A catalyst for the synthesis of low-viscosity polyα-olefins and its application

Abstract

The application discloses a catalyst for synthesizing low-viscosity poly-alpha-olefin and application thereof, and belongs to the field of catalysts for synthesizing poly-alpha-olefin. The catalyst comprises a main catalyst and a cocatalyst, and a benzoxazoline-alcohol metal complex is used as the main catalyst and an organic boron or alkyl aluminum oxane is used as the cocatalyst. When the catalyst system is used for synthesizing poly-alpha-olefin synthetic oil, the catalyst has the advantages of non-toxicity, environmental friendliness, high catalyst activity, high raw material utilization rate, high product yield, low product pour point, wide use temperature range and the like.

Description

Technical Field

[0001] This invention belongs to the field of catalyst preparation, specifically relating to a catalyst for synthesizing low-viscosity polyα-olefins and its applications. Background Technology

[0002] Polyalphaolefins (PAOs) are an important class of synthetic lubricant base oils. Originally developed to meet military needs, they are now widely used in aerospace, automotive, and machinery industries. PAOs are obtained through the catalytic polymerization and hydrogenation of alpha-olefins. They possess a regular, sparse molecular structure, with trimers, tetramers, and pentamers as their main components. They exhibit excellent viscosity-temperature properties, thermal stability, low volatility, and low-temperature fluidity, making them widely used as base oils for mid- to high-end lubricants. Based on viscosity, PAOs can be classified into high-viscosity PAOs, medium-viscosity PAOs, and low-viscosity PAOs. High-viscosity PAOs have a viscosity range of 40–1000 mmHg. 2 / s, can be used in harsh lubrication applications with high load and strong shear, and is usually used in combination with low viscosity base oils to formulate industrial gear oils and automotive gear oils with different ISO viscosity grades. It can also be used as automotive gear and heavy-duty transmission oil, high temperature industrial gear and circulating oil, industrial hydraulic fluid, gas turbine oil for land applications, etc.

[0003] The performance of PAO products is determined by the degree of polymerization and molecular weight distribution of the oligomer products. Generally, the viscosity and thermal stability of the product increase with the increase of the carbon number of the PAO molecule, while more side-chain structures and relatively short straight-chain segments are beneficial for PAO to maintain good flowability even at low temperatures. By changing the composition of the catalyst system and the reaction conditions, the product distribution of the oligomerization reaction can be controlled, thereby adjusting the performance of the PAO product. The chemical structure of low-viscosity PAO is a relatively regular isoalkanes with long side chains, which has the characteristics of high viscosity index, low pour point, good oxidation stability, high flash point and low volatility. It plays an irreplaceable role in cutting-edge fields such as aerospace and military industry, and is also an important raw material for the production of high-grade lubricating oils in industries such as high-end automobiles, wind power, high-speed rail, and intelligent manufacturing. With the advancement of internal combustion engine and various mechanical equipment technologies, the market requirements for lubricating oil performance are becoming increasingly stringent, and the application of PAO synthetic base oils is receiving increasing attention, with market demand for PAO constantly increasing. However, due to constraints such as raw material supply, production technology, and environmental protection, China still mainly relies on imports for low-viscosity PAO. Therefore, in recent years, China has been continuously strengthening its research on low-viscosity PAO.

[0004] Catalysts used in the synthesis of PAO mainly include aluminum trichloride catalysts, boron trifluoride catalysts, Ziegler-Nata catalysts, metallocene catalysts, and ionic liquid catalysts. Co-catalysts are an important component of metallocene catalytic systems and are generally divided into two main categories: alkylaluminoxanes and organoborides. Alkylaluminoxanes include methylaluminoxanes, ethylaluminoxanes, butylaluminoxanes, and mixtures thereof. These co-catalysts need to reach a certain proportion in the catalytic system to exert their catalytic effect; typically, the Al / Zr ratio is 500:1, 1000:1, or even 1500:1 and 2000:1. Alkylaluminoxanes are extremely reactive, undergoing violent reactions with strong exothermic reactions upon contact with moisture and oxygen in the air. Therefore, the large quantities required, their unstable nature, and their high cost limit the application of this type of co-catalyst.

