Showing papers on "Ammonia published in 2020"
TL;DR: The combined results of online differential electrochemical mass spectrometry (DEMS) and density functional theory (DFT) calculations demonstrated that the electron transfer from Cu 2 O to Cu at the interface could facilitate the formation of * NOH intermediate and suppress the hydrogen evolution reaction, leading to high selectivity and Faradaic efficiency.
Abstract: Unveiling the active phase of catalytic materials under reaction conditions is important for the construction of efficient electrocatalysts for selective nitrate reduction to ammonia. The origin of the prominent activity enhancement for CuO (Faradaic efficiency: 95.8 %, Selectivity: 81.2 %) toward selective nitrate electroreduction to ammonia was probed. 15 N isotope labeling experiments showed that ammonia originated from nitrate reduction. 1 H NMR spectroscopy and colorimetric methods were performed to quantify ammonia. In situ Raman and ex situ experiments revealed that CuO was electrochemically converted into Cu/Cu2 O, which serves as an active phase. The combined results of online differential electrochemical mass spectrometry (DEMS) and DFT calculations demonstrated that the electron transfer from Cu2 O to Cu at the interface could facilitate the formation of *NOH intermediate and suppress the hydrogen evolution reaction, leading to high selectivity and Faradaic efficiency.
528 citations
TL;DR: In this paper, a copper-incorporated crystalline 3,4,9,10-perylenetetetracarboxylic dianhydride was used to synthesize ammonia from nitrate ions.
Abstract: Ammonia (NH3) is essential for modern agriculture and industry and is a potential energy carrier. NH3 is traditionally synthesized by the Haber–Bosch process at high temperature and pressure. The high-energy input of this process has motivated research into electrochemical NH3 synthesis via nitrogen (N2)–water reactions under ambient conditions. However, the future of this low-cost process is compromised by the low yield rate and poor selectivity, ascribed to the inert N≡N bond and ultralow solubility of N2. Obtaining NH3 directly from non-N2 sources could circumvent these challenges. Here we report the eight-electron direct electroreduction of nitrate to NH3 catalysed by copper-incorporated crystalline 3,4,9,10-perylenetetracarboxylic dianhydride. The catalyst exhibits an NH3 production rate of 436 ± 85 μg h−1 cm−2 and a maximum Faradaic efficiency of 85.9% at −0.4 V versus a reversible hydrogen electrode. This notable performance is achieved by the catalyst regulating the transfer of protons and/or electrons to the copper centres and suppressing hydrogen production. Electrochemically reducing nitrogen-containing molecules could provide less energy-intense routes to produce ammonia than the traditional Haber–Bosh process. Here the authors use a catalyst comprising Cu embedded in an organic molecular solid to synthesize ammonia from nitrate ions.
514 citations
TL;DR: In this article, a wide-range investigation of the oxidation mechanism of ammonia was performed in a jet-stirred reactor and a flow reactor under lean conditions (0.01 ≤ Φ ≤ 0.375).
Abstract: A complete understanding of the mechanism of ammonia pyrolysis and oxidation in the full range of operating conditions displayed by industrial applications is one of the challenges of modern combustion kinetics. In this work, a wide-range investigation of the oxidation mechanism of ammonia was performed. Experimental campaigns were carried out in a jet-stirred reactor and a flow reactor under lean conditions (0.01 ≤ Φ ≤ 0.375), such to cover the full range of operating temperatures (500 K ≤ T ≤ 2000 K). Ammonia conversion and the formation of products and intermediates were analyzed. At the same time, the ammonia decomposition reaction, H-abstractions and the decomposition of the HNO intermediate were evaluated ab initio, and the related rates were included in a comprehensive kinetic model, developed according to a first-principles approach. Low-temperature reactor experiments highlighted a delayed reactivity of ammonia, in spite of the high amount of oxygen. A very slow increase in NH3 consumption rate with temperature was observed, and a full reactant consumption was possible only ∼150–200 K after the reactivity onset. The use of flux analysis and sensitivity analysis allowed explaining this effect with the terminating effect of the H-abstraction on NH3 by O2, acting in the reverse direction because of the high amounts of HO2. The central role of H2NO was observed at low temperatures (T < 1200 K), and H-abstractions from it by HO2, NO2 and NH2 were found to control reactivity, especially at higher pressures. On the other side, the formation of HNO intermediate via NH2 + O = HNO + H and its decomposition were found to be crucial at higher temperatures, affecting both NO/N2 ratio and flame propagation.
