Fibrous Catalyst Research Articles

Preparation of Palladium Nano-Particles by Electrospinning and its Application in Hydrogenations

a novel fibrous catalyst containing palladium nano-particles was produced via electrospinning technique. The fibrous catalyst was characterized by scanning electron microscopy and transmission electron microscopy respectively, the results showed that the diameter of fiber was about 200 nm and the palladium (Pd) particles were in the range of 30~40 nm. The catalyst was tested in hydrogenations of α-olefins, cyclohexene and nitrobenzol in ethanol at room temperature under 1 atmosphere hydrogen. The results showed that the titled catalyst had high activity in the hydrogenations of α-olefins, cyclohexene and nitrobenzol.

Rapid Biodiesel Fuel Production Using Novel Fibrous Catalyst Synthesized by Radiation-Induced Graft Polymerization

An efficient fibrous catalyst for the biodiesel fuel production has been synthesized by radiation-induced graft polymerization of 4-chloromethylstyrene onto a nonwoven polyethylene (NWPE) fabric followed by amination with trimethylamine (TMA) and further treatment with NaOH. The degree of grafting of NWPE fabric and TMA group density of fibrous catalyst could easily and reproducibly be controlled within a range of up to 340% and 3.6 mmol-TMA/g-catalyst, respectively. In the transesterification of triglycerides and ethanol using the synthesized fibrous catalyst, the conversion ratio of triglycerides reached 95% after 4 h reaction at 50°C.

Development of Environmentally Friendly Modified Fe-PAN Fibrous Catalyst and Its Application in Degradation of Dye

Modified Fe-PAN fibrous catalyst (Fe-AO-PAN) was formulated at the room temperature by the reaction of amidoxime (AO) modified polyacrylonitrile (PAN) fiber (AO-PAN) with FeCl3, which was in turn used as an environmentally friendly heterogeneous photocatalyst in the oxidative degradation reaction of the standard target dye Rhodamine B in the presence of hydrogen peroxide. This paper investigated the influences of the iron ion concentration in solution (CFe) and reaction temperature to the iron ion content in Fe-AO-PAN catalyst (CFe-AO?PAN); studied the effects of CFe-AO?PAN, pH, intensity of light irradiation and etc. on the decoloration rate of the dye; and analyzed the oxidative degradation procedure of the dye by ultraviolet-visible light spectrum analysis. The results indicate that CFe-AO?PAN increases with the rise of CFe or reaction temperature; the decoloration rate of Rhodamine B increases with the rise of CFe-AO?PAN or radiation intensity, as well as the decrease of initial concentration of the dye; and Fe-AO-PAN shows higher catalytic activity in the solution of pH less than or equal to 6.0, however lower catalytic activity in a strongly basic medium. In addition, ultraviolet-visible light spectrum analysis proves that Fe-AO-PAN can effectively catalyze the break of azo bond and aromatic ring in the dye molecular, but can not be reutilized efficiently.

Fitting of kinetic parameters of NO reduction by CO in fibrous media using a genetic algorithm

An empirical model is fitted to the performance of NO reduction by CO gas on an alumina fibrous catalyst support media. The model is highly non-linear and contains 13 fitted parameters. To fit the reaction kinetic parameters in the model to the experimental results, a genetic algorithm was applied to search for the best fit parameter values. The fitted model and experimental results for Pd, Pt and Rh catalysts are in good agreement. The effects of NO decomposition by varying fiber diameter, media depth, and catalyst particle size on rhodium catalyst can be calculated from the model. The model results show the temperature of complete NO decomposition decreases with greater media depth, higher fractional area of coverage by the catalyst particles, and with smaller catalyst particle size.

