Formation Of CO Research Articles

Synthesis of n-Propanol from CO2 Electroreduction on Bicontinuous Cu2O/Cu Nanodomains.

n-propanol is an important pharmaceutical and pesticide intermediate. To produce n-propanol by electrochemical reduction of CO2 is a promising way, but is largely restricted by the very low selectivity and activity. How to promote the coupling of *C1 and *C2 intermediates to form the *C3 intermediate for n-propanol formation is challenging. Here, we propose the construction of bicontinuous structure of Cu2O/Cu electrocatalyst, which consists of ultra-small Cu2O nanodomains, Cu nanodomains and large amounts of grain boundaries between Cu2O and Cu nanodomains. The n-propanol current density is as high as 101.6 mA cm-2 at the applied potential of -1.1 V vs. reversible hydrogen electrode in flow cell, with the Faradaic efficiency up to 12.1 %. Moreover, the catalyst keeps relatively stable during electrochemical CO2 reduction process. Experimental studies and theoretical calculations reveal that the bicontinuous structure of Cu2O/Cu can facilitate the *CO formation, *CO-*CO coupling and *CO-*OCCO coupling for the final generation of n-propanol.

Exploring the thermal decomposition mechanism of nitromethane via a neural network potential

A new neural network potential (NNP) is constructed to reveal the thermal decomposition mechanism of nitromethane (NM). The NNP model possesses both ab initio accuracy and empirical force fields efficiency, which allows the investigation of the entire decomposition process of NM from an atomic perspective. A series of molecular dynamics simulations are performed for NM decomposition, and the main reaction channels are further examined with transition state theory and quantum calculation. The results show that the C-N bond breaking is the dominant initial decomposition channel of NM at high temperature, and the stable product H2O can be consumed for the formation of NH3 and CO2. The complex reaction network is established, and the generation process of each main product is discussed in detail. The NNP gives an atomic insight into the complex reaction dynamics of NM and can be extended to investigate the reaction mechanism of more CHON based energetic materials.

Carbon dioxide hydrate crystallization thickening & morphology in a micro-confined environment for carbon capture & sequestration processes

Carbon dioxide capture and sequestration (CCS) are critical processes that are necessary to mitigate the impacts of climate change. In pipelines used for CCS and for ocean sequestration, the formation of CO2 hydrates can occur and be detrimental to the safety and integrity of the CCS equipment and process. Understanding the crystallization thickening behavior of CO2 hydrates is vital for understanding hydrate formation in CO2 pipelines and in other CCS applications, such as sequestration and CO2 capture or storage. In this study, a microfluidic chip reactor was used to crystalize and thicken CO2 hydrates at the channel walls. The morphology of the CO2 hydrates was visually analyzed and quantified using in situ Raman spectroscopy. Two hydrate layers were consistently observed. An annealed, dense layer of hydrate shared an interface with liquid water, while a porous hydrate layer shared an interface with CO2 gas. Capillary-like pore spaces could be observed in the porous layer, which confirms one proposed mechanism for hydrate film thickening. Subcooling (0.5–1.5 K), pressure (2.51, 3.10 MPa), and flow rate of CO2 (0.167, 1.67 mm3/s) were studied for their impact on the overall CO2 hydrate film thickness over time. Over the ranges of these chosen parameters, only CO2 flow rate was found to have a significant impact on the thickening of CO2 hydrates, and a higher flow rate led to thicker crystalline hydrate films. A first principles mass transfer model for hydrate film thickness was developed and applied to the measurement data collected for overall hydrate film thickness.

Optimal Dynamic Regimes for CO Oxidation Discovered by Reinforcement Learning.

