Enhanced oxygen absorption into bisulphite solutions containing transition metal ion catalysts

The sulphite oxidation reaction was studied by measuring the oxygen absorption flux from a nitrogen mixture across an unbroken interface into 11 of unsparged, agitated sulfite (10–30 mM) and catalyst (0.01–100 mM Fe, Mn, Co, Cu, Cr, Ni) solution at pH 4–6 and 50°C. The catalytic action of Fe was solubility-limited at 0.01 mM at pH 5 resulting in an enhancement factor of 2.4 at all higher concentrations. Since Mn and Co do not begin to show enhancement until about 1 mM, Fe was the strongest of the three below this level. 0.05–1 mM thiosulfate was an effective inhibitor for Mn catalysed systems but degraded into inert products. Thiosulfate had much less effect on Fe catalysed oxidation. EDTA inhibited Fe catalysis at concentrations equal or above that of the Fe. Catalytic synergism was quantified for combinations of Mn with the other metals. Mn-Fe couples caused absorption fluxes of up to five times that which would be expected from separate individual catalytic contributions.     

Solvent-free liquid phase oxidation of benzyl alcohol to benzaldehyde by molecular oxygen using non-noble transition metal containing hydrotalcite-like solid catalysts

Performance of Co–Al, Ni–Al, Cu–Al, Zn–Cu–Al, Mg–Fe, Co–Fe, Ni–Fe, Mn–Cr, Co–Cr, Ni–Cr, Zn–Cr and Cu–Cr hydrotalcite-like solid catalysts has been evaluated for the liquid phase oxidation of benzyl alcohol to benzaldehyde using molecular oxygen as an oxidizing agent in the absence of any solvent. The Mn and Cu containing hydrotalcite-like solids show good catalytic activity in the oxidation and hence these are promising catalysts for the solvent-free oxidation reaction.     

Shape- and Composition-Controlled Pt–Fe–Co Nanoparticles for Electrocatalytic Methanol Oxidation

We report the preparation of several shape and composition-controlled platinum-based nanoparticles: Pt–Fe nanocubes, Pt–Fe–Co nanocubes, Pt–Fe–Co branched nanocubes, Pt–Fe–Co nanoparticles with low cobalt content, and Pt–Fe–Co nanoparticles with high cobalt content. Pt–Fe–Co branched nanocubes, in particular, showed the best activity and durability for electrocatalytic methanol oxidation.     

Transition metal-doped heteropoly catalysts for the selective oxidation of methacrolein to methacrylic acid

Heteropoly compounds with the general formula Cs₁M_0.5^x+H_3?0.5xP_1.2Mo₁₁VO₄₀ (M= Fe, Co, Ni, Cu or Zn) and Cs₁Cu_yH_3?2yP_1.2Mo₁₁VO₄₀ (y = 0.1, 0.3 or 0.7) were synthesized and then used as catalysts for the selective oxidation of methacrolein to methacrylic acid. The effects of the transition metals on the structure and activity of the catalysts were investigated. FTIR spectra showed that the transition metal-doped catalysts maintained the Keggin structure of the undoped catalysts. X-ray diffraction results indicated that before calcination, the catalysts doped with Fe and Cu had cubic secondary structures, while the catalysts doped with Co, Ni or Zn had both triclinic and cubic phases and the Co-doped catalyst had the highest content of the triclinic form. Thermal treatment can decrease the content of the triclinic phase. NH₃ temperature-programmed desorption and H₂ temperature-programmed reduction results showed that the transition metals changed the acid and redox properties of the catalysts. The addition of Fe or Cu had positive effects on the activities of the catalyst which is due to the improvement of the electron transfer between the Fe or Cu and the Mo. The effects of the copper content on structure and catalytic activity were also investigated. The Cs₁Cu_0.3H₂P_1.2Mo₁₁VO₄₀ catalyst had the best performance for the selective oxidation of methacrolein to methacrylic acid.     

Transition metal doped mesoporous titania with a crystalline framework as catalysts for oxidation of -bromotoluene to -bromobenzaldehyde

Transition metal M (M = Mn, Fe, Co, Ni, Cu, and Zn) doped mesoporous titania with a crystalline framework was employed as catalysts for the oxidation of p-bromotoluene (PBT) to p-bromobenzaldehyde (BBD) in acetic acid using aqueous hydrogen peroxide as oxidant. It was found that mesoporous TiO₂ doped with those metals (Fe, Co and Ni) whose atomic radii are relatively smaller exhibited higher conversion rate of PBT. Among these catalysts, the Co/meso-TiO₂ exhibited high substrate conversion and good product (p-bromobenzaldehyde) selectivity plus it can be reused once with almost the same activity. The effect of different Ti/Co (molar) ratio on the activities of Co/meso-TiO₂ was also investigated.     

