CA1064829A - Process for the separation of 1,3-butadiene by selective adsorption on a zeolite adsorbent - Google Patents
Process for the separation of 1,3-butadiene by selective adsorption on a zeolite adsorbentInfo
- Publication number
- CA1064829A CA1064829A CA232,853A CA232853A CA1064829A CA 1064829 A CA1064829 A CA 1064829A CA 232853 A CA232853 A CA 232853A CA 1064829 A CA1064829 A CA 1064829A
- Authority
- CA
- Canada
- Prior art keywords
- butadiene
- adsorbent
- type
- zeolite
- crystalline aluminosilicate
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C7/00—Purification; Separation; Use of additives
- C07C7/12—Purification; Separation; Use of additives by adsorption, i.e. purification or separation of hydrocarbons with the aid of solids, e.g. with ion-exchangers
- C07C7/13—Purification; Separation; Use of additives by adsorption, i.e. purification or separation of hydrocarbons with the aid of solids, e.g. with ion-exchangers by molecular-sieve technique
Abstract
ABSTRACT OF THE DISCLOSURE
A process for the separation of 1,3-butadiene from a feed mixture comprising 1,3-butadiene and at least one other C4 unsaturate.
A feed stream containing 1,3-butadiene and at least one other C4 un-saturate is contacted with an adsorbent comprising a crystalline alumino-silicate selected from the group consisting of type X structured and type Y structured zeolites containing at the exchangeable cationic sites at least one cation selected from the group consisting of lithium, sodium, potassium, rubidium, cesium, and barium to effect the selective adsorption of 1,3-butadiene. The 1,3-butadiene adsorbed by the adsorbent is there-after recovered as a purified product.
A process for the separation of 1,3-butadiene from a feed mixture comprising 1,3-butadiene and at least one other C4 unsaturate.
A feed stream containing 1,3-butadiene and at least one other C4 un-saturate is contacted with an adsorbent comprising a crystalline alumino-silicate selected from the group consisting of type X structured and type Y structured zeolites containing at the exchangeable cationic sites at least one cation selected from the group consisting of lithium, sodium, potassium, rubidium, cesium, and barium to effect the selective adsorption of 1,3-butadiene. The 1,3-butadiene adsorbed by the adsorbent is there-after recovered as a purified product.
Description
i48;~
It is well known in the separation art tnat cer-tain crystalline aluminosilicates can be used to se?arate hydrocarbon species from mix-tures thereof. In particular, the separation of normal paraEfins from branched chained parafins can be accomplished by using the type ~ zeolites which have pore openinys from 3 to 5 Angstroms. Such a separation process is disclosed for example in U.S. Patents
It is well known in the separation art tnat cer-tain crystalline aluminosilicates can be used to se?arate hydrocarbon species from mix-tures thereof. In particular, the separation of normal paraEfins from branched chained parafins can be accomplished by using the type ~ zeolites which have pore openinys from 3 to 5 Angstroms. Such a separation process is disclosed for example in U.S. Patents
2,985,589 and 3,201,491. ~hese adsorben-ts allow a separa-tion based on the physical size differences in the molecules by allowing the smaller or normal hydrocarbons to be passed in-to the cavities within the crystalline aluminosilicate adsorbent, while excluding the larger or branched chain ;~
molecules.
U.S. Patents 3,265,750 and 3,510,423, for example, disclose processes in which larger pore diameter ~eolites such as the type X or type Y structured zeolites can be ; used to separate olefinic hydrocarbons. ;~
. ~ ~
In addition to separating hydrocarbon t~ es, the type X or type Y zeolite have also been employed in processes to separate individual hydrocarbon isomers. In the process ¦ described in U.S. Patents 3,668,730; 3,668,732; 3,626,020, and 3,686,342, for example, they are used to separate desired xylene isomers; in U.S. Patent 3,668,267 they are .
used to separate particular alkyl substitu-ted naphthalenes.
The present invention relates to a process ~or the separation of lr3-butadiene from a ~eed mixture compris-ing L,3-butadiene and at least one other C4 unsaturate with a particular crystalline aluminosilicate adsorbent.
: . ` ~ .
.' ' ~
1~ 32~
I have found that an adsorben-t comprisiny a crystalline aluminosilicate zeolite selected from the group consisting of type X structured and type Y structured zeo-lites containing one or more selected cations a-t excha~seable . 5 cationic sites exhibi-ts selectivity for 1,3-butadiene with :............... respect to other hydrocarbons present in a feed mixture .. comprising 1,3-butadiene thereby making separation of 1,3-butadiene by so!id-bed selective adsorption possible.
In brief summary, my inven-tion is, in one embodi-~ 10 ment, a process for separating 1,3-butad.iene from a feed i mixture comprising 1,3-butadiene and at least one other ., C4 unsaturate which process comprises contacting a-t ad-sorption conditions said mix-ture with an adsorbent compris- ;~
iny a crystalline aluminosilicate selected from t~pe X `
'--:
structured and type Y structured zeolites containing at ¦ least one cation selected from lithium, sodium, potassi~, } rubidium, cesium, and barium at the exchangeable cationic sites thereby selectively~ adsorbing 1,3-butadiene from said :
: mixture.
-~ 20 Other embodiments and objects of the present . invention encompass details about feed mixtures, adsor-~ - bents, desorbents, and operating conditions all OL which .-are hereinafter disclosed in the following discussion of : each of these facets of the present invention.
;:~ 25 The process of this invention provides a.superior :~
.. ~ - alternative to such methods of concentrating or separating -~ 1,3-butadiene as: extractive distillation with selective solvents; selective adsorption with cuprous salt solutions;
: -3-.. . ' ' `.
,.
, ., .. ~ ,.
. , . . , . , :.
~4829 azeotropic distillation ~ith ammoni.a; and sulfone fo~ma-tion. Of these methods, only the first two have achieved commercial prominence.
Butadiene, industrially the most important diole- .
fin, is used to produce polymer components used, for example, in synthetic rubber and is also used as a chemical inter-mediate for a great variety of compounds.
Adsorbents which can be used ln the process of this invention are generally referred to as crystalline aluminosilicates or molecular sie~es and can comprise both the natural and synthetic aluminosilicates. ~-- The type X structured and type Y structured .`: ~
zeolites as used in this specification shall include. ~j ; crystalline aluminosilicates having a three dimensional interconnected cage structure and can specifically be ~ -defined in U.S. Patents 2,882,244 and 3,130,007. The terms "type X structured" and "type Y structured" zeolites as used herein shall lnclude all zeolites which have a general structure as represented in the above two cited : -20 patents and additionally, shall specifically include those crystalline aluminosilicates produced from either of the zeolites described in U.S. Patent 2,882,244 and 3,130,007 ,' as starting materials by various ion-exchange techniques or thermal treatments or combinations thereof to modify ~
the properties (such as pore diameter or cell size) of the .. ;. .
type X or type Y zeolite starting material. As an example, .
the modified type Y zeolite produced by the thermal treat-men-t of an ammonium-exchanged type Y zeolite in the presence .
;:
,~
~'.~ ., :,~ . ~ , . . :
o~ water vapor as described in U.S. Paten-t 3,506,400 s~all be included within the term "t:ype Y struc-tured zeolite"
as shall any zeolite produced by subseq4en-t ion-exchang2 of the modified type Y zeolite so produced. In the most limiting sense only these terms refer to type X and type Y zeolites.
The type X structured zeoli-tes can be represented ;l in terms of mole oxides as represented in formula 2 belo.~:
Formula 2 ( 9--2)M2/n:A123:(2-5+0.5)siO2:y~20 ; ..
¦ where "M" represents at least one cation having a valence of not more than 3, "n" represen-ts the valence of "M", and "y" is a value up to about 9 depending upon the iden_ity ; of "M" and the degree of hydration of the crystalline : 15 structure.
. The -type Y structured zeolites can be represen ed -~
¦ in terms of the mole oxides for the sodium form as repre~
sented by Formula 3 below:
~3 Formula 3 (o~g*0~2)Na2O:A12O3:WSiO2 yH2o ~ where "w" is a value of greater than about 3.up to 8, and : "y" may be any value up to abou-t 9. -. Adsorbents contemplated herein include not only .
the sodium form of the type X and type Y zeolites but also ~.
. 25 crystalline materials obtained from such a zeolite by . partial or complete replacement of sodium cations at the . exchangeable cationic sites with other individual cations.
or group of cations. The term "exchangeable cationic ,.,i, ;
;: , , - - , ~. .: .. ~ : :
~:16~8z~
sites" generally reEers -to -the sites occupied by sodium cations present in the type X and ~ype Y zeoli-tes as in-dicated in Formula 2 and Formula 3 above. Sodium cations originally present a-t these si.tes can b~ replaced or ex-changed with o-ther cations.
Cationic or base exchange methods are generally known to those familiar wi-th the field of crystalline alu-minosilicate production. They are generally per~ormed by contacting the zeolite with an aqueous solution of the i 10 soluble salt of the cations desired to be placed upon the zeolite. The desired degree of exchange takes plac~ be-fore the sieves are removed from the aqueous solu,ion, washed and dried to a desired water content. It is con-templated that cation exchange operations may take place using individual solutions of desired cations placed on the zeolite or using an exchange solution containing a mixture of cations, where two or more desired cations are placed on the zeolite. ;
.
The cations which can be placed upon the zeolite ¦ 20 adsorbent include those of Group I-A, Group II-A, GroupVIII-A, and the Group I-s metals of the Periodic Table of lemen-ts. -Eor the purposes of this invention, cations to be used on the adsorbent shall include cations selected from the above-mentioned groups and with the limi-ation that the cation or cations to be used be selective towards ~, 1,3-butadiene from the other feed stock components. Pref- -- erably the zeolite adsorbent will contain at least one `
: . ~, .
~ -6- ~
., . ~ .
::
. ::
1~164!3~9 cation selected from the group consisting of lithium, sodium, potassium, rubidium, cesium, and ~arium at the ; exchangeable cationic sites. More preEerably the z201ite absorbent will contain at least one cation selected from the group consisting of sodium, potassium, and b~rium since cations from this group selectively adsorb 1,3-butadiene from other feèd mixture componen-ts in a highly selective manner.
When singular cations are base exchanyed upon a zeolite, the singular cations can comprise anywhere from ~ 5 up to 75 wt. % on a relative volatile free basis of the! zeolite depending upon the molecular weight of the material exchanged upon the zeolite. I-t is con-templated that when single ions are placed upon the zeolite that they may be on the zeolite in concentrations of from about 1~ to about ~;
100~ of the original cations present (ge-nerally sodlum~
upon the zeolite prior to its being ion-exchanged. By knowin~ the empirical formula, including the silica to ~ alumina ratio of the zeolite used, its water content~ and¦ 20 the percentage of binder used if any, it is possible to ~-calculate the percentage of ion exchange that has taken - place.
When two or more cations are placed upon the zeolite, there are two parameters in which one can operate - 25 in order to effecti~ely produce a zeolite having tne maxi-mum selective properties. One of the parameters is the extent of the zeolite ion exchange which is determined ~`~
by the length of time, temperature, and cation concentra-. '' ' .
. , . .
. .
