Selective Production Of Ethylene Research Articles

Unlocking Copper-Free Interfacial Asymmetric C-C Coupling for Ethylene Photosynthesis from CO2 and H2O.

Solar-driven carbon dioxide (CO2) reduction into C2+ products such as ethylene represents an enticing route toward achieving carbon neutrality. However, due to sluggish electron transfer and intricate C-C coupling, it remains challenging to achieve highly efficient and selective ethylene production from CO2 and H2O beyond capitalizing on Cu-based catalysts. Herein, we report a judicious design to attain asymmetric C-C coupling through interfacial defect-rendered tandem catalytic centers within a sulfur-vacancy-rich MoSx/Fe2O3 photocatalyst sheet, enabling a robust CO2 photoreduction to ethylene without the need for copper, noble metals, and sacrificial agents. Specifically, interfacial S vacancies induce adjacent under-coordinated S atoms to form Fe-S bonds as a rapid electron-transfer pathway for yielding a Z-scheme band alignment. Moreover, these S vacancies further modulate the strong coupling interaction to generate a nitrogenase-analogous Mo-Fe heteronuclear unit and induce the upward shift of the d-band center. This bioinspired interface structure effectively suppresses electrostatic repulsion between neighboring *CO and *COH intermediates via d-p hybridization, ultimately facilitating an asymmetric C-C coupling to achieve a remarkable solar-to-chemical efficiency of 0.565% with a superior selectivity of 84.9% for ethylene production. Further strengthened by MoSx/WO3, our design unveils a promising platform for optimizing interfacial electron transfer and offers a new option for C2+ synthesis from CO2 and H2O using copper-free and noble metal-free catalysts.

Electrodes Modified with Overlayers for Enhanced CO2 Reduction Selectivity

Like many electrocatalytic reactions involving the transfer of multiple protons and electrons, the CO2 reduction reaction frequently exhibits poor selectivity among many possible products. In this presentation, I will describe our laboratory’s efforts to design electrochemical platforms that enable the control over proton transfer dynamics to electrocatalysts using molecular and polymeric overlayers with the goal of increasing product selectivity and understanding reaction mechanism. This platform is generally applicable to both molecular and metallic systems, and we demonstrate how it can be used to improve the selectivity of nonprecious metal O2 reduction and NO3 - reduction catalysts.For the CO2 reduction reaction, this strategy as applied to metal electrodes is also broadly germane and is used to modulate catalyst reactivity such that it results in the selective production of ethylene, ethanol, methanol, carbon monoxide, and methane, with examples for each with Faradaic efficiencies in excess of 70%. A common theme is that the hydrophobicity of the metal-overlayer interface frequently controls product selectivity and can steer the site of protonation events at intermediates. In this manner, for example, the selectivity of catalysts between the C2 products ethanol and ethylene can be dictated. To aid in mechanistic understanding and catalyst characterization, the majority of these studies are conducted on nominally flat metal electrodes. However, we will also describe ongoing efforts to nanostructure these CO2 reduction systems to develop selective catalysts that operate at high current densities.

High yield electrosynthesis of oxygenates from CO using a relay Cu-Ag co-catalyst system

As a sustainable alternative to fossil fuel-based manufacture of bulk oxygenates, electrochemical synthesis using CO and H2O as raw materials at ambient conditions offers immense appeal. However, the upscaling of the electrosynthesis of oxygenates encounters kinetic bottlenecks arising from the competing hydrogen evolution reaction with the selective production of ethylene. Herein, a catalytic relay system that can perform in tandem CO capture, activation, intermediate transfer and enrichment on a Cu-Ag composite catalyst is used for attaining high yield CO-to-oxygenates electrosynthesis at high current densities. The composite catalyst Cu/30Ag (molar ratio of Cu to Ag is 7:3) enables high efficiency CO-to-oxygenates conversion, attaining a maximum partial current density for oxygenates of 800 mA cm−2 at an applied current density of 1200 mA cm−2, and with 67 % selectivity. The ability to finely control the production of ethylene and oxygenates highlights the principle of efficient catalyst design based on the relay mechanism.

Titania-supported Cu Single Atom Catalyst for Electrochemical Reduction of Acetylene to Ethylene at Low-Concentrations with Suppressed Hydrogen Evolution.

