A process for the preparation of n-alkanes

Abstract

The application discloses a method for preparing normal paraffin, comprising the following steps: contacting isomeric alkanes and hydrogen with a catalyst in a reactor, and reacting to obtain normal paraffin; the isomeric alkanes are selected from at least one of isobutane and isopentane; the catalyst is composed of a double-layer spherical carrier and a noble metal active component loaded on the surface of the double-layer spherical carrier; and the noble metal active component is selected from at least one of platinum, palladium and gold.

Description

Technical Field

[0001] This application relates to a method for preparing n-alkanes, which belongs to the field of chemical engineering. Background Technology

[0002] The trienes (ethylene, propylene, and butadiene) produced by steam cracking are fundamental raw materials for the petrochemical industry and are widely used in the production of synthetic materials such as plastics, rubber, and fibers. These chemicals play a crucial role in industrial production, providing modern society with a large number of basic chemical products and advanced functional materials. Among the trienes, ethylene is the most in-demand basic chemical raw material, and domestic steam cracking capacity for ethylene exceeds 80% of the total ethylene production capacity. The main feedstock for domestic steam cracking units is naphtha, but the yield of ethylene from naphtha cracking is usually only around 30%. Furthermore, the yield of ethylene from the cracking of isoalkanes in naphtha is much lower than that from n-alkanes, and the composition of the feedstock has a significant impact on the ethylene yield. Generally, the yield of branched alkanes is much lower than that of n-alkanes.

[0003] Furthermore, with the rapid development of catalytic cracking and hydrocracking processes, the production of isobutane and isopentane is increasing, necessitating their efficient utilization. Using isobutane and isopentane as steam cracking feedstocks to produce ethylene and propylene yields only about one-third of those using n-butane and n-pentane. Therefore, pre-normalizing isobutane and isopentane before using them for steam cracking to produce ethylene and propylene can significantly improve the yields of these products, demonstrating high application value. Summary of the Invention

[0004] The purpose of this invention is to provide a catalyst for the normalization of isoparaffins, which has the characteristics of high catalytic activity, good selectivity, and low deactivation, and can catalytically convert isoparaffins with low efficiency in steam cracking to ethylene into normal paraffins with higher efficiency.

[0005] According to one aspect of this application, a method for preparing n-alkanes is provided, comprising the following steps:

[0006] In a reactor, isoparaffins and hydrogen are brought into contact with a catalyst and reacted to obtain n-paraffins;

[0007] The isoalkane is selected from at least one of isobutane and isopentane;

[0008] The catalyst consists of a double-layered spherical support and a noble metal active component supported on the surface of the double-layered spherical support.

[0009] The precious metal active component is selected from at least one of platinum, palladium and gold.

[0010] The catalyst is obtained through the following steps:

[0011] The catalyst was obtained by mixing a bilayer spherical support with an aqueous solution containing a noble metal precursor, drying, calcining, and reducing with hydrogen.

[0012] The noble metal precursor is selected from at least one of chloroplatinic acid, tetraammineplatinum chloride, platinum nitrate, palladium nitrate, palladium chloride, ammonium chloropalladate, and tetraammineplatinum chloride.

[0013] The drying temperature is 30–120°C;

[0014] The drying time is 1 to 12 hours;

[0015] The roasting temperature is 300–600°C;

[0016] The roasting time is 1 to 10 hours;

[0017] The temperature for hydrogen reduction is 300–500°C;

[0018] The hydrogen reduction time is 1 to 12 hours.

[0019] The double-layered spherical carrier is obtained through the following steps:

[0020] (1) Mix molecular sieve I, boehmite, ammonium chloride and additive I, and roll them into balls to obtain a spherical core;

[0021] (2) Mix the spherical core, molecular sieve II, kaolin, silica sol and additive II, roll them into balls, dry them and calcine them to obtain the double-layer spherical carrier.

[0022] The molecular sieve I is a hydrogen-type molecular sieve, selected from at least one of ZSM-11 molecular sieve, ZSM-22 molecular sieve, ZSM-23 molecular sieve, β molecular sieve, Y molecular sieve and MOR molecular sieve;

[0023] The auxiliary agent I is selected from at least one of aluminum sol, water, dilute nitric acid, oxalic acid, phosphoric acid, and acetic acid;

[0024] The mass ratio of molecular sieve I, pseudoboehmite, ammonium chloride, and auxiliary agent I is 1-40:2-25:1-10:1-10.

