Low-temperature Reaction Research Articles

Ceria-based supported metal catalysts for the low-temperature water-gas shift reaction.

Water-gas shift (WGS) reaction is a crucial step for the industrial production of hydrogen or upgrading the hydrogen generated from fossil or biomass sources by removing the residual CO. However, current industrial catalysts for this process, comprising Cu/ZnO and Fe2O3-Cr2O3, suffer from safety or environmental issues. In the past decades, ceria-based materials have attracted wide attention as WGS catalysts due to their abundant oxygen vacancies and tunable metal-support interaction. Strategies through engineering the shape or crystal facet, size of both metal and ceria, interfacial-structure, etc., to alter the performances of ceria-based catalysts have been extensively studied. Additionally, the developments in the in situ techniques and DFT calculations are favorable for deepening the understanding of the reaction mechanism and structure-function relationship at the molecular level, comprising active sites, reaction path/intermediates, and inducements for deactivation. This article critically reviews the literature on ceria-based catalysts toward the WGS reaction, covering the fundamental insight of the reaction path and development in precisely designing catalysts.

Construction of robust Ni-based catalysts for low-temperature Sabatier reaction.

CO2 hydrogenation to methane, namely, CO2 methanation or Sabatier reaction, is a significant approach to convert CO2 and H2 to storable and transportable CH4. Low reaction temperature is the key to industrialization and has attracted plenty of research interest. Ni-based catalysts are commonly utilized owing to their favorable properties of excellent activity and economical price. However, it is still challenging to perform the Sabatier reaction under temperatures lower than 300 °C owing to the inertness of CO2. Hence, in this article, we summarize the advances of four important design principles of the Ni-based catalysts for low-temperature Sabatier reaction, namely, optimizing Ni active sites, tuning support properties, considering metal-support interactions, and choosing a suitable preparation method, which provides deep insights for the design of low-temperature CO2 methanation catalysts. Additionally, typical low-temperature CO2 methanation reaction mechanisms with *CO or *HCOO as the main intermediate and perspectives on this topic have been provided. We highlight that the rare-earth oxide-supported Ni-based catalysts with the potential reaction mechanism and corresponding reactor design would be promising for low-temperature Sabatier reaction.

Synthesis of ethyl furfuryl ether via etherification of furfuryl alcohol with ethanol over montmorillonite K10.

Ethyl furfuryl ether (EFE), which is synthesized via etherification of furfuryl alcohol (FFalc) with ethanol over Brønsted acid catalysts, is used as an additive in gasoline to reduce its consumption and CO2 emission. In this work, we demonstrate that the performance of this synthesis route can be improved by using commercially available, low-cost, and environmentally friendly montmorillonite K10, which produces EFE in a relatively high yield of 45.3% and a FFalc conversion of 94.2% at a low reaction temperature of 393 K within 1 h. Other commercially available clay minerals showing Brønsted acidity, namely, kaolinite and halloysite, were also used in the etherification reaction under identical conditions. The catalytic performance followed the order of montmorillonite K10 > halloysite > kaolinite, which is consistent with that of the Brønsted acidities determined via acid-base titration. The spent montmorillonite K10 showed a catalytic performance comparable to that of the fresh catalyst after calcination.

Borylation and rearrangement reactions of azasilaanthracenes to afford B,N-doped nanographenes.

