Urea Production Research Articles

Benzo-fused Nitrogen Heterocycles by Asymmetric Ring Expansion and Stereochemically Retentive Re-contraction of Cyclic Ureas.

Benzo-fused nitrogen heterocycles are common features of bioactive molecules, and the enantioselective synthesis of their substituted analogues is an important goal. In this paper we demonstrate a practical and mechanistically intriguing approach to the enantioselective synthesis of 1-arylbenzazepines and their analogues. The reaction sequence starts with an asymmetric migratory ring expansion of indoline, tetrahydroquinoline, or tetrahydrobenzazepine ureas on treatment with a chiral lithium amide base. Treatment of the ring-expanded ureas with acid triggers a two-atom ring contraction-an 'azatropic shift' in which one urea nitrogen displaces the other-with almost complete retention of stereochemistry. Aminolysis of the urea products provides enantioenriched 1-aryl-tetrahydrobenzazepine derivatives and their congeners, including an analogue of an intermediate in the synthesis of the drug solifenacin. Deuteration, in situ IR, and DFT studies provide evidence for the mechanisms of the reaction steps.

Preparation of Oriented Superhydrophobic Surface to Reduce Agglomeration in Preparing Melt Marbles.

Numerous innovative granulation techniques utilizing the concept of liquid marbles have been proposed before. However, these processes frequently encounter issues such as collisions, aggregation, and fragmentation of liquid/melt marble during the granulation process. In this study, the oriented superhydrophobic surface (OSS) was successfully prepared by utilizing copper wire to solve the above problem, facilitating efficient batch production and guided transportation of uniform marbles. The parameters and mechanisms of this process were thoroughly studied. The optimized structure is that the copper wire spacing (d) and height (h) are set as 1.0 and 0.1 mm, respectively. This resulted in a surface contact angle (CA) of 156° and anisotropic sliding (ΔSA) of 16.3 ± 1.34°. Using the prepared substrate, high-quality urea products were successfully obtained through the controlled transport of urea melt marbles. The mechanism of guided and directional drag reduction, based on the solid/solid contact on the surface, is proposed. These findings in this study have significant implications for improving granulation processes.

Potential and electric double-layer effect in electrocatalytic urea synthesis

Electrochemical synthesis is a promising way for sustainable urea production, yet the exact mechanism has not been fully revealed. Herein, we explore the mechanism of electrochemical coupling of nitrite and carbon dioxide on Cu surfaces towards urea synthesis on the basis of a constant-potential method combined with an implicit solvent model. The working electrode potential, which has normally overlooked, is found influential on both the reaction mechanism and activity. The further computational study on the reaction pathways reveals that *CO-NH and *NH-CO-NH as the key intermediates. In addition, through the analysis of turnover frequencies under various potentials, pressures, and temperatures within a microkinetic model, we demonstrate that the activity increases with temperature, and the Cu(100) shows the highest efficiency towards urea synthesis among all three Cu surfaces. The electric double-layer capacitance also plays a key role in urea synthesis. Based on these findings, we propose two essential strategies to promote the efficiency of urea synthesis on Cu electrodes: increasing Cu(100) surface ratio and elevating the reaction temperature.

Industrial scale fouling of heat exchangers in isocyanate production

The fouling of a commercial stainless steel (AISI 316L) during the manufacture of polymeric methylene diphenyl diisocyanate (pMDI) has been studied using laboratory‐based fouling apparatus that simulates commercial production conditions. The goal of the work is to understand the mechanisms behind the corrosion and fouling during isocyanate production with a view to improving process efficiency, not only in this process, but also others using similar plant and processes. Steel coupons were exposed to a solution of pMDI and solid amine hydrochloride, with hydrogen chloride gas being bubbled through the reaction cell. A number of different conditions were investigated, the variables being pMDI concentration, HCl gas flow duration, immersion time and temperature. Following the fouling experiments the coupons were removed from the fouling rig, photographed, and examined by XPS and ToF‐SIMS; principal component analysis was used to extend the ToF‐SIMS analysis to identify organic fouling products. The extent of fouling is shown to be relatively insensitive to pMDI concentration, but significantly influenced by continual HCl flow and increased temperature, features which increase the extent of substrate corrosion thought to be a precursor to the fouling process itself. Both XPS and ToF‐SIMS confirm the formation of various nickel chlorides in the corrosion process. Urea and metal corrosion products are found to co‐exist on certain (random) areas of the coupon surface.

