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Relevant bibliographies by topics / Alkane Oxidation

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Academic literature on the topic 'Alkane Oxidation'

Author: Grafiati

Published: 4 June 2021

Last updated: 20 February 2023

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Journal articles on the topic "Alkane Oxidation"

1

van Beilen, Jan B., Martin Neuenschwander, Theo H. M. Smits, Christian Roth, Stefanie B. Balada, and Bernard Witholt. "Rubredoxins Involved in Alkane Oxidation." Journal of Bacteriology 184, no. 6 (March 15, 2002): 1722–32. http://dx.doi.org/10.1128/jb.184.6.1722-1732.2002.

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ABSTRACT Rubredoxins (Rds) are essential electron transfer components of bacterial membrane-bound alkane hydroxylase systems. Several Rd genes associated with alkane hydroxylase or Rd reductase genes were cloned from gram-positive and gram-negative organisms able to grow on n-alkanes (Alk-Rds). Complementation tests in an Escherichia coli recombinant containing all Pseudomonas putida GPo1 genes necessary for growth on alkanes except Rd 2 (AlkG) and sequence comparisons showed that the Alk-Rds can be divided in AlkG1- and AlkG2-type Rds. All alkane-degrading strains contain AlkG2-type Rds, which are able to replace the GPo1 Rd 2 in n-octane hydroxylation. Most strains also contain AlkG1-type Rds, which do not complement the deletion mutant but are highly conserved among gram-positive and gram-negative bacteria. Common to most Rds are the two iron-binding CXXCG motifs. All Alk-Rds possess four negatively charged residues that are not conserved in other Rds. The AlkG1-type Rds can be distinguished from the AlkG2-type Rds by the insertion of an arginine downstream of the second CXXCG motif. In addition, the glycines in the two CXXCG motifs are usually replaced by other amino acids. Mutagenesis of residues conserved in either the AlkG1- or the AlkG2-type Rds, but not between both types, shows that AlkG1 is unable to transfer electrons to the alkane hydroxylase mainly due to the insertion of the arginine, whereas the exchange of the glycines in the two CXXCG motifs only has a limited effect.

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2

HAGGIN, JOSEPH. "ALKANE PARTIAL OXIDATION." Chemical & Engineering News 74, no. 12 (March 18, 1996): 6–7. http://dx.doi.org/10.1021/cen-v074n012.p006.

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3

Du, Wenzhou, Yue Wang, Xuelin Liu, and Lulu Sun. "Study on Low Temperature Oxidation Characteristics of Oil Shale Based on Temperature Programmed System." Energies 11, no. 10 (September 29, 2018): 2594. http://dx.doi.org/10.3390/en11102594.

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Oil shale is a kind of high-combustion heat mineral, and its oxidation in mining and storage are worth studying. To investigate the low-temperature oxidation characteristics of oil shale, the temperature, CO, alkane and alkene gases were analyzed using a temperature-programmed device. The results showed that the temperature of oil shale underwent three oxidation stages, namely a slow low-temperature oxidation stage, a rapid temperature-increasing oxidation stage, and a steady temperature-increasing stage. The higher the air supply rate is, the higher the crossing point temperature is. Similar to coal, CO also underwent three stages, namely a slow low-temperature oxidation stage, a rapid oxidation stage, and a steady increase stage. However, unlike coal, alkane and alkene gases produced by oil shale underwent four stages. They all had a concentration reduction stage with the maximum drop of 24.20%. Statistical classification of inflection temperature of various gases as their concentrations change showed that the temperature of 140 °C is the key temperature for group reactions, and above the temperature of 140 °C, all alkane and alkene gases underwent the rapid concentration increase stage.

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Centi, G. "Selective heterogeneous oxidation of light alkanes. What differentiates alkane from alkene feedstocks?" Catalysis Letters 22, no. 1-2 (March 1993): 53–66. http://dx.doi.org/10.1007/bf00811769.

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5

Nagababu, Penumaka, Steve S. F. Yu, Suman Maji, Ravirala Ramu, and Sunney I. Chan. "Developing an efficient catalyst for controlled oxidation of small alkanes under ambient conditions." Catal. Sci. Technol. 4, no. 4 (2014): 930–35. http://dx.doi.org/10.1039/c3cy00884c.

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Catalysis of alkane oxidation by a tricopper complex. The tricopper complex can mediate efficient conversion of small alkanes to their corresponding alcohols without over oxidation under ambient conditions.

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6

Marı́n, Mercedes M., Theo H. M. Smits, Jan B. van Beilen, and Fernando Rojo. "The Alkane Hydroxylase Gene of Burkholderia cepacia RR10 Is under Catabolite Repression Control." Journal of Bacteriology 183, no. 14 (July 15, 2001): 4202–9. http://dx.doi.org/10.1128/jb.183.14.4202-4209.2001.

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ABSTRACT In many microorganisms the first step for alkane degradation is the terminal oxidation of the molecule by an alkane hydroxylase. We report the characterization of a gene coding for an alkane hydroxylase in aBurkholderia cepacia strain isolated from an oil-contaminated site. The protein encoded showed similarity to other known or predicted bacterial alkane hydroxylases, although it clustered on a separate branch together with the predicted alkane hydroxylase of a Mycobacterium tuberculosis strain. Introduction of the cloned B. cepacia gene into an alkane hydroxylase knockout mutant of Pseudomonas fluorescens CHAO restored its ability to grow on alkanes, which confirms that the gene analyzed encodes a functional alkane hydroxylase. The gene, which was namedalkB, is not linked to other genes of the alkane oxidation pathway. Its promoter was identified, and its expression was analyzed under different growth conditions. Transcription was induced by alkanes of chain lengths containing 12 to at least 30 carbon atoms as well as by alkanols. Although the gene was efficiently expressed during exponential growth, transcription increased about fivefold when cells approached stationary phase, a characteristic not shared by the few alkane degraders whose regulation has been studied. Expression of the alkB gene was under carbon catabolite repression when cells were cultured in the presence of several organic acids and sugars or in a complex (rich) medium. The catabolic repression process showed several characteristics that are clearly different from what has been observed in other alkane degradation pathways.

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Hamamura, Natsuko, Chris M. Yeager, and Daniel J. Arp. "Two Distinct Monooxygenases for Alkane Oxidation inNocardioides sp. Strain CF8." Applied and Environmental Microbiology 67, no. 11 (November 1, 2001): 4992–98. http://dx.doi.org/10.1128/aem.67.11.4992-4998.2001.