An air-stable B3,N3-containing dibenzobisanthene (8) was prepared in 29% yield by heating a 1,3,5-tri(azasilaanthryl)benzene (5) with BBr3 (180 °C). Under these conditions, the reaction does not stop after threefold SiMe2/BBr exchange but proceeds further via two rearrangement and two intramolecular C-H borylation steps. Some mechanistic details were unveiled by using smaller model systems and applying lower reaction temperatures. According to X-ray crystallography, compound 8 has a helically distorted scaffold. Due to its multiple resonance structure, it shows a narrow-band blue-green emission (λem = 493 nm; ΦPL = 84%; FWHM = 0.20 eV; THF); samples measured in PMMA gave prompt and delayed fluorescence lifetimes of 10.7 ns and 136 μs, respectively. The optical properties of 8 and of structurally related species were also investigated by quantum-chemical means: most of these compounds exhibit a small energy gap ΔEST between the lowest excited singlet (S1) and triplet (T1) states and a non-negligible spin-orbit coupling (SOC) between S1 and T1/T2, demonstrating their potential as thermally activated delayed fluorescence (TADF) emitters.

Utilising Polyester and Steel Slag‐Derived Metal/Carbon Composites as Catalysts in Biodiesel Production

Synthetic textiles such as polyesters are essential for daily life. However, large‐scale production generates large amounts of waste. This study introduces a new approach for valorising polyester textile waste (PTW) by transforming it into a catalyst for biodiesel production via pyrolysis. Specifically, a metal/carbon composite (PTW + steel slag [SS] composite—PSC) with enhanced catalytic properties was prepared by pyrolysing PTW with SS. The alkaline metals in SS facilitate the carbonisation of PTW via decarboxylation, resulting in a PSC rich in carbon, iron, and alkaline compounds. This composite featured mesopores that were larger than the micropores (MPs) typically found in PTW char. The use of porous material (silica) in thermally induced transesterification has been proven to be an efficient method for biodiesel production, achieving a yield of 97.20 wt.% in 1 min (faster than the 93.82 wt.% yields in 60 min observed from conventional alkali‐catalysed transesterification). However, the high reaction temperature (≥ 360°C) poses economic/technical challenges. To overcome this, PSC has been employed as a catalyst in thermally induced transesterification, leveraging its mesoporous structure and high alkaline content, particularly calcium oxide. The PSC achieved a biodiesel yield of 98.10 wt.% at a markedly lower reaction temperature of 120°C within 1 min. This performance was not attainable using silica or PTW char under similar conversion conditions. These findings highlight the potential of PSC produced through the pyrolysis of PTW and SS as effective catalysts for biodiesel production. This process is a promising strategy for converting waste into valuable resources and mitigating the environmental impacts associated with polyester waste.

Ozone-assisted low temperature oxidation of indene: An experimental and computational study

Elucidating the oxidation chemistry of polycyclic aromatic hydrocarbons (PAHs) aids in understanding the degradation reaction processes of PAHs, as well as their competitive roles in PAH growth. In this work, ozone-assisted oxidation of indene, the smallest prototype PAH molecule, was investigated in an atmospheric jet stirred reactor at 400–550 K. Ab initio quantum chemistry calculations were conducted to characterize the oxidation kinetics of indene and interpret the experimental observations. Fingerprint oxidation products including 2-(2-oxoethyl) benzoic acid, 2-(formylmethyl) benzaldehyde, 1,2-indanedione and 1-indanone were identified by synchrotron vacuum ultraviolet photoionization mass spectrometry. The initial C9H8O3 adduct resulting from O3-addition to indene exhibits high instability and is primarily detected as 2-(2-oxoethyl)benzoic acid following ozonolysis reactions. Minor amounts of vinylhydroperoxide were also observed as isomeric products of the C9H8O3 adduct. Theoretical calculations indicate that indene ozonolysis is highly structure-dependent, where the conformation of the C9H8O3 adduct determines the configuration of the resulting Criegee intermediates (CI). The distinctive reaction pathways introduced by the bifunctionalized characteristics of indene-derived large CIs are emphasized in this study. syn-Configuration CI features more conversion pathways compared to anti-CI due to the interaction between CI functionality and the neighboring aldehyde group, among which the bicyclic ring-closure reaction yielding secondary ozonide is most favored. The dioxirane intermediates generated from anti-CIs can undergo the Crossed Acid-forming channel to yield the target acid products, which provides an alternative way for dioxirane conversion. Further theoretical analyses demonstrate that ozonolysis is not the exclusive mechanism for indene oxidation under O3-assisted conditions. Instead, it is accompanied by low-temperature reactions initiated by OH/O2, leading to key products such as 2-(formylmethyl) benzaldehyde and 1-indanone. The present work aims to unravel the elusive chemistry involved in the O3-initiated oxidation of indene, providing new insights into the distinctive kinetics introduced by large bifunctionalized CIs in the ozonolysis of structurally similar PAHs.

