准气相反应法中煅烧温度对ZrO2微球结构特性的影响

采用新颖的准气相反应法, 合成出了球形度好、表面光滑的ZrO₂微球. 通过对产物的SEM, TEM和XRD表征, 研究了煅烧温度对ZrO₂球结构特性的影响. 结果表明: 经600～800 ℃煅烧后, 生长完好的ZrO₂球, 其显微结构为均匀多孔结构, 纳米晶粒呈花生样的长条形状; ZrO₂球的相由主要的立方相和少量的四方相组成.     

ZrO2球的准气相反应合成

提出了一种工艺简单、成本低廉的准气相反应合成ZrO₂球的新方法. 通过对产物的SEM观测表明: 该方法制备的ZrO₂粒子为较好的球形, 球表面光滑; 其平均粒径1.71 μm, 标准偏差0.49 μm; 球有三种结构: 均匀致密结构、核心疏松外层致密结构和空心结构; 经600 ℃煅烧后, XRD分析确定ZrO₂球的相组成主要为立方相.     

ZrO2球的准气相反应合成

提出了一种工艺简单、成本低廉的准气相反应合成ZrO2球的新方法．通过对产物的SEM观测表明：该方法制备的ZrO2粒子为较好的球形,球表面光滑;其平均粒径1．71μm,标准偏差0．49um;球有三种结构：均匀敛密结构、核心疏松外层致密结构和空心结构;经600℃煅烧后,XRD分析确定ZrO2球的相组成主要为立方相．     

ZrO2中空微球的模板法制备及吸附性能研究

以油菜花粉为生物模板,通过温和易控的水浴-陈化法制备了纳/微米结构ZrO2中空微球.利用扫描电子显微镜(SEM)、红外光谱(FTIR)、X射线能谱(EDS)、X射线衍射(XRD)、比表面孔隙度分析、热分析等对所制备的产物和前驱体进行了表征,并对产物的吸附性能进行了初步的研究.结果表明,ZrO2中空微球的球壳由纳米粒子构筑并形成介孔结构.花粉模板前处理方式不同,其模板作用不同,可以获得两种不同球壳厚度、表面形貌和比表面积的ZrO2中空微球.其中"镂空"结构的ZrO2微球对铬黑T有良好的吸附性能.对ZrO2中空结构形成的机理进行了分析和讨论.     

焙烧温度对微乳液法负载铂制备的Pt-S2O82-/ZrO2-Al2O3催化剂异构化性能的影响

过微乳液法负载Pt制备了Pt-S₂O₈^2-/ZrO₂-Al₂O₃(Pt-SZA-X) 催化剂,并采用XRD、BET、FT-IR、TPR、TEM等手段对催化剂进行了表征。以正戊烷异构化反应为探针,考察了焙烧温度对催化剂异构化性能的影响。结果表明,焙烧温度对Pt-SZA-X的还原温度影响不大,但催化剂表面S含量随着焙烧温度的升高而下降;焙烧温度为600~650℃时形成O=S=O结构,此时S与催化剂载体结合比较稳定;焙烧温度为650℃时,可得到单一的ZrO₂四方晶相,焙烧温度高于650℃时,比表面积迅速降低,催化剂表面S⁶⁺流失严重。在不同温度下焙烧得到的催化剂中,经650℃焙烧的催化剂具有适宜的超强酸位和比表面积,异构化活性最高。在反应温度为230℃、反应压力2.0 MPa、氢烃物质的量比4:1、质量空速1.0 h^-1时,催化异戊烷产率达到60.8%。     

制备方法对CuO-CeO2/ZrO2催化CO氧化性能的影响

以ZrO2为载体、采用不同的浸渍次序制备了3种CuO-CeO2/ZrO2催化剂并在不同的温度(500,650和800℃)下进行焙烧,利用X射线衍射(XRD)、程序升温还原(H2-TPR和CO-TPR)及CO程序升温脱附(CO-TPD)技术对所制备的催化剂进行了表征,并采用色谱流动法考察了其催化CO低温氧化反应性能。结果表明,当焙烧温度为650℃时,3种催化剂的CO催化氧化活性均最佳,且三者的催化活性大小顺序为:CuO/CeO2/ZrO2>CuO-CeO2/ZrO2>CeO2/CuO/ZrO2。结合催化剂的表征和活性测试结果,我们认为高分散的CuO是CO的吸附中心,有利于CO的低温氧化反应,而大颗粒的CuO几乎对CO没有吸附作用,不利于CO的低温氧化反应。在3种催化剂中,CuO/CeO2/ZrO2催化剂具有最佳的低温还原特性和最大的CO2脱附峰面积,相应地具有最佳的催化氧化活性。     

