Feed Gas Research Articles

Ionic liquid-ethanol mixed solvent design exemplified for the decarbonization of shale gas and biogas

Shale gas and biogas, recognized as “clean” energy sources, hold the potential to replace fossil fuels, necessitating efficient decarbonization processes. This study proposes a mixed solvent, combining ionic liquid (IL) and ethanol, for a cost- and energy-effective decarbonization approach. Initially, a computer-aided molecular method optimizes the IL molecule structure, identifying 1-hydroxy-3-methyl-pyridinium trifluoroacetate ([OHMPY][CF3COO]) through solving a formulated mixed-integer nonlinear programming (MINLP) problem. The [OHMPY][CF3COO]-ethanol mixed solvent's performance is validated in shale gas and biogas decarbonization across diverse gas compositions and feed conditions. A comprehensive comparison with the traditional MDEA-based CO2 removal process is conducted, evaluating energy, economic, and environmental aspects. Results indicate that the [OHMPY][CF3COO]-ethanol decarbonization process offers 30.65%-41.48% power savings, a 3.68%-17.18% reduction in investment costs, and an 18.08%–22.45% decrease in CO2 emissions. These findings underscore the significant potential of the proposed IL-ethanol binary mixed solvent in decarbonization processes.

Novel ethane recovery process from natural gas using ZIF-8/water–glycol slurry: Techno-economic and energy consumption evaluation

Ethane recovery is a vital step in natural gas processing and can provide raw material for ethylene production. The widely used cryogenic separation process is energy intensive, and the absorption-adsorption coupling process based on porous ZIF-8 slurry (SorbPro I) has been proven to be more energy-efficient. To further reduce energy consumption, this paper proposes a novel process with two absorption-adsorption columns (SorbPro II) and establishes its mathematical model by equilibrium stage method. Taking the natural gas with an ethane content of 6.19 mol% at 300,000 Nm3/d as a case study, the operating parameters of SorbPro I and SorbPro II are optimized by sensitivity analysis, and ethane recovery ratio of both processes can reach 90 %. The techno-economic/energy consumption evaluations of the two processes are conducted. Results show that the total annualized cost and the energy consumption per Nm3 feed gas of SorbPro II are 41.7 % and 47.7 % lower than those of SorbPro I, respectively. It indicates that SorbPro II has the same separation performance as SorbPro I, but is more economical.

Selective CO2 Capture from CO2/N2 Gas Mixtures Utilizing Tetrabutylammonium Fluoride Hydrates.

Gas hydrates, a type of inclusion compound capable of trapping gas molecules within a lattice structure composed of water molecules, are gaining attention as an environmentally benign gas storage or separation platform. In general, the formation of gas hydrates from water requires high-pressure and low-temperature conditions, resulting in significant energy consumption. In this study, tetrabutylammonium fluoride (TBAF) was utilized as a thermodynamic promoter forming a semi-clathrate-type hydrate, enabling gas capture or separation at room temperature. Those TBAF hydrate systems were explored to check their capability of CO2 separation from flue gas, the mixture of CO2 and N2 gases. The formation rates and gas storage capacities of TBAF hydrates were systematically investigated under various concentrations of CO2, and they presented selective CO2 capture behavior during the hydrate formation process. The maximum gas storage capacities were achieved at 2.36 and 2.38 mmol/mol for TBAF·29.7 H2O and TBAF·32.8 H2O hydrate, respectively, after the complete enclathration of the feed gas of CO2 (80%) + N2 (20%). This study provides sufficient data to support the feasibility of TBAF hydrate systems to be applied to CO2 separation from CO2/N2 gas mixtures based on their CO2 selectivity.

