A process for the efficient conversion of isomeric alkanes

Abstract

This invention discloses a method for the efficient conversion of isoparaffins, comprising the following steps: contacting a raw material containing isoparaffins and hydrogen with a catalyst in a reactor, reacting to obtain a product containing small molecule alkanes; wherein the isoparaffins are selected from at least one of isobutane, isopentane, neopentane, isohexane, and 3-methylpentane; wherein the small molecule alkanes are selected from at least one of ethane, propane, and n-butane; the catalyst is obtained by the following steps: mixing a metal acidic functional component, a metal basic functional component, a matrix precursor, a phosphorus auxiliary component precursor, a molding aid, and water, kneading, molding, and vacuum drying to obtain the catalyst.

Description

Technical Field

[0001] This invention relates to a method for the efficient conversion of isoparaffins, belonging 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 vital role in industrial production, providing modern society with a large number of basic chemical products and advanced functional materials.

[0003] Ethylene is the most in-demand basic chemical raw material among trienes. 95% of the world's ethylene is produced using steam cracking, and China's domestic steam cracking ethylene production capacity exceeds 80% of the total ethylene production capacity. Steam cracking to produce ethylene is a non-catalytic thermal processing method. The ethylene yield is determined by the overall composition of the feedstock. Generally, the yield of branched alkanes is much lower than that of n-alkanes, and the yield of long-chain alkanes is lower than that of short-chain alkanes.

[0004] The main feedstock for domestic steam cracking units is naphtha, but the yield of ethylene from naphtha cracking is usually only around 30%, while the isoalkanes in naphtha are typically only around 10%, far lower than ethane (about 80%), propane (about 40%), and n-butane (about 40%). Converting the naphtha fraction, especially the isoalkanes, into ethane, propane, and n-butane before feeding it into the steam cracking unit can significantly increase the ethylene yield. Summary of the Invention

[0005] The purpose of this invention is to provide a highly efficient catalyst for the conversion of isoparaffins, its preparation method, and its applications. The catalyst exhibits high catalytic activity, good selectivity, and is not easily deactivated, and can catalytically convert isoparaffins with low efficiency in steam cracking to ethylene into high-quality steam cracking feedstocks such as ethane, propane, and n-butane.

[0006] According to one aspect of the present invention, a method for the efficient conversion of isoparaffins is provided, comprising the following steps:

[0007] In a reactor, a raw material containing isoparaffins and hydrogen is brought into contact with a catalyst and reacted to obtain a product containing small molecule alkanes.

[0008] The isoalkane is selected from at least one of isobutane, isopentane, neopentane, isohexane, and 3-methylpentane;

[0009] The small molecule alkane is selected from at least one of ethane, propane, and n-butane;

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

[0011] The catalyst is obtained by mixing the acidic metal functional component, the basic metal functional component, the matrix precursor, the phosphorus auxiliary component precursor, the molding aid, and water, kneading, molding, and vacuum drying.

[0012] The mass hourly space velocity (MSV) of the isoalkanes is 0.2–10 h⁻¹. -1 ;

[0013] The molar ratio of hydrogen to isoalkanes is 0.5 to 10:1;

[0014] The reaction temperature is 350–550°C;

[0015] The reaction is carried out at a pressure of 0.1–5 MPa.

[0016] The matrix precursor is selected from at least one of zirconium sol, aluminum sol, titanium sol, silica sol, boehmite, silica, kaolinite, and sepiolite.

[0017] The molding aid is selected from at least one of citric acid, nitric acid, sulfuric acid, hydrochloric acid, tartaric acid, polyethylene glycol, polyvinyl alcohol, glycerol, acetic acid, and soluble starch.

[0018] The precursor of the phosphorus adjuvant component is selected from at least one of phosphoric acid, sodium phosphate, sodium dihydrogen phosphate, ammonium dihydrogen phosphate, and ammonium phosphate.

[0019] The mass ratio of the metal acidic functional component, the metal basic functional component, the matrix precursor, the phosphorus auxiliary component precursor, and the molding aid is 2.5–5.5:1.0–3.5:1.7–2.3:0.2–0.3:1;

[0020] The vacuum drying temperature is 90–130°C;

[0021] The vacuum drying time is 2–20 hours;

[0022] The vacuum degree of the vacuum drying process is -30 to -80 kPa.

[0023] The metal acid functional component is obtained through the following steps:

[0024] An aqueous solution containing lanthanum and nickel compounds was added to a hydrogen-type molecular sieve until adsorption saturation, then allowed to stand, dried (I), calcined (I), and reduced with hydrogen (I) to obtain the metal acidic functional component.

