Catalyst Beads Research Articles

A simple granulation technique for preparing high-porosity nano copper oxide(II) catalyst beads

A simple and efficient method was developed for fabricating spherical granules of CuO catalyst via a three-step procedure. In the first step, copper oxide nanoparticles were synthesized by hydrothermal decomposition of copper nitrate solution under supercritical condition. Then, they were immobilized in the polymeric matrix of calcium alginate, and followed by high-temperature calcination in an air stream as the third step, in which carbonaceous materials were oxidized, to result in a pebble-type catalyst of high porosity. The produced CuO nanoparticles were characterized by transmission electron microscopy (TEM) that revealed an average size of 5 nm, X-ray diffractometry (XRD), and thermo gravimetric (TG) analysis. The catalysts were further investigated by BET test for measurement of their surface area, and by temperature-programmed reduction analysis (H 2-TPR) for determination of catalytic activity. The results demonstrated that immobilization of the CuO nanoparticle in the polymeric matrix of calcium alginate, followed by calcination at elevated temperatures, could result in notable mechanical strength and enhanced catalytic activity due to preservation of the high surface area, both valuable for practical applications.

Preparation and performance of TS-1/SiO 2 egg-shell catalysts

A monolayer of zeolite nanoparticles was deposited uniformly on SiO 2 beads’ surface by a new seeding method based on the combined use of organic linker and dip-coating procedure. The seeds were transformed into a well-intergrown TS-1 zeolite film and characterizations by SEM and XRD indicated that the film has a preferred (0 1 1) orientation. EDXS, XPS and UV–vis spectroscopies confirmed the successful preparation of egg-shell TS-1/SiO 2 catalysts. Thin shell catalysts (i.e., <11 μm) were more active for styrene oxidation. Conversion reaction rate of 8.9 mmol g −1 h −1 and turnover frequency of 28 h −1 were obtained with aromatic aldehydes (i.e., benzaldehyde and phenyl acetaldehyde) being the main products. Greater mass transfer resistance made thick shell catalysts less efficient with lower specific conversion rate of 6.9 mmol g −1 h −1 and turnover frequency of 25 h −1. Also, the extra-framework titanium resulting from the longer synthesis led to poorer selectivity. Egg-shell TS-1/SiO 2 catalyst beads were shown to be resistant to attrition and were easier to separate and recover from reaction.

Heterogeneous Aromatic Amination of Aryl Halides with Arylamines in Water with PS‐PEG Resin‐Supported Palladium Complexes

Catalytic aromatic amination is achieved in water under heterogeneous conditions by the use of immobilized palladium complexes coordinated with the amphiphilic polystyrene-poly(ethylene glycol) resin-supported di(tert-butyl)phosphine ligand. Aromatic amination of aryl halides with diphenylamine and N,N-double arylation of anilines with bromobenzene were found to proceed in water with broad substrate tolerance to give the triarylamines in high yield with high recyclability of the polymeric catalyst beads. Very little palladium leached from the polymeric catalyst under the water-based reaction conditions to provide a green and clean (metal-uncontaminated) protocol for the preparation of triarylamines, including the optoelectronically active N,N,N',N'-tetraaryl-1,1'-biphenyl-4,4'-diamines (TPDs).

Cover Picture: Heterogeneous Aromatic Amination of Aryl Halides with Arylamines in Water with PS-PEG Resin-Supported Palladium Complexes (Chem. Asian J. 8/2010)

Catalytic aromatic amination …︁ …︁ has been achieved in water under heterogeneous conditions using immobilized palladium complexes of an amphiphilic polystyrene-poly(ethylene glycol) resin-supported di(tert-butyl)phosphine ligand. In their Full Paper on page 1788 ff., Y. Hirai and Y. Uozumi present the aromatic amination of aryl halides with diphenylamine and the N,N-double arylation of anilines with bromobenzene in water with broad substrate tolerance to afford triarylamines, including the optoelectronically active N,N,N′,N′-tetraaryl-1,1′-biphenyl-4,4′-diamines (TPDs), in high yield with high recyclability of the polymeric catalyst beads.

