Note: Descriptions are shown in the official language in which they were submitted.
-1 2 ~
"PROCESS AND ADSORBENT FOR SEP~RATING CO~
FROM A MIXTURE THEREOF WITH HYDROCAR~ON'
FIELD OF THE INVENTTON
This invention relates to a process for the
purification of hydrocarbons contaminated with CO2. More
specifically, this invention relates to a process for the
removal of carbon dioxide and, optionally, water from
hydrocarbons using clinoptilolites adsorbent. The
clinoptilolites used may be either natural clinoptilolites
or clinoptilolites which have been modified by ion-
exchange with one or more o~ a number of metal cations.
BACKGROUND OF THE INVENTION
It is known that mixtures of molecules havingdiffering sizes and shapes can be separated by contacting
the mixture with a molecular sieve into which one compo-
nent of the mixture to be separated is more strongly
adsorbed by the molecular sieve than the other. The
strongly adsorbed component is preferentially adsorbed by
the molecular sieve and leaves behind outside the molecu-
lar sieve a mixture ~hereinafter re~erred to as the "firstproduct mixture") which is enriched in the weakly or non-
adsorbed component as compared with the original mixture.
The first product mixture is separated ~rom the molecular
sieve and the conditions of the molecular sieve varied
(typically either the temperature of or the pressure upon
the molecular sieve is altered), so that the adsorbed
2 ~ g
-2-
~aterlal ~esomes desorbea, thereby prsduc~ng ~ ~econd
~ix~ure ~hich i~ enric~ed in She adsorbed component ~s
c~mpared with the original mixture.
Whatever ~he exact details of the apparatus
and process steps used ln ~uch a process, cr~tical
factors include the capacity of the molecular sieYe for
the more adsorbable components and the selactivity of
the molecular sieve (iOe., th~ ratio in which the
. components to be separated are adsorbed). In many ~uch
processes, z~olites are the preferred ~dsorbents because
o~ their high adsorption capacity and, when chosen so
that their pores are of an appropriate size, their high
selectivity.
Most prior art attempts to use zeolites in the
separation ~f gaseous mixtures have bean made with
synthetic zeolitesO Although natural zeolites are
readily available ~t low cost, hitherto the natural
zeoli~es have not been favored as adsorbents b~cause it
has been felt that the natural zeolites are not
sufficiently consistent in compos~tion to be useful as
adsorbents $n such processes. However, there are
relatively ~ew ~ynthetic zeolites with pore sizes in the
range of a~out 3 to 4 A, which Ls the pore size range of
~nterest for ~ number of potentially important gaseous
separations t for example ~aparation of carbon diox~de
~rom ~ethane and other hydrocarbons, including ethylene
2 ~
-3-
~nd propylen~, ha~lng kinetic diameter~ not gre~t~r tha~
about 5 A.
As a result o~ th~ lack o~ zeol~te~ havlng
pore sizes ~n the range of 3 to 4 A, certain ~mportant
industrial separations are conducted rather
inefficiently. For exampl2, in the manufacture of
polyethylene, so-called ~thylene streams are produced
which contain ethylene, ethane and propane, together
with traces (typically of the order of 10 parts per
million) of carbon dioxide. It is necessary to lower
the already ~mall proportion of carbon dioxide further
before the ethylene ~tream reaches th~ polymerization
reactor, because the presence of even a few paxts per
: million of carbon dioxide poisons commercial ethylene
lS polymerization catalysts. At present, carbon dioxide
removal is usually effected by passing the ethylene
stream through a bed of calcium zeolite A. Although
calcium A zeoli.~e is an efficient adsorber of carbon
dioxide, it ~lco adsorbs relatively large guan~itie~ of
ethylene, and given the much greater partial pressure of
~thylene in th~ ethylene ~tream, the quantity of
ethylene adsorbed is much greater than that of carbon
dioxide. ~hus, relatively large guantities of ethylene
~re wa~ted in the removal o~ the traces of car~on
dioxide. Similar problems are encounter~d in the
propylene ~tream used to manufacture polypropyle~e.
2 ~
-4-
Clinoptilolit~s are ~ Xnown cl~ss o~
natur~l zeolites which have not hitherto been u~2d
~xtensi~ely ~or separation o~ gaseous mixtures, nlthough
a few such sPparat~ons are described in the literature.
For example, ~uropean Patent Application No. 84850131.8
(Publication No. ~32 239) describes a procesC for the
separation of oxygen and argon using as the adsorbent
raw clinoptilolite (i.e., clinopt~lolite which has not
been sub~ectsd to any ion-exchange~.
Industrial Gas Separation (published by the
American Chemical Society), Chapter 11, Franki2wicz and
Donnell, ~ethane/Nitrogen Gas Separation over the
Zeolite Clinoptilolite by the Selecti~e Adsorptio~ of
Nitrogen (1983) describes separ tion of gaseous ~ixtures
of me~hane and nitrogen using both raw clinoptilolitP
and clinoptilolite which had been ion-exchanged with
calcium.
