CeO2-Al2O3复合载体负载Ni基催化剂催化COx共甲烷化性能

通过浸渍沉淀法分别制备Ni/Al₂O₃、Ni/CeO₂和Ni/CeO₂-Al₂O₃催化剂，并对其分别进行不同CO/CO₂比例下COx共甲烷化性能评价。发现Ni/Al₂O₃催化剂催化CO转化为CH4的能力明显高于Ni/CeO₂，而催化CO₂甲烷化的性能则相反。采用Ni/CeO₂-Al₂O₃催化剂，可以在提高CO转化率的同时而不降低CO₂转化率。结合BET、XRD、TPR、TPD和原位红外等各种表征手段，发现CeO₂掺杂虽然降低了催化剂的比表面积和金属Ni的分散度，但却可明显提高其吸附活化CO₂的能力，这主要是由于具有较高含量氧空位的CeO₂的掺杂可以提高载体表面碱性位，促使共甲烷过程中CO_...     

Co3O4-MMT催化剂的制备及其N2O催化分解性能

以MMT为载体，采用原位聚合-配位沉积法制备3种不同Co负载量的Co₃O₄-MMT催化剂。采用N₂物理吸附、XRD和TEM对载体和催化剂进行表征，并在连续流动微反装置上考察其N₂O催化分解性能。结果表明，与Co₃O₄催化剂相比，Co₃O₄-MMT催化剂的比表面积显著增大，且活性组分Co₃O₄具有较高的分散状态。Co₃O₄-MMT催化剂的催化活性随着Co含量的增加先升后降，其中0.015Co-MMT表现出最佳的催化活性，其活性远高于Co₃O₄催化剂，同时，该催化剂还表现出良好的催化稳定性和较好的杂质气体耐受性。     

CeO_2纳米棒负载Co催化CO脱除NO_x的机理

以碱法水热合成径向尺寸6~10nm的CeO_2纳米棒,采用湿法浸渍在纳米棒上负载不同含量的Co氧化物。通过实验探究Co含量改变对脱硝性能的影响原理,实验结果显示浸渍方案为3g CeO_2∶30ml 10%(质量分数)硝酸钴溶液时,脱硝效率最高,在NO与CO摩尔比为1∶5,体积空速为30000h~(-1),无氧状态下,250℃即能达到70%以上的效率。采用氮气吸附、XPS、TEM以及XRD测试不同钴含量催化剂的物化性质,与催化性能结果比对分析后得出Co的添加是通过改变催化剂表面的活性官能团来提高效率,其中Co_2O_3对于催化CO与NO_x进行反应具有较高的效率,提高催化剂中Co_2O_3的比重可以将高效率温度段降低,CoO在一定程度上对CO与NO_x反应具有负面作用,而Co_3O_4对低温阶段N_2O选择性影响较大。     

CeO2改性Ni/γ-Al2O3催化剂上顺酐加氢制备丁二酸酐

采用等体积浸渍法制备CeO₂改性Ni/γ-Al₂O₃催化剂,通过BET、XRD、H₂-TPR和SEM等对催化剂结构及物化性能进行表征,考察Ni-CeO₂/γ-Al₂O₃催化剂对顺酐催化加氢制备丁二酸酐催化性能的影响。结果表明,引入适量CeO₂可提高催化剂活性组分Ni的分散度,增加催化剂比表面积,提高催化剂热稳定性。采用负载CeO₂质量分数5%的Ni-CeO₂/γ-Al₂O₃催化剂,在反应温度120 ℃、反应压力2.0 MPa和空速0.6 h^-1条件下,顺酐转化率为99.5%,丁二酸酐选择性为99.4%。     

CeO2含量对柴油机商用稀土SCR催化剂脱硝性能的影响

考察了不同CeO₂含量对柴油机商用稀土选择性催化还原（SCR）催化剂NH₃-SCR性能的影响。通过X射线衍射、N₂吸附-脱附、X射线光电子能谱、H₂-程序升温还原和NH₃-程序升温脱附等表征手段对催化剂的结构及性能进行了研究。研究发现，CeO₂含量对催化剂的晶体结构没有影响，添加后促进了稀土催化剂表面SiO₂的分散，从而对催化剂的脱硝性能及水热老化性能产生影响；CeO₂含量影响催化剂的织构性质，较大的孔体积和适当的比表面有利于催化剂水热老化后催化剂的脱硝性能的提高；随着CeO₂含量从14%增加到20%，其表面Ce含量呈先降低后升高的趋势，其中Ce⁴⁺含量与催化剂的水热老化后催化剂的脱硝性能成正相关；CeO₂含量的增加会阻碍稀土催化剂中其他组分的还原或增加其热稳定性，从而影响催化剂的还原能力和酸性位数量；通过脱硝性能测试，稀土催化剂中CeO₂的最佳含量为16%。     

