Catalytic Air Oxidation Research Articles

Petrochemicals: the chemistry of catalyzed air oxidation of fossil hydrocarbons

The reaction mechanisms and the selective products formed during the air oxidation of some important industrial paraffins and arenes catalysed homogeneously by transition metal complexes such as Cu(I), Co(II), and Mn(II) are discussed. In addition, the main uses of the major products generated from these catalytic air oxidation processes are summarized.

Catalyzed Air Oxidation of Thiosalts

AbstractMill tailings waters containing thiosalts, when discharged into river systems constitute a severe environmental pollution problem. Complete oxidation of thiosalts to sulfuric acid by chemical means and neutralization of the acid prior to discharge of the effluent to receiving streams has long been considered a viable solution to the problem; subject to development of a simple and economic means of oxidation of thiosalts in large volumes of wastewater. In this context, the possibility of using catalyzed air oxidation of thiosalts to sulfate became the subject of active research and investigation ever since our finding of the ability of suitably complexed copper ions to catalyze the oxidation of thiosulfate by molecular oxygen. Extensive research has been carried out on the design and development of heterogeneous catalysts having this property. This work has involved the preparation of a number of polymer supported copper complexes for utilization in the air oxidation of polythionates. Recently, att...

Catalyzed Air Oxidation of Thiosalts

Mill tailings waters containing thiosalts, when discharged into river systems constitute a severe environmental pollution problem. Complete oxidation of thiosalts to sulfuric acid by chemical means and neutralization of the acid prior to discharge of the effluent to receiving streams has long been considered a viable solution to the problem; subject to development of a simple and economic means of oxidation of thiosalts in large volumes of wastewater. In this context, the possibility of using catalyzed air oxidation of thiosalts to sulfate became the subject of active research and investigation ever since our finding of the ability of suitably complexed copper ions to catalyze the oxidation of thiosulfate by molecular oxygen. Extensive research has been carried out on the design and development of heterogeneous catalysts having this property. This work has involved the preparation of a number of polymer supported copper complexes for utilization in the air oxidation of polythionates. Recently, attention has been focused on the application of copper sulfide containing materials for this oxidation process. The results obtained in this comprehensive study are summarized and discussed.

Catalytic air-oxidation reactions promoted by cationic complexes of rhodium(I): competitive ketonization, allylic oxidation and epoxidation of olefins

Rhodium(I) complexes [Rh(LL) 2]BF 4 with bidentate ligands LL (among which diphosphines) are able to catalyze the air oxidation of olefins in mild conditions and in (primary and secondary) alcohol solutions. The primary oxidation products are ketones, epoxides and allyl ethers. The selectivities for any one of the products depend on the nature of the olefin employed. Ketonization is predominant in the case of terminal linear alkenes and cyclooctene, while other cyclic olefins mainly yield products of allylic oxidation, as do terminal branched olefins. Acyclic internal olefins oxidize slowly to a mixture of ketones and allyl ether. In almost all cases little, but significant, epoxidation occurs.

Cuprous oxide catalyzed air oxidation of thiosulfate and tetrathionate

Thiosulfate (S 2O 3 2−) and tetrathionate (S 4O 6 2−)are oxidized to sulfate by air at atmospheric pressure and 50–70°C in the presence of cuprous oxide (Cu 2O) as catalyst. Sulfate is produced from S 2O 3 2− by series-parallel reaction paths involving S 4O 6 2− as an intermediate. The rate data obtained for air oxidation of S 2O 3 2− on Cu 2O agree well with a pseudo-homogeneous first order kinetic scheme, yielding values of rate constants for series parallel reaction paths which have been used in modelling the catalyzed air oxidation of S 2O 3 2−. Air oxidation of S 4O 6 2− on Cu 2O proceeds at a higher rate in the presence of S 2O 3 2− than in its absence. Cu 2O is less active than Cu 2S for the air oxidation of S 2O 3 2−, as shown by the rate constant values which for Cu 2O catalyzed oxidation are an order of magnitude smaller than those for the Cu 2S catalyzed oxidation.

