Biotreatment of refinery spent-sulfidic caustic using an enrichment culture immobilized in a novel support matrix

Sodium hydroxide solutions are used in petroleum refining to remove hydrogen sulfide (H₂S) and mercaptans from various hydrocarbon streams. The resulting sulfide-laden waste stream is called spent-sulfidic caustic. An aerobic enrichment culture was previously developed using a gas mixture of H₂S and methylmercaptan (MeSH) as the soleenergy source. This culture has now been immobilized in a novel support matrix, DuP ont BIO-SEP^TM beads, and is used to biotreat a refinery spent-sulfidic caustic containing both inorganic sulfide and mercaptans in a continuous flow, fluidized-bed column bioreactor. Complete oxidation of both inorganic and organic sulfur to sulfate was observed with no breakthrough of H₂S and <2 ppmv of MeSH produced in the bioreactor outlet gas. Excessive buildup of sulfate (>12 g/L) in the bioreactor medium resulted in an upset condition evidenced by excessive MeSH breakthrough. Therefore, bioreactor performance was limited by the steady-state sulfate concentration. Further improvement in volumetric productivity of a bioreactor system based on this enrichment culture will be dependent on maintenance of sulfate concentrations below inhibitory levels.

     

A preliminary cost analysis of the biotreatment of refinery spent-sulfidic caustic

Caustics are used in petroleum refining to remove hydrogen sulfide from various hydrocarbon streams. Spent-sulfidic caustics from three refineries have been successfully biotreated on the bench and pilot scale, resulting in neutralization and removal of active Sulfides. Sulfides were completely oxidized to sulfate byThiobacillus denitrificans strain F. Microbial oxidation of sulfide produced acid, which at least partially neutralized the caustic. A commercial-scale treatment system has been designed that features a bioreactor with a suspended culture of flocculatedT. denitrificans, a settler and acid and nutrient storage and delivery systems. A cost analysis has been performed for nine cases representing a range of spent caustic sulfide and hydroxide concentrations at a base treatment rate of 10 gpm. This analysis shows that refinery spent-sulfidic caustic can be biotreated for 4-8.3￠/gal.     

Extraction of Mercaptans from Light Hydrocarbon Mixtures with Aqueous Ammonia

Results of laboratory studies of the extraction of light mercaptans (methyl, ethyl, and propyl mercaptans) from hydrocarbons mixtures with a 25% aqueous solution of ammonia (caustic ammonia) are presented and discussed. It is shown that aqueous ammonia can in principle be used for controlled demercaptanization of light hydrocarbon fractions and liquefied hydrocarbon gases containing hydrogen sulfide and lower mercaptans. The advantage of this demercaptanization method over the conventional processes of alkali treatment is that there is no stage of oxidative catalytic regeneration of a spent alkali and there are no its highly toxic wastes, sulfurousalkaline waste waters. The regeneration of a spent (saturated with sulfurous compounds) aqueous ammonia can be comparatively easily performed by its heating (boiling), which leads to a hydrolytic decomposition of ammonium sulfides and mercaptides to release their constituent gases: hydrogen sulfide, mercaptans, and ammonia. Ammonia is recycled into the process as freshly prepared (regenerated) caustic ammonia.

     

Complexes of Copper(I) with Dimercapto Compounds as Catalysts for Oxidation of Mercaptans and Hydrogen Sulfide with Molecular Oxygen in Aqueous Solutions

The conditions for formation of complexes of copper(I) with mercapto compounds in aqueous- alkaline solutions and the catalytic activity of these complexes in oxidation of mercaptans and hydrogen sulfide was studied. The kinetic characteristics of these catalysts were compared with those of catalysts based on cobalt phthalocyanines. A method was proposed for suppressing formation of the thiosulfate ion in oxidation of H₂S to elemental sulfur.     

Titanium–salan‐catalyzed asymmetric sulfoxidations with H2O2: design of more versatile catalysts

Titanium–salan complexes with 3,3’‐diphenyl substituents in the salicylidene rings of the salan ligand are efficient sulfoxidation catalysts, capable of catalyzing the asymmetric oxidation of bulky aryl benzyl sulfides with H₂O₂ with good to high enantioselectivities. In this paper, substituent effects on titanium‐salan‐catalyzed enantioselective oxidation of sulfides to sulfoxides have been systematically investigated. Titanium–salan catalysts with halogen substituents at the 5,5’‐positions (3,3’‐H₂dihydrogen substituted) have been found to catalyze the oxidation of both bulky aryl benzyl sulfides and small alkyl phenyl sulfides with good to high enantioselectivities. Kinetic data witness a direct attack of the sulfide to the electrophilic active oxygen species; a consistent reaction mechanism is proposed. Copyright © 2013 John Wiley & Sons, Ltd.     

