Gas Sweetening Research Articles

Exploring aminomethylcoumarins: versatile synthesis, structural diversity, and ADME prediction

This research presents a highly efficient method for synthesizing diverse aminomethylcoumarin libraries through the interaction of Mannich bases of coumarins and primary amines. The developed amination process demonstrated versatility and compatibility with various substituents. Reactions were completed within short timeframes, yielding high-purity products with substantial yields, as well as facilitating the scale-up of the process. The synthesized derivatives exhibited structural diversity, incorporating carboxylic and amino groups, as well as amide, hydrazide, and hydroxamic acid moieties. In silico ADME predictions highlighted the potential of these aminomethylcoumarins as promising candidates for further optimization in the development of oral chemotherapeutic agents

Cost details from front-end engineering design of piperazine with the advanced stripper

This Front-End Engineering Design (FEED) was funded by the U.S. Department of Energy (DOE) to estimate the cost to capture and compress 90 % of the CO2 from an existing natural gas combined cycle (NGCC) in Denver City, Texas, USA. The FEED used the PZAS (Piperazine with the Advanced Stripper) 2 G amine scrubbing technology developed and modeled by The University of Texas at Austin. This FEED is unique in providing more public cost details than other FEEDs funded by DOE. The primary objective of the FEED was to provide a comprehensive estimate for the total installed cost of the capture plant. The estimated capital cost of NGCC at the Mustang Station is $727 million for a capacity of 460 MW and 1.6 million tonnes CO2/yr. This includes a contingency of $104.6 million and a contractor's profit of $60.1 million. The total direct field cost is $384.1 million. With an optimistic fuel value of $3/MMBtu, the estimated cost of capture varies from $85/t at 4 % IRR/85 % load to $170/t at 10 % IRR/52 % load. Air cooling is technically feasible but expensive. The air cooling systems for the water wash and pump-around intercooling account for 23.4 % of the direct cost. The gas-fired boilers represent only 4 % of the direct costs, but steam extraction would reduce energy cost, free up cooling water, and reduce the direct costs of processing additional flue gas and CO2 from the boilers. The absorbers represent 9.6 % of the direct cost in this FEED with no direct contact cooler and only 7.6 m of packing. The solvent cross exchangers are less expensive than expected (2.5 % of direct costs). Doubling the number of these exchangers could reduce the heat duty from 3.0 to 2.5 GJ/t CO2.

Simple model for water wash performance in amine scrubbing for CO2 capture

In amine-based capture systems, a water wash is necessary to remove gaseous amine to minimize atmospheric emissions and maximize amine recovery. Water wash simulation requires rigorous thermodynamic and kinetic models like those for absorption and stripping systems. An offline water wash model has been developed based on simplified thermodynamic and mass transfer assumptions to simulate a single-stage water wash for flue gas from gas-fired turbines with little or no aerosol, and to expedite simulations without needing to utilize process modeling software. Calculation of activity coefficients using both Pitzer–Debye–Hückel and Debye–Hückel theory suggest that the liquid phase in a typical water wash will be ideal due to the dilute concentration of molecular and ionic species.Vapor phase piperazine (PZ) is predicted with a driving force based on the volatility of the free amine that has not reacted with other species or dissociated into its ionic form, and the predicted outlet concentration is nearly identical to that predicted by rigorous Aspen PlusⓇ simulations. The predicted UT FEED outlet concentration is 220 ppb compared to 260 ppb predicted by Aspen PlusⓇ.Single-stage water washes are predicted to have single ppm concentration of MEA leaving the wash outlet flue gas. Amino-methyl-propanol (AMP) is predicted to be reduced to 10–30 ppm by a single-stage wash, and is predicted to be a difficult-to-capture amine without further washing steps. This prediction correlates with published TCM data from an ALIGN-CCUS campaign. Amine compounds at a similar or lower volatility to that of PZ are predicted to be reduced to ppb levels via a single-stage wash.

