Auxiliary effect of additives

such as cyclohexane

in supercritical CO2 fluid on the preparation of octenyl succinic acid cassava starch was investigated

and the types of additives

volume rate of additive to supercritical CO2

amount of esterification agent

reaction temperature

pressure and reaction time on the effect of degree of substitution and reaction efficiency were explored in a bath reactor set-up. The NMR

SEM and XRD were used to examine esterification groups

particle surface morphology and crystalline structure. The results revealed that the additive could improve the solubility of the supercritical CO2 medium to esterification agent

and the cyclohexane additive showed the optimal synergistic effect with reaction efficiency of about 3.0 times higher than that without the additive when 1.5% cyclohexane was added. Meanwhile

the optimum reaction conditions were found as follows: reaction temperature of 90℃

pressure of 12 MPa

time of 3 h and esterification agent of 4% with the degree of substitution and the reaction efficiency are 0.0191 and 61%

respectively

and even the reaction efficiency was up to 83% by using 2% esterification agent. Analysis of product structure characterization showed that the esterification groups were introduced into the starch molecules

and small particle characteristics and A-type crystal structure were still remained

but the particle surface morphology was partially destroyed and the crystallinity was reduced. All the results indicated that the cyclohexane can increase reaction efficiency and improve esterification reaction condition.