CN109694744B - Method for recovering dewaxing solvent for lube-oil feedstock and method for dewaxing lube-oil feedstock - Google Patents
Method for recovering dewaxing solvent for lube-oil feedstock and method for dewaxing lube-oil feedstock Download PDFInfo
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- CN109694744B CN109694744B CN201711000233.1A CN201711000233A CN109694744B CN 109694744 B CN109694744 B CN 109694744B CN 201711000233 A CN201711000233 A CN 201711000233A CN 109694744 B CN109694744 B CN 109694744B
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- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
- C10G73/00—Recovery or refining of mineral waxes, e.g. montan wax
- C10G73/02—Recovery of petroleum waxes from hydrocarbon oils; Dewaxing of hydrocarbon oils
- C10G73/06—Recovery of petroleum waxes from hydrocarbon oils; Dewaxing of hydrocarbon oils with the use of solvents
- C10G73/08—Organic compounds
- C10G73/22—Mixtures or organic compounds
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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
Abstract
The invention relates to the field of dewaxing of lubricating oil raw oil, and discloses a method for recovering a dewaxing solvent of lubricating oil raw oil and a method for dewaxing the lubricating oil raw oil. The recovery method comprises the step of contacting a solution containing raw dewaxed lubricating oil and an organic solvent with a composite nanofiltration membrane, wherein the composite nanofiltration membrane comprises a support membrane and a separation membrane layer, the molecular weight cut-off of the composite nanofiltration membrane is 400-550Da, the contact pressure is 2-6MPa, the support membrane is polyacrylonitrile, and the separation membrane layer is prepared by curing the side chain modified polysiloxane acrylate shown in the formula I. The permeate obtained by the recovery method of the invention has higher average content of organic solvent, the composite nanofiltration membrane has stable average flux, is less influenced by the temperature of the solution in the recovery solution system, and is easy to realize continuous and stable production.
Description
Technical Field
The invention relates to the technical field of a lubricating oil raw oil dewaxing process, in particular to a method for recovering a lubricating oil raw oil dewaxing solvent and a method for dewaxing a 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.2·h) 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 method also needs to provide a large amount of high-quality electric energy in operation, and the energy consumption is high.
Disclosure of Invention
The invention aims to provide a method for recovering a dewaxing solvent of lubricating oil raw oil and a method for dewaxing the 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 method for recovering the dewaxing solvent of the raw oil of lubricating oil has the advantages that the average content of the organic solvent in the permeate liquid obtained by the method is higher, the coverage range of the operating temperature is wide, the average flux of the nanofiltration membrane used by the method in the recovery process is stable, the influence of the temperature of the solution in a solution recovery system is small, and the method has a good effect on temperature fluctuation balance in production; in addition, the process steps are simple.
In order to achieve the above object, the first aspect of the present invention provides a method for recovering a dewaxing solvent of lubricating oil feedstock, the method comprising contacting a solution containing dewaxed lubricating oil feedstock and an organic solvent with a composite nanofiltration membrane, wherein the composite nanofiltration membrane comprises a support membrane and a separation membrane layer, the molecular weight cut-off of the composite nanofiltration membrane is 400-550Da, the contact pressure is 2-6MPa, the support layer is polyacrylonitrile, the separation membrane layer is prepared by curing side chain modified polysiloxane acrylate shown in formula I,
in the formula (I), a is 25-500, b is 1-25, and c is 0-20;
R1is an alkyl or aryl group having from 1 to 30 carbon atoms, which is independent of each other, identical or different, optionally having at least one of an ether functional group, an ester functional group, an epoxy functional group and an alcohol functional group; r2Are, independently of one another, identical or different:R1、R3and R4；R3Are each, independently of one another, identical or different organic radicals having one or more acrylate groups, R4Are the same or different polyether groups.
According to a second aspect of the present invention, there is also provided a process for dewaxing a lubricant basestock, the process comprising: mixing raw oil of lubricating oil with an organic solvent, cooling, crystallizing and filtering the obtained mixture to obtain a filtrate containing the dewaxed raw oil of lubricating oil and the organic solvent, wherein the method comprises recovering the organic solvent from the filtrate by adopting the method.
