WO2020259595A1 - 一种复合层聚结型吸附剂及制备方法 - Google Patents

一种复合层聚结型吸附剂及制备方法 Download PDF

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WO2020259595A1
WO2020259595A1 PCT/CN2020/098147 CN2020098147W WO2020259595A1 WO 2020259595 A1 WO2020259595 A1 WO 2020259595A1 CN 2020098147 W CN2020098147 W CN 2020098147W WO 2020259595 A1 WO2020259595 A1 WO 2020259595A1
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molecular sieve
adsorbent
mass
silicon
group
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PCT/CN2020/098147
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English (en)
French (fr)
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高宁宁
王辉国
刘宇斯
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中国石油化工股份有限公司
中国石油化工股份有限公司石油化工科学研究院
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Priority to US17/596,943 priority Critical patent/US20220258124A1/en
Application filed by 中国石油化工股份有限公司, 中国石油化工股份有限公司石油化工科学研究院 filed Critical 中国石油化工股份有限公司
Priority to JP2021577011A priority patent/JP7429717B2/ja
Priority to KR1020227003092A priority patent/KR20220025044A/ko
Publication of WO2020259595A1 publication Critical patent/WO2020259595A1/zh

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    • B01J20/02—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material
    • B01J20/10—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material comprising silica or silicate
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    • B01J20/10—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material comprising silica or silicate
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    • B01J20/28002—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof characterised by their form or physical properties characterised by their physical properties
    • B01J20/28004—Sorbent size or size distribution, e.g. particle size
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    • B01J20/28014—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof characterised by their form or physical properties characterised by their form
    • B01J20/28033—Membrane, sheet, cloth, pad, lamellar or mat
    • B01J20/28035—Membrane, sheet, cloth, pad, lamellar or mat with more than one layer, e.g. laminates, separated sheets
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    • B01J20/3007—Moulding, shaping or extruding
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    • B01J20/30—Processes for preparing, regenerating, or reactivating
    • B01J20/3042—Use of binding agents; addition of materials ameliorating the mechanical properties of the produced sorbent
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    • C01B39/00—Compounds having molecular sieve and base-exchange properties, e.g. crystalline zeolites; Their preparation; After-treatment, e.g. ion-exchange or dealumination
    • C01B39/02—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof; Direct preparation thereof; Preparation thereof starting from a reaction mixture containing a crystalline zeolite of another type, or from preformed reactants; After-treatment thereof
    • C01B39/20—Faujasite type, e.g. type X or Y
    • C01B39/22—Type X
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C15/00—Cyclic hydrocarbons containing only six-membered aromatic rings as cyclic parts
    • C07C15/02—Monocyclic hydrocarbons
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    • C07C15/08—Xylenes
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C7/00—Purification; Separation; Use of additives
    • C07C7/12—Purification; Separation; Use of additives by adsorption, i.e. purification or separation of hydrocarbons with the aid of solids, e.g. with ion-exchangers
    • C07C7/13—Purification; Separation; Use of additives by adsorption, i.e. purification or separation of hydrocarbons with the aid of solids, e.g. with ion-exchangers by molecular-sieve technique
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D15/00—Separating processes involving the treatment of liquids with solid sorbents; Apparatus therefor
    • B01D15/08—Selective adsorption, e.g. chromatography
    • B01D15/10—Selective adsorption, e.g. chromatography characterised by constructional or operational features
    • B01D15/18—Selective adsorption, e.g. chromatography characterised by constructional or operational features relating to flow patterns
    • B01D15/1807—Selective adsorption, e.g. chromatography characterised by constructional or operational features relating to flow patterns using counter-currents, e.g. fluidised beds
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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    • B01D15/00—Separating processes involving the treatment of liquids with solid sorbents; Apparatus therefor
    • B01D15/08—Selective adsorption, e.g. chromatography
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    • B01D15/18—Selective adsorption, e.g. chromatography characterised by constructional or operational features relating to flow patterns
    • B01D15/1814—Selective adsorption, e.g. chromatography characterised by constructional or operational features relating to flow patterns recycling of the fraction to be distributed
    • B01D15/1821—Simulated moving beds
    • B01D15/185—Simulated moving beds characterized by the components to be separated
    • B—PERFORMING OPERATIONS; TRANSPORTING
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    • B01J2220/00—Aspects relating to sorbent materials
    • B01J2220/40—Aspects relating to the composition of sorbent or filter aid materials
    • B01J2220/42—Materials comprising a mixture of inorganic materials
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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    • B01J2220/40—Aspects relating to the composition of sorbent or filter aid materials
    • B01J2220/48—Sorbents characterised by the starting material used for their preparation
    • B01J2220/4806—Sorbents characterised by the starting material used for their preparation the starting material being of inorganic character
    • B—PERFORMING OPERATIONS; TRANSPORTING
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    • B01J2220/00—Aspects relating to sorbent materials
    • B01J2220/50—Aspects relating to the use of sorbent or filter aid materials
    • B01J2220/60—Use in several different columns
    • B01J2220/603—Use in several different columns serially disposed columns

Definitions

  • the invention relates to a coalescing adsorbent and a preparation method thereof, and specifically to an adsorbent using X molecular sieve as an active component and a preparation method thereof.
  • Paraxylene (PX) is an important basic chemical raw material, mainly used to produce polyester fibers.
  • Adsorption separation technology includes an adsorbent that can selectively adsorb p-xylene and a continuous countercurrent simulated moving bed adsorption separation process.
  • the use of high-performance adsorbents is the key to obtaining high-purity p-xylene products.
  • the active component of the p-xylene adsorbent for industrial adsorption and separation is mostly X molecular sieve.
  • the X molecular sieve and clay are mixed uniformly in a certain proportion, and the adsorbent pellets are obtained after rolling ball molding, drying, roasting and cation exchange.
  • Compressive strength, selectivity, adsorption capacity and mass transfer performance are important indicators for evaluating adsorbents.
  • CN1275926A discloses a coalescing zeolite adsorbent, the active component is X molecular sieve with Si/Al atomic ratio of 1 to 1.15, and the binder is zeolitizable clay. After alkali treatment, the clay can be converted into X molecular sieve, and higher compressive strength and adsorption capacity can be obtained.
  • CN1565718A adopts small crystal X molecular sieve with a grain size of 0.1-0.4 microns as the active component of the adsorbent to improve the mass transfer performance of the adsorbent and increase the adsorption capacity.
  • CN101497022A discloses a coalescing adsorbent and a preparation method thereof.
  • a pore former is added to the mixed powder for preparing the adsorbent to form a large number of intercrystalline pores with concentrated pore distribution in the adsorbent particles after crystal transformation , Thereby significantly improving the mass transfer performance of the adsorbent.
  • US3558732 discloses a system for the adsorption and separation of p-xylene with mixed carbon eight aromatic hydrocarbons using toluene as a desorbent.
  • the active component of the adsorbent used is BaKX molecular sieve. Compared with the case of benzene as the desorbent, it has better adsorption selectivity and Product purity.
  • the purpose of the present invention is to provide a composite layer coalescing adsorbent and a preparation method.
  • the adsorbent is suitable for the process of adsorbing and separating PX from C 8 aromatic hydrocarbons using light aromatic hydrocarbons as desorbents, and has high adsorption selectivity. And good mass transfer performance.
  • the present invention provides a composite layer coalescing adsorbent, comprising an outer adsorbent layer containing low silicon X molecular sieve and an inner adsorbent layer containing high silicon X molecular sieve.
  • the ratio is 2.07 to 2.18
  • the silica/alumina molar ratio of the high silica X molecular sieve is 2.2 to 2.5, based on the total amount of the adsorbent
  • the adsorbent includes 95.0 to 100% by mass of the X molecular sieve and 0-5.0% by mass of the matrix
  • the cation sites of the X molecular sieve in the adsorbent are occupied by group II and A metals or shared by group I and A metals.
  • the present invention uses X molecular sieves with two different silicon oxide/alumina molar ratios, high and low, as the active component of the composite layer coalescing adsorbent, and the adsorbent containing high silicon X molecular sieve is placed in the inner layer with low silicon content.
  • the adsorbent of X molecular sieve is placed on the outer layer.
  • the coalescing layer composite adsorbent suitable for adsorptive separation PX from C 8 aromatics, to lighter aromatics adsorptive separation process as a desorbent can be separated to improve the purity of the desired product, improve the production capacity of the adsorptive separation means.
  • Figure 1 shows the X-ray diffraction (XRD) spectrum of the low-silicon X molecular sieve prepared in Example 1.
  • Figure 2 is a scanning electron microscope (SEM) photograph of the low silicon X molecular sieve prepared in Example 1.
  • Figure 3 is an SEM photo of the low silicon X molecular sieve prepared in Example 2.
  • Figure 4 is the XRD spectrum of the high silica X molecular sieve prepared in Example 3.
  • Figure 5 is an SEM photograph of the high-silicon X molecular sieve prepared in Example 3.
  • Figure 6 is a schematic diagram of a small simulated moving bed adsorption separation.
  • X molecular sieve also called X-type molecular sieve, X-zeolite or X-type zeolite
  • the adsorption active component is used as the inner layer (hereinafter, sometimes referred to as the inner layer), and the adsorbent containing low silicon X molecular sieve is used as the outer layer (hereinafter, sometimes also referred to as the outer layer).