Preparation of Chitosan Grafting Acrylic Acid Supported Palladium Fibrous Catalyst and its Application in Hydrogenation

Chitosan grafting acrylic copolymer (CTS-g-AA) supported Nano palladium catalyst was obtained in this paper. Chitosan grafting acrylic copolymer (CTS-g-AA) was prepared firstly and palladium was supported on CTS-g-AA; then nano fibrous catalyst was gained via electrospinning technique. The title catalysts were characterized by TEM, SEM and IR, the diameter of nanofiber was about 70~200 nm, the size of metal particles were in a range of 10~40 nm, and palladium particles dispersed on nanofibers homogeneously. The catalyst was applied to catalyze α-octene hydrogenation in normal temperature and pressure. The results showed that the conversion of α-octene was 99%, and the yield of octane was 65% by double-metal catalyst.

Methanol Synthesis from CO 2 Hydrogenation with a Cu/Zn/Al/Zr Fibrous Catalyst

A highly active Cu/Zn/Al/Zr fibrous catalyst was developed for methanol synthesis from CO 2 hydrogenation. Various factors that affect the activity of the catalyst, including the reaction temperature, pressure and space velocity, were investigated. The kinetic parameters in Graaf's kinetic model for methanol synthesis were obtained. A quasi-stable economical process for CO 2 hydrogenation through CO circulation was simulated and higher methanol yield was obtained.

The relation between surface composition of Pd–Cu/ACC catalysts prepared by selective deposition and their denitrification behavior

Abstract Pd–Cu catalysts supported on activated carbon cloth (Pd–Cu/ACC), prepared by selective catalytic deposition, showed a high activity (92% conversion) and selectivity (ca 93%) in the liquid phase hydrogenation of nitrates to nitrogen. From this study, first knowledge on the surface composition of a family of Cu–2 wt%Pd/AC bimetallic catalysts and their remarkable influence on the catalytic behavior in nitrate hydrogenation could be obtained. The results of the surface composition determination by the combination of CO chemisorption and HRSEM reveal a specific orientation for the Cu metal deposition on the core Pd crystallites, probably of Pd–Cu bimetallic islets and free Pd atoms. The main differences between samples with different Cu loadings are attributed to changes in these two metallic phases over the surface of metallic particles and they are reflected in the activity and selectivity of nitrate hydrogenation. The results reveal that TOF Cu , i.e., the number of nitrate ions consumed per second per active surface Cu seems to be independent of surface composition, while TOF Pd was found to increase with surface Cu, indicating the bifunctional nature of the Cu–Pd sites responsible for the nitrate reduction by red–ox reaction. Also, the surface ratio of Pd–Cu sites that catalyze nitrate-to-nitrite hydrogenation, to Pd sites, which catalyze the hydrogenation of nitrite to nitrogen, should be optimal. This might offer novel possibilities for the design of fibrous catalyst showing better performance.

Immobilization of Oligostyrene-Prolinol Conjugates into Polystyrene via Electrospinning and Applications of these Fibers in Catalysis

This paper reports the synthesis of prolinol-oligostytrene conjugates and their immobilization into a polystyrene matrix by using the electrospinning process. Via this approach fibers with a large surface area (fiber diameter of 1.2 µm) containing the prolinol conjugate are readily obtained. The fibers are shown to be catalytically active in a test Michael reaction. The fibrous catalyst system can readily be removed from the reaction mixture and be reused. However, a decrease of the catalyst activity was noticed upon recycling the fibrous catalyst systems.

Preparation of a fibrous catalyst containing palladium nanoparticles and its application in hydrogenation of olefins

AbstractA novel fibrous catalyst containing palladium nanoparticles was produced via electrospinning technique. The fibrous catalyst was characterized by scanning electron microscopy and transmission electron microscopy respectively, the results show that the diameter of fiber was about 200 nm and the palladium (Pd) nanoparticles was in the range of 30–40 nm. The size and shape of Pd particles on the fiber can be adjusted by changing the concentration of polymer or amount of PdCl2 in the electrospun solution. The catalyst was tested in hydrogenation of α‐hexene and α‐octene in ethanol at room temperature. The catalytic experimental results show that the activity of the titled catalyst was 4.7 times higher than that of PdCl2/γ‐Al2O3 and higher than that of PdCl2 on poly(styrene‐divinylbenzene) resin catalyst (Zharmagambetov et al., J Mol Catal A: Chemical, 177, 165 (2001)). POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers

Structural transformations in polyacrylonitrile during modification and fabrication of fibres and films with catalytic properties

A number of problems arise in creating fibrous catalysts with high activity, and the quality and area of the catalyst are dependent on solving these problems. They primarily concern the catalytic activity of the metal and the strength of its attachment to the fibre, the mechanical strength of the fibre itself, and the stability of the catalyst formed. All of these problems are related to selection of the conditions of modification of the initial polymer used as the fibrous support and the technology of attaching the metal to it. Copolymeric polyacrylonitrile (PAN) fibre is the almost irreplaceable initial material for fibrous catalysts [1-5]. This polymer, due to the presence of reactive nitrile groups, allows deliberate structural modification in the course of polymer-analog transformations [3] and thus makes it possible to obtain a polydentate ligand which can be used to coordinate the metal atom during subsequent transformations. Iron-containing fibrous catalysts are relatively universal [1, 5, 6]. The main process questions in formation of active sites of trivalent iron ions on PAN fibre have been solved. However, more detailed studies are required on formation of functional group complexing agents, realized by treating the initial fibre with an aqueous solution of a mixture of hydroxylamine hydrochloride and hydrazine hydrochloride followed by treatment in aqueous solutions of NaOH and FeCl 3 ⋅6H 2 O. The purpose of our studies was to search for parameters for creating a Fe 3+ -containing catalyst which would ensure the optimum (from a practical point of view) activity and stability of the catalyst while preserving acceptable strength of the PAN fibre. We conducted the studies of the structural transformations of polyacrylonitrile during modification on industrially manufactured PAN complex fibre made with the thiocyanate method from the ternary copolymer of acrylonitrile (92.3%), methyl acrylate (6.2%), and itaconic acid (1.5%) and modeled on PAN films. The ratio of the concentrations of hydrazine and hydroxylamine hydrochlorides (0.5-1), modifying solution pH (2-10), holding time (0.25-2 h), and treatment temperature (100-150°C) were varied in preliminary studies. The treatment temperature in the aqueous solution of NaOH was 95-100°C and the duration was 30-120 sec. We note that by varying the conditions of modification, these groups — ligands — can be contained in the constructed polymer support with different statistical weight. The strength of attachment of Fe 3+ and the stability of the catalyst are essentially a function of their ratio [5]. The optimum parameters for modification of PAN fibre that most completely satisfy the above requirements were selected based on the results of these studies. Let us report the basic modification parameters by stages: ratio of the concentrations of hydrazine and hydroxylamine hydrochlorides of 0.715, temperature of 110-130°C, pH = 6, the treatment time is correlated with the temperature by the dependence τ = 1.85⋅10 5 exp(—0.072t), treatment with aqueous solution for 30 sec, holding in 5% aqueous solution of iron chloride for 2 h.

A Cu/Zn/Al/Zr Fibrous Catalyst that is an Improved CO2 Hydrogenation to Methanol Catalyst

A series of Cu/Zn/Al/Zr CO2 hydrogenation to methanol catalysts containing different ratios of Al/Zr were prepared using a co-precipitation procedure. SEM, TEM, and XRD characterization showed that all the catalysts comprised crystallites in a fibrous structure and their Cu/Zn crystallite dispersions were better than that of a commercial (COM) catalyst. It is suggested that the high dispersion and stability of the Cu/Zn crystallites due to the fibrous structure enhanced CO2 hydrogenation, and the added Zr component further improved the catalyst. A 5% Zr addition gave a methanol space time yield 80% higher than that on the COM catalyst.

