Highly stable molecular sieve and preparation of normal paraffin hydroisomerization catalysts therefrom

Abstract

The present application relates to a kind of high-stability molecular sieve and normal paraffin hydroisomerization catalyst prepared by it, the high-stability molecular sieve of the present application is obtained by the activation of one-dimensional mesoporous silicon-aluminum molecular sieve by fluoride, and organic amine repair.It is repaired to the framework structure of one-dimensional mesoporous silicon-aluminum molecular sieve, increases the crystallinity of existing molecular sieve, reduces uncoordinated saturated framework structure, promotes Lewis acidic site in molecular sieve to be converted into acidic site, and improves its tolerance degree to oxygen-containing compounds under high temperature and high pressure reaction conditions, enhances the hydrophobic property of molecular sieve carrier, improves reaction activity and isomer yield, and realizes the stability of catalyst structure in the presence of oxygen-containing compounds and the improvement of catalytic stability.The catalyst prepared by the high-stability molecular sieve of the present application is applied to the hydroisomerization reaction of model compounds or fischer-tropsch synthesis wax oil, and the conditions are mild, conversion rate is high, isomer hydrocarbon proportion is high, catalyst stability is good, and tolerance degree to oxygen-containing compounds is high.

Description

Technical Field

[0001] This invention belongs to the field of catalyst technology, specifically relating to a highly stable molecular sieve and a n-alkane hydroisomerization catalyst prepared therefrom. Background Technology

[0002] my country's energy characteristics are "abundant in coal and scarce in oil". Therefore, producing oil products through coal gasification and Fischer-Tropsch synthesis to replace petrochemicals is of great strategic significance for alleviating the increasingly tense contradiction between energy supply and demand, sustainable development and social stability.

[0003] Fischer-Tropsch synthesis feedstocks can be derived from coal, natural gas, coalbed methane, and biomass, making them widely available. The products of Fischer-Tropsch synthesis contain extremely low levels of non-ideal components such as aromatics, sulfur, and nitrogen, making them excellent raw materials for high-quality diesel and lubricating oil bases. However, since most Fischer-Tropsch synthesis products are n-alkanes with high pour and freezing points and poor low-temperature fluidity, it is necessary to upgrade and modify them using hydroisomerization technology. Furthermore, the products contain a certain amount of oxygen-containing compounds such as alcohols, acids, aldehydes, and ketones, which can easily damage the catalyst structure and reduce catalytic performance during isomerization, placing higher demands on catalyst stability and tolerance to oxygen-containing compounds.

[0004] Hydroisomerization catalysts for n-alkanes are mostly bifunctional catalysts, with the supported metal component and acidic support providing the functions of addition / dehydrogenation and isomerization, respectively. One-dimensional ten-membered ring silica-alumina molecular sieves, in particular, possess the function of an acidic support and exhibit excellent pore shape selectivity, which can enhance the activity, selectivity, and stability of the isomerization catalyst. Therefore, silica-alumina molecular sieves such as ZSM-23, ZSM-22, ZSM-48, Nu-10, and Theta-1 have broad application prospects in the hydroisomerization reaction of n-alkanes. However, most silica-alumina molecular sieves cannot tolerate high concentrations of oxygen-containing compounds, exhibiting prominent problems such as silica-alumina migration, framework structure collapse, reduced catalytic performance, and catalyst deactivation during high-temperature, high-pressure isomerization reactions, hindering the development and application of this technology.

[0005] The report "The Effect of Ethanol on the Alkane Isomerization Performance of Pt / SAPO-11 and Pt / ZSM-22 Catalysts" suggests that ethanol has a significant impact on the isomerization performance of Pt / ZSM-22 catalysts. With increasing ethanol content, the activity and isomer selectivity of the catalyst gradually decrease, and the silicon-aluminum ZSM-22 molecular sieve has poor resistance to oxygen-containing compounds.

[0006] In the hydroisomerization of long-chain alkanes, oxygen-containing compounds tend to adsorb onto the uncoordinated, unsaturated silicon-aluminum structures in the molecular sieve framework. This leads to desilication and dealuminization of the molecular sieve framework during the reaction (≥280℃, ≥1.0MPa), resulting in framework collapse, decreased pore shape selectivity, and a rapid and significant reduction in catalytic activity, selectivity, and stability. The uncoordinated, unsaturated silicon and aluminum structures in the molecular sieve mostly exist as Lewis acid sites and cannot function effectively in the hydroisomerization of long-chain alkanes. The skeletal rearrangement at acidic sites is a key factor leading to low activity and low isomer yield of isomer catalysts.

