Values Of Reaction Rate Research Articles

Thermally synthesized hematite (α-Fe2O3) nanoparticles as efficient photocatalyst for visible light dye degradation.

In recent years, water pollution has become a pressing global issue because of the continuous release of organic dyes from various industries. Therefore, finding an easy way to remove these harmful dyes from water has drawn the attention of researchers. This study investigates the removal of toxic Rose Bengal (RB) dye using hematite nanoparticles as a visible light photocatalyst without any additive. It is observed that by controlling particle size, quantity of the nanoparticles and reaction temperature, the dye degradation can be improved up to 95.33% with a half-life of 26 min. To understand photodegradation kinetic behavior, the Langmuir-Hinshelwood kinetic equation can be employed. The scavenger test indicated that the OH* radicals majorly led to the photodegradation process. The reaction rate values strongly depended on the size, quantity of the nanoparticles and reaction temperature. Controlling the optimizing condition, faster reaction rate (k = 0.027 min-1) can be achieved as compared to earlier reports. It is also noted that the change in the degradation efficiency of the reused catalyst is negligible when compared to the fresh one. Here, the dye degradation mechanism is discussed. Overall, this study reveals that hematite nanoparticles can be used as efficient photocatalyst for dye degradation applications by optimizing the controlling factors. These observations provide novel perspectives on the development of effective and sustainable photocatalytic technologies for pollution control and water treatment applications.

Mixed Convection Over an Exponentially Stretching Surface with the Effect of Radiation and Reaction

This study investigates the mixed convection on a vertically oriented exponentially stretching surface, considering the exponential distributions of velocity, concentration and temperature. The governing highly nonlinear partial differential equations (PDEs) are transmuted into highly nonlinear ordinary differential equations (ODEs) by considering appropriate similarity variables. The highly nonlinear differential equations are solved numerically using the Hermite wavelet method (HWM) in MATHEMATICA 12. The obtained results show excellent agreement with previous studies focusing on different special cases of the problem. A parametric analysis of the physical parameters is shown and illustrative numerical results are presented graphically. The analysis incorporates the radiation, chemical reaction and cross-diffusion effects. The interaction between radiation and chemical reaction is particularly relevant in high-temperature systems, such as combustion, industrial furnaces, photochemistry, polymerization and certain chemical reactions. The results indicate that an increase in radiation enhances the temperature profile in the momentum boundary layer. Higher reaction rate values lead to a decrease in the concentration profile, while an increase in the Dufour value results in increased velocity and temperature and decreased concentration.

Using ion exchange chromatography for the purification of glyoxylate reductase from corn leaves and studying its characteristics

The purpose of this study was to obtain a purified preparation of the studied enzyme from corn leaves and to study its characteristics. In this work, kinetic and regulatory parameters of glyoxylate reductase were calculated for leaves of 14-day-old corn (Zea mays) seedlings grown hydroponically at 25°C. The following methods were used during the study: sample homogenisation, four-step purification including ammonium sulphate for desalting, gel filtration on G-25 columns, and ion exchange chromatography using DEAE-sephacel, as well as electrophoresis on polyacrylamide gels and quantitative analysis of protein. To study the properties of the enzyme, we used electrophoretically homogenous preparations. The influence of pH, substrate concentration, and cofactor on the rate of the enzymatic reaction was determined by a series of measurements with different values of the enzymatic reaction rate. As a result of four-stage purification, we obtained a homogeneous preparation with a specific activity of167 E/mg of protein. Ion exchange chromatography was important for purification; we obtained 1 peak of enzyme activity upon desorption in 104 mM sodium chloride. Studying the properties of glyoxylate reductase showed a significant dependence of activity on pH. The optimal pH value was 6.5 units.

