CA1290312C

CA1290312C - Process for the removal of no from fluid streams using a water-soluble polymeric chelate of a polyvalent metal

Info

Publication number: CA1290312C
Application number: CA000531490A
Authority: CA
Inventors: Robert R. Grinstead
Original assignee: Dow Chemical Co
Current assignee: Dow Chemical Co
Priority date: 1986-03-10
Filing date: 1987-03-09
Publication date: 1991-10-08
Anticipated expiration: 2008-10-08
Also published as: DK123387D0; JPS62269732A; EP0241141A3; AU597622B2; EP0241141A2; NO168019B; NO870969L; NZ219525A; CN87101791A; NO870969D0; US4708854A; NO168019C; CN1007889B; DK123387A; AU6913887A

Abstract

ABSTRACT

The present invention concerns to a cyclic continuous process and for the removal of NO and SO2 from a variety of fluid streams. A fluid stream containing NO and SO2 is contacted with an aqueous solution of a composition having a water-soluble organic polymeric chelate containing a polyvalent metal, e.g ., Fe (11). The NO is catalytically absorbed and in the presence of SO2, the imidodisulfonate is formed. Optionally, a reducing agent, such as sodium hydrogen sulfide, is added to maintain the polyvalent metal in the reduced state. The process next includes removal of the imidodisulfonate formed. The separation of water and low molecular weight materials and products, e.g. molecular weight below 500, usually occurs by ultrafiltration or dialysis, with recycle and re-use of the polyvalent metal chelate.

Description

lZ903~.~

PROCESS FOR THE REMOVAL
OF NO FROM FLUID STREAMS USING A COMPOSITION OF
A WATER-SOLUBLE POLYMERIC CHELATE AND POLYVALENT M~TAL

This invention concerns a process wherein a fluid stream 5 comprising a noxious gas, e.g., nitric oxide tNO), and sulfur dioxide (S02) is treated with a composition having a water-soluble polymeric chelate of a polyvalent metal to adsorb the nitric oxide. Water and the imidodisulfonate subsequently formed are separated from the polymeric chelate by means such as dTalysis or ultrafiltration. The 10 polyvalent metal chelate is then recycled and re-used. More specifTcally, the present invention relates to a process of removing NO from a gas stream using an aqueous solution of a water-soluble polymeric chelate of iron in the Fe ~Il) state, separating the imidoclisulfonate and a portion of the water by concentrating the 15 aqueous water-soluble polymeric chelate of iron using uitrafiltration or dialysisr and recycling and re-using the polymeric chelate of iron tll) .

U.S. Patent 4,448,899 discloses a process for removing NO
20 from a gas stream by absorption with a water-soluble iron (Il) chelate. The SX and NO pollutants dissolved in the absorbent during regeneration are converted to hydrogen sulfide and nitrogen, respectively .
31 ,375A-F -1-~290:3~.2 U . S . Patent 4,423,158 discloses introducing a monomeric chelate-forming group into a polymer such as polystyrene. There is obtained an adsorbant for bivalent or multivalent metal ions which are useful in ion-exchange chromatography. The reference does not 5 disclose the water-soluble polymeric chelates of the present invention which are useful to remove noxious NO from fluid streams.
U.S. Patents 3,984,522 and 4,044,101 disclose a process for removing NO from a gas stream the use of a solution containing a monomeric iron chelate and sulfite or sulfide. There is no disclosure 10 regarding using a polymeric chelate of a metal, with separation of water and low molecular weight products and materials, from the chelate .
U.S. Patents 4,079,118 and 4,091,074 disclose a process for the absorption of N0 in a solution of ferric (or ferrous) 15 ion-ethylenediamine tetraacetic acid (EDTA) and sulfite. The liquid is treated to recover S02, then by a complex procedure recovers iron by alkaline precipitation with recycle of the iron and EDTA and separation of the dithionate and other products for disposal. In this process, monomeric EDTA is lost by the system.
U.S. Patents 3,991,161; 3,992,508; 4,055,623 and 4,087,372, disclose processes for absorbing NO in sulfite solutions containing iron salts to produce imidodisulfonates with subsequent hydrolysis to ammonium sulfate. There is no discussion of polymeric chelates or the problems encountered during the separation of excess water and 25 buildup of products, by-products and materials.
It is known by the number of techniques described above to treat a stack gas with a monomeric organic chelate of iron ( 11 ) . A
31,375A-F -2-129()~ 2 problem with these processes is that the efficient separation of excess water, products which build up during the reaction and byproducts from the monomeric organic chelate of iron l l l ) from the aqueous stream is usually difficult and very costly. A portion of the expen-5 sive iron-monomeric organic chelate is lost during separation of the low molecular weight materials, and cannot be recovered. It is there-fore highly desirable to have a process where the expensive organic polymeric iron ~III) or iron (Il) chelate is separated easily from a waste stream originally containing NO, where the organic polymeric 10 chelate of iron is recycled and used again and again. The present invention provides such a process.
The present invention concerns a process for the removal of NO from a fluid stream comprising mixtures of NO and SO2, which process comprises:
(A) contacting the fluid stream in a contacting zone with an aqueous reaction solution at a temperature of between 10 and 90C, the reaction itself comprising an effective amount of a composition having a water-soluble organic polymeric chelate containing a polyvalent metal, wherein the chelate has a weight 20 average molecular weight between 1,000 and 500,000 and wherein the chelate is:
. (a) -~CH2~CH2~N)~n Xl wherein X1 in each polymer unit is independently -H or R-wherein R is -CH2COOH, -CH2CH2COOH, -CH2-P(=O) (OH)2, 31, 375A-F -3-~ Z9 -CH~

wherein R1 and R2 are each independently -CH3, -SO3H, -Cl, -H, or -COOH and n is an integer between 5 and 20,000;
(b) -(CH -CH2N) wherein X2 in each polymer unit is -H, -CH2CH(OH)CH2OH, -CH2CH (OH)CH2CI or HO-CH-CH2- ( N-CH 2CH2) qN

wherein R3, R4 and R5 are each independently R as defined hereinabove, p is~ an integer between 5 and 20,000; and q is an integer 0, 1, 2, 3 or 4;
~c) -(CH2-CH-O)-r x3 wherein X3 in each polymer unit is independently -OH, -Cl or R;4 ( N-CH 2-CH2) -N

