CN1146374A - Nitrogen-selective zeolitic adsorbent for use in air separation process - Google Patents

Abstract

In using calcium-exchanged forms of zeolite X as selective adsorbents for nitrogen in PSA air separation process, it has been discovered that, particularly under certain temperature and pressure conditions, superior performance is not, as is generally believed, obtained when the calcium content is at a maximum, but rather when thedegree of calcium exchange is in the range of 60 to 89 equivalent percent and only when the framework Si/Al2 ratio of the zeolite is within the range of 2.0 to 2.4.

Description

The nitrogen that is used for air-separating technology is selected the zeolite adsorbents of absorption

The present invention relates to the application of new zeolite adsorbent in air-separating technology in short, so that selective absorption nitrogen, more specifically to the following application of nitrogen selected adsorbent in air-separating technology, this adsorbent contains skeleton Si/AL ₂Than the X type zeolite that is 2.0～2.4, contain 60～89% (equivalent) Ca at available cation exchange center ⁺⁺Ion, 10～40% (equivalent) Na ⁺Ion and 0-10% (equivalent) K ⁺Ion is wherein by Ca ⁺⁺Na ⁺And K ⁺The total cation equivalent that cation provides is at least 90%.

It is an important industrial operation that air separation becomes main component nitrogen of its two and oxygen, will produce hundreds billion of square feet nitrogen and oxygen its every year.Under the occasion that one of these two kinds of components need in a large number, the oxygen that needs in for example making steel; The cryogenic separation system of investment may be worthwhile, adopts deep cooling separating method usually.For the less operation of requirement, also available transformation attached (PSA) explained hereafter oxygen and nitrogen.In PSA, the adsorbent that compressed air demonstrates preferential adsorption by a kind of component in to key component through pumping is the mansion layer fixedly, and the product that therefore obtains being rich in the component of not adsorbing (or less absorption) flows out logistics.Compare with deep cooling process for separating, the equipment that the PSA air-separating technology needs is quite simple, and maintenance is also quite easy.But, to compare with cryogenic separation, the product recovery rate of PSA technology is lower, and energy consumption is higher.Owing to these reasons, the improvement of adsorptive separation technology remains an important target.Improved main means are to find and develop better adsorbent.

The crystalline zeolite molecular sieve is as the application of nitrogen selected adsorbent, and particularly selecting adsorption of nitrogen from air is that everybody is familiar with in this specialty.For this reason, US-A-3140931 has proposed the zeolite that a class aperture is at least 4.6 dusts.US-A-3140932 proposes specific zeolite species---and contain and at least aly among Sr, Ba or the Ni be used for this separation as cationic X type zeolite.US-A-3140933 discloses the relevant strong point of the various alkali metal cation type zeolites that comprise X type zeolite.In US-A-4557736, binary ion-exchange type X type zeolite is considered to the preferred adsorbent of adsorption of nitrogen from air.In US-A-4481018, one group of activation condition of avoiding skeleton and cation hydrolysis in the polyvalent cation type faujasite is basically disclosed.These compositions, particularly Mg ²⁺, Ca ²⁺, Sr ²⁺And/or Ba ²⁺Cationic composition is considered to the superior adsorbent of separating nitrogen from air.Based on the N that obtains by gas-chromatography research ₂/ O ₂Selectivity numerical value, US-A-4481018 points out Ca ²⁺Exchange degree is high more, and the selectivity and the capacity of faujasite-type adsorbent adsorption of nitrogen from air are big more.Disclosed minimum calcium content is 50%, and preferred adsorbent contains greater than 80% (equivalent) calcium cation.In a word, for the application in nitrogen separates, background technology is regarded calcium, strontium and lithium cation as component that zeolite adsorbents needs.The other cation is regarded as not too as sodium to be needed.

Fig. 1 for respectively behind 40 ℃, 20 ℃ and 0 ℃ following 10.7 kPas (1.55 pounds/square inch) desorptions CaNa * 2.0 (be Si/AL ₂Than being 2: 1, contain Ca ²⁺Na ⁺Cationic X type zeolite) the residual adsorbance of nitrogen is with the variation of calcium exchange degree.

Fig. 2 is respectively in the variation with the calcium exchange degree of 40 ℃, 20 ℃ and the Δ nitrogen adsorbance of 0 ℃ of following CaNaX2.0 between 14.7～1.55 pounds/square inch.

Fig. 3 operates the variation of selectivity with the calcium exchange degree at the nitrogen of 40 ℃, 20 ℃ and 0 ℃ following CaNaX2.0 respectively.

Fig. 4,5 and 6 is respectively in the variation with the calcium exchange degree of the residual adsorbance of the nitrogen of 40 ℃, 20 ℃ and 0 ℃ following CaNaX2.3, Δ adsorbance and operation selectivity.

Fig. 7,8 and 9 is respectively in the variation with the calcium exchange degree of the residual adsorbance of the nitrogen of 40 ℃, 20 ℃ and 0 ℃ following CaNaX2.5, Δ adsorbance and operation selectivity.

Figure 10 is the desorption rate of 22 ℃ of following CaX2.0 (97%Ca).

Figure 11 is the desorption rate of 22 ℃ of following CaNaX2.0 (75%Ca).

Figure 12 is the desorption rate of 22 ℃ of following CaNaX2.3 (97%Ca).

Figure 13 is the desorption rate of 22 ℃ of following CaNaX2.3 (77%Ca).

Figure 14 is the desorption rate of 22 ℃ of following CaX2.5 (97%Ca).

Figure 15 is the desorption rate of 22 ℃ of following CaNaX2.5 (77%Ca).

Find X type zeolite, particularly Si/AL now surprisingly ₂Mol ratio is 2.0～2.4 X type zeolite, and they have the cation of charge balance, contains 60～89 (preferred (60～80) % (equivalent) Ca ^#Cation, 10～40% (equivalent) Na ⁺Cation and) 0～10% (equivalent) K ⁺Cation is wherein by Ca ⁺⁺, Na ⁺And K ⁺The total cation equivalent that provides is at least 90%, and this X type zeolite exchanges to the identical X type zeolite that is greater than or less than above-mentioned degree as the adsorbent of air separation than calcium in pressure swing adsorption technique under 50～20 ℃, 5～506.5 kPas (0.05～5.0 atmospheric pressure) much effective.

