PD Source Research Articles

Regional distribution and sources of Au, Pd and Pt in moss and O-,B- and C-horizon podzol samples in the European Arctic

A cost-effective analytical method for analysing various terrestrial sample materials for noble metals at detection limits in the sub-ppb range has been developed. The method has been used to analyse c. 600 samples of moss, O-, B- and C-horizon samples collected from a large area (188,000 km 2 ) in the European Arctic at a sample density of 1 site/300 km 2 . For the first time reliable analytical data for Au, Pd and Pt for a large, statistically representative number of samples from four different sample materials can be reported. The regional distribution of Au, Pd and Pt in moss and O-horizon samples provides clear evidence that the Russian nickel industry on the Kola Peninsula is emitting Au and platinum group elements (PGEs). However, maps and profiles for moss and the O-horizon also demonstrate that the emissions of one of the very few and largest Pd emission sources on earth cannot be traced further than 200 km on the ground before reaching background values. The predominant natural geochemical characteristics of the study area are visible in the maps of the B- and C-horizon samples even when using such low-density sampling. Furthermore, the data allow estimation of realistic ‘background values’ for these three elements in the four sample materials. By collecting four interrelated sample materials from a large area it is possible to detect unusual processes leading to the enrichment of certain elements in specific compartments of the ecosystem. Most dramatic is a greater than four-fold higher Pt concentration in the B-horizon of arctic podzols compared to all other media. Platinum concentrations are also slightly higher in the O-horizon than in the C-horizon. Palladium shows a tendency to organic binding. Moss is actively enriching Pd and shows even higher Pd concentrations than in the O-horizon. The highest Au values can be found in the deepest soil layers (C-horizon). Natural, geogenic sources influence Au concentrations measured in moss and the O-horizon as much as industrial emissions.

Monitoring of the exposure to platinum-group elements for two Italian population groups through urine analysis

It is well recognized that automobile catalytic converters are the main source of Pd, Pt and Rh (also called platinum-group elements (PGEs)) in an urban atmosphere. Over recent years, urinary biomonitoring of PGEs has gained considerable importance in assessing the individual human exposure to these elements. This paper reports the concentration ranges of PGEs in the urine of 257 Italian subjects, aged between 23 and 88 years. Subjects were selected on the basis of standardized criteria in two different Italian cities, so as to represent a small urban area surrounded by an essentially rural environment and characterized by low automobile-traffic density (Foligno) and a large urban area with almost constant high-traffic conditions (Rome). The determination of PGEs was performed by sector field inductively coupled plasma-mass spectrometry (SF-ICP-MS) after 1:4 (v/v) dilution of the samples. The 5th and 95th percentiles for PGEs in urine of subjects living in Foligno were the following (in ng l −1): Pd 1.99–17.2, Pt 0.24–3.08 and Rh 0.53–14.8. The 5th and 95th percentiles in the urine of subjects from the area of Rome were (in ng l −1): Pd 0.71–17.0, Pt 0.49–8.13 and Rh 4.10–38.6. Platinum and Rh median concentration values showed large and significant differences ( P<0.0001) between the two urban settings considered (0.52 and 3.50 ng l −1 for Pt and Rh in Foligno, respectively, and 1.70 and 12.85 ng l −1 for Pt and Rh in Rome, respectively). On the other hand, no striking differences were found in the Pd concentration (median value of 6.02 ng l −1 in Foligno versus 7.79 ng l −1 in Rome). The sex variable correlates only with Pd concentration ( P=0.05), pointing out that in males concentrations are higher than in females.

Efficient Route to 1,3‐Di‐N‐imidazolylbenzene. A Comparison of Monodentate vs Bidentate Carbenes in Pd‐Catalyzed Cross Coupling.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Catalytic Activity of Pd(II) and Pd(II)/DAB‐R Systems for the Heck Arylation of Olefins.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Geochemistry of the late Permian No. 30 coal seam, Zhijin Coalfield of Southwest China: influence of a siliceous low-temperature hydrothermal fluid

