Process for the preparation of methanol and composition suitable for use as a catalyst in said process

Process for the preparation of methanol by contacting a gaseous mixture comprising carbon monoxide and hydrogen with a novel catalytic system formed by combining (a) a copper salt (b) an alcohol, and (c) a complex hydride, and allowing the combined components to react.

FIELD OF THE INVENTION 
The invention relates to a process for the preparation of methanol from a 
gaseous mixture comprising carbon monoxide and hydrogen and to a catalyst 
composition suitable for use in said process. 
BACKGROUND OF THE INVENTION 
A process for the preparation of methanol is described in U.S. Pat. No. 
4,619,946 comprising reacting carbon monoxide and hydrogen at relatively 
low temperature in the presence of a catalytic system derived from sodium 
hydride, a sodium alcoholate and an acetate of nickel, palladium or 
cobalt. The alcoholate applied is preferably a lower alkanolate having 1-6 
carbon atoms. As metal salt nickel acetate is preferably used. The 
catalyst is subjected to a conditioning or activating step for a prolonged 
time with a gaseous mixture comprising carbon monoxide and hydrogen at 
such an elevated temperature and elevated pressure that a substantial 
amount of carbon monoxide and hydrogen is consumed for this conditioning. 
In U.S. Pat. No. 4,614,749 a process is disclosed for the preparation of 
methanol by reaction of carbon monoxide and hydrogen in the presence of a 
slurry catalyst system resulting from combination of (1) a reducing agent 
comprising sodium hydride-alcohol and an acetate of nickel, palladium or 
cobalt, and (2) a carbonyl complex of one of the group VI metals. 
Another process for the preparation of methanol is described in Japanese 
Patent No. 56-169,634. This process comprises reacting carbon monoxide and 
hydrogen in the presence of a catalyst comprising a nickel compound and a 
metal alkoxide. The catalyst to be used for this process may be prepared 
by mixing a nickel compound with an alkali metal alkoxide. It is preferred 
to use a liquid organic diluent. It is observed that this Japanese 
application teaches a person skilled in the art, that a high reaction rate 
may be reached by preparing the catalyst system with the use of a 
substantially alcohol free organic diluent and that it is desirable that 
an alcohol be not present in the reaction system at the commencement of 
the reaction. Moreover from this Japanese patent application and 
especially from its example 2, it clearly appears that at low temperature 
only small amounts of methanol are produced in favour of production of 
methyl formate in large amounts. 
In Japanese Patent No. 56-110631 a process is described for the preparation 
of methanol comprising the use of a catalytic system derived from a 
hydride, an alcoholate and a copper salt. Relatively high reaction 
temperatures and pressures are necessary in order to obtain a reasonable 
yield of methanol. 
Although improvements in the performances of the catalyst systems as 
described hereinbefore, could be reached as compared to those used in the 
conventional methanol manufacturing processes, requiring severe 
conditions, the still growing demand for cheaper methanol as starting 
material for a still increasing area of chemical syntheses evoked 
continuing research efforts for a further improved methanol manufacturing 
process as compared to the currently operated high pressure processes. 
With the term improved methanol manufacturing process is meant a process 
utilizing a catalyst having enhanced activity at low temperatures, and 
retaining its activity for a long time under economically more attractive 
operating conditions. 
An object of the present invention is therefore to provide such an improved 
manufacturing process for methanol, as well as to provide an improved 
catalytic system therefor. 
SUMMARY OF THE INVENTION 
The instant process comprises contacting a gaseous mixture comprising 
carbon monoxide and hydrogen with a catalytic system obtainable by 
combination of: 
component (a): a copper salt, 
component (b): an alcohol, and 
component (c): a complex hydride, 
and allowing the combined components to react.

