LaCoO₃ 혼합산화물 촉매를 지지할 담체의 개발에 관한 연구

고성운,김철현 安東大學校 工業技術硏究所 1994 공업기술연구논문집 Vol.1 No.1

We could support LaCoO₃-type mixed oxide catalysts on MgO. In these cases, the activities were somewhat constant rigardless of the degree of A-site vacancy. All the supported and unsupported catalysts were poisoned by SO₂, but the durability of the supported catalysts were far better because of their high surface areas. Pt or Pd did not improved the catalytic activities or the resistance against SO₂ poisoning.

H₂ 및 CO에 의한 LaCoO₃ 촉매의 환원

고성운,김철현 安東大學校 工業技術硏究所 1996 공업기술연구논문집 Vol.3 No.1

With the perovskite-type oxide catalyst, LaCoO_(3), a study was performed on the reduction properties of catalyst by H_(2) and CO with TGA, XRD and FT-IR. The reduction of LaCoO_(3) in H_(2) atmosphere was a quantitative process with two steps. In the first reduction step at 320∼480℃, LaCoCO_(3) was reduced to LaCo_(1-X)O_(2.5) and xCo. These were further reduced to the final products, La_(2)O_(3) and metallic Co, through the second step at 600∼670℃. The LaCoO_(3) catalyst was reduced in CO atmoshpere via three-step process, La_(2)O_(3) and carbonate of cobalt was formed as the final products at 850℃. In the first and second step, LaCoO_(3) was changed to LaCoO_(2.5) and LaCoO_(3), respectively. These oxygen-deficient intermediates formed carbonates by CO adsorption.

La_(1-x)A_(x)CoO₃형 촉매에서의 CO 산화반응

고성운 安東大學校 工業技術硏究所 1996 공업기술연구논문집 Vol.3 No.1

With the perovskite-type oxide catalysts such as LaCoO_(3), Ce-, Th-, Sr- or Ba-substituted LaCoO_(3) and A-site vacant LaCoO_(3), a study was performed on the catalytic activities and the properties of the active sites for CO oxidation, which is one of the principal reactions of automobile exhaust control. The active sites were Co^(4+) for CO oxidation. Ce- or Th-substituted LaCoO_(3) and A-site vacant LaCoO_(3) showed high activities for CO oxidation. Calcination of the catalyst at higher temperature reduced Co^(4+) with decreasing the activities for CO oxidation. LaCoO_(3) with some A-site vacancies was highly active in CO oxidation.

LaCoO₃계 페롭스카이트 촉매에서의 NO 환원반응

고성운,김철현 安東大學 1996 安東大學 論文集 Vol.18 No.1

With the perovskite-type oxide catalysts such as LaCoO_(3), Ce-, Th-, Sr- or Ba-substituted LaCoO_(3) and A-site vacant LaCoO_(3), a study was performed on the catalytic activities and the properties of active sites for NO reduction, which is the principal reaction of automobile exhaust control. The active sites were oxygen vacancies for NO reduction. LaCoO_(3) showed highest activities for NO reduction. Calcination of the catalysts at higher temperature created more vacancies in lattice oxygen with improving the activities for NO reduction. Sr- and Ba-substituted LaCoO_(3) catalysts, which are known to be reduced more easily and expected to be more active in NO reduction, showed lower activities for NO reduction than LaCoO_(3) or Ce-substituted LaCoO_(3). It seems that a catalyst, in oder to show high activity for NO reduction, must have appropriate oxygen vacancies.

BaFeO3촉매상의 CO산화반응과 열분석을 통한 촉매조성변화

고성운 安東大學 1987 安東大學 論文集 Vol.9 No.1

SO_(2) 피독에 강한 자동차 배기가스 정화용 백금 대체촉매의 개발을 목적으로 폐롭스카이트형의 BaFeO_(3) 촉매를 사용하여 CO산화반응에 대한 촉매활성을 측정하였고 열분석에 의하여 촉매상태의 변화를 알아보았다. BaFeO_(3)촉매는 촉매의 환원-재산화과정 중 재산화가 어렵기 때문에 촉매활성이 매우 낮았으며 재산화속도를 빠르게 하기 위하여 Fe를 Zr, Ti및 Sn으로 치환한 결과 촉매활성이 증가하였으며, 그 중 Sn으로 치환한 때가 가장 효과적이었다. 또 Ba을 Sn으로 치환하여도 촉매활성은 크게 향상되었다. Instead of Pt, BaFeO3 can probably be used in a catalytic converter of exhaust gas, because the active center of BaFeO_(3) is highly resistive to SO2 poisoning. In CO oxidation reaction, the catalytic activity is very low due to very slow reoxidation rate of the catalyst. Substitution of Zr, Ti and Sn for Fe increase the catalytic activity with increasing the reoxidation rate. Of these elements, Sn is the most effective. Substitution of Sr for Ba also increase the Catalytc activity.

