Note: Descriptions are shown in the official language in which they were submitted.
12,204
This invention relates to a process for the
manuracture o,~ al~ylene glyco~s, such as ethylene glycol
and propylene glycol, by the hydrolysis of the correspond-
ing all.~ylene oxide, such as ethylene oxide and propylene
oxide. More particularly, this invention involves the
catalytic hydrolysis of such a:Ll~ylene oxides in the presence
of C2 via a glycol ester intermediate to the corresponding
alXylene glycols. The hydrolysis is preferably carried out
in the presence of an organic solvent.
The prior art states that alkylene oxides can
be hydrolyzed to produce the corresponding alkylene
glycols. For e~ample, German patent No. 2,141,470 reacts
ethylene o~ide in aqueous streams in the presence of salts
of carboxylic acid and C2 pressures in excess of about
438 psig and up to 730 psig and temperatures in the range
of 160 to 200~C to give selectivity to monoethylene
glycol in the range of 74 to 99 weight percent. The
German patent describes that nigh CO2 pressures are more
ravorable towards producing higher quality monoethylene
glycol product and these pressures are between 30 and
~Q atmospheres (43~ to 730 psig) at temperatures in the
range of 150 to 300C.
German patent ~o. 2,3;9,497 hydrolyzes ethylene
o~ide to monoethylene glycol and concentrates the C02 in
the aqueous stream. The reaction is carried out with C02
pressures in excess of 400 psig and with dilute solutions
of ethylen~ o~ide.
:
. ~ ~ ~
. ,, ~.
~1~3$:~
12,204-C
U. S. Patent No. 376~9,343 to Levin et al describes
the hydrolysis of ethylene oxide in the presence o:E carbon
dioxide to yield ethylene glycol. Levin et al speculates
that hydrolyzing ethylene oxide in the presence of water
and carbon dioxide forms, in somle instances, a transitory
ethylene carbonate intermediate which is hydrolyzed to
ethylene glycol. According to this patent, basic compounds
such as carbonates, bicarbonates or hydroxides of alkali
metals are utilized for the purpose of diminishing "the
fo~mation of dialkylene glycols and accelerate the re-
action", see column 2, lines 26-30, of U. S. Patent
3,629,343. In the practice of that process, such basic
compounds are employed in combination with halo salts of
tetraalkylammonium compounds. The examples in this patent
illustrate the basic compounds as including sodium bi-
carbonate, potassium bicarbonate, sodium carbonate, and
sodium hydroxide. In the examples of this patent, the
maximum yield of noalkylene glycol was 95.5 percent,
based on initial alkylene oxide concentration.
The subject matter of this patent has been care-
fully reviewed by the Stanford Research Institute, in the
private report entitled "Ethylene Glycols, Glycol Ethers
and Ethanolamines," Process Economic Program, Report No.
70 (1970). In Report No. 70, a careful consideration was
given to British Patent No. 338,026, published in 1970. The
author of the report notes the postulation of the reactions `
which take place in the process of the aforementioned
British Patent, which is, the reaction of ethylene oxide
3 ;
- 12,204
~133S;;~Z
T.vith carbon dio~id- to for~ e;hylene carbonat2 and the
hydrolysis of the ethylene carbonate to form monoethylene
glycol. ~ccording to the patenl, these reactions are
erfected si~ultaneously. However, in a continuous oper-
ation employing multiple reac~ors, the first reactor
involves the utilization of a carDonation catalyst and
carbon dioxide and the second reactor, in series with the
rirst, employs hydrolysis using various bases. Report
~o. 70 attempts to characterize 2 continuous process from
tne data whic'n is contained ln the aforementionèd Britisn
Patent. In characterizing a continuous process, the report
points out that the water to o~ide feed ratios were 1.04 to
L and 1.06 to 1 in the two e~amples demonstrating a con-
tinuous process~ In the second reactor, in which the base,
water and carbon dioxide were provided, the temperature
was 200C and the pressure in the whole system was 25 to
30 atmospheres~ that is, 367.~ pounds per square inch to
4'.1 pounds per s~,uare inch, respectively.
According to the author of the report, it is -~
believed that muc~ of the critical materials of construct-
ion will have to be e~pensive Monel clad construction.
In charact2rizing the continuous process that the authors
have discussed in the report, there is an assumption that
90~/, or the catalyst can be recycled T~hich is regarded as
econo~ically important. In defining catalyst recycle,
the following is stated:
.. - . .