[0007] In summary, the hydroisomerization of n-alkanes using efficient and stable catalysts is an important development direction for realizing the high-value application of Fischer-Tropsch synthesis technology and the preparation of clean fuels and chemicals. However, the tolerance of isomerization catalysts to oxygen-containing compounds is often overlooked, especially with the rapid development of biomass-to-oil technology, the influence of oxygen-containing compounds (alcohols, acids, aldehydes, and ketones, etc.) in oil products on hydroisomerization catalysts has become an increasingly critical issue. Therefore, it is necessary to employ easy-to-operate and highly reproducible techniques to repair the framework structure of one-dimensional ten-membered ring siliceous aluminosilicate molecular sieves, reduce uncoordinated saturated framework structures, and promote the transformation of Lewis acidic sites in the molecular sieve. The key issues that need to be addressed in isomerization catalysts are to enhance the hydrophobicity of the molecular sieve support by creating acidic sites, thereby increasing the activity and isomer yield of the isomerization catalyst, and improving its tolerance to oxygen-containing compounds under high temperature and high pressure reaction conditions. Summary of the Invention

[0008] The aim is to overcome the problems of low catalytic activity and isomer yield when molecular sieves are used in the hydroisomerization reaction of long-chain alkanes, and the molecular sieve structure is damaged and catalytic performance is reduced due to the influence of oxygen-containing compounds. The aim is to provide a highly stable molecular sieve and a catalyst for preparing n-alkanes hydroisomerization using it.

[0009] A method for preparing a highly stable molecular sieve includes the following steps:

[0010] (1) Mix the fluoride, organic amine and water evenly to prepare a mixed solution;

[0011] (2) Add one-dimensional ten-membered ring silica-alumina molecular sieve to the mixed solution, mix evenly under stirring speed of 50-800 rpm and temperature of 0-80℃, then pour into the reaction vessel, and react under temperature of 50-200℃ for 2-100 h.

[0012] (3) Separate solid and liquid again, wash thoroughly with water, dry at 60-150℃ for 3-24h, and calcine the dried sample in a muffle furnace at 300-600℃ for 2-6h.

[0013] Preferably, the mixing time in step (2) is 0.5 to 24 hours.

[0014] Preferably, the mass ratio of the one-dimensional ten-membered ring silica-alumina molecular sieve, fluoride, and organic amine is 1:0.025 to 1:0.5 to 10.

[0015] Preferably, the mass ratio of the total mass of fluoride and organic amine to water in the mixed solution prepared in step (1) is 0.5-10:5-50.

[0016] Preferably, the reaction in the reactor can be carried out under dynamic or static conditions.

[0017] According to the method of the present invention, preferably, the fluoride includes at least one selected from hydrogen fluoride, ammonium fluoride, ammonium hydrogen fluoride, tetrabutylammonium fluoride, tetrapropylammonium fluoride, tetraethylammonium fluoride, and tetramethylammonium fluoride.

[0018] According to the method of the present invention, preferably, the organic amine includes at least one selected from 1,6-hexanediamine, n-butylamine, triethylamine, cyclohexylamine, tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, tetrapentylammonium hydroxide, tetrahexylammonium hydroxide, dimethylethylenediamine, and ethylenediamine.

[0019] According to the method of the present invention, preferably, the one-dimensional mesoporous silica-alumina molecular sieve includes at least one of ZSM-23, ZSM-22, ZSM-48, Nu-10, and Theta-1 one-dimensional mesoporous silica-alumina molecular sieves. More preferably, the one-dimensional mesoporous silica-alumina molecular sieve can be potassium-type molecular sieve powder, sodium-type molecular sieve powder, ammonia-type molecular sieve powder, or hydrogen-type molecular sieve powder. Preferably, the silica-to-alumina ratio of the molecular sieve powder is 30 to 200.

[0020] According to the method of the present invention, preferably, the mass ratio of the one-dimensional mesoporous silica-alumina molecular sieve, fluoride and organic amine is 1:0.025 to 1:0.5 to 10, and the mass ratio of the total mass of fluoride and organic amine to water is 0.5 to 10:5 to 50.

[0021] According to the method of the present invention, preferably, the mixing process can be a single, double, or multiple mixing. The single mixing is to mix the aqueous solution of organic amine and fluoride and the molecular sieve powder all at once. The double mixing is to mix a certain proportion of the aqueous solution of organic amine and fluoride with the molecular sieve powder for a certain period of time, and then add the remaining aqueous solution of organic amine and fluoride to the suspension and mix thoroughly. The multiple mixing process is carried out in the same manner.

[0022] A second aspect of the present invention provides a highly stable molecular sieve obtained by the above-described preparation method.

[0023] A third aspect of the present invention provides a high-stability molecular sieve-based n-alkane hydroisomerization catalyst.

[0024] Preferably, the above-mentioned high-stability molecular sieve n-alkane hydroisomerization catalyst and active component are used in combination. More preferably, the active component is Pt, Pd and / or Ni; more preferably, the weight ratio of the high-stability molecular sieve n-alkane hydroisomerization catalyst to the active component is 100:(0.01-3), preferably 100:(0.2-0.6).