Therefore, the invention belongs to be used for from the circulation separating technology of the mixture separating nitrogen of oxygen, this technology comprises that (a) provides one the adsorption bed of the faujasite of crystalline texture as adsorbent arranged, the skeleton Si/AL of faujasite ₂Mol ratio is 2.0～2.4, contains 60～89% (equivalent) Ca ⁺⁺Cation, 10～40% (equivalent) Na ⁺Cation and 0～10% (equivalent) K ⁺Cation is wherein by Ca ^#, Na ⁺And K ⁺The total cation equivalent that provides is at least 90%; (b) under-20 ℃ to 50 ℃ the mixture of described nitrogen and oxygen is sent into described adsorption bed, until the bed internal pressure rises to 13.8～506.8 kPas (2～73.5 pounds/square inch), so nitrogen is selected to be adsorbed on the described zeolite adsorbents; (C) oxygen of emitting not absorption from adsorption bed under adsorptive pressure is as product with (d) bed layer pressure is dropped to 101.4～0.7 kPas of last desorption pressure (14.7～0.1 pounds/square inch) and make the nitrogen desorption of absorption, and emits the nitrogen of desorption from bed.

In particularly preferred embodiment of the present invention, the Sio of X type zeolite ₂/ Al ₂O ₃Mol ratio is 2.0～2.35, and its cation contains 65～80% calcium and 20～35% sodium cations, does not have potassium cationic basically.

As you know, the quadrupole moment of nitrogen is 0.31A ³, it is more eager to excel in whatever one does than oxygen with the cationic interaction of zeolite owing to this reason, and the latter's quadrupole moment only is about 0.10A ³Owing to absorb more strongly, according to thermodynamic principles, nitrogen from the mixture of nitrogen and oxygen selective absorption on zeolite.This selectivity of nitrogen absorption is to utilize the basis of many air-separating technologies of fixed bed transformation adsorption-desorption circulation.The cationic character of zeolite is the greatest factor that influences nitrogen adsorptive selectivity and capacity.Shown that lithium and calcium demonstrate the affinity strong especially to nitrogen as the zeolite cation.

US-A-4481018 discloses, and improves the influence of calcium content.This patent is thought reach higher selectivity and capacity when the calcium cations is surpassed about 80% (equivalent).The raising of nitrogen adsorption efficiency belongs to the used calcium of X type zeolite and other multivalent metal cations mainly are in dehydration/deshydroxy state.Owing to these reasons, those skilled in the art generally understand, and under the occasion of special metal cationic form to nitrogen demonstration good adsorption properties of zeolite, the cationic content of special metal is high more, and the performance in air separation is just good more.

Unexpectedly find now, under the X type zeolite situation of calcium exchange, when calcium content is in maximum, under certain temperature and pressure, in air separation, can not obtain the highest performance, not as the calcium exchange degree is 60～89% (equivalents), particularly during 65～80% (equivalents).Even find more surprisingly, by reducing improvement that the calcium exchange degree produces only at the Sio of X type zeolite ₂/ Al ₂O ₃Than in 2.0～2.4 scopes, just obtaining effective adsorbent.

Though do not wish to be bound by any particular theory, more believe till now be since the calcium sun from charge density, and do not consider some other factor.At least with regard to the X type zeolite of calcium exchange (hereinafter claiming CaNaX), the nitrogen adsorptive selectivity has complicated relation with capacity and cation composition, temperature and pressure condition zeolite structured and that adsorbent contacts with nitrogenous gas.

The nitrogen adsorptive selectivity of the CaNaX composition of being reported in the document usually is to measure with chromatographic technique, and the pressure of nitrogen on adsorbent is very low.Because the nitrogen adsorptive selectivity of CaNaX is very sensitive to pressure, the high selectivity numerical value of being reported is not useable for higher nitrogen and presses.The present invention to small part based on this discovery, decide on the calcium exchange degree, the nitrogen adsorptive selectivity of CaNaX can raise and significantly descends with pressure.In addition, the nitrogen pressure during the pressure ratio chromatogram of using in the adsorption step of the air-separating technology of actual industrial scale is measured is much higher.So, with the selectivity of chromatography determination seldom with industrial pressure swing adsorption technique in adsorption step relevant.

In the PSA air-separating technology, desorption is necessary processing step.For effective adsorbent, the shortest desorption time at interval in the nitrogen adsorbance must reach maximum slippage, so with minimum oxygen product or with little vavuum pump with regard to regenerable sorbent.In other words, for an effective desorption is arranged in the PSA air-separating technology, what adsorbent had low nitrogen affinity under desorption or flushing pressure is necessary.Because the nitrogen pressure during chromatogram is measured is that the high nitrogen adsorptive selectivity that chromatogram observes shows that such adsorbent has relatively poor desorption performance in PSA technology in the desorption pressure of PSA technology.

It is desirable to, for the PSA air separation, adsorbent under low pressure should show low closing property of nitrogen system, and under high pressure should show high closing property of nitrogen.In the fact of theoretical and practical experience confirmation, such nitrogen absorber can not be arranged.Ci situation is the adsorbent that the nitrogen adsorptive selectivity raises and significantly do not descend with adsorptive pressure slightly.

According to the present invention, found adsorbent, along with the calcium ion-exchanged degree is depended in the decline of closing property of nitrogen pressure rising nitrogen system to a great extent for CaNaX.For high calcium X type zeolite, the above calcium X of 90% or 90% (equivalent) type zeolite just, the nitrogen adsorption affinity descends very fast.For 60～89%Ca is arranged ^#The CaNaX of exchange degree, the nitrogen affinity under very low pressure is not really high, and when pressure raise, it can not descend rapidly again.Therefore, the nitrogen operation selectivity of the CaNaX of medium calcium exchange can be higher than the selectivity of high CaX.The more important thing is that under desorption pressure, nitrogen is easy to desorption from the CaNaX of medium exchange, so the regeneration of adsorbent is much easier.Therefore the overall performance of the specific CaNaX composition that uses among the present invention is more much better than the performance of the CaX of higher exchange degree.

