WO2010100069A1

WO2010100069A1 - Process to make olefins from organics and paraffins

Info

Publication number: WO2010100069A1
Application number: PCT/EP2010/052392
Authority: WO
Inventors: Giacomo Grasso; Nikolai Nesterenko; Sander Van Donk
Original assignee: Total Petrochemicals Research Feluy
Priority date: 2009-03-03
Filing date: 2010-02-25
Publication date: 2010-09-10

Abstract

The present invention relates to a process to make light olefins, in a XTO process, from an oxygen-containing, halogenide-containing or sulphur-containing organic feedstock comprising : a) providing a catalyst comprising zeolitic molecular sieves containing at least 10 membered ring pore openings or larger in their microporous structure, b) providing an XTO reaction zone, c) contacting said oxygen-containing, halogenide-containing or sulphur-containing organic feedstock in the XTO reactor with the catalyst at conditions effective to convert at least a portion of the feedstock to form a XTO reactor effluent comprising light olefins and a heavy hydrocarbon fraction; d) separating said light olefins from said heavy hydrocarbon fraction; e) fractionating said heavy hydrocarbon fraction to remove the essential part of the aromatics and recovering a heavy hydrocarbon fraction having a reduced aromatics content; f) recycling at least a part of said heavy hydrocarbon fraction having a reduced aromatics content at the inlet of the XTO reaction zone; wherein, to adjust the proportion of C4+ paraffins recycled at the inlet of the XTO reaction zone, a fraction of the stream recycled at step f) is purged.

Description

PROCESS TO MAKE OLEFINS FROM ORGANICS AND PARAFFINS

[Field of the invention]

The present invention relates to a process to make olefins from heteroatomic organics and more precisely an XTO (organics to olefins) process.

The limited supply and increasing cost of crude oil has prompted the search for alternative processes for producing hydrocarbon products. One such process is the conversion of oxygen-containing (by way of example methanol), halogenide-containing or sulphur-containing organic compounds to hydrocarbons and especially light olefins (by light olefins is meant C2 to C₄ olefins) or gasoline and aromatics. In the present application said oxygen- containing, halogenide-containing or sulphur-containing organic compounds are also referred as "X". In the present application the conversion of said oxygen- containing (also referred as oxygenates), halogenide-containing or sulphur- containing organic compounds to hydrocarbons and especially light olefins is referred as XTO process. The interest in the XTO process is based on the fact that feedstocks, especially methanol can be obtained from coal, hydrocarbon residu's, biomass, organic waste or natural gas by the production of synthesis gas, which is then processed to produce methanol. The XTO process produces light olefins such as ethylene and propylene as well as heavy hydrocarbons such as butenes and above. These heavy hydrocarbons are recycled in the XTO reactor to increase ethylene and propylene. The XTO process is also known as MTO in case of methanol (methanol to olefins) process.

[Background of the invention]

In a MTO reactor the catalyst ZSM5-like produces not only olefins but also aromatics and paraffins. The outlet of the reactor is fractionnated to recover the light olefins, then a heavy hydrocarbon fraction is recycled to the MTO reactor. In the recycled feed to the reactor (Boiling point lower than benzene = C4-C6) the paraffin are therefore present. The paraffins tend to accumulate: a purge is needed. However, it seems that increasing the amount of paraffins into the olefins synthesis reactor (the MTO reactor) leads to reduce the production of paraffins.

The present invention consists in leaving the paraffins accumulating in the recycled feed (therefore in the feed entering the MTO reactor) so to reach a paraffins/olefins ratio (advantageously higher than 0.8 preferably higher than 1 wt/wt) such that the purge is minimized and the yield of propylene is maximized. However, the ratio paraffins/olefins must be also lower than 10 to avoid high cost of pumping for the recycle (recycled stream/MeOH < 5 wt/wt, possibly lower than 3).

JP2007297363 A proposes a catalyst to reduce the formation of aromatic compounds when olefin C4+ and methanol (or DME) (C4+/MeOH = 0.1 -10) are co-fed. The recycle is not mentioned.

JP2007302652 A is dedicated to control aromatics and paraffins production by cofeeding Methanol/DME and C4+ in presence of a diluent. C4+ Olefins/MeOH (mol/mol) is between 0.5 and 10. The sum of C4+ olefins + MeOH + DME is between 20 and 80vol% of the total feed of the reactor (diluent = 20-80%). The diluent can be: paraffin, aromatic, water vapour, CO2, CO, N2, Ar, He However, only N2 is used in the examples.

JP2008081417 A describes a process in which MeOH/DME are reacted with C4+ olefins (C4+/MeOH = 0.1 -10), C4+ olefins recycled to the methanol/DME reactor. JP2008084137 A describes a process in which C4+ + Methanol are co-fed (C4+/MeOH = 0.1 -10) on catalyst for propylene production. The catalyst has cage type zeolite structure (see list in the patent). The sum of C4+, methanol and/or DME must be below 90mole % preferably between 20% and 70% of the total inlet stream.

JP2008081438 A describes a process in which a two-reactor scheme is employed. Recycle of < = C2 - on the first of two reactors then C4+ on the second of the two reactors.

1^st embodiment: the effluents of the two reactors are mixed.

2^nd embodiment: the two reactors are in series with the feeding of methanol in between the two (with the C4+ recycle).

CH4 and ethane are recycled but it is not clear in which amount.

C3- in < = C2- must be lower than 10% preferably 5wt%. lnerts are mentioned:

% C4+ in the co-feed is between 30 and 70 (20-80)wt%.

Butadiene 2% or less into second reactor (with C4+) ^■* partial dehydrogenation. To avoid coking.

Aromatics below 0.05 mol /mol C4+ to avoid alkylation and formation of higher molecular weight compounds.

Paraffins are mentioned among other compounds as diluting gas. If they play a role, it seems to be the role of the diluent. Nothing said about paraffins' amount

Both C2- flow and C4+ flow are between 10 and 99% of the C2- and C4+ outlet respectably, preferably 50-95%.

C4+ can come from sources other than MTO.

JP2088106046 A describes a process in which selective hydrogenation of C4- C5 olefins after other olefin producing reactor and before an Methanol/olefins MTP reactor. The C4 are not reacted also with a C2- stream. The risk of butane make seems not to be mentioned. JP2008106056 A is similar to JP2008081438 A but with co-feed of fresh C2- in the first reactor. Once more the C2- is recycled/fed on the first reactor, C4- on the second. In a third scheme:

- methane and ethane are suggested to be added in the stream passing through the DIMERIZATION reactor together with the hydrocarbon reactants.

In a fourth scheme (comparative): C2- and C4- recycled on the same reactor but no selective reduction of dienes AND paraffins are not mentioned !

JP2008100994 A describes a process in which to produce propylene methanol and/or DME are fed together with C4+ recycled (and, optionally, from another source) into the reactor. The C4+ recycled or fed contains paraffins and it is good if it contains also butadiene and aromatic. The ratio paraffins/olefins is not specified. C2- is not recycled. A part of the effluents C4+ is sent to cracking (preferably after hydrogenation to have more paraffins therefore easy cracking). The recycled cut is mainly C4-C5 with the aromatics being sent elsewhere.