  • the inner layer the inner layer
  • the outer layer hereinafter, sometimes also referred to as the outer layer
  • the outer adsorbent contains X molecular sieve (low silicon X molecular sieve) with a low silica/alumina molar ratio, which is beneficial to improve the adsorbent's p-xylene (PX) relative to ethylbenzene
  • X molecular sieve low silicon X molecular sieve
  • PX p-xylene
  • EB p-xylene
  • the inner adsorbent contains X molecular sieve (high silica X molecular sieve) with a high silica/alumina molar ratio, which can provide higher para-xylene relative to meta-xylene (MX) and para-xylene relative to ortho-xylene.
  • X molecular sieve high silica X molecular sieve
  • MX meta-xylene
  • OX xylene
  • the content of X molecular sieve in total refers to the total content of X molecular sieve contained in the adsorbent, which includes high-silicon X molecular sieve, low-silicon X molecular sieve and X molecular sieve formed after kaolin mineral transformation.
  • Matrix content refers to the total amount of matrix contained in the inner and outer layers.
  • X molecular sieve cation sites refer to all the cation sites in the X molecular sieve contained in the composite layer coalescing adsorbent.
  • the composite layer coalescing adsorbent of the present invention includes 95.0-99.5 mass% X molecular sieve and 0.5-5.0 mass% matrix.
  • the composite layer coalescing adsorbent may also include 97.0-99.5 mass% X molecular sieve and 0.5-3.0 mass% matrix.
  • the content of low-silicon X molecular sieve in the composite layer coalescing adsorbent is 5-40% by mass, preferably 10-40% by mass of the total amount of X molecular sieve.
  • the silica/alumina molar ratio of the low-silicon X molecular sieve in the outer layer is 2.07-2.18.
  • the low-silicon X molecular sieve in the outer layer is preferably an X molecular sieve autopolymer, which is formed by agglomeration of nano-scale X molecular sieve crystals with smaller crystal grains.
  • the particle size of the self-polymer is preferably 1.0 to 3.0 microns, more preferably 1.0 to 2.0 microns, and the crystal particle size of the nano-sized X molecular sieve is preferably 0.1 to 0.8 nanometers.
  • the silica/alumina molar ratio of the high silica X molecular sieve in the inner layer is 2.2 to 2.5, preferably 2.2 to 2.4.
  • the crystal grain size of the high-silicon X molecular sieve is preferably 0.1-2.5 microns, more preferably 0.5-2.0 microns.
  • the matrix described in the adsorbent is the residue after in-situ crystallization of kaolin minerals.
  • the kaolin mineral is selected from at least one of kaolinite, dickite, perlite, refractory and halloysite.
  • the cation sites of the X molecular sieve are occupied by Group II A metals or occupied by Group I A metals and Group II A metals.
  • the group II A metal is preferably Ba
  • the group I A metal is preferably at least one of K, Li and Na.
  • the molar ratio of barium oxide to I A metal oxide is 2-60, preferably 5 ⁇ 46.
  • the composite layer adsorbent of the present invention is preferably in the shape of small spheres, and the average particle size of the small spheres is preferably 300-850 microns.
  • the preparation method of the adsorbent of the present invention includes the following steps:
  • Rolling ball molding mix the high-silicon X molecular sieve and the binder uniformly at a mass ratio of 88-95:5-12, and place them in the turntable while rolling while spraying water to make the solids aggregate into small balls as the core; Then add the powder mixed with low silicon X molecular sieve and binder in a mass ratio of 88 ⁇ 95:5 ⁇ 12, continue to spray water and roll to form the outer layer of the pellets, take pellets with a particle size of 300 ⁇ 850 microns, and dry them Baked at 500 ⁇ 700°C,
  • In-situ crystallization take the pellets calcined in step (1), perform in-situ crystallization treatment with an alkali solution, and then dry.
  • the alkali solution is a mixed solution of sodium hydroxide and potassium hydroxide, and mixed
  • concentration of hydroxide ion in the solution is 0.1 ⁇ 3.0 mol/L, and the molar ratio of K + /(Na + +K + ) is 0.1 ⁇ 0.6.
  • Ion exchange cation exchange the pellets dried in step (2) with a soluble salt solution of group II A metal or a soluble salt of group II A metal and a soluble salt of group I A metal, and then dry ,activation.
  • the step (1) is to roll the X molecular sieve and the binder into a ball.
  • the X molecular sieve with different silica/alumina molar ratios are mixed with the binder respectively, and the balls are divided into two batches for roll forming. That is, the mixture of high-silicon X molecular sieve and binder is rolled into small balls as the inner core, that is, the inner adsorbent layer, and then the mixture of low-silicon X molecular sieve and the binder is added to roll to form the outer layer of the small ball, which is formed Outer adsorbent layer.
  • the low-silicon X molecular sieve used in step (1) rolling ball molding is 5-40% by mass, preferably 10-40% by mass of the total added X molecular sieve.
  • the mass ratio of the high-silicon X molecular sieve to the binder used in step rolling is preferably 10-15:1, and the mass ratio of the low-silicon X molecular sieve to the binder used is preferably 10-15:1.
  • the binder is a kaolin mineral.
  • the kaolin mineral is selected from kaolinite, dickite, perlite, refractory, halloysite or a mixture thereof.
  • the mass fraction of the crystalline substance in the kaolin mineral is at least 90%, preferably 93-99%.
  • the equipment for forming the ball in step (1) can be a turntable, a dragee or a roller.
  • the equipment for forming the ball in step (1) can be a turntable, a dragee or a roller.
  • the equipment for forming the ball in step (1) can be a turntable, a dragee or a roller.
  • When rolling the ball put the uniformly mixed solid raw materials into the rotating equipment, and spray water while rolling to make the solid powder adhere and agglomerate into small balls.
  • the amount of water added during rolling is 6-22% of the total solid mass, preferably 6-16%.
  • the balls are sieved, and the balls with a particle size of 300-850 microns are taken, dried, and calcined at 500-700°C to obtain an adsorbent precursor.
  • the drying temperature is preferably 60-110°C, and the time is preferably 2-12 hours.
  • the firing temperature is preferably 520 to 600°C, and the time is preferably 1.0 to 6.0 hours.
  • the kaolin minerals in the pellets are transformed into metakaolin, so as to facilitate the in-situ transformation into X molecular sieve in step (2).
  • step (2) is a step of in-situ crystallization of the pellets prepared in step (1).
  • the lye used for in-situ crystallization is a mixed solution of sodium hydroxide and potassium hydroxide, wherein hydrogen and oxygen.
  • concentration of root ions is preferably 0.2 to 1.6 mol/liter, and the molar ratio of K + /(Na + +K + ) is preferably 0.15 to 0.45.
  • the liquid/solid ratio when the kaolin mineral is crystallized in situ with a mixed solution of sodium hydroxide and potassium hydroxide is preferably 1.5-5.0 L/kg.
  • the crystallization temperature for in-situ crystallization of the kaolin mineral into an X-type molecular sieve is preferably 80-100°C, more preferably 85-100°C, and the time is preferably 0.5-8 hours.
  • the pellets after in-situ crystallization are dried, the drying temperature is preferably 60-110°C, and the time is preferably 2-12 hours.
  • step (3) is a step of performing cation exchange on the dried pellets in step (2).
  • the group II and A metals are preferably Ba.
  • the soluble salt of the group II A metal is preferably barium nitrate or barium chloride.
  • the soluble salt of the group IA metal is preferably at least one of nitrate and chloride.
  • the group I A metal is preferably at least one of K, Li and Na.
  • the cation exchange in step (3) can be carried out in a kettle type or column type vessel, preferably continuous exchange in a column type vessel.
  • Switching temperature is preferably 40 ⁇ 120 °C, more preferably 85 ⁇ 95 °C
  • time is preferably 5 to 25 hours, more preferably from 8 to 16 hours, preferably exchange liquid hourly space velocity of 0.2 to 10 -1, more preferably 2 to 8 - 1 .
  • the composite layer coalescing adsorbent contains both ions selected from group IIA metals and ions selected from group IA metals
  • soluble salts of group IIA metals and IA can be used.
  • the mixed solution of the soluble salt of the group metal can simultaneously perform cation exchange on the pellets dried in step (2).
  • the soluble salt solution of the group II A metal and the soluble salt solution of the group IA metal can also be prepared separately, and then the (2)
  • the dried pellets are subjected to cation exchange, which can be carried out firstly for ion exchange for group II A metals, and then for ion exchange for group IA metals, or first for ion exchange for group IA metals, and then for ion exchange for group II and A metals.
  • the pellets after the cation exchange in step (3) are washed, dried, and activated to remove sodium ions and water to obtain a composite layer coalescing adsorbent.
  • the drying and activation in step (3) can be carried out in flowing hot air or nitrogen.
  • the drying temperature is preferably 40 to 120°C, more preferably 60 to 110°C, and the time is preferably 5 to 60 hours, more preferably 18 to 40 hours.
  • the activation temperature is preferably 150-250°C, more preferably 160-220°C, and the time is preferably 5-20 hours, more preferably 5-10 hours.
  • the low-silicon X molecular sieve is preferably an X molecular sieve autopolymer, and its preparation method includes the following steps:
  • step (iii) The molecular sieve synthesis system of step (ii) is hydrothermally crystallized at 50-120°C for 2 to 72 hours, and the solid obtained after crystallization is washed and dried to obtain X molecular sieve autopolymer.
  • K + /(K + +Na + ) is preferably 0.2 to 0.5.
