Catalytic Action Research Articles

Catalytic Action of Nitric Acid on The Hydrolysis of ETS-40 Ethyl Silicate

The effect of concentrated nitric acid on the hydrolysis rate of ETS-40 ethyl silicate hasbeen studied. The duration and maximum temperature of ethyl silicate hydrolysis at different temperatures of the components have been determined. The formation of silica particles in the xerogel structure is shown. The influence of the ETS-40 hydrolysis on the particles size and concentration has been examined. The structure of the xerogel and the composition of the formed particles have been investigated using scanning electron microscopy (SEM) and energy dispersion analysis (EDX).

Impact of As-Prepared and Purifıed Multi-Walled Carbon Nanotubeson the Liquid-Phase Aerobic Oxidatıon of Hydrocarbons

The article presents simple kinetic approaches to study the effect of multi-walled carbon nanotubes (MWCNTs) additives on the aerobic oxidation of hydrocarbons and to propose real acceptable mechanisms of the process. The aerobic liquid phase low-temperature oxidation of ethylbenzene conducted in the presence of multi-walled carbon nanotubes has been used as a model pattern. Kinetic analysis established the catalytic action associated with the presence of the iron compounds in inner channels of MWCNTs. These compounds are identified as ferric carbides provoking decomposition of the ethylbenzene hydroperoxide and thereby suppressing the competitive route of alky-peroxide radicals addition to the nanocarbon cage. Thus the reaction finally proceeds in the autocatalytic mode.Contradictory conclusions on the effect of CNTs on the oxidation chain processes existing in the literature are associated with the lack of control over nature and content of metal impurities in channels of nanotubes.

Room temperature conversion of Mg to MgH2 assisted by low fractions of additives

In recent works, it was noticed that Mg/MgH2 mixed with additives by high energy ball milling allows temperature reductions of H2 absorption/desorption without necessarily changing thermodynamic properties. Thus, the objective of this work was to investigate which additives, mixed in low fractions with MgH2 powder would act as efficient hydrogen absorption/desorption catalysts at low temperatures, mainly at room temperature (RT). MgH2 mixtures with 2 mol% additives (Fe, Nb2O5, TiAl and TiFe) were prepared by high energy reactive ball milling (RM). MgH2–TiFe mixture showed the best results, both during desorption at 330 °C and absorption at RT. The hydrogen absorption was ≈ 2.67 wt% H2 in 1 h and ≈ 4.44 wt% H2 in 16 h (40% and 67% of maximum theoretical capacity, respectively). The MgH2–TiFe superior performance was attributed to the hydrogen attraction by the created high energy interfaces and strong TiFe catalytic action facilitating the H2 flow during Mg/MgH2 reactions.

Integrated CoO nanoparticles@porous carbon nanosheets arrays on carbon cloth as cathode for rechargeable Zn-air batteries

Rechargeable Zn-air batteries attract much attention because of their high theoretical specific capacity and low cost. However, building an integrated air electrode possessing multiple functions such as catalytic action, current collector as well as the carrier is still a challenge. To raise the catalytic efficiency of the air electrode, hierarchical integrated electrodes assembled by porous carbon nanosheets arrays and CoO nanoparticles on carbon cloth are well designed and prepared. The surface morphology and the catalyst phase of the hierarchical electrode are characterized by SEM, XRD and XPS methods respectively. The electrochemical performances of the electrodes are evaluated by three-electrode system and two-electrode Zn-air battery. The results show that, the hierarchical structure provides abundant platform for catalytic reaction and promotes the transfer of reactants/products, indicating excellent rate and cyclic properties of the batteries.

