Note: Descriptions are shown in the official language in which they were submitted.
~L~5~
PROD~C'rION OF C2-C6 ALIPHATIC ALCOHOLS
(D-~78,276-F)
BACKGROUND OF TEIE INVENTION
Field of the Invention
This invention relates to a process for preparing
lower aliphatic alcohols. More particularly, this invention
relates to the production of a mixture of lower aliphatic
alcohols characterized by containing a substantial proportion
of alcohols having from 2 to 6 carbon atoms.
Lower aliphatic alcohols have been proposed as fuel
extenders or as replacements for gasoline for fueling internal
combustion engines. Certain mixtures of lower aliphatic
alcohols have the EPA approval for use and are currently being
marketed in the United States. The lower aliphatic alcohols
can be produced from domestically available non-petroleum
sources, and their use in fuels would serve to lessen the
dependence o the nation on imported petroleum and petroleum
products.
Elydrogen and carbon monoxide, or a synthesis gas
mixture of hydrogen and carbon monoxide, can be react~d to orm
lower aliphatic alcohols. The synthesis gas feed stream can be
produced rom non-petroleum sources, such as coal, biomass or
other hydrocarbonaceous materials. The synthesis gas mixture
itsel is produced in a partial oxidation reaction of the
hydrocarbonaceous material in co~mercially available processes
such as coal gasification.
Numerous catalytic processes have heen studied in
attempts to provide a viable process for the production of
aliphatic alcohols from synthesis yas or from a mixture o
hydrogen and carbon monoxide. Hexetofore, the emphasis has
been primarily directed to the production of methanol. In
contrast~ the present process is directed to a method for
producing an alcohol mixture containing a substantial amount of
aliphatic alcohols having from 2 to 6 carbon atoms. Under
:
~a~
69(~
60~ 2772
selected reaction condltions, this process is effective for pro-
ducing a ~raction of higher aliphatic alcohols, i.e. an alcohol
fraction consisting of C2 to C6 alcohols, which represents the
major or predominant alcohol production in this process.
_isclosure Statement
U.S. 1,201,850 discloses a method for the production of
hydrocarbons and oxygenated compouncls oE hydrocarbons by passiny
an oxide of carbon and hydrogen over a heated ca-talytic agent
under a pressure exceeding 5 atmospheres. ~ number oE catalytic
materials are disclosed as well as the fact that a basic compound,
such as an alkaline metal hydroxide, can be used with the pre-
scribed catalytic agents.
U.S. 1,625,929 discloses a process for producing
methanol in which the catalyst contains copper, cobalt and a
metallic halide.
U.S. 3,345,427 discloses a dehydrogenation catalyst and
process in which the catalys-t consists of nickel, molybdenum and
alkali metal oxides on an alumina support.
U.S. 4,096,164 discloses a process for reacting hydrogen
and carbon monoxide in the presence oE a solid catalyst comprising
rhodium with molybdenum or tungsten to produce two carbon atom
oxygenated hydrocarbons in which e-thanol is the major component.
U.S. 4,199,522 discloses a Fischer-Tropsch process for
producing oleEins.
U.S. 4,235,801 and 4,246,186 disclose the produc-tion of
alcohols from a mixture of carbon monoxide and hydrogen in the
presence of a rhenium catalyst.
~i~56~C~3
60288-2772
U.S. 4,380,589 discloses a Fischer-Tropsch process :Eor
producing nydrocarbons with irnproved selectivity to C2-C4 ole~ins
by contacting hydrogen and carbon monoxide in the presence of a
catalyst. The catalyst disclosed comprises molybdenum, a promoter
cornprising alkali or alkaline earth
- 2a -
.,
6 9 C)~
60288-2772
metal, and a binder comprising an iron-containing calcium
aluminate cement.
South A~rican Patent No. 8,401,982 discloses a process
for producing alcohols from synthesis gas using a catalyst
containing molybdenum with tungsten, rhenium and an alkali metal.
United Stat~s Patent 4,492,772 discloses a similar process in
~hich the catalyst contains rhenium, molybdenum and potassium.