[0025] The lanthanum compound is selected from at least one of the soluble salts of lanthanum;

[0026] The nickel compound is selected from at least one of the soluble salts of nickel;

[0027] The hydrogen form molecule is selected from at least one of ZSM-5, MCM-22, SAPO-11, and MOR;

[0028] The temperature of the drying process I is 100–130°C;

[0029] The drying time for step I is 4–20 hours;

[0030] The temperature of the calcination I is 500–600°C;

[0031] The roasting time for step I is 2 to 10 hours;

[0032] The temperature of hydrogen reduction I is 500–600°C;

[0033] The hydrogen reduction I time is 1 to 10 hours;

[0034] In the aforementioned metal acidic functional component, the mass ratio of lanthanum, nickel, and hydrogen-type molecular sieve compound is 0.001–0.02:0.01–0.08:1.

[0035] The mass of lanthanum and nickel is expressed as the mass of the elements themselves.

[0036] The basic metal functional component is obtained through the following steps:

[0037] An aqueous solution containing a noble metal precursor is added to an alkaline material until adsorption saturation, then allowed to stand, dried (II), calcined (II), and reduced with hydrogen (II) to obtain the metal acidic functional component.

[0038] The noble metal precursor is selected from at least one of chloroplatinic acid, tetraammineplatinum nitrate, platinum nitrate, ruthenium trichloride, ammonium hexachlororuthenate, and ruthenium nitrate.

[0039] The alkaline material is selected from at least one of cesium ion-type X molecular sieve, cesium ion-type Y molecular sieve, cesium ion-type L molecular sieve, calcium silicate, and hydroxyapatite;

[0040] The temperature of the drying II process is 100–130°C;

[0041] The drying time for step II is 4–20 hours;

[0042] The temperature of the second calcination is 450–550°C;

[0043] The roasting time for II is 4–12 hours;

[0044] The temperature of hydrogen reduction II is 250–450°C;

[0045] The hydrogen reduction II process takes 1–10 hours.

[0046] In the alkaline functional component, the mass ratio of noble metal to alkaline material is 0.001 to 0.02:1;

[0047] The mass of precious metals is measured by the mass of the precious metal element.

[0048] The beneficial effects that this invention can produce include:

[0049] The catalyst provided by this invention comprises a metal acidic functional component, a metal basic functional component, a matrix, and a phosphorus auxiliary component. The metal acidic functional component catalyzes the efficient cracking of hydrocarbon molecules, while the metal basic functional component not only catalyzes the normalization of isoparaffins to improve the cracking efficiency of hydrocarbon molecules and reduce methane formation in the cracking reaction, but also catalyzes the hydrogenation saturation of reaction intermediates, reducing catalyst coking and thus extending catalyst lifetime. The matrix disperses the various functional components in the catalysis, improving the catalyst's mass and heat transfer efficiency. The phosphorus auxiliary component stabilizes reaction intermediates, promotes synergistic catalytic effects among different functional components, thereby increasing reaction conversion and effectively suppressing side reactions.

[0050] The catalyst preparation method provided by this invention is simple, easy to operate, and has good repeatability. It is suitable for large-scale industrial production and can efficiently catalyze the cracking reaction of isopentane. It has the characteristics of high catalytic activity, good selectivity, and low deactivation. Detailed Implementation

[0051] The present invention will now be described in detail with reference to the embodiments, but the present invention is not limited to these embodiments.

[0052] 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.

[0053] Example 1: Preparation of the metal acidic components MA1 to MA7

[0054] The saturated water absorption of the hydrogen-type molecular sieve was determined using the saturated water absorption method. Then, based on the saturated water absorption, the target lanthanum loading, and the target nickel loading, the concentrations of lanthanum nitrate and nickel nitrate in the modified solution were calculated. Based on these calculations, a modified solution containing lanthanum nitrate and nickel nitrate was prepared.

[0055] The modified solution was uniformly added to the hydrogen-type molecular sieve until adsorption saturation, then allowed to stand at room temperature for 24 hours, dried in an oven, and calcined in a muffle furnace. The calcined sample was then loaded into a quartz tube reactor and reduced under a hydrogen atmosphere to obtain the metallic acidic components MA1–MA7.

[0056] The types of hydrogen-type molecular sieves used in the preparation of the above-mentioned acidic metal components, the lanthanum loading (based on metal content), the nickel loading (based on metal content), the drying temperature and drying time, the calcination temperature and calcination time, the hydrogen reduction temperature and hydrogen reduction time, and other preparation conditions are shown in Table 1.

[0057] Table 1 Preparation conditions of metal acid components MA1 to MA7

[0058]

[0059] Example 2: Preparation of basic metal components MB1-MA10

[0060] The saturated water absorption of the alkaline material was determined using the saturated water absorption method. Then, based on the saturated water absorption and the target loading of the noble metal, the concentration of the noble metal precursor in the modified solution was calculated. Based on the calculation results, a modified solution containing the noble metal precursor was prepared.

