Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
BACKGROUND OF THE INVENTION
The ether Or the lnventlon has been tradltlonally
prepared by the use Or a strong mlneral acld, e.g. sulfurlc
scld. Such strong aclds under the process conaitions are
very corrosive ~nd cause ~lgnlricant problems when applled
on a commerclal scale. A~ a result, there has been a contlnuous
search for an lmproved proces6 Or hlgh erflciency that avolds
these corroslon problems.
Acidlc lon exchange reslns, whlch 8180 ha~e been
used ~8 catalysts ~or the preparatlon Or the etherso~ the
lnventlon, cannot be used at temperatures hlgher than 70_~5GC.
due to thelr poor thenm~l stabillty. Thl8 llmltatlon results
ln long reactlon times and low throu~hput per unlt volume
Or a reactlon ves~el.
j Another problem assoclated wlth the known processe~
18 the rormatlon Or undeslrably ~ large quantities Or dimethyl
25 1 ether The present lnventlon also deals wlth thls probl-m and
l substantlally reduees the amount Or thls undeslrable by-product.
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SUMMARY OF Tn~ lNVENTION
The present inventlon 18 a process for the preparation
of methyl-t-alkyl ethers comprising reacting a mixture of
a tertiary olefin Or the formula RHC = C~ wherein R is H
or alkyl and Rl i8 alkyl and methanol ln the liquld phase ln
the presence of ~ homogeneQu :--free heteropoly acid catalyst having the formulaHn Aa Dc Oy XH20
wherein A 18 P, B, Sl, Ge, Sn, As, Sb,
U, Mn, Re, Cu, Nl, Co, Fe, Ce,
Th, Cr or mlxture thereor; and
D is Mo, W, ~ or mlxture thereof;
and whereln a ~ O.l - lO;
c = 6 - 18;
n 18 the number of acldic hydrogens
ln the cataly~t;
y 18 the number of oxygens in the
catalyst; and
x 18 the moles of water of
crystallization.
Using the process of the invention, high yields of methyl-t-
butyl ether and other t-alkyl methyl ethers are obtalned wlth
very desirable low concentrations of by-product dimethyl ether.
The central aspect of the present lnvention is the
use Or the partlcular catalysts noted ln the formula above in
the liquid phase reaction of lsobutylene or of a tertlary
olefln and methanol to g~Ye methyl-t-alkyl ether. The tertiary
olefin has the formula RHC = CRl wherein R ifi H or an alkyl
and Rl 1~ alkyl. The catalysts are suitably any of tho6e
catalyst~ delimlted by the formula above. In a preferred
embodiment, the molybdenum, tungsten and vanadium are employed
separately. Thi8 18 conven~ently accom}~ hed ln the fo~nula
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by settlng D separately e~ual to molybdenum~ tungsten or
~anadium. 0~ speclal interest ln the present lnvention are
tho~e catalyst~ that contaln phosphorus, ~lllcon and germanlum.
mi8 iB accomplished by settlng A equal to phosphorus, slllcon
or gormanlum.
The number Or H20 molecules contained ln the cat~lyst
as water of crystalllzatlon can vary wldely, dependlng
on the method o~ preparation and on the aftertreatment of
the catalyst. Thus ln each catalyst X mQy range from zero
to about 40 Furthermore, an lnteractlon between the "acldlc"
hydrogens and the water Or crystalllzatlon may occur such
that the value o~ n 1B changed. This may occur e.g. upon
partlal reductlon of a catalyst of the abo~e formula,
The catalysts Or the lnventlon are p repared by
known tech~lques. Speclflc preparatlons o~ these catalysts
are shown in the worklng examples of thl~ speclricatlon.
~roadly, however, the cat~lysts of the lnventlon may be
prepared by any of the technlques known ln the art.
The catalyst employed ln the reactlon 18 BUltably
employed elther as a dlssolved component o~ the llquld mlxture
or as a heterogeneous cataly~t. Either form glves the very
desirable results of the present inventlon with the homogeneous
liquld mlxture being preferred because of the substantlally
greater contactlng efficlency.
