A germanium modified catalyst for catalytic reforming of c3-c9 paraffins and its preparation method and application

Abstract

The application belongs to the technical field of petroleum chemical industry, and particularly relates to a germanium modified catalyst for C3-C9 paraffin catalytic reforming and a preparation method and application thereof. The germanium modified catalyst for C3-C9 paraffin catalytic reforming is obtained by adopting an impregnation method to obtain a Ge modified molecular sieve carrier and then using an atomic layer deposition technology to deposit noble metal. The catalyst is prepared by adopting a combination of the impregnation method and the atomic layer deposition, the performance of the catalyst obtained by the method in a catalytic paraffin dehydrogenation and cyclization reaction for preparing aromatic hydrocarbon is better than that of a catalyst prepared by using a single method, the modification of Ge on the active metal is obvious, the hydrogenolysis reaction is inhibited, especially the C1-C4 by-products are inhibited, the selectivity of the target aromatic hydrocarbon is increased to more than 90%, the carbon deposition is obviously reduced, the catalyst life is prolonged, and the catalyst has a good industrial application prospect.

Description

Technical Field

[0001] This invention belongs to the field of coal / petrochemical technology, specifically relating to a germanium-modified catalyst for catalytic reforming of C3-C9 alkane chains, its preparation method, and its application. Background Technology

[0002] The information disclosed in this background section is intended only to enhance understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] Coal indirect liquefaction (Fischer-Tropsch synthesis) is an important measure to achieve clean and efficient utilization of coal. However, this technology produces a large amount of straight-chain alkanes, which have low value. How to convert them into high-value light aromatic hydrocarbons has always been a goal pursued by scientists. Efficient and stable catalysts play a central role in alkane reforming technology. Traditional Pt reforming catalysts rely on halogenation (Cl... - Using alumina as a support, the selectivity for aromatic hydrocarbons in the aromatization of medium- and long-chain alkanes (n-C6, n-C7) is low, and the proportion of C1-C4 byproducts in hydrogenolysis is high (approximately 40%). Furthermore, Cl... - It is prone to leakage during the reaction, which can corrode equipment, cause blockages, and contaminate the final product. Meanwhile, to maintain the high dispersion of the active metal and reduce the carbon deposition rate, a continuous supply of Cl is required. - This catalyst is added to the reaction system to maintain dynamic equilibrium. Therefore, there is an urgent need to develop green, efficient, highly aromatic, and long-life catalysts that are compatible with the long-chain alkane reforming process in coal-to-oil products.

[0004] Pt / zeolite catalytic systems can be prepared by loading noble metal Pt onto KL, HZSM-5, Hβ, and HY zeolites for the catalytic reforming of alkanes. These catalysts can improve the aromatization activity and selectivity of n-C6 to n-C9 alkanes. To further improve catalytic performance, scientists added catalytic promoters to the Pt / zeolite catalysts. However, the inventors found that using conventional techniques to load noble metal Pt and promoters resulted in poor dispersion of Pt within the zeolite, difficulty in controlling the placement of Pt, and the inability of the promoters to enter the zeolite framework, thus leading to poor final catalytic performance. Summary of the Invention

[0005] To overcome the above problems, this invention provides a germanium-modified catalyst for catalytic reforming of C3-C9 alkanes, its preparation method, and its application.

[0006] To achieve the above technical objectives, the present invention adopts the following technical solution:

[0007] The first aspect of this invention provides a method for preparing a germanium-modified catalyst for catalytic reforming of C3-C9 alkanes, comprising:

[0008] (1) The germanium source was dispersed in the first solvent, and then the molecular sieve support was immersed in the solution. After standing at room temperature, the solvent was removed and then calcined to obtain the Ge-modified molecular sieve support.

[0009] (2) The Ge-modified molecular sieve support is dispersed in a second solvent to obtain a suspension. The suspension is uniformly coated on the substrate surface, dried, and then transferred to a reaction chamber for pulse deposition and purging of the noble metal source. Then, pulse deposition and purging of the oxidant are performed. The pulse deposition and purging of the noble metal source and the oxidant are repeated to obtain the germanium-modified catalyst for the catalytic reforming of C3-C9 alkanes.

[0010] In a second aspect, the present invention provides a germanium-modified catalyst for catalytic reforming of C3-C9 alkanes prepared by the above-described preparation method.

