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Effects of Supports and Promoter Ag on Pd Catalysts for Selective Hydrogenation of Acetylene 总被引:1,自引:0,他引:1
SiO2, a-Al2O3, g-Al2O3, ZrO2 and CeO2 were used as supports and Ag as promoter to study their effects on Pd catalysts for selective hydrogenation of acetylene. The catalysts were prepared by impregnated synthesis and characterized by XRD, BET and TEM. The catalytic reaction was carried out in a fixed-bed reactor. Overall, the low specific surface area supports were better to increase the ethylene selectivity at high conversion rate of acetylene. Among the four Pd catalysts on low specific surface area supports, the catalyst on low specific surface area SiO2 (LSA-SiO2) retained a high ethylene selectivity even at complete conversion, while the other catalysts showed significant decrease in the selectivity at complete conversion. The performance of Pd/LSA-SiO2 was important to decrease the loss of ethylene in selective hydrogenation of trace acetylene in ethylene. Addition of Ag to Pd/LSA-SiO2 significantly decreased the formation of ethane, C4 alkenes and green oil, and improved the ethylene selectivity to 90% when Pd:Ag=1:1 and 1:3(w). When the ratio of Pd to Ag was above 1, the activity of Pd-Ag bimetallic catalyst was similar to that of Pd monometallic catalyst, and the selectivity of ethylene increased with increasing of amount of Ag. When the ratio of Pd to Ag was below 1, the activity of bimetallic catalyst decreased with increasing of amount of Ag, while the selectivity of ethylene was kept unchanged. The optimum temperature was 200~230℃ for 0.02%(w)Pd-0.02%(w)Ag/LSA-SiO2 to give a high ethylene selectivity and low formation of green oil. 相似文献
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Woo Jae Kim Chang Hun Choi Sang Heup Moon 《Korean Journal of Chemical Engineering》2002,19(4):617-621
Variation in the selectivity of ethylene produced by acetylene hydrogenation in an integral reactor was analyzed as a function
of the hydrogen/acetylene ratio in the reaction stream at the reactor inlet. The analyses were made for two sample catalysts,
which showed different dependence of the ethylene selectivity on the reactant composition. Even a small mismatch between the
hydrogen/acetylene ratio at the reactor inlet and the ratio for converted reactants caused a large change in the ethylene
selectivity along the reactor position, particularly when the conversion was high. The results of this study indicate two
important factors to be considered in the design and operation of acetylene hydrogenation process: the hydrogen/acetylene
ratio in the reactor inlet should be controlled close to the ratio for converted reactants; and catalysts showing high ethylene
selectivity over a wide range of the hydrogen/ acetylene ratio are required for the design of a highly selective hydrogenation
process.
This paper is dedicated to Professor Wha Young Lee on the occasion 相似文献
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Ji Hoon Lee Seok Ki Kim In Young Ahn Woo-Jae Kim Sang Heup Moon 《Korean Journal of Chemical Engineering》2012,29(2):169-172
Effects of Ni addition on the performance of Pd-Ag/Al2O3 catalysts in the selective hydrogenation of acetylene were investigated. Ni-added Pd-Ag catalysts showed higher conversions
than Ni-free Pd-Ag catalyst under hydrogen-deficient reaction conditions, hydrogen/acetylene <2.0, due to the spillover of
hydrogen from reduced Ni to Pd and the suppression of hydrogen penetration into the Pd bulk phase, which enriched the Pd surface
with hydrogen. Ethylene selectivity was also increased by Ni addition because the amounts of surface hydrogen originating