. .~ ,;; . - . , . . , , -' ; . ' ' . ' , ~L~648Z~
tion. The other par~meter is the ratio of individual, cations placed on the zeolite. In lnstances in which the cation pairs comprise a Group I-A metal and a Group II-A metal, the weight ratio of these two respective com-ponents ~pon the zeolite can vary anywhere from about less than one up to about one hundred depending upon the molecu-lar weiyht of the Group I-A or Group II-A metal. -Because of the reactive nature of 1,3-butadiene, it is very importan-t that the adsorbent possess little ~ ;
or no catalytic activity toward polymerization or isomer-ization which would either degrade the product quality, ! reduce the overall yield of desired produc-t or possibly degrade adsorbent performance. We have found that for the separation of 1,3-butadiene the polymerization effects of the adsorbent are of primary concern. Unless the adsorbent possesses little or no polymerization activity, ¦ 1,3-butadiene will rapidly polymerize. It is thought that such activity is due primarily to the presence o~5 hydrogen 1 cations within the zeolite or the binder used to pro~uce ¦ 20 the adsorben-t particles. I have discovered that ion-! exchanginy a starting material comprlsing a type X or type Y structured zeolite with a dilute aqueous solution ~-¦ of sodium or potassium hydroxide elimina-tes such acid sites ! and produces a finished adsorbent with little or no cata-lytic activity. This ion-exchange step is then followed by subsequent ion-exchanges with the desired cation or cations. During these subsequent ion-exchange steps and washes, it is important that the pH of the exchange medium _~
~ .
. .
: .. ~. .
4~
be maintained at or above 7 to avoid recreatin~ acid sites.
Butadiene is syn-thesized commercially in the United States by four methods: 1) by catalytic dehydro-genation of concentrated n-butylenes; 2) by catalytic dehydrogenation of n-butane; 3) as a by-product, in rather - low yield, from severe high-temperature cracking of liquld hydrocarbons for production of unsaturates; and 4) frorn - ethyl alcohol by a combination of catalytic dehydrogenation and dehydration. The first two methods are the most fr~
quently used methods.
~ All of the conversion processes yield products -¦ in which 1,3-butadiene is mixed with other closely boiling ¦ hydrocarbons. For example, when concentrated 2-butene and l-butene are catalytically dehydrogenated to produce 1,3-~ butadiene the stabilized effluent from this operation con-``¦ tains, in addition to 1,3-butadiene, unreacted isomeric n-butenes, some n-butane, isobutane, isobutylene, appre-ciable concentration of C3 components, and small concen-¦ 20 trations of components heavier than C4 hydrocarbons.
Table 1 below lists the hydrocarbons frequently found in crude butadiene fractions from such sources.
The relative amounts of these hydrocarbons present in crude butadiene vary considerably, depending upon the type o, ~:
hydrocarbon conversion process employed. Other C~ unsat-urates, primarily mono-olefins, are always presen, in major ~ amoun-ts. Non-conjugated diolefins and acetylenes are minor ;¦ constituents, but they generally increase with lncreasing .,' ,, ~648'~
tempera-ture cluring hydrocarbon conversion. For the most part, however, they are hiyhly objectionable contaminants in purified butadiene and hence their concentrations in the latter must be carefully controlled.
Ordinarily fractionation alone is incapable OL
separating 1,3-butadiene of the desired purity (ordinarily 98 wt. % or higher) from these mixtures. Commercially butadiene is separated from olefins and paraffins primarily by extractive distillation with selective solvents and by ~ 10 selective adsorption with cuprous salt solutions.
j A polar solvent is employed in extractive dis-. tillation processes to increase the volatility of some componen-ts in the mixture relative to other components in . the mixture with the resul-t that separation of the desired 15 component by distillation is made possible. Polar solvents such as acetonitrile, acetone, furfural, dimethyl_ormamide, dioxane, phenol, and N-methylpyrrolidone, and their corres~
. ponding aqueous admixtures have been used in extractive distillation processes for 1,3-butadiene separation.
.
. ~'' . ' ' ~
~ . :
.
`".''' . ''~' '.
: , -10- ' ;' ' . ' .
.
, , ~ .
~L~648Z~
TABLI~ 1 COMPOUNDS IN A TYPICAL CRUDE BUTADIENE
FRACTIONS AND T~IEIR NO~AL BOILING POINTS
Compound B.p., C.
Paraffins:
_ Propane -42.1 Isobutane -11.72 .
n-Butane - 0.55 . Mono-olefins: ~:
Propylene (propene) -47.6 Isobutylene (methylpropene) - 6.93 Butene - 6.32 trans-2-butene 0.86 : cis-2-butene 3.64 ~ - :
molecules.
U.S. Patents 3,265,750 and 3,510,423, for example, disclose processes in which larger pore diameter ~eolites such as the type X or type Y structured zeolites can be ; used to separate olefinic hydrocarbons. ;~
. ~ ~
In addition to separating hydrocarbon t~ es, the type X or type Y zeolite have also been employed in processes to separate individual hydrocarbon isomers. In the process ¦ described in U.S. Patents 3,668,730; 3,668,732; 3,626,020, and 3,686,342, for example, they are used to separate desired xylene isomers; in U.S. Patent 3,668,267 they are .
used to separate particular alkyl substitu-ted naphthalenes.
The present invention relates to a process ~or the separation of lr3-butadiene from a ~eed mixture compris-ing L,3-butadiene and at least one other C4 unsaturate with a particular crystalline aluminosilicate adsorbent.
: . ` ~ .
.' ' ~
1~ 32~
I have found that an adsorben-t comprisiny a crystalline aluminosilicate zeolite selected from the group consisting of type X structured and type Y structured zeo-lites containing one or more selected cations a-t excha~seable . 5 cationic sites exhibi-ts selectivity for 1,3-butadiene with :............... respect to other hydrocarbons present in a feed mixture .. comprising 1,3-butadiene thereby making separation of 1,3-butadiene by so!id-bed selective adsorption possible.
In brief summary, my inven-tion is, in one embodi-~ 10 ment, a process for separating 1,3-butad.iene from a feed i mixture comprising 1,3-butadiene and at least one other ., C4 unsaturate which process comprises contacting a-t ad-sorption conditions said mix-ture with an adsorbent compris- ;~
iny a crystalline aluminosilicate selected from t~pe X `
'--:
structured and type Y structured zeolites containing at ¦ least one cation selected from lithium, sodium, potassi~, } rubidium, cesium, and barium at the exchangeable cationic sites thereby selectively~ adsorbing 1,3-butadiene from said :
: mixture.
-~ 20 Other embodiments and objects of the present . invention encompass details about feed mixtures, adsor-~ - bents, desorbents, and operating conditions all OL which .-are hereinafter disclosed in the following discussion of : each of these facets of the present invention.
;:~ 25 The process of this invention provides a.superior :~
.. ~ - alternative to such methods of concentrating or separating -~ 1,3-butadiene as: extractive distillation with selective solvents; selective adsorption with cuprous salt solutions;
: -3-.. . ' ' `.
,.
, ., .. ~ ,.
. , . . , . , :.
~4829 azeotropic distillation ~ith ammoni.a; and sulfone fo~ma-tion. Of these methods, only the first two have achieved commercial prominence.
Butadiene, industrially the most important diole- .
fin, is used to produce polymer components used, for example, in synthetic rubber and is also used as a chemical inter-mediate for a great variety of compounds.
Adsorbents which can be used ln the process of this invention are generally referred to as crystalline aluminosilicates or molecular sie~es and can comprise both the natural and synthetic aluminosilicates. ~-- The type X structured and type Y structured .`: ~
zeolites as used in this specification shall include. ~j ; crystalline aluminosilicates having a three dimensional interconnected cage structure and can specifically be ~ -defined in U.S. Patents 2,882,244 and 3,130,007. The terms "type X structured" and "type Y structured" zeolites as used herein shall lnclude all zeolites which have a general structure as represented in the above two cited : -20 patents and additionally, shall specifically include those crystalline aluminosilicates produced from either of the zeolites described in U.S. Patent 2,882,244 and 3,130,007 ,' as starting materials by various ion-exchange techniques or thermal treatments or combinations thereof to modify ~
the properties (such as pore diameter or cell size) of the .. ;. .
type X or type Y zeolite starting material. As an example, .
the modified type Y zeolite produced by the thermal treat-men-t of an ammonium-exchanged type Y zeolite in the presence .
;:
,~
~'.~ ., :,~ . ~ , . . :
o~ water vapor as described in U.S. Paten-t 3,506,400 s~all be included within the term "t:ype Y struc-tured zeolite"
as shall any zeolite produced by subseq4en-t ion-exchang2 of the modified type Y zeolite so produced. In the most limiting sense only these terms refer to type X and type Y zeolites.
The type X structured zeoli-tes can be represented ;l in terms of mole oxides as represented in formula 2 belo.~:
Formula 2 ( 9--2)M2/n:A123:(2-5+0.5)siO2:y~20 ; ..
¦ where "M" represents at least one cation having a valence of not more than 3, "n" represen-ts the valence of "M", and "y" is a value up to about 9 depending upon the iden_ity ; of "M" and the degree of hydration of the crystalline : 15 structure.
. The -type Y structured zeolites can be represen ed -~
¦ in terms of the mole oxides for the sodium form as repre~
sented by Formula 3 below:
~3 Formula 3 (o~g*0~2)Na2O:A12O3:WSiO2 yH2o ~ where "w" is a value of greater than about 3.up to 8, and : "y" may be any value up to abou-t 9. -. Adsorbents contemplated herein include not only .
the sodium form of the type X and type Y zeolites but also ~.
. 25 crystalline materials obtained from such a zeolite by . partial or complete replacement of sodium cations at the . exchangeable cationic sites with other individual cations.
or group of cations. The term "exchangeable cationic ,.,i, ;
;: , , - - , ~. .: .. ~ : :
~:16~8z~
sites" generally reEers -to -the sites occupied by sodium cations present in the type X and ~ype Y zeoli-tes as in-dicated in Formula 2 and Formula 3 above. Sodium cations originally present a-t these si.tes can b~ replaced or ex-changed with o-ther cations.
Cationic or base exchange methods are generally known to those familiar wi-th the field of crystalline alu-minosilicate production. They are generally per~ormed by contacting the zeolite with an aqueous solution of the i 10 soluble salt of the cations desired to be placed upon the zeolite. The desired degree of exchange takes plac~ be-fore the sieves are removed from the aqueous solu,ion, washed and dried to a desired water content. It is con-templated that cation exchange operations may take place using individual solutions of desired cations placed on the zeolite or using an exchange solution containing a mixture of cations, where two or more desired cations are placed on the zeolite. ;
.
The cations which can be placed upon the zeolite ¦ 20 adsorbent include those of Group I-A, Group II-A, GroupVIII-A, and the Group I-s metals of the Periodic Table of lemen-ts. -Eor the purposes of this invention, cations to be used on the adsorbent shall include cations selected from the above-mentioned groups and with the limi-ation that the cation or cations to be used be selective towards ~, 1,3-butadiene from the other feed stock components. Pref- -- erably the zeolite adsorbent will contain at least one `
: . ~, .
~ -6- ~
., . ~ .
::
. ::
1~164!3~9 cation selected from the group consisting of lithium, sodium, potassium, rubidium, cesium, and ~arium at the ; exchangeable cationic sites. More preEerably the z201ite absorbent will contain at least one cation selected from the group consisting of sodium, potassium, and b~rium since cations from this group selectively adsorb 1,3-butadiene from other feèd mixture componen-ts in a highly selective manner.