In Situ Investigation of Electrochemically Mediated Carbon Capture and Release Via Quinone Chemistry in Aqueous Media

The development of devices capable of capturing and sequestering carbon dioxide emissions directly from air or at point sources is motivated by mitigating climate change. Electrochemically driven carbon capture and release at ambient temperature and pressure through the formation of complexes with organic redox active molecules [1,2] or via pH swing caused by proton-coupled electron transfer during molecular redox events [3,4] has shown promising results for carbon capture and release in terms of energy cost, scalability and safety compared to the state of the art amine scrubbing technologies [5].Quinones are organic molecules containing an unsaturated six-member ring with two carbonyl groups. They exhibit two potential mechanisms of CO2 capture. (a) Upon electrochemical reduction, the carbonyl groups within quinones provide sites for nucleophilic addition of carbon dioxide which results in the formation of a quinone-CO2 adduct (CO2reversibly bound by quinones). (b) Depending on the pKa of the quinone and the local pH, the electrochemical reduction of the compound can be proton-coupled, creating hydroxide, which captures CO2 as carbonate or bicarbonate.In this work, we introduce in situ electrochemical characterization and in situ fluorescence microscopy to separately quantify the two aforementioned contributions toward capture of CO2 at partial pressures ranging from 0.1 bar to 0.4 mbar. The non-invasive in situ analytical methods introduced in this work are used to distinguish, with sub-second time resolution, between the oxidized, reduced and adduct species by their electrochemical and fluorescence signatures. The results of this study permits us to understand the underlying simultaneous contributions of quinone-CO2 adduct path and the pH-swing path toward carbon capture and release and, additionally, introduces powerful non-invasive methods for gathering insights on similar systems. 1X. Li, X. Zhao, Y. Liu, T.A. Hatton, and Y. Liu, "Redox-tunable lewis bases for electrochemical carbon dioxide capture", Nature Energy 7, 1065 (2022). 2Y. Liu, H.Z. Ye, K.M. Diederichsen, T. Van Voorhis, and T.A. Hatton, "Electrochemically mediated carbon dioxide separation with quinone chemistry in salt-concentrated aqueous media", Nat Commun 11, 2278 (2020). 3S. Jin, M. Wu, Y. Jing, R.G. Gordon, and M.J. Aziz, "Low energy carbon capture via electrochemically induced pH swing with electrochemical rebalancing", Nat Commun 13, 2140 (2022). 4S. Jin, M. Wu, R.G. Gordon, M.J. Aziz, and D.G. Kwabi, "pH swing cycle for CO2 capture electrochemically driven through proton-coupled electron transfer", Energy & Environmental Science 13, 3706 (2020). 5G.T. Rochelle, "Amine scrubbing for CO2 capture", Science 325, 1652.

Electrochemically Mediated Amine Regeneration for Efficient CO2 Separation: Development and Characterization of Blend Electrolytes

Climate change mitigation necessitates the development of effective carbon dioxide (CO2) separation technologies. A wide range of electrochemical processes were recently developed for CO2 separation from various sources, including high concentration streams such as power plant flue gas and dilute streams like air [1]. Our focus is on the electrochemically mediated amine regeneration process, which is inspired by the conventional amine scrubbing process. This novel electrochemical approach offers a sustainable and potentially lower energy alternative for CO2 separation, with reduced absorbent degradation rates [2-4]. In this presentation, we discuss our latest findings on absorbent development, with a primary focus on the electrochemical aspects. We have tested several blended amine electrolytes and investigated their impact on the electrochemical performance of the system. Key parameters, such as resistance components and heterogeneous kinetic rate transfer, were examined using electrochemical impedance spectroscopy (EIS) and rotating disk electrode (RDE) techniques, respectively. Our results demonstrate significantly improved electrochemical performance for the newly developed blend electrolyte compared to benchmark single amine systems. Furthermore, we have successfully designed and implemented a large-scale continuous electrochemical cell using the novel electrolyte formulation. This system has demonstrated efficient and continuous CO2 separation from simulated industrial power plant flue gas, paving the way for sustainable CO2 separation technologies.