Catalysed air oxidation of thiosulfate and tetrathionate for pollution abatement

Thiosulfate and tetrathionate are oxidized to sulfate by air at atmospheric pressure in the presence of CuS, Cu 2S or chalcopyrite (CuFeS 2) concentrate under mild temperature conditions (30–60°C). In the presence of CuS and Cu 2S, sulfate is produced from thiosulfate by series-parallel reaction paths involving tetrathionate as an intermediate product. However, in the presence of chalcopyrite which contains ferric iron, thiosulfate is rapidly and quantitatively oxidized to tetrathionate which then undergoes slow oxidation to sulfate. Of the three chalcopyrite concentrates used in this work; viz., Opemiska, Bethlehem and Lornex, best results were obtained with the Opemiska concentrate. In the presence of this material used as a 15% slurry in water, 450 ppm thiosulfate (S 2O 3 2−) is completely oxidized to sulfate by air in 24 hours at 30°C and in 9 hours at 40°C. Use in slurry reactors in continuous operation over several weeks shows that the catalytic activity of the chalcopyrite concentrate remains constant, obviating the need for any regeneration treatment. The rate data obtained with CuS, Cu 2S and chalcopyrite concentrates agree well with a pseudo-homogeneous first order kinetic scheme, yielding values of rate constants for series-parallel reaction paths which have been used in modelling, successfully, the catalyzed air oxidation of thiosulfate.

Kinetics of the catalytic air oxidation of o-xylene over a commercial V 2O 5-TiO 2 catalyst

The gas-phase oxidation of o-xylene over a commercial V 2O 5-TiO 2 catalyst was studied in fixed bed non-isothermal reactor. The experiments were carried out at initial o-xylene concentrations which differed greatly from each other. The following reaction network was suggested. ▪ It is suggested to use the Langmuir-Hinshelwood kinetic model in which a surface reaction between o-xylene and oxygen, chemisorbed on separate active centres, is the limiting step. It seems that the redox model is not adequate for the kinetic description of o-xylene oxidation.

Catalytic air oxidation of benzoin in the presence of dioxomolybdenum(VI) complexes with sulphur chelate ligands

Catalytic air oxidation of benzoin to benzil in N,N-dimethylformamide (dmf) occurred in the presence of [MoO2(cysS-OR)2][cysS-OR = S-deprotonated cysteine alkyl ester; R = Me (1) or Et (2)], [MoO2(S2CNEt2)2](3) or [MoO2(cysS-NHC10H21)2](4)(cysS-NCH10H21= S-deprotonated cysteine n-decylamide), [Mo2O3(cysS-OMe)4](5), or [Mo2O3(S2CNEt2)4](6) with conversions of 1 500, 1 200,1 000, 1 800, 1 300, and 900%([Mo]/[benzoin]= l/20, 20 h, 30 °C), respectively. The initial first-order rate constants ranged from 0.012 to 0.048 s–1(per mol of catalyst). Slow deactivation of the catalysis by complexes (1)–(3) was observed due to the formation of di-µ-oxo binuclear molybdenum(V) complexes from µ-oxo binuclear molybdenum(V) complexes. The oxidation in the presence of (4) proceeds without deactivation. In the stoicheiometric reduction of complex (2) with benzoin the absence of any e.s.r. signal due to a mononuclear molybdenum(V) species indicates that a molybdenum(IV) species formed by a two-electron transfer process is aerobically converted into a µ-oxo binuclear molybdenum(V) complex. An 1H n.m.r. study showed that the initial proton transfer from the benzoin OH group to MoO is followed by elimination of a proton from the benzoin methine group to form a carbonyl group.

Catalyzed air oxidation for treatment of thiosalt effulents

Continuous slurry reactor runs of two to four weeks duration were carried out for catalyzed air oxidation of thiosalts under a variety of conditions using poly (4-vinylpyridine) - Cu (II) and quaternized poly (4-vinylpyridine) - Cu (II) catalysts. Results obtained indicate that these catalysts have high activity and relatively long-term catalyst stability for thiosalt waste streams of < 1000 ppm thiosalt level. Using 2% (w/w) slurries of the poly (4-vinylpyridine) Cu (II) catalyst, effective oxidation of 700 ppm S 2O 3 2− influent to an effluent of < 100 ppm total thio-salts can be carried out continuously for at least one month when operating at 20 to 30°C with solution flow rates of$˜1l/h and aeration of 1300 XXX/h using a two-stage reactor system comprised of 12 l reactors. At higher thiosalt influent levels (i.e. > 1600 ppm) increased reaction temperatures enable depletion to < 100 ppm thiosalt effluent levels for up to one week of continuous operation. The catalysts deactivate much more readily at these higher influent levels as a result of greater copper losses and appreciable adsorption of S 2O 3 2− and S 4O 6 2−. The behaviour of continuous slurry reactors employed in the experimental studies, by use of batch reaction data for the poly (4-vinylpyridine) Cu (II) catalyzed oxidation of thiosalts, can be modelled successfully. Quaternized poly (4-vinylpyridine) Cu (II) catalyst has good long-term stability and copper losses are very low. The poly (4-vinylpyridine) Cu (II) catalyst, however, is susceptible to appreciable oxidation of the polymer matrix on long-term usage. This oxidation of the polymer matrix results in a substantial loss in the activity of the regenerated catalyst.