31 ,375A-F -4-1290~ 2 wherein R3, R4 and R5 are as defined hereinabove; r is an integer between 10 and 20,000, and s is an integer between 1 and 4;
(d) -(CH2-CH)-t C-O
x4 wherein X4 in each polymer unit is independently -OH, -OCH3, -OCH2CH3 or NH-(CH2-CH2-NI )X-cH2-cH2 N.~

wherein R3, R4 and R5 are as defined hereinabove, ~ is an integer between 10 and 20,000; and x is an integer between 1 and 4;
(e) -(CH2-CH-)-y wherein X5 in each polymer unit is independently -OH, -Cl or --( N-CH2-CH2) z-N

wherein R3, R4 and R5 are as defined hereinabove; y is an integer between 10 and 20,000, and z is an integer between 1 and 4;

31 ,375A-F -5-~290~

11 ( H2)a lC~- IN-(CH2CH2- 1 )b-CH2CH2]_ wherein X6 in each polymer unit is independently -CH2CH(OH)CH2OH, -CH2CH(OH)CH2CI, or HO-CH-CH2( N-CH2CH2)CN

wherein v is between 10 to 10, 000, a is 6, b is 1 to 4, c is. 1 to 4; and R3, R4 and R5 are as defined hereinabove;
(g) H
-[CH2CH2-ll-N-(CH2cH2 1 )m] 9 wherein X7 in each polymer unit is independently -H, -CH2CH(OH~CH2OH, -CH2CH(OH)CH2CI, or HO-CH-CH2-( 1~CH2~CH2)q~N\

wherein m is an integer from 1 to 4, g is between 10 to 10,000, and q, R3, R4 and R5 are as defined hereinabove;
(h) j' I (CH2)6 1 ~CH2)6 1 C 2 1 2 l X8 Xg x1o OH w wherein X8, X9 and X1 0 in each polymer unit are each independently -H, -CH2CH (OH)CH2CI, -CH2CH (OH)CH2OH, or 31 ,375A-F -6-~ 29()~ .2 t /R4 HOCH~CH2(~N~CH2CH2)qN\

wherein q, R3, R4 and R5 are as defined hereinabove, and w is between 10 and 10, 000, or (i) mixtures of polymeric chelates (a) to ~h) 5 with the proviso that the overall ratio of -H, -OCH3, -OCH2CH3, -Cl, or -OH to substituent in each of X1, X2, X3, X4, X5, X6, X7, X8, Xg or X10 in each polymeric chelant (a to h) hereinabove is between about 10/90 and 90/10;
(B) separating the fluid stream and the resulting aqueous 10 phase containing the polymeric chelate ~ iron (Il) and imidodi-sulfonate of step (A) (C) concentrating the aqueous phase repeated in step (B) by means effective to remove a portion of the water and other mono-meric reaction products having a molecular weight below 500 and;
(D) recycling the concentrated aqueous solution produced in step (C) to the contacting zone of step (A).
In a preferred embodiment, the polyvalent metal in the chelate i5 iron ( I l ) .
I n another preferred embodiment, in step ( C), a portion of 20 the aqueous solution is separated from the polymeric chelate by membrane separation means, selected from ultrafiltration or dialysis.
Figure 1 illustrates a process in which an aqueous solution of an organic polymeric chelate of a polyvalent metal of this invention i~ applied to the removal of NO and 52 contained in a fluid stream~
31, 375A-F -7-.,.. ~,,. -1 ~0.~1~

suc:h as from a stack gas from a power plant. The organic polymericchelate of ferrous ( l l ) ion NO is a transient intermediate which instantaneously reacts with the bisulfite HS03 formed by the reaction of S2 with water to form the imidodisulfonate ion, HN(503)2 . A
5 portion of the water is separated from water and low molecular weight material using dialysis or ultrafiltration techniques. The organic polymeric chelate of ferric ion is continuously recycled and re-used.
The process eliminates the environmental pollution problem associated with the discharge of an effluent stream containing toxic and noxious 10 nitric oxide.
Figure 2 shows a comparison of the saturation capacity of the iron ( l l ) chelates to remove NO.
This section is organized in the following order: fluid streams, the water-soluble polymeric chelates, the poly~alent metals 15 and the separation means for water and low molecular weight mate-rials. In the following section, the process and results are discussed .
Fluid Streams In the present invention, "fluid stream" refers to any 20 gaseous, liquid or combination gaseous-liquid stream. These fluid streams include, for example, stack gases from a power plant, com-bustion gases from the burning of natural gas, petroleum, oil shale, coal and the like.
The Water-Soluble Polymeric Chelates Any otherwise inert water-soluble polymeric chelate capable of chelating a polyvalent metal is suitable in the present process.
Inert in this context is defined as not detrimentally reactive in the 31, 375A-F -8-12903~2 g reaction to an intolerable extent. Polymeric chelates having a molecu-lar weight between 500 and 1,000,000 are preferred in the present process. Polymeric chelates having a molecular weight between 1000 and 500,000 are more preferred.
Those polymers having a backbone chain with pendant groups capable of chelating metals are preferred.
It is also contemplated that mixtures of ~he water-soluble organic polymeric chelates described hereinabove are useful in the present invention. The concentration of the polymer should be at a 1~ level so as to provide up to about 1-gram equivalent weight of the chelating group per liter of solution.
A more detailed description of the preparation for these various organic polymeric chélates is provided below and as part of the Examples. The pendant group in each repeating unit of the 15 polymer is selected from those designated groups in the following description and in the Examples. Some polyamines and polyethers used in synthesis are described in Table 1 below.