A glven heteropoly acld may be used as a heterogeneous
catalyst ir lt is lnsoluble ln the reactlon medium. In ~uch
a c~se lt may be used alone, or supported on carrier materials,
~uch as ~illca, alumlna, kieselguhr, bentonite clay~ and otherR.
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The concentratlon Or the cataly~t ln the llquid
phase reactlon mlxture may vary wldely. For the homogeneou6
cataly~ts, it i8 moBt convenient to state the catalyst
concentratlon in terms of weight percent. The welght percent
of the catalyste may vary wlthln very broad limlts, but lt
ha~ been found that weight percentageB of about 0.1 to about
5~ are preferred. For the heterogeneous catalyst eystem6 lt
18 most common to have a flxed-bed of the cataly~t through
whlch the reactant feed 1B pasned. Thus, there 18 no slgnlflcant
relatlonshtp between the amount Or catalyst and the amount o~
( the reactlon mlxture.
m e proce6s condition~ for the llquid pha~e reactlon
may vary wldely, but ln normal practlce, the temperature
range~ from about lO to 200 C. and the reactlon 1~ normally
conducted under atmospherlc or ~uperatmo~pherlc pre~sure,
Of special lnterest in the procen~ of the lnventlon are
reaction~ conducted at temperatures o~ 70 to 150 C. u~lng
superatmo~pherlc pressure. m e contact tlme of the~e reaction
~onditlons will vary substantially. The contact tlme may
range ~rom as low as a few seconds to a number of hours
depending upon the state of the catalyst employed, the
reaction temperature and the pre~sure. The molar ratio of
the tertlary ole~in to methanol may vary widely ~o long as
the predomlnant product i6 the tertlary alkyl methyl ether.
Sultably, the molar ratlo~ are about 0.3 to about 10 moles
of methanol per mole o~ olefin.
In addition to the~e process variables, other
modi~ication~ of the reaction may be used. For example,
a ~uitable solvent may be employed that will not deleteriously
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arfect the reaction and that 18 conveniently removed from
the reactlon product. m e reactlon 1B 6ultably conducted ln
any reactor that can accommodate a llquld pha~e reaction.
Thu~, a ~t~rred and heated pressure vessel contalning the
reactants with the catalyst dlssolved ln them may be used
~or a commerclal batch operatlon. In a contlnuous operatlon,
the reactants wlth the cataly~t dlssolved may be pa~sed through
a heated tubular reac,tor (packed with lnert materlal for
improved heat trans~er), such that the product, and any
unreacted materlal, are contlnuou~ly removed. In a heterogeneous
reactlon, the lnsoluble catalyst may constltute the whole
or part Or the reactor packlng.
SPECIFIC EMBODDMENTS
Exam~le~ 1-18 _ Preparatlon Or methyl_t-butyl ether
uelng varlous catalyst6.
The h~teropoly acids used as catalysts of thls
lnventlon were prepared by mlxlng solutlons of theoretical
amounts of a soluble~molybdate or tungstate with a salt
solutlon contalnlng the hetero atom ~ollowed by acldlfylng~
heatlng~ extractlng the heteropoly acld with ether, then
crystalllzlng rrom the ether soltuion
H4GeW12040 XH20 used in Example 12 was prepared
as rollowB:
A ~olution A wa6 prepared by stirring and heatlng
3.9 g. powdered GeO2 (37 mlllimoles) and 14.2 g. Or 50
~-l aqueous NaOH (178 milliequivalent~) in 100 ml. water.
-~ A solutlon B was made by dissolving 159 g.
Na2W04.2H20 (482 mlllimoles) ln 400 ml. cold water, and addlng
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approxlmately 80 ml. Or 15% hydrochlorlc acld, wlth ~tlrrlng,
untll the pH value o~ the solution became 6.8~.7.o.
Solutlons A and B were comblned, stlrred ~nd heated.