12,204
~3L3;3 SZ2
"The system ,~or catalyst recycle, based
on crystallization from the cooled, heavy ends,
wit~ recycle of a thickened catalyst slurry,
is quite uncertain, re~uiring data on solubi-
lity relationships and other factors, which
are not available."
Thus, the process as describe~ in Levin et al
and characterized in the Stanford Research Institute Report
is a continuous process which utilizes pressures in eæcess
of 367 pounds per square inch. Additionally, said process
uses halo salts of tetralkylammonium compounds along with
the basic catalysts so that halide is present in an
aqueous syste~. The halide creates corrosion proble~s and
thus necessitates the use of eactors made out of costly
specialized materials to prevent corrosion. Figure 5.1 of
the report schematically illustrates equip~ent and process
desisn for making "ethylene glycols by carbonation process."
Presence of halides in the column bottoms illustrated in
Figure 5.1 would result in hi~her concentrations of heavy
residual material. In addition, as the report points out,
catalyst recycle would be very difficult.
Literature reports by N.N. Lebedev et al entitled
'~inetics and Selectivity In Ethylene Oxide Hydrolysis T.~hen
Catalyzed By Salts ofCarboxylic Acids," translated from
~inetika i Kataliz, Vol. 17, No. 4, pp. 888-892, July-
.~ugust, 1976 (hereina~ter Report I) and N.N. Lebedev et al,
"Selectivity or ~-Oxide Hydrolysis Catalyzed by Carbonates,"
translated from Kinetika i Kataliz, Vol. 1, No. 3, pp. 583- `-
588, ~lay-June, 1976, (hereinafter Repor~ II) describe studies
,
: ..
L2 ~0~
11335~ '
T.~herein glycol esters are produced _rom ethylene oxide
and a ubsequently hydrolyzed to the glycol.
In Re?ort I it is sho~n that when ethylene oxide is
hydrolyzed in aqueous solutions of carboxylic acid salts,
ethylene glycol is ~ormed in quantitative yield. Poly-
glycols are or~ed only in parallel alkaline and non-
catalytic hydrolysis reactions. Report I then concludes
that due to the marked contribution from alkaline hydroly-
sis (formed from reaction (II), page 775) when carbonate
and oxalate ~also acetate and formate) ions are used as
catalysts, the greatest yield of monoglycol (monoethylene
glycol) occurs when bicarbonate ions are used as catalysts.
Report II describes t~e selectivity of ~ -o~ide
hydrolysis catalyzed by carbonates. Specifically, ethyl-
ene oxide is hydrolyzed to ethylene glycol with and without
catalyst and with and without C02 at pressures of 0 to 146 ~ ;
?sig, Report IT states on page ;12:
"~t high bicarbonate and glycidol concentrations
the steady alkali concentration reaches values at
which alkaline hydrolysis is fast and leads to an
increase in the yield of polyglycerols. '~ydrolysis
under the pressure of carbon dioxide pro~o~es the
reverse conversion of alkali to bicarbonate and
heightens the glycerol yield, the calculated values
of the latter coinciding under these conditions
~ith the experimental values (Fig, 3, Table 3). .
Propylane and ethylena glycol carbonates are
hydrolyzed far more ra?idly. For this reason,
even at high reagent concentrations the steady
alkali concentration is low and carbon dioxide has
no affect on the distribution of the products of
these reactions."
~lso, neither o ;he processes as described in Reports I
and II utilize an organic solvent.
::
... . ~
~335~Z ~2,204
Tne process or this lnvention is directed to
the manufacture of alkylene g~ycols, such as ethylene and
propylene glycol, by t~e ~ydrolysis of the corresponding
alkylene oæide, such as ethylene or proplyler~e oæide,in
the presence o~ C02 at a t-mperature between about 85 and
400C and pressure of less than about 350 psig, in the
presence of selected catalysts. Preferably t'ne reaction
is affected in an organic solvent.
It has been discovered that the process of the
present invention is very selective toward the formation
o~ monoethylene glycol. ~dditionally, the process of the
present invention does not require the use of a halide ion
containing compound,which halide ion necessitates ~'ne
use of special equipment to prevent corrosion caused by
the halide ion. The process Ot this invention does not
suffer from any problem in catalyst recycle and it can be
carried out in conventional metal equipment, suc'n as stain-
less steel. Moreover, the process of the present invention
takes place under conditions of temperatures and pressures
e~isting in commercial operations which means that the
present process can be used with equipment which is avail-
able in existing co~mercial racilities. This is quite
important since little if any investment in new equipment
would be required~ ~oreover, it has been ~ound that the
initial concentràtlon of alkylene oxide 'nas no effect on
the product distribution so that concentrated alkylene
.. . . . . . .
