A process for the aromatization of alkanes

Abstract

This invention belongs to the field of catalytic reforming technology and relates to a method for alkane aromatization. The method involves carrying out the alkane aromatization reaction in a fixed-bed reactor loaded with a molded catalyst composed of platinum, non-acidic zeolite molecular sieves, and carbonized organic products. The catalyst preparation process includes two steps: powder molding and platinum loading. By controlling the type and amount of organic matter, a molded catalyst with high mechanical strength, suitable for fixed-bed reactions, and excellent alkane aromatization performance can be obtained.

Description

Technical Field

[0001] This invention relates to a method for the aromatization of alkane, belonging to the field of catalytic reforming technology. Background Technology

[0002] Aromatics are important gasoline blending components and chemical industry feedstocks, primarily derived from catalytic reforming processes. In this process, alkanes and cycloalkanes in naphtha undergo dehydrogenation, cyclization, isomerization, and cracking reactions, resulting in structural rearrangement to form aromatics. Currently, mainstream catalytic reforming processes utilize metal-acid bifunctional catalysts (Lin Shixiong. Petroleum Refining Engineering [M]. Beijing: Petroleum Industry Press. 2000). These catalysts exhibit high catalytic activity for cycloalkanes, but their activity and selectivity for converting alkanes to aromatics are not ideal. In recent years, a technique using platinum-catalyzed C6-C8 alkanes supported by non-acidic zeolite molecular sieves has emerged for aromatization. This technology can efficiently convert low-octane, low-aromatic-potential feedstocks into aromatics, thus attracting widespread attention from researchers.

[0003] In the above-mentioned alkane aromatization reaction, the catalyst needs to be made into particles of specific size and shape to meet the requirements of continuous fixed-bed operation. During catalyst molding, chemical binders need to be added to improve the adhesion and agglomeration of the powder to be molded (Li Xiaotao. Research progress of molecular sieve molding technology [J]. Industrial Catalysis, 2016, 24(3): 19-27). However, the above-mentioned chemical binders are dispersed between zeolite molecular sieve / catalyst particles and may react with them, thereby affecting the performance of the molded product. This effect is particularly significant for alkane aromatization catalysts constructed with non-acidic zeolite molecular sieves and platinum. For example, Kumar et al. found that for Pt / KL catalysts supported by KL-type zeolite molecular sieves, acidic binders cause Pt particles to be in an electron-deficient state, thereby inhibiting their aromatization performance; they further screened magnesium-containing alumina binders for the preparation of Pt / KL catalyst profiles (KUMAR M, SAXENA AK, NEGI BS, et al. Role of pore size analysis in development of zeolite reforming catalyst[J].CatalysisToday, 2008, 130(2): 501-508). Loginova et al. screened the most suitable binder for KL molecular sieve formation for the aromatization process of n-octane (LOGINOVAA N, SVIDERSKII SA, MOROZOVA YV, et al. Effect of the composition of a nonacid n-alkane cyclization catalyst on its physicochemical and catalytic properties[J]. Petroleum Chemistry, 2018, 58(10): 876-883).

[0004] Constructing zeolite molecular sieve preforms in a self-supporting manner can avoid the influence of chemical binders on zeolite molecular sieves (Wang Deju, Liu Zhongneng, Yang Weimin, et al. Progress in the preparation and application of binder-free zeolite molecular sieves [J]. Petrochemical Technology, 2007, 36(10): 1061-1066). This method can also be used to prepare alkane aromatization catalysts. For example, patent document CN102476809B discloses a method for preforming barium-containing L-type zeolite molecular sieves using kaolin as raw material. In this method, kaolin, barium source, binder, pore-forming agent and water are first mixed evenly according to a certain proportion and feeding method, and then shaped, dried and calcined to obtain L-type zeolite molecular sieve preforms; then the preforms are mixed evenly with crystallization liquid containing alkali and fluoride, crystallized at a certain temperature for a certain time, and after separation, washing and drying, barium-containing L-type zeolite molecular sieves are finally obtained. Patent document CN102895992B discloses a method for preparing an alkane aromatization catalyst. In this method, solid silica and silica sol are first pre-formed; then, solid sodium aluminate and potassium hydroxide are added to deionized water to obtain a crystallization solution; next, the pre-formed body is added to the crystallization solution, and hydrothermal crystallization is performed at 100-180℃. The mixture is then filtered, washed, and dried to obtain an L-type zeolite molecular sieve support. Using this support, a catalyst with a Pt mass fraction of 0.3%-1% is prepared by impregnation. Although the aromatization catalyst obtained by the above method exhibits excellent performance, self-supporting molding requires the design of a specific preparation route for a particular zeolite molecular sieve, and the process is often much more complex than that of bonded molding. Therefore, the application scope of this method is very limited.

