NZ215131A - Process for manufacturing olefins from methnol and/or dimethyl ether - Google Patents

Description

New Zealand Paient Spedficaiion for Paient Number £15131 iwiwwi—mi'w> Priority Date(s): . *2.

Complete Specification Filed: /■?.

Class: .C.Q .<ro7rC£/327..

Publication Date: ...

P.O. Journal. No: .../.r?P.....

NO DRAWINGS PATENTS FORM NO. 5 215 13 1 NEW ZEALAND PATENTS ACT 1953 COMPLETE SPECIFICATION "PROCESS FOR CCNVERTING METHANOL OR DIMETHYLEIHER TO OLEFINS" -if WE msmUT FPANCAIS DU PETROIT. a French Professioncil Body of 4, Avenue de Bois-Preau 92502 Rueil-Malmaison, France, hereby declare the invention, for which-i/we pray that a patent may be granted to-fne/us, and the method by which it is to be performed, to be particularly described in and by the following statement ■ -1- 'followed by ptfe TA.) 21513 l*w The invention concerns a process for manufacturing, in particular, propylene, with the simultaneous formation of butenes in a substantially lower proportion, by converting methanol and/or dimethylether in the pre-sence of certain aluminosilicates.

BACKGROUND OF THE INVENTION The conversion of methanol to hydrocarbons is a remarkable reaction, known since a long time, and during which carbon-carbon bonds are formed from Cj "radicals", which are formed from methanol In the presence of certain acid catalysts. However this conversion has only become of industrial importance in the seventies and this in relation with two events : - the discovery of sufficiently active, and particularly selective catalysts capable to convert methanol to hydrocarbons and particularly to motor gasoline, and - the policy of the oil-producing countries resulting in a disruption of the economical and technical data in the petrochemical and oil 15 industries.

The most part of the world methanol production originates from natural gas, but it is also obtained from heavier hydrocarbons after a convenient conversion, by fermentation, by distillation of wood etc... and from coal or from any other material of high content of carbon 20 derivatives.

With its new technique for converting methanol to hydrocarbons, Mobil Company has introduced on the market other sources for synthesized motor fuels in addition to those of the conventional processes of Fischer-Tropsch and Bergius.

Economically, the production of hydrocarbons from methanol seems to be more competitive than the other existing techniques for synthesizing motor fuel from coal. 215 13 2 By a suitable selection of the catalyst and a convenient adaptation of the operating conditions, it is possible to direct the conversion of methanol towards the production of light or heavier hydrocarbons, of aroma-tics or olefins.

The present invention more particularly concerns a process for manufacturing propylene from methanol or dimethylether or a mixture thereof, said process being certainly of high interest in the present economical conditions.

As a matter of fact propylene is one of the oldest basic products for 10 chemical and petrochemical industry and is one of the very important light olefins. It is widely used for manufacturing alkylates and polymerization gasolines in order to improve the octane number of the motor fuels.

It has also been used In very substantial amounts for manufacturing 15 plastic materials such as polypropylene and also for manufacturing other products such as : acrylonitrile, propylene oxide, propanol, cumene etc...

Up to now, propylene was mainly obtained as a product of oil refinery and mainly by steam-cracking of naphthas.

But the oil economical conjuncture has oriented the refining opera-20 tions towards steam-cracking of heavier products instead of "naphtha" cuts, thus decreasing the propylene production.

It is hence of interest to attempt to obtain said product by other means, as according to the present process.

Many works have for object the conversion of methanol to hydro-25 carbons which conversion takes place in the presence of catalysts.

The mostly used catalysts are zeolites or contain zeolites which are crystallized alumlno-silicates and seem perfectly convenient for this type of conversion : - in view of their acid properties, and - as a result of their perfectly defined structure, the size of their 5 lntercrystalline channels being of the same order of magnitude as the size of the organic molecules housed therein during the reaction.

The major disadvantage of this reaction of methanol conversion to hydrocarbons is the quick deactivation of the catalyst due to irreversible deposits of very condensed organic products ("coke").

