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Патент USA US3028234

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Apnl 3, 1962
w. H. SCHECHTER ETAL
3,028,221
CONTINUOUS PROCESS FOR THE PRODUCTION 0F BORANES
Filed Dec. 15, 1958
CONDENSER
RECTIFICATION
WATER
SECTION
I
‘
.*
-
NON CONDENSABLES
To vENT
REFLUX
ACCUMULATOR
NuH
IN WHITE 0II.——>
'
-
-
I-IB(ocH3Q2
/
+B(ocI-I3)3
P
STRIPPING
TO PRODUCT STORAGE
-—
sEcTIoN
EI(ocH3)3
NuB(ocH3‘)4 SOLUTION
VAPOR
IN 5% WHITE on.
B(°¢H_,>3
REBOILER/
BOTTOMS
HOLD
TAI-IK
TI
5 EARN~
REBO'LER
SECT'ON
NoB(ocH3)4 SLURRY
IN 50 °/. WHITE 0n.
MAKE-UP
B(0C H93
WHITE 0“.
Ia(ocII3)3
WILLIAM H. scI-IEcHTER
DURLAND K. SHUMWAY INVENTOR.
ALVIN MURCHISON
BEN/2A of A6“
United States Patent 0 " ICC
3,028,221
Patented Apr. 3, 1962
2
1
formed by the back reaction, only very low yields of di
methoxyborane are obtained.
3,028,221
CONTINUOUS PROCESS FOR THE PRODUCTION
According to this invention, the back reaction consum
OF BORANES
William H. Schechter, Bradfordwoods, Durland K. Shum
way, Valencia, and Alvin Murchison, Evans City, Pa.,
ing dimethoxyborane and producing sodium borohydride
This invention relates to a process for the preparation
of dimethoxyborane and more particularly to its prepara
tion by the continuous reaction of sodium hydride and
tion of methyl borate and a small amount of dimethoxy
is essentially eliminated by maintaining a low dimethoxy
borane concentration in the reaction phase. The desired
assignors to Callery Chemical Company, Pittsburgh,
low concentration of dimethoxyborane is maintained by
ha, a corporation of Pennsylvania
rapidly removing it from the condensed reaction phase
Filed Dec. 15, 1958, Ser. No. 780,626
by vaporization. The vaporized product, since it is in
12 Claims. (Cl. 23-204)
10 equilibrium with a liquid phase containing a high propor
borane, contains a high proportion of methyl borate and
a small amount of dimethoxyborane.
For example, the vapor in equilibrium with a con
methyl borate.
It has been discovered by Carpenter, Bush and Schech 15 densed reaction phase containing 1 part dimethoxyborane
to 100 parts of methyl borate contains about 2.2% di
methoxyborane and'97.8% methyl borate; a condensed
ership with this application, that dimethoxyborane can
reaction phase containing 0.5 part dimethoxyborane to
be recovered by contacting sodium hydride and liquid
100 parts of methyl borate is in equilibrium with a vapor
methyl borate using at least 2 moles of methyl borate for
each mole of sodium hydride and heating the mixture to 20 containing about 1.3% dimethoxyborane. The liquid
ter, Ser. No. 441,636, ?led July 6, 1954, of common own
produce a vapor product containing dimethoxyborane.
The dimethoxyborane is formed according to the overall
_ vapor equilibrium is- affected slightly by the presence of
an inert third ?uid, such as mineral oil, since there is some
equation
change in the relative volatilities of dimethoxyborane and
to completion. Continuous processing is economically
quired for vaporization may be added through the walls
methyl borate. In addition to the methyl borate con
25 sumed by chemical reaction, there must be added a large
The rate at which the dimethoxyborane was produced
amount of methyl borate to make up for that removed
from these reactions was relatively slow as the reaction
from the reaction phase in the vaporized product. This
required from several hours to several days to proceed
methyl borate may be added as a liquid, and the heat re
unfeasible when such relatively long reaction times are 30 of the container or through heating coils or other conven
required, and hence the method suffers from all the disad~
tional methods. The necessary heat and methyl borate is
vantages inherent in batch chemical processing, e.g. the
preferably added simultaneously by feeding methyl borate
necessity of loading and unloading for each reaction and
vapor. If there is not su?icient methyl borate supplied
the varying rate of production due to changing condi
the dimethoxyborane concentration will increase, di
tions and concentrations during the course of batch reac 35 verting a certain portion into the back reaction, and the
tions. In addition, the by-product sodium tetramethoxy
remainder will be recovered as a vapor product from the
borate is a voluminous solid product and mechanical
reaction at a higher dimethoxyborane concentration. It
handling of this material in continuous processing equip
is apparent that the higher the rate of dimethoxyborane
ment is dii?cult.