Heterogeneous reactive extraction for an intensified alcohol production process

The heterogeneously catalysed hydration of olefins with ion exchange resins in randomly packed trickle bed and flooded bed reactors is a widely used process for the production of sec. alcohols, e.g. isopropyl alcohol (IPA). Typically, such processes are operated at temperatures ranging from 130 °C to 190 °C and pressures between 6 MPa and 10 MPa. Therefore, alcohol and water are in liquid state and the olefin is in liquid or supercritical state, respectively. The alcohol is formed in the water swollen gel phase of the macroporous ion exchanger and may be extracted by means of an olefin rich organic phase which is immiscible with the aqueous phase surrounding the catalyst beads. In presently operated industrial processes the importance of this simultaneous extraction is not fully considered. By the continuous removal of alcohol from the catalyst phase the driving forces for the reaction can be maintained on a high level and the selectivity for alcohol production can be improved. This work proposes a new reactor concept where the reactor is equipped with a structured catalytic packing for enhanced mass transfer performance. The new reactor then operates as a heterogeneous reactive extraction column offering similar advantages like reactive distillation processes. Furthermore, the modified reactor concept leads to a less energy demanding product purification sequence significantly lowering the operative costs for the process. As a result, the analysis of processes as a whole can be a promising approach to process intensification especially when modifications to one process unit affect other units.

Preparation of alkali-resistant, Sil-1 encapsulated nickel catalysts for direct internal reforming-molten carbonate fuel cell

Abstract A thin layer of silicalite-1 zeolite membrane was grown on the surface of Ni/SiO 2 and Ni/Al 2 O 3 catalyst beads after seeding and secondary regrowth to create core–shell catalysts that are resistant to alkali poisoning from direct internal reforming-molten carbonate fuel cell (DIR-MCFC). The zeolite shell thickness was optimized to prevent poisoning and minimize diffusion resistance. An out-of-cell test was designed to simulate the fuel cell operating conditions, which showed that the new core–shell catalysts maintained a high activity similar to the original fresh catalyst in spite of the exposure to alkali vapor at high temperature. The conventional Ni/SiO 2 and Ni/Al 2 O 3 catalysts suffered higher than 80% decrease in activity for steam reforming of methane reaction (SRM).

Spatially Resolved NMR Thermometry of an Operating Fixed-Bed Catalytic Reactor

An MRI-based approach for the thermometry of an operating packed-bed catalytic reactor was implemented. It was employed for the spatially resolved NMR thermometry of the bed of Pd/gamma-Al2O3 catalyst beads in the course of propylene hydrogenation reaction. This was achieved by detecting the spatially resolved axial 1D profiles of the 27Al NMR signal intensity of Al2O3 in the course of the reaction. The experimental results demonstrate a clear correlation between the 27Al NMR signal intensity and the catalyst temperature measured with a thermocouple (25-250 degrees C), and reveal the existence of pronounced temperature gradients along the catalyst bed.

Polystyryl‐BEMP as an Efficient Recyclable Catalyst for the Nucleophilic Addition of Nitroalkanes to α,β‐Unsaturated Carbonyl Compounds under Solvent‐Free Conditions

Abstract2‐tert‐Butylimino‐2‐diethylamino‐1,3‐dimethylperhydro‐1,3,2‐diazaphosphorine supported on polystyrene (PS‐BEMP) is an efficient catalyst for the addition of nitroalkanes (1–1.5 equiv.) to α,β‐unsaturated carbonyl compounds (1.0 equiv.) in the absence of a reaction medium (solvent‐free conditions). The corresponding γ‐nitro carbonyl compounds have been isolated in excellent yields but the catalyst can be satisfactorily recovered and used for only 3 times due to the magnetic stirring which caused crunching of the catalyst beads thus hampering its complete recovery. To optimize the catalyst’s reuse and improve the environmental efficacy of solvent‐free conditions, the first solvent‐free cyclic continuous‐flow reactor has been set up. This reactor has allowed the product to be isolated in an almost quantitative yield by using a very small amount of organic solvent, making the recovery and reuse of the catalyst efficient and reproducible.

Methodology of mechanical characterization of coated spherical materials

The aim of this work was to develop a methodology for the mechanical characterization of catalyst beads with a core-shell structure and more especially for coated spherical granules. Supports composed of an alpha alumina core coated by gamma alumina shell were shaped by pan coating to this purpose. The proposed methodology started with the characterization of the microstructure of the coating and the highlight of potential macro defects within. Thereafter three tests simulating mechanical stress, such as impact, compression (bulk crushing test), and shear (drum attrition test) are used. The operational parameters of these tests were also optimised in order to stress preferentially the shell of the coated materials. Among the evaluated tests, drum attrition seems to be most efficient for characterizing coated spherical granules.

