Coexistence Of H2S Research Articles

Effect of coexistence of H2S on production of hydrogen and solid carbon by methane decomposition using Fe catalyst

Biogas derived from livestock manure and food residue contains CO2 and H2S as well as methane. The effect of CO2 and H2S coexistence on the production of hydrogen and solid carbon by methane decomposition over iron oxide catalysts was investigated. The catalytic activity for methane decomposition was decreased by the coexistence of H2S. Moreover, the activity decrease was aggravated by the coexistence of CO2 as well as H2S, and higher temperature was required to mitigate the activity decrease by the coexistence of CO2. By increasing the amount of catalyst, the upstream catalyst was preferentially poisoned, but the downstream catalyst developed catalytic activity thanks to its sacrifice. With 2 g of catalyst, the maximum conversion of pure methane was about 85% at 840 °C, but it was slightly less than 80% in the presence of H2S or H2S + CO2. When the catalyst amount was increased to 4 g, the conversion of pure methane was about 90% at 800 °C, but 84% in the presence of H2S and 80% in the presence of H2S + CO2. The poisoning by H2S was irreversible at low temperatures but became reversible at higher temperatures. Since H2S is adsorbed by the deposited carbon, the procedure for further removal of H2S may be omitted. The coexistence of H2S also affected the shape of the deposited carbon. Although carbon-based catalysts are known to be effective for methane decomposition in the presence of H2S, iron oxide catalysts have the advantage of superior methane conversion at low temperatures. By flowing methane with CO2 and H2S from the downstream side after the reaction flowing from the upstream side for a certain period of time, the catalytic lifetime was drastically extended and the amount of hydrogen and solid carbon produced was dramatically increased, compared to the case of flowing from upstream all the way.

Role of NaCl, CO2, and H2S on Electrochemical Behavior of 304 Austenitic Stainless Steel in Simulated Oil Industry Environment

The electrochemical behavior of 304 austenitic stainless steel (304ASS) was studied by different methods such as potentiodynamic polarization, EIS, SEM, and Raman spectroscopy. Potentiodynamic polarization data suggest that 304 ASS could be more susceptible to corrosion due to the presence of H2S. The coexistence of H2S and Cl−-type ionic species in 304 ASS lead to a decrease in the corrosion resistance as compared to the H2S-free condition. It is seen that CO2 helps form a passive layer on the metallic surface, which eventually decreases its corrosion rate. Raman spectroscopy analysis shows that the passive layer developed under different condition consists of FeCO3, FeS2, Fe2O3, Fe(OH)2, etc. SEM images further confirm that elemental S− and Cl− can infiltrate the passive film and cause the passive film to deteriorate.

Stability of an Electrodeposited Nanocrystalline Ni-Based Alloy Coating in Oil and Gas Wells with the Coexistence of H₂S and CO₂.

The stability of an electrodeposited nanocrystalline Ni-based alloy coating in a H2S/CO2 environment was investigated by electrochemical measurements, weight loss method, and surface characterization. The results showed that both the cathodic and anodic processes of the Ni-based alloy coating were simultaneously suppressed, displaying a dramatic decrease of the corrosion current density. The corrosion of the Ni-based alloy coating was controlled by H2S corrosion and showed general corrosion morphology under the test temperatures. The corrosion products, mainly consisting of Ni3S2, NiS, or Ni3S4, had excellent stability in acid solution. The corrosion rate decreased with the rise of temperature, while the adhesive force of the corrosion scale increased. With the rise of temperature, the deposited morphology and composition of corrosion products changed, the NiS content in the corrosion scale increased, and the stability and adhesive strength of the corrosion scale improved. The corrosion scale of the Ni-based alloy coating was stable, compact, had strong adhesion, and caused low weight loss, so the corrosion rates calculated by the weight loss method cannot reveal the actual oxidation rate of the coating. As the corrosion time was prolonged, the Ni-based coating was thinned while the corrosion scale thickened. The corrosion scale was closely combined with the coating, but cannot fully prevent the corrosive reactants from reaching the substrate.

Effect of H2S concentration on the corrosion behavior of pipeline steel under the coexistence of H2S and CO2

The effect of H2S concentration on H2S/CO2 corrosion of API-X60 steel was studied by scanning electron microscopy, a weight-loss method, potentiodynamic polarization tests, and the electrochemical impedance spectroscopy technique. It is found that the corrosion process of the steel in an environment where H2S and CO2 coexist at different H2S concentrations is related to the morphological structure and stability of the corrosion product film. With the addition of a small amount of H2S, the size of the anode reaction region is decreased due to constant adsorption and separation of more FeS sediment or more FeHS+ ions on the surface of the steel. Meanwhile, the double-layer capacitance is diminished with increasing anion adsorption capacity. Therefore, the corrosion process is inhibited. The general corrosion rate of the steel rapidly decreases after the addition of a small amount of H2S under the coexistence of H2S and CO2. With a further increase in H2S concentration, certain parts of the corrosion product film become loose and even fall off. Thus, the protection provided by the corrosion product film worsens, and the corrosion rate tends to increase.

Study and Application for Corrosion-Resistant Material Selection of Tubing and Casing in Sour Gas Reservoirs under Coexistence of H<sub>2</sub>S and CO<sub>2</sub>

For natural gas well with high content of CO2 and H2S, very serious corrosion in the gas well string is an important factor of gas production system life. In order to ensure the long-term development of gas wells, this paper mainly study the corrosion-resistant material selection of tubing and casing in sour gas reservoirs under coexistence of H2S and CO2 and proposes the optimization idea and technique of tubing and casing material selection. By taking Puguang gas field as an example, this paper optimizes the material selection of production casing for Puguang gas field. By testing, the optimal materials of gas well string in Puguang gas field have good performance of erosion resistance

Hygienic and Chemical Studies on Effluent Water (I) : Determination of Formaldehyde in Waste Water

Nash reported that HCHO reacted with acetylacetone in the presence of excess ammonia to produce 3, 5-diacetyl-1, 4-dihydrolutidine (DDL). The joint commitee of Association of British Chemical Manufactures and Society for Analytical Chemistry proposed DDL-colorimetry as a standard for detection of HCHO in effluent water. The authors investigated further on DDL-colorimetry and obtained the following results. After 20 min. at 60° and pH 6.5 the coloration of DDL formed was maximum. The color of DDL-solution was stable for 72 hr. in a sealed container and able to be determined spectrophotometrically at 425 mμ when 1∼8 ppm. of HCHO was present. Coexistence of H2S with HCHO in effluent water inhibited the formation of DDL, but the addition of zinc acetate solution at the time of distillation could remove this disturbance. By distillation repeated three times with addition of water 100 % of HCHO in effluent water was recoverable.