Ammonia Generation Research Articles

Hydrogen desorption from MgH2+NH4Cl/graphene composites at low temperatures

MgH2 is considered one of the most promising candidates for solid-state hydrogen storage. However, the dehydrogenation of MgH2 generally happens at temperatures above 250 °C even after catalyzing and/or nano-confining modifications, thus embarrassing the practical use of MgH2 in fuel cells. NH4Cl is a cheap chemical which has mature synthesis technologies in large industrial productions. The protonic H (Hδ+) in NH4Cl and the hydridic H (Hδ−) in MgH2 have coulomb interaction which allow MgH2 to release hydrogen at milder temperatures. In this article, by designing the molar ratio of MgH2 and NH4Cl as 2:1 (equal molar ratio of Hδ+ and Hδ−), the hydrogen release peak temperature can be decreased to 164.8 °C, and the ammonia generation is remarkably suppressed. In particular, graphene introduction to the 2MgH2+NH4Cl composite can further reduce the hydrogen release temperature to 161.2 °C and improve the hydrogen purity up to 97.26%. It is revealed that the smaller particle size and the better dispersion of 2MgH2+NH4Cl/graphene composite allows better interaction between Hδ+ and Hδ−, which brings down the hydrogen desorption temperature and improves the hydrogen purity.

Ammonia production using iron nitride and water as hydrogen source under mild temperature and pressure

Ammonia generation was studied in the reaction between water and nitrogen-containing iron at 323 K and atmospheric pressure. Similar to metallic Fe, the interstitial compound Fe3N reduced water through Fe oxidation to produce hydrogen gas, while the N combined with atomic hydrogen to produce ammonia as a byproduct. The addition of carbon dioxide to this system accelerated the reaction with concomitant consumption of carbon dioxide. The promoted ammonia production upon addition of carbon dioxide can be attributed to the generation of atomic hydrogen from the redox reaction of carbonic acid and Fe, as well as removal of used Fe from the reaction system through the formation of a soluble carbonato complex. When carbonate was added to the reaction system, the production rates of ammonia and hydrogen increased further. The results here confirmed that ammonia can be synthesized from iron nitride under mild conditions by utilizing carbon dioxide.

A Green Synthesis of Ru Modified g-C 3 N 4 Nanosheets for Enhanced Photocatalytic Ammonia Synthesis

Nitrate is a crucial environmental pollutant, and its risk on ecosystem keeps increasing. Photocatalytic conversion of nitrate to ammonia can simultaneously achieve the commercialization of environmental hazards and recovery of valuable ammonia, which is green and sustainable for the planet. However, due to the thermodynamic and kinetic energy barriers, photocatalytic nitrate reduction usually involves a higher selectivity of the formation of nitrogen that largely limits the ammonia synthesis activity. In this work, we reported a green and facile synthesis of novel metallic ruthenium particle modified graphitic carbon nitride photocatalysts. Compare with bulk graphitic carbon nitride, the optimal sample had 2.93-fold photocatalytic nitrate reduction to ammonia activity (2.627 mg/h/g cat ), and the NH 3 selectivity increased from 50.77% to 77.9%. According to the experimental and calculated results, the enhanced photocatalytic performance is attributed to the stronger light absorption, nitrate adsorption, and lower energy barrier for the generation of ammonia. This work may provide a facile way to prepare metal modified photocatalysts to achieve highly efficient nitrate reduction to ammonia.

Electrochemical ammonia synthesis from nitrite assisted by in situ generated hydrogen atoms on a nickel phosphide catalyst.

Investigating green and effective means for ammonia synthesis is an important but challenging task. Electrochemical ammonia synthesis (EAS) from an indirect route (N2 → NOx → NH3) provides a feasible alternative strategy. The key step in this route is the reduction of NOx to NH3 instead of N2, which requires the investigation of efficient catalysts with high selectivity of NH3. Herein, we initially demonstrate a highly efficient electrochemical reduction of NO2- to NH3 with nickel phosphide (Ni2P) as the catalyst. The system exhibits low onset potential (0.2 V vs. RHE) and high faradaic efficiency (>90%) for EAS. Experimental results and theoretical calculations reveal that the in situ generated hydrogen atoms on the surface of Ni2P greatly promote the reduction of NO2- to NH3.