Integration of the Urea Fertilizer Industry Process Safety Index

The chemical industry has different stages of the production process, depending on the materials used and the products produced. Typically, previous approaches only use one or two parameters. The focus of this study is on a safety assessment metric called the Index Process Safety Value (IPSV). The evaluation process using IPSV involves initially identifying parameters, evaluating each parameter using IPSV, and then integrating the assessments. Integration assessments can be used to ascertain the level of risk involved in the standardization process. Standardization is carried out to ensure the specific attributes of each industrial process flow. Where in this standardization there are variations in index values and levels of potential danger. This main and initial process is the core of the Urea production process stages. Of the several stages of the urea production process, the one with the highest level of danger is during the production of Urea in the synthesis process, namely in the Reactor (DC101) with an index value of 0.4, while the lowest is in the urea synthesis process, namely in the Condenser (EA101) with the average index value is 0.28. This IPSV method can be used to analyze process safety, especially for the urea synthesis unit at Factory 5 of PT Pupuk Kaltim

Decarbonizing the Fertilizers Sector: An Alternative Pathway for Urea and Nitric Acid Production

Abstract In order to alleviate the environmental impact that nitrogen fertilizers production is responsible for, several efforts have been addressed to incentivize the partial or total decarbonization of the supply chains of ammonia and its derivatives. The decarbonization of the nitrogen fertilizers sector might help not only improve its carbon footprint, but also reduce its dependence on international market prices of natural gas. To this end, in this work, two fertilizers production plants, namely nitric acid and urea, are integrated into a kraft pulp mill via black liquor gasification to supply the renewable input required by the chemical processes. The performance of the proposed systems is assessed and compared in the light of thermodynamic, economic, and environmental indicators. The choice of the utility system has been driven by the interrelation of the market conditions, as well as the extent of the energy integration of the chemical plants. As a result, the exergy efficiency of the integrated plants remains competitive against the conventional kraft pulp mill thanks to the optimal selection of the operating conditions of the utility system. This efficiency indicator compares the exergy input with the minimum theoretical work needed to reversibly produce the chemicals out from the components in the environment. Furthermore, the overall CO2 emissions balance achieves negative values for some scenarios, pointing out the potential for atmospheric CO2 depletion when the integrated processes are implemented. The indirect emissions of the biomass supply chain proved to have a great impact on the CO2 balance. Finally, the findings suggest that both nitric acid and urea production have positive incremental net present values across the range of carbon taxes considered, indicating the economic viability of these integrated systems vis-à-vis the traditional standalone pulp and fertilizers production plants.

Use of irradiated chitosan as a matrix for slow-release urea and in vitro fermentation characteristics of slow-release urea supplementation in ruminant rations

Background and Aim: Irradiated chitosan can be used as a matrix for slow-release urea (SRU) production. This study aimed to (1) determine the optimal formulation of irradiated chitosan matrix for controlling nitrogen release and (2) evaluate the characteristics of SRU in vitro fermentation based on irradiated chitosan as a feed supplement. Materials and Methods: In the first phase of the investigation, four chitosan-based SRU formulations with varying amounts of acrylamide (3 and 5 g) and gamma irradiation (5 and 10 kGy) were evaluated. Scanning electron microscopy, Fourier transform mid-infrared spectroscopy, and ammonia release characteristics were used to observe morphological, functional group, and ammonia release characteristics. In the second phase of research, the most effective SRU formulation was utilized as a supplement to ruminant rations based on rice straw, sorghum straw, and alfalfa. Gas production, rumen fermentation characteristics, and methane gas production were observed in vitro. Results: On the basis of surface image analysis, the four SRU formulas generate a similar appearance. Compared with untreated urea, the SRU3 formula reduced the percentage of ammonia emission by 12.85%–27.64% after 24 h of incubation (p = 0.05), as determined by the first phase study. SRU3 became the basis for the second testing phase. The addition of SRU3 did not affect the optimal gas production in vitro. SRU3 treatment produced less gas than Optigen® treatment (p = 0.05). With regard to rumen fermentation and digestibility, Optigen® yielded better results than SRU3 (p = 0.05). However, the treatment with SRU3 resulted in reduced methane production compared to that in the control (p = 0.05). Conclusion: Irradiated chitosan as an SRU matrix may control the release of ammonia in the rumen medium. The SRU3 formulation is the most effective. The addition of SRU to rice straw-based rations reduces methane production without affecting in vitro digestibility. Keywords: fermentation characteristics, irradiated chitosan, ruminant, slow-release urea.