from the Pd bulk phase, which was responsible for the full hydrogenation of ethylene to ethane, were decreased due to the
presence of Ni at the sub-surface of Pd-Ag particles. Added Ni also modified the geometric nature of the Pd surface by blocking
large ensembles of Pd into isolated ones, which eventually improved ethylene selectivity. 相似文献
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Transition-metal oxides added to Pd/SiO2 improve significantly the activity and the ethylene selectivity of the catalyst in acetylene hydrogenation, which is caused by the interaction between the oxides and the Pd surface similar to the case of the oxide-supported catalysts. It has been confirmed through experiments that metal oxides spread on and modify both geometrically and electronically the Pd surface after the catalyst is reduced at 500°C. Such a behavior of metal oxides in the catalyst is correlated well with their promotional effect on the catalyst performance. That is, the oxides on the Pd surface retard the sintering of the dispersed Pd particles, suppress the adsorption of ethylene in the multiply-bound mode, and facilitate the desorption of ethylene produced by acetylene hydrogenation. Among the three metal oxides examined in this study, Ti oxide is found to have the most promotional effect. 相似文献
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Zhi-Jian Zhao Jiubing Zhao Xin Chang Shenjun Zha Liang Zeng Jinlong Gong 《American Institute of Chemical Engineers》2019,65(3):1059-1066
Selective hydrogenation of acetylene is an important reaction for production of polymer grade ethylene. The green oil formation has great influence on the selectivity and activity of acetylene selective hydrogenation. This article describes a density functional theory study on the C + H hydrogenation reaction and C + C coupling reaction on the (111) surface of Ag, Cu, Pd, Pt, Rh, and Ir. The activity of acetylene selective hydrogenation is examined by the effective barrier for ethylene formation. A comparison between the reaction barrier of ethylene hydrogenation and desorption is used to identify the selectivity for ethylene formation. The barriers of three pathways for 1,3-butadiene formation suggest that acetylene and vinyl coupling reaction is the favorable pathway. The stability of catalysts is evaluated by the selectivity of 1,3-butadiene, which follows the order of Pt(111) > Ir(111) > Rh(111) > Pd(111) > Cu(111) > Ag(111). Furthermore, the relationship between acetylene adsorption energy and effective barrier of ethylene formation and 1,3-butadiene formation has been established to well understand the catalytic properties of different metals. © 2018 American Institute of Chemical Engineers AIChE J, 65: 1059–1066, 2019 相似文献
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Kunyaluck Kontapakdee Joongjai Panpranot Piyasan Praserthdam 《Catalysis communications》2007,8(12):2166-2170
Anatase and rutile TiO2 were used for preparation of the TiO2 supported Pd and Pd–Ag catalysts for selective hydrogenation of acetylene. It was found that Pd/TiO2-anatase exhibited higher acetylene conversion and ethylene selectivity than rutile TiO2 supported ones. However, addition of Ag to Pd/TiO2-anatase catalyst resulted in lower ethylene selectivity while that of Pd/TiO2-rutile increased. It is suggested that Ag addition suppressed the beneficial effect of the Ti3+ sites presented on the anatase TiO2 during selective acetylene hydrogenation whereas without Ti3+, Ag promoted ethylene selectivity by blocking sites for over-hydrogenation of ethylene to ethane. 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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M. V. Nazarov A. I. Laskin I. R. Ilyasov A. A. Lamberov A. Sh. Bikmurzin V. M. Shatilov 《Catalysis in Industry》2013,5(2):143-147
