KR100936848B1 - Method of removing dimethyl ether from an olefin stream - Google Patents

Abstract

The present invention relates to a process for removing dimethyl ether from an olefin stream. The process includes distilling the olefin stream to separate dimethyl ether from the olefin stream including propane. The olefin stream can then be further distilled to provide a polymerizable grade ethylene stream and a polymerizable grade propylene stream, each stream containing up to about 10 wppm dimethyl ether.

Description

METHOD OF REMOVING DIMETHYL ETHER FROM AN OLEFIN STREAM}             

The present invention relates to the removal of dimethyl ether from an olefin stream. In particular, the present invention relates to the removal of dimethyl ether from an olefin stream by distillation to produce polymerizable grade ethylene and polymerizable grade propylene streams.

This application claims the application of German Patent Application No. 101 50 479.9, filed October 16, 2001, US Patent Application No. 60 / 345,666, filed December 31, 2001, and the United States, filed July 15, 2002. Patent Application No. 10 / 196,530, the disclosure of each of which is hereby fully incorporated by reference, claims priority.

Olefins, in particular C ₂ and C ₃ olefins, are preferred as sources for producing derivative products such as oligomers, for example expensive olefins, and polymers such as polyethylene and polypropylene. Olefin sources were typically prepared by cracking petroleum feedstocks.

U.S. Patent 5,090,977 discloses a process for preparing olefins by steam cracking. The process involves separating the olefin product into methane, hydrogen, ethane, ethylene, propylene and C ₅₊ streams. The disclosed separation process preferentially produces propylene and produces no propane, butane, butene or butadiene streams at all.

However, oxygenate feedstocks have become an alternative to petroleum feedstocks for the production of large quantities of olefins, in particular ethylene and propylene for the production of expensive olefins and plastic materials. Generally, olefins are prepared by catalytically converting oxygenate to olefins by contacting the oxygenate component with a molecular sieve catalyst. This process works catalytically, for example according to Scheme 1 below:

For example, US Pat. No. 4,499,327 discloses a process for preparing olefins from methanol using any one of a variety of silicoaluminophosphate (SAPO) molecular sieve catalysts. This method is carried out at a temperature of 300 to 500 ° C., a pressure of 0.1 to 100 atmospheres, and a weight hourly space velocity (WHSV) of 0.1 to 40 hr ⁻¹ . The method is very selective for producing ethylene and propylene.

U. S. Patent No. 6,121, 504 also discloses a process for preparing olefin products from oxygenate feeds using molecular sieve catalysts. Water and other unwanted byproducts are contacted with the quenching medium to remove from the olefin product. After contact with the quenching medium, a light product fraction containing the desired olefin but including other minor constituents such as dimethyl ether, methane, CO, CO ₂ , ethane, propane and water, as well as unreacted oxygenate feedstock Obtained.

One more particularly undesirable byproduct