Process for the production of dialkylnaphthalenes and use thereof

Abstract

The present invention relates to a method for producing dialkylnaphthalene and use of the dialkylnaphthalene in the production of heat transfer oil. The method for producing dialkylnaphthalene of the present invention comprises the following steps: 1) subjecting naphthalene to an alkylation reaction with an alkylating agent to obtain crude alkyl naphthalene, 2) subjecting the crude alkyl naphthalene to a disproportionation reaction to obtain a reaction product comprising dialkylnaphthalene, wherein the content of free naphthalene is each independently maintained at 0.5 wt% or more, based on the total weight of each reaction system, throughout the reaction process of step 1) and step 2). The heat transfer oil composition of the present invention has the advantages of low carbon residue and low kinematic viscosity.

Description

Technical Field

[0001] This invention relates to the field of heat transfer oil technology. More specifically, this invention relates to a method for manufacturing dialkylnaphthalene and the use of said dialkylnaphthalene in the manufacture of heat transfer oil. Background Technology

[0002] Diisopropylnaphthalene, as a new generation of synthetic high-temperature heat transfer oil, has the following characteristics: simple structure, high purity, colorless and odorless, making it suitable for the factory operating environment; low viscosity, superior to most L-QC 320 heat transfer oils, resulting in good pumpability, low resistance, excellent heat transfer effect, and rapid heating and cooling; an extremely low pour point of -46℃, ensuring good low-temperature start-up of the system and adaptability to cold northern climates, eliminating the need for additional heating in the heat transfer oil system; furthermore, its high flash point and auto-ignition point enhance safety. Therefore, diisopropylnaphthalene heat transfer oil has been widely used in petrochemical, chemical fiber printing and dyeing, and synthetic materials industries.

[0003] Carbon residue is an evaluation of the degree to which heat transfer oils form polymers. It is generally a mixture of polycyclic aromatic hydrocarbons (PAHs), gums, asphaltenes, and resins. The carbon residue value can roughly determine the coking tendency of the heat transfer oil during use. Combined with other indicators, it can determine the degree of refining of the heat transfer oil; a more refined heat transfer oil has a lower carbon residue value. When the content of gums, asphaltenes, and PAHs in the heat transfer oil is high, the carbon residue will increase, and the carbon will be harder. When the carbon residue mass fraction reaches 1.5%, a large amount of gum and coke will be deposited in the equipment, causing blockages. The heat transfer coefficient of coking differs greatly from that of metal, increasing energy consumption and making it impossible to maintain the required process temperature. Sometimes, it can also generate large temperature and pressure differences in the hot oil furnace, and in severe cases, it can cause bubbling and leakage in the furnace tubes, leading to accidents, thus requiring oil replacement. Therefore, the carbon residue content is one of the main factors affecting the physical properties of heat transfer oils, making the preparation of heat transfer oils with low carbon residue particularly important. Summary of the Invention

[0004] The inventors of this invention discovered that molecular sieve catalysts exhibit strong selectivity for the products, and that the content of polyisopropylnaphthalene and byproducts such as olefin oligomerization lead to an increase in carbon residue. To overcome the problem of high carbon residue in existing technologies, this invention provides a composition with thermal conductivity, its preparation method, and its application. This composition, used as a heat transfer oil, has the advantage of low carbon residue. This invention is based on this discovery. Existing technologies remove naphthalene as much as possible to shift the equilibrium to the left; this invention retains a portion of the naphthalene in the raw materials, which can effectively control the distribution of reaction products and reduce the amount of carbon residue in the product.

[0005] According to a first aspect of the present invention, a method for manufacturing dialkylnaphthalene is provided, comprising the following steps: 1) subjecting naphthalene to an alkylating agent (preferably propylene) for an alkylation reaction to obtain crude alkylnaphthalene (e.g., isopropylnaphthalene); 2) subjecting the crude alkylnaphthalene to a disproportionation reaction to obtain a reaction product containing dialkylnaphthalene, wherein throughout the entire reaction process in steps 1) and 2), the content of free naphthalene is maintained independently at 0.5% by weight or more (preferably maintained independently at 1-5% by weight) based on the total weight of each reaction system.

[0006] According to a second aspect of the present invention, a heat-conducting oil composition is provided, comprising isopropylnaphthalene, diisopropylnaphthalene, and triisopropylnaphthalene, wherein, based on 100% by weight of the total weight of the composition, let the content of triisopropylnaphthalene be X (in weight%), and let the content of isopropylnaphthalene be Y (in weight%), then the following relationship is simultaneously satisfied:

[0007] Relationship 1: 35% ≥ X + Y ≥ 2%, preferably 25% ≥ X + Y ≥ 5%.

[0008] Relationship 2: X = aY + b, where a is a value between 0.2 and 10, and b is a value between 0.5 and 5.