Experimental and kinetic modeling study on the low-temperature decomposition and autoignition of 2-Azido-N,N-dimethylethanamine: A promising green mono- and bi-propellant

2-Azido-N,N-Dimethylethanamine (DMAZ) is a promising candidate for mono- and bi- propellant. However, the fundamental gas-phase combustion experiments have not been reported, and its chemical kinetic mechanism is not well understood. Therefore, the ignition delay times (IDTs) of DMAZ were measured utilizing a rapid compression machine and a shock tube, covering a wide temperature range of 570 – 960 K, at 10 and 20 bar with varying equivalence ratios. DMAZ was surprisingly found to undergo decomposition at temperatures as low as 600 K, leading to a pressure rise within the chamber. The low-temperature decomposition characteristics of DMAZ were systematically investigated under various fuel concentrations and pressures. A kinetic model of DMAZ was developed, incorporating quantum chemistry calculations for the thermodynamic data of new species and the rate constants of H-atom abstractions. The newly measured IDTs and characteristic decomposition times (CDTs) were further adopted in the model validation. Results show that DMAZ mainly decomposes through N–N2 bond fissions, which are also the major reaction pathways during autoignition. O2 addition to the radicals derived from the decomposition products and subsequent reactions contribute to most of the low-temperature reactivity in DMAZ oxidation. The current kinetic model can reasonably predict the IDTs and CDTs, as well as their dependencies on pressure, equivalence ratio, and fuel concentration.

A detailed high-pressure oxidation study of n-pentanal

Oxidation of n-pentanal is studied in a jet-stirred reactor at 10 atm for four dilute mixtures with equivalence ratios 0.3, 0.5, 1 and 2 and between 500–1150 K. A detailed kinetic sub-mechanism is developed and used along with the mechanisms representing the oxidation of two branched isomers of pentanal, namely 2- and 3-methylbutanal. At all conditions, n-pentanal showed a strong low-temperature reactivity and an NTC region. Among the experimentally observed species, ones related to the low-temperature oxidation of n-butyl radicals can be found, consolidating the importance of the (N-1) alkyl radicals in aldehyde chemistry. The kinetic mechanism showed good agreement against the data as well as other speciation data at atmospheric pressure from literature. The present data are also compared to previous similar studies on the oxidation of C3–C5 aldehydes in the same JSR and where n-pentanal shows the highest global reactivity.

Na2Ti3O7@RF@Ag Heterostructures as Efficient Substrates for SERS and Photocatalytic Applications.

A multi-step procedure was effectively employed to synthesize innovative three-dimensional (3D) heterostructures encompassing sodium titanate (Na2Ti3O7) nanowire cores, an intermediate resorcinol-formaldehyde (RF) layer, and outer silver (Ag) nanoparticle sheaths, referred to as Na2Ti3O7@RF@Ag heterostructures. Initially, a one-step hydrothermal technique facilitated the direct growth of single-crystal Na2Ti3O7 nanowires onto a flexible Ti foil. Subsequently, a two-step wet chemical process facilitated the sequential deposition of an RF layer and Ag nanoparticles onto the Na2Ti3O7 nanowires at a low reaction temperature. Optimal concentrations of silver nitrate and L-ascorbic acid can lead to the cultivation of Na2Ti3O7@RF@Ag heterostructures exhibiting heightened surface-enhanced Raman scattering (SERS), which is particularly beneficial for the detection of rhodamine B (RhB) molecules. This phenomenon can be ascribed to the distinctive geometry of the Na2Ti3O7@RF@Ag heterostructures, which offer an increased number of hot spots and surface-active sites, thereby showcasing notable SERS enhancement, commendable reproducibility, and enduring stability over the long term. Furthermore, the Na2Ti3O7@RF@Ag heterostructures demonstrate remarkable follow-up as first-order chemical kinetic and recyclable photocatalysts for the photodecomposition of an RhB solution under UV light irradiation. This result can be attributed to the enhanced inhibition of electron-hole pair recombination and increased surface-active sites.

