Synthesis of Porous Cobalt Oxide and Its Performance for H2S Removal at Room Temperature

Pilot-Scale Experimental Study on the Coupling of Venturi-Bubbling Reactor to Promote the Absorption of Leaked H2S

Natural gas generates varying concentrations of H2S during natural formation and extraction, and H2S leak accidents are frequent, posing a significant threat to the safety of human life and the environment. Conventional treatment technology equipment is large and does not meet the emergency requirements of the complex topographical gas field. This study aimed to design a pilot-scale method coupling the venturi and bubbling reactors to reduce equipment size and improve emergency capabilities for the absorption of leaked H2S. It found that the ring system self-priming venturi reactor, which was suitable only for the coarse treatment of toxic gases, maintained an absorption efficiency of around 50% under most operating conditions, with substantial variations due to changes in process parameters, but that redundancy of the bubbling reactor was high. With the synergistic effect of venturi and bubbling, the coupling process had an extremely high absorption efficiency, basically more than 95%. The experiments also showed that the H2S concentration at the outlet of the venturi-bubbling reactor increased with increasing inlet gas concentration and gas volume. The absorption performance improved significantly on increasing Fe3+ concentration; it increased first and then remained constant, and the optimum Fe3+ concentration for the absorption of leaked H2S was 21 000 mg/m3. The absorption performance decreased with increasing submergence height and then remained stable after the size of the inlet approached 600 mm, whereas the overall absorption efficiency of the venturi-bubbling reactor remained constant. The optimum operating temperature range was 10 °C-50 °C. The experimental system kept the outlet concentration below the emergency discharge standard for a continuous period of 48 h following practical use in the gas field and resulting in significant enhancement in mass transfer performance, fully satisfying the emergency requirements.

Development of CuO/Cu4(OH)6SO4 Nanoparticle Mixtures to Optimize the H2S Adsorption

In this paper, we report the H2S adsorption behavior of a sorbent composed of mixtures of tenorite (CuO) and brochantite [Cu4(OH)6SO4]. These materials are readily prepared through the addition of NaOH(aq) to CuSO4(aq). They can be loaded onto polymer foams to create effective filters that can remove malodorous H2S gas, as evidenced by breakthrough tests. X-ray diffraction shows that the ratio of the two compounds in the mixture can be finely tuned by varying the amount of NaOH(aq) that is added to the reaction mixture. X-ray photoelectron spectroscopy shows that brochantite, like tenorite, has the ability to chemically adsorb H2S. Correlation of the H2S breakthrough data with scanning transmission electron microscopy measurements shows that the most effective sorbents contain nanoscale needle-like particles. These are likely to be formed largely by the tenorite phase. The samples with the greatest H2S adsorption efficacy contained less than 20% tenorite in the mixture, where these particles had the greatest abundance. The application of this sorbent onto porous substrates to create effective filters, along with the synthetic ease of its production, could allow this methodology to find use in a number of areas where H2S poses a problem. This could include areas where protective clothing is required to adsorb the gas from environments where there is a high level of H2S, for example, in wastewater treatment plants, oil and gas wells, or in the medical sector, where it could be deployed as filter media.

Bimetallic-MOF-Derived ZnxCo3-xO4/Carbon Nanofiber Composited Sorbents for High-Temperature Coal Gas Desulfurization

Desulfurization sorbent with a high active component utilization is of importance for the removal of H₂S from coal gas at high temperatures. Thus, the hypothesis for producing Zn_xCo_3-xO₄/carbon nanofiber sorbents via the combinations of electrospinning, in situ hydrothermal growth, and carbonization technique has been rationally constructed in this study. Zn_xCo_3-xO₄ nanoparticles derived from metal-organic frameworks are uniformly loaded on the electrospun carbon nanofibers (CNFs) with high dispersion. Zn_xCo_3-xO₄/CNFs sorbents possess the highest breakthrough sulfur adsorption capacity (12.4 g S/100 g sorbent) and an excellent utilization rate of the active component (83.2%). The excellent performance of Zn_xCo_3-xO₄/CNFs can be attributed to the synergetic effect of the hierarchical structure and widely distributed Zn_xCo_3-xO₄ on the CNFs supporter. The decomposition of Zn/Co-ZIFs not only generates the nucleus of oxides but also realizes their physical isolation through the formation of carbon grids on the surface of CNFs, avoiding the aggregation of oxides. Furthermore, Zn_xCo_3-xO₄/CNFs sorbents show an overwhelming superiority over the ZnO/CNFs sorbent, which is attributed to the introduction of Co and then the promotion of the stability of Zn at high temperatures. The presence of Co also accelerates the adsorption of H₂S on the active site of the oxide surface. The presented method is beneficial for promoting desulfurization performances and producing sorbents with high utilization of active components.