[0009] Technical effect

[0010] This invention discovers that naphthalene has the function of inhibiting the formation of residual carbon or residual carbon precursors. The alkylation unit can effectively inhibit propylene polymerization and improve the selectivity of isopropyl naphthalene by controlling the proportion of naphthalene, thus inhibiting residual carbon formation. Distillation separation controls the proportion of naphthalene to ensure the naphthalene content in the feed for the disproportionation reaction, thereby effectively inhibiting the formation of heavy components in the disproportionation reaction and ensuring that the residual carbon content in diisopropyl naphthalene heat transfer oil is controlled at an extremely low level. This invention controls the composition of the reaction feedstock, which affects the residual carbon value of the product. For naphthalene and propylene alkylation, increasing propylene conversion, inhibiting propylene polymerization, improving isopropyl naphthalene selectivity, and reducing polypropyl naphthalene selectivity help reduce the residual carbon content of isopropyl naphthalene and diisopropyl naphthalene. For the disproportionation reaction, introducing a small amount of naphthalene into the feedstock can inhibit the formation of triisopropyl naphthalene and even tetraisopropyl naphthalene, effectively reducing the residual carbon content of the diisopropyl naphthalene product. This product is more suitable for high-temperature heat transfer oils. Detailed Implementation

[0011] The specific embodiments of the present invention will be described in detail below. However, it should be noted that the scope of protection of the present invention is not limited to these specific embodiments, but is determined by the claims in the appendix.

[0012] All publications, patent applications, patents, and other references mentioned in this specification are incorporated herein by reference. Unless otherwise defined, all technical and scientific terms used in this specification have the meanings commonly understood by those skilled in the art. In case of conflict, the definitions in this specification shall prevail.

[0013] When this specification uses the prefixes “known to those skilled in the art,” “prior art,” or similar terms to derive materials, substances, methods, steps, apparatus, or components, the objects derived from such prefixes cover those commonly used in the art at the time of this application, but also include those that are not currently commonly used but will become generally recognized in the art as suitable for similar purposes.

[0014] In the context of this invention, all numerical values ​​of parameters (e.g., quantity or condition) should be understood to be modified by the term “about” in all cases, regardless of whether “about” actually appears before the numerical value.

[0015] In the context of this invention, the term "numerical value" includes both integers and decimals.

[0016] In the context of this invention, "substantially" means that deviations that are acceptable or reasonable to those skilled in the art are permitted, such as deviations within ±2%, ±1%, ±0.5%, or ±0.1%.

[0017] In the context of this invention, pore size, pore volume, and specific surface area (BET) were determined using an ASAP2600 surface analyzer (USA). Samples were degassed under vacuum at 400°C for 2 hours, followed by adsorption and desorption under liquid nitrogen conditions. Specific surface area was calculated using the BET method, and pore size was calculated using the BJH method.

[0018] In the context of this invention, the surface morphology was measured using a Philips XL-30 scanning electron microscope.

[0019] In the context of this invention, the crystal phase analysis was performed on a Bruker D8 Advance X-ray diffractometer. Instrument operating conditions: Cu target, Kα radiation source, graphite monochromator, tube voltage 40 kV, tube current 40 mA, scanning range 5°–50°, scanning speed 2° / min.

[0020] In the context of this invention, the Si, Al coordination environment employs a Bruker AMX 400MHz solid-state NMR.

[0021] In the context of this invention, the component content was determined by gas chromatography analysis, and the product analysis was performed using an HP6890 chromatography-mass spectrometry system 7890A-5795C.

[0022] In the context of this invention, the bromine index was analyzed using a Metrohm 917 Coulometer.

[0023] In the context of this invention, the method for testing grain size is as follows: observe the surface morphology of the grains using SEM, measure the grain size of 30 grains, and then calculate the average value.

[0024] In the context of this invention, the specific surface area is measured using a surface analyzer.

[0025] In the context of this invention, the method for measuring X-ray diffraction is an X-ray diffractometer.

[0026] In the context of this invention, the carbon residue value is obtained by testing according to the method of GB / T17144-1997.

[0027] In the context of this invention, the methods for measuring boiling range and boiling point are GB / T 616-2006 and GB / T 615-2006.

[0028] In the context of this invention, the pour point is determined by the method of GB / T3535-2006.

[0029] In the context of this invention, kinematic viscosity is measured by the method of GB / T265-1998.

[0030] In the context of this invention, the degradation rate is obtained by testing according to the method in GB / T 23800-2009. As described in section 4.1 of the national standard, the degradation rate is the sum of the mass fractions of high-boiling-point substances, low-boiling-point substances, gas-phase decomposition products, and non-evaporable products.

[0031] Unless otherwise specified, all percentages, parts, ratios, etc. mentioned in this instruction manual are based on weight, and the pressure is gauge pressure.

[0032] In the context of this invention, any two or more embodiments or aspects of this invention can be arbitrarily combined, and the resulting technical solutions are part of the original disclosure of this specification and also fall within the protection scope of this invention.

