PREPARATION OF OLEFINS FROM CRUDE METHANOL

PREPARATION D'OLEFINES A PARTIR DE METHANOL BRUT

English Abstract

O.Z. 0050/033724
Abstract of the disclosure: A process for the preparation
of C2-C5-olefins from crude methanol and/or dimethyl
ether by catalytic conversion at an elevated temperature
in the presence of a zeolite, containing iron oxide, as
the catalyst. The raw material used for the process
is undiluted crude methanol and/or dimethyl ether.

Claims

We claim:- O.Z. 0050/033724
1. A process for the preparation of C2-C5-olefins
from crude methanol and/or dimethyl ether by catalytic
conversion at an elevated temperature in the presence of
a zeolite-containing catalyst, wherein the zeolite contains
iron oxide.
2. A process as claimed in claim 1, wherein undilu-
ted crude methanol and/or dimethyl ether is used as the
starting material.

Description

ggo
Preparation of olefins from crude methanol
Recently, endeavors to use methanol for the preparation
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 convért 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 exampler 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
for aromatization reactions. However, the reaction can be
directed toward 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~ inders. 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 dis-
closed have the disadvantage 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 main 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
contains iron oxide.
In a preferred embodiment, crude methanol is
lo reacted over the zeolite catalyst, containing iron oxide,
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 formad 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
a particular advantage of the invention that the conver-
sion of crude methanol or dimethyl ether to C2-C5-olefins

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can be carried out without a diluent.
The zeolites described in German Patent Applica-
tion P 28 31 611.2 can be used as zeolite catalysts con-
taining iron oxide. These catalysts are distinguished
by particularly high activity and selectivity, and in
addition by a very long life between successive regenera-
tion steps;
The Examples which follow illustrate the process
according to the invention.
EXAMPLE
eparation of the zeolite containin~ iron oxide:
lo Three solutions are prepared. Solution 1 con-
sists of 326.6 g of technical-grade waterglass (containing
8% by weight of Na20 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, 24.7 g of
96 per cent strength sulfuric acid and 12.4 g of Fe2(S04)3
. 18 H20. Solutions 2 and 3 are successively added to
solution 1, whilst stirring. The resulting mixture 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 resulting zeolite, containing iron oxide, is
mixed with boehmite in a ratio such that the zeolite con-
tent in the mixture is about 65% by weight, based on
ar,hydrous and amine-free product~
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The mixture is then 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:
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 o~ 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 380C
Temperature rise 220C
Pressure ^ 1.4 bar
Throughput 200 g of crude methanol/h
Total throughput 3,000 g
Conversion 95-100%
The reaction product obtained has the following
composition:
Liquid hydrocarbons, 15~ by weight, based on CH2 employed
Gaseous hydrocarbons, 85% by weight, based on CH2 employed,
and containing the following:
Olefins C2 10% by volume
C3 50% " "
C4 20% " "
c5 6% 1~ n

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Paraffins Cl 4% by volume
C2 ~ 1%
C3 2%
C4 4% "
Remainder 3% " "