CN109692572B - Method for recovering dewaxing solvent for light lubricating oil raw oil and method for dewaxing light lubricating oil raw oil - Google Patents
Method for recovering dewaxing solvent for light lubricating oil raw oil and method for dewaxing light lubricating oil raw oil Download PDFInfo
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- CN109692572B CN109692572B CN201711001285.0A CN201711001285A CN109692572B CN 109692572 B CN109692572 B CN 109692572B CN 201711001285 A CN201711001285 A CN 201711001285A CN 109692572 B CN109692572 B CN 109692572B
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
- B01D61/02—Reverse osmosis; Hyperfiltration ; Nanofiltration
- B01D61/027—Nanofiltration
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
- B01D71/06—Organic material
- B01D71/58—Other polymers having nitrogen in the main chain, with or without oxygen or carbon only
- B01D71/62—Polycondensates having nitrogen-containing heterocyclic rings in the main chain
- B01D71/64—Polyimides; Polyamide-imides; Polyester-imides; Polyamide acids or similar polyimide precursors
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- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10M—LUBRICATING COMPOSITIONS; USE OF CHEMICAL SUBSTANCES EITHER ALONE OR AS LUBRICATING INGREDIENTS IN A LUBRICATING COMPOSITION
- C10M177/00—Special methods of preparation of lubricating compositions; Chemical modification by after-treatment of components or of the whole of a lubricating composition, not covered by other classes
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2311/00—Details relating to membrane separation process operations and control
- B01D2311/14—Pressure control
Abstract
The invention relates to the technical field of a lubricating oil raw oil dewaxing process, and discloses a method for recovering a light lubricating oil raw oil dewaxing solvent and a method for dewaxing the light lubricating oil raw oil. The recovery method comprises the step of contacting a solution containing the light dewaxing lubricating oil raw oil and an organic solvent with a nanofiltration membrane, wherein the nanofiltration membrane is a nanofiltration membrane prepared from P84 polyimide, the interception molecular weight of the nanofiltration membrane is 200-300Da, the contact pressure is 1-6MPa, and the light dewaxing lubricating oil raw oil is crude oil fraction with the boiling range of 280-500 ℃. The permeate obtained by the recovery method of the dewaxing solvent provided by the invention has higher average content of the organic solvent, better effect of recovering the dewaxing solvent at normal temperature and simple process steps; and the average flux of the nanofiltration membrane used in the method is higher, so that the energy consumption of the method is lower, and the material consumption in the method is reduced.
Description
Technical Field
The invention relates to the technical field of lubricating oil dewaxing processes, in particular to a method for recovering a dewaxing solvent of light lubricating oil raw oil and a method for dewaxing the light lubricating oil raw oil.
Background
The lubricating oil is a product which has the widest application field in petrochemical products and is closest to consumers, is an important material related to the national civilization and national safety, and is called as 'blood' of modern industry. Meanwhile, the lubricating oil is a product with high technical content and high benefit. From the analysis of the general oil refining industry, the efficiency of producing lubricating oil is obviously higher than that of fuel oil. In the production process of lubricating oil, because the petroleum fraction contains long-chain normal paraffin, namely, wax, when the temperature is reduced, the wax can wrap the surrounding lubricating oil components to be separated out to form a network structure, and the fluidity of the lubricating oil is influenced. Dewaxing is therefore an essential step in the production of lubricating oils.
There are generally two methods for dewaxing lubricating oils in commercial processes, solvent dewaxing and hydrodewaxing. Solvent dewaxing is the first method used in the production of lubricating oils and is now the most widely used method. More than half of the dewaxing processes currently available on the market for lubricating oils employ solvent dewaxing. The development of a combined solvent dewaxing and hydrogenation process has further extended the life of solvent dewaxing.
However, solvent dewaxing has its own drawbacks, such as the need for a large amount of phase change heat in solvent recovery to complete solvent recovery, which consumes energy and increases VOC emission, thus creating great environmental pressure. With the increasing concern on health and safety, the pressure of energy and environmental protection brought by the recovery of a large amount of solvents enters the sight of people, and a new method capable of reducing energy consumption and environmental pollution is urgently needed in industry to solve the problem of solvent recovery.
