以TiO2多孔微球为载体的CuO/TiO2催化剂的制备、表征及CO氧化催化性能

利用高分子反相悬浮聚合技术结合溶胶-凝胶法制备了纳米TiO2晶粒组成的多孔微球. 以TiO2多孔微球为载体, 利用浸渍法制备了CuO/TiO2催化剂, 用示差扫描量热法、热重分析、X 射线衍射和X射线光电子能谱(XPS)对TiO2多孔微球和催化剂进行了表征, 并对其进行了CO催化氧化性能的评价. 结果表明, 于500 ℃焙烧的TiO2多孔微球基本为锐钛矿型结构, 其粒径为19.5 nm. XPS结果表明, 催化剂中载体和活性组分存在相互作用, Cu除了以Cu2+的形式存在外, 还以部分Cu+和Cu0的形式存在. CO催化氧化研究结果表明, 催化剂的催化活性与浸渍液的浓度和催化剂的焙烧温度有关. 用0.5 mol/L Cu(NO3)2·3H2O溶液浸渍得到的催化剂和于200 ℃焙烧得到的催化剂具有较好的催化活性.     

炭载体的预处理对钌催化剂金属分布状态及催化性能的影响

活性炭经不同方法处理后作为钌催化剂的载体,利用N2物理吸附、CO化学吸附和XRD等实验手段对载体的比表面、孔结构和催化剂的金属分布状态进行表征,并对催化剂进行氨合成活性评价.结果表明活性炭载体经气相法氧化处理后,能够增大炭载体的比表面,改善孔结构,提高钌催化剂的热稳定性和氨合成催化活性.     

用于光氧化水放氧的分子筛担载过渡金属氧化物催化剂的表面结构及特性表征

用IR,PAS,XRD和DTA,TGA及XPS,SEM对Na-Y型分子筛担载的过渡金属氧化物催化剂的表面结构和特征进行了研究.结果表明,单元RuO_2/Y催化剂的活性相分布均匀,价态单一,Ru:O≤2,RuO_2微晶粒线度为30—40(?),催化剂表面上存在L酸和B酸中心。对于分浸或共浸Ru-Fe复合催化剂,它们的表面结构、金属价态、微晶粒线度均有所不同,并存在着不同的金属与金属或担体间的强相互作用(或化学作用),因而它们的催化活性差异也大。同晶型的RuO_2,IrO_2及其复合的催化剂的结构性能变化不大,都具有较高的催化活性。     

形貌、晶粒大小不同的ZSM-5分子筛的表征及催化性能的研究

对3种不同形貌、晶粒大小的ZSM—5分子筛催化剂进行了表征和催化性能的研究．用XRD、SEM和NH3—TPD等方法对ZSM—5分子筛进行表征，结果表明小品粒分子筛的结晶度优于大晶粒分子筛，其酸性随着晶粒的减小而增强．对于MTG反应，ZSM—5分子筛酸性、晶粒大小和晶体形貌等因素对其催化活性产生显著影响．小晶粒的ZSM—5分子筛更有利于C5 和C9 的生成，而大晶粒的ZSM—5分子筛对对二甲苯的选择性高．TG结果表明ZSM—5分子筛上积炭覆盖酸性中心是导致催化失活的主要因素．     

CTAB辅助制备ZnO及其光催化脱色性能研究

本文采用并流沉淀法在CTAB辅助下制备了纳米ZnO光催化剂(ZnO-CTAB),以甲基橙为模拟有机污染物对催化剂的光催化脱色性能进行了考察。用BET比表面(BET)、X射线粉末衍射(XRD)、紫外可见漫反射光谱(DRS)和表面光电压谱(SPS)对所制备的催化剂进行了表征,结果表明ZnO-CTAB的比表面是ZnO比表面的3倍多,添加CTAB后制备的氧化锌晶粒尺寸更小,ZnO-CTAB局部呈不规则的蜂窝,CTAB辅助制备纳米ZnO有利于光诱导电荷分离。光催化性能测试结果表明ZnO-CTAB催化活性显著提高,ZnO-CTAB催化甲基橙脱色的速率常数ZnO脱色速率常数的3倍。     