Fundamentals and Rational Design of Heterogeneous C‐N Coupling Electrocatalysts for Urea Synthesis at Ambient Conditions

AbstractElectrocatalytic C‐N coupling reaction is regarded as a promising strategy for achieving clean and sustainable urea production by coreducing CO2 and nitrogen species, thus contributing to carbon neutrality and the artificial nitrogen cycle. However, restricted by the sluggish adsorption of reactants, competitive side reactions, and multistep reaction pathways, the electrochemical urea production suffers from a low urea yield rate and low selectivity so far. In order to comprehensively improve urea synthesis performance, it is crucial to develop highly efficient catalysts for electrochemical C‐N coupling. In this article, the catalyst‐designing strategies, C‐N coupling mechanisms, and fundamental research methods are reviewed. For the coreduction of CO2 and different nitrogen species, several prevailing reaction mechanisms are discussed. With the aim of establishing the standard research system, the fundamentals of electrocatalytic urea synthesis research are introduced. The most important catalyst‐designing strategies for boosting the electrocatalytic urea production are discussed, including heteroatom doping, vacancy engineering, crystal facet regulation, atom‐scale modulation, alloying and heterostructure construction. Finally, the challenges and perspectives are proposed for future industrial applications of electrochemical urea production by C‐N coupling.

Characteristics of N Transformation of Humic Acid Urea in Different Circle Layers of the Fertisphere: A Simulated Experiment

Due to its broad yield-increasing effect and low cost, humic acid urea (HAU) has become one of the leading modified fertilizers worldwide. The fertisphere is the primary space where urea (U) granules participate in the soil nitrogen cycle, forming a nutrient concentration gradient centered on the point of fertilization. The closer the circle layers to the urea granule in the fertisphere, the higher the nitrogen concentration. However, HAU in this microregion remains poorly understood. The differences in the transformation process from the inside to outside circle layers of the U and HAU fertispheres were simulated and studied using soil incubation experiments under 20, 10, 2, 1, and 0.2 g kg−1 nitrogen inputs. The 20 and 10 g kg−1 inputs represent the layers closest to the urea granule. Within the first seven days, HAU treatment showed higher concentrations of soil ammonia-N content than U treatment within the two layers closest to the fertilizer core, while exhibiting lower concentrations under the farthest two layers. Under 2 g kg−1 nitrogen input, the nitrate nitrogen under the HAU treatment was significantly higher than that in the U treatment, indicating a higher nitrification rate. During the 42-day incubation period, soil mineral nitrogen content under the HAU treatment was higher than that for the U treatment in the two closest circles. On the 42nd day, the residual urea-N under the HAU treatment was significantly higher than that for the U treatment when the nitrogen input was higher than 1 g kg−1. The effect of higher fertilizer preservation and supply capacity of HAU in Fluvo-aquic soil was achieved by changing the urease activity and nitrification rate in fertisphere ranges closer to the fertilizer core. An improved understanding of the high-efficiency mechanism of HAU in the fertisphere process will contribute to the development of new-generation high-efficiency urea products.

