Tieu ban Khoa hoc vdt lieu ISBN: 978-604-913-011-3 ANH HirONG CUA TIEN CHAT COBALT DEN TINH CHAT CUA XUC TAC C0/AI2O3 TRONG CHUYEN HOA CO THANH NHIEN LIEU LONG INFLUENCE OF COBALT PRECURSOR ON PROPERTIES AND ACTIVITY OF C0/AI2O3 CATALYSTS FOR FTS PROCESS Lu-u Cam Loc, Nguyen Manh Huan, Lac Kien Trieu, Bui Thanh Huong, Dang Thi Ngoc Yen Viin Cdng nghi Hda hgc, I. Mgc DTnh Chi, Q.I, TP. Hd CM Minh E-mail; lclac(a>yast-hcm. ac. vn Tom tat Trong nghiin cim dd diiu chi cdc xuc tdc Cobalt mang trin y-AhOs xu ly bdng amoniac vd amoni nitrat dugc diiu chi tit cobah acetat vd dugc nghien cim trong phdn irng tdng hgp hydrocarbon long tit carbon monoxide. Thdnh phdn tdi uu ciia Co trong xiic tdc dugc diiu chi tit cobalt acetat la 20%, trong khi tit cobalt nitrat la 15%. Hiiu sudt tgo hydrocarbon Idng tit tiin chdt cobalt acetat cao han tit cobalt nitrat. Abstract: Catalysts on the basis of cobalt oxide supported on y-A^Os modification by ammonia and ammonium nitrate have been prepared from cobah acetate and studied in the reaction of synthesis of liquid hydrocarbons from carbon monoxide. The optimal contents of cobalt in catalysts prepared from cobalt acetate have been shown to be 20 wt.%o, while the optimal content of cobalt in catalysts prepared from cobalt nitrate has been found to be 15 wt.%. The liquid hydrocarbon yield obtained on the sample with 20 M't. % of Co from cobalt acetate precursor was higher than that from cobalt nitrate. I. Md DAU Trong cdng trinh nghien cim trudc day [1], chiing tdi da dieu che va nghien ciiu tinh chit va hgat do cua cac xuc tac cobalt tir cobalt nitrat tam tren y-A^Oa (Merk) dugc xir ly bing dung dich NH3 va NH4NO3 cho phan iing tdng hgp FT. Kit qua nghien cim cho thiy, xir ly •y-A^Os bang NH3 va NH4NO3 lam giam sd tam axit, lam suy ylu tuang tac cua Co vdi chit mang, nhd dd C03O4 ket tinh tdt hon, tinh khir cua xiic tac tang va han cbl su tao thanh aluminat cobalt boat tinh thap, dan tdi tang hieu suat tao hydroeacbon Idng. Ndng do dung dich NH3 va NH4NO3 tdi uu tuong iing la 10 % va 15 % va cac xiic tac cd ham lugng Co phii hgp nhit la 15%. Cac xiic tac 15%Co/Al203 tren chat mang xir ly bing dung dich 10%NH3 va 15%NH4N03 dugc ky hieu tuong iing la 15Co(N)Al-N10 va 15Co(N)Al-NN15. Tren 15Co(N)Al-N10 hieu suat tao C5+ dat cao nhat la 46%, cao gip 1,3 lin so vdi chit mang khdng xir ly, vdi do chuyen hda CO bang 72%, do chgn lgc C5+, CH4 va C2-C4 tuang iing 64 ; 10 va 26% d 240°C va 7 atm. Tiln chat khac nhau dan den tuong tac khac nhau cua cac hat