Integrating CO₂ capture with electrochemical conversion offers a promising pathway to reduce the energy penalty associated with conventional solvent regeneration. In this context, the development of suitable solvents is crucial. In this study, we develop a non-aqueous Monoethanolamine (MEA)-based solvent composed of Choline Chloride (ChCl) and Ethylene Glycol (EG), designed to function simultaneously as a CO₂ absorbent and an electrolyte in an electrolyzer, thereby eliminating the need for intermediate solvent regeneration steps. Vapor-liquid equilibrium (VLE) measurements were performed to quantify chemical CO₂ absorption, while N₂O was used as an analogue gas to assess the physical CO₂ absorption. Although conventional 30 wt.% aqueous MEA exhibited stronger CO₂ binding at low CO₂ partial pressures (≤1 kPa), our non-aqueous MEA solvent demonstrated markedly higher capacities at moderate to high CO₂ partial pressures (up to 500 kPa), reaching up to 1.2, 1.1, and 0.9 mol CO₂/mol MEA at 25, 40, and 65 °C, respectively, exceeding the theoretical equilibrium limit of aqueous MEA. FTIR spectroscopy identified a transition from predominant carbamate formation at low CO₂ partial pressures to increased carbonate formation derived from EG, together with enhanced physical dissolution at higher CO₂ concentrations, indicating distinct and pressure-dependent reaction pathways. Evaluation of key physical properties, including viscosity, electrical conductivity, and thermogravimetric analysis (TGA), highlighted the critical role of solvent formulation in enabling process integration. While incorporation of ChCl increased viscosity due to its ionic nature, it substantially enhanced thermal stability and provided intrinsic ionic conductivity required for electrochemical operation. Overall, this work demonstrates how solvent composition design in non-aqueous solvent systems enables high CO₂ capacity, tunable reaction chemistry, and electrochemical compatibility, offering a practical pathway toward integrated, energy-efficient carbon capture and utilization technologies.

CO₂ feedstock obtained from point sources, such as chemical industries or fossil fuel-based power plants, typically contains gaseous contaminants such as SO_x, NO_x, H₂S, and COS, which can be detrimental to the catalysts used to electrochemically convert CO₂/CO into valuable fuels and chemicals. A significant suppression of C₂₊ products is observed even in the presence of 10 ppm of these impurities due to catalyst poisoning and a selectivity change. Hence, it is necessary to have an upstream cleaning process to maintain a high selectivity toward high value C₂₊ products and to reduce the operational costs associated with frequent catalyst regeneration or replacement. We present a comprehensive process model and technoeconomic analysis of an integrated large-scale two-step CO₂/CO electroreduction plant that produces C₂₊ products including ethylene, acetic acid, ethanol, and n-propanol, using blast furnace gas obtained from a steel manufacturing facility as feedstock. Detailed modeling and integration of the upstream cleaning units, CO₂/CO electrolyzers, and the downstream separation of gas/liquid products are performed using Aspen Plus. Our analysis shows that the large-scale two-step CO₂/CO electroreduction process is not profitable under the base case scenario and requires significant improvements in electrolyzer performance, reduction in capital costs, and favorable market conditions to improve the economics. The upstream cleaning units only contribute to ∼15% of the CAPEX and ∼8% OPEX of the entire plant, while the electrolyzers contribute to ∼63% of the total CAPEX and OPEX. A positive net present value ($54M), a payback time of 13 years, and an internal rate of return of 12.8% can be achieved when the electrolyzer capital cost is $10,000/m² (−50%) and electricity price is $20/MWh (−50%), with current densities of 750 mA/cm² (+50%) for both electrolyzers and cell voltages of 2.5 V (−17%) for CO₂R and 2.0 V (−20%) for COR electrolyzers, and when the product prices are 35% higher than the current market prices. Incorporating an energy-saving coelectrolysis process or integration into facilities that can directly utilize the products can accelerate the commercialization of the two-step CO₂/CO electroreduction process.

