Toshishige M. Suzuki

Ion chromatographic separation of rare-Earth elements using a nitrilotriacetate-type chelating resin as the stationary phase.

The chromatographic retention behavior of rare-earth elements (REEs) on a chelating resin having a nitrilotriacetate group (NTA gel) was evaluated. The capacity factors for a series of REEs on the NTA gel were in fairly good agreement (R(2) = 0.978) with the stability constants of the corresponding NTA complexes. The NTA gel was applied to the column stationary phase for the ion chromatographic separation of REE. A favorable separation of a series of REEs was achieved within 15 min using a gradient elution of nitric acid. The separated REE ions were detected using the postcolumn derivatization method with chlorophosphonazo III as a colorization reagent. The present chromatographic system, interfaced with inductively coupled plasma mass spectrometry, was applied for the simultaneous determination of 14 REEs.

Preparation of porous chelating resin containing linear polymer ligand and the adsorption characteristics for harmful metal ions

Abstract A linear copolymer consisting of maleic anhydride and methylvinylether has been immobilized on the interior surface of porous polymer beads. The modified polymer beads thus obtained have formed the starting material for the preparation of metal selective chelating resins by the reaction of the maleic anhydride moiety with appropriate ligands. Cysteamine has been grafted as the pendant ligand and the resulting chelating resin (cysteamine resin) maintains a high porosity and large specific surface area. On the basis of scanning electron microscopy (SEM) and electron dispersion X-ray (EDX) analyses, the linear polymer is distributed from the outer layer to the inner pores of the resin beads. The adsorption characteristics of the cysteamine resin for Cd 2+ and Pb 2+ have been examined with respect to the percentage extraction, adsorption isotherm and reproducibility upon adsorption–regeneration cycles. The chelating resin shows a remarkably high adsorption rate, which has been attributed to the porous nature of the resin and geometrical flexibility of the ligand. Quantitative removal of Cd 2+ and Pb 2+ from aqueous solution has been demonstrated by the column procedure packed with the cysteamine resin.

Hydrogenation of nitrile in supercritical carbon dioxide: a tunable approach to amine selectivity

The use of supercritical carbon dioxide (scCO2) on the hydrogenation of benzonitrile was investigated over Pd and other metal catalysts. Without any additive, benzonitrile was hydrogenated to benzylamine with high conversion (90.2%) and selectivity (90.9%) using the Pd/MCM-41 catalyst. A strong influence of CO2 pressure on the conversion and selectivity were observed. As the CO2 pressure increases, the conversion was increased, and after reaching the maximum at around 8–10 MPa, it decreased. Moreover, simply by tuning the CO2 pressure, it is possible to obtain benzylamine or dibenzylamine. For instance, at lower pressure CO2 acts as a protecting agent, leading to the formation of the primary amine, but at higher pressure, the yield of primary amine as well as the solubility of the imine intermediate in CO2 increases, which results high selectivity for dibenzylamine. A plausible mechanism has been proposed to show the role of CO2 on the selectivity toward primary and secondary amines. The results confirm that the presence of CO2 is mandatory for the formation of benzylamine with high selectivity. Furthermore, the other reaction parameters, such as reaction time, H2 pressure, temperature etc., also affect the conversion as well as selectivity of benzylamine. This process has been extended to the hydrogenation of a series of different nitrile compounds.

Production of linear alkane via hydrogenative ring opening of a furfural-derived compound in supercritical carbon dioxide

A simple method has been described to accomplish the formation of linear alkane with >99% selectivity in supercritical carbon dioxide under very mild conditions using Pd/Al-MCM-41 catalyst. The linear alakne was formed through the hydrogenation and dehydration/hydrogenation of 4-5-(5-(hydroxymethyl)furan-2-yl)but-3-en-2-one, which is an aldol condensation product of 5-hydroxymethyl furfural and acetone.

Preparation and complexation properties of polystyrene resins containing diethylenetriamine derivatives

Abstract Styrene-divinylbenzene copolymer resins containing a series of diethylenetriamine derivatives have been prepared and characterized. The multidentate ligands are covalently bound to the polymer matrix without causing inter- and intrastrand bridging structures. The properties of the present chelating resins have been examined with respect to the uptake of transition metal ions.

An attempt to achieve the direct hydrogenolysis of tetrahydrofurfuryl alcohol in supercritical carbon dioxide

The use of supercritical carbon dioxide (scCO2) in the hydrogenolysis of tetrahydrofurfuryl alcohol was investigated over a Rh supported MCM-41 catalyst (metal loading ≈ 1%). Without any additive, tetrahydrofurfuryl alcohol was converted to 1,5-pentanediol with high conversion (80.2%) and selectivity (91.2%) under mild reaction conditions (temperature = 80 °C and H2 pressure = 4 MPa). The effects of different variables like CO2 and H2 pressure, temperature and the reaction time were also optimized. A strong influence of CO2 pressure on the conversion was observed. The conversion was increased with pressure due to the enhanced solubility of tetrahydrofurfuryl alcohol in CO2 and reached the maximum at 14 MPa, as the single phase (CO2–H2–substrate) was formed, but the selectivity of 1,5-pentanediol remained unaltered. On the other hand, H2 pressure also changed the conversion as well as the selectivity. Temperature was found to play an important role in enhancing the catalytic efficiency; conversion of the substrate was increased along with the temperature, but the selectivity of 1,5-pentanediol dropped after reaching 120 °C. The Rh catalyst exhibited strikingly different product distribution under the solvent-less conditions compared to scCO2. In addition, instead of CO2, when the reaction was carried out in H2O, the conversion and the selectivity of 1,5-pentanediol decreased substantially. However, addition of only 7 MPa of CO2 modified the conversion and the product selectivity. Under similar reaction conditions, hydrogenolysis of THFA over a Pd catalyst provides a maximum of 50% conversion and the product distribution was different in comparison with Rh catalysts.

