Note: Descriptions are shown in the official language in which they were submitted.
.~ ~067061
The present invention relates to a process for
separating epoxidation and hydroxylation catalysts from residues
from distillation. In a particular aspect thereof the present
invention relates to a process for recovering catalysts in the
epoxidation and hydroxylation of olefinic compounds with hydrogen
peroxide.
It is known that compounds of particular transition
elements are very effective catalysts in the epoxidation and
hydroxylation of olefinic compounds. Epoxidation and hydroxyla-
tion catalysts are primarily compounds of transition metals suchas zirconium, vanadium, columbium, tantalum, chromium, molybdenum,
tungsten, rhenium, uranium. These catalysts are used frequently
in the form of their salts but also in the form of organo-metallic
compounds. When the catalysts are used as organic compounds,
then they are used in the presence of basic components such as
lithium, sodium, potassium, rubidium, cesium, magnesium, calcium,
strontium or barium (see, for example, US Patent 3,351,635).
Heteropoly acids of elements of group VI of the periodic system
are also used (see US Patent 2,754,325). Organic peroxides and
hydrogen peroxides may be used as oxidizing agents.
In the processes for the catalytic epoxidation and
hydroxylation of olefinic compounds residues from distillation
are obtained which contain high-boiling, primarily polymeric
organic compounds as well as the catalyst compounds. These high-
boiling organic compounds cannot be used industrially and must
therefore be destroyed. Since the above catalysts are compounds
which contain valuable metals, the recovery of these metals is
very important. The combustion of the organic components of the
residues from distillation in the presence of catalysts in a
standard combustion furnace causes considerable difficulties,
which render such combustion virtually impossible (see laid-
open German Specification 2,252,938). Therefore, according to
the process of this la~d-open German specification the catalyst-
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containing residue from distillation is evaporated to dryness
in an evaporator with an oscillating blade, first, to obtain
the major portion of the organic components in a combustible
form and, second, to be able to separate most of the catalyst.
An evaporator constructed in this manner is subjected to
relatively great wear so that foreign metals get into the dischar-
ged solids and may thus be extracted with the separated catalyst.
These foreign metals are so concentrated in the end that the
catalyst can no longer be recycled. Moreover the discharged
solids also contain carbonized material, some of which is soluble,
for example, with water or organic solvents, in the extraction
of the catalyst and can cause problems in the subsequent reuse
of the catalyst.
The present invention provides for the complete recovery
of the metals from the catalyst compounds and the destruction of
the high-boiling and primarily polymeric compounds contained in
the residues from distillation in the catalytic epoxidation and
hydroxylation of olefinic compounds in a manner which has a
favourable effect on the environment.
According to the present invention the residue which is
obtained upon distilling off the epoxidation or hydroxylation
product and contains the high-boiling organic compounds and the
catalyst is passed into an inert material, which is in a
fluidized motion. The organic components contained in the resi-
due from distillation are burned with oxygen or oxygen-containing
gases and the metallic compounds of the catalyst are deposited
on the fluidized material or in the solids separators connected
to the outlet side of the reactor
According to the present invention therefore there is
provided a process for the separation of a catalyst employed
in the epoxidation or hydroxylation of an olefinic compound with
a peroxy compound in a reactor,distilling off the epoxidized or
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hydroxylated product and separation of the catalyst from the
distillation residue containing said catalyst and said high
boiling organic compounds, said catalyst being a compound of a
transition metal, the improvement comprising introducing the
distillation residue into a bed of fluidized inert solid particles,
burning the organic compounds of said distillation residue
with an oxygen containing gas while in contact with said fluidized
particles and separating fluidized particles containing a compound
of the metal employed in the catalyst from the waste gas of said
burning.
It is known that compounds of specific transition metals
are particularly effective catalysts in the epoxidation and hydro-
xylation of water-soluble olefinic compounds, for example, of
allyl alcohol, with hydrogen peroxide. Compounds of vanadium,
molybdenum and tungsten have been found to be suitable. Tungsten
compounds are particularly preferred for the epoxidation. Since
due to its high price the catalyst is a principal economic
factor in the process, there exist, particularly for tungsten,
a number of processes for recovering the tungsten - containing
catalyst. Thus, in the epoxidation or hydroxylation of allyl
alcohol to glycide or glycerin aqueous reaction solutions are
obtained from which the catalyst must be recovered.