Covalent Crosslinking of High-Density Polyethylene Trimethylammonium-Based Radiation-Grafted Anion Exchange Membranes for Reduced Water Uptakes and Swelling

Anion exchange membranes (AEMs) are polymer membranes of varying thickness (10 - 50 µm) with covalently bound quaternary ammonium cations, which have been evaluated in fuel cells (AEMFCs) and green hydrogen electrolysis.1,2 Radiation-grafted AEMs made from high-density polyethylene (RG-HDPE) with ca. 30 microns hydrated thickness exhibit high hydroxide conductivities, promising mechanical stabilities, and high AEMFC performances.1,3 The enhanced water transport properties is hypothesized to be from nano and microscale level structural and morphological changes.3 Our best performing ultrathin RG-HDPE films exhibited excellent conductivity and AEMFC performance retention over the 400 h.3 However, the water uptake of RG-HDPE film is ca. 150%, hence, it is important to add a controlled amount of crosslinking.4-7 In previous studies of radiation-grafted membranes for use in reverse electrodialysis, crosslinking + amination was achieved by using a heated amination fabrication step involving a mixture of liquid, high boiling point mono-amines (such as N-methylpiperidine) and a crosslinking diamine (such as N,N,N',N'-tetramethyl-1,6-hexane diamine - TMHDA).8 However, a thermal method is not viable or safe when using the commonly supplied aqueous solutions of dissolved trimethylamine (TMA) gas. This presentation will discuss a variety of approaches, to target controlled TMHDA-crosslinking of TMA-based RG-AEMs, targeting reduced water uptakes and swelling with retention of ion conductivity (Figure 1). The most promising approach involved two steps with the initial amination of the poly(VBC)-grafted HDPE intermediate membranes using a sub-stoichiometric amount of TMHDA. Square wave voltammetry analysis of the solution recovered from amination step 1 confirmed complete reaction of the added TMHDA. In the second step, the membranes were then quickly [important] reacted with aqueous TMA to complete the amination process. TMA can displace TMHDA-based head-groups after long step 2 amination times, hence, we emphasize the use of short TMA amination times in the second step.

Fabrication and Characterization of Novel Pebax2533/POSS-FS Nanocomposite Membranes for CO2 Removal

In this work, novel mixed matrix membranes (MMMs) were fabricated by incorporation of octatrimethylsiloxy polyhedral oligomeric silsesquioxane (POSS) and fumed silica (FS) as nanoparticle fillers into poly(ether-block-amides) (Pebax2533) as polymer matrix in order to carbon capture and remove acid gas from natural gas. Fourier transforms infrared (FTIR) spectroscopy proved the chemical structure of the nanocomposites and field-emission scanning electron microscopy (FESEM) unveiled the appropriate filler dispersion and adhesion between fillers and polymer. Thermogravimetric analysis (TGA) showed that all the samples have reasonable thermal stability which is enhanced by nanoparticles. The permeability and selectivity of pure CO2, CH4, and N2 gases were measured in the 4-10bar pressure difference range. The incorporation of studied nanoparticles caused improve performance including the permeability and selectivity relative to the neat Pebax. In 4bar and 0.1wt% POSS, CO2 permeability raised by 87%, while the highest increase in CO2/CH4 selectivity is at 2wt% POSS. The gas transport and free volume were also interpreted by densitometry showing that the addition of the fillers had a positive effect on the free volume and chain packing of the polymeric membranes.

Adsorption-based post-combustion carbon capture assisted by synergetic heating and cooling

Adsorption carbon capture has shown its superiority in energy consumption and cost investment when compared with common amine scrubbing technologies. However, high regeneration energy demand of adsorbents is still a challenge for large-scale application. This paper proposes a temperature vacuum swing adsorption system integrated with auxiliary heating and cooling technology. Absorption chiller and double-stage absorption heat transformer (DAHT) are introduced from the perspective of adsorption and desorption process of CO2 capture system. Results indicate that when the duration of each step increases from 25 min to 45 min, the CO2 recovery rate decreases from almost 100 %–75.7 %, and CO2 purity increases slightly from 89.6 % to 91.1 %. Considering the temperature grade of waste heat, heat consumption of the absorption chiller assisted system is lower than that of DAHT for original and adjusted cases at a generation temperature of 58 °C. If the desorption temperature decreases from 120 °C to 100 °C, heat consumption of the absorption chiller decreases from 1.90 GJ·ton−1 to 1.76 GJ·ton−1, but the average capture capacity decreases from 306.3 ton·ton−1ad to 272.1 ton·ton−1ad. It is demonstrated that both absorption chiller and absorption heat transformer could be promising solutions to reducing the energy consumption of CO2 capture system. Absorption chiller has a priority over DAHT in regions with low temperature heat sources. Moreover, a tradeoff between adsorbent loss and heat consumption should be found when choosing the appropriate heat pump for practical application.

