Tổng hợp và nghiên cứu khả năng xúc tác của các oxit kim loại kiểu spinen trong phản ứng điều chế stiren từ etylbenzen

190 Tong hop va nghien cdu kha nang xuc tac ciia cac oxit kim loai.<br /> <br /> <br /> <br /> TONG HOP VA NGHIEN ClTU KHA NANG XUC TAC<br /> CUA CAC OXIT KIM LOAI KIEU SPINEN TRONG PHAN ITNG<br /> DIEU CHE STIREN TU ETYLBENZEN<br /> <br /> <br /> Hoa Hiru Thu, Vii Thanh Nam<br /> Trudng Dai hpc Khoa hpc Tu nhien<br /> Ha Thu Huang<br /> Vien Ddu Khi<br /> Nguyen Thj Thu Ha<br /> TT Nghien ciru vd Phdt trien Che bien Ddu khi<br /> <br /> TOM TAT<br /> Hien nay stiren dugc sdn xudt vai sdn lugng tren todn cdu Id khodng 16 trieu tdn/ndm<br /> theo hai qud trinh: dehydro hda etylbenzen vd epoxi hda propen bdng<br /> etylbenzenhydroperoxit. Dehydro hda etylbenzen la qud trinh dugc sic dung rdng rdi trong<br /> cdng nghiep. Trong qud trinh ndy. nguai ta diing cdc xiic tdc tren ca sa sdt oxit vd nhiet<br /> dp phdn icng cao khodng 87OK trong su cd mat cua hai nuac. Cdc xiic tdc ky thudt thuang<br /> chira mpt luang nhd mdt sd oxit kim logi khdc ddng vai trd ldm chdt tdng tdc cdu triic.<br /> Idm dn dmh xiic tdc vd ngdn ngira sir kit tinh lgi ciia pha hogt dpng xuc tdc. Ddi vai cdc<br /> xiic tdc sdt oxit, chdt tdng tdc thudng Id KiO, nhung dp hogt dpng ciia xiic tdc vdn gidm<br /> ddn trong qud trinh phdn irng.<br /> Ddi vai viec sdn xudt stiren. ngodi qud trinh dehydro hda etylbenzen a quy md cdng<br /> nghiep, cdn cd cdc qud trinh khdc dang dugc nghiin cim. Trong bdo cdo ndy, chiing tdi<br /> tdng hgp mpt vdi ddy xiic tdc oxU kim logi kiiu spinen AB2.,rB., 'O4 (A =Ni'', Cu''; B=Cr^'<br /> vd B '=Fe : x=0; 0,5; 1; 1.5 vd 2) theo cdc phuang phdp khdc nhau: phdn icng a trgng<br /> thdi rdn vd ddng kit tiia, xdc dinh mdt sd ddc trung cdu tnic vd tinh chdt be mat cua<br /> chiing. vd ddnh gid khd ndng xiic tdc cua chiing trong phdn irng dehydro hda etylbenzen<br /> thdnh stiren. Cdc kit qud thuc nghiem da chi ra rdng cdc spinen ddy CuCr2.:,Fefi4<br /> (x=0;0,5;l;l,5;2) cd dp hogt dpng xiic tdc cao nhdt trong phdn img oxi dehydro hda<br /> etylbenzen thdnh stiren trong su cd mat ciia hai nuac.<br /> <br /> MODAU<br /> Trong nhtrng nam gan day, stiren dugc tieu thy ngay cang tang. Stiren duge diing<br /> lam nguyen lieu dau eho tdng hgp cac polime va copolime. San lugng stiren tren thi gidi<br /> vao khoang 16 trieu tan/nam [9]. Stiren dugc san xuit theo bai each: (1) dehydro hda<br /> etylbenzen va (2) epoxi hda propen bang etylbenzenhidropeoxit vdi sy cd mat ciia eae xiic<br /> tac phuc molipden va stiren thu duge nhu mdt san pham phy trong qua trinh phan ung [1].