It is known that the adsorption properties of
many zeolites, and hence their ability to separate
gaseous mixtures, can be varied by incorporating various
metal cations into ~he ~eolite , typically by
ion-exchange or impregnation. For exa~ple, U.S. Patent
No. 2,882,243 to Milton describe~ the use of zeolite A
having a silica/alumina ratio o~ 1~85 ~ 0~5 and
containing hydrogen, amm~nium, alkali ~etal, alkaline
earth m~tal or transition metal cations. Ihe patent
2 ~ 9
~tates ~hat R A 2eolite adsorbs w~ter and exclude~
hydrocarbon~ and alcohol~, while Ca A zeolite adsorb3
~tra~ght-chain hydrocarbons but excludes branched-ehain
~nd aromatic hydrocarbons.
In most cases, the changes in the adsorption
properties of zeolites ~ollowing ion-exchange are
consistent with a physic~l blocking of the pore opening
by the cation introduced; in general, in any given
zeolite, the larger the radius o~ the ion introduced,
the s~aller the pore diameter of the treated zeolite
(for ~xample, the pore diameter of ~ A zeolite is
~maller than that of Na ~ zeolite), as measured by the
size of the molecules which can be adsorbed into the
zeolite.
It has now been discovered that
clinoptilolites (both natural clinoptilolites and
clinoptilolites which have been ion-exchanged with any
one or more of a n~mber of metal cations) exhibit
adsorption properties which are use~ul in the separation
of carbon dioxide ~rom hydrocarbons. In contrast to
mo~t prior art zeolites ~odified by ion-excha~ge, ~h~
pore sizes, and hence the adsorption properties, of ion-
~xchangsd clinoptilolites are not ~ ple function of
the ioJlic radius of the ~xchanged cations.
.
.
2 01~ ~ 6 ~
SUMMARY OF THE INVENTION
This ~nvention provides a process for carbon dioxide
from a mixture thereof with a hydrocarbon having a kinetic
diameter of not more than about 5 Angstroms, which process
comprises contacting the mi~ture with an adsorbent containing
clinoptilolite at C02 adsorption conditions, thereby causing
the carbon dioxide to be selectively adsorbed into the
clinoptilolite. If the hydrocarbon also contains water as an
impurity, contacting the hydrocarbon with the clinoptilolite
will normally remove the water as well as the carbon dioxide.
Desirably, the hydrocarbon contains from 1 to 5, preferably 1
to 4, carbon atoms and is an acyclic hydrocarbon.
This invention also provides a modified
clinoptilolite adsorbent wherein at least about 40 percent of
the ion-exchangeable cations originally present in the natural
clinoptilolite are replaced by sodium and a cation selected
from sodium, potassium, calcium, magnesium, barium, strontium,
zinc, copper, cobalt, iron, manganese and mixtures thereof,
the modified clinoptilolite adsorbent being produced by a
process comprising subjecting a natural clinoptilolite to a
first ion-exchange step with a solution containing sodium
cations until at least about ~0 percent of the ion-
exchangeable non-sodium cations in the natural clinoptilolite
have been replaced by sodium cations, thereby producing a
sodium clinoptilolite, and thereafter subjecting the resulting
sodium clinoptilolite to a second ion-exchange step with a
_7~ 6 9
solution containing any one or more of lithium, sodium,
potassium, calcium, magnesium, barium, strontium, zinc,
copper, cobalt, iron and manganese cations until the
desired degree of ion-exchange with the non-sodium cation
is attained.
DETAILED DESCRIPTION OF THE INVENTION
This invention provides a process for separating
a minor proportion of carbon dioxide from a mixture
thereof with a hydrocarbon having a kinetic diameter of
not more than about 5 Angstroms, which process comprises
contacting the carbon-dioxide-containing hydrocarbon with
a clinoptilolit adsorbent at CO2 adsorption conditions.
The clinoptilolites used in the process of the present
invention may be natural clinoptilolites. However, being
natural materials, clinoptilolites are variable in
composition; chemical analysis shows that the cations in
clinoptilolite samples from various mines vary widely.
Moreover, natural clinoptilolites frequently contain
substantial amounts of impurities, especially soluble
silicates, which may cause difficulties in the aggregation
or pelletization of the clinoptilolite (discussed in more
detail below), or may cause undesirable side-effects which
would inhibit practicing this invention.
Accordingly, before being used in the process of
the present invention, it is preferred that the
clinoptilolites be modified by ion-exchange with at
- 2 ~
-B-
lea~t one ~etal cation. A~ong ~he cation~ ~hlch c~n
u3e~ully be ion-exchanged lnto clinoptilolite~ are
lithiu~, sodium, potass~u~, ~agnesiu~t calc~um,
strontium, bariu~, z~nc, ~opper, cobalt, iron and
manganese cations. Desirably, the lon-exchange i5
continued until at least about 40 percent of the cations
in the natural clinoptilolite have been replaced by one
or more of these cat~ons. The pre~erred metal cations
for treatment of the clinoptilolites used in the process
of the present invention are lithium, ~odiu~, calcium,
magnesium, barium and strontium cations, with sodium
being especially preferred. When 60dium is used as the
ion-exchange metal cat~on, it is preferred that the
ion-exchange b~ continued until at least about 50
percent of the total cations in the clinoptilolite ~re
replaced by sodium cations.
