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The present paper studies the energy intensity of ammonia production by a freely oscillating microbubble placed in an infinite domain of liquid. The initial content of the bubble is a mixture of hydrogen and nitrogen. The bubble is expanded isothermically to a maximum radius, then it is “released” and oscillates freely. The input energy is composed of the potential energy of the bubble at the maximum radius, the energy required to produce hydrogen, and the pumping work in case a vacuum is employed. The chemical yield is computed by solving the underlying governing equations: the Keller–Miksis equation for the radial dynamics, the first law of thermodynamics for the internal temperature and the reaction mechanism for the evolution of the concentration of the chemical species. The control parameters during the simulations are the equilibrium bubble size, initial expansion ratio, ambient pressure, the initial concentration ratio of hydrogen and the material properties of the liquid. At the optimal parameter setup, the energy intensity is 90.17GJ/t that is 2.31 times higher than the best available technology, the Haber–Bosch process. In both cases, the hydrogen is generated via water electrolysis.

Abstract Ammonia (NH3) is regarded as a renewable energy source as well as an important molecule for agricultural applications. The energy‐intensive Haber‐Bosch method produces large amounts of CO2 gas during ammonia production. As an alternative, there has recently been much interest in the electrocatalytic production of NH3 via the electrochemical nitrogen reduction reaction (ENRR) process utilizing renewable energy under ambient condition. Herein, we report a conducting carbon–supported manganese phthalocyanine electrocatalyst as an efficient electrocatalyst for ENRR applications. The MnPc electrocatalyst exhibited the activity with an ammonia production rate of 61.8 μg h−1mg−1cat with Faradaic efficiency (FE) of 31.3% @–0.4 V vs. RHE, respectively, under ambient condition in 0.1 M HCl solution whereas MnPc/C electrocatalyst exhibited an enhanced the productivity with an ammonia yield rate of 127.7 μg h−1mg−1cat with FE of 35.3% @–0.4 V vs. RHE, respectively. The reliability of N origin in ammonia formation is demonstrated by 1H‐NMR experiments and multiple control analysis. These results open the way for the further study of carbon‐supported transition‐metal phthalocyanine compounds for electrochemical nitrogen fixation to NH3.

Nitrogen-fixing bacteria such as cyanobacteria have the capability to fix atmospheric nitrogen at ambient temperature and pressure, and intensive cultivation of cyanobacteria for fertilizer could lead to its use as an “environmentally friendly” replacement or supplement for nitrogen (N) fertilizer derived from the Haber–Bosch process. Prior research has focused on the use of N-fixing bacteria as a soil inoculum, and while this can improve crop yields, yield improvements are generally attributed to plant-growth-promoting substances produced by the bacteria, rather than to biological N fixation. The intensive cultivation of cyanobacteria in raceways or bioreactors can result in a fertilizer that provides N and organic carbon, as well as potentially similar growth-promoting substances observed in prior research work. On-farm or local production of cyanobacterial fertilizer could also circumvent infrastructure limitations, economic and geopolitical issues, and challenges in distribution and transport related to Haber–Bosch-derived N fertilizers. The use of cyanobacterial N fertilizer could have many agronomic and environmental advantages over N fertilizer derived from the Haber–Bosch process, but study of cyanobacteria as a replacement for other N fertilizers remains very limited. Scientific and practical challenges remain for this promising but as-yet unproven approach to maintaining or improving soil N fertility.

Decarbonisation means reducing or ideally eliminating the greenhouse gas emissions by evaluating all processes in a system from a “low-carbon” perspective. This review describes the current state of the fertiliser industry, and the options and recommendations for its decarbonisation. Decarbonisation of the fertiliser industry can be achieved with the developing technologies in terms of raw materials, energy usage, and operating conditions in the fertiliser production processes. Low-carbon fertilisers can be realised with the improvements that can be made in the life cycle of the fertiliser, from the derivation of the raw materials to the formation of the final products. Today, many decarbonisation studies with new technologies that can be created in ammonia production, which is the most energy-intensive process in the fertiliser industry, are at the research stage. This paper reviews the use of hydrogen source in ammonia production and achieving biomass gasification or electrolysis with low carbon footprints, reducing greenhouse gas emissions in nitric acid production, integrating carbon capture and storage technologies into the fertiliser processes, and increasing the efficiency of low-carbon agricultural practices.