coban vdi chit mang ciing nhu anh hudng den hoat tinh va kha nang phat triln mach dudi dieu kien FTS. Kraum [2] cho ring, boat tinh xuc tac cQng nhu do phan tan Co tren xiic tac 12%Co/Ti02 dilu cbl tir 298 Hgi nghi Khoa hoc ky' niim 35 ndm Viin KH&CNVN-Hd Ngi -10/2010 tiln chit hiiu ca cao ban xiic tac vdi tien chit la coban nitrat. Trong khi do Sun [3] va Wang [4] lai cho thiy ddi vdi xiic tac Co/Si02 va Co/SBA-15 tiln chit Co(CH3COO)2 va Co(N03)2 cho kit qua nhu nhau. Theo cac tac gia, trong trudng hgp xiic tac hr tien chat hiiu ca, Co cd do phan tan cao, nhung miic khir rat thap do tuong tac manh giiia oxit coban va be mat silic, cdn tren xiic tac tir nitrat cobalt do phan tan Co thap, nhung miic do khir cua ion cobalt cao ban dan din do chuyin hda CO cao hon. Cobalt tren xiic tac dieu che tir tien chat hiru ca tdn tai d dang cac cluster kich tbudc nano ben trong cac mao quan ciia SBA-15. Ohtsuka [5] thiy ring, Co cd ngudn gdc tir acetate tren SBA-15 cd hgat do rat thap ngay ca khi ham lugng Co la 20%, ngugc lai, xiic tac dieu che tir coban nitrat hoac hdn hgp acetate va nitrat cho su chuyen hda CO den 85-90% va dat dugc hieu suat Idn cho cac hydroeacbon Cio-C20- Nhin chung, su anh hudng cua tien chat cobalt len tinh chat xiic tac la chua rd rang va CO cbl tuong tac tien chat vdi chat mang van chua sang td. Muc dich cua bai bao la nghien ciiu su anh hudng cua tien chat den tinh chat xiic tac, nham tim ra dieu kien tdi uu trong dieu che xiic tac cobalt. II. THVC NGHIEM Chit mang la Y-AI2O3 (Merk) xir ly bing dung djch 10%NH3 hoac 15% NH4NO3 theo qui trinh neu trong [1]. Cac xuc tac Co mang tren Y-AI2O3 dugc dieu che tir Co(CH3COO)2 .4H2O (Merk) theo phuang phap tam nhu trong [1]. Dien tich be mat rieng (SBET) ciia xiic tac dugc nghien ciiu bang phuong phap hap phu BET, thanh phan pha - bang phuang phap XRD, tinh khir - phuong phap khir chuang trinh nhiet do (TPR), tinh axit - phuang phap hap phu - giai hap amoniac va anh be mat cua xiic tac - phuang phap FE- SEM/EDS dugc trinh bay cu the trong [1]. Xiic tac dugc ky hieu nhu sau, thi du, 20Co(Ac)Al-N10, la xiic tac chiia 20%Co mang tren y-Al203, xir ly bang NH3lO%, dieu che tir cobalt acetat. Trudc khi phan iing xiic tac dugc boat hda bang ddng khi H2 d nhiet do 400°C, ap suat 2 at, trong 4 gid, luu lu(Dng ddng tdng la 4 lit/gid. Hoat tinh cua xiic tac trong qua trinh tdng hgp Fischer- Tropsch dugc thuc hien trong so do ddng vi lugng, dudi ap suat 7 atm, tdc do the tich ddng V = 3 L/h; ty le moi H2/CO = 2, khdi lugng chit xiic