Order Of Pd Research Articles

Tumor response heterogeneity, a powerful independent predictor of treatment outcome in advanced lung adenocarcinoma.

e21146 Background: Tumor response heterogeneity (TRH) to treatment is common across different foci within the same cancer patient. However, the effect of heterogeneity on clinical outcome remains unclear. Here, we developed a quantitative assessment of TRH and explored the correlation of TRH with the clinical outcome. Methods: In this retrospective study, the main eligibility criteria were: patients with advanced lung adenocarcinoma, 3-10 measured foci, ECOG 0-1 and received first-line chemotherapy or targeted therapy. Percent change of the longest diameter in each measurable lesion were quantified with RECIST1.1. TRH score was the absolute value of the dispersion coefficient of the percentage value of each target lesion. Patients were randomly divided into a learning and a validation set. The optimal cutoff value of TRH score was identified according to progression free survival information in the discovery cohort. Then, we confirmed and analyzed the correlation of TRH scores with clinicopathological features in the validation cohort. The Next-generation sequencing was performed for mechanism exploration. Results: Between January 2016 and December 2020, 174 patients were enrolled, 101 (58.0%) treated with platinum-based doublet chemotherapy and 73 (42.0%) with targeted therapy. Median follow-up was 19.8 months (95% CI, 14.5 to 25.0). In the discovery cohort (n = 85), 0.46 was defined as the optimal cut-off point of TRH score. Patients with high TRH score had poor PFS (median PFS 4.5 months vs. 15.8 months, HR 4.43; 95% CI 2.14 to 9.16; P < 0.001) compared to those with low TRH score. In validation cohort (n = 89), high TRH score was confirmed to be associated with significantly shorter PFS (median PFS 5.1 months vs. 12.9 months, HR 2.69; 95% CI 1.59 to 4.55; P < 0.001). The median value of TRH score followed the order of PD, SD and PR ( P < 0.001). Patients with high TRH score had poor ORR (30.0% vs. 68.0%; Fisher's exact test, P < 0.001) compared with those with low TRH score. In all population, high TRH score was further confirmed as an independent biomarker for PFS by univariate and multivariate analysis. Moreover, TRH score were able to further distinguish the outcomes in PR and SD subgroup. In PR, high TRH score was associated with significantly shorter PFS in PR subgroup (HR 2.79; 95% CI 1.24 to 6.29; P < 0.001) and SD subgroup (HR 2.55; 95% CI 1.44 to 4.49; P = 0.002), respectively. Compared with low TRH score, high TRH score was associated with higher tumor mutation burden and high frequency variation of cell cycle signal pathway. Conclusions: TRH score, a novel parameter for evaluating tumor response heterogeneity, was a powerful independent predictor of outcome in advanced lung adenocarcinoma. The TRHscore further stratifies patients with the same RECIST assessment results and is a useful addition to the RECIST assessment system. Further prospective studies are warranted.

Ni/Cu/Ag promoted Pd/Al2O3 catalysts prepared by electroless co-deposition for enhanced butane dehydrogenation

In this study, performance of Ni, Cu and Ag promoted palladium catalysts supported on alumina was investigated for butane dehydrogenation. The activity, selectivity, yield and stability were studied in temperature range of 100–600 °C under atmospheric pressure. The catalysts were prepared by modified electroless co-deposition of metals on alumina support. The co-deposition of 10 mol% promoters along with palladium, increased activity, selectivity and yield of butene, depending on the nature of promoter. The addition of copper increased the activity more significantly while, silver increased the selectivity. Addition of nickel proved to be least effective in improving performance of supported palladium catalyst. At 550 °C, the conversion order was Pd–Cu/Al (34.4%) > Pd–Ag/Al (25.6%) > Pd–Ni/Al (21.4%) > Pd/Al (17.9%) and the total butene selectivity order was Pd–Ag/Al (91.9%) > Pd/Al (90.5%) > Pd–Cu/Al (85%) > Pd–Ni/Al (61.5%). The overall yield of butene was highest for Pd–Cu/Al, in the order of Pd–Cu/Al (29%) > Pd–Ag/Al (23%) > Pd/Al (16%) > Pd–Ni/Al (13%) at 550 °C. Further, increase in copper content increased the yield of butene and highest yield of 32% was observed for Pd–Cu20/Al with 20 mol% copper. The palladium metal was in strong interaction with the promoter metals, forming alloys. Higher activity of these alloys enhanced performance of the promoted catalysts. The stability of the catalysts was also enhanced by addition of promoters. The stability order was Pd–Ag/Al (30%) > Pd–Cu/Al (50%) > Pd–Ni/Al (61%) > Pd/Al (76%) over 10 h on stream study. The silver promoted catalyst showed the lowest deactivation of 30%.

