Note: Descriptions are shown in the official language in which they were submitted.
7935
PROCESS
This invention relates to a hydroformylation process,
more par-ticularly a process for the hydroformyla-tion of an
alkene-l -to a corresponding aldehyde product containing
5. one more carbon atom than the starting olefin.
Hydroformylation is a well-known ~rocess involving
reaction of a mixture of hydrogen and carbon monoxide with
the olefinic group of a terminal olefin, Depending on the
choice of catalyst, the resulting product may be aldehydic
10. or alcoholic in nature. Although -the catalysts originally
proposed were based on cobalt~ more recently there have
been proposed catalysts based on rhodium. Such rhodium
based catalysts have the advantage that the pressure of
operation is much lower -than the pressures necessary when
15. using cobalt catalysts and that produc-t recovery is much
- simpler than is the case when using a cobal-t catalys-t. In
addition~ when utilising propylene or a higher -terminal
olefin to produce butyraldehyde or the correspondlng higher
aldehyde, the rhodium catalysts generally permit,-the attain-
20. ment of higher n~/iso-product ratios than can be achieved
using cobalt catalysts. Since the n-aldehyde usually has
a higher value -than the iso-aldehyde, this adds to the
economic attractions of the rhodium-catalysed processes.
Commercial plants have been built to manufacture
25. propionaldehyde from ethylene and butyraldehyde from
propylene utilising a low pressure process involving a
rhodium catalyst. An outline of the process is given in
"Chemical Engineering", December 5, 1977, pages 110 to 115.
The process is also described in West German Offenleg~gs-
30. schrift 2715685. Further details can be fo~d, for
~L2~:;32.
example, in United States Patent Speciflcation No. 3527809
and in British Patent Speciflcation No. 1338237.
As described in the afore-mentioned "Chemical
Engineerlng~l artlcle the gas~recycle system adopted in the
5. original two plants built for propionaldehyde and butyralde-
hyde production respectively at Texas City, Texas, U.S.A.
and at Ponce, Puerto Rico, involves removal of the product
as vapour in an overhead strea~ taken from the hydro-
formylation reactor. After air cooling -to condense
lO. aldehyde product the unreacted gases, including unreacted
olefinJ are separated from the condensate,compressed and
recycled to the hydroformylation reactor. In the butyralde-
hyde plant the liquid condensate stream con-tains appreciable
amounts of dissolved gases, mainly propylene and propane;
15. these are distilled out in a product s-tripping column and
are recycled as gas to the hydroformylation reactor.
Whilst this gas recycle process is eminently suitable
for use in the production of propionaldehyde from ethylene
or of butyraldehyde from propylene by hydro~ormyla-tion, the
20. lesser volatility of the alclehyde product in -the case of
higher olefins, such as butene-l, requires that a corres-
pondingly higher gas recycle rate must be used in order to
remove the aldehyde from the reactor at essentially the
same rate as that at which it is formed in order to
25~ prevent an increase in volume of the liquid phase in the
reactor and an undesirable increase in the proportion of
polymeric aldehyde condensation products therein. This in
turn requires the use of large recycle gas compressors
which are extremely expensive items of equipment and
3.
!~ contr~bute significantly to the cost~ o~ in~talllng and
operating the plant.
It would be desirable to provide a process ~or the
hydroformylation of alkenes, particularly butene-l and
5. higher alkenes, whereby the convenient method of product
recovery afforded by gas recycle is coupled with use o~ a
relatively small gas recycle compressor.
It is accordingly an object of the invention to
provide a process ~hereby aldehydes can be efficiently and
10. economically produced by hydroformylation of a terminal
olefin in the presence of a rhodium complex catalyst
utilising a gas recycle method and a gas recycle compressor
that is as s~all as practicable.
According to the present invention there is described
15. a process for the production of an aldehyde by hydroformy-
lation of an alkene in the presence of a rhodium complex
catalyst comprising: . .