X‐ray absorption spectroscopy study of synthetic cobalt blue pigments similar to Kangxi blue and white porcelain

A series of cobalt blue pigments, which were synthesized based on the chemical compositions of the blue pigments in Kangxi blue and white porcelain, were investigated by Co, Mn, and Fe K‐edge and L_2,3‐edge X‐ray absorption spectroscopy to determine the oxidation states and species of the elements and to discern their impact on the blue color. The results reveal that Co is bivalent and mainly located at tetrahedral sites, which is the main parameter controlling the blue color. Mn is mainly present as Mn²⁺, or Co_xZn_1‐xAl₂O₄ and Fe is mainly present as Fe³⁺. In particular, Fe³⁺ substitutes the Al in CoAl₂O₄ and occupies octahedral sites with a high Mn content. All the synthetic cobalt blue pigments can form a solid solution with various end‐members or an intermediate solution spinel. The spectroscopic determination of the oxidation states and speciation of Co, Mn, and Fe furthers understanding of the coloration of blue pigments in blue and white porcelain.     

Carbon-supported cobalt–iron catalysts for ammonia synthesis

The cobalt, iron and Co–Fe catalysts deposited on carbon were prepared, characterised (XRD, H₂ TPD) and studied in ammonia synthesis at 90 bar (H₂:N₂ = 3:1). Partly graphitised carbon material obtained via high temperature treatment (1900 °C) of commercial activated carbon was used as a support for the active metals (10 wt.%) and barium or potassium were used as promoters. XRD studies of unpromoted materials have shown that cobalt (5–20% in Co + Fe) dissolves in the iron phase (alloy formation); the average sizes of crystallites (20–30 nm) are roughly independent of the metal kind (Co, Fe, Co–Fe). The effect of Ba and that of K on the catalyst performance proved to be strongly dependent on the choice of an active phase (Co or Fe or Co–Fe). In the case of Co/C, the promotional effect of barium was extremely large. Furthermore, the Ba–Co/C system was found to be less inhibited by the ammonia product than Ba–Fe/C. At low temperature (400 °C) and at high conversion (8% NH₃ in the gas), the surface-based reaction rate (TOF) for Ba–Co/C is about six times higher than that for Ba–Fe/C.     

Oxidation of propane with oxygen, nitrous oxide and oxygen/nitrous oxide mixture over Co- and Fe-zeolites

Oxygen, nitrous oxide and their mixture was used in oxidation of propane over CoH(Fe)–BEA and parent H(Fe)-zeolites (containing trace concentrations of Fe) of beta and ZSM-5 structures. CoH(Fe)–BEA zeolite exhibited a substantial increase in propene yield (from 2.0 to 6.8%), if together with molecular oxygen, nitrous oxide was used. No other oxygenates were detected. With increasing concentration of molecular oxygen in the propane/nitrous oxide/oxygen mixture, a synergetic effect of oxygen and nitrous oxide resulting in nearly threefold increase in propene yield was observed. At the reaction conditions studied, the highest propane conversion (15.8%) with 61.9% selectivity to propene and propene yield of 9.8%, and the sum of selectivities to oxygenates of 10.3% (foremost propyl alcohol and propanal) was achieved with the steamed H(Fe)–MFI zeolite when a mixture of nitrous oxide and oxygen was used. It is concluded that, the oxidation activity of nitrous oxide originates from specific Fe species, present in CoH(Fe)–BEA and H(Fe)-zeolites, exhibiting extra-ordinary activity in hydroxylation of propane to propyl alcohol (dehydrated to propene) and its further oxidation to propanal, whereas Co ions contribute only to propane oxidation to propene and carbon oxides.     

Co—Fe催藻土催化剂上肉桂醛的选择加氢——反应性能的研究

在固定床反应器中对肉桂醛选择加氢制肉桂醇的反应性能进行了研究。考察了Co-Fe催化剂的活性和选择性;Co负载量、助剂Fe对催化剂选择加氢性能的影响;考察了反应温度、压力、H2的空速等对肉桂醛在催化剂上加氢性能的影响。结果表明,钴／硅藻土催化剂的最佳钴负载量为12％,助催化剂和主催化剂的最佳比为Fe／Co=0．20（mol／mol）。最佳反应温度为423K,反应的压力越高越有利于催化反应,但压力大于4MVa后,肉桂醛的转化率和肉桂醇的选择性提高幅度不大,宜控制在4MVa左右。空速对肉桂醇的选择性影响不大,但空速越高肉桂醛的转化率越低,催化反应中宜控制较低的氢气空速为佳。     

