Note: Descriptions are shown in the official language in which they were submitted.
~27~33~6
68878-32
OLEFIN EPOXIDATION IN A POLAR MEDIUM
(D~80,313-C1)
BACKGROUND OF THE INVENTION
Field of the Invention
This invention relates to the molybdenum-catalyzed
epoxidation of C3 to C20 olefins with tertiary butyl
hydroperoxide or tertiary amyl hydroperoxide in liquid phase in
a polar reaction medium.
Prior Art
The epoxldation o~ olefins to give various oxide
compounds has long been an area of study by those skilled in
the art. It is well known that the reac~ivities of the various
olefins differs wlth the number of substituents on the carbon
atoms involved in the double bond. Ethylene
' A
~7~33~6
itself has the lowest relative rate of epoxidation, with
propylene and other alpha olefins being the next slowest.
Compounds of the formula R2C=CR2 where R simply represents
alkyl or other substituents may ~e epoxidized fastest.
S Of course, the production of ethylene oxide from
ethylene has long b en known to be accomplished by reaction
with molecular oxygen over a silver catalyst. Numerous
patents have issued on various silver-catalyzed processes
for the production of ethylene oxide.
Unfortunately, ~he silver catalyst route is poor
for olefins other than ethylene. For a long time the com-
mercial production of propylene oxide could only be accom-
plished via the cumbersome chlorohydrin process.
Another commercial process for the manufacture of
substituted oxides from alpha olefins such as propylene was
not discovered until U. S. Patent 3,351,635 taught that an
organic oxide compound could be made by reacting an olefini-
cally unsaturated compound with an organic hydroperoxide in
the presence of a molybdenum, tungsten, titanium, columbium,
tantalum, rhenium, selenium, chromium, zirconium, tellurium
or uranium catalyst. U. S. Patent 3,350,422 teaches a simi-
lar process using a soluble vanadium ca~alyst. ~olybdenum
is the preferred catalyst. A substantial excess of olefin
relative to the hydroperoxide is taught as the normal pro~
25 cedure for the reaction. See also U. S. Patent 3,526,645 -
which teaches the slow addition of organic hydroperoxide to
an excess of olefin as preferred.
However, even though this work was racognized as
extremely important in the development of a commer~ial
~2~7~3~
propylene oxide process that did not depend on the chloro-
hydrin route, it has been recognized that the molybdenum
process has a number of problems. For example, large quan-
tities of the alcohol corresponding to the peroxide used
were formed; if t-butyl hydroperoxide was used as a
co-reactant, then a use or market for t-butyl alcohol is
required. With propylene, various undesirable propylene
dimers, sometimes called hexenes, are formed. Besides being
unde~irable in tha~ propylene is consumed, problems are
caused in separating the desired propylene oxide from the
product mix. In addition, the molybdenum catalyst may not
be stable or the recovery of the catalyst for recycle may be
poor.
A number of other me~hods for the production of
alkylene oxides from epoxidizing olefins (particularly
propylene) have been proposed. U. S. Patent 3,666,777 to
Sargenti reveals a process for epoxidizing propylene using a
molybdenum-containing epoxidation catalyst solution prepared
by heating molybdenum powder with a stream containing unre-
acted tertiary butyl hydroperoxide used in the epoxidationprocess as the oxidizing agent and polyhydric compounds.
The polyhydric compounds are to have a molecular weight from
200 to 300 and are to be formed a~ a by-product in the epoxi-
dation process. A process for preparing propylene oxide by
direct oxidation of propylene with an organic hydroperoxide
in the presence of a catalyst (such as molybdenum or vanad-
ium) is described in British Patent 1,338,015 to Atlantic-
Richfield. The improvemen~ therein resides in the inclusion
of a free radical inhibitor in the reaction mixtuxe ~o help
eliminate the formation of C5 to C7 hydrocarbon by-products
which must be removed by extractive distillation. Proposed
free radical inhibitors are tertiary butyl catechol and
2,6-di-t-butyl-4-methyl phenol.
Stein, et al. in U. S. Patent 3,849,451 have
improved upon the Kollar process of U. S. Patents 3,350,422
and 3,351,~35 by requiring a close control of the reaction
temperature, between 90-200C and autogeneous pressures,
among other parameters. Stein et al. also suggest the use
of several reaction vessels with somewhat higher temperature
in the last zones to insure more complete reaction. The
primary benefits seem to be improved yields and reduced side
reactions. Prescher et al. in U. S. Reissue Patent No.
Re.31,381 disclose a process for the preparation of propylene
oxide from propylene and hydrogen peroxide wherein plural
reactors such as stirred kettles, tubular reactors and loop
reactors may be used~ They recommend, as an example, the
use of a train of several stirred ket~les, such as a cascade
of 3 to 6 kettle reactors or the use of 1 to 3 stirred
kettles arranged in series followed by a tubular reactor~
Russell U. S. Patent No. 3,418,430 discloses a
process for producing propylene oxide by reacting propylene
with an organic hydroperoxide in solvent solution in the
presence of a metallic epoxidation catalyst, such as a
compound of molybdenum at a mole ratio of propylene to hydro-
peroxide of 0.5:1 to 100:1 (preferably 2:1 to 10:1) at a
temperature of -20 to 200C (preferably 50-120C) and a
pressure of about atmospheric to 1000 psia, with a low
olefin conversion per pass (e~g., 10-30~) whexein unreacted
oxygen is removed from the unreacted propylene.
Sheng et al. U. S. Patent No. 3,434,975 discloses
a method for making molybdenum compounds useful to catalyze
the reaction of olefins with organic hydroperoxides wherein
metallic molybdenum is reacted with an organic hydroperoxide,
such as tertiary butyl hydroperoxide, a peracid or hydrogen
peroxide in the presence of a saturated Cl-C4 alcohol.
The molybdenum-cataly~ed epoxidation of alpha
olefins and alpha substituted olefins with relatively less
~table hydroperoxides may be accomplished according ~o U. S.
10 Patent 3,862,961 to Sheng, et al. by employing a cxitical
amount of a stabilizing agent consisting of a C3 to Cg
secondary or tertiary mcnohydric alcohol. The preferred
alcohol seems to be tertiary butyl alcohol. Citric acid is
used to minimize the iron-ca~alyzed decomposition of the
organic hydroperoxide without adversely affecting the reac-
tion between the hydroperoxide and the olefin in a similar
oxirane producing proce$s taught by Herzog in U. S. Patent
3,928,393. ~he inventors in U. S. Patent 4,217,287 discov-
ered that i barium oxide is present in the reaction mixture,
the cataly~ic epoxidation of olefins with organic hydroper-
oxides can be successfully carried out with good selectivity
to the epoxide based on hydroperoxide converted when a
relatively low olefin to hydroperoxide mole ratio is used.
The alpha-olefinically unsaturated compound must be added
~5 incrementally to the organic hydroperoxide to provide an
excess of hydroperoxide khat is effective.
