催化剂活性组分的负载方法对CVD法制备碳纳米管的影响

催化剂是影响CVD法制备碳纳米管的主要因素。本文报道了用配合浸渍法制备的催化剂在碳纳米管制备中的应用。XRD和TEM研究表明：与普通浸渍法制备的催化剂（B－Co/SiO2)相比,用配合浸渍法制备的催化剂（A－Co/SiO2)颗粒小,金属分散度高,生成碳纳米管的温度低。对于配合浸渍法制备的催化剂（A－Co/SiO2),低温（650－750℃）有利于生成直径小且管径均匀的碳纳米管;高温（800－900℃）容易生成直径大且层数多的碳纳米管或碳纳米棒。     

Oxidation of Carbon Monoxide over Cu/CeO_2 Catalysts Prepared by SMAI

Introduction Carbon monoxide is ubiquitous air pollutants emitted by many sources. Total oxidation of carbon monoxide to carbon dioxide is employed to meet environmental regulations in an economic way. Precious metals (Pt, Pd) are well-known oxidation catalysts with high activity and stability, and are widely used for exhaust gas emission control. However, the high cost of precious metals and their sensitivity to sulfur poisoning have long motivated the search for substitute catalysts. …     

溶剂化金属原子浸渍法制备高分散Au/TiO2低温CO氧化催化剂

用溶剂化金属原子浸渍法制备了不同金含量的高分散Ａｕ／ＴｉＯ２催化剂,ＸＲＤ和ＴＥＭ测定结果表明,随着金含量的增加,金颗粒度增大,但直径都在１．８～３．５ｎｍ范围内,ＸＰＳ研究表明上于金属态,Ａｕ／ＴｉＯ２在低温下就显示出较高的ＣＯ知性,３２３Ｋ时ＣＯ的转化率可达到１００％,金颗粒度为１．８ｎｍ的Ａｕ／ＴｉＯ２催化剂活性最高。     

改性纳米HZSM-5沸石催化剂上C5～C8混合烷烃的芳构化反应

在小型固定床反应器上研究了水蒸气钝化及过渡金属(Ni,Co,Cu,Zn)改性对调变纳米HZSM-5沸石催化剂上C5~C8混合烷烃芳构化反应的作用.采用NH3-TPD和Py-FT-IR方法表征了改性催化剂的表面酸性质,并与其催化芳构化性能进行了关联.结果表明,在450℃下进行水蒸气钝化能显著提高催化剂的芳构化选择性,减少甲烷和乙烷等低碳烷烃的生成;催化剂进一步用锌盐或铜盐溶液浸渍改性,可以显著提高催化剂的抗积炭失活能力.这是由于水蒸气钝化能适当减少沸石表面的酸量,降低酸强度,而铜、锌改性可进一步减少B酸中心,增加L酸中心,并与B酸中心协同作用形成具有脱氢活性的催化中心,从而影响混合烷烃的活化方式与芳构化路径.     

制备方法对Pd催化剂上丙烯选择性还原NO反应性能的影响

 采用三种不同方法制备了氧化铝负载的Pd催化剂．比表面积测定\r\n结果表明,与浸渍法相比,溶胶－凝胶加浸渍法和溶胶－凝胶法制备的\r\nPd／Al2O3样品具有较大的比表面积,但抗烧结性能不佳．其中采用溶\r\n胶－凝胶法制备的样品中,由于Pd分散于体相中,表面的活性位相对较\r\n少,造成催化剂在NO选择性还原反应中的活性较差;而将Pd浸渍于溶胶\r\n－凝胶法制得的Al2O3载体上所获得的催化剂比表面积较大,活性较好\r\n．添加CeO2的样品活性总体上比Pd／Al2O3样品高．其中采用溶胶－凝\r\n胶法制备的样品比表面积不大,并且XRD数据表明Al2O3和CeO2是高度分\r\n散并均匀地搀杂在一起的,不象在浸渍法制备的样品中那样以大晶粒的\r\n形式存在,因而CeO2的助剂作用没有充分体现出来,催化剂的活性比浸\r\n渍法制备的样品差一些．     

