Addition Of NH Research Articles

NF3 synthesis using ClF3 as a mediator

Synthesis of NF3 using NH4F/nHF and F2 with ClF3, NF2Cl, and NFCl2 intermediates was conducted by sequential reaction testing for more than 100 h. Results demonstrated that NF3 can be synthesized with yield of more than 90% - fluorine molecule base. The ClF3 produced as a by-product can be recycled for reaction with NH4F/nHF. Improving the yield necessitates ClF3 recovery rate improvement, but characteristics of using ClF + F2 = ClF3 as an equilibrium reaction can be overcome with a two-step reaction. NH4F/nHF can be recycled continuously by controlling the n value in NH4F/nHF through NH3 addition and HF extraction. Using ClF3 as a mediator and NH3 and F2 as raw materials, NF3 synthesis was achieved at atmospheric pressure.

Analysis of air-staged combustion of NH3/CH4 mixture with low NOx emission at gas turbine conditions in model combustors

The NOx formation characteristics have been numerically investigated in the NH3/CH4 fired model combustor consisting of perfectly stirred reactors (PSR) and plug flow reactors (PFR) with 84-species Tian mechanism at gas-turbine relevant conditions of 23 atm and 1873 K at the combustor outlet. Specifically, the impacts of NH3 dilution on NOx formation were first studied in a non-staged model combustor consisting of one PSR representing main combustion zone and one PFR representing post-combustion zone over a wide range of the volumetric ratio of NH3 in the NH3/CH4 fuel. It was found that the NOx emission increases sharply with the NH3 addition mainly through the enhanced HNO pathway in the main reaction zone. Recognizing that the NOx formation via the HNO pathway is limited by the availability of oxygen, the effects of fuel/air equivalence ratio on NOx formation were then quantified under different levels of NH3 dilution. It was revealed that at fuel-rich conditions, the NOx formation via HNO pathway can be offset by the reduction via other pathways, such as pathways related to NHi, leading to the overall low NOx emission. Finally, an air-staged model combustion system was proposed, in which the equivalence ratio in the primary stage was chosen to be 1.5 to take advantage of the low NOx emission under fuel-rich conditions. The air split among the two stages was determined by the fixed outlet temperature of 1873 K. A parametric study demonstrated that less than 30 ppm NOx emission can be achieved with simple two-stage combustion even when the volumetric ratio of the NH3 reaches 40%, which is dramatically lower than the one of thousands ppm in the non-staged combustion. The results were further verified with the 47-species Konnov mechanism, demonstrating the great potential of air-staged combustion for low NOx emission in the NH3/CH4 fired combustion.

Extinction limits and structure of counterflow nonpremixed methane-ammonia/air flames

An experimental and computational investigation on the fundamental combustion characteristics of methane (CH4)-ammonia (NH3) blends is conducted to confirm their potential as a clean fuel with low carbon dioxide (CO2) emissions and determine their reasonable burning conditions, considering counterflow nonpremixed CH4NH3/air flames. Extinction limits and structure of the nonpremixed CH4NH3/air flames are measured and predicted. Results show that flames gradually become orange and the flame thickness increases with NH3 addition, compared with the pure CH4/air flames. Also, flames can sustain less NH3 at high strain rates. Compared with the pure CH4/air flames, CH4NH3/air flames exhibit remarkable reduction of CO2 emissions with moderate reduction of combustion stability limits and no remarkable temperature drop in the flame, supporting the potential of CH4NH3 blends as a clean fuel with low CO2 emissions. However, additional investigations for reducing the enhanced NOx emissions mainly via the fuel NOx mechanism with NH3 addition are needed. Finally, the quantitative discrepancy among the present measurements and predictions merits the development of a new reaction mechanism which is optimized for the reaction of CH4NH3 fuel blends and air.

One-pot synthesis of (1RS,21SR)-diethyl 2-[23-amino-22-eth-oxy-carbonyl-8,11,14-trioxa-25-aza-tetra-cyclo-[19.3.1.02,7.015,20]penta-cosa-2,4,6,15(20),16,18,22-heptaen-25-yl]but-2-endioate.

