Gas-solid Reaction Research Articles

Relatively low temperature defluorination and carbon coating in CFx by dimethyl silicone oil/polyethylene glycol for enhancing performance of lithium primary battery

Because of the presence of electrochemically inactive C-F2 bond and poor electronic conductivity of C-F, the discharge performance of lithium fluorocarbon (Li/CFx) batteries is limited, despite their extensive use in commercial fields. In this study, dimethyl silicone oil/polyethylene glycol was adopted to improve the performance of CFx through relatively low temperature (350 °C) defluorination and carbon coating. The uniform mixing of dimethyl silicone oil with CFx and the subsequent gas–solid reaction enables mild defluorination, transforming C-F2 into semi-ionic C-F with high conductivity. Furthermore, this dimethyl silicone oil/ polyethylene glycol treated CFx under 350 °C prevent the thermal decomposition of C-F during both of the defluorination and carbon coating process, resulting in improving the electrical performance and capacity protection of CFx. Specifically, the modified CFx cathode exhibits a 2.7 V discharge platform, a discharge capacity of 859.1 mAh/g and the energy density of 1889.7 Wh kg−1 at 0.01C. This approach allows for large scale adjustments of CFx with excellent performance, making it easy to industrialization.

SO3 removal by submicron absorbents synthesized via inhibition method: The product layer grows like parallel peaks

Injecting calcium hydroxide powder into the flue gas is an effective strategy for SO3 removal. However, commercial calcium hydroxide has several disadvantages, including large particle size, low efficiency, and unsuitability for excessive grinding. In this work, sub-micron calcium hydroxide was synthesized by an inhibition method and its performance for SO3 removal from flue gas was investigated on a pilot-scale platform (120 Nm3/h). When the concentration of sodium alginate solution was 100 mg/L, the average particle size of calcium hydroxide decreased from 13.66 µm to 0.84 µm, which improved the SO3 removal (92.1 %) and conversion of the absorbent. The results of the fixed-bed experiments indicate that the absorption kinetics of the reaction is consistent with the Bangham model. In addition, density functional theory verifies that calcium hydroxide captures SO3 by chemisorption. The AFM image shows that the calcium sulfate whiskers produced during the reaction grow like parallel peaks on the adsorbent surface. The calculations suggest that the driving force for SO3 adsorption originates from Ca-p orbital (Ca(OH)2) and O-s orbital (SO3) hybridization. This study complements the island growth mechanism for gas-solid two-phase reactions and provides an effective method for removing SO3 from flue gas in coal-fired power plants. In addition, it will provide an important reference for the development of submicron adsorbents.

Nitrogenation of Nd(Fe,Mo)12 powders for sintered magnets

The intermetallic Rare Earth-Fe12 (REFe12) compounds are considered as the strongest candidates for alternative high-performance permanent magnet material, thanks to the combination of high magnetocrystalline anisotropy, high Curie temperature and moderate saturation magnetization. However, the NdFe12 based compounds suffer from a weak uniaxial magnetocristalline anisotropy at room temperature. The insertion of light elements, like nitrogen, induces a strong uniaxial anisotropy and an increase of the Curie temperature as well. Nevertheless, the nitrogenation of these compounds have proved to be tricky, as the reaction kinetics is very slow at moderate temperatures, whereas the decomposition of the 1–12 phase occurs at higher temperatures. In the present study the aim is to develop nitrogenated powders suitable for the manufacture of Nd(Fe,Mo)12N-based sintered magnets, starting from Nd(Fe,Mo)12 precursors prepared by strip-casting. The nitrogenation of Nd(Fe,Mo)12 powders was undertaken to analyze the mechanisms of reaction and to determine the experimental conditions allowing to avoid both the formation of α-Fe and the nitrogenation of the Nd-rich intergranular phase. Structural and magnetic investigations are performed on the parent alloys and the nitrogenated powders, allowing to identify the mechanism of the solid-gas reaction and to determine, for the first time to our knowledge, the nitrogen thermodynamic equilibrium pressure between the 1–12 phase and its nitride.

