共查询到20条相似文献,搜索用时 187 毫秒
1.
2.
3.
4.
5.
6.
Pd纳米粒子负载的碳纳米纤维是催化Sonogahira偶合反应的良好催化剂,其高长径比使之易于从反应混合物中过滤分离;金属纳米粒子与碳纤维间的强相瓦作用使其具有良好的多次重复使用性.通过电纺丝技术和碳化技术制备了Pd金属纳米粒子负载的电纺碳纳米纤维,透射电镜观察显示最终碳化温度及在该温度下的停留时间是影响钯纳米粒子尺寸及其在纤维中分布的主要因素.并通过所得复合纳米纤维对Sonogahira偶合反应的催化活性研究,发现475~575℃这一温度范围是制备具有良好催化活性的金属钯纳米粒子负载的碳纳米纤维的最佳的碳化温度段. 相似文献
7.
以新型纳米多孔碳为载体,负载钯纳米颗粒,制备出了一种新型的负载型纳米催化剂。该催化剂具有较高的催化活性,能够在室温条件下实现芳基末端炔烃的合成,并且催化剂在重复回收四次之后,催化活性和结构都没有发生明显的变化。 相似文献
8.
《山东陶瓷》2023,(2):64-73
氧化铈催化剂已经在催化领域被广泛研究与应用。本文讨论了氧化铈的合成技术对形貌、尺寸与性能的影响,通过不同温度与碱浓度制备的三种不同形貌的氧化铈来探讨形貌对催化活性的影响。不同的二氧化铈纳米形貌表面氧缺陷浓度的变化被认为与晶体层选择性暴露在不同纳米结构中有关,催化活性顺序为:棒>立方体>颗粒。CeO2的形貌不仅对纯CeO2催化剂的催化性能具有巨大影响,对铈负载催化剂也具有很大影响,但氧化铈形貌对铈负载催化剂的催化行为是特定于情况的。不同的负载物与不同的氧化铈形貌复合后的催化性能主要由活性位点,表面氧空位,金属-载体相互作用、污染物降解过程等多方面共同决定。本文还介绍了氧化铈复合催化剂在臭氧催化、催化降解挥发性有机物及光催化领域的优势与进展。 相似文献
9.
实现非贵金属催化剂在加氢反应中的广泛应用对工业催化领域具有重要意义,新型碳包裹非贵金属催化剂因其优异的结构稳定性和催化加氢性能而备受关注。本文综述了近年来碳包裹非贵金属催化剂及其制备方法的研究进展,归纳总结了不同制备方法对碳包裹结构的影响以及其优缺点,并介绍了碳包裹非贵金属催化剂在硝基类芳烃、羰基类芳烃、苯酚、喹啉加氢以及费托合成等加氢反应中的催化性能以及稳定性表现。文中提出:目前该催化剂亟需解决的问题是实现金属粒子尺寸以及碳壳结构的可控调变,今后的一个研究方向是进一步探索能够简便调节催化剂结构并且经济可行的制备方法。 相似文献
10.
11.
12.
《Chemical engineering science》2003,58(3-6):687-695
A metal-organic chemical vapor deposition (MOCVD) technique was used to prepare heterogeneous metallic catalyst supported on activated carbon. A new system design was built to achieve higher metal loading within a shorter preparation time. In the optimization of system parameters, higher metal loading can be achieved by using longer deposition time, optimum carrier gas flow rate, higher operating temperature of either evaporation zone or a deposition zone or a smaller amount of porous support. Several techniques were carried out to characterize the catalyst such as physisorption, X-ray diffraction, inductively coupled plasma—optical emission spectroscopy and scanning electronic microscopy assisted with the Energy dispersive X-ray spectroscopy (SEM-EDX). It was found that the BET specific surface area and total adsorption volume of the prepared catalysts were reduced after metal deposition, due to the formation of the deposited copper onto the porous media both externally and internally. The morphology of the cylindrical Cu/AC was analyzed by SEM-EDX. The results show that the metal was deposited with a reasonably uniform distribution onto the inner part of the porous support. 相似文献
13.
