Kinetic Study Of Reaction Research Articles

Heterophase of Bismuth Titanate as a Photocatalyst for Rhodamine B Degradation

Various studies have been made to obtain high efficiency photocatalysts. Auvirillius bismuth titanate oxide is known to have good photocatalytic activity to degrade dyestuffs. However, recombination is still an obstacle to photocatalytic efficiency. To overcome recombination and increase photocatalytic activity, it is proposed to synthesize bismuth titanate heterophase. Heterophase can enhance the formation of the synergistic effect of electrons, which effectively stimulates the transfer of electrons from 1 phase to another. This study aims to determine the photocatalytic ability of bismuth titanate heterophase for degradation of a rhodamine B. Bismuth titanate was synthesized by hydrothermal method using Bi2O3 and TiO2 precursors. The results of X-ray diffraction characterization showed that the synthesized bismuth titanate formed 2 phases, namely Bi4Ti3O12 (78.2 %) and Bi12Ti0.9O19.8 (21.8 %). In addition, it is also known that the volume of the synthesized bismuth titanate crystal lattice has a smaller volume than the standard synthesized in previous studies. The photocatalytic ability of bismuth titanate evaluated using 10 mg/L rhodamine B showed that it took 240 min to degrade 98 % of dye. Reaction kinetics studies showed that bismuth titanate has a reaction rate constant efficiency of 120 % better than TiO2 for the Langmuir- Hinshelwood 1st-order kinetic model. Then the reuse ability was evaluated, showing that after 3 times of uses, bismuth titanate only decreased 5 %, whereas TiO2 decreased by 7 % in degradation. HIGHLIGHTS Bismuth titanate heterophase Bi4Ti3O12/Bi12Ti9O19.8 has been synthesized using precursors Bi2O3 and TiO2 by hydrothermal method. Bismuth titanate heterophase has better photocatalytic ability than TiO2 in degrading rhodamine B. The ability to reuse bismuth titanate heterophase showed that after 3 uses there was no significant decrease in activity. GRAPHICAL ABSTRACT

Reversible and Non-Competitive Inhibition of Cyclooxygenase by Indobufen for Efficient Antiplatelet Action and Relief of Gastrointestinal Irritation.

Clinically, indobufen is widely used for the treatment of antiplatelet aggregation and anticoagulation. Prior studies have discovered that abnormal platelet function can be promptly restored to normal when the drug is stopped. Herein, through the study of the enzyme reaction kinetics, we demonstrated that the inhibitory effect of indobufen on cyclooxygenase-1 (COX-1) was reversible and non-competitive. Specifically, the cyclooxygenase inhibition experiment showed that the level of 6-keto-PGF1α in the gastric mucosa of the indobufen-treated groups was significantly higher than that of the aspirin group (###p < 0.001), indicating a higher level of PGI2 in and a better physiological state of the gastric mucosa. Moreover, the rat gastric ulcer index and mucosal section experiments further confirmed the relief of gastrointestinal irritation and the adverse reaction rate of the indobufen-treated group compared to those of the aspirin group. Furthermore, indobufen was verified to exert reversible inhibitory activity on the heme group of COX-1 and thus reversibly inhibit COX-1 activity. In general, compared with aspirin, the long-term oral administration of indobufen yields a lower risk of gastrointestinal symptoms, such as ulcers.

Combining α-Al2O3 Packing Material and a ZnO Nanocatalyst in an Ozonized Bubble Column Reactor to Increase the Phenol Degradation from Wastewater