Pilot tests of SGA-2M promoted Pd/Al2O3 catalyst in the selective hydrogenation of acetylene are performed on an industrial ethane-ethylene fraction in a system of two serially arranged adiabatic flow reactors. The optimum process conditions under which the conversion of acetylene reaches 100% at a selectivity of 68.2% with respect to ethylene are determined: system pressure, 21 atm; hydrocarbon feedstock hourly space velocity (HSV), 1500 h?1, carbon monoxide concentration, 7 ppm; H2: C2H2 molar ratio at the first and second hydrogenation stages, 1.0: 1.0 and 1.4: 1.0; inlet temperature of the first and second reactors, 40 and 55°C, respectively. The interregeneration service life of the SGA-2M catalyst under optimum conditions is estimated at 12 months. SGA-2M catalysts can be recommended for purifying ethane-ethylene fractions containing up to 2 vol % of acetylene. 相似文献
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Pd催化乙炔选择性加氢是石脑油蒸汽裂解和煤基电石乙炔路径制备聚合级乙烯的关键。传统的Pd基催化剂使用成本较高且选择性和稳定性较差。本文综述了近年来乙炔选择性加氢催化剂结构敏感性及其调控方面的相关研究进展,重点介绍了包括活性金属粒径、纳米颗粒形貌和电子结构等对乙炔选择性加氢反应性能的重要作用,进而阐明了催化剂结构调控的目标与方向。进一步归纳总结了针对该反应特性的催化剂结构定向调控的研究进展,主要包括合金和金属间化合物催化剂、单原子及其合金催化剂的设计。通过合理地调控催化剂结构,优化关键物种的吸脱附和反应动力学行为,能够显著提高乙炔加氢催化剂的选择性及稳定性。在未来的研究中,如何针对该反应特性,构筑高效、稳定和低成本的催化剂将会是该体系催化剂研究的重点与难点。 相似文献
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《Journal of Industrial and Engineering Chemistry》2014,20(6):4183-4187
In this paper, we describe a novel method for selectively attaching TiO2 promoters on Pd surfaces in Pd/SiO2 catalysts using selective chemical vapor deposition (CVD). Ti was selectively deposited on Pd active sites over a SiO2 support under a hydrogen atmosphere when titanium tetraisopropoxide was used as a Ti precursor. The Pd–Ti/SiO2 catalyst modified by CVD exhibits approximately 1.8 times higher ethylene selectivity than the un-modified Pd/SiO2 catalyst in the selective hydrogenation of acetylene due to the effective geometric modification of the Pd surface, which is beneficial to ethylene selectivity, by the selectively deposited Ti species. 相似文献
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T.V. Choudhary C. Sivadinarayana A.K. Datye D. Kumar D.W. Goodman 《Catalysis Letters》2003,86(1-3):1-8
Hydrogenation of acetylene has been investigated on Au/TiO2, Pd/TiO2 and Au-Pd/TiO2 catalysts at high acetylene conversion levels. The Au/TiO2 catalyst (avg. particle size: 4.6 nm) synthesized by the temperature-programmed reduction-oxidation of an Au-phosphine complex on TiO2 showed a remarkably high selectivity to ethylene formation even at 100% acetylene conversion. Au/TiO2 prepared by the conventional incipient wet impregnation method (avg. particle size: 30 nm), on the other hand, showed negligible activity for acetylene hydrogenation. Although the Au catalysts showed a high selectivity for ethylene, the acetylene conversion activity and catalyst stability were inferior to the Pd-based catalysts. Au-Pd catalysts prepared by the redox method showed high acetylene conversions as well as high selectivity for ethylene. Interestingly Au-Pd catalysts prepared by depositing Pd via the incipient wetness method on Au/TiO2 showed very poor selectivity (comparable to mono-metallic Pd catalysts) for ethylene. High-resolution transmission electron microscopy (TEM) studies coupled with energy dispersive X-ray spectroscopy (EDS) showed that while the redox method produced bimetallic Au-Pd catalysts, the latter method produced individual Pd and Au particles on the support. 相似文献
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Xinxiang Cao Arash Mirjalili James Wheeler Wentao Xie Ben W.-L. Jang 《Frontiers of Chemical Science and Engineering》2015,9(4):442-449