Enhanced dissolution rate of magnesium hydroxide via magnesia/ammonium acetate hydration system: statistical optimization and possible mechanism

AbstractBACKGROUNDThe dissolubility of magnesium hydroxide is often the main factor limiting its application effect in the environmental field, and the dissolution rate of magnesium hydroxide during its synthesis is also worthy of attention. In this paper, response surface methodology was used to synthesize magnesium hydroxide with different dissolution rates through a magnesium oxide/ammonium acetate hydration system, and the possible formation mechanism as well as dissolution performance is discussed.RESULTSCompared with the hydration temperature and time, the concentration of ammonium acetate has a more significant effect on the dissolution rate of hydrated magnesium hydroxide. A maximum dissolution rate of 43.8 ± 0.3 mmol min−1 mol−1 magnesium hydroxide could be obtained when the working factors were ammonium acetate concentration 15 g L–1, hydration temperature 75.5 °C and time 112 min.CONCLUSIONThe correlation study between structural characterization and the dissolution test shows that the complexation and replacement of acetate, in situ generation and release of ammonia appear to have some critical effects on magnesium hydroxide crystallization behaviour and induce the formation of thin, curved and defective structures. Crystals with such structures have been reported to have a higher dissolution activity. The results of this study provide an indication for screening hydration synthetic agents of high‐dissolution‐rate magnesium hydroxide. © 2020 Society of Chemical Industry (SCI)

Thermodynamic performance analysis and environmental impact assessment of an integrated system for hydrogen and ammonia generation

A novel multigeneration plant that's using natural gas for power, hydrogen, ammonia, and hot water generation, is planned and analyzed, in the current paper. The suggested combined plant integrated with four sub-systems, which are the Brayton cycle, reheat Rankine cycle, the high-temperature steam electrolyzer for hydrogen production, and ammonia synthesis processes. Also, thermodynamic analysis and environmental impact assessment are conducted for the designed plant and sub-systems. Moreover, the sustainability index analysis of this proposed study is conducted. The effects of some important indicators on the performance and on the environmental impact of the modeled system and sub-processes are also studied. According to analyses results, it is noted that the energetic and exergetic efficiencies of the suggested system are 51.83% and 70.27%, respectively, and also the total CO2 emission rate is 11.4 kg/kWh for the integrated plant. Furthermore, the total irreversibility rate is computed as 40007.68 kW, and furthermore, the combustion chamber has a maximum irreversibility rate with 20,033 kW, among the proposed plant components.

Photo-ammonification of low molecular weight dissolved organic nitrogen by direct and indirect photolysis

The photo-ammonification process plays a crucial role in the transformation of dissolved organic nitrogen (DON) to dissolved inorganic nitrogen (DIN). However, previous studies have primarily focused on DON biotransformation than on abiotic processes. This study investigated the photo-ammonification process of nine model low molecular weight (LMW) DON molecules (e.g., amino acids, nucleotides, and urea) under the influence of different light sources. The results showed that photo-ammonification of model DON was mainly induced by UV light, while negligible contribution by visible light was found. Depending on their molecular structures, amino acids yielded different ammonia amounts, whereas negligible photo-ammonification was observed for nucleotides and urea. As for the reactive species, OH promoted ammonia yields of all the model amino acids; 3CDOM⁎ contributed to the photo-ammonification of six amino acids; 1O2 only had a positive impact on ammonification of tryptophan, histidine, and tyrosine; and CO3− accelerated ammonia generation from histidine and methionine. In natural water samples, tryptophan, tyrosine, histidine, and methionine generated significant ammonia. OH and 1O2 were speculated as the contributing reactive species based on kinetic studies as well as significant fluorescent humic-like and tyrosine-like substances degradation in irradiated samples compared to the raw samples characterized by the EEM-PARAFAC analysis. The negative linear correlations between photo-ammonification rates and the ELUMO–EHOMO of the amino acids emphasized the importance of the role of the molecular structure. Overall, these results revealed the LMW DON photo-ammonification mechanism in sunlit surface waters and highlighted its significance in the nitrogen biogeochemical cycle as well as water quality management.

