CN116422289B - N is got rid of from refinery gas 2 Molecular sieve of (2), preparation method and application thereof - Google Patents

N is got rid of from refinery gas 2 Molecular sieve of (2), preparation method and application thereof Download PDF

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CN116422289B
CN116422289B CN202310366831.XA CN202310366831A CN116422289B CN 116422289 B CN116422289 B CN 116422289B CN 202310366831 A CN202310366831 A CN 202310366831A CN 116422289 B CN116422289 B CN 116422289B
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molecular sieve
rho
gas
adsorption
refinery
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CN116422289A (en
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胡云峰
包强
陈智睿
王博萱
胡怡
梁丹
夏海月
孙鹏来
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Daqing Guanghe Technology Co ltd
Northeast Petroleum University
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Northeast Petroleum University
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
    • 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
    • B01J20/16—Alumino-silicates
    • B01J20/18—Synthetic zeolitic molecular sieves
    • B01J20/186—Chemical treatments in view of modifying the properties of the sieve, e.g. increasing the stability or the activity, also decreasing the activity
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/02—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by adsorption, e.g. preparative gas chromatography
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
    • B01J20/30—Processes for preparing, regenerating, or reactivating
    • B01J20/305—Addition of material, later completely removed, e.g. as result of heat treatment, leaching or washing, e.g. for forming pores
    • B01J20/3057—Use of a templating or imprinting material ; filling pores of a substrate or matrix followed by the removal of the substrate or matrix
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
    • B01J20/30—Processes for preparing, regenerating, or reactivating
    • B01J20/3078—Thermal treatment, e.g. calcining or pyrolizing
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
    • B01J20/30—Processes for preparing, regenerating, or reactivating
    • B01J20/3085—Chemical treatments not covered by groups B01J20/3007 - B01J20/3078
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • 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
    • C01B39/46—Other types characterised by their X-ray diffraction pattern and their defined composition
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • 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
    • C01B39/46—Other types characterised by their X-ray diffraction pattern and their defined composition
    • C01B39/48—Other types characterised by their X-ray diffraction pattern and their defined composition using at least one organic template directing agent
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2253/00—Adsorbents used in seperation treatment of gases and vapours
    • B01D2253/10—Inorganic adsorbents
    • B01D2253/106—Silica or silicates
    • B01D2253/108—Zeolites
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2257/00—Components to be removed
    • B01D2257/10—Single element gases other than halogens
    • B01D2257/102—Nitrogen
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2002/00—Crystal-structural characteristics
    • C01P2002/70—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data
    • C01P2002/72—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data by d-values or two theta-values, e.g. as X-ray diagram
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/01—Particle morphology depicted by an image
    • C01P2004/03—Particle morphology depicted by an image obtained by SEM

Abstract

The invention discloses a preparation method and application of a silicon-aluminum molecular sieve for removing nitrogen from refinery gas, wherein the molecular sieve is a silicon-aluminum molecular sieve with RHO configuration; the preparation method of the molecular sieve comprises the steps of carrying out ion exchange on a potassium salt and an RHO silicon aluminum molecular sieve to obtain the K-RHO silicon aluminum molecular sieve; due to the complex composition of the refinery gas, the composition contains H 2 And CH (CH) 4 、C 2 H 6 、C 2 H 4 、C 3 H 8 、C 3 H 6 And low molecular hydrocarbon components are difficult to separate. Solves the problem that the prior method is used for removing N from the multi-component refinery gas 2 The problem of non-ideal adsorbent performance in the PSA process, and an effective technical means is provided for improving the heat value of refinery gas.

Description

N is got rid of from refinery gas 2 Molecular sieve of (2), preparation method and application thereof
Technical Field
The invention relates to a molecular sieve, in particular to a molecular sieve which comprises a molecular sieve bodyRemoval of N from refinery gas 2 A preparation method and application thereof, belonging to the field of gas adsorption separation.
