Regenerable Co-ZnO-based nanocomposites for high-temperature syngas desulfurization

H2S is a common impurity in the syngas derived from municipal solid waste gasification. For power generation using advanced technologies, such as gas engines/turbines or solid oxide fuel cells, reducing the H2S content to acceptable levels is required. This work investigated the desulfurization performance of bimetallic particles by adding different metals (Fe, Cr, Co, Ni) into ZnO-based nanocomposites. At 400 degrees C, the Co-ZnO demonstrated 26.3, 5.0, 1.7 times higher sulfur uptake from a model syngas (composed of 100 ppmv H2S, 15 vol% CO, 5 vol% CO2, 15 vol% H-2, 15 vol% H2O and N-2 (balance)) than pure ZnO, Cr-ZnO and Fe-ZnO, respectively. This could be attributed to the formation of p-n heterojunction between the n-type ZnO and p-type Co3O4, accelerating surface reaction kinetics. Although the Ni-ZnO showed a better performance at 400 degrees C, at an elevated temperature of 600 degrees C, the Co-ZnO demonstrated 1.2 times higher sulfur capacity compared to Ni-ZnO. Furthermore, the Co-ZnO nanocomposite was subjected to 3 cycles of high-temperature desulfurization (600 degrees C) and regeneration. The results showed that its high desulfurization efficiency was retained after the tests. This could enable a high-temperature desulfurization of hot syngas and hence an increase in the electrical efficiency of waste-to-energy facilities.