FR2577549A1 - PROCESS FOR CONVERTING METHANOL OR DIMETHYLETHER TO OLEFINS - Google Patents

Abstract

THE INVENTION CONCERNS A PROCESS FOR CONVERTING METHANOL OR DIMETHYL ETHER TO OLEFINS IN THE PRESENCE OF A DESALUMINATED MORDENITE, THE REAGENT (METHANOL OR DIMETHYL ETHER) BEING DILUTED IN A GAS OR IN WATER VAPOR. IT IS CHARACTERIZED IN THAT THE OLEFINS OBTAINED ARE FRACTIONED WITH A VIEW TO RECYCLING AT LEAST PART OF THE OLEFINS WITH AT LEAST 4 CARBON ATOMS PER MOLECULE. THE INVENTION APPLIES IN PARTICULAR TO THE PRODUCTION OF PROPYLENE.

Description

l

  The invention relates to a method of manufacturing including propylene.

  accompanied by the formation of butanes, much less important, by the transformation of methanol and / or dimethyl ether into

  presence of some aluminosilicates.

  The transformation of methanol into hydrocarbons is a remarkable reaction, known for a long time, during which there is formation of carbon-carbon bonds from "radicals" in

  C1 which are formed from methanol in the presence of certain catalytic

  acidic lysers. But this transformation did not become

  since the 1970s and this because of two events: o discovery, catalysts sufficiently active, and especially selective, able to transform methanol into hydrocarbons,

and in particular in gasoline auto.

  and the oil-producing country policy leading to a disruption of economic and technical data in

  petroleum and petrochemical industries.

  Most of the world's methanol production

  comes from natural gas, but it is also obtained from hydrocarbon

  heavier bures, after an adequate transformation, by fermentations by distillation of the wood, etc., and also from coal, or any

  another material rich in carbon derivatives.

  With their new technique of transforming methanol into hydrocarbons, Mobil has introduced other sources of synthetic fuels on the market in addition to those of conventional processes.

Fischer-Tropsch and Bergius.

  Economically, obtaining hydrocarbons from methanol seems to be more competitive than other existing techniques

  fuel synthesis from coal.

  With a suitable choice of catalyst and an adequate adjustment of the operating conditions, it is possible to direct the transformation of methanol towards obtaining light or heavier hydrocarbons, to

  obtaining aromatics or olefins.

  The present invention relates more particularly to a process for producing propylene from methanol or dimethyl ether or from their mixture, a process which is of interest in the current economic context. Indeed propylene is one of the oldest products of

  chemical and petrochemical industry, occupying a very important place

  aunt among the light olefins.

  It is widely used in the preparation of alkylates and

  polymerization to improve the octane number of the fuels.

  It is also used and very important quantities in the preparation of plastics such as polypropylene and also in the preparation of other products such as: acrylonitrile, propylene oxide, propanol, cumene etc. Until now, propylene was mainly obtained as a by-product of petroleum refining and mainly steam cracking.

naphthas.

  But the oil economic situation has led to the steam cracking of heavier products, abandoning that of

  cuts "naphtha" which results in a decrease in the production of propylene.

  It is therefore interesting to consider obtaining this product by another route, hence the interest of the present process. There is a lot of work on the transformation of methanol into hydrocarbons, which takes place in the presence of catalysts. The most used catalysts are or contain

  zeolites which are crystalline alumino-silicates and appear to be

  suitable for this type of transformation: - because of their acidic properties - and because of their perfectly defined structure, the dimensions of their intercrystalline channels being of the same order of magnitude as the

  dimensions of the organic molecules staying there during the reaction.

  The major disadvantage that occurs in this conversion reaction of methanol into hydrocarbons is the rapid deactivation

  catalyst caused by irreversible deposits of organic products.

very condensed substances ("coke").

  There are many works in the literature that try to solve this problem. They seek to

  by various means, the catalytic properties of these alumino-

  silicate-es trying to give them greater selectivity and

  as a result to decrease the formation of "coke" on their surface.

  The object of the present invention being a process for the production of olefins from methanol or dimethyl ether, a catalyst optimized for the production of light olefins has been used for this purpose.

  which is described in European Patent No. 0084 748 of January 4, 1982.

  In the said patent, it is used for the production of unsaturated hydrocarbons essentially having 2 to 5 carbon atoms per molecule, a zeolite-based catalyst modified so as to increase very much.

  considerably its life and selectivity.

  This modification consists in dealuminizing a zeolite of the type

synthetic mordenite.

  For this modified zeolite to have good selectivity in the production of olefins, it is necessary for the Si / Al ratio (in atoms) to be between 80 and 150. However, it has been found that by operating under certain operating conditions, which is the object of this patent, it was possible to significantly improve the yields of propylene obtained. According to the invention, the best yields of olefins having from 2 to 5 and preferably 3 to 4 carbon atoms per molecule are obtained by reacting methanol in the presence of a dealuminated zeolite.

  and / or dimethylether, at a sufficient temperature, and by diluting sufficiently

  the reagent with at least one gas (nitrogen, hydrogen,

  carbon, carbon dioxide) or water vapor.