Efficient Solar Driven Upgrading of N2 to Urea Through Photoredox Reactions on Pt Cluster/TiO2

AbstractSynthetic nitrogen fertilizers, such as urea, are instrumental in augmenting agricultural output and addressing the demands of a growing population. Nevertheless, conventional urea production heavily relies on energy‐intensive processes. In this study, an environmentally friendly photocatalytic method is proposed for directly and selectively synthesizing urea from nitrogen (N2) and methanol (CH3OH using a Pt cluster‐decorated TiO2 catalyst (Pt cluster/TiO2). Remarkably, the Pt cluster/TiO2 exhibits outstanding urea synthesis performance with a rate of 105.68 µmol g−1 h−1 and N‐selectivity of 97.29 ± 0.79%, representing the highest level of photocatalytic urea synthesis from N2. Further analysis with density functional theory (DFT) calculation reveals that the “σ–π*” donor–acceptor interaction occurred between Pt clusters and N2, efficiently reducing the N2 hydrogenation barrier. EPR experiments demonstrate that photogenerated electrons (e−) and hole (h+) are synchronously consumed through N2 reduction and CH3OH oxidation, thereby accelerating urea synthesis. The crucial step of C─N coupling is initiated by the reaction between *NH─NH and *CHO intermediate, facilitated by the low energy barrier on Pt cluster/TiO2. This work suggests an mild route of urea production and provides profound insights into the underlying chemistry of the C─N coupling reaction, which can guide the sustainable synthesis of essential indispensable chemicals.

Environmental Impact Assessment of Rice–Wheat Rotation Considering Annual Nitrogen Application Rate

Rice–wheat rotation is a widely adopted multiple-cropping system in the Yangtze River Basin, China. Nitrogen (N) fertilizer is a key factor in regulating crop yield; however, only a few studies have considered the impact of annual N application on the yield, environmental impacts, and economic profits of rice–wheat rotation systems. In this study, a field experiment was conducted in the Jiangsu Province from 2020 to 2022. The rice and wheat seasons included six and five N fertilizer application rates, respectively (Rice: 0, 180, 240, 300, 360, and 420 kg N ha−1; Wheat: 0, 180, 240, 300, and 360 kg N ha−1), combined to form a total of 30 treatments. Life-cycle assessment was used to evaluate the environmental impacts of rice–wheat rotation under different N application treatments, using area, yield, and economic profit as functional units. Ten environmental impact categories were selected, including global warming. The results showed that grain yield did not consistently increase with an increase in N application, and the annual yield was the highest when 300 and 240 kg N ha−1 (R300W240 treatment) was applied in the rice and wheat seasons, respectively. The area-based weighting index of the R300W240 treatment ranked 20th among the 30 treatments, while the yield- and profit-based weighting indices were the lowest among the 30 treatments, decreasing by 14.9% and 28.7%, respectively, compared to the other treatments. The R300W240 treatment was the optimal annual N application strategy for rice–wheat rotation. Among the 10 environmental impacts considered, urea production contributed significantly to over eight environmental impacts, whereas the pollutant losses caused by its application contributed significantly to six environmental impacts. These findings reveal the dependence of the rice–wheat rotation system on the unsustainable use of N fertilizer and indicate that N fertilizer management practices should be further optimized to improve the environmental sustainability of grain production in the future.

The industry transformation from fossil fuels to hydrogen will reorganize value chains: Big picture and case studies for Germany

In many industries, low-carbon hydrogen will substitute fossil fuels in the course of the transformation to climate neutrality. This paper contributes to understanding this transformation. This paper provides an overview of energy- and emission-intensive industry sectors with great potential to defossilize their production processes with hydrogen. An assessment of future hydrogen demand for various defossilization strategies in Germany that rely on hydrogen as a feedstock or as an energy carrier to a different extent in the sectors steel, chemicals, cement, lime, glass, as well as pulp and paper is carried out. Results indicate that aggregate industrial hydrogen demand in those industries would range between 197 TWh and 298 TWh if production did not relocate abroad for any industry sector. The range for hydrogen demand is mainly due to differences in the extent of hydrogen utilization as compared to alternative transformation paths for example based on electrification. The attractiveness of production abroad is then assessed based on the prospective comparative cost advantage of relocating parts of the value chain to excellent production sites for low-carbon hydrogen. Case studies are provided for the steel industry, as well as the chemical industry with ethylene production through methanol and the production of urea on the basis of ammonia. The energy cost of the respective value chains in Germany is then compared to the case of value chains partly located in regions with excellent conditions for renewable energies and hydrogen production. The results illustrate, that at least for some processes – as ammonia production – relocation to those favorable regions may occur due to substantial comparative cost advantages.

