Thermal decomposition of Ni(II) and Fe(III) acetates and their mixture

The thermal decomposition of the ferric and nickel acetate salts has been followed. It was found that the heating rate affects the decomposition steps. For a heating rate of 1 K min^–1 the product is either Fe₂O₃ or NiO. For a higher heating rate the suboxides are obtained and reoxidized again on further heating. The decomposition of the mixed salt is an overlap of the DTA for the separate salts but the decomposition reactions are shifted to lower temperatures.We would like to thank Prof. Dr. N. Afify, Phys. Dept., Fact. Science, Assiut University, for experimental assistance and valuable discussions.     

镍前驱体对非负载型镍催化剂上甲烷分解活性的影响

 分别以硝酸镍和乙酸镍为前驱体, 采用沉淀法制备了非负载型 Ni 催化剂, 运用 X 射线衍射、H2-程序升温还原及 CH4 程序升温表面反应对催化剂进行了表征, 并考察了 Ni 催化剂上 CH4 分解反应活性. 结果表明, 以乙酸镍为前驱体制得的 NiO 样品粒子尺寸较小, 较易被还原, 还原后得到的催化剂催化 CH4 分解活性和稳定性较高; 而以硝酸镍为前驱体制得的 NiO 样品粒子尺寸较大, 较难被还原, 还原后催化剂上 CH4 分解活性和稳定性较低. 制备过程中乙酸镍与溶剂乙二醇所形成的配合物是获得尺寸较小 NiO 样品的关键.     

混合硝酸镍和醋酸镍制备的催化剂的特征和催化加氢抗硫性能

使用直接还原镍盐前体[Ni(NO_3)_2/γ-Al_2O_3, NiAc_2/γ-Al_2O_3或Ni (NO_3)_2-NiAc_2/γ-Al_2O_3]和镍氧化物前体的方法制备催化剂,研究了它们的 表面特征和甲苯加氢抗硫性能。还原镍盐得到的催化剂比还原其焙烧成的氧化物制 得的催化剂金属的还原和分散程度高。Ni(NO_3)_2-NiAc_2/γ-Al_2O_3分解得到的 氧化物前体的TPR在约415 ℃出现了较小数量的块状NiO的还原峰;而Ni(NO_3)_2- NiAc_2/γ-Al_2O_3的TPR中镍盐分解成氧化物时的耗氢量变小。用氢溢流的概念和 镍盐分解时的耗氢量可以将TPR的结果和金属的分散性关联起来。在镍盐前体催化 剂上甲苯的加氢具有较高的活性,而两种盐摩尔比为1：1时,盐前体催化剂反应活 性出现了一极大值,同时盐和氧化物前体催化剂都给出了抗硫性能的极大值。     

Thermogravimetric Investigations of Nickel-Oxide Thin Films and Powders

Classical TG analysis of films supported on micro-cover glasses was performed in order to determine the appropriate processing temperature to achieve electrochemically active NiO_xH_y thin films. As deposited films made from three different precursors (Ni-acetate, nitrate and sulphate) and their corresponding powders were also investigated. From dynamic TG measurements the onset decomposition temperature could be determined. It was found out that the starting temperature of the mass change of thin films is approximately 30 degrees lower than that of the powders. A broader decomposition range was also observed for thin films. Furthermore, the isothermal treatment of films deposited on conducting substrate at 270 and 300°C was performed and by cyclic voltametry the importance of temperature and time of heating was proved. Films obtained at higher temperatures (>300°C) are electrochemically inert because of the NiO phase formation. This revised version was published online in August 2006 with corrections to the Cover Date.     

NiFe_2O_4/NiO纳米复合材料的制备及电催化水氧化性能

以镍铁水滑石为单一前驱体,通过高温焙烧制备了NiFe_2O_4/NiO纳米复合材料,对该纳米复合材料在碱性介质中电催化水的氧化性能进行了研究.结果表明,相比于化学共沉淀法制备的单独NiFe_2O_4、NiO及其物理混合物NiFe_2O_4+NiO,NiFe_2O_4/NiO纳米复合材料具有更高的电催化水氧化活性和更好的循环稳定性.电流密度为10 m A/cm2时过电位仅为364 m V.     