[0025] The fourth aspect of the present invention provides a method for preparing the above-mentioned n-alkane hydroisomer catalyst, comprising mixing a highly stable molecular sieve with a peptide solvent and an extrusion aid in a weight ratio of 1:(0.01-0.5):(0.01-0.4) and extruding the mixture into strips, drying it at 90-180°C for 4-48 h, and then calcining it at 300-750°C for 4-24 h.

[0026] Preferably, the adhesive solvent is one or more of nitric acid, citric acid, and tartaric acid.

[0027] Preferably, the extrusion aid is guar gum powder and / or graphite powder.

[0028] The fifth aspect of this invention provides the above-mentioned catalyst for the hydroisomerization reaction of model compounds or Fischer-Tropsch synthetic wax oils. In particular, it is used for the hydroisomerization reaction of a mixture of model compounds or Fischer-Tropsch synthetic wax oils with an oxygen-containing compound content of 0–20 wt.%. The oxygen-containing compound in the model compound is selected from alcohols, acids, aldehydes, and ketones with different carbon numbers, preferably alcohols, acids, aldehydes, and ketones with oxygen-containing functional groups located at the carbon chain ends. The proportion of the oxygen-containing compound is 0–20 wt.%, preferably 0–10 wt.%.

[0029] The Fischer-Tropsch synthetic wax oil feedstock is selected from Fischer-Tropsch synthetic wax, Fischer-Tropsch synthetic wax hydrocracking tail oil, or Fischer-Tropsch synthetic wax hydrorefining tail oil. The oxygen-containing compounds in the Fischer-Tropsch synthetic wax oil feedstock are selected from alcohols, acids, aldehydes, and ketones with more than 4 carbon atoms, preferably alcohols, acids, aldehydes, and ketones with oxygen-containing functional groups located at the carbon chain ends. The proportion of oxygen-containing compounds is 0–20 wt.%, preferably 0–10 wt.%.

[0030] Compared with existing technologies, this invention has the following advantages: One-dimensional ten-membered ring silica-alumina molecular sieves are commonly used in hydroisomerization reactions, providing a complete synthetic route. However, the molecular sieve framework typically contains uncoordinated saturated silicon and aluminum structures, resulting in significant problems such as low catalytic activity, low isomer yield, and poor tolerance to oxygen-containing compounds in the hydroisomerization reaction of n-alkanes. This invention employs post-processing techniques to repair the existing molecular sieve framework structure, increasing the crystallinity of the existing molecular sieve, reducing uncoordinated saturated structural sites, enhancing the hydrophobic properties of the molecular sieve support, improving the activity and isomer yield of the prepared isomer catalyst in the isomerization reaction of model compounds and Fischer-Tropsch synthetic wax oils, and achieving stability of the catalyst structure and improved catalytic stability in the presence of oxygen-containing compounds. The molecular sieve repair method provided by this invention is simple and has low production costs. The catalyst of this invention, when applied to the hydroisomerization reaction of Fischer-Tropsch synthetic oils, exhibits mild conditions, high conversion rate, high isomer hydrocarbon ratio, good catalyst stability, and high tolerance to oxygen-containing compounds. Attached Figure Description

[0031] Figure 1 These are transmission electron microscope images of Comparative Example 1 (left) and Example 1 (right);

[0032] Figure 2 The XRD patterns are those of the molecular sieves obtained in Examples 1, 2, 5, 6 and Comparative Example 1, and the XRD patterns of the molecular sieves obtained in Examples 3, 7, 8 and Comparative Examples 2 and 3.

[0033] Figure 3 Molecular sieves obtained in Example 2 and Comparative Example 1 29 Si MAS NMR spectrum and 27 Al MAS NMR spectrum;

[0034] Figure 4 These are the thermogravimetric analysis data of the samples from Example 2 and Comparative Example 1 after they were saturated with water.

[0035] Figure 5 This is a comparison of the isomerization reaction performance of the catalysts in Example 2 and Comparative Example 1 under different conditions;

[0036] Figure 6 The results are the stability test results of the catalyst obtained in Example 2 when the mixture of n-hexadecane and 1-butanol is used as raw material;

[0037] Figure 7 The results are the stability test results of the catalyst obtained in Example 2 when the mixture of n-hexadecane and 1-heptanol is used as raw material;

[0038] Figure 8 This is a schematic diagram of the repair process of the present invention. Detailed Implementation

[0039] To make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be described in further detail below with reference to the accompanying drawings, but the present invention is not limited thereto.

[0040] Example 1

[0041] A method for preparing a highly stable molecular sieve includes the following steps:

[0042] (1) Prepare an aqueous solution by mixing 420 g of tetraethylammonium hydroxide and 30 g of ammonium fluoride in 1000 g of water.