The membrane separation method for recovering dewaxing solvent has been developed, and in 1998 Mobil oil company has built a first membrane separation method for recovering acetone-benzene solvent in Bomantel oil refinery, which is named MAX-DEWAX. In Max-Dewax dewaxing method of Mobil corporation, a spiral wound polyimide film is attached to the front of a distillation apparatus to separate 25-40% of a cold solvent, and this method can reduce the distillation load, and can reduce the cooling load by circulating the obtained cold solution to the downstream side of a chiller. However, in the Max-Dewax dewaxing method, the interception rate and the average flux of the membrane (Matrimid5218) used in the operation process are low, about 40 percent of solvent is only recovered under the condition of the operation pressure of 4.1MPa, and the average flux is only 12.9L/(m m.sup.m.sup.2H), the retention rate is 96%; moreover, the method has poor effect of recovering the solvent at normal temperature; in addition, the method has low operation temperature, so that the membrane must be cleaned regularly, and the process is complex; in addition, the methodIn operation, a large amount of high-quality electric energy needs to be provided, and the energy consumption is high.
Disclosure of Invention
The invention aims to provide a method for recovering a dewaxing solvent of light lubricating oil raw oil and a method for dewaxing the light lubricating oil raw oil, aiming at overcoming the problems of higher energy consumption and material consumption in the process of recovering an organic solvent by rectifying by using a ketone-benzene dewaxing device in the prior art. The average content of the organic solvent in the permeate obtained by the method for recovering the dewaxing solvent of the light lubricating oil raw oil is higher, the effect of recovering the dewaxing solvent at normal temperature (particularly 10-30 ℃) is better, and the process steps are simple; and the average flux of the nanofiltration membrane used in the method is higher, so that the energy consumption of the method is lower, and in addition, the material consumption in the method is reduced.
In order to achieve the above object, the first aspect of the present invention provides a method for recovering a dewaxing solvent of light lubricating oil raw oil, which comprises contacting a solution containing light dewaxed lubricating oil raw oil and an organic solvent with a nanofiltration membrane, wherein the nanofiltration membrane is a nanofiltration membrane prepared from P84 polyimide, the cut-off molecular weight of the nanofiltration membrane is 200-300Da, the contacting pressure is 1-6MPa, and the light lubricating oil raw oil is a crude oil fraction with a boiling range of 280-500 ℃.
According to a second aspect of the present invention, there is also provided a process for dewaxing a light lubricant base stock, the process comprising: mixing light lubricating oil raw oil with an organic solvent, cooling, crystallizing and filtering the obtained mixture to obtain a filtrate containing the light lubricating oil raw oil and the organic solvent, wherein the light lubricating oil raw oil is a crude oil fraction with a boiling range of 280-500 ℃, and the method comprises the step of recovering the organic solvent from the filtrate by adopting the recovery method.
The method filters the solution containing the dewaxed lubricating oil raw oil and the organic solvent by adopting a specific nanofiltration membrane (the nanofiltration membrane prepared from P84 polyimide), the average flux of the organic solvent of the nanofiltration membrane is higher, and the average content of the organic solvent in the permeation solution penetrating through the nanofiltration membrane is higher. The nanofiltration membrane is adopted to recover the organic solvent at normal temperature (particularly at 10-30 ℃), the recovery effect is good, and 65-75% of the organic solvent in the filtrate can be recovered; the average flux of the nanofiltration membrane is higher, so that the energy consumption of the recovery method is lower; furthermore, the material consumption in the process is reduced.
In addition, the recovery method of the light lubricating oil raw oil dewaxing solvent provided by the invention is simple to operate, does not need to clean the nanofiltration membrane periodically, and is beneficial to industrial production.
Detailed Description
The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value, and such ranges or values should be understood to encompass values close to those ranges or values. For ranges of values, between the endpoints of each of the ranges and the individual points, and between the individual points may be combined with each other to give one or more new ranges of values, and these ranges of values should be considered as specifically disclosed herein.
