High-activity non-noble metal Ni-based hydroisomerization catalyst and application thereof
阅读说明：本技术 一种高活性的非贵金属Ni基加氢异构化催化剂及其应用 (High-activity non-noble metal Ni-based hydroisomerization catalyst and application thereof ) 是由 傅雯倩 张磊 唐天地 白雪瑞 卜俊峰 郭亮 于 2021-06-18 设计创作，主要内容包括：本发明属于长链烷烃加氢异构化领域,公开了一种高活性的非贵金属Ni基加氢异构化催化剂及其应用,本发明制备得结构缺陷的ZSM-22沸石,为了调变ZSM-22沸石载体的酸性,对SD-ZSM-22沸石载体进行铵交换处理,将沸石骨架中的K～(+)离子交换成H～(+),变为H型沸石,得到SD-HZSM-22沸石样品,将镍盐溶液浸渍在SD-HZSM-22载体上,室温静置后干燥、煅烧得催化剂前驱体。催化剂应用长链烷烃加氢异构化反应中,在Ni的负载量仅为1.0％时,反应温度280℃,操作压力2.0Mpa的条件下具有十分显著的加氢异构活性和异构体选择性,在非贵金属催化剂加氢异构化催化技术领域中取得巨大进步。(The invention belongs to the field of long-chain alkane hydroisomerization and discloses a high-activity non-noble metal Ni-based hydroisomerization catalyst and application thereof, ZSM-22 zeolite with a structural defect is prepared by the invention, in order to modulate the acidity of a ZSM-22 zeolite carrier, ammonium exchange treatment is carried out on the SD-ZSM-22 zeolite carrier, and K in a zeolite framework is subjected to ammonium exchange treatment + Ion exchange to H + Changing into H-type zeolite to obtain SD-HZSM-22 zeolite sample, and soaking nickel salt solution in SAnd (3) standing the D-HZSM-22 carrier at room temperature, drying and calcining to obtain the catalyst precursor. When the catalyst is applied to the hydroisomerization reaction of long-chain alkane, when the load of Ni is only 1.0 percent, the reaction temperature is 280 ℃, and the operation pressure is 2.0Mpa, the catalyst has very obvious hydroisomerization activity and isomer selectivity, and makes great progress in the technical field of the hydroisomerization catalysis of non-noble metal catalysts.)
1. A high activity non-noble metal Ni-based hydroisomerization catalyst, characterized by: firstly preparing ZSM-22 zeolite containing structural defects, then carrying out ammonium exchange treatment on an SD-ZSM-22 zeolite carrier to obtain H-type zeolite, marking as SD-HZSM-22, loading a nickel salt on the SD-HZSM-22 carrier, drying and calcining to obtain a catalyst precursor.
2. The high activity non-noble metal Ni-based hydroisomerization catalyst according to claim 1, characterized in that: the preparation method of the catalyst comprises the following steps:
(1) sequentially dissolving an aluminum source and a potassium source in deionized water, then adding a small molecular organic template agent to obtain a solution, stirring the solution, adding a silicon source to form silicon-aluminum gel, filling the silicon-aluminum gel into a kettle, and crystallizing at a low temperature to form initial gel; adding a high molecular polymer into the initial gel, uniformly stirring, loading into a kettle, crystallizing at high temperature, washing, and calcining at high temperature to obtain ZSM-22 zeolite containing structural defects, which is marked as SD-ZSM-22;
(2) carrying out ammonium exchange treatment on the SD-ZSM-22 zeolite carrier prepared in the step (1): mixing an SD-ZSM-22 zeolite sample with an ammonium chloride solution, performing high-temperature treatment, filtering, putting the filtered sample into a dilute nitric acid solution, stirring at room temperature, and then filtering, drying and roasting the sample to obtain an SD-HZSM-22 sample;
(3) dissolving inorganic salt containing nickel in distilled water, dipping the obtained solution on a SD-HZSM-22 carrier drop by drop, standing for more than 12 hours at room temperature, drying and calcining to obtain a catalyst precursor, and reducing and activating to obtain Ni/SD-HZSM-22.
