Low-temperature Reaction Research Articles

Synthesis of high-value CaCO3 via indirect CO2 fixation utilized blast furnace slag

Ultrasonic and bubbling carbonation method achieved precipitation of CaCO3 was described as a particularly advantageous method for synthesizing low-dispersity vaterite CaCO3. Herein, high-purity vaterite CaCO3 microspheres with regular morphology was synthesized from blast furnace slag (BFS) through mineral phase leaching, precipitation impurity removal, and CO2 solidification in ultrasonic reaction field. The results demonstrated that the method employed for distributing bubbling CO2 under an ultrasonic field aided both CO2 fixation and indeed the formation of homogenized vaterite. And vaterite synthesis is further aided by factors such as low initial calcium ion concentration, low reaction temperature, high CO2 concentration, and short aging time. Furthermore, a sphere-dumbbell-sphere mechanism has been proposed as a possible growth mechanism for the spheroidal structures. Finally, large-scale production of high value-added vaterite CaCO3 would eventually be attained at carbonation temperature of 20 ℃, Ca2+ concentration of 0.1 mol·L−1, CO2 proportion in the gas mixture of 70 %.

Sustainable and recyclable thermosets with performances for high technology sectors. An environmental friendly alternative to toxic derivatives

This study focuses on the development of environmentally friendly and chemically recyclable thermosets using or a renewable based monomer, the triglycidyl ether of phloroglucinol (TGPh), or a commercial non-toxic tris(4-hydroxyphenyl) methane triglycidyl ether (THPMTGE) monomer. The recyclable polyester thermosets were prepared by crosslinking the two monomers with hexahydro-4-methylphthalic anhydride (HMPA) or methyl nadic anhydride The TGPh-based formulations exhibited lower reaction temperatures and narrower reaction intervals. Additionally, these systems showed higher tan δ values (189°C–199°C), higher crosslinking densities (7.6–7.8 mmol cm−3) and compact networks, crucial for high-performance industries. Tensile tests demonstrated the remarkable mechanical properties of the thermosets, including high Young modulus (1.3–1.4 GPa), tensile stress (55–69 MPa), and an elongation at break around 3%–8%. Moreover, the thermosets exhibited complete dissolution at a temperature of 170°C, with depolymerization times of approximately 2.5 h for TGPh-based resins and 4.5 h for THPMTGE-based formulations. In conclusion, this study shows that sustainable and eco-friendly thermosets with excellent physico-chemical and thermo-mechanical properties, low hydrophilicity, and rapid dissolution capacity can be developed. These thermosets offer a viable alternative to non-recyclable and toxic resins in high-end industrial applications.

Antimicrobial activity of Cobalt doped Cerium Oxide (Co-CeO2) nanoparticles against selected food pathogens

This present work is to investigate the antibacterial activity of CeO2 nanoparticles on five foodborne pathogens. Low-temperature solid-state reactions were used to create co-doped CeO2 nanoparticles (Co-CeO2 NPs). In the current work, the impact of Co-doping on polycrystalline CeO2 samples synthesized using the co-precipitation method at room temperature for Co-doping concentrations of 0.5%, 1%, 3%, and 5% is discussed. Rietveld refinement of the X-ray diffraction patterns confirms that the Co-doped CeO2 samples have a face-centred cubic structure. This shows that the Co ions have been successfully integrated into the CeO2 lattice. Also, the UV-Vis-NIR absorption spectra confirm that redshifts do happen in the Co-doped CeO2 samples, which shows that the band gap energy decreases as the number of Co ions grows. In an antibacterial test against five pathogenic microbes, S. aureus, M. luteus, Enterobacter aerogenes, S. typhi, and Pseudomonas aeruginosa, Co-doped cerium oxide nanoparticles significantly slowed the growth of all five pathogens, both in liquid and solid growth conditions. These results show that Co-doped CeO2 nanoparticles have strong antibacterial properties against foodborne pathogens. This suggests that they could be used as promising bionanomaterials for in vivo therapeutic uses.

