The paper describes the influence of a series of bis(arylimino)acenaphthenes (R-bian) and mono(arylimino)acenapthenones (R-mian) in the aerobic oxidation of cumene. The imines facilitate the decomposition of minor impurities of cumene hydroperoxide, thereby acting as catalysts for the oxidation of cumene. The relative reactivity of imines in the oxidation of cumene is correlated with the relative electron-withdrawing ability of the aryl functional groups of CF3-Ph>dpp, tmp. This is demonstrated by the reactivity of dpp-mian, tmp-mian and dpp-bian, tmp-bian<CF3-Ph-bian. A comparable interaction between R-bian and NHPI enhances the solubility of the radical catalyst in cumene and intensifies NHPI-catalyzed oxidation to attain 25-30 % conversion of cumene with dpp-bian and tmp-bian promoters. The reported results present a straightforward organocatalytic system based on the utilization of imines as catalysts and promoters.

The properties of Pd-modified Cu-ZSM-5 catalysts in liquid-phase methane peroxidation have been studied. The catalysts were prepared by polycondensation of Cu2+ and Pd2+ ions in the zeolite pores. Solutions of ammonia or ammonium complexes of one of the introduced metals were used as an alkaline agent promoting the polycondensation of hydrated metal ions. The electronic states of Cu2+ and Pd2+ ions and the acidic and redox properties of the catalysts, as well as their textural characteristics, were studied. Associated Cu2+ ions and polynuclear hydroxo/oxo complexes of Cu2+/Pd2+ ions were found to form in the pores during polycondensation, which are located in the channels and on the surface of zeolite crystallites. The addition of Pd affects the redox, acidic, and catalytic properties of Cu-ZSM-5, but this effect does not always lead to increased selectivity of the process with respect to liquid oxygenates (methanol and formic acid). Among the bimetallic catalysts, Cu/Pd-ZSM-5 was the most active catalyst, which was most selective for liquid oxidation products; it was synthesized by introducing [Cu(NH3)4]2+ ions after Pd2+ ions. It was assumed that its catalytic characteristics are associated with the lower strength of Cu2+–LAS and higher stability of isolated Cu2+ ions and polynuclear PdO-like clusters against reduction compared with the same characteristics of the sample obtained by simultaneous introduction of Cu2+ and Pd2+.

Cumene hydroperoxide (CHP) is the most important product or intermediate in the oxidative processing of cumene. In the present study, cooperative action of NHPI catalyst with Fe(acac)(3)/Phen additives in oxidation of cumene has been described in terms of oxidation rate and selectivity for products, notably CHP, under variable conditions. The oxidation characteristics were influenced by promoting additives, the main function of which was to generate an active PINO radical. An abundance of the additives might enhance the non-selective conversion of intermediates and decomposition of CHP, which led to a decrease in CHP selectivity. The addition of 0.0003 mol% Fe(acac)(3) was sufficient to initiate NHPI catalyzed fast cumene oxidation and very selective CHP production at 50 degrees C. Phen showed an impressive multifaceted effect, as the increase in its amount initially lowered the CHP selectivity and then increased to 95% with a large excess of Phen over Fe(acac)(3). That was due to the different ability of iron complexes of various compositions to react to NHPI and to CHP. UV-VIZ spectroscopy and DFT calculation was used to elucidate assistance of Phen in reduction of Fe(acac)(3) with NHPI and creation of Fe-II/Fe-III-Phen(2or3) complexes as reversible single-electron carriers upon catalysis by NHPI. In addition, the selective formation of CHP contributes to the resistance of NHPI to degradation during catalysis.

Highly efficient oxidation of isopropylbenzene mediated by the system of NHPI/Fe(acac)(3)/Phen has been carried out at temperature as low as 60 degrees C. Significant improvement of catalysis by NHPI was associated with an enhanced oxidizing ability of Fe(III) tandem with Phen, which caused the intense generation of PINO. Furthermore, NMR observations revealed formation of a hydrogen-bonded NHPI-Phen adduct soluble in acetonitrite and isopropylbenzene. Based on this phenomenon, the system was applicable for the oxidation of solvent-free isopropylbenzene. The promise of the system of NHPI/Fe(acac)(3)/Phen for the selective synthesis of isopropylbenzene hydroperoxide was demonstrated by oxidation at a low content of Fe(acac)(3).