When singular cations are base exchanyed upon a zeolite, the singular cations can comprise anywhere from ~ 5 up to 75 wt. % on a relative volatile free basis of the! zeolite depending upon the molecular weight of the material exchanged upon the zeolite. I-t is con-templated that when single ions are placed upon the zeolite that they may be on the zeolite in concentrations of from about 1~ to about ~;
100~ of the original cations present (ge-nerally sodlum~
upon the zeolite prior to its being ion-exchanged. By knowin~ the empirical formula, including the silica to ~ alumina ratio of the zeolite used, its water content~ and¦ 20 the percentage of binder used if any, it is possible to ~-calculate the percentage of ion exchange that has taken - place.
When two or more cations are placed upon the zeolite, there are two parameters in which one can operate - 25 in order to effecti~ely produce a zeolite having tne maxi-mum selective properties. One of the parameters is the extent of the zeolite ion exchange which is determined ~`~
by the length of time, temperature, and cation concentra-. '' ' .
. , . .
. .
. .~ ,;; . - . , . . , , -' ; . ' ' . ' , ~L~648Z~
tion. The other par~meter is the ratio of individual, cations placed on the zeolite. In lnstances in which the cation pairs comprise a Group I-A metal and a Group II-A metal, the weight ratio of these two respective com-ponents ~pon the zeolite can vary anywhere from about less than one up to about one hundred depending upon the molecu-lar weiyht of the Group I-A or Group II-A metal. -Because of the reactive nature of 1,3-butadiene, it is very importan-t that the adsorbent possess little ~ ;
or no catalytic activity toward polymerization or isomer-ization which would either degrade the product quality, ! reduce the overall yield of desired produc-t or possibly degrade adsorbent performance. We have found that for the separation of 1,3-butadiene the polymerization effects of the adsorbent are of primary concern. Unless the adsorbent possesses little or no polymerization activity, ¦ 1,3-butadiene will rapidly polymerize. It is thought that such activity is due primarily to the presence o~5 hydrogen 1 cations within the zeolite or the binder used to pro~uce ¦ 20 the adsorben-t particles. I have discovered that ion-! exchanginy a starting material comprlsing a type X or type Y structured zeolite with a dilute aqueous solution ~-¦ of sodium or potassium hydroxide elimina-tes such acid sites ! and produces a finished adsorbent with little or no cata-lytic activity. This ion-exchange step is then followed by subsequent ion-exchanges with the desired cation or cations. During these subsequent ion-exchange steps and washes, it is important that the pH of the exchange medium _~
~ .
. .
: .. ~. .
4~
be maintained at or above 7 to avoid recreatin~ acid sites.
Butadiene is syn-thesized commercially in the United States by four methods: 1) by catalytic dehydro-genation of concentrated n-butylenes; 2) by catalytic dehydrogenation of n-butane; 3) as a by-product, in rather - low yield, from severe high-temperature cracking of liquld hydrocarbons for production of unsaturates; and 4) frorn - ethyl alcohol by a combination of catalytic dehydrogenation and dehydration. The first two methods are the most fr~
quently used methods.
~ All of the conversion processes yield products -¦ in which 1,3-butadiene is mixed with other closely boiling ¦ hydrocarbons. For example, when concentrated 2-butene and l-butene are catalytically dehydrogenated to produce 1,3-~ butadiene the stabilized effluent from this operation con-``¦ tains, in addition to 1,3-butadiene, unreacted isomeric n-butenes, some n-butane, isobutane, isobutylene, appre-ciable concentration of C3 components, and small concen-¦ 20 trations of components heavier than C4 hydrocarbons.
Table 1 below lists the hydrocarbons frequently found in crude butadiene fractions from such sources.
The relative amounts of these hydrocarbons present in crude butadiene vary considerably, depending upon the type o, ~:
hydrocarbon conversion process employed. Other C~ unsat-urates, primarily mono-olefins, are always presen, in major ~ amoun-ts. Non-conjugated diolefins and acetylenes are minor ;¦ constituents, but they generally increase with lncreasing .,' ,, ~648'~
tempera-ture cluring hydrocarbon conversion. For the most part, however, they are hiyhly objectionable contaminants in purified butadiene and hence their concentrations in the latter must be carefully controlled.
Ordinarily fractionation alone is incapable OL
separating 1,3-butadiene of the desired purity (ordinarily 98 wt. % or higher) from these mixtures. Commercially butadiene is separated from olefins and paraffins primarily by extractive distillation with selective solvents and by ~ 10 selective adsorption with cuprous salt solutions.
j A polar solvent is employed in extractive dis-. tillation processes to increase the volatility of some componen-ts in the mixture relative to other components in . the mixture with the resul-t that separation of the desired 15 component by distillation is made possible. Polar solvents such as acetonitrile, acetone, furfural, dimethyl_ormamide, dioxane, phenol, and N-methylpyrrolidone, and their corres~
. ponding aqueous admixtures have been used in extractive distillation processes for 1,3-butadiene separation.
.
. ~'' . ' ' ~
~ . :
.
`".''' . ''~' '.
: , -10- ' ;' ' . ' .
.
, , ~ .
~L~648Z~
TABLI~ 1 COMPOUNDS IN A TYPICAL CRUDE BUTADIENE
FRACTIONS AND T~IEIR NO~AL BOILING POINTS
Compound B.p., C.
Paraffins:
_ Propane -42.1 Isobutane -11.72 .
n-Butane - 0.55 . Mono-olefins: ~:
Propylene (propene) -47.6 Isobutylene (methylpropene) - 6.93 Butene - 6.32 trans-2-butene 0.86 : cis-2-butene 3.64 ~ - :
3-Methyl-l-butene 18.8 i Diolefins ¦ Propadiene (allene) -34.3 1,3-Butadiene - 4,54 1,2-Butadiene 10.3 1,4-Pentadiene 26.12 ¦ Acetylenes:
¦ ~ Methylacetylene -23.2 :~ Vinylacetylene 5.0 .~ Ethylace-tylene 8.6 ;;
. 25 Butadiyne (biacetylene) 10.3 . Dimethylacetylene 27.1 `. ~' , ~' ~ j ,.' . , ~.
:~
.
1~6~1~Z5~ ~
In the conventional extract~ve distillation pro-cesses, the butanes and butenes e~hibit an enhanc~d vola-tility relative ~o the diolefinic and acotylenic materi~ls and are recnvered as an o~erhead product from the extrac-tlve distillation zoneO The less volat~le hydrocarbons, e.g., the diolefins and higher acetylenes,are separ~ted ~ -~
. .
together ~ith the polar solvent as the bottoms produc~ from - the extractive distillation zone. The butadiene product is reco~ered directly from ehe bottsms product in a strip-ping zone at ele~ated temperature~ The energy requlred to effect the separation ln the extractive distillation zone and in the stripping ~one is supplied by reboilers attached to each zone.
The extractive distiLlation method suffers from :. :
several disadvantag~s. One disadvanta~e is that relatively `~;
large amo~nts of energy are required to reboil both ths -~ extracti~e distillation zone~ which is typically a 100 plate colum~ and the stripping %one~ Another disadvan~
::.., ~
- tage islbhat solvent losses occur in several ways during extractive dis~illation. Physical losses occur from leak~
age and from carryover in the raffinate. Other losses occur ro~ chemical reactlvity or thermal degradation of the solvent. In the case o phenol for lnseance~ a hi8h boiling iaactive sludge forms from reaction with traces of i ., . ,~ ~dienes present in ehe hydrocarbon fesd~ Furfural is sens~
tive to elevated temperatures in the presPnce of oxygen, water~ or unsaturated hydrocarbons resulting in polymeriza-tion. ~hus~ contiNuous redistillation of a portion of the -: . ~
.. , ;
i .
~ ~12-1~364~
circulating solvent or intermittent redistillation of the -total solvent inven-tory is usually required to rernove such solvent impurities. Acldi-tionally, control o~ the extractive distillation is usually difEicul-t. The tempera-ture gradient in the tower does not correlate with the ac-tual separation being carried out. Control is usually by material balance supplemen-ted by frequent produce SaM-ples and analyses and in some cases spectroscopic or chro-matographic instruments have been employed for continuous analysis to aid in tower operation.
~' Selective absorption with cuprous salt solutions is also co~mercially used to purify butadiene from crude fractions derived from both thermal cracking and catalytic dehydrogenation processes. The solubility of a hydrocarbon :
¦ 15 in solutions of this type generally increases wi-th the de- ;
- gree of unsaturation, butadiene being many times more solu-.: . ~.
ble than the closely-boiling butenes. Essentially three processing s-teps are involved in this purification opera-tion, an absorption stage in which butadiene, along with a portion of the mono-olefins and other unsaturates, is dis- ;
solved in the solvent; an enrichment stage, generally ;
- effected by a combination of heating and stripping with ~¦ enrlched butadiene, in which essentially all of the dis-solved hydrocarbons except butadiene are stripped from the solvent; and a desorption sta~e in which purified butadiene is stripped from the enriched solvent. By appropriate re-cycling of steams between these stages, high recoveries ' ~ -13-~: ~.~
. ', ' ' .
..
'~
,':
: ;
~.'.' .. - - , :, i.: . .
.. . . .
of butadiene can be obtained. Like extr~ctive distilla- ;
tion, however, this process also has rather high energy re~uirements c~nd has the same attendant problems of circu-lating-solvent life and con-tamination of degradation.
- The process of my invention avoids the problems associated with reactive circulating solvents and provides - a process less difficult in operation by which high purity butadiene can be produced at operating costs at least competitive with those of existing processes.
To separate 1,3-butadiene from a feed mixture containing 1,3-butadiene and at least one -ot~her=l-~ C4 unsat-urate by the process of our invention, the mixture is con-tacted with a particular adsorbent and the butadiene is -~ .
. :.
more selectively adsorbed and retained by the adsorbent while the less selectively adsorbed obher C4 unsaturate is removed from the interstitial void spaces between the par-ticles of adsorbent and the surface of the adsorbent. The adsorbent containing the more selectively adsorbed 1,3- ~
. .,~- , .
butadiene is referred as a "rich" adsorbent -- rich in the more selectively adsorbed 1,3-butadiene.
; The more selectively adsorbed feed component is commonly referred to as the extract component of the feed -: : :: ~ ., .
mixture, while the less selectively adsorbed component is `~ -referred to as the raffinate component. Fluid streams ;~
leaving the adsorbent comprising an extract component and ` ~ -comprising a raffinate component are referred to, respec-tively, as the extract stream and the raffinate stream. As ~;~
previously mentioned, the crude butadiene feed mixtures `~
, , ' '' ` '` ,"
~64~;~9 will ~Isually contain many components -- primarily C3's and C~'s -- and it will therefore be recognized that all of the components presen-t in the -feed mixture, other -than 1,3-butadiene, will be less selectively adsorbed by the adsor~ent with respect to 1,3-butadiene. Thus, the raf-finate stream will contain as raffinate components all of the feed componen-ts besides 1,3-bu-tadiene and the extract stream will contain 1,3-butadiene as the extract component.