[0005] Similar to the self-supporting zeolite molecular sieve forming process described above, in the preparation of carbon materials, high-molecular organic compounds such as pitch are often used as chemical binders. The forming purpose is achieved by creating a carbon-carbon composite structure between the carbon material powder to be formed and the carbonization product of the binder (Yang Yongbin, Dong Yinrui, Zhong Qiang, et al. Application and research progress of high-temperature coal tar pitch binder carbonization and consolidation in carbon profiles [J]. Chemical Industry and Engineering Progress, 2022, 41(12): 6419-6429). However, it is traditionally believed that organic binders are not suitable for the chemical bonding of zeolite molecular sieves. The reasons are, firstly, that organic binders will oxidize and decompose during high-temperature calcination; secondly, zeolite molecular sieves are difficult to link with carbon through covalent bonds.

[0006] By altering the heat treatment method of powders, some high-molecular-weight organic compounds can also act as binders for inorganic powders. Patent document CN1181917C discloses a mixed metal catalyst containing a flammable binder. This flammable binder is formed by the pyrolysis of organic polymers in an inert atmosphere at 300-600℃. The organic polymers include polyacrylonitrile, phenolic plastics, polyamides, polyurethanes, cellulose and its derivatives, hemicellulose materials, polyfurfuryl alcohol, styrene-divinylbenzene copolymers, phenolic resins, furan resins, polyimide resins, polyphenylene resins, phenolic foams, and polyurethane foams. Patent document CN107029668B discloses a honeycomb molecular sieve-activated carbon composite adsorbent. This adsorbent is prepared by mixing Y-type molecular sieves, activated carbon powder, expanded graphite, silica sol, organic binder, and deionized water through steps such as mixing, kneading, vacuum kneading, aging, honeycomb extrusion molding, low-temperature microwave shaping, and microwave vacuum sintering. The aforementioned organic binders are sodium carboxymethyl cellulose, sodium hydroxymethyl cellulose, polyvinyl alcohol, phenolic resin emulsion, and acrylic resin emulsion. Patent document CN111115631B discloses a method for preparing coffee grounds-based molded porous carbon material. This method uses coffee grounds as raw material, mixing them with solvents, extrusion aids, binders, and structural reinforcing agents, followed by kneading, extrusion molding, drying, carbonization, and activation to obtain porous carbon. The aforementioned binders are starch, sodium carboxymethyl starch or montmorillonite, sepiolite, silicates, silica sol, sodium silicate, dilute nitric acid, and phosphoric acid.

[0007] The high-molecular-weight organic compounds capable of forming carbonization products with specific morphologies are not limited to the substances mentioned above. For example, patent document CN116272874B discloses a method for preparing plastic carbon materials. This method involves mixing treated waste plastic particles with ferric chloride, adding water, freeze-drying, and pyrolyzing to obtain plastic carbon materials. The aforementioned waste plastic particles are polyethylene, polypropylene, polyethylene terephthalate, and polymethyl methacrylate. Zhang Wenjun, on the other hand, used polyphenylene sulfide nonwoven fabric as a carbon source to design and prepare carbon materials for supercapacitors with different morphologies and structures (Zhang Wenjun. Preparation and Electrochemical Energy Storage Research of Polyphenylene Sulfide Derivative Carbon-Based Composite Materials [D]. Tianjin University of Technology, 2023). Summary of the Invention

[0008] This invention aims to provide a method for the aromatization of alkane that overcomes the shortcomings of existing technologies. To achieve this objective, the invention employs the following technical solution:

[0009] Alkane aromatization reaction was carried out in a fixed-bed reactor containing a molded catalyst composed of platinum, non-acidic zeolite molecular sieves, and organic carbonization products.

[0010] In the alkane aromatization method provided by the present invention, the mass fraction of platinum in the catalyst is 0.1%-2%, preferably 0.2%-1%, and more preferably 0.25%-0.5%.

[0011] In the alkane aromatization method provided by this invention, the alkane is one or more of C6-C8 n-alkanes.