Using Coal Coke for N-Sorption with an Al-based Nitrogen Carrier during Chemical Looping Ammonia Generation

Chemical looping ammonia generation (CLAG) is thought to be another method for clean utilization of fossil fuels, because fossil fuels can be thoroughly converted into chemical material, CO, and no...

Ultrathin bismuth oxyiodide nanosheets for photocatalytic ammonia generation from nitrogen and water under visible to near-infrared light

Artificial photosynthesis of ammonia using atmospheric nitrogen and water is a sustainable but challenging alternative to the Haber-Bosch process. Bismuth oxyiodide (BiOI) is a promising candidate due to its superior light absorption capability (bandgap of around 1.8 eV) and abundant surface oxygen vacancies. However, its improper band edge positions made it inactive for overall water-splitting and N2 fixation. In this work, ultrathin BiOI nanosheets were synthesized through a simple surfactant (PVP) assisted hydrothermal route. The nanosheets split pure water into H2 and O2 and converted nitrogen and water into ammonia under visible or near-infrared light. PVP capping not only reduced the thickness of BiOI sheets but also upshifted its band edge positions due to the surface electric dipole induced by polyvinyl pyrrolidone molecules on the BiOI surface, thus enabling the water oxidation and nitrogen reduction half reactions simultaneously.

Evaluation of a hybrid process of magnetic ion-exchange resin treatment followed by ozonation in secondary effluent organic matter removal

The presence of effluent organic matter (EfOM) and organic micro-pollutants (OMPs) in secondary effluent is receiving increasing concern due to their potential impacts on the aquatic environment and human health. In this study, the removal characteristics of EfOM by magnetic ion-exchange resin (MIEX), ozonation, and the hybrid process of MIEX followed by ozonation (M + O) were compared by measuring the bulk organic indicators (BOIs), OMPs, bio-toxicity, and fluorescence. Furthermore, the desorption characteristics of MIEX were comprehensively studied. Ozonation could reduce the OMPs, total fluorescence (TF), genotoxicity, and oestrogenic activity more effectively than MIEX, with reductions of 80.3%, 97.8%, 98.9%, and 94.6%, respectively. The M + O process was capable of removing more EfOM than the individual MIEX or ozonation processes and could reduce the genotoxicity and oestrogenic activity to the detection limit. By implementing MIEX as a pre-treatment, the generation of ammonia–nitrogen and nitrate–nitrogen was effectively reduced in the subsequent ozonation process as MIEX adsorbed organic nitrogen and nitrite-nitrogen. The different regenerants influenced the OMP desorption performance of MIEX by changing the desorption mechanisms, and NaCl + NaOH was the best regenerant due to its high total OMP desorption efficiency. Parallel factor analysis coupled with self-organising maps further explained the differences in fluorescence desorption due to the addition of NaOH to the regenerated solution. Pearson correlation analysis indicated the potential of using spectroscopic indicators, such as ultraviolet absorbance and TF, to assess the evolution of OMPs and bio-toxicity during the M + O and MIEX desorption processes.