[0025] The molecular sieve II is selected from hydrogen-type ZSM-5 molecular sieve;

[0026] The auxiliary agent II is obtained by mixing at least one of aluminum nitrate, small-pore alumina and aluminum sulfate with an inorganic acid or an organic acid, wherein the mass content of the inorganic acid or organic acid is 20-50 wt%.

[0027] The mass ratio of the spherical core, molecular sieve II, kaolin, silica sol, and additive II is 1–20:1–30:1–10:1–10:1–10.

[0028] The drying temperature is 80–120°C;

[0029] The drying time is 1 to 12 hours;

[0030] The calcination temperature is 300–600°C;

[0031] The calcination time is 1 to 10 hours.

[0032] The reaction temperature is 300–600°C;

[0033] The reaction pressure is 0.3–3 MPa.

[0034] The molar ratio of the isoalkane to hydrogen is 0.1 to 2:1;

[0035] The mass hourly space velocity (MSV) of the isoalkanes is 0.1–2 h⁻¹. -1 .

[0036] The beneficial effects that this application can produce include:

[0037] (1) The invention of this invention is to provide a simple and efficient catalyst for the normalization of isoparaffins. The catalyst contains a noble metal active component and a bilayer spherical support. It has high catalytic activity and strong stability. The preparation method is simple and the reaction conditions are easy to control.

[0038] (2) The method of this invention is simple and the reaction conditions are easy to control. It is a simple and efficient method for preparing a catalyst for the normalization of isopentane. The catalyst can effectively catalyze the normalization of isopentane under mild conditions. The catalyst of this invention has excellent reaction performance in the isopentane conversion reaction, such as high isopentane conversion rate and high n-pentane selectivity, and the reaction conditions are mild. The operation is simple, and the catalyst is easy to prepare and can be recycled. Detailed Implementation

[0039] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.

[0040] Unless otherwise specified, all raw materials used in the embodiments of this application were purchased through commercial channels.

[0041] Example 1

[0042] (1) Take 30 parts by weight of ZSM-11 molecular sieve, 20 parts by weight of boehmite, 5 parts by weight of ammonium chloride and 10 parts by weight of aluminum sol and mix them evenly. Put the above mixture into a rotary molding machine, adjust the tilt angle of the turntable to 55° and the rotation speed of the turntable to 20 rpm. Spray a 1.5% acetic acid aqueous solution onto the molding material through a sprayer. The molding time is 30 min to obtain spherical material with a diameter of 1.0 to 1.5 mm. Dry the obtained material at 120°C for 12 h and calcine at 500°C for 2 h to obtain a spherical core.

[0043] (2) Mix 30 parts by weight of ZSM-5 molecular sieve, 5 parts by weight of silica sol, 3 parts by weight of aluminum nitrate, 3 parts by weight of 5% nitric acid mixture and 20 parts by weight of the spherical core obtained in step (1) evenly, and then put it into a rotary molding machine. Adjust the tilt angle of the turntable to 60° and the rotation speed of the turntable to 10 rpm. Spray a 1.5% citric acid aqueous solution onto the molding material through a sprayer. The molding time is 10 min, and spherical material with a diameter of 1.5-2 mm is obtained. Dry the obtained material at 120°C for 12 h and calcine at 550°C for 2 h to obtain a double-layer spherical carrier.

[0044] (3) Chloroplatinic acid was dissolved in deionized water to prepare a precursor solution. The amount of chloroplatinic acid used was calculated based on the loading of platinum on the spherical support being 0.2 wt%. The precursor solution was added dropwise to the bilayer spherical support using an equal-volume impregnation method. The catalyst was dried at 120 °C for 12 h and calcined at 600 °C for 2 h to obtain catalyst 1. # .

[0045] Example 2

[0046] (1) Take 30 parts by weight of ZSM-22 molecular sieve, 15 parts by weight of boehmite, 5 parts by weight of ammonium chloride and 10 parts by weight of water and mix them evenly. Put the above mixture into a rotary molding machine, adjust the tilt angle of the turntable to 55° and the rotation speed of the turntable to 20 rpm. Spray a 1.5% acetic acid aqueous solution onto the molding material through a sprayer. The molding time is 30 min to obtain spherical material with a diameter of 1.0 to 1.5 mm. Dry the obtained material at 120°C for 12 h and calcine at 500°C for 2 h to obtain a spherical core.