Transition of characteristic explosion limits: From hydrogen to diethyl ether

In this work, the explosion limits of three different fuels: hydrogen (H2), propane (C3H8, C3), and diethyl ether (DEE, C2H5OC2H5, C4), are investigated based on detailed chemical kinetics. The results reveal that the explosion limit of H2O2 exhibits the typical Z-shape, while C3H8O2 exhibits a single-NTC response, and DEE-O2 displays a double-NTC response. Sensitivity analysis indicates that the appearance of the NTC response in both the C3 and DEE fuels is intricately linked to low-temperature reaction paths. Moreover, the extents of the NTC responses are comparable for these two fuels with similar low-temperature reaction paths, but operate under different temperature conditions. Specifically, the double-NTC response observed in DEE is attributed to its primary CH and CO bonds, generating C4 and C2 radicals. The oxygen addition and the subsequent pathways of these radicals dominate in distinct temperature ranges. In contrast, C3H8 only possesses the CH bond, resulting in a single-NTC response, as OH radicals are mainly released by C3 radicals through oxygen addition, isomerization, and decomposition reactions. The results of binary fuel mixtures with H2 addition indicate that the reactivity of H2 controls the low-pressure and high-temperature regime, while the C3 and DEE fuels dominate the high-pressure and low-temperature regime. Additionally, a triangular crossover regime is identified between these two regimes due to the switchover of the reactivity. Sensitivity analysis further reveals the transition of the dominating reactions related to different fuels at various pressure-temperature regimes. Finally, based on the explosion limits of the multi-component mixtures, a detailed explosion regime diagram is proposed for carbon-free fuel (H2), alkane fuel (C3H8), and oxygenated ether fuel (DEE). This new regime diagram provides valuable insights for the investigation and utilization of ether fuels and the mixture of different fuels.

A revised reaction kinetic mechanism for the oxidation of methyl formate

The combustion kinetics of methyl formate (MeFo), a promising oxygenated, highly knock-resistant e-fuel, is investigated in this work. The potential energy surfaces (PESs) of the low-temperature oxidation reactions of MeFo radicals were determined at the CCSD(T)-F12/cc-pVTZ-F12//B2PLYP-D3/cc-pVTZ level of theory and their rate coefficients were obtained with RRKM/master equation. The thermochemical properties of relevant intermediate species were calculated by using the G4 method. A chemical mechanism for the oxidation of MeFo was developed by adding fuel-specific reactions taken from a literature model into a well-validated base mechanism, and incorporating the newly calculated rate constants of elementary reactions and thermochemical properties of species. The fuel-specific mechanism was further revised in terms of reaction channels and rate coefficients for improved prediction accuracy. In particular, the O2 addition to hydroperoxy radicals (QOOH), the isomerization of peroxy hydroperoxy radicals (OOQOOH), the subsequent ketohydroperoxide (KET) decomposition, and the formally direct pathways of MeFo radicals (R) with O2 were added for the completeness of consumption pathways, in conjunction with the reaction channels of alkoxy radicals (RO) and hydroperoxides (ROOH). For good model prediction accuracy of ignition delay times, especially in the high-temperature range, the resulting mechanism was optimized by modifying the rate constants of several important H-atom abstraction reactions of MeFo within their uncertainty limits. The performance of the proposed mechanism is demonstrated through extensive validation against literature data obtained from different experimental configurations. Finally, the underlying reaction pathways of MeFo are explored by means of reaction flux analysis with the newly developed chemical mechanism.Novelty and significance statement: This work proposes a new reaction kinetic mechanism for the oxidation of methyl formate. Quantum chemistry calculation at high level of theory was performed to explore the low-temperature chemistry of MeFo. The reaction mechanism was improved by including missing reaction channels, incorporating theoretically calculated rate and thermochemical data, and modifying rate constants of sensitive reactions. The mechanism has been validated successfully against extensive data available in the literature covering a wide range of conditions and facilities. By using this new mechanism, reaction pathway analysis is performed to provide insights into the oxidation chemistry of MeFo.