providing a hydroformylation zone containing a liquid
charge comprising (aj a rhodium complex catalyst;wherein
20. rhodium is in complex combination with carbon monoxide and
a triorganophosphine, (b) excess triorganophosphine, (c)
liquid aldehyde product, and (d) polymerlc aldehyde
condensation products;
feeding liquid reactant alkene to the hydroformylation
25. zone;
supplying make up hydrogen and carbon monoxide to the
hydroformylation zone;
maintaining in the hydroformylation zone temperature
and pressure conditions effective for the hydroformylation
2~63
of the reactant alkene;
recovering from the hydroformylation zo~e an
overhead vapour stream containing reactant alkene, hydrogen,
carbon monoxide, alkene hydrogenation product(s), aldehyde
product and higher boiling aldehyde condensation producks
containing hydroxyl group~;
subjecting the vapour stream to condensation
conditions to condense therefrom condensible components
comprising unreacted alkene, aldehyde product, and higher
boiling aldehyde condensation products containing hydroxyl ~roups;
recycling non-condensed componen-~s of the
vapour stream comprising hydrogen and carbon monoxide to
the hydro~ormylation zone;
recovering aldehyde product; and
- 1, recycling unreacted alkene in liquid form to
the hydroformylation zone.
The inven-tion is applicable to any alkene capable
of undergoing hydroformylation -to gi~e an aldehyde that is
relatively volatile~ There is, however, little advantage
2~ in utilising the process in the hydroformylation of
ethylene since e~pensive refrigeration is required in order
to liquefy the reactant ethylene and to condense unreacted
; ethylene ~rom the overhead vapour stream. The process
can be applied in the hydroformylation of propylene but
experience has shown that the gas recycle process of West
German Offenlegungsschrift 2715685 is commercially
satis~actory. It is thus preferred to uti3ise C~ or higher
alkenes in the process of the invention. For practical
. .~
~''
2~
- 5 ~
purposes octene-l is probably the highes-t olefin -that
can be utilised satisfactorily in the process of the
invention. Preferably the olefin comprises butene-l,
pentene-l, hexene-l, 2-methyl-butene-1, 3-methyl-bu-tene-
1, 2-methyl-pentene-1, 3-methyl-pentene-1, 4-methyl--
pentene-l or 2-ethyl-butene-1.
Although the process of the inven-tion can be
practised with an essentially pure alkene-l feedstock,
mixed hydrocarbon fractions containing, in addition to
terminal olefins, internal olefins and/or alkanes can
also be utillsed. The proportion of alkene-l in such
a rnixed hydrocarbon fraction may vary within wide limits,
for example from about 10 mole /0 or up to about 90 mole
% alkene-l or more. Typically~ however, such a mixed
hydrocarbon frac-tion comprises from about 20 mole %
up to about 80 mole % of alkene-l.
The alkene-l containing feedstock is
desirably substantially free from inhibi-tors, such
as dienes (e.g. butadiene), and from catalys-t poisons,
such as sulphurous cornpounds and chlorine compounds.
A satisfac-tory procedure for removal of dienes, such as
butadiene, comprises hydrofining. Higher sulphurous
impurities can be removed to an acceptable level by
contact of the feedstock with alurnina followed by
zinc oxide. Copper-impregnated carbon can be used to
reduce -the level of chlorinated impurities to a
sufficiently low level.
119~Z~G3
6 --
The ratio of hydrogen to carbon monoxide
in the make up stream preferably lies in the region
of l:l by volume. As i6 well known such H2/C0
mix-tures can be produced by conventional syn-thesis gas
plants using hydrocarbon reforming -techniques or partial
oxidation of hydrocarbons. Experience has shown -that
metal carbonyls, sulphur compounds and chlorine-con-tain-
ing compounds are undesirable components of the H2/C0
make up stream. Hence it is desirable to submit the
make up synthesis gas to purifica-tion for the removal
of these impurities.
Hydroformylation is effected in -the liquid
reaction medium in the presence of a ca-talytically
effective amount of the rhodium complex catalyst.
Typically the rhodium complex catalyst concentra-tion
ranges from about 20 parts per million~ calculated
as rhodium metal, up to about 1000 par-ts per million
or more. There is no advantage general~y in using
concentrations of rhodium in excess of abou-t 500 parts
per million and usually, on the grounds of expense
alone, it will be preferred to opera-te at a rhodium
complex catalyst concentration of not more than about
~00 parts per million, calculated as rhodium metal.
Typical operating conditions utilise rhodium complex
catalyst concentrations of from about 50 par-ts per
million up to about 150 parts per million, calcula-ted
as rhodium metal.
