Catalytic Conversions in Aqueous Media. Part 2. A Novel and Highly Efficient Biphasic Hydrogenation of Renewable Methyl Esters of Linseed and Sunflower Oils to High Quality Biodiesel Employing Rh/TPPTS Complexes

An unusual high catalytic activity (TOF = 117,000 h⁻¹) and high catalyst productivity (TON = 9,700) have been achieved in the first example of partial hydrogenation of renewable polyunsaturated crude methyl esters of linseed and sunflower oils catalyzed by water soluble Rh/TPPTS complexes [TPPTS = P(C₆H₄-m-SO₃Na)₃] in aqueous/organic two-phase systems to afford monounsaturated fatty esters which is biodiesel first generation of improved oxidative stability, energy and environmental performance at a low pour point. This exceptionally high catalytic activity contrast with the general perception that industrially applied water soluble Rh/TPPTS catalysts normally exhibit very low rates in the conversions of higher molecular weight starting materials in aqueous/organic two-phase systems. For part 1 of this series see Ref. [14].     

Catalytic conversions in water, part 8: carbonylation and hydrocarboxylation reactions catalyzed by palladium trisulfonated triphenylphosphine complexes

The water-soluble Pd(tppts)₃ complex (tppts=P(C₆H₄-m-SO₃Na)₃) is an active catalyst for the carbonylation of benzylic type alcohols in aqueous/organic two-phase systems in the presence of a Brønsted acid cocatalyst. For example, 1-(4-isobutylphenyl)ethanol afforded 2-(4-isobutylphenyl)propionic acid in 82% selectivity at 83% conversion and 5-hydroxymethylfurfural (HMF) gave 5-formylfuran-2-acetic acid in 72% selectivity at 90% conversion. In the latter case, use of an acid with a strongly coordinating anion led to the preferential formation of the reduction product 5-methylfurfural (MF), e.g. HI afforded MF in >99% selectivity. Pd(tppts)₃ is also an usual active catalyst (T.O.F.>2500) for the biphasic hydrocarboxylation of propene to n- and isobutyric acid, being substantially more active than the analogous Pd/PPh₃ in organic media.     

Catalytic activity of supported metal particles for sulfuric acid decomposition reaction

Production of hydrogen by splitting of water in the thermochemical sulfur-based cycles that employs the catalytic decomposition of sulfuric acid into SO₂ and O₂ is of considerable interest. However, all of the known catalytic systems studied to date that consist of metal particles on oxide substrates deactivate with time on stream. To develop an understanding of the factors that are responsible for catalyst activity, we investigate the fresh activity of several platinum group metals (PGM) catalysts, including Pd, Pt, Rh, Ir, and Ru supported on titania at 850 °C and perform an extensive theoretical study (density-functional-theory-based first-principles calculations and computer simulations) of the activity of the PGM nanoparticles of different size and shape positioned on TiO₂ (rutile and anatase) and Al₂O₃ (γ- and η-alumina) surfaces. The activity and deactivation of the catalytic systems are defined by (i) the energy barrier for the detachment of O atoms from the SO_n (n = 1, 2, 3) species, and (ii) the removal rate of the products of the sulfuric acid decomposition (atomic O, S, and the SO_n species) from metal nanoparticles. We show that these two nanoscale features collectively result in the observed experimental behavior. The removal rate of the reaction products is always lower than the SO_n decomposition rates. The relation between these two rates explains why the “softer” PGM nanoparticles (Pd and Pt) exhibit the highest initial catalytic activity.     

Effect of selenium-position on the redox responsivity of isomeric selenium-containing anionic surfactants

