Average Particle Size Of Catalyst Research Articles

Production of high purity MoO3 from spent catalyst of formaldehyde synthesis process via a novel two-step leaching-cementation method

This study presents a two-step methodology for producing high-purity MoO3 from spent FORMOX process catalysts. In the first step, a leaching process with a Na2CO3 solution is used to get molybdenum out of formaldehyde synthesis catalyst. The second step involves molybdenum-ion cementation in the presence of metallic zinc powder and plates. The leaching process is thoroughly explored using the design of experiments (DOE) to analyze critical parameters such as temperature, leaching time, Na2CO3/Mo stoichiometric ratio, and catalyst average particle size. A robust quadratic model with an R2 value exceeding 97 % is developed, serving as a predictive tool for molybdenum extraction. Through rigorous numerical optimization, the optimal conditions for 100 % extraction were found to be 74.5 °C, 92.3 min, a stoichiometric ratio of 2.52, and a particle size of 183 μm. However, the use of zinc powder in the cementation stage introduces impurities due to increased solution pH and reduced zinc dissolution. The strategic adoption of zinc plates mitigates these challenges, resulting in a notable enhancement of the final product's purity. Over 91 % of MoO4-2 ions with a purity surpassing 99.8 % are successfully obtained as hexagonal MoO3 powder at 85 °C with an initial solution pH of 1.0 after 15 min of the cementation process.

Response surface methodology optimization of electrode modification parameters toward hydrazine electrooxidation on Pd/MWCNT/GCE

In this study, MWCNT supported Pd (Pd/MWCNT) was synthesized by NaBH4 reduction method as catalyst for hydrazine electrooxidation reaction (HEOR). Characterization methods namely inductively coupled plasma mass spectrometry (ICP-MS), elemental mapping, and scanning electron microscopy with energy dispersive X-ray (SEM-EDX) were used to analyze the surface morphology and metal composition of the catalysts. The Pd/MWCNT catalyst's average particle size is estimated to be 6.35 nm based on SEM images. Glassy carbon electrode (GCE) modification parameters namely the amount of catalyst ink transferred to the GCE surface (Vs), ultrasonication time of the catalyst ink (tu), and the drying time of the Pd/MWCNT/GCE (td) were optimized by using response surface methodology as 4.92 μL, 1 min and 19.52 min, respectively. Experimental specific activity value for HEOR was obtained as 7.13 mA cm-2 with 2.59% deviation under optimum conditions. Optimization of electrode preparation conditions is an inexpensive and facile method that could be used to improve the performance of anode catalysts for fuel cells.

Parametric Study on Intrinsic Reaction for Straight Run Heavy Naphtha Hydrodesulfurization over CoMo/Al2O3 Catalyst

The present study aimed to investigate the intrinsic reaction of hydrodesulfurization (HDS) for a real Straight Run Heavy Naphtha (SRHN) over CoMo-S/Al2O3 catalyst in a fixed- bed reactor. Influence of the process parameters on sulfur removal was investigated by regulating the temperature (T = 320-380 oC), pressure (P = 20 to 35 bar), weight hour space velocity (WHSV = 2.5 to 5.0 h-1) and catalyst average particle size (dp =361 to 3950 μm). Mears and Weisz-Prater criteria were estimated and utilized to validate the intrinsic reaction condition. Operating variables were optimized at (T = 360 oC, P = 30 bars, WHSV = 2.5 h-1, dp= 361 μm) to obtain an optimum sulfur removal of 93.4% under intrinsic reaction conditions. Experimental results showed that % activity of sulfur removal increases to 93.4% as temperature increased to 360oC but it reduces to 90.3% as space velocity increased to 5.0 h-1. Kinetic parameters of the intrinsic reaction rate were estimated and compared with published data. Long-time test was performed on the sulfided catalyst to investigate its activity.

Performance enhancement and optimization of photocatalytic cyanide degradation in aqueous solution using Zn (II) and Fe (III) oxides as nanostructure supported on activated carbon