Thermal and kinetic study of nickel trifluoromethanesulphonate,trifluoroacetate and acetate

The reason of comparing thermal behaviour and kinetics of some nickel compounds, is justified by the influence of anion on it, besides supplying information on the stability of the salts. In this work, Ni(TMS)₂·6H₂O, Ni(TFA)₂·3H₂O and Ni(Ac)₂·2H₂O, were synthesized and characterized by microanalysis, atomic absorption molar, conductance and thermal analysis. Thermogravimetric curves indicate that the decomposition of the salts occurs in the range 295–1169 K and the NiO is the final residue. Non-isothermal kinetic evaluation from thermogravimetric data was used to determine energies of activation and pre-exponential factors.     

Study on the Reaction Behavior of Some Trinuclear Complexes of Transition Metals: [Fe_2M(μ_3-O) (μ-O_2CCH_3)_6(H_2O)_3]·xH_2O by the Method of Probe Reaction of Acetic Acid

INTRoDUCTIoNRecentlywehaveproposedamethodofchemicalprobereaction(l3forstudyingthereactionbehaviorsoftransitionmetalcomplexes.BythismethodtheserlalresultswereobtainedusingtheC,H, H,OandC2H2 H2astheprobereactions[1~53.Here-inisfurtherpresentedanotherkindoftheprobereaction--theacetoniaztionofaceticacidbydecarboxylationoverfourcomp1exeswithgeneralformula[Fe2M(p3-O)(p-O,CCH,),(H,O),j.xH,O,whereM=Fe(m),Mn(n),Co(I)andNi(n)'whichafterwardswillbedenotedas[Fe2M0AHjforsimplicity(N0te:inthe…     

Thermal decomposition of 4-amino-1,2,4-triazolium nitrate under infrared laser heating

The objective of this work is to study the behavior of an ionic liquid, 1-H-4-amino-1,2,4-triazolium nitrate, during thermal decomposition driven by an infrared laser (10.6 μm). The focus was to understand the initial decomposition reactions and subsequent reactions that lead to ring decomposition and eventually to ignition. A triple quadrupole mass spectrometer with molecular beam sampling was used to obtain gaseous decomposition species of the sample. The principal mass peaks that may contain multiple masses were analyzed through tandem mass techniques. The experiments were conducted at a laser heat flux of 100 W/cm² in helium at 1 atm. To assist in interpreting the data, three other materials were also tested, 4-amino-1,2,4-triazolium hydrochloride, 4-amino-1,2,4-triazole, and 1-H-1,2,4-triazole. The results show that the most probable route to initiate the decomposition of the 1-H-4-amino-1,2,4-triazolium nitrate is through proton transfer from N₁ site to the nitrate forming a neutral pair, nitric acid and amino-triazole. Subsequent reactions involve decomposition of the neutral pair and their interactions.     

固相配位化学反应研究 XXXX: 硝普钠与锰(II)、钴(II)、镍(II)、铜(II)氯化物的固相反应

本文用气相色谱、红外光谱和Mossbauer谱等手段, 研究了硝普钠与锰(II)、钴(II)、镍(II)、铜(II)氯化物在氢气氛中的固相反应, 发现过渡金属盐的存在或多或少地影响了硝普钠的分解方式, 其中CuCl~2.2H~2O与硝普钠室温时就反应生成Cu[Fe(CN)~5NO].χH~2O; 在较高温度下, CoCl~2.6H~2O和NiCl~2.6H~2O与硝普钠的固相反应催化了硝普钠迅速分解; 而氯化锰与硝普钠的固相反应与纯配合物较为接近。探讨了第一步反应可能的机理, 并计算了反应动力学参数。     

Effects of nickel(II) oxide on the thermal decomposition of alkali persulfates

The thermal decomposition of Na₂S₂O₈ and K₂S₂O₈ has been studied derivatographically in the presence of NiO at various molar mixtures. Experiments have proved that the first decomposition stage (persulfate into pyrosulfate) is independent of the amount of the oxide present. During the second decomposition stage (pyrosulfate into sulfate) which occurs in the melt, NiO plays the role of lowering the melting, the initial and final decomposition temperatures of pyrosulfates. The lowest melting temperatures recorded for Na₂S₂O₈ and K₂S₂O₈ are 320 and 280°C, respectively.A mechanism has been proposed to describe the catalytic action of NiO on the thermal decomposition of alkali pyrosulfates. The mechanism makes use of the semiconductivity of NiO and the availability of electron-rich centers in the pyrosulfate group to help the formation of an adsorption complex between them.NiO reacts to some extent with alkali pyrosulfates forming the yellow NiSO₄ and alkali sulfates as separate products.NiO and NiSO₄ form eutectic mixtures with alkali sulfates melting at temperatures lower than those of the pure salts.     