Metal nanoparticles are widely used as heterogeneous catalysts to activate adsorbed molecules and reduce the energy barrier of the reaction. Reaction product yield depends on the interplay between elementary processes: adsorption, activation, desorption, and reaction. These processes, in turn, depend on the inlet gas composition, temperature, and pressure. At a steady state, the active surface sites may be inaccessible due to adsorbed reagents. Periodic regime may thus improve the yield, but the appropriate period and waveform are not known in advance. Dynamic control should account for surface and atmospheric modifications and adjust reaction parameters according to the current state of the system and its history. In this work, we applied a reinforcement learning algorithm to control CO oxidation on a palladium catalyst. The policy gradient algorithm was trained in the theoretical environment, parametrized from experimental data. The algorithm learned to maximize the CO2 formation rate based on CO and O2 partial pressures for several successive time steps. Within a unified approach, we found optimal stationary, periodic, and nonperiodic regimes for different problem formulations and gained insight into why the dynamic regime can be preferential. In general, this work contributes to the task of popularizing the reinforcement learning approach in the field of catalytic science.

Cobalt(VI)-oxo species-mediated selective oxidation of electron-rich organic contaminants by Co-loaded hydroxylated g-C3N4 with high resistance to an inhibitory effect of background constituents

Understanding of the selectivity of high-valent cobalt-oxo species (Co(IV)O) toward diverse organic pollutants with different characteristics in the presence of background constituents remains limited. Here, we prepared Co-loaded hydroxyl group-grafted graphitic carbon nitride (Co-OHCN) using a facile method for the effective formation of Co(IV)O. The role of the hydroxyl group in anchoring Co ions was investigated using several characterization methods (TEM, XRD, FT-IR, and XPS). Co-OHCN exhibited superior efficiency in degrading 4-chlorophenol (4-CP) (98.0 % ± 0.3 %) within 15 min of peroxymonosulfate (PMS) activation reaction. In the Co-OHCN/PMS system, Co(IV)O had the highest steady-state concentration ([Co(IV)O] = 1.40 × 10−10 M), significantly exceeding that of other reactive oxygen species (ROS) ([SO4−] = 9.22 × 10−13 M, [OH] = 1.82 × 10−13 M). The dominant role of Co(IV)O in 4-CP degradation was further revealed through scavenger tests, probe methods, and electrochemical analysis. Additionally, the anti-interference of Co(IV)O in the degradation of electron-rich organic substrates to background constituents (NOM and halide ions) was systemically validated using three organic pollutants with different ionization potential values (diclofenac, 4-CP, and benzoic acid). This study provides insight into an efficient strategy for Co(IV)O -mediated pollutant elimination and organic substrate-dependent selectivity of Co(IV)O during water decontamination.

Stabilized ε-Fe2C catalyst with Mn tuning to suppress C1 byproduct selectivity for high-temperature olefin synthesis

Accurately controlling the product selectivity in syngas conversion, especially increasing the olefin selectivity while minimizing C1 byproducts, remains a significant challenge. Epsilon Fe2C is deemed a promising candidate catalyst due to its inherently low CO2 selectivity, but its use is hindered by its poor high-temperature stability. Herein, we report the successful synthesis of highly stable ε-Fe2C through a N-induced strategy utilizing pyrolysis of Prussian blue analogs (PBAs). This catalyst, with precisely controlled Mn promoter, not only achieved an olefin selectivity of up to 70.2% but also minimized the selectivity of C1 byproducts to 19.0%, including 11.9% CO2 and 7.1% CH4. The superior performance of our ε-Fe2C-xMn catalysts, particularly in minimizing CO2 formation, is largely attributed to the interface of dispersed MnO cluster and ε-Fe2C, which crucially limits CO to CO2 conversion. Here, we enhance the carbon efficiency and economic viability of the olefin production process while maintaining high catalytic activity.

Synergetic Cu0 and Cu+ on the surface of Al2O3 support enhancing methanol steam reforming reaction