  • the high silica X molecular sieve of the present invention can be prepared by conventional methods. It is preferably prepared by the following method, which includes the following steps:
  • the molar ratio of 3 is 0.01 to 2.0%, preferably 0.1 to 1.0%,
  • step (iii-1) The molecular sieve synthesis system of step (ii-1) is hydrothermally crystallized at 50-120°C for 2 to 72 hours, and the solid obtained after crystallization is washed and dried to obtain the high-silicon X molecular sieve of the present invention .
  • the aluminum source used for synthesizing molecular sieve can be selected from at least one of low alkalinity sodium metaaluminate, aluminum oxide, aluminum hydroxide, aluminum sulfate, aluminum chloride, aluminum nitrate, and sodium aluminate.
  • the Na 2 O content in the low alkalinity sodium metaaluminate is 7.6 to 23.7 mass%, preferably 8 to 14 mass%, and the Al 2 O 3 content is preferably 7.0 to 15.0 mass%.
  • the potassium source used for synthesizing molecular sieve is selected from at least one of potassium hydroxide, potassium fluoride, potassium chloride, potassium bromide, potassium iodide, potassium carbonate, potassium nitrate and potassium sulfate.
  • the silicon source used for synthesizing molecular sieve is selected from at least one of ethyl orthosilicate, silica sol, water glass, sodium silicate, silica gel, and white carbon black.
  • the inorganic base is preferably sodium hydroxide.
  • the temperature for hydrothermal crystallization of the molecular sieve synthesis system is preferably 70-110°C, more preferably 80-100°C, and the time is preferably 3-24 hours.
  • the composite layer adsorbent provided by the present invention is suitable for liquid phase adsorption and separation of p-xylene from carbon eight aromatic hydrocarbons, and the desorbent used for adsorption and separation is preferably toluene.
  • the liquid phase adsorption separation can be carried out in a multi-column series connection mode, or can be carried out in a simulated moving bed realized by means of a rotary valve or a solenoid valve group.
  • the operating pressure of adsorption separation is 0.3-1.5MPa, and the operating temperature is 120-180°C.
  • the three important indicators to measure the performance of adsorbents are adsorption capacity, selectivity, and the adsorption and desorption rate of separating target products (such as p-xylene).
  • a dynamic pulse experimental device can be used to determine the adsorption selectivity of the adsorbent and the adsorption and desorption rate of the separated target product.
  • the device is composed of feed system, adsorption column, heating furnace, pressure control valve and so on.
  • the adsorption column is a stainless steel tube of ⁇ 6 ⁇ 1800 mm.
  • the inlet at the lower end of the adsorption column is connected with the feed and nitrogen system, and the outlet at the upper end is connected with a pressure control valve, and then connected with an effluent collector.
  • the method for determining the adsorption selectivity of the adsorbent is as follows: load the weighed adsorbent particles with a particle size of 300 ⁇ 850 ⁇ m into the adsorption column for compaction, dehydrate and activate at 160 ⁇ 190°C in a nitrogen atmosphere; then pass in the desorbent Eliminate the gas in the system. Increase the system pressure to 0.8MPa, the temperature to 145°C, stop passing the desorbent, pass in 8ml pulsed feed liquid at a volumetric space velocity of 1.0 hour -1 , the feed liquid contains tracer that is not adsorbed , Then pass the desorbent at the same volumetric space velocity, and take 3 drops of desorbent samples every 2 minutes and analyze by gas chromatography.
  • the tracer that is not adsorbed can be used to obtain the dead volume of the adsorption system.
  • the midpoint of the half-width of the tracer is taken as the zero point, and the net retention volume R from the midpoint of the half-width of each component to the zero point is determined.
  • the net retention volume of any component is directly proportional to the distribution coefficient at adsorption equilibrium, reflecting each The force between the components and the adsorbent, the ratio of the net retention volume of the two components is the selectivity ⁇ , for example, the ratio of the net retention volume of PX to the net retention volume of EB is the ratio of the adsorption performance of the adsorbent to PX and EB , Is the adsorption selectivity of PX relative to EB, recorded as ⁇ P/E ; the ratio of the net retention volume of PX to the net retention volume of MX is the ratio of the adsorption performance of the adsorbent to PX and MX, and is the ratio of PX to MX The adsorption selectivity is denoted as ⁇ P/M ; the ratio of the net retention volume of PX to the net retention volume of OX is the ratio of the adsorption performance of the adsorbent to PX and OX, and is the adsorption selectivity of PX relative to
  • the adsorption rate of PX [S A ] 10-90 and the desorption rate [S D ] 90-10 are introduced .
  • the adsorption rate [S A ] 10-90 is the volume of desorbent required for the PX concentration in the pulse desorption curve of PX to rise from 10% to 90%
  • the analytical rate [S D ] 90-10 is the PX concentration in the desorption curve from The volume of desorbent required to reduce 90% to 10%, [S A ] 10-90 /[S D ] 90-10 ratio is defined as the adsorption selectivity ⁇ PX/T between PX and desorbent.
  • the toluene gas phase adsorption experiment is used to determine the adsorption capacity of the adsorbent.
  • the specific operation method is: contact the nitrogen carrying toluene (toluene partial pressure is 0.5MPa) with a certain mass of adsorbent at 35°C until the toluene reaches adsorption balance.
  • the mass difference of the adsorbent before and after toluene adsorption the adsorption capacity of the tested adsorbent is calculated from the following formula.
  • the method to determine the adsorption performance of the adsorbent Take 50 grams of adsorbent and conduct a liquid phase pulse experiment to measure the adsorption selectivity and the adsorption and desorption rate of PX.
  • the desorbent used in the experiment is 30% by volume of toluene (T) and 70% by volume. Heptane.
  • the composition of the pulse feed liquid is ethylbenzene (EB), p-xylene (PX), m-xylene (MX), o-xylene (OX), n-nonane (NC9) and 75% by volume each accounting for 5 vol% Desorbent, of which n-nonane is a tracer.
  • the particle size is 1.4 microns
  • the X molecular sieve crystal particle size in the self-polymer is 0.6 nanometers
  • its silica/alumina molar ratio measured by X-ray fluorescence spectroscopy (XRF) is 2.09.
  • the low silicon X molecular sieve was prepared according to the method of Example 1, except that in step (2) 5.84 kg of sodium hydroxide, 11.56 kg of potassium hydroxide, 53.73 kg of deionized water, 32.35 kg of low alkalinity sodium metaaluminate solution, 23.33 kg
  • the water glass and 0.49 kg of the directing agent prepared in step (1) are added to the reaction kettle, stirred and mixed uniformly to form a molecular sieve synthesis system.
  • the above molecular sieve synthesis system is hydrothermally crystallized, filtered, washed and dried to obtain low-silicon X molecular sieve c.
  • XRD shows that it is pure X molecular sieve.
  • the scanning electron microscope photo is shown in Figure 3, showing that low-silicon X molecular sieve is X molecular sieve crystal self-aggregate ,
  • the self-polymer particle size is 1.3 microns
  • the X molecular sieve crystal particle size in the self-polymer is 0.5 nanometers
  • the silica/alumina molar ratio measured by XRF is 2.16.
  • Rolling ball molding Take 88 kilograms (the mass of the fire base, the same below) of the high-silicon X molecular sieve b prepared in Example 3 and 6.62 kilograms of kaolin (90% by mass of crystallized substance, the same below) and mix uniformly to obtain mixture I, 5 kg of low silicon X molecular sieve a prepared in Example 1 and 0.38 kg of kaolin were mixed uniformly to obtain mixture II. Put the mixture I into the turntable and spray an appropriate amount of deionized water while rolling to make the solid powder aggregate into small balls as the inner core, and then add the mixture II to continue spraying and rolling to form the outer layer of the small balls. The amount of water sprayed during rolling is 8% by mass of the total solid powder. After sieving, the pellets with a particle size of 300-850 microns are taken, dried at 80°C for 10 hours, and calcined at 540°C for 4 hours.
  • Ion exchange load 130 ml of the pellets dried in step (2) into an ion exchange column for cation exchange.
  • the volumetric space velocity of -1 is continuously exchanged at 0.1MPa and 94°C for 8 hours, and the total amount of mixed solution is 5000 ml.
  • adsorbent A the inner layer of which is high in silicon
  • the inner adsorbent layer of X molecular sieve, the outer layer is the outer adsorbent layer containing low silicon X molecular sieve, the content of X molecular sieve is 98.6% by mass, the content of matrix is 1.4% by mass, and the molar ratio of BaO to K 2 O in the adsorbent is 36.
  • the composite layer adsorbent was prepared according to the method of Example 4, except that in step (1) 78 kg of the high silica X molecular sieve b prepared in Example 3 and 5.87 kg of kaolin were mixed uniformly to make Mixture I, 15 kg of the low silica prepared in Example 1 X molecular sieve a and 1.13 kilograms of kaolin were mixed uniformly to make mixture II.
  • the adsorbent B was obtained by rolling ball molding, in-situ crystallization and ion exchange.
  • the inner layer was the inner adsorbent layer containing high silicon X molecular sieve, and the outer layer was containing The outer adsorbent layer of the low-silicon X molecular sieve, in which the X molecular sieve content is 98.4% by mass and the matrix content is 1.6% by mass, respectively, 1 g and 50 g of adsorbent B were taken to determine the toluene adsorption capacity and adsorption performance. The results are shown in Table 1.
