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1 Jurnal f the Krean Ceramic Sciety Vl. 44, N. 6, pp. 35~330, 007. Effect f ph n Pre Characteristics in Synthesis f High Prus AlO(OH) Gel by Hydrlysis f Al and Na Mixed Slutin Byung-Ki Park, Dng Uk Che, and Jae Rck Lee Energy Materials Research Center, Krea Research Institute f Chemical Technlgy, Daejen , Krea (Received June 13, 007; Accepted June 5, 007) Al Na yw ƒ w w š»œ AlO(OH) w phƒ»œp e w» Á Á w yw l ( ; ) ABSTRACT High prus AlO(OH) gel is used in precursr f ceramic material, cating material and prus catalyst. Fr use f these, nt nly physichemical cntrl fr particle mrphlgy, pre characteristic and peptizatin but als studies f synthetic methd fr preparatin f high prus AlO(OH) gel were required. In this study, high prus AlO(OH) gel was prepared thrugh the aging and filtratin prcess f aluminum hydrxides gel precipitated by the hydrlysis reactin f Na C slutin and Al and Na mixed slutin. In this prcess, ptimum synthetic cnditin f AlO(OH) gel having excellent pre vlume as studying the effect f hydrlysis ph n gel precipitates has been studied. Hydrlysis ph brught abut numerus changes n crystal mrphlgy, surface area, pre vlume and pre size. Physichemical prperties f gel were investigated as using XRD, TEM, TG/DTA, FT-IR and N BET methd. Key wrds : Al, Mineralizer, Prus material, Catalyst, Alumina ceramic 1. ù ƒ SiO Al š» w, q w. y k w» ù v p w yw e š» w. w š š q z û ùküš, 1600 C ¾ š w, š û p š. ù 1950 l yw, š» w š, 1960 l w» w, yw w ƒ» w ù w. ù χ, ρ, η, γ, δ, θ, β, α ù Al(OH, AlO(OH) Crrespnding authr : Byung Ki Park bkpark@krict.re.kr Tel : Fax : y. yw ù AlO(OH), η, γ, δ, θ, β α-al. AlO(OH) γ-al x š,,» t š. 1-7) Farkas, Gad w AlO(OH) 9,10) w q ƒ š, w d d w x w. AlO(OH) (AlOOH) d Al ~ 1.8 sww š. 5 ~ 10 nm j» ƒ X- z q l ƒs š bradw p vj ùkü. AlO(OH) k t 500 m /g w š k z»œ vƒ 1. cc/g, 400 ~ 500 C w t k w 30 wt% ùkü γ-al. w p ƒ behmite gibbsiteù bayerite g w» w, gibbsite w mw ù y g w w, ƒ w g 35

2 36»Á Á w ye, š» ƒ w g w g ƒ. œ AlO(OH) y p» w xk, t,»œ v š»œj» p w w, ye w œ AlO(OH) w, Ÿy ƒ, ƒ w ph, š»œp y ƒ ùkù. Al 7wt% Al ƒw Al 4.1 wt% Al w š,» Na ƒw yw w, Na C ƒ w jš g aluminum hydrxides e g. Na û w ye j w. ye w š»œ AlO(OH) w w Na ƒ ƒ w phƒ AlO(OH) p w ùkü, XRD, TG/DTA, FTIR, TEM N BET w w.. x.1. x e œ AlO(OH) w w» w Al 4.1% Al (Aldrich) Na (Duksan Pure Chem., 99%) ww yw w, ƒ w j» w e Na C (Duksan Pure Chem., 99%) w w. e heating mantle(ms-dm604) 1 l 3 v j w š, ³ w ƒ w w» w micrprcessr peristaltic rv(mdel : ) w... x»œp ùkü AlO(OH) ƒ w ph k w» w Al 4.1% Al 41 g Na 100 g ww yw 6% Na C 5 ml/min ƒ ww ph 6, 7, 8, 9 ƒƒ w. z e 90 C w 0 w w z 110 C 4 w w. ƒ w phƒ 6 û e j» š, phƒ 9 w NaAl(OH) (CO AlO(OH). x Fig. 1 ùkü. Fig. 1. Preparatin prcess f high prus AlO(OH) gel..3. e e y w» w X- z»(xrd, Rigaku Denk ) w, interval 0.0, scan speed 5 /min w 5 θ 80 w. e O-H, Al-O, Al-OH, H-O-H, C-O C-O-O w w» w Ÿ»(FT-IR, MIDAC GRAMS/386) w 1 400~4,000 cm q rp w. e w» w œ»» 10 C/min 800 C¾ ƒ w (TG/DTA, Dupnt,000) w. xk y n x (TEM, TECNAI G ) wš, t,»œ v»œj» y N BET (ASAP 000, Micr. Inst.) d w. 3. š 3.1. xk y Al ~ 1.8 sww AlO(OH) (00), (10), (140), (031), (00), (051) X- z ƒ 14.4, 8., 38.3, 48.9, 64.1 š 7.0 ùkù, z j». Fig. ƒ w ph y XRD. ph 6 w x ƒ¾ X- z ql ùkü š, ph 7 8 AlO(OH) ùkþ, ph 9 AlO(OH) NaAl(OH) (CO wì. Fig. 3 TEM (a) phƒ û xk š x w wz

