Note: Descriptions are shown in the official language in which they were submitted.
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HOE 84/F 013
The present invention relates to a process for the
production of olefins from methanol in a tray-type reactor.
~erman Offenlegungsschrift 2,755,299, US Patent
4,062,905, U5 Patent 3,911,041, US Patent 4~079,096~
US Patent 3,979,47Z and German Offenlegungsschrift ZD615,150
have disclosed processes in which louer alcohols are con-
verted to olefins over zeolites. In European Patent
Application O60D103, the use of polytropically operated
tube bundle reactors or isothermal fluidized-bed reactors
and the working-up of the reaction m;xture from the con-
version of methanol over zeolites are described, whilst
the use of a tray-type reactor ;s sa;d to be d;sadvantageous
because of the difficulties in temperature control. A
two-stage process comprising a methanol dehydration stage
to give dimethyl ether and water, and the subsequent con-
version of the resulting ether-rich mixture over zeolites
in an adiabatically operated tray-type reactor ;s the sub-
ject of European Patent Application 088,494. The dehydra-
tion stage before the actual conversion to olefins is pre-
scribed as indispensable~ In addition, the use of catalystbeds with radial flow, in order to reduce the pressure drop
and thus to increase the selectivity, is described~
It ~as therefore the object to develop a process
which converts methanol to lo~er olefins in a tray-type
reactor in one stage, i.e. ~ithout a preceding dehydration
stage, economicaLly and with a high selectivity~
The invention therefore relates to a process for
the production of olefins from methanol in a tray-type
reactor, which comprises carrying out the process over
zeolite catalysts.
In view of the state of the art according to the
abovementioned European Patent Applications 0,088,494 and
0,060,103~ it is surprising that methanol can be converted,
without a preceding separate dehydration stage, to lower
olefins with h;gh selectivity in a tray-type reactor under
adiabatic reaction conditions; it was not foreseeable that
-- 3
temperature control ;n a tray~type reactor ;s quite manage-
able, contrary to the assertion in European Patent Appli
cation 0,060,103.
The process according to the inven~ion has the great
econom;c advan~age of single-s~age operation and, in ad-
ditionO avoids the crack;ng of methanol into C0 and hydro-
gen, ~hich zlways occurs to a certain extent in the de-
hydration step in t~o-stage processes~ Compared ~;th poly-
tropic operation in the tube bundle reactor, the conversion
in the tray-type reac~or has the advantage of a lo~er pres-
sure drop, ~hich leads to an increase in the selectivity
to lower olefins. The arrangement of the zeolite cata-
lyst on trays makes poss;ble, in particuLar when the rad;al
reactor principle is applied, an easy and very quick change
of the catalyst and an unusual flexibility ~ith respect
to varying catalyst qualities or types and adaptation to
the spec;fic conversion characteristics of these catalysts~
The starting material used for the process according
to the invention is a ~ater/methanol mixture in vapour
form, the water fraction being 40 to 80X M/M, preferably
50 to 70% M/M. Since the catalyst activity decreases ~ith
time during the reaction, the reactor discharge contains
varying quantities of dimethyl ether. This ether can be
separated off and added to the feed mixture, and it can
25 amount to 0 to 25X M/M, preferably 0 to 15X M/M, of the
total feed m;xture~
The liquid hourly space velocity of the total feed
mixture is in general chosen to be bet~een 0.5 and 2D h 1,
preferably 2 to 15 h 1
The zeolite catalysts used are above all those of
the pentasil type. The term pentasils is taken here as
defined by Kokotailo and Meier t"Pentasil family of hish
silicon crystalline materials" in Speclal Publication No. 33
of the Chemical Society London 1980): the pentasil family
comprises, for example~ the synthetic zeolites ZSM-5 tUS
Patent 3,702,886), ZSM-8 t~r;tish Patent 1,334~243), ZSM-11
tUS Patent 3,709,979~ and ZSM-23 tUS Patent 4,076,842).