According to the first aspect of the invention, the method for recovering the dewaxing solvent of the lubricating oil raw oil comprises the step of contacting a solution containing the light dewaxing lubricating oil raw oil and the organic solvent with a nanofiltration membrane, wherein the nanofiltration membrane is a nanofiltration membrane prepared from P84 polyimide, the cut-off molecular weight of the nanofiltration membrane is 200-300Da, the contact pressure is 1-6MPa, and the light lubricating oil raw oil is crude oil fraction with the boiling range of 280-500 ℃.
In the present invention, the lubricating oil refers to a finished oil composed of a base oil and additives.
In the present invention, light lubricant base stock refers to stock used for producing light lubricant base oil.
In the invention, the molecular weight cut-off of the nanofiltration membrane refers to the molecular weight of the corresponding organic matter when the cut-off rate of the solute is 90% under a dilute solute system of a toluene solvent at 25 ℃ and 0.5 MPa.
According to the method of the present invention, in order to facilitate the recovery of the organic solvent, the average content of the organic solvent in the permeate is preferably made higherThe average flux of the organic solvent of the nanofiltration membrane is 50-80L/(m)2H), more preferably 60 to 76L/(m)2·h)。
According to the method of the present invention, the average content of the organic solvent in the permeate liquid may be generally 98% by weight or more based on the total amount of the permeate liquid obtained by permeating through the nanofiltration membrane.
In the present invention, the flux of the organic solvent in the nanofiltration membrane refers to the volume of the permeate per membrane area that permeates through the membrane in a unit time under a certain pressure and temperature. The average flux of the organic solvent of the nanofiltration membrane refers to the average flux of the permeate of the nanofiltration membrane over the entire variation of the solution containing the dewaxed lubricant oil and the organic solvent from the initial concentration of the solution before permeation to the final concentration of the solution obtained after permeation through the nanofiltration membrane at a certain pressure and temperature.
In the present invention, the content of the organic solvent in the permeate obtained through the nanofiltration membrane is based on the total weight of the permeate obtained through the nanofiltration membrane. The average content of the organic solvent in the permeate refers to the average concentration of the solution containing the light dewaxed lubricant oil feedstock and the organic solvent from the content of the organic solvent in the permeate obtained by starting to permeate the nanofiltration membrane to the content of the organic solvent in the permeate obtained by finally permeating the nanofiltration membrane.
According to the method, the nanofiltration membrane can be a symmetric or asymmetric nanofiltration membrane prepared from P84 polyimide by various methods in the field, and can also be a commercial P84 polyimide nanofiltration membrane. For example, a nanofiltration membrane made of P84 polyimide formed by random copolymerization of a compound represented by formula (1) and a compound represented by formula (2). Specific membrane preparation methods can be referred to the method disclosed in example 7 in CN 101678286A.
Among them, the weight ratio of the compound represented by the formula (1) to the compound represented by the formula (2) may be (70:30) to (90:10), more preferably (75:25) to (85:15), and still more preferably 80: 20.
According to the treatment method, the assembly mode of the nanofiltration membrane can be used in various conventional modes, and the nanofiltration membrane is preferably used in the forms of a hollow fiber type membrane module, a roll type membrane module, a tubular type membrane module and a plate type membrane module, and is further preferably used in the forms of a roll type module and/or a plate type module.
According to the method of the present invention, the nanofiltration membranes are arranged in such a manner that the organic solvent can be recovered from the solution containing the light dewaxed lubricant oil feedstock and the organic solvent, and generally, the nanofiltration membranes may be arranged in the form of a single set of nanofiltration membrane modules or in parallel of two or more sets of nanofiltration membrane modules.
According to the method of the present invention, in order to increase the average flux of the organic solvent of the nanofiltration membrane and the average content of the organic solvent in the permeate, and to improve the recovery effect of the organic solvent, the contact pressure is preferably 2 to 5MPa, and more preferably 2.5 to 4 MPa.
According to the method of the present invention, the temperature at which the nanofiltration membrane is contacted with the solution is set to a temperature at which the organic solvent can be recovered from the solution containing the light dewaxed lubricant oil feedstock and the organic solvent, and generally, the temperature at which the nanofiltration membrane is contacted may be from-10 to 50 ℃, preferably from 0 to 40 ℃, and more preferably from 10 to 30 ℃.