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ABSTRACT Alkane monooxygenases in Nocardioides sp. strain CF8 were examined at the physiological and genetic levels. Strain CF8 can utilize alkanes ranging in chain length from C2 to C16. Butane degradation by butane-grown cells was strongly inhibited by allylthiourea, a copper-selective chelator, while hexane-, octane-, and decane-grown cells showed detectable butane degradation activity in the presence of allylthiourea. Growth on butane and hexane was strongly inhibited by 1-hexyne, while 1-hexyne did not affect growth on octane or decane. A specific 30-kDa acetylene-binding polypeptide was observed for butane-, hexane-, octane-, and decane-grown cells but was absent from cells grown with octane or decane in the presence of 1-hexyne. These results suggest the presence of two monooxygenases in strain CF8. Degenerate primers designed for PCR amplification of genes related to the binuclear-iron-containing alkane hydroxylase fromPseudomonas oleovorans were used to clone a related gene from strain CF8. Reverse transcription-PCR and Northern blot analysis showed that this gene encoding a binuclear-iron-containing alkane hydroxylase was expressed in cells grown on alkanes above C6. These results indicate the presence of two distinct monooxygenases for alkane oxidation in Nocardioides sp. strain CF8.

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Bruheim, Per, Harald Bredholt, and Kjell Eimhjellen. "Effects of Surfactant Mixtures, Including Corexit 9527, on Bacterial Oxidation of Acetate and Alkanes in Crude Oil." Applied and Environmental Microbiology 65, no. 4 (April 1, 1999): 1658–61. http://dx.doi.org/10.1128/aem.65.4.1658-1661.1999.

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ABSTRACT Mixtures of nonionic and anionic surfactants, including Corexit 9527, were tested to determine their effects on bacterial oxidation of acetate and alkanes in crude oil by cells pregrown on these substrates. Corexit 9527 inhibited oxidation of the alkanes in crude oil byAcinetobacter calcoaceticus ATCC 31012, while Span 80, a Corexit 9527 constituent, markedly increased the oil oxidation rate. Another Corexit 9527 constituent, the negatively charged dioctyl sulfosuccinate (AOT), strongly reduced the oxidation rate. The combination of Span 80 and AOT increased the rate, but not as much as Span 80 alone increased it, which tentatively explained the negative effect of Corexit 9527. The results of acetate uptake and oxidation experiments indicated that the nonionic surfactants interacted with the acetate uptake system while the anionic surfactant interacted with the oxidation system of the bacteria. The overall effect of Corexit 9527 on alkane oxidation by A. calcoaceticus ATCC 31012 thus seems to be the sum of the independent effects of the individual surfactants in the surfactant mixture. When Rhodococcus sp. strain 094 was used, the alkane oxidation rate decreased to almost zero in the presence of a mixture of Tergitol 15-S-7 and AOT even though the Tergitol 15-S-7 surfactant increased the alkane oxidation rate and AOT did not affect it. This indicated that there was synergism between the two surfactants rather than an additive effect like that observed forA. calcoaceticus ATCC 31012.

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Shul’pin, Georgiy B., Yuriy N. Kozlov, and Lidia S. Shul’pina. "Metal Complexes Containing Redox-Active Ligands in Oxidation of Hydrocarbons and Alcohols: A Review." Catalysts 9, no. 12 (December 9, 2019): 1046. http://dx.doi.org/10.3390/catal9121046.

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Ligands are innocent when they allow oxidation states of the central atoms to be defined. A noninnocent (or redox) ligand is a ligand in a metal complex where the oxidation state is not clear. Dioxygen can be a noninnocent species, since it exists in two oxidation states, i.e., superoxide (O2−) and peroxide (O22−). This review is devoted to oxidations of C–H compounds (saturated and aromatic hydrocarbons) and alcohols with peroxides (hydrogen peroxide, tert-butyl hydroperoxide) catalyzed by complexes of transition and nontransition metals containing innocent and noninnocent ligands. In many cases, the oxidation is induced by hydroxyl radicals. The mechanisms of the formation of hydroxyl radicals from H2O2 under the action of transition (iron, copper, vanadium, rhenium, etc.) and nontransition (aluminum, gallium, bismuth, etc.) metal ions are discussed. It has been demonstrated that the participation of the second hydrogen peroxide molecule leads to the rapture of O–O bond, and, as a result, to the facilitation of hydroxyl radical generation. The oxidation of alkanes induced by hydroxyl radicals leads to the formation of relatively unstable alkyl hydroperoxides. The data on regioselectivity in alkane oxidation allowed us to identify an oxidizing species generated in the decomposition of hydrogen peroxide: (hydroxyl radical or another species). The values of the ratio-of-rate constants of the interaction between an oxidizing species and solvent acetonitrile or alkane gives either the kinetic support for the nature of the oxidizing species or establishes the mechanism of the induction of oxidation catalyzed by a concrete compound. In the case of a bulky catalyst molecule, the ratio of hydroxyl radical attack rates upon the acetonitrile molecule and alkane becomes higher. This can be expanded if we assume that the reactions of hydroxyl radicals occur in a cavity inside a voluminous catalyst molecule, where the ratio of the local concentrations of acetonitrile and alkane is higher than in the whole reaction volume. The works of the authors of this review in this field are described in more detail herein.

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Cooley, Richard B., Bradley L. Dubbels, Luis A. Sayavedra-Soto, Peter J. Bottomley, and Daniel J. Arp. "Kinetic characterization of the soluble butane monooxygenase from Thauera butanivorans, formerly ‘Pseudomonas butanovora’." Microbiology 155, no. 6 (June 1, 2009): 2086–96. http://dx.doi.org/10.1099/mic.0.028175-0.

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Soluble butane monooxygenase (sBMO), a three-component di-iron monooxygenase complex expressed by the C2–C9 alkane-utilizing bacterium Thauera butanivorans, was kinetically characterized by measuring substrate specificities for C1–C5 alkanes and product inhibition profiles. sBMO has high sequence homology with soluble methane monooxygenase (sMMO) and shares a similar substrate range, including gaseous and liquid alkanes, aromatics, alkenes and halogenated xenobiotics. Results indicated that butane was the preferred substrate (defined by k cat : K m ratios). Relative rates of oxidation for C1–C5 alkanes differed minimally, implying that substrate specificity is heavily influenced by differences in substrate K m values. The low micromolar K m for linear C2–C5 alkanes and the millimolar K m for methane demonstrate that sBMO is two to three orders of magnitude more specific for physiologically relevant substrates of T. butanivorans. Methanol, the product of methane oxidation and also a substrate itself, was found to have similar K m and k cat values to those of methane. This inability to kinetically discriminate between the C1 alkane and C1 alcohol is observed as a steady-state concentration of methanol during the two-step oxidation of methane to formaldehyde by sBMO. Unlike methanol, alcohols with chain length C2–C5 do not compete effectively with their respective alkane substrates. Results from product inhibition experiments suggest that the geometry of the active site is optimized for linear molecules four to five carbons in length and is influenced by the regulatory protein component B (butane monooxygenase regulatory component; BMOB). The data suggest that alkane oxidation by sBMO is highly specialized for the turnover of C3–C5 alkanes and the release of their respective alcohol products. Additionally, sBMO is particularly efficient at preventing methane oxidation during growth on linear alkanes ≥C2, despite its high sequence homology with sMMO. These results represent, to the best of our knowledge, the first kinetic in vitro characterization of the closest known homologue of sMMO.

