Ammonia Generation Research Articles

Fluorescent hydrogel test kit coordination with smartphone: Robust performance for on-site dimethoate analysis

Precise monitoring of pesticide with portable device was challenging because it required high sensitivity, short response time, strong stability and excellent selectivity. Herein, we newly constructed a stimuli-responsive hydrogel (SRHg)-based portable kit by embedding copper nanoparticles (CuNPs) in agarose hydrogel. In this work, dimethoate as inhibitor of urease restrained the generation of ammonia, which reduced in-situ etching of CuNPs, resulting in the fluorescence color response of test kit under ultraviolet illumination. Interestingly, by means of smartphone-based nanocolorimetry, the photo image of portable kit could be translated into digital information using ImageJ software, achieving a direct quantitative tool for dimethoate identification. The simplicity of SRHg-based portable kit combined with smartphone-based color recognition not only improved the analysis sensitivity (detection limit of 1.0 μg L−1), accuracy and stability, but also simplified operation process and shortened sample-to-answer analysis time (55 min), demonstrating that the methodology met the needs of daily testing and provided a new sight for on-site monitoring of food safety and human health.

The potential of proton exchange membrane–based electrolysis technology

Abstract Hydrogen is an important chemical feedstock for many industrial applications, and today, more than 95% of this feedstock is generated from fossil fuel sources such as reforming of natural gas. In addition, the production of hydrogen from fossil fuels represents most carbon dioxide emissions from large chemical processes such as ammonia generation. Renewable sources of hydrogen such as hydrogen from water electrolysis need to be driven to similar production costs as methane reforming to address global greenhouse gas emission concerns. Water electrolysis has begun to show scalability to relevant capacities to address this need, but materials and manufacturing advancements need to be made to meet the cost targets. This article describes specific needs for one pathway based on proton exchange membrane electrolysis technology.

Generation and Emission of Ammonia During the Full-Scale Composting of Sewage Sludge

The generation and emission of ammonia (NH3) were studied using a continuous monitoring system in an established sewage sludge treatment plant. Results showed that NH3 generation within the pile differed from the emissions at the pile surface during composting. The maximum NH3 concentration reached 600 mg m−3 inside the composting pile and 200 mg m−3 in the outlet gas. The mass of N determined in NH3 generations was 9.97 g kg DM−1, which was 2.57 times higher than the mass of N in NH3 emissions. The highest NH3 generation and emission masses in one aeration cycle occurred during the mesophilic (10.19 mg kg−1) and early thermophilic (6.91 mg kg−1) phases. The relationship between NH3 generation rates and time during one aeration cycle and different composting phases could be expressed as a logarithmic equation, and the relationship between NH3 emission rate and time could be expressed as a quadratic equation.

Integrated system of thermochemical cycle of ammonia, nitrogen production, and power generation

Ammonia (NH3) is one of the most valuable chemicals due to its multipurpose utilization in many applications. Beside major application as fertilizer in agriculture, NH3 is a promising hydrogen (H2) carrier because it has a high content of H2 and technically available storage and transportation systems. At present, most of NH3 is synthesized from a series of steam reforming process to the feedstock of H2 and nitrogen (N2) production, followed with the catalytic Haber-Bosch reaction. In this study, an integrated system of N2 production system, NH3 synthesis system and a power generation process is proposed to produce NH3 efficiently. Thermochemical cyclic process of an endothermic reaction of Al2O3 reduction by carbon in N2 atmosphere, is coupled with oxidation/steam-hydrolysis of aluminum nitride (AlN) back to Al2O3, producing NH3 without catalyst and the need of H2 production system. The thermal energy required for reduction reaction is covered by the heat generated during exothermic reaction and combustion process, and the remaining heat is utilized in power generation. Heat circulation optimization is carried out by applying the enhanced process integration, resulting in a highly efficient system. The proposed system is analyzed through an adjustment of the main parameters: oxidation temperature, steam turbine inlet pressure, and temperature, to observe their effect on system performance and efficiency. The proposed system can reach a very high system efficiency of 69.3%. The oxidation reaction temperature is observed to play major role in determining the system performance due to temperature dependent NH3 yield.

