A low-carbon alkane hydroisomerization catalyst, its preparation method and application

Abstract

This invention discloses a low-carbon alkane hydroisomerization catalyst, its preparation method, and its applications. The catalyst comprises Pt / N-TiO2 / Al2O3 and a molecular sieve; wherein the catalyst is characterized by EPR, showing a significant TiO2 concentration at g = 1.987. 3+ Characteristic peaks. The catalyst of this invention is used in the hydrogenation isomerization reaction of low-carbon alkanes. The catalyst not only has higher activity and selectivity, but also excellent stability.

Description

Technical Field

[0001] This invention belongs to the field of alkane isomerization reaction, specifically relating to a low-carbon alkane hydroisomerization catalyst, its preparation method, and its application. Background Technology

[0002] The isomerization of n-alkane can selectively generate high-octane isoalkanes from low-octane n-alkanes, representing an effective pathway to address the environmental crisis. According to relevant literature (GUISNET M. “Ideal” bifunctional catalysis over Pt-acid zeolites[J]. Catalysis Today, 2013, 218-219:123-134.), this reaction follows a typical metal-acid bifunctional synergistic catalytic mechanism. The n-alkane first undergoes dehydrogenation at the metal active site to generate a n-alkene. Subsequently, the n-alkene diffuses to the acidic sites of the molecular sieve and undergoes skeletal isomerization, generating an isoalkene intermediate. This intermediate then returns to the metal site for hydrogenation to generate the target product, the isoalkane. The catalyst is the core of this process; its metal active sites are generally provided by noble metals such as Pt and Pd, primarily used to complete the dissociation of hydrogen, alkane dehydrogenation, and subsequent hydrogenation of the alkene intermediate. de Jong et al. (Nanoscale intimacy in bifunctional catalysts for selective conversion of hydrocarbons. Nature. 2015, 528: 245-248) developed a class of catalysts that selectively deposit Pt centers on the surface of alumina to obtain Pt / Al2O3 components. By combining these with molecular sieves, they achieved the efficient synthesis of isomers of the target product.

[0003] Al₂O₃, as an inert support, lacks defect sites for anchoring Pt sites and is unfavorable for the adsorption and activation processes of hydrogen and alkanes. Introducing reducible oxides, such as TiO₂, is an effective strategy to optimize the electronic configuration of the Pt center and improve metal utilization efficiency. However, under prolonged hydrogen exposure, the strong interaction between TiO₂ and the Pt center leads to the active metal Pt being gradually encapsulated by a TiO₂ oxide layer, severely inhibiting the adsorption and activation of hydrogen and n-hexane on the metal surface. This, in turn, results in decreased catalyst stability, increasing economic and operating costs. Therefore, how to enhance the configurational stability in such systems is a problem that needs to be solved. Summary of the Invention

[0004] To address the aforementioned problems in the existing technology, this invention provides a low-carbon alkane hydroisomerization catalyst, its preparation method, and its application. The catalyst of this invention exhibits not only good activity and selectivity in the hydroisomerization reaction of n-alkanes, but also excellent stability.

[0005] The first aspect of this invention provides a low-carbon alkane hydroisomerization catalyst, wherein the catalyst comprises Pt / N-TiO2 / Al2O3 and a molecular sieve; the catalyst is characterized by EPR, and a significant TiO2 appears at g = 1.987. 3+ Characteristic peaks.

[0006] Furthermore, the catalyst was characterized using EPR, and Ti appeared at g = 1.987. 3+ The relative intensity of the characteristic peak is 5 to 50, preferably 30 to 50.

[0007] Furthermore, in the catalyst, Pt / N-TiO2 / Al2O3 refers to Pt-supported N-TiO2 / Al2O3, where N-TiO2 / Al2O3 refers to Al2O3 supported on N-TiO2, and N-TiO2 refers to nitrogen-modified TiO2.

[0008] Furthermore, in the catalyst, the content of molecular sieve, based on the mass of the catalyst, is 30.0 wt% to 70.0 wt%, for example, but not limited to, 30.0 wt%, 35.0 wt%, 40.0 wt%, 45.0 wt%, 50.0 wt%, 55.0 wt%, 60.0 wt%, 65.0 wt%, 70.0 wt%, and any value within the range formed by any two of these values.

[0009] Furthermore, in the catalyst, the content of Pt / N-TiO2 / Al2O3, based on the mass of the catalyst, is 30.0 wt% to 70.0 wt%, for example, but not limited to, 30.0 wt%, 35.0 wt%, 40.0 wt%, 45.0 wt%, 50.0 wt%, 55.0 wt%, 60.0 wt%, 65.0 wt%, 70.0 wt%, and any value within the range formed by any two of these values.

[0010] Furthermore, in the Pt / N-TiO2 / Al2O3, based on the mass of the catalyst, the content of Pt is 0.01wt% to 2.0wt%, the content of Al2O3 is 25.0wt% to 55.0wt%, the content of N element is 0.02wt% to 1.5wt%, and the content of TiO2 calculated as Ti element is 1.0wt% to 10.5wt%.

[0011] Further, the Pt content in the Pt / N-TiO2 / Al2O3 is 0.01wt% to 2.0wt%, for example, but not limited to, 0.01wt%, 0.02wt%, 0.04wt%, 0.06wt%, 0.08wt%, 0.10wt%, 0.13wt%, 0.15wt%, 0.2wt%, 0.3wt%, 0.4wt%, 0.5wt%, 0.6wt%, 0.7wt%, 0.8wt%, 0.9wt%, 1.0wt%, 1.5wt%, 2.0wt%, and any value within the range formed by any two of these values.

