Gas chromatographic determination of rate constants in bimolecular gaseous reactions

Summary Rate constants for bimolecular reactions in the gas phase, under diffusion controlled conditions, can easily be determined by the reversed-flow gas chromatography (RF-GC) technique. The analysis of the diffusion band by means of a simple PC programme gives directly an apparent, second-order rate constant for gaseous reactions. By varying the amounts of the reactants, one can calculate the true order of the reaction and the true non-first-order rate constant of gaseous reactions. The calibration problem of the analytical techniques in non-first-order reaction kinetics is absent as are other disadvantages connected with carrier gas flow, peak shape and their instrumental spreading. The method can be used for atmospheric reactions and was applied in the gaseous reaction systems: SO₂+NO₂, SO₂+Br₂, C₆H₆+NO₂, C₆H₅CH₃+NO₂ and C₃H₆+NO₂ with various concentrations of reactants in nitrogen. The effect of the NO₂ concentration on the apparent second-order rate constant of C₂H₄+NO₂ at 333.2 K was also studied. Finally, the effect of sun light pre-irradiation of C₂H₂+NO₂ in nitrogen was investigated.     

Interference of nitrite and nitrogen dioxide on mercury and selenium determination by chemical vapor generation atomic absorption spectrometry

In this study, a systematic investigation was performed concerning the interference of nitrogen oxides on the determination of selenium and mercury by hydride generation atomic absorption spectrometry (HG AAS) and cold vapor atomic absorption spectrometry (CV AAS). The effect of nitrate, nitrite and NO₂ dissolved in the condensed phase was evaluated. No effect of NO₃⁻ on Se and Hg determination was observed up to 100 mg of sodium nitrate added to the reaction vessel. The Se signal was reduced by about 80% upon the addition of 6.8 mg NO₂⁻. For Hg, no interference of nitrite was observed up to 20 mg of NO₂⁻. A complete suppression of the Se signal was observed when gaseous NO₂ was introduced into analytical solutions. For Hg, a signal decrease between 8 and 13% occurred. For Se, bubbling argon or heating the solution was not able to recover the original absorbance values, whereas Hg signals were recovered with these procedures. When gaseous NO₂ was passed directly into the atomizer, Se signals decreased similarly to when NO₂ was bubbled in analytical solutions. The addition of urea, hydroxylamine hydrochloride and sulfamic acid (SA) was investigated to reduce the NO₂ effect in sample digests containing residual NO₂, but only SA was effective in reducing the interference. Based on the results, it is possible to propose the use of SA to prevent interferences in Se and Hg determinations by HG AAS and CV AAS, respectively.     

Quantitative Fourier Transform Infrared Analysis of Gas Phase Cigarette Smoke and Other Gas Mixtures

Abstract

A new method for the analysis of selected components in complex gas mixtures has been developed utilizing a relatively inexpensive Fourier transform infrared spectrometer and a continuous flow gas cell. the method was used to monitor nitric oxide and nitrogen dioxide concentrations in cigarette smoke with time.

Using multivariate least-square regression analysis, it is possible to simultaneously quantitate both NO and NO₂, even in the presence of overlapping peaks. Using this method, the oxidation of nitric oxide in the presence of isoprene in cigarette smoke and in a model system was followed with time. the method also can be applied to other compounds in smoke or to any other gaseous mixture.     

Determination of Sulfur in Petroleum Coke Combining Closed Vessel Microwave-Induced Combustion and Inductively Coupled Plasma-Optical Emission Spectrometry

Abstract

A new procedure based on closed vessel Microwave-Induced Combustion (MIC) technique is proposed for the decomposition of petroleum coke and further determination of sulfur by Inductively Coupled Plasma-Optical Emission Spectrometry (ICP-OES). The procedure is based on sample ignition by microwave radiation using closed quartz vessels pressurized with oxygen and use of NH₄NO₃ as an ignition aid. The nature and concentration of absorbing/refluxing solution were studied, as well as the operational parameters related to MIC technique. Results were compared with those obtained by conventional wet digestion in closed vessels, certified reference materials (agreement was better than 98%), and also using ion chromatography for S determination.     