  • the composite layer adsorbent was prepared according to the method of Example 4, except that in step (1) 68 kg of the high silica X molecular sieve b prepared in Example 3 and 5.13 kg of kaolin were mixed uniformly to make Mixture I, and 25 kg of the low silica prepared in Example 1 X molecular sieve a and 1.87 kilograms of kaolin are mixed uniformly to make mixture II.
  • the adsorbent C is obtained by rolling ball forming, in-situ crystallization and ion exchange.
  • the inner layer is the inner adsorbent layer containing high silicon X molecular sieve
  • the outer layer is containing
  • the content of X molecular sieve is 98.5% by mass and the content of matrix is 1.5% by mass.
  • the composite layer adsorbent was prepared according to the method of Example 4, except that in step (1) 78 kg of the high silica X molecular sieve b prepared in Example 3 and 5.87 kg of kaolin were mixed uniformly to make mixture I, and 15 kg of the low silica prepared in Example 2 X molecular sieve c and 1.13 kilograms of kaolin were mixed uniformly to make mixture II.
  • the adsorbent D was obtained by rolling ball molding, in-situ crystallization and ion exchange.
  • the inner layer was an inner adsorbent layer containing high silicon X molecular sieve, and the outer layer was containing The outer adsorbent layer of the low-silicon X molecular sieve, in which the X molecular sieve content is 97.9% by mass, and the matrix content is 2.1% by mass.
  • the composite layer adsorbent was prepared according to the method of Example 4, except that in step (1) 68 kg of the high-silicon X molecular sieve b prepared in Example 3 and 5.13 kg of kaolin were mixed uniformly to make a mixture I, and 25 kg of the low-silicon prepared in Example 2 X molecular sieve c and 1.87 kilograms of kaolin were mixed uniformly to make mixture II. After rolling ball molding, in-situ crystallization and ion exchange, adsorbent E was obtained.
  • the inner layer was an inner adsorbent layer containing high silicon X molecular sieve, and the outer layer was containing The outer adsorbent layer of the low-silicon X molecular sieve, in which the X molecular sieve content is 98.0% by mass, and the matrix content is 2.0% by mass.
  • adsorbent E Take 1 g and 50 g of adsorbent E, respectively, to determine the toluene adsorption capacity and adsorption performance. The results are shown in Table 1.
  • the composite layer adsorbent was prepared according to the method of Example 4, except that in step (1) 58 kg of the high silica X molecular sieve b prepared in Example 3 and 4.37 kg of kaolin were mixed uniformly to make a mixture I, 35 kg of the low silica prepared in Example 2 X molecular sieve c and 2.63 kg of kaolin were mixed uniformly to make mixture II. After rolling ball molding, in-situ crystallization and ion exchange, adsorbent F was obtained.
  • the inner layer was an inner adsorbent layer containing high silicon X molecular sieve
  • the outer layer was In the outer adsorbent layer of low-silicon X molecular sieve, the content of X molecular sieve is 98.2% by mass and the content of matrix is 1.8% by mass.
  • adsorbent G wherein the content of X molecular sieve is 98.3% by mass and the content of matrix is 1.7% by mass, respectively 1 g and 50 g of adsorbent G were tested for toluene adsorption capacity and adsorption performance. The results are shown in Table 1.
  • the adsorbent was prepared according to the method of Comparative Example 1, except that 93 kilograms of the high silica X molecular sieve b prepared in Example 2 and 7 kilograms of kaolin were mixed uniformly, and the adsorbent H was obtained by rolling ball molding, in-situ crystallization and ion exchange, wherein The X molecular sieve content is 97.5% by mass, and the matrix content is 2.5% by mass. Take 1 g and 50 g of adsorbent H, respectively, to determine the toluene adsorption capacity and adsorption performance. The results are shown in Table 1.
  • adsorbent I was prepared, wherein the content of X molecular sieve was 98.5 mass% and the content of matrix was 1.5 mass%. Take 1 g and 50 g of adsorbent I, respectively, to determine the toluene adsorption capacity and adsorption performance. The results are shown in Table 1.
  • the adsorbent was prepared according to the method of Comparative Example 3, except that 25 kg of the low silicon X molecular sieve c prepared in Example 2 was used instead of the low silicon X molecular sieve a to obtain adsorbent J, wherein the content of X molecular sieve was 98.0% by mass and the content of matrix was 2.0% by mass. Take 1 g and 50 g of adsorbent J, respectively, to determine the toluene adsorption capacity and adsorption performance. The results are shown in Table 1.
  • the small-scale simulated moving bed device includes 24 adsorption columns connected in series, each of which is 195 mm in length and 30 mm in inner diameter, and the total amount of adsorbent is 3300 ml.
  • the ends of the 24 columns connected in series are connected by circulating pumps to form a closed loop, as shown in Figure 6.
  • the 24 adsorption columns are divided into four sections, that is, 7 adsorption columns between the adsorption raw materials (column 15) and raffinate (column 21) It is the adsorption zone.
  • the 9 adsorption columns between the extraction solution (column 6) and the adsorption material (column 14) are the purification zone, and the 5 adsorption columns between the desorbent (column 1) and the extraction solution (column 5) are desorption Zone, the three adsorption columns between the raffinate (column 22) and the desorbent (column 24) are buffers.
  • the temperature of the entire adsorption system is controlled at 145°C and the pressure is 0.8MPa.
  • the desorbent toluene and raw materials were continuously injected into the simulated moving bed at the flow rates of 2118 ml/hour and 1925 ml/hour respectively, and the extraction liquid and the extraction liquid were extracted at the flow rates of 1540 ml/hour and 2503 ml/hour respectively.
  • Remaining liquid extraction device The composition of the raw materials is 9.3% by mass of ethylbenzene, 18.5% by mass of p-xylene, 45.5% by mass of meta-xylene, 17.4% by mass of o-xylene and 9.3% by mass of non-aromatic components.
  • a small simulated moving bed device was loaded with adsorbent B, and the experiment of adsorption and separation of p-xylene was carried out according to the method of Example 10.
  • the purity of p-xylene obtained under stable operation state was 99.80% by mass, and the yield was 98.95% by mass.
  • a small simulated moving bed device was loaded with comparative adsorbent G, and the adsorption and separation experiment of p-xylene was carried out according to the method of Example 10.
  • the purity of p-xylene obtained under stable operation state was 98.71% by mass, and the yield was 97.55% by mass.
  • a small-scale simulated moving bed device was loaded with comparative adsorbent H, and the experiment of adsorption and separation of p-xylene was carried out according to the method of Example 10.
  • the purity of p-xylene obtained under stable operation state was 98.86% by mass, and the yield was 97.43% by mass.
  • a small simulated moving bed device was loaded with comparative adsorbent I, and the adsorption and separation experiment of p-xylene was carried out according to the method of Example 10.
  • the purity of p-xylene obtained under stable operation state was 99.26% by mass, and the yield was 98.05% by mass.
  • a small simulated moving bed device was loaded with comparative adsorbent J, and the adsorption and separation experiment of p-xylene was carried out according to the method of Example 10.
  • the purity of p-xylene obtained under stable operation state was 99.10% by mass, and the yield was 98.01% by mass.

