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Effect of La-Modified Supporter on H₂S Removal Performance of Mn/La/Al₂O₃ Sorbent in a Reducing Atmosphere

Li, Haifeng, Su, Sheng, Peng, Yan, Wu, Linkang, Xu, Kai, Liu, Lijun, Qing, Mengxia, Hu, Song, Wang, Yi, Xiang, Jun
Industrial & engineering chemistry process design and development 2019 v.58 no.19 pp. 8260-8270
X-ray diffraction, adsorption, aluminum oxide, desulfurization, durability, hydrogen, hydrogen sulfide, manganese, manganese monoxide, nitrogen, scanning electron microscopy, sorbents, sulfur, temperature
High temperature sorbents for removing H₂S comprising manganese oxide and Al₂O₃ support modified with La loadings were prepared with wet impregnation. The removal of H₂S and the regeneration of sorbents were conducted at 850 °C to investigate the effect of the support modified with La on the desulfurization ability and durability of the Mn/La/Al₂O₃ sorbents. The fresh sorbent, first sulfide sorbent, and fourth regenerated sorbent were characterized by nitrogen isothermal adsorption, X-ray power diffraction, scanning electron microscopy, and H₂ temperature-programmed reduction. The results showed that the highest initial breakthrough sulfur capacity (BSC) was obtained with Mn/0.78%La/Al₂O₃(M/0.78L), and the initial BSC decreased with increased La loadings due to the inhibiting of excessive La on the reaction between MnO and H₂S. The BSC of sorbents with lower La loadings suffered more serious deactivation than MnₓOy/Al₂O₃ during successive desulfurization–regeneration cycles, and the BSC durability of sorbents increased with an increase in La loadings and calcination temperature of La/Al₂O₃. Mn/4.83%La/Al₂O₃ with La/Al₂O₃ calcined at 900 °C (M/4.83H) had the best BSC durability, which was better than the BSC durability of MnₓOy/Al₂O₃ (M) during several desulfurization–regeneration cycles. The characterization results showed that the structure of the M/4.83H sorbent was more stable than other sorbents. The M/4.83H sorbent derived the La(AlO₃) phase, which could maintain the structural stability of the sorbent during several desulfurization–regeneration cycles. The formation of the LaAlO₃ phase may inhibit MnₓOy from dissolving into Al₂O₃, which was beneficial for the durability of sorbents during several successive desulfurization–regeneration cycles.