The methanol steam reforming (MSR) reaction was a crucial pathway for hydrogen production, with Cu-based catalysts widely applied. It was established that the isolated Cu0-site path and Cu+-site path were responsible for methanol conversion. However, a “Seesaw Effect” existed between the activation of *CH3O and the formation of CO2. Specifically, Cu0 site favored *CH3O activation but facilitated the reverse water gas shift (RWGS) process. Conversely, Cu+ site suppressed CO and promoted CO2 formation but had a reduced ability for *CH3O dehydrogenation. In this work, a Cu0-Cu+ synergy path was proposed, Cu0 sites activate CH3OH into *CH2O, and the subsequent conversion of *CH2O is catalyzed over the Cu+ site. Characterization and calculation results demonstrated that this synergy path subtly avoids two rate-determining steps (*CH3O → *CH2O on Cu+ sites and bi-*CHOO → *CO2 on Cu0 site). The migration of *CH2O from the Cu0 site to Cu+ sites was a critical step in constructing a synergy path. Moreover, MSR performance was governed by the quantity of synergy sites (Cu0/Cu+) and the amount of matched Cu0-Cu+ sites, both of which could be adjusted by varying the Cu loading (1–20%). An optimal 9% Cu enhanced the synergy interaction, with a Cu0/Cu+ ratio of 1.2 and the highest amount of Cu0-Cu+ sites (609.4 μmol/g), giving rise to high methanol conversion and low CO concentration. The discovery in this work provided theoretical guidance for constructing high-performance Cu-based catalysts.

Study on the characteristics of microwave pyrolysis of pine wood catalyzed by bimetallic catalysts prepared with microwave-assisted hydrothermal char

Bimetallic hydrothermal char catalysts (Co-Ni/MHC, Fe-Co/MHC, Fe-Ni/MHC) were prepared through ionic hydrothermal methods and microwave high-temperature activation. During catalyst preparation, different metals synergistically promoted the formation of ordered carbon structures such as carbon nanotubes and carbon microspheres, respectively. Serving both as microwave absorbers and catalysts for the microwave pyrolysis of pine wood, the bimetallic catalysts exhibited distinct advantageous characteristics. Fe-Ni/MHC exhibited excellent microwave absorption properties and was able to assist the PW to heat up rapidly at a rate of 6.17 °C/s, benefiting from which PW achieved a high bio-oil yield of 44.0 % in the microwave-assisted catalytic pyrolysis process. Using Co-Ni/MHC as a catalyst resulted in bio-oil with up to 42.7 % styrene content and had good catalytic effects on the formation of CO and H2. This study provides a scientific reference for the application of hydrothermal treatment and microwave-assisted pyrolysis in biomass pyrolysis technology.

Imaging the Collision Energy-Dependent Charge-Transfer Dynamics between the Spin-Orbit Ground Ar+(2P3/2) Ion and CO.

The collisional charge-transfer reaction between Ar+(2P3/2,1/2) and CO represents one of the most studied ion-molecule systems; many controversies persist among different studies, and the detailed quantum state-to-state charge-transfer dynamics remains unknown. Here, differential cross sections of the charge-transfer process between the spin-orbit ground Ar+(2P3/2) ion and CO are reported at three center-of-mass collision energies of 1.02, 0.72, and 0.40 eV using a home-built three-dimensional velocity-map imaging-based ion-molecule crossed beam setup. At all three collision energies, the direct energy resonant charge-transfer mechanism dominates the reaction, featuring predominantly forward scattering with the CO+ product population peaking at the v' = 6 and v' = 7 vibrational levels. Only at the lowest collision energy of 0.40 eV is the significant backward peaked scattering product observed, with CO+ populated from v' = 4 to v' = 8. There is no obvious evidence for the formation of CO+ in excited electronic state A2Π+, in qualitative accord with previous theoretical predictions.

Unraveling the interaction of co-encapsulated Saccharomyces cerevisiae and Metarhizium brunneum in calcium alginate-based attract-and-kill beads.