Many works reported in the technical literature attempt to give a solution to this problem. Their object is to modify, by various means, the catalytic properties of said alumino-silicates in order to confer them a higher selectivity and hence to decrease the "coke" formation at their surface.

The invention having for object a process for selectively producing olefins from methanol or dimethylether, it has been used for this purpose a catalyst optimized for the production of light olefins, as disclosed in the European patent N° 0084 748 of January 4, 1982.

Said patent discloses the use, for producing unsaturated hydrocarbons having essentially 2 to 5 carbon atoms per molecule, of a catalyst consisting mainly of modified zeolite so as to very considerably increase its life-time and selectivity.

This modification consists in dealuminating a zeolite of synthetic mordenite type.

Said modified zeolite, in order to have a good selectivity for olefins production, must have a Si/Al ratio (atoms) ranging from 80 to 150. 215 13 4 Now it has been observed that, by proceeding under specific operating conditions which are the object of the present invention, it was possible to noticeably improve the propylene yields.

SUMMARY OF THE INVENTION According to the invention, the best yields of olefins having 2 to 5 5 and preferably 3 to 4 carbon atoms per molecule are obtained by reacting, in the presence of a dealuminated zeolite, methanol and/or dimethylether at a sufficient temperature and by sufficiently diluting the reactant with at least one gas (nitrogen, hydrogen, carbon monoxide, carbon dioxide) or steam.

In practice, the reactant (methanol and/or dimethylether), diluted with a carrying gas or with steam, is reacted over at least one catalyst of the dealuminated mordenite type, at a pressure ranging from 0.01 to 3 MPa and preferably from 0. 1 to 0.5 MPa and at a temperature ranging from 300°C to 650°C, preferably from 350°C to 550°C.

The reactant concentration in the gas (or steam) passing over the catalyst bed will range from 5 to 75 % by volume, preferably from 25 to 60%.

The hourly volume flow rate or liquid hourly space velocity (LHSV) will range from 0.5 to 100 liters of liquid methanol per liter of cata-20 lyst and per hour, preferably from 0.5 to 50 liters.

The products flowing out from the reaction zone are conveyed to a separation zone wherefrom the obtained olefins are separated from the unre-acted reactant (methanol and/or dimethylether), which is at least partly recycled, and from the one or more reactant diluents (gas or steam) which 25 may also be recycled. The obtained hydrocarbons are then subjected to separation in order to recover, on the one hand, a cut of high content of olefinic hydrocarbons having 2 to 3 carbon atoms per molecule and, on the 215131 other hand, a cut containing a major part of higher olefins having at least 4 carbon atoms per molecule, said cut generally containing also butanes.

It has been observed, and this is one of the object of the invention, 5 that when feeding with at least a part of said cut of higher olefins the reactor input where it is contacted with the catalyst bed jointly with ^ methanol and/or dimethylether, two advantages were obtained : - on the one hand, a part of the heat produced by the reaction is removed , and - on the other hand, the yield to propylene and the catalyst life-time are noticeably increased.

Preferably 20 to 60% by weight of said cut of higher olefins are recycled. Although the examples illustratinq the invention are performed with only a fixed bed of catalyst, this technique must not be considered 15 as limitative.

As a matter of fact, the catalyst may be arranged in two or more successive beds, in one or more reactors. This arrangement has the advantage to make easier the removal of heat evolved during the reaction.

The catalysts may also be used as moving bed contained in one or more 20 moving bed reactors, said technique providing for an easier removal of the —v heat evolved during the reaction and having also the advantage of increa- sing the space velocity of the reactants with a selectivity improvement : the charge successively flows through each reactor or reaction zone in axial or radial flow (radial meaning a flow from the center towards the 25 periphery or from the periphery towards the center). The reaction zones ; are arranged in series, for example side-by-side or superposed. The charge ■ —> successively flows through each of the reaction zones, with introduction of charge or of intermediary recycle between the reaction zones in order mi„.".,l mi I, .....Jb.—: - ■■■■ '■15131 6 to control the thermal level of the reaction by addition or removal of heat ; fresh catalyst is Introduced at the top of the first reaction zone with the fresh charge ; then it flows progressively downwardly through said zone, wherefrom it is progressively withdrawn at the bottom, 5 and, by any convenient means (particularly lift for reactors placed side-by-side), it is conveyed to the top of the next reaction zone wherethrough It progressively flows also downwardly, and so on, up to the last reaction zone, at the bottom of which the catalyst is also progressively withdrawn and then fed to a regeneration zone. From the output of the re-10 generation zone the catalyst is progressively reintroduced at the top of the first reaction zone. The various catalyst withdrawals are effected effected progressively, as above-mentioned, i.e. either periodically or continuously. Continuous withdrawals are preferred to periodical withdrawals.