Abstract

本发明提供一种复合层聚结型吸附剂，包括含低硅X分子筛的外吸附剂层和含高硅X分子筛的内吸附剂层，所述的低硅X分子筛的氧化硅/氧化铝摩尔比为2.07～2.18，所述的高硅X分子筛的氧化硅/氧化铝摩尔比为2.2～2.5，以吸附剂的总量计，所述吸附剂包括95.0～100质量％的X分子筛和0～5.0质量％的基质，所述吸附剂中X分子筛的阳离子位为II A族金属占据或为I A族金属和II A族金属共同占据。该吸附剂适用于采用轻质芳烃作为解吸剂的从C 8芳烃中吸附分离PX的过程，具有较高的吸附选择性和良好的传质性能。

Description

一种复合层聚结型吸附剂及制备方法 技术领域
本发明涉及一种聚结型吸附剂及制备方法，具体地说，涉及一种以X分子筛为活性组分的吸附剂及其制备方法。
背景技术
对二甲苯(PX)是重要的基础化工原料，主要用于生产聚酯纤维。目前，工业上普遍采用吸附分离方法从混合碳八芳烃中分离对二甲苯。吸附分离技术包括可选择性吸附对二甲苯的吸附剂和连续逆流的模拟移动床吸附分离工艺。其中，高性能吸附剂的使用是获得高纯度对二甲苯产品的关键。
工业用吸附分离对二甲苯吸附剂的活性组元多为X分子筛，将X分子筛与粘土按一定比例混合均匀，经滚球成型、干燥、焙烧和阳离子交换后得到吸附剂小球。抗压强度、选择性、吸附容量和传质性能是评价吸附剂的重要指标。
US3997620发现与BaKX相比，X分子筛经过Sr 2+和Ba 2+交换后，虽然对二甲苯/间二甲苯(PX/MX)和对二甲苯/邻二甲苯(PX/OX)选择性有所降低，但是对二甲苯/乙苯(PX/EB)和对二甲苯/对二乙苯(PX/PDEB)选择性显著提高。
CN1275926A公开了一种聚结型沸石吸附剂，活性组元为Si/Al原子比为1～1.15的X分子筛，粘结剂为可沸石化的粘土。经碱处理后可使粘土转化为X分子筛，获得较高的抗压强度和吸附容量。
CN1565718A采用晶粒粒径为0.1～0.4微米的小晶粒X分子筛作为吸附剂的活性组元，以提高吸附剂的传质性能和提高吸附容量。
CN101497022A公开了一种聚结型吸附剂及其制备方法，该方法通过在制备吸附剂的混合粉料中加入造孔剂，使转晶后的吸附剂颗粒内形成大量孔分布集中的晶间孔，从而显著提高吸附剂的传质性能。
US3558732公开了一种以甲苯为解吸剂的混合碳八芳烃吸附分离对二甲苯的体系，所用吸附剂活性组分为BaKX分子筛，较之苯为解吸剂的情况，具有更好的吸附选择性和产品纯度。
发明内容
本发明的目的是提供一种复合层聚结型吸附剂及制备方法，该吸附剂适用于采用轻质芳烃作为解吸剂的从C 8芳烃中吸附分离PX的过程，具有较高的吸附选择性和良好的传质性能。
本发明提供一种复合层聚结型吸附剂，包括含低硅X分子筛的外吸附剂层和含高硅X分子筛的内吸附剂层，所述的低硅X分子筛的氧化硅/氧化铝摩尔比为2.07～2.18，所述的高硅X分子筛的氧化硅/氧化铝摩尔比为2.2～2.5，以所述吸附剂的总量计，所述吸附剂包括95.0～100质量％的X分子筛和0～5.0质量％的基质，所述吸附剂中X分子筛的阳离子位为II A族金属占据或为I A族金属和II A族金属共同占据。
本发明采用高、低两种不同氧化硅/氧化铝摩尔比的X分子筛作为复合层聚结型吸附剂的活性组分，并将含高硅X分子筛的吸附剂置于内层，含低硅X分子筛的吸附剂置于外层。所述复合层聚结型吸附剂适用于从C 8芳烃中吸附分离PX，以轻质芳烃作为解吸剂的吸附分离过程，可提高分离目的产物的纯度，提高吸附分离装置的生产能力。
附图说明
图1为实例1制备的低硅X分子筛的X射线衍射(XRD)谱图。
图2为实例1制备的低硅X分子筛的扫描电镜(SEM)照片。
图3为实例2制备的低硅X分子筛的SEM照片。
图4为实例3制备的高硅X分子筛的XRD谱图。
图5为实例3制备的高硅X分子筛的SEM照片。
图6为小型模拟移动床吸附分离示意图。
具体实施方式
本发明所描述的任何实施方式均可以与本文中的一种或多种其他实施方式自由结合，由此而形成的技术方案或技术思想均视为本发明原始公开或原始记载的一部分，而不应被视为是本文未曾披露或预期过的新内容，除非本领域技术人员认为该结合是明显不合理的。
本发明的复合层聚结型吸附剂中，X分子筛(也称为X型分子筛、X沸石或X型沸石)为吸附活性组分。具体而言，本发明将含高硅X分子筛的吸附剂作为内层(以下，有时也简称为内层)，将含低硅X分子筛的吸附剂作为外层(以下，有时也简称为外层)制成复合层吸附剂。
本发明的复合层聚结型吸附剂中，外层吸附剂含低氧化硅/氧化铝 摩尔比的X分子筛(低硅X分子筛)，有利于提高吸附剂对二甲苯(PX)相对于乙苯(EB)的吸附选择性，进行吸附分离时，外层吸附剂可较少地将乙苯吸附于吸附剂中。另一方面，内层吸附剂含高氧化硅/氧化铝摩尔比的X分子筛(高硅X分子筛)，能够提供更高的对二甲苯相对于间二甲苯(MX)以及对二甲苯相对于邻二甲苯(OX)的吸附选择性，由此，可以提高复合层吸附剂整体从C 8芳烃中吸附分离PX的性能。
本发明吸附剂中，以总量计的X分子筛含量是指吸附剂中含有的X分子筛的总含量，其包括高硅X分子筛、低硅X分子筛和高岭土矿物转晶后生成的X分子筛。基质含量是指内层和外层中所含的基质总量。另外，X分子筛阳离子位是指复合层聚结型吸附剂中所含X分子筛中所有的阳离子位。
可选地，本发明所述的复合层聚结型吸附剂包括95.0～99.5质量％的X分子筛和0.5～5.0质量％的基质。所述的复合层聚结型吸附剂还可包括97.0～99.5质量％的X分子筛和0.5～3.0质量％的基质。
在本发明的一个实施方式中，复合层聚结型吸附剂中低硅X分子筛的含量为X分子筛总量的5～40质量％、优选10～40质量％。
本发明中，外层所述的低硅X分子筛的氧化硅/氧化铝摩尔比为2.07～2.18。外层所述的低硅X分子筛优选为X分子筛自聚体，所述的自聚体由晶粒较小的纳米级X分子筛晶粒聚集而成。所述自聚体的粒径优选1.0～3.0微米、更优选1.0～2.0微米，纳米级X分子筛的晶粒粒径优选0.1～0.8纳米。
本发明中，内层所述的高硅X分子筛的氧化硅/氧化铝摩尔比为2.2～2.5，优选2.2～2.4。在本发明的一个实施方式中，所述高硅X分子筛的晶粒粒径优选0.1～2.5微米、更优选0.5～2.0微米。
本发明中，吸附剂中所述的基质为高岭土矿物经原位晶化转晶后的剩余物。所述的高岭土矿物选自高岭石、地开石、珍珠石、耐火石和埃洛石中的至少一种。
本发明所述吸附剂中，X分子筛的阳离子位为II A族金属占据或为I A族金属和II A族金属共同占据。所述的II A族金属优选Ba，I A族金属优选K、Li和Na中的至少一种。当X分子筛的阳离子位由Ba离子和I A族金属离子共同占据时，其中氧化钡与I A族金属氧化物的摩尔比(氧化钡/I A族金属氧化物)为2～60、优选5～46。
本发明所述的复合层吸附剂优选为小球状，小球的平均粒径优选300～850微米。
本发明所述吸附剂的制备方法，包括如下步骤：
(1)滚球成型：将高硅X分子筛与粘结剂按88～95∶5～12的质量比混合均匀，放入转盘中边滚动边喷水，使固体聚集成小球，作为内核；再加入低硅X分子筛与粘结剂按88～95∶5～12的质量比混合的粉料，继续喷水滚动以形成小球外层，取粒径300～850微米的小球，干燥后于500～700℃焙烧，
(2)原位晶化：取(1)步焙烧后的小球，用碱溶液进行原位晶化处理，然后干燥，所述的碱溶液为氢氧化钠和氢氧化钾的混合溶液，混合溶液中氢氧根离子浓度为0.1～3.0摩尔/升，K +/(Na ++K +)摩尔比为0.1～0.6，
(3)离子交换：用II A族金属的可溶性盐溶液或者用II A族金属的可溶性盐和I A族金属的可溶性盐的溶液对(2)步干燥后的小球进行阳离子交换，然后干燥、活化。
上述方法中，(1)步是将X分子筛与粘结剂滚球成型，滚球时将不同氧化硅/氧化铝摩尔比的X分子筛分别与粘结剂混合，分成先后两批次滚动成型。即，先将高硅X分子筛与粘结剂的混合物滚动成小球，作为内核，即内吸附剂层，再加入低硅X分子筛与粘结剂的混合物滚动，形成小球外层，即形成外吸附剂层。
在本发明的一个实施方式中，(1)步滚球成型所用低硅X分子筛为加入的X分子筛总量的5～40质量％、优选10～40质量％。(1)步滚球成型所用高硅X分子筛与粘结剂的质量比优选10～15∶1，所用低硅X分子筛与粘结剂的质量比优选10～15∶1。
在本发明的一个实施方式中，所述粘结剂为高岭土矿物。所述高岭土矿物选自高岭石、地开石、珍珠石、耐火石、埃洛石或它们的混合物。所述高岭土矿物中晶化物质的质量分数至少为90％、优选93～99％。
在本发明的一个实施方式中，(1)步滚球成型的设备可为转盘、糖衣锅或滚筒。滚球成型时，将混合均匀的固体原料放入转动设备中，边滚动边喷水使固体粉末粘附团聚成小球。滚球时水的加入量为固体总质量的6～22％、优选6～16％。