[0033] According to one embodiment of the present invention, a method for manufacturing dialkylnaphthalene is disclosed. According to the present invention, the dialkylnaphthalene is preferably diisopropylnaphthalene. The inventors of the present invention have discovered that the diisopropylnaphthalene manufactured by the present invention, through a coupled reaction of alkylation and alkyl transfer, combined with the inhibition of naphthalene-induced carbon residue formation, can produce a higher quality diisopropylnaphthalene for use in high-temperature heat transfer oils. The present invention effectively produces diisopropylnaphthalene heat transfer oils with lower carbon residue through the coupling of two reactions. This heat transfer oil also features low kinematic viscosity, low pour point, and good thermal stability.

[0034] According to one embodiment of the present invention, the manufacturing method includes step 1): subjecting naphthalene to an alkylating agent via an alkylating reaction to obtain crude alkylnaphthalene. According to the present invention, the alkylating agent can be any alkylating agent conventionally used in the art, specifically including at least one of methanol, isopropanol, and propylene, with propylene being preferred. According to the present invention, when propylene is used as the alkylating agent, the alkylnaphthalene is isopropylnaphthalene, that is, naphthalene with an isopropyl group.

[0035] According to one embodiment of the present invention, the molar ratio of naphthalene to the alkylating agent is 1-10 (preferably 2-10). The inventors of the present invention have discovered that an excessively low styrene-to-olefin ratio reduces the selectivity of isopropyl naphthalene, leading to excessive formation of polyisopropyl naphthalene, reducing propylene conversion, and resulting in an excessively high bromine index in the product. According to the present invention, the conversion rate of the alkylating agent is 99.9% or higher (preferably 99.95-99.99%).

[0036] The disproportionating feedstock is obtained by distillation separation, and the disproportionating feedstock contains a small amount of unseparated naphthalene and crude alkyl naphthalene. According to one embodiment of the present invention, based on 100% by weight of the total weight of the crude alkyl naphthalene, the content of alkyl naphthalene is 80% by weight or less (preferably 50% by weight or less), the content of dialkyl naphthalene is <7% by weight (preferably <6% by weight), and the balance is heavy components or impurities. The content of the small amount of naphthalene in the disproportionating feedstock is 0.5% by weight or more (preferably 5% > naphthalene > 1% by weight). The inventors of the present invention have found that retaining a small amount of naphthalene in the distillation fraction for subsequent disproportionation reaction can effectively suppress the formation of heavy components such as triisopropylnaphthalene in the disproportionation reaction. Excessive naphthalene will reduce the conversion rate of isopropylnaphthalene in the disproportionation reaction, which is not economical.

[0037] According to one embodiment of the present invention, the bromine index of the disproportionation feedstock is 0-100 mgBr / 100g (preferably 0-80 mgBr / 100g). The inventors of this invention have discovered that the product of the alkylation reaction has a low bromine index, and through the disproportionation reaction, the final bromine index of the diisopropylnaphthalene heat transfer oil can be further reduced to 0-50 mgBr / 100g (preferably 0-20 mgBr / 100g). This is mainly because trace amounts of unsaturated components undergo alkylation reactions with naphthalene in the system, transforming into saturated components, thereby reducing the bromine index of the product. The bromine index reflects the content of unsaturated components, which are prone to polymerization and the formation of char residue. The diisopropylnaphthalene heat transfer oil of this invention has an extremely low bromine index; therefore, the diisopropylnaphthalene obtained by this invention has an extremely low char residue.

[0038] According to one embodiment of the present invention, the operating conditions of the alkylation reaction further include: a reaction temperature of 120-250°C (preferably 150-200°C), a reaction pressure of 1-3.5 MPaG (preferably 2-3 MPaG), and a mass hourly space velocity (HHSV) of the alkylating agent of 0.05-3 h⁻¹. -1 (Preferred 0.1-1h) -1 ).

[0039] According to one embodiment of the invention, the alkylation reaction is carried out in the presence of an alkylation catalyst. According to the invention, the alkylation catalyst can be selected from catalysts conventionally used in the alkylation of naphthalene in the art, but preferably, the selectivity of the alkylation catalyst for polyalkyl naphthalene is less than 20% (preferably less than 15%). The inventors of the invention have found that larger zeolite channels and specific surface areas are beneficial to the occurrence of the alkylation reaction and the transport of product molecules. As a specific example, the alkylation catalyst preferably comprises a molecular sieve having twelve-membered ring channels and an optional binder. The molecular sieve having twelve-membered ring channels is preferably selected from at least one of Y-type molecular sieves and MCM-22 molecular sieves. More specifically, the Y-type molecular sieve, for example, has a silica-alumina molar ratio of 5-12, an average particle size of 10-500 nm, and a specific surface area >500 m². 2 / g. More specifically, the MCM-22 molecular sieve, for example, has a silica-alumina molar ratio of 15-40 and a specific surface area of ​​380-550 m². 2 / g. Specifically, at least one of refractory oxides can be cited as a binder, preferably selected from at least one of silica and alumina. Additionally, as an example, based on 100% by weight of the total weight of the alkylation catalyst, the content of the molecular sieve is 55-90% by weight, and the content of the binder is 10-45% by weight.