Background
Refinery gases of different compositions are produced after crude oil is extracted and sent to a refinery for processing. The low molecular hydrocarbon is removed from the refinery gas, and N is needed before the refinery equipment is started 2 Purging the pipeline, boosting the equipment to remove residual impurities and reach the working pressure of the equipment, and then conveying the refinery gas to each device for full use; at the same time, in order to ensure the production safety of the ethylene plant in the refinery, the ethylene refrigeration compressor needs to select a proper sealing arrangement, and when the plant is in trial stop, N 2 Can be used as auxiliary buffer gas to protect the sealing structure from being polluted. Thus, finally, there is not only hydrogen, methane, ethane, ethylene and other small-molecular hydrocarbons present in the refinery gas, but also a large amount of N 2 . This part N 2 The heat value of the refinery gas can be reduced, the combustion performance of the refinery gas is affected, and N is removed from the refinery gas 2 Can effectively improve the economic value of the refinery gas.
The existing cryogenic rectification, solvent absorption, membrane separation and adsorption separation are commonly used for separating N 2 But for separating N from complex-composition refinery gases 2 There are various disadvantages.
The low temperature rectification process is to liquefy the material gas with high pressure through throttle expansion for several times and separate the two gases based on the difference in the relative volatilities of nitrogen and methane. In the main component of the refinery gas, N 2 Has a boiling point of 77K, H 2 Boiling point of 20.2K, CH 4 Has a boiling point of 112K, C 2 H 6 Boiling point of 185K, C 2 H 4 Is 169.3K. Although N 2 Has a larger boiling point difference with other components, but still requires low temperature conditions to separate N from refinery gas 2 . In recent years, cryogenic rectification processes have made great progress in optimizing the flow and operation. Such as placing a reboiler/condenser in the lower pressure column to reduce equipment and refrigeration losses; the higher pressure column is provided with a reboiler to increase N 2 Is removed from (a)Effects, etc.
Chinese patent publication No. CN106500460a discloses a nitrogen removal device for natural gas liquefaction. Such devices require that the raw material composition must remain relatively fixed; when the composition of the raw materials changes greatly in a short time, the deep freezing denitrification device often cannot normally operate. The deep freezing process is suitable for large-scale denitrification device (the treatment capacity is preferably more than 1.4X10) for treating high-pressure natural gas with relatively high nitrogen content 6 m 3 /d) and the nitrogen removed does not need to be boosted again, so that most of the energy required for denitrification can be provided by the work of expansion of this portion of nitrogen. The cryogenic rectification technology requires huge equipment, high requirements and high energy consumption, and therefore equipment investment is very large.
The solvent absorption process utilizes the solubility difference of hydrocarbon such as methane and the like and nitrogen in a (special) solvent system to realize separation. Taking the most representative Mala process in the process as an example, the adopted patent solvent is mainly C with branched methyl, ethyl and propyl 8 ～C 10 And (3) aromatic hydrocarbon, and adding some organic solvents such as propylene carbonate, sulfolane, polyethylene glycol dimethyl ether and the like, and realizing the separation of nitrogen and hydrocarbon by combining the regulation and control of technological parameters in the operation process.
A petroleum conditioning plant process is disclosed in U.S. patent No. US10287509B 2. The process is a typical solvent absorption process, adopts an absorption flash evaporation technical scheme, and realizes regeneration by step-by-step depressurization flash evaporation. The solvent system for the Mala process is characterized by being difficult to foam, difficult to degrade, basically free of corrosiveness, low in vapor pressure and freezing point, and suitable for sulfur-containing or sulfur-free gases. Meanwhile, the process raw material gas does not need deep dehydration, so that the investment and the cost are greatly reduced. The process can also be combined with the recovery of natural gas condensate (GL) by a freezing method, thereby improving the recovery rate of NGL.