Note: Synthesis,Characterization and Crystal Structures of the Coordination Polymers [Cu(II)(NO3)2(BBMB) and [Mn(II)Cl2(BBMB)2] [BBMB = 1,4-Bis(1-Benzimidazolylmethyl) Benzene]

Two novel coordination polymers, [Cu(II)(NO₃)₂(bbmb)] _n (1) and [Mn(II)(Cl₂)(BBMB)₂] (2) [bbmb = 1,4-bis(1-benzimidazolylmethyl)benzene], were synthesized and characterized by IR and thermal analyses. Single-crystal X-ray diffraction analysis shows that Polymer 1 exhibits a distorted metal tetrahedron in its structure, involving two nitrogen atoms from bbmb ligands and two oxygen atoms from NO₃ groups. Each Cu(II)(NO₃)₂ unit is bridged by bbmb to form a zigzag chain structure. Polymer 2 possesses a two-dimensional network. The coordination environment around Mn(II) is a distorted octahedron and its solid-state structure exhibits a layered packing mode. In the polymers the two coordinating nitrogen atoms on bridging bbmb ligands are trans to the central benzene plane.     

Ultraviolet laser photoacoustic spectrometric determination of sulfur dioxide in mixtures containing larger amounts of nitrogen dioxide

Concentrations of sulfur dioxide in the nl l^?1 range are quantitatively measured in gaseous mixtures containing a large excess of nitrogen dioxide by using ultraviolet laser photoacoustic spectrometry. Mixtures containing SO₂ as a minority component are prepared by gas permeation methods. Photoacoustic spectra with 0.5 cm^?1 resolution in the 299.7–303.1 nm region are presented and are used to identify the spectral signatures of each component needed for selective detection. A procedure for the determination of both SO₂ and NO₂ is presented with major emphasis on the sensitivity and dynamic range of SO₂ detection. Concentrations of SO₂ as low as 1.45 nl l^?1 are detected in the presence of 901 nl l^?1 NO₂ in nitrogen at 1 atm total pressure. The effect of adding water vapor (from 17 to 66% relative humidity) is described.     

Interaction of polynuclear palladium (I) carbonyl carboxylates with gaseous NO: X-ray structure of eight-nuclear clusters Pd8(μ-CO)4(μ-OOCR)4[μ-N(O)O–]4

The reaction of palladium carbonyl carboxylates Pd₆(CO)₆(RCOO)₆ with gaseous nitrogen monoxide was investigated. These clusters were found to promote the NO disproportionation into N₂ and NO₂ under mild conditions. The reaction is accompanied with the oxidation of coordinated carbon monoxide. These processes result in unusual eight-nuclear palladium carboxylate clusters Pd₈(CO)₄(NO₂)₄(RCOO)₈.     

Synthesis and structural characterization of nitrite-coordinating CoII and CoIII complexes as models for the reaction center of Co-substituted nitrite reductase

Co^II and Co^III complexes containing nitrite and tridentate aromatic amine compounds [bis(6-methyl-2-pyridylmethyl)amine (Me₂bpa) and bis(2-pyridylmethyl)amine (bpa)] have been prepared as models of the catalytic center in Co-substituted nitrite reductase: [Co^II(Me₂bpa)(NO₂)Cl]₂ · acetone (2), Co^II(Me₂bpa)(NO₂)₂ (3), Co^II(bpa)(NO₂)Cl (4), Co^II(bpa)(NO₂)₂ (5), Co^III(Me₂bpa)(NO₂)(CO₃) (6), and Co^III(bpa)(NO₂)₃ (7). The X-ray crystal structure analyses of these Co^II and Co^III complexes indicated that the geometries of the cobalt centers are distorted octahedral and the Me₂bpa and bpa with three nitrogen donors exhibit mer- (2, 3, and 7) and fac-form (4 and 6). The coordination mode of nitrite depends on the cobalt oxidation state, to Co^II through the oxygen (nitrito coordination, O- and O,O-coordination) and to Co^III through nitrogen (nitro coordination, N-coordination mode). These findings are consistent with the results of their IR spectra, except that another oxygen of the O-coordinated nitrito group in 3 might interact weakly with Co^II according to its IR spectrum. Reductions of the nitrite in 2, 3, 4, and 5 to nitrogen monoxide were not accelerated in the presence of proton, perhaps due to the nitrito coordination in these Co^II complexes.     

