Precious metal catalysts in the clean-up of biomass gasification gas Part 1: Monometallic catalysts and their impact on gasification gas composition

Abstract

The performance of Rh, Ru, Pt, and Pd on modified commercial zirconia support (m-ZrO 2) was compared to a benchmark Ni/m-ZrO 2 catalyst in the presence of H 2S in the clean-up of gasification gas from tar, methane, and ammonia. The aim was to produce ultra clean gas applicable for liquid biofuel production. In general, the activity towards the decomposition decreased in the order of aromatic hydrocarbons, ethylene > methane > ammonia. Hydrocarbon decomposition on m-ZrO 2 supported Rh, Ni, and Ru catalysts mainly occurred at 800–900 °C through reforming and/or dealkylation reactions. Aromatic hydrocarbon decomposition reactions proceeded on Pt/m-ZrO 2 and Pd/m-ZrO 2 via oxidation reactions at temperatures of 600–800 °C, while at 900 °C, the reforming and/or dealkylation reactions were dominating also on Pt/m-ZrO 2 and Pd/m-ZrO 2 catalysts. During longer test runs of ten hours at 800 °C, the activity of the Rh/m-ZrO 2 catalyst declined in the presence of 100 ppm H 2S due to the sulfur poisoning effects, coke formation, and the particle size growth. Although the performance of Rh/m-ZrO 2 declined, it still remained better than Ni/m-ZrO 2 both towards naphthalene and total aromatic hydrocarbon, while only Ni/m-ZrO 2 and Ru/m-ZrO 2 decomposed ammonia in the presence of sulfur. Nevertheless, the most promising catalyst for clean gas production was Rh/m-ZrO 2.