La_(1-x)Ba_xCo_(0.8)Ni_(0.2)O_3复合氧化物的制备及其对CO催化燃烧性能

采用溶胶-冷冻干燥法制备了La1-xBaxCo0.8Ni0.2O3(x=0~0.4)催化剂粉体。用X射线衍射(XRD)、比表面测定仪(BET)和扫描电子显微镜(SEM)等分析手段对催化剂的结构和形貌进行了表征,并考察了催化剂的最佳焙烧温度和催化活性。研究表明,催化剂的最佳焙烧温度为600℃。掺杂Ba2+后,催化剂以钙钛矿相和BaCO3相共存,不能形成单一的钙钛矿型结构。催化活性测试表明,当x=0.2时,催化剂对CO的催化活性最高(T90%=126℃)。     

大晶粒ZSM-5分子筛的合成及其催化性能的研究

ZSM-5分子筛对许多正碳离于反应有优异的择形催化性能。近年来的研究表明,ZSM-5沸石的晶粒大小对其催化活性、选择性和稳定性有显著影响。如对甲苯歧化、甲苯与甲醇的甲基化反应,大晶粒ZSM-5分子筛对生成对二甲苯有较高的选择性。对于二甲笨液相异构化反应,小晶粒ZSM-5沸石具有较高的催化活性和选择性。我们用“直接法”合成了大晶粒(34×116μ)ZSM-5沸石分子筛,比较了不同晶粒大小ZSM-5分子筛催化剂在一些反应中的催化性能。大晶粒ZSM-5分子筛系不用有机胺,直接用水玻璃、硫酸铝、硫酸为原料合成的。用光学显微镜、扫描电镜观察所得分子筛的晶粒外形和大小,取5—6个有代表性的晶粒计算其平均尺寸。用BET重量法测定分子筛对正己烷、环己烷和水的吸附量。用X—射线衍射分析样品的物相。在160—200℃温度范围内考察了晶化温度对晶粒大小的影响,所得结果如表1。     

有序介孔碳载钯的制备、表征及对甲酸的电催化氧化性能

通过浸渍法和硫引入贵金属法分别制备了主要负载在介孔碳主孔道(MPC/Pd-1)和负载在介孔碳孔壁上小介孔中[MPC/(S)Pd-2]的两类负载型钯电催化剂, 用XRD, SEM, TEM和电化学等方法表征了其结构和电催化性能. 循环伏安结果表明, 有序介孔碳载钯催化剂MPC/Pd-1和MPC/(S)Pd-2对甲酸氧化的催化活性分别是商用钯黑催化剂的4.0和2.4倍. MPC/Pd-1中的钯位于介孔碳的主孔道上, 增加了催化剂/电解质/反应物三相界面的面积, 使得其比MPC/(S)Pd-2的催化活性更高.     

CO 在 Ni/TiO_2、Ni/Nb_2O_5和 Ni/Al_2O_3催化剂上的氢化反应

镍对一氧化碳加氢反应的催化活性与选择性的影响往往因载体不同而异,据不少文献报道,这是由于金属镍与载体间的相互作用不同所致。本文探索负载型催化剂的镍晶粒大小、催化活性和产品分布与载体本身可还原性的关系。文献指出,载体TiO_2与Nb_2O_5中金属组分经氢气还原处理后其价数会降低,然而Al_2O_3则不能,因此本文选用TiO_2和Nb_2O_5作为可还原性载体,而Al_2O_3作为非还原性载体。另外,为阐明催化剂晶粒大小与反应活性的关系,测定了反应条件下的镍晶粒的变化。     

浸渍法制备的苯部分加氢制环已烯催化剂的表征

利用XRD和BET比表面测定等手段对的钌催化剂进行了表征。研究结构表明,催化剂的活性与Ru原子的分散度和Ru微晶的晶粒度有关,Ru微晶在5nm左右,催化剂活性最好,催化剂合适的孔径分布范围为25nm-70nm,平均孔径大者,选择性较好。孔的有效表面积大者,活性较好。     

Magnesium chloride-supported,high-mileage catalysts for olefin polymerization. V. BET,porosimetry, and x-ray diffraction studies