The catalyst used according to this invention is prepared and has the same performances as disclosed in the European patent N° 0084748. It consists essentially of a dealuminated mordenite whose Si/Al atomic ratio is higher than 80, preferably from 80 to 96 and more particularly from 87 to 90, with a Na^O content lower than 0.1 % by weight and whose speci- fic surface, after shaping, with an optional addition of about 5 to 40 %, for example 10 %, by weight, of a clayish binding agent, ranges from 390 to 600 m'Vg and preferably from 420 to 550 m^/g and has a total pore volume ranging from 0.540 to 0.650 cm^/g and preferably from 0.550 to 0.600 cm^/g ; its pore volume, for pores of a diameter higher than -9 3 3 lOnm (10 x 10 m), ranging from 0.350 cm /g to 0.550 cm /g and preferably from 0.400 to 0.500 cm^/g, and its bed density for pellets of about 3x2 mm, ranging preferably from 0.600 to 0.700 g/cc.

The following examples, illustrating the invention, have been performed with a catalyst containing, as major constituent, a pelletized "I'i WfiW! IBWWW»»^W8 lJ - 21513 1 7 (3x2 mm) dealuminated mordenite whose characteristics are as follows : Surface 450 m^/g Total pore volume 595 cm^/g Pore volume for pores > 10 nm 0.460 cm^/g Bed density (packed) 0.650 g/cm^ (for balls of 3 x 2 mm) Sl/Al ratio (atom) 89.2 The charge was a 50/50 mixture by weight of water and methanol. The reaction was conducted in a pilot unit having a straight vertical reac- tor containing 40 cm^ (26 g) of pelletized catalyst (3x2 mm) including 10 % of clayish binder (specific surface of the catalyst mass of 455 m2/g).

The catalyst has been brought to a temperature of 500°C in an air flow of 250 1/h, previously dried by passage through an alumina bed for 15 2 hours.

After this pretreatment, the 50/50 by weight mixture of methanol with steam is passed through the catalyst bed.

The operating conditions, which are the same in all the following examples, are : Pressure atmospheric Temperature 460°C LHSV 1 h"1 (liter/h) The test is considered as completed when the sum of produced C^, im,, 21513 8 and olefins becomes smaller than 10 % by weight of the initial yield. This time is about 50 hours.

EXAMPLES In the following examples the whole unconverted methanol amount and the whole steam amount were recycled.

Example 1 This test has been conducted for 50 hours under the above-mentioned conditions without recycling of the C* hydrocarbons (charge : 50 % by weight water, 50 % by weight methanol).

Example 2 This example was conducted in the same operating conditions as in example 1 but with a recycling of at least a portion of the obtained C* 10 hydrocarbons.

The charge composition here including the recycle, was then as follows : Water 50 % by weight Methanol 42.5 % by weight C* recycle 7.5 % by weight At the reactor output and after separation of steam and of unreacted alcohol, the hydrocarbons effluent is fed to a distillation zone where- from are separated, from the column bottom, the C* hydrocarbons, 215^5 9 amounting to 12.51 % by weight of the total charge fed to the reaction zone (water, alcohol and hydrocarbons) and having, by weight, the following composition : Butanes 15.10 Butenes 63.15 C* 18.15 Aromatics 3.60 At the top of the fractionation zone are withdrawn the C^, C^, and Chydrocarbons containing more than 90 % by weight of propylene.

