Power-to-X (P2X) converts excess renewable energy into hydrogen and then renewable fuels like methanol, addressing hydrogen storage costs. Methanol synthesis uses catalysts such as Cu/ZnO/Al2O3, with performance influenced by pressure, hydrogen-to-carbon ratio, and temperature. Therefore, accurate modelling, using kinetics like Graaf et al. Langmuir-Hinshelwood-Hougen-Watson type model, material, momentum, and energy balances within the reactor, is essential. Based on these models, the performance of methanol synthesis was analysed. Specifically, analysis of bed porosity (epsilon pm = 0.1 - 0.5), stoichiometric ratio of hydrogen-to-carbon (SH = 1 - 3), Gas-Hourly-Space-Velocity (GHSV = 1400 - 8400 h- 1), temperature (200 - 280 degrees C) and pressure (20 - 60 bar) on the methanol synthesis performance for both dynamic and steady-state conditions was performed via COMSOL Multiphysics. This was followed by a thermostatic regulation of the reaction temperature between 239 - 241 degrees C, model application to simulate an in-house laboratory digital twin Micromeritics reactor, in addition to an industrial-sized reactor.

The transition to renewable energy is driving sustainable chemical production methods, with power-to-X (P2X) technologies offering promising solutions. This study presents a comparative life cycle assessment (LCA) of adiabatic and isothermal sorption-enhanced methanol synthesis (SEMS) processes, across eight scenarios, varying in reactor configurations, electrolysis power sources, and methanol synthesis electricity use. Seven impact categories are evaluated, with results showing that all SEMS scenarios achieve significantly lower global warming potential (GWP) than the reference case of methanol production via steam reforming of natural gas. Adiabatic SEMS scenarios range from 71.7 to 519.7 kg CO2 eq. per t MeOH, while isothermal SEMS scenarios range from 72 to 529 kg CO2 eq. per t MeOH, significantly outperforming the conventional methanol production process (980 kg CO2 eq. per t MeOH). These results indicate that SEMS-based methanol achieves 71.6-96.1% GHG savings, meeting the Renewable Energy Directive (RED II) 70% threshold for sustainability. The impacts of both corresponding adiabatic and isothermal SEMS scenarios are similar, with only slight variations. Furthermore, 61% of the impact categories analyzed across all SEMS scenarios exhibit lower impacts than the reference case. Uncertainty and sensitivity analyses revealed that electricity demand associated with water electrolysis was the dominant factor affecting system-level environmental performance of the SEM process. These findings highlight SEMS, when powered by renewable energy, as one possible solution within the P2X framework for sustainable methanol production. This study also emphasizes the critical role of integrating renewable energy into chemical processes to support industrial decarbonization and to accelerate the energy transition.

Methanol is a promising fuel and important intermediate chemical in the transformation of renewable power to chemical products since it can be directly synthesized from captured CO2 and electrolytic H2. However, the intermittency of renewable power generation poses challenges to green methanol production process design and operation, necessitating high operational flexibility to facilitate coupling with intermittent renewable power. In this study, a green crude methanol (a mixture of methanol and water from methanol synthesis) production process was dynamically modeled. The results show that the minimum load of the model is 20 %, with maximum allowable ramping rates of 3.25 %/minute for ramp-down and 2.10 %/minute for ramp-up between full and minimum load. The introduction of a standby mode, in which a make-up H2 stream is supplied when electrolytic H2 is unavailable, allows continuous operation of the process at the minimum load. With the constructed control structure, the model demonstrates that the process can effectively handle continuous variations of electrolytic H2 input.

