Method for preparing C12 olefin through propylene tetramerization

Abstract

The invention belongs to the field of propylene oligomerization catalysis, and discloses a method for preparing C12 olefin by tetramerization of propylene, which comprises the following steps: carrying out oligomerization reaction on propylene by using a solid acid regulated supported sulfate catalyst, then separating light components C6 and C9 olefin, and carrying out co-oligomerization on the light components C6 and C9 olefin and propylene through reflux to generate C12 olefin, the conversion rate of propylene is 99.5%, and the total yield of C12 olefin is 75%. According to the method, low-value olefin is converted into high-value C12 olefin, the economic value of the whole process is greatly improved, and in addition, the conversion rate of propylene and the stability of the catalyst are also effectively improved through modification of the solid acid on the supported sulfate catalyst. The reaction is environment-friendly, mild in condition and high in raw material utilization rate, and has a relatively good industrial application prospect.

Description

Technical Field

[0001] This invention belongs to the field of propylene oligomerization catalysis and relates to a method for the tetramerization of propylene to produce dodecylene. Background Technology

[0002] C16 dodecylene is a highly reactive organic chemical raw material with significant applications in several key industrial sectors, including detergents, lubricants, and polymers, due to its abundant chemical conversion potential. With the continuous advancement of green chemistry and biomanufacturing technologies, the uses of C16 dodecylene are expanding towards sustainable energy and materials, and future market demand is expected to grow steadily.

[0003] In industrial applications, dodecylene is a key raw material for the preparation of linear alkylbenzene (LAB). Sulfonation of LAB yields sodium linear alkylbenzene sulfonate (LAS), a mainstream anionic surfactant widely used in laundry detergents, shampoos, and other daily chemical products, holding a major share of the global surfactant market. Furthermore, polyalphaolefin (PAO) lubricants synthesized from 1-dodecene possess excellent high and low temperature stability, oxidation resistance, and thermal stability, and are widely used in aero-engines, high-end automotive lubricants, and industrial gear oils, effectively reducing equipment wear and extending oil change intervals. These lubricant additives can also significantly improve the viscosity index and anti-wear properties of oils, meeting lubrication requirements under extreme operating conditions. In the polymer field, dodecylene can be used as a comonomer to improve the properties of polyethylene (PE) and polypropylene (PP), enhancing the materials' flexibility, impact resistance, and processing flowability, making it suitable for food packaging films, medical devices, and automotive interior products. Meanwhile, C16 dodecenes can be derived into dodecenyl succinic anhydride (DOSA), used as an epoxy resin curing agent and coating additive, enhancing coating adhesion and chemical corrosion resistance, making it suitable for marine corrosion protection, industrial coatings, and electronic packaging materials. In the energy sector, high-purity C16 dodecenes can be used as aviation fuel additives, improving combustion efficiency, reducing carbon deposit formation, and decreasing emissions of pollutants such as nitrogen oxides, contributing to the aviation industry's energy conservation and carbon reduction goals. Furthermore, C16 dodecenes are also important raw materials for the synthesis of dodecyl mercaptan (used as a rubber polymerization regulator) and dodecylphenol (used as an antioxidant and surfactant intermediate). Therefore, developing cost-effective and large-scale production methods for C16 dodecenes is of paramount practical significance. Currently, with the widespread application of propane dehydrogenation and coal-to-olefins technologies in China, propylene production capacity has increased significantly. How to convert propylene into high-value-added fine chemical products such as high-carbon olefins has become crucial for enhancing industrial competitiveness. Developing selective polymerization technology for propylene to prepare C16 dodecenes is of paramount importance for increasing the added value of low-chain olefins, achieving the domestic production of C16 dodecenes, and overcoming technical challenges in the fields of new materials and fine chemicals.

[0004] Currently, the propylene oligomerization technologies widely used in industry each have their own characteristics, but also corresponding technical bottlenecks. The SPAC process uses phosphoric acid-diatomaceous earth as a catalyst, has a simple process flow and good raw material adaptability, but the catalyst life is relatively short, and the amount of water injected during the reaction must be precisely controlled. If the moisture content is not properly controlled, the catalyst is prone to mudding and agglomeration, leading to deactivation and potentially clogging pipelines and corroding equipment. The MOGD process uses zeolite molecular sieve catalysts, avoiding the water injection problem, but these catalysts are prone to deactivation due to carbon buildup during the reaction, especially impurities such as dienes in the raw materials, which significantly accelerate this process. The Difasol process uses a nickel complex catalyst system based on ionic liquids. This catalyst has good stability and is easy to separate, but its industrial application faces challenges: the reaction requires large-scale equipment, and the post-processing of the product is complex, requiring multiple separation steps such as ammonia washing, alkali washing, and water washing, resulting in high overall investment and operating costs, thus preventing large-scale production. Domestic research and industrialization have also made positive progress. A two-stage superposition process has been innovatively developed. This technology first converts propylene into products such as nonene in a reactor equipped with a solid phosphoric acid catalyst. Then, a portion of the nonene and propylene are further reacted in a second reactor equipped with a solid superacid catalyst. This allows for flexible adjustment of the nonene to dodecene production ratio to meet different downstream market demands and for applications in high-end lubricant additives. Overall, existing mainstream propylene oligomerization technologies still face challenges in terms of catalyst life, selectivity, and economics.