Experimental study on charging and discharging characteristics of copper finned metal hydride reactor for stationary hydrogen storage applications

With the shift in power generation methods from conventional to renewable, the need for energy storage has increased, and hydrogen as a carrier has great potential. The storage of hydrogen is one of the main obstacles to the effective deployment of the hydrogen economy. Since metal hydride offers a higher energy density than conventional methods, it can potentially be used to store and deliver hydrogen. Also, the metal hydride hydrogen storage system is the primary element of the energy storage system that connects hydrogen production and consumption. Therefore, the present study is focused on the development and testing of a metal hydride reactor. In the present experimental study, 9 kg of La0.7Ce0.1Ca0.3Ni5 is loaded in a single tube copper finned reactor attached to an external jacket, and the charging and discharging characteristics related to hydrogen storage are analysed along with variations in its thermal performance under various operating conditions. Also, the effect of HTF temperature on the hydrogen release performance of the copper finned reactor is studied under constant discharge pressure and constant discharge flow rate. Further, a comparison has been made between the copper and aluminium finned reactors. This fabricated copper finned reactor attained volumetric and gravimetric storage densities of 21.78 kg per m3 of H2 and 0.77%, respectively. The results indicated that La0.7Ce0.1Ca0.3Ni5 filled within the copper finned reactor stores 1.45 wt.% (130.7 g) of hydrogen in 680 s, corresponding to 25 bar feed gas pressure. At the HTF temperature of 60 °C, the copper-finned reactor discharged 1.42 wt.% (127.3 g) of hydrogen in 1450 s, showing the release of 98% of the stored mass of hydrogen. Further, the developed copper finned MH reactor could supply hydrogen at a constant rate of 13 lpm with a capability of 90% discharge even at a discharge temperature of 30 °C. Beside this, the comparative results showed that adding copper fins showed a considerable improvement over aluminium fins during discharging compared to the charging process. The copper-finned reactor consumed 20.9% and 23.6% less time to release 1 wt.% of hydrogen than the aluminium-finned reactor at discharge temperatures of 40 °C and 50 °C, respectively.

THE COMPARISON OF OXIDATION EFFICIENCY OF REACTIVE OXYGEN SPECIES (ROS): PILOT SCALE OF MICROBUBBLE TECHNOLOGIES WITH OXYGEN CONCENTRATION

The objective of this study is to assess and compare the effectiveness of an oxidizing agent. Within the field of advanced oxidation processes (AOPs), ozone, a highly reactive gas, generates reactive oxygen species (ROS) as byproducts through chemical reactions. The study employed a dielectric barrier discharge (DBD) plasma generator to produce ozone gas. This study was carried out under different gas source conditions, including both air and oxygen. Additionally, the ROS produced as byproducts from the interaction between ozone gas and water were measured using oxidation-reduction potential (ORP) values. The ORP values exhibit strong foundational attributes for both ozone dissolution and ROS oxidation efficiency. To extend the interaction duration between ozone gas and water, a stone diffuser was utilized to introduce ozone gas into the water. This mechanism resulted in the creation of ozone microbubbles through a process known as cavitation. The results illustrate a positive relationship between the flow rate and ozone yield. This trend reached its highpoint with the highest observed ozone concentrations approximately 14.11 mg/L for oxygen and 4.55 mg/L for air both achieved at a flow rate of 11 L/min. Furthermore, the highest ozone concentrations were recorded at 15.17 mg/L for oxygen and 12.59 mg/L for air after a 10 min discharge period. Interestingly, ozone generated from oxygen feed gas exhibited a higher concentration yield than that from air feed gas. Moreover, the ORP value displayed a continuous increase with longer treatment times, eventually stabilizing at around the 15 min. This pattern corresponded to the water reaching its highest the ORP values approximately 821 mV for oxygen and 569 mV for air. In summary, this study emphasizes the potential benefits of utilizing ozone as an effective oxidant in both gaseous (ozone gas) and liquid (ROS) phases. It especially emphasizes the essential role played by the generation of ozone and ROS from an oxygen-fed gas source. Moreover, it highlights the significance of maintaining an optimal flow rate of 11 L/min and a discharge duration of 10 min for achieving the highest ozone concentration. Similarly, a treatment time of 15 min for the liquid phase is recommended to maximize ORP values. Both of these values indicate the highest potential advantages for producing an effective oxidant.