The ozonation reaction in a bubble column reactor (BCR) has been widely used in the removal of phenol from wastewater, but the phenol removal efficiency in this type of reactor is limited because of low ozone solubility and reactivity in the system. In the present study, the phenol degradation in the BCR was enhanced by using α-Al2O3 as a packing material and a ZnO nanocatalyst. The reactor diameter and height were 8 cm and 180 cm, respectively. The gas distributor was designed to include 52 holes of a 0.5 mm diameter. Also, the gas holdup, pressure drop, and bubble size were measured as a function of the superficial gas velocity (i.e., 0.5, 1, 1.5, 2, 2.5, and 3 cm/s). The evaluation of the hydrodynamic parameters provided a deeper understanding of the ozonation process through which to select the optimal operating parameters in the reactor. It was found that the best superficial gas velocity was 2.5 cm/s. A complete (100%) phenol removal was achieved for phenol concentrations of 15, 20, and 25 ppm at reaction times of 80, 90, and 100 min, respectively; this was achieved by using α-Al2O3 packing material and a ZnO nanocatalyst in the BCR. Additionally, a reaction kinetics study was conducted to describe the ozonation reaction in BCR. The first-order reaction assumption clearly describes the reaction kinetics with an R2 = 0.991. Finally, the applied treatment method can be used to efficiently remove phenol from wastewater at a low cost, with a small consumption of energy and a simple operation.

Sustainable toxic dye removal and degradation from wastewater using novel chitosan-modified TiO2 and ZnO nanocomposites

TiO2 and ZnO-embedded chitosan-based nanocomposites were prepared, immobilized on borosilicate glass, and applied for the degradation of the binary dye mixture of methylene blue and methyl orange under solar irradiation. XRD of the nanocomposites showed the existence of the anatase phase of TiO2 in the nanocomposites with crystalline sizes ranging from 13.92 nm to 17.82 nm. The FESEM results showed disintegration of the agglomerated TiO2 due to Chitosan resulting in the reduction of particle size (20.6 ± 4.6 µm to 2.9 ± 0.9 µm). BET specific surface area of TiO2/ZnO/Chitosan was 2.29 times that of pure TiO2 in addition to the reduction of bandgap energy from 3.17 eV to 2.84 eV. The photocatalytic experiment for TiO2, TiO2/Chitosan, TiO2/ZnO, and TiO2/ZnO/Chitosan showed the degradation of Methylene Blue to be 78.48%, 83.65%, 86.06%, and 91.22%, respectively and 72.53%, 80.18%, 84.3%, and 88.9%, respectively for methyl orange under solar irradiation for 5 h. The formation of heterojunction with ZnO and the enhanced adsorption capacity of Chitosan resulted in enhanced photocatalytic degradation. The reusability test of the nanocomposites showed no substantial reduction in the degradation percentage after 5 cycles of use. The reaction kinetic study suggested that the first-order model was the best-fitted kinetic model. The first order rate constant for TiO2/ZnO/Chitosan was found to be 7.88 × 10−3 min−1 and 7.10 × 10−3 min−1 for degradation MB and MO, respectively. Thus, the outcome of the experiment suggests that the application of TiO2 doped with ZnO and Chitosan results in enhanced degradation of persistent organic contaminants in textile wastewater.

Atmospheric degradation of dimethyl sulfone mediated by [rad]OH, [rad]Cl and NO3[rad], and the C-centered dimethyl sulfone radical + 3O2 reaction: A kinetics and mechanistic study

Mechanistic and kinetics studies of the gas phase reactions of dimethyl sulfone (DMS(O)2; CH3S(O)2CH3) mediated by hydroxyl radical (OH), chlorine atom (Cl) and nitrate radical (NO3) have been extensively investigated using quantum chemistry calculations along with kinetic modeling. The reaction of DMS(O)2 + OH/Cl/NO3 can in principle undergo abstraction and substitution pathways. The results revealed the dominant path to be abstraction of an H-atom from the methyl group of DMS(O)2 by OH, Cl and NO3, with barriers of 2.1, 4.2, and 9.8 kcal mol−1 respectively relative to their starting reactants, to produce CH2S(O)2CH3. The barrier heights for the substitution paths involved in the DMS(O)2 + OH, DMS(O)2 + Cl and DMS(O)2 + NO3 reactions were found to be very high (>30 kcal mol−1) and therefore inaccessible under tropospheric conditions. The rate coefficients for all possible H-atom abstractions associated with the DMS(O)2 + OH, DMS(O)2 + Cl and DMS(O)2 + NO3 reactions were calculated using Master equation solver for multi-energy well reactions (MESMER) code in the temperature range of 200–320 K and 1 atm. The overall rate coefficients for the reaction of DMS(O)2 initiated by OH radical, Cl atom and NO3 radical at 298 K and 1 atm were estimated to be 4.6 × 10−13, 9.1 × 10−14 and 3.7 × 10−15 cm3 molecule−1 s−1, respectively. The atmospheric lifetime of DMS(O)2 with respect to its reactions with OH, Cl and NO3 was also estimated. The major product CH2S(O)2CH3 further reacts with ground state molecular oxygen (3O2) to form the CH3S(O)2CH2OO adduct. Computational methods also showed that the rate of unimolecular isomerization of the CH3S(O)2CH2OO adduct is slow compared to its reactions with NO and hydroperoxyl (HO2) radical. Ultimately, the CH3S(O)2CH2OO adduct leads to formation of formic acid, sulfur dioxide, formaldehyde, methanol, carbon dioxide, sulfene, and OH radical as final products under high NO and HO2 radical atmospheric conditions.