Electrochemical acetylene reduction (EAR) is a promising strategy for removing acetylene from ethylene-rich gas streams. However, suppressing the undesirable hydrogen evolution is vital for practical applications in acetylene-insufficient conditions. Herein, weimmobilized Cu single atoms on anatase TiO2 nanoplates (Cu-SA/TiO2 ) for electrochemical acetylene reduction, achieving an ethylene selectivity of ∼97% with a 5vol.% acetylene gas feed (Ar balance). At the optimal Cu single atom loading, Cu-SA/TiO2 wasable to effectively suppress HER and ethylene over-hydrogenation even when using dilute acetylene (0.5vol.%) or ethylene-rich gas feeds, delivering a 99.8% acetylene conversion, providing a turnover frequency of 8.9 × 10-2 s-1 , which is superior to other EAR catalysts reported to date. Theoretical calculations showed that the Cu single atoms and the TiO2 support acted cooperatively to promote charge transfer to adsorbed acetylene molecules, whilst also inhibiting hydrogen generation in alkali environments, thus allowing selective ethylene production with negligible hydrogen evolution at low acetylene concentrations. This article is protected by copyright. All rights reserved.

Al-Doped Octahedral Cu2O Nanocrystal for Electrocatalytic CO2 Reduction to Produce Ethylene.

Ethylene is an ideal CO2 product in an electrocatalytic CO2 reduction reaction (CO2RR) with high economic value. This paper synthesised Al-doped octahedral Cu2O (Al-Cu2O) nanocrystal by a simple wet chemical method. The selectivity of CO2RR products was improved by doping Al onto the surface of octahedral Cu2O. The Al-Cu2O was used as an efficient electrocatalyst for CO2RR with selective ethylene production. The Al-Cu2O exhibited a high % Faradic efficiency (FEC2H4) of 44.9% at -1.23 V (vs. RHE) in CO2 saturated 0.1 M KHCO3 electrolyte. Charge transfer from the Al atom to the Cu atom occurs after Al doping in Cu2O, optimizing the electronic structure and facilitating CO2RR to ethylene production. The DFT calculation showed that the Al-Cu2O catalyst could effectively reduce the adsorption energy of the *CHCOH intermediate and promote the mass transfer of charges, thus improving the FEC2H4. After Al doping into Cu2O, the center of d orbitals shift positively, which makes the d-band closer to the Fermi level. Furthermore, the density of electronic states increases due to the interaction between Cu atoms and intermediates, thus accelerating the electrochemical CO2 reduction process. This work proved that the metal doping strategy can effectively improve the catalytic properties of Cu2O, thus providing a useful way for CO2 cycling and green production of C2H4.

Bifunctional Gas Diffusion Electrode Enables In-situ Separation and Conversion of CO2 to Ethylene from Dilute Stream.

The requirement of concentrated CO2 feedstock significantly limits the economic feasibility of electrochemical CO2 reduction (eCO2 R) as it often involves multiple intermediate processes, including CO2 capture, energy intensive regeneration, compression, and transportation steps. Herein, we report on a bifunctional gas diffusion electrode (BGDE) for separation and electrolysis of CO2 from a low concentration CO2 stream (∼10 vol%). We demonstrate a BGDE for selective production of ethylene (C2 H4 ) by combining high density polyethylene-derived porous carbon (HPC) as a physisorbent with polycrystalline copper as conversion catalyst. Our BGDE shows substantial tolerance to 10 vol% CO2 exhibiting a Faradaic efficiency of ∼45% towards C2 H4 at a current density of 80mA/cm2 over 11hrs, outperforming previous reports that utilised such partial pressure (PCO2 = 0.1 atm and above) at ambient conditions and unaltered polycrystalline copper as catalyst. Molecular dynamics simulation and mixed gas permeability assessment reveal that such selective performance is ensured by high CO2 uptake of microporous HPC as well as continuous desorption owing to molecular diffusion and concentration gradient created by binary flow (CO2 |N2 ) within sorbent boundary. We conclude based on detailed technoeconomic analysis that our in-situ process has the potential to be economically compelling by precluding the C2 H4 production cost associated with the energy intensive intermediate steps of conventional decoupled process. This article is protected by copyright. All rights reserved.

One-Step Synthesis of CuxOy/TiO2 Photocatalysts by Laser Pyrolysis for Selective Ethylene Production from Propionic Acid Degradation.