formation the more rapidly methyl borate must be sup
It is an object of this invention to provide a simple 40 plied to maintain the desired methoxyborane concentra
economical method whereby dimethoxyborane may be
tion. The rate of dimethoxyborane formation increases
continuously produced in good yields.
with decreasing particle size of the sodium hydride react
This invention is predicated on the discovery that the
ant. It is generally preferred to use sodium hydride with
reaction of sodium hydride and methyl borate to produce
a nominal diameter of 20 to 50 microns; when more
dimethoxyborane can be made to go rapidly to comple 45 ?nely divided sodium hydride is used it is mechanically
tion by keeping the amount of dimethoxyborane in the
dif?cult to supply methyl borate at a fast enough rate,
liquid or condensed reaction phase at less than about 1
and when coarser sodium hydride is used the reaction is
part for every 100 parts of methyl borate, and on the dis
slowed and a longer reaction time is required.v
'
covery that the by-product sodium tetra-methoxyborate
The ?gure schematically illustrates a preferred method
is solvated and the solvate is soluble in the condensed 50 of preparing dimethoxyborane according to this invention
reaction phase if a massive excess of methyl borate is
and will hereinafter be described in detail.
maintained in the condensed reaction phase.
It is preferred to introduce sodium hydride to the reac
It is believed that the reaction of sodium hydride and
tion as a slurry in a saturated hydrocarbon since there
methyl borate proceeds rapidly, probably through some
are a number of di?iculties encountered in using a dry
intermediate to ‘produce dimethoxyborane according to 55 sodium hydride feed that can be overcome only by the
use of special complicated feeding systems. For example,
NaH+B(OCH3),->intermediate
,
Intermediate-I-B(OCH,),-> BH(OCH,),+NaB(OCH;,),
The dimethoxyborane formed, however, will react with
the sodium tetramethoxyborate product, sodium hydride 60
reactant, and probably the intermediates, to form sodium
borohydride. For example,
dry sodium hydride is a ?re hazard since it is extremely
reactive with atmospheric moisture producing hydrogen
and sut‘?cient heat to ignite the hydrogen. Furthermore,
when excess sodium hydride and methyl borate vapor are
contacted, conditions that would exist for example at the
discharge opening of a dry sodium hydride feeder, they
react to form a solid of much greater volume than the
The sodium borohydride formed by this back reaction will 65 original sodium hydride. This solid is adherent and com
pacts easily, resulting in jamming of the feeding equip
react with methyl borate to form dimethoxyborane only
at a very slow rate. Unless the back reaction producing
sodium borohydride is prevented the reaction must be
continued for a long period of time to obtain a substan
ment. These ditiiculties are not encountered when a feed
of sodium hydride in hydrocarbon is used because of the
protective action of the hydrocarbon ?lm. Any saturated
hydrocarbon may be used as the suspending liquid, al
tial yield of dimethoxyborane; conversely, if continuous 70
though it is preferred to use a hydrocarbon of low vola
reactors with feasibly short resident times are used and
tility to facilitate the separation of the volatile reaction
the conditions are such that the sodium borohydride is
8,028,221
product from the suspending liquid. Commercial white
oils or mineral oils are particularly desirable. It is gener
ally preferred to use a feed containing at least 40% white
4
reactor. It is essential that this return stream does not
contain too high a proportion of dimethoxyborane, so
7, that the equilibrium dimethoxyborane concentration in
oil, and preferably more than 60% White oil, as such
the reactor section is not increased to too high a value.