Reactions of Single-electron Oxidation and Reduction of Sulfides of the Azulene Series

Single-electron oxidation in acetonitrile and reduction in DMF of sulfides of 3-RS-1,4-dimethyl-7- ethylazulenes (R = Me, Et, Ph, p-MeC₆H₄, p-MeOC₆H₄, N-1-phenyltetrazolyl) leads to stable radical cations and radical anions, respectively. The found reduction potentials of sulfides of the azulene series are close to those of natural and synthetic bioantioxidants. In the radical cations the unpaired electron is essentially delocalized over the cyclopentadienyl fragment of the molecule, and the sulfide group in large measure defines the distribution of spin density. In the radical anion spin density is delocalized in the tropylium cycle, and the influence of the sulfide group is insignificant. Electrochemical oxidation of unsubstituted 1,4-dimethyl-7-ethylazulene results in the formation of a dimeric radical cation.     

Oxidation of hydrogen sulfide by an enrichment from sour water coproduced with petroleum

We have previously demonstrated that the chemoautotroph and facultative anaerobeThiobacillus denitrificans may be readily cultured aerobically or anoxically in batch and continuous reactors on hydrogen sulfide under sulfide-limiting conditions. A sulfide-tolerant strain ofT. denitrificans (strain F) was isolated by enrichment and recently used in a successful field test of a microbial process for the treatment of sour water coproduced with petroleum at an Amoco Production Co. site in Wyoming. Prior to the initiation of this field test, it was determined that the sour water at this site contained low concentrations of indigenous autotrophs, which could grow on thiosulfate as an energy source. Samples of this sour water have now been used to produce an enrichment culture for sulfide oxidizers. This enrichment has been characterized with respect to hydrogen sulfide oxidation, response to oxygen, pH and temperature optima, and sulfide tolerance. The enrichment was shown to be strictly aerobic and to grow on sulfide as an energy source with complete oxidation of sulfide to sulfate. The enrichment has a tolerance of sulfide comparable to that ofT. denitrificans strain F. However, the enrichment has a higher optimum temperature (35°C) than strain F and was shown to oxidize sulfides over a much broader range of pH values (3.5–10).

     

Mechanism of (Salen)manganese(III)‐Catalyzed Oxidation of Aryl Phenyl Sulfides with Sodium Hypochlorite

The oxidation of 4‐substituted phenyl phenyl sulfides was carried out with several oxo(salen)manganese(V) complexes in MeCN/H₂O 9 : 1. The kinetic data show that the reaction is first‐order each in the oxidant and sulfide. Electron‐attracting substituents in the sulfides and electron‐releasing substituents in salen of the oxo(salen)manganese(V) complexes reduce the rate of oxidation. A Hammett analysis of the rate constants for the oxidation of 4‐substituted phenyl phenyl sulfides gives a negative ρ value (ρ=?2.16) indicating an electron‐deficient transition state. The log k₂ values observed in the oxidation of each 4‐substituted phenyl phenyl sulfide by substituted oxo(salen)manganese(V) complexes also correlate with Hammett σ constants, giving a positive ρ value. The substituent‐, acid‐, and solvent‐effect studies indicate direct O‐atom transfer from the oxidant to the substrate in the rate‐determining step.     

L‐Proline–H2O2: A New Chemoselective Approach for Oxidation of Sulfides to Sulfoxides

A facile and selective oxidation of sulfides to sulfoxides using an L‐proline–H₂O₂ system for structurally divergent sulfide substrates with excellent yields at ambient conditions is reported.     

Estimation of the activity of catalysts and the reactivity of organosulfur compounds

The kinetics of hydrogenolysis of various classes of organosulfur compounds were studied in the presence of MeAlCl ₄ catalysts (Me=Li, Na, K). The reactions were conducted at 100–250°C without introduction of hydrogen into the reaction zone, but in the presence of hydrocarbons capable of acting as hydride—ion donors; these donors were necessary for H ₂ S formation. A series of catalytic activities and optimal reaction conditions for each catalyst were determined from the rate constants of hydrogenolysis at the C-S bond. Reactivities of mercaptans, sulfides, disulfides, and thiophene were estimated.Institute of Chemistry, Bashkir Scientific Center, Ural Branch, Russian Academy of Sciences, Ufa 450054. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 3, pp. 562–564, March, 1992.     