In order to estimate the potentiality of a certain material, should consider following three standards: 1. the residual adsorbance of nitrogen, i.e. nitrogen adsorbance under desorption pressure as PSA air separation adsorbent.Good PSA air separation adsorbent should have the residual adsorbance of low nitrogen.2. nitrogen Δ adsorbance, i.e. adsorbance under adsorptive pressure and poor between the adsorbance under the desorption pressure.Good PSA air separation adsorbent should have high nitrogen Δ adsorbance.3. operation selectivity promptly is defined as nitrogen Δ adsorbance divided by oxygen Δ adsorbance.Good air separation adsorbent should have high operation selectivity to nitrogen.

In the performance of the adsorbent of air separation, the temperature of carrying out air-separating technology also is important factor.Industry PSA air separator is tun normally, and with respect to the required time of a large amount of adsorbents in heating or the cooled containers, the process cycles time is than short.Therefore, process cycles is in adiabatic condition or near carrying out under the adiabatic condition.The heat of adsorption of nitrogen on the CaNaX zeolite is significant.The heat that absorption discharges be fed with the product band of gas forward, and accumulation forms hot forward position.The hot forward position of a part can be by the product band of gas from adsorption tower.Remaining part is taken back adsorption tower with hot forward position in the desorption of process cycles.In desorption process, from adsorbent, remove nitrogen and consume kinetic energy, the temperature of nitrogen and adsorbent is descended.Desorption heat produces cold forward position in bed.Wherein a part is left bed with waste gas.All the other a part of cold forward positions borrow feeding gas oppositely to pass through adsorption tower in next adsorption step.

After adsorption/desorption circulation many times, can reach stable state.Under stable state, some part of bed may be much colder than peripheral part.So, use its absorption property can not be absolutely necessary because of the excessive impaired adsorbent of such variations in temperature.The present invention part is based on such judgement: the absorption property of the X type zeolite of high calcium exchange is easy to the infringement that descended by temperature, but under the situation of the CaNaX of medium exchange, just can not be subjected to such infringement.Even appropriateness reduces residual adsorbance of nitrogen and the operation selectivity that reduces nitrogen absorption that adsorption temp also can improve the X type zeolite of high calcium exchange greatly.Our research work determines that also adiabatic desorption can bigger temperature fall on causing than CaNaX on the high CaX.

In the PSA air-separating technology, the productivity ratio of adsorbent is not only determined by nitrogen Δ adsorbance and nitrogen adsorption operations selectivity, and is determined by the length of circulation timei.The adsorbent that can work in shorter circulation timei will have higher productivity ratio.Can how soon regenerate and be ready to next adsorption step by adsorbent circulation timei is decided.It is faster to have found that nitrogen is gone up desorption from the last desorption of the CaNaX of medium exchange than the CaX from the height exchange.

In a word, after having considered PSA air separation condition, find that the CaNaX of medium calcium exchange is better than the CaX of highly exchange.

The present invention illustrates and illustrates in order to the data shown in listed data and Fig. 1～15 among Table I～V.Following adsorbent composition, their preparation method and test method are used to obtain above-mentioned data:

The preparation of raw material X type zeolite compositions

Prepared Si/Al ₂Mol ratio is respectively 2.0,2.3 and 2.5 X type zeolite sample.Si/Al ₂Than be 2.0 sample according to BP 1580928 disclosed technology, synthetic 70 ℃ of following hydro-thermals with NaOH, potassium hydroxide, sodium metasilicate, aluminium hydroxide and water as raw material, obtain mixing Na ⁺-K ⁺Cation X type zeolite, just NaKX2.0.As initial crystalline product, NaKX2.0 contains 25% (equivalent) K that has an appointment ⁺Cation, all the other are Na ⁺Cation.By using the ion-exchange fully of the NaCl aqueous solution, K ⁺Cation is gone up substantially all by Na ⁺Sun is from removing and replacing.

Hereinafter some of report are tested (just not add on the zeolite ocean product of adhesive) on the online zeolite sample and are carried out, and use the zeolite aggregation of band adhesive in other tests.Under one situation of back, the palygorskite type carclazyte of adhesive for obtaining by F/oridin company with trade mark Minuge/.Make the aggregation of bead and extrusion form with the familiar conventional method of this specialty.

In order to prepare the adsorbent of part calcium exchange, use intermittently switching technology.The zeolite of powder type or aggregated forms is immersed in 80～95 ℃ of calcium chloride solutions under constantly stirring.Usually this operation continues 1～2 hour.Control the calcium exchange degree by the zeolite of use and the quantity of calcium chloride.In order to prepare the X type zeolite powder of high calcium exchange, use the technology that repeatedly exchanges with a large amount of excess chlorination calcium.In order to prepare the X type zeolite polymers collection of high calcium exchange, use the post switching technology.The zeolite aggregation is placed in the post of heating, and with the calcium chloride solution of preheating by pillar, the sodium or the potassium ion that exchange removed in displacement and flushing.The further detailed content of ion-exchange step is in the embodiment of following numbering.

Embodiment 1

Skeleton Si/Al is disclosed in this embodiment ₂Than the CaNaX preparation of compositions, composition and the adsorption property that are 2.0.These compositions are called CaNX2.0.The CaNaX2.0 sample prepares with the aggregation of 8 * 12 native bonding bead forms of batch ion exchange NaX2.0.Usually, the 50 original NaX2.0 beads of gram (dry weight) are added to Ca (OH) ₂, pH value is adjusted to 1～2 liter of 0.15～1MCaCl of 9.0 ₂In the aqueous solution.Under each situation, according to the Ca that will reach ^#Ion-exchange degree is selected CaCl ₂The correct number of solution and concentration.If necessary, with repeatedly intermittently exchanging the product that can obtain the desired ion exchange degree.In each intermittently exchange, at CaCl ₂Stir the bead contain zeolite in the solution, simultaneously solution is heated to 90 ℃ from normal temperature, continue to stir 1 hour after being heated to 90 ℃.Through bead filtered and recycled in Buchner funnel of exchange, and with Ca (OH) ₂Regulate 500 milliliters of hot washes of PH to 9.0.After this, bead is in 1 premium on currency, at 90 ℃ and Ca (OH) ₂The pH value of regulating stirred 30 minutes for 9.0 times, with filtered and recycled with at air drying.Total has prepared seven CaNaX2.0 samples that hereinafter are called 1a-1g.The detailed data of preparation and the chemical composition of product are listed down Table I and Table II respectively in.All aggregation beads all contain 12% (weight) carclazyte adhesive.