<br /> Phan img dehydro hda etylbenzen tuomg ty phan img dehydro hda cac ankan. Qua trinh<br /> dehydro hda etylbenzen thdng thudng la mdt qua trinh thu nhiet, thuan nghjeh, cin quay<br /> vdng chat tham gia phan img (etylbenzen). va ty le boi nudc/etylbenzen cao. Bdi vay qua<br /> trinh nay can sir dung xuc tac. Cac xuc tac truyen thdng cho phan img la sit oxit dugc<br /> tang tdc bang KiO [3, 4, 6]. Tuy nhien, ngudi ta thay rang do boat dgng ciia xuc tae bj<br /> Tuygn tap bao cao Hgi nghj KHCN "30 nSm Phu khi Vift Nam: Cff hgi mdi, thach thde mdi' 191<br /> <br /> giam di mdt each bit thuan nghich trong qua trinh su dung do cac ion K^ chuyen djch tir<br /> bl mat vao sau trong tbi tich xuc tac [4, 7]. Chinh vi the viec tim kiem xuc tac mdi cho<br /> phan img nay dugc cac nha san xuit edng nghiep ciing nhu cae nha khoa hgc xuc tae quan<br /> tam, ddng thdi nhilu ky thuat dugc dua ra de nang cao hieu qua san xuat stiren. Cac ky<br /> thuat lam tang bieu suat stiren ed the gdm cac giai phap:<br /> • Dehydro hda etylbenzen, tiep theo oxi hda hidro de cung cap nhiet cho phan img<br /> dehydro hda thu nhiet va lam chuyen djch can bang ve phia tao thanh stiren.<br /> • Oxidehidro hda phat nhiet de lam chuyen djch can bang phan img ve phia tao<br /> thanh san pham va tien banh phan img d nhiet do thap hon.<br /> • Diing mang xuc tac de chuyen djch can bang ve phia tao thanh stiren va tien banh<br /> phan img d nhiet do thap hom.<br /> Bang 1 dudi day trinh bay kha nang xuc tac, cac ky thuat san xuat stiren va hien<br /> trang iing dyng cua cae ky thuat nay trong san xuat stiren [8].<br /> Bang 1: So sanh cac hieu nang xiic tac ciia cac giai phap ky thuat khae nhau<br /> de san xuat stiren tir etylbenzen<br /> Ky thudt Do chgn loc Nhiet do Hien trgng<br /> Xiic tde<br /> sdn xudt stiren, % phdn irng, °C icng dung<br /> Dehydro hda 90 600 - 650 Fe/K/Cr/O Cdng nghiep<br /> Dehydro hda/<br /> 90 605 Cdng nghe SMART Thuang mai<br /> oxi hda hidro<br /> Oxi dehidro hda 90 350 Carbon molsieve Nghien ciiu<br /> Oxi dehidro hda 90 480 V/Mg/O Nghien cim<br /> Ky thuat mang 94 625 Fe/K/V/Li/Cr/O Nghien cim<br /> <br /> Trong nhdng nam gan day, cd nhieu cdng trinh cdng bd kha nang xuc tac tdt cua<br /> cac oxit kim loai kieu spinen cho phan img dehydro hda etylbenzen thanh stiren [5]. Cac<br /> oxit kim loai kieu spinen cd cac cation kim loai phan bd tren cac mat tinh the (110) va<br /> (111) cd kha nang xue tae eho cac phan urng dehydro hda bidrocacbon. isopropanol,<br /> xiclohexanol [1]. Trong bao cao nay chiing tdi dieu che mdt vai day spinen bae ba cd cdng<br /> thuc chung: AB2.xB,'04 (C) day A = Ni^^, Cu^^; B = Cr^^ va B' = Fe^^), xac djnh cac dac<br /> trung cau true va hinh thai cua chung va danh gia kha nang xue tae eua chiing trong phan<br /> ung oxi dehydro hda etylbenzen thanh stiren.<br /> <br /> THUC NGHIEM<br /> \. Dieu che spinen<br /> Cd nhieu phuong phap dieu che spinen bae ba. Trong bao cao nay, chung tdi sir<br /> dyng bai phuomg phap dieu che spinen AB2.xBx'04 (x = 0; 0, 5; 1; 1,5 va 2) dugc trinh bay<br /> dudi day.