[0005] Complexes formed by BF3 with proton donors such as alcohols, water, or carboxylic acids are favored as catalysts for polymerization reactions due to their high conversion rate and good selectivity in α-olefin polymerization. In foreign countries, over 80% of low-viscosity PAO production uses BF3 complexes as catalysts for 1-decene polymerization. There are also reports of using bis(isopropylcyclopentadiene)zirconium dichloride as a catalyst to synthesize low-viscosity PAO. Zhang Zhifeng et al. conducted research on the synthesis of low-viscosity PAO using BF3 / n-butanol as a catalyst and 1-decene as a raw material. Under optimal process conditions of a reaction temperature of 30 °C and a BF3 to n-butanol molar ratio of 2.0, they prepared low-viscosity PAO with a 1-decene conversion rate of 99.8%. The product was mainly composed of trimers and tetramers, with mass fractions of 64.5% and 27.5%, respectively, and also contained small amounts of dimers (2.4%) and pentamers (5.6%). The kinematic viscosity of the product at 100 °C was 4.80 mm. 2 The viscosity index was 132, and the freezing point was -60 °C. Chu Hongling et al. used a BF3 / acetic acid complex as a catalyst. Under the conditions of a reaction temperature of 30 °C, a reaction pressure of 0.2 MPa, a reaction time of 2 h, and a mass ratio of fresh BF3 / acetic acid complex to 1-decene of 1:100, the conversion rate of 1-decene reached 99.4%, the total content of trimers and tetramers reached a maximum of 82.6%, and the kinematic viscosity of the product at 100 °C was 4.33 mm². 2 The viscosity index was 134, and the pour point was -53 °C. Cao Yuanyuan et al. used BF3 as a catalyst to investigate the effects of α-olefin type, α-olefin dosage, reaction pressure, reaction temperature, and reaction time on the performance of PAO products. The results showed that the optimal process conditions were a mixed decene:1-dodecene molar ratio of 3:1, a reaction temperature of 25 °C, a pressure of 0.4 MPa, and a reaction time of 2 h. Under these conditions, the conversion rate of the mixed decene feedstock was 98.1%, and the kinematic viscosity of the PAO product at 100 °C was 6.02 mm² / s, and at 40 °C it was 34.72 mm² / s.2 The viscosity index was 120, and the pour point was -48 °C. Li Zhenhua catalyzed the polymerization of 1-decene using a BF3 / n-butanol catalytic system. 1-Decanene and n-butanol were added to the reactor, and BF3 gas was introduced to carry out the reaction, resulting in a kinematic viscosity of 4.1 mm² at 100 °C. 2 A low-viscosity synthetic oil with a viscosity index of 136 and a pour point of -72 °C was produced by Goze. This high-quality polyolefin synthetic oil was prepared by copolymerizing octene, decene, and dodecene using BF3 as the main catalyst and a mixture of butanol and butyl acetate as a co-catalyst. The molar ratio of butanol to butyl acetate was 3:1, the reaction time was 1 h, and the polymerization product, after post-treatment, had a kinematic viscosity of 4 mmHg at 100 °C. 2 The product has an oligomer yield of 87.6% and a pour point of -63 °C.

[0006] The catalysts used in the current technology for synthesizing low-viscosity PAO are mostly BF3. However, BF3 Lewis acid is highly corrosive and forms highly irritating HF when it comes into contact with water vapor in the air, causing equipment corrosion. In addition, BF3 is toxic, which greatly limits its application. Very few industrial plants in China use BF3 to synthesize low-viscosity PAO. Summary of the Invention

[0007] The purpose of this invention is to provide a catalyst for the synthesis of low-viscosity poly-α-olefins and its application.