The chemical industry needs new methods for sourcing carbon-containing feedstocks from renewable sources to decrease CO2 emissions and reduce reliance on fossil fuels. Ethylene, a crucial base chemical used for making polymers and ethylene oxide, is primarily produced through steam cracking of fossil feedstocks. However, an evolving technology is the electrochemical reduction of CO2 or CO to produce ethylene. The study assesses the environmental, economic and energetic performance of a new biomass-based process that produces ethylene based on the electrochemical reduction of CO. The results are based on mass and energy balances from process simulation. The CO is produced by either gasification of biomass or combustion of biomass with CO2 capture and CO2 electrolysis. Besides ethylene, the process produces acetic acid, ethanol, oxygen and hydrogen as by-products which are purified and sold. The annual output varies between 36 and 68 kt ethylene with a biomass input of 157 kt. The levelized cost of ethylene ranges from 3,920 to 7,163 €/t with the gasification routes being the most cost-effective. The ethylene price is heavily dependent on electricity price, current density, operating voltage, and by-product prices. The carbon efficiency of the gasification-based routes is lower (64%) than the combustion-based routes (85%–86%). However, the energy efficiency is higher for the gasification-based routes (42%) compared to the combustion-based routes (28%). Conversion of ethanol to ethylene increases the ethylene yield with minimal impacts on the ethylene price. In terms of CO2 emissions, the gasification-based routes show lower emissions. Scenarios using wind power show a significant emission reduction potential compared to fossil products.

Plastics are essential materials for modern societies, but their production contributes to significant environmental is-sues. Power-to-X processes could produce plastics from captured CO2 and hydrogen with renewable electricity, but these technologies may also face challenges from environmental perspective. This paper focuses on environmental sus-tainability assessment of CO2-based low-density polyethylene (LDPE) compared to bio-based LDPE. Life cycle assess-ment has been applied to study climate impacts and land use related biodiversity impacts of different plastic production scenarios. According to the climate impact results, the carbon footprint of the produced plastic can be neg-ative if the energy used is from wind, solar, or bioenergy and the carbon captured within the plastic is considered. In terms of biodiversity, land-use related biodiversity impacts seem to be lower from CO2-based polyethylene compared to sugarcane-based polyethylene. Forest biomass use for heat production in CO2-based polyethylene poses a risk to sig-nificantly increase biodiversity impacts. Taken together, these results suggest that CO2-based LDPE produced with re-newable electricity could reduce biodiversity impacts over 96 % while carbon footprint seems to be 6.5 % higher when compared to sugarcane-based polyethylene.

Sorption enhanced synthesis has been previously shown to improve carbon dioxide hydrogenation to methanol by mitigating the thermodynamic limitations. This work investigates the efficiency of methanol synthesis via sorption enhanced carbon dioxide hydrogenation focusing on determining the optimal process parameters. The study is based upon a fully dynamic experimentally validated model of the process which is extended to account for adsorbent regeneration, downstream product separation and recirculation of the unreacted gases. An additional reactor configuration with a guard adsorbent layer is proposed for production of high purity methanol product. A multi-objective optimization study is performed to investigate the tradeoff between methanol production rate and product purity. The obtained results indicate that for synthesis of high purity methanol product, the optimal values of reactor temperature and catalyst mass fraction in the bed are 215 degrees C/0.65 and 235 degrees C/0.50 for the adiabatic and quasi isothermal reactors, respectively.(c) 2022 The Author(s). Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

A sorption-enhanced process for hydrogenation of CO2 to methanol was designed and investigated by mathematical modelling and techno-economic analysis. The modelling methodology combined dynamic modelling of the cyclic reactor operation with pseudo-steady state modelling of the overall process. With continuous adsorption of water in the sorption-enhanced process, highly pure methanol (> 99%) was produced without downstream distillation. The dynamic reactor cycle was designed and optimized to maximize the methanol production rate. The cycle and the process were modelled in two reactor configurations: adiabatic and isothermal. Under the default cost assumptions for the raw materials (CO2 50 (sic)/t, hydrogen 3000 (sic)/t) the adiabatic configuration was found more competitive in terms of the overall methanol production cost, at 1085 (sic)/t compared to 1255 (sic)/t for the isothermal case. The cost estimate for the adiabatic case was found comparable to a reference process representing conventional CO2 hydrogenation to methanol (1089 (sic)/t). In addition to the methanol process, the developed modeling method has potential in the design of other sorption-enhanced processes.