Lattice Oxygen in Photocatalytic Gas–Solid Reactions: Participator vs. Dominator

AbstractLattice‐oxygen activation has emerged as a popular strategy for optimizing the performance and selectivity of oxide‐based thermocatalysis and electrolysis. However, the significance of lattice oxygen in oxide photocatalysts has been ignored, particularly in gas–solid reactions. Here, using methane oxidation over a Ru1@ZnO single‐atom photocatalyst as the prototypical reaction and via 18O isotope labelling techniques, we found that lattice oxygen can directly participate in gas–solid reactions. Lattice oxygen played a dominant role in the photocatalytic reaction, as determined by estimating the kinetic constants in the initial stage. Furthermore, we discovered that dynamic diffusion between O2 and lattice oxygen proceeded even in the absence of targeted reactants. Finally, single‐atom Ru can facilitate the activation of adsorbed O2 and the subsequent regeneration of consumed lattice oxygen, thus ensuring high catalyst activity and stability. The results provide guidance for next‐generation oxide photocatalysts with improved activities and selectivities.

Lattice Oxygen in Photocatalytic Gas-Solid Reactions: Participator vs. Dominator.

Lattice-oxygen activation has emerged as a popular strategy for optimizing the performance and selectivity of oxide-based thermocatalysis and electrolysis. However, the significance of lattice oxygen in oxide photocatalysts has been ignored, particularly in gas-solid reactions. Here, using methane oxidation over a Ru1@ZnO single-atom photocatalyst as the prototypical reaction and via 18O isotope labelling techniques, we found that lattice oxygen can directly participate in gas-solid reactions. Lattice oxygen played a dominant role in the photocatalytic reaction, as determined by estimating the kinetic constants in the initial stage. Furthermore, we discovered that dynamic diffusion between O2 and lattice oxygen proceeded even in the absence of targeted reactants. Finally, single-atom Ru can facilitate the activation of adsorbed O2 and the subsequent regeneration of consumed lattice oxygen, thus ensuring high catalyst activity and stability. The results provide guidance for next-generation oxide photocatalysts with improved activities and selectivities.

Simultaneous tracking of ultrafast surface and gas-phase dynamics in solid-gas interfacial reactions.

Real-time detection of intermediate species and final products at the surface and near-surface in interfacial solid-gas reactions is critical for an accurate understanding of heterogeneous reaction mechanisms. In this article, an experimental method that can simultaneously monitor the ultrafast dynamics at the surface and above the surface in photoinduced heterogeneous reactions is presented. This method relies on a combination of mass spectrometry and femtosecond pump-probe spectroscopy. As a model system, the photoinduced reaction of methyl iodide on and above a cerium oxide surface is investigated. The species that are simultaneously detected from the surface and gas-phase present distinct features in the mass spectra, such as a sharp peak followed by an adjacent broad shoulder. The sharp peak is attributed to the species detected from the surface, while the broad shoulder is due to the detection of gas-phase species above the surface, as confirmed by multiple experiments. By monitoring the evolution of the sharp peak and broad shoulder as a function of the pump-probe time delay, transient signals are obtained that describe the ultrafast photoinduced reaction dynamics of methyl iodide on the surface and in the gas-phase. Finally, SimION simulations are performed to confirm the origin of the ions produced on the surface and in the gas-phase.

Cordierite ceramic membrane preparation using gas solid reaction growth for nanoparticles filtration

Mullite whiskers have been successfully grown on the surface of cordierite honeycomb ceramics by the gas-phase growth method. The cilia-like structure can significantly improve the filtration precision. The acicular mullite whiskers grew on the cordierite present nanometer-sized (200–300 nm) diameters and micrometer-sized (1–2 μm) lengths. Owing to mullite whiskers growth on surface of pores, the morphology of pores is changed and the microstructure change will lead to filtration precision increasing. The composites with the largest ratio of length/diameter mullite whiskers possess the highest filtration precision, which can reach 122.42 nm, 255.00 nm and 458.67 nm in intercepting different particle size of nano-SiO2, respectively. Moreover, the bending strength of the cordierites were enhanced due to the generation of mullite whiskers, these generated whiskers intersected with each other forming many unfixed lap-jointing points. The porous ceramics membrane with the unique microstructure has great potential application in gas-solid separation field and liquid-solid separation field.