V2O5@CeO2核壳微球结构的脱硝催化剂制备及其抗硫性能

利用静电自组装法制备了V₂O₅@CeO₂核壳微球结构,并负载在TiO₂上。考察了分散剂六偏磷酸钠（SHP（对表面zeta电位的影响,采用扫描电镜（SEM（、投射电镜（TEM（观察了核壳结构的形貌,并在固定床上进行了脱硝性能测试,并通过比表面积（BET（、氨气吸附漫反射（in situ DRIFTS（等进行表征。结果表明：SHP使纳米颗粒表面带负电,且一定范围内SHP浓度越高,zeta电位越大;含质量分数1%V₂O₅、5% CeO₂的催化剂,在260~400℃间具有80%以上的脱硝效率,对比了该核壳结构与传统浸渍法制备催化剂的抗硫抗水性,烟气中含15%（体积分数（H₂O,SO₂含量较低时,脱硝性能优于传统浸渍法制备的催化剂。     

Fe2O3对V2O5-WO3/TiO2催化剂表面性质及其性能的影响

催化剂是选择性催化还原(SCR)脱硝技术的核心,研究Fe对钒钛系SCR催化剂脱硝活性及SO₂/SO₃转化率的影响具有重要意义。采用等体积浸渍法制备了不同Fe/V质量比的Fe₂O₃-V₂O₅-WO₃/TiO₂催化剂,并进行表征,研究Fe对钒钛系SCR催化剂脱硝活性及SO₂/SO₃转化率的影响,并讨论Fe对于钒钛系SCR催化剂表面性质的影响。结果表明,随着催化剂表面Fe₂O₃含量增加,催化剂的脱硝效率及二氧化硫氧化率均是先上升后下降,当Fe/V质量比为3.0时,催化剂的脱硝效率和二氧化硫氧化率均达到最大值91.78%、1.01%。XPS及H₂-TPR结果表明,随着Fe₂O₃含量增加,催化剂表面钒活性组分的相对含量及V⁴⁺/V⁵⁺比减小,催化剂表面吸附氧(O_α)浓度增加,催化剂的氧化能力增强。NO-TPD结果表明,随着Fe₂O₃含量增加,催化剂表面吸附NO的能力增强。     

WO3改性Cu/CeO2催化剂选择性催化氧化乙二胺的性能研究

以CeO₂为载体、Cu物种为主要活性位点,采用浸渍法制备了一系列WO₃改性Cu/CeO₂催化剂。研究了WO₃质量分数对乙二胺(EDA)选择性催化氧化(SCO)性能的影响,并通过XRD、XPS、H₂-TPR、NH₃-TPD等方法对催化剂的物理化学性质进行了分析表征。结果表明,WO₃改性的Cu/CeO₂催化剂的N₂选择性大幅提高,其中Cu/5W/CeO₂在337℃时对EDA实现了100%的转化率,该温度条件下NO_x的浓度大幅降低,同时具有较好的活性和选择性。表征结果表明,WO₃的引入显著提高了催化剂的酸性位点数量,促进了对反应副产物NO_x的催化还原,提高了反应的N₂选择性。     

Co3O4催化臭氧氧化降解水中酮基布洛芬的研究

以Co(NO₃)₂·6H₂O和尿素为原料制备了9种Co₃O₄催化材料，考察了其对水中酮基布洛芬(KTP)的催化臭氧氧化降解效能。结果表明，与单独臭氧氧化相比，所制备的Co₃O₄对水中KTP的催化臭氧氧化降解率提高了12.0%～63.8%，且在n[Co(NO₃)₂·6H₂O]:n(尿素)=4:1、煅烧温度400℃下制备得到的Co₃O₄催化剂催化活性最高。SEM、XRD、FTIR、XPS、BET等表征分析显示，该Co₃O₄催化剂表面呈覆盖细小微粒的球状颗粒，晶相为立方相，且表面含有丰富的羟基，表面羟基密度为1.075×10^-5 mol/m²。机理研究证实，Co₃O₄对水中KTP的非均相催化臭氧氧化降解...     