[Brief description of the invention]

The present invention relates to a process to make light olefins, in a XTO process, from an oxygen-containing, halogenide-containing or sulphur- containing organic feedstock comprising : a) providing a catalyst comprising zeolitic molecular sieves containing at least 10 membered ring pore openings or larger in their microporous structure, b) providing an XTO reaction zone, c) contacting said oxygen-containing, halogenide-containing or sulphur- containing organic feedstock in the XTO reactor with the catalyst at conditions effective to convert at least a portion of the feedstock to form a XTO reactor effluent comprising light olefins and a heavy hydrocarbon fraction; d) separating said light olefins from said heavy hydrocarbon fraction; e) fractionating said heavy hydrocarbon fraction to remove the essential part of the aromatics and recovering a heavy hydrocarbon fraction having a reduced aromatics content; f) recycling at least a part of said heavy hydrocarbon fraction having a reduced aromatics content at the inlet of the XTO reaction zone; wherein, to adjust the proportion of C4+ paraffins recycled at the inlet of the XTO reaction zone, a fraction of the stream recycled at step f) is purged.

In an embodiment, in the stream recycled at the inlet of the XTO reaction zone, the weight ratio of C4+ paraffins to the olefins in said stream is above 0.8 and under 10. Advantageously said ratio is above 1 and under 10.

In an embodiment the purpose is to minimise the purge and maximize the light olefins production. In another embodiment the addition of paraffins leads to a higher production of olefins, this is based on the discovery that in these conditions paraffins can enhance the light olefins production and/or can be converted to valuables components.

Ethylene can also be recycled at the inlet of the XTO reactor, this increase the propylene production.

The XTO reaction zone can be made of one or more reactors.

It is desirable to have a substantially 100% conversion of the organic compound in the XTO reactor. This conversion rate is adjusted by optimization of contact time, reaction temperature and the frequency of regeneration of the catalyst.

With regards to said effluent of the XTO process, "light olefins" means ethylene and propylene and the "heavy hydrocarbon fraction" is defined herein as the fraction containing hydrocarbons having a molecular weight greater than propane, which means hydrocarbons having 4 carbon atoms or more and written as C₄ ⁺. The C₄ ⁺ fraction can also contain co-boiling X-containing compounds, like methanol and other oxygenates.

When "X" is methanol the effluent of the XTO reaction zone comprises, in addition of the light olefins and a heavy hydrocarbon fraction, methane, water and optionally unconverted methanol. They are removed by usual means from the XTO effluent and then the effluent is fractionnated to produce light olefins and the heavy hydrocarbon fraction of step d). Very minor amounts of ethane and propane can be present in the light olefins fraction of step d).

According to an embodiment the catalyst is a molecular sieve selected from the list of MFI, MOR, MEL, clinoptilolite, FER, FAU, MWW, BETA, MCM- 41 , ZSM-21 , ZSM-22, ZSM-23, ZSM-42, ZSM-57, LTL or a mixture thereof. More preferably, the molecular sieve is selected from the group of MFI, MOR, MEL, clinoptilolite, FER or a mixture thereof. In the case of MFI, the molecular sieve is preferably a ZSM-5 zeolite. In another embodiment, the molecular sieve is preferably obtained without direct addition of template. Said molecular sieve can be modified with metals and/or P.

Preferably, the average pore size of the molecular sieve is at least 0.5 nm. Said molecular sieve before modification with M and P, can be calcined, steamed, ion-exchanged, treated with acid solution or it may undergo other treatments leading to dealumination. Dealumination of the molecular sieve can be performed simultaneously with the phosphorous modification.

According to an embodiment the catalyst is a P-modified zeolite. These phosphorus modified molecular sieves of the present invention are prepared based on MFI, MOR, MEL, clinoptilolite or FER crystalline aluminosilicate molecular sieves having an initial Si/AI ratio advantageously between 4 and 500. These P-modified zeolites can also be obtained based on cheap crystalline alumosilicates with low Si/AI ratio (below 30). This provides a lower final catalyst cost. The catalyst made of a P-modified zeolite can be the P-modified zeolite itself or it can be the P-modified zeolite formulated into a catalyst by combining with other materials that provide additional hardness or catalytic activity to the finished catalyst product.

According to a first embodiment said P-modified zeolite is made by a process comprising in that order:

- selecting a zeolite (advantageously with Si/AI ratio between 4 and 500) among H⁺ or NH₄ ⁺-form of MFI, MEL, FER, MOR, clinoptilolite;

- introducing P at conditions effective to introduce advantageously at least 0.05 wt% of P;

- separation of the solid from the liquid if any;

- an optional washing step or an optional drying step or an optional drying step followed by a washing step;

- a calcination step.

Optionally the process to make said P-modified zeolite comprises the steps of steaming and leaching. The method consists in steaming followed by leaching. It is generally known by the persons in the art that steam treatment of zeolites, results in aluminium that leaves the zeolite framework and resides as aluminiumoxides in and outside the pores of the zeolite. This transformation is known as dealumination of zeolites and this term will be used throughout the text. The treatment of the steamed zeolite with an acid solution results in dissolution of the extra-framework aluminiumoxides. This transformation is known as leaching and this term will be used throughout the text. Then the zeolite is separated, advantageously by filtration, and optionally washed. A drying step can be envisaged between filtering and washing steps. The solution after the washing can be either separated, by way of example, by filtering from the solid or evaporated. P can be introduced by any means or, by way of example, according to the recipe described in US 3,911 ,041 , US 5,573,990 and US 6,797,851. The separation of the liquid from the solid is advantageously made by filtering at a temperature between 0-90⁰C, centhfugation at a temperature between 0-90⁰C, evaporation or equivalent. Optionally, the zeolite can be dried after separation before washing. Advantageously said drying is made at a temperature between 40-600⁰C, advantageously for 1 -10h. This drying can be processed either in static conditions or in a gas flow. Air, nitrogen or any inert gases can be used. The washing step can be performed either during the filtering (separation step) with a portion of cold (<40°C) or hot water (> 40 but <90°C) or the solid can be subjected to a water solution (1 kg of solid/4 liters water solution) and treated under reflux conditions for 0.5-10 h followed by evaporation or filtering. Final calcination step is performed advantageously at the temperature 400-700⁰C either in static conditions or in a gas flow. Air, nitrogen or any inert gases can be used.

The catalyst made of a P-modified zeolite can be the P-modified zeolite itself or it can be the P-modified zeolite formulated into a catalyst by combining with other materials that provide additional hardness or catalytic activity to the finished catalyst product.

According to an embodiment of the invention the phosphorous modified zeolite is made by a process comprising in that order:

- selecting a zeolite ( advantageously with Si/AI ratio between 4 and 500, from 4 to 30 in a specific embodiment) among H⁺ or NH₄ ⁺-form of MFI, MEL, FER, MOR, clinoptilolite;

- steaming at a temperature ranging from 400 to 87O⁰C for 0.01 -20Oh;

- leaching with an aqueous acid solution at conditions effective to remove a substantial part of Al from the zeolite;

- introducing P with an aqueous solution containing the source of P at conditions effective to introduce advantageously at least 0.05 wt% of P;

- separation of the solid from the liquid;

- an optional washing step or an optional drying step or an optional drying step followed by a washing step; - a calcination step.

Optionally between the steaming step and the leaching step there is an intermediate step such as, by way of example, contact with silica powder and drying.

According to a second embodiment the catalyst of the combined XTO- OC process is a catalyst composite made by a process comprising the following steps:

a), selecting a molecular sieve having pores of 10-or more-membered rings b). contacting the molecular sieve with a metal silicate comprising at least one alkaline earth metal, such that the composite comprises at least 0.1 wt% of silicate.

The molecular sieve is preferably brought into contact with the metal silicate by one of the following two methods:

- During the formulation step of the catalyst by mechanically blending the molecular sieve with the metal silicate forming a precursor to be used in the formulation step;

- Physical blending of the previously formulated molecular sieve and the previously formulated metal silicate in situ in the XTO and/or OC reaction medium.