This paper describes the influence of siliceous low-temperature hydrothermal fluid on the elemental concentrations and mineralogical characteristics of the late Permian anthracitic ( R o,max=3.58%) coal seam (No. 30) from the Zhijin Coalfield in western Guizhou Province, SW China. Coal samples were examined using instrumental neutron activation analysis, inductively coupled plasma-mass spectroscopy, inductively coupled plasma-atomic emission spectrometry, X-ray fluorescence, powder X-ray diffraction, scanning electron microscopy equipped with energy-dispersive X-ray, and isotope analysis. The modes of occurrence of elements were determined using a sequential chemical extraction procedure. The studies indicate that the No. 30 coal seam has a very high content of veined quartz (vol. 9.4%), whose isotope values of δ 30Si and δ 18O are 0.6‰ and 15.4‰, respectively, indicating that the quartz originated from siliceous low-temperature hydrothermal fluid (formation temperature 160–220 °C) rather than detrital material of terrigenous origin or magmatic hydrothermal inputs. Results of scanning electron microscopy equipped with energy-dispersive X-ray and sequential chemical extraction procedure show that the veined quartz is the dominant source of Fe, Cu, U, Pd, Pt and Ir, which are as high as 2.31%, 356, 8, 2.1, 2.43, and 0.006 μg/g in this coal seam, respectively. The studies have also found that elements, such as Fe and Cu are mainly in the veined quartz and they do not occur as sulfides in this coal seam, in sharp contrast to many other coal seams in China. The geochemical and mineralogical anomalies of the coal are attributed to the siliceous low-temperature hydrothermal fluid.

RZnI vs. R2Zn in Pd(0)-catalyzed cross-coupling reactions with thioimidates

Thioimidates 1-Z undergo facile cross-coupling with Pd(0)–RZnI but are inert to Pd(0)–R2Zn. This difference is due to the lower Lewis acidity of R2Zn, as opposed to lower nucleophilicity. Various sources of RZnI (R = Me, Et) and Pd(0) were evaluated for their convenience and reactivity.Key words: thioimidates, cross-coupling, dialkylzincs, alkylzinc iodides.

A quasi patriarch in the state of Epirus: The autocephalous archbishop of "Boulgaria" (Ohrid) Demetrios Chomatenos

The paper sketches the life and work of the archbishop of the autocephalous Byzantine archbishopric of Boulgaria/CAmd, Demetrios Chomatenos (fungit 1216-1236). His main work, the corpus of records Ponemata diaphora (=PD), appeared in 2002 in a critical edition in Vol. 38 of the CFHB. The PD prove to be a first quality historical source, also for the history of Serbia. This present paper is thus based on numerous new findings from the analysis of the PD and other relevant sources. In particular, it deals with the quasi-patriarchal self-understanding and work of Chomatenos, who was an excellent canonist and nomotriboumenos (legal expert): The increased rivalry between Nicaea and Epirus in the years 1215-1230 enabled him to act like a patriarch in the area controlled by the rulers of Epirus. In so far as he reached beyond the boundaries of his archbishopric in this connection, as a rule he acted with the consent of further metropolitans and bishops in the state of Epirus who ? unlike him ? were formally subject to the patriarch. This also applies for the coronation of Emperor Theodores Doukas which he carried out in 1227.

Efficient Route to 1,3-Di-N-imidazolylbenzene. A Comparison of Monodentate vs Bidentate Carbenes in Pd-Catalyzed Cross Coupling

A new bis(carbene) ligand architecture has been developed and was evaluated in the Suzuki-Miyaura cross-coupling reaction of various aryl halides with phenylboronic acid. Several new bis(carbene) ligands were tested in different carbene:Pd ratios. Pd(OAc)(2) and Pd(2)(dba)(3) were compared for efficiency as a Pd source. It was found that the Pd(OAc)(2)/bis(carbene) system formed a catalyst for the activation of chlorobenzene. [reaction: see text]

Platinum, palladium and rhodium content in road dust, tunnel dust and common grass in Bialystok area (Poland): a pilot study

