NF_3 decomposition over Al_2O_3 reagents without water

Several Al2O3 samples were prepared by a precipitation method coupled with ultrasonic treatment,and NF3 decomposition without water over Al2O3 reagents is carried out.The effect of preparation parameters of Al2O3 reagents,such as precipitating agents,structure directing agents,and calcining temperatures on their reactivity for NF3 decomposition has been investigated.The results show that NF3 can be decomposed completely at 400-C,and full conversion of NF3 maintains 580 min over the best Al2O3 reagent,calcined at 600-C which was prepared using both PEG-2000 and Tween-60 as structure directing agents,ammonia as a precipitating agent.     

Effective modification of MgO with surface transition metal oxides for NF3 decomposition

NF3 decomposition over transition metal oxides coated MgO reagents in the absence of water is investigated. The results show that NF3 can be decomposed completely over pure MgO but the time of NF3 steady full conversion kept as short as 80 min, while the reactivities of coated MgO reagents were remarkably enhanced by transition metal oxides, for example the time of NF3 complete conversion over 12%Fe/MgO extended to 380 min. It is suggested that not only an increase in surface area but also a significant enhancement in the fluorination of MgO substrate caused by the surface transition metal oxides result in an improved reactivity of coated MgO reagents for NF3 decomposition.     

NF/rGO/Co_3O_4/NiO电极的制备及在超级电容器中的应用

以泡沫镍(NF)为集流体,在优化好的电位、时间和浓度下,将还原氧化石墨烯(rGO)、金属氧化物(Co_3O_4和NiO)直接生长在泡沫镍上,制备了NF/rGO/Co_3O_4和NF/rGO/Co_3O_4/NiO电极.运用三电极体系对电极材料进行了恒流充放电(GCD)和交流阻抗(EIS)等测试.结果表明,复合材料NF/rGO/Co_3O_4/NiO具有较高的比容量(电流密度为2 A/g时,比容量达到1188.6 F/g)和较好的循环稳定性(2000周充放电后,稳定性达到80.5%).该材料还具有较高的倍率性能,当电流密度由2 A/g增至12 A/g时,倍率性能仍能达到75.7%.     

Effect of Transition Metals (Cu, Co and Fe) on the Autothermal Reforming of Methane over Ni/Ce0.2Zr0.1Al0.7Oδ Catalyst

The transition metals (Cu, Co, and Fe) were applied to modify Ni/Ce0.2Zr0.1Al0.7Oδ catalyst.The effects of transition metals on the catalytic properties of Ni/Ce0.2Zr0.1Al0.7Oδ autothermal reforming of methane were investigated. The Ni-supported catalysts were characterized by XRD, TPR and XPS.Tests in autothermal reforming of methane to hydrogen showed that the addition of transition metals (Cu and Co) significantly increased the activity of catalyst under the conditions of lower reaction temperature,and Ni/Cu0.05Ce0.2Zr0.1Al0.65Oδ was found to have the highest conversion of CH4 among all catalysts in the operation temperatures ranging from 923 K to 1023 K. TPR, XRD and XPS measurements indicated that the cubic phases of CexZr1-xO2 solid solution were formed in the preparation process of catalysts.Strong interaction was found to exist between NiO and CexZr1-xO2 solid solution. The addition of Cu improved the dispersion of NiO, inhibited the formation of NiAl2O4, and thus significantly promoted the activity of the catalyst Ni/Cu0.05Ce0.2Zr0.1Al0.65Oδ.     

过渡金属氧化物催化剂上NH3 分解Claus反应机理研究

运用浸渍法制备了七种过渡金属氧化物催化剂.对于NH3 分解反应均可获得很高的NH3转化率;对于NH3分解Claus反应则可以获得较高的SO2转化率和单质硫选择性.通过比较发现Co3O4-TiO2和Fe2O3-TiO2催化剂的低温活性比较高.经过XRD表征发现,在NH3分解Claus反应中,催化剂的活性相可能是过渡金属硫化物.结合活性评价和XRD表征结果提出了NH3分解Claus反应的机理.     