[0005] Chinese patent CN106732700A relates to a method for preparing a catalyst by loading phosphotungsten molybdenum oxide active components onto a TiO2 support using an in-situ sol-gel method. This method has advantages such as high catalytic activity and good stability in propylene oligomerization. However, its preparation process is complex and the reaction temperature is high, which brings difficulties and challenges to its industrial application.

[0006] Chinese patent CN120040256A provides a catalyst for perfluorosulfonic acid supported on silica, which has the advantages of mild reaction conditions and good selectivity. However, it has the disadvantage of poor catalyst stability. After reuse, the conversion rate and selectivity decrease significantly, making it unsuitable for long-term use.

[0007] Chinese patent CN109908944B discloses a catalyst in which molecular sieves are loaded onto an alumina support on a supported catalyst, forming a core-shell structure of alumina encapsulated by molecular sieves. Although it exhibits good activity and selectivity in propylene oligomerization, it still fails to solve the drawbacks of easy clogging of molecular sieve channels and poor catalyst stability. Overall, the propylene oligomerization process still suffers from problems such as low reaction efficiency, uncontrollable reaction, harsh reaction conditions, and easy catalyst deactivation.

[0008] Chinese patent CN117258808A uses a catalyst in which nickel sulfate is supported on alumina and then impregnated with nitrate. It has the advantages of simple catalyst preparation, good catalyst stability and high conversion rate, but the limited C12 selectivity of its product affects its economic value.

[0009] Chinese patent CN114555544A provides a method for preparing a catalyst containing crystalline molecular sieves and a catalyst containing phosphoric acid. Under the reaction conditions, low-branched propylene oligomers can be obtained with high selectivity. Although the lifespan of the catalyst is extended by using a molecular sieve catalyst (zeolite catalyst) with a long service life, the problems of phosphoric acid component mudding and loss and difficulty in catalyst regeneration still exist.

[0010] In summary, due to limitations in the reaction mechanism, it is difficult to improve the selectivity of propylene oligomerization for the single-pass preparation of C12 olefins. Improving the reaction process to increase the overall yield of C12 is feasible in current research, and has significant economic benefits and industrial application value. Summary of the Invention

[0011] The purpose of this invention is to overcome the limitations of the propylene oligomerization reaction mechanism and provide a solid acid-modified supported sulfate catalyst that catalyzes the oligomerization reaction of high-pressure liquid propylene with C6 and C9 olefins separated and refluxed after the reaction in a fixed-bed reactor, thereby significantly improving the yield of C12 olefins. It has the advantages of high total C12 yield, long catalyst lifetime, and simple preparation method.

[0012] The technical solution of the present invention: A catalyst used in a method for the tetramerization of propylene to produce dodecylene is primarily composed of a sulfate structure supported on alumina, with the addition of a certain amount of solid acid to regulate the active sites. The introduction of solid acid not only increases the acidity of the active sites but also alters the electronic state of the metal species, thereby improving the selectivity of the product, dodecylene. The specific steps are as follows: Step 1: Dissolve alumina and sulfate in deionized water and stir evenly for 6-12 hours; remove free water by rotary evaporation to obtain sulfate precursor loaded on alumina; place the sulfate precursor loaded on alumina at 100-120°C. o Dry in a C oven for 6-12 hours, then in a tube furnace at 400-600°C. o Calcining at C for 2-4 hours yields sulfate supported on alumina; Step 2: Mix the sulfate supported on the alumina obtained in Step 1 with solid acid in deionized water and stir evenly for 6-12 hours; after removing free water by rotary evaporation, a solid acid-modified supported sulfate catalyst is obtained; place the solid acid-modified supported sulfate catalyst at 100-120°C. o Dry in a C oven for 6-12 hours, then in a tube furnace at 400-600°C.o Roast at 2-4 h under C to obtain a solid acid-modified supported sulfate catalyst; wherein, the mass ratio of the sulfate supported on alumina to the solid acid is 95:5-85:15; Step 3: React in a fixed-bed reactor. Using propylene as the raw material and a solid acid-modified supported sulfate catalyst, react at a temperature of 30-180 o °C, a pressure of 2-10 MPa, and a mass hourly space velocity of 0.5-15 h -1 under the conditions, carry out the propylene oligomerization reaction; after the product is separated by a rectification device, <C9 olefins are refluxed (reflux ratio is 0.5-2), and co-oligomerization reaction occurs with propylene, and the remaining >C9 olefin products are separated to obtain dodecene.