Membrane-based CO 2 capture processes can be implemented via two distinct approaches: employing membrane contactors to intensify absorption-based postcombustion capture or using gas separation membranes to selectively separate CO 2 from gaseous streams such as flue gases. The background theory of membrane contactors and mass transfer models is detailed in this chapter, including resistances-in-series, mass transfer resistance factors, and the effect of membrane wetting on mass transfer. In the context of CO 2 separation, absorbent solutions, membrane materials, and process design are also discussed. Membrane compatibility with CO 2 absorbing solutions is a significant challenge for membrane contactors. A proper selection of membrane-solvent combinations is critical to avoid membrane wetting and degradation during long-term operation. Furthermore, the performance of existing polymeric gas separation membranes is limited by a compromise between CO 2 permeability and selectivity. As a result, effective CO 2 capture necessitates complex multistage processes with a large membrane surface area. Other types of membranes, in addition to polymeric membranes, have shown promising performance but have yet to be demonstrated in practical installations. Both approaches have been tested on a small scale, and feasibility studies have confirmed their potential competitiveness. However, these technologies have yet to be widely deployed and commercialized. This is probably partly explained by nontechnological barriers, similar to conventional CO 2 capture processes.

In this work, a modular millireactor (MMR) is designed and modeled using the computational fluid dynamics (CFD) tool OpenFOAM. First, the method is validated against a conventional packed bed reactor (PBR) model (1D) with Aspen Plus. Next, the method is applied to study the effects of pressure (2-6 MPa) and temperature (483-533 K) on the performance of the MMR. Conjugate heat transfer (CHT) CFD results for the MMR are compared against a corresponding PBR at isothermal conditions. For the MMR, the methanol yield is shown to vary between 9-23 % within the studied parameter range. Overall, the MMR outperforms the PBR at conditions studied in this work. The maximum difference in methanol yield between MMR and the PBR is noted to be a factor of 1.71 at 533 K and 5 MPa. Such a large discrepancy advocates the usage of 3D CHT/CFD.(c) 2022 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license (http:// creativecommons.org/licenses/by/4.0/).

CO2absorption into aqueous potassium glycinate in a polypropylene membrane contactor was modelled using two alternative models: a 1D model and a 1D-2D model considering axial diffusion in the liquid phase. Models were fitted to experimental data using various fitting parameters, which were compared. Experiments were carried out under industrially relevant conditions characterized by CO2-loaded absorbent entering the contactor and high degree of reactant conversion over the contactor. The experiments and models were developed to specifically investigate the effect of changes in solution CO2loading at contactor inlet. This is a key issue rarely reported in the literature, especially for amino acid salt solutions. Unexpectedly, the 1D model was found to explain the experimental results more accurately compared to the more complex 1D-2D model. This was the case for the base models, using only the membrane mass transfer coefficient as a fitting parameter, and the final models introducing secondary fitting parameters. The 1D model was found to show the best experimental fit following fitting of the equilibrium constant used in prediction of the enhancement factor. The 1D-2D model showed the best fit following correction of potassium glycinate diffusivity as a function of solution CO2loading. The 1D approach was found to result in a computationally effective model with good fit to the present experimental data. This model provides a good basis for further development and could be considered for use in contactor design and optimization studies. It is suggested that various model simplifications led to inability of the 1D-2D model to accurately predict the experimental results.

