CN109704362B - ZSM-48 molecular sieve and preparation method and application thereof - Google Patents
ZSM-48 molecular sieve and preparation method and application thereof Download PDFInfo
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Abstract
The invention relates to the field of molecular sieve materials, in particular to a ZSM-48 molecular sieve and a preparation method and application thereof. The molecular sieve has a silica/alumina molar ratio of 120-300; contains a mesoporous structure and has a closed hysteresis loop at a low-temperature nitrogen adsorption-desorption curve P/P0-0.4-0.99, and the starting position of the closed hysteresis loop is at a position P/P0-0.4-0.7. The catalyst formed by adopting the ZSM-48 molecular sieve as the solid acid has better isomeric pour point depressing capability, and the target product in the product has high yield and low pour point.
Description
Technical Field
The invention relates to the field of molecular sieve materials, in particular to a ZSM-48 molecular sieve and a preparation method and application thereof.
Background
The molecular sieve material has high acidity and high specific surface area, and is an excellent acidic catalyst. Meanwhile, the molecular sieve material has strong chemical stability and hydrothermal stability, and is difficult to be corroded and dissolved by reactants to be damaged. Compared with the commonly used homogeneous catalyst, the molecular sieve material catalyst can be directly recycled without separation, and simultaneously, the environmental pollution and the product pollution are avoided. The specific surface area and other pore structure parameters of the molecular sieve material have important influence on the catalytic performance of the molecular sieve, so that the preparation of the molecular sieve with special pores is an important research direction in the chemical field.
CN1350981A discloses a preparation method of high-silicon Beta zeolite, which mainly comprises the following steps: firstly, the crystallized Beta zeolite slurry is subjected to ammonium exchange, filtered, dried, roasted and demoulded, then is treated by using organic acid or inorganic acid, and finally is subjected to pressurized hydrothermal treatment to finally obtain the Beta zeolite with the silicon-aluminum ratio of 60-80.
CN1769169A discloses a method for synthesizing Beta zeolite with step pore canals, which mainly comprises the following steps: directly performing ammonium salt treatment on zeolite subjected to low-temperature nucleation and high-temperature crystallization, filtering and drying, performing three-section temperature-controlled roasting and demolding, performing acid treatment under a mild condition, and performing pressurized hydrothermal treatment, wherein the silicon-aluminum ratio of the obtained Beta zeolite reaches 80-120, and the Beta zeolite has three pore size distributions of 0.1-1.7nm, 1.7-6nm and 10-90nm, so that the surface utilization rate of the Beta zeolite is greatly improved, but the micropore volume of the obtained sample is not large enough, and the contribution of the pore volume mainly comes from mesopores and macropores (the total volume of the mesopores and the macropores accounts for more than 67 percent of the total pore volume).
CN104353484A discloses a preparation method of a low-cost strong-acid hierarchical pore Beta zeolite, relates to a preparation method of a hierarchical pore Beta zeolite, and aims to solve the problem of acidity weakening of an existing desiliconized post-treatment hierarchical pore Beta zeolite molecular sieve. The method comprises the following steps: firstly, calcining Beta zeolite to obtain microporous hydrogen type Beta zeolite; adding the microporous hydrogen type Beta zeolite into an alkaline solution, stirring, washing and drying to obtain sodium type desiliconized hierarchical porous Beta zeolite; adding the sodium desiliconized hierarchical pore Beta zeolite into an ammonium nitrate aqueous solution for exchange, and calcining to obtain hydrogen desiliconized hierarchical pore Beta zeolite; fourthly, adding the hydrogen-type desiliconized hierarchical pore Beta zeolite into an acid solution, stirring, washing, drying, and then repeating the third step to obtain the strong acid hierarchical pore Beta zeolite.
CN103964458A discloses a Beta zeolite with high silica-alumina ratio hierarchical pore canals and a preparation method thereof. The Beta zeolite has pore diameter distribution of pore channels below 2nm, 5-11nm and above 50nm, wherein the micropore volume is 0.19cm3More than one gram, and the total volume of the mesopores and the macropores is 0.35cm3More than g, the silicon-aluminum ratio is more than 90, and the specific surface area is 400m2More than g. The preparation method comprises the following steps: carrying out first acid treatment on raw material Beta zeolite; roasting the Beta zeolite subjected to the first acid treatment for the first time; and carrying out second acid treatment on the Beta zeolite subjected to the first roasting to obtain the Beta zeolite with the high silica-alumina ratio and the multilevel pore channels. The preparation method of the patent application is simple and efficient to operate, and the prepared Beta zeolite with high silica-alumina ratio and hierarchical pore channels has strong acid, thermal and hydrothermal stability and good diffusion performance.