tac = 3 g va trong viing nhiet do 220 - 280°C. De phan hch ham lugng CO, sir dung cot mao quan HP-PLOT MolecularSeive 5A (chieu dai 30 m, dudng kinh trong 0,12 pm) vdi detector dan nhiet TCD. Dau dd FID va cot HP-1 (chieu dai 30 m, dudng kinh trong 0,12 pm) dugc dung de phan tich do chgn lgc cua nhung hydroeacbon C5+. IIL KET QUA VA THAO LUAN 1) Cac dac trung ly-hda ciia cac mau xiic tac. Bdng 1. Diin tich bi mat riing (SBET) cua chdt xuc tdc, nhiit do khu cue dgi fTmwJ vd muc do khu cua C03O4 (Kred) trong cdc mdu xuc tdc diiu che tit cobalt acetate Mau 10Co(Ac)Al-N10 20Co(Ac)Al-N10 25Co(Ac)Al-N10 10Co(Ac)Al-NN15 20Co(Ac)Al-NN15 25Co(Ac)Al-NN15 20Co(Ac)Al** SBET, m^/g 109,99 90,13 85,46 90,00 89,18 71,08 58,33 T "C -' maxh ^ 423 465 430 418 460 460 440 Kredh % 6,43 15,10 11,77 11,39 13,00 11,69 8,76 •' max2: *— 760 - 745 744 - 760 765 KredJ, %0 2,34 - 3,10 1,56 - 1,15 1,56 Kred > Idng, % %,11 15,10 14,87 12,95 13,00 12,84 10,32 299 Tiiu ban Khoa hoc vdt lieu ISBN: 978-604-913-011-3 *) chdt mang la y-A^Os (Merk) khdng xit ly Tinh chat ly - hda cua xiic tac dugc trinh bay trong bang 1 cho thiy, khi tang ham lugng coban dien tich be mat rieng giam. Dien tich bl mat rieng ciia cac xiic tac mang tren y- AI2O3 xir ly cao gap 1,5 lan miu 20Co(Ac)Al. Trong dd xiic tac mang tren y-Al203 xir ly NH3 cd SBET cao hon ddi chiit. Tuong tu nhu xiic tac dugc dieu che tir Cobalt nitrat, trong phd XRD (hinh la va lb) ciia tat ca cac xiic tac dieu che tir cobalt acetate deu cd cac peak dao ddng dac trung ciia C03O4 (20 = 19,2°, 31,6°, 36,8°, 59,5° va 65,5°) va y-Al203 (29 = 20°, 45,8° va 67,1° ) cd cudng do rat yeu, cho thay trong cae xiie tac nay cobalt tdn tai d pha tinh the C03O4, cdn chat mang ket tinh kem. Cudng do cac peak dac trung cho tinh the C03O4 cua mau chiia 20%Co la manh nhat. Ngoai ra, cac xiic tac chiia 20%Co mang tren chat mang bien tinh cudng do dao dgng cua 00304 cao ban dao ddng cua nd tren xiic tac tren chat mang khdng bien tinh. Dieu dd cho thay viec xir ly thuy nhiet y-Al203 vdi cac dung dich NH3 va NH4NO3 da lam giam su tuong tac giira Co va chat mang, hinh thanh tinh the coban oxit tren be mat Idn ban. - J'sfJKf^'K.,—^r' ^^w\A^v^/^v^''V^^'' AI.O, ft AIjU, Y^i". i • .^'YM^'i* V*iN*».w.^J W*-1 WNfV^H-WV»-uM'«/«'ll^'.W '"^'^ 2iCciAlN10 A^j/ jJ 'Vjufm-i! K^•(^^l^J;yl^J^*^v/v• vA Hinh la. Phd XRD cua xiic tdc Co mang Irin y- AI2O3 xu ly bdng NH3: I)I0Co(Ac)Al-NI0; 2) 20Co(Ac)Al-N10; 3) 25Co(Ac)Al-N10 .10COAI-NN15 .^/Vr^*»V.