Fabrication of Na0.4MnO2 Microrods for Room-Temperature Oxidation of Sulfurous Gases

Phase pure Na_0.4MnO₂ microrods crystallized in the orthorhombic symmetry were fabricated for the wet oxidation of H₂S and SO₂ gases at room temperature. The material was found highly effective for the mineralization of low concentrations of acidic gases. The material was fully regenerable after soaking in a basic H₂O₂ solution.

Fe-Ti bimetal oxide adsorbent for removing low concentration H2S at room temperature

ABSTRACTHerein, a series of Fe-Ti bimetal oxide adsorbents were prepared by reduction-co-precipitation method, and their performance in removing low concentration H₂S at room temperature was investigated. The adsorbents were characterized by X-Ray diffraction (XRD), Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), Ultraviolet Visible diffuse reflectance spectroscopy (UV-Vis-DRS), X-Ray photoelectron spectroscopy (XPS) and N₂ adsorption-desorption. The results showed that the addition of Ti increased the specific surface area, pore volume and small oligomeric Fe₂O₃ of ferrihydrite. When the Fe/Ti molar ratio was 8:1, Fe-Ti bimetal oxide formed a large amount of oligomeric Fe₂O₃, and its specific surface area and pore volume reached 344.99 m²/g and 0.34 cm³/g, respectively. At this time, Fe-Ti bimetal oxide exhibited the highest breakthrough sulfur capacity of 222.8 mg/g. High temperature calcination caused Fe-Ti bimetal oxide to form small specific surface area and pore volume, and produced crystalline α-Fe₂O₃. And the breakthrough sulfur capacity of Fe-Ti bimetal oxide decreased with the increasing calcination temperature. In addition, the desulfurization process conformed to the unreacted shrinking nucleus model.

Synthesis of ZnO-CuO and ZnO-Co3O4 Materials with Three-Dimensionally Ordered Macroporous Structure and Its H2S Removal Performance at Low-Temperature

H2S is a common but hazardous impurity in syngas, biogas, or natural gas. For some advanced power generation technologies, such as integrated gasification combined cycle (IGCC), solid oxide fuel cells, H2S content needs to be reduced to an acceptable level. In this work, a series of highly porous Zn-Cu and Zn-Co composites with three-dimensionally ordered macropores (3DOM) structure were synthesized via the colloidal crystal template method and used to remove H2S at 150 °C and one atm. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), nitrogen adsorption studies, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) were carried out to analyze the fresh and spent adsorbents. The results show that all the adsorbents possess well-ordered macropores, a large surface area, and a highly dispersed active phase. The relative content of Zn and (Cu or Co) has a significant influence on the desulfurization performance of adsorbents. The addition of CuO significantly increases the sulfur capacity and 3DOM-Zn0.5Cu0.5 shows the largest sulfur capacity of all the adsorbents, reaching up to 102.5 mg/g. The multiple adsorption/regeneration cycles of 3DOM-Zn0.5Cu0.5 and 3DOM-Zn0.5Co0.5 indicate that the as-prepared adsorbents are stable, and the sulfur capacity can still exceed 65% of the fresh adsorbents after six cycles.

