Spherical Catalyst Research Articles

Diffusion and Surface Reaction in Porous Cubical Catalyst: A Mathematical Approach

Background: Catalysts are the most vital part of any chemical industry. Catalyst is a substance that affects the rate of reaction, but the catalyst itself does not take part in the reaction. Catalysts offer different pathways of reaction by diffusing the reactant inside it to provide a large surface area within a small volume, thus, lowering the activation energy of molecules for reaction. Most of the catalytic reactions take place in a liquid- solid or gas-solid interface where catalysts are mostly porous in nature. Spherical and cubic-shaped catalyst particles are commonly used in different industries. Methods: In the first phase of the present study, the physics behind the diffusion inside the catalyst pellet has been discussed. In the second part, governing differential equations have been established at a steady-state condition. For solving the differential equation, the equation is made dimensionless. Physical boundary conditions were used to solve the diffusion equation. The assumption of writing the differential equation of the reaction is elementary. Then, the Thiele modulus is derived in terms of the reaction and geometrical parameter (Length). Results and Conclusion: In the third part, the differential equation is solved for firstorder reaction with some constant values of the Thiele modulus, and three-dimensional plots are obtained using numerical analysis. After that, the obtained Thiele modulus and effectiveness factor plot are compared to draw the conclusion of rate limiting reaction and internal diffusion.

Fabrication of platinum-doped WS2 hollow spheres catalyst for high-efficient hydrogen evolution reaction

Fabrication of platinum-doped WS2 hollow spheres catalyst for high-efficient hydrogen evolution reaction

Hollow carbon sphere encapsulated nickel nanoreactor for aqueous-phase hydrogenation-rearrangement tandem reaction with enhanced catalytic performance

As green chemistry, aqueous-phase reactions play a vital role in modern fine chemical synthesis. Herein, an encapsulated nickel in a hollow carbon sphere (Ni@HCS) catalyst was constructed to effectively catalyze an aqueous-phase hydrogenation-rearrangement tandem (AP-HRT) reaction, in which water was employed as the solvent and reactant simultaneously. The activity is relevant to the HCS and Ni loading. The optimal Ni@HCS catalyst can release 100% furfural conversion and 99.1% cyclopentanone selectivity at 150 °C and can maintain its activity after 10 cycles of experiments. The superior catalytic performance comes from the fact that each independent Ni@HCS can be treated as an individual nanoreactor with a void-confinement effect, which not only reduces the side reactions due to the size-selective effect but also prevents active metal from leaching under harsh conditions. The reaction mechanism of FAL AP-HRT was further investigated via kinetic experiments combined with DFT calculations.

Spherical NiCo-MOFs catalytic hydrogenolysis of lignin dimers and enzymatic lignin to value-added liquid fuels under nitrogen atmosphere

Ni-based MOFs catalysts are promising candidates that can be used to achieve biomass valorization following the process of selective hydrogenolysis process. Here we report a spherical NiCo-based MOFs catalyst, which provides a larger BET surface to enhance 2-phenoxy-1-phenylethan-1-ol molecules enrichment and promote the hydrogenolysis on spherical NiCo-based MOFs catalyst surface. In addition, the synergistic interaction between Ni and Co species also shows great effect on catalytic hydrogenolysis of 2-phenoxy-1-phenylethan-1-ol molecules and enzymatic lignin. The yields of ethylcyclohexane and cyclohexanol are dramatically improved to more than 90 mol% over Ni3Co1-based MOFs catalyst under nitrogen atmosphere. Various lignin dimers derivatives are investigated over Ni3Co1-based MOFs catalyst, which indicates oxygen-containing functional groups played a critical role in the hydrogenolysis process. Isopropanol is used as solvent in the hydrogenolysis of 2-phenoxy-1-phenylethan-1-ol molecules and enzymatic lignin. 21% of H2 is observed in the GC/MS, suggesting that it is a catalytic transfer hydrogenolysis process. Catalytic hydrogenolysis of enzymatic lignin is also carried out under 280 ℃ over optimal Ni3Co1-based MOFs catalyst for 6 h, giving highest lignin oil yield (75.6 wt%) and lower O/C ratio (0.17). This work can be extended to different biomass valorizations to promote the catalytic behavior of spherical MOFs catalysts.

