Analysis Of Reaction Kinetics Research Articles

Contact electro catalysis driven degradation of malachite green dye by RGO/ZnO nanohybrid

This work demonstrates the potential of reduced graphene/zinc oxide (RGO/ZnO) nanohybrid for the degradation of malachite green dye (MG) via involving the mechanochemistry contact electro catalysis (CEC) approach through electronic transfer. Dielectric and piezoelectric RGO/ZnO nanohybrid in contact with aqueous medium offers electron transfer via direct catalytic reaction at solid-liquid interface which promotes CEC process than that of conventional photocatalysis. RGO/ZnO nanohybrid is prepared via ultrafast microwave irradiation method in 60 s using Mangifera indica leaves extract as a green reducing agent. The prepared RGO/ZnO nanohybrid is characterized by X-ray diffraction (XRD), Raman spectroscopy, Fourier-transform infrared spectroscopy (FTIR) and UV–Visible (UV–Vis) spectroscopy. XRD analysis reveals the formation of pure ZnO with wurtzite hexagonal phase and signature reflection of the RGO. Raman, FTIR and UV–Vis spectroscopy results confirm the presence of bands corresponding to ZnO and RGO and hence the formation of RGO/ZnO nanohybrid without any impurity phase. Field emission-scanning electron microscopy (FE-SEM) reveals the growth of spherical shaped ZnO nanoparticles over the RGO matrix. The average particle size of ZnO nanoparticles is ⁓ 9.2 nm. Catalytic properties of RGO/ZnO nanohybrid is investigated by using 10 mg and 20 mg dosage in aqueous solution of MG. About 85.72 % degradation efficiency for MG in 60 min is achieved by using 20 mg RGO/ZnO nanohybrid via sonication through CEC process. Probably, contact electrolysis at ZnO-water interface induces electronic exchange and generation of free radicals to degrade the dye molecules. Reaction kinetics analysis reveals the suitability of the pseudo first-order kinetics for dye degradation and reusability of RGO/ZnO nanohybrid confirms its excellent stability up to three cycles with 60 % degradation ability. This research establishes RGO/ZnO nanohybrid as highly promising catalytic agents for wastewater treatment and hazard free CEC approach.

Preparation of a novel DNA-imprinted sensor based on chitosan and its highly sensitive detection of Pb2+

Lead ion is very harmful to the environment, so it is very important to study its detection methods. In this study, a novel electrochemical sensor was constructed by modifying deoxyribonucleic acid (DNA) on the electrode, which can be used for the detection of Pb2+ in the environment. Part of the mixed solution of chitosan (CS) and Pb2+ template ions was dropped onto the surface of a glassy carbon electrode. CS-Pb2+ film was cross-linked through sodium tripolyphosphate. And a novel DNA-imprinted sensor was prepared by electrodepositing CS-Pb2+ thin film with gold nanoparticles (AuNPs), removing Pb2+ templates, and immobilizing specific double-stranded DNA. The electroactive area, surface morphology, sensitivity, and electrochemical reaction mechanism of the DNA-imprinted sensor were analyzed. The elementary reaction steps were studied through electrochemical reaction kinetics analysis. The experimental results indicate that the DNA-imprinted electrochemical biosensor can quantitatively detect Pb2+ in the range of 10–100 μM (R2 = 0.9935), and its detection limit is 6.5074 μM (3σ/slope). The sensitivity of the electrochemical biosensor is 1.55233 × 10−6 A/μM, and its active areas is 6.233 cm2. The desorption mechanism and adsorption mechanism have been explored through dynamic parameter analysis. The novel DNA imprinted electrochemical biosensor developed in this paper provides a robust method for detecting lead ions in solution. Additionally, it establishes a solid groundwork for detecting other metal ions.