Catalytic Hydrogenation Property of Methyl Benzoate to Benzyl Aldehyde over Manganese-Based Catalysts with Appropriate Oxygen Vacancies

The synthesis of benzaldehyde, a compound widely utilized in food, medicine, and cosmetics, was achieved through a one-step catalytic hydrogenation using the cost-effective raw material, methyl benzoate. This process aligns with the principles of atom economy and green production. Despite the development of numerous high-performance catalysts by scholars, the challenge remains in achieving lower reaction temperatures, ideally below 400 °C. In this study, a series of MnOx/γ-Al2O3 catalysts were meticulously prepared using the precipitation-impregnation method. These catalysts featured supports calcined at various temperatures and distinct manganese active components. Characterization techniques such as X-ray diffraction (XRD), N2 physical adsorption, Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), H2 temperature programmed reduction (H2-TPR), and NH3 temperature-programmed desorption (NH3-TPD) were employed to analyze the structure and surface properties of the catalysts. Notably, the optimized reaction temperature was found to be 360 °C. The catalyst exhibited the most favorable performance when the calcination temperature of the support was 500 °C and the Mn/Al molar ratio reached 0.18. Under these conditions, the catalyst demonstrated the most suitable oxygen vacancy concentration, yielding impressive results: a conversion rate of 87.90% and a benzaldehyde selectivity of 86.1%. These achievements were attained at 360 °C, atmospheric pressure, a hydrogen to methyl benzoate molar ratio of 40:1, and a Gas Hourly Space Velocity (GHSV) of 800 h−1. This research underscores the potential for optimizing catalysts to enhance the efficiency and sustainability of benzaldehyde synthesis.

Selective Synthesis of Defect-Rich LaMnO3 by Low-Temperature Anion Cometathesis.

The synthesis of complex oxides at low temperatures brings forward aspects of chemistry not typically considered. This study focuses on perovskite LaMnO3, which is of interest for its correlated electronic behavior tied to the oxidation state and thus the spin configuration of manganese. Traditional equilibrium synthesis of these materials typically requires synthesis reaction temperatures in excess of 1000 °C, followed by subsequent annealing steps at lower temperatures and different p(O2) conditions to manipulate the oxygen content postsynthesis (e.g., LaMnO3+x). Double-ion exchange (metathesis) reactions have recently been shown to react at much lower temperatures (500-800 °C), highlighting a fundamental knowledge gap for how solids react at lower temperatures. Here, we revisit the metathesis reaction, LiMnO2 + LaOX, where X is a halide or mixture of halides, using in situ synchrotron X-ray diffraction. These experiments reveal low reaction onset temperatures (ca. 450-480 °C). The lowest reaction temperatures are achieved by a mixture of lanthanum oxyhalide precursors: 2 LiMnO2 + LaOCl + LaOBr. In all cases, the resulting products are the expected alkali halide salt and defective La1-ϵMn1-ϵO3, where ϵ = x/(3 + x). We observe a systematic variation in defect concentration, consistent with a rapid stoichiometric local equilibration of the precursors and the subsequent global thermodynamic equilibration with O2 (g), as revealed by computational thermodynamics. Together, these results reveal how the inclusion of additional elements (e.g., Li and a halide) leads to the local equilibrium, particularly at low reaction temperatures for solid-state chemistry.