Insight into catalytic effects of alkali metal salts addition on bamboo and cellulose pyrolysis

Alkali metal compounds have vital influence on biomass pyrolysis conversion. In this study, cellulose, and bamboo catalytic pyrolysis with different alkali metal salts catalysts (KCl, K2SO4, K2CO3, NaCl, Na2SO4, and Na2CO3) were investigated in the fixed-bed reaction system. The effects of cations (K+ and Na+) and anions (Cl-, SO42−, and CO32-) on the evolution properties of biochar, bio-oil, and gas products were explored under both in-situ and ex-situ catalytic pyrolysis. Results showed that alkali metal salts facilitated the yields of biochar and gases at the expense of that of bio-oil. Alkali metal chloride and sulfate showed a weaker catalytic effect, while alkali metal carbonate greatly promoted the generation of gas products and increased the condensation degree of biochar. With the addition of K2CO3 and Na2CO3, cyclopentanones content was over 50% from cellulose catalytic pyrolysis, and phenols content (mainly alkylphenols) reached over 80% from bamboo catalytic pyrolysis. Moreover, solid-solid catalytic reactions with K2CO3 and Na2CO3 catalysts had an important role in strikingly promoting conversion of pyrolysis products, and the solid-solid and gas-solid catalytic reactions with alkali metal carbonate catalysts were stronger than those with alkali metal chloride and sulfate catalysts. Furthermore, the possible catalytic pyrolysis mechanism of alkali metal salts on biomass pyrolysis was proposed, which is important to the high-value utilization of biomass.

Gas-Solid Reaction Synthesis and Electrocatalytic Oxygen Reduction of Pt-Skin L10-PtFe/C.

Compared to Pt/C, the atomic ordered Pt-based intermetallic compounds can deliver higher efficiency and reliable stability, and they are considered one of the ideal cathode catalysts for the next generation of fuel cells. This work proposed a simple ferrocene atmosphere annealing method to improve commercial Pt/C and convert Pt to L10-PtFe. After further acid etching treatment, the obtained carbon-supported Pt-skin L10-PtFe (Pt-skin L10-PtFe/C) with superfine particle size (∼3.3 nm) not only was highly dispersed on the carbon but possesses a thin Pt skin, like the armor of L10-PtFe. As excepted, the ORR activity of Pt-skin L10-PtFe/C (0.375 A mg-1; 0.921 mA cm-2) is far better than that of commercial Pt/C (0.121 A mg-1; 0.260 mA cm-2), and its stability is also greatly improved. Our proposed gas-solid reaction is straightforward and has great potential in producing Pt-based intermetallic catalysts on a large scale.

Kinetic analysis of reversible solid-gas reactions in films: application to the decomposition of CaCO$$_3$$ and BaCO$$_3$$ carbonates

AbstractTo determine the decomposition conditions of carbonates in the form of films, we investigated the dependence of the kinetics on carbon dioxide partial pressure, temperature and film thickness. Three different analyses allow us to determine the functional dependence of the decomposition onset temperature on the CO$$_2$$ 2 partial pressure, of the reaction rate on the temperature and of the kinetics on the film thickness. The latter analysis also reveals geometrical aspects of the reaction mechanism. Experiments have been carried out with CaCO$$_3$$ 3 and BaCO$$_3$$ 3 films. The simple geometry of the films and their relatively fast heat and gas transport allow the reaction kinetics to be easily explored.

Fuel reactor simulation for coal chemical looping process: Effects of ash on flow behavior

Chemical looping gasification (CLG) is an environmentally friendly strategy for using coal that has significant promise for application in reality. Nevertheless, the process of generating and accumulating ash from coal presents obstacles to the advancement of this technology. To fully comprehend the effects of ash from coal on the internal flow properties of a fuel reactor (FR). The Computational Particle Fluid Dynamics (CPFD) approach was applied to predict the CLG with coal at the FR, uncovering distinctive flow properties of gas-solid reactions. This study investigated the effects of ash particles content, polydispersity and sphericity on the flow behavior within the bed. The simulation accurately predicted the motion of the bubbles within the FR, and the gas phase composition distribution at the outlet is closer to the experimental data. Introducing coal ash creates a reduction in the concentration of ilmenite, resulting in a drop in the rates of the related reactions. The narrow particles diameter distribution among coal ash facilitates the particles arrangement in the bed and improves the overall reaction. The addition of moderately irregular-shaped coal ash particles has a certain positive effect on improving the gas-solid contact.