Embodiment 2

Six Si/Al have been prepared with the same procedure of describing among the embodiment 1 ₂Mol ratio is NaX powder sample and two bead samples of 2,3 calcium exchange.The main difference point of method is that the medium temperatures in these preparation intermediate ions exchanges are 95 ℃, rather than among the embodiment 1 used 90 ℃.Be called the detailed data of 2a～2h sample and the chemical composition of ion-exchange product and list down Table I and Table II respectively in.

Embodiment 3

With so synthetic Si/Al ₂Mol ratio is that 2.5 8 * 12 bonding beads of NaX type zeolite carclazyte carry out Ca ^#Ion-exchange has prepared four samples that are called 3a～3d, and sample 3a and 3b carry out ion-exchange with the batch technique of embodiment 1 and 2, and sample 3c and 3d carry out ion-exchange with the post switching technology, wherein CaCl ₂The aqueous solution is by being equipped with the heated beam of the bead that contains zeolite.The detailed data of ion-exchange and the chemical composition of trade-to product are listed in respectively in Table I and the Table II.

Embodiment 4

Nitrogen and the oxygen adsorption isotherm of sample 1a～1g that under 40 ℃, 20 ℃, 0 ℃ and-20 ℃, activates and the raw material NaX2.0 of embodiment 1 with Sartorius balance mensuration.Sample activates in glass tube, and oil diffusion pump and liquid nitrogen trap are housed in the system, is heated to 510 ℃ from room temperature in 10 hours, and keeps under 510 ℃ 6 hours.Pressure reaches 1.33 * 10 when activation finishes ^-6KPa (1 * 10 ^-5Torr).In nitrogen and the measurement of oxygen adsorption isotherm, the temperature of each test specimen is controlled by the method that sample is placed on the sample room in constant temperature bath or the official stove (if necessary).Between 0～506.7 kPa (0～73.5 pound/square inch), get 13 data points.By the nitrogen adsorbance under accurate 10.7～101.4 kPas (1.55～14.7 pounds/square inch) of extrapolation mensuration.Also be determined at 25.5 kPas of oxygen adsorbances under (3.7 pounds/square inch) by extrapolation.25.5 the nitrogen Δ adsorbance between kPa (3.7 pounds/square inch) and 0 kPa (0 pound/square inch) obtains operating selectivity divided by oxygen Δ adsorbance.Residual adsorbance, Δ adsorbance and operate optionally ordered series of numbers and go into down Table III and paint into Fig. 1,2 and 3.

Embodiment 5

Press the method for the description in the foregoing description 4, measured the residual adsorbance of nitrogen, nitrogen Δ adsorbance and the nitrogen operation selectivity of NaX2.3 and the CaNX2.3 sample 2a～2h of embodiment 2 respectively.The result lists Table IV in.All these samples all do not add the zeolite powder of adhesive, just do not contain carclazyte.Fig. 4,5 and 6 discloses residual adsorbance and has operated the variation of selectivity with calcium exchange degree and adsorption temp.

Embodiment 6

Press the method for describing in the foregoing description 4, measured the residual adsorbance of nitrogen, nitrogen Δ adsorbance and the nitrogen operation selectivity of NaX2.5 and CaNaX2.5 sample 3a, 3b and the 3c of embodiment 3 respectively.The result lists in the Table V.Fig. 7,8 and 9 discloses residual adsorbance and has operated the variation of selectivity with calcium exchange degree and adsorption temp.

Embodiment 7

In order to assess adsorbent required desorption time in PSA circulation, with the Sartorius balance measurement nitrogen desorption rate.The adsorbent of activation at first contacts with nitrogen down at 101.3 kPas (1 atmospheric pressure).After reaching adsorption equilibrium, with the vavuum pump gas of finding time rapidly.Termination of pumping when pressure reaches 1.4 kPas (0.2 pound/square inch).Approximately needed for 10 seconds and reach this pressure.Make adsorbent reach its balance then, and the weightlessness of continuous monitoring adsorbent.Final pressure in the Sartorius balance is relevant with the adsorption capacity of adsorbent.For the CaNaX of Different Silicon aluminum ratio and different calcium exchange degree, final pressure is in the scope of 1.72～2.62 kPas (0.25～0.38 pounds/square inch).Because the desorption of nitrogen heat is big, the rapid desorption under adiabatic condition descends the temperature of adsorbent.Vacuum desorption in the Sartorius balance is more near adiabatic process.But, be difficult to directly to measure the temperature of sample in the Sartorius balance, so relatively estimate temperature behind the desorption with the nitrogen adsorption isotherm of 20 ℃, 0 ℃ and-20 ℃ respectively by residual adsorbance.

(a) the sample 1g of embodiment 1, the Si/Al of high calcium exchange (97%) ₂Mol ratio is 2.0 X type zeolite, and its nitrogen desorption curve is plotted in Figure 10.In order to obtain data, the sample of vacuum activation at first in the Sartorius balance with 112.4 kPas (16.3 pounds/square inch) under nitrogen balance.Rapidly balance is evacuated to then 1.38 kPas (0.2 pounds/square inch), makes sample reach balance, pressure is raised to 2.62 kPas (0.38 pounds/square inch) as a result.By being extrapolated to nitrogen that 2.62 kPas (1.5 to 0.38 pounds/square inch) determine under 20 ℃, 0 ℃ and-20 ℃ from 10.3 kPas, estimate that the equilibrium adsorption capacity under 2.62 kPas (0.38 pounds/square inch) is also painted into Figure 10.It seems that from these data the desorption the Sartorius balance seems to make the temperature of zeolite sample to be cooled to about 0 ℃.

(b) use basically and the identical method of above-mentioned (a) part, measure the nitrogen desorption curve that embodiment 1 contains the cationic Id sample of 75% (equivalent) calcium.These data are painted into Figure 11.Final nitrogen pressure in balance is that 172 kPas (0.25 pounds/square inch) and residual adsorbance are about 0.09 mM/gram.Draw in 172 kPas (0.25 pounds/square inch) (by 10.3 kPas (1.5 pounds/square inch) extrapolation) and the nitrogen balance adsorbances (also painting) of 20 ℃, 0 ℃ and-20 ℃ following expectation from observation, it seems that the temperature of sample drops to about 10 ℃ in desorption process into Figure 11.

