Note: Descriptions are shown in the official language in which they were submitted.
This invention relates to catalysts and their use in the synthesis of
alcohol mixcures containing methanol and hlgher a]cohols.
The synthesis of aliphatic alcohols from synthesis gases or,
respectively, from carbon monoxide and hydrogen is known. Depending on the
type of catalyst and on the reaction conditions used, these processes are referred
to a Synol, Oxyl, and Isobutyl Oil Synthesis.
In the Synol synthesis alkalized iron-melt catalysts have mainly been
used, wilich are obtained by modification of catalysts originally developed for
the Fischer-Tropsch synthesis. The process conditions used were temperatures
of 190-200 C., pressures of 18-25 bar, and space velocities of 100 - 200 liters
per hour and liter of catalyst, at a H2/CO ratio of l in the fresh gas
(DE-PS 933,388). The liquid reaction products contain about 42 wt.% aliphatic
alcohols having a boiling point of 40 - 420C., the balance being other oxygen
compounds, such as esters, aldehydes, detones and carboxylic acids, as well as
hydrocarbons.
The Oxyl synthesis (DE-PS 902 851, DE-PS 897 698 and 923 127) was
carried out at temperatures of 180 - 220 C., pressures oE 10 - 30 bar, space
velocities of 100 - 300 liters synthesis gas per hour and liter of catalyst,
the H2/CO ratio in the fresh gas being 1.2 to 2:1. Iron precipitation catalysts
promoted with cerium or vanadium were used. In addition to abo~t 55 wt.%
aliphatic alcohol, the liquid reaction products contained other oxygen-
containing compounds as well as hydrocarbons. Mainly C2 to C18 alcohols were
formed, the percentage decreasing with increasing number of carbons.
In addition, modified iron catalysts with potassium, chromium,
manganese and barium as activators were used, which led to an increased percentage
of oxygen-containing compounds (DE-PS 937 706, 959 911 and 967 944).
These two syntheses having the disadvantage that the selectivity of
the formation of aliphatic alcohols is rather low, and separation from the other
-- 1 --
'
re~ction products constitutes a complicated and expensive process.
The Iso~utv:l 0;1 syntllesis was carrled out pre~erably with alkali-
promotecl zinc oxidc ancl chromium oxide catalysts at temperatures of 400 - 450 C.
and pressures of ~50 - 350 bar. Besldcs methanol (about 50 wt.%), isobutanol
predominated in the reaction products (about ll - 14 wt.%), the balance being
hlgher aliphatic a]cohols, other oxygen-containing compounds and water.
About 1950, the Synol, Oxyl, and Isobutyl Oil syntheses were replaced
by more economical methods for the production of alcohols through the newly
developed Oxo synthesis and, respectively, the hydration of olefins. Later
iron-, copper-, boron- and potassium-containing catalysts were developed
(United States Patents 124 908, 243 606 and 386 899), which were used for the
synthesis of aliphatic alcohols from CO and H2 (~2/CO ratio lO) at temperatures
of 160 - 225C., pressures of 100 - 300 bar and space velocities of 2000 liters
synthesis gas per hour and liter of catalyst. At a conversion of 14 mol.% the
content of oxygen-containing compounds was about 60 - 90 wt.7" the percentage
of primary aliphatic alcohols rising up to 80% depending on the type of catalystused and the reaction conditions applied.
Although in this synthesis the yield of aliphatic alcohols is high,
the process has disadvantages similar to the ones already described. Oxygen-
containing compounds are formed having a boiling point range up to 450C., inwhich C2 to C18 alcohols are represented.
As the production of aliphatic alcohols via the Oxo synthesis or the
hydration of olefins depends directly on petroleum as the raw material and in
view of the worsening raw material situation in recent years, new ways are
being sought which are intended to help alleviate the dependence of the petro-
chemical industry on petroleum impor~s.
The present invention makes available catalysts which permit the
synthesis of alcohol mixtures containing methanol and higher alcohols from
-- 2 --
synthesls gas or from carbon monoxide and hydrogen, the composition of the
product alcohols belng llmited mainly to Cl to C4 alcohols, and the percentage
of the indlvidual alcohols being controllable by the selection of the catalyst
composition and of the reac~lon conditions. In addition, by means of these
catalysts the carbon monoxide conversion can take place under relatively mild
reaction conditions (temperatures to 400C. and pressures to 150 bar). It
has been found that copper- and zinc-containing catalysts and also optionally
containing aluminum, which previously were used only for low-pressure methanol
synthesis, are suitable as starting catalysts for the preparation of catalysts
according to the present invention.