Automobile traffic is the main source of Pt, Pd and Rh, i.e. platinum-group elements (PGEs), contamination in urban areas and there is growing concern about the effects of these emerging contaminants for people living in these areas. PGE contents were determined in samples of road dust, tunnel dust and common grass as well as pine needles collected from the residential areas of Białystok, northeast Poland. High resolution (HR) and quadrupole inductively coupled plasma mass spectrometry (ICP-MS) were compared for their adequacy in the environmental analysis of Pt and Rh. Palladium was determined by total X-ray fluorescence (TXRF) and HR-ICP-MS after matrix separation by reductive co-precipitation with Hg. The highest PGEs concentration was found in road dust samples. Platinum content in road dust varied from 34.2 to 110.9 ng g−1, while that of Rh from 6.0 to 19.7 ng g−1. The mean concentration of Pd in this matrix was 32.8 ng g−1 as determined by TXRF analysis and 42.2 ng g−1 by HR-ICP-MS. The highest Pt concentration in tunnel dust was found in the size fraction below 75 μm (22.3–23.3 ng g−1). The mean concentrations of PGEs in grass were 8.63 ng g−1 for Pt, 0.65 ng g−1 for Rh and 3.2 ng g−1 for Pd. The concentration of PGEs in pine needles was below the limits of detection of the methods used.

Platinum, palladium and rhodium content in road dust, tunnel dust and common grass in Białystok area (Poland): a pilot study

Automobile traffic is the main source of Pt, Pd and Rh, i.e. platinum-group elements (PGEs), contamination in urban areas and there is growing concern about the effects of these emerging contaminants for people living in these areas. PGE contents were determined in samples of road dust, tunnel dust and common grass as well as pine needles collected from the residential areas of Białystok, northeast Poland. High resolution (HR) and quadrupole inductively coupled plasma mass spectrometry (ICP-MS) were compared for their adequacy in the environmental analysis of Pt and Rh. Palladium was determined by total X-ray fluorescence (TXRF) and HR-ICP-MS after matrix separation by reductive co-precipitation with Hg. The highest PGEs concentration was found in road dust samples. Platinum content in road dust varied from 34.2 to 110.9 ng g −1, while that of Rh from 6.0 to 19.7 ng g −1. The mean concentration of Pd in this matrix was 32.8 ng g −1 as determined by TXRF analysis and 42.2 ng g −1 by HR-ICP-MS. The highest Pt concentration in tunnel dust was found in the size fraction below 75 μm (22.3–23.3 ng g −1). The mean concentrations of PGEs in grass were 8.63 ng g −1 for Pt, 0.65 ng g −1 for Rh and 3.2 ng g −1 for Pd. The concentration of PGEs in pine needles was below the limits of detection of the methods used.

Catalytic activity of Pd(II) and Pd(II)/DAB-R systems for the Heck arylation of olefins

Palladium-catalyzed reactions of aryl bromides with various olefins involving Pd(II)/diazabutadiene (DAB-R) systems have been investigated. The scope of a coupling process using Pd(II) sources and an α-diimine as ligand in the presence of Cs 2CO 3 as base was tested using various substrates. The Pd(OAc) 2/DAB-Cy ( 1, DAB-Cy=1,4-dicyclohexyl-diazabutadiene) system presents the highest activity with respect to electron-neutral and electron-deficient aryl bromides in coupling with electron rich olefins. The synthesis and X-ray characterization of a Pd(II)-diazabutadiene ligand is reported. Extensive optimization experiments showed that another Pd(II) source, Pd(acac) 2 (acac=acetylacetonate), proved to activate aryl bromides at high temperatures, low catalyst loadings when the appropriate concentration of n Bu 4NBr additive was employed. The effect of the DAB-Cy ligand is important at very low catalyst loadings and high temperatures. Pd(acac) 2 and Pd(acac) 2/DAB-Cy precatalysts were very effective for the arylation of various olefins with aryl bromides with respect to reaction rate, catalyst loadings, and functional group tolerance.

About the significance of pd measurements in liquids

This paper presents investigations concerning the variations and significance of PD measurements in mineral oil, when detectors with different frequency response are used. Typical durations of discharge phenomena in liquids are much longer than in other media, and the measurement technique must be adapted accordingly. However, depending on the application concerned, this is not always possible. In this study, experiments and calculations are carried out to determine typical errors produced when classical RLC measurement impedances with various frequency responses are used to measure PD's in liquids. Experiments are done with corona and creeping discharges in mineral oil, and compared with corona and spark discharges in air. These examples allow us to conclude that when a calibrated high frequency PD measurement system is used, the ratio of measured to actual charge is much lower for discharges in liquids than in gases. If measurements are carried out on a practical device that may include various types of PD sources, the high frequency measurement system will strongly underestimate discharges in liquids compared to other discharge types. This discrepancy versus discharge type increases when the frequency response of the measurement system is increased.