The molecular sieve could be selected from the list of MFI, MOR, MEL, clinoptilolite, FER, FAU, MWW, BETA, ZSM-21 , ZSM-22, ZSM-23, ZSM-42, ZSM-57, LTL, or a mixture of thereof. Preferably, the MFI is a ZSM-5 zeolite. More preferably, the molecular sieve is selected from the group of MFI, MOR, MEL, clinoptilolite, FER or a mixture thereof. In another embodiment, the molecular sieve is preferably obtained without direct addition of template. Said molecular sieve and/or said catalyst composite containing the molecular sieve and the metal silicate can be post-treated by calcinations, reductions or steaming. In the case of using zeolites as molecular sieve components, phosphorus can be introduced before, simultaneously or after blending with the metal silicate.

The composition of the catalyst composite comprises: at least 10 wt % of a molecular sieve having pores of 10-or more-membered rings at least one metal silicate comprising at least one alkaline earth metal, such that the catalyst composite comprises at least 0.1 wt % of silicate optionally metal phosphates optionally matrix material optionally a binder.

According to a third embodiment, the catalyst of the combined XTO- OC process is an alkaline earth or rare earth metal -P-modified molecular sieve (M-P-modified molecular sieve) made by a process comprising the following steps:

a), selecting at least one molecular sieve selected from one of:

-a P-modified molecular sieve which contains at least 0.3 wt% of P -a molecular sieve which is modified with P prior to or during step b) introducing at least 0.3 wt % of P b). contacting said molecular sieve with an alkaline earth or rare earth metal-containing compound (M-containing compound) to introduce at least 0.05 wt% of the alkaline earth or rare earth metal M.

Optionally, the contact of the molecular sieve with the P-containing compound and the M-containing compound can be performed simultaneously.

The introduction of the alkaline earth or rare earth metal (M) is performed by bringing the molecular sieve in contact with a solution of one or more M- containing compounds. Said solution can contain a higher concentration of the alkaline earth or rare earth metal than that found in the final M-P-modified molecular sieve. The modification of molecular sieves with phosphorous is known per se. This modification is carried out by treating molecular sieves with P-compounds in aqueous or non-aqueous media, by chemical vapor deposition of organic P- compounds or impregnation. The catalyst can be pre-formulated with binder or not. The preferred P-compounds used typically for this purpose can be selected from the group of phosphoric acid, NH₄H₂PO₄ or (NH₄)₂HPO₄. The M-containing compound can be selected from organic compounds, salts, hydroxides and oxides. These compounds may also contain phosphorus. It is essential that these compounds are present in solubilized form, before bringing them into contact with the molecular sieve or by forming a solution when in contact with the molecular sieve.

The final molar ratio M/P in the M-P-molecular sieve is preferably less than 1.

The molecular sieve can be selected from the list of MFI, MOR, MEL, clinoptilolite, FER, FAU, MWW, BETA, MCM-41 , ZSM-21 , ZSM-22, ZSM-23, ZSM-42, ZSM-57, LTL or a mixture thereof. More preferably, the molecular sieve is selected from the group of MFI, MOR, MEL, clinoptilolite, FER or a mixture thereof. In the case of MFI, the molecular sieve is preferably a ZSM-5 zeolite. In another embodiment, the molecular sieve is preferably obtained without direct addition of template.

[Detailed description of the invention]

As regards the first embodiment of the invention, and the selected zeolite, advantageously it is a crystalline alumosilicate of the MFI family or the MEL family. An example of MFI silicates is ZSM-5. An example of an MEL zeolite is ZSM-11 which is known in the art. Other examples are described by the International Zeolite Association (Atlas of Zeolite Structure Types, 1987, Butterworths).

Crystalline silicates are microporous crystalline inorganic polymers based on a framework of XO₄ tetrahydra linked to each other by sharing of oxygen ions, where X may be trivalent (e.g. Al, B, . . . ) or tetravalent (e.g. Ge, Si, . . . ). The crystal structure of a crystalline silicate is defined by the specific order in which a network of tetrahedral units are linked together. The size of the crystalline silicate pore openings is determined by the number of tetrahedral units, or, alternatively, oxygen atoms, required to form the pores and the nature of the cations that are present in the pores. They possess a unique combination of the following properties: high internal surface area; uniform pores with one or more discrete sizes; ion exchangeability; good thermal stability; and ability to adsorb organic compounds. Since the pores of these crystalline alumosilicates are similar in size to many organic molecules of practical interest, they control the ingress and egress of reactants and products, resulting in particular selectivity in catalytic reactions. Crystalline alumosilicates with the MFI structure possess a bi-directional intersecting pore system with the following pore diameters: a straight channel along [010]: 0.53-0.56 nm and a sinusoidal channel along [100]: 0.51-0.55 nm. Crystalline alumosilicates with the MEL structure possess a bi-directional intersecting straight pore system with straight channels along [100] having pore diameters of 0.53-0.54 nm.

Advantageously the selected MFI, MEL, FER, MOR, clinoptilolite (or H⁺ or NH₄ ⁺-form MFI, MEL, FER, MOR, clinoptilolite) has an initial atomic ratio Si/AI of 100 or lower and from 4 to 30 in a specific embodiment. The conversion to the H⁺ or NH₄ ⁺-form is known per se and is described in US 3911041 and US 5573990.

In the steam treatment step, the temperature is preferably from 420 to 870⁰C, more preferably from 480 to 760⁰C. The pressure is preferably atmospheric pressure and the water partial pressure may range from 13 to 100 kPa. The steam atmosphere preferably contains from 5 to 100 vol % steam with from 0 to 95 vol % of an inert gas, preferably nitrogen. The steam treatment is preferably carried out for a period of from 0.01 to 200 hours, advantageously from 0.05 to 200 hours, more preferably from 0.05 to 50 hours. The steam treatment tends to reduce the amount of tetrahedral aluminium in the crystalline silicate framework by forming alumina.

The leaching can be made with an organic acid such as citric acid, formic acid, oxalic acid, tartaric acid, malonic acid, succinic acid, glutaric acid, adipic acid, maleic acid, phthalic acid, isophthalic acid, fumaric acid, nithlotriacetic acid, hydroxyethylenediaminetriacetic acid, ethylenediaminetetracetic acid, trichloroacetic acid trifluoroacetic acid or a salt of such an acid (e.g. the sodium salt) or a mixture of two or more of such acids or salts. The other inorganic acids may comprise an inorganic acid such as nitric acid, hydrochloric acid, methansulfuric acid, phosphoric acid, phosphonic acid, sulfuric acid or a salt of such an acid (e.g. the sodium or ammonium salts) or a mixture of two or more of such acids or salts.

Advantageously the final P-content is at least 0.05 wt% and preferably between 0.3 and 7 w%. Advantageously at least 10% of Al, in respect to parent zeolite MFI, MEL, FER, MOR and clinoptilolite, have been extracted and removed from the zeolite by the leaching.

Then the zeolite either is separated from the washing solution or is dried without separation from the washing solution. Said separation is advantageously made by filtration. Then the zeolite is calcined, by way of example, at 400⁰C for 2-10 hours.

The residual P-content is adjusted by P-concentration in the aqueous acid solution containing the source of P, drying conditions and a washing procedure if any. A drying step can be envisaged between filtering and washing steps.

The P-modified zeoilite can be used as itself as a catalyst. In another embodiment it can be formulated into a catalyst by combining with other materials that provide additional hardness or catalytic activity to the finished catalyst product. Materials which can be blended with the P-modified zeolite can be various inert or catalytically active materials, or various binder materials. These materials include compositions such as kaolin and other clays, various forms of rare earth metals, phosphates, alumina or alumina sol, titania, zirconia, quartz, silica or silica sol, and mixtures thereof. These components are effective in densifying the catalyst and increasing the strength of the formulated catalyst. The catalyst may be formulated into spray-dried particles. The amount of P modified zeoilite which is contained in the final catalyst product ranges from 10 to 90 weight percent of the total catalyst, preferably 20 to 70 weight percent of the total catalyst.