Although it is possible by the process of this invention to produce high purity (98~ or greater), 1,3-butadiene at high recoveries, it will be appreciated that an extract component is never completely adsorbed by the adsorbent, nor is a raffinate component completely non-adsorbed by the adsorbent. Therefore, small amounts of a raffinate component can appear in the extract stream, and, likewise, small amounts of an extract component can appear in the raffinate stream. The extract and raffinate streams then are further distinguished from each other and from -the feed mixture by the ratio of the concentrations of an extract component and a specific raffinate ~omponent, both appearing in the particular stream. For example, the ratio ofconcentration of the more selectively adsorbed l,3-buta-diene to the concentration of less selectively adsorbed butene-l will be highest in the extract stream, next high-est in the feed mix-ture, and lo~est in the raEfinate stream.
Likewise, the ratio of the less selectively adsorbed butene-l to the more selectively adsorbed l,3-butadiene ~ill be high-est in the raffinate stream, next highest in the feed mix-ture, and the lowest in the extract stream.
--15-- ' ':
- -: ~: . -i:: . : -.
. -, . .. . .
~641~Z~
;
The adsorbent c~n be contalned in one or more cha~bers where through progra~med flow i~to and out of the chambers separation of the diene is effected. The adsor-bent may be contacted wlth a desorbent material which i~
capable of displacing the adsorb~d 193-butadiene fro~ the adsorbent. Alternati~ely, the 1,3-butadiene could bs removed fr~ the adsorbent by purging or by increasin~ the temperature of the adsorbent or by decreasing ~he pressure of the cha~ber o~ ves~el coneaining the adsorbent or by a coDbination of these means.
The adsorbent may be e~ployed in the form of a dense compact fixed bed which is alternatively contac~ed with the eed mixture and ~ desorbent material (hereinafter - -described). In the simplest embodiment of the invention the adsorbent is employed in the form of a single static bed in which case the process is only semi~continuous.
A set of two or ~ore static beds ~ay be employed in fixed- i, bPd coneacting with appropriate valving so that the feed ~ ~
~ixtur~ is passed throu~h one or more adsorbent beds ~hile - ~ ~ ;
the desorbent material is passed through one or more of the other beds in the set. The flow of ~eed mi~ture and de- -sorbent ma~erial may be either up or down through the ad- -sorbent. Any of the conventional apparatus employed in static bed fluld-solid contacting may be used.
Movlng bed or simula~ed moving-bed systems, how-ever, have a ~uch 8reater separation efficiency than fi~ed adsorben~ bed systems and are therefore preferred.
1064BZ~
Speclfically~ the more preferred processlng flow sche~es which can be utilized to effect the process of this invention are those known in the art as simulated moving-bed countercurrent syseems. One such system incl~des the flow scheme described in U.S.Patent ~,985,589 issued to D. B. Broughton. Thls patent generally described the processing sequence involYed in a particular simula~ed moving-bed countercurrent solid~fluid contacting process.
In fact, the processing sequence generally descrihed in ~ ;
that patent is the preferred mode of operating the separa-tion process disclosed herein.
~ith thst processing sequence therefore9 ~n~ -embodiment of my invention is a process for separating 173-butadiene frvm a feed mixture comprising 1~3-butadiene and ae least one other C4 unsaturate which process comprises the steps of: contacting said mixture at adsorption condi~
tions with a particular ~eolitic adsorbent to effect ehe selective adsorption of 1,3-butadisne; withdra~ing fro~ the ` ~-~
adsorbent a stream ccmprising the less seleceively ~dsorbed other C4 unsaturate; contac~ing the adsorbent at desorp-tion condi~ions with a desorbent m~terial to effect the -`
removal of the selectively adsorbed 1~3-butadiene from the --adsorbent; and, withdrawing fro~ the adsorbent ~ stream ... . . .
co~prising tesorbent ~aterial and 1~3-butadiene.
Preferred operating conditions for both adsorp~
tion ~nd desorption of this particular embodiment of my inven~ion include a temperature within the range of from ~ .
:
~ -17~
. . . . . ~ .. . .
21 to 232C. and a pressure within the range of fro~ .
about 1 to 35 atmospheres. E'urthermore, both adsorption and desorption are preferably affected at conditions selected to maintain liquid phase throu~hout the process ~_ operation.
Adsorption and desorption could, of course, be conducted both in the vapor phase or liquid phase or one ~
operation may be conducted in the vapor phase and the other ~ ' in the liquid phase. Operating pressures and temperatures for adsorption and desorption migh-t be the same or different.
The desorbent materials which can be used in the ~ .
various processing schemes employing this adsorbent will vary depending on the type of operation employed. The ~ `
term "desorbent material" as used herein means any fluid substance capable of removing a selectively adsorbed feed component from the adsorbent. In the swing-bed system in which the selectively adsorbed feed component is removed ~;
from the adsorbent by a purge stream, gaseous hydrocarbons such as methane, ethane, etc , or other types of gases such as nitrogen or hydrogen may be used at elevated tempera-tures or reduced pressure or both to effecti~ely purge the adsorbed feed component from the adsorbent. i However, in processes which are generally operated ~ ;
at substantially constant pressures and temperatures to insure liquid phase, the desorbent material relied upon must be judiciously selected in order that it may displace the adsorbed feed component from the adsorbent with rea-sonable mass flow rates and also without unduly pre~enting ~.
. ~ : , :.,: :
iO~'Z~ .
the extract component from displacincJ the desorbent i~ a following adsorption cycle.
Desorben-t materials which can be used in the process of this invention should additionally be substances which are easily separable from the feed mixture that is , passed into the process. In desorbing the preferentially ¦ adsorbed component of -the Eeed, ~oth desorbent material and the extract component are removed from the adsorbent j in admixture. Withou-t a method of separation of these two materials, the purity of the ex-tract component of the feed stock would not be very high since it would be dilu_ed ¦ with desorbent. It is conternplated tha-t any desorbent ¦ material used in this process will have a substantially j different average boiling point than that of the feed mixture. More specifically, "substantially di~ferent"
shall mean that the difference between the average boiling ~-points shall be at least about 20F. The boiling range of the desorbent material could be higher or lower than tha~
of the feed mixture. The use of a desorbent material ha~ing -~
a substantially different average boiling point than ~a-of the feed allows separation of desorbent material from feed components in the extract and raffinate streams by simple fractionation or other methods thereby permitting reuse of desorbent material in -the process.
~5 Desorbent materials which can be used in the process of this invention include paraffins, olefins, aromatics, ethers, alcohols, cyclic dienes, and ketones.
In -the preferred isothermal, isobaric, liquid-phase .
, : ~ : : , . . ~, . i operation of` the process of my invention, I have found that desorbent materials compris:ing olefins, aromatics or mixtures of o]efins and aromatics are particularly effec--tive. Speci~ically, desorbent materials comprising linear olefins, such as octene-l for example J and aromatics such as benzene and toluene all of wh:ich are easily separable from 1,3-butadiene by conventional distillation are espe-cially preferred for this type of operation. Mixtures of olefins or aromatics, or olefins and aromatics with paraf-fins have, additionally, been found -to be effective desor-bent materials. The paraffins can include straight or branched chain paraffins or cycloparaffins having a boil-ing point substantially different from the feed to allow separation from feed components. Typical concentrations of an olefin or an aromatic or an olefin and an aromatic~ when used in admixtures with a paraffin can be from a few volume percent'up to near 100 vol. % of~theltotal desorkent mate-rial and preferably will be within the range of from about 25 vol. % to about 100 vol. ~0 with an even more preferred 20 range being from about 50 vol. % to about 100 vol. % of the total desorbent material.
With the types and some operating features of processes employing adsorbents to separate 1,3-butadiene by selective adsorption now in mind, one can appreciate that certain characteristics of adsorbents are highly de-sirable, if not absolutely necessary, to the successful -~
operation of a selective adsorption process. Among such characteristics are: adsorptive capacity for some volume -" :~
.
~ -20-~., :10~48~9 oE an extract component per volume o~ adsorbenti the selec-tive adsorption of an extract component with res~ect to a raE~inate component and the desorbent material; suffi~
~ ciently fast rates of adsorption and desorption of the ¦ 5 extrac-t component to and from the adsorbent; an~, little or no catalytic activity Eor undesired reactions such as polymeri~ation and isomerization.
Capacity of the adsorben-t for adsorbing a spe-cific volume of an extract component is, of course, a necessityi without such capacity the adsorbent is useless for adsorptive separa-tion. Furthermore, the hi~her the adsorbent's capacity for an extract component, the better is the adsorbent. Inereased capacity of a partieular adsorbent makes it possible to reduee the amount of adsor-bent needed to separate the extract componen-t contained in a particular charge rate of feed mixture. A reduction in the amount of adsorbent required Eor a specific adsorptive separation reduces the cost of the separation process.
It is important that the good initial capacity of the ad- -sorbent be maintained during ac-tual use in the separation process over some economieally desirable life.
The second neeessary adsorbent eharacteristic is the ability of the adsorbent to separate components of -the feed; or, in other words, that the adsorbent possess adsorptive selectivi-ty, (B), for one component as compared to another component. Selectivity can be express'2d not only for one feed mixture component as compared to another but can also be expressed between any feed mixture co~ponent . -~, -21- ;
. ~ ' , '`~ ~
-.- :: .- , . . .: -; . - , ' , ~, , .
i~48~9 and the desorbent. The selectivity, (B), as used through-out this specification is defined as the ratio of -the two components of the adsorbed phase over the ratio of the same two components in -the unadsorbecl phase at equilibrium con- ;~
ditions.
Selectivity is shown as Equation 1 below:
Equation 1 Selectivity = (B) , Eol. ~ercent C/vol. ercen_ ~ A
ol. percent C/vol. p~e~rcent ~3U
where C and D are two components of the feed represented in volume percent and the subscripts A and U represent the adsorbed and unadsorbed phases respectively. The equilibrium conditions as defined here were determined when the feed passing over a bed of adsorbent did no-t change composition after contacting the bed of adsorbent. In other words, there was no new transfer of material occurring between the unadsorbed and adsorbed phases.
As can be seen where the selectivity of two com-ponents approaches 1.0 there is no preferential adsorption of one component by the adsorbent. As the (B) becomes less than or greater than 1.0 there is a preferential selectivity by the adsorbent of one component. When comparing the selec-tivity by the adsorbent of one component C over component D, -a (B) larger than 1.0 indicates preferential adsorp-tion of component C within the adsorbent. A (B) less tha~ l.U would ,~
indicate that component D is preferentially adsorbed leaving an unadsorbed phase richer in componen* C and an adsorbed `' ;
~ .
~i .
.
. . . .. .. ..
1~69~!3Z9 phase richer in component D. Desorben-ts ideally ~Jould have a selectivity equal to about 1 or slightly less than 1. ~
The third.important characteristic is the rate : 5 of exchange of the extract component of the feed mlxture material or, in other words, the relative rate of desorp-tion o the extract component. This characteristic relates .,~.
to the amoun-t of desorbent material -that must be employed ~ .
i in the process to recover the extract component ~rom the ¦ 10 adsorbent; faster rates of exchange reduce the amount of desorbent material needed to remove the extract component, It is also necessary that the adsorbent possess .
little or no catalytic activity toward polymerization or isomerization of any of the feed components. Such activity :
might effect adsorbent capacity or selec-tivity or product ~-yields or all of these. Polymerizati.on tends primarily to degrade the adsorbent in addition to reducing yields some-what. Polymerization effects are generally considered to be primarily physical impediments which can prevent the adsorption of the extract component by obstructing the :
surface of the adsorbent and the pores present in the struc~
ture of the adsorbent. This shortens the useful life of ~:
the adsorbent and makes necessary frequent regeneration :
treatments to restore the adsorptive properties o the adsorbent. Isomerization activity tends primarily to de-crease the yield of a desired feed component. It is the `
elimination of polymerization activity which we have found to be of primary concern rather than isomerization activity ~ :
-23- ~ :
. , ` ..