[0012] In the alkane aromatization method provided by the present invention, the molar ratio of hydrogen to alkanes in the reaction raw materials is 0.5-20, preferably 1-10.

[0013] In the alkane aromatization method provided by this invention, the reaction temperature is 300-700℃ or 300-600℃.

[0014] In the alkane aromatization method provided by the present invention, the reaction pressure is ≤2MPa, preferably ≤1MPa.

[0015] In the alkane aromatization method provided by this invention, the liquid hourly space velocity (LHSV) of the reactant alkane is 0.1-10 h⁻¹. -1 Preferred 1-5h -1 .

[0016] In the alkane aromatization method provided by the present invention, the catalyst is reduced with hydrogen before the reaction, the reduction temperature is 200-600℃, and the reduction time is 0.2-24h.

[0017] The above-mentioned shaped catalyst, composed of platinum, non-acidic zeolite molecular sieve, and organic carbonization products, is obtained through the following steps:

[0018] Step a: The mixture containing the powder to be formed, organic binder, and dispersant is extruded into strips, dried, and carbonized in a non-oxidizing atmosphere. The powder to be formed is either a platinum-loaded non-acidic zeolite molecular sieve or a platinum-free non-acidic zeolite molecular sieve.

[0019] Step b involves immersing a platinum-containing solution onto a carrier, drying it, and then heat-treating it. The carrier is either non-acidic zeolite molecular sieve powder or a molded body composed of non-acidic zeolite molecular sieve powder and carbonized organic binder products.

[0020] In the above method for preparing the alkane aromatization catalyst, the order of steps a and b can be interchanged. That is, it can be carried out according to the following process:

[0021] First, a mixture containing unloaded platinum non-acidic zeolite molecular sieve powder, organic binder, and dispersant is extruded into strips, dried, and carbonized in a non-oxidizing atmosphere. Then, a platinum-containing solution is immersed in the molded body obtained in the previous step, which is composed of the carbonized product of non-acidic zeolite molecular sieve powder and organic binder, dried, and calcined in a non-oxidizing atmosphere.

[0022] Alternatively, you can follow the procedure below:

[0023] First, a platinum-containing solution is impregnated onto non-acidic zeolite molecular sieve powder, dried, and calcined. Then, a mixture containing the platinum-loaded non-acidic zeolite molecular sieve powder obtained in the previous step, an organic binder, and a dispersant is extruded, dried, and carbonized in a non-oxidizing atmosphere.

[0024] Zeolite molecular sieves are composed of framework central cations and O 2- An open framework structure is formed according to the "(4;2)-connection" mode. The central cation in the framework is typically B. 3+ Al 3+ Si 4+ P 5+ Ti 4+ Cr 3+ Fe 3+ Ga 3+ 、Ge 4+ Zr 4+ or Sn 4+ The type and number of central cations in the framework determine whether the framework is charged. Zeolite and aluminum silicate phosphate molecular sieve frameworks are negatively charged, while all-silica molecular sieves and aluminum phosphate molecular sieve frameworks are electrically neutral. The negative charge on the zeolite molecular sieve framework is balanced by guest cations. When the guest cation is H... + When the guest cation is an alkali metal or alkaline earth metal ion, the zeolite molecular sieve exhibits acidity; when the guest cation is an alkali metal or alkaline earth metal ion, the zeolite molecular sieve exhibits alkalinity. All-silica molecular sieves and aluminum phosphate molecular sieves, because they do not contain guest cations, are neutral in the absence of structural defects.

[0025] Based on the above characteristics of zeolite molecular sieves, the so-called non-acidic zeolite molecular sieves in the alkane aromatization method provided by this invention refer to the following two types of zeolite molecular sieves:

[0026] (1) Zeolite molecular sieves with uncharged skeletons;

[0027] (2) Zeolite molecular sieves with a negatively charged framework, the negative charge of which is balanced by lithium, sodium, potassium, magnesium, calcium, strontium and barium ions outside the framework.

[0028] In the alkane aromatization method provided by this invention, the framework type of the non-acidic zeolite molecular sieve is one or more of AFI, AEL, *BEA, FAU, LTL, and MAZ.

[0029] The preparation process of the above catalyst includes two steps: powder forming and platinum loading. By controlling the type and amount of organic matter, a formed catalyst with high mechanical strength, suitable for fixed-bed reaction, and excellent alkane aromatization performance can be obtained.

