(685d) Biomass Gasification: Catalytic Tar Removal Using Ni-Zeolite Catalysts

Authors: 
Buchireddy, P. R., Mississippi State University


Biomass is considered as a potential feedstock for sustainable energy production that can be converted to chemicals, fuels, electricity etc., either by thermochemical or biological processes. Gasification is one of the thermochemical methods of converting biomass to synthetic gas (CO and H2), which could potentially be used to produce different chemicals such as acetic acid and ethanol via chemical or biological processes and/or generate electricity by using engines, turbines, fuel cells etc. However, the synthetic gas produced may contain different organic (Tars) and inorganic impurities, which have the potential to damage the process equipment used in different conversion processes. Hence, the synthetic gas has to be cleaned to remove these impurities, and the extent to which the gas has to be cleaned is dictated by the end use application.

Research is being carried out to evaluate different nickel supported Zeolite-Y catalysts for tar destruction. Nickel supported Y-Zeolites with different SiO2/Al2O3 ratios (5.2, 30, 80) were tested to evaluate the effect of catalyst acidity on tar removal in the temperature range of 550-750 OC. Also, nickel supported on Silica/Alumina catalyst was prepared and tested. Catalyst characterization was performed using XRD, BET, and SEM on the catalysts evaluated. Tests were carried out on a laboratory scale flow reactor with naphthalene as a tar model compound. The results of these experiments showed that Ni on Zeolite-Y had better naphthalene removal efficiencies compared with Silica/Alumina catalyst, which could be attributed to the higher surface area and acidity of the zeolite. Also, the acidity of the zeolite support had a significant effect of naphthalene removal efficiencies. Removal efficiencies decreased with an increase in the acidity of the catalyst. This could be due to the formation of coke and NiAl2O4, which was confirmed by the TGA and XRD analysis. Tests were also carried out to evaluate the effect of varying nickel loading on zeolite, naphthalene loading, steam to carbon ratio, and gas hourly space velocity, the results of which will be presented.