Study On Preparation Of3-hydroxypropionic Acid By Hydration Of Acrylic Acid

3-Hydroxypropionic acid (3-HP) is considered as a potential building block either for organic synthesis or high performance polymers. However, no large scale process is presently available despite many efforts following biological and chemical routes. Compared with biological process, the reaction on technology process of hydration of acrylic to produce3-HP can avoid some disadvantages, such as, immature production process, a long time of fermentation, cumbersome process of purification product and low productivity. A green process for producing acrylic acid is highly desirable, because3-HP is expensive and its hydration rules is less conducted.Acrylic acid(AA) hydration is an acid-catalyzed reaction. Ion-exchange resins, zeolite and solid inorganic acids are used in hydration reaction, but there are some disadvantages such as low activity and poor stability. However, the studies on these catalysts are few and a suitable catalyst for this hydration has to be developed. Therefore we begin the research on liquid acid-catalyzed acrylic acid hydration to find the optimum conditions, including the acid type, acidity, and other factors affecting hydration. Based on these findings, a series of the design and preparation of the acrolein hydration catalyst were developed and the reactivity and selectivity of catalysts were improved. The main research work and conclusions are as follows.1. Proton acid(such as phosphoric acid and sulfuric acid) were used as catalysts for the hydration of acrylic acid, the basic conditions were systematically studied, and factors such as temperature, time, pH, types of acid were investigated. According to the yield of3-HP, the results showed that the effect was influenced by acidity to a certain extent, and hydrogen ion activity regardless of its source. The optimum reaction conditions of hydration is as follows:phosphoric acid as catalyst, pH=0.60, 120℃of temperature and3hours of reaction time.2. When Lewis acid was used in acrylic acid hydration, the influences of reaction conditions, e.g. types of Lewis acid, n(Lewis acid)/n(acrylic acid), reaction time were investigated by single-factor. The results showed that the conversion of acrylic acid was66.12%and3-HP selectivity reached to79.61%.3. In a flask reactor, best catalysts(D072and D850) were selected for hydration of acrylic acid from6kinds of acidic ion-exchange resins. The effects of temperature, time, amount of catalyst were respectively researched on conversion and selectivity, as well as the stability of catalysts.4. The reaction products of synthesis of3-HP were qualitatively analyzed, and composition and formation of the by-products were identified by GC-MS. The target product of3-HP was quantitatively analyzed by HPLC with area normalization method.5. In this paper, the yield of3-HP by resin is lower than proton acid, but it can avoid the cumbersome separation of catalysts. Besides, it provides a new synthesis technology of3-HP.6. The intrinsic kinetic of hydration of acrylic acid was investigated in the presence of an acidic cation exchange resin catalyst. Further research on reaction mechanism was discussed by analysing the reaction process using kinetics.