209 citations
04 May 2020
TL;DR: In this article, the authors used a stainless steel cloth-based support for tetrahydrofuran synthesis paired with hydrogen oxidation, achieving an ammonia partial current density of 8.8 ± 1.4 µm/cm−2 and a Faradaic efficiency of 35 ± 6% using a lithium-mediated approach.
Abstract: Electrochemical transformations in non-aqueous solvents are important for synthetic and energy storage applications. Use of non-polar gaseous reactants such as nitrogen and hydrogen in non-aqueous solvents is limited by their low solubility and slow transport. Conventional gas diffusion electrodes improve the transport of gaseous species in aqueous electrolytes by facilitating efficient gas–liquid contacting in the vicinity of the electrode. Their use with non-aqueous solvents is hampered by the absence of hydrophobic repulsion between the liquid phase and carbon fibre support. Herein we report a method to overcome transport limitations in tetrahydrofuran using a stainless steel cloth-based support for ammonia synthesis paired with hydrogen oxidation. An ammonia partial current density of 8.8 ± 1.4 mA cm−2 and a Faradaic efficiency of 35 ± 6% are obtained using a lithium-mediated approach. Hydrogen oxidation current densities of up to 25 mA cm−2 are obtained in two non-aqueous solvents with near-unity Faradaic efficiency. The approach is then applied to produce ammonia from nitrogen and water-splitting-derived hydrogen. Non-polar gaseous reactants such as N2 and H2 exhibit low solubility and slow transport in non-aqueous solvents and conventional gas diffusion electrodes cannot avoid non-aqueous electrolyte penetration. Here, transport limitations and catalyst flooding in tetrahydrofuran are overcome by using a stainless steel cloth-based support for lithium-mediated ammonia synthesis paired with H2 oxidation.
207 citations
TL;DR: Results from this study suggest that Bi5O7Br with rich oxygen vacancies can be used as high-performance photocatalysts towards nitrogen fixation.
Abstract: Photocatalytic nitrogen fixation represents a green alternative to the conventional Haber–Bosch process in the conversion of nitrogen to ammonia. In this study, a series of Bi5O7Br nanostructures w...
206 citations
TL;DR: Ammonia is considered to be a potential medium for hydrogen storage, facilitating CO2-free energy systems in the future as mentioned in this paper, and is also considered safe due to its high auto ignition temperature, low condensation pressure and lower gas density than air.
Abstract: Ammonia is considered to be a potential medium for hydrogen storage, facilitating CO2-free energy systems in the future. Its high volumetric hydrogen density, low storage pressure and stability for long-term storage are among the beneficial characteristics of ammonia for hydrogen storage. Furthermore, ammonia is also considered safe due to its high auto ignition temperature, low condensation pressure and lower gas density than air. Ammonia can be produced from many different types of primary energy sources, including renewables, fossil fuels and surplus energy (especially surplus electricity from the grid). In the utilization site, the energy from ammonia can be harvested directly as fuel or initially decomposed to hydrogen for many options of hydrogen utilization. This review describes several potential technologies, in current conditions and in the future, for ammonia production, storage and utilization. Ammonia production includes the currently adopted Haber–Bosch, electrochemical and thermochemical cycle processes. Furthermore, in this study, the utilization of ammonia is focused mainly on the possible direct utilization of ammonia due to its higher total energy efficiency, covering the internal combustion engine, combustion for gas turbines and the direct ammonia fuel cell. Ammonia decomposition is also described, in order to give a glance at its progress and problems. Finally, challenges and recommendations are also given toward the further development of the utilization of ammonia for hydrogen storage.
200 citations
TL;DR: In this article, the authors proposed an efficient and clean avenue for ammonia synthesis, via electroreduction of nitrate which could be obtained from industrial wastewater, domestic sewage, sodium nitrate ore, and nitrification of bacteria and electrochemical oxidation of nitrogen, which simultaneously upgraded the nitrate to high-value ammonia.