3 Al (SO ) 와 Na SO 혼합용액의 가수분해에 의한 고기공 AlO(OH) 겔의 합성에서 ph가 기공특성에 미치는 영향 37 응축이 발생하기 때문이다. 또한 수용액 상태에서 생성된 겔 입자의 결정성장은 [AlO(OH)] 층 사이에 존재 하는 OH 에 의해서 결정되는데, 가수분해 초기 ph 및 최 종 ph가 낮을수록 [AlO(OH)] 층 사이에 OH 가 많이 존 재하게 되고, 층 사이의 거리가 증가하여 [AlO(OH)] 층의 뒤틀림현상이 초래되어 결정성장이 둔화되게 된다. 이 는 가수분해 ph가 낮을수록 석출된 겔의 밀도가 증가하 여 [AlO(OH)] 층 사이에 존재하는 OH 들이 물로 응축되 어 이탈되는 속도가 낮아져 결정성장이 억제되는 것으로 볼 수 있다. 그러나 가수분해 ph가 증가하여 ph 9 이상 일 경우에는 석출된 겔이 Fig. 의 X-선 회절패턴과 Fig. 3(d)의 TEM 사진에서 보는 것처럼 NaAl(OH) (CO) 구조 의 염을 생성시킨다. 가열온도에 따른 중량감소 및 열 시차의 변화를 Figs. 4 및 5에 나타내었다. 그림에서 ph 7~9 범위에서 가수분 11,14-18) - - 1) Fig.. XRD patterns f gel precipitates as functin f the hydrlysis ph. Fig. 4. Fig TG curves f gel precipitates as functin f the hydrlysis ph. TEM micrgraphs f gel precipitates as functin f the hydrlysis ph: (a) ph 6, (b) ph 7, (c) ph 8, and (d) ph 9. 겔만 관찰되었다. 그러나 (b)에서와 같이 가수분해 ph 7 부터는 가느다란 AlO(OH) 침상입자가 석출되기 시작하 였고, 가수분해 ph 8인 (c)는 결정이 성장하여 침상입자 의 크기가 증가하였으며, (d)는 더욱 더 성장한 AlO(OH) 침상입자와 우측 하단부에서와 같이 커다란 NaAl(OH) (CO) 결정이 함께 석출되는 것을 관찰할 수 있다. 침상 의 결정은 크기가 작고 가느다란 형태를 나타내다가 가 수분해 ph가 증가할수록 길이와 두께가 증가하는 것을 알 수 있다. 이는 가수분해 ph가 증가하면 결정성장을 위 한 활성화에너지가 증가하여 작은 크기의 가느다란 침상 결정은 빠르게 성장하고, 시간이 경과함에 따라 입자간 3 Fig. 5. DTA curves f gel precipitates as functin f the hydrlysis ph. 제 44 권 제 6호(007)