Suzuki-Miyaura Cross-Coupling of Amides by N-C Cleavage Mediated by Air-Stable, Well-Defined [Pd(NHC)(sulfide)Cl2] Catalysts: Reaction Development, Scope, and Mechanism.

The Suzuki-Miyaura cross-coupling of amides by selective N-C acyl bond cleavage represents a powerful tool for constructing biaryl ketones from historically inert amide bonds. These amide bond activation reactions hinge upon efficient oxidative addition of the N-C acyl bond to Pd(0). However, in contrast to the well-researched activation of aryl halides by C(sp2)-X oxidative addition, very few studies on the mechanism of C(acyl)-N bond oxidative addition and catalyst effect have been reported. Herein, we report a study on [Pd(NHC)(sulfide)Cl2] catalysts in amide N-C bond activation. These readily prepared, well-defined, air- and moisture-stable Pd(II)-NHC catalysts feature SMe2 (DMS = dimethylsulfide) or S(CH2CH2)2 (THT = tetrahydrothiophene) as ancillary ligands. The reaction development, kinetic studies, and reaction scope are presented. Extensive DFT studies were conducted to gain insight into the mechanism of C(acyl)-N bond oxidative addition and catalyst activation. We expect that [Pd(NHC)(sulfide)Cl2] precatalysts featuring sulfides as well-defined, readily accessible ancillary ligands will find application in C(acyl)-X bond activation in organic synthesis and catalysis.

Determination of uric acid in serum by SERS system based on VO-MnCo2O4/Ag nanozyme

The level of uric acid is crucial to human health. Octahedral oxygen vacancy MnCo2O4/Ag (VO-MnCo2O4/Ag) nanozyme was successfully prepared by simple hydrothermal, calcination and self-reduction methods. VO-MnCo2O4/Ag nanozyme is rich in Mn2+/Mn3+ and CO2+/CO3+ redox electron pairs, large specific surface area and oxygen vacancies. VO-MnCo2O4/Ag nanozyme showed high uricase-like activity and peroxidase-like activity. At the same time, the SERS signal of the detected molecule could be significantly enhanced after the catalytic reaction of the VO-MnCo2O4/Ag nanozyme. The Km values of VO-MnCo2O4/Ag nanozyme for H2O2 and TMB were 0.04 mM and 0.027 mM respectively. Based on the uric acid oxidase-like and peroxidase-like activities of VO-MnCo2O4/Ag, we developed a label-free, sensitive, and reliable SERS uric acid detection system. The detection linear range of uric acid is 0.01 μM–1000 μM and the detection of limit is 7.8 × 10−9 M. The results show that the sensing system has good accuracy, sensitivity, selectivity, and stability. It can be applied to the determination of samples under different conditions. This study provides profound insights into the design of enzyme-like activity regulation and SERS properties regulation of nanozymes, provides guidance for the study of reaction kinetics and catalytic mechanism of nanozymes, and has broad application prospects in the field of nanozymes and SERS sensing analysis.