31 ,375A-F -9-1290;~12 TA B LE
POLYAMINES USED AS STARTING MATERIALS
FOR POLYCHELATOR SYNTHESIS
.
, uegree Ot MOleCUlar Polym. Weight Nature of Aminea (û. P. ) Range Chain E-100b 6 250-300 Branched PEI-6 15 600 Branched Hydrolyzed PEOx 50c 2000 Linear Purifloc C-31d 500 10,000-30,000 Branched Hydrolyzed PEOx 500f 20,00û Linear PEI-600 1500 60,000 Branched Hydrolyzed PEOx 50009 500,000 Linear a. PEI = polyethyleneimine; PEOx, polyethyloxazoline, PEI is a polymer of molecular weight 60,000 (CORCAT* 600) and is ob-tained from Cordova Chemical Company. The nitrogen content is determined by drying a sample, and elemental analysis of the sol id .
b . E-100 -- is a byproduct of ethylenediamine manufacture and is a low molecular weight branched polymer containing about six ethyleneamine groups.
c. 100% hydrolyzed d. Purifloc~ C-31 -- is a polyethylene amine product of the Dow Chemical Company, Midland, Michigan.
25 e. Probably also partially crosslinked.
f. 8596 hydrolyzed g. 97% hydrolyzed *Trademark 31,375A-F -10-~yl ~ 29~)~31X

One embodiment of the chelate designated (a) (CH2-CH2- 1 ) n where X1 is either -H or -CH2COOH (CHELATE A) is prepared by dissolving polyethyleneimine (CORCAT 150 or CORCAT 600, available 5 from the Cordova Chemical Company) in water followed by reaction with excess sodium chloroacetate in the presence of strong base.
In the synthesis of the pendant polymeric chelants-(a) to ~h), the procedure usually includes the addition of the pendent group to an available polymeric backbone. However, under the reaction 10 conditions, not all of the possible chelant additions occur on the polymer backbone. Thus, in chelate (a) where the repeating unit is:
-CH2CH2N-CH2CH2- 1 -CH2CHi N -(CH2CH2N)n-3 X1 x~ xt x~
some of the pendent groups, X1; are -H and others are, for example, -CH2COOH, e.g.:
15 -CH2CH2N-CH2CH2- I-CH2CH2- 1 (CH2CH2 1 )n-3 H CH2COOH H H ~orCH2COOH) This type of random pattern of addition occurs for the pendant chelant groups in the poiymeric chelants [(a) to lh)].
If the polymer backbone contains a pendant epoxide group, e . g .:
20 -CH2CH-CH2O, then after addition, if all epoxide groups do not react further, then the chemical groups -CH2CH(OH)CH2OH, or CH2CH~OH)CH2CI are pendant groups from the polymer backbone.

31, 375A-F -11-1290~ 2 Another embodiment of the polymeric chelate designated ~a) -[CH2-CH2-N(X1)~n-, where X1 in each polymer unit is either is -H
or -CH2P(=O) (OH)2 (CHELATE B) is prepared by dissolving polyethyleneimine in water and reaction with 5 phosphoric acid and formaldehyde. The process described by R. S.
Mitchell in U.S. Patent 3,974,0~0 for the monomer may be adapted using the polymeric imine.
A further embodiment of the polymeric chelate (a) designated -(CH2-CH2-N)-, where X1 in each polymer unit is -H or:

CH2 ~\R~

and R1 and R2 are each methyl (CHELATE C), is obtained by dissolving polyethyleneimine in water followed by treatment with 2,4-dimethylphenol and formaldehyde. The general procedure de-scribed by G. Grillot and W. Gormley, Jr., J. Amer. Chem. Soc., 15 Vol. 67, pp. 1968ff (1945) for the monomer is adapted using the polymeric imine.
One embodiment of the polymeric chelate designated (b) where X2 in each polymer unit is either -H or -cH2cH(oH)cH2N(cH2cooH)cH2cH2N(cH2cooH)2 and q is 20 (CHELATE D), is obtained by first reacting epichlorohydrin, OCH2CH(CH2CI), with ethylenediamine-triacetic acid to produce O-CH2-CHCH2-N-(CH2COOH)CH2CH2N(CH2COOH)2, foilowed by 31, 37SA-F -12-12903~.~

reaction with polyethyleneimine. The procedure described above, for CHELATE A, may also be adapted. For those polymers where q is 2, 3 or 4, the ethylenediamine is replaced with the corresponding diethylenetriamine, triethylenetetraamine and tetraethylene-pentamine, 5 respectively.
Another embodiment is of the polymeric chelate designated (b), wherein X2 in each polymer unit is either -H or ~CH2CH(OH)CH2[N(R3)CH2CH2]qN(R4)(R5), p is about 20,000, q is 0, and R3, R4 and R5 are each -CH2COOH tCHELATE D-1 ), 10 iminodiacetic acid is dissolved in water and epichlorhydrin, about a 20% excess is added. The product is extracted with a chlorinated hydrocarbon such as methylene chloride to remove the unreacted epichlorhydrin. To this aqueous solution is added a 33% aqueous solution of polyethyleneimine, e.g., CORCAT 600, the solution is 15 heated and further treated with sodium hydroxide at a pH of 9 to 10.
The chelate solution is used without further purification.
One embodiment of the polymeric chelate designated ~c), wherein X3 in each polymer unit is either -OH or -[NC(R3)CH2CH2]sN(R4) (R5), r is about 100 and R3, R4 and R~ are 20 each -CH2COOH (CHELATE E) is prepared by treating polyepichlorGhydrin with ethylenediamine in the presence of base followed by treatment with excess sodium chloroacetate.
One embodiment of the chelate designated ld), wherein X4 in each polymer unit is either -OH or 25 -NHlCH2CH2N(R3)]xCH2CH2N(R4)(R5), t is 10a, x is 1 and R3, R4 and R5 are each -CH2COOH ( CHELATE F) is prepared by the 31, 375A-F -13-.X90~Z

treatment of poly(ethylacrylate) with diethylenetriamine followed by treatment with sodium chloroacetate in the presence of a strong base.
One embodiment of the chelate designated (e), where X5 in each polymer unit is either -OH or -[N(R3)CH2CH2]zN(R4~(R5), and R3, R4 and R5 are each -CH2COOH, y is 100 and z is 1 ( CHELATE
G) is the treatment of poly(vinylbenzylchloride) with ethylenediamine in the presence of strong base. The product in the presence of base, is next treated with excess sodium chloroacetate. By replacement of ethylenediamine with diethylenetriamine, triethylene 10 tetraamine, and the like, the higher homologues are produced.
One embodiment of the chelate designated (f) where X6 in each polymer unit is either -CH2CH(OH)CH20H or -cH2cH(oH)cH2[NtR3)cH2cH2]cN(R4)(Rs) where R3, R4 and R5 are each -CH2COOH and c is 1 (CHELATE H) is obtained by the treat-15 ment of the commercial polymer KYMENE*557H (which is obtained fromthe Hersules Corporation of Wilmington, Delaware) with ethylenediamine triacetic acid.
One embodiment of the chelate designated (g) where X7 in each polymer unit is either -H or 20 -cH2(oH)cH2[N(R3)-cH2cH2]cN(R4)(Rs) is 1 and R3, R4 and R5 are each -CH2COOH (CHELATE J), is obtained by reacting the polymer of methylacrylate and ethylenediamine with the epoxide adduct formed by the treatment of iminodiacetic acid with epichlorohydrin.
One embodimen~ of the chelate designated (h) where X8, X9 and X1 o in each polymer unit are each independently -H or *Trademark 3 1 , 375A-F -14-1290~3~.X