Remediation of oil-drilling cuttings by ozonation in a bubble flow reactor

Oil-drilling cuttings (ODCs) are the major wastes generated during oil/gas exploration and extraction. In the present work, a new method based on ozonation is suggested for the remediation of ODCs at ambient conditions, without pre-drying. During the ozonation process, the pressure drop across the gas phase along with the pH, redox potential, and temperature of liquid phase are monitored with the aid of built-in sensors. Occasionally, solid and liquid samples are collected to measure the total organic carbon (TOC) of each phase as a function of time, while the concentration of the total petroleum hydrocarbons (TPH) is measured before and after the completion of treatment. The maximum TOC removal efficiency for the solid phase reached ∼60% and that of TPH ∼ 40% whereas the energy efficiency was ∼ 0.1 kWh/g-TOC. The main mechanisms of ODC remediation are the mass-transfer of organic species from the solid to aqueous phase, and the direct oxidation by dissolved ozone, whereas their synergistic action is reflected in fluctuations of TOC concentration in liquid phase. The TOC removal efficiency of the solid phase increases with the flow rate decreasing, the ozone concentration increasing, and the mass ratio of ODC to seawater (SW) increasing. Ozonation in the liquid phase after its separation from treated ODC proceeds very fast through the direct oxidation by ozone. The process energy efficiency is favoured for low ozone concentration, low gas flow rate, high ODC to SW mass ratio, oxygen as feed gas, and without the addition of sodium dodecyl sulphate (SDS) as surfactant.

Permeance of Condensable Gases in Rubbery Polymer Membranes at High Pressure.

The gas transport properties of thin film composite membranes (TFCMs) with selective layers of PolyActive™, polydimethylsiloxane (PDMS), and polyoctylmethylsiloxane (POMS) were investigated over a range of temperatures (10-34 °C; temperature increments of 2 °C) and pressures (1-65 bar abs; 38 pressure increments). The variation in the feed pressure of condensable gases CO2 and C2H6 enabled the observation of peaks of permeance in dependence on the feed pressure and temperature. For PDMS and POMS, the permeance peak was reproduced at the same feed gas activity as when the feed temperature was changed. PolyActive™ TFCM showed a more complex behaviour, most probably due to a higher CO2 affinity towards the poly(ethylene glycol) domains of this block copolymer. A significant decrease in the permeate temperature associated with the Joule-Thomson effect was observed for all TFCMs. The stepwise permeance drop was observed at a feed gas activity of p/po ≥ 1, clearly indicating that a penetrant transfer through the selective layer occurs only according to the conditions on the feed side of the membrane. The permeate side gas temperature has no influence on the state of the selective layer or penetrant diffusing through it. The most likely cause of the observed TFCM behaviour is capillary condensation of the penetrant in the swollen selective layer material, which can be provoked by the clustering of penetrant molecules.

An Ultra‐stable Supramolecular Framework Based on Consecutive Side‐by‐side Hydrogen Bonds for One‐step C2H4/C2H6 Separation

AbstractThe one‐step efficient separation of high‐purity C2H4 from C2H4/C2H6 mixtures by hydrogen‐bonded organic frameworks (HOFs) faces two problems: lack of strategies for constructing stable pores in HOFs and how to obtain high C2H6 selectivity. Herein, we have developed a microporous Mortise‐Tenon‐type HOF (MTHOF‐1, MT is short for Mortise‐Tenon structure) with a new self‐assembly mode for C2H4/C2H6 separation. Unlike previous HOFs which usually possess discrete head‐to‐head hydrogen bonds, MTHOF‐1 is assembled by unique consecutive side‐by‐side hydrogen bonds, which result in mortise‐and‐tenon pores decorated with orderly arranged amide groups and benzene rings. As expected, MTHOF‐1 exhibits excellent stability under various conditions and shows clear separation trends for C2H6/C2H4. The IAST selectivity is as high as 2.15 at 298 K. More importantly, dynamic breakthrough experiments have demonstrated that MTHOF‐1 can effectively separate the C2H6/C2H4 feed gas to obtain polymer‐grade C2H4 in one step even under high‐humidity conditions.