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Dissertations / Theses on the topic "Alkane Oxidation"

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Kleinschmidt, Olaf. "Photokatalytische Oxidation von Alkenen und Alkanen mit Sauerstoff an belichtetem Titandioxid." [S.l. : s.n.], 2001. http://deposit.ddb.de/cgi-bin/dokserv?idn=962781142.

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Grootboom, Natasha Denise. "Alkane oxidation using metallophthalocyanine as homogeneous catalysts." Thesis, Rhodes University, 2002. http://hdl.handle.net/10962/d1007794.

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Iron polychlorophthalocyanine (FePc(Cl)₁₆) and tetrasulfophthalocyanine ([M¹¹TSPc]⁴) complexes of iron, cobalt and manganese are employed as catalysts for the oxidation of cyclohexane using tert-butyl hydroperoxide (TBHP), chloroperoxybenzoic acid (CPBA) and hydrogen peroxide as oxidants. Catalysis using the FePc(Cl)₁₆ was performed in a dimethylformamide:dichloromethane (3 :7) solvent mixture. For the [Fe¹¹TSPc]⁴⁻, [Co¹¹TSPc]⁻ and [Mn¹¹TSPc]⁴⁻catalysts, a water:methanol (1:9) mixture was employed. The products of the catalysis are cyclohexanone, cyclohexanol and cyclohexanediol. The relative percentage yields, percentage selectivity and overall percentage conversion of the products depended on types of oxidant, or catalyst, concentrations of substrate or catalysts and temperature. TBHP was found to be the best oxidant since minimal destruction of the catalyst and higher selectivity in the products were observed when this oxidant was employed. Of the four catalysts investigated [Fe¹¹TSPc]⁴⁻ yielded the highest overall percentage conversion of 20%.The mechanism of the oxidation of cyclohexane in the presence of the FePc(Cl)₁₆ and [M¹¹TSPc]⁴⁻ involves the oxidation of these catalysts, forming an Fe(IlI) phthalocyanine species as an intermediate. Electrocatalysis using [Co¹¹TSPc]⁴⁻ as catalyst, employed an aqueous pH 7 buffer medium for electro-oxidation of 4-pentenoic acid. An enone is suggested as the only oxidation product of 4-pentenoic acid. No degradation of [Co¹¹TSPc]⁴⁻ was observed during the electrocatalytic process. In this process water was used as a source of oxygen therefore eliminating the production of by products from oxidant as in the case of TBHP and CPBA. This system was studied In an attempt to set up conditions for alkane electrocatalytic oxidation.

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Beilen, Jan Berthold van. "Alkane oxidation by Pseudomonas oleovorans: genes and proteins." [S.l. : [Groningen : s.n.] ; University Library Groningen] [Host], 1994. http://irs.ub.rug.nl/ppn/292892500.

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Shang, Yuan. "Teabag technology in long chain alkane selective oxidation." Thesis, Cardiff University, 2014. http://orca.cf.ac.uk/66336/.

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This thesis describes the searching, preparation, characterization and catalytic evaluation of active catalysts for the terminal selectivity of long chain linear alkanes. The focus of the thesis is the study of shape selective materials, including the organic material cyclodextrins, and the inorganic material, zeolite and zeolitic membranes. Prepared catalysts were performed with n-decane or n-hexane as models to produce the terminal oxidation products 1-decanol, 1-hexanol, decanoic acid and hexanoic acid. Studies with the Andrews glass reactor showed a stable terminal selectivity of 5%-9% in the autoxidation of n-hexane in short time reactions. A comparison between the Andrews glass reactor and Parr stainless steel reactor showed that the autoxidation reactions can get higher conversion but lower terminal selectivity in the stainless steel reactor than the glass reactor. Most of the metal/support catalysts showed very low conversion and very poor terminal selectivity. Increasing the temperature leads to higher conversion but results in more cracked products and less selectivity for oxygenated C10 products. The most active catalyst was 5 w.t.% Au/TiO2. However, these catalysts did not show good terminal alcohol selectivity (<3%); whereas the cracked acid selectivity was high (32.0%). Cyclodextrin covered Au/SiO2 catalysts showed limited changes in terminal selectivities (1-2%). Zeolite 4A, silicalite-1, ZSM-5, zeolite X/Y coated catalysts were successfully synthesized with alumina and silica sphere supports. The most attractive oxidation results were performed by zeolite X/Y and zeolite 4A coated silica catalysts in n-hexane liquid phase oxidation, iv especially for with short reaction time. With zeolite X/Y membrane, in a 30 min reaction, the terminal selectivity was 16%, while the terminal selectivity for the blank reactions was 0-9%. With longer reaction time, the terminal selectivity decreased to 6-7%. Zeolite 4A membrane can produce a terminal selectivity of 13% in 4 h reactions.

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Guo, Chris. "Alkane Oxidation Catalysis by Homogeneous and Heterogeneous Catalyst." Thesis, The University of Sydney, 2005. http://hdl.handle.net/2123/622.