(c) use and the identical method of above-mentioned (a) part, side has been decided the nitrogen desorption curve that embodiment 2 contains the cationic zh sample of 97% (equivalent) calcium.These data are painted into Figure 12.Final nitrogen pressure in balance is that 2.55 kPas (0.37 pounds/square inch) and residual adsorbance are about 0.38 mM/gram.Determine respectively that by the method that is extrapolated to 2.55 kPas (1.5 pounds/square inch to 0.37 pound/square inch) from 10.34 kPas under 20 ℃, 0 ℃ and-20 ℃, the nitrogen balance adsorbance under 2.55 kPas (0.37 pounds/square inch) also is plotted in Figure 12.It seems and in desorption process, make sample temperature drop to about 3 ℃.

(d) use and the identical method of above-mentioned (a) part, measured the nitrogen desorption curve that embodiment 2 contains the cationic zg sample of 77% (equivalent) calcium.These data are painted into Figure 13.Final nitrogen pressure is that 1.93 kPas (0.28 pounds/square inch) and residual adsorbance are about 0.07 mM/gram in balance.Determine respectively under 20 ℃, 0 ℃ and-20 ℃,, also to paint by the method that is extrapolated to 1.93 kPas (1.5 pounds/square inch to 0.28 pound/square inch) from 10.34 kPas into Figure 13 in the nitrogen balance adsorbance that 1.93 kPas (0.28 pounds/square inch) are estimated down.Draw from these data, it seems that the temperature that makes sample in desorption process drops to about 5 ℃.

(e) use and the identical method of above-mentioned (a) part, measured the nitrogen desorption curve that embodiment 3 contains the cationic sample 3d of 98% (equivalent) calcium.These data are painted into Figure 14.Final nitrogen pressure is that 2.62 kPas (0.38 pounds/square inch) and residual adsorbance are about 0.18 mM/gram in balance.Determine respectively under 22 ℃, 30 ℃ and-20 ℃,, also to paint by the method that is extrapolated to 2.62 kPas (1.5 to 0.38 pounds/square inch) from 10.34 kPas into Figure 14 in the nitrogen balance adsorbance that 2.41 kPas (0.35 pounds/square inch) are estimated down.It seems that the temperature that makes sample in desorption process drops to-13 ℃ approximately.

(f) use and the identical method of above-mentioned (a) part, measured the nitrogen desorption curve that embodiment 3 contains the cationic sample 3b of 77% (equivalent) calcium.These data are painted into Figure 15.Final nitrogen pressure is that 56.88 handkerchiefs (8.25 pounds/square inch) and residual adsorbance are about 0.06 mM/gram in balance.Draw from the nitrogen balance adsorbance (also painting) of observation, it seems that the temperature that makes sample in desorption process drops to about 3 ℃ into Figure 15 in 2.41 kPas (0.35 pounds/square inch) and 22 ° and 0 ℃ following expectations.Measure the nitrogen balance adsorbance of estimating by the method that is extrapolated to 1.72 kPas (1.5 to 0.25 pounds/square inch) from 10.34 kPas.

Measure the efficient of air separation by following three parameters, just nitrogen Δ adsorbance, nitrogen operation selectivity and the residual adsorbance of the nitrogen under desorption pressure with adsorbent.Consider in these parameters and the specification table and the data of accompanying drawing, comprise following concrete observed result, can clearly determine superiority of the present invention.

The adsorpting data that adds the bonding X2.0 sample of carclazyte is listed Table III in.Fig. 1 is that the residual adsorbance of nitrogen is mapped to the calcium exchange degree.It confirms that along with the calcium cations increase of zeolite adsorbents, the desorption of nitrogen becomes more and more difficult, so the residual adsorbance of nitrogen increases.At calcium content is 90% or 90% when above, and the residual adsorbance of nitrogen becomes so high, so that product is impure becomes a serious problem.The nitrogen residual content is also to responsive to temperature.90% calcium content and the 0 ℃ of operating temperature residual content that makes nitrogen that combines reaches unacceptable high-load.Because cooling always occurs in PSA technology, these digital proofs 90% or 90% above calcium exchange may damage the effect of X2.0 in more than one modes.

Fig. 2 provides the variation of the nitrogen Δ adsorbance of CaNaX2.0 between 101.3～10.69 kPas (14.7～1.55 pounds/square inch) with calcium content and adsorption temp.Along with calcium content increases, nitrogen Δ adsorbance also increases at first.After the Δ adsorbance reaches a wide maximum, begin to descend.These digital proofs, the calcium exchange degree is greater than 90% or all be undesirable less than 60%.

Fig. 3 provides the operation selectivity of X2.0 with calcium exchange degree and variation of temperature.Here be the obvious example that Temperature Influence can surpass the cation influence.Under 40 ℃, nitrogen operation selectivity increases with the increase of calcium content.At 85%Ca ⁺⁺Reach peak value near the exchange degree, begin then to descend.20 ℃ of following peak operation selectivity in 60～80% calcium content scopes.Below 0 ℃ or 0 ℃, the operation selectivity ratios CaNaX2.0 of NaX2.0 is higher.Nitrogen adsorptive selectivity at-20 ℃ of following CaNaX2.0 is more much lower than NaX2.0.

The adsorpting data of X2.3 sample is listed Table IV in.Fig. 4,5 and 6 provides the variation with calcium exchange degree and adsorption temp of residual adsorbance, Δ adsorbance and the operation selectivity of X2.3.Because these samples do not contain carclazyte, its adsorbance is than the sample height that adds adhesive accordingly.The result of X2.3 sample and the result of X2.0 are similar.Obvious 90 ℃ or 90% above cation are Ca ⁺⁺The use of X2.3 and technological temperature to be 0 ℃ all be undesirable.For the environmental condition process cycles that great temperature departure is arranged, calcium content is at least 60% and select most less than 90% CaNaX2.3.Usually, the operation selectivity ratios CaNaX2.0 adsorbent of CaNaX2.3 is low.

The adsorpting data that adds the X2.5 bead of adhesive is listed Table V in.These data and residual adsorbance, Δ adsorbance and operation selectivity provide an attractive example to calcium exchange degree mapping (Fig. 7,8 and 9): the performance of PSA adsorbent is not by single structural parameters decision.Silica alumina ratio and calcium content no less important.Along with calcium content increases, the nitrogen Δ adsorbance of X2.5 increases, and nitrogen operation selectivity descends.This point is identical with the variation that observes in X2.0 and X2.3 situation basically, but serious difference is arranged in detail.The nitrogen Δ adsorbance of CaNaX2.5 in 60～90% calcium scopes is more much lower than corresponding X2.3 and X2.0.This is that CaNaX2.5 is not used in main cause of the invention process.

