Study On The Chemical Synthesis Process Of Poly(3-hydroxybutyrate)

Biodegradable plastics are of promising future to replace the undegradable plastics used widely which are the main cause of 'white pollution'. Poly 3-hydroxybutyrate is a plastic which can be degraded completely by biology. At present, it is produced by biological ferment and the price is high, so it can't be used widely. This paper study the chemical synthesis route of producing PHB and this study has great importance in environmental protection and economy. This paper studied 3-hydroxybutyraldehyde oxidization, 3-hydroxybutic acid esterfication, and 3-hydroxybutyrate polymerization three kinds of synthesis routes to produce PHB. The route that 3-hydroxybutyraldehyde was oxidizated to produce 3-hydroxybuty acid using loop reactor replacing kettle reactor. The loop reactor ejecting below was designed and a set of apparatus of oxidization reaction was established. The effects on the yield and conversion of the oxidization reaction of reaction time, catalyst content, solvent content, reaction temperature, reaction pressure, the rate of entering gas were fully studied through the orthogonal test. The optimum reaction conditions were investigated and obtained. The optimum reaction condition were as follow: reaction time 5 hours; catalyst content, 0.5%(wt%); the ratio of solvent content to raw material was 1:1; reaction temperature, 50℃; reaction pressure, 1MPa; the rate of entering gas, 0.3l/min. The yield and conversion of reaction were 88.99% and 90.86% respectively at above optimum conditions. This paper put forward new methods using high performance liquid chromatography to analyze the content of 3-hydroxybutyraldehyde and the esterification ramification of gas chromatography to analyze the content of 3-hydroxybutyric acid. In this paper, a set of experimental device of esterifying 3-hydroxybutyric acid was designed. The most properly catalyst p-toluene sulfonic acid of esterification reaction was selected by comparing the experimental results of three kinds of catalyst. The optimum reaction conditions were as follow: the ratio of mol. of ethanol, 3-hydrobutyric acid and catalyst was 24 to 20 to 1. The azeotropic solvent was cyclohexane and the dehydration solvent was calcium oxide. The reaction time was 3 hours. The yield of 3-hydroxybutyrate was up to 96.6%. 3-Hydroxybutyrate polymerized by itself is the most properly synthesis method of producing PHB in industrial scale. A set of experimental device was designed to produce PHB and the most properly catalyst of polymerizing 3-hydroxybutyrate was catalyst B. The optimum reaction conditions were as follow: reaction temperature 150℃, reaction pressure below 10-2 Pa. Extending the reaction time, the molecular weight will increase gradually. This paper also studied the biodegradation of PHB which were made by both chemical synthesis and fermentation. It was found that Pseudomonas spp. was the strongest microbe and the chemically synthesized PHB can be degraded completely by the microbe in the soil. The velocity of liquid circulating is one of main characteristic parameters of Loop Reactor. In order to realize the amplification in the industrial scale, this paper put forward an estimation equation of the rate of liquid circulation by scaling the energy of the whole reactor. The results using this equation comparing to Provic equation obtained by the experimental data estimated the rate of liquid circulation of our experimental conditions were very nearly. In order to provide fundamental data for the study of reaction theory, for dynamics study and for engineering calculation, a set of apparatus to measure vapor-liquid phase equilibrium was designed. The data were measured of 3-hydroxybutyraldehyde and 3-hydroxybutyric acid at different temperature and pressure. Wilson equation was used to correlate this experimental data and the parameters of Wilson equation were correlated.