固相浸渍法和湿浸渍法制备CuO/CeO2催化剂及其CO氧化性能的对比研究

采用固相浸渍法和常规湿浸渍法制备了一系列CuO/CeO₂催化剂,并结合X射线衍射（XRD）、氢气-程序升温还原（H₂-TPR）、激光拉曼光谱（LRS）、原位漫反射红外光谱（in situ DRIFTS）、X射线光电子能谱（XPS）等手段考察了制备方法对催化剂结构性质及其在CO氧化反应中性能的影响. XPS和H₂-TPR结果表明,固相浸渍法更有利于得到高分散的铜物种,并促进CuO物种的还原. LRS结果表明,相比于湿浸渍法,固相浸渍法能产生更多氧空位,而这些氧空位可以活化参与反应的O₂. CO氧化活性测试结果表明,当铜负载量相同时,固相浸渍法制备的催化剂相比于湿浸渍法表现出更好的催化性能. 结合多种表征结果发现,催化剂CO氧化性能与其表面氧空位和Cu⁺-CO浓度紧密相关,提出了CuO/CeO₂催化剂在CO氧化反应中可能的协同作用机制.     

Characterization of the active phase of NiMo/Al2O3 hydrodesulfurization catalysts

The active phase of the NiMo/Al₂O₃ catalyst for hydrodesulfurization reactions has been investigated in this work. Special attention has been focused on the effect of the order of metal impregnation on the formation of the active phase in the reaction. The Mo and Ni oxides and their sulfides on the alumina were investigated by XPS and DRS analyses. The Ni-Mo oxides or precursor of the active phase which are chemically bonded between Mo and Ni were also confirmed from the binding energy shifts of the XPS peaks. The amount of Ni-Mo oxides was determined after the formation of metal oxides during calcination. The Ni-Mo sulfide (active phase) was then induced through sulfidation. It was important that Mo should be located at the tetrahedral sites on the alumina with a high Mo dispersion. These results indicated that there are two important factors in preparing highly efficient Ni-Mo catalysts; one is that Mo should be located at the tetrahedral coordination on Al₂O₃ in high dispersion (Mo/Al₂O₃) and the other is that the Ni species should be supported on MoAl₂O₄ to form Ni-Mo oxides which change into the Ni-Mo sulfide active sites by sulfidation.     

Spectroscopic analysis and in situ monitoring of impregnation and extraction of polymer films and powders using supercritical fluids

A range of vibrational spectroscopic techniques are used to monitor supercritical fluid extraction and impregnation of polymers. Impregnation processes of this type show potential as alternative apporaches to the synthesis of polymer based catalysts and new materials. Methods have been devised using conventional Fourier transform infrared spectroscopy for real time monitoring of the extraction and impregnation of polyethylene films using an organometallic complex, CpMn(CO)₃ (Cp = η⁵ ? C₅ H₅) as a spectroscopic probe. Both low and high density powdered polyethylene may be impregnated using supercritical carbon dioxide. The resulting materials are analysed using FTIR photoacoustic spectroscopy, diffuse reflectance infrared spectroscopy and FT Raman spectroscopy to probe both the impregnated bulk of the polymer and surface-coated material. © 1994 John Wiley & Sons, Inc.     

镍基气凝胶催化CH_4-CO_2重整制取合成气反应的研究 Ⅰ.制备方法对NiO-CeO_2-Al_2O_3催化剂物化性质的影响

采用浸渍法、溶胶 凝胶过程与普通干燥、超临界干燥过程相结合的方法制备了具有不同结构特点的NiO CeO2 Al2 O3催化剂 ,分别为浸渍型催化剂 (iNCA)、干凝胶催化剂 (xNCA)和气凝胶催化剂 (aNCA) ,利用BET、TEM、XRD、TPR、NH3 TPD、H2 TPD等方法对各催化剂样品的物化性质进行了考察。研究结果表明 ,经 82 3K焙烧后 ,镍含量为 9%的各催化剂样品中镍物种均分散良好 ;与iNCA相比 ,以溶胶 凝胶法为基础制备的xNCA和aNCA中镍物种与载体的相互作用强并且存在状态均一 ;三种催化剂中 ,气凝胶样品具有比表面积高、堆密度低、表面酸中心数多及表面镍分散度高的特点。