[0012] Further, the content of Al2O3 in the Pt / N-TiO2 / Al2O3 is 25.0wt% to 55.0wt%, for example, but not limited to, 25.0wt%, 30.0wt%, 35.0wt%, 40.0wt%, 42.0wt%, 44.0wt%, 46.0wt%, 48.0wt%, 50.0wt%, 55.0wt%, and any value within the range formed by any two of these values.

[0013] Further, the N content in the Pt / N-TiO2 / Al2O3 is 0.02wt% to 1.5wt%, for example, but not limited to, 0.02wt%, 0.04wt%, 0.06wt%, 0.08wt%, 0.09wt%, 0.1wt%, 0.13wt%, 0.15wt%, 0.2wt%, 0.25wt%, 0.3wt%, 0.35wt%, 0.4wt%, 0.45wt%, 0.5wt%, 0.55wt%, 0.6wt%, 0.65wt%, 0.7wt%, 0.75wt%, 0.8wt%, 1.0wt%, 1.5wt%, and any value within the range formed by any two of these values.

[0014] Further, the content of TiO2 in the Pt / N-TiO2 / Al2O3, calculated as Ti element, is 1.0wt% to 10.5wt%, for example, but not limited to, 1.0wt%, 2.0wt%, 2.5wt%, 3.0wt%, 3.5wt%, 4.0wt%, 4.5wt%, 5.0wt%, 5.5wt%, 6.0wt%, 7.0wt%, 8.0wt%, 8.5wt%, 9.0wt%, 10.0wt%, 10.5wt%, and any value within the range formed by any two of these values.

[0015] Furthermore, in the Pt / N-TiO2 / Al2O3, Al in Al2O3 VThe proportion of the total Al species (five-coordinated Al species) is 30% to 60% based on Al atoms, preferably 30% to 50%, for example, but not limited to, 30%, 35%, 40%, 45%, 50%, and any value within the range formed by any two of these values.

[0016] Furthermore, in the Pt / N-TiO2 / Al2O3, the Pt grain size is 0.20 to 0.50 nm, for example, but not limited to, 0.20 nm, 0.25 nm, 0.30 nm, 0.35 nm, 0.40 nm, 0.45 nm, 0.50 nm, and any value within the range formed by any two of these values.

[0017] Furthermore, the molecule is screened from at least one of ZSM-5, ZSM-11, ZSM-22, ZSM-35, Beta, MOR, and Y, preferably at least one of ZSM-5, ZSM-11, and ZSM-22.

[0018] Furthermore, in the molecular sieve, the SiO2 / Al2O3 molar ratio is 20–150, and the specific surface area is 200–800 m². 2 / g, pore volume is 0.12~0.30cm³ 3 / g.

[0019] A second aspect of the present invention provides a method for preparing the above-mentioned catalyst, comprising the following steps:

[0020] (1) Mix titanium source, nitrogen-containing reagent and alumina, adjust pH value to 2-3, let stand, dry and heat treat to obtain N-TiO2 / Al2O3;

[0021] (2) Load Pt onto the N-TiO2 / Al2O3 obtained in step (1) to obtain Pt / N-TiO2 / Al2O3;

[0022] (3) The Pt / N-TiO2 / Al2O3 obtained in step (2) is mixed with molecular sieve to obtain the catalyst.

[0023] Further, preferably, the method for preparing the alumina includes: mixing urea, thiourea and an aluminum source, subjecting the mixture to heat treatment, and calcining to obtain alumina.

[0024] Furthermore, in the method for preparing alumina, the solvent used for mixing is a water-alcohol (preferably ethylene glycol) mixed solvent.

[0025] Furthermore, in the method for preparing alumina, the aluminum source is selected from one or more of aluminum chloride, aluminum nitrate, aluminum sulfate, aluminum carbonate, aluminum acetate, aluminum phosphate, alumina, aluminum isopropoxide, aluminum sol, or boehmite, preferably one or more of aluminum chloride, aluminum isopropoxide, or aluminum sol.

[0026] Furthermore, in the method for preparing alumina, the mass ratio of urea, thiourea, aluminum source (calculated as Al2O3), alcohol, and water is: urea:thiourea:Al2O3:alcohol:H2O = 0.1-2.0:0.05-1.5:5-25:10-100:30-100.

[0027] Furthermore, in the method for preparing alumina, the temperature of the heat treatment is 90–190°C, preferably 120–180°C; the treatment time of the heat treatment is 0.5 h–96 h, preferably 10 h–72 h.

[0028] Furthermore, in the method for preparing alumina, after the heat treatment, the alumina undergoes conventional steps such as filtration, washing, and drying, followed by calcination to obtain the alumina. The calcination temperature is 250–550℃, preferably 350–550℃; the calcination time is 0.5h–24h, preferably 4h–12h.

[0029] Further, in step (1), the titanium source is one or more of tetrabutyl titanate, titanium tetrachloride, and titanium isopropoxide.

[0030] Further, in step (1), the nitrogen-containing reagent is one or more of melamine, lysine, and glutamic acid.

[0031] Furthermore, in step (1), the solvent used for mixing is a water-alcohol (preferably ethanol) mixed solvent.

[0032] Further, in step (1), the mass ratio of titanium source (based on TiO2), nitrogen-containing reagent, alumina (based on Al2O3), alcohol, and water is TiO2:nitrogen-containing reagent:Al2O3:alcohol:H2O = 0.1~1.0:0.5~5.0:0.5~10:50~500:50~200, preferably 0.5~1.0:2.5~4.5:0.5~10:100~200:10~100. The alcohol and water are derived from a water-alcohol mixed solvent.