The title compound, C30H34N2O9 (4), is a product of the Michael reaction of aza-crown ether with dimethyl acetyl-enedi-carboxyl-ate modified by an addition of NH3 (aq.) at 298 K. The aza-14-crown-4-ether ring adopts a bowl conformation. The dihedral angle between the planes of the benzene rings fused to the aza-14-crown-4-ether moiety is 8.65 (5)°. The tetra-hydro-pyridine ring has a boat conformation. The mol-ecular conformation is supported by one N-H⋯O and two C-H⋯O intra-molecular hydrogen bonds. Both heterocyclic and amino N atoms have essentially planar configurations (sums of the bond angles are 359.35 and 358.00°). Compound 4 crystallizes as a racemate consisting of enanti-omeric pairs of the 1R,21S diastereomer. In the crystal, mol-ecules of 4 are connected by N-H⋯O hydrogen bonds, forming chains along [100]. According to the PASS program (computer prediction of biological activities), compound 4 may exhibit anti-allergic (72% probability) and anti-asthmatic (67%) activity, as well as be a membrane permeability inhibitor (65%).

Abatement of SF6 in the presence of NH3 by dielectric barrier discharge plasma

In this paper, the degradation rate, energy yield and the degradation by-products of SF6 was studied when different concentrations of NH3 were added. When NH3 concentration increased from 0 to 2%, the degradation rate efficiency(DRE) of SF6 increased from 60% to 97.23% under the flow rate of 50ml/min and 94W input power. The energy yield(EY) reached 4.16g/kWh. In addition, we found that increasing the flow rate to 250ml/min, the DRE decreased to 58.71%, but the EY increased to 12.55g/kWh. The main gas by-products are SOF2, SO2F2, SO2, OF2, HF and NF3. When the concentration of initial NH3 increased, the SO2 concentration increased while the concentrations of SOF2, SO2F2, SOF4 decreased. In addition, we found that a pale yellow film formed on the surface of the reactor wall. XPS analysis showed that the solid products were mainly S, NH3HF and NH4HF2. The emission spectra show that NH3 addition can effectively promote the formation of active particles and increase plasma density.The addition of NH3 can convert some of the sulfur and fluorine into solid products and reduce the production of toxic gases.

XPS and IR studies of plasma polymers layer deposited from allylamine with addition of ammonia

The plasma polymerization of allylamine was often investigated to modify polymer surfaces with primary amino groups. However, this deposition process is characterized by a significant loss of NH2 groups originally present in allylamine. To compensate this loss of NH2 groups in the deposited plasma polymer layer ammonia was added to the plasma process. Indeed, huge amount of nitrogen could be incorporated into the plasma polymer using addition of ammonia but the yield in primary amino groups was not increased. Extensive side-reactions were observed.Such NH2 group-enriched polymer surfaces are interesting for bio-applications.The influence of NH3 addition to allylamine on the yield of primary amino groups was characterized using FTIR-ATR, X-ray photoelectron spectroscopy and differential scanning calorimetry.

Preparation of Ag Nanoparticles in Ammonia by Using EDM and a Study of the Relationships Between Ammonia and Silver Nanoparticles

This study used deionized water and ammonia (0.02%) as dielectric fluids and then employed electronic discharge machine to ionize them, with the arc-focused energy melting the surface of silver electrode rods. After the condensation of the dielectric fluid, silver nano-colloids were prepared under two conditions, named as Ag and Ag(NH3), respectively. The optical properties of the two samples were compared by a UV–Vis spectrum analyzer (UV–Vis), and the zeta potential was measured by Zetasizer. We then utilized a transmission electron microscope to observe the shape, size, and distribution of silver nanoparticles. The results showed that with the addition of NH3, the size of silver nanoparticles decreased, the concentration of nano-colloid increased, and the dispersive suspension of nano-colloid became better.