The feed gas stream was cooled to 247K by a propane refrigeration system and a small amount of condensate was removed and fed to the lower portion of the solvent absorber at an operating pressure of about 2.7 MPa. The raw material gas and the absorption solvent descending from the top of the tower are subjected to gas-liquid mass transfer in the tower from bottom to top, so that hydrocarbon components mainly comprising methane are selectively absorbed and enter a liquid phase. When the feed gas leaves the top of the column, it becomes a nitrogen stream with very little hydrocarbon content. The solvent discharged from the bottom of the absorption tower adopts a four-stage flash evaporation mode, and the rich solvent with the pressure of about 2.7MPa is gradually reduced to 0.14MPa. Because a small amount of nitrogen components are inevitably absorbed in the process of absorbing methane by the solvent, in order to improve the denitrification efficiency and the product quality of the natural gas, the gas flow with higher nitrogen content discharged from the primary flash tank is compressed and then returned to the absorption tower for secondary absorption.
The disadvantages of this process are: because a small amount of nitrogen components are inevitably absorbed in the process of absorbing methane by the solvent, the nitrogen content of the gas discharged from the flash tank is high, and the gas is required to be recycled repeatedly. And hydrogen is difficult to be absorbed by the solvent and discharged to the atmosphere, resulting in waste of resources.
The process of removing impurities in natural gas by membrane separation is widely applied to the gas purification industry from the middle of the 80 s of the 20 th century. The separation of the components is realized by utilizing the difference of the dissolution and diffusion rates of the components in the separation membrane. Materials used for membrane separation can be classified into cellulose esters and non-cellulose esters. Common membrane structures can be further classified into homogeneous membranes, asymmetric membranes, microporous symmetric membranes, aluminum membranes, polyamide phase inversion membranes, nanotube membranes, and the like. CH (CH) 4 Dynamic diameter of (2)And N 2 Dynamic diameter of (2)The separation membrane selectively permeated with the molecular diameter size is not applicable to the denitrification of natural gas because of a small difference.
Chinese patent No. CN202110619274.9 discloses a nitrogen-containing natural gas membrane separation process with enhanced permeation selectivity at low temperature. The separation membrane can well separate methane, and the product gas contains 96% methane, but does not realize separation of H 2 . It can be seen that the separation membrane removes H 2 The effect of (2) is not remarkable and one separation of H is not achieved 2 Is effective in (1).
PSA technology is an effective gas separation technology. The PSA technology has wide application range, is suitable for gas separation with large treatment capacity, is used for solving the requirements of large-scale and ultra-large industrial gas, is also suitable for removing trace impurities and purifying gas, and is especially suitable for removing high-concentration low-boiling impurities which are difficult to remove by other methods. The pressure swing adsorption process has the advantages of normal temperature operation, simple flow, convenient maintenance, short cycle period, large treatment capacity, high product gas purity, low energy consumption, high automation degree and the like, and becomes an important separation technology in the fields of industrial gas and environmental protection.
In the aspect of recycling industrial by-product gas, the PSA technology is successfully used for purifying, separating and purifying various industrial by-product gases such as refinery tail gas, coke oven gas, methanol purge gas, metallurgical by-product gas, calcium carbide tail gas, yellow phosphorus tail gas, landfill gas, chloroethylene tail gas and the like, thereby realizing H 2 、CO、CO 2 、CH 4 、C 2 H 4 、C 2 H 6 、CH 2 ＝CHCl、C 2 H 2 And recycling the components. Has positive significance for energy conservation, consumption reduction, pollutant reduction and carbon dioxide emission reduction of related enterprises, and plays a positive role in realizing carbon neutralization targets in the future.
Currently, the industry commonly uses isolated N 2 The adsorbent of (2) is activated carbon, aluminosilicate molecular sieve and titanium silicate molecular sieve ETS-4. The activated carbon has been studied and paid attention to because of low cost, easy ion exchange, strong recoverability, high thermal stability, etc., but the activated carbon is used for adsorbing and separating N from small molecular hydrocarbon 2 In application, the activated carbon shows a characteristic of separating N from refinery gas 2 The separation coefficient is low, and the adsorption capacity is small; the commonly used A-type, X-type, 5A-type and 13X-type molecular sieves have high adsorption capacity to ethylene, ethane, methane and hydrogen and cannot absorb N 2 Separated from these four gases; a Ba-ETS-4 titanium silicalite molecular sieve disclosed in U.S. Pat. No. 3,182-A for methane denitrification, which molecular sieve adsorbs N 2 The Ba-ETS-4 titanium-silicon molecular sieve has the defects of high capacity, low adsorbent selectivity parameter and the like. Therefore, there is still a need for improvement in subsequent studies on these defects.
