M_(0.5)Co_(2.5)O_4(M=La,Ce,Pr,Nd)尖晶石型复合氧化物催化剂催化分解N_2O性能

采用共沉淀法制备了M_(0.5)Co_(2.5)O_4(M=La,Ce,Pr,Nd)钴基尖晶石型复合氧化物催化剂,运用XRD、SEM、H_2-TPR和O_2-TPD-TG等对催化剂物化性能进行表征,并在固定床微型反应器中评价催化剂催化分解N_2O性能。结果表明,稀土金属掺杂改性的钴基尖晶石型复合氧化物催化剂粒径明显减小,比表面积增加,氧化还原性能得到改善,催化分解N_2O活性提高,其中,M_(0.5)Co_(2.5)O_4催化剂催化分解N2O温度低,T10和T95分别为342℃和499℃。     

二氧化硅辅助制备CuCo2O4纳米尖晶石及其催化性能

采用无定型氧化硅辅助制备了CuCo_2O_4纳米尖晶石氧化物,研究了其在对硝基苯酚催化还原中的催化活性。采用X射线衍射仪、扫描电子显微镜等对Cu Co_2O_4纳米尖晶石的形成机制、晶相结构、微观相貌等进行研究。结果表明:基于有机硅前驱体获得的无定型氧化硅可以与Cu Co_2O_4尖晶石氧化物有效复合,有利于抑制Cu Co_2O_4粒子尺寸的长大,并且不会与Cu Co_2O_4发生相间反应。进而通过Na OH热碱溶液处理可以高效刻蚀Cu Co_2O_4–无定型氧化硅复合氧化物中二氧化硅,从而生成纳米尺度Cu Co_2O_4尖晶石粒子,其微观形貌与粒子尺寸与传统方法制备的Cu Co_2O_4明显不同,具有更高的孔隙率和更小的晶粒尺寸。相对于传统方法制备的Cu Co_2O_4尖晶石材料,以无定型氧化硅辅助制备的Cu Co_2O_4纳米尖晶石具有更高的催化活性与稳定性。     

Fe掺杂对La_(0.9)Sr_(0.1)Co_(1-x)FexO_3催化剂同时净化NO和碳烟活性规律研究

采用柠檬酸-EDTA络合法制备了纳米钙钛矿催化剂La_(0.9)Sr_(0.1)Co_(1-x)FexO_3,催化剂具有较好的同时去除NO和碳烟(soot)催化活性,其中La_(0.9)Sr_(0.1)Co_(0.7)Fe_(0.3)O_3展现出最佳的催化活性,其在380.0℃时NO转化率为32.5%,soot最大燃烧速率温度(T_m)为368.5℃。H_2-程序升温还原(H_2-TPR)和NO-程序升温脱附(NO-TPD)结果表明,Fe掺杂能显著提高催化剂低温还原性能、表面氧物种活性及NO吸附性能,这有利于其改善催化活性。X射线光电子能谱(XPS)结果表明,Fe掺杂能增加催化剂表面吸附氧浓度和高价离子(Co~(4+)),这对提高催化氧化能力至关重要。采用颗粒物捕集器(DPF)作为载体涂覆CeO_2涂层用于负载La_(0.9)Sr_(0.1)Co_(0.7)Fe_(0.3)O_3催化剂进行柴油机台架实验,结果表明该催化剂具有较好的同时去除NO_x和soot催化活性,最大NO转化率为23.0%,T_m为341.0℃,表明Fe掺杂对提高催化活性至关重要。     

Au/La_2O_3+Co_3O_4催化剂制备及其对CO催化氧化性能和稳定性的研究

为了能够得到高催化活性、高热稳定性的Au催化剂,本文选择了混合氧化物La_2O_3+Co_3O_4为载体,制备了两种Au/La_2O_3+Co_3O_4催化剂,并考察了此催化剂对CO氧化反应的催化活性及稳定性。实验结果表明:Au/La_2O_3+Co_3O_4催化剂活性好于250℃焙烧的Au/La_2O_3+Co_3O_4(C)催化剂,Au/La_2O_3+Co_3O_4(C)催化剂稳定性好于Au/La_2O_3+Co_3O_4催化剂。     