An Ultra-stable Supramolecular Framework Based on Consecutive Side-by-side Hydrogen Bonds for One-step C2H4/C2H6 Separation.

The one-step efficient separation of high-purity C2H4 from C2H4/C2H6 mixtures by hydrogen-bonded organic frameworks (HOFs) faces two problems: lack of strategies for constructing stable pores in HOFs and how to obtain high C2H6 selectivity. Herein, we have developed a microporous Mortise-Tenon-type HOF (MTHOF-1, MT is short for Mortise-Tenon structure) with a new self-assembly mode for C2H4/C2H6 separation. Unlike previous HOFs which usually possess discrete head-to-head hydrogen bonds, MTHOF-1 is assembled by unique consecutive side-by-side hydrogen bonds, which result in mortise-and-tenon pores decorated with orderly arranged amide groups and benzene rings. As expected, MTHOF-1 exhibits excellent stability under various conditions and shows clear separation trends for C2H6/C2H4. The IAST selectivity is as high as 2.15 at 298 K. More importantly, dynamic breakthrough experiments have demonstrated that MTHOF-1 can effectively separate the C2H6/C2H4 feed gas to obtain polymer-grade C2H4 in one step even under high-humidity conditions.

Supermassive black hole spin evolution in cosmological simulations with OpenGadget3

The mass and spin of massive black holes (BHs) at the centre of galaxies evolve due to gas accretion and mergers with other BHs. Besides affecting the evolution of relativistic jets, for example, the BH spin determines the efficiency with which the BH radiates energy. Using cosmological, hydrodynamical simulations, we investigate the evolution of the BH spin across cosmic time and its role in controlling the joint growth of supermassive BHs and their host galaxies. We implemented a sub-resolution prescription that models the BH spin, accounting for both BH coalescence and misaligned accretion through a geometrically thin, optically thick disc. We investigated how BH spin evolves in two idealised setups, in zoomed-in simulations and in a cosmological volume. The latter simulation allowed us to retrieve statistically robust results for the evolution and distribution of BH spins as a function of BH properties. We find that BHs with $ M BH grow through gas accretion, occurring mostly in a coherent fashion that favours spin-up. Above $ M BH the gas directions of subsequent accretion episodes are often uncorrelated with each other. The probability of counter-rotating accretion and hence spin-down increases with BH mass. In the latter mass regime, BH coalescence plays an important role. The spin magnitude displays a wide variety of histories, depending on the dynamical state of the gas feeding the BH and the relative contribution of mergers and gas accretion. As a result of their combined effect, we observe a broad range of values of the spin magnitude at the high-mass end. Reorientation of the BH spin direction occurs on short timescales ($ 10$ Myr) only during highly accreting phases ($ f Edd 0.1$). Our predictions for the distributions of BH spin and spin-dependent radiative efficiency as a function of BH mass are in very good agreement with observations.

Tungsten-doped high-silica CHA zeolite membranes with improved hydrophobicity for CO2 separation

