PTQ Q2 2023 Issue

Vacuum distillation

Aromatic extraction

Solvent dewaxing

Finishing

Ranate oil

Dewaxed oil

Atmospheric residue

Vacuum distillates

Base lubricant

Vacuum residue

Waxes

Wax to consumers

De - oiled wax

Deasphalted oil

Propane deasphalting

Wax de - oiling

Wax nishing

Asphalt

Figure 2 Processing scheme for base lubricating oil production through solvent route

As aforementioned in the vacuum distillation step, the fractionating quality obtained between cuts is critical for these streams to reach quality requirements like flash point and viscosity. After the vacuum distillation step, the side cuts are pumped to the aromatic extraction unit, and the vacuum residue is sent to the propane deasphalting unit. The propane deasphalting process seeks to remove heavier fractions from vacuum residue, which can be applied as lubricating oil. The propane deasphalting units dedicated to producing lubricating oils apply pure propane as solvent because this solvent has higher selectivity to remove resins and asphaltenes from deasphalted oil. In the aromatic extraction step, the process streams are put in contact with solvents selective to remove aromat- ics compounds, mainly polyaromatics. The main objective in removing these compounds is that they have a low vis- cosity index and low chemical stability, which is strongly undesired in lubricating oils. Understanding that nitrogen and sulphur compounds are normally present in polyaro- matic structures, this step removes a significant portion of the sulphur and nitrogen content. The solvents normally applied in the aromatics extraction process are phenol, fur- fural, and N-methyl pyrrolidone. The subsequent step is to remove the linear paraffin with high molecular weight through solvent extraction. This step is important because these compounds prejudice the lubricating oils flow at low temperatures. A typical solvent

employed in the solvent dewaxing units is methyl-isobutyl- ketone (MIK), but some process plants apply toluene and/or methylethylketone (MEK) for this purpose. After paraffin removal, the lubricating oil is sent to the finishing process. In this step, heteroatom compounds are removed, including oxygen, sulphur, and nitrogen. These compounds can give colour and chemical instability to the lube oil. Furthermore, some remaining polyaromatic mol- ecules are also removed. Some process plants with low investment and processing capacity apply a clay treatment in this step. However, modern plants with higher process- ing capacity use mild hydrotreating units. This is espe- cially important when the petroleum processed has higher contaminants content. In this case, the clay bed saturates very quickly. The paraffin removed from lubricating oils is treated to remove the excess oil in the unit (wax de-oiling unit). In this step, the process stream is treated at reduced temperatures to remove the low branched paraffin, which has a low melt - ing point. Similar to lubricating oils, the subsequent step is a finishing process to remove heteroatoms (N,S,O) and to sat - urate polyaromatic compounds. A hydrotreating process is generally applied in the paraffin case with sufficient severity to saturate the aromatic compounds to reach food-grade quality in the final product. Changes in the lubricants market As previously cited, the solvent route can produce only Group I lubricant oils. However, lube oils employed in severe work conditions (large temperature variations) need higher saturated compounds content and higher viscosity index. In this case, it is necessary to apply the hydrorefining route. A significant limitation in lubricant production via the solvent route is the necessity of paraffinic crude oils that tend to present higher costs and reduce the operational flexibility of refiners, especially when related to the crude oil supply in a geopolitical crisis scenario. Despite the relevant strategic questions like crude oil prices and supply, Group I lubricating oils tend to lose mar- ket share quickly due to poor performance in comparison with the remaining groups, especially considering automo- tive industry technological developments and lubricants specifications. This fact is one of the most relevant capital investments, driving forces towards improving refining hardware capacity to produce high-quality lubricating oils through the hydrore- fining route. Another relevant factor that negatively impacts

125%

0% 8% 7% 16%

2 %

100%

5% 10% 8%

5% 10% 12%

75%

22%

25%

31%

50%

54%

25%

44%

39%

2015

2020

2030

Para ff inic G roup I Naphthenic

Para ff inic G roup II Synthetic

Para ff inic G roup III Other

Figure 3 Base oils market distribution Credit: STATISTA, 2023

PTQ Q2 2023