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Abstract Cobalt-based complexes are widely used in industry and organic synthesis as catalysts for the oxidation of hydrocarbons. The Co/Mn/Br (known as "CAB system") catalyst system is effective for the oxidation of toluene. The Co/Mn/Br/Zr catalyst system is powerful for the oxidation of p-xylene, but not for the oxidation of toluene. [Co3O(OAc)5(OH)(py)3][PF6] (Co 3+ trimer 5) is more effective than [Co3O(OAc)6(py)3][PF6] (Co 3+ trimer 6) as a catalyst in the CAB catalyst system. Higher temperatures favour the oxidation of toluene. Zr 4+ does not enhance the oxidation of toluene. Zr 4+ could inhibit the oxidation of toluene in the combination of Co/Br/Zr, Co/Mn/Zr or Co/Zr. NHPI enhances the formation of benzyl alcohol, but the formation of other by-products is a problem for industrial processes. Complex(es) between cobalt, manganese and zirconium might be formed during the catalytic reaction. However, attempts at the preparation of complexes consisting of Co/Zr or Mn/Zr or Co3ZrP or Co8Zr4 clusters failed. The oxidation of cyclohexane to cyclohexanone and cyclohexanol is of great industrial significance. For the homogeneous catalysis at 50 o C and 3 bar N2 pressure, the activity order is: Mn(OAc)3 �2H2O > Mn12O12 cluster > Co 3+ trimer 6 > [Co3O(OAc)3(OH)2(py)5][PF6]2 (Co 3+ trimer 3) > Co 3+ trimer 5 > Co(OAc)2 �4H2O > [Co2(OAc)3(OH)2(py)4][PF6]-asym (Co dimerasym) > [Co2(OAc)3(OH)2(py)4][PF6]-sym (Co dimersym); whereas [Mn2CoO(OAc)6(py)3]�HOAc (Mn2Co complex) and zirconium(IV) acetate hydroxide showed almost no activity under these conditions. But at 120 o C and 3 bar N2 pressure, the activity order is changed to: Co dimerasym > Co(OAc)2 �4H2O > Co trimer 3 and Mn(OAc)3 �2H2O > Co 3+ trimer 6 > Mn2Co complex > Co 3+ trimer 5 > Co dimersym > Mn12O12 cluster. The molar ratio of the products was close to cyclohexanol/cyclohexanone=2/1. Mn(II) acetate and zirconium(IV) acetate hydroxide showed almost no activity under these conditions. Among those cobalt dimers and trimers, only the cobalt dimerasym survived after the stability tests, this means that [Co2(OAc)3(OH)2(py)4][PF6]-asym might be the active form for cobalt(II) acetate in the CAB system. Metal-substituted (silico)aluminophosphate-5 molecular sieves (MeAPO-5 and MeSAPO-5) are important heterogeneous catalysts for the oxidation of cyclohexane. The preparation of MeAPO-5 and MeSAPO-5 and their catalytic activities were studied. Pure MeAPO-5 and MeSAPO-5 are obtained and characterised. Four new pairs of bimetal-substituted MeAPO-5 and MeSAPO-5(CoZr, MnZr, CrZr and MnCo) were prepared successfully. Two novel trimetal-subtituted MeAPO-5 and MeSAPO-5 (MnCoZr) are reported here. Improved methods for the preparation of four monometal-substituted MeAPO-5 (Cr, Co, Mn and Zr) and for CoCe(S)APO-5 and CrCe(S)APO-5 are reported. Novel combinational mixing conditions for the formation of gel mixtures for Me(S)APO-5 syntheses have been developed. For the oxidation of cyclohexane by TBHP catalysed by MeAPO-5 and MeSAPO-5 materials, CrZrSAPO-5 is the only active MeSAPO-5 catalyst among those materials tested under conditions of refluxing in cyclohexane. Of the MeAPO-5 materials tested, whereas CrCeSAPO-5 has very little activity, CrZrAPO-5 and CrCeAPO-5 are very active catalysts under conditions of refluxing in cyclohexane. MnCoAPO-5, MnZrAPO-5 and CrAPO-5 are also active. When Cr is in the catalyst system, the product distribution is always cyclohexanone/cyclohexanol equals 2-3)/1, compared with 1/2 for other catalysts. For MeAPO-5, the activity at 150 o C and 10 bar N2 pressure is: CrZrAPO-5 > CrCeAPO-5 > CoZrAPO-5. For MeAPO-5 and MeSAPO-5, at 150 o C and 13 bar N2 pressure, the selectivity towards cyclohexanone is: CrZrAPO-5 > CrZrSAPO-5 > CrCeAPO-5 > CrAPO-5 > MnCoAPO-5 > MnZrAPO-5; and the selectivity towards cyclohexanol is: MnZrAPO-5 > CrZrAPO-5 > MnCoAPO-5 > CrZrSAPO-5 > CrCeAPO-5 > CrAPO-5. Overall the selectivity towards the oxidation of cyclohexane is: CrZrAPO-5 > CrZrSAPO-5 > CrCeAPO-5 > CrAPO-5 > MnCoAPO-5 > MnZrAPO-5. The amount of water in the system can affect the performance of CrCeAPO-5, but has almost no effect on CrZrAPO-5. Metal leaching is another concern in potential industrial applications of MeAPO-5 and MeSAPO-5 catalysts. The heterogeneous catalysts prepared in the present work showed very little metal leaching. This feature, coupled with the good selectivities and effectivities, makes them potentially very useful.

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Guo, Chris. "Alkane Oxidation Catalysis by Homogeneous and Heterogeneous Catalyst." University of Sydney. Chemistry, 2005. http://hdl.handle.net/2123/622.