Thermal decomposition of peroxy acetyl nitrate CH3C(O)OONO2

The thermal decomposition of peroxy acetyl nitrate (PAN) is investigated by low pressure flash thermolysis of PAN highly diluted in noble gases and subsequent isolation of the products in noble gas matrices at low temperatures and by density functional computations. The IR spectroscopically observed formation of CH3C(O)OO and H2CCO (ketene) besides NO2, CO2, and HOO implies a unimolecular decay pathway for the thermal decomposition of PAN. The major decomposition reaction of PAN is bond fission of the O-N single bond yielding the peroxy radical. The O-O bond fission pathway is a minor route. In the latter case the primary reaction products undergo secondary reactions whose products are spectroscopically identified. No evidence for rearrangement processes as the formation of methyl nitrate is observed. A detailed mapping of the reaction pathways for primary and secondary reactions using quantum chemical calculations is in good agreement with the experiment and predicts homolytic O-N and O-O bond fissions within the PAN molecule as the lowest energetic primary processes. In addition, the first IR spectroscopic characterization of two rotameric forms for the radical CH3C(O)OO is given.     

Thermal deamination kinetics of tris(ethylenediamine)nickel(II) sulphate in the solid-state

Thermogravimetric techniques have been used to study the kinetics of thermal deamination of tris(ethylenediamine)nickel(II) sulphate. The complex was synthesized and characterized by various chemical and spectral techniques. Thermal decomposition studies were carried at different heating rates (5, 10, 15 and 20°C min⁻¹) in dynamic air. The complex undergoes a four-stage decomposition pattern. The stages are not well resolved. Decomposition path can be interpreted as a two-stage deamination, and a two-stage decomposition. Reaction products at each stage were separated and identified by means of IR and XRD. The morphology of the complex and the residue were studied by means of SEM. Final residue of the decomposition was found to be crystalline NiO. The deamination kinetics was studied using model-free isoconversional methods viz., Friedman, Flynn-Wall-Ozawa (FWO) and Kissinger-Akahira-Sunose (KAS) methods. It is observed that the activation energy varies with the extent of conversion; indicating the complex nature of the deamination reaction.     

Lanthanum nitrate decomposition by both temperature programmed heating and citrate gel combustion

Thermal decomposition of lanthanum nitrate to lanthanum oxide was carried out by both temperature programmed heating (TPH) and citrate-gel combustion. The temperature programmed heating was carried out under flow of oxidizing (air), neutral (nitrogen) and reducing (25 vol.% hydrogen+argone mixture) gases, and the processes were controlled by simultaneous thermogravimetry and differential thermal analysis. It was shown that hydrogen atmosphere helps to reduce temperatures of all decomposition steps. The results of TPH were utilized to check the nature of residues in the products of lanthanum nitrate-to-oxide conversion performed via citrate-gel combustion technique.     

(NEt(4))(2)[Fe(CN)(2)(CO)('S(3)')]: an iron thiolate complex modeling the [Fe(CN)(2)(CO)(S-Cys)(2)] site of [NiFe] hydrogenase centers