[0011] A third aspect of the present invention provides the application of the above-mentioned germanium-modified catalyst for catalytic reforming of C3-C9 alkanes in the preparation of aromatic hydrocarbons by catalytic reforming of C3-C9 alkanes.

[0012] A fourth aspect of the present invention provides a method for the catalytic reforming of C3-C9 alkanes to prepare aromatic hydrocarbons, comprising:

[0013] Using a fixed-bed or moving-bed reactor, the aforementioned germanium-modified catalyst for catalytic reforming of C3-C9 alkanes is used to mix C3-C9 alkanes under hydrogen-exposed or non-hydrogen-exposed conditions.

[0014] The beneficial effects of this invention are as follows:

[0015] (1) Adding germanium source using conventional impregnation method facilitates the entry of Ge atoms into the molecular sieve framework, thereby enabling Ge atoms to perform isomorphic substitution of molecular sieve framework atoms to construct noble metal adsorption sites with specific structures. Introducing noble metals into the molecular sieve cage for anchoring enhances the interaction between the noble metal and the molecular sieve support, improving its stability. Atomic layer deposition (ALD) can control the growth and placement of noble metal particles, solving the problem of controlling the placement of noble metals using conventional impregnation method. It also improves the dispersibility of noble metal particles, prevents their aggregation, enhances catalyst stability, and extends catalyst lifespan. Furthermore, Ge has a relatively mild effect on the electronic structure regulation of Pt; Ge can quench unpaired electrons in Pt-Ge metal clusters for deep dehydrogenation of olefins, effectively improving catalytic activity and product selectivity.

[0016] (2) The present invention uses a combination of impregnation and atomic layer deposition to prepare catalysts. The catalysts obtained by this method have better performance than those prepared by a single method in the catalytic dehydrogenation cyclization reaction of alkanes to prepare aromatics. Ge significantly modifies the active metal, inhibits the occurrence of hydrogenolysis reaction, especially inhibits C1-C4 byproducts, improves the selectivity of target aromatics to more than 90%, significantly reduces carbon deposition, and extends catalyst life, which has good prospects for industrial application. Attached Figure Description

[0017] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0018] Figure 1 The image shows the XRD pattern of the PtGe / KL catalyst prepared in Example 1.

[0019] Figure 2 The image shows a TEM image of the PtGe / KL catalyst prepared in Example 1.

[0020] Figure 3 The image shows the XRD pattern of the PtGe / KL catalyst prepared in Comparative Example 1.

[0021] Figure 4 This is a TEM image of the PtGe / KL catalyst prepared in Comparative Example 1. Detailed Implementation

[0022] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0023] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0024] A first typical embodiment of the present invention provides a method for preparing a germanium-modified catalyst for catalytic reforming of C3-C9 alkanes, comprising:

[0025] (1) The germanium source was dispersed in the first solvent, and then the molecular sieve support was immersed in the solution. After standing at room temperature, the solvent was removed and then calcined to obtain the Ge-modified molecular sieve support.

[0026] (2) The Ge-modified molecular sieve support is dispersed in a second solvent to obtain a suspension. The suspension is uniformly coated on the substrate surface, dried, and then transferred to a reaction chamber for pulse deposition and purging of the noble metal source. Then, pulse deposition and purging of the oxidant are performed. The pulse deposition and purging of the noble metal source and the oxidant are repeated to obtain the germanium-modified catalyst for the catalytic reforming of C3-C9 alkanes.

[0027] In one or more embodiments, in step (1), the germanium source includes one or more of dimethyl germanium dichloride, germanium sulfide, trimethyl germanium chloride, tetraethyl germanium, germanium isopropoxide, germanium oxide, triethyl germanium chloride, germanium tetrachloride, and germanium dichloride.

[0028] In one or more embodiments, in step (1), the first solvent is one or more of ethanol, water, diethyl ether, acetone and methanol.

[0029] In one or more embodiments, in step (1), the molecular sieve includes one or more of KL molecular sieve, Y-type molecular sieve, MFI-type molecular sieve, and β-molecular sieve.

[0030] In one or more embodiments, in step (1), the standing time at room temperature is 2 to 50 hours.

[0031] In one or more embodiments, in step (1), the mass ratio of germanium element in the germanium source to molecular sieve support is 0.001% to 30%:1.

