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.
Kun Chen,Huihuang Fang,Simson Wu,Xi Liu,Jianwei Zheng,Song Zhou,Xinping Duan,Yichao Zhuang,Shik Chi Edman Tsang,Youzhu Yuan
The direct hydrogenation of CO 2 to methanol has become a very active research field because CO 2 can be prospectively recycled to mitigate greenhouse effect and store clean synthetic fuels. This reaction can be catalyzed by supported Cu catalysts and the catalysts display strong support or promoter effects. Sintering of Cu species accelerates the separation of Cu–oxide interfaces, reduces the active component, and diminishes the methanol selectivity. In this work, we report a Cu catalyst supported on La-modified SBA-15, where the Cu–LaO x interface is generated through the interaction of highly dispersed Cu nanoparticles with LaO x species bedded into the SBA-15 pore wall. The optimized Cu 1 La 0.2 /SBA-15 catalyst can achieve methanol selectivity up to 81.2% with no deterioration in activity over 100 h on stream compared with the La-free catalyst. A thorough study reveals that La species not only significantly improve the CO 2 adsorption but also enhance Cu dispersion to produce well-dispersed active sites. The H/D exchange experiments show that the methanol synthesis displays a strong thermodynamic isotope effect and the Cu–LaO x interface plays a crucial role for the methanol synthesis rate in CO 2 /D 2 feed. In situ DRIFTS studies reveal that *HCOO and *OCH 3 species are the key intermediates formed during the activation of CO 2 and methanol synthesis over the Cu 1 La 0.2 /SBA-15 catalyst.
Mengliang Gao,Jie Gao,Ge Pu,Cong Yuan,Xingqiang Lu
The redox activity and thermal stability of oxygen carriers (OCs) during multi-cycle processes are important performance criteria. In this paper, the effects of three supports, i.e., ZrO2, TiO2, and YSZ (yttria-stabilized zirconia), on the reactivity, redox stability, hydrogen recovery capacity, and purity, as well as the sintering behavior of La-modified CoFe2O4 (LCF) OCs, were investigated. The results indicated that the unsupported LCF had severe sintering behavior, the aggregation of grains, the collapse of pore structure, and surface densification after multiple cycles led to a significant reduction in its activity. Meanwhile, the interaction between different supports and active components had a remarkable influence on fuel conversion and hydrogen recovery capacity. The formation of Fe2TiO5 in LCF6T4 weakened the initial reduction activity of the OC. Also, phase separation occurred after multiple cycles, forming separated Fe2O3 and TiO2, which further accelerated the sintering and resulted in irreversible deactivation. In contrast, LCF6Z4 and LCF6YZ4 exhibited excellent initial activity and cyclic stability, which was attributed to their improved pore structure and surface properties. Interestingly, the generated La2Zr2O7 pyrochlore structure was also conducive to the enhancement of cyclic stability properties for OCs. In addition, all OCs displayed high-purity hydrogen (>99.5%) generation properties. Overall, the ion-conductive YSZ-supported OC showed excellent reactivity and stability. After 11 cycles, the fuel conversion deactivation and hydrogen production deactivation for LCF5YZ5 were merely 6.23 and 8.26%, respectively.
危险品化学品经营许可证（带存储）