139 citations
TL;DR: In this paper, it was shown that neither nanoparticulate carbon-supported gold, nor bismuth powder are active catalysts for the electrocatalytic dinitrogen reduction.
Abstract: The results presented herein unambiguously demonstrate that neither nanoparticulate carbon-supported gold, nor bismuth powder are active catalysts for the electrocatalytic dinitrogen reduction, but...
139 citations
TL;DR: Sulfur dioxide (SO2), ammonia (NH3), hydrogen sulfide (H2S), nitrogen dioxide (NO2), and nitric oxide (NO) are toxic gases from industrial exhaust as discussed by the authors.
Abstract: Sulfur dioxide (SO2), ammonia (NH3), hydrogen sulfide (H2S), nitrogen dioxide (NO2), and nitric oxide (NO) are toxic gases from industrial exhaust, which could lead to acid rain, air pollution, hea...
106 citations
TL;DR: Kinetic analysis and isotope experiments combined with density functional theory (DFT) calculations indicate that the nitrogen vacancies in CeN can activate both N2 and H2 during the reaction, which accounts for the much higher catalytic performance than other reported nonloaded catalysts for ammonia synthesis.
Abstract: Ammonia is one of the most important feedstocks for the production of fertilizer and as a potential energy carrier. Nitride compounds such as LaN have recently attracted considerable attention due ...
89 citations
TL;DR: In this paper, the synergistic effect of hydrogen peroxide and ammonia on lignin was analyzed using modern analytical techniques including elemental analysis, gel permeation chromatography (GPC), Fourier transform infrared (FT-IR), and two-dimensional heteronuclear single-quantum coherence nuclear magnetic resonance (2D-HSQC NMR) spectroscopy.
TL;DR: A CaFH solid solution with low activation energy for catalytic ammonia synthesis at lower temperatures is reported that uses a stable electron-donating heterogeneous catalyst, cubic CaFH, a solid solution of CaF 2 and CaH 2 formed at low temperatures.
Abstract: The lack of efficient catalysts for ammonia synthesis from N2 and H2 gases at the lower temperature of ca. 50 °C has been a problem not only for the Haber–Bosch process, but also for ammonia production toward zero CO2 emissions. Here, we report a new approach for low temperature ammonia synthesis that uses a stable electron-donating heterogeneous catalyst, cubic CaFH, a solid solution of CaF2 and CaH2 formed at low temperatures. The catalyst produced ammonia from N2 and H2 gases at 50 °C with an extremely small activation energy of 20 kJ mol−1, which is less than half that for conventional catalysts reported. The catalytic performance can be attributed to the weak ionic bonds between Ca2+ and H− ions in the solid solution and the facile release of hydrogen atoms from H− sites. Ammonia synthesis via the Haber–Bosch process typically takes place at an elevated temperature in order to achieve a reasonable rate. Here the authors report on a CaFH solid solution with low activation energy for catalytic ammonia synthesis at lower temperatures.
TL;DR: The results demonstrated that microwave pyrolysis biochar can be a promising solution for growing nitrifying bacteria in aquaponic system for simultaneous toxic ammonia remediation and generation of nitrate for growing vegetable in aquaculture industry.
TL;DR: Ammonia has proved to be an effective alternative to hydrogen in low-temperature fuel cells via its direct ammonia oxidation reaction (AOR), however, the kinetically sluggish AOR has prohibit... as discussed by the authors.
Abstract: Ammonia (NH3) has proved to be an effective alternative to hydrogen in low-temperature fuel cells via its direct ammonia oxidation reaction (AOR). However, the kinetically sluggish AOR has prohibit...
TL;DR: In this article, a coal-fired furnace with capacity of 1.2MWth was used to evaluate the characteristics of ammonia co-firing with different ammonia guns, and it was shown that CO2 emission can be reduced in proportion to the cofiring ratio as expected.
TL;DR: Ammonia is a crucial nutrient used for plant growth and as a building block in the pharmaceutical and chemical industry, produced via nitrogen fixation of the ubiquitous atmospheric N2.