Among the numerous configurations of molecular sieves, the RHO configuration of a aluminosilicate molecular sieve, when in the hydrothermally synthesized form, can be described by the general formula: m is M x/n [(AlO 2 ) x (SiO 2 ) y ]·mH 2 O, wherein M represents a cation having a valence of n, x is the number of aluminum oxide tetrahedra in the unit cell, y is the number of silicon oxide tetrahedra in the unit cell, and M is the number of water molecules in the unit cell. The framework of RHO consists of a body centered cubic arrangement of truncated cubes-octahedra or α -cages. According to theoretical calculations, wherein these truncated octahedra or α -cages are connected by a double octamembered ring. Detailed configuration studies have shown that this RHO configuration is exceptionally flexible and particularly sensitive to cations and temperature. The key for determining the adsorption separation performance of the RHO configuration molecular sieve provides a basis for developing an efficient adsorbent.
Disclosure of Invention
In view of this, the present invention provides a process for removing N from refinery gas 2 Compared with the existing molecular sieve, the molecular sieve of the formula (I) and the preparation method and application thereof can effectively improve the removal of N from refinery gas 2 The adsorbent selectivity of (a) is used for solving the technical problems in the prior art.
In order to achieve the above purpose, the present invention adopts the following technical scheme:
n is got rid of from refinery gas 2 The molecular sieve is K-RHO molecular sieve or Na, cs-RHO molecular sieve.
The invention also provides a preparation method of the molecular sieve, wherein the preparation method of the Na, cs-RHO molecular sieve comprises the following steps:
(1) Mixing an aluminum source with a mineralizer and a template agent to obtain an aluminum source precursor solution;
(2) Mixing an aluminum source precursor solution with a silicon source to obtain a molecular sieve mother solution;
(3) And (3) aging the molecular sieve mother liquor by 293-303K and crystallizing by 363-403K to obtain the Na, cs-RHO molecular sieve.
Based on the technical scheme, the invention can also be improved as follows:
further, the aluminum source is at least one of hydrated alumina, aluminum hydroxide and sodium metaaluminate;
the mineralizer is at least one of NaOH and KOH solution;
the template agent is at least one of 18-crown ether-6, csOH and RbOH solution;
the silicon source is at least one of fumed silica, silica sol, tetraethoxysilane and water glass.
The preparation method of the K-RHO molecular sieve comprises the following steps:
and (3) carrying out ion exchange on the potassium salt and the Na, cs-RHO molecular sieve, and calcining the exchange product to obtain K-RHO.
Based on the technical scheme, the invention can also be improved as follows:
further, the potassium salt is nitrate, hydrochloride, sulfate or phosphate;
further, the K-RHO molecular sieve has K + The ion exchange degree is 20-95%;
the temperature for carrying out the ion exchange is 343-363K, the time is 1-5 h, and the mass ratio of the potassium salt to the Na, cs-RHO is 1:5-1:10.
Further, the temperature rising rate of the calcination treatment is 1.8-3.0K/min, the temperature is 773-873K, and the time is 3-7 h.
Further, the method also comprises the operation of drying treatment before calcining the exchange product, wherein the temperature of the drying treatment is 333-383K, and the time is 10-13 h.
