METHOD FOR PREPARING LOW-POUR POINT, HIGH-AROMATIC, AND ENVIRONMENTAL-FRIENDLY RUBBER OIL BY COMBINING EXTRACTION AND DEWAXING

Description

CROSS REFERENCE TO RELATED APPLICATION

This patent application claims the benefit and priority of Chinese Patent Application No. 202411017817.X filed with the China National Intellectual Property Administration on Jul. 29, 2024, the disclosure of which is incorporated by reference herein in its entirety as part of the present application.

TECHNICAL FIELD

The present disclosure relates to the technical field of petrochemicals, and more specifically to a method for preparing a low-pour point, high-aromatic, and environmental-friendly rubber oil by combining extraction and dewaxing, which has an international patent classification of C10G.

BACKGROUND

Rubber oil, as a type of oil used in rubber processing and production, includes rubber filler oil and operating oil, and generally adopts mineral oil, or vegetable oil and synthetic oil. Rubber oil that complies with requirements of the Regulation on the registration, evaluation, authorisation and restriction of chemicals (REACH) is called environmental-friendly rubber oil, and is called petroleum-based plasticizer in China. That is, a benzo[a]pyrene (BaP) content in an added oil directly put on the market or used in the manufacture of tires should be less than 1 mg/kg, while a total content of 8 polycyclic aromatic hydrocarbons (PAHs, including benzo[a]pyrene (BaP), benzo[e]pyrene (BeP), benzo[a]anthracene (BaA), benzo[k]fluoranthene (BkFA), benzo[b]fluoranthene (BbFA), chrysene (CHR), benzo[j]fluoranthene (BjFA), dibenzo[a,h]anthracene (DBahA) should be less than 10 mg/kg. High-aromatic and environmental-friendly rubber oil refers to environmental-friendly rubber oil containing more aromatic components, and generally has a higher aromatic carbon rate (C_A) and excellent compatibility with rubber, and processed rubber products using the high-aromatic and environmental-friendly rubber oil do not produce oil (sweating) and show desirable stability.

The high-aromatic and environmental-friendly rubber oil generally adopts extract oil as a raw material. The extract oil is a heavy oil with high aromatic content produced as a byproduct of the lubricant production. In the traditional production of lubricants, furfural, phenol, and N-methylpyrrolidone (NMP) are used as extraction solvents to extract a wax oil to obtain the extract oil and a raffinate oil. The raffinate oil could be used as a base oil for the lubricants after dewaxing, while the extract oil containing a large amount of heavy aromatics and colloids is a high-viscosity heavy oil.

However, when the lubricants are produced using a normal production process, namely a process of solvent refining and then dewaxing, the extract oil produced might contain wax. When the extract oil containing wax is used as a raw material to produce rubber plasticizers, the rubber plasticizers have a high pour point due to the high wax content. Rubber processing companies need to heat the rubber before use, and the presence of wax could also affect the performance of the rubber. Therefore, it is of great significance to produce a low-wax content, low-pour point, and high-aromatic rubber oil.