|«l.A^W.r^vnVAA^VV^^*'' :20CoAI-NN15 :25CoAI-NNI5 Mbeta-: Hinh lb. Phd XRD cita xiic tdc Co mang Iren f AI2O3 xu ly bdng NH4NO3 I)I0Co(Ac)Al-NN15 2) 20Co(Ac)Al-NNI5; 3) 25Co(Ac)Al-NNI5 Phd TPR ciia tat ca cac xiic tac deu cd hai miii khir. Mui khir thir nhat vdi nhiet do kbit cue dai trong khoang T^ax 1 ^ 420-465°C img vdi sir khir ciia C03O4 va miii khir nhd thir hai vdi Tmax,2 troug khdang 745-765°C, dac trung cho su khir ciia cac ion Co2+ lien kit vdi chit mang hoac ciia spinel C0AI2O4 [6]. Tir bang 1 ta thay, tang ndng do coban trong cac xiic tac, nhiet do khir cue dai va mirc do khir tang, dat cue dai khi ndng do Co trong xiic tac la 20%, sau dd giam khi tiep tuc tang ham lugng Co len den 25%. So vdi mau khdng biln tinh, nhiet do khir cue dai Tmax.i ciia hai xuc tac mang tren y-Al203 bien tinh deu cao hon va mirc do khir tang tir 10,3% tren mau 20Co(Ac)Al len 15,1 va 13 % tuong ung ddi vdi hai mau 20Co(Ac)Al-N10 va 20Ca(Ac)Al-NN15. Nhu vay, xir ly chit mang bing NH3 hoac NH4NO3 lam tang do ket tinh va tinh khir ciia C03O4 trong xiic tac. Bdng 2. Kit qud do hdp phu - gidi hdp NH3 cua cdc xiic tdc diiu chi lu cobalt acetate Ky hieu 10Co(Ac)Al-N10 15Co(Ac)Al-N10 20Co(Ac)Al-N10 25Co(Ac)Al-N10 10Co(Ac)Al-NN15 15Co(Ac)Al-NN15 Yeu 1,754 2,389 3,104 1,566 2,451 3,668 Mat do tam Trung 0,635 0,921 0,152 0,215 1,208 0,564 axit 3inh (mmolNHs/lOOg) Manh 1,682 1,091 0,519 0,465 0,752 0,564 Tdng 4,071 4,402 3,775 2,246 4,411 4,795 300 Hoi nghi Khoa hoc ky- niim 35 ndm Viin KH&CNVN - Hd Not -10/2010 20Co(Ac)Al-NN15 25Co(Ac)Al-NN15 20Co(Ac)Al-M 3,820 3,328 2,344 1,002 0,725 0,429 0,993 0,599 0,608 5,815 4.652 3,382 Ket qua do mat do tam axit ciia cac xiic tac mang tren y-Al203 dugc trinh bay trong bang 2. Tir bang 2 ta thay, mat do tam axit yeu cua cac xiic tac tren cac chit mang y-Al203 khac nhau tang khi ham lugng Co tang tir 10 len din 20% va giam xudng khi ham lugng Co tiep tuc tang den 25%. So vdi xiic tac mang tren Al-M, cac xiic tac mang tren Al-NlO va AI- NN15 cd mat do tam axit yeu nhieu ban. Anh SEM ( hinh 3) ciia cac xuc tac 20CoAl-NlO, 2OC0AI-NNI5, 2OC0AI-M cho thay, tren bl mat ciia hai xiic tac mang tren Al-NlO va Al- NN15 deu cd nhiing hat Co min nim xen va phii len cac tinh thi y-Al203 hat Idn. So vdi mau mang tren y-Al203(Merck), tren cac xuc tac mang tren y-Al203 biln tfnh cac hat Co phan tan deu va nhd hon. Anh EDS cho thay sir phan tan ciia cac thanh phin tren xiic tac tuang ddi ddng deu. a) 20Co(Ac)Al b) 20Co(Ac)Al-NlO Hinh 3. Anh SEMvd EDS cua cdc xitc tdc tdi uu mang trin y-Al20j e) 20Co(Ac)Al-NN15 2) Hoat tinh cua