The invention also provides the method for removing N from the refinery gas 2 For removing N from a feed gas 2 The raw material gas is H 2 And a low molecular hydrocarbon component, the low molecular hydrocarbon being CH 4 、C 2 H 6 、C 2 H 4 、C 3 H 8 、C 3 H 6 。
The specific steps are that the molecular sieve is activated by degassing treatment at the temperature of 473-673K, the activated molecular sieve is placed in an adsorption tower and kept at a constant temperature, and the degassing time is 1-6 h;
the raw material gas is conveyed to an adsorption tower at 248-323K and is boosted to the adsorption pressure of 500-1500 kPa, the raw material gas enters an adsorption stage and outputs product gas, and the adsorbed nitrogen comes out of a desorption phase at the low pressure of 0-100 kPa and can be directly discharged as waste gas or used as fuel;
the number of the adsorption towers is at least one.
The invention has the following beneficial effects:
the invention adsorbs and separates N from refinery gas 2 Is a molecular sieve with RHO configuration, which is not only used for separating N from refinery gas 2 Provides a new adsorption material for separating N from refinery gas 2 The technology adds a new alternative approach; compared with the existing configuration molecular sieve, the adsorption materials have better adsorbent selectivity, and provide powerful technical support for effective utilization of refinery gas.
Drawings
FIG. 1 is an X-ray diffraction (XRD) pattern of the Na, cs-RHO molecular sieve of example 1 of the invention;
FIG. 2 is a Scanning Electron Microscope (SEM) image of a Na, cs-RHO molecular sieve of example 1 of the invention;
FIG. 3 is a chart showing the adsorption of N by K-RHO molecular sieve 298K of example 2 of the invention 2 、CH 4 、C 2 H 6 、C 2 H 4 And H 2 Adsorption isotherms of (2);
FIG. 4 shows the adsorption of N by 298K of the comparative molecular sieve of the present invention 2 、CH 4 、C 2 H 6 、C 2 H 4 And H 2 Adsorption isotherms of (2).
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
Example 1
1. The preparation of Na, cs-RHO comprises the following specific steps:
weighing 1.35g of 18-crown ether-6%>98%) was completely dissolved in 7.84g deionized water, and 1.8g cesium hydroxide (99.9%) and 0.5g sodium hydroxide were added in this order>98 percent) is stirred and dissolved, and 1.82g of sodium metaaluminate is added>98%) is added to the above solution and stirred well, then 15g of silica sol (30% SiO) is added 2 ) Stirring continuously, placing into magnetic stirrer, sealing to avoid water loss, and aging at normal temperature for 24 hr under stirring continuously. Transferring the obtained initial gel into a polytetrafluoroethylene lining, screwing up a reaction kettle, putting into a dynamic crystallization box, programming to heat, and heating to a crystallization temperature of 383K at a heating rate of 4.25K/min for 96 hours. And (3) after cooling, carrying out suction filtration on the synthesized Na, cs-RHO by using deionized water, washing, then placing a filter cake into a 373K drying box for drying for 24 hours, calcining the dried sample in a muffle furnace, heating to 823K at a heating rate of 2.08K/min, and keeping for 4 hours at 823K to obtain powdery Na, cs-RHO. The molecular formula of the prepared RHO is as follows: 2Na 2 O·Cs 2 O·3Al 2 O 3 ·12SiO 2 ·11H 2 O。
2. Determination of the configuration
XRD and SEM analyses were performed on samples of Na, cs-RHO prepared, and the results are shown in FIGS. 1 and 2, respectively, and it can be seen from FIG. 1 that the samples have the following characteristic peaks:
2 theta has a diffraction peak (110 crystal plane) in the range of 8-9;
2 theta has a diffraction peak (211 crystal plane) in the range of 14-15;
2 theta has a diffraction peak (310 crystal plane) in the range of 18-19;
2 theta has a diffraction peak (411 crystal face) in the range of 25-25.5;
2 theta has a diffraction peak (420 crystal plane) in the range of 26-27;
2 theta has a diffraction peak (510 crystal plane) in the range of 30-31;
2 theta has a diffraction peak (521 crystal face) in the range of 32-33;
2 theta has a diffraction peak (600 crystal face) in the range of 35-36;
the Na, cs-RHO synthesized in example 1 has RHO molecular sieve configuration (PDF card number 27-0015), has high crystallinity, and accords with the description of RHO structure by the International molecular sieve Association.