Since clinoptilolite is a natural ~aterial,
the particle sizes o~ the commercial product varies, and
the particle size of the clinoptilolite may ~fect the
speed and completeness of the ion-exchange react~on. In
general, it ~s recomme~ded that th p~rticle size of the
clinopt1101ite used in the ion-exchange reaction be not
great~r than about 2.38 mm in diameter (8 U.S. Mesh).
Although the particle sizes of many commercial
clinoptilolites axe greater, their particle
sizes are readily reduced by grinding or
- 2 ~
_9_
other techn~qu~s wh~ch ~ill be ~a~lliar to those ~k~ d
in the lon-exchange o~ ~olecular sieves.
~echn$gues ~or the ion-exchange of zeol1tes
~uch as clinoptilolite are well-known to those ~killed
in the molecular sieve art, and hence will not be
described in detail herein. In the lon-exchange, the
cation is conveniently present in the eolution in the
form of a soluble salt--typically it is chloride. It is
desirable that the ion-exchange be continued until at least
about 40 percent, and preferably 60 percent, of the cations
in the original clinoptilolite have been replaced, and
in most cases it is convenient to continue the ion-
exchange until no further amount of the desired cation
can easily be introduced into the clinoptilolite. To
secure maxi~um replacement o~ the original
j clinoptilolite cations, it is recommended that the ion-
! exchange be conducted using a ~olution containing a
guantity of the cation to be introduced which is ~rom
a~out 2 to ~bsut 100 ti~es the ion-exchange capacity of
the clinoptilolite. Typically the ion-exchange s~lution
will contain ~rom abouk 0.1 to about 5 moles per liter
of the cation, and will be contacted with the original
clinoptilolite for at least about 1 hour~ The ion-
exchange ~ay be conduGted at ambient temperature~ -
although in ~any cases carrying out the ~on-exchange at
r~
10--
~levated temperatur~, u~ually 1~5~ than lOO-C,
accel~rates the ~on-exchange proce~.
Since clinoptilolite 15 ~ natur~l ~aterial of
variable composit~on, the cations present ~n the raw
clinoptilolite vary, although typically the cations
include a major proportion of alkali ~etals. It is
typically found that, even after the most exhaustive
ion-exchan~, a proportion of the original
. clinoptilolite cations can not be replaced by oth~r
cations. However, the presence of this ~mall proportion
o~ the original clinoptilolit~ cations does not
interfere with the use o~ the ion-exchanged
clinoptilolites in the process o~ the present invention.
Any of the modified ~linoptilolites of the
present invention can be prepared directly by
ion-exchange of natural clinoptilolite with the
', appropriate cation. ~owever, in practice such direct
ion-exchange may not be the ~ost economical or practical
technique. Being natural ~inerals, clinoptilolites ~re
variable in composition and requently contain
substantial amounts o~ impurities, especially ~olubl~
silicates. ~o ensure as complete an ion-exchange as
possible, and al o to remove impurities, it is desirable
to ef~ect th~ ion-sxchanye of the clinoptilolite usi~g a
large excess of the cation which it is deslred to
~ntroduce. How~ver; if, for example, a large exces~ of
2 ~
barium is used in such an ion-exchange, the disposal and/or
recovery of barium from the used ion-exchange solution
presents a difficult environmental problem, in view of the
limitations on release of poisonous barium salts into the
environment. Furthermore, some impurities, including some
silicates, which are removed in a sodium ion-exchange are not
removed in a barium ion-exchange because the relevant barium
compounds are much less soluble than their sodium
counterparts.
In addition, when the modified clinoptilolites of
the present invention are to be used in industrial adsorbers,
it is preferred to aggregate (pelletize) the modified
clinoptilolite to control the macropore diffusion to increase
the crush strength of the resulting adsorber material and to
minimize pressure drop in the adsorber. If the binderless
clinoptilolite is used as the adsorbent, the clinoptilolite
may compact, thereby blocking, or at lPast significantly
reducing flow through, the column. Those skilled in molecular
sieve technology are aware of conventional techniques for
aggregating molecular sieves; such techniques ~sually involve
mixing the molecular sieve with a binder, which is typically a
clay, forming the mixture into an aggregate, typically by
extrusion or bead formation, and heating the formed molecular
sieve/clay mixture to a temperature of about 600-700C to
convert the green aggregate into one which is resistant to
crushing.
2 ~
, .
-12-
~ he binder~ u~ed t~ aggreg~te ~he
clinoptilolites ~y in~lude clay~ ailicas, aluminas,
Detal oxides ~nd m~xtures thereof. In add~tion, the
cl~noptilolites m~y be formed with material~ such as
silica, alumina, silica-alum$na, silica-magnesia,
6ilica-zirconia, 6ilica-thoria, silica-berylia, and
silica-titania, as well as ternary composltions, such as
6ilica-alumina-thoria, silica-alumina~zirconia and clays
present as binders. The relative proportions oP the
above materials and the clinoptilolltes may vary widely
with the clinoptilolite conten~ ranging between 1 and 99
percent by weight of the composite with 70 to 95 percent
typlcally being preferred. Where the clinoptilolite is to
be formed into aggregates prior to use, such aggregates are
desirably about 1 to about 4 mm. in diameter.