Anchoring Mo on C9N4 monolayers as an efficient single atom catalyst for nitrogen fixation

This work reports a novel Mo-based SAC catalyst (Mo@C 9 N 4 ), which exhibits excellent activity and selectivity toward electrochemical nitrogen reduction reaction with favorable limiting potential of 0.40 V. Electrochemical nitrogen fixation via a convenient and sustainable manner, exhibits an intriguing prospect for ammonia generation under ambient conditions. Currently, the design and development of high-efficiency and low-cost electrocatalysts remains the major challenge confronting nitrogen reduction reaction (NRR). Herein, anchoring the single Mo atom on the C 9 N 4 substrate (Mo@C 9 N 4 ) to form an efficient single-atom catalyst (SAC) is proposed for the conversion of N 2 to NH 3 . By employing density functional theory (DFT) calculations, we demonstrated that gas phase N 2 can be sufficiently activated and efficiently reduced to NH 3 on the surface of Mo@C 9 N 4 . Meanwhile, we found that the NRR dominantly occurred on the Mo center via a preferred distal pathway with favorable limiting potential of 0.40 V. Importantly, the as-established Mo@C 9 N 4 catalyst exhibits an outstanding structural stability and good selectivity toward NRR. These findings provide a promising platform for designing Mo-based SACs for electrochemical N 2 fixation.

基于 EEMD-GRU 的黄羽鸡舍冬季氨气浓度预测模型

In winter, the poor ventilation conditions in broiler houses may lead to high ammonia concentration, which affects the health of yellow-feather broilers or even causes the death of many broilers. This research used a machine learning model to predict the ammonia concentration in a broiler house during winter. After analysis, it was found that the ammonia generation in the broiler house was a gradual accumulation featured by non-linear data. After the broilers entered the broiler house for several days, and the ammonia concentration reached a certain value, a ventilation system was used for regulating the concentration. Firstly, the back-propagation (BP) neural network model and gated recurrent unit (GRU) model were used for predicting the ammonia concentration, respectively. Then, ensemble empirical mode decomposition (EEMD) was performed on the time series data of ammonia concentration in the broiler house. After that, the EEMD-GRU prediction model has been established for the intrinsic mode function (IMF) components and the temperature and humidity data in the broiler house. Finally, all component results were summarized to obtain the final prediction result. A comparison was conducted among the prediction results obtained by the above three models. The results show that the root mean square errors of the above three models are 6.2 ppm, 4.4 ppm, and 2.4 ppm, respectively, and the average absolute errors were 4.9 ppm, 2.8 ppm, and 1.6 ppm, respectively. It could be seen that the EEMD-GRU model had higher accuracy in predicting the ammonia concentration in the broiler house. The EEMD-GRU model can effectively predict the ammonia concentration in broiler houses, facilitating the feedback to the central system for timely adjustment.

Artificial, Photoinduced Activation of Nitrogenase Using Directed and Mediated Electron Transfer Processes

Nitrogenase, a bacteria-based enzyme, is the sole enzyme that is able to generate ammonia by atmospheric nitrogen fixation. Thus, improved understanding of its utilization and developing methods to artificially activate it may contribute to basic research, as well as to the design of future artificial systems. Here, we present methods to artificially activate nitrogenase using photoinduced reactions. Two nitrogenase variants originating from Azotobacter vinelandii were examined using photoactivated CdS nanoparticles (NPs) capped with thioglycolic acid (TGA) or 2-mercaptoethanol (ME) ligands. The effect of methyl viologen (MV) as a redox mediator of hydrogen and ammonia generation was tested and analyzed. We further determined the NPs conductive band edges and their effect on the nitrogenase photoactivation. The nano-biohybrid systems comprising CdS NPs and nitrogenase were further imaged by transmission electron microscopy, visualizing their formation for the first time. Our results show that the ME-capped CdS NPs–nitrogenase enzyme biohybrid system with added MV as a redox mediator leads to a five-fold increase in the production of ammonia compared with the non-mediated biohybrid system; nevertheless, it stills lag behind the natural process rate. On the contrary, a maximal hydrogen generation amount was achieved by the αL158C MoFe-P and the ME-capped CdS NPs.