Effect of the oligomeric unsaturated polyketone (UPK) additive on the rheological properties, vulcanization, and structural characteristics of elastomeric compositions based on butadiene and nitrile-butadiene rubbers containing N-cyclohexyl-2-benzothiazolylsulfenamide (sulfenamide C) as vulcanizing accelerator is investigated. It was demonstrated using IR and NMR spectroscopy that sulfenamide C reacts with polyketone. A mechanism for such interaction, which includes the sequential addition of benzothiazyl sulfide and amine fragments to the oligomeric chain, was proposed.

The deep processing of heavy oil increases the production of hydrocarbon gases. The resulting butanes do not always find an equivalent market. A mixture of oxygenates with a high octane number is obtained in this work via oxidation of industrial isobutane fraction. The reaction proceeds both in with and without using Au/Silicalite-1 and Cu/SiO 2 as catalysts. The influence of factors that reduce the formation of undesirable impurities (hydroperoxides, peroxides, and acids) is studied. Tert -butyl alcohol (TBA) obtainable with a selectivity of 64–69% and butane conversion of 55–69% is a target product. TBA has a RON of 113. Alcohols and ketones having RONs within 106–115 appear together with TBA during the oxidation. The best result was obtained for a Cu/SiO 2 catalyst. More than 18% of TBA and 2.9 times more ketones are removed from a unit volume of a reaction space in the presence of a catalyst than during oxidation without a catalyst. The total productivity of the products suitable as high-octane components is 40 g/(L h), while the RON of this mixture is ≈111. A mixture of oxygenates including TBA has a lower volatility than that of methyl tert -butyl ether, which is especially important for the stability of gasolines in summer.

The application of nitrous oxide as an alternative oxidant provides new opportunities for selective oxidation of olefins. Here, we studied for the first time the thermal oxidation of isobutene with N2O in the liquid phase. The study revealed that the oxidation proceeds via 1,3-dipolar cycloaddition of N2O to the CC bond by two routes forming unstable 4,5-dihydro-[1,2,3]-oxadiazole intermediates. The main route (the contribution of 91%) includes the addition of the N2O oxygen to the second carbon atom in olefin. In this case, the oxadiazole decomposes with the CC bond cleavage yielding acetone, methylene (:CH2), and N2. The methylene then readily reacts with isobutene and benzene (solvent). The minor route involves the addition of the N2O oxygen to the first carbon atom and the oxadiazole decomposition with a hydrogen shift leading to isobutanal and N2.

Selective oxidation of cyclohexene to cyclohexenyl hydroperoxide catalyzed by N-hydroxyphthalimide (NHPI) was studied. Kinetic observations and 13C and 1H NMR spectroscopy showed that accumulation of cyclohexenyl hydroperoxide was accompanied by deactivation of the catalyst. A mechanism of the deactivation through phthalimido N-oxyl radical (PINO) addition to vinyl position of olefin was suggested. Responsible for the deactivation, PINO-C6H10-OOH hydroperoxide adducts were detected in the reaction conditions, and their molecular structure was elucidated by DFT technique. The mechanism explained an unexpected experimental effect, that is, lowering the oxygen partial pressure improved the stability of NHPI without decrease in production of cyclohexenyl hydroperoxide.

Liquid phase oxidation of olefins with nitrous oxide is a promising synthetic route to ketones. The effect of cis/trans isomerism on the reactivity of olefins towards N2O and on the reaction mechanism was studied for the first time using 3-heptene oxidation as an example. Our experimental study revealed that cis- and trans-isomers of 3-heptene have similar reactivity and yield the same set of products. However, the cis/trans isomerism of the olefin has a pronounced effect on the reaction route involving the cleavage of the initial CC bond and, accordingly, on the products ratio. The yield of ketones is lower for the trans-isomer due to higher contribution of the cleavage route.

The reaction of tyre rubber crumb with nitrous oxide (N2O) in an organic solvent at 180-230 degrees C and pressure of 3-5 MPa was studied. The process is accompanied by controllable destruction of vulcanised rubber with the formation of a plastic reclaim product consisting of a sol and gel fractions. The amount of the sol fraction increases proportionally to the conversion of the rubber C=C bonds in the reaction with N2O and can be regarded as a measure of the degree of vulcanisate destruction. The method is applicable to the recycling of both rubber crumb and tyre chips. (C) 2012 Elsevier Ltd. All rights reserved.

Activity and selectivity of supported Ni, Pt, and Pd catalysts were studied in the liquidphase reductive amination of cyclohexanone at temperatures ranging from 100 to 150 °C. The catalyst 20% Ni/SiO 2 is most active and selective providing a maximum yield of cyclohexylamine. The influence of the reaction conditions on the parameters of the catalytic process was studied. A detailed analysis of the reaction products was carried out using 13 C NMR spectroscopy and gas chromatography coupled with mass spectrometry (GC-MS). This made it possible to refine the reaction mechanism and to identify a new by-product earlier unknown in the literature.