Extraction behaviors of platinum group metals in simulated high-level liquid waste by a hydrophobic ionic liquid bearing an amino moiety

A hydrophobic ionic liquid including an amino moiety ([DiOcAPmim][NTf2]) was synthesized. Its extraction behaviors towards Pd(II), Ru(III), Rh(III) were investigated in nitric acid aqueous solution as a function of contact time, effect of concentration of nitric acid, effect of temperature, and effect of co-existing metal ions. The extraction kinetics of Pd(II) was fairly fast and extraction equilibrium can be attained within only 5 min under the [HNO3] = 2.05 M. When [HNO3]< 1 M, the extraction percentage of Pd(II), Ru(III), Rh(III) were all above 80%. When [HNO3] reached 2 M, all of the extraction percentage decreased and in an order of Pd(II)>Ru(III)>Rh(III). When [HNO3]> 2 M, the extraction performance gradually recovered. The effect of temperature can slightly affect the extraction performance of Pd(II). Furthermore, in simulated high-level liquid waste, [DiOcAPmim][NTf2] showed a better preference towards Pd(II) under the interference of various other co-existing metal ions.

Catalytic dehydrogenation study of dodecahydro-N-ethylcarbazole by noble metal supported on reduced graphene oxide

Through systematical experiments, a comparative study was conducted concerning several graphene-supported noble metal catalysts for dehydrogenation of dodecahydro-N-ethylcarbazole (12H-NEC). It was found that the catalytic activity of the prepared graphene-supported noble metal catalysts was following the order of Pd > Pt > Rh > Ru > Au for the dehydrogenation process. Pd supported on reduced graphene oxide (rGO) prepared by one-pot in situ synthesis has much more excellent catalytic performance than other kinds of catalysts investigated for comparison, simultaneously the using amount of noble metals can obviously be decreased. To be specific, at 453 K, the final dehydrogenation product catalyzed by the novel catalyst of Pd/rGO is N-ethylcarbazole (NEC) and the process selectivity was increased from 44.77% (commercial Pd/Al2O3) to 97.65%, as well as the dehydrogenation ratio reached 99.14%. In addition, the novel catalyst is also superior to other reported catalysts in terms of dehydrogenation performance of 12H-NEC. Its dehydrogenation activity at 443 and 433 K of Pd/rGO was tested and the catalytic performance keeps stable at the two temperatures. Based on the experimental data, kinetic calculation was carried out and some fundamental parameters regarding reaction kinetics was obtained.

Biorecovery of Palladium from Simulated Wastewaters and Its Catalytic Property for Methylene Blue

By using Enterococcus faecalis Z5 strain (CCTCC M2012445) as a microbial resource, this study explored the possibility of recovering palladium (Pd) in the form of nanoparticles by adding an electron donor; investigated the Pd biorecovery efficiency of three kinds of simulated wastewaters including industrial waste processing leachates (IW) , printed circuit board scrap (PCBS) , and spent automotive catalyst (SAC); and analyzed the effect of other metal ions contained in simulated wastewater on Pd biorecovery efficiency. The results showed that the E. faecalis Z5 could recover Pd(Ⅱ) as palladium nanoparticles from the three simulated wastewaters. X-ray diffraction and transmission electron microscopy analysis indicated that the recovered product was Pd nanoparticles that were about 10 nm in size and mainly distributed in the periplasm of the cells. The order of Pd(Ⅱ) biorecovery efficiency from the three kinds of wastewaters was IW> SAC> PCBS. The biosorption efficiencies for IW, SAC, and PCBS were 99.8% (6 h), 99.7% (8 h), and 90.3% (12 h), respectively, and the bioreduction efficiencies were 99.9% (4 h), 99.9% (6 h), and 80.4% (36 h). Other metal ions contained in the simulated wastewaters such as Pt(Ⅳ), Au(Ⅲ), Ag(Ⅰ), Cu(Ⅱ), and Fe(Ⅱ) affected both the biosorption and bioreduction processes. The degree of matrix effects on the Pd(Ⅱ) bioreduction efficiency were in the order Au(Ⅲ)> Pt(Ⅳ)> Cu(Ⅱ)> Ag(Ⅰ)> Fe(Ⅱ). Further doping the recovered Pd nanoparticles with ferriferous oxide enabled the products to catalyze the degradation of methylene blue in heterogeneous Fenton reactions, which showed 96.7% degradation rate of methyl blue within 80 min.