~l~lZS~63
-- 7 --
The triorganophosphine ligand may be an
aliphatic phosphine, such as -tributyl phosphine, but
is preferably an aromatic phosphine, such as
triphenylphosphine, tri~ methoxyphenyl) phosphine,
trinaph-thylphosphine, tri-tolylphosphine, ~-N,N~
dimethylaminophenyl diphenylphosphine, and the likeO
The preferred ligand is triphenylphosphine. During
the course of hydroformylation utilising a rhodium com-
plex catalyst small quantities of alkyl diphenylphos-
phines may be formed by interaction between the
triphenylphosphine ligand and the reactant alkene in
the presence of the rhodium cornplex catalyst. Thus,
when hydroformylating propylene, for example, small
amounts of propyl diphenyl phosphine may be formed as
by-product.
The liquid reaction medium contains excess
triorganophosphine ligand. Preferably there are a-t
least about 2 moles o-~ free ligand for every gram
atom of rhodium present. Usually i-t will be preferred
to operate in the presence of at least 10 moles of
free ligand, typically in the presence of at least 75
moles, for example at least 100 moles, of free
triorganophosphine ligand per gram atom of rhodium.
The upper limit of the amount of free triorganophosphine
ligand is not particularly critical and is dictated
by the solubility thereof in the liquid reaction medium3
as well as by economic and commercial consideratlons.
h~J~3
-- 8 --
Although not so expensive as the rhodium inventory,
the capi-tal cost of the triphenylphosphine inventory
is no-t an insignificant factor. Under typical
operating conditions the free triorganophosphine ligand
constitutes from about 2% to about 25% by weight of
the liquid reaction medium.
The rhodium complex catalyst may be formed
by methods known in the art. For example, hydridocar-
bonyl tris(triphenylphosphine) rhodium (I) is a
crystalline solid and may be introduced into the
hydroformylation reactor as such. Alternatively a
catalyst precursor, such as rhodium carbonyl triphenyl-
phosphine acetylacetonate or rhodium dicarbonyl
acetylacetonate may be introduced into the reac-tor and
the active catalytic species, which has been postulated
to be hydridocarbonyl tris(triphenylphosphine) rhodium
(I), generated in situ under hydroformylation conditions
in the presence o~ excess triphenylphosphine. Other
suitable precursors include Rh203~ Rh~(C0)12 and
Rh6(CO)16.
The liquid reaction medium fur.ther includes
aldehyde product and polymeric aldehyde condensation
products. The nature of such polymeric condensation
products (e.g. dimers, trimers, and te-tramers) and a
postula-ted mechanism for their formation are discussed
in British Patent Specification No. 1338237
~s,
'~
3~3
.. ~.
g
The ratio of aldehyde to pol~neric aldehyde
condensation products in the liquid reac-tion mixture
may vary within wide limits. Typically this ratio
lies in the range of from about 1:4 to about 4:1 by
weight, e.g. about 1:1 by weight.
In the hydroformylation zone conditions are
maintained which are effective for hydroformylation of
the reactant alkene. Typically the tempera-ture lies
in the range o~ from about 50C up to about 160C or
10 more. The temperature should be at least as high as
that required to effect hydroformylation but not so
high as to destroy the catalyst or to cause undesirable
isomerization of terminal olefins to non-terminal
olefins. Usually the temperature will lie in the
15 range of from about 70C to about 140C, e.g. in -the
range of from abou-t 90~C to about 130C.
The total pressure in the hydroformylation zone
will usually be about 50 kg/cm2 ab,solu-te or less and
is preferably less -than about 20 kg/cm absolute.
Typically the partial pressure at-tributable to the
olefin is less than abou' 4.0 kg/cm2 absolute and is
preferably less than about 1.5 kg/cm2 absolute. The
total partial pressure attrlbutable to hydrogen and
carbon monoxide is typically less than about 10 kg/cm2
absolute. Usually the carbon monoxide partial pressure
ranges from about 0.1 kg/cm2 absolute to about 1.5 kg/cm2
absolu-te whilst the hydrogen partlal pressure preferably
~2~3
~,~b -- L O
lies in the range of from about 1.5 kg/cm2 absolute
to about 7.5 kg/cm~ absolute.
The overhead vapour stream from the
hydroformylation zone is subjected to condensa-tion
conditions to condense therefrom condensible components
comprising unreacted alkene, aldehyde product, and
aldehyde condensation products. In one procedure
condensation is effected in a single stage so that
there is obtained a mixture of condensed alkene,
10 aldehyde product and aldehyde condensation products.
