Addition Of Sulfur Compounds Research Articles

Surface Chemistry and Degradation Processes of Dense La0.6Sr0.4CoO3–δ Thin Film Electrodes

The changes of the surface morphology and the surface chemistry of LSC thin films grown on different substrates were tracked for 100 hours under SOFC operation conditions. Atomic force microscopy was used to monitor the formation of particles at the LSC surface. Depending on the thin film structure (polycrystalline vs. epitaxial), different particle formation dynamics were observed. Electron microscopy was employed to investigate the chemistry of the segregated particles and revealed that the particles were Sr- and S-rich. Secondary ion mass spectrometry and X-ray photoelectron spectroscopy measurements were performed on degraded LSC thin films, which also found significant amounts of sulfur on the LSC surface, despite no deliberate addition of sulfur compounds, as well as A-site cation enrichment. Impedance spectroscopy was used to track the polarization resistance of LSC grown on YSZ over the same degradation period and a strong increase inthe polarization resistance and in its activation energy was revealed (1.09 to 1.73 eV). The experimental results indicate that sulfur adsorption on LSC surfaces is omnipresent in the investigated conditions and even trace amounts of sulfur compounds present in nominally pure measurement gases account for particle formation and multiple degradation effects under operating conditions.

Novel photoanodes based on (Mo-Cr) co-doped titania nanotube for highly efficient photocathodic protection performance of stainless steel

Mo-doped, Cr-doped, and Mo-Cr co-doped titania nanotube arrays were synthesized through the single step anodization of titanium. Mo-Cr co-doped titania nanotubes prepared showed great improvement on photocatalytic activity in the protection of stainless steel (403SS) under visible light irradiation compared with Mo and Cr mono-doped titania. The open-circuit potential (OCP) of 403SS (in 3.5 wt% aqueous NaCl) coupled with the best co-doped sample (Cr50:Mo50-TNT) was reduced from −240 to −690 mV, while the electrode potential was maintained at −320 mV even upon turning the light off. This study also identified the effect of the addition of sulfur compounds as hole scavengers on the photoelectrochemical (PEC) properties and photoelectrochemical cathodic protection (PCP) by the best Mo-Cr co-doped titania nanotube. Sodium sulfate and sulfite, sodium thiosulfate, sodium sulfide, potassium metabisulfite and thiourea have been used as hole scavengers. The order of photocurrent is as follows: Na2S > K2S2O5 > CS(NH2)2 > Na2S2O3 > no hole scavengers > Na2SO4 > Na2SO3. Mo-Cr co-doped titania nanotube show much more favorable PCP impact on 403SS than the pure titania sample, according to the results of the changes in the potentials and current densities. Furthermore, the results finally proved that sodium sulfide is the most appropriate hole scavenger.

Upgrading of sawdust pyrolysis oil to hydrocarbon fuels using tungstate-zirconia-supported Ru catalysts with less formation of cokes

Abstract Using a continuous flow reactor, bio-oil prepared by the pyrolysis of sawdust was upgraded to produce petroleum-like deoxygenated hydrocarbon fuels. Dispersed tiny bio-char particles in the raw bio-oil were removed by extraction using diethyl ether to suppress solid-particle-nucleated coking. Noble metal catalysts, instead of molybdenum-based catalysts, were selected to avoid the continuous addition of sulfur compounds. Among the catalysts, tungstate-zirconia-supported Ru catalysts (Ru/WZr) exhibited high hydrodeoxygenation activity and less formation of cokes, which characteristics are important in the development of feasible upgrading processes. The investigation of catalysts used in this study demonstrates that the larger quantity of Bronsted acid sites compared to Lewis acid sites suppresses the formation of cokes.