Selective epoxidation of olefins with cumene
hydroperoxide (CHP) can be accomplished at high CHP to
olefin ratios if barium oxide is present with the molybdenum
catalyst as reported by Wu and Swift in "Selective Olefin
--5--
~27B~
Epoxidation at High Hydroperoxide to Olefin Ratios,~ ournal
_ Catalysis, Vol. 43, 380-383 (1976).
Catalysts other than molybdenum have been tried.
Copper polyphthalocyanine which has been activated by contact
with an aromatic heterocyclic amine is an effectiYe catalyst
for t.he oxidation of certain aliphatic and alicyclic compounds
(propylene, for instance) as discovered by Brownstein, e~ al.
de~cribed in U. S. Patent 4,028~423.
Various methods for preparing molybdenum ca~alysts
useful in these olefin epoxidation methods are described in
the following patents: U. S. 3~362,972 to Kollar; U. S.
3,480,563 to Bonetti, et al.; U. S. 3,578,690 to Becker;
U. S. 3,953,362 and U. S. 4,009,122 both to Lines, et al.
It has also been proposed to use the tertiary
butyl alcohol that is formed when propylene is reacted with
tertiary butyl hydrop~roxide as an intermediate in the syn-
thesis of another organic compound. Thus, Schneider, in
U. S. Patent No. 3,801,667, proposes a method for the prepa-
ration of isoprene wherein, as ~he second step of a six step
process, tertiarybutyl hydroperoxide is reacted with propyl-
ene in accordance wi~h U. S. Patent No. 3,418,340 to provide
tertiary butyl alcohol. Connor et al. in U. S. Patent No.
3,836,603 propose to use the tertiary butyl alcohol as an
intermediate in a multi-step process for the manufacture of
p-xylene.
Also pertinent to the subject discov~ry are those
patents which address schemes for separating propylene oxide
from the other by-products produce.d. These patents demon-
strate a high concern for separating out the useful propylene
oxide from the close boiling hexene oligomers. Tt would be
~27B~
a great progression in the art if a method could be devised
where the oligomer by-products would be produced not at all
or in such low proportions that a separate separation step
would not be necessary as in these patents.
U. S. Patent 3,464,897 addresses the separation of
propylene oxide from other hydrocarbons having boiling
points close to propylene oxide by distilling the mixturP in
the presence of an open chain or cyclic paraffin containing
from 8 to 12 carbon atoms. Similarly, prspylene oxide can
be separated from water using identical entrainers as dis-
closed in U. S. Patent 3,607,669. Propylene oxide is puri-
fied from its by-products by fractionation in the presence
of a hydrocarbon having from 8 to 20 carbon atoms according
to U. S. Patent 3,843,488. Additionally, U. S. Patent
15 3,909,366 teaches that propylene oxide may be purified with
respect to contaminating paraffinic and olefinic hydocarbons
by extractive distillation in the presence of an aromatic
hydrocarbon havin~ from 6 to 12 carbon atoms.
SUMMARY OF T~ INVENTION
This invention is directed to a process wherein a
hydroperoxide charge s~ock (t-butyl hydroperoxide or t-amyl
hydroperoxide~ is reacted with a C3 to C20 olefin charge
stock in liquid phase in a reaction zone in the presence of
25 a catalytically effective amount of a soluble molybdenum
catalyst to form a product olefin epoxide corresponding to
the olefin charge stock and a product alcohol corresponding
to the hydroperoxide charge ~t-butyl alcohol or t-amyl
alcohol), which process is improved in accordance with the
present invention by maintaining a reaction medium composed
~7~
of more than 60 wt.~ of polar components (hydroperoxide
charge stock, product alcohol and product epoxide) in the
reaction zone by charging to the reaction zone at least
about a 30 wt.% solution of the hydroperoxide charge stock
in the corresponding product alcohol and chargi~g said ole-
fin charge stock to said reaction zone in an amount relative
to the amount of said charged so,ution of charged hydroper-
oxide in product alcohol sufficient to provide a ratio of
from about 0.5 to about 2 moles of charged olefin per mole
of charged hydroperoxide.
The preferred olefin charge stock is propylene and
the preferred hydroperoxide charge stock is t-butyl hydro-
peroxide. The corresponding epoxide in this situation is
propylene oxide and the corresponding product alcohol is
t-butyl alcohol.
BACRGROUND OF THE INVENTION
Under ambient conditions t-butyl hydroperoxide and
t-amyl hydroperoxide are comparatively stable materials.
However, as temperature increases, these hydroperoxides tend
to become "destahilized" so that thermal and/or catalytic
decomposition will be initiated leading to the formation of
unwanted by-products such as ketones, lower molecular weight
alcohols, tertiary alcohols, oxygen, e~c. This is a par-
ticularly troublesome problem at temperatures of 50 to
180C (e.g., 100 to 130C) which are normally used when
such a hydroperoxide is catalytically reacted with an olefin
to form an olefin epoxide. This problem can be at least
partially overcome by conducting the epoxidation reaction in
the presence of an excess of the olefin reactant. However,
~ 2~7B~
the unreacted olefin must be separated from the epoxide
reaction product for recycle and such separations are accom-
plished with progressively more difficulty as the molecular
weight of the olefin reactant increases. Problems can be
encountered even with the lower molecular weight olefins
and, in any event, the u~ility costs associated with the
recovery and recycle of significant quantities of the olafin
reactant add an appreciable burden to the cost of manufacture
of the corresponding olefin epoxide and alcohol reaction
products.
Further, use of excess propylene in order to in-
crease reaction rate and therefore reduce the side reactions
of TBHP or TAHP leads to the serious problem of propylene
dimer formation. ~he formation of dimer is a second order
reaction and hence is accelerated as the concen~ration of
propylene increases. Also, the use of excess propylene
affords a more non-polar medium which in turn tends to ren-
der the molybdenum catalys~ less soluble during the reaction.
DETAILED DESCRIPTION OF THE PREFERRED EMBODXMENT
It ha~ been discovered in accordance with the
present in~ention that in the production of olefin epoxides
by reacting a C3~C20 olefin with t-butyl hydroperoxide or
t-amyl hydroperoxide in liquid phase in the presence of a
catalytically effective amount of a soluble molybdenum
catalyst that an unexpectedly high selectivity to olefin
epoxide, on the basis of hydroperoxide converted, can he
obtained when the hydroperoxide is charged to the reaction
zone in at least a 30 wt.% solution of the corresponding
product alcohol and the olefin is charged to the reaction
~'7~
zone in an amount relative to the hydroperoxide charged to
the reaction zone such that about 0.5 to 2 moles of olefin
are charged per mole of hydroperoxide chaxged.
Reactants and Catalysts
The method of this invention can be used to epoxi-
dize C3-C20 olefinically unsaturated compound suchs as
substituted and unsubstituted aliphatic and alicyclic ole-
fins. The process i5 particularly useful in epoxidizing
compounds having at least one double bond situated in the
alpha position of a chain or internally. Representative
compounds include propylene, normal butylene, isobutylene,
pentenes, methyl pentenes, hexenes, octenes, dodecenes,
cyclohexene, substituted cyclohexenes, butadiene, styrene,
substituted styrenes, vinyl toluene, vinyl cyclohexene,
phenyl cycloh~xenes and the like.