Hg0 removal performance of magnetic raffinate slag-based sorbents: Mechanism study on oxidation modification

The sulfur-containing carbon-based sorbent was regarded as potential sorbent for the removal of toxic elemental mercury (Hg0). However, due to its lower reaction temperature and the stronger Hg0 oxidation capacity of oxides at higher temperature, oxidation modification on sulfur-containing raffinate slag-based sorbents was proposed in the study. The effects of O2, H2O2 and KMnO4 oxidation modification on Hg0 removal performance and physicochemical properties of sorbents were investigated. The oxidation modification had little effect on pore structure of sorbents, but mainly affected the content and valence state of sulfur and oxygen elements. Compared with H2O2 oxidation, KMnO4 oxidation was more conducive to forming active lattice oxygen (Oα). The valence state of manganese bound with Oα influenced Hg0 capture a lot, and Oα in MnO2 showed strong oxidation capacity to Hg0. Active S22−and Oα in A850-0.1KMnO4-12h sorbent could both promote the Hg0 removal with HgS and HgO formed in used sorbent. The saturated magnetization of A850-0.1KMnO4-12h sorbent was 5.39 emu·g−1, making it possible to separate mercury-containing sorbents from fly ash. It showed good resistance to low concentration of SO2, and NO could promote its Hg0 removal ability. Meanwhile, KMnO4 oxidation successfully improved the Hg0 removal performance at higher reaction temperature and gas hourly space velocity.

Numerical study on the effect of a two-stage pilot injection strategy on the performance of medium-speed diesel/natural gas dual-fuel marine engine

The need to reduce marine engine emissions continues to grow with the implementation of stricter emission standards. Numerical simulations were conducted to study the effect of a two-stage pilot diesel injection strategy on combustion and emissions in a medium-speed diesel/natural gas dual-fuel marine engine. A comprehensive analysis was performed on the start of the first pilot diesel injection (SOI1) and the proportion of the first pilot diesel injection (POI1), identified as two coupling factors of the injection strategy. The results indicated a significant improvement in indicated thermal efficiency (ITE) of over 48% and a reduction in nitrogen oxide (NOx) emissions of over 50% compared to the baseline single-stage injection strategy can be achieved through the use of high POI1 and delayed SOI1. In addition, the first pilot diesel spray covered the squish and piston bowl regions, enhancing the reactivity of the fuel-air mixture in these regions. The mass fraction of CH2O and H2O2 radicals determined the distribution of reactivity in different regions and characterized the transition process from low-temperature reaction to high-temperature reaction. The strategy of high POI1 and delayed SOI1 resulted in a better low-temperature reaction distribution, reducing combustion duration, improving ITE, and decreasing NOx, HC, CO emissions at medium load condition.

Highly active novel K2CO3 supported on MgFe2O4 magnetic nanocatalyst for low-temperature conversion of waste cooking oil to biodiesel: RSM optimization, kinetic, and thermodynamic studies

An innovative K2CO3/MgFe2O4 (KC/MGF) magnetic nanocatalyst for effective biodiesel generation from WCO is demonstrated here. To examine the physiochemical and morphological features of the catalyst, several characterization methods such as XRD, FT-IR, SEM-EDX, HR-TEM, AFM, XPS, BET, CO2-TPD, and VSM are used on the as-synthesized magnetic nanocatalyst. Optimization of K2CO3 loading on MgFe2O4 is achieved and 30KC/MGF was found as the optimum ratio. Response surface methodology (RSM) via central composite design (CCD) is constructed using optimization margins to clarify the optimal parametric conditions; catalyst loading (4–6 wt%), reaction time (90–120 min), and methanol to oil ratio (6:1–9:1) at a fixed low operating reaction temperature (50 ºC). The obtained optimum reaction conditions are 4.4 wt% catalyst loading, 108 min reaction time, 6.6:1 methanol to oil ratio, at 50 ºC achieving ca. 92.9% biodiesel conversion. 30KC/MGF is an energy-conserving magnetic nanocatalyst with excellent basicity that operates at low temperatures, for a markedly short period of time, and with a low methanol-to-oil molar ratio. Kinetics and thermodynamic parameters are estimated i.e., activation energy (Ea), change of enthalpy of activation (ΔH#), and change of entropy of activation (ΔS#) to be 31.5 kJ mol−1, 28.9 kJ mol −1, and −188.8 J mol−1 K−1, respectively. Gibbs free energy (ΔG#) is appraised at 308, 313, and 318 K to be 87.1, 88, and 88.9 kJ mol−1, respectively. Due to K+ leaching, utilizing 30KC/MGF in sequential runs results in a significant activity plummet. The catalyst activity is recovered by re-impregnation with K2CO3 precursor solution, resulting in the same high FAME conversion as fresh 30KC/MGF. Finally, the physicochemical properties of biodiesel are investigated and determined to be compliant with international American and European standards.