slurries are more easily pumped and handled than thicker
The remarkable elfect of the dimethoxyborane con
centration in the condensed reaction phase on the yield
Thus for example, in a reaction in which the methyl
borate boil up ratio to sodium hydride fed was 160 lbs.
per 1b., with a nominal residence time of thirty minutes,
whenethe re?ux return from the recti?cation column con
of dimethoxyborane is illustrated by the following single
tained 0.8% dimethoxyborane the yield of dimethoxy
slurries.
stage continuous reactions. The reactor consisted of a 10 borane recovered was 85%. However, under the same
reaction conditions, when the re?ux return contained
jacketed autoclave 3 inches in diameter and 6 inches long
2.8% dimethoxyborane the yield was only 56%. The
equipped with an agitator, a liquid over?ow tube that
composition of this return stream can be predicted from
maintained a 3 inch liquid depth in the reactor and suit
normal distillation calculations, and adjusted by chang
able ?ush, feed, and discharge lines. The reactor was
?ushed with nitrogen to remove air and moisture, and 15 ing the number of plates, take-o?f rate and re?ux ratio '
in the recti?cation section.
the entire reaction was run in the absence of air and mois
The hydrocarbon fed to the reactor as a sodium hy
ture to prevent loss of hydrogen and possible explosion.
dride suspending medium acts as an inert diluent in the
The reactor was ?lled with methyl borate and heat was
reaction. It is'preferred to keep the concentration of this
supplied through the walls of the autoclave to give the
desired rate of methyl borate vaporization. Liquid make 20 hydrocarbon in the condensed reaction phase below about
25%, i.e., less than about 25 parts hydrocarbon to 100
up methyl borate was fed into the reactor. A slurry con
parts of methyl borate, since at high concentrations the
taining 3% sodium hydride in white oil was continuously
fed to the reactor. The vaporized material was continu
reraction is slowed considerably because of the diluent
e ect.
ously removed overhead, condensed, collected and ana
lyzed, and the slurry of condensed reaction phase was 25 A preferred method for continuously producing dimeth
oxyborane according to this invention is illustrated in
continuously removed through the liquid over?ow tube.
FIGURE 1. The sodium hydride reactant is fed to a
central plate of a plate column. The stripping section,
moles of methyl borate were vaporized for each mole of
the section below the feed plate, functions as a continuous
sodium hydride fed and the nominal residence time of the
sodium hydride was 20 minutes (nominal residence 30 countercurrent reactor. The recti?cation section, the
section above the feed plate, concentrates the dilute di
time=volume rate of slurry feed/liquid volume of re
methoxyborane product recovered from the stripping sec
actor). The overhead product from the reactor contained
tion. The methyl borate vapor fed to the column is sup
2.95% dimethoxyborane corresponding to a liquid reac
In one reaction the boil up rate was adjusted so that 5.3
tion phase containing about 1.3% dimethoxyborane, and
plied from the reboiler section. The operation and func
the yield was only 17.8%. In a second reaction, the boil 35 tion of these sections are hereinafter described in detail.
Feed plate and stripping section.—A slurry of the re
up ratio was 58.5 and the residence time was 11.9 minutes;
actant sodium hydride in white oil is fed to the central
the overhead product contained only 1.3% dimethoxy
plate of the dimethoxyborane reactor-column, where it
borane and yield was 71.4%.