Polytrimethylsilylpropyne with the decomposition temperature 205°C was synthesized and characterized. The effect of chemical modification by polytrimethylsilylpropyne on the gas chromatographic properties of polymeric adsorbents and the diatomite carrier for the selective separation of C 1 –C 10 hydrocarbons, alcohols and aromatic and sulfur-containing compounds was studied.

The kinetics and mechanism of noncatalytic liquid-phase oxidation of but-1-ene and but-2-ene with nitrous oxide in a benzene solution in the temperature range from 180 to 240°C were studied. Oxidation proceeds via the 1,3-dipolar cycloaddition mechanism to form carbonyl compounds. Both of these reactions occur with close rates and activation energies and have the first orders with respect to the alkene and N 2 O. A considerable fraction (39%) of but-1-ene involved in oxidation undergoes cleavage at the double bond yielding propanal and an equivalent amount of methylene, the latter producing ethylcyclopropane and cycloheptatriene. The oxidation of but-2-ene proceeds with a minimum bond cleavage and affords methyl ethyl ketone with 84% selectivity. Regularities of the oxidation of terminal and internal alkenes C 2 —C 8 with nitrous oxide were analyzed using the previously published data.

A detailed in situ C-13 and H-1 NMR spectroscopic characterization of the following families of alkylperoxo complexes of titanium is presented: Ti(eta(2)-OOtBu)(n) (OiPr)(4-n), where n = 1-4; binuclear complexes [(iPrO)(3)Ti(mu-OiPr)(2)Ti(OiPr)(2)(eta(2)-OOtBu)] and [(eta(2)-OOtBu)(iPrO)(2)Ti(mu-OiPr)(2)Ti(OiPr)(2)(eta(2)-OOtBu)]; complexes with beta-diketonato ligands: Ti(LL)(2)(OEt)(eta(2)-OOtBu), Ti(LL)(2)(Oipr)(eta(2)-OOtBu), Ti(LL)(2) (eta(2)-OOtBu)(2), Ti(LL)(2)(OtBu)(eta(1)-OOtBu), where HLL = acetylacetone, dipivaloylmethane. These alkylperoxo complexes could not be isolated due to their instability and were studied in situ at low temperatures. Whereas the side-on (eta(2)) coordination mode of tert-butylperoxo ligand is generally preferable, the end-on (eta(1)) coordination caused by spatial hindrance from surrounding bulky ligands is found in two cases. The quantitative data on the reactivity of alkylperoxo complexes found towards sulfides and alkenes were obtained. The system TiO(acac)(2)/tBuOOH in C6H6 was reinvestigated using C-13 and H-1 NMR spectroscopy. The structure of the complex Ti(acac)(2){CH3C(O)(OOtBu)COO} actually formed in this system was elucidated. Four types of titanium(IV) alkylperoxo complexes were detected in the Sharpless-Katsuki catalytic system using C-13 NMR spectroscopy. (C) 2003 Elsevier Science B.V. All rights reserved.

The kinetic data on ethylene polymerization over homogeneous catalysts based on -1,6-bis[1-(2,6-dimethylphenylimino)ethyl]pyridineiron(II) and cobalt(II) chlorides (LMCl2, M = Fe, Cc) with different aluminium-organic activators (MAO, AlMe3, Al(i-BU)(3)) are reported. LFeCl2 is very effective with AlMe3 and Al(i-Bu)(3) as activator and LCoCl2 is highly active in the presence of AlMe3. For MAO as activator, the activity depends on the content of free AlMe3 in MAO. Maximal activity has been found for MAO completely purified from free AlMe3. According to H-1 and H-2 NMR study, formation of the similar neutral intermediates of the type [LFe(II)Me(mu-Me)(2)AlMe2] have been detected for LFeCl2/AlMe3 and LFeCl2/MAO catalysts. In the system LCoCl2/MAO, the complex of the type LCo(II)Me(X).MAO (X = Me or CI) with terminal Co-Me group is detected. Interaction of LCoCl2 with AlMe3 results in the formation of diamagnetic Co(I) species.Highly active supported catalysts SiO2/LFeCl2 + AIR(3) and SiO2/MAO/LFeCl2 have been prepared. In contrast to homogeneous systems, the supported catalysts are stable at elevated temperatures of polymerization (70 degreesC) and produce high molecular mass polyethylene with improved morphology. (C) 2002 Elsevier Science B.V All rights reserved.