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Abstract Cobalt-based complexes are widely used in industry and organic synthesis as catalysts for the oxidation of hydrocarbons. The Co/Mn/Br (known as "CAB system") catalyst system is effective for the oxidation of toluene. The Co/Mn/Br/Zr catalyst system is powerful for the oxidation of p-xylene, but not for the oxidation of toluene. [Co3O(OAc)5(OH)(py)3][PF6] (Co 3+ trimer 5) is more effective than [Co3O(OAc)6(py)3][PF6] (Co 3+ trimer 6) as a catalyst in the CAB catalyst system. Higher temperatures favour the oxidation of toluene. Zr 4+ does not enhance the oxidation of toluene. Zr 4+ could inhibit the oxidation of toluene in the combination of Co/Br/Zr, Co/Mn/Zr or Co/Zr. NHPI enhances the formation of benzyl alcohol, but the formation of other by-products is a problem for industrial processes. Complex(es) between cobalt, manganese and zirconium might be formed during the catalytic reaction. However, attempts at the preparation of complexes consisting of Co/Zr or Mn/Zr or Co3ZrP or Co8Zr4 clusters failed. The oxidation of cyclohexane to cyclohexanone and cyclohexanol is of great industrial significance. For the homogeneous catalysis at 50 o C and 3 bar N2 pressure, the activity order is: Mn(OAc)3 �2H2O > Mn12O12 cluster > Co 3+ trimer 6 > [Co3O(OAc)3(OH)2(py)5][PF6]2 (Co 3+ trimer 3) > Co 3+ trimer 5 > Co(OAc)2 �4H2O > [Co2(OAc)3(OH)2(py)4][PF6]-asym (Co dimerasym) > [Co2(OAc)3(OH)2(py)4][PF6]-sym (Co dimersym); whereas [Mn2CoO(OAc)6(py)3]�HOAc (Mn2Co complex) and zirconium(IV) acetate hydroxide showed almost no activity under these conditions. But at 120 o C and 3 bar N2 pressure, the activity order is changed to: Co dimerasym > Co(OAc)2 �4H2O > Co trimer 3 and Mn(OAc)3 �2H2O > Co 3+ trimer 6 > Mn2Co complex > Co 3+ trimer 5 > Co dimersym > Mn12O12 cluster. The molar ratio of the products was close to cyclohexanol/cyclohexanone=2/1. Mn(II) acetate and zirconium(IV) acetate hydroxide showed almost no activity under these conditions. Among those cobalt dimers and trimers, only the cobalt dimerasym survived after the stability tests, this means that [Co2(OAc)3(OH)2(py)4][PF6]-asym might be the active form for cobalt(II) acetate in the CAB system. Metal-substituted (silico)aluminophosphate-5 molecular sieves (MeAPO-5 and MeSAPO-5) are important heterogeneous catalysts for the oxidation of cyclohexane. The preparation of MeAPO-5 and MeSAPO-5 and their catalytic activities were studied. Pure MeAPO-5 and MeSAPO-5 are obtained and characterised. Four new pairs of bimetal-substituted MeAPO-5 and MeSAPO-5(CoZr, MnZr, CrZr and MnCo) were prepared successfully. Two novel trimetal-subtituted MeAPO-5 and MeSAPO-5 (MnCoZr) are reported here. Improved methods for the preparation of four monometal-substituted MeAPO-5 (Cr, Co, Mn and Zr) and for CoCe(S)APO-5 and CrCe(S)APO-5 are reported. Novel combinational mixing conditions for the formation of gel mixtures for Me(S)APO-5 syntheses have been developed. For the oxidation of cyclohexane by TBHP catalysed by MeAPO-5 and MeSAPO-5 materials, CrZrSAPO-5 is the only active MeSAPO-5 catalyst among those materials tested under conditions of refluxing in cyclohexane. Of the MeAPO-5 materials tested, whereas CrCeSAPO-5 has very little activity, CrZrAPO-5 and CrCeAPO-5 are very active catalysts under conditions of refluxing in cyclohexane. MnCoAPO-5, MnZrAPO-5 and CrAPO-5 are also active. When Cr is in the catalyst system, the product distribution is always cyclohexanone/cyclohexanol equals 2-3)/1, compared with 1/2 for other catalysts. For MeAPO-5, the activity at 150 o C and 10 bar N2 pressure is: CrZrAPO-5 > CrCeAPO-5 > CoZrAPO-5. For MeAPO-5 and MeSAPO-5, at 150 o C and 13 bar N2 pressure, the selectivity towards cyclohexanone is: CrZrAPO-5 > CrZrSAPO-5 > CrCeAPO-5 > CrAPO-5 > MnCoAPO-5 > MnZrAPO-5; and the selectivity towards cyclohexanol is: MnZrAPO-5 > CrZrAPO-5 > MnCoAPO-5 > CrZrSAPO-5 > CrCeAPO-5 > CrAPO-5. Overall the selectivity towards the oxidation of cyclohexane is: CrZrAPO-5 > CrZrSAPO-5 > CrCeAPO-5 > CrAPO-5 > MnCoAPO-5 > MnZrAPO-5. The amount of water in the system can affect the performance of CrCeAPO-5, but has almost no effect on CrZrAPO-5. Metal leaching is another concern in potential industrial applications of MeAPO-5 and MeSAPO-5 catalysts. The heterogeneous catalysts prepared in the present work showed very little metal leaching. This feature, coupled with the good selectivities and effectivities, makes them potentially very useful.

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Sheppard, T. L. "Development of copper zeolite catalysts for selective alkane oxidation." Thesis, Queen's University Belfast, 2014. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.676734.

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Selective partial oxidation of methane to methanol was investigated over Cu-ZSM-5 with two main objectives: to improve catalytic activity through modification of the catalyst surface; and to work towards a low-temperature, gas phase catalytic process through building an understanding of the catalytic cycle. Na-ZSM-5 was modified by the commercial silylating agent BSTFA, synthesising a range of functionalised catalysts from 0.2-20% silylation by weight. Successful silylation was confirmed by DRIFTS. Following aqueous copper exchange td form functionalised Cu-ZSM-5, analysis by BET and transmission IR revealed selective exchange of catalytically active copper in the zeolite channels at 1-2% silylation, with reduced exchange of inactive copper on the external surface. The latter was also observed during TEM. A large increase in catalytic activity was determined by TPO-MS analysis. Silylation was therefore used to increase the proportion of catalytically active copper present, with potential application in the synthesis of more active catalysts.

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Yip, Wing-ping, and 葉永平. "Alkane C-H bond oxidations and alkene dihydroxylations by oxorutheniumcomplexes of chelating tertiary amine ligands." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2004. http://hub.hku.hk/bib/B31246254.

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England, Jason. "Multidentate N-donor ligands in transition metal catalysed alkane oxidation." Thesis, Imperial College London, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.424716.

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Chung, Elena Yin-Yin. "Investigation of Chemical Looping Oxygen Carriers and Processes for Hydrocarbon Oxidation and Selective Alkane Oxidation to Chemicals." The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1469182957.

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Books on the topic "Alkane Oxidation"

1

Haines, Alan H. Methods for the oxidation of organic compounds: Alkanes, alkenes, alkynes, and arenes. London: Academic Press, 1985.

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1923-, Calvert Jack G., ed. Mechanisms of atmospheric oxidation of the alkanes. Oxford: Oxford University Press, 2008.

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Peebles, Jason A. Alkane oxidations in a micellar/mitalloporphyrin catalytic system. Ottawa: National Library of Canada, 1994.

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Rudakov, E. S. Reakt͡s︡ii alkanov s okisliteli͡a︡mi, metallokompleksami i radikalami v rastvorakh. Kiev: Nauk. dumka, 1985.

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Rubaĭlo, V. L. Liquid-phase oxidation of unsaturated compounds. Commack, N.Y: Nova Science, 1993.

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Bhakta, P. Alkaline oxidative leaching of gold-bearing arsenopyrite ores. Washington, D.C: Bureau of Mines, U.S. Dept. of the Interior, 1989.

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Bhakta, P. Alkaline oxidative leaching of gold-bearing arsenopyrite ores. Washington, DC: Dept. of the Interior, 1989.

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Owen, Neil Eric. The alkaline nitrobenzene oxidation of model compounds and solid fuel derivatives. Birmingham: Aston University. Department of Chemical Engineering and Applied Chemistry, 1986.

