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MoO<sub>3</sub> 촉매상에서의 메탄올 부분산화반응
김정희,박윤석,이호인,Kim, Jeong-Hi,Park, Youn-Seok,Lee, Ho-In 한국공업화학회 1991 공업화학 Vol.2 No.2
고진공계에서의 열탈착실험을 통하여 $MoO_3$ 촉매상에서의 $CH_3OH$ 분해 및 부분산화반응에 관한 연구를 수행하였다. $CH_3OH$는 촉매표면에 methoxy($-OCH_3$)와 수소원자(-H)의 형태로 흡착되어 있다가 흡착수소원자가 methoxy 와 재결합하면서 425 K에서 $CH_3OH$로 탈착하였으며, methoxy로부터 수소원자가 떨어져 나가면서 545 K에서 HCHO가 탈착되었다. 이때 반응에 의해서 생성된 물은 428 K에서 탈착하는 ${\alpha}$-피크와 586 K에서 탈착하는 ${\beta}$-피크를 보였으며, ${\alpha}$-피크는 표면에 형성된 hydroxyl 에 기인하는 탈착피크, ${\beta}$-피크는 methoxy가 수소를 잃으면서 HCHO의 형태로 촉매표면에서 탈착하면서 남긴 표면수소원자와 격자산소가 반응하여 생성된 물에 각각 기인하는 것으로 보였다. 선흡착된 산소원자는 $CH_3OH$의 분해흡착을 촉진시킴으로써 $CH_3OH$의 흡착량을 증가시킨 반면, 선흡착된 물은 분해흡착하여 $CH_3OH$의 흡착점을 점유함으로써 $CH_3OH$의 흡착량을 감소시켰다. The dissociation and partial oxidation of $CH_3OH$ on polycrystalline $MoO_3$ powder catalyst were studied using thermal desorption spectrometry(TDS) under high vacuum condition. $CH_3OH$ was dissociatively adsorbed on $MoO_3$ in the forms of surface methoxy($-OCH_3$) and atomic hydrogen(-H). $CH_3OH$ desorbed at 425 K via the re-association of methoxy and adsorbed hydrogen atom, and HCHO desorbed at 545 K through the bond breakage of C-H in methoxy. Water TDS spectra showed two desorption peaks, that is, ${\alpha}$-peak at 428 K and ${\beta}$-peak at 586 K. It was suggested that ${\alpha}$-peak was due to the hydroxyl formed on $MoO_3$ surface during the dissociation of $CH_3OH$, and that ${\beta}$-peak was from the association of lattice oxygen and surface hydrogen atom formed by the bond breakage of C-H in methoxy. Pre-adsorbed oxygen on the surface of $MoO_3$ catalyst increased the amount of adsorption of $CH_3OH$ by promoting the dissociation of $CH_3OH$ on the surface, whereas pre-adsorbed water decreased the amount of adsorption of $CH_3OH$ by blocking of adsorption sites for $CH_3OH$.
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김정희,박윤석,이호인 ( Jeong Hi Kim,Youn Seok Park,Ho In Lee ) 한국공업화학회 1991 공업화학 Vol.2 No.2
고진공계에서의 열탈착실험을 통하여 MoO_3촉매상에서의 CH_3OH 분해 및 부분산화반응에 관한 연구를 수행하였다. CH_3OH는 촉매표면에 methoxy (-OCH_3)와 수소원자 (-H) 의 형태로 흡착되어 있다가 흡착 수소원자가 methoxy와 재결합하면서 425K에서 CH_3OH로 탈착하였으며, methoxy로부터 수소원자가 떨어져 나가면서 545K에서 HCHO가 탈착되었다. 이때 반응에 의해서 생성된 물은 428K에서 탈착하는 α-피크와 586K에서 탈착하는 β-피크를 보였으며, α-피크는 표면에 형성된 hydroxyl에 기인하는 탈착피크, β-피크는 methoxy가 수소를 잃으면서 HCHO의 형태로 촉매표면에서 탈착하면서 남긴 표면수소원자와 격자산소가 반응하여 생성된 물에 각각 기인하는 것으로 보였다. 선흡착된 산소원자는 CH_3OH의 분해흡착을 촉진시킴으로써 CH_3OH의 흡착량을 중가시킨 반면, 선흡착된 물은 분해흡착하여 CH_3OH의 흡착점을 점유함으로써 CH_3OH의 흡착량을 감소시켰다. The dissociation and partial oxidation of CH_3OH on polycrystalline MoO_3 powder catalyst were studied using thermal desorption spectrometry(TDS) under high vacuum condition. CH_3OH was dissociatively adsorbed on MoO_3 in the forms of surface methoxy(-OCH_3) and atomic hydrogen(-H). CH_3OH desorbed at 425 K via the re-association of methoxy and adsorbed hydrogen atom, and HCHO desorbed at 545 K through the bond breakage of C-H in methoxy. Water TDS spectra showed two desorption peaks, that is, α-peak at 428 K and β-peak at 586 K. It was suggested that α-peak was due to the hydroxyl formed on MoO_3 surface during the dissociation of CH_3OH, and that β-peak was from the association of lattice oxygen and surface hydrogen atom formed by the bond breakage of C-H in methoxy. Pre-adsorbed oxygen on the surface of MoO_3 catalyst increased the amount of adsorption of CH_3OH by promoting the dissociation of CH_3OH on the surface, whereas pre-adsorbed water decreased the amount of adsorption of CH_3OH by blocking of adsorption sites for CH_3OH.