Synergetic enhancement of CO2 direct air capture with monoethanolamine-impregnated MIL-101(Cr) MOFs

To mitigate the greenhouse effect caused by the increase of CO2 concentration in the atmosphere, research attention has shifted towards CO2 Direct Air Capture (DAC) techniques. Despite that metal organic frameworks (MOFs) functionalized with various amines are promising to serve as suitable CO2 DAC adsorbent, there is few, if any, reports utilizing monoethanolamine (MEA), the most commonly employed in amine scrubbing technologies, as adsorption active sites. Herein, we have successfully impregnated MEA into MIL-101(Cr), resulting in a notably high CO2 adsorption capacity up to 1.20 mmol/g and an impressive amine utilization efficiency of 23% under low CO2 partial pressure (400 ppm). This improved capture efficiency can be attributed to the presence of hydroxyl groups, which alter the reaction dynamics between CO2 and amine groups. DAC simulation studies predominantly utilize synthetic air to replicate the DAC performance of adsorbents, yet precisely emulating air with artificially mixed gases remains an insurmountable challenge. To overcome this, we designed a system capable of testing DAC performance and employed MEA-impregnated MIL-101(Cr) for DAC testing. The adsorbent achieved pseudo-equilibrium DAC capacities of 2.15 and 1.50 mmol/g under humid and dry conditions, respectively, signifying an enhancement in DAC performance under humid condition. Our study offers novel perspectives for DAC adsorbent research, encompassing both material and equipment considerations.

Power to gas and top gas recycling integration in an oxygen blast furnace steelmaking industry

A new process concept integrating power to methane with top gas recycling in an oxygen blast furnace (BF) is investigated to reduce the emission intensity of steelmaking. Power to gas produces synthetic methane using hydrogen (H2) generated by an electrolyser operated with renewable electricity, and CO2 captured from the BF gas by amine scrubbing supplied with heat from the methanation process. The clean gas from the amine scrubbing is recycled and injected in the BF (via top gas recycling), together with synthetic methane. A parametric analysis is performed to vary the amount of top gas recycled (from 0 kg/tHM to 270 kg/tHM). Based on the results, CO2 equivalent emissions can decrease by 34% using power to gas technology, and by 30% with power to gas and top gas recycling (compared to conventional BFs). Nevertheless, if both integrations are present, additional benefits on the specific energy consumption (12.0 MJ/tHM), and specific cost (130 €/tHM) are achieved, compared to only applying power to gas (17.5 MJ/tHM and 233 €/tHM). In all cases, the downstream thermal energy needs of the steel plant are fulfilled, contrarily to conventional top gas recycling concepts. The main conclusion is that top gas recycling should be considered together with PtG technology, and vice versa, when integrated in blast furnace ironmaking, in order to both abate emissions while supplying downstream energy needs.

Energy, exergy, economic, and environmental analysis of natural gas sweetening process using lean vapor compression: a comparison study

Abstract Gas sweetening with an aqueous solution of diethanolamine is a crucial and common process in natural gas processing. However, the process, particularly in the solvent regeneration section, consumes a substantial amount of energy, significantly escalating the cost of gas. This paper presents a simulation and optimization of an existing natural gas refinery plant using a lean vapor compression method. The simulation results indicate that the current process requires 2.73 GJ/tacid gas for solvent regeneration, with exergy destruction of 14,120.59 kW in the solvent regeneration section. The total annualized cost for the current process is 11.68 M$. A modified scheme is proposed to address the issue of high energy consumption and the associated costs. The proposed scheme demonstrates significant improvements in the aforementioned parameters. Specifically, energy for solvent regeneration, exergy destruction in the solvent regeneration section, total annualized cost, and cost of gas are reduced by 16.12 %, 25.04 %, 20.97 %, and 20 % compared to the current process, respectively. These improvements enhance the thermoeconomic indexes, making the proposed scheme a viable and cost-effective alternative to the current process.