-C;H2CH(OH)CH2OH or -cH2cH(oH)cH2-N(R3)cH2cH2N(R4) (R5) where R3, R4 and R5 are each -CH2COOH, the added group is obtained by reacting the commercialiy available FIBRABON*35 (from the Diamond Shamrock Co., Cieveland, Ohio) with ethylene-5 diamine-triacetic acid in the presence of base (CHELATE K).
Generally, in the overall polymeric chelants (a) to (h), the ratio of -H (or -OCH3,-OCH2CH3, -OH or -Cl) to substituent in each of X1 to X1 0 iS between 10/90, more preferably the ratio in between 10/90 and 40/60.
A more detailed description of the preparation for these organic polymeric chelates is provided below as part of the Examples.
The Polyvalent Metals Generally, any polyvalent metal can be used in the present invention as the metal component of the polymeric chelate to remove 15 NO, but iron, copper, cobalt and manganese are preferred. Iron is particularly preferred. The polyvalent metal chelate should be capable of acting as a catalyst to instantaneously complex NO and should then be capable of regeneration.
Separation Means for Water and Low Molecular Weight Materials The means to separate the organic polymeric chelate from the water and water-soluble low molecular weight products and mate-rials can employ any single or combination of techniques suitable for this purpose. Preferably, membrane separation, such as ultrafiltration or dialysis are used. More preferably, ultrafiltration is 25 employed using a membrane consisting of any of a variety of synthetic polymers in the shape of a film, hollow fiber or the like. Particularly useful for the removal of water and low molecular weight products 31, 375A-F -15-;.. , *Trademark 129(~ 2 (less than 500 daltons) while retaining the water-soluble polymeric chelate are membranes, such as Spectrapor 6 (2000 molecular weight maximum permeability).
The use of ultrafiltration membranes in the separation of 5 components of an aqueous solution is described by P. R. Klinkowski in Kirk-Othmer: Encyclopedia of Chemical Technology, Vol. 23, pages 439-461. The use of dialysis membranes in separation is described by E. F. Leonard in Kirk-Othmer:_Fncyclopedia of Chemical Technology, Vol. 7, pages 564-579.
In Figure 1, the gas stream is, for example, from a stack gas containing up to about 1 . 0 percent by volume of NO, preferably between 0 . 02 and 0 . 05 percent by volume, or a chemical stream containing up to about 1.0 percent by volume of NO. In some gas streams, the NO is about 250 parts per million (ppm). Sulfur dioxide 15 tSO2) is also normally a product of combustion. In the present process the 52 content is generally between 0.05 and 0.02 percent by volume. The gas stream ~line 1 ) enters column 2 which contains an aqueous admixture comprising an aqueous solution about 1-molar and a water-soiuble polymeric chelate containing a polyvalent metal.
20 Fe~ l l ) is preferred and will be used hereafter. It is understood that Fe( l l l ~ ~oxidized form) and Fe~ reduced form) will be representative of any comparable polyvalent metal. The pressure of the feed gas is general Iy not critical and may vary from between 10 and 100 pounds per square inch gause (psig) in Pascal (Pa) units 25 (169 KPa and 777 KPa), preferably between 15 and 50 psig (201 KPa and 439 KPa). Optionally, a reducing agent is added to the process in an amount effective to reduce the chelate Fetlll) to chelate Fe(ll).
31 , 375A-F -16-~290~3~.2 A preferred reducing agent is an aqueous solution ~f NaSH. The reducing agent may be added through a~y of the lines of Figure 1 in which aqueous solution is added. Preferably, the NaSH solution is added through line 13.
A fresh aqueous solution of the polymeric chelate Fe ( l l ) described above is added through line 3. Usually the gas stream is 5 simply contacted with the aqueous stream, although a countercurrent configuration of the gas rising through a column of aqueous chelate solution is preferred. The temperature of the aqueous admixture is between 10 and 90C, preferably between 20 and 80C, more preferrably between 50 and 70C. A contact time between the 10 aqueous admixture and the gas is usually 1 sec and 2 min, with between 2 sec and 1 min being preferred. This time period is sufficient to adsorb substantially all of the NO to the Fe(l 1) chelate and to react with the bisulfite present to produce the imidodisulfanate. It has been determined that a 0.05 M Fe(ll)-EDTA
15 process requires a Fesidence time of 2 to 3 seconds to remove 90% of the NO from a gas stream containing 250 ppm of NO, while a CM PEI
150 system under the same process conditions requires about 15 seconds of residence time.
The purified gas stream then leaves column 2 via line 4.
20 Generally, the purified gas exiting in line 4 meets standard environ-mental emission standards.
In the aqueous admixture, the NO has been converted by the Fe(ll)-containing polymeric chelate to chelate ~Fe(ll)- NO, which instantaneously combines with HSO3 present to produce primarily 25 iminodisulfonate. Other products are possible, but the predominant reaction is:
SO3 ~2HN(5O3)2 + SO4= + H+ + H O
31, 375A-F -17-~290~