Condensation is generally effected by cooling the
vapour stream. Depending on the pressure of the
vapour stream cooling may be achieved by air cooling,
by external cooling agalnst cooling water, or by
15 refrigeration. The resulting condensed mixture may
then be distilled to separate unreacted alkene, which
appears overhead, from aldehyde product and aldehyde
condensation products, which appear as a bot-toms
produc-t. The resulting aldehyde product-rich bot-toms
20 product may then be further purified, e.g. by re-
distillation in order -to separate aldehydes from
aldehyde condensation products, and possibly also to
separate n-aldehyde from iso-aldehyde. The overhead
product from the first-mentioned distillation step is
cooled by air cooling, by external water cooling or
by refrigeration as appropriate, in order to condense
unreacted alkene for return to the hydroformylation
zone.
/
l~Z~63
In an alternative procedure the vap~ur stream
. . ,
from the hydroformylation zone is subjected -to a two
stage condensation procedure by cooling in two stages.
In the first stage an aldehyde-rich condensate is
- 5 obtained, containing also aldehyde condensation products,
whilst unreacted alkene(s) pass(es) on still in vapour
form to be condensed in the second stage. In this
case the aldehyde-rich condensate can be further
worked up, for example as described above by
distillation and re-distillation, whilst second
stage condensate containing most of the unreacted
alkene is cycled to the hydroformylation zone.
In the process of the invention non-
condensed components of the vapour stream from -the
hydroformylation zone are recycled to the hydroformy-
lation zone. It will usually be preferred to conduct
the process so -that the rate of recycle of such non-
condensed components -to the hydroformylation'zone is
at least sufficient to remove aldehyde produc-t in -the
vapour s-tream as fast as it is formed. Preferably a
gas cycle rate is chosen that is at least sufficient
to remove also aldehyde condensation products in the
vapour s-tream as fast as they are produced~ In this
way build up o~ uid in the hydroformylation zone
can be prevented. In operation, control of the
volume of liquid in the hydroformylation zone can be
achieved by appropriate choice of temperature, pressure
~Z~63
- 12 -
and gas recycle ra-te, and by recycle of one or more
of the condensed components o the vapour s-tream
(e,g. unreacted alkene, aldehyde product and/or
aldehyde condensation products) to the hydroformylation
zone.
To prevent build up in the system of inert
materials introduced with the reac-tan-ts or formed as
by-products in the process (e.g. alkene hydrogenation
product(sj)purge streams may be taken. Thus a purge
stream may be taken of -the non-condensed components
of the vapour stream in order to limit the quantity
of, for example, nitrogen in the reaction system.
In the process of the invention the hydroformylation
conditions may be chosen so that essentially only
terminal olefins are hydroformyla-ted whilst non-
terminal olefins pass unchanged through the hydroformy-
lation zone and hence behave as inert materials. Hence
it wiLl usually be desirable to purge also a part of
-the unreacted alkene-containing stream :in order to
limit the amount of non-terminal olefins, as well
as paraffin(s) formed as hydrogenation by-product(s),
in the system. If the alkene feed stream to the
plant is a mixed olefin feedstock, e.g. a mlxed 'ou-tenes
feedstock, a preenrichment column can be used in order
to separate by distillation an alkene-l rich overhead
fraction from a bottoms product containing olefins
that are lnert towards the rhodium complex hydroformy-
lation catalyst employed. In this case a par-t of the
unreacted alkene-containing stream can be returned
to this preenrichment column so that non-terminal
olefins and hydrogena-tion product(s) are purged as
part o~ -the bottoms product therefrom.
~ In order -that the invention may be clearly
understood and readily carried into effect a
preferred hydroformylation process according to the
invention will now be descrlbed by way of example
only, with reference to the accompanying drawing
which is a diagramma-tic flow sheet of a plant for
the production of _-valeraldehyde from a butene-l
containing feed stream and of a modi-fication -thereof~
Referring to the drawing a mixed C4
hydrocarbon liquid feed stream is passed-by line 1
to a pretreatment zone 2 in which it is ~reed from
light sulphurous impurities such as H2S, COS and
me-thyl mercaptan by passage in -turn through beds
of ac-tive A1203 and ZnO and also from chlorine- -
containing impurities by subsequent passage through
a bed of copper-impregnated carbon (Girdler G32J
catalyst, obtainable from Girdler Chemicals Inc., of
Louisville, Kentucky, United States of America). In
passing through -the bed of active A1~03 any COS
present is hydrolysed to H2S due to the presence o
.