[0032] In one or more embodiments, in step (1), the calcination temperature is 200–650°C and the time is 2.5–20 h.

[0033] In one or more embodiments, in step (2), the second solvent is one or more of ethanol, water, diethyl ether, acetone and methanol.

[0034] In one or more embodiments, in step (2), the precious metal is one or more of platinum, palladium and iridium.

[0035] Preferably, in step (2), the noble metal source is one or more of the following: dichlorotetramineplatinum, chloroplatinic acid hexahydrate, tetraammineplatinum nitrate, platinum acetylacetonate, dichlorodiamminecyclohexaneplatinum, trimethyl-methylcyclopentadiene platinum, potassium chloroplatinate, platinum nitrate, palladium chloride, dichlorotetraminepalladium, hexafluoroacetylacetonate palladium, palladium nitrate, palladium acetate, palladium acetylacetonate, sodium tetrachloropalladium, ammonium chloropalladium, trimethylpalladium acetate, tetraaminopalladium nitrate, iridium chloride, iridium acetate, sodium chloroiridium hexahydrate, iridium acetylacetonate, iridium tetrachloride, sodium hexanitrobiridium, potassium hexachloroiridium, and potassium hexachloroiridium.

[0036] In one or more embodiments, in step (2), the temperature of the reaction chamber is 200–450°C.

[0037] In one or more embodiments, in step (2), the duration of the noble metal source pulse is 0.01 to 0.5 s; the deposition time is 10 to 60 s; and the purging time is 30 to 100 s.

[0038] In one or more embodiments, in step (2), the oxidant is one or more of oxygen, ozone and hydrogen peroxide.

[0039] In one or more embodiments, in step (2), the duration of the oxidant pulse is 0.5 to 2 s; the deposition time is 30 to 100 s; and the purging time is 50 to 120 s.

[0040] In one or more embodiments, in step (2), the mass ratio of the deposited noble metal element to the molecular sieve is 0.01% to 5%: 1.

[0041] A second typical embodiment of the present invention provides a germanium-modified catalyst for catalytic reforming of C3-C9 alkanes prepared by the above preparation method.

[0042] The third typical embodiment of the present invention provides the application of the above-mentioned germanium-modified catalyst for catalytic reforming of C3-C9 alkanes in the preparation of aromatic hydrocarbons by catalytic reforming of C3-C9 alkanes.

[0043] A fourth typical embodiment of the present invention provides a method for preparing aromatic hydrocarbons by catalytic reforming of C3-C9 alkanes, comprising:

[0044] Using a fixed-bed or moving-bed reactor, the aforementioned germanium-modified catalyst for catalytic reforming of C3-C9 alkanes is used to mix C3-C9 alkanes under hydrogen-exposed or non-hydrogen-exposed conditions.

[0045] In one or more embodiments, the molar ratio of hydrogen / inert gas to alkane is 1.0 to 20.0.

[0046] In one or more embodiments, the mass hourly space velocity (WHSV) of the alkane is 0.2–20 h⁻¹. -1 The total reaction pressure is 0.1–5.0 MPa; the reaction temperature is 300–650 °C.

[0047] To enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments.

[0048] Example 1

[0049] 0.17 g germanium tetrachloride and 1 mL hydrochloric acid (0.1 mol / L) were dispersed in 10 mL deionized water, and 10 g KL molecular sieve was added. The mixture was allowed to stand at room temperature for 12 h. The solid was filtered and dried overnight in an oven at 120 °C. The solid was then transferred to a muffle furnace and calcined at 500 °C for 6 h to obtain the Ge / KL molecular sieve support.

[0050] A Ge / KL molecular sieve support was dispersed in 10 mL of ethanol to obtain a suspension. This suspension was then uniformly coated onto a quartz plate, dried at room temperature, and placed in an atomic layer deposition chamber for noble metal atomic deposition. The chamber temperature was 200 °C. Trimethyl-methylcyclopentadiene platinum was used as the Pt source, ozone as the oxidant, and high-purity nitrogen as the carrier gas at a flow rate of 50 sccm. The Pt source pulse duration was 0.05 s, deposition time 20 s, and purge time 40 s. The ozone pulse duration was 1 s, reaction time 40 s, and purge time 60 s. After six consecutive cycles of pulse deposition and purge with the noble metal source and oxidant, the PtGe / KL catalyst was obtained.