According to the process of the US Patent No. 2 869
986 tungstic acid can be absorbed from acid solutions (pH<3) on
aluminium oxide. The absorbed tungstic acid can be recovered with
a solution of caustic soda and the aluminium oxide is regenerated
at the same time. However, the tungstic acid must in turn be
isolated from the regenative solution by precipitating with strong
acids (HNO3, HCl, H2SO4). In total this means a relatively large
expanditure for the recovery of the catalyst.
Ion exchangers can also be used instead of aluminium
oxide (see German Patent No 1 114 468). The tungstic acid is
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precipitated from the eluates with strong acids.
After the hydroxylation of the allyl alcohol the remov-
al of tungstic acid from the glycerin solution can be carried out
by adding calcium chloride to the glycerin solution the tungstic
acid dissolved in said solution is precipitated and separated
while the insoluble calcium tungstate is formed. For reuse as
tungstic acid reprecipitation with acids must also be carried out
(see German Patent No 1 230 000). However, by precipitating the
tungstic acid with strong acids waste waters containing substan-
tial amounts of salts are obtained.
All the above processes mentioned hereinbefore have theadditional disadvantage that the catalyst cannot be recovered
quantitatively.
Accordingly the present invention relates to a process
in which the catalyst, i.e., the usual alkali metal vanadates,
alkali metal molybdates and alkali metal tungstates (see Wiberg,
Anorganische Chemie, 24th and 25th edition, page 476 and 477),
can be reused without prior precipitation.
According to a particularly preferred aspect of the
invention the residue which is obtained upon distilling off the
epoxidation or hydroxylation product and which contains the cata-
lyst is passed into an inert material, which is in a fluidized
motion. The organic components contained in the residue from
distillation are burned with oxygen or with oxygen-containing
gases, whereupon the catalyst compound deposited on the fluidized
inert material, together with the proportion of catalyst compound
obtained in the solids separator connected the outlet side of the
reactor, is dlssolved out with water and the solution obtained
is used again for the epoxidation or hydroxylation. The catalyst
thus obtained from the residue from distillation can be reused
directly for the epoxidation or hydroxylation, as mentioned above
According to said preferred aspect of the present
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invention therefore there is provided a process for the recovery
of a catalyst employed in the epoxidation or hydroxylation of
a water soluble olefinic compound with hydrogen peroxide in a
reactor, distilling off the epoxidized or hydroxylated product
and separation of the catalyst from the distillation residue,
containing said catalyst, and high boiling organic compounds,
said catalyst being a water soluble compound of vanadium, molyb-
denum or tungsten,the improvement comprising introducing the
distillation residue into a bed of fluidized inert, water insolu-
ble solid particles, burning the organic components of said
distillation residue with an oxygen containing gas at a temper-
ature below the melting point of said catalyst while in contact
with said fluidized particles, removing a portion of said inert
solid particles containing said water soluble compound from the
burning zone, dissolving said water soluble catalyst compoundin
water and separating the aqueous solution from said inert solid
particles.
The alkali metal salts mentioned hereinbefore are the
sodium, potassium and lithium salts, primarily the sodium salts.
Any hard, chemically inert material can be used as flu-
idized material, such as, quartz sand, silicon carbide, highly
burned alumina for example, corundum and highly burned clay
for example, chamotte. The particle size is suitably from 0.1 to
5 mm, preferably from 0.5 to 1.5 mm.
A reactor of any conventional construction can be used
as the fluidization reactor. It may be constructed such that
continuous or discontinuous exchange of the fluidized material
in the reactor, i.e., the fluidized material coated with the
catalyst, with fresh fluidized material may be carried out
by means of two fundamentally different methods. According to the
first method, a specific amount of the fluidized material coated
with the catalyst is continuously or discontinuously discharged
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from the lower portionof the reactor. Approximately at the same
time the same amount of fresh fluidized material is continuously
or discontinuously fed to the fluidization reactor. According
to the second method, the fluidization reactor is provided
with an overflow and after the continuous and discontinuous
addition of fresh fluidized material the same amount of fluidized
material, the major portion of which is coated with the catalyst,
flows off continuously or discontinuously by way of the overflow,
for example, into a cyclone connected at the outlet end.
Apart from oxygen, oxygen-containing gases, primarily
air, are used. The amount of gas used must be so adjusted that
the fluidization of the entire particle spectrum of fluidized
material is assured.
If the combustion of the organic components of the
residue from distillation in the fluidization reactor is to be
complete, i.e., so that the waste gas is almost free from carbon
monoxide, whic~ is necessary for protecting the environment, then
the maximum amount of product which can be put through is
determined by the amount of gas applied. The gas can be preheated
by hot gases if required.
