A process for normalizing isomeric alkanes

Abstract

The application discloses a method for normalizing isomeric alkanes, which comprises the following steps: contacting isomeric alkanes and hydrogen with a catalyst in a reactor to obtain normal alkanes; the isomeric alkanes are selected from at least one of isobutane and isopentane; the catalyst is composed of an acidic carrier, a noble metal active component supported on the surface of the acidic carrier and an auxiliary element; the noble metal active component is selected from at least one of Pt and Pd; the auxiliary element is selected from at least one of Ce, Sn, La, Fe, Co, Ni and Cu; and the carrier is selected from at least one of molecular sieve, Al2O3 modified SO4 2‑ -WO3-ZrO2; the mass ratio of the noble metal active component to the acidic carrier in the catalyst is 0.0001-0.01:1; and the mass ratio of the auxiliary element to the acidic carrier is 0.0001-0.008:1.

Description

Technical Field

[0001] This application relates to a method for the normalization of isomeric alkanes, belonging to the field of chemical engineering. Background Technology

[0002] With the rapid development of catalytic cracking and hydrocracking processes, the production of isobutane and isopentane has increased, necessitating their efficient utilization. As basic chemical feedstocks, ethylene and propylene, low-carbon olefins, are experiencing continuous industrial development and increasing demand. However, 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, normalizing isobutane and isopentane for steam cracking to produce ethylene and propylene is of significant application value. Currently, research on normalization reactions, especially on the normalization of isopentane, is still limited. Summary of the Invention

[0003] The purpose of this invention is to provide a method for the normalization of isoparaffins, wherein the catalyst involved in the method is used in the normalization process of C4 or C5 isoparaffins, has high catalytic performance, the product has high selectivity for normalized alkanes, and the catalyst has high stability.

[0004] According to one aspect of this application, a method for the normalization of isomeric alkanes is provided, comprising the following steps:

[0005] In a reactor, isoparaffins and hydrogen are brought into contact with a catalyst and reacted to obtain n-paraffins;

[0006] The isoalkane is selected from at least one of isobutane and isopentane;

[0007] The catalyst is composed of an acidic support and noble metal active components and auxiliary elements supported on the surface of the acidic support.

[0008] The noble metal active component is selected from at least one of Pt and Pd;

[0009] The auxiliary element is selected from at least one of Ce, Sn, La, Fe, Co, Ni, and Cu;

[0010] The carrier is selected from molecular sieves and alumina-modified SO4. 2- At least one of -ZrO2 and WO3-ZrO2;

[0011] In the catalyst, the mass ratio of the noble metal active component to the acidic support is 0.0001 to 0.01:1;

[0012] The mass ratio of the auxiliary element to the acidic carrier is 0.0001 to 0.008:1.

[0013] The catalyst is obtained through the following steps:

[0014] The acidic support was mixed with an aqueous solution containing a noble metal precursor and an auxiliary element precursor, dried, calcined, roasted in situ, and reduced with hydrogen to obtain the catalyst.

[0015] 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.

[0016] The auxiliary element precursor is selected from at least one of cerium nitrate, tin chloride, lanthanum nitrate, ferric sulfate, cobalt nitrate, copper sulfate, and nickel nitrate;

[0017] The drying temperature is 30–120°C;

[0018] The drying time is 1 to 15 hours;

[0019] The calcination temperature is 300–600°C;

[0020] The calcination time is 1 to 10 hours;

[0021] The in-situ roasting temperature is 300–800℃;

[0022] The in-situ roasting time is 6–8 hours;

[0023] The atmosphere for in-situ roasting is an air atmosphere;

[0024] The temperature for hydrogen reduction is 300–500°C;

[0025] The hydrogen reduction time is 2 to 5 hours.

[0026] The silica-to-alumina ratio of the molecular sieve is 10–75;

[0027] The molecular sieve is selected from at least one of Y molecular sieve, β molecular sieve, ZSM-5 molecular sieve, ZSM-35 molecular sieve, ZSM-22 molecular sieve, ZSM-23 molecular sieve, and MOR molecular sieve.

[0028] The alumina-modified SO4 2- -ZrO2 is obtained through the following steps:

[0029] ZrOCl2, Al(NO3)3, and water were mixed and stirred. Concentrated ammonia was added dropwise until the pH reached 10. The mixture was allowed to stand, filtered, washed, and dried (I). Then, it was soaked in dilute sulfuric acid, filtered, washed, dried (II), and calcined (I) to obtain the alumina-modified SO4. 2- -ZrO2.

