Method for dewaxing extract oil and rubber oil

Abstract

A method for dewaxing of an extract oil and a rubber oil is provided, where a composite solvent including a polar solvent and a solubilizer is used as a dewaxing solvent, the polar solvent is N-methylpyrrolidone (NMP), and the solubilizer is at least one selected from the group consisting of benzene, toluene, and xylene. The method includes: mixing the composite solvent with the extract oil or the rubber oil at a temperature higher than a precipitation temperature of a wax, subjecting a resulting mixture to cooling crystallization and filtration to obtain a wax paste and a filtrate, and then independently subjecting the wax paste and the filtrate to solvent recovery by heating evaporation to obtain a wax and a dewaxed oil, respectively.

Description

CROSS REFERENCE TO RELATED APPLICATION

[0001] This patent application claims the benefit and priority of Chinese Patent Application No. 202411017523.7 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

[0002] The present disclosure relates to the technical field of petrochemicals, and more specifically to a method for dewaxing of an extract oil and a rubber oil, which has an international patent classification of C10G.BACKGROUND

[0003] 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 resins is a high-viscosity heavy oil. The extract oil could be used as an asphalt blending agent to produce a heavy-duty asphalt and improve the elongation and penetration of the asphalt. In addition, the extract oil is also a raw material for producing a rubber oil. Polycyclic aromatic hydrocarbons (PAHs) could be extracted by re-extracting the extract oil, thereby obtaining a rubber oil (also namely the rubber plasticizer in China) with a low content of the PAHs.

[0004] However, when the lubricants are produced using a normal production process, namely a process of solvent refining and then dewaxing, a resulting extract oil might contain wax. The wax has an adverse effect on the properties of asphalt, and high wax content of asphalt might also deteriorate the low-temperature performance of the asphalt. In addition, when the extract oil containing wax is used as a raw material to produce rubber oil, the rubber oil has a high pour point due to the high wax content. Moreover, the presence of wax could also affect the performance of the rubber. Therefore, it is of great significance to dewax the extract oil and the rubber oil to produce low-pour point and dewaxed extract oil and rubber oil.

[0005] Oil dewaxing is generally conducted by solvent dewaxing, urea dewaxing, hydroisomerization dewaxing, and hydrodewaxing. Since the extract oil contains a large amount of resin 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 generally in dewaxing of lubricants. Solvent dewaxing generally uses a composite solvent as a dewaxing solvent, and the composite solvent is generally a compound 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 and crystallization, and then filtering to separate a wax paste and a filtrate. These processes are generally aimed at a wax oil or a raffinate oil with high wax content and low viscosity as raw materials, and wax crystals generated by cooling are large and easy to be filtered. For an extract oil and a rubber oil produced by re-extraction using the extract oil as a raw material, since there is a large amount of heavy aromatics and resins, the obtained product has high viscosity, dark color, and low wax content, and the wax in the extract oil and rubber oil is mainly isomerized wax with a low condensation point. 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, clogging of pores on a filter cloth, and difficulty in filtering. There is also a large temperature difference in dewaxing, making the dewaxing of the extract oil and the rubber oil a major problem. To solve these problems, the Petrochemical Research Institute of Sinopec has conducted research, using a 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 filter aid (5% addition) and high production cost (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).

[0006] Aiming at the problems existing in the dewaxing of the extract oil and the rubber oil, the present disclosure proposes a novel method, using N-methylpyrrolidone (NMP) as a polar solvent and benzene, toluene, and xylene as a solubilizer. The polar solvent and the solubilizer together form a composite solvent as a dewaxing solvent, which could solve the problem that wax crystals of a conventional dewaxing solvent in the dewaxing of extract oil are small and difficult to be filtered. Detailed contents of the present disclosure are as follows.SUMMARY

[0007] 1. The present disclosure provides a method for dewaxing of an extract oil and a rubber oil, including the following steps:

[0008] (1) mixing a polar solvent and a solubilizer to obtain a composite solvent, and then mixing the composite solvent with the extract oil or the rubber oil to obtain a mixed solution, wherein a temperature for the mixing is slightly higher than a precipitation temperature of a wax in the extract oil, wherein the polar solvent is N-methylpyrrolidone (NMP), and the solubilizer is at least one selected from the group consisting of benzene, toluene, and xylene;

[0009] (2) cooling the mixed solution to a temperature of −20° C. to 10° C. and then holding at the temperature for 5 minutes to 30 minutes;

[0010] (3) filtering an obtained cooled mixed solution to obtain a wax paste and a filtrate;

[0011] (4) subjecting the wax paste to a first solvent recovery by a first heating evaporation to obtain a wax; and

[0012] (5) subjecting the filtrate to a second solvent recovery by a second heating evaporation to obtain a dewaxed oil.

[0013] 2. In the method according to 1, a volume ratio of the polar solvent to the solubilizer is in a range of (30-70):(70-30).

[0014] 3. In the method according to 1, a volume ratio of the composite solvent to the extract oil in in a range of (2-4):1.

[0015] In the present disclosure, the method might be combined with existing dewaxing results of lubricant solvents and a cooling rate could be adjusted to make the wax crystals larger and the filtering effect better.ADVANTAGEOUS EFFECTS OF THE PRESENT DISCLOSURE

[0016] In the present disclosure, the method could solve the problem that wax crystals in a conventional dewaxing solvent during dewaxing of the extract oil are small and difficult to be filtered. In the present disclosure, the wax crystals are large, the oil content is low, and the dewaxing temperature difference is small, such that the pour point of an obtained dewaxed oil is low. 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.DETAILED DESCRIPTION OF THE EMBODIMENTS

[0017] The present disclosure will be described in detail below with reference to specific examples to facilitate further understanding of the present disclosure.EXAMPLE 1

[0018] 100 g of an extract oil with a pour point of 28° C. was added into 300 mL of a composite solvent consisting of NMP and benzene at a volume ratio of 50:50. A resulting mixture was heated to 40° C., stirred evenly, cooled to −16° C. at a cooling rate of 2° C. / min and held at the −16° C. for 10 min. A resulting system was vacuum-filtered with an acid-resistant glass funnel of model G3 at a rate of 37 mL / min for 11 min. A resulting wax paste and a filtrate were subjected to heating evaporation, respectively, resulting solvents were removed, to obtain a wax having a melting point of 45° C. and a dewaxed oil having a pour point of 2° C., respectively. A yield of the wax is 10.25%.COMPARATIVE EXAMPLE 1

[0019] An extract oil and a filter the same as those in Example 1 were used. 100 g of the extract oil was added into 300 mL of a composite solvent consisting of butanone and toluene at a volume ratio of 50:50. A resulting mixture was heated to 40° C., stirred evenly, cooled to −16° C. at a cooling rate of 2° C. / min and held at the −16° C. for 10 min. A resulting system was vacuum-filtered with an acid-resistant glass funnel the same as that in Example 1 (re-washed and dried before use) at a rate of 24 mL / min for 17 min. A resulting wax paste and a filtrate were subjected to heating evaporation respectively, resulting solvents were removed to obtain a wax having a melting point of 42° C. and a dewaxed oil having a pour point of 5° C. A yield of the wax is 15.2%.

[0020] It can be seen from the Example 1 and the Comparative Example 1 that the method according to the present disclosure could increase the dewaxing rate, reduce the oil content in the wax, and improve the dewaxing effect.EXAMPLE 2

[0021] An extract oil and a filter the same as those in Example 1 were used. 100 g of the extract oil was added into 300 mL of a composite solvent consisting of NMP and toluene at a volume ratio of 30:70. A resulting mixture was heated to 40° C., stirred evenly, cooled to −16° C. at a cooling rate of 3° C. / min and held at the −16° C. for 5 min. A resulting system was vacuum-filtered with an acid-resistant glass funnel the same as that in Example 1 (re-washed and dried before use) at a rate of 34 mL / min for 12 min. A resulting wax paste and a filtrate were subjected to heating evaporation respectively, resulting solvents were removed to obtain a wax having a melting point of 45° C. and a dewaxed oil having a pour point of 1° C. A yield of the wax is 11.6%.EXAMPLE 3