As regards the second embodiment of the invention, The molecular sieves that can be used in the invention are preferably zeolites, for example crystalline silicates, more precisely aluminosilicates. Crystalline silicates are microporous crystalline inorganic polymers based on a framework of XO₄ tetrahydra linked to each other by sharing oxygen ions, where X may be trivalent (e.g. Al, B, . . . ) or tetravalent (e.g. Ge, Si, . . . ). The crystal structure of a crystalline silicate is defined by the specific order in which a network of tetrahedral units are linked together. The size of the crystalline silicate pore openings is determined by the number of tetrahedral units, or, alternatively, oxygen atoms, required to form the pores and the nature of the cations that are present in the pores. They possess a unique combination of the following properties: high surface area; uniform pores with one or more discrete sizes; ion exchangeability; good thermal stability; and ability to adsorb organic compounds. Since the pores of these crystalline aluminosilicates are similar in size to many organic molecules of practical interest, they control the ingress and egress of reactants and products, resulting in particular selectivity in catalytic reactions.

The selected molecular sieve can be made with the help of the seeding technique, but advantageously they are made without template. However, the seeds themselves may have been made with a template, which means in this case that the molecular sieve is made without direct addition of a template. It is preferred that the molecular sieve used in the invention is made without direct addition of template. The molecular sieves selected for the purposes of this invention have pores of the size of 10 or more-membered rings. It can be envisaged to use molecular sieves, which have pores consisting of 10, 12 or more members.

The selected molecular sieve according to the present invention has an average pore size of at least 0.5, preferably from 0.5 to 10, more preferably from 0.5 to 5 and most preferably at least from 0.5 to 0.9 nm.

The selected molecular sieve has an initial atomic ratio Si/AI of at least 4 and not greater than 500. The Si/AI atomic ratio is measured by chemical analysis, for example using XRF and/or NMR. It includes only those Al that are part of the framework structure of the molecular sieve.

As regards to the selected molecular sieve, advantageously it is selected from the group of MFI, MOR, MEL, clinoptilolite, FER, FAU, MWW, BETA, ZSM-21 ,

ZSM-22, ZSM-23, ZSM-42, ZSM-57, LTL, or mixtures thereof, according to the

International Zeolite Association (Atlas of Zeolite Structure Types, 1987,

Butterworths). Preferably it is selected from group of the MFI, MOR, MEL, clinoptilolite, FER or a mixture of thereof. More preferably, the MFI is a ZSM-5 zeolite.

In another embodiment, the molecular sieve selected from the group of MFI,

MOR, MEL, clinoptilolite, FER or a mixture of, is preferably obtained without direct addition of template.

The molecular sieve may be used as synthesised to form the catalyst composite. Prior to formulation of the catalyst composite the molecular sieve may undergo further treatments including steaming, leaching (e.g. acid leaching), washing, drying, calcination, impregnation and ion exchanging steps. In addition or alternatively, these steps can also be carried out after formulation of the catalyst composite.

In a particular embodiment of the invention, the molecular sieve can be modified either prior to or after introduction of the metal silicate. Preferably, the molecular sieve has undergone some form of modification prior to the metal silicate introduction. By modification, it is meant herein that the molecular sieve may have undergone steaming, leaching (e.g. acid leaching), washing, drying, calcination, impregnation or some form of ion-exchange. This means that at least a portion of the cations originally comprised in the crystal structure can be replaced with a wide variety of other cations according to techniques well known in the art. The replacing cations can be hydrogen, ammonium or other metal cations, including mixtures of such cations.

The selected molecular sieve is then formulated into a catalyst composite to comprise at least 10 % by weight of a molecular sieve as described herein and at least one metal silicate comprising at least one alkaline earth metal, such that the composite comprises at least 0.1 % by weight of silicate. At least one of the metal silicates comprised in the catalyst composite includes at least one alkaline earth metal, preferably Ca. Metal silicates are insoluble in water and alkaline earth metal ions, particularly calcium, are polyvalent and possess a large radius in the hydrated state. Thus, without wishing to be bound by theory, it is thought that the ion exchange reaction with the molecular sieve occurs very slowly, as the alkaline earth metal ion must lose many of its strongly coordinated water molecules in order to penetrate into the micropores of the molecular sieve structure. As a result, the alkaline earth metal ions expose only the acid sites located on the external surface of the molecular sieve, and thus increasing the selectivity of the catalyst.

Furthermore, without wishing to be bound by theory, it is thought that the presence of silicate anions further improve the catalytic properties of the catalyst composite. The silicate anions, for example, can supply silicon atoms to heal defects in the molecular sieve. This can thus lead to additional stabilisation of the catalyst under severe hydrothermal conditions. As a result the metal silicate acts as a catalyst promoter. The metal silicate can comprise more than one alkaline earth metal selected from Ca, Mg, Sr and Ba.

The metal silicates may also comprise other metals selected from one or more of the following: Ga, Al, Ce, In, Cs, Sc, Sn, Li, Zn, Co, Mo, Mn, Ni, Fe, Cu, Cr, Ti and V. Preferably, the other metal is selected from one or more of Al, Mg, Ce, Co and Zn or mixtures thereof. These bi-, tri- or polymetal silicates can be synthesised according to any method known in the art. This can be for example by ion exchange in the solution or solid state (Labhsetwar et al., Reactivity of Solids, Vol. 7, Issue 3, 1989, 225-233).

The silicate anion can be present in any form in the solid metal silicate. Examples include SiO₃ ^2", SiO₄ ^4", Si₂O₇ ^6", Si₃Oi₀ ^8" and the like.

The preferred catalyst promoter is a calcium silicate with a very open and accessible pore structure. An even more preferred catalyst promoter comprises a synthetic crystalline hydrated calcium silicate having a chemical composition of Ca6Si6θi₇(OH)₂ which corresponds to the known mineral xonotlite (having a molecular formula 6CaO.6SiO₂.H₂O).

Generally, a synthetic hydrated calcium silicate is synthesised hydrothermally under autogeneous pressure. A particularly preferred synthetic hydrated calcium silicate is available in commerce from the company Promat of Ratingen in Germany under the trade name Promaxon.

In order to demonstrate the thermal stability of xonotlite, and therefore the applicability of xonotlite as a catalyst promoter in MTO and OC, commercial xonotlite sold under the trade name Promaxon D was calcined in ambient air at a relative humidity of about 50% at 650° C for a period of 24 hours. The initial xonotlite had a crystalline phase Ca6Si6θi₇(OH)₂ with a BET surface area of 51 m²/gram and a pore volume (of less than 100 nanometres) of 0.35 ml/gram. After calcination at 650° C, the carrier retained its crystallinity, which corresponds to that of xonotlite. Thus after a 24 hour calcination at 650° C, the crystalline phase still comprised xonotlite (Ca₆Si₆Oi₇(OH)₂) with a BET surface area of 47.4 m²/gram and a pore volume (less than 100 nanometres) of 0.30 ml/gram.

Other examples of metal silicates comprising alkaline earth metals include CaAI₂Si₂Os, Ca₂AI₂SiO₇, CaMg(Si₂O₆)_x, as well as mixtures thereof.

Before mixing with the molecular sieve said metal silicate compounds may be modified by calcination, steaming, ion-exchange, impregnation , or phosphatation. Said metal silicates may be an individual compound or may be a part of mixed compounds.

