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《化学工业与工程技术》2018,(1):40-45
通过改变铜锌系合成气制异丁醇催化剂的载体及添加不同助剂,以提高原料的利用率和目的产物异丁醇的选择性。以Cu,Zn,Zr等金属离子的硝酸盐为原料,采用并流共沉淀的方式制得铜锌系催化剂。在催化剂主要活性组分铜和锌摩尔比为1∶1的基础上,在反应压力5 MPa、反应温度350℃、空速8 000 h~(-1)、混合气组成中n(H_2)∶n(CO)=2、催化剂装填量2.0 mL、反应时间10 h的条件下,考察了不同载体和助剂对异丁醇选择性的影响。结果表明:以Zr作为载体时,异丁醇的选择性最高,液相产物的时空收率也较高,异丁醇的时空收率最大;从提高异丁醇的选择性来考虑,Cu,Zn,Zr摩尔比为3∶3∶2的催化剂较合适;助剂Mn和Pd的加入有利于提高液相产物收率及异丁醇选择性。 相似文献
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为了避免柠檬酸溶胶-凝胶法制备过程中环境问题, 采用共沉淀法制备了Cu-Mn-Ce复合氧化物催化剂, 以催化燃烧甲苯为模型反应, 考察了沉淀剂对Cu-Mn-Ce催化结构和性能的影响。结果表明, 以NaOH作为沉淀剂催化剂效果最佳, 其次为NH3·H2O、K2CO3、Na2C2O4。采用NaOH作为沉淀剂, 氢氧化物前体在焙烧活化过程中更易使Cu、Mn离子进入CeO2的立方结构, 形成具有缺陷结构的CeO2固溶体, 从而提高了表面氧浓度和活动性, 在燃烧反应中表现出更优异的催化特性。 相似文献
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采用Shimadzu DT-40型热分析仪,研究了不同原始铁氧化物组成对氨合成熔铁催化剂的还原性能的影响。发现催化剂的还原性能和活性与母体相组成的关系具有相似的规律性。当母体中两种物相共存时,催化剂的还原过程是按物相分阶段依次进行的,其结果使还原速度变慢,还原温度升高,亦使还原后催化剂的活性降低。氨合成催化剂的还原性能与其活性具有一致性,愈易还原的催化剂,其活性亦愈高。研究结果表明,在熔铁催化剂中,Fe_(1-x)O基氨合成催化剂还原速度最快、还原温度最低,其活性亦最高。 相似文献
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分别以机械混合法与溶胶凝胶法所得的钛硅氧化物TiO_2SiO_2与TiO_2-SiO_2为载体制备了NiMo基催化剂,以含20%小桐子油的正辛烷溶液为原料,在连续流动固定床反应器中考察了催化剂的加氢脱氧性能,并采用X射线衍射(XRD)、氮气物理吸附(BET)、扫描电镜(SEM)和NH3程序升温脱附(NH_3-TPD)等技术对催化剂和TiSi复合氧化物载体进行了表征。结果表明,与TiO_2-SiO_2相比,机械混合法制得的TiO_2SiO_2具有双介孔结构特征、较规则的表面形貌和较多的L酸性中心;溶胶凝胶法制得的TiO_2-SiO_2的表面形貌规则性则较差,负载Ni、Mo的孔道堵塞导致所得催化剂的比表面积和孔容急剧减小,在高温反应条件下TiO_2-SiO_2中的Ti—OH—Si键结构形成的B酸中心对催化剂HDO性能的促进作用较小。催化剂性能的评价结果表明NiMo/TiO_2SiO_2催化剂的加氢脱氧活性优于NiMo/TiO_2-SiO_2催化剂的加氢脱氧性能。 相似文献
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负载型金属催化剂的催化性能主要取决于金属活性中心的设计.本工作采用密度泛函理论计算研究了氮掺杂石墨烯(NC)负载不同金属活性中心,即同核双原子(CuCu@NC,RhRh@NC和CoCo@NC)和异核双原子催化剂(CuRh@NC,RhCo@NC和CuCo@NC)上合成气合成C2氧化物反应.结果 表明:6类双原子催化剂均具... 相似文献
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通过CO脉冲化学吸附以及对吸附态CO和co+H_2反应进行程序升温表面反应(TPSR),发现1%Ru/siO_2和1%Ru/AL_2O_3催化剂的CO吸附量随焙烧温度的升高而降低。且根据513K和室温吸附co的TPSR不同,认为存在两类不同活性中心。Ⅰ类中心:金属钌与载体的相互作用弱,易吸附CO;Ⅱ类中心:金属与载体的相互作用强,较难吸附CO。随焙烧温度升高,金属与载体作用增强,Ⅱ类中心增多。在微型流动反应器上CO中压加氢发现经673K焙烧的样品的活性及长链烃的生成量和烯/烷比均大于120℃烘干的样品,因此认为,Ⅰ类中心为加氢中心,Ⅱ类中心为链增长中心。 相似文献
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This paper is a survey of the main facts and concepts concerning the effect of additives on the structure and physicochemical and catalytic properties of oxide catalysts in selective oxidation reactions. The phenomena occurring in monophasic and supported mixed oxides containing the additives, including modification of structure, solid state reactions, segregation, defect formation, and spill-over of the reactants, are briefly described. The effect of additives on acid--base and redox properties, and on their bearing on catalytic performance are discussed, with particular emphasis on alkali metal additives. The perspectives of further studies on the problem are proposed. 相似文献
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CO Hydrogenation to Light Alkenes Over Mn/Fe Catalysts
Prepared by Coprecipitation and Sol-gel Methods 总被引:3,自引:0,他引:3
CO hydrogenation to light alkenes was carried out on manganese promoted iron catalysts prepared by coprecipitation and sol-gel
techniques. Addition of manganese in the range of 1–4 mol.% by means of coprecipitation could improve notably the percentage
of C2=~C4= in the products, but it was not so efficient when the sol-gel method was employed. XRD and H2-TPR measurements showed that the catalyst samples giving high C2=~C4= yields possessed ultrafine particles in the form of pure α-(Fe1-xMnx)2O3, and high quality in lowering the reduction temperature of the iron oxide. Furthermore, these samples displayed deep extent
of carburization and different surface procedures to the others in the tests of Temperature Programmed Surface Carburization
(TPSC). The different surface procedures of these samples were considered to have close relationship with the evolving of
surface oxygen. It was also suggested that for the catalysts with high C2=~C4= yields, the turnover rate of the active site could be kept at a relatively high level due to the improved reducing and carburizing
capabilities. Consequently, there would be a large number of sites for CO adsorption/dissociation and an enhanced carburization