The method adopts the specific composite nanofiltration membrane to filter the solution containing the raw dewaxed lubricating oil and the organic solvent, so that the average content of the organic solvent in the permeate liquid penetrating through the composite nanofiltration membrane is higher. 40-50% of organic solvent can be recovered by adopting the composite nanofiltration membrane; in the whole solvent recovery process, the average flux of the composite nanofiltration membrane is stable, the influence of the solution temperature in a solution recovery system is small, the method has a good effect of balancing temperature fluctuation in production, and continuous and stable production is favorably realized.
In addition, the recovery method provided by the invention is simple to operate, does not need to clean the composite nanofiltration membrane regularly, 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 invention provides a method for recovering a dewaxing solvent of lubricating oil raw oil, which comprises the step of contacting a solution containing the dewaxing lubricating oil raw oil and an organic solvent with a composite nanofiltration membrane, wherein the composite nanofiltration membrane comprises a support membrane and a separation membrane layer, the molecular weight cut-off of the composite nanofiltration membrane is 400-550Da, the contact pressure is 2-6MPa, the support membrane is polyacrylonitrile, the separation membrane layer is prepared by solidifying side chain modified polysiloxane acrylate shown in formula I,
in the formula (I), a is 25-500, b is 1-25, and c is 0-20;
R1is an alkyl or aryl group having from 1 to 30 carbon atoms, which is independent of each other, identical or different, optionally having at least one of an ether functional group, an ester functional group, an epoxy functional group and an alcohol functional group; r2Are, independently of one another, identical or different: r1、R3And R4；R3Are each, independently of one another, identical or different organic radicals having one or more acrylate groups, R4Are the same or different polyether groups.
In the present invention, in the formula (I), a, b, c, R1、R2、R3And R4Is defined in relation to a, b, c, R in CN102665879A1、R2、R3And R4The definitions are the same.
According to the method, the composite nanofiltration membrane can be a commercial composite nanofiltration membrane or a composite nanofiltration membrane prepared by a common method, so long as the composite nanofiltration membrane comprises the support membrane and the separation membrane layer. For example, specific methods for preparing films can refer to the methods for preparing films disclosed in the specification of CN102665879A (see paragraphs [ 0090 ] of CN 102665879A); the nanofiltration composite membrane can also be a commercially available product, such as a composite nanofiltration membrane with the trade mark of select B or select A, which is purchased from the winning specialty Chemicals company.
In the present invention, the lubricating oil refers to a finished oil composed of a base oil and additives.
In the present invention, the lubricant base stock refers to a stock used for producing a lubricant base oil.
In the present invention, a dewaxed lubricant base stock refers to a dewaxed lubricant base stock formed by subjecting a lubricant base stock to a solvent dewaxing process.
In the invention, the molecular weight cut-off of the composite nanofiltration membrane refers to the molecular weight of organic matters corresponding to the condition that the cut-off rate of a solute under a dilute solute system of a toluene solvent reaches 90% at 25 ℃ and 0.5 MPa.
According to the method provided by the invention, in order to facilitate the recovery of the organic solvent and enable the average content of the organic solvent in the permeate to be higher, the average flux of the organic solvent of the nanofiltration membrane is preferably 20-40L/(m)2H), more preferably 26 to 38L/(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 composite nanofiltration membrane.
In the present invention, the flux of the organic solvent in the composite nanofiltration membrane refers to the volume of the permeate per membrane area that permeates the composite nanofiltration membrane per unit time under a certain pressure and temperature. The average flux of the organic solvent of the nanofiltration membrane is the average value of the flux of the permeate of the composite nanofiltration membrane during the whole process of the change of the solution containing the dewaxed lubricant oil raw 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 composite nanofiltration membrane under a certain pressure and temperature.
In the present invention, the content of the organic solvent in the permeate obtained by permeating the composite nanofiltration membrane is based on the total weight of the permeate obtained by permeating the composite nanofiltration membrane. The average content of the organic solvent in the permeate refers to the average concentration of the solution containing the dewaxed lubricant base oil and the organic solvent from the content of the organic solvent in the permeate obtained by starting to permeate through the composite nanofiltration membrane to the content of the organic solvent in the permeate obtained by finally permeating through the composite nanofiltration membrane.