The metal silicate can be brought into contact with the molecular sieve by a simultaneous formulation step of a blend of the metal silicate with the molecular sieve or in situ blending of separately formulated materials in the reaction medium prior to the XTO or OC process. Said contact can be realised by mechanically blending of the molecular sieve with the alkaline earth metal- comprising metal silicate. This can be carried out via any known blending method. Blending can last for a period of time starting from 1 minute up to 24 hours, preferably from 1 min to 10 hours. If not carried out in the XTO or OC reactor in situ, it can be carried out in a batchwise mixer or in a continuous process, such as in an extruder e.g. a single or twin screw extruder at a temperature of from 20 to 300⁰C under vacuum or elevated pressure. Said contact may be performed in an aqueous or non-aqueous medium. Prior to the formulation step, other compounds that aid the formulation may be added, like thickening agents or polyelectrolytes that improve the cohesion, dispersion and flow properties of the precursor. In case of oil-drop or spray-drying a rather liquid (high water content) is prepared. In another embodiment, the contact is carried out in the presence of phosphorus containing compounds. In a particular embodiment, the contact is carried out in the aqueous medium at pH lower than 5, more preferably lower than 3.

Either prior to, after or simultaneously with the formulation step to form the composite, other components may be optionally blended with the molecular sieve. In a particular embodiment, the molecular sieve can be combined with other materials that provide additional hardness or catalytic activity to the finished catalyst product. Materials, which can be blended with the molecular sieve, can be various inert or catalytically active matrix materials and/or various binder materials. Such materials include clays, silica and/or metal oxides such as alumina. The latter is either naturally occurring or in the form of gelatinous precipitates or gels including mixtures of silica and metal oxides. In an embodiment, some binder materials can also serve as diluents in order to control the rate of conversion from feed to products and consequently improve selectivity. According to one embodiment, the binders also improve the attrition of the catalyst under industrial operating conditions.

Naturally occurring clays, which can be used as binder, are for example clays from the kaolin family or montmorillonite family. Such clays can be used in the raw state as mined or they can be subjected to various treatments before use, such as calcination, acid treatment or chemical modification. In addition to the foregoing, other materials which can be included in the catalyst composite of the invention include various forms of metals, phosphates (for instance metal phosphates, wherein the metal is chosen from one or more of Ca, Ga, Al, Ca, Ce, In, Cs, Sr, Mg, Ba, Sc, Sn, Li, Zn, Co, Mo, Mn, Ni, Fe, Cu, Cr, Ti and V), alumina or alumina sol, titania, zirconia, quartz, silica or silica sol, and mixtures thereof. Examples of possible phospates include amorphous calcium phosphate monocalcium phosphate, dicalcium phosphate, dicalcium phosphate dehydrate, α- or β- thcalcium phosphate, octacalcium phosphate, hydroxyapatite etc.

Examples of possibly binary oxide binder compositions include, silica-alumina, silica magnesia, silica-zirconia, silica-thoria, silica-beryllia, silica-titania, calcium- alumina. Examples of ternary binder compositions include for instance calcium- silica-alumina or silica-alumina-zirconia.

These components are effective in increasing the density of the catalyst and increasing the strength of the formulated catalyst. The catalyst usable in fluidised bed reactors has substantially spherical shape, formed typically by spray-dhying. Generally, the size of the catalyst particles can vary from about 20 to 500 μm, more preferable from 30 to 100 μm The crystal size of the molecular sieve contained in the catalyst composite, is preferably less than about 10 μm, more preferably less than about 5 μm and most preferably less than about 2 μm. The amount of molecular sieve, which is contained in the final catalyst composite ranges from 10 to 90 % by weight of the total catalyst composite, preferably 20 to 70 % by weight. According to another embodiment, non-modified molecular sieves were first formulated with a binder and matrix materials and then modified with phosphorous and alkaline earth metal silicates.

According to a further particular embodiment, molecular sieves were optionally dealuminated and then modified with phosphorous during the formulation step.

Introduction of the alkaline earth metal silicate can be performed during the formulation step or on the formulated solid.

According to a preferred embodiment, molecular sieves were first optionally dealuminated and modified with phosphorous and then formulated. Introduction of the metal is performed simultaneously with the phosphorous modification step and/or on the already formulated catalyst.

After formulation, the catalyst composite may undergo further treatments including further steaming, leaching, washing, drying, calcination, impregnations and ion exchanging steps. If the molecular sieve was not modified with phosphorus prior to the formulation step of the blend i.e. the step introducing the metal silicate to the molecular sieve, it may be carried out after such a step. According to a specific feature of this second embodiment, the molecular sieve is a phosphorus-modified (P-modified) zeolite. Said phosphorus-modified (P-modified) zeolite has already described above.

As regards the third embodiment of the invention, the molecular sieves have already been described in the second embodiment. Prior to P- modification and/or to the alkaline earth or rare earth metal-modification (M- modification), the molecular sieve may undergo further treatments including steaming, leaching (e.g. acid leaching), washing, drying, calcination, impregnation and ion exchanging steps. In addition or alternatively, these steps can also be carried out during or after P-modification. By ion exchanging steps, it is meant herein that at least a portion of the cations originally comprised in the crystal structure are replaced with a wide variety of other cations according to techniques well known in the art. The replacing cations can be hydrogen, ammonium or other metal cations, including mixtures of such cations. For the purposes of this invention, modification of the molecular sieve with P must be carried out prior to or during M-modification, if the selected molecular sieve is not already P-modified. Preferably, the P-modification is carried out via a dealuminating steaming step followed by a leaching step using any acidic solution containing a source of P, preferably a solution of phosphoric acid. Preferably, the P-modified molecular sieve comprises at least 0.3% of phosphorus by weight of the molecular sieve.

According to one embodiment of the invention, the molecular sieve can be modified with phosphorus according to the process comprising the following steps, in the order given:

- steaming of the molecular sieve at a temperature ranging from 400 to 87O⁰C for 0.01 -20Oh;

- leaching with an aqueous acid solution containing the source of P at conditions effective to remove a substantial part of Al from the molecular sieve and to introduce at least 0.3 % of phosphorus by weight of the molecular sieve;

Further modification can then be carried out according to the following steps, in the order given:

- separation of the solid from the liquid;

- a calcination step.

Preferably, separation, optional washing and drying steps and calcination are carried out after introduction of the M-containing compound to the molecular sieve. The metal M can be any alkaline earth or rare earth metal. Preferably the alkaline earth metal is Ca. However, it is also possible to use Mg, Sr and Ba. Possible rare earth metals include La and Ce.

In the steam treatment step, the temperature is preferably from 420 to 870⁰C, more preferably from 480 to 760⁰C. The pressure is preferably atmospheric pressure and the water partial pressure may range from 13 to 100 kPa. The steam atmosphere preferably contains from 5 to 100 vol % steam with from 0 to 95 vol % of an inert gas, preferably nitrogen. The steam treatment is preferably carried out for a period of from 0.05 to 200 hours, more preferably from 0.05 to 50 hours. It is generally known by the persons in the art that steam treatment of molecular sieves results in aluminium that leaves the molecular sieve framework and resides as aluminiumoxides in and outside the pores of the molecular sieve. This transformation is known as dealumination of molecular sieves and this term will be used throughout the text.

The treatment of the steamed molecular sieve with an acid solution results in dissolution of the extra-framework aluminiumoxide. This transformation is known as leaching and this term will be used throughout the text. The leaching with an aqueous acid solution containing the source of phosphorus is advantageously made under reflux conditions, meaning boiling temperature of the solution.