! Although the iOn-exchanye(s) needed to produce
the modified clinoptilolites of this invention may be
cond~cted either before or after aggregation, it i~
often lnadvisable to subject raw clinoptilolite to the
process of conver ion to the aggregate, 6ince variaus
impuriti~s ~ay be affected by the heat required ~or
aggregation and may interfer~ with the formation of
aggregates. However, in ~ome cases, ~t may also be
desir~ble to avoid Fub~cting 60me ~odified
cl~noptilolites of the invention to the heat reguired
~or aggregatlon, ~ince certain of these ~odi~ied
2 ~ 9
-13~
cl~nopt~lol~tes ~re a~ected by heat, ~ discuss~d in
more d~tall below.
To ~oid the aforementioned di~iculti~, it
ts generally preferred to produce modifiQd
S clinoptilolites of t~e present invention other than
~odium clinoptilolite by first sub~ecting raw
clinoptilolite to ~ sodium ion-exchange, aggregating the
~odium clinoptilolite thus produced, and then effecting
a second ion-exchange on t~e aggregat2d material to
introduc~ the desir~d non-sodium c~tions. ~hen ~ 60dium
clinoptilolite itself is to be used, it is in general
not necessary to carry out a second sodium ion-exchange
a~ter aggregation; the aggregated 80~ium clinoptilolite
may be used without urther processing and ~ives
satisfactory results, which do not appear to be
æigni~icantly improved by a sec~nd ion-exchange.
Before being used in the processes of the
present invention, the clinoptilolites need to be
activated by heating. If the clinoptilolite is
aggregated as discussed abov~, ths heat required ~or
aggregation will normally be ~u~ficient to e~fect
activation ~l~o, 80 ~hat no furt~er hea~ing is reguired.
I~, however, ~he clinoptilolite is not to bs aggregated,
~ ~eparate activation ~tep will usually be reguira~.
2~ ~odium clinoptilolite can be activated by heating ~n air
or vacuum to approximately 350-C for about 9 hour~ The
temperature needed ~or activati9n o~ ~ny ~peci~en o~
el~noptllolit¢ is easily determined by routine ~mpiri~al
tests which pose no d~fficulty to those ~k~lla~ ln
molecular sieve technology.
If the modified clinoptilolites are produced by
the preferred double exchange process di~cussed above, in
which a raw clinoptilolite is ~irst ~odium
? ion-exchanged, the resultant sodium clinoptilolite
aggregated, and finally the aggregated ~od~um clinoptilolite
is ion-exchanged with the desired non-sodium cation,
it is normally necessary to effect a second activation
of the final product; however, the activation
temperature required is not as high as that required ~or
aggregation, and consequently one avoids exposing the
clinoptilolite product of the second ion-exchange step
to aggregation temperatures. In some cases, it is desirable
i to limit the temperatures to which some o~ the twice exchanged
clinoptilolites of the present invention are exposed
~ince exposure of the modified ~linoptilolit~ to
excessive temperat~res may cau~e ~tructural damage o~
the clinoptilolite which may rend~r it less ef~ective in
the process of the present in~ention.
The process o~ the present invention is
primarily intQnded for re~oval of traces of car~on
2S ~ioxide ~rom hydrocar~ons, especially ethylene ~treams
(comprising mai~ly ethylene and ~thane) sur~ as those
2 ~
-15-
u~ed in ~e produc:tion Or poly~thylene ~and th¢
corre~ponaing propylene stream~, comprising malnly
propylene and propane, such as those u~ed ~n the
manufacture o~ polypropylene), where the presence of
e~en a few parts per million of carbon dioxide causes
~evere poisoning of the polymerization catalyst. In
such streams, the carbon dioxide content of the gas i8
normally not greater than about 200 vol. parts per million,
and the carbon dioxide partial pressure not greater ~han
about 20 Torr. (0.026 atmospheres or 2.67 kPa). As alread~
mentioned, sodium clinoptilolite is the preferred material for
this process. The same process will remove any water which
~ay be present in the hydrocarbon stream, and this
removal of water is also desirable ~ince water, even in
very small amounts, is active as a polymerizatio~
! catalyst p~ison.
I The present process ~ay also be use~ul for the
~eparation o~ carbon dioxide ~rom methane or other
hydrocarbons for use in ~ process such ag ~te~m
reforming. The present invention ~ay ~lso be used to
separate carbon dioxide ~rom butanes and butenes~ or
even larger hydrocarbons (for example n-h~xane) which
have kinetic diameters not greater than about 5 ~.
Since these types o~ processes involve th~
6eparation Or minor amounts o~ carbon dioxid~ (and
optionally water) impurity ~rom ~uch larger amounts of
2 ~ ~ r~ ~3 ~ 9
- 6-
hydrocarbons, they may be effected in the conventional manner
by simply passing the hydrocarbon stream through a bed of the
clinoptilolite maintained at CO2 adsorption conditions
including a temperature in the range of -15 to 60C and a
pressure selected to achieve the target flow rate of the input
stream through the bed. The bed is normally in aggregate
form. As the operation of the process continues, there
develops in the bed a so-called "front" between the
clinoptilolite loaded with carbon dioxide and clinoptilolite
not so loaded, and this front moves through the bed in the
direction of gas flow. Before the front reaches the
downstream end of the bed (which would allow impure
hydrocarbon gas to leave the bed), the bed is regenerated by
cutting off the flow of the feed hydrocarhon gas mixture and
passing through the bed a purge gas which causes desorption of
the carbon dioxide ~and water, if any i5 present) from the
bed. In industrial practice, the purge gas is typically
nitrogen or natural gas heated to a temperature in the range
of 50 to 350C, and such a purge gas is also satisfactory int
he processes of the present invention.