A SIMPLE APPROACH TOWARDS TUNING MORPHOLOGY OF MICROCRYSTALLINE CELLULOSE

Microcrystalline cellulose (MCC) is a purified cellulose derivative. It is a white, highly oriented form of cellulose most commonly used in food, cosmetic, and pharmaceutical industries due to its advantageous properties of high crystallinity, large surface area, good compressibility etc. MCC is a high value added material that is widely used in pharmaceutical companies. For such applications, a large surface area of MCC is important. In this study, MCC was prepared from cellulosic fibres with a specific cross-section, i.e. trilobal, to produce trilobal microcrystalline cellulose (TMCC), which has a large surface area. This MCC is produced by a simple acid hydrolysis process. The process parameters in the production of MCC were optimised to maintain the cross-sectional shape of the fibres, even after conversion to MCC. The obtained MCC was characterized by various analytical techniques, such as Fourier transform-infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), B.E.T surface and X-ray diffraction (XRD) analyses. The cross and longitudinal morphology of the produced MCC was confirmed by scanning electron microscopy (SEM). The study shows that strong hydrolysis conditions, such as higher temperatures of 50 to 55 °C, lead to distortion of the cross-section, while lower reaction temperatures, i.e. 25 to 30 °C, help maintain a trilobal morphology. It was also found that the thermal stability of TMCC is higher, compared to that of regular MCC. The maximum decomposition temperature of TMCC was 304 °C, while it was 270 °C for regular MCC. The crystallinity index of all MCC was in a similar range. In addition, the water retention value (WRV) of TMCC was higher than that of circular MCC, indicating effectiveness of the increased surface area. The maximum WRV for MCC and TMCC was 66 and 85%, respectively.

Simple chemical synthesis of CeO2 nanoparticles for toxic NO2 gas detection

CeO2 nanoparticles (NPs) were synthesized using a cost-effective simple chemical method without any surfactant or additives at low temperature and short reaction time. The various techniques employed to investigate effect of annealing temperatures on structural, morphological and chemiresistive properties of the prepared CeO2 NPs, which were decorated on the glass substrates by drop casting technique. The CeO2 NPs exhibited cubic crystal structure and porous morphology, with specific surface area 52.92 m2/g for the C3 sample. This specific surface area is significant for achieving superb gas sensing performance. The optimized operating temperature was 150 °C, illustrated outstanding response of 57% towards 100 ppm, 12% response to 1 ppm of toxic NO2 gas was observed than other test gases with good reproducibility, excellent response (tres), recovery (trec) time, and notable stability (85%). The interaction between NO2 gas molecules and CeO2 NPs surface is analysed by impedance spectroscopy.

Experiment and Numerical Studies of the Effect of Equivalent Ratio on Combustion Characteristics in Fluidized Bed Gasifier

The effect of equivalent ratio on fluidized bed gasifier on using kernel mixed palm cake as feedstock was studied experimentally and numerically. A 3-D numerical model of the reactor, similar to the experimental setup, was created using the commercial computational fluid dynamics (CFD) software ANSYS 2019 (Fluent). The fuel feed rate was fixed at 3 kg/hour and the mass flow rate of the air was varied, setting it to equivalent ratios (ER) of 0.1, 0.3, 0.5, and 0.7. The axial temperature profile in the reactor was compared between experimental measurements and numerical simulations and a good agreement was found. Carbon monoxide and volatiles increased when the equivalent ratio decreased, according to the simulations. It was found that ER = 0.1 and ER = 0.3 are suitable equivalent ratios, although the former would not give continuous combustion due to too low reactor temperature.

