A method for one-pot synthesis of long-chain alkylated methylnaphthalene base oil with poly-alpha-olefin as alkylating monomer

Abstract

The present application relates to the technical field of synthetic lubricating oil base oil, and particularly relates to a method for synthesizing long-chain alkylated methylnaphthalene base oil by one-pot method with poly-alpha-olefin as alkylating monomer, which comprises the following steps: firstly, polymerizing alpha-olefin to prepare polymerized long chain, then adding methylnaphthalene dropwise to perform alkylation reaction, and adding anhydrous AlCl3 catalyst in batches during the reaction process. The alpha-olefin comprises one or more mixtures of 1-octene, 1-decene, 1-dodecene and the like; the methylnaphthalene is 1-methylnaphthalene and / or 2-methylnaphthalene. Compared with the traditional alkylated naphthalene base oil preparation method, the present application controls the pre-polymerization time of alpha-olefin under the condition of no solvent, and then performs alkylation reaction with methylnaphthalene, which significantly improves the flash point, rotary oxygen bomb time (oxidation stability) and viscosity index of the product, and has a lower pour point. The process is simple in operation, good in reproducibility, and the obtained base oil has excellent comprehensive performance.

Description

Technical Field

[0001] This invention relates to the field of synthetic lubricating oil base oil technology, specifically to a method for synthesizing long-chain alkylated methylnaphthalene base oil using polyα-olefin as the alkylating monomer in a "one-pot" process. Background Technology

[0002] Alkyl naphthalene base oils are synthetic lubricants with excellent oxidation stability. They are typically prepared by alkylation of long-chain olefins with naphthalene. Currently, commercially available alkyl naphthalenes are prepared by alkylation of naphthalene and its derivatives with long-chain α-olefins. This process usually involves adding long-chain α-olefins dropwise to naphthalene and its derivatives, followed by vacuum distillation to remove unreacted raw materials. However, this method cannot introduce excessively long side chains, resulting in slightly inferior viscosity index, oxidation stability, and flash point. Its viscosity index and flash point are relatively low, and its oxidation stability still has room for improvement. Summary of the Invention

[0003] In view of the shortcomings of the prior art, the purpose of this invention is to provide a method for synthesizing long-chain alkylated methylnaphthalene base oil in a one-pot process using polyα-olefin as alkylating monomer. The method significantly improves the overall performance of the product by changing the order of feeding and the reaction control method.

[0004] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: A method for synthesizing long-chain alkylated methylnaphthalene base oil using polyα-olefins as alkylating monomers in a one-pot process includes the following steps: In the presence of anhydrous AlCl3 catalyst, α-olefins are first subjected to a prepolymerization reaction to generate polymerized α-olefin long chains. Then, methylnaphthalene is added dropwise to the reaction system to carry out the alkylation reaction.

[0005] In a preferred embodiment of the present invention, the anhydrous AlCl3 catalyst is added in batches with equal mass and equal time intervals.

[0006] In a preferred embodiment of the present invention, the α-olefin is any one or more of 1-octene, 1-decene, 1-nonene, 1-dodecene, 1-tetradecene, 1-hexadecene, and coal-derived α-mixed olefins; and the methylnaphthalene is any one or more of 1-methylnaphthalene and 2-methylnaphthalene.

[0007] In a preferred embodiment of the present invention, the prepolymerization reaction time is 0.5 h to 2 h; the methylnaphthalene addition time in the alkylation reaction is 1 h to 2 h, and the total reaction time is 4 h to 7 h.

[0008] In a preferred embodiment of the present invention, the temperature of the prepolymerization reaction is 60°C to 120°C; the temperature of the alkylation reaction is 60°C to 120°C.

[0009] In a preferred embodiment of the present invention, the total mass ratio of anhydrous AlCl3 to α-olefin and methylnaphthalene is 0.5~4:100; further, the total mass ratio of anhydrous AlCl3 to α-olefin and methylnaphthalene is 3:100; the molar ratio of methylnaphthalene to α-olefin is 1:2~6; further, the molar ratio of methylnaphthalene to α-olefin is 1:2.

[0010] In a preferred embodiment of the present invention, the method is carried out under solvent-free conditions.

