Chemical Synthesis Of Monomers Of Poly 3-Hydroxybutyrate

3-Hydroxybutyric acid and ethyl 3-hydroxybutyrate are the main monomers forproducing PHB, an important biodegradable plastic. By far, they have not beenproduced on commercial scale. Therefore, the synthesis of PHB monomers is of greatimportance.In this paper the effects of the structure parameters of the 0.5L loop reactor onthe oxidation of 3-hydroxybutanal were studied. The optimal structures are the ratioof inner and outer tube diameter (d/D) being 0.71, the ratio of inner and outer tubeheight(h/H) being 0.40, sparger with 50% porosity, the volume ratio of filler toreaction mass being 4.0%. In the optimum loop reactor, with pressure being 1MPa,temperature being 60 ℃, oxygen flow rate being 0.018m3/h, the mass ratio of solventand catalyst cobalt acetate to 3-hydroxybutanal being 100%, 0.5%, reaction timebeing 4.5h, the average yield was 88.9%.3-Hydroxybutic acid was synthesized in another 4L loop reactor designed andmanufactured. The orthogonal analysis showed that reaction time was the mostremarkable effect factor for the yield. The minor factors are the solvent amount andthe reaction pressure. The optimal reaction conditions are: time being 5h, pressurebeing 1MPa, oxygen flow rate being 0.16m3/h, temperature being 60 ℃, mass ratio ofsolvent and catalyst cobalt acetate to 3-hydroxybutanal being 140%, 0.5%respectively. Under the above conditions, the average yield was 88.1%.Preparation of ethyl 3-hydroxybutyrate from 3-hydroxybutyric acid and ethanolwas studied. The yield of ethyl 3-hydroxybutyrate could reach 95.5% under thefollowing conditions: 3-hydroxybutyric acid 1.0 mol, ethanol 1.2mol , SO42-/Fe2O310g, cyclohexane 50 mL, CaO56.3 g (or 92.3g molecular sieve or 17.1g MgSO4),time 3h. The synthesis method of methyl 3-hydroxybutyrate was primarilydetermined.