A Comparative Study of Zinc Phosphate and Zirconium-Based Conversion Coatings on Galvannealed Steel: Effect on Corrosion Performance of Electrocoated Systems

The efficacy of an electrocoated system that uses a Zr-based conversion coating was assessed to protect galvannealed (GA) steel. The aim was to determine if a Zr-based system has the potential to replace a system with a traditional zinc phosphate (ZnP) conversion coating, where there are concerns for the environmental and economic sustainability. A comparative study between the two conversion coatings, and a control system with no conversion coating, is presented. Data from AC and DC electrochemistry are utilized with surface analysis investigations of pristine specimens, where scanning electron microscopy, x-ray photoelectron spectroscopy, and x-ray diffraction have been used to determine the mechanism through which protection, or coating failure, occurs. Further investigations study surface morphology and stability of specimens during immersion in a simulated electrocoat bath, and their effect on the performance of fully electrocoated systems. The corrosion current density (icorr) for bare, ZnP, and Zr-based conversion coated specimens in chloride-containing solution with no electrocoat were found to be approximately 1.90 µA/cm2, 0.30 µA/cm2, and <0.01 µA/cm2, respectively. Rp values of 0.05 kΩ, 4.2 kΩ, and 20.7 kΩ were recorded for bare, ZnP and Zr-based specimens, respectively. The corrosion current density (icorr) for bare, ZnP, and Zr-based conversion coated specimens under chloride-containing conditions with electrocoat were found to be 3.82 µA/cm2, 0.53 µA/cm2, and 0.06 µA/cm2, respectively. |Z| values at 0.01 Hz (|Z|0.01 Hz) were measured, yielding 45.5 GΩ, 47.4 GΩ, and 31.6 GΩ for bare, ZnP, and Zr-based pretreatments respectively, demonstrating excellent barrier properties after electrocoating. Hydrogen evolution reaction (HER) rate values of 3.52 × 10−2 mol·m−2·s−1, 3.12 × 10−2 mol·m−2·s−1, and 2.94 × 10−2 mol·m−2·s−1 were recorded for the bare, ZnP, and Zr-based systems, respectively. This study produced a ranking order of HER rate. This was bare > ZnP > Zr-based. These results suggest that the Zr-based system is less prone to HER, interfering with the electrocoat deposition process. A performance ranking order for pretreated and electrocoated systems was established, where Zr-based > ZnP > control. The level of thickness and roughness provided by the conversion coating is speculated to be the controlling factor for coating performance, where the ZnP conversion coating was found to provide a thicker layer with greater surface coverage beneficial for a uniform electrocoat film build.

Machine learning approach for the effectual production of a novel esterase and its application in bioremediation of dairy effluent

The present work intends to maximize the production of an industrially important novel esterase from Trichoderma harzianum using both machine learning and statistical approaches and its application in the bioremediation of dairy effluent. Significant medium compounds, such as almond oil, casein, NaH2PO4, and trace elements, were screened from a pool of carbon, nitrogen, oil and surfactant sources along with other micronutrients using a first order statistical design. The optimum value of screened parameters was found using response surface methodology that resulted in the maximum esterase production of 2985.31 U/L. Artificial neural network trained with the experimental response of RSM experiments coupled with genetic algorithm optimization technique has resulted in the maximum esterase production of 3256.73 U/L, which is 150-folds higher as compared to the unoptimized condition and also found to be the higher than the outcome of statistical optimization. Dairy effluent was used for the production of esterase as well as for its bioremediation. At 50% load, the maximum reduction in chemical oxygen demand and the production of esterase were observed to be 46.84% and 34.12 U/L, respectively. The COD reduction of diary effluent was modelled using Michaelis-Menten kinetics and the kinetic parameters, half saturation constant (Km) and maximum reaction rate (rmax) value were evaluated as 286.88 mg/L and 26.04 mg/L/d, respectively.

Catalytic effect of N-phenylaminopropyl polyheadral oligomeric silsesquioxane in the synthesis of hybrid nanocomposites based on polycyanurate