[0061] The modified solution was uniformly added to the alkaline material until adsorption saturation, then allowed to stand at room temperature for 24 hours, dried in an oven, and calcined in a muffle furnace. The calcined sample was then placed in a quartz tube reactor and reduced under a hydrogen atmosphere to obtain the alkaline metal components MB1–MB10.

[0062] The preparation conditions for the above-mentioned alkaline materials used in the preparation of alkaline components, including the types and loading amounts of noble metals (based on metal content), the types of noble metal precursors, drying temperature and time, calcination temperature and time, and hydrogen reduction temperature and time, are shown in Table 2.

[0063] Table 2 Preparation conditions of metal acid components MB1 to MB10

[0064]

[0065]

[0066] Example 3: Preparation of catalysts Cat.1 to Cat.12

[0067] The acidic metal component prepared in Example 1, the basic metal component prepared in Example 2, the matrix, the phosphorus auxiliary component precursor, the molding aid, and water were mixed in a certain proportion, then kneaded, shaped, and vacuum dried to prepare catalysts Cat.1 to Cat.12.

[0068] The catalyst preparation conditions, including the types and amounts of basic metal components, matrix, phosphorus auxiliary component precursors and molding aids, vacuum drying temperature, vacuum degree and time, etc., are shown in Table 3.

[0069] Table 3. Preparation conditions of catalysts Cat.1 to Cat.12*

[0070]

[0071]

[0072]

[0073] *Soluble calculations are based on a dry basis.

[0074] Comparative Example 1

[0075] The catalyst of Comparative Example 1 was prepared by uniformly mixing 45 parts by weight of hydrogen-form MOR molecular sieve, 25 parts by weight of cesium ion-form X molecular sieve, 5 parts by weight of zirconium sol, 5 parts by weight of silica sol, 5 parts by weight of pseudoboehmite, 5 parts by weight of silica, 3 parts by weight of ammonium dihydrogen phosphate, 4 parts by weight of tartaric acid and 6 parts by weight of polyethylene glycol, then kneading, molding, and drying at 110°C under vacuum of -60 kPa for 8 h.

[0076] Comparative Example 2

[0077] The catalyst of Comparative Example 2 was prepared by uniformly mixing 70 parts by weight of the acidic metal component MA4, 5 parts by weight of zirconium sol, 5 parts by weight of silica sol, 5 parts by weight of pseudoboehmite, 5 parts by weight of silica, 3 parts by weight of ammonium dihydrogen phosphate, 4 parts by weight of tartaric acid and 6 parts by weight of polyethylene glycol, then kneading, molding, and drying at 110°C under a vacuum of -60 kPa for 8 h.

[0078] Comparative Example 3

[0079] Comparative Example 3 catalyst was prepared by uniformly mixing 70 parts by weight of the basic metal component MB1, 5 parts by weight of zirconium sol, 5 parts by weight of silica sol, 5 parts by weight of pseudoboehmite, 5 parts by weight of silica, 3 parts by weight of ammonium dihydrogen phosphate, 4 parts by weight of tartaric acid and 6 parts by weight of polyethylene glycol, then kneading, molding, and drying at -60 kPa and 110°C for 8 h.

[0080] Example 4: Evaluation of the catalyst's activity in converting isoalkanes

[0081] The catalytic performance of catalysts Cat.1–Cat.12 prepared in Example 3 and the comparative catalyst in producing high-quality steam cracking feedstock from isoalkanes was evaluated using a fixed-bed reactor with an inner diameter of 9 mm and a catalyst loading of 2 mL. Feedstock containing isoalkanes and hydrogen were introduced for the reaction. The products were analyzed online using an Agilent 7890A chromatograph. The catalyst activity was evaluated based on indicators such as isoalkane conversion and selectivity for high-quality steam cracking feedstocks (ethane, propane, and n-butane). The calculation methods for each indicator are as follows:

[0082]

[0083] [Isoalkanes] 进 The mass flow rate (g / h) of the isoalkane feedstock at the reactor inlet is [isoalkane]. 出 The mass flow rate (g / h) of unconverted isoalkane feedstock at the reactor outlet, [ethane]. 出 [Propane] 出 [n-Butane] 出 and [hydrocarbon products] 出 The values ​​represent the mass flow rates (g / h) of ethane, propane, n-butane, and all hydrocarbon products at the reactor outlet, respectively. The catalysts used in experiments exp1–exp18, along with the reaction conditions and catalyst activities, are shown in Table 4.