Attract-and-kill (AK) beads are biological, microbial insecticides developed as an alternative to synthetic soil insecticides. For wireworm control, beads are based on calcium alginate/starch co-encapsulating the carbon dioxide (CO2) producing yeast Saccharomyces cerevisiae H205 as the attract component, and the entomopathogenic fungus Metarhizium brunneum CB15-III as the kill component. However, the physicochemical processes inside beads during co-cultivation are still unclear. Here we reveal for the first time the spatiotemporal conditions of oxygen and pH inside AK beads measured with microelectrodes and describe the impact of S. cerevisiae on CO2 and conidia formation. Measurements revealed a steep oxygen gradient already 2 days after co-encapsulation, with an internal hypoxic zone. Encapsulating either S. cerevisiae or M. brunneum already decreased the average pH from 5.5 to 4.7 and 4.6, respectively. However, on day 3, co-cultivation lead to temporal strong acidification of beads down to pH 3.6 which followed the maximum CO2 productivity and coincided with the maximum conidiation rate. Decreasing the yeast load decreased the total CO2 productivity to half, and the conidial production by 93%, while specific productivities normalized to 1% yeast load increased eight-fold and three-fold, respectively, with day 3 being an exception. Our findings indicate a general beneficial interaction between M. brunneum and S. cerevisiae, but also suggest competition for resources. These findings will contribute to develop innovative co-formulations with maximum efficiency to save application rates and costs. © 2024 The Author(s). Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Characterization and impact of oxygenates in post-consumer plastic waste-derived pyrolysis oils on steam cracking process efficiency

Mechanical recycling of mixed packaging waste has limitations due to challenging separation into pure polyolefin streams which often leads to low quality recyclates. A solution to improve overall recycling rates of polyolefins is chemical recycling. One promising approach is conversion into a liquid product via pyrolysis and subsequent steam cracking of the pyrolysis oil towards light olefins. In this study, distilled fractions of pyrolysis oils from PE and PP-rich waste were characterized via GC × GC including normal and reversed-phase column configurations with a special focus on oxygenated components. Distilled pyrolysis oils were subsequently steam cracked in 20/80 weight‐based blends with conventional naphtha. All pyrolysis oil samples contained substantial amounts of oxygenates (1–10 wt%) which poses a huge challenge for steam cracker feedstocks and it was found that ketones are the most prevailing oxygenate group. Steam cracking experiments showed slightly increased ethylene yields of the blends compared to pure fossil naphtha, with the PE-derived samples outperforming the PP-derived samples. Furthermore, diesel-range distillation cuts led to higher formation of heavy products compared to the naphtha-range cuts. Increased formation of CO was observed as a consequence of the substantial oxygen contamination which can be a deal-breaker in industrial steam crackers. This work shows that distilled pyrolysis oils with conventional naphtha are promising steam cracking feedstocks if intermediate processing steps are performed to remove the oxygenates and other impurities using, for instance, hydrotreatment. With the findings of this work, such upgrading processes can be designed in a more effective way.

Bimetallic cobalt-cerium oxides activated fenton-like process for organic contaminant removal: Role of high-valent cobalt species modulated by oxygen vacancies

Cobalt-cerium bimetallic oxides (CoCeOx) with rich oxygen vacancies (OVs) were prepared by solvothermal method for peroxymonosulfate (PMS) activation efficiently, and the effect of OVs on reactive species formation was discussed. Carbamazepine (CBZ), a widely used anti-epileptic drug, also a typical pharmaceutical and personal care products (PPCPs) in the water environment, could be removed by 98 % in 40 min with low addition of CoCeOx and PMS in the CoCeOx/PMS system. Through a series of quenching experiments and electron paramagnetic resonance, it was confirmed that the main reactive species for decontamination were high-valent cobalt oxygen species (Co(IV)). Through the OVs detection and the contribution calculation of radicals and non-radicals on CBZ removal, it was found that OVs promoted the transformation from radicals to non-radicals (mainly Co(IV)) in the systems. In addition, cerium doping played an important role in promoting Co (II) / Co (III) cycle and OVs regeneration. Density functional theory (DFT) calculation revealed the formation process of Co(IV), and further proved that OVs could promote the formation of Co(IV). Evaluated by quantitative structure–activity relationship (QSAR) analysis, the ecotoxicity of CBZ and its main intermediates was significantly decreased. Overall, this study deepens the understanding of OVs promoting the formation of high-valent metal oxygen species (HVMO), as well as provides feasibility for the removal of refractory organics in wastewater.

Single-atom nickel sites boosting Si nanowires for photoelectrocatalytic CO2 conversion with nearly 100% selectivity.

