CO2 Conversion Processes Research Articles

Performance Intensification of CO 2 Methanation by Co-Feeding Oxygen Over Various Ru-Based Catalysts

Auto-methanation (AM), which autonomously progresses at room temperature (approximately 25 °C), is an effective reaction for converting CO2 to CH4 and can thus reduce the processing costs. In this study, the AM reaction over various Ru-based catalysts with different support materials positively proceeded by selecting reaction conditions such as the O2 concentration and gas flow rate. The progression of AM was the best over the Ru/CeO2 catalyst, followed by the Ru/ZrO2 and Ru/Al2O3 catalysts. The progression of AM over the Ru/SiO2 catalyst was slow. The rapid progress of AM over the Ru/CeO2 catalyst was attributed to the presence of oxygen defects on the CeO2 support that accelerates the hydrogen–oxygen combustion as well as to the differences in the CO2 and H2O adsorption characteristics between the CeO2 support and other supports. Even when the Ru-based catalyst underwent H2 reduction at low temperature, AM could proceed over each catalyst. The Ru/CeO2 catalyst was advantageous over other catalysts because AM proceeds only when H2 gas is supplied at room temperature without external heating. X-ray photoelectron spectroscopy indicated that the Ru species on the Ru/CeO2 catalyst are in a metallic state owing to H2 reduction at room temperature, which is associated with AM progression. Moreover, AM proceeded via H2 reduction at 75 °C over the Ru/ZrO2 catalyst and at 150 °C over the Ru/Al2O3 catalyst. The progression of methanation through such low-temperature reduction can strengthen the CO2 conversion process.

Band Position-independent Piezo-electrocatalysis for Ultrahigh CO2 Conversion.

Piezo-electrocatalysis as an emerging mechano-to-chemistry energy conversion technique opens multiple innovative opportunities and draws great interest over the past decade. However, the two potential mechanisms in piezo-electrocatalysis, i.e., screening charge effect and energy band theory, generally coexist in the most piezoelectrics, making the essential mechanism remain controversial. Here, for the first time, we distinguish the two mechanisms in piezo-electrocatalytic CO2 reduction reaction (PECRR) through a narrow-bandgap piezo-electrocatalyst strategy using MoS2 nanoflakes as demo. With conduction band of -0.12eV, the MoS2 nanoflakes are unsatisfied for CO2 -to-CO redox potential of -0.53eV, yet they achieve an ultrahigh CO yield of ∼ 543.1 μmol·g-1 ·h-1 in PECRR. Potential band position shifts under vibration are still unsatisfied with CO2 -to-CO potential verified by a combination analysis of theoretical investigation and piezo-photocatalytic experiment, further indicating that the mechanism of piezo-electrocatalysis is independent of band position. Besides, MoS2 nanoflakes exhibit unexpected intense "breathing" effect under vibration and enable the naked-eye-visible inhalation of CO2 gas, independently achieving the complete carbon cycle chain from CO2 capture to conversion. The CO2 inhalation and conversion processes in PECRR are revealed by a self-designed in situ reaction cell. This work brings new insights into the essential mechanism and surface reaction evolution of piezo-electrocatalysis. This article is protected by copyright. All rights reserved.

Direct-air capture conversion of CO2 in fixed-bed microreactors with immobilized formate dehydrogenase and glucose dehydrogenase: Concept feasibility

Conversion of CO2 from the atmosphere (via direct air capture) into formate via an enzyme-mediated CO2 reduction process, coupled with in situ regeneration of NADH, in fixed-bed microreactors (FBMRs) with co-immobilized oxygen-tolerant formate dehydrogenase (FDH) from Cupriavidus necator and glucose dehydrogenase (GDH) was proposed for the first time. Intensified CO2 conversion process was explored at different operating conditions, FDH and GDH loadings, NADH and glucose concentrations via a 3D model describing the two-phase flow, mass transport in two fluid phases, and diffusion-reactions in enzymatic layer. Enzymatic reduction of CO2 in FBMRs, with an appropriate FDH loading and an efficient glucose/GDH NADH regeneration system (with appropriate glucose and GDH loadings) that suppresses formate oxidation, allows higher CO2 conversions due to enhanced interphase mass transfer and gas-liquid interfacial area. FBMRs need to be designed and operated under appropriate conditions to ensure that the benefit generated by the high CO2 reduction rate outweighs the cost of pressure drop and the formate needs be removed from reaction system to maintain a concentration that ensures no formate inhibition for CO2 reduction reaction. FBMRs perform much better in summer, with lower pressure drop. Overall, FBMRs with immobilized FDH/GDH enzymes, integrated in modular units, are attractive for green CO2 conversion.