还原剂对Pd/Pb_(2-x)Mn_8O_(16)催化剂微观结构与催化性能的影响

以Hollandite型氧化物Pb_(2-x)Mn_8O_(16)为载体,Na BH4、甲醛和乙二醇为还原剂,采用液相沉积还原法制备了3种载Pd催化剂,并利用X射线衍射(XRD)、透射电子显微镜(TEM)、X射线光电子能谱(XPS)等技术对催化剂进行表征,分析了不同还原剂对催化剂微观结构、氧化还原性质及其在苯酚氧化羰基化反应中催化性能的影响。实验结果表明,Na BH4的强还原性破坏了载体Pb_(2-x)Mn_8O_(16)的结构;与甲醛相比,以乙二醇为还原剂所得的纳米钯粒子在载体上的分布更加均匀,Pd粒子的平均尺寸为4.1 nm。其中采用乙二醇为还原剂制备的Pd/Pb_(2-x)Mn_8O_(16)催化合成碳酸二苯酯的收率最高,达15.6%。     

Cu/Mn/Ce三元氧化物催化剂对甲苯催化燃烧性能的研究

采用浸渍法制备了不同Cu/Mn/Ce摩尔比的铜锰铈三元复合氧化物催化剂。通过XRD、和H_2-TPR对催化剂的晶相结构和晶格氧的移动性进行了表征和分析,采用常压气-固反应装置考察了不同的铜锰铈摩尔比对催化氧化甲苯性能的影响,并讨论了催化剂晶相组成、氧移动性与催化活性的关系。结果显示,铜锰氧化物复合形成的新相Cu1.4Mn1.6O4是具有更高催化活性的中心,Ce O_2的加入提高了Cu_(1.4)Mn_(1.6)O_4分散度,从而增强了催化剂的氧移动性,提高了催化剂的活性和氧化能力。当Cu/Mn/Ce摩尔比为1:1:4时,催化氧化甲苯的活性最佳,T95%为282.6℃,CO_2选择性为100%。     

晶化温度对Co_3O_4催化分解N_2O的性能影响

以乙酸钴为钴源,采用溶剂辅助水热法制备Co_3O_4复合金属氧化物。利用XRD、SEM、BET、H2-TPR、XPS、N_2OTPSR和O2-N_2O-TPSR等对催化剂的理化性质进行表征,在固定床微型反应器中评价催化剂催化分解N_2O活性,考察了晶化温度对催化剂催化分解N_2O活性的影响。结果表明,溶剂辅助水热法制备的Co_3O_4催化剂具有尖晶石结构,晶化温度影响催化剂形貌、氧化还原性能和催化分解N_2O活性。N_2O-TPSR和O2-N_2O-TPSR测试结果表明,表面吸附氧在Co_3O_4催化分解N_2O中起重要作用。其中,晶化温度为160℃制备的Co_3O_4催化剂氧化还原性能好,催化分解温度低,在反应气体组成(体积分数)为0.68%N_2O、0.88%O2、Ar为平衡气的(流量为80 mL/min)条件下,T10和T95分别为266℃和410℃。     