Elucidating the Impact of Polyol Functional Moieties on Exothermic Poly(urethane-urea) Polymerization: A Thermo-Kinetic Simulation Approach

The pursuit of sustainable polyurethane (PU) product development necessitates a profound understanding of precursor materials. Particularly, polyol plays a crucial role, since PU properties are heavily influenced by the type of polyol employed during production. While traditional PUs are solely derived from hydroxyl functionalized polyols, the emergence of amine-hydroxyl hybrid polyols has garnered significant attention due to their potential for enhancing PU product properties. These hybrid polyols are characterized by the presence of both amine and hydroxyl functional groups. However, characterizing these polyols remains a daunting challenge due to the lack of established experimental testing standards for properties, such as fractional hydroxyl and amine moieties and thermo-kinetic parameters for amine reactions with isocyanates. Additionally, characterization methods demand extensive time and resources and pose risks to health and the environment. To bridge these gaps, this study employed computational simulation via MATLAB to determine the moieties’ fractions and thermo-kinetic parameters for hybrid polyols. The computational method integrated energy balance and reaction kinetics analysis for various polyols to elucidate the influence of functional moieties on the thermo-kinetic behavior of PU formations. Validation of the simulated results was conducted by comparing their experimental and simulated prepolymer and foam temperature profiles, highlighting the direct influence of fractional moieties on PU formations. The comparisons revealed an average relative error of less than 5%, indicating the accuracy and credibility of the simulation. Thus, this study represents a pivotal opportunity for advancing knowledge and driving sustainable developments in bio-based polyol characterization for PU production streamlining and formulation optimization.

Isothermal reduction and comparative analysis of reaction kinetics of sponge iron produced from hematite-charcoal reaction using non-contact direct reduction method

The challenge of making sponge iron, or direct reduced iron (DRI), is hard to overstate. These are a key feed for metallurgical operations while iron extraction sets these limits, which include scarcity of metallurgical coke, poor environmental impact, and high production cost. Thus, the non-contact direct reduction process of DRIs has the potential to significantly reduce carbon deposition and CO2 emission from the ironmaking process. This work produced sponge iron from commercially acquired hematite ore using an alternative reducing agent (i.e. charcoal) under specified isothermal conditions. Comparative analysis of reaction kinetics models including Ginstein−Brounshtein and Shrinking core models was also performed to ascertain the resistances that control the reaction rate for reduction degree up to 98.1%. The reduction kinetics were found to be described by reaction control time and activation energies based on a shrinking core model as the reduction time lasted for 120 min at temperatures 843–1273 K. At temperatures above 973–1073 K, the rate-limiting step was found to be solely an interfacial chemical reaction process, with an apparent activation energy of 196.1 kJ/mol. In addition, a slowing trend was observed for iron ore sample sizes 10–20 mm as a result of ash layer infiltration around the inner-core structure of the DRI metal matrix. The DRI morphological characteristics were performed using Scanning Electron Microscopy (SEM) and Electron Dispersive Spectrometry (EDS) to ascertain the mineralogical and morphological properties of the DRI samples. The XRF analysis confirms that the raw iron ore sample is hematite. Its iron content is 70.04% metallic iron (TFe) which has 83.59% Fe2O3 The SEM/EDS image also revealed the presence of micropores on the DRI morphology. This indicates that the reduction ratio and swelling extent rise with the temperature and time. This happens for all DRI sizes. However, the EDS result confirms the presence of gangue elements within the DRI metal matrix and mineralogical structure. The DRI contains very high silicon content up to 33.90%. So, a fluxing experiment is needed using limestone (CaCO3) or quicklime (CaO) quicklime to remove gangue (silicate, aluminate) from the DRI matrix. At the set reduction temperatures, the largest metallization degree of 93.05% at 1273 K for a reduction time of 120 min was achieved. This showed that the overall reduction process still follows the expected chronological order since the NDR process uses CO gas from preheated charcoal. This makes DRI be produced from raw hematite under non-contact reduction bases. Therefore, the NDR technique offers a viable option for sponge iron production in modern-day iron and steelmaking processes.

Capacity of Ca-based slags for carbon capture

Efficiency in reutilization of Ca-based waste for carbon capture has gained high interest. Besides, the CO2 capture mechanism will be influenced by several operating parameters. Observation of carbonation by Ca-based slags (desulfurization slag/De-S, electric arc furnace/EAF slag, and bottom ash/BA) in this study indicated that De-S had the highest Ca(OH)2 content (73%) and largest surface area which led to the best slag utilization. This slag was further applied in the test under various operating conditions including temperature, space velocity, and the content of gas impurity (H2O and SO2). Higher temperature and lower space velocity promoted efficient carbonation. De-S endured the presence of ≤5% water vapor content in the simulated gas. Higher SO2 content in the simulated gas initiated the formation of CaSO4 and declined the CO2 capture capacity. Discussion in this study was complemented by the characterization of slags before and after carbonation process along with reaction kinetics analysis.