Mn/carbon sphere catalyst for heterogeneous activation of peroxymonosulfate for methylen blue removal

One of the latest innovations in textile waste treatment is advanced oxidation processes (AOPs) methods using an oxidizing agent capable of producing sulfate radicals (SO4•). This study aims to determine the activity of the Mn/Carbon sphere catalyst in the oxidation process, reduce the dye content by using a combination of peroxymonosulfate (PMS) and Mn/Carbon sphere catalyst as an oxidizing agent, and determine the optimum conditions in the process of reducing dye levels in the water. A hydrothermal process carried out the catalyst synthesis process to produce black carbon from D-glucose solution, then impregnated with variations of 3% and 5% of Mn metal. The degradation of methylene blue (artificial waste) of 25mg/L (1:10 dilution) was carried out for 120 minutes with variations in the catalyst mass of 0.001, 0.002, 0.003, and 0.004g and the mass of PMS 0.01, 0.02, 0.03, and 0, 04g in 100ml sample. Mn/Carbon sphere catalyst was able to activate PMS and was able to degrade methylene blue by 88.16%. The optimum condition for reducing the methylene blue levels in the water is at a concentration of 1g/L PMS and a Mn/Carbon sphere catalyst (5% Mn metal) 0.5g/L with an efficiency of 88.16%.

A spherical multishell hollow carbon-based catalyst with a controllable N-species content for the oxygen reduction reaction in air-breathing cathode microbial fuel cells

Schematic illustration of the fabrication of a spherical metal–organic framework.

Large Particle Spherical Poly-Ionic Liquid-Solid Base Catalyst for High-Efficiency Transesterification of Ethylene Carbonate to Prepare Dimethyl Carbonate

Large Particle Spherical Poly-Ionic Liquid-Solid Base Catalyst for High-Efficiency Transesterification of Ethylene Carbonate to Prepare Dimethyl Carbonate

Fast Estimation of Reaction Rates in Spherical and Non-Spherical Porous Catalysts

Fast Estimation of Reaction Rates in Spherical and Non-Spherical Porous Catalysts

Triboelectric effects in catalyst feeders of fluidized-bed polymerization reactors

Solid material in fluidized-bed polymerization reactors consists of two components with different triboelectric properties. The main material is a granular polymer with the particle size from ∼100 to >1000 μm. The second component, very small in volume, is fresh catalyst, spherical particles with the diameter from 20 to 40 μm. Small loads of catalyst particles are periodically fed into the reactors through narrow metal tubes with a gas flow (nitrogen or monomer).This catalyst injection process leads to accumulation of a significant electric charge on the catalyst particles. This paper describes results of laboratory experiments aimed at determining sources of electrostatics generation in spherical catalyst particles passing through narrow tubes, a possible mechanism of the charging and methods of its mitigation.

Rationally-designed sandwiched nanostructures boosting Fe-N based catalysts toward efficient oxygen reduction electrocatalysis in acidic medium

The development of acidic-available noble-metal-free oxygen reduction reaction (ORR) catalysts with high activity and good long-term durability is of significant importance for efficient proton exchange membrane fuel cells, but is still very challenging. Herein, we develop originally a facile wet-chemical-adsorption, pyrolysis and post-etching strategy to effectively intercalate Fe clusters among two nitrogen-doped carbon (NC) layers, forming unique hollow spherical nanostructures with sandwiched NC/Fe/NC shells as an active ORR catalyst. Thanks to the sandwiched nanostructure and the active Fe-N species, this as-prepared hollow sandwiched NC/Fe/NC catalyst could present superior ORR activity in an acidic medium, with a nice onset potential of 0.92 V and decent diffusion-limited current density of ~5.1 mA/cm2. The NC/Fe/NC catalyst manifests strong methanol tolerance and outstanding durability during a long-term acidic ORR operation, being a promising alternative to Pt-based catalysts toward efficient proton exchange membrane fuel cells. Synchrotron radiation characterizations and X-ray photoemission spectroscopy reveal at the atomic-level that the abundant robust Fe–N bonds presented in the sandwiched shells of hollow NC/Fe/NC spherical catalyst contribute substantially to high electrochemical activity and superior corrosion-resistance for efficient 4e¯ ORR in acidic electrolyte.