Co-M(M=La,Ce, Fe,Mn, Cu,Cr)复合金属氧化物催化分解N2O

通过共沉淀法制备了一系列Co-M(M= La, Ce, Fe, Mn, Cu, Cr)复合金属氧化物及纯Co3O4催化剂, 考察了其催化分解N2O 的活性. 结果表明在研究的系列催化剂中, Co-Ce 复合氧化物催化剂具有最好的催化分解N2O的活性; 其活性与Ce/Co 摩尔比有直接的关系, 当Ce/Co 摩尔比为0.05 时(CoCe0.05 催化剂)催化活性最佳; 当有NO 和O2共存时, 可能在催化剂活性中心上形成表面硝酸盐或亚硝酸盐吸附物种而使其活性受到较大影响. 通过对Co-M 催化剂的XRD、BET、O2-TPD及H2-TPR 等表征结果的分析, 发现作为主要活性位的Co2+的氧化还原能力是影响催化剂活性的主要原因. 这是因为根据反应机理, N2O 的表面分解步骤与Co2+氧化成Co3+的能力相关, 而吸附氧的脱附与Co3+还原成Co2+的能力相关. 在所研究的催化剂中, 添加除CeO2之外的其它过渡金属氧化物时, 催化剂中Co3+/Co2+的氧化还原能力降低, 因此其催化性能降低. 另外, 添加不同过渡金属氧化物也改变了N2O 催化分解反应的速控步骤.     

常温下 MnO2/Al2O3催化剂催化臭氧氧化甲苯反应

采用浸渍法制备了Al2O3负载的5种过渡金属氧化物催化剂,考察了它们在常温下催化臭氧氧化甲苯的性能,并运用程序升温还原、程序升温氧化、N2吸附-脱附和X射线光电子能谱对催化剂进行了表征.结果表明,NiO/Al2O3,CoO/Al2O3和MnO2/Al2O3催化剂上活性氧中心数量较少,臭氧与甲苯转化率较高;而Fe2O3/...     

CF4 decomposition over solid ternary mixture NaF-Si-MO（MO=La2O3,CeO2,Pr6O-（11）,Nd2O3,Y2O3）

A solid ternary mixture consisting of NaF,silicon and one metal oxide such as La2O3,CeO2,Pr6O11,Nd2O3,and Y2O3 was prepared and usedas de-fluorinated reagent for CF4 decomposition.The results show that 90% conversion of CF4 can be reached initially over NaF-Si-La2O3,NaF-Si-CeO2,NaF-Si-Nd2O3,and NaF-Si-Y2O3 at 850 C.The fresh and used reagents were characterized using XRD and XPS techniques.It was found that the active components of NaF and metal oxides in NaF-Si-CeO2,NaF-Si-Pr6O11,NaF-Si-Nd2O3,and NaF-Si-Y2O3 weretransformed into inert phases of mixed metal fluorides and silicates,respectively,resulting in an ineffective utilization of these de-fluorinatedreagents,whereas no inert phases from NaF and La2O3 can be observed in the used NaF-Si-La2O3,indicating the NaF-Si-La2O3 reagent couldbe utilized more efficiently than the other reagents in CF4 decomposition.     

On the Thermal Decompositions of the Trivalent Trioxalato Complexes of Al, Cr, Mn, Fe and Co

The thermal decompositions of the complexes K₃[M(ox)₃]3H₂O(M=Al, Cr, Mn, Fe, Co; ox=C₂O₄^2–) were studied. Dehydration of the complexes occurs up to 200°C, this being a three-step process for M=Al, Cr, Mn and Co, and a two-step process for M=Fe. Decomposition of the dehydrated complexes proceeds in several steps. For M=Al, Cr and Fe, the decomposition takes place with the evolution of CO, whereas for M=Mn and Co the decomposition of the oxalate ligand yields solid C besides CO. The temperature of CO liberation decreases in the series Cr<Al<Co<Mn<Fe. For M=transition metal, this trend can be explained by the fact that the strength of the C—C bond in the oxalate ligand decreases in the series Cr<Co<Mn<Fe.This revised version was published online in November 2005 with corrections to the Cover Date.     

