43-48_ TC Khoa Hoc Va Cong Nghe_2008_T.46_ So 5

7/24/2019 43-48_ TC Khoa Hoc Va Cong Nghe_2008_T.46_ So 5

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TP CH KHOA HC V CNG NGH Tp 46, s5, 2008 Tr. 43-48

TNG HP V NGHIN CU VT LIU HP THDU TBMA

PHN 2. NGHIN CU CU TRC V TNH CHT NHIT CA MTSDN XUT A-X-TAT XENLULOZTB MA

PHM TNG SN,BCH THANH

1. MU

Hin nay, vt liu hp thdu chyu c chto tcc loi polyme hu ctng hp,khng bphn husinh hc nhPP, PE, PU, polyeste, polyamit, sau khi sdng li gy ra s nhim mi trng th cp nghim trng[3]. gii quyt vn ny, ngi ta tp trungnghin cu v pht trin l vt liu hp thdu mi, thn thin vi mi trng v bphn husinh hc tcc sn phm v phthi nng nghip nhrm r, b ma...[2 - 9].

Trong cng trnh trc, chng ti trnh by mt skt qunghin cu mt syu tnhhng ln ng a-x-tyl ho xenluloztb ma phthi vi tc nhn a-x-tyl ho l anhydrit a-x-tic v xc tc l N-bromosuccinimide (NBS). xc nh cc iu kin tt nht ca phnng ny l: nhit phn ng khong 110-120oC; thi gian phn ng khong 6 - 7 gi; hmlng ca xc tc NBS nm trong khong t1,25 g n 1,50 g trong 100 ml anhydrit a-x-tic.Vi cc iu kin trn, c th tng hp c cc dn xut a-x-tat xenlulozkhc nhau tbma phthi vi mc a-x-tyl ho (DAc) thay i t0,18 n 2,92 [10].

Trong bi bo ny, chng ti tip tc trnh by mt skt qunghin cu cu trc v tnhcht chu nhit ca ca mt s dn xut a-x-tat xenluloz t b ma bng phng php phhng ngoi FTIR v phng php thay i trng lng theo nhit TGA.

2. PHN THC NGHIM

2.1. Tng hp cc dn xut a-x- tat xenluloztb ma phthi vi anhydrit a-x-tc vxc tc N-bromosuccinimide (NBS)

Cho 10 g b ma th c loi b lignin, hemixenluloz, cc hp cht phenol,pectinphn trn vo bnh thu tinh 4 cdung tch 500 ml c trang bsinh hn hi lu,

my khuy t, nhit kthungn 200o

C v ng dn kh ni-t(N2). Cho 300 ml anhydrit a-x-tcv mt lng xc tc NBS vi nng l 1 g/100 ml anhydrit a-x-tc. Phn ng c tin hnhnhit khong 110oC v ko di trong thi gian khong 6 - 7 gi. Sau hn hp phn ngc hxung nhit phng, c lc loi xenluloztb ma th cha phn ng v sau c kt ta trong metanol. Sn phm kt ta l cc dn xut a-x-tat xenlulozth c lmsch bng phng php chit Soxhlet vi cn etanol loi bxc tc v anhydrit a-x-tc d.Sau cng, sn phm a-x-tat xenlulozsch c sy trong tsy chn khng 50oC 60oCn trng lng khng i.

2.2. Cc phng php nghin cu


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Nghin cu phn ng a-x-tyl ho v dn xut a-x-tat xenlulozbng phng php phFTIR. Cc iu kin o: nghin nh mu, p vin to mng KBr v chp trn my Nexus670-FTIR- Nicolet trong vng t500 cm-1n 4.000 cm-1.

Nghin cu khnng chu nhit ca cc mu ca xenluloz tb ma trc phn ng vcc dn xut a-x-tat xenlulozbng phng php phn tch sthay i trng lng theo nhitTGA trn my (Thermogravimetric Analysis). Cc mu c chp trn my TGA (ShimadzuTA50, Japan) vi cc iu kin o: trong kh ni-t, vn tc nng nhit l 10oC/pht trongkhong nhit tnhit phng n 700oC.

3. KT QUV THO LUN

Hnh 1 trnh by phhng ngoi FTIR ca xenlulozb ma trc khi phn ng v Hnh 2l phhng ngoi FTIR dn xut a-x-tat xenlulozvi DAc ~2,92. Ta thy c tt ccc dihp thquan trng nht c trng cho xenlulozban u nh3000-3500, 2844, 2.723, 1662,

1447, 1373, 1085, 836 cm

-1

. Vng hp thkh rng 3300 - 3500 c trng cho dao ng ho trca lin kt O-H trong cc nhm hydroxyl. Thng thng, di hp thc trng cho dao ngho trca lin kt O-H nm vng 3400 - 3500 cm-1v kh hp, song do c sto cu hydroni v ngoi phn txenluloznn di hp th bmrng. nh hp th2844, 2723 cm-1c trng cho dao ng ho trca lin kt C-H trong cc nhm metylen (CH2) v metin (CH).nh 1662 cm-1 lin quan n cc dao ng ca nc bxenlulozhp th. nh hp th1447 cm

-1lin quan n dao ng ho trca lin kt -C-O-C- trong kt glycosidic -(14) v

nh hp th836 cm-1tng ng vi sdao ng bt i xng ca C1-H trong kt glycosidic-(14).

