A method for preparing high-purity heptane

Abstract

The present invention belongs to the technical field of high-purity n-heptane preparation, and specifically relates to a method for preparing high-purity heptane. The preparation method comprises the following steps: (1) preparing an adsorbent; (2) raw naphtha enters a hydrorefining reactor to undergo desulfurization, olefin saturation and other refining reactions to obtain refined naphtha; (3) the refined naphtha enters an adsorption tower containing the adsorbent prepared in step (1) to undergo adsorption separation and desorption to obtain desorbed oil; (4) using the desorbed oil as a raw material, separating high-purity n-heptane and high-purity n-hexane through a distillation device. The high-purity n-heptane prepared by the method of the present invention has a purity of ≥99.5% and a high yield.

Description

Technical Field

[0001] The invention belongs to the technical field of high-purity n-heptane preparation, and particularly relates to a method for preparing high-purity heptane. Background Art

[0002] n-Heptane is a straight-chain saturated alkane with the chemical formula , one of the various isomers of heptane. As an important organic solvent and chemical raw material, n-heptane is widely used in pharmaceuticals, coatings, paints, and fine chemicals. Its purity directly impacts the quality and performance of the final product. Currently, the purity of n-heptane available on the market is typically above 90%. However, with industrial development and technological advancements, the purity requirement for n-heptane has risen to over 99.5% for certain high-end applications, such as electronic-grade chemicals and specialized analytical reagents, and demand is becoming increasingly urgent.

[0003] Chinese patent CN107586250B discloses a method for producing high-purity n-hexane and high-purity n-heptane using naphtha adsorption separation desorption oil as the raw material. The method processes the naphtha adsorption separation desorption oil through distillation to produce a high-purity n-hexane solvent product with a purity >99% and a high-purity n-heptane solvent product with a purity >99%, with recovery yields of >80% and >78%, respectively. The naphtha adsorption separation desorption oil used in this method is derived from naphtha that has been pretreated with hydrogenation and then separated by adsorption over a 5A molecular sieve to produce a desorption oil rich in n-alkanes. In practice, it has been found that the n-alkanes in the desorption oil obtained by adsorption separation over a 5A molecular sieve are not stable, especially when the n-alkanes are low, and the n-heptane purity cannot reach 99.5%, and the yield of this method is also unsatisfactory. Summary of the Invention

[0004] The present invention aims to provide a method for preparing high-purity heptane, which uses a specific adsorbent to separate and absorb a desorbed oil with a high content of normal alkanes, and then produces normal heptane with a purity of ≥99.5% through a continuous distillation process, while also improving the yield.

[0005] In order to achieve the above object, the present invention provides the following technical solutions:

[0006] A method for preparing high-purity heptane comprises the following steps:

[0007] (1) Preparing an adsorbent, comprising the following steps:

[0008] S1: Mixing HY molecular sieve and MCM-41 molecular sieve to obtain a mixed molecular sieve;

[0009] S2: immersing the mixed molecular sieve in hydrochloric acid, stirring, filtering, and calcining the solid to obtain a calcined molecular sieve;

[0010] S3: completely immerse the calcined molecular sieve in a toluene solution of hexamethyldisilazane, reflux, filter, wash the solid, and vacuum dry to obtain a passivated molecular sieve;

[0011] S4: completely immerse the passivated molecular sieve in an ethanol solution of nitrobenzoic acid, stir, filter, and heat the solid under a nitrogen atmosphere to obtain a nitrophenyl group-bonded molecular sieve;

[0012] S5: completely immersing the nitrophenyl group-bonded molecular sieve in an aqueous solution of magnesium nitrate, shaking, filtering, and calcining the solid to obtain a molecular sieve loaded with metal oxide;

[0013] S6: degassing the metal oxide-loaded molecular sieve in a nitrogen atmosphere to obtain an adsorbent;

[0014] (2) The raw naphtha enters the hydrotreating reactor and undergoes a refining reaction to obtain refined naphtha;

[0015] (3) The refined naphtha enters an adsorption tower containing the adsorbent prepared in step (1) for adsorption separation and desorption to obtain desorbed oil;

[0016] (4) Using the desorbed oil as a raw material, high-purity n-heptane and high-purity n-hexane are separated by a distillation device; the distillation device comprises two distillation towers connected in sequence, namely a hexane distillation tower and a heptane distillation tower, wherein high-purity n-hexane is cut out from the top of the hexane distillation tower, and high-purity n-heptane is cut out from the top of the heptane distillation tower.

