메조구조 실리카 및 탄소 물질의 표면 특성 조절

학위논문(박사) - 한국과학기술원 : 화학과, 2001.2, [ xii, 90 p. ]The ordered mesoporous silica is a new class of mesostructured materials that are synthesized via supramolecular assembly route between surfactant micelles and silica species. In this work, post-synthesis approaches to the surface modification of mesoporous silicas were investigated in order to improve the hydrothermal stability and catalytic activities of the mesostructured materials. Mesoporous silica materials with various structures such as MCM-41 (hexagonal), MCM-48 (cubic Ia3d), SBA-1 (cubic Pm3n), MSU-1 (disordered) and KIT-1 (disordered) were synthesized following hydrothermal procedures using surfactants and silica species. The as-synthesized MCM-41 and MCM-48 materials were heated in salt solutions at 373 K over prolonged periods. The mesoporous silica materials after these treatments exhibited outstanding hydrothermal stability, compared with untreated samples. It has been found out that the improvement of the hydrothermal stability occurred through local re-structuring of the silica frameworks during the salting periods. However, the re-construction of the local frameworks caused no apparent changes in the mesostructural order. The optimum "salting" conditions depended on structures and synthesis methods of the mesostructured silica mateirals, as well as the nature and the concentration of the salts. The mesostructured porous materials (or mesoporous materials) in the pure silica form lack catalytic activity and ion exchange capacity. These physicochemical properties can be improved by incorporation of other metal elements such as Al, Ti, Fe and Mn during syntheses. However, the direct incorporation of metals into the synthesis starting mixtures often causes a severe loss in the structural order. Therefore, a post-synthesis of metal incorporation into the silica frameworks has been developed in this work. In this method, as-synthesized silica materials were washed with a HCl-ethanol mixture or calcined, in order to remove the surfactan...한국과학기술원 : 화학과

Carbon molecular sieve materials, methods for preparing thesame and uses thereof

본 발명은 구조 규칙성 탄소 분자체 물질, 이의 제조 방법 및 이의 용도에 관한 것으로, 좀 더 상세하게는 (A) 분자체 물질에 탄수화물의 수용액과 산의 혼합물을 흡착시키거나 고분자의 전구체를 포함하는 유기물을 흡착시키는 단계; (B) 상기 (A)단계에서 분자체 기공 내에 흡착된 흡착물들을 건조 및 중합시키는 단계; (C) 상기 (B)단계에서 형성된 분자체 물질과 중합된 흡착물의 혼합물에 다시 추가의 탄수화물의 수용액과 산의 혼합물 또는 고분자의 전구체를 포함하는 유기물을 재흡착시켜 건조 및 중합시키는 단계; (D) 상기 (C)단계에서의 혼합물을 열분해시켜 탄소화시키는 단계; 및 (E) 상기 (D)단계에서의 탄소화된 혼합물에서 분자체의 무기물 골격을 불산 또는 수산화나트륨 수용액으로 제거시키는 단계로 제조된 탄소 분자체 물질, 이의 제조 방법 및 이의 용도에 관한 것이다. 본 발명에 따른 탄소 분자체는 균일한 크기의 기공과 규칙적인 구조를 가지기 때문에 촉매, 흡착제, 담지체, 센서, 전극 물질 등으로 많은 응용이 가능하다.탄소분자체, 탄수화물, 유기물, 산, 촉

계면활성제-실리카 준결정상의 형성과정 중에 첨가된 염의 효과

학위논문(석사) - 한국과학기술원 : 화학과, 1997.2, [ vii, 46 p. ]Recently, a new synthetic approach to obtain mesoporous molecular sieves has been discovered by scientists at the Mobil corporation, using the formation of surfactant-silica mesostructures. The surfactant-silica mesostructures consist of a periodic array of the silica frameworks which are templated by the surfactant micelles. The mesostructures are obtained by self organization of the silica frameworks surrounding the surfactant micelles during the hydrothermal reaction in an aqueous solution of surfactant and silica sources. MCM-41, one of the mesoporous molecular sieves thus obtained, has uniform hexagonal arrays of cylindrical channels with the cross-sectional diameter controllable in the range of 2 - 10 nm. The MCM-41 material has attracted much attentions as adsorbents, catalysts, and hosts for large molecules due to its large pore diameter compared with conventional zeolites. However, practical applications of the MCM-41 have been severely inhibited by its weak hydrothermal stability compared with zeolites. The present work has been performed in order to improve the weak hydrothermal stability of MCM-41. Various inorganic and organic salts such as LiCl, NaCl, KCl, $CH_3COONa$, $Na_4EDTA$, $K_4EDTA,$Na_2SO_4$and$NaNO_3$were added to the synthetic mixture after permitting the hydrothermal reaction to proceed. The effects of the salts were investigated with X-ray diffraction and magic angle spinning (MAS)$^29Si$ NMR spectroscopy. MCM-41 materials obtained by using proper amount of salts during the synthesis process showed no sign of structural losses in XRD after heating in boiling water for 12 h, while the structure of MCM-41 synthesized without adding salts was completely lost. Thus, hydrothermal stability of MCM-41 was improved by salt effect. In view of the salt effect on the formation of the surfactant-silica mesostructure, it is reasonable that the anions constituting the salt can moderate electrostatic interaction between the positively charge...한국과학기술원 : 화학과