Ethane steam reforming over a platinum/alumina catalyst: effect of sulphur poisoning

In this study we have examined the adsorption of hydrogen sulfide and methanethiol over platinum catalysts and examined the effect of these poisons on the steam reforming of ethane. Adsorption of hydrogen sulfide was measured at 293 and 873 K. At 873 K the adsorbed state of hydrogen sulfide in the presence of hydrogen was SH rather than S, even though the Pt:S ratio was unity. The effect of 11.2 ppm hydrogen sulfide or methanethiol on the steam reforming of ethane was studied at 873 K and 20 barg. Both poisons deactivated the catalyst over a number of hours, but methanethiol was found to be more deleterious, reducing the conversion by almost an order of magnitude, possibly due to the co-deposition of sulfur and carbon. Changes in the selectivity revealed that the effect of sulfur was not uniform on the reactions occurring, with the production of methane reduced proportionally more than the other products, due to the surface sensitivity of the hydrogenolysis and methanation reactions. The water-gas shift reaction was affected to a lesser extent. No regeneration was observed when hydrogen sulfide was removed from the feedstream in agreement with adsorption studies. A slight regeneration was observed when methanethiol was removed from the feed, but this was believed to be due to the removal of carbon rather than sulfur. The overall effect of sulfur poisoning was to reduce activity and enhance hydrogen selectivity

Controllable thioester-based hydrogen sulfide slow-releasing donors as cardioprotective agents

Hydrogen sulfide (H2S) is an important signaling molecule with promising protective effects in many physiological and pathological processes. However, the study of H2S has been impeded by the lack of appropriate H2S donors that could mimic its slow-releasing process in vivo. Herein, we report the rational design, synthesis, and biological evaluation of a series of thioester-based H2S donors. These cysteine-activated H2S donors release H2S in a slow and controllable manner. Most of the donors comprising an allyl moiety showed significant cytoprotective effects in H9c2 cellular models of oxidative damage. The most potent donor 5e decreased the mitochondrial membrane potential (MMP) loss and lactate dehydrogenase (LDH) release in H2O2-stimulated H9c2 cells. More importantly, donor 5e exhibited a potent cardioprotective effect in an in vivo myocardial infarction (MI) mouse model by reducing myocardial infarct size and cardiomyocyte apoptosis. Taken together, our studies demonstrated that these new allyl thioesters are potential cardioprotective agents by releasing H2S

Investigation of industrial compositions SONKOR as corrosion inhibitors of mild steel in neutral media containing hydrogen sulfide

Electrochemical and corrosion behavior of mild steel in neutral media containing hydrogen sulfide has been investigated by weight-loss and electrochemical methods and protective effect of industrial compositions SONKOR has been determined. It has been shown that in 3 % NaCl compositions SONKOR have weak protective effect but it increases greatly in presence of hydrogen sulfide in the solution. At concentration of H2S = 0,6 gram per liter maximal protective effect has SONKOR 9801 (85.57 %) and SONKOR 9920А (81.97 %). Inhibitors SONKOR 9021С (70.82 %), 9510А (73.11 %) и 9701 (67.87 %) show less protective effect

Photochemical Decomposition of Hydrogen Sulfide

Hydrogen sulfide is an extremely toxic gas which is generated from both nature factors and human factors. A proper method for the efficient decomposition of hydrogen is of great importance. Using traditional Claus process, hydrogen sulfide could be decomposed into hydrogen oxide and sulfur. One drawback of this process is that the energy stored in hydrogen sulfide is partially wasted by the formation of hydrogen oxide. In fact, the energy could be utilized for the generation of hydrogen, a potential energy source in future, or other chemical products. Various methods that could possibly make better use of hydrogen sulfide have been studied in recent years, like thermal decomposition, plasma method, electrochemical method, and photochemical method. In particular, there have been high hopes in photochemical method due to the possible direct solar energy conversion into chemical energy. Unlike traditional photocatalytic water splitting, hydrogen sulfide decomposition is more accessible from the thermodynamic point of view. Photocatalytic hydrogen sulfide decomposition could occur in both gas phase and solution phase and various systems have been reported. Besides, the photoelectrochemical decomposition of hydrogen sulfide is also highlighted. In this chapter, we will simply introduce the current situation for photochemical decomposition of hydrogen sulfide