Experimental Evaluation of Chemical Reactions Involved in Ultrasonic-Assisted Absorption of Bulk CO2

As the most mature natural gas sweetening process, absorption has always been improved to meet the separation requirement. Recently, ultrasonic irradiation has been proposed as a technique that can intensify CO2 absorption. However, further studies are still required, particularly focusing on the sonochemical effect. Since the influence of the sonochemical effect on the reaction pathway is still debatable, attention must be given to verifying the influence of ultrasonic irradiation on the chemical reactions of CO2 absorption. Hence, this work aims to evaluate the influence of OH˙ radicals generated by the sonochemical effect on the chemical reactions involved during CO2 absorption using promoter-free methyldiethanolamine (MDEA). For the evaluation, various samples under irradiated and non-irradiated conditions are analyzed using the HPLC characterization technique. The results show that the hypothesis of changing the reaction pathway due to the presence of the sonochemical effect is invalid. However, it can accelerate the generation of hydroxyl radicals (OH˙) via water sonolysis. Thus, the origin of sonochemistry in aqueous solutions is defined as water sonolysis. The analysis of the CO2 absorption rate also demonstrates the presence of accelerated chemical reactions (contributed by the OH˙ radicals), which could potentially make the slow kinetic MDEA more practical for industrial application.

Developing High-Capacity Solid "Molecular Basket" Sorbents for Selective CO2 Capture and Separation.

ConspectusSince carbon-based energy continues to dominate (over 80%) the global primary energy supply, carbon dioxide capture, utilization, and sequestration (CCUS) is deemed to be a promising and viable option to mitigate greenhouse gas emissions and climate change, for which CO2 capture is critical to the overall success of CCUS. Although liquid amine scrubbing is a mature technology for carbon capture, it is energy-intensive and costly due to energy consumption in solvent heating and water evaporation apart from the energy needed to break amine-CO2 bonding. To address this challenge, Song's group developed a new design approach for adsorptive CO2 capture and separation, namely, "molecular basket" sorbents (MBS), without the need for dealing with solvent heating and water evaporation. The solid MBS consisting of polymeric amines (such as PEI) immobilized into nanoporous materials (such as SBA-15) possesses a high capacity for CO2 capture with high selectivity, fast kinetics, and good regenerability. Consequently, MBS can greatly reduce energy consumption and carbon capture cost. Conventional adsorbents such as zeolites, activated carbon, alumina, and silica have low adsorption capacities, and their use of CO2 adsorption requires prior removal of moisture and cooling of flue gas (∼35 °C). On the contrast, the CO2 sorption capacity of MBS can even be promoted by the presence of moisture/steam and reaches the best performance closer to flue gas temperature (∼75 °C). This Account presents an overview of our research progress in the material development and fundamental understanding of MBS for CO2 capture and the separation of CO2 from various gas streams. It begins with an illustration of the MBS concept, followed by efforts to improve the performance and pilot-scale demonstration of MBS for CO2 capture. With the systematic characterization of MBS by various ex situ and in situ techniques, a better understanding is developed for the CO2 sorption process mechanistically. Furthermore, this Account demonstrates how the fundamental understanding of the CO2 sorption mechanism promotes the further development of more robust and advanced sorbent materials with improved CO2 sorption capacity, kinetics of sorption and desorption, and cyclic stability. Finally, an outlook is provided for the future design and development of novel sorbent materials and the CO2 sorption process for various gas streams including flue gas, biogas, air, and hydrogen streams.

Assessment of Safety Barrier Performance in Environmentally Critical Facilities: Bridging Conventional Risk Assessment Techniques with Data-Driven Modelling

The failure of emission control systems in industrial processes undergoing emission regulations can cause severe harm to the environment. In this context, safety engineering principles can be applied to analyze process deviations and identify suitable safety barriers to mitigate harmful emissions during critical events. However, the selection, design, and assessment of proper safety barriers may be complex due to several contingencies such as the inability to perform extensive field tests on systems under strict emission regulations. In this study, an approach is proposed to couple conventional hazard identification techniques with a digital model of a flue gas treatment system to support the identification and performance assessment of safety barriers for emission control. Resilience analysis is used to evaluate the behavior of the most relevant safety barrier options, selected through a screening with conventional hazard identification tools. Barriers are simulated using the digital model of the system, gathering key information for their design and evaluation, and overcoming the limitations to field tests at the real plant. The methodology is illustrated with reference to acid gas removal in waste-to-energy facilities, a relevant example of an emission control system that is typically exposed to significant process deviations.