In FIG. 2, A is a graph of the scan results, and B is a magnified view of A. As can be seen from FIG. 2, the particles are uniformly distributed and have a particle size of about 2 to 3. Mu.m, and as can be seen, the sample has a high crystallinity and is less amorphous.
The RHO type zeolite molecular sieve is a small Kong Gecheng aluminosilicate zeolite which, when subjected to hydrothermal synthesis, can be described by the general formula: m is M x/n [(AlO 2 ) x (SiO 2 ) y ]·mH 2 O, wherein M represents a cation having a valence of n, x is the number of aluminum oxide tetrahedra in the unit cell, y is the number of silicon oxide tetrahedra in the unit cell, M is the number of water molecules in the unit cell, and the framework of the zeolite RHO consists of a body-centered cubic arrangement of truncated cubes-octahedra or alpha-cages. According to theoretical calculations, wherein these truncated octahedra or α -cages are connected by a double octamembered ring. Detailed configuration studies have shown that this RHO configuration is exceptionally flexible and particularly sensitive to cations and temperature. The key of the RHO molecular sieve adsorption separation performance is determined, and a foundation is provided for the development of the efficient adsorbent.
Example 2
Preparation of K-RHO molecular sieves
4g of the Na, cs-RHO molecular sieves synthesized in example 1 were each mixed with 200mL of 1.1M potassium nitrate solution in a round bottom flask. Then put into a magnetic stirrer, a condensing tube is arranged, and ion exchange is carried out for 2 hours in a 353K water bath kettle, thus obtaining a filter cake.
And (3) placing the filter cake after suction filtration and flushing into a 373K drying box for drying for 24 hours, calcining the dried molecular sieve in a muffle furnace, heating to 823K at a heating rate of 2.76K/min, and maintaining for 4 hours at 823K to obtain the K-RHO after ion exchange. Repeating the ion exchange steps once again, and obtaining the K-RHO molecular sieve after twice ion exchange, wherein the ion exchange degree is 82% and 90% respectively.
Example 3
K-RHO molecular sieve for removing N from refinery gas 2 Adsorption separation performance of (3)
K-RHO of example 2 at different degrees of exchange was used for N 2 And H is 2 、CH 4 、C 2 H 4 、C 2 H 6 The adsorption isotherm was measured on a high pressure physisorption analyzer, 1g of K-RHO was weighed, the molecular sieve was degassed at 523K at the test site for 2h to activate the sample, and the adsorption temperature was maintained at 298K with a thermostatic water bath.
The PSA process typically performs adsorption at 0 to 2500kPa and desorption at atmospheric or vacuum conditions, so the gas working capacity is the difference between its adsorption and desorption pressures.
The specific operation is as follows: the raw material gas is conveyed to an adsorption tower at 248-323K and is boosted to the adsorption pressure of 500-1500 kPa, the raw material gas enters an adsorption stage and outputs product gas, and the adsorbed nitrogen comes out of a desorption phase at the low pressure of 0-100 kPa and can be directly discharged as waste gas or used as fuel;
wherein the number of the uniform steps and the number of the adsorption towers can be further increased in order to improve the recovery rate of the product gas and increase the treatment scale of the device.
The adsorption isothermal curves were fitted by Langmuir adsorption model as shown in fig. 3, and fitting parameters were obtained in the adsorption isothermal curves. Calculation of N of K-RHO molecular sieves at different ion exchange degrees Using Henry constant (K) and equilibrium Selectivity (α) 2 、CH 4 、C 2 H 6 、C 2 H 4 And H 2 The adsorbent selectivity parameters (S) and the results are shown in table 1.