[0047] (2) Take 30 parts by weight of ZSM-5 molecular sieve, 10 parts by weight of kaolin, 3 parts by weight of aluminum nitrate, 3 parts by weight of a 5% nitric acid mixture, and 20 parts by weight of the spherical core obtained in step (1). Mix them evenly and place them in a rotary molding machine. Adjust the tilt angle of the turntable to 60° and the rotation speed of the turntable to 10 rpm. Spray a 1.5% citric acid aqueous solution onto the molding material through a sprayer. The molding time is 10 min, and spherical materials with a diameter of 1.5-2 mm are obtained. Dry the obtained material at 120°C for 12 h and calcine at 550°C for 2 h to obtain a double-layer spherical carrier.

[0048] (3) Tetraammineplatinum chloride was dissolved in deionized water to prepare a precursor solution. The amount of chloroplatinic acid was calculated based on the loading of platinum metal on the spherical support being 0.2 wt%. The precursor solution was added dropwise to the bilayer spherical support using an equal-volume impregnation method. The catalyst was dried at 120 °C for 12 h and calcined at 600 °C for 2 h to obtain catalyst 2. # .

[0049] Example 3

[0050] (1) Take 30 parts by weight of ZSM-11 molecular sieve, 5 parts by weight of boehmite, 5 parts by weight of ammonium chloride and 5 parts by weight of water and mix them evenly. Put the above mixture into a rotary molding machine, adjust the tilt angle of the turntable to 55° and the rotation speed of the turntable to 20 rpm. Spray a 1.5% acetic acid aqueous solution onto the molding material through a sprayer. The molding time is 30 min to obtain spherical material with a diameter of 1.0 to 1.5 mm. Dry the obtained material at 120°C for 12 h and calcine at 500°C for 2 h to obtain a spherical core.

[0051] (2) Take 30 parts by weight of ZSM-5 molecular sieve, 10 parts by weight of kaolin, 3 parts by weight of aluminum nitrate, 3 parts by weight of a 5% nitric acid mixture, and 20 parts by weight of the spherical core obtained in step (1). Mix them evenly and place them in a rotary molding machine. Adjust the tilt angle of the turntable to 60° and the rotation speed of the turntable to 10 rpm. Spray a 1.5% citric acid aqueous solution onto the molding material through a sprayer. The molding time is 10 min, and spherical materials with a diameter of 1.5-2 mm are obtained. Dry the obtained material at 120°C for 12 h and calcine at 550°C for 2 h to obtain a double-layer spherical carrier.

[0052] (3) Tetraammineplatinum chloride was dissolved in deionized water to prepare a precursor solution. The amount of chloroplatinic acid was calculated based on the loading of platinum metal on the spherical support being 0.2 wt%. The precursor solution was added dropwise to the bilayer spherical support using an equal-volume impregnation method. The catalyst was dried at 120 °C for 12 h and calcined at 600 °C for 2 h to obtain catalyst 3. # .

[0053] Example 4

[0054] (1) Take 30 parts by weight of ZSM-23 molecular sieve, 15 parts by weight of boehmite, 5 parts by weight of ammonium chloride and 5 parts by weight of dilute nitric acid and mix them evenly. Put the above mixture into a rotary molding machine, adjust the tilt angle of the turntable to 55° and the rotation speed of the turntable to 20 rpm. Spray a 1.5% acetic acid aqueous solution onto the molding material through a sprayer. The molding time is 30 min to obtain spherical material with a diameter of 1.0 to 1.5 mm. Dry the obtained material at 120°C for 12 h and calcine at 500°C for 2 h to obtain a spherical core.

[0055] (2) Take 30 parts by weight of ZSM-5 molecular sieve, 5 parts by weight of silica sol, 3 parts by weight of aluminum nitrate, 3 parts by weight of a 5% nitric acid mixture, and 20 parts by weight of the spherical core obtained in step (1). Mix them evenly and place them in a rotary molding machine. Adjust the tilt angle of the turntable to 60° and the rotation speed of the turntable to 10 rpm. Spray a 1.5% citric acid aqueous solution onto the molding material through a sprayer. The molding time is 10 min to obtain spherical material with a diameter of 1.5-2 mm. Dry the obtained material at 120°C for 12 h and calcine at 550°C for 2 h to obtain a double-layer spherical carrier.

