Tổng hợp và đặc trưng vật liệu xúc tác cho phản ứng chuyển hóa LPG thành Olefin nhẹ

58 Tong hop va die trung vat lieu xuc tic cho phan dng...<br /> <br /> <br /> <br /> TONG HOP VA DAC TRlTNG VAT LIEU XUC TAC CHO PHAN iTNG<br /> CHUYEN HOA LPG THANH OLEFIN NHE<br /> <br /> <br /> Le Thanh Son, Ngd Kim Thanh<br /> Pham Thj Hdng Diic, Hoang Hiep<br /> Trudng Dgi hpc Khoa hpc Ttr nhien<br /> <br /> <br /> <br /> TOM TAT<br /> Cdc oxit kim logi chuyen tiep nhu V2OS hoae Ti02 mang tren vat lieu mao qudn<br /> trung binh hodc vdt lieu vi mao qudn la cdc he vdt lieu cd tinh oxy hod khic phdn tdn tren<br /> nen cd dien tich be mat lan ldm xuc tdc cho qud trinh oxy dehydro hod ankan thdnh anken<br /> tic ngudn LPG sdn cd vd re tien thdnh cdc sdn phdm cd gid tri han dang duac quan tdm<br /> sdu sdc. Bdo cdo de cap chi tiet den qud trinh tdng hap vd ddc trung cdc he xiic tdc<br /> V20j/MCM-48 vd Ti02/ZSM-5, buac ddu thdo ludn kit qud thu duac cua qud trinh chuyen<br /> hod LPG thdnh cdc olefin nhe.<br /> <br /> MODAU<br /> Khi hoa Idng (LNG) va khi dau Idng (LPG) dugc dua vao sir dyng mdt each phd<br /> bien tren the gidi mudn hon rat nhieu so vdi cac nhien lieu dau md khae nhu xang, dau<br /> DO, FO nhung lai cd tdc do phat trien rat manh me tren khap the gidi vdi mirc tang trudng<br /> ve san xuat va tieu thy khi deu rat cao do nhiing uu viet cua nhien lieu ly tudng nay cho<br /> theky mdi [1].<br /> Tren the gidi, LPG da trd thanh ngudn nhien lieu thdng dyng trong cdng nghiep va<br /> dan dyng. Dac biet, LPG cd img dyng quan trgng trong hoa dau - la nguyen lieu cho steam<br /> cracking, oxy hoa butan thanh anhydrit maleic, dehydro hoa propan thanh propylen va<br /> reforming thanh hydrocarbon thom .<br /> Cdng nghiep khi va thj trudng khi Viet Nam dang bude vao giai doan phat triln<br /> nhanh chdng. San lugng khi md Bach Hd la 4 trieu mVngay va Nam Cdn Son la 20 trieu<br /> mVngay. Khi dau Idng LPG tir nha may Dinh Cd cd san lugng 340.000 tin/nam va nha<br /> may lge dau sd 1 cd san lugng khoang 250.000 tan/ nam [5].<br /> Do nhu cau sir dyng olefin ngay cang gia tang dan den sy quan tam, nghien ciiu sau<br /> qua trinh oxy dehydro hoa ankan thanh anken tir ngudn LPG san cd va re tiln thanh cac<br /> san pham cd gia trj hon.<br /> Vat lieu mao quan trung binh vdi dudng kinh Id tir 20 den 100A° duge sir dung lam<br /> chat hap phy va chat xiic tac. MCM-48 cd cau true lap phuang, thudc nhdm khdng gian<br /> Ia3d. He thdng mang khdng gian ba chieu dan xen nhau cua cae kenh trong MCM-48<br /> dugc coi la nguyen nhan lam giam bdt viec nghen cac kenh dan khi nd dugc sir dyng lam<br /> chat hap phu hay chat mang xiic tac.