Production Of C2H6 Research Articles

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.

Photoelectrochemical C–H activation of methane to methyl radical at room temperature

Visible light illumination induced CH4oxidation over a WO3photoanode. The production of C2H6implies the formation of methyl radicals through photoelectrochemical activation of methane.

Highly selective photocatalytic reduction of CO2 to ethane over Au-O-Ce sites at micro-interface

To date, the efficient photocatalytic conversion of CO2 into high-value C2 products remains a great challenge. Herein, the Au-CeO2 nanocomposite with Au-O-Ce sites at the micro-interface was developed to achieve a highly selective conversion of CO2 into C2H6. This can be partially ascribed to the formation of key intermediates of COCO* was confirmed via in-situ Fourier transform infrared (FTIR) spectroscopy, indicating that the Au-CeO2 micro-interface could prompt the multi-electron reduction of CO* before desorption, and enable the production of C2 species. Moreover, theoretical calculations suggested that Au-O-Ce sites at the micro-interface could reduce the energy barriers for the formation of COOH* and COCO*, facilitating the production of C2H6. Therefore, the Au-CeO2 nanocomposite exhibited a C2H6 production rate of 11.07 µmol g−1 h−1 and high electron selectivity of 93.1 % (product selectivity: 65.3 %), which is comparable with most state-of-the-art photocatalysts.

P and Cu Dual Sites on Graphitic Carbon Nitride for Photocatalytic CO2 Reduction to Hydrocarbon Fuels with High C2 H6 Evolution.

The light-driven CO2 reduction to multi-carbon products is especially meaningful, while the low efficiency of multi-electron transfer and sluggish C-C coupling greatly hinder its development. Herein, we report a photocatalyst comprising of P and Cu dual sites anchored on graphitic carbon nitride (P/Cu SAs@CN), which achieves a high C2 H6 evolution rate of 616.6 μmol g-1 h-1 in reducing CO2 to hydrocarbons. The detailed spectroscopic characterizations identify the formation of charge-enriched Cu sites, where the isolated P atoms serve as hole capture sites during photocatalysis. Theoretical simulations combined with in situ FTIR measurement reveal a kinetically feasible process for the formation of C-C coupling intermediate (*OC-COH) and confirm the favorable production of C2 H6 on the P/Cu SAs@CN photocatalyst. This work offers new insights into the photocatalyst design with atomic precision toward highly efficient photocatalytic CO2 conversion to high value-added carbon products.

P and Cu Dual Sites on Graphitic Carbon Nitride for Photocatalytic CO2 Reduction to Hydrocarbon Fuels with High C2H6 Evolution

AbstractThe light‐driven CO2 reduction to multi‐carbon products is especially meaningful, while the low efficiency of multi‐electron transfer and sluggish C−C coupling greatly hinder its development. Herein, we report a photocatalyst comprising of P and Cu dual sites anchored on graphitic carbon nitride (P/Cu SAs@CN), which achieves a high C2H6 evolution rate of 616.6 μmol g−1 h−1 in reducing CO2 to hydrocarbons. The detailed spectroscopic characterizations identify the formation of charge‐enriched Cu sites, where the isolated P atoms serve as hole capture sites during photocatalysis. Theoretical simulations combined with in situ FTIR measurement reveal a kinetically feasible process for the formation of C−C coupling intermediate (*OC−COH) and confirm the favorable production of C2H6 on the P/Cu SAs@CN photocatalyst. This work offers new insights into the photocatalyst design with atomic precision toward highly efficient photocatalytic CO2 conversion to high value‐added carbon products.

Tailoring the oxidation state of metallic TiO through Ti3+/Ti2+ regulation for photocatalytic conversion of CO2 to C2H6