United States Patent 4,661,525 is directed to a process
for producing lower aliphatic alcohols from a mixture of carbon
monoxide and hydrogen.
Previous catalytic processes have been notably effective
for converting carbon monoxide and hydrogen feedstocks into hydro-
carbons or methanol, but none have been particularly effective for
providing high yields of a lower aliphatic alcohol mixture
charac~erized by having a substantial or greater weight amount of
alcohols having from 2 to 6 carbon atoms as compared to the co-
produced methanol.
SUMMARY OF THE INVE~TION
It has been discovered that a mixture of carbon monoxide
and hydrogen can be reacted to form a mixture of lower aliphatic
alcohols containing a substantial amount of aliphatic alcohols
having from 2 to 6 carbon atoms. This reaction is conductecl by
contacting a ieed mixture such as synthesis gas with a novel
catalyst composition which exhibits good selectivity for the
production of C2-C6 aliphatic alcohols under suitable conditions
of temperature and pressure. The effective catalyst composition
comprises a mixture of molybdenuYD, a metal from the group
~ "r~ ,
.,,, .~
~5~9~
60288-2772
consisting of cobal~, iron and nickel, and copper. This metal
catalyst composition is modified by the addition of a critical
amount of an alkali metal promoter from khe class consisting of
potassium, cesium and rubiclium in an amount ranging from about 1.8
to 13.0 micromoles of alkali per square meter of surface area of
the catalyst thereby forming a promoted or modified catalyst.
DETAIL~D EHBODIMENTS OF THE I~VE~TION
In accordance with this invention, a mixture of carbon
monoxide and hydrogen a~, for example, a synthesis gas mixture of
said reactants, is reacted over a catalyst comprising molybdenum,
a metal from the group consisting of cobalt, iron and nickel, and
copper, which has been modified by ~he addition of a promoter from
the group consisting of potassium, cesium and rubidium, said
promoter being employed at a concentration ranging ~rom about 1.8
to 13.0 micromoles of alkali per square meter of surface area of
the catalyst. The nature and the concentration of the promoter on
the catalyst are critical. Concentrations of promoter outside of
the prescribed range result in a sharp reduction in the effective-
ness of this process.
According to one aspect of the present invention there
ls provided a method for preparing lower aliphatic alcohols
characterized by producing a substantial proportion of aliphatic
alcohols having from 2 to 6 carbon atoms which comprises reacting
carbon monoxide and hydrogen in the presence of a catalyst at a
temperature from about 240 to about 400C, a pressure from about
500 to about 3000 psl and a gas hourly space velocity of at least
1000, said catalyst comprising from about 5 to about 50 weight
- 4 -
.~.
~5~9~)~
S028~-2772
percent of molybdenum calculated as MoO3, rom about 0.3 to about
15 weiyht pe~cent of a metal selected from ~he group consisting of
cobal-t, iron and nickel, calculated as CoO, Fe203 or NiO,
respectively, and from about 1.5 to 8 weight percent of copper,
calculated as CuO, and the balance a support, said catalyst being
modified by the addition of an alkali metal promoter from the
class consisting of potassium, cesium and rubidlum in an amount
ranging from about 1.8 to 13.0 micromoles of said alkali metal per
square of catalyst surface area.
According to a further aspect of the present invention
there is provided a method for preparing lower aliphatic alcohols
in which ~he weight ratio of the C2-C6 alcohols to methanol is
greater than 1 which comprises reacting carbon monoxide and
hydrogen in the presence of a catalyst at a temperature from about
270 to 360C, a pressure from about 750 to 2500 psi ancl a gas
hourly space velocity in the range from about 10,000 to 30,000,
said catalyst comprising from about 7 to 30 weight percent of
molybdenum calculated as MoO3, from about 0.5 to 10 weight percent
of a metal or mixture of metals selected from the group consisting
of cobalt, iron and nickel calculated as CoO, Fe203 or NiO
respectively, and from about 2 to 6 waight percent of copper
calculated as CuO, and the balance an alumina support, said
catalyst being modified by the addition of an alkali metal
promoter from the class consisting of potassium, cesium and
rubiclium in an amount ranging from about 2.2 to 10.0 micromoles of
said alkali metal per square meter of catalyst surface area.