[0030] In the alkane aromatization method provided by this invention, the organic binder is specifically one or more of polystyrene, polyvinyl alcohol, polymethyl methacrylate, polyphenylene ether, or phenolic resin. Differences in production processes can lead to differences in the physicochemical properties of the aforementioned organic binders. For example, currently industrially produced polystyrene includes subcategories such as general-purpose polystyrene, high-impact polystyrene, expandable polystyrene, and metallocene polystyrene; the solubility of polyvinyl alcohol in water varies significantly with changes in the degree of hydrolysis; and commercially available phenolic resins exist in various forms such as aqueous solutions, alcoholic solutions, and solids. The alkane aromatization catalyst preparation method provided by this invention does not limit the specific subcategories of polystyrene, polyvinyl alcohol, polymethyl methacrylate, polyphenylene ether, or phenolic resin used; the organic binder used can be in the form of powder, fluid, or solution dissolved in a dispersant during addition.

[0031] In the alkane aromatization method provided by this invention, the dispersant is one or more of water, methanol, ethanol, benzene, toluene, xylene, acetone, dichloromethane, trichloromethane, or carbon tetrachloride. The above-mentioned dispersant does not chemically react with platinum or non-acidic zeolite molecular sieves during mixing and molding, and is removed during the drying process of the molded body. Adding a dispersant allows the organic binder to dissolve and swell, thereby improving its contact and mixing with the non-acidic zeolite molecular sieve. Simultaneously, adding a dispersant also facilitates smooth molding operations. Therefore, the choice of dispersant type is determined by the physicochemical properties of the organic binder used. For example, polystyrene is soluble in benzene, toluene, xylene, dichloromethane, chloroform, or carbon tetrachloride; polyvinyl alcohol, with a hydrolysis degree of 86%-90%, is readily soluble in water; polymethyl methacrylate is soluble in dichloromethane, chloroform, or carbon tetrachloride; polyphenylene ether is soluble in benzene, toluene, or chloroform; and phenolic resins are soluble in water, methanol, ethanol, or acetone depending on the curing stage. The method for preparing the alkane aromatization catalyst provided by this invention does not limit the amount of dispersant. In practice, the amount should be determined based on factors such as the absorption capacity of the non-acidic zeolite molecular sieve, the solubility properties of the organic binder, and the requirements of the extrusion molding operation.

[0032] In the alkane aromatization method provided by the present invention, the mass ratio of the powder to be formed to the organic binder is 0.8-4.5, preferably 1-3.5.

[0033] In the alkane aromatization method provided by this invention, the extrusion molding process is well known to those skilled in the art, as described by Zhang Jiguang (Zhang Jiguang. Catalyst Preparation Process Technology [M]. Beijing: China Petrochemical Press, 2004), Ertl et al. (ERTL G, H, The monograph by F, et al., Handbook of Heterogeneous Catalysis [M]. 2nd ed. Weinheim: Wiley, 2008, elaborates on this topic in detail.

[0034] In the alkane aromatization method provided by the present invention, the drying atmosphere is air, and the drying temperature is room temperature to 250°C.

[0035] The selection of the non-oxidizing atmosphere required for carbonization in the alkane aromatization method provided by this invention is well known to those skilled in the art. The non-oxidizing atmosphere may contain one or more of hydrogen, helium, methane, carbon monoxide, carbon dioxide, nitrogen, and argon.

[0036] In the alkane aromatization method provided by the present invention, the carbonization temperature is 450-750℃, preferably 500-700℃; and the carbonization time is 0.1-5h, preferably 2-4h.

[0037] In the alkane aromatization method provided by the present invention, the calcination temperature is 200-500℃, preferably 300-450℃; the calcination time is 0.1-24h, preferably 1-8h.

[0038] In the alkane aromatization method provided by the present invention, by adjusting the amount of powder to be molded, the type and amount of organic binder, and the carbonization conditions, the mass fraction of carbon in the catalyst can usually be controlled within the range of 5%-25%.

[0039] The most significant difference between the alkane aromatization method provided by this invention and the prior art is that:

[0040] A molded body formed by combining carbonized products of an organic binder with platinum and non-acidic zeolite molecular sieves in a specific ratio is used as an alkane aromatization catalyst.

