SC-CO_2氛围中制备Ni/CNTs催化剂催化性能研究

碳纳米管负载金属镍催化剂可以用于甲醇常压气相羰基化反应,但是甲醇转化率及乙酸收率均不理想。本文在SC-CO2氛围中,利用SC-CO2在碳纳米管中较高的扩散性能,将金属镍粒子带入碳纳米管内腔,以提高金属镍在载体表面的分散度,从而提高催化剂的催化性能。结果显示,此法制备出的催化剂,其甲醇转化率及乙酸收率均比由普通浸渍法制备的催化剂显著提高;制备催化剂时SC-CO2最佳温度为308.15 K,最佳压强为15.0 MPa。     

Fe-Mo/MgO催化剂CVD法制备碳纳米管

研究了Fe-Mo／MgO催化剂裂解乙炔制备碳纳米管的反应条件。结果表明,反应气氛对碳纳米管的生长具有明显的影响,在Hz或Ar气氛下,所得碳纳米管的质量较差,而在N2-H2(1：1体积比)和Ar-H2(5．5：1体积比)气氛下乙炔裂解可制得纯度好、收率较高的碳纳米管。电镜观察发现在Ar-H2气氛下所制备碳纳米管的直径(平均直径为18nm)明显小于在N2-H2气氛下所制备碳纳米管(平均直径为30nm),这便于通过反应气氛的调节来控制碳纳米管的直径。用Fe-Mo／MgO做催化剂、乙炔为碳源,Ar-H2反应气氛下．850℃左右、反应30min所得碳纳米管的质量、产率最佳。     

CVD法制备碳纳米管的催化剂研究

CVD法制备单壁碳纳米管时有几个不可忽略的影响因素,其中催化剂的选取与制备极为重要,许多研究者采用不同的催化剂,获得了不同产量与质量的碳纳米管。本文主要从催化剂的选取和制备方法入手,综述了催化剂对碳纳米管制备的影响。     

碳纳米管制备工艺条件的研究

用柠檬酸络合法制备Ni—La—Mg型催化剂，催化裂解甲烷合成碳纳米管，研究了催化剂制备过程中柠檬酸浓度和活化温度对催化剂性能及碳纳米管制备的影响，同时也考察了反应时间、反应气流速和反应温度对碳纳米管制备的影响，从而得到最佳的制备碳纳米管的工艺条件。     

基于微反应器制备催化剂的老化研究

传统间歇反应混合效率低,制备的催化剂颗粒均匀性较差.基于微反应器制备了Fe-Mo/Al2O3催化剂,提高了共沉淀过程混合的均匀性,考察了老化温度及老化时间对催化剂微结构及碳纳米管形貌的影响.并借助于BET、SEM、Raman等检测方法对催化剂及碳纳米管进行表征.研究表明:在催化剂制备过程中老化时间、老化温度均会影响催化...     

煤基碳纳米管制备技术和生长机理研究进展

我国煤炭资源丰富,但现阶段以燃烧、热解和气化等为主的传统利用方式存在资源浪费、环境污染和经济效益低等问题,且我国以煤炭资源为主题的能源结构在短期内不会发生改变,因此,清洁、高效利用是新时期煤炭资源的立足点和首要任务。另一方面,碳纳米管因其独特的一维结构在力学、电学和热学等方面具有优异的特性,使其在复合材料、电子材料和能源材料等领域具有广泛的应用,但是碳纳米管制备成本偏高的问题较为突出,严重限制了其大规模的应用,现阶段急需开发新型、环境友好的碳纳米管制备技术。宏量、低成本的煤基碳纳米管制备技术可以同时较好地解决上述2个问题。笔者基于文献重点分析了反应原料、放电气氛和催化剂等因素对电弧放电法和等离子体射流法2种煤基直接制备碳纳米管技术的影响,讨论了原料种类、催化剂、反应温度、升温速率和反应气氛等因素对化学气相沉积法-煤基间接碳纳米管制备技术的影响过程。分析发现,在电弧放电法和等离子体射流法中,原料种类对碳纳米管产物的产量具有重要作用,放电气氛对碳纳米管产物的类型具有重要影响,催化剂对碳纳米管产物产量和类型均具有重要影响;在化学气相沉积法中,原料种类对碳纳米管产物形貌、长径比和有序度等性质具有重要影响,催化剂对碳纳米管产物的生长过程具有重要影响,反应温度和升温速率对碳纳米管产物的管径变化和类型具有重要影响,反应气氛可改变催化剂的催化效果。此外,总结了煤基碳纳米管直接和间接制备技术中碳纳米管的生长机理的类型及特点:其中,直接制备技术中碳纳米管生长过程符合碎片式生长机理,而间接制备技术中碳纳米管生长过程可分为气-液-固(VLS)、气-固-固(VSS)、气相成核(VPN)和阶梯式等类型。分析认为应当深入开展以下工作:探究煤、煤热解气和商业煤气等廉价原料制备碳纳米管的过程,进而建立和完善原料与碳纳米管产物之间的关系体系;开发新型、高效的煤基碳纳米管催化剂制备技术;建立新的碳纳米管生长模型,进一步丰富和完善碳纳米管生长模型体系。     