A nitrogen purge operation leaves the bed loaded with
nitrogen. To remove this nitrogen, it is only necessary to
pass one or two bed volumes of the hydrocarbon stream through
the bed; the resultant gas leaving the bed is mixed with
nitrogen and should normally be discarded. The loss of gas
resulting from such discarding is negligible, since the
purging and subse~uent removal of nitrogen only require to be
J
-a7-
per~or~d af~er the pas~age o~ hun~reds or thousand~ of
bed volumes of impure hydrocarbon.
I~ the process o~ the pres~nt ~nvsntion is to
be u~ed ~o Beparate carbon dioxide ~rom hydrocarbons
containing larger amounts of carbon dioxide (of the
order of 10 percent), other conventionzl pressure swing
adsorption and temperatur~ ~wing adsorption techniques
may be used inlieu of or in combination with the instant
process. Such techniques are well known to tho~e skilled in
lO molecular sieve technology; see, for example, U.S. Patents Nos.:
3,430,418
3,738,~8~
3,986,849
4,398,926
4, S89, 888 and
4,723,966,
! and British Patent No. 1,536,995.
It should be noted that the change in pore
eize of the cl~noptilolite after ion-exchange is ot a
simple function of the ~onic radiuc of th~ cation
~ntroduced. It has been determin~d empirically, by
measuring the adsorption of variou~ly ~ized gas
molecules into ~on-exchanged clinoptilolites, tha~ the
order o~ pore sizes in such ~linoptilolites ~:
CaClino ~ NaCl~no ~ ~iClino < ~gClino
~ Zn~lino < XClino ~ Sr~lino < BaClino
2 ~ ' fl
18-
wh~re ~Clino" r~presents the cllnopt$101it~ lattice
~ra~Qwork. Since calciu~ and ~a~nesium catlons have
~onic radii smaller than 6trontium and barium ~ations,
and ~ince sodium and lith~um cations hav2 ioni~ radii
smaller than potassium cations, increase in radiuu of
~on-exchanged cation does not always correlate with
decrease in pore size of th~ clinoptilolite, and thus,
unlike many other zeolites, the change in pore ~ze of
. ion-exchanged clinoptilolites cannot be a simple matter
o~ pore blocking.
Although ion-exchange of clinoptilol~te does
produce a modified clinoptilolite having a consistent
pore size, the exact pore size depends not only upon the
metal cation(s) exchanged but also upon the ther~al
treatment of the product following ion-exchange. In
general, there is a t~ndency for the pore size of the
~odified clinoptilolites of this in~ention to decrease
with exposure to increasing temperatura. Accordingly,
in selecting an activation temperature for the ~odi~ied
clinoptilolites, care should be taken not to heat
modified clinoptilolites to temperatures which cause
reductions in pore size o s~vere as to adversely affect
the performance of the modified clinoptilolite in the
process of the present invention.
Although the behavior of khe modified
clinoptilolites on exposure to heat does limit ~he
2~ ~a~s
--19~
activation temper~tures ~h~ch can ~e e~ployed, ~he
ther~al reduction ~n pore ~ize ~oe~ o~f~r the
po~sibillty of ~ e tuning~ the pore size Or ~ modified
clinoptilolite to opti~ze its performancQ in the
process of the present invention.
~ he following Examples are given, though by
way o~ illustration only, to show preferred processes of
the present invention. All adsorption measurements are
. at 23'C unless otherwise stated. ~urthermore, all
separation factors given in the form
"Separation factor X/Y"
are calcul~ted by:
Separation factor X/Y e p~ /Px . ~
where Px and Py are the partial pressures of components X and Y
in the feed gas respectively and Lx and Ly are the corresponding
loadings of X and Y in the adsorbent expressed as millimoles
per gram of adsorbent.
EX~MPLES
Example 1: Natural Clinoptilolites
Seven different samples of commercially available natural
or raw clinoptilolites were used in these experimen~s and as
starting materials for the preparation of some of the
modified clinoptilolites prepared in the later Examples. The
chemical analyses of these natural clinoptilolites are
shown in Table 1 below, while carbon dioxide and
ethane separation data are shown in Table 2.
2 ~
--20--
For coDIp~ri~on~ Tal: lQ 2 include~ dat~ for zeolit~ 5A,
comm~rcial ~nat~ri~l u~ed ~or gas separat~ons.