Promoting effect and kinetic analysis of Fe-Co bimetallic doping on the LaMnO3 catalytic activity for methane combustion

To enhance the catalyst’s properties, a modified sol–gel method is developed in this study, and a unique perovskite catalyst, LaMnxFeyCo1-x-yO3, is successfully synthesized by doping Fe-Co into the lattice of LaMnO3. The catalytic activity of the synthesized catalysts is initially determined by applying them to methane oxidation. Then, the structural, chemical, and surface properties of these catalysts are systematically evaluated utilizing XRD, BET, O2-TPD, H2-TPR, SEM, and XPS analyses. The modified LaMn0.8Fe0.15Co0.05O3 is shown to exhibit excellent activity (T90 at 486.5 ℃) in methane catalytic combustion, comparable to several standard noble metal materials. Experimental findings indicate that such perovskite structures have a larger specific surface area, an elevated molar ratio of Mn4+, desirable low-temperature reducibility, and excellent oxygen mobility relative to the original LaMnO3. Meanwhile, more efficient electron transfer from Mn4+/Mn3+ redox cycles, as well as the emergence of oxygen defects, significantly contribute to the robust interaction between Fe-Co and LaMnO3. Further reaction kinetic analysis is conducted to determine changes in species components and identify possible catalytic pathways. Notably, Fe-Co co-doping leads to an improvement in the increase of lattice oxygen and CH4 adsorption. In addition, the MVK kinetic mechanism governs methane combustion over LaMn0.8Fe0.15Co0.05O3. This study provides new insights into enhancing energy conversion performance and efficient utilization of ventilation air methane (VAM) through the implementation of highly efficient perovskites.

Modulating local environment for electrocatalytic CO2 reduction to alcohol

The fundamental drivers for the selective CO2 electroreduction reaction (CO2RR) to alcohol (e.g. C2H5OH) or alkene (e.g. C2H4) still remain unexplored. Previous studies mainly focus on catalyst engineering to enhance electrocatalytic performance, while the selectivity to alcohol has reached a bottleneck. Here, we modulate local environment to reveal the contribution of *CO and *H reaction intermediates in the selectivity of CO2 to alcohol/alkene on Cu electrocatalyst. Through modifications on local CO2 concentration, varied *CO/*H coverage ratios can be achieved. Based on the reaction kinetics analysis, we find that there is a direct connection between local CO2 concentration and interfacial *CO and *H coverage, which finally affects the selectivity of CO2 to alcohol or alkene. To verify this principle, polyvinylidene fluoride (PVDF), a hydrophobic binder, were selected and introduced into the catalyst surface for further enhancement of interfacial *CO/*H coverage. With PVDF decoration, alcohol/alkene ratio increased from 0.69 to 1.35. The Faradic Efficiency of alcohol is up to 37.5 % under a high current density of 800 mA cm–2 (a partial current density of 300 mA cm–2), surpassing most reported Cu-based materials. Our findings provide a fundamental guidance for CO2RR to alcohol under an industrial-level current density.

In Situ Chemical Modulation of Graphitization Degree of Carbon Fibers and Its Potassium Storage Mechanism.

Graphite is considered to be the most auspicious anode candidate for potassium ion batteries. However, the inferior rate performances and cycling stability restrict its practical applications. Few studies have investigated the modulating the graphitization degree of graphitic materials. Herein, a nitrogen-doped carbon-coated carbon fiber composite with tunable graphitization (CNF@NC) through etching growth, in-situ oxidative polymerization, and subsequent carbonization process is reported. The prepared CNF@NC with abundant electrochemical active sites and a rapid K+/electron transfer pathway, can effectively shorten the K+ transfer distance and promote the rapid insertion/removal of K+. Amorphous domains and short-range curved graphite layers can provide ample mitigation spaces for K+ storage, alleviating the volume expansion of the highly graphitized CNF during repeated K+ insertion/de-intercalation. As expected, the CNF@NC-5 electrode presents a high initial coulombic efficiency (ICE) of 69.3%, an unprecedented reversible volumetric capacity of 510.2 mA h cm-3 at 0.1 A g-1 after 100 cycles with the mass-capacity of 294.9 mA h g-1. The K+ storage mechanism and reaction kinetic analysis are studied by combining in-situ analysis and first-principles calculation. It manifests that the K+ storage mechanism in CNF@NC-5 is an adsorption-insertion-insertion mechanism (i.e., the "1+2" model). The solid electrolyte interphase (SEI) film forming is also detected.