The aqueous mixture containing HN(5O3)2 and water-soluble polymeric chelate of Fe(ll) is removed in a continuous manner through line 5, optionally to a pump and through line 6 to a degassing and depressurization unit 7. Additional gases are evolved through line 8.
The polymeric chelate-containing aqueous solution is conveyed via line 9 to a separator unit 10. Separator 1a uses means to separate excess water, imidodisulfonate and low molecular weight products and byproducts. Generally, ultrafiltration or dialysis is used, with ultrafiltration being preferred. The water and low molec-10 ular weight materials, such as inorganic products, etc. having a molecular weight of less than 1000, preferably less than 500, are conveyed away through line 11 and disposed of in an environmentally acceptable manner. The polymeric chelate is then conveyed through line 12. Some permeabilities of monomeric and polymeric chelates of 15 iron ( l l ) and iron ( l l l ) using ultrafiltration and dialysis are shown below, in Table ll in Example 9.
The polymeric chelate containing the polymeric chelate metal Fe(ll) is then conveyed through line 12 to contacting zone 2 to begin the reaction process cycle again. As needed, make-up water, poly-20 meric chelate and polyvalent metal are added to the process throughline 13.
In Figure 1 the vertical line (having the arrowhead) between the pump and the degassing unit 8, and connects line 6 and horizontal line 12, is an optional feature. This line will have a 25 controlling valve to adjust the flow of liquid through it. In the event that not all of the aqueous solution leaving contact unit 2 needs to pass through separation unit 10, then a portion of the aqueous 31 ,375A-F -18-~290~.2 solution in line 6 is optionally moved (shunted) through the vertical line to return to contact unit 2 via line 12.
In Figure 2 is shown, the time needed to saturate the iron ( l l ) chelate with NO . About 24 minutes is needed to saturate the 5 monomeric EDTA Fe(ll) with NO. The polymeric Fe(ll) chelates show saturation of NO under comparable conditions, e.g., between 18 and 30 minutes.
Figure 2 shows that the polymeric chelates of Fe[ll) have comparable absorption of NO under similar conditions. Figure 2 has lO the following conditions: Gas Flow = 1.2 LiterslMin, 250 ppm NO in N2; solution = 120 ml 0. 025 M FeS~4; chelator concentration is 1 Og6 excess over Fer based in 2 N/Fe (except PEI 6 which is 12096 excess);
pH = 7+ 0.5, temperature = 55C. The symbols used are:(3= EDTA;
a - CM PEI 6; ~ = CM Purifloc~ 31; V = CM Polyethyloxazoline, dp =
15 500.
The following Exam~3les are to be construed as being illustrative and are not to be limiting in any way . The X1 to X1 0 pendant group in each polymer unit is selected from those indicated.

31 ,375A-F -19-~290~'312 Example 1 Preparation of Polymeric Chelate ~a) Based on Polyethyleneimine ~PEI) [CHELATE A: X1 is -H or -CH2CO()H]
(a)Polyethyleneimine 11 g [degree of polymerization (DP) tS00] is dissolved in water (200 ml) to produce a solution of 1.25 molar (in amine nitrogen3. To the aqueous solution is added sodium chloroacetate (31 g, a 5g6 excess) with stirring while maintaining the reaction mixture at about 60C. A pH electrode is used to monitor 10 the reaction and 50% sodium hydroxide is added to maintain the pH
above about 10. After 40 minut~s of reaction the reaction is com-plete, and the reaction mixture is allowed to cool. The aqueous solution is diluted to 1.0 M (amine nitrogen) and used without further purification .

Example 1 A
Preparation of Polymeric Chelate (a) lCHELATE B: X1 is -H or -CH2 P(=O)(OH)2]
To a 500 ml flask eq~ipped with a water condenser and dropping funnel is added 99 g (0.6 mole) of 49.9% orthophosphorous 20 acid (which also contained 9.4 g of hydrogen chloride) and 5.2 g of 3796 hydrochloric acid. The total moles of hydrogen chloride used is 0.4, The resultant mixture is then allowed to heat by the addition of 14 g of CORCAT 150 (Cordova Chemical Co.) as a 33~6 aqueous solution of polyethyleneimine containing 0.1 mole of amine nitrogen.
25 The polyamine is added over a period of 8 to 10 minutes while the reaction mixture achieves a temperature of about 70-75C. The 31 ,375A-F -20-~2~0~ .2 reaction mixture is then heated for about 20 minutes to the boiling temperature thereby producing a homogenous clear solution having a boiling point of between 110-11 5C. The resulting clear aqueous solution is maintained at boiling for about 2 hrs., and 22 g (0.66 5 mole) of paraformaldehyde is added. After the 2-hr. period, the clear reaction mixture is kept boiling for an additional 30 min and cooled to about 25-30C. The clear solution has an amber color, and contains about 5096 by weight of the polyethyleneimine phosphonate which was used without further purification.

10Example 1 B
Preparation of Polymeric Chelate (a) [CHELATE C: X is -H or 6-methylene-2, 4-dimethylphenol]
_ To a 13 g aqueous solution (33%) of polyethyleneimine CORCAT 150 (from Cordova Chemical Company) containing 0.1 mole of 15 available amine nitrogen is added 10.8 g of p-cresol (0.1 mole). The solution is maintained below 20C, while a 379c aqueous formaldehyde solution (0.11 mole) is added slowly with stirring. The solution is allowed to stand for an hour at ambient temperature and then warmed to 80C for 2 hrs. The aqueous solution is used without purification 20 in subsequent experiments.

31, 375A-F -21-129()~ .2 Example 2 Preparation of Polymeric Chelate (b) CHELATE D: X2 is -H or -CH2 CH(oH)cH2N(cH2cooH)cH2cH2-N(cH2cooH)2 This preparation was performed in two steps: (t ) attachment of ethylenediamine to the polymer; and (2) conversion of the amine to the ethylenediaminetriacetic acid.
Step 1: 23.5 Grams of polyepichlorhydrin (0.25 Mole monomer unit) and 94 grams of 85% ethylenediamine (1.3 moles) were 10 dissolved in 50 ml isopropanol and 25 ml of toluene and refluxed (about 1 00C) for six hrs . As the reaction proceeded additional isopropanol was added to maintain homogeneity, with the final system being about 75/25 isopropanofi/toluene. The reaction was followed by titrating aliquots for chloride ion with~ silver nitrate. Next, 20 grams 15 of 50% NaOH (0.25 mole) was added, the solid NaCI which formed was filtered, washed with ethanol, and the liquid was removed in a vacu-um evaporator at 55C~ Although some NaCI remained in the product, the elemental analysis gave a C:H:N mole ratio of 4.6:12.1:2.00 (Ex-pected mole ratio was 5:12:2).
Step 2: This intermediate was taken up in about 200 ml of water-, to which 3. 3 moles of sodium chloroacetate was added per mole of nitrogen. The system was kept at about 60C and a pH of about 10 for about one hr. At this point a white precipitate (presumably NaCI) was filtered off, the pH was adjusted to about 2 (the expected 25 isoelectric point), at which point considerable white solid formed.
This solid was filtered and found to be EDTA, presumably formed because all of the unreacted ethylenediamine had not been removed 31,375A-F -22-~ X90~ .2 during the vacuum evaporation. The filtrate was dialyzed against abcut 4 liters of water.
An estimate of the ethylenediaminetriacetic acid content of the dialyzed (polymeric) material was made by titrating an aliquot 5 with iron (Ill). About one-third of the exp~cted chelant groups were found in the polymer fraction.