A catalytic composite membrane reactor system for hydrogen production from ammonia using steam as a sweep gas

For catalytic reactions involving H2 extraction, the membrane reactor is an attractive option for enhancing the equilibrium and kinetics while eliminating excessive purification steps. In this study, a steam carrier adopted composite membrane reactor system is developed to produce pure H2 (>99.99%) from ammonia with high H2 productivity (>0.35 mol-H2 gcat−1 h−1) and ammonia conversion (>99%) at a significantly reduced operating temperature (<723 K). Coupling of a custom developed palladium/tantalum composite metallic membrane and ruthenium on lanthanum-doped alumina catalysts allowed stable operation of the membrane system with significant mass transfer enhancement. Various reactor assemblies involving as-fabricated membranes and catalysts are experimentally compared to suggest the optimal configuration and operating conditions for future applications. Steam is adopted as a sweep gas, presenting efficient H2 recovery (>91%) while replacing conventionally utilized noble carrier gases that require additional gas separation processes. The steam carrier presents similar membrane reactor performance to that of noble gases, and the water reservoir used for steam generation acts as an ammonia buffer via scrubbing effects. Finally, electricity generation is demonstrated using a commercial fuel cell along with process simulation, substantiating potential of the proposed membrane system in practical applications for H2 production from ammonia and on-site power generation.

Nitrogen transformation stages into ammonia in broiler production: sources, deposition, transformation and emission to environment

Air quality is a major factor in intensive livestock management because air is the main vehicle for the dissemination of physical, chemical, and biological agents that affect the health and welfare of animals and humans. Ammonia is the main gaseous pollutant generated in poultry production. In this study, a literature review was conducted to highlight each nitrogen transformation stage during poultry production, while explaining the conversion mechanisms from the ingestion of crude protein to nitrogen volatilization into the atmosphere as ammonia gas. In summary, the steps for the synthesis of uric acid and the excretion of poultry, mineralization of nitrogen present in excreta, and volatilization of ammonia from litter are presented. Based on this review, the importance of understanding the sources and processes involved in ammonia generation and emission in poultry production is clear, thereby allowing the adoption of assertive measures that could minimize negative effects caused by ammonia emission.

Efficiently enhanced nitrogen fixation performance of g-C3N4 nanosheets by decorating Ni3V2O8 nanoparticles under visible-light irradiation

Population growth, climate change, and global warming have led researchers to be interested in utilizing eco-friendly methods for the nitrogen reduction process. It has found that nitrogen molecule can be converted into ammonia in ambient conditions using photocatalysts under visible light. In the present work, a novel visible-light active nanocomposite was fabricated, in which different percentages of Ni3V2O8 nanoparticles (10, 15, 20, and 30%) were decorated on graphitic carbon nitride nanosheets (abbreviated as NGCN/NiVO). Then, morphology, textural, optical properties, and crystal structure of the photocatalysts were studied in detail. The results displayed that the NGCN/NiVO (20%) photocatalyst has significant catalytic performance in the ammonia generation process in comparison with the NGCN and GCN, which is 2.3 and 8 times higher, respectively. The stability of NGCN/NiVO (20%) nanocomposite, as a vital parameter, was evaluated for five runs. Also, the impact of electron scavengers, solvent, and pH of media was examined. Finally, a possible mechanism for the considerable enhancement of nitrogen photofixation efficiency was suggested.

Assessing Nutrient Removal in Stormwater Runoff for Urban Farming with Iron filings-based Green Environmental Media