Effect of metal oxide/alumina on catalytic deoxygentation of biofuel from physic nut residues pyrolysis

Rapid catalytic thermal conversion of Physic nut (Jatropha curcas) residues for upgrading the released vapors was performed using analytical pyrolyzer-gas chromatography/mass spectrometry at 873 K. Conditioning of the evolved vapor product is required since the main vapor products formed without catalysts typically contained around 60% fatty acids, while the total hydrocarbon yields were only 12%. Catalysts tested were alumina (Al2O3) alone and modified by 5 wt% impregnation with various transition metal salts and then calcined to metal oxides. A significant decrease in the proportion of oxygenated compounds (including acids) from 73% without a catalyst to less than 10% with, and an increased conversion to hydrocarbons of more than 70% was obtained with the metal/Al2O3 catalysts at a Jatropha:catalyst (J:C) ratio of 1:10. The product selectivity was greatly increased as the J:C ratio was increased from 1:1 to 1:10. The total hydrocarbon selectivity of the metal/Al2O3 catalysts was increased in the order of Pd > Ni > Ce > Ru > La > none > Co > Mo, with the highest proportion of total hydrocarbons obtained being 75%. In addition, only a low yield (<2%) of polycyclic aromatic hydrocarbons was obtained from the conversion of Jatropha curcas residues. However, these catalysts adversely promoted N-containing compounds, suggesting that a further denitrogenation process is necessary. Nevertheless, the overall performance of these transition metal/Al2O3 catalysts is acceptable and they can be considered as good candidates for bio-oil upgrading.

Hydrogenation of CO2 over supported noble metal catalysts

The catalytic activity of supported noble metal catalysts for the CO2 methanation reaction has been investigated with respect to the nature (Rh, Ru, Pt, Pd), loading (0.1–5.0wt.%) and mean crystallite size (1.3–13.6nm) of the dispersed metallic phase. It has been found that the turnover frequency (TOF) of CO2 conversion for TiO2-supported catalysts increases following the order of Pd<Pt<Ru<Rh, with Rh being about 3 times more active than Pd. Selectivity toward methane depends strongly on the noble metal catalyst employed and is significantly higher for Rh and Ru catalysts compared to Pt and Pd, which mainly promote production of CO via the RWGS reaction. Conversion of CO2 at a given temperature increases significantly with increasing Ru loading in the range of 0.1–5.0wt.%. Results of kinetic measurements show that the CO2 hydrogenation reaction is structure sensitive, i.e., catalytic activity is strongly influenced by metal crystallite size. In particular, for Ru/TiO2 and Ru/Al2O3 catalysts, the normalized turnover frequency (TOF divided by the length of the perimeter of the metal-support interface) increases by two orders of magnitude with increasing ruthenium crystallite size in the range of 0.9–4.2nm and 1.3–13.6nm, respectively. FTIR experiments provide evidences that CO2 hydrogenation reaction occurs via intermediate formation of adsorbed CO species (Rux-CO, Run+(CO)x, (TiO2)Ru-CO) produced via the RWGS reaction. Part of this species interacts with adsorbed hydrogen atoms producing methane, whereas the remaining species desorbs to yield CO in the gas phase. The CO2 hydrogenation pathway does not change with variation of Ru crystallite size. However, the relative intensity of the band due to CO species linearly bonded on reduced Ru crystallites (Rux-CO) increases significantly with increasing Ru particle size, indicating that Rux-CO species could potentially being the reactive surface intermediates.