溶胶-凝胶法制备ZrO2/SiO2纳米复合材料的研究

利用溶胶-凝胶法制备了ZrO2/SiO2纳米复合物室温磷光材料,通过各条件的优化,最终确定溶剂为异丙醇、Zr摩尔掺杂百分含量为15%、550℃下煅烧3h得到的纳米ZrO2/SiO2复合物的室温磷光发光性能较好,其最大激发波长为280nm、发射波长为460nm,且磷光寿命为0.56s。     

不同晶型氧化锆对Pd/ZrO2催化剂活性和稳定性影响

Pd/ZrO2是甲烷低温燃烧研究较为广泛的催化剂,其中载体ZrO2对稳定PdO起到了重要作用。 采用水热法合成了纯相的M-ZrO2和T-ZrO2,然后采用浸渍法制备了Pd/M-ZrO2和Pd/T-ZrO2催化剂,并考察了不同晶型ZrO2对催化剂的活性和稳定性的影响。 结果表明,Pd/M-ZrO2催化剂的活性和稳定性明显优于Pd/T-ZrO2。 结合XRD、TEM和TPO表征结果,发现Pd/M-ZrO2活性高的原因是PdO分散性更好,Pd/M-ZrO2较好的稳定性与PdO和ZrO2的作用方式有关。     

煅烧温度对TiO2/SiO2混合氧化物表面酸量的影响

采用共沉淀法制备了高钛含量的复合氧化物TiO2／SiO2．用BET、XRD、FT-IR和正胺吸附等分析手段，研究了煅烧温度对TiO2／SiO2表面酸量的影响．研究发现，随着煅烧温度的升高，TiO2／SiO2表面羟基密度、比表面积逐渐减少，TiO2晶粒尺寸变大，造成TiO2／SiO2表面酸量降低．当煅烧温度达到600℃到800℃之间，表面酸量基本不再改变．     

制备方法对WO3/ZrO2结构的影响

WO3/ZrO2 catalysts prepared from Zr(OH)4 and crystallized ZrO2 have been characterized by means of XRD, LRS (qualitative and quantitative), and the specific sufrace area has been measured. The influence of the preparation method, the contents of WO3 in the samples and the calcination tempearture on the specific surface areas of the samples, the phase of support and the structural states of active component has been studied. The results show: (1) WO3 can disperse on ZrO2 as a monolayer; (2) WO3 dispersed on Zr(OH)4 as a monolayer retards the crystalline growth of the support on calcination, makes it crystallizing into a metastable tetragonal modification, and prevents the inter- crystalline sintering between the crystallites of ZrO2. These factors would result in an increase in the specific surface area of WO3／ZrO2 prepared from Zr(OH)4. As the content of WO3 in the sample comes up to its monolayer capacity, this effect is displayed most fully. A chemical reaction can occur between WO3 and Zr(OH)4 (or the tetragonal ZrO2) at a high temperature(800℃),producing some superacid sites on the surface. By these views, the main experimental facts published in the literatures can been interpreted satisfactotily.     

焙烧温度对Mn/Al2O3-TiO2催化剂结构及氧化NO性能的影响

采用溶胶凝胶法和浸渍法制备10%Mn/Al_2O_3-TiO_2催化剂,借助TPO、XRD、O_2-TPD、Raman、XPS等手段,考察焙烧温度(450~650℃)对催化剂结构以及氧化NO性能的影响。TPO结果表明催化剂活性随焙烧温度的升高先增后减,其中焙烧温度为550℃时催化剂活性最好。XPS结果显示随着焙烧温度的升高(450~550℃),催化剂表面Mn~(3+)的含量逐渐升高,与催化剂活性的强弱成对应关系,并且催化剂晶格氧含量下降,而表面化学吸附氧从40.9%增加到64.8%。Raman分析显示550℃焙烧时,催化剂表面存在丰富的Mn_2O_3活性物种,并且O_2-TPD分析也表明随着焙烧温度的升高,晶格氧向表面化学吸附氧流动,提高了化学吸附态氧物种的含量。这些结果表明Mn_2O_3可能是NO氧化起主要作用的活性Mn物种,释放更多的表面化学吸附氧物种,将有助于促进NO的催化氧化。     

