Base oils are the most important components of lubricants. Various types of lubricants contain a weighted avenge of —95% base oils.

Lubricants are widely used in various technology sectors, e.g., rocket, nuclear, and space. The reliability and service life of equipment depends largely on the quality and correct use of lubricants. A current trend in technology development is increased lubricant service life and redaction of technical service costs. Development of hydrogenation processes is the main direction in production of base oils that meet current operating and environmental requirements. The most promising processes in this direction are associated with the use of hydrocracking residue (HCR) [1].

Only rather viscous HCR obtained at pressures above 10 MPa can be used to produce high-quality base oils meeting current requirements for API classification [2].

Therefore, unconverted residue from fuel hydrocracking seemed promising for producing API group II and III oils. This would require use of selective purification and solvent deparaffinization. The present work analyzed HCR obtained from vacuum gasoil on a hydrocracking unit with up to 75% conversion (reactor pressure up to 15 MPa).

Table 1 presents the physicochemical characteristics of the HCR (type A). The hydrocracking unit feedstock was vacuum gasoil AVT and its mixtures with extract, petrolatum fraction 340°C-EP, and heavy coking gasoil.

Table 1
Full size table

HCR typically had a high viscosity index and high gel point.

Narrow fractions were produced from the HCR using laboratory vacuum distillation according to ASTM D 5236 of HCR in a Fisher apparatus with residual pressure 1 mm Hg to give clearly separated fractions at a slow distillation rate. Table 2 presents the results [3,4,5].

Table 2
Full size table

The fractional composition of the HCR (type A) became lighter if oil purification extracts were used as feedstock.

Table 3 presents the physicochemical characteristics of the fractions obtained after distillation. Fractions 440-480, 480-520, and >520°C had the greatest viscosity indices.

Table 3
Full size table

Gel points could be lowered by deparaffinization of HCR (type A) without separation into fractions using a MEK/toluene 40/60 mixture in a 3/1 ratio at filtration temperature —25°C. The yield of deparaffinized HCR was 89% of the feedstock mass.

The physicochemical characteristics of deparaffinized oil from HCR (type A) without separation into fractions were:

Density at 20°C, kg/m3 832

Kinematic viscosity, mm2/s

at 40°C 25.71

at 100°C 5.075

Viscosity index 128

Refractive index at 50°C 1.467

Gel point, °C —14

Yield, % 89

The obtained sample of deparaffinized oil had a high viscosity index (>120) and rather low gel point. The physicochemical characteristics of the paraffins from HCR (type A) were:

Melting point, °C 44

Refractive index at 50°C 1.4495

Three fractions of HCR (type A) (410-440, 440-480. and 480-520°C) were deparaffinized using an MEK/toluene 40/60 mixture in a 3/1 ratio at filtration temperature —25°C to increase the yield of deparaffinized oil and to produce oils of various viscosities.

Table 4 presents the physicochemical characteristics of deparaffinized oils from narrow fractions 410-440,440-480, and 480-520°C.

Table 4
Full size table

The obtained from fraction 480-520°C had the highest viscosity index (>120). Furthermore, the obtained deparaffinized oils had low gel points and could be used to produce current commercial oils for various applications.

Table 5 presents characteristics of HCR(typeA) narrow paraffin fractions410-440,440-4130, and 480-520°C.

Table 5
Full size table

Selective purification of HCR by N-methylpyrrolidone at 65°C with a solvent:feedstock ratio of 1.2:1 and without separation into fractions was studied in the next stage of the work became the color of HCR during storage and transportation was reported to be unstable [3,4,5].

The gel point could be lowered by deparaffinization of the HCR (type A) raffinate using an MEK/toluene 40/60 mixture in a 311 ratio at filtration temperature —25°C. The yield of deparaffinized oil from HCR (type A) raffinate was 94 mass% for feedstock and 88 mass% for the corresponding HCR [4].

Table 6 presents the physicochemical characteristics of the raffinate, extract, and deparaffinized oil of HCR (type A). The obtained deparaffinized oil had a high viscosity index (136) and high gel point (-4°C). Thus, all obtained products were high quality and could be used to produce current commercial oils. It is noteworthy that the oil samples obtained from HCR that were only deparaffinized became darker than oil samples that were selectively purified and deparaffinized after storage for one month in the light.

Table 6
Full size table

The raffinate, hydrocracking oil component, and paraffins obtained during pilot testing were studied by us. Table 7 presents the physicochemical properties.

Table 7
Full size table

The color of the samples changed considerably (to dark-brown) after storage for a month in the light. Furthermore, the hydrocracking oil component had become more cloudy. This was explained by the much lower purity under pilot-testing conditions than in the laboratory.

It is noteworthy that the viscosity indices of the raffmate and oil component obtained on the industrial unit wen much inferior to those of analogous laboratory samples.

The chemical composition and physicochemical characteristics of the HCR met requirements for feedstock for hydrocncking oils. Selective purification with high yields could be used to improve the oil physicochemical properties. Fraction 440-480°C was considered the most acceptable for producing oil using selective purification and solvent deparaffinization. The overall oil yield per HCR was up to 50 wt.%. The oil quality met all requirements for API group base oils. Base oils from HCR did not darken during storage in the light and did not lose their properties. The low-viscosity deparaffinized oil from fraction 410-440°C could be used as a base for various hydraulic fluids, transformer oils, and oils for electrospark stands. The product from selective purification and deparaffmization of HCR without separation into fractions could be used to produce high-quality motor oils. Deparaffinized oil from fractions 440-480 and 480-520°C could be used to produce high-quality motor and hydraulic oils.