Catalytic Partial Oxidation of Methane over Ni/CeO2-ZrO2-Al2O3

Nickel catalysts supported on CeO2-ZrO2-CeO2,ZrO2-Al2O3 and Al2O3 were prepared and characterized by means of X-ray diffraction（XRD）,BET areas,H2 temperature-programmed reduction（H2-TPR）,and X-ray photoelectron spectroscopy（XPS）.Through the test of catalytic partial oxidation of methane（CPOM）,Ni/CeO2-ZrO2-Al2O3 displayed the highest activity,which resulted from its largest BET area and best NiO dispersion.Furthermore,Ni/CeO2-ZrO2-Al2O3 maintained a long-time stability in CPOM,which was attributed to its best coking resistance among all the prepared catalysts.     

Promotional effect of CeO2 and Y2O3 on CuO/ZrO2 catalysts for methane combustion

Catalytic combustion of methane was conducted by using a Cu-based catalyst prepared by the plasma-assisted impregnation method. The properties of the catalysts were surveyed by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and temperature-programmed reduction (H2-TPR). The results showed that the activity of CuO/ZrO2 with the CeO2 and Y2O3 was obviously increased compared with the CuO/ZrO2 catalyst, which was examined in relation to the structure and surface characteristics and might be correlated with their surface oxygen species and redox properties. Among the investigated catalysts, the Ce-CuO/ZrO2 sample exhibited the highest activity for methane combustion.     

Effect of Fe2O3 Loading Amount on Catalytic Properties of Monolithic Fe2O3/Ce0.67Zr0.33O2 -Al2O3 Catalyst for Methane Combustion

Ce0.67Zr0.33O2-Al2O3 solid solution was prepared by the co-precipitation method. Fe2O3-based catalysts supported on the solid solution were obtained by the impregnation method. The article revealed that the optimal loading amount of Fe2O3 on Ce0.67Zr0.33 O2-Al2O3 in our experimental condition for catalytic combustion of methane was 8% （ mass fraction）. The prepared catalysts were characterized by BET, TPR, XRD analyses, and their catalytic activity was investigated after being calcined at 873 K and after being aged in water gas at 1273 K. When the loading amount of Fe203 was 8% （ mass fraction）, the catalyst held the highest activity, and the best temperature speciality and thermal stability. The complete-conversion temperature of methane for fresh and aged sample was 788 and 838 K, respectively. The range between the light-off temperature and the complete-conversion temperature was only 15 K. The characterization results of XRD indicated that Fe2O3 was well dispersed on the Ce0.67Zr0.33O2-Al2O3 matrix. The results of BET and TPR were in good harmony with the catalytic activity results.     

La_2O_3掺杂对V_2O_5-WO_3/TiO_2催化剂SCR性能的影响

通过共沉淀法将La组分掺入到TiO_2载体中,采用浸渍法将V和W组分负载到La_2O_3-TiO_2复合氧化物上,制备出V2O5-WO3/La_2O_3-TiO_2催化剂。考察不同La_2O_3掺杂量对其NH3催化还原NO性能的影响,同时通过多种物理化学手段进行表征分析。XRD,NH_3-in situ DRIFTS,H_2-TPR,XPS和UV-vis DRS测试结果表明,元素La与Ti以La-O-Ti键相互作用,生成高度分散的镧物种,也使得TiO_2具有更好的热稳定性,但由于LaO_x物种与VO_x物种和WO_x物种之间的相互作用,降低了催化剂的氧化还原性和表面Brnsted酸数量,从而降低了其催化活性。     