Microbial removal of sulfur dioxide from a gas stream with net oxidation to sulfate

A study has been conducted of the feasibility of utilizing the sulfate reducing bacteriumDesulfovibrio desulfuricans and the chemoautotrophThiobacillus denitrificans as a basis of a microbial process for the removal of sulfur dioxide from a gas with net oxidation to sulfate. In reactors-in-series, SO₂ was reduced to H₂S in the first stage by D.desulfuricans. The H₂S was then stripped with nitrogen and sent to a second stage where it was oxidized to sulfate by T.denitrificans. A sulfur balance demonstrated complete reduction of SO₂ to H₂S in the first stage and complete oxidation of H₂S to sulfate in the second stage.     

Catalytic Systems for the H<Subscript>2</Subscript>S Wet Oxidation at room Temperature

The catalytic wet oxidation process is the most attractive process for small-scale hydrogen sulfide (H₂S) removal from natural gas. The catalytic wet oxidation process is anticipated to be cost effective and simple so that it can be used for treating sour gases containing small amounts of H₂S and can be easily operated even in isolated sites. The development of effective catalyst is the key technology in the wet catalytic oxidation of H₂S. The scale of operation for the process has to be flexible so its use will not be limited by the flow rates of the gas to be treated. The heterogeneous catalytic wet oxidation of H₂S has been attempted on activated carbons, but the H₂S removal capacity still shows the low removal efficiency. The catalytic wet oxidation of H₂S was studied over Fe/MgO for an effective removal of H₂S. In order to develop a sulfur removal technology, one has to know what surface species of catalyst are the most active. This article discusses the following systematic studies: (i) the catalytic preparation to disperse Fe metal well on MgO support for enhancing H₂S removal capacity, (ii) the effect of the catalytic morphology on the activity of Fe/MgO for the H₂S wet oxidation, (iii) the influence of precursor and support on the activity of Fe/MgO for catalytic wet oxidation of H₂S to sulfur.     

Facile and Selective Oxidation of Sulfides to Sulfoxides by t-Butyl Hydroperoxide in Aqueous Medium

The oxidation of sulfides to sulfoxides with TBHP in water only occurs selectively with high yields and permits the sulfoxides to be prepared without using organic solvents. When the reaction is performed in aqueous sulfuric acid with a H₂SO₄/sulfide molar ratio of 20/1, the oxidation rate is greatly increased.     

Asymmetric oxidation of sulfides catalyzed by chiral (salen)Mn(III) complexes with a pyrrolidine backbone

Catalytic properties of a series of chiral (pyrrolidine salen)Mn(III) complexes for asymmetric oxidation of aryl methyl sulfides were evaluated. Moderate activity, good chemical selectivity and low enantioselectivity were attained with iodosylbenzene as a terminal oxidant. Enantioselectivity of sulfide oxidation was affected slightly by polar solvent and the sulfoxidation carried out in THF for thioanisole and in CH₃CO₂Et for electron‐deficient sulfides gave better enatioselctivities. The addition of the donor ligand PPNO (4‐phenylpyridine N‐oxide) or MNO (trimethylamine N‐oxide) only has a minor positive effect on the enantioselectivity. Also explored was the steric effect of the N_aza‐substituent in the backbone of (pyrrolidine salen)Mn(III) complexes on the enantioselectivity of sulfide oxidation. The sulfides' access pathway is discussed based on the catalytic results. Copyright © 2006 John Wiley & Sons, Ltd.     

Chemical transformations of organic sulfides during hydrogenolysis in the presence of metal chloride complexes

Desulfurization of organic sulfides in hydrocarbon solvents in the presence of aqua complexes of metal chlorides H[MAlCl₄OH] that exhibit lower acidity as compared to AlCl₃ proceeds under mild conditions (450–525 K, atmospheric pressure) without external introduction of hydrogen. The process occurs with cleavage of C-S bonds and through intermediate formation of mercaptans to give H₂S and the corresponding hydrocarbons. The reaction is accompanied by cleavage of C-C bonds in the groups surrounding the organosulfur moiety, in thiacyclane rings, as well as in hydrocarbon solvent molecules, resulting in the formation of a wide spectrum of gaseous and liquid products.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1998–2002, October, 1995.     

Biosynthesis of Heliotropin by a Novel Strain of <Emphasis Type="Italic">Serratia liquefaciens</Emphasis>

The present study has been conducted towards isolation of bacteria capable of producing heliotropin via microbial conversion. Strain ZMT-1 capable of synthesizing heliotropin efficiently was obtained by enrichment culture of soil samples and a high-throughput screening method, and identified as Serratia liquefaciens. Heliotropin was identified by gas chromatography and gas chromatography–mass spectrometry analysis. In addition, the culture medium was optimized to improve heliotropin yield by experimental designs. The application of a Plackett–Burman design found that NH₄NO₃ and K₂HPO₄?3H₂O have significant effects on heliotropin production. Central composite design experiments were further used to predict the optimal concentrations of NH₄NO₃ and K₂HPO₄?3H₂O, which were 1.0 and 0.5 g/l, respectively. After the optimization of cultural medium, heliotropin yield was increased by 4.52-fold when compared with the unoptimized minimal medium. This study is the first to report the biosynthesis of heliotropin by S. liquefaciens. S. liquefaciens ZMT-1 can produce heliotropin efficiently, indicating its potential as one heliotropin-producing strain.     