1~33S22
12,204-C
oxide solutions may be treated according to the process
of the present invention. Furthermore~ the process of
the present invention may be utilized to treat the major
waste streams emanating from a process in which ethylene
oxide is carbonated and subsequently hydrolyzed to mono-
ethylene glycol as set forth in United States Patent No.
4,117,250.
Another advantage of the present invention is that
the hydrolysis can be utilized using waste water obtained
10 from industrial reactions, such as, the scrubber waters in ~;
ethylene oxide production, thereby providing an ecological
advantage through the operation of the process.
In the practice of this invention, an alkylene
oxide is reacted with C02 and particular catalysts to form,
in situ, a cyclic or acyclic carbonate intermediate. This
intermediate is hydrolyzed, using only a small excess of
water, to form the alkylene glycol and regenerate C02.
C2 can function in the reaction as a selective
catalyst (it supplies a kinetically preferred reaction
path by means of a carbonate intermediate which
hydrolyzes to give the desired product) and also C02 can
eliminate free hydroxide ions in solution, which hydroxide
ions cause loss of selectivity to monoethylene glyco'. The
process of the present invention is preferably carried out
in the presence of an organic solvent. The organic solvent
helps control the hydroxide ions and C02 in the liquid phase
~ . ~
- .
3SZ2
12 . 204-C
which allows the use of more active catalysts, such as
potassium carbona~e, lower C02 reaction pressures, and lower
operating temperatures, while producing higher monoethylene
glycol yields.
The catalysts which can be used in the present
invention are basic compounds suitable for producing a
glycol ester intermediate and include the alkali and
alkaline earth metal salts of carbonates, bicarbonates,
hydroxides, and phosphates. These catalysts include
potassium hydroxide, potassium acetate, potassium phosphate,
potassium oxalate, and the like.
The catalysts which may be used in the process of
this invention include compounds which contain one to three
nitrogen atoms, which ~hen incorporated into protic medium
~nder carbon dioxide pressure produce the carbonate salt,
including a double salt. These catalysts include
guanidine carbonate, ENH2C(=NH)NH2]H] CO3;
substituted guanidine carbonate
~NR2C (=NH) NR2 ] H] 2CO3
wherein R is ,.ndependently an alkyl radical
of 1 to 5 carbon atoms or aryl radical of 6 or
7 carbon atoms; ammonium uranyl carbonate,
j~ `
.. ..
:
12,~0~
11335:~2
~ )2C03 U02C03 ~H20] wher2in x is an integer defining the
water of h~dration and is generally 2; am~onium carbonate,
(~H4)2C03; substituted a.~monium carbonate,
(R NH4_n)~C03 T~herein ~ is as previously defined and n is an
int~ger or 1 to '.
The catalyst may be added as t~e salt or it may be
rormed in situ.
The amount of cataltst which is provided with the
initi21 eed o} reactants may range between about 0.10 to
about 15.0 w2isht percent, based on the total weight of
initial reactants. Preferably, the amount of
t~e catalyst is about 0 S to about 10.0 weight percent, and
most pref2rably, the greatest catalytic effect, for t~e amount
or^ catalyst employed, is achieved when the catalys~ amount
ranGes between O.S and about 5 0 w2ight percent, based on the
to~al weight of initial raact2nts. In characterizing the
catalyst concentration, it has been characterized in terms of
its salt. ~`
The temperature which is n_cessary to hydrol~tze
the al7.~ylene oxide can be as low as 85 and one might con-
te~plate that the maximum temperatura is about '00C. How-
2ver, it ~s pre~erred that a minimum temperatur2 o~ 100C
be employed and that the maYimum temperature be 7~ept below
300C. In the most prarerred operation or the reaction, it
is desired that the temperature be bet~.~een about 120C and
about 130C.