The regulation and stabilization of the oxidation state to promote the conversion of CO2 to C2 fuel still faces many challenges. Based on the principle of charge balance, we creatively propose a co-doping strategy to adjust the surface oxidation state distribution of metallic catalysts. A TiO-based photocatalyst co-doped with Zn and N was synthesized by ammonia assisted one-step calcination method, named ZN-TC. XPS characterization shows that Zn and N adjust the valence states of adjacent Ti elements respectively, so that the surface of TiO maintains a relatively stable Ti3+/Ti2+ ratio. Under visible light irradiation, the material can catalyze CO2 into CO (324.11 μmol·g−1·h−1) and C2H6 (10.27 μmol·g−1·h−1) in the liquid phase. The selectivity of C2H6 reached 14.45%. When irradiated with near-infrared light, ZN-TC shows 100% CO selectivity because the photon energy is not enough to support the catalytic hydrogenation of CO2. Theoretical calculations and experiments proved that Zn and N elements mainly act on the B-1 band to regulate the Ti valence state. In-situ DRIFTS and in-situ Raman tests confirmed the function of oxidation state adjustment to promote the C-C coupling on the catalyst surface to produce ethoxy groups, which ultimately led to the production of C2H6.

Plasma-catalytic CO2 hydrogenation to ethane in a dielectric barrier discharge reactor

Anthropogenic greenhouse gas emissions have caused changes to the Earth’s climate, resulting in catastrophic weather events that are becoming more frequent and intense. Developing carbon-neutral processes for CO2 conversion powered by renewable energy is one way of attaining a circular economy, as waste CO2 is converted to a new carbon-containing product, without also being created as a by-product during the process. Plasma-catalysis is gaining increasing interest for CO2 conversion and utilisation under mild conditions, particularly CO2 conversion to green chemicals and fuels using renewable hydrogen, as this electrified process can easily be combined with clean and renewable energy to ensure a carbon-neutral process. Previous studies have mainly focussed on the production of methane from CO2 and H2; however, ethane (C2H6) is a much more valuable product. In this work, we report a non-thermal plasma-catalytic process for the conversion of CO2 into C2H6 in a dielectric barrier discharge (DBD) reactor. The influence of a variety of alumina-supported metal catalysts (Ru, Cu, Ni and Fe) on the plasma-catalytic CO2 hydrogenation to C2H6 was evaluated. The Ru catalyst attained the highest selectivity towards C2H6, at almost 40%. The Ru catalyst also increased the energy efficiency of the process to around 18%, in comparison to the plasma reaction using pure alumina (12%). The Ru catalyst also achieved the highest H2 conversion at 29%. Plasma-assisted production of C2H6 is a new promising process for the utilisation of CO2 via carbon-neutral electrified gas conversion.

Methane coupling and hydrogen evolution induced by palladium-loaded gallium oxide photocatalysts in the presence of water vapor

Non-oxidative coupling of methane (NOCM, 2CH4 → C2H6 + H2) is a reaction that can directly produce ethane and hydrogen at the same time, and gallium oxide (Ga2O3) powder has been reported as an effective photocatalyst for NOCM at room temperature. In this study, we investigated the reaction conditions for Pd-loaded Ga2O3 photocatalysts to improve the production rate of C2H6 and H2. We found that the 0.1 wt% Pd/Ga2O3 exhibited high selectivity of C2H6 (75.8%, carbon-based) under the conditions of steam reforming of methane. Photocatalytic NOCM seems to proceed in the presence of small amount of water. An increase in water vapor pressure (PH2O) was essential for the steady production of C2H6 and H2. The C2H6 production rate was 0.79 μmol min−1 for 50 mg of Pd/Ga2O3 powder at PH2O = 3.6 kPa. The apparent quantum efficiency (AQE) for C2H6 production was 5.1%, which is much higher than that of conventional photocatalytic NOCM in the absence of water vapor. The importance of water adsorbates on the photocatalyst surface was suggested by water vapor adsorption isotherm and Fourier transform infrared (FT-IR) spectroscopy. It is revealed that multilayered water molecules adsorbed on the photocatalyst surface play a role as a reaction field that promotes the dehydrogenative coupling of CH4.

Time-resolved mid-infrared dual-comb spectroscopy

Dual-comb spectroscopy can provide broad spectral bandwidth and high spectral resolution in a short acquisition time, enabling time-resolved measurements. Specifically, spectroscopy in the mid-infrared wavelength range is of particular interest, since most of the molecules have their strongest rotational-vibrational transitions in this “fingerprint” region. Here we report time-resolved mid-infrared dual-comb spectroscopy, covering ~300 nm bandwidth around 3.3 μm with 6 GHz spectral resolution and 20 μs temporal resolution. As a demonstration, we study a CH4/He gas mixture in an electric discharge, while the discharge is modulated between dark and glow regimes. We simultaneously monitor the production of C2H6 and the vibrational excitation of CH4 molecules, observing the dynamics of both processes. This approach to broadband, high-resolution, and time-resolved mid-infrared spectroscopy provides a new tool for monitoring the kinetics of fast chemical reactions, with potential applications in various fields such as physical chemistry and plasma/combustion analysis.

