Note: Descriptions are shown in the official language in which they were submitted.
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Preparation of olefins from crude methanol
Recently, endeavors tQ use methanol for the pre-
paration of olefins have aroused increasing interest.
Methanol can easily be prepared from coal by means of well-
established technologies, via coal gasification and the
preparation of synthesis gas. Should it prove possible to
convert methanol economically to lower olefins, the further
conversion processes which are at present conventionally used
' in the chemical industry could be retained if coal was used
as the raw material. Hence, processes have been developed
in recent years for preparing olefins from methanol and/or
dimethyl ether. Such a process is described, for example,
in German Laid-Open Application DOS 2,615,150 published on
October 21, 1976. The catalyst used in this process is
the aluminosilicate zeolite ZSM-5, which in fact is a
catalyst foraromatization reactions. However, the reaction
can be directed towards the formation of olefins by taking
various measures, in particular by reducing the residence
time. Other measures which favor olefin formation are the
dilution of methanol or of dimethyl ether with inert gases,~
or the dilution of the catalyst with binders. Experience
shows that high olefin yields can only be achieved if the
methanol and/or dimethyl ether is very greatly diluted
with inert gases. Hence, the process is uneconomical.
Other processes which have been disclosed have the dis-
s advantage that the catalyst throughput is low, and that
the catalyst carbonizes rapidly. There is therefore
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great interest in a simple process which permits complete
conversion of crude methanol and/or dimethyl ether into
hydrocarbons consisting in the maln of C2-C5-olefins.
We have found that C2-C5-olefins are obtained in
a simple manner from crude methanol and/or dimethyl ether
by catalytic conversion at an elevated temperature in the
presence of a zeolite-containing catalyst, if the zeolite
has been prepared from technical-grade waterglass with the
aid of hexamethylenediamine, without addition of a metal
salt.
In a preferred embodiment, crude methanol is re-
acted over the zeolite catalyst according to the invention
at between atmospheric pressure and about 30 bar, and at
from 300 to 700C, preferably from 400 to 650C. Crude
methanol for the purposes of the invention means methanol
containing up to about 30% by weight of water, ie. the
product formed in the synthesis of methanol. Other
lower alcohols may also be present in the crude methanol.
The catalyst throughput, expressed in g of methanol and/or
dimethyl ether/g of catalyst.h is advantageously selected
to be such that the latter compounds are converted as
completely as possible, thereby eliminating separation
and recycling problems. In general, therefore, the
throughput is of the order of from 2 to 50, preferably
from 5 to 15, g/g of zeolite.h. However, it is poss-
ible to select higher throughputs, or to dilute the
starting materials with an inert gas, for example nitro-
gen, without adverse effect on the composition of the
hydrocarbon mixture formed. At the same time it is
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a particular advantage of the invention that the conver-
sion of crude methanol or dimethyl ether to C2-C5-olefins
can be carried out without a diluent.
The zeolites described in German Patent Applica-
tion P 28 31 344.0 published on March 15, 1979 can be used
as zeolite catalysts. These catalysts are distinguished
by particularly high activity and selectivity.
The example which follows illustrates the
invention.
EXAMPLE
Preearation of the zeolite:
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Three solutions are prepared. Solution 1 con-
sists of 326.6 g of technical-grade waterglass (contain-
ing 8~ by weight of Na2O and 28% by weight of SiO2~ and
352 g of water.
Solution 2 consists of 300 g of a 50 per cent
strength aqueous hexamethylenediamine solution and solution 3
consists of 508.3 g of water and 24.7 g of 96 per cent
strength sulfuric acid. Solutions 2 and 3 are successively
added to solution 1, whilst stirring. The resulting
solution is heated for 5 days at 150C under its autogenous
pressure in a steel autoclave. The resulting product is
filtered off, washed and dried at 100C.
Preparation of the catalyst from the zeolite:
The zeolite obtained is mixed with boehmite in
a ratio such that the zeolite content in the mixture is
about 65% by weight, based on anhydrous and amine-free
~ product. The mixture is then
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- kneaded with water and extruded to form strands of 1 mm
diameter. These are calcined at 540C, then treated
with an aqueous ammonium sulfate solution at 80C,
filtered off, washed and dried
Conversion of crude methanol to olefins:
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20 g (dry weight) of this catalyst are introduced
into a flow-tube reactor of 20 mm diameter and the acti-
vity in respect of the conversion of crude methanol to
olefins is tested. The reaction conditions and experi-
mental results are shown in the Table which follows.
The reaction products wereanalyzed by gas chromatography.
Entry temperature 400C
Temperature rise 200C
Pressure 1.3 bar
Throughput 170 g of crude methanol/h
; Total throughput 1,000 g
Conversion 95-100%
The reaction product obtained has the following
composition:
Liquid hydrocarbons, 18% by weight, based on CH2 employed
Gaseous hydrocarbons, 82% by weight, based on CH2 employed,
and containing the following:
Olefins C2 20% by volume
C3 43% " ~I
C4 16% " "
Cs 5% "
Paraffins Cl 4 " "
C2 traces
C3 2% by volume
- C4 10% " "