Mathematical modelling of thermal microexplosion in a catalyst granule with point sources of heat release

A mathematical model of heat and mass transfer in a spherical catalyst granule is proposed. Exothermic synthesis reactions are carried out on point active centres located inside a porous ceramic granule. From the surface of the granule the heat of catalytic reactions is removed into liquid synthesis products. The rate of a chemical reaction is modelled by a modified Arrhenius law. In contrast to the homogeneous model of a catalytic granule methods for calculating heat transfer processes in a system of point, active centres do not develop. An iterative procedure is suggested to calculate the unknown temperature and concentration of the reagent at the active centre. It is shown that the temperature of the active centres is significantly higher than in the volume of the granule. The results of modelling a thermal explosion with increasing granule size and reactor temperature are presented.

Bimetallic Modified Mud Sphere Catalyst Enhanced Electrocatalytic Oxidation and Persulfate Advanced Oxidation for the Degradation of Sulfamethazine

Bimetallic Modified Mud Sphere Catalyst Enhanced Electrocatalytic Oxidation and Persulfate Advanced Oxidation for the Degradation of Sulfamethazine

Bimetallic Modified Mud Sphere Catalyst Enhanced Electrocatalytic Oxidation and Persulfate Advanced Oxidation for the Degradation of Sulfamethazine

Bimetallic Modified Mud Sphere Catalyst Enhanced Electrocatalytic Oxidation and Persulfate Advanced Oxidation for the Degradation of Sulfamethazine

Comparative analysis of the dual origins of the N2O byproduct on MnOx, FeOx, and MnFeOx sphere catalysts for a low-temperature SCR of NO with NH3

The formation mechanism of N2O byproduct from NSCR and NH3 over-oxidation dual pathways on MnOx, FeOx, and MnFeOx sphere catalysts were revealed during the low-temperature SCR process.

Fabrication of copper supported porous silica–alumina hollow spheres for catalytic decomposition of nitrous oxide

Copper supported porous silica–alumina hollow sphere catalysts were prepared using surfactant micelles to control the size distribution of interparticle spaces in the hollow sphere shells.

Effect of antioxidants and blending with diesel on partially hydrogenated fish oil biodiesel to upgrade the oxidative stability

Fish oil derived biodiesel has susceptibility to oxidation due to its higher polyunsaturated fatty acid content. Therefore, to control the rapid oxidation process, partial hydrogenation of fish oil biodiesel under 0.5 MPa pressure of H2 by using 0.5% Pd supported on Al2O3 spherical catalyst was done. It showed 8.0 h of oxidation stability after 1.0 h reaction higher than non‑hydrogenated fish oil biodiesel (0.1 h). A decrease in the rate of polyunsaturation (>95%) was achieved after 1.5 h of selective hydrogenation reaction with 17.3 h oxidation stability. Simultaneously, addition of antioxidants, such as3,5-di-tert-butyl-4-hydroxytoluene and tert-butylhydroquinone, to hydrogenated biodiesel was also performed to enhance its induction period more. Hydrogenated biodiesel was further blended with diesel to increase induction period and reduce the pour point. Thus, iodine value, viscosity, acid value and peroxide value of hydrogenated fish oil biodiesel met the EN 14214:2012 standard to be implemented as commercial automobile fuel.

Degradation of Formaldehyde over MnO2/CeO2 Hollow Spheres: Elucidating the Influence of Carbon Sphere Self-Sacrificing Templates.

Here, we prepare a MnO2/CeO2 hollow sphere catalyst using the carbon sphere as a self-sacrificing template for formaldehyde (HCHO) removal. In the feed gas of 20 ppm of HCHO (balanced by N2) + 20 vol % O2, a HCHO removal efficiency of 70% was achieved at 20 °C and full conversion was reached at around 47 °C at GHSV = 50,000 mL (gcat h)−1 for MnO2/CeO2 hollow spheres. The catalytic performance and structural and chemical properties of MnO2/CeO2 hollow spheres for the removal of core carbon spheres were explored, and the influence of using the carbon sphere as a self-sacrificing template was proved by comparing with carbon@MnO2/CeO2 (a core carbon sphere with a MnO2/CeO2 shell) and nonmorphologic MnO2/CeO2. The properties of the MnO2/CeO2 hollow spheres are significantly improved compared to carbon@MnO2/CeO2 (removal efficiency of 45% at 150 °C) and MnO2/CeO2 (removal efficiency of 46% at 20 °C) as a result of an evolution in the interaction between Mn/Ce and carbon. This increase in the interaction strength seems to (i) increase the oxygen vacancy, (ii) promote the oxygen species mobility, and (iii) improve the chemical stability of the MnO2/CeO2 hollow spheres. We believe that these results are beneficial to the fabrication of binary transition metal oxides and applications of them in HCHO removal.