Highly Efficient and Selective Generation of Ammonia and Hydrogen on a Graphdiyne-Based Catalyst.

The emergence of zerovalent atom catalysts has been highly attractive for catalytic science. For many years, scientists have explored the stability of zerovalent atom catalysts and demonstrated their unique properties. Here, we describe an atom catalyst (AC) with atomically dispersed zerovalent molybdenum atoms on graphdiyne (Mo0/GDY) with a high mass content of Mo atoms (up to 7.5 wt %) that was synthesized via a facile and scalable process. The catalyst shows both excellent selectivity and activity in the electrochemical reduction of nitrogen and in the hydrogen evolution reaction in aqueous solutions at room temperature and pressure. It is noted that this catalyst is the first bifunctional AC for highly efficient and selective ammonia and hydrogen generation. The catalytic process of our catalyst is well understood, the structure is defined, and the performance is excellent, providing a solid foundation for the generation and application of the new generation of catalysts.

Fate of sterols, polycyclic aromatic hydrocarbons, pharmaceuticals, ammonia and solids in single-stage anaerobic and sequential anaerobic/aerobic/anoxic sludge digestion

Emerging contaminants (ECs), such as pharmaceuticals, sterols and polycyclic aromatic hydrocarbons (PAHs) are frequently detected in the environment. ECs are refractory, toxic, tend to bioaccumulate and have a potential to disrupt the endocrine system of living organisms. These compounds are only partially eliminated in wastewater treatment plants (WWTPs). Due to their hydrophobic nature, they tend to accumulate in sludge. However, the fate of the majority of ECs in sludge treatment processes is not fully understood. In this study, the effect of a sequential anaerobic/aerobic/anoxic (AN/AERO/ANOX) digestion and a conventional single-stage AN digestion (as control) was investigated on mixed primary and secondary sludge. Digesters were operated at an overall solid retention time (SRT) of 18 days. The steady-state results have shown that sequential AN/AERO/ANOX digestion configurations improved the removal of three classes of ECs (e.g., sterols, PAHs and pharmaceuticals) by either reducing their accumulation or enhancing their removal. Moreover, sequential AN/AERO/ANOX digestion also achieved 45% less ammonia generation, 20% faster digestate dewaterability and 4% enhanced volatile solids removal compared to single-stage AN digestion.

Ammonia generation by tryptophan synthase drives a key genetic difference between genital and ocular Chlamydia trachomatis isolates

A striking difference between genital and ocular clinical isolates of Chlamydia trachomatis is that only the former express a functional tryptophan synthase and therefore can synthesize tryptophan by indole salvage. Ocular isolates uniformly cannot use indole due to inactivating mutations within tryptophan synthase, indicating a selection against maintaining this enzyme in the ocular environment. Here, we demonstrate that this selection occurs in two steps. First, specific indole derivatives, produced by the human gut microbiome and present in serum, rapidly induce expression of C. trachomatis tryptophan synthase, even under conditions of tryptophan sufficiency. We demonstrate that these indole derivatives function by acting as de-repressors of C. trachomatis TrpR. Second, trp operon de-repression is profoundly deleterious when infected cells are in an indole-deficient environment, because in the absence of indole, tryptophan synthase deaminates serine to pyruvate and ammonia. We have used biochemical and genetic approaches to demonstrate that expression of wild-type tryptophan synthase is required for the bactericidal production of ammonia. Pertinently, although these indole derivatives de-repress the trpRBA operon of C. trachomatis strains with trpA or trpB mutations, no ammonia is produced, and no deleterious effects are observed. Our studies demonstrate that tryptophan synthase can catalyze the ammonia-generating β-elimination reaction within any live bacterium. Our results also likely explain previous observations demonstrating that the same indole derivatives inhibit the growth of other pathogenic bacterial species, and why high serum levels of these indole derivatives are favorable for the prognosis of diseased conditions associated with bacterial dysbiosis.

