CN100344352C

CN100344352C - Process for separating mixture of benzene and nitrogen gas by X-type fluorite film

Info

Publication number: CN100344352C
Application number: CNB2005100465870A
Authority: CN
Inventors: 王金渠; 李邦民; 韩玲; 鲁金明
Original assignee: Dalian University of Technology
Current assignee: Dalian University of Technology
Priority date: 2005-06-03
Filing date: 2005-06-03
Publication date: 2007-10-24
Anticipated expiration: 2025-06-03
Also published as: CN1724129A

Abstract

The present invention belongs to the field of the preparative technique and the application of an inorganic membrane, which relates to the separation of the mixture of one or more kind of organic macromolecule gas and inorganic small molecule gas. The present invention is characterized in that sol is prepared according to the molar proportions of SiO2: Al2O3 = 3.85 to 4.2, Na2O: SiO2 = 1.2 to 1.5, and H2O: Na2O = 55, and an alpha-Al2O3 ceramic tube is used as a carrier which is processed by grinding, acid and alkali; then, aX-type zeolite membrane is synthesized by crystallization at low temperature (95 to 105 DEG C) for 20 to 48 hours under hydrothermal condition, and the zeolite membrane is arranged in 0.2 to 0.25 mol/L of silver nitrate solution at 95 DEG C for ion exchange for 5 to 8 hours to obtain an AgX zeolite membrane; finally, the tube coated by the membrane is arranged in a membrane separation device of which both sides have the pressure difference controlled at 10 to 60 kpa, and the separating factor of benzene and nitrogen is 10 to 40. The present invention has the advantages that the benzene and the nitrogen are separated at normal temperature, the structure is simple and the energy consumption is low, and the present invention has the wide application foreground.

Description

X type zeolite membrane is used for the method that benzene separates with nitrogen mixture

Technical field

The invention belongs to inoranic membrane technology of preparing and application, the synthetic and organic macromolecule gas and the inorganic molecules separation of gaseous mixture that relate to inoranic membrane are used, and specially refer to the separation method of benzene and nitrogen.

Background technology

At present petroleum chemical industry has the storage and the use of a large amount of benzene, all is to seal benzene with nitrogen on the technology, therefore can produce in a large number by the saturated nitrogen of benzene, and benzene storage tank breathing pipe is with 100-120Nm ³Benzene and nitrogen mixture that/h contains 24Mol% left and right sides benzene directly are disposed to atmosphere, do not recycle, and have not only wasted valuable resource, and have polluted environment.

Reclaim the adoptable technology of benzene from separating of benzene and nitrogen mixture at present and mainly contain the condensation separation method, absorption method and membrane separation process etc. are several.

The condensation separation method is with the gaseous mixture condensation liquefaction that pressurizes, and utilizes rectifying that nitrogen is separated with benzene again.Because the boiling point of nitrogen is-195.8 ℃, the boiling point of benzene is 80.4 ℃, need high pressure and low temperature as if the mixture liquefaction with both, so its energy consumption is very high, and equipment investment is big, and economic benefit is low.

Absorption method is that employing is an adsorbent to active carbon or the NACF that benzene has very high selection absorption property, adsorbs benzene at low temperatures, inhales the residual air nitrogen purge.When adsorbent bed reaches capacity, reclaim benzene through the high temperature desorb.The concentration of benzene is about 24% in the benzene storage tank breathing gas, adopts absorption method to reclaim benzene, certainly will need a large amount of adsorbents, causes equipment volume huge, high temperature desorption energy consumption height, and the cooling difficulty, equipment drops into high, has restricted industrial applications.