[0017] The present invention obtains a mesoporous-microporous composite molecular sieve by mixing HY molecular sieve and MCM-41 molecular sieve in a specific ratio, which has both macroporous diffusion channels and microporous selective adsorption sites. The pores are first activated by calcination and the template is removed. Then, the silane groups cover the acid sites on the surface of the molecular sieve to reduce the adsorption of n-heptane by passivating the acid sites. Then, the nitrophenyl groups are anchored on the surface of the molecular sieve through hydrogen bonds, and π-electron acceptor groups are introduced to enhance the adsorption of aromatic hydrocarbons. Finally, It is loaded on the surface of the molecular sieve through ion exchange, and magnesium oxide nanoparticles are generated after calcination and loaded on the molecular sieve. The alkaline surface of MgO and the methyl groups of the branched isomers interact strongly with each other through van der Waals forces, which can selectively adsorb the branched isomers while rejecting straight-chain n-heptane.

[0018] The weight ratio of HY molecular sieve to MCM-41 molecular sieve is (2-3):1.

[0019] The present invention can improve the purity and yield of n-heptane by using two molecular sieves in a specific ratio. This is mainly because the pore size of the MCM-41 mesopore allows branched isomers and aromatic hydrocarbons to diffuse quickly into the HY microporous area, avoiding the low adsorption efficiency of traditional microporous molecular sieves due to large diffusion resistance. The straight-chain molecules of n-heptane need to extend their conformation in the micropores, resulting in entropy reduction, while branched isomers are easier to enter due to their compact structure. Microporous screening intercepts some branched isomers, and the MCM-41 molecular sieve captures large molecular aromatic hydrocarbons: n-heptane is repelled by spatial steric hindrance in the pores, enhancing the adsorption of branched isomers. Through the optimized design of the mixing ratio (2-3):1, sufficient microporous adsorption sites are ensured to cover the main impurities.

[0020] Preferably, in S2, the stirring temperature and time are 80-85°C and 4-6h; in S3, the reflux temperature and time are 120-130°C and 12-15h; in S4, the stirring temperature and time are 60-65°C and 8-10h; in S4, the heating temperature and time are 300-320°C and 2-4h; in S5, the oscillation time is 4-6h.

[0021] Preferably, in step (2), the refining reaction uses a hydrorefining catalyst, and the refining reaction conditions are: pressure 1.7-2.3 MPa, temperature 240-260°C.

[0022] Preferably, in step (3), the adsorption pressure is 0.5-1.0 MPa, the desorption pressure is 0.5-1.0 MPa; the adsorption temperature is 250-320°C, the desorption temperature is 250-320°C; the adsorption time is 20-30 minutes, and the desorption time is 20-30 minutes.

[0023] Preferably, in step (4), the operating temperature of the hexane distillation tower is: the top temperature is 67°C, the bottom temperature is 128°C, and the operating pressure is 0.05 MPa; and the operating temperature of the heptane distillation tower is: the top temperature is 97°C, the bottom temperature is 145°C, and the operating pressure is 0.05 MPa.

[0024] Preferably, in the desorbed oil in step (4), the mass content of normal paraffins is ≥99.5%, the mass content of sulfur is ≤0.5 ppm, the mass content of nitrogen is ≤0.5 ppm, the bromine index is ≤5 mgBr / 100 g, and the mass content of aromatics is ≤10 ppm.

[0025] Preferably, in step (4), the middle part of each distillation tower is fed, and the bottom material of the previous tower is the feed for the next tower.

[0026] Preferably, in step (4), the reflux ratio of the hexane distillation tower is 3-4, the theoretical plates are 70, and the processing load is 4.6 L / h; the reflux ratio of the heptane distillation tower is 3-5, the theoretical plates are 80, and the processing load is 4.0 L / h.

[0027] Preferably, the hydrotreating catalyst used in the hydrotreating reaction in step (2) is Ø2.0×2-8mm clover particles with a specific surface area of ​​≥150m 2 / g, bulk density 0.72-0.82g / cm 3 , radial compressive strength ≥150N / cm.

