NHIN EA THE Gl6l
Lim TRV KHI METAN TV BA CA PHE
Trong nhieu nguon nang IUdng hoa thach khac nhau, metan tiT lau da dUdc cdng nh^n la nguon nhien lieu sach, neu dUdc sii dung rpng rai c6 the giup gi^m thieu cac hien tUdng bien ddi khi hdu tren toan cau. Tuy nhien hien tai de sif dung, khi metan thUdng dUdc nen trong cac binh khi Idn, cdng kenh va nguy hiem. Trong no lUc tim kiem mot vat lieu lUu trD metan an toan va kinh te hdn, nhom nghien cdu cua giao sU Kwang-Sun Kim thupc Hoc vien Khoa hpe va Cong nghe Quoc gia Ulsan (Han Qudc) da de nghj s\i dung ba ca phe de tdng hdp thanh than hoat tfnh d nhieu nhiet dp hoat hoa khac nhau. Ket qua nghien cufu khong chi dem lai mpt gi^i phap giau tinh sinh thai khi tan dung ba thdi ca phe, ma con tao ra mpt vat lieu hap phu dUa tren carbon c6 dien tich be mat rieng Idn, the tich lo xdp Idn va kh^ nang lUu truf metan hieu quk.
Metan - nllng liroing hoa thach cua tuung iai gin Gia tang khi thai tii cfic hoat ddng cua con ngudi dUde xem la nguydn nhfin chinh gay ra bidn dli khi hfiu vdi nhdng hfiu qufi khd Iddng. Theo thdng kg cua NASA, trong sudt 650.000 nam, hfim Iddng CO^ trong khi quyin chda bao gid vupt qufi 300 ppm, tuy nhien chl tii nam 1950 trd lgi day, ham lupng CO^ da tang nhanh bao dpng va dgt den mdc 400 ppm. Lupng CO^
nfiy chd yeu den tU qua trinh ddt chay nhien lieu hda thach (than dfi, xang dfiu) nham phue vu cho nhiing nhu cfiu ve nang lupng va di chuyen eCia con ngudi.
Su gia tfing nhanh chdng COj, dfi khien trfii dfit am dan len, ha qufi lfi mdc nddc biln trdn tofin cfiu da tang hon 17 cm [1], vijng Greenland mfit td 150 den 250 km^
bang mdi nam va tinh acid cua cfic dai dUPng da tang 30% [2, 3]. Chfnh vi vgy nhieu nghidn cdu da va dang hudng den viec phat trien cfic ngudn nhien lieu xanh, sach khdng chl nham tiet kiem nang IUdng ma edn gdp phan gifim thieu nhdng finh hddng xfiu cua qua trinh ddt nhien lieu ddi vdi mdi trudng sinh thai. Theo dd, ngudn khi thien nhien, vdi thanh phan chfnh la metan, khi dupc nen lgi cd thi trd thanh mot ngudn nhidn lieu hda thgch sgch hdn so vdi cfic ngudn nhidn lieu truyen thdng [4, 5].
Metan la mdt phfin td khf dupc tao bdi 4 nguyen td hydro vfi 1 nguyen tuf carbon, khi ddt chfiy, day la hydrocarbon thai ra lupng carbon ft nhat, nhd dd trd ndn thfin thien vdi moi trudng [6]. Thdng ke cho thay, lupng CO2 thofit ra td qufi trinh ddt chfiy metan thap hPn 25% so vdi xang, 16% so vdi khi propan ldng, 30% so vdi dfiu diesel va 75% so vdi than da. Khfi nang hinh thfinh ozon cua metan cung thap hon 80% so vdi xang
va 50% so vdi dfiu diesel ciJng khi propan ldng. Hdn nda, ngUpc lai vdi xang va dfiu diesel, khi thfii ra td qua trinh ddt metan khdng chda du Iddng carbon, benzene va khdng sinh ra cfic hgt byi vi t h i (PM10). Nhdng tfnh chfit nfiy khidn nhidu nha khoa hpe tren thd gidi xem metan nhU mdt ngudn nang lUpng thay thd trong tUdng lai gfin, vda sCf dyng lam nhien lieu cho cac dpng eo, vda dung de che tgo pin nhien lieu [7].