[0043] (2) 50 g of ZSM-22 molecular sieve (silicon-to-aluminum ratio of 100) was mixed with a aqueous solution of tetraethylammonium hydroxide and ammonium fluoride and stirred at 50 °C and 50 rpm for 2 h. The mixture was then transferred to a reaction vessel and statically reacted at 170 °C for 20 h. Afterward, the solid and liquid phases were separated by vacuum filtration, and the sample was thoroughly washed and dried at 60 °C for 24 h. The dried sample was then calcined in a muffle furnace at 550 °C for 4 h to obtain the repaired ZSM-22 molecular sieve, which was named Z1. The transmission electron microscope image and XRD pattern of sample Z1 are shown below. Figure 1 , Figure 2 As shown, the crystallinity and acidity results calculated from XRD data are listed in Table 1.

[0044] (3) The obtained Z1 molecular sieve was mixed with 1.45g aluminum sol and 1.8g oxalic acid and kneaded into shape. Then it was dried at 180℃ for 12h and calcined at 600℃ for 6h to obtain an acidic carrier.

[0045] (4) Weigh 1.45g of molybdenum nitrate, dissolve it in deionized water to form a solution, drop the solution onto an acidic support, dry it in an oven at 180℃ for 12h, and finally calcine it at 400℃ for 8h to obtain the catalyst precursor.

[0046] (5) Weigh 1.35g of indium nitrate and dissolve it in deionized water to form a solution. Add the solution dropwise to the catalyst precursor described in step (4), then dry it in an oven at 160°C for 18 hours, and finally calcine it at 400°C for 12 hours. The catalyst A1 is finally obtained.

[0047] Example 2

[0048] A method for preparing a highly stable molecular sieve includes the following steps:

[0049] (1) Prepare an aqueous solution of 1900g ammonium bifluoride and tetrabutylammonium hydroxide, wherein 20g of ammonium bifluoride and 380g of tetrabutylammonium hydroxide are added.

[0050] (2) 50 g of ZSM-22 molecular sieve (silicon-to-aluminum ratio 45) was mixed with 500 g of ammonium bifluoride and tetrabutylammonium hydroxide aqueous solution at 30 °C and 50 rpm for 0.5 h. Then, 600 g of ammonium bifluoride and tetrabutylammonium hydroxide aqueous solution was added, and the mixture was stirred at 40 °C and 100 rpm for 2 h. Next, 800 g of ammonium bifluoride and tetrabutylammonium hydroxide aqueous solution was added, and the mixture was stirred at 40 °C and 150 rpm for 12 h. Finally, the mixture was transferred to a reaction vessel and statically reacted at 150 °C for 24 h. After the reaction was complete, the sample was washed until the filtrate was neutral. The resulting sample was dried at 120 °C for 8 h, and then calcined in a muffle furnace at 500 °C for 3 h to obtain the repaired ZSM-22 molecular sieve, which was named Z2. The XRD pattern of sample Z2 is shown below. Figure 2 As shown, the crystallinity and acidity calculated from XRD data are listed in Table 1, and the NMR results of Z2 solid were examined. 29 Si MAS NMR spectrum and 27 AlMAS NMR spectrum as shown Figure 3 .

[0051] (3) The obtained Z2 molecular sieve was mixed with 23g silica sol and 2.5g tartaric acid and kneaded into shape. Then it was dried at 180℃ for 6h and calcined at 450℃ for 9h to obtain an acidic carrier.

[0052] (4) Weigh 1.56g of palladium nitrate, dissolve it in deionized water to form a solution, drop the solution onto an acidic support, dry it in an oven at 120℃ for 14h, and finally calcine it at 600℃ for 4h to obtain the catalyst precursor.

[0053] (5) Weigh 2.31g of cerium nitrate, dissolve it in deionized water to form a solution, add the solution dropwise to the catalyst precursor described in step (4), then dry it in an oven at 140℃ for 10h, and finally calcine it at 400℃ for 4h. The catalyst A2 is finally obtained.

[0054] Example 3

[0055] The catalyst was prepared according to the method described in Example 2, except that the molecular sieve used was ZSM-48, which was named Z3. The XRD pattern of sample Z3 is shown below. Figure 2 As shown, the crystallinity and acidity results calculated from its XRD data are listed in Table 1, and catalyst A3 was finally obtained.

[0056] Example 4

[0057] (1) Prepare an aqueous solution of 1500g ammonium bifluoride and tetrabutylammonium hydroxide, wherein 20g ammonium bifluoride and 380g tetrabutylammonium hydroxide are added.