[0051] The structure of the PtGe / KL catalyst obtained in this example was analyzed by X-ray diffraction (XRD) and high-resolution scanning transmission microscopy (TEM), and the results are as follows. Figure 1 and Figure 1 As shown, from Figure 1 As can be seen, the Pt loading did not affect the crystal phase of the molecular sieve, and no diffraction peaks related to Pt active species appeared. From... Figure 2 It can be seen that the Pt clusters are relatively uniformly distributed and distributed along the pore direction.

[0052] Comparative Example 1

[0053] 0.13 g of chloroplatinic acid hexahydrate and 0.15 g of germanium tetrachloride were weighed and dissolved in 20 mL of deionized water. 10 g of KL molecular sieve was weighed and added to the above solution. The mixture was allowed to stand at room temperature for 12 h. The solid was filtered and dried overnight in an oven at 120 °C. The solid was then transferred to a muffle furnace and calcined at 350 °C for 6 h to obtain a bimetallic supported PtGe / KL catalyst.

[0054] The structure of the PtGe / KL catalyst obtained in this comparative example was analyzed by X-ray diffraction (XRD) and high-resolution scanning transmission microscopy (TEM), and the results are as follows: Figure 3 and Figure 4 As shown, from Figure 3 As can be seen, the Pt loading did not affect the crystal phase of the molecular sieve, and no diffraction peaks related to Pt active species appeared. From... Figure 4 It can be seen that the Pt clusters exhibited partial aggregation, and the particle size was not very uniform.

[0055] Comparative Example 2

[0056] 10g of KL molecular sieve was dispersed in 10mL of ethanol to obtain a suspension. The suspension was uniformly coated onto a quartz plate, dried at room temperature, and then placed in an atomic layer deposition chamber for atomic deposition. The temperature of the reaction chamber was 200℃. Initially, germanium tetrachloride was used as the Ge source, hydrogen as the reducing agent, and high-purity nitrogen as the carrier gas at a flow rate of 50 sccm. The Ge source pulse time was 0.1s, the deposition time was 30s, and the purge time was 60s. The hydrogen pulse time was 2s, the reaction time was 30s, and the purge time was 60s. This deposition process was repeated 5 times to obtain the Ge / KL molecular sieve support. Next, noble metal atomic deposition was performed. The temperature of the reaction chamber was 200℃, trimethyl-methylcyclopentadiene platinum was used as the Pt source, ozone as the oxidant, and high-purity nitrogen as the carrier gas at a flow rate of 50 sccm. The Pt source pulse duration was 0.05 s, the deposition time was 20 s, and the purge time was 40 s. The ozone pulse duration was 1 s, the reaction time was 40 s, and the purge time was 60 s. After repeating the pulse deposition and purge cycle of the noble metal source and oxidant for 6 consecutive cycles, the PtGe / KL catalyst was obtained.

[0057] Comparative Example 3

[0058] 10 g of KL molecular sieve was dispersed in 10 mL of ethanol to obtain a suspension. The suspension was uniformly coated onto a quartz plate, dried at room temperature, and then placed in an atomic layer deposition chamber for atomic deposition. The temperature of the reaction chamber was 200 °C. Initially, germanium tetrachloride was used as the Ge source, hydrogen as the reducing agent, and high-purity nitrogen as the carrier gas at a flow rate of 50 sccm. The Ge source pulse time was 0.1 s, the deposition time was 30 s, and the purge time was 60 s. The hydrogen pulse time was 2 s, the reaction time was 30 s, and the purge time was 60 s. This deposition process was repeated 5 times to obtain a Ge / KL molecular sieve support. Next, 0.13 g of chloroplatinic acid hexahydrate was weighed into 10 mL of deionized water, and 10 g of the obtained Ge / KL support was added. The mixture was allowed to stand at room temperature for 12 h. The solid was filtered and dried overnight in an oven at 120 °C. The solid was then transferred to a muffle furnace and calcined at 400 °C for 6 h to obtain a bimetallic supported PtGe / KL catalyst.