[0033] Furthermore, in step (1), the acidic reagent used to adjust the pH value is one or more of glacial acetic acid, hydrochloric acid, nitric acid, and sulfuric acid.

[0034] Furthermore, in step (1), the settling time is 10h to 90h.

[0035] Further, in step (1), the drying is preferably spray drying. The conditions for spray drying are: inlet temperature of 180-220°C and outlet temperature of 80-100°C.

[0036] Furthermore, in step (1), the heat treatment includes ball milling and flash calcination.

[0037] Furthermore, the ball milling adopts a planetary ball mill; preferably, the ball milling conditions include: a ball milling speed of 300-800 r / min, more preferably 500-800 r / min; and a ball milling time of 20 min-12 h, more preferably 30 min-2 h.

[0038] Further, the flash calcination processing conditions include: the flash calcination processing atmosphere is an ammonia atmosphere, wherein the ammonia volume content in the ammonia atmosphere is 5% to 100%; the flash calcination processing temperature is 400 to 700°C, preferably 500 to 650°C; the flash calcination processing electric field strength is 150 V / cm to 550 V / cm, preferably 400 V / cm to 550 V / cm; and the flash calcination processing current density is 15 to 100 mA / mm². 2 Preferably, it is 25–65 mA / mm 2 The flash burning time is 5s to 10min, preferably 2s to 60s.

[0039] Further, preferably, in step (2), the method of loading Pt includes: adding the Pt precursor solution dropwise to the suspension of N-TiO2 / Al2O3 for reaction, and then heat-treating to obtain Pt / N-TiO2 / Al2O3.

[0040] Furthermore, in the method for loading Pt, the Pt precursor is preferably chloroplatinic acid; the Pt concentration in the Pt precursor solution is 0.001 mg. Pt / mL~2.50mg Pt / mL, preferably 0.1mg Pt / mL~1.5mg Pt / mL.

[0041] Furthermore, in the method of loading Pt, the preparation process of the N-TiO2 / Al2O3 suspension is as follows: first, the N-TiO2 / Al2O3 obtained in step (1) is mixed with water and stirred for 0.1h to 1.0h, then hydrochloric acid is slowly added dropwise to adjust the pH value to 0.5 to 3.5, and stirring is continued for 0.5h to 2.0h.

[0042] Further, in the method for loading Pt, the reaction time is 0.5 h to 10.5 h. After the reaction is complete, the mixture is first filtered, washed, and dried, and then heat-treated to obtain Pt / N-TiO2 / Al2O3. The drying conditions are as follows: temperature 40–120 °C, time 2 h to 15 h. The heat treatment conditions are as follows: temperature 250–500 °C, preferably 350–500 °C, time 0.5 h to 24 h, preferably 4 h to 12 h.

[0043] Furthermore, in step (3), the mixing is a physical mixing, and the mixing method includes grinding, ball milling, etc.

[0044] A third aspect of the invention also provides the application of the above-described catalyst in the catalytic isomerization reaction of low-carbon alkane.

[0045] Furthermore, the low-carbon alkane is at least one of the n-alkanes having 4 to 8 carbon atoms; preferably at least one of n-pentane, n-hexane, n-heptane, and n-octane.

[0046] Further, the reaction conditions include: a reaction temperature of 200–405 °C, a reaction pressure of 1.0–4.0 MPa, a molar ratio of hydrogen to low-carbon alkanes of 0.5–10.0, and a mass hourly space velocity (HHSV) of the low-carbon alkanes of 0.2–8.0 h⁻¹. 1 .

[0047] Compared with the prior art, the present invention has the following superior effects:

[0048] 1. This invention provides a novel alkane hydroisomerization catalyst comprising Pt / N-TiO2 / Al2O3 and a molecular sieve; wherein the catalyst is characterized by EPR, and a significant TiO2 content is observed at g = 1.987. 3+ Characteristic peaks, preferably Al in Al2O3 V It accounts for 30% to 60% of the total Al species. The components in the catalyst work synergistically and can significantly improve the catalyst stability and the yield of isomer products in the hydrogenation reaction of n-alkane isomerization.

[0049] 2. In the catalyst of this invention, in particular, TiO2 is modified with N, which increases the Ti content in the bulk TiO2 phase. 3+ The ratio of Pt to TiO2 can optimize the dispersion of Pt centers and inhibit the formation of TiO2 coatings on Pt centers. By comprehensively coordinating the various steps in the preparation process, the resulting catalyst has higher activity and selectivity, and exhibits excellent structural stability in long-term alkane isomerization reactions.

[0050] 3. The catalyst of this invention is used in the hydroisomerization reaction of low-carbon alkanes. The isomer yield can reach 76.2% after 1 hour of reaction and can be maintained at 76.0% after 1000 hours of reaction. The particle size of Pt crystals can be maintained at 0.26 nm after 1000 hours of reaction. Detailed Implementation

[0051] To more clearly illustrate the technical solution of the present invention, the following specific embodiments are listed. However, those skilled in the art will readily understand that the description of the embodiments is for illustrative purposes only and should not, and will not, limit the invention as described in detail in the claims.