[0058] (2) 50g of ZSM-22 molecular sieve (silicon-to-aluminum ratio 45) was mixed with 500g of ammonium bifluoride and tetrabutylammonium hydroxide aqueous solution at 0℃ and 200rpm for 2h. Then, 500g of ammonium bifluoride and tetrabutylammonium hydroxide aqueous solution was added, and the mixture was stirred at 50℃ and 200rpm for 3h. Next, 500g of ammonium bifluoride and tetrabutylammonium hydroxide aqueous solution was added, and the mixture was stirred at 80℃ and 50rpm for 2h. Finally, the mixture was transferred to a reaction vessel and statically reacted at 150℃ for 2h. After the reaction was complete, the sample was washed until the filtrate was neutral. The resulting sample was dried at 120℃ for 8h, and then calcined in a muffle furnace at 500℃ for 3h to obtain the repaired ZSM-22 molecular sieve, which was named Z4. The XRD pattern of sample Z4 is shown below. Figure 2 As shown, the crystallinity and acidity calculated from XRD data are listed in Table 1.

[0059] (3) The obtained Z2 molecular sieve was mixed with 24g silica sol and 2.5g tartaric acid and kneaded into shape. Then it was dried at 180℃ for 6h and calcined at 450℃ for 9h to obtain an acidic carrier.

[0060] (4) Weigh 1.56g of palladium nitrate, dissolve it in deionized water to form a solution, drop the solution onto an acidic support, dry it in an oven at 120℃ for 14h, and finally calcine it at 600℃ for 4h to obtain the catalyst precursor.

[0061] (5) Weigh 2.31g of cerium nitrate, dissolve it in deionized water to form a solution, add the solution dropwise to the catalyst precursor described in step (4), then dry it in an oven at 140℃ for 10h, and finally calcine it at 400℃ for 4h. The catalyst A4 is finally obtained.

[0062] Example 5

[0063] The catalyst was prepared according to the method described in Example 2, except that 280 g of 1,6-hexanediamine was used to replace tetrabutylammonium hydroxide in Example 2 for the repair of the molecular sieve. The resulting molecular sieve was named Z5, and the final catalyst A5 was obtained. The XRD pattern of the Z5 sample is shown below. Figure 2 As shown, the crystallinity and acidity results calculated from its XRD data are listed in Table 1.

[0064] Example 6

[0065] The catalyst was prepared according to the method described in Example 2, except that 17.57 g of tetramethylammonium fluoride was used to replace ammonium bifluoride in Example 2 for the remediation of the molecular sieve. The resulting molecular sieve was named Z6, and the final catalyst A6 was obtained. The XRD pattern of the Z6 sample is shown below. Figure 2 As shown, the crystallinity and acidity results calculated from its XRD data are listed in Table 1.

[0066] Example 7

[0067] (1) Mix 400g of dimethylethylenediamine and 50g of hydrogen fluoride in 1000g of water to form a mixed solution.

[0068] (2) 50 g of ZSM-48 molecular sieve (silicon-to-aluminum ratio of 150) was mixed with dimethylethylenediamine and hydrogen fluoride aqueous solution at 60 °C and 100 rpm for 2 h. The mixture was then transferred to a reaction vessel and dynamically reacted at 150 °C for 12 h. Afterward, the mixture was separated by vacuum filtration, thoroughly washed, and dried at 120 °C for 20 h. The dried sample was then calcined in a muffle furnace at 400 °C for 6 h to obtain the repaired molecular sieve Z7. The XRD pattern of the Z7 sample is shown below. Figure 2 As shown.

[0069] (3) The obtained Z7 molecular sieve was mixed with 4.6g tartaric acid and 15g graphite powder and kneaded into shape. Then it was dried at 180℃ for 12h and calcined at 600℃ for 6h to obtain an acidic carrier.

[0070] (4) Weigh 2.43 g of zinc nitrate, dissolve it in deionized water to form a solution, drop the solution onto an acidic support, dry it at 180 °C for 12 h, and finally calcine it at 400 °C for 8 h to obtain the catalyst precursor.

[0071] (5) Weigh 1.65g of palladium nitrate, dissolve it in deionized water to form a solution, add the solution dropwise into the catalyst precursor described in step (4), dry it in an oven at 160°C for 18h, and finally calcine it at 400°C for 12h to obtain catalyst A7.

[0072] Example 8

[0073] The catalyst was prepared according to the method described in Example 7, except that 280 g of 1,6-hexanediamine was used to replace the tetrabutylammonium hydroxide in Example 7 for the repair of the molecular sieve. This 280 g catalyst was named Z8, and the final catalyst A8 was obtained. The XRD pattern of the Z8 sample is shown below. Figure 2 As shown.

[0074] Comparative Example 1

[0075] A method for preparing a catalyst, comprising the following steps:

[0076] (1) The untreated ZSM-22 molecular sieve (silicon-to-aluminum ratio of 45) raw powder was named ZD1. ZD1 was mixed with 24g of silica sol and 2.5g of tartaric acid, kneaded into shape, dried at 180℃ for 6h, and calcined at 450℃ for 9h to obtain the acidic support. The XRD pattern of the ZD1 sample is shown below. Figure 2 As shown, the crystallinity and acidity results calculated from XRD data are listed in Table 1. Solid-state NMR analysis was also performed on sample ZD1.29 Si MAS NMR spectrum as shown Figure 3 , 27 Al MAS NMR spectrum as shown Figure 5 .