[0040] According to one embodiment of the present invention, the manufacturing method further includes refining the crude alkyl naphthalene, for example by distillation, before performing step 2) as described below, to separate and remove at least a portion (e.g., more than 90% by weight) of free naphthalene, thereby obtaining refined alkyl naphthalene. According to the present invention, the free naphthalene refers to the unreacted raw material naphthalene remaining after the alkylation reaction has ended. According to the present invention, the distillation is performed such that, for example, the content of free naphthalene is more than 0.5% by weight (preferably 1-5% by weight) based on 100% of the total weight of the refined alkyl naphthalene. To achieve this objective, the operating conditions of the distillation may include, for example, a column top temperature of 215-236°C, a column top pressure of 101-150 kPa, a reflux ratio of 0.5-5, and a theoretical plate number of 15-40, but the present invention is not limited thereto.

[0041] According to one embodiment of the present invention, the manufacturing method further includes step 2): subjecting the crude alkyl naphthalene (obviously also including the refined alkyl naphthalene described above in this specification) to a disproportionation reaction to obtain a reaction product containing dialkyl naphthalene.

[0042] According to one embodiment of the present invention, the disproportionation reaction can be carried out in any manner conventionally known in the art, for example, under operating conditions including: a reaction temperature of 150-280°C (preferably 170-230°C), a reaction pressure of 0.5-3 MPaG (preferably 0.5-2 MPaG), and a mass hourly space velocity of 0.1-10 h⁻¹. -1 (Preferred 0.5-3h) -1 ).

[0043] According to one embodiment of the invention, the disproportionation reaction can be carried out in the presence of a disproportionation catalyst. According to the invention, the disproportionation catalyst can be any catalyst conventionally used in the art for this purpose, specifically, for example, a solid acid catalyst. As the solid acid catalyst, specifically, at least one of 12-membered ring channel catalysts can be included, preferably at least one selected from organosilicon zeolite catalysts and Beta zeolite, more preferably an organosilicon zeolite catalyst.

[0044] According to one embodiment of the present invention, the Beta zeolite has a silica-alumina molar ratio of 20-50, an average particle size of 10-500 nm, and a specific surface area of ​​>400 m². 2 / g.

[0045] According to one embodiment of the present invention, the organosilicon zeolite catalyst comprises organosilicon microporous zeolite and optionally a binder. For example, based on 100% by weight of the total weight of the organosilicon zeolite catalyst, the content of the organosilicon microporous zeolite is 55-90% by weight, and the content of the binder is 10-45% by weight. Preferably, according to the present invention, the molar composition of the organosilicon microporous zeolite is: (1 / n)Al₂O₃:SiO₂:(m / n)R (where n = 15-50, m = 0.01-50, and R is C1-20 straight-chain or branched alkyl, C2-20 straight-chain or branched alkenyl, or C6-12 aryl). More preferably, the organosilicon zeolite has a layered structure with an average layer thickness of 0.7-10 nm. Furthermore, the specific surface area of ​​the organosilicon zeolite is preferably 380-550 m². 2 / g. According to a further preferred embodiment of the invention, the Si in the organosilicon microporous zeolite... 29 The NMR solid-state NMR spectrum contains at least one Si atom between -80 and +50 ppm. 29Nuclear magnetic resonance peaks. Additionally, preferably, the X-ray diffraction pattern of the organosilicon microporous zeolite exhibits maximum d-interval values ​​at 12.4±0.2, 10.5±0.3, 9.3±0.3, 6.8±0.2, 6.1±0.2, 5.5±0.2, 4.4±0.2, 4.0±0.2, 3.5±0.1, and 3.3±0.1 Å.

[0046] According to the present invention, throughout the entire reaction process of the manufacturing method, particularly at the end of step 1) or the beginning of step 2, the content of free naphthalene is essentially at its minimum. Based on the total weight of each reaction system, the content of free naphthalene is independently maintained at 0.5% by weight or more, preferably 1-5% by weight. The inventors of the present invention have found that excessive naphthalene will inhibit the disproportionation reaction of isopropyl naphthalene and reduce the formation of diisopropyl naphthalene, while excessively low or no naphthalene will lead to the formation of more triisopropyl naphthalene and will also cause an increase in the amount of residual carbon in the product. More preferably according to the present invention, before the disproportionation reaction in step 2) ends, the entire manufacturing method (including reaction steps and purification steps, etc.) meets the requirements of the present invention for the content of free naphthalene: that is, based on the total weight of each material system that may contain alkyl naphthalene and / or dialkyl naphthalene, the content of free naphthalene is independently maintained at 0.5% by weight or more, preferably 1-5% by weight.

[0047] According to one embodiment of the present invention, the manufacturing method further includes purifying the reaction product containing dialkylnaphthalene (e.g., distillation) to obtain a purified product. According to the present invention, this purification removes unwanted substances such as naphthalene from the reaction product as much as possible.