Effect of solvent composition on oxide morphology during flame spray pyrolysis of metal nitrates

The effect of solvent composition on particle formation during flame spray pyrolysis of inexpensive metal-nitrates has been investigated for alumina, iron oxide, cobalt oxide, zinc oxide and magnesium oxide. The as-prepared materials were characterized by electron microscopy, nitrogen adsorption, X-ray diffraction (XRD) and disc centrifugation (XDC). The influence of solvent parameters such as boiling point, combustion enthalpy and chemical reactivity on formation of either homogeneous nanoparticles by evaporation/nucleation/coagulation (gas-to-particle conversion) or large particles through precipitation and conversion within the sprayed droplets (droplet-to-particle conversion) is discussed. For Al(2)O(3), Fe(2)O(3), Co(3)O(4) and partly also MgO, the presence of a carboxylic acid in the FSP solution resulted in homogeneous nanoparticles. This is attributed to formation of volatile metal carboxylates in solution as evidenced by attenuated total reflectance spectroscopy (ATR). For ZnO and MgO rather homogeneous nanoparticles were formed regardless of solvent composition. For ZnO this is attributed to its relatively low dissociation temperature compared to other oxides. While for MgO this is traced to the high decomposition temperature of Mg(NO(3))(2) together with Mg(OH)(2)?MgO transformations. Cobalt oxide (Co(3)O(4)) nanoparticles made by FSP were not aggregated but rather loosely agglomerated as determined by the excellent agreement between XRD- and XDC-derived crystallite and particle sizes, respectively, pointing out the potential of FSP to make non-aggregated particles.     

CF4在Al2O3基金属氧化物上的分解反应

考察了在无水条件下γ-Al2O3基金属氧化物M-Al2O3(M=Mg、La、Ba、Ce、Ni、P)与CF4反应转化为金属氟化物的反应. 结果表明, 在所筛选的金属氧化物中, γ-Al2O3的初活性较高, 但由于CF4分解时产生的强放热效应使未反应的γ-Al2O3发生了α相变, 致使CF4转化率急剧下降, 反应温度越高, γ-Al2O3的α相变越快, 活性下降就越快. CF4在MgO-Al2O3上分解时, Mg物种比Al优先氟化生成了MgF2, Mg物种的氟化反应及其产生的强放热效应使MgAl2O4结构发生了解体. 在Al2O3表面负载助剂P、Ni,提高了其热稳定性, 抑制了CF4高温分解时未反应的Al2O3发生α相变, 使更多的γ-Al2O3参与了CF4分解反应.     

Formation of CO(x)-free H2 and cup-stacked carbon nanotubes over nano-Ni dispersed single wall carbon nanohorns

Transitional metals (M) were dispersed on single-wall carbon nanohorns (M/SWCNHs, M = Fe, Co, Ni, Cu) by simple thermal treatment of the deposited metal nitrate without H(2) reduction. Nanometallic Ni particles on SWCNH were evidenced by high-resolution transmission electron microscopic observation and X-ray photoelectron spectroscopy. The nano-Ni dispersed on SWCNH showed the highest CH(4) decomposition activity; the activity of used transitional metals decreases in the order Ni ? Co > Fe ? Cu. On the other hand, the reaction rate over Ni/SWCNH was much larger than that over Ni/Al(2)O(3), and the former provided CO(x)-free H(2) and cup-stacked carbon nanotubes, while Ni/Al(2)O(3) produced CO(x) in addition to H(2). SWCNH was superior to Al(2)O(3) as the catalyst support of Ni for the CH(4) decomposition reaction.     