In the search for complexes modeling the [Fe(CN)(2)(CO)(cysteinate)(2)] cores of the active centers of [NiFe] hydrogenases, the complex (NEt(4))(2)[Fe(CN)(2)(CO)('S(3)')] (4) was found ('S(3)'(2-)=bis(2-mercaptophenyl)sulfide(2-)). Starting complex for the synthesis of 4 was [Fe(CO)(2)('S(3)')](2) (1). Complex 1 formed from [Fe(CO)(3)(PhCH=CHCOMe)] and neutral 'S(3)'-H(2). Reactions of 1 with PCy(3) or DPPE (1,2-bis(diphenylphosphino)ethane) yielded diastereoselectively [Fe(CO)(2)(PCy(3))('S(3)')] (2) and [Fe(CO)(dppe)('S(3)')] (3). The diastereoselective formation of 2 and 3 is rationalized by the trans influence of the 'S(3)'(2-) thiolate and thioether S atoms which act as pi donors and pi acceptors, respectively. The trans influence of the 'S(3)'(2-) sulfur donors also rationalizes the diastereoselective formation of the C(1) symmetrical anion of 4, when 1 is treated with four equivalents of NEt(4)CN. The molecular structures of 1, 3 x 0.5 C(7)H(8), and (AsPh(4))(2)[Fe(CN)(2)(CO)('S(3)')] x acetone (4 a x C(3)H(6)O) were determined by X-ray structure analyses. Complex 4 is the first complex that models the unusual 2:1 cyano/carbonyl and dithiolate coordination of the [NiFe] hydrogenase iron site. Complex 4 can be reversibly oxidized electrochemically; chemical oxidation of 4 by [Fe(Cp)(2)PF(6)], however, led to loss of the CO ligand and yielded only products, which could not be characterized. When dissolved in solvents of increasing proton activity (from CH(3)CN to buffered H(2)O), complex 4 exhibits drastic nu(CO) blue shifts of up to 44 cm(-1), and relatively small nu(CN) red shifts of approximately 10 cm(-1). The nu(CO) frequency of 4 in H(2)O (1973 cm(-1)) is higher than that of any hydrogenase state (1952 cm(-1)). In addition, the nu(CO) frequency shift of 4 in various solvents is larger than that of [NiFe] hydrogenase in its most reduced or oxidized state. These results demonstrate that complexes modeling properly the nu(CO) frequencies of [NiFe] hydrogenase probably need a [Ni(thiolate)(2)] unit. The results also demonstrate that the nu(CO) frequency of [Fe(CN)(2)(CO)(thiolate)(2)] complexes is more significantly shifted by changing the solvent than the nu(CO) frequency of [NiFe] hydrogenases by coupled-proton and electron-transfer reactions. The "iron-wheel" complex [Fe(6)[Fe('S(3)')(2)](6)] (6) resulting as a minor by-product from the recrystallization of 2 in boiling toluene could be characterized by X-ray structure analysis.     

A kinetic investigation on the pyrolysis of Seguruk asphaltite

The pyrolysis of Seguruk asphaltite has been investigated using thermogravimetric analysis at atmospheric pressure between 293 to 1223 K at different linear heating rates of 5, 10 and 20 K min⁻¹ under nitrogen as ambient gas. There was a two-stage thermal decomposition. Thermal decomposition started around 630 K for stage 1 for the slowest heating rate. On the other hand, for the same heating rate and stage 2, thermal decomposition started around 950 K. These values were shifted to higher temperatures with increasing heating rate. In this study, two different Coats-Redfern methods were applied to thermal degradation of Seguruk asphaltite.     

甲醇在FeS2(100)完整表面的吸附和分解

采用基于第一性原理的密度泛函理论结合周期平板模型方法, 研究了甲醇分子在FeS₂(100)完整表面的吸附与解离. 通过比较不同吸附位置的吸附能和构型参数发现: 表面Fe位为有利吸附位, 甲醇分子通过氧原子吸附在表面Fe位, 吸附后甲醇分子中的C―O键和O―H键都有伸长, 振动频率发生红移; 甲醇分子易于解离成甲氧基CH3O和H, 表面Fe位仍然是二者有利吸附位. 通过计算得出甲醇在FeS₂(100)表面解离吸附的可能机理: 甲醇分子首先发生O―H键的断裂, 生成甲氧基中间体, 继而甲氧基C―H键断裂, 得到最后产物HCHO和H₂.     

Kinetics of thermal decomposition of iron(III) dicarboxylate complexes

Summary Tris(dicarboxylate) complexes of iron(III) with oxalate, maleate, malonate and phthalate viz. K₃[Fe(C₂O₄)₃]×3H₂O (1), K₃[Fe(OOCCH₂COO)₃]×3H₂O (2), K₃[Fe(OOCCH=CHCOO)₃]×3H₂O (3), K₃[Fe(OOC-1,2-(C₆H₄)-COO)₃]×3H₂O (4) have been synthesized and characterized using a combination of physicochemical techniques. The thermal decomposition behaviour of these complexes have been investigated under dynamic air atmosphere upto 800 K. All these complexes undergo a three-step dehydration/decomposition process for which the kinetic parameters have been calculated using Freeman-Carrol model as well as using different mechanistic models of the solid-state reactions. The trisoxalato and trismalonato ferrate(III) complexes undergo rapid dehydration at lower temperature below 470 K. At moderately higher temperatures (i.e. >600 and 500 K, respectively) they formed bis chelate iron(III) complexes. The trismalonato and trismaleato complexes dehydrate with almost equal ease but the latter is much less stable to decomposition and yields FeCO₃ below 760 K. The cis-dicarboxylate complexes particularly with maleate(2-) and phthalate(2-) ligands are highly prone to the loss of cyclic anhydrides at moderately raised temperatures. The thermal decomposition of the tris(dicarboxylato)iron(II) to iron oxide was not observed in the investigated temperature range up to 800 K. The dehydration processes generally followed the first or second order mechanism while the third decomposition steps followed either three-dimensional diffusion or contracting volume mechanism.     