[0028] Preferably, the purity of the high-purity n-heptane obtained in step (4) is ≥99.5%, and the yield of high-purity n-heptane is ≥20%.

[0029] The lower reflux ratio used in the present invention can produce high-purity n-heptane. Under the premise of ensuring product quality, the energy consumption is reduced by lowering the reflux ratio, thereby achieving the goal of energy conservation and emission reduction.

[0030] Compared with the prior art, the advantages and beneficial effects of the present invention are:

[0031] 1. This invention utilizes a modified mixture of HY and MCM-41 molecular sieves in a specific ratio to produce an adsorbent that improves the purity and yield of n-heptane. The purity of high-purity n-heptane is ≥99.5%, and the yield is ≥20%. The resulting high-quality product can meet the needs of high-end applications. The purity and yield of n-hexane are also improved.

[0032] 2. Compared with the prior art, the present invention uses a lower reflux ratio to produce high-purity n-heptane. While ensuring product quality, the lower reflux ratio reduces energy consumption and achieves the goal of energy conservation and emission reduction. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 The present invention is a flow chart of a method for preparing high-purity heptane. DETAILED DESCRIPTION

[0034] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0035] The raw materials used in the following examples of the present invention are all commercially available commodities:

[0036] HY molecular sieve, Aos Catalytic Materials (Dalian) Co., Ltd., pore size 0.74nm, grain size 0.5-10μm.

[0037] MCM-41 molecular sieve, Aos Catalytic Materials (Dalian) Co., Ltd., pore size 2-5nm, grain size 1-10μm.

[0038] Clover particles: diameter 2.0mm, length 2-8mm, specific surface area 150~200m 2 / g, bulk density 0.80g / cm 3 , radial compressive strength 150~200N / cm.

[0039] Example 1

[0040] This embodiment provides a method for preparing high-purity heptane, comprising the following steps:

[0041] (1) Preparing an adsorbent, comprising the following steps:

[0042] S1: Mixing HY molecular sieve and MCM-41 molecular sieve in a weight ratio of 2.5:1 to obtain a mixed molecular sieve;

[0043] S2: The mixed molecular sieve was completely immersed in 1.1 mol / L hydrochloric acid, stirred at 82°C for 5 h, filtered, and the solid was calcined at 560°C for 7 h to obtain a calcined molecular sieve;

[0044] S3: The calcined molecular sieve was completely immersed in a toluene solution of hexamethyldisilazane with a concentration of 13 wt%, refluxed at 125°C for 14 h, filtered, and the solid was washed with toluene and ethanol in sequence, and vacuum dried to obtain a passivated molecular sieve;

[0045] S4: The passivated molecular sieve was completely immersed in a 6 wt% nitrobenzoic acid ethanol solution, stirred at 62 ° C for 9 h, filtered, and the solid was heated at 310 ° C for 3 h under a nitrogen atmosphere to obtain a nitrophenyl group bonded molecular sieve;

[0046] S5: The nitrophenyl group-bonded molecular sieve was completely immersed in a 0.1 mol / L magnesium nitrate aqueous solution, shaken at 25°C and 160 rpm for 5 h, filtered, and the solid was calcined at 460°C for 4 h to obtain a metal oxide-loaded molecular sieve;

[0047] S6: Degas the metal oxide-loaded molecular sieve at 300° C. for 4 h in a nitrogen atmosphere to remove residual organic matter and obtain an adsorbent.

[0048] (2) Preparation of desorbed oil: The refined naphtha is subjected to a secondary hydrogenation refining reaction. The reaction part uses a hydrogenation refining catalyst. At a pressure of 2.0 MPa and a temperature of 250°C, the trace sulfur contained in the raw material is converted into hydrogen sulfide which is easy to remove. At the same time, a small amount of olefins are saturated and converted into alkanes to obtain refined naphtha. The refined naphtha is sent to an adsorption tower containing an adsorbent for adsorption. The adsorption tower has a height-to-diameter ratio of 4.0, an adsorption pressure of 0.7 MPa, and an adsorption temperature of 290°C. The desorbent is n-tetradecane, and the flow rate is 2m 3 / (m 3Desorbent h) n-tetradecane was injected for desorption at a desorption pressure of 0.7 MPa and a desorption temperature of 290°C. The adsorption time was 25 minutes, and the desorption time was 25 minutes, to obtain a desorbed oil. The desorbed oil had a n-alkanes mass content of ≥99.5%, a sulfur mass content of ≤0.5 ppm, a nitrogen mass content of ≤0.5 ppm, a bromine index of ≤5 mgBr / 100 g, and an aromatics mass content of ≤10 ppm.