Organic-inorganic nanocomposites based on heat-resistant crosslinked polycyanurate (PCN) and N-phenylaminopropyl polyhedral oligomeric silsesquioxane (NPAP-POSS), containing eight reactive secondary amino groups, were synthesized using the in situ reactive formation method. Fourier transmission infrared (FTIR) spectroscopy and dynamic differential scanning calorimetry (DSC) methods were used to study the effect of NPAP-POSS on the kinetics of bisphenol E dicyanate ester (DCBE) polycyclotrimerization during the formation of PCN in PCN/NPAP-POSS nanocomposites. The content of the nanofiller was varied from 0.05 to 1.00 wt.%. Based on the results of FTIR spectral studies, the main kinetic peculiarities of PCN formation were found and their changes under the action of NPAP-POSS nanofiller were determined. A significant catalytic effect of NPAP-POSS on the polycyclotrimerization of DCBE was found, which is confirmed by a decrease in the time of the onset of auto-acceleration, an acceleration of the conversion of cyanate groups of DCBE and the formation of triazine cycles of PCN, an increase in the values of the maximum reaction rate, a decrease in the duration of the reaction, etc. The dynamic DSC method also confirmed the catalytic effect of NPAP-POSS on the formation of PCN in the nanocomposites and established the main kinetic characteristics depending on the content of the nanofiller: a significant decrease in the temperature of the exothermic maximum, an increase in the reaction enthalpy, non-monotonic changes in the induction period and reaction rate, etc. From the analysis of the experimental data, it was concluded that the detected changes in the kinetics of the in situ reaction formation of PCN/NPAP-POSS nanocomposites and the recorded catalytic effect of the nanofiller are due to the fact that two chemical processes occur during the synthesis of the nanocomposites: chemical interaction of –O–C≡N groups of DCBE with secondary –NH groups of NPAP-POSS, which led to further embedding of nanoparticles into the resulting polymer matrix and the direct polycyclotrimerization of DCBE with formation of hybrid polycyanurate network. Schemes of the sequential reactions explaining the catalytic effect of the nanofiller in the synthesis of hybrid PCN/NPAP-POSS nanocomposites are proposed. It was concluded that under the selected conditions of the synthesis, the greatest catalytic effect of the nanofiller is manifested at its content of 0.10 wt.%, since for this sample the maximum shift of the reaction exothermic peak towards lower temperatures, the maximum reaction rate, and the minimum induction period and reaction start temperature were recorded. The results of the research make it possible to optimize the synthesis of heat-resistant materials promising for use in special-purpose structures.

The Characteristics of Urease Enzyme of Green Bean Seeds (Vigna radiata L.) and Its Activity as An Antifungal Against Candida albicans

Urease is an enzyme responsible for catalyzing the hydrolysis reaction of urea into CO2 and NH3. The urease isolated in this study came from green bean seeds. The urease enzyme was then tested for its antifungal activity against Candida albicans. The research aims to extract and characterize the urease enzyme from green bean seeds and explore its potential use as an antifungal agent. Green bean seeds were smoothed with a mortar and pestle, followed by homogenization using a stirrer and cold centrifugation. The crude extract of the urease enzyme was assessed for its activity through the Nessler method and measured by employing a UV-Vis spectrophotometer at a wavelength of 500 nm. The well-diffusion method was conducted to determine the antifungal activity of rough enzyme extracts against C. albicans. Positive controls were 100% ketoconazole, and negative controls used a pH buffer of 7. The characterization of the urease enzyme from green bean seeds revealed the optimum urease activity at a concentration of 0.25 M, pH level of 7, and an incubation temperature of 35°C with a value of 32.115 U/mL. Maximum reaction rate (Vmax) and Michaelis-Menten constant value (KM) were obtained at 56.497 U/mL and 0.215 M, respectively. Antifungal tests of C. albicans resulted in strong inhibitory activity at a concentration of 100% crude urease extract of 12 mm inhibition zone. The inhibitory concentration value grows at least 0.5% by 0.25 mm and positive control of 19.802 mm.

Efficient catalytic combustion of propane at low temperature based on ignition effect caused by amorphous atomic-layer Pt clusters

Developing highly active catalysts for hydrocarbon combustion at low temperatures is paramount but yet challenging. The crystal form of carrier and the dispersion degree of active species have great influence on propane combustion catalysts, but its internal mechanism is still unclear. In this study, the amorphous atomic-layer Pt clusters (AL) and Pt single atoms (SA) on TiO2 with various crystal phases were prepared and used as propane combustion catalysts, where the as-synthesized Pt/a-TiO2 catalyst with atomic-layer Pt clusters exhibited better catalytic performance. The Pt/a-TiO2-AL could achieve a 90 % propane conversion (T90) at 230 °C, with the highest reaction rate (39.57 × 10−7 mol g−1 s−1) and TOF value (7.72 × 10−2 s−1) at 240 °C. Kinetic studies showed that oxygen had a lower inhibitory effect on Pt/a-TiO2-AL compared to that on the Pt/p-TiO2-AL and Pt/r-TiO2-AL catalysts; simultaneously, the Pt/a-TiO2-AL catalyst presented lower apparent activation energy compared with Pt/a-TiO2-SA. DFT results showed that atomic-layer Pt clusters on TiO2 had the lower formation energy of oxygen vacancy than Pt single atoms due to the synergistic effect between adjacent exposed Pt atoms in the fully exposed atomic-layer Pt clusters, which had a higher activation capacity for oxygen and thus accelerated propane combustion through the ignition effect (rapid activation of oxygen and rapid combustion of propane). Our primary results provide a promising approach for the creation of high-efficiency Pt-based catalysts, specifically tailored for the catalytic combustion of volatile organic compounds (VOCs).