CN102602958A discloses a method for preparing mesoporous mordenite molecular sieves. The method comprises the following steps: dissolving an aluminum source in a sodium hydroxide solution, adding a silicon source, strongly stirring and dispersing at room temperature for a period of time, mixing the uniformly dispersed silicon source and aluminum source solution at room temperature to prepare a glue, adding a dealuminized mordenite molecular sieve as a seed crystal, strongly stirring and uniformly mixing at room temperature, transferring to a reaction crystallization kettle, carrying out crystallization reaction at 150-170 ℃ for 0.5-3 days, and carrying out conventional suction filtration, washing and drying to obtain a solid product. However, although the mesoporous mordenite molecular sieve prepared by the method contains accumulated mesopores, the technical point shows that the mesoporous mordenite molecular sieve is not a real mesopore but a secondary pore formed by accumulating the particles of the molecular sieve, so that certain catalytic performance is not substantially improved and improved, and the mesopores have low stability and can collapse quickly after hydrothermal treatment.
CN103073020A discloses a hierarchical pore zeolite molecular sieve and a preparation method and application thereof. The preparation method specifically comprises the following steps: the method for preparing the hierarchical zeolite molecular sieve by assembling silanized zeolite seed crystals under hydrothermal conditions by using a cationic surfactant as a template. The method overcomes the problem that the multistage pore zeolite cannot be prepared due to the mismatching between the conventional cationic surfactant and the zeolite template. The prepared material realizes the composition of micropores and mesopores, and is a highly crystallized multi-level pore channel zeolite molecular sieve. However, in this method, substantially, organosilane is grafted to a seed crystal by a specific functional group reaction, and the resulting product is combined with a cationic surfactant to prepare a mesoporous molecular sieve, wherein mesopores are formed by the guidance of the cationic surfactant, and mesopores having a pore diameter of about 2.4nm are formed by the hard template action of the organosilane. The seed crystal selected in the invention is microporous molecular sieve, which is added into a preparation system after silanization, the hydrophobic property of the seed crystal is utilized to increase the effect of the seed crystal on the hydrophobic end of a surfactant micelle so as to reduce the interaction between two guiding agents, but the formed mesopores still do not have a regular structure, and whether the addition of the seed crystal reduces the dosage of a template agent is not reported.
CN104891526A discloses a preparation method of a mesoporous molecular sieve with high hydrothermal stability. The method comprises the following steps: (1) preparing a first Y-type molecular sieve precursor: (2) and (3) crystallization: adding seed crystals into a first Y-type molecular sieve precursor, adjusting the pH value to 0.5-5, stirring at 20-50 ℃ for 10-24 h, aging at 20-50 ℃ for 2-24 h to obtain an assembled product, transferring the assembled product into a microreactor with a polytetrafluoroethylene lining, transferring the assembled product and the reactor into an autoclave, crystallizing at 100-200 ℃ for 10-48 h, filtering, washing and drying to obtain the high-stability mesoporous molecular sieve. Firstly, a precursor of the microporous molecular sieve is prepared, the mesoporous-microporous molecular sieve is used for preparing the mesoporous molecular sieve as a seed crystal, two methods of molecular sieve precursor assembly and seed crystal are combined, and the mesoporous molecular sieve with high stability is obtained under the condition of not using an organic template agent. Not only greatly reduces the preparation cost of the molecular sieve, but also saves the process of calcining the template agent and reduces the energy consumption.
CN1683245C discloses a rare earth-containing high-silicon Y-type zeolite and a preparation method thereof. The zeolite contains rare earth, and has a Si/Al ratio of 5-30, an initial unit cell constant of 2.430-2.465nm, and a ratio of the equilibrium unit cell constant to the initial unit cell constant of at least 0.985. The preparation method of the zeolite comprises the step of contacting the rare earth-containing Y-type zeolite with silicon tetrachloride, wherein the contact is carried out in a reaction device, the device comprises a reaction kettle, a feed inlet and a gas outlet, the reaction kettle also comprises a stirrer inside, the gas outlet is provided with a gas-solid separator, the hole diameter and the porosity of a hole contained in the gas-solid separator ensure that gas can pass through but zeolite solid particles can not pass through, a stirring rod of the stirrer extends out of the reaction kettle, the rare earth-containing Y-type zeolite is contacted with the carbon tetrachloride gas under the stirring of the stirrer, the contact temperature is 100-500 ℃, the contact time is 5 minutes to 10 hours, and the weight ratio of the rare earth-containing Y-type zeolite to the carbon tetrachloride is 1: 0.05-0.5, the Si/Al ratio of the rare earth-containing Y-type zeolite is 3-8, and the unit cell constant is 2.45-2.48 nm. The method ensures that the silicon tetrachloride gas and the molecular sieve solid particles are in contact reaction more uniformly, avoids the phenomenon that the molecular sieve solid particles are agglomerated into compact blocks, can reduce the labor intensity, can reduce the environmental pollution, obviously reduces the production cost, and is easy to carry out large-scale industrial application.