The structures of intermediates generated by the activation of 2,6-bis[1-(2,6-dimethylphenylimino)ethyl]pyridineiron(II) chloride ( 1 ) with various cocatalysts, methylalumoxane (MAO), trimethylaluminum (TMA), and TMA in combination with B(C 6 F 5 ) 3 and Ph 3 CB(C 6 F 5 ) 4 , is studied by 1 H and 2 HNMR spectroscopy. The 1/AlMe 3 system exhibits a higher catalytic activity in ethylene polymerization than the 1/MAO system. The activity of the latter decreases sharply with a decrease in the amount of AlMe 3 in MAO. Neutral Fe(II) complexes rather than cationic intermediates are suggested to be active components in both catalytic systems.

Using 51V, 17O, 13C and 1H NMR spectroscopy, vanadium(V) alkylperoxo complexes VO(OOtBu)k(OnBu)3-k, where k = 1, 2 and 3, were characterized in the reaction of VO(OnBu)3 with tBuOOH in CH2Cl2.

In this work the first-order rate constants of self-decomposition of hydroperoxo and alkylperoxo complexes [Fe(bpy)2(OOH)Py](NO3)2 (2a-Py), [Fe(phen)2(OOH)Py](NO3)2 (2b-Py) and [Fe(bpy)2(OOtBu)CH3CN](NO3)2 (3a-CH3CN) were determined in the presence of various substrates and at various temperatures. It was observed, that the alkylperoxo species are far less stable than corresponding hydroperoxo intermediates, k=1.2×10−2 s−1 (3a-CH3CN in CH3CN at −10°C) and k=2×10−4 s−1 (2a-Py in CH3CN at −10°C). The sixth ligand (Py in 2a-Py and 2b-Py; CH3CN in 3a-CH3CN) can be replaced by other donor molecules B in appropriate solvent systems. Using d9-tBuOOH, 2D NMR signals of tBuOO moieties of complexes 3a-CH3CN, 3a-CH3OH and 3a-H2O were observed. The rate of decomposition of hydroperoxo complexes [Fe(bpy)2(OOH)B](NO3)2 (2a-B), where B are derivatives of Py (3-Br-Py, 3-Me-Py, 4-Me-Py and 4-Me2N-Py) increases with the growth of basisity of B (push effect). Such effect is markedly smaller for alkylperoxo species [Fe(bpy)2(OOtBu)B](NO3)2 (3a-B). The addition of organic substrates (cyclohexane, cyclohexene, methyl phenyl sulfide) in concentrations up to 3 M at −10°C to +20°C does not noticeably change the rate of self-decomposition of 2a-B, [Fe(phen)2(OOH)B](NO3)2 (2b-B) and 3a-B. Thus the intermediates concerned do not directly react with organic substrates. The reactivity patterns of 2a-B, 2b-B and 3a-B were characteristic for free radical oxidation. OH· and HO2· radicals were trapped in solution containing 2a-Py, and tBuOO· free radicals were detected in solution in the presence of 3a-B. The determined rates of self-decomposition of complexes 2a-B, 2b-B and 3a-B can be used for evaluation of the upper limit for their reactivity towards organic substrates.

Using 13 C and 1 H NMR spectroscopy, titanium(IV) alkylperoxo complexes Ti(OO t Bu) n (O i Pr) 4−n with n=1, 2, 3 and 4 were characterized in the reaction of Ti(O i Pr) 4 with t BuOOH in CH 2 Cl 2 and CDCl 3 .

Using stable nitroxyl radical 2,2,6,6-tetramethylpiperidine-N-oxyl (TEMPO) as a spin probe, Lewis acidic sites of methylaluminoxane (MAO) were identified. It was found that MAO contains two types of acidic sites. TEMPO, coordinated to the sites I and II, exhibits in the EPR spectra triplet (go=2.0047, aN=18.6 G) and triplet of sextets (go=2.0045, aN=19.6 G and aAl=1.7 G), respectively (aN and aAl are constants of hyperfine structure from the corresponding nucleus). According to EPR measurements, concentration of sites I is close to that of sites II, and MAO contains one site of each type per 100±30 aluminium atoms. The adducts of TEMPO with sites I are less stable than those with sites II. Based on the values of aAl and relative stabilities of the adducts with TEMPO, the acidic sites I and II were attributed to coordinatively unsaturated aluminium atoms in AlOMe2 and AlO2Me environment, respectively. From the EPR spectra of coordinated TEMPO, the average radius of MAO oligomers (AlOMe)n was evaluated to be 5.8 Å at 20°C, which corresponds to the value of n=15–20. Thus, the major part of MAO contains not more than one Lewis acidic site per one oligomeric (AlOMe)n molecule.