Evaluation of hydrogen and carbon monoxide mass transfer and a correlation between the myoglobin-protein bioassay and gas chromatography method for carbon monoxide determination

Abstract

Syngas fermentation to biofuel is often plagued by mass transfer limitations of sparingly soluble gases, namely carbon monoxide (CO) and hydrogen (H₂), in the aqueous phase. In this study, the volumetric mass transfer coefficients (k_La) for H₂ and CO were examined in a gas-lift reactor coupled with a 20 μm bulb diffuser. Furthermore, a correlation between the myoglobin-protein bioassay (liquid samples) and the head space gas analysis via gas chromatography (GC) for CO was developed for the same reactor configuration. The highest k_La values of 97.2 and 129.6 h⁻¹ were observed for H₂ and CO, respectively at gas flow rates of 5.0 L min⁻¹. The k_La values determined using GC equipped with a thermal conductivity detector (GC-TCD) and myoglobin-protein bioassay methods for different CO gas flow rates were highly correlated with correlation (R²) factors of 0.99 (without microorganisms) and 0.987 (with Clostridium carboxidivorans culture media). This study confirms that the myoglobin-protein bioassay, which is a much simpler, faster and cheaper method compared with GC analysis, can be used as a reliable method for determining the volumetric mass transfer coefficient of CO in syngas fermentation studies.