Ammonia generation by tryptophan synthase drives a key genetic difference between genital and ocular Chlamydia trachomatis isolates

Ammonia generation by tryptophan synthase drives a key genetic difference between genital and ocular Chlamydia trachomatis isolates

Experimental Study and Model Predictive Control of a Lean-Burn Gasoline Engine Coupled With a Passive Selective Catalytic Reduction System

Lean-burn gasoline engines have demonstrated 10–20% engine efficiency gain over stoichiometric engines and are widely considered as a promising technology for meeting the 54.5 miles-per-gallon (mpg) corporate average fuel economy standard by 2025. Nevertheless, nitrogen oxides (NOx) emissions control for lean-burn gasoline for meeting the stringent Environmental Protection Agency tier 3 emission standards has been one of the main challenges toward the commercialization of highly efficient lean-burn gasoline engines in the United States. Passive selective catalytic reduction (SCR) systems, which consist of a three-way catalyst (TWC) and SCR, have demonstrated great potentials of effectively reducing NOx emissions for lean gasoline engines at low cost. However, passive SCR operation may cause significant fuel penalty since rich engine combustion is required for ammonia generation. The purpose of this study is to develop a model-predictive control (MPC) scheme for a lean-burn gasoline engine coupled with a passive SCR system to minimize the total equivalent fuel penalty associated with passive SCR operation while satisfying stringent NOx and ammonia (NH3) emissions requirements. Simulation results demonstrate that the MPC approach can reduce the fuel penalty by 43.9% in a simulated US06 cycle and 28.0% in a simulated urban dynamometer driving schedule (UDDS) cycle, respectively, compared to the baseline control, while achieving over 97% DeNOx efficiency and less than 15 ppm tailpipe ammonia slip. The proposed MPC controller can potentially enable highly efficient lean-burn gasoline engines while meeting the stringent Environmental Protection Agency tier 3 emission standards.

Thermochemical and Techno-Economic Evaluation of Ammonia Synthesis Via Lithium-Molten Salt Processes

Ammonia is an attractive carbon-free energy carrier as it is easily liquified, transported and stored at a lower energy penalty than other non-carbon containing fuels. Anhydrous ammonia production occurs today in large Haber-Bosch (H-B) plants fueled from natural gas. Industrial (H-B) plant techno-economics are poorly suited for remote small-scale ammonia production from renewable energy. Highly efficient ammonia synthesis in small-scale H-B systems does not exist, thus stimulating research towards a low temperature and pressure processes. The thermodynamics of low temperature ammonia synthesis are quite favorable however, the high activation energy for nitrogen reduction requires efficient catalysts and high temperatures. Electrochemistry offers a means to activate the process at lower temperatures however this has proven to be very challenging [1]. Direct electrochemical protonation of nitrogen at low temperatures has produced rates on the order of 10-9 to 10-10 moles/cm2-sec, many orders of magnitude too low for industrial production [2]. Nitrogen reduction on lithium metal occurs spontaneously; hence molten lithium salt processes may prove to be attractive for ammonia generation [3,4,5]. We have evaluated the thermodynamics and techno-economics of intermediate temperature NH3 synthesis processes, based on the spontaneous electro-reduction of nitrogen in lithium ion systems where the potential for lithium is close to metal deposition and the subsequent formation of lithium nitride. The advantage of the molten salt lithium processes is the reaction is autocatalytic however the direct protonation of Li3N with hydrogen yields lithium amide. Protonation with water does yield ammonia however the reaction is very exothermic. The electrolysis of the LiOH product is also a major obstacle as the reaction between LiOH and Li produces Li2O[6]. To overcome this difficulty, we have also evaluated alternative iodide and bromide cycles were lithium electrowinning is known to be viable. The techno-economics of the processes were also considered in a preliminary study.

