| The production and sales of biological base material poly?3-hydroxybutyrate??PHB?are increasing rapidly,causing serious environmental problems and huge resources waste.The study of PHB recycling technology has attracted more and more attention.Ionic liquid,as an environmentally friendly green solvent or catalyst,is used in many chemical reactions,is expected to replace the traditional non-environment benign acid or base catalyst system.In this thesis,Ionic liquids are designed and synthesized as reaction medium or catalysts,to recover monomers or chemical products under mild reaction conditions,without using any traditional acid or base catalysts.This approach can overcome many disadvantages of traditional methods,such as catalysts cannot be reused,equipment corrosion,waste emissions and severe conditions.This method is expected to provide theoretical support in chemical recycling of waste polyester materials.In this chapter,methanolysis of poly?3-hydroxybutyrate??PHB?was investigated using ferric chloride?FeCl3?as catalyst.The influence of different reaction time,reaction temperature,the amount of catalyst,and the methanol dosage on the conversion of PHB and yield of methyl 3-hydroxybutyrate were investigated.The optimum reaction conditions were obtained: the reaction temperature was 140 ?,reaction time was 2.0 h,n?FeCl3?:n?PHB?=0.05:1,n?CH3OH?:n?PHB?=5.0:1.Under the above conditions,the conversion of PHB and yield of methyl 3-hydroxybutyrate were 91.1% and 88.3%,respectively.The purity and structure of the product were analyzed.Under the optimum conditions,we also studied the effects of different alcohols on PHB alcoholysis,the effect of methanol alcoholysis is best.The reuse performance of FeCl3 in PHB methanolysis was studied.The catalyst FeCl3 could be recycled up to 6 times with no apparent decrease in catalytic activity.Moreover,the possible mechanism and kinetic of the reaction were proposed.The result shown that this reaction was first-order kinetic reaction with activation energy of 34.17 KJ/mol.Basis on the experiment,Lewis acid ionic liquid 1-butyl-3-methylimidazolium tetrachloroferrate?[Bmim]Cl-FeCl3?was designed and synthesized,the acidic and structural features were characterized.Then their catalytic effect were investigated,the effects of n?[Bmim]Cl?:n?FeCl3?,catalyst dosage,temperature,time and methanol dosage on methanolysis results of PHB were examined.The optimum reaction conditions were obtained: n?[Bmim]Cl?:n?FeCl3?=1:2,the reaction temperature was 140 ?,reaction time was 3.0 h,n?CH3OH?:n?PHB?=5.0:1,n?[Bmim]ClFeCl3?:n?PHB?=0.05:1.Under the above conditions,the conversion of PHB and yield of methyl 3-hydroxybutyrate were 94.1% and 85.0%,respectively.The product purity and structure were also characterized.Under the optimum conditions,we also studied the effects of different alcohols on PHB alcoholysis,the effect of methanol alcoholysis is best.The reuse performance of [Bmim]Cl-FeCl3 in PHB methanolysis was studied.The catalyst [Bmim]Cl-FeCl3 could be recycled up to 6 times with no apparent decrease in catalytic activity.The structure of the ionic liquid also has no change and the stability is good.Moreover,the possible mechanism and kinetic of the reaction were proposed.The result shown that this reaction was first-order kinetic reaction with activation energy of 27.44 KJ/mol.Basis on the experiment,Bronsted-Lewis acidic ionic liquid 1-?3-sulfonic acid?-propyl-3-methylimidazole chloroironinates?[HO3S-?CH2?3-mim]Cl-FeCl3?was designed and synthesized,the acidic and structural features were characterized.The experimental results show that the higher the acidity of ionic liquid,the higher the conversion rate of PHB.The better ionic liquid [HO3S-?CH2?3-mim]Cl-FeCl3?1:1?was been selected.The effects of catalyst dosage,temperature,time and methanol dosage on methanolysis results of PHB were examined.The optimum reaction conditions were obtained: the reaction temperature was 140 ?,reaction time was 3.0 h,n?[HO3S-?CH2?3-mim]Cl-FeCl3?:n?PHB?=0.05:1,n?CH3OH?:n?PHB?=5.0:1.Under the above conditions,the conversion of PHB and yield of methyl 3-hydroxybutyrate were 98.5% and 87.4%,respectively.The product purity and structure were also characterized.Under the optimum conditions,we also studied the effects of different alcohols on PHB alcoholysis,the effect of methanol alcoholysis is best.The reuse performance of [HO3S-?CH2?3-mim]Cl-FeCl3 in PHB methanolysis was studied.The catalyst [HO3S-?CH2?3-mim]Cl-FeCl3 could be recycled up to 6 times with no apparent decrease in catalytic activity.The structure of the ionic liquid also has no change and the stability is good.Moreover,the possible mechanism and kinetic of the reaction were proposed.The result shown that this reaction was first-order kinetic reaction with activation energy of 24.74 KJ/mol.In a word,Lewis acid FeCl3?Lewis acidic ionic liquids [Bmim]Cl-FeCl3 and Bronsted-Lewis acidic ionic liquids [HO3S-?CH2?3-mim]Cl-FeCl3 were showed better catalytic effect.Investigation also showed that the catalytic activity of [HO3S-?CH2?3-mim]Cl-FeCl3 was higher than that of [Bmim]Cl-FeCl3 and FeCl3.To our knowledge,there is no report in literature about the study mentioned above. |
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