Hnh 1. Phhng ngoi FTIR ca xenlulozb ma trc khi phn ng

Trong phhng ngoi FTIR (Hnh 8) ca dn xut a-x-tat xenlulozvi DAc ~2,92 tacng nhn thy c tt ccc di hp thquan trng nht c trng cho cu trc n vmt xchl anhydro--D glucopyranoz (vit tt l AGU) ca phn t xenluloz ban u nh 3400 -3500, 2844, 2723, 1662, 1447, 1373, 1085, 836 cm

-1. Tuy nhin y, ta ddng nhn thy

rng, vng hp thc trng cho dao ng ho trca lin kt O-H trong cc nhm hydroxyl(OH) khng rng nhtrong hnh 6 (vng 3300 - 3500 cm-1) m hp li rt nhiu (3400 - 3500


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cm-1). iu chng t cc nhm hydroxyl (OH) trong phn t xenluloz phn ng vianhydrit a-x-tic to thnh cc dn xut a-x-tat, ph vcc cu hydro. c bit, sxut hinca mt nh hp thmi vi cng mnh 1731 cm-1 c trng cho dao ng ho trca

lin kt (C=O) ca nhm este (a-x-tat xenluloz), chng minh rng, phn ng gia ccnhm hydroxyl (OH) trong phn t xenluloz vi anhydrit a-x-tic xy ra dn n s tothnh lin kt este este trong phn ta-x-tat xenluloz.

Trong phhng ngoi FTIR (hnh 2) ca dn xut a-x-tat xenlulozvi DAc ~2,92 (muM36 trong bng 4), khng thy xut hin ca cc di hp th1840, 1760 v 1700 cm-1 [14],c trng cho anhydrit a-x-tic cha phn ng v a-xt a-x-tic, sn phm phca phn ng a-x-tylho xenlulozb ma (S3). iu ny cng chng t a-x-tat xenluloz, sn phm chnh ca

phn ng a-x-tyl ho xenlulozb ma, c lm sch hon ton tcc sn phm ph.

Hnh 2. Phhng ngoi FTIR dn xut a-x-tat xenlulozvi DAc ~2,92

Cc tnh cht nhit ca xenluloz b ma trc khi phn ng v ca dn xut a-x-tatxenlulozcng c nghin cu bng phng php phn tch s thay i trng lng theo

nhit TGA. Hnh 3 l gin TGA ca xenlulozb ma trc khi phn ng. Hnh 4 l ginTGA ca dn xut a-x-tat xenlulozvi DAc ~0,97. Cn hnh 5 l gin TGA ca dnxut a-x-tat xenlulozvi DAc ~2,92.Tgin TGA ca xenlulozb ma trc khi phnng (hnh 3) ta thy rng xenlulozb ma trc khi phn ng bt u phn hukhong 250 255oC; nhit m xenlulozb ma trc khi phn ng mt 50% trng lng l khong371

oC. Dn xut a-x-tat xenlulozvi DAc ~0,97 li bt u phn hukhong nhit thp

hn, khong di 200oC ( thp hn ti 55-600C) (hnh 4) v nhit m mu a-x-tatxenlulozvi DAc ~2,92 mt 50% trng lng cng thp hn, khong 367oC (thp hn khong3-4

0C).


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Hnh 3. Gin TGA ca xenlulozb ma trc khi phn ng(a) v ca dn xuta-x-tat xenlulozvi DAc ~0,97(b)

Hnh 3.Gin TGA ca dn xut a-x-tat xenlulozvi DAc ~2,92

a) b)


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iu l th l khi dn xut a-x-tat xenluloz c gi tr DAc cao hn, ~2,92 (mu M36trong bng 4) th khong nhit bt u phn hu li thp hn rt nhiu khong trn di200

oC (thp hn ti 55 60oC) (hnh 4) v nhit m mu a-x-tat xenlulozvi DAc

~2,92 mt 50% trng lng cng thp hn rt nhiu, khong 358o

C (thp hn khong 13o

C) sovi xenlulozb ma trc khi phn ng. Ni mt cch khc, cc dn xut a-x-tat xenlulozcgi trDAc cng cao th khnng chu nhit cng thp. Tt cnhng quan st trn cho thy,xenlulozb ma trc khi phn ng c khnng chu nhit cao hn so vi cc dn xut a-x-tatxenluloz. Khnng chu nhit thp hn ca cc dn xut a-x-tat xenluloz so vi khnngchu nhit xenlulozb ma trc khi phn ng lin quan cht chn shnh thnh cc lin ktcu hydro ni v ngoi phn txenluloz.