<br /> 0. Phuang phdp phdn irng a trang thdi rdn<br /> Trong phuomg phap nay, chung tdi da dung eae kim loai oxit NiO, Cr203 va Fe203 cd<br /> do tinh khilt PA lam nguyen lieu diu dl dilu ebl cac spinen NiCr2.xFex04 (x = 0; 0, 5; 1;<br /> 1,5 va 2). Caeh lam nhu sau: Dau tien, tinh toan cae lugmg kim loai oxit theo cdng thue d<br /> tren ein phai lay, sau dd can lay lugmg oxit da tinh duge tren can phan tich. Trdn cac oxit<br /> kim loai trong cdi su that can than trong 30 phut sao eho cae oxit phan tan that diu trong<br /> 192 Tdng hgp va nghien cdu kha nang xiie tac cua eae oxit kim loai<br /> <br /> <br /> bdn hgp. Tilp theo dem ep vien bdt xue tae dudi ap lye 2000N/em^. Cho cac vien xuc tae<br /> nay vao chen nung va dat chen nung ehiia xue tac vao Id nung va ddt ndng Id nung den<br /> 1300°C. Giir nhiet do ciia Id nung d 1300°C trong 4 gid. Dl ngudi xue tac trong binh hut im<br /> sau dd dap vd vien xuc tac va ray lay cae hat xue tae cd dudng kinh tir 0,5 den 1mm.<br /> Phan ung hda bgc tao thanh spinen d nhiet do cao 1300°C nhu sau:<br /> 2NiO + XFCJOB + (2-x)Cr203 -> 2NiCr2.xFex04<br /> Khi X = 0, phan img tao thanh spinen nhu sau:<br /> NiO + Cr203 -> NiCr204<br /> Chung tdi ciing dieu che hai loai spinen NiCr2.xFex04 va CuCr2.xFex04 (x = 0; 0, 5;<br /> 1; 1,5 va 2) bing phuomg phap ddng ket tiia de so sanh va ngudn kim loai la cae nitrat kim<br /> loai tuong iing.<br /> b. Phuang phdp ddng ket tda<br /> Bang 2: Cac mau spinen thu dvcre bang cac phirotig phap dieu che khae nhau<br /> Sd Cac s pinen<br /> Phuang phap dieu che<br /> TT Cdng thirc Ky hiiu<br /> 1 NiCr204 NC 1 (I)<br /> 2 NiCri_5Feo,504 NCF 2 (I)<br /> 3 Phan img d trang thai ran NiCrFe04 NCF 3 (I)<br /> NiCro,5Fei,504 NCF 4 (I)<br /> 4<br /> NiCr204 NF 5 (I)<br /> 5<br /> 6 NiCr204 NC 1 (II)<br /> 7 NiCri,5Feo,504 NCF 2 (II)<br /> 8 Ddng ket tiia NiCrFe04 NCF 3 (II)<br /> 9 NiCro,5Fei,504 NCF 4 (II)<br /> 10 NiFe204 NF 5 (II)<br /> 11 CuCr204 CC I (II)<br /> 12 CuCri_5Feo,504 CCF 2 (II)<br /> 13 Ddng ket tiia CuCrFe04 CCF 3 (II)<br /> 14 CuCro,5Fei,504 CCF 4 (II)<br /> 15 CuFe204 CF 5 (II)<br /> Day la mdt phuong phap dom gian va rit thuan tien dl dilu ehi cac spinen bae ba.<br /> Trong phuomg phap nay, chiing tdi dung ngudn kim loai la cac nitrat: Ni(NO3)3.6H20,<br /> Cu(N03)2.6H20, Cr(N03)3.9H20 va Fe(N03)3.9H20, tit ca ed do tinh khilt PA (Aldrich).<br /> Cac spinen NiCr2.xFex04 va CuCr2.xFex04 dugc dilu chi nhu sau: Diu tien, tinh toan cac<br /> lugmg mudi kim loai can thiet phai liy theo edng thirc eua spinen mudn dilu ebl. Can cac<br /> lugmg mudi tren can phan tieh va hda tan chung vao nude sao cho thu dugc cae dung djch<br /> mudi 10% theo trgng lugng. Trdn cae dung djch mudi trong cdc 1 lit va ddt ndng dung<br /> djch den 80°C. Giir dung djch d nhiet do nay va trong khi khuiy manh them vao dd timg<br /> phin nhd dung djch NH4OH 5% din khi pH = 7. Giir nhiet do cua dung djch d 80°C trong<br /> 5 gid de ket tiia hoan toan cac kim loai. Lge kit tua va rira din hit NO ~ bing nude cit.<br /> Lay ket tua vao ede va siy khd d 120°C trong 6 gid. Trong khi siy d 120°C ed thi<br /> loai dugc nude bj hap phy va tao nen mdt phan cac lien ket kim loai - oxi - kim loai trong<br /> khdi ran thu duge. Cudi cung, nung chit rin d 750°C trong 4 gid. Bing cae each nay<br /> Tuyin tap bao cao Hgi nghj KHCN "30 nam DSu khi Vift Nam: Co hgi mdi, thach thde mdi" 193^<br /> <br /> <br /> 2. Cac phu-oTig phap vat ly nghien cihi xiic tac<br /> Cae gian dd nhilu xa tia X ciia tat ca cac mau deu dugc ghi tren may SIEMENS<br /> D5005 diing ngudn CuK^ vdi do dai sdng ciia tia X la 1,5406A. Cac anh SEM dugc chup<br /> tren may JSM 5410 LV, Japan.