焙烧温度对Mn/Al2O3-TiO2催化剂结构及氧化NO性能的影响

采用溶胶凝胶法和浸渍法制备10% Mn/Al₂O₃-TiO₂催化剂,借助TPO、XRD、O₂-TPD、Raman、XPS等手段,考察焙烧温度(450~650 ℃)对催化剂结构以及氧化NO性能的影响。TPO结果表明催化剂活性随焙烧温度的升高先增后减,其中焙烧温度为550 ℃时催化剂活性最好。XPS结果显示随着焙烧温度的升高(450~550 ℃),催化剂表面Mn³⁺的含量逐渐升高,与催化剂活性的强弱成对应关系,并且催化剂晶格氧含量下降,而表面化学吸附氧从40.9%增加到64.8%。Raman分析显示550 ℃焙烧时,催化剂表面存在丰富的Mn₂O₃活性物种,并且O₂-TPD分析也表明随着焙烧温度的升高,晶格氧向表面化学吸附氧流动,提高了化学吸附态氧物种的含量。这些结果表明Mn₂O₃可能是NO氧化起主要作用的活性Mn物种,释放更多的表面化学吸附氧物种,将有助于促进NO的催化氧化。     

Monolith Manganese-Based Catalyst Supported on ZrO2-TiO2 for NH3-SCR Reaction at Low Temperature

Monolith catalysts were prepared using TiO₂ and ZrO₂-TiO₂ as supports with MnO₂ as active component and Fe₂O₃ as promoter. The catalytic activities at low temperature and stability at high temperature for selective catalytic reduction of NO_x with NH₃ (NH₃-SCR) in the presence of excessive O₂ were studied after the catalysts calcined at different temperatures. The catalysts were characterized by X-ray diffraction (XRD), specific surface area measurements (BET), oxygen storage capacity (OSC), and temperature programmed reduction (H₂-TPR). The results indicated that the catalyst supported on ZrO₂-TiO₂ had excellent stability at high temperature, and possessed high specific surface area and oxygen storage capacity, and had strong redox property. The results of the catalytic activities indicated that the monolith manganese-based catalyst using ZrO₂-TiO₂ as support had evidently improved the activity of NH₃-SCR reduction reaction at low temperature, and it showed great potential for practical application.     

Preparation of ZrO2-TiO2-CeO2 and Its Application in the Selective Catalytic Reduction of NO with NH3

TiO₂,ZrO₂-TiO₂,andZrO₂-TiO₂-CeO₂ were prepared by co-precipitation method and characterized by X-ray diffraction (XRD), specific surface area measurements (BET), temperature programmed desorption (NH₃-TPD), oxygen storage capacity (OSC), and temperature programmed reduction (H₂-TPR). The results showed that ZrO₂-TiO₂-CeO₂ exhibited large number of surface strong acid, possessed some oxygen storage capacity, and strong redox property. The three materials were used as supports and the monolith catalysts were prepared with 1% (w) V₂O₅ and 9% (w)WO₃ for selective catalytic reduction (SCR) of NO with ammonia in the presence of excessive O₂, and the results of catalytic activity showed that the catalyst used ZrO₂-TiO₂-CeO₂ as support yielded nearly 100% NO conversion at 275 °C at a gas hourly space velocity (GHSV) of 10000 h⁻¹, and it had the best catalytic activity and showed great potential for practical application.     

不同焙烧温度对Cu/γ-Al2O3催化剂铜物种结构的影响

用XRD和EXAFS研究了焙烧温度(35─1000 ℃)和负载量(质量分数为5－15％Cu)对于Cu/γ-Al_2O_3催化剂铜物种的影响。低于700 ℃焙烧时,铜以高分散状态存在。根据Cu~(2+)同时占据八面体(Oh)和四面体(Td)两种位置,对第一壳层的Cu-O配位峰进行了拟合。结果显示,随着焙烧温度增加,铜氧配位距离逐渐增加,Cu~(2+)(Oh)/Cu~(2+)(Td)的比例降低,并且Cu~(2+)(Oh)与氧的平均配位数从5.1变成6.0．这表明Cu~(2+)离子由Oh位向Td位迁移,同时向内层扩散使表面配位不饱和的氧缺顶畸变八面体部分变为配位饱和的对称八面体。900 ℃和更高温度的焙烧,使铜离子扩散进载体相形成CuAl_2O_4。