[0048] According to one embodiment of the present invention, the operating conditions for the distillation include: a column top temperature of 180-280°C, a column top pressure of 2-50 kPaA, a reflux ratio of 0.5-5, and a theoretical plate number of 15-40. According to the present invention, the purified product is obtained from the reboiler. Here, the purified product generally has a boiling range of 290°C or higher, preferably in the range of 290-340°C, and more preferably in the range of 295-320°C.

[0049] According to one embodiment of the present invention, the char residue of the refined product is not higher than 0.01% by weight (preferably 0.002-0.005% by weight). The inventors of the present invention have discovered that the char residue is related to the non-evaporable products in the deterioration rate; the higher the char residue, the greater the value of non-evaporable products.

[0050] According to one embodiment of the present invention, the bromine index of the refined product is <100 mgBr / 100g (preferably <80 mgBr / 100g). The inventors of the present invention have discovered that diisopropylnaphthalene heat transfer oil has both an extremely low bromine index and an extremely low carbon residue content.

[0051] According to one embodiment of the present invention, based on the total weight of the refined product as 100% by weight, the content of isopropylnaphthalene is 1-18% by weight (preferably 2-13% by weight), the content of diisopropylnaphthalene is 75-98% by weight (preferably 84-95% by weight), and the content of triisopropylnaphthalene is 1-15% by weight (preferably 3-12% by weight).

[0052] According to one embodiment of the present invention, when the refined product is used as a heat transfer oil composition, its degradation rate under conditions of 330°C and 720h is not greater than 5% (preferably not greater than 3%).

[0053] According to one embodiment of the present invention, the manufacturing method further includes recycling the naphthalene-containing material obtained by the refining process back to the alkylation reaction to achieve the recycling of naphthalene.

[0054] The inventors of this invention have discovered that the dialkylnaphthalene prepared by this method has a high proportion of 2,6-diisopropylnaphthalene, generally accounting for more than 34 wt% of the total dialkylnaphthalene, preferably more than 37 wt%, and is particularly useful for the separation and purification of 2,6-diisopropylnaphthalene. Therefore, according to one embodiment of the present invention, a method for manufacturing 2,6-diisopropylnaphthalene is provided, comprising the following steps: 1) manufacturing diisopropylnaphthalene using the manufacturing method described in any of the preceding claims of this specification; 2) isomerizing the diisopropylnaphthalene to obtain 2,6-diisopropylnaphthalene. Alternatively, according to one embodiment of the present invention, a method for manufacturing 2,6-naphthalenedicarboxylic acid is also provided, comprising the following steps: 1) manufacturing diisopropylnaphthalene using the manufacturing method described in any of the preceding claims of this specification; 2) isomerizing the diisopropylnaphthalene to obtain 2,6-diisopropylnaphthalene; 3) manufacturing 2,6-naphthalenedicarboxylic acid from 2,6-diisopropylnaphthalene. Alternatively, according to one embodiment of the present invention, a method for manufacturing a polyester is further disclosed, comprising the following steps: 1) manufacturing diisopropylnaphthalene by the manufacturing method described in any of the preceding claims of this specification; 2) isomerizing the diisopropylnaphthalene to obtain 2,6-diisopropylnaphthalene; 3) manufacturing 2,6-naphthalenedicarboxylic acid from 2,6-diisopropylnaphthalene; and 4) manufacturing a polyester from 2,6-naphthalenedicarboxylic acid. According to the present invention, the isomerization separation can be carried out in any manner conventionally known in the art, such as adsorption separation or crystallization separation, without particular limitation. According to the present invention, 2,6-naphthalenedicarboxylic acid can be manufactured from 2,6-diisopropylnaphthalene in any manner conventionally known in the art, such as catalytic oxidation reaction, without particular limitation. According to the present invention, polyesters, such as PEN, PBN, LCP, etc., can be manufactured from 2,6-naphthalenedicarboxylic acid in any manner conventionally known in the art, without particular limitation.

[0055] According to one embodiment of the present invention, a heat-conducting oil composition is disclosed, comprising isopropylnaphthalene, diisopropylnaphthalene, and triisopropylnaphthalene. According to the present invention, the diisopropylnaphthalene contained in the heat-conducting oil composition, or the heat-conducting oil composition itself, can be manufactured by the manufacturing method described above. The inventors of the present invention have discovered that the heat-conducting oil composition can be used alone for LQD-330 heat-conducting oil even without conventional heat-conducting oil additives (such as isopropyl biphenyl, substituted or unsubstituted terphenyl, etc.), which is a significant advantage of the present invention compared to the prior art.

[0056] According to one embodiment of the present invention, taking the total weight of the composition as 100% by weight, let the content of triisopropylnaphthalene be X (in weight%), and the content of isopropylnaphthalene be Y (in weight%), then the following relationship is simultaneously satisfied. The inventors of the present invention have discovered that if Y is too low, or if the proportion of Y is too low compared to X, it will lead to an increase in the kinematic viscosity of the heat transfer oil and an increase in the pour point. If Y is too high, the thermal stability at high temperatures will decrease. Therefore, if the content of X is too low, or if the proportion of Y is too low compared to Y, it will lead to an increase in the kinematic viscosity of the heat transfer oil and an increase in the pour point.