.~
'~
~6~ :
in the process of my inventlon. It is, therefore~ exeremely important that the catalytic activity be substantially rèduced or preferably totally eliml~ated by proper methods of ~anufacture of a selected adsorbent.
Whlle reducing the temperature of the operations of the adsorption process in which ehe catalytic activity is present ~ill substantially reduce ~he catalytiç ac~ivity because of the associated reduction in the rate of reaction, this procedure in adsorptiYe separation processes employing molecular sieves is generally not desirable because the ;~
reduction in temperature also reduces ehe rates of adsorp- -tion and desorption of the ex~ract componen~.
In order to test various adsorbents to me~sure ~he characteristics of adsorptive capacity and selectivlty, a dynamic testing apparatus is employed. The apparatus consists of an adsorbent chamber of approximately 70 cc volume having inlet and outlet portlon at opposite ends of ~`
the chamber. The chamber Is contained within a temperature control means, and, in addition, pressure cont~ol equipment is used to operate the cha~ber at a cons~ant predetermined pressure. Chromatographic analysis equipment can bc at-tached to the outlet line of khe cha~ber and used to analyze ehe effluent stream leaving ~he adsorbent chamberO
A pulse test, performed usin~ this apparatus and the following general procedure3 is used to determine selec-ti~ities and other data for ~arious adsorbent systems. An adsorbent system comprises a particular adsorbent, feed ~;
material~ and desorbent material~ The adsorbent is filled -2~-. - : ~ . - . , . . ,, :
8Z~
to equllibrlum with a particular clesorb~nt ~aterial by passing the desorbent material throu~h the adsorbent cham~
; ber. At a convenient time, a pulse of feed containing known COnCentratiDns of a non-adsorbed paraffinic tracer ~n-nonaDe for instance), 1~3-butadier~e, and at leas~ one other C4 unsaturate all diluted in desorbent material ~s inJec~ed ~ into the test chamber for a duration of several minutes~
Desorbent flow is resumed, and the tracer and the other feed components are el~ted as in a liquid-solid chromatographic operation. The effluent can be analyzed by on-stream chro-matographic equipment and traces of the envelopes of corres-ponding feed component peaks developed. Alternatively, effluent samples can be collected periodically and later analyzed separately by gas chromatography.
From information derived from the chromatographic traces~ adsorbent performance can be ra~ed in terms of capacity index for an ex~ract comp~nent9 selectivity for one ~eed co~ponent with respect to the other (osually an ~-~
extract c~mponent with respect to a raffinate component) and the rate of desorption of extract component by the de-sorbentO The capacity index may be charactsrized by the distance between the cen~er of the peak envelope of the extract component and the peak en~elope of the tracer c~m~
ponent or some other known reference pointO It is expressed in terms of the volume in cub~c centimeters of desorbent pumped during thisitime interval~ Selec~ivity) (~), for the extract compcnent with respect ~o raffinate component is characteri7-ed by the ratio of the distance between ~he ~25-.... , , ~, . . . . .............. . . .
,. , ,,, . - . . ,. , . , . ::
.
1~6~3Z9 center oE the extract componen-t peak envelope and -the tracer peak envelope (or other reEerence point) to -the correspondin~ distance for the rafinate component. The rate of exchange of the extract componen-t can ~enerally be characterized by the width of -the extrac-t componen~ peak envelope at half intensity. The narrower the peak width, the faster the desorption rate. The desorption rate can also be characterized by the distance between the center of the tracer peak envelope and the disappearance of the extract component which has ~ust been desorbed. This dis-tance is again the volume of desorbent pumped during this time interval.
To translate this type oE data into a practical separation process requires actual testing of the best sys-tem in a continuous countercurrent liquid-solid contact-ing device. The general operating principles of such a ~ ~
device has been previously described and are found in i ;
Broughton U.S. Patent 2,985,589. A specific laboratory-size apparatus utilizing these principles is described inde Rosset et al U.S. Patent 3,706,812. The equipment com-prises multiple adsorbent beds with a number of access lines attached to dis-tribu-tors within the beds and terminat-ing at a rotary distributing valve. At a given valve posi-tion, feed and desorbent are being introduced -through two ~ 25 of the lines and raffinate and extract are being withdrawn :
through two more. All remaining access lines are inactive and when the position o~ the distributing valve is advanced by one index, all active positions will be advanced by one ~, .. . . . . .
.
9 ~ :
bed. This simulates a condition ln which -the adsorbent physically moves in a direc-tion coun-tercurrent to the liquid flow. Additional details on the above-mentioned adsorbent testing apparatus and adsorbent evalua-tion techniques may be found in the paper "Separation of C8 Aroma-tics by Adsorption"
by A. J. de Rosset, R. W. Neuzil, D. J. Korous, and D. H.
Rosback presented at the American Chemical Society, Los Angeles, Cali~ornia, March 28 through April 2, 1971.
The feasibilit~ o~ separating 1,3-butadiene from ` 10 a feed mixture comprising 1,3 butadiene and at least one other C4 unsaturate by selective adsorption, which was demonstrated by pulse test results, may be confirmed by continuous -testing in the laboratory-sized apparatus de- -scribed above.
EXA~1PLE
¦ The following example is presented to fu~her ~-~
¦ illustrate the basis and benefit of -the presen-t invention ¦ ~ and is not intended to limit the scope of the invention.
This example presents results of pulse tests which were performed using a particular adsorbent primarily to determine selectivities of the adsorbent Eor 1,3-buta~
- diene relative to other C4 unsaturates. The selectivity numbers obtained illustrate the adsorbent's ability to separate 1,3-butadiene from the o-ther C4 unsaturates.
The particular adsorbent employed was a potassium exchanged Type X structured zeolite which contained a small portion of binder ma-terial and which was approximately 20-40 mesh particle size.
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. .
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" . :' ' . ' . ': ' ' :. . ., ' lO~B2~
.
The adsorben-t ~as prepa.red Erom base material comprising commercially available 13X zeolite in the form of nominal 1/16 x 1/8-inch extrudate. This base material.
was ground to produce 20-40 U.S. Standard Mesh particle size material and this ground base material was then ion-exchanged with a dilute aqueous caustic solution (about 4 -. wt. % NaOH) for the purpose of eliminating catalytic activity . oE the final adsorbent. The zeolite was then ion-exchanged with a potassium chloride solu-tion to give a volatile-free :
3 lo potassium oxide conten-t of about 9 wt % and the adsorbent j was then dried to a water level of 1.4 wt. % before it was 3 utilized in the pulse test apparatus. The adsorbent was placed in a 70 cc adsorbent column which was maintained at constant temperature and at constant pressure to ensure liquid-phase operation during the entire test procedure for each pulse test performed. The column effluent was ~
sampled every 2.5 minutes by an automatic sampling chro- ` .-matograph.
The feed mixture utilized comprised 20 vol. % ;~
each of butene-l, cis-butene-2, trans-butene-2, isobutylene, and 1,3-butadiene, to which was added a small amount of n-butane as a "tracer" for reference purposes. The mix-`
ture was injected into the test column in pulses of 3.6 cc each. Different desorbent materials comprising octene-l or benzene or toluene were employed for the various pulse tests.
The effluent was analyzed by the on-stream chro-matographic equipment and traces of the envelopes of com-. ' ~.
.
. ' . ' .
.
::. ~ . . . , ~: :
. ~.: : : . .. ..
.: . . . - :
¦ ~ Methylacetylene -23.2 :~ Vinylacetylene 5.0 .~ Ethylace-tylene 8.6 ;;
. 25 Butadiyne (biacetylene) 10.3 . Dimethylacetylene 27.1 `. ~' , ~' ~ j ,.' . , ~.
:~
.
1~6~1~Z5~ ~
In the conventional extract~ve distillation pro-cesses, the butanes and butenes e~hibit an enhanc~d vola-tility relative ~o the diolefinic and acotylenic materi~ls and are recnvered as an o~erhead product from the extrac-tlve distillation zoneO The less volat~le hydrocarbons, e.g., the diolefins and higher acetylenes,are separ~ted ~ -~
. .
together ~ith the polar solvent as the bottoms produc~ from - the extractive distillation zone. The butadiene product is reco~ered directly from ehe bottsms product in a strip-ping zone at ele~ated temperature~ The energy requlred to effect the separation ln the extractive distillation zone and in the stripping ~one is supplied by reboilers attached to each zone.
The extractive distiLlation method suffers from :. :
several disadvantag~s. One disadvanta~e is that relatively `~;
large amo~nts of energy are required to reboil both ths -~ extracti~e distillation zone~ which is typically a 100 plate colum~ and the stripping %one~ Another disadvan~
::.., ~
- tage islbhat solvent losses occur in several ways during extractive dis~illation. Physical losses occur from leak~
age and from carryover in the raffinate. Other losses occur ro~ chemical reactlvity or thermal degradation of the solvent. In the case o phenol for lnseance~ a hi8h boiling iaactive sludge forms from reaction with traces of i ., . ,~ ~dienes present in ehe hydrocarbon fesd~ Furfural is sens~
tive to elevated temperatures in the presPnce of oxygen, water~ or unsaturated hydrocarbons resulting in polymeriza-tion. ~hus~ contiNuous redistillation of a portion of the -: . ~
.. , ;
i .
~ ~12-1~364~
circulating solvent or intermittent redistillation of the -total solvent inven-tory is usually required to rernove such solvent impurities. Acldi-tionally, control o~ the extractive distillation is usually difEicul-t. The tempera-ture gradient in the tower does not correlate with the ac-tual separation being carried out. Control is usually by material balance supplemen-ted by frequent produce SaM-ples and analyses and in some cases spectroscopic or chro-matographic instruments have been employed for continuous analysis to aid in tower operation.
~' Selective absorption with cuprous salt solutions is also co~mercially used to purify butadiene from crude fractions derived from both thermal cracking and catalytic dehydrogenation processes. The solubility of a hydrocarbon :
¦ 15 in solutions of this type generally increases wi-th the de- ;
- gree of unsaturation, butadiene being many times more solu-.: . ~.
ble than the closely-boiling butenes. Essentially three processing s-teps are involved in this purification opera-tion, an absorption stage in which butadiene, along with a portion of the mono-olefins and other unsaturates, is dis- ;
solved in the solvent; an enrichment stage, generally ;
- effected by a combination of heating and stripping with ~¦ enrlched butadiene, in which essentially all of the dis-solved hydrocarbons except butadiene are stripped from the solvent; and a desorption sta~e in which purified butadiene is stripped from the enriched solvent. By appropriate re-cycling of steams between these stages, high recoveries ' ~ -13-~: ~.~
. ', ' ' .
..
'~
,':
: ;
~.'.' .. - - , :, i.: . .
.. . . .
of butadiene can be obtained. Like extr~ctive distilla- ;
tion, however, this process also has rather high energy re~uirements c~nd has the same attendant problems of circu-lating-solvent life and con-tamination of degradation.