Equilibrium of argon plasma particles at high pressure

The density value and plasma reaction rate are the physical quantities needed to produce plasma. Both are used to estimate the heat energy and operating time of the plasma. Argon plasma at atmospheric pressure is widely used in industry. Density values and plasma reaction rates were obtained by computational modeling using the continuity equation and the Arrhenius equation obtained from experimental data. Five argon species were used in this research including Ar*, Ar+, Ar2+, Ar, and electron. Plasma equilibrium occurs in time intervals of 10-12 – 10-3 seconds with a temperature of 2 eV. The overall thermal argon plasma equilibrium density ranges within the interval 109 – 1016 m-3. The value of the fastest reaction rate obtained is equal to 2.482 × 104 m-3.s-1 until the smallest reaction rate is obtained equal to 14.613 × 10-34 m-3.s-1.

New type of basket stationary bed reactor for heterogeneous biocatalysis

Effectiveness of catalytic processes using heterogeneous biocatalysts depends not only on the activity of the enzyme, but also on the efficiency of the used reactor. In this paper, we present a novel design of a basket reactor with a stationary catalyst bed (StatBioChem). The developed design was compared to a commercially available rotating bed reactor (SpinChem®). The biocatalysts used were invertase and acyltransferase from Mycobacterium smegmatis (MsAcT) immobilised on macroporous silica supports. The obtained values of initial reaction rate, both in the reaction of saccharose hydrolysis and 2,2-dimethyl-1,3-propanediol (NPG) transesterification, were twice higher for the StatBioChem reactor. A similar relationship was also observed regarding the process efficiency expressed as STY.

Insights into the catalytic performance of LDHs-derived CoAlO oxides with different anions intercalation for propane total oxidation

Constructing effective and stable non-noble metal catalysts is of great significance and prospect for catalytic oxidation of stable light alkanes at low temperature. Herein, the CoAlO oxide catalysts derived from the CoAl layered double hydroxides (LDHs) intercalated with CO32–, CH3COO– (Ac), SO42-, NO3– and citrate (CA) anions were prepared, and their catalytic performances for propane oxidation were investigated. Among all CoAlO catalysts, the CoAlO-Ac-3 catalyst (CH3COO– anion intercalation) exhibited better catalytic activity for propane oxidation (T90 = 300 °C), with the highest reaction rate (2.79 × 10-7 mol g−1 s−1) and TOF value (0.13 × 10-3 s−1) at 240 °C. Characterization results revealed that the interlayer anions affected the valence distribution of metals and surface active oxygen species, and CH3COO– anion intercalation CoAlO-Ac catalyst showed the highest Co3+/Co2+ molar ratio and active oxygen species. Combining with Raman and in-situ DRIFTS results, the lattice distortion of catalyst caused by the interlayer anions promoted the migration of active oxygen species, thus accelerating the propane adsorption and activation. Meanwhile, CoAlO-Ac-3 catalyst exhibited excellent stability and water resistance for propane oxidation.

Copper(II) Complexes with Carnosine Conjugates of Hyaluronic Acids at Different Dipeptide Loading Percentages Behave as Multiple SOD Mimics and Stimulate Nrf2 Translocation and Antioxidant Response in In Vitro Inflammatory Model.