[0041] The present invention has the following beneficial effects:

[0042] The alkane aromatization method provided by this invention can be carried out in a fixed-bed reactor, and the catalyst exhibits high mechanical strength and excellent alkane aromatization performance. The catalyst preparation method is simple to operate and can be easily implemented in catalyst preparation processes of different scales, including experimental research and industrial production. Detailed Implementation

[0043] The following embodiments will further illustrate the present invention. However, the present invention is not limited to the following embodiments.

[0044] In the following examples, the radial compressive strength of the obtained samples was determined using a particle strength tester, and the determination and calculation were performed according to the chemical industry standard HG / T 2782-2011. The carbon content of the obtained samples was determined using an organic elemental analyzer, and the samples were vacuum dried at 150°C for 12 hours before weighing.

[0045] Example 1

[0046] Zeolite molecular sieve powder and platinum-loaded zeolite molecular sieve powder were synthesized according to the method disclosed in Example 1 of patent document CN104107716B. This zeolite molecular sieve is a potassium-containing alkaline zeolite molecular sieve with an LTL-type framework and Al as the central cation in the framework. 3+ Si 4+ Fe 3+ .

[0047] Using the above-mentioned zeolite molecular sieve powder as a carrier, an equal volume of Pt(NH3)4Cl2 aqueous solution was impregnated, dried, and then calcined at 350℃ in air atmosphere for 5 hours to obtain alkaline zeolite molecular sieve powder containing 0.5% Pt by mass.

[0048] Take 5g of the above powder, add 5g of polyphenylene ether and 3.5g of chloroform, and mix thoroughly. Using a powder tablet press equipped with a 2mm orifice diameter die, manually extrude the mixture into strips at an extrusion pressure of 7MPa, and air-dry at room temperature to obtain the precursor. Place the precursor in a hydrogen stream, heat it to 200℃ at 10℃ / min and hold for 1h, then heat it to 500℃ at 5℃ / min and hold for 2h. After cooling to 200℃ in the hydrogen stream, switch to a nitrogen stream and purge for 2h. After the temperature drops to room temperature, slowly expose the sample to air to obtain the alkane aromatization catalyst. The radial compressive strength of this catalyst is 49 N·cm. -1 The carbon mass fraction is 13%.

[0049] In the above carbonization process, the catalyst has already undergone hydrogen reduction, so further reduction is unnecessary. The catalyst is crushed, and 20-40 mesh particles are sieved and loaded into a fixed-bed reactor for alkane aromatization. The alkane feedstock is n-hexane. The reaction temperature is 450℃, and the reaction pressure is 0.5 MPa. The liquid hourly space velocity (LHSV) of n-hexane is 2 h⁻¹. -1 The molar ratio of hydrogen to n-hexane was 3. The product composition was analyzed online using gas chromatography. After 4 hours of reaction, the conversion rate of n-hexane was 46%, and the selectivity for benzene was 89%.

[0050] Compare with Example 1

[0051] The zeolite molecular sieve powder obtained in Example 1 was shaped using alumina as a binder, and the shaping operation was the same as in Example 1. The difference was that the extrusion raw material was a mixture of Fe-containing alkaline LTL-type zeolite molecular sieve, pseudoboehmite, guar gum powder, and dilute nitric acid (10% by mass) in a mass ratio of 20:6:1:30. The extruded precursor was air-dried and then calcined at 550°C in air for 4 hours to obtain the zeolite molecular sieve shaped body. The radial compressive strength of this shaped body was 58 N·cm. -1 .

[0052] The above-mentioned molded body was loaded with an aqueous solution of Pt(NH3)4Cl2 by impregnation, dried, and then calcined at 350°C in air for 5 hours to obtain an alkane aromatization catalyst containing 0.5% Pt by mass.

[0053] The alkane aromatization catalyst obtained in Comparative Example 1 was crushed, and 20-40 mesh particles were sieved and loaded into a fixed-bed reactor. A hydrogen stream was introduced into the reactor for catalyst reduction, and the temperature was increased to 200°C at 10°C / min and held for 1 hour, then increased to 500°C at 5°C / min and held for 2 hours. After the temperature dropped to 450°C, the alkane aromatization reaction was carried out under the reaction conditions described in Example 1. After 4 hours of reaction, the hexane conversion was 67%, and the benzene selectivity was 36%.