<br /> Tuygn tap bao cio Hpi nghj KHCN "30 nim Dau khi Vift Nam: Co' hpi mdi, thach thde mdi" 59^<br /> <br /> <br /> ZSM-5 la zeolit cd ham lugng Si cao, xiic tac cho nhilu qua trinh tdng hgp him co<br /> hoa diu quan trgng. ZSM-5 thudng dugc tdng hgp bing phuong phap sol-gel sir dyng chit<br /> tao ciu triic. Mac dii chit tao ciu tnic ddng vai trd quan trgng, song ed nhieu nhugc diem<br /> nhu dat tiln, ddi hdi qua trinh phan buy nhiet sau tdng hgp, gay d nhiem mdi trudng. Vi<br /> vay, viec tdng hgp zeolit ZSM-5 khdng diing chat tao catr-triic dugc quan tam hon.<br /> V2O5 va Ti02 la cac oxit kim loai chuyen tiep mang tren vat lieu ke tren se tao ra cac<br /> he xuc tac cd tinh oxy hoa khir phan tan tren nen cd dien tich be mat ldn cho phan iing<br /> oxy dehydro hoa ankan thanh olefin.<br /> <br /> THU'C NGHIEM<br /> <br /> 1. Tdng hop V2O5/MCM-48<br /> <br /> a. Ngudn nguyen lieu<br /> - Dung djch thuy tinh Idng 10%) (Si/AI = 1,5)<br /> - Chit boat ddng bl mat trung tinh: C|2H25(C2H40)40H [C,2(EO)4]<br /> - Chat boat ddng be mat cation: Cetyl Trimetyl Amoni Bromua (CTABr) Vanadi<br /> pentoxit V2O5<br /> - Axitoxalic C2H2O4<br /> b. Phuang phdp tdng hap<br /> Hoa tan 52,08g CTABr va 9,04g C,2(EO)4 trong 765g nude cit. 500g dung dich<br /> Na2Si03 10%) dugc rdt vao dung djch chat boat ddng be mat chira trong Ig polypropylen<br /> va dugc lac manh trong vai phiit. Sau do hdn hgp dugc khuay 30 phut. Hdn hgp phan ung<br /> dugc giir d IOO°C trong I2h. Sau dd hdn hgp dugc lam lanh den nhiet do phdng va dieu<br /> chinh pH tdi 10 bang dung djch axit axetic 30%). Hdn hgp dugc ddt ndng lan nira tdi<br /> 100°C trong 24h. Lge kit tiia, rira bing dung djch hon hgp HCI va EtOH, nung d 550°C<br /> trong 4h [2, 6].<br /> MCM-48 dugc tam dung dich vanadi oxalat (dieu che bang each hoa tan V2O5 vao<br /> axitoxalic) cd ham lugng da tinh toan dugc bd sung nude vira dii udt vdi MCM-48, trdn<br /> ky d nhiet do phdng, say d 100°C trong 24h va nung d 500''C trong 4h.<br /> <br /> 2. Tdng hop Ti02/ZSM-5<br /> a. Ngudn nguyen lieu<br /> - Thuy tinh Idng (Viet Nam) I I,I6%Na20; 3I,l%Si02 (d = l,357g/ml)<br /> - Al2(S04)3.18H2O, H2S0498%, (Trung Quoc)<br /> - Mim zeolit ZSM-5 (Phap) cd ty le Si/AI = 50<br /> b. Ph uang ph dp tdng h pp<br /> H2SO4 98% dugc pha loang 70 lan va hda tan Al2(S04)3.I8H20. H2SO4 da pha loang<br /> dugc them tir tir ddng thdi vdi qua trinh khuiy va gia nhiet vao thiiy tinh Idng dl dilu<br /> chinh pH. Sau dd, cho tir tir dung djch mudi nhdm vao dung djch thuy tinh Idng da dilu<br /> 60 Tong hpp v i die tru-ng vat lifu xiic t i c cho phan dng.<br /> <br /> <br /> chinh pH, tilp tyc khuay va dun ndng cho den khi thu dugc he gel ddng nhat, cd pH « 12.<br /> Cac he gel duge chuin bj sao cho ty le Si/AI trong gel la 40. Them mam zeolit ZSM-5,<br /> bing 0,03%o lugng silic trong he, vao he gel da ddng nhat, ngirng gia nhiet va tiep tuc<br /> khuiy trong 30 phiit dl mim ZSM-5 phan tan deu.<br /> Qua trinh kit tinh dugc thuc hien trong binh teflon 200ml va binh thep khdng gi<br /> 1,2L d nhiet do 170°C trong 24h. San phim kit tinh duge gan ling, Igc hiit chan va rira<br /> din pH trung tinh, lam khd d IOO°C trong 5 gid va nung d 500°C trong 5 gid [3, 7].