Study on the conversion mechanism of CO2 to O2 in pulse voltage dielectric barrier discharge at Martian pressure

CO2 constitutes around 95 % of the atmosphere on Mars, and its in-situ utilization is of great value. O2 is a significant target product transformed from CO2 that can support both human respiration and fuel combustion, its conversion mechanism remains unclear. In this study, using a dielectric barrier discharge (DBD) with parallel plate electrodes, simulation and experimental results are combined to discuss the discharge characteristics and CO2 conversion process, under Mars conditions. The DBD was driven by a repetitive frequency microsecond pulse voltage. According to the discharge current, the discharge process can be split into four stages, namely the positive (negative) discharge stage and the positive (negative) discharge extinguishing stage. With a contribution up to 98 % and primarily taking place in the positive discharge extinguishing stage, the recombination decomposition reaction of electron and CO+2 is the primary pathway of O2 synthesis. At the position near the edge of the cathode potential drop zone, electron impact ionization of CO2 ground state molecules dominates the formation of CO+2. Under the range of pulse parameters considered in this paper, increasing the pulse width can lengthen the time of recombination decomposition reaction of electron and CO+2 in positive discharge extinguishing stage, which is favorable for the formation of O2. Likewise, reducing the pulse's rising edge can increase the discharge intensity and CO+2 density, which is also favorable to O2 production.

Opportunities to reduce energy consumption and CO₂ emissions from ironmaking blast furnace using CO₂ electrolysis to CO for carbon recycling

The blast furnace (BF) ironmaking is an energy-intensive process and the largest source of CO₂ emissions in an integrated steel mill. We evaluated the potential energy, fresh coke savings and associated reductions in CO₂ emissions for a BF operation if some CO₂ in the BF gases were converted to CO using an electrochemical CO₂ conversion process and that CO was recycled to the BF. As an added benefit, the electrochemical process produces H₂ and O₂, which helps iron ores reduction and oxygen enrichment. This paper presents a mathematical model of BF that integrates CO₂ capture, CO₂ electrolysis, and gas injection. Our results show that integrating a CO₂ to CO electrolysis process in a traditional ironmaking plant could reduce coke consumption from 386 kg/tHM to 260 kg/tHM at a 9% oxygen enrichment rate. A maximum 40% reduction in the CO₂ emissions per ton of hot metal can be reached. However, the total energy consumption of the process increases when the CO₂ electrolysis unit is included. Consequently, realising these potential CO₂ savings requires the availability of zero-carbon electricity from renewable sources. Improvements in the selectivity and efficiency of the CO₂ electrolysis in the future may enhance the overall economics and efficiency of this process.

Recent progress in reductive carboxylation of C-O bonds with CO2.

Transformation of carbon dioxide (CO2) into value-added organic compounds has attracted increasing interest of scientific community in the last few decades, not only because CO2 is the primary greenhouse gas that drives global climate change and ocean acidification, but also because it has been regarded as a plentiful, nontoxic, nonflammable and renewable one-carbon (C1) feedstock. Among the various CO2-conversion processes, carboxylation reactions represent one of the most beautiful and attractive research topics in the field, since it offers the possibility for the construction of synthetically and biologically important carboxylic acids from various easily accessible (pseudo)halides, organosilicon, and organoboron compounds. The purpose of this review is to summarize the available literature on deoxygenative carboxylation of alcohols and their derivatives utilizing CO2 as a carboxylative reagent. Depending on the C-O compounds employed, the paper is divided into five major sections. The direct dehydroxylative carboxylation of free alcohols is discussed first. This is followed by reductive carboxylation of carboxylates, triflates, and tosylates. In the final section, the only reported example on catalytic carboxylation of fluorosulfates will be covered. Notably, special attention has been paid on the mechanistic aspects of the reactions that may provide new insights into catalyst improvement and development, which currently mainly relies on the use of transition metal catalysts.