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Lundin, Angelica. Quantum chemical studies of olefin epoxidation and benzyne biradicals. Göteborg, Sweden: Göteborg University, Faculty of Science, 2007.

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Shilov, A. E. Metal complexes in biomimetic chemical reactions: N₂ fixation in solution, activation, and oxidation of alkanes, chemical models of photosynthesis. Boca Raton, Fl: CRC Press, 1996.

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Book chapters on the topic "Alkane Oxidation"

1

Cavani, Fabrizio, Alessandro Chieregato, Jose M. López Nieto, and Jean-Marc M. Millet. "Gas-Phase Oxidation of Alkanes." In Alkane Functionalization, 159–88. Chichester, UK: John Wiley & Sons, Ltd, 2018. http://dx.doi.org/10.1002/9781119379256.ch9.

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Nesterov, Dmytro S., Oksana V. Nesterova, and Armando J. L. Pombeiro. "Alkane Oxidation with Multinuclear Heterometallic Catalysts." In Alkane Functionalization, 125–40. Chichester, UK: John Wiley & Sons, Ltd, 2018. http://dx.doi.org/10.1002/9781119379256.ch7.

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Sutradhar, Manas, Luísa M. D. R. S. Martins, M. Fátima C. Guedes da Silva, and Armando J. L. Pombeiro. "Alkane Oxidation with Vanadium and Copper Catalysts." In Alkane Functionalization, 319–36. Chichester, UK: John Wiley & Sons, Ltd, 2018. http://dx.doi.org/10.1002/9781119379256.ch16.

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Martins, Luísa M. D. R. S. "Alkane Oxidation with C-Scorpionate Metal Complexes." In Alkane Functionalization, 113–23. Chichester, UK: John Wiley & Sons, Ltd, 2018. http://dx.doi.org/10.1002/9781119379256.ch6.

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Kuznetsov, Maxim L. "Nontransition Metal Catalyzed Oxidation of Alkanes with Peroxides." In Alkane Functionalization, 485–501. Chichester, UK: John Wiley & Sons, Ltd, 2018. http://dx.doi.org/10.1002/9781119379256.ch22.

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Liu, Chih-Cheng, Yi-Fang Tsai, Wondemagegn H. Wanna, Ravirala Ramu, Damodar Janmanchi, Sunney I. Chan, and Steve S. F. Yu. "Selective Oxidation of Alkanes by Metallo-Monooxygenases and Their Nanobiomimetics." In Alkane Functionalization, 293–317. Chichester, UK: John Wiley & Sons, Ltd, 2018. http://dx.doi.org/10.1002/9781119379256.ch15.

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Dominelli, Bruno, Anja C. Lindhorst, and Fritz E. Kühn. "CH Bond Oxidation with Transition-Metal-Based Carbene Complexes." In Alkane Functionalization, 105–11. Chichester, UK: John Wiley & Sons, Ltd, 2018. http://dx.doi.org/10.1002/9781119379256.ch5.

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Costas, Miquel. "Alkane Oxidation with Biologically Inspired Nonheme Iron Catalysts Based in the Triazacyclononane Ligand Scaffold." In Alkane Functionalization, 251–68. Chichester, UK: John Wiley & Sons, Ltd, 2018. http://dx.doi.org/10.1002/9781119379256.ch13.

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Taylor, Stuart H., Justin S. J. Hargreaves, Graham J. Hutchings, and Richard W. Joyner. "Methanol Oxidation Over Oxide Catalysts." In Methane and Alkane Conversion Chemistry, 339–45. Boston, MA: Springer US, 1995. http://dx.doi.org/10.1007/978-1-4615-1807-5_36.

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Walker, G. Stewart, and Jacek A. Lapszewicz. "Catalytic Studies of Methane Partial Oxidation." In Methane and Alkane Conversion Chemistry, 265–70. Boston, MA: Springer US, 1995. http://dx.doi.org/10.1007/978-1-4615-1807-5_28.

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Conference papers on the topic "Alkane Oxidation"

1

Harstad, Kenneth, and Josette Bellan. "A Simplified Model of Alkane Oxidation." In 46th AIAA Aerospace Sciences Meeting and Exhibit. Reston, Virigina: American Institute of Aeronautics and Astronautics, 2008. http://dx.doi.org/10.2514/6.2008-975.

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Harstad, Kenneth, and Josette Bellan. "Modeling of Alkane Oxidation using Constituents and Species." In 47th AIAA Aerospace Sciences Meeting including The New Horizons Forum and Aerospace Exposition. Reston, Virigina: American Institute of Aeronautics and Astronautics, 2009. http://dx.doi.org/10.2514/6.2009-1368.

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Qu, Yakun, Jun Long, and Han Zhou. "On the Chain Initiation Mechanism in the High Temperature Oxidation Process of C8 Alkane." In 3rd Workshop on Advanced Research and Technology in Industry (WARTIA 2017). Paris, France: Atlantis Press, 2017. http://dx.doi.org/10.2991/wartia-17.2017.25.

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Jones, E. G., and W. J. Balster. "Application of a Sulphur-Doped Alkane System to the Study of Thermal Oxidation of Jet Fuels." In ASME 1992 International Gas Turbine and Aeroengine Congress and Exposition. American Society of Mechanical Engineers, 1992. http://dx.doi.org/10.1115/92-gt-122.

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A system of diphenyldisulphide in hexadecane was selected for modeling the formation of insolubles in jet fuels. The system was stressed in a series of flask tests at 185°C under fixed oxygen flow. The quantity of filterable insoluble solids and insoluble gums was measured as a function of time and found to increase linearly following an initial induction period. Rates associated with the linear growth were evaluated for a series of oxygen flows to obtain the oxygen dependence of insoluble-solid and insoluble-gum formation. Results indicate that insoluble gums and insoluble solids are formed by independent processes. Bulk and surface rates show a linear correlation, indicating that the precursors to insolubles formed in the bulk and those formed on the surface are similar.

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Bourque, Gilles, Darren Healy, Henry Curran, John Simmie, Jaap de Vries, Viktorio Antonovski, Benjamin Corbin, Christopher Zinner, and Eric Petersen. "Effect of Higher-Order Hydrocarbons on Methane-Based Fuel Chemistry at Gas Turbine Pressures." In ASME Turbo Expo 2007: Power for Land, Sea, and Air. ASMEDC, 2007. http://dx.doi.org/10.1115/gt2007-28039.