In an effort to produce alkenes in an energy-saving way, this study presents for the first time a photocatalytic process that allows for the obtention of ethylene with high selectivity from propionic acid (PA) degradation. To this end, TiO2 nanoparticles (NPs) modified with copper oxides (CuxOy/TiO2) were synthetised via laser pyrolysis. The atmosphere of synthesis (He or Ar) strongly affects the morphology of photocatalysts and therefore their selectivity towards hydrocarbons (C2H4, C2H6, C4H10) and H2 products. Specifically, CuxOy/TiO2 elaborated under He environment presents highly dispersed copper species and favours the production of C2H6 and H2. On the contrary, CuxOy/TiO2 synthetised under Ar involves copper oxides organised into distinct NPs of ~2 nm diameter and promotes C2H4 as the major hydrocarbon product, with selectivity, i.e., C2H4/CO2 as high as 85% versus 1% obtained with pure TiO2.

Selective production of ethylene from CO2 over CuAg tandem electrocatalysts

The electrochemical reduction reaction of CO2 (CO2RR) is desirable for decreasing CO2 concentration in the atmosphere and producing value-added chemicals. The development of advanced catalysts is a key challenge for the practical application of CO2RR. Recently, the bimetallic catalysts with two or more reaction sites acting synergistically are one of the most interesting catalysts. Herein, CuAg bimetallic catalysts with various Cu/Ag ratios are synthesized by the ultrasonic spray pyrolysis (USP) method for the selective production of ethylene (C2H4) via CO2RR. The electrocatalytic performances of the CuAg catalysts with different compositions are evaluated in a full flow single cell and the Cu90Ag10 exhibits 1.5 times the higher C2H4 Faradaic efficiency and the C2H4 current density at a cell voltage of 2.2 V than the bare Cu. Ag in the bimetallic catalysts provides additional CO via desorption-re-adsorption and diffusion process for CC coupling on the Cu surface to synthesize C2H4. In addition, the improved performance of the Cu90Ag10 is attributed to not only the synergistic effect between Cu and Ag but also the appropriate Cu/Ag ratio.

Selective Ethylene Production from CO2 and CO Reduction via Engineering Membrane Electrode Assembly with Porous Dendritic Copper Oxide.

Gas-fed zero-gap electrolyzers have recently emerged as attractive systems for limiting ohmic losses and costs associated with electrolytes and for optimizing energy efficiencies. Here, we report that using a dendritic Cu oxide (D-CuO) material deposited on a gas diffusion layer as the cathode of a gas-fed zero-gap membrane electrode assembly (MEA) system results in a very selective conversion of CO to ethylene. More specifically, CO reduction yielded ethylene with an FE up to 68% at 100-125 mA·cm-2 with H2 as the only other gaseous product and the electrolysis could be carried out for several hours with good stability. Ethylene was also the major product during CO2 electrolysis (FE = 41%) at 125-150 mA·cm-2, reflecting the high selectivity of D-CuO for ethylene production. Such systems are relevant for tandem CO2 electroreduction processes, allowing energy efficiencies above 30%.

Catalytic Dehydrogenation of Ethane: A Mini Review of Recent Advances and Perspective of Chemical Looping Technology

Dehydrogenation processes play an important role in the petrochemical industry. High selectivity towards olefins is usually hindered by numerous side reactions in a conventional cracking/pyrolysis technology. Herein, we show recent studies devoted to selective ethylene production via oxidative and non-oxidative reactions. This review summarizes the progress that has been achieved with ethane conversion in terms of the process effectivity. Briefly, steam cracking, catalytic dehydrogenation, oxidative dehydrogenation (with CO2/O2), membrane technology, and chemical looping are reviewed.

Co and Mo Co-doped Fe2O3 for Selective Ethylene Production via Chemical Looping Oxidative Dehydrogenation