Hydrogen sulfide inhibits the renal fibrosis of obstructive nephropathy

Hydrogen sulfide has recently been found decreased in chronic kidney disease. Here we determined the effect and underlying mechanisms of hydrogen sulfide on a rat model of unilateral ureteral obstruction. Compared with normal rats, obstructive injury decreased the plasma hydrogen sulfide level. Cystathionine-β-synthase, a hydrogen sulfide-producing enzyme, was dramatically reduced in the ureteral obstructed kidney, but another enzyme cystathionine-γ-lyase was increased. A hydrogen sulfide donor (sodium hydrogen sulfide) inhibited renal fibrosis by attenuating the production of collagen, extracellular matrix, and the expression of α-smooth muscle actin. Meanwhile, the infiltration of macrophages and the expression of inflammatory cytokines including interleukin-1β, tumor necrosis factor-α, and monocyte chemoattractant protein-1 in the kidney were also decreased. In cultured kidney fibroblasts, a hydrogen sulfide donor inhibited the cell proliferation by reducing DNA synthesis and downregulating the expressions of proliferation-related proteins including proliferating cell nuclear antigen and c-Myc. Further, the hydrogen sulfide donor blocked the differentiation of quiescent renal fibroblasts to myofibroblasts by inhibiting the transforming growth factor-β1-Smad and mitogen-activated protein kinase signaling pathways. Thus, low doses of hydrogen sulfide or its releasing compounds may have therapeutic potentials in treating chronic kidney disease

Photo-electrochemical Hydrogen Sulfide Splitting using SnIV-doped Hematite Photo-anodes

© 2016 The Authors. Published by Elsevier B.V.Spray-pyrolysed SnIV-doped α-Fe2O3 photo-anodes were used for photo-assisted splitting of HS- ions in alkaline aqueous solutions, producing polysulfide (Sn2 -) ions together with hydrogen at the cathode. Subsequent aerial oxidation of polysulfide could be used to produce elemental sulfur. At an applied electrode potential of 1.07 V (RHE) and an irradiance of 5.6 kW m- 2, stable photocurrents of ca. 11 A m- 2 (2 × 10- 3 A W- 1) were recorded over 75 h, polysulfide concentrations increasing linearly with time. Despite being predicted thermodynamically to form iron sulfide(s) in sulfide solutions, such photo-anodes appeared to be stable. In comparison with conventional water splitting under alkaline conditions, the coupled processes of hydrogen sulfide ion oxidation and water reduction had a lower energy requirement

Effects of porewater hydrogen sulfide on the feeding activity of the subsurface deposit-feeding polychaete, Clymenella torquata, Leidy

The effects of porewater hydrogen sulfide concentrations on the feeding and tube-building activity of the subsurface, deposit-feeding polychaete, Clymenella torquata were experimentally determined in the laboratory. Porewater hydrogen sulfide concentrations were manipulated by injecting a buffered, isotonic sodium sulfide solution into the experimental chambers. Fecal material was collected and weighed and tube-building activity was monitored daily. Fecal production was negatively correlated with porewater hydrogen sulfide concentration during experiments conducted in June and July. Hydrogen sulfide concentrations greater than 1000 μM in June and 700 μM in July resulted in reduced fecal production. Fecal production was not correlated with porewater hydrogen sulfide concentration in experiments conducted in September and October, and some worms in the September experiment were surprisingly tolerant of porewater hydrogen sulfide concentrations as high as 3.8 mM. The lower tolerance of C. torquata to porewater hydrogen sulfide concentrations during the June and July experiments compared to the September and October experiments indicates that worms in the field became acclimated to increasing porewater hydrogen sulfide levels as temperatures increased. Tube-building frequencies were higher in worms in the June and July experiments than in the September and October experiments. In addition, experiments demonstrated that Clymenella is capable of modifying the porewater hydrogen sulfide concentration at depth in the sediment around its tube possibly by irrigation activities. These results suggest that porewater hydrogen sulfide concentrations may have significant non-lethal effects on the ecology of this species. Acquired tolerance to increased hydrogen sulfide concentrations may enable organisms to survive and feed under conditions in which other organisms cannot, making possible the exploitation of a niche used by relatively few benthic polychaetes. Porewater chemistry should be monitored and regulated during experiments on feeding rates and bioturbation in soft-bottom infaunal organisms