Thus the invention provides a catalyst for the synthesis of an
alcohol mixture comprising methanol and higher alcohols which comprises a
ma~or portlon by weight of the oxides of copper and zinc in intimate associa-
tlon with each other; a promotional amount of a promoting compound of
potassium and optionally of a compound selected from the group consisting of
chromium, cerium, lanthanum, manganese, and thorium, or mixtures thereof.
The oxides of copper and zinc may be derived for example through
(a) coprecipitation of insoluble salts from an aqueous solution of the soluble
salts of chromium and zinc; filtration of the insoluble salts; and calcination
of the insoluble salts to convert the salts to their oxides. In an alternative
method, the oxides of copper and zinc may be derived from (b~ the formation of
an ammine complex containing ions of copper and zinc, decomposition of the
ammine complex to form heat decomposable salts of copper and zinc; and con-
version of the heat decomposable salts of copper and zinc to their oxides.
A thermal stabilizing metal oxide is optionally included in
intimate association with the oxides of copper and zinc as, for example,
aluminum oxide which may be incorporated by for instance coprecipitation of an
insoluble salt thereof from the aqueous solution containing the soluble salts
-- 3 --
of chromium and zinc as well as of the metal in the first of the afore-
mentioned methods of preparation of the oxides or by suspension of a hydrated
metal oxide gel in~o the ammine complex formed in the second of the afore-
mentioned methods followed by decomposition of the ammine complex onto the
gel and calcination.
The promoter compounds are of potassium and of the group of
chromium, cerlum, lanthanum, manganese, thorium and other alkali metals or
mixtures thereof, and may be added at any production stage, for example by
coprecipitation with the oxides or impregnation of the oxides with solutions
of the promoter compounds followed by calcination, or impregnation after
calcination with further calcination following.
Calcination is suitable carried out at a temperature of 350-450 C.
in the aforementioned methods.
For method (a) the alksli metal compounds when used need not be
added separately. Frequently the alkali cations of an alkaline medium used
for the coprecipitation, contained in the precipitate, are sufficient.
Compounds of potassium are essential to the efficency of this catalyst. Other
alkali metal compounds such as rubidium or cerium may be added.
The precipitates or preproducts obtained according to both process
variations can be compacted to shapes, e.g. pellets, tablets and extrusions,
before impregnatlon with the promoter compounds or alkali metal compounds or
alternati~vely thereafter, i.e. immediately before the calcining, with the
optional addition of lubricants, such as graphite. For example, cylindrical
tablets of a diameter and a length of 3-5 mm can be prepared.
The composition of the starting catalysts may vary within wide
limits. A preferred embodiment of the invention is characterized in that the
starting catalyst contains about 18 to 45 wt.%, preferably about 25-to 40 wt.%
copper oxide; about 24 to 50 wt.%, preferably about 30 to 45 wt.% zinc oxide;
-- 4 --
~;V,
,~
~L~ ~Y~ 3~
about S to 25 wt.%, preferably about 10 to 18 wt.% aluminum oxide, and about
0.03 to 3~4 wt.%, preferably about 1.7 to 2.5 wt.% potassium (calculated as
K20), copper and zinc being present in an atomlc ratio of about 0.4 to 1.9.
The promoter compounds are usually present in total quantities of
about 3 - 18 wt,% (calculated as oxides). The oxides may be present in
various valences.
In a preferred embodiment~ the catalysts according to the invention
can be obtained either (a) a precipitate is obtained from a solution of
water-soluble salts, in particular the nitrates, of the principal components
and the promoter elements, by addition of alkali metal carbonate, in particular
potassium carbonate, at about 50 to 80 C., preferably at about 60 to 70 C.,
this precipitate being separated, washed and dried; or (b) the oxide mixture
obtained by thermal decomposition of a copper-zinc-amminocarbonate solution in
the presence of suspended aluminum oxide is impregnated vith salts~ preferably
nitrates, of the promoter elements; and the product obtained according to (a)
or (b) is calcined at about 350 to 450C., preferably at about 380 to 400 C.
In variant (a) as water-soluble salts of the principal components
and of the promoter elements, besides the nitrates, other salts for example
the chlorides and sulfates are suitable. In these cases, however, the washing
of the precipitates must be done more thoroughly. Also the acetates are well
suited, as acetate residues can be totally removed during calcination. The
precipitation is usually carried out to a pH value of 6 - 8, preferably
6.8 - 7,2. The precipitate can be separated from the aqueous medium in the
usual manner, e.g. by filtering. The washing can be effected on the filter
or by slurrying the precipitate with deionized water.