Polymerization of 3‐ethynylthiophene with homogeneous and heterogeneous Rh catalysts

Abstract3‐Ethynylthiophene (3ETh) was polymerized with Rh(I) complexes: [Rh(cod)acac], [Rh(nbd)acac], [Rh(cod)Cl]2, and [Rh(nbd)Cl]2 (cod is η2:η2‐cycloocta‐1,5‐diene and nbd η2:η2‐norborna‐2,5‐diene), used as homogeneous catalysts and with the last two complexes anchored on mesoporous polybenzimidazole (PBI) beads: [Rh(cod)Cl]2/PBI and [Rh(nbd)Cl]2/PBI used as heterogeneous catalysts. All tested catalyst systems give high‐cis poly(3ETh). In situ NMR study of homogeneous polymerizations induced with [Rh(cod)acac] and [Rh(nbd)acac] complexes has revealed: (i) a transformation of acac ligands into free acetylacetone (Hacac) occurring since the early stage of polymerization, which suggests that this reaction is part of the initiation, (ii) that the initiation is rather slow in both of these polymerization systems, and (iii) a release of cod ligand from [Rh(cod)acac] complex but no release of nbd ligand from [Rh(nbd)acac] complex during the polymerization. The stability of diene ligand binding to Rh‐atom in [Rh(diene)acac] catalysts remarkably affects only the molecular weight but not the yield of poly(3ETh). The heterogeneous catalyst systems also provide high‐cis poly(3ETh), which is of very low contamination with catalyst residues since a leaching of anchored Rh complexes is negligible. The course of heterogeneous polymerizations is somewhat affected by limitations arising from the diffusion of monomer inside catalyst beads. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2776–2787, 2008

Feasibility studies and dynamics of catalytic liquid phase esterification reactions in a micro plant

We present a new micro reactor concept which is suitable for investigations of heterogeneously catalyzed liquid phase reactions. In the set-up two reactants are mixed in a commercially available interdigital micro mixer. The outlet of the micro mixer is connected to a modular micro reactor that consists of stacked plates. Each plate contains a milled meandering channel filled with catalyst beads. By using a variable number of plates the residence time can be manipulated and thus adjusted for a specific task. The synthesis of butyl acetate is considered as a model reaction since it has been investigated in detail in conventional reaction systems. In a first step, some experimental results of the heterogeneously catalyzed reaction are presented. In the second part, the set-up is operated as a chromatographic reactor. Dynamic behaviour is investigated applying the frontal analysis mode and the elution chromatography mode.

Properties and efficiency of a Pt/Al2O3 catalyst applied in a solid fuel thermo-accumulating furnace

A prototype of a solid fuel thermo-accumulating furnace has been developed. In order to achieve a higher combustion efficiency, a Pt/Al2O3 catalyst in the form of 3 ? 0.3 mm spheres was applied, which enabled further combustion of flue gases within the furnace. Experimental investigation of the influence of the catalyst on the conversion of CO has been done for different operation regimes and positions of the catalyst. Paper presents selected results regarding CO emission during wood and coal combustion. Investigations suggest a considerable effect of the catalyst and a strong influence of the catalyst position to CO emission reduction. The microstructure of the catalyst beads, characterized by selective chemisorption of CO, has shown the decrease of the number of Pt sites as a consequence of blockage by coke deposits formed during the combustion of solid fuel. .

Loss of coherence in a population of diffusively coupled oscillators

The authors investigate the relationship between the natural frequency distribution of diffusively coupled chemical oscillators and their entrainment by pacemakers. The system consists of micrometer-sized catalyst beads which are coupled to their neighbors by diffusion of the activator/inhibitor species through the catalyst-free Belousov-Zhabotinsky (BZ) reaction solution. The frequency distribution is measured as a function of the beads' number of neighbors. With the maximum number of neighbors, either target waves or disordered patterns are observed in the reaction domain and there is a shift to higher frequencies than those observed in the natural frequency distribution. The loss of coherence between neighbor oscillators is quantified by a decrease in the phase synchronization index. The experimental results are reproduced in simulations which demonstrate that the decrease in the degree of synchronization is correlated with the appearance of a small fraction of permanently excited beads in BZ populations of high mean frequency and/or large width.