Activation of Peroxymonosulfate by Surface-Loaded Noble Metal Nanoparticles for Oxidative Degradation of Organic Compounds.

This study demonstrates the capability of noble metal nanoparticles immobilized on Al2O3 or TiO2 support to effectively activate peroxymonosulfate (PMS) and degrade select organic compounds in water. The noble metals outperformed a benchmark PMS activator such as Co(2+) (water-soluble) for PMS activation and organic compound degradation at acidic pH and showed the comparable activation capacity at neutral pH. The efficiency was found to depend on the type of noble metal (following the order of Pd > Pt ≈ Au ≫ Ag), the amount of noble metal deposited onto the support, solution pH, and the type of target organic substrate. In contrast to common PMS-activated oxidation processes that involve sulfate radical as a main oxidant, the organic compound degradation kinetics were not affected by sulfate radical scavengers and exhibited substrate dependency that resembled the PMS activated by carbon nanotubes. The results presented herein suggest that noble metals can mediate electron transfer from organic compounds to PMS to achieve persulfate-driven oxidation, rather than through reductive conversion of PMS to reactive sulfate radical.

Effect of Defective Graphene Flake for Catalysts of Supported Pd Nanocubes toward Glucose Oxidation Reaction in Alkaline Medium

The effect of defective graphene flake (DGF) as supports for Pd nanocubes (Pd NCs) in the catalysis of d-glucose oxidation reaction (GOR) was studied. The DGF used to support the Pd NCs were prepared via both a sonoelectrochemical method (DGFSECM) and a chemical reduction method (DGFCM). The comparable data supported by the diffraction electron pattern of transmission electron microscope (TEM) and X-ray diffraction (XRD) spectra evidence that the corners of the Pd NCs faced up toward the both DGF supports, leading to an increase in the XRD intensity of the Pd (111) peak. Additionally, a fair electrochemical comparison of the DGF support effect on GOR catalysis via Pd NCs in a NaOH electrolyte indicated that the DGFSECM-supported Pd NCs (Pd NC/DGFSECM) and DGFCM-supported Pd NCs (Pd NC/DGFCM) demonstrated earlier onset potentials and an overall order of Pd NC/DGFSECM > Pd NC/DGFCM > commercial Pd/C catalyst > Pd NCs for the peak charge accompanying the formation of glucolactone was obtained. Through the use of a DGFSECM substrate, the electrochemical surface area and charge transfer resistance toward GOR were significantly improved. In addition, as supported by the catalytic activity for GOR, Pd NC/DGFSECM showed remarkable sensitivity and tolerance to foreign substances in the application as a non-enzymatic glucose sensor, where Pd NC/DGFSECM showed higher two-period sensitivities of 74 and 45.86 μA·mM−1·cm−2 for 0.25–5 and 5–24 mM d-glucose, respectively. The high recovery in serum sample analyses further confirmed the potential of Pd NC/DGFSECM as glucose sensors.

A comparison of physically and chemically defective graphene nanosheets as catalyst supports for cubic Pd nanoparticles in an alkaline oxygen reduction reaction

An electrostatic attraction method is utilized for successfully attaching 10nm Pd nanocubes on reduced graphene nanosheet (RGN) surfaces. The RGNs used to support the Pd nanocubes are prepared via both a sonoelectrochemical method (RGNSECM) and a chemical reduction method (RGNCM). X-ray photoelectron spectroscopic analyses indicate the domination of physical defects and C-OH groups on the surfaces of RGNSECM and RGNCM, respectively. The linear scanning voltammograms, taken using rotating ring-disk electrode analyses in alkaline oxidation-reduction reactions (ORRs), show that the Pd nanocubes supported by RGNSECM (Pd cubes/RGNSECM) and RGNCM (Pd cubes/RGNCM) show improved onset potentials of 0.1V on the order of Pd cubes/RGNSECM>Pd cubes/RGNCM>Pt/C∼Pd/C>Pd nanocubes for their catalytic disk currents in the electron-transfer region. Mass-transfer-corrected Tafel diagrams demonstrate that RGNSECM, which contains a greater number of physical defects, facilitated greater active sites of these Pd nanocubes due to its greater surface area, and thus better promoted ORRs. In terms of the kinetic current density, a greater mass activity (7.85×10−2mA·μg−1) is observed for the Pd cubes/RGNSECM composite. Additionally, the durability test reveals that RGNSECM could provide good strength to stabilize Pd nanocubes during a long ORR period.