Reaction Mechanism and Kinetics Study of Wheat Polysaccharide via Modified Reductor Technique in Bead Making Process

The reaction mechanism and kinetics investigation of the substitution of titanium in wheat flour polysaccharide (referred to here as titaniumation) in aqua medium during bead making process was carried out. The use of the Modified Reductor Technique was implored to study the reaction kinetics. The study was carried out at varying temperatures between 25 – 70oC. The study showed that the titaniumation of the wheat polysaccharide molecules increased with time and temperature. Hence, at 25oC, the degree of titaniumation (DT) of the ring increased from 0.41 % to 0.49 % and at elevated temperature of 70oC, DT increased from 0.58 to 0.94 % as time progressed from 30 to 210 mins, respectively, while keeping both amount of wheat polysaccharide and TiO2 constant, and thus achieving &gt;1.9-fold. This also implies that the titaniumation of wheat polysaccharide using TiO2 is favourable at elevated temperature. The study was able to reveal that the reaction mechanism of the titaniumation of the polysaccharide molecules is an electrophilic substitution reaction, favouring the ortho position, while the kinetics study showed that the titaniumation reaction is of first order reaction.

CeO2/Cu2O/Cu Tandem Interfaces for Efficient Water-Gas Shift Reaction Catalysis.

Metal-oxide interfaces on Cu-based catalysts play very important roles in the low-temperature water-gas shift reaction (LT-WGSR). However, developing catalysts with abundant, active, and robust Cu-metal oxide interfaces under LT-WGSR conditions remains challenging. Herein, we report the successful development of an inverse copper-ceria catalyst (Cu@CeO2), which exhibited very high efficiency for the LT-WGSR. At a reaction temperature of 250 °C, the LT-WGSR activity of the Cu@CeO2 catalyst was about three times higher than that of a pristine Cu catalyst without CeO2. Comprehensive quasi-in situ structural characterizations indicated that the Cu@CeO2 catalyst was rich in CeO2/Cu2O/Cu tandem interfaces. Reaction kinetics studies and density functional theory (DFT) calculations revealed that the Cu+/Cu0 interfaces were the active sites for the LT-WGSR, while adjacent CeO2 nanoparticles play a key role in activating H2O and stabilizing the Cu+/Cu0 interfaces. Our study highlights the role of the CeO2/Cu2O/Cu tandem interface in regulating catalyst activity and stability, thus contributing to the development of improved Cu-based catalysts for the LT-WGSR.

An Efficient and Mild Method for the Alkylation of p-Cresol with tert-Butyl Alcohol

The synthesis 2-tert-butyl-4-methylphenol is of great significance because of its wide application in industry, and the development of a highly efficient catalyst is necessary for the alkylation of p-cresol and tert-butyl alcohol. Here, an efficient and mild method was established. Caprolactam was chosen as the hydrogen-bonding acceptor; p-toluenesulfonic acid was employed as the hydrogen-bonding donor, and a deep eutectic solvent (DES) was prepared to catalyze the alkylation reaction. The structure of the deep eutectic solvent catalyst was characterized by 1H NMR spectra, thermogravimetric analysis, and Fourier transform infrared spectra (FT-IR). In addition, response surface design based on the Box–Behnken method was employed to optimize the alkylation reaction process parameters, and the study of reaction kinetics was also carried out subsequently. The recycle performance of the catalyst was evaluated by recovery experiments, and a good result was obtained. By drawing comparisons with the literature reported, we provide a mild method for the synthesis of 2-tert-butyl-4-methylphenol.

Photocatalytic Degradation of Sulfamethoxazole from a Synthetic Pharmaceutical Wastewater Using Titanium Dioxide (TiO2) Powder as a Suspended Heterogeneous Catalyst

Some medications in aquatic media pose a serious environmental risk. Sulfamethoxazole (SMX) is a member of the sulfonamide group. Photocatalysis offers a promising technique to degrade organic pollutants into environmentally friendly substances. This study examined the effect of operating conditions (pH, time, and temperature) of the ultraviolet (UV)/TiO2 photocatalytic process on the degradation of SMX in an aqueous solution. Decreasing the pH value positively affects SMX degradation, and better removal values were obtained at a pH equal to 4. The optimum operating conditions for complete degradation in a solution containing 500 mg/L of SMX, TiO2 0.5 mg/L irradiation time of 420 min, and pH 4. Under these conditions, Chemical Oxygen Demand (COD) removal was 62.6% at a temperature of 25 ℃. The effect of temperature was studied at three temperatures (25, 40, and 60 ℃) with pH 4. The elevation of temperature increased the COD removal rate to 99.62% at 60 ℃. Finally, the results of the reaction kinetics study showed that a first-order kinetics model described organic contamination removal data over time, and the obtained activation energy was 42.195 kJ/mol.