Uat lifiu Idb trdf metan
Ngfiy nay, metan thudng dupc trO trong cfic binh xylanh khi nen, vdn rfit nfing ne va nguy hilm. Vi vfiy, tong hdp nhdng vat lieu khdi lupng thap cd khfi nang hap phy va luu trd metan d ap suat thap nhU polymer, vat lidu khung hOu cP hda tri (COF), vat lidu khung cO kim (MOP) vfi vfit lieu dua tren carbon dang la mfit hudng nghien edu thu hut nhieu sd chu y [8, 9]. Trong nhQng vat lidu nay, vat lieu dua tren carbon td ra la Ung vien ly tddng cho myc dich lUu trd metan eung nhU eac khi khfic nhd vao khdi lupng nhe, bfin vOng va gia thanh tUPng ddi thfip [10, l i ] . HPn nda, chi phi sfin xufit vfit lieu hap phu metan dUa trdn carbon ed thi dupc giam thilu dang ke neu nguyen lidu carbon ddpc Ifiy td ngudn cd sfin va it tdn kem, ching hgn nhd td nhdng chfit thfii. HUdng nghien cdu nay da dUde nhifiu nhdm trien khai, trdn nhifiu ngudn carbon khac nhau, ed the ke den nhU Idp xe phd thfii [12], lignin [13], vd ca cao [14], hgt siriguela va hat nho [15] nhfim tdng hpp than hogt tinh cho muc dfch hap phy SCX, H^S, metan, a-lactalbumin, huyet thanh bd va cac pham nhudm hdu
CO.
Trong mot nghien cdu gan day, giao su Kwang-Sun
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s^Nfi NGHE Vi^ Nam So 1 nam 2016
NHIN EA THE GlOl
:.p^ ife''
•U'/i^
• ^ . '. A. _ ' Hinh 1. inh hien vi di^n tU quit cda cac miu (a) AMC-700, (b) AMC-800. (c) AMC-900 Kim cimg nhdm nghidn cdu thude Khoa Hda hoc. Hocvien Khoa hpe vfi Cdng nghe Qudc gia Ulsan (Hfin Qudc) dfi tdng hpp thanh cdng than hoat tfnh td ba ea phe, mdt sfin pham thfii td qufi trinh sCf dyng ca phe, nham tgo ra mpt hd vfit lieu mdi dung cho Idu trO metan [16]. Cfi pha ifi mdt trong nhOng sfin phim ndng nghiep cd sfin Iddng Idn nhat the gidi, vdn dddc sd dung cliCi yeu trong thdc udng. Theo hidp hpi ca phd qudc td, mdi nam cd hPn 120 tridu bao cfi phe (logi 60 kg) dUde sfin xufit. Lddng ca phd nay, sau khi dddc che bien, tao ra mdt khdi lddng Idn ba ca phd, thddng bj thai triic tiep ra mdi trUdng. Vi vfiy, viec tan dyng ba ca phe ed the dem lai Ipi ich kinh te va mdi trddng rat Idn. Ngofii ra, gifio su Kwang-Sun Kim da sCf dyng phUdng phap KOH xam nhgp, mpt phupng phfip tong hpp mdt giai doan khdng can qufi trinh Ipc KOH du, nhd vfiy tidt kidm tham thdi gian vfi chi phf.
Tdng hdp dian hoat tfnh Ur ba ca phfi
Trong nghien cdu cda nhdm, ba thfii cfi phe dupc thu td nhdng hgt ca pha Colombia 100%. Qua trinh tong hpp than hogt tinh td ba ea phe nfiy dddc thue hidn qua nhieu giai dogn. Dfiu tien, khofing 100 g ba ca phe dupc hda vao 100 ml dung djch KOH 7M, khuay trdn d 65°C trong 24 gid. He huyen phii sau dd ddpc do vfio dTa ket tmh, say d 10b°C de lam bay hdi nddc, thu lay chfit ran Ifi hon hpp gida bfi ca phe vfi KOH.
Toan bd chfit rfin se dupc hogt hda bang each nung trong mdi trddng khi Ar, trong ehdn nung bang thgch anh, sudt 1 gid d cfic nhiet dp khfic nhau: 700, 800 va 900°C (Ifin Idpt ddpc ky hieu la AMC-700, AMC-800 vfi AMC-900). Tde dd nfing nhiet ddpc ed djnh 7°C/phut.
Nhidt dd nung khdng vUdt qua 900°C de trfinh chen nung thgch anh bi phfi huy dddi tfic dyng cda KOH [17].
Sau khi hogt hda, mfiu ddpc rufa trong nude cat hai Ifin de loai bd toan bd KOH du va lpe lay ket tua. Cudi cung mfiu dupe sfiy qua ddm d 80°C d l thu ddpc sfin pham than hogt tfnh mong mudn.