According to the treatment method, the composite nanofiltration membrane can be assembled in various conventional manners, and preferably, the composite nanofiltration membrane is used in the forms of hollow fiber type membrane modules, spiral wound type membrane modules, tubular type membrane modules and plate type membrane modules, and further preferably in the forms of spiral wound type modules and/or plate type modules.
According to the method of the present invention, the arrangement of the composite nanofiltration membranes is based on the purpose of recovering the organic solvent from the solution containing the dewaxed lubricant oil feedstock and the organic solvent, and generally, the arrangement may be in the form of a single-group nanofiltration membrane module or in the form of two or more groups of composite nanofiltration membrane modules arranged in parallel.
According to the method of the invention, in order to stabilize the average flux of the organic solvent of the composite nanofiltration membrane and to increase 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 2.5 to 5.5MPa, and more preferably 3 to 5 MPa.
According to the method of the present invention, the temperature of the contact between the composite nanofiltration membrane and the solution is controlled to achieve the purpose of recovering the organic solvent from the solution containing the dewaxed lubricant base oil and the organic solvent, and generally, the contact temperature may be-20 ℃ to 50 ℃, preferably-15 ℃ to 40 ℃, and more preferably-10 ℃ to 40 ℃.
According to the method, the solution can be contacted with the composite nanofiltration membrane at the temperature of between 20 ℃ below zero and 50 ℃, or the solution is firstly in the temperature range of between 20 ℃ below zero and 50 ℃ and then contacted with the composite nanofiltration membrane, and preferably, the solution is firstly in the temperature range of between 20 ℃ below zero and 50 ℃ and then contacted with the composite nanofiltration membrane.
According to the method disclosed by the invention, the time for contacting the solution with the composite nanofiltration membrane can be reasonably selected according to the content of the organic solvent in the permeate obtained by permeating the composite nanofiltration membrane, and is not described herein again.
According to the method of the present invention, the content of the dewaxed lubricant base oil is such that the organic solvent can be recovered from the solution by using the composite nanofiltration membrane, and generally, the content of the dewaxed lubricant base oil may be 15 to 25 wt%, preferably 18 to 24 wt%, based on the total amount of the solution.
According to the process of the present invention, the lubricant base stock is a crude oil fraction used for producing a lubricant base stock, preferably at least one of a normally four-line fraction, a reduced two-line fraction, a reduced three-line fraction, a reduced four-line fraction and a deasphalted lubricant base stock obtained by crude oil distillation, and more preferably at least one of a reduced three-line fraction, a reduced four-line fraction and a deasphalted lubricant base stock.
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 process for dewaxing a lubricating oil feedstock, the process comprising: mixing raw oil of lubricating oil with an organic solvent, cooling, crystallizing and filtering the obtained mixture to obtain a filtrate containing the dewaxed raw oil of lubricating oil and the organic solvent, wherein the method comprises recovering the organic solvent from the filtrate by adopting the recovery method.
According to the method of the present invention, the lube oil feedstock is identical to that described above and will not be described herein.