[0011] In a preferred embodiment of the present invention, the method further includes a post-processing step of the crude product obtained after the reaction: filtering the crude product to remove solid impurities, neutralizing it to neutral with an alkali-alcohol solution, then performing vacuum distillation to recover unreacted monomers and oligomers, and finally performing decolorization treatment to obtain polymerized long-chain alkyl methyl naphthalene base oil.

[0012] In a preferred embodiment of the present invention, the alcohol in the alkali-alcohol solution can be recovered and reused; the monomers and oligomers produced by vacuum distillation can be recycled for alkylation reactions.

[0013] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention, through a specific feeding sequence of "polymerizing α-olefins first, then alkylating methylnaphthalene", and especially by controlling the prepolymerization time of α-olefins, results in a final product (polymerized long-chain alkyl methylnaphthalene base oil) that has a higher viscosity index, a higher flash point, and better oxidation stability (significantly extended rotating bomb oxidation time) compared to alkylnaphthalene base oils prepared by traditional methods.

[0014] 2. This invention employs a batch-addition of catalyst, which helps control the exothermic reaction and makes the reaction process more stable. Experiments have shown that this process has good reproducibility, and the products obtained from multiple parallel experiments have stable performance.

[0015] 3. The reaction of this invention is carried out under solvent-free conditions, avoiding the use of volatile organic solvents. Furthermore, the alcohols and unreacted monomers generated during the post-processing can be recovered and reused, conforming to the principles of green chemistry and effectively reducing production costs. Attached Figure Description

[0016] Figure 1 The infrared spectrum of the polymerized long-chain alkyl methylnaphthalene base oil prepared in Example 1 of this invention. Detailed Implementation

[0017] The following detailed description, in conjunction with embodiments of the present invention and accompanying drawings, provides a clear and complete illustration of the technical solutions in these embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0018] It should be noted that all technical terms used in this invention are for the purpose of describing specific embodiments only and are not intended to limit the scope of protection of this invention. Unless otherwise specified, all raw materials, reagents, instruments and equipment used in the following embodiments of this invention can be purchased from the market or prepared by existing methods.

[0019] This invention relates to a method for one-pot synthesis of long-chain alkylated methylnaphthalene base oil using polyα-olefins as alkylating monomers.

[0020] In a first aspect, the present invention provides a method for synthesizing long-chain alkylated methylnaphthalene base oil using poly-α-olefins as alkylating monomers in a "one-pot" process, which is a method of first polymerizing long-chain α-olefins.

[0021] In a first aspect, the present invention provides a method for synthesizing long-chain alkylated methylnaphthalene base oil in a one-pot process using poly-α-olefin as the alkylating monomer. The method is a method for preparing the base oil by alkylation reaction of methylnaphthalene with a long chain of polymeric α-olefin.

[0022] In one embodiment of the first aspect, the α-olefin is any one or more of 1-octene, 1-decene, 1-nonene, 1-dodecene, 1-tetradecene, 1-hexadecene, and coal-derived α-mixed olefins.

[0023] In one embodiment of the first aspect, the methylnaphthalene includes any one or more of 1-methylnaphthalene and 2-methylnaphthalene.

[0024] In a second aspect, the present invention provides a method for synthesizing long-chain alkylated methylnaphthalene base oil using polyα-olefins as alkylating monomers in a one-pot process, the method comprising the following steps: S1: After heating a certain mass of α-olefin to a specified temperature, anhydrous AlCl3 is added in batches at equal intervals to a reactor containing α-olefin to carry out a prepolymerization reaction. The catalyst is added in 10 to 20 batches. The α-olefin prepolymerization reaction time is 0.5 h to 2 h at 60 to 120 °C to obtain polymerized α-olefin long chains.

[0025] S2: Add methylnaphthalene dropwise to the reaction system to carry out the alkylation reaction. The addition is completed within 1 to 2 hours, at 60 ℃ to 120 ℃. The total reaction time is 4 to 7 hours.

[0026] S3: After filtering the crude product to remove insoluble solid impurities, it is neutralized with an alkali-alcohol solution and then decolorized.