N_2O分解催化剂Co-Al尖晶石型复合氧化物制备参数的优化

以柠檬酸为配合剂,用溶胶-凝胶法制备了一组不同组成的Co-Al复合氧化物(CoAl_2O_4、CoCo0.5Al1.5O4、CoCoAlO_4、CoCo_(1.5)Al_(0.5)O_4、Co_3O_4),用于催化分解N_2O.用N_2物理吸附、X射线衍射(XRD)、扫描电镜(SEM)、H2程序升温还原(H2-TPR)、X射线光电子能谱(XPS)等技术对催化剂进行了结构表征,考察了复合氧化物组成、母液pH值、配合剂用量等制备参数对催化剂活性的影响.结果表明:用Al取代Co_3O_4中部分Co制备Co-Al复合氧化物,提高了催化剂的比表面积和催化活性,其中组成为CoCo_(1.5)Al_(0.5)O_4、母液pH=2、柠檬酸/金属离子(摩尔比)为1的催化剂活性较高.在CoCo_(1.5)Al_(0.5)O_4表面浸渍K2CO3溶液制得K改性催化剂,弱化了钴-氧化学键,提高了催化活性.其中0.02K/CoCo1.5Al0.5O4催化剂在有氧有水气氛400℃连续反应50h,N_2O转化率达97.1%.     

Cladding transition metal oxide particles with graphene oxide sheets: an efficient protocol to improve their structural stability and lithium ion diffusion rate

Journal of Solid State Electrochemistry - Transition metal oxides (TMOs), such as Fe3O4, Co3O4, and NiO, assume large lithium ion storage capacities, but suffer severe structure pulverization and...     

EFFECTS OF ALKALI AND RARE EATTH METAL OXIDES ON THE THERMAL STABILITY AND THE CARBON DEPOSITION OVER A NiO/Al_2O_3 CATALYST

采用固定床流动反应装置、ＣＯ吸附、ＴＧ、ＴＰＯ、ＸＰＳ和ＸＲＤ等手段考察了ＮｉＯ／Ａｌ２Ｏ３和ＬｉＮｉＬａＯ／Ａｌ２Ｏ３催化剂上的甲烷部分氧化反应。实验结果表明，ＬｉＮｉＬａＯ／Ａｌ２Ｏ３对甲烷部分氧化反应具有较高的反应活性。锂和镧的添加不仅改善了活性组分镍的分散度，而且提高了ＮｉＯ／Ａｌ２Ｏ３的抗积碳能力和热稳定性     

Unusual reactivity of methylene group adjacent to pyridine-2-carboxamido moiety in iron(III) and cobalt(III) complexes

The Fe(III) and Co(III) complexes of the ligand N-(2-picolyl)picolinamide (pmpH; H represents the dissociable amide hydrogen), namely, [Fe(pmp)(2)]BF(4) (1) and [Co(pmp)(2)]ClO(4) (2), have been synthesized and structurally characterized. The [bond]CH(2)[bond] moiety of pmp(-) in [M(pmp)(2)](+) (M = Fe, Co) is very reactive and is readily converted to carbonyl (C[double bond]O) group upon exposure to dioxygen. Such conversion results in [M(bpca)(2)]ClO(4) complexes (M = Fe (3), Co (5); bpcaH = bis(2-pyridylcarbonyl)amine) which have been characterized by spectroscopy and X-ray diffraction. The structure of 5 is reported here for the first time. The reactivity of the [bond]CH(2)[bond] moiety of pmp(-) has so far precluded the isolation of 1 although other metal complexes of pmp(-) have been reported years ago. The CH(2) --> C[double bond]O transformation arises from the tendency of the coordinated pmp(-) ligand to achieve further conjugation in the ligand framework and provides a better way to synthesize the metal complexes of bpcaH ligand. Reaction of 3 with NaH affords Fe(II) complex [Fe(bpca)(2)] (4) without any reduction of the ligand frame.     