The invention finds its greatest utility in the
epoxidation of primary or alpha olefins and propylene is
epoxidized particularly advantageously by the inventive
process.
It has been surprisingly discovered that the method
of this invention does not work equally well for all hydro-
peroxides. For example, with cumene hydroperoxide at low
propylene excesses, the selectivity to propylene oxide,
based on cumene hydroperoxide convexted is poor.
Tertiary butyl hydroperoxide (TB~P) and tertiary
amyl hydroperoxide ~TAHP) are the hydroperoxides to be used
in accordance with the present invention. Tertiary butyl
hydroperoxide is preferred.
-10-
~ 3~ 68878-32
The TBHP should be charged in at least a 30 ~7t.~
solution in t-butyl alcobol, and preferably about a 40 to 75
wt.% solution.
Ca~alysts suitable for the epoxidation me~hod of this
invention are molybdenum catalysts tha~ are soluble in the
reaction medium.
Examples of suitable soluble catalysts include
molybdenum compoundfi such as molybdenum octoate, molybdenum
naphthenate, molybdenum acetyl ace~onate, molybdenum/alcohol
complexes, molybdenum/glycol complexes, etc.
Other catalysts found to be useful are the molybdenum
complexes of alkylene glycols with molybdenum compounds.
Briefly, ~hese complexes are made by reac~ing an ammonium-
containing molybdenum compound with an alkylene glycol in the
presence of water at an elevated temperature, such as about 80
to 130C. The ammonium-containing molybdenum compound is
preferably ammonlum heptamolybdate tetrahydrate or ammonium
dimolybdate hydrate. The alkylene glycols are preferably
ethylene glycol and/or propylene glycol although others have
been found to be useful.
Still other catalysts found to be useful ln the
practice of the present invention are molybdenum complexes of
monohydric alcohols. Briefly, an
_L2 7 ~
alkanol such as 2-ethyl hexanol is reacted with a molybdenum
oxide in the presence of ammonium hydroxide or by reactiny
the alkanol with ammonium heptamolybdate in the presence of
a controlled amount of water.
s
Reaction Conditions
The epoxidation reaction may be conduc~ed at a
temperature in the range of 50-180C with a preferred range
of between 90 and 140C. An especially preferred range is
100 to 130C with about 110C-120C being the most preferred
single stage operating temperatureO
It has been discovered that the u e of only a
small molar excess of olefin contributes to increased oxide
concentrations, increased oxide selectivities and yields
increased recoverable molybdenum. These benefits are due to
the more polar reaction media (low propylene, high TB~P/TBA)
which tends to stabilize TBHP and render the molybdenum
catalyst more active and soluble throughout ~he entire reac-
tion period. The lower ~emperatures of our invention further
contribute to the catalyst's stability and prevents TB~P
decomposition via undesired pathways.
The catalyst concentrations in the method of this
invention should be in the range of 50 to 1,000 ppm (0.01
to 0.10 wt.%) based on the total reactant charge. Catalyst
~5 concentration is calculated as molybdenum metal. A pre-
ferred range is 200 to 600 ppm. Generally, about 250-500
ppm is the most preferred level. These catalyst levels are
higher than those presently used in prior art methods, which
tend to run from 50 to 200 ppm. Moreover, it has been dis-
covered that the method of the present invention provides a
~.2'7~
process wherein the molybdenum catalyst is retained in solu-
tion in the medium during the life of the reackionO
The epoxidation reaction of this in~ention is
carried out in the presence of a polar solvent. The polar
solvent should correspond to the hydroperoxide reactant
(i.e., have the same carbon skeleton as the hydroperoxide).
Tertiary butyl hydroperoxide and T~A are copro-
duced commercially by the oxidation of isobutane and if TBRP
is used as the hydroperoxide, TBA is the polar solvent. The
TBA coproduced with the TBHP will normally ~upply all of the
polar solvent required for the present invention.
It is preferred that the solution of TBHP in TBA
contain very little water, between zero and 1 wt.~. Pref-
erably~ the water level should be less than 0.5 wt.%.
The reaction can be carried out to achieve a
hydroperoxide conversion, typically 96 to 99~, while stillmaintaining high epoxide selectivities, typically also 96 to
99% basis the hydroperoxide reactedO For both of these
values to be simultaneously so high is very unusual. This
is important ~ecause the profitability of a commercial ole-
fin epoxide plant, to a significant extent~ is increased as
the yield of olefin epoxide increases.
The reaction time may vary considerably, from
minutes to hours. Generally, the reaction times run from
thirty minutes to three or four hours with 1.5-2.0 hours
being about average. The preferred single stage reaction
time/temperature is two hours at 110-120C. Preferably the
reaction is conducted in two or more temperature stages.
The reaction procedure generally begins by charging
the olefin to the reaction vessel. Next, the hydroperoxide,
~13-
~2~
polar solvent and catalyst may be added and the contents
heated to the desired reaction temperature. Alternatively,
the olefin reactant may be heated to, at or near the prefer-
red reaction ~emperature, and then the hydroperoxide, polar
solvent and catalyst may be added~ Further heat may be
provided by the exotherm of the reaction. The reaction is
then allowed to proceed for the desired amount of time at
the reaction temperature, generally 110-120C, or conducted
for 1 hour at 50-120C followed by 1 hour at 120-150C. The
mixture is cooled down and the oxide recovered. Generally,
for the method of this invention, the oxide concentration
runs from about 24-28% for propylene/TB~P mole ratio of 1.6-
1.9:1 tTBHP wt.~ is 68-80%) and from about 31-32~ for
propylene/TB~P mole ratio of 1.1:1-1.2:1 (TB~P content is
68-80 wt.%).
A series of reactors helps to achieve the objec-
tives of high reaction medium polarity and low olefin
concentration. The use of staged reactors makes it possible
to stage the addition of olefin to thereby increase reactor
medium polarity and in the case of propylene, to fur~her
decrease the formation of propylene dimer. This concept can
be further improved by using a continuously stirred tank
ractor (CSTR) or a series of CSTR's because a CSTR inherently
provides a lower concentration of reactants than a plug flow
reactor (PFR).
A more effective approach is to use a CSTR or a
series of CSTR's followed by one or more plug flow reactors
because conversion can be more effectively forced to comple-
tion in a plugged flow reactor.
It is possible and, indeed, desirable ~o operate
each stage at a progressively higher temperature.
As an example, the CS~R may be operated at a
temperature in the range of about 70 to 115C, 90 to 115C
being preferred, with 100-110C as the most preferred reac-
tion temperature range. The PFR should be operated at a
higher temperature, from over 115C to 150C, with 120-140C
as the most preferred range. The plug from reactor can be
of any of a number of designs known to those skill~d in the
art such as jacketed reactors, with heat transfer, adiabatic
reactors and combinations thereof. The effluent from the
CSTR may be termed an intermediate reaction mixture since
the reaction is not complete. The residenc2 time of the
reactants in each reactor is left to the operator although
it is preferred that they be adjusted so that about 30 wt.%
to about 50 wt.% of the TBHP is converted in the CSTR.