Electrochemical CO₂ reduction to CO offers a sustainable route for converting CO₂ into value-added chemicals and fuels. However, CO₂ streams derived from industrial sources often contain SO₂ impurities that severely poison conventional metal-based catalysts. Here, we report a nitrogen-doped carbon catalyst that exhibits pronounced tolerance and stability for CO₂-to-CO conversion in the presence of SO₂ (100–10,000 ppm). The catalyst maintains over 90% Faradaic efficiency toward CO during 8 h of electrolysis at −1.0 V vs RHE with 100 ppm of SO₂, whereas Ag foil electrodes undergo rapid deactivation. Density functional theory calculations combined with surface analyses indicate that weak SO₂ adsorption and the absence of stable sulfur accumulation on nitrogen-doped carbon strengthen its resistance to impurity-induced deactivation, in contrast to Ag catalysts that form Ag₂S. Gas-fed tests in a membrane electrode assembly (MEA) electrolyzer further confirm that nitrogen-doped carbon sustains high CO selectivity at elevated current densities, while Ag nanoparticles suffer irreversible sulfur poisoning. These results demonstrate that nitrogen-doped carbon is intrinsically resistant to SO₂-induced deactivation and highlight its potential as a robust catalyst for CO₂ electroreduction under impurity-containing conditions.

The olive oil market, valued at almost €14 billion in 2023 has tripled its produc-tion over the last 60 years, reaching 3.27 109 kg in 2020. Spain leads the production, accounting for 70% in the European Union and 45% worldwide. This land-intensive in-dustry has significant social, environmental, economic, and territorial impacts, with de-centralized waste generation being a major concern. Sustainable waste management is a fundamental objective. One potential solution is using this waste for low-carbon hydro-gen production through thermochemical processes (e.g. gasification or pyrolysis). This is particularly relevant when hydrogen-consuming industries are nearby. Given this con-text, this work proposes a methodology for assessing the potential of olive grove residues from a sustainability perspective. Our approach uses high-level data from public sources to estimate transport costs and greenhouse gas emissions associated with biomass collec-tion. We identify and quantify suitable waste sources, their locations, and associated hy-drogen production potential. The application of the method is validated through a case study in southern Spain, a major olive oil producer with significant industrial hydrogen consumers nearby. Results indicate that using only available olive grove residues is not currently sustainable for meeting the region’s hydrogen demand, covering merely 0.6% of requirements. This result is the consequence of the current use of olive grove biomass, suggesting the need for revised waste management strategies or alternative resources to increase sustainable hydrogen production. The application of the proposed methodology to other regions can help identify the sustainable potential of using this and similar wastes to produce low-carbon hydrogen.

Recent research in chemical plant operation shows increasing interest in dynamic process operation as part of designed operating strategy for reasons such as increased dependency on renewable energy, and process intensification. Conventional analyses of fixed bed reactors are developed for steady state optimization and may not be adequate for dynamic operation. In fact, the important metrics and targets in dynamic process design are not entirely clear. The first objective of this article is to provide a state-of-the-art survey categorize types of dynamic operation, and rank the available common modelling and analytical tools suitable for quantification of dynamic process variables. The article then examines a case study of 1D and 2D model differences in a methanol steam reforming reactor. The case study shows model prediction differences of up to 15% for conversion, and up to 50% for CO concentration at the outlet during extreme load changes. The study concludes that the complexity of analytical and numerical techniques for dynamic processes is notably higher compared to steady state analyses, but appropriate tools and procedures are currently lacking.