Fabrication of high-flux defect-free hollow fiber membranes derived from a phenolphthalein-based copolyimide for gas separation

In the realm of gas purifications, hollow fiber membranes have gained significant prominence due to their unique advantages. However, achieving defect-free membranes poses a considerable challenge. In this study, we addressed this challenge with a novel copolymer, 6FDA-DAM:DAP(2:1), comprising 4,4′-(hexafluoroisopropylidene) diphthalic anhydride (6FDA), 2,4.6-Trimethy-m-phenylenediamine (DAM), and a phenolphthalein-derived diamine of 3,3′-diaminophenolphthalein (DAP). We found that defect-free hollow fiber membranes could be prepared when 20 wt% or more ethanol was added in the polymer dope solution, but this led to the formation of oval hollow fibers that would be flattened under high pressure. We solved this limitation by lowering ethanol content to 15 wt%, adding 2 wt% LiNO3, and increasing the air–gap distance. These measures reduced the difference in phase inversion rates between the surface region and the bulk phase of the nascent hollow fiber. The CO2 permeance of this defect-free hollow fiber membrane reached 282 GPU with a CO2/CH4 selectivity of 50.2. Highly permeable defective hollow fiber membranes were also developed using a polymer dope without LiNO3 and a low THF content of 5 wt%. After coated by silicone rubber, CO2 permeance of the membrane reached 554 GPU with a CO2/CH4 selectivity of 45.0. In mixed gas tests, the two membranes exhibited O2 permeances of approximately 43.3 and 75.3 GPU, with O2/N2 selectivities of 5.5 and 5.4, respectively. Their CO2 permeances were 281 and 465 GPU, with CO2/CH4 selectivities of 45 and 41, CO2/N2 selectivities of 35.7 and 33.3, respectively. These separation performances were among the best of state-of-art polymeric hollow fiber membranes and demonstrated great potential for gas separation applications such as natural gas sweetening, flue gas treatment, and air separation.

Monitoring, modeling, and optimization of parameters affecting the recovery efficiency of acid gases from a sweetening unit

Amine processes are the advanced technology available today for the removal of carbon dioxide (CO2) and hydrogen sulfide (H2S) acid gases. Methyldiethanolamine (MDEA) is a well-known tertiary amine used selectively for the removal of carbon dioxide from natural gas. There are many parameters that can affect the efficiency of separating these acid gases from natural gas. In this paper, we have studied, modeled, and optimized different operating parameters of sour gas feed and MDEA solution which affect the CO2 recovery efficiency from an existing sweetening unit. These operating parameters are the sour gas feed temperature and pressure, volume ratio (%) of carbon dioxide in the feed gas, amine inlet temperature, and amine circulation rate. Actual data were collected from an industrial CO2 sweetening unit over one year. These data were used to study the effect of the studied operating parameters on the recovery efficiency of CO2 from the sweetening unit. All studied operating parameters were found to have an impact on the recovery efficiency of the removed gases. A response surface methodology approach was used in Design-Expert software version 13 to model the relationship between considered operating parameters and CO2 recovery efficiency. In addition, Design Expert numerical optimization has been used to maximize CO2 recovery efficiency. The results showed that the optimal range of sour gas feed temperature is 34.71 to 45.56 °C, sour gas feed pressure is 8.32 to 10.04 barg, the volume ratio (%) of carbon dioxide in the sour gas feed is 8.51 to 10.15, the temperature of the amine is 38.03 to 43.96 °C, and the amine circulation rate is 788.39 to 1122.35 m3/h. The presented work can be considered as a guideline for increasing the recovery efficiency of CO2 for both new and existing sweetening units.

Strategic management of energy consumption and reduction of specific energy consumption using modern methods of artificial intelligence in an industrial plant

Given the importance of energy and its role in sustainable gas production, paying special attention to its consumption indicators in all industries, especially oil & gas is very important. The energy consumption index parameter, which equals the ratio of energy consumption to gas production, is one of the most significant indicators of the gas refinery. Artificial intelligence can be used to evaluate the effects of different parameters and find the factors influencing energy performance. Important variables such as inlet gas from various sources, the energy consumption of each part, and the amount of waste refinery gas are collected on different days of the year, then using the least square support vector machine method and networking and sensitivity analysis of the impact of each variable separately. The role of each in this parameter is determined so that it can be used to provide appropriate solutions to reduce energy consumption and the energy consumption index parameter for sustainable gas production. According to the results of this study, the steam unit has a 14 % impact on the energy consumption index, and the gas sweetening unit has an 18 % impact on gas consumption. So, more research on the optimization of these two units is necessary.