cdc xuc tdc Bdng 3. Dd chuyin hda CO (Xco), do chgn lgc hydrocgebon C5+ (Scs ) vd hiiu sudt tgo hydroeacbon Cj+ CP) eiia cdc mdu xiic tdc Ky hieu inau lOCo(Ac) Al-NlO 15Co(Ac) •\1-N10 20Co(Ac) \I-Ml) :.K\i(Ac) 220"C ^CO SC5+ 35,9 38,2 74,9 46,2 75,0 75,4 65,2 65,7 Y 26,9 28,8 48,8 30,4 240''C ^CO SC5+ Y 260°C ^CO % 43,5 65,5 93,6 69.5 70.4 61,4 49.19 40.8 30,6 40,3 46 28,4 57,8 86,6 99,7 95,7 SC5+ 55,0 38,9 35,9 22,2 Y 31,8 33.7 35.8 21.2 280''C ^CO 81.0 100 100 100 SC5+ 32,4 23.9 28.6 14.2 Y 26,3 23,9 28,6 14,2 301 Tieu ban Khoa hgc vdt lieu ISBN: 978-604-913-011-3 Al-NlO lOCo(Ac) A1-NNI5 15Co(Ac) AI-NN15 20Co(Ac) A1-NNI5 25Co(Ac) AI-NNI5 20Co(Ac) Al-M 21,9 41,9 59,2 58,7 43,8 81,0 69,2 73,6 54,7 74,1 17,7 29,0 43,6 32,1 32,4 31,7 62,8 88,4 83,4 77,1 66,7 58,9 52,2 33,7 49,2 21,2 37,0 46,1 28,1 38,0 50,7 86,7 99,8 95,5 91,7 53,9 32,7 32,8 19,2 38,9 27,4 28,4 32,8 18,4 35,7 69,5 100 100 100 100 35,4 15.1 23,4 14,4 21,4 24,6 15,1 23,5 14,4 21,4 San pham ciia phan iing la cae parafin Cr C13. Do dd, ngoai san pham chinh la cac parafin C5+, cdn cd cac san pham phu la cac parafin nhe C1-C4. Tir bang 3 ta thay, khi tang nhiet do do chuyin hda CO tang, cdn do chgn lgc tao parafin C5+ giam, do dd hieu suat tao C5+ dat cao nhit d nhiet do tdi uu. Phan Idn xiic tac cd nhiet do cho Y cao nhat la 220 - 240°C. Tren cac y-Al203 khac nhau hieu suat Y dat cao nhat khi ham lugng phii Co la 20%. Dilu nay dugc giai thich la do cac xuc tac nay cd C03O4 ket tinh tdt nhat, mure do khir va mat do tam axit yeu cao nhat, nen cd do chuyen hda cao nhat. So vdi xiic tac 2OC0AI-M, nhiet do tdi uu cho phan iing ciia xiic tac 20Co(Ac)Al-N10, giam tir 240°C xudng cdn 220°C va hieu suat phan iing tang tir 38% len 48,8%, cdn tren xiic tac 20Co(Ac)Al-NN15, hieu suat phan img dat 46,1% d nhiet do phan iing tdi uu 240°C. Cac xiic tac tren chat mang bien tinh, su gia tang manh me do chuyen hda CO la nguyen nhan true tiep ciia viec cai thien hieu suat phan ung. So sdnh hogt tinh cua cdc xdc tdc tot nhat dieu che tir Co(N03)2 vd Co(CH3COO)2 Bdng 4. So sdnh ddc trung l-y - hda vd hgat tinh ciia cdc xiic tdc tdt nhdt diiu chi tit tiin chdt coban nitrat vd acetat (T- nhiit do tdi im) Xuc tac 15Co(N)Al 15Co(N)Ai-N10 15Co(N)Al-NN15 20Co(Ac)Al 20Co(Ac)Al-N10 20Co(Ac)Al-NN15 SBET. m'/g 91,9 83,0 109,7 58,33 90,13 89,18 T "C 306. 