Green Synthesis Technology Of Dimethyl Malonate

Dimethyl malonate (DMM) is an important pharmaceutical intermediate and is widely used in various types of organic synthesis reactions. Current general industrial production methods of DMM are cyanidation and carbonylation. However the problems of these two methods are difficult to overcome:low yields comes with cyanidation method and during the production, the use of highly toxic sodium cyanide is prone to cause environmental pollution and personal injury; in carbonylation production process, rhodium, palladium and other precious metal are requierd to catalyze the reaction, which increases the cost. Moreover, harsh reaction conditions make the process more dangerous. The research aims to develop a process that uses dimethyl carbonate and methyl acetate as raw materials, through the Claisen condensation (hereinafter referred to as "ester condensation reaction") to synthesis DMM. In this method, the raw materials are cheap and easy to get. No toxic substances involved in the reaction, without the use of a noble metal catalyst and mild reaction conditions make the reaction is an ideal environmentally friendly process. DMM can be turned into 1,3-propanediol by catalytic hydrogenation, which is the key monomer of new polyester PTT, of which the demand is increasing year by year. Therefore the research on the new process is of applied importance.In this experiment, the ester condensation reaction is researched, including the selection of catalyst and the optimization of reaction conditions. In the course of the research, the positive correlation between the conversion of the reaction with the amount of catalyst was found. Consequently, the reaction is controlled by the liquid solid mass transfer process (the product is coated on the catalyst surface, and the reaction is blocked). In order to separate the product from the catalyst, acidification of the product is necessary. To solve the loss of catalyst in process of acidification, the recycle and regeneration of catalyst is explored. Due to the high energy-consumption of the process, process for the synthesis of DMM or 1,3-PDO by gas-phase method is also preliminarily researched. The contents and results are as follows:(1) Several different catalysts are employed in the ester condensation reaction to investigate the catalytic effect, including sodium methylate, potassium methylate, sodium tert-butylate, potassium tert-butylate, ethylene glycol sodium, sodium hydride etc. After taken the reaction conversion rate, selectivity and subsequent separation into consideration, potassium methylate is selected as the catalyst for this ester condensation reaction.(2) With potassium methoxide being used as catalyst, different reaction conditions are studied. The parameters include reaction time, reaction temperature, feed ratio, the amount of catalyst etc. The final selected reaction conditions:reaction temperature= 90℃, reaction time= 2h, n(DMC):n(MAC):n(cat)= 5:1:1.8.(3) Methanol and water are studied as acidifying agents respectively. The study results show that when water is applied as acidifying agents, the acidification is more completed and much better.(4) Synthesis of DMM/1,3-PDO by gas-phase method is researched, and the possibility of synthesizing 1,3-PDO by one step method was found.(5) The reaction that use potassium hydroxide and methanol as raw materials to produce potassium methoxide is studied and the reaction conditions are determined. In the final solid product, the percentage of free alkali can be as low as 3.211%. When the product is applied in the claisen ester condensation reaction, satisfactory results can be obtained.