The effect of Se-position on the redox responsivity of three isomeric selenium-containing surfactants (C_mSeC_nSO₄Na, n = 3, 8, and 11, m + n = 15) was investigated under the conditions of monomer, micelle, and adsorbed layer at the liquid paraffin-water interface. The divalent selenide group in C_mSeC_nSO₄Na (the reduction form, C_mSeC_nSO₄Na-Re) was oxidized to a more hydrophilic tetravalent selenoxide by the oxidation with H₂O₂ to afford C_mSeOC_nSO₄Na (the oxidation form, C_mSeC_nSO₄Na-Ox), and the selenoxide group of C_mSeC_nSO₄Na-Ox could be reduced to selenide by the reduction with Na₂SO₃ to form C_mSeC_nSO₄Na-Re again. In the oxidation process of the monomeric C_mSeC_nSO₄Na in water, no obvious difference in the oxidation responsivity among three Se-position isomers was observed. In contrast, a remarkable effect of the Se-position on the oxidation responsivity was observed in the cases of C_mSeC_nSO₄Na self-assemblies, including micelles and adsorbed layers at the liquid paraffin-water interface. Both the steric hindrance of the well-organized self-assemblies and the hydrophobic microenvironment of the selenide group in the self-assemblies hindered the Se atom from reacting with H₂O₂. The greater n, the harder was the oxidation of Se with H₂O₂. In the reduction process of C_mSeC_nSO₄Na-Ox, the hydrophilic selenoxide group was exposed outright to water, allowing the selenoxide group to readily react with Na₂SO₃ regardless of whether C_mSeC_nSO₄Na-Ox was self-assembled or not.     

Ethylene polymerization by alkylidene‐bridged asymmetric dinuclear titanocene/MAO systems

Two asymmetric alkylidene‐bridged dinuclear titanocenium complexes (CpTiCl₂)₂(η⁵‐η⁵‐C₉H₆(CH₂)_nC₅H₄), 1 (n = 3) and 2 (n = 4) have been prepared by treating two equivalents of CpTiCl₃ with the corresponding dilithium salts of the ligands C₉H₇(CH₂)_nC₅H₅ (n = 3, 4). Additionally, Ti(η⁵:η⁵‐n‐BuC₅H₄C₅H₅)Cl₂ (3) and Ti(η⁵:η⁵‐n‐BuC₉H₆C₅H₅)Cl₂ (4) were synthesized as corresponding mononuclear complexes. All complexes were characterized by ¹H, ¹³C NMR, and IR spectroscopy. Homogenous ethylene polymerization catalyzation using those complexes has been conducted in the presence of methylaluminoxane (MAO). The influences of reaction parameters, such as [MAO]/[Cat] molar ratio, catalyst concentration, ethylene pressure, temperature, and time have been studied in detail. The results showed that the catalytic activities of both dinuclear titanocenes were higher than those of the corresponding mononuclear titanocenes. Although the two dinuclear complexes were different in only one [CH₂] unit, the catalytic activity of 2 was about 50% higher than that of 1; however, the molecular weight of polyethylene (PE) obtained by 2 was lower than that obtained from 1. The molecular weight distribution of PE produced by these dinuclear complexes reached 6.9 and 7.3, respectively. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3317–3323, 2006     

Fluorous Surface‐Active Distannoxane Catalysts

Fluorous distannoxanes (XR^f₂SnOSnR^f₂X)₂⋅n H₂O (R_f=C₆F₁₃C₂H₄) ( 1 : X=C₈F₁₇SO₃, n=10; 4 : X=Cl, n=0) ( 1 ) catalyze the Mukaiyama aldol reaction and the allylation of aldehydes with tetraallyltin at room temperature in fluorous/organic biphasic solvent systems, in which the reactions proceed more rapidly than in a single organic or fluorous solvent. Due to the unique surface activity of 1 , the catalyst, organic substrate(s), and reagent(s) are distributed in both organic and fluorous phases to facilitate smooth reactions. Upon dilution with toluene after the reaction, the catalyst concentrates to the fluorous phase, while the organic substances migrate to the organic phase to effect facile catalyst recovery and recycling. By virtue of such a unique solvophilicity, a new version of fluorous biphase technology has been developed.     