contacts the re?uxing liquid from the recti?cation sec
Since it is necessary to maintain very low dimethoxy
borane concentrations in the condensed reaction phase, 40 tion and the vapors from the stripping section. On the
feed plate and in the stripping section there occurs simul~
the concentration of the dimethoxyborane in the vapor
taneously ( l) the reaction of sodium hydride with methyl
product will also be very low. The heat required to pro
borate, (2) the formation and dissolution of sodium
vide the necessary methyl borate boil up may be con
tetramethoxyborane-methyl borate solvate, and (3) the
served to concentrate the product by combining the re
actor with a recti?cation column. For example, several 45 formation and distillative separation of dimethoxyborane
from the condensed reaction phase. The condensed re
reactions were performed using a two stage reactor,
action phase contains the hydrocarbon suspending liquid,
similar to the single stage reactor described above, in com
re?uxing methyl borate, as well as the reactants and re
bination with a recti?cation column. The reactor con
action products. The concentration of dimethoxyborane
sisted of two stirred autoclaves equipped with suitable
inlet and outlet connections. The sodium hydride-white 50 in the condensed reaction phase is higher on the feed plate
than on any other plate in the stripping section due to the
oil slurry was fed into the ?rst reactor, and the condensed
distillation occurring in the stripping section. In order
reaction phase over?owed from the ?rst reactor into
to obtain essentially quantitative yields of dimethoxy
the second reactor, and over?owed from the second re
borane, by repressing the back reaction to sodium boro
actor. The methyl borate was fed into the second reactor
and the vapors from the second reactor passed into the 55 hydride, it is necessary to keep the concentration of di
methoxyborane in the feed plate at less than 1% and pref
?rst reactor and the ?nal vapor product was discharged
erably less than 0.5%. The vapor in equilibrium with
from the ?rst reactor. The vapor product stream from
such a condensed reaction phase contains from about 1.3
the ?rst reactor was passed into the bottom of a recti?ca
to 2.2% dimethoxyborane. This requires that from about
tion column consisting of 2 inch pipe packed with Mr
inch beryl saddles, which was equipped with a condenser, 60 45 to 75 pounds of methyl borate must be vaporized or
boiled up, through the stripping section for each pound
re?ux accumulator and divider, and a product receiver.
of dimethoxyborane produced, which is equivalent to a
The liquid re?ux from the recti?cation column was re
boil up ratio of about 150 to 250 pounds of methyl borate
turned to the ?rst stage of the two stage reactor. In this
for each pound of sodium hydride fed.
thoxyborane concentration but the product recovered 65 The reaction produces by product tacky solids that will
compact and build up a solid crust that eventually plugs
from the combined reactor and recti?cation column can
the vapor and liquid passages between plates in the
be concentrated to any degree desired. It is normally
preferred to recover a product containing no more than
stripping section. In order to permit continuous reactions
15 to 20% dimethoxyborane if it is desired to store the
for long periods without the periodic cleaning of the
product since at higher concentrations the dimethoxy 70 stripping section, it is necessary to have a condensed re
borane tends to disproportionate to diborane and methyl
action phase of su?icient volume to dissolve all the by
borate. It must be noted that the re?ux stream from
product sodium tetramethoxyborate-methyl borate sol
the recti?cation column to the reactor will contain some
vate. The sodium tetramethoxyborate-methyl borate sol
dimethoxyborane, and this will result in a change in
vate is metastable, spontaneously decomposing into in
manner the reaction section can be run at a low dime
equilibrium concentration of dimethoxyborane, in the 75 soluble sodium tetramethoxyborate and methyl borate.
8,028,221
This is evidenced by the fact that sodium tetramethoxy
borate is insoluble in methyl borate, and does not form
the solvate, and that the solubility of the solvate de
creases with time. The solvate is formed only when the
sodium tetramethoxyborate is formed by reaction in the
presence of excess methyl borate. For example, the
solubility of freshly prepared sodium tetramethoxyborate
6
plugging of the boiler tubes. Under these conditions it
is necessary either to have parallel boilers that may be
alternatingly used in cleaning and operating cycles or to
stop operation of the column periodically to clean the
boiler. The fouling of the boiler tubes can be substantial
ly eliminated by precipitating the sodium tetramethoxy
borate from the column e?luent prior to its passage
through the boiler. We have found that this can be
accomplished by maintaining a high concentration of
tion containing 39% white oil and 61% methyl borate
at various time intervals. After thirty minutes the solu 10 white oil in a circulating reboiler system, and by feeding
the liquid column eflluent into the circulating system
bility express in moles of sodium tetramethoxyborate dis
upstream of the boiler. The reboiler section as illustrated
solved per 1000 grams of methyl borate (total, including
in FIGURE 1, consists essentially of a bottoms hold tank,
that required to form the solvate) was .14, after ninety
methyl borate solvate was measured at 68° C. in a solu
a circulation pump, and the reboiler. The white oil con
minutes was .02 and after twenty-four hours was .017.