Effects of sulfur on lead partitioning during sludge incineration based on experiments and thermodynamic calculations

Experiments in a tubular furnace reactor and thermodynamic equilibrium calculations were conducted to investigate the impact of sulfur compounds on the migration of lead (Pb) during sludge incineration. Representative samples of typical sludge with and without the addition of sulfur compounds were combusted at 850°C, and the partitioning of Pb in the solid phase (bottom ash) and gas phase (fly ash and flue gas) was quantified. The results indicate that three types of sulfur compounds (S, Na2S and Na2SO4) added to the sludge could facilitate the volatilization of Pb in the gas phase (fly ash and flue gas) into metal sulfates displacing its sulfides and some of its oxides. The effect of promoting Pb volatilization by adding Na2SO4 and Na2S was superior to that of the addition of S. In bottom ash, different metallic sulfides were found in the forms of lead sulfide, aluminosilicate minerals, and polymetallic-sulfides, which were minimally volatilized. The chemical equilibrium calculations indicated that sulfur stabilizes Pb in the form of PbSO4(s) at low temperatures (<1000K). The equilibrium calculation prediction also suggested that SiO2, CaO, TiO2, and Al2O3 containing materials function as condensed phase solids in the temperature range of 800–1100K as sorbents to stabilize Pb. However, in the presence of sulfur or chlorine or the co-existence of sulfur and chlorine, these sorbents were inactive. The effect of sulfur on Pb partitioning in the sludge incineration process mainly depended on the gas phase reaction, the surface reaction, the volatilization of products, and the concentration of Si, Ca and Al-containing compounds in the sludge. These findings provide useful information for understanding the partitioning behavior of Pb, facilitating the development of strategies to control the volatilization of Pb during sludge incineration.

Effect of sulfur and its compounds on the performance of graphite electrooxidation in molten carbonate

Direct carbon fuel cells are promising power sources with their performance significantly depending on the electrooxidation activity of carbon fuel. The impurities in the carbon fuel may affect the anode reactions. Sulfur and some of its inorganic compounds (CaSO4, K2SO3, K2S, FeS2) were added in molten carbonate and their effect on graphite electrooxidation was investigated. Cyclic voltammograms of gold electrode with addition of these sulfur compounds showed CaSO4 was stable and other compounds were electrochemically oxidized to high valence state sulfur compounds at operating voltage range. Linear sweep voltammetry of graphite with addition of sulfur compounds exhibited enhanced current density compared to pure graphite electrooxidation. Chronoamperometry was carried out to examine steady-state test of graphite electrooxidation in presence of sulfur compounds and the results indicated the enhanced current densities were caused by improved Boudouard reaction for CaSO4 and sulfur electrooxidation for other compounds, respectively. These inorganic sulfur compounds had no impact on electrooxidation process of graphite.

Etching Rate Enhancement of Copper by Adding Sulfur Compounds in Chemical-Mechanical Polishing Slurries

In the chemical mechanical polishing (CMP) process, we have discovered that the Cu etching rate can be enhanced without affecting the Cu slurry's pH by adding a small amount of the sulfur compounds MPS and Na2S2O3. Adding the sulfur compounds to the H2O2 slurry results in an increment in the oxidation reduction potential (ORP). The electrochemical model (mixed potential) showed that the ORP increment leads to enhancement of the Cu oxidizing reaction. Because XPS and Raman analysis of the Cu surface revealed that the Cu etching rate in CMP is limited by the Cu oxidizing reaction, we concluded that the Cu etching rate is enhanced by the addition of sulfur compounds to the Cu oxidizing reaction to increase the ORP increment.

Effect of the addition of sulfur compounds on the hydroformylation of 1-hexene catalyzed by rhodium systems

The effect of the addition of triphenylphosphine sulfide, thiophene, benzo[b]thiophene and dibenzo[b,d]thiophene on the hydroformylation of 1-hexene catalyzed by rhodium complexes RhH(CO)4, RhH(CO)2(PPh3)2 and RhH(CO)2(diphos) was studied. The addition of these sulfur compounds did not affect the activity of non modified rhodium precatalysts, decreased the activity of the PPh3-modified one and increased the activity of the diphos-modified ones, which is indicative of the sulfur tolerance of these precatalysts. The linear to branched ratio (l/b) varied from 0.5 to 3.4 for the non-modified precatalyst, and from 1.7 to 3.3 for the phosphine-modified ones.