《Carbon》2013
The reduction of the platinum amount for efficient PEM (polymer electrolyte membrane) fuel cells was achieved by the use of graphene/carbon composites as catalyst support. The influences of the carbon support type and also of the catalyst preparation method on the fuel cell performance were investigated with electrochemical, spectroscopic and microscopic techniques. Using pure graphene supports the final catalyst layer consists of a dense and well orientated roof tile structure which causes strong mass transport limitations for fuels and products. Thus the catalysts efficiency and finally the fuel cell performance were reduced. The addition of different carbon additives like carbon black particles or multi-walled carbon nanotubes (MWCNT) destroys this structure and forms a porous layer which is very efficient for the mass transport. The network structure of the catalyst layer and therefore the performance depends on the amount and on the morphology of the carbon additives. Due to optimizing these parameters the platinum amount could be reduced by 37% compared to a commercial standard system. 相似文献
14.
甲醇氧化电催化剂是决定直接甲醇燃料电池(direct methanol fuel cells, DMFCs)性能、寿命与成本的关键。为获得高功率密度和低生产成本的DMFCs,设计合成具有组成、结构、形貌可控的阳极催化剂备受关注。阳极催化剂的颗粒尺寸、粒径分布、形貌结构、稳定性、分散性以及催化活性都和负载它的载体息息相关,而碳基载体材料由于其优异的性能被广泛应用于DMFCs领域。本文分别介绍了酸性环境和碱性环境中甲醇氧化反应的机理,然后对不同形式的碳基载体材料,例如炭黑、介孔碳、碳纳米材料、氧功能化碳、杂原子掺杂碳、以及金属氧化物改性碳作为催化剂载体在DMFCs领域中的应用进行了综述,最后对DMFCs的发展趋势进行了展望。 相似文献
15.
《Carbon》2013
Reactant shape selective catalysis occurs when substrates of different sizes and shapes are consumed at different rates over catalysts that combine molecular sieving transport processes with reaction. By contrast the same substrates react at nearly equivalent rates over catalysts that have large, open pores that do not induce any form of molecular sieving. Here we describe the design and synthesis of reactant shape selective catalysts for liquid phase hydrogenation reactions. Using an emulsion polymerization of furfuryl alcohol, we have made catalysts that consist of microporous carbon nanospheres within which are embedded platinum nanoparticles. The porosity of the carbon spheres was found to be a key parameter affecting catalyst activity and selectivity; porosity was varied by adding pore forming agents, such as polyethylene glycol with different molecular weights, during synthesis, or by mild oxidation of the as-synthesized catalyst using carbon dioxide. In addition to increasing porosity to reduce mass transfer limitations, a synthesis of smaller carbon spheres (<200 nm) was devised to reduce the micropore diffusion length. Decreasing the particle size of the catalyst by adjusting the surfactant composition during polymerization, improved the effectiveness factor by approximately one order of magnitude making it as active as a comparable standard metal catalyst. 相似文献
16.