γ-Al_2O_3负载的Ni_xCo_(1-x)Co_2O_4催化剂N_2O催化分解性能

以K_2CO_3为沉淀剂,γ—Al_2O_3为载体,采用共沉淀法制备了负载质量分数为30%和具有Co_3O_4尖晶石结构的Ni_xCo_(1-x)Co_2O_4复合金属氧化物催化剂(x分别为0、0.1、0.2、0.3、0.4、0.5、0.6、0.7、0.8、0.9和1.0),确定了最适宜的x值。考察了焙烧温度对催化剂的影响,对制备的样品进行了XRD、BET、SEM和H_2-TPR等表征,在微反装置上对催化剂进行N_2O催化分解活性评价。结果表明,适宜的x值为0.5,焙烧温度为800℃。N_2O和O_2浓度是影响催化剂的N_2O催化分解转化率的主要因素,低浓度有利于提高N_2O催化分解转化率。掺杂还原性气体(如CO和NO)加速了N_2O催化分解反应,有利于提高催化剂的N_2O催化分解转化率。在模拟工业装置反应尾气[φ(N_2O)=12%、φ(O_2)=16.8%和其他混合气体]条件下,催化剂N_2O完全催化分解温度为612℃,满足实际工业生产装置运行要求(小于750℃)。     

介孔Co_3O_4/Al_2O_3催化氧化甲醛的性能研究

采用溶胶-凝胶法制备了介孔Al_2O_3载体,采用浸渍法制备了系列介孔Co_3O_4/Al_2O_3催化剂,考察了活性组分Co_3O_4的质量百分含量(2%、8%、16%和32%)对催化氧化甲醛性能的影响。研究表明,当Co_3O_4的质量百分含量为16%时,介孔催化剂16%Co_3O_4/Al_2O_3对甲醛的完全氧化反应具有最佳的催化活性,在80℃可将甲醛完全氧化。BET和H_2-TPR表征揭示,催化剂的比表面积和孔容,促进了催化剂中Co_3O_4的高度分散;催化剂拥有低温还原能力,可以提高催化剂催化氧化甲醛的性能。     

MnCoNiO陶瓷材料制备及其电学特性研究

采用固相反应法制备Mn_1.47Co_(1.095-X)Ni_(0.435+X)O_4(X=0~0.343)热敏陶瓷。利用XRD、SEM以及电性能测试等手段表征了陶瓷相组成、微观结构和材料的电学特性。结果表明:当Ni含量≤0.484(x=0.049)时,陶瓷体为单一尖晶石结构,并且随着Ni含量的增加,衍射峰强度逐渐增强;当Ni含量≥0.533(x=0.098)时,出现Mn_2O_3衍射峰,且随着Ni含量的进一步增加,Mn_2O_3衍射峰强度增强,尖晶石衍射峰强度减弱,陶瓷体为尖晶石和Mn_2O_3混合相。在1150℃到1250℃烧结温度范围内,通过调节Ni元素含量,Mn_1.47Co_(1.095-X)Ni_(0.435+X)O_4陶瓷室温电阻率从1815.3Ω·cm变化到171439Ω·cm。     

ACr_2O_4尖晶石氧化物(A=Co,Zn,Mn,Cu)上二氯甲烷的催化燃烧:A位阳离子的影响

采用溶胶-凝胶法制备4种不同ACr_2O_4尖晶石氧化物(A=Co,Zn,Mn,Cu),考察A位阳离子对ACr_2O_4尖晶石氧化物的性质以及对二氯甲烷催化燃烧性能的影响,并对催化剂进行SEM、HRTEM、H_2-TPR、NH_3-TPD以及XPS等表征。结果表明,A位离子显著影响催化剂的可还原性和表面酸性,催化剂催化活性顺序为CoCr_2O_4Zn Cr_2O_4Mn Cr_2O_4CuCr_2O_4。结合表征结果,认为催化剂活性与其可还原性能和表面酸性存在密切关系。CoCr_2O_4由于具有最佳的可还原性和较高的表面酸性,具有最高的催化活性;而CuCr_2O_4由于具有最低的表面酸性导致其催化活性最低。     