The physical state of the material obtained during the various stages of preparation of a typical MgCl₂-supported, high-mileage propylene polymerization catalyst was studied by BET, mercury porosimetry, and x-ray diffraction techniques. The starting MgCl₂ and the substance after HCl treatment have negligible BET surface areas. Mercury porosimetry showed that they have large pores with radii > 200 nm which are probably crevices between MgCl₂ crystallites. The most pronounced physical changes occur during dry porcelain ball milling in the presence of ethyl benzoate. After 60 h or more of ball milling the material had a 5.1–7.3 m² g^?1 BET surface area, twice the pore surface area, and a smaller pore radius than before ball milling and a large reduction in crystallite sizes to almost ultimate dimensions. The crystallites were probably held together by complexation with ethyl benzoate in the form of large agglomerates. Subsequent reactions with p-cresol and triethyl aluminum had minor effects in further reduction of the MgCl² crystallite size but efficiently brokeup the agglomerates. The final refluxing with TiCl₄ increased the BET surface area to 110–150 m² g^?1 but may have increased the crystallite size somewhat due to cocrystallization of TiCl₃ and AlCl₃ with MgCl₂. There may have been only 8–10 crystallites in each catalyst particle. The surface structure of the catalyst resembled those of the classical Ziegler-Natta γ-TiCl₃·0.33 AlCl₃ catalyst.     

Sol–gel synthesis,characterization and catalytic activity of mesoporous γ-alumina prepared from boehmite sol by different methods

In this study, boehmite sols were used as alumina precursors for preparing mesoporous γ-aluminas by two different methods. In one case polyethylenimine was used as a structure-directing agent, and in another case ultrasound treatment was applied. Nitrogen physisorption showed that aluminas that had been prepared by these methods demonstrated different porous structures. The sample obtained without additional treatment had closely packed spherical particles and pores had ink-bottle neck morphology. Ultrasound treatment led to the transformation of ink-bottle pores into cylindrical form and to the increase in surface area and pore volume. Aluminas prepared using polyethylenimine as a template showed larger cylindrical wormhole-like mesopores with a broader pore size distribution, high surface area and pore volume. Catalytic tests showed that textural properties as well as crystallite size were very important parameters of synthesized samples which affected the catalytic activity in the methanol dehydration reaction. It was found that γ-Al₂O₃ prepared by ultrasound treatment had large crystallite size and demonstrated high catalytic activity.     

Broad Molecular Weight Polypropylene Synthesis using Mixed Internal Donor Incorporated Magnesium Dichloride Supported Titanium Catalyst

Magnesium dichloride supported titanium tetrachloride catalyst with mixed internal donor, comprised of ethylbenzoate and sulfolane, were synthesized. The composition characteristics of catalysts indicate incorporation of sulfolane to max 8.2 wt%, in addition to ethylbenzoate. The amount of incorporated donors in solid catalyst is dependent on the sulfolane concentration and reaction temperature of the process. A physical characteristics study of catalyst indicated that morphology, crystallite size, surface area, pore volume and titanium distribution have not been influenced much by incorporation of the second internal donor (sulfolane). The catalysts, in combination with triethyl aluminum as cocatalyst and p-ethoxyethylbenzoate as external donor, show good activity for propylene polymerization. The polypropylene synthesized with an optimized catalyst system shows broad molecular weight distribution as compared to ethylbenzoate based catalyst.     

制备高碳醇Cu-Fe系催化剂的比表面积、孔结构和孔径分布

用ＡＳＡＰ－２０００型物理吸附仪,研究了制备高碳醇Ｃｕ－Ｆｅ系催化剂的比表面积、孔结构、孔容积和孔径分布等．结果表明,随着焙烧温度的提高,比表面积下降;在相同的焙烧温度下,组成和沉淀过程的ｐＨ值也影响其表面积大小．催化剂的活性与反应可利用的表面积相关．根据吸附－脱附等温线,确定了催化剂的孔结构及孔径分布的变化规律．数据表明,孔径分布和孔容积对催化剂的活性至关重要,平均孔径（４Ｖ／Ａ,根据ＢＥＴ）可作为衡量Ｃｕ－Ｆｅ系催化剂活性高低的一个参数．焙烧温度的选择是使催化剂具有适宜的孔径分布和较大的孔容积,因而具有较高活性的重要条件     

沉淀还原法制备高性能CO2加氢合成甲醇Cu/ZnO/Al2O3催化剂

由铜基催化剂催化CO2+H2合成甲醇是有效利用CO2的潜在途径[1～5]. 但传统的催化剂对该反应的催化活性及选择性均很低[3～5], 因而寻求具有高活性及高选择性的新型催化剂已成为重要研究课题[4,6]. Cu/ZnO系列催化剂的制备方法和助剂对催化剂的性质及CO2加氢合成甲醇的反应性能有显著影响[6～10], 传统的气相还原活化铜基催化剂的过程常伴随强烈的热效应, 导致催化剂活化过程存在耗时长及还原条件难以控制等问题[11]. 本文采用沉淀-还原法, 用KBH4溶液对新鲜制备的碳酸盐共沉淀进行液相化学还原处理, 直接得到高活性及高选择性的还原态Cu/ZnO/Al2O3甲醇合成催化剂, 并可通过改变催化剂表面Cu+/Cu0活性物种的相对比例来改善催化剂的活性及选择性.     

