Adsorption Properties of MFI-Type Zeolite Films for Upgrading of Biofuels

Abstract: With the depleting reservoirs of fossil fuels, increasing environmental concerns for flue-gas emissions from fossil-fuel combustion and growing world population, the need for the development of new sustainable fuels is higher than ever. However, to be able to compete with today’s mature technologies for production of fuels from fossil sources, new efficient processing alternatives for upgrading of biofuels must be developed.   Bio-fuels produced by e.g. fermentative processes are promising alternatives to traditional chemicals and fuels produced from fossil sources. Recovery of biofuels by selective membranes and adsorbents has been identified as promising energy efficient recovery routes.In this work, adsorption properties of MFI-type zeolite films were studied using in situ ATR-FTIR spectroscopy in order to understand the adsorption properties of these zeolites.   Single component adsorption isotherms of butanol and water vapor were determined at different temperatures using ATR-FTIR spectroscopy. The Langmuir and Sips model were successfully fitted to experimental data, and the fitted parameters obtained in this work were in very good agreement with values reported in the literature. Adsorbed amounts of butanol and water from binary vapor mixtures were extracted from the infrared spectra as well as the adsorption selectivities. The silicalite-1 film prepared in fluoride medium found to be significantly more butanol selective due to the exceptionally low density of defects in the structure.   Biogas (methane) is another promising biofuel that is commonly produced by anaerobic degradation of biomass. However, before it may be used, contaminants have to be removed from the gas; two of the most abundant contaminants in biogas are carbon dioxide and water vapor. Adsorption of a ternary mixture of methane, carbon dioxide and water vapor in zeolite Na-ZSM-5 has been studied at various compositions and temperatures using ATR–FTIR spectroscopy. The amount adsorbed determined from experimental data were compared to predictions by the Ideal Adsorbed Solution Theory (IAST). This result confirms that Na-ZSM-5 could be a promising membrane material for upgrading of biogas.