The rate of destruction of the solvate increases with in 15 centration in the bottoms hold tank is maintained at a
creasing temperature. It is apparent therefore that if ex
tended residence times are used in the stripping section
that a higher volume of liquid must be present to assure
high level, preferably at about 50%, and the white oil
concentration in the entire reboiler section is higher than
that which would be in equilibrium with the bottom plate
of the column. The liquid e?‘luent from the column may
the solubility of the by-product sodium tetramethoxy
borane-methyl borate solvate. The solvate solubility is 20 be fed to the reboiler section either in the bottoms hold
tank, or to the lines between the bottoms hold tank and
also dependent upon the concentration of white oil in the
the reboiler. The dissolved solids in the liquid column
condensed reaction phase and the temperature of the
e?luent are immediately precipitated when the e?‘luent
condensed reaction phase. To illustrate, the solubility
is mixed with the reboiler liquid containing a high propor
of the solvate (moles salt/ 1000 g. methyl borate) after
thirty minutes contact at 68° C. was .015 in a solution 25 tion of white oil. The resultant slurry is then passed
through the reboiler where the required methyl borate is
containing 53.6 wt. percent white oil; .046 in a solution
vaporized. The bottoms hold tank also serves as a vapor
containing 47.3 wt. percent white oil; .138 in a solution
disengager to separate the vaporized methyl borate. The
containing 39 wt. percent white oil; and .175 in a solution
make-up methyl borate and white oil, if required, is fed
containing 34 wt. percent white oil. The solubility in a
solution containing 25 wt. percent white oil after two and 30 to the reboiler section.
The followingreaction illustrates the operation of the
one-half hours contact was .018 at 24° C., and .184 at
preferred column-reactor. The column-reactor was a
68° C. It is preferred to keep the concentration of white
bubble cap column of conventional design, two feet in
oil in the reaction phase at less than about 25% to
diameter, about 50 feet high, and with 30 plates spaced
facilitate dissolution of the sodium tetramethoxyborate, as
well as to minimize the effect of the diluent on the re— 35 at 15 inches. Each plate contained one 4 inch down
comer, 17 caps, and operated with a 1 inch liquid seal.
action rate.
A slurry containing 25.4% sodium hydride in white oil
Recti?cation section.—The vapor product from the
was feed to the sixth plate (from the top) at a rate of 21.1
stripping section contains only about 1 to 2 percent dimeth
pounds of sodium hydride per hour. The vapor rate in
oxyborane in methyl borate. When a non-volatile white
> oil is used as a suspending liquid for the sodium hydride 40 the column was 4000 pounds per hour, giving a boil up
ratio of 190 pounds of methyl borate for each pound
fed to the column there is essentially no suspending liquid
of sodium hydride fed. The re?ux ratio, the pounds of
vaporized from the stripping section. The recti?cation
re?ux returned to the top of the column per pound of
section serves to concentrate the product and is designed
product removed, was 8.7. The column e?luent was a
according to conventional distillation methods. If it is
desired to recover and store dimethoxyborane for further 45 solution of sodium tetramethoxyborate solvate in 95%
methyl borate-5% mineral oil. The slurry bottoms prod
reaction or use, the product is concentrated to about 20%
dimethoxyborane in methyl borate.
Dimethoxyborane
uct from the boiler section contained 26.3% solids in a
liquid containing 48% white oil and 52% methyl rate.
The overhead condensed product contained 6.04%
portionation reaction is best carried out in a distillation 50 dimethoxyborane in methyl borate and contained 96.4%
of the hydridic hydrogen fed. A small amount of dis
column in which dimethoxyborane is simultaneously con
proportionation occurred in the column, and 1.42% of
centrated and separated from the disproportionation prod
disproportionates to diborane and methyl borate accord
ing to 6BH(OCH3)3->B2H6+4B(OCH3)3. This dispro
the hydridic hydrogen fed was recovered as diborane.
uct methyl borate, as is disclosed in Huff and Schechter,
The total yield of dimethoxyborane based on hydridic
Ser. No. 510,527, ?lled May 23, 1955, and now aban
doned, of common ownership with this application. 55 hydrogen was 96.4% and the total yield of dimethoxy
borane and diborane was 97.82%. The 2.18% loss was
Thus, if it is preferred to produce diborane directly
distributed between losses to hydrogen gas, caused by
from the reactor column, the recti?cation section may
reaction with traces of hydrolytic impurities in the sys
be run at total liquid re?ux, so that it functions as a dis
proportionation reactor, and the non-condensible di
tem, and to unreacted material containing hydridic hy
drogen in the bottoms product. Samples of the liquid
borane formed is vented from the condenser.