Pore-Specific Anisotropic Etching of Zeolitic Imidazolate Frameworks by Carboxylic Acid Vapors.

Anisotropic etching is a powerful way to customize metal-organic frameworks with advanced nanostructures, but it is still in its infancy. Herein, we proposed an unprecedented etching strategy that created anisotropic hollow structures in various zeolitic imidazolate framework (ZIF) nano/single crystals via pore-specific carving. The etching occurred through a newly discovered gas-solid reaction where carboxylic acid vapors bind with ligands in ZIFs at room temperature to form ionic liquid (IL). A series of experiments were conducted to decode the origin of anisotropy and the "hollowing out" effect. We found that large pore openings on {111} facets provide access for the entry of carboxylic acid vapors and the outflow of the IL, resulting in pore-dependent anisotropy features. The unique "etching after adsorption" mechanism and the adsorption capacity of the IL enable acid vapors to hollow out nanocrystals and even single crystals. By altering carboxylic acids and ligands in ZIFs, the etching process can be precisely tuned from the inside out or the outside in. This new method demonstrates broad universality and brings unprecedented morphologies and complexities. It may offer great opportunities for achieving purposeful modification of ZIFs and the rational construction of intricate architectures.

Photothermal-boosted S-scheme heterojunction of α-Fe2O3@NiOx for high-selective reduction of CO2 to CO

Self-heating photothermal catalysis, combining light promotion and thermal activation, offers unique advantages for CO2 conversion. The meticulous design of active sites and light-absorbing materials is crucial for high-performance photothermal catalysts. Herein, a S-Scheme heterostructure composed of NiOx subunits with abundant oxygen vacancies (Vo) bonded with α-Fe2O3 nanoplatelets has been fabricated for solar-driven photothermal catalytic CO2 reduction. Under continuous full-spectrum light irradiation (0.3 W·cm−2), the α-Fe2O3@NiOx hybrids exhibited a CO yield rate of 199.3 μmol∙g−1·h−1 in a gas–solid reaction models with near-unity selectivity. Additionally, the apparent quantum yield for CO production at 420 nm reaches 1.56 %. The prominent activity is attributed to three key factors: (1) The Vo-rich NiOx facilitates the accumulation of photogenerated electrons and activation of chemisorbed CO2. (2) The implemented S-Scheme heterostructures boost interfacial charge-transfer and provide spatially separated catalytic sites for efficient overall CO2 reduction. (3) The substantial photothermal effect of NiOx, which arises from nonradiative exciton recombination, induces local heating of the catalyst, thereby enhancing reaction kinetics. This work provides valuable insights into the utilization of a photothermal-photocatalytic S-Scheme heterojunction system for the photothermal catalytic CO2 reduction.

Novel concept for 3D-printed, baffled micro-fluidized beds for the regulation of bubble behavior and the suppression of solid back-mixing: Experiments and simulations

In Micro-Fluidized Beds (MFBs), large bubbles (or slugs) and strong solid back-mixing might hinder good mixing, heat and mass transfer, while reducing conversion rates, and limiting selectivity in certain gas–solid reactions. In this study, a series of novel baffled MFBs were produced using 3D-printing. The influence of the number and position of baffles on the regulation of bubble performance and solid back-mixing in MFBs was investigated through fluidization experiments and Two-Fluid Model (TFM) simulations. The results show that the introduction of baffles effectively suppress slug formation and expand the bubbling regime. Baffles placed at mid-height disrupt fully developed slugs more effectively than those at the bottom. Increasing the number of baffles enhances bubble-breaking efficiency. Numerical simulations suggest that baffles positioned in the lower portion of the bed are more effective for the inhibition of global solid back-mixing. This study shed new light on the design and optimization of baffled MFBs.

Constructing An Oxyhalide Interface for 4.8 V-Tolerant High-Nickel Cathodes in All-Solid-State Lithium-Ion Batteries.