Zeolite 13X and 5A were modified with nickel using three different methods: evaporation impregnation, deposition precipitation, and ion-exchange for comparison in CO₂ methanation. The catalysts were tested in a lab scale fixed bed reactor and their physico-chemical properties were characterized by XRD, SEM-EDX, TEM, STEM-EDX, nitrogen physisorption, H₂-TPR and NH₃-TPD. The physico-chemical characterization results of Ni modified 13X and 5A zeolite catalysts showed that the zeolite structure did not change after the Ni modification by different catalyst synthesis methods, although the surface area and micro-pore volume decreased. The average diameter of NiO and the NiO cluster size range of Ni zeolite catalyst synthesized with ion exchange are smaller than the catalysts prepared by the evaporation impregnation and deposition preparation. Ni dispersed well through 13X, while a lot of Ni appeared on the crystal outer surface of 5A zeolite. Evaporation impregnation and deposition precipitation prepared Ni13X catalysts exhibited a higher activity than ion-exchange prepared samples on CO₂ methanation. The catalyst performance of Ni5A-IE and Ni13X-IE zeolite catalysts, which were synthesized using the ion-exchange method for CO₂ methanation was limited by the actual loading of Ni. The Ni 13X catalysts have less CH₄ selectivity which could be attributed to their lower acidity. Ni13X-EIM catalyst showed good catalytic stability at 360 °C, with no catalyst deactivation during a 200 h catalyst stability test.

The olive oil industry is an important source of agricultural residues throughout its value chain, ranging from intermediate process slurries to relatively dry content pruning residues. Among them, crude olive pomace (COP) is of particular interest since it is abundant, low cost and can be a promising source for bioenergy. Nevertheless, because COP is phytotoxic and has a high moisture content and low energy density, it represents a challenge to conventional processes that usually require a dry and homogenous material. The main novelty of this study is the use of a transition metal catalyst and a central composite design (CCD) approach to optimize the conversion of COP through hydrothermal liquefaction (HTL) into valuable products. Results show that catalytic HTL is capable of converting up to half of the COP into bio-oil. Higher process temperatures resulted in lower bio-oil yields but larger higher heating value (HHV) and lower N content. The bio-oils produced at higher temperatures also show lower concentration of phenols and regarding biochar, a low inorganic content. Without any further upgrading, COP bio-oils produced by HTL are rich in valuable compounds such as oleic acid, phenolic compounds and ketones that can be used in the polymer industry or as chemical intermediates. The highest bio-oil yield was 51.96 wt% at 330 ºC for 30 min and 7.5 wt% catalyst with a HHV of 22.0 MJ/kg. At those operational conditions, the biochar yield was 16.49 wt% with a HHV of 8.9 MJ/kg. The major minerals found in the biochars (CaO, SiO₂ and P₂O₅) suggests that biochar could be well-suited for use in soil applications or as materials for adsorption, especially the non-catalytic ones. Furthermore, the experimental results acquired from HTL of COP were used to develop a global kinetic model. Using an explicit Runge-Kutta method, the kinetic parameters were calculated. After comparing the global kinetic model with a linear system of ordinary differential equations (ODEs) based on the CCD models, results indicate that this approach is more effective in predicting the yields of HTL products.

Hydrogen economy is spreading across the maritime sector in response to increasingly stringent regulations for shipping emissions. The challenging on-board hydrogen logistics are often mitigated with hydrogen carriers such as methanol. Research on methanol reforming to hydrogen for fuel cell feed is conducted mostly in steady state, overlooking dynamic reactor operation and its effects on the power production system. Forced reactor operations induce fluctuations of CO content in the reformate potentially harmful to the PEM fuel cell, and drops in methanol conversion causing inefficient operation. In present research, simulations with a physical 2D unsteady model of a packed bed methanol steam reforming reactor resulted in methanol conversion drop durations of up to a minute. Additionally, temporary increases of CO content up to 112% were observed. Throughput ramp ups most notably impact the conversion, while ramp downs negatively affect selectivity. The investigation on reactor geometry concludes that larger tube diameters increase transient time and CO spikes, while they decrease with reactor length. Amplified unsteady effects are also observed with larger changes in input process variables. The results imply that heat transfer rate to the reactor are most often the detrimental factor for transient effects and durations in practice. Following this work, inclusion of realistic heating methods is recommended, instead of uniform tube temperatures used in present simulations. Heating system characteristics are necessary for realistic evaluation of the methanol reformer constraint on fuel cell feed demand in fully integrated systems.