High-silica CHA (SSZ-13) zeolites membranes, with pore size between the molecular size of CO2 and N2 or CH4, are promising for some industrial CO2 separation process. Considering water is typically present in these industrial gas feed and the negative impact of moisture on the membranes’ gas permeation, it is highly desirable to increase the surface hydrophobicity of membranes to reduce the adsorption of water. In this paper, a W-doping strategy was proposed to increase the hydrophobicity of SSZ-13 membranes by eliminating the silanols on the surface, and the W-doped high-silica CHA (W-SSZ-13) zeolite membranes were prepared for the first time. Characterizations such as SEM, XRD, and XPS confirmed the successful incorporation of W into CHA membrane. The incorporation of W reduced the pore mouth size, and the W-SSZ-13 zeolite membranes showed improved CO2/N2 and CO2/CH4 separation performance. After W-doping, the maximum separation factors (αmax) for the CO2/N2 mixture with equimolar composition under dry conditions increased from 8.8 to 16.9, and for the equimolar CO2/CH4 mixture, the value increased from 105.9 to 176. The W-SSZ-13 membranes also showed better separation performance under wet conditions. For both systems, the W-SSZ-13 membrane showed higher αmax and less CO2 permeance reductions, indicating a more resistance in wet conditions.

Condition‐dependent NOx adsorption/desorption over Pd/BEA: A combined microreactor and in situ DRIFTS study

AbstractPd/BEA is chosen as a model passive NOx adsorber (PNA) to elucidate the effect of the feed gas composition on the NOx adsorption/desorption behavior. The Brønsted acid and the partially hydrolyzed framework Al (P‐HAl(OH)) sites in HBEA adsorb NO and NO2 under dry conditions. Moreover, the performance of HBEA is not affected by CO, while CO inhibits nitrate formation and promotes NO adsorption via the Pd(NO)(CO) complexes formation over Pd/BEA. H2O inhibits NO adsorption over the Brønsted acid and P‐HAl(OH) sites, and ionic Pd is the only active site for NOx adsorption under wet conditions. Furthermore, NO adsorption over hydrated Pd (Pd2+(OH)(NO)(H2O)3) is weaker than NO adsorption over bare ionic Pd (Z2[Pd2+(NO)], Z[Pd2+(OH)(NO)]). Dehydration of Pd2+(OH)(NO)(H2O)3 forms more stable Z[Pd2+(OH)(NO)] during desorption. The NO adsorption capacity of Pd/BEA improves in the presence of CO under both dry and wet conditions by forming a stable carbonyl–nitrosyl complex.

On the formation of ammonia from the thermal decomposition of hydroxylammonium nitrate vapor

The ionic liquid hydroxylammonium nitrate (HAN) is a promising propellant for various types of spacecraft propulsion systems. With respect to combustion and plasma-based electric propulsion, the thermal decomposition of HAN into gas phase species provides a convenient feed gas supply. While the decomposition of HAN in the liquid phase has been extensively studied, little is known about the decomposition chemistry of HAN vapor interacting with heated surfaces. The ability to decompose HAN vapor on a reactive surface could provide a means to control the feed gas composition and enhance the performance of spacecraft propulsion systems.In this initial qualitative study, HAN was vaporized and thermally decomposed using porous 316-stainless-steel and quartz disks under vacuum conditions. Decomposition products with low vapor pressures would condense on an in-line quartz tube which was subsequently collected and analyzed with Raman spectroscopy, NMR spectroscopy, and FT-IR spectroscopy. At temperatures above 440 K the 316-stainless-steel system produced significant quantities of ammonia which reacted with vaporized nitric acid to form ammonium nitrate. Temperatures below 440 K yielded partial HAN decomposition which resulted in a binary mixture of HAN and ammonium nitrate. The degree to which HAN was consumed was determined by analysis of the 1008 cm−1N-OH asymmetric Raman band of HAN and the 1049 cm−1 symmetric stretching Raman band of the nitrate ion, NO3−. The quartz system yielded significantly different results with no ammonium nitrate detected at temperatures above 440 K. Reformed HAN was the primary product detected at lower temperatures. The difference in reported measurements and visual observations highlights the distinct differences in HAN vapor decomposition chemistry from the two materials examined.

Boosting CO2 Electroreduction over a Covalent Organic Framework in the Presence of Oxygen.