ZIF‐67 Derived Co/NC Nanoparticles Enable Catalytic Leuckart‐type Reductive Amination of Bio‐based Carbonyls to N‐Formyl Compounds

AbstractIt is of great significance to develop non‐precious metal catalysts with excellent catalytic activity, stability, and acid resistance for biomass valorization. Herein, catalytic amination of biomass carbonyl compounds was achieved via a Leuckart‐type reaction over Co nanoparticles (NPs) embedded N‐doped carbon catalyst, which was prepared by thermolysis of ZIF‐67 precursor at different temperatures in the N2 atmosphere. The Co/NC‐800 catalyst exhibited excellent catalytic activity and recyclability in furfural reductive amination to mono‐substituted formamide, which was attributed to the synergistic catalytic action of Co NPs and nitrogen base sites of the catalyst. The reductive amination mechanisms were elucidated by theoretical calculations, and showed that the initial formation of C−N bond was derived from the condensation of furfural and formamide, followed by dehydration to form C=N double bond, which was then reduced by hydrogen species Co−H− and NH+. The developed catalytic system was applicable to different carbonyls for the synthesis of corresponding N‐formyl compounds with up to 99 % yield.

Ultrasensitive luteolin electrochemical sensor based on zeolitic imidazolate frameworks-derived cobalt trioxide @ nitrogen doped carbon nanotube/amino-functionalized graphene quantum dots composites modified glass carbon electrode

The accurate determination of luteolin is of great significance for food and pharmaceutical industry. Herein, an ultrasensitive electrochemical sensor for luteolin based on zeolitic imidazolate frameworks (ZIF)-derived cobalt trioxide @ nitrogen doped carbon nanotube/amino-functionalized graphene quantum dots composites modified glass carbon electrode (Co3O4@N-CNTs/NH2-GQDs/GCE) was constructed. The Co3O4@N-CNTs composites were synthesized through direct pyrolysis of ZIF-67 in the N2 atmosphere, which exhibited outstanding electrochemical performance for luteolin due to the conductivity of N-CNTs and the catalytic action of Co3O4. Under optimized conditions, the Co3O4@N-CNTs /NH2-GQDs/GCE exhibited a linear range of 0.5–1000 nM for detecting luteolin, with a low detection limit (LOD) of 0.1 nM (S/N = 3). Furthermore, the sensor was successfully applied for the detection of luteolin in Chrysanthemum extracts.

Study on the inhibition effect of citric acid on coal spontaneous combustion

Transition metals ions in coal can accelerate the coal spontaneous combustion by reducing the activation energy of the coal-oxygen reaction during coal oxidation. The catalytic action of metal ions may be decreased by adding metal chelators to coal. In this article, an environment-friendly metal chelating agent, citric acid, was proposed as an inhibitor of coal spontaneous combustion. Experiments were carried out to investigate the inhibitory effect of citric acid on coal spontaneous combustion. The results showed that the generation of CO, CO2 and the consumption of O2 in the oxidation of inhibited coal samples were much lower than those of raw coal. Compared to raw coal, the crossing point temperature of inhibited samples increased by 9–12 °C, and the advent time of the crossing point temperature was delayed by 30 to 40 min. In addition, the temperature of the characteristic points of the experimental coal samples after inhibition was higher than that of raw coal. The reaction enthalpy of inhibited coal samples was smaller than raw coal when experimental samples entered the rapid combustion stage. Through Fourier Transform infrared spectroscopy (FTIR) experiments, it was found that the amount of -CH3 and -CH2- groups in coal samples increased after inhibition, but the amount of -COOH and C=O groups decreased. Scanning electron microscope (SEM) analysis showed that the surface of the coal sample became smoother and the pore size decreased after citric acid treatment. In conclusion, citric acid has a good inhibitory effect on different types of coal.