[0077] (2) Weigh 1.56g of palladium nitrate, dissolve it in deionized water to form a solution, drop the solution onto an acidic support, dry it in an oven at 180℃ for 12h, and finally calcine it at 400℃ for 8h to obtain the catalyst precursor.

[0078] (3) Weigh 1.35g of indium nitrate and dissolve it in deionized water to form a solution. Add the solution dropwise to the catalyst precursor described in step (4). Then dry it in an oven at 160°C for 18 hours and finally calcine it at 400°C for 12 hours. The catalyst D1 is finally obtained.

[0079] Comparative Example 2

[0080] (1) Dissolve 50g of hydrogen fluoride in 1000g of water.

[0081] (2) 50g of ZSM-48 (silicon-to-aluminum ratio of 50) was added to the solution and mixed thoroughly at 100rpm. The mixture was then added to a reaction vessel and reacted at 150℃ for 12h. Afterward, the mixture was separated by vacuum filtration, thoroughly washed, and dried at 120℃ for 20h. The dried sample was then calcined in a muffle furnace at 400℃ for 6h to obtain molecular sieve ZD2. The XRD pattern of the ZD2 sample is shown below. Figure 2 As shown.

[0082] (3) The obtained ZD2 molecular sieve was mixed with 4.6g tartaric acid and 15g graphite powder and kneaded into shape. Then it was dried at 180℃ for 12h and calcined at 600℃ for 6h to obtain an acidic carrier.

[0083] (4) Weigh 2.43g of zinc nitrate, dissolve it in deionized water to form a solution, drop the solution onto an acidic support, dry it at 180℃ for 12h, and finally calcine it at 400℃ for 8h to obtain the catalyst precursor.

[0084] (5) Weigh 1.65g of palladium nitrate, dissolve it in deionized water to form a solution, add the solution dropwise into the catalyst precursor described in step (4), dry it in an oven at 160°C for 18h, and finally calcine it at 400°C for 12h to obtain catalyst D2.

[0085] Comparative Example 3

[0086] (1) Dissolve 400g of dimethylethylenediamine in 1000g of water.

[0087] (2) 50g of ZSM-48 (silicon-to-aluminum ratio of 150) was added to the solution and mixed thoroughly at 100 rpm. The mixture was then added to a reaction vessel and reacted at 150℃ for 12 h. Afterward, the mixture was separated by vacuum filtration, thoroughly washed, and dried at 120℃ for 20 h. The dried sample was then calcined in a muffle furnace at 400℃ for 6 h to obtain molecular sieve ZD3. The XRD pattern of the ZD3 sample is shown below. Figure 2 As shown.

[0088] (3) The obtained ZD3 molecular sieve was mixed with 4.6g tartaric acid and 15g graphite powder and kneaded into shape. Then it was dried at 180℃ for 12h and calcined at 600℃ for 6h to obtain an acidic carrier.

[0089] (4) Weigh 2.43g of zinc nitrate, dissolve it in deionized water to form a solution, drop the solution onto an acidic support, dry it at 180℃ for 12h, and finally calcine it at 400℃ for 8h to obtain the catalyst precursor.

[0090] (5) Weigh 1.65g of palladium nitrate, dissolve it in deionized water to form a solution, add the solution dropwise into the catalyst precursor described in step (4), dry it in an oven at 160°C for 18h, and finally calcine it at 400°C for 12h to obtain catalyst D3.

[0091] Performance testing

[0092] 1. Catalytic reaction performance test

[0093] Using catalysts A1-A8 described in Examples 1-8 and catalysts D1-D3 of Comparative Examples 1-3, with n-hexadecane as raw material, in a fixed-bed reactor, under the following process conditions: reaction temperature 250-310°C, hydrogen partial pressure 3.0 MPa, and volume hourly space velocity 1.5 h⁻¹. -1 The hydroisomerization reaction was carried out at a hydrogen-to-oil volume ratio of 800, and the catalytic performance results are shown in Table 2. Figure 5 As shown.

[0094] Using catalysts A1-A8 described in Examples 1-8 and catalysts D1-D3 of Comparative Examples 1-3, a mixture of n-hexadecane and 1-butanol was used as raw material in a fixed-bed reactor under the following process conditions: reaction temperature 250–310 °C, hydrogen partial pressure 3.0 MPa, and volume hourly space velocity 1.5 h⁻¹. -1 The hydroisomerization reaction was carried out at a hydrogen-to-oil volume ratio of 800, and the catalytic performance results are shown in Table 2. Figure 5 As shown.

