Separation of metallic sulfonates and base oils in the prepared detergent-dispersants by gel permeation chromatography

Abstract

Gel permeation chromatography(GPC) was applied to the separation of metallic sulfonates in additive concentrates, which used as detergent-dispersants for preparing lubricating oils. The experiment was carried out using a model LC-07 ( Japan Anal. Ind. Co.) equipped with UV and RI detector. The GPC condition was as follows; column: JAI Gel 4 (polystyrene gel cross-linked with divinylbenzene, core size: 25Å), 20 mmφ×600 mm, detector: differential refractometer, eluent: benzene, 3 ml/min. 3 ml of 5% additive concentrates in benzene solution was poured into a column. In GPC, metallic sulfonates tend to increase their miscelle size in benzene solution compared with that in chloroform or tetrahydrofuran solution. The increment of apparent molecular weight of metallic sulfonates showed the separation of sulfonates from base oils in additive concentrates be possible. Neutral, basic and overbased calcium sulfonates were separated into two portions, a calcium sulfonates fraction and a base oils fraction. That is, calcium sulfonates with different basicity eluted respectively in the range of elution volume from 180 to 190 ml and were obtained as resinous form. On the other hand, base oils eluted in the pure state over 210 ml of elution volume. However, about 2% of total eluate was obtained from the fraction between 190 and 210 ml. This was identified as a mixture of calcium sulfonates and base oils. This is caused by the molecular weight distributions of hydrocarbon part of calcium sulfonates and also of base oils. The separation profiles of basic, overbased barium and magnesium sulfonates were identical with those of calcium sulfonates. It was found that GPC could be applied to the separation of miscelle associated metallic sulfonates in solution and useful qualitative informations about sulfonates in additive concentrates or lubricating oils could be obtained by this method.