An urgent ecological issue is the threat posed by invasive species, which are becoming more widespread especially in Africa. These encroachments damage ecosystems, pose a threat to biodiversity, and outcompete local plants and animals. This article focuses on converting Acacia Mellifera from Namibia, commonly known as encroacher bush (EB) into high-quality drop-in intermediates for the chemical and transport industry via hydrothermal liquefaction (HTL). HTL tackles the growing need for sustainable energy carriers while simultaneously halting the spread of the invasive species. A surface response methodology was used to optimize the HTL process for the following operational conditions: temperature (250–340 °C), residence time (5–60 min) and catalyst loading (0–10 wt%). The catalyst of choice was determined after evaluating the energy recovery (ER) of four different catalysts (Zeolite, La₂O₃, Hydrotalcite, Ni/SiO₂–Al₂O₃) under the same HTL operational conditions. The results indicate that the addition of hydrotalcite results in high yields of bio-crude oil (13–28 wt%), without compromising the high heating value (HHV, 26–31 MJ/kg), water content (0.47 wt%) or increasing the content of oxygenated compounds compared to the non-catalytic experiment. For the experimental conditions tested, we observed a global maximum in conversion in the 330 °C and 30 min range. Our findings indicate that the most significant factor on the conversion of EB into bio-crude oil was temperature, followed by the catalyst loading. Furthermore, biochars produced at 330 °C and 30 min show potential as solid biofuels with HHVs up to 28.30 MJ/kg.

The recent interest in the production of green hydrogen through water electrolysis is hampered by its high cost when compared to steam methane reforming. To overcome this disadvantage, some studies explore replacing oxygen production with hydrogen peroxide at the anode, which has a higher value. Existing electrocatalysis research primarily focuses on hydrogen peroxide synthesis, neglecting process design and separation. Additionally, hydrogen peroxide’s thermodynamic instability in alkaline conditions and the existence of other ions make the separation difficult. This paper proposes a novel concept for the paired water electrolysis process that can be used to improve green hydrogen production economics through valuable chemical coproductions. Valorizing hydrogen peroxide to sodium percarbonate as the final product was chosen to address hydrogen peroxide separation challenges. An electrolyzer stack of 2 MW was chosen, incorporating a recirculating structure, and a boron-doped diamond anode to enhance the hydrogen peroxide production as the base case. According to the techno-economic analysis, for a 2 MW electrolyzer stack, capital expenditure was calculated as 64.5 M€, operational expenses as 21.6 M€, and revenue was calculated as 2.5 M€, resulting in a negative cash flow of −19.1 M€. Results revealed that the process can be profitable (breakeven point) at a capacity of approximately 308 electrolyzer stacks, which is 616 MW in capacity. A sensitivity analysis was conducted to determine how cost drivers including electricity price, anode price, Faradaic efficiency, price of the products and tax subsidy affect the breakeven point. A breakeven point of 60 electrolyzer stacks (120 MW) was found with a 100% increase in the sodium percarbonate sale price. In comparison, a theoretical 100% Faradaic efficiency in the anode material would result in a breakeven point of 38 electrolyzer stacks (76 MW). Even a more realistic 75% Faradaic efficiency leads to a breakeven plant size of 75 stacks (150 MW). Further, multiple two-parameter sensitivity analyses were conducted to assess the relations between Faradaic efficiency, sodium percarbonate sale price and anode material price. For instance, if sodium percarbonate price increases by 100% and Faradaic efficiency increases to 75%, the breakeven capacity drops down to 13 stacks (26 MW). Despite facing economic challenges for the proposed process design based on available technologies, the techno-economic analysis highlights key targets for future works. It also provides valuable insights into the economic feasibility of simultaneously producing hydrogen and sodium percarbonate through water electrolysis, indicating promising potential for the future.