CN102050459A discloses a method for preparing a high-silicon molecular sieve, wherein the method comprises flowing the molecular sieve with an inert carrier gas under the carrying of the inert carrier gas flow, and mixing with gas-phase SiCl4Contacting molecular sieve with gas-phase SiCl in a flowing state4The contact time of (a) is from 10 seconds to 100 minutes. The method for preparing the high-silicon molecular sieve can realize the molecular sieve and SiCl4The contact reaction of (2) is continuously carried out, and the molecular sieve and SiCl can be controlled by controlling the flow rate of the carrier gas and the length of the tubular reactor4The time of contact, thereby enabling the molecular sieve to be contacted with SiCl4The contact reaction of (2) is sufficiently carried out in the tubular reactor.
CN1565969A discloses a TON type molecular sieve and a preparation method thereof. The inventive TON type molecular sieve SiO2/Al2O3The molar ratio is 30-300, and the main characteristic peak intensity and position of an XRD result are different from those of the existing TON type molecular sieve. In the synthesis process of the molecular sieve, diamine compounds and nitrogen-containing heterocyclic compounds are used as double templates, and the TON type molecular sieve is obtained through full crystallization reaction.
Disclosure of Invention
The invention aims to provide a high-silicon mesoporous-containing ZSM-48 molecular sieve and a preparation method and application thereof, and a catalyst formed by using the molecular sieve as a solid acid has better isomeric pour point depressing capability, higher target product yield and lower product pour point.
The invention provides a ZSM-48 molecular sieve, wherein the molar ratio of silicon oxide to aluminum oxide of the molecular sieve is 120-300; contains a mesoporous structure and has a closed hysteresis loop at a low-temperature nitrogen adsorption-desorption curve P/P0-0.4-0.99, and the starting position of the closed hysteresis loop is at a position P/P0-0.4-0.7.
The invention also provides a method for preparing the ZSM-48 molecular sieve, which comprises the following steps:
(1) filtering the crystallized mother liquor to form a filter cake with the dry basis content of 5-30%;
(2) directly roasting the filter cake to obtain a molecular sieve precursor;
(3) subjecting the molecular sieve precursor to a hydrothermal treatment;
(4) and filtering, washing and drying the hydrothermal treatment product.
The invention also provides application of the ZSM-48 molecular sieve as a solid acid.
The inventor of the invention has found through a great deal of research that the ZSM-48 molecular sieve with special physicochemical properties can be prepared by properly chemically treating the crystallized mother liquor in the preparation process of the molecular sieve, and specifically, the ZSM-48 molecular sieve has a high silica-alumina ratio and contains a mesoporous structure, the molecular sieve precursor is rich in penta-coordinated aluminum, and the molecular sieve finished product contains little penta-coordinated aluminum and even does not basically contain penta-coordinated aluminum.
In the practical application process, the catalyst formed by using the ZSM-48 molecular sieve as the solid acid has better isomerization pour point depressing capability, and the target product in the product has high yield and low pour point.
Detailed Description
The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value, and such ranges or values should be understood to encompass values close to those ranges or values. For ranges of values, between the endpoints of each of the ranges and the individual points, and between the individual points may be combined with each other to give one or more new ranges of values, and these ranges of values should be considered as specifically disclosed herein.
The ZSM-48 molecular sieve has the characteristic of high silicon. ZSM-48 molecular sieves prepared according to methods conventional in the art typically have a silica to alumina molar ratio of less than 100. The ZSM-48 molecular sieve of the present invention has a silica/alumina molar ratio of 120 to 300, and specifically may have any value in a range of, for example, 120, 130, 140, 150, 160, 170, 180, 190, 200, 210, 220, 230, 240, 250, 260, 270, 280, 290, 300, or any two of these values. Preferably, the ZSM-48 molecular sieve has a silica/alumina molar ratio of 150-200.
The ZSM-48 molecular sieve disclosed by the invention contains a mesoporous structure. ZSM-48 molecular sieves prepared according to conventional methods in the art are typically microporous molecular sieves, not containing a mesoporous structure. On the low temperature nitrogen adsorption-desorption curve of the ZSM-48 molecular sieve of the present invention, a closed hysteresis loop appears in the adsorption branch and the desorption branch at P/P0 ═ 0.4-0.99, and the start position of the closed hysteresis loop is at P/P0 ═ 0.4-0.7, whereas the ZSM-48 molecular sieve prepared in the prior art does not have this feature, i.e., no hysteresis loop or the start position of the hysteresis loop appears at higher partial pressure in this interval (usually at P/P0> 0.7). Preferably, the start position of the closed hysteresis loop is at P/P0-0.4-0.6.
The ZSM-48 molecular sieve is characterized by a nitrogen adsorption BET (Brunner-Emmet-Teller) method, and the mesoporous area in the molecular sieve can be 50m2/g～250m2The specific surface area of the molecular sieve can be 150m2/g～400m2The proportion of the mesoporous area to the specific surface area may be 20% to 70%, preferably 25% to 65%.
