem 84, 13669(1994) 63 N Netchakun, S Phanichphant, K Chiang, R Amal, Effects of transition metal ion doping on the photocatalytic activity of Ti02 PARTECH 2007 64 Cristiana Di Valentin, Chemical Physics, 339, 44(2007) 65 Luu Cam Loc, Nguyen Tri, Nguyen Qu6c Tuan, Tap chi Khoa hpc C6ng nghe 45(4), 51(2007) 66 Nguyen Qu6c Tuan, Luu Cam Loc, H6 ST Th6ang, Tap chi Hoa hpc 47 (3), 292 (2009) 67 Luu Cam Loc, Nguyen Quoc Tuan, Ho Si Thoang, Synthesis and Characterization of Fe-Dopted Ti02 Photoeatalyst By Sol-Gel Method, lOP Publishing, Adv Natur Scien.: Nanoscience and Nanotech., N l , 015008 (Online) (2010) 36