共查询到19条相似文献,搜索用时 93 毫秒
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乙烯主要通过石脑油和柴油热裂解制取,乙烯原料气中带有体积分数为0.3%~3%的乙炔,该微量乙炔会毒化乙烯聚合催化剂。工业上通常用选择加氢法将乙炔转化为乙烯,但钯基催化剂一直都存在选择性低、稳定性差等缺点。梳理近几年对乙炔选择性加氢反应及其催化剂的研究,并探讨制备方法、活性组分、助剂和载体对催化剂结构和性能的影响;叙述不同催化剂的制备方法在乙炔加氢反应中的应用,制备方法可以有效改变活性组分的表面物理性质,影响活性组分对乙烯的吸脱附性能。最后,展望了乙炔加氢催化剂未来的研究方向。 相似文献
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对苯选择性加氢反应特性、催化剂的研究现状及进展、影响催化剂性能的主要反应条件等方面作了细致的探讨 ,在此基础上提出了提高苯选择性加氢制环己烯收率的可能途径。 相似文献
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选择性加氢合成芳樟醇催化剂的研究进展 总被引:3,自引:0,他引:3
综合介绍了选择性加氢合成芳樟醇催化剂的国内外研究情况。催化加氢合成芳樟醇,主要采用固体催化剂,活性组分大多为Pd,载体通常为CaCO3、BaSO4、Al2O3、金属材料,改性剂为铅、铋、锰或吡啶、喹啉、含硫化合物,转化率可达100%,选择性在98%以上。 相似文献
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催化选择加氢去除乙烯中微量乙炔是石化工业重要的反应过程,工业钯基催化剂选择性低、催化剂使用寿命较短。本文综述了近年来国内外乙炔选择性加氢钯基催化剂的研究进展。主要探讨了过渡金属、金属氧化物与非金属配体助剂能调变钯粒子空间结构,隔离分散钯粒子并与钯粒子产生电子效应;阐明了钯粒子尺寸与织构形貌的调控能改变钯的晶面结构,影响钯对乙烯的吸脱附和对氢气的活化与解离性能;评述了单一氧化物、复合金属氧化物、碳材料等载体为催化剂提供合适的表面酸碱性并加强了与活性中心之间的相互作用,稳定钯粒子抑制其发生迁移与团聚。提高乙烯选择性与催化剂稳定性是该研究的重点与难点,负载型钯基催化剂的发展方向是构建高分散钯粒子,并在反应过程中保持稳定。 相似文献
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Selective hydrogenation of fatty acids and methyl esters of fatty acids to obtain fatty alcohols–a review 下载免费PDF全文
María A Sánchez Gerardo C Torres Vanina A Mazzieri Carlos L Pieck 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2017,92(1):27-42
In this paper, a review is presented of the evolution of different catalytic systems and operating conditions used in the selective hydrogenation of acids and esters of fatty acids to obtain fatty alcohols, which have broad industrial applications in the oleochemical industry. In addition, the current status of the different technologies used industrially (Lurgi, Davy and Henkel) for obtaining fatty alcohols, as well as major global sources of raw materials for the oleochemical industry are put forward. Finally, the reaction mechanisms of the selective hydrogenation process of oleic acid and methyl oleate to obtain the corresponding unsaturated alcohol as well as the new catalysts proposed by researchers are described. © 2016 Society of Chemical Industry 相似文献
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Güldem Üstün 《Journal of the American Oil Chemists' Society》1996,73(2):203-210
Fatty acid methyl esters (FAME) and resin acids (RA) were separated from tall oil by selective adsorption. Commercial nonmodified
molecular sieve 13X was used as adsorbent. The adsorption isotherms of fatty acids (FA), FAME, and RA on molecular sieve 13X
at 25°C were determined using various solvents. The solvents were methanol, ethanol, isopropanol, acetone, benzene, hexane,
isooctane, petroleum ether (40–60°C), and petroleum naphtha (80–180°C). With each solvent, FA and RA were adsorbed to a greater
extent than FAME. Adsorption isotherms for RA and FAME in binary adsorption systems were also determined using petroleum ether,
petroleum naphtha, benzene, and isopropanol. For each component in the binary adsorption, the equilibrium amounts are lower
than the values for pure component adsorption. The adsorption of FAME decreased in the presence of RA markedly in petroleum
ether and petroleum naphtha. This fact may be the indication of the phenomenon of selective adsorption. Separation was accomplished
by adding a solution of esterified tall oil in solvents used in the binary adsorption systems, through a column packed with
molecular sieve 13X. With petroleum naphtha, FAME and RA were recovered in yields of 93 and 94%, respectively, from esterified
tall oil. Petroleum naphtha gave the best results. The effects of particle size of adsorbent and flow rate of solvent on the
efficiency of the separation were also investigated in fixed-bed column studies. The particle size of adsorbent did not apparently
alter the results. Changes in the particle size should not significantly change the number of available adsorption sites in
a microporous molecular sieve. 相似文献
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Marianne Lilja Hallberg Daobin Wang Magnus Härröd 《Journal of the American Oil Chemists' Society》1999,76(2):183-187
Wax esters were transesterified from fatty acid methyl esters of rapeseed and a fatty alcohol (1-hexadecanol, 16:0). The amounts of both the substrates were fixed to 0.1 mmol and an immobilized enzyme, Lipozyme, was used as catalyst. The experiment was performed following a statistic central composite design with five variables. The enzyme/lipid ratio was varied between 0.3–0.9 of the substrate weight and the enzyme was equilibrated to different water activities varying from 0.11 to 0.44. A temperature range of 50–80°C was investigated and the reaction time lasted up to 40 min. A solvent, isooctane, constituted 0–30% of the substrate weight. The first experimental series was performed in small closed test tubes. In the second series the caps of the test tubes were off to evaporate the methanol produced during the reaction. The highest initial reaction rate was 9.6 gwax esters/genzyme · h. It appeared when: the enzyme/lipid ratio was low, 0.3, the temperature was high, 80°C; no isooctane was present; and the water activity was below 0.11. The initial reaction rate was independent of the caps on the test tubes. With the large amount of enzyme the yield of wax esters was above 70% after 10 min in both experimental series. In the reaction with caps, the reaction reached equilibrium at 83% after 20 min at 80°C. However, without caps the continuous evaporation of methanol increased the equilibrium constantly, and after 40 min at 80°C a yield of 90% was reached. 相似文献