Elaborating the improving SO2 resistance mechanism of CeWTi catalysts through framework confined ordered mesoporous structures for low-temperature NH3-SCR reaction

It is still a significant challenge that enhancing SO2 tolerance on the Ce-based catalyst in NH3-SCR reaction at low temperature. In this paper, an ordered mesoporous Ce-W-Ti-E catalyst with a framework confined structure had been constructed. The active components were directly constrained in the ordered mesoporous TiO2 structure, forming the framework confined ordered mesoporous structure. The ordered mesoporous structures in the framework structure provided better specific surface area and abundant active sites for the catalyst. In addition, the confinement effect of the framework structure enhanced the interaction between Ce, W and Ti, thus speeding up the electron transfer efficiency and enhancing the redox capacity of the catalyst. Furthermore, the introduction of W also supplemented a large amount of surface acid sites, which can inhibit the adsorption of SO2 on the catalyst surface, reduce the deposition of sulfate and well protect the active sites from SO2 attack with the help of special confinement effect. Therefore, the framework confined structure Ce-W-Ti-E catalyst in the whole process of SCR showed a wide operating temperature window, better stability and strong sulfur resistance, thus extended the catalyst lifetime in the NH3-SCR process.

Effect of functional groups on spontaneous combustion characteristics of high water-rich coal after long-term soaking and drying

ABSTRACT Spontaneous combustion of waterlogged coal accounts for many coal mine fire accidents. The soaking process affects the chemical properties of the coal, causing it to be highly susceptible to spontaneous combustion. Changes in functional groups of highly water-rich coals after flooding and drying are discussed, and the structural parameters were characterized by infrared spectroscopy (FTIR). The results show that the highest aliphatic hydrocarbons, oxygenated functional groups, and aromatic hydrocarbons are reached when air-dried after soaking for 30 days. The substitution of the dumb ring is changed with growing immersion time. C-O rose from 13% to 26% at 30 days and remained constant. Methyl and self-conjugated hydroxyl groups are increasing. Analysis of the structural parameters revealed that aromaticity decreases and increases with soaking time, while the degree of fatty chaining increases and decreases. Prolonged water immersion and air-drying change the coal’s aromatization and aliphatic chain structure, resulting in the continuous loss of the branched chains, thus making the skeleton of coal more sparse and the low-temperature oxidation reactions easier to carry out. It is sufficient to show that the theoretical basis for prevention and control of highly water-rich coal combustion after long-term immersion and drying is provided.

Depleted uranium oxide supported nickel catalyst for autothermal CO2 methanation in non-adiabatic reactor under induction heating

Undoped nickel-based catalysts supported on depleted uranium oxide allow one to carry out CO2 methanation process under extremely low reaction temperature under atmospheric pressure and powered by a contactless induction heating. By adjusting the reaction conditions, the catalyst is able to perform CO2 methanation reaction under autothermal process operated inside a non-adiabatic reactor, without any external energy supply. Such autothermal process is possible thanks to the high apparent density of the UOx which allows one to confine the reaction heat in a small catalyst volume in order to confine the exothermicity of the reaction inside the catalyst and to operate the reaction at equilibrium heat in-heat out. Such autothermal operation mode allows one to significantly reduce the complexity of the process compared to that operated using adiabatic reactor, where complete insulation is required to prevent heat disequilibrium, in order to reduce as much as possible, the heat exchange with the external medium. The catalyst displays an extremely high stability as a function of time on stream as no apparent deactivation. It is expected that such new catalyst with unprecedented catalytic performance could open new era in the field of heterogeneous catalysis where traditional supports show their limitations to operate catalytic processes under severe reaction conditions.