3. The high activity non-noble metal Ni-based hydroisomerization catalyst according to claim 2, characterized in that: the concentration of the ammonium chloride solution in the step (2) is 1mol/L, and the solid-liquid ratio of the SD-ZSM-22 to the ammonium chloride solution is 1: 20.
4. the high activity non-noble metal Ni-based hydroisomerization catalyst according to claim 2, characterized in that: the high-temperature treatment in the step (2) is to treat the K in the zeolite framework at the temperature of 100 ℃ for 4 hours+Ion exchange to H+To form H-type zeolite; the roasting condition is 500 ℃ for 3 h.
5. The high activity non-noble metal Ni-based hydroisomerization catalyst according to claim 2, characterized in that: the inorganic salt containing nickel is nickel nitrate, nickel carbonate, nickel citrate or nickel chloride; the nickel salt impregnation solution is fed with Ni which is 0.63-10.2 wt.% of the mass of the SD-HZSM-22 sample calculated as NiO; the calcination temperature was 450 ℃.
6. The high activity non-noble metal Ni-based hydroisomerization catalyst according to claim 1, characterized in that: the loading of the Ni on the SD-HZSM-22 carrier is 1.0 wt%.
7. Use of a high activity non-noble metal Ni-based hydroisomerization catalyst according to any of claims 1 to 6, characterized in that: the Ni/SD-HZSM-22 is used as a catalyst in the hydroisomerization of long-chain alkane.
8. Use of a high activity non-noble metal Ni-based hydroisomerization catalyst according to claim 7, characterized in that: the catalyst precursor is added in H2Finishing reduction activation under the atmosphere, reducing the temperature to the reaction temperature after activation, introducing n-dodecane raw material liquid in a plunger pump continuous feeding mode, wherein the reaction conditions are as follows: the reaction temperature is 240 ℃ and 300 ℃, the reaction pressure is 2.0MPa, H2Volume ratio of oil/600: 1, weight hourly space velocity of 2.2h-1。
9. The use of a high activity non-noble metal Ni-based hydroisomerization catalyst according to claim 8, characterized in that: the reaction temperature was 280 ℃.
Technical Field
The invention belongs to the field of long-chain alkane hydroisomerization, and particularly relates to a method for preparing a non-noble metal Ni catalyst loaded by ZSM-22 zeolite serving as a carrier and a performance study on the hydroisomerization of long-chain alkanes such as n-dodecane.
Background
The bifunctional catalyst is widely used in the refining process of oil products, such as an acidic porous zeolite-supported Pd or Pt catalyst used in the oil product hydroisomerization process, wherein a noble metal Pd or Pt provides a metal center and plays a role in dehydrogenation-hydrogenation; the acidic porous zeolite is a source of acid centers and has the function of carbon chain skeleton isomerization. In addition, the catalyst plays an important role in the process of generating high-quality lubricating oil in one step through hydrodeoxygenation and skeletal isomerization in the renewable biomass molecular conversion. Due to the excellent dehydrogenation-hydrogenation properties of noble metals, such catalysts mostly provide metal centers with noble metals Pd or Pt. However, noble metal catalysts are mostly adopted in the industry at present, and the noble metal resources are limited and expensive, so that the production cost of the catalyst is extremely high, and the industrial application of the catalyst is limited. Therefore, the development of a non-noble metal isomerization catalyst having excellent performance has been a hot topic of research.
In recent years, researchers have made a lot of research work around the development of non-noble metal hydroisomerization catalysts, and mainly focus on the selection of active metals, the preparation method of the catalysts, porous zeolite materials with different topological structures, and the like. It was found that the metallic Ni catalyst has excellent catalytic performance compared to other transition metal catalysts such as Cu, Co, Mo or W. It is noted that Ni atoms have a lower polarizability than Pt, which is a noble metal, and form relatively weak van der waals force with the zeolite support, resulting in unstable activity and easy accumulation and deactivation of the Ni catalyst during the reaction. Although one uses a novel catalyst preparation method, such as ethanol co-solvent preparationPreparing a Ni catalyst, synthesizing the Ni-SAPO-11 catalyst by a one-pot method, and using a ZSM-5 nanosheet zeolite carrier, so that the interaction between Ni and the carrier is promoted to a certain extent, and the metal dispersion degree is improved; in order to solve the problem, in earlier work, P species is introduced in the preparation process of the Ni catalyst, and smaller Ni is formed through subsequent activation treatmentxPyParticles of prepared supported NixPyZSM-22 catalyst, but NixPyThe hydrogenation-dehydrogenation capability of the phase is low, high isomer yield (80%) can be obtained only by needing higher reaction temperature (330-; in addition, the ZSM-22 carrier has higher property requirement, and the surface of the zeolite carrier cannot have strong acid centers, otherwise, the over-cracking reaction is caused, and the yield of isomer products is greatly reduced. In fact, there is still a large gap between the hydroisomerization performance of non-noble metal catalysts and noble metal catalysts, and how to design and prepare high-performance Ni-based hydroisomerization catalysts that are comparable to noble metal Pt still faces a great challenge.