It is a challenge to design a photocathode with well-defined active sites for efficient photoelectrocatalytic CO2 reduction. Herein, single-atom Ni sites are integrated into Si nanowires to develop a novel photocathode, denoted as Ni-NC/Si. The photocathode demonstrates a stable faradaic efficiency for CO production, approaching nearly 100% at -0.6 V vs. RHE. The introduction of single-atom Ni sites provides sufficient active sites for CO2 reduction, thereby improving the selectivity towards CO formation.

Interaction between radio-oxidized polypropylene and gaseous HCl. Part 2. Kinetics and reaction mechanisms

In Part 1 of this article, evidence of cross-infection effects of polyolefins and halogenated polymers present in the long-lived intermediate-level waste (LL-ILW) packages was shown. We choose to study the interaction between polypropylene and one of the main degradation products of PVC, i.e. HCl. Polyolefins and chlorinated polymers were chosen because they are the two most abundant classes of polymer types found in the LL-ILW packages. We showed that the interaction between HCl and pristine or radio-oxidized PP results in HCl consumption and in CO2, H2O and CO formation. The object of the present article is to further study the reaction mechanisms. Using derivative methods at room temperature, the reaction of HCl with hydroperoxide was documented while alcohols seem stable. A model taking into account HCl diffusion, sorption in PP and reaction with hydroperoxide is insufficient to explain the observed HCl consumption kinetics. We concluded that HCl consumption is not only due to physical sorption and to chemical reaction with a unique oxidized compound, but multiple reactions with different oxidation products should be considered as well.

Development of Technology and a Convertеr for Neutralizing Greenhouse Gases Emitted from Automobiles

The article touches upon the issues of global warming associated with carbon dioxide (CO2) emissions into the atmosphere from vehicle internal combustion engines (ICE). To neutralize existing greenhouse gases emitted by ICE, in particular CO2, the interaction of the latter with various chemicals has been studied. The dynamics of exhaust gas emissions from ICE cylinders were observed. The experimental research was conducted to develop a greenhouse gas neutralization technology. Carbon dioxide neutralization converter with three neutralization batteries and a homogenization device is presented. This converter can guarantee CO2 neutralization of up to 92%. The formation of CO2 in the cylinders of modern petrol engines is due to the final combustion of the air-petrol fuel mixture. The combustion of the latter in the cylinder can be heterogeneous and diffusive. In addition, CO2 is generated in large quantities during diffusion combustion. The most effective method of diffusive combustion was chosen by the constructors of modern ICE, which is the formation of an artificial turbulent gas-dynamic condition for the fuel mixture due to the increase in the temperature of the air adsorbed in the cylinder, which ensures the engine's thermal energy efficiency coefficient of up to 35%. The CO2 volume in the exhaust gases of such engines reaches up to 16%. Thus, considering the perfection of modern ICE design for providing a high-efficiency reaction for the hydrocarbon oxidation in the fuel mixture in the combustion chamber, it becomes apparent that the presence of about 16% CO2 in the fractional composition of emitted dissolved gases is a serious problem in terms of increasing the volume of greenhouse gases in the atmosphere. Therefore, the goal of this article is to develop a reduction technology.

The Surface Chemistry of Methanol on Pd(111) and H-Pd(111) Surfaces: C-O Bond Cleavage and the Effects of Metal Hydride Formation.

Palladium catalysts are frequently employed in processes where methanol is an energy vector or carrier, being useful for the synthesis of methanol from mixtures of carbon dioxide and hydrogen (CO2/H2) or its steam reforming on demand. Results of synchrotron-based ambient pressure X-ray photoelectron spectroscopy for the adsorption of methanol on a Pd(111) model catalyst show a rich surface chemistry and complex phenomena that strongly depend on pressure and temperature. At low pressures (<10-6 Torr) and temperatures (<300 K), CO is the dominant decomposition product. As the pressure increases, cleavage of C-H, O-H, and C-O bonds is observed, and at elevated temperatures (400-600 K) the formation of CO and CHx/C fragments compete on the surface. Thus, existing reaction networks for methanol decomposition must be modified. Furthermore, surface and subsurface hydrogen (coming from PdHx) play a significant role in the stability and removal of CHx and C species.