[0059] Comparative Example 4

[0060] 10 g of KL molecular sieve was dispersed in 10 mL of ethanol to obtain a suspension. The suspension was uniformly coated onto a quartz plate, dried at room temperature, and then placed in an atomic layer deposition chamber for Pt atomic deposition. The temperature of the reaction chamber was 200 °C. Trimethyl-methylcyclopentadiene platinum was used as the Pt source, ozone as the oxidant, and high-purity nitrogen as the carrier gas at a flow rate of 50 sccm. The Pt source pulse time was 0.05 s, the deposition time was 20 s, and the purge time was 40 s. The ozone pulse time was 1 s, the reaction time was 40 s, and the purge time was 60 s. After six consecutive cycles of pulse deposition and purge of the noble metal source and oxidant, the Pt / KL catalyst was obtained. 0.17 g germanium tetrachloride and 1 mL hydrochloric acid (0.1 mol / L) were dispersed in 10 mL deionized water, and 10 g Pt / KL catalyst was added. The mixture was allowed to stand at room temperature for 12 h. The solid was filtered and dried overnight in an oven at 120 °C. The solid was then transferred to a muffle furnace and calcined at 500 °C for 6 h to obtain the Ge / KL molecular sieve support.

[0061] Comparative Example 5

[0062] 0.13 g of chloroplatinic acid hexahydrate was weighed and dispersed in 10 mL of deionized water. 10 g of KL molecular sieve was added and allowed to stand at room temperature for 12 h. The solid was filtered and dried overnight in an oven at 120 °C. The solid was then transferred to a muffle furnace and calcined at 400 °C for 6 h to obtain a bimetallic supported Pt / KL catalyst.

[0063] The Pt / KL catalyst was dispersed in 10 mL of ethanol to obtain a suspension. The suspension was uniformly coated onto a quartz plate, dried at room temperature, and then placed in an atomic layer deposition chamber. The temperature of the reaction chamber was 200 °C. Germanium tetrachloride was used as the Ge source, hydrogen as the reducing agent, and high-purity nitrogen as the carrier gas with a flow rate of 50 sccm. The Ge source pulse time was 0.1 s, the deposition time was 30 s, and the purging time was 60 s. The hydrogen pulse time was 2 s, the reaction time was 30 s, and the purging time was 60 s. The above deposition was repeated 5 times to obtain the PtGe / KL catalyst.

[0064] Experimental Example 1

[0065] Using the reforming of n-heptane to produce aromatics as a probe reaction, the performance of the catalysts prepared in Example 1 and Comparative Examples 1-5 was evaluated. The steps were as follows: 0.3 g (40-60 mesh) of catalyst was mixed with quartz sand of the same mesh size, and 20-40 mesh quartz sand was used as packing material. The catalyst was treated in pure hydrogen at 500°C for 1 h, and then pumped into the liquid feed for reaction. The hydrogen-to-hydrogen molar ratio was 6, and the space velocity was 0.68 h⁻¹. -1 The reaction pressure was 0.1 MPa, and all products were analyzed by online chromatography. The results are shown in Table 1.

[0066] Table 1. Catalytic performance of the catalysts prepared in Example 1 and Comparative Examples 1-5

[0067]

[0068]

[0069] As shown in Table 1, the catalyst prepared by combining impregnation and atomic layer deposition exhibits superior performance compared to catalysts prepared by a single method in the catalytic dehydrogenation cyclization of alkanes to produce aromatics. Ge significantly modifies the active metal, inhibiting the hydrogenolysis reaction, especially suppressing C1-C4 byproducts, thereby increasing the selectivity of the target aromatics to over 90%, significantly reducing carbon deposition, and extending catalyst life, demonstrating promising prospects for industrial application.

[0070] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a germanium-modified catalyst for catalytic reforming of C3-C9 alkanes, characterized in that, include: (1) The germanium source was dispersed in the first solvent, and then the molecular sieve support was immersed in the solution. After standing at room temperature, the solvent was removed and then calcined to obtain the Ge-modified molecular sieve support. (2) The Ge-modified molecular sieve support is dispersed in a second solvent to obtain a suspension. The suspension is uniformly coated on the substrate surface, dried, and then transferred to a reaction chamber for pulse deposition and purging of the noble metal source. Then, pulse deposition and purging of the oxidant are performed. The pulse deposition and purging of the noble metal source and the oxidant are repeated to obtain the germanium-modified catalyst for the catalytic reforming of C3-C9 alkanes. In step (1), Ge atoms enter the molecular sieve framework and undergo isomorphic substitution of the molecular sieve framework atoms to construct noble metal adsorption sites with specific structures. In step (1), the calcination temperature is 500~650 ℃ and the time is 2.5~20 h.