[0057] Relationship 1: 35% ≥ X + Y ≥ 2%, preferably 25% ≥ X + Y ≥ 5%.

[0058] Relationship 2: X = aY + b, where a is a value between 0.2 and 10, and b is a value between 0.5 and 5.

[0059] According to one embodiment of the present invention, based on the total weight of the composition as 100% by weight, the content of isopropylnaphthalene is 1-18% by weight (preferably 2-13% by weight), the content of diisopropylnaphthalene is 75-98% by weight (preferably 84-95% by weight), and the content of triisopropylnaphthalene is 1-15% by weight (preferably 3-12% by weight).

[0060] According to one embodiment of the present invention, the kinematic viscosity of the heat transfer oil composition at 0°C is less than 60 mm. 2 / s (preferably 30-50mm) 2 / s). The inventors of this invention have discovered that an excess of X or a higher proportion of X compared to Y leads to an increase in the kinematic viscosity of the heat transfer oil.

[0061] According to one embodiment of the present invention, the pour point of the heat transfer oil composition is -65 to -45°C (preferably -65°C to -55°C). The inventors of the present invention have discovered that an excessive amount of X, or a higher proportion of X compared to Y, leads to an increase in the pour point of the heat transfer oil.

[0062] According to the present invention, the heat transfer oil composition can be manufactured according to the method for manufacturing dialkylnaphthalene as described above in this specification. Furthermore, by adjusting the purification conditions of the reaction product containing dialkylnaphthalene, particularly adjusting the boiling range of the purified product, a heat transfer oil composition conforming to the present invention can be readily obtained. Therefore, it is preferred that the boiling range of the heat transfer oil composition (i.e., the purified product) is above 290°C (preferably in the range of 290-340°C, more preferably in the range of 295-320°C).

[0063] Example

[0064] The present invention will be further described in detail below with reference to examples and comparative examples, but the present invention is not limited to these examples.

[0065] Example 1

[0066] (1) Alkylation reaction of naphthalene and propylene: The alkylation catalyst contains MCM-22 molecular sieve (silicon-aluminum molar ratio 25, specific surface area 450m²). 2 The mixture consisted of MCM-22 molecular sieve (g) and alumina, with a weight ratio of 3:1 to alumina, a naphthalene molar ratio of 3:1, a temperature of 180℃, and a propylene mass hourly space velocity of 0.1 h⁻¹. -1 At a pressure of 2.8 MPa, the propylene conversion rate was 99.99%.

[0067] (2) The naphthalene in the alkylation product is separated and removed. The naphthalene content in the separated product is 2.5%, and the bromine index of the product is 46 mgBr / 100g.

[0068] (3) Disproportionation reaction: The catalyst for the disproportionation reaction is an organosilicon zeolite catalyst, which contains organosilicon microporous zeolite and alumina. The weight ratio of organosilicon microporous zeolite to alumina is 3:1. The organosilicon microporous zeolite selected is the organosilicon microporous zeolite in Example 2 of CN 101239726A. The temperature is 200℃ and the mass hourly space velocity is 0.5h. -1 Pressure 1 MPa.

[0069] (4) Distillation: Separate the components with a boiling range of 295-315℃.

[0070] The characterization results of the obtained products are listed in Table 1 and Table 2, respectively.

[0071] Example 2

[0072] 1) The alkylation reaction of naphthalene and propylene. The alkylation catalyst contains MCM-22 molecular sieve (silicon-to-aluminum molar ratio 25, specific surface area 450 m²). 2 The mixture consisted of MCM-22 molecular sieve (g) and alumina, with a weight ratio of 3:1 to alumina, a naphthalene molar ratio of 3:1, a temperature of 180℃, and a propylene mass hourly space velocity of 0.1 h⁻¹. -1 At a pressure of 2.8 MPaG, the conversion rate of propylene was 99.99%. In addition to the remaining naphthalene, the composition of the crude alkyl naphthalene product was 59.5% naphthalene, 36.3% isopropyl naphthalene, 4.1% diisopropyl naphthalene, and 0.1% triisopropyl naphthalene.

[0073] 2) Most of the naphthalene in the crude alkyl naphthalene product is separated and removed by distillation (top pressure 105 kPa, top temperature 218 °C). The naphthalene content in the purified alkyl naphthalene product after separation is 1.2%, and the bromine index is 59 mgBr / 100g.

[0074] 3) The refined alkylnaphthalene product was subjected to a disproportionation reaction. The catalyst for the disproportionation reaction was an organosilicon zeolite catalyst, which contained organosilicon microporous zeolite and alumina, with a weight ratio of organosilicon microporous zeolite to alumina of 3:1. The organosilicon microporous zeolite selected was the one from Example 2 of CN 101239726A. The disproportionation reaction was carried out at a temperature of 200°C and a mass hourly space velocity (HHSV) of 0.5 h⁻¹. -1 Pressure 1 MPaG.

