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

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.