The usual kind of apparatus, such as gravity separa-
tors or cyclone air separators or dust separators are used
as solids separators.
The reactor temperatures are suitably between 500 and
approximately 1000C or between 500C and the melting points
of the corresponding catalyst-containing compounds when these
melting points are belo~ 1000C.
The reactor temperatures are controlled and kept
constant with conventional coolers and coolants. The excess
h~at of combustion which is removed by the coolant can be used
for producing energy, for example, for generating steam or for
operating a turbine. The excess heat of combustion is the
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residual heat upon drawing off the amount of heat required for
heating the reactants to reaction temperature and upon removal
of the amount of heat radiated by the reactor. For example, the
reactor wall and cooling pipes or cooling plates installed in the
fluidization reactor can be used as coolers. For example, the
known nitrite/nitrate melts can be used as coolants.
Upon leaving the reactor the waste gas containing the
solid particles is passed to a solids separator, preferably a
cyclone, where the major portion of the entrained solid particles
is separated. If required, the waste gas can subsequently be
subjected to a further purification by separating the fine dust
which was not separated in the solids separator, particle sizes
lower than approximately 10 to 30 ~ for example, by means of
filters or by washing with water.
The residue from distillation which is to be used is
recovered in a known manner, for example, with the aid of
circulation evaporators or falling film evaporators.
The metal compounds of the catalysts are obtained
almost entirely on the fluidized mateiral and in the solids
separator. The manner in which the recovered metal compounds
are converted into a fresh catalyst depends on the kind of
catalysts to be reused. The examples providea number of possi-
bilities.
In the particularly preferred aspect of the present
invention the discharged fluidized material and the material
separated in the solids separator are combined and treated with
water or with the aqueous solution from the gas washer. The
amount is preferably adjusted to the desired concentration of
the solution to be reused. The recovered catalyst solution can
be reused immediately.
The residue from distillation can be recovered in the
usual manner, for example, with the aid of circulation evaporators
~06706~
or falling-film evaporators. The process is applicable to the
epoxidation and hydroxylation of water-soluble olefinic compounds,
such allyl alcohol, crotyl alcohol, methallyl alcohol or
cyclopentenol-3.
The present invention will be further illustrated by
way of the accompanying drawings in which
Fig. 1 is a flow sheet of the process according to one
embodiment of the present invention; and
Fig. la is a flow sheet according to the particularly
preferred aspect of the present invention.
When the catalyst-containing residue from the distil-
lation is not pumpable, then it can be converted into a pumpable
state either by heating or by diluting with water. During the
dilution heating can also be applied.
Referring to Fig. 1 the reactor 6 is heated to the
desired temperature, suitably, to least 500C. which can be
achieved with the aid of a starting heater, the fluidization
reactor 6 being heated to the temperature required for initiating
the combustion reaction either directly by the hot exhaust gases
or by the air heated by heat exchange in the starting heater.
After the start of the combustion reaction in the fluidization
reactor 6 excess heat of reaction is removed by a cooling system.
The residue from distillation is then pumped by way
of pipe 1 into the lower portion of the reactor 6. At the same
time air is blown through by way of pipe 2 in order to avoid
possible clogging. The principal amount of the air required for
both the combustion and the fluidization is supplied by way of
pipe 3 and preheated if required by way of the heat exchanger 12.
A salt bath 5, which, for example, contains conventional
nitrite-nitrate melts, is preferalby used for heating the fluidiz-
ation reactor 6. Upon putting the reactor into operation the
salt bath serves for transmitting the heat. The excess heat of
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cOmbustion can be used for producing energy, as for example, for
generating steam, by means of a heat exchanger 19 mounted in
the salt bath. The fluidized material is added through pipe 7
and removed together with the metallic compounds of the catalysts
through pipe 4.
The fluidized material which contains the metallic
compounds is passed to a tank 14, where it is washed with water,
liquors, acids or organic solvents such as aliphatic alcohols,
if a recovery is intended. The fluidized material is then sep-
arated from the solution, dried and returned to the fluidization
reactor through pipe 17.
The exhaust air, from the reactor 6 which contains only
small amounts of carbon monoxide for environmental reasons, is
passed through pipe 8 into the cyclone 9, where entrained solids
are separated. These solids are also passed through line 10
to the washing tank 14. The outgoing air, which is still hot,
serves for heating the fresh air 12 and is subjected to purifi-
cation in order to separate the fine dust by means of a filter
or by ~ashing (13).