According to the method, the solution can be contacted with the nanofiltration membrane at the temperature of-10 to 50 ℃, or the solution is firstly in the temperature range of-10 to 50 ℃ and then contacted with the nanofiltration membrane, and preferably, the solution is firstly in the temperature range of-10 to 50 ℃ and then contacted with the nanofiltration membrane.
According to the method disclosed by the invention, the time for contacting the solution with the nanofiltration membrane can be reasonably selected according to the content of the organic solvent in the permeate obtained by permeating the nanofiltration membrane, and is not described again.
According to the method of the present invention, the content of the light dewaxed lubricant oil feedstock is such that the organic solvent can be recovered from the solution by using a nanofiltration membrane, and generally, the content of the light dewaxed lubricant oil feedstock may be 15 to 25 wt%, preferably 20 to 25 wt%, based on the total amount of the solution.
According to the method of the invention, the light lubricating oil raw oil is a crude oil fraction with a boiling range of 280-500 ℃, and in order to enable the average flux of the organic solvent of the nanofiltration membrane and the average content of the organic solvent in the permeate to be higher, the light lubricating oil raw oil is preferably at least one of a normal four line, a reduced line and a reduced line obtained by crude oil distillation, and is further preferably a reduced line.
In the present invention, the normal four lines, the minus two lines and the minus three lines refer to crude oil fractions obtained by distilling crude oil.
According to the method of the present invention, the organic solvent may be any of various organic solvents capable of dewaxing a lube-oil feedstock, and generally, the organic solvent may be a mixture of an aromatic hydrocarbon and a monoketone having 3 to 8 carbon atoms. Preferably, the aromatic hydrocarbon is monoalkyl benzene and/or benzene, and in order to better recover the dewaxing organic solvent of the lubricating oil, it is further preferable that the monoketone is one or more of methyl ethyl ketone, acetone, 2-butanone, 2-pentanone, 3-pentanone and 2-hexanone; the alkyl in the monoalkylbenzene is C1-C4 alkyl, and more preferably the monoalkylbenzene is one or more of toluene, ethylbenzene and propylbenzene. Most preferably, the organic solvent is a mixture of methyl ethyl ketone and toluene.
According to the method of the present invention, the ratio of the amount of the monoketone to the amount of the aromatic hydrocarbon may be selected appropriately according to the ratio of the dewaxed organic solvent used in the prior art, and in general, the weight ratio of the monoketone to the aromatic hydrocarbon may be (50:50) to (75:25), and in order to obtain a better recovery effect of the dewaxed organic solvent, the weight ratio of the monoketone to the aromatic hydrocarbon is preferably (60:40) to (70: 30).
According to a second aspect of the present invention, there is provided a method for dewaxing a light lubricant oil feedstock, the method comprising: mixing light lubricating oil raw oil with an organic solvent, cooling, crystallizing and filtering the obtained mixture to obtain a filtrate containing the light dewaxed lubricating oil raw oil and the organic solvent, wherein the light lubricating oil raw oil is a crude oil fraction with a boiling range of 280-500 ℃, and the method comprises the step of recovering the organic solvent from the filtrate by adopting the recovery method.
In the present invention, the light lubricating oil raw oil is the same as described above and will not be described herein.
According to the method of the present invention, the ratio of the amount of the light lubricant oil to the organic solvent used is such that dewaxing of the light lubricant oil can be achieved, and the weight ratio of the light lubricant oil to the organic solvent may be generally (16:84) to (24:48), and preferably (19:82) to (22:55) in order to improve the recovery effect of the organic solvent.
According to the method of the present invention, the organic solvent may be any of various organic solvents capable of dewaxing light lube base oil, and the specific selection of the organic solvent is consistent with the above description, and will not be described herein again.
According to the method of the present invention, the mixing of the light lube-oil feedstock and the organic solvent is carried out under conditions that the lube-oil feedstock can be dissolved, and generally, the mixing may be carried out at 20 to 40 ℃ and the duration of the mixing may be 1 to 120 min. In order to obtain a better dissolution effect, the mixing may preferably be carried out at 25-40 ℃ and the duration of the mixing may be 30-120 min.