[0049] (3) Preparation of high-purity n-heptane and high-purity n-hexane: Using desorbed oil as raw material, high-purity n-heptane and high-purity n-hexane are prepared by distillation equipment; the distillation equipment includes two distillation towers connected in sequence, namely a hexane distillation tower and a heptane distillation tower, with feed in the middle of each distillation tower, and the bottom material of the previous tower is the feed of the next tower. The top of the hexane distillation tower is 67°C, the bottom of the tower is 128°C, the pressure is 0.05MPa, the reflux ratio of the hexane distillation tower is 4, the theoretical plates are 70, and the processing load is 4.6L / h; the top of the heptane distillation tower is 97°C, the bottom of the tower is 145°C, the pressure is 0.05MPa, the reflux ratio of the heptane distillation tower is 4, the theoretical plates are 80, and the processing load is 4.0L / h. High-purity n-hexane is cut out from the top of the heptane distillation tower, and high-purity n-heptane is cut out from the top of the heptane distillation tower.

[0050] Example 2

[0051] This embodiment provides a method for preparing high-purity heptane, comprising the following steps:

[0052] (1) Preparing an adsorbent, wherein the preparation method of the adsorbent comprises the following steps:

[0053] S1: Mixing HY molecular sieve and MCM-41 molecular sieve in a weight ratio of 2:1 to obtain a mixed molecular sieve;

[0054] S2: The mixed molecular sieve was completely immersed in 1.0 mol / L hydrochloric acid, stirred at 80°C for 6 h, filtered, and the solid was calcined at 550°C for 8 h to obtain a calcined molecular sieve;

[0055] S3: The calcined molecular sieve was completely immersed in a toluene solution of hexamethyldisilazane with a concentration of 12 wt%, refluxed at 130° C. for 12 h, filtered, and the solid was washed with toluene and ethanol in sequence, and vacuum dried to obtain a passivated molecular sieve;

[0056] S4: The passivated molecular sieve was completely immersed in a 7 wt% nitrobenzoic acid ethanol solution, stirred at 65 ° C for 8 h, filtered, and the solid was heated at 320 ° C for 2 h under a nitrogen atmosphere to obtain a nitrophenyl group bonded molecular sieve;

[0057] S5: The nitrophenyl group-bonded molecular sieve was completely immersed in a 0.1 mol / L magnesium nitrate aqueous solution, shaken at 20°C and 200 rpm for 4 h, filtered, and the solid was calcined at 480°C for 3 h to obtain a metal oxide-loaded molecular sieve;

[0058] S6: Degas the metal oxide-loaded molecular sieve at 300° C. for 4 h in a nitrogen atmosphere to remove residual organic matter and obtain an adsorbent.

[0059] (2) Preparation of desorbed oil: The refined naphtha is subjected to a secondary hydrogenation refining reaction. The reaction part uses a hydrogenation refining catalyst. At a pressure of 2.0 MPa and a temperature of 250°C, the trace sulfur contained in the raw material is converted into hydrogen sulfide which is easy to remove. At the same time, a small amount of olefins are saturated and converted into alkanes to obtain refined naphtha. The refined naphtha is sent to an adsorption tower containing an adsorbent for adsorption. The adsorption tower has a height-to-diameter ratio of 4.0, an adsorption pressure of 0.7 MPa, and an adsorption temperature of 290°C. The desorbent is n-tetradecane, and the flow rate is 2 m 3 / (m 3 Desorbent h) n-tetradecane was injected for desorption at a desorption pressure of 0.7 MPa and a desorption temperature of 290°C. The adsorption time was 25 minutes, and the desorption time was 25 minutes to obtain a desorbed oil. The desorbed oil had a n-alkane content of ≥99.5% by mass, a sulfur content of ≤0.5 ppm by mass, a nitrogen content of ≤0.5 ppm by mass, a bromine index of ≤5 mgBr / 100 g, and an aromatic hydrocarbon content of ≤10 ppm by mass.