碳纳米管改性对Au/CeO2催化剂乙醇部分氧化制氢的影响

采用沉积沉淀法制备了一系列碳纳米管改性的Au/CeO₂催化剂,以乙醇部分氧化制氢为探针反应,研究了碳纳米管对Au/CeO₂催化剂乙醇部分氧化性能的影响,并运用XRD、TPR、BET等方法对催化剂进行了表征。结果表明,碳纳米管的添加提高了Au/CeO₂催化剂的比表面积、孔容和吸氧量,催化剂的氢气选择性先随碳纳米管添加量的增加而大幅增加,碳纳米管的添加量达6%～10%时,氢气选择性达到43%。进一步提高碳纳米管的含量,氢气选择性增加幅度不大。碳纳米管的添加可以有效抑制副产物CO的产生。     

自蔓延燃烧法制备纳米氧化铁及其用于碳纳米管制备的研究

利用溶胶一凝胶自蔓延燃烧法制备出了纳米氧化铁,并用其作为碳纳米管制备的催化剂。实验表明：该方法制备的氧化铁是一种优良的多壁碳纳米管催化剂,使生成的碳纳米管管壁光滑,管径分布均匀,纯度高。     

碳纳米管在催化中的应用进展

简要介绍了碳纳米管的基本结构、特点以及制备方法,概述了碳纳米管在国内用作催化剂或催化剂载体的应用进展情况。     

催化剂中镍含量对CVD法制备碳纳米管的影响

为了提高CVD法（低温催化裂解烷烃类气体法）制备碳纳米管的产率，研究了镍/硅藻土催化剂的镍含量对制备碳纳米管的影响。采用透射电子显微镜（TEM）对还原后的催化剂和产物碳纳米管进行了分析。结果表明，催化剂中镍含量在一定范围内（6.4%-25.9%)，随着镍含量增加，催化剂活性提高，碳纳米管产率提高。但随镍含量的继续增加，催化剂的活性开始下降，碳纳米管的产率也相应下降。     

SnO2-Cu2O/CNTs复合催化剂的制备及对FOX-12热分解的催化性能

以氯化铜、四氯化锡和碳纳米管为原料,采用浸渍法和液相化学沉积法相结合制得SnO2-Cu2O/CNTs复合催化剂,采用XRD、SEM、TEM、EDS等对催化剂进行表征,并用DsC研究催化剂对FOX-12热分解特性的影响.结果表明,纳米金属氧化物以5～10nm的球形颗粒形态附着在碳纳米管表面,分散较均匀.催化剂使N-脒基脲...     

Co—Mo／MgO作催化剂CVD法制备碳纳米管

研究了催化剂的制备方法对合成碳纳米管的影响,分别采用溶胶凝胶法、浸渍法和燃烧法制备了Co-Mo／MgO催化剂,并以乙炔为碳源,Ar气为保护气,在750-950℃常压下生长碳纳米管。采用TEM对所得产物进行了表征,结果表明,对于Co-Mo／MgO体系,相对浸渍法和燃烧法,溶胶凝胶法是很好的选择,可以得到数量与质量均较好的碳纳米管,并讨论了溶胶凝胶法制备碳纳米管的过程中工艺参数的择优。     

负载铁SBA-15分子筛催化热解甲醇制备碳纳米管

采用水热合成法制备了SBA-15,利用液相浸渍法合成负载铁SBA-15介孔分子筛,在常压下用所合成的含铁SBA-15介孔分子筛为催化剂通过CVD法成功制备了碳纳米管。采用X射线粉末衍射、扫描电子显微镜、拉曼光谱等方法对合成的样品进行了表征。且合成的碳纳米管质量好,表面没有无定形碳粒子被发现。     

立式浮动催化裂解法连续制备碳纳米管

改进了原有立式浮动催化裂解法制备碳纳米管的装置与工艺，省略了繁琐的催化剂制备工艺，催化剂前驱体在气体带动下直接进入反应器，实现了连续化制备碳纳米管，产量约为4g／h，纯度达80％。     

High utilization platinum deposition on single-walled carbon nanotubes as catalysts for direct methanol fuel cell

This research aims to enhance the activity of Pt catalysts, thus to lower the loading of Pt metal in fuel cell. Highly dispersed platinum supported on single-walled carbon nanotubes (SWNTs) as catalyst was prepared by ion exchange method. The homemade Pt/SWNTs underwent a repetition of ion exchange and reduction process in order to achieve an increase of the metal loading. For comparison, the similar loading of Pt catalyst supported on carbon nanotubes was prepared by borohydride reduction method. The catalysts were characterized by using energy dispersive analysis of X-ray (EDAX), transmission electron micrograph (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectrum (XPS). Compared with the Pt/SWNTs catalyst prepared by borohydride method, higher Pt utilization was achieved on the SWNTs by ion exchange method. Furthermore, in comparison to the E-TEK 20 wt.% Pt/C catalyst with the support of carbon black, the results from electrochemical measurement indicated that the Pt/SWNTs prepared by ion exchange method displayed a higher catalytic activity for methanol oxidation and higher Pt utilization, while no significant increasing in the catalytic activity of the Pt/SWNTs catalyst obtained by borohydride method.     