Ammonia borane dehydrogenation tendencies using Pt4, Au4, and Pt2Au2 clusters as catalysts

Small metallic clusters -mediated gas phase catalysis studies give lights to understand simple and complex catalytic processes, and help in the discovery and explanation of non-traditional “molecular-scale” catalytic systems. In this framework and in the context of clean energy sources based on hydrogen, a comparative study about ammonia borane (AB = NH3BH3) dehydrogenation tendencies, using Pt4, Au4, and Pt2Au2 clusters as catalysts, is made. Molecular details on thermal, kinetic (mechanistic) and reactivity factors are revealed. Our results indicate that all the metal tetramers studied here tends to dehydrogenate the ammonia borane molecule, being the processes exothermic, exergonic and fast. Among the studied catalysts, Pt2Au2 shows the best results, because is capable of easily detach several hydrogen atoms, with high probability of taking them out simultaneously, both from B and N, which helps in avoiding the breakage of B–N bond of AB, what is known to produce the poisoning of the catalyst by ammonia generation.

Electrochemical Dinitrogen Reduction to Ammonia by Mo2N: Catalysis or Decomposition?

Instead of catalyzing electrochemical reduction of N2, we found that tetragonal Mo2N undergoes decomposition and results in the generation of ammonia. The present results call urgent attention to the need to carefully evaluate the catalytic nature of the dinitrogen reduction reaction by nitrogen-containing materials.

An all-solid-state Z-scheme TiO2/ZnFe2O4 photocatalytic system for the N2 photofixation enhancement

In this report, environmental and energy issues were deal with a Z-scheme photocatalytic system toward the synthetic ammonia by N2 photofixation. Different from traditional double-charge-transfer model, a direct all-solid-state Z-scheme system of modified TiO2 (MT) loaded with ZnFe2O4 (ZFO) was obtained by solvothermal-calcination method, in which calcination temperature is crucial for the mesoporous structure and formation of Z-scheme TiO2/ZnFe2O4. At ambient temperature and pressure, the MT/ZFO photocatalyst presented the ammonia generation rate of about 1.48 μmol/L/min, which is higher than that of single MT or ZFO. The photocatalytic activity enhancement of ammonia generation was attributed to the Z-scheme charge transfer model with a more negative reduction potential in the conduction band of ZnFe2O4. Combining the commonly TiO2 and ZnFe2O4 by a special method shows a desirable Z-scheme photocatalytic system, which can be extended to the fabrication of other Z-scheme photocatalyst according to the various application need.

Testosterone Modulates Renal Ammonia Metabolism

Ammonia metabolism is the primary component of net acid excretion and thus has a critical role in acid‐base homeostasis. Our recent studies show there are substantial sex‐dependent differences in ammonia metabolism that correlate with sex‐dependent differences in renal structure and in expression of proteins involved in ammonia generation and transport. This study's objective was to determine the role of testis‐derived testosterone in these differences. We used 4 month‐old C57BL/6 male mice divided into 3 groups: orchiectomy plus placebo (ORCH+P), ORCH plus testosterone (ORCH+T), and sham operated control (SOC). We replaced testosterone using time‐delayed pellets implanted subcutaneously; ORCH+P received a similar pellet that did not release testosterone. Plasma testosterone levels did not differ significantly between ORCH+T and SOC mice (ORCH+T, 159±36; SOC, 120±140; P = NS). Mice were studied four weeks after surgery. Food, and thus protein, intake, which is a major determinant of endogenous acid production, was similar in all three groups (SOC, 12.3±1.7; OCRH+P, 12.6±1.2; ORCH+T, 13.3±1.2 g/d; P=NS). Despite similar food intake, ORCH+P mice excreted more ammonia than did SOC mice; this was reversed by testosterone replacement (ORCH+P, 135±32; SOC, 55±13; ORCH+T, 48±28 μmol/day; P<0.001). Similar findings were observed in a separate set of ORCH+P and SOC mice studied at 8 weeks. ORCH decreased kidney size, and this was completely reversed by testosterone replacement (ORCH+P, 187±18; SOC, 220±16; ORCH+T, 236±19 mg; P<0.001). In parallel, proximal tubule volume density in the ORCH+P kidney was less than in the SOC kidney, and testosterone replacement completely reversed this difference (ORCH+P, 47±2; SOC, 63±1; ORCH+T, 62±1%; P<0.001). Phosphoenolpyruvate (PEPCK), a major proximal tubule (PT) ammonia generating protein, was significantly greater in ORCH+P mice than SOC mice, and this effect was completely reversed by testosterone replacement. Glutamine synthetase, which recycles ammonia, and NBCe1, a basolateral PT transporter that regulates PT ammonia metabolism, did not differ significantly between the groups. Expression of NKCC2, which mediates thick ascending limb ammonia reabsorption, was significantly greater in ORCH+P mice than SOC mice, and this effect was completely reversed by testosterone replacement. Finally, renal androgen receptor (AR) mRNA and protein expression were detected by real‐time RT‐PCR and immunoblot analysis, and immunohistochemistry showed AR expression throughout the proximal tubule (PT), with no detectable expression in non‐PT epithelial cells. These findings demonstrate that the loss of testis‐derived sex steroid hormones dramatically alters ammonia excretion, proximal tubule structure, and expression of key proteins involved in ammonia metabolism and transport. Furthermore, these dramatic changes derived from the loss of testis‐derived sex steroid hormones were reversed by physiologic testosterone replacement. We conclude that testosterone, likely acting through AR, decreases ammonia excretion through its effects on proximal tubule structure and on several key proteins involved in ammonia metabolism and transport.Support or Funding InformationNIH R01‐DK045788, R01‐DK107798 and 5T32‐DK‐104721.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Electrochemical Ammonia Generation Directly from Nitrogen and Air Using an Iron-Oxide/Titania-Based Catalyst at Ambient Conditions.