Soap-based detergent formulations: XVII. Synthesis and surface active properties of alkylbenzene derived amine oxides

Amine oxides C_nH_2n+1C₆H₄SO₂NH(CH₂)₃-NMe₂—O⁻ were prepared for testing as lime soap dispersing agents in phosphate free, soap-based, sodium silicate built laundry detergents. These amine oxides were synthesized via a three step route from a variety of pure 1-phenylalkanes and also from a commerical detergent alkylate mixture. The process included (a) the sulfonation of the phenylalkane with chlorosulfonic acid, (b) reaction of the resulting alkarylsulfonyl chloride with H₂N(CH₂)₃NMe₂ or with H₂N(CH₂)₃N(CH₂CH₂OH)₂ under anhydrous conditions, and (c) oxidation with aqueous H₂O₂. The amine oxides were water soluble and in some instances isolable as crystalline hydrates. They were found to be thermally stable below 125 C and highly surface active. Optimum detergency and lime soap dispersability were achieved by the model compound of alkyl chain length n=8. This was in contrast to the behavior of the related amphoteric sulfobetaine series C_nH_2n+1C₆H₄SO₂NH(CH₂)₃NMe₂(CH₂)₃-SO₃ ⁻, whose optimum detergency and lime soap dispersability previously had been observed to reach a maximum at chain length n=12. Detergency screening tests showed that soap-based detergents formulated with the sulfobetaines outperformed the ones formulated with the amine oxides. Presented at the AOCS Meeting, Dallas, April 1975.     

α-sulfonated fatty acid esters: II. Solution behavior of α-sulfonated fatty acid polyethylene glycol esters

Sodium α-sulfonated, fatty acid polyethylene glycol monoesters [C _m H_2m+1CH(SO₃Na)COO(C₂H₄O) _n H] and diesters [C _m H_2m+1CH(SO₃Na)COO(C₂H₄O) _n COCH(SO₃Na)C _m H_2m+1], wherem=10–16 andn=1–35, were prepared by esterification of α-sulfonated, fatty acids with polyethylene glycols, followed by neutralization with NaOH. Crude products were purified by reversed-phase column chromatography on an octadecyl-modified silica gel. Characteristic solution behavior of these α-sulfonated fatty acid esters was, examined, and the following features were observed. All monoesters prepared in this work had Krafft points below 0°C and also possessed good calcium stabilities. Critical micelle concentrations of the monoesters increased monotonously, as a rule, with an increase in the number of oxyethylene units. These results suggest that the polyethylene glycol residue of the monoester behaves as a hydrophile. On the other hand, diesters possessed high water solubility, low foamability, and critical micelle concentrations that were lower by a factor of ten compared to those of the monoesters.     

Synthesis and transition metal coordination of 2-(azidomethyl) phenyl isocyanide

The reaction of 2-(chloromethyl)phenyl formamide, 2-(CH₂Cl)C₆H₄NHCHO, with NaN₃ in DMSO at room temperature affords 2-(azidomethyl)phenyl formamide, 2-(CH₂N₃)C₆H₄NHCHO (1), which is then dehydrated to 2-(azidomethyl)phenyl isocyanide, 2-(CH₂N₃)C₆H₄NC, (2) upon reaction with SOCl₂ in DMF at low temperature. The coordination ability of the isocyanide 2 has been tested towards some Pt(II), Pd(II) and W(0) metal complexes to yield derivatives of the type [PtCl₂(CNC₆H₄-2-CH₂N₃)₂], [PdCl₂(CNC₆H₄-2-CH₂N₃)(PPh₃)] and [W(CO)₅(CNC₆H₄-2-CH₂N₃)], respectively.     

Hydroformylierung von Buta-1,3-dien und butadienhaltigen Kohlenwasserstoffraktionen nach dem Zweiphasenverfahren

Two-phase Hydroformylation of Buta-1,3-diene and Hydrocarbon Mixtures Containing Buta-1,3-diene The two-phase hydroformylation of buta-1,3-diene with (HRh(CO)[P(m-C₆H₄SO₃Na)₃]₃ the Kuntz catalyst system with excess P(m-C₆H₄SO₃Na)₃) gives high yields of C₅-monoaldehydes. Main product in this mixture is the reactive trans- and cis-pent-3-enal. In consecutive reactions the pent-3-enal is partially hydrogenated to n-pentanal, but also-favoured by the protolytic milieu of the two-phase reaction- aldol condensated to 2-propenylheptadienal. The hydrogenation product of the propenylheptadienal, 2-propylheptanol-1, is a good plasticizer alcohol with a wanted low vapour pressure. Especially promising is the two-phase hydroformylation of the unrefined C₄-fraction of the naphtha pyrolysis: after a more than 95 per cent conversion of the buta-1,3-diene also more than 80 per cent of the n-but-1-ene in the C₄-fraction is hydroformylated mainly to wanted n-pentanal. Less than 5–10% of the n-but-2-enes and the isobutene in the C₄-fraction react under these conditions to oxo-products (2- and 3-methylbutanal). Acetylenic compounds in the C₄-fraction are converted quantitatively into products.     

