A Combined Deep Eutectic Solvent–Ionic Liquid Process for the Extraction and Separation of Platinum Group Metals (Pt,Pd, Rh)

Recovery of platinum group metals from spent materials is becoming increasingly relevant due to the high value of these metals and their progressive depletion. In recent years, there is an increased interest in developing alternative and more environmentally benign processes for the recovery of platinum group metals, in line with the increased focus on a sustainable future. To this end, ionic liquids are increasingly investigated as promising candidates that can replace state-of-the-art approaches. Specifically, phosphonium-based ionic liquids have been extensively investigated for the extraction and separation of platinum group metals. In this paper, we present the extraction capacity of several phosphonium-based ionic liquids for platinum group metals from model deep eutectic solvent-based acidic solutions. The most promising candidates, P₆₆₆₁₄Cl and P₆₆₆₁₄B2EHP, which exhibited the ability to extract Pt, Pd, and Rh quantitively from a mixed model solution, were additionally evaluated for their capacity to recover these metals from a spent car catalyst previously leached into a choline-based deep eutectic solvent. Specifically, P₆₆₆₁₄Cl afforded extraction of the three target precious metals from the leachate, while their partial separation from the interfering Al was also achieved since a significant amount (approx. 80%) remained in the leachate.     

An experimental and theoretical study of pyrrolidine pyrolysis at low pressure

Pyrrolidine serves as a model substance for a series of saturated nitrogenated heterocycles in plants, including certain amino acids such as proline and hydroxyproline. Thus the pyrolysis of this compound was investigated regarding the increasing interest on biofuels. The pyrolysis of pyrrolidine diluted with 95% argon was studied in a flow reactor at 40 mbar over the temperature range from 950 to 1450 K. Isomer-specific assignment and quantification was performed using molecular-beam mass spectrometry and ionization with tunable synchrotron vacuum ultraviolet radiation. The prominent decomposition pathways were analyzed based on the quantified mole fractions of pyrolysis species. Computations including an ab initio calculation and kinetic modeling for the primary fuel decomposition were used to refine the analysis and reveal the combustion chemistry of this saturated heterocyclic compound. Based on the theoretical calculation, a new pathway for the isomerization reaction pyrrolidine → CH₂CHCH₂CH₂NH₂ via a diradical intermediate was proposed. The rate constant calculations showed that this channel has a large contribution to pyrrolidine pyrolysis.     

An experimental laminar flame investigation of dual-fuel mixtures of C4 methyl esters with C2–C4 hydrocarbon base fuels

Blending petroleum-based fuels with biofuel components is deemed attractive to reduce soot and CO₂ emissions, but fundamental studies of the combustion behavior of such fuel blends suited for model development and validation remain rather scarce. To contribute to the understanding of the combustion chemistry effects of such blending strategies, we have investigated laminar premixed low-pressure flames of three hydrocarbon base fuels, namely 1-butene (1-C₄H₈), isobutene (i-C₄H₈), and ethene (C₂H₄), blended each with two different ester fuels, namely methyl crotonate (C₅H₈O₂, MC) and methyl butanoate (C₅H₁₀O₂, MB). A series of 13 flames with different argon dilution was investigated to study effects of the specific fuel structure on the combustion chemistry. Full speciation analyses were performed for fuel-rich (? = 1.6) conditions by electron ionization molecular-beam mass spectrometry (EI-MBMS). More than 35 species in the range of C₀–C₇ were identified and quantified in these flames, resulting in ～450 mol fraction profiles. The experimental data were compared to simulations by the kinetic model reported by Yang et al. [Proc. Combust. Inst. 2011, Phys. Chem. Chem. Phys. 2013] that was chosen because it includes basic mechanisms of all studied fuels. Overall, the agreement of experiment and this model seems satisfactory but calls for further improvements regarding ester as well as hydrocarbon sub-mechanisms. It was noted that the unsaturation degree in the methyl esters affects the formation of hydrocarbons, that depend mainly on the structure of the respective base fuel, and of oxygenated intermediates. The methyl esters have different decomposition pathways leading to some specific oxygenated species. Both methyl esters promote the formation of formaldehyde and methanol, while acetic acid is significantly increased by the presence of MB. The effect of the ester addition is also influenced by the species pool of the respective hydrocarbon base fuel.     