Review on Ru-Based and Ni-Based Catalysts for Ammonia Decomposition: Research Status, Reaction Mechanism, and Perspectives

Hydrogen (H2) is a zero-carbon and high-energy-density fuel promising to replace fossil fuels for power generation and clean energy. However, hydrogen still faces enormous challenges in terms of production, transportation, and storage. Ammonia (NH3) is a promising H2 (17.7 wt %) carrier that easily overcomes the difficulties associated with H2 storage and transport. However, for the NH3 decomposition hydrogen production reaction, the biggest challenge at present is to achieve complete conversion of ammonia under a relatively high space velocity (about 30,000 mL·gcat–1·h–1) at low-temperature conditions (about 350 °C) with reasonable price catalysts. At present, the most efficient ammonia decomposition catalyst is a Ru-based catalyst doped with K, Ba, and Cs and supported on various carbon supports and metal oxides. Otherwise, the catalysts that exhibited the most outstanding activity among non-noble metal catalysts are nickel-based, and because of their low cost, nickel is regarded as a reasonable alternative candidate material for NH3 decomposition. Advances in the study of reaction kinetics of ammonia decomposition reactions and whether the rate-determining step of the ammonia decomposition reaction is the cleavage of the first N–H bond or the desorption of nitrogen gas are also discussed. This review provides a comprehensive consideration of the recent development of Ru-based and Ni-based catalysts and proposed mechanisms of ammonia decomposition on them are examined. The effects of preparation methods, support, and promoters on catalyst activity were studied and theoretical bases for the design of future catalysts are presented. At last, a brief introduction to catalytic membrane reactor technology in recent years is given. This review can serve as a comprehensive work for designing novel catalysts.

Reaction kinetics study in direct chemical looping process based on a multi-step reaction scheme

The investigation into reaction kinetics provides fundamental insights for reactor design in biomass thermochemical conversion. This work studied the kinetics of biomass chemical looping process based on a multi-step model. Cellulose, xylan, and lignin were employed as biomass representatives. The individual step in the multi-step scheme was formulated with a mass-balance equation form, requiring fewer parameters and thus less computational cost. In addition, the decomposition characteristics of different biomass samples in the presence of oxygen carrier (Fe2O3) were analyzed, and the effects of Fe2O3 on the kinetic parameters of reaction steps were investigated. The results revealed that volatiles pyrolyzed from cellulose and xylan were almost not involved with Fe2O3 reduction at high temperatures (∼1000 K) while playing a major role in terms of lignin (∼1050 K). Moreover, adding OC did not always positively affect the activation energy; in particular, it decreased the activation energy of xylan yet elevated the activation energies of cellulose (at low-temperature zone) and lignin to some extent.

Biomass pellet fueled chemical looping gasification: Reaction kinetics study with a fluidized bed - thermogravimetric analysis

Biomass pellets show the advantages of higher energy density, lower transportation and storage costs compared to powder biomass, making them attractive for future industrial applications. In this work, a fluidized bed-thermogravimetric analysis (FB-TGA) is developed. The gas-solid process for gram-scale biomass pellets under fluidization state at high temperature is characterized. The effects of gasification agents, bed material components and operating conditions on devolatilization and char gasification are investigated. The devolatilization is revealed to be a rapid phase transition process of volatiles, of which the rate is mainly affected by the intense heat and mass transfer with increasing temperature. While the char gasification is significantly slower, taking more than 600 s for all conditions, therefore be considered as the rate-control step. The hematite oxygen carrier can effectively promote the char gasification by breaking the concentration balance of gas components near the char surface. The char reaction kinetics is fitted based on the isothermal differential method. Results show that the cylindrical geometrical contraction model exhibits an excellent linear correlation. With a mass ratio of oxygen carrier/quartz sand of 1:9, the average activation energies of 130.58 kJ/mol and 104.17 kJ/mol are obtained when CO2 and steam as gasifying agents.

