Search

Rh performance may not correlate with Rh particle size in automotive catalysts. Therefore, we studied the relation between Rh surface state and catalyst light-off performance by XPS analysis to find the cause. As a result, we found that there were metal Rh state, oxidized Rh state and highly oxidized Rh state in Rh surface state. In addition, we found that more metal Rh particles were produced by reduction treatment when the catalysts had both more oxidized Rh particles and less highly oxidized Rh particles. Furthermore, we found that Rh performance correlated with proportion of metal Rh particles. [ABSTRACT FROM AUTHOR]

Chloride is one of the effective medium in which platinum group metals (PGMs) can be brought into a solution, thus chlorocomplexes are particularly important in the process chemistry of PGMs separations. Rh (III) chlorocomplexes are poorly extracted into organic solvents, which is due to the charge of the complex as well as those inert character in a solution, that is, formation of RhCl6-n(H2O)n(3-n) - (n=1-6) . The problem of solvent extraction of Rh from chloride solutions has not yet been solved and there is no effective industrial extractant for Rh. PGMs are traditionally separated from one another and the other metals by a complex series of selective precipitation techniques. These are generally inefficient in terms of the degree of separation achieved. Solvent extraction applied to refining process for PGMs offers several advantages over the traditional precipitation methods. Adding Sn (II) to a Rh (III) feed is a good procedure which can be used to make Rh react more easily to extraction, however, stripping of Rh from the loaded organic pahse is very difficult. In the present study, the extraction of Rh from hydrochloric acid solutions with tri-n-octylamine (TOA) and tri-octyl methyl ammonium chloride (TOMAC) were tested to clarify the effect of addition of Sn (II) on the extraction of Rh and stripping of Rh.

Supramolecular chemistry is concerned with interactions between molecules, how they can recognize each other, assemble and function on a molecular scale. It provides a bottom up approach to nanoscale systems with applications ranging from biology to materials science. Merging of nanoparticles or nanotechnology, in a wide sense, with self-assembled systems such as liquid crystal displays (LCDs), may attract the attention of researchers who are interested in inaugurating new combinations of different fields. This study aims to synthesize supramolecule-stabilized rhodium nanoparticles and using them to develop novel display materials. Crown ether-stabilized rhodium nanoparticles and calixarene-stabilized rhodium (CA-Rh) nanoparticles have an average diameter of a single nanometer. The power consumption of this TN-LCDs in the presence of CA-Rh rhodium nanoparticles was low. The contrast ratio in the presence of CA-Rh nanoparticles is much better than that in the absence. [ABSTRACT FROM AUTHOR]

The measurement methods of contrast to noise ratio (CNR) and signal difference to noise ratio (SDNR) in digital mammography are different among several quality assurance (QA) guidelines, that is, the type of pixel value (PV), phantom shape, location of aluminum plate, and the size of region of interest (ROI) principally differ in data acquisition. We compared CNR (SDNR) obtained from three QA guidelines. They are the European Reference Organisation for Quality Assured Breast Screening and Diagnostic Services (EUREF), the International Electrotechnical Commission (IEC), and the International Atomic Energy Agency (IAEA). In EUREF and IEC, CNR was calculated using linearized pixel value (LPV). In IAEA, because the type of pixel value to use in SDNR was not specified, SDNR was calculated using PV and LPV, and CNR was calculated using LPV. Target/filter combinations are molybdenum/molybdenum (Mo/Mo) and molybdenum/rhodium (Mo/Rh). Applied various tube voltages are 25, 30, and 35 kV, and various phantom thicknesses are 20, 45, and 70 mm of polymethyl methacrylate (PMMA). The PV-SDNR of IAEA showed the largest value among the three methods, following LPV-CNR of IEC, LPV-CNR of EUREF at 20 mm PMMA thickness. In IAEA, SDNR changed by the kind of pixel value (PV or LPV). When CNR is calculated, every researcher should describe the type of guidelines, the kind of pixel value, and formula for calculation.

This review describes new syntheses of organofluorine compounds taking advantage of the special properties of fluorine compounds as synthones. The main reactions presented are as follows: 1) Trifluoromethylation of aryl or alkyl halides. Application of this reaction for the synthesis of fluorine analogues of nucleic acid bases is discussed. 2) Some syntheses of trifluoromethyl compounds using the Diels-Alder or the 1,3-dipolar reaction, trifluoromethylated carbene, and photoreaction. 3) The Friedel-Crafts reaction of 3,3,3-trifluoropropene, where linear alkylation occurs due to electronic effect of the trifluoromethyl group in good contrast with the Friedel-Crafts reaction of propene. 4) The ene reaction of trifluoromethylated carbonyl compounds, which work as good enophiles. Application of this reaction to the synthesis of trifluoro analogues of terpenes is discussed. 5) The ene reaction of trifluoromethylated imines. 6) Reaction of halothane, which has a highly acidic hydrogen and two halogens adjacent to the trifluoromethyl group and shows interesting reactivities with various bases and metals to give products with unexpected structures. 7) Reaction of 2-bromo-2,2-difluoroacetate with Cu, where the cross-coupling reaction, Michael-type reaction, and radical reaction for different types of difluoroacetates are presented. 8) Reaction of 2-bromo-2,2-difluoroacetate in the presence of Rh catalyst. This reaction provided a new methodology for the introduction of fluoroalkyl substituents to the alpha-position of alpha,beta-unsaturated ketones. The Rh catalyst solved some difficulties in the introduction of difluoroacetate to carbonyl compounds (Reformatsky reaction). Application of this reaction to imines provided easy access to beta,beta-difluoro-beta-lactams.

Novel fluoroalkylated products where a CF(2)COOEt group was introduced at the alpha-position of alpha,beta-unsaturated ketones or the Reformatsky-type products have been obtained selectively by the reaction of BrCF(2)COOEt and alpha,beta-unsaturated ketones with Et(2)Zn in the presence of RhCl(PPh(3))(3) depending on the solvents. Furthermore, the novel alpha-fluoroalkylated products could synthesize by using various halofluoroalkyl compounds (R(f)-X) instead of BrCF(2)COOEt. On the other hand, this Reformatsky-type reaction by imines gave difluoro-beta-lactams or 3-amino-2,2-difluorocalboxylic esters without or with MgSO(4) . 7H(2)O, selectively.