A method for refining C5 alkanes

Abstract

This invention discloses a method for refining C5 alkanes. The method includes contacting a C5 alkane raw material with a refining agent to obtain refined C5 alkanes. The refining agent comprises a molecular sieve and rare earth metal components, wherein the micropore volume of the molecular sieve accounts for 10% to 40% of the total pore volume. Using this method, the refining agent has a long service life and the purity of the refined C5 alkanes can be improved. The C5 alkanes refined by this method are particularly suitable for the production of foaming agents.

Description

Technical Field

[0001] This invention belongs to the field of petrochemical technology, and specifically relates to a method for refining C5 alkanes. Background Technology

[0002] Pentane has a wide range of applications, including as a foaming agent, solvent, and chemical raw material. The downstream applications of pentane are relatively concentrated, primarily in the production of foaming agents for polyurethane products, polystyrene foam (EPS), and linear low-density polyethylene (LLDPE) solvents. In recent years, pentane has also been used to replace Freon as a refrigerant in air conditioning and as an expanding agent in tobacco to reduce tar and nicotine content. Pentane feedstock mainly comes from oil refineries, primarily through two routes: direct distillation of light hydrocarbons from oil fields and production of pentane from C5 hydrocarbons as a byproduct during petroleum refining processes such as cracking to produce ethylene or gasoline. C5 alkanes mainly contain five-carbon alkanes such as n-pentane and isopentane. Currently, industrially obtained pentane generally contains a certain amount of pentene. Because removing olefins from high-purity C5 alkanes is difficult, hydrogenation reactions can typically remove up to about 200 ppm. Reducing it to 50 ppm would increase costs and complicate the equipment.

[0003] With the continuous advancement of polyethylene production technology, the requirements for the solvent isopentane have become more stringent, and the restrictions on the olefin content in it have been continuously tightened, with the olefin content dropping to below 50 ppm or even higher.

[0004] There are two main methods for upgrading C5 alkanes: one is refining through hydrogenation, and the other is refining through molecular sieve adsorption. To obtain C5 alkanes with ultra-low olefin content, a hydrogenation saturation reaction combined with molecular sieve adsorption refining is used. The hydrogenation process can be either single-stage or two-stage. Single-stage hydrogenation requires a hydrogenation catalyst with high hydrogenation activity and good hydrogenation depth. In two-stage hydrogenation, the C5 feedstock undergoes a first-stage hydrogenation process to remove dienes and alkynes, followed by a second-stage hydrogenation process to produce saturated alkanes. After hydrogenation, the C5 alkanes undergo purification, typically using molecular sieve adsorption of olefins, or further purification with clay.

[0005] Zhang Deshun et al. reported in their development of isopentane production technology (Shandong Chemical Industry, 2013, (42), 33) that high-purity pentane was distilled and then the olefin content was reduced to about 50 ppm using molecular sieve adsorption. CN107573204A uses modified ZSM-5 molecular sieve, and by loading the molecular sieve with copper or silver, the olefin content in the product can be reduced to below 10 ppm. After deactivation, nitrogen purging is used. All of the above molecular sieve refining agents need to be regenerated in a short period of time.

[0006] Currently, the method of improving C5 alkanes by molecular sieve refining and adsorption has technical problems such as short service life, poor regeneration effect, and low purity of C5 alkanes. Summary of the Invention

[0007] The technical problem this invention aims to solve is the short service life, poor regeneration effect, and low purity of C5 hydrocarbons in existing molecular sieve refining agents. This invention provides a method for refining C5 hydrocarbons for use in foaming agent production. Using this method, the refining agent has a long service life and can improve the purity of the C5 hydrocarbons. The refined C5 hydrocarbons are particularly suitable for producing foaming agents.

[0008] The first aspect of the present invention provides a method for refining C5 alkanes, comprising: contacting a C5 alkane raw material with a refining agent to obtain refined C5 alkanes, wherein the refining agent comprises: a molecular sieve and a rare earth metal component, wherein the micropore volume of the molecular sieve accounts for 10% to 40% of the total pore volume.