,
2 ~
-21-
Ç ~ ç;~ elinoptilslite
~wt. percentL ~ E E G
~oss on 12.6 15,2 13.2 11.6 13.6 13.8 13.3
ignition
Al2O3 14.188 12.618 12.903 12.670 13.426 13.573 13.379
(anhydrous)
sio 72.883 75.236 76.152 75.924 75.9~4 74.710 75.779
(a ~ydrous)
Na20 3.547 2.252 4.090 3.801 3.831 3.840 3.656
(anhydrous)
X~o 1.796 2.170 4.078 4.355 2.280 2.541 1.984
~anhydrous)
MgV 1.796 2.123 0.325 0.575 0.714 1.044 0.734
(anhydrous)
CaO 3.3~1 2.724 1.039 1.403 1.887 2.390 2.434
(anhydrous)
SrO 0.049 0.018 - 0.032 0.345 0.563 0.406
(anhydrous~
BaO 0.135 0.051 - 0.376 0.071 0.246 0.248
(anhydrous)
Fe2O3 2.208 3.054 0.919 0.989 1.262 1.508 1.292
tanhydrous)
~ABLE 2
linoptilol~te
Adsorption
lwt. percent) A ~ C ~ ~ ~ G 5A
Co , 5 ~orr, 5.1 5.6 6.8 6.1 5.8 ~.9 ~.4 8.
3 ~ours
C2H4, 0.981 2.177 0.990 ~.904 1.453 1.098 2.222 7.700
700 Torr
3 hour~
Separation 463 229 612 601 356 398 257 95
~actor
C02/C2H~
2 ~
-22-
From the d~ta ~n ~ble 2, lt ~ e seen th~t all the
~even d insptilolite ~pecimens had carbon diox~de/e~hane
~2p2rat~0n ~actors ~ubstantially better than tha~ of
zeol$te 5A.
~xample 2 : Sodium ~lino~tilollte
1500 Gm. (dry weight) of clinoptilolite C in Example 1
was ground to particles having a diameter of 0.3 to 0.59 mm
; (30 x 50 U.S. mesh) and placed in a jacketed glass column. The
column was heated to 80C by passing oil through the jacket,
and 30 liters of 1.86 N sodium chloride solution was passed
through the column at a flow rate of 19 ml/minute for 16 hours.
The clinoptilolite was then washed by passing distilled
water through the column, and dried in air at ambient
temperature.
The ~odium ~linoptilolite thus produced was
subjected to chemical analysis and its ads~rption
properties were measured using a ~cBain quartz spring
b~lance. Before being used in the adsorption tests, the
eodium clinoptilolite was activated by heating to 375-C
under vacuum ~or one hour.
Part of the sodium clinoptilolite was then
6ubjected to a second ~odium ion-exchange. 200 Grams of
the sodium clin4ptilollte were treated in th ~ame
colu~n ~s before ~y passing ~ liters o~ 0.5 ~ ~odium
chloride soluticn ov~r ~he clinoptilolite or 16 hours.
The chemical analysis and adsorption properties o~ the
2 ~ 9
-23-
doubly-~xchanged ~odium ~linoptilollte wQre then
~easured in the ~a~e manner a~ b~ore.
~ he chemical analyses of both ~odium
clinoptilolltes ~re ~hown in Table 3 below, and their
adsorption properties are shown in Table 4, along with
those of 5A zeolite; in both cases, the singly-exchanged
material is designated "NaClino", while the doubly-
exchanged ~aterial is designated "NaNaClino". For
comparative purposes, the chemical analysis and
adsorption data ~or th~ clinoptilolite C ~tarting
material (given in ~ables 1 and 2 above) are repeated in
Tables 3 and 4.
TABLE 3
Component
(wt. percent) NaClino NaNaClino Clino C
Loss on 13.3 14.5 13.2
ignition
A1203 13.033 12.982 12.903
( anhydrOUS )
Si0 79.123 78~246 76.152
(a ~ydrous)
Na20 6.332 6~199 4.090
(anhydrous)
Y~O 1.465 0.750 4.07a
(anhydrous)
~g~ 0.219 - 0.325
(anhydrous)
CaO 0.27~ 0.199 1.039
(anhydrous)
F~03 0.980 ~ 0.919
(anhydrous)
2 ~
D;a J, el~
cent~ 1~aÇll~ 1~ Çl~no~
C0 ~ ~ ~orr, ~ .8 ~.2
3 hou~s
~, 700 ~orr~ 0.1000.100 - -
3 ~our#
S~pflrat~on a749 ~47 ~380
r~tDr
CO2/~
l~lat~r~ 4.7 ~orr 13.4 _ ~3,~
S~para~lon 17 84 8 - 27 68
~ac'c4r
~20~C%4
ctH6, 50 ~r~ 0.1000~100 - 3. l
3 hours
aoparatlon - 23go - 132
ft.~tor
~2~ 2~
Sep~ration 36B 354 - 18
fa~tor
~02~C2H~
C2H4 S0 ~orr 0.3000.200 ~ 4.8
3 hour~
~eparatlon ~ 7
iactor
HzO/C2~4, 50 To~
~epar~ti~n li5 1
~at~)r
Co2/C2H~ ~ 50 Torr
~, 7~ ~o7:~ ~ 0.507 ~.g9P 7.7
3 h~urs
~par~ on - 620~ - S
~CtQ~
HzOJC~H~,, 700 ~o~r
~a~c~on ~ 5
~e~3E
CO2/~2Hf" 700 To~r
2 ~
-25~
Fro~ the data ln Tablo~ 3 and ~, ~t w~ e
~een that ~oth the ~ingly and doubly-exchanged ~odium
clinoptilol$tes would be use~ul ~or the 6eparat~0n of
carbon diox~de ~nd water ~rom hydrocarbon gas ~trea~s,
S that both are superior to the untreated C11noptilolite C
~or this purpose, and that all three of the
~linoptilolites are much bett~r than 5A zeolite. The
second ~odium ion-exchange does no~ appre~iably increase
. the sodium content of the ~linoptilol~te, but does
reduce the potassium and calc~um contents. However,
since the second ~odium ion-exchange does not
appreciably increase the relevant separatisn ~actors, in
general a si~gl~ ~odium ion-exchange would be sufficient
to provide a material 6uitable for use in the process of
the present invention.