촉매에서 점 격자결함과 소성온도가 촉매활성에 미치는 영향

박병수,고성운 安東大學 1987 安東大學 論文集 Vol.9 No.1

LaCoO_(3)의 A점을 격자결함으로 치환한 촉매들의 CO산화반응에 대한 촉매활성을 비교검토함으로써 이를 촉매와 La_(0.95)Ce_(0.05)CoO_(3) 촉매의 활성점이 Co^(4+)이며 La_(0.95)Ce_(0.05)CoO_(3) 촉매에 섞여 있는 CeO_(2)는 조촉매로 작용하는 것을 알 수 있었다. 촉매의 소성온도를 높이면 격자산소결함의 생성으로 Co^(4+)가 소멸되기 때문에 촉매활성은 감소하였다. 그러나 이들 촉매는 SO_(2)에 의해 쉽게 피독되었으며 그 피독되는 정도는 A점 결함이 증가할수록, 저온에서 소성될수록 더 심하였다. In the CO oxidation reaction, we compared the activities of the catalysts which are partially vacant in the A site of LaCoO_(3). We concluded that the active centers of such catalysts and La_(0.95)Ce_(0.05)CoO_(3) are Co^(4+) ions. The CeO_(2) in the La_(0.95)Ce_(0.05)CoO_(3) catalyst acts as a promoter. The catalytic activities were decreased with increasing the calcination temperature due to the increment of the oxygen vacancy. But all the catalysts were largely deactivated by SO_(2) poisoning. The deactivation was more rapid in the lower-temperature calcined and higher A-site vacant catalysts.

Analytical Head-space Supercritical Fluid Extraction Methodology for the Determination of Organochlorine Compounds in Aqueous Matrix

Ryoo, Keon-Sang,Ko, Seong-Oon,Hong, Yong-Pyo,Choi, Jong-Ha,Kim, Yong-gyun,Lee, Won-Kyoung Korean Chemical Society 2006 Bulletin of the Korean Chemical Society Vol.27 No.5

The proposed head-space supercritical fluid extraction (SFE) methodology as an alternative to an existing conventional procedure was explored for the determination of organochlorine compounds in aqueous matrix. In this study, polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs) were utilized as target analytes. To enhance the recovery efficiency, the factors such as the $CO _2$ density, the extraction time, and the extraction mode were investigated. Furthermore, the analytical procedures and the results obtained were compared with those provided by the conventional method (the U.S. EPA method 8080). Under the optimized conditions, i.e., a combination of static with dynamic SFE mode at 2,000 psi and 40 ${^{\circ}C}$, the head-space SFE methodology gave equivalent or better to the conventional method in recovery efficiencies with clear advantages such as simple sample treatment and fast analysis time as well as reduced solvent and reagent consumption.

Single-crystal Structure of Partially Dehydrated Partially Mg²⁺-exchanged Zeolite Y (FAU), |Mg_30.5Na₁₄(H₂O)_2.5|[Si₁₁₇Al₇₅O₃₈₄]-FAU

Kim, Hu-Sik,Ko, Seong-Oon,Lim, Woo-Taik Korean Chemical Society 2011 Bulletin of the Korean Chemical Society Vol.32 No.10

The single-crystal structure of partially dehydrated partially $Mg^{2+}$-exchanged zeolite Y, ${\mid}Mg{30.5}Na_{14}(H_2O)_{2.5}{\mid}$ [$Si_{117}Al_{75}O_{384}$]-FAU per unit cell, ${\alpha}$ = 25.5060(1) ${\AA}$, dehydrated at 723 K and $1{\times}10^{-4}$ Pa, has been determined by single-crystal X-ray diffraction techniques in the cubic space group Fd$\bar{3}$ m at 100(1) K. The structure was refined using all intensities to the final error indices (using only the 561 reflections with $F_{\circ}$ > $4{\sigma}(F_{\circ})$) $R_1$ = 0.0377 (Based on F) and $R_2$ = 0.1032 (Based on $F^2$). About 30.5 $Mg^{2+}$ ions per unit cell are found at four different crystallographic sites. The 14 $Mg^{2+}$ ions occupy at site I at the center of double 6-ring (Mg-O = 2.231(3) ${\AA}$, O-Mg-O = $89.15(11)^{\circ}$ and $90.85(11)^{\circ}$). Four $Mg^{2+}$ ions are found at site I' in the sodalite cavity; the $Mg^{2+}$ ions are recessed 1.22 ${\AA}$ into the sodalite cavity from their 3-oxygen plane (Mg-O = 2.20(3) ${\AA}$ and O-Mg-O = $92.3(14)^{\circ}$). Site II' positions (opposite single 6-rings in the sodalite cage) are occupied by 2.5 $Mg^{2+}$ ions, each coordinated to an $H_2O$ molecule (Mg-O = 2.187(20) ${\AA}$ and O-Mg-O = $114.2(16)^{\circ}$). The 10 $Mg^{2+}$ ions are nearly three-quarters filled at site II in the supercage, being recessed 0.12 ${\AA}$ into the supercage (Mg-O = 2.123(4) A and O-Mg-O = $119.70(19)^{\circ}$). About 14 $Na^+$ ions per unit cell are found at one crystallographic site; the $Na^+$ ions are located at site II in the supercage (Na-O = 2.234(7) ${\AA}$ and O-Mg-O = $110.5(4)^{\circ}$).