[0030] The settling time is 1 to 10 hours;

[0031] The temperature of the drying process I is 30–120°C;

[0032] The drying time for step I is 1–12 h.

[0033] The concentration of the dilute sulfuric acid is 0.25 mol / L;

[0034] The temperature of the drying II process is 30–120°C;

[0035] The drying time for step II is 1–12 hours;

[0036] The temperature of the calcination I is 550–750°C;

[0037] The roasting time for step I is 1 to 10 hours;

[0038] The atmosphere for roasting I is an air atmosphere.

[0039] The WO3-ZrO2 is obtained through the following steps:

[0040] A solution containing ZrOCl2 is mixed with a solution containing ammonium metatungstate and ammonium hydroxide in a sealed container, heated, filtered, washed, dried (III), and calcined (II) to obtain the WO3-ZrO2.

[0041] The heating temperature is 50–120°C;

[0042] The heating time is 1 to 20 hours.

[0043] The temperature of the drying III process is 30–120°C;

[0044] The drying time for step III is 1–12 hours;

[0045] The temperature of the second calcination is 600–750°C;

[0046] The roasting time for the second stage is 1 to 10 hours.

[0047] The reactor is selected from one of a fixed-bed reactor, a fluidized-bed reactor, and a moving-bed reactor.

[0048] The reaction temperature is 200–600°C;

[0049] The reaction pressure is 0.001–5 MPa;

[0050] The liquid hourly space velocity (LHSV) of the isoalkanes is 0.1–4 h⁻¹. -1

[0051] The molar ratio of hydrogen to isoalkanes is 0.01 to 4:1.

[0052] The beneficial effects that this application can produce include:

[0053] This invention provides a method for efficiently preparing low-carbon n-alkanes from low-carbon isoalkanes in one step through catalysis. This method has the advantages of a short process flow, simple operation, and low energy consumption, and can improve steam cracking feedstocks. The catalyst used in the above method comprises a noble metal active component, an acidic support, and an auxiliary agent. This catalyst exhibits high catalytic activity and good selectivity in the above-mentioned method for preparing low-carbon n-alkanes, and the preparation process is simple, easy to operate, and has good reproducibility, making it suitable for large-scale industrial production. Detailed Implementation

[0054] The present invention will now be described in detail with reference to the embodiments, but the present invention is not limited to these embodiments.

[0055] Unless otherwise specified, all raw materials used in the examples are commercially available, and the instruments and equipment are configured with parameters recommended by the manufacturer.

[0056] Example 1

[0057] (1) ZrOCl2·8H2O and Al(NO3)3·9H2O were dissolved in deionized water in a 1:1 ratio. Concentrated ammonia was added dropwise under stirring until the pH reached 10. The mixture was allowed to stand at room temperature for 5 hours, filtered, washed with deionized water, and the resulting precipitate was dried at 110℃ for 12 hours. The solid was then soaked in 0.25 mol / L dilute sulfuric acid for 2 hours, filtered, washed with deionized water, dried, and calcined at 550℃ in air for 2 hours to obtain alumina-modified SO4. 2- -ZrO2.

[0058] (2) The saturated adsorption method was used to determine the alumina-modified SO4. 2- - The saturated water absorption capacity of ZrO2, based on the alumina-modified SO4 2- The concentration of the impregnation precursor solution was calculated based on the saturated water absorption of ZrO2, the target loading of platinum (0.2 wt% by metal element mass), and the target loading of cerium (0.14 wt% by metal element mass). According to the calculation results, chloroplatinic acid and cerium nitrate were used to prepare the impregnation precursor solution.

[0059] (3) The impregnation precursor solution obtained in (2) is uniformly added to the alumina-modified SO4 in step (1). 2- The catalyst was subjected to adsorption saturation in ZrO2, then allowed to stand overnight at room temperature, dried at 120°C for 12 hours, and calcined at 550°C for 2 hours to obtain catalyst 1. # .

[0060] Example 2

[0061] (1) The ZrOCl2·8H2O solution was mixed with a solution containing ammonium metatungstate and ammonium hydroxide under stirring to obtain a slurry with a pH of about 9.0. The slurry was placed in a reactor and hydrothermally treated at 100°C for 16 hours. The product was filtered, washed with deionized water, dried at 120°C overnight, and then calcined at 600°C for 2 hours to obtain WO3-ZrO2 support.