A mechanistic study of the hydrolysis of tetrafluoromethane on γ-alumina

CF4 is one of the representative and environmentally hazardous perfluorinated compounds. Even though their decomposition via a catalytic thermal process is an effective process for dissociating C-F bonds by employing catalysts with Lewis acid sites, the related mechanisms are unclear. Herein, we report a theoretical mechanism for the hydrolysis of tetrafluoromethane (CF4) on an γ-alumina surface via density functional theory calculations. The overall reaction mechanism was divided into two steps: CF2O formation and CO2 formation. After the dissociative adsorption of CF4 to the strongest Lewis acid site on the surface of the catalyst, several pathways of defluorination reaction were investigated considering the presence of water and the order of reaction steps. Regardless of the reaction pathway considered, the rate-determining step of the overall reaction was found to be the first dissociation of the C-F bond in CF4, which has the highest energy barrier of 42.31 kcal/mol. Interestingly, oxygen vacancies were readily formed on the catalyst surface during several reaction pathways following its interaction with the reaction intermediate, and these sites could be replaced by fluorine atoms detached from CF4. Our findings suggest that facile desorption of HF, in addition to the presence of strong acidic sites on the catalyst surface for C-F bond dissociation, is critical for improving the CF4 hydrolysis.

Redox behavior of unsubstituted cobalt phthalocyanine in nanostructured Langmuir-Schaefer films

Although the properties of unsubstituted metal tetrapyrroles in solutions have received attention in numerous work, the physico-chemistry of their thin films remains poorly investigated. In this work, we constructed thin films of unsubstituted cobalt phthalocyanine on the surface of quartz plates and indium tin oxide (ITO) electrodes using the Langmuir-Schaefer (LS) and drop casting techniques. In LS films, CoPc species are involved in strong intermolecular interactions, which result in formation of CoPc nanostructures and prominent changes in the ultraviolet-visible spectrum. Electrochemical reduction of CoPc in LS films at −0.9 V (versus silver chloride electrode) results in formation of Co(I) species. In contrast to the highly reactive nature of Co(I)Pc in solution, these species generated in thin films are relatively resistant to dioxygen due to the dense packing of CoPc units. These findings can further the development of CoPc-based resistive sensors utilizing not only common Co(II), but also Co(I) species, which may possess different sensitivity toward analytes.

Thermo-chemical processes for the sustainable utilization of oil-bearing biomass: A case study on apricot seed valorization

This study investigated the thermochemical processing of defatted residue to achieve zero-waste utilization of oil-bearing biomass using apricot seed as the model compound. Defatted apricot seeds (DAS) obtained after oil extraction from apricot seed were valorized through pyrolysis platform, focusing on enhancing sustainability using CO2 as the reaction medium. The results showed that CO2 plays a crucial role in the pyrolysis process, leading to an enhanced CO formation through homogeneous reaction between CO2 and volatile matters stemming from DAS. Specifically, CO2 oxidized volatile matters while simultaneously reducing to CO and influenced the morphological properties of DAS biochars (DASBs), leading the development of pores with sizes of less than 16 nm and exceeding 50 nm. The larger pore size of DASBs fabricated under N2 and CO2, compared to 2 nm (the molecular size of triglycerides), makes them suitable as porous materials for thermally induced transesterification. The presence of alkaline metals in DASBs expedited thermally induced transesterification. At ≤ 330 °C, DASB fabricated under CO2 condition exhibited faster reaction kinetics than under N2 condition. This suggests that the use of CO2 in the fabrication of DASB results in favorable surface properties conducive to the thermally induced transesterification of apricot oil.

A Strategy for Enhanced Carbon Storage: A Hybrid CO2 and Aqueous Formate Solution Injection to Control Buoyancy and Reduce Risk

A Strategy for Enhanced Carbon Storage: A Hybrid CO2 and Aqueous Formate Solution Injection to Control Buoyancy and Reduce Risk