The precursor of the ZSM-48 molecular sieve of the invention is rich in penta-coordinated aluminum, and the finished molecular sieve has little or even no penta-coordinated aluminum. Specifically, the content of penta-coordinated aluminum in the precursor of the ZSM-48 molecular sieve is 4 to 30 wt%, preferably 10 to 30 wt%; and the content of penta-coordinated aluminum in the finished molecular sieve is 3 wt% or less, preferably 2 wt% or less, more preferably 1 wt% or less, and most preferably no penta-coordinated aluminum is contained.
The invention also provides a preparation method of the ZSM-48 molecular sieve. Generally, the preparation of the aluminum-containing molecular sieve can be divided into steps of colloid formation, crystallization, post-treatment and the like. In order to obtain the ZSM-48 molecular sieve, the post-treatment step in the synthesis process of the aluminum-containing molecular sieve needs to be specially treated, and the specific steps are as follows:
(1) filtering the crystallized mother liquor to form a filter cake with the dry basis content of 5-30 wt%;
(2) directly roasting the filter cake to obtain a molecular sieve precursor;
(3) subjecting the molecular sieve precursor to a hydrothermal treatment;
(4) and filtering, washing and drying the hydrothermal treatment product.
In the step (1), the mother liquor after crystallization is filtered for the purpose of removing the synthesis mother liquor. The invention is particularly limited with respect to the dry content of the filter cake formed by filtration. Specifically, the dry content of the filter cake is 5-30%, preferably 6-15%. When the dry basis content in the filter cake is out of the above range, the physicochemical properties of the prepared molecular sieve are out of the range defined by the present invention. In the present invention, "dry basis" is defined as: the mass percentage of the material after roasting at 600 ℃ for 4 hours to the mass of the material before roasting.
In the step (2), the filter cake formed in the step (1) is directly roasted at a high temperature without being dried. In the present invention, the temperature of the calcination may be 400-600 ℃, preferably 450-550 ℃. The heating rate during the calcination may be 10 to 100 ℃/min, preferably 20 to 50 ℃/min. The calcination time may be 1 to 12 hours, preferably 2 to 6 hours. The roasting environment can be a natural environment, namely oxygen-containing gas is not required to be specially introduced during roasting. Because the baking is carried out even under the natural environmentAnd (3) burning, wherein water in the filter cake can oxidize the template agent and can react with aluminum in the molecular sieve to form non-framework aluminum. In particular, the product treated by step (2) in the present invention (i.e., the molecular sieve precursor) contains a significant amount of penta-coordinated non-framework aluminum (i.e., penta-coordinated aluminum). Penta-coordinated non-framework aluminum is defined as27And a peak with chemical shift Be of 15-40 ppm in an Al NMR spectrum.27Al NMR spectroscopic measurement conditions can be found in publications such as Guoling Zhao et Al, Applied Catalysis A: General 299(2006) 167-.
In the present invention, the amount of penta-coordinated aluminum in the product treated in step (2), i.e., the molecular sieve precursor, is 4 to 30% by weight, preferably 10 to 30% by weight.
In the step (2), the sample after the roasting treatment can be naturally cooled, and the target temperature is preferably room temperature.
In step (3), the medium for the hydrothermal treatment is preferably acidic water. In the present invention, the acidic water means containing H+H of (A) to (B)2And (4) O solution. Wherein H2O is a conventional process to obtain a liquid material called "water". H+Is the ion released by the dissociation of organic acid and/or inorganic acid. To obtain the acidic water, at least one of hydrochloric acid, sulfuric acid, phosphoric acid, nitric acid, citric acid, acetic acid, maleic acid, oxalic acid, nitrilotriacetic acid, 1, 2-cyclohexanediaminetetraacetic acid, citric acid, tartaric acid and malic acid, preferably hydrochloric acid and/or citric acid, may be added to the "water". The content of the inorganic acid and/or the organic acid in the acidic water may be 0.1 to 5M, preferably 0.2 to 2M.
In step (3), the liquid-solid volume ratio of the hydrothermal treatment may be 5 to 200, preferably 20 to 100.
In the step (3), the temperature of the hydrothermal treatment may be 100 to 300 ℃, preferably 100 to 200 ℃.
In the step (3), the hydrothermal treatment may be performed for a time of 0.5 to 24 hours, preferably 1 to 12 hours, and more preferably 1 to 4 hours.
In step (3), the hydrothermal treatment is preferably carried out in a closed vessel, and the pressure of the hydrothermal treatment is preferably the autogenous pressure of the closed vessel under hydrothermal conditions.
In the step (4), the molecular sieve is required to be filtered and washed after being treated in the step (3). Among them, the filtration method may be a method known to those skilled in the art. The washing process can be water washing with deionized water, and the water washing is finished until the pH value of the filtrate is 6-8, preferably 6-7. The pH measurement of the solution may be performed using pH paper or a pH meter, and the measurement method is well known to those skilled in the art.