60 on each plate in the stripping section were taken and
Reboiler secti0n.—In a conventional reboiler the liquid
analyzed for total active hydrogen content. This showed
that the reaction was essentially complete at only 8 plates
below the feed plate, which is equivalent to a nominal
material not vaporized is discharged as a liquid bottoms 65 residence time of approximately 5 minutes.
According to the provisions of the patent statutes, we
product. The liquid e?iuent from the stripping section
have
explained the principle and mode of practicing my
in this column reactor is a solution of sodium tetra
invention, have described what we consider to be its best
methoxyborane-rnethyl borate solvate. When the liquid
embodiments. However, we wish to have it understood
is passed through a conventional reboiler the increased
temperature and increased concentration of the white 70 that, within the scope of the appended claims, the inven.—
e?luent from the bottom of the column is passed through
a reboiler, which vaporizes a portion of the material which
is returned to the bottom plate of the column, and the
oil cause both a decrease in solubility of the solvate and
tion maybe practiced otherwise than'as speci?cally de
breaking of the solvate to form insoluble sodium tetra
methoxyborate. When this‘ occurs, the "solids tend to
scribed.
cake out on the boiler tubes, resulting in a lower heat
We claim:
1. A method of preparing dimethoxyborane that com
transfer coe?icient through the boiler tubes and eventual 75 prises the steps of contacting a slurry of sodium hydride
8,028,221
8
v
me a saturated hydrocarbon with excess methyl borate
150 pounds of methyl borate for each pound of sodium
to form a reaction mixture, maintaining the concentra
tion of dimethoxyborane in said reaction mixture at less
hydride fed, the column re?ux forming a reaction mix
ture with the sodium hydride slurry, said reaction mixture
than about 1 part dimethoxyborane to 100 parts of methyl
containing su?icient methyl borate to dissolve the result
borate by continuously vaporizingdimethoxyborane from
the reaction mixture, and recovering the dimethoxyborane.
ing sodium tetramethoxyborate solvate, continuously re
moving a bottoms product consisting essentially of sodium
tetramethoxyborate, methyl borate and hydrocarbon, and
continuously recovering an overhead product containing
dimethoxyborane.
8. A method according to claim 7 in which the methyl,
10
. 2. A method of preparing dimethoxyborane that com
prises the steps of contacting a slurry of sodium hydride
and a saturated hydrocarbon with excess methyl borate
to form a reaction mixture, said reaction mixture contain
ing less than about 25 parts hydrocarbon to 100 parts
borate vapor is supplied from a still reboiler section
comprising a recirculation loop and a boiler, maintain
of methyl borate, maintaining the concentration of dimeth
dimethoxyborane to 100 parts methyl borate by continu
ing the boiler temperature such that the boiler liquid ef
?uent contains about 50% hydrocarbon, feeding the col
‘ ously vaporizing dimethoxyborane from the reaction mix
15 umn re?ux to the circulation loop upstream of said boil
oxyborane in said reaction mixture at less than 1 part
er, and returning the methyl borate vapor boiler e?luent
ture, and recovering the dimethoxyborane.
3. A method of preparing dimethoxyborane that com
prises the steps of continuously contacting a slurry of
sodium hydride and a saturated hydrocarbon with liquid
to the bottom. of the distillation column.