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A chemical kinetics mechanism designed for the oxidation of methane-hydrocarbon blends at elevated pressures was used to study the effect of higher-order hydrocarbons on ignition delay time and flame speed at gas turbine conditions. The mechanism was developed from recent data and modeling conducted by the authors, including pressures above 30 atm, temperatures as low as 700 K, and alkane additives from C2H6 through C5H12. Calculations focused on three target natural gas mixtures containing CH4 mole fractions from 62.5 to 98%. The results show the effects that pressure, temperature, and hydrocarbon content have on the combustion chemistry of the fuel-air mixtures. For example, autoignition times exhibit nonlinear trends with increasing pressure and decreasing temperature. Experiments in the authors’ laboratories are ongoing, and an overview of the related facilities is provided.

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Lim, D. F., X. F. Ang, J. Wei, C. M. Ng, and C. S. Tan. "Copper to Copper Direct Bonding Assisted by Self-Assembled Monolayer." In ASME 2010 International Mechanical Engineering Congress and Exposition. ASMEDC, 2010. http://dx.doi.org/10.1115/imece2010-38565.

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In this article, a self-assembled monolayer (SAM) is applied onto the copper surface in an attempt to lower the required bonding temperature. Alkane-thiol with 6-carbon chain length is used and tested for bonding experiment. The adsorption of SAM is confirmed by the sharp rise of the water contact angle measurement and the reduced in the surface roughness. Next, the desorption of SAM is done at a high temperature anneal (<300°C) in an inert ambient and its properties are characterized by the water contact angle measurement and XPS. It is found that the water contact angle measurement decreases sharply close back to the contact angle of the pure blanket copper surface after annealing of SAM. The XPS results also show the ability of SAM in protecting Copper surface from oxidation. Finally, shear test is performed on Cu-Cu structures bonded at low temperature (250°C) in order to verify the SAM behavior in protecting the copper surface from oxidation and enhancement for bonding. The wafer pairs with and without SAM are intentionally exposed in clean room environment for few days. The bonded pieces are diced and subject to shear stress and results show that with SAM protection, shear strength is improved due to the enhancement in grain growth as a result of cleaner surface.

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Mohamed, A. Abd El-Sabor, Amrit Bikram Sahu, Snehasish Panigrahy, Gilles Bourque, and Henry Curran. "The Ignition of C1–C7 Natural Gas Blends and the Effect of Hydrogen Addition in the Low and High Temperature Regimes." In ASME Turbo Expo 2022: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2022. http://dx.doi.org/10.1115/gt2022-82305.

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Abstract New ignition delay time (IDT) measurements for two natural gas (NG) blends composed of C1 – C7 n-alkanes, NG6 (C1:60.625%, C2:20%, C3:10%, C4:5%, nC5:2.5%, nC6:1.25%, nC7:0.625%) and NG7 (C1:72.635%, C2:10%, C3:6.667%, C4:4.444%, nC5:2.965%, nC6:1.976%, nC7:1.317%) by volume with methane as the major component are presented. The measurements were recorded using a high-pressure shock tube (HPST) for stoichiometric fuel in air mixtures at reflected shock pressures (p5) of 20–30 bar and at temperatures (T5) of 987–1420 K. The current results together with rapid compression machine (RCM) measurements in the literature show that higher concentrations of the higher n-alkanes (C4 – C7) ∼1.327% in the NG7 blend compared to the NG6 blend result in the ignition for NG7 being almost a factor of two faster than NG6 at compressed temperatures of (TC) ≤ 1000 K. This is due to the low temperature chain branching reactions that occur for higher alkane oxidation kinetics in this temperature range. On the contrary, at TC > 1000 K, NG6 exhibits ∼20% faster ignition than NG7 primarily because about 12% of the methane in the NG7 blend is primarily replaced by ethane (∼10%) in NG6, which is significantly more reactive than methane at these higher temperatures. The performance of NUIGMech1.2 in simulating these data is assessed and it can reproduce the experiments within 20% for all the conditions considered in the study. We also investigate the effect of hydrogen addition to the auto-ignition of these NG blends using NUIGMech1.2 which has been validated against the existing literature for natural gas/hydrogen blends. The results demonstrate that hydrogen addition has both an inhibiting and promoting effect in the low- and high-temperatures regime, respectively. Sensitivity analyses of the hydrogen/NG mixtures are performed to understand the underlying kinetics controlling these opposite ignition effects. At low temperatures, H-atom abstraction by ȮH radicals from C3 and larger fuels are the key chain-branching reactions consuming the fuel and providing the necessary fuel radicals which undergo low temperature chemistry (LTC) leading to ignition. However, with the addition of hydrogen to the fuel mixture, the competition for ȮH radicals by H2 via the reaction H2+ȮH↔Ḣ+H2O reduces the progress of the LTC of the higher hydrocarbon fuels thereby inhibiting ignition. At higher temperatures, since Ḣ+O2↔Ö+ȮH is the most sensitive reaction promoting reactivity, the higher concentrations of H2 in the fuel mixture leads to higher Ḣ atom concentrations leading to faster ignition due to an enhanced rate of the Ḣ+O2↔Ö+ȮH reaction.

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Guolin, Jing, Qin Shaopeng, and Li Ming. "Oxidation of Alkanes in Supercritical Water." In 2009 International Conference on Energy and Environment Technology (ICEET 2009). IEEE, 2009. http://dx.doi.org/10.1109/iceet.2009.395.

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Santi, Claudio, Marcello Tiecco, Lorenzo Testaferri, Chun-wing Steven Si, Stefano Santoro, Blerina Gjoka, and Benedetta Battistelli. "Selenium catalyzed oxidation of alkynes in aqueous media." In The 13th International Electronic Conference on Synthetic Organic Chemistry. Basel, Switzerland: MDPI, 2009. http://dx.doi.org/10.3390/ecsoc-13-00227.

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Reinert, Ana Paula, Beatriz Jacob Furlan, Rafael Silva Ribeiro Gonçalves, Fabrizio Carneiro da Silva, Fernando Gallego Dias, Lauber Martins, Juan Ordonez, and JOSÉ VIRIATO COELHO VARGAS. "HYDROGEN GENERATION BY ALUMINUM OXIDATION IN ALKALINE SOLUTION." In 26th International Congress of Mechanical Engineering. ABCM, 2021. http://dx.doi.org/10.26678/abcm.cobem2021.cob2021-0621.

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Reports on the topic "Alkane Oxidation"

1

Scott Han. Millisecond Oxidation of Alkanes. Office of Scientific and Technical Information (OSTI), September 2011. http://dx.doi.org/10.2172/1025808.

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Serov, Alexey, and Plamen Atanassov. Development of PGM-free Catalysts for Hydrogen Oxidation Reaction in Alkaline Media. Office of Scientific and Technical Information (OSTI), June 2018. http://dx.doi.org/10.2172/1456241.