Thermal behaviour of Ni(II) nitrate hydrate and its aerosols

Fine, hollow, spherical particles with an average size of one micronmeter were formed through pyrolysis of aerosol of nickel nitrate solution. The aerosol product obtained by fast heating to 450°C consisted of tiny crystallites of NiO, hydrated nitrate, and other non-crystalline phase(s). By heating above 480°C, it consisted only of crystalline NiO. To understand the reactions occurring during the aerosolization process, thermal analysis was conducted on nickel nitrate hexahydrate in stagnant and flowing air using different heating rates. The mechanism for the decomposition of nickel(II) nitrate hexahydrate is proposed.

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Zusammenfassung Durch Pyrolyse eines Aerosols von Nickelnitratlösung werden feinkörnige, hole, kugelförmige Partikel mit einer durchschnittlichen Größe von einem Mikrometer gebildet. Das durch schnelles Erhitzen auf 450°C erhaltene Aerosolprodukt bestand aus winzigen NiO-Kristallen, aus hydratiertem Nitrat und aus anderen nichtkristallinen Phasen. Durch Erhitzen über 480°C erhält man ausschließlich kristallines NiO. Zum Verständnis der während des Aerosolierungsvorganges ablaufenden Reaktionen wurde in ruhender und dynamischer Luftatmosphäre sowie bei verschiedenen Aufheizgeschwindigkeiten eine Thermoanalyse von Nickelnitrat-Hexahydrat durchgeführt. Im Ergebnis konnte ein Mechanismus für die Zersetzung von Nickel(II)-nitrat-Hexahydrat entwickelt werden.

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We gratefully acknowledge support of this research by the Regents of Texas A & M University through the AUF-sponsored Materials Science and Engineering Program.     

K改性Ni-Co-Al三元复合氧化物催化分解N2O

制备了(Ni+Co)/Al=3、Ni/Co=0.2(原子比)的NiCoAl三元类水滑石样品,焙烧获得NiCoAl复合氧化物,表面浸渍K₂CO₃溶液制备了K改性催化剂,用于N₂O分解反应,考察了K负载量、焙烧温度等制备参数和O₂、H₂O等反应气氛对催化剂活性的影响。用BET、XRD、H₂-TPR、XPS等技术表征了催化剂的组成结构。结果表明,K的表面改性提高了催化剂对N₂O分解反应的催化活性,其中,400℃预焙烧NiCoAl类水滑石制得复合氧化物,初湿浸渍K₂CO₃溶液,K的负载量为K/(Ni+Co)=0.05,400℃ 再焙烧制备的催化剂活性较高,有氧有水条件下500℃ 反应时N₂O可完全分解;在NiCoAl复合氧化物表面负载K₂CO₃组分,降低了催化剂表面Co、Ni元素的电子结合能,弱化了表面Co-O、Ni-O化学键,从而提高了催化剂活性和抗水性能。     

Differential scanning calorimetry of sodium and potassium nitrates and nitrites

Differential scanning calorimetry (DSC) experiments were performed with NaNO₃, KNO₃, (Na,K)NO₃, NaNO₂ and KNO₂ over the temperature range 350–990 K. Endothermic peaks, indicative of decomposition reactions, were observed to occur in the single salts above their melting points. The equimolar mixture of sodium and potassium nitrate did not decompose in the temperature range specified. The nitrites began to decompose at 800±10 K. Sodium nitrate began to decompose at 840±10 K and potassium nitrate began to decompose at 820±20 K. These results were compared with previously reported differential thermal analysis investigations of NaNO₃ and KNO₃.