The composition by weight of said cut of very high propylene content is as follows : Methane 1.28 % Ethane 0.16 % Ethylene 5.13 % Propane 1.20 % Propylene 92.23 % 100.00 % The cut containing the C* hydrocarbons amounts to 12.51 % by weight of the total amount of products fed to the reaction zone ; 20 59.95 % by weight of this cut are fed as recycle to the reaction zone, this recycle amounting to 7.5 % by weight of the total charge fed to said zone.

The remainder of said cut (i.e. 40.05 %) is fed for example to the gasoline pool.

The following table reports the composition by weight of the products 21513 obtained in examples 1 and 2 in proportion of the charge (after 50 hours of treatment).

TABLE I EXAMPLE 1 EXAMPLE 2 Products Products Methanol 2.73 2.34 Dimethylether 0.19 0.16 Water 76.50 72.52 C^to C^parafflnic hydrocarbons 0.33 0.33 Ethylene 0.66 0.64 Propylene 11.50 ■¥ 7.50 12.51 From the obtained results as reported in the above table, it is ob- """\ 15 served that, when operating in the conditions of example 1, i.e. without Vv_x recycling the obtained hydrocarbons, the propylene production amounts to 25.57 kg for 100 kg of converted methanol, whereas when recycling said hydrocarbon cut, 28.63 kg of propylene are obtained for 100 kg of converted methanol. 215131 11

Claims (9)

WHAT WE CLAIM IS:

1 - A process for manufacturing olefins containing 2 to 5 carbon atoms per molecule, from a reactant consisting of methanol or dimethylether or a mixture thereof, performed in the presence of at least one catalyst whose major constituent is dealuminated mordenite of a Si/Al atomic ratio 5 higher than 90, of a Na^O content lower than 0.1 % by weight, of a specific surface, after shaping, ranging from 390 to 600 m^/g, of a total pore volume ranging from 0.540 to 0.650 cm^/g, of a pore volume _9 for pores of a diameter higher than 10 nm (10 x 10 m) ranging from 0.350 to 0.550 cm^/g, wherein the reactant is diluted with a carrying 10 gas or with steam, the concentration of said reactant in the carrying gas or steam fed to the reaction zone ranging from 5 to 75 % by volume, the hourly volume flow rate (LHSV) ranging from 0.5 to 100 liters of liquid reactant per liter of catalyst and per hour, the temperature ranging from 300 to 650°C and the pressure from 0.01 to 3 MPa, said process being cha-15 racterized in that, after separation of the olefins from the reactant and from the reactant diluent (gas or steam), the olefins are fractionated so as to recover, on the one hand, a cut essentially containing hydrocarbons of 2 to 3 carbon atoms per molecule and, on the other hand, a cut containing, as major part, higher olefins having at least 4 carbon atoms per 20 molecule, said last cut being at least partly recycled to the reaction zone.

2 - A process according to claim 1, wherein 5 to 40 % by weight of clay binder are added to the dealuminated mordenite.

3 - A process according to one of the claims 1 and 2, wherein the Si/Al 25 atomic ratio of the dealuminated mordenite ranges frcm 80 to 95.

4 - A process according to claim 3,wherein the pore volume, for pores of diameter larger than 10 nm, ranges from 0.400 to 0.500 cm^/g. 'vA V':. •> c ••• 31 MAR 1988 \. •>» ■■Lc 2151 12

5 - A process according to one of claims 1 to 4, wherein 20 to 60 % by weight of the cut containing, as a major part, higher olefins, are recycled.

6 - A process according to one of claims 1 to 5, for producing propylene in a major proportion.

7 - A process according to one of claims 1 to 6, wherein at least one part of the unreacted reactant (methanol or dimethylether) and at least one part of the gas or steam used to dilute said reactant are recycled.

8 - A process as claimed in claim 1 as hereinbefore described with reference to any one of the Examples.

9 - An olefin containing up to 1 to 5 carbon atoms per molecule when manufactured according to the process as claimed in claim 1 and as hereinbefore described in any one of the Examples. BALDWIN, SON & CAREY 3 f MAR 1988