Reversible Transition of Semiconducting PtSe2 and Metallic PtTe2 for Scalable All-2D Edge-Contacted FETs.

Two-dimensional (2D) transition metal dichalcogenide (TMD) layers are highly promising as field-effect transistor (FET) channels in the atomic-scale limit. However, accomplishing this superiority in scaled-up FETs remains challenging due to their van der Waals (vdW) bonding nature with respect to conventional metal electrodes. Herein, we report a scalable approach to fabricate centimeter-scale all-2D FET arrays of platinum diselenide (PtSe2) with in-plane platinum ditelluride (PtTe2) edge contacts, mitigating the aforementioned challenges. We realized a reversible transition between semiconducting PtSe2 and metallic PtTe2 via a low-temperature anion exchange reaction compatible with the back-end-of-line (BEOL) processes. All-2D PtSe2 FETs seamlessly edge-contacted with transited metallic PtTe2 exhibited significant performance improvements compared to those with surface-contacted gold electrodes, e.g., an increase of carrier mobility and on/off ratio by over an order of magnitude, achieving a maximum hole mobility of ∼50.30 cm2 V-1 s-1 at room temperature. This study opens up new opportunities toward atomically thin 2D-TMD-based circuitries with extraordinary functionalities.

Rapid synthesis of Cu-SSZ-39 and study of phosphorus poisoning in NH3-SCR

Cu-SSZ-39 has attracted great interest due to its excellent NH3-SCR activity and hydrothermal stability. However, impediments such as high synthesis costs, lengthy preparation duration, and the issue of phosphorus-induced deactivation have hampered its widespread commercialization. Herein, H2O2 was first introduced into the synthesis system dedicated to the rapid synthesis of SSZ-39, and the crystallization time was shortened to 3 d. Various characterization techniques were used to analyze deeply the structure–activity relationship of the resulting Cu-SSZ-39 catalysts before and after phosphorus poisoning. Our findings revealed a pronounced decline in acidic sites and active copper species as Cu-SSZ-39 underwent deeper phosphorus poisoning, leading to the formation of Cu-P species and a consequential reduction in the low-temperature activity of the catalyst. Surprisingly, hydrothermal treatment of the poisoned catalyst allowed the decomposition of Cu-P species to generate active Cu2+ species, alleviating the poisoning effect. It was also shown that phosphorus poisoning did not affect the low-temperature reaction mechanism of Cu-SSZ-39, which still followed the “L-H” reaction pathway. Finally, it was unexpectedly found that the anti-phosphorus poisoning performance of 0.9C-Cu-SSZ-39 significantly improved after mesopores were introduced.

(Best Presentation Award - 2nd Place) Investigating Low Temperature Reaction Mechanisms of Alloy Anodes for Lithium-Ion Batteries