Resolution and signal-to-noise in analysis of carbohydrate isomers by graphitised carbon chromatography with charged aerosol detection

The effects of co-eluents and additives on separation and signal-to–noise ratio in analyses of monosaccharides by graphitised carbon chromatography (GCC) in combination with charged aerosol detection were studied. Design of experiments was used to model and predict the elution of two monosaccharide isomers, galactose and glucose and the corresponding amine at varying isocratic conditions, including concentration of water-soluble co-eluent, flow and temperature. The study confirmed the well-known order of eluent strength of the co-eluents investigated but showed that the eluent strength of MeOH was significantly lower than that of ACN, and at co-eluent concentrations ≥5% (v/v) IPA approached that of THF. Addition of NH3 increased retention and improved both peak shape and separation but the detector response decreased with increasing NH3 concentration lowering the signal-to-noise ratio. The best combination of response, retention and separation was obtained at 0.1% NH3. Increasing column temperature in the range of 15–50°C resulted in decreased retention times and resolution. The corresponding Van’t Hoff correlations showed negative adsorption enthalpies indicating an exothermic adsorption process driven by a decrease in entropy minimising the surface energy of the system. Isocratic elution with MeOH as co-eluent offered limited possibilities for optimisation of resolution due to the opposite effects of changes in co-eluent concentration and changes in flow rate. Elution with acetonitrile as co-eluent showed possibilities for optimisation of the resolution within the range of flow rates of 0.6-0.95mL/min and co-eluent concentrations of 0.1–0.3%, with the highest resolution predicted at 0.1% acetonitrile and a flow rate of 0.81mL/min. Saccharides in the size range DP1–4, including amino, acetamido, and deoxy sugars, were separated using a binary gradient method. Higher retention was observed for increasing degree of polymerisation (DP) and N-acetylated saccharides were retained longer than non-substituted saccharides of corresponding DP. Partial resolution of two lacto-N-tetrasaccharide positional isomers was obtained.

Formation of NO and NH in NH3-doped CH4 + N2 + O2 flame: Experiments and modelling

Co-combustion of 5200 ppm NH3 with a stoichiometric, atmospheric pressure, CH4 + N2 + O2 flame has been investigated with experiments and kinetic modelling. Profiles of the amidogen (NH) radical and nitric oxide (NO) have been measured using laser-induced fluorescence, the latter being quantitatively determined. Temperature profiles were measured using Rayleigh scattering and thermocouple, the nonintrusive measurements were considered more reliable and were used for evaluation of LIF data as well as input for flame modelling. Experimental results are compared with predictions of a chemical mechanism developed by Mendiara and Glarborg (2009), with simulations based on solution of energy equation as well as on experimental temperature profiles as input. Compared with a neat flame, the NH3-doped flame shows a shift in position ∼0.7 mm downstream, as established from the measurements of the NH profile. Modelling prediction of post-flame NO concentrations in the NH3-doped flame, around 1160 ppm, was within the evaluated uncertainty with experimental data (1460 ppm). Reaction path analysis indicated NH2 as a key species in the formation of NO and N2 from the nitrogen added to the flame by NH3. Altogether, the mechanism predicts concentration levels rather well but fails to predict the shift in flame position obtained with addition of NH3 to the rather slowly burning hydrocarbon flame.

Controlling bromate formation in the Co(II)/peroxymonosulfate process by ammonia, chlorine-ammonia and ammonia-chlorine pretreatment strategies

The Co(II)/peroxymonosulfate (Co(II)/PMS) process, producing sulfate radicals (SO4•-), effectively removes organic pollutants in water, while producing a significant amount of bromate (BrO3−) in the presence of bromide (Br−). This paper investigates the ammonia (NH3) addition, chlorine-ammonia (Cl2-NH3) and ammonia-chlorine (NH3-Cl2) pretreatment strategies in controlling BrO3− formation in 20 min in the Co(II)/PMS process at pH 4.0. The addition of NH3 retarded the BrO3− formation, but only at a reduction level of about 9.5% for NH3 concentration of 50 μM, and was mainly attributed to the protonation of NH3 at pH 4 (99.99% as NH4+, did not react with HOBr). Both the Cl2-NH3 and NH3-Cl2 pretreatment strategies at HOCl and NH3 dosages of 15 and 50 μM, respectively, reduced 95% or more of the overall BrO3− formation and retarded the BrO3− formation, with the NH3-Cl2 pretreatment strategy outperforming Cl2-NH3. The reduction of the BrO3− formation was mainly attributed to the formation of monochloramine (NH2Cl) in both pretreatment strategies. NH2Cl effectively outcompetes SO4•- to react with HOBr and forms NHBrCl, with the apparent reaction rate constant between NH2Cl and HOBr more than 100 times faster than that between SO4•- and HOBr. However, the oxidation/degradation of NHBrCl in the Co(II)/PMS process reforms HOBr, and, although less in quantity, is oxidized to BrO3− at higher Co(II) and Br− concentrations. Thus, the NH3-Cl2 and Cl2-NH3 pretreatment strategies inhibit the BrO3− formation more significantly at lower Co(II) and Br− concentrations. In all cases, the generation of SO4•- in 20 min was not affected by the implementation of the three BrO3− pretreatment strategies.