[0009] Further, the molecular sieve is selected from one or more of ten-membered ring, twelve-membered ring silica-alumina molecular sieves, and silica-alumina-phosphorus molecular sieves, preferably from one or more of needle zeolite, potassium pyroxene zeolite, L zeolite, VPI-5, Y zeolite, X zeolite, ω zeolite, β zeolite, MOR molecular sieve, ZSM-3, ZSM-4, ZSM-18, ZSM-20, SAPO-5, SAPO-34, SAPO-11, MCM-22, ZSM-5, ZSM-11, ZSM-12, MCM-22, silica zeolite-1, and silica zeolite-2. More preferably, at least one of MOR, β zeolite, ZSM-5, SAPO-11, USY molecular sieve, and MCM-22 is selected.

[0010] Furthermore, the rare earth metal is selected from one or more of La, Ce, Pr, Lu, Nd, and Dy.

[0011] Furthermore, based on the weight of the refined preparation, it includes: a molecular sieve content of 35% to 95% and a rare earth metal content of 0.01% to 15%.

[0012] Furthermore, the refined preparation also contains a binder component selected from one or more of silicon dioxide and aluminum oxide. Based on the weight of the refined preparation, the binder component content is 1% to 50%.

[0013] Furthermore, in the C5 alkane raw material, the mass content of C5 alkane accounts for more than 40%, preferably more than 60%, and the mass content of C5 olefins is 30-2000 ppm, preferably 50-1000 ppm, more preferably 100-700 ppm, and even more preferably 200-700 ppm.

[0014] Furthermore, the operating conditions for contacting the C5 alkane feedstock with the refining agent are as follows: pressure 0.01–8.0 MPa, temperature 60–200 °C, and mass hourly space velocity 0.1–20 h⁻¹. -1 Preferably, the pressure is 0.1 MPa to 4.0 MPa, the temperature is 80 to 180 °C, and the mass hourly space velocity is 0.5 to 6.0 h⁻¹. -1 .

[0015] Furthermore, the refined C5 alkanes, by mass fraction, have a C5 olefin removal rate of 30% or more, preferably 85% or more, even more preferably 95% or more, and still more preferably 99% or more.

[0016] Furthermore, in the refined C5 alkane, the mass content of C5 olefins is 1 to 200 ppm, preferably, the mass content of C5 olefins is below 30 ppm, more preferably, the mass content of C5 olefins is below 20 ppm, and even more preferably, the mass content of C5 olefins is below 10 ppm.

[0017] Furthermore, the number of days in which the mass content of C5 olefins in the refined C5 alkane is below 30 ppm (preferably below 20 ppm, more preferably below 10 ppm) reaches more than 30 days.

[0018] Furthermore, the refined C5 alkanes are suitable for the production of foaming agents.

[0019] Furthermore, the refining agent of the present invention can be regenerated after the de-olefin reaction, under the following regeneration conditions: calcination at 350–700°C for 0.5–48 hours in an oxygen-containing atmosphere. Under the same evaluation conditions, the service life of the regenerated refining agent is more than 70% of that of the fresh refining agent, more preferably more than 80%, and even more preferably more than 90%.

[0020] A second aspect of the present invention provides a C5 alkane refining agent comprising: a molecular sieve and a rare earth metal component, wherein the micropore volume of the molecular sieve accounts for 10% to 40% of the total pore volume.

[0021] Further, the molecular sieve is selected from one or more of ten-membered ring, twelve-membered ring silica-alumina molecular sieves, and silica-alumina-phosphorus molecular sieves, preferably from one or more of needle zeolite, potassium pyroxene zeolite, L zeolite, VPI-5, Y zeolite, X zeolite, ω zeolite, β zeolite, MOR molecular sieve, ZSM-3, ZSM-4, ZSM-18, ZSM-20, SAPO-5, SAPO-34, SAPO-11, MCM-22, ZSM-5, ZSM-11, ZSM-12, MCM-22, silica zeolite-1, and silica zeolite-2. More preferably, at least one of MOR, β zeolite, ZSM-5, SAPO-11, USY molecular sieve, and MCM-22 is selected.

[0022] Furthermore, the rare earth metal is selected from one or more of La, Ce, Pr, Lu, Nd, and Dy.