[0052] In this invention, electron paramagnetic resonance (EPR) spectroscopy is used to analyze Ti in the N-TiO2 bulk phase. 3+ Semi-quantitative analysis of concentration was performed using Ti, which appeared at g = 1.987. 3+ The relative intensities of characteristic peaks are expressed. The reference catalyst consists of molecular sieves and Pt / TiO2 / Al2O3 (i.e., Pt supported on TiO2 / Al2O3, differing from the catalyst of this invention only in the use of nitrogen-free modified TiO2), such as catalyst D3 prepared in Comparative Example 3 of this invention. The reference catalyst shows Ti at g = 1.987. 3+ The intensity of the characteristic peak is I1, and the catalyst of this invention exhibits Ti at g = 1.987. 3+ If the intensity of the characteristic peak is I2, then the relative intensity is I2 / I1. Electron paramagnetic resonance (EPR) spectroscopy was performed using a Bruker A200 instrument with the following parameters: modulation amplitude 4.00 GHz, power 1.0 mW, test temperature 7 K, and receiver gain 10000.

[0053] In this invention, Al in Al2O3 V The proportion of (five-coordinated Al species) to total Al species is adopted using 27 Al single-pulse MAS NMR was measured on a Bruker 600MHz AVANCE III nuclear magnetic resonance spectrometer (14.1T), with a resonance frequency of 156.4MHz, a rotation speed of 22kHz, a π / 6 pulse with a pulse width of 1μs, a sampling interval of 0.5s, and 1024 samplings.

[0054] In this invention, the horizontal flash furnace used for flash sintering is model GSL-1600X-FS3KW.

[0055] The relevant parameters of the ZSM-5 molecular sieve powder used in the embodiments and comparative examples of this invention are as follows: SiO2 / Al2O3 (molar ratio) = 25, specific surface area (S BET ) = 425m 2 / g, pore volume = 0.12cm 3 / g.

[0056] The relevant parameters of the ZSM-22 molecular sieve powder used in the embodiments and comparative examples of this invention are as follows: SiO2 / Al2O3 (molar ratio) = 40, specific surface area (S BET ) = 500m 2 / g, pore volume = 0.21cm 3 / g.

[0057] In the embodiments and comparative examples of this invention, the reaction products were analyzed using an Agilent 7890B gas chromatograph.

[0058] In the embodiments and comparative examples of this invention, the formulas for calculating conversion rate and isomer selectivity are as follows:

[0059] Conversion rate (%) = 1 - (mass of n-hexane in the reaction product / mass of n-hexane in the feed) × 100%;

[0060] Isomer selectivity (%) = (mass of isohexane in the product / total mass of the product) × 100%;

[0061] Isomer yield (%) = conversion rate × isomer selectivity × 100%.

[0062] To facilitate understanding of the present invention, the following embodiments are provided. However, these embodiments are merely for the purpose of helping to understand the present invention and should not be regarded as specific limitations of the present invention.

[0063] Comparative Example 1

[0064] (1) Tetrabutyl titanate, melamine, and commercial Al2O3 were added to a mixture of ethanol and water (the mass ratio of tetrabutyl titanate (calculated as TiO2), melamine, commercial Al2O3, ethanol, and water was TiO2:melamine:Al2O3:ethanol:H2O = 0.5:2.5:10:200:50). Glacial acetic acid solvent was added dropwise while stirring until the pH value reached 2.5. After standing for 24 hours, the resulting suspension was spray-dried (the spray-drying parameters were: air inlet...). The inlet temperature was 200℃, the outlet temperature was 100℃, and the feed rate was 10mL / min. The resulting powder was ball-milled in a planetary ball mill (speed 500r / min) for 60min, and then compressed into tablets. The tablets were then placed in a horizontal flash furnace for flash calcination. The furnace was connected in series in a circuit and heated to 550℃. An electric field was applied under a 65% NH3 / 35% N2 atmosphere for flash calcination. The flash calcination conditions were an electric field strength of 400V / cm and a current density of 35mA / mm². 2 After 30 seconds, N-TiO2 / Al2O3-D1 was obtained.

[0065] (2) Add 2g of N-TiO2 / Al2O3-D1 to 100g of deionized water and stir for 1.0h. Then slowly add hydrochloric acid to adjust the pH to 3.5 and continue stirring for 2.0h. During the stirring process, add 10mL of 0.5mg hydrochloric acid dropwise. P A solution of H2PtCl6·6H2O with a concentration of t / mL was stirred for 3 hours, filtered, and washed with 1.5 L of deionized water. The resulting filter cake was dried in an oven at 100 °C for 12 hours, and then air-treated at 500 °C for 6 hours to obtain Pt / N-TiO2 / Al2O3-D1.

[0066] (3) Mix 1g of Pt / N-TiO2 / Al2O3-D1 with 1g of ZSM-5 molecular sieve powder and grind to obtain catalyst D1. By mass, the catalyst contains 0.13wt% Pt, 50.0wt% molecular sieve, and 47.99wt% Al2O3.

[0067] Comparative Example 2

[0068] (1) Dissolve urea, thiourea, and aluminum nitrate in a water-ethylene glycol mixed solvent in a certain proportion and stir to obtain a transparent solution. Transfer the solution to a hydrothermal reactor. The mass ratio of urea, thiourea, aluminum nitrate (calculated as Al2O3), ethanol, and water is urea:thiourea:Al2O3:ethanol:H2O = 0.1:0.05:5:100:100. Then treat at 150℃ for 12 hours, and after filtration, washing, and drying, air treat at 500℃ for 6 hours to obtain Al2O3-D2.

[0069] (2) Add 2g of Al2O3-D2 to 100g of deionized water and stir for 1.0h. Then slowly add hydrochloric acid to adjust the pH to 3.5 and continue stirring for 2.0h. During the stirring process, add 40mL of 0.5mg hydrochloric acid dropwise. P A solution of H2PtCl6·6H2O with a concentration of t / mL was stirred for 3 hours, filtered, and washed with 1.5 L of deionized water. The resulting filter cake was dried in an oven at 100 °C for 12 hours, and then air-treated at 500 °C for 6 hours to obtain Pt / Al2O3-D2.