[0054] The results of Example 1 and Comparative Example 1 show that the alkane aromatization catalyst provided by the present invention can meet the requirements of fixed-bed alkane aromatization reaction for catalyst mechanical strength and catalytic performance, and its catalytic performance is superior to that of catalysts prepared by alumina bonding method.

[0055] Compare with Example 2

[0056] The preparation process of the alkane aromatization catalyst described in Example 1 was repeated, except that the amounts of polyphenylene ether and chloroform were changed to 12 g and 8.4 g, respectively. The radial compressive strength of this catalyst was 61 N·cm. -1 The mass fraction of carbon in it is 33%.

[0057] The catalytic performance of the alkane aromatization catalyst obtained in Control Example 2 was evaluated using the reaction conditions described in Example 1. The results showed that after 4 hours of reaction, the conversion rate of n-hexane was 26%, and the benzene selectivity was 59%.

[0058] The results of Example 1 and Comparative Example 2 show that the obtained alkane aromatization catalyst can also be formed even outside the range of organic carbonization product content provided by this invention, and the strength of the formed catalyst increases. However, compared with the catalyst where the ratio of the powder to be formed to the organic binder is within the range provided by this invention, its catalytic performance decreases sharply. Therefore, controlling the ratio of the powder to be formed to the organic binder is a necessary means to achieve efficient conversion of alkanes to obtain aromatics.

[0059] Example 2

[0060] Following the method disclosed by Wang et al. (WANG L, XU Y, WEI Y, et al. Structure-directing role of amines in the ionothermal synthesis[J]. Journal of the American Chemical Society, 2006, 128: 7432-7433), di-n-propylamine was used as a structure-directing agent to synthesize an AFI-type framework with Al as the central cation. 3+ and P 5+ The non-acidic zeolite molecular sieve was calcined at 550℃ for 12 hours.

[0061] 3.5g of powdered thermosetting phenolic resin was mixed with an equal mass of ethanol, and 5g of the aforementioned non-acidic zeolite molecular sieve powder was added and mixed thoroughly. The resulting mixture was molded according to the procedure described in Example 1 and dried and cured at 120°C for 12 hours to obtain a precursor. The precursor was placed in a nitrogen stream and heated to 350°C at a rate of 5°C / min, then heated to 650°C at a rate of 2°C / min and held at that temperature for 2 hours to obtain a molded body composed of non-acidic zeolite molecular sieve powder and organic carbonization products. The radial compressive strength of this molded body was 69 N·cm. -1 .

[0062] The resulting molded body was crushed and sieved to obtain 20-40 mesh particles. An aqueous solution of H₂PtCl₆ was loaded onto the particles using an equal-volume impregnation method. After drying, the particles were calcined at 450°C for 2 hours in a nitrogen atmosphere to obtain an alkane aromatization catalyst containing 0.25% Pt by mass. The carbon content of this catalyst was 24% by mass.

[0063] The above-mentioned alkane aromatization catalyst was loaded into a fixed-bed reactor. A hydrogen stream was introduced into the reactor for catalyst reduction, and the temperature was increased to 450℃ at a rate of 5℃ / min and held at this temperature for 2 hours. The temperature was then increased to 470℃ for the alkane aromatization reaction. The alkane feedstock was n-octane, the reaction pressure was 0.2 MPa, and the liquid hourly space velocity (LHSV) of n-octane was 3 h⁻¹. -1 The molar ratio of hydrogen to n-octane was 9. The product composition was analyzed online using gas chromatography. After 4 hours of reaction, the conversion of n-octane was 67%, and the selectivity for C8 aromatics was 42%.

[0064] Compare with Example 3

[0065] The preparation process of the alkane aromatization catalyst described in Example 2 was repeated, except that the powdered thermoplastic phenolic resin was replaced with starch. The resulting catalyst was an irregularly shaped strip with cracked marks.

[0066] The results of Example 2 and Comparative Example 3 show that although the catalyst obtained using the method for preparing the alkane aromatization catalyst provided by this invention is composed of a non-acidic zeolite molecular sieve and organic carbonization products, the selection of organic raw materials is not arbitrary. When the organic binder selection range provided by this invention is exceeded, the mechanical strength of the resulting alkane aromatization catalyst decreases sharply, failing to meet the requirements of fixed-bed reactions.