Recovery of degraded LiCoO2 through a CO2 -assisted low-temperature thermal reduction approach

Recycling spent lithium-ion batteries (LIBs) using chemical-saving and energy-effective pathways has been pursued to minimize the secondary environmental footprints. In this study, a sealed stainless-steel reactor was selected to achieve CO2-assisted low-temperature thermal reduction of spent LiCoO2 by carbon at 500 °C. The thermal reduction was provoked by the in-situ generated CO that resulted from the reaction of carbon and CO2. More importantly, MgCO3 was used as a CO2 holder to provide CO2 at elevated temperatures and MgO can be used to absorb CO2 to regenerate MgCO3, enabling the CO2 as a clean additive in the reduction reaction. Using this low-temperature reduction coupled with the carbonate pyrolysis approach, the selective recovery of Li reached 94.21%. The spatial isolation of MgCO3 at the bottom layer, graphite at the middle layer, and LiCoO2 at the top layer in the same reactor avoids complex separation. In addition, LiCoO2 is directly regenerated by the obtained CoO/Co3O4 and Li2CO3, and regenerated LiCoO2 exhibits good electrochemical performance with a discharge capacity retention of 94.0% after 300 cycles. Overall, the carbonate pyrolysis in the close-reactor is a promising approach to achieving a low-temperature reduction reaction by using CO2 as a clean agent to recycle spent LIBs.

Research on the Mechanism of Low-Temperature Oxidation of Asphaltene.

Asphaltene extracted from heavy oil was oxidized by a mixture of propionic anhydride and hydrogen peroxide at a low temperature of 50 °C. Elemental analysis, infrared analysis, proton nuclear magnetic resonance analysis, and gas chromatograph/mass spectrometer analysis results indicated that oxygen addition, side chain cleavage, and condensation reactions mainly occurred in the oxidation process. The oxidation products were divided into 28% methanol solubles and 72% methanol insolubles. There were mainly fatty acids and fatty acid esters in the methanol solubles. There were also small amounts of aromatic compounds with low condensation in the methanol solubles, and the alkyl side chains were mostly short ones. The degree of aromatic ring condensation in the methanol insolubles was slightly higher than that of the pristine asphaltene. There were still some long unbroken chains in the methanol insolubles after the low-temperature reaction. The molecular dynamics simulation results show that the distribution of propionic anhydride around the asphaltene molecules can promote the oxidation of asphaltene. This low-temperature oxidation technology can be used to process asphaltenes to improve the profitability of heavy-oil-processing enterprises.

Experimental and modeling study on the autoignition characteristics of methyl stearate in a rapid compression machine

With the extensive exploration of advanced combustion modes and the increasing demand for engines with extremely high efficiency and low emissions, biodiesel has garnered significant attention and research as a renewable fuel source that boasts a wide range of raw materials. The ignition delay times (IDT) of methyl stearate, one of the main components in biodiesel, were measured in a new heated rapid compression machine (RCM). The data were obtained for the equivalence ratio of 0.3–0.8 and the compressed temperatures ranging from 820 K to 1000 K under three different pressures of 8, 10, and 12 bar. The influence of compressed temperature, compressed pressure, equivalence ratio, and oxygen mole fraction on ignition delay times was systematically discussed under experimental conditions, revealing the autoignition characteristics of methyl stearate in intermediate temperatures. Besides, the CRECK model and a skeletal model were verified against the experimental results, revealing that the model obtained by analogy significantly overestimates the low-temperature reactivity of methyl stearate. Furthermore, appropriate adjustments were made to the pre-exponential factors for the low-temperature elementary reactions in the CRECK model based on sensitivity analysis. The results indicate that the present model with optimization can well capture the dependence of the IDTs on the operating parameters under the investigated conditions, and the simulation results are in satisfactory agreement with the experimental data. Finally, the optimized model was verified against the experimental data from both the shock tube and jet-stirred reactor. To the authors' knowledge, this study represents the first gas-phase RCM experiment conducted on pure methyl stearate, which is a waxy solid at room temperature.

Manipulating Oxygen Vacancies to Spur Ion Kinetics in V2O5 Structures for Superior Aqueous Zinc‐Ion Batteries

