基于硫酸介质的乙二醛常压氧气氧化制备尿囊素

研究了以硫酸和氯化铝为酸性介质,亚硝酸钠为催化剂,常压氧气氧化乙二醛制备乙醛酸,进而在不添加酸性催化剂的条件下直接合成尿囊素的技术路线。通过对各影响因素的考察确定了氧化反应适宜的工艺条件为:乙二醛质量分数25%,钠醛比0.2、酸醛比0.4、反应温度25℃、反应时间3h,在此条件下,乙醛酸收率为76.12%;缩合反应适宜的工艺条件为:乙醛酸尿素投料比1∶4,反应温度75℃,反应时间3h,此时尿囊素的收率可达60.75%。

PREPARATION OF ALLANTOIN FROM GLYOXAL BY ATMOSPHERIC OXYGEN OXIDATION WITH SULFURIC ACID AS A MEDIUM

The technical route of allantoin synthesis was studied,which was characterized with the glyoxylic acid preparation by oxygen oxidation of glyoxal at ambient pressure with sulfuric acid and aluminum chloride as acid medium,and sodium nitrite as catalyst first,then direct synthesis of allantoin without the addition of acid catalyst.The suitable process conditions for the oxidation were determined after investigation of affecting factors,that is,mass concentration of glyoxal was 25%,the molar ratio of sodium nitrite to glyoxal was 0.2,molar ratio of sulfuric acid to glyoxal was 0.4,reaction temperature was 25 ℃ and reaction time was 3 h.Under these conditions,the yield of glyoxylic acid was up to 76.12%.The suitable conditions for condensation reaction were as follows: the molar ratio of glyoxylic acid to urea was 1∶4,reaction temperature was 75 ℃ and reaction time was 3 h.Under these conditions,the yield of allantoin was up to 60.75%.