Example 2A
Preparation of Polymeric Chelate (b) CHELATE D-l: X is -H or -CH2CH(OH)CH2N(CH2COOH)2, q=0, p=20,000 14,3 Grams (0.1 mole) of iminodiacetic acid was dissolved in 100 ml of water. To this solution was added 0.12 mole epichlor-hydrin, about a 20% excess. After allowing the solution to stand for an hour at ambient temperature it was extracted with 50 ml of methyl-15 ene chloride to remove the unreacted epichlorhydrin. To the aqueousphase from this extrattion was added 14.7 grams of a 3396 solution of polyethyleneimine CORCAT 600 (Cordova Chem. Co., Muskegon, Michigan), an amount determined to contain 0.1 mole of nitrogen.
The solution was heated to 60C, while sodium hydroxide solution (10 20 N) was added at a rate sufficient to maintain the pH in the range of 9-10. After about 30 minutes the reaction was complete and the resulting solution, which now contained the polyethyleneimine with iminodiacetic acid groups attached to it, was used without purification in subsequent experiments.

31, 375A-F -23-1 290~.2 Example 3 Preparation of Polymeric Chelate (c) CHELATE E: X3 is -OH or -[N(CH2COC)H)CH2CH2]N(CH2COOH)2 22.4 Grams (0.1 mole) of ethylenediamine triacetic acid is 5dissolved in 100 ml of water. To this solution is added 0.12 mole of polyepichlorohydrin (HYDRIN 10 x 1 DP ~ 40), (B.F. Goodrich, Cleveland, Ohio), about a 20% excess in 100 ml of toluene/methylene chloride (50/50; v/v) . To this two-phase solution is added 0. 01 mole to tetrabutyl ammonium chloride as a phase transfer catalyst. The 10 solution is allowed to stir vigorously for about an hour at ambient temperature. The HCI produced is taken up by the addition of sodTum hydroxide. The aqueous polymeric chelate was subsequently used without purification. -Example 4 Preparation of Polymeric Chelate (d) CHELATE F: X4 is -OH or -NH[CH2CH2N(CH2COOH)]-CH2CH2N(CH2COOH)2, t is 100 and x is 1 Poly(methylacrylate) 186 g., equivalent to one mole of formula weight of the monomeric methyl acrylate) is dissolved in about 20 300 ml of toluene, and 520 g of diethylenetriamine (5 moles) were added. The solution is heated to 40-50C for an hour and the excess amine and toluene were evaporated under vacuum. The residue is taken up in 500 ml of water and 348 g. of sodium chloroacetate (3. 0 mol) are added to the solution, and heated to about 60C for about 30 25 minutes while sodium hydroxide- is added at a rate sufficient to 31 ,375A-F -24-~90~

maintain the pH at 9-10. This solution, which had the desired struc-ture is used without further purification in subsequent experiments.
Example 5 Preparation of Polymeric Chelate (e) 5CHELATE G: X5 is -OH or -N(CH2COOH)CH2CH2N~CH2COOH)2 and y is 100 Polyvinyibenzyl chloride ( 15 g ., equivalent to 0 .1 mole of monomer units) is dissolved in 100 ml of methylene chloride, and 30 g of ethylene diamine (0.5 mole) are added. The solution is warmed to 10 40C and stirred for 2 hours. The excess amine and methylene chloride are evaporated under vacuum. The resulting polymer is taken up in 200 ml of water and carboxymethylated as in the preceding example. The resulting polymer has the desired structure, and is used further without purification.

15Example 6 Pre aration of Pol meric Chelate (f) P Y
CHELATE H: X6 is -H or -CH2CH(OH)CH2N(CH2COOH)-CH2CH2N(CH2COOH)2 Eighty grams of the polymer KYMENE 557H l0.1 mole monomer 20 equivalent) (Hercules Corporation, Wilmington, Delaware), which is a copolymer of adipic acid, diethylenetriamine and epichlorhydrin was added to a solution of 46 g of ethylenediaminetriacetic acid in about 200 ml of water ~a twofold excess). The solution was heated to 80C
for two hours. The resulting solution which contained the desired 25 polymer (vi) was used without further purification in subsequent experiments .
31, 375A-F -25-~ 2~0~3~.2 Example 7 Preparation of Polymeric Chelate (g) CHELATE J; X7 is -H or -CH2CH(OH)CH2N(CH2COOH) -CH2CH2N(CH2COOH)2 m is 1 and g is about 100.
A solution of an adduct of epichlorhydrin and iminodiacetic acid, as prepared in Example 2A, is added to an equimolar quantity of a polymer solution made by reacting equimolar quantities of methyl acrylate and ethylenediamine. The solution is heated to 80C for 2 hours, and the resulting polymer is used in subsequent experiments.

Example 8 Preparation of Polymeric Chelate (h) CHELATE K; X8, Xg and X10 in each polymer unit are either -H, -CH2CH (OH ) CH2OH or -CH2CH(OH)CH2N(CH2COOH)CH2CH2N(CH2COOH)2 Fifty four grams of the commercial polymer FIBRABON 35 (Diamond Shamrock Corporation, Cleveland, Ohio) which contains 100 millimoles of active epichlorhydrin groups, is mixed with a solution of 4~ grams of ethylenediaminetriacetic acid (0 . 2 mole), the solution is heated to 60C. and sodium hydroxide is added at a rate sufficient to 20 maintain the pH at about 9-10. After about 2 hours, the reaction is over, and. the solution is used in subsequent experiments.