- . . , -. ,, . . . . ; . ~ , . ~
1~33S2~ 12,204
The pressure at l~hich the reaction is carried
out should be less than about 350 psig. The preferred
operating pressure is between about 100 and about 300 psig,
and the most preferred operating pressure is between about
150 and about 275 psig~
The organic solvent which is used in the practice
of the present invention has the following characteristics:
high C02 absorbtivity; high ethylene oxide absorbtivity;
inert towards ethylene oxide; totally miscible with the
reaction medium; and it should be a solvent which is easily
separated from the product. Any liquid at the reaction
temperature,which is miscible with the alkylene oxide and
the glycol product can be, to the extent that it continues
to be miscible in the syste~, a solvent provided that it is
not reactive with either the alkylene oxide reactant, the
glycol produced or the catalyst employed. These solvents
include ketones, esters, or ethers,such as acetone, alkylene
carbonate and dioxane. It is desirable that the alkylene
carbonate employed would produce an alkylene glycol the same
as the product glycol being produced.
The solvent is added in amounts of from about 5.0
to 60 weight percent,based on the weight of total feed.
Preferably, the solvent is added in amounts of from about
10 to 40 weight percent.
The initial mole ratio of water to alkylene oxide
which is employed in the hydrolysis reaction, that is, the
amount of water which is combined with the alkylene oxide
11 ~`
;. . :- .. .
1133522 12,20~
in the reaction zone in order to effect hydrolysis, should
be at least one mole of water per mole of alkylene oxide,
However, fro~ a practical standpoint, in order to achieve
the ~ind of performance characterized for the process of
this invention, one should employ at least about 1,0 mole
of water and at most about 20 moles of water for each mole
of alkylene oxide. The preferred ratio is about 2.0 to 11
and most preferred 4 to 10. The mole ratios of water to
alkylene oxide will of course vary when organic solvent is
used in the reaction. -
The process of this invention may be carried out
as a batch reaction or as a continuous process. The batch
reactions may be carried out in pressure resistant vessels
~suita~ly constructed to withstand the pressures of this
reaction.
The process, as stated, may be employed in a
conventional autoclave or can be effected in a glassware
type of equipment when operated at moderate pressures, It
may also be employed in a plug-flow reactor utilizing con-
ventional procedures to effect the process continuously.
Solvent may be recycled and catalyst may be recovered. The
process is very advantageously employed by concentrating
the catalyst over a vacuum evaporator and recycling it to
the reaction.
The reaction may be carried out for very short
periods of time in terms of fractions of a second and if
desired may be carried out over reaction periods amounting
, . . . . .
~335Z2 12,204
to hours, if desiredO These conditions of reaction are
governed by the amounts of solvent and catalyst employed,
the pressure and teTnperature employed, and like considera-
tions.
The following examples depict various modes in
the practice of this invention including those modes which
are considered to be best for the practice of this invention.
It is not intended that this invention shall be limited by
the examples.
~33S22
12,204-C
Examples 1 to 28
The reactor system was a 300 cc, 316 stainless
steel, Parr bomb filled with provisions for batchwise
charging of reactants, a gas charge tube, thermocouple,
stirrer, electric heating mantel &nd cooling coil.
During operation, the reactor was charged with --
a mixture of distilled water (mole/1), catalyst (molell),
and solvent (mole/l) and heated to reaction temperature.
When the desired reaction temperature (C shown in the
Table) was reached, either carbon dioxide or nitrogen
was sparged into the reactor. The reactor was brought
to 100 psig below the desired operating pressure. At
this point ethylene oxide (mole/l) was charged to the
reactor. The system was brought to operating pressure
(psig shown in the Table) and allowed to react for a
period of one hour.
Upon completion of the run, the reactor contents
were discharged and weighed. The quantity of liquid pro~
duct was used to estimate the overall reactor mass balance.
The liquid product was analyzed for water (weight percent
by the Karl Fisher method) and monoethylene glycol, di-
ethylene glycol and triethylene glycol (weight percent by
vpc) to determine conversions and efficiency. The vpc
employed used a 10 ft by 1/8 inch stainless steel column
packed with Tenax - GC (Tradename).
The following Table lists the catalyst, the '
atmosphere (C0~ or nitrogen), reaction pressure '
(P, psig), reaction temperature (T, C), and the moles per
14
12,204
113352~
liter of ethylene oxide (E0), water, catalyst and
solvent used. The weight percent of monoethylene
glycol (~EG), diethylene glycol (DEG) and triethylene
glycol (TEG) produced,are set forth in the Table.
The reaction was carried out to at least 94
percent and in most cases greater than 98 percent
conversions of ethylene oxide to glycols as shown
in the Table. The differences in percent conversions
was due to differences in rates of reaction for the~
respective catalyst and reaction parameters for that
particular experiment.
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