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Levitskaia, Tatiana G., Brian M. Rapko, Amity Anderson, James M. Peterson, Sayandev Chatterjee, Eric D. Walter, Herman M. Cho, and Nancy M. Washton. Speciation and Oxidative Stability of Alkaline Soluble, Non-Pertechnetate Technetium. Office of Scientific and Technical Information (OSTI), September 2014. http://dx.doi.org/10.2172/1378055.

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Rapko, B. M., C. H. Delegard, and M. J. Wagner. Oxidative dissolution of chromium from Hanford tank sludges under alkaline conditions. Office of Scientific and Technical Information (OSTI), August 1997. http://dx.doi.org/10.2172/555261.

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Rapko, B. M., G. J. Lumetta, and M. J. Wagner. Oxidative dissolution of chromium from Hanford Tank sludges under alkaline conditions. Office of Scientific and Technical Information (OSTI), July 1996. http://dx.doi.org/10.2172/266870.

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Rapko, B. M. Oxidative alkaline dissolution of chromium from Hanford tank sludges: Results of FY 98 studies. Office of Scientific and Technical Information (OSTI), August 1998. http://dx.doi.org/10.2172/290879.

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Klier, Kamil, Jean Paul Lange, and Richard G. Herman. Partial oxidation of light alkanes in transition metal ion containing zeolites: Quarterly technical progress report for the period December 15, 1988--March 14, 1989. Office of Scientific and Technical Information (OSTI), April 1989. http://dx.doi.org/10.2172/6431598.

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NN Krot, VP Shilov, AM Fedoseev, NA Budantseva, MV Nikonov, AB Yusov, AYu Garnov, et al. Development of Alkaline Oxidative Dissolution Methods for Chromium (III) Compounds Present in Hanford Site Tank Sludges. Office of Scientific and Technical Information (OSTI), July 1999. http://dx.doi.org/10.2172/8396.

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Desbarats, A. J., and J. B. Percival. Hydrogeochemistry of mine tailings from a carbonatite-hosted Nb-REE deposit, Oka, Quebec, Canada. Natural Resources Canada/CMSS/Information Management, 2023. http://dx.doi.org/10.4095/331256.

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Environmental impacts associated with the mining of carbonatite deposits are an emerging concern due to the demand for critical metals. This study investigates the chemistry of tailings seepage at the former Saint Lawrence Columbium mine near Oka, Québec, Canada, which produced pyrochlore concentrate and ferroniobium from a carbonatite-hosted Nb-REE deposit. Its objectives are to characterize the mineralogy of the tailings and their pore water and effluent chemistries. Geochemical mass balance modeling, constrained by aqueous speciation modeling and mineralogy, is then used to identify reactions controlling the chemical evolution of pore water along its flow path through the tailings impoundment. The tailings are composed mainly of REE-enriched calcite (82 wt. %), biotite (12 wt. %) and fluorapatite (4 wt. %). Minor minerals include chlorite, pyrite, sphalerite, molybdenite and unrecovered pyrochlore. Secondary minerals include gypsum, barite and strontianite. Within the unsaturated zone, pore water chemistry is controlled by sulfide oxidation and calcite dissolution with acid neutralization. With increasing depth below the water table, pore water composition reflects gypsum dissolution followed by sulfate reduction and FeS precipitation driven by the oxidation of organic carbon in the tailings. Concomitantly, incongruent dissolution of biotite and chlorite releases K, Mg, Fe, Mn, Ba and F, forming kaolinite and Ca-smectite. Cation exchange reactions further remove Ca from solution, increasing concentrations of Na and K. Fluoride concentrations reach 23 mg/L and 8 mg/L in tailings pore water and effluent, respectively. At a pH of 8.3, Mo is highly mobile and reaches an average concentration of 83 µg/L in tailings effluent. Although U also forms mobile complexes, concentrations do not exceed 16 µg/L due to the low solubility of its pyrochlore host. Adsorption and the low solubility of pyrochlore limit concentrations of Nb to less than 49 µg/L. Cerium, from calcite dissolution, is strongly adsorbed although it reaches concentrations (unfiltered) in excess of 1 mg/L and 100 µg/L in pore water and effluent, respectively. Mine tailings from carbonatite deposits are enriched in a variety of incompatible elements with mineral hosts of varying reactivity. Some of these elements, such as F and Mo, may represent contaminants of concern because of their mobility in alkaline tailings waters.

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Rempel, K. U., A. E. Williams-Jones, and K. Fuller. An experimental investigation of the solubility and speciation of uranium in hydrothermal ore fluids. Natural Resources Canada/CMSS/Information Management, 2021. http://dx.doi.org/10.4095/328995.

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Experimental data on the solubility and speciation of uranium in hydrothermal solution is required to improve genetic models for the formation of ore deposits, yet very few data of this type have been published. Of particular interest is the oxidation state of the uranium in solution, as conventional wisdom suggests that U is dissolved in the oxidized U(VI) state and precipitated as reduced U(IV) minerals, yet recent experiments have shown ppm-level solubility for U(IV). This study investigated the mobility of reduced U(IV) and oxidized U(VI) in acidic (pH = 2), fluoride- bearing and alkaline (pH = 10), chloride-bearing solutions at 100-200°C and 1 to 15.8 bars (0.1-1.58 MPa). Preliminary data for the mobility of U(IV) in pH 2 fluids with 0.01 m F- show concentrations of 1.76 to 3.92 ppm U at 200°C, indicating that, contrary to common belief, the reduced U(IV) can be transported in solution. We have also conducted experiments on U(VI) solubility in pH 2 fluoride-bearing, and pH 10 chloride-bearing solutions. Uranium concentrations in the F- -bearing experiments ranged from 624 to 1570 ppm (avg. 825 ppm, n = 6) at 100°C, 670 to 1560 ppm (avg. 931 ppm, n = 4) at 150°C, and 3180 to 7550 ppm (avg. 5240, n = 9) at 200°C. In comparison, U concentrations in the Cl- -bearing runs range from 86.1 to 357 ppm (avg. 185 ppm, n = 15) at 200°C. Clearly, oxidized U(VI) is very readily mobilized in hydrothermal fluids. However, the measured concentrations of U(VI) are independent of those of F- or Cl-, suggesting the formation of U oxide or hydroxide species rather than U chlorides or fluorides. These experimental data will be verified and supplemented in future experiments, which will be used to derive the stoichiometry and thermodynamic constants for the dominant uranium species in hydrothermal solutions. The data from this study will then be integrated into a comprehensive genetic model for uranium ore-forming systems.

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