TABLE 1K-RHO vs N 2 、CH 4 、C 2 H 6 、C 2 H 4 And H 2 Adsorption performance data results of (2)
Note that: 1. adsorbent selectivity parameters:
2.N 2 working capacity=q N2(1000kPa) -Q N2(100kPa)
3.82％N 2 N of K-RHO with 82% ion exchange degree 2 Adsorption data, 90% N 2 And other corresponding adsorption data for K-RHO with an ion exchange degree of 90%
As can be seen from Table 1 and FIG. 3, C 2 H 6 And CH (CH) 4 The adsorbent selectivity parameter (S) of (C) is higher, reaching 394.98 and 212.01, for H 2 、C 2 H 4 The selectivity parameters of (2) reach 104.89 and 65.87 respectively, and Table 2 and FIG. 3 show that K-RHO can well remove N from refinery gas under the conditions of 298K and 100-1000 kPa 2 . The combination of PSA rules and the data of the process show that the low temperature and the high pressure are more favorable for absorbing and separating nitrogen, and the absorption pressure is 500-1500 kPa under the absorption conditions that the absorption temperature is 248-323K and the absorption pressure is K-RHO is used for removing N 2 The effect is obvious. In addition, RHO with increased K exchange is beneficial to adsorbing more N 2 。
An important factor in PSA separation is the variation in the adsorption of the two components during the pressure variation cycle. The adsorption capacity of an adsorbent refers primarily to the difference in the amount of high pressure adsorption and low pressure desorption adsorption of the more readily adsorbed components. In short, the adsorption capacity depends on the amount of adsorption under mixing conditions (i.e., with a binary component isotherm). However, the requirement for calculation parameters can be met with adsorption isotherms of pure components. The comparison of the adsorption capacities of the two components can be used as an ideal judgment method for the adsorption performance of a special pressure swing adsorption cycle. The better the adsorption performance of the adsorbent, the higher the S value of the adsorbent.
Comparative example
Compared with the prior different adsorption materials and the K-RHO synthesized in the embodiment 2, the method for removing N from refinery gas 2 Is separated from the other components.
The 5A molecular sieve is 0.75 CaO.0.25 Na 2 O·Al 2 O 3 ·2SiO 2 ·4.5H 2 O, silicon-aluminum ratio is about 2, taking bar shape as an example, diameter is 1.6mm, granularity is 99%, specific surface area is 750m 2 Per gram, bulk density of 700kg/m 3 The porosity is 47%, the abrasion rate is 0.15%, the compressive strength is 25N/cm, the static water adsorption is 25%, and the packaging water content is 1%.
13X molecular sieve is Na 2 O·Al 2 O 3 ·2.45SiO 2 ·6H 2 O, si/Al ratio of about 1.25, for example, a bar shape, a diameter of 1.6mm, a particle size of 99%, a specific surface area of 800m 2 Per gram, bulk density 600kg/m 3 The porosity is 50%, the abrasion rate is 0.1%, the compressive strength is 35N/cm, the static water adsorption is 30%, and the packaging water content is 1%.
For the 5A molecular sieve and the 13X molecular sieve, respectively, N was adsorbed by pressure swing as in example 2 2 、CH 4 、C 2 H 6 、C 2 H 4 And H 2 The results of the adsorption performance data are shown in Table 2 and FIGS. 4A and 4B.
Table 25A molecular sieves, 13X vs N 2 、CH 4 、C 2 H 6 、C 2 H 4 And H 2 Adsorption performance data results of (2)
Table 2 and FIGS. 4A and 4B show the results of comparing the molecular sieve 5A and 13X versus N of the background art of the present disclosure 2 And the adsorptive properties of other components.
The 5A molecular sieves used as adsorbents although shown to be H 2 Excellent adsorbent selectivity parameters of 66.76, exhibiting N 2 For H 2 Excellent separation effect. But due to the pair CH 4 、C 2 H 6 、C 2 H 4 The working adsorption capacities were too high, 11.61, 11.10 and 6.20 respectively, resulting in smaller adsorbent selectivity parameters. Therefore, the 5A molecular sieve is not suitable for removing N from refinery gas components with complex components 2 。
The 13X molecules used as adsorbents, although exhibiting smaller H than the 5A molecular sieves 2 Adsorption capacity of 0.02 and adsorbent selectivity parameter of 18.09, shows excellent separationN 2 、H 2 Effects. But it is to CH 4 、C 2 H 6 、C 2 H 4 Exhibits very low adsorbent selectivity parameters of 0.27, 0.117 and 0.104, respectively, and does not remove N well 2 Therefore, the method is not suitable for removing N from refinery gas components with complex components 2 。
The K-RHO of the embodiment of the disclosure effectively inhibits CH by comprehensively comparing the K-RHO, the 5A molecular sieve, the 13X molecular sieve and the like 4 、C 2 H 6 、C 2 H 4 And H 2 Adsorption capacity of (C) to N is improved 2 The selective parameters of the adsorbent for other components can effectively remove N 2 The purpose of the gas.