According to the method of the present invention, the crystallization temperature is such that paraffin can be precipitated from the light lubricating oil feedstock, and generally, the crystallization temperature may be from-40 ℃ to-15 ℃, preferably from-25 ℃ to-15 ℃.
According to the process of the present invention, the time of crystallization can be chosen appropriately according to the crystallization temperature, and in general, the duration of crystallization can be from 1 to 120 min. Further preferably, the crystallization is performed with stirring.
The present invention will be described in detail below by way of examples.
(1) The three-line-reduced fraction, the normal four-line fraction and the two-line-reduced fraction of the light lubricating oil raw oil with the crude oil boiling range of 280-plus 500 ℃ are from China petrochemical cyclopentadienyl petrochemical company;
(2) the retention rate of the nanofiltration membrane was tested according to the analysis method of residue in petroleum products specified in GB/T498-1987. The residue analysis method used a balance of a ten-thousandth gram high-precision electronic balance. Calculating according to the measured rejection rate of the nanofiltration membrane
a. The formula of the content of the organic solvent in the permeate obtained by permeating the nanofiltration membrane is specifically as follows:
b. the method for measuring the average content of the organic solvent in the permeate liquid comprises the following steps:
(3) the flux test method of the organic solvent of the nanofiltration membrane comprises the following steps: the permeate side was sampled for 2min with a graduated cylinder, the sample volume read and multiplied by 30 to obtain the result divided by the membrane area.
Average flux of organic solvent of nanofiltration membrane (L/(m)2H)) - (total volume of permeate) ÷ permeation time (h) ÷ membrane area (m)2)
(4) The membrane separation device used in the invention is a membrane separation lab-scale device. The device comprises a high-pressure resistant mother liquor tank, can resist 69bar pressure, has a volume of 600mL, and is provided with stirring. Two sets of membrane separation modules, which can bear 69bar pressure, and the membrane separation device also comprises: a power pump, a pressure control panel and five pipelines.
During the experiment, the used membrane is cut into a round shape with the size similar to that of the gasket in the membrane separation assembly, and the round shape is placed into the membrane separation assembly to combine the experiment device. The filtrate outlet is connected with a glass horn bottle with scales, two outlets of the horn bottle are connected with latex tubes, one section of the latex tube is sealed by hemostatic forceps, the other end of the latex tube is connected with the filtrate outlet, and in order to balance the pressure in the horn bottle, a small gap is reserved between the latex tubes connected with the filtrate outlet and can be communicated with the air.
(5) The nanofiltration membrane used in the invention is subjected to membrane washing operation before use. The specific method comprises the following steps: in order to wash away the protective layer on the membrane surface and to adapt the membrane to the separation system, the membrane is washed before its first use. The solvent used for washing the membrane is a mixed solvent of toluene and methyl ethyl ketone, and the mass ratio of the methyl ethyl ketone to the toluene is 50: 50-80: and 20, selecting according to the specific mixture ratio of the used mixed solvent, and sampling from a 10mL small barrel from a filtrate port for 2 minutes every half hour until the values of three continuous sampling are the same, namely finishing membrane washing. When the liquid in the mother liquor tank is less than 200mL, the filtrate is poured back to the mother liquor tank.
Example 1
(1) Stirring and mixing 150g of reduced fraction with crude oil boiling range of 358-500 ℃ with 400g of a ketobenzene organic solvent at 30 ℃, wherein the mixing duration is 0.5h, cooling the obtained mixture to-25 ℃ for crystallization, filtering after 1h to obtain a filtrate containing the light dewaxed lubricant raw oil and the ketobenzene organic solvent, and the ketobenzene organic solvent used for dewaxing is a mixture formed by mixing methyl ethyl ketone and toluene, wherein the weight ratio of methyl ethyl ketone to toluene is 60: 40;
(2) adding 500mL of ketobenzene solvent formed by mixing methyl ethyl ketone and toluene into a mother liquor tank of a membrane separation device, wherein the mass ratio of the methyl ethyl ketone to the toluene is 60:40, and adding a sheared organic solvent-resistant nanofiltration membrane (an asymmetric organic solvent-resistant nanofiltration membrane purchased from Shanghai Special chemistry (Shanghai) Co., Ltd.), wherein the cut-off molecular weight is 200Da, and the membrane area is 0.0014m2) Putting the membrane into a membrane separation module, connecting a membrane separation device, starting a power pump, filling high-purity nitrogen into a mother liquor tank, keeping the pressure at 30bar, and washing the membrane. Emptying the solvent of the system after the membrane washing is finished, and adding the filtrate containing the light dewaxing lubricating oil raw oil and the ketone-benzene organic solvent obtained in the step (1) into a mother liquor tank500mL, based on the total amount of the solution, the content of the light dewaxed lubricant raw oil in the solution is 25 wt%, the mass fraction ratio of methyl ethyl ketone/toluene in the solvent is 60:40, the system pressure is kept at 4MPa, the temperature of the mother liquor tank is controlled to be 30 ℃ by water bath, a concentration experiment (membrane separation experiment) is started after the system continuously runs for 4h, and the sampling results are shown in Table 1.