[0067] Example 3

[0068] The preparation process of the alkane aromatization catalyst described in Example 2 was repeated, except that 3.5g of powdered thermosetting phenolic resin and 3.5g of ethanol were replaced with 5g of polyvinyl alcohol (87%-89% hydrolyzed) and 5g of water. The radial compressive strength of the resulting molded body was 58 N·cm. -1 The carbon mass fraction in the alkane aromatization catalyst is 19%.

[0069] The performance of the alkane aromatization catalyst obtained in Example 3 was evaluated using the reaction conditions described in Example 2. The results showed that after 4 hours of reaction, the n-octane conversion was 69%, and the C8 aromatic selectivity was 43%.

Claims

1. A method for aromatizing alkane, characterized in that: The reaction is carried out in a fixed-bed reactor with a hydrogen to alkane molar ratio of 0.5-20 in the reactants, a reaction temperature of 300-700℃, a reaction pressure ≤2MPa, and a liquid hourly space velocity (LHSV) of alkane in the reactants of 0.1-10h⁻¹. -1 ; The reaction uses a molded catalyst formed by combining platinum, non-acidic zeolite molecular sieves, and organic carbonization products via any of the following routes. Route a: First, take 0.8-4.5 parts by mass of unloaded platinum non-acidic zeolite molecular sieve powder and 1 part by mass of organic binder, mix with dispersant, extrude into strips, dry, and carbonize in a non-oxidizing atmosphere at 450-750℃ for 0.1-5h to obtain a molded body; then impregnate the molded body with a platinum-containing solution, dry, and calcine in a non-oxidizing atmosphere to obtain a catalyst. The calcination temperature is 200-500℃, preferably 300-450℃, and the calcination time is 0.1-24h, preferably 1-8h. Alternatively, route b involves first impregnating a platinum-containing solution onto a non-acidic zeolite molecular sieve powder, drying and calcining it at a temperature of 200-500℃, preferably 300-450℃, for a calcination time of 0.1-24h, preferably 1-8h; then taking 0.8-4.5 parts by mass of the platinum-loaded non-acidic zeolite molecular sieve powder obtained in the previous step, 1 part by mass of an organic binder, mixing it with a dispersant, extruding it into strips, drying it, and carbonizing it in a non-oxidizing atmosphere at 450-750℃ for 0.1-5h to obtain the catalyst; The resulting catalyst contains 0.1%-2% platinum by mass, preferably 0.2%-1%, and more preferably 0.25%-0.5%.

2. The method for alkane aromatization according to claim 1, characterized in that: The alkanes are one or more of the C6-C8 n-alkanes; before the reaction, the catalyst is reduced with hydrogen at a temperature of 200-600℃ for a time of 0.2-24h.

3. The method for alkane aromatization according to claim 1, characterized in that: The molar ratio of hydrogen to alkanes in the reactants is 1-10, the reaction temperature is 300-600℃, the reaction pressure is ≤1MPa, and the liquid hourly space velocity (LHSV) of the alkanes is 1-5h⁻¹. -1 .

4. The method for alkane aromatization according to claim 1, characterized in that: The non-acidic zeolite molecular sieve framework type is one or more of AFI, AEL, *BEA, FAU, LTL, and MAZ.

5. The method for alkane aromatization according to claim 1 or 4, characterized in that: Non-acidic zeolite molecular sieves are zeolite molecular sieves with an uncharged framework or zeolite molecular sieves whose negative charge is balanced by one or more of the following ions: lithium, sodium, potassium, magnesium, calcium, strontium, and barium.

6. The method for alkane aromatization according to claim 1, characterized in that: The organic binder is one or more of polystyrene, polyvinyl alcohol, polymethyl methacrylate, polyphenylene ether, or phenolic resin.

7. The method for alkane aromatization according to claim 1, characterized in that: The dispersant is one or more of the following: water, methanol, ethanol, benzene, toluene, xylene, acetone, dichloromethane, trichloromethane, or carbon tetrachloride.

8. The method for alkane aromatization according to claim 1, 5, or 6, characterized in that: In catalyst preparation route a, the mass ratio of unplatinum-supported non-acidic zeolite molecular sieve powder to organic binder is 1-3.5, and in route b, the mass ratio of platinum-supported non-acidic zeolite molecular sieve powder to organic binder is 1-3.

5.

9. The method for alkane aromatization according to claim 1, characterized in that: The carbonization temperature is 500-700℃.

10. The method for alkane aromatization according to claim 1, characterized in that: The carbonization time is 2-4 hours.