Al2O3催化剂结构对催化臭氧化活性的影响

以Al₂O₃为催化剂催化臭氧化处理邻苯二甲酸二甲酯. 通过XRD、比表面积、孔结构、FTIR和活性评价等方法对催化剂的物化性质及催化活性进行了研究, 考察了焙烧温度、成型粒径对催化剂活性的影响. 结果表明, Al₂O₃催化剂对臭氧化降解邻苯二甲酸二甲酯具有很高的催化活性, 反应120 min后, 总有机碳(TOC)的去除率从单独臭氧氧化的23.9%提高到55.1%; 焙烧温度对催化剂的活性具有很大的影响, 600 ℃催化剂催化活性最高; 随着焙烧温度的升高, Al₂O₃晶型经历了从γ-Al₂O₃到θ-Al₂O₃到α-Al₂O₃的转变, 催化剂的比表面积、焙烧得到的孔容逐渐变小, 晶体粒径变大, 表面•OH数量减少, 催化活性下降. Al₂O₃成型粒径的减小, 提高了催化剂的外比表面积, 减小了内部传质扩散的影响, 从而提高了催化活性.     

Pt/ZrO2-Al2O3催化剂催化氧化C3H6和CO性能

采用共沉淀法合成了ZrO₂与Al₂O₃的不同质量比的ZrO₂-Al₂O₃复合氧化物,并以此为载体通过等体积浸渍法制备了1.5% Pt/ZrO₂-Al₂O₃（w/w）催化剂。以C₃H₆和CO为反应物的催化性能评价显示,在系列催化剂中以Pt/Zr（0.4）-Al催化剂催化氧化活性最为优异,其C₃H₆和CO的起燃温度（T₅₀）小于125℃,完全转化温度（T₉₀）小于150℃。采用XRD、低温N₂吸附、H₂-TPR、CO脉冲吸附等分析表征技术探索了催化剂物相结构、比表面积、颗粒尺寸等对催化活性的影响规律。结果发现,ZrO₂-Al₂O₃复合氧化物具有Al₂O₃材料的介孔织构和大比表面积特性,且产生了Al_xZr_1-xO_y固溶体新物相。适当的ZrO₂与Al₂O₃的质量比,是改善Pt与ZrO₂-Al₂O₃的相互作用强度,促进贵金属Pt的分散,提升Pt/ZrO₂-Al₂O₃催化剂的低温氧化活性的关键。     

Pt/ZrO2-Al2O3催化剂催化氧化C3H6和CO性能

采用共沉淀法合成了ZrO₂与Al₂O₃的不同质量比的ZrO₂-Al₂O₃复合氧化物,并以此为载体通过等体积浸渍法制备了1.5% Pt/ZrO₂-Al₂O₃（w/w）催化剂。以C₃H₆和CO为反应物的催化性能评价显示,在系列催化剂中以Pt/Zr（0.4）-Al₂O₃催化剂催化氧化活性最为优异,其C₃H₆和CO的起燃温度（T₅₀）小于125℃,完全转化温度（T₉₀）小于150℃。采用XRD、低温N₂吸附、H2-TPR、CO脉冲吸附等分析表征技术探索了催化剂物相结构、比表面积、颗粒尺寸等对催化活性的影响规律。结果发现,ZrO₂-Al₂O₃复合氧化物具有Al₂O₃材料的介孔织构和大比表面积特性,且产生了Al_xZr_1-xO_y固溶体新物相。适当的ZrO₂与Al₂O₃的质量比,是改善Pt与ZrO₂-Al₂O₃的相互作用强度,促进贵金属Pt的分散,提升Pt/ZrO₂-Al₂O₃催化剂的低温氧化活性的关键。     