新型CeO2-Fe2O3联合催化剂用于催化CO还原NO

采用3种不同的方法合成新型的以Fe₂O₃颗粒为载体的Ce-Fe复合氧化物催化剂,探究不同制备方式的复合氧化物催化剂的催化CO还原NO性能,并通过X射线衍射(XRD)、拉曼光谱(Raman)、氢气-程序升温还原(H2-TPR)、X射线光电子能谱(XPS)表征来对催化剂进行探究。结果证明Ce-Fe复合氧化物具有较高的催化活性,硝酸水热法Ce-Fe复合氧化物在900℃时脱硝率可达到99%以上。XRD中显示硝酸水热样品中CeO₂峰向高角度偏移,并且晶格常数变小。Raman结果说明硝酸水热样品CeO₂的振动峰向左大幅度偏移,结合XRD说明硝酸水热法可以形成Ce-O-Fe固溶体。H2-TPR说明氧化还原性:硝酸水热法>硝酸浸渍法>普通浸渍法。XPS结果说明硝酸水热法形成的Ce-O-Fe固溶体可以促进Fe³⁺向Fe²⁺、晶格氧向吸附氧的转换,这体现出复合催化剂Ce、Fe之间的联合作用。在整个反应过程中Fe₂O₃作为载体可以提供大量晶格氧,Ce-O-Fe固溶体的存在决定了复合催化剂的高催化活性。     

Ni/Y_2O3-Al2O3 catalysts for hydrogen production from steam reforming of ethanol at low temperature

Y2O3-Al2O3 with different mole ratios of Y:Al were prepared by co-precipitation method. Catalysts Ni/Y2O3, Ni/Al2O3 and Ni/ Y2O3-Al2O3 were prepared by impregnation method. The result of BET showed that Al2O3 with relative high surface area was in favor of Ni distribution, whilst the TPR test demonstrated that composite support had appropriate synergistic effect between active constituent and sup-port, and NiO could be reduced more easily than loaded on the single support. H2-TPD test indicated that the catalyst NYA11 had lots of ac-tivity sites where H could be desorbed easily, which led to hydrogen-rich production over the catalyst. Composite support catalysts exhibited high activity for ethanol steam reforming (SRE), and the supported catalyst with composite of 1:1 mole ratio of Y:Al exhibited the optimum catalytic properties for SRE. Ethanol could be completely converted over catalyst NYA11 even at 450 °C, and there had no inactivation after 60 h continuous reaction, hydrogen yield appeared maximum 35.9% at 400 °C, and tended to increase with increasing H2O/EtOH molar ratio and feed flow rate.     

Effect of cobalt doping on ceria-zirconia mixed oxide： Structural characteristics, oxygen storage/release capacity and three-way catalytic performance

The effect of Co doping on ceria-zirconia mixed oxides was investigated for Co 0.1 Ce 0.6 Zr 0.3 O x sample prepared by sol-gel method. The Pd-only three-way catalyst (TWC) was obtained by incipient wetness impregnation with 0.5 wt.% Pd loading. The structural and oxygen handling properties were analyzed by X-ray diffraction (XRD), H 2 -temperature programmed reduction (H 2 -TPR) and the dynamic oxygen storage capacity (DOSC). The introduction of Co into ceria-zirconia lattice strongly modified the mobility of oxygen and enhanced the DOSC performance. Pd-only TWC based on the Co 0.1 Ce 0.6 Zr 0.3 O x support exhibited superior activity for water-gas shift and steam reforming and amplified amplitude of stoichiometric window.     

固体超强酸S_2O_8~(2-)/TiO_2-WO_3的制备及其催化性能研究

用溶胶-凝胶法制备了固体超强酸S2O82-/TiO2-WO3,并对其进行了XRD与IR表征,用乙酸乙酯合成模型反应考察了其催化性能,系统研究了WO3的含量、焙烧温度等制备条件对S2O82-/TiO2-WO3性能的影响。实验表明:在(NH4)10W12O41.xH2O质量分数为5.0%、焙烧温度为500℃条件下通过溶胶-凝胶法制备的固体超强酸S2O82-/TiO2-WO3,其载体为微细且晶格不太完整的锐钛矿型TiO2,比表面积较大,具有比浸渍法制备的SO42-/TiO2更高的硫含量和更强酸性,并具有较高的催化酯化活性和稳定性,在反应条件为:醇酸摩尔比1.48∶1、催化剂用量为冰醋酸的6.0%、反应时间2.0h,乙酸转化率可达74.1%(不加分水器)。催化剂在无需任何再生的条件下重复使用,活性下降趋势平缓,显示良好的稳定性。     