LaCoO3 계 페롭스카이트에서의 CO 및 O2 흡착 특성

고성운,김영호,김철현,이호인 ( Seong Oon Ko,Young Ho Kim,Chul Hyun Kim,Ho In Lee ) 한국공업화학회 1995 공업화학 Vol.6 No.4

페롭스카이트형 산화물인 LaCoO₃와 LaCoO₃의 A점을 Ce로 치환하거나 또는 격자결함으로 만든 촉매들에 관하여 TPD를 통해 CO 및 O₂의 흡착특성을 관찰하였다. LaCoO₃계 촉매상에서 CO는 세 가지 흡착상태를 보였으며, 이들은 580℃∼660℃와 700℃에서 CO로, 730℃∼800℃에서 CO₂로 각각 탈착하였다. CO 흡탈착에 대한 LaCoO₃의 Ce 치환효과는 고온소성시 거의 나타나지 않았으나, 저온에서 소성되면 금속-격자산소간의 결합력 약화로 인하여 CO의 흡착량이 증가하며 탈착온도도 고온으로 이동하였다. 고온에서 소성된 LaCoO₃계 촉매상에서 O₂는 O^(2-)와 O₂^-의 흡착상태로 흡착하여 각각 500℃ 부근과 800℃ 부근에서 탈착하였고, 저온에서 소성된 촉매에서는 O^(2-), O₂^- 이외에 O^-로 보이는 흡착상태가 있었으며, 이 상태의 O₂는 300℃에서 흡착시킬 때 630℃∼700℃에서 탈착하였다. LaCoO₃의 A점을 Ce로 치환하거나 격자결함으로 만들었을 때는 촉매에 존재하는 CeO₂ 등 다른 phase의 영향으로 O₂의 탈착량이 크게 증가하였다. The adsorptive behaviors of CO and O₂ were studied using the technique of thermal desorption spectroscopy on the perovskite-type oxides such as LaCoO₃, Ce-substituted LaCoO₃, and A-site vacant LaCoO₃. CO adsorbed on LaCoO₃-type oxides in three different types, desorbing as CO at 580℃∼660℃ and 700℃, respectively, and as CO₂ at 730℃∼800℃. For the catalysts calcined at high temperatures, the effect of A-site substitution with Ce on CO adsorption was negligible, but for those at low temperatures, CO adsorbed more in quantity and desorbed at higher temperature due to weaker bond-strength between metal and lattice oxygen. On the LaCoO₃-type catalysts calcined at high temperatures, the adsorbed species of oxygen were O^(2-) and O₂^-, desorbing at about 500℃ and 800℃, respectively. On the catalysts calcined at low temperatures, another adsorbed species, which might be O^-, desorbed at 630℃∼700℃ when adsorbed at 300℃. For the Ce-substituted LaCoO₃ and A-site vacant LaCoO₃, the amount of O₂desorption was very large due to the effect of other phases such as CeO₂.

Single-Crystal Structures of Li⁺-exchanged Zeolite X (FAU, Si/Al = 1.09) from Aqueous Solution Depends on Ion-exchange Temperatures at 293 and 333 K

Kim, Hu-Sik,Ko, Seong-Oon,Lim, Woo-Taik Korean Chemical Society 2012 Bulletin of the Korean Chemical Society Vol.33 No.10

Two single crystals of fully dehydrated partially $Li^+$-exchanged zeolite X were prepared by the exchange of Na-X, $Na_{92}Si_{100}Al_{92}O_{384}$ (Si/Al = 1.09), with $Li^+$ using aqueous 0.1 M $LiNO_3$ at 293 (crystal 1) and 333 K(crystal 2), followed by vacuum dehydration at 623 K and $1{\times}10^{-6}$ Torr for 2 days. Their structures were determined by single-crystal synchrotron X-ray diffraction techniques in the cubic space group $Fd{\overline{3}}$ at 100(1) K. Their structures were refined using all intensities to the final error indices (using the 1281 and 883 reflections for which ($F_o$ > $4{\sigma}(F_o)$) $R_1/R_2$ = 0.075/0.244 and 0.074/0.223 for crystals 1 and 2, respectively. Their compositions are seen to be ${\mid}Li_{86}Na_6{\mid}[Si_{100}Al_{92}O_{384}]$-FAU and ${\mid}Li_{87}Na_5{\mid}[Si_{100}Al_{92}O_{384}]$-FAU, respectively. In crystal 1, 17 $Li^+$ ions per unit cell are at site I', 15 another site I', 30 at site II, and the remaining 16 at site III; 2 $Na^+$ ions are at site II and the remaining 4 at site III'. In crystal 2, 32 and 30 $Li^+$ ions per unit cell fill sites I' and II, respectively, and the remaining 25 at site III'; 2 and 3 $Na^+$ ions are found at sites II and III', respectively. The extent of $Li^+$ exchange increases slightly with increasing ion exchange temperature from 93% to 95%.