(1)步滚动成球后的小球，经过筛分，取粒径为300～850微米的小球，将其干燥、于500～700℃焙烧制得吸附剂前体。所述干燥温度优选60～110℃，时间优选2～12小时。在本发明的一个实施方式中，焙烧温度优选520～600℃，时间优选1.0～6.0小时。经过焙烧后，小球内的高岭土矿物转化为偏高岭土，以便于(2)步原位转晶为X分子筛。
本发明上述方法中，(2)步为将(1)步制备的小球进行原位晶化的步骤，原位晶化所用的碱液为氢氧化钠和氢氧化钾混合溶液，其中氢氧根离子的浓度优选0.2～1.6摩尔/升，K +/(Na ++K +)摩尔比优选0.15～0.45。
(2)步中用氢氧化钠与氢氧化钾的混合溶液对高岭土矿物进行原位晶化处理时的液/固比优选1.5～5.0L/kg。将高岭土矿物原位晶化为X型分子筛的晶化温度优选80～100℃、更优选85～100℃，时间优选0.5～8小时。将原位晶化后的小球干燥，所述的干燥温度优选60～110℃，时间优选2～12小时。
本发明上述方法中，(3)步为对(2)步干燥后的小球进行阳离子交换的步骤。所述的II A族金属优选Ba。所述II A族金属的可溶性盐优选硝酸钡或氯化钡。所述I A族金属的可溶性盐优选其硝酸盐和氯化物中的至少一种。所述I A族金属优选为K、Li和Na中的至少一种。
(3)步所述阳离子交换可在釜式或柱式容器中进行，优选在柱式容器中连续交换。交换的温度优选40～120℃、更优选85～95℃，时间优选5～25小时、更优选8～16小时，交换液体积空速优选0.2～10时 -1、更优选2～8时 -1。
在本发明的一个实施方式中，复合层聚结型吸附剂中同时含有选自II A族金属的离子和选自IA族金属的离子的情况下，可采用II A族金属的可溶性盐和IA族金属的可溶性盐的混合溶液同时对(2)步干燥后的小球进行阳离子交换，也可分别配制II A族金属的可溶性盐溶液和IA族金属的可溶性盐溶液，然后分别对(2)步干燥后的小球进行阳离子交换，可先进行II A族金属的离子交换，再进行IA族金属的离子交换，或先进行IA族金属的离子交换，再进行II A族金属的离子交换。
将(3)步阳离子交换后的小球进行洗涤、干燥、活化，除去钠离 子和水，得到复合层聚结型吸附剂。
(3)步所述干燥、活化可在流动的热空气或氮气中进行，所述干燥温度优选40～120℃、更优选60～110℃，时间优选5～60小时、更优选18～40小时。所述的活化温度优选150～250℃、更优选160～220℃，时间优选5～20小时、更优选5～10小时。
本发明中，所述低硅X分子筛优选为X分子筛自聚体，其制备方法包括如下步骤：
(i)将硅源、铝源、水和氢氧化钠按照摩尔比为SiO 2/Al 2O 3＝2～25，Na 2O/Al 2O 3＝3～30，H 2O/Al 2O 3＝100～500的比例混合，在0～60℃、优选20～50℃老化1～72小时，制成导向剂，
(ii)将无机碱、钾源、铝源、硅源、(i)步制备的导向剂和水混合均匀形成分子筛合成体系，使得合成体系中各物料的摩尔配比为：SiO 2/Al 2O 3＝2.0～2.5，M 2O/SiO 2＝1.8～4.0，H 2O/SiO 2＝40～96，K +/(K ++Na +)＝0.10～0.65，其中M为Na和K，所加导向剂中Al 2O 3的量与分子筛合成体系中总的Al 2O 3的摩尔比为0.01～2.0％、优选0.1～1.0％，
(iii)将(ii)步的分子筛合成体系于50～120℃水热晶化2～72小时，晶化后所得固体经洗涤、干燥，得到X分子筛自聚体。
上述方法(i)步中，优选将硅源、铝源、水和氢氧化钠按照摩尔比为SiO 2/Al 2O 3＝8～21，Na 2O/Al 2O 3＝10～25，H 2O/Al 2O 3＝100～400的比例混合。
上述方法(ii)步中，合成体系中各物料的摩尔配比优选为：SiO 2/Al 2O 3＝2.0～2.5，M 2O/SiO 2＝2.5～4.0，H 2O/SiO 2＝50～80。K +/(K ++Na +)优选0.2～0.5。
本发明所述的高硅X分子筛可用常规方法制备。优选通过以下方法制备，其包括如下步骤：
(ii-1)将无机碱、铝源、硅源、上述(i)步制备的导向剂和水混合均匀形成分子筛合成体系，使得合成体系中各物料的摩尔配比为：SiO 2/Al 2O 3＝2.5～3.0，Na 2O/SiO 2＝0.7～1.8，H 2O/SiO 2＝40～96，所加导向剂中Al 2O 3的量与分子筛合成体系中总的Al 2O 3的摩尔比为0.01～2.0％、优选0.1～1.0％，
(iii-1)将(ii-1)步的分子筛合成体系于50～120℃水热晶化2～72小时，晶化后所得固体经洗涤、干燥，得到本发明所述的高硅X分子筛。
上述制备X分子筛方法中，合成分子筛所用的铝源可选自低碱度偏铝酸钠、氧化铝、氢氧化铝、硫酸铝、氯化铝、硝酸铝和铝酸钠中的至少一种。所述低碱度偏铝酸钠中Na 2O含量为7.6～23.7质量％、优选8～14质量％，Al 2O 3含量优选7.0～15.0质量％。
上述制备X分子筛方法中，合成分子筛所用的钾源选自氢氧化钾、氟化钾、氯化钾、溴化钾、碘化钾、碳酸钾、硝酸钾和硫酸钾中的至少一种。
上述制备X分子筛方法中，合成分子筛所用的硅源选自正硅酸乙酯、硅溶胶、水玻璃、硅酸钠、硅胶和白炭黑中的至少一种。
上述制备X分子筛方法中，所述无机碱优选氢氧化钠。
上述制备X分子筛方法中，所述将分子筛合成体系进行水热晶化的温度优选为70～110℃，更优选80～100℃，时间优选为3～24小时。
本发明提供的复合层吸附剂适用于从碳八芳烃中液相吸附分离对二甲苯，吸附分离所用的解吸剂优选甲苯。所述液相吸附分离可采用多柱串联方式进行，也可采用借助旋转阀或电磁阀组实现的模拟移动床进行。吸附分离的操作压力为0.3～1.5MPa，操作温度为120～180℃。
衡量吸附剂性能的三个重要指标为吸附容量、选择性和分离目标产物(如对二甲苯)的吸附、解析速率。
为评价吸附剂的吸附性能，可使用动态脉冲实验装置测定吸附剂的吸附选择性和分离目标产物的吸附、解吸速率。该装置由进料系统、吸附柱、加热炉、压力控制阀等组成。吸附柱为Φ6×1800毫米的不锈钢管。吸附柱下端入口与进料和氮气系统相连，上端出口接压力控制阀，再与流出物收集器连接。
吸附剂吸附选择性的测定方法为：将称量的粒径为300～850μm的被测吸附剂颗粒装入吸附柱震实，在氮气气氛中于160～190℃脱水活化；再通入解吸剂排除系统中的气体。将系统压力升至0.8MPa，温度升至145℃，停止通入解吸剂，以1.0时 -1的体积空速通入8毫升脉冲进料液，进料液中含有不被吸附的示踪剂，之后以同样的体积空速通入解吸剂，每隔2分钟取3滴脱附液样品，用气相色谱分析。以脱附用解吸剂体积为横坐标，脉冲进料液各组分浓度为纵坐标，绘制出脉冲进料液各组分的脱附曲线。其中，不被吸附的示踪剂可用来获得吸附系统的死体积。将示踪剂半峰宽的中点作为零点，测定各组分半峰宽中 点到零点的净保留体积R，任意组分的净保留体积与吸附平衡时的分配系数成正比，反映了各组分与吸附剂间的作用力，两组分净保留体积之比即为选择性β，如PX的净保留体积与EB的净保留体积之比即为吸附剂对于PX和EB吸附性能之比，为PX相对于EB的吸附选择性，记为β P/E；PX的净保留体积与MX的净保留体积之比即为吸附剂对于PX和MX吸附性能之比，为PX相对于MX的吸附选择性，记为β P/M；PX的净保留体积与OX的净保留体积之比即为吸附剂对于PX和OX吸附性能之比，为PX相对于OX的吸附选择性，记为β P/O。
为了表示PX的吸附、解吸速率和PX与T(甲苯)之间的吸附选择性，引入PX的吸附速率[S A] 10-90和解吸速率[S D] 90-10。吸附速率[S A] 10-90为PX的脉冲脱附曲线中PX浓度从10％上升到90％所需的解吸剂体积，解析速率[S D] 90-10为脱附曲线中PX浓度从90％下降到10％所需的解吸剂体积，[S A] 10-90/[S D] 90-10比值定义为PX与解吸剂之间的吸附选择性β PX/T。
下面通过实例进一步说明本发明，但本发明并不限于此。
实例中，采用甲苯气相吸附实验测定吸附剂的吸附容量，具体操作方法为：在35℃下，使携带甲苯的氮气(甲苯分压为0.5MPa)与一定质量的吸附剂接触，直到甲苯达到吸附平衡。根据甲苯吸附前后吸附剂的质量差由下式计算出被测吸附剂的吸附容量。
Figure PCTCN2020098147-appb-000001
其中，C为吸附容量，单位为毫克/克；m 1为吸附甲苯前被测吸附剂的质量，单位为克；m 2为吸附甲苯后被测吸附剂的质量，单位为克。