<br /> Cac phd hong ngoai chuyen hda Fourier, FTIR duge ghi tren may Nicolet-760,<br /> Magra, USA.<br /> Dien tich be mat rieng eua mau duge do tren may Auto sorb 01 Quantachrom, USA.<br /> 3. He thdng phan irng danh gia do hoat dong xiic tac va phan tich san pham long<br /> Phan ling oxidehydro hda duge tien hanh d pha hoi trong mdt dng phan img chua<br /> mdt ldp xuc tac cd dinh. Ong phan img dugc ddt ndng bang mdt Id dien, dugc khdng che<br /> bang mdt thiet bj dieu khien ky thuat sd. Nhiet do duge theo ddi bang mdt cap nhiet dien<br /> va hien thj tren thiet bj do. Chat phan iing dugc dua vao vung xuc tac qua mdt may bom<br /> xilanh ed the dieu khien duge tde do bom. San pham ldng dugc thu lay sau khi lam lanh<br /> qua dng sinh ban va dem phan tich tren may sac ky khi khdi phd GC-MS HP6890.<br /> <br /> KET QUA VA THAO LUAN<br /> Cac spinen la cac dung djch ran thdng thudng dugc dieu che tuy theo img dyng cua<br /> chung. Cac spinen cd the dugc hinh thanh d cac nhiet do khae nhau phu thudc vao cae tien<br /> chat dugc su dyng de dieu che chung. Trong phuomg phap phan img d trang thai ran, tat<br /> ca cac tien chat deu nam dudi dang eae oxit kim loai nen nhiet do phan img rat cao,<br /> 1300°C:<br /> 2NiO + xFe203 + (2-x)Cr203 I300"C > 2NiCr7-vFevO.<br /> (x = 0;0,5;l;I,5;2)<br /> Day la qua trinh don gian nhung rat tdn nang lugng dien.<br /> Trong cac phan iimg d trang thai ran nay, NiO tdn tai d trang thai ran vdi cau tnic lap<br /> phuang tam khdi, sd phdi tri cua Ni^"^ va O"^" la 6; Cr203 va Fe203 cd cau tnic luc phuong,<br /> trong khi dd cae spinen cd cau tnic lap phuomg tam mat. Cac cau tnic nay kha gan nhau<br /> nen d nhiet do 1300"C (nhiet do rat xa diem ndng chay cua cac oxit va spinen) nhung<br /> spinen van dugc hinh thanh. Trong thdi gian nung, mang cac anion O^' coi nhu dung yen,<br /> cdn cac cation Ni^"^, Cr''"^, Fe^"^ chuyen ddi vao cae vj tri tu dien va bat dien cua cau tnic<br /> spinen tao nen san pham phan ting. Qua trinh khuech tan cua eae cation kim loai hinh<br /> thanh spinen cd the dugc hinh dung nhu sau (Hinh I).<br /> Pha spinen<br /> Pha NiO<br /> <br /> N.^* Ni^<br /> <br /> Cr^ Fe^<br /> <br /> <br /> Pha Cr:0, Pha FejO,<br /> <br /> <br /> <br /> <br /> Hinh 1: Sff do tao thanh spinen bae ba NiCr2.xFe,04 d nhiet do cao<br /> 194 Tong hgp va nghien cdu kha nang xiic tac ciia cac oxit kim loai •.,<br /> <br /> <br /> <br /> That vay, tat ca cac gian dd nhieu xa ciia cae san phim NC 1 (I), NCF 2 (I), NCF 3<br /> (I), NCF 4 (I), NF 5 (I), (Hinh 2) cho phep khang djnh cac spinen da duge hinh thanh.