The embrane method gas separation is the high-new isolation technics that grows up these decades.Mist is by membrane separator the time, and one or more gases optionally see through film under motive force effects such as pressure or concentration, thereby reaches the purpose of separation.Compare with other separation methods, the film separation has no phase transformation, and normal-temperature operation does not need heating desorption or desorption, and energy consumption is low, and flow process is simple, advantages such as small investment.Be subjected to the common concern of enterprise and scientific and technological circle, become research and development, the focus of applying.Human coated heat cross-linking methods such as France's membrane material and the Guizard of process National Laboratory are being fluoridized Vingon (Polyvinylidene Fluoride, PVDF) and polyether sulfone (polyether Sulfone, PES) synthesized the organic film of trimerization fluoro siloxanes (Fluorosiloxane ter-Polymers on the asymmetric carrier, FST), and carried out air with this film---1, the test of 2-benzene permeability and separation, the result shows, in air 1, when 2-benzene content is 25mol%, 1, the permeability of 2-benzene is 6.5 * 10 ^-4m ³/ m ²SPa shows good separating property.But organic film exists saturating amount few, and solvent resistance can be poor, and membrane structure is subject to solvent and destroys, the shortcoming that membrane lifetime is short.

Zeolite molecular sieve film is a kind of novel membrane separation technique that grew up in recent years, and it is to realize the molecule screening by the duct of molecular sieve, thereby obtains higher separation factor.X type molecular sieve bore diameter is 0.74nm, selective to benzene on the aperture, and silver ion can replace be used in the X type zeolite molecular sieve balancing charge sodium ion, by silver ion to its modification, because silver ion can form coordinate bond with unsaturated hydrocarbons in the molecule sieve aperture, so can being benzene, the effect of chemical bond forms surface absorption complex compound on the film surface, high-adsorption-capacity and high selectivity are arranged, contain cation in the zeolite bug hole simultaneously, around cation, just form powerful electric field like this.Also, unsaturated and easy polar molecule had preferential selection suction-operated just because of the relation of electrostatic force.Selection absorption by to benzene makes it in the fenestra road capillary condensation take place, and stops nitrogen to pass through, and realizes the separation of mist.

Summary of the invention

The purpose of this invention is to provide a kind of at normal temperatures just can Separation of Benzene and the membrane separating method of nitrogen, utilize this method to prepare a kind of zeolite membrane with special pore size distribution, cation on this film can be adsorbed onto benzene the film surface by the effect of valence bond power, the capillary condensation phenomenon takes place in benzene in its hole simultaneously, and then stop passing through of inorganic molecules nitrogen, realize the separation of mist.

Key of the present invention is synthetic X type molecular screen membrane, realizes that technical scheme of the present invention is, according to SiO ₂: Al ₂O ₃=3.85-4.2, Na ₂O: SiO ₂=1.2-1.5, H ₂O: Na ₂The preparation of mole proportioning colloidal sol, the wherein Al of O=55 ₂O ₃Raw material adopt gibbsite, aluminum sulfate or alchlor, SiO ₂Raw material adopt waterglass, silicic acid, Ludox or the unformed silica of various activity, Na ₂The raw material of O adopts NaOH, and water is deionized water, is made into colloidal sol through stirring, adopts α-Al ₂O ₃Support tube, the aperture of support tube are 3-5 μ m, porosity 30-50%.Support tube is through polishing and soda acid processing before synthetic, 95 ℃-105 ℃ of low temperature under hydrothermal condition then, and crystallization 20-48h synthesizes X type molecular screen membrane.Synthetic molecular screen membrane to neutral, is used N with rinsed with deionized water then ₂Gas carries out penetration testing, if gas permeation is arranged, then repeats crystallization, and is airtight until the film pipe, prepares the X zeolite membrane with separating property, then with zeolite membrane liquor argenti nitratis ophthalmicus intermediate ion exchange 5-8h at 0.2-0.25mol/L under 95 ℃; After the ion-exchange treatment, the film pipe is at room temperature used rinsed with deionized water, at 100 ℃ of dry 1d, at last the film pipe is placed membrane separation device then, control both sides pressure reduction is in 10-60kPa, and the separation factor of benzene and nitrogen is between 10-40.

The zeolite membrane that the present invention obtains through the Ag ion-exchanged, the structure of its film and outward appearance are confirmed through fluorescence spectrum and stereoscan photograph analysis.

Effect of the present invention is to have realized at normal temperatures separating of benzene and nitrogen that equipment is simple with benefit, and energy savings can be avoided environmental pollution again simultaneously, has reclaimed valuable resource, has improved existent environment of people.