[0070] (3) Mix 1g of Pt / Al2O3-D2 with 1g of ZSM-5 molecular sieve powder and grind to obtain catalyst D2. By mass, the catalyst contains 0.13wt% Pt, 50.0wt% molecular sieve, and 49.87wt% Al2O3.

[0071] Comparative Example 3

[0072] (1) Dissolve urea, thiourea, and aluminum nitrate in a water-ethylene glycol mixed solvent in a certain proportion and stir to obtain a transparent solution. Transfer the solution to a hydrothermal reactor. The mass ratio of urea, thiourea, aluminum nitrate (calculated as Al2O3), ethylene glycol, and water is urea:thiourea:Al2O3:ethylene glycol:H2O = 2.0:1.5:10:100:100. Then treat at 150℃ for 12 hours, and after filtration, washing, and drying, air treat at 500℃ for 6 hours to obtain Al2O3-D3.

[0073] (2) Tetrabutyl titanate and Al2O3-D3 were added to a mixture of ethanol and water (the mass ratio of tetrabutyl titanate, Al2O3-D3, ethanol, and water was 0.5:10:200:50, calculated as TiO2). Glacial acetic acid was added dropwise while stirring until the pH reached 2.5. After standing for 24 hours, the resulting suspension was spray-dried (the spray-drying parameters were an air inlet temperature of 200°C). The powder obtained was ball-milled for 60 minutes in a planetary ball mill (500 r / min) at an outlet temperature of 100℃ and a feed rate of 10 mL / min. After being pressed into tablets, it was placed in a horizontal flash furnace for flash calcination. The furnace was connected in series in a circuit and heated to 550℃. An electric field was applied under a 65% NH3 / 35% N2 atmosphere for flash calcination. The flash calcination conditions were an electric field strength of 400 V / cm and a current density of 35 mA / mm². 2 After 30 seconds, TiO2 / Al2O3-D3 was obtained.

[0074] (3) Add 2g TiO2 / Al2O3-D3 to 100g deionized water and stir for 1.0h. Then slowly add hydrochloric acid to adjust the pH to 3.5 and continue stirring for 2.0h. During the stirring process, add 10mL of 0.5mg hydrochloric acid dropwise. P A solution of H2PtCl6·6H2O with a concentration of t / mL was stirred for 3 hours, filtered, and washed with 1.5 L of deionized water. The resulting filter cake was dried in an oven at 100 °C for 12 hours, and then air-treated at 500 °C for 6 hours to obtain Pt / TiO2 / Al2O3-D3.

[0075] (4) Mix 1g of Pt / TiO2 / Al2O3-D3 with 1g of ZSM-5 molecular sieve powder and grind to obtain catalyst D3. By mass, the catalyst contains 0.13wt% Pt, 50.0wt% molecular sieve, and 47.37wt% Al2O3.

[0076]

Example 1

[0077] (1) Dissolve urea, thiourea, and aluminum nitrate in a water-ethylene glycol mixed solvent in a certain proportion and stir to obtain a transparent solution. Transfer the solution to a hydrothermal reactor. The mass ratio of urea, thiourea, aluminum nitrate (calculated as Al2O3), ethylene glycol, and water is urea:thiourea:Al2O3:ethylene glycol:H2O = 2.0:1.5:10:100:100. Then treat at 150℃ for 12 hours, and after filtration, washing, and drying, calcine in air at 500℃ for 6 hours to obtain Al2O3-S1.

[0078] (2) Tetrabutyl titanate, melamine, and Al2O3-S1 were added to a mixture of ethanol and water (the mass ratio of tetrabutyl titanate (calculated as TiO2), melamine, Al2O3-S1, ethanol, and water was TiO2:melamine:Al2O3-S1:ethanol:H2O = 0.5:2.5:10:200:50). Glacial acetic acid was added dropwise while stirring until the pH reached 2.5. After standing for 24 hours, the resulting suspension was spray-dried (spray drying parameters were as follows). The air inlet temperature was 200℃, the outlet temperature was 100℃, and the feed rate was 10mL / min. The resulting powder was ball-milled in a planetary ball mill (speed 500r / min) for 60min, and then pressed into tablets. The tablets were then placed in a horizontal flash furnace for flash calcination. The furnace was connected in series in a circuit and heated to 550℃. An electric field was applied under a 65% NH3 / 35% N2 atmosphere for flash calcination. The flash calcination conditions were an electric field strength of 400V / cm and a current density of 35mA / mm². 2 After 30 seconds, TiO2-Al2O3-S1 was obtained.

[0079] (3) Add 2g of N-TiO2 / Al2O3-S1 to 100g of deionized water and stir for 1.0h. Then slowly add hydrochloric acid to adjust the pH to 3.5 and continue stirring for 2.0h. During the stirring process, add 10mL of 0.5mg hydrochloric acid dropwise. P A solution of H2PtCl6·6H2O with a concentration of t / mL was stirred for 3 hours, filtered, and washed with 1.5 L of deionized water. The resulting filter cake was dried in an oven at 100 °C for 12 hours, and then air-treated at 500 °C for 6 hours to obtain Pt / N-TiO2 / Al2O3-S1.

[0080] (4) Mix 1g of Pt / N-TiO2 / Al2O3-S1 with 1g of ZSM-5 molecular sieve powder and grind to obtain catalyst S1. By mass, the catalyst contains 0.13wt% Pt, 50.0wt% molecular sieve, and 47.37wt% Al2O3.