Effects of a second iron-dextran injection administered to piglets during lactation on differential gene expression in liver and duodenum at weaning.

Six female littermate piglets were used in an experiment to evaluate the mRNA expression in tissues from piglets given one or two 1mL injections of iron dextran (200mg Fe/mL). All piglets in the litter were administered the first 1mL injection < 24h after birth. On day 7, piglets were paired by weight (mean body weight = 1.72 ± 0.13kg) and one piglet from each pair was randomly selected as control (CON) and the other received a second injection (+Fe). At weaning on day 22, each piglet was anesthetized, and samples of liver and duodenum were taken from the anesthetized piglets and preserved until mRNA extraction. differential gene expression data were analyzed with a fold change cutoff (FC) of |1.2| P < 0.05. Pathway analysis was conducted with Z-score cutoff of P < 0.05. In the duodenum 435 genes were significantly changed with a FC ≥ |1.2| P < 0.05. In the duodenum, Claudin 1 and Claudin 2 were inversely affected by + Fe. Claudin 1 (CLDN1) plays a key role in cell-to-cell adhesion in the epithelial cell sheets and was upregulated (FC = 4.48, P = 0.0423). Claudin 2 (CLDN2) is expressed in cation leaky epithelia, especially during disease or inflammation and was downregulated (FC = -1.41, P = 0.0097). In the liver, 362 genes were expressed with a FC ≥ |1.2| P < 0.05. The gene most affected by a second dose of 200mg Fe was hepcidin antimicrobial peptide (HAMP) with a FC of 40.8. HAMP is a liver-produced hormone that is the main circulating regulator of Fe absorption and distribution across tissues. It also controls the major flows of Fe into plasma by promoting endocytosis and degradation of ferroportin (SLC4A1). This leads to the retention of Fe in Fe-exporting cells and decreased flow of Fe into plasma. Gene expression related to metabolic pathway changes in the duodenum and liver provides evidence for the improved feed conversion and growth rates in piglets given two iron injections preweaning with contemporary pigs in a companion study. In the duodenum, there is a downregulation of gene clusters associated with gluconeogenesis (P < 0.05). Concurrently, there was a decrease in the mRNA expression of genes for enzymes required for urea production in the liver (P < 0.05). These observations suggest that there may be less need for gluconeogenesis, and possibly less urea production from deaminated amino acids. The genomic and pathway analyses provided empirical evidence linking gene expression with phenotypic observations of piglet health and growth improvements.

Efficient C-N coupling for urea electrosynthesis on defective Co3O4 with dual-functional sites.

Urea electrosynthesis under ambient conditions is emerging as a promising alternative to conventional synthetic protocols. However, the weak binding of reactants/intermediates on the catalyst surface induces multiple competing pathways, hindering efficient urea production. Herein, we report the synthesis of defective Co3O4 catalysts that integrate dual-functional sites for urea production from CO2 and nitrite. Regulating the reactant adsorption capacity on defective Co3O4 catalysts can efficiently control the competing reaction pathways. The urea yield rate of 3361 mg h-1 gcat-1 was achieved with a corresponding faradaic efficiency (FE) of 26.3% and 100% carbon selectivity at a potential of -0.7 V vs. the reversible hydrogen electrode. Both experimental and theoretical investigations reveal that the introduction of oxygen vacancies efficiently triggers the formation of well-matched adsorption/activation sites, optimizing the adsorption of reactants/intermediates while decreasing the C-N coupling reaction energy. This work offers new insights into the development of dual-functional catalysts based on non-noble transition metal oxides with oxygen vacancies, enabling the efficient electrosynthesis of essential C-N fine chemicals.

Boosting urea synthesis in simulated flue gas electroreduction by adjusting W–W electronic properties

Porous catalyst with dual catalytic sites realizes efficient electrocatalytic production of urea from flue gas via adjusting W–W electronic properties.

Electrochemical urea production using carbon dioxide and nitrate: state of the art and perspectives

The minireview highlights recent developments in designing electrocatalysts for the co-reduction of CO2 and nitrates into urea. It also discusses advanced detection methods for intermediates and final products, as well as future research prospects.