Ammonia was produced electrochemically from nitrogen/air in aqueous alkaline electrolytes by using a Fe2O3/TiO2 composite catalyst under room temperature and atmospheric pressure. At an applied potential of 0.023 V versus reversible hydrogen electrode, the rate of ammonia formation was 1.25 × 10-8 mmol mg-1 s-1 at an overpotential of just 34 mV. This rate increased to 2.7 × 10-7 mmol mg-1 s-1 at -0.577 V. The chronoamperometric experiments on Fe2O3/TiO2/C clearly confirmed that Fe2O3 along with TiO2 shows superior nitrogen reduction reaction activity compared to Fe2O3 alone. Experimental parameters such as temperature and applied potential have a significant influence on the rate of ammonia formation. The activation energy of nitrogen reduction on the employed catalyst was found to be 25.8 kJ mol-1. Real-time direct electrochemical mass spectrometry analysis was used to monitor the composition of the evolved gases at different electrode potentials.

BN Pairs Enriched Defective Carbon Nanosheets for Ammonia Synthesis with High Efficiency.

Electrochemical synthesis has garnered attention as a promising alternative to the traditional Haber-Bosch process to enable the generation of ammonia (NH3 ) under ambient conditions. Current electrocatalysts for the nitrogen reduction reaction (NRR) to produce NH3 are comprised of noble metals or transitional metals. Here, an efficient metal-free catalyst (BCN) is demonstrated without precious component and can be easily fabricated by pyrolysis of organic precursor. Both theoretical calculations and experiments confirm that the doped BN pairs are the active triggers and the edge carbon atoms near to BN pairs are the active sites toward the NRR. This doping strategy can provide sufficient active sites while retarding the competing hydrogen evolution reaction (HER) process; thus, NRR with high NH3 formation rate (7.75 µg h-1 mgcat. -1 ) and excellent Faradaic efficiency (13.79%) are achieved at -0.3 V versus reversible hydrogen electrode (RHE), exceeding the performance of most of the metallic catalysts.