4 38»Á Á wwš w e 400 C z vjƒ ùkù, AlO(OH) ü OH ƒ k γ-al. ƒ w ph 8 ~ C vjƒ ùkù. 300 C vj ü sw NaAl(OH) (COƒ NaAlO ùkù vj. ù ph 8 NaAlO w vj ƒ û ùkù, AlO(OH)». wr, Na ƒw š Al ƒ wwš w AlO(OH) k ƒ w phƒ 10 wš»œp w AlO(OH) š šwš. 19,0) ù Na w û ph w, ƒ w phƒ 7~8 AlO(OH) š, ƒ w ph 8 AlO(OH) NaAl(OH) (CO xk wì. Na C w Al ƒ w Na y y ƒ g j w q ù w yw yw» ³ w ƒ v w. 3.. rp y ƒ w ph XRD Ÿ y w. Fig. 6 w 110 C 4 g rp w. AlO(OH) r 1 3,800~,400 cm w, 1,630 cm»œ w w 1 O-H, 1,00~1, cm O-H š 1,000~400 cm Al-O ) w 3,90 1 cm (O-H) w 1 1, 3,100 cm 1,071 cm AlO(OH) ü Al-OH w. 1),090 cm 1 w O-H w w ùkù rp. ƒ w 15) AlO(OH) rp ùkù w. l ph 6 ~ 9 ƒ w AlO(OH). ù ph 6 Fig. X- z ƒ ûš, w Fig. 5 DTA š vjƒ AlO(OH) w» w xk q. ph 8 ~ 9 1,600 ~ 1,000 cm r ùkù 1 w, ü AlO(OH) NaAl(OH) (CO wì sw w ùkü 1. 1,600 cm C-O-O, 1,800 cm 1 CH CH 3 š 1,00 cm r 1 C-O t»œ y Na w Al ƒ w w e t,»œ v»œj»»œp y w. Fig. 7 ƒ w ph e t /k w plttingw. xk ƒ w phƒ 7 w vƒ ûš û k š Fig. 6. FT-IR spectra f gel precipitates as functin f the hydrlysis ph. Fig. 7. N ads./des. istherm f gel precipitates as functin f the hydrlysis ph. w wz

5 Al Na yw ƒ w w š»œ AlO(OH) w phƒ»œp e w 39 Table 1. Final ph f Gel Precipitates Hydrlysis ph Aging Time (h) Final ph Table. Pre Characteristics f Gel Precipitates Hydrlysis ph BET Surface Area (m /g) Pre Vlume (cc/g) Pre Diameter (Å) ew x w. x ƒ w phƒ û e ƒ ƒw š, Table 1 z phƒ w aluminum hydrxides gel w. w w AlO(OH) w y y ƒ û w»œ w». Table»œ w t ƒw»œ v ùkù w. Na w ƒ w phƒ 8 e e AlO(OH) š,»œ wì j»»œ j»œ w Fig. 8 Table j t»œ v ù kü. ù ƒ w phƒ 9»œ w»œ v ùkü t Fig. 8. Pre size distributins f gel precipitates as functin f the hydrlysis ph. wš AlO(OH) NaAl(OH) (CO g, w» ww.» œ v e» w ƒ w ph 8 w wù, ww AlO(OH) e» w ƒ w ph 7~8 w w. 4. Al Na yw Na C ƒ g k w œ AlO(OH) w, e yw p ƒ w ph w,. 1) ƒ w phƒ 6 AlO(OH) w, w t»œ vƒ û e. ) ƒ w phƒ 7~8 AlO(OH), t 350 ~ 450 m /g jš,»œ vƒ 0.58 ~ 0.9 cc/g e. 3) ƒ w phƒ 9 AlO(OH) NaAl(OH) (CO y e, t 189 m /g ûš,»œ v 1.7 cc/g j ƒw e. REFERENCES 1. R. K. Oberlander, Aluminas fr Catalysts-Their Preparatin and Prperties, Appl. Ind. Catalysis, (1984).. P. Nrtier and M. Sustelle, Alumina Carriers fr Autmtive Pllutin Cntr, Catalysis and Autmtive Pllutin Cntrl, ed. by Crucq and A. Frennet, Elsevier Sci. Pub (1987). 3. R. B. Bagwell and G. L. Messing, Critical Factr in the Prductin f Sl-Gel Derived Prus Alumina, Key Eng. Mater., (1996). 4. C. Misra, Aluminum Oxide (Hydrate), Encyclpedia f Chem. Tech., 4th ed., (199). 5. L. K Hudsn, C. Misra and K. Wefers, Aluminum Oxide, Ullmann s Encyclpedia f Ind. Chem., 5th ed., Al (1985). 6. B. C. Lippens and J. J. Steggerda, Active Alumina, Physical and Chemical Aspects f Adsrbents and Catalysts, (1970). 7. R. Dale Wsley, Activated Alumina Desiccants, Alumina Chemicals, nd ed. Am. Ceram. Sc., (1990). 8. W. A. Deer, R. A. Hwie and J. Zussman, Rck Frming Minerals, Lngmans, Lndn, (1969). 9. L. Farkas, P. Gad and P. E. Wermer, Mat Res. Bull., 1 44«6y(007)

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