A series of copper(II) complexes with the formula [Cu2+Hy(x)Car%] varying the molecular weight (MW) of Hyaluronic acid (Hy, x = 200 or 700 kDa) conjugated with carnosine (Car) present at different loading were synthesized and characterized via different spectroscopic techniques. The metal complexes behaved as Cu, Zn-superoxide dismutase (SOD1) mimics and showed some of the most efficient reaction rate values produced using a synthetic and water-soluble copper(II)-based SOD mimic reported to date. The increase in the percentage of Car moieties parallels the enhancement of the I50 value determined via the indirect method of Fridovich. The presence of the non-functionalized Hy OH groups favors the scavenger activity of the copper(II) complexes with HyCar, recalling similar behavior previously found for the copper(II) complexes with Car conjugated using β-cyclodextrin or trehalose. In keeping with the new abilities of SOD1 to activate protective agents against oxidative stress in rheumatoid arthritis and osteoarthritis diseases, Cu2+ interaction with HyCar promotes the nuclear translocation of erythroid 2-related factor that regulates the expressions of target genes, including Heme-Oxigenase-1, thus stimulating an antioxidant response in osteoblasts subjected to an inflammatory/oxidative insult.

Linear stability analysis of chemical mechanism, Listanalchem: A tool for the search of spontaneous mirror symmetry breaking

Homochirality, the phenomenon by which one of two virtually identical (non-superimposable mirror images) compounds is favored over the other in the chemistry of life, has been regarded as a requisite for the emergence of all living things on earth. Spontaneous mirror symmetry breaking has been proposed to produce the imbalance. Under this framework, Frank presented, in his foundational article “On spontaneous asymmetric synthesis”, a simple chemical reaction network that displays spontaneous symmetry breaking for a specific set of reaction rates. Research has since focused on finding more complex and plausible models, each one with its advantages and disadvantages. Nevertheless, finding reaction rate values that make a model exhibit spontaneous symmetry breaking is a complex task, even for specially crafted models. LInear STability ANALysis of CHEmical Mechanism, Listanalchem, is a method and software for the search for appropriate reaction rates. It includes four different algorithms inspired by the analysis of Frank's network. Two classical algorithms are also included in Listanalchem: the Trace-Determinant plane and the Stoichiometric Network Analysis by Bruce Clarke. Listanalchem reads a chemical reaction network from plain text and runs one or more of the available algorithms according to the user selection. Listanalchem is tested and verified by studying classical, modified, and recent models proposed to explain the origin of biological homochirality.•Listanalchem allows a fast and reliable search for instability behavior in chemical mechanisms that pretend to explain spontaneous mirror symmetry breaking.•Listanalchem contains several model examples, including the most cited in the related literature.•Listanalchem is a tool that tests models that pretend to explain the origin of biological homochirality, helps find errors, and aids in designing new models.

Influence of precursor compounds on the structural and catalytic properties of CoNiMo/SBA-15 catalysts used in the hydrodesulfurization of dibenzothiophene

In the present research project, it was studied in detail how the incorporation of different precursor compounds and the supplementary addition of amounts of nickel in the MoS2 slabs can influence the structural and catalytic properties of trimetallic CoNiMo catalysts supported on SBA-15 mesoporous support with precise control of the amount and nature of the promoters. The catalysts were prepared by the incipient impregnation method using ammonium heptamolybdate and cobalt and nickel acetate, and nitrate as precursors adding nickel in molar amounts (5, 10, and 20%) of the cobalt atomic loading. Adding the Ni in small amounts allows us to keep the (Co + Ni)/(Co+Ni+Mo) molar ratio near 0.3. The catalysts formed were labeled according to the precursor compounds used (CoNixMo-Ac for acetates and CoNixMo-N for nitrates), where x is the percentage of nickel. Catalysts were then characterized by N2 adsorption-desorption isotherms, X-ray diffraction, high-resolution transmission electron microscopy, and X-ray photoelectron spectroscopy. Catalysts were tested in the HDS of dibenzothiophene (DBT).Results show a significant impact of adding small amounts of nickel and the type of precursor compounds used for the CoNiMo trimetallic catalysts on the final HDS activity. In the case of the catalysts prepared with cobalt and nickel acetates, it was observed that the initial reaction rate values increased as the amount of Ni increased, being the CoNi5Mo-Ac, the catalyst with the lower catalytic activity. Increasing the amount of Ni causes an increase in the HDS of DBT. In the case of the catalysts prepared with nitrates, it could be observed a similar effect. The catalyst with the higher catalytic activity in both series was the CoNi20Mo-Ac. These results agree with the TEM analysis in which a decrease in the slab length of the MoS2 could be regarded as the de Ni amount increase. This means that the type of precursor used has an essential effect on the catalysts since modify their properties and catalytic activity and suggests that the materials synthesized with acetate precursors can help to improve the intrinsic activity of the HDS sites.