Continuous visbreaking of heavy oil in medium and high-pressure steam environments

Continuous visbreaking of heavy oil in a tubular reactor was studied under pressurized steam environments at 10 MPa (MPS) and 18 MPa (HPS). Within the operating range considered, heavy oil and pressurized steam exhibit a liquid-vapor two-phase structure. During the transition from the MPS environment to the HPS environment, the dissolution of water into the oil phase is promoted, thereby reducing the viscosity of the oil phase. According to the lumped reaction kinetics analysis, the reaction behavior of the lumped component VR2 with a boiling point higher than 700 °C determines the visbreaking efficiency in the early visbreaking stage to a large extent. Dealkylation of VR2 and condensation of the lightest lumped component show sensitive responses to improved diffusion in the oil phase. At 400 °C and a space time of 37 min, visbreaking in HPS environment can achieve a viscosity reduction rate of 90%. Meanwhile, the asphaltene content of the product is lower than the feedstock value.

Toward Rational Design of Nickel Catalysts for Thermocatalytic Decomposition of Methane for Carbon Dioxide‐Free Hydrogen and Value‐Added Carbon Co‐Product: A Review

AbstractThermocatalytic decomposition of methane provides opportunities for hydrogen (H2) production with no emission of carbon dioxide. However, high‐value carbon products need to be produced for economic deployment of thermocatalytic decomposition and to achieve a minimum H2 selling price below the U.S, Department of Energy target of $ 1/kg H2. In this review, we re‐evaluate data on catalyst development reported in the literature and propose correlations between catalyst characteristics, catalytic stability, and properties of carbon co‐products. In the first part of the review, growth mechanisms for carbon nanotubes using state‐of‐the‐art chemical vapor deposition are reviewed to catalog the effects of catalyst characteristics, the influence of carbon sources, interactions between metal particles and supports, and metal particle sizes on carbon growth. In the second part, representative developments in mono‐, bi‐, and tri‐metallic nickel catalysts are highlighted. We present kinetic analysis of reactions catalyzed by mono‐metallic nickel catalysts, which generates a correlation between metal particle size and catalyst stability. Rational design of Ni‐based catalysts for TCD of methane requires attention to the size of the metal particle and effective normalization of the reaction rates. Further attention to the distribution of the metal particle sizes may help identify catalyst properties that contribute longevity and selectivity to processes that use them. While it is tempting to focus on the highest valued carbon products (e. g., CNTs and CFs), analysis of the markets for other carbon products suggests that a more flexible approach may generate comparable returns without the risk associated with specialization.

Exploring oral drug delivery: In vitro release and mathematical modeling of hydrophobic drug (Na-L-thyroxine) and its cyclodextrin inclusion complex in chitosan microparticles

Na-l-Thyroxine (Na-l-Thy) is a frequently prescribed synthetic hormone for hypothyroidism treatment. Despite its efficacy, its hydrophobic nature poses a challenge for achieving optimal bioavailability. To address this, researchers explored various delivery methods, including micro-formulations and nano-formulations, for precise and prolonged release of hydrophobic and hydrophilic drugs. In this study, we developed micro-formulations with cyclodextrin and chitosan. Docking studies identified γ-cyclodextrin as the preferred option for forming a stable complex with Na-l-Thyroxine compared to α, and β-cyclodextrins. Two micro-formulations were prepared compared: Na-l-Thyroxine loaded on chitosan (CS + Na-l-Thy) and Na-l-Thyroxine and γ-cyclodextrin inclusion complex (IC) loaded on chitosan (CS + IC). CS + IC exhibited superior encapsulation efficiency (91.25 %) and loading capacity (18.62 %) compared to CS + Na-l-Thy (encapsulation efficiency: 70.24 %, loading capacity: 21.18 %). Characterization using FTIR, SEM, and TGA validated successful encapsulation of Na-l-Thy in spherical microparticles with high thermal stability. In-vitro release studies at pH 1.2 and 7.4 showed that the CS + IC microparticles displayed gradual, consistent drug release compared to CS + Na-l-Thy -Thy. Both formulations showed faster release at pH 1.2 than at pH 7.4. Reaction kinetics analysis of release studies of CS + Na-l-Thy and CS + IC were best described by Higuchi kinetic model and Korsemeyer-Peppas kinetic model respectively. This study suggests that the CS + IC microparticles are an effective and stable delivery system for sustained release of hydrophobic Na-l-Thy.