Amount of said acid solution is advantageously between 2 and 10 litres per kg of molecular sieve. A typical leaching period is around 0.5 to 24 hours. Advantageously the aqueous acid solution containing the source of P in the leaching step has a pH of 3, advantageously 2, or lower. Advantageously said aqueous acid solution is a solution of phosphorus acids, a mixture of phosphorus acids and organic or inorganic acids or mixtures of salts of phosphorus acids and organic or inorganic acids. The phosphorus acids or the corresponding salts can be of the phosphate ([PO₄]^3", being tribasic), phosphite ([HPO₃]^2", being dibasic), or hypophosphite ([H₂PO₂]^1", being monobasic), type. Of the phosphate type also di- or polyphosphates ([P_nO₃n+i]^(n+2)") can be used. The other organic acids may comprise an organic acid such as citric acid, formic acid, oxalic acid, tartaric acid, malonic acid, succinic acid, glutaric acid, adipic acid, maleic acid , phthal ic acid , isophthal ic acid , fumaric acid, n i t r i l ot r i a c et i c a c i d , h yd roxye t h y l e n ed i a m i n et r i a ce t i c a c i d , ethylenediaminetetracetic acid, trichloroacetic acid trifluoroacetic acid or a salt of such an acid (e.g. the sodium salt) or a mixture of two or more of such acids or salts. The other inorganic acids may comprise an inorganic acid such as nitric acid, hydrochloric acid, methansulfuhc acid, sulfuric acid or a salt of such an acid (e.g. the sodium or ammonium salts) or a mixture of two or more of such acids or salts.

It has been found that phosphorus acid is very efficient in complexing the extra- framework aluminiumoxides and hence removing them from the molecular sieve solid material. Unexpectedly, a larger quantity of phosphorus than what could be expected from the typical pore volume of the molecular sieve and assuming that the pores of the molecular sieves are filled with the used phosphorus acid solution, stays in the solid molecular sieve material. Both factors i.e. dealumination and the retention of P, stabilise the lattice aluminium in the zeolitic lattice, thus avoiding further dealumination. This leads to a higher hydrothermal stability, tuning of the molecular sieve's properties and adjustment of acid properties, thereby increasing the molecular sieve's selectivity. The degree of dealumination can be adjusted by the steaming and leaching conditions.

Advantageously, the final P-content of the molecular sieve is at least 0.3wt% and preferably between 0.3 and 7 w%. Advantageously at least 10% of Al have been extracted and removed from the molecular sieve by the leaching. The residual P-content is adjusted by the P-concentration in the leaching solution, separating conditions during the separation of the solid from the liquid and/or the optional washing procedure during which impregnation and/or adsorption can also take place. A drying step can be envisaged between the separation and/or washing steps.

The molecular sieve is then either separated from the washing solution or is dried without separation from the washing solution. Said separation is advantageously made by filtration. Then the molecular sieve is calcined, by way of example, at 400⁰C for 2-10 hours.

M-modification of the molecular sieve is carried out either on an already P- modified molecular sieve or during/after the P-modification process. P- modification can be carried out as described above wherein the sieve is dealuminated by steaming, then leached with a P-containing acid solution. In this case, advantageously, treatment of the molecular sieve with the M- containing solution is performed after the leaching or washing step i.e. after the phosphorous compound has been added and P-modification has taken place and before the separation step. However, the introduction of M to the molecular sieve can also be envisaged:

- during the leaching step,

- before the washing step but after leaching and drying

- on calcined molecular sieves that have been contacted with P

- on molecular sieve that has not been leached to introduce P but has been contacted with P during the washing step

Introduction of M on the molecular sieves can be performed either by impregnation or by adsorption from an aqueous solution of M-containing compounds.

The introduction of the M-containing compound can be done at temperatures ranging from ambient temperature up to the boiling point of the solution.

The concentration of the M-containing compound in the solution is at least 0.05- M, preferably between 0.05 and 1.0 M. The amount of the alkaline earth or rare earth metal (M) in the M-P-molecular sieves can vary from at least 0.05 % by weight, preferably 0.05 to 7 % by weight, most preferably from 0.1 to 4 % by weight.

Prior to formulation of the catalyst composite the molecular sieve may undergo further treatments including steaming, leaching (e.g. acid leaching), washing, drying, calcination, impregnation and ion exchanging steps. In addition or alternatively, these steps can also be carried out after formulation of the catalyst composite.

The alkaline earth or rare earth metal M is preferably selected from one or more of: Mg, Ca, Sr, Ba, La, Ce. More preferably, M is an alkaline earth metal. Most preferably, M is Ca. Particularly in the case of P-modification via steaming and leaching, M can be a rare earth metal such as La and Ce.

The M-containing compound is preferably in the form of an organic compound, a salt, hydroxide or oxide. The compound is preferably in a solubilized form when bringing it into contact with the molecular sieve. Alternatively, the solution of the M-containing compound can be formed after bringing the molecular sieve in contact with said compound.

Possible M-containing compounds include metal M compounds such as metal M sulphate, formate, nitrate, acetate, halides, oxyhalides, borates, carbonate, hydroxide, oxide and mixtures thereof. These can be for example, calcium sulphate, formate, nitrate, acetate, halides, oxyhalides, borates, carbonate, hydroxide, oxide and mixtures thereof.

The M-containing compound may also include other metals chosen from one or more of Mg, Sr, Ba, Ga, Al, Ce, In, Cs, Sc, Sn, Li, Zn, Co, Mo, Mn, Ni, Fe, Cu, Cr, Ti and V. The M-containing compounds may also additionally comprise phosphorus.

Those M-containing compounds, which are poorly water-soluble, can be dissolved to form a well-solubilized solution by heating and/or by modifying the pH of the solution by addition of phosphoric, acetic or nitric acid or corresponding ammonium salts of said acids. The concentration of the M- containing compound is at least 0.05 M.

The alkaline earth and rare earth metals M, in particular Ca, possess a large hydration sphere radius in the hydrated state. Thus, without wishing to be bound by theory, it is thought that the ion exchange reaction with the acid sites located on the inside of the micropore structures of the molecular sieve occurs very slowly. As a result, the chosen metal M exposes only the acid sites located on the external surface of the molecular sieve, and thus increasing the selectivity of the catalyst.

In the case of P-modified molecular sieves, M-modification leads to the formation of mixed M-AI-phosphates on the external surface. Taking into account that phosphorous is bound with the alkaline earth or rare earth metal M more strongly than with Al, this modification leads to stabilization of phosphorous on the external surface of the molecular sieve where the phosphorous is the most labile. However, it is essential, that all the M atoms located on the external surface are saturated with phosphorous. This can be guaranteed in the presence of an excess of phosphorous and by the presence of M in solution form, which is, for example, used to wash the excess phosphorous away preventing a plugging of the entrance to micropores.

Formulation into a catalyst composite can be carried out once the M-P-modified molecular sieve has been obtained i.e. other components may be optionally blended with the molecular sieve. (However, the M-P-modified molecular sieve can also be used as such as a catalyst.)

According to one embodiment, the prepared M-P-modified molecular sieve is co-formulated into a catalyst composite to comprise at least 10 % by weight of the M-P-molecular sieve as described herein and at least 0.05 % by weight of M and at least 0.3 % by weight of phosphorous, both in relation to the weight of the molecular sieve.

In a particular embodiment, the molecular sieve can be combined with other materials that provide additional hardness or catalytic activity to the finished catalyst product. Materials, which can be blended with the molecular sieve, can be various inert or catalytically active matrix materials and/or various binder materials. Such materials include clays, silica and/or metal oxides such as alumina.

According to another embodiment, non-modified molecular sieve was first formulated with a binder and a matrix materials and then modified with phosphorous and metals. According to particular embodiment, molecular sieves were optionally dealuminated and then modified with phosphorous during formulation step. Introduction of the metal can be performed during the formulation step or on the formulated solid.