[0060] (3) Preparation of high-purity n-heptane and high-purity n-hexane: Using desorbed oil as raw material, high-purity n-heptane and high-purity n-hexane are prepared by distillation equipment; the distillation equipment includes two distillation towers connected in sequence, namely a hexane distillation tower and a heptane distillation tower, with feed in the middle of each distillation tower, and the bottom material of the previous tower is the feed of the next tower. The top of the hexane distillation tower is 67°C, the bottom of the tower is 128°C, the pressure is 0.05MPa, the reflux ratio of the hexane distillation tower is 4, the theoretical plates are 97, and the processing load is 4.6L / h; the top of the heptane distillation tower is 97°C, the bottom of the tower is 145°C, the pressure is 0.05MPa, the reflux ratio of the heptane distillation tower is 4, the theoretical plates are 80, and the processing load is 4.0L / h. High-purity n-hexane is cut out from the top of the heptane distillation tower, and high-purity n-heptane is cut out from the top of the heptane distillation tower.

[0061] Example 3

[0062] The difference between this embodiment and embodiment 1 is that in S4, the heating temperature and time are 300° C. and 2 h.

[0063] Example 4

[0064] The difference between this embodiment and embodiment 1 is that in S4, the heating temperature and time are 320° C. and 4 h.

[0065] Example 5

[0066] The difference between this embodiment and embodiment 1 is that in step (2), the conditions of the refining reaction are: pressure 1.7 MPa, temperature 240°C.

[0067] Example 6

[0068] The difference between this embodiment and embodiment 1 is that in step (2), the conditions of the refining reaction are: pressure 2.3 MPa, temperature 260°C.

[0069] Example 7

[0070] The difference between this embodiment and embodiment 1 is that in step (3), the adsorption pressure is 0.5 MPa, the desorption pressure is 0.5 MPa; the adsorption temperature is 250°C, the desorption temperature is 250°C; the adsorption time is 20 minutes, and the desorption time is 20 minutes.

[0071] Example 8

[0072] The difference between this embodiment and embodiment 1 is that in step (3), the adsorption pressure is 1.0 MPa, the desorption pressure is 1.0 MPa; the adsorption temperature is 320°C, the desorption temperature is 320°C; the adsorption time is 30 minutes, and the desorption time is 30 minutes.

[0073] Comparative Example 1

[0074] The difference between this comparative example and Example 1 is that the adsorbent is replaced by a mixed molecular sieve, and the mixed molecular sieve includes HY molecular sieve and MCM-41 molecular sieve in a weight ratio of 2.5:1.

[0075] Comparative Example 2

[0076] The difference between this comparative example and Example 1 is that step S1 is different.

[0077] Specifically: S1: mixing HY molecular sieve and MCM-41 molecular sieve in a weight ratio of 1.5:1 to obtain a mixed molecular sieve.

[0078] Comparative Example 3

[0079] The difference between this comparative example and Example 1 is that step S1 is different.

[0080] Specifically: replace the mixed molecular sieve with HY molecular sieve.

[0081] Comparative Example 4

[0082] The difference between this comparative example and Example 1 is that the preparation method of the adsorbent is different.

[0083] The preparation method of the adsorbent comprises the following steps:

[0084] S1: Mixing HY molecular sieve and MCM-41 molecular sieve in a weight ratio of 2.5:1 to obtain a mixed molecular sieve;

[0085] S2: The mixed molecular sieve was completely immersed in 1.1 mol / L hydrochloric acid, stirred at 82°C for 5 h, filtered, and the solid was calcined at 560°C for 7 h to obtain a calcined molecular sieve;

[0086] S3: The calcined molecular sieve was completely immersed in a toluene solution of hexamethyldisilazane with a concentration of 13 wt%, refluxed at 125°C for 14 h, filtered, and the solid was washed with toluene and ethanol in sequence, and vacuum dried to obtain a passivated molecular sieve;

[0087] S4: The passivated molecular sieve was completely immersed in a 0.1 mol / L magnesium nitrate aqueous solution, shaken at 25°C and 160 rpm for 5 h, filtered, and the solid was calcined at 460°C for 4 h to obtain a molecular sieve loaded with metal oxide;

[0088] S5: Degas the metal oxide-loaded molecular sieve at 300° C. for 4 h in a nitrogen atmosphere to remove residual organic matter and obtain an adsorbent.

