| With the growing awareness of environmental protection, the air quality is increasing in our country, and increasingly demands for motor vehicle exhaust restriction. In order to improve the exhaust quality of diesel emission by making diesel fuel low sulfur, the low sulfur diesel fuel have been achieved by increasing the use of refining processes such as hydrotreating. Using low sulfur or ultra low sulfur diesel to meet the environmental requirements, however there is the increasing problem of engine life caused by wear and damage with the decreasing lubricity of low sulfur diesel, especially in recent years, Injection system were put into application rules, improving the working pressure oil pump, it is a higher requirement that the lubricity of diesel fuel for diesel pump. The bio-additives in market have a good effect for improving the lubricity of hydrogenated diesel. But the acid value of bio-additives is too high, and this high acid value of diesel fuel additives will react with the dispersant additives of high base value to destruct the colloidal centers, calcium and magnesium salts of carboxylic acids generated will cause fuel filter clogging, affecting the normal operation of the engine may even damage the engine parts. Therefore, a low acid value anti-wear additive for improving the lubricity of hydrogenated diesel fuel is a new clean diesel technologies need to overcome bottlenecks.Firstly, the physicochemical properties of hydrogenated diesel fuel and its fractions produced by hydro-refining, hydro-upgrading, and hydro-cracking were analyzed. The lubricity of diesel fuel and its fractions were measured by a high-frequency reciprocating rig. The relationships of lubricities between the fractions were discussed. And the ultra-low sulfur diesel on the lubrication mechanism was discussed by XPS. The prediction model for the lubricity of hydrogenated diesel with the sulfur content below 200 g/g with three parameters of viscosity, nitrogen content and cycloalkane content was established by using the stepwise linear regression method. The coefficient, R, reached up to 0.981. The relationship between the lubricity of hydrogenated diesel and their physicochemical properties was revealed.Secondly, effects of different polar substances on the lubricity of diesel fuel by hydro-upgrading were studied. The order for improving the lubricity of diesel with the same dosage is:acid> Vegetable Oils> cells esters> binary ester> alcohol> symmetrical ether> asymmetric ether. The research of density functional theory by different polar functional groups with the iron surface density was carried out, the results show that the additive with alcohol and ester would enhanced the interaction between additive molecules and the metal, thereby it has a good synergies to improve lubricity for reducing the friction interface.Then, the components of bio-diesel as the addition to improve the lubrication performance of ultra low sulfur diesel fuel by hydro-cracking were studied. The results indicates that the key substance of bio-diesel to improve the diesel fuel from hydrocracking is the extremely small amounts of polar impurities such as glycerol, free fatty acids, partially reacted acylglycerols (monoacylglycerols and diacylglycerols), as well as residual starting material (triacylglycerols), not the monoalkyl esters in the major components of bio-diesel. This also verifies the results of density functional theory by different polar functional groups with the iron surface density.Subsequently, it is the orientation that the key components of bio-diesel for improving the lubricity of ultra low sulfur diesel fuel, the synthetic conditions for the substances with functional groups of hydroxyl and ester were investigated, monoglyceride ricinoleate was optimized, the product yield of monoglyceride ricinoleate can reach up to 83.5% by esterification distillation with reaction temperature 180℃, molar ratio of ricinoleic acid to glycerol 1:1.2. The compatibility issue between monoglyceride ricinoleate and hydrogenated diesel was resolved by AEA compound. The compatibility mechanism was also discussed. The composition of anti-wear additive was optimized by the proportion of monoglyceride ricinoleate and ricinoleic acid. The additive of Z01 was prepared with mass proportion of monoglyceride ricinoleate, ricinoleic acid and AEA at 100:43:11. The wear scar diameter of hydrogenated diesel fuel decreased from 689μm to 422μm with 200μg/g of Z01.Finally, the compatibility of home-made anti-wear additive Z01 with anti-static additive, scale up and preliminary industrial application were evaluated. The results show that good compatibility of Z01 with anti-static additive, good stability for storage and scale up. The anti-wear performance of Z01 and similar products of domestic and abroad additives were compared. In the same dosage, the performance of two domestic additives XL-66, DL-4940 is almost equal, and the performance of the foreign additives F-01 and home-made Z01 is almost equal, while the performance of domestic additives is better. The acid vale of Z01 is only about 30% of domestic additives, about 60% of foreign product. The price is similar with domestic additives, and slightly lower than foreign product F01. The properties of hydrogenated diesel with different anti-wear agents were also investigated. The results indicate that it has no effect on properties except a slight increase in acid value of diesel. Improve the acid of diesel by Z01 is the smallest with 500μg/g, only about 30% of domestic additives, about 60% of foreign product. The results show that the home-made additive of Z01 has the low acid value, good improve the lubricity of hydrogenated diesel. The lubricity of hydrogenated diesel fuel with anti-wear additive of Z01 can meet the requirements for the national standard GB/T 19147-2003, avoid excessively high acid value for the impaction on diesel engine. It is enhanced the reseach and development technology of domestic high-quality anti-wear additives for hydrogenated diesel. It is a great significance for further adapted to requirements of clean diesel. Anti-wear mechanisms by several different anti-wear additives were investigated in the research process, and it is enriched the application basic theory for improving the lubricity of hydrogenated diesel.
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