1,115 research outputs found
Enhanced production of long-chain polyunsaturated fatty acids (LC-PUFAs) by overexpressing heterologous and endogenous fatty acid elongase genes in Nannochloropsis salina
No full textEnhancing the production of long-chain polyunsaturated fatty acids (LC-PUFAs) in Nannochloropsis salina by overexpressing the heterologous and endogenous fatty acid elongase genes
No full textSelective synthesis of C3–C4 hydrocarbons through carbon dioxide hydrogenation on hybrid catalysts composed of a methanol synthesis catalyst and SAPO
No full textDirect synthesis of hydrocarbons through carbon dioxide hydrogenation was investigated over hybrid catalysts composed of methanol synthesis catalysts (Cu/ZnO/ZrO2 and Cu/ZnO/Al2O3) and molecular sieves (H-ZSM-5, SAPO-5 and SAPO-44). It was found that the hybrid catalyst with SAPO-5 or SAPO-44 was effective for the synthesis of C-2+ hydrocarbons. The high hydrocarbon yield appears to be due to the abundance of weak- and medium-strength acid sites in SAPO, which could be evidenced through temperature-programmed desorption of ammonia. The product distribution of hydrocarbon products was influenced by the acidity as well as the pore size of the molecular sieves. The selectivity to isobutane was the highest on the hybrid catalysts with SAPO-5. Propane was the main product on the hybrid catalyst with SAPO-44. Carbon dioxide conversion increased with reaction temperature, but a maximum yield of C-2+ hydrocarbon was obtained at 340 degrees C. An increase in contact time lowered the carbon monoxide formation and increased the hydrocarbon formation. Addition of carbon monoxide or ethene to the feed increased the hydrocarbon yield, The reaction pathway to hydrocarbons is thought to be composed of methanol synthesis from carbon dioxide and hydrogen, methanol/dimethyl ether to lower alkene, alkene oligomerization, isomerization and hydrogenation to alkane
Catalytic properties of potassium- or lanthanum-promoted Co/gamma-Al2O3 catalysts in carbon monoxide hydrogenation
No full textThe effects of potassium or lanthanum additives on the catalytic properties of alumina-supported cobalt catalysts were examined through carbon monoxide hydrogenation reaction. The catalysts were characterized by hydrogen or carbon monoxide chemisorption, oxygen titration, and temperature-programmed desorption. The reactions were carried out at 270 degreesC and atmospheric pressure. When a small amount of potassium was added to alumina-supported cobalt catalysts, the amount of hydrogen adsorption decreased more significantly than that of carbon monoxide adsorption, and the extent of reduction also decreased. With the addition of potassium, the overall carbon monoxide conversion decreased, while the selectivity to higher hydrocarbon and olefin increased. The effect of lanthanum on activity and selectivity in carbon monoxide hydrogenation was less significant than the effect of potassium. Temperature-programmed desorption showed that the presence of additives changed the adsorbed state of CO on cobalt
A study on methanol synthesis through CO2 hydrogenation over copper-based catalysts
No full textIn CO2 hydrogenation over Cu/ZrO2 based catalysts, the methanol formation activity could be correlated with copper dispersion. The reaction intermediates of methanol synthesis were carbonate, formate, formaldehyde and/or methoxy, and the rate determining step for methanol synthesis seems to be the conversion of formate into formaldehyde or methoxy
Effect of magnesium promoter on nickel/kieselguhr catalysts in triglyceride oil hydrogenation
No full textThe effects of a magnesium promoter on the catalytic properties of kieselguhr-supported nickel catalysts were examined through a triglyceride oil hydrogenation reaction. The catalysts were characterized with respect to their BET surface area, pore size distribution, hydrogen chemisorption, temperature-programmed reduction (TPR), and X-ray diffraction (XRD). The reactions were performed at 180degreesC and 45 psi. By adding a small amount of magnesium to a kieselguhr-supported nickel catalyst, the BET surface area increases as a result of an increase in microporosity. With the addition of magnesium, the catalysts were more difficult to reduce, but presented a higher metallic area. In the hydrogenation of triglyceride oil, the 4 wt% magnesium-promoted catalyst showed the highest activity, which appeared to be due to an increase of the metallic area as well as maintaining mesoporosity to avoid limited diffusion
Highly valuable chemicals production from catalytic upgrading of radiata pine sawdust-derived pyrolytic vapors over mesoporous MFI zeolites
No full textThe catalytic upgrading of pyrolytic vapors derived from radiata pine sawdust was carried out over mesoporous MEI zeolite synthesized using an amphiphilic organosilane. Its catalytic activity was compared with those of conventional HZSM-5 and mesoporous material from HZSM-5 (MMZ(ZSM-5)). The effect of gallium incorporation into mesoporous MEI zeolite on the product distribution and chemical composition of bio-oil was also investigated. The catalysts synthesized were characterized using ICP, XRD, N(2)-sorption, NH(3)-TPD, and H(2)-TPR methods. After catalytic upgrading, products were analyzed by GC-TCD, GC-FID, GC-MS, and Karl Fischer titration. The mesoporous MEI zeolite exhibited the best activity in deoxygenation and aromatization during the upgrading of pyrolytic vapors. In particular, mesoporous MEI zeolite showed high selectivity for highly valuable aromatics, such as benzene, toluene, and xylenes (BTX), even though it decreased the overall organic fraction of the bio-oil. The incorporation of gallium into the mesoporous MEI zeolite increased both the organic fraction of the bio-oil and resistance to coke deposition. Moreover, the selectivity for BTX aromatics was enhanced when the appropriate amount of gallium was introduced. (C) 2010 Elsevier B.V. All rights reserved.R.R. acknowledges support from the Korean Ministry of
Education, Science and Technology through the National Honor
Scientist Program
Combinatorial Search of (Bi,Ce)4Ti3O12 and (Bi,La,Ce)4Ti3O12 Prepared by Liquid Source Misted Chemical Deposition (LSMCD) and Multi-Target Sputtering
No full textCharacterization of (Bi, Ce, La)4Ti3O12 thin film ofr FRAM capacitor prepared by combinatorial liquid source misted chemical deposition (LSMCD) process
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