In this study, the effect of halide anions on the selectivity of the CO₂ reduction reaction to CO was investigated in choline-based ethylene glycol solutions containing different halides (ChCl : EG, ChBr : EG, ChI : EG). The CO₂RR was studied using silver (Ag) and gold (Au) electrodes in a compact H-cell. Our findings reveal that chloride effectively suppresses the hydrogen evolution reaction and enhances the selectivity of carbon monoxide production on both Ag and Au electrodes, with relatively high selectivity values of 84 % and 62 %, respectively. Additionally, the effect of varying ethylene glycol content in the choline chloride-containing electrolyte (ChCl : EG 1 : X, X=2, 3, 4) was investigated to improve the current density during CO₂RR on the Ag electrode. We observed that a mole ratio of 1 : 4 exhibited the highest current density with a comparable faradaic efficiency toward CO. Notably, an evident surface reconstruction process took place on the Ag surface in the presence of Cl⁻ ions, whereas on Au, this phenomenon was less pronounced. Overall, this study provides new insights into anion-induced surface restructuring of Ag and Au electrodes during CO₂RR, and its consequences on the reduction performance on such surfaces in non-aqueous electrolytes.

Electrochemical ammonia synthesis via the nitrogen reduction reaction (NRR) has been poised as one of the promising technologies for the sustainable production of green ammonia. In this work, we developed extensive process models of fully integrated electrochemical NH ₃ production plants at small scale (91 tonnes per day), including their techno-economic assessments, for (Li-)mediated, direct and indirect NRR pathways at ambient and elevated temperatures, which were compared with electrified and steam-methane reforming (SMR) Haber-Bosch processes. The levelized cost of ammonia (LCOA) of aqueous NRR at ambient conditions only becomes comparable with SMR Haber-Bosch at very optimistic electrolyzer performance parameters (FE > 80% at j ≥ 0.3 A cm ⁻²) and electricity prices (<$0.024 per kW h). Both high temperature NRR and Li-mediated NRR are not economically comparable within the tested variable ranges. High temperature NRR is very capital intensive due the requirement of a heat exchanger network, more auxiliary equipment and an additional water electrolyzer (considering the indirect route). For Li-mediated NRR, the high lithium plating potentials, ohmic losses and the requirement for H ₂, limits its commercial competitiveness with SMR Haber-Bosch. This incentivises the search for materials beyond lithium.

The anodic co-production of hydrogen peroxide (H₂O₂) during alkaline water electrolysis has gained interest as a sustainable alternative for anthraquinone oxidation. However, electrochemical H₂O₂ production is often studied with idealized laboratory setups to determine the H₂O₂ formation kinetics. In this work, we perform the reaction with industrially relevant operating principles using a flow cell with separately recirculating anolyte and catholyte. We then fit the data to an analytical model that we derive based on mole balances that accounts for anodic generation, anodic oxidation, and bulk disproportionation of H₂O₂, as well as electrolyte volumes and electrode surface area. We performed experiments at 100, 200, and 300 mA cm^-2 to derive values for the reaction system. At 200 mA cm^-2, we found a generation rate of 0.037 mmol min^-1 cm^-2 (FE_H2O2 = 59%) and an anodic decomposition rate constant of 0.304 cm min^-1, with a bulk disproportionation rate constant of 1.85 × 10^-3 min^-1. We successfully applied our model to two sources in literature to derive values for their systems as well. In all cases, the contribution of anodic oxidation of H₂O₂ was found to be the larger loss mechanism in comparison to bulk disproportionation. Using the analytical model, we show that decreasing the reservoir volume is a simple way to increase the H₂O₂ concentration over time. Further refinement of the model can be achieved through the use of mass transfer relationships based on electrolyzer geometries to describe the anodic oxidation of H₂O₂ in the mole balance equations.

Long transport distances and extended storage of biomass pellets especially in humid environments provide a suitable setting for enhanced degradation in the form of moisture sorption, cracking and attrition. We developed an optically transparent, low-cost and environmentally friendly coating to reduce moisture sorption and storage degradation of pellets. The developed coating is a hybrid sol–gel, based on tetraethoxysilane (TEOS) and 3-glycidoxypropyl-trimethoxysilane (GPTMS) precursors. We coated two types of untreated and one type of torrefied wood pellets and stored them in a climate chamber during 1 month simulating a ship's hold, at a constant condition of 40 °C and 85% relative humidity. After 1 month of storage, the mean water contact angle increased by a factor of two compared to the uncoated ones. The lower wettability of the sol-gel coated untreated pellets compared to the non-coated torrefied pellets might provide an alternative to torrefaction.