Numerical study of wall cooling effects on diesel spray combustion characteristics under different ambient conditions

The effects of wall cooling on diesel spray combustion characteristics and engine performance are varied under different environmental conditions and the reasons remain to be further analyzed. The systematic explanation of its influence laws can effectively help the cooling system design and fault isolation under changing working conditions. Therefore, the effect mechanism of wall temperature on the diesel spray combustion characteristics under different ambient temperature and pressure conditions is numerically revealed through the combination of CFD simulation and chemical reaction kinetics analysis. During the calculation model validation, the simulation results showed good agreement with the experimental results and good adaptability to the change in wall temperature. The results show that high ambient temperature and pressure lead to the acceleration of the reaction rate, and high pressure also slows down the fuel diffusion, which eventually causes the fuel to undergo more reaction processes before hitting the wall and being in the relatively late stage of the low-temperature reaction process. In the process of low-temperature reaction and heat accumulation, the effect of temperature drop in the late stage of the reaction is less than that in the early stage due to more heat accumulation before cooling. This ultimately leads to diesel ignition being delayed by low wall temperatures under low ambient temperature and pressure conditions, while diesel spray at high ambient temperatures and pressures has a stronger anti-interference ability to the wall temperature.

Electrocatalytic Reduction of Benzyl Bromide during Single Ag Nanoparticle Collisions.

Previous reports of the electrocatalytic activity of Ag nanoparticles (AgNPs) toward the reduction of organic halides have been limited to measurements of immobilized nanoparticle ensembles. Here, we have investigated the electrochemical reduction of benzyl bromide (PhCH2Br) occurring at single AgNPs (4.2 to 37 nm radius) in methanol, where the effects of nanoparticle size on catalytic behavior can be more thoroughly examined and rigorously quantified. AgNP collisions at a 6.3 μm radius Au ultramicroelectrode (UME) result in measurable electrocatalytic amplification currents from the reduction of PhCH2Br, where collision events are indicated by a sudden step increase in the reduction current recorded in the current-time trace. The dependence of the height of these steps on the applied potential allowed for an analysis of reaction kinetics based on the Butler-Volmer model, resulting in an estimation of the standard rate constant (k0) as a function of AgNP size. Measured values of k0 range from 4.0 × 10-4 to 8.0 × 10-4 cm/s on AgNPs with radii of 14, 29, and 37 nm, whereas k0 was found to be 6.2 × 10-4 cm/s at a 12.3 μm radius Ag disk UME. The results indicate that the kinetics of PhCH2Br reduction are independent of AgNP size and are similar to the reaction kinetics observed at a Ag UME. The frequency of observed particle collisions was found to be dependent on particle size, where 14 nm radius AgNPs resulted in the highest-frequency collisions. The potential- and size-dependent interactions of AgNPs with the Au UME are discussed in terms of the DLVO theory.

Physicochemical synergistic effect of microwave-assisted Co-pyrolysis of biomass and waste plastics by thermal degradation, thermodynamics, numerical simulation, kinetics, and products analysis

Understanding the physicochemical synergistic effect of microwave-assisted co-pyrolysis (MACP) of biomass and waste plastics is crucial for efficient conversion and improving the quality of bio-oil. Thermal degradation, thermodynamics, and numerical simulation of co-pyrolysis of the corncob (CC) and polystyrene (PS) were conducted. Results showed that the co-pyrolysis of CC and PS had a positive physical synergistic and compatible effect in reducing energy consumption and accelerating reaction rate. The reaction kinetics analysis and pyrolysis products analysis found that the co-pyrolysis of CC and PS had a positive chemical synergistic effect. The co-pyrolysis both effectively reduced the pyrolysis activation energy and improved the yield and quality of bio-oil. Significantly, the sample of CC/PS (1:2) had the highest yield of bio-oil (52.3 wt%) and the highest relative content of aromatics (95.0 area%) in co-pyrolysis, while 450 °C was the most ideal pyrolysis temperature. This work indicated that the MACP of CC and PS showed a positive physicochemical synergistic effect, and provided theories and approaches for the production of bio-oil from the biomass and waste plastics by MACP.