测定吸附剂吸附性能方法：取50克吸附剂，进行液相脉冲实验测其吸附选择性和PX的吸附、解吸速率，实验所用解吸剂为30体积％的甲苯(T)和70体积％的正庚烷。脉冲进料液组成为各占5体积％的乙苯(EB)、对二甲苯(PX)、间二甲苯(MX)、邻二甲苯(OX)、正壬烷(NC9)和75体积％的解吸剂，其中正壬烷为示踪剂。
实例1
以下实例制备本发明所述的低硅X分子筛
(1)制备导向剂
将4.02千克氢氧化钠，7.81千克去离子水、5.32千克低碱度偏铝酸钠溶液(Al 2O 3含量为9.99质量％、Na 2O含量为10.93质量％，下同)和23.24千克水玻璃(SiO 2含量为20.17质量％、Na 2O含量为6.32质量％，下同)加入反应釜中，搅拌混合均匀，35℃静置老化24小时，得到导向剂。导向剂中各物料的摩尔配比为SiO 2/Al 2O 3＝15，Na 2O/Al 2O 3＝16，H 2O/Al 2O 3＝320。
(2)制备低硅X分子筛
将7.50千克氢氧化钠、8.67千克氢氧化钾、51.59千克去离子水、35.16千克低碱度偏铝酸钠溶液、23.30千克的水玻璃和0.54千克(1)步制备的导向剂加入反应釜中，搅拌混合均匀形成分子筛合成体系。分子筛合成体系中各物料总的摩尔配比为：SiO 2/Al 2O 3＝2.30，M 2O/SiO 2＝3.25，H 2O/SiO 2＝70，其中M为K和Na，K +/(K ++Na +)＝0.30，加入的导向剂中Al 2O 3的量与分子筛合成体系中总的Al 2O 3的摩尔比为0.2％。
将上述分子筛合成体系继续搅拌半小时，形成乳白色溶胶，转移到反应釜中，95℃水热晶化12小时，过滤，所得固体用去离子水洗涤至滤液pH＝8～9，80℃干燥12小时，得到低硅X分子筛a，其XRD谱图见图1，显示为纯X分子筛，扫描电镜照片(SEM)见图2，显示低硅X分子筛为X分子筛晶粒自聚体，自聚体的粒径为1.4微米，自聚体中的X分子筛晶粒粒径为0.6纳米，X射线荧光光谱(XRF)测得其氧化硅/氧化铝摩尔比为2.09。
实例2
按实例1方法制备低硅X分子筛，不同的是(2)步中将5.84千克氢氧化钠、11.56千克氢氧化钾、53.73千克去离子水、32.35千克低碱度偏铝酸钠溶液、23.33千克的水玻璃和0.49千克(1)步制备的导向剂加入反应釜中，搅拌混合均匀形成分子筛合成体系。分子筛合成体系中各物料总的摩尔配比为：SiO 2/Al 2O 3＝2.50，M 2O/SiO 2＝3.25，H 2O/SiO 2＝70，其中M为K和Na，K +/(K ++Na +)＝0.40，加入的导向剂中Al 2O 3的量与分子筛合成体系中总的Al 2O 3的摩尔比为0.2％。
将上述分子筛合成体系水热晶化，过滤，洗涤干燥后得到低硅X 分子筛c，XRD显示其为纯X分子筛，扫描电镜照片见图3，显示低硅X分子筛为X分子筛晶粒自聚体，自聚体粒径为1.3微米，自聚体中的X分子筛晶粒粒径为0.5纳米，XRF测得的氧化硅/氧化铝摩尔比为2.16。
实例3
制备本发明所述的高硅X分子筛
将1.07千克氢氧化钠、58.40千克去离子水、30.18千克低碱度偏铝酸钠溶液、23.34千克的水玻璃和0.46千克实例1(1)步制备的导向剂加入反应釜中，搅拌混合均匀形成分子筛合成体系。分子筛合成体系中各物料总的摩尔配比为SiO 2/Al 2O 3＝2.70，Na 2O/SiO 2＝1.25，H 2O/SiO 2＝70，加入的导向剂中Al 2O 3的量与分子筛合成体系中总的Al 2O 3的摩尔比为0.2％。
将上述分子筛合成体系继续搅拌半小时，形成乳白色溶胶，转移到反应釜中，95℃水热晶化12小时，过滤，所得固体用去离子水洗涤至滤液pH＝8～9，80℃干燥12小时，得到高硅X分子筛b，其XRD谱图见图4，显示为纯X分子筛，扫描电镜照片(SEM)见图5，显示其晶粒粒径为1.0微米，基本没有自聚体形成，XRF测得的氧化硅/氧化铝摩尔比为2.26。
实例4
制备本发明所述的复合层吸附剂
(1)滚球成型：取88千克(灼基质量，下同)实例3制备的高硅X分子筛b和6.62千克高岭土(晶化物质含量90质量％、下同)混合均匀，得混合物I，5千克实例1制备的低硅X分子筛a和0.38千克高岭土混合均匀，得混合物II。将混合物I放入转盘中边滚动边喷入适量的去离子水，使固体粉末聚集成小球，作为内核，再加入混合物II继续喷水滚动成型，形成小球外层。滚球时喷入的水量为固体粉末总量的8质量％。经筛分，取粒径为300～850微米的小球，80℃干燥10小时、540℃焙烧4小时。
(2)原位晶化：将64千克(1)步焙烧后的小球置于200升氢氧化钠与氢氧化钾混合溶液中，混合溶液中氢氧根离子浓度为0.3摩尔/ 升，K +/(Na ++K +)摩尔比为0.2，于95℃原位晶化处理4小时，取晶化后固体水洗至洗涤液pH小于10，80℃干燥10小时。
(3)离子交换：将130毫升(2)步干燥后的小球装入离子交换柱中进行阳离子交换，用0.18摩尔/升的硝酸钡和0.07摩尔/升的氯化钾混合溶液以6.0时 -1的体积空速于0.1MPa、94℃连续交换8小时，混合溶液总用量为5000毫升。离子交换完成后，将固体于70℃用700毫升去离子水洗涤，70℃氮气气氛干燥30小时，氮气气氛中于180℃脱水活化6小时，制得吸附剂A，其内层为含高硅X分子筛的内吸附剂层，外层为含低硅X分子筛的外吸附剂层，其中X分子筛含量为98.6质量％，基质含量为1.4质量％，吸附剂中BaO与K 2O的摩尔比为36。
取1.0克吸附剂A，测定其甲苯吸附容量，结果见表1。
取50克吸附剂A，进行液相脉冲实验测定其吸附选择性和PX的吸附、解吸速率，测得的吸附性能见表1。
实例5
按实例4的方法制备复合层吸附剂，不同的是(1)步中取78千克实例3制备的高硅X分子筛b和5.87千克高岭土混合均匀制成混合物I，15千克实例1制备的低硅X分子筛a和1.13千克高岭土混合均匀制成混合物II，经滚球成型、原位晶化和离子交换得到吸附剂B，其内层为含高硅X分子筛的内吸附剂层，外层为含低硅X分子筛的外吸附剂层，其中X分子筛含量为98.4质量％，基质含量为1.6质量％，分别取1克及50克吸附剂B，测定甲苯吸附容量及吸附性能，结果见表1。
实例6
按实例4的方法制备复合层吸附剂，不同的是(1)步中取68千克实例3制备的高硅X分子筛b和5.13千克高岭土混合均匀制成混合物I，25千克实例1制备的低硅X分子筛a和1.87千克高岭土混合均匀制成混合物II，经滚球成型、原位晶化和离子交换得到吸附剂C，其内层为含高硅X分子筛的内吸附剂层，外层为含低硅X分子筛的外吸附剂层，其中X分子筛含量为98.5质量％，基质含量为1.5质量％，分别取1克及50克吸附剂C，测定甲苯吸附容量及吸附性能，结果见表 1。
实例7
按实例4的方法制备复合层吸附剂，不同的是(1)步中取78千克实例3制备的高硅X分子筛b和5.87千克高岭土混合均匀制成混合物I，15千克实例2制备的低硅X分子筛c和1.13千克高岭土混合均匀制成混合物II，经滚球成型、原位晶化和离子交换得到吸附剂D，其内层为含高硅X分子筛的内吸附剂层，外层为含低硅X分子筛的外吸附剂层，其中X分子筛含量为97.9质量％，基质含量为2.1质量％，分别取1克及50克吸附剂D，测定甲苯吸附容量及吸附性能，结果见表1。
实例8
按实例4的方法制备复合层吸附剂，不同的是(1)步中取68千克实例3制备的高硅X分子筛b和5.13千克高岭土混合均匀制成混合物I，25千克实例2制备的低硅X分子筛c和1.87千克高岭土混合均匀制成混合物II，经滚球成型、原位晶化和离子交换得到吸附剂E，其内层为含高硅X分子筛的内吸附剂层，外层为含低硅X分子筛的外吸附剂层，其中X分子筛含量为98.0质量％，基质含量为2.0质量％，分别取1克及50克吸附剂E，测定甲苯吸附容量及吸附性能，结果见表1。
实例9
按实例4的方法制备复合层吸附剂，不同的是(1)步中取58千克实例3制备的高硅X分子筛b和4.37千克高岭土混合均匀制成混合物I，35千克实例2制备的低硅X分子筛c和2.63千克高岭土混合均匀制成混合物II，经滚球成型、原位晶化和离子交换得到吸附剂F，其内层为含高硅X分子筛的内吸附剂层，外层为含低硅X分子筛的外吸附剂层，其中X分子筛含量为98.2质量％，基质含量为1.8质量％，分别取1克及50克吸附剂F，测定甲苯吸附容量及吸附性能，结果见表1。
对比例1
将93千克实例1制备的低硅X分子筛a与7千克高岭土混合均匀，放入转盘中边滚动边喷入适量的去离子水，使固体粉末聚集成小球，滚球时喷入的水量为固体粉末总量的8质量％。经筛分，取粒径为300～850微米的小球，80℃干燥10小时、540℃焙烧4小时。再按照实例4中(2)步的方法原位晶化，(3)步的方法进行离子交换，制得吸附剂G，其中X分子筛含量为98.3质量％，基质含量为1.7质量％，分别取1克及50克吸附剂G，测定甲苯吸附容量及吸附性能，结果见表1。