The low spin - high spin equilibrium in the S2-state of the water oxidizing enzyme

In Photosystem II (PSII), the Mn4CaO5-cluster of the active site advances through five sequential oxidation states (S0 to S4) before water is oxidized and O2 is generated. Here, we have studied the transition between the low spin (LS) and high spin (HS) configurations of S2 using EPR spectroscopy, quantum chemical calculations using Density Functional Theory (DFT), and time-resolved UV-visible absorption spectroscopy. The EPR experiments show that the equilibrium between S2LS and S2HS is pH dependent, with a pKa ≈ 8.3 (n ≈ 4) for the native Mn4CaO5 and pKa ≈ 7.5 (n ≈ 1) for Mn4SrO5. The DFT results suggest that exchanging Ca with Sr modifies the electronic structure of several titratable groups within the active site, including groups that are not direct ligands to Ca/Sr, e.g., W1/W2, Asp61, His332 and His337. This is consistent with the complex modification of the pKa upon the Ca/Sr exchange. EPR also showed that NH3 addition reversed the effect of high pH, NH3-S2LS being present at all pH values studied. Absorption spectroscopy indicates that NH3 is no longer bound in the S3TyrZ state, consistent with EPR data showing minor or no NH3-induced modification of S3 and S0. In both Ca-PSII and Sr-PSII, S2HS was capable of advancing to S3 at low temperature (198 K). This is an experimental demonstration that the S2LS is formed first and advances to S3via the S2HS state without detectable intermediates. We discuss the nature of the changes occurring in the S2LS to S2HS transition which allow the S2HS to S3 transition to occur below 200 K. This work also provides a protocol for generating S3 in concentrated samples without the need for saturating flashes.

The effect of NH3·H2O addition in Ni/SBA-15 catalyst preparation on its performance for carbon dioxide reforming of methane to produce H2

Three kinds of Ni catalysts loaded on SBA-15 were prepared by impregnation method, adding NH3·H2O or C2H2O4 in the impregnant, and applied to CO2 reforming (DRM) of methane to generate hydrogen at 750 °C. The results showed that the catalyst prepared with NH3·H2O addition exhibited high activity and stability. TEM, H2-TPR, XPS, XRD, and TG-MS characterization indicated that with addition of NH3·H2O (0.1 mol L−1) in the preparation process, small nickel oxide particles, with average size of about 7 nm, were obtained on the catalyst, and the strong association between support and Ni species made them uniformly dispersed, enabling the capacity to resist carbon deposition and metal sintering, which contributed to the excellent activity, stability and selectivity for the DRM to H2 production.

Hydrothermal Liquefaction Enhanced by Various Chemicals as a Means of Sustainable Dairy Manure Treatment

Because of the increase in concentrated animal feeding operations, there is a growing interest in sustainable manure management. In this study, hydrothermal liquefaction (HTL) of dairy manure enhanced by various chemicals (NH3·H2O, H3PO4, and glycerol) was proposed as a sustainable alternative for the dairy manure management. The applications of NH3·H2O and H3PO4 during HTL could significantly enhance the production of liquid chemicals. The addition of NH3·H2O or glycerol increased the amounts of non-polar toluene, xylene, and other benzene-contained compounds, while the use of H3PO4 produced high amounts of acids, pyridine, 3-methyl-pyridine, 2,6-dimethyl-pyrazine, 2-cyclopenten-1-ones, and phenols. The biochars produced via HTL showed a significant increase in the surface area/pore volume and relatively higher N, P, C, and other minerals, and may serve as a good soil amendment and nutrient source. The preliminary energy analyses showed that the energy consumption of this process might be reduced to 50% of the original energy content of the feedstock, and the energy payback period was about 3.5 years. Combining all advantages, HTL of dairy manure might increase the sustainability of the farming operation via producing energy products, fine chemicals, and biochars.

