PTQ Q2 2025 Issue

Impact of hydrocracker catalyst changes on crude oil selection

Produce high-quality, on-spec base oils from a greater variety of crude oils, including those previously considered the lower threshold for crude quality

Bilge Karahan, Merve Çinbar and Nilay Aktaş Tupraş Peter Nymann Topsoe

B ase oil production requires crude oil with a high par- affinic content, which restricts the choice of crude oil types. Crude oil rich in paraffins is more expensive compared to other varieties. Therefore, oil refineries must gain flexibility in crude oil selection to increase the profit margin. Several methods can be adopted to address this lim - itation, and co-processing of unconverted oil (UCO) from the hydrocracker is one of the best practices. Topsoe has supplied hydrocracking catalysts involving sev - eral cycles for Tüpraş. In the most recent cycle, the installed catalyst system was modified to provide a higher viscosity index (VI) of the UCO to potentially enable use in the refinery base oil plant. Using high VI UCO from the hydrocracker pro - vides better quality base oil production and enables the use of a wider range of crudes. When processing crude oil with low paraffin content at the refinery, the base oil fails to meet the minimum VI specifica - tion. To improve VI of the base oil, UCO co-processing has proven to be an effective solution. Co-processing of a higher VI UCO enables greater flexibility in crude oil selection. Besides improving VI values, co-processing UCO also boosts the yield of base oil products. Base oil production includes several modes, namely spindle oil, light neutral, heavy neu - tral, and bright stock modes. In the heavy neutral mode, UCO co-processing is required to achieve the desired VI specifi - cations. For the light neutral mode, co-processing with UCO enhances yield improvements. Conversely, UCO cannot be co-processed in spindle and bright stock modes due to the significant difference in viscosities (at 100°C) between UCO and these products.

Base oil process configuration The base oil complex in İzmir Refinery was designed for the production of Group I base oils consisting of four different grades: spindle oil, light neutral oil, heavy neutral oil, and bright stock oil. The complex (see Figure 1 ) consists of a vacuum distillation unit (VDU), propane deasphalting unit (PDU), furfural extraction unit (FEU), MEK-toluene dewaxing unit (MDU), and a hydrofinishing unit (HFU). VDU and PDU are running in continuous mode. FEU, MDU, and HFU oper - ate in batch mode for different products. The production of Group I base oils begins with vacuum gasoil (VGO), a heavy product derived from the crude unit. Impurities, ranging from 50-80%, are removed using sol - vents. However, the treated base oil still contains paraffins, which need to be eliminated. This is achieved through a dewaxing process, where solvents cool the oil to low temper - atures, causing the wax to solidify. The key refining steps in Group I base oil production are vacuum distillation to remove metals and heavy asphaltic compounds, separating the oil into different viscosity fractions. Deasphalting eliminates asphaltenes, which can form carbon deposits when the oil is exposed to heat. The deasphalting unit is used when the lube plant produces bright stock. The furfural extraction unit removes aromatic compounds, particularly multi-ring aromatics, to enhance thermal stabil - ity and VI. The MEK-toluene dewaxing unit removes wax to improve cold flow properties such as pour point. The hydrof - inishing unit improves the colour and stability of the final base oil. It is always better to decrease reliance on crude oil quality in

Spindle distillate

Base oil

Distillate

Ranate

WFO

Light distillate

Storage

FEU

MDU

HFU

VDU

(Bright stock Heavy neutral Light neutral Spindle oil)

Heavy distillate

HCU UCO

Bright distillate

Extract

Wax

PDA

Figure 1 Process scheme of lube oil production

PTQ Q2 2025