Reactive extraction of 1,3-propanediol from model mixture of fermentation broth

Abstract

This study deals with the development of novel carbon based catalyst for use in reactive extraction to separate 1,3-PDO from a model solution of the fermentation broth, derived biologically from conversion of glycerol, the by-product of biodesel production. The catalyst was synthesized by incomplete carbonization of naphthalene in sulfuric acid at 523 K. The surface area and pore volume of the catalyst were found to be 1.1 m2 g-1 and 0.07 cm3 g-1, respectively. The acidity of the catalyst measured by Inductively Coupled Plasma-Mass Spectrometry (ICP-MS was 1.46 mmol/g). The presence of sulfonic functional group was also confirmed by Nicolet Fourier Transfor Infared Spectroscopy (FTIR). In addition, the thermogravimetric analysis (TGA) results show that the catalyst was stable up to the temperature of 200°C. The test of the catalyst for the acetalization of acetaldehyde and 1,3-PDO in aqueous solution indicated its applicability for such reaction, and the optimal quantity of the catalyst required for this reaction was 0.7 g/ g 1,3-PDO, giving the conversion of approximately 92% after 2 h of reaction at 35°C. Compared with those of commercial ion-exchange catalysts (Dowex 50-WX4-200 and Ambelite IR120), the reaction in the presence of the novel carbon based catalyst took longer (2h) than that in presence of the commercial catalysts (about 1 h). The inferiority in the reactivity of the carbon based catalyst was possibly due to the lower acidity and lower surface area (1.1 vs. 300 for Dowex 50-WX4-200 and 1000 m2/g for Ambelite IR120) and pore volume (0.07 vs 1.2 for both Dowex 50-WX4-200 and Ambelite IR120). In addition to acetalization reaction, reactive extraction was also carried out using ethyl-benzene as an extractant and the effects of temperature (15, 20, 25, 30, 35 °C) and initial 1,3-PDO (20, 40, 60, 80, 100 g/l) concentrations were determined. The initial reaction rate and the reaction conversion were found to increase as the temperature increased. On the other hand, as the initial 1,3-PDO increased, the initial reaction rate increased, but the conversion (after 60 min) decreased. At 40 g/L of initial 1, 3-PDO solution, a typical concentration of 1, 3-PDO derived from the fermentation process, the conversion was found to be 78.92% after 60 min for reactive extraction at 35°C. Compared with the conversion achieved by acetalization alone (without the presence of the extract phase), the conversion of reactive extraction was 20% higher for the same reaction condition. In addition, in this study,the novel catalyst was proven to be suitable for the reverse hydrolysis reaction to convert 2-MD to the desirable 1,3-PDO with the conversion expected to be higher than 99%. Finally, the results on multiple acetalization in aqueous solution in the presence of the catalyst indicated that the possibility of reusing, however the reactivity of the catalysts decreased about 43% Although the reactivity and the reusability of the carbon based catalyst was found to be inferior to the commercial Dowex 50-WX4-200 and Ambelite IR120, experimental results suggested a possibility of improving the carbon based catalysts properties further, possibly by improving the porosity, surface area, and acidity through optimal process conditions. The results of this study thus confirm the potential application of the lower cost carbon based catalyst to replace the expensive polymeric ion exchange resins for 1,3-PDO reactive extraction.