[0022] An extract oil and a filter the same as those in Example 1 were used. 100 g of the extract oil was added into 300 mL of a composite solvent consisting of NMP and xylene at a volume ratio of 70:30. A resulting mixture was heated to 40° C., stirred evenly, cooled to −16° C. at a cooling rate of 3° C. / min and held at the −16° C. for 10 min. A resulting system was vacuum-filtered with an acid-resistant glass funnel the same as that in Example 1 (re-washed and dried before use) at a rate of 45 mL / min for 9 min. A resulting wax paste and a filtrate were subjected to heating evaporation respectively, resulting solvents were removed to obtain a wax having a melting point of 45° C. and a dewaxed oil having a pour point of 0° C. A yield of the wax is 12.3%.EXAMPLE 4

[0023] 100 g of a rubber oil having a pour point of 36° C. was added into 300 mL of a composite solvent consisting of NMP, benzene, and toluene at a volume ratio of 40:30:30. A resulting mixture was heated to 50° C., stirred evenly, cooled to −10° C. at 1° C. / min and held at the −10° C. for 20 min. A resulting system was vacuum-filtered with an acid-resistant glass funnel the same as that in Example 1 (re-washed and dried before use) at a rate of 40 mL / min for 10 min. A resulting wax paste and a filtrate were subjected to heating evaporation respectively, resulting solvents were removed to obtain a wax having a melting point of 46° C. and a dewaxed oil having a pour point of 9° C. A yield of the wax was 15.2%.EXAMPLE 5

[0024] 100 g of a rubber oil having a pour point of 36° C. was added into 400 mL of a composite solvent consisting of NMP, benzene, toluene, and xylene at a volume ratio of 50:20:20:10. A resulting mixture was heated to 50° C., stirred evenly, cooled to −10° C. at a cooling rate of 1° C. / min and held at the −10° C. for 30 min. A resulting system was vacuum-filtered with an acid-resistant glass funnel the same as that in Example 1 (re-washed and dried before use) at a rate of 42 mL / min for 12 min. A resulting wax paste and a filtrate were subjected to heating evaporation respectively, resulting solvents were removed to obtain a wax having a melting point of 46° C. and a dewaxed oil having a pour point of 10° C. A yield of the wax was 12.3%.

[0025] Using the rubber oil, a butanone-toluene mixed solvent as a dewaxing solvent, with a same solvent-oil ratio and cooling rate, a filtration time was 17 min, a filtration rate was 29.8 ml / min, and the pour point of the dewaxed oil was 12° C. This indicates that the method according to the present disclosure has a higher filtration rate.

[0026] Certainly, the present disclosure may further include other various embodiments. 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.

Claims

1. A method for dewaxing of an extract oil and a rubber oil, comprising the following steps:(1) mixing a polar solvent and a solubilizer to obtain a composite solvent, and then mixing the composite solvent with the extract oil or the rubber oil to obtain a mixed solution, wherein a temperature for the mixing the composite solvent with the extract oil or the rubber oil is higher than a precipitation temperature of a wax in the extract oil, wherein the polar solvent is N-methylpyrrolidone, and the solubilizer is at least one selected from the group consisting of benzene, toluene, and xylene;(2) cooling the mixed solution to a temperature of −20° C. to 10° C. and then holding at the temperature of −20° C. to 10° C. for 5 minutes to 30 minutes to obtain a cooled mixed solution;(3) filtering the cooled mixed solution to obtain a wax paste and a filtrate;(4) subjecting the wax paste to a first solvent recovery by a first heating evaporation to obtain the wax; and(5) subjecting the filtrate to a second solvent recovery by a second heating evaporation to obtain a dewaxed oil.

2. The method for dewaxing of the extract oil and the rubber oil of claim 1, wherein a volume ratio of the polar solvent to the solubilizer is in a range of 30-70:70-30.

3. The method for dewaxing of the extract oil and the rubber oil of claim 1, wherein a volume ratio of the composite solvent to the extract oil is in a range of 2:1 to 4:1.