Catalytic mechanism of TiO2 quantum dots on the de/re-hydrogenation characteristics of magnesium hydride

In the present study, the catalyst anatase titanium dioxide (TiO2) quantum dots (QDs) of size ∼ (2.50–4.00)nm was successfully synthesized by the hydrothermal method. The formation of TiO2: QDs has been established by UV–Vis spectroscopy and confirmed by transmission electron microscopy. Here, we report the catalytic action of TiO2:QDs on de/re-hydrogenation properties of magnesium hydride (MgH2/Mg). By catalyzing MgH2 through this catalyst, the onset desorption temperature of MgH2 gets reduced significantly from ∼360 °C (for ball-milled MgH2) to ∼260 °C. Moreover, the Mg-TiO2: QDs sample absorbed a significant amount of hydrogen up to ∼6.10 wt% in just 77sec at 280 °C. Improved rehydrogenation kinetics has been found even at lower temperatures by absorbing ∼5.30 wt% in 74 s at 225 °C and ∼5.0 wt% of hydrogen in 30 min at 100 °C. Based on structural,.microstructural, and XPS investigations, a feasible mechanism for improved hydrogen sorption and cyclic stability in MgH2 catalyzed with TiO2:QDs has been explained and discussed. To our knowledge, no studies have been carried out on the sorption of hydrogen in MgH2 catalyzed by TiO2:QDs.

Role of Aberrantly Activated Lysophosphatidic Acid Receptor 1 Signaling Mediated Inflammation in Renal Aging.

The increasing load of senescent cells is a source of aging, and chronic inflammation plays a pivotal role in cellular senescence. In addition, senescent renal tubular epithelial cells are closely associated with renal aging. Lysophosphatidic acid (LPA) is a bioactive lipid mainly produced by the catalytic action of autotaxin (ATX), and its ligation to LPA receptor-1 (LPAR1) is associated with chronic inflammation and renal fibrosis; however, its role in renal aging is unclear. Male 2-, 12-, and 24-month-old C57BL/6 mice and Human renal proximal tubular epithelial cells (HRPTEpiC) were used in the present study. DNA damage and oxidative stress-induced senescence were simulated using doxorubicin (DOXO) and H2O2, respectively. The aged kidney showed decreased renal function, increased fractional mesangial area, and tubulointerstitial fibrosis. Both aged kidney and senescent cells showed increased levels of LPAR1, Nuclear factor κB (NF-κB), and inflammatory cytokines. In addition, LPAR1-knockdown reduced NF-κB and subsequent inflammatory cytokine induction, and NF-κB-knockdown resulted in decreased LPAR1 expression. Our study revealed a positive feedback loop between LPAR1 and NF-κB, which reinforces the role of inflammatory response, suggesting that blocking of aberrantly activated LPAR1 may reduce excessive inflammation, thereby providing a new possible therapeutic strategy to attenuate renal aging.

Pd/Alumina Catalysts for Beneficial Transformation of Harmful Freon R-22

Chlorodifluoromethane (R-22), the most abundant freon in the atmosphere, was subjected to successful hydrodechlorination in the presence of palladium supported on γ-alumina, at a relatively low reaction temperature (180 °C). The combination of catalytic actions of alumina (performing freon dismutation) and Pd nanoparticles (catalyzing C–Cl bond splitting in the presence of hydrogen) results in the transformation of freon into valuable, chlorine-free products: methane and fluoroform, the mixture of which is used in plasma etching of silicon and silicon nitride. Very highly metal dispersed Pt/Al2O3 catalysts, with metal particles of ~1.3 nm in size, are not as effective as Pd/Al2O3, resulting in only partial dechlorination. A long-term dechlorination screening (3–4 days) showed good catalytic stability of Pd/alumina catalysts.