According to a modification of variant (b), the oxide mixture can
be obtained by mechanical mixing of the individual oxides of the principal
components Also, similar to variant (a), the oxides of the principal
-- 5 --
_ .
~ ~3~
components can be precipitated ~ointly, whereupon the product oxide mixture is
impregnated with the salts of the promoter elements.
~ e potasslum compound, can also be applied by a re-impregnation
of the startlng catalysts already impregnated with promoter compounds and
optionally precalcined. The catalysts thus impregnated are sub~ected to a
re-calcination~ Thereafter the potassium content (calculated as K20) is
preferably 0.03 - 3.4 wt.%, in particular about 1.7 - 2.5 wt.%.
As potassium compounds in all impregnations preferably potassium
hydroxide, potassium carbonate, potassium hydrogen carbonate, potassium
acetate, potassium chromate or dichromate or respectively mixtures thereof
are used. The preferred compound is potassium carbonate. The use of potassium
chromate or dichromate has the advantage that the promoter element chromium
and the potassium can both be introduced in the form of a single compound.
The re-lmpregnation is usually followed by a re-calcination at
about 350 - 450 C., preferably at about 380 - 400 C.
The catalyst ls normally activated by subjecting it to a reducing
after-treatment. This ls preferably carrled out by first reducing lt using an
inert gas such as nitrogen containing a small amount of hydrogen. Normally
the nitrogen contains initially about 2.0 vol.% hydrogen. Then the hydrogen
proportion is gradually increased, until finally the reduction is carried out
with pure hydrogen. The reduction takes place generally at atmospheric
pressure, and simultaneously wlth the increase in the proportion of hydrogen
in the reducing gas, the temperature is gradually increased from about 145,
preferably from 170, to 350C. Activation at a space velocity of about 1000
to 2000 liters reduction gas per hour and liter of catalyst is customary.
Under these conditions the reduction generally takes 16 - 18 hours.
The present invention also includes the use of the aforementioned
catalysts in the synthesis of alcohol mixtures containing methanol and higher
-- 6 --
alcollols. rhuS thc inv~nt:ion provides a process ~or the synthesis of an alcohol
mixture comprising meLIIa~ol alld higher alcolloLs which comprise.s the steps of:
passing a synthesis gas mix~:ure oE carbon oxides and hydrogen at a temperature
in the range of about 250 to 400C. and at a pressure in the range of from
about 80 to lS0 bar over a catalyst comprising a major portion hy weight of the
oxides of copper and zlnc in intimate association with each other and a
promotional amount of a promoting compound selected from the group consisting
of chromium, cerium, lanthanum, manganese, thorium and an alkali metal.
Preferably the synthesis is carried out at about 350C. and at a
pressure of about 100 bar. In a preferred embodiment the space-temperature
velocity is 1000 to 10000, most preferably about 3000 liters per hour and
liter of catalyst, with a process gas which contains about 25 to 30 vol.%,
preferably about 27 vol.% C0; about 0 to 8 vol.% N2; about 0 to 5 vol.% C02;
about 0 to 5 vol.% CH4; balance H2.
The reaction products are cooled to about 10 - 15 C. to condense the
liquid products, whereupon the components of the gaseous and liquid products are
measured and analyzed separately by gas chromatographically.
It was found that when using catalysts which contained only copper
and zinc or respectively copper, zinc and aluminum, only 1 - 2 or respectively
1 - 4 wt.% higher alcohols were obtained as liquid reaction products besides
90 - 94 wt.% methanol. By the introduction of 0.03 - 3.4 wt.% potassium into
the copper-, zinc- and aluminum-containing catalysts, the percentage of higher
alcohols rose to about 8 - 15 wt.%, while the yield of liquid reaction products
decreased on the whole. Further it was noted that the intial activity of such
catalysts having a copper-zinc atomic ratio of 2 - 3 : 1 clearly decreased aftera running time of 200 hours. The preferred catalysts of the invention having
a copper-zinc atomic ratio of 0.4 - 1.9 had longer lives.
Doping with chromium as chromium (III) oxide in an amount of 2 -
-- 7 --
10 wt.~ led not only Lo an increascd proportion of lligher aliphatic alcohols
in Lhe liquid reaction products (20 - 30 wt.%), but also to a further improvement
in catalyst liFe. In the C2 to C5 alcohol fraction, propanols and butanols
predominated) in particular propanol-l.