Preferably, pentasils containing ~itanium, zirconium
~.~5~7'
~, ..
and/or hafn;um, as descr;hed in Gerrnan Offenlegungsschrift
3,141,283 and 2,141,Z85, are used~ Amonyst the~e, zircono-,
titano- and/or hafno-sil~cates or -aluminosil;cates of ZSM-
5 structure are above aLl suitable, preferably those having
the follo~ing composit;on, expressed in molar ratios of
the oxides:
SiO2 : ~0 - 0.15) Al203 : (0~002 - 1.0) M02~ in
particular
SiO2 : ~0 005 - 0-1) Al203 : (0.01 - 0.4) M0
M being zirconium, titan;um and/or hafnium
These zeolites can be prepared by methods such as
those described also for the synthesis of the z1rconium-,
titanium- or hafnium-free 7eolite ZSM-5, for exàmple ~ith
~he use of alkylammonium salts ~US Patent 3,70Z~886), of
tr;alkylamines in the simultaneous presence of alkylating
agents ~German Auslegeschrift 2,212~810), of diamines
(German Offenlegungsschrift 2,831,334) and/or of seed cry-
stals in the presence or absence of alcohols and/or ammonium
hydroxide (US Patent 4,199,556).
A preferred process for the synthesis for the said
zeolites compr;ses mixing zirconium, titanium and/or hafnium
as well as silicone, sodium and tetrapropylammonium com-
pounds and, in the case of the aluminosilicates, also
aluminum compounds in addition~ with ~ater and heating this
mixture in a closed vessel. Furthermore, seed crystals
can be added to this mixture before heating.
These starting compounds are in general employed in
the following ratio, expressed in molar ratios of the oxides:
SiO2 : ~0 - 0.2) Al203 : ~0.01 - 1.0) MOz
~0.01 - 0.5) Na20 : ~0~02 - 1~0) R20 : lS - 1ûO) H20,
preferably in the ratio of
SiO2 : ~0~01 - 0.1) Al203 : ~0~01 ~ 0.4) M02 :
~0.02 - 0~3) Na20 : (0~03 0~6) R20 : ~10 - 40) H20,
M being zirconium, titanium and/or hafnium and R being
tetrapropylammonium.
The compounds used can be, for example: silica gel,
sodium silicate, aluminum hydroxide, aluminum sulfate, sodium
alum;nate, aluminum halides, aluminum metahydroxide, zirconium
~ - 5 ~
halides~ zirconium sulfate, zirconyl chloride~ titanium
halides, titanium sulfate, hafnium halides, hafnium
sulfa~e, sodium hydroxideO sodlum suLfate~ sodium halides,
tetrapropylam Inonium hydroxide and tetrapropylam~onium
halides. However, other silicon~ aluminum, zirconium,
titan;um, hafn;um, sodium and alkylammonium compounds are
also suitable for the preparation of the zeolites.
The mixture of the particular chosen compounds ~ith
water is in general heated for 18 to 360 hours, preferably
24 to 240 hours, at a temperature between 100 and 200C,
preferably between 130 and 170C, in a closed vessel.
The zeolites formed are isolated in the conventional
mannerO for example by filtration, washed and dried. They
can be converted by known methods ;nto the catalyt;cally
act;ve forms, for example by calc;nat;on and/or ion exchange
~D.W~ Breck, Zeolite Molecular Sieves, 1974~.
It ~as not foreseeable that especially the Ti-,
Zr- and/or Hf-conta;n;ng pentasils have a part;cularly hiyh
select;v;ty for C2- to C4-olef;ns in the s;ngle-stage
process according to the invention~ The inlet temperature
at each of the trays is 270 to 400C~ The inlet tempera-
tures in the individual trays can be selected independently
of one another. They can be kept constant during the reac-
tion or, if the catalyst activity is decreasing, they can
be raised within the said temperature range. To maintain
the seLected temperatures, the heat of reaction is removed
between the trays by means of indirect or direct (injection)
cooling. Preferably, the heat of react;on ;s utilized for
the formation of hydrocarbons by in~ectin0 liquid methanol/
water mixtures with a ~ater fractlon of 40 to 80% M/M be-
t~een the tray¢. The pressure should be selected such
that 1.5 to 10 bar, preferably 1.5 to 4.5 bar, still pre-
vail at the reactor outlet.