DRIFT study of CO chemisorption on organometallics-derived Pd/MgO catalysts: the effect of chlorine

Magnesia-supported palladium catalysts were prepared from chemical vapour deposition (CVD) of [Pd(C₃H₅)(C₅H₅)] and incipient wetness impregnation of [Pd(C₃H₅)Cl]₂ and [Pd(acac)₂]. DRIFT spectroscopy of adsorbed CO on prereduced catalysts indicates that the electronic state of metal particles depends on the preparation methodology and markedly on the organometallic precursor. Inn-heptane reforming at 500°C, the highest activity and selectivity were shown by the CVD-based system. Chloride ions deriving from the impregnation solvent exchange with surface hydroxyls. Acidic Mg-Cl sites are thus formed, which induce a beneficial effect on the catalytic properties. The reforming activity collapsed when a chlorine-containing precursor was used, due to a partial coverage of the palladium surface with chemisorbed chlorine atoms.     

Poly-dioxybiphenyl phosphazene random copolymers with pendant 3-hydroxy-propyl groups and polycaprolactone branches

The polyphosphazenes {[NP(O₂C₁₂H₈)]_0.75[NP(O-C₆H₄-CH₂-CH₂-CH₂-OH)(O-C₆H₅)]_0.25}_n and {[NP(O₂C₁₂H₈)]_0.75[NP(O-C₆H₄-(CH₂-CH₂-CH₂-OH))₂]_0.25}_n, having pendant -OH groups, have been synthesized by the direct reaction of the intermediate {[NP(O₂C₁₂H₈)]_0.75[NP(Cl)₂]_0.25}_n with the heterobifunctional reagent HO-C₆H₄-(CH₂)₃OH in the presence of Cs₂CO₃ which specifically activates the phenolic OH in the presence of the alkylic hydroxyl. The Sn(Oct)₂ promoted ring-opening polymerization of ?-caprolactone at 110 °C on the terminal OH groups gave well defined polycaprolactone (P-CL) branched polyphosphazenes in good yield. The effects of the branching on the crystallization behaviour as well as the thermal stability of the new polymers have been studied.     

Synthesis of Pd（C4H2O4）（C4H8N2）0.5 Complex and the Catalytic Activity for Oxidative Carbonylation of Phenol

A novel complex Pd（C4H2O4）（C4H8N2）0.5 has been synthesized by solvent thermal synthesis and used as a heterogeneous catalyst for direct synthesis of diphenyl carbonate （DPC） by oxidative carbonylation of phenol. In the reaction system of Pd（C4H2O4）（C4H8N2）0.5/Cu（OAc）2/ tetrabutylammonium bromide/ hydroquinone/ 4A molecular sieves, the effect of reaction temperature, time and CO pressure on catalytic activity were investigated, and the results revealed that the catalyst could catalyze oxidative carbonylation of phenol effectively. Under suitable reaction conditions of T=90℃, t=4 h, p（O2）=0.3 MPa, p（CO）=3.9 MPa and CH2Cl2 as solvent, the turnover number （TON） of diphenyl carbonate can reach about 13.50 （mol-DPC/mol-Pd）, which is higher than the TON for oure PdCl2 under the same reaction conditions.     

