共查询到17条相似文献,搜索用时 93 毫秒
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采用固定床微型反应器考察Cu/ZnO和Cu/SiO2催化剂在醋酸甲酯加氢制乙醇反应中的稳定性,分别反应1 000 h和750 h后,Cu/ZnO和Cu/SiO2催化剂均失活。采用物理吸附、DTG、原位XRD和H2-TPR等对失活前后Cu/ZnO和Cu/SiO2催化剂进行比较。结果表明,Cu/ZnO和Cu/SiO2催化剂在醋酸甲酯加氢制乙醇反应中失活机理不同,Cu/ZnO 催化剂失活的主要原因是Cu晶粒长大,催化剂上ZnO晶粒同时长大;Cu/SiO2催化剂失活主要原因是积炭物种对催化剂孔道的堵塞和对活性位的覆盖。 相似文献
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合成气经草酸二甲酯加氢制乙二醇工艺是非石油路线合成大宗化学品的新兴路线。在我国贫油、少气和煤炭相对丰富的能源结构条件下,该工艺路线的研究具有重要的现实意义和战略意义。对草酸二甲酯加氢制备乙二醇铜基催化剂的失活原因进行分析,重点讨论催化剂烧结、积炭、中毒、溶剂、反应气氛和物理磨损对催化剂稳定性的影响。通过添加助催化剂以稳定催化剂中Cu价态分布,有效抑制Cu晶粒团聚长大速率。加强反应过程的基础研究,即草酸二甲酯存在的解离方式、反应气氛和溶剂的影响、高聚物的形成机制以及如何抑制高聚物等方面尚待进一步研究。注重催化剂的工程化开发,加强成型方式、扩散过程和反应体系杂质的影响研究。 相似文献
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采用水热法合成不同极化率的ZnO载体来制备Cu/ZnO催化剂,研究了ZnO极化率对Cu/ZnO催化剂的物理化学性质和催化活性的影响。通过对样品进行N2-吸附、SEM、TPR、XPS、XRD、ICP-OES和N2O滴定等表征,发现极化率对催化剂的物理结构性质和铜物种的分散状态影响不大,但强烈影响Cu/ZnO催化剂的催化活性。随着极化率降低,催化活性先上升后下降。高极化率的催化剂由于具有更多的ZnOx氧缺陷结构和更强的Cu-ZnO相互作用,利于Cu-ZnOx的形成。 相似文献
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在生物基甘油与乙酸的酯化反应中添加催化剂,从催化剂的选择、浓度、反应时间、醋酐添加量等方面进行研究。实验结果表明,当低浓度硫酸(<1.0%)作为催化剂时,显著地缩短了甘油酯化反应时间,与无催化剂工艺相比,从22 h减少至6.0 h以内,能节省大量的酯化用能耗。制得产品的GTA含量大于99.8%、酸度小于0.002 0%、色泽为10#(铂-钴)、水分为0.016%,质量指标符合YC/T 144和GB 29938等相关国家标准;采用硫酸工艺制得的产品经长期贮存,不会出现严重的“返酸”现象;通过对反应机理进行分析,证明了二乙酸甘油酯分子结构的空间位阻作用减缓了第三步的反应速率;对GTA在烟用滤嘴丝束材料的应用进行分析,证明了酸度、水分、含量之间的关系。 相似文献
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硝基苯催化加氢合成对氨基苯酚反应中,加氢Pt/C催化剂的稳定性决定生产成本。实验结果表明,催化剂循环使用10次,将失活催化剂过滤,在60%的硝酸溶液中加热回流3 h,用去离子水充分洗涤后,催化剂可恢复部分活性。第一次硝酸活化处理后,催化剂还可以使用4次左右。采用原子吸收、BET、SEM及XRD等测试方法对新鲜催化剂和经过重复实验的催化剂进行表征,结果表明,催化剂失活的主要原因为有机物覆盖在催化剂表面造成表面积下降和孔堵塞,致使催化剂丧失活性中心。在催化剂使用过程中,活性组分Pt流失及Pt 金属晶粒长大也会导致催化剂失活。 相似文献
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《Journal of Industrial and Engineering Chemistry》2014,20(3):988-993
Deactivation of co-precipitated Cu/Zn catalyst caused by exposure to either alkylthiols or dialkyl disulfides in catalytic hydrogenation of dodecyl methyl ester to dodecanol is explored in a stirred batch reactor. Catalytic activity decrement is highly dependent on levels of poisons, types of thiols/disulfides, chain length of alkanes. XRD, EDS and XPS are employed to characterize the fresh and spent Cu/Zn catalysts. It is evident that sulfuric species prefer to attack zinc oxide, forming chemically adsorbed Zn-SR at low sulfur levels, and ZnS is formed in the highly reductive atmosphere before sulfuric species attacking copper (forming Cu7S4 or Cu31S16). 相似文献
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Deepak S. Thakur Brian D. Roberts Geoffrey T. White Ross D. Rieke 《Journal of the American Oil Chemists' Society》1999,76(8):995-1000
The present work demonstrates the rate-limiting effect of varying levels of both glycerine and monoglyceride through a series of batch hydrogenations of fatty dodecyl methyl ester, using copper chromite as the catalyst. Reactions were carried out at 3000 psig H2, 280°C with catalyst levels varying between 1.25 and 1.80%. With increasing contaminant levels of glycerine (0.0, 0.1, 0.5, 5 wt%), conversion of fatty methyl ester to alcohol is correspondingly reduced (95, 89, 80, 2 wt%). On a molar basis of contaminant, monoglyceride equally reduces the conversion of methyl ester to alcohol. In both cases the latent appearance of fatty-fatty ester results from the slower hydrogenation rate. Chemistry is proposed outlining the thermal decomposition of glycerine or glyceride to intermediate components (acetol and acrolein), leading to the generation of propanediols. Experimental studies indicate that diols effectively deactivate the copper chromite catalyst, limiting the rate of fatty methyl ester hydrogenation. Catalyst deactivation is not permanent, suggesting catalyst site blockage by physical adsorption of the polyhydroxyl components. The complete understanding of this interaction holds promise for the development of glycerine/monoglyceride-insensitive catalysts. In addition, a brief overview of methyl ester hydrogenation inhibition effects of some heteroelements, water, and soap is presented. 相似文献
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Hui Huang Guiping Cao Chunling Fan Shaohong Wang Shujia Wang 《Korean Journal of Chemical Engineering》2009,26(6):1574-1579
The effect of water on Cu/Zn catalyst prepared by co-precipitation for hydrogenation of methyl laurate in a slurry phase was
studied using a stirred autoclave reactor system. The catalysts were characterized by means of XRD, BET, H2-TPR, SEM and TEM. The results indicate that catalytic activity decreases with increased amount of water in methyl laurate.