In the step (4), the drying treatment of the molecular sieve is not particularly limited, and may be carried out, for example, by drying at 120 ℃ for 6 hours in accordance with a conventional method.
In the process according to the invention, the mother liquor after crystallization can be prepared according to methods conventional in the art, for example, in US patent application US 5961951. In one embodiment, the process for preparing the crystallized mother liquor comprises: preparing silicon-containing solution, aluminum-containing solution and alkaline liquid, mixing the above-mentioned liquids, making colloid, then making crystallization at a certain temperature.
The invention also provides application of the ZSM-48 molecular sieve as a solid acid. The catalyst formed by adopting the ZSM-48 molecular sieve as the solid acid has better isomeric pour point depressing capability, and the target product in the product has high yield and low pour point.
The present invention will be described in detail with reference to examples, but the scope of the present invention is not limited thereto.
In the following examples and comparative examples, the content of each element in the measurement sample was analyzed and measured by a 3271E type X-ray fluorescence spectrometer commercially available from Nippon chemical and electric machines industries, and the sample was baked at 600 ℃ for 3 hours before the measurement.
In the following examples and comparative examples, the specific surface area and the external surface area of the sample were measured by using an automatic adsorption apparatus model DIGISORB 2500 of Micromeritics, USA, and the sample was baked at 600 ℃ for 3 hours before the test, and the measurement method was performed according to the ASTM D4222-98 standard method.
In the following examples and comparative examples, dry basis means the percentage of the weight of the product obtained after calcination of a certain amount of material in a muffle furnace at 600 ℃ for 4 hours in an air atmosphere, to the weight of the material before calcination. I.e. dry basis (weight of product obtained after calcination ÷ weight of material before calcination) × 100%.
Example 1
(1) Preparation of crystallized mother liquor
45 g of white carbon black and 1.25 g of analytically pure Al are taken2(SO4)3·18H2O, 1.88 g of analytically pure NaOH and 39.3 g of hexamethylenediamine are used. Mixing hexanediamine, white carbon black and 200 g of deionized water, and adding NaOH and Al2(SO4)3·18H2O and 272 g of deionized water, then mixing the two solutions, stirring for 1h, transferring the mixture into a reaction kettle, and crystallizing the mixture for 72 hours at 160 ℃.
(2) Preparation of the Filter cake
And (2) filtering the crystallized mother liquor prepared in the step (1), and continuing to pump and filter for 5 minutes when no filtrate exists on a filter cake to obtain a filter cake F-1, wherein the dry content of the filter cake F-1 is 11.2%, and the molar ratio of silicon oxide to aluminum oxide is 30.2.
(3) Preparation of molecular Sieve precursors
The filter cake F-1 was warmed from room temperature to 450 ℃ at a temperature rise rate of 25 ℃ per minute and held at that temperature for 4 hours. And in the temperature rising process, the roasting furnace is a closed roasting furnace, and the molecular sieve precursor C-1 is obtained.
(4) Preparation of molecular sieve finished product
Putting the molecular sieve precursor C-1 into a HCl solution with the concentration of 1M for closed hydrothermal treatment. Wherein the liquid-solid ratio is 50, the temperature of the hydrothermal treatment is 180 ℃, the time of the hydrothermal treatment is 3 hours, after the hydrothermal treatment is finished, the product is filtered and washed until the pH value of the filtrate is 7, and after drying for 4 hours at 120 ℃, the product is roasted for 4 hours at 550 ℃, and the finished product H-1 of the ZSM-48 molecular sieve is obtained.
The ZSM-48 molecular sieve of the invention has a closed hysteresis loop at the low-temperature nitrogen adsorption-desorption curve P/P0-0.4-0.99, and the initial position of the closed hysteresis loop is at the position P/P0-0.4-0.5.
Comparative example 1
A ZSM-48 molecular sieve was prepared according to the method of example 1, except that in step (2), filtration was continued for 50 minutes with no filtrate on the filter cake to obtain a filter cake DF-1, the dry content of which filter cake DF-1 was 46.5%. To prepare a finished product DH-1 of the ZSM-48 molecular sieve.
Example 2
A ZSM-48 molecular sieve was prepared according to the method of example 1, except that, in the step (3), the filter cake F-1 was raised from room temperature to 350 ℃ at a temperature raising rate of 5 ℃/min and then kept at the same temperature for 14 hours. And in the temperature rising process, the roasting furnace is a closed roasting furnace, and the molecular sieve precursor C-2 is obtained. And obtaining a finished product H-2 of the ZSM-48 molecular sieve.