AYerage residence times in the CSTR and the PFR will be
adjusted in the manner known to those of ordinary skill in
the art, based on the other reaction conditions such as
catalyt concentrations, reaction temperatures, etc.
PREPARATION OF _ ROPYLE~r DXID--/ROM PRO ~L--NE
It has been discovered that under the reaction
conditions or the present invention propylene oxide can be
produced at high concentrations ~24-32%), high selectivi~ies
(96-99%) on the basis of t-butyl hydroperoxide conver~ed and
high yields (94-98%) of propylene oxide produced on the
basis of t-butyl hydroperoxide charged. One particularly
preferred set of operating conditions, especially for a
3~
con~inuous process include charging the propylene and hydro-
peroxide reactants at a low molar ratio of propylene to
hydroperoxide (e.g., about 0.5 to about 2 moles of propylene
charge per mole of hydroperoxide charge). Another preferred
procedure is the use of staged temperatures so tha~ the
first 0.5 to 1.5 hours of the reaction are conduc~ed a~ a
lower temperature t50-120~C) and the second stage also
usually an 0.5 to about 1.5 hour reaction time, is conducted
at a higher temperature (usually 120-150C).
A low molar ratio of propylene to TBHP is further
aided by optional staged addition of prvpylene to a staged
plurality of reactors. By this technique~ buildup of olefin
at any one point in the staged series of reac~ors, relative
to the hydroperoxide, is minimized.
Normally, the charge ra~io of propylene to hydro-
peroxide is thought to be variable over the range of from
about 2:1 to 20:11 expressed as a mole ratio. An initial
mole ratio of olefin to hydroperoxide of less than 2:1 has
been thollght to be undesirable because of a loss of selec-
tivity. In this invention, the initial mole ratio of olefin
to hydroperoxide of the feed should not exceed 2.0:1. The
broad range, expressed in terms of the charge rates of the
propylene and the TB~P to a continuously stirred tank reac-
tor is from 0.5:1 to 2.0:1, and preferably from 0.9:1 to
1.8:1. Most preferably, the mole ratio of olefin to hydro-
peroxide in the feed is 1.05:1 to 1.35:1.
When excess propylene is charged, the ratio of
propylene to TBHP in the CSTR will be different from ~he
initial charge ratio because both propylene and TBHP are
consumed in the reaction that takes place. In ~his case, as
~2~7~33~
the TB~P conversion increases, so does the ratio of propyl-
ene to TB~P. For example, if the initial molar feed ratio
of the charged propylen and TBHP i5 1.15 moles of propylene
per mole of TBHP, and if the rate of withdrawal of reaction
medium from the CSTR is such that about a 50% conversion of
~he TBHP is main~ained in the CSTR, the average mole ratio
of unreacted propylQne to unreacted TBHP will be about
1.3:1. If the rate of withdrawal of the reaction medium is
such that about a 90% conversion of TBHP is main~ained in
the CSTR, the average mcle ratio of unreacted propylene to
unreacted TBHP will be about 2.5:1.
In this same situation, and if it be assumed tha~
the TBHP is charged as a 70 wt.% solution of TBHP in tertiary
butyl alcohol (TBA), the charge to the CSTR will be composed
of about 72.7 wt.~ of polar materials (the sum of the
weights of TBHP and TBA charged, divided by the sum of the
weights of propylene, TBHP and TBA charged.) During the
course of the reaction, the propylene (a non-polar material)
is converted to propylene oxide (a polar material) so ~hat
at the 50% TB~P conversion level mentioned above, the reac-
tion medium will be composed of about 84.6 wt.~ of polar
materials (the s~m of the weights of unreactad TB~P, TBA
charged, TBA formed as a reaction product and propylene
oxide divided by the said sum of these four materials and
unreacted propylene). A~ the 90% TBHP conversion level
mentioned above, the reaction mediwm will be composed of
about 94 wt.~ of polar materials on thi 5 same basis.
The method and apparatus of this invention are
illustrated but not limited by the following examples.
-17-
REACTION MEDIUM POLARITY
Example l
In order to demonstrate the importance of the
polari~y of the reaction medium in the practice of the
pr~cess of the present invention, three series of batch runs
were made using propylene, propane, ~ertiary bu~yl hydro-
peroxide and ~er~iary bu~yl alcohol as feed ma~erials.
In all of the runs, the catalyst that was used was
a molybdenum/ethylene glycol complex prepared ~s follows:
Catalyst Prepara ion
To a one=liter round-bottomed Morton flask fitted
with a mechanical stirrer, a nitrogen inlet, a thermometer,
a Dean Stark trap, a condenser and a nitrogen bubbler, were
added 100 g. of ammonium heptamolybdate tetrahydrat~ and 300
g of ethylene glycol~ The reaction mixture was heated to
85-110C for a~out 1 hour with nitrogen slowly passin~
through the flask. At the end of that time, the reaction
was essentially complete and essentially all of the ammonium
heptamolybdate was dissolved~ ~he reaction mixture was
subjected to an aspirator vacuum at a temperature of abou~
85-95C for about 1.5 hours and then reheated to 90-100C
for an additional hour. On cooling, there was obtained 2
clear liquid catalyst composition conkaining 16.1% molyb-
denum by Atomic Absoxption spectroscopy, 1.17~ nitrogen(Xj~ldahl) and 1.67% water (Karl Fisher analysis).
Epoxidation Runs
The epoxidation runs summarized in Tables 1 and 2
where made in a 300 ml. stainless steel autoclave~ The
-18-
3~
propylene feed component was charged at ambient temperature
and ~hen the t-butyl hydroperoxide (TBHP) feed component was
charged premixed with 0.38 grams of the catalyst. This
provided for a catalyst concentration of about 350 ppm of
catalyst in the reaction medium. For the pure Propylene
runs, the TBHP feed component consisted of abou~ a 72.36
wt.~ solution of TB~P in t-butyl alcohol which contained
about 0.2 wt.~ of water. For the Propylene/Propane runs
wherein propane was added to the propylene feed component
and for the Propylene/TBA runs wherein additional t-butyl
alcohol was added to the TBHP feed componentl the TBHP feed
component consisted of a 73.0 wt.% solu~ion of TB~P in
t-butyl alcohol that contained about 0.2 wt.% of water. The
quantities of feed component were adjusted for each of the
lS runs in order to provide the desired mole ratio of propylene
to TBHP shown in Tables 1 and 2.
Thus, by way of example, in Run No. 1 of Table 1,
the propylene feed component consisted of about 49.4 grams
of propylene and the T~HP feed component consisted of about
20 93.36 g. of TB~IP, about 35.4 g. of t-butyl alcohol, about
0.2S gram of water and about 0.38 gram of catalyst.