2. The method for preparing the germanium-modified catalyst for catalytic reforming of C3-C9 alkanes as described in claim 1, characterized in that, In step (1), the germanium source includes one or more of dimethyl germanium dichloride, germanium sulfide, trimethyl germanium chloride, tetraethyl germanium, germanium isopropoxide, germanium oxide, triethyl germanium chloride, germanium tetrachloride, and germanium dichloride; Alternatively, in step (1), the molecular sieve includes one or more of KL molecular sieve, Y-type molecular sieve, MFI type and β molecular sieve.

3. The method for preparing the germanium-modified catalyst for catalytic reforming of C3-C9 alkanes as described in claim 1, characterized in that, In step (1), the time for standing at room temperature is 2 to 50 hours.

4. The method for preparing the germanium-modified catalyst for catalytic reforming of C3-C9 alkanes as described in claim 1, characterized in that, In step (1), the mass ratio of germanium element to molecular sieve support in the germanium source is 0.001%~30%:1; In step (2), the mass ratio of the deposited noble metal element to the molecular sieve is 0.01%~5%:

1.

5. The method for preparing the germanium-modified catalyst for catalytic reforming of C3-C9 alkanes as described in claim 1, characterized in that, In step (2), the precious metal is one or more of platinum, palladium and iridium.

6. The method for preparing the germanium-modified catalyst for catalytic reforming of C3-C9 alkanes as described in claim 5, characterized in that, In step (2), the noble metal source is one or more of the following: dichlorotetramineplatinum, chloroplatinic acid hexahydrate, tetraammineplatinum nitrate, acetylacetonate platinum, dichlorodiamminecyclohexaneplatinum, trimethyl-methylcyclopentadiene platinum, potassium chloroplatinate, platinum nitrate, palladium chloride, dichlorotetraminepalladium, hexafluoroacetylacetonate palladium, palladium nitrate, palladium acetate, acetylacetonate palladium, sodium tetrachloropalladium, ammonium chloropalladium, trimethylpalladium acetate, tetraaminopalladium nitrate, iridium chloride, iridium acetate, sodium chloroiridium hexahydrate, acetylacetonate iridium, iridium tetrachloride, sodium hexanitrobiridium, potassium hexachloroiridium, and potassium hexachloroiridium.

7. The method for preparing the germanium-modified catalyst for catalytic reforming of C3-C9 alkanes as described in claim 1, characterized in that, In step (2), the temperature of the reaction chamber is 200~450 ℃; Alternatively, in step (2), the duration of the noble metal source pulse is 0.01~0.5s; the deposition time is 10~60s; and the purging time is 30~100s. Alternatively, in step (2), the oxidant is one or more of oxygen, ozone, and hydrogen peroxide; Alternatively, in step (2), the duration of the oxidant pulse is 0.5 to 2 seconds; the deposition time is 30 to 100 seconds; and the purging time is 50 to 120 seconds.

8. The germanium-modified catalyst for catalytic reforming of C3-C9 alkanes prepared by the method described in any one of claims 1 to 7.

9. The application of the germanium-modified catalyst for catalytic reforming of C3-C9 alkanes as described in claim 8 in the preparation of aromatic hydrocarbons by catalytic reforming of C3-C9 alkanes.

10. A method for preparing aromatic hydrocarbons by catalytic reforming of C3-C9 alkanes, characterized in that, include: Using a fixed-bed or moving-bed reactor, and employing the germanium-modified catalyst for catalytic reforming of C3-C9 alkanes as described in claim 7, C3-C9 alkanes are mixed under hydrogen-exposed or non-hydrogen-exposed conditions.

11. The method for preparing aromatic hydrocarbons by catalytic reforming of C3-C9 alkanes as described in claim 10, characterized in that, The molar ratio of hydrogen / inert gas to alkanes is 1.0~20.0; Alternatively, the WHSV of alkanes is 0.2–20 h⁻¹. -1 The total reaction pressure is 0.1~5.0 MPa; the reaction temperature is 300~650℃.

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