DETAILED DESCRIPTION OF THE INVENTION 
The anion of the salt in component (a) may be derived from a great variety 
of acids. It is preferred that the salt in component (a) is a salt of a 
carboxylic acid or sulphonic acid. Among these acids preference is given 
to alkanoic acids having 1-10 carbon atoms in the chain or to aromatic 
sulphonic acid. More preferably formic acid, acetic acid, oxalic acid or 
p-toluene sulphonic acid are used. Examples of carboxylic acids from which 
component (a) also may be derived are dicarboxylic acids such as malonic 
acid, dimethylmalonic acid, succinic acid, glutaric acid, adipic acid, 
pimelic acid, suberic acid, azelaic acid, phthalic acid, isophthalic acid 
and terephthalic acid. The carboxylic acids from which component (a) may 
be derived may contain substituents, for example alkoxy groups, 
particularly those having not more than five carbon atoms, hydroxy groups, 
cyano groups and fluorine, chlorine, bromine and iodine atoms. Examples of 
such carboxylic acids are glycolic acid, 2-hydroxypropionic acid, 
3-hydroxypropionic acid, glyceric acid, tartronic acid, malic acid, 
tartaric acid, tropic acid, benzilic acid, salicylic acid, anisic acid, 
gallic acid, 3,5-dichlorobenzoic acid, 3,5-dibromobenzoic acid, 
cyanoacetic acid, monofluroacetic acid, difluoroacetic acid, 
trifluoroacetic acid and trichloroacetic acid. Other examples of suitable 
acids from which component (a) may be derived are propanoic acid, butanoic 
acid, 2-methylpropanoic acid, pentanoic acid, 3-methylbutanoic acid, 
2,2-dimethylpropanoic acid, hexanoic acid, heptanoic acid and octanoic 
acid, hydrochloric acid, sulphuric acid, nitric acid, phosphoric acid, 
methyl sulphonic acid and trifluoromethyl sulphonic acid. Further, 
compounds as copper acetylacetonate may also be used. 
A mixture of the salts in question may be used in component (a), for 
example formate and oxalate, formate and acetate, or acetate and oxalate. 
The salts in component (a) may contain crystal water, but are preferably 
free therefrom. 
The alcohol of component (b) may be aromatic or cycloaliphatic but is 
preferably aliphatic. Preference is given to alkanols, in particular to 
those having in the range of from 1 to 20 carbon atoms per molecule. Among 
the latter alkanols those having of from 4 to 12 carbon atoms per molecule 
are preferred, because such alkanols can be easily separated from methanol 
by means of distillation. Examples of such alkanols are tert-butyl 
alcohol, tert-pentyl alcohol, hexanol, heptanol and alkanols having of 
from 8 to 12 carbon atoms per molecule. Tert-butyl alcohol and tert-pentyl 
alcohol are particularly preferred. Dihydric alcohols may also be used, 
for example ethylene glycol, propylene glycol, 1,3-dihydroxypropane, 
1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol or 
1,2-pentanediol. Component (b) may also be glycerol. 
Component (b) may be a mixture of alcohols, for example of tert-butyl 
alcohol and ethylene glycol or of tert-pentyl alcohol and 1,4-butanediol. 
Component (c) may be a complex hydride derived from an alkali metal and a 
metal of Group III of the Periodic Table. The alkali metal is suitably 
chosen from lithium, sodium and potassium. The Group III metal is suitably 
chosen from boron and aluminium. Preferred complex hydrides are 
LiAlH.sub.4, NaAlH.sub.4, KAlH.sub.4, LiBH.sub.4, NaBH.sub.4 and 
KBH.sub.4. More preferably borohydrides are used, especially sodium 
borohydride. Further, complex hydrides containing one or more alkyl, 
alkoxy, aryloxy or cyano groups may be used. Suitable compounds in this 
respect are LiBEt.sub.3 H, NaAlEt.sub.2 H.sub.2, LiAlH(OMe).sub.3, 
LiAlH.sub.3 (O-tBu), LiAL(Et.sub.3 CO).sub.3 H, NaB(OAc).sub.3 H, and 
NaBH.sub.3 CN. Other suitable complex hydrides, e.g. NaBH.sub.2 S.sub.3, 
may also be used. Mixtures of two or more complex hydrides are also 
included. 
If desired, an alcoholate of an alkali metal or an alcoholate of an 
alkaline earth metal may also be combined in the catalytic system. This 
alcoholate is preferably a lithium, sodium or a potassium alcoholate. 