Lithium-ion batteries (LIBs) are the battery of choice for most energy storage applications, including personal electronic devices and electric vehicles. However, poor low temperature performance, resulting from hindered solid state diffusion, slow desolvation kinetics, and dendrite formation, limits their use in nascent applications that require operation below -20 ºC, like electric aviation and space exploration. A small number of previous studies have shown that anode materials that electrochemically alloy with lithium ions can be cycled at temperatures as low as -40 ºC with significantly improved performance compared to graphite. Despite their improved low-temperature performance, reaction mechanisms and degradation behavior for these materials at low temperatures are poorly understood. This work aims to fill this gap in understanding by investigating the structural pathways during reactions of alloy anodes at low temperatures as well as characterizing their mechanical and electrochemical degradation. Electrode cross sectioning and scanning electron microscopy reveal that rapid capacity decay in antimony anodes at -40 ºC is a result of increased lithium trapping as well as particle fracture due to mechanical damage associated with volume change. We show that rapid capacity degradation of antimony at -40 ºC can be mitigated through the use of nanoscale particles. While nanoscale particles have been studied extensively at room temperature, little is known about they behave at low temperatures. Through SEM cross-sectioning and the galvanostatic intermittent titration technique (GITT), we show that the improvement in stability is likely due to faster kinetics related to the shorter diffusion length and increased mechanical stability resulting in less lithium trapping at low temperatures. Additionally, X-ray diffraction measurements were carried out as a function of temperature on micron- and nanosized antimony particles, as well as tin and graphite, to determine the composition and structure of lithiated phases formed at low temperatures. The results show that reduced temperatures alter phase transformation behavior in certain alloy materials. Overall, this work provides improved mechanistic understanding of alloy anodes at low temperatures, setting the stage for enhanced electrochemical performance.

Enhanced low-temperature H2-selective catalytic reduction performance and selectivity of Pt/ZSM-5–TiO2 washcoated monolithic catalysts for NOx reduction

Hydrogen-selective catalytic reduction (H2-SCR) is a promising technology for reducing nitrogen oxide (NOx) emissions at low temperatures, but the selectivity of this process is limited by the generation of N2O. To achieve enhanced denitrification (deNOx) performance, H2-SCR catalysts with mixed zeolite and TiO2 supports washcoated on monolithic cordierite were developed. The catalyst support, active metal type and content, and monolithic cordierite cell density significantly influenced the H2-SCR performance. The xPt/TiO2 catalysts (where x is the metal content, wt.%) achieved >90% NOx conversion 135–180 °C, whereas the xPd/TiO2 catalysts exhibited poor H2-SCR activity, with <30% NOx conversion. In contrast to 0.5Pt/TiO2, the 0.5Pt/zeolite catalysts achieved high NOx conversion at 140–150 °C (91% at 140 °C for 0.5Pt/ZSM-5 > 89% at 140 °C for 0.5Pt/BETA >85% at 150 °C for 0.5Pt/SSZ-13), suggesting that zeolite supports significantly promote H2-SCR activity at low reaction temperatures. For the 0.5Pt/ZSM-5 washcoated monolithic catalyst, increasing the cell density from 400 to 900 cpsi significantly improved the NOx conversion from 52% to 90% at 100 °C owing to the increased geometric surface area and open frontal area of monolithic cordierite. For catalyst with mixed supports (0.5Pt/yZSM-5zTiO2) changing the ZSM-5/TiO2 ratio (y:z) from 25:75 to 90:10 increased the low-temperature NOx conversion from 39% to 89% at 100 °C, indicating that the deNOx characteristics can be tuned. With NO as the reactant, the 0.5Pt/90Z10T catalyst produced the lowest N2O share (8–17%) within the temperature window of maximum NOx conversion, resulting in an increased N2 share (83–88%). Thus, the synergetic effect of mixed ZSM-5/TiO2 catalyst supports can enhance low-temperature NOx conversion and mitigate N2O formation.

Enhanced Low-Temperature Activity and Hydrothermal Stability of Ce-Mn Oxide-Modified Cu-SSZ-39 Catalysts for NH3-SCR of NOx