III-VI compound semiconductor indium selenide (In2Se3) nanowires: Synthesis and characterization

The authors report the synthesis of one-dimensional indium selenide nanowire, a III-VI group compound semiconductor nanostructure with potential applications in data storage, solar cells, and optoelectronics. Nanoscale gold particles were used as catalysts and growth was also demonstrated using indium as self-catalyst. The growth mechanism is confirmed to be vapor-liquid-solid process by in situ heating experiments in which In and Se were found to diffuse back into the gold catalyst bead forming a Au–In–Se alloy that was molten at elevated temperatures. The morphology, composition, and crystal structure of the In2Se3 nanowires (NWs) were analyzed by scanning electron microscopy, energy dispersive x-ray spectroscopy, and high-resolution transmission electron microscopy.

Feasibility study of hydrogen generation from sodium borohydride solution for micro fuel cell applications

This paper presents work on hydrogen generation from sodium borohydride (NaBH 4) solution that could have great application in micro fuel cells. A hydrogen test method has been developed, which is very effective for sustained measurement of the generation rate and yield of hydrogen. The hydrogen is supplied to a proton exchange membrane fuel cell. The discharged current is measured by a computer-controlled electronic load system connecting to the fuel cell where hydrogen generation rate and yield are calculated. The study is focused on the slow release of hydrogen. The results show that if the concentration of NaBH 4 solution is 10%, no solid substance is formed and the catalyst supported on the ion-exchange resin beads remains unchanged. The hydrogen generation can be controlled by inserting or removing the catalyst into/from the solution, which can be applied to a micro fuel cell. When the concentration of NaBH 4 solution is 20%, however, the catalyst beads are broken up and dispersed in the solution (probably by the NaBO 2 crystallization force) and give rise to uncontrollable generation of hydrogen.

Enzyme-Catalyzed Regioselective Modification of Starch Nanoparticles

The selective esterification of starch nanoparticles was performed using as catalyst Candida antartica Lipase B (CAL-B) in its immobilized (Novozym 435) and free (SP-525) forms. The starch nanoparticles were made accessible for acylation reactions by formation of Aerosol-OT (AOT, bis(2-ethylhexyl)sodium sulfosuccinate) stabilized microemulsions. Starch nanoparticles in microemulsions were reacted with vinyl stearate, e-caprolactone, and maleic anhydride at 40 °C for 48 h to give starch esters with degrees of substitution (DS) of 0.8, 0.6, and 0.4, respectively. Substitution occurred regioselectively at the C-6 position of the glucose repeat units. Infrared microspectroscopy (IRMS) revealed that AOT-coated starch nanoparticles diffuse into the outer 50 μm shell of catalyst beads. Thus, even though CAL-B is immobilized within a macroporous resin, CAL-B is sufficiently accessible to the starch nanoparticles. When free CAL-B was incorporated along with starch within AOT-coated reversed micelles, CAL-B was als...

Evaluating the activities of immobilized TiO2 powder films for the photocatalytic degradation of organic contaminants in water

In a previous paper [J. Mater. Sci. 38 (2003) 823] we have described the preparation and characterization of conventional alkoxide sol–gel derived TiO2 films [J. Mater. Sci. 23 (1988) 2259] and of TiO2 powder enriched alkoxide sol–gel derived films. The powder films were prepared on flat stainless steel substrates and on glass beads. These films were characterized for various parameters like particle size, crystal phase, pore size, thickness and mechanical properties. In our current study, the photocatalytic activities of these sol–gel derived TiO2 films were studied utilizing a quartz batch reactor. The quartz batch reactor was characterized for parameters like mixing, recycle, aeration and UV radiation flux, and the TiO2 coated substrates were used as the photocatalyst. The activities of the catalyst films were evaluated by measuring the degradation rate of 4-chlorobenzoic acid used as a model organic pollutant. Immobilized TiO2 powder films on stainless steel containing a mixture of anatase and rutile phases were found to be more effective than films that were substantially composed of anatase phase particles. The activity of glass beads coated with TiO2 powder was compared to the activity of commercially available TiO2 catalyst beads. While the activity of the commercially available TiO2 catalyst beads was higher there was significant attrition of the TiO2 catalyst film. The films on the glass beads possessed better mechanical properties than the commercial catalyst beads and their activity can be significantly improved by optimizing the film synthesis process parameters.

