Study On Synthesis Of Modified Rosin Sucrose Esters

Rosin and sucrose are very rich in China, and both of them are natural and renewable resources. However, most of rosin is now exported as raw material and most of sucrose is mainly used as cheap food, so exploitation of their deep processing products to raise their extra value is a research project worthy of carrying out deeply. The three-ring phenanthrene skeleton in molecules of rosin is hydrophobic as the long-chain alkyl group in higher fatty acids, and hydrophilic groups can be introduced through the carboxyl groups in the resin acids of rosin, so rosin can be used as raw material to synthesize surfactants. Sucrose is a polyhydroxyl-alcohol with excellent hydrophilic ability. Therefore, nonionic surfactants can be prepared from rosin and sucrose if esterification reaction can take place between resin acids in rosin and sucrose under some conditions. Hydrogenated rosin and disproportionated rosin are two dominant varieties of modified rosin with good antioxygenic activity. In this dissertation, hydrogenated rosin sucrose esters and disproportionated rosin sucrose esters were synthesized by transesterification method and O-acylation method, respectively. The synthesis of modified rosin sucrose esters meets the need of green chemistry and sustainable development, and it can enrich the varieties of surfactants as well as provide a new possible route for the deep processing of rosin and sucrose.In order to provide an intermediate used in synthesizing hydrogenated rosin sucrose esters, hydrogenated rosin ethyl esters were prepared by direct esterification reaction of hydrogenated rosin with ethanol under solvent-free condition and in the presence of DRC as catalyst. Various factors such as reaction temperature, catalyst dosage, reaction time, the ratio of ethanol to hydrogenated rosin which may influence the esterification rate were investigated. The optimum conditions were found to be as follows: reaction temperature 180℃, catalyst dosage 6% (based on the weight of hydrogenated rosin ), reaction time 6h, the ratio of ethanol to hydrogenated rosin 3:l(mol).The esterification rate amounted to 92.2 % under the above optimum conditions. Meanwhile, the ion exchange chromatography was used to purify the prepared crude hydrogenated rosin ethyl esters by the removal of the unreacted resin acids in the hydrogenated rosin. The molecular structures in the hydrogenated rosin ethyl esters were not changed after the column chromatography, so the refined hydrogenated rosin ethyl esters can be used as the intermediate to synthesize hydrogenated rosin sucrose esters (HRSE).HRSE were synthesized by transesterification reaction of the hydrogenated rosin ethyl esters with sucrose under solvent-free condition and in the presence of soap as emulsifier and catalyst. Some influence factors such as reaction temperature, usage of emulsifier and reaction pressure were investigated. The target product was analyzed and characterized by TLC, IR, 13C —NMR, UV , HPLC and HPLC — MS methods. The analysis result showed that hydrogenated rosin sucrose mono-esters, with the high content of 97.98%, were the absolutely dominant constituent of HRSE, and that the newly-formed ester group in the target product was possibly attached to the C-1' of the fructose ring in sucrose. It can be also concluded from the critical micelle concentration (CMC) of the target product (CMC=0.9×10-2mol.L-1, corresponding surface tension σCMC=47mN.m-1) that HRSE have satisfying surface activity. Besides, HRSE were also tentatively synthesized by transesterification under microwave irradiation, and were compared with the HRSE synthesized by traditional heating method in some characterization aspects such as TLC and IR. The result showed that HRSE can also be synthesized by transesterification under microwave irradiation.Disproportionated rosin chloride was prepared at first by the reaction of disproportionated rosin with SOCl2. Then, DRSE (disproportionated rosin sucrose esters) were synthesized by O-acylation reaction of the disproportionated rosin chloride with sucrose.