Pd/MnOx+Pd/γ-Al2O3整体式催化剂降解地表臭氧

用高锰酸钾与硝酸锰氧化还原反应制备了高活性的氧化锰(MnO_x)催化组分,用胶溶法制备了高比表面积的γ-Al₂O₃载体,分别用等体积浸渍法制备了Pd/MnO_x和Pd/γ-Al₂O₃催化剂,然后将两者机械混合涂覆于堇青石上制得Pd/MnO_x+Pd/γ-Al₂O₃整体式催化剂。采用X射线衍射(XRD)、X射线光电子能谱(XPS)、程序升温还原(H₂-TPR)和低温N₂吸附-脱附对催化剂进行了表征。考察了在300至700℃焙烧MnO_x对催化剂降解地表O₃活性的影响。结果表明,Pd和MnO_x之间存在协同作用;MnO_x焙烧温度对催化剂活性有一定的影响,其中以600℃焙烧时催化剂的活性最高,O₃的起始(12℃)转化率达到88%,完全转化温度为18℃。MnO_x的物相和催化剂表面的吸附氧物种对催化活性影响较大,适当比例的MnO₂和Mn₂O₃共存有利于O₃分解,表面吸附氧为O₃分解的活性氧物种。     

高活性固体碱Na2O/Al2O3-MgO的合成与表征

过量NaOH易引起铝离子流失,造成以Al₂O₃-MgO为载体的催化剂性能不稳定,为此以NH₃为沉淀剂制备了Mg-Al共沉淀物,进而通过Na₂CO₃浸渍、老化、焙烧处置,制备了Na₂O/Al₂O₃-MgO催化剂,借助XRD、SEM、SEM-EDS、TG-DSC、N₂吸附-脱附等手段对其结构及形貌进行表征,以蒜头果油甲酯化率对其活性进行评价,结果表明：采用共沉淀-浸渍的处理方法可以获得类水滑石片层结构的催化剂前驱体,该前驱体主要分解温度在200~500℃之间,经高温煅烧处理后所得催化剂中有Na-Al及Na-Mg-Al氧化物形成。制备高活性Na₂O/Al₂O₃-MgO催化剂的条件为：镁铝离子比n_Mg/n_Al=3∶1~1∶3、老化时间12 h、焙烧温度550℃、焙烧时间5 h。以n_Mg/n_Al=1∶1时制备的催化剂进行验证实验发现,所得催化剂比表面积为30 m²·g^-1、平均孔径为8.8 nm,是一种介孔催化剂,该催化剂在蒜头果油甲酯化实验中表现出高的催化活性,蒜头果油甲酯化率最高达到96.4%。     

面向异丁烷脱氢介孔γ-Al2O3基催化剂的合成及其高催化性能

采用溶剂蒸发自组装法调控载体形貌及孔道结构,成功制备了有序介孔氧化铝载体。以铬氧物种为活性组分,碱金属钾为助剂,采用浸渍法制备负载型催化剂,用于异丁烷催化脱氢反应,研究了反应温度、原料流速、催化剂粒径等因素对催化性能的影响。采用X射线粉末衍射、透射电子显微镜、N₂物理吸附、氢气程序升温还原及热重等表征方法探讨了载体形貌、孔道结构与催化性能的构效关系,结果表明,低温下有利于控制异丙醇铝的水解和缩合及介孔γ-Al₂O₃的研制。与常规的γ-Al₂O₃相比,所制备的介孔γ-Al₂O₃的有更大的比表面积和良好的有序性,在600℃、101.325kPa、GHSV=1 000 h^-1的条件下,10%（w/w）Cr₂O₃/γ-Al₂O₃催化剂性能最佳,异丁烷的转化率达63.1%,异丁烯的选择性达到85.5%。与传统的催化剂相比,介孔Cr₂O₃/γ-Al₂O₃催化剂具有大的比表面积,高度分散的活性组分,优良的催化性能和良好的抗积碳能力。     