[0056] (3) Tetraammineplatinum chloride was dissolved in deionized water to prepare a precursor solution. The amount of chloroplatinic acid was calculated based on the loading of platinum metal on the spherical support being 0.2 wt%. The precursor solution was added dropwise to the bilayer spherical support using an equal-volume impregnation method. The catalyst was dried at 120 °C for 12 h and calcined at 600 °C for 2 h to obtain catalyst 4. # .

[0057] Example 5

[0058] (1) Take 30 parts by weight of MOR molecular sieve, 5 parts by weight of boehmite, 3 parts by weight of ammonium chloride and 5 parts by weight of dilute nitric acid and mix them evenly. Put the above mixture into a rotary molding machine, adjust the tilt angle of the turntable to 55° and the rotation speed of the turntable to 20 rpm. Spray a 1.5% acetic acid aqueous solution onto the molding material through a sprayer. The molding time is 30 min, and spherical materials with a diameter of 1.0 to 1.5 mm are obtained. The obtained material is dried at 120°C for 12 h and calcined at 500°C for 2 h to obtain a spherical core.

[0059] (2) Take 30 parts by weight of ZSM-5 molecular sieve, 5 parts by weight of silica sol, 5 parts by weight of aluminum nitrate, 3 parts by weight of a 5% nitric acid mixture, and 20 parts by weight of the spherical core obtained in step (1). Mix the above materials evenly and place them in a rotary molding machine. Adjust the tilt angle of the turntable to 60° and the rotation speed of the turntable to 10 rpm. Spray a 1.5% citric acid aqueous solution onto the molding material through a sprayer. The molding time is 10 min to obtain spherical materials with a diameter of 1.5-2 mm. Dry the obtained material at 120°C for 12 h and calcine at 550°C for 2 h to obtain a double-layer spherical carrier.

[0060] (3) Platinum nitrate was dissolved in deionized water to prepare a precursor solution. The amount of chloroplatinic acid was calculated based on the loading of platinum on the spherical support being 0.2 wt%. The precursor solution was added dropwise to the bilayer spherical support using an equal-volume impregnation method. The catalyst was dried at 120 °C for 12 h and calcined at 600 °C for 2 h to obtain catalyst 5. # .

[0061] Example 6 Comparative Example 1

[0062] Take 30 parts by weight of MOR molecular sieve, 30 parts by weight of ZSM-5 molecular sieve, 5 parts by weight of silica sol, 5 parts by weight of aluminum nitrate, and 3 parts by weight of 5% nitric acid mixture and mix them evenly. After the above materials are evenly mixed, put them into a rotary molding machine, adjust the tilt angle of the turntable to 60°, and the rotation speed of the turntable to 10 rpm. Spray a 1.5% citric acid aqueous solution onto the molding material through a sprayer. The molding time is 10 min, and spherical materials with a diameter of 1.5-2 mm are obtained. The obtained material is dried at 120℃ for 12 h and calcined at 550℃ for 2 h to obtain the carrier.

[0063] A precursor solution was prepared by dissolving chloroplatinic acid in deionized water. The amount of chloroplatinic acid used was calculated based on a platinum loading of 0.2 wt% on the spherical support. The precursor solution was added dropwise to the support using an equal-volume impregnation method. The catalyst was dried at 120 °C for 12 h and calcined at 600 °C for 2 h.

[0064] Example 7 Comparative Example 2

[0065] Take 30 parts by weight of ZSM-11 molecular sieve, 30 parts by weight of ZSM-5 molecular sieve, 5 parts by weight of silica sol, 5 parts by weight of aluminum nitrate, and 3 parts by weight of 5% nitric acid mixture and mix them evenly. After the above materials are evenly mixed, put them into a rotary molding machine, adjust the tilt angle of the turntable to 60°, and the rotation speed of the turntable to 10 rpm. Spray a 1.5% citric acid aqueous solution onto the molding material through a sprayer. The molding time is 10 min, and spherical materials with a diameter of 1.5-2 mm are obtained. The obtained material is dried at 120℃ for 12 h and calcined at 550℃ for 2 h to obtain the carrier.

[0066] A precursor solution was prepared by dissolving chloroplatinic acid in deionized water. The amount of chloroplatinic acid used was calculated based on a platinum loading of 0.2 wt% on the spherical support. The precursor solution was added dropwise to the support using an equal-volume impregnation method. The catalyst was dried at 120 °C for 12 h and calcined at 600 °C for 2 h.