<br /> Cho 1,2ml Ti(OC3H7)4 vao 30ml C3H7OH, chia lam nhilu lin rdi tim len 3gZSM-5<br /> bing khuay tir chan khdng. Din khi can khd thi nung d 500°C thu dugc Ti02/ZSM-5 10%.<br /> <br /> 3. Nghien ciru dac tru-ng xiic tac<br /> Cac mau xiic tac da tong hgp dugc trudc va sau khi tam dugc xac djnh cau triic va<br /> bl mat bing phd hdng ngoai IR (FTIR 760 Nicolet - Trung tam Hoa Diu, Trudng<br /> DHKHTN), nhieu xa tia X XRD (Siemen D5005 - Trung tam Vat lieu, Trudng<br /> DHKHTN), dien tich bl mat rieng SBET (ASAP 2000 - Trung tam Vat lieu xuc tac,<br /> DHBKHN), anh TEM (Vien Ve sinh djch te Trung uong), anh SEM (Trung tam Vat lieu,<br /> Trudng DHKHTN).<br /> <br /> 4. Danh gia hoat tinh xuc tac<br /> Bude dau chiing tdi da nghien cim do boat ddng cua cac xiic tac thu dugc bang phan<br /> ling oxy dehydro hoa LPG thanh cac olefin nhe. Phan iing oxy dehydro hoa LPG dugc<br /> tien hanh theo phuong phap dng ddng lien tuc. Ddng khi LPG duge dan qua thiet bi Flow-<br /> Meter va Id phan ung d cac nhiet do khae nhau. San pham dugc phan tich bang thiet bj sac<br /> ky khi khoi phd GC-MS HP-6890 (cdt HP-5, PE Siloxane, 30m x 0,25mm x 0,32 // m).<br /> <br /> KET QUA vA T H A O L U A N<br /> <br /> 1. Cau true khong gian cua MCM-48 va ZSM-5<br /> Cac nghien ciiu gan day da khang djnh cau tnic khdng gian cua MCM-48 la Ia3d<br /> (Hinh I) va he thdng mao quan ciia zeolit ZSM-5 (Hinh 2) [6, 7].<br /> <br /> Ciu Injc m«o qutn<br /> >uclAe<br /> S.4K$.6A<br /> <br /> <br /> <br /> <br /> Hinh 1: Cau true khong gian Hinh 2: He thong mao quan cua ZSM-5<br /> ciia MCM-48<br /> Tuyen tap bio cio Hpi nghj KHCN "30 nim Dau khf Vift Nam: Co hpi mdi, thich thiic mdi' 61<br /> <br /> 2. Tinh chSt cSu true cua cac vat lieu thu dirffc<br /> a. Pho nhiiu xg tia X (XRD)<br /> Cac pic d gia trj 29 thip diing de dac tnmg cho ciu tnic vat lieu MQTB. Kit qua<br /> Hinh 3 cho thiy pie nhieu xa d 20 == 2,2 - 2,3° (d|oo) dac trung cho vat lieu mao quan trung<br /> binh vdi khoang each of xap xi 40A°. Ket qua XRD cho thiy ciu tnic lap phuong Ia3d vdi<br /> ham lugng san pham cao ciia MCM-48 thu dugc (Hinh 3).<br /> V N U - H i S O e C 05005. Mau MCMW (Lan • )<br /> <br /> <br /> <br /> <br /> Hinh 3: Ket qua nhilu xa tia X ciia vat lieu MCM-48<br /> Ket qua do nhieu xa XRD cua gel tdng hgp da cho mam ZSM-5 trudc khi ket tinh<br /> khdng thay xuat hien pic nhieu xa. Mdt viing nhieu xa nen d khoang 20° dac trung cho<br /> nhieu xa nen cua silieat vd djnh hinh. Ham lugng ZSM-5 them lam mam qua nhd de cd<br /> the xuat hien pic nhilu xa (khdng dua hinh ket qua XRD ciia gel va mam d day).