All-solid-state lithium batteries (ASSBs) have received increasing attentions as one promising candidate for the next-generation energy storage devices. Among various solid electrolytes, sulfide-based ASSBs combined with layered oxide cathodes have emerged due to the high energy density and safety performance, even at high-voltage conditions. However, the interface compatibility issues remain to be solved at the interface between the oxide cathode and sulfide electrolyte. To circumvent this issue, we propose a simple but effective approach to magic the adverse surface alkali into a uniform oxyhalide coating on LiNi0.8Co0.1Mn0.1O2 (NCM811) via a controllable gas-solid reaction. Due to the enhancement of the close contact at interface, the ASSBs exhibit improved kinetic performance across a broad temperature range, especially at the freezing point. Besides, owing to the high-voltage tolerance of the protective layer, ASSBs demonstrate excellent cyclic stability under high cutoff voltages (500 cycles~94.0 % at 4.5 V, 200 cycles~80.4 % at 4.8 V). This work provides insights into using a high voltage stable oxyhalide coating strategy to enhance the development of high energy density ASSBs.

Multi-dimensional CFD-Mask R-CNN and CFD-watershed segmentation approach for multiphase non-catalytic gas-solid reactions: A case study for hydrogen reduction of porous iron oxide pellets

The direct reduction of iron oxide (DRI) using hydrogen is a promising method for clean steelmaking. Previous studies used one-dimensional models to explore this non-catalytic gas–solid reaction, but they lacked accuracy in assessing the impact of pellet shape. To tackle this issue, a multi-dimensional computational fluid dynamic (CFD) method has been employed, integrating a novel porous three-interface unreacted shrinking core model (USCM) to explore the effects of pellet shape through multiphase reactions of Fe2O3 → Fe3O4 → FeO → Fe by pure hydrogen. The model incorporates Knudsen, molecular, and effective diffusion mechanisms, alongside a continuous porosity function. Validation against previous experiments within a temperature range of 800–1000 °C and varying porosity is performed by solving four partial differential equations (PDEs) of mass and momentum balance in a porous media using the finite element method (FEM). Subsequently, a dataset comprising 754 images of pellets from the industrial DRI unit is collected and applied for the mask region-based convolutional neural network (Mask R-CNN) algorithm coupled with CFD, to draw geometries and simulate DRI to study indentations and protrusions of pellets. Furthermore, watershed segmentation is applied to investigate the shapes and real sizes of pellets from their images. The Mask R-CNN achieves intersection over union (IoU), precision, and recall percentages of 86.1 %, 87.3 %, and 87.2 % on average, respectively. Pellet shape investigations reveal notable discrepancies in wustite phase profiles and porosity. A nuanced impact is discerned regarding the DRI in 2D shape deviation, while 3D model errors in solid conversion time range from 3 % to 12.8 %.

Predictive study of drying process for limonite pellets using MLP artificial neural network model

Due to the decline in high-grade iron ore production, the utilization of low-grade iron ore, such as limonite, has become necessary. Limonite contains a significant amount of bound water, which requires a drying process prior to use. Excessive heat stress caused by the evaporation of bound and free water during the drying of limonite pellets can lead to pellet disintegration and adversely affect gas-solid reactions. In recent years, artificial neural network (ANN) has been developing continuously in the fields of modeling and intelligent control, and has been widely used. Many predecessors used artificial neural network model to study the drying process of natural organic matter, and analyzed the factors affecting the drying rate of organic matter. In this study, we employed big data analysis, specifically Multilayer Perceptron (MLP) artificial neural networks, to analyze the drying process of limonite pellets and successfully established a predictive drying model applicable to limonite pellets. The MLP artificial neural network demonstrated excellent fitting between predicted and experimental values, with a maxi-mum R2 value of 0.999. The artificial neural network for drying developed in this study provides technical guidance for industrial material drying, reduces the workload of manual measurements, and minimizes energy consumption.

