Experimental Study And Process Simulation Of Synthesis Of Adipic Dihydrazide

Adipic dihydrazide (ADH) is a bifunctional compound with a symmetricstructure. It is mainly used in paint additives, metal deactivators, watertreatment agents, inks, adhesives and other industries. It can be reacted withfunctional monomer diacetone acrylamide (DAAM) at room temperature forself-crosslinking to prepare hydrophilic resins.ADH was prepared with high purity using adipic acid, methanol andhydrazine hydrate as the raw materials by two-step. Adipic acid was firstesterified with methanol. The experimental results showed that the molar ratioof methanol to adipic acid was4, the best catalyst was found to be potassiumhydrogen sulfate at5.5%of the weight of adipic acid and the optimal reactiontime was1h, giving dimethyl adipate at a yield of77%and a purity of99.86%based on gas chromatographic analysis. Dimethyl adipate was then reactedwith80%hydrazine hydrate using methanol as the solvent. The molar ratiosof both hydrazine hydrate and methanol to dimethyl adipate were found to be4, the optimal reaction time was1.5h at room temperature and the ADH yieldwas99%with a purity of99.54%based on high performance liquidchromatography analysis. The ADH structure was verified by IR spectrumanalysis and its melting point was determined to be180.86℃by a differentialthermal analysis, which is in good agreement with the literature.The two-step synthesis of ADH was simulated using Aspen software andthe two schemes with methanol and ethanol as raw material, respectively,were compared. When methanol was used for esterification, part dimethyladipate was distilled which entered into the second reaction, and theremainder was recycling in order to make the apparent yield of esterificationwas100%. When ethanol was used for esterification, toluene was added toform a toluene-ethanol-water ternary azeotrope to remove water, which couldmake the yield of esterification reach to100%. The esterification productswere used as the raw materials of Hydrazide reaction directly. The simulationresults showed that the energy consumption of ethanol as raw material is200%higher than that methanol and the equipment investment is100%higher.After comprehensive comparison, it is concluded that the scheme of methanol as raw material is more suit for industrial production of ADH.