The pH value was adJusted to about 3 with 65 ml. addltlonal
15% ~1, then 20 ml. 30~ HCl was added in portions. The
solutlon was bolled ~or two hour~ and allowed to evaporate
to about 400 ml. resldu~l volume. The mlxture was then cooled
ln an lce-bath to 18C., ml~ed with 50 ml. concentrated HCl,
and poured through a fllte~ lnto a separating ~unnel, followed
by addltion o~ 250 ml. ether ~n portlons, wlth lntermlttent
shaklng. Another 50 ml. concentrated HCl was added, the
mlxture shaken, then allowe~ to separate. m ree llquld
layers separated, the lowest layer conta'ned the product
heteropoly acld dlssolved in ether. It was separated,
~lltered and the ether evaporated ln a water bath at 50C.
m e resldual ~olld was dlssolved ln 80 ml. water9 filtered~
mlxed wlth 20 ml. concentrated HCl, and the extractlon with
ether was repeated as above. m e ether extract was mixed
wlth 50 ml. water, the ether removed by evaporatlon, and the
concentrated solutlon ~lowly evaporated to dryness ln a
vacuum dessiccator. The whlte, crystalllne solld thus
obtalned welghed 77 g. The other c&taly~ts of the Table
were prepared in essentially the same manner.
The catalysts were u~ed to prepare methyl-t-butyl
~ther ln a one-llter laboratory pres~ure reactlon vessel
equlpped wlth a stlrrer, charging ports, a thermocouple, a
pressure gage and a blowout dlsc.
me procedure used in Example 1 o~ the Table was
as ~ollows:
-- 6 --
`` ` 107Z~86
The catalyst H4SiMol2O40 XH2O(0.9 g.) was char~ed
to the pressure vessel, the vessel was closed and evacuated.
A mixture of 56 g. isobutylene ~1 mole) and 128 g. methanol
(4 moles), confined under its own vapor pressure in a small
steel bomb, was charged to the reaction vessel by suction,
through one of th~ charging ports. The reaction vessel was
then heated with agitation at 135C. for one hour. The pressure
in the vessel rose initially to 220 p.s.i., then decreased
to 150 p.s.i. The catalyst was completely soluble in the
reaction mixture. After the reaction, the reaction vessel
was cooled to 0C. and the reaction mixture was analyzed by
gas chromatography. The catalysts, catalyst concentrations,
molar ratios of reactants and results are shown in the following
Table.
The results of these reactions are given in the
Table where the conversion and selectivity are defined as
follows:
moles of reactant reacted x 100
% conversin = moles of reactant charged
moles of methyl-t-butyl ether obtained
% selectivity = moleS of isobutylene reacted
Also included as a part of the results is the amount of by-
product dimethyl ether that is formed. This result is expressed
in terms of the percent of charged methanol that is converted
to dimethyl ether.
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It ls seen ~ro~ the above data that the productlon
Or methyl-t-butyl ether uslng the catalysts Or the ln~entlon
gives hlgh converslon of the l~obutylene at ~ery hlgh
selectlvlty. It 1~ al80 ~een from the data that the yleld
Or dlmethyl ether 18 maintaln~d withln a ~ery deslrable low
range.
- Preparation of t-amyl methyl ether.
Using the procedure of Example 1, 100 g.
2-methylbutene-2 (1.43 mole) and 46 g. methanol (1,43 ~ole)
were reacted for 90 minutes ~t 135C, ln the presence of
0.5 wt,% (0.73 g,) of ~4SlM012040~XH20 as catalyst. The
catalyst was soluble ln the reaction mixture. Ihe converaion
of the olefln was 34.4%, that of methanol was 28.4~. ffle
product contalned 28.2 wt,% o~ t-amyl methyl ether; athe
selectivity ba~ed on converted 2-methylbutene-2 WAS 80.2%.
- Preparation of t-amyl methyl ether.
U8ing the procedure of Example 1, 70 g.
2-methylbutene-2 (1.0 mole) was reacted with 96 g. methanol
t3.0 moles) for 90 minute~ at 135C, ln the pre~ence of
1-0 wt-% (1-7 g.) of H4SlM012040 XH20. m e converslon o~
the ole~ln was 46.o~, that of methanol 14.6~. The product
contained 28 wt.~ of t-amyl methyl ether; the selectivity
ba~ed on converted 2-methylbutene-2was 95~.
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