Electrosynthesis of α-Amino Acids from NO and other NOx species over CoFe alloy-decorated Self-standing Carbon Fiber Membranes

The conversion of industrial exhaust gases of nitrogen oxides into high-value products is significantly meaningful for global environment and human health. And green synthesis of amino acids is vital for biomedical research and sustainable development of mankind. Herein, we demonstrate an innovative approach for converting nitric oxide (NO) to a series of α-amino acids (over 13 kinds) through electrosynthesis with α-keto acids over self-standing carbon fiber membrane with CoFe alloy. The essential leucine exhibits a high yield of 115.4 μmol h⁻¹ corresponding a Faradaic efficiency of 32.4 %, and gram yield of products can be obtained within 24 hours in lab as well as an ultra-long stability (>240 h) of the membrane catalyst, which could convert NO into NH₂OH rapidly attacking α-keto acid and subsequent hydrogenation to form amino acid. In addition, this method is also suitable for other nitrogen sources including gaseous NO₂ or liquidus NO₃⁻ and NO₂⁻. Therefore, this work not only presents promising prospects for converting nitrogen oxides from exhaust gas and nitrate-laden waste water into high-value products, but also has significant implications for synthetizing amino acids in biomedical and catalytic science.     

Thermal decomposition of [Cd(NH<Subscript>3</Subscript>)<Subscript>6</Subscript>](NO<Subscript>3</Subscript>)<Subscript>2</Subscript>

Thermal decomposition of [Cd(NH₃)₆](NO₃)₂ was studied by thermogravimetry (TG) with simultaneous differential thermal analysis (SDTA) for two samples and at two different sets of measurement parameters. The gaseous products of the decomposition were on-line identified by evolved gas analysis (EGA) with a quadruple mass spectrometer (QMS). The decomposition of the title compound proceeds, for both cases, in the three main stages. In the first stage, deammination of [Cd(NH₃)₆](NO₃)₂ to [Cd(NH₃)](NO₃)₂ undergoes by three steps and 5/6 of all NH₃ molecules are liberated. At second stage the liberation of residual 1/6NH₃ molecules and the formation of Cd(NO₃)₂ undergoes. However, during this process simultaneously a two-step oxidation of a part of ammonia molecules also takes place. In a first step as a result a mixture of ammonia, water vapour and nitrogen is formatted. At the second step, subsequent oxidation of a next part of NH₃ molecules undergoes. As a result, a mixture of nitrogen oxide, nitrogen and water vapour is formatted, what for these both steps clearly indicates the EGA analysis. The third stage of the thermal decomposition is connected with the melting and subsequent decomposition of residual Cd(NO₃)₂ to oxygen, nitrogen dioxide and solid CdO. Additionally, third sample was measured by differential scanning calorimetry (DSC) and the results are fully consistent with those obtained by TG.     

Thermodynamic Dissociation Constants for [MPy4(NO3)2]*2Py Clathrates (M=Mn,Co, Ni,Cu)

Abstract

Stoichiometry and thermodynamic parameters of the title clathrates dissociation have been studied with thermoanalytical and strain method techniques. The [MPy₄(NO₃)₂]^*2Py (M = Mn, Co, Ni) clathrates dissociate with collapsing clathrate porous phase and destruction of the host complex to give the respective tripyridine complexes and gaseous pyridine. The [CuPy₄(NO₃)₂]^*2Py dissociates with collapsing clathrate phase but giving the host [CuPy₄(NO₃)₂] complex as individual phase, with the tripyridine complex forming in further course of decomposition. The comparison of the thermodynamic dissociation parameters for the [MPy₄(NO₃)₂]^*2Py series with M = Mn, Co, Ni, Cu, Zn and Cd shows that the differences in the stability of the compounds do not correlate with structural parameters of the clathrates but depend on the nature of the metal cation in the host complex. Thermodynamic stability of these clathrate phases follows the general sequence of stabilty for complexes of the 3d transition metals known as Irwing-Williams sequence: Mn<Fe<Co<Ni<Cu>Zn. These results disclose the main issue of instability of the [MPy₄(NO₃)₂]^*2Py clathrates as instability of the respective host complexes.     

Nitrogen Oxide Fluorides

Oxyfluorides of nitrogen, i.e. compounds containing the grouping F? N? O, have been known for many years in the form of simple compounds, such as NOF and NO₂F. Detailed studies of physical, structural, and chemical aspects of this class of compounds have been conducted only in recent years, after the potential of N? F compounds as rocket propellants had been recognized. Several novel types of oxyfluorides of nitrogen, such as difluorohydroxyl amines, RO? NF₂, or trifluoroamine oxide, F₃NO, have been discovered recently. A further major development in O? N? F chemistry is indicated by the discovery that compounds of great chemical potential are formed between HF and NOF or NO₂F, respectively. The compound O₂NOF, although not an oxyfluoride of nitrogen, will also be discussed in this review, because of its particular chemical relationship to NO₂F.     