金属卟啉催化氧化环己烷反应的研究进展

为了筛选仿生催化氧化环己烷反应的优异催化剂。重点归纳总结了用做仿生催化空气氧化环己烷反应的金属卟啉化合物的类型和种类。其中,研究最为活跃的是中位取代（meso-）四苯基卟啉及其衍生物的金属配合物,络合的金属种类主要是过渡金属Fe、Mn、Co。金属卟啉仿酶催化剂品种中,主要有单金属卟啉、双核金属卟啉和固载金属卟啉等3种类型,其中研究较为成熟的是单金属卟啉催化剂,且苯环上取代吸电子基团的金属卟啉仿酶催化剂的催化活性较高。     

钼铁催化剂上对二甲苯气相选择性氧化合成对苯二甲醛的研究

采用溶胶-凝胶法合成了钼铁催化剂,通过该催化剂,利用空气中的O₂进行对二甲苯选择性氧化,制备出对苯二甲醛。催化剂的活性评价结果表明,在n(Mo)∶n(Fe)∶n(Co)=2.4∶1∶0.02和焙烧温度500 ℃条件下,催化剂的活性最高;反应温度为500 ℃和空速5 500 h^-1时,对苯二甲醛的收率达到59.2%。FT-IR和XRD结果证实,催化剂的活性组分为Fe₂(MoO₄)₃与少量的MoO₃,二者具有协同作用。     

A new hybrid porphyrin-heteropolyacid material: Synthesis,characterization and investigation as catalyst in Baeyer–Villiger oxidation. Synergistic effect

A new tetraphenylporphyrin-tungstophosphoric acid hybrid was synthesized and physico-chemically characterized by different techniques. This hybrid, its molybdenum analogue, tungstophosphoric and molybdophosphoric acids as well as their Mn, Fe and Co salts were applied in Baeyer–Villiger oxidation of cyclohexanone to caprolactone with molecular oxygen. Due to the synergistic effect porphyrin-heteropolyacid hybrids exhibit similar catalytic activity as appropriate heteropoly salts and much higher activity than parent heteropolyacids.     

Low-cost nanostructured Fe2O3-based composite catalysts synthesized by mechanical milling for CO oxidation reaction

In this work, the catalytic properties of low-cost nanostructured iron oxide have been improved by the mechanical milling method through combination with copper and cobalt oxide. Synthesized catalysts were characterized by X-ray diffraction, transition electron microscopy, and Brunauer–Emmet–Teller techniques. Also, the catalytic activity and stability of the powders for CO oxidation reaction were investigated. Results indicated that the catalytic activity of the powders has significantly improved after mechanical milling. Minimum complete conversion temperatures for Co–Fe and Cu–Fe composite oxide catalysts were around 245 and 275°C, respectively. No decline in the activity of the catalysts was observed during the long-term stability test. Furthermore, catalytic activity of the composite powders, especially Co–Fe improves at subsequent cycles. In general, cycle durability, stability at high temperature and reaction rate of the iron oxide powder has been improved using it as Cu–Fe and Co–Fe oxide composites.     

LaMn1-x-yFexCoyO3-δ钙钛矿载氧体用于化学链部分氧化

采用溶胶-凝胶法制备了B位Fe和Co共取代的LaMn_1-x-yFe_xCo_yO_3-δ钙钛矿型复合氧化物,并用于化学链甲烷部分氧化制合成气。X射线衍射（XRD）结果表明Fe和Co均进入了LaMnO₃的晶格形成钙钛矿晶相,活性和稳定性测试表明LaMn_1/3Fe_1/3Co_1/3O_3-δ载氧体具有最佳的化学链甲烷部分氧化性能。CH₄程序升温还原（CH₄-TPR）表征发现LaMn_1/3Fe_1/3Co_1/3O_3-δ具有比LaBO₃（B=Co, Mn, Fe）更高的甲烷活化能力和晶格氧迁移性能。甲烷恒温脉冲反应（CH₄-pulse reaction）进一步证实了B位离子的协同作用可以提高LaBO₃（B=Co, Mn, Fe）的表面反应速率。程序升温氢气还原（H₂-TPR）表明,LaMn_1/3Fe_1/3Co_1/3O_3-δ中晶格氧具有适中的氧化还原能力,适合用于化学链甲烷部分氧化。     

LaMn1-x-yFexCoyO3-δ perovskite based oxygen carriers for chemical looping partial oxidation

LaMn_1-x-yFe_xCo_yO_3-δ perovskite-type composite oxides co-substituted with B-site Fe and Co were prepared by the sol-gel method, and used for the chemical looping partial oxidation of methane to syngas. The XRD results suggest that Fe and Co were incorporated into the lattice of LaMnO₃ and formed perovskite phase. Reactivity and stability tests show that LaMn_1/3Fe_1/3Co_1/3O_3-δ oxygen carrier has the best reaction performance. CH₄-TPR results indicate that LaMn_1/3Fe_1/3Co_1/3O_3-δ has higher methane activation and lattice oxygen migration rates than those of LaBO₃ (B=Co, Mn, Fe). CH₄-pulse reaction further confirms that the synergistic effect of B-site ion substitution can improve the surface reaction rate of LaBO₃ (B=Co, Mn, Fe). H₂-TPR results show that the lattice oxygen in LaMn_1/3Fe_1/3Co_1/3O_3-δ has moderate redox capacity, which is suitable for partial oxidation of methane.     