Geochemical Influence on Diversity and Microbial Processes in High Temperature Oil Reservoirs

The diversity of thermophilic microbial assemblages detected within two neighboring high temperature petroleum formations was shown to closely parallel the different geochemical regimes existing in each. A high percentage of archaeal 16S rRNA gene sequences, related to thermophilic aceticlastic and hydrogenotrophic methanogens, were detected in the natural gas producing Rincon Formation. In contrast, rRNA gene libraries from the highly sulfidogenic Monterey Formation contained primarily sulfur-utilizing and fermentative archaea and bacteria. In addition to the variations in microbial community structure, microbial activities measured in microcosm experiments using high temperature production fluids from oil-bearing formations also demonstrated fundamental differences in the terminal respiratory and redox processes. Provided with the same suite of basic energy substrates, production fluids from the South Elwood Rincon Formation actively generated methane, while thermophilic microflora within the Monterey production fluids were dominated by hydrogen sulfide producing microorganisms. In both cases, molecular hydrogen appeared to play a central role in the stimulation of carbon and sulfur cycling in these systems. In methanogenic production fluids, the addition of sulfur compounds induced a rapid shift in the terminal electron accepting process, stimulating hydrogen sulfide formation and illustrating the metabolic versatility of the subsurface thermophilic assemblage. The high similarity between microbial community structure and activity corresponding with the prevalent geochemical conditions observed in deep subsurface petroleum reservoirs suggests that the resident microflora have adapted to the subsurface physicochemical conditions and may actively influence the geochemical environment in situ.

Regiospecific hydrogenation of quinolines and indoles in the heterocyclic ring

AbstractQuinolines, indoles, acridine, and carbazole were hydrogenated using a large variety of heterogeneous catalysts in hydrocarbon solvents in an effort to achieve selective hydrogenation of the heterocyclic ring. When quinolines were hydrogenated using supported platinum, palladium, rhodium, ruthenium, or nickel metal catalysts in the presence of hydrogen sulfide, carbon disulfide, or carbon monoxide, there was exclusive hydrogenation of the heterocyclic ring to give only 1,2,3,4‐tetrahydroquinolines. Use of iridium, rhenium, molybdenum(VI) oxide, tungsten(VI) oxide, chromium(III) oxide, iron(III) oxide, cobalt(II) oxide‐molybdenum(VI) oxide, or copper chromite catalysts also caused exclusive hydrogenation of the heterocyclic ring even without addition of sulfur Compounds or carbon monoxide. Hydrogenation of indoles using platinum, rhenium, or, in some cases, nickel catalysts (with or without sulfur Compounds) occurred exclusively in the heterocyclic ring to give indolines, but conversions were affected by indole‐indoline equilibria.

シアン化銅メッキのメッキ条件および添加剤の電着応力におよぼす影響について

The internal stress in electrodeposited copper from cyanide baths is one of the very important factors since the copper is widely used as an undercoat for nickel and other platings. This paper reports the stress measured by Right Flat Strip method under various electrolytic conditions as well as various bath compositions and additives.The results obtained were summarized as follows.(1) There were little effects of bath compositions and other electrolytic conditions on internal stress.(2) The addition of inorganic compounds (particularly the compounds, which seem to be deposited together with copper) increased the tensile stress with the increase in its amount of addition or increase in current density. However, the addition of a very small ammunt of lead compounds decreased the tensile stress.(3) The addition of sulfur compounds containing free sulfur increased tensile stress with the increase in their amount of addition or increase in PR current density.(4) The addition of most of organic compounds had no remarkable effects on the internal stress.