[0075] 4) The component with a boiling range of 290-320℃ was separated by distillation (reduced pressure distillation, top pressure 10 kPaA, top temperature 165℃) as the purified dialkylnaphthalene product.

[0076] The characterization results of the obtained purified dialkylnaphthalene products are listed in Tables 1 and 2, respectively.

[0077] Example 3

[0078] (1) Alkylation reaction of naphthalene and propylene: The alkylation catalyst contains Y-type molecular sieve (silicon-to-aluminum molar ratio of 5, crystal size of 320 nm) and alumina. The weight ratio of Y-type molecular sieve to alumina is 4:1, the molar ratio of naphthalene to propylene is 4:1, the temperature is 150℃, and the propylene mass hourly space velocity is 0.2 h⁻¹. -1 At a pressure of 2.8 MPa, the conversion rate of propylene was 99.98%, and the bromine index of the product was 64 mgBr / 100g. The product contained 68.9% naphthalene, 28.7% isopropylnaphthalene, 2.36% diisopropylnaphthalene, and 0.04% triisopropylnaphthalene.

[0079] (2) Remove naphthalene from the alkylation product: the naphthalene content in the product after separation is 3.2%.

[0080] (3) Disproportionation reaction: The catalyst for the disproportionation reaction is Beta zeolite catalyst, which contains Beta zeolite and alumina. The weight ratio of Beta zeolite to alumina is 4:1. Commercially available Beta zeolite (silicon-alumina molar ratio 20) is selected. The temperature is 210℃ and the mass hourly space velocity is 0.5h⁻¹. -1 Pressure 1 MPa.

[0081] (4) Distillation: Separate the components with a boiling range of 295-315℃.

[0082] The characterization results of the obtained products are listed in Table 1 and Table 2, respectively.

[0083] Example 4

[0084] Same as Example 1, except that the alkylation reaction has a different benzene-to-olefin ratio, here the naphthalene-to-olefin molar ratio is 0.8:1.

[0085] The characterization results of the obtained products are listed in Table 1 and Table 2, respectively.

[0086] Example 5

[0087] Same as Example 1, except that the alkylation reaction has a different benzene-to-olefin ratio, here the naphthalene-to-olefin molar ratio is 10:1.

[0088] The characterization results of the obtained products are listed in Table 1 and Table 2, respectively.

[0089] Example 6

[0090] Same as Example 1, except that the alkylation reaction has a different benzene-to-olefin ratio, here the naphthalene-to-olefin molar ratio is 1.5:1.

[0091] The characterization results of the obtained products are listed in Table 1 and Table 2, respectively.

[0092] Example 7

[0093] Same as Example 1, except that the naphthalene content in the separated product in step two is 0.5%.

[0094] The characterization results of the obtained products are listed in Table 1 and Table 2, respectively.

[0095] Example 8

[0096] Same as Example 1, except that the naphthalene content in the separated product is 10% in step two.

[0097] The characterization results of the obtained products are listed in Table 1 and Table 2, respectively.

[0098] Example 9

[0099] Same as Example 1, except for the final distillation: the fraction with a boiling range of 295-330°C was obtained.

[0100] The characterization results of the obtained products are listed in Table 1 and Table 2, respectively.

[0101] Example 10

[0102] Same as Example 1, except for the final distillation: the fraction with a boiling range of 285-340°C was obtained.

[0103] The characterization results of the obtained products are listed in Table 1 and Table 2, respectively.

[0104] Comparative Example 1

[0105] Same as Example 1, except that the naphthalene content in the separated product in step two is 0.2%.

[0106] The characterization results of the obtained products are listed in Table 1 and Table 2, respectively.

[0107] Comparative Example 2

[0108] Same as Example 1, except that the alkylation reaction has a different benzene-to-olefin ratio, here the naphthalene-to-olefin molar ratio is 1:3.

[0109] The characterization results of the obtained products are listed in Table 1 and Table 2, respectively.

[0110] Comparative Example 3

[0111] (1) Alkylation reaction of naphthalene with propylene: Same as step 1 in Example 1.

[0112] (2) The product in the alkylation product is distilled to separate the components with a boiling range of 295-315℃.

[0113] The characterization results of the obtained products are listed in Table 1 and Table 2, respectively.

[0114] Comparative Example 4

[0115] Same as Example 1, except for the final distillation: the fraction with a boiling range of 295-360°C was obtained.

[0116] The characterization results of the obtained products are listed in Table 1 and Table 2, respectively.

[0117] Comparative Example 5

[0118] Same as Example 1, except for the final distillation: the fraction with a boiling range of 300-310°C was obtained.

[0119] The characterization results of the obtained products are listed in Table 1 and Table 2, respectively.

[0120] Comparative Example 6

[0121] Same as Example 1, except for the final distillation: the fraction with a boiling range of 270-295°C was obtained.

[0122] The characterization results of the obtained products are listed in Table 1 and Table 2, respectively.