The data of Fig. 1 show that along with calcium content in the zeolite increases, residual adsorbance of nitrogen or nitrogen adsorbance increase sharply under 10.7 kPas (2.55 pounds/square inch).Increment rate and adsorption temp are inversely proportional to.Under 0 ℃, the residual adsorbance of the X2.0 of 97% calcium exchange is 0.79 mM/gram, is higher than its Δ adsorbance (0.74 mM/gram).Therefore, it is much more difficult to use the CaX2.0 adsorbent to produce pure oxygen down at 0 ℃.Under 20 ℃, the residual adsorbance of its nitrogen is 0.39 mM/gram, and this value is higher, but is to use this adsorbent of appropriate process circulation time also can work.On the other hand, using calcium content is 76% (equivalent), is 0.46 mM/gram 0 ℃ of residual adsorbance of following nitrogen, roughly the same under 20 ℃ of it and CaX.The residual adsorbance of CaNaX2.0 under 20 ℃ is 0.25 mM/gram.CaNaX2.0 (76%) even also can work under 0 ℃ is so it is very favourable.

Referring to Fig. 2, be that 75% o'clock nitrogen Δ adsorbance is a maximum at 0 ℃ of following calcium content.Under 20 ℃ and 40 ℃, calcium content is that about 90% o'clock nitrogen Δ adsorbance is a peak value.According to nitrogen Δ adsorbance, the CaNaX2.0 of 75% exchange has tangible benefit than the CaX2.0 of 97% exchange.

Show that in Fig. 3 the CaNaX2.0 of 76% exchange has higher operation selectivity than the CaX2.0 of 97% exchange under 20 ℃ and 0 ℃.These data acknowledgements have greater flexibility under the situation of using CaNaX2.0 ratio use CaX2.0 under the selected process conditions.

According to the desorption curve of Figure 10 and Figure 11, desorption is one minute as can be seen, and the residual adsorbance on sample 1g (CaX2.0 (97%Ca)) is 6 times of sample 1d (CaNaX2.0 (75%Ca)).These data show that highly the zeolite of Jiao Huan the fewer exchange of zeolite needs the longer recovery time.Another important conclusions of these data is that the zeolite that highly exchanges behind the desorption may have much lower temperature than the zeolite of medium exchange.Adsorption temp descends and makes height Ca ⁺⁺The X type zeolite of exchange goes wrong, because their poor efficiency at low temperatures.

The nitrogen desorption curve of CaX2.3 (97%Ca) and the equilibrium adsorption capacity of expectation under 2.55 kPas (0.37 pounds/square inch) are painted into Figure 12.CaNaX2.3 (77%Ca) and the equilibrium adsorption capacity of expectation under 1.72 kPas (0.25 pounds/square inch) are painted into Figure 13.The residual adsorbance of CaNaX2.3 is about 0.05 mM/gram, and the temperature of its estimation is about 9 ℃ behind the desorption.Equally, the X2.3 of 77%Ca exchange is more effective adsorbent than the X2.3 of 97% exchange.

The nitrogen desorption curve of CaX2.5 (97%Ca) and the equilibrium adsorption capacity of expectation under 262 kPas (38 pounds/square inch) are painted into Figure 13.The nitrogen desorption curve of CaNaX2.5 (77%Ca) and the adsorption capacity of expectation under 1.72 kPas (0.25 pounds/square inch) are painted into Figure 14.The residual adsorbance of CaX2.5 is about 0.17 mM/gram, estimates that the temperature behind the desorption is-13 ℃ approximately.The equilibrium adsorption capacity of CaNaX2.3 is about 0.07 mM/gram, estimates that the temperature behind desorption is-3 ℃ approximately.See that it is astonishing that CaNaX2.5 has the residual adsorbance that is equivalent to-3 ℃.But this point and CaNaX2.5 with respect to CaNaX2.0 and CaNaX2.3 are that relatively poor PSA adsorbance is consistent.

The preparation method of Table I sample and explanation

Sample type	Sample	The preparation method *	Form
				?MaX2.0 ?CaNaX2.0 ?CaNaX2.0 ?CaNaX2.0 ?CaNaX2.0 ?CaNaX2.0 ?CaNaX2.0 ?CaNaX2.0 ?NaX2.3 ?CaNaX2.3	????1a ????1b ????1c ????1d ????1e ????1f ????1g ????2a	Raw material (1) batch ion exchange NaX2.0 bead is used 0.15M CaCl 2, pH9,90 ℃ of 1hr. (1.5) batch ion exchange NaX2.0 bead is used 0.23M CaCl 2, pH9,90 ℃ of 1hr. (2.0) batch ion exchange NaX2.0 bead is used 0.3M CaCl 2, pH9,90 ℃ of 1hr. (1.5) batch ion exchange NaX2.0 bead is used 0.57M CaCl 2, pH9,90 ℃ of 1.5hr. (4.0) batch ion exchange NaX2.0 bead is used 0.6M CaCl 2, pH9,90 ℃ of 1hr. (10) batch ion exchange NaX2.0 bead is used 1M CaCl 2, pH9,90 ℃ of 1hr. (2) be (10) batch ion exchange in turn then, uses CaCl 2Raw material (0.8) CaCl 2Batch ion exchange NaX2.3 powder, 0.4M, pH9,95 ℃	8 * 12 beads, 8 * 12 beads, 8 * 12 beads, 8 * 12 beads, 8 * 12 beads, 8 * 12 beads, 8 * 12 bead powder powder