[0081]

Example 2

[0082] (1) Dissolve urea, thiourea, and aluminum sulfate in a water-ethylene glycol mixed solvent in a certain proportion and stir to obtain a transparent solution. Transfer the solution to a hydrothermal reactor. The mass ratio of urea, thiourea, aluminum sulfate (calculated as Al2O3), ethylene glycol, and water is urea:thiourea:Al2O3:ethylene glycol:H2O = 2.0:1.5:5:100:60. Then treat at 150℃ for 12 hours, and after filtration, washing, and drying, air treat at 500℃ for 6 hours to obtain Al2O3-S2.

[0083] (2) Tetrabutyl titanate, melamine, and Al2O3-S2 were added to a mixture of ethanol and water (by mass, tetrabutyl titanate is calculated as TiO2, and the mass ratio of melamine, Al2O3-S2, ethanol, and water is TiO2:melamine:Al2O3-S2:ethanol:H2O = 0.2:2.0:10:200:10). Glacial acetic acid was added dropwise while stirring until the pH reached 2.5. After standing for 24 hours, the resulting suspension was spray-dried (spray drying...). The parameters were: air inlet temperature 200℃, outlet temperature 100℃, and feed rate 10mL / min. The obtained powder was ball-milled in a planetary ball mill (500r / min) for 60min, then compressed into tablets and placed in a horizontal flash furnace for flash calcination. The furnace was connected in series in the circuit and heated to 650℃. An electric field was applied under a 95% NH3 / 5% N2 atmosphere for flash calcination. The flash calcination conditions were: electric field strength 450V / cm and current density 35mA / mm². 2 After 30 seconds, N-TiO2 / Al2O3-S2 was obtained.

[0084] (3) Add 2g of N-TiO2 / Al2O3-S2 to 100g of deionized water and stir for 1.0h. Then slowly add hydrochloric acid to adjust the pH to 3.5 and continue stirring for 2.0h. During the stirring process, add 10mL of 0.5mg hydrochloric acid dropwise. P A solution of H2PtCl6·6H2O with a concentration of t / mL was stirred for 3 hours, filtered, and washed with 1.5 L of deionized water. The resulting filter cake was dried in an oven at 100 °C for 12 hours, and then air-treated at 500 °C for 6 hours to obtain the Pt / N-TiO2 / Al2O3-S2 component.

[0085] (4) Mix 1g of Pt / N-TiO2 / Al2O3-S2 with 1g of ZSM-5 molecular sieve powder and grind to obtain catalyst S2. By mass, the catalyst contains 0.13wt% Pt, 50.0wt% molecular sieve, and 47.78wt% Al2O3.

[0086]

Example 3

[0087] (1) Dissolve urea, thiourea, and aluminum sulfate in a water-ethylene glycol mixed solvent in a certain proportion and stir to obtain a transparent solution. Transfer the solution to a hydrothermal reactor. The mass ratio of urea, thiourea, aluminum sulfate (calculated as Al2O3), ethanol, and water is urea:thiourea:Al2O3:ethanol:H2O = 2.0:0.05:25:100:100. Then treat at 150℃ for 12 hours, and after filtration, washing, and drying, air treat at 500℃ for 6 hours to obtain Al2O3-S3.

[0088] (2) Add titanium tetrachloride, lysine, and Al2O3-S3 to a mixture of ethanol and water (the mass ratio of titanium tetrachloride (calculated as TiO2), lysine, Al2O3-S3, ethanol, and water is TiO2:lysine:Al2O3-S3:ethanol:H2O = 0.8:5.0:10:100:10). While stirring, add glacial acetic acid solvent dropwise until the pH value is 2.5. After standing for 24 hours, spray dry the obtained suspension (spray drying parameters are air). The inlet temperature was 200℃, the outlet temperature was 100℃, and the feed rate was 10mL / min. The resulting powder was ball-milled in a planetary ball mill (400r / min) for 30min, then compressed into tablets and placed in a horizontal flash furnace for flash calcination. The furnace was connected in series in a circuit and heated to 700℃. An electric field was applied under a 95% NH3 / 5% N2 atmosphere for flash calcination. The flash calcination conditions were an electric field strength of 450V / cm and a current density of 35mA / mm². 2 After 30 seconds, N-TiO2 / Al2O3-S3 was obtained.

[0089] (3) Add 2g of N-TiO2 / Al2O3-S3 to 100g of deionized water and stir for 1.0h. Then slowly add hydrochloric acid to adjust the pH to 3.5 and continue stirring for 2.0h. During the stirring process, add 5mL of 0.5mg hydrochloric acid dropwise. P A solution of H2PtCl6·6H2O with a concentration of t / mL was stirred for 3 hours, filtered, and washed with 1.5 L of deionized water. The resulting filter cake was dried in an oven at 100 °C for 12 hours, and then air-treated at 500 °C for 6 hours to obtain Pt / N-TiO2 / Al2O3-S3.

[0090] (4) Mix 1g of Pt / N-TiO2 / Al2O3-S3 with 1g of ZSM-22 molecular sieve powder and grind to obtain catalyst S3. By mass, the catalyst contains 0.06wt% Pt, 50.0wt% molecular sieve, and 44.94wt% Al2O3.

