The production process of lubricating oil
Traditional production processes
In the 1930s, the production of lubricating oil base oil was mainly carried out using physical methods, namely the "old three sets" traditional process consisting of solvent refining, solvent dewaxing, and clay supplementary refining to produce lubricating oil base oil.
(1) Solvent refining. Solvent refining is an important step in the production process of lubricating oil, which mainly removes polycyclic aromatic hydrocarbons, resins, asphaltenes, etc. from the oil, improving the viscosity temperature properties, antioxidant stability, residual carbon value, color and other properties of lubricating oil. This process is relatively mature, and commonly used solvents include furfural, phenol, and N-methylpyrrolidone (NMP).
(2) Solvent dewaxing. The solvent dewaxing process mainly includes four parts: crystallization, filtration, solvent recovery, and freezing. Its purpose is to remove paraffin from the oil and reduce the pour point of lubricating oil base oil. This process has technical advantages in processing lighter raw materials, with high yield of dewaxed oil and high viscosity index. In order to reduce energy consumption, save operating costs, and reduce investment, domestic and foreign lubricant base oil production enterprises have adopted a combined process of solvent dewaxing and wax deoiling. In recent years, there have been significant improvements in technology such as energy conservation and improving oil and wax yields.
(3) White clay is refined and supplemented. Baitu supplementary refining is the process of fully mixing oil and Baitu at a certain temperature, utilizing the adsorption performance of the active Baitu surface, and removing nitrides, resins, asphaltenes, naphthenic acid soaps, unsaturated hydrocarbons, selective solvents, water, mechanical impurities, etc. from lubricating oil through heating, evaporation, filtration and other processes. This improves the color of the oil, reduces residual carbon, and enhances the antioxidant stability and anti emulsification degree of the oil. [1]
Hydrogenation production process
The ideal components in base oil are branched alkanes (isomers) and monocyclic alkanes with long alkyl side chains, while the non ideal components are polycyclic aromatic hydrocarbons and polycyclic alkanes. The traditional solvent refining process selectively extracts and removes low viscosity index polycyclic hydrocarbons and other heterocyclic compounds (such as sulfur, nitrogen compounds, resins, etc.), thereby improving the viscosity index of the oil and improving its color and antioxidant stability. This physical separation method can only retain the original ideal components in the raw material, and the improvement of base oil yield, viscosity index, and other properties is limited. Lubricating oil hydrogenation treatment is a method of deep hydrogenation conversion, which transforms polycyclic hydrocarbons into ideal components and almost completely removes heterocyclic compounds, resulting in high base oil yield and more significant improvement in various quality indicators of the oil.
The chemical reactions that occur during the hydrogenation process mainly include: ① removal of heterocyclic compounds; ② Aromatic saturation, ring opening and isomerization of cycloalkanes are the main reactions that increase viscosity index; ③ Normal alkanes or low branched isomeric alkanes undergo hydroisomerization to high branched isomeric alkanes; ④ Hydrocracking of alkanes and hydrogenation dealkylation reactions of alkanes with long alkyl side chains. This type of reaction will lead to the production of light oil, resulting in a decrease in the yield of base oil. The first three are favorable reactions, and the fourth is the reactions that need to be suppressed.
Heterogeneous dewaxing process
With the increasingly strict environmental protection regulations and the development of the mechanical industry (especially the automotive industry), higher requirements have been put forward for the performance of lubricating oil. In order to produce these high-performance lubricating oils, especially when preparing large-span multi-stage internal combustion engine oils, it is necessary to use base oils with low volatility and high viscosity index, i.e. VI greater than 120 and saturation greater than 90%. The API III base oil, which is mainly composed of isomeric alkanes, has these performance characteristics and can meet the above requirements. The use of solvent dewaxing and catalytic dewaxing processes cannot produce Class III base oils, as these two processing methods can only remove high viscosity index n-alkanes from the oil, resulting in low viscosity index of the base oil. These high viscosity index n-alkanes cannot be converted into high viscosity index, low pour point isomeric alkanes, which not only results in low base oil yield but also cannot meet the specifications of high-quality base oils. The basic principle of isomerization dewaxing is to isomerize high pour point n-alkanes into low pour point branched alkanes under the action of specialized molecular sieve catalysts. Isomerization dewaxing has become an important means of producing API III base oils in contemporary times. The industrialized lubricant isomerization dewaxing technology mainly includes Isodewaxing technology from Chevron and MSDW technology from Exxon Mobil.