Catalytic Oxidative Coupling of Methane Assisted by Electric Power over a Semiconductor Catalyst

Abstract Oxidative coupling of methane (OCM) on La2O3 semiconductor catalysts at 423 K external temperature was investigated. DC power supplied from two electrodes in a catalyst bed enabled stable and selective production of C2H6 and C2H4 over Sr–La2O3 (Sr/La = 1/200 and 1/20), but plasma reactions proceeded over other catalysts. The electrical conductivity of the semiconductor catalyst was important for controlling this reaction. A high yield of C2 (49% selectivity, 51.3% O2 conversion) was obtained using 2.7 W of electricity at a lower external temperature (423 K).

A kinetic modeling study of ethylene pyrolysis

A kinetic model is presented for the pyrolysis of ethylene at pressures ranging from 0.8 to 27 kPa and temperatures from 774 to 1023 K. The model is based on experimental measurements of C2H2, C2H6, C3H6, 1-C4H8, and 1,3-C4H6. In this temperature range the reaction is initiated by the disproportionation of C2H4 and the observed products result from reactions of the C2H3 and C2H5 radicals produced in this process. The C2H2 and 1,3-C4H6 result from reactions of C2H3 while C2H6, C3H6, and 1-C4H8 result from reactions of C2H5. C2H2 is produced exclusively by the decomposition of the C2H3 radical. This process is in its falloff region throughout the range of experimental conditions examined and the yield of C2H2 provides a measure of the degree of falloff. The production of 1,3-C4H6 is controlled by the reaction C4H7 –> C4H6 + H. The rate constants for this reaction were independent of pressure and are given as a function of temperature by k = 2.2 × 1013 exp (-19.6 × 103/T). Production of C2H6 is controlled by the reaction C2H5 + C2H4 –> C2H6 + C2H3. The rate constant for this reaction is given as a function of temperature by k = 5.83 × 1011 exp (-14.6 × 103/T). C3H6 is produced by decomposition of 2-C4H9 and is controlled kinetically by the isomerization reaction 1-C4H9 –> 2-C4H9. The temperature dependence of the rate constants obtained for this reaction leads to a preexponential factor of approximately 3 × 1016 and an activation energy of approximately 200 kJ mol-1. The yield of 1-C4H8 is controlled by 1-C4H9 –> 1-C4H8 + H. The rate constants for this reaction were independent of pressure and are given as a function of temperature by k = 2.97 × 1012 exp (-17.1 × 103/T). Key words: kinetic modeling, ethylene pyrolysis.

Detection of abundant ethane and methane, along with carbon monoxide and water, in comet C/1996 B2 Hyakutake: evidence for interstellar origin.

The saturated hydrocarbons ethane (C2H6) and methane (CH4) along with carbon monoxide (CO) and water (H2O) were detected in comet C/1996 B2 Hyakutake with the use of high-resolution infrared spectroscopy at the NASA Infrared Telescope Facility on Mauna Kea, Hawaii. The inferred production rates of molecular gases from the icy, cometary nucleus (in molecules per second) are 6.4 X 10(26) for C2H6, 1.2 X 10(27) for CH4, 9.8 X 10(27) for CO, and 1.7 X 10(29) for H2O. An abundance of C2H6 comparable to that of CH4 implies that ices in C/1996 B2 Hyakutake did not originate in a thermochemically equilibrated region of the solar nebula. The abundances are consistent with a kinetically controlled production process, but production of C2H6 by gas-phase ion molecule reactions in the natal cloud core is energetically forbidden. The high C2H6/CH4 ratio is consistent with production of C2H6 in icy grain mantles in the natal cloud, either by photolysis of CH4-rich ice or by hydrogen-addition reactions to acetylene condensed from the gas phase.