Model reactions of molybdo-oxidase. Importance of water on the air oxidation of PPh3 by catalysis of [Mo VI O2(Cys-OR)2](Cys-OR = S-deprotonated cysteine ester; R = Me, Et, Pri, or CH2Ph) in NN-dimethylformamide

Catalytic air oxidation of PPh3 using [MoVIO2(Cys-OR)2](Cys-OR = S-deprotonated cysteine ester; R = Me, Et, Pri, or CH2Ph) in NN-dimethylformamide was found to require the presence of water. 18-Oxygen of H218O has been shown to be involved in the oxidation of PPh3 both stoicheiometrically and catalytically. However, a large excess of water prevents the catalytic redox cycle. The results of e.s.r. and 1H n.m.r. spectra of the reduced species from [MoVIO2(Cys-OR)2] indicate that a mononuclear Mov complex [MoO(OH)(Cys-OR)2] is probably involved in the catalytic cycle, while [Mov2O3(Cys-OR)4] is not. An increase in the bulkiness of R increases the turnover numbers of the oxidation.

Cysteine-Thiolato Dioxomolybdenum(VI) Species Supported by Water Soluble Poly(ethylene glycol) as a Molybdo-Oxidase Model. Its Enhanced Oxidative Ability in Water as Shown by the CD Spectral Investigation

Water-soluble MoO2(cys-O-PEG)2 as a model for molybdo-oxidases was prepared from t-butyloxycarbonyl-L-cysteine(S-acetamidomethyl)-O-(CH2CH2O)n–OH (t-Boc-Cys(Acm)-O-PEG, n=45), and HgCl (t-Boc-cys-O-PEG). The macromolecular Mo(VI) complex readily decomposed in water, forming a disulfide derived from the cys-PEG ligands. MoO2(cys-O-PEG)2 in water causes the catalytic air oxidation of PPh3 or P(OMe)3. The role of the hydrophobic environment surrounding the active site of molybdenum oxidase was found to protect the Mo(VI)/ Mo(V) site from water in bulk. The model dioxo-Mo(VI) complexes are generally insoluble in water thus making it impossible to examine their redox behavior toward biological redox agents.

Oxygen-18 study of nonaqueous-phase oxidation of sulfur dioxide

In a study of the mechanisms of atmospheric sulfate formation, oxygen isotope ratios were measured in sulfates and in the SO 2 and water vapors from which they were formed, in the absence of liquid water. In a 3-ℓ glass chamber, SO 2 and water vapor of various 18O contents were isotopically equilibrated, and then air oxidation of the SO 2 to sulfate was performed by four different methods: high-voltage discharges, NO 2 addition, gamma irradiation and adsorption on activated charcoal. Isotopic equilibration between SO 2 and water vapor proceeded rapidly, resulting in a strong dependence of the δ 18O of the sulfate on that of the water vapor. Oxidation of SO 2 on dry charcoal occurred through the apparent formation of 9-oxygen, 2-sulfur, chemisorbed molecules which decomposed to sulfate in leach water. The δ 18 O SO 2− 4 vs δ 18 O H 2 O relationships observed for these four nonaqueous-phase oxidations of SO 2 to sulfate, together with those in three previously reported aqueous-phase oxidations ( Fe 3+-catalyzed air oxidation, charcoal-catalyzed air oxidation and H 2 O 2 oxidation), were compared to sulfate in rain and snow collected at Argonne, IL. The δ 18 O of sulfate in precipitation water was significantly higher than could be accounted for by any of the several oxidation reactions that were investigated as possible pathways in the formation of secondary sulfates in the atmosphere, either singly or in combination.

Direct gas chromatographic determination of the products of catalytic air oxidation of n-butene-1 to maleic anhydride in the gaseous reaction mixture

Direct gas chromatographic determination of the products of catalytic air oxidation of n-butene-1 to maleic anhydride in the gaseous reaction mixture

Kinetics of the catalytic air-oxidation of o-xylene measured in a tube-wall-catalytic reactor

The kinetic parameters in a complex reaction network (oxidation of o-xylene over V 2O 5) were derived by multiresponse analysis of rate data from a tube-wall-catalytic reactor using two different catalysts. The 2D model of this reactor was reduced to 1-D format by a systematic method of analysis which was computationally acceptable. The results show that the incorporation of T i O 2 into V 2O 5, alters the kinetic parameters so that precursors of phthalic anhydride are less in evidence than is the case with V 2O 5 alone.