To produce a low-pour point rubber oil, the extract oil could be dewaxed or the rubber oil could be dewaxed. Oil dewaxing is generally conducted by solvent dewaxing, urea dewaxing, hydroisomerization dewaxing, and hydrodewaxing. Since the extract oil contains a large amount of colloid and heavy aromatics, it is not suitable to use the urea dewaxing, hydroisomerization dewaxing, and hydrodecondensation. The solvent dewaxing is a commonly used traditional dewaxing process, and is generally used in dewaxing of lubricants. Solvent dewaxing generally uses a composite solvent as a dewaxing solvent. The composite solvent generally consists of acetone, butanone, and methyl isobutyl ketone (MIBK) with toluene and benzene. Currently, the commonly used composite solvents are butanone-toluene and acetone-benzene. The MIBK could be used alone as a dewaxing solvent. The composite solvent is mixed with an oil to be dewaxed, and subjected to cooling to crystallize, and then filtering to separate a wax paste and a filtrate. In these processes, wax oil or raffinate oil with high wax content and low viscosity are generally used as raw materials, and wax crystals generated by cooling are large and easy to be filtered. For the extract oil and the rubber oil produced from the extract oil, since there is a large amount of heavy aromatics and colloids, the obtained products have high viscosity, dark color, and low wax content, and wax in the extract oil is mainly isomerized wax. As a result, when using a composite solvent composed of acetone, butanone, and MIBK with toluene and benzene as a dewaxing solvent, there are problems such as fine wax crystals, easy clogging of pores on a filter cloth, and difficulty in filtering. There is also a large temperature difference in dewaxing, making the dewaxing of extract oil and rubber oil a major problem. To solve this problem, the Petrochemical Research Institute of Sinopec has conducted research, using the traditional toluene-butanone composite solvent as a dewaxing solvent, and the dewaxing solvent is mixed with the extract oil and a resulting mixture was subjected to cooling. During the dewaxing, a dewaxing aid is added as a filter aid to solve the difficulty in filtration. However, this process has disadvantages of large amount of the filter aid (5% addition) and high production costs (Guan Cuishi et al., Production of environmentally friendly rubber extender oil from high pour point aromatic-rich feeds, Petroleum Processing and Petrochemicals, 2013, 44 (8): 33-36). The dewaxing of rubber oil also encounters the same difficulties as the dewaxing of the extract oil.

Whether it is dewaxing the extract oil or the rubber oil, the oil needs to be dewaxed by solvent, which virtually increases the equipment investment and a lot of energy consumption, and the newly constructed equipment also occupies a lot of land resources. Therefore, removing the wax from rubber oil during the production could lower production cost, reduce investment, and save land resources.

The research team has proposed a novel patent (ZL 201710703433.7) for a process of producing rubber oil by extracting wax-containing extract oil as a raw material, which can produce high-aromatic rubber filler oil. The present disclosure proposes a novel method, which is further improved on the basis of the above patent, where a dewaxing step is added in the method to solve the problem that the traditional dewaxing solvent has small wax crystals and is difficult to be filtered in the dewaxing of the rubber oil. Accordingly, a low-pour point, high-aromatic, and environmental-friendly rubber oil could be prepared through the novel method. Detailed contents of the present disclosure are as follows.

SUMMARY

1. The present disclosure provides a method for preparing a low-pour point, high-aromatic, and environmental-friendly rubber oil by combining extraction and dewaxing, including the following steps:

• • (1) conducting the extraction in an extraction tower, where a primary extraction solvent is introduced into an upper section of the extraction tower, a raw oil is introduced into a middle-lower section of the extraction tower, and a secondary extraction solvent is introduced into a lower section of the extraction tower, wherein the primary extraction solvent is N-methylpyrrolidone (NMP), the raw oil is an extract oil, and the secondary extraction solvent is a C7-C12 alkane;
  • (2) subjecting a material at a bottom of the extraction tower (also known as an extract) to solvent recovery to obtain a secondary extract oil;
  • (3) mixing a substance flowing out from a top of the extraction tower (also known as a raffinate), a solubilizer and a part of the primary extraction solvent sent by a pump in a static mixer, subjecting a resulting mixture to cooling to a temperature of −15° C. to 10° C. in a cooler, and then filtering in a filter to obtain a wax paste and a filtrate, wherein the solubilizer is at least one selected from the group consisting of benzene, toluene, and xylene;
  • (4) subjecting the wax paste to a second solvent recovery by a first heating evaporation to obtain a wax; and
  • (5) subjecting the filtrate to a third solvent recovery by a second heating evaporation to obtain a dewaxed oil, namely the low-pour point, environmental-friendly rubber oil.

2. In the method for preparing the low-pour point, environmental-friendly rubber oil by combining extraction and dewaxing according to 1, a mass ratio of the primary extraction solvent introducing into the upper section of the extraction tower to the raw oil is in a range of 2:1 to 3.5:1.

3. In the method for preparing the low-pour point, environmental-friendly rubber oil by combining extraction and dewaxing according to 1, the lower section of the extraction tower is at a temperature of 40° C. to 60° C., and the upper section of the extraction tower is at a temperature of 60° C. to 80° C.