[0089] Comparative Example 5

[0090] The difference between this comparative example and Example 1 is that the preparation method of the adsorbent is different.

[0091] The preparation method of the adsorbent comprises the following steps:

[0092] S1: Mixing HY molecular sieve and MCM-41 molecular sieve in a weight ratio of 2.5:1 to obtain a mixed molecular sieve;

[0093] S2: The mixed molecular sieve was completely immersed in 1.1 mol / L hydrochloric acid, stirred at 82°C for 5 h, filtered, and the solid was calcined at 560°C for 7 h to obtain a calcined molecular sieve;

[0094] S3: The calcined molecular sieve was completely immersed in a toluene solution of hexamethyldisilazane with a concentration of 13 wt%, refluxed at 125°C for 14 h, filtered, and the solid was washed with toluene and ethanol in sequence, and vacuum dried to obtain a passivated molecular sieve;

[0095] S4: The passivated molecular sieve was completely immersed in a 6 wt% nitrobenzoic acid ethanol solution, stirred at 62 ° C for 9 h, filtered, and the solid was heated at 310 ° C for 3 h under a nitrogen atmosphere to obtain a nitrophenyl group bonded molecular sieve;

[0096] S5: In a nitrogen atmosphere, the molecular sieve bonded with the nitrophenyl group was degassed at 300° C. for 4 h to remove residual organic matter and obtain an adsorbent.

[0097] Performance Testing

[0098] High-purity n-hexane and high-purity n-heptane were prepared using the preparation methods of high-purity heptane in Examples 1-8 and Comparative Examples 1-5. The compositions were measured by gas chromatography. The purities and yields are shown in Table 1.

[0099] Purity: the mass of n-heptane (n-hexane) in the top cut fraction of the n-heptane (n-hexane) distillation tower / the total mass of the top cut fraction of the n-heptane (n-hexane) distillation tower × 100%;

[0100] Yield: Mass of the top cut of the n-heptane (n-hexane) distillation tower / mass of naphtha feedstock × 100%.

[0101] Table 1 Product purity and yield test results

[0102] High purity n-heptane purity% High purity n-heptane yield % High purity n-hexane purity% High purity n-hexane yield% Example 1 99.62 21.13 99.41 23.54 Example 2 99.57 20.64 99.35 22.67 Example 3 99.53 20.36 99.37 22.86 Example 4 99.58 20.58 99.42 23.11 Example 5 99.55 20.27 99.38 22.59 Example 6 99.61 20.41 99.45 22.77 Example 7 99.54 20.39 99.40 22.80 Example 8 99.59 20.50 99.49 23.27 Comparative Example 1 99.03 18.32 99.07 20.18 Comparative Example 2 99.45 20.01 99.23 22.13 Comparative Example 3 99.39 19.94 99.26 21.74 Comparative Example 4 99.26 19.02 99.19 21.10 Comparative Example 5 99.21 18.89 99.12 21.32

[0103] As shown in Table 1, the purity and yield of n-heptane and n-hexane in Examples 1-8 are significantly improved compared with the prior art.

[0104] In Comparative Example 1, unmodified molecular sieve was used as the adsorbent, and the purity and yield of n-heptane and n-hexane decreased significantly.

[0105] In Comparative Examples 2 and 3, the raw material ratios of the molecular sieves were changed, and the purity and yield of n-heptane and n-hexane decreased, indicating that the HY molecular sieve and the MCM-41 molecular sieve at a specific ratio produced a synergistic effect.

[0106] The modification methods of the adsorbents in Comparative Examples 4 and 5 are different, and the purity and yield of n-heptane and n-hexane decrease. This shows that only by modifying the mixed molecular sieve in Example 1 can the purity and yield of the product be better improved.