Ofic linh \ih mat vfi khfi nfing hfip phu metan
Cfic mfiu AMD sau khi didu chd Ifin lupt ddpc khao sat hinh thai be mfit, dien tich be mfit ridng va kha nfing hfip phu khi metan. Hinh 1 trinh bay finh hien vi dign td quet cua 3 mfiu AMC-700, AMC-800 va AMC- 900. Cfi ba mfiu vgt ligu trong nghien eUu eua gifio sU Kwang-Sun Kim ddu cho thfiy hinh thai d^c trung eua than hoat tinh, vdi bfi mat gd ghd, sd lupng l6 xdp Idn.
NhOng lo xdp nay ed hinh dang khfi tddng ddng vdi Id xdp cua cfic vgt ligu sd dung trong tu dign hoae pin Lithium. Khi nhidt dd nung tfing, hinh thai cda cae mau thay doi khdng dfing k l .
De tim hieu rd hdn finh hddng cCia nhi^t dp hogt hda Idn tfnh chat cua eac mfiu, nhdm nghidn cdu da tidn hfinh khao sat dign tieh be mat ridng va kfch thUdc lo xdp thdng qua qua trinh hap phu dang nhiet khf N^
6 77K (hinh 2). DIen tich be mat rieng dUPc tfnh theo md hinh BET trong khi t h i tfch lo xdp dupc tinh theo md hinh NLDFT. Khi nung d 700°C, sfin pham than hoat tinh chi cd dien tich be mat rieng dgt 536,5 m^g'^ cung vdi the tfch 16 xdp khofing 0,32 em^.g'.
Tuy nhien, khi nhiet dp nung tang den QOCC, ket qufi hap phu dang nhiat N^ cho thay dien tich bd mat rieng va the tich Id xdp dfi tang gap ddi, Ifin lUdt dat cfic gifi tri 1.040,3 m^.g-^ va 0,635 cm^.g ^ Dieu nay chCing td nhiet dp nung trong phuong phap KOH xam nhap ed finh hudng mgnh den tfnh chat be mat cua vat ligu. Mdt each tdng qufit, nhiet dp hoat hda vat lieu cfing cao se dan ddn sd gia tang dd xdp micro va dp xdp meso. Vdi dien tieh be mat rieng va kich thUde 16 xdp Idn nhfit, mau AMC-900 td ra la vat lieu hap phu tiem nang nhfit trong cfic mfiu. Hdn nQa, kdt qua tinh tofin theo md hinh NLDFT eung cho thfiy hau hdt cfic Id xdp cd kfch thude khofing 0,6 nm, vdn lfi kfch thude phil hop d l hfip phy hieu qua cac phfin ttf khi nhd nhu CH,vaCO„[18,19].
Solnam2016 ^ ^ ^ 45
NHIN EA THE GlOl
Hinh 2: dddng ding nhiet hap phu N^ tren cac miu than hoat tinh dieu che tO ba ck phe
Qua trinh khao sat hfip phu CH^ dUdc thdc hien Iren he thdng Belsorp mini ll (Nhfit Bfin). Cfic mfiu ddpc xCf iy d 200°C trong ehan khdng trong vdng 12 gid rdi cho tien hfinh hap phu metan d 273K va ap sufit thap 100 kPa.
Hinh 3 trinh bay dudng eong hap phu metan dang nhidt ciia cfic mfiu. Tif cfic ket qufi nghien cdu ve hinh thfii va dd xdp cua vfit lidu, mau AMC-900 dupe cho Ifi mau cd klifi nang hfip phu tdt nhat. ThUc td chdng minh mfiu AMC-900 cd khfi nang hfip phu mdt lupng Idn metan, vdi dung lupng hap phu cue dai dgt 1,96 mmol.g"\ trong khi hai mfiu AMC-700 va AMC-800 chi hfip phu metan vdi dung lupng 1,7 mmol.gV
Hinh 3: dU lieu hip phu metan dudi ap suit thap tren cic miu than hoat tinh d273K Nhu v a y chi td bfi ca phd va mot phUdng phap hogt hda don gian, nhdm nghien cdu eda gifio sd Kwang-Sun Kim da tong hdp thanh cdng vat lieu than hoat tfnh cd kha nang hfip phy va lUu trQ metan hieu qua. Thanh cdng cua nghidn cdu nay khong chi cho phep tao ra mot vgt lieu lUu trQ metan gia thanh re ma cdn tiep tye cung cd cho xu hudng nghien cdu tfii che nhQng nguyen lieu thai trong cupc sdng trd thanh nhQng vat lieu cd ich, vda giiip cai thifin mdi trudng, vda gdp phfin giai quyet nhQng nhu cfiu cija xa hdi loai ngudi gi
L T K (tdng hpp)
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