Synthesis Of Hypercrosslinked Polystyrene Resin And Its Application In Decolorization Of Fruit Juices

Hypercrosslinked polystyrene resin is a kind of excellent adsorbent resin due to its high specific surface area and swelling property. At present, decolorization via resin adsorption is widely used in fruit juice industry, but the commercial adsorbent resins cannot meet the demand of fruit juice decolorization because of their low decolorizing capacity and poor regeneration performance. The aim of this thesis is to systhesize and screen hypercrosslinked polystyrene resin with excellent decolorizing performance for fruit juices. The thesis is composed of the following three parts.(1) Highly crosslinked polystyrenes with the cross-linking degree of55%,63%and80%was used as the starting materials. Hypercrosslinked polystyrene resin HC-1was synthesized by post-crosslinking reaction of the pendant vinyl groups. Hypercrosslinked polystyrene resin HC-2was synthesized by chloromethylation and post-crosslinking reaction. Hypercrosslinked polystyrene with tertiary amino groups, HC-2-AN, was synthesized by amination reaction of HC-2with dimethylamine. Adsorption property of the hypercrosslinked resins was investigated by using rutin as the adsorbate. The results showed that the adsorption isotherm of all the resins for rutin fitted the Freundlich isothermal adsorption equation. The adsorption process was an exothermic process. The adsorption capacity of HC-1for rutin was significantly higher than that of HC-2because of its higher specific surface area and pore volume. HC-2-AN possessed higher adsorption capacity and adsorption enthalpy (absolute value) because of multiple hydrogen bonding as compared with HC-2. The adsorption capacity of the resins with different cross-linking degree was mainly determined by the pore volume distribution of the resins.(2) Slightly crosslinked polystyrene based hypercrosslinked polystyrene resin HC-J was prepared by chloromethylation and Friedel-Crafts postcrosslinking reaction of macroporous polystyrene with low crosslinking degree. Adsorption property of the hypercrosslinked resins was investigated by using rutin as the adsorbate. The results showed that the adsorption capacity of HC-J for rutin was significantly higher than that of HC-2-AN because of its higher specific surface area. HC-J was used in juice decolorization to solve the problems existing in the process of using commercial decolorization resin. The optimal synthesis process of the HC-J resin was as following: a crosslinking degree of8%for the initial polymer, the mixture of cyclohexanol and200#gasoline with a mass ratio of0.5:0.7as porogen, chloromethylation temperature of40℃, and chlorine content of the chloromethylated polystyrene higher than18%. The decoloration performance of HC-J was better than that of the commercial resins.(3) A series of HC-J resins was systhesized by adjusting the post-crosslinking reaction time. Hypercrosslinked polystyrene with tertiary amino groups HC-J-AN was synthesized by amination reaction of HC-J with dimethylamine. The decolorization properties of each resin were tested. The results showed that the specific surface area of HC-J and the exchange capacity of HC-J-AN and the decolorization rate of all resins decreased as the post-crosslinking time increased. The decolorization performance of HC-J-AN was significantly better than HC-J due to the role of hydrogen bonding. The optimal post-crosslinking time of HC-J was6h.