In Run No. 2 of Table 1, the propylene feed compo-
nent consisted of about 34.65 grams of propylene and about
35.45 grams of propane. The TB~P feed component consisted
25 of about 71.72 grams of TB~Pt about 26.33 g. of t-butyl
alcohol, about 0.2 g. of water and about 0.38 g. of catalyst.
In Run No. 3 of Table 1, the propylene feed compo-
nent consisted of about 36.4 g. of propylene and the TBHP
feed component consisted of about 74.36 g. of TBHP, about
_l9W
~ ~7~33~$
64.27 g. of t-butyl alcohol, about 0.2 g. of water and about
0.38 g. of catalyst.
All of the runs reported in Table 1 were conducted
at 120C for about 2.0 hrs. All of the runs reported in
Table 2 were conducted at 110C for 1.0 hour and 130C for
1.0 hour.
The reactants ~mployed and the results obtained
are reported in Tables 1 and 2.
-20-
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3~
Turning first to Table 1, it will be noted that
the runs have been arranged in "tripletsn, based on the mole
ratio of propylene to TB~P, with each set of "triplets~
having a progressively increasing mole ratio of propylene to
~BHP. With reference to Column 4, reporting the results
obtained in terms of propylene oxide selectivity, based on
TBHP, it will be noted that when the polarity of the charge
was reduced in Run No. 1 through the addition of a mole of
propane, so that the polar components of the charge ~TBHP
and TBA) consti~uted only about 5802 wt~% of the charge,
there was a significan~ loss of selectivity, as compared
with Run No~ 2 of the present invention wherQ the polar
components of the charge constituted abou~ 74.6 wt.%. Run
No. 3 wherein the polarity of the charge was increased
through the use of an equivalent amoun~ of additional TBA,
based on the amount of propane u~ed in Run No. 1, so the t~e
polar components of the charge constituted about 80.6 wt.%
of the charge demonstrates that the poor selactivity of Run
No. 1 was due to a reduction in the polarity of the charge
rather than a ~dilu~ion~ of ~he reactants. ~un 3 had the
same "dilution" realtive to Run 2, as did Run 1.
The same effec~ on propylene oxide selectivity
basis TB~P reacted is noted in the second~ third and fourth
set of data "triplets" (Runs 4-12).
~5 For the fif~h set of triplets ~Runs 13-15), it can
be ca].culated that only 40.9 wt.% of the charge components
were polar for Run No. 13 and that only 58.3 wt.% of the
charge components were polar for Run No. 14, but essentially
equivalent results were obtained. As shown by Run No. 15,
increasing the percentage of polar components in the charge
to 72.8 wt~ only marginally improved the selectivity of the
TBHP to propylene oxide. At higher initial propylene to
TBHP ratios (1.9-2.1 to 1) the effect of polar media sta-
bilization of TBHP and catalyst is "washed-out" by the
increased rates of reaction (less TB~P) product by increased
propylene concentration. The penalty for increased propyl
ene concentration is increased propylene dimer ~ade as
evidenced by results in col D 8.
In the next set of data (Runs 16-19), the polar
components constituted about 32.2 wt.% , 52.2 wt.%, and 47.1
wt.% in runs 16-18. Essentially equivalent results were
obtained. There w~s no improvement in the selectivity of
the TBHP to propylene oxide in Run No. 19 wh~n the polar
components constituted about 67.1 w~.% of the charge. Note
from Column 8, however, that there was a fur~her significant
increase in the amount of propylene dimer that was formed at
the higher mole ratios of propylene to TBHP of-Runs 16-21
which are outside the scope of the present invention. In
runs 16-21 the selectivities of TBHP to propylene oxide were
essentially equal because of the "wash" carried by sharply
increased reaction rates (less TBHP decomposition becau~e
of increased propylene to TBHP mole ratios).
Turning next to Table 2, it will be seen that the
pattern is repeated, in Runs 22, 25 and 28 when the polar
components constituted 58.4 wt~%, 54.7 wt.% and 52.2 wt.~,
respectively, of the charge component~, the selectivity to
the TBHP to propylene oxide (Column 4) was significantly
less than the selectivity obtained in Runs 23, 26 and 27 of
the present invention where the polar components constituted
74.5 wt.~, 71.6 wt.% and 69.6 wt.%, respectively, of the
-~4
~27B3~
charge. The selectivities of Runs 22, 25 and 28 were also
significantly less than the selectivities obtained in
Runs 24, 27 and 30 where the polar components constituted
79.3 wt.%, 78.2 wt.% and 76.0 wt.%, respectively of the
charge.
EXAMPLE 2
Examples 2-4 show the importance of relatively
high catalyst concentrations on the yields, selectivities,
and conversions when the epoxidations are conducted at low
reaction temperatures.
To a 300 ml 316 stainless steel autoclave (purged
with nitrogen) was added 43.9g (1.0452 moles) of propylene
at room temperature. Also at room temperature was added a
premixed solution of 88.2g of TBHP (consisting of 60.75%
TBH~, 38.91% TBA and 0.34% water) and O.9g of molybdenum 2-
ethyl-l-hexanol (5.96~ molybdenum) catalyst. The molybdenum
2-ethyl-1-hexanol catalyst was made by heating 29.0g of
molybdenum trioxide with 299.5g 2-ethyl-1-hexanol and 20 ml
concentrated NH40H and 250 ml toluene from room temperature
to 140C over a 1-3/4 hour period removiny about 9 ml water
and 165 ml toluene. The heating continued from 140C to
153C for another 4.25 hours at which poin~ about 16 ml
water and 234 ml toluene had been recovered. The reaction
mixture was fil~ered and the fil~rate appeared ~o contain
water so it was dried ove~ molecular sieves. The dried
material was refiltered and analyzed for molybdenum and
found to contain 5.96~ molybdenum. This was the O.9g of
catalyst that was premixed with the TBHP solution and
charged to the autoclave at room temperature after the
-25-
propylene was added. The mole ratio of propylene/TBHP in
this run was 1.75:1 and TB~P/TBA was 1.2801 and the catalyst
level was 0.0403 wt.% molybdenum basis total reactor charge.
The autoclave was heated with stirring to 110C over a 30
minute period and held at 110C for 90 minutes. The reac-
tion mixture was cooled to room temperature and sampled
under pressure. The total weight of the product recovered
was 133.0g and the total weight of the liquid product (after
propylene was stripped) was 93.0g.
The liquid produc~ was analyzed and found ~o con-
tain 1.18~ TBHP.
Grams of TB~P remaining o 1.0974g
moles of TBHP remaining - 0.0122
moles TBHP reacted = moles fed - moles remaining
moles TB~P reac~ed = 0.5954 - 0.0122 = 0.5832
Conversion TB~P = moles reacted = 0.5832 = 97.94%
moles fed 0.5954
The total product analyzed under pressure was
found to contain 24.729 wt.% propylene oxide and 0.152 wt.%
propylene glycol. It should further be noted that the total
product contains only 13O922~ propylene unreacted.
