No abstract

Cotton stalks (CS) are considered a good candidate for fuel-ethanol production due to its abundance and high carbohydrate content, but the direct conversion without pretreatment always results in extremely low yields due to the recalcitrant nature of lignocelluloses. The present study was undertaken to investigate the effect of various chemical and physicochemical pretreatment methods, i.e., alkali, microwave-assisted acid, organosolv, hydrothermal treatment, and sequentially organosolv and hydrothermal pretreatment, on chemical composition of CS and subsequent ethanol production applying pre-hydrolysis and simultaneous saccharification and fermentation (PSSF) at high solid loading. The best results in terms of ethanol production were achieved by the sequential combination of organosolv and hydrothermal pretreatment (32.3 g/L, using 15% w/v substrate concentration and 6 h pre-hydrolysis) with an improvement of 32% to 50% in ethanol production compared to the other pretreatments. Extending pre-hydrolysis time to 14 h and increasing substrate concentration to 20% w/v, ethanol production reached 47.0 g/L (corresponding to an ethanol yield of 52%) after 30 h of fermentation.

A kinetic model for the transesterification of a cotton seed oil with ethanol in the presence of water is proposed. The effect of water content in the reacting mixture on the transesterification reaction is studied. The dependence of the equilibrium constants and reaction rate constants on the water content is presented. Equilibrium was reached within less than 30 min reaction time in all cases. The increase of the water content results in decrease of the conversion level of the oil. By increasing the ethanol/oil ratio the conversion of triglyceride increases and the concentration of mono-and diglyceride in the product mixtures are reduced.

No abstract

No abstract