Unconventional Deposite of Pt and Pd: A Review with Implications for Exploration

ABSTRACT In this paper we review potential “unconventional” (i.e., amagmatic) sources of Pt and Pd. We list several geological environments in which Pt and Pd have been concentrated to economic grades (if not tonnages). One is intracratonic rifts where hot oxidized brines are generated by surface evaporation and/or halite dissolution and circulate to depth through a preponderance of oxidized lithologies. Pt and Pd occur with U or Cu and with minor Au. Second is deformed passive margin sequences rich in carbonaceous metasedimentary rocks where Pt and Pd occur with Au or Ni and Mo. Hydrothermal fluids in this environment are most likely to be relatively reduced and obtain sulfur for transport of PGE as bisulfıde complexes from the pyritic and carbonaceous host rocks. Third are surface environments where oxidized low-salinity waters, buffered by atmospheric oxygen, interact with Pt- and Pd-enriched source rocks such as ophiolitic ultramafıc rocks. In the known deposits, Pt and Pd are potential byproducts to Au, Cu, Ni, Mo, or U. A low-risk exploration strategy is to recognize potential for Pt and Pd enrichment in similar deposits. A high-risk exploration strategy acknowledges the possibility that Pt and Pd may be offset, or even remote from the other metal concentrations and may be a primary exploration target. Reactive transport modeling is suggested as a predictive exploration tool.

Suzuki—Miyaura Cross‐Coupling Reactions Mediated by Palladium/Imidazolium Salt Systems.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Transfer function-based partial discharge localization in power transformers: a feasibility study

Statistical studies have shown that failures of bushings, winding insulation, and online tap changers are the main causes for long-duration outages of transformers. This article investigates the development of an instrument for supervising the conditions of transformer units. The use of sectional winding transfer functions (SWTFs) for online PD evaluation in power transformers has several advantages: localization of PD sources, discrimination between PDs inside or outside of the transformer, and evaluation of actual PD amplitudes along the winding. Direct measurement of SWTFs-when different points along the coil are accessible-and use of these SWTFs for PD evaluation and localization has shown excellent results. In order to use this method at transformers on site, an appropriate modeling method is needed for the computation of the SWTFs using only measurements at the transformer terminals. A detailed modeling approach based on discrete RLC circuit elements has been studied and different algorithms used for parameter estimation and optimization. This model is applicable in practical cases for a limited frequency range if genetic algorithms (GAs) are used for parameter optimization. A new method based on traveling wave theory has been investigated using genetic algorithms to search for the optimum parameters of a partial differential equation that describes the transient behavior of the coil. This method has shown potential in solving SWTF calculation problems for different transformers.

1,2-Oxopalladation versus pi-allyl palladium route. A regioconvergent approach to a key intermediate for cyclopentanoids synthesis. New insights into the Pd(II)-catalyzed lactonization reaction.

Regioconvergent synthesis of the key lactone 1 from an equimolar mixture of the two olefins 4 and 5 was achieved by unique Pd(II) chemistry. The synthetic versatility of lactone 1 has been demonstrated in the synthesis of iridoids and of the endo-Corey lactone 2, which is a key intermediate for the F(2)-isoprostane synthesis. Upon exposure of the sodium salts of 4 and 5 to a catalytic amount of Pd(OAc)(2) under oxygen, in the presence of AcOH, an isomeric lactone 12 was obtained in addition to the title compound 1. The Pd(II) lactonization was optimized by fine-tuning all the factors participating in the catalytic cycle: solvent, oxidant, co-oxidant, and Pd(II) source. The Hosokawa's heterobimetallic couple emerged as the catalyst of choice. With a Cu(II)-Pd(II) couple, the redox process was transferred to copper, and the formal oxidation state of palladium remained constant during the reaction. By virtue of this new methodology, lactone 1 was obtained in a rewarding 60% yield, along with isomeric lactone 12 in 30% yield. A detailed mechanistic study was carried out in order to elucidate the formation of lactones 1 and 12. Lactone 1 was formed from either olefin 8 or olefin 10; on the other hand, lactone 12 was formed exclusively from olefin 10. An intramolecular 1,2-acyloxypalladiation was invoked for the transformation of 8 into 1, whereas the pi-allyl complexes 13 and 11 were involved in the transformation of olefin 10 into 12 and 1, respectively.