According to preferred embodiment, molecular sieves was first optionally dealuminated and modified with phosphorous and then formulated. Introduction of the metal is performed simultaneously with modification with phosphorous step or/and on formulated catalyst.

The catalyst composite may also optionally comprise binder and/or matrix material and/or metal phosphate. Preferably, the amount of molecular sieve, which is contained in the final catalyst composite can range from 10 to 90 % by weight of the total catalyst composite, more preferably from 20 to 70 % by weight. The concentration of M in the formulated catalyst can be higher than the M concentration in the molecular sieve alone, because the binder or matrix material may also contain some M-compounds.

Naturally occurring clays, which can be used as binder, are for example clays from the kaolin family or montmorillonite family. Such clays can be used in the raw state as mined or they can be subjected to various treatments before use, such as calcination, acid treatment or chemical modification.

In addition to the foregoing, other materials which can be included in the catalyst composite of the invention include various forms of metals, phosphates (for instance metal phosphates, wherein the metal is chosen from one or more of Ca, Ga, Al, Ca, Ce, In, Cs, Sr, Mg, Ba, Sc, Sn, Li, Zn, Co, Mo, Mn, Ni, Fe, Cu, Cr, Ti and V), alumina or alumina sol, titania, zirconia, quartz, silica or silica sol, and mixtures thereof. Examples of possible phosphates include amorphous metal phosphates, and metal phosphates such as calcium phosphates e.g. monocalcium phosphate, dicalcium phosphate, dicalcium phosphate dehydrate, α- or β- tricalcium phosphate, octacalcium phosphate, hydroxyapatite etc. Examples of possibly binary binder compositions include, silica-alumina, silica magnesia, silica-zirconia, silica-thoha, silica-beryllia, silica-titania, calcium- alumina and calcium silicate. Examples of ternary binder compositions include for instance calcium-silica-alumina or silica-alumina-zirconia.

With regards to the XTO reaction zone, in this process a feedstock containing an oxygen-containing, halogenide-containing or sulphur-containing organic compound contacts the above described catalyst in a reaction zone of a reactor at conditions effective to produce light olefins, particularly ethylene and propylene. Typically, the oxygen-containing, halogenide-containing or sulphur- containing organic feedstock is contacted with the catalyst when the oxygen- containing, halogenide-containing or sulphur-containing organic compound is in vapour phase. Alternately, the process may be carried out in a liquid or a mixed vapour/liquid phase. In this process, converting oxygen-containing, halogenide- containing or sulphur-containing organic compounds, olefins can generally be produced at a wide range of temperatures. An effective operating temperature range can be from about 200⁰C to 700⁰C. At the lower end of the temperature range, the formation of the desired olefin products may become markedly slow. At the upper end of the temperature range, the process may not form an optimum amount of product. An operating temperature of at least 300° C, and up to 600⁰C is preferred.

The pressure also may vary over a wide range. Preferred pressures are in the range of about 5 kPa to about 5 MPa, with the most preferred range being of from about 50 kPa to about 0.5 MPa. The foregoing pressures refer to the partial pressure of the oxygen-containing, halogenide-containing, sulphur- containing organic compounds and/or mixtures thereof.

The process can be carried out in any system using a variety of fixed bed or fluidized bed reactors. The process can be conducted in a single reaction zone or a number of reaction zones arranged in series or in parallel. After a certain time-on-stream the catalyst needs to be regenerated. This regeneration is carried out either in situ (fixed beds) or in a regeneration zone (fluidized beds). The commercial scale reactor systems can be operated at a weight hourly space velocity (WHSV) of from 0.1 hr^"1 to 1000 hr^"1.

One or more inert diluents may be present in the feedstock of the XTO reaction zone, for example, in an amount of from 1 to 95 molar percent, based on the total number of moles of all feed and diluent components fed to the reaction zone. Typical diluents include, but are not necessarily limited to helium, argon, nitrogen, carbon monoxide, carbon dioxide, hydrogen, water, aromatic compounds, and mixtures thereof. The preferred diluents are water and nitrogen. Water can be injected in either liquid or vapour form.

The use of a diluents can provide two advantages. The first advantage is that it reduces the partial pressure of the X and hence will improve the selectivity for light olefins, mainly propylene. The result is that lower reaction temperatures can be used. Generally, the lower the partial pressure of X, the higher the light olefin selectivity. There exist an optimum for light olefin yield depending on the partial pressure, reaction temperature and catalyst properties.

The second advantage of using a diluents is that it can acts as a heat sink for the exothermic X conversion. So the higher the specific molar heat capacity, the more heat can be absorbed by the diluents. This second advantage might be less important in case of fluidised bed reactors as the latter are known to be excellent reactors to run at near homogeneous temperature throughout the catalyst bed. It is preferred that the diluents can be easily separated from the light olefins products, preferentially by simply phase separation. Hence a preferred diluents is water. Diluents can be added from 1 to 95 mole percent of the combined feed (X + diluents), preferably from 10 to 75 mole percent.

According to a specific embodiment essentially no water (or steam) is injected as diluent of the feedstock sent to the XTO reactor. However it means that the feedstock can contain the water already contained in the fresh oxygen- containing, halogenide-containing or sulphur-containing organic feedstock or the steam used to engage the proper flowing and purging of catalyst in fluidised bed reactors of the XTO reactor. In the present invention the paraffins are not diluents but enhance olefins production.

The oxygenate feedstock is any feedstock containing a molecule or any chemical having at least an oxygen atom and capable, in the presence of the above catalyst, to be converted to olefin products. The oxygenate feedstock comprises at least one organic compound which contains at least one oxygen atom, such as aliphatic alcohols, ethers, carbonyl compounds (aldehydes, ketones, carboxylic acids, carbonates, esters and the like). Representative oxygenates include but are not necessarily limited to lower straight and branched chain aliphatic alcohols and their unsaturated counterparts. Examples of suitable oxygenate compounds include, but are not limited to: methanol; ethanol; n-propanol; isopropanol; C₄-C2o alcohols; methyl ethyl ether; dimethyl ether; diethyl ether; di-isopropyl ether; formaldehyde; dimethyl carbonate; dimethyl ketone; acetic acid; and mixtures thereof. Representative oxygenates include lower straight chain or branched aliphatic alcohols, their unsaturated counterparts. Analogously to these oxygenates, compounds containing sulphur or halides may be used. Examples of suitable compounds include methyl mercaptan; dimethyl sulfide; ethyl mercaptan; di-ethyl sulfide; ethyl monochloride; methyl monochlohde, methyl dichlohde, n-alkyl halides, n-alkyl sulfides having n-alkyl groups of comprising the range of from about 1 to about 10 carbon atoms; and mixtures thereof. Preferred oxygenate compounds are methanol, dimethyl ether, or a mixture thereof.

In XTO effluent among the olefins having 4 carbon atoms or more there are more then 50 weight % of butenes.

With regards to said effluent of the XTO process, "light olefins" means ethylene and propylene and the "heavy hydrocarbon fraction" is defined herein as the fraction containing hydrocarbons having a molecular weight greater than propane, which means hydrocarbons having 4 carbon atoms or more and written as C₄ ⁺. The C₄ ⁺ fraction can also contain other co-boiling X-containing compounds, like methanol and other oxygenates. As regards the XTO reactor, for certain chemical reactor applications, the fixed bed reactors can have major disadvantages. When the reaction is fast and highly exothermic or endothermic, hot or cold spots will form in the packed beds and deteriorate the reactor performance. Sintering, plugging, and fluid maldistribution can also occur much more readily in packed beds in particular when coke deposition is rather fast. Comparing to fixed beds, fluidized beds can provide significant advantages when reactions are in particular highly exothermic or endothermic. The reaction can also be made in a moving bed.