Control of the microstructure and surface chemistry of graphene aerogels via pH and time manipulation by a hydrothermal method.

Three-dimensional graphene aerogels of controlled pore size have emerged as an important platform for several applications such as energy storage or oil-water separation. The aerogels of reduced graphene oxide are mouldable and light weight, with a porosity up to 99.9%, consisting mainly of macropores. Graphene aerogel preparation by self-assembly in the liquid phase is a promising strategy due to its tunability and sustainability. For graphene aerogels prepared by a hydrothermal method, it is known that the pH value has an impact on their properties but it is unclear how pH affects the auto-assembly process leading to the final properties. We have monitored the time evolution of the chemical and morphological properties of aerogels as a function of the initial pH value. In the hydrothermal treatment process, the hydrogel is precipitated earlier and with lower oxygen content for basic pH values (∼13 wt% O) than for acidic pH values (∼20 wt% O). Moreover, ∼7 wt% of nitrogen is incorporated on the graphene nanosheets at basic pH generated by NH3 addition. To our knowledge, there is no precedent showing that the pH value affects the microstructure of graphene nanosheets, which become more twisted and bent for the more intensive deoxygenation occurring at basic pH. The bent nanosheets attained at pH = 11 reduce the stacking by the basal planes and they connect via the borders, hence leading eventually to higher pore volumes. In contrast, the flatter graphene nanosheets attained under acidic pH entail more stacking and higher oxygen content after a long hydrothermal treatment. The gravimetric absorption capacity of non-polar solvents scales directly with the pore volume. The aerogels have proved to be highly selective, recyclable and robust for the absorption of nonpolar solvents in water. The control of the porous structure and surface chemistry by manipulation of pH and time will also pave the way for other applications such as supercapacitors or batteries.

NOx removal by NH3 and flammable additives in the selective non-catalytic reduction (SNCR) process

Reducing nitrogen oxides (NOx) emissions is becoming much more difficult and expensive for stricter environmental requirements. NOx emission restriction could not be achieved only by primary NOx reduction methods. This paper presents results of experimental research work of NOx removal by selective non-catalytic reduction (SNCR) technology. Experiments were performed in the temperature range of 1000–1200 oC to investigate the effects of additives (NH3, CH4, C2H2 and mixture of C3H8/C4H10). Comparing additives effects of NOx reduction while burning furniture production waste received that with NH3 additive reduces 56% of primary NOx. Flammable additives can reduce up to 76 % NOx emissions in exhaust gasses. Results showed that SNCR technology with flammable additives can change traditional NOx reduction additives and this technology can be easily installed in existing boilers.DOI: http://dx.doi.org/10.5755/j01.mech.23.5.16331

Efficient reduction of nitric oxide using zirconium phosphide powders synthesized by elemental combination method

Zirconium phosphide (ZrP) powders were synthesized by elemental combination method via the direct reaction of zirconium powders with red phosphorus, and characterized by XRD, SEM, XPS, XRF, SAED and TEM measurements. The obtained ZrP powders were found to exhibit apparent activity in the ready eliminateion of nitric oxide (NO) via facile redox reactions, and the elimination dynamics was evaluated within the context of various important experimental parameters, such as reaction temperature and gas concentration. At a fixed amount of ZrP powders, an increasing amount of NO would be eliminated with increasing reaction temperature, and complete conversion of NO to N2 could be reached in the range of 700 to 800 °C. The addition of NH3 also facilitated NO elimination at a fixed reaction temperature. Furthermore, of the products of the elimination process, zirconia (ZrO2) powder is a kind of biocompatible material, red phosphorus can be used to produce safety matches, organophosphorous pesticide and phosphor bronze, and the produced N2 might be collected and used as a protective gas or be converted into liquid nitrogen for other purposes.