Synthesis, characterization and thermal properties of cobalt(II), nickel(II) and copper(II) complexes of 2,6-bis(3,4,5-trimethyl-N-pyrazolyl)pyridine): the crystal structure of [Co(btmpp)(H2O)2(NO3)]NO3

Co(II), Ni(II) and Cu(II) nitrate complexes with btmpp, namely ([Co(btmpp)(H₂O)₂(NO₃)]NO₃ (1), [Ni(btmpp)(H₂O)(NO₃)]NO₃ (2) and [Cu(btmpp)(MeOH)(NO₃)]NO₃ (3), where btmpp = 2,6-bis(3,4,5-trimethyl-N-pyrazolyl)pyridine), have been synthesized and characterized by physicochemical and spectroscopic methods. The crystal structure of complex 1 has been determined by single crystal diffraction at 100K. In all the complexes, btmpp is coordinated in a tridentate mode through its nitrogen atoms. One of the nitrates in complex 1 is terminally bonded to the metal center through the oxygen atom, whereas the other one is out of the coordination sphere. The Co(II) atom in complex 1 is hexa-coordinated with a CoN₃O₃ distorted octahedral environment. Decomposition of three complexes was analyzed thermogravimetrically. All three complexes decompose similar to explosive material.     

The preparation and reactivity of metal-containing monomers. 54. Thermolysis of the acrylamide monomer [Co(CH2=CHCONH2)4(H2O)2](NO3)2

The kinetics and pathways of thermolysis of the Co(II) complex with acrylamide, [Co(CH₂=CHCONH₂)₄(H₂O)₂](NO₃)₂ (1) were studied. The rate of gas evolution is satisfactorily approximated by a first-order equation of autocatalysis. The composition of gaseous and solid products of thermolysis of 1 was studied by IR spectroscopy, mass spectrometry, and electronic microscopy. Thermal transformations of acrylamide complex 1 include three macro stages: dehydration, polymerization of the dehydrated monomer, and thermooxidative destruction of the resulting polymer.     

Experimental characterization of gaseous species emitted by the fast pyrolysis of biomass and polyethylene

This study aims to experimentally characterize the carbonaceous and nitrogenous species, from the flash pyrolysis of millet stalks and polyethylene plastic bags, using the device of the tubular kiln, coupled to two gas analyzers: Analyzer Fourier Transform Infrared (FTIR) and an analyzer Infrared Non-Dispersive (IRND). Gaseous products analyzed are: CH₄, C₂H₂, C₂H₄, C₃H₈, C₆H₆, CO, CO₂, NO₂, NO, N₂O, HCN and NH₃. Whatever the temperature of thermal degradation, the pyrolysis shows us that in terms of mass:

• •For the millet stalks, the gaseous compounds are formed mainly CO and CO₂ to the carbonaceous species, HCN and NH₃, for the nitrogenous species analyzed;
• •As regards the polyethylene bags, hydrocarbons for carbonaceous species and HCN, NH₃ and NO₂ for the nitrogenous species, are most abundant.

In addition, the results suppose that in our experimental conditions, the hydrocarbon which is involved primarily in the formation of CO is ethylene C₂H₄. At the end of this characterization, we determined the rate of carbon and nitrogen found in the volatile gas. With millet stalks we have about 45% of volatile carbon and 15% of the nitrogen of fuel that are found in gaseous products. The results obtained with the plastic bags give 68% carbon and 15% nitrogen found in the nitrogenous species analyzed.     

Syntheses,crystal structures,and electrochemical characterizations of two octahedral iron(III) complexes with Schiff base of pyridoxal and aminoguanidine

This article presents the synthesis, physico-chemical, in particular voltammetric, characteristics of two iron(III) complexes with pyridoxal aminoguanidine (PLAG), [Fe(PLAG)Cl₂(H₂O)]Cl (1) and [Fe(PLAG)₂](NO₃)₃ (2). As expected, the zwitterion of the chelate ligand is coordinated tridentate through oxygen of phenol and nitrogen atoms of azomethine and imino groups of the aminoguanidine fragment. In both complexes, Fe(III) is distorted octahedral. [Fe(PLAG)₂](NO₃)₃ (2) is the first bis(ligand) complex with this ligand. Cyclic voltammetric characteristics of the ligand and complexes were studied in DMF in the presence of TBAP or LiCl as supporting electrolytes. The complexes are unstable in this solvent, especially in the presence of an excess of chloride, thus forming several reducible species whose stabilities and behaviors were characterized.     