Mathematical modelling of a diesel common-rail system

In diesel common-rail systems, the exact knowledge of the injection pressure is important to accurately control the injected diesel mass and thus the combustion process. This paper focuses on the mathematical modelling of the hydraulic and mechanical components of a common-rail system in order to describe the dynamics of the diesel rail pressure. Based on this model, an average model is derived to reduce the model complexity and to allow for a fast calculation of the mass flow into the rail for different crank shaft revolution speeds and openings of the fuel metering unit. The main purpose of this average model is to serve as a basis for a model-based (non-linear) controller design. The stationary accuracy of the models is validated by means of measurement data.     

pH-Triggered Recovery of Organic Polymer Photocatalytic Particles for the Production of High Value Compounds and Enhanced Recyclability

Pseudo-homogeneous polymeric photocatalysts are an emerging class of highly efficient and tunable photocatalytic materials, where the photocatalytic centers are easily accessible. The creation of highly efficient photocatalytic materials that can be rapidly separated and recovered is one of the critical challenges in photocatalytic chemistry. Here, we describe pH-responsive photocatalytic nanoparticles that are active and well-dispersed under acidic conditions but aggregate instantly upon elevation of pH, enabling easy recovery. These responsive photocatalytic polymers can be used in various photocatalytic transformations, including Cr^VI reduction and photoredox alkylation of indole derivative. Notably, the cationic nature of the photocatalyst accelerates reaction rate of an anionic substrate compared to uncharged species. These photocatalytic particles could be readily recycled allowing multiple successive photocatalytic reactions with no clear loss in activity.     

Fluorinated Analogues to the Pentuloses of the Pentose Phosphate Pathway

Fluorinated carbohydrates are valuable tools for enzymological studies due to their increased metabolic stability compared to their non-fluorinated analogues. Replacing different hydroxyl groups within the same monosaccharide by fluorine allows to influence a wide range of sugar–receptor interactions and enzymatic transformations. In the past, this principle was frequently used to study the metabolism of highly abundant carbohydrates, while the metabolic fate of rare sugars is still poorly studied. Rare sugars, however, are key intermediates of many metabolic routes, such as the pentose phosphate pathway (PPP). Here we present the design and purely chemical synthesis of a set of three deoxyfluorinated analogues of the rare sugars d -xylulose and d -ribulose: 1-deoxy-1-fluoro-d -ribulose ( 1DFRu ), 3-deoxy-3-fluoro-d -ribulose ( 3DFRu ) and 3-deoxy-3-fluoro-d -xylulose ( 3DFXu ). Together with a designed set of potential late-stage radio-fluorination precursors, they have the potential to become useful tools for studies on the complex equilibria of the non-oxidative PPP.     

Biomolecular Binding under Confinement: Statistical Predictions of Steric Influence in Absence of Long-Distance Interactions

We propose a theoretical model for the influence of confinement on biomolecular binding at the single-molecule scale at equilibrium, based on the change of the number of microstates (localization and orientation) upon reaction. Three cases are discussed: DNA sequences shorter and longer than the single strain DNA Kuhn length and spherical proteins, confined into a spherical container (liposome, droplet, etc.). The influence of confinement is found to be highly dependent on the molecular structure and significant for large molecules (relative to container size).     

Redox-Active Hybrid Polyoxometalate-Stabilised Gold Nanoparticles

We report the design and preparation of multifunctional hybrid nanomaterials through the stabilization of gold nanoparticles with thiol-functionalised hybrid organic–inorganic polyoxometalates (POMs). The covalent attachment of the hybrid POM forms new nanocomposites that are stable at temperatures and pH values which destroy analogous electrostatically functionalised nanocomposites. Photoelectrochemical analysis revealed the unique photochemical and redox properties of these systems.     

Thermosetting Shape Memory Polymers and Composites Based on Polybenzoxazine Blends,Alloys and Copolymers

When dealing with smart polymers, in particular with shape memory polymers, the polymer type and composition specify the overall material properties and in particular the extent of the shape memory effect. Polybenzoxazines as a polymer with high potential for structural applications represent a promising component for materials with both shape memory effect and structurally interesting material properties. This minireview gives insight into how the shape memory effect, in particular the shape recovery event, is influenced by internal factors such as polymer structure, morphology and external factors such as filler addition.     

Structure and Bonding of La2NiBi

La₂NiBi was synthesized by heating a cold pressed pellet of the elements in a sealed and evacuated silica tube at 1070 K. The structure was determined via powder and single crystal X‐ray diffraction. La₂NiBi crystallizes orthorhombically, in the space group Pnma: a = 838.88(6), b = 455.61(11), c = 1210.4(2) pm and V = 0.46261(14) nm³ (wR = 0.1002, 1001 F² values, 26 variables, Z = 4). La₂NiBi represents a higher congener of La₂NiSb and adopts a ternary ordered version of the Bi₃Ni structure type. Similar to La₂NiSb, the nickel atoms form infinite zigzag chains (259 pm Ni–Ni) with trigonal‐prismatic lanthanum coordination. One rectangular face of the lanthanum prism is capped by a bismuth atom (333.08–364.74 pm La–Bi, 281.18 pm Ni–Bi). These zigzag chains run along the b axis. DFT based band structure calculations and DOS representations suggest metallic behavior. This was confirmed via temperature dependent impedance spectroscopic measurements. A Seebeck coefficient of –10 μV · K^–1 in the temperature range up to 873 K substantiates this finding. Thermal analyses show that the compound is stable up to 873 K under inert gas conditions and degrades at higher temperatures. The magnetic measurements show almost no grain boundary nickel impurities characterizing La₂NiBi as a weak Pauli paramagnet.