environment on the catalyst surface, so that the process of hydrogenation could be suppressed relatively to a low level. As
a result, the percentage of the light alkenes in the products could be raised. 相似文献
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Synthesis and catalytic properties of eggshell cobalt catalysts for the Fischer-Tropsch synthesis 总被引:3,自引:0,他引:3
Enrique Iglesia Stuart L. Soled Joseph E. Baumgartner Sebastian C. Reyes 《Topics in Catalysis》1995,2(1-4):17-27
CO diffusional restrictions decrease C5+ synthesis rates and selectivity within large (1–3 mm) catalyst pellets often required in Fischer-Tropsch (FT) synthesis reactors. Eggshell catalysts, where Co is located preferentially near outer pellet surfaces, reduce the severity of these transport restrictions and lead to higher synthesis rates and C5+ selectivity. Maximum C5+ selectivities occur on catalysts with intermediate shell thickness, within which transport restrictions limit the removal of reactive olefins but not the arrival of reactants at catalytic sites. A new synthetic technique leads to sharp distributions of active sites near outer pellet surfaces by controlling the rate of imbibition of cobalt nitrate melts. Also, slow reduction of the impregnated salt leads to moderate Co dispersions (0.05–0.10) even at high local Co loadings present within shell regions. 相似文献
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费托合成催化剂的研究进展 总被引:1,自引:0,他引:1
介绍了费托合成的研究现状,分析了费托合成催化剂的组成,重点评述了恬性组分、载体、助剂等因素在催化剂制备过程中对催化剂的活性、选择性等方面的影响,并对费托合成催化剂研究领域存在的问题进行了探讨。 相似文献
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Sharif Zaman 《Catalysis Reviews》2013,55(1):41-132
Recent literature on synthesis gas conversion to higher alcohols over Mo-based catalysts is reviewed. Density functional theory calculations show that Mo-CO adsorption is weakened by C, P, or S ligands and this facilitates CO dissociation, either directly on Mo2C, or by H-assisted dissociation on MoS2, Mo2C, and MoP. Consequently, Mo-based catalysts have high hydrocarbon selectivity unless they are promoted with alkali metals and/or Group VIII metals. Promoted MoS2 and MoP have alcohol selectivities of ~80 C atom % (CO2-free basis) at typical operating conditions (5–8 MPa, H2/CO = 2–1, 537–603 K), whereas on promoted Mo2C, alcohol selectivities are ~60%. The kinetics of the synthesis gas conversion reactions over Mo-based catalysts have mostly been described by empirical power law models and the alcohol and hydrocarbon product distributions are consistent with a CO insertion mechanism for chain growth. 相似文献
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Gold deposited on various oxides with high dispersion was found to be active for the hydrogenation of CO2 at temperatures between 150 and 400°C. Product selectivities greatly depended on the nature of support oxide. Acidic oxides like TiO2 gave higher CO2 conversions but low methanol yields. Zinc oxide component was indispensable for selective methanol synthesis. Significantly, large particle size effect of gold was observed and smaller gold particles gave higher methanol productivity per exposed surface area of gold. This can be explained by an increase in the perimeter area of gold particles with a decrease in particle size. Methanol yield was greatly enhanced in a Au/ZnO---TiO2 catalyst probably due to an increase in gold-zinc oxide interface. 相似文献
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《国际聚合物材料杂志》2012,61(1-2):29-39
Abstract Transterification of Ethylene Glycol and DiMethyl Terephthalate, through the use of different acetates as catalysts, for producing Bis(2-HydroxyEthyl)Terephthalate under isothermal conditions, was studied from the point of view of the kinetics involved. Best results were obtained by employing zinc acetate and a second order reaction was determined from the experimental data. 相似文献
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考察了碱金属(Li、Na、K、Cs)对CO加氢制备低碳醇Cu-Fe-Co基催化剂反应性能的影响.研究发现:碱金属的添加能明显降低甲烷化反应,提高催化剂活性,使醇分布向碳链增长方向转移;碱金属Na的添加对催化剂活性的提高影响最大,与未添加碱金属的催化剂相比,液体产物中总醇质量分数提高45.98%,其中C2+醇和C5+醇在总醇中的摩尔分数分别提高了21.88%和22.89%,尾气中CH4摩尔分数下降42.83%.XRD结果表明,碱金属的加入使Cu、Fe、Co三种组分在载体上分散性加强,增加了CO与活性组分的接触位点从而使碳链增长;FE-SEM结果表明,碱金属Na的添加提高了催化剂孔隙结构和活性组分的均匀性和稳定性,同时减轻了催化剂积炭现象,提高了醇收率. 相似文献