Abstract: Ammonia is a crucial nutrient used for plant growth and as a building block in the pharmaceutical and chemical industry, produced via nitrogen fixation of the ubiquitous atmospheric N2. Current ind...
TL;DR: A boron compound has been shown to mediate the one-pot binding, cleavage and reduction of N 2 to ammonium salts under mild conditions through a complex cascade mechanism involving multiple reduction–protonation sequences.
Abstract: The industrial reduction of dinitrogen (N2) to ammonia is an energy-intensive process that consumes a considerable proportion of the global energy supply. As a consequence, species that can bind N2 and cleave its strong N-N bond under mild conditions have been sought for decades. Until recently, the only species known to support N2 fixation and functionalization were based on a handful of metals of the s and d blocks of the periodic table. Here we present one-pot binding, cleavage and reduction of N2 to ammonium by a main-group species. The reaction-a complex multiple reduction-protonation sequence-proceeds at room temperature in a single synthetic step through the use of solid-phase reductant and acid reagents. A simple acid quench of the mixture then provides ammonium, the protonated form of ammonia present in fertilizer. The elementary reaction steps in the process are elucidated, including the crucial N-N bond cleavage process, and all of the intermediates of the reaction are isolated.
TL;DR: In this paper, the presence of all possible sublimation products of five different ammonium salts in the comet 67P/Churyumov-Gerasimenko measured by the ROSINA instrument onboard Rosetta was reported.
Abstract: Cometary comae are generally depleted in nitrogen. The main carriers for volatile nitrogen in comets are NH3 and HCN. It is known that ammonia readily combines with many acids, such as HCN, HNCO and HCOOH, encountered in the interstellar medium as well as in cometary ice to form ammonium salts (NH4+X−) at low temperatures. Ammonium salts, which can have a substantial role in prebiotic chemistry, are hard to detect in space as they are unstable in the gas phase and their infrared signature is often hidden by thermal radiation or by, for example, OH in minerals. Here we report the presence of all possible sublimation products of five different ammonium salts in the comet 67P/Churyumov–Gerasimenko measured by the ROSINA instrument onboard Rosetta. The relatively high sublimation temperatures of the salts leads to an apparent lack of volatile nitrogen in the coma. This then also explains the observed trend of higher NH3/H2O ratios with decreasing perihelion distances in comets. A dust impact event detected by the ROSINA mass spectrometer towards the end of the Rosetta mission brings evidence of the presence of ammonium salts in comets. Ammonium salts can store enough nitrogen to explain the observed nitrogen depletion in comets and may have a role in amino acid formation.
TL;DR: An unintended consequence of industrial nitrogen fixation through the Haber-Bosch process is nitrate (NO3−) and nitrite (NO2−) contamination of ocean, ground, and surface waters from fertilizer run.
Abstract: An unintended consequence of industrial nitrogen fixation through the Haber–Bosch process is nitrate (NO3–) and nitrite (NO2–) contamination of ocean, ground, and surface waters from fertilizer run...
TL;DR: In this paper, the results obtained show a 20% reduction in the TAN and a 30% reduction of volatile fatty acids by a moderate in-situ ammonia stripping with and without stripping.
TL;DR: This work illustrates the power of precise control over a catalytic material, simultaneous kinetic and spectroscopic interrogation over a wide range of reaction conditions, and computational strategies tailored to capture those reaction conditions to reveal in microscopic detail the mechanistic features of a complex and widely practiced catalysis.
Abstract: ConspectusCopper-exchanged chabazite (Cu-CHA) zeolites are catalysts used in diesel emissions control for the abatement of nitrogen oxides (NOx) via selective catalytic reduction (SCR) reactions wi...
TL;DR: In this article, the stability limits of theoretically-premixed ammonia-hydrogen-air flames are measured in a laboratory-scale swirl combustor for a wide range of ammonia fractions in the ammonia and hydrogen fuel blend.
TL;DR: In this paper, a cradle-to-gate environmental assessment of conventional and greener hydrogen production routes integrated with ammonia synthesis is carried out according to ReCIPe impact assessment method, and the results show that natural gas-based ammonia synthesis integrated with chemical looping hydrogen production gives the highest reduction in Global Warming Potential while six out of the nine investigated impact indicators suffer an increase between 30% and 60%.