Example 3
A ZSM-48 molecular sieve was prepared according to the method of example 1, except that, in the step (3), the filter cake F-1 was raised from room temperature to 850 ℃ at a temperature raising rate of 15 ℃/min and kept at the same temperature for 4 hours. And introducing air in the temperature rising process, wherein the air flow rate is 1.0 liter/minute, and obtaining the molecular sieve precursor C-3. And obtaining a finished product H-3 of the ZSM-48 molecular sieve.
Example 4
A ZSM-48 molecular sieve was prepared according to the method of example 1, except that in step (4), the molecular sieve precursor C-1 was put into a citric acid solution having a concentration of 1.0M to perform a closed hydrothermal treatment. Wherein the liquid-solid ratio is 100, the temperature of the hydrothermal treatment is 180 ℃, the time of the hydrothermal treatment is 2 hours, after the hydrothermal treatment is finished, the product is filtered and washed by water until the pH value of the filtrate is 7, and after the filtrate is dried at 120 ℃ for 4 hours, the product is roasted at 550 ℃ for 4 hours to obtain the finished product H-4 of the ZSM-48 molecular sieve.
Example 5
A ZSM-48 molecular sieve was prepared according to the method of example 1, except that in step (4), the molecular sieve precursor C-1 was put into a citric acid solution having a concentration of 0.05M to be subjected to closed hydrothermal treatment. Wherein the liquid-solid ratio is 10, the temperature of the hydrothermal treatment is 90 ℃, the time of the hydrothermal treatment is 0.1 hour, after the hydrothermal treatment is finished, the product is filtered and washed until the pH value of the filtrate is 7, and after drying for 4 hours at 120 ℃, the product is roasted for 4 hours at 550 ℃ to obtain the finished product H-5 of the ZSM-48 molecular sieve.
Example 6
A ZSM-48 molecular sieve was prepared according to the method of example 1, except that in step (4), molecular sieve precursor C-1 was put into a hydrochloric acid solution having a concentration of 1M to be subjected to closed hydrothermal treatment. Wherein the liquid-solid ratio is 50, the temperature of the hydrothermal treatment is 180 ℃, the time of the hydrothermal treatment is 3 hours, after the hydrothermal treatment is finished, the product is filtered and washed by water until the pH value of the filtrate is 4, and after the filtrate is dried at 120 ℃ for 4 hours, the product is roasted at 550 ℃ for 4 hours to obtain the finished product H-6 of the ZSM-48 molecular sieve.
Comparative example 2
A mother liquor after crystallization was prepared according to procedure (1) in example 1, followed by filtration, and the filter cake obtained after filtration was dried at 120 ℃ for 4 hours and then calcined at 550 ℃ for 4 hours, to obtain molecular sieve precursor DC-2. And (2) carrying out ammonium exchange treatment on the molecular sieve precursor DC-2 and 10 times of volume of 0.5M hydrochloric acid solution at 90 ℃ for 4 hours, filtering, then carrying out ammonium exchange treatment on the molecular sieve precursor DC-2 and 10 times of volume of 0.5M hydrochloric acid solution at 90 ℃ for 4 hours, and finally filtering, drying and roasting at 550 ℃ for 4 hours to obtain the ZSM-48 molecular sieve finished product DH-2.
Comparative example 3
A mother liquor after crystallization was prepared according to procedure (1) in example 1, followed by filtration, and the filter cake obtained after filtration was dried at 120 ℃ for 4 hours and then calcined at 850 ℃ for 4 hours, to obtain molecular sieve precursor DC-3. And (2) carrying out ammonium exchange treatment on the molecular sieve precursor DC-3 and 10 times of volume of 0.5M hydrochloric acid solution at 90 ℃ for 4 hours, filtering, then carrying out ammonium exchange treatment on the molecular sieve precursor DC-3 and 10 times of volume of 0.5M hydrochloric acid solution at 90 ℃ for 4 hours, and finally filtering, drying and roasting at 550 ℃ for 4 hours to obtain the ZSM-48 molecular sieve finished product DH-3.
Test example 1
(1) The mesoporous area and the specific surface area of the molecular sieve finished products prepared in the above examples and comparative examples were measured by using an automatic adsorption apparatus model DIGISORB 2500 of Micromeritics, usa, and the ratio of the mesoporous area to the specific surface area was calculated, and the results are shown in table 1 below.
(2) The contents of the respective elements in the molecular sieve precursors and the molecular sieve finished products prepared in the above examples and comparative examples were analyzed and measured by a 3271E type X-ray fluorescence spectrometer commercially available from japan physical and electrical machines industries, and the silicon-aluminum ratio and the content of penta-coordinated aluminum were determined, and the results are shown in table 1 below.
TABLE 1
Test example 2
The molecular sieve finished products prepared in the above examples and comparative examples were mixed with 40 g of alumina, extruded, and dried, respectively, to obtain carrier strips E-1 to E-6 and DE-1 to DE-3, respectively.