Herein, we propose an oxygen-containing species coordination strategy to boost CO2 electroreduction in the presence of O2. A two-dimensional (2D) conjugated metal-covalent organic framework (MCOF), denoted as NiPc-Salen(Co)2-COF that is composed of the Ni-phthalocyanine (NiPc) unit with well-defined Ni-N4-O sites and the salen(Co)2 moiety with binuclear Co-N2O2 sites, is developed and synthesized for enhancing the CO2RR under aerobic condition. In the presence of O2, one of the Co sites in the NiPc-Salen(Co)2-COF that coordinated with the intermediate of *OOH from ORR could decrease the energy barrier of the activation of CO2 molecules and stabilize the key intermediate *COOH of the CO2RR over the adjacent Co center. Besides, the oxygen species axially coordinated Ni-N4-O sites can favor in reducing the energy barrier of the intermediate *COOH formation for the CO2RR. Thus, NiPc-Salen(Co)2-COF exhibits high oxygen-tolerant CO2RR performance and achieves outstanding CO Faradaic efficiency (FECO) of 97.2 % at -1.0 V vs. the reversible hydrogen electrode (RHE) and a high CO partial current density of 40.3 mA cm-2 at -1.1 V in the presence of 0.5 % O2, which is superior to that in pure CO2 feed gas (FECO=94.8 %, jCO=19.9 mA cm-2). Notably, the NiPc-Salen(Co)2-COF achieves an industrial-level current density of 128.3 mA cm-2 in the flow-cell reactor with 0.5 % O2 at -0.8 V, which is higher than that in pure CO2 atmosphere (jCO=104.8 mA cm-2). It is worth noting that an excellent FECO of 86.8 % is still achieved in the presence of 5 % O2 at -1.0 V. This work provides an effective strategy to enable the CO2RR under O2 atmosphere by utilizing the *OOH intermediates of ORR to boost CO2 electroreduction.

A Numerical Study on the Process of the H2 Shaft Furnace Equipped with a Center Gas Distributor

In order to explore technically feasible options for improving the performance of the H2 shaft furnace (HSF), a previously built and validated computational fluid dynamics (CFD) model was employed in the current work to assess the potential of the operation based on a center gas distributor (CGD). A set of simulations was performed to mimic scenarios where different amounts of feed gas (0–30% of 1400 Nm3/t-pellet) are injected via the CGD located at the bottom of the HSF. The results showed that a relatively large stagnant zone (approximately 8.0-m in height and 0.3-m in diameter) exists in the furnace center where the gas flows are weak owing to an overly shortened penetration depth of the H2 stream solely injected from the circumferentially installed bustle-pipe. When adopting the CGD operation, however, the center gas flows can be effectively enhanced, consequently squeezing the stagnant zone and thus leading to a better overall performance of the HSF. In particular, the uniformity of the final reduction degree (mean values ranging from 0.8846 to 0.8896) of the solid phase (i.e., pellets) is well improved under the investigated condition where the total gas feed rate is fixed at 1400 Nm3/t-pellet. As for the final mean reduction degree of solid and top gas utilization degree, the two performance indicators rise to maximal values when the CGD feed ratio is increased to 20% and then slightly drop with a further increase in the ratio.

Boosting CO2 Electroreduction over a Covalent Organic Framework in the Presence of Oxygen