[0027] S4: The post-processed product is subjected to vacuum distillation to remove the reactive monomers and oligomers, yielding polymerized long-chain alkyl methyl naphthalene base oil.

[0028] In one embodiment of the second aspect, in steps S1 and S2, the total mass ratio of anhydrous AlCl3 and α-olefin to methylnaphthalene is 0.5 to 4:100, preferably 3:100.

[0029] In one embodiment of the second aspect, in steps S1 and S2, the molar ratio of methylnaphthalene to α-olefin is 1:2 to 6, preferably 1:2.

[0030] In one embodiment of the second aspect, in steps S1 and S2, anhydrous AlCl3 is added in batches of equal mass and at equal intervals, and the catalyst is added in 10 to 20 batches with an interval of 0.25 h between each addition. The α-olefin prepolymerization reaction time is 0.5 h to 2 h, preferably 20 batches, and preferably 0.5 h.

[0031] In one embodiment of the second aspect, in step S2, the alkylation reaction of methylnaphthalene is carried out by adding it dropwise to the reaction system, which is completed within 1 h to 2 h, with the preferred addition time being 1 h.

[0032] In one embodiment of the second aspect, in steps S1 and S2, the reaction temperature is 60~120°C, and the yield is higher at different temperatures, resulting in polymerized long-chain alkyl methyl naphthalene base oils of different viscosities.

[0033] Viscosity determination method: Viscosity was determined according to standard GB / T 265-1988 using an ELB-KVD10 automatic kinematic viscosity analyzer. The flow time of each sample was measured three times at 40 ℃ and 100 ℃ respectively. The kinematic viscosity was then calculated using the formula shown below: ν=c·t In the above calculation formula, ν represents kinematic viscosity, with units of mm. 2 / s; t represents flow time in seconds; c represents pipe constant in mm. 2 / s.

[0034] Flash point determination method: The flash point was determined according to standard GB / T 3536-1983 using an AKD-K106 fully automatic open-face flash point tester. Each sample was measured three times, and the average value was taken as the final result.

[0035] Pour point determination method: According to GB / T 3535 "Determination of Pour Point of Petroleum Products", the pour point of the oil product was tested using the SYD-510D petroleum product pour point tester manufactured by Shanghai Changji Geological Instrument Co., Ltd. The pour point of each sample was repeated 3 times and the average value was taken as the final result.

[0036] Method for determining oxidation stability: The rotation time of the oxygen bomb was determined using the WZ-S0193Z automatic rotating oxygen bomb tester manufactured by Dalian Wuzhou Petroleum Equipment Co., Ltd., in accordance with NB / SH / T 0193-2022 "Determination of Oxidation Stability of Lubricating Oils - Rotating Oxygen Bomb Method".

[0037] In the following examples, anhydrous AlCl3, 1-methylnaphthalene, and 2-methylnaphthalene were purchased from Shanghai Titan Technology Co., Ltd.

[0038] 1-Octene, 1-decene, 1-dodecene, 1-tetradecene, and 1-hexadecene were purchased from Chevron Corporation; 1-nonene and coal-derived α-mixed olefins were purchased from Inner Mongolia Yitai Group Co., Ltd.

[0039] Example 1 (1) At 60°C, anhydrous AlCl3 was added to 1-dodecene in 20 batches of equal mass, with an interval of 0.25 hours between each batch. After the 1-dodecene prepolymerization reaction was completed for 0.5 hours (i.e., without prepolymerization, proceed directly to the next step), 2-methylnaphthalene was added dropwise over 1 hour. The molar ratio of 2-methylnaphthalene to 1-dodecene was 1:2, and the total mass ratio of anhydrous AlCl3 to (1-dodecene + 2-methylnaphthalene) was 3:100. The total reaction time was 5 hours.

[0040] (2) After the reaction was completed, the crude product was treated with an alkali-alcohol solution to remove the catalyst, followed by vacuum distillation to remove unreacted monomers and oligomers. Finally, the product was decolorized to obtain a yellow, transparent, oily liquid, which is the polymerized long-chain alkyl methylnaphthalene base oil. Infrared spectroscopy analysis of the product yielded the following results: Figure 1 As shown, the formation of the target product was confirmed, and the physicochemical properties of the product are shown in Table 1.