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。     

MgFe0.1Al1.9O4 的合成及其催化乙苯与 CO2 的氧化脱氢反应

 以柠檬酸为络合剂, 采用溶胶-凝胶法制备了具有尖晶石结构的 MgFe_0.1Al_1.9O₄ 催化剂, 并将其用于催化乙苯与 CO₂ 氧化脱氢反应. 运用 X 射线衍射、X 射线能量色散光谱分析、红外光谱、热重-差热、N₂ 吸附-脱附和 H₂ 程序升温还原等技术对催化剂进行了表征. 结果表明, 在 650 ºC 以上焙烧即可制得结构确定、组成均一的 Mg-Fe-Al-O 复合氧化物催化剂, 其中 Fe 物种主要以同晶取代的形式存在于尖晶石骨架中. 随着焙烧温度的升高, 尖晶石结晶度提高, Fe 物种还原能力下降, 催化剂晶粒度增大, 比表面积降低. 700 ºC 焙烧制备的 MgFe_0.1Al_1.9O₄ 具有较好的催化乙苯与 CO₂ 氧化脱氢反应活性和稳定性.     

K2CO3含量对Ni-Cu-Mn-K/Al2O3水煤气变换催化剂结构和性能的影响

以γ-Al₂O₃为载体，采用等体积浸渍法，制备了不同K₂CO₃含量的Ni-Cu-Mn-K/Al₂O₃水煤气变换催化剂，采用低温N₂吸附、XRD、TPD和TPR，考察了K₂CO₃含量对催化剂结构和性能的影响。结果表明:K₂CO₃的加入使催化剂的还原温度有所提高，适量的K₂CO₃能增加活性组分的电子密度，从而增强其给电子活化CO的能力，提高催化剂的活性。但过量的K₂CO₃使得催化剂比表面积和孔容降低，且导致催化剂对CO吸附过强，催化活性降低。当Ni-Cu-Mn-K/γ-Al₂O₃催化剂中K₂CO₃的添加量为7.5%时，且催化剂经530 ℃耐热15 h后，在350 ℃时水煤气变换反应中CO转化率达62.29%。     

Ce1-XMnXO2-a复合氧化物催化剂甲烷催化燃烧性能的研究

采用水热法合成了系列Ce_1-XMn_XO_2-a-T(X=0.0，0.1，0.2，0.3，0.5，0.7，0.9，1.0；T表示焙烧温度)，T=500，650，800 ℃)复合氧化物催化剂用于甲烷的催化燃烧。通过XRD、N₂吸/脱附、TG-DSC、UV-Vis-DRS和TPR表征手段研究了不同组成催化剂的物理化学性质及其对甲烷催化燃烧活性。结果表明，在500 ℃焙烧的情况下Mn进入CeO₂晶格形成均相固溶体催化剂的最大取代值为0.7，而当Mn继续增加时则出现Mn₂O₃晶相偏析，同时各催化剂具有较高的比表面积；随着焙烧温度的升高，进入CeO₂晶格的Mn最大取代值逐渐减少，650和800 ℃时分别为0.5和0.3，且比表面积相应降低。Ce_1-XMn_XO_2-a-800催化剂的还原行为大致呈现三阶段，即为Mn₂O₃ → Mn₃O₄的还原(340～420 ℃)，Mn₃O₄ → MnO的还原(420～480 ℃)和体相氧化铈的还原(700～900 ℃)，且Mn的引入整体上提高了催化剂的可还原能力。甲烷催化燃烧活性评价结果表明，比表面积并非影响催化剂活性的主要因素，影响催化剂甲烷催化活性的主要因素为催化剂的组成、可还原能力和焙烧温度；而其中以Ce_0.3Mn_0.7O_2-a-800催化剂表现出较高的甲烷催化燃烧活性，在甲烷转化率为10%和90%时的温度分别为430 和613 ℃。进一步考察Ce_0.3Mn_0.7O_2-a在不同温度(500、650、800和1 000 ℃)焙烧后的催化活性表明，随着焙烧温度的提高催化剂催化活性降低。     

CO oxidation over Co3O4/SiO2 catalysts: Effects of porous structure of silica and catalyst calcination temperature