1 g of tetraammineplatinum dichloride and 3.2 g of citric acid are poured into 100g of deionized water and stirred until uniform. 80 g of the above carrier strip was poured into the above solutions, respectively, and immersed at room temperature for 4 hours to obtain a catalyst precursor. The catalyst precursor was subsequently dried at 120 ℃ for 4 hours. Then roasting the catalyst under the condition of introducing air flow, wherein the roasting temperature is 450 ℃, the roasting time is 4 hours, and the gas-agent ratio is 2.0L/(g.h), so as to obtain a semi-finished catalyst. And putting the semi-finished catalyst into 100g of deionized water solution containing 3.2 g of citric acid again, soaking for 4 hours, and drying at 120 ℃ for 4 hours to obtain catalysts Cat-1 to Cat-6 and D-Cat-1 to D-Cat-3 respectively.
100g of the catalysts Cat-1 to Cat-6 and D-Cat-1 to D-Cat-3 of 20-30 meshes are respectively put into a reaction tube and reduced for 4 hours in a hydrogen atmosphere, the reduction temperature is 400 ℃, and the hydrogen pressure is normal pressure during reduction. After the reduction is finished, the temperature is reduced to 120 ℃, the tail oil enters hydrocracking, the reaction temperature is 310 ℃, and the volume space velocity of the oil is 1.0h-1The hydrogen pressure was adjusted to 10.0MPa, and the hydrogen flow rate was adjusted to 500 in terms of the hydrogen-oil volume ratio. The hydrocracking tail oil properties are shown in table 2 below, and the catalyst evaluation results are shown in table 3 below.
TABLE 2
| Analysis item | Analyzing data | Analytical method |
| Density/(kg/m) at 20 DEG C3) | 843.6 | SH/T0604-2000 |
| Kinematic viscosity/(mm)2/s) | ||
| 80℃ | 7.021 | GB/T 265-88 |
| 100℃ | 4.664 | GB/T 265-88 |
| Pour point/. degree.C | +42 | |
| Mass fraction of nitrogen/(μ g/g) | <1 | |
| Sulfur mass fraction/(μ g/g) | 3 | SH/T 0842-2010 |
TABLE 3
| Catalyst and process for preparing same | Pour point | Yield/% | Viscosity index |
| Cat-1 | -29 | 63.3 | 139 |
| Cat-2 | -31 | 54.3 | 134 |
| Cat-3 | -23 | 51.6 | 128 |
| Cat-4 | -29 | 63.1 | 138 |
| Cat-5 | -33 | 52.5 | 132 |
| Cat-6 | -31 | 62.6 | 138 |
| D-Cat-1 | -15 | 41.1 | 117 |
| D-Cat-2 | -13 | 44.2 | 118 |
| D-Cat-3 | -14 | 47.3 | 120 |
As can be seen from the data in Table 3 above, the catalyst formed by using the ZSM-48 molecular sieve of the present invention as the solid acid has good isomerization and pour point depressing capabilities, and the target product in the product has high yield and low pour point.
The preferred embodiments of the present invention have been described above in detail, but the present invention is not limited thereto. Within the scope of the technical idea of the invention, many simple modifications can be made to the technical solution of the invention, including combinations of various technical features in any other suitable way, and these simple modifications and combinations should also be regarded as the disclosure of the invention, and all fall within the scope of the invention.
Claims (22)
1. A ZSM-48 molecular sieve is characterized in that the molar ratio of silica to alumina of the molecular sieve is 120-300; contains a mesoporous structure and has a closed hysteresis loop at a low-temperature nitrogen adsorption-desorption curve P/P0-0.4-0.99, and the starting position of the closed hysteresis loop is at a position P/P0-0.4-0.7;
the content of penta-coordinated aluminum in a finished product of the molecular sieve is less than 3 weight percent based on the total alumina content of the molecular sieve calculated by oxides;
the preparation method of the ZSM-48 molecular sieve comprises the following steps:
(1) filtering the crystallized mother liquor to form a filter cake with the dry basis content of 5-30%;
(2) directly roasting the filter cake to obtain a molecular sieve precursor;
(3) subjecting the molecular sieve precursor to a hydrothermal treatment;
(4) filtering, washing and drying the hydrothermal treatment product;
wherein the medium for the hydrothermal treatment is acidic water;
the penta-coordinated aluminum content of the molecular sieve precursor is 4-30 wt% calculated on oxide and based on the total alumina content of the molecular sieve.
2. The molecular sieve of claim 1, wherein the molecular sieve has a silica to alumina molar ratio of from 150 to 200.
3. The molecular sieve of claim 1, wherein the start position of the closed hysteresis loop is at P/P0 ═ 0.4-0.6.
4. The molecular sieve of claim 1, wherein the amount of penta-coordinated aluminum in the precursor of the molecular sieve is from 10 to 30 wt% on an oxide basis and based on the total alumina content of the molecular sieve.
