Papers by Keyword: H₂S

Abstract: A colorimetric approach for the quantitative detection of H2S based on a NiO@r-GO composite was developed in this study and is simple, quick, and low-cost. Bimetallic porous material NiO@r-GO with iodide adsorption into their framework have been shown to boost catalytic activity. In this study, we present a new method for enhancing NiO@r-GO peroxidase-like activity. Comparatively, the kinetic measurements of NiO@r-GO demonstrate that it has a great affinity for substrates, facilitating electron transport, as opposed to HRP. Improvements in the activity of NiO@r-GO are attributable to the synergistic effect of the two compounds and to the speedy electron transfer process. This method is very sensitive for H₂S colorimetric technique with a LOD of 0.58 nM.

Abstract: Titanium dioxide and gold nanoparticles were synthesized using an environmentally friendly method to deposit undoped and Au-doped TiO₂ thin films on silicon and glass substrates via the spray pyrolysis technique. The effect of the Au nanoparticles concentrations on structural, morphological, and hydrogen sulfide (H₂S) gas sensing characteristics of TiO₂ thin films were investigated. An X-ray diffraction pattern confirmed the polycrystalline structure of the films deposited on glass and Si substrates with a dominant rutile phase and the formation of additional mixed-phases of Ti-Au bonding. According to a Field Emission-Scanning Electron Microscopy investigation, the cluster size ranged from 20 to 180 nm depending on the concentration of AuNPs. The sensing response of the prepared films was tested against H₂S at different operating temperatures. The effect of growing a mixture of titanium-gold phases as a suitable catalyst for hydrogen sulfide sensitivity is also discussed.

Abstract: Corrosion behavior of the alloys 1.7386 (P9), 1.4462, 1.4841, 1.4959 (Alloy 800HT) and 2.4816 (Alloy 600) was tested for 24, 72 and 240 h between 480 – 680 °C. The testing gas atmosphere contained 3.8 vol. % HCl, 200 ppm H₂S and CO, CO₂ and N₂. It simulated conditions present in a thermal cracking process for post-consumer plastics. Samples were analyzed by metallography, SEM/EDX and XRD after corrosion experiments. Additionally, their mass loss during the test was evaluated. A multilayered structure of corrosion products grew on the samples during the corrosion experiments. The composition of the corrosion products depended not on the material, but on the testing temperature. At 680 °C chromium sulphide formed the outer layer, followed by a chromium oxide layer. Below these two layers a chlorine containing layer was observed. At 480 °C mainly nickel sulphide was detected, besides chromium oxide and iron- and chromium chloride. Especially at higher testing temperatures FeCl₂ was not observed directly on the samples, but as colorless crystals at the colder parts of the testing equipment. At 680 °C the mass loss of the samples decreased with increasing nickel content. However, this effect changed entirely at lower testing temperatures. At 480 °C 1.7386 and 2.4816 showed nearly the same mass losses.

Abstract: Cost factors must be considered in the development of Yan'an gas field. In order to evaluate the applicability of economical 80S steel in the sulfur gas reservoir environment of Yan'an gas field, the indoor corrosion test was conducted to evaluate the resistance of 80S steel to uniform corrosion and SCC resistance in CO₂/H₂S coexisting corrosion environment, and combined with relevant standards. The security was analyzed. The results show that the uniform corrosion rate of 80S steel is the largest at 50 °C, and it decreases first and then increases with the increase of temperature. When the loading stress is 496.8MPa (552MPa×90%),the test duration was 720h. One sample cracked and the other two parallel samples did not cracked Comprehensive anti-uniform corrosion performance and anti-SCC performance, it is believed that 80S steel has certain risks in the corrosive environment of Yan'an gas field. It needs to cooperate with other anti-corrosion measures and monitor the service of the well string at any time.

Abstract: This research aimed to modify of diatomite and leonardite for adsorption of hydrogen sulfide (H₂S) gas. The effect of chemical loading on surface modification was studied. Natural diatomite and leonardite were obtained through the natural deposits in Lampang Province, Thailand. Diatomite and leonardite were modified using chemical methods with calcination at 450 °C. The chemical composition and phase structure of adsorbents were characterized by X–Ray fluorescence spectroscopy (XRF) and X–ray diffraction (XRD), respectively. The morphology and disperse energy of the elements were investigated by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The functional group was identified by Fourier transform infrared spectroscopy (FT–IR). The efficiency of adsorption of H₂S gas was studied. H₂S gas in this study was synthesized by the chemical reaction between sodium sulfide (Na₂S) and sulfuric acid (H₂SO₄). The concentration of hydrogen sulfide was measured by an H₂S gas detector. The performance of the modified diatomite and leonardite for adsorption of H₂S was compared. It was found that modified diatomite has better efficiency than modified leonardite for the adsorption of H₂S gas. After modification process, the adsorption efficiency increased while the adsorption time decreased.