Steam effects over Pd/Ce0.67Zr0.33O2-Al2O3 three-way catalyst

Ceria-zirconia-alumina (CZA) solid solution was prepared by sol-gel method in the present study. 0.5 wt.% Pd supported on CZA was prepared by incipient wetness impregnation. The steam effects for CO and C3H8 oxidation, three-way catalytic activity and stoichiometric window property were studied. The light-off temperature of the CO oxidation reaction shifted to a lower temperature due to the water-gas shift (WGS) reactions. The oxidation of C3H8 was enhanced due to the steam reforming (SR) reactions. The steam promoted the C3H8 oxidation and NO reduction in three-way catalytic reaction. The amplitude of stoichiometric window was amplified by the addition of water to the feed stream.     

Influence of V2O5 Addition on Reduction of NO by C3H6 over Pt/V2O5/Al2O3 Monolithic Catalyst

Pt/V2O5/Al2O3 and Pt/Al2O3 monolithic catalysts were prepared by wet impregnation method, and the influence of V2 O5 addition on the catalytic activity for NO reduction by C3 H6 under lean burn condition was investigated in detail.The results show that Pt/V2O5/Al2O3 has better activity of NO reduction than Pt/Al2O3 , adding V2O5 to Pt catalyst makes the temperature window of NO reduction shift further to a lower temperature region.The activity of NO reduction decreases and there is a similar degree of deactivation over the two catalysts in the presence of SO2 in feed gas.Moreover, adding V2 O5 to Pt catalyst resulted in improvement of resistance to SO2 oxidation, which decreases the emission of sulfate particulate.Thermal aging treatment counteractes the promoting effect of V2O5 on NO reduction.     

CuO/γ-Al2O3催化剂制备、表征及其催化湿式氧化含氰废水活性研究

采用浸渍法制备了用于催化湿式氧化工艺的负载型CuO/γ-Al2O3催化剂,采用XRD、FT-IR、SEM对其进行了表征,并以CN-为目标污染物,考察了CuO/γ-Al2O3催化剂的催化活性和稳定性。试验研究表明：催化剂中的活性组分Cu是以CuO的形式存在,并且成功负载于载体γ-Al2O3;对于初始质量浓度为2 000 mg/L的含氰废水,反应温度为130℃,搅拌速度为600 r/min,pH值为8,催化剂投加量为0.5 g/L,氧化剂30%H2O2用量为5 mL/L废水时,反应时间30 min,CN-去除率可达到99%以上;重复使用30次后,催化活性大幅度降低。     

Nd3+-TiO2催化剂的制备及对合成甲醇的影响

用等体积浸渍法和溶胶凝胶法制备了两种Nd3+-TiO2催化剂,并用X射线衍射、透射电镜和紫外可见吸收光谱等技术表征了催化剂的形貌、结构及吸光性能,对比研究了两种Nd3+-TiO2催化剂对二氧化碳和水合成甲醇反应体系的催化活性,探索了最佳的Nd掺杂量、体系反应温度、二氧化碳压力、光照时间。试验表明,尽管两种合成方法所得的催化剂最佳的Nd掺杂量相差不大,但用溶胶凝胶法制备的Nd3+-TiO2催化剂平均粒径更小,分布均匀,对目的反应的催化效果更好。     

Growth and interface of amorphous La2Hf2O7/Si thin film

Amorphous La2Hf2O7 thin films were deposited on Si(100) substrate by pulsed laser deposition (PLD) method under different con-ditions. The interfacial states of the La2Hf2O7/Si films were studied by synchrotron X-ray reflectivity (XRR) and X-ray photoelectron spec-troscopy (XPS). When grown under vacuum condition, silicate, silicide and few SiOx were formed in the interface layer. However, the Hf-silicide formation could be effectively eliminated by the ambient oxygen pressure during film growth. The result revealed that the La2Hf2O7/Si interlayer was intimately related with growth condition. Insufficient supply of oxygen would cause Hf-silicide formation at the interface and it could be most effectively controlled by the ambient oxygen pressure during film growth.     