Electrification of CO2 conversion into chemicals and fuels: Gaps and opportunities in process systems engineering

Conversion of CO2 into C1 and C2+ chemicals and fuels via electricity has emerged as an important piece in achieving a carbon-neutral economy as it allows the emitted CO2 to be recycled as a carbon source. Specifically, direct electrochemical reduction and indirect conversion via hydrogenation (with green hydrogen) have been widely studied. Yet, most of the electrochemical conversion technologies remain at low technology readiness levels (TRLs) and need further development before full-scale deployment. Process systems engineering can play a significant role through different phases of this development, particularly in the design, evaluation, and scale-up of the electrified conversion processes despite their early-stage nature. In this paper, we review the recent technological developments and process-level analyses of electrified CO2 conversion technologies. Then, we present two case studies: (i) early-stage evaluation of ten electrified conversion processes in terms of sustainability and (ii) optimal sizing of the electrified systems under the intermittency of renewable electricity. Through the literature survey and the case studies, our perspectives are shared on how the process systems engineering field can contribute in addressing the potential issues that arise in electrifying CO2 conversion processes.

Gallium Nitride‐based Materials as Promising Catalysts for CO2 Reduction: A DFT Study on the Effect of CO2 Coverage and the Incorporation of Mg Doping or Substitutional In

AbstractCatalytic CO2 conversion to fuels and chemicals is important for mitigating the climate change and reducing the dependence on fossil resources. In order to achieve this goal on a large industrial level, effective catalysts need to be developed. Among them, gallium nitride (GaN) and related Mg‐doped and In‐alloyed systems have been proven as efficient materials for the reduction of highly stable CO2 molecules. This work presents a density functional theory (DFT) investigation, performing periodic boundary condition (PBC) calculations which allow to employ a more extended surface for a detailed analysis of the CO2 coverage, and the effect of Mg doping and In alloying on the CO2 adsorption and its conversion to CO. The results show the great potential of GaN(100) surfaces to simultaneously bind and strongly activate multiple CO2 molecules, which is a crucial aspect for an efficient CO2 conversion process. Moreover, the presence of Mg‐dopant on the top layer is found to be more beneficial for the CO2 adsorption and activation with respect to both the pristine and In‐alloyed system, and this effect is further improved by the inclusion of a second impurity on the top layer. In line with the previous experimental findings, these calculations support the potential of pristine GaN(100) to catalyze the CO2‐to‐CO reduction. The results presented here offer crucial information for the development of more efficient and selective catalysts for the CO2 reduction.

Mechanistic In Situ ATR-FTIR Studies on the Adsorption and Desorption of Major Intermediates in CO2 Electrochemical Reduction on CuO Nanoparticles.

Increasing levels of carbon dioxide (CO2) from human activities is affecting the ecosystem and civilization as we know it. CO2 removal from the atmosphere and emission reduction by heavy industries through carbon capture, utilization, and storage (CCUS) technologies to store or convert CO2 to useful products or fuels is a popular approach to meet net zero targets by 2050. One promising process of CO2 removal and conversion is CO2 electrochemical reduction (CO2ER) using metal and metal oxide catalysts, particularly copper-based materials. However, the current limitations of CO2ER stem from the low product selectivity of copper electrocatalysts due to existing knowledge gaps of the reaction mechanisms using surfaces that normally have native oxide layers. Here, we report systematic control studies of the surface interactions of major intermediates in CO2ER, formate, bicarbonate, and acetate, with CuO nanoparticles in situ and in real time using attenuated total reflection Fourier-transform infrared spectroscopy (ATR-FTIR). Spectra were collected as a function of concentration, pH, and time in the dark and the in absence of added electrolytes. Isotopic exchange experiments were also performed to elucidate the type of surface complexes from H/D exchange. Our results show that the organics and bicarbonate form mostly outer-sphere complexes mediated by hydrogen bonding with CuO nanoparticles with Gibbs free energy of adsorption of about -25 kJ mol-1. The desorption kinetics of the surface species indicated relatively fast and slow regions reflective of the heterogeneity of sites that affect the strength of hydrogen bonding. These results suggest that hydrogen bonding, whether intermolecular or with surface sites on CuO nanoparticles, might be playing a more important role in the CO2ER reaction mechanism than previously thought, contributing to the lack of product selectivity.

Recent Progress in Integrated CO2 Capture and Conversion Process Using Dual Function Materials: A State-of-the-Art Review

CO2, despite its role as the primary greenhouse gas, is well-accepted as the most affordable and abundant nontoxic C1 source. Integrated CO2 capture and conversion (ICCC) is an emerging and promising process capable of reducing CO2 emissions and in-situ producing value-added products such as CH4 and syngas. This article reviews the recent research progress on the ICCC process, with an emphasis on the development of dual function materials (DFMs). The ICCC process with the combination of different CO2 catalytic conversions is first discussed from a thermodynamic point of view. The influence of operation parameters on the performance of DFMs is also summarized in detail. Then, the development of DFMs categorized by the catalytic component (i.e., Ni, Ru, etc.) is reviewed, including their performance and potential reaction mechanisms. Finally, the challenges and prospects of the ICCC process are highlighted.