31, 375A-F -26-~29~ .2 Example 9 Chelation of I ron ( l l ) by Polymeric Chelating Agents Various polymeric chelates are obtained by treating the polymeric chelant with iron at pH 7. The results of ~hese reactions 5 is shown in Table l l .
TABLE l l CHELATION OF IRON (Il) BY POLYMERIC CHELATING AGENTS
Ratio W is the mole ratio of nitrogen in chelating monomer or polym~r to iron at point of incipient precipitation at room temperature. pH in 10 all tests is 7 + 0.5.

Chelator ( Fe), Molar W
__ EDTA 0 . 03 2 . 0 MBEDTA 0 . 03 2 . 2 Sym . EDDA 0. 03 > 10 DTDA 0. 015 > 9 DTPA 0.03 2.5 TTHA 0 . 05 2 . 3 CM E-100 0.04 3,4 CM PEI 6 0. 045 3 . 2 CM PEOx, DP-50 0.025 5 CM PEOx, DP-1000 0. 025 4 CM PEOx, DP-10, 000 0 . 015 4 . 2 CM C-31 ~Dow Chemical) 0.04 5 EDTA - Ethylenediamine tetracetic acid 25 MBEDTA - Methyl-p-benzylethylenediaminetriacetic acid Sym. EDDA - Sym. Ethylenediaminediacetic acid DTDA - Diethylenetriaminediacetic acid DTPA - Diethylenetetraaminepentaacetic acid TTHA - Triethylenetetraaminehexaacetic acid 3 0 CM - Carboxymethyl PEI - Polyethyleneimine PEOx - ~olyethyleneoxazoline The following Examples are to be construecl as being illustrative and are not limiting in any way. For X1 to X1 0 in the Examples, the 31 ,375A-F -27-~290~3~.~

pendant group ;n each polymer unit of the polymer is selected fro those designated. It is also to be understood that from the description herein that if complete or partial addition of the pendant chelating group on the polymer backbone is desired, the 5 experimental synthesis conditions need only to be adjusted. That is, if only partial substitution is required adjustment to shorter reaction times, lower concentrations of reactants, lower reaction temperatures and those techniques known in the art are used. For more complete or complete addition of the pendant chelating group to the polymer 10 backbone, longer reaction times, higher concentration of reactants nad higher reaction ternperatures are used. The molecular weights of the polymers described herein are usually expressed as the weight average molecular weight.
Example 1 0 NO Absorption Using Polymeric Chelate of Iron (Il) A number of polymeric chelates containing iron l l l ) were treated with NO in aqueous solution. The results are shown in Table 111 wherein the mole ration of NO to iron ( 11 ) is shown . The polymeric chelates absorb NO to an extent comparable to the 2~ monomeric chelates.

31 ,375A-F -28-~9o~ z aC~C C~
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Q C Q ~ 3 a~ E ~ ~
Cl iL Q F--U U--U E u u E u F E u u E~ r n c E u _ _ o ~ ~ ~ ~ E
_ v~_ ~ o 1~ ~ r~ o o 1~ 1~ 1~ o o ~ ~ o~ 1~ ~ co ~ A ~
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m z ~ w .' Q'-t~ O ~ ~ _ E c X ~ ,~!!
O ~ E
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a,~ZI I o o c ~_ ~ In u^, ~ l ~ ~--E

¦ ~ 6 ~ ~-- u w Ou~ ~.a~
~ Z T U~ Q Q a 31, 375A-F -29-~2~0~

Example 1 1 Dialysis of Iron Polymeric Chelating Agents In the dialysis, 100 ml of iron (Il) organic chelate, made up to be about 0.1 molar in iron, was dialyzed into two liters of de-ionized water overnight. The ~M PEI 150 and CM PEI 600 polymeric chelating agents were dialyzed through SPECTROPOR 1, from Van Waters ~ Rogers, San Francisco, California which has a nominal molecular weight cut-off of about 6000-8000 . I n both cases, about 3-5% of the iron was lost. The CM PEI 6 solution was dialyzed 10 through SPECTROPOR 6 lVan Waters ~ Rogers) which has a cut-off of about 2000. In this case about 10% of the iron was lost.

Example 12 Ultrafiltration of Iron Polychelates The ultrafiltration tests wer0 performed in an Amicon Model 15 52 cell which is a cylindrical chamber with a 43 mm diameter (12.5 cm) membrane asi the bottom surface. The cell volume is about 60 ml and the cell contains a suspended magnetic stirring bar to reduce polarization effects. In a run, a 25-ml volume of solution was placed in the cell and the gas space was connected to an air line maintained 20 at 15 psi.
Three membranes were used for this study, al I obtained from the Amicon C:orporation of l)anvers, Massachusetts. They were designated as UM 05, UM 2 and PM 10 having nominal molecular weight cutoffs of 500, 1000 and 10,000, respectively. The iron was 25 determined by the standard thiocyanate method.

The results are shown below in Table IV.
31, 375A-F -30-~290~.2 TABLE IV

_ Polychelator Membrane _ Rejection Rejection FlowRejection Flow % 9~ gsfd* 96 gsfd*
CM PEI 600 89 98 1 . 3 91 6 ~dialyzed) 99 2. 8 95 16 :; CM PEI 150 (dialyzed) 95 1.4 97 9 CM PEI 6 80-90 0 . 8 25 28 ( dia Iyzed )61 go < 0 . 3 CM E-100 84 92 0 . 6 27 40 Deionized H2O only 5 100 ~CM PEI -- Carboxymethyl polyethyieneimine, etc. ]
20 Rejection 96 values are averages over steady state portion of run.
Flow values are interpolated or extrapolated to 0.10M Fe.
Rejection 96--the amount of chelate (or material ) which did not pass through the membrane.
*gsfd = gal/ft2 x day 2 5 As can be seen from Table IV, polychelates based on carboxymethylated polyethyleneimine 6 (CM PEI 6, about 15 monomer units) or larger polymers are fairly well rejected by ultrafiltration membranes having cut-offs in the molecular weight range of 1000-10,000. CM PEI 6 is strongly rejected (80-9096) by Amicon*UM 2 30 membrane thaving a cut-off value of 1000), but poorly (20-3096) by *Trademark 31, 375A-F -31-.~

1290~

PM 10 (cut-off 10,000). Higher polymers CM PEI 150 and CM PEI 600 are both strongly rejected 95-99% by both membranes.
At a concentration of 0 .1 M chelated i ron ( I l l ) output from an Amicon UM 2 membrane is about 1 gai lon per square foot per day 5 (gsfd) with the polychelators of Table l l l at a pressure of 15 psig (201 KPa). For the PM 10 membrane, the output is 6-30 gsfd.
Output was strongly dependent upon iron concentration.