Ammonia, in other words synthetic nitrogen, helped humanity to increase its population by increasing the agricultural production yields and will be the key component of feeding the future growth. In addition to its existing uses mainly in fertilizer production, ammonia has promising prospects in shipping industry as a maritime fuel and in power generation thanks to its carbon-free molecular structure makes it a good substitute for fossil fuels in decarbonization efforts. In this study, while evaluating current production methods and main use cases, alternative production methods and developing use cases were examined.

With the synthesis of ammonia with chemical methods, global carbon emission is the biggest threat to global warming. However, the dependence of the agricultural industry on ammonia production brings with it various research studies in order to minimize the carbon emission that occurs with the ammonia synthesis process. In order to completely eliminate the carbon emissions from ammonia production, both the hydrogen and the energy needed for the operation of the process must be obtained from renewable sources. Thus, hydrogen can be produced commercially in a variety of ways. Many processes are discussed to accompany the Haber Bosch process in ammonia production as potential competitors. In addition to parameters such as temperature and pressure, various plasma catalysts are being studied to accelerate the ammonia production reaction. In this study, various alternative processes for the capture, storage and complete removal of carbon gas released during the current ammonia production are evaluated and the current conditions related to the applicability of these processes are discussed.In addition, it has been discussed under which conditions it is possible to produce larger capacities as needed in the processes studied in order to reduce carbon gas emissions during ammonia production in order to provide raw material source for fertilizer production and energy sector. However, if the hydrogen gas required for ammonia production is produced using a solid oxide electrolysis cell, the reduction in the energy requirement of the process and in this case the reduction of energy costs shows that it will play an important role in determining the method to be used for ammonia production. In addition, it is predicted that working at lower temperature (

Metal–organic frameworks (MOFs) are coordination polymers with high porosity that are constructed from molecular engineering. Constructing MOFs as photocatalysts for the reduction of nitrogen to ammonia is a newly emerging but fast-growing field, owing to MOFs’ large pore volumes, adjustable pore sizes, controllable structures, wide light harvesting ranges, and high densities of exposed catalytic sites. They are also growing in popularity because of the pristine MOFs that can easily be transformed into advanced composites and derivatives, with enhanced catalytic performance. In this review, we firstly summarized and compared the ammonia detection methods and the synthetic methods of MOF-based materials. Then we highlighted the recent achievements in state-of-the-art MOF-based materials for photocatalytic nitrogen fixation. Finally, the summary and perspectives of MOF-based materials for photocatalytic nitrogen fixation were presented. This review aims to provide up-to-date developments in MOF-based materials for nitrogen fixation that are beneficial to researchers who are interested or involved in this field.

Abstract Ammonia production is essential for sustaining the demand for providing food for the growing population. Being a great source of hydrogen, it has significant potential in turning out to be a viable candidate for the future hydrogen economy. Ammonia has a high hydrogen content of about 17.6 wt %, is easier to liquefy and is produced in large quantities. Even though large-scale production of ammonia is significant globally, it is used predominantly as a fertilizer. It used also as a transport fuel for vehicles because of its low carbon emissions. Ammonia as an energy storage media is realized in many countries with infrastructure for transportation and distribution already put into place. Currently, the Haber–Bosch process is employed globally in industrial ammonia production and is a high energy expending process requiring large capital investment. In realizing a much economic pathway given the large-scale ammonia production growth forecast, it is necessary to seek new and improved methods for large-scale ammonia production. Amongst them, photoelectrochemical and electrochemical approaches stand as most promising towards nitrogen reduction to ammonia owing to their design features, lesser complexity, and economical in terms of the conventional ammonia production system. Several catalyst materials are investigated which include metal oxides, metals sulfides, carbon-based catalysts, and metal nitrides are all currently being pursued better utilization of their catalytic property towards nitrogen fixation and the minimization of the competing hydrogen evolution reaction (HER). In this article, we have summarized the design and reaction mechanisms for photoelectrochemical and electrochemical nitrogen fixation with the inherent challenges and material- related issues in realizing the Nitrogen Reduction Reaction (NRR).