Estimation of uncertainty in the determination of nitrogen oxides emissions

This paper presents a methodology for estimation of uncertainty on a reference test method for the determination of nitrogen oxides concentration in gaseous emissions from stationary sources. As a first stage for identification of uncertainty sources, the test method is carefully reviewed in detail. Afterwards, these sources are quantified, bearing in mind its partial uncertainty, allowing the determination of the combined uncertainty and, finally, the expanded uncertainty. The calculation procedure was implemented into an excel calculation file. Using this file and considering several numerical applications from real situations, uncertainities around 15 mg/Nm³ over determined concentrations of 350 mg/Nm³ of NO _x (expressed as NO₂) were obtained.     

Gas-phase oxidation of vinyltrifluorosilane with nitrogen dioxide under the action of a pulse CO<Subscript>2</Subscript> laser

A chemical reaction between C₂H₃SiF₃ and NO₂ induced by radiation from a pulse CO₂ laser was studied by mass spectrometry and IR spectroscopy. The composition of gaseous products was determined. A macrokinetic approach was developed to study bimolecular reactions initiated by pulsed IR radiation. The procedure developed allowed us to answer the question of whether the test reaction occurs under conditions when the molecules of only one reactant are vibrationally excited or under conditions of equal vibrational temperatures. The use of this approach to the reaction between C₂H₃SiF₃ and NO₂ demonstrated that its acceleration was due to the equilibrium heating of the system.     

On the Interaction of Cold Atmospheric Pressure Plasma with Surfaces of Bio-molecules and Model Polymers

We review studies of surface-interaction mechanisms for a surface microdischarge (SMD) and an atmospheric pressure plasma jet (APPJ) with model polymers and biomolecules in our laboratory. We discuss the influence of plasma source type, operating parameters, and gaseous environments on surface modifications and biological deactivation. We focus on mild, remote conditions where the visible plasma plume does not contact the surface. For an APPJ fed with Ar, the interaction of the plasma plume with O₂ and/or N₂ gaseous environments leads to oxidation and surface-bound NO_x even on materials containing neither oxygen nor nitrogen. The APPJ also modifies photo-sensitive polymers. Using optical filters, these modifications were shown to result in part from irradiation with vacuum ultraviolet (VUV) photons in a spectral range corresponding to Ar excimer emission. No VUV-induced effects were seen for the SMD source operated with O₂/N₂. SMD treatments using O₂/N₂ mixtures result in surface oxidation and nitridation. A new surface-bound species, NO₃, has been measured on the polymers and biomolecules. Depending on the gas chemistry and film molecular structure, the NO₃ surface concentration can reach 10 %. Both surface NO₃ on plasma-treated films of lipopolysaccharide (LPS), an immune stimulating biomolecule found in bacteria such as E. c oli, and overall surface oxidation correlate with LPS biological deactivation as evaluated using an enzyme-linked immunosorbent assay. Ambient humidity was studied using the SMD and was found to decrease overall surface modifications including NO₃ and biodeactivation for O₂-rich conditions. Lastly, we discuss possible mechanisms and compare our results with published simulation studies.     

Synthesis and characterization of Pr(III), Nd(III) and Er(III) complexes with 2,6-pyridinedimethanol

The reactions of Ln(NO₃)₃?6H₂O (Ln=Pr, Nd or Er) with the potentially tridentate O,N,O chelating ligand 2,6-pyridinedimethanol (H₂pydm) in a 1:2 M ratio were investigated, and complexes with the formula [Ln(H₂pydm)₂(NO₃)₂](NO₃) (Ln=Pr or Nd) (1 and 2) and [Er(H₂pydm)₃](NO₃)₃ (3) were isolated. The compounds contain 10-coordinate Pr(III) and Nd(III) ions that crystallize in the triclinic space group P-1 while the 9-coordinate Er(III) complex crystallizes in the monoclinic system (P2₁/n). A new lanthanide complex, [Pr(H₂pydm)₃](Cl)₃?DMF (4), has been synthesized by reaction of PrCl₃?6H₂O and H₂pydm. The nine-coordinate Pr(III) is bound to three H₂pydm ligands. X-ray crystal structures of 1–4 reveal that the ligand coordinates tridentate via the pyridyl nitrogen and the two hydroxyl oxygens. The electronic absorption spectra of 1–4 show 4f–4f transitions.