Comparative Study on The Photocatalytic Hydrogen Production from Methanol over Cu-, Pd-, Co- and Au-Loaded TiO2

Photocatalytic hydrogen production from a methanol-water solution was investigated in a semi-continuous reactor over different metal-loaded TiO2 catalysts under UltraViolet (UV) light irradiation. The catalysts were mainly prepared by the incipient wetness impregnation method by varying the metal weight ratio in the range of 1-10 wt%. The effects of metal loading and H2 pre-treatment on the photocatalytic activity were investigated. In addition, the activity of the catalysts was also compared with a reference Au-TiO2 catalyst from the World Gold Council (WGC). The photocatalysts were characterized by using X-Ray Diffraction (XRD) and N2 physisorption before and after the activity measurements. The photocatalytic activity decreased in the order of Pd > Au > Cu > Co in the comparative study of Cu-TiO2 , Co-TiO2 , Au-TiO2 and Pd-TiO2 . Optimum hydrogen evolution was achieved with 5 wt% Pd-TiO2 and 5 wt% Cu-TiO2 .

Inhibition of Metal Hydrogenation Catalysts by Biogenic Impurities

We show that supported Ni, Pt, and Pd catalysts used for liquid phase hydrogenation are inhibited by the biogenic impurities present in biologically-derived feedstocks used to produce high-value chemicals. The effects of thiamine HCl, cysteine, methionine, biotin, tryptophan, niacin, threonine, and p-aminobenzoic acid were elucidated by collecting adsorption isotherms of these species and by quantifying their influence on the rate of cyclohexene hydrogenation at 323 K. Inhibition increases in the order of Pd < Pt < Ni and generally correlates with the binding energies of sulfur and nitrogen. The equilibrium constants reported here for adsorption of these species on Ni, Pt, and Pd can facilitate the design of separation systems and new catalysts used for upgrading biologically-produced platform molecules.

Effect of oxidative heat-treatment on electrochemical properties and oxygen reduction reaction (ORR) activity of Pd–Co alloy catalysts

Pd–Co catalysts of various compositions are subjected to heat-treatment in an oxygen-containing atmosphere (5% oxygen and 95% argon by volume) and the catalysts are found to form oxides. On exposure to electrochemical conditions, the oxides get reduced in the potential range of 0.05–0.4V of the voltammogram and the voltammetric features of the heat-treated catalyst are comparable to that of the corresponding as-prepared catalyst of same composition. The trends in electrochemical surface area (ESA), current due to formation of adsorbed-oxygenated species and activity towards oxygen reduction reaction (ORR) with catalyst composition are similar and they are in the order of Pd≪Pd1.5Co<PdCo<Pd6.3Co<Pd2Co<Pd3Co. The ORR activity of the catalyst subjected to the oxidative thermal treatment is higher than that of Pd and the corresponding as-prepared catalyst of same composition.

새로운 광증감제 사용에 따른 UDMA 복합수지의 특성

Purpose: The purpose of this study was to know the availability of two photosensitizers, PD, DA, as a photosensitizer instead of CQ in UDMA dental composite resin. We want to know photopolymerization effect of UDMA unfilled resin and surface hardness of composite resin containing PD and DA were compared with those of CQ, most widely used photosensitizer for dental composite resins. Methods: The photopolymerization effect of UDMA studied by FT-IR spectroscopy increased with irradiation time and the amount of photosensitizer. Knoop hardness of experimental composite resins prepared by the addition of the photosensitizer content and irradiation time. Results: The relative photopolymerization effect of UDMA increased in the order of PD > CQ > DA. The composite resin of UDMA containing DA or PD, which shows better Knoop hardness than that containing CQ. Conclusion: PD and DA show as effective photosensizers, suitable for UDMA dental composite resin compare with a higher efficiency than CQ.