In order to limit climate change, fast greenhouse gas reductions are required already before 2030. Ethanol commonly produced by fermentation of sugars derived either from starch-based raw material such as corn, or lignocellulosic biomass is an established fuel decarbonizing the transport sector. We present a novel selective and flexible process concept for the production of ethanol with electricity and lignocellulosic biomass as main inputs. The process consists of several consecutive steps. First synthesis gas from gasification of biomass is purified by filtration and reforming and fed to methanol synthesis. The produced methanol is fed to acetic acid synthesis, together with a carbon monoxide-rich stream separated from the synthesis gas by membranes. Finally, acetic acid is hydrogenated to yield ethanol. With the exception of acetic acid hydrogenation, the overall process consists of technically mature subprocesses. Each process step was modelled in Aspen Plus to generate the mass and energy balances for the overall process. Additionally, the CO 2 emissions and economic feasibility were assessed. Three separate cases were investigated. In the first two cases, the syngas carbon (CO and CO 2 ) was split between methanol and acetic acid synthesis. The cases included either allothermal (case A) or electrically heated reforming (case B). In case C, maximum amount of CO was sent to acetic acid synthesis to maximize the acetic acid output, requiring a small additional carbon dioxide input to methanol synthesis. In all cases, additional hydrogen to methanol synthesis was provided by water electrolysis. Each case was designed at biomass input of 27.9 MW and the electrolyzer electricity requirement between 36 and 43.5 MW, depending on the case. The overall energy efficiency was calculated at 53–57%, and carbon efficiencies were above 90%. The lowest levelized cost of ethanol was 0.65 €/l, at biomass cost of 20 €/MWh and electricity cost of 45 €/MWh and production scale of approximately 42 kt ethanol per year. The levelized cost is competitive with the current biological route for lignocellulosic ethanol production. The ethanol price is very sensitive to the electricity cost, varying from 0.56 to 0.74 €/l at ±30% variation in electricity cost.

This research work presents the integration of polypropylene hollow fiber membrane contactor-based CO2 absorption unit using aqueous sodium hydroxide (NaOH) as the absorbent solution, and precipitation of highquality calcium carbonate by addition of calcium chloride. The integrated crystallization process bypasses the need for cost-intensive energy regeneration of the absorbent solution. Given the lifetime of high added value precipitated calcium carbonate, the proposed approach for integrating solid particle formation and a carbon dioxide mitigation technique can be considered as a potential post-combustion technology for carbon capture, utilization and sequestration (CCUS). The overall CO2 mass transfer coefficient in the membrane contactor and subsequent crystallization process was investigated by conducting the experiments at different operating conditions. For a maximum hydroxide concentration of 5.01 mol L- 1, an overall mass transfer coefficient of 2.25 & sdot;10-4 m s- 1 and CO2 flux of 2.45 & sdot; 10-4 mol m-2 s- 1 were obtained for a 0.5 L min- 1 of gas flow rate. The proposed liquid-liquid crystallization process produces a narrow size distribution of micron-sized calcium carbonate with a mean diameter of 3-8 & micro;m that can be used in the paper, coatings, food and biomedical industries.

The ambitious CO2 emission reduction targets for the transport sector set in the Paris Climate Agreement require low-carbon energy solutions that can be commissioned rapidly. The production of gasoline, kerosene, and diesel from renewable methanol using methanol-to-olefins (MTO) and Mobil’s Olefins to Gasoline and Distillate (MOGD) syntheses was investigated in this study via process simulation and economic analysis. The current work presents a process simulation model comprising liquid fuel production and heat integration. According to the economic analysis, the total cost of production was found to be 3409 €/tfuels (273 €/MWhLHV), corresponding to a renewable methanol price of 963 €/t (174 €/MWhLHV). The calculated fuel price is considerably higher than the current cost of fossil fuels and biofuel blending components. The price of renewable methanol, which is largely dictated by the cost of electrolytic hydrogen and renewable electricity, was found to be the most significant factor affecting the profitability of the MTO-MOGD plant. To reduce the price of renewable fuels and make them economically viable, it is recommended that the EU’s sustainable transport policies are enacted to allow flexible and practical solutions to reduce transport-related emissions within the member states.