[0013] The sulfate is one of iron sulfate, cobalt sulfate, and nickel sulfate, and the molar ratio of the metal element in the sulfate to the aluminum element is between 0.5-1.5.

[0014] The solid acid is one of chromic acid, tungstic acid, vanadic acid, and molybdic acid, and the mass of the solid acid accounts for 5%-15% of the total mass of the solid acid-modified supported sulfate catalyst.

[0015] Advantages of the present invention: (1) A reflux device is added in the process of the present invention, which solves the problem of limited yield of C12 olefins in the single-pass conversion of propylene, thereby greatly improving the economic value of the overall process.

[0016] (2) The present invention uses a solid acid to modify the supported sulfate catalyst. The solid acid increases the acidity of the active center and changes the electronic state of the metal species, thereby enabling a higher yield of C12 olefins.

[0017] (3) The catalyst preparation method of the present invention is simple, inexpensive, and the performance remains stable after long-term reaction. Under relatively mild conditions, propylene is converted into C12 olefins with higher added value, and it can be widely applied in industrial production. Brief description of the drawings

[0018] Figure 1 is a process flow diagram for preparing dodecene by propylene oligomerization.

[0019] Figure 2 is the XRD pattern of tungstic acid-modified alumina-supported nickel sulfate catalyst.

[0020] Figure 3 is the stability test result of tungstic acid-modified alumina-supported nickel sulfate catalyst in the propylene oligomerization reaction. Specific embodiments

[0021] The following further illustrates the specific embodiments of the present invention in combination with the drawings and technical solutions.

[0022] Example 1: Preparation of Supported Sulfate Catalyst Weigh 10g of γ-Al₂O₃ and a certain amount of Fe₂(SO₄)₃·9H₂O and dissolve them in 200ml of deionized water, wherein the molar ratio of iron to aluminum is 1. Stir the mixture evenly at 1000-3000 rpm for 6 hours. Place the mixture on a rotary evaporator, evacuate it, and rotate it at 120 rpm. Slowly heat the mixture using a water bath, maintaining the water bath temperature at 70°C. o Continue at approximately 120°C until all the water has evaporated. Then place at 120°C. o The product was dried in a C oven for 12 hours to remove most of the remaining moisture. After being removed and ground into powder, it was placed in a tube furnace and heated at a flow rate of 40 mL / min for both oxygen and argon. o Heating to 500 C / min at a rate of C / min o The catalyst Fe2(SO4)3 / Al2O3 was obtained by maintaining the temperature at C for 2 hours.

[0023] The catalyst obtained above was compressed into tablets and sieved to obtain catalyst particles of 40-60 mesh. 3g of these catalyst particles were used in a single-pass oligomerization reaction of propylene at a reaction pressure of 3.0 MPa and a reaction temperature of 140°C. o C. Mass-time space velocity 1.0 h⁻¹ -1 .

[0024] Examples 2-3: The conditions were the same as in Example 1, except that the sulfate Fe2(SO4)3·9H2O was replaced with CoSO4·7H2O and NiSO4·6H2O, respectively, to obtain the catalysts CoSO4 / Al2O3 and NiSO4 / Al2O3.

[0025] Table 1 Effect of different sulfate catalyst compositions on propylene oligomerization yield

[0026] Examples 4-5: The conditions are the same as in Example 3, except that the molar ratio of nickel to aluminum is changed from 1 to 0.5 and 1.5 respectively.

[0027] Table 2 Effect of NiSO4 / Al2O3 catalyst composition with different nickel-aluminum ratios on propylene oligomerization yield

[0028] Example 6 A certain amount of chromic acid (H2CrO4) was weighed and mixed with the catalyst from Example 4 in 200 ml of deionized water, wherein the mass of chromic acid accounted for 5% of the total mass. The mixture was stirred uniformly at 1000-3000 rpm for 6 hours. The mixture was then placed on a rotary evaporator, evacuated, and rotated at 120 rpm. A water bath was used to slowly heat the mixture, maintaining the water bath temperature at 70°C. o Continue at approximately 120°C until all the water has evaporated. Then place at 120°C. o The product was dried in a C oven for 12 hours to remove most of the remaining moisture. After being removed and ground into powder, it was placed in a tube furnace and heated at a flow rate of 40 mL / min for both oxygen and argon. o Heating to 500 C / min at a rate of C / min o The catalyst NiSO4 / Al2O3(H2CrO4) was obtained by maintaining the temperature at C for 2 hours.