[0008] To achieve the above technical effects, the present invention is implemented through the following technical solution:

[0009] A catalyst for synthesizing low-viscosity poly-α-olefins, the catalyst comprising a main catalyst and a co-catalyst;

[0010] The structural formula of the main catalyst is as follows:

[0011]

[0012] M can be Ti, Zr, Hf, or Fe.

[0013] Furthermore, X above is chlorine or bromine.

[0014] Furthermore, the aforementioned cocatalyst is an organoboron or alkylaluminoxane.

[0015] Furthermore, the aforementioned organoboron is one or more of [Ph3C][B(C6F5)4], [PhMe2NH][B(C6F5)4], and B(C6F5)3; the aforementioned alkylaluminoxane is one or more of methylaluminoxane, ethylaluminoxane, n-propylaluminoxane, and n-butylaluminoxane.

[0016] Furthermore, the molar ratio of aluminum in the alkylaluminoxane to the metal in the main catalyst is 10-1000:1; the molar ratio of boron in the organoboron to the metal in the main catalyst is 1-300:1.

[0017] The catalyst prepared above is used in the synthesis of low-viscosity polyα-olefins. The steps are as follows: using α-olefins as raw materials, adding catalysts, and carrying out polymerization reactions.

[0018] Furthermore, the aforementioned α-olefin is one or a mixture of several of 1-octene, 1-nonene, 1-decene, 1-undecene, 1-dodecene, 1-tetracene, and 1-tetradecene.

[0019] Furthermore, the polymerization reaction temperature is 50-140 °C, and the main catalyst in the above catalyst is dissolved in one of n-hexane, cyclohexane, methylcyclohexane, and toluene.

[0020] The beneficial effects of this invention are as follows: for the first time, benzoxazolin-ol metal complexes are used as the main catalyst in metallocene catalysts, which can prepare low viscosity PAO. The product has low viscosity, low pour point, can utilize mixed raw materials, improves PAO product yield and overall yield. Attached Figure Description

[0021] Figure 1 The steps for synthesizing the benzoxazolin-ol metal complex of Example 1 are as follows.

[0022] Figure 2 For compound a 1 HNMR spectrum.

[0023] Figure 3 This is the mass spectrum of compound a.

[0024] Figure 4 For compound b 1 HNMR spectrum. Detailed Implementation

[0025] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. The illustrative embodiments and descriptions of the present invention are only used to explain the present invention and are not intended to limit the present invention.

[0026] Example 1

[0027] Synthesis of benzoxazolin-ol metal complexes

[0028] (1) Take a dry round-bottom flask (100 mL), add lactic acid (5 mL, 55 mmol), p-toluenesulfonic acid (PTSA, 570 mg, 5.5 mmol), o-aminophenol (6 g, 55 mmol), and toluene (25 mL) in sequence. The resulting suspension is heated and stirred at 110 °C for 8 hours in a Dean-Stark apparatus. After the reaction is complete, cool to room temperature and separate the two phases to obtain an aqueous phase and an organic phase. Extract the organic phase with ethyl acetate (4 × 10 mL). Then collect the organic phase and dry it with anhydrous Na2SO4. Evaporate the solvent by vacuum distillation to obtain a mixture. Use (ethyl acetate / n-hexane volume ratio = 50 / 1) as the eluent and purify the mixture by column chromatography to obtain product intermediate a as a brown solid (6.04 g, separation rate 67%) (NMR spectrum and mass spectrum are shown in [reference needed]). Figure 2 and Figure 3 Its structural characterization data are as follows:

[0029] 1 H NMR (σ (ppm) 7.29~7.39 (Ar- H , 4H), 5.12 (-C- H , 1H), 4.44 (-O- H ,1H), 7.71 (-C H 3 , 3H));

[0030] HRMS calculated value: C9H9O2N(M+H) + : 164.18, measured value: 164.07.