499,720 464,730 397,446, 737 440,765 465 460 Kr,U. % 6,60 7,10 11,10 10,32 15,10 13,00 T,°C 260 240 220 240 220 240 Xco, % 79,8 71,7 64 77,1 93,6 88,4 Sc5+, % 43,9 63,7 70 49,2 49,1 52,2 Y, % 35,0 45,7 44,8 38,0 48,8 46,1 Tuong tu xiic tac dieu che tir coban axetat, do chuyen hda CO tren xuc tac dilu cbl tir coban nitrat ciing dat gia tri cao nhat la 100% d nhiet do 280°C. Tuy nhien, d nhiet do thip (220°C), do chuyen hda CO tren xiic tac dieu che tir coban axetat eao hon so vdi xuc tac dilu cbl tir coban nitrat. Dieu nay dugc giai thich la do cac xuc tac dilu cbl tir Co(CH3COO)2 cd miirc do khir cao ban, phan tan min hon ( cudng do cac vach phd ciia C03O4 ylu ban so vdi xiic tac dilu che tir cobalt nitrat). Hai xiic tac cd hieu suit tao C5+ cao nhit trong hai nhdm xiic tac la 15Co(N)Al-N10 va 20Co(Ac)Al-N10 vdi hieu suit Y tuong iing bing 45,7% va 48,8%. Vay chit mang xir ly bang dung dich 10% NH3 tdt hon xir ly bing NH4NO3 va tiln chit cobalt acetate phii hgp hon so vdi cobalt nitrat. Hieu suat phan iing tao C5+ dat gia tri cao nhit la 48,8% d Xco = 75% va Sc5-^= 65% d nhiet do 220°C tren xuc tac 20Co(Ac)Al- NIO. 302 Hoi nghi Khoa hoc ky- niim 35 ndm Viin KH&CNVN - Hd Ngi -10'2010 Loi cam on: Cac tac gia chan thanh cam on Ban chu nhifm Hudrig Khoa hgc vat heu da tao dieu kien cho chung tdi thuc hien dl tai ""Nghien ciiu che tao chat xiic tac de chuyen hda hdn hgp CO va CO2 thanh nhien lieu Idng': Day la mgt phan ket qua ciia de tai. TAI LIEU THAM KHAO: 1. Luu cim Lgc, Lam Thi Thanh Tam, Nguyen Manh Huan, Lac Kien Trieu, Dang Thi Nggc Yen, Hd ST Thoang, Anh hudng ciia sir biin tinh AI2O3 din tinh chdt ciia xiic tdc C0/AI2O3 trong chuyin hda CO thdnh nhiin lieu Idng, Toan van HN Hda hgc toan qudc. Ha Ngi 11/2010 2. Kraum M. and B. Manfred, Applied Catalysis A, 186, 189 (1999) 3. Sun S. L., N. Tsubaki, K. Fujimoto, Appl Catal A, 202, 121(2000) 4. Wang Y., M. Noguehi, Y. Takahashi, Y. Ohtsuka, Catalysis Today, 68, 3(2001). 5. Ohtsuka Y., Y. Takahashi, M. Noguehi, T. Arai, S. Takasaki, N. Tsubouchi, Y. Wang, Catalysis Today, 89, 419(2004). 6. Amoldy P. and Moulijn J. A., J. Catal., 93, 38(1985). 303 . uu ciia Co trong xiic tdc dugc diiu chi tit cobalt acetat la 20%, trong khi tit cobalt nitrat la 15%. Hiiu sudt tgo hydrocarbon Idng tit tiin chdt cobalt acetat cao han tit cobalt nitrat monoxide. The optimal contents of cobalt in catalysts prepared from cobalt acetate have been shown to be 20 wt.%o, while the optimal content of cobalt in catalysts prepared from cobalt nitrate has. cua C03O4 (Kred) trong cdc mdu xuc tdc diiu che tit cobalt acetate Mau 1 0Co( Ac)Al-N10 2 0Co( Ac)Al-N10 2 5Co( Ac)Al-N10 1 0Co( Ac)Al-NN15 2 0Co( Ac)Al-NN15 2 5Co( Ac)Al-NN15 2 0Co( Ac)Al** SBET,