Study Of The Effect Of Chemical Composition Of Lube Base Oil On Its Light Stability

In this paper,the aromatics of the third-stage vacuum gas oil from Maoming were separated into component 1 based on mono-aromatics,component 2 based on di-aromatics and component 3 based on poly-aromatics by the liquid-solid adsorption chromatography,and the aromatics in these three components were identified with the help of refractive index,UV and MS.Then the component 1,component 2,component 3,quinoline,indole,DBTH and a variety of lubricating oil additive were used as model compounds to study the effect of different ring-number aromatics,basic nitrogen compounds,non-basic nitrogen compounds,sulfur compounds and lubricating oil additives on the light stability of lube base oil.In addition,the chemical composition of two kinds of lube base oil with different light stability were analyzed and compared,and the sediments deposited from the lube base oil A were characterized by means of elemental analysis,XPS,FT-IR and FT-ICR MS,which determined the basic structure of the sediments.Finally,the feasibility of improving the light stability of lube base oil by adsorption method was also studied.The results showed that the main chemical composition of the three components were mono-aromatics,di-aromatics and poly-aromatics respectively.Among them,the mono-aromatics had no effect on the light stability of lube base oil,and the effect of di-aromatics was small,while the effect of poly-aromatics was obvious.The effect of nitrogen compounds on the light stability of lube base oil was especially significant,and the effect of non-basic nitrogen compounds was far greater than the effect of basic nitrogen compounds.Low content of thiophenic sulfur compounds made the light stability of lube base oil worse,while high content of thiophenic sulfur compounds could inhibit the light stability of lube base oil deterioration.Different types of additives had different effects on the light stability of lube base oil.It could be judged that the polar component containing heteroatoms was the reason to cause the different light stability of two kinds of lube base oil by comparing the chemical composition of lube base oil A and B.The sediments deposited from lube base oil A was polar compounds composed of carbon,hydrogen,oxygen,sulfur and nitrogen.The content of oxygen was higher than other heteroatoms,which mainly existed in C=O and C-O-C,N appeared mainly as amine and S mainly existed in R-SO₃H and SO₄^2-.Therefore,it further indicated that the small amount of polar compounds in lube base oil A was the main reason to cause the degradation of its light stability.The small amount of polar compounds in lube base oil A could be effectively removed by adsorption refining,improving its light stability significantly.