Cationic polymerization of 2-vinylthiophene - the polymer structure formation

Summary The cationic polymerization of 2-vinylthiophene (VT) has been studied in solution and on the surface of silica particles. For this purpose different cationically active initiators have been used, e.g. SnCl₄, CF₃SO₃H, and CF₃COOH in homogeneous solution as well as (4-CH₃OC₆H₄)₂CH-Cl and (C₆H₅)₃CCl in conjunction with silica nanoparticles in a slurry. For all experiments a high conversion of VT to oligomers with M_n= 1500 −2000 g/mol (M_w/M_n= 1.4) (Tg = 109 °C) and oligoVT/silica hybrid particles, respectively, have been observed. The different head and endgroups have been ascertained by means of MALDI TOF spectroscopy. Different NMR spectra analyses of the oligomers show that both the vinyl double bond and the five position of the thiophene ring are involved in the propagation reaction. Received: 23 April 2001/Revised version: 25 July 2001/Accepted: 25 July 2001     

Catalytic behaviour of La4PdO7 based catalysts when exposed to car exhaust conditions

The catalytic properties of ex situ prepared La₄PdO₇ were studied under automotive exhaust conditions. Monophasic La₄PdO₇ was deposited onto-Al₂O₃ coated cordierite monoliths and light-off curves were recorded under oxidising and reducing conditions. Initially the catalytic activity for oxidation of CO and C₃H₆ and reduction of NO was low but after the catalyst had been exposed to a reducing atmosphere of simulated car exhaust composition at 600°C a three-way catalytic behaviour was obtained with aT ₅₀ value of about 340°C. Using oxidising conditions and a similar activation procedure, a catalyst with CO and C₃H₆ oxidation activity (T ₅₀=405° C) but minor activity for reduction of NO was obtained. This behaviour is interpreted in terms of La₄PdO₇ being decomposed and nanosized PdO particles being formed; these in turn are reduced to Pd and Pd is the catalytically active component in the catalyst. These conclusions are supported by X-ray diffraction, infrared spectroscopy, scanning and transmission electron microscopy studies combined with element analysis of freshly prepared and thermally activated catalysts.     

Study of vanadium(IV) species and corresponding electrochemical performance in concentrated sulfuric acid media

The vanadium(IV) ion is found to form the [VO(SO₄)(H₂O)₄]·H₂O complex, as well as the dimer, [VO(H₂O)₃]₂(μ-SO₄)₂, in concentrated H₂SO₄ media. Their formation mechanisms were investigated by UV–Visible spectroscopy (UV–Vis), Raman spectroscopy, X-ray diffraction (XRD), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). UV–Vis spectroscopy study showed that [VO(SO₄)(H₂O)₄]·H₂O concentration in H₂SO₄ solution was proportional to concentrations of VO²⁺ and SO₄²⁻. The increased deviation from the near centrosymmetry of the octahedral complexes is due to the replacement of an equatorial water oxygen in [VO(H₂O)₅]SO₄ by a sulfate oxygen in [VO(SO₄)(H₂O)₄]·H₂O. The dimer shows symmetrical structure, which correlates very well with non-activity in UV–Vis spectroscopic analysis. Structural information on both vanadium(IV) species can be confirmed by Raman and XRD measurements of crystals from the supersaturated solution of VOSO₄ in 1 M, 6 M and 12 M sulfuric acid. A solution of vanadium(IV) (0.05 M) in 12 M H₂SO₄, in which the vanadium(IV) species is [VO(H₂O)₃]₂(μ-SO₄)₂, exhibits a reversible redox behavior near 1.14 V (vs. SCE) on the carbon paper electrode.     

Micellization of Anionic Sulfonate Gemini Surfactants and Their Interactions With Anionic Polyacrylamide