无铬CO高温变换催化剂的研究 Ⅰ.氧化铬对CO高变催化剂结构与性能的影响 W

通过ＸＲＤ，ＢＥＴ和ＸＰＳ表征及反应活性测定表明，ＣＯ高温变换催化剂中加入的助剂ＣｒＯ３在制备及还原过程中，能进入Ｆｅ３Ｏ４晶格，使晶胞参数增大，晶粒度变小，分散度提高，比表面积和孔容积增大，孔结构改善而提高催化剂活性和稳定性。     

Properties of nanoporous carbon powders prepared from phenol-formaldehyde resin

Formation of the pore structure of nanoporous carbon materials and their physical properties were studied in relation to the composition of stocks of phenol-formaldehyde resin and starch. The dependences of the specific surface area, resistivity, interplanar spacing d ₀₀₂ and crystallite size on the degree of thermolysis during activation were determined.     

浸渍法制备的苯部分加氢制环己烯催化剂的表征

利用XRD和BET比表面测定等手段对钌催化剂进行了表征 .研究结果表明 ,催化剂的活性与Ru原子的分散度和Ru微晶的晶粒度有关 ,Ru微晶在 5nm左右 ,催化剂活性最好 .催化剂合适的孔径分布范围为 2 5nm～ 70nm ,平均孔径大者 ,选择性较好 .孔的有效表面积大者 ,活性较好     

Methanol-to-Olefin Conversion over Zeolite Catalysts: Active Intermediates and Deactivation

Methanol-to-olefin (MTO) conversion over various zeolites with different topologies, Si/Al molar ratios, and crystallite sizes were investigated to verify the effects of pore shape and size, acidity, and external surface area on the catalytic activity, product selectivity, and deactivation. The IR and electron spin resonance (ESR) study of zeolite catalysts used in MTO also proceeded to deduce the active intermediates formed in their cages or pores. The zeolites with 8 membered-ring (MR) pore entrances such as CHA, ERI, LTA, and UFI commonly exhibited high selectivity to lower olefins due to their small entrances, but the CHA catalyst with the smallest cage maintained its activity longer than other 8MR zeolites. The slow condensation of polymethylbenzene (PolyMB) to polyaromatic hydrocarbons (PAH) on MOR zeolite with a high Si/Al molar ratio due to its low concentration of strong acid sites resulted in a slow deactivation. The extremely small crystallites of H-SAPO-34 and H-ZSM-5 less than 100 nm showed an adverse effect in MTO; while the large crystallites above 1,000 nm also exhibited poor catalytic performance because of their small external surface. The study of IR regarding the adsorbed and occluded materials on zeolites demonstrated the effect of pore shape and size on the active intermediates: the zeolites with larger pores and cages allowed the formation of alkylbenzenes with long alkyl groups which preferred to be condensated to PAH. The well-resolved hyperfine splitting of ESR spectra observed on H-SAPO-34 used in MTO clearly illustrated the presence of hexamethylbenzenium radical cations. The small intersections of phosphorous-modified H-ZSM-5 allowed the formation of tetramethylbenzenium radical cations in MTO. The formation of PolyMB radical cations, their role as active intermediates and the effect of topology, acidity, and crystallite size of zeolites on their deactivation were discussed.     

Relationship between formation conditions, properties, and crystallite size of boehmite

Boehmites (gamma-AlOOH) with a variety of crystallite sizes were prepared under various precipitation conditions from solutions of aluminum nitrate and sodium aluminate and also by hydrothermal treatment of a commercial boehmite powder. The relationships between the crystallite size and other properties of the boehmites were investigated. Crystalline boehmite was formed in the pH range 7 to 10 while gels precipitated below pH 7 and bayerite (Al(OH)3) formed at pH 11. The crystallite size of the boehmite increased at higher pH, higher temperature of the precursor solution, and longer aging time. As the crystallite size of the boehmite increased, the specific surface area, pore volume, and excess water decreased. Boehmites of small crystallite size, called pseudoboehmite, showed broadened X-ray peak widths and increased d-spacing of the 020 reflection. These changes are attributed to the small crystallite size (smaller numbers of stacking layers) and also to excess water in the interlayers of the boehmite structure.