Referring to Fig. la the residue is then pumped
through pipe 1' into the lower portion of the reactor 6'. At
the same time air is blown through pipe 2' in order to avoid
possible clogging. The mixture is dosed into the reactor
through pipe 3'. The principal amount of the air required for
both the combustion and the fluidization is supplied through
pipe 4' and preheated when required.
The reactor 6' is heated to the desired temperature
suitably at least 500C.which can be achieved with the aid of
a starting heater the fluidization reactor 6' being heated to
the temperature required for initiating the combustion reaction
either directly by the hot exhaust gases or by the air heated
by heat exchange in the starting heater. After the start of the
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combustion reaction in the fluidization reactor 6' excess
heat of reaction is removed by a cooling system. A salt bath,
which, for example, contains the conventional nitrite-nitrate
melts, is preferably used for heating the fluidization reactor 6'.
When the salt bath is used for cooling on putting the reactor
6' into operation it removes the heat set free and thus keeps
the temperature on a constant level. Fluidized material is
added through the pipe 7' and removed together with the catalyst,
through pipe 5'. The catalyst-containing fluidized material
passes from pipe 5 into a tank 13', where it is leached with
water supplied through pipe 14'. The aqueous catalyst solution
is separated from the fluidized material and may be fed directly
to the epoxidation reaction through pipe 15'. The dried fluid-
ized material is returned to the fluidization reactor through
pipe 16'.
The exhaust air, from the reactor 6' which contains
only small amounts of carbon monoxide for environmental reasons,
is passed through pipe 8' into the cyclone 9', where entrained
solids are separated. These separated solids are also passed
through line lO' to the washing tank 13' and freed from the
catalyst. The exhaust air is then subjected to a further
purification, for example, by means of a filter device 12'
by washing.
An advance in the art of the broad process according
to the invention lies in that the entire carbon-containing
proportion of the residue from distillation in the presence of
metal-containing catalysts is burned in a single stage. The
metallic compounds of the catalysts which are thus obtained
are not contaminated either by organic by-products or by foreign
ions.
A significant advance in the art of the preferred
aspect of the process according to the invention is that the
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catalyst is recovered quantitatively. Moreover it is recovered
in such a form that it can be reused. The yields obtained with
the recovered catalyst are practically the same as those obtained
with a fresh catalyst. Moreover, the process has a favourable
effect on the environment due to the absence of salt-containing
waste waters and since there are no problems with outgoing air.
The present invention will be further illustrated
by way of the ~ollowing Examples.
Example 1
The process was carried out continuously over a
period of five days in the epoxidation or hydroxylation of allyl
alcohol with aqueous hydrogen peroxide to glycide or glycerin in
the presence of sodium hydrogen tungstate a residue from
distillation is obtained which consists of 20% by weight of the
catalyst, the remainder being glycerin or polyglycerin. This
residue from distillation is mixed with water in the ratio of 4
to 8 : 1 (residue from distillation to water) and heated to a
temperature of 70 to 80C. The mixture, which now is pumpable,
is fed to the bottom of the reactor (approximately 2 kg per hour)
while at the same time approximately 8 cu m of air are blown into
the reactor per hour. By way of a flow tray further 16 cu m of
air, preheated to approximately 350C, are supplied per hour.
The fluidization reactor (height 2400 mm, diameter
150 mm, Cr-Ni steel~ is surrounded by a salt bath (nitrite-
nitrate melt) which serves first for heating and later, when
the reactor is an operation, as a heat acceptor. The excess
heat of combustion is utilized for generating steam, by means
of a heat exchanger installed in the salt bath. Quartz sand
having a particle size of 0.5 to 1.5 mm is used as fluidized
material.
The reactor is heated to 540C with the aid of the
salt bath. After the start of the combustion the temperatures
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in the reactor are from 580 to 650C. The combustion is complete
so that the waste gas contains only small amounts of carbon
monoxide (approximately 0.1% by ~olume).
Every hour approximately 2 to 3 litres of sand
are replaced. The discharged sand, which contains the tungstate,
is leached with the corresponding amount of water so that an
approximately 4 to 8% by weight tungstate solution is obtained.
The sand washed out is separated, dried and returned to the
reactor.
The sand and tungstate particles entrained by the waste
gas are separated in a cyclone and also washed out. The exhaust
air, which is still hot, is used in a heat exchanger in order
to heat the fresh air required for the combustion. For further
purification, the cooled waste gases are then passed over a
washer. The wash water obtained which contains small amounts
of tungstate is used for diluting the residue from distillation.