<br /> <br /> W U H N - S l b M t N i UioOa Li>*« W«u Nt-I. N\,h^, NLh,<br /> <br /> <br /> <br /> <br /> Hinh 2: Gian do nhieu xa tia X ciia cac spinen NiCr2.xFex04 (x = 0; 0,5; 1; 1,5; 2)<br /> thu duffc bang phirotig phap phan irng d trang thai ran<br /> Cae qua trinh phan iing d trang thai ran nay cd the tuong tu nhu qua trinh ket tinh<br /> vdi su sap xep lai eua Ni^"^ vao vj tri tu dien va Cr^"^, Fe^"^ vao cac vj tri bat dien. Vi the,<br /> cae vi tinh the spinen dugc hinh thanh luc ban dau cd the xem chung nhu eae mam ket<br /> tinh tao dieu kien cho su hinh thanh tinh the spinen. Anh SEM cua mau NC 1 (I) da minh<br /> hga giai thich tren (Hinh 3).<br /> <br /> <br /> <br /> <br /> (a) (b)<br /> Hinh 3: Anh SEM ciia cac mau spinen<br /> a) Mau NiCr204 thu dugc bang phuang phap phan ung d trang thai rin<br /> b) Mau NiCr204 thu dugc bang phuomg phap ddng ket tua<br /> Tu Hinh 3, ta cung cd thi thiy cd tinh tbI NC 1 (I) ldn hom NCF 3 (II). Cac kit qua<br /> nghien cuu bang IR dugc trinh bay trong Bang 3 cung khang djnh ciu tnic eua spinen da<br /> thu duoc.<br /> Tuygn tap bao eao Hdi nghj KHCN "30 nam Dgu khi Vift Nam: Cff hgi mdi, thach thde mdi'' 195<br /> <br /> Bang 3: Cac vung hap thu trong pho hong ngoai cua cac mau spinen<br /> Cac bang h ap thu trong hong ngoai cua cac mau, cm"'<br /> Dao dpng ciia cdc Dao dpng eiia cdc Su cd mat cua Su cd mdt<br /> Cac spinen lien kit kim logi - lien kit kim logi - nitrat NO] cua nude<br /> oxi trong tu dien oxi trong bdt dien -1670 f3]<br /> -1390 f3J<br /> -620 [3] -530 f3J<br /> NC 1 (I) 600 447 —<br /> NCF 2 (I) 638 495 — —<br /> NCF 3 (I) 627 466 — —<br /> NCF 4 (I) 633 433 — —<br /> NF 5 (II) 627 423 — —<br /> NC 1 (II) 610 517 — 1634<br /> NCF 2 (II) 604 507 1378 1664<br /> NCF 3 (II) 664 554 1344 1638<br /> NCF 4 (II) 621 514 1439 —<br /> NF 5 (II) — — — —<br /> CC 1 (II) 630 528 — 1644<br /> CCF 2 (II) 620 456 1342 1634<br /> CCF 3 (II) 625 529 1351 1656<br /> CCF 4 (II) 625 449 1341 —<br /> CF 5 (II) 595 443 1338 1<br /> Cac mau ran thu dugc bang phuong phap ddng ket tua ciing dugc chup nhieu xa tia<br /> X (XRD). Cac ket qua thu dugc dugc trinh bay trong Bang 4 khang djnh cac chat ran dd<br /> la cac spinen mong mudn.<br /> Bang 4: Cac khoang each mang lirdi (dhik) dirtfc tinh tu* cac gian do nhieu xa tia X cua<br /> cac mau: NiCr2-xFex04 va CuCr2.xFex04 thu diro"c bang phirotig phap dong ket tua so vdi<br /> NiCr2.xFex04 thu dirac bang phirotig phap phan irng d trang thai ran<br /> <br /> Mat dhik theo dhik cua cac spinen NiCr2-xFex04 thu dugc ban^; phuong phap ddng ket tua<br /> tai lieu NC 1 (II) NCF 2 (II) NCF 3 (II) NCF 4 (II)<br /> hlk<br /> [3]<br /> 111 4,81 4,81 4,80 4,80 4,79<br /> 220 2,93 2,95 2,94 2,95 2,95<br /> 311 2,40 2,50 2,51 2,51 2,51<br /> 222 2,40 2,40 2,40 2,41 2,40<br /> 400 2,08 2,08 2,08 2,08 2,08<br /> 422 1,70 1,70 1,69 1,70 1,69<br /> dhik cua cac spine;n CuCr2-xFex04 thu dugc banj; phuong phap ddng ket tua<br /> CC 1 (II) CCF 2 (II) CCF 3 (II) CCF 4 (II) CCF 5 (II)<br /> 111 4,81 4,80 4,79 4,79 4,79 4,79<br /> 220 2,93 2,94 2,93 2,94 2,94 2,95<br /> 311 2,40 2,51 2,51 2,51 2,51 2,49<br /> 222 2,40 2,41 2,41 2,31 2,42 4,42<br /> 400 2,08 2,08 2,06 2,07 2,09 2,09<br /> 196 Tdng hop va nghien cdu kha nang xuc tac ctia cac oxit kim loai...