AbstractVanadium‐based intercalation materials have attracted considerable attention for aqueous zinc‐ion batteries (ZIBs). However, the sluggish interlaminar diffusion of zinc ions due to the strong electrostatic interaction, severely restricts their practical application. Herein, oxygen vacancy‐enriched V2O5 structures (Zn0.125V2O5·0.95H2O nanoflowers, Ov‐ZVO) with expanded interlamellar space and excellent structural stability are prepared for superior ZIBs. In situ electron paramagnetic resonance (EPR) and X‐ray diffraction (XRD) characterization revealed that numerous oxygen vacancies are generated at a relatively low reaction temperature because of partially escaped lattice water. In situ spectroscopy and density functional theory (DFT) calculations unraveled that the existence of oxygen vacancies lowered Zn2+ diffusion barriers in Ov‐ZVO and weakened the interaction between Zn and O atoms, thus contributing to excellent electrochemical performance. The Zn||Ov‐ZVO battery displayed a remarkable capacity of 402 mAh g−1 at 0.1 A g−1 and impressive energy output of 193 Wh kg−1 at 2673 W kg−1. As a proof of concept, the Zn||Ov‐ZVO pouch cell can reach a high capacity of 350 mAh g−1 at 0.5 A g−1, demonstrating its enormous potential for practical application. This study provides fundamental insights into formation of oxygen‐vacant nanostructures and generated oxygen vacancies improving electrochemical performance, directing new pathways toward defect‐functionalized advanced materials.

Deactivation induced by metal sulfate over MnCeOx catalyst in NH3-SCR reaction at low temperature

Sulfate adsorption is one of the factors that cause the poisoning of catalyst in the low-temperature NH3 selective catalytic reduction reaction (NH3-SCR). In this paper, by controlling the co-adsorption time of SO2 and O2 at 150 °C, a range of sulfated MnCeOx catalysts with different contents of metal sulfate species were prepared to reveal the influence of metal sulfate species content on the catalytic performances and reaction mechanisms at low temperature. The catalytic activity below 250 °C rapidly decreases with increasing metal sulfate species content. The results of characterizations shed light on the reduction of specific surface area, Mn4+ and Ce3+ content, and redox ability of MnCeOx owing to the formation of metal sulfate species. Further experiments reveal that metal sulfate species preferentially absorb on MnOx domains rather than on CeO2 domains, and the adsorbed metal sulfate species can suppress the Eley-Rideal and the Langmuir–Hinshelwood reaction mechanisms over the sulfated MnCeOx. All the above results are detrimental to the activity of sulfated MnCeOx in the low-temperature NH3-SCR reaction.

Oxygen exchange and phase stability of Y0.8Ca0.2BaCo4-xMxO7+δ (M = Fe, Ga, Al)

Using the sol-gel method, the complex oxides Y0.8Ca0.2BaCo4-xMxO7, where M = Fe, Ga, and Al, with swedenborgite-type structure, were synthesized. The slight replacement of Y by Ca is shown to facilitate doping at cobalt sites. The introduction of iron in place of cobalt is accompanied by a shift in the low-temperature oxygen exchange reaction to higher temperatures. The codoped oxides Y0.8Ca0.2BaCo3.8M0.2O7 demonstrate phase stability at heating in air up to 1000 °C.

Characterization of Low-Temperature Enzymatic Reactions through Heterologous Expression and Functional Analysis of Two Beta-Glucosidases from the Termite Symbiotic Bacterium Elizabethkingia miricola Strain BM10

Characterization of Low-Temperature Enzymatic Reactions through Heterologous Expression and Functional Analysis of Two Beta-Glucosidases from the Termite Symbiotic Bacterium Elizabethkingia miricola Strain BM10

Review of Plasma Processing for Polymers and Bio-Materials Using a Commercial Frequency (50/60 Hz)-Generated Discharge

This manuscript introduces the properties and diverse applications of plasma generated using commercial frequencies of 50/60 Hz. Commercial frequency (CF) derived plasma exhibits characteristics similar to DC discharge but with an electrical polarity and a non-continuous discharge. Due to the low-frequency nature, the reactor configurations usually are capacitively coupled plasma type. The advantages of this method include its simple power structure, low-reaction temperature, and low substrate damage. The electrical polarity can prevent charge buildup on the substrates and deposited films, thereby reducing substrate damage. The simple, low-cost, and easy-to-operate power structure makes it suitable for laboratory-scale usage. Additionally, the various applications, including plasma-enhanced vapor deposition, sputtering, dielectric barrier discharge, and surface modification, and their outcomes in the CF-derived plasma processes are summarized. The conclusion drawn is that the CF-derived plasma process is useful for laboratory-scale utilization due to its simplicity, and the results of the plasma process are also outstanding.