[0062] (2) The saturated water absorption of alumina-modified WO3-ZrO2 was measured by the saturated adsorption method. Based on the saturated water absorption of WO3-ZrO2, the target loading of platinum (0.4 wt% by mass of metal element) and the target loading of cerium (0.56 wt% by mass of metal element), the concentration of the impregnation precursor solution was calculated. Based on the calculation results, chloroplatinic acid and cerium nitrate were used to prepare the impregnation precursor solution.

[0063] (3) The impregnation precursor solution obtained in (2) was uniformly added to the WO3-ZrO2 support in step (1) until adsorption saturation, then allowed to stand at room temperature overnight, dried at 120℃ for 12 h, and calcined at 550℃ for 2 h to obtain catalyst 2. # .

[0064] Example 3

[0065] (1) Weigh a certain mass of ZSM-35 with a silicon-to-aluminum ratio of 20.

[0066] (2) The saturated water absorption of ZSM-35 was measured by the saturated adsorption method. Based on the saturated water absorption of ZSM-35, the target loading of platinum (0.1 wt% by metal element mass) and the target loading of lanthanum (0.07 wt% by metal element mass), the concentration of the impregnation precursor solution was calculated. Based on the calculation results, chloroplatinic acid and lanthanum nitrate were used to prepare the impregnation precursor solution.

[0067] (3) The impregnation precursor solution obtained in (2) was uniformly added to the ZSM-35 support in step (1) until adsorption saturation was achieved. Then, it was allowed to stand at room temperature overnight, dried at 120°C for 12 h, and calcined at 550°C for 2 h. Catalyst 3 was obtained. # .

[0068] Example 4

[0069] (1) Weigh a certain mass of ZSM-5 with a silicon-aluminum ratio of 45.

[0070] (2) The saturated water absorption of ZSM-5 was measured by the saturated adsorption method. Based on the saturated water absorption of ZSM-5, the target loading of platinum (0.1 wt% by mass of metal element) and the target loading of nickel (0.07 wt% by mass of metal element), the concentration of the impregnation precursor solution was calculated. Based on the calculation results, tetraammineplatinum chloride and nickel nitrate were used to prepare the impregnation precursor solution.

[0071] (3) The impregnation precursor solution obtained in (2) was uniformly added to the ZSM-5 support in step (1) until adsorption saturation, then allowed to stand at room temperature overnight, dried at 120℃ for 12 h, and calcined at 550℃ for 2 h to obtain catalyst 4. # .

[0072] Example 5

[0073] (1) Weigh a certain mass of ZSM-22 with a silicon-to-aluminum ratio of 70.

[0074] (2) The saturated water absorption of ZSM-22 was measured by the saturated adsorption method. Based on the saturated water absorption of ZSM-22, the target loading of platinum (0.1 wt% by mass of metal element) and the target loading of nickel (0.07 wt% by mass of metal element), the concentration of the impregnation precursor solution was calculated. Based on the calculation results, tetraammineplatinum chloride and nickel nitrate were used to prepare the impregnation precursor solution.

[0075] (3) The impregnation precursor solution obtained in (2) was uniformly added to the ZSM-22 support in step (1) until adsorption saturation, then allowed to stand at room temperature overnight, dried at 120℃ for 12 h, and calcined at 550℃ for 2 h. Catalyst 5 was obtained. # .

[0076] Example 6 Comparative Example

[0077] A certain mass of ZSM-5 molecular sieve was taken. The saturated water absorption of ZSM-5 was measured using the saturated adsorption method. Based on the saturated water absorption of ZSM-5 and the target platinum loading (0.1 wt% by metal element mass), the concentration of the impregnation precursor solution was calculated. According to the calculation results, chloroplatinic acid was dissolved in deionized water to prepare the impregnation precursor solution. The obtained impregnation precursor solution was uniformly added to the ZSM-5 molecular sieve until adsorption reached saturation. The mixture was then allowed to stand overnight at room temperature, dried at 120℃ for 12 h, and calcined at 550℃ for 2 h to obtain the catalyst.

[0078] Example 7: Evaluation of the catalyst's isoalkane conversion activity

[0079] Catalyst 1 prepared in Examples 1-5 # ~5 # The catalytic performance of the comparative catalysts for the normalization of isoparaffins 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 at 460 °C for 2 h, the catalyst was reacted with a feedstock containing isoparaffins and hydrogen. The products were analyzed online using an Agilent 7890A chromatograph. The catalyst activity was evaluated based on indicators such as isobutane conversion and selectivity for high-quality cracked feedstock. The calculation methods for each indicator are as follows:

[0080]

[0081] Isoalkanes 进 The mass flow rate (kg / h) of isoalkanes at the reactor inlet; isoalkanes 出 and n-alkanes 出 The values ​​represent the mass flow rates (kg / h) of isoalkanes and n-alkanes at the reactor outlet, respectively. Catalyst Evaluation: The catalysts used in Examples 1–9, along with the catalyst pretreatment conditions, reaction conditions, and the isoalkan conversion activities of the catalysts, are shown in Table 1.