The catalyst is in 0eneral arran~ed on 3 to 10 trays,
preferably on 4 to 8 trays. The flow through the beds can
be axial, in the conventionaL manner, but the principle of
the radial tray reactor is preferred for constructional
and economic reasons. The bed heights in the flo~ direction
'7
-- 6 --
result from the conversion characteristics of the ~eolites
employed and amount in gen0ral to 0.1 to 2 m, preferably
0.2 to 1.6 m.
The reaction mixture leaving at the outlet of ~he
S last tray is separated 1nto a gas fraction and liquid frac~
tion~ and the gas fraction composed of C1 - to C4 hydro~
carbons and dimethyl ether, is freed by conventional ab;
sorption or rectification processes from dimethyl ether~
which in general is recycled. The remaining hydrocarbon
1û mixture is ~orked up by proven methods of refinery tech
nology. The aqueous fraction is isolated from the liquid
phase, and the unconverted methanol contained therein and
small quantities of dimethyl ether are recycled to the re-
actor. The C5-hydrocarbons obtained in a small quan-
tity can be processed either to water fuels or to ra~materials for the chemical ;ndustryc
The processing to ra~ materials for the chemical
industry is of special economic importance because of the
high proportion of Cg-aromatics ;n the organic part of
the liquid phase and the unusually high p-xylene content
in these aromat;cs.
The process will now be described in accordance
with a preferred embodiment with reference to the drawings
in which:
Figure 1 is a flow sheet of the process of the
invention showing the preferred arrangement of the trays in
a mutually parallel arrangement;
Flgure 2 shows a longitudinal section of the
preferred radial-type cylindrical tray reactors for the
process of the invention.
~.~
- ~A -
,Z,.~
The way in ~hich the process according to the in-
vention is carried out in a part;cuLarly advantageous
embodiment, namely with the trays in a mutually parallel
arrangement, ;s illustrated in F-igure 1~
Methanol is passed from the stock vessel 1 via l;ne
2 into the mixer 3 and is mixed therein ~ith recycled
aqueous methanol from line 4~ This mixture is passed via
line 5 into the vaporizer/mixer unit 6, where it is mixed,
after vaporization, uith recycled dimethyl ether from Line
7~ The mixture of ~ater, methanol and dimethyl ether
passes via line 8 into the heat exchanger 9, is heated
there;n to 270 to 4ûOC and fed via l;ne 10 to the tray
11a. Liquid water/methanol mixture is injected from line
5 v;a the l;nes 12 - 15 into the lines 16 - 19 between the
trays 11 a - e. The reaction product composed of water,
olef;n-rich hydrocarbon mixture, d;methyl ether and un
converted methanol is passed via line 20 into the heat
.~,.,.,~,
b
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exchanger 21 and is cooled therein to a ~emperature which
permits the reac~ion product, after it has pas3ed through
line 22, to be used in the heat e~changer 9 for heating
the feed mixture to the reactor ;nlet temperature. The
reaction product leaves the heat exchanger 9 through line
23 and passes into the separator Z4. In the latter, the
gas phase 25, ~he C5-hydrocarbon phase 26 and the metha-
nol-containing water phase 27 are separated The ~ater
phase contains in general 0 to ZOX M/M of methanol, small
quantities of dimethyl ether and traces of acetic acid,
methyl acetate and acetone, but these do not adversely
affect the process. A part of the water phase 27 is passed
via line 4 to the mixer 3 for preparing the feed m;xture.