O2/N2与O2/CO2气氛下Fe2O3与K2CO3对无烟煤催化燃烧反应性的影响

利用综合热分析仪研究了O2/N2与O2/CO2气氛下Fe2O3与K2CO3对无烟煤催化燃烧反应性的影响。结果表明,在O2/CO2气氛下,Fe2O3与K2CO3均可以催化无烟煤粉的燃烧,但其催化作用要弱于O2/N2气氛,且在低氧气浓度的O2/CO2气氛下对Fe2O3与K2CO3的抑制作用大于高氧气浓度。氧气浓度为20%~80%时,K2CO3在O2/N2气氛下催化煤粉前期燃烧使燃烧由反应控制转变为扩散控制,Fe2O3则只在氧气浓度为20%时能改变煤粉前期燃烧的控制步骤;而Fe2O3与K2CO3在O2/CO2气氛下均只能在氧气浓度为20%时改变煤粉前期燃烧的控制步骤,由反应控制转变为扩散控制。     

Effect of praseodymium additive on CeO_2(ZrO_2)/TiO_2 for selective catalytic reduction of NO by NH_3

A series of praseodymium added CeO_2(ZrO_2)/TiO_2 catalysts separately prepared by methods of sol-gel and impregnation were tested for selective catalytic reduction of NO, and characterized by X-ray diffraction(XRD), N_2-brumauer-emmett-teller(N_2-BET), NH_3-temperature programmed desorption(NH_3-TPD), H_2-temperature programmed reduction(H_2-TPR), PL spectra, Raman spectra, electron paramagnetic resonance(EPR) and X-ray photoelectron spectroscopy(XPS), respectively. Influence of preparation method on catalytic performance was studied. Results showed that the influence of Pr addition on catalytic performance of the CeO_2(ZrO_2)/TiO_2 catalysts was different between the sol-gel method and the impregnation method. The Pr addition tended to interact with TiO_2 and formed the structure of Ti-O-Pr in the sol-gel method while it was more likely to interact with CeO_2 forming the structure of Ce-O-Pr in the impregnation method. The total acid amount and redox properties of the catalysts prepared by sol-gel method decreased with the addition of Pr element, which resulted in decrease of catalytic activity. In contrast, the Pr-added catalyst prepared by impregnation method was found to possess easier reducibility, more total acid amount and higher proportion of Ce~(3+) species, which was favourable for higher catalytic activity.     

Effects of La_2O_3 contents on the Pd/Ce_（0.8）Zr_（0.2）O_2-La_2O_3 catalysts for methanol decomposition

The catalytic behaviors of Pd (1.4 wt.%) catalysts supported on CeO2-ZrO2 promoted with La2O3 were investigated for methanol decomposition. The measurements of inductively coupled plasma emission spectroscopy (ICP), N2 adsorption-desorption (BET), powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), temperature-programmed reduction (TPR) and oxygen storage capacity (OSC) were used to characterize the properties of catalysts. The catalysts' activities were tested in a fixed bed continuous ...     

Modification of Cu/ZSM-5 catalyst with CeO_2 for selective catalytic reduction of NO_x with ammonia

Cu/ZSM-5 and CeO_2-modified Cu/ZSM-5 catalysts were prepared by a wetness impregnation method. The addition of CeO_2 was found to enhance the NO_x selective catalytic reduction(SCR) activity of the catalyst at low temperatures, but the high-temperature activity was weakened. The catalysts were characterized by X-ray diffraction(XRD), nitrogen physisorption, inductively coupled plasma optical emission spectrometry(ICP-OES), X-ray photoelectron spectroscopy(XPS), electron paramagnetic resonance(EPR), H_2 temperature-programmed reduction(TPR) and NH_3 temperature-programmed desorption(TPD). The results showed that more CuO clusters instead of isolated Cu~(2+) species were obtained on the modified catalyst. These active CuO clusters, as well as the Cu-Ce synergistic effect, improved the redox property of the catalyst and low-temperatures SCR activity via promoting the oxidation of NO to NO_2 and fast SCR reaction. The loss in high-temperatures activity was attributed to the enhanced competitive oxidation of NH_3 by O_2 and decreased surface acidity of the catalyst.     