- The process of my invention avoids the problems associated with reactive circulating solvents and provides - a process less difficult in operation by which high purity butadiene can be produced at operating costs at least competitive with those of existing processes.
To separate 1,3-butadiene from a feed mixture containing 1,3-butadiene and at least one -ot~her=l-~ C4 unsat-urate by the process of our invention, the mixture is con-tacted with a particular adsorbent and the butadiene is -~ .
. :.
more selectively adsorbed and retained by the adsorbent while the less selectively adsorbed obher C4 unsaturate is removed from the interstitial void spaces between the par-ticles of adsorbent and the surface of the adsorbent. The adsorbent containing the more selectively adsorbed 1,3- ~
. .,~- , .
butadiene is referred as a "rich" adsorbent -- rich in the more selectively adsorbed 1,3-butadiene.
; The more selectively adsorbed feed component is commonly referred to as the extract component of the feed -: : :: ~ ., .
mixture, while the less selectively adsorbed component is `~ -referred to as the raffinate component. Fluid streams ;~
leaving the adsorbent comprising an extract component and ` ~ -comprising a raffinate component are referred to, respec-tively, as the extract stream and the raffinate stream. As ~;~
previously mentioned, the crude butadiene feed mixtures `~
, , ' '' ` '` ,"
~64~;~9 will ~Isually contain many components -- primarily C3's and C~'s -- and it will therefore be recognized that all of the components presen-t in the -feed mixture, other -than 1,3-butadiene, will be less selectively adsorbed by the adsor~ent with respect to 1,3-butadiene. Thus, the raf-finate stream will contain as raffinate components all of the feed componen-ts besides 1,3-bu-tadiene and the extract stream will contain 1,3-butadiene as the extract component.
Although it is possible by the process of this invention to produce high purity (98~ or greater), 1,3-butadiene at high recoveries, it will be appreciated that an extract component is never completely adsorbed by the adsorbent, nor is a raffinate component completely non-adsorbed by the adsorbent. Therefore, small amounts of a raffinate component can appear in the extract stream, and, likewise, small amounts of an extract component can appear in the raffinate stream. The extract and raffinate streams then are further distinguished from each other and from -the feed mixture by the ratio of the concentrations of an extract component and a specific raffinate ~omponent, both appearing in the particular stream. For example, the ratio ofconcentration of the more selectively adsorbed l,3-buta-diene to the concentration of less selectively adsorbed butene-l will be highest in the extract stream, next high-est in the feed mix-ture, and lo~est in the raEfinate stream.
Likewise, the ratio of the less selectively adsorbed butene-l to the more selectively adsorbed l,3-butadiene ~ill be high-est in the raffinate stream, next highest in the feed mix-ture, and the lowest in the extract stream.
--15-- ' ':
- -: ~: . -i:: . : -.
. -, . .. . .
~641~Z~
;
The adsorbent c~n be contalned in one or more cha~bers where through progra~med flow i~to and out of the chambers separation of the diene is effected. The adsor-bent may be contacted wlth a desorbent material which i~
capable of displacing the adsorb~d 193-butadiene fro~ the adsorbent. Alternati~ely, the 1,3-butadiene could bs removed fr~ the adsorbent by purging or by increasin~ the temperature of the adsorbent or by decreasing ~he pressure of the cha~ber o~ ves~el coneaining the adsorbent or by a coDbination of these means.
The adsorbent may be e~ployed in the form of a dense compact fixed bed which is alternatively contac~ed with the eed mixture and ~ desorbent material (hereinafter - -described). In the simplest embodiment of the invention the adsorbent is employed in the form of a single static bed in which case the process is only semi~continuous.
A set of two or ~ore static beds ~ay be employed in fixed- i, bPd coneacting with appropriate valving so that the feed ~ ~
~ixtur~ is passed throu~h one or more adsorbent beds ~hile - ~ ~ ;
the desorbent material is passed through one or more of the other beds in the set. The flow of ~eed mi~ture and de- -sorbent ma~erial may be either up or down through the ad- -sorbent. Any of the conventional apparatus employed in static bed fluld-solid contacting may be used.
Movlng bed or simula~ed moving-bed systems, how-ever, have a ~uch 8reater separation efficiency than fi~ed adsorben~ bed systems and are therefore preferred.
1064BZ~
Speclfically~ the more preferred processlng flow sche~es which can be utilized to effect the process of this invention are those known in the art as simulated moving-bed countercurrent syseems. One such system incl~des the flow scheme described in U.S.Patent ~,985,589 issued to D. B. Broughton. Thls patent generally described the processing sequence involYed in a particular simula~ed moving-bed countercurrent solid~fluid contacting process.
In fact, the processing sequence generally descrihed in ~ ;
that patent is the preferred mode of operating the separa-tion process disclosed herein.
~ith thst processing sequence therefore9 ~n~ -embodiment of my invention is a process for separating 173-butadiene frvm a feed mixture comprising 1~3-butadiene and ae least one other C4 unsaturate which process comprises the steps of: contacting said mixture at adsorption condi~
tions with a particular ~eolitic adsorbent to effect ehe selective adsorption of 1,3-butadisne; withdra~ing fro~ the ` ~-~
adsorbent a stream ccmprising the less seleceively ~dsorbed other C4 unsaturate; contac~ing the adsorbent at desorp-tion condi~ions with a desorbent m~terial to effect the -`
removal of the selectively adsorbed 1~3-butadiene from the --adsorbent; and, withdrawing fro~ the adsorbent ~ stream ... . . .
co~prising tesorbent ~aterial and 1~3-butadiene.
Preferred operating conditions for both adsorp~
tion ~nd desorption of this particular embodiment of my inven~ion include a temperature within the range of from ~ .
:
~ -17~
. . . . . ~ .. . .
21 to 232C. and a pressure within the range of fro~ .
about 1 to 35 atmospheres. E'urthermore, both adsorption and desorption are preferably affected at conditions selected to maintain liquid phase throu~hout the process ~_ operation.
Adsorption and desorption could, of course, be conducted both in the vapor phase or liquid phase or one ~
operation may be conducted in the vapor phase and the other ~ ' in the liquid phase. Operating pressures and temperatures for adsorption and desorption migh-t be the same or different.
The desorbent materials which can be used in the ~ .
various processing schemes employing this adsorbent will vary depending on the type of operation employed. The ~ `
term "desorbent material" as used herein means any fluid substance capable of removing a selectively adsorbed feed component from the adsorbent. In the swing-bed system in which the selectively adsorbed feed component is removed ~;
from the adsorbent by a purge stream, gaseous hydrocarbons such as methane, ethane, etc , or other types of gases such as nitrogen or hydrogen may be used at elevated tempera-tures or reduced pressure or both to effecti~ely purge the adsorbed feed component from the adsorbent. i However, in processes which are generally operated ~ ;
at substantially constant pressures and temperatures to insure liquid phase, the desorbent material relied upon must be judiciously selected in order that it may displace the adsorbed feed component from the adsorbent with rea-sonable mass flow rates and also without unduly pre~enting ~.
. ~ : , :.,: :
iO~'Z~ .
the extract component from displacincJ the desorbent i~ a following adsorption cycle.
Desorben-t materials which can be used in the process of this invention should additionally be substances which are easily separable from the feed mixture that is , passed into the process. In desorbing the preferentially ¦ adsorbed component of -the Eeed, ~oth desorbent material and the extract component are removed from the adsorbent j in admixture. Withou-t a method of separation of these two materials, the purity of the ex-tract component of the feed stock would not be very high since it would be dilu_ed ¦ with desorbent. It is conternplated tha-t any desorbent ¦ material used in this process will have a substantially j different average boiling point than that of the feed mixture. More specifically, "substantially di~ferent"
shall mean that the difference between the average boiling ~-points shall be at least about 20F. The boiling range of the desorbent material could be higher or lower than tha~
of the feed mixture. The use of a desorbent material ha~ing -~
a substantially different average boiling point than ~a-of the feed allows separation of desorbent material from feed components in the extract and raffinate streams by simple fractionation or other methods thereby permitting reuse of desorbent material in -the process.
~5 Desorbent materials which can be used in the process of this invention include paraffins, olefins, aromatics, ethers, alcohols, cyclic dienes, and ketones.
In -the preferred isothermal, isobaric, liquid-phase .
, : ~ : : , . . ~, . i operation of` the process of my invention, I have found that desorbent materials compris:ing olefins, aromatics or mixtures of o]efins and aromatics are particularly effec--tive. Speci~ically, desorbent materials comprising linear olefins, such as octene-l for example J and aromatics such as benzene and toluene all of wh:ich are easily separable from 1,3-butadiene by conventional distillation are espe-cially preferred for this type of operation. Mixtures of olefins or aromatics, or olefins and aromatics with paraf-fins have, additionally, been found -to be effective desor-bent materials. The paraffins can include straight or branched chain paraffins or cycloparaffins having a boil-ing point substantially different from the feed to allow separation from feed components. Typical concentrations of an olefin or an aromatic or an olefin and an aromatic~ when used in admixtures with a paraffin can be from a few volume percent'up to near 100 vol. % of~theltotal desorkent mate-rial and preferably will be within the range of from about 25 vol. % to about 100 vol. ~0 with an even more preferred 20 range being from about 50 vol. % to about 100 vol. % of the total desorbent material.
With the types and some operating features of processes employing adsorbents to separate 1,3-butadiene by selective adsorption now in mind, one can appreciate that certain characteristics of adsorbents are highly de-sirable, if not absolutely necessary, to the successful -~
operation of a selective adsorption process. Among such characteristics are: adsorptive capacity for some volume -" :~
.
~ -20-~., :10~48~9 oE an extract component per volume o~ adsorbenti the selec-tive adsorption of an extract component with res~ect to a raE~inate component and the desorbent material; suffi~
~ ciently fast rates of adsorption and desorption of the ¦ 5 extrac-t component to and from the adsorbent; an~, little or no catalytic activity Eor undesired reactions such as polymeri~ation and isomerization.
Capacity of the adsorben-t for adsorbing a spe-cific volume of an extract component is, of course, a necessityi without such capacity the adsorbent is useless for adsorptive separa-tion. Furthermore, the hi~her the adsorbent's capacity for an extract component, the better is the adsorbent. Inereased capacity of a partieular adsorbent makes it possible to reduee the amount of adsor-bent needed to separate the extract componen-t contained in a particular charge rate of feed mixture. A reduction in the amount of adsorbent required Eor a specific adsorptive separation reduces the cost of the separation process.
It is important that the good initial capacity of the ad- -sorbent be maintained during ac-tual use in the separation process over some economieally desirable life.
The second neeessary adsorbent eharacteristic is the ability of the adsorbent to separate components of -the feed; or, in other words, that the adsorbent possess adsorptive selectivi-ty, (B), for one component as compared to another component. Selectivity can be express'2d not only for one feed mixture component as compared to another but can also be expressed between any feed mixture co~ponent . -~, -21- ;
. ~ ' , '`~ ~
-.- :: .- , . . .: -; . - , ' , ~, , .
i~48~9 and the desorbent. The selectivity, (B), as used through-out this specification is defined as the ratio of -the two components of the adsorbed phase over the ratio of the same two components in -the unadsorbecl phase at equilibrium con- ;~
ditions.