From the experimental results in table 1, it can be found that 69.8% of the organic solvent was recovered, the average content of the organic solvent in the permeate obtained through the nanofiltration membrane reached 99.7%, and the average flux of the nanofiltration membrane during the solvent recovery process was 60L/(m)2·h)。
TABLE 1
Example 2
(1) Stirring and mixing 170g of reduced fraction with crude oil boiling range of 358-500 ℃ with 500g of a ketobenzene organic solvent at 32 ℃, wherein the mixing duration is 1h, cooling the obtained mixture to-20 ℃ for crystallization, and filtering after 2h to obtain a filtrate containing the light dewaxed lubricant raw oil and the ketobenzene organic solvent, wherein the ketobenzene organic solvent used for dewaxing is a mixture formed by mixing methyl ethyl ketone and toluene, and the weight ratio of methyl ethyl ketone to toluene is 70: 30;
(2) the concentrated solution in example 1 was evacuated, 500mL of the filtrate containing the light dewaxed lubricant oil raw oil and the organic solvent of ketone benzene obtained in step (1) was added to the mother liquor tank, based on the total amount of the solution, the content of the light dewaxed lubricant oil raw oil in the solution was 23 wt%, the mass fraction ratio of methyl ethyl ketone/toluene in the solvent was 70:30, the system pressure was maintained at 3.5MPa, the temperature of the mother liquor tank was controlled in a water bath at 25 ℃, and a concentration experiment (membrane separation experiment) was started after the system was continuously operated for 4 hours, and the sampling results are shown in table 2. The nanofiltration membrane used in this example was the same as the nanofiltration membrane used in example 1.
From the experimental results in Table 2, it was found that 69.3% of the recovered organic solvent was equivalent to the organic solvent in the permeate obtained by permeating the nanofiltration membraneThe average content of the solvent reaches 99.7 percent, and the average flux of the nanofiltration membrane in the solvent recovery process is 64L/(m)2·h)。
TABLE 2
Example 3
(1) Stirring and mixing 150g of reduced fraction with crude oil boiling range of 358-500 ℃ with 450g of a ketobenzene organic solvent at 35 ℃, wherein the mixing duration is 1h, cooling the obtained mixture to-15 ℃ for crystallization, and filtering after 2h to obtain a filtrate containing the light dewaxed lubricant raw oil and the ketobenzene organic solvent, wherein the ketobenzene organic solvent used for dewaxing is a mixture formed by mixing methyl ethyl ketone and toluene, and the weight ratio of methyl ethyl ketone to toluene is 60: 40;
(2) 500mL of a ketobenzene solvent formed by mixing methyl ethyl ketone and toluene is added into a mother liquor tank of a membrane separation device, wherein the weight ratio of the methyl ethyl ketone to the toluene is 60:40, and a sheared organic solvent-resistant nanofiltration membrane (the organic solvent-resistant nanofiltration membrane is a P84 polyimide membrane which is prepared according to the method disclosed in embodiment 7 of CN101678286A and has asymmetric molecular weight cutoff of 250Da, and the membrane area is 0.0014m2) Putting the membrane into a membrane separation module, connecting a membrane separation device, starting a power pump, filling high-purity nitrogen into a mother liquor tank, keeping the pressure at 30bar, and washing the membrane. And (3) emptying the solvent of the system after the membrane washing is finished, adding 500mL of filtrate containing the light dewaxed lubricant oil raw oil and the organic solvent of the ketobenzene obtained in the step (1) into a mother liquor tank, wherein the total amount of the solution is taken as a reference, the content of the light dewaxed lubricant oil raw oil in the solution is 22 wt%, the mass fraction ratio of methyl ethyl ketone/toluene in the solvent is 60:40, the system pressure is kept at 3MPa, the temperature of the mother liquor tank is controlled to be 30 ℃ by water bath, and the concentration experiment is started after the system continuously runs for 4 hours, wherein the sampling result is shown in Table 3.