[0029] The catalyst obtained above was compressed into tablets and sieved to obtain catalyst particles of 40-60 mesh. 3g of these catalyst particles were used in a single-pass oligomerization reaction of propylene at a reaction pressure of 3.0 MPa and a reaction temperature of 140°C. o C. Mass-time space velocity 1.0 h⁻¹ -1 .

[0030] Examples 7-8: The conditions were the same as in Example 6, except that the added solid acid H2CrO4 was replaced with H2WO4 and H2MoO4, respectively, to obtain catalysts NiSO4 / Al2O3(H2WO4) and NiSO4 / Al2O3(H2MoO4). Table 3 Effect of NiSO4 / Al2O3 catalyst composition with different solid acid modifications on propylene oligomerization yield

[0031] Examples 9-10 The conditions are the same as in Example 7, except that the mass of the solid acid is changed from 5% to 10% and 15% of the total mass, respectively.

[0032] Table 4. Effect of different amounts of solid acid added on the NiSO4 / Al2O3 (H2WO4) catalyst on propylene oligomerization yield.

[0033] Example 11 Using the catalyst in Example 9, product reflux copolymerization was carried out. After the product of propylene copolymerization was separated by a distillation unit, the C6 and C9 olefins were refluxed back to the reactor. The propylene feed rate was adjusted so that C6, C9 and propylene underwent copolymerization reaction at a mass reflux ratio of 0.5. The remaining C12 and C15 olefins were separated as products.

[0034] Examples 12-13 The conditions are the same as in Example 11, except that the reflux ratio is changed from 0.5 to 1 and 1.5 respectively.

[0035] Table 5. Effect of reflux reaction at different reflux ratios on propylene oligomerization yield.

[0036] Example 14 The catalyst from Example 12 was subjected to a catalyst stability test under its reaction conditions, and the test results are as follows: Figure 3 As shown.

Claims

1. A method for the tetramerization of propylene to produce dodecylene, characterized in that, The steps are as follows: Step 1: Dissolve alumina and sulfate in deionized water and stir evenly for 6-12 hours; remove free water by rotary evaporation to obtain sulfate precursor loaded on alumina; place the sulfate precursor loaded on alumina at 100-120°C. o Dry in a C oven for 6-12 hours, then in a tube furnace at 400-600°C. o Calcining at C for 2-4 hours yields sulfate supported on alumina; Step 2: Mix the sulfate supported on the alumina obtained in Step 1 with solid acid in deionized water and stir evenly for 6-12 hours; after removing free water by rotary evaporation, a solid acid-modified supported sulfate catalyst is obtained; place the solid acid-modified supported sulfate catalyst at 100-120°C. o Dry in a C oven for 6-12 hours, then in a tube furnace at 400-600°C. o Calcination at C for 2-4 hours yields a solid acid-modified supported sulfate catalyst. Step 3: React in a fixed-bed reactor. Using propylene as a raw material, a solid acid-modified supported sulfate catalyst is employed, and the reaction is carried out at a temperature of 30 - 180 o °C, a pressure of 2 - 10 MPa, and a mass hourly space velocity of 0.5 - 15 h -1 . Under these conditions, an oligomerization reaction of propylene is carried out. After the product is separated by a distillation unit, the C9 olefins are refluxed and undergo a co-oligomerization reaction with propylene, and the remaining C9+ olefin products are separated to obtain dodecene.

2. The method for producing dodecylene from propylene tetramerization according to claim 1, characterized in that, The sulfate is one of ferric sulfate, cobalt sulfate, and nickel sulfate, and the molar ratio of the metal element to the aluminum element in the sulfate is between 0.5 and 1.

5.

3. The method for producing dodecylene from propylene tetramerization according to claim 1, characterized in that, The solid acid is one of chromic acid, tungstic acid, vanadic acid, and molybdic acid, wherein the mass of the solid acid accounts for 5%-15% of the total mass of the solid acid-modified supported sulfate catalyst.

4. The method for producing dodecylene from propylene tetramerization according to claim 1, characterized in that, The mass ratio of sulfate loaded on the alumina to solid acid is 95:5-85:

15.

5. The method for producing dodecylene from propylene tetramerization according to claim 1, characterized in that, The reflux ratio is 0.5-2.

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