In this study, we investigate Co and/or Mo doped Fe₂O₃ (CoₓMo₁–ₓ/Fe₂O₃, x = 0, 0.2, 0.3, 0.4, and 1) as redox catalysts for chemical looping oxidative dehydrogenation (CL-ODH) of ethane. Under the cyclic redox reaction mode, the five as-prepared samples behave differently toward ethane conversion. Among the five redox catalysts, CoFe₂O₄ (x = 1) is highly reactive and tends to overoxidize ethane into CO₂, while Mo/Fe₂O₃ (x = 0) exhibits promising ethylene selectivity but inferior H₂ removal capability. By tuning the molar ratio of Co/(Co + Mo), 87.4% ethylene selectivity at 56.2% ethane conversion can be achieved by the Co₀.₃Mo₀.₇/Fe₂O₃ (x = 0.3) redox catalyst at 825 °C and 6000 h–¹. C₂H₆-TPR results show that the selectivity of Co₀.₃Mo₀.₇/Fe₂O₃ alters as the ODH reaction proceeds due to the dynamic change of surface properties of the redox catalyst in the reaction. XPS results indicate that a relatively low Fe content as well as a high Mo content at the near-surface of the redox catalyst is beneficial for its ethylene selectivity in CL-ODH of ethane. DFT calculations reveal that Co cations in the Co₀.₃Mo₀.₇/Fe₂O₃ structure are responsible for the activity and H₂ combustion capability of the redox catalyst, while Mo plays a key role in tuning the ethylene selectivity.

Identification of earth-abundant materials for selective dehydrogenation of light alkanes to olefins

Selective ethane dehydrogenation (EDH) is an attractive on-purpose strategy for industrial ethylene production. Design of an effective, stable, and earth-abundant catalyst to replace noble metal Pt is the main obstacle for its large-scale application. Herein, we report an experimentally validated theoretical framework to discover promising catalysts for EDH, which combines descriptor-based microkinetic modeling, high-throughput computations, machine-learning concepts, and experiments. Our approach efficiently evaluates 1,998 bimetallic alloys by using accurately calculated C and CH3 adsorption energies and identifies a small number of new promising noble-metal-free catalysts for selective EDH. A Ni3Mo alloy predicted to be promising is successfully synthesized, and experimentally proven to outperform Pt in selective ethylene production from EDH, representing an important contribution to the improvement of light alkane dehydrogenation to olefins. These results will provide essential additions in the discovery and application of earth-abundant materials in catalysis.

High Conversion of Syngas to Ethene and Propene on Bifunctional Catalysts via the Tailoring of SAPO Zeolite Structure

Direct conversion of syngas to light olefins using bifunctional catalysts containing both oxides and zeolites represents a promising alternative in comparison with Fischer-Tropsch synthesis. It is still a great challenge to achieve highly selective production of ethylene and propylene at a satisfying CO conversion for potentially industrial applications. Here, we report that a high selectivity to ethylene and propylene can be achieved by tailoring silicoaluminophosphate zeolite structure and acid site strength. By comparing bifunctional catalysts composed of ZnCr oxide and different zeolites with 8-membered ring openings, we achieve the total selectivity of 76.4% in ethylene and propylene at a CO conversion as high as 38.2% by catalysts containing SAPO-17 zeolite (ERI framework). The detailed hydrocarbon distribution is nearly identical to that in the methanol-to-olefins reaction. The high selectivity can be rationalized due to both smaller 8-membered ring openings and the weaker Brønsted acid strength of SAPO-17 zeolites.

Product Control in Conversion of Ethanol on MIL‐101(Cr) with Adjustable Brønsted Acid Density

AbstractMIL‐101(Cr) with adjustable Brønsted acid density was prepared via post‐synthetic sulfation strategy, which was carried out with sulfuric acid in the presence of trifluoromethanesulfonic anhydride, using nitromethane as solvent. XRD, TG, EDS, XPS, IR, NH3‐TPD and acid‐base titration were used to characterize structure and acidity. Adopting conversion of ethanol as a probe reaction, gas‐solid catalytic characteristics on MIL‐101(Cr) and post‐synthetic sulfated MIL‐101(Cr) in a micro fixed‐bed reactor were studied by continuous feeding. Combined with the regulation of reaction parameters, selective production of ethylene (100 %) or diethyl ether (99 %) could be achieved.

Electro-derived Cu-Cu2O nanocluster from LDH for stable and selective C2 hydrocarbons production from CO2 electrochemical reduction