From the experimental results in Table 3, it was found that 72% of the organic solvent was recovered, the average content of the organic solvent in the permeate obtained through the nanofiltration membrane reached 99.1%, and the nanofiltration membrane was used during the solvent recovery processThe average flux was 72L/(m)2·h)。
TABLE 3
Example 4
(1) Stirring and mixing 110g of a normal four-line fraction with a boiling range of 280-378 ℃ of crude oil and 370g of a ketone benzene organic solvent at 40 ℃, wherein the mixing duration is 0.5h, cooling the obtained mixture to-20 ℃ for crystallization, filtering after 1.5h to obtain a filtrate containing the light dewaxed lubricant raw oil and the ketone benzene organic solvent, and the ketone benzene organic solvent used for dewaxing is a mixture formed by mixing methyl ethyl ketone and toluene, wherein the weight ratio of the methyl ethyl ketone to the toluene is 70: 30;
(2) the concentrated solution in example 3 was evacuated, 500mL of the filtrate containing the light dewaxed lubricant oil raw oil and the organic solvent of ketone benzene obtained in step (1) was added to the mother liquor tank, and based on the total amount of the solution, the content of the light dewaxed lubricant oil raw oil in the solution was 20 wt%, the mass fraction ratio of methyl ethyl ketone/toluene in the solvent was 70:30, the system pressure was maintained at 2.7MPa, the temperature of the mother liquor tank was controlled in a water bath at 30 ℃, and a concentration experiment (membrane separation experiment) was started after the system was continuously operated for 4 hours, and the sampling results are shown in table 4. The nanofiltration membrane used in this example was the same as the nanofiltration membrane used in example 3.
From the experimental results in table 4, it can be found that the average content of the organic solvent in the permeate obtained by permeating the nanofiltration membrane is 98.25% corresponding to 72% recovery of the ketone-benzene organic solvent, and the average flux of the nanofiltration membrane during the solvent recovery process is 75L/(m)2·h)。
TABLE 4
Example 5
(1) Stirring and mixing 140g of reduced linear fraction with a crude oil boiling range of 310-450 ℃ and 450g of a ketobenzene organic solvent at 25 ℃, wherein the mixing duration is 2h, cooling the obtained mixture to-25 ℃, crystallizing, filtering after 1h to obtain a filtrate containing the light dewaxed lubricant raw oil and the ketobenzene organic solvent, and the ketobenzene organic solvent used for dewaxing is a mixture formed by mixing methyl ethyl ketone and toluene, wherein the weight ratio of methyl ethyl ketone to toluene is 63: 37;
(2) adding 500mL of ketobenzene solvent formed by mixing methyl ethyl ketone and toluene into a mother liquor tank of a membrane separation device, wherein the weight ratio of the methyl ethyl ketone to the toluene is 63:37, and adding a sheared organic solvent-resistant nanofiltration membrane (an asymmetric organic solvent-resistant nanofiltration membrane purchased from Shanghai Special chemistry (Shanghai) Co., Ltd.), wherein the cut-off molecular weight is 280Da, and the area of the membrane is 0.0014m2) Putting the membrane into a membrane separation module, connecting a membrane separation device, starting a power pump, filling high-purity nitrogen into a mother liquor tank, keeping the pressure at 30bar, and washing the membrane. And (3) emptying the solvent of the system after the membrane washing is finished, adding 500mL of filtrate containing the light dewaxed lubricant oil raw oil and the organic solvent of the ketobenzene obtained in the step (1) into a mother liquor tank, wherein the total amount of the solution is taken as a reference, the content of the light dewaxed lubricant oil raw oil in the solution is 21 wt%, the mass fraction ratio of methyl ethyl ketone/toluene in the solvent is 63:37, the system pressure is kept at 4MPa, the temperature of the mother liquor tank is controlled to be 10 ℃ by water bath, a concentration experiment (membrane separation experiment) is started after the system continuously runs for 4h, and the sampling result is shown in Table 5.