Ignition Delay Times and Chemical Reaction Kinetic Analysis for the Ammonia–Natural Gas Blends

Ignition Delay Times and Chemical Reaction Kinetic Analysis for the Ammonia–Natural Gas Blends

EFFECT OF HMX CONTENT ON THERMAL SAFETY CHARACTERISTICS OF MODIFIED DOUBLE-BASE PROPELLANTS

In order to explore the thermal safety characteristics of modified double-base propellants, differential scanning calorimetry (DSC) was used to study the thermal decomposition of modified double-base propellants with high melting explosive (HMX) content of 0%, 21%, and 40%, respectively. The thermal decomposition temperatures at the heating rates of 2, 5,10, and 20°C·min<sup>-1</sup> were obtained. The apparent activation energy, pre-exponential factor, reaction rate, Gibbs free energy, activation enthalpy, and activation entropy were calculated by thermal reaction kinetics analysis. The response characteristics of modified double-base propellants with different HMX contents were obtained through slow cook-off, 5 s explosion point, and methyl violet chemical stability tests to characterize the thermal safety of propellants. The insensitivity of modified double-base propellant containing HMX was further studied by flame sensitivity and mechanical sensitivity tests. The results showed that when HMX content was 21%, the apparent activation energy was the highest, the slow cook-off response was the lowest, the 5 s explosion point response temperature was the highest, the methyl violet test paper had the longest discoloration time, and the flame sensitivity and mechanical sensitivity were the lowest; With the increase of HMX content, the first decomposition peak temperature of DSC moves backward, and the apparent activation energy decreases. The slow cook-off response temperature of the double-base propellant moves to the high-temperature direction, and the response level increases accordingly. When the HMX content is 40% or more, the response level is explosive, which cannot pass the slow cook-off test. After HMX component is added into the sample, its 5 s explosion point temperature moves to high temperature, and the trend of rise is obvious. The discoloration time of methyl violet test paper is prolonged, and the thermal stability of modified double-base propellant is improved; The flame sensitivity and the mechanical sensitivity decreased, which was helpful to improve the low vulnerability of the formula.

High-capacity all-solid-state Li-ion battery using MOF-derived carbon-encapsulated iron phosphide as anode material

Iron Phosphide (Fe2P) particles embedded within in-situ generated tubular carbon structures uniformly doped with nitrogen heteroatoms (Fe2P @ NC) have been investigated as an anode in all-solid-state lithium-ion batteries (ASSLIBs). The designed morphology offered a number of suitable features, such as high conductivity, robust framework, and abundant redox active sites for augmenting overall battery performance. As anode, Fe2P @ NC has provided a high lithiation/delithiation capacity of 1214.8 mA h/g /1367.01 mA h/g at a current density of 66.6 mA/g (100 μA) with a high coulombic efficiency (>100%). Further, Fe2P @ NC also demonstrated an excellent rate performance and moderate structural stability during cycling. The charge storing mechanism for Fe2P @ NC investigated via ex-situ X-ray diffraction (XRD) and X-ray Photoelectron Spectroscopy (XPS) studies indicates irreversible conversion of Fe2P → Li3P & Fe in the initial cycle and reversible Li3P ↔ LiP reaction in subsequent cycles. Analysis of reaction kinetics for Fe2P @ NC nanocomposite is carried out using CV measurements at different scan rates. This study explores the possibility of MOF-derived iron-phosphide-based composite material as a high-performance anode for ASSLIBs.