[0031] (2) Take a dry and clean Shrek bottle, and add intermediate product a (0.85 g, 5.2 mmol), ZrCl4 (0.61 g, 2.6 mmol), and dichloromethane (20 mL) under a nitrogen atmosphere. Stir the reaction mixture overnight at room temperature. After the reaction is complete, filter, wash three times with dichloromethane and pentane, and dry in a vacuum drying oven to obtain the final product b, which is the benzoxazolino-ol metal complex (e.g., Figure 1 As shown), the yield was 85% (NMR spectrum shown). Figure 4 Its structural characterization data are as follows:

[0032] 1 H NMR (400 MHz, CDCl3) δ 7.35 (d, Ar-H , 2H), 7.12 (ddd, Ar-H , 2H), 7.02(ddd, Ar-H , 4H), 4.47 (q, -CH,2H), 1.56 (d, -CH 3 , 6H).

[0033] Application Example 1

[0034] Catalyst preparation:

[0035] Weigh 32.4 mg of benzoxazolin-ol metal complex in a glove box and dissolve it in 10 ml of toluene to obtain the main catalyst solution. Take 6 mL of 1 mol / L methylaluminoxane (MAO) / toluene solution (purchased from Grace Trading (Shanghai) Co., Ltd.) as a co-catalyst. The molar ratio of aluminum in the co-catalyst to zirconium in the main catalyst is 300:1.

[0036] Validation of catalyst performance:

[0037] A 250 ml flask equipped with a magnetic stirrer was connected to a double-row pipeline. The air in the reaction flask was removed by evacuation and replaced with high-purity nitrogen 3-4 times. 60 g of 1-decene reaction raw material was added, and the temperature was raised to 80℃. After 10 min, the co-catalyst MAO / toluene solution and the main catalyst solution were added. After reacting for 1 h, 10 ml of hydrochloric acid-ethanol solution (hydrochloric acid:ethanol volume ratio of 1:9) was injected into the flask to terminate the reaction. The flask was washed three times with water, and its composition was analyzed by chromatography. The results are shown in Table 1.

[0038] Application Example 2

[0039] Same as Application Example 1, except that the reaction temperature is 100℃. The data results are shown in Table 1.

[0040] Application Example 3

[0041] Same as Application Example 1, except that the reaction temperature is 120°C. The data results are shown in Table 1.

[0042] Application Comparative Example 1

[0043] Similar to Application Example 1, except that the catalyst used was bis(isopropylcyclopentadiene)zirconium dichloride. The data results are shown in Table 1.

[0044] Application Comparative Example 2

[0045] Similar to Application Example 2, except that the catalyst used is bis(isopropylcyclopentadiene)zirconium dichloride. The data results are shown in Table 1.

[0046] Application Comparative Example 3

[0047] Similar to Application Example 3, except that the catalyst used was bis(isopropylcyclopentadiene)zirconium dichloride. The data results are shown in Table 1.

[0048] Application Example 4

[0049] Similar to Application Example 1, except that the reaction raw materials are 30g of 1-decene and 30g of 1-octene. The data results are shown in Table 2.

[0050] Application Example 5

[0051] Similar to Application Example 1, except that the reaction raw materials are 30g of 1-decene and 30g of 1-dodecene. The data results are shown in Table 2.

[0052] Application Example 6

[0053] Similar to Application Example 1, except that the reaction raw materials are 20g of 1-octene, 20g of 1-decene and 20g of 1-dodecene. The data results are shown in Table 2.

[0054] Application Comparative Example 4

[0055] Similar to Application Example 4, except that the catalyst used was bis(isopropylcyclopentadiene)zirconium dichloride. The data results are shown in Table 2.

[0056] Application Comparative Example 5

[0057] Similar to Application Example 5, except that the catalyst used was bis(isopropylcyclopentadiene)zirconium dichloride. The data results are shown in Table 2.

[0058] Application Comparative Example 6

[0059] Similar to Application Example 6, except that the catalyst used was bis(isopropylcyclopentadiene)zirconium dichloride. The data results are shown in Table 2.

[0060] Table 1. Composition, viscosity, and pour point analysis of polymer products obtained from Application Examples 1-3 and Comparative Examples 1-3.