4. In the method for preparing the low-pour point, environmental-friendly rubber oil by combining extraction and dewaxing according to 1, a volume ratio of the part of the primary extraction solvent to the solubilizer mixed with the substance flowing out from the top of the extraction tower is in a range of (40-50):(60-50).

5. In the method for preparing the low-pour point, environmental-friendly rubber oil by combining extraction and dewaxing according to 1, a volume ratio of the solubilizer to the raw oil is in a range of 1:1 to 3:1.

Beneficial Effects of the Present Disclosure

In the present disclosure, the method could produce high-aromatic and environmental-friendly rubber oil while solving the problems that wax crystals in a conventional dewaxing solvent during dewaxing of the extract oil and rubber oil are small and difficult to be filtered. The method according to the present disclosure has the advantages of large wax crystals, low oil content, and small dewaxing temperature difference, thus a resulting rubber oil has a low pour point. Compared with traditional solvent dewaxing, the filtration rate is increased by 30% to 50% and the dewaxing temperature difference is reduced by 5° C. to 10° C. Another advantage of the method according to the present disclosure is that the raffinate could be dewaxed with the original solvent without conducting solvent recovery, which could reduce investment and save energy. Compared with a process of distilling the raffinate to recover the solvent to obtain a raffinate oil, and then using the raffinate oil to conduct solvent dewaxing by using a traditional toluene-butanone mixed solvent, the energy consumption is reduced by not less than 20%.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGURE shows a schematic diagram for a production process of the method according to the present disclosure, where numeral references are listed below: 1 refers to a solubilizer tank, 2 refers to a primary extraction solvent tank, 3 refers to a raw oil tank, 4 refers to a secondary solvent tank, 5, 6, 7, 8 refer to pumps, 9 refers to an extraction tower, 10, 11, 12, 14 refer to heat exchangers, 13 refers to a mixer and 15 refers to a filter.

As shown in the FIGURE, the primary extraction solvent enters from an upper section of the extraction tower through the pump 6, the raw oil enters from a middle section of the extraction tower through the pump 7, and the secondary solvent enters from a lower section of the extraction tower through the pump 8. An extract flowing out from a bottom of the extraction tower is subjected to solvent recovery to obtain a secondary extract oil, and a raffinate flowing out from a top of the extraction tower and the solubilizer (from the pump 5) and a part of the primary extraction solvent enter the heat exchanger 14 through the mixer 13 to conduct cooling, and then enter the filter 15 to conduct filtration to obtain a wax paste and a filtrate. The wax paste is subjected to solvent recovery to obtain a wax, and the filtrate is subjected to solvent recovery to obtain a low-pour point, high-aromatic, and environmental-friendly rubber oil. An extraction section between an upper feed port (primary extraction solvent inlet) and a middle feed port (raw oil inlet) of the extraction tower is called a first extraction section, an extraction section between the raw oil inlet and a lower feed port (secondary solvent inlet) of the extraction tower is called a second extraction section.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The present disclosure will be described in detail below with reference to specific examples to further illustrate the present disclosure.

Example 1

A small extraction tower in the laboratory was used, and a process was shown in the figure. The extraction tower has an inner diameter of 33 mm and is filled with a wire mesh filler. A first extraction section has a height of 2 m, and a second extraction section has a height of 1 m. A primary extraction solvent was NMP and a secondary solvent was heptane. A fourth vacuum side stream extract oil produced by an oil refinery of China was used as a raw oil, and the extract oil had a pour point of 38° C. A weight ratio of the NMP, raw oil and heptane was 2.5:1:0.5. A temperature of the second extraction section from bottom to top was 50° C. to 55° C., a temperature of the first extraction section from bottom to top was 55° C. to 70° C., a raffinate was obtained at a top of the tower, and an extract was obtained at a bottom of the tower. Benzene and NMP were added to the raffinate, where the benzene was added at 100% (volume) of a raw oil flow, and the NMP was added at 100% of the benzene. A resulting mixture was mixed in a mixer, and then entered into a heat exchanger and cooled to −15° C. A cooled mixture was filtered through a filter to obtain a wax paste and a filtrate. The wax paste was subjected to solvent recovery to obtain a wax, with a yield of 12% of the raw oil. The filtrate was subjected to solvent recovery to obtain an environmental-friendly rubber oil, with a yield of 55%, a PCA content of 2.9%, a benzo[a]pyrene content of 0.2 μg/g, and a total content of eight carcinogens of 2.1 μg/g. The contents of eight carcinogen monomers are all less than 1 μg/g, the aromatic carbon rate C_A is 25.0%, and the pour point is 4° C., thus meeting requirements of the low-pour point, high-aromatic, and environmental-friendly rubber oil. The study found that wax crystals had large particles and their filtration was relatively smooth without clogging the filter.