过渡金属改性Ce-M-Ox(M=Cu,Co, Mn和Fe)催化剂在NH3-SCR反应研究

采用共沉淀法制备了CeO₂上负载不同过渡金属元素Ce-M(M=Fe、Mn、Cu、Co)催化剂,研究了不同金属负载对CeO₂基催化剂脱硝活性影响。CeO₂催化剂中加入适量的过渡金属可降低催化剂结晶度,提高催化剂的氧化还原性和表面酸性,从而影响催化剂在NH₃-SCR中的催化性能。Ce-Fe、Ce-Mn催化剂中Fe³⁺和Mn³⁺的大量存在可提高催化剂的Lewis和Br?nsted酸性位点,提升催化剂对NH₃的吸附与活化性能,从而提升其催化性能。Ce-Mn催化剂具有优越的低温活性,Ce-Fe展现了较好的中高温活性,这与其催化剂的表面酸性密切相关。     

Catalytic performance of Co3O4/CeO2 and Co3O4/CeO2–ZrO2 composite oxides for methane combustion: Influence of catalyst pretreatment temperature and oxygen concentration in the reaction mixture

The influence of catalyst pre-treatment temperature (650 and 750 °C) and oxygen concentration (λ = 8 and 1) on the light-off temperature of methane combustion has been investigated over two composite oxides, Co₃O₄/CeO₂ and Co₃O₄/CeO₂–ZrO₂ containing 30 wt.% of Co₃O₄. The catalytic materials prepared by the co-precipitation method were calcined at 650 °C for 5 h (fresh samples); a portion of them was further treated at 750 °C for 7 h, in a furnace in static air (aged samples).

Tests of methane combustion were carried out on fresh and aged catalysts at two different WHSV values (12 000 and 60 000 mL g⁻¹ h⁻¹). The catalytic performance of Co₃O₄/CeO₂ and Co₃O₄/CeO₂–ZrO₂ were compared with those of two pure Co₃O₄ oxides, a sample obtained by the precipitation method and a commercial reference. Characterization studies by X-ray diffraction (XRD), BET and temperature-programmed reduction (TPR) show that the catalytic activity is related to the dispersion of crystalline phases, Co₃O₄/CeO₂ and Co₃O₄/CeO₂–ZrO₂ as well as to their reducibility. Particular attention was paid to the thermal stability of the Co₃O₄ phase in the temperature range of 750–800 °C, in both static (in a furnace) and dynamic conditions (continuous flow). The results indicate that the thermal stability of the phase Co₃O₄ heated up to 800 °C depends on the size of the cobalt oxide crystallites (fresh or aged samples) and on the oxygen content (excess λ = 8, stoichiometric λ = 1) in the reaction mixture. A stabilizing effect due to the presence of ceria or ceria–zirconia against Co₃O₄ decomposition into CoO was observed.

Moreover, the role of ceria and ceria–zirconia is to maintain a good combustion activity of the cobalt composite oxides by dispersing the active phase Co₃O₄ and by promoting the reduction at low temperature.     

Co3O4/CeO2 composite oxides for methane emissions abatement: Relationship between Co3O4–CeO2 interaction and catalytic activity

Co₃O₄/CeO₂ composite oxides with different cobalt loading (5, 15, 30, 50, 70 wt.% as Co₃O₄) were prepared by co-precipitation method and investigated for the oxidation of methane under stoichiometric conditions. Pure oxides, Co₃O₄ and CeO₂ were used as reference. Characterization studies by X-ray diffraction (XRD), BET, temperature programmed reduction/oxidation (TPR/TPO) and X-ray photoelectron spectroscopy (XPS) were carried out.

An improvement of the catalytic activity and thermal stability of the composite oxides was observed with respect to pure Co₃O₄ in correspondence of Co₃O₄–CeO₂ containing 30% by weight of Co₃O₄. The combined effect of cobalt oxide and ceria, at this composition, strongly influences the morphological and redox properties of the composite oxides, by dispersing the Co₃O₄ phase and promoting the efficiency of the Co³⁺–Co²⁺ redox couple. The presence in the sample Co₃O₄(30 wt.%)–CeO₂ of a high relative amount of Ce³⁺/(Ce⁴⁺ + Ce³⁺) as detected by XPS confirms the enhanced oxygen mobility.