Scheduling‐informed optimal design of systems with time‐varying operation: A wind‐powered ammonia case study

The time‐varying operation of chemical plants offers economic advantages, particularly in the presence of time‐sensitive electricity markets and renewable energy generation. However, the uncertainty and short‐timescale variability associated with renewable energy production, as well as the nonconvex process and cost models typically associated with chemical processes, make finding the optimal design of such systems challenging. In this work, a new approach is presented to finding the optimal design of systems with time‐varying operation, called scheduling‐informed design, whereby the optimal operation of many designs is determined and the resulting cost correlations into the optimal design problem are embedded. This method is applied to a case study of wind‐powered ammonia generation and showed that it greatly improves the computational tractability of the optimal design problem and predicts with greater accuracy operating costs realized because of uncertainty in forecasting. © 2018 American Institute of Chemical Engineers AIChE J, 65: e16434 2019

Electrochemical Reduction of N2 to NH3 at Low Potential by a Molecular Aluminum Complex.

Electrochemical generation of ammonia (NH3 ) from nitrogen (N2 ) using renewable electricity is a desirable alternative to current NH3 production methods, which consume roughly 1 % of the world's total energy use. The use of catalysts to manipulate the required electron and proton transfer reactions with low energy input is also a chemical challenge that requires development of fundamental reaction pathways. This work presents an approach to the electrochemical reduction of N2 into NH3 using a coordination complex of aluminum(III), which facilitates NH3 production at -1.16 V vs. SCE. Reactions performed under 15 N2 liberate 15 NH3 . Electron paramagnetic resonance spectroscopic characterization of a reduced intermediate and investigations of product inhibition, which limit the reaction to sub-stoichiometric, are also presented.

Extracellular urease from Arthrobacter creatinolyticus MTCC 5604: scale up, purification and its cytotoxic effect thereof

Urease is a potent metalloenzyme with diverse applications. This paper describes the scale up and purification of an extracellular urease from Arthrobacter creatinolyticus MTCC 5604. The urease production was scaled-up in 3.7L and 20L fermentor. A maximum activity of 27 and 27.8U/mL and a productivity of 0.90 and 0.99 U/mL/h were obtained at 30h and 28h in 3.7 and 20L fermentor, respectively. Urease was purified to homogeneity with 49.85-fold purification by gel filtration and anion exchange chromatography with a yield of 36% and a specific activity of 1044.37 U/mg protein. The enzyme showed three protein bands with molecular mass of 72.6, 11.2 and 6.1kDa on SDS-PAGE and ~ 270kDa on native PAGE. The cytotoxic effect of urease was assessed in vitro using cancer cell lines (A549 and MG-63) and normal cell line (HEK 293). Urease showed its inhibitory effects on cancer cell lines through the generation of toxic ammonia, which in turn increased the pH of the surrounding medium. This increase in extracellular pH, enhanced the cytotoxic effect of weak base chemotherapeutic drugs, doxorubicin (50µM) and vinblastine (100µM) in the presence of urease (5U/mL) and urea (0-4mM) significantly.

G-C3N4 nanosheets decorated with carbon dots and CdS nanoparticles: Novel nanocomposites with excellent nitrogen photofixation ability under simulated solar irradiation

Photocatalytic nitrogen fixation, as one of the best alternatives to Haber-Bosch process, is a low–cost, eco-friendly, and mild technology that needs more efforts to find efficient photocatalysts with high stability. In this research, novel graphitic carbon nitride nanosheets/carbon dots/CdS (denoted as CN-NS/CDs/CdS) nanocomposites by prominent nitrogen photofixation capability under simulated solar irradiation were fabricated with decoration of CDs and CdS nanoparticles over CN-NS thorough a microwave-assisted method. The prepared ternary photocatalysts were investigated by XRD, EDX, SEM, TEM, HRTEM, UV–vis DRS, PL, FT-IR, TGA, BET, and EIS analyses. The results showed that photocatalytic activity of the CN-NS/CDs/CdS (30%) nanocomposite was 17.1, 5.64, 5.38, and 4.51-folds greater than those of the bulk CN, CN-NS, pure CdS, and CN-NS/CDs samples, respectively. Moreover, an insignificant loss in the activity of photocatalyst after several cycles displayed its high stability, which is vital for the sustainable photocatalytic procedures. The effects of CdS loading, pH of solution, electron scavenger, and solvent on the ammonia generation rate were also investigated and discussed. Eventually, a probable mechanism for the significantly enhancement of N2 photofixation performance was proposed.