Fe掺杂对La0.9Sr0.1Co1-xFexO3催化剂同时净化NO和碳烟活性规律研究

采用柠檬酸-EDTA络合法制备了纳米钙钛矿催化剂La_0.9Sr_0.1Co_1-xFe_xO₃,催化剂具有较好的同时去除NO和碳烟(soot)催化活性,其中La_0.9Sr_0.1Co_0.7Fe_0.3O₃展现出最佳的催化活性,其在380.0℃时NO转化率为32.5%,soot最大燃烧速率温度(T_m)为368.5℃。H₂-程序升温还原(H₂-TPR)和NO-程序升温脱附(NO-TPD)结果表明, Fe掺杂能显著提高催化剂低温还原性能、表面氧物种活性及NO吸附性能,这有利于其改善催化活性。X射线光电子能谱(XPS)结果表明,Fe掺杂能增加催化剂表面吸附氧浓度和高价离子(Co⁴⁺),这对提高催化氧化能力至关重要。采用颗粒物捕集器(DPF)作为载体涂覆CeO₂涂层用于负载La_0.9Sr_0.1Co_0.7Fe_0.3O₃催化剂进行柴油机台架实验,结果表明该催化剂具有较好的同时去除NO_x和soot催化活性,最大NO转化率为23.0%,T_m为341.0℃,表明Fe掺杂对提高催化活性至关重要。     

Catalytic decomposition of N2O over CeO2 promoted Co3O4 spinel catalyst

A series of CeO₂ promoted cobalt spinel catalysts were prepared by the co-precipitation method and tested for the decomposition of nitrous oxide (N₂O). Addition of CeO₂ to Co₃O₄ led to an improvement in the catalytic activity for N₂O decomposition. The catalyst was most active when the molar ratio of Ce/Co was around 0.05. Complete N₂O conversion could be attained over the CoCe0.05 catalyst below 400 °C even in the presence of O₂, H₂O or NO. Methods of XRD, FE-SEM, BET, XPS, H₂-TPR and O₂-TPD were used to characterize these catalysts. The analytical results indicated that the addition of CeO₂ could increase the surface area of Co₃O₄, and then improve the reduction of Co³⁺ to Co²⁺ by facilitating the desorption of adsorbed oxygen species, which is the rate-determining step of the N₂O decomposition over cobalt spinel catalyst. We conclude that these effects, caused by the addition of CeO₂, are responsible for the enhancement of catalytic activity of Co₃O₄.     

Partial oxidation of methane to synthesis gas over Co/Ca/Al2O3 catalysts

A series of calcium-modified alumina-supported cobalt catalysts were prepared with a two-step impregnation method, and the effect of calcium on the catalytic performances of the catalysts for the partial oxidation of methane to syngas (CO and H₂) was investigated at 750 °C. Also, the catalysts were characterized by XRD, TEM, TPR and (in situ) Raman. At 6 wt.% of cobalt loading, the unmodified alumina-supported cobalt catalyst showed a very low activity and a rapid deactivation, while the calcium-modified catalyst presented a good performance for this process with the CH₄ conversion of 88%, CO selectivity of 94% and undetectable carbon deposition during a long-time running. Characterization results showed that the calcium modification can effectively increase the dispersion and reducibility of Co₃O₄, decrease the Co metal particle size, and suppress the reoxidation of cobalt as well as the phase transformation to form CoAl₂O₄ spinel phases under the reaction conditions. These could be related to the excellent catalytic performances of Co/Ca/Al₂O₃ catalysts.     

Cu-Mn氧化物催化N_2O直接分解性能

分别以Cu(NO_3)_2·3H_2O和50%Mn(NO_3)_2水溶液为铜源和锰源,K_2CO_3为沉淀剂,采用沉淀法和共沉淀法制备单一Cu、Mn氧化物催化剂和Cu-Mn-O复合氧化物催化剂,用于催化N_2O直接分解反应,并利用N_2物理吸附-脱附、XRD、FT-IR和TPR等进行表征。结果表明,单一Cu和Mn氧化物分别以体相CuO和Mn2O_3物相形式存在,Cu-Mn-O复合氧化物中除形成CuMn_2O_4尖晶石物相外,还有一定量小晶粒CuO,较单一氧化物具有更加优异的还原性能,表现出较高的催化N_2O直接分解活性。在空速10 000 h~(-1)和N_2O体积分数0.1%条件下,Cu-Mn-O复合氧化物催化剂可在440℃催化N_2O完全分解,分别较单一Cu和Mn氧化物催化剂降低了40℃和60℃。     