Doctor of Philosophy

dissertationHydrogen sulfide (H2S) is a toxic gas with a distinct rotten-egg odor. While the detrimental affects of H2S on human health have been known for hundreds of years, it has recently become apparent that low levels of endogenously produced hydrogen sulfide are cytoprotective. In fact hydrogen sulfide is an important signaling molecule in a variety of systems resulting in a large range of physiological effects, from vasodilatory to antiinflammatory. However, the exact roles played by hydrogen sulfide, its concentrations in serum and tissues, and the enzymes that produce it are still being investigated. It seems that a lack of tools with which to accurately measure in vivo concentrations of hydrogen sulfide has stalled progress in the field. Herein we report several novel, fluorescent probes with which to detect endogenous concentrations of hydrogen sulfide both in vitro and in biological samples. These probes utilize an arylazide moiety that is selectively reduced by hydrogen sulfide to produce a signal. We show that this signal is concentration-dependent in a linear manner up to 300 !M hydrogen sulfide. We also show that these probes are sensitive down to 200 nM hydrogen sulfide. Additionally, we have applied these probes in assays to study hydrogen sulfide-producing enzymes, cystathionine "-synthase (CBS), cystathionine #-lysase (CGL), and tryptophan synthase (TS). By discovering selective inhibitors of these enzymes, we can modulate hydrogen sulfide production in vivo. Lastly, we have applied a series of lanthanide-based fluorescent probes to detect hydrogen sulfide in the petrochemical industry. These probes utilize a similar arylazide moiety as an antenna. The lanthanide center can be excited after reaction with H2S to give a signal with a long lifetime. By delaying the readout, it is possible to see this signal over a highly fluorescent background, such as crude oil. These probes have been used to study the presence of hydrogen sulfide in two sour water samples as well as five samples of crude oil obtained from the Tesoro Corporation

Hydrogen sulfide: potent regulator of vascular tone and stimulator of angiogenesis

Hydrogen sulfide is the "third" gasotransmitter on the rise in cardiovascular research. Recent studies show that hydrogen sulfide has a great potential in the regulation of vascular tone of systemic arteries and many molecular targets are discussed. However, the complex mechanism of vascular tone regulation by hydrogen sulfide is only incompletely understood. It seems that a potent interaction of hydrogen sulfide with vascular endothelial growth factor (VEGF) becomes important in angiogenesis, in the process of wound healing, but also in tumor angiogenesis. Hydrogen sulfide exerts anti-inflammatory effects and it could be a pharmacological target in vascular dysfunction in association with obesity-related hypertension as well as in tumor development and progression. However, the underlying molecular pathways still need to be revealed. This review primarily focuses on the regulatory role of hydrogen sulfide in controlling vascular tone. We attempt to provide recent insights into mechanisms by which CSE-dependent hydrogen sulfide plays a role in the regulation of vascular tone by perivascular adipose tissue. The role of KCNQ channels and other ionic permeation pathways as key targets will be discussed. Recent findings which are summarized in this paper provide new insights into molecular mechanisms of hydrogen sulfide that are crucial for understanding vascular dysfunction in cardiovascular disease and possibly angiogenesis. Future research will be extended to investigate the therapeutic potential of hydrogen sulfide and their targets such as KCNQ channels in cardiovascular diseases, angiogenesis and tumor genesis

Odor Monitoring at the New Orleans East Bank Wastewater Treatment Plant

Hydrogen Sulfide is a corrosive, odorous, and hazardous gas that can cause issues for wastewater collection systems and treatment plants. When evaluating hydrogen sulfide concentrations it is important to consider the source, odor causing mechanism, and its level of toxicity. In this study, continuous hydrogen sulfide monitoring was performed for 8 locations within the New Orleans East Bank Wastewater Treatment Plant for a span of 5 months. Hot spots within the plant are located and data analysis is performed based on daily and hourly averages of hydrogen sulfide concentrations. The data was configured to show peak hydrogen sulfide concentrations at specific time intervals throughout the day