[0023] Furthermore, based on the weight of the refined preparation, it includes: a molecular sieve content of 35% to 95% and a rare earth metal content of 0.01% to 15%.

[0024] Furthermore, the refined preparation also contains a binder component selected from one or more of silicon dioxide and aluminum oxide. Based on the weight of the refined preparation, the binder component content is 1% to 50%.

[0025] Furthermore, the refined preparation can be prepared by the following method: kneading molecular sieves and binder precursors together, followed by drying and calcination to obtain the refined preparation; wherein rare earth metal components are introduced into the refined preparation before kneading, during kneading, or after calcination.

[0026] Furthermore, the molecular sieve is an ammonium-type or hydrogen-type molecular sieve. The binder precursor is one or more of an alumina precursor (such as boehmite) or a silica precursor (silica sol).

[0027] Furthermore, the rare earth metal source before the rare earth metal component is introduced into the refining agent is one or more of nitrates, halides, and sulfates.

[0028] Furthermore, rare earth metal components can be introduced into the refining agent before kneading and molding by ion exchange with molecular sieves. Rare earth metal components can be introduced into the refining agent after molding and calcination by impregnation, such as equal-volume impregnation. Specific introduction methods can be carried out according to conventional procedures.

[0029] Furthermore, conventional molding aids, such as lubricants, pore-forming agents, and pectinic acids, can be added during the kneading process. These can be selected from one or more of guar gum powder, polyethylene glycol, and cellulose. The drying conditions after molding are as follows: 20–200℃, drying time 0.5–50 hours. The calcination conditions are as follows: calcination temperature 350–700℃, calcination time 0.1–20 hours.

[0030] Compared with the prior art, the purification method of C5 alkane of the present invention has the following beneficial effects:

[0031] The inventors discovered that refining and removing olefins from C5 alkane feedstocks with low olefin content is extremely difficult, generally making it challenging to maintain a C5 olefin content below 50 ppm while ensuring a long service life of the refining agent (over one month). Further research revealed that using molecular sieves with a specific micropore volume ratio in combination with rare earth metals, while extending the service life of the refining agent, yields excellent refining results for C5 alkanes with low olefin content, thus leading to this invention. This invention utilizes molecular sieves with a micropore volume ratio of 10%–40% in combination with rare earth metals for the refining and olefin removal of C5 alkanes. This method can handle feedstocks with low olefin content, achieving a long service life for the refining agent and reducing the mass content of C5 olefins in the refined C5 alkanes to below 10 ppm. Detailed Implementation

[0032] The present invention will be described in detail below with reference to the embodiments, but the scope of protection of the present invention is not limited to the embodiments.

[0033] In this invention, pore volume and pore distribution were measured using the BET method and a liquid nitrogen adsorption-desorption apparatus. The measurement method is as follows: the test was conducted at the liquid nitrogen saturation temperature (77K), and N2 isothermal adsorption-desorption curves were obtained by different relative pressures. The pore volume and pore distribution were then calculated. The relative pressure during the experiment ranged from 0.001 to 0.995.

[0034] Example 1

[0035] Take 100g of H-type ZSM-5 molecular sieve (SiO2 / Al2O3 molar ratio of 40, micropore volume accounting for 20% of total pore volume), 65g of pseudoboehmite (containing 67wt% alumina), 12g of guar gum powder, 2.0g of lanthanum nitrate, 6.0g of 65wt% nitric acid, and an appropriate amount of water, knead them into a mold, dry at 120℃ for 12 hours, and calcine at 550℃ for 3 hours to obtain the refined preparation.

[0036] Take 5g of the refined preparation, using a C5 alkane feedstock containing 60% pentane, 630ppm pentene, 35% hexane, more than 4% hexane, and the remainder being less than butane (by mass fraction), and process it over 5 hours. -1The reaction was evaluated at 2.9 MPa and 150 °C. After 15 days, the pentene content in the product was 6.0 ppm. The space velocity was further reduced to 1.2 h⁻¹. -1 After 90 days, the pentene content in the exported product was 7.2 ppm.