Example 3 : Potassium clinoptilolite
200 Gm. ~dry weight) of the singly-exchanged
sodium clinoptilolite prepared in Example 2 was placed
~ in a iacketed glass column. The c~lumn was heated to
80-C by passing o~l through the jacket, ~nd 9 liter~ of
0.5 ~ potassium chloride solution was passed through the
column at a flow ra~e of 9 mlJ~inute ~or 16 hours. The
slinop~ilolite was then washed by pass~ng distilled
water through the column, and dried in air at a~bient
temperature.
2 ~
-26-
.~
~ he po~a~iu~ clinoptllol~S~ ~hu~ produce~ was
~ub~ected to chemical ~nalysi~ ~nd ~t~ ad~orption
properties were measured u~ing a McBa~n quartz ~pring
balance. Before being used i~ the adsorption test~, the
potassium clinoptilolite was activated 'Qy heating to
375-C under vacuulD ~or one hour. The resul~s are shown
in Tables 5 and 6 ~elow.
ABLE 5
Component
~wt. percent! XClino
L~ss cn 12 . 4
igni~ion
Al203 12 982
(anhydrous~ -
SiO 76. 027
( ar~ydrous )
Na 0 0.251
( a~hydrous )
10 . 5~6
(anhydrous)
MgO
(anhydrous)
CaO 0.148
(anhydrous)
2 ~
-27-
~o~LQ~
CO2, 5 ~orr, 5.4
3 hours
CH , 700 Torr, 1.1
3 ~ours
Separatlon 250
factor
C2/CH4
Watert 4.7 Torr ~1.0
Separation 1324
factor
H2/CH4
C2H6, 50 Torr 2.3
3 hours
Separation 85
factor
H20/Cj!H6
Separation 16
factor
C02/C2H6
C2H4 50 Torr 2.2
3 hours
Separation 83
factor
H20/C2H4
Separation 16
~actor
~02/C~
These results ~ndicate that the potassi~m
clinoptilolite was ~ble to separate carbon dioxide ~nd
water from hydrocarbon ~treams, but that its r~levant
~eparation factors were lower than those of the natural
2~5~
~28-
cllnoptllolite ~ro~ wh~ch i~ i~ der~ved or Sho~e o~ ~he
~odiu~ clinoptilol~tes prepared in Example 2 above~
Th~se ad~orption results also demonstrate
that, contrary to what would be expected on the basis of
the ionic radii of ~he cat~ons involved tNa4 has a
Pauling ionic radius o~ O.95 A, while g~ has a Pauling
ionic radius of 1.3~ A), the potassium clinoptilolite
has a substantially qreater pore ~ize than the ~odium
- clinoptilolite. Accordingly, the pore size of a
modified clinoptilolite of this inve~tion cannot be
predicted from a knowledge of the ionic radius of the
cation introduced and the normal pore blocking ~echanism
which is typical of the zeolites, and thus the cation
~ust affect the pore gize of the ~linoptilolite by ~ome
~echanism other than simple physical pore blocking.
, Example 4 : Separation of carbon dioxide from ethylene
! streams usin~ zeolite 5A and sodium clinoptiloli~
A colu~n 1 inch internal diameter by 5 feet
was filled with zeolite 5A (a commercial product ~old by
UOP) in the form of pellets 1.6 mm (1/16 inch)
ir. diameter. An ethylene feed stream containing
rom 1~ to 70 parts per ~illion by volume o~ carb~n dioxide
was passed through the column at 3721 kPa (525 psi~.) and 90 F
at a flow rate of 1.98 m /hr. (70 standard cubic feet per hour).
~12e effluent from the column w~s initially ~r~e fro~
carhon dioxide; howeYer, after 6.9 hours of operation,
2 ~
o29 ~
carbon disxide began to ~ppear ~n ~he ef ~luen~ and
z~ached a concentration of 10 perGent of its
csncantration ln the ~eed . At an average carbon diox~ de
concentration in the feed o~ 45 parts per milllon by
volume, the eguilibrium carbon dioxide loading of the
zeol~te was 0.31 weight percent.
A sodium clinoptilolite was prepared by a
single ion-exchange of a clinoptilol~te with E;odium chloride.
The sodium clinoptilolite was formed into 1.6 mm (1/16 inch)
diameter pellets using 5 percent by weight Avery clay
binder, and tested for its ability to remove carbon
dioxide from the ethylene ~eed ~tream under the ~ame
conditions as described for zeolite 5A. Breakthrough o~
carbon dioxide occurred only after 43 hours of
operation, and at an average carbon dioxide
concentration in the feed of 46 parts per million by
volume, the eguilibriu~ carbon dioxide loading of ~he
clinoptilolite was 1.63 weight percent, 5.3 times the
equilibrium loading o~ the 5A zeolite. Thus, the ~odium
clinoptilolite was greatly ~uperior to the SA zeolite in
removing carbon dioxide fro~ the ethylene feed ~tre~m.