Catalytic Activity of Palladium(II) and Osmium(VIII) on the Oxidation of Chloramphenicol by Copper(III) Periodate Complex in Aqueous Alkaline Medium—A Comparative Kinetic and Mechanistic Approach

Chloramphenicol is considered a prototypical broad band spectrum antibiotic, alongside the tetracyclines, and finds extensive applications in pharmaceuticals. Hence, its oxidation kinetic study is of much significance in understanding the mechanistic profile in biological systems. In this regard, a systematic study of oxidation of chloramphenicol (CHP) by diperiodatocuprate(III) (DPC) in the presence of micro amounts (10–8 mol/dm3) of Pd(II) and Os(VIII) catalysts has been investigated spectrophotometrically in aqueous alkaline medium at a constant ionic strength of 0.10 mol dm–3. The reaction between CHP and DPC in alkaline medium exhibits 1:2 stoichiometry in both catalyzed reactions (CHP:DPC). The oxidation products in both reactions were found to be the same and were identified and confirmed by IR, GC-MS, and 1H NMR. The order with respect to DPC concentration was unity, while the order with respect to CHP concentration varied from first order to zero order as the concentration of CHP increased. The rates increased with increase in [OH–] and decreased with increase in [IO4–]. The order with respect to [Pd(II)] and [Os(VIII)] was unity. It is observed that the catalytic efficiency for the title reaction is in the order of Pd(II) > Os(VIII). The catalytic constant was also determined at different temperatures for both reactions. The proposed mechanisms and the derived rate laws are in concurrence with the observed kinetics. The activation parameters with respect to the limiting step of the mechanism were calculated, and the thermodynamic quantities were also determined. Kinetic experiments suggest that [Cu(H2IO6)(H2O)2], [Pd(OH)2Cl2]2–, and [OsO4(OH)2]2– are the reactive oxidizing species of Cu(III), Pd(II), and Os(VIII).

Well-dispersed Pd 3Pt 1 alloy nanoparticles in large pore sized mesocellular carbon foam for improved methanol-tolerant oxygen reduction reaction

Oxygen reduction reaction (ORR) catalysts, Pd 3Pt 1 nanoparticles with methanol tolerance, are supported on various carbon supports: mesocellular carbon foam (MSU-F-C), CMK-3, and Vulcan XC-72. The particle size of Pd 3Pt 1 (∼5 nm) is larger than the pore size of CMK-3 (∼3 nm), resulting in the agglomeration of Pd 3Pt 1 nanoparticles on the external surface of the CMK-3. The large surface area and large pore size of MSU-F-C allows a high degree of dispersion of Pd 3Pt 1 nanoparticles inside the pores. Due to its highly dispersed state, the Pd 3Pt 1/MSU-F-C shows higher ORR activity than Pd 3Pt 1/Vulcan XC-72 and Pd 3Pt 1/CMK-3. The charge transfer resistance ( R ct), as measured by electrochemical impedance spectroscopy, increases in the order of Pd 3Pt 1/CMK-3 > Pd 3Pt 1/Vulcan XC-72 > Pd 3Pt 1/MSU-F-C. Pd 3Pt 1/MSU-F-C is methanol tolerant at 400 rpm in the presence of 0.5 M CH 3OH, while methanol oxidation peaks are observed in the case of Pd 3Pt 1/Vulcan XC-72 and Pd 3Pt 1/CMK-3.

Effect of Central Metals in the Porphyrin Ring on Photocurrent Performance of Cellulose Langmuir-Blodgett Films

Role-sharing functionalized cellulose derivatives having Mg, Zn, Cu, and Pd porphyrins are used for photocurrent generation system fabricated by the LB technique, mimicking the array of natural photosynthetic light-harvesting systems. These polymers exhibited different absorption and redox properties in solution depending on the central metal ions. On visible light illumination, the LB film generated anodic photocurrent in the order of Pd > free base > Zn > Cu > Mg. By inserting Pd ion, using myristoyl group, and adjusting the DS, the photocurrent quantum yield was 6.9 times as great as that of conventional porphyrin cellulose. These findings may provide opportunities for the design of a new class of organic solar cells, based on cellulose molecular characteristics.