The effects of cerium and lanthanum as prollloters were similar to those
of chromium. Both elements led to higher y:ields of liquid reaction products,
with preferential formation of isobutanol.
The comblned promotion with chromium and thorium (5 - 10% Cr2O3,
5 - 10% ThO2) resulted not only in higher yields of liquid products, but also
in larger quantities of propanols and butanols, in particular isobutanol.
The action of chromium and manganese in combination (3 - 5% Cr203,
5 - 10% MnO) resulted in highly preferential formation of ethanol and propanols,
in particular ethanol.
The results achieved with the catalysts of the invention show that by
controlled promotion (chromium-manganese or chromium-thorium) an alcohol mixture
can be obtained which contains, i~ addition to methanol, higher aliphatic
alcohols, either preferably ethanol and propanol-l or isobutanol (2-methyl-
propanol-l) and propanol-l.
It is advantageous moveover that with the use of these catalysts mainly
Cl to C6 alcohols are formed and the quantity of undesired hydrocarbons is less
than 5%.
An alcohol mixture consisting of methanol and higher aliphatic alcohols,
in particular propanols and butanols, can be used as fuel alone or blended
with gasoline for the operation of Otto engines. If mixed with gasoline, no
phase separation will occur due to the presence of the higher alcohols if
accidentally a small amount of water~gets into the gasoline.
Moreover, the alcohol mixture obtained with the aid of the catalysts
of the invention constitutes a raw material source for the chemical industry.
-- 8 --
Afte{ separation of thF~ methanol by distillation and further fractionation of
the higher aliphatic a~cohols, additional fractions can be obtained, and it is
possible to use the C2 and C3 alcohols for ~he production of ethylene and
propylene and the C4 a:Lcohols for the produccion of solvents and plasticizers.
If processing of the higher aliphatic alcohols is For the production of olefins,
it is advisable to use chromiu~ and manganese-doped catalysts particularly.
The invention is explained in a non-limiting manner by the following
examples.
Example 1
In 9000 ml of a copper amminocarbonate solution containing 4.11 g
Cu/100 ml, 8.8 g NH3/100 ml and 7.4 g CO2/100 ml, were dissolved 355 g zinc
oxide with agitation, adding 177 g A1203. With continued agitation and replace-
ment of evaporated water, the suspension was thermally decomposed by boiling
until a sample gave a colorless filtrate. The precipitate was filtered and the
resulting filter cake was calcined in a thin layer at 400C. for 4 hours. The
product obtained was mixed with 2% of its weight of natural graphite and
compacted to cylindrical tablets of 3 mm diameter and 3 mm in length.
150 g of the product tablets were immersed at room temperature for
20 minutes in an aqueous solution of 96.5 g K2CO3 in 200 ml water and then
dried for 2 hours at 120C. and calcined for 3 hours at 400C. Table I shows
the chemical composition and the BET surface of the catalyst designated 0.
In a tubular reactor heated with a liquid medium (tube diameter 18 mm,
tube length 1000 mm) 30 ml of catalyst 0 were activated with a gas consisting
of 1.2 vol.% H2, balance N2, for 40 hours at 145 - 450 C. The temperature rise
between 145 - 250C. was about 2 C./hour; after reaching 250 C., the catalyst
was treated with pure hydrogen for 5 hours, and during this time the temperature
was raised to 350C. Then synthesis gas having a composition of
_ g _
29.5 vol.
C2 1.5 "
C~14 1.4 "
N2 5.0 "
H2 balance
was supplied to the reactor, a pressure of 100 bar and a space velocity of 2600
litersof gas per hour and liter of catalyst being adjusted. The results of this
test and the composition of the reaction products are summarized in Tables II
and III.
Example 2
The thermal decomposition of a copper amminocarbonate solution and the
filtering and calcining were carried out as described in Example l. The product
obtained was admixed with a solution of l90 g Cr(N03)3.9H20 in 200 ml deionized
water and then calcined for 3 hours at 400C. The oxides were then mixed
with 2% of their weight of natural graphite and compacted to cylindrical
tablets of 3 mm diameter of 3 mm length.
150 g of these tablets were then immersed in K2C03 solution, dried
and calcined as described in Example l.
The chemical composition and the BET surface of the catalyst designated
1 are shown in Table I. The activation of catalyst 1 and the reaction with
synthesis gas were carried out as in Example l. The results of this test and
the composition of the reaction products are shown in Tables II and III.