A Modified Method for the Synthesis and Characterization of a Novel Surface-Enriched (with Active Site) Polymer-Supported Phase Transfer Catalyst Using Vinyltoluene as a Functionality and Its Catalytic Efficiency in Dichlorocarbene Addition to Olefines—A Kinetic Study

A modified method with respect to an earlier conventional procedure was successfully attempted and we now report the new procedure for the synthesis of surface-grafting technique by the delayed addition of inexpensive vinyltoluene (VT) functionality to the partially polymerized supporting monomers viz., styrene (St) and divinylbenzene (DVB) via suspension polymerization. The resulting copolymer beads containing surface-enriched with methyl group were converted into a catalyst by chlorination followed by a quaternization process. Two groups (I and II) of SE-PSPTC beads were prepared by fixing the crosslinking amount (DVB) as 2% and 6%, respectively, 25% of VT as a common active site functionality and the rest of the contribution was styrene. Each group contains six different catalysts based on the concentration of active sites on the surface which in turn depends upon the partial polymerization time (PPT) of St/DVB i.e., 0, 3, 6, 9, 12, and 15 hrs. These two different groups and 6 different catalysts categories in each were prepared with the objective to learn the influence of higher/lower crosslinking in the process of surface-grafting of poly(VT) on poly(St/DVB) and to determine the optimized partial polymerization time to bring the maximum active site on the surface. The level of enrichment of an active site of all the catalysts were determined through [chloride], FT-IR, SEM, EDAX, and ESCA analyses. The gradual increase of [chloride], C-N peak intensity from FT-IR, rough surface/nodules concentration from SEM, % of surface chloride from EDAX, decreasing/increase trend of surface carbon/surface chloride in ESCA analyses starting with 0 VT to 15 VT irrespective groups, confirms the gradual increase of active site on the surface beads based on the PPT. The results of [chloride], spectral analyses and the rate constants of all the catalysts in dichlorocarbene addition to various olefines ensure that 9 VT-SE-PSPTC was the best catalyst beads in both the groups due to its two-fold enhancement rather than the conventional catalyst (0 VT) of both groups although we had added the same amount of VT in both preparations.

Coalescence Rate Constant of Slug in a Gas Fluidized Bed.

In order to understand the characteristics of slug coalescence, the slug frequency has been measured by a differential pressure method in a gas-fluidized bed of i.d. 0.1 m and height 2.25 m, at ambient temperature and pressure, and with respect to variations of bed height (0.23–0.93 m) and gas velocity (U – Umf = 0.0190–0.139 m/s). Air was used as fluidizing gas and a fresh FCC catalyst (Geldart’s group A particle, dp = 0.070 mm, ρs = 1600 kg/m3, Umf = 0.0113 m/s) and glass bead (Geldart’s group B particle, dp = 0.168 mm, ρs = 2486 kg/m3, Umf = 0.0303 m/s) as bed materials.The slope of a frequency decrease accompanying with a gas velocity increase at different bed heights was similar in the bed of Geldart’s group-A particle. So was the slope of frequency decrease with bed height at different constant gas velocities. The mechanism controlling slug coalescence was found to be different between Geldart group-A and B particles. The slug coalescence model proposed by Yamazaki et al. (1984) was extended to the case with gas velocity as a variable. The slug coalescence rate constant leveled off after an initial decrease in the bed of Geldart’s group-B particle. However, it increased in the bed of Geldart’s group-A particle as the gas velocity increased. Correlation on the slug coalescence rate constant that includes effects of gas velocity, temperature and particle properties has been proposed in each different slug growth regime.

Mass transfer characteristics in a large-scale slurry bubble column reactor with organic liquid mixtures

The mass transfer coefficients ( k L a) and bubbles size distribution were measured in a large-scale (0.316-m inside diameter, 2.8-m high) slurry bubble column reactor (SBCR) for H 2, CO, N 2 and CH 4 in two organic liquid mixtures (Isopar-M and a hexanes mixture) in the presence and absence of two solids (iron oxides catalyst and glass beads) in a wide range of pressure (0.17– 0.8 MPa ), superficial gas velocity (0.08– 0.2 m/ s ), and solid concentration (0– 36 vol% ). The k L a values were found to intimately follow the behavior of the bubble size distribution under the operating conditions used, as they appeared to increase with pressure and gas velocity and dramatically decrease when operating with high solid concentrations. The effect of high solid concentrations in the reactor prevailed over the effect of pressure on the bubble size distribution by creating large gas bubbles with significantly small gas–liquid interfacial areas, leading to small k L a values. Thus, industrial SBCRs operating with high catalyst loading could likely operate in a mass transfer-controlled regime due to the expected low k L a values.