[0123] Table 1

[0124]

[0125] Table 2

[0126]

[0127] As can be seen from the results in Tables 1 and 2, the thermally conductive composition of the present invention has the advantages of lower char residue, better flowability, and lower pour point.

Claims

1. A method for manufacturing a dialkylnaphthalene (preferably diisopropylnaphthalene), comprising the following steps: 1) Naphthalene is subjected to an alkylating agent (preferably propylene) to undergo an alkylation reaction to obtain crude alkyl naphthalene (e.g., isopropyl naphthalene). 2) The crude alkyl naphthalene is subjected to a disproportionation reaction to obtain a reaction product containing dialkyl naphthalene. Throughout the entire reaction process in steps 1) and 2), the content of free naphthalene is maintained independently at 0.5% by weight or more (preferably 1-5% by weight) based on the total weight of each reaction system.

2. The manufacturing method of claim 1, wherein before the disproportionation reaction is completed, throughout the entire manufacturing method, the content of free naphthalene is individually maintained at 0.5% by weight or more, preferably 1-5% by weight, based on the total weight of each material system that may contain alkylnaphthalene and / or dialkylnaphthalene.

3. The manufacturing method according to claim 1, wherein the bromine index of the crude alkyl naphthalene is 0-100 mgBr / 100g (preferably 0-80 mgBr / 100g).

4. The manufacturing method according to claim 1, wherein the molar ratio of naphthalene to the alkylating agent is 1-10 (preferably 2-10).

5. The manufacturing method of claim 1, wherein the alkylation reaction is carried out in the presence of an alkylation catalyst, the alkylation catalyst having a selectivity of less than 20% (preferably less than 15%) for polyalkylnaphthalenes.

6. The manufacturing method of claim 1 further includes, prior to step 2), refining the crude alkyl naphthalene (e.g., by distillation) to separate and remove at least a portion (e.g., more than 90% by weight) of the free naphthalene to obtain refined alkyl naphthalene.

7. The manufacturing method of claim 1 further includes purifying the reaction product containing dialkylnaphthalene (e.g., by distillation) to obtain a purified product.

8. A heat transfer oil composition comprising isopropylnaphthalene, diisopropylnaphthalene, and triisopropylnaphthalene, wherein, based on 100% by weight of the total composition, let the content of triisopropylnaphthalene be X (in weight%), and the content of isopropylnaphthalene be Y (in weight%), then the following relationship is simultaneously satisfied: Relationship 1: 35% ≥ X + Y ≥ 2% (preferably 25% ≥ X + Y ≥ 5%) Relationship 2: X = aY + b, where a is a value between 0.2 and 10, and b is a value between 0.5 and 5.

9. The composition of claim 8, wherein the char residue value is not higher than 0.01% by weight (preferably 0.002-0.005% by weight).

10. The composition of claim 8, wherein the bromine index is <100 mgBr / 100 g (preferably <80 mgBr / 100 g).

11. The composition of claim 8, wherein, based on 100% by weight of the total composition, the content of isopropylnaphthalene is 1-18% by weight (preferably 2-13% by weight), the content of diisopropylnaphthalene is 75-98% by weight (preferably 84-95% by weight), and the content of triisopropylnaphthalene is 1-15% by weight (preferably 3-12% by weight).

12. The composition of claim 8, wherein the kinematic viscosity at 0°C is less than 60 mmHg. 2 / s (preferably 30-50mm) 2 / s).

13. The composition of claim 8, wherein the pour point is -65 to -45°C (preferably -65°C to -55°C).

14. The composition of claim 8, wherein the degradation rate under conditions of 330°C and 720h is not greater than 5% (preferably not greater than 3%).

15. The composition of claim 8, wherein the diisopropylnaphthalene or the heat-conducting oil composition is manufactured by the manufacturing method of any one of claims 1-7.

16. The composition of claim 8 does not contain conventional heat transfer oil additives (such as isopropyl biphenyl, substituted or unsubstituted terphenyl, etc.).

17. A method for manufacturing 2,6-diisopropylnaphthalene, comprising the following steps: 1) To manufacture diisopropylnaphthalene by the manufacturing method according to any one of claims 1-7. 2) The diisopropylnaphthalene was isomerized to obtain 2,6-diisopropylnaphthalene.

18. A method for manufacturing 2,6-naphthalenedicarboxylic acid, comprising the following steps: 1) To manufacture diisopropylnaphthalene by the manufacturing method according to any one of claims 1-7. 2) Isomerization separation of the diisopropylnaphthalene yields 2,6-diisopropylnaphthalene. 3) Production of 2,6-naphthalenedicarboxylic acid from 2,6-diisopropylnaphthalene.

19. A method for manufacturing polyester, comprising the following steps: 1) Manufacturing diisopropylnaphthalene by the manufacturing method according to any one of claims 1-7; 2) Isomerizing the diisopropylnaphthalene to obtain 2,6-diisopropylnaphthalene. 3) Production of 2,6-naphthalenedicarboxylic acid from 2,6-diisopropylnaphthalene. 4) Polyesters are produced from 2,6-naphthalenedicarboxylic acid.

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