[0041] Example 2 The reaction temperature was changed to 70℃, and the rest of the operation was the same as in Example 1. The physical and chemical properties of the product are shown in Table 1 and Table 2.

[0042] Example 3 The reaction temperature was 80℃, and the rest of the operation was the same as in Example 1. The physical and chemical properties of the product are shown in Table 1.

[0043] Example 4 The reaction temperature was 80℃. 2-methylnaphthalene was replaced with 1-methylnaphthalene. The rest of the operation was the same as in Example 1. The physicochemical properties of the product are shown in Table 1.

[0044] Comparative Example 1 Commercially available alkylnaphthalene base oil, ExxonMobil Synestic™ 5, was used. Its physicochemical properties are shown in Table 1.

[0045] Comparative Example 2 Commercially available alkylnaphthalene base oil, model Synesstic™ 12, was used. Its physicochemical properties are shown in Table 1.

[0046] Comparative Example 3 Commercially available alkyl naphthalene base oil, model DowSyn AN4, was used. Its physicochemical properties are shown in Table 1.

[0047] Example 5 (Effect of different prepolymerization times) At 80°C, the prepolymerization reaction time of 1-dodecene was set to 0, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, and 3.5 hours, respectively. The remaining operations were the same as in Example 2. The physicochemical properties of the product are shown in Table 3.

[0048] Example 6 (Comparison with Traditional Methods) Anhydrous AlCl3 was added to a 2-methylnaphthalene solution in one step at 80°C, followed by the dropwise addition of 1-dodecene over one hour. The molar ratio of 1-dodecene to 2-methylnaphthalene was 1:2, and the total reaction time was 5 hours. The remaining procedures were the same as in Example 2. This is a conventional alkylation method; the physicochemical properties of the product are shown in Table 3.

[0049] Example 7 (Effect of different catalyst dosages) The reaction temperature was 80℃, and the total mass ratio of anhydrous AlCl3 to (1-dodecene + 2-methylnaphthalene) was set to 0.5:99.5, 1:99, 2:98, 3:97, and 4:96, respectively. The remaining operations were the same as in Example 1. The physicochemical properties of the product are shown in Table 4.

[0050] Example 8 (The effect of different batch numbers of catalysts) The reaction temperature was 80℃. Anhydrous AlCl3 was added in batches of 10, 15, and 20, respectively. The remaining operations were the same as in Example 1. The physicochemical properties of the product are shown in Table 5.

[0051] Comparative Example 4 The reaction temperature was 80℃. The prepolymerization time of 1-dodecene was changed to 0.5 hours, and 2-methylnaphthalene was replaced with naphthalene. The remaining operations were the same as in Example 1. The physicochemical properties of the product are shown in Table 1.

[0052] Results Analysis Depend on Figure 1 It can be known that 3050 cm -1 The peak represents the stretching vibration of the aromatic ring CH, at 1608 cm⁻¹. -11510 cm -1 1463 cm -1 This is the skeletal vibration peak of the carbon-carbon double bond in the aromatic ring, a hallmark of the aromatic ring, 809 cm⁻¹. -1 739 cm -1 It is an out-of-plane bending vibration of the aromatic ring CH, in the range of 810~730 cm. -1 The absorption peaks within this range represent fingerprint regions at different substitution sites of naphthalene; 2955 cm⁻¹ -1 The peak is the stretching vibration peak of CH3, at 2921 cm⁻¹. -1 2850 cm -1 The peak is the stretching vibration peak of CH2, at 721 cm⁻¹. -1 The absorption peak at the specified position corresponds to the absorption peak of the long-chain methylene group. The positions of the absorption peaks above indicate that the product contains both naphthalene and long-chain alkanes, thus proving the reaction was successful.

[0053] Table 1 compares the physicochemical properties of polymerized long-chain alkyl methyl naphthalene base oil and commercially available alkyl naphthalene base oil. A performance comparison was made between the polymerized long-chain alkyl methyl naphthalene base oil described in this invention, commercially available alkyl naphthalene base oil, and alkyl naphthalene base oil prepared using naphthalene. The results show that, compared to the alkyl naphthalene base oils in Table 1, the polymerized long-chain alkyl methyl naphthalene base oil has a better viscosity index, a higher flash point, a lower pour point, and a longer rotating bomb oxidation time.