Grams propylene oxide = 32.8896g
moles PO = 0.5671
5 = = moles PO = 0.5671 = 97.23%
moles TBHP 0.5832
reacted
Yield of PO ~= moles PO = 0O5671 = 95.24
moles TBHP 0.5954
fed
The same liquid product was also analyzed by
atomic absorption spectroscopy and found to contain 526 ppm
molybdenum, or a 91.5% molybdenum recovery.
-26-
~2~d~3q:~
EXAMPLE 3
To a 300 ml 316 stainlPss steel au~oclave (purged
with nitrogen) was added 45.3g (1.07857 moles~ of propylene.
Also at room temperature was added a premixed solution of
88.15g of TBHP (consisting of 60.75% TBHP, 38.91% TBA, and
0.34% water) and 0.45g of molybdenum 2-e~hyl-1-hexanol cata-
lyst (5.96% molybdenum) whose preparation was described in
Example 2. In this epoxidation the mole ratio of propylene
to TBHP was 1.81:1 and the mole ratio of TB~P/~BA was 1.28:1
and the amount of moly catalys~ was 0.0200 wt.~ basis total
reactor charge. The amount of catalyst used here is about
half that used in Example 2. ~ere again the low propylene
to TBHP ratio leads to sharply increased molybdenum
recoveries.
The autoclave was heated with stirring to 110C
over a 30 minute period and held at 110C for 90 minutes.
The reaction mixture wa~ cooled to room temperature and
sampled under pressure. The total weight of the product re-
covered was 133.9g and the weight of the liquid product
(after propylene was stripped) was 94.2g~ The liquid prod-
uct was analyzed and contained 264 ppm molybdenum or a 93.0
molybdenum recovery.
The liquid product was analyzed and found to still
contain 3.92% TBHP.
Grams of TBHP remaining - 94.2 x 3.92% = 3.69264g
moles TBHP remaining - 0.0410 moles
moles TBHP reacted = moles fed - moles remaining
moles TBHP reacted = 0.59S0 - 0.0410 0.5540
Conversion TBHP = moles reacted = 0.5540 = 93.11%
moles fed 0.5950
-~7-
3~
The total product analyzed under pressure ~7as
found to contain 22.928 wt.~ propylene oxide and 16.14%
unreacted propylene.
grams propylene oxide = 133.9 x 22.928~ = 30.70g
moles propylene oxide = 0.5293 moles
Selectivity to PO = moles PO = 0u5293 = 9S.54%
moles TB~P 0.5540
reacted
Yield PO = moles PO = 0.5293 = 88O96
moles T~P fed 0.5950
In essentially identical runs, except that the
catalys~ concentration was reduced in Example 3, the yield
of propylene oxide was some 6~ lower ~han in Example 2 with
the higher catalyst concentration. Note, however, that the
molybdenum recovery (soluble molybdenum) in the reactor
effluent in Example 3 was very high (93.0%) and even higher
than in ~xample 2 ~91.5%).
EXAMPLE 4
To a nitrogen purged 300 ml 316 stainless steel
autoclave was added 48.3g (1.1500 moles) of propylene at
room temperature. To the propylene was added a premixed
solution of TBHP (124.2g) and molybdenum catalyst (1.2 g).
The TBHP part of the premixed TBHP/molybdenum catalyst solu-
tion consisted of 124.2g having the following composition:
60.50~ TBHP, 39.30% TBA and 0.2% water. The mQlybdenum
catalyst part of the premixed ~B~P/molybdenum catalyst ~olu-
tion consisted of 1.2g of the molybdenum 2-ethyl-1-hexanol
(6.50~ molybdenum content) catalyst.
The concentrated molybdenum catalyst was prepared
by mixing 299.5g 2-ethyl-1-hexanol with 29.0g MoO3 and to
this mixture was added 20 ml of concentrated ammonium hy-
droxide. The catalyst preparation reaction mixture was
-28-
~27B3'~
heated to 180~ and held there for five hours removing some
21 ml of water. The reaction mixture was cooled and filter-
ed. Atomic absorption analysis indicated the molybdenum
content of the filtrate was 6.50% (97.7~ molybdenum incorpo-
rated into soluble catalyst form).
In this reaction the propylene to TBHP mole ratio
was only 1.38:1 and the mole ratio of TB~P/T~A was 1.27 1.
The amount of molybdenum catalyst used was 0.0449 wt~%
molybdenum basis total reactor charge. The autoclave and
contents were heated to llO~C with stirring for 120 minutes
(2.0 hours). The reaction mixture was cooled and pressured
out into two sample bombs.
The ~otal product weight was 173.5g
The total weight of liquid product was 142.2g
The liquid product was examined and found to con-
tain 1.70% TBH~.
grams TBHP remaining = 2.4174g
moles TBHP remaining = 0.026g
moles TBHP reacted = moles fed moles remaining
moles TBHP reacted = 0.8349 - 0.0269
moles TBHP reacted - 0.8080
Conversion = 0.8080 - 96.78%
0.83~9
The liquid product was analyzed by atomic absorp-
tion spectroscopy and found to contain 527 ppm molybdenum,
which is essentially a 96.1% recovery of molybdenum.
9rAMPL-5 - ~
Examples 5 and 6 were conducted similarly to Ex-
amples 2-4, except that different molybdenum 2-ethyl hexanol
catalysts were utilized. The results, however, are essen-
tially similar, very high recoveries of soluble molybdenum
at the end of the reaction (96.0~ in both runs). These
-2~-
3~b~
results are su~marized in brief tahular form below. The
runs were conducted at 110~C for 1.5 hours.
~E 3
Prcpylene/ ppm %
Wt~ m~ly ~ mole Po PO PO moly in ly
EX. c~d ratio Wt.% Yield Sel. ~. Liquid RecoverY
4 0.0402 1.79:1 2~.71 g5~65 98.25 97.35 506 96.0
0.0393 1.82:1 25.28 97.57 99.86 97~71 498 96.0
When research into this area was first begun, it
was discovered that results improved dramatically when dry
T~HP (le~s than 0.4 wt.~ ~29) was used instead of the com-
mercially available TBHP. Therefore, it is preferred that
the TB~P/TBA solutions contain very little water, 0.5 wt.%
or less. In our initial propylene epoxidation experiments,
high olefin/hydroperoxide mole ratios were chosen because of
the repeated mention in patents and the literature that
selectivities are lower when propylene/TBHP mole ratios are
low. Over 130 epoxidation runs were conducted at propylene/
TBHP molec ratios of 6:1-10:1. At these ratios various
catalysts and changes in conditions seemed to have no large
effec~ on epoxidation result~O Further, the molybdenum
recoveries at 6-10:1 ratios were in the 60-80% range.
However, when low initial propylene/TBHP mole
ratios were used in an attempt to find a method which would
help differentiate between the many molybdenum catalysts
being synthesized, it was surprisingly discovered that the
propylene oxide selectivities were excellent, provided that
reaction temperatures, residence times, and molybdenum
catalyst concentrations were adjusted properly.
-30-
It has been further discovered that enhancement of
the results is achieved when the epoxidation reaction is
conduc~ed at comparatively low reaction temperature using
comparatively high concentrations of molybdenum catalyst.
