Imidazoles Ionic Liquid Microwave In The Synthesis Of Poly (aspartic Acid Method

The purpose of this paper is to investigate different influence of acid medium andneutral medium on L-aspartic dissolve and polyaspartic acid synthesis.[Hmim]HSO₄asBr nsted acid,[Bmim]Br as Lewis acid and [Bmim]BF₄as neutral nature of theimidazole ionic liquid had been selected as PASP synthesis reaction media. Meanwhileto impove the classic polyaspartic acid synthesis method, Polyaspartic acid （PASP） wassynthesized in the medium of ionic liquids under microwave by polymerization usingL-aspartic acid as raw material in the first time. Because microwave reaction heat thereactant is in side heating method. Reactants is heated evenly, water in the reactionsystem is discharged easily, reaction rate and polycondesation reaction is promoted bymicrowave meathod.This paper studied the dissolution process of L-Asp and initial polymerizationtemperature in ionic liquid. Influence of product yield and scale inhibition ratio bydifferent kinds of recation conditions was studied, the best imidazole ionic liquid hadbeen selected. Polymerization yield and scale inhibition ratio was affected by the L-Aspand ionic liquid mass ratio, reaction temperature and polymerization time had beenstudied. Influence of Viscosity-average Molecular Weight by all kinds of recationconditions had been studied. Effect of configuration by hydrolysis temperature wasstudied. Contrast test of have H3PO4or no in neutral ionic liquid was done. Thecharacteristics of the infrared spectrum and UV-VS spectrum of the mixture[Hmim]HSO₄and L-Asp were analyzed, preliminary deduced the process of H⁺catalyzeL-Asp reaction mechanism according the theory of amide dehydration.The results showed that the dissolving capacity of the Lewis acid ionic liquid isbest, the Br nsted acid ionic liquid is better than the neutral ionic liquid. The reactiontemperature of Br nsted acid ionic liquid is lowest, the reaction temperature of Lewisacid ionic liquid is lower than the neutral ionic liquid. The results show that the yieldand scale inhibition rate of synthesis of PASP in [Hmim]HSO₄ionic liquid have higherthan the other two kinds of ionic liquid, the [Hmim]HSO₄ionic liquid is the best reaction system. The results show that the optimal conditions of polymerization are theL-Asp ratio of ionic liquid quality is1.6:1, microwave power is320W, reaction time is260seconds, under this conditions, PASP yield ratio is96.12%, the scale inhibition rateis96.77%. The Viscosity-average Molecular Weight less than6000could besynthetize by this way, the main factors affect the Viscosity-average MolecularWeight is microwave power and polymerization time. Reaction system provide H⁺could rise the PASP yield ratio. Infered process of H⁺catalytic L-Asp was that: H⁺and carboxylic acid anion of L-Asp combined with carboxylic acid, carboxyl had higheractivity. The oxygen in carboxyl had strong negative nature and would combine withH⁺.Then carbonyl carbon became carboniummion. H⁺consumption leaded to-NH⁺3inL-Asp toward generated-NH₂. And carboniummion provided favorable condition forNitrogen atom in-NH₂attacking carboxyl. Then intermediate of amide was generated,amide bone was generated after a series of H⁺transfer.