5. The molecular sieve of claim 1 or 4, wherein the amount of penta-coordinated aluminum in the finished molecular sieve is 1 wt.% or less, calculated as oxide and based on the total alumina content of the molecular sieve.
6. The molecular sieve of claim 5, wherein the molecular sieve is free of penta-coordinated aluminum in the final product on an oxide basis and based on the total alumina content of the molecular sieve.
7. The molecular sieve of claim 1, wherein in step (2), the calcination temperature is 450-550 ℃.
8. The molecular sieve of claim 1, wherein in step (3), the liquid-solid volume ratio of the hydrothermal treatment is 5-200; the temperature of the hydrothermal treatment is 100-300 ℃; the time of the hydrothermal treatment is 0.5 to 24 hours.
9. A process for preparing the ZSM-48 molecular sieve of any of claims 1-8, comprising the steps of:
(1) filtering the crystallized mother liquor to form a filter cake with the dry basis content of 5-30%;
(2) directly roasting the filter cake to obtain a molecular sieve precursor;
(3) subjecting the molecular sieve precursor to a hydrothermal treatment;
(4) filtering, washing and drying the hydrothermal treatment product;
wherein the medium of the hydrothermal treatment is acidic water.
10. The process of claim 9, wherein in step (1), the filtration forms a filter cake having a dry content of 6-15% on a dry basis.
11. The method as claimed in claim 9 or 10, wherein, in the step (2), the temperature of the calcination is 400-600 ℃.
12. The method as claimed in claim 11, wherein, in the step (2), the temperature of the calcination is 450-550 ℃.
13. The method according to claim 9 or 10, wherein, in the step (3), the acidic water contains an inorganic acid and/or an organic acid, and the content of the inorganic acid and/or the organic acid is 0.1M to 5M.
14. The method according to claim 13, wherein, in the step (3), the acidic water contains an inorganic acid and/or an organic acid, and the content of the inorganic acid and/or the organic acid is 0.2M to 2M.
15. The method according to claim 9 or 14, wherein, in step (3), the acidic water contains at least one of hydrochloric acid, sulfuric acid, phosphoric acid, nitric acid, citric acid, acetic acid, maleic acid, oxalic acid, nitrilotriacetic acid, 1, 2-cyclohexanediaminetetraacetic acid, tartaric acid, and malic acid.
16. The process according to claim 9 or 10, wherein in step (3), the liquid-solid volume ratio of the hydrothermal treatment is 5-200; the temperature of the hydrothermal treatment is 100-300 ℃; the time of the hydrothermal treatment is 0.5 to 24 hours.
17. The process according to claim 16, wherein, in step (3), the liquid-solid volume ratio of the hydrothermal treatment is 20-100; the temperature of the hydrothermal treatment is 100-200 ℃; the time of the hydrothermal treatment is 1-12 hours.
18. The method according to claim 17, wherein, in the step (3), the hydrothermal treatment is performed for 1 to 4 hours.
19. The method according to claim 9, wherein the hydrothermal treatment is carried out in a closed vessel and the pressure of the hydrothermal treatment is the autogenous pressure of the closed vessel under hydrothermal conditions.
20. The method according to claim 9 or 10, wherein in the step (4), the washing is carried out by washing with deionized water until the pH value of the filtrate is 6-8.
21. The method as claimed in claim 20, wherein in step (4), the washing is carried out by washing with deionized water until the pH value of the filtrate is 6-7.
22. Use of the ZSM-48 molecular sieve of any of claims 1-8 as a solid acid.
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| CN105800635A (en) * | 2016-02-29 | 2016-07-27 | 中国科学院山西煤炭化学研究所 | Preparation method of ZSM-48 molecular sieve with mesoporous-microporus hierarchical structure |
| CN106608635A (en) * | 2015-10-27 | 2017-05-03 | 中国石油化工股份有限公司 | Preparation method of ZSM-48 molecular sieve |
| CN107282097A (en) * | 2016-04-12 | 2017-10-24 | 中国石油化工股份有限公司 | A kind of hydroisomerization catalyst and its preparation method and application |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN106608635A (en) * | 2015-10-27 | 2017-05-03 | 中国石油化工股份有限公司 | Preparation method of ZSM-48 molecular sieve |
| CN105800635A (en) * | 2016-02-29 | 2016-07-27 | 中国科学院山西煤炭化学研究所 | Preparation method of ZSM-48 molecular sieve with mesoporous-microporus hierarchical structure |
| CN107282097A (en) * | 2016-04-12 | 2017-10-24 | 中国石油化工股份有限公司 | A kind of hydroisomerization catalyst and its preparation method and application |
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| Title |
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| Creating mesopores in ZSM-48 zeolite by alkali treatment：Enhanced catalyst for hydroisomerization of hexadecane;Miao Zhang et al.;《Journal of Energy Chemistry》;20160114;第25卷;第539-541页"摘要"、"3.1 催化剂表征"和"3.2 碱处理效果" * |
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