Cu-SSZ-39 zeolite with an AEI structure exhibits excellent hydrothermal stability and can be a potential alternative to Cu-SSZ-13 zeolite SCR catalysts for NOx removal in diesel vehicles. However, the inferior low-temperature performance of Cu-SSZ-39 leads to substantial NOx emissions during the cold-start period, impeding its practical application. In this study, Ce-Mn oxide-modified Cu-SSZ-39 catalysts (CeMnOx/Cu-SSZ-39) and references (CeO2/Cu-SSZ-39 and MnOx/Cu-SSZ-39) were prepared by the ion-exchange of Cu ions followed by impregnation of the oxide precursors, with the aim of enhancing the NH3-SCR performance at low temperatures. The modified catalysts exhibited improved low-temperature activity and hydrothermal stability compared to the unmodified counterpart. In particular, CeMnOx/Cu-SSZ-39 showed the highest activity among the three catalysts and achieved NOx conversions above 90% within the temperature range of 180 °C to 600 °C, even after undergoing hydrothermal aging at 800 °C. Experimental results indicated that the synergistic effect between Ce and Mn in CeMnOx improves the redox properties and acidity of the catalyst due to the presence of Ce3+, Mn4+, and abundant adsorbed oxygen species, which facilitate low-temperature SCR reactions. Furthermore, the interaction of CeMnOx with Cu-SSZ-39 stabilizes the zeolite framework and hinders the agglomeration of Cu species during the hydrothermal aging process, contributing to its exceptional hydrothermal stability. The kinetics and NO oxidation experiments demonstrated that CeMnOx provides access to fast SCR reaction pathways by oxidizing NO to NO2, resulting in a significant increase in low-temperature activity. This study provides novel guidelines for the design and preparation of Cu-SSZ-39 zeolite with outstanding SCR performance over a wide temperature range.

Fe/amorphous-Al2SiO5 composites fabricated by low-temperature solid-phase reaction densification achieve synergistically enhanced structural and soft magnetic properties

To date, an urgent problem for various metal-based soft magnetic composites (SMCs) is that it is difficult to simultaneously achieve high strength and optimum magnetic performance, which actually restricts their large-scale applications in many electromagnetic fields. In this work, we have tried to resolve this basic problem by proposing a new concept of low-temperature solid-phase reaction densification instead of conventional particle-deformation densification to fabricate high-performance metal-based SMCs. Specifically, fully-densified nanoscale amorphous Al2SiO5 coating layers are formed through a solid phase reaction at 500 °C between initially-prepared nano-sized amorphous SiO2 and amorphous Al2O3, and meanwhile coated in situ on the surface of deformed Fe to fabricate novelly-structured Fe/amorphous-Al2SiO5 SMCs. The low-temperature solid-phase reaction for fabrication of Fe/amorphous-Al2SiO5 SMCs can avoid negative effects of high processing temperature for conventional metal-based SMCs on their structure and magnetism resulting in their high strength, increased resistivity, low core loss and high saturation magnetic inductions. Thus, Fe/amorphous-Al2SiO5 SMCs show synergistically enhanced structural and soft magnetic properties, which exceed those of most conventional metal-based SMCs. This work also provides a special and useful insight into the design and applications of metal-based composites needing both functional and structural properties.

High shear reactor for glycerolysis—Interesterification palm stearin‐olein blend: Reaction kinetics and physical properties

AbstractStructured lipids containing high monoacylglycerol (MAG) and diacylglycerol (DAG) (SLs‐MDAG) were synthesized by chemical glycerolysis‐interesterification using sodium metasilicate as the catalyst in High Shear Reactor (HSR). The objective of this research was to investigate the effect of temperature on the glycerolysis‐interesterification kinetics at relatively low temperatures in an HSR and the physical product properties. The reaction was performed using immiscible and highly viscous reactants at various temperatures (80–120°C) and a mixing rate of 2000 rpm for 5 h. Results showed that the reaction rate constant exponentially increased as temperature increased. Triacylglycerol (TAG) conversion was 2.5 fold greater at 110 and 120°C compared to lower reaction temperatures (80 and 90°C). MAG and DAG increased by about 18.3% and 13.4%, respectively, as the reaction temperature increased from 80 to 120°C. The product's melting point, hardness, and color were also improved by increasing temperature. In summary, SLs‐MDAG could be produced at a relatively low temperature (110°C) using HSR. The glycerolysis‐interesterification kinetic displayed an exponential relationship, even though it did not precisely fit the Arrhenius model.