  In practice, the reagent (methanol and / or

  thylether) diluted with a carrier gas or water vapor on at least one dealuminated mordenite type catalyst, at a pressure of between 0.1 and 3 MPa, and preferably between 0.01 and 0.5 MPa and at a temperature of between 300 ° C. and 650 ° C., and preferably between

350 C and 550 C.

  The concentration of reagent in the gas (or water vapor) entering the catalytic bed will be between 5 and 75% by volume,

  and preferably between 25 and 60%.

  The hourly volumetric flow rate (LSVH) will be between 0.5 and 10 liters of liquid methanol per liter of catalyst per hour, and

preferably between 0.5 and 5 liters.

  The products leaving the reaction zone are directed to a separation zone where the olefins obtained are separated from the reactant (methanol and / or dimethyl ether) which has not reacted, and which is recycled at least in part, and from the reagent diluents (gas or water vapor) that can also be recycled The hydrocarbons obtained are then subjected to separation in order to recover on the one hand a fraction rich in olefinic hydrocarbons with 2 and 3 carbon atoms per molecule and d on the other hand a section containing for the most part higher olefins having at least 4 carbon atoms per molecule, this section also generally containing butanes. It has been observed, which constitutes the object of the present invention, that if at least a portion of this higher olefin fraction was sent to the reactor inlet where it contacted the catalyst bed together with methanol and / or dimethylether, two before on the one hand it eliminates a part of the calories produced by the reaction and on the other hand it significantly increases the yield of propylene and

the life of the catalyst.

  Preferably, 20 to 60% by weight of this oil cut will be recycled.

  higher fines. Although the examples presented, and which illustrate the pre-

  invention, are carried out on a single fixed bed, it is necessary to

  that this technique is not limiting.

  Indeed the catalyst can be arranged also in two or more

  successive beds, arranged in one or more reactors. This provision

  the advantage of allowing a better evacuation of calories

produced by the reaction.

  The catalysts may also be used in a moving bed which may be contained in one or more moving-bed reactors: The feedstock circulates successively in each reactor or reaction zone following an axial or radial flow (radial meaning a flow from the center to the periphery or from the periphery towards the center). The reaction zones are arranged in series, for example side by side or superimposed. The charge flows successively through each of these reaction zones, with charge introduction or intermediate recycling between the reaction zones in order to control the thermal level of the reaction by supply or by evacuation of the calories; the fresh catalyst is introduced at the top of the first reaction zone where the fresh feed is introduced; it then flows

  gradually from top to bottom of this area where it is racked progressively

  from below, and by any suitable means (especially lift in the case of reactors arranged side by side) it is transported to the top of the next reaction zone in which it flows gradually also from top to bottom, and so right down to the last reaction zone down which the catalyst

  is also withdrawn gradually and then sent to a zone of

  eration. At the exit of the regeneration zone, the catalyst is

  gradually reintroduced into the top of the first reaction zone.

  The various catalyst withdrawals are carried out as indicated ci

  "progressively", that is to say either periodically or continuously

  bare. Continuous racking is preferred over periodic racking.

  The catalyst used in the present invention, a catalyst whose preparation and performances have been described in European Patent No. 0084748, is based on dealuminized mordenite having an Si / Al (atomic) ratio of greater than 80, preferably of between 80 and more. especially between 87 and 90, a Ma.sub.2 content of less than 0.1% by weight, a specific surface, after shaping with the optional addition of about 5 to 40%, for example 10%, by weight of a binder clay, between 390 and 600 m 2 / g, and preferably between 420 and 550 m 2 / g, a total pore volume of between 0.540 and 0.650 cm 3 / g, and preferably between 0.550 and 0.600 cm 3 / g; a pore volume, for pores with a diameter of greater than (10 x 10-9 m) nm /, between 0.350 cm3 / g and 0.550 cm3 / g and preferably between 0.400 and 0.500 cm3 / g, and preferably bed density for

  pellets of 3 x 2mm approximately, between 0.600 and 0.700.

  The examples which follow and which illustrate the present invention were made with a dealuminized and pelletized mordenite catalyst (3 × 2 mm) having the following characteristics Surface .........

  ..................... 450 m2 / g Total pore volume .................... 595 cm / g Porous volume for pores> lOnm ... 0,460 cm3 / g Density in bed (packed) ................ 0,650 g / cm3 (for 3 x 2mm balls) Si / Al ratio (atom) .................. 89.2 The feed used was a 50/50 mixture by weight of water and DTD: methanol. The reaction was conducted in a pilot unit with a reaction

  upright starter containing 40 cm3 (26 g) of the pelletized catalyst (3 x

  2 mm) containing 10% clay binder (specific surface area of the catalyst mass).

  455 m 2 / g). The catalyst was heated to a temperature of 500 ° C. under an air flow rate of 250 l / h, and beforehand separated by passing through a bed.

of alumina, for 2 hours.

  After this pretreatment, we then pass through the cataract

  lytic 50/50 by weight of methanol-steam.