Table I (set forth hereinafter) gives results obtained
~L~S~3;:~
G0288-2772
fro~ this process at differ~nt concen~rations of the copper
component in the ca-talyst. The Table gives the values for C
alcohol produc-tivlty in terms of grams of alcohol per gram of
catalyst per hour. The Table fuxther expresses the concentration
of the novel component copper as copper oxide (CuO) in the
catalyst. Data in the Table show that a process which employs a
copper-containing potassium-promoted cobalt molybdenum catalyst
conducted at 343C is effective for the production of substantial
amounts of C2-C6 lower aliphatic alcohols. The selectivity of the
catalyst for C2-C6 alcohol production is surprisingly improved
when the copper concentration in the catalyst is about 1.5 weight
percent or more calculated as CuO.
In United States Patent No. 4,661,525, it has been shown
that the critical concentration range for the alkali promoter is
an amount from about 1.8 to 13.0 micromoles of alkali per square
meter of surface area of the catalyst. A preferred alkali
promoter concentration is from 2.2 to 10.0 micromoles of alkali
per square meter of catalyst surface area with the most preferred
alkali promoter concentration being from about 2.5 to about 9.0
micromoles of alkali per square meter of catalyst surface area.
Preferably the support is from about 60 to 80 wei~ht percent of
the catalyst. The metal components of the catalyst may be in the
free or comhined form.
The catalyst can be prepared in a number of ways known
in the art. In general, the use of a catalyst support or carrier
comprising a relatively refractory, porous, adsorptive and high
surface area material is preferred. Conventional carriers or
- 5a -
;6~3
60~88-2772
supports, such as alumina, sllica, titan1a, maynesia, silica-
alumina and boron phosphates, are suitable support materials for
preparing the catalyst for this process. The disclosl1re in United
Sta~es 4,098,683 is illustrative.
A preferred method for preparlng the catalyst is to
impregnate a carrier, such as alumlna, with a source of molybdenum
generally in the form of a soluble salt, then with a metal from
the class of cobalt, nickel and iron, generally also in the iorm
of a soluble salt and finally with copper in the form of a soluble
salt. The impregnation of the carrler wlth the catalyst metals
can be done simultaneously or step-wise. The impregnated carrier
is dried and then calcined according to known procedures.
It is essential that the catalyst be modified, i.e.
~reated or impregnated, with an alkali metal promoter from the
group of potassium, cesium or rubidium generally in the form o~ a
salt. The treated or modified catalyst is then subjected to
reduction with hydrogen gas generally by heating the promoted
catalyst at a temperature between about 300 and 500C for an
extended period, usually 2 to 8 hours.
The catalyst comprises from about 5 to 50 weight percent
of molybdenum calculated as molybdenum trioxide, from about 0.3 to
15 weight percent of a metal from the group consisting of cobalt,
nickel and iron calculated as the respective oxide CoO, NiO or
Fe203 or mixtures thereof, and
- 5b -
~ .
,
~56~
from about 1.5 to 8 weigh~ percent of copper as copper oxid~
(CuO), with the balance being the support. A preferred
catalyst composition comprises from about 7 to 30 weight
percen~ of molybdenum trioxide, from about 0.5 to 10 weight
percent of cobalt, nickel, or iron oxide or a combination
thereof and from about 2 to 6 weight percent of copper. Still
more preferred is a catalyst comprising from about 7 to 12
weight percent molybdenum, from about 1.5 to 5 weight percent
of a me~al from the group consisting of cobalt, iron and nickel
or a mixture thereof and from about 2.5 to 5 weight percent of
copper, all calculated as hereinabove described.
The catalyst should have a surface area of 125 m2/gm
(square meters per gram of catalyst) or more. A more effective
catalyst will have a surface area from about 150 to 350 m2/gm
and the most preferred will have a surface area from about 160
to 300 m /gm.