<br /> Hinh 4 cho thay gian dd nhieu xa XRD ciia miu tdng hgp deu bao gdm cac pic co<br /> ban cd cudng do ldn iing vdi gdc 26 la : 8°, 9° va nhdm pic tir 22° - 25° dac trung cho<br /> ZSM-5. Tuy nhien, cac pic nhieu xa 8°, 9° cua mau tdng hgp dugc thap hon nhdm pic 22°<br /> - 25°, trong mau ZSM-5 chuin nhdm pic 22° - 25° cao hon. Cac pic nhieu xa 8°, 9° cang<br /> thap khi so sanh vdi nhdm pic 22° - 25° khi ty le Si/AI trong gel tdng hgp cang thap, dieu<br /> nay lien quan tdi ty le tang len cua Al trong cac mau ZSM-5 tdng hgp dugc. Ket qua cho<br /> thay da thu dugc mau ZSM-5 vdi ty le Si02/Al203 tuong iing vdi ty le ciia gel ban dau<br /> khoang 40.<br /> <br /> VNU-HN-SiEMENSDSOOS-Mau ZecSlc 2SV^5<br /> <br /> <br /> <br /> <br /> lii ir£±tM AMk^V!^-V^<br /> I<br /> 2-The(a • Scale<br /> <br /> <br /> <br /> <br /> Hinh 4: Ket qua nhieu xa tia X cua ZSM-5<br /> 62 Tdng hop va dac trung vat lifu xiic tie cho phan dng...<br /> <br /> <br /> Cac kit qua nhieu xa da X ciia V2O5/MCM-48 va Ti02/ZSM-5 (khdng chi ra d day)<br /> cho thay cac oxit kim loai chuyen tiep tren phan tan diu tren bl mat vat lieu, khdng lam<br /> thay ddi cau tnic hoae bien dang cae vat lieu nen thu dugc va Ti02d dang anatas hoat<br /> dgng.<br /> b. Phd hdng ngogi IR<br /> Cac nhdm dao ddng lien ket cua cac mau ZSM-5 tdng hgp tuong ty mau chuan<br /> trong dai phd hdng ngoai 400 - 1200cm''. Dao ddng ndi tai ciia cac tir dien T-O gdm: dao<br /> ddng hda trj bat ddi xiing ~ 1100 va 1200cm'' (triing vdi viing dao ddng lien ket ngoai tii<br /> dien), dao ddng hda trj ddi xirng 650 - 700cm'' (khdng rd rang), bien dang lien ket T-0<br /> (khdng bj chdng lap). Dao ddng lien ket ngoai tir dien T-O-T gdm: dao ddng vdng kep ~<br /> 550cm'' (khdng bj chdng lap), dao ddng hda trj bat ddi xiing - nam chdng trong viing<br /> triing vdi dao ddng ndi tai cua cac tir dien, dao ddng hda trj ddi xirng ~ 790cm'' (Hinh 6).<br /> Ket qua tuong ty thu dugc ddi vdi phd IR cua MCM-48, dao dgng hoa trj ddi xung ~<br /> 470cm'', ddng hda trj bat ddi xirng ~ 1106cm"', dao dgng hda tri ddi xirng ~ 790em''<br /> (Hinh 5).<br /> <br /> <br /> <br /> <br /> 2CTO<br /> <br /> <br /> <br /> <br /> 4000 2000<br /> <br /> Wyrtfiurribeis (crri-1)<br /> <br /> <br /> <br /> Hinh 5: Pho IR cua mau MCM-48 Hinh 6: Pho IR ciia mau ZSM-5<br /> <br /> 2. Tinh chat be mat ciia cac he xiic tac thu du-o-c<br /> <br /> a. Dien tich bi mat theo phuang phdp BET<br /> <br /> Dua vao dudng ding nhiet hip phy - giai hip N2 d -196°C cho thiy miu MCM-48<br /> thu dugc eho hieu qua hip phu cao vdi kich thudc Id khoang 24A°, cd SBET la 360m^g''.<br /> b. Anh TEM vd SEM cua cdc he vat lieu tdng hap duac<br /> Anh TEM ciia miu MCM-48 thu dugc cho thiy cac ciu tnic Id thu dugc cd su sip<br /> xip rit trat ty, ddng diu (Hinh 7). Hinh 8 cho thiy miu ZSM-5 tong hgp chiia cac tinh thi<br /> hinh lye lang, kha hoan thien, day la mdt trong nhirng hinh dang dac trung cua ZSM-5<br /> Kich thudc tinh the ZSM-5 thu dugc kha ldn va ddng diu (kich thudc khoang 2|am). Tuy<br /> nhien, cdn thay mdt lugng nhd gel aluminosilicat vd djnh hinh va tinh the nhd dang hinh<br /> hop chir nhat, hinh dang dac trung ciia tinh the mordenit.