Catalytic valorization of glycerol in the absence of external hydrogen: Effect of the Cu/ZrO2 catalyst mass and solvent

The glycerol valorization by heterogeneous catalysis to produce high-value-added chemicals is mainly carried out in the presence of high pressures of molecular hydrogen, a highly flammable gas whose main production in our days depends on fossil fuels. Therefore, an attractive alternative to explore is hydrogen in-situ generation in the catalytic process. Herein, we investigated the liquid-phase catalytic valorization of 80% wt. glycerol in different solvents such as water, 2-propanol, and acetone using a Cu/ZrO2 catalyst in the absence of external hydrogen. Firstly, the mass effect of the Cu/ZrO2 in the glycerol aqueous medium was evaluated finding an optimum mass of 250 mg for glycerol conversion. At these conditions, an initial reaction rate value of 2.63 × 10−3 molgly·gcat−1·min−1 was observed while the main products were hydroxyacetone (HA) and 1,2-propanediol (1,2-PDO). The use of 2-propanol as solvent and hydrogen donor molecule in the glycerol conversion induced the hydrogenation of hydroxyacetone towards 1,2-PDO. The ratio between the selectivity of 1,2-PDO/HA was found to be higher than that observed for the catalytic experiment with water. For the conversion of glycerol in the presence of acetone as a solvent it was noted the occurrence of acetalization reaction of glycerol with acetone and the main product observed was 4-hydroxymethyl-2,2-dimethyl-1,3-dioxalane or solketal. Density functional theory (DFT) calculations were included to gain insight into the reaction mechanisms of the hydroxyacetone hydrogenation to the formation of 1,2-PDO on Cu/ZrO2 catalyst. Four possible pathways were considered. The elementary steps include several intramolecular hydrogen atom transfer steps and two hydrogen addition steps. The hydrogen sources would come from adsorbed hydroxyl species of the aqueous reaction medium on ZrO2 support.

Viscous dissipation and variable viscosity impacts on oscillatory heat and mass transfer of gravity-driven reactive flow along heated plate

The species chemical reaction is an especially significant event in transient fluids. This is a crucial element that raises the temperature as a result of a noticeable rise in reaction rates. Hydrometallurgical industries and chemical engineering, such as the manufacturing of polymers and the processing of food, put a significant amount of concentration with consequences of chemical reactions on heat and mass transport. The effects of chemical reaction, reduced gravity, viscous dissipation, and viscosity on oscillatory heat and mass properties of gravity-driven reactive flow across an inclined heated plate at three positions cos30°, cos45°, and cos60° are the main objective of this work. To elaborate material quantities, the computational mathematical model is developed. The viscosity of fluid is considered as a function of temperature. The non-dimensional model is transformed into non-oscillating and oscillating parts by using Stokes factors. For the convergence of numerical outcomes, the primitive formulation is used. The graphical and numerical findings are obtained through FORTRAN language and Tecplot-360 software. It was found that the velocity of fluid increases for lower values of reaction rate but decreases for higher reaction rate. It can be seen that the significant magnitude of oscillatory heat transfer increases as the Prandtl number increases. It is also examined that amplitude of shearing stress increases at each angle as the reduced gravity increases. The prominent amplitude in the oscillating in heat and mass transfer for minimum viscosity is noted along the inclined heated plate.

Stable Sulfonic MCM-41 Catalyst for Furfural Production from Renewable Resources in a Biphasic System

An MCM-41-SO3H catalyst with 14 wt% S was successfully synthesized to be used in furfural production from xylose and hemicellulose in a biphasic n-butanol/water system. The precursor MCM-41 and the acid-functionalized MCM-41-SO3H catalyst were characterized by XRD, FTIR, TEM, N2 physisorption, ICP-MS, TPD-NH3, and XPS. The characterization results indicated that the sulfonic process partially decreased the ordered mesoporous structure and increased the acid strength of the initial MCM-41. The catalytic performance of the xylose conversion was evaluated in a batch-type reactor using different biphasic ecological and renewable n-butanol/water ratios (1:1, 1.5:1, 2:1, and 2.5:1) as dissolvent at 170 °C. The effect of the dissolvent mixture was clearly seen from the larger initial reaction rate and TOF values for the 1.5:1 ratio. This catalytic behavior indicated that a proper proportion of n-butanol/water dissolvent mixture enhanced the solubility of the substrate in the n-butanol-rich mixture and prevented the deactivation of acidic sulfonated surface groups. To achieve transformation of lignocellulosic raw material to value-added products, the MCM-41-SO3H catalyst was also used for the production of furfural. The recycling evaluation tests indicated that for the recovered catalyst submitted to a sulfonation process, the yield of furfural was closer to the fresh catalyst.