2~3~3
traces of water in the feed stream; -the active A1203
bed also serves partially -to remove H2S and rne-thyl
mercaptan (CH~SH). The ZnO bed then removes any
remaining H2S and CH~SH. Particularly if the feed
stream con-tains traces of molecular oxygen (for
example by reason of a previous metal carbonyl removal
step) some conversion of methyl mercaptan to dimethyl
sulphide (CH3SCH3) may also occur.
The C4 hydrocarbon liquid feed stream
passes on through lines 3 and 4 to a hydroforrnylation
reactor 5~
Hydroformylation reactor 5 contains a
- catalytic a~ount of a rhodium-containing hydroformy-
lation catalyst comprising rhodiurn complexed with
carbon monoxide and triphenylphosphine dissolved in
a liquid phase containing, in addition to product
n-valeraldehyde, polyrneric aldehyde condensa-tion
products such as -krimers, The ca-talytic species
has been postulated -to be hydridocarbonyl -tris
(triphenylphosphine) rhodium (I), which has -the
~ormula HRh(CO)(PPh3)3, and can be generated in situ
during the hydroformylation reaction from a suitable
catalyst precursor, such as (2,4-pentandionato)
dicarbonyl rhodium (I), i e. the rhodium dicarbonyl
complex formed with acetylacetone, or rhodiurn
carbonyl triphenylphosphine acetylacetonate. A
description of such a hydroforrnylation catalyst can
363
5 --
be found, for example, in United Sta-tes Patent
Specification No. 3527809. The use of aldehyde
condensation products as a solvent for the rhodium
complex catalyst is described in British Patent
Specification No. 1338327J In addi-tion to the
rhodium complex catalyst the liquid phase in the
hydroformylation reactor 5 also con-tains an excess of
triphenyl phosphine. The mole ra-tio of triphenyl
phosphine:rhodium is approximately ~75:1.
The temperature in reactor 5 is maintained
at 110C by circulating cooling water or steam, as
appropriate through coil 6. An impeller 7 rotated
by a suitable motor (not shown) is provided in order
to mix thoroughly the contents of the hydroformylation
reactor 5.
A hydrocarbon feedstock, such as natural
- gas, naphtha or a gas oil, is supplied through line
8 to a syn-thesis gas plant 9 (for example a partial
oxidation plant or a s-tearn reforming plant). An
approxirnately 1:1 H2:C0 mixture passes on from plant
9 through line 10 to a purification section 11 in
which the synthesis gas is freed from impurities such
as carbonyls, sulphurous compounds and chlorinated
compounds. The purified synthesis gas is then fed
through lines 12 and 13 to a sparger 14 in hydroformy-
lation reactor 5.
Z~ 3
- 16 -
A vaporous stream is removed from hydroformy-
lation reactor 5 overhead through line 15. After
passage through a demis-ter 16 which is provided with
a return line 17 -to reactor 5 for condensed liquid,
this stream passes on through line 18 to condenser 19
and is cooled therein to 660C by means of cooling
water supplied through line 20. The resulting gas/
condensate mixture is supplied through line 21 to a
product separator 22 from which a gaseous mixture is
removed via line 23. The gaseous mixture flows on
through line 24. A part thereof is purged through
line 2.5, whilst the remaînder is recycled via lines
26, 27 and 13 to hydroformylation reactor 5 by means
of recycle compressor 28. The rate of gas recycle
through line 27 is suffici.ently high, in relation
to the tempera-ture and pressure conditions prevailing
in reactor 5, to remove product _-valeraldehyde in
the vapour stream in line 18 at the rate at ~hich
it is formed in reactor 5.
The liquid condensate is removed from
product separator 22 through line 29 and fed to a
distillation column 30 which contains 20 trays; its
working tempera-ture is 193C.
A gas stream, consisting essentially of
unreacted butene-l, CiS- and trans-butene-2 and
saturated C4 alkànes~ is removed overhead via line 31
and is cooled to a temperature of 85~6~C in condenser
2~3
- 17 -
32 whlch is supplied with coollng water through line
33. The resulting li~uid hydrocarbons are -then fed
via line 34 to reflux drum 35. A gas purge is with-
drawn through line 36.
The liquid butenes-containing stream is
pumped from reflux drum 35 through line 37 by means
of pump ~8; of this stream a part is returned to
column ~0 through line ~9, whilst the remainder is
supplied to line 40. A major part of the liquid
butenes-containing stream in line 40 is returned to
hydroformylation reactor 5 through lines 41~ ~r2 7 43
and 4,.whilst a purge stream is removed from the
system through line 44.
