Steam reforming of volatile fatty acids from organic wastes

Abstract

Hydrogen is becoming more an attractive alternative energy source due to the depletion of fossil fuel and the environmental issues. Fuel cell using hydrogen as fuel has higher fuel efficiency than conventional gasoline and diesel engines. It produces only water as a product without any pollutant emission. However, hydrogen is currently produced from nonrenewable sources such as natural gas and petroleum, which is accompanied by high $CO_2$ emissions. On the other hand, biomass can be used to produce hydrogen without a net change of $CO_2$ in the atmosphere and will play an important role as a renewable and sustainable hydrogen sources in the future. In this study, we consider the reforming of VFAs obtained from acid fermentation of food-wastes on the alumina-supported various catalysts. The steam reforming of a few different short chain carboxylic acids typically found in VFAs (e.g., acetic, propionic, butyric acid) were studied. The influence of reaction conditions such as temperature, oxygen to carbon ratio (O/C) and gas hourly space velocity (GHSV) were investigated. Temperature-programmed oxidation (TPO), X-ray diffraction (XRD) and pore size distribution were used to characterize coke deposition on the catalysts. Catalytic steam reforming of VFAs using alumina supported platinum catalysts was studied in a fixed-bed quartz reactor (20 mm O.D., 18 mm I.D., 400 mm height) at various temperatures between 300 and 600℃. The influence of reaction conditions such as temperature, oxygen to carbon ratio (O/C) and gas hourly space velocity (GHSV) was investigated. VFAs were successfully converted to COx and hydrogen. The hydrogen yield was up to 60% based on typical stoichiometry at 600℃ and GHSV of 25,000 $h^{-1}$. Temperature-programmed Oxidation (TPO), X-ray diffraction (XRD) and pore size distribution were used to characterize coke deposition. Any graphitic carbon on catalysts was not identified by XRD, which implies that amorphous coke formed in the small s...