[0084] Table 4. Reaction conditions and catalyst activities for experiments exp1–exp18

[0085]

[0086]

[0087] In the experiments shown in Table 4, samples were taken and analyzed every 2 hours. The results in the table are the average values ​​over 100 hours. Experiment exp11 was run continuously for 2000 hours, and no significant decrease in conversion or selectivity was observed, indicating that the catalyst has good stability.

[0088] The above description is merely a few embodiments of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any modifications or alterations made by those skilled in the art without departing from the scope of the technical solution of the present invention 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 efficient conversion of isoparaffins, characterized in that, At least the following steps are included: A raw material containing isoparaffins and hydrogen is brought into contact with a catalyst in a reactor and reacted to obtain a product containing small molecule alkanes. The isoalkane is selected from at least one of isobutane, isopentane, neopentane, isohexane, and 3-methylpentane; The small molecule alkane is selected from at least one of ethane, propane, and n-butane; The catalyst is obtained through the following steps: The catalyst is obtained by mixing the acidic metal functional component, the basic metal functional component, the matrix precursor, the phosphorus auxiliary component precursor, the molding aid, and water, kneading, molding, and vacuum drying.

2. The method according to claim 1, characterized in that, The mass hourly space velocity (MSV) of the isoalkanes is 0.2–10 h⁻¹. -1 ; The molar ratio of hydrogen to isoalkanes is 0.5 to 10:1; The reaction temperature is 350–550°C; The reaction is carried out at a pressure of 0.1–5 MPa.

3. The method according to claim 1, characterized in that, The matrix precursor is selected from at least one of zirconium sol, aluminum sol, titanium sol, silica sol, boehmite, silica, kaolinite, and sepiolite. The molding aid is selected from at least one of citric acid, nitric acid, sulfuric acid, hydrochloric acid, tartaric acid, polyethylene glycol, polyvinyl alcohol, glycerol, acetic acid, and soluble starch; The precursor of the phosphorus adjuvant component is selected from at least one of phosphoric acid, sodium phosphate, sodium dihydrogen phosphate, ammonium dihydrogen phosphate, and ammonium phosphate. The mass ratio of the metal acidic functional component, the metal basic functional component, the matrix precursor, the phosphorus auxiliary component precursor, and the molding aid is 2.5–5.5:1.0–3.5:1.7–2.3:0.2–0.3:1; The vacuum drying temperature is 90–130°C; The vacuum drying time is 2–20 hours; The vacuum degree of the vacuum drying process is -30 to -80 kPa.

4. The method according to claim 1, characterized in that, The metal acid functional component is obtained through the following steps: An aqueous solution containing lanthanum and nickel compounds was added to a hydrogen-type molecular sieve until adsorption saturation, then allowed to stand, dried (I), calcined (I), and reduced with hydrogen (I) to obtain the metal acidic functional component. The lanthanum compound is selected from at least one of the soluble salts of lanthanum; The nickel compound is selected from at least one of the soluble salts of nickel; The hydrogen form molecule is selected from at least one of ZSM-5, MCM-22, SAPO-11, and MOR; The temperature of the drying process I is 100–130°C; The drying time for step I is 4–20 hours; The temperature of the calcination I is 500–600°C; The roasting time for step I is 2 to 10 hours; The temperature of hydrogen reduction I is 500–600°C; The hydrogen reduction I time is 1 to 10 hours; In the aforementioned metal acidic functional component, the mass ratio of lanthanum, nickel, and hydrogen-type molecular sieve compound is 0.001–0.02:0.01–0.08:

1. The mass of lanthanum and nickel is expressed as the mass of the elements themselves.

5. The method according to claim 1, characterized in that, The basic metal functional component is obtained through the following steps: An aqueous solution containing a noble metal precursor is added to an alkaline material until adsorption saturation, then allowed to stand, dried (II), calcined (II), and reduced with hydrogen (II) to obtain the metal acidic functional component. The noble metal precursor is selected from at least one of chloroplatinic acid, tetraammineplatinum nitrate, platinum nitrate, ruthenium trichloride, ammonium hexachlororuthenate, and ruthenium nitrate. The alkaline material is selected from at least one of cesium ion-type X molecular sieve, cesium ion-type Y molecular sieve, cesium ion-type L molecular sieve, calcium silicate, and hydroxyapatite; The temperature of the drying II process is 100–130°C; The drying time for step II is 4–20 hours; The temperature of the second calcination is 450–550°C; The roasting time for II is 4–12 hours; The temperature of hydrogen reduction II is 250–450°C; The hydrogen reduction II process takes 1–10 hours. In the alkaline functional component, the mass ratio of noble metal to alkaline material is 0.001 to 0.02:1; The mass of precious metals is measured by the mass of the precious metal element.

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