The catalytic performances of Co3O4/SiO2 catalysts prepared by incipient wetness impregnation for CO oxidation were investigated using three kinds of silica as carriers with different pore sizes of 7.7, 14.0 and 27.0 nm. The effects of calcination temperature on the catalyst surface and micro structure properties as well as catalytic performance for the oxidation of carbon monoxide were also studied. All catalysts were characterized by N2 adsorption-desorption, XRD, XPS, FTIR, H2-TPR and O2-TPD. It was found that the properties and crystal size of cobalt-containing species strongly depended on the pore size of silica carrier. While the silica pore size increased from 7.7 to 27.0 nm, the Co3O4 crystal size increased from 8.5 to 13.5 nm. Moreover, it was demonstrated that if the spinel crystal structure of Co3O4 was obtained at a calcination temperature as low as 150 ℃, the catalyst sample would have a high Co3O4 surface dispersion and a increase of surface active species, and thus exhibit a high activity for the oxidation of carbon monoxide.     

负载Ni催化剂用于乙二醇蒸汽重整制氢催化性能研究

采用等体积浸渍法和共沉淀法制备了Ni催化剂,在固定床反应器上考察了Ni负载量、焙烧温度、反应温度等因素对乙二醇低温重整制氢反应活性和选择性的影响。应用X射线衍射、氮物理吸附、H₂程序升温还原等技术对负载型Ni催化剂进行了表征。结果表明,共沉淀法制备的Ni/CeO₂催化剂具有较小的NiO颗粒与CeO₂载体颗粒粒径,催化活性较高。添加少量氧化钴到Ni/CeO₂催化剂中可使H₂收率达72.6%,EG转化率达93.1%。在CeO₂中添加Al₂O₃能提高负载Ni催化剂的活性,乙二醇转化率达94.0%,H₂收率达67.0%;但添加SiO₂则使其活性明显变差。     

焙烧温度对 Pd/Al2O3 催化剂上甲烷燃烧反应性能的影响

 考察了载体与催化剂焙烧温度对 Pd/Al2O3 催化剂上低浓度甲烷催化燃烧反应性能的影响. 采用 X 射线衍射、透射电镜、N2 物理吸附、NH3 程序升温脱附和 O2 程序升温氧化等手段对载体和催化剂进行了表征. 结果表明, 焙烧温度对催化剂活性及稳定性的影响显著. 随着载体焙烧温度的升高, Al2O3 的比表面积、物相结构、酸中心的数量及强度明显改变, 相应的 Pd/Al2O3 催化剂中载体与 Pd 的相互作用减弱, Pd 分散度降低. 当载体焙烧温度为 1 100 °C, Pd/Al2O3 焙烧温度为 200 °C 时, 所得催化剂在 260 h 的连续反应中, 甲烷转化率始终维持在 99%以上.     

Effect of Calcination Temperature and Pretreatment with Reaction Gas on Properties of Co/γ‐Al2O3 Catalysts for Partial Oxidation of Methane

The effects of calcination temperature and feedstock pretreatment on the catalytic performance of Co/γ‐Al₂O₃ catalysts were studied for partial oxidation of methane (POM) to synthesis gas, with emphasis on the role of feedstock pretreatment. The physicochemical properties of the catalysts were characterized by N₂ adsorption, X‐ray diffraction (XRD), transmission electron microscopy (TEM), H₂ temperature‐programmed reduction (H₂‐TPR), and Raman spectroscopy. The results showed that the pretreatment of the catalyst by reaction gas significantly improved the catalytic activity and stability for the POM reaction. On the other hand, the effect of calcination temperature was less significant. Although the initial activity was increased by an increased calcination temperature, the catalyst without the feedstock pretreatment suffered a rapid deactivation. The reaction‐atmosphere pretreatment was revealed as a process that mainly modified the surface structure of the catalyst. In that process, the formation of a CoAl₂O₄‐like compound led to high Co metal dispersion after reduction, and the transformation of the carrier into α‐Al₂O₃ occurred over the catalyst surface. Both the high dispersion of cobalt and the presence of α‐Al₂O₃ surface phase were assumed as the important factors resulting in an excellent catalytic performance in terms of high activity and high stability.     