Metal organic framework derived NaCoxOy for room temperature hydrogen sulfide removal

Novel NaCoxOy adsorbents were fabricated by air calcination of (Na,Co)-organic frameworks at 700 °C. The NaCoxOy crystallized as hexagonal microsheets of 100-200 nm thickness with the presence of some polyhedral nanocrystals. The surface area was in the range of 1.15-1.90 m2 g-1. X-ray photoelectron spectroscopy (XPS) analysis confirmed Co2+ and Co3+ sites in MOFs, which were preserved in NaCoxOy. The synthesized adsorbents were studied for room-temperature H2S removal in both dry and moist conditions. NaCoxOy adsorbents were found ~ 80 times better than the MOF precursors. The maximum adsorption capacity of 168.2 mg g-1 was recorded for a 500 ppm H2S concentration flowing at a rate of 0.1 L min-1. The adsorption capacity decreased in the moist condition due to the competitive nature of water molecules for the H2S-binding sites. The PXRD analysis predicted Co3S4, CoSO4, Co3O4, and Co(OH)2 in the H2S-exposed sample. The XPS analysis confirmed the formation of sulfide, sulfur, and sulfate as the products of H2S oxidation at room temperature. The work reported here is the first study on the use of NaCoxOy type materials for H2S remediation.

Removal of Hydrogen Sulfide From Various Industrial Gases: A Review of The Most Promising Adsorbing Materials

The separation of hydrogen sulfide (H2S) from gas streams has significant economic and environmental repercussions for the oil and gas industries. The present work reviews H2S separation via nonreactive and reactive adsorption from various industrial gases, focusing on the most commonly used materials i.e., natural or synthetic zeolites, activated carbons, and metal oxides. In respect to cation-exchanged zeolites, attention should also be paid to parameters such as structural and performance regenerability, low adsorption temperatures, and thermal conductivities, in order to create more efficient materials in terms of H2S adsorption. Although in the literature it is reported that activated carbons can generally achieve higher adsorption capacities than zeolites and metal oxides, they exhibit poor regeneration potential. Future work should mainly focus on finding the optimum temperature, solvent concentration, and regeneration time in order to increase regeneration efficiency. Metal oxides have also been extensively used as adsorbents for hydrogen sulfide capture. Among these materials, ZnO and Cu–Zn–O have been studied the most, as they seem to offer improved H2S adsorption capacities. However, there is a clear lack of understanding in relation to the basic sulfidation mechanisms. The elucidation of these reaction mechanisms will be a toilsome but necessary undertaking in order to design materials with high regenerative capacity and structural reversibility.

Facile and Versatile Sol-Gel Strategy for the Preparation of a High-Loaded ZnO/SiO2 Adsorbent for Room-Temperature H2S Removal

Preparation of well-dispersed ZnO nanograins is necessary to improve their reactivity toward room-temperature H₂S removal. However, the challenge to design such a ZnO-based adsorbent with high ZnO loading is yet to be fulfilled. Herein, a facile sol-gel strategy is reported for the preparation of ZnO/SiO₂ adsorbents for efficient H₂S removal, by innovating a gel-drying method and simultaneously controlling ZnO grain formation through optimizing the molar ratio of ethylene glycol (EG)/nitrates in its precursors. The fabricated adsorbent embedded well-dispersed ZnO nanograins, of approximately 10-15 nm, into a SiO₂ matrix (57 wt % ZnO loading) and thus yielded a high H₂S removal capacity of 108.9 mg S/g sorbent. Therein, EG was used as a modifier for inhibiting the formation of a denser SiO₂ network during the gel drying process and was used as a fuel for promoting the decomposition of nitrates and increasing the surface area of the composites in the subsequent calcination. Modulating the molar ratio of EG/nitrates ≤ 2 in precursors or traditional drying of the gel in an oven should be avoided because these would lead to the oxidation of EG by metallic nitrates and form carboxylate complexes during the gel-drying process. Although the produced ZnO grains had a very small size of less than 5 nm, a layer of monodentate ZnCO₃ impurity was formed on the ZnO surface, which will drastically decrease the reactivity of ZnO toward H₂S. According to the encouraging results from CuO and Co₃O₄, this strategy has proved to be versatile for the preparation of other metal oxide/SiO₂ adsorbents.