Urea production: An absolute environmental sustainability assessment

The demand for urea, as the most popular global nitrogen fertilizer, is on the rise and as such, its performance in an environmentally sustainable perspective relative to planetary boundaries is high on the agenda. The increasing interest in nitrogen fertilizers is to improve agricultural methods for a better production rate, but can it become environmentally sustainable? Which is due to the significant contribution of fertilizers in the anthropogenic impacts of industrial activities on nature, should be considered. Here, a system analysis based on real data using life cycle assessment linked to the planetary boundaries framework (PB-LCIA) was conducted to study the performance of total urea consumption in Iran, 1.8E+6 metric tons per year. In LCA, midpoint and endpoint methods (ReCiPe 2016) and for AESA, a PB-LCIA methodology was utilized. Results showed that global warming potential, freshwater eutrophication, and marine eutrophication contribute 1.37E+09 kg CO2 eq, 1.63E+04 kg P eq, and 1.28E+04 kg N eq, respectively, while the GHG emissions of combustion, electricity, and natural gas sweetening have the most contribution to global warming by 35, 24 & 15 %, respectively. Regarding absolute sustainability, global warming, ocean acidification, and biochemical N exceed this activity's assigned share of safe operating space (SoSOS). However, choosing different sharing principles can influence to what extent this activity exceeds or stays within the assigned SoSOS; accordingly, the Nitrogen Biogeochemical flows depend on the sharing principle. Ultimately, the total Iranian urea consumption as fertilizer is not absolutely sustainable. The promising point is that producing sustainable electricity and feedstocks could lead to more sustainable urea fertilizers.

Room temperature synthesis of N-substituted pyrrolidone from levulinic acid and nitrobenzene via a tandem hydrogenation and reductive amination process

N-substituted pyrrolidone is one type of organic small molecules with high added values. The synthesis of N-substituted pyrrolidone via a tandem hydrogenation and reductive amination of biomass-derived levulinic acid (LA) with nitroarenes is an attractive route, but has rarely been reported, especially at room temperature. Herein, various Pt-based catalysts were used for the one-pot hydrogenation/reductive amination of LA with nitrobenzene and 96.0% yield of 5-methyl-N-phenyl-2-pyrrolidone (MNPP) was achieved over 0.5Pt/Nb2O5 at 30 °C, 24 h. Deep investigations demonstrated that the strongest ability of Nb2O5 to activate CO bond in LA and the hydrogenation ability of small size of Pt particles were the key factors to realize room temperature synthesis over 0.5Pt/Nb2O5. This Pt/Nb2O5 catalyst was reused 5 runs without obvious deactivation and it can be extended to various N-substituted pyrrolidone’s synthesis directly from LA and different nitroarenes at room temperature. This work would be helpful for designing more efficient reductive amination catalysts.

Electrification of amine-based CO2 capture utilizing heat pumps

Capturing CO2 is necessary to abate the climate crisis. Amine CO2 capture is the most mature technology but suffers from high thermal energy consumption for solvent regeneration. Heat pumps are a proven technology with which to electrify industrial processes. This study investigates an integrated heat pump system used to electrify an amine CO2 capture unit for a biogas upgrading process using aqueous monoethanolamine. The study evaluates the potential of such integrated systems through the overall energy consumption at varied stripper pressures between 0.313 to 1.813 bara and includes a techno-economic analysis to determine the levelized cost. The most optimal heat pump scenario utilizes a vacuum operated stripper at 0.513 bara and reduces the overall energy consumption by 68 % compared to a classical amine scrubbing unit. The techno-economic analysis shows that the levelized costs for biogas upgrading per MWh of produced biomethane may be reduced by up to 33 % from 47 €/MWh to 31 €/MWh by implementing heat pump electrification systems and a vacuum operated stripper compared to a scenario using natural gas.