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김정희,이호인,우창수 한국공업화학회 2000 응용화학 Vol.4 No.1
The catalysts for the direct conversion of carboxylic acid to ketene and alkylketene dimer (AKD) by catalytic dehydration reaction with high yields were investigated. Direct conversion of high molecular weight carboxylic acid to ketene and AKD via abstracting a water molecule by silica catalyst could avoid the hazard of toxic chemicals and minimized unwanted wastes. Among the various metal oxides which could produce ketenes, only silicas showed the activity for AKD formation. When using typical amorphous silica powders (surface area: about 300 ㎡/g, with closed pores), the yields were very low regardless of pore size (60, 100, 150 Å ). On the other hand, mesoporous silicas (M41S, with open pores) gave higher yields of AKD in spite of smaller pore sizes (20-100 Å). The higher yields were caused by the easy transfers of the reactant and products along the open pores of M41S. Higher silianol concentration also could give higher yield of AKD.
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김정희,이호인,우창수 한국공업화학회 2000 응용화학 Vol.4 No.2
The factors in the catalytic dehydration of carboxylic acid to form ketene on silica were studied. Many research efforts have been concentrated on the ketene synthesis using low molecular weight carboxylic acid(C₂-C₄). However; there is no report so far on the ketene synthesis using high molecular weight carboxylic acid, and the reason may be attributed to the difficulties in controlling the reaction condition and analysis. We carried out ketene synthesis in vacuum using high molecular weight carboxylic acid as a reactant and checked the factors which affect catalytic activity. The concentration of silanol was decreased by raising the pretreatment temperature of the catalysts, and was proportional to the catalytic activity. Consequently, it was confirmed that surface silanol was the active site. By changing the thickness of the catalyst bed and the degree of vacuum, the short contact time of the reaction also was confirmed to play an important role in getting higher ketene yield.
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김정희,이호인,김현국 한국공업화학회 2001 응용화학 Vol.5 No.2
Catalytic dehydration of carboxylic acid on mesoporous silica was investigated. Direct conversion of high molecular weight carboxylic acid to ketene and ketene derivatives was observed. Besides the alkyl ketene dimer (AKD), stearic anhydride and β-keto acid were also formed. AKD is so reactive that it can easily react with water to become ketone via β-keto acid as an intermediate. However, among the catalytic dehydration products, β-keto acid was major product with high yield, but ketone was not detected. In the catalytic dehydration condition, β-keto acid was made from the ring opening of AKD mainly by silanol group. It was the most important key factor to shorten the contact time in catalyst layer for raising the yield of AKD by preventing the formation of β-keto acid.
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MCM - 41 을 이용한 아세트산으로부터의 케텐 합성
김정희,이호인,우창수 한국공업화학회 2001 응용화학 Vol.5 No.2
Ketene was made from acetic acid over MCM-41. Ketene could be separated with other byproducts by using low temperature trap, and reacted with acetic acid to form acetic anhydride. Acetic anhydride was not formed without catalyst and could be only formed via ketene intermediate over silica catalyst. Increases of the carrier flow rate caused the increase in activity and the optimum temperature was 823 K. The activity of MCM-41 was much higher than that of amorphous silica which had no pore.
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