Synthesis of methanol from carbon dioxide is affected by thermodynamic limitations and excessive formation of water that might have a detrimental impact on methanol production rate and catalytic activity. To overcome these effects, sorption enhanced (SE) carbon dioxide hydrogenation to methanol with selective in-situ adsorption of water is investigated both experimentally and via process simulation. A significant improvement in the process performance due to the thermodynamic equilibrium shift, achieved as a result of selective water removal, is reported. Depending on the process conditions, during the SE phase, outlet methanol concentration is ca. 150-290% of the steady state values recorded after the adsorbent saturation. For carbon monoxide this factor is ca. 220-510%. The effect of process parameters such as reactor pressure, temperature, overall gas flowrate and catalyst-to-adsorbent ratio is thoroughly addressed. Reactor pressure is demonstrated to affect methanol production during the SE phase to the greatest extent. Particularly, increasing reactor pressure above 40 bar enhances methanol formation during the SE phase at the cost of decreasing carbon monoxide production, thus improving process selectivity. Although increasing reactor temperature above 250 degrees C favors carbon monoxide formation, it results in suppressed methanol production and considerable shortening of the SE phase duration. Because of the RWGS reaction fast kinetics, the variations in gas hourly space velocity and amount of the adsorbent loaded in the reactor affect production of methanol more than carbon monoxide. The parameters describing kinetics of the involved reactions and water adsorption are adjusted based on the acquired experimental data.

In the present study, a crystallization monitoring unit consisting of an in-situ digital microscope camera and real-time image analysis is utilized for monitoring and control of a micron-sized, liquid-liquid crystallization of calcium carbonate. The crystallization process is integrated with a membrane contactor-based carbon dioxide capture process to demonstrate a sustainable CO2-to-chemical unit operation. The measurement probe transilluminates the crystal suspension and provides a live view from the crystallizer. In a series of open-loop experiments, the effects of several operating conditions such as feed flow rate and volumetric power on crystal size and particle count are investigated. For comparison purposes, solid product crystals are assessed with an offline laser diffraction technique. In the closed-loop experiments, the controlled variable is average particle diameter, and the manipulated variable is mixing intensity. The implemented set-point tracking PI controller generates actuating signals based on real-time image analysis measurement of the crystal size. Experimental results demonstrate a practical approach for measuring micron-sized particle suspensions, which is a challenge for particles with a mean diameter smaller than 15-20 mu m, provides insights into the mixing intensity-based particle size controllability in fast-reaction precipitation systems and offers a framework to implement a direct design feedback control policy. (c) 2021 The Author(s). Published by Elsevier B.V. on behalf of Institution of Chemical Engineers. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