[0107] The above is a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for preparing high-purity heptane, characterized in that: The following steps are involved: (1) Preparing an adsorbent, comprising the following steps: S1: mixing HY molecular sieve and MCM-41 molecular sieve to obtain a mixed molecular sieve; S2: immersing the mixed molecular sieve in hydrochloric acid, stirring, filtering, and calcining the solid to obtain a calcined molecular sieve; S3: completely immersing the calcined molecular sieve in a toluene solution of hexamethyldisilazane, refluxing, filtering, washing the solid, and vacuum drying to obtain a passivated molecular sieve; S4: completely immersing the passivated molecular sieve in an ethanol solution of nitrobenzoic acid, stirring, filtering, and heating the solid under a nitrogen atmosphere to obtain a nitrophenyl group-bonded molecular sieve; S5: completely immersing the nitrophenyl group-bonded molecular sieve in an aqueous solution of magnesium nitrate, shaking, filtering, and calcining the solid to obtain a molecular sieve loaded with metal oxide; S6: degassing the molecular sieve loaded with metal oxide in a nitrogen atmosphere to obtain an adsorbent; (2) The raw naphtha enters the hydrotreating reactor and undergoes a refining reaction to obtain refined naphtha; (3) The refined naphtha enters an adsorption tower containing the adsorbent prepared in step (1) for adsorption separation and desorption to obtain desorbed oil; (4) Using the desorbed oil as a raw material, separating high-purity n-heptane and high-purity n-hexane through a distillation device; the distillation device comprises two sequentially connected distillation towers, namely a hexane distillation tower and a heptane distillation tower, wherein the top of the hexane distillation tower cuts off high-purity n-hexane, and the top of the heptane distillation tower cuts off high-purity n-heptane; Among them, the weight ratio of HY molecular sieve and MCM-41 molecular sieve is (2-3):

1.

2. The method for preparing high-purity heptane according to claim 1, wherein In S4, the heating temperature and time are 300-320° C. and 2-4 h.

3. The method for preparing high-purity heptane according to claim 1, wherein In step (2), the refining reaction uses a hydrogenation refining catalyst, and the refining reaction conditions are: pressure 1.7-2.3 MPa, temperature 240-260°C.

4. The method for preparing high-purity heptane according to claim 1, wherein In the step (3), the adsorption pressure is 0.5-1.0 MPa, the desorption pressure is 0.5-1.0 MPa; the adsorption temperature is 250-320°C, the desorption temperature is 250-320°C; the adsorption time is 20-30 minutes, and the desorption time is 20-30 minutes.

5. The method for preparing high-purity heptane according to claim 1, wherein In the step (4), the operating temperature of the hexane distillation tower is: the top temperature is 67°C, the bottom temperature is 128°C, and the operating pressure is 0.05 MPa; and the operating temperature of the heptane distillation tower is: the top temperature is 97°C, the bottom temperature is 145°C, and the operating pressure is 0.05 MPa.

6. The method for preparing high-purity heptane according to claim 1, wherein The desorbed oil in step (4) has a normal paraffin content of ≥99.5% by mass, a sulfur content of ≤0.5 ppm by mass, a nitrogen content of ≤0.5 ppm by mass, a bromine index of ≤5 mgBr / 100 g, and an aromatic hydrocarbon content of ≤10 ppm by mass.

7. The method for preparing high-purity heptane according to claim 1, characterized in that: In the step (4), the middle part of each distillation tower is fed, and the bottom material of the previous tower is the feed of the next tower.

8. The method for preparing high-purity heptane according to claim 7, characterized in that: In the step (4), the reflux ratio of the hexane distillation tower is 3-4, the theoretical plates are 70, and the processing load is 4.6 L / h; the reflux ratio of the heptane distillation tower is 3-5, the theoretical plates are 80, and the processing load is 4.0 L / h.

9. The method for preparing high-purity heptane according to claim 8, characterized in that: The hydrotreating catalyst used in the hydrotreating reaction in step (2) is clover particles, and the specific surface area of ​​the clover particles is ≥150m 2 / g, bulk density 0.72-0.82g / cm 3 , radial compressive strength ≥150N / cm.

10. The method for preparing high-purity heptane according to claim 1, characterized in that: The purity of the high-purity n-heptane obtained in step (4) is ≥99.5%, and the yield of the high-purity n-heptane is ≥20%.

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