Anionic sulfonate gemini surfactants 8‐s‐8(SO₃)₂ and 12‐s‐12(SO₃)₂ (s = 3, 6) were synthesized, and their micellization in aqueous solution at 25.0 °C and pH 9 was investigated. The results show that the critical micelle concentrations (CMC) of 8‐s‐8(SO₃)₂ are more than 2 orders of magnitude larger than those of 12‐s‐12(SO₃)₂, but the spacer length has a relatively small impact on the CMC. Moreover, the interactions of n‐s‐n(SO₃)₂ (n = 8, 12; s = 3, 6) with anionic polyacrylamide (PAM) at 25.0 °C and pH 9 were investigated using surface tensiometry, rheolgy, and scanning electron microscopy (SEM). The results indicate that the surface tension and rheological properties of PAM depend on the concentration of n‐s‐n(SO₃)₂. Below the critical aggregation concentration of C₁, surface tension is sharply reduced, the surface tension of n‐s‐n(SO₃)₂/PAM is lower than n‐s‐n(SO₃)₂ alone, but viscosity is almost unchanged with increasing C_{n‐s‐n(SO3)2}. Above C₁, surface tension reduces very slowly until the saturated concentration of C₂ is reached. Above C₂, surface tension rapidly reduces until C_M is attained, suggesting free n‐s‐n(SO₃)₂ micelles begin to form. In the region of C₁–C_M, the viscosity significantly increases. Above C_M, surface tension is basically unchanged and these curves coincide with those of the single surfactant system. Moreover, the viscosity is almost constant. The SEM images indicate that fibrous aggregates are formed below C₁, then transformed into multilayer fibrous aggregates above C₁, and further into fiber‐braided‐structured and spider‐web‐structured aggregates above C_M. The variation of viscosity is closely associated with the transformation of aggregates.     

Ethylene polymerization by 3‐oxa‐pentamethylene bridged asymmetric dinuclear titanocene/MAO system

An asymmetric 3‐oxa‐pentamethylene bridged dinuclear titanocenium complex (CpTiCl₂)₂(η⁵‐η⁵‐C₉H₆(CH₂CH₂OCH₂CH₂)C₅H₄) ( 1 ) has been prepared by treating two equivalents of CpTiCl₃ with the corresponding dilithium salts of the ligand C₉H₇(CH₂CH₂OCH₂ CH₂)C₅H₅. The complex 1 was characterized by ¹H‐, ¹³C‐NMR, and elemental analysis. Homogenous ethylene polymerization catalyzed using complex 1 has been conducted in the presence of methylaluminoxane (MAO). The influences ofreaction parameters, such as [MAO]/[Cat] molar ratio, catalyst concentration, ethylene pressure, temperature, and time have been studied in detail. The results show that the catalytic activity and the molecular weight (MW) of polyethylene produced by 1 /MAO decrease gradually with increasing the catalyst concentration or polymerization temperature. The most important feature of this catalytic system is the molecular weight distribution (MWD) of polyethylene reaching 12.4, which is higher than using common mononuclear metallocenes, as well as asymmetric dinuclear titanocene complexes like [(CpTiCl₂)₂(η⁵‐η⁵‐C₉H₆(CH₂)_nC₅H₄)] (n = 3, MWD = 7.31; n = 4, MWD = 6.91). The melting point of polyethylene is higher than 135°C, indicating highly linear and highly crystalline polymers. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

New potential silane coupling agents

The synthesis of two new potential silane coupling agents is described and commented on. These agents are HOSiPcOSi-(CH₃)₂CH₂CH₂C₆H₄CH₂I-m and p and HOSiPcOSi(CH₃)₂-CH₂CH₂C₆H₄CH₂NHCH₂CH₂NH₂-m and p (Pc = phthalocyaninato ligand). In addition, a discussion of agents of the general class to which these two agents belong is given. In this discussion some of the special features of agents of this class are pointed out, e.g., the octahedral coordination of the silicon atoms in the agents having the potential to oxygen-bridge to glass surfaces. Special features of the glass-polymer linkages which these agents have the potential to form are also pointed out. Finally, the synthesis of the model isomer mixture HOSi-PcOSi(CH₃)₂CH₂CH₂C₆H₄CH₂N (CH₂CH₃)₂-m and p is described, and a very brief discussion of this model mixture is given.     

Theoretical Estimation of Acid Strength of Fluorine Hydrogen-Boron Fluoride Complexes

Abstract

The calculation of complexes R _n BF_3-n . HF (there is R = CH₃ and C₂H₅) has been carried out by the quantum-chemical semi-empirical MNDO method in Dewar and Teel parameterization. The geometrical and electronic structure of these complexes was obtained. On an example of simple H-acids we estimated their acid strength. We found that irrespective of the ligand surrounding of B atom the complexes R _n BF_3-n HF have rather high acid strength (pK _a = 17.9 14.9).