A bottoms product, consisting essentially
of n-valeraldehyde product and containing a minor
proportion of iso-valeraldehyde is withdrawn from
column 30 through line 45. Part of this bottoms
product is passed to line 46 fo:r puri.fica-tio.n (e.g.
redis-tillation) and/or further processing and/or
storage. The remainder of this bottoms produc-t is
recycled -through line 47, reboiler 48 and line 49 -to
column 30. Reboiler 48 is heated by means of steam
supplied through line 50.
In order to prevent build-up of "heavies"
in the solution in the hydroformylation reactor 5 a
bleed stream is removed via line 51 and passed to a
~L9tZ'3~3
- 18 -
regeneration section 52. "Heavies", eOg. valeraldehyde
tetramers of a formula analogous to ~ormulae (VI) and
(VII3 of British Patent Specification No. 1338237,
and -triphenylphosphine oxide are removed through llne
53. (Triphenylphosphine oxide may be formed due to -the
presence of traces of oxygen in one of the feed
streams to the hydroformylation reactor 5). Regenerated
solution is recycled to hydroformylation reactor 5
through line 54.
If desired "heavies" removal zone 52 can be
dispensed with. Instead spent reactor solution can be
withdrawn from the reactor 5 via line 51 and passed to
storage, the rate of withdrawal being sufficien-t to
prevent build-up of "heavies" in the reactor 5. At
the same tirne fresh catalys-t or catalyst precursor is
added via line 54 a-t a rate sufficient to main-tain the
rhodium concen-tration at approxima-tely the chosen level.
Such fresh catalyst can be dissolved in an approprlate
volume of liquid aldehyde product toge-ther wi-th a
corresponding amount of free triphenylphosphine. The
s-tored spent catalyst solution can be treated for
the recovery of triphenyl phosphine and rhodium from
which fresh catalyst or catalyst precursor can be
manufactured.
A typical method of "heavies" removal in
zone 52 involves extraction of the bleed s-tream in
line 51 in a conventional mixer-settler, after cooling
~J ~ 3
~ 19 --
to ambient temperature and depressurising, wi-th
phosphoric acid or with an aqueous solution of
phosphoric acid containing at least about 40~o by
weight~ and preferably at least about 600/o by weight,
of orthophosphoric acid. This phosphoric acid ex-tract,
which contains essentially all the active rhodium
catalyst and free triphenylphosphine, is then
neutralised in the presence of a suitable organic
hydrophobic solvent, e.g. n-valeraldehyde trimer,
and the resulting organic phase recycled to reactor
5 through line 54 after drying. The organic residue
from the phosphoric acid extraction step, on the
other hand, is passed to storage via line 53; this
- organic residue contains catalytically inactive
rhodium and triphenylphosphine oxide, as well as high
boiling n-valeraldehyde condensation products. Such
catalytically inactive rhodium may be present due -to
traces of ca-talyst poisons in -the feed s-treams to the
reactor 5.
As thus described condensation is effected
from the vapour stream from reactor 5 in a single
stage, i.e. condenser 19. It is alternatively possi~le
to effect condensation in two stages~ In this case
condenser 19 is operated at a somewhat higher temperature
so that unreacted alkene passes on uncondensed in line
21 to produc-t separator 22. Non-condensed components
of the vapour stream pass on via line 23 are taken via
~'
~ - 20 -
line 55 to a second s-tage condensation zone 56 in which
unreacted alkene is condensed~ Cooling wa-ter is
supplied to second stage condensation ~one 56 through
line 57. A gas/liquid mixture passes on through line
58 to a further product separator 59 from which a
liquid butenes-rich fraction is withdrawn through line
60 for recycling to the hydroformylation reactor 5
through lines ~2, 43 and 4. Uncondensed gases pass
on through line 61 to line 26 for recycle to the
reactor 5. There is no flow in line 24 in this
modi~ication of the plant.