Example 2

A small extraction tower in the laboratory was used, and a process was shown in the figure. The extraction tower has an inner diameter of 33 mm and is filled with a wire mesh filler. A first extraction section has a height of 2 m, and a second extraction section has a height of 1 m. A primary extraction solvent was NMP and a secondary solvent was a C6-C10 mixed alkane. A fourth vacuum side stream extract oil produced by an oil refinery of China was used as a raw oil, and the extract oil had a pour point of 38° C. A weight ratio of the NMP, raw oil, and the secondary solvent was 2.5:1:0.3. A temperature of the second extraction section from bottom to top was 40° C. to 55° C., a temperature of the first extraction section from bottom to top was 55° C. to 80° C., a raffinate was obtained at a top of the tower, and an extract was obtained at a bottom of the tower. Toluene and NMP were added to the raffinate, where the toluene was added at 300% of a raw oil flow, and the NMP was added at 200% of the raw oil flow. A resulting mixture was mixed in a mixer, and then entered into a heat exchanger and cooled to −10° C. A cooled mixture was filtered through a filter to obtain a wax paste and a filtrate. The wax paste was subjected to solvent recovery to obtain a wax, with a yield of 10% of the raw oil. The filtrate was subjected to solvent recovery to obtain an environmental-friendly rubber oil, with a yield of 56%, a PCA content of 2.4%, a benzo[a]pyrene content of 0.2 μg/g, and a total content of eight carcinogens of 2.1 μg/g. The contents of eight carcinogen monomers are all less than 1 μg/g, the aromatic carbon rate C_A is 25.0%, and the pour point is 8° C., thus meeting requirements of the low-pour point, high-aromatic, and environmental-friendly rubber oil. The study found that wax crystals had large particles and their filtration was relatively smooth without clogging the filter.

Example 3

A small extraction tower in the laboratory was used, and a process was shown in the figure. The extraction tower has an inner diameter of 33 mm and is filled with a wire mesh filler. A first extraction section has a height of 2 m, and a second extraction section has a height of 1 m. A primary extraction solvent was NMP and a secondary solvent was heptane. A fourth vacuum side stream extract oil produced by an oil refinery of China was used as a raw oil, and the extract oil had a pour point of 38° C. A weight ratio of the NMP, the raw oil, and the heptane was 2.0:1:0.4. A temperature of the second extraction section from bottom to top was 50° C. to 55° C., a temperature of the first extraction section was from bottom to top 55° C. to 70° C., a raffinate was obtained at a top of the tower, and an extract was obtained at a bottom of the tower. Xylene and NMP were added in the raffinate, where the xylene was added at 150% of a raw oil flow, and the NMP was added at 150% of the raw oil flow. A resulting mixture was mixed in a mixer, and then entered into a heat exchanger and cooled to 10° C. A cooled mixture was filtered through a filter to obtain a wax paste and a filtrate. The wax paste was subjected to solvent recovery to obtain a wax, with a yield of 6% of the raw oil. The filtrate was subjected to solvent recovery to obtain an environmental-friendly rubber oil, with a yield of 58%, a PCA content of 2.4%, a benzo[a]pyrene content of 0.2 μg/g, and a total content of eight carcinogens of 2.1 μg/g. The contents of eight carcinogen monomers are all less than 1 μg/g, the aromatic carbon rate C_A is 25.0%, and the pour point is 18° C., thus meeting requirements of the low-pour point, high-aromatic, and environmental-friendly rubber oil. The study found that wax crystals had large particles and their filtration was relatively smooth without clogging the filter.

