Synergetic Improvement of the Reactive Performance of Hydrogen Sulfide Adsorption on a Three-Dimensional Ordered Macroporous La-Doped ZnO Sorbent

Herein, a three-dimensionally ordered macroporous (3DOM) La-doped zinc oxide and silica composite was prepared and fabricated for the middle-temperature hydrogen sulfide (H₂S) removal. Different pore sizes and La dopant effects were analyzed by various characteristic techniques as well as their performance on precise desulfurization (outlet H₂S concentration < 0.1 ppm) were evaluated. The morphology analysis showed that the series synthesized La_0.05Zn_0.95O_1±δ/SiO₂ samples were guided as a typical 3DOM framework. As a result, the sample 3D-230LZS, with the SiO₂ mixture of 50 wt %, PS precursor average size of 230 nm, and La dopant molar ratio to Zn ion of 0.05:0.95, revealed the best desulfurization precision and efficiency due to the textural properties with high surface area, well-dispersed ZnO particles, and well ranked interconnected macropores with abundant mesopores, which markedly accelerates gaseous reactants diffusion compared with that of the bulk sorbent. What is more, by elevating the surficial electron density of zinc cation and oxygen transfer capability, the synergistic effect is believed to be profitable for La_0.05Zn_0.95O_1±δ/SiO₂ sulfidation, which also contributes to preserve a stable performance over multiple sulfidation/regeneration cycles. During different atmosphere effects estimation, benefiting from a macro-mesopore skeleton with interconnected channels, the humidity tolerance of the sorbent could be maintained under 5 vol % of vapors, while the reaction capacity dropped sharply after more vapor injection. On the other hand, the existence of hydrogen in the H₂S flow made a slightly positive impact on desulfurization since it creates a reducing circumstance for Zn–O and Zn–S bonds as well as the converting effect of ZnSO₄, leading to more active sites. At the same time, a trace amount of O₂ contributed to a promotion effect on desulfurization due to the fact that the La dopant can create a synergistic effect of catalytic oxidation and adsorption.