Recently, CO 2 conversion by electrochemical tool into value-added chemicals has been considered as one of the most promising strategies to offer sustainable development in energy and environment. In this contribution, we investigated electro-derived composites from Cu-based layered double hydroxide (LDH) for CO 2 electrochemical reduction. The Cu-Cu 2 O based nanocomposite (HPR-LDH) were derived by using electro-strategy from LDH having the stability up to 20 h and selectivity toward C 2 H 4 with faraday efficiency up to 36% by significantly suppressing CH 4 and H 2 with respect to bulk Cu foil. A highly negative reduction potential derived catalyst (HPR-LDH) maintained long-term stability for the selective production of ethylene over methane, and a small amount of Cu 2 O was still observed on the catalyst surface after CO 2 reduction reaction (CO 2 RR). Moreover, such unique strategy for electro-derived composite from LDH having small nanoparticles stacked each other grown on layered structure, would provide new insight to improve durability of O Cu combination catalysts for C C coupling products during electrochemical CO 2 conversion by suppressing HER. The XRD, SEM, ESR, and XPS analyses confirmed that the long-term ethylene selectivity of HPR-LDH is due to the presence of subsurface oxygen. The designed composite catalyst significantly enhances the stability and selectivity, and also decreases the over potential for CO 2 electro-reduction. We predict that the new designed LDH 2D-derived composites may attract new insight for transition metal and may open up a new direction for known structural properties of selective catalyst synthesis regarding effective CO 2 reduction reaction. A new type of electro-catalysts derived from layer double hydroxides for CO 2 electrochemical reduction into C 2 hydrocarbon was developed, which exhibited outstanding CO 2 electrochemical reduction capacity, high faradic efficiency products selectivity and excellent production stability.

Frontispiz: Highly Selective Production of Ethylene by the Electroreduction of Carbon Monoxide

Frontispiz: Highly Selective Production of Ethylene by the Electroreduction of Carbon Monoxide

Frontispiece: Highly Selective Production of Ethylene by the Electroreduction of Carbon Monoxide

Frontispiece: Highly Selective Production of Ethylene by the Electroreduction of Carbon Monoxide

Solar-driven plasmonic tungsten oxides as catalyst enhancing ethanol dehydration for highly selective ethylene production

Non-metallic plasmonic materials, as alternatives to costly noble metals, have drawn numerous attention owning to their unique localized surface plasmon resonance (LSPR) effect. Herein, we report non-metallic plasmonic tungsten oxide (WO3−x) nanowire bundles with abundant oxygen vacancy (OVs) that gives efficient activity for ethylene production from ethanol dehydration under full spectrum light irradiation. A remarkable ethylene generation rate of 16.9 mmol g−1 h−1 was achieved with high selectivity (94.9 %) over the WO3−x-5 nanowires with maximum oxygen vacancies, which was 16 times higher than 1.0 mmol g−1 h−1 (selectivity of 90.5 %) of WO3−x-20 nanoplates with low oxygen vacancies. Such impressive performance is ascribed to the synergistic effect of plasmonic hot electrons and photothermal effect. This work is expected to provide new insights on photo-induced ethanol dehydration for highly selective ethylene production.

Highly Selective Production of Ethylene by the Electroreduction of Carbon Monoxide.

Conversion of carbon monoxide to high value-added ethylene with high selectivity by traditional syngas conversion process is challenging because of the limitation of Anderson-Schulz-Flory distribution. Herein we report a direct electrocatalytic process for highly selective ethylene production from CO reduction with water over Cu catalysts at room temperature and ambient pressure. An unprecedented 52.7 % Faradaic efficiency of ethylene formation is achieved through optimization of cathode structure to facilitate CO diffusion at the surface of the electrode and Cu catalysts to enhance the C-C bond coupling. The highly selective ethylene production is almost without other carbon-based byproducts (e.g. C1 -C4 hydrocarbons and CO2 ) and avoids the drawbacks of the traditional Fischer-Tropsch process that always delivers undesired products. This study provides a new and promising strategy for highly selective production of ethylene from the abundant industrial CO.

Highly Selective Production of Ethylene by the Electroreduction of Carbon Monoxide

AbstractConversion of carbon monoxide to high value‐added ethylene with high selectivity by traditional syngas conversion process is challenging because of the limitation of Anderson‐Schulz–Flory distribution. Herein we report a direct electrocatalytic process for highly selective ethylene production from CO reduction with water over Cu catalysts at room temperature and ambient pressure. An unprecedented 52.7 % Faradaic efficiency of ethylene formation is achieved through optimization of cathode structure to facilitate CO diffusion at the surface of the electrode and Cu catalysts to enhance the C−C bond coupling. The highly selective ethylene production is almost without other carbon‐based byproducts (e.g. C1–C4 hydrocarbons and CO2) and avoids the drawbacks of the traditional Fischer–Tropsch process that always delivers undesired products. This study provides a new and promising strategy for highly selective production of ethylene from the abundant industrial CO.