Example 4

A small extraction tower in the laboratory was used, and a process was shown in the figure. The extraction tower has an inner diameter of 33 mm and is filled with a wire mesh filler. A first extraction section has a height of 2 m, and a second extraction section has a height of 1 m. A primary extraction solvent was NMP and a secondary solvent was petroleum ether. A fourth vacuum side stream extract oil produced by an oil refinery of China was used as a raw oil, and the extract oil had a pour point of 38° C. A weight ratio of the NMP, the raw oil and the petroleum ether was 2.0:1:0.4 (by weight). A temperature of the second extraction section from bottom to top was 50° C. to 55° C., a temperature of the first extraction section from bottom to top was 55° C. to 70° C., a raffinate was obtained at a top of the tower, and an extract was obtained at a bottom of the tower. solubilizer and NMP were added to the raffinate, where the solubilizer was a mixture of benzene and toluene and added at 150% of a raw oil flow, and the NMP was added at 150% of the raw oil flow. A resulting mixture was mixed in a mixer, and then entered a heat exchanger and cooled to 10° C. A cooled mixture was filtered through a filter to obtain a wax paste and a filtrate. The wax paste was subjected to solvent recovery to obtain a wax, with a yield of 6% of the raw oil. The filtrate was subjected to solvent recovery to obtain an environmental-friendly rubber oil, with a yield of 58%, a PCA content of 2.4%, a benzo[a]pyrene content of 0.2 μg/g, and a total content of eight carcinogens of 2.1 μg/g. The contents of eight carcinogen monomers are all less than 1 μg/g, the aromatic carbon rate C_A is 25.0%, and the pour point is 18° C., thus meeting requirements of the low-pour point, high-aromatic, and environmental-friendly rubber oil. The study found that wax crystals had large particles and their filtration was relatively smooth without clogging the filter.

Example 5

A small extraction tower in the laboratory was used, and a process was shown in the figure. The extraction tower has an inner diameter of 33 mm and is filled with a wire mesh filler. A first extraction section has a height of 2 m, and a second extraction section has a height of 1 m. A primary extraction solvent was NMP and a secondary solvent was a C12 alkane. A fourth vacuum side stream extract oil produced by an oil refinery of China was used as a raw oil, and the extract oil had a pour point of 38° C. A weight ratio of the NMP, the raw oil and C12 was 2.0:1:0.4. A temperature of the second extraction section from bottom to top was 60° C. to 70° C., a temperature of the first extraction section from bottom to top was at 70° C. to 80° C., a raffinate was obtained at a top of the tower, and an extract was obtained at a bottom of the tower. solubilizer and NMP were added to the raffinate, where the solubilizer was a mixture of benzene, toluene, and xylene in a ratio of 1:1:1 and added at 200% of a raw oil flow, and the NMP was added at 150% of the raw oil flow. A resulting mixture was mixed in a mixer, and then entered into a heat exchanger and cooled to 0° C. A cooled mixture was filtered through a filter to obtain a wax paste and a filtrate. The wax paste was subjected to solvent recovery to obtain a wax, with a yield of 10% of the raw oil. The filtrate was subjected to solvent recovery to obtain an environmental-friendly rubber oil, with a yield of 56%, a PCA content of 2.8%, a benzo[a]pyrene content of 0.3 μg/g, and a total content of eight carcinogens of 4.2 μg/g. The contents of eight carcinogen monomers are all less than 1 μg/g, the aromatic carbon rate C_A is 24.5%, and the pour point is 10° C., thus meeting requirements of the low-pour point, high-aromatic, and environmental-friendly rubber oil. The study found that wax crystals had large particles and their filtration was relatively smooth without clogging the filter.

It can be seen from the above examples that the method of the present disclosure could be used to prepare the low-pour point, highly-aromatic, and environmental-friendly rubber oil. Certainly, the present disclosure may further include other various examples. A person skilled in the art could make various corresponding modifications and variations according to the present disclosure without departing from the spirit and essence of the present disclosure, but all these corresponding modifications and variations shall fall within the scope defined by the appended claims in the present disclosure.