Stabilities and electrical conductivities of electrode materials for use in H2S-containing gases

Stabilities and conductivities of sulfides and lithiated sulfides derived from La_0.9Sr_0.1Ga_0.8Cr_0.2O₃, LaCr_0.9Ti_0.1O₃, Y_0.9Ca_0.1FeO₃, and SrCo_0.8Fe_0.2O₃ are studied in a gas mixture of 96% H₂ and 4% H₂S at 900 °C using X-ray diffraction, microscopy, and impedance spectroscopy. Results indicate that the sulfide and lithiated sulfide derived from Y_0.9Ca_0.1FeO₃ exhibit not only high stability but also high electrical conductivity, implying that they are viable candidate electrode materials for H₂S polishing and for solid oxide fuel cells using H₂S-containing fuels. In contrast, the lithiated sulfides derived from La_0.9Sr_0.1Ga_0.8Cr_0.2O₃ and LaCr_0.9Ti_0.1O₃ exhibit relatively low electrical conductivity, although their chemical and thermal stability appear to be very good. On the other hand, the lithiated sulfides derived from SrCo_0.8Fe_0.2O₃ show inadequate chemical stability under the testing conditions even though the electrical conductivity appears to be good.     

The performance of a Ru?Mo sulfide catalyst for H2S decomposition

A γ-alumina-supported bimetallic Ru-Mo sulfide catalyst preparedvia precipitation from homogeneous solution (PFHS) has been used to effect the abstraction of H₂ from H₂S. The decomposition reaction was also carried out over Al₂O₃-supported RuS₂ and MoS₂ catalysts synthesizedvia PFHS. The performance of bimetallic system exceeded (ca. 40%) the simple additive activities of the constituent monometallic sulfide catalysts and about 2–3 times the individual activities of the monometallic sulfide samples, suggesting chemical synergism between Ru and Mo in the Ru-Mo catalyst. In particular, comparison with other catalysts in the literature showed that specimens preparedvia PFHS exhibited better activities than those from direct sulfidation of the metal oxide. Kinetic study over the Ru-Mo bimetallic sulfide catalyst in a quartz micro-reactor at 110 kPa and between 783–973 K revealed a 1st order dependency on H₂S partial pressure and an activation energy of about 92 kJ mol⁻¹. The irreversible adsorption of H₂S on a coordinatively unsaturated site is thought to be the rate-limiting step.     

The formation of mixed copper sulfide—silver sulfide membranes for copper( II)-selective electrodes: Part II. Relation between structure and electrochemical behaviour of the electroactive material

Mixed copper sulfide—silver sulfide precipitates used for copper-selective electrodes have been studied by x-ray powder diffractometry, scanning electron microscopy and solubility measurements, in order to find an explanation for the high limit of detection, measured in calibration experiments as well as in titrations. X-ray diffraction showed that some precipitates consisted of ternary sulfides (mainly jalpaite, Ag_1.5 ,Cu_0.5 S), while others were mixtures of the binary sulfides. The presence of ternary sulfides could be correlated with optimal electrochemical and mechanical characteristics. The solubility measurements showed extraordinarily high solubilities for these sulfides. Evidence is given that these high solubilities are caused by the oxidation of copper(I) present in the ternary compound, the reaction being Cu₂S ? CuS + Cu²⁺ + 2e^-. S.e.m. photographs gave some additional information about the structure and the particle size of several precipitates.     

Gas-chromatographic determination of volatile sulfur-containing impurities in industrial emissions and aqueous solutions

Procedures are developed for determining volatile sulfur-containing impurities, hydrogen sulfide, simple mercaptans, sulfides, and disulfides in air and aqueous solutions. The procedures are based on the principle’s headspace gas chromatography and equilibrium preconcentration. The procedures differ from the officially approved ones in that the operations of sampling and sample preparation to gas-chromatographic analysis considerably reduce the loss of hydrogen sulfide and mercaptans unstable in humid air. The procedures provide the determination of sulfur-containing substances at the level of their maximum permissible concentrations (MPC) in industrial emissions and natural waters and the analytical range of four orders of magnitude; they can be implemented on gas chromatographs with flame ionization and flame photometric detectors, a quartz capillary column, and a thermostated gas-sampling valve.