Investigation of various catalysts for partial oxidation of tar from biomass gasification

• NiO-catalyst more active in partial oxidation of tar than perovskite-type materials.
• KCl increases catalytic activity, HCl and H2S poison the catalyst.
• CuO-sorbent captures H2S and enhances naphthalene conversion.
• Naphthalene completely converted at 450 °C despite presence of H2S.

The formation of tar during biomass gasification limits the use of the product gas in small scale CHP units like gas engines. Catalytic partial oxidation can be applied to remove tar and convert it into fuel gas by using a catalyst under sub-stoichiometric addition of oxygen. In the present study, different catalyst materials, i.e. several perovskite-type materials and one Ni-based catalyst, which shall be used in combination with an oxygen carrier material, were investigated in lab-scale experiments regarding their catalytic activity in partial oxidation of naphthalene as model tar compound. Furthermore, the influence of the trace substances HCl, KCl, and H2S on the performance of the Ni-based catalyst being the best performing catalyst was tested. Since the Ni-based catalyst is significantly poisoned by H2S, it was also tested in combination with a CuO-based sorbent. In addition to H2S reduction, the sorbent increased the catalytic activity of the entire system significantly, so that naphthalene was almost completely converted at temperatures above 450 °C despite the presence of 140 ppm H2S.

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