The aqueous tungstate solution can be used directly
for the epoxidation of allyl alcohol with hydrogen peroxide.
158 g (273 moles) of allyl alcohol, 200 g of water
33 g of the aqueous sodium-tungstate solution recovered
(with 4.9% of tungstic acid) is put into a round-bottomed flask
and heated to 45C. 97g (1 mole) of a 35.6~ hydrogen peroxide
are added dropwise within 10 minutes with stirring. After three
hours the hydrogen-peroxide reaction rate is quantitative. The
yield of the glycide reaction is 85% of the theoretical yield,
relative to hydrogen peroxide.
Example 2 tComparison Example using fresh tungstate solution)
158 g of allyl alcohol and 200 g of water are put
into a l-litre three-necked bottle fitted with stirrer, dropping
funnel, thermometer and reflux condenser. 1.5 g of NaHWO3 are
dissolved in 33 ml of water and added. The solution is heated
to 45C. While stirring, 97 g of a 35.6% hydrogen peroxide
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are added dropwise within 10 minutes. After three hours the
hydrogen peroxide reaction rate is quantitative. The yield
of the glycide reaction is 86% of the theoretical yield, relative
to hydrogen peroxide.
Example 3
Crotyl alcohol or methallyl alcohol may also be used
instead of the allyl alcohol usedinthe Examplesland 2. The
corresponding data are listed in Table 1. The conditions of the
reaction are the same as those in example l and 2.
~able 1
epoxide yield (%)
~_
fresh catalyst recovered catalyst epoxide
obtained
crotyl alcohol 83.2 82.5 2,3-epoxy
butanol-l
methallyl alcohol 55.2 54.7 1,2-epoxy-2-
methyl pro-
panol-3
_ _
NaHMoO4 is used instead of NaHWOin amanner analogousto
that of Example l and2. 58 g (l mole) of allyl alcohol and 3 g
of NaHMoO4, dissolved in 74 ml of H20, are put into a three-
necked bottle fitted with stirrer, inside thermometer, cooler
and dropping funnel and heated to 60C. 102 g (1.1 moles) of
a 36.7% H2O2 are added dropwise over one hour. After four
hours the H2O2 reaction rate is quantitative. The yield of
glycerine is 70%. When using the recovered Mo catalyst
analogously to Example 1 the yield of glycerine was 67%.
Example 5
Vanadium (Na2HVO4+NaH2VO4) was used instead of the
tungsten used in Examples l and 2. The amounts were the same.
The reaction temperature was 60C and the reaction time 24 hours.
10670~;1
The yield of glycerine relative to H2O2 applied was 20% with the
fresh catalyst and 22% with the recovered catalyst.
The concentration of the hydrogen peroxide for the
epoxidation or hydroxylation is not critical. Commercial
concentrations (in % by weight) are preferably used.
Example 6
In the epoxidation of cyclohexene with cumene hydrogen
peroxide in the presence of vandyl acetyl acetonate to 1,2-
epoxy cyclohexene a residue from distillation which contains the
vanadium compound is obtained. This residue from distillation is
burned in a manner analogous to that of Example 1.
The vanadium pentoxide thus formed is deposited on
the fluidized material or in the cyclone. The vandium pentoxide
is separated from the fluidized material by means of liquors.
From these aqueous vanadate solutions the vanadium or its
compounds can be recovered by means of conventional methods. By
heating the vanadium-pentoxide-containing fluidized material
with an alcohol, for example, propanol, the vanadium pentoxide
can be converted into the corresponding vanadic ester.
Example 7
In the epoxidation of propylene with tertiary butyl
peroxide in the presence of columbium phthalate to propylene
oxide a residue from distillation which contains the columbium
compound is obtained. This residue from distillation is burned
in amanner analogous to that of Example 1.
The columbium pentoxide thus formed is deposited on the
fluidized material or in the cyclone. The columbium pentoxide
is separated from the fluidized material by means of liquors.
These wash solutions are processed by means of conventional methods.
Example 8
In the epoxidation or hydroxylation of allyl alcohol
with aqueous hydrogen peroxide to glycide or glycerin, calcium
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tungstate, which also is obtained in the residue from distillation,
can be used instead of sodium hydrogen tungstate (Example 1).
This residue from distillation is burned in a manner similar
to that of Example 1. The calcium tungstate is deposited on the
fluidized material or in the cyclone and can be recovered there-
from.
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