Abstract: WO₃ nanostructure with nanocube morphology was synthesized through acidification of Na₂WO₄·2H₂O, which were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Moreover, the result of the present work implied that the sensor fabricated by nanocube WO₃ could detect the level of 330 ppb H₂S, which is much lower than the threshold limit value of 10 ppm. Compared with other results, the nanocube WO₃ sensor shows higher sensitivity, excellent selectivity and faster response/recovery to H₂S. Especially, the best operating temperature of this nanocube WO₃ for H₂S detection is 100 °C.

Abstract: The p-Cu_xO core/n-ZnO shell heterostructure nanowire (NW) arrays were fabricated by thermal decomposition. Based upon the core/shell nanowire-based all oxide p-n junctions. The samples were analyzed by XRD, SEM, EDS and TEM. X-ray diffraction (XRD) analysis showed that the p-Cu_xO core/n-ZnO shell NW consisted of phase of p-Cu_xO and wurtzite phase of n-ZnO. The morphology analysis showed average diameter and length of nanowires of ̴ 50 to 200 nm and ̴ 10 to 30 µm, respectively. The EDS spectrum confirmed the presence of required elements in the p-Cu_xO core /n-ZnO shell NWs. It was found that Zn, O and Cu are distributed over the wire areas according to a ratio of 1:2 by atomic% ratio of Cu:Zn to get good core/shell structure. The TEM characterizations showed that the n-ZnO shell nanoparticles were comprised of n-ZnO polycrystalline nanoparticles (NPs) on the surface of p-Cu₂O core NWs. The H₂S gas sensing properties of the p-Cu_xO/n-ZnO NWs were evaluated in air containing dilute H₂S gas at sensing temperatures (T) of 350°C. The response of 20.6 for p-Cu_xO/n-ZnO NW sensor to H₂S gas was enhanced compared to that of the n-ZnO NW. The enhanced response of p-Cu_xO/n-ZnO NW sensor is due to increasing surface area, the increased amount of chemisorbed oxygen species on NP surface and the increased conductivity.

Abstract: The nickel-iron-chromium-based alloy, Incoloy alloy 800, was corroded at 600, 700 and 800 °C for 10-70 h under 1 atm of total pressure in three different atmospheres, viz., 1 atm of N₂, N₂/H₂O, and N₂/H₂O/H₂S-mixed gases. The corrosion rates always increased with addition of H₂O and, much more seriously, with the addition of H₂S gas. In N₂ and N₂/H₂O gases, oxidation prevailed. In N₂/H₂O/H₂S gases, sulfidation dominated. The corrosion resistance increased in the T22 steel displayed better resistance to oxidation and sulfidation than Fe-2Mn-0.5Si steel, owing to the presence of Cr. Strong enrichment of Cr and the presence of Ni and Fe were noticeable in the inner scale. Chromium sulfidized to FeCr₂S₄ in N₂/H₂O/H₂S gases, which was responsible for the enhanced sulfidation resistance of T22 compared with Fe-2.0Mn-0.5Si steel.

Abstract: The purpose of this work is to synthesize undoped and Cu-doped ZnO sorbents by citrate-gel method and compare desulfurization efficiency, particularly H₂S, at 150°C and 300°C. The undoped ZnO result shows a single phase of hexagonal zincite while the CuO monoclinic phase appeared with ZnO hexagonal phase in Cu-doped compositions (denoted by ZCx where x = mol% of Cu). The microstructure and surface area have been investigated by SEM and BET, respectively. The surface area decreases with the amount of Cu and all of them have a porous structure with small grains. The desulfurization performance of all specimens have been investigated by fixed-bed reactor. The results from breakthrough time indicate ZC20 sorbent has highest sulfur sorption capacity at 300°C. The XRD results show ZnO and CuO in ZC20 can absorb sulfur and completely transform to ZnS, cubic CuS and hexagonal CuS at 300°C.

Abstract: H₂S adsorption and dissociation on MoP(010) were investigated using density functional theory (DFT) together with periodic slab models. Several different possibilities for H₂S, SH, S and H adsorption were considered. Our results show that the H₂S, SH and H prefer to adsorb at bridge site, while S adsorbs preferentially at hcp and bridge sites. Additionally, the optimum co-adsorption configurations for SH/H and S/H were determined. The results indicate that the co-adsorbed species repel each other slightly on MoP(010) surface. Finally, the potential energy profile of H₂S dissociation on MoP(010) surface was given out. The dissociation energy barriers of the S–H bond scission exhibit that H₂S prefers to dissociate on MoP(010) surface. When compared with MoP(001) surface, the obvious differences in H₂S decomposition arise demonstrate that the MoP-based catalysts are structure-sensitive.