In situ synthesized Pd nanoparticles supported on B-MCM-41: an efficient catalyst for hydrogenation of nitroaromatics in supercritical carbon dioxide

In situ synthesis of Pd nanoparticles supported on boron (B)-substituted MCM-41 (B-MCM-41) with Si/B ratio varying from 100 to 5 was carried out by hydrothermal method using H3BO3 as B source. The textural properties as well as thermal stability of the resultant material were investigated by XRD, TEM, FTIR and TG-DTA. Highly ordered materials were obtained depending on the Si/B ratio, which also influenced the particle size of Pd as well as dispersion. Pd/B-MCM-41 was a promising catalyst for the hydrogenation of nitrobenzene in supercritical carbon dioxide with exceptionally faster reaction rate [turnover frequency (TOF) = 5.2 × 105 h−1 (144 s−1)] and high yield of aniline (100%). The observed reaction rate was strongly influenced by the Pd particle size related to Si/B ratio and physical properties of CO2 such as pressure- and temperature-dependent solvent power. A comparison of catalytic activity with the Pd supported only on silica material of similar particle size inferred that the presence of even a small amount of B significantly changes the reaction rate from 70 (only Si) to 105 s−1 (Si/B = 100). In addition, TOF of Pd/B-MCM-41 was high when compared with other Pd catalysts supported on Al-MCM-41 and Ga-MCM-41 obtained by a similar method, and follows the order: B (144 s−1) > Ga (31.2 s−1) > Al (10.2 s−1). The remarkable advantage of the present catalytic system involves low metal content (∼1%), easy separation and it is successfully employed for the hydrogenation of substituted nitroaromatics, nitrile and phenol under mild reaction conditions. Furthermore, the catalyst was recyclable up to the 7th recycle without any loss of catalytic activity.

Determination of trace metals in sea-water by inductively coupled plasma mass spectrometry interfaced with an ion chromatographic separation system: effectiveness of nitrilotriacetate chelating resin as the column stationary phase for preconcentration and elimination of matrix effects

Trace metals in sea-water were determined by ion chromatography (IC)–inductively coupled plasma mass spectrometry (ICP-MS). A nitrilotriacetate (NTA)-type chelating resin was applied to the separation and enrichment of the analyte metal ions. Transition metals and rare earth elements except Mn were retained on the NTA resin column whereas alkali and alkaline earth metals were eluted from the column by elution with 0.5 mM nitric acid. The NTA resin can simplify the procedure for matrix elimination and enrichment of analyte metals since mineral acids can be used as eluents. A linear calibration and repeatability of the signal intensity of ICP-MS were obtained in the determination of trace metals at the <1 µg l–1 level. This method was applied to the analysis of the Open Ocean Sea-Water Reference Material NASS-4. The analytical values (for Co, Ni, Cu, Zn, No, Cd, Sb, Pb and U) were in good agreement with the certified values. By using ammonium acetate buffer solution (pH 5.28) in the preconcentration step, Mn was also retained quantitatively on NTA resin, and the analytical values of the metals (Mn, Co, Ni, Cu, Zn, No, Cd, Sb, Pb and U) contained in NASS-4 were in good agreement with the certified values.

Dynamic control of gold nanoparticle morphology in a microchannel flow reactor by glucose reduction in aqueous sodium hydroxide solution.

Continuous flow synthesis of gold nanoparticles was demonstrated using a microchannel reactor with glucose reduction in aqueous alkaline medium. Particle size, morphology, and visual/optical properties of the dispersion liquid were controlled dynamically by tuning of the rate of NaOH addition. Characteristic star-like nanoparticles formed spontaneously as a quasi-stable state, but they changed the morphology to round shape and showed spectral change over time.

Simple and rapid hydrogenation of p-nitrophenol with aqueous formic acid in catalytic flow reactors

Summary The inner surface of a metallic tube (i.d. 0.5 mm) was coated with a palladium (Pd)-based thin metallic layer by flow electroless plating. Simultaneous plating of Pd and silver (Ag) from their electroless-plating solution produced a mixed distributed bimetallic layer. Preferential acid leaching of Ag from the Pd–Ag layer produced a porous Pd surface. Hydrogenation of p-nitrophenol was examined in the presence of formic acid simply by passing the reaction solution through the catalytic tubular reactors. p-Aminophenol was the sole product of hydrogenation. No side reaction occurred. Reaction conversion with respect to p-nitrophenol was dependent on the catalyst layer type, the temperature, pH, amount of formic acid, and the residence time. A porous and oxidized Pd (PdO) surface gave the best reaction conversion among the catalytic reactors examined. p-Nitrophenol was converted quantitatively to p-aminophenol within 15 s of residence time in the porous PdO reactor at 40 °C. Evolution of carbon dioxide (CO2) was observed during the reaction, although hydrogen (H2) was not found in the gas phase. Dehydrogenation of formic acid did not occur to any practical degree in the absence of p-nitrophenol. Consequently, the nitro group was reduced via hydrogen transfer from formic acid to p-nitrophenol and not by hydrogen generated by dehydrogenation of formic acid.