A spillover approach to oxidation catalysis over copper and manganese mixed oxides

The activity of a hopcalite-type catalyst for H₂ and CO oxidation is compared with that of single-phase oxides CuO, Mn₂O₃ and CuMn₂O₄ (spinel) and a mixture of 1:1 CuO and Mn₂O₃ in order to elucidate the effects that are responsible for the high catalytic activity of the former. The reaction rates over the hopcalite catalyst calcined at 550°C (a mixture of CuO, Mn₂O₃ and CuMn₂O₄) are very close to those of the physical mixture of CuO and Mn₂O₃, being much greater than the rates over the single-phase oxides. CuO, Mn₂O₃ and CuMn₂O₄ show a kinetic compensation behavior both in H₂ and CO oxidation. By taking into account the activation energies and the reducibility measured by TPR it was concluded that the oxidation reactions over CuO follow a redox mechanism using lattice oxygen, while over Mn₂O₃ the mechanism is associative involving adsorbed oxygen species. Based on the TPR and kinetic results, the synergy between copper and manganese oxides in hopcalite and in the CuO–Mn₂O₃ mixture is assigned to a spillover effect.     

过渡金属Ni对Pd/Al_2O_3催化剂甲烷催化燃烧性能的影响

考察过渡金属Ni对Pd/Al_2O_3催化剂甲烷催化燃烧活性的影响以及过渡金属负载量及循环条件对甲烷降解性能的影响,采用扫描电镜、N_2吸附-脱附以及H_2程序升温还原技术对催化剂进行表征。结果表明,过渡金属Ni的添加对催化剂在(375~475)℃下的甲烷催化燃烧活性产生影响。催化剂经多次重复使用后,催化燃烧活性提高。分析原因为经过渡金属Ni改性后,可与载体形成NiAl_2O_4尖晶石,促进活性组分形成较小晶粒,并改善活性组分分散度,提高催化剂催化活性。     

Au/LaCo_(1-x)Ce_xO_3催化剂的制备及其对CO催化氧化性能的研究

为进一步提高催化剂活性,用Ce对LaCoO3载体进行改性,并采用溶胶-凝胶法制备系列LaCo1-xCexO3(x=0~0.5)载体。其中,x=0.1和0.2时,载体为钙钛矿结构。采用沉积-沉淀法制备Au/LaCo1-xCexO3(x=0.1、0.2)催化剂,通过XRD、BET和H2-TPR等方法对催化剂进行催化活性评价及稳定性表征测试。结果表明,Au/LaCo0.9Ce0.1O3和Au/LaCo0.8Ce0.2O3催化剂能够在90℃将CO完全转化,在此温度进行的连续20h和30h的寿命实验中,CO转化率保持100%,催化活性和稳定性均优于Au/LaCoO3催化剂。表明掺杂Ce改性载体,能够提高催化剂活性和稳定性。     

Preparation and characterisation of supported La0.8Sr0.2MnO3+x

Three supported La_0.8Sr_0.2MnO_3+x catalysts were prepared, one supported on lanthanum-stabilised alumina and two supported on a NiAl₂O₄ spinel. The catalysts were characterised using X-ray diffraction, transmission electron microscopy and surface area measurements following heat-treatments at temperatures up to 1200°C in air. In the alumina-supported catalyst, a reaction occurred between the active phase and the support at high temperatures, indicating that these materials would be unsuitable for high temperature catalytic combustion. Only in the NiAl₂O₄-supported catalysts were the supported perovskite phases found to be stable at high temperature. These catalysts showed good methane combustion activity.