جستجوی مقالات مرتبط با کلیدواژه "urea" در نشریات گروه "ریاضی"

This study relates to an improved method for they preparation of hydrazodicarbonamide, an intermediate in the preparation of azodicarbonamide which is useful as a chemical blowing agent. Hydrazodicarbonamide is prepared by reaction of urea and hydrazine in acidic medium. Hydrazine is a relatively expensive chemical and this is reflected in the cost of materials derived from it. Accordingly any means of effecting a substantial increase in the yield of hydazodicarbonamide from hydrazine is commercially very important. By Series of comparative experiments, Factors of influencing the yield of biurea which is prepared from the condensation reaction between hydrazine hydrate and urea are studied.

Oleamide is amide derivative of oleic acid that is frequently used as slip agent in polymer industry. The present study explores the kinetic of oleamide synthesis by ammonolysis reaction between oleic acid and urea instead of ammonia gas at atmospheric pressure in the presence of AlCl3 catalyst. The effect of oleic acid : urea molar ratio, temperature and catalyst concentration on the reaction kinetic was investigated and reaction rate constants were calculated. At low molar ratio of oleic acid:urea (i.e. up to 1:2), the reaction followed an overall second order kinetic and at higher molar ratio (i.e. 1:4 and 1:5), the pseudo first order dependence of rate respect to oleic acid was dominant at three examined temperatures and catalyst concentrations. The values of rate constant were increased by increasing the temperature and urea as well as AlCl3 concentration in which the highest amount was attributed to the operational condition of oleic acid: urea molar ratio of 1:4, temperature of 200 °C and AlCl3 catalyst concentration of 1 wt% that was selected as optimum condition for oleamide synthesis.

The present paper explores a new economical method for the synthesis of oleamide in the presence of catalyst at atmospheric pressure. Oleamide is mainly synthesized by ammonolysis of fatty acid or esters with ammonia gas at high pressure. Yet, using the urea instead of ammonia gas provides an economical reaction at atmospheric pressure. The structure of synthesized oleamide is characterized by FTIR analysis. The effect of oleic acid / urea molar ratio, time and temperature of reaction as well as amount of catalyst on the acid values or conversion of reaction is studied. The optimum condition for the synthesis of oleamide from oleic acid and urea is obtained to be oleic acid / urea molar ratio of 1:4, temperature of 200 ℃ and time reaction of 180 min with 1 wt% catalyst concentration. At this condition the acid value of 56 was achieved. Also, the reaction mechanism and kinetic were investigated in which ammonolysis followed pseudo-first order kinetics.

An improved and facile preparation of 3,7-dinitro-1,3,5,7-tetraazabicyclo [3,3,1] nonane (DPT) has been developed starting from urea. In the procedure DPT was synthesized via N,N’-dinitrourea (DNU) as intermediate and various operating parameters such as temperature, pH and molar ratio of reagents have been optimized to give maximum yield of the desired product. The low cost method is concise, operationally simple and offers high purity and satisfactory yield of DPT.