AbstractHerein, we propose an oxygen‐containing species coordination strategy to boost CO2 electroreduction in the presence of O2. A two‐dimensional (2D) conjugated metal‐covalent organic framework (MCOF), denoted as NiPc‐Salen(Co)2‐COF that is composed of the Ni‐phthalocyanine (NiPc) unit with well‐defined Ni−N4−O sites and the salen(Co)2 moiety with binuclear Co−N2O2 sites, is developed and synthesized for enhancing the CO2RR under aerobic condition. In the presence of O2, one of the Co sites in the NiPc‐Salen(Co)2‐COF that coordinated with the intermediate of *OOH from ORR could decrease the energy barrier of the activation of CO2 molecules and stabilize the key intermediate *COOH of the CO2RR over the adjacent Co center. Besides, the oxygen species axially coordinated Ni−N4−O sites can favor in reducing the energy barrier of the intermediate *COOH formation for the CO2RR. Thus, NiPc‐Salen(Co)2‐COF exhibits high oxygen‐tolerant CO2RR performance and achieves outstanding CO Faradaic efficiency (FECO) of 97.2 % at −1.0 V vs. the reversible hydrogen electrode (RHE) and a high CO partial current density of 40.3 mA cm−2 at −1.1 V in the presence of 0.5 % O2, which is superior to that in pure CO2 feed gas (FECO=94.8 %, jCO=19.9 mA cm−2). Notably, the NiPc‐Salen(Co)2‐COF achieves an industrial‐level current density of 128.3 mA cm−2 in the flow‐cell reactor with 0.5 % O2 at −0.8 V, which is higher than that in pure CO2 atmosphere (jCO=104.8 mA cm−2). It is worth noting that an excellent FECO of 86.8 % is still achieved in the presence of 5 % O2 at −1.0 V. This work provides an effective strategy to enable the CO2RR under O2 atmosphere by utilizing the *OOH intermediates of ORR to boost CO2 electroreduction.

Polarized hydroxyapatite, a ceramic nanocatalyst to convert automotive carbon emissions into ethanol

This paper is aimed to develop ultrananoporous polarized hydroxyapatite (HAp) catalyst and evaluate its performance in transforming CO2 into useable ethanol considering three different scenarios: 1) a batch reaction using a mixture of CO2 and CH4 as feeding gas; 2) a batch reaction using as reactant exhaust gases captured from the fumes of diesel vehicles; and 3) a continuous flow reaction using pure CO2 as feeding gas. Ultrananoporous HAp scaffolds were prepared using a four-step process: 1) as prepared HAp powder was mixed with 60% wt. of a commercial hydrogel at low-temperature; 2) the resulting paste was shaped at low temperature to reduce the adhesion between the metallic tools and the mixture, enhancing the homogeneity of the sample; 3) the shaped paste was calcined in air by applying 1000 ºC during 2 h to eliminate the hydrogel; and 4) an external DC electric field of 3 kV/cm was imposed at 1000 ºC during 1 h to the calcined scaffold. The resulting polarized scaffolds both ultrananoporosity and catalytic activation. Thus, the mass: volume ratio of the ultrananoporous catalyst was much lower than that of conventional HAp catalyst (718 vs 5093 g/L. Furthermore, the ethanol yield was much higher (up to a factor of ×21.4) for the ultrananoporous catalyst than for the compact one, allowing us to conclude that ultrananoporous polarized HAp catalyst is a promising technology for transforming CO2 into valuable chemical products from highly polluted gases, especially those coming from road, sea and air transport.

Effect of thermal gas quenching on NOx production by atmospheric pressure rotating arc Plasma: A pathway towards Eco-Friendly fertilizer

Plasma nitrogen fixation allows an alternative ammonia production path compared to the classical industrial Haber-Bosch process, due to the emergence of low-cost and environment friendly renewable energy. However, the high energy cost due to high-temperature reaction condition and reverse reactions in typical “warm” plasmas (gliding arc and rotating gliding arc) lies as a bottleneck of its industrial application. As a possible solution to enhance the efficiency of the process, the effect of thermal gas quenching on nitrogen fixation by rotating arc plasma are investigated. The NOx (i.e. NO, NO2) yield, energy cost, and NOx selectivity are obtained under variable operating conditions (i.e. oxygen fraction in the feed gas, arc length, specific energy input, varying quench gas and quenching ratio). With the help of quenching, the maximum achievable NOx concentration was enhanced from 5.16 to 5.8%. The enhancement is achieved by mitigating loss reactions through quenching and it is supported by the integration of experimental findings, plasma diagnostics using optical emission spectroscopy, and the application of a zero-dimensional chemical kinetic model.