Galvanic replacement, co-impregnation and sequential impregnation have been employed to prepare Pd-Cu bimetallic catalysts with less than 1 wt-% Cu and ca. 0.03 wt-% Pd for selective hydrogenation of acetylene in excess ethylene. High angle annular dark field-scanning transmission electron microscopy (HAADF-STEM) and H2 chemisorption results confirmed that Pd-Cu single-atom alloy structures were constructed in all three bimetallic catalysts. Catalytic tests indicated that when the conversion of acetylene was above 99%, the selectivity of ethylene of these three single atom alloy catalysts was still more than 73%. Furthermore, the single atom alloy catalyst prepared by sequential incipient wetness impregnation was found to have the best stability among the three procedures used. 相似文献
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Size-controlled Pd nanoparticles (PdNPs) were synthesized in aqueous solution, using sodium car-boxymethyl cellulose as the stabilizer. Size-controlled PdNPs were supported onα-Al2O3 by the incipient wetness impregnation method. The PdNPs onα-Al2O3 support were in a narrow particle size distribution in the range of 1-6 nm. A series of PdNPs/α-Al2O3 catalysts were used for the selective hydrogenation of acetylene in ethylene-rich stream. The results show that PdNPs/α-Al2O3 catalyst with 0.03%(by mass) Pd loading is a very effective and sta-ble catalyst. With promoter Ag added, ethylene selectivity is increased from 41.0%to 63.8%at 100 &#176;C. Comparing with conventional Pd-Ag/α-Al2O3 catalyst, PdNPs-Ag/α-Al2O3 catalyst has better catalytic performance in acety-lene hydrogenation and shows good prospects for industrial application. 相似文献
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Alvin H. Weiss Jeng-Shiang Tsaih Genadi V. Antoshin Masayoshi Kobayashi Akio Nakagawa Nguyen Duc Tien Truong Tanh Tanh 《Catalysis Today》1992,13(4):697-698
Ethylene, produced by steam cracking of hydrocarbons, contains acetylene, which is hydrogenated to purify the ethylene for polymerization. The process is low temperature, < 80°C, and catalysts are typically peripherally deposited 0.03% Pd/Al2O3. Industrial experience, as well as experimentation at WPI, is that ethane yields are 100 to 150% of the acetylene in the feed at about 70% conversion. The reason for the problem is that catalyst pellet temperatures are far higher than gas stream temperatures, in order to transfer heat generated by reaction through the boundary layer to the gas stream. 相似文献
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乙烯是石化工业中最重要的工业原料之一,然而乙烯产品中少量乙炔杂质的存在会直接影响乙烯的下一步应用。乙炔选择性催化加氢被认为是脱除乙炔杂质最有效的方法之一。本文综述了乙炔选择性加氢催化剂近年来的研究进展,介绍了乙炔选择加氢的反应机理,归纳总结了活性组分、助剂、载体以及结构对乙炔加氢催化剂性能的影响。鉴于Pd基催化剂仍然是工业应用的主流催化剂,文中综述了Pd基催化剂的研究现状和目前存在的一些挑战,同时提出了催化性能优化的建议。最后,就如何进一步提高乙炔选择性加氢催化剂性能的发展趋势进行了归纳,主要从单原子合金催化剂、催化剂微观调控以及电化学炔烃加氢方面进行论述,为未来提高乙炔加氢催化剂的性能提供了指导方向。 相似文献
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以一氧化碳和乙炔为探针分子,采用原位红外光谱技术研究了Pd-Ag/ Al2O3和Pd/ Al2O3催化剂上乙炔加氢反应以及催化剂本身的表面形态,动态考察了乙炔加氢的气相反应行为、CO吸附以及催化剂表面吸附物种的变化。结果表明,在Pd-Ag/ Al2O3催化体系中,由于Ag的加入而受到几何效应和电子效应的共同影响,引起了催化剂表面形态的改变从而改变了催化剂的性能。另外,乙炔加氢反应会导致钯催化剂表面形成由长分子链的饱和烃组成的碳氢化合物层,该碳氢化合物层有可能是加氢反应形成的绿油。 相似文献
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乙炔加氢是乙烯工业中的重要精制反应。以α-Al2O3作为载体,采用分步等量浸渍法制备了不同Pd/Ag配比的加氢催化剂,使用N2物理吸附、XRD、ICP、XPS、TEM和CO化学吸附等手段表征催化剂的结构和组成,根据正交实验设计方案进行动力学实验,建立了微观反应动力学模型,并根据动力学模拟结果和动力学参数值的变化分析了Ag助剂含量对乙炔加氢反应动力学的影响。研究结果表明,以Pd-Ag催化剂上碳二加氢的DFT计算结果为基础参数来源,经过吸脱附步骤活化能的优化,微观反应动力学模型可以很好地模拟不同Pd/Ag配比催化剂上的乙炔加氢反应动力学结果;在所研究范围内,各催化剂上加氢反应的表面最丰物种皆为C2H4*,速率控制步骤为乙烯基加氢,不会随着Ag含量的不同发生变化;但是Ag含量的增加显著降低了氢气脱附活化能,提高了乙烯的选择性,这可能与Ag含量的提高增加了催化剂表面Ag和Pd之间的电子转移现象有关。 相似文献