The Effect of Cobalt on the Degradation of Methyl β-D-Gluco-Pyranoside by Oxygen in Aqueous Sodium Hydroxide Solution

Abstract

The effect of Co(II) (0 to 0.25 mW CoSO₄) on the degradation of methyl β-D-glucopyranoside (MBG) at 120°C in 1.25M NaOH with 0.68 MPa oxygen pressure was studied. When the Co(II) was increased from 0.00 to 0.01 to 0.05 mM the MBG half-life decreased from 12 to 6 to 1.5 hours, reflecting approximately a 0.5 order kinetic dependence on cobalt. An oxidation-reduction cycle between Co(II) and Co(III) involving oxidation of Co(II) by oxygen and oxidation of the glucoside by Co(III), hydroxyl radical, or superoxide is proposed for the degradation. At the 0.25 mM Co(II) addition level highly adsorptive Co(OH)₂ formed prior to reaction initiation with oxygen and removed otherwise soluble cobalt from solution. This resulted in lower rates of MBG degradation than obtained even at 0.01 mM Co(II) addition. However, Co(II) solubility could be enhanced if silicate anions or polyols (including MBG) were added to the alklaine medium prior to the Co(II) addition. In reactions initially containing 0.25 mM soluble Co(II), an adsorptive precipitate, presumably CoO(OH), gradually formed after reaction initiation with oxygen. Precipitation of the Co(III) solid coincided with a rapid decline in the rate of MBG degradation. Cobalt had little effect on the products of MBG degradation.     

微气泡强化磷酸介质中Fe2+高效氧化研究

为实现酸性介质中Fe2+的高效分离，工业中常采用双氧水氧化法将Fe2+转化为溶解度更低的Fe3+而实现铁的析出，该方法双氧水利用率低，经济性差，亟待开发酸性介质中新型的Fe2+低成本高效氧化法。基于微气泡在酸性介质中可爆裂生成活性氧原理，本工作开发了微气泡强化氧化Fe2+技术，研究了曝气头尺寸、反应温度、酸浓度等对微气泡强化氧化Fe2+及羟基自由基生成的影响，确定了反应的最佳条件为90℃、30wt% H3PO4、0.22 μm孔径曝气头，在上述条件下，30 min Fe2+氧化率可达约99%，与现行H2O2氧化效果相当，大大降低工艺经济成本。同时，本工作对微气泡强化Fe2+氧化的机理进行了研究，确定了微气泡爆裂生成的主要活性氧为羟基自由基，并研究了曝气头尺寸、反应温度、酸浓度等对羟基自由基生成的影响，获得了酸性介质中羟基自由基生成的调控规律。     

Alterung des polybutadies bei anwesenheit von metallverbindungen

In the ageing of industrial polybutadienes the effect of decomposition products of ZIEGLER–NATTA catalysts could not be distinguished from other Important factors. However, the additional introduction of Co, Ti or Ni compounds (components of the ZIEGLER-NATTA catalysts) has influenced the oxidation process. The effect of different acetylacetonates (Ti, Co, Ni, V, Al, Cc, Mn, Cu) on the oxidation of purified polybutadiene in presence or in absence of an antioxidant has further been studied. The apparent activation energies of oxidation have been estimated and possible mechanismus of the actions of metal compounds in the oxidation of polybutadiene have been proposed.     

Steam Reforming of Ethanol Over Cobalt Catalyst Modified with Small Amount of Iron

Steam reforming of ethanol was examined over Co/SrTiO₃ with addition of another metal—Pt, Pd, Rh, Cr, Cu, or Fe—for promotion of the catalytic activity. Ethanol conversion and H₂ yield were improved greatly by adding Fe or Rh at 823 K. Although Rh addition promoted CH₄ formation, Fe addition enhanced steam reforming of ethanol selectively. A suitable amount of Fe loading was in the window of 0.33–1.3 mol%. A comparative study of the reaction over a catalyst supported on SiO₂ was conducted, but no additional effect of Fe was observed on the Co/SiO₂ catalyst. High activity of Fe/Co/SrTiO₃ catalyst came from interaction among Fe, Co, and SrTiO₃.