Industrial production of many chemicals and chemical products depends primarily on fossil resources. Lignocellulosic biomass, which is the most abundant and sustainable biomass on earth, is a potential renewable resource for the production of a wide range of products (e.g., chemicals, fuels, materials) that could be used to replace products currently produced by the petrochemical industry. Large amounts of lignocellulosic materials are generated as waste by-products of various industrial and agro-based processes. Efficient valorization of such materials would lead to lower greenhouse gas emissions and waste volumes and would bring considerable economic benefits. Various approaches are available for the conversion of lignocellulosic materials into high-value products. In this work, partial wet oxidation (WO) by molecular oxygen is proposed as a potential industrial process for the production of chemicals, particularly low-molecular carboxylic acids, from lignocellulosic biomass waste. The study investigated the catalytic potential of two homogenous heteropoly acid catalysts for the partial WO of lignin based on their effectiveness as regards carboxylic acid yield and lignin conversion. Recovery of the carboxylic acids produced was studied using solvent extraction. Additionally, an enzyme-mediated approach for coproduction of cellulose nanocrystals (CNCs) and fermentable sugars is proposed. In this work, alkaline lignin and cellulose (wood pulp and filter paper) were used as a model of lignocellulosic feed materials for the partial WO and enzymatic hydrolysis experiments, respectively. Formic acid, acetic acid, and succinic acids are among the major products produced by the partial WO of lignin in alkaline and neutral aqueous solutions. In this work, optimum reaction conditions to obtain the maximum yield of products were investigated. An important finding is that in an alkaline medium, the overall yield of products from partial WO decreased at higher lignin concentration. It was found that this reduction could be attributed to repolymerization/condensation side reactions of lignin fragments that compete with oxidative lignin depolymerization reactions. Of the two catalysts studied, the phosphomolybdate catalyst (H3PMo12O4) provided the best results in terms of both the lignin conversion rate and the total yield of carboxylic acids. Although both heteropolyacids showed different catalytic behaviors, the reaction pathway of the lignin oxidation seems to be determined by the type of addenda atom in the HPA catalyst, with Mo favoring a selective oxidation reaction. In addition, it was found that recovery of the two catalysts could be easily achieved, which would make partial lignin WO an environmentally friendly and potentially economically viable process. In the solvent extraction studies, various types of extractants were evaluated. Different factors were considered in the solvent selection process. Of the tested solvents, Alamine 336 and 2-methyltetrahydrofuran (2-MTHF) solvents showed the most promising results and both solvents can be used to recover the studied components from aqueous solutions. It was found that the use of toluene as a diluent for Alamine 336 prevented the formation of a third intermediate liquid phase. The impacts of introducing a cellulase-cocktail treatment system before an acid hydrolysis process for isolating CNCs from a cellulose-based model feedstock were investigated. It was found that for a given weight of feedstock, the enzyme-mediated approach improved CNC yield (8–86 wt.%) from acid hydrolysis. Another important finding was that significant recovery of fermentable sugars (20–60 wt.%), which would otherwise have entered the acid waste stream, is achievable with this method. These findings indicate the potential of enzymatically mediated acid hydrolysis processes for the coproduction of fermentable sugars, thus providing additional revenue, and for improvement of the acid hydrolysis efficiency, thus offsetting CNC production costs.

Mass transfer performance of a polypropylene hollow-fiber membrane contactor as part of a continuously operated CO2 capture unit with amino acid salt (potassium glycinate) absorbent and vacuum solvent regeneration was studied. The effects of key operating parameters on the absorption mass transfer characteristics were explored. Without vacuum stripping, absorption rate was found to be limited by low CO2 desorption efficiency from the loaded absorbent solution in the stripping unit, resulting in high solvent CO2 loadings and limited chemical absorption rates. Introduction of vacuum stripping greatly improved desorption performance, resulting in improved steady-state absorption performance. The overall mass transfer coefficient increased at higher stripping temperatures and lower vacuum pressures in the range of 60-80 degrees C and 300-800 mbar (abs). The overall mass transfer coefficient increased with increasing liquid flow rate, and the highest value reached was 1.8.10(-4) m s(-1). The individual mass transfer coefficients in absorption were calculated based on mass transfer correlations and experimental data, including estimation of the enhancement factor for chemical absorption. The overall mass transfer resistance was found to be dominated by the liquid-side resistance, at almost 90 % of the total resistance. The estimated membrane mass transfer coefficient was low compared to a theoretical value assuming non-wetted operation, suggesting potential partial wetting of the membrane. Stable performance of the unit and the membrane contactor was demonstrated during a stability test with over 30 h of operation.

Applicability of Raman spectroscopy for time-resolved gas composition monitoring during direct methanol synthesisviacarbon dioxide hydrogenation was investigated. A series of methanol synthesis experiments with varied reactor conditions was conducted and the reactor outlet stream was analyzed with in-line gas Raman spectroscopy. Concentrations of H-2, CO(2)and CO were determined directly from the acquired spectral data. For evaluation of methanol and water content a data reconciliation algorithm was developed. The algorithm involves estimation of the occurring chemical reactions' extents by iterative minimization of the difference between concentration values acquired from the experimental data and concentration values computed based on the mass conservation principle. The obtained experimental concentrations were compared and validated against the results of the reactor mathematical modeling, which is based upon a well-established kinetic interpretation of the process. The findings indicate good repeatability and accuracy of the developed gas analysis system, which together with the advantageous temporal resolution of the method, make Raman spectroscopy a promising technique for fast response monitoring of the process.