Performance of CoMoS catalysts supported on nanoporous carbon in the hydrodesulfurization of dibenzothiophene and 4,6-dimethyldibenzothiophene 总被引:3,自引:0,他引:3
Jung Joon Lee Sangjin Han Heeyeon Kim Jae Hyun Koh Taeghwan Hyeon Sang Heup Moon 《Catalysis Today》2003,86(1-4):141-149
A new type of nanoporous carbon with a large surface area and mesoporosity was prepared and used as a support for a hydrodesulfurization (HDS) catalyst. The overall activity of CoMoS catalysts for the HDS of dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT) is affected by the type of support used for preparing the catalyst and decreases in the order of CoMo/(nanoporous carbon)>CoMo/(activated carbon)>CoMo/Al2O3. The surface area of activated carbon is the largest among these three types of supports but is significantly lowered after metal loading during the preparation of the catalyst. On the other hand, the surface areas of the other two supports are largely preserved after metal loading. The intrinsic activity of the catalysts, estimated by dividing the overall HDS rate by the amount of NO adsorbed on the catalyst, shows a trend that is different from that for the overall activity, and follows the order of CoMo/(nanoporous carbon)≈CoMo/Al2O3>CoMo/(activated carbon). The low intrinsic activity of CoMo/(activated carbon) compared to that of the other two catalysts, particularly in the case of 4,6-DMDBT HDS, is obtained because the diffusion of reactants into the catalyst pores is significantly limited. This is not observed with other catalysts supported on nanoporous carbon and alumina. From the results of this study, we conclude that nanoporous carbon is a promising support for HDS catalysts, compared to conventional supports such as alumina and activated carbon, because it has a large surface area and a high mesoporosity, both of which are beneficial to the preparation of highly dispersed metal catalysts without significant pore blocking due to the dispersed metal particles. 相似文献
17.
芳环加氢反应是最重要的合成反应之一,钌炭催化剂在芳环加氢反应中具有优异的催化性能。综述钌炭催化剂的制备方法和载体性质对钌炭催化剂的影响以及钌炭催化剂在苯、苯甲酸和对苯二甲酸二甲酯等芳环加氢反应中的应用进展。负载型钌炭催化剂的制备方法主要有浸渍法、沉淀法和升华法,超声辅助浸渍法可将大部分钌纳米粒子引入到炭载体的孔道内部,得到限域型负载钌炭催化剂。而镶嵌式钌炭催化剂主要是指通过原位炭化的方法将钌粒子部分镶嵌在炭的孔壁上,一步得到钌炭催化剂,其制备方法主要有软模板剂法和硬模板剂法。除制备方法外,炭的骨架结构、表面性质及氮掺杂对钌炭催化剂的性能影响也较大。镶嵌式钌炭催化剂具有钌纳米粒子和炭载体之间的相互作用强、催化剂抗流失及烧结性能好,在芳环加氢反应中表现出卓越的催化性能和稳定性。随着新制备技术的出现,新型镶嵌式钌炭催化剂将可能实现产业化。 相似文献
18.
从过渡金属硫化物催化剂活性相理论出发,认为在加氢催化剂制备过程中保证活性组分的适度分散和金属-载体之间适度的相互作用能提高加氢催化剂的性能。本文针对加氢处理催化剂的制备技术,综述了添加有机助剂、平衡吸附法、浆液浸渍法等浸渍改进技术以及水热沉积法、原位晶化法、化学气相沉积法等新型的制备技术,并介绍了相关的国内外研究进展。分析指出有机助剂能与载体、金属作用,进而改变金属在载体表面的存在形态,有利于高活性CoMoS相的生成;水热沉积法和原位晶化法能够使活性组分在载体上均匀吸附沉积,从而实现活性组分在载体上的分散,并形成堆积程度更高的高活性Ⅱ型活性中心。 相似文献
19.
20.
负载固相的催化剂因其简便的分离循环操作以及可观的催化性能而广受关注,但存在反应活性较差、金属流失量较大、催化剂制备成本较高等问题。本文首先从不同负载材料的角度综述了近年来该类催化剂最新的研究进展,主要探讨了载体的表面性质、催化剂的制备方法、膦配体等对催化性能的影响;最后介绍了新型的单原子催化剂所取得的突破性进展。分析表明:具有"类均相"特点的多孔有机聚合物的催化活性很好,而超支化聚合物功能化的磁性纳米催化剂的稳定性更佳。另外还对负载型铑催化剂未来的研究方向进行了展望:需要进一步加深对多孔有机聚合物的化学结构的理解,以便对其更好地表征;借助一些先进的表征技术如高角环状暗场扫描透射电镜和密度泛函理论的计算来深入研究载体结构对单原子催化剂的催化性能的影响。 相似文献