[0037] Example 2

[0038] Take 100g of H-type β-zeolite (SiO2 / Al2O3 molar ratio of 35, micropore volume accounting for 23% of total pore volume), 65g of pseudoboehmite (containing 67wt% alumina), 12g of polyethylene glycol, 3.0g of cerium nitrate, 6g of 65wt% nitric acid, and an appropriate amount of water, knead them into a mold, dry at 120℃ for 12 hours, and calcine at 650℃ for 0.5 hours to obtain the refined preparation.

[0039] Take 5g of the refined preparation and, using a C5 alkane feedstock (by mass fraction) containing 60% pentane, 630ppm pentene, 35% hexane, and more than 4% hexane, with the remainder being butane or less, for 3.0h... -1 The reaction was evaluated at 2.5 MPa and 140 °C. After 45 days, the pentene content in the product was 3.2 ppm.

[0040] Example 3

[0041] Take 100g of H-type MOR molecular sieve (SiO2 / Al2O3 molar ratio of 20, micropore volume accounting for 15% of total pore volume), 100g of pseudoboehmite (containing 67wt% alumina), 0.5g of potassium niobate, 12g of cellulose, 6g of 65wt% nitric acid, and an appropriate amount of water, knead them into a mold, dry at 120℃ for 12 hours, and calcine at 500℃ for 3.5 hours to obtain the purified preparation.

[0042] Take 5g of the refined preparation and, using a C5 alkane feedstock (by mass fraction) containing 70% pentane, 310ppm pentene, 25% hexane, and more than 3% hexane, with the remainder being butane or less, for 5.0h... -1 The reaction was evaluated at 2.5 MPa and 130 °C. After 60 days, the pentene content in the product was 6.5 ppm.

[0043] Example 4

[0044] Take 80g of H-type Y molecular sieve (SiO2 / Al2O3 molar ratio of 5, micropore volume accounting for 12% of total pore volume), 100g of pseudoboehmite (containing 67% alumina), 10.0g of lanthanum nitrate, 12g of guar gum powder, 6g of 65wt% nitric acid, and an appropriate amount of water, knead them into a mold, dry at 120℃ for 12 hours, and calcine at 450℃ for 5 hours to obtain the refined preparation.

[0045] Take 5g of the refined preparation and, using a C5 alkane feedstock (by mass fraction) containing 70% pentane, 310ppm pentene, 25% hexane, and more than 3% hexane, with the remainder being butane or less, for 5.0h... -1 The reaction was evaluated at 2.5 MPa and 130 °C. After 45 days, the pentene content in the product was 5.8 ppm.

[0046] Example 5

[0047] Take 150g of H-type USY molecular sieve (SiO2 / Al2O3 molar ratio of 7, micropore volume accounting for 23% of total pore volume), 40g of pseudoboehmite (containing 67wt% alumina), 1.0g of lanthanum nitrate, 6.0g of cerium nitrate, 15g of guar gum powder, 6g of 65wt% nitric acid, and an appropriate amount of water, knead them into a mold, dry at 120℃ for 12 hours, and calcine at 580℃ for 2 hours to obtain the purified preparation.

[0048] Take 5g of the refined preparation and, using a C5 alkane feedstock (by mass fraction) containing 70% pentane, 310ppm pentene, 25% hexane, and more than 3% hexane, with the remainder being butane or less, for 10.0h... -1 The reaction was evaluated at 3.5 MPa and 180 °C. Initially, the pentene content in the product was 1.1 ppm, and after 45 days, the pentene content in the product was 5.1 ppm.

[0049] Example 6

[0050] Take 150g of H-type SAPO-11 molecular sieve (SiO2 / P2O5 / Al2O3 = 0.5-0.8:1:1, molar ratio, micropore volume accounts for 20% of the total pore volume), 40g of pseudoboehmite (containing 67wt% alumina), 2.0g of lanthanum nitrate, 15g of guar gum powder, 6g of 65% nitric acid, and an appropriate amount of water, knead them into a mold, dry at 120℃ for 12 hours, and calcine at 680℃ for 0.5 hours to obtain the refined preparation.