[0054] As shown in Table 1, the base oils prepared in Examples 1 to 3 of this invention exhibit better or significantly better rotational oxygen bomb time (479-566 min), flash point (218-248℃), and viscosity index (94-114) than commercially available products (Comparative Examples 1 to 3), demonstrating superior overall performance. Example 4, using 1-methylnaphthalene, showed a relatively weak performance improvement.

[0055] Table 1 compares the physicochemical properties of polymerized long-chain alkyl methyl naphthalene base oil and commercially available alkyl naphthalene base oil. Table 2 shows the physicochemical properties of the polymerized long-chain alkyl methylnaphthalene base oil prepared in three parallel experiments in Example 2. It can be seen that there were no significant differences in the various properties, indicating that the process of this invention is stable and has good reproducibility.

[0056] Table 2 shows the physicochemical properties of the polymeric long-chain alkyl methylnaphthalene base oil prepared in three parallel experiments in Example 2. Table 3 compares the physicochemical properties of polymerized long-chain alkyl methyl naphthalene base oils prepared by different olefin polymerization times with those prepared by conventional methods. Example 6 describes a conventional method for preparing alkyl naphthalenes by adding anhydrous AlCl3 catalyst in a single step and then dropwise adding olefins.

[0057] The performance of the polymerized long-chain alkyl methyl naphthalene base oil described in this invention was compared with that of alkyl naphthalene base oil prepared by conventional methods. The results showed that the viscosity index and rotating bomb time of the product were significantly improved after α-olefin prepolymerization for 0.5 h. As the α-olefin prepolymerization time was extended, the yield and rotating bomb time of the obtained product showed a decreasing trend. Furthermore, after 2 h of prepolymerization, further increasing the time did not significantly improve the viscosity index and rotating bomb time. In contrast, compared with alkyl naphthalene base oil prepared by conventional methods, the products prepared by prepolymerization for 0.5 to 1.5 h showed better performance in terms of oxidation stability.

[0058] As shown in Table 3, compared with no prepolymerization (0 hours), prepolymerization for 0.5 hours significantly improved the viscosity index (94→114) and the rotating bomb time (547→566 min) of the product. When the prepolymerization time exceeded 1.5 hours, the oxidative stability decreased sharply. This indicates that a suitable prepolymerization time (0.5-1.5 hours) is crucial for improving product performance. Compared with the conventional method in Example 6, the product prepared within the preferred prepolymerization time window of this invention exhibits superior oxidative stability.

[0059] Table 3 compares the physicochemical properties of polymerized long-chain alkyl methyl naphthalene base oils prepared by different olefin polymerization times with those prepared by traditional methods. Table 4 compares the physicochemical properties of polymerized long-chain alkyl methylnaphthalene base oils prepared with different catalyst dosages. From the above physicochemical property results, it can be seen that when the catalyst dosage is 0.5 wt%, the product yield is 56.8%; increasing the catalyst dosage to 1.0 wt% increases the yield to 99.1%; further increasing the catalyst dosage does not significantly change the yield, but the viscosity index and rotating bomb time gradually increase. Further increasing the catalyst content leads to a decrease in the corresponding physicochemical properties. Therefore, a catalyst ratio of 3:97 is selected as the optimal catalyst dosage.

[0060] As shown in Table 4, the yield was low (56.8%) when the catalyst dosage (mass ratio) was below 1%. When the dosage reached 1%, the yield exceeded 99%. However, further increasing the catalyst dosage to 2%–4% resulted in a trend of first increasing and then decreasing the viscosity index and rotating bomb time, reaching an optimal value at 3% (VI=132, rotating bomb time=138 min). Therefore, a catalyst-to-total feed mass ratio of 3:97 is considered optimal.

[0061] Table 4 compares the physicochemical properties of polymerized long-chain alkyl methylnaphthalene base oils prepared with different catalyst dosages. As shown in Table 5, increasing the number of catalyst batches (from 10 to 20) significantly improved the product yield (85.4%→99.2%) and the rotating bomb time (117→138 min). This is because finer batch feeding helps control the intensity of the reaction and local overheating, thereby improving product quality and process reproducibility.