The preparation method and the explanation of Table I (continuing) sample

Sample type	Sample	The preparation method *	Form
				?CaNaX2.3 ?CaNaX2.3 ?CaNaX2.3 ?CaNaX2.3 ?CaNaX2.3 ?CaNaX2.3 ?CaX2.3 ?NaX2.5 ?CaNaX2.5 ?CaNaX2.5 ?CaX2.5 ?CaX2.5	????2b ????2c ????2d ????2e ????2f ????2g ????2h ????3a ????3b ????3c ????3d	(1.0)CaCl 2Batch ion exchange NaX2.3 powder, 0.33M, pH9,95 ℃ of (1.2) CaCl 2Batch ion exchange NaX2.3 powder, 0.4M, pH9,95 ℃ of (2.4) CaCl 2Batch ion exchange NaX2.3 powder, 0.83M, pH9,95 ℃ of (5.0) CaCl 2Batch ion exchange NaX2.3 powder, 0.83M, pH9,95 ℃ of (10) CaCl 2Batch ion exchange NaX2.3 powder, twlce, 1.9M, 95 ℃ of (1.0) CaCl 2Batch ion exchange NaX2.3 bead (6) CaCl post ion-exchange NaX2.3 bead pH9,95 ℃ of ratio samples (1.2) CaCl 2Batch ion exchange NaX2.5 bead, pH8,95 ℃ of (2) CaCl 2Batch ion exchange NaX2.5 bead, pH8,95 ℃ of (6) post ion-exchange NaX2.5 beads, pH8,95 ℃ of (6) post ion-exchange NaX2.5 beads, pH8,95 ℃	Powder powder powder powder powder 8 * 12 beads 8 * 12 beads 16 * 40 orders 8 * 12 beads 8 * 12 beads 8 * 12 beads 8 * 12 beads

* the Na that will exchange of the numeric representation in the bracket with respect to zeolite ⁺The CaCl that ion uses ₂Stoichiometric number.

The chemical analysis results of Table II sample

Sample type	Sample number	????LOI *% (weight)	????Al 2O 3% (weight) butt	????SiO 2% (weight) butt	????Na 2O % (weight) butt	CaO % (weight) butt	Calcium content, equivalent
								????NaX2.0		????21.60	????32.40	????45.28	????18.11		????0.00
????CaNaX2.0	????1a	????23.80	????32.94	????45.28	????8.65	????10.45	????0.57
								????CaNaX2.0	????1b	????24.00	????33.03	????45.39	????6.32	????12.64	????0.69
????CaNaX2.0	????1c	????24.30	????33.29	????45.84	????4.91	????14.00	????0.76
								????CaNaX2.0	????1d	????23.80	????33.07	????47.28	????5.13	????13.52	????0.75
????CaNaX2.0	????1e	????24.50	????33.11	????43.30	????3.13	????15.89	????0.85
								????CaNaX2.0	????1f	????24.70	????32.93	????45.55	????2.05	????16.60	????0.90
????CaNaX2.0	????1g	????24.90	????33.69	????45.94	????0.67	????18.24	????0.97
????NaX2.3			????25.20	????35.00	????14.80		????0.00
								????CaNaX2.3	????2a	????27.80	????34.21	????46.68	????8.09	????11.25	????0.61
????CaNaX2.3	????2b	????26.60	????34.20	????47.28	????6.46	????12.82	????0.69
								????CaNaX2.3	????2c	????28.10	????34.49	????47.15	????6.11	????13.32	????0.71
????CaNaX2.3	????2d	????27.20	????34.48	????46.84	????4.24	????14.97	????0.80
								????CaNaX2.3	????2e	????28.30	????34.59	????47.00	????2.72	????16.46	????0.87
????CaX2.3	????2f	????28.55	????33.45	????46.89	????0.66	????19.03	????0.97
								????CaNaX2.3	????2g	????25.00			????4.26	????12.64	????0.77
????CaNaX2.3	????2h	????26.10	????31.80	????49.53	????0.18	????17.49	????0.99
								????NaX2.5		????24.40	????32.54	????48.54	????17.72	????0.00	????0.00
????CaNaX2.5	????3a	????25.20	????31.02	????50.94	????6.42	????11.43	????0.66
								????CaNaX2.5	????3b	????25.10			????4.33	????13.09	????0.77
????CaNaX2.5	????3c	????26.20			????0.41	????16.49	????0.98
								????CaX2.5	????3d	????25.10			????0.40	????17.24	????0.98

^*Calcination loss under LOI=1000 ℃

The air adsorpting data of Table III X2.0

???????A	????B	????C	????D	????E	??????F	?????G	???????N
								Sample type	Ca content, % (equivalent)	Sample number	Adsorption temp ℃	Nitrogen adsorbance mM/gram under 1.55 psia	Nitrogen Δ adsorbance mM/gram (14.7-1.55) psia	At 3.7psia oxygen adsorbance mM/gram	Nitrogen operation selectivity, nitrogen Δ adsorbance under 3.7psia/oxygen Δ adsorbance
????NaX2.0	????0		????41.5	????0.03	????0.21	????0.02	????10.32
								????CaNaX2.0	????57	????1a	????40	????0.06	????0.36	????0.03	????11.74
????CaNaX2.0	????69	????1b	????40	????0.08	????0.42	????0.04	????11.83
								????CaNaX2.0	????76	????1c	????40	????0.14	????0.57	????0.04	????12.86
????CaNaX2.0	????85	????1e	????40	????0.18	????0.72	????0.05	????13.78
								????CaNaX2.0	????90	????1f	????40	????0.22	????0.75	????0.06	????12.79
????CaNaX2.0	????97	????1g	????40	????0.23	????0.69	????0.06	????12.32
								????NaX2.0	????0		????22	????0.05	????0.36	????0.03	????10.85
????CaNaX2.0	????57	????1a	????21	????0.13	????0.55	????0.05	????10.74
								????CaNaX2.0	????69	????1b	????21	????0.17	????0.63	????0.05	????12.07
????CaNaX2.0	????76	????1c	????20.6	????0.25	????0.75	????0.07	????11.52
								????CaNaX2.0	????85	????1e	????21	????0.34	????0.84	????0.08	????10.75
????CaNaX2.0	????90	????1f	????21.7	????0.40	????0.85	????0.08	????10.39
								????CaNaX2.0	????97	????1g	????20	????0.39	????0.74	????0.09	????8.60
????NaX2.0	????0		????0	????0.07	????0.51	????0.06	????12.69
								????CaNaX2.0	????57	????1a	????0	????0.26	????0.74	????0.07	????10.09
????CaNaX2.0	????69	????1b	????0	????0.32	????0.79	????0.08	????9.87
								????CaNaX2.0	????76	????1c	????0	????0.46	????0.85	????0.10	????8.57
????CaNaX2.0	????85	????1e	????0	????0.62	????0.84	????0.13	????6.65
								????CaNaX2.0	????90	????1f	????0	????0.75	????0.79	????0.14	????5.55
????CaNaX2.0	????97	????1g	????0	????0.79	????0.74	????0.15	????4.91