Novel Fibrous Catalyst in Advanced Oxidation of Photographic Processing Effluents

A novel fibrous catalyst was used to destroy the pollutants in Kodak Non-Silver-Bearing (NSB) photographic processing effluents with high chemical oxygen demand (COD) value. The oxidation activity of the catalyst was evaluated in terms of COD reduction of the effluent. The effects of concentrations of hydrogen peroxide and effluent, amount of catalyst, reaction time and temperature on the COD reduction were studied. In addition, the combination of catalysis with UV treatment on the COD reduction of the effluent was also investigated. Based on the experimental results, room temperature is preferred for the catalytic oxidation of NSB effluent. It was found that COD reduction of the effluent depends on the amount of hydrogen peroxide added to the feed in relation to the mass of catalyst used. Significant COD reduction (up to 52%) is achieved after 4 hours of catalytic treatment. Extending the duration of catalysis up to 24 hours gives further slight decrease in COD value.

Asymmetric C–C bond formation with l-prolinol derived chiral catalysts immobilized on polymer fibers

N-(4-Vinylbenzyl)-α,α-diphenyl- l-prolinol was immobilized on polyethylene fibers by electron beam induced pre-irradiation grafting using styrene as a co-monomer. The resulting polymer supported catalyst P2 was utilized in asymmetric C–C bond forming reactions and its performance compared with those of previously prepared fibrous cross-linked α,α-diphenyl- l-prolinol P1 and homogeneous model compounds. The fibrous catalyst yields similar enantioselectivities in the asymmetric addition of diethylzinc to benzaldehyde as its homogeneous reference reaction and can be recycled with minimal loss of activity. When P2 was used as the catalyst in the addition of phenylacetylene to benzaldehyde, the corresponding propargylic alcohol was obtained with enantiomeric excesses of up to 91%.

Acoustic and visual study of bubble formation processes in bubble columns staged with fibrous catalytic layers

High-speed images of bubbly flow coupled with simultaneous passive acoustic measurements were carried out in a bubble column staged with structured fibrous catalysts. Local observations made with a high-speed camera system allow a detailed understanding of the influence of fabric structure on bubble formation processes and the determination of the Sauter bubble diameter. With acoustic measurements, the building frequency of bubble swarm formation is identified to be a linear function of the superficial gas velocity. Due to bubble size and building frequency of bubble swarm the percentage of simultaneously operative sites (holes at which bubbles were formed simultaneously) is calculated.

Comparative study of TAME synthesis on ion-exchange resin beads and a fibrous ion-exchange catalyst

The reaction rates to tert.-amyl methyl ether (TAME) with the ion-exchange resin bead catalysts (A16, A35 and XE586) and a fibrous catalyst (SMOPEX-101) were measured as a function of temperature (323–353 K) with stoichiometric amount of reagents fed to a continuous stirred tank reactor. When the reaction rates were assessed against the weight or acid capacities of the catalysts, the activity order was A35>A16>SMOPEX-101>XE586. When the rates were calculated versus the square of the acid capacity, the activities of the catalysts were similar. This indicated a dual-site mechanism. The rates of TAME formation and the isomerisation of isoamylenes as a function of temperature (333–353 K) and the feed MeOH/isoamylene molar ratio (0.5–2.0), as well as the decomposition of TAME, were then measured in a batch reactor with the ion-exchange fibre (SMOPEX-101) as catalyst. Kinetic modelling results favoured a single-site mechanism for the isomerisation and a dual-site mechanism for the etherification. The activation energy was determined to be 116.7 kJ mol −1 for the isomerisation of 2M1B to 2M2B, 92.7 kJ mol −1 for the etherification of 2M1B to TAME and 93.0 kJ mol −1 for the etherification of 2M2B to TAME.

