Biomass conversion to syngas via gasification produces certain level of by-products such as tar and inorganic impurities (sulfur, potassium, phosphorus etc.). Nickel, a commonly used catalyst for hydrocarbon steam reforming, suffers reduced reforming activity by small amounts of sulfur (S) or potassium (K) while resistance against deleterious carbon whisker formation increases. However, the combined effect of biomass derived gas phase alkali at varying concentrations together with sulfur on tar reforming catalyst performance under realistic steady-state conditions is unknown. Prior to this study, a methodology was successfully developed to monitor these effects by precise K dosing as well as K co-dosing with S. A setup consisting of a 5 kW biomass fed atmospheric bubbling fluidized bed gasifier, a high temperature hot gas ceramic filter, and a catalytic reactor operating at 800 <sup>ο</sup>C was used in the experiments. Two test periods were conducted, 30 hours with 1 ppm potassium chloride (KCl) dosing and 6 hours without KCl dosing. Studying the results (Fig. 1), it can be concluded that although K is known to block active Ni sites and decrease activity in traditional steam reforming, it appears to lower the surface S coverage (θ<sub>s</sub>) at active Ni sites (K and S anti-correlates in bed and in reactor inlet versus time on stream as well as ongoing microscopic analysis suggesting S/Ni system modification due to K adsorption) and increase methane and tar reforming in the present application. In addition, previously unknown relevant concentrations of K on typical Ni based reforming catalyst during realistic operating conditions was established.

Biomass-derived gas-phase alkali as a tar reforming catalyst promoter in sulfur-laden biomass gasification gas

251st National Meeting (2016)

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