Suzuki−Miyaura Cross-Coupling Reactions Mediated by Palladium/Imidazolium Salt Systems

Nucleophilic N-heterocyclic carbenes (NHC) have been used as ancillary ligands in palladium-mediated Suzuki−Miyaura cross-coupling reactions involving aryl chlorides or aryl triflates with arylboronic acids. The scope of the coupling process using Pd(0) or Pd(II) sources and an imidazolium salt in the presence of a base, Cs2CO3, was tested using various substrates. The Pd(OAc)2 or Pd2(dba)3/IMes·HCl (2, IMes = 1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene) system presents very high activity with respect to electron-neutral and electron-rich aryl chlorides. The ligand IPr·HCl (3, IPr = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene) is also effective for the Suzuki−Miyaura cross-coupling involving a wide spectrum of aryl chlorides and aryl triflates. The general protocol developed has been applied successfully to the synthesis of an antiinflammatory drug (Fenbufen) and to a key intermediate in the synthesis of sartans. Mechanistically, palladium-to-ligand ratio studies support an active palladium spec...

PD pattern recognition for stator bar models with six kinds of characteristic vectors using BP network

The application of six different kinds of characteristic vectors to recognize PD sources is studied. Four kinds of model bars are used to simulate typical partial discharges in generator stator winding. The PD signals were measured by using a computer aided digital sampling system. The sampling results are processed by six kinds of feature extraction methods and different characteristic vectors are obtained. Then these vectors are used as input patterns for BP network. Recognition results using all six kinds of vectors are reasonable. Further analysis shows that vectors formed by moment features or fractal dimensions possess fairly good abilities of pattern identification and data compression.

Palladium fluoride complexes: one more step toward metal-mediated C-F bond formation.

The first molecular complexes of palladium containing a Pd-F bond, both fluorides and bifluorides, were synthesized and fully characterized in the solid state and in solution. Reactivity studies of the Pd fluoride complexes revealed their unexpected stability and unusual chemical properties, different from the hydroxo, chloro, bromo, and iodo analogues. A novel efficient method to generate "naked fluoride" was developed using [(Ph(3)P)(2)Pd(F)Ph]. The naked fluoride from the Pd source fluorinated dichloromethane, deprotonated chloroform, and catalyzed di- and trimerization of hexafluoropropene under uncommonly mild conditions.

Amination reactions of aryl halides with nitrogen-containing reagents mediated by palladium/imidazolium salt systems.

Nucleophilic N-heterocyclic carbenes have been conveniently used as catalyst modifiers in amination reactions involving aryl chlorides, aryl bromides, and aryl iodides with various nitrogen-containing substrates. The scope of a coupling process using a Pd(0) or Pd(II) source and an imidazolium salt in the presence of a base, KO(t)Bu or NaOH, was tested using various substrates. The Pd(2)(dba)(3)/IPr.HCl (1, IPr = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene) system presents the highest activity with respect to electron-neutral and electron-rich aryl chlorides. The ligand is also effective for the synthesis of benzophenone imines, which can be easily converted to the corresponding primary amines by acid hydrolysis. Less reactive indoles were converted to N-aryl-substituted indoles using as supporting ligand the more donating SIPr.HCl (5, SIPr = 1,3-bis(2,6-diisopropylphenyl)-4,5-dihydroimidazol-2-ylidene). The Pd(OAc)(2)/SIPr.HCl/NaOH system is efficient for the N-arylation of diverse indoles with aryl bromides. The general protocol developed has been applied successfully to the synthesis of a key intermediate in the synthesis of an important new antibiotic. Mechanistically, palladium-to-ligand ratio studies strongly support an active species bearing one nucleophilic carbene ligand.