Structural and catalytic properties of vanadia-based fibrous catalysts in toluene partial oxidation

Structured vanadia-based catalysts in the form of woven fabrics were successfully synthesised by incipient-wetness impregnation and sol–gel methods. The catalysts were investigated by Raman, X-ray photo-electron spectroscopies as well as high-resolution transmission electron microscopy (HRTEM). The spectroscopic results revealed that the elemental fibres consisted of a silica core covered by vanadia/titania. The modification of fibre silica surface by alumina resulted in a support with an increased dispersion of active vanadia/titania layer. Crystalline anatase was not found to be necessary for the formation of active surface vanadia species. Drying of titania layer without calcination led to a higher vanadia dispersion on titania. Structured fibrous vanadia-based catalysts demonstrated comparable activity and identical selectivity towards the products of toluene partial oxidation (benzaldehyde and benzoic acid) as granulated vanadia/titania with the same vanadium coverage. The transient response technique was applied to elucidate the role of the support on the active species. Thus, the V 2O 5/TiO 2/SiO 2 woven fibre fabrics show promise for hydrocarbon partial oxidation, providing advantages due to its open macro-structure suitable for design of structured catalytic beds.

Investigation of the mechanical and physico-chemical properties of a modified PAN fibrous catalyst

In our previous work a polyacrylonitrile (PAN) fibre was modified by hydrazine and hydroxylamine under alkaline conditions [1] to enable ligation of transition metal cations to the fibre surface so as to produce a novel oxidation catalyst analogous to a heterogeneous Fentons catalyst. The fibre was characterised with regard to its BET surface area, mechanical strength, distribution of cation content and resilience to organic solvents, acids and bases. Whilst modification had reduced the mechanical strength of the PAN fibre by half, strength indices were still sufficient for use as a catalyst in industrial applications. SEM and EDAX studies of cross-sections of the fibre showed that transition metal (Fe 3+) cation distribution was surface only, penetrating 3–4 μm into the fibre. Both fibre integrity and cation content were found to be resilient to organic solvents, acids and bases over pH 2–12. These features together with its ability to decompose H 2O 2 demonstrate that the fibre has enormous potential for use as an oxidation catalyst in the decomposition of a range of industrial effluents and waste waters.

Part 1. Production of a modified PAN fibrous catalyst and its optimisation towards the decomposition of hydrogen peroxide

A novel heterogeneous Fentons catalyst for the destruction of pollutants in waste waters by the decomposition of H 2O 2 was produced by modifying a polyacrylonitrile (PAN) fibre by treatment with a mixture of hydrazine (HD) and hydroxylamine (HA) to introduce chelating functional groups onto the fibre surface. These functional groups are used to ligate the transition metal cations Fe 3+, Co 2+, Ni 2+ and Cu 2+ to the fibre to act as the active catalytic sites for decomposition of the hydrogen peroxide. The hydrazine and hydroxylamine concentrations in the modifying solution, pH and duration of alkaline treatment were optimised with respect to the strength of the metal fixation on the polymer matrix and the rate of decomposition of hydrogen peroxide in aqueous solution. The optimum conditions were found to be [N 2H 4] = 30 g/l, [NH 2OH] = 42 g/l, pH 9.5 followed by a further alkaline treatment of short duration. The fibrous catalyst produced was successfully tested in real textile effluent oxidation from dyeing and finishing processes and showed potential in the area of effluent treatment particularly in advanced oxidation processes for the oxidative decomposition of organic pollutants in industrial effluents and waste waters.

Hydrogenation of Citral Over a Polymer Fibre Catalyst

A polymer-supported Pd catalyst was investigated in hydrogenation of citral (3,7-dimethyl-2,6-octadienal), which is a stereoisomer with an isolated and a conjugated double bond as well as a carbonyl group. The catalyst was a fibrous polymer-supported catalyst modified with functional groups and immobilized metals. A comparison of the polymer-supported catalyst with conventional catalysts was made.

227 触媒バグフィルタの開発(第 1 報) : 繊維状触媒の開発とバグフィルタへの適用

We developed the fibrous catalysts which had high activity in decomposition of organic chlorine compounds and reduction of NO by NH_3. The catalyst fiber composed of V_2O_5 and TiO_2 exhibited favorable structural properties (large specific surface area of more than 200m^2/g and large pore volume of more than 0.20(cm)^3/g) and capability to stabilize V_2O_5 in a well dispersed form up to high loading. A catalytic bag filter was produced by placing a layer of the catalyst fiber within a nonwoven fabric of heat resistant polymer fiber.