Disclosure of Invention
The invention provides a method for preparing a nickel-loaded catalyst by taking ZSM-22 zeolite with structural defects as a carrier and high-efficiency catalytic hydroisomerization performance on n-dodecane.
The purpose of the present invention is to develop a hydroisomerization catalyst that is less expensive and has superior performance than noble metal Pt catalysts.
The method comprises the following specific implementation steps:
(1) synthesis and post-treatment of ZSM-22 zeolite with structural defects: sequentially dissolving an aluminum source and a potassium source in deionized water, then adding a small molecular organic template agent to obtain a solution, stirring the solution, adding a silicon source to form silicon-aluminum gel, filling the silicon-aluminum gel into a kettle, and crystallizing at a low temperature to form initial gel; adding high molecular polymer into the initial gel, uniformly stirring, loading into a kettle, crystallizing at high temperature, washing, and calcining at high temperature to obtain ZSM-22 zeolite containing structural defects, which is marked as SD-ZSM-22, wherein the preparation method and conditions refer to CN 201810566615.9;
(2) for adjusting the acidity of the ZSM-22 zeolite support, the method of (1) aboveThe SD-ZSM-22 zeolite carrier is subjected to ammonium exchange treatment: putting a certain amount of nano ZSM-22 zeolite sample and 1mol/L ammonium chloride solution into a three-neck flask, wherein the solid-liquid mass ratio is 1: 20, in an oil bath at 100 ℃ for 4h, in order to remove K from the zeolite framework+Ion exchange to H+And changed to H-type zeolite, the filtered sample was stirred in dilute nitric acid solution at pH 3 at room temperature for 24H to remove a small amount of non-framework aluminum species present in the pores of the zeolite. Then the sample is filtered, dried at 100 ℃ overnight and roasted at 500 ℃ for 3h to obtain an SD-ZSM-22 zeolite sample which is recorded as SD-HZSM-22. By NH4 +Solution exchange is carried out to prepare H-type ZSM-22 zeolite, so that the surface of the zeolite contains a large amount of B acid centers;
(3) dissolving inorganic salt containing nickel (Ni) in distilled water, dropwise adding the obtained solution onto the SD-HZSM-22 carrier, standing at room temperature for more than 12 hours, drying at 100 ℃, and calcining at 450 ℃ to obtain a catalyst precursor; the impregnation solution is added with Ni which is calculated to be 0.63-10.2 wt.% of the mass of the SD-HZSM-22 sample in the form of NiO to obtain a catalyst precursor, and the Ni/SD-HZSM-22 catalyst is obtained after reduction and activation.
(4) Evaluation of catalyst Activity: and (4) tabletting and forming the catalyst precursor prepared in the step (3), sieving, taking 1.0g of 40-60-mesh catalyst sample, uniformly mixing the sample with 1.5g of 40-60-mesh quartz sand, and filling the mixture into a constant-temperature area of a fixed bed reactor. At H2The reduction activation of the catalyst precursor is completed under the atmosphere, which comprises the following steps: firstly, the catalyst precursor is heated to 120 ℃ from room temperature at the speed of 10 ℃/min and is kept for 1H, H2The flow rate is 150 mL/min; then raising the temperature to the target temperature (the temperature of Ni metal is 450 ℃) at 2 ℃/min and keeping the temperature for 3H, H2The flow rate was 150 mL/min. After the reaction temperature was lowered, the n-dodecane starting material solution was introduced by means of a continuous feed by means of a plunger pump. The reaction conditions are as follows: the reaction temperature is 240 ℃ and 300 ℃, the reaction pressure is 2.0MPa, H2Volume ratio of oil/600: 1, weight hourly space velocity of 2.2h-1。
The SD-ZSM-22 zeolite of the invention is synthesized by raw materials, such as silica sol solution as a silicon source, aluminum sulfate octadecahydrate as an aluminum source, alkaline potassium hydroxide as a potassium source, 1, 6-hexanediamine as a small molecular template agent and high molecular quaternary ammonium salt solution synthesized in a laboratory as a high molecular polymer, and the molecular weight of the solution is about 2 ten thousand.