[0095] 2. Stability performance test

[0096] Two mL of catalysts A2 and D1 were packed into a fixed-bed reactor. A mixture of n-hexadecane and 1-butanol was used as feedstock, with 1-butanol comprising 5.5 wt.%. The process conditions were: reaction temperature 300 °C, hydrogen partial pressure 3.0 MPa, and volume hourly space velocity 1.5 h⁻¹. -1 A hydroisomerization reaction was carried out at a hydrogen-to-oil volume ratio of 700 and continued for 500 hours. Under these conditions, the catalyst stability test results are as follows: Figure 5 As shown.

[0097] Two mL of catalysts A2 and D1 were packed into a fixed-bed reactor. A mixture of n-hexadecane and 1-heptanol was used as feedstock, with 1-heptanol comprising 8.0 wt.%. The process conditions were: reaction temperature 305 °C, hydrogen partial pressure 2.0 MPa, and volume hourly space velocity 1.3 h⁻¹. -1 A hydroisomerization reaction was carried out at a hydrogen-to-oil volume ratio of 800 and continued for 500 hours. Under these conditions, the catalyst stability test results are as follows: Figure 7 As shown.

[0098] 3. Catalytic performance test when using Fischer-Tropsch refined wax and a mixture of Fischer-Tropsch refined wax and 1-heptanol as raw materials.

[0099] Using catalyst A2 as described in Example 2 and catalyst D1 as described in Comparative Example 1, refined wax from Fischer-Tropsch synthesis (distillation range: 350–450°C) was used as raw material in a fixed-bed reactor under the following process conditions: reaction temperature 330°C, hydrogen partial pressure 3.0 MPa, and volume hourly space velocity 1.5 h⁻¹. -1 The hydroisomerization reaction was carried out at a hydrogen-to-oil volume ratio of 800, and the catalytic performance results are shown in Table 3.

[0100] Using catalyst A2 as described in Example 2 and catalyst D1 as described in Comparative Example 1, a mixture of Fischer-Tropsch synthesis refined wax (distillation range: 350–450 °C) and 1-heptanol was used as raw material in a fixed-bed reactor under the following process conditions: reaction temperature 330 °C, hydrogen partial pressure 3.0 MPa, and volume hourly space velocity 1.5 h⁻¹. -1 The hydroisomerization reaction was carried out at a hydrogen-to-oil volume ratio of 800, and the catalytic performance results are shown in Table 3.

[0101] This invention proposes that during the repair process, uncoordinated and unsaturated Si and Al species (such as Si-OH) located at the crystal boundary of the silica-alumina molecular sieve are activated by the fluorides in the repair agent, detach from the framework structure, and combine with organic amines in the repair agent. They then migrate back into the molecular sieve structure, interacting with uncoordinated lattice defect sites in the framework to form a saturated four-coordinate structure. Finally, during high-temperature calcination, the organic amines decompose and are removed, forming a more fully coordinated molecular sieve framework structure. A schematic diagram of the repair process is provided using ZSM-23 molecular sieve (MTT topology) as an example. Figure 8 As shown.

[0102] Depend on Figure 1 It can be seen that, compared with the unrepaired Comparative Example 1 sample, the outer surface of the repaired Example 1 sample is flatter and there is no obvious uneven morphology. This indicates that some unsaturated coordination components are saturated through the repair reaction process under the action of the repair agent, and the molecular sieve structure is more complete.

[0103] Figure 2 The results show that after the repair treatment, the XRD diffraction peak positions of the samples in each embodiment did not shift significantly, but the diffraction peak intensities increased substantially, indicating that the repair process helps to make the molecular sieve phase structure more complete. The crystallinity data calculated from the XRD spectra are listed in Table 1. Obviously, compared with the unrepaired Comparative Example 1 sample, the XRD crystallinity of the samples in each embodiment is significantly improved.

[0104] Figure 3 This indicates that the sample after repair treatment... 29 In the Si MAS NMR spectrum, the chemical shifts in the range of -105 to -110 ppm represent uncoordinated saturated silicon species (such as Si-OH). Compared with the untreated Comparative Example 1 sample, the silicon spectrum of Example 2 shows a narrowing trend, and the NMR peaks of uncoordinated silicon species almost completely disappear, indicating that after the repair treatment, the uncoordinated Si in the aluminosilicate molecular sieve is transformed into a saturated four-coordinated structure. 27 In the Al MAS NMR spectrum, Comparative Example 1 without repair treatment has uncoordinated non-framework Al species at a chemical shift of 0. Example 2, which was obtained after repair treatment, has no uncoordinated non-framework Al, indicating that after repair treatment, the uncoordinated Al species in the silica-alumina molecular sieve are transformed into a coordinated four-coordinated structure through activation and repair processes by the repair agent.

[0105] Table 1 shows the acidity results of the molecular sieve samples before and after remediation. It can be seen that for ZSM-22 or ZSM-48 molecular sieves, the number of Lewis acid sites in the molecular sieve structure decreases after the remediation reaction, while... The increase in the number of acidic sites indicates that the remediation treatment transformed some Lewis acidic sites (mostly formed by unsaturated coordinated Si and Al species) into... Acidic sites (mostly saturated coordinated -Si-O-Al- structures).

