The Synthesis Of Slow-release Nitrogen Fertilizer-polymer Carbonyl Urea And Study Of Process Conditions

This thesis with urea as the starting material, methanol as conversion agent, the slowrelease nitrogen fertilizer-polymer carbonyl urea was synthesized through two steps reaction.First, urea and methanol as raw material, urea translated methyl carbamate (MC) under hightemperature, medium pressure, without the presence of catalyst made; Second, MC as rawmaterial, urea as sealing agent, polymer carbonyl urea (PCU) was synthesized in the presenceof initiator, at the same time, recovery of methanol, the recycle of methanol is realized. Thefirst step reaction by-product of ammonia was recoveried and transfered into the ureasynthesis device, the urea is synthesized throught by-product of ammonia react with carbondioxide, ammonia and greenhouse gas carbon dioxide recycle were realized.The methyl carbamate was synthesized with urea and methanol as raw materials. Theproduct was characterized by melting point and infrared spectrum (FTIR), nuclear magneticresonance (1H NMR) and other modern detection means, which confirm that product wasmethyl carbamate; Through orthogonal and optimization experiments, the optimum reactioncondition for synthesis of methyl carbamate was obtained as follows: reaction temperaturewas160℃, reaction time was3h, n (urea):n (methanol)=1:7; By the method of eliminatingby-product ammonia, the chemical equilibrium moves in the direction of positive reaction,reaction conversion rate increased from58.9%to85.7%.Polymer carbonyl urea was synthesized under the condition of methyl carbamate as araw material, potassium methoxide or potassium carbonate as the initiator, and urea as sealingagent. The structure of polymer was characterized by melting point and infrared spectrum(FTIR), X-ray diffraction (XRD) and nuclear magnetic resonance (13C NMR), structure ofproduct has been confirmed as polymer carbonyl urea; The thermal stability of polymercarbonyl urea was studied by thermogravimetric (TG) and differential scanning calorimetry(DSC); The weight and molecular weight distribution of polymer carbonyl urea weredetermined by gel permeation chromatography (GPC). Through orthogonal and optimization experiments, the optimum reaction condition for synthesis of polymer carbonyl urea wasobtained as follows: when potassium methoxide as initiator, potassium dosage of2g whichwas used for initiator, reaction time was10h, reaction temperature was165℃, n (urea):n(MC)=1:10, this moment, the reaction conversion rate was83.1%; When potassiumcarbonate as initiator, the dosage of potassium carbonate was6g, reaction temperature was160℃, reaction time was6h, and n (urea):n (MC)=1:10, this moment, the reactionconversion rate was78.4%.The water solubility of PCU was3.94g/100ml-4.44g/100ml, it is equivalent to thewater solubility of urea (180g/100ml) of2.19%~2.44%; The hydrostatic nutrient releaseperiod of polymer carbonyl urea was studied by hydrostatic release experiments.