(279f) Pilot Scale Evaluation of Ni-Based Reforming Catalyst Performance for Syngas Production

Biomass gasification is an economical thermochemical route from plant-based materials to liquid fuels. Product gas from this process is comprised of synthesis gas, tars, olefins, and other hydrocarbon impurities which must be transformed into synthesis gas in order to achieve a suitable feed stream for a fuel synthesis process. Model compounds are often used to evaluate reforming catalysts for achieving a pure synthesis gas stream. However, these model compounds do not capture the severity of the conditions that a catalyst will likely undergo in a real biomass gasification product stream. This study compares results for catalyst deactivation between a 1/2 ton-per-day pilot plant biomass gasification system and a bench scale system using model synthesis gas. A nickel based reforming catalyst (6 wt-% NiO, 2.4 wt-% MgO, 3.9 wt-% K₂O) was developed and compared to several industrial catalysts of varying nickel content for this work. Oak was gasified in an indirectly heated, steam blown gasifier in a half ton per day pilot plant to produce a raw product gas stream. A slip stream of this product gas was fed to a packed bed reactor loaded with catalyst, and the products were analyzed by molecular mass beam spectrometry (MBMS) for tar speciation and gas chromatography for light gas quantification. Post-reaction catalyst samples were analyzed using XRD, SEM, TPR, and coke removal techniques to quantify the amount of carbon deposited on the catalyst. The oak gasification product stream produced in the pilot plant was modeled in a bench scale system using bottled gases. Olefins and alkanes were estimated using ethylene. Product gas was analyzed using gas chromatography. Post bench scale reaction catalysts were characterized in the same way as post pilot scale catalysts. Reaction and characterization results from both pilot scale and bench scale operation will be compared and discussed during this work. It was found that due to the high concentration of hydrogen sulfide in the stream, nickel-based catalysts were deactivated according to the amount of nickel contained within them. As a result, several new catalyst compositions are proposed, and were tested on the bench scale using the modeled oak product gas composition.