PtCu Nanoparticle Catalyst for Electrocatalytic Glycerol Oxidation: How Does the PtCu Affect to Glycerol Oxidation Reaction Performance by Changing pH Conditions?

In this work, we show that finding and controlling optimum pH environments with Pt-based alloy catalysts can create high catalytic performances for electrocatalytic glycerol oxidation reaction (EGOR). Compared to a Pt/C catalyst, the PtCu/C alloy catalyst has higher reaction rate and turnover frequency (TOF) values by increasing the pH. Specifically, the reaction rate and TOF of the PtCu/C catalyst at pH 13 were 2.93 and 6.65 times higher than those of Pt/C, respectively. The PtCu/C catalyst also showed lower onset potential value and higher mass and specific activities than the Pt/C by increasing the pH. This indicates that the Cu in the PtCu alloy improves the catalytic activity for the EGOR in an OH− group-rich environment. In the case of the PtCu/C catalyst at a high pH condition, the selectivities of tartronic acid and oxalic acid tended to increase as the selectivity of lactic acid decreased. This result means that the PtCu alloy follows primary alcohol oxidation pathways, which are more favorable in an OH− group-rich environment than with only Pt. This study proposes that it is critical to optimize and control the reaction conditions for developing efficient EGOR catalysts.

Highly selective hydrogenation of arenes over Rh nanoparticles immobilized on α-Al2O3 support at room temperature

Selective hydrogenation of arenes is a crucial process not only for the hydrogen storage and transport but also for the synthesis of important pharmaceutical intermediates. Herein, a series of α -Al2O3-supported catalysts prepared using different metals were tested for the arenes hydrogenation of lignin derivatives at room temperature. The kinetic studies reveal that Rh-1/α -Al2O3 exhibits both the highest reaction rate and TOF value for the conversion of diphenyl ether and toluene. The XRD, TEM, XPS and XAS analyses suggest that the distribution of the metal Rh nanoparticles on α -Al2O3 support for Rh-1/ α -Al2O3 catalyst is mainly responsible for the H2 activation/dissociation and subsequent arenes hydrogenation. The density functional theory calculation indicates the stronger adsorption capacity of toluene and guaiacol on Rh (200) than that on Rh (110) and Rh (220). Stable Rh-1/ α -Al2O3 can contribute to the improvement of the arenes hydrogenation of lignin derivatives to produce high-value-added platform chemicals at room temperature.

Surface states modulation of topological insulator Bi2Se3 by noble metal decoration for gas sensing kinetic engineering

The chemical reaction of gas adsorption/desorption is strongly correlated with the surface state of sensitive films. Thus, understanding the surface state and kinetic process of gas-sensing reactions is crucial to design highly active sensing films. In this study, bismuth selenide (Bi2Se3) was selected as the platform to clarify those matters. The noble metal nanocrystals (Au, Ag and Pt) were decorated on the (001) surface of layered Bi2Se3 to tune the surface state and improve the dynamical gas sensing parameter. The response and response rate toward 10 ppm of NO2 were respectively improved by 2.5 and 3.8 times by the Au decoration, and 2.3 and 3.2 times by the Ag decoration, and 1.3 and 2.7 times by the Pt decoration. The gas adsorption/desorption isotherm was established to analyze the reaction kinetic parameters of the response (S), kinetic reaction rate (kr and k-r) and beta value (β). These results demonstrate that noble metals can greatly promote the reaction kinetic parameters by modulation the surface state. Especially, the Au10 sample acquired maximum kr values of 633.963, which is 9.3 times higher than pure Bi2Se3. This work provides an important strategy for designing gas sensing performance between topological insulators and noble metal particles.