Among the alcoholates preference is given to sodium and potassium 
alkoxides, particularly to those having of from 1 to 20 carbon atoms per 
molecule, more particularly of from 1 to 6 carbon atom per molecule, such 
as sodium methoxide, sodium ethoxide, sodium propoxide, sodium butoxide, 
sodium isobutoxide, sodium tert-pentoxide, potassium tert-butoxide and 
potassium 2-methyldode-2-oxide. 
The combination and reaction of components (a), (b) and (c) in the process 
according to the present invention may be carried out at a temperature 
which is not critical and may vary within wide ranges. The combination and 
reaction can be carried out at relatively low temperature, preferably in 
the range of from 0.degree. C. to 100.degree. C. Very good results are 
usually obtained at temperatures in the range of from 30.degree. C. to 
60.degree. C. 
It has, furthermore, been found that the activity of the catalytic system 
can be further enhanced by a pre-treatment. According to a preferred 
embodiment of the present invention the catalytic system is pre-treated by 
contacting it for a prolonged time with a gaseous mixture comprising 
carbon monoxide and hydrogen at such an elevated temperature and elevated 
pressure that no substantial consumption of carbon monoxide and hydrogen 
takes place. Usually, a period of from 10 min to 5 h at a temperature 
between 30.degree. C. and 120.degree. C., preferably between 50.degree. C. 
and 90.degree. C., and a pressure between 5 and 100 bar is sufficient for 
the pre-treatment. The pre-treatment has reached its end where the 
pressure progressively starts decreasing which is a signal for formation 
of substantial amounts of methanol. Surprisingly, the present 
pre-treatment consumes very little carbon monoxide and hydrogen but yet 
results in the formation of a catalytic system having a considerably 
enhanced activity for the production of methanol. At the end of the 
pre-treatment the temperature may be adjusted to the required reaction 
temperature, which is a value at which substantial amounts of methanol are 
produced. This adjustment may be an increase of the temperature, but it is 
also possible that the temperature can be decreased. Such an increase or 
decrease of the temperature will usually be over a range of 10.degree. C. 
to 50.degree. C. It is, however, possible, that no adjustment of the 
temperature is required at all, pre-treatment and methanol production 
being carried out at substantially the same temperature. 
The process according to the present invention may be carried out at a 
temperature and a pressure which are not critical and may vary within wide 
ranges. Preferably, a temperature of from 60.degree. C. to 150.degree. C., 
more preferably of from 80.degree. to 120.degree. C. and a pressure of 
from 5 to 100 bar, more preferably of from 20 to 80 bar, still more 
preferably of from 30-60 bar are used. 
The process according to the present invention may be carried out with an 
organic diluent in which the catalytic system is present, at least partly, 
as a suspension. Suitably, a weight ratio of organic diluent to component 
(a) of from 0.1 to 5000 is used, but this weight ratio may be lower than 
0.1 or higher than 5000. Any inert diluent may in principle be used. 
Examples of suitable diluents are ketones, such as acetone, methyl ethyl 
ketone, methyl isobutyl ketone, acetophenone, cyclohexanone and 
acetylacetone; ethers such as anisole, 2,5,8-trioxanonane (also referred 
to as "diglyme"), diethyl ether, diphenyl ether, diisopropyl ether and 
tetrahydrofuran; aromatic hydrocarbons, such as benzene, toluene, the 
three xylenes and ethylbenzene; halogenated aromatic compounds, such as 
chlorobenzene and o-dichlorobenzen; halogenated alkanes, such as 
dichloromethane and carbontetrachloride; alkanes, such as hexane, heptane, 
octane, 2,2,3-trimethylpentane and kerosene fractions; cycloalkanes, such 
as cyclohexane and methylcyclohexane; nitriles, such as benzonitrile and 
acetonitrile; sulphoxides, such as dimethyl sulphoxide; sulphones, such as 
diisopropyl sulphone, tetrahydrothiophene-1,1-dioxide (also referred to as 
"sulfolane"), 2-methyl-4-butylsulfolane and 3-methylsulfolane. Mixtures of 
two or more solvents may be used. Very good results have been obtained 
with ethers. 