[0106] Table 1 shows the crystallinity and acidity results of the molecular sieve samples obtained in each example and comparative example.

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[0109] Note: The crystallinity of the unrepaired ZSM-22 (ZD1) and unrepaired ZSM-48 molecular sieve powders was set to 100%. The samples from Comparative Example 1 and Example 2 were placed in an environment with 77% humidity to fully absorb water for 24 hours, and their water content was subsequently examined by thermogravimetric analysis (TGA). It is generally believed that mass loss below 200°C is attributed to the removal of adsorbed water from the molecular sieve material. Compared to Comparative Example 1, the water absorption of the sample from Example 2 was significantly lower, further demonstrating that the remediation treatment helps to promote a more regular molecular sieve structure, thereby improving its hydrophobicity. Therefore, in the hydroisomerization reaction, on the one hand, oxygen-containing compounds are less likely to adsorb onto the remediated molecular sieve support; on the other hand, the destructive effect of water formed by the hydrogenation of oxygen-containing compounds on the molecular sieve structure is significantly reduced. Therefore, the improved coordination saturation and hydrophobicity of the remediated molecular sieve framework structure are beneficial to the enhancement of the catalyst's hydroisomerization reaction activity, isomer yield, and stability.

[0110] Compared with untreated one-dimensional ten-membered ring silica-alumina molecular sieve catalysts, repairing the molecular sieve framework structure can significantly improve the catalytic activity and isomer yield in the hydroisomerization reaction of model compounds, see [reference needed]. Figure 5 And Table 2; When using Fischer-Tropsch refined wax as raw material, the pour point of the isomer product decreased significantly (-39℃), and the viscosity index was 143.6 centistokes, see Table 3; The repaired catalyst can withstand high concentrations of oxygen-containing compounds, and all indicators remained unchanged during the 500-hour stability test, with no obvious deactivation, see Table 3. Figure 6 , Figure 7 This laid the foundation for its industrial application.

[0111] Table 2 shows the catalytic reaction performance results of Examples 1-6 and Comparative Example 1 using n-hexadecane and a mixture of n-hexadecane and 1-butanol as raw materials.

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[0113] Table 3 shows the catalytic reaction performance results of Examples 1-6 and Comparative Example 1 using Fischer-Tropsch refined wax and a mixture of Fischer-Tropsch refined wax and 1-heptanol as raw materials.

[0114]

Claims

1. A method for preparing a highly stable molecular sieve, characterized by, Includes the following steps: (1) Mix the fluoride, organic amine and water evenly to prepare a mixed solution; (2) Add one-dimensional ten-membered ring silica-alumina molecular sieve to the mixed solution, mix evenly at a stirring speed of 50~800 rmp and a temperature of 0~80℃, then pour into a reaction vessel and react at a temperature of 50~200℃ for 2~100 h. (3) Separate solid and liquid again, wash thoroughly with water, dry at 60~150 ℃ for 3~24 h, and calcine the dried sample in a muffle furnace at 300~600 ℃ for 2~6 h; The mass ratio of the one-dimensional ten-membered ring silica-alumina molecular sieve, fluoride and organic amine is 1:0.025~1:0.5~10; the mass ratio of the total mass of fluoride and organic amine to water in the mixed solution prepared in step (1) is 0.5~10:5~50. The fluoride includes at least one of hydrogen fluoride, ammonium fluoride, ammonium hydrogen fluoride, tetrabutylammonium fluoride, tetrapropylammonium fluoride, tetraethylammonium fluoride, and tetramethylammonium fluoride. The organic amine includes at least one of 1,6-hexanediamine, n-butylamine, triethylamine, cyclohexylamine, tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, tetrapentylammonium hydroxide, tetrahexylammonium hydroxide, dimethylethylenediamine, and ethylenediamine.

2. The preparation method according to claim 1, characterized in that, The one-dimensional ten-membered ring silica-alumina molecular sieve includes at least one of ZSM-23, ZSM-22, ZSM-48, Nu-10, and Theta-1.

3. The highly stable molecular sieve obtained by the preparation method according to claim 1 or 2.

4. A catalyst for the hydroisomerization of n-alkanes, characterized in that, It includes the highly stable molecular sieve as described in claim 3.

5. The method for preparing the n-alkane hydroisomerization catalyst according to claim 4, characterized in that, The process involves mixing a highly stable molecular sieve with a binder and an extrusion aid in a weight ratio of 1:(0.01-0.5):(0.01-0.4), extruding the mixture into strips, drying it at 90-180℃ for 4-48 hours, and then calcining it at 300-750℃ for 4-24 hours.

6. The application of the n-alkane hydroisomerization catalyst according to claim 4, characterized in that, Used for hydroisomerization of model compounds or Fischer-Tropsch synthetic wax oils.

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