Integrated kinetics-computational fluid dynamic-optimization for catalytic hydrogenation of CO2 to formic acid

As enormous research findings indicate, carbon dioxide (CO2) can be converted to important products such as formic acid using catalytic hydrogenation of CO2 technologies. In this work a three-dimensional computational fluid dynamic (CFD) reactor model for the catalytic hydrogenation of CO2 to formic acid in the presence of triethylamine and water was developed, and the nature of the flow and reaction occurring inside the reactor was demonstrated. A kinetic model which estimates kinetic rate expressions was also developed and validated using experimental data. The kinetic parameters from the kinetic model were used as reaction source terms for the CFD reactor model development. Sensitivity analyses were performed on the design variables by integrating the kinetic parameters from the developed kinetic model. The Bayesian optimization algorithm was used to optimize the catalytic CO2 hydrogenation reactor. The optimal design was acquired, and the CO2 conversion increased by 32.6% compared to the initial base case. An optimized reactor design was proposed for the catalytic hydrogenation of CO2 to formic acid within a catalytic trickle-bed reactor based on the integration of reaction kinetic modeling and CFD analysis. The integrated kinetic-CFD-optimization framework proposed in this work was effectively applied to the catalytic CO2 hydrogenation reactor and the results reported on this work could give important design and operational insight to the further development of catalytic CO2 hydrogenation reactors for CO2 to formic acid conversion in carbon capture and utilization applications.

Incorporation of Ag on stable Pt/CeO2 for low-temperature active and high-temperature stable CO oxidation catalyst

Advanced engine technologies and environmental restrictions require new-generation automotive catalysts to be low-temperature (LT) active and high-temperature (HT) stable simultaneously. Here, incorporation of Ag over high temperature (800 °C) treated Pt/CeO2 was applied to address the challenge. Strong Pt-O-Ce bonds in Pt/CeO2 helped improve thermal stability dramatically. Detailed reaction kinetics analysis indicated Eley-Rideal (ER) mechanism for Ag/CeO2 catalysts and Mars-van Krevelen (Mvk) mechanism for both Pt/CeO2 and Ag/Pt/CeO2 catalyst. After calcined at 800 °C, CO adsorbed on ionic Pt site could be readily oxidized by neighbouring oxygen species at a temperature as low as 132 °C over Ag/Pt/CeO2, about 60 °C lower than Pt/CeO2 and Ag/CeO2. Raman spectroscopy and XPS results suggested that incorporation of Ag created more oxygen defects over Pt/CeO2 and oxygen species on Ag nanoparticles might be more active than bare Pt/CeO2 which would enhance the low-temperature activity for Ag/Pt/CeO2. It might be an effective and cost-efficient approach to develop new catalysts for vehicle emission oxidation.

Immobilization of enzymes on functionalized cellulose nanofibrils for bioremediation of antibiotics: Degradation mechanism, kinetics, and thermodynamic study

The deteriorating environmental conditions due to increasing emerging recalcitrant pollutants raised a severe concern for its remediation. In this study, we have reported antibiotic degradation using free and immobilized HRP. The functionalized cellulose support was utilized for efficient immobilization of HRP. Approximately 13.32 ± 0.52 mg/g enzyme loading was achieved with >99% immobilization efficiency. The higher percentage of immobilization is attributed to the higher surface area and carboxylic groups on the support. The kinetic parameter of immobilized enzymes was Km = 2.99 mM/L for CNF-CA@HRP, which is 3.5-fold more than the Michaelis constant (Km = 0.84794 mM/L) for free HRP. The Vmax of CNF-CA@HRP bioconjugate was 2.36072 mM/min and 0.558254 mM/min for free HRP. The highest degradation of 50, 54.3, and 97% were achieved with enzymatic, sonolysis, and sono-enzymatic with CNF-CA@HRP bioconjugate, respectively. The reaction kinetics analysis revealed that applying ultrasound with an enzymatic process could enhance the reaction rate by 2.7–8.4 times compared to the conventional enzymatic process. Also, ultrasound changes the reaction from diffusion mode to the kinetic regime with a more oriented and fruitful collision between the molecules. The thermodynamic analysis suggested that the system was endothermic and spontaneous. While LC-MS analysis and OTC's degradation mechanism suggest, it mainly involves hydroxylation, secondary alcohol oxidation, dehydration, and decarbonylation. Additionally, the toxicity test confirmed that the sono-enzymatic process helps toward achieving complete mineralization. Further, the reusability of bioconjugate shows that immobilized enzymes are more efficient than the free enzyme.