[0082] Table 1. Reaction conditions and catalyst activity of Examples 1-9

[0083]

[0084] 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 the normalization of isomeric 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 is composed of an acidic support and a noble metal active component and auxiliary elements supported on the surface of the acidic support. The noble metal active component is selected from at least one of Pt and Pd; The auxiliary element is selected from at least one of Ce, Sn, La, Fe, Co, Ni, and Cu; The carrier is selected from molecular sieves and alumina-modified SO4. 2- At least one of -ZrO2 and WO3-ZrO2; In the catalyst, the mass ratio of the noble metal active component to the acidic support is 0.0001 to 0.01:1; The mass ratio of the auxiliary element to the acidic carrier is 0.0001 to 0.008:

1.

2. The method according to claim 1, characterized in that, The catalyst is obtained through the following steps: The acidic support was mixed with an aqueous solution containing a noble metal precursor and an auxiliary element precursor, dried, calcined, roasted in situ, and reduced with hydrogen to obtain the catalyst.

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 auxiliary element precursor is selected from at least one of cerium nitrate, tin chloride, lanthanum nitrate, ferric sulfate, cobalt nitrate, copper sulfate, and nickel nitrate; The drying temperature is 30–120°C; The drying time is 1 to 15 hours; The calcination temperature is 300–600°C; The calcination time is 1 to 10 hours; The in-situ roasting temperature is 300–800℃; The in-situ roasting time is 6–8 hours; The atmosphere for in-situ roasting is an air atmosphere; The temperature for hydrogen reduction is 300–500°C; The hydrogen reduction time is 2 to 5 hours.

4. The method according to claim 1, characterized in that, The silica-to-alumina ratio of the molecular sieve is 10–75; The molecular sieve is selected from at least one of Y molecular sieve, β molecular sieve, ZSM-5 molecular sieve, ZSM-35 molecular sieve, ZSM-22 molecular sieve, ZSM-23 molecular sieve, and MOR molecular sieve.

5. The method according to claim 1, characterized in that, The alumina-modified SO4 2- -ZrO2 is obtained through the following steps: ZrOCl2, Al(NO3)3, and water were mixed and stirred. Concentrated ammonia was added dropwise until the pH reached 10. The mixture was allowed to stand, filtered, washed, and dried (I). Then, it was soaked in dilute sulfuric acid, filtered, washed, dried (II), and calcined (I) to obtain the alumina-modified SO4. 2- -ZrO2.

6. The method according to claim 5, characterized in that, The settling time is 1 to 10 hours; The temperature of the drying process I is 30–120°C; The drying time for step I is 1–12 hours; The concentration of the dilute sulfuric acid is 0.25 mol / L; The temperature of the drying II process is 30–120°C; The drying time for step II is 1–12 hours; The temperature of the calcination I is 550–750°C; The roasting time for step I is 1 to 10 hours; The atmosphere for roasting I is an air atmosphere.

7. The method according to claim 1, characterized in that, The WO3-ZrO2 is obtained through the following steps: A solution containing ZrOCl2 is mixed with a solution containing ammonium metatungstate and ammonium hydroxide in a sealed container, heated, filtered, washed, dried (III), and calcined (II) to obtain the WO3-ZrO2.

8. The method according to claim 7, characterized in that, The heating temperature is 50–120°C; The heating time is 1 to 20 hours; The temperature of the drying III process is 30–120°C; The drying time for step III is 1–12 hours; The temperature of the second calcination is 600–750°C; The roasting time for the second stage is 1 to 10 hours.

9. The method according to claim 1, characterized in that, The reactor is selected from one of a fixed-bed reactor, a fluidized-bed reactor, and a moving-bed reactor.

10. The method according to claim 1, characterized in that, The reaction temperature is 200–600°C; The reaction pressure is 0.001–5 MPa; The liquid hourly space velocity (LHSV) of the isoalkanes is 0.1–4 h⁻¹. -1 The molar ratio of hydrogen to isoalkanes is 0.01 to 4:1.

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