Hydrogen sulfide (H2S) is a fatal impurity in industrial gas feeds, such as syngas, biogas and natural gas. For many emerging technologies, such as integrated coal gasification combined cycle (IGCC) power plants and solid oxide fuel cells, reducing the H2S content in the feed to the level of below 1ppm is required. At present, some methods including alcohol amine absorption, adsorption, ionic liquid absorption etc. have been developed to remove H2S from gas streams. Among these methods, adsorption over metal oxides (primarily ZnO) has received more and more attentions for the merits of low cost and high activity. However, bulk ZnO adsorbents have large particle size, insufficient porosity and low surface area, which lead to slow sulfurization and low utilizaition. In addition, high temperature causes severe sintering of the ZnO particles, further impairing the desulfurization performance. In order to address these issues, Encapsulating the ultrafine ZnO nanoparticles in a porous matrix is one possible solution. Thus, in this work, a series of adsorbents composed of highly dispersed, ultrasmall ZnO nanoparticles fixed in porous materials were prepared and test for H2S removal at 150oC. Transmission electron microscopy (TEM), nitrogen adsorption-desorption measurement, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and solid state nuclear magnetic resonance (ssNMR) were carried out to characterize the fresh and spent adsorbents. The results show that the as-prepared adsorbents possessed large surface areas and highly dispersed active species. The grain size of ZnO was less than 3 nm, when the ZnO species was anchored by interacting with the silanol groups. The multiple adsorption-regeneration tests show that the the adsorbents were recyclable and the sulfur capacity can exceed 80% of that of the fresh ones even after 4 cycles.

Highly dispersed ultrasmall ZnO nanoparticles fixed in porous matrix for deep sulfur removal

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