Pd负载磁性多壁碳纳米管催化对氯苯酚脱氯的研究

以FeCl3和碳纳米管为原料,采用水热合成法合成磁性碳纳米管,以硼氢化钠为还原剂,制备了磁性钯碳纳米管催化剂（Pd／MWCNTs—Fe3O4）,用于对氯苯酚催化脱氯,探讨了反应温度、底物浓度以及有机溶剂对催化脱氯反应的影响。结果表明,催化剂循环利用6次以后,其脱氯活性仍可以达到100％,选择性可达80％以上。     

La—Mg—Ni系贮氢合金／ZnO催化剂CVD法制备碳纳米管

贮氢合金催化生长碳纳米管是当今研究的一个热点。我们采用溶胶一凝胶法合成I五一Mg—Ni系贮氢合金／ZnO催化剂,在化学气相沉积法下催化裂解丙烯生长碳纳米管。实验结果表明,随着还原温度和长碳温度的不断降低,La—Mg—Ni系贮氢合金／ZnO催化剂催化生长的碳纳米管产量先增大再减小,呈正态分布,其中在650—600℃条件下可得到产量较高且管径较大的碳纳米管。     

Microwave-assisted synthesis and pulse electrodeposition of palladium nanocatalysts on carbon nanotube-based electrodes

The deposition of Pd nanoparticles prepared by microwave-assisted synthesis (MS) and pulse electrodeposition (PE) on networks of multiwall carbon nanotubes (CNTs) was investigated. The CNTs were grown directly on microscaled carbon paper using catalytic chemical vapor deposition. Both MS and PE methods enabled the quick formation of nanosized Pd particles over a CNT surface without any additional thermal reduction. Cyclic voltammetry and electrochemical impedance spectroscopy were used to examine the electrochemical behavior of the Pd catalysts. The Pd catalyst prepared with the MS method not only offers a higher active coverage for adsorption/desorption of hydrogen but also a more stable durability toward acid electrolytes when compared with that of the catalyst prepared with the PE method. The electrochemical surface area of the Pd catalyst was approximately 1.38 times than that of the Pt catalyst, which was also prepared with MS method. The equivalent series resistance for all the catalyst electrodes was kept between 2.07 and 2.25 Ω after potential cycling. Based on the results, the Pd catalyst is found to be a feasible alternative to the Pt catalyst because of its low cost, durability, and high catalytic activity.     

Purification of MWCNTs grown on a nanosized unsupported Fe-based powder catalyst

An unsupported Fe-based powder catalyst was prepared by coprecipitation of iron and aluminum ions followed by solid state reaction by a novel preparative route. Although metal particles were not supported on hard-to-reduce oxide, this catalyst showed nanometric dimensions.The catalyst was used for growing MWCNTs by thermal chemical vapor deposition (TCVD). Most applications require nanotube purification after growth, consisting in the separation of the nanotubes from other phases. A variety of purification processes, both chemical and physical, have been reported in the literature to remove metal catalyst, catalyst support and undesired carbonaceous phases from MWCNTs. In this work we report on an effective purification method for the removal of the catalyst, since the as-grown nanotubes did not show significant content of any other carbon phases. The purification consisted of an acid treatment for the metal catalyst dissolution. A comparison between nitric acid and a mixture of nitric and hydrochloric acid is provided. Morphological (SEM), structural (XRD) and spectroscopic (XPS, Raman) analyses were performed on catalyst and nanotubes, both before and after the purification.     

碳包铁颗粒和放射状碳纳米管微观结构的研究

以苯和甲苯为碳源，二茂铁为催化剂前驱体，含硫化合物为助催化剂，采用竖式炉流动催化法，通过减小载人的氢气量以改变催化剂颗粒的状态及反应条件，获得了碳包铁颗粒以及放射状碳纳米管，运用TEM和HRTEM对其形貌和结构进行了分析，并初步探讨了其生长机理。结果表明，在碳源、催化剂和炉温分布相同的条件下，氢气量为5400mL／min时形成直线型和弯曲型两种不同形态的碳纳米管，后者管径大于前者。氢气量为2000mL／min时，产物90％以上为碳包铁颗粒，其平均直径约为530nm，其中还有少量放射状碳纳米管，其外径为45—50nm，内径为3—5nm，管径较为均匀。