Flower like strontium molybdate for efficient energy conversion applications

Novel and cost-effective electrocatalysts are most important materials considered for the renewable energy conversion applications. Metal molybdates have gained great attention because of oxygen evolution reaction (OER). These products still need to be improved for practical applications. In this work, SrMoO4 nanostructures were successfully synthesized via trouble-free co-precipitation method. Scheelite-type tetragonal-phase SrMoO4 nanostructures were substantiated using X-ray diffraction. Raman spectra confirmed existence of MoO42-group whereas Fourier transform infrared spectra corroborated different functional groups in well-crystallized SrMoO4 material. Morphologies of the prepared SrMoO4 nanostructures were identified by using the scanning electron microscopy images. The high surface area and porosity of electrocatalysts significantly enhanced the electrochemical performance. Then, the surface area, pore diameter and pore volume of SM2 were 13 m2/g, 4.474 nm and 0.004 cc/g, respectively. The existence of unique flower like morphology and spindle-like rods of SrMoO4 material confirmed the OER activity with elevated 409 F/g specific capacitance. Compared to different molar ratios of SrMoO4 materials, 1:5 M ratios of SrMoO4 nanostructures showed outstanding catalytic action toward OER performance with 187 mV at 10 mA/cm2 and a small 20.5 mV/dec Tafel slope. In addition, SM2 electrode showed better durability in 16 h chronoamperometry test without any decay. Therefore, optimizing the proper molar ratio of SrMoO4 material is one of the important parameters to obtain a good candidate for electrochemical water-splitting applications.

A high-performance room temperature benzene gas sensor based on CoTiO3 covered TiO2 nanospheres decorated with Pd nanoparticles

A benzene sensor based on Pd doped CoTiO3/TiO2 (Pd-CTT) nanocomposite was reported in this paper. The surface morphology and structure composition of the samples were investigated by SEM, TEM, XRD and XPS. The benzene sensing performance of the sensors with different ratios of CoTiO3 and TiO2 was studied at room temperature (RT) of 25 °C. The gas sensing performance of the sensor was further improved by the construction of Pd-CTT ternary composite sensing material. The results show that the sensor has remarkable sensing performance for benzene, including excellent linear response, rapid detection speed, good repeatability and stability. The Pd-CTT sensor showed a high response (Rg/Ra = 33.46 @ 50 ppm) to benzene, with detection limit as low as 100 ppb. The excellent benzene sensing properties of Pd-CTT sensor are attributed to the formation of CoTiO3/TiO2 p-n heterojunction and catalytic action of Pd. This work highlights the unique advantage of Pd-CTT nanocomposite for benzene sensor.

Carbon Microsphere-Supported Metallic Nickel Nanoparticles as Novel Heterogeneous Catalysts and Their Application for the Reduction of Nitrophenol.

Nickel nanoparticles are gaining increasing attention in catalysis due to their versatile catalytic action. A novel, low-cost and facile method was developed in this work to synthesize carbon microsphere-supported metallic nickel nanoparticles (Ni-NP/C) for heterogeneous catalysis. The synthesis was based on carbonizing a polystyrene-based cation exchange resin loaded with nickel ions at temperatures between 500 and 1000 °C. The decomposition of the nickel-organic framework resulted in both Ni-NP and carbon microsphere formation. The phase composition, morphology and surface area of these Ni-NP/C microspheres were characterized by powder X-ray diffraction, Raman spectroscopy, scanning electron microscopy and BET analysis. Elemental nickel was found to be the only metal containing phase; fcc-Ni coexisted with hcp-Ni at carbonization temperatures between 500 and 700 °C, and fcc-Ni was the only metallic phase at 800–1000 °C. Graphitization and carbon nanotube formation were observed at high temperatures. The catalytic activity of Ni-NP/C was tested in the reduction of 4-nitrophenol to 4-aminophenol by sodium borohydride, and Ni-NP/C was proved to be an efficient catalyst in this reaction. The relatively easy and scalable synthetic method, as well as the easy separation and catalytic activity of Ni-NP/C, provide a viable alternative to existing nickel nanocatalysts in future applications.

High-Efficiency Wastewater Purification System Based on Coupled Photoelectric–Catalytic Action Provided by Triboelectric Nanogenerator

HighlightsTriboelectric nanogenerator (TENG)/carbon dots-TNs supported over three-dimensional graphene aerogel (3DGA@CDs-TNs) system was constructed.TENG and 3DGA@CDs-TNs present excellent degradation activity toward brilliant green (88.26%, 40 min) and direct blue 5B (89.6%, 90 min).The coupling interaction of photocatalysis and TENG leads to an enhanced removal ability.The degradation pathways for brilliant green and direct blue 5B are proposed.