Design of Full-Temperature-Range RWGS Catalysts: Impact of Alkali Promoters on Ni/CeO2.

Reverse water gas shift (RWGS) competes with methanation as a direct pathway in the CO2 recycling route, with methanation being a dominant process in the low-temperature window and RWGS at higher temperatures. This work showcases the design of multi-component catalysts for a full-temperature-range RWGS behavior by suppressing the methanation reaction at low temperatures. The addition of alkali promoters (Na, K, and Cs) to the reference Ni/CeO2 catalyst allows identifying a clear trend in RWGS activation promotion in both low- and high-temperature ranges. Our characterization data evidence changes in the electronic, structural, and textural properties of the reference catalyst when promoted with selected dopants. Such modifications are crucial to displaying an advanced RWGS performance. Among the studied promoters, Cs leads to a more substantial impact on the catalytic activity. Beyond the improved CO selectivity, our best performing catalyst maintains high conversion levels for long-term runs in cyclable temperature ranges, showcasing the versatility of this catalyst for different operating conditions. All in all, this work provides an illustrative example of the impact of promoters on fine-tuning the selectivity of a CO2 conversion process, opening new opportunities for CO2 utilization strategies enabled by multi-component catalysts.

High-Performance Ligand-Protected Metal Nanocluster Catalysts for CO2 Conversion through the Exposure of Undercoordinated Sites

Previous experimental breakthroughs reveal the potential to create novel heterogeneous catalysts for the electroreduction of CO2 to a high-value product CO using ligand-protected Au-based nanoclusters. Since the chemical composition and geometric structures have been precisely defined, it is possible to adopt robust design guidelines for the development of practical catalysts and to fundamentally elucidate the underlying reaction mechanism. In this short review, the computational progress made to understand the experimentally observed reduction process on the following subset of materials—Au25(SR)18−, Au24Pd(SR)18, Au23(SR)16− and Au21Cd2(SR)16−—is described. A significant finding from our first-principles mechanistic studies is that CO2 conversion on the fully ligand protected nanoclusters is thermodynamically unfavorable due to the very weak binding of intermediates on the surface region. However, the reaction becomes feasible when either Au or S sites are exposed through the removal of a ligand. The results particularly point to the role of undercoordinated S sites in the creation of highly functional heterogeneous catalysts that are both active and selective for the CO2 conversion process. The incorporation of dopants could significantly influence the catalytic reactivity of the nanoclusters. As demonstrated in the case of the monopalladium substitution in Au25(SR)18−, the presence of the foreign atom leads to an enhancement of CO production selectivity due to the greater stabilization of the intermediates. With the Cd substitution doping of Au23(SR)16−, the improvement in performance is also attributed to the enhanced binding strength of the intermediates on the geometrically modified surface of the nanocluster.

Formation and polymorph transformation trends of metal carbonate in inorganic CO2 conversion process using simulated brine: Study for post-treatment of industrial brine via CO2 conversion

To improve inorganic carbon capture utilization (CCU) technology, practical solution for global warming technology, we studied the formation and transformation trends of mineral carbonation using simulated brine. we converted CO2 into inorganic compounds, metal carbonate, using CO2 saturated aqueous monoethanolamine (MEA) solution. The produced metal carbonate varied according to the simulated brine's cation component, resulting from ion interactions in the system. It turns out that the common ion effect, which occurred due to the system's ion interactions involving changes of ionic atmosphere and salinity of the system, was the main reason for the various carbonation trends. Salting- out effect dominantly occurred in the single precipitation system whereas salting-in effect occurs in multi precipitation system (system CM and system CMN). However, salting-out effect also occurred in system CMN because of Na+. Moreover, we also found that Na+, which was overlooked in prior studies regarding polymorph transformation, also affects polymorph transformation. The interactions between the abovementioned effects involved the variation in the results. This variation interrupted the wide usage of the technology. However, through the study, we suggest ambient estimation of the final product with cation component. It would help future studies and demonstration of the inorganic CCU technology using brine.