Alternatively, a commercially available catalyst
comprising molybdenum, one or more of the metals from the class
consisting of sobalt, nickel and iron, and copper meeting the
foregoing specifications can be impregnated or modified by
treatment with the prescribed alkali metal and then reduced
under hydrogen and treated as noted above.
The carbon monoxide and hydrogen employed to form the
lower aliphatic alcohols in this process can be provided from
any available source. One particularly useful source is
synthesis gas produced in the gasification of hydrocarbonaceous
materials, such as coals and biomassO An effective gasifica-
tion process is described in U.S. 3,54~,291 wherein a hydro-
carbonaceous fuel is partially oxidized with a free oxygen-
containing gas in a gas generator. In general, the mole ratio
of hydrogen to carbon monoxide employed in this process should
range from about 0.1 to 50 moles of hydrogen per mole of carbon
monoxide with the preferred ratio being from about 0.5 to 20
moles of hydrogen per mole of carbon monoxide.
The reaction conditions for effecting the conversion
of the carbon monoxide-hydrogen feed into lower aliphatic
alcohols employing the prescribed catalyst of t~e invention
303
include a reaction temperature ranging from about 2~0 to about
400C with a preferred temperature range being from about 270
to 360C and the most preferred temperature being from about
290 to about 350C. The effective pressure range for this
process is from about 3.4 X 106 Pa (500 psi) to about 2.4 X
107 Pa (3500 psi). The preferred pressure range is from about
5.1 X 106 Pa (750 psi) to about 1.7 X 107 Pa (2500 psi~.
The space velocity employed to effect the conversion
of carbon monoxide and hydrogen over the prescribed catalyst to
the aliphatic alcohols is a vital feature of this process. In
general, the space velocity, that is the volume of gas passed
through a given volume of catalyst per hour expressed as
GHSV(hr 1), must be at least 1000. A preferred range is from
about 5000 to about 50,000. A highly effective process is
realized when the space velocity employed ranges from about
10,000 to about 30/000. Under preferred conditions the ratio
of weight percent of C2-C6 alcohols to weight percent methanol
can exceed 1, and more preferably can be from 1.25 to 2.
The present invention is more fully described in the
following Examples. The reactor used for this work was a 1"
I.D. type 316 stainless steel tube. lOcc of the catalyst was
diluted with 90cc of alpha alumina and packed into the reactor.
The catalyst was reduced for 4 hours, at 400C, at a pressure
25 of 1500 psig with a flow of hydrogen gas at 2.5 liters per
minute. The catalyst was then cooled to reaction temperature
and subjected to a mixture of hydrogen and carbon monoxide in a
ratio of 2:1, at a pressure o 1500 psig and a GHSV of
28,000 hr 1.
The product emerging from the reactor was sent
through a condensor which liquefied the alcohols and water
products. The resulting liquid was analyzed by gas chroma-
tography. The non-condensable gas was also analyzed by gas
chromatography.
The selectivity to hydrocarbons, methanol, and
alcohols containing 2 to 6 carbon atoms is set forth in the
table. The alcohol production in grams of alcohol per gram o~
-7-
catalyst per hour is also set forth in the table~ Selectivity
is defined as the percentage of carbon atoms converted from
carbon monoxide to a specified compound or compounds.
~XAMPLE 1
A promoted catalyst was prepared by impregnating a
commercially available catalyst comprising cobalt and
molybdenum on an alumina carrier first with a solution of
copper nitrate, and after calcination with a solution of
potassium carbonate. The commercial catalyst was made by Armak
catalyst division, Pasadena, Texas and sold under the name
Ketjen KF 124 LD~ The copper nitrate solution was made by
dissolving 1.2 grams of copper nitrate in 50cc of distilled
water which was then added to 98.8 grams of the catalyst. The
impregnated catalyst was then dried and calcined at 450C for
several hours. After calcination a solution of 5.9 grams of
potassium carbonate, in distilled water, was added to 33.0
grams of the calcined catalyst. This was then dried in a
nitrogen purged vacuum oven at 135C for several hours. The
chemical analysis of the catalyst is set forth in the table
under Example 1.