Directing Reaction Pathways on Supported Metal Catalysts with Low-Density Self-Assembled Monolayers

Controlling reactant adsorption on catalyst surfaces is crucial to reaction activity and selectivity. One method for improving selectivity is by imposing steric constraints to bias the reactant binding orientation. In this study, thiol self-assembled monolayers (SAMs) were deposited onto Pt/Al2O3 catalysts as a method for controlling activity and selectivity via steric effects. In addition to a full monolayer, a low-density SAM-coated catalyst was employed. A number of characterization techniques demonstrated the successful deposition of homogeneous low-density SAMs on the metal surface with reduced site-blocking compared to a full high-density monolayer. Reaction kinetic studies showed increased benzyl alcohol hydrodeoxygenation (HDO) selectivity for both SAM-modified catalysts. This was attributed to the inability of the reactant to adsorb on the catalyst with the aromatic ring parallel to the surface, thus preventing decarbonylation and ring hydrogenation reaction pathways. Additionally, SAM density influenced reaction activity significantly, with the low-density-modified SAM catalyst being more active than the catalyst coated with a full monolayer. Moreover, liquid-phase hydrogenation reactions were used to investigate the relationship between SAM density and reactivity for reactant molecules of various sizes. In all cases, the low-density SAM improved reaction rates relative to dense SAMs. The effect of controlling ligand density depended on the type of reaction: high ligand densities greatly diminished ring hydrogenation, while HDO was largely unaffected, suggesting a potential strategy for size-selective reaction rate and selectivity control.

Pyrolyzed magnetic NiO/carbon-derived nanocomposite from a hierarchical nickel-based metal-organic framework with ultrahigh adsorption capacity

Herein, a simple one-pot solvothermal approach is used to create magnetic porous carbon nanocomposites which obtained from a nickel-based metal-organic framework (Ni-MOF) and examined for their ability to uptake methyl orange (MO) dye. Derived carbons with exceptional porosity and magnetic properties were created during the different pyrolysis temperatures of Ni-MOF (700, 800, and 900 °C) under a nitrogen atmosphere. The black powders were given the names CDM-700, CDM-800, and CDM-900 after they were obtained. A variety of analysis methods, including FESEM, EDS, XRD, FTIR, VSM, and N2 adsorption-desorption were used to characterize as-prepared powders. Furthermore, adsorbent dosage, contact time, pH variation, and initial dye concentration effects was investigated. The maximum adsorption capacities were 307.38, 5976.35, 4992.39, and 2636.54 mg/g for Ni-MOF, CDM-700, CDM-800, and CDM-900, respectively, which show the ultrahigh capacity of the resulted nanocomposites compared to newest materials. The results showed that not only the crystallinity turned but also the specific surface area was increased about four times after pyrolyzing. The results showed that the maximum adsorption capacity of MO dye for CDM-700 was obtained at adsorbent dosage of 0.083 g/L, contact time of 60 min, feed pH of 3, and temperature of 45 °C. The Langmuir model has the best match and suggests the adsorption process as a single layer. According to the results of reaction kinetic studies using well-known models, the pseudo-second-order model (R2 = 0.9989) displayed high agreement with the experimental data. The synthesized nanocomposite is introduced as a promising superadsorbent for eliminating dyes from contaminated water due to strong recycling performance up to the fifth cycle.

Enhancing Photocatalytic Efficiency of Spent Tea Leaf Powder on ZnIn2S4 Incorporation: Role of Surface Charge on Dye Degradation.