Selectivity is shown as Equation 1 below:
Equation 1 Selectivity = (B) , Eol. ~ercent C/vol. ercen_ ~ A
ol. percent C/vol. p~e~rcent ~3U
where C and D are two components of the feed represented in volume percent and the subscripts A and U represent the adsorbed and unadsorbed phases respectively. The equilibrium conditions as defined here were determined when the feed passing over a bed of adsorbent did no-t change composition after contacting the bed of adsorbent. In other words, there was no new transfer of material occurring between the unadsorbed and adsorbed phases.
As can be seen where the selectivity of two com-ponents approaches 1.0 there is no preferential adsorption of one component by the adsorbent. As the (B) becomes less than or greater than 1.0 there is a preferential selectivity by the adsorbent of one component. When comparing the selec-tivity by the adsorbent of one component C over component D, -a (B) larger than 1.0 indicates preferential adsorp-tion of component C within the adsorbent. A (B) less tha~ l.U would ,~
indicate that component D is preferentially adsorbed leaving an unadsorbed phase richer in componen* C and an adsorbed `' ;
~ .
~i .
.
. . . .. .. ..
1~69~!3Z9 phase richer in component D. Desorben-ts ideally ~Jould have a selectivity equal to about 1 or slightly less than 1. ~
The third.important characteristic is the rate : 5 of exchange of the extract component of the feed mlxture material or, in other words, the relative rate of desorp-tion o the extract component. This characteristic relates .,~.
to the amoun-t of desorbent material -that must be employed ~ .
i in the process to recover the extract component ~rom the ¦ 10 adsorbent; faster rates of exchange reduce the amount of desorbent material needed to remove the extract component, It is also necessary that the adsorbent possess .
little or no catalytic activity toward polymerization or isomerization of any of the feed components. Such activity :
might effect adsorbent capacity or selec-tivity or product ~-yields or all of these. Polymerizati.on tends primarily to degrade the adsorbent in addition to reducing yields some-what. Polymerization effects are generally considered to be primarily physical impediments which can prevent the adsorption of the extract component by obstructing the :
surface of the adsorbent and the pores present in the struc~
ture of the adsorbent. This shortens the useful life of ~:
the adsorbent and makes necessary frequent regeneration :
treatments to restore the adsorptive properties o the adsorbent. Isomerization activity tends primarily to de-crease the yield of a desired feed component. It is the `
elimination of polymerization activity which we have found to be of primary concern rather than isomerization activity ~ :
-23- ~ :
. , ` ..
.~
'~
~6~ :
in the process of my inventlon. It is, therefore~ exeremely important that the catalytic activity be substantially rèduced or preferably totally eliml~ated by proper methods of ~anufacture of a selected adsorbent.
Whlle reducing the temperature of the operations of the adsorption process in which ehe catalytic activity is present ~ill substantially reduce ~he catalytiç ac~ivity because of the associated reduction in the rate of reaction, this procedure in adsorptiYe separation processes employing molecular sieves is generally not desirable because the ;~
reduction in temperature also reduces ehe rates of adsorp- -tion and desorption of the ex~ract componen~.
In order to test various adsorbents to me~sure ~he characteristics of adsorptive capacity and selectivlty, a dynamic testing apparatus is employed. The apparatus consists of an adsorbent chamber of approximately 70 cc volume having inlet and outlet portlon at opposite ends of ~`
the chamber. The chamber Is contained within a temperature control means, and, in addition, pressure cont~ol equipment is used to operate the cha~ber at a cons~ant predetermined pressure. Chromatographic analysis equipment can bc at-tached to the outlet line of khe cha~ber and used to analyze ehe effluent stream leaving ~he adsorbent chamberO
A pulse test, performed usin~ this apparatus and the following general procedure3 is used to determine selec-ti~ities and other data for ~arious adsorbent systems. An adsorbent system comprises a particular adsorbent, feed ~;
material~ and desorbent material~ The adsorbent is filled -2~-. - : ~ . - . , . . ,, :
8Z~
to equllibrlum with a particular clesorb~nt ~aterial by passing the desorbent material throu~h the adsorbent cham~
; ber. At a convenient time, a pulse of feed containing known COnCentratiDns of a non-adsorbed paraffinic tracer ~n-nonaDe for instance), 1~3-butadier~e, and at leas~ one other C4 unsaturate all diluted in desorbent material ~s inJec~ed ~ into the test chamber for a duration of several minutes~
Desorbent flow is resumed, and the tracer and the other feed components are el~ted as in a liquid-solid chromatographic operation. The effluent can be analyzed by on-stream chro-matographic equipment and traces of the envelopes of corres-ponding feed component peaks developed. Alternatively, effluent samples can be collected periodically and later analyzed separately by gas chromatography.
From information derived from the chromatographic traces~ adsorbent performance can be ra~ed in terms of capacity index for an ex~ract comp~nent9 selectivity for one ~eed co~ponent with respect to the other (osually an ~-~
extract c~mponent with respect to a raffinate component) and the rate of desorption of extract component by the de-sorbentO The capacity index may be charactsrized by the distance between the cen~er of the peak envelope of the extract component and the peak en~elope of the tracer c~m~
ponent or some other known reference pointO It is expressed in terms of the volume in cub~c centimeters of desorbent pumped during thisitime interval~ Selec~ivity) (~), for the extract compcnent with respect ~o raffinate component is characteri7-ed by the ratio of the distance between ~he ~25-.... , , ~, . . . . .............. . . .
,. , ,,, . - . . ,. , . , . ::
.
1~6~3Z9 center oE the extract componen-t peak envelope and -the tracer peak envelope (or other reEerence point) to -the correspondin~ distance for the rafinate component. The rate of exchange of the extract componen-t can ~enerally be characterized by the width of -the extrac-t componen~ peak envelope at half intensity. The narrower the peak width, the faster the desorption rate. The desorption rate can also be characterized by the distance between the center of the tracer peak envelope and the disappearance of the extract component which has ~ust been desorbed. This dis-tance is again the volume of desorbent pumped during this time interval.
To translate this type oE data into a practical separation process requires actual testing of the best sys-tem in a continuous countercurrent liquid-solid contact-ing device. The general operating principles of such a ~ ~
device has been previously described and are found in i ;
Broughton U.S. Patent 2,985,589. A specific laboratory-size apparatus utilizing these principles is described inde Rosset et al U.S. Patent 3,706,812. The equipment com-prises multiple adsorbent beds with a number of access lines attached to dis-tribu-tors within the beds and terminat-ing at a rotary distributing valve. At a given valve posi-tion, feed and desorbent are being introduced -through two ~ 25 of the lines and raffinate and extract are being withdrawn :
through two more. All remaining access lines are inactive and when the position o~ the distributing valve is advanced by one index, all active positions will be advanced by one ~, .. . . . . .
.
9 ~ :
bed. This simulates a condition ln which -the adsorbent physically moves in a direc-tion coun-tercurrent to the liquid flow. Additional details on the above-mentioned adsorbent testing apparatus and adsorbent evalua-tion techniques may be found in the paper "Separation of C8 Aroma-tics by Adsorption"
by A. J. de Rosset, R. W. Neuzil, D. J. Korous, and D. H.
Rosback presented at the American Chemical Society, Los Angeles, Cali~ornia, March 28 through April 2, 1971.
The feasibilit~ o~ separating 1,3-butadiene from ` 10 a feed mixture comprising 1,3 butadiene and at least one other C4 unsaturate by selective adsorption, which was demonstrated by pulse test results, may be confirmed by continuous -testing in the laboratory-sized apparatus de- -scribed above.
EXA~1PLE
¦ The following example is presented to fu~her ~-~
¦ illustrate the basis and benefit of -the presen-t invention ¦ ~ and is not intended to limit the scope of the invention.
This example presents results of pulse tests which were performed using a particular adsorbent primarily to determine selectivities of the adsorbent Eor 1,3-buta~
- diene relative to other C4 unsaturates. The selectivity numbers obtained illustrate the adsorbent's ability to separate 1,3-butadiene from the o-ther C4 unsaturates.
The particular adsorbent employed was a potassium exchanged Type X structured zeolite which contained a small portion of binder ma-terial and which was approximately 20-40 mesh particle size.
: :
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" . :' ' . ' . ': ' ' :. . ., ' lO~B2~
.
The adsorben-t ~as prepa.red Erom base material comprising commercially available 13X zeolite in the form of nominal 1/16 x 1/8-inch extrudate. This base material.
was ground to produce 20-40 U.S. Standard Mesh particle size material and this ground base material was then ion-exchanged with a dilute aqueous caustic solution (about 4 -. wt. % NaOH) for the purpose of eliminating catalytic activity . oE the final adsorbent. The zeolite was then ion-exchanged with a potassium chloride solu-tion to give a volatile-free :
3 lo potassium oxide conten-t of about 9 wt % and the adsorbent j was then dried to a water level of 1.4 wt. % before it was 3 utilized in the pulse test apparatus. The adsorbent was placed in a 70 cc adsorbent column which was maintained at constant temperature and at constant pressure to ensure liquid-phase operation during the entire test procedure for each pulse test performed. The column effluent was ~
sampled every 2.5 minutes by an automatic sampling chro- ` .-matograph.
The feed mixture utilized comprised 20 vol. % ;~
each of butene-l, cis-butene-2, trans-butene-2, isobutylene, and 1,3-butadiene, to which was added a small amount of n-butane as a "tracer" for reference purposes. The mix-`
ture was injected into the test column in pulses of 3.6 cc each. Different desorbent materials comprising octene-l or benzene or toluene were employed for the various pulse tests.
The effluent was analyzed by the on-stream chro-matographic equipment and traces of the envelopes of com-. ' ~.
.
. ' . ' .
.
::. ~ . . . , ~: :
. ~.: : : . .. ..
.: . . . - :
4~:9 ponent peaks were developed. Yrom informa-tion derive~
from the chromatographic traces, selectivities of the adsorben-t for 1,3-bu-tadiene with respect to butene-l and with respec-t to the o-ther C4's in the feed material were ¦ S obtained in the manner previously described. Additionally 3 the wid-ths of the butadiene peak envelopes, at half inten-:~! sity, were measured as an indication of -the rate of exchange I of butadiene with different desorbent materials. Results . ::
.j , .
! obtained for eleven pulse tests, A through K, are shown in ~:~
the Table 2 below.
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aJ ~) ~ V a~ a) a) N . N C) E~ S~ 1 O O -1-) a) a) N r~ N 1` N i~ r~ ~
: ID Id -1~ 1 -IJ I O N ~) ~ C_) O a) ~1 ~) - O
a~ Q -l C) t) O ~; O O I . a) I a) I Q Q O I
~1 O O 0 ~-1 0-~1 0 Q s~ Q ~ ~ \ c . ::~ U~ ~ op o~Oo\ C~O oP o~ o~ o~ o~ 0~ ~ ~ ~
J (~ ~1 o~ I ~1 ~
O ~ ~ ~ ~ O O '~ O
O O O O ~ ~1 0 0 0 0 0 0 0 :- ~ O o ~
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OO OO O ~ oO oo ~U~ o o oo o ~1~ ~ r~ ~ r~) r~ r~ ~ ~ ~ ~ oo ,~
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The selectivity values shown Eor -the eleven'pulse ; tests demonst,ra-te first o:E all the adsorbent's ability to selectively adsorb 1,3-butadiene f:rom a feed stream con- ~ .
taining 1,3-butadiene and at leas-t one other C4 unsaturate, .'~ .
thereby making possible the butadiene separation process of this invention. All selectivities were at least about
from the chromatographic traces, selectivities of the adsorben-t for 1,3-bu-tadiene with respect to butene-l and with respec-t to the o-ther C4's in the feed material were ¦ S obtained in the manner previously described. Additionally 3 the wid-ths of the butadiene peak envelopes, at half inten-:~! sity, were measured as an indication of -the rate of exchange I of butadiene with different desorbent materials. Results . ::
.j , .