[0091]

Example 4

[0092] (1) Dissolve urea, thiourea, and aluminum chloride in a water-ethylene glycol mixed solvent in a certain proportion and stir to obtain a transparent solution. Transfer the solution to a hydrothermal reactor. The mass ratio of urea, thiourea, aluminum chloride (calculated as Al2O3), ethanol, and water is urea:thiourea:Al2O3:ethanol:H2O = 2.0:0.05:25:100:100. Then treat at 180℃ for 10 h, and after filtration, washing, and drying, air treat at 550℃ for 10 h to obtain Al2O3-S4.

[0093] (2) Tetrabutyl titanate, glutamic acid, and Al2O3-S4 were added to a mixture of ethanol and water (the mass ratio of titanium tetrachloride (calculated as TiO2), glutamic acid, Al2O3-S4, ethanol, and water was TiO2:glutamic acid:Al2O3-S4:ethanol:H2O = 1.0:3.0:10:100:10). Glacial acetic acid was added dropwise while stirring until the pH reached 2.5. After standing for 24 hours, the resulting suspension was spray-dried (see spray drying instructions). The air inlet temperature was 200℃, the outlet temperature was 100℃, and the feed rate was 10mL / min. The resulting powder was ball-milled in a planetary ball mill (400r / min) for 30min, then compressed into tablets and placed in a horizontal flash furnace for flash calcination. The furnace was connected in series in a circuit and heated to 700℃. An electric field was applied under a pure NH3 atmosphere for flash calcination. The flash calcination conditions were: electric field strength 550V / cm and current density 25mA / mm². 2 After 20 seconds, N-TiO2 / Al2O3-S4 was obtained.

[0094] (3) Add 2g of N-TiO2 / Al2O3-S4 to 100g of deionized water and stir for 1.0h. Then slowly add hydrochloric acid to adjust the pH to 3.5 and continue stirring for 2.0h. During the stirring process, add 10mL of 0.5mg hydrochloric acid dropwise. P A solution of H2PtCl6·6H2O with a concentration of t / mL was stirred for 3 hours, filtered, and washed with 1.5 L of deionized water. The resulting filter cake was dried in an oven at 100 °C for 12 hours, and then air-treated at 500 °C for 6 hours to obtain Pt / N-TiO2 / Al2O3-S4.

[0095] (4) Mix 1g of Pt / N-TiO2 / Al2O3-S4 with 1g of ZSM-22 molecular sieve powder and grind to obtain catalyst S4. By mass, the catalyst contains 0.13wt% Pt, 50.0wt% molecular sieve, and 40.77wt% Al2O3.

[0096]

Example 5

[0097] (1) Dissolve urea, thiourea, and aluminum chloride in a water-ethylene glycol mixed solvent in a certain proportion and stir to obtain a transparent solution. Transfer the solution to a hydrothermal reactor. The mass ratio of urea, thiourea, aluminum chloride (calculated as Al2O3), ethanol, and water is urea:thiourea:Al2O3:ethanol:H2O = 2.0:1.0:15:100:100. Then treat at 180℃ for 10 h, and after filtration, washing, and drying, air treat at 550℃ for 10 h to obtain Al2O3-S5.

[0098] (2) Add tetrabutyl titanate, glutamic acid, and Al2O3-S5 to a mixture of ethanol and water (the mass ratio of titanium tetrachloride as TiO2, glutamic acid, Al2O3-S4, ethanol, and water is TiO2:glutamic acid:Al2O3-S5:ethanol:H2O = 1.0:0.5:10:100:10). Glacial acetic acid solvent was added dropwise during stirring until the pH reached 2.5. After standing for 24 hours, the resulting suspension was spray-dried (spray drying parameters: air inlet temperature 200℃, outlet temperature 100℃, feed rate 10mL / min). The resulting powder was ball-milled in a planetary ball mill (speed 300r / min) for 30 minutes, then compressed into tablets and placed in a horizontal flash furnace for flash calcination. The furnace was connected in series with a circuit and heated to 400℃. An electric field was applied under a pure NH3 atmosphere for flash calcination. The flash calcination conditions were: electric field strength 550V / cm, current density 15mA / mm². 2 After 10 seconds, N-TiO2 / Al2O3-S5 was obtained.

[0099] (3) Add 2g of N-TiO2 / Al2O3-S5 to 100g of deionized water and stir for 1.0h. Then slowly add hydrochloric acid to adjust the pH to 3.5 and continue stirring for 2.0h. During the stirring process, add 10mL of 0.5mg hydrochloric acid dropwise. P A solution of H2PtCl6·6H2O with a concentration of t / mL was stirred for 3 hours, filtered, and washed with 1.5 L of deionized water. The resulting filter cake was dried in an oven at 100 °C for 12 hours, and then air-treated at 500 °C for 6 hours to obtain Pt / N-TiO2 / Al2O3-S5.

[0100] (4) Mix 1g of Pt / N-TiO2 / Al2O3-S5 with 1g of ZSM-22 molecular sieve powder and grind to obtain catalyst S5. By mass, the catalyst contains 0.13wt% Pt, 50.0wt% molecular sieve, and 40.77wt% Al2O3.

[0101]

Example 6

[0102] Catalysts S1-S5 and D1-D3 were pressed into tablets and sieved through a 20-40 mesh sieve. 0.6 g of each catalyst was placed in a fixed-bed reactor and subjected to reduction at a rate of 10 °C / min from room temperature to 450 °C for 2 h under a hydrogen atmosphere. The temperature was then lowered to 250 °C for catalyst evaluation. The evaluation conditions were as follows: temperature 270 °C, pressure 2.0 MPa, hydrogen to n-heptane molar ratio 6.0, and n-heptane mass hourly space velocity (WHSV) 4.5 h⁻¹. 1 The isomer yields of each catalyst after 1 hour of reaction, the isomer yields after 1000 hours of reaction, and the Pt grain size after 1000 hours of reaction are shown in Table 2.