Phonon-assisted upconversion luminescence thermal enhancement of NaYS2:Yb3+,Nd3+ for optical temperature sensing

Upconversion luminescence presents obvious advantages in optical temperature sensing, nevertheless the application in complex scenarios is limited by luminescence thermal quenching. Herein, NaYS2:Yb3+,Nd3+ phosphors are synthesized by the solid-gas reaction method and used for temperature sensing. A series of emissions for Nd3+ from visible to near-infrared region are achieved based on energy transfer from Yb3+ to Nd3+ under 980 nm excitation. With elevating the temperature, significant thermal enhancement effect of nearly three orders of magnitude is detected in near-infrared emission of 4F7/2 → 4I9/2, which is attributed to phonon-assisted energy transfer of Yb3+→Nd3+ and the corresponding thermal population effect. The thermal behaviors of thermally coupled energy levels for 4G7/2/2G9/2 and 4F7/2/4F5/2 in NaYS2:Yb3+,Nd3+ are evaluated by luminescence intensity ratio technique. Remarkably, the optical thermometer based on the enhanced emission of 4F7/2/4F5/2 shows excellent temperature measurement performance, which is expected to be applied in wide-temperature-range and highly-sensitive temperature sensing. These results not only provide a pathway to realize high performance temperature sensing, but also heighten the understanding of UC emission thermal enhancement.

Insights into Activation Pathways of Recovered Carbon Black (rCB) from End-of-Life Tires (ELTs) by Potassium-Containing Agents.

This study explores the conversion of recovered carbon black (rCB) from end-of-life tires (ELTs) into activated carbons (ACs) using potassium-based activators, targeting enhanced textural properties development. The research focuses on the interaction between potassium and rCB, with the aim of understanding the underlying mechanisms of rCB activation. The study investigates several parameters of KOH activation, including the KOH/rCB mass ratio (1:3 to 1:6), activation temperatures (700-900 °C), activation time (1-4 h), and heating rate (5-13 °C/min). It also assesses the effects of different potassium salts (KCl, K2CO3, CH3COOK, and K2C2O4) on porosity and surface characteristics of the rCB/ACs. Furthermore, the role of the physical state of KOH as an activator (solid and gas-solid) was examined, alongside a comparative analysis with NaOH to evaluate the distinct effects of potassium and sodium ions. Optimal conditions were identified at an 800 °C activation temperature, a 7 °C/min heating rate, a 1:5 KOH/rCB ratio, and a 4 h activation period. X-ray diffraction analysis showed the formation of several K-phases, such as K2CO3, K2CO3·1.5H2O, K4(CO3)2·(H2O)3, KHCO3, and K2O. The effectiveness of the potassium salts was ranked as follows: KOH > K2C2O4 > CH3COOK > K2CO3 > KCl, with KOH emerging as the most effective. Notably, the gas-solid reaction of KOH/rCB was indicated as a contributor to the activation process. Additionally, it was concluded that the role of KOH in enhancing the textural properties of rCB was primarily due to the interaction of K+ ions with the graphite-like structure of rCB, compared to the effects observed with NaOH. This research introduces novel insights into the specific roles of different potassium salts and KOH activation conditions in optimizing the textural characteristics of rCB/ACs.

Atomically Resolved Transition Pathways of Iron Redox.

The redox transition between iron and its oxides is of the utmost importance in heterogeneous catalysis, biological metabolism, and geological evolution. The structural characteristics of this reaction may vary based on surrounding environmental conditions, giving rise to diverse physical scenarios. In this study, we explore the atomic-scale transformation of nanosized Fe3O4 under ambient-pressure H2 gas using in-situ environmental transmission electron microscopy. Our results reveal that the internal solid-state reactions dominated by iron diffusion are coupled with the surface reactions involving gaseous O or H species. During reduction, we observe two competitive reduction pathways, namely Fe3O4 → FeO → Fe and Fe3O4 → Fe. An intermediate phase with vacancy ordering is observed during the disproportionation reaction of Fe2+ → Fe0 + Fe3+, which potentially alleviates stress and facilitates ion migration. As the temperature decreases, an oxidation process occurs in the presence of environmental H2O and trace amounts of O2. A direct oxidation of Fe to Fe3O4 occurs in the absence of the FeO phase, likely corresponding to a change in the water vapor content in the atmosphere. This work elucidates a full dynamical scenario of iron redox under realistic conditions, which is critical for unraveling the intricate mechanisms governing the solid-solid and solid-gas reactions.