~xamples 5 18: Adsorptio~ propertie~ of various modi~ied
clinoptilolites
A number of modi~ied ~linoptilolites were
prepared in substant~ally the 6ame way as in E:x~mple ~
~bove, and their ~dsorption properties were determined
2 ~ 9
-30-
usi~g the ~cB~n ~pring balance, in ~ome ca~es ~ft~r
p~lletization ~ith clay. The method~ of preparation ~re
sum~arized in Table 7 below; in th~ column headed
~Start~ng Nateri~l", NClino Al' etc refers to the natural
5 clinopt~lolites described in Example 1 above, wh~le
"NaClino" refers to the 6inaly-exchanged material
produced in Example Z above. A ~_n in the column headed
~Binder" indicates that the modi~ied clinoptilolite was
not pelletized before the adsorption me~surements were
made. Chemical analyses of the modified clinoptilolites
are given in Table 8 and adsorption data in Table 9.
All adsorption measurements were taken at 23-C. A prime
(') following the Clinoptilolite letter indicates
matsrial from the same deposit as the corresponding
clinoptilolite in Example 1 above, but from a different
lot of ore.
2 ~
--3 ~--
~ ' ,
Sta~t~n~
Na~lino 0.4N ~Cl lOOx QXC
N~Cllno o.ZM M~C12 20x oxc~
7 ~Cl.~no 0.2SN ~12 lOx ex~es~ -
8 ~Cllr~o 0. ~5M ~C12 lox ~xce~
~Cl~no o~aM ~Clz ~00~ 1~X¢05~1 -
10 ~llno E' Aa 2x~ple 2
11 Cllno E~ ~.aM RCl20X ~xce~ -
12 ~1 irlo E ~ lM ~5gC1~ 12X ~xoe~s 5% Av~y
- cl~y
13 CllnP E ~ ~ 3M ~la~ Ox exce~ -
~4 ~llno ~' 0.3M ~a~lz lOx eX~e~ S~ A~ary
cl~y
Cl~no A' Ae ~Sxa~ple ~ -
16 Clino A~ XCl~ lO0X exc~ss
17 Cl~no B' A~ Exa~ple 2
lC Cllr~o ~ XCl, 101~ exo~
,
!
,
,
2 ~
o
0l o ~ o -- o o ~ -- ~
~I N ~ ~ ~ O ~ O _
~ -- N ~ ~
~1 _ N V~ -- '
_¦ ~ N ~ N
`O O O 1~ ~ ~ N
~111 ~ H ;~ O _ O _ _
--I ~1 -- ~ o e~ o o ~
O O ~ ~ N ~ID
Nl _ ~ N N N O O --
R ~ ~ ~ H N
o ~ o o o o o
~1 ~ ~ ~ ~ ~ ;~3 ~ O
l ~ r` ;~ ~ .
0~1 ~ N ~ O _ C O N O 1
N ~
~ ~ d ;~ ~ - o ~ 2
~ N ~! o
~4 ICi N N 0` N~ ~0
O O ~ ~ ~O
æ
0
r4 ~ ~ _ O _ ~ O O P~ _ -
--:!1 3 -
eo~, ~ 7~r~ 2 ~ a.6s ~.~7 S.~l ~.U ~ .n
- .
Cll, ~0 7~rr, ~.~2 0.90 ~.09 l.S~ O.~ 8 0.~0 l.n 0.12 1.U
hs~
S~r~tion 7~6 ~13 1522 1~2 SW ~70 0S4 ~ 18~0 19S
t~ r
C~21CN~
ibt~ .r Torr13.062 13.9l,3 12.~0 1~ ?
~pui~lenL4al ~051 105~4 1109
t-etor
h2~1cN~,
~2116. 50 Torr 0.~8 0.~3 0.10 i.r6 ~ 0.4~ Z,t5 0.~7 2.59
~ b~J,ii
r~tlon 515 7~qt2~ 1l2
t~or
N2~tC~N6
S~p~rd~ 1 114t~3 ~0 ~ 4 13
~et~r
Co2lc~
e2~l~, 50 ~orr ~,~19 0.8~ 0;~ S 0.55 3,1~~ hwrg
tiX Z3~ ~t~ 6
f~e~l~t
H~0~211
~2~ tlsn ~ 571 ~ ~ 11 50 ~0
~......
~e~6P
co2/~all~
,.
2~Q~
34-
The above data show that the ~odi~ied
clinoptilol~tes stronsly ~d~orb ~ar~on dioxide ~nd water
but have low adsorptions o~ ~ethane, ~thylene ~nd
ethane, 50 that these clinoptilolites are use~ul ~or
5 separating carbon d~oxide and water from hydrocarbon
strea~s. ~he potassium and zinc clinoptilolites ~re
comparable to zeolite 5A in thelr ability to effect
these ~eparations ~see the data for zeolite 5A in ~able
4 above), while the other modified clinoptilolites have
~eparation factors much better than zeolite 5A, and
should thus provide better selectivity îor the
eparation of carbon dioxide and water from methane,
ethane, and ethylene. Sodlum clinoptilolite is superior
to potassium clinoptilolite independent of the source of
the ore.