不同载体Ni基负载型催化剂对甲烷部分氧化制合成气催化行为研究

采用浸渍法制备了单一载体(Al₂O₃、ZrO₂、CeO₂)和ZrO₂、CeO₂改性的Al₂O₃复合载体的Ni催化剂,考察了在甲烷部分氧化制备合成气反应中的催化性能。通过N₂-物理吸附、H₂程序升温还原、X射线衍射、NH₃程序升温脱附和程序升温氧化等技术对催化剂进行了表征。结果表明,在单一载体催化剂中,Ni/Al₂O₃具有较大的比表面积,其初始反应活性较高,但该催化剂表面易形成大量的积炭而快速失活。Ni/ZrO₂和Ni/CeO₂催化剂比表面积较小,活性金属Ni在其表面分散性差,催化剂具有较低的CH₄转化率。而CeO₂和ZrO₂改性的Al₂O₃复合载体催化剂,具有较大的比表面积,反应活性明显高于单一载体催化剂。CeO₂-Al₂O₃复合载体催化剂具有最高的反应活性和较好的反应稳定性。同时表明,含CeO₂催化剂反应后表面积炭较少,CeO₂的储放氧功能增强了催化剂对O₂的活化,提高催化剂活性的同时,可以抑制积炭的生成。     

CoAl_2O_4/蜂窝陶瓷催化剂的制备及其催化臭氧化性能

采用涂覆法制备了CoAl_2O_4/蜂窝陶瓷催化剂。利用X射线衍射、N_2吸附-脱附和透射电镜等方法对所制备的催化剂进行了表征,并分析了其催化臭氧化降解对苯二酚的效能。结果表明,CoAl_2O_4/蜂窝陶瓷的晶相属于典型的尖晶石结构,具有较大的比表面积、孔容和孔径,分别达到77 m~2·g~(-1)、0.001 7 cm~3·g~(-1)和3.9 nm。CoAl_2O_4/蜂窝陶瓷催化臭氧化对苯二酚的去除率高达81.2%,COD去除率可达47.7%。在叔丁醇存在的条件下,对苯二酚的去除率显著下降,说明CoAl_2O_4/蜂窝陶瓷催化臭氧化遵循羟基自由基机理。     

CoAl2O4/蜂窝陶瓷催化剂的制备及其催化臭氧化性能

采用涂覆法制备了CoAl₂O₄/蜂窝陶瓷催化剂。利用X射线衍射、N₂吸附-脱附和透射电镜等方法对所制备的催化剂进行了表征,并分析了其催化臭氧化降解对苯二酚的效能。结果表明,CoAl₂O₄/蜂窝陶瓷的晶相属于典型的尖晶石结构,具有较大的比表面积、孔容和孔径,分别达到77 m²·g^-1、0.001 7 cm³·g^-1和3.9 nm。CoAl₂O₄/蜂窝陶瓷催化臭氧化对苯二酚的去除率高达81.2%,COD去除率可达47.7%。在叔丁醇存在的条件下,对苯二酚的去除率显著下降,说明CoAl₂O₄/蜂窝陶瓷催化臭氧化遵循羟基自由基机理。     

Ni/Al2O3 catalysts for CO methanation: Effect of Al2O3 supports calcined at different temperatures

The correlation between phase structures and surface acidity of Al₂O₃ supports calcined at different temperatures and the catalytic performance of Ni/Al₂O₃ catalysts in the production of synthetic natural gas (SNG) via CO methanation was systematically investigated. A series of 10 wt% NiO/Al₂O₃ catalysts were prepared by the conventional impregnation method, and the phase structures and surface acidity of Al₂O₃ supports were adjusted by calcining the commercial γ-Al₂O₃ at different temperatures (600–1200 °C). CO methanation reaction was carried out in the temperature range of 300–600 °C at different weight hourly space velocities (WHSV = 30000 and 120000 mL·g^?1·h^?1) and pressures (0.1 and 3.0 MPa). It was found that high calcination temperature not only led to the growth in Ni particle size, but also weakened the interaction between Ni nanoparticles and Al₂O₃ supports due to the rapid decrease of the specific surface area and acidity of Al₂O₃ supports. Interestingly, Ni catalysts supported on Al₂O₃ calcined at 1200 °C (Ni/Al₂O₃-1200) exhibited the best catalytic activity for CO methanation under different reaction conditions. Lifetime reaction tests also indicated that Ni/Al₂O₃-1200 was the most active and stable catalyst compared with the other three catalysts, whose supports were calcined at lower temperatures (600, 800 and 1000 °C). These findings would therefore be helpful to develop Ni/Al₂O₃ methanation catalyst for SNG production.     