4. KT LUN

nghin cu phn ng a-x-tyl ho xenlulozb ma vi anhydrit a-x-tic bng bngphhng ngoi (FTIR). Cc tnh cht nhit ca xenlulozb ma trc khi phn ng v ca dnxut a-x-tat xenlulozcng c nghin cu bng phng php phn tch sthay i trnglng theo nhit ( TGA). Cc kt qu nghin cu khng nh rng, phn ng gia ccnhm hydroxyl trong phn txenlulozvi anhydrit a-x-tic xy ra, to thnh cc dn xut a-x-tat, ph vcc cu hydro lm thay i vcbn tnh cht chu nhit ca vt liu, trong cc dn xut a-x-tat xenlulozc gi trDAc cng cao th khnng chu nhit cng thp.

TI LIU THAM KHO

1. T. Lim, X. Huang - Evaluation of kapok (Ceiba pentandra(L.) Gaertn.) as a natural hollowhydrophobic-oleophilic fibrous sorbent for oil spill cleanup, Chemosphere 66(5) (2007)955-963.

2. T. R. Annunciado, T. H. D. Sydenstricker, S. C. Amico - Experimental investigation ofvarious vegetablle fibres as sorbent materials for oil spills, Marine Pollution Bulletin 50(2005) 1340-1346.

3. C. Teas, S. Kalligeros, F. Zanikos, S. Stournas, E. Lois, and G. Anastopoulos -Investigation of the effectiveness of absorbent materials in oil spills cleanup, Desalination

140(3) (2001) 259-264.

4. X. F. Sun, R. C. Sun, J. X. Sun - Acetylation of sugarcane bagasse using NBS as a catalystunder mild reaction cobditions for the production of oil sorption-active materials,

Bioresource Technology 95(2004) 343-350.

5. G. R. Fiho, S. F. da Cruz, D. Pasquini, D. A. Cerqueira, V. de S. Prado, R. M. Nascimentode Assuncao - Water flux through cellulose triacetate films produced from heterogeneous

acetylation of sugar cane bagasse, J. Mem. Sci. 177(2000) 225-231.

6. M. O. Adebajo, R. L. Frost - Acetylation of raw cotton for oil spill cleanup application: anFTIR and 13C MAS NMR spectroscopic investigation, Spectrochimica Acta, Part A60(2004) 2315-2321.

7. H. El-Saied, A. H. Basta, B. N. Barsoum, M. M. Elberry - Cellulose membranes forreverse osmosis, Part 1.RO cellulose acetate membranes including a composite with

polypropylene, Desalination 159(2003) 171-181.


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8. B. Karimi, H. Seradj - N-bromosuccinimide (NBS), a novel and highly effective catalystfor acetylation of alcohols under mild reaction conditions, Synlett 4(2001) 510-519.

9. G. R. Filho, R. M. N. Assuncao, J. G. Vieira, C. S. Meireles, D. A. Cerqueira, H. S.

Barud, S. J. L. Ribeiro, Y. Messaddeq - Characterization of methylcellulose producedfrom sugar cane bagasse cellulose: Crystallinity and thermal properties, Polymer

Degradation and Stability 20(2006) 1-6

10. Phm Tng Sn, Bch Thanh - Tng hp v nghin cu vt liu hp thdu tb ma.Phn 1: Nghin cu mt siu kin phn ng a-x-tyl ho xenluloztb ma, Tp chKhoa hc v Cng ngh46(4) (2008) 99-105.

SUMMARY

PREPARATION AND CHARACTERIZATION OF OIL ABSORBENTS FROM

SUGARCANE BAGASSE CELLULOSE

PART 2. STUDY ON THE STRUCTURE AND THERMAL PROPERTIES OF

CELLULOSE ACETATES DERIVED FROM SUGARCANE BAGASSE

CELLULOSE

The acetylation reaction between sugarcane bagasse cellulose and acetic anhydride using

N-bromosuccinimide as a catalyst was investigated by Infrared Spectroscopy (FTIR). The

thermal properties of the cellulose acetates obtained were characterized by Thermal Gravimetric

Analysis (TGA). The analytical data showed that the acetylation reaction between sugarcane

bagasse cellulose and acetic anhydride took place, and that the higher the degree of acetylation

the cellulose acetates have the lower the thermal stability they exhibit.

a ch: Nhn bi ngy 15 thng 8 nm 2007

Vin Ho hc, Vin Khoa hc v Cng nghVit Nam.

43-48_ TC Khoa Hoc Va Cong Nghe_2008_T.46_ So 5

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