[0103] Table 1. Composition and properties of the catalysts obtained in each example.

[0104]

[0105] Note: 'a' represents the Ti at g = 1.987 relative to catalyst D3 in each example. 3+ The relative intensity of characteristic peaks;

[0106] b represents Al in Al2O3 V The proportion of five-coordinated Al species to the total Al species.

[0107] Table 2 Evaluation results of the catalysts obtained in each example

[0108]

[0109] The specific embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combining the various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A low carbon alkane hydroisomerization catalyst characterized in that, The catalyst comprises Pt / N-TiO2 / Al2O3 and molecular sieve; the catalyst is characterized by EPR, and obvious Ti 3+ characteristic peak appears at g = 1.

987.

2. The catalyst according to claim 1, characterized in that, The catalyst was characterized by EPR, and Ti appeared at g = 1.987 3+ The relative intensity of the characteristic peak is 5-50, preferably 30-50.

3. The catalyst of claim 1, wherein Al in the Al2O3 in the Pt / N-TiO2 / Al2O3 V from 30% to 60%, preferably from 30% to 50%, of the total Al species in terms of Al atoms.

4. The catalyst of claim 1, wherein The Pt grains in the Pt / N-TiO2 / Al2O3 have a grain size of 0.20–0.50 nm.

5. The catalyst of claim 1, wherein The molecules are screened from at least one of ZSM-5, ZSM-11, ZSM-22, ZSM-35, Beta, MOR, and Y, preferably at least one of ZSM-5, ZSM-11, and ZSM-22.

6. The catalyst of claim 1, wherein In the catalyst, based on the mass of the catalyst, the content of molecular sieve is 30.0 wt% to 70.0 wt%, and the content of Pt / N-TiO2 / Al2O3 is 30.0 wt% to 70.0 wt%. Preferably, in the Pt / N-TiO2 / Al2O3, based on the mass of the catalyst, the content of Pt is 0.01wt% to 2.0wt%, the content of Al2O3 is 25.0wt% to 55.0wt%, the content of N element is 0.02wt% to 1.5wt%, and the content of TiO2 calculated as Ti element is 1.0wt% to 10.5wt%.

7. A method for preparing the catalyst according to any one of claims 1-6, comprising the following steps: (1) Mix titanium source, nitrogen-containing reagent and alumina, adjust pH value to 2-3, let stand, dry and heat treat to obtain N-TiO2 / Al2O3; (2) Load Pt onto the N-TiO2 / Al2O3 obtained in step (1) to obtain Pt / N-TiO2 / Al2O3; (3) The Pt / N-TiO2 / Al2O3 obtained in step (2) is mixed with molecular sieve to obtain the catalyst.

8. The preparation method according to claim 7, characterized in that, In step (1), the titanium source is one or more of tetrabutyl titanate, titanium tetrachloride, and titanium isopropoxide; And / or, in step (1), the nitrogen-containing reagent is one or more of melamine, lysine, and glutamic acid; And / or, in step (1), the solvent used for mixing is a water-alcohol mixture.

9. The production method according to claim 8, characterized by, In step (1), the mass ratio of titanium source (calculated as TiO2), nitrogen-containing reagent, aluminum oxide (calculated as Al2O3), alcohol, and water is: TiO2: nitrogen-containing reagent: Al2O3: alcohol: H2O = 0.1~1.0: 0.5~5.0: 0.5~10: 50~500: 50~200.

10. The preparation method according to claim 7, characterized in that, In step (1), the acidic reagent used to adjust the pH value is one or more of glacial acetic acid, hydrochloric acid, nitric acid, and sulfuric acid.

11. The preparation method according to claim 7, characterized in that, In step (1), the settling time is 10h to 90h; And / or, in step (1), the drying is preferably spray drying; preferably, the spray drying conditions include: an inlet temperature of 180-220°C and an outlet temperature of 80-100°C.

12. The method of claim 7, wherein, In step (1), the heat treatment includes ball milling and flash calcination. Preferably, the ball milling is a planetary ball mill; the ball milling conditions include: a ball milling speed of 300-800 r / min, preferably 500-800 r / min; and a ball milling time of 20 min-12 h, preferably 30 min-2 h. Preferably, the flash calcination processing conditions include: the flash calcination atmosphere is an ammonia atmosphere, wherein the ammonia volume content in the ammonia atmosphere is 5% to 100%; the flash calcination temperature is 400 to 700°C, preferably 500 to 650°C; the flash calcination electric field strength is 150 V / cm to 550 V / cm, preferably 400 V / cm to 550 V / cm; and the flash calcination current density is 15 to 100 mA / mm². 2 Preferably, it is 25–65 mA / mm 2 The flash burning time is 5s to 10min, preferably 2s to 60s.

13. The application of the catalyst according to any one of claims 1-6 or the catalyst prepared by any one of claims 7-12 in the catalytic isomerization reaction of low-carbon alkane.

14. Use according to claim 13, characterized in that, The low-carbon alkane is at least one of the n-alkanes having 4 to 8 carbon atoms; preferably at least one of n-pentane, n-hexane, n-heptane, and n-octane.

15. The use according to claim 13, characterized in that, The reaction conditions include: the reaction temperature is 200-405℃, the reaction pressure is 1.0-4.0MPa, the molar ratio of hydrogen to low-carbon alkane is 0.5-10.0, the mass space velocity of low-carbon alkane is 0.2-8.0h -1 .

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