[0051] Take 5g of the refined preparation and, using a C5 alkane feedstock (by mass fraction) containing 70% pentane, 310ppm pentene, 25% hexane, and more than 3% hexane, with the remainder being butane or less, for 4.0h... -1 The reaction was evaluated at 3.5 MPa and 180 °C, and the initial product contained 2.1 ppm of pentene.

[0052] Example 7

[0053] Take 150g of H-type MCM-22 molecular sieve (SiO2 / Al2O3 = 30, molar ratio, micropore volume accounts for 12% of the total pore volume), 20g of pseudoboehmite and silica sol (silica sol containing 67wt% alumina and 30% silica), 2.0g of niobium oxalate, 15g of guar gum powder, 6g of 65wt% nitric acid, and an appropriate amount of water, knead them into a mold, dry at 120℃ for 12 hours, and calcine at 530℃ for 2 hours to obtain the refined preparation.

[0054] Take 5g of the refined preparation and, using a C5 hydrocarbon feedstock (by mass fraction) containing 60% pentane, 200ppm butene, 300ppm pentene, 29% butane, less than 7.0% propane, and the remainder being hexane or higher, process it for 3.0 hours. -1 The reaction was evaluated at 3.5 MPa and 120 °C. After 30 days, the pentene content in the product was 7.5 ppm and the butene content was 5.5 ppm, indicating stable performance.

[0055] Example 8

[0056] Take 75g of H-type β-zeolite (SiO2 / Al2O3 = 30, molar ratio, micropore volume accounts for 15% of the total pore volume) and 75g of H-type USY molecular sieve (SiO2 / Al2O3 = 5.1, molar ratio, micropore volume accounts for 30% of the total pore volume), along with 20g of pseudoboehmite and silica sol (containing 67wt% alumina), 15g of guar gum powder, 6g of 65wt% nitric acid, and an appropriate amount of water, knead into a mold, dry at 120℃ for 12 hours, and calcine at 580℃ for 2 hours. Take 50g of the calcined material and further impregnate it with 20g of lanthanum nitrate solution (mass concentration 15%), dry at 120℃ for 10 hours, and calcine at 550℃ for 3 hours to obtain the refined product.

[0057] Take 5g of the refined preparation, using a C5 hydrocarbon feedstock containing 60% pentane, 200ppm butene, 300ppm pentene, 29% butane, less than 7.0% propane, and the remainder being hexane or higher (by mass fraction), and process it over 3.0h. -1 The reaction was evaluated at 3.5 MPa and 120 °C. After 120 days, the pentene content in the product was 15 ppm and the butene content was 5.0 ppm, indicating stable performance. Following evaluation, the product was calcined in air at 530 °C for 3 hours. Then, under the same conditions, the product was evaluated again. Initially, the pentene content was 3.1 ppm, increasing to 17 ppm after 120 days.

[0058] Comparative Example 1

[0059] Take 100g of H-type ZSM-5 molecular sieve (SiO2 / Al2O3 molar ratio of 40, micropore volume accounting for 7.0% of total pore volume), 65g of pseudoboehmite (containing 67wt% alumina), 12g of guar gum powder, 6.0g of 65wt% nitric acid, and an appropriate amount of water, knead them into a mold, dry at 120℃ for 12 hours, and calcine at 550℃ for 3 hours to obtain the refined product.

[0060] Take 5g of the refined preparation and place it in a C5 alkane feedstock containing 60% pentane, 630ppm pentene, 35% hexane, more than 4% hexane, and the remainder being less than butane (by mass fraction) for 5 hours. -1 The reaction was evaluated at 2.9 MPa and 150 °C, and the pentene content in the product was 20 ppm. The reaction was unstable, and the pentene content increased to 200 ppm after 18 days.

[0061] Comparative Example 2

[0062] Take 100g of H-type ZSM-5 molecular sieve (SiO2 / Al2O3 molar ratio of 40, micropore volume accounting for 20% of total pore volume), 65g of pseudoboehmite (containing 67wt% alumina), 12g of guar gum powder, 6.0g of 65wt% nitric acid, and an appropriate amount of water, knead them into a mold, dry at 120℃ for 12 hours, and calcine at 550℃ for 3 hours to obtain the refined product.