The SD-ZSM-22 zeolite carrier prepared by the invention has a large number of structural defects on the surface, which is very important for preparing a highly dispersed Ni catalyst.
The invention needs to modulate the acidity of SD-ZSM-22, such as acid treatment, to improve the acid strength and acid content of zeolite, which is important for preparing high-performance hydroisomerization catalyst.
The Ni loading of the nickel catalyst prepared by using ZSM-22 as a carrier is not more than 2.0 wt%, otherwise, the excessive metal loading can cause NiO on the surface of zeolitexThe existence form of NiO is changed, part of NiOxThe presence of NiO phase is disadvantageous in terms of catalytic performance. Further preferably, the amount of Ni supported is 1.0 wt%.
The optimum reaction temperature for the catalyst of the invention is preferably 280 ℃ at which the catalyst exhibits the highest yield of dodecane isomer (81.1%).
The nickel salt is nickel nitrate, nickel carbonate, nickel citrate or nickel chloride and the like.
Compared with the prior art, the invention has the following excellent effects: (1) according to the invention, the surface skeleton structure defect of the prepared ZSM-22 carrier is utilized, so that the carrier and metal have relatively strong interaction, and the problem of Ni species agglomeration is avoided; (2) when the supported amount of Ni on the carrier is 1.0 wt% or less, NiO having more structural defects is formed on the surface of the catalystxThe species form a Ni particle active phase with good dispersity after reduction, the average particle size is about 2.2nm, and finally the prepared Ni catalyst has very obvious hydroisomerization activity and isomer selectivity, the reaction temperature only needs 280 ℃, and the method is a great progress of hydroisomerization catalytic technology innovation in terms of energy and catalyst cost saving.
Drawings
FIG. 1 shows the n-dodecane conversion and isomer yield as a function of Ni metal loading (reaction conditions: 280 ℃, 2.0MPa, weight hourly space velocity 2).2h-1，H2Volume ratio/oil 600).
FIG. 2 relationship between Ni/SD-HZSM-22#2 and Pt/HZSM-22 catalyst catalytic performance versus temperature; (a) n-dodecane conversion, (b) isododecane selection, (c) isododecane yield.
FIG. 3 stability evaluation of Ni/SD-ZSM-22#2 catalyst (reaction conditions: 280 ℃, 2.0MPa, weight hourly space velocity 2.2 h)-1，H2Volume ratio/oil 600).
Detailed Description
For further understanding of the objects, contents and advantages of the present invention, the following detailed description will be given of specific embodiments of the present invention, but the present invention is not limited to the examples described below, and may be freely combined depending on the actual situation.
Preparation of SD-HZSM-22 carrier:
(1)0.3gAl2(SO4)3·18H2dissolving O in 30mL of deionized water, adding 0.9g of KOH after fully dissolving to obtain a clear solution, slowly adding 2g of 1, 6-hexanediamine, stirring for 1 hour, then adding 10g of silica sol solution, and stirring for 1 hour to form silicon-aluminum gel (1.0 Al)2O3/15K2O/100SiO2/37HD/3800H2O), placing the gel in a kettle, crystallizing the gel for 6 hours at the temperature of 50 ℃, taking the kettle to obtain initial gel, and adding 2g of high molecular polymer(s) (in the amount of 2 g) into the initial gel under the stirring conditionMolecular weight was found to be about 2 ten thousand, but not limited thereto), stirring was continued for 4 hours, and the mixture was stirred in a kettle and statically crystallized at 160 ℃ for 48 hours. After washing, filtering and calcining for 15 hours at 500 ℃, a zeolite sample is obtained, and the nano ZSM-22 zeolite containing the mesoporous structure is obtained.