Bi4TaO8Cl/Bi heterojunction enables high-selectivity photothermal catalytic conversion of CO2-H2O flow to liquid alcohol

The high-selectivity solar-driven catalytic production of value-added fuels, such as liquid alcohol from CO2, represents an ideal energy storage and conversion pathway. However, catalysts facilitating a practical CO2 reduction approach are currently unavailable. The present work addresses this issue by developing a novel Bi4TaO8Cl/Bi heterojunction. The Bi4TaO8Cl/Bi heterojunction photocatalysts exhibit remarkable photon-to-thermal conversion and can attain a heating rate as great as 160.64 °C/s under solar irradiation with average light intensity of 365 mW/cm2, which is significantly greater than the 40.94 °C/s heating rate attained by pristine Bi4TaO8Cl photocatalysts. The proposed photothermal catalyst overcomes the high CO production obtained via conventional Bi4TaO8Cl photocatalysts, and thereby obtains high liquid alcohol (methanol and ethanol) selectivities of 92% and 76% under broadband and strictly visible light irradiation, respectively, for CO2-H2O mixtures in a flow reactor at a temperature of 200 °C. Analyses demonstrate that the superior CO2 reduction performance of the Bi4TaO8Cl/Bi heterojunction photocatalysts can be attributed to increased optical absorption, bidirectional charge transfer across the Bi4TaO8Cl/Bi interface, and the surface plasma resonance of the Bi nanoparticles. Accordingly, this work provides a novel strategy for the production of value-added liquid fuels in future CO2 conversion processes.

Recent advances in CO2 capture and reduction.

Given the continuous and excessive CO2 emission into the atmosphere from anthropomorphic activities, there is now a growing demand for negative carbon emission technologies, which requires efficient capture and conversion of CO2 to value-added chemicals. This review highlights recent advances in CO2 capture and conversion chemistry and processes. It first summarizes various adsorbent materials that have been developed for CO2 capture, including hydroxide-, amine-, and metal organic framework-based adsorbents. It then reviews recent efforts devoted to two types of CO2 conversion reaction: thermochemical CO2 hydrogenation and electrochemical CO2 reduction. While thermal hydrogenation reactions are often accomplished in the presence of H2, electrochemical reactions are realized by direct use of electricity that can be renewably generated from solar and wind power. The key to the success of these reactions is to develop efficient catalysts and to rationally engineer the catalyst-electrolyte interfaces. The review further covers recent studies in integrating CO2 capture and conversion processes so that energy efficiency for the overall CO2 capture and conversion can be optimized. Lastly, the review briefs some new approaches and future directions of coupling direct air capture and CO2 conversion technologies as solutions to negative carbon emission and energy sustainability.

Mechanistic insights into the CO2 capture and reduction on K-promoted Cu/Al2O3 by spatiotemporal operando methodologies

Integrated CO2 capture and conversion processes bring the promise of drastic abatement of CO2 emission together with its valorisation to chemical building blocks such as CH4 and CO.

Dynamic Active Sites in Bi5O7I Promoted by Surface Tensile Strain Enable Selective Visible Light CO2 Photoreduction.

Surface defects with abundant localized electrons on bismuth oxyhalide catalysts are proved to have the capability to capture and activate CO2. However, bismuth oxyhalide materials are susceptible to photocorrosion, making the surface defects easily deactivated and therefore losing their function as active sites. Construction of deactivation-resistant surface defects on catalyst is essential for stable CO2 photoreduction, but is a universal challenge. In this work, the Bi5O7I nanotubes with surface tensile strain are synthesized, which are favorable for the visible light-induced dynamic I defects generation. The CO2 molecules absorbed on I defects are constantly reduced by the incoming photogenerated electrons from I-deficient Bi5O7I nanotubes and the successive protonation of CO2 molecules is thus highly promoted, realizing the selective CO2 conversion process via the route of CO2-COOH--CO. The efficient and stable photoreduction of CO2 into CO with 100% selectivity can be achieved even under visible light (λ >420 nm) irradiation benefited from the dynamic I defects as active sites. The results presented herein demonstrate the unique action mechanism of light-induced dynamic defects during CO2 photoreduction process and provide a new strategy into rational design of deactivation-resistant catalysts for selective CO2 photoreduction.