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Combustion characteristics of fatty acid methyl esters derived from recycled cooking oil 总被引:1,自引:0,他引:1
The goal of this study is to find out the exhaust emissions differences produced by different kinds of fatty acid methyl esters (FAME) derived from used cooking oils and animal fats, as well as the importance of the purification step in exhaust emissions production. A total of 120 L of waste vegetable oil and 30 L of waste frying oil were collected and converted into three batches of FAME. There were two batches of FAME produced from waste vegetable oil (B01 and B02), and one batch of FAME produced by mixing 2% of waste frying oil with waste vegetable oil (B03). The FAMEs used in this study had higher density, kinematic viscosity, and flash point, but a lower gross heating value, when compared to the premium diesel. The B01 engine produced higher CO formation and the diesel-fuelled engine produced higher CO than the B02 and B03 did for engine speeds higher than 1400 rpm. Most of the FAME fuels produced higher CO2 than the diesel fuel did. The FAME fuels emitted higher NOx and PM, but lower SO2, than the diesel fuel. CnH2n+2, diphenyl sulfone (C12H10O2S), and diethyl phthalate (C12H14O4) can be selected as the character index for the combustion of FAME. 相似文献
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Hydrogenation of fatty acid methyl esters to fatty alcohols at supercritical conditions 总被引:2,自引:0,他引:2
Sander van den Hark Magnus Härröd Poul Møller 《Journal of the American Oil Chemists' Society》1999,76(11):1363-1370
Extremely rapid hydrogenation of fatty acid methyl esters (FAME) to fatty alcohols (FOH) occurs when the reaction is conducted in a substantially homogeneous supercritical phase, using propane as a solvent, over a solid catalyst. At these conditions, the limitations of hydrogen transport are eliminated. At temperatures above 240°C, complete conversion of the starting material was reached at residence times of 2 to 3 s, which is several orders of magnitude shorter than reported in the literature. Furthermore, formation of by-products, i.e., hydrocarbons, could be prevented by choosing the right process settings. Hydrogen concentration turned out to be the key parameter for achieving the above two goals. As a result of the supercritical conditions, we could control the hydrogen concentration at the catalyst surface independently of the other process parameters. When methylated rapeseed oil was used as a substrate, the hydrogenation catalyst was deactivated rapidly. However, by using methylated sunflower oil, a catalyst life similar to that obtained in industrial processes was achieved. Our results showed that the hydrogenation of FAME to FOH at supercritical conditions is a much more efficient method than any other published process. 相似文献
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Nolwenn Dubois Chantal Barthomeuf Jean‐Pascal Berg 《European Journal of Lipid Science and Technology》2006,108(1):28-32
It is essential to have simple rapid methods for the determination of fatty acid structures. Traditionally, fatty acids are analysed by gas chromatography using their methyl ester derivatives (FAME). However, their corresponding mass spectra exhibit molecular ions but are usually devoid of ions indicative of structural features and, notably, the position of double bounds on the aliphatic chains [1]. In the most useful approach to structure determination, the carboxyl group is derivatised with a reagent containing a nitrogen atom. Recently, a convenient method for preparing picolinyl esters from intact lipids has been published [2]. However, some problems occurred in our laboratory when this method was used, leading to some modifications and optimisation. Thus, hexane and water have been added while sodium bicarbonate has been removed in order to lower contamination. Temperature and length of the reaction have then been optimised in order to get 100% derivatisation for different kinds of lipids (45 °C and 45 min for FAME). Finally, a comparison of the response factors has confirmed the better sensitivity of the picolinyl derivative against FAME (five times more). 相似文献
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Evidence of thermal decomposition of fatty acid methyl esters during the synthesis of biodiesel with supercritical methanol 总被引:1,自引:0,他引:1
Joaquín Quesada-Medina Pilar Olivares-Carrillo 《The Journal of Supercritical Fluids》2011,56(1):56-63
New evidence on the thermal decomposition of fatty acid methyl esters during biodiesel synthesis in supercritical conditions is presented. Thermal decomposition products were detected chromatographically, by applying the UNE-EN 14105:2003 standard, as a broad single peak during the determination of glycerides in the reaction samples. These degradation products could be quantified chromatographically by the above standard because the area of the peak was proportional to the disappearance of the polyunsaturated fatty acid methyl esters, which contain two or more double bonds (methyl linoleate and linolenate), generated during biodiesel synthesis from soybean oil. In the experimental conditions tested, thermal decomposition reactions of these unsaturated fatty acid methyl esters began to appear at 300 °C/26 MPa, and were more intense as the temperature rose. For its part, the main saturated fatty acid methyl ester (methyl palmitate) generated during the reaction was hardly decomposed at all in the experimental conditions tested and only began to disappear at 350 °C/43 MPa. 相似文献