Adsorption and surface complexation modeling of palladium, rhodium and platinum in surficial semi-arid soils and sediment

Sorption isotherms, time-dependent adsorption and surface complexation modeling studies were used to investigate the post-depositional mobility of three of the platinum group-elements (Pd, Rh, and Pt) in semi-arid soil and sediment samples with varying surface properties. The acidity constants (Log K a1 and Log K a2 ), optimized from batch titration data, ranged from 4.69 to 5.34 for Log K a1 and from −6.51 to −7.61 for Log K a2 , suggesting the occurrence of both protonation and deprotonation reactions on the solid surfaces. Partition coefficients and removal rates of the metals had a general trend of Pd > Pt > Rh. The sediment sample, with the highest clay content and exchangeable cation concentrations, also had the highest affinity for the metals. The times required for sediment to adsorb 63% of the metals were 2.63 h, 4.08 h and 10.64 h for Pd, Pt and Rh, respectively. The FITEQL program successfully optimized the conditional binding constants of the metals on the solids from batch adsorption data. The constants decreased in the order of Pd > Rh > Pt, which was consistent with the observed high affinity of the solids for Pd. The modeling results also showed that aqueous Pd was the least sensitive to pH followed by Rh and Pt. However, metal adsorption below the points of zero net proton charges (ca. pH 6.7) is attributable to the involvement of permanent negatively charged binding sites in the adsorption process. Notably, partition coefficients, removal rates and conditional binding constants all showed a high affinity of Pd for the solids. A similarity between the model outputs and the batch adsorption data indicates the suitability of the model for describing the mobility and retention of the three metals in semi-arid soils and sediments.

Kinetic and mechanistic studies of the interaction of 2-mercapto pyridine with dichloro[1-alkyl-2-(arylazo)imidazole]palladium(II) complexes

Nucleophilic substitution of Pd(RaaiR′)Cl2 [(RaaiR′ = 1-alkyl-2-(arylazo)imidazole, p-R-C6H4-N=N-C3H2NN-1-R′; where R = H(a)/ Me(b)/ Cl(c) and R′ = Et(1)/Bz(2)] with 2-Mercaptopyridine (2-SH-Py) in acetonitrile (MeCN) at 298 K, to form [Pd2(2-S-Py)4], has been studied spectrophotometrically under pseudo-first-order conditions and the analyses support the nucleophilic association path. The reaction follows the rate law, Rate = {k 0 + k [2-SH-Py] 0 2 }[Pd(RaaiR′)Cl2]: first order in Pd(RaaiR′)Cl2 and second order in 2-SH-Py. The rate of the reaction follows the order: Pd(RaaiEt)Cl2 (1) < Pd(RaaiBz)Cl2 (2) and Pd(MeaaiR′)Cl2 (b) < Pd(HaaiR′)Cl2 (a) < Pd(ClaaiR′)Cl2 (c). External addition of Cl− (LiCl) and HCl suppresses the rate (Rate ∝ 1/[Cl−]0 & ∝1/[HCl]0). The reactions have been studied at different temperatures (293–308 K) and activation parameters (Δ‡ H° and Δ ‡ S°) of the reactions were calculated from the Eyring plot and support the proposed mechanism.

Selective hydrogenation of citral with transition metal complexes in supercritical carbon dioxide

Abstract The activity and selectivity of the transition metal complexes formed from Ru, Rh, Pd and Ni with triphenylphosphine (TPP) have been investigated for hydrogenation of citral in supercritical carbon dioxide (scCO2). High activities are obtained with Ru/TPP and Pd/TPP catalysts, and the overall activity is in the order of Pd≈Ru > Rh > Ni. The Ru/TPP complex is highly selective to the formation of unsaturated alcohols of geraniol and nerol. In contrast, the Pd/TPP catalyst is more selective to partially saturated aldehydes of citronellal. Furthermore, the influence of several parameters such as CO2 and H2 pressures, N2 pressure and reaction time has been discussed. CO2 pressure has a significant impact on the product distribution, and the selectivity for geraniol and nerol can be enhanced from 27% to 75% with increasing CO2 pressure from 6 to 16 MPa, while the selectivity for citronellol decreases from 70% to 20%. Striking changes in the conversion and product distribution in scCO2 could be interpreted with variations in the phase behavior and the molecular interaction between CO2 and the substrate in the gas phase and in the liquid phase.