Example 1 3 Adsorption of NO with Polymeric Chelate of Fe(ll) and Separation The polymeric chelate of Example 1 containing Fe ( I I ) at a concentration of 0,025M in Fe(ll) and 0.050M in S2O3 is dialyzed using a Spectrapor 6 (2000 MW cut-off), area 4.5 cm2. Na25O4 (0.050M) is used as the dialysate solution. About 100 ml of dialysate 15 is used. The permeability of the Fe(ll)-chelate is 0,7 x 10 2 cm/hr and for 523 iS 0 - 6 -Additional permeabilities were obtained using the Fe(ll) andFe(lll) chelate shown in Table V below.

31 ,375A-F -32-129()~'3~ ;2 ~ E ; r aJI D~ a : ~ O
O~ ~ ~ O O O O O

~ @

3 1 ~ 3 7 5 A- F - 3 3 -1 290~ .2 It is apparent from Table V that the polymeric chelates are not separated by dialysis through the membrane to the extent that the monomeric chelate is dialyzed.

Example 1 -Removal of NO and SO
A gas stream from an oil combustion unit having a concen-tration of NO of 0.011 weight percent and SO2 of 0.03 weight percent enters a contact vessel which contains an aqueous solution containing 1.0 percent by weight of iron (Il) (based on the total weight of the 10 mixture) as the polymeric chelate of carboxymethyl polyethyleneimine CM PEI6. The chelate is supplied at 5096 molar excess based on iron and the pH of the system is about 7. The pressure of the fluid gas is about 15 psig (201KPa) and the temperature of the reaction is 55C. A contact time of 60 seconds is used. rhe NO and SO2 are 15 converted to HNtSO3)2 which remains in solution. The aqueous solution is then subjected to ultrafiltration using an Amicom UM2 membrane and apparatus. The CM PEI 6 is retained in the aqueous solution while the low molecular weight water and HN(SO3)2 are sPparated. The retained aqueous solution containing the CM PEI 6 20 Fe~ll) is recycled to the contact vessel.
While only a few embodiments of the invention have been shown and described herein, it will become apparent to those skilled in the art that various modifications and changes can be made in the process to remove NO and 52 from fluid streams using polymeric 25 organic chelates of a polyvalent metal without departing from the spirit and scope of the present invention. All such modifications and 31, 375A-F -34-~290~3~.2 changes coming within the scope of the appended claims are intended to be covered thereby.

31, 375A-F -35-

Claims

1. A process for the removal of NO from a fluid stream comprising mixtures of NO and SO2, which process comprises:
(A) contacting the fluid stream in a contacting zone with an aqueous reaction solution at a temperature of between 10° and 90°C, the reaction itself comprising an effective amount of a composition having a water-soluble organic polymeric chelate containing a polyvalent metal, wherein the chelate has a weight average molecular weight between 1,000 and 500,000 and wherein the chelate is:
(a) wherein X1 in each polymer unit is independently -H or R-wherein R is -CH2COOH, -CH2CH2COOH, -CH2-P(=O)(OH)2, or wherein R1 and R2 are each independently -CH3, -SO3H, -Cl, -H, or -COOH and n is an integer between 5 and 20,000;
(b) wherein X2 in each polymer unit is -H, -CH2CH(OH)CH2OH, -CH2CH(OH)CH2Cl or 31,375A-F

wherein R3, R4 and R5 are each independently R as defined hereinabove, p is an integer between 5 and 20,000; and q is an integer 0, 1, 2, 3 or 4;

(c) wherein X3 in each polymer unit is independently -OH, -Cl or wherein R3, R4 and R5 are. as defined hereinabove; r is an integer between 10 and 20,000, and s is an integer between 1 and 4;
(d) wherein X4 in each polymer unit is independently -OH, -OCH3, -OCH2CH3 or wherein R3, R4 and R5 are as defined hereinabove, t is an integer between 10 and 20,000; and x is an integer between 1 and 4;
(e) wherein X5 in each polymer unit is independently -OH, -Cl or wherein R3, R4 and R5 are as defined hereinabove; y is an integer between 10 and 20,000, and z is an integer between 1 and 4;
(f) wherein X6 in each polymer unit is independently -CH2CH(OH)CH2OH,-CH2CH(OH)CH2Cl, or wherein v is between 10 to 10,000, a is 6, b is 1 to 4, c is 1 to 4 and R3, R4 and R5 are as defined hereinabove;

31,375A-F

(g) wherein X7 in each polymer unit is independently -H, -CH2CH(OH)CH2OH, -CH2CH(OH)CH2Cl, or wherein m is an integer from 1 to 4, g is between 10 to 10,000, and q, R3, R4 and R5 are as defined hereinabove;
(h) w wherein X8, X9 and X10 in each polymer unit are each independently -H, -CH2CH(OH)CH2Cl, -CH2CH(OH)CH2OH, or wherein q, R3, R4 and R5 are as defined hereinabove, w is between about 10 and 10,000; or (1) mixtures of polymeric chelates (a) to (h) with the proviso that the overall ratio of -H, -OCH3, -OCH2CH3, -Cl, or -OH to substituent in each of X1, X2, X3, X4, X5, X6, X7, X8, X9 or X10 in each polymeric chelant (a to h) hereinabove is between about 10/90 and 90/10;

31,375A-F -39-(B) separating the fluid stream and the resulting aqueous phase containing the polymeric chelate iron (III) and imidodisulfonate of step (A);

(C) concentrating the aqueous phase repeated in step (b) by means effective to remove a portion of the water and other monomeric reaction products having a molecular weight below 500 and;

(D) recycling the concentrated aqueous solution produced 80 in step (c) to the contacting zone of step (A).

2. The process of Claim 1 wherein in step (C) a portion of the aqueous solution is separated from the polymeric chelate by means selected from ultrafiltration and dialysis.

3. The process of Claim 2 wherein the means for removal in step (c) is ultrafiltration.

4. The process of Claim 2 wherein in step (A) the metal is iron.

5. The process of Claim 1 or 4 wherein the water-soluble chelate has the formula of chelate (C):
wherein R is between about 15 and 20.

31,375A-F -40-