Optionally, in order to adjust the propylene to ethylene ratio of the process, ethylene in whole or in part can be recycled over the XTO reactor and advantageously converted into more propylene

These ways of operation allow to respond with the same equipment and catalyst to market propylene to ethylene demand.

The method of making the olefin products from an oxygenate feedstock can include the additional step of making the oxygenate feedstock from hydrocarbons such as oil, coal, tar sand, shale, biomass, waste and natural gas. Methods for making oxygenate feedstocks are known in the art. These methods include fermentation to alcohol or ether, making synthesis gas, then converting the synthesis gas to alcohol or ether. Synthesis gas can be produced by known processes such as steam reforming, autothermal reforming and partial oxidation in case of gas feedstocks or by reforming or gasification using oxygen and steam in case of solid (coal, organic waste) or liquid feedstocks. Methanol, methylsulfide and methylhalides can be produced by oxidation of methane with the help of dioxygen, sulphur or halides in the corresponding oxygen-containing, halogenide-containing or sulphur-containing organic compound.

One skilled in the art will also appreciate that the olefin products made by the oxygenate-to-olefin conversion reaction using the molecular sieve of the present invention can be polymerized optionally with one or more comonomers to form polyolefins, particularly polyethylenes and polypropylenes. The present invention relates also to said polyethylenes and polypropylenes.

[Examples]

PP-ZSM5 catalyst (at least 10-member zeolite )

WP = 1.25 bar

PT entrance catalyst bed = 550⁰C.

PWHSV MeOH on CH2 base = 1.6 or 4.0 g CH2/g catalyst ^* h iFeeds compositions

20% I-C4, 40%1-butene, 34% 2-butene, 6% 1 -butene

60% I-C4, 20%1-butene, 17% 2-butene, 3% 1 -butene

^Analysis by GC and μGC (for detection of CO and CO2, not identified on GC)

^Methanol Conversion >99.9%

^Recycle ratio for (C4+)Par:

(C4+)Par/MeOH = gCH2 (C4+)p_ar/g CH2 MeOH ^Recycle ratio for (C4+)oief

(C4+)Olef/MeOH = gCH2 (C4+)θlef/g CH2 MeOH PRecycle ratio for (C2-) :

(C2-)Olef/MeOH = gCH2 (C2-)Olef/g CH2 MeOH ^Combined Feed ratio:

( (C2-) + C4+ + MeOH ) / MeOH

^The catalyst P-ZSM5 was prepared following the recipe given in Sample 13 of patent:

(WO 2009/016155) USE OF PHOSPHORUS MODIFIED MOLECULAR SIEVES IN CONVERSION OF ORGANICS TO OLEFINS A sample of zeolite ZSM-5 (Si/AI=13) in H-form was steamed at 550OC for 6h. 100g of the steamed zeolite were subjected to a contact with 25g of 85wt% H3PO4 at reflux condition for 4h followed by cooling down and addition of 120 ml of aqueous solution containing 7g of dispersed xonotlite. The resulted slurry was keeping under stirring for approximately 1 h followed by addition of 30Og of low sodium silica sol (34wt% SiO2 in water). Then the solution was stirred for one hour and spray-dried. The spray-dried solid was dried at 200oC for 16h and washed with water at room temperature for 2h followed by filtering, drying and calcinations at 700OC.

PThe schemes have been built considering the dienes in the olefins' pool: the amount of the different compounds and the final yields have been calculated based on this assumption. iA selective hydrogenation of the dienes to olefins must be forecasted in the process scheme on the on the recycle pattern.

Case A1 : WHSV = 4.Oh^"1, no recycle (the C4-C6 consists of compounds having more than 3 carbon atoms and boiling point lower than benzene's).

Case A2: WHSV = 4.Oh^"1, recycle of C2- and C4-C6 (consisting of compounds having more than 3 carbon atoms and boiling point lower than benzene's) cuts with the C4-C6 cut containing 20%wt of paraffins.

Case A3: WHSV = 4.Oh^"1, recycle of C2- and C4-C6 (consisting of compounds having more than 3 carbon atoms and boiling point lower than benzene's) cuts with the C4-C6 cut containing 60%wt of paraffins.

Case B1 : WHSV = 4.Oh^"1, no recycle (the C4+ cut consists of all compounds having more than 3 carbon atoms excluding the aromatics).

Case B2: WHSV = 4.Oh^"1, recycle of C2- and C4+ cuts (the C4+ cut consists of all compounds having more than 3 carbon atoms excluding the aromatics) in which the C4+ cut containing 20%wt of paraffins.

Case B3: WHSV = 4.Oh^"1, recycle of C2- and C4+ cuts (the C4+ cut consists of all compounds having more than 3 carbon atoms excluding the aromatics) in which the C4+ cut containing 60%wt of paraffins.

Claims

1 Process to make light olefins, in a XTO process, to make light olefins, in a XTO process, from an oxygen-containing, halogenide-containing or sulphur-containing organic feedstock comprising : a) providing a catalyst comprising zeolitic molecular sieves containing at least 10 membered ring pore openings or larger in their microporous structure, b) providing an XTO reaction zone, c) contacting said oxygen-containing, halogenide-containing or sulphur- containing organic feedstock in the XTO reactor with the catalyst at conditions effective to convert at least a portion of the feedstock to form a XTO reactor effluent comprising light olefins and a heavy hydrocarbon fraction; d) separating said light olefins from said heavy hydrocarbon fraction; e) fractionating said heavy hydrocarbon fraction to remove the essential part of the aromatics and recovering a heavy hydrocarbon fraction having a reduced aromatics content; f) recycling at least a part of said heavy hydrocarbon fraction having a reduced aromatics content at the inlet of the XTO reaction zone; wherein, to adjust the proportion of C4+ paraffins recycled at the inlet of the XTO reaction zone, a fraction of the stream recycled at step f) is purged.

2 Process according to claim 1 wherein the catalyst is a P-modified zeolite.

3 Process according to claim 2 wherein the P-modified zeolite is made by a process comprising in that order:

- separation of the solid from the liquid if any; - an optional washing step or an optional drying step or an optional drying step followed by a washing step;

- a calcination step.

4 Process according to claim 2 wherein the phosphorous modified zeolite is made by a process comprising in that order:

- steaming at a temperature ranging from 400 to 87O⁰C for 0.01 -20Oh;

- separation of the solid from the liquid;

- a calcination step.

5 Process according to claim 1 wherein the catalyst is a catalyst composite made by a process comprising the following steps:

6 Process according to claim 1 wherein the catalyst is an alkaline earth or rare earth metal P-modified molecular sieve (M-P-modified molecular sieve) made by a process comprising the following steps: a), selecting at least one molecular sieve selected from one of:

-a P-modified molecular sieve which contains at least 0.3 wt% of P -a molecular sieve which is modified with P prior to or during step b) introducing at least 0.3 wt % of P b). contacting said molecular sieve with an alkaline earth or rare earth metal- containing compound (M-containing compound) to introduce at least 0.05 wt% of the alkaline earth or rare earth metal M.

7 Process according to any one of the preceding claims wherein ethylene is recycled to the inlet of the XTO reactor.

8 Process according to any one of the preceding claims wherein ethylene is further polymerized optionally with one or more comonomers.

9 Process according to any one of the preceding claims wherein propylene is further polymerized optionally with one or more comonomers.

10 Process according to any one of the preceding claims wherein, in the stream recycled at the inlet of the XTO reaction zone, the weight ratio of C4+ paraffins to the olefins in said stream is above 0.8 and under 10.

11 Process according to claim 10 wherein said ratio is above 1 and under 10.