Single-Atom Catalysis: From Simple Reactions to the Synthesis of Complex Molecules.

To date, the scope of single-atom catalysts (SAC) in liquid-phase transformations is rather limited owing to stability issues and the inability to activate complex substances. This calls for a better design of the catalyst support that can provide a dynamic coordination environment needed for catalytic action, and yet retain robustness against leaching or aggregation. In addition, the chemical orthogonality of SAC is useful for designing tandem or multicomponent reactions, in which side reactions common to metal nanoparticles are suppressed. In this review, the intrinsic mechanism will be highlighted that controls reaction efficiency and selectivity in SAC-catalyzed pathways, as well as the structural dynamism of SAC under complex liquid-phase conditions. These mechanistic insights are helpful for the development of next-generation SAC systems for the synthesis of high-value pharmaceuticals through late-stage functionalization, sequential and multicomponent strategies.

Biochemical Investigation of 3-Sulfopropionaldehyde Reductase HpfD.

Sulfoquinovose is the polar headgroup of plant sulfolipids and is a globally abundant organosulfur compound, and its degradation by bacteria is an important component of the sulfur cycle. Sulfoquinovose degradation by certain bacteria, including Escherichia coli, produces dihydroxypropanesulfonate (DHPS), which is further converted by anaerobic bacteria into 3-hydroxypropanesulfonate (3-HPS), through the catalytic action of DHPS dehydratase (a member of the glycyl radical enzyme family), and sulfopropionaldehyde reductase HpfD (a member of the metal-dependent alcohol dehydrogenase family). Here we report biochemical investigation of Hungatella hathewayi HpfD. In addition to 3-HPS, HpfD also displayed high catalytic activities for NAD+ -dependent oxidation of 4-hydroxybutanesulfonate (4-HBS) and γ-hydroxybutyrate (GHB). The highest activity was obtained with Fe2+ or Mn2+ as the divalent metal cofactor. Bioinformatics studies suggest that, in addition to DHPS degradation, 3-HPS and γ-aminobutyrate (GABA) degradations also involve HpfD homologs.

How Transformation Catalysts Take Catalytic Action

The challenges that are associated with the 17 United Nations sustainable development goals are wickedly complex and interconnected in nature. Because they require transformational changes at the systems level, the pace of change has, so far, been nowhere near fast enough to meet the goals by 2030. In this paper, we analyze the catalytic actions of a novel form of organizing that could potentially facilitate the timely achievement of transformational aspirations such as the SDGs: the transformation catalyst (TC). By identifying 27 TCs and analyzing their vision, mission, values, and their practices represented on their websites, we elaborate the following four key ways that TCs are distinctive from other entities, and therefore potentially more capable of facilitating transformational changes at the systems level: (1) TCs have transformation agendas that target systems-level solutions to bring about large-scale and fundamental changes in the relevant system(s), as opposed to more incremental or fragmented approaches; (2) TCs engage in catalytic actions, such as connecting, cohering, and amplifying the work of partners and collaborators; (3) TCs clearly acknowledge the current status quo, attributions, and urgency (i.e., sensemaking) of the issues on which they focus; and finally, (4) TCs embody systems orientation. In exploring how TCs work, we hope to build a solid conceptual framework for understanding the nature of transformative catalytic action on societal issues, and consolidate our understanding of what elements are needed if TCs are to work, providing a starting point for future research.