Effects of pretreatment and reduction on the Co/Al2O3 catalyst for CO hydrogenation

The purpose of this study was to investigate the effect of preadsorbed CO at different temperatures, calcination temperatures, the combined influence of reduction temperature and time, and pretreatment using hydrogen or syngas as reduction agents on the F-T synthesis （FTS） activity and selectivity of Co/Al2O3 catalyst. The reactivity of the carbon species at higher preadsorption temperature with H2 in TPSR decreased, whereas the carbon-containing species showed higher reactivity over Co/Al2O3 catalyst with low calcination temperature. This agreed well with the order of catalytic activity for F-T synthesis on this catalyst. The catalytic activity of the catalyst varied with reduction temperature and time remarkably. CODEX optimization gave an optimum reduction temperature of 756 K and reduction time of 6.2 h and estimated C5＋ yield perfectly. The pretreatment of Co/Al2O3 catalyst with different reduction agents （hydrogen or syngas） showed important influences on the catalytic performance. A high CO conversion and C5＋ yield were obtained on the catalyst reduced by hydrogen, whereas methane selectivity on the catalyst reduced by syngas was much higher than that on the catalyst reduced by hydrogen.     

Enhancement of ammonia dehydrogenation by introduction of oxygen onto cobalt and iron cluster cations

Reactions of oxygen-chemisorbed cobalt and iron cluster cations (Co(n)O(m)(+) and Fe(n)O(m)(+); n = 3-6, m = 1-3) with an NH(3) molecule have been investigated in comparison with their bare metal cluster cations at a collision energy of 0.2 eV by use of a guided ion beam tandem mass spectrometer. We have observed three kinds of reaction products, which come from NH(3) chemisorption with and without release of a metal atom from the cluster and dehydrogenation of the chemisorbed NH(3). Reaction cross sections and branching fractions are strongly influenced by the number of oxygen atoms introduced onto the metal clusters. Oxygen-chemisorbed metal clusters with particular compositions such as Co(4)O(+), Co(5)O(2)(+), and Fe(5)O(2)(+) are extremely reactive for NH(3) dehydrogenation, whereas Co(4)O(2)(+) and Fe(4)O(2)(+) exhibit high reactivity for NH(3) chemisorption with metal release. The enhancement of dehydrogenation for specific compositions can be interpreted in terms of competition between O-H and neighboring Co-H (or Fe-H) formation.     

Ni/Al2O3和Fe/Al2O3催化剂催化乙醇水蒸气重整制氢的对比研究

甲醇、乙醇等低碳醇催化重整制氢是燃料电池氢源的重要技术之一.乙醇和甲醇相比,更容易存储,低毒且可以从生物质经发酵获得[1,2].乙醇可以通过裂解、部分氧化、水蒸气重整和氧化重整等途径制氢[3~6].已有的文献表明,Pt、Ru、Rh、Pd等贵金属可有效地催化乙醇重整反应,载体多选用     

铜对Mn/Al_2O_3氨还原SO_2到单质硫催化性能的影响

ＳＯ2 是危害最为严重的大气污染物之一 ,也是造成酸雨的元凶。将ＳＯ2 选择性还原为单质硫 ,既能消除ＳＯ2 对环境的污染 ,又能回收单质硫 ,具有特别重要的意义。根据所用的还原剂的不同 ,催化还原ＳＯ2 到单质硫可分为Ｈ2 、炭、烃类 (主要是ＣＨ4 )、ＣＯ和ＮＨ3还原法[1] 。氨还原法是基于氨的催化分解生成Ｎ2 和Ｈ2 混合气 ,其中的Ｈ2 再还原ＳＯ2 到硫和Ｈ2 Ｓ ,然后进行高温Ｃｌａｕｓ反应生成单质硫。Ｐａｉｋ[2 ] 等以第四周期过渡金属硫化物载于Ａｌ2 Ｏ3 作为催化剂 ,研究了Ｈ2 还原ＳＯ2 为单质硫的反应 ,认为过渡金属硫化物是…