The aim of this paper is the steady state and dynamic simulations of the ammonia unit of Shiraz petrochemical complex and system behavior study versus the feed flow rate change for producing a good quality product. The ammonia unit consists of the reformer units, shift converter units, carbon dioxide absorption unit, methanation unit, and ammonia synthesis unit. For this purpose, in the first step, the ammonia unit is simulated at a steady state using the Aspen Plus 2006.5 simulator. In the following stage, the required parameters are entered into the software for the dynamic simulation. The Aspen Plus was exported to Aspen dynamic. In this study, PI and PID controllers, as basic controllers, were automatically added and tuned by the Tyreus–Luyben tuning method. Finally, in order to ensure the accuracy of the proposed control structure, the feed flow rate increased by 5%. The results show that, first of all, the simulation accuracy at steady and dynamic states are optimal so that the mean errors are -0.01% and -0.02% for steady and dynamic states, respectively. The controlling structure can well control the 5% feed increase.

The aim of this paper is the steady state and dynamic simulations of the ammonia unit of Shiraz petrochemical complex and system behavior study versus the feed flow rate change for producing a good quality product. The ammonia unit consists of the reformer units, shift converter units, carbon dioxide absorption unit, methanation unit, and ammonia synthesis unit. For this purpose, in the first step, the ammonia unit is simulated at a steady state using the Aspen Plus 2006.5 simulator. In the following stage, the required parameters are entered into the software for the dynamic simulation. The Aspen Plus was exported to Aspen dynamic. In this study, PI and PID controllers, as basic controllers, were automatically added and tuned by the Tyreus–Luyben tuning method. Finally, in order to ensure the accuracy of the proposed control structure, the feed flow rate increased by 5%. The results show that, first of all, the simulation accuracy at steady and dynamic states are optimal so that the mean errors are -0.01% and -0.02% for steady and dynamic states, respectively. The controlling structure can well control the 5% feed increase.

Due to its essential use as a fertilizer, ammonia synthesis from nitrogen and hydrogen is considered to be one of the most important chemical processes of the last 100 years. Since then, an enormous amount of work has been undertaken to investigate and develop effective catalysts for this process. Although the catalytic synthesis of ammonia has been extensively studied in the last century, many new catalysts are still currently being developed to reduce the operating temperature and pressure of the process and to improve the conversion of reactants to ammonia. New catalysts for the Haber–Bosch process are the key to achieving green ammonia production in the foreseeable future. Herein, the history of ammonia synthesis catalyst development is briefly described as well as recent progress in catalyst development with the aim of building an overview of the current state of ammonia synthesis catalysts for the Haber–Bosch process. The new emerging ammonia synthesis catalysts, including electride, hydride, amide, perovskite oxide hydride/oxynitride hydride, nitride, and oxide promoted metals such as Fe, Co, and Ni, are promising alternatives to the conventional fused‐Fe and promoted‐Ru catalysts for existing ammonia synthesis plants and future distributed green ammonia synthesis based on the Haber–Bosch process.

Activity of ammonia synthesis catalyst in the Haber-Bosch process is studied for the case of feeding the process with intermittent and impurity containing hydrogen stream from water electrolysis. Hydrogen deficiency due to low availability of renewable energy is offset by increased flow rate of nitrogen, argon, or ammonia, leading to off-design operation of the Haber-Bosch process. Catalyst poisoning by ppm levels of water and oxygen is considered as the main deactivation mechanism and is evaluated with a microkinetic model. Simulation results show that catalyst activity changes considerably with feed gas composition, even at exceptionally low water contents below 10ppm. A decreased hydrogen content always leads to lower poisoning of the catalyst. It is shown that ammonia offers less flexibility to the operation of Haber-Bosch process under fluctuating hydrogen production compared to nitrogen and argon. Transient and significant changes of catalyst activity are expected in electrolysis coupled Haber-Bosch process.

Ammonia (NH3) is one of the key agricultural fertilizers and to date, industries are using the conventional Haber-Bosh process for the synthesis of NH3 which requires high temperature and energy. To overcome such challenges and to find a sustainable alternative process, researchers are focusing on the photocatalytic nitrogen fixation process. Recently, the effective utilization of sunlight has been proposed via photocatalytic water splitting for producing green energy resource, hydrogen. Inspired by this phenomenon, the production of ammonia via nitrogen, water and sunlight has been attracted many efforts. Photocatalytic N2 fixation presents a green and sustainable ammonia synthesis pathway. Currently, the strategies for development of efficient photocatalyst for nitrogen fixation is primarily concentrated on creating active sites or loading transition metal to facilitate the charge separation and weaken the N⁻N triple bond. In this investigation, we review the literature knowledge about the photocatalysis phenomena and the most recent developments on the semiconductor nanocomposites for nitrogen fixation, following by a detailed discussion of each type of mechanism.