[0061]

[0062] As shown in Table 1, compared with the bis(isopropylcyclopentadiene)zirconium dichloride catalyst, the products obtained by preparing polyα-olefins using the benzoxazoline-alcohol metal complex catalyst all exhibited low viscosity and yields exceeding 80%. The products were predominantly C30 and C40, with very few high-polymer products of C50 and above, resulting in low kinematic viscosity and pour point. Compared with Comparative Example 1, the product from Example 1 not only had lower viscosity and a higher viscosity index, but also a higher yield and a lower pour point. Furthermore, increasing the temperature was beneficial in reducing kinematic viscosity and pour point.

[0063] The introduction of the benzoxazolin-ol macroligand increases the steric hindrance of the metallocene catalyst, similar to a confinement effect, which is beneficial for improving catalyst activity and the directed synthesis of oligomers (>C20), thus increasing yield. Furthermore, while traditional catalysts for synthesizing low-viscosity PAO (bis(isopropylcyclopentadiene)zirconium dichloride) possess high catalytic activity and the ability to catalyze the formation of low-viscosity PAO, their thermal stability is poor. These catalysts rely solely on the interaction between the central metal and cyclopentadiene, and are prone to disintegration and deactivation at elevated temperatures. Additionally, when hydrogen atoms in the ortho-alkyl substituents approach the central metal, a non-junction effect occurs, leading to hydrogen trapping and deactivation of the active species. This catalyst utilizes a sterically hindered benzoxazolin-ol structure to impede the rotation of the N-aryl NC bond axis, thereby improving thermal stability. The macrocyclic organic framework within the structure also provides significant protection for the active center.

[0064] Table 2. Composition, viscosity, and pour point analysis of polymer products obtained in Application Examples 4-6 and Comparative Examples 4-6.

[0065]

[0066] As can be seen from the data in Table 2, the products obtained by preparing poly-α-olefins using benzoxazolin-ol metal complex catalysts with different raw materials have higher effective product yields for C30-C50 compared with those obtained by the classic non-bridged metallocene catalyst bis(isopropylcyclopentadiene)zirconium dichloride. Furthermore, the products have lower kinematic viscosity and lower pour point at 100℃.

[0067] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made within the scope of the claims of the present invention should be included in the scope of the present invention.

Claims

1. A catalyst for use in the synthesis of low viscosity polyalphaolefins, characterized in that, The catalyst comprises a main catalyst and a cocatalyst; The structural formula of the main catalyst is: ； M is Ti, Zr, Hf or Fe; X is chlorine or bromine.

2. The catalyst of claim 1, wherein: The cocatalyst is organic boron or alkyl aluminum oxide.

3. The catalyst of claim 2, wherein: The organic boron is one or several of [Ph3C][B(C6F5)4], [PhMe2NH][B(C6F5)4] and B(C6F5)3; the alkyl aluminum oxide is one or several of methyl aluminum oxide, ethyl aluminum oxide, n-propyl aluminum oxide and n-butyl aluminum oxide.

4. The catalyst of claim 3, wherein: The molar ratio of aluminum in the alkyl aluminum oxide to the metal in the main catalyst is 10-1000:1; the molar ratio of boron in the organic boron to the metal in the main catalyst is 1-300:

1.

5. Use of a catalyst according to any one of claims 1 to 4 for the synthesis of low viscosity polyalphaolefins, characterized in that: An α-olefin is used as a raw material, and a catalyst is added to perform a polymerization reaction.

6. Use according to claim 5, characterized in that: The α-olefin is one or a mixture of several of 1-octene, 1-nonene, 1-decene, 1-undecene, 1-dodecene, 1-tridecene and 1-tetradecene.

7. Use according to claim 5, characterized in that: The polymerization reaction temperature is 50-140 ℃, and the main catalyst in the catalyst is dissolved in one of n-hexane, cyclohexane, methylcyclohexane and toluene.

Images