  The operating conditions, which are the same in all the examples that follow, were: Pressure ............. atmospheric Temperature ......... 460 C LHSV ...... ........... I h The test is considered complete when the sum of the C2, C3, C4 olefins produced becomes less than 10% by weight of the yield.

  initial. This time is after about 50 hours.

E XEMPLES

  In these examples, all the unconverted methanol was recycled.

  and all the water vapor used.

Example I

  This test was carried out for 50 hours under the conditions indicated above, without recycling of C4 hydrocarbons (filler: 50% by weight of water,

% by weight of methanol).

Example 2

  It was also realized under the same market conditions, as-

  in example 1 but with a recycling of a part of the hydrocarbons in

C + 4 obtained.

  The composition of the feed was therefore here, with recycling included, the following: Water ................. 50% by weight Methanol .......... 42.5% by weight

  Recycling C4 ........ 7.5% by weight.

  At the outlet of the reactor and after separation of the water vapor and the unreacted alcohol, the hydrocarbon effluent is sent to a distillation zone where the C4 hydrocarbons are separated off at the bottom of the column. , which represents 12.51% by weight of the total charge entering the reaction zone (water, alcohol and hydrocarbons) and having by weight the following composition: Butanes ............. 15, 10 Butenes ............. 63,15 +

C5 .................. 18.15

Aromatic ......... 3,60

  At the head of the fractionation zone, the hydrocarbons are

  resen C1, C2 and C3 containing more than 90% by weight of propylene.

  The composition by weight of this very high propylene cut is as follows: Methane ............. 1.28% Ethane .............. 0, 16% Ethylene ............ 5,13% Propane ............. 1,20% Propylene .........

  92.23%, 00% The fraction containing the C + 4 hydrocarbons represents 12.51% by weight of all the products entering the reaction zone; 59.95% by weight of this cup is sent to the reaction zone for recycling, this recycling constituting 7.5% by weight of the total charge. DTD: arriving in this zone.

  The rest of this cut (40.05 7) is sent, for example,

to the gasoline pool.

  In the following table is presented the weight composition of the products obtained in Examples 1 and 2 with respect to the load

  (after 50 hours of treatment).

EXAMPLE 1 EXAMPLE 2

  Products Products Methanol 2.73 2.34 Dimethylether 0.19 0.16 Water 76.50 72, 52 Hydrocarbons C1 to 0.33 0.33 C3 paraffinics Ethylene 0.66 0.64 Propylene 11.50

+ 7.50 12.51

C4

TABLE I

  From the results obtained and presented in the table above, it is found that operating under the conditions of Example 1, that is to say without recycling C4 hydrocarbons obtained, we obtain a production of propylene of 25.57 kg per 100 kg of processed methanol, while if one operates by recycling the said hydrocarbon fraction one obtains

  28.63 kg of propylene per 100 kg of processed methanol.

Claims (6)

  1) Process for producing olefins containing 2 to 5 carbon atoms per molecule, from a reagent which is methanol or dimethyl ether or a mixture thereof, carried out in the presence of at least one dealuminized mordenite catalyst having an Si / Al atomic ratio greater than 80, an Na 2 O content of less than 0.1% by weight, a specific surface, after shaping, of between 390 and 600 m 2 / g, a total pore volume of between 0.540 and 0.650 cm 3 / g, a pore volume, for pores with a diameter greater than 10 nm (10 × 10 -9 m) of between 0.350 and 0.550 cm 3 / g, and carried out by passing the diluted reagent with a carrier gas or with water, the concentration of said reactant in the carrier gas or water vapor, entering the reaction zone, being between 5 and 75% by volume, the hourly volumetric flow rate (LSVH) being between 0.5 and 10 liters of liquid reagent per liter of catalyst and per hour, the temperature between 300 and 650 ° C. and the pressure between 0.1 and 3 MPa, the process being characterized in that, after separating the olefins from the reactant and the reagent diluent (gas or water vapor), the fraction is separated off. olefins so as to collect on the one hand a section containing essentially hydrocarbons containing 2 and 3 carbon atoms per molecule, and on the other hand a section containing for the most part upper olefins containing at least 4 carbon atoms per molecule, this last cut being recycled at least   partly in the reaction zone.   2) Process according to claim 1, wherein one adds, by weight, to 40% of a clay binder to dealuminated mordenite.   3) Method according to one of claims 1 and 2, wherein the   Si / Al atomic ratio of the dealuminated mordenite is between and 95.   4) Process according to claim 3, wherein the pore volume for pores of diameter greater than 10 nm. is between 0.400 and 0.500 cm3 / g.   Method according to one of claims 1 to 4, wherein   recycle 20 to 60% by weight of the cup containing for the most part upper oldfines.   6) Method according to one of claims 1 to 6 for obtaining mostly propylene.   7) Method according to one of claims 1 to 6 wherein   partially recycles at least the unreacted reagent (methanol or dimethyl ether) and at least partly the gas or water vapor that was used to dilute the reagent.