In addition, it has been also surprisingly discovered that a
high proportion of the molybdenum charged emerged as soluble
molybdenum and this proportion increased uon reduction of
the propylene/TBHP cnarge ratio. Further, it was found that
low ratios of propylene to T~HP in the charge lead to low
by-product propylene dimer make.
Table 4 gives data about the concentration of
propylene dimer in reactor effluents. Propylene dimer was
determined in reactor effluents using a GC mass spectrome~er.
Propylene dimer, as notedl is an objectionable by-product
because it co-distills with propylene oxide and is best
separated from propylene oxide by a costly extractive dis-
tillation. The cost of the extractive distillation towers
as well as the utilities cost to operate such a purification
unit is very high. The examples of ~able 5 where the con-
ventional propylene oxide process conditions are used revealsthat the propylene dimer levels seen in Table ~ are surpris-
ingly low.
Table 5 presents examples where results are im-
proved even further with high TBHP concentrations together
with low propylene/TBHP mole ratios, reaction staging and
lower catalyst levels. These examples represent the prefer-
red reaction conditions and at 1.1-1.2:1 propylene/TB~P mole
ratios. The examples of Table 6 show that the molybdenum
catalyst may be recycled with good results.
-31-
Examples 21 through 25 of Table 7 show the results
obtained when the inventive process was scaled up 3.3 fold
to a lO00 ml reactor. The only procedural difference in
these examples was that after the propylene was charged to
the reactor, it was heated up to, at or near the reaction
temperature before the TB~P/TBA/catalyst solution was added.
Exotherm was allowed to carry the reaction to the desired
temperature. Even at these quantities, excellent results
are maintaLned.
Ta~le 5A gives typical catalyst prepara~ions in-
volving 2-ethyl-l-hexanol and ammonium heptamolybdate.
Table 8 presents examples which demonstrate that
the reaction can proceed successfully with a two-part re-
actor scheme. A CSTR is followed by a PFR at a slightly
higher temperature. Low propylene/TBHP ratios are again
demonstrated. Catalyst recoveries are sometimes reported as
slightly greater than 100%. The excess should be taken as
experimental errox, and ~he recovery taXen as essentially
quantitative.
The inventive process provides high concentrations
of propylene oxide (24-32%) and utilizes much less propylene
due to the lower propylene~TBHP mole ratio and polar reac-
tion media. In this process, 4 to 16% of the propylene is
unreacted. Our selectivities (moles of propylene oxide
formed per mole of TBHP consumed) do not drop as we lower
the propylene/TBHP mole ratio. ~urprisingly, increased
selectivities to propylene oxide basis TBHP are observed.
This is because the media is more polar.
It is surprising that selectivities to the alkyl-
ene oxide are at least 96~, concentrations of the alkylene
~32-
~7~3~6
oxide in the product stream can be at least 24~, yields to
the alkylene oxide are at least 94% and hydroperoxide con~
versions are at least 96%, all simultaneously, using the
method of this invention. Further, it is surprising that
molybdenum recoveries at the lower ratios of propylene/TBHP
generally are >90%.
-33-
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1 ~ ~ ~ 1 0
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~ydroperoxid~ Choice
Representative runs were made to demonstrate that
t-amyl hydroperoxide may also be used in the practice of the
present invention.
EX~MPLE 32
Cata~ t Preparation
To a one-liter round-bottomed Morton flask fitted
with a mechanical stirrer, a nitrogen inlet, a thermometer,
a Dean Stark trap, a condenser and a nitrogen bubbler, were
added 100 g. of either ammonium heptamolybdate (Catalyst A)
or ammonium dimolybda~e (Catalyst B) and 300 g of ethylene
glycol. Th~ re2ction mixture was heated to 85-110C for
about l hour with nitrogen slowly passing through the flask.
At the end of that time, the reaction was essentially com-
plete and essentially all of the ammonium molybdate was
dissolved. The reaction mixture was subjected to an aspira-
tor vacuum at a temperature of about 85-95C for about 1.5
hours and then reheated to 90-100C for an additional hour.
On cooling, there was obtained a clear liquid catalyst
composition containing (Catalyst A) 16.1% molybdenum by
Atomic Absorption spectroscopy~ 1.17~ nitrogen (Kjeldahl)
and 1.67% water ~Karl Fisher analysis). The acid number of
the catalyst (mg KOH per gram of sample) was found to be
8Q.94 and 167.85 in duplicate analyses and (Catalyst B)
13.~4 molybdenum by ~tomic Absorption spectroscopy.
Epoxidation ~uns
The epoxidation runs summarized in Table 9 where
made in a 300 ml. stainless steel autoclave. The propylene
-41-
3~i
feed component was charged at ambient temperature and then
the t-amyl hydroperoxide (TA~P) feed component was charged
premixed with 0~38 grams of the catalyst. This provided for
a catalyst concentration of about 350 ppm of catalyst in the
reaction medium. The TA~P feed component consisted of about
a 70 wt.~ solution of T~HP in t-amyl alcohol (TAA) which
contained about 0.2 wt.% of water. The reaction conditions
employed and the results obtained are summarized in Table 9.
-42-
1~'7B3~
~1
~ ~ ~ r~
~ ~ ~:r
o~
o
_, ~ ~
dP I~
_I ~ !!; dP
$ ~^ u~e
5 ~ ~ ~ ,,
--~ 0-rl 0 ~ W _I ~ ~ tS
q ~ ~ ~ O r~
,~ ,,
P~ _I ~ r~
~ o ~ ~ ~
~ ~ ~ 0
J _~ ~; ~ u~ i
c~ L~ ~ 2
UO~
u~ ~ o o ~a ~
O O
oo
~vl o o
~ gJO ~ ~ ~ ~
~1o
o o
m
From Table 9 it will be seen that in both instances
there was excellent selectivity for the propylene oxide and
an excellane conversion of the t-amyl hydropero~ide.
In an attempt to broaden the scope of the instant
invention, VariQUS experiments were run using a hydroper-
oxide other than TBHP or TAHP -- in ~his case cumene hydro-
peroxide (CHP)~ I~ was surprisingly discovered tha~ while
TBHP and C~P behave similarly at high propylene to hydro-
peroxide mole ratios, at the low ratios of thi~ invention,
below about 2:1, their behaviors divarged. The propylene
oxide yields using CHP remained low when the propylene to
cumene hydroperoxide mole ratios were low in contrast ~o the
propylene oxide yields obtained using TB~P when high cata-
lyst concentrations were used in both instances. When CHP
was used in the low ratio examples propylene oxide selec-
tivities, basis CHP reacted, did increase when catalyst
concentration increased, but not nearly to the extent that
they did when TBHP was used in similar examples. Thus, it
was also discovered that the choice of the hydroperoxide is
also crucial in obtaining good resul~s, particularly wifh
respect to the method of this invention. This discovery
will be explored in detail with respect to the following
examples. These examples were conducted according to the
procedures outlined earlier using the parameters noted in
the tables.