Description of drawings

Accompanying drawing is the apparatus structure schematic diagram of X type molecular screen membrane Separation of Benzene and nitrogen.

Among the figure: 1 cold-trap, 2 vavuum pumps, 3 gaseous mixtures, 4 needle valves, 5 Pressure gauges, 6 membrane separators, 7 film pipes, 8 chromatograms, 9 flowmeters.

The specific embodiment

Be described in detail the specific embodiment of the present invention and most preferred embodiment below in conjunction with accompanying drawing.

Embodiment:

The colloidal sol preparation: with the Ludox is the silicon source, and aluminium isopropoxide is the aluminium source, and NaOH is that alkali source and deionized water are raw material, according to SiO ₂: Al ₂O ₃=3.85-4.2, Na ₂O: SiO ₂=1.2-1.5, H ₂O: Na ₂The mole proportioning of O=55 is prepared colloidal sol under powerful stirring.

The carrier preliminary treatment: at first that carrier surface is smooth with 400#, 600#, 800# sand papering before synthesizing, use ultrasonic oscillation again, flush away surface and hole inner suspension particle soaked 1-2 hour with acid or alkali then, and ultrasonic wave is washed to neutrality, dries stand-by.

Film preparation: the pretreated support tube of learning from else's experience, shut with poly tetrafluoroethylene at two ends, vertically put into the stainless steel crystallizing kettle, slowly add still in along tube wall colloidal sol, be put into after sealing in the baking oven that is heated to uniform temperature in advance, the crystallization certain hour takes out, and cools off naturally and is washed till neutrality with deionized water.Air drying 1-2d, at 100 ℃ of dry 1-2d, before roasting through N ₂If test still ventilative, then repeats crystallization to airtight.

The film roasting: in air atmosphere according to certain heating and cooling program roasting film pipe, to remove the crystallization water in the fenestra.Heating rate is: 0.5-1K/min, rate of temperature fall is: 1-2K/min.

Cation-modified: with homemade molecular screen membrane pipe at 100 ℃ down behind the dry 2h, getting film pipe, silver nitrate and deionized water joins in the there-necked flask, normal pressure, constant temperature 95 degree, carry out ion-exchange under the stirring condition, behind the exchange certain hour taking-up of the film pipe after the modification is poured in the beaker, use deionized water rinsing 3-4 time.

According to the method described above the modified zeolite film that makes is installed in the membrane separation device shown in the drawings, the pressure reduction at film two ends is controlled at 30Kpa, and benzene air inlet side concentration is 19.2%, and air inlet effluent speed is 180ml/min; Tail gas concentration is 2.8%, flow velocity 146ml/min, and the separation factor of the two is 36.

Claims

1. an X type zeolite sieve membrane is used for the method that benzene separates with nitrogen mixture, it is characterized in that according to SiO ₂: Al ₂O ₃=3.85-4.2, Na ₂O: SiO ₂=1.2-1.5, H ₂O: Na ₂The preparation of mole proportioning colloidal sol, the wherein Al of O=55 ₂O ₃Raw material can adopt gibbsite, aluminum sulfate or alchlor, SiO ₂Raw material can adopt waterglass, silicic acid, Ludox or the unformed silica of various activity, Na ₂The raw material of O adopts NaOH, and water is deionized water, and these raw materials are made into colloidal sol through stirring according to the above ratio, adopts α-Al ₂O ₃Support tube, the aperture of support tube are 3～5 μ m, porosity 30-50%; Before synthetic, support tube after treatment, the synthetic X type molecular screen membrane of 95 ℃ of-105 ℃ of crystallization 20-48h of low temperature under hydrothermal condition, before roasting through N ₂If test still ventilative, then repeats crystallization to airtight, then with zeolite membrane liquor argenti nitratis ophthalmicus intermediate ion exchange 5-8h at 0.2-0.25mol/L under 95 ℃; After the ion-exchange treatment, the film pipe is at room temperature used rinsed with deionized water, at 100 ℃ of dry 1d, at last the film pipe is placed membrane separation device then, control both sides pressure reduction is in 10-60kPa, and the separation factor of benzene and nitrogen is between 10-40.