Abstract: Ammonia synthesis is a topic of high interest in the industry as the market continues to expand and demand increases. The current ammonia production route is very energy and carbon-intensive, relying greatly on natural gas both as feedstock as well as for heat and power generation within the plant. In the present work, a cradle-to-gate environmental assessment of conventional and greener hydrogen production routes integrated with ammonia synthesis is carried out according to ReCIPe impact assessment method. Hydrogen production through conventional steam methane reforming coupled with gas-liquid carbon dioxide absorption by amines and chilled ammonia, electrolysis, and iron-based chemical looping are analysed and compared. Mass and energy balances from process flow modelling are used as inputs for the environmental evaluation using Life Cycle Assessment. The system boundaries considered in this work include: i) main processes: ammonia production, hydrogen production, carbon dioxide separation; ii) upstream processes: nitrogen, natural gas, ilmenite, Methyl-DiEthanol-Amine, chilled ammonia and catalysts supply chains, iii) downstream processes: carbon dioxide compression, transport and storage, degradation/disposal of solvents/oxygen carrier. The results show that natural gas-based ammonia synthesis integrated with chemical looping hydrogen production gives the highest reduction in Global Warming Potential while six out of the nine investigated impact indicators (excluding Global Warming Potential) suffer an increase between 30% and 60%. In the case of hydrogen produced from electrolysis, unless the electricity necessary for electrolysis is obtained from non-fossil sources, it results in the highest overall emissions to air, water and soil.
TL;DR: NiO and NiO-TiO2 nano-catalysts were synthetized using solution combustion synthesis (SCS) method and tested toward ammonia oxidation in synthetic and real wastewater as mentioned in this paper.
TL;DR: Overall these results indicated that EL-MNP@zeolite had significant potential as a nano-remediation strategy to simultaneously remove cationic ammonium and anionic phosphate from wastewaters.
TL;DR: In this paper, a comprehensive environmental life cycle assessment of heat and power production through solid oxide fuel cells (SOFCs) fueled by various chemical feeds namely; natural gas, hydrogen, ammonia and methanol.
TL;DR: In this article, a cyclic PSA unit was used to produce a high-purity hydrogen stream for fuel cell applications from a synthetic mixture with a molar composition of 58% H2, 25% N2, 15% CH4 and 2% Ar, based on ammonia purge gas.
TL;DR: The photocatalyst mechanism study revealed that [Formula: see text] was the predominant reactive oxygen species in the ammonia photodegradation.
TL;DR: In this paper, the authors used bipolar membrane electrodialysis to remove ammonium from water and to simultaneously produce concentrated dissolved ammonia, without using chemicals, and the energy consumption and current efficiency were assessed throughout sequencing batch experiments.
TL;DR: The PNOCRA process is presented, combining plasma-assisted nitrogen oxidation and Lean NOx Trap technology, adopted from diesel engine exhaust gas aftertreatment technology, which achieves an energy reduction over 4-fold compared to the state-of-the-art plasma-enabled ammonia synthesis from N2 and H2 with reasonable yield.
Abstract: Ammonia is an industrial large-volume chemical, with its main application in fertilizer production. It also attracts increasing attention as a green-energy vector. Over the past century, ammonia production has been dominated by the Haber-Bosch process, in which a mixture of nitrogen and hydrogen gas is converted to ammonia at high temperatures and pressures. Haber-Bosch processes with natural gas as the source of hydrogen are responsible for a significant share of the global CO2 emissions. Processes involving plasma are currently being investigated as an alternative for decentralized ammonia production powered by renewable energy sources. In this work, we present the PNOCRA process (plasma nitrogen oxidation and catalytic reduction to ammonia), combining plasma-assisted nitrogen oxidation and lean NOx trap technology, adopted from diesel-engine exhaust gas aftertreatment technology. PNOCRA achieves an energy requirement of 4.6 MJ mol-1 NH3 , which is more than four times less than the state-of-the-art plasma-enabled ammonia synthesis from N2 and H2 with reasonable yield (>1 %).