Example 3
The thermal decomposition of a copper amminocarbonate solution and the
filtration and calcining were carried out as described in Example l. The
product was processed as described in Example 2; but instead of chromium(III)-
nitrate solution an aqueous solution of 97.4 g cerium(IlI)-nitrate hexahydrate
in 200 ml water was added. 150 g of the product tablets were immersed in K2C03
-- 10 --
solution, dried ancl c~l.c.ined as described in Example l.
rhe chemiccll compositioll and the BIT surface of tllis catalyst designated
2 are given in Table :t. The activatioll o~ catalyst 2 with hydrogen and
the reaction with syntll~is gas were carried out as in Example 1. The results
oE this test and the composition of the reaction products are shown in
Tables Il and III.
Example 4
The thermal decomposition of a copper amminocarbonate solution and the
filtering and calcining were carried out as described in Example 1. The product
obtained was processed as described in Example 2; however, instead of
chromium(III)-nitrate solution, an aqueous solution of 97.8 g lanthanum
nitrate hexahydrate was added. 150 g of the tablets thus obtained were immersedin K2CO3 solution, dried, and calcined, as described in Example 1.
The chemical composition and the BET surface of this catalyst designated
3 are shown in Table I. The activation of catalyst 3 with hydrogen and the
reaction with synthesis gas were carried out as in Example 1. The results
of this test and the composition of the reaction products are shown in
Tables II and III.
Example 5
The thermal decomposition of a copper amminocarbonate solution and
the filtering and calcining were carried out as described in Example 1. The
product obtained was processed as described in Example 1.
150 g of the tablets thus obtained were immersed for 20 minutes at
room temperature in an aqueous solution of 209.5 g K2Cr2O7 in 200 ml water
and then dried for 2 hours at 120C. and calcined for 3 hours at 400C. The
chemical composition and the BET su~fact of this catalyst designated 4 are shown
in Table I.
The activation of catalyst 4 with hydrogen and the reaction with
synthesis gas were carried out according to Example 1. The results of this
test and the composition of the reaction products are shown in Tables II and
III.
_ample 6
600 g K2CO3 were dissolved in 2 liters of deionized water and
heated to 60 - 80 C. 285.2 g Cu(NO3)2.3H20, 188.2 g Zn(NO3)2,
131-6 g Cr(N03)3.9H2o, 52.3 ~ Th(NO3)4.4H20 and 276 g Al(N03)3.9H2O were
dissolved in 2 liters deionized water and slowly added into the K2CO3 solution
with stirring; the temperature was maintained at 60 - 80C. After mixing with
the nitrate solution, the pH was adjusted to 6.8 - 7.0 by addition of a small
quantity of aqueous K2C03 solution, whereupon stirring was continued for
another 30 minutes. Then the precipitate was filtered, and the filter cake was
washed until nitrate-free by repeated slurrying with 2 liters of deionized
water each time (ring analysis). The washed filter cake was dried for
15 hours at 120C. and calcined for 3 hours at 400 C. The calcined product
was mixed with 2% of its weight of natural graphite and compacted to
cylindrical tablets 3 mm in diameter and 3 mm long. Onto 150 g of the tablets
thus obtained, a solution of 8.4 g K2C03 dissolved in 30 ml H2O, was sprayed;
this was followed by drying at 120 C. for 2 hours and calcining at 400C.
for 3 hours.
The chemical composition and the BET surface of the catalyst marked 5
are given in Table I.
The activation of catalyst 5 with hydrogen and the reaction with
synthesis gas were carried out as in Example 1. The results of this test
and the composition of the reaction products are shown in Tables II and III.
Example 7
560 g K2C03 were dissolved in 2 liters deionized water and precipitated
and processed with a solution of 285.2 g Cu(NO3)2.3H2O, 217.6 g Zn(N03)2,
- 12 -
~L3L~
3)2 2 ~ 65-8 ~ Cr(N()3)3.9ll20 and 276 g ~l(No ) 9H O in
2 liters deioni~ed ~ater, as dcscribcd in Example 6.
Onto 150 g of t:he product tablets wns sprayed a solution of
8.4 g K2C03 dissolved in 30 ml water; this was followed by drying for 2 hours
at 120C. and calcining for 3 hours at 400 ('.
The chemical composition and the 13ET surface of this catalyst
designated 6 are SilOWIl in Table 1.
The activation of catalyst 6 with hydrogen and the reaction with
synthesis gas were carried out as in Example l. The results of this test and
the composition of the reaction products are shown in Tables Il and III.
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