^*Psia is a pound/square inch

The absorption of air data of Table IV X2.3

????A	?????B	????C	?????D	?????E	?????F	????G	??????N
								Sample type	Ca content, % (equivalent)	Sample number	Adsorption temp ℃	Nitrogen adsorbance mM/gram under 1.55 psia	Nitrogen Δ adsorbance mM/gram (14.7-1.55) psia	At 3.7 psia oxygen adsorbance mM/grams	Nitrogen operation selectivity, nitrogen Δ adsorbance under 3.7psia/oxygen Δ adsorbance
?NaX2.3	????0		????40.5	????0.03	????0.27	???0.03	????9.28
								?CaNaX2.3	????60.6	????2a	????40	????0.08	????0.45	???0.04	????11.58
?CaNaX2.3	????68.7	????2b	????40	????0.11	????0.51	???0.04	????11.76
								?CaNaX2.3	????70.7	????2c	????40	????0.12	????0.55	???0.04	????12.64
?CaNaX2.3	????79.6	????2d	????40	????0.18	????0.64	???0.05	????12.12
								?CaNaX2.3	????87.0	????2e	????40	????0.22	????0.67	???0.06	????11.72
?CaNaX2.3	????97	????2f	????40	????0.25	????0.76	???0.07	????10.58
								?NaX2.3	????0		????21.1	????0.06	????0.43	???0.04	????10.67
?CaNaX2.3	????60.6	????2a	????20.6	????0.15	????0.59	???0.05	????11.26
								?CaNaX2.3	????68.7	????2b	????20	????0.20	????0.66	???0.06	????11.29
?CaNaX2.3	????70.7	????2c	????23.7	????0.22	????0.71	???0.06	????11.00
								?CaNaX2.3	????79.6	????2d	????21.6	????0.32	????0.78	???0.08	????10.25
?CaNaX2.3	????87.0	????2e	????20	????0.41	????0.76	???0.09	????8.79
								?CaNaX2.3	????97	????2f	????20	????0.47	????0.85	???0.11	????7.88
?NaX2.3	????0		????0	????0.10	????0.69	???0.06	????12.22
								?CaNaX2.3	????60.6	????2a	????0	????0.27	????0.78	???0.08	????9.98
?CaNaX2.3	????68.7	????2b	????0	????0.41	????0.82	???0.10	????8.35
								?CaNaX2.3	????70.7	????2c	????0	????0.43	????0.83	???0.10	????8.19
?CaNaX2.3	????79.6	????2d	????0	????0.59	????0.81	???0.13	????6.39
								?CaNaX2.3	????87.0	????2e	????0	????0.66	????0.73	???0.14	????5.06
?CaNaX2.3	????97	????2f	????0	????0.78	????0.73	???0.17	????4.39

The air adsorpting data of Table V X2.5

Sample type	Ca content, % (equivalent)	Sample number	Adsorption temp	Nitrogen adsorbance mM/gram under 1.55ps ia	Nitrogen Δ adsorbance mM/gram (14.7-1.55) psia	At 3.7 Psia oxygen adsorbance mM/grams	Nitrogen operation selectivity, nitrogen Δ adsorbance under 3.7 psia/oxygen Δ adsorbance
????NaX2.5	????0		????40	????0.03	????0.25	????0.03	??????8.97
								????CaNaX2.5	????66	??????3a	????40	????0.10	????0.27	????0.02	??????11.32
????CaNaX2.5	????77	??????3b	????40	????0.13	????0.49	????0.04	??????11.42
								????CaNaX2.5	????98	??????3c	????40	????0.26	????0.68	????0.07	??????9.53
								????NaX2.5	????0		????22.7	????0.05	????0.37	????0.03	??????10.85
????CaNaX2.5	????66	??????3a	????20.6	????0.14	????0.48	????0.05	??????9.48
								????CaNaX2.5	????77	??????3b	????21	????0.23	????0.54	????0.05	??????10.50
????CaNaX2.5	????98	??????3c	????22	????0.45	????0.72	????0.11	??????6.54
????NaX2.5	????0		????0	????0.10	????0.63	????0.05	??????12.98
								????CaNaX2.5	????66	??????3a	????0	????0.24	????0.57	????0.07	??????7.80
????CaNaX2.5	????77	??????3b	????0	????0.41	????0.64	????0.10	??????6.57
								????CaNaX2.5	????98	??????3c	????0	????0.75	????0.66	????0.18	??????3.63

Claims (4)

1. the adsorbent of the pressure swing adsorption technique that is used to circulate, this technology is by selection absorption separating nitrogen from the mixture of nitrogen and oxygen of nitrogen, and this adsorbent contains skeleton SiO ₂/ Al ₂O ₃Mol ratio is 2.0～2.4 and contains 60～89% (equivalent) Ca ⁺⁺Cation, 10～40% (equivalent) Na ⁺Cation and 0～10% (equivalent) K ⁺Cationic X type zeolite, Ca ⁺⁺, Na ⁺And K ⁺The total cation equivalent that provides is at least 90%.

2. according to the adsorbent of claim 1, it is further characterized in that, the SiO of X type zeolite ₂/ Al ₂O ₃Mol ratio is 2.0～2.35, and its cation contains 65～80% calcium cations and 20～35% sodium cations, is substantially free of potassium cationic.

3. one kind is used for from the circulation technology of the mixture separating nitrogen of nitrogen and oxygen, and this technology may further comprise the steps:

(a) provide the adsorption bed of the adsorbent that claim 1 or claim 2 regulation is housed;

(b) mixture of described nitrogen and oxygen is sent into described adsorption bed under-20～50 ℃, until voltage rise to 13.8 kPa to 506.8 kPas (2 to 73.5 pounds/square inch) and nitrogen are selected to be adsorbed on the described adsorbent in the bed;

(c) under adsorptive pressure, from adsorption bed, give off the oxygen of not absorption basically as product; And

(d) bed layer pressure is dropped to the nitrogen desorption that the interior final desorption pressure of 101.4 to 0.7 kPas of (14.7 to 0.1 pounds/square inch) scopes makes absorption, from bed, give off the nitrogen of desorption then.

4. according to the technology of claim 3, wherein the mixture of nitrogen and oxygen is an air.

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