Tables 10 and 11 show the overriding inf luence of
mole ratio of propylene to CHP. When CHP is used, the
selectivity to propylene oxide, basis CHP reacted, decreases
rapidly with decreasing charge ratios of propylene to C~P.
Examples 32 36 demonstrate that with d~creasing propylene/C~P
~44-
33~
charge ratio, propylene oxide selectivity decreases while
dimer content (on a ~pure PO" basis, i.e. propylene distilled
out) generally increases, at low catalyst levels (69-78
ppm). Examples 37 and 38 demonstrate a similar trend for
medium catalyst levels tabout 250 ppm), while Examples 39-45
reveal that these undesirable result6 hold true even for
catalyst concentrations that are high (400 449 ppm).
With CHP, the propylene dimer make does not de-
crease with lower propylene/C~P charge ratio as it does with
lower propylene/TBHP charge ratios. Actually, the dimer
make tends to increase with decreasing initial propylene/C~P
ratios. Further, note that Table 10 shows these trends for
two different CHP concentrations of CHP in cumyl alcohol, 30
and 59%, and that the lower C~P amount (30%) actually gives
better results to PO selectivity.
Table 12 recasts some previous examples in a form
which demonstrates that while keeping the propylene/CHP mole
charge ratio constant (a~out 3:1 for Examples 34, 37 and 39,
and about 1.3:1 for Examples 35 and 41) and increasing the
catalyst levels from the 60-80 ppm molybdenum catalyst range
to ~he 250 to 450 ppm catalys~ range, the propylene oxide
selectivity, basis CHP reacted, CHP conversion and propylene
oxide yields all increase. Even the propylene dimer make
decreases. However, also note that for Examples 35 and 41
at low propylene/CHP ratios, propylene oxide selectivities,
basis CHP reacted, are still low. Thus, it appears that
when CHP is used, high reactant ratios should be maintained,
in contrast to the case where TBHP is used and excellent
propylene oxide selectivities, basis TBHP reacted, are
achievable with low propylene/TBHP mole ratios.
-45-
7B3~
Table 13 presents four previous examples plus two
new ones t50 and 51) to demonstrate that at a given catalyst
level (250 or 400-450 ppm) that propylene oxide selectivity,
basis CHP rPacted, decreases and propylene dimer make in-
creases when the C~P concentration increases from 30 to 59%.Propylene oxide yields also decrease.
~ able 14 presen~s the previous examples recast
into yet another form to demonstrate that at propylene~CHP
charge ratios of 1.3:1 to 1.4~ is impo~sible ~o achieve
high PO selec~ivi~ies or yields by varying either the CHP
concentration (30.0 to 43 to 59~) or the catalyst concentra-
tion (60 to 250 to 450 ppm basis to~al charge.) In fact, at
reactant mole ratios of 1.301 to 1.4:1, it appears that the
optimum catalyst level may be the 200 to 350 ppm range.
Notice that the propylene dimer make increases with de-
creasing PO selectivity and decreases with increasing PO
selec~ivity. This latter relationship is not seen with
TBHP.
The CHP results seen herein are to some extent
20 confirmed by Kollar in U. S. Patent 3,351,635 (see Table 10)
where it is seen that CHP conversion and epoxide selectivity
decrease with decreasing mole ratio. The in~en~ion herein
of using high catalyst concentrations was not discovered
therein, even to the limited extent possible with CHP, as
opposed to thè dramatic improvement possible with TBHP.
Finally, an Example 55 was conducted substantially
the same as Example 39 except that it was performed in a
single one-hour, 90C step as opposed to ~he staged reaction
of Example 3g (one hour at 90C followed by one hour at
30 110C). Other minor differences were a charge ratio of 7.18:1
-46-
33~6
instead of 7.03:1 and a catalyst concentration of 79 ppm in-
stead of 78. As with TBHP, the CHP conversion was much
lower (66% as compared with Example 39's 97.7%).
-47-
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Olefin_Choice
Alth~ugh propylene has been used in the prior
examples of the present invention as a matter of convenience
and to provide for comparative data, other C3-C20 olefins
may also be used in the practice of the present invention.
This is illustrated by the following specific examples.
When the higher olefins such as C4 to C20 are epoxidized, it
is important to obtain an essentially qUantitiYe conversion
of the olefin to the epoxide because the feed stock nd
epoxide reac~ion product have similar physical properties
and are separated only with great difficulty.
EXAMPLE 33
To a l-liter round bottomed Morton (fluted flask
equipped with a mechanical stirrer, Dean Stark ~rap, ther-
mometer, N2 inlet and bubbler, was added 35.31g of ammonium
heptamolybdate tetrahydrate from Climax Molybdenum Co.
(molecular weight - 1235.86, g atoms moly - 0.2000,
(NH4~6Mo7O24.4H2O) followed by 182.32g of 2 ethyl-l-hexanol
20 (99~ purity, alfa, molecular weight = 130.2, moles = 1.4)
and 1404 ml H2O. Note the mole ratio ~f alcohol (2-ethyl~l-
hexanol) to g atoms molybdenum = 7.0/l and the mole ratio of
added H2O/g atoms molybdenum = 4.0/l. The reaction mixture
was heated slowly to 178C and held at 178-180C for five
hours during which time 29 ml H2O were xemoved with the Dean
Stark trap. The cooled reaction mixture was filtered
through glass filter paper to remove solids. The filtrate
w~ight 176.3g.
-53-
~2~7~3~6
~ molybdenum in filtrate by AA = 10.1%
% N in filtrate by Rjeldahl = 0.34%
g molybdenum fed = 19.187
g moly "out" in (soluble) filtrate = 17.81
% molybdenum lncorporated in catalyst = 92.80%
EXAMPLE 34
To a 250 ml round-bottomed flask ~itted with mag-
ne~ic stirring bar, thermometer, condenser, N2 inlet and
bubbler was added 42.0g of octene-l (molecular weight 112,
0.375 moles) followed by 35.5g of 72008% TB~P with 0.39g of
10 molybdenum catalyst 5810-60 (10.1% molybdenum) premixed with
the ~BHP/TBA. The reaction mixture was heated slowly to
95C (exothermed to 99C) and then held there (93-96C~ for
2.0 hours. Af~er cooling, the reac~ion mix~ure was solids
fr~e and weighed 74.1gn
15 wt.% TBHP = 1.70%
wt.% octene oxide = 46.182
wt.~ octene = 12.677%
g octene oxide = 34.221
moles epoxide = 0.26735
Selectivity = 0.26785
C8 epoxide 1.2703 = 98.91
Yield = 0.26735
20 C8 epoxide 0.2843 = 94.03
g TB~P remaining G 1 . 2597
moles TBHP remaining = 0.0140
moles TB~P fed = 0.2843
moles TB~P reacted = .2703
Conver~ion = 2703
TBHP .2843 - 95.08%
5
Several other examples are given in the table
attached. The procedures and apparatus were exactly like
that in Example 34.
-54-
~27~33~6
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Many modifications could b~ made by one ski 1 led inthe art in the invention without changing its spirit or
scope which are defined only by the appended claims.
