다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

The interest in nanoscale materials stems from the fact that new properties are acquired at this length scale and, equally important, that these properties * To whom correspondence should be addressed. Phone, 404-8940292; fax, 404-894-0294; e-mail, mostafa.el-sayed@ chemistry.gatech.edu. † Case Western Reserve UniversitysMillis 2258. ‡ Phone, 216-368-5918; fax, 216-368-3006; e-mail, burda@case.edu. § Georgia Institute of Technology. 1025 Chem. Rev. 2005, 105, 1025−1102

Chemistry and properties of nanocrystals of different shapes.

Ordered mesoporous materials in catalysis

Advances in the development of novel cobalt Fischer-Tropsch catalysts for synthesis of long-chain hydrocarbons and clean fuels.

CO2 conversion covers a wide range of possible application areas from fuels to bulk and commodity chemicals and even to specialty products with biological activity such as pharmaceuticals. In the present review, we discuss selected examples in these areas in a combined analysis of the state-of-the-art of synthetic methodologies and processes with their life cycle assessment. Thereby, we attempted to assess the potential to reduce the environmental footprint in these application fields relative to the current petrochemical value chain. This analysis and discussion differs significantly from a viewpoint on CO2 utilization as a measure for global CO2 mitigation. Whereas the latter focuses on reducing the end-of-pipe problem “CO2 emissions” from todays’ industries, the approach taken here tries to identify opportunities by exploiting a novel feedstock that avoids the utilization of fossil resource in transition toward more sustainable future production. Thus, the motivation to develop CO2-based chemistry does...

Sustainable Conversion of Carbon Dioxide: An Integrated Review of Catalysis and Life Cycle Assessment

Pore Size Effects in Fischer Tropsch Synthesis over Cobalt-Supported Mesoporous Silicas

The effect of support mesoporous structure and cobalt content on cobalt dispersion and reducibility was studied using two series of Fischer–Tropsch (FT) silica supported cobalt catalysts. The first series of the catalysts was supported by an SBA-15 periodic mesoporous silica with narrow pore size distribution, the second series was supported by a commercial mesoporous silica with broader pore size distribution. It was shown that in a wide range of cobalt surface densities (0–50 Co/nm 2 ), cobalt dispersion in silica supported catalysts was largely influenced by support texture. Cobalt dispersion was higher in Co catalysts supported by the SBA-15 silica with a pore diameter of 9.1 nm than in the commercial mesoporous silica with an average pore diameter of 33 nm. A more than 10-fold increase in cobalt surface density did not result in any noticeable sintering of Co 3 O 4 particles in SBA-15 periodic mesoporous silicas; the cobalt dispersion seems to be maintained by catalyst mesoporous structure. The effect of support pore diameter on cobalt dispersion was less significant for the catalysts supported by commercial silicas with broader pore size distribution. At the range of cobalt surface densities from 5 to 15 Co/nm 2 , higher Fischer–Tropsch reaction rates were observed over cobalt catalysts supported by the SBA-15 periodic mesoporous silica. This effect was attributed to higher cobalt dispersion in these catalysts. An increase in cobalt surface densities did lead to any significant changes in hydrocarbon selectivities and in chain growth probabilities for both series of supported catalysts.

Fischer–Tropsch synthesis over silica supported cobalt catalysts: mesoporous structure versus cobalt surface density

Structure and catalytic performance of Pt-promoted alumina-supported cobalt catalysts under realistic conditions of Fischer–Tropsch synthesis

The effect of porosity in a wide range of mesopore diameters (dp = 20−330 A) on the dispersion and reducibility of cobalt species in mesoporous silicas is examined using nitrogen adsorption, X-ray diffraction, thermogravimetric analysis, and in situ X-ray absorption. It is shown that modification of mesoporous silicas by cobalt via aqueous impregnation results in small Co3O4 crystallites located in the pores of silicas. The sizes of these crystallites increase with increasing mesopore diameters. In situ X-ray absorption and thermogravimetric analyses show that the reduction of Co3O4 crystallites in hydrogen leads to CoO and Co metal particles. The porous structure of the supports strongly affects the extent of cobalt reduction. It is found that smaller particles in the narrow pores (20−50 A) are much more difficult to reduce to metal species than larger ones situated in the broad pores (>50 A) of mesoporous silicas.

Anne Griboval-Constant

Papers

Pore Size Effects in Fischer Tropsch Synthesis over Cobalt-Supported Mesoporous Silicas

Fischer–Tropsch synthesis over silica supported cobalt catalysts: mesoporous structure versus cobalt surface density

Structure and catalytic performance of Pt-promoted alumina-supported cobalt catalysts under realistic conditions of Fischer–Tropsch synthesis

Pore-Size Control of Cobalt Dispersion and Reducibility in Mesoporous Silicas

Cobalt dispersion, reducibility, and surface sites in promoted silica-supported Fischer–Tropsch catalysts