<br /> Tuyen tap bio cio Hpi nghi KHCN "30 nim Diu khi Vift Nam: Co hpi mdi, thich thde mdi" 63<br /> <br /> <br /> <br /> <br /> V*,i'7»<br /> <br /> <br /> <br /> <br /> Hinh 7: Anh TEM cua MCM-48 Hinh 8: Anh SEM ciia ZSM-5<br /> <br /> 4. Phan li-ng oxy dehydro hoa LPG thanh olefin nhe<br /> Bude dau chiing tdi da khao sat boat tinh xiic tac ciia cac he vat lieu V2O5/MCM-48<br /> va Ti02/ZSM-5 thu dugc bang phan ung oxy dehydro hoa PLG (thanh phan chii yeu la<br /> butan va propan) thanh olefine nhe d 300°C va 400°C. Cac ket qua phan tich tir thiet bj<br /> sac ky khi khdi phd GC-MS HP-6890 cho thay cac san pham olefin nhe la: buten-1,<br /> buten-2, I-propen-2-metyl va mdt sd san pham ndi ddi cd chira oxy. Ket qua chi tiet thanh<br /> phan, ham lugng cac san pham thu dugc se dugc cdng bd d cac cdng trinh tiep theo.<br /> <br /> KET LUAN<br /> Chiing tdi da tien hanh tdng hgp va thu duge eae vat lieu mao quan trung binh<br /> MCM-48 va vi mao quan ZSM-5. Vat lieu MCM-48 duge tim V2O5 va ZSM-5 dugc tim<br /> Ti02. Cac ket qua dae trung cac he vat lieu xiic tae thu duge eho thay cac oxit kim loai<br /> chuyen tiep d dang boat ddng, phan tan tdt, khdng lam thay ddi hoae bien dang cau true<br /> cac vat lieu nen da tdng hgp dugc. Chiing tdi da tien hanh danh gia hoat tinh xiic tae cua<br /> cac he vat lieu thu dugc bang phan iing oxy dehydro hoa LPG thanh olefin nhe. Cac ket<br /> qua ban dau cho thiy cac san pham khi chii yeu cd chiia cac olefin mong mudn.<br /> <br /> <br /> TAI LIEU THAM KHAO<br /> 1. Bao cao ''Nghien ciru vd dp dung chuyen ddi sic dung nhien lieu truyen thdng sang khi<br /> thien nhien vd LPG". Tdng cong ty Dau khi Viet Nam, 2005.<br /> 2. Le Thanh Son, Ngo Kim Thanh, Doan Van Mon, 2005. Synthesis and characterization<br /> of MCM-48. The 2"^* International Symposium on Advance Materials in Asia-Pacific<br /> Rim, p. 114 - 115. Hanoi, April 2005.<br /> 3. Luong Van Huin, Le Thanh Son, Hoa Htiii Thu, 2004. Tdng hap zeolit ZSM-5 bdng<br /> phuang phdp gdy mdm. Tap ehi Khoa hgc. So 1, tr. 135 - 140, Dai hgc Qudc gia Ha<br /> Ndi, 2004.<br /> 2Z Tong hop va die tru-ng vat lifu xiic t i c cho phan irng...<br /> <br /> <br /> 4. M.N.B. Sathler, J.G. Eon, 1998. The influence of niobium on the acidity and structure<br /> of gamma-alumina-suppported vanadium oxides. Braz. J. Chem. Eng. Vol. 15, No.<br /> 2, San Paulo, June 1998.<br /> 5. Nghien cim phdt trien thi truang tieu thu khi/LPG giai dogn din ndm 2005. Tdng cdng<br /> ty Diu khi Viet Nam, 2005.<br /> 6. Ryong Ryoo, Sang Hoon Joo, Ji Man Kim, 1999. Energetically favored formation of<br /> MCM-48 from cationic-neutral surfactant mixtures. J. Phys. Chem, 103, p. 7435 -<br /> 7440, 1999.<br /> 7. Tran Trung Ninh, 1999. ZeoUt ZSM-5, tdng hap ddc trung vd tinh chdt xuc tdc. Luan<br /> an Tiln sy Hoa hgc, Tnrdng DHKHTN, Ha Ndi, 1999.<br />