(2) Carrying out ammonium exchange treatment on the nano ZSM-22 zeolite carrier in the step (1): a nanometer ZSM-22 zeolite sample and 1mol/L ammonium chloride solution are filled into a three-neck flask, wherein the solid-liquid ratio is 1: 20, in an oil bath at 100 ℃ for 4h, in order to remove K from the zeolite framework+Ion exchange to H+Changing into H-type zeolite, and filteringThe product was stirred at room temperature in dilute nitric acid solution at pH 3 for 24h to remove a small amount of non-framework aluminum species present in the pores of the zeolite. Then the sample is filtered, dried at 100 ℃ overnight and roasted at 500 ℃ for 3h to obtain an SD-ZSM-22 zeolite sample which is recorded as SD-HZSM-22.
Example 1:
2.0g of SD-HZSM-22-De carrier, 0.0519g of Ni (NO)3)2·6H2Dissolving O in 3.0mL of distilled water, dropwise adding the dissolved O into 2g of SD-HZSM-22 powder after the dissolved O is completely dissolved, standing at room temperature for more than 12 hours, drying in a 100 ℃ oven for 12 hours, tabletting the prepared dried product under certain pressure, taking 40-60 meshes, and calcining in air at 450 ℃ for 3 hours to obtain a catalyst precursor; finally at H2Was reduced (at 450 ℃ C. for 3 hours) in the atmosphere of (2), and was identified as Ni/SD-ZSM-22#1 catalyst. Wherein the loading of Ni is 0.5 wt.% in mass percent.
Example 2:
2.0g of SD-HZSM-22-De carrier, 0.1038g of Ni (NO)3)2·6H2Dissolving O in 3.0mL of distilled water, dropwise adding the dissolved O into 2g of SD-HZSM-22 powder after the dissolved O is completely dissolved, standing at room temperature for more than 12 hours, drying in a 100 ℃ oven for 12 hours, tabletting the prepared dried product under certain pressure, taking 40-60 meshes, and calcining in air at 450 ℃ for 3 hours to obtain a catalyst precursor; finally at H2Was reduced (at 450 ℃ C. for 3 hours) in an atmosphere of (2), and was identified as Ni/SD-ZSM-22#2 catalyst. Wherein the loading of Ni is 1.0 wt.% in mass percent.
Example 3:
2.0g of SD-HZSM-22-De carrier, 0.4152g of Ni (NO)3)2·6H2Dissolving O in 3.0mL of distilled water, dropwise adding the dissolved O into 2g of SD-HZSM-22 powder after the dissolved O is completely dissolved, standing at room temperature for more than 12 hours, drying in a 100 ℃ oven for 12 hours, tabletting the prepared dried product under certain pressure, taking 40-60 meshes, and calcining in air at 450 ℃ for 3 hours to obtain a catalyst precursor; finally at H2Is reduced (at 450 ℃ for 3 hours) in an atmosphere marked Ni-SD-ZSM-22#3 catalyst. Wherein the loading of Ni was 4.0 wt.% in mass percent.
Example 4:
2.0g of SD-HZSM-22-De carrier, 0.8304g of Ni (NO)3)2·6H2Dissolving O in 3.0mL of distilled water, dropwise adding the dissolved O into 2g of SD-HZSM-22 powder after the dissolved O is completely dissolved, standing at room temperature for more than 12 hours, drying in a 100 ℃ oven for 12 hours, tabletting the prepared dried product under certain pressure, taking 40-60 meshes, and calcining in air at 450 ℃ for 3 hours to obtain a catalyst precursor; finally at H2Was reduced (at 450 ℃ C. for 3 hours) in an atmosphere of (2), and was identified as Ni/SD-ZSM-22#4 catalyst. Wherein the loading of Ni is 8.0 wt.% in mass percent.