AbstractBACKGROUNDCyanide is a toxic compound used in gold mining, steel, electroplating and chemical industries. In this research, different mole ratios of Fe3+/ZnO supported on powder activated carbon (PAC) in the presence of H2O2 under UV irradiation were used to degrade cyanide contamination. The photocatalyst was characterized by XRD, XRF, FESEM, TEM and BET and response surface methodology was applied to assess the individual and interaction effects of several operating factors on cyanide degradation efficiency and to determine the optimization conditions.RESULTSThe results indicated that the average particle size of catalyst ranged from 20 to 60 nm. pH had the largest effect on response and there was interaction between initial cyanide concentration and pH. Decreasing the initial cyanide concentration and pH, while increasing the catalyst dosage, hydrogen peroxide concentration and irradiation time improved the cyanide degradation efficiency. The experimental result of cyanide degradation efficiency under optimum conditions ([CN]− = 250 mg L−1, photocatalyst = 1.4 g L−1, irradiation time = 180 min, pH=10, mole ratio of Fe3+/ZnO=6% and [H2O2] = 300 mg L−1) was about 98%. Photocatalytic activity was maintained even after seven successive cycles.CONCLUSIONThe synthesized reusable high activity nanostructure photocatalyst can be considered an applicable and environmentally friendly catalyst for the decontamination of cyanide‐polluted water. © 2017 Society of Chemical Industry

Fe3O4@OA–Pd and Mo10V2@NSiO2 nanoparticles: an efficient and reusable catalytic system for Heck reaction under ligand free conditions

This paper reports the use of a novel catalytic system composed of H5PMo10V2O40 supported on nano silica (Mo10V2@NSiO2) and palladium-deposited, oleic-acid-coated Fe3O4 (Fe3O4@OA–Pd) nanoparticles, as reusable catalysts for Heck coupling reaction under ligand and base free conditions. The average particle size of catalyst was measured to be about 9 nm by transmission electron microscopy. The immobilized palladium on oleic acid coated Fe3O4 was found to be effective in the Heck arylation of various aryl bromides and especially less reactive aryl chlorides with styrene in the presence of heteropoly acid. This method has the advantages of high yields, elimination of ligand and base, simple methodology and easy workup. Interestingly, the novel catalytic system could be recovered in a facile manner from the reaction mixture and recycled several times without any significant loss in catalytic activity. Structural changes of recovered Mo10V2@NSiO2 and Fe3O4@OA–Pd were investigated before reusing for the next runs. Finally, synchronized reusability of both components of our catalytic system has been investigated in the model reaction.

Preparation of Low Pt-Decorated Ru/C Catalyst and Electrochemical Research

The Ru/C nanocomposites with loading of 20wt% were prepared by ethylene glycol in the presence of XC-72. Carbon-supported Ru nanoparticles were decorated with Pt by spontaneous deposition method after Ru surface oxides were reduced in the hydrogen atmosphere at 180 for 2h. TEM indicated that the average particle size of catalyst was about 4nm with excellent dispersion and the XRD analyzing results showed that Pt had decorated on surface of Ru. The anti-poisoning ability was studied by pre-adsorbing CO striping voltammetric curves in 0.1M HClO4. Catalytic activities of the prepared Pt/Ru/C were studied by cyclic voltammetry in a solution of 0.5 mol/L CH3OH + 0.1 mol/L HClO4. The results showed that the oxidation current density was far more than 60wt% RuPt/C (E-TEK) and 20wt% Pt/C (Johnson Matthey). At the same time, the study also showed that the prepared catalyst not only had a higher catalytic activity to methanol, but also had lower Pt loading.

Synthesis of highly improved Ziegler‐Natta catalyst

AbstractThe effects of media viscosity, mixing speed, and injection time on catalyst average particle size (APS), particle size distribution (PSD), and morphology in both conditions, with and without emulsifier, were investigated. Supports were prepared using a so‐called recrystallization method; then they were catalyzed under the same condition. To show the effects of emulsifier on the final product's properties such as catalyst activity, polymer isotacticity, and so on, two types of catalysts were polymerized and finally their results were compared. Scanning electron microscopy micrographs were used for morphological study. Results show that by increasing the media viscosity and injection time, APS of the catalyst support was decreased. But by increasing the mixing speed, APS was decreased and PSD was broadened. It was found that emulsifier reduces the sensitivity of APS and PSD of catalyst when the support preparation conditions are changed. Consequently, by employing emulsifier, highly improved catalyst was produced. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Spent refinery catalyst as a synergistic agent in intumescent formulations: influence of the catalyst's particle size and constituents

Spent oil-cracking catalyst from the FCC process was incorporated into an ammonium polyphosphate and pentaerythritol intumescent mixture, both as received, and after milling and sifting. The influence of the catalyst's average particle size on flame retardancy performance was investigated by UL-94 rating standard, limiting oxygen index (LOI), thermogravimetric analysis (TGA) and cone calorimetry. The effect of each of the catalyst's components on the fire resistance of the final composite was also studied. The results show that the best flame-retarding properties are obtained with the finest catalyst fraction and that, of all its components, only the silica–aluminates, such as kaolin and zeolite, affect flame performance to a significant extent.