505 resultados para atmosfera de CO2


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Assessment of the potential CO2 emission reduction by development of non-grain-based ethanol in China is valuable for both setting up countermeasures against climate change and formulating bioethanol policies. Based on the land occupation property, feedstock classification and selection are conducted, identifying sweet sorghum, cassava, and sweet potato as plantation feedstocks cultivated from low-quality arable marginal land resources and molasses and agricultural straws as nonplantation feedstocks derived from agricultural by-products. The feedstock utilization degree, CO2 reduction coefficient of bioethanol, and assessment model of CO2 emission reduction potential of bioethanol are proposed and established to assess the potential CO2 emission reduction by development of non-grain-based bioethanol. The results show that China can obtain emission reduction potentials of 10.947 and 49.027 Mt CO2 with non-grain-based bioethanol in 2015 and 2030, which are much higher than the present capacity, calculated as 1.95 Mt. It is found that nonplantation feedstock can produce more bioethanol so as to obtain a higher potential than plantation feedstock in both 2015 and 2030. Another finding is that developing non-grain-based bioethanol can make only a limited contribution to China's greenhouse gas emission reduction. Moreover, this study reveals that the regions with low and very low potentials for emission reduction will dominate the spatial distribution in 2015, and regions with high and very high potentials will be the majority in 2030.

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Hydrogenolysis of mono(cyclopentadienyl)-ligated rare-earth-metal bis(alkyl) complexes Cp'Ln-(CH2SiMe3)2(THF) (Ln = Y (1a), Dy (1b), Lu (1c); Cp' = C5Me4SiMe3) with PhSiH3 afforded the mixed hydride/alkyl complexes [Cp'Ln(mu-H)(CH2SiMe3)(THF)](2) (Ln = Y (2a), Dy (2b), Lu (2c)). The overall structure of complexes 2a-c is a C-2-symmetric dimer containing a planar symmetric Ln(2)H(2) core at the center of the molecule. Deprotonation of ArOH (Ar = C6H2-Bu-t(2)-2,6-Me-4) by the metal alkyl group of 2a-c led to formation of the mixed hydride/aryloxide derivatives [Cp'Ln(mu-H)(OAr)](2) (Ln = Y (3a), Dy (3b), Lu (3c)), which adopt the dimeric structure through hydride bridges with trans-accommodated terminal aryloxide groups.

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CO2-in-Water (C/W) emulsion was formed by using a nonionic surfactant of poly (ethylene oxide)-poly (propylene oxide)-poly (ethylene oxide) (P123), and palladium nanoparticles were synthesized in situ in the present work. The catalytic performance of Pd nanoparticles in the C/W emulsion has been discussed for a selective hydrogenation of citral. Much higher activity with a turnover frequency (TOF) of 6313 h(-1) has been obtained in this unique C/W emulsion compared to that in the W/C microemulsion (TOF, 23 h(-1)), since the reaction was taking place not only in the surfactant shell but also on the inner surface of the CO2 core in the C/W emulsion. Moreover, citronellal was obtained with a higher selectivity for that it was extracted to a supercritical carbon dioxide (scCO(2)) phase as formed and thus its further hydrogenation was prohibited. The Pd nanoparticles could be recycled several times and still retain the same selectivity, but it showed a little aggregation leading to a slight decrease in conversion.

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一种超临界CO↓[2]提取翅果精的方法是将富含有植物甾醇等不皂化物的翅果全果原料粉碎成10-40目的粉状物在萃取压力15~35MPa,萃取温度31.1~60℃条件下进行超临界萃取;在压力4~10MPa,温度10~80℃条件下分离得含植物甾醇的翅果混合萃取物;将此混合物在10-25℃静置沉析后,通过离心或过滤手段,进行固液分离,液体部分得翅果油,固体物得翅果精。本发明采用含外果皮的翅果全果为原料,获得了富含植物甾醇、维生素E等的翅果精及翅果油产品,可广泛应用于医疗、食品和化妆品等行业。

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Hexaalkylguanidinium halides exhibit an efficient catalytic activity in the synthesis of cyclic carbonates from, epoxides and carbon dioxide. By this method cyclic carbonates can be obtained in a high yield and a high selectivity at a low temperature and atmospheric pressure. This procedure is easy for the product isolation and recycling of the catalyst.

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一种超临界CO2流体干燥制备纳米ZrO2的方法是将氨水加入硝酸氧锆水溶液中,调节pH值到5-10,陈化,抽滤,用乙醇置换凝胶中的水,得醇凝胶;超临界CO2流体连续通过醇凝胶,含有乙醇的CO2分离器,乙醇析出回收,CO2循环利用,待分离器中不再有乙醇析出时得到原粉;将原粉升温至673-1073K,保温,冷却,得到ZrO2粉体。本发明具有生产成本,工艺简单,容易控制,易于实现工业化的优点。