Study Of Manufacturing High Grade Lube Oil Base Stocks From Intermediate Crude Oil By Medium Pressure Hydrotreating Process

A medium pressure hydrotreating process for manufacturing high-grade lube oil base stocks has been developed by RIPP. In order to have this technology used successfully in refinery, the reaction kinetics, influence of hydrocarbon composition of feedstocks and reaction conditions on lube base oil stocks are studied.All hydrotreating tests are conducted in a 300mL pilot plant. The test conditions are temperature of 360- 380 0C, hydrogen partial pressure of 6.4-12.OMPa, 112/Oil ratio of 1000 Nm3/m3 and LHSV of 0.3-l.5h'. Feedstocks used in tests are Iranian light crude VGO, its raffinate by mild furfural solvent refining and raffinate by conventional furfural solvent refining. With those feedstocks, a three-lumping kinetic model and a five-lumping kinetic model are developed, the influence of feedstocks and test conditions on the composition, VI (Viscosity Index) and photostability of lube oil base stocks produced is also investigated intensively.It is found that those two kinetic models can fit the experimental data satisfactorily with second reaction order to aromatics and first reaction order to other components. The result of parameters' calculation indicates that the property of feedstocks affects rate constants greatly, lumping components of the feed with less aromatics have larger rate constants than that of feed with more aromatics. At the test condition of hydrogen partial pressure eiiiployed, temperature has little affect on rate constant of aromatic component, but great function to that of others. On contrast, pressure has great affect on rate constant of aromatics. As hydrogen partial pressure increasing, the rate constant of aromatics becomes large, but the rate constants of other components have little changed.The distribution pattern of composition of hydrotreated base oils is different according to various feedstocks and test conditions. The feedstock containing less aromatics content makes hydrotreated base oils mainly be composed of isoparaffin and mononuclear or dinuclear naphthenic hydrocarbon and mononuclear aromatics. At the test condition of hydrogen partial pressure employed, temperature has little affect to aromatics, but the amount of tn-nuclear and tetra-nuclear naphthenic hydrocarbon in base oils is decreased evidently as temperature is increased. Hydrogen partial pressure is only to promote the disappearance of aromatics tremendously.VI has close correlation to the group chemical composition of hydrotreated lube oil base stocks. With the increasing content of isoparaffln and the decreasing content of aromatics, VI is increased. Naphthenic hydrocarbon is not a monotonic function of VI, it emerges a peak value as VI changes.The photostability of hydrotreated lube oil base stocks becomes worse when there is a large amount of polyaromatics in it. The polyaromatics, which have not been completely hydrogenated in hydrotreating process, is the key factor to ruin the oil photo-property. The result of photo-test indicates that the stability of base oils is good when there is little polyaromatics in it.