<br /> <br /> <br /> 422 1,70 1,70 —<br /> dhik ciia cac spinen NiCr2-xFex04 thu dugc bang phuong phap phan img d<br /> trang thai ran<br /> NC 1 (I) NCF 2 (I) NCF 3 (I) NCF 4 (I)<br /> 111 4,81 4,80 4,79 4,79 4,81<br /> 220 2,93 2,95 2,90 2,93 2,93<br /> 311 2,40 2,51 2,48 2,50 2,50<br /> 222 2,40 2,41 — — 2,40<br /> 400 2,08 2,08 2,07 2,07 2,07<br /> 422 1,70 1,70 1,69 1,69 1,69<br /> Tu cac dir kien thye nghiem duge trinh bay d tren cho thay qua phuomg phap ddng<br /> kit tua cd thi dilu chi dugc cac spinen bae ba AB2.xBx'04 (A = Ni ^, Cu "^; B = Cr va B'<br /> = Fe^"") d nhiet do thip hom, 750°C so vdi nhiet do cua phuomg phap phan img d tr^ng thai<br /> rin, 1300°C dilu ehi NiCr2.xFex04. Mgt nh^n xet nira la theo phuong phap ddng kit<br /> tua cd hat cua spinen nhd hom, cd dien tich be mat khoang 20m /g (Hinh 3).<br /> Ta bilt ring: thanh phin xue tac, phuong phap dieu che xuc tac, cac dieu kien<br /> dilu chi nhu nhiet do, mdi trudng phan ung, v.v... anh hudng tdi do boat dgng xiic tac<br /> cua chung. Bang 5 trinh bay cac ket qua danh gia do boat dgng xiic tac ciia cac spinen<br /> trong phan ung oxi dehydro hda etylbenzen thanh stiren.<br /> Bang 5: Thanh phan ciia san pham long thu du-ffc trong phan uiig oxi dehydro hoa<br /> etylbenzen thanh stiren d nhiet do khae nhau, toe do ddng khdng khi 1,01/ph,<br /> toe do the tich 0,6h"'<br /> Nhiet dp Do chuyen hda Dp chgn lge Hieu suat<br /> Xiic tac etylbenzen, % stiren, % toluen+benzen, %<br /> phan ling, ^C<br /> 350 12,31 45,31 54,69<br /> NC 1 (I) 400 17,71 39,52 60,48<br /> 450 33,79 36,80 63,20<br /> 350 14,15 66,29 32,71<br /> NCF 2 (I) 400 21,32 61,30 38,70<br /> 450 38,14 53,20 45,19<br /> 350 19,20 92,90 6,18<br /> NCF 3 (I) 400 34,47 92,40 6,54<br /> 450 61,43 91,21 8,70<br /> 350 18,71 78,07 21,41<br /> NCF 4 (I) 400 31,38 70,07 28,16<br /> 450 47,65 64,30 35,40<br /> 350 16,25 78,29 21,45<br /> NF5(I) 400 28,69 69,45 30,06<br /> 450 46,44 59,12 35,22<br /> 350 21,72 56,06 40,15<br /> NC 1 (II) 400 22,52 57,63 41,23<br /> 450 32,37 40,76 55,58<br /> 350 26,45 72,60 20,33<br /> NCF 2 (II) 400 34,15 65,15 30,75<br /> 450 40,26 64,47 33,51<br /> 350 21,17 92,14 6,74<br /> NCF 3 (II) 400 43,43 85,60 13,21<br /> 450 58,82 82,60 16,79<br /> NCF 4 (II) 350 16,67 87,58 11,56<br /> Tuygn tap bao cao Hdi nghj KHCN "30 nam DSu khi Vift Nam: Cff hgi mdi, thach thde mdi" J ^<br /> <br /> <br /> 400 38,43 71,13 24,43<br /> 450 43,52 69,63 30,04<br /> 350 15,71 79,83 18,81<br /> NCF 5 (II) 400 28,36 72,52 24,63<br /> 450 40,08 60,13 37,69<br /> 350 35,27 93,69<br /> CCl 47,03 70,72 —<br /> 400<br /> (II)'*' 450 98,21 47,76<br /> 350 30,42 92,78<br /> CCF 2 —<br /> 400 51,62 89,43<br /> (II)'*' 450 70,14 57,15<br /> 350 40,01 78,27<br /> CCF 3 —<br /> 400 70,23 90,17<br /> (II)'*' 450 70,23 69,20<br /> 350 39,56 81,17<br /> CCF 4 —<br /> 400 65,42 72,06<br /> (II)'*' 450 78,95 70,45<br /> 350 29,94 95,19<br /> CF 5 (II)''' 400 38,18 96,72 —<br /> 450 52,12 78,84<br /> Ghi chu: * Cac dieu kien phan img tren cac xiic tac nay gidng nhu cac dieu kien tren cac xiic<br /> tac khae nhumg khdng cd hai nude.