Understanding hydroxyl radicals addition to CO[formula omitted] on [formula omitted]-Fe2O3(1 1 0) surface photocatalyst for organic compounds production

In this work, Density Functional Theory (DFT) calculations were performed to assess the photo-catalytic properties of hematite (α-Fe2O3) and the atomistic modeling of the CO2 conversion mechanism to organic molecules on such a surface. The reaction pathways for the CO2 simulated photo-transformation were modeled with the string method. The reaction mechanism obtained by DFT calculations evidenced the H2O2 molecules reduction instead of the CO2 reduction at the first step, inducing •OH radical formation. The following CO2 activation is induced by the addition of the •OH radical through one of the π∗ bonds of CO2 molecule, unlike the commonly reported CO2 reduction, resulting in the bicarbonate anion. The emergence of carbonic acid is followed by carbon reduction reactions up to methanol. According to the adsorption energies and topological analysis of the bond critical points, the intermediates exhibited closed-shell interactions with the hematite surface. Electronic structure properties were evaluated at the DFT+U＋J level. Opto-electronic parameters were also evaluated experimentally; giving validity to the results obtained by the DFT. This work also shows the first theoretical insight into the conversion of CO2 with H2O2 into H2CO3, HCOOH, CH2O and CH3OH on the hematite (1 1 0) surface. Additionally, to support the theoretical elucidation, a mixture of iron oxides (Fe2O3- FeOOH) nanoparticles were prepared in accordance to recent published results suggesting a heterogeneous catalytic process, instead a homogeneous Fenton’s method to evaluate the photocatalytic properties and the redox-potential to degrade CO2. One of the predominant phases observed in the iron oxide mixture corresponds to hematite. Moreover, the photocatalytic process of CO2 conversion with iron oxide nanoparticles was experimentally performed. The formation of methanol was evidenced via FTIR analysis.

Causation of catalytic activity of Cu-ZnO for CO2 hydrogenation to methanol

The catalytic active sites over the universal Cu-ZnO based catalysts for CO2 hydrogenation to methanol are still the subject of intense debate. Herein, unified first-principle calculations for the CO2 conversion processes over the controversial catalytic active sites, i.e., Cu crystal steps, Zn-doped Cu sites, Cu/ZnO interfaces, and the Cu and Zn closest packing crystal facets, are implemented, which is verified with the experimental facts based on support-free catalysts of porous hollow nanospheres that eliminate the interferences from the catalyst supports. We discover that the enhanced catalytic activity corresponds to the uplifted and spin-polarized density of states owing to the hybridization of Cu and Zn species, and prove that Cu/ZnO interfaces and Zn-doped Cu sites play significant roles among the catalytic active sites, and successively participate in the CO2 conversion, of which initial step should primarily be the hydrogen-free CO2 dissociation, differing from the preconceived viewpoint of hydrogen-assisted dissociation of CO2.

Screening of CO2 utilization routes from process simulation: Design, optimization, environmental and techno-economic analysis

This work aims at evaluating potential direct CO2 conversion processes through systematic screening and process simulation. Fifteen direct routes converting CO2 to carbonates or carbamates, with in situ chemical dehydration using 2-cyanopyridine (2-CP) are focused. The work covers an extensive examination (and supplement) on the physical properties, selection of promising routes, process simulation, optimization, environmental, and techno-economic evaluation. Firstly, three promising routes were selected, producing dimethyl carbonate (DMC), dipropyl carbonate (DPC), and Isopropyl N-phenylcarbamate (IPPhCM), based on three criteria: azeotropic search, product selectivity and reacting conditions. Next, the corresponding processes were simulated, optimized, heat-integrated, and systematically compared with the previously-proposed diethyl carbonate (DEC) process through environmental and economic analysis. From environmental analysis, the CO2 emission rate (CO2-e, in kg/kg-product) was 0.067, 0.088, −0.040 and −0.154 for producing DMC, DPC, IPPhCM and DEC, respectively. By reducing the excess ratio used for reaction (i.e. 2-CP/alcohol or amine/alcohol), the CO2-e improved to −0.122, −0.086, and −0.117 for producing DMC, DPC and IPPhCM, respectively. Finally, the minimum required selling prices (MRSP) at 15 % internal rate of return (IRR) were determined, with the unit price of 2-CP, 2-picolinamide (2-PA), and the reactor residence time regarded as uncertainties. The MRSPs for DMC, DPC, IPPhCM and DEC are found in the range of 1.50–4.96, 2.29–4.24, 2.07–4.06 and 1.12–2.81 (all in USD/kg), respectively. Future studies exploring the commercial availability and the regeneration of 2-CP, and the feasibility of reducing the excess ratio and the reaction residence time are considered helpful.