For comparison with a noble metal Pt catalyst, ZSM-22 zeolite without structural defects is synthesized, the post-treatment steps are the same as those of SD-ZSM-22 zeolite, and the obtained H-type ZSM-22 zeolite is marked as HZSM-22. The method adopts an isometric impregnation method to prepare the noble metal Pt catalyst, and according to the report of related documents, the loading amount of Pt is determined to be 0.5 wt.%, and the specific steps are as follows:
example 5:
HZSM-22 support 2.0g, 0.0268g of H2PtCl6·6H2Dissolving O in 3.0mL of distilled water, dropwise adding the dissolved O into 2g of HZSM-22 powder after the O is completely dissolved, standing at room temperature for more than 12 hours, drying in an oven at 100 ℃ for 12 hours, tabletting the prepared dried product under certain pressure, taking 40-60 meshes, and calcining in air at 450 ℃ for 3 hours to obtain a catalyst precursor; finally at H2Reduced (at 400 ℃ C. for 3 hours) in an atmosphere of (C.), labeled as Pt/HZSM-22 catalyst.
Evaluation of catalyst Activity: the catalyst precursor prepared in the embodiment 1-5 is tableted, molded and sieved, 1.0g of 40-60 mesh catalyst sample is taken, and is uniformly mixed with 1.5g of 40-60 mesh quartz sand, and the mixture is loaded into a constant temperature area of a fixed bed reactor. At H2The reduction activation of the catalyst is completed under the atmosphere, which comprises the following steps: the catalyst precursor is first raised from room temperature to 120 deg.c at 10 deg.c/min and maintained for 1 hr, H2Flow rate 150mLMin; then raising the temperature to the target temperature (450 ℃) at the speed of 2 ℃/min and keeping the temperature for 3H, H2The flow rate was 150 mL/min. After the reaction temperature is reduced, the n-dodecane raw material liquid is introduced in a continuous feeding mode by a trace plunger pump. The reaction conditions are as follows: the reaction temperature is 240 ℃ and 300 ℃, the reaction pressure is 2.0MPa, H2Volume ratio of oil/600: 1, weight hourly space velocity of 2.2h-1。
Wherein, FIG. 1 shows the relationship between the conversion rate of n-dodecane and the yield of isomers as a function of the Ni metal loading; wherein the reaction conditions are as follows: 280 ℃, 2.0MPa and weight hourly space velocity of 2.2h-1，H2The volume ratio/oil was 600.
As can be seen from fig. 1, the conversion and isomerization selectivity of n-dodecane gradually increased with increasing Ni loading, and when Ni loading is 1.0 wt.%, the conversion and isomer yield are the best, 88.3% and 81.1%, and further increasing Ni loading results in no significant change in n-dodecane conversion, while the isomer yield is slightly decreased, mainly because Ni loading is higher, so that the hydrogenolysis reaction of the reaction molecules occurs and the product yield is reduced.
FIG. 2 shows the relationship between the catalytic performance and temperature of Ni/SD-HZSM-22#2 and Pt/HZSM-22 catalysts, with the n-dodecyl conversion and isomer yield increasing gradually between the two catalysts as the reaction temperature increases. However, for Ni/SD-HZSM-22#2, the conversion of n-dodecane and the isomer yield reached the best (81.1%) when the reaction temperature reached 280 ℃, above which the conversion remained essentially unchanged, while the higher reaction resulted in an increase in cracking activity, leading to a decrease in isomer yield. A similar phenomenon was observed on the Pt/HZSM-22 catalyst, but the highest isomer yield of 63.7% was obtained at a reaction temperature of 300 ℃. The catalytic performance of the catalyst is lower than that of a Ni/SD-HZSM-22#2 catalyst.
If the ZSM-22-De carrier used in the 201911361122.2 patent is adopted, part of the framework is dealuminized and collapsed after the acid modulation treatment, and the catalytic reaction is carried out under the same conditions after the same Ni is loaded, and the result shows that the catalytic performance of the ZSM-22-De carrier is poorer at 280 ℃, and the effect of the ZSM-22-De carrier can not be achieved.
FIG. 3 is a stability evaluation of Ni/SD-HZSM-22#2 catalyst(reaction conditions: 280 ℃, 2.0MPa, weight hourly space velocity of 2.2h-1，H2Volume ratio/oil 600).