Correlating with the results from the above characterization, it is found that the main causes for the water deactivation
of the Cu/Zn catalyst were the water occlusion of active catalyst sites by the low solubility of water in the substrate and
the promotion of crystal growth, as well as the Cu/Zn catalyst agglomeration in the presence of water. 相似文献
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Kwang-Deog Jung Oh-Shim Joo Sung-Hwan Han Sung-Jin Uhm In-Jae Chung 《Catalysis Letters》1995,35(3-4):303-311
The deactivation of Cu/ZnO catalyst during methanol dehydrogenation to form methyl formate has been studied. The Cu/ZnO catalyst was seriously deactivated under the reaction conditions: various temperatures of 493, 523 and 553 K, atmospheric pressure and methanol GHSV of 3000 ml (STP)/g-cat h. The weight loss due to reduction of ZnO in the Cu/ ZnO catalyst was monitored by a microbalance. X-ray induced Auger spectroscopy of Zn(L3M4,5M4,5) showed the increase in the concentration of metallic Zn on the catalyst surface after the reaction. Temperature-programmed reduction (TPR) of the Cu/ZnO catalyst with methanol demonstrated that the reduction of ZnO in Cu/ ZnO was suppressed by introduction of CO2 into the stream of helium-methanol. As the concentration of CO2 in the feed gas increased, the weight loss of the Cu/ZnO catalyst due to the reduction of ZnO decreased. The deactivation of the Cu/ZnO catalyst in the methanol dehydrogenation was also retarded by the addition of CO2. In particular, oxygen injection into the reactant feed regenerated the Cu/ ZnO catalyst deactivated during the reaction. Based on these observations, the cause of deactivation of the Cu/ZnO catalyst has been discussed. 相似文献
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Fatty methyl ester hydrogenation to fatty alcohol part I: Correlation between catalyst properties and activity/selectivity 总被引:1,自引:3,他引:1
Ross D. Rieke Deepak S. Thakur Brian D. Roberts Geoffrey T. White 《Journal of the American Oil Chemists' Society》1997,74(4):333-339
Fatty alcohols, derived from natural sources, are commercially produced by hydrogenation of fatty acids or methyl esters in
slurry-phase or fixed-bed reactors. One slurry-phase hydrogenation of methyl ester process flows methyl esters and powdered
copper chromite catalyst into tubular reactors under high hydrogen pressure and elevated temperature. In the present investigation,
slurry-phase hydrogenations of C12 methyl ester were carried out in semi-batch reactions at nonoptimal conditions (i.e., low hydrogen pressure and elevated
temperature). These conditions were used to accentuate the host of side reactions that occur during the hydrogenation. Some
14 side reaction routes are outlined. As an extension of this study, copper chromite catalyst was produced under a number
of varying calcination temperatures. Differences in catalytic activity and selectivity were determined by closely following
side reaction products. Both activity and selectivity correlate well with the crystallinity of the copper chromite surface;
they increase with decreasing crystallinity. The ability to follow the wide variety of side reactions may well provide an
additional tool for the optimized design of hydrogenation catalysts. 相似文献
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椰油甲酯中压加氢制脂肪醇动力学研究 总被引:1,自引:0,他引:1
使用装有20mL催化剂的固定床反应器,在反应温度515K~533K、反应压力4 5MPa~9 0MPa、椰子油甲酯流量8 4mL·h-1~21 6mL·h-1及氢气标准流量100L·h-1~190L·h-1的反应条件下,采用均匀设计方法,安排了实验全过程。通过对实验取得的一系列椰子油甲酯加氢制脂肪醇转化率试验数据,根据化学反应方程式和滴流床反应器模型进行了逐步回归数理统计分析处理,确定了反应动力学参数,建立了反应动力学模型,得出由转化率表示的动力学方程。得到的结论是在实验条件下甲酯中压催化加氢制脂肪醇反应为滴流床型式,滴流床指数0 426,反应级数2级。 相似文献