The catalysts stability under reaction conditions was investigated by XRD and XPS analysis of the used samples, paying particular attention to the Co₃O₄ phase decomposition. Methane oxidation tests were performed over fresh (as prepared) and thermal aged samples (after ageing at 750 °C for 7 h, in furnace). The resistance to water vapour poisoning was evaluated for pure Co₃O₄ and Co₃O₄(30 wt.%)–CeO₂, performing the tests in the presence of 5 vol.% H₂O. A methane oxidation test upon hydrothermal ageing (flowing at 600 °C for 16 h a mixture 5 vol.% H₂O + 5 vol.%O₂ in He) of the Co₃O₄(30 wt.%)–CeO₂ sample was also performed. All the results confirm the superiority of this composite oxide.     

Steam reforming of ethanol over Co3O4/CeO2 catalysts prepared by different methods

In this paper, Co₃O₄/CeO₂ catalysts for steam reforming of ethanol (SRE) were prepared by co-precipitation and impregnation methods. The catalysts prepared by co-precipitation were very active and selective for SRE. Over 10%Co₃O₄/CeO₂ catalyst, ethanol conversion was close to 100% and hydrogen selectivity was about 70% at 450 °C. The catalysts were characterized by X-ray diffraction, temperature-programmed reduction (TPR) and BET surface area measurements. The preparation method influenced the interaction between cobalt and CeO₂ evidently. The incorporation of Co ions into CeO₂ crystal lattice resulted in weaker interaction between cobalt and ceria on catalyst surface. In comparison with catalysts prepared by impregnation, more cobalt ions entered into CeO₂ lattice, and resulted in weaker interaction between active phase and ceria on surface of Co₃O₄/CeO₂ prepared by co-precipitation. Thus, cobalt oxides was easier to be reduced to metal cobalt which was the key active component for SRE. Meanwhile, the incorporation of Co ions into CeO₂ crystal lattice was beneficial for resistance to carbon deposition.     

Direct decomposition of nitric oxide over Ba catalysts supported on CeO2-based mixed oxides

The direct decomposition of nitric oxide (NO) over barium catalysts supported on various metal oxides was examined in the absence and presence of O₂. Among the Ba catalysts supported on single-component metal oxides, Ba/Co₃O₄ and Ba/CeO₂ showed high NO decomposition activities, while Ba/Al₂O₃, Ba/SiO₂, and Ba/TiO₂ exhibited quite low activities. The effect of an addition of second components to Co and Ce oxides was further examined, and it was found that the activities were significantly enhanced using Ce–Mn mixed oxides as support materials. XRD results indicated the formation of CeO₂–MnO_x solid solutions with the cubic fluorite structure. O₂-TPD of the CeO₂–MnO_x solid solutions showed a large desorption peak in a range of relatively low temperature. The BET surface areas of the CeO₂–MnO_x solid solutions were larger than those of pure CeO₂ and Mn₂O₃. These effects caused by the addition of Mn are responsible for the enhanced activities of the Ba catalysts supported on Ce–Mn mixed oxides.     

Promotion effect of residual K on the decomposition of N2O over cobalt–cerium mixed oxide catalyst

A series of cobalt–cerium mixed oxide catalysts (Co₃O₄–CeO₂) with a Ce/Co molar ratio of 0.05 were prepared by co-precipitation (with K₂CO₃ and KOH as the respective precipitant), impregnation, citrate, and direct evaporation methods and then tested for the catalytic decomposition of N₂O. XRD, BET, XPS, O₂-TPD and H₂-TPR methods were used to characterize the catalysts. Catalysts with a trace amount of residual K exhibited higher catalytic activities than those without. The presence of appropriate amount of K in Co₃O₄–CeO₂ may improve the redox property of Co₃O₄, which is important for the decomposition of N₂O. When the amount of K was constant, the surface area became the most important factor for the reaction. The co-precipitation-prepared catalyst with K₂CO₃ as precipitant exhibited the best catalytic performance because of the presence of ca. 2 mol% residual K and the high surface area. We also discussed the rate-determining step of the N₂O decomposition reaction over these Co₃O₄–CeO₂ catalysts.     