对比例2
按对比例1的方法制备吸附剂，不同的是将93千克实例2制备的高硅X分子筛b与7千克高岭土混合均匀，经滚球成型、原位晶化和离子交换得到吸附剂H，其中X分子筛含量为97.5质量％，基质含量为2.5质量％。分别取1克及50克吸附剂H，测定甲苯吸附容量及吸附性能，结果见表1。
对比例3
将25千克实例1制备的低硅X分子筛a、68千克实例2制备的高硅X分子筛b与7千克高岭土混合均匀后，放入转盘中边滚动边喷入适量的去离子水，使固体粉末聚集成小球，滚球时喷入的水量为固体粉末总量的8质量％。经筛分，取粒径为300～850微米的小球，80℃干燥10小时、540℃焙烧4小时。再按照实例4中(2)步的方法原位晶化，(3)步的方法进行离子交换，制得吸附剂I，其中X分子筛含量为98.5质量％，基质含量为1.5质量％。分别取1克及50克吸附剂I，测定甲苯吸附容量及吸附性能，结果见表1。
对比例4
按对比例3的方法制备吸附剂，不同的是用25千克实例2制备的低硅X分子筛c代替低硅X分子筛a，制得吸附剂J，其中X分子筛含量为98.0质量％，基质含量为2.0质量％。分别取1克及50克吸附剂J，测定甲苯吸附容量及吸附性能，结果见表1。
实例10
在连续逆流的小型模拟移动床上用吸附剂A进行分离对二甲苯实验。
所述小型模拟移动床装置包括24根串联的吸附柱，每根柱长195毫米，柱内直径30毫米，吸附剂的总装填量为3300毫升。在串联的24根柱子首尾两端用循环泵连接构成一个封闭的环路，如图6所示。吸附原料、解吸剂、提取液、提余液四股进、出物料将24根吸附柱分成四个区段，即吸附原料(柱15)和提余液(柱21)之间的7根吸附柱为吸附区，提取液(柱6)和吸附原料(柱14)之间的9根吸附柱为提纯区，解吸剂(柱1)和提取液(柱5)之间的5根吸附柱为解吸区，提余液(柱22)和解吸剂(柱24)之间的3根吸附柱为缓冲区。整个吸附体系的温度控制为145℃，压力为0.8MPa。
操作过程中，分别以2118毫升/时和1925毫升/时的流量向上述模拟移动床中连续注入解吸剂甲苯和原料，并分别以1540毫升/时和2503毫升/时的流量将提取液和提余液抽出装置。所述原料组成为：乙苯9.3质量％、对二甲苯18.5质量％、间二甲苯45.5质量％、邻二甲苯17.4质量％、非芳烃组分9.3质量％。
设定循环泵流量为4890毫升/时，每隔80秒四股物料同时向与液体流向相同的方向移动1根吸附柱(图6中，从实线至虚线位置，以此类推)。在稳定的操作状态下吸附剂A获得的对二甲苯的纯度为99.80质量％，收率为98.53质量％。
实例11
在小型模拟移动床装置上装填吸附剂B，按实例10的方法进行吸附分离对二甲苯实验，稳定操作状态下获得的对二甲苯的纯度为99.80质量％，收率为98.95质量％。
对比例5
在小型模拟移动床装置上装填对比吸附剂G，按实例10的方法进行吸附分离对二甲苯实验，稳定操作状态下得到的对二甲苯的纯度为98.71质量％，收率为97.55质量％。
对比例6
在小型模拟移动床装置上装填对比吸附剂H，按实例10的方法进行吸附分离对二甲苯实验，稳定操作状态下得到的对二甲苯的纯度为98.86质量％，收率为97.43质量％。
对比例7
在小型模拟移动床装置上装填对比吸附剂I，按实例10的方法进行吸附分离对二甲苯实验，稳定操作状态下得到的对二甲苯的纯度为99.26质量％，收率为98.05质量％。
对比例8
在小型模拟移动床装置上装填对比吸附剂J，按实例10的方法进行吸附分离对二甲苯实验，稳定操作状态下得到的对二甲苯的纯度为99.10质量％，收率为98.01质量％。
表1
Figure PCTCN2020098147-appb-000002

Claims (18)

  1. 复合层聚结型吸附剂，包括含低硅X分子筛的外吸附剂层和含高硅X分子筛的内吸附剂层，所述的低硅X分子筛的氧化硅/氧化铝摩尔比为2.07～2.18，所述的高硅X分子筛的氧化硅/氧化铝摩尔比为2.2～2.5，以吸附剂的总量计，所述吸附剂包括95.0～100质量％的X分子筛和0～5.0质量％的基质，所述吸附剂中X分子筛的阳离子位为II A族金属占据或为I A族金属和II A族金属共同占据。
  2. 按照权利要求1所述的吸附剂，其特征在于所述吸附剂包括95.0～99.5质量％的X分子筛和0.5～5.0质量％的基质。
  3. 按照权利要求1所述的吸附剂，其特征在于吸附剂中所述低硅X分子筛的含量为X分子筛总量的5～40质量％。
  4. 按照权利要求1所述的吸附剂，其特征在于所述低硅X分子筛为X分子筛自聚体，X分子筛自聚体的粒径为1.0～3.0微米，纳米级X分子筛的晶粒粒径为0.1～0.8纳米。
  5. 按照权利要求1所述的吸附剂，其特征在于所述高硅X分子筛的晶粒粒径为0.1～2.5微米。
  6. 按照权利要求1所述的吸附剂，其特征在于所述的II A族金属为Ba，I A族金属为K、Li和Na中的至少一种。
  7. 按照权利要求1所述的吸附剂，其特征在于所述的基质为高岭土矿物经原位晶化转晶后的剩余物。
  8. 按照权利要求7所述的吸附剂，其特征在于所述的高岭土矿物选自高岭石、地开石、珍珠石、耐火石和埃洛石中的至少一种。
  9. 权利要求1或2所述吸附剂的制备方法，包括如下步骤：
    (1)滚球成型：将高硅X分子筛与粘结剂按88～95∶5～12的质量比混合均匀，放入转盘中边滚动边喷水，使固体聚集成小球，作为内核，再加入低硅X分子筛与粘结剂按88～95∶5～12的质量比混合的粉料，继续喷水滚动形成小球外层，取粒径300～850微米的小球，干燥后于500～700℃焙烧，
    (2)原位晶化：取(1)步焙烧后的小球，用碱溶液进行原位晶化处理，然后干燥，所述的碱溶液为氢氧化钠和氢氧化钾的混合溶液，混合溶液中氢氧根离子浓度为0.1～3.0摩尔/升，K +/(Na ++K +)摩尔比 为0.1～0.6，
    (3)离子交换：用II A族金属的可溶性盐溶液或者用II A族金属的可溶性盐和I A族金属的可溶性盐的溶液对(2)步干燥后的小球进行阳离子交换，然后干燥、活化。
  10. 按照权利要求9所述的方法，其特征在于(1)步中，滚动成球水的加入量为固体粉料总量的6～22质量％。
  11. 按照权利要求9所述的方法，其特征在于(1)步中低硅X分子筛占加入的X分子筛总量的5～40质量％。
  12. 按照权利要求9所述的方法，其特征在于用碱溶液进行原位晶化处理的温度为80～100℃。
  13. 按照权利要求9所述的方法，其特征在于(3)步中，用II A族金属的可溶性盐和I A族金属的可溶性盐的混合溶液对(2)步干燥后的小球进行阳离子交换；或用II A族金属的可溶性盐溶液或I A族金属的可溶性盐的溶液分别对(2)步干燥后的小球进行阳离子交换。
  14. 按照权利要求9所述的方法，其特征在于所述II A族金属的可溶性盐选自硝酸钡或氯化钡，I A族金属的可溶性盐选自其硝酸盐和氯化物中的至少一种。
  15. 按照权利要求14所述的方法，其特征在于所述的I A族金属为K、Li和Na中的至少一种。
  16. 按照权利要求9所述的方法，其特征在于所述的低硅X分子筛为X分子筛自聚体，其制备方法包括如下步骤：
    (i)将硅源、铝源、水和氢氧化钠按照摩尔比为SiO 2/Al 2O 3＝2～25，Na 2O/Al 2O 3＝3～30，H 2O/Al 2O 3＝100～500的比例混合，在0～60℃老化1～72小时，制成导向剂，
    (ii)将无机碱、钾源、铝源、硅源、(i)步制备的导向剂和水混合均匀形成分子筛合成体系，使得合成体系中各物料的摩尔配比为：SiO 2/Al 2O 3＝2.0～2.5，M 2O/SiO 2＝1.8～4.0，H 2O/SiO 2＝40～96，K +/(K ++Na +)＝0.10～0.65，其中M为Na和K，所加导向剂中Al 2O 3的量与分子筛合成体系中总的Al 2O 3的摩尔比为0.01～2.0％，
    (iii)将(ii)步的分子筛合成体系于50～120℃水热晶化2～72小时，晶化后所得固体经洗涤、干燥，得到X分子筛自聚体。
  17. 按照权利要求16所述的方法，其特征在于所述铝源选自低碱 度偏铝酸钠、氧化铝、氢氧化铝、硫酸铝、氯化铝、硝酸铝和铝酸钠中的至少一种。
  18. 按照权利要求17所述的方法，其特征在于所述的低碱度偏铝酸钠中Na 2O含量为7.6～23.7质量％，Al 2O 3含量为7.0～15.0质量％。
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