The K-RHO molecular sieve in the present disclosure is more suitable for PSA to remove N from refinery gas with high selectivity 2 。

Claims (4)

1. N is got rid of from refinery gas 2 The use of the molecular sieve of (2) for removing N from a feed gas 2 The raw material gas is H 2 And a low molecular hydrocarbon component, the low molecular hydrocarbon being CH 4 、C 2 H 6 、C 2 H 4 、C 3 H 8 、C 3 H 6；
The molecular sieve is a K-RHO molecular sieve;
the preparation method of the K-RHO molecular sieve comprises the following steps: carrying out ion exchange on potassium salt and Na, cs-RHO molecular sieve, and calcining the exchange product to obtain K-RHO;
the temperature rising rate of the calcination treatment is 1.8-3.0K/min, the temperature is 773-873K, and the time is 3-7 h;
the preparation method of the Na, cs-RHO molecular sieve comprises the following steps:
(1) Mixing an aluminum source with NaOH, csOH and 18-crown ether-6 to obtain an aluminum source precursor solution;
(2) Mixing an aluminum source precursor solution with a silicon source to obtain a molecular sieve mother solution;
(3) Aging the molecular sieve mother liquor at 293-303K, and crystallizing at 363-403K at a heating rate of 4.25K/min to obtain a Na, cs-RHO molecular sieve;
the aluminum source is at least one of hydrated aluminum oxide, aluminum hydroxide and sodium metaaluminate;
the silicon source is at least one of fumed silica, silica sol, tetraethoxysilane and water glass;
k of the K-RHO molecular sieve + The ion exchange degree is 82-95%;
the potassium salt is nitrate, hydrochloride, sulfate or phosphate.
2. A process for removing N from refinery-related gas according to claim 1 2 The molecular sieve application is characterized in that the ion exchange is carried out at 343-363K for 1-5 h, and the mass ratio of the potassium salt to the Na, cs-RHO is 1:5-1:10.
3. A process for removing N from refinery gas according to claim 1 2 The molecular sieve is characterized by further comprising the operation of drying treatment before calcining the exchange product, wherein the temperature of the drying treatment is 333-383K, and the time is 10-13 h.
4. The use according to claim 1, characterized in that the specific step is to degas at a temperature of 473-673K to activate the molecular sieve, place the activated molecular sieve in an adsorption tower and keep the temperature constant for a degassing time of 1-6 h;
the raw material gas is conveyed to an adsorption tower at 248-323K and is boosted to the adsorption pressure of 500-1500 kPa, the raw material gas enters an adsorption stage and outputs product gas, and the adsorbed nitrogen is discharged from a desorption phase at the low pressure of 0-100 kPa and is directly discharged as waste gas or used as fuel;
the number of the adsorption towers is at least one.
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US10646848B2 (en) * 2017-09-28 2020-05-12 Air Products And Chemicals, Inc. RHO adsorbent compositions, methods of making and using them
US10343139B2 (en) * 2017-09-28 2019-07-09 Air Products And Chemicals, Inc. Processes using improved RHO adsorbent compositions

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CN109422276A (en) * 2017-08-30 2019-03-05 中国科学院大连化学物理研究所 A kind of molecular sieve of containing transition metal and its preparation method and application
CN114749145A (en) * 2022-04-28 2022-07-15 东北石油大学 Molecular sieve for adsorbing and separating nitrogen and methane and preparation method thereof

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