Ultrasound-assisted co-precipitation synthesis of mesoporous Co3O4–CeO2 composite oxides for highly selective catalytic oxidation of cyclohexane

The one-step highly selective oxidation of cyclohexane into cyclohexanone and cyclohexanol as the essential intermediates of nylon-6 and nylon-66 is considerably challenging. Therefore, an efficient and low-cost catalyst must be urgently developed to improve the efficiency of this process. In this study, a Co₃O₄–CeO₂ composite oxide catalyst was successfully prepared through ultrasound-assisted co-precipitation. This catalyst exhibited a higher selectivity to KA-oil, which was benefited from the synergistic effects between Co³⁺/Co²⁺ and Ce⁴⁺/Ce³⁺ redox pairs, than bulk CeO₂ and/or Co₃O₄. Under the optimum reaction conditions, 89.6% selectivity to KA-oil with a cyclohexane conversion of 5.8% was achieved over Co₃O₄–CeO₂. Its catalytic performance remained unchanged after five runs. Using the synergistic effects between the redox pairs of different transition metals, this study provides a feasible strategy to design high-performance catalysts for the selective oxidation of alkanes.     

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.     

Influence of metal oxides on the catalytic behavior of Au/Al2O3 for the selective reduction of NOx by hydrocarbons

The reduction of NO by propene in the presence of excess oxygen over mechanical mixtures of Au/Al₂O₃ with a bulk oxide has been investigated. The oxides studied were: Co₃O₄, Mn₂O₃, Cr₂O₃, CuO, Fe₂O₃, NiO, CeO₂, SnO₂, ZnO and V₂O₅. Under lean C₃H₆-SCR conditions, these oxides (with the exception of SnO₂) convert selectively NO to NO₂. When mechanically mixed with Au/Al₂O₃, the Mn₂O₃ and Co₃O₄ oxides and, to a much greater extent, CeO₂ act synergistically with this catalyst greatly enhancing its SCR performance. It was found that their synergistic action is not straightforwardly related to their activity for NO oxidation to NO₂. The exhibited catalytic synergy may be due to the operation of either remote control or a bifunctional mechanism. In the later case, the key intermediate must be a short-lived compound and not the NO₂ molecule in gas-phase.     

Development of Ni catalysts for tar removal by steam gasification of biomass

Catalytic performance of Ni/CeO₂/Al₂O₃ catalysts prepared by a co-impregnation and a sequential impregnation method in steam gasification of real biomass (cedar wood) was investigated. Especially, Ni/CeO₂/Al₂O₃ catalysts prepared by the co-impregnation method exhibited higher performance than Ni/Al₂O₃ and Ni/CeO₂/Al₂O₃ prepared by the sequential impregnation method, and the catalysts gave lower yields of coke and tar, and higher yields of gaseous products. The Ni/CeO₂/Al₂O₃ catalysts were characterized by thermogravimetric analysis, temperature-programmed reduction with H₂, transmission electron microscopy and extended X-ray absorption fine structure, and the results suggested that the interaction between Ni and CeO₂ became stronger by the co-impregnation method than that by sequential method. Judging from both results of catalytic performance and catalyst characterization, it is found that the intimate interaction between Ni and CeO₂ can play very important role on the steam gasification of biomass.     

Co3O4 based catalysts for NO oxidation and NOx reduction in fast SCR process

Reaction activities of several developed catalysts for NO oxidation and NO_x (NO + NO₂) reduction have been determined in a fixed bed differential reactor. Among all the catalysts tested, Co₃O₄ based catalysts are the most active ones for both NO oxidation and NO_x reduction reactions even at high space velocity (SV) and low temperature in the fast selective catalytic reduction (SCR) process. Over Co₃O₄ catalyst, the effects of calcination temperatures, SO₂ concentration, optimum SV for 50% conversion of NO to NO₂ were determined. Also, Co₃O₄ based catalysts (Co₃O₄-WO₃) exhibit significantly higher conversion than all the developed DeNO_x catalysts (supported/unsupported) having maximum conversion of NO_x even at lower temperature and higher SV since the mixed oxide Co-W nanocomposite is formed. In case of the fast SCR, N₂O formation over Co₃O₄-WO₃ catalyst is far less than that over the other catalysts but the standard SCR produces high concentration of N₂O over all the catalysts. The effect of SO₂ concentration on NO_x reduction is found to be almost negligible may be due to the presence of WO₃ that resists SO₂ oxidation.