Propane combustion over supported Pd catalysts

We prepared Pd catalysts supported on various metal oxides, viz. γ-Al₂O₃, α-Al₂O₃, SiO₂–Al₂O₃, SiO₂, CeO₂ and TiO₂ by an incipient wetness method and applied them to propane combustion. Several techniques: N₂ physisorption, inductively coupled plasma-atomic emission spectroscopy (ICP-AES), CO chemisorption, temperature-programmed reduction (TPR) and temperature-programmed oxidation (TPO) were employed to characterize the catalysts. Pd/SiO₂–Al₂O₃ showed the least catalytic activity at high temperatures among Pd catalysts supported on irreducible metal oxides, viz. SiO₂, Al₂O₃ and SiO₂–Al₂O₃. Pd/γ-Al₂O₃ was much superior for this reaction to Pd/α-Al₂O₃. The Pd catalyst supported on reducible metal oxides (CeO₂ and TiO₂) with a less specific surface area showed the higher catalytic activity compared with that supported on reducible metal oxides with a higher specific surface area, even though the former had a less Pd dispersion than the latter. In the case of Pd/SiO₂–Al₂O₃, the initially reduced Pd catalyst was superior to the fully oxidized one. The oxidation of metallic Pd occurred in the presence of O₂ with increasing reaction temperature, which resulted in the change in the catalytic activity.     

Fe-Mn-Cu-Ce/Al2O3 as an efficient catalyst for catalytic ozonation of bio-treated coking wastewater: Characteristics,efficiency, and mechanism

It is important to develop a catalyst that has high catalytic activity and can improve the degradation efficiency of refractory organic pollutants in the catalytic ozonation process. In this study, Fe-Mn-Cu-Ce/Al₂O₃ was synthesised via impregnation calcination for catalytic ozonation of bio-treated coking wastewater. The physical and chemical characteristics of the catalysts were analysed using X-ray diffraction (XRD), X-ray fluorescence spectrometry (XRF), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and Brunauer–Emmett–Teller nitrogen adsorption–desorption methods. The effects of catalyst dosage, pH, and reflux ratio on the degradation efficiency of wastewater were examined in laboratory-scale experiments. The chemical oxygen demand (COD) removal rate of bio-treated coking wastewater was estimated to be 52.76 % under optimal conditions. The experiments on the catalytic mechanism demonstrated that the surface hydroxyl formed by the Lewis acid sites on the surface of the catalyst can react with ozone as the active site forming the active oxygen (·OH, ·O₂^–, and ¹O₂), thereby efficiently degrading the organic pollutants in coking wastewater. Furthermore, a pilot-scale experiment on the catalytic ozonation of bio-treated coking wastewater was carried out using an Fe-Mn-Cu-Ce/Al₂O₃ catalyst, while the effects of the initial pollutant concentration, ozone concentration, and gas flow on the COD removal rate were studied on a pilot scale. It was found that the COD removal rate of the wastewater was ～ 60 % under optimal parameters. After the treatment, the wastewater steadily reached the coking wastewater discharge standard (COD < 80 mg/L), while the operating cost of catalytic ozonation reached ～ 0.032$/m³, thereby paving the way toward economic engineering applications. The COD degradation kinetics in the bio-treated coking wastewater followed pseudo-second-order kinetics. Three-dimensional fluorescence and gas chromatography–mass spectrometry revealed that macromolecular organic pollutants in the bio-treated coking wastewater were greatly degraded. In summary, Fe-Mn-Cu-Ce/Al₂O₃ exhibited good reusability, high catalytic activity, and low cost and has a wide application prospect in the treatment of coking wastewater.