绿色溶剂和基于电位突跃测定油品酸值

Determination of Acid Number in Oils by Potential Jump with Green Solvents

提出了一种使用绿色溶剂和完全基于电位突跃判别终点的油品酸值的测定方法。对国家标准方法(GB/T 7304)进行改进,以石油醚组合弱碱性醇胺试剂替代甲苯,同时增强油品的弱酸性物质表观酸度和抽提能力,采用碱度更强和配制简便的四甲基氢氧化铵(TMAH)替代氢氧化钾标准溶液,省去了间硝基苯酚非水溶液辅助指示终点,扩大了油品应用范围,提高了方法的准确度。结果表明,酸值测定结果与GB/T7304方法一致,可以测定0.005mg(KOH)/g以上的油品酸值,其相对标准偏差不大于3.0%。该法已在日常工作中应用,结果满意。

A new method for determination of acid number in oils was developed. The method was modified from the GB/TT304 method and was entirely based on potential jump with green solvents. Toluene in mixture solvents was replaced by petroleum ether in combination with alkalescence hydramine,in which weak acidic materials could be extracted and apparent acidity could be enhanced. Quaternary ammonium hydroxide with higher basicity was used as titrant instead of potassium hydroxide. The end point was determined completely with potential jump, avoiding auxiliary estimation with m-nitrophenol buffer solution and the drawbacks of toxic and short period validity. Through this proposed method, the range of application was expanded and the accuracy was improved. The results of acid number were in accordance with GB/T7304 with relative deviation less than 3.0 %. The minimum of quantitation was 0. 005 mg（KOH）/g. The method has been successfully applied to the determination of actual oil samples with satisfying results.