Nitrogen-doped (N-doped) carbon catalysts have been widely studied for electrochemical CO₂ reduction to CO. However, the correlation between the physicochemical properties of N-doped carbon catalysts and their electrocatalytic performance for the CO₂RR is still unclear. Herein, a series of N-doped biochar catalysts with different physicochemical properties were synthesized by tuning the carbonization temperature and N-doping level and used for the CO₂RR to analyze the structure-performance relationship. The prepared catalysts exhibited massive differences in maximum faradaic efficiency to CO from 26.8 to 94.9% at around −0.8 to −0.9 V vs RHE. In addition, we find that simply increasing the specific surface area and N-doping level of the catalysts does not effectively improve the catalytic performance for the CO₂RR. A multivariate correlation analysis reveals a negative correlation between the N-doping content and the electrochemical performance. The porous structural properties exhibit a positive correlation to the FE_CO but almost no correlation to j_CO. Interestingly, improving the degree of graphitization, surface hydrophobicity, the abundance of defects, and optimizing the porosity of the N-doped biochar catalyst can efficiently enhance the catalytic performance for the CO₂RR. We conclude that comprehensively analyzing the synergistic effect of various properties of N-doped biochar is critical to reveal structure-activity relationships.

The oil palm industry has been under public scrutiny during the last decades due to environmental and social issues related to its practices. Oil palm (Elaeis guineensis Jacq.) trunks (OPTs) are of special interest as they are left idle in the field after the replanting process which is performed every 25 years. This common practice results in harvesting challenges, phytosanitary risks, and a loss of bioenergy potential. Due to their high moisture content and fibrous nature, OPTs present a problem for traditional conversion processes that require a dry and homogeneous material. This study evaluates the feasibility of converting OPTs into a bio-crude oil and biochar to increase the sustainability of the oil palm sector. To date, research efforts have primarily focused on hydrothermal liquefaction (HTL) of OPT without catalysts, resulting in a limited understanding of the potential of OPTs. Thus, the main novelty of this work is the evaluation of the effects of catalyst dosage (0–5 wt%) on the bio-oil yield, reaction temperature (260–300^∘C), and residence time (15–60 min) using a half-fraction experimental design methodology. For this, OPTs extracted from two plantations in Guatemala were used. The maximum bio-oil yield (26.77 ± 3.60 wt%) was found at 260^∘C for 15 min and 5 wt% catalyst with a high heating value (HHV) of 19.29 ± 1.33 MJ kg⁻¹. Nonetheless, the bio-oils produced without a catalyst at 300^∘C and 15 min have higher HHV (27.63 ± 1.35 MJ kg⁻¹) and are similar to Diesel fuel based on their H/C and O/C ratio. These results indicate that there is a potential trade-off between the bio-crude oil mass yield and HHV when using the catalyst.

N-doped carbon materials can be efficient and cost-effective catalysts for the electrochemical CO₂ reduction reaction (CO₂RR). Activators are often used in the synthesis process to increase the specific surface area and porosity of these carbon materials. However, owing to the diversity of activators and the differences in physicochemical properties that these activators induce, the influence of activators used for the synthesis of N-doped carbon catalysts on their electrochemical performance is unclear. In this study, a series of bagasse-derived N-doped carbon catalysts is prepared with the assistance of different activators to understand the correlation between activators, physicochemical properties, and electrocatalytic performance for the CO₂RR. The properties of N-doped carbon catalysts, such as N-doping content, microstructure, and degree of graphitization, are found to be highly dependent on the type of activator applied in the synthesis procedure. Moreover, the overall CO₂RR performance of the synthesized electrocatalysts is not determined only by the N-doping level and the configuration of the N-dopant, but rather by the overall surface chemistry, where the porosity and the degree of graphitization are jointly responsible for significant differences in CO₂RR performance.