Ensuring urban areas have access to clean drinking water, safe food supply, and uncontaminated water bodies is essential to the good health of millions of urban residents. This paper presents the functionality of Iron Filings-based Green Environmental Media (IFGEM) in terms of nutrient removal efficiencies to support water quality management and urban farming. IFGEM uses recycled materials such as tire crumb and iron filings to help remove nutrients with essential physicochemical properties. In this study, IFGEM were proven effective and sustainable through an isotherm study, a column study of reaction kinetics, and a microstructure examination under various inlet nutrient concentration levels. IFGEMs exhibited over 90% nitrate removal, as well as 50–70% total phosphorus removal, under most inlet conditions. These promising results make IFGEM suitable for treating stormwater runoff, wastewater effluent, and agricultural discharge via varying ex situ treatment units in flexible landscape environments. In addition, the byproduct of ammonia generation permits possible reuse of spent IFGEM as soil amendments in crop land, gardens and yards, and green roofs for urban farming. Findings may help secure urban food supply chains and harmonize nutrients, soil, water, and waste management in different urban environments.

An improved Wellman-Lord process for simultaneously recovering SO2 and removing NOX from non-ferrous metal smelting flue gas

An improved Wellman-Lord process is developed with electrochemical reactor, which can effectively recycle and reuse SO2 and NOX from flue gas. The process features to (a) remove and recycle NOX while recovering SO2 with the process of electrochemical denitrification; and (b) solve the problem of pipeline blockage caused by oxidation by-products with ammonium- wet absorption method. The crystallization temperature of the absorption solution reduces more than 50.0% after NH4+ is gradually added to Na2SO3. More than nearly 75.0% of (NH4)2SO4 added can ensure that it does not crystallize under the same conditions. The crystallization temperature decreases 44.16% and 54.69% with the absence of SO32− (solute of 20% wt) and HSO3− (solute of 28% wt), respectively, when the interference concentration reaches 80%. The absorption efficiencies of 5% Na2SO3 and 5% (NH4)2SO3 reach 98.18% and 98.47% for SO2 and 98.38% and 93.44% for NO2, respectively. Co3O4/Ti cathode exhibits nitrate removal efficiency of 93.67% and ammonia generation efficiency of 85.56%. The concentration of nitrate-N reduces 86.30% and ammonia-N increases 71.40% when the reaction proceeds for 11 h with intermittent injection conditions. The effect of pH on nitrogen removal with the presence of ammonium is also studied.

Ammonia recovery from concentrated solution by designing novel stacked FCDI cell

Ammonia recovery from wastewater gained increasing attention worldwide with the growing world population. However, subsequent treatment of the recovered ammonia was still complex and challenging. Therefore, a proof of concept approach by designing a novel stacked flow electrode capacitive deionization (FCDI) cell was presented in this study, to achieve ammonia recovery and generation of value-added products. Ammonium sulfate was generated successfully in the product chamber with K2SO4 worked as an additive. To avoid the influence of the co-existing ions, the effect of a monovalent cation-selective exchange membrane (M-CEM) was emphasized in the stacked FCDI cell. Compared with the standard cation exchange membrane (S-CEM), the product purity increased from around 50% to 85%, while the ratio of NH4+ towards co-existing cations increased almost 2 times by using M-CEM. To illustrate the reasons for the enhanced ion selectivity, the characterizations of both membranes were conducted by Electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM), Fourier transform infrared spectrometry (FTIR) and X-ray diffractometry (XRD). Therefore, this study indicated that the novel design and efficient operation of the stacked FCDI reactor is an alternative way for ammonia recovery and generation as value-added products, as well as a possible approach to scaling up.

Sustainable production of ammonia fertilizers from biomass

AbstractNitrogen is the most limiting plant nutrient. Inexpensive natural gas has substantially reduced costs of ammonia fertilizer for intensive agriculture in the developed world, but its excessive use negatively impacts downstream ecosystems. By contrast, the availability of ammonia fertilizer is a major economic bottleneck for agriculture in developing countries. A dedicated lignocellulosic biomass crop could supply sufficient substrate to generate optimal nitrogen fertilizer on less than 5% of a grower's food crop acreage. Reimagining ammonia generation using biomass could significantly enhance sustainable agricultural productivity in developing countries when combined with emerging catalytic technologies. © 2020 Society of Chemical Industry and John Wiley &amp; Sons, Ltd