In the 1930s, the production of lubricating oil base oil was mainly carried out using physical methods, namely the "old three sets" traditional process consisting of solvent refining, solvent dewaxing, and clay supplementary refining to produce lubricating oil base oil.
(1) Solvent refining. Solvent refining is an important step in the production process of lubricating oil, which mainly removes polycyclic aromatic hydrocarbons, resins, asphaltenes, etc. from the oil, improving the viscosity temperature properties, antioxidant stability, residual carbon value, color and other properties of lubricating oil. This process is relatively mature, and commonly used solvents include furfural, phenol, and N-methylpyrrolidone (NMP).
(2) Solvent dewaxing. The solvent dewaxing process mainly includes four parts: crystallization, filtration, solvent recovery, and freezing. Its purpose is to remove paraffin from the oil and reduce the pour point of lubricating oil base oil. This process has technical advantages in processing lighter raw materials, with high yield of dewaxed oil and high viscosity index. In order to reduce energy consumption, save operating costs, and reduce investment, domestic and foreign lubricant base oil production enterprises have adopted a combined process of solvent dewaxing and wax deoiling. In recent years, there have been significant improvements in technology such as energy conservation and improving oil and wax yields.
(3) White clay is refined and supplemented. Baitu supplementary refining is the process of fully mixing oil and Baitu at a certain temperature, utilizing the adsorption performance of the active Baitu surface, and removing nitrides, resins, asphaltenes, naphthenic acid soaps, unsaturated hydrocarbons, selective solvents, water, mechanical impurities, etc. from lubricating oil through heating, evaporation, filtration and other processes. This improves the color of the oil, reduces residual carbon, and enhances the antioxidant stability and anti emulsification degree of the oil. [1]
Hydrogenation production process
The ideal components in base oil are branched alkanes (isomers) and monocyclic alkanes with long alkyl side chains, while the non ideal components are polycyclic aromatic hydrocarbons and polycyclic alkanes. The traditional solvent refining process selectively extracts and removes low viscosity index polycyclic hydrocarbons and other heterocyclic compounds (such as sulfur, nitrogen compounds, resins, etc.), thereby improving the viscosity index of the oil and improving its color and antioxidant stability. This physical separation method can only retain the original ideal components in the raw material, and the improvement of base oil yield, viscosity index, and other properties is limited. Lubricating oil hydrogenation treatment is a method of deep hydrogenation conversion, which transforms polycyclic hydrocarbons into ideal components and almost completely removes heterocyclic compounds, resulting in high base oil yield and more significant improvement in various quality indicators of the oil.
The chemical reactions that occur during the hydrogenation process mainly include: ① removal of heterocyclic compounds; ② Aromatic saturation, ring opening and isomerization of cycloalkanes are the main reactions that increase viscosity index; ③ Normal alkanes or low branched isomeric alkanes undergo hydroisomerization to high branched isomeric alkanes; ④ Hydrocracking of alkanes and hydrogenation dealkylation reactions of alkanes with long alkyl side chains. This type of reaction will lead to the production of light oil, resulting in a decrease in the yield of base oil. The first three are favorable reactions, and the fourth is the reactions that need to be suppressed.
Heterogeneous dewaxing process
With the increasingly strict environmental protection regulations and the development of the mechanical industry (especially the automotive industry), higher requirements have been put forward for the performance of lubricating oil. In order to produce these high-performance lubricating oils, especially when preparing large-span multi-stage internal combustion engine oils, it is necessary to use base oils with low volatility and high viscosity index, i.e. VI greater than 120 and saturation greater than 90%. The API III base oil, which is mainly composed of isomeric alkanes, has these performance characteristics and can meet the above requirements. The use of solvent dewaxing and catalytic dewaxing processes cannot produce Class III base oils, as these two processing methods can only remove high viscosity index n-alkanes from the oil, resulting in low viscosity index of the base oil. These high viscosity index n-alkanes cannot be converted into high viscosity index, low pour point isomeric alkanes, which not only results in low base oil yield but also cannot meet the specifications of high-quality base oils. The basic principle of isomerization dewaxing is to isomerize high pour point n-alkanes into low pour point branched alkanes under the action of specialized molecular sieve catalysts. Isomerization dewaxing has become an important means of producing API III base oils in contemporary times. The industrialized lubricant isomerization dewaxing technology mainly includes Isodewaxing technology from Chevron and MSDW technology from Exxon Mobil.