9. A method of preparing dimethoxyborane that com
prises continuously contacting a slurry of sodium hydride
methyl borate to form a reaction mixture, maintaining 20 and a saturated hydrocarbon with methyl borate in the
central portion of a distillation column operating at par
the concentration of dimethoxyborane in said reaction
tial re?ux, boiling up through the column at least about
mixture at less than about 1 part dimethoxyborane to
150 pounds of methyl borate for each pound of sodium
100 parts of methyl borate by countercurrently contact
hydride fed, the column re?ux forming ‘a reaction mix
ing said reaction mixture with methyl borate vapor, using
at least about 150 pounds of methyl borate vapor for 25 ture with the sodium hydride slurry, said reaction mix
ture containing less than about 25 parts of hydrocarbon
each pound of sodium hydride, and recovering the resul
to 100 parts of methyl borate, said reaction mixture con
tant vapor product containing dimethoxyborane.
taining su?icient methyl borate to dissolve the resulting
4. A method of preparing dimethoxyborane that com
sodium tetramethoxyborate solvate, continuously remov
prises the steps of continuously contacting a slurry of
sodium hydride and a saturated hydrocarbon with liquid 30 ing a bottoms product consisting essentially of sodium
tetramethoxyborate, methyl borate and hydrocarbon, and
methyl borate to form a reaction mixture, countercur
continuously recovering an overhead product containing
rently contacting said reaction mixture with methyl borate
dimethoxyborane.
vapor, using at least about 150 pounds of methyl borate
10. A method according to claim 9 in which the hy
vapor for each pound of sodium hydride, distilling the
resultant vapor product, recovering the overhead prod 35 drocarbon is a white oil.
11. A method of preparing diborane that comprises
uct containing dimethoxyborane, and returning the bot
continuously contacting a slurry of sodium hydride and
toms product to supply liquid methyl borate to the re
a saturated hydrocarbon in the central portion of a dis
action mixture.
5. A method of preparing dimethoxyborane that com
tillation column operating at total re?ux, boiling up
prises the steps of continuously contacting a slurry of 40 through the column at least 150 pounds of methyl borate
for each pound of sodium hydride, the column re?ux
sodium hydride and a saturated hydrocarbon with liquid
forming a reaction mixture with the sodium hydride
slurry, said reaction phase containing su?icient methyl
mixture containing less than about 25 parts of hydrocar
borate to dissolve the resulting sodium'tetramethoxy
bon for each 100 parts of methyl borate, countercurrently
contacting said reaction mixture with methyl borate va 45 borate solvate, continuously removing a bottoms prod
uct consisting essentially of sodium tetramethoxyborate,
por, using at least about 150 pounds of methyl borate
methyl borate, and mineral oil, and continuously dis
vapor for each pound of sodium hydride, distilling the
charging overhead the resultant non-condensable di
resultant vapor product, recovering the overhead prod
borane.
uct containing dimethoxyborane, and returning the bot-_
12. A method of preparing at least one borane from
toms product to supply liquid methyl borate to the re 50
the group consisting of dimethoxyborane and diborane
action mixture.
that comprises continuously contacting a slurry of sodium
6. A method of preparing dimethoxyborane that com
hydride and a saturated hydrocarbon with at least 150
prises continuously contacting a slurry of sodium hydride
pounds of methyl borate for each pound of sodium hy
and a saturated hydrocarbon with methyl borate in the
central portion of a distillation column operating at par 55 dride in the central portion of a distillation column, con
tinuously removing a bottoms product consisting essené
tial re?ux, continuously removing a bottoms product con
tially
of sodium tetramethoxyborate, methyl borate, and
sisting essentially of sodium tetramethoxyborate, methyl
hydrocarbon, and continuously recovering an overhead
methyl borate to form a reaction mixture, said reaction
borate, and hydrocarbon, and continuously recovering
an overhead product containing dimethoxyborane.
r
7. A method of preparing dimethoxyborane that com 60
prises continuously contacting a slurry of sodium hydride
and a saturated hydrocarbon with methyl borate in the
central portion of a distillation column operating at par
tial re?ux, boiling up through the column at least about 65
product containing the borane.
References Cited in the ?le of this patent
UNITED STATES PATENTS
2,461,661
2,534,533
Schlesinger et al. ______ -_ Feb. 15, 1949
I
Schlesinger et a1. _..__-..- Dec. 19, 1950
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