From the experimental results in Table 5, it can be found that 71.4% of the organic solvent was recovered, the average content of the organic solvent in the permeate obtained through the nanofiltration membrane reached 98.3%, and the average flux of the nanofiltration membrane during the solvent recovery process was 75L/(m)2·h)。
TABLE 5
From the results, the average content of the organic solvent in the permeate obtained by the recovery method is higher, the average flux of the nanofiltration membrane prepared from the P84 polyimide is higher, the effect of recovering the dewaxing solvent at normal temperature (particularly, at 10-30 ℃) is better, and the process steps are simple.
The preferred embodiments of the present invention have been described above in detail, but the present invention is not limited thereto. Within the scope of the technical idea of the invention, many simple modifications can be made to the technical solution of the invention, including combinations of various technical features in any other suitable way, and these simple modifications and combinations should also be regarded as the disclosure of the invention, and all fall within the scope of the invention.
Claims (7)
1. A method for dewaxing light lubricating oil raw oil, which comprises the following steps: mixing light lubricating oil raw oil with an organic solvent, cooling, crystallizing and filtering the obtained mixture to obtain a filtrate containing the light dewaxed lubricating oil raw oil and the organic solvent, wherein the light lubricating oil raw oil is a crude oil fraction with a boiling range of 280-500 ℃, and the method is characterized by comprising the steps of recovering the organic solvent from the filtrate,
the method for recovering the organic solvent comprises the following steps: contacting a filtrate containing light dewaxing lubricating oil raw oil and an organic solvent with a nanofiltration membrane, wherein the cut-off molecular weight of the nanofiltration membrane is 200-300Da, the contact pressure is 1-6MPa, the light lubricating oil raw oil is a crude oil fraction with a boiling range of 280-500 ℃, the organic solvent is a mixture formed by methyl ethyl ketone and toluene, the weight ratio of the methyl ethyl ketone to the toluene is (60:40) - (70:30), and the average flux of the organic solvent of the nanofiltration membrane is 50-80L/(m: 30)2H) an average content of the organic solvent in the permeate is 98% by weight or more based on the total amount of the permeate obtained by permeating the nanofiltration membrane, wherein the nanofiltration membrane is made of a P84 polyimide obtained by randomly copolymerizing a compound represented by the formula (1) with a compound represented by the formula (2),
the light lubricating oil raw oil is a three-way oil,
the content of the light dewaxing lubricating oil raw oil is 15-25 wt% based on the total amount of the filtrate,
the contact temperature is 10-30 ℃, and the contact pressure is 2.5-4 MPa.
2. The method of claim 1, wherein the nanofiltration membrane has an average flux of organic solvent of 60-76L/(m)2·h)。
3. The method of claim 1, wherein the nanofiltration membrane is used in the form of at least one of a hollow fiber membrane module, a spiral wound membrane module, a tubular membrane module, and a plate membrane module.
4. The process according to claim 1, wherein the nanofiltration membranes are used in the form of roll-to-roll and/or plate modules.
5. The method according to claim 1, wherein the weight ratio of the light lubricant oil feedstock to the organic solvent is (16:84) - (24: 48).
6. The method of claim 1, wherein the mixing is performed at 20-40 ℃ and the duration of the mixing is 1-120 min.
7. The process according to claim 1, wherein the temperature of the crystallization is from-40 ℃ to-15 ℃ and the duration of the crystallization is from 1 to 120 min.
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| WO1997012013A1 (en) * | 1995-09-28 | 1997-04-03 | Mobil Oil Corporation | Dynamic selectivation membrane separation process |
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| WO2000006526A1 (en) * | 1998-07-30 | 2000-02-10 | Mobil Oil Corporation | Recovery of aromatic hydrocarbons using lubricating oil conditioned membranes |
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