The remainder of the water phase~ namely the quantity ~hich
corresponds to the ~ater resulting from the formation of
hydrocarbons~ is passed through l;ne 28 ;nto the column 29
where the methanol is distilled off from the water. The
methanol is recycled through line 30 into the stock vessel
1~ The water is taken off via line 31 and d;scarded. The
C5-phase 26 is taken off via line 32 and passed to pro-
cessing to g;ve water fuel or ra~ products for the chemical
industry. The gas phase 25, composed of C1- to C4-
hydrocarbons (mainly unsaturated), dimethyl ether and small
quantities of C0, H2 and C02~ is passed through line
33 ;nto the separation stage 34 and freed there by distil-
lation or absorption/desorption from dimethyl ether, which
is recycled through line 7. The product freed from ether
is taken off via line 35 and processed to pure C2- to
C4-oLefins by kno~n processes.
The exothermic heat of react;on severely l;m;ts the
feasible ca~alyst bed heights. It therefore becomes neces-
sary to spread the catalyst over a large area at a low bed
height. As compared with a plane arrangement, the cylin-
drical arrangement of the catalyst in the rad1al reactor
enables large flow surfaces to be accommodated ;n a small
space. Moreover, the expensive steps required with a plane
arrangement for uniform distr;but;on of the product stream
over the entire bed are no longer necessary. The radial
~t~ f~ 7
type of construction of the trays has the add;tlonaL ad~
vantage that ~hey can be arranged parallel ~Fig~re 1~ ~he
resulting small overall he~ght of the complete reactor and
the ready accessihil1~y of the individual tray packin~s
~llo~ a rapid chanye of catalyst In part~cul3r, the
packinys can be prepared outside the traysD ~ith a uniform
bulk density in all parts of the packing~
Figure 2 sho~s a long;tudinal section of the tray
11a of a tray reactor 11 a - e of radial-type cylindrical
des;gn. The feed mix~ure o~ ~ater, methanol and dimethyl
ether passes through line 10 into the inlet channel 36 of
the tray 11a. The stream of reactants passes in ~he radial
direction through the catalyst packing 38 ~hich is bounded
by the perforated concentric flow surfaces 37 and 39~
The gas stream ;s then deflected into the out~et channel
40 and emerges through line 16 at an increased temperature
~due ~o the exothermic heat~ from the tray 11a~ To lower
the inlet temperature of the next tray, liquid ~ethanol/
~ater mixture is fed in through line 12, and a homogeneous
distribu~ion of the components and of the temperature is
obtained in the static mixer 41 before the reaction m;x-
ture is fed via l;ne 16 to the next ~ray.
A s~xing, ~h;ch is particularly favorable ;n eco-
nomic terms, of such a radial tray 11a is obtained ~hen
the cross-sect~onal area Fe of the inlet channel 36 and
the cross-sectional area Fa of the outlet channel 40 are
small compared ~ith the total mean flow surface Fk of the
- cylindrical catalyst packin~ 3a. These areas are obtained
fro~ the equ~t1ons
Fe= ~ Fa= 4 [A2-(E~2K)2] ~ Fk~ n(E~K)}I
Fk relatin~ to the geometr~cal center of the cylindr~cal
catalyst packing 38. H here is the height of the packing
38 and K is its thickness, E is the dia~eter of the inlet
channel 36 and A is the diameter of the outlet channel 40.
Preferably, Fe is ~ 0~02 to 0~1 and Fa is = 0.04 to
Fk Fk
~.,?~ 3 ~'
0.2, in part;cular fe = 0.05 to 0.08 and fa ~ 0~1 to U~15.
-
Fk Fk
~;th operation with;n these ranges, a very un;form flow
velocity ;s obta;ned.
The proces~ accord;n~ to the ;nvent~on makes it
possible, independently of the hitherto operated cracking
of light naphtha cuts from crude oil refining, ~o produce
lower olefins, startin0 from natural gas, coal and other
gasif;able raw materials, with higher selectivity than in
10 naphtha cracking.