[0067] Example 8: Evaluation of the normal-phase activity of the catalyst in isopentane

[0068] Catalyst 1 prepared in Examples 1-7 # ~5 # The catalytic performance of isopentane n-phase catalysts was evaluated using a fixed-bed reactor with an inner diameter of 9 mm and a catalyst loading of 2 mL. After reduction with hydrogen, the catalyst was reacted with isopentane and hydrogen gas. The products were analyzed online using an Agilent 7890A chromatograph. The catalyst activity was evaluated based on isopentane conversion and n-pentane selectivity. The calculation methods for each indicator are as follows:

[0069]

[0070] isopentane 进 The mass flow rate (kg / h) of isopentane at the reactor inlet; isopentane 出 and n-pentane 出 The values ​​represent the mass flow rates (kg / h) of isopentane and n-pentane at the reactor outlet, respectively. Table 1 shows the catalysts used in catalyst evaluation experiments 1–7, the catalyst pretreatment conditions, the reaction conditions, and the catalyst activities.

[0071] Table 1. Reaction conditions and catalyst activities for Experiments 1-7

[0072]

[0073] The above description is merely a few embodiments of this application and is not intended to limit this application in any way. Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of this application using the disclosed technical content are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A method for preparing n-alkanes, characterized in that, Includes the following steps: In a reactor, isoparaffins and hydrogen are brought into contact with a catalyst and reacted to obtain n-paraffins; The isoalkane is selected from at least one of isobutane and isopentane; The catalyst consists of a double-layered spherical support and a noble metal active component supported on the surface of the double-layered spherical support. The precious metal active component is selected from at least one of platinum, palladium and gold.

2. The method according to claim 1, characterized in that, The catalyst is obtained through the following steps: The catalyst was obtained by mixing a bilayer spherical support with an aqueous solution containing a noble metal precursor, drying, calcining, and reducing with hydrogen.

3. The method according to claim 2, characterized in that, The noble metal precursor is selected from at least one of chloroplatinic acid, tetraammineplatinum chloride, platinum nitrate, palladium nitrate, palladium chloride, ammonium chloropalladate, and tetraammineplatinum chloride. The drying temperature is 30–120°C; The drying time is 1 to 12 hours; The roasting temperature is 300–600°C; The roasting time is 1 to 10 hours; The temperature for hydrogen reduction is 350–600°C; The hydrogen reduction time is 1 to 12 hours.

4. The method according to claim 2, characterized in that, The double-layered spherical carrier is obtained through the following steps: (1) Mix molecular sieve I, boehmite, ammonium chloride and additive I, and roll them into balls to obtain a spherical core; (2) Mix the spherical core, molecular sieve II, kaolin, silica sol and additive II, roll them into balls, dry them and calcine them to obtain the double-layer spherical carrier.

5. The method according to claim 4, characterized in that, The molecular sieve I is a hydrogen-type molecular sieve, selected from at least one of ZSM-11 molecular sieve, ZSM-22 molecular sieve, ZSM-23 molecular sieve, β molecular sieve, Y molecular sieve and MOR molecular sieve; The auxiliary agent I is selected from at least one of aluminum sol, water, dilute nitric acid, oxalic acid, phosphoric acid, and acetic acid; The mass ratio of molecular sieve I, pseudoboehmite, ammonium chloride, and auxiliary agent I is 1-40:2-25:1-10:1-10.

6. The method according to claim 4, characterized in that, The molecular sieve II is selected from hydrogen-type ZSM-5 molecular sieve; The auxiliary agent II is obtained by mixing at least one of aluminum nitrate, small-pore alumina and aluminum sulfate with an inorganic acid or an organic acid, wherein the mass content of the inorganic acid or organic acid is 20-50 wt%. The mass ratio of the spherical core, molecular sieve II, kaolin, silica sol and additive II is 1-20:1-30:1-10:1-10:1-10; The drying temperature is 80–120°C; The drying time is 1 to 12 hours; The calcination temperature is 300–600°C; The calcination time is 1 to 10 hours.

7. The method according to claim 1, characterized in that, The reaction temperature is 300–600°C; The reaction pressure is 0.3–3 MPa.

8. The method according to claim 1, characterized in that, The molar ratio of the isoalkane to hydrogen is 0.1 to 2:1; The mass hourly space velocity (MSV) of the isoalkanes is 0.1–2 h⁻¹. -1 .

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