Kinetics of the catalytic air-oxidation of o-xylene measured in a tube-wall-catalytic reactor

The kinetic parameters in a complex reaction network (oxidation of o-xylene over V 2O 5) were derived by multiresponse analysis of rate data from a tube-wall-catalytic reactor using two different catalysts. The 2D model of this reactor was reduced to 1-D format by a systematic method of analysis which was computationally acceptable.

Effects of an interchain disulfide bond on tropomyosin structure: Differential scanning calorimetry

An interchain disulfide bond is readily formed between cysteines located at equivalent positions (190) on each of the two chains of rabbit skeletal tropomyosin (Tm) by Cu”-catalyzed air oxidation [ 1,2] or by Nbsz reaction [3] . In order to determine how this crosslink affects the structure of Tm and what relevance it may have to its function, we studied the thermal and denaturant induced unfolding profiles by spectroscopic methods [4]. Two effects of the crosslink were apparent in the unfolding profiles. A shift of the major unfolding transition to higher temperature or greater denaturant (GuHCI) concentrations and the appearance of a pretransition in the 30&45”C region or the O-2 M GuHC1 region. Previous comprehensive studies of Tm unfolding which were done in the presence of reducing agent to prevent disulfide bond formation obtained evidence that partially unfolded intermediates exist prior to the beginning of the major transition and that the appearance of dissociated subunit species coincided with the major unfolding transition (2-3 M GuHCl)

The prediction of the performance of packed-bed catalytic reactors in the air-oxidation of o-xylene

The kinetics of the catalytic air-oxidation of o-xylene to phthalic anhydride over various commercial V 2O 2 and TiO 2-V 2O 2 catalysts are extended and a model derived which correctly predicts the temperature and yield profiles in a quasi-isothermal fixed-bed reactor of commercial dimensions. The model predicts the relative freedom from thermal “run-away” of commercial fixed-bed reactors and is used to demonstrate the possibilities of operation at elevated Xylene concentrations. In what follows, XH, TA, PI and PA refer to o-xylene o-tolualdehyde, phthalide and phthalic anhydride respectively, sometimes abbreviated to A, B, C and D.

Kinetics of vapor-phase oxidation of methyl alcohol on vanadium pentoxide-molybdenum trioxide catalyst

The vapor phase catalytic air oxidation of methanol to formaldehyde over vanadium pentoxide-molybdenum trioxide was investigated between 250 and 530 °C at atmospheric pressure. By using gas chromatographic technique, accurate analysis of the products were obtained, and the effects of several process variables on the conversion of methanol and the selectivity of the catalyst for formaldehyde formation were determined. The maximum yield of formaldehyde (100% selectivity) and more than 99% conversion were achieved at 466 °C for a W F ratio of 31.7 g h/mole, containing 8% methanol in the feed. The rate expression, r = [ k 1p M 1 + ( k 1p M 2k 2 p O 2 0.5 )] , deduced assuming a steady state involving a two-stage irreversible oxidation-reduction process represented the data very satisfactorily.

Platinum catalyzed air oxidation of hindered phenols

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTPlatinum catalyzed air oxidation of hindered phenolsEugene F. Lutz and Paul H. WilliamsCite this: J. Org. Chem. 1969, 34, 11, 3656–3658Publication Date (Print):November 1, 1969Publication History Published online1 May 2002Published inissue 1 November 1969https://doi.org/10.1021/jo01263a107RIGHTS & PERMISSIONSArticle Views53Altmetric-Citations4LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (376 KB) Get e-Alerts Get e-Alerts

Kinetics of cupric oxide catalysed oxidation of propylene in a stirred reactor

AbstractThe catalytic air oxidation of propylene to acrolein over a supported copper oxide catalyst was investigated in a continuous stirred vessel reactor between 375° and 450°C at atmospheric pressure. The effect of temperature, ratio of oxygen to propylene in feed and total feed rate (or contact time) on the conversion of propylene and the yield of acrolein were determined. It was found that with an increase in temperature, ratio of oxygen to propylene and contact time, the yield drops considerably though conversion increases.A study of the mixing characteristics of the stirred vessel reactor was carried out by following the conversion at various stirrer speeds.The kinetic data obtained were tested to determine the most probable model by the Hougen‐Watson method. The model that satisfactorily correlated the data describes the rate‐controlling step as the surface reaction occurring between adsorbed propylene, a vacant site and oxygen in the gas phase. The following Hougen‐Watson type rate equation has been proposed The constants in the rate equation have been expressed as a function of temperature.