Rui Cao,Langlang Wang,Xueqian Wang,Yibing Xie,Xiang Li,Ping Ning
The low-temperature conversion of corrosive carbonyl sulfide (COS) in steel by-product gas is essential for the clean utilization of this gas. Herein, La-Ti@K catalysts doped with La nanoparticles were shown to exhibit significant photopromoted thermocatalytic activity and stability under UV light irradiation. At a reaction temperature of 60 °C, the TOF value increased from 4.84 × 10 -4 s −1 (TiO 2 , thermal treatment) to 8.43 × 10 -4 s −1 (La-Ti@K, photothermal treatment), and the H 2 S selectivity exceeded 99%. This was because La doping increased the density of basic sites on TiO 2 , which promoted the continuous dissociation of H 2 O in the system and the regeneration of –OH under UV irradiation. Moreover, the photogenerated electrons from TiO 2 were transferred to La to maintain the metallic La nanoparticles, as well as to ensure the activation and photothermal hydrolysis of COS. The presence of a suitable electron-metal-support interaction (EMSI) between the electron-rich La nanoparticles and TiO 2 might be responsible for these phenomena. In addition, theoretical calculations revealed that light-induced electron transfer was conducive to H 2 O dissociation and COS activation, while La doping reduced the free energy of the hydrolysis reaction. This work demonstrates the effectiveness of La-Ti@K catalyst in COS photothermal hydrolysis and provides a theoretical basis for further understanding of the photothermal catalytic mechanism.
Rui Cao,Xueqian Wang,Langlang Wang,Fangxian Cao,Xiang Li,Lu Wang,Jinghao Xiang,Ping Ning
The introduction of surface basic sites to COS hydrolysis catalysts can improve H 2 O activation and COS adsorption, leading to enhanced catalytic performance. However, maximizing the concentration of basic sites remains a challenge due to the limited exposed surface area of these catalysts. Herein, a La/Al 2 O 3 catalyst with abundant alkaline sites to catalyze the hydrolysis of COS was prepared by a simple ammonia-assisted hydrothermal method. This synthesized La/Al 2 O 3 catalyst exhibits a thin rod-like structure formed by the random accumulation of nanoparticles. Lanthanum, one of the most abundant rare earth metals, is an ideal doping aid to further promote the COS-catalyzed hydrolysis performance of Al 2 O 3 . Characterization studies show that the proper lanthanum loading effectively enhances the formation of basic sites, leading to improved lattice oxygen reactivity and –OH adsorption capacity. As a result, the prepared La-loaded Al 2 O 3 nanorod sample with abundant basic sites exhibits nearly 100 % COS conversion and total H 2 S yield at 160 °C. In addition, the reaction pathways and deactivation mechanisms for selective catalytic hydrolysis of COS on the La-doped Al 2 O 3 catalyst were revealed by using in situ DRIFTS to evaluate COS adsorption and hydrolysis. Density functional theory calculations showed that La loading enhances the electron transfer between the La and Al atoms, improves the formation of basic sites, and enhances the adsorption of –OH. This study provides new insights into the design of efficient alumina-based catalysts for the catalytic hydrolysis of COS.
To improve the activity of COS hydrolysis catalysts in a complex atmosphere is a significant challenge for blast furnace gas purification. Alumina-based hydrolysis catalysts were prepared with four alkali/alkaline earth metals (Na, K, Mg and Ca) respectively by the simple impregnation method to explore the chlorine-resistance mechanism of catalysts. Among four catalysts, Na/Al 2 O 3 and K/Al 2 O 3 catalysts showed a higher hydrolysis conversion of COS reaching 98 % for 12 h in the absence of HCl, due to the higher contents of weak basic sites as active sites for COS adsorption and more migratory oxygen species participating in COS hydrolysis. Especially, K/Al 2 O 3 has the highest catalytic activity in that it is easy to adsorb COS and H 2 O due to their high absolute adsorption energy. The presence of HCl inhibits the hydrolysis of COS owing to the acidification of active components and competitive adsorption with COS and H 2 O. It has been further found that HCl also inhibits the migration of oxygen species and deposition of sulfur species, but HCl still has a stronger inhibitory effect on COS hydrolysis than the deposition of sulfur species. The introduction of alkali metal as sacrificial sites protects the structure of alumina-based catalysts, avoiding the combination of HCl and Al-O to generate Al-Cl. Na/Al 2 O 3 has the best Cl-resistance mainly due to the high content of medium basic sites and great bond energy of Na-O with HCl. This research offers valuable guidance for the rational design and preparation of alumina-based catalysts with a good Cl-resistance and for the applications of blast furnace gas purification.
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