Stability and Regeneration of Catalysts for the Destruction of Tars from Bio-mass Black Liquor Gasification

Abstract

The goal of this project was to develop catalytic materials and processes that would be effective in the destruction of tars formed during the gasification of black liquor and biomass. We report here the significant results obtained at the conclusion of this two year project. A one year no-cost extension of this project was requested and approved. Task 1.Was completed. We identified Group VIII transition metal catalysts as active for the gasification of benzene (model tar compound) using steam. These catalysts, however, don't have any sulfur tolerance. We have identified Group VI B sulfide materials such as tungsten sulfide or CobaltMolybdenum sulfides as active catalysts for the reaction, and with good tolerance towards sulfur.Task 2. ThermoChem. Inc. and Kellogg Brown Root were identified as potential partners for the industrial site pilot reactor studies. However, no pilot scale work could be done because their gasification reactors didn't come on stream which was a necessary step before we could go and perform the pilot scale reactor testing of the chosen catalysts. However, all the pieces and designs were completed to carry out such studies.Task 3. Was completed. It involved characterization of aged catalysts. X-ray diffraction studies showed that Group VIII transition metal catalysts lost their activity in the presence of sulfur, due to the formation of sulfide and sulfate phases. Also complex phase transformations were observed in the presence of alkali compounds.Task 4. Was completed. The goal was to develop effective regeneration methods. It was found that sulfur-poisoned Group VIII transition metal catalysts could not be regenerated using oxidation or steam treatments at elevated temperatures. Our efforts focused instead on the regeneration of carbondeactivated catalysts. The efforts to regenerate Co-Mo catalysts using oxidation treatment were successful in removing carbon. The resulting material was subsequently sulfided. It was possible to achieve original catalytic activity even after three weeks of aging.With the exception of pilot scale testing of the chosen catalysts, all other objectives for the project were completed.3