<br /> Cac ket qua dugc trinh bay d Bang 5 cho thay kha nang xuc tac tdt cua cac spinen<br /> trong phan iing oxidehydro hda etylbenzen thanh stiren. Cac ket qua nay eiing ehi ra rang<br /> khi nhiet do phan img tang, do chuyen hda etylbenzen tang, do chgn lge stiren giam.<br /> Trong khoang nhiet do tir 350°C din 450°C, cac spinen NiCrFe04 3 (I), NiCrFe04 3 (II),<br /> CuCrFe04 3 (II) (vdi x = 1) cho do boat ddng xuc tac va do chgn lge stiren cao nhat.<br /> Trong phan img oxidehydro hda etylbenzen thanh stiren tren cae xuc tac CuCrFe04,<br /> vai trd eiia nude rat quan trgng. Sy ed mat cua nude da loai dugc eae phan ung phy nhu<br /> dealkyl hda etylbenzen thanh benzen va etylen, cracking lien ket C-C cua nhdm etyl trong<br /> phan tu etylbenzen. Trong khi dd cac phan iimg phy nay xay ra kha manh cimg vdi phan<br /> ling chinh, oxidehydro hda etylbenzen thanh stiren tren cac xiie tac NiCr2.xFex04 (I) va<br /> (II). Cd the sy ed mat cua nude gay nen hien tugng hap phy canh tranh can trd cac phan<br /> img phu xay ra. Dya tren mdt sd edng bd trong nhirng nam gan day [10] va eae ket qua<br /> dugc trinh bay trong Bang 5, chung tdi cd the gai thich sy phirc tap cua phan img oxi<br /> dehydro hda etylbenzen tren cac xuc tac NiCr2.xFex04 (I) va (II) nhu sau:<br /> Dau tien, oxi bi hap phy tren Id trdng cua be mat xuc tac hinh thanh oxi bj hap phy<br /> (0„-.):<br /> 3+<br /> - O 2 + Me'^ (O:.) + Me<br /> 2<br /> Sau dd cac phan iing dom phan tu xay ra theo co che Langmuir-Hinshelwood dan<br /> ien san pham phan img.<br /> • Qud trinh tdch hidnia tren cdc tdm kim logi Fe^^ hay Cr^* (Me^^):<br /> <br /> CH3<br /> <br /> ^H H<br /> Me3+ 02-Me3+02- 3+ o2-Me2+02-<br />  Tdng hgp va nghien cdu kha nang xuc tac cua cac oxit kim loai...<br /> 198<br /> <br /> Qud trinh did gdy lien kit C-C:<br /> <br /> <br /> CH—CH2- C2H4<br /> -CH CH2 =<br /> H<br /> <br /> ]^e3+02-Me2+02-<br /> r<br /> 3+02-Me2+02<br /> Me'<br /> Me3+02-Me2+02-<br /> <br /> <br /> <br /> <br /> C2H4<br /> ^H« + gas<br /> <br /> Me3+o2-Me3+o2-<br /> Me3+ 02-Me2+02-<br /> <br /> <br /> <br /> <br /> -CH3 * gas<br /> <br /> <br /> Me3+ 02-Me3+02-<br /> <br /> • Oxi dehidro hda ion cacboni trung gian:<br /> • H<br /> <br /> <br /> <br /> H^- CH2=CH2 + Oad<br /> (*H-^CH2—H ^<br /> -K>.ad<br /> <br /> I<br /> Me3+ 0 2 - M e 2 + 0 - Me3+02-Me2+0ret<br /> <br /> <br /> H H<br /> <br /> <br /> / ( ^ \ — C H 2 = CH2+ Me3+ o2- Me2+ 0 ^ 1 + Oad<br /> <br /> <br /> <br /> Qud trinh lap lgi:<br /> 20H" ^ H 2 0 + 0 2-_<br /> 1<br /> Me^^ + 2 02^Me^^+0;;rf<br /> . 2-<br /> O „g, la Oxi tir mang ludi spinen<br /> O "^ la Oxi bi hap phu<br /> O day, Me^"^ cd the la Cr^"^ hay Fe^"^. Ca hai cation nay la eae tam axit Lewis cd kha<br /> nang giir nhan phenyl nhu nhau va cd kha nang tach hidrua tuong ty.