Voltammetric determination of ascorbic acid by using a disposable screen printed electrode modified with Cu(OH)2 nanorods

The authors describe a disposable non-enzymatic sensor for ascorbic acid (AA) that was obtained by modifying a screen printed electrode (SPE) with Cu(OH)2 nanorods (NRs). The NRs were synthesized by a wet chemical process which involves sequential addition of NH3 and NaOH to CuSO4 solution. NR formation was confirmed by thermogravimetric, spectroscopic, microscopic, and diffraction studies. The Cu(OH)2 NRs were mixed with carbon ink and printed onto an SPE. Electrochemical detection of AA was carried out at pH 7.4, at a typical voltage as low as 0 mV versus saturated calomel electrode with a scan rate of 100 mV/s, and is assumed to involve the chemical reduction of Cu(II) by AA followed by electrochemical oxidation of Cu(I). The sensor has a linear response in the 0.0125 to 10 mΜ AA concentration range. Response to AA is free from interference by urea, glucose, uric acid, dopamine, metal ions such as Fe2+, Zn2+ and Ni2+, NaCl, KCl and ethanol. It was applied to the determination of AA in a vitamin C tablet and in urine.

A composite reactor with wetted-wall column for mineral carbonation study in three-phase systems.

Despite the availability of various reactors designed to study gas-liquid reactions, no appropriate devices are available to accurately investigate triple-phased mineral carbonation reactions involving CO2 gas, aqueous solutions (containing divalent cations), and carbonate minerals. This report presents a composite reactor that combines a modified conventional wetted-wall column, a pH control module, and an attachment to monitor precipitation reactions. Our test and calibration experiments show that the absorption column behaved largely in agreement with theoretical predictions and previous observations. Experimental confirmation of CO2 absorption in NaOH and ethanolamine supported the effectiveness of the column for gas-liquid interaction. A test run in the CO2-NH3-MgCl2 system carried out for real time investigation of the relevant carbonation reactions shows that the reactor's performance closely followed the expected reaction path reflected in pH change, the occurrence of precipitation, and the rate of NH3 addition, indicating the appropriateness of the composite device in studying triple-phase carbonation process.

Amidine Production by the Addition of NH3 to Nitrile(s) Bound to and Activated by the Lewis Acidic [Re6(μ3-Se)8]2+ Cluster Core.

Acetonitrile bound to and activated by the Lewis acidic [Re6(μ3-Se)8]2+ cluster core was transformed into acetamidine in quantitative yield using NH3 as the nucleophile at room temperature. The amidine ligand was removed by treating the cluster-acetamidine complexes with trifluoroacetic acid in CH3CN, affording amidinium trifluoroacetate and the starting acetonitrile complexes.

Ligation kinetics as a probe for relativistic effects: Ligation of atomic coinage metal cations with ammonia

The kinetics for ammonia ligation of the three (d10) transition metal coinage cations Cu+, Ag+ and Au+ were measured in an attempt to assess the role of relativistic effects in reaction kinetics. Measurements of several main-group cations were included for comparison: the alkali (s0) cations K+, Rb+ and Cs+, the alkaline-earth (s1) cations Ca+, Sr+ and Ba+ and the p0 atomic cations Ga+, In+ and Tl+. Measurements were performed at room temperature in helium bath gas at 0.35Torr using an Inductively-Coupled Plasma/Selected-Ion Flow Tube (ICP/SIFT) tandem mass spectrometer. The atomic cations are produced at ca. 5500K in an ICP source and are allowed to decay radiatively and to thermalize by collisions with argon and helium atoms prior to reaction. Rate coefficients are reported for ammonia addition, the only reaction channel that was observed with all these cations. A strong enhancement in the rate of addition of NH3 to Au+ was observed for the coinage metal cation period in contrast to the continuous decline in rate down the periodic table that was seen for the main group s0, s1 and p0 cations. We attribute this rate enhancement to the enhancement in the Au+-NH3 binding energy expected from relativistic effects. Comparisons are made with the periodic trends that we have reported previously for the rates of ligation of the coinage metal cations with O2, D2O, N2O, CO2, CS2, CH3F and SF6 and that we measured with pyridine. For seven of the nine ligands that were investigated, rate enhancement with Au+ provided an indirect experimental measure of relativistic effects.