EXAMPLE 2
A second promoted catalyst was made as in example 1,
however, the ca~alyst was impregnated with a solution made by
dissolving 4.8 grams of copper nitrate in 50cc of distilled
water, which was added to 95.2 grams of the catalyst. After
drying and calcination a solution of 5.6 grams of potassium
carbonate, dissolved in distilled water, was added to 32 grams
of the calcined catalyst. This was then dried in a vacuum oven
for several hours. The chemical analysis of the catalyst is
set forth in the table under example 2.
EXAMPLE 3
A promoted catalyst was made as in example 1 r
however, the catalyst was impregnated with a solution made by
dissolving 9.5 grams of copper nitrate in 50cc of distilled
~r~ k -8-
9i~
water, ~hich ~as added to 90.5 grams of the catalyst. After
drying and calcination a solution of 5.1 grams of potassium
carbonate, dissolved in distilled water, was added to 29.0
grams of the calcined catalyst. The catalyst was then dried in
a vacuum oven at 135C for s~veral hours. The chemical
analysis of this catalyst is set forth in the table under
example 3.
EXAMPI,E 4
-
A promoted catalyst was made as in example 1,
however, the catalyst was impregnated with a solution made by
dissolving 18.2 grams of copper nitrate in 60cc of distilled
water, which was added to 81.0 grams of the catalyst. Aftex
drying and calcination a solution of 13.1 grams of potassium
carbonate, dissolved in distilled water, was added to the
calcined catalyst. The cat,alyst was then dried at 125~C for
several hours, The chemical analysis of this catalyst is set
forth in the table under example 4.
This catalys~ was tested in a 0.5 liter stainless
steel Berty~ type recirculating gradientless reactor from,,
Autoclave Engineers. 20cc of catalyst was used~ The
conditions for the test were the same as ~hose previously
described except that the hydxogen flow during reduction was 5
liters per minute instead of 2.5 liters per minute~
EXAMPLE 5
A promoted catalyst was made as in example 1,
however, no copper nitrate was added. 30 grams of potassium
carbonate, dissolved in 90cc of distilled water was added to
170 grams of the base catalyst (KF 124 LD). This was then
dried at 135C for several hours. The chemical analysis of
this catalyst is set forth in the table under example 4.
~ ~r~ ~a r k
_g_
o~
TABLE I
EXAMPLE 1 2 3 4 5
~Comp.)
Cataly~t Composition
Wt%
3 9-9 9-5 9.5 8.7 9.7
CoO 3.4 3.4 3.4 3.0 3.1
10 CuO 0.4 1.7 3.4 6.2 -~-
A123 78.3 77.9 75.7 73.1 78.3
K2O 8.0 7.5 8.0 9.0 8.9
H2/CO Ratio 2.0 2.0 2.0 2.0 2.0
15 Temperature C 343 343 343 3~3 343
GHSV(HR ) 28,00028,00028,00028,00028,000
Pressure Pa lx107 lx107 lx107 lx107 lx107
-Mole K = 6.2 5.8 6.2 6.9 6.9
M
Selectivity 1%) To
C2 48 51 42 48 46
25 C1-C6 Hydrocarbons 20 21 21 32 31
MeOH 12 10 14 7 7
C2-C6 Alcvhols 19 17 22 13 17
Alcohol Production 0.240.35 0.50 0.42 0.27
IG/G-hr)
C2-C6 Alcohols Wt% _ 1.6 1.7 1.6 1.8 2.4
MeOH Liquids Wt%
C2+Alc.Prod. (G/G-hr3 0.150.22 0.30 0.27 0.19
--10--
The foregoing examples demonstrate that a process for the
production of lower aliphatic alcohols from a mixture of carbon
monoxide and hydrogen within the critical parameters for the
prescribed catalyst modified or promoted with the specified
alkali metal is effective for produc.ing a high yield of C2-C6
aliphatic alcohols in relation to the production of methanolO