Mathematical Analysis of Non-Isothermal Reaction–Diffusion Models Arising in Spherical Catalyst and Spherical Biocatalyst

The theory of dynamical systems and their widespread applications involve, for example, the Lane–Emden-type equations which are known to arise in initial- and boundary-value problems with singularity at the time t=0. The main objective of this paper is to make use of some mathematical analytic tools and techniques in order to numerically solve some reaction–diffusion equations, which arise in spherical catalysts and spherical biocatalysts, by applying the Chebyshev spectral collocation method. The proposed scheme has good accuracy. The results are demonstrated by means of illustrative graphs and numerical tables. The accuracy of the proposed method is verified by a comparison with the results which are derived by using analytical methods.

Oxide-derived Tin Nanospheres for Efficient CO2 Electroreduction to Formate

Rational design and engineering of electrocatalysts for electrochemical CO2 reduction (CO2RR) is crucial to effectively, selectively converting CO2 into carbon-neutral chemicals and fuels. In this work, we have developed hierarchical tin oxide nanosphere electrocatalysts to boost the production of formate. Three-dimensional (3D) SnO2 spheres constructed from small crystalline nanoparticles exhibited 71-81% Faradaic efficiencies (FE) and energy efficiency (40-50%) toward formate production at partial current densities of 22-72.4 mA/cmgeo 2 from -0.9 V to -1.3 V vs. the reversible hydrogen electrode (RHE). Such hierarchical sphere-like catalysts outperformed non-hierarchical SnO2 nanoparticles and commercially benchmarking catalysts, achieving a peak 81% FE at superior formate current density of ~50 mA/cmgeo 2 at -1.2 V vs. RHE. The spherical oxide-derived Sn catalysts were highly stable up to 36 hours, preserving long-term partial current density of ~ 45 mA/cmgeo 2 and 68% FE for formate. Such an outstanding performance can be credited to the 3D hierarchical structure, which offers enlarged surface area, larger number of electrochemically active sites, and strongly suppressed H2 evolution. Our results may provide more guidelines for the introduction of hierarchical porosity into CO2RR electrocatalysts for large-scale applications.

Novel high dispersion and high stability cobalt-inlaid carbon sphere catalyst for hydrogen generation from the hydrolysis of sodium borohydride

It is noteworthy that a competent catalyst would be conductive to promote the efficiency of hydrogen generation in the hydrolysis of sodium borohydride. However, most current catalysts are suffered from active particle agglomeration or degradation, which are difficult to meet the requirements of continuous and efficient hydrolysis of sodium borohydride to produce hydrogen. Herein, novelly high dispersion and high stability cobalt-inlaid carbon sphere catalysts were prepared using a one-step co-pyrolysis method for the first time. The ultrafine Co nanoparticles are evenly embedded in the carbon spheres by adjusting the synthesis conditions such as amount of ammonia and hydrothermal temperature. As demonstrated, the Co@C-462-145 catalyst (462 μL of ammonia, 145 ℃ of hydrothermal temperature), displayed good catalytic activity for the hydrolysis of sodium borohydride, exhibiting high hydrogen generation rate of 5392 mLH2•min−1•gCo-1 and low Arrhenius activation energies of 32.7 kJ/mol. Significantly, the Co@C-462-145 showed excellent durability retaining 85.2% of initial catalytic activity after five consecutive runs with almost no aggregation and shedding phenomenon. The outstanding catalytic performance of Co@C-462-145 should be attributed to the uniform dispersion and stabilization of the Co nanoparticle. This provides a probable strategy for the preparation of efficient carbon-supported cobalt-based catalysts in the future.