"NOVOSIBIRSK" MUD VOLCANO AND EVIDENCE OF ITS ACTIVATIONS (LAKE BAIKAL)

An integrated study of mud volcanoes in the World Ocean is important for making assessment of potential geological-ecological disasters caused by rapid large-volume gas discharge into the water column and mud volcano eruptions at the bottom. The study of mud-volcanic activity in the past and determination of its periodicity are pioneering for the Baikal. The mud volcanoes and other hydrate-bearing structures are largely concentrated in the Middle Baikal basin along the tectonic faults. The most representative example of these phenomena is the "Gydratny" fault, four of six structures along which are mud volcanoes. An integrated geological-geophysical study (seismoacoustic and hydroacoustic sounding and geological sampling) of the "Novosibirsk" mud volcano, the largest and well-pronounced feature of the lake bottom relief, confirmed its structural identity with classical submarine mud volcanoes. The "Novosibirsk" mud volcano possesses all major elements of other single hydrate-bearing mud volcanoes of the lake which include volcanic cone in the bottom relief, vertical acoustically not transparent feeding channel, mud-volcanic breccia, gas saturation, and gas hydrates. This makes it one of the reference hydrate-bearing mud volcanic-type structures of Lake Baikal.The analysis of the bottom hydroacoustic profiling yielded evidence of the Late Pleistocene mud-volcanic eruptions shaped as two layers-flows at sub-bottom depths of 15 and 26 m (30 and 50 kyr ago, respectively). The presence of mud-volcanic breccia beneath the thin Holocene diatomic silt deposits testifies to the Holocene mud volcano activation due to the warm fluid rising from the depths to the volcano roots along the active segment of the tectonic fault in accordance with the model of the "Baikal-type" mud volcanism. Using the "Novosibirsk" mud volcano and the "Gydratny" fault as an example, it can be shown that the past tectonic activity of the Baikal basin may be determined based on the knowledge of the structure and evolution of the mud volcanoes of the lake.

Importance of Site Diversity and Connectivity in Electrochemical CO Reduction on Cu.

Electrochemical CO2 reduction on Cu is a promising approach to produce value-added chemicals using renewable feedstocks, yet various Cu preparations have led to differences in activity and selectivity toward single and multicarbon products. Here, we find, surprisingly, that the effective catalytic activity toward ethylene improves when there is a larger fraction of less active sites acting as reservoirs of *CO on the surface of Cu nanoparticle electrocatalysts. In an adaptation of chemical transient kinetics to electrocatalysis, we measure the dynamic response of a gas diffusion electrode (GDE) cell when the feed gas is abruptly switched between Ar (inert) and CO. When switching from Ar to CO, CO reduction (COR) begins promptly, but when switching from CO to Ar, COR can be maintained for several seconds (delay time) despite the absence of the CO reactant in the gas phase. A three-site microkinetic model captures the observed dynamic behavior and shows that Cu catalysts exhibiting delay times have a less active *CO reservoir that exhibits fast diffusion to active sites. The observed delay times and the estimated *CO reservoir sizes are affected by catalyst preparation, applied potential, and microenvironment (electrolyte cation identity, electrolyte pH, and CO partial pressure). Notably, we estimate that the *CO reservoir surface coverage can be as high as 88 ± 7% on oxide-derived Cu (OD-Cu) at high overpotentials (-1.52 V vs SHE) and this increases in reservoir coverage coincide with increased turnover frequencies to ethylene. We also estimate that *CO can travel substantial distances (up to 10s of nm) prior to desorption or reaction. It appears that active C-C coupling sites by themselves do not control selectivity to C2+ products in electrochemical COR; the supply of CO to those sites is also a crucial factor. More generally, the overall activity of Cu electrocatalysts cannot be approximated from linear combinations of individual site activities. Future designs must consider the diversity of the catalyst network and account for intersite transportation pathways.