Continuous and controllable synthesis of MnO2 adsorbents for H2S removal at low temperature

H2S is an extremely noxious impurity generated from nature and chemical industrial processes. High performing H2S adsorbents are required for chemical industry and environmental engineering. Herein, α-, γ-, and δ-MnO2 adsorbents with high sulfur capacity were synthesized through a continuous-flow approach with a microreactor system, achieving much higher efficiency than hydrothermal methods. The relationship between crystal structure and synthesis conditions such as residence time, reaction temperature, concentration of K+ in solution and reactant ratio is discussed. According to the H2S breakthrough tests at 150 °C, continuously prepared α-, γ-, and δ-MnO2 exhibited sulfur capacities of 669.5, 193.8 and 607.6 mg S/g sorbent, respectively, which was at a high level among the reported adsorbents. Such enhanced performance is related to the large surface area and mesopore volume, high reducibility, and a large number of oxygen species with high reactivity and mobility. Manganese sulfide and elemental sulfur were formed after desulfurization, which indicated the reaction consisted of two steps: redox and sulfidation of the sorbents. This study provides an innovative design strategy for the construction of nanomaterials with high H2S adsorption performances.

Anchoring Cu-N active sites on functionalized polyacrylonitrile fibers for highly selective H2S/CO2 separation

As an essential part of clean energy, natural gas is often mixed with varying degrees of H₂S and CO₂, which poses a serious environmental hazard and reduces the fuel's calorific value. However, technology for selective H₂S removal from CO₂-containing gas streams is still not fully established. Herein, we synthesized functional polyacrylonitrile fibers with Cu-N coordination structure (PANF_EDA-Cu) by an amination-ligand reaction. The results showed that PANF_EDA-Cu exhibited a remarkable adsorption capacity (143 mg/g) for H₂S at ambient temperature, even in the presence of water vapor, and showed a good separation of H₂S/CO₂. X-ray absorption spectroscopy results confirmed the Cu-N active sites in as-prepared PANF_EDA-Cu and the formed S-Cu-N coordination structures after H₂S adsorption. The active Cu-N sites on the fiber surface and the strong interaction between highly reactive Cu atoms and S are the main reasons for the selective removal of H₂S. Additionally, a possible mechanism for the selective adsorption/removal of H₂S is proposed based on experimental and characterization results. This work will pave the way for the design of highly efficient and low-cost materials for gas separation.

Review of Hydrogen Sulfide Removal from Various Industrial Gases by Zeolites

Hydrogen sulfide (H2S) removal from various industrial gases is crucial because it can cause huge damage to humans, the environment, and industrial production. Zeolite possesses huge specific surface area and well-developed pore structure, making it a promising adsorbent for H2S removal. This review attempts to comprehensively compile the current studies in the literature on H2S removal in gas purification processes using zeolites, including experimental and simulation studies, mechanism theory, and practical applications. Si/Al ratio, cations of zeolite, industrial gas composition and operating conditions, and H2S diffusion in zeolites affect desulfurization performance. However, further efforts are still needed to figure out the influence rules of the factors above and H2S removal mechanisms. Based on an extensive compilation of literature, we attempt to shed light on new perspectives for further research in the future.