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 305-600, 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 (007 6 13 ; 007 6 5 ) 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 E-mail : bkpark@krict.re.kr Tel : +8-4-860-70 Fax : +8-4-861-445 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 1.0 ~ 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
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 : 7014-10) 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 1.0 ~ 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
Al (SO ) 와 Na SO 4 3 4 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. 3. 3 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)
38»Á Á wwš w e 400 C z vjƒ ùkù, AlO(OH) ü OH ƒ k γ-al. ƒ w ph 8 ~ 9 300 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, 1,00~1,000 1 1 cm O-H š 1,000~400 cm Al-O. 15-18) 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. 3.3. 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
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 6 0 4.36 7 0 8.4 8 0 9.5 9 0 9.90 Table. Pre Characteristics f Gel Precipitates Hydrlysis ph BET Surface Area (m /g) Pre Vlume (cc/g) Pre Diameter (Å) 6 90 0.3 44 7 433 0.58 54 8 358 0.90 100 9 189 1.7 70 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, 3 63-110 (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. 75-300 (1987). 3. R. B. Bagwell and G. L. Messing, Critical Factr in the Prductin f Sl-Gel Derived Prus Alumina, Key Eng. Mater., 115 45-64 (1996). 4. C. Misra, Aluminum Oxide (Hydrate), Encyclpedia f Chem. Tech., 4th ed., 317-330 (199). 5. L. K Hudsn, C. Misra and K. Wefers, Aluminum Oxide, Ullmann s Encyclpedia f Ind. Chem., 5th ed., Al 557-594 (1985). 6. B. C. Lippens and J. J. Steggerda, Active Alumina, Physical and Chemical Aspects f Adsrbents and Catalysts, 4 171-11 (1970). 7. R. Dale Wsley, Activated Alumina Desiccants, Alumina Chemicals, nd ed. Am. Ceram. Sc., 41-50 (1990). 8. W. A. Deer, R. A. Hwie and J. Zussman, Rck Frming Minerals, Lngmans, Lndn, 5 111-116 (1969). 9. L. Farkas, P. Gad and P. E. Wermer, Mat Res. Bull., 1 44«6y(007)
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