Photocatalytic degradation of dye contaminants using nanocomposite adsorbents has emerged as a promising solution for wastewater treatment. Owing to its abundant availability, eco-friendly composition, biocompatibility, and strong adsorption activity, spent tea leaf (STL) powder has been extensively explored as a viable dye-adsorbent material. In this work, we report spectacular enhancement in the dye-degradation properties of STL powder on incorporation of ZnIn2S4 (ZIS). The STL/ZIS composite was synthesized using a novel, benign, and scalable aqueous chemical solution method. Comparative degradation and reaction kinetics studies were performed onto an anionic dye, Congo red (CR), and two cationic dyes, Methylene blue (MB) and Crystal violet (CV). The degradation efficiencies of CR, MB, and CV dyes were obtained to be 77.18, 91.29, and 85.36%, respectively, using the STL/ZIS (30%) composite sample after the 120 min experiment. The spectacular improvement in the degradation efficiency of the composite was attributed to its slower charge transfer resistance (as concluded by the EIS study) and optimized surface charge (as concluded by ζ potential study). Scavenger tests and reusability tests deciphered the active species (•O2-) and reusability of the composite samples, respectively. To the best of our knowledge, this is the first report to demonstrate improvement in the degradation efficiency of STL powder on ZIS incorporation.

Fe-based oxygen carrier for the chemical looping combustion of CO, H2, and CH4 syngas in fluidized bed reactor under interruption of H2S

Chemical looping combustion (CLC) reduces the CO2 capturing cost, elevates combustion efficiency, and prevents NOx formation. This study applied Fe2O3/SiO2 and Fe2O3/Al2O3 oxygen carriers to react with H2, CO and CH4 under different operating setup and examined the interference of H2S. Examination was also conducted on the reaction kinetics, cycle test, and characterization of oxygen carriers. Reduction of oxygen carrier from Fe2O3 to between FeO and Fe occurred during the reaction. The higher syngas concentration led to higher diffusion capacity and promoted utilization of oxygen carriers. Carbon deposition was enhanced by excess concentration of CO and CH4. Involvement of H2S led to declining of performance due to the presence of carbonyl sulfide (COS) and FeS. With Fe2O3/SiO2, application of multiple redox cycles reduced the utilization value to 43 % due to formation of Fe2SiO4. Analysis of exhausted gas after reaction was applied in study of proposed reaction mechanism. Study of reaction kinetics using Type I deactivation test indicated a well fitted result with experimental data with R2 in the range of 0.9605–0.9976. Thus, compared to other studies with discussion only on CO, H2, or CH4 in CLC, this study offered a comprehensive research on interruption of H2S, characterization, and reaction kinetics.

Musa champa peduncle waste-derived efficient catalyst: Studies of biodiesel synthesis, reaction kinetics and thermodynamics

Musa champa peduncle waste-derived efficient catalyst: Studies of biodiesel synthesis, reaction kinetics and thermodynamics

Rapid removal of methylene blue by a heterogeneous photo-Fenton process using economical and simple-synthesized magnetite–zeolite composite

A hetero-Fenton zeolite-supported Fe3O4 catalyst was synthesized using a simple impregnation–precipitation method. The structure, morphology, and components of the catalyst were characterized using various analytical methods (XRD, SEM, and ICP-MS). Subsequently, the catalyst was used to degrade the azo dye methylene blue (MB), via a heterogeneous photo-Fenton process under UV irradiation in an aqueous solution. This study investigated the influence of different parameters on MB decolorization efficiency, such as the initial concentration of hydrogen peroxide, amount of catalyst, initial dye concentration, and reusability of the catalyst. The removal efficiency was nearly 100% within only 5 min with an initial concentration of methylene blue of 50 mg L−1 under the following experimental conditions: a pH solution of 3, a catalyst of 0.6 g L−1, an H2O2 concentration of 66 mg L−1, and a UV lamp power of 6 W. Moreover, the Fe3O4/zeolite A catalyst (Fe/ZA) showed good stability in the photo-Fenton degradation of methylene blue after four consecutive cycles, implying that the Fe/ZA catalyst could be a potential wastewater treatment option. Furthermore, the findings of the reaction kinetics study demonstrate that the kinetics of the dye removal reaction can be fitted using the Langmuir–Hinshelwood model for heterogeneous catalytic reactions.