Dynamic tracking and identification of tissue-specific secretory proteins in the circulation of live mice

Secretory proteins are an essential component of interorgan communication networks that regulate animal physiology. Current approaches for identifying secretory proteins from specific cell and tissue types are largely limited to in vitro or ex vivo models which often fail to recapitulate in vivo biology. As such, there is mounting interest in developing in vivo analytical tools that can provide accurate information on the origin, identity, and spatiotemporal dynamics of secretory proteins. Here, we describe iSLET (in situ Secretory protein Labeling via ER-anchored TurboID) which selectively labels proteins that transit through the classical secretory pathway via catalytic actions of Sec61b-TurboID, a proximity labeling enzyme anchored in the ER lumen. To validate iSLET in a whole-body system, we express iSLET in the mouse liver and demonstrate efficient labeling of liver secretory proteins which could be tracked and identified within circulating blood plasma. Furthermore, proteomic analysis of the labeled liver secretome enriched from liver iSLET mouse plasma is highly consistent with previous reports of liver secretory protein profiles. Taken together, iSLET is a versatile and powerful tool for studying spatiotemporal dynamics of secretory proteins, a valuable class of biomarkers and therapeutic targets.

Catalytic, theoretical, and biological investigation of an enzyme mimic model.

Artificial catalyst studies were always stayed at the kinetics investigation level, in this work bioactivity of designed catalyst were shown by the induction of biomineralization of the cells, indicating the possible use of enzyme mimics for biological applications. The development of artificial enzymes is a continuous quest for the development of tailored catalysts with improved activity and stability. Understanding the catalytic mechanism is a replaceable step for catalytic studies and artificial enzyme mimics provide an alternative way for catalysis and a better understanding of catalytic pathways at the same time. Here we designed an artificial catalyst model by decorating peptide nanofibers with a covalently conjugated catalytic triad sequence. Owing to the self-assembling nature of the peptide amphiphiles, multiple action units can be presented on the surface for enhanced catalytic performance. The designed catalyst has shown an enzyme-like kinetics profile with a significant substrate affinity. The cooperative action in between catalytic triad amino acids has shown improved catalytic activity in comparison to only the histidine-containing control group. Histidine is an irreplaceable contributor to catalytic action and this is an additional reason for control group selection. This new method based on the self-assembly of covalently conjugated action units offers a new platform for enzyme investigations and their further applications. Artificial catalyst studies always stayed at the kinetics investigation level, in this work bioactivity of the designed catalyst was shown by the induction of biomineralization of the cells, indicating the possible use of enzyme mimics for biological applications.

Preparation of CNTs Coated with Polydopamine–Ni Complexes and Their Catalytic Effects on the Decomposition of CL-20

To improve the condensed-phase reaction rate of ε-CL-20, polydopamine (PDA)–nickel complex-coated multiwalled carbon nanotubes (CNTs) have been prepared and used as combustion catalysts. The PDA–Ni complex has been prepared and in situ coprecipitated with ε-CL-20 by an antisolvent crystallization process in its dimethyl sulfoxide (DMSO) solution. It has been shown that crystalline CL-20 composites included with PDA–Ni complexes are polygon-shaped with a smooth surface and an average diameter of 10–15 μm, whereas it is 140 μm for raw ε-CL-20 crystals. The catalytic reactivity of the complex on thermolysis of CL-20 has been investigated using the differential scanning calorimetry (DSC) and thermogravimetry (TG)-coupled Fourier transform infrared (FT-IR) spectroscopy technique. It has been found that CNT@PDA–Ni complexes have catalytic effects on the decomposition of ε-CL-20 by decreasing/shifting of the exothermic peak from Tp = 240.1 to 238.7 °C. The FT-IR spectra of CL-20 decomposition products under the effect of the catalyst predominantly show peaks at 1274, 1644 and 1596, 1912, 2265, and 1956–1800 cm–1, indicating the presence of fragments with N2O, NO2, NO, HNCO, and NO/CO, respectively. The change in the ε-CL-20 decomposition mechanism should be attributed to the catalytic action of CNT, decreasing the formation of NO2. Also, under the effect of the carbon-based catalyst, the HNCO formation was detected at another temperature in comparison with raw CL-20, with peak absorption at 224.1 vs 232.3 °C and the evolution was completed at 250.8 vs 246.2 °C, respectively.