[0063] Take 5g of the refined preparation and mix it with raw materials containing 60% pentane, 630ppm pentene, 35% hexane, more than 4% hexane, and the remainder being less than butane (by mass fraction) for 5 hours. -1 The reaction was evaluated at 2.9 MPa and 150 °C. The initial product contained 20.0 ppm of pentene, which increased to 200 ppm after 5 days of reaction.

[0064] Comparative Example 3

[0065] A Cu-type ZSM-5 molecular sieve (SiO2 / Al2O3 molar ratio of 600, micropore volume accounting for 7.0% of total pore volume) prepared according to the method in Example 1 of CN107573204A was used as a purification agent (the molecular sieve was used directly as an adsorbent without being shaped). A C5 alkane feedstock containing 60% pentane, 630 ppm pentene, 35% hexane, and more than 4% hexane, with the remainder being less than butane (by mass fraction) was used. The mixture was heated for 1.0 h. -1 The reaction was evaluated at 0.5 MPa and 30 °C. The pentene content in the product was 20 ppm after 2 hours. After 1 day of reaction, the pentene content increased to 480 ppm.

[0066] The specific embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combining the various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for purifying C5 alkanes, comprising: A C5 alkane feedstock is contacted with a refining agent to obtain refined C5 alkane, wherein the refining agent comprises a molecular sieve and rare earth metal components, and the micropore volume of the molecular sieve accounts for 10% to 40% of the total pore volume; The molecular sieve is selected from at least one of MOR, β-zeolite, ZSM-5, SAPO-11, USY molecular sieve, and MCM-22; the rare earth metal is selected from one or more of La, Ce, Pr, Lu, Nd, and Dy. The refined preparation contains a binder component, which, based on the weight of the refined preparation, includes: a molecular sieve content of 35% to 95%, a rare earth metal content of 0.01% to 15%, and a binder component content of 1% to 50%.

2. The method according to claim 1, characterized in that, The C5 alkane raw material contains more than 40% C5 alkane by mass and 30-2000 ppm C5 olefin by mass.

3. The method according to claim 1, characterized in that, The C5 alkane raw material contains more than 60% C5 alkane by mass and 50-1000 ppm C5 olefin by mass.

4. The method according to claim 1, characterized in that, The C5 alkane feedstock contains 100-700 ppm of C5 olefins by mass.

5. The method according to claim 1, characterized in that, The operating conditions for contacting the C5 alkane feedstock with the refining agent are as follows: pressure 0.01~8.0 MPa, temperature 60~200℃, and mass hourly space velocity 0.1~20 h⁻¹. -1 .

6. The method according to claim 1, characterized in that, The operating conditions for contacting the C5 alkane feedstock with the refining agent are as follows: pressure 0.1 MPa~4.0 MPa, temperature 80~180℃, and mass hourly space velocity (HHSV) 0.5~6.0 h⁻¹. -1 .

7. The method according to any one of claims 1-6, characterized in that, The refined C5 alkanes, by mass fraction, have a C5 olefin removal rate of over 30% from the C5 alkane raw material. And / or, the mass content of the carbon pentanes in the refined carbon pentanes is 1~200 ppm; And / or, the number of days in which the mass content of C5 olefins in the refined C5 alkanes is below 30 ppm reaches more than 30 days.

8. The method according to any one of claims 1-6, characterized in that, The refined C5 alkanes have a C5 olefin removal rate of over 85% by mass fraction. And / or, in the refined C5 alkane, the mass content of C5 olefins is less than 30 ppm; And / or, the number of days in which the mass content of C5 olefins in the refined C5 alkanes is below 20 ppm reaches more than 30 days.

9. The method according to any one of claims 1-6, characterized in that, The refined C5 alkanes have a C5 olefin removal rate of over 95% by mass fraction. And / or, in the refined C5 alkane, the mass content of C5 olefins is less than 20 ppm; And / or, the number of days in which the mass content of C5 olefins in the refined C5 alkanes is below 10 ppm reaches more than 30 days.

10. The method according to any one of claims 1-6, characterized in that, The purified C5 alkane contains less than 10 ppm of C5 olefins by mass.

11. The method according to any one of claims 1-6, characterized in that, The refined C5 alkane is used to produce foaming agents.