Exploration of earth-abundant transition metals (Fe, Co, Ni) doped on W18O49 system as electrocatalysts for urea productiont

The conversion of inert N2 and CO2 into urea by electrocatalytic technology not only reduces the cost of urea synthesis in future, but also alleviates the environmental pollution problem caused by carbon emission in traditional industrial production. However, facing downside factors such as strong competitive reactions and unclear reaction mechanism, the design of high-performance urea catalysts is imminent. This study demonstrates that W18O49 system doped heteronuclear metals (TM = Fe, Co, Ni) can effectively solve the problem of competitive adsorption between N2 and CO2 and realize the co-adsorption of N2 and CO2 at diverse sites. Their theoretical limiting voltages for urea production on TM-W18O49 (TM = Fe, Co, Ni) systems are −0.46 V, −0.42 V and −0.52 V, respectively. The results are all lower than that of the contrastive voltage in pristine W18O49 system (-0.91 V), further indicating the rationality and necessity of single-atom doped strategy for the co-reduction of two molecules. Specially, Co-W18O49 can theoretically inhibit the side reactions of NRR, CO2RR, and HER, which deserve future experimental exploration in future. The study suggests that doping heteronuclear metal into transition metal oxides is a feasible scheme to solve competitive adsorption and improve catalytic performance.

Mild and scalable synthesis of a high performance CrFeCoNiRu0.05 high entropy nano-alloy/carbon electrocatalyst for efficient urea production with a chelate-based ionic liquid

We firstly reported synthesis of CrFeCoNiRu0.5 high-entropy alloy nanoparticles using an ionic liquid. The CrFeCoNiRu0.5 high-entropy alloy provides exceptionally high electrocatalytic activity for green urea synthesis.

Selective urea electrosynthesis via nitrate and CO2 reduction on uncoordinated Zn nanosheets.

Electroreduction of NO3- and CO2 to urea (ENCU) represents a fascinating strategy to enable waste NO3-/CO2 removal and sustainable urea production. Herein, uncoordinated Zn nanosheets (U-Zn) are developed as a highly selective ENCU catalyst, exhibiting the highest urea-faradaic efficiency of 31.8% with the corresponding urea yield rate of 39.3 mmol h-1 g-1 in a flow cell. Theoretical calculations and electrochemical spectroscopic measurements reveal that the high ENCU performance of U-Zn arises from the critical role of uncoordinated Zn sites that can promote both key steps of *NO2/CO2 coupling and *CO2NH2 protonation to *COOHNH2, while retarding the competitive side reactions.

Theoretical study on the synthesis of urea by series electrocatalysis of lithium main group embedded in COF structure

Replacement of the Harber-Bosch process for urea production by electrochemical reduction is an attractive alternative that reduces chemical energy consumption, reduces environmental pollution and improves efficiency. Among them, the method of electrochemical coupling of N2 and CO2 to produce urea has been widely used, but the inertness of nitrogen and nitrogen bond and high dissociation energy make it difficult to activate N2. Meanwhile, the method of synthesis of urea by NO3RR came into being. Nitrate in sewage is more abundant and convenient than nitrogen raw material, and more importantly, the dissociation energy of NO bond is much lower than that of NN. In this study, the transition metal embedded lithium COF catalyst was taken as an example, and the optimal electrocatalyst was selected through screening and synthesis energy barrier comparison to study the mechanism of urea synthesis. We studied the NRR and NO3RR paths, respectively, and found that the NRR synthesis of urea was optimal on the LiTaS-Pc VPPs catalyst, with a limiting potential value of −0.57V, and the NO3RR synthesis of urea was optimal on the LiVS-Pc VPPs catalyst, with a limiting potential value of −0.39V. It is found that NO3RR on the lithium catalyst is relatively better, and the required limit potential value is lower. In addition, the advantage of choosing lithium metal doping as catalyst in our study is that HER can be well inhibited, and the desorption of urea is easier than that of transition metal doping (taking molybdenum as an example). This study points out the direction for the electrocatalytic synthesis mechanism of urea, and provides a new idea for the selection of catalysts, paving the way for the future production of urea.