! obtained for eleven pulse tests, A through K, are shown in ~:~
the Table 2 below.
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a)~ ~:: ~ ~ D r~
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aJ ~) ~ V a~ a) a) N . N C) E~ S~ 1 O O -1-) a) a) N r~ N 1` N i~ r~ ~
: ID Id -1~ 1 -IJ I O N ~) ~ C_) O a) ~1 ~) - O
a~ Q -l C) t) O ~; O O I . a) I a) I Q Q O I
~1 O O 0 ~-1 0-~1 0 Q s~ Q ~ ~ \ c . ::~ U~ ~ op o~Oo\ C~O oP o~ o~ o~ o~ 0~ ~ ~ ~
J (~ ~1 o~ I ~1 ~
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The selectivity values shown Eor -the eleven'pulse ; tests demonst,ra-te first o:E all the adsorbent's ability to selectively adsorb 1,3-butadiene f:rom a feed stream con- ~ .
taining 1,3-butadiene and at leas-t one other C4 unsaturate, .'~ .
thereby making possible the butadiene separation process of this invention. All selectivities were at least about
5 or yreater~
, The data also indicates the general eflects o temperature on selectivity and on the rate of exchange o~
. 10 butadiene with the adsorbent material as measured by the , .
butadiene peak half width. Specifically, tests A and B
employed the same desorbènt material but were conducted at 55C. and 95C. respec-tively. At the higher temperatures ;~
of 95C. the selectivities decreased from 6.7 and 16.8 .'~
' 15 respectively at 55C. to 5.2 and 9.0 respectively at 95C. ~' . but at the higher temperature the rate oE exchange of buta-diene with the de.sorbent material was faster than that at the ;
lower temperature as evidenced by the narrower butadiene .
peak width. These effects are shown again by the results of pulse tests F and G.
Also shown by the data is the general effect of - the concentration of the olefin or aromatic in the desorbent ,'.
material upon the rate of exchanye of butadiene.with the desorbent material. Generally, faster exchange rates are ' ,,.;
obtained with higher olefin or aromatic concentrations as evidenced by the narrower butadiene peak widths. Specifi-;~ cally this is shown by comparing the results of tests A
and C, the results of tests J and K, and the results o.
tests E, F, G, and H.
-31- ~ ', ;`, ,,:
~ , '.
, The data also indicates the general eflects o temperature on selectivity and on the rate of exchange o~
. 10 butadiene with the adsorbent material as measured by the , .
butadiene peak half width. Specifically, tests A and B
employed the same desorbènt material but were conducted at 55C. and 95C. respec-tively. At the higher temperatures ;~
of 95C. the selectivities decreased from 6.7 and 16.8 .'~
' 15 respectively at 55C. to 5.2 and 9.0 respectively at 95C. ~' . but at the higher temperature the rate oE exchange of buta-diene with the de.sorbent material was faster than that at the ;
lower temperature as evidenced by the narrower butadiene .
peak width. These effects are shown again by the results of pulse tests F and G.
Also shown by the data is the general effect of - the concentration of the olefin or aromatic in the desorbent ,'.
material upon the rate of exchanye of butadiene.with the desorbent material. Generally, faster exchange rates are ' ,,.;
obtained with higher olefin or aromatic concentrations as evidenced by the narrower butadiene peak widths. Specifi-;~ cally this is shown by comparing the results of tests A
and C, the results of tests J and K, and the results o.
tests E, F, G, and H.
-31- ~ ', ;`, ,,:
~ , '.
Claims (15)
PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A process for separating 1,3-butadiene from a feed mix-ture comprising 1,3-butadiene and at least one other C4 unsaturate which process comprises contacting at adsorption conditions said mixture with an adsorbent comprising a crystalline aluminosilicate selected from type X structured zeolite and type Y structured zeolite containing at least one cation selected from lithium, sodium, potassium, rubidium, cesium, and barium at the exchangeable cationic sites within said zeolite thereby selectively adsorbing 1,3-butadiene from said mixture.
2. The process of Claim 1 characterised in that the 1,3-butadiene-containing adsorbent is contacted at desorption conditions with a desorbent material to remove 1,3-butadiene therefrom as a fluid extract stream.
3. A process for separating 1,3-butadiene from a feed mixture comprising 1,3-butadiene and at least one C4 mono-olefin which process comprises the steps of:
(a) contacting said mixture at adsorption conditions with an adsorbent comprising a crystalline aluminosilicate selected from type X
structured zeolite and type Y structured zeolite containing at least one cation selected from lithium, sodium, potassium, rubidium, cesium, and barium at the exchangeable cationic ~ within said zeolite thereby selectively adsorbing 1,3-butadiene;
(b) withdrawing from the adsorbent a stream comprising the less selectively adsorbed C4 mono-olefin;
(c) contacting the adsorbent at desorption conditions with a desorbent material to effect the removal of said 1,3-butadiene from the adsorbent; and (d) withdrawing from the adsorbent a stream comprising desorbent material and 1,3-butadiene.
(a) contacting said mixture at adsorption conditions with an adsorbent comprising a crystalline aluminosilicate selected from type X
structured zeolite and type Y structured zeolite containing at least one cation selected from lithium, sodium, potassium, rubidium, cesium, and barium at the exchangeable cationic ~ within said zeolite thereby selectively adsorbing 1,3-butadiene;
(b) withdrawing from the adsorbent a stream comprising the less selectively adsorbed C4 mono-olefin;
(c) contacting the adsorbent at desorption conditions with a desorbent material to effect the removal of said 1,3-butadiene from the adsorbent; and (d) withdrawing from the adsorbent a stream comprising desorbent material and 1,3-butadiene.
4. The process of Claim 3 characterised in that the adsorbent is employed in the form of a simulated moving bed.
5. The process of any of Claims 1 to 3 characterised in that said crystalline aluminosilicate is a type X structured zeolite.
6. The process of any of Claims 1 to 3 characterised in that said crystalline aluminosilicate is a type Y structured zeolite.
7. The process of any of Claims 1 to 3 characterised in that said adsorption and desorption conditions include temperatures within the range of from 21 to 232°C and pressures from 1 to 35 atmospheres to insure the liquid phase.
8. The process of any of Claims 1 to 3 characterised in that said crystalline aluminosilicate contains potassium cations at the cationic exchangeable sites.
9. The process of any of Claims 1 to 3 characterised in that said crystalline aluminosilicate adsorbent contains sodium cations at the exchangeable cationic sites.
10. The process of any of Claims 1 to 3 characterised in that said crystalline aluminosilicate contains barium at the exchangeable cationic sites.
11. The process of any of Claims 1 to 3 characterised in that said crystalline aluminosilicate contains barium and potassium cations at the cationic exchangeable sites.
12. The process of any of Claims 1 to 3 characterised in that said crystalline aluminosilicate comprises type X structured zeolite con-taining potassium cations at the exchangeable cationic sites.
13. The process of Claim 2 or 3 characterised in that said de-sorbent material has substantially different boiling point than that of the feed mixture.
14. The process of Claim 2 or 3 characterised in that said desorbent material comprises a linear mono-olefinic hydrocarbon.
15. The process of Claim 2 or 3 characterised in that said desorbent material comprises benzene or toluene.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US49679374A | 1974-08-12 | 1974-08-12 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1064829A true CA1064829A (en) | 1979-10-23 |
Family
ID=23974160
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA232,853A Expired CA1064829A (en) | 1974-08-12 | 1975-08-05 | Process for the separation of 1,3-butadiene by selective adsorption on a zeolite adsorbent |
Country Status (6)
| Country | Link |
|---|---|
| JP (1) | JPS5143702A (en) |
| CA (1) | CA1064829A (en) |
| DE (1) | DE2535818C3 (en) |
| FR (1) | FR2281910A1 (en) |
| GB (1) | GB1509586A (en) |
| IT (1) | IT1041175B (en) |
Families Citing this family (12)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5398541A (en) * | 1977-02-10 | 1978-08-29 | Gastar Corp | Hot water utilization m ethod |
| US4570029A (en) * | 1985-03-04 | 1986-02-11 | Uop Inc. | Process for separating isoprene |
| US5220102A (en) * | 1991-12-23 | 1993-06-15 | Uop | Process for separating normal olefins from non-normal olefins |
| US6215037B1 (en) * | 1998-10-27 | 2001-04-10 | The Regents Of The University Of Michigan | Method for selective adsorption of dienes |
| US6911569B1 (en) | 2000-08-07 | 2005-06-28 | The Regents Of The University Of Michigan | Sulfur resistant adsorbents |
| JPWO2013183742A1 (en) * | 2012-06-08 | 2016-02-01 | 協和化学工業株式会社 | Aluminum silicate and method for producing the same |
| JP5955135B2 (en) * | 2012-07-04 | 2016-07-20 | 昭和電工株式会社 | Gas separation material containing metal complex of oxocarbonic acid and method for separating hydrocarbon gas |
| CN104395268B (en) * | 2012-09-18 | 2016-03-23 | 昭和电工株式会社 | 1,3-butadiene is separated material and uses the separation method of this separation material |
| JP5980091B2 (en) * | 2012-10-30 | 2016-08-31 | 昭和電工株式会社 | Method for separating 1,3-butadiene and separation membrane |
| WO2014103778A1 (en) * | 2012-12-26 | 2014-07-03 | 昭和電工株式会社 | Gas separation material using metal complex and gas separation method |
| US9957285B2 (en) | 2013-07-26 | 2018-05-01 | Showa Denko K.K. | Metal complex, adsorbent, separating material, and 1, 3-butadiene separation method |
| JP6305405B2 (en) | 2013-07-26 | 2018-04-04 | 昭和電工株式会社 | 1,3-butadiene separator and separation method using the separator |
-
1975
- 1975-08-05 CA CA232,853A patent/CA1064829A/en not_active Expired
- 1975-08-07 IT IT5086975A patent/IT1041175B/en active
- 1975-08-11 GB GB3333375A patent/GB1509586A/en not_active Expired
- 1975-08-11 FR FR7524950A patent/FR2281910A1/en active Granted
- 1975-08-12 JP JP9801775A patent/JPS5143702A/en active Granted
- 1975-08-12 DE DE19752535818 patent/DE2535818C3/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| DE2535818A1 (en) | 1976-04-01 |
| FR2281910B1 (en) | 1978-10-27 |
| IT1041175B (en) | 1980-01-10 |
| GB1509586A (en) | 1978-05-04 |
| DE2535818B2 (en) | 1978-06-08 |
| DE2535818C3 (en) | 1979-02-15 |
| JPS5250762B2 (en) | 1977-12-27 |
| JPS5143702A (en) | 1976-04-14 |
| FR2281910A1 (en) | 1976-03-12 |
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