[0062] Table 5 compares the physicochemical properties of polymerized long-chain alkyl methylnaphthalene base oils prepared by adding catalysts in different batches. The performance results above show that the product yield and the rotating bomb time gradually increase with the increase of batches. At the same time, adding more batches with catalyst can better control the reaction temperature, thereby ensuring the reproducibility of product performance.

[0063] In summary, the one-pot synthesis process provided by this invention, through the specific steps of "polymerizing α-olefins first and then alkylating methylnaphthalene", combined with key process parameters such as batch addition of catalyst and control of prepolymerization time, can significantly improve the viscosity index, flash point and oxidation stability of long-chain alkylated methylnaphthalene base oil. It is a novel synthesis method with good application prospects.

[0064] It should be noted that when numerical ranges are involved in this invention, it should be understood that both endpoints of each numerical range and any value between the two endpoints can be selected. Since the steps and methods used are the same as in the embodiments, preferred embodiments are described here to avoid redundancy. Although preferred embodiments of the invention have been described, those skilled in the art, once they understand the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of this invention.

[0065] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A method for one-pot synthesis of long-chain alkylated methylnaphthalene base oil using polyα-olefins as alkylating monomers, characterized in that, Includes the following steps: In the presence of anhydrous AlCl3 catalyst, α-olefins are first prepolymerized to generate polymerized α-olefin long chains. Then, methylnaphthalene is added dropwise to the reaction system to carry out the alkylation reaction.

2. The method for one-pot synthesis of long-chain alkylated methylnaphthalene base oil using polyα-olefin as alkylating monomer according to claim 1, characterized in that, The anhydrous AlCl3 catalyst was added in batches with equal mass and equal time intervals.

3. The method for one-pot synthesis of long-chain alkylated methylnaphthalene base oil using polyα-olefin as alkylating monomer according to claim 1, characterized in that, The α-olefin is any one or more of 1-octene, 1-decene, 1-nonene, 1-dodecene, 1-tetradecene, 1-hexadecene, and coal-derived α-mixed olefins; the methylnaphthalene is any one or more of 1-methylnaphthalene and 2-methylnaphthalene.

4. The method for one-pot synthesis of long-chain alkylated methylnaphthalene base oil using polyα-olefins as alkylating monomers according to claim 1, characterized in that, The prepolymerization reaction takes 0.5 h to 2 h; the methylnaphthalene is added dropwise in the alkylation reaction for 1 h to 2 h, and the total reaction time is 4 h to 7 h.

5. The method for one-pot synthesis of long-chain alkylated methylnaphthalene base oil using polyα-olefin as alkylating monomer according to claim 1, characterized in that, The temperature of the prepolymerization reaction is 60℃~120℃; the temperature of the alkylation reaction is 60℃~120℃.

6. The method for one-pot synthesis of long-chain alkylated methylnaphthalene base oil using polyα-olefin as alkylating monomer according to claim 1, characterized in that, The total mass ratio of anhydrous AlCl3 to α-olefin and methylnaphthalene is 0.5~4:100; the molar ratio of methylnaphthalene to α-olefin is 1:2~6.

7. The method for one-pot synthesis of long-chain alkylated methylnaphthalene base oil using polyα-olefin as alkylating monomer according to claim 1, characterized in that, The method is carried out under solvent-free conditions.

8. The method for one-pot synthesis of long-chain alkylated methylnaphthalene base oil using polyα-olefin as alkylating monomer according to claim 1, characterized in that, It also includes a post-processing step for the crude product obtained after the reaction: filtering the crude product to remove solid impurities, neutralizing it to neutral with an alkali-alcohol solution, then performing vacuum distillation to recover unreacted monomers and oligomers, and finally performing decolorization to obtain polymerized long-chain alkyl methyl naphthalene base oil.

9. The method for one-pot synthesis of long-chain alkylated methylnaphthalene base oil using polyα-olefin as alkylating monomer according to claim 8, characterized in that, The alcohol in the alkali-alcohol solution can be recovered and reused; the monomers and oligomers produced by vacuum distillation can be recycled for alkylation reactions.

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