掺钕氧化钪激光透明陶瓷纳米粉体的合成及研究

研究了化学共沉淀法合成Nd:Sc2O3纳米粉的工艺.以Sc2O3为基质材料,掺杂0.5％(原子分数)的Nd3+,添加适量聚乙二醇(PEG)和(NH4)2SO,作为分散剂,以氨水(NH3·H2O)和碳酸氢铵(NH4HCO3)混合溶液作复合沉淀剂,采用化学共沉淀法获得了碱式稀土碳酸盐前躯体,在1100℃下煅烧该前躯体4h,制备出性能良好的Nd:Sc2O3纳米粉.采用热重-差热分析仪(TG/DSC)、红外光谱分析仪(IR)、X射线衍射仪(XRD)、透射电子显微镜(TEM)等测试手段对Nd:Sc2O3前躯体和煅烧后的粉体进行表征.实验结果表明:在室温下,用氨水和碳酸氧铵混合溶液作为复合沉淀剂合成出的前躯体为碱式稀土碳酸盐.通过XRD和EDS能谱分析,Nd3+完全固溶于Sc2O3的立方晶格中,这将有利于制备激光透明陶瓷.在1100℃的温度下煅烧此前躯体得到的Nd:Sc2O3纳米粉具有颗粒粒度小(约50 nm)、分散性好、团聚程度轻、结晶良好的性能.因此,采用此工艺合成的粉体将有可能制备出的Nd:Sc2O3透明陶瓷.     

Structure and oxygen storage capacity of Pd/Pr/CeO_2-ZrO_2 catalyst:effects of impregnated praseodymia

Praseodymium(Pr) was impregnated to CeO2-ZrO2 solid solution by an impregnation method.The as-obtained Pr modified CeO2-ZrO2 was impregnated with 1 wt.% Pd to prepare the catalysts.The structure and reducibility of the fresh and hydrothermally aged catalysts were characterized by X-ray diffraction(XRD),Raman,X-ray photoelectron spectroscopy(XPS),CO chemisorption and H2 temperature-programmed reduction(H2-TPR).The oxygen storage capacity(OSC) was evaluated with CO serving as probe gas.Effects of impregnated Pr on the structure and oxygen storage capacity of catalysts were investigated.The results showed that the aged Pr-impregnated samples had much higher OSC and better reducibility than the unmodified ones.The scheme of structural evolutions of the catalysts with and without Pr was also established.Partial of the impregnated Pr diffused into the bulk of CeO2-ZrO2 during ageing,which inhibited the sintering,and increased the amount of oxygen vacancies in CeO2-ZrO2 support.Furthermore,those impregnated Pr species which covered on the surface of the support obstructed the strong metal-support interaction between Pd and Ce so as to reduce the encapsulation of Pd as well as the back spill-over of the oxygen during the catalytic process.     

不同晶相MnO2催化剂的NH3-SCO反应性能

以柴油车尾气净化过程中氨逃逸的治理为背景,采用水热合成法制备了不同晶相(α-,β-和δ-)MnO₂、并考察晶相结构对低温氨气选择性催化氧化(NH₃-SCO)反应性能的影响;并运用多种手段,如X射线衍射(XRD)、扫描电子显微镜(SEM)、氮气低温吸-脱附、X射线光电子能谱(XPS)、氢气程序升温还原(H2-TPR)、氧气程序升温脱附(O₂-TPD)、氨气程序升温脱附(NH₃-TPD)等对催化剂的组织结构、化学状态和氧化还原性能进行表征。研究结果发现MnO₂的晶相结构和隧道结构与氨气选择性催化氧化反应性能密切相关。具有独特的[2×2]隧道结构的α-MnO₂具有最佳的反应性能,NH3可在175℃实现全转化且N₂选择性为94%,其在120℃时的反应速率是具有层状结构δ-MnO₂的12倍。α-MnO₂表面具有较高的Mn³⁺/Mn⁴⁺比有利于催化剂氧化还原性能的提高和对氧的活化,丰富的酸中心和酸量有助于对NH3吸附和活化;二者的共同作用使得该催化剂具有良好的反应性能。