If desired the C~ hydrocarbon feed stream
can be subjected to a pre-enrichment step so as to
boost the proportion of butene-l in the feed strearn
to the reactor 5. This purified C4 hydrocarbons can
be passed -through line 62 to a~spli-tter column 63
instead of passing on direc-tly via liné 3 to reac-tor
5. Column 63 contains 108 -trays. A bu-tene-l rich
stream is rernoved overhead -through line 64, whilst a
bo-ttoms product rich in butene-2 is removed through
line 65 and is recirculated through line 66 to reboiler
67 before being returned to splitter column 6~ through
line 68. Reboiler 67 i5 heated with steam supplied
through line 69. A liquid purge, which is rich in
cis-and trans-butene-2 and also contains any high
boiling sulphurous irnpurities such as dimethyl sulphide,
is removed -through line 70.
- 21 -
- The butene-l rich stream in line 64 is
passed through condenser 71 which is supplied with
cooling water through line 72. The resul-ting liquid
condensa-te passes on through line 73 to re~lux drum
74O Drum 74 is provided with a vent line 75. The
liquid butene-l rich liquid stream is pumped from
drum 74 through line 76 by means of pump 77 and on
through line 78. Part of this stream is returned to
split-ter column 63 -through line 79, whilst the
remainder passes on ~Tia lines 80 and 4 -to hydroformy-
lation reactor 5.
When a pre-enrichment step is incorporated in
the process of the invention, line 44 can be dispensed
wi-th. Instead a part of thé bu-tene-1 containing liquid
stream in line 42 can be passed to column 63 via line
81. In this case the purged materials, which would
otherwise have been removed from the system in line
44, are removed in line 70.
The invention is-further illus-trated with
reference to the following Example.
Example
Utilising the plant illustrated in full lines
in the drawing, a mixed C4 hydrocarbon liquid feed
stream is supplied via line 1 to the pretrea-tment zone
2.
The compositions ~in mole %), flow rates,
temperatures, and pressures in various of the important
lines in -the plant are set out below in Table 1.
~L4Z~3
-- 22 --
~'
~D
I
~î o. O o~ ~ ~ ~ ~ ~D O
~ ~ ~ ~O ~ ~ ~ ~ O O
.. ~ ' ' O N 1~ ` ri ~i 0 0 0 0 E I
~ O ~ ~ ~ O C~
~1 ~ O O O tD O o GO ~ C~l
~ ~ ~ C\l
~D
a~ ~ 0~ ~
~ O ~ -
1 ~1 0C~:) o ~ 1 ~ O 1~ 0
O .1~ ~ 15~ t\l O O ~ ~ ~1 ~ I O
~ C~i ~ ~ r~ O C~ O O ' O ~
H ¦ O
a) o ~D ~ ~ ~ ~D O ~,
a~ ~ ~ O ~ILO ~ O O
( ~ O O O
~1 ~D ~I r I
C\l ~ C)
~i
a) rd I h ~ h rd ~ ~1 c~ Iv
O rd h
o ~ ~ ~
/
363
'3 - 2~ -
r~
~ ~ I
a). .
~U~ ~ o
.~, ~ o~ ~
,~~ ~ .
.
~ 0 ~
a~
~ ,.~ o~
~ ~1
a~
C~ r~l .
U~ . - .
. ~ ~ ~D
Q) ~ U~ ~D
~ ~ o o o
rd ~ ~ ~D ~
.~
o '`Jl ~
~ ~1 ~
~i ' ,
C~ L~ U~
U~ ~
. . . .
o . oo
h
+, ~ h~
h c~
oO ~ V U~ C~
~L~: ~ ~,o U:~
~o
or ! hO a) h
V h.~
1~ 63
~,
- - 24 -
O-ther ~signiican-t flow rates are set out
below ln Table 2:-
, I
2~63
- 25 -
~ ~ ,
`. , ~
. ~1-
o_,
. ~ ~
C~
o .,
,_
.
,_ ~
I'~D
~ I-
o~
~Z~3
- 26 -
The overall conversion of butene-l to n- and i_
,
~ ~ valeraldehydes is 8404%~ The n-/iso-aldehyde ratio is
.
25.6:1. The resulting aldehyde product can be subjected
without further purification to conventional aldolization,
dehydration and reduction to yield an acceptable C10-
plasticiser alcohol consisting predominantly of 2-
propylheptanol.
The stream in line 44 is rich in butene-2
and can be used, for example, in the production of
- 10 butylate petroleum or methyl ethyl ketone.
~ It will be appreciated by those skilled in the
art that, since the butenes are recycled in the liquid
phase to ~he hydroformylation reactor in the form of
plant illustrated in the drawing, the gas recycle
compressor can be considerably smaller than would be
the case if the unreacted butenes were recycled in the
gas phase.