<br /> <br /> KET LUAN<br /> <br /> 1. Chung tdi da tdng hgp ba day spinen theo hai phuong phap phan iing d trang thai<br /> ran va ddng ket tua. Phuong phap ddng ket tua thuan lgi hom vi nhiet do cin thilt<br /> eho sy tao thanh spinen thap hon.<br /> 2. Chung tdi da su dyng eae phuomg phap vat ly XRD, IR, SEM, SBET dl kilm tra<br /> Tuygn tap bao cao Hgi nghj KHCN "30 nam DSu khi Vift Nam: Cff hgi mdi, thach thde mdi" 199<br /> <br /> <br /> cau tnic cac spinen thu dugc. Cae ket qua da khang djnh cac san pham thu dugc<br /> cd cau tnic spinen.<br /> 3. Cac spinen cd do boat ddng va do chgn lge stiren cao trong phan img oxi<br /> dehydro hda etylbenzen thanh stiren dae biet khi cd mat hoi nude.<br /> 4. Phan ung oxi dehydro hda etylbenzen tren cac spinen NiCr2.xFex04 (I) va (II) rit<br /> phiic tap, ngoai phan ung chinh tao thanh stiren cdn cd cac phan iing phu anh<br /> hudng tdi chat lugng stiren.<br /> <br /> <br /> TAI LIEU THAM KHAO<br /> 1. Cavani F., Trifigo F., 1995. Alternative processes for the production of styrene. Appl.<br /> Catal. A: General, 133, 1995, p. 219 - 239.<br /> 2. Gabr R.M., Girgis et al., 1997. Effect of spinel (ZnCr204) formation on the texture,<br /> electrical conduction and catalytic behaviour of the ZnO-Cr20i system. Materials<br /> Chemistry and Physics, 39, 1994, p. 53 - 62.<br /> 3. Inui T., Anpo M., Izui K., Yanagida S., Yamaguchi T., 1998. Dehydrogenation of<br /> ethylbenzene over iron oxide-based catalyst in the presence of carbon dioxide. Studies<br /> in surface science and catalysis. 114, 1998, p. 415 - 418.<br /> 4. John Jebarathinam N., Eswaramoorthy M., Krishnasamy V., 1996. Nonoxidative and<br /> oxidative dehydrogenation of ethylbenzene over Zn-Fe-Cr tenary spinel system. Appl.<br /> Catal. A: General, 145, 1996, p. 57 - 74.<br /> 5. Kung H.H., Kung M,C., 1997. Oxidative dehydrogenation ofalkanes over vanadium-<br /> magnesium-oxides. Appl. Catal. A: General, 157, 1997, p. 105 - 116.<br /> 6. Lee E.H., 1973. Iron oxide catalysts for dehydrogenation of ethylbenzene in the<br /> presence of steam. Catalysis reviews, 1973, p. 285 - 305.<br /> 7. Mihajlova A., Andreev A., Shopor D., et al., 1987. New iron based catalyst for<br /> dehydrogenation of ethylbenzene to styrene obtained by decomposition of metal salts<br /> in organic solvent. Proc.Vl"^ Int. Symp. Heterogeneous catalysis, Sofia, 1987, Part 2,<br /> p. 4 3 6 - 4 4 1 .<br /> 8. Perrin R., Scharff J.P., 1993. Chimie Industrielle Vol I. Masson, Paris-Milan-<br /> Barcelone-Bom.<br /> 9. Tuyen Mai, 2002. Petrochemical and organic industries: Opportunities and<br /> challenges. Proceedings of the Conference on Refinery and Petrochemical Technology<br /> in the XX - XXI century, Hanoi, 20-21 Dee., 2002.<br /> 10. Thu Hoa Huu, Chau Trinh Ngoc, Due Truong Dinh, 2002. Synthesis of ternary spinels<br /> NiCr2-xFe^04 and their catalytic activity in oxidative dehydrogenation of ethylbenzene<br /> to styrene. Proceedings of the Conference on Refinery and Petrochemical Technology<br /> in the XX - XXI century, Hanoi, 20-21 Dee., 2002.<br />