The examples which follo~ are intended to explain
the invention, without limiting it in any way.
A) GENERAL TEST CONDITIONS
The apparatus consists of an axial-flo~ tray-type
reactor ~;th 4 tube-shaped trays tinternal diameter 100 mm)
of corros;on-resistant steel, ~herein the catalyst tempera-
ture is measured in direct contact by means of several
thermocouples in each case9 and recorded. The reactor is
brought to the reaction temperature by external heating
and an interspace sealed on all sides guarantees adiabatic
operation.
The feed mixture is passed through a vaporizer and
a superheater to the first bed. To remove the heat of
reaction, such a quantity of methanol/~ater mixture is fed
in at a controlled rate bet~een the trays that, after pass-
ing through a mixing section, the prescribed inlet tempera-
ture on the next bed is reached. The outlet of the last
tray is follo~ed by a heat exchanger ~hich cools the reac-
tion mixture and separates it into a gas phase and a liquid
phase~ The gas phase i,s measured volumetrically and ana-
lyzed by on-line gas chromatography. The liquid phase is
~eighed, and the C5 hydrocarbon phase is separated off
and ~eighed~ The tuo liqu~d phases are analyzed off-line~
The reactor makes it possible to investigate the
gas and liquid compositions after the individual trays.
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HOE 84/F 013
~) ~EST RESULTS
Comparison example and Example 1:
Methanol/water i5 fed ~n a ratlo of 1 : 2 M/M. The
composition of the reactor discharges is shown in Table 1.
In the comparison example, an H-ZSM 5 zeol;te pre-
pared according to Example 1 of US Paten~ 3,70Z,886 is
used~
In Example 1, a zirconium pentasil~ prepared as
follows according to Example 1 of German Offenlegungsschrift
1C 3,141,285, ;s used.
1.66 9 of sodium aluminate (54% M/M of AL203,
41X M/M of Na20) and 1.48 0 of sodium hydroxide are dis-
solved in 20 y of 20X M/M aqueous tetrapropylammonium
hydroxide solution (Solution A). A further solution
(Solution ~) is prepared by dissolving 6Z g of 40X M/M
of colloidal silica gel in Z30 9 of ZOX M/M aqueous tetra-
propylammonium hydroxide solution and concentrating this
solution in a rotary evaporator to a total of Z20 9
Solution A and Solution B are mixed with one another~
3.78 9 of zirconylchloride ZrOCl2 ~ 8 H20 are added
to this mixture, ~ith intensive stirring~ The resulting
suspension is homogenized and heated for 120 hours at 160C
in a closed vessel~ The product formed is filtered off,
~ashed with water and dried at 120C. This gives 27.3 9
of zircono-aluminosilicate.
The X-ray diffraction analysis shows a highly crys-
talline product of ZSM-5 structure. The chemical analysis
of the product calcined for 16 hours at 540C sho~s the
following composition, expressed in molar ratios of the
oxides:
SiO2 : 0.035 ZrO2 : 0~026 Al203 : 0.023 Na20~
~ n the comparison example and in Example 1, the
reaction temperature is in each case 330C at the tray
inlets, and the total liquid hourly space velocity is
5 x h 1 in both cases~
~o~
TA~LE 1- COMPOSITIONS OF THE REACTOR DISCHhRGES (% M/M)1)
Compar~son Example 1
example
D;~ethyL ether 36,5 29~8
CO~ COz, H2 0,4 0,9
Methane 0.6 1.1
Ethane 0.1 0.1
Propane 3~7 Z~9
autane 6.9 7.8
10 C5 12~7 10.6
Aromatics 8.5 8,0
EthyLene 21.7 25 . 6
Propylene 13.3 18.Z
Butene 4.6 2~9
Methanol conversion to
hydrocarbons (Z) 51 50
____________________________.
1) The figures given correspond to a 12 hour average.