The process according to the present invention is preferably carried out 
using a molar ratio of component (b) to component (a) of from 0.5:1 to 
100:1 and, more preferably, from 1:1 to 50:1, still more preferably from 
2:1 to 25:1, but the use of molar ratios below 0.5 and above 100 is not 
excluded. The process may be carried out using a molar ratio of component 
(c) to component (a) of from 0.1 to 1 to 100 to 1, preferably of from 1 to 
1 to 10 to 1, more preferably of from 2 to 1 to 5 to 1. 
In a preferred embodiment the process of the present invention is carried 
out in the presence of a certain amount of a basic nitrogen compounds. 
Preferred basic nitrogen compounds are aromatic nitrogen compounds in 
which the nitrogen atom forms a part of the aromatic system, e.g. 
pyridine, quinoline etc. Especially preferred is pyridine. Suitably, a 
molar ratio of basic nitrogen compound to component (a) of from 0.5 to 1 
to 50 to 1 is used, preferably 1 to 1 to 10 to 1. 
The carbon monoxide and hydrogen may be used as pure gases or diluted with 
an inert gas such as a noble gas or nitrogen. The process according to the 
present invention may be carried out using a molar ratio carbon monoxide 
to hydrogen in the gaseous mixture which is not critical and may vary 
within wide ranges, suitably of from 1:0.2 to 1:20. The carbon monoxide 
and hydrogen may be obtained by partial oxidation of hydrocarbons, for 
example of natural gas. 
The methanol produced according to the invention forms another feature of 
the invention. It may be used for a variety of purposes, for example for 
the manufacture of synthetic gasoline, as a fuel component and for the 
production of methyl tert-butyl ether. 
The process according to the present invention may be carried out 
batchwise, semi-continuously or continuously. 
The invention also relates to a novel composition obtainable by combination 
of: 
component (a): a copper salt, 
component (b): an alcohol, and 
component (c): a complex hydride, and 
allowing the combined components to react. 
Said novel composition may be used as a catalytic system in the process 
according to the present invention. 
The ranges and limitations provided in the instant specification and claims 
are those which are believed to particularly point out and distinctly 
claim the instant invention. It is, however, understood that other ranges 
and limitations that perform substantially the same function in 
substantially the same way to obtain the same or substantially the same 
result are intended to be within the scope of the instant invention as 
defined by the instant specification and claims. 
The invention will be described the the following examples which are 
provided for illustration purposes and are not to be construed as limiting 
the invention. 
Each experiment was carried out in a 300 ml Hastelloy C autoclave 
(Hastelloy is a trade mark) provided with a magnetic stirrer. The reaction 
mixtures were analyzed by means of gas-liquid chromatography. 
EXAMPLE 1 
The autoclave was charged under a nitrogen atmosphere with diglyme (50 ml), 
copper acetate (5 mmol), sodium borohydride (20 mmol) and methanol (10 ml, 
8 g), heated to a temperature of 50.degree. C. and stirred for 1 hour. 
Potassium t-butanolate (60 mmol) was added, the autoclave was sealed and a 
mixture of 1 volume of carbon monoxide and 2 volumes of hydrogen was added 
until a pressure of 45 bar was obtained. 
The autoclave was heated for 5 hours at 100.degree. C. while keeping the 
pressure between 30 and 60 bar (average 45 bar) by intermittently 
introducing said mixture of carbon monoxide and hydrogen. A water-white 
solution was obtained containing 11 grams of methanol (3 grams formed). 
EXAMPLE 2 
Example 1 was repeated using 10 mmol copper acetate instead of 5 mmol. 
Yield: 4 grams of methanol were formed. 
Comparative Example A 
Example 2 was repeated, however, no methanol was used. Yield: 0.6 g of 
methanol. 
EXAMPLE 3 
Example 1 was repeated using pentanol (50 ml) in stead of diglyme as 
solvent. No methanol was used. Yield. 6.0 g of methanol. 
EXAMPLE 4 
Example 1 was repeated using pentanol (50 ml) in stead of diglyme as 
solvent. Pyridine (10 mmol) was added to the reaction mixture. No methanol 
was used. The reactor temperature was 80.degree. C. Yield: 4.0 g of 
methanol.