According to the method of the present invention, the amount ratio of the dewaxed lubricant base oil to the organic solvent is such that the lubricant base oil can be dewaxed, and the weight ratio of the dewaxed lubricant base oil to the organic solvent may be generally (15:85) to (25:50), and preferably (16:84) to (24:60) 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 a lubricating 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 lube-oil feedstock with 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 heavy lubricant base oil, and generally, the crystallization temperature may be from-30 ℃ to-10 ℃, 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 deasphalted lubricating oil base oil raw material with the crude oil boiling range of 557-700 ℃, the reduced linear fraction with the crude oil boiling range of 410-580 ℃ and the reduced linear fraction with the crude oil boiling range of 358-500 ℃ are all from China petrochemical Ma Ming Shi Su;
(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 140g of deasphalted lubricant base oil raw material with the crude oil boiling range of 557-700 ℃ and 525g of ketone-benzene organic solvent at 30 ℃, wherein the mixing duration is 0.5h, cooling the obtained mixture to-25 ℃, crystallizing, filtering after 1h to obtain filtrate containing the dewaxed lubricant base 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 60: 40;
(2) 500mL of ketobenzene solvent formed by mixing methyl ethyl ketone and toluene is added 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 a sheared organic solvent-resistant composite nanofiltration membrane (the organic solvent-resistant composite nanofiltration membrane is purchased from creative special chemistry, the cut-off molecular weight is 550Da, the product mark is select B, 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) after the membrane washing is finished, evacuating the solvent of the system, adding 500mL of filtrate containing the raw dewaxed lubricating oil and the organic solvent of the ketobenzene obtained in the step (1) into a mother liquor tank, wherein the content of the raw dewaxed lubricating oil in the solution is 18 wt% based on the total amount of the solution, the weight ratio of methyl ethyl ketone to toluene in the solvent is 60:40, the system pressure is kept at 4MPa, the temperature of the mother liquor tank is controlled at 10 ℃ by an alcohol bath, and a concentration experiment (membrane separation experiment) is started after the system continuously runs for 4 hours, wherein the sampling results are shown in Table 1.
From the experimental results in Table 1, it can be found that 50% of the organic solvent of ketone benzene is recovered, the average content of the organic solvent in the permeate obtained by permeating the nanofiltration membrane is 99%, and the amount of the organic solvent in the solvent recovery process is equal to that in the nanofiltration membraneThe average flux of the filters was 30.7L/(m)2·h)。
TABLE 1
Example 2
(1) Stirring and mixing 120g of deasphalted lubricant base oil raw material with a crude oil boiling range of 557-700 ℃ and 400g of ketone-benzene organic solvent at 32 ℃, wherein the mixing duration is 1h, cooling the obtained mixture to-20 ℃ for crystallization, filtering after 2h to obtain filtrate containing the 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 60: 40;
(2) the concentrated solution in example 1 was evacuated, 500mL of the filtrate containing the dewaxed lubricant oil raw oil and the organic solvent of ketobenzene obtained in step (1) was added to the mother liquor tank, and based on the total amount of the solution, the content of the dewaxed lubricant oil raw oil in the solution was 20% by weight, the weight ratio of methyl ethyl ketone/toluene in the solvent was 60:40, the system pressure was maintained at 4.5MPa, the temperature of the mother liquor tank was controlled by a water bath at 20 ℃, 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 composite nanofiltration membrane used in example 1.
From the experimental results in table 2, it can be found that 45% of the organic solvent is recovered, the average content of the organic solvent in the permeate obtained by permeating the nanofiltration membrane is 98.55%, and the average flux of the nanofiltration membrane in the solvent recovery process is 35L/(m)2·h)。
TABLE 2
Example 3
(1) Stirring and mixing 110g of crude oil with a boiling range of 410-580 ℃ minus tetralin fraction and 350g of a ketone-benzene organic solvent at 35 ℃, wherein the mixing duration is 1h, cooling the obtained mixture to-15 ℃, crystallizing, filtering after 2h, and obtaining a filtrate containing the dewaxed lubricant oil raw oil and the ketone-benzene organic solvent, wherein the ketone-benzene 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 65: 35;
(2) 500mL of ketobenzene solvent formed by mixing methyl ethyl ketone and toluene is added into a mother liquor tank of a membrane separation device, wherein the mass ratio of the methyl ethyl ketone to the toluene is 65:35, and a sheared organic solvent-resistant nanofiltration membrane (the organic solvent-resistant composite nanofiltration membrane is purchased from creative specialty chemistry, the molecular weight cut-off is 500Da, the product mark is select A, 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) after the membrane washing is finished, evacuating the solvent of the system, adding 500mL of filtrate containing the raw dewaxed lubricating 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 raw dewaxed lubricating oil in the solution is 21 wt%, the weight ratio of methyl ethyl ketone to toluene in the solvent is 65:35, the system pressure is kept at 0MPa, the temperature of the mother liquor tank is controlled at 0 ℃ by an alcohol bath, and a concentration experiment (membrane separation experiment) is started after the system continuously runs for 4 hours, wherein the sampling results are shown in Table 3.
From the experimental results in Table 3, it can be found that 41% 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 average flux of the nanofiltration membrane during the solvent recovery process was 29.9L/(m)2·h)。
TABLE 3
Example 4
(1) Stirring and mixing 110g of crude oil with a boiling range of 410-580 ℃ minus tetralin fraction and 350g 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 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 65: 35;
(2) the concentrated solution in example 3 was evacuated, 500mL of the filtrate containing the dewaxed lubricant oil raw oil and the organic solvent of ketobenzene obtained in step (1) was added to the mother liquor tank, based on the total amount of the solution, the content of the dewaxed lubricant oil raw oil in the solution was 22% by weight, the mass fraction ratio of methyl ethyl ketone/toluene in the solvent was 65:35, the system pressure was maintained at 3.0MPa, the temperature of the mother liquor tank was controlled by a water bath at 40 ℃, a concentration experiment (membrane separation experiment) was started after 4 hours of continuous operation of the system, and the sampling results are shown in table 4. The nanofiltration membrane used in this example was the same as the composite nanofiltration membrane used in example 3.
From the experimental results in Table 4, it can be found that 55% of the ketone-benzene solvent is recovered, the average content of the organic solvent in the permeate obtained by permeating the nanofiltration membrane is 98.0%, and the average flux of the nanofiltration membrane in the solvent recovery process is 37.9L/(m)2·h)。
TABLE 4
Example 5
(1) Stirring and mixing 100g of reduced fraction with crude oil boiling range of 358-500 ℃ with 290g of a ketobenzene organic solvent at 25 ℃, wherein the mixing duration is 2h, cooling the obtained mixture to-25 ℃ for crystallization, filtering after 1h to obtain a filtrate containing the 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/toluene is 70: 30;
(2) 500mL of ketone-benzene solvent formed by mixing methyl ethyl ketone and toluene is added into a mother liquor tank of a membrane separation device, wherein the mass ratio of the methyl ethyl ketone to the toluene is 70:30, a sheared organic solvent-resistant nanofiltration membrane (the organic solvent-resistant nanofiltration membrane is a composite organic solvent-resistant nanofiltration membrane prepared by the method disclosed in the paragraph [ 0090 ] of the specification in the patent CN 102665879A) is added, and the support membrane is a composite organic solvent-resistant nanofiltration membranePolyacrylonitrile, the separation membrane layer is the same as that in select B membrane, the molecular weight cut-off is 400Da, 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) after the membrane washing is finished, emptying the solvent of the system, adding 500mL of filtrate containing the raw dewaxed lubricating 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 raw dewaxed lubricating oil in the solution is 24 wt%, the weight ratio of methyl ethyl ketone to toluene in the solvent is 70:30, the system pressure is kept at 3.5MPa, the temperature of the mother liquor tank is controlled to be-10 ℃, a concentration experiment (membrane separation experiment) is started after the system continuously runs for 4 hours, and the sampling results are shown in Table 5.
From the experimental results in Table 5, it can be found that 40% of the ketone-benzene solvent is recovered, the average content of the organic solvent in the permeate obtained by permeating the nanofiltration membrane is 99.15%, and the average flux of the nanofiltration membrane in the solvent recovery process is 26.6L/(m)2·h)。
TABLE 5
Example 6
(1) Stirring and mixing 90g of reduced fraction with crude oil boiling range of 358-500 ℃ with 300g of organic solvent of ketobenzene at 35 ℃, keeping mixing duration for 1h, cooling the obtained mixture to-15 ℃ for crystallization, filtering after 2h to obtain filtrate containing raw oil of dewaxed lubricating oil and organic solvent of ketobenzene, wherein the organic solvent of ketobenzene used for dewaxing is a mixture formed by mixing methyl ethyl ketone and toluene, the weight ratio of methyl ethyl ketone/toluene is 70:30,
(2) the concentrated solution in example 5 was evacuated, 500mL of the filtrate containing the dewaxed lubricant oil stock oil and the organic solvent of ketobenzene obtained in step (1) was added to the mother liquor tank, and based on the total amount of the solution, the content of the dewaxed lubricant oil stock oil in the solution was 20% by weight, the system pressure in the solvent was 70:30 and 3MPa was maintained, the temperature of the mother liquor tank was controlled in a water bath at 30 ℃, and the concentration experiment (membrane separation experiment) was started after 4 hours of continuous operation of the system, and the sampling results are shown in table 6. The nanofiltration membrane used in this example was the same as the composite nanofiltration membrane used in example 5.
From the experimental results in Table 6, it can be found that 45% of the organic solvent was recovered, the average content of the organic solvent in the permeate obtained through the nanofiltration membrane reached 98.1%, and the average flux of the nanofiltration membrane during the solvent recovery process was 37.65L/(m)2·h)。
TABLE 6
The results show that the recovery method provided by the invention has the advantages that the average content of the organic solvent in the permeate liquid penetrating through the composite nanofiltration membrane is higher, the average flux of the composite nanofiltration membrane is stable, the influence of the temperature of the solution in a solution recovery system is smaller, the operation process is stable, the continuous and stable production is easy to realize, 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 (9)
1. A method for recovering a dewaxing solvent of raw lubricating oil comprises the step of contacting a solution containing the raw dewaxing lubricating oil and an organic solvent with a composite nanofiltration membrane, wherein the composite nanofiltration membrane consists of a support membrane and a separation membrane layer, the molecular weight cut-off of the composite nanofiltration membrane is 400-550Da, the contact pressure is 2-6MPa, the support membrane is polyacrylonitrile, the separation membrane layer is prepared by solidifying side chain modified polysiloxane acrylate shown in a formula I,
in the formula (I), a is 25-500, b is 1-25, and c is 0-20;
R1is an alkyl or aryl group having from 1 to 30 carbon atoms, which is independent of each other, identical or different, optionally having at least one of an ether functional group, an ester functional group, an epoxy functional group and an alcohol functional group; r2Are, independently of one another, identical or different: r1、R3And R4；R3Are each, independently of one another, identical or different organic radicals having one or more acrylate groups, R4Are the same or different polyether groups,
the average flux of the organic solvent of the composite nanofiltration membrane is 20-40L/(m)2H) the organic solvent is a mixture of methyl ethyl ketone and toluene,
the average content of organic solvents in the permeate is more than 98 weight percent based on the total amount of the permeate obtained by permeating the composite nanofiltration membrane, the lubricating oil raw oil is at least one of a three-line cut fraction, a four-line cut fraction and a deasphalted lubricating oil base oil raw material, the weight ratio of methyl ethyl ketone to toluene is (60:40) - (70:30), the content of the dewaxed lubricating oil raw oil is 15-25 weight percent based on the total amount of the solution,
the temperature of the contacting is-10 ℃ to 40 ℃; the contact pressure is 3-5 MPa.
2. The method of claim 1, wherein the average flux of organic solvent of the composite nanofiltration membrane is 26-38L/(m)2·h)。
3. The method of claim 1, wherein the lubricant base stock is a crude oil fraction used to produce a lubricant base stock.
4. The method of claim 1, wherein the composite 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.
5. The process according to claim 1, wherein the composite nanofiltration membrane is used in the form of a roll-to-roll module and/or a plate module.
6. A process for dewaxing a lube basestock, comprising: a method for recovering an organic solvent from a filtrate comprising a dewaxed lube base oil and an organic solvent, which comprises mixing a lube base oil with an organic solvent, cooling and crystallizing the mixture and filtering the mixture, wherein the method comprises recovering the organic solvent from the filtrate by the method according to any one of claims 1 to 5.
7. The method according to claim 6, wherein the weight ratio of the lube base oil to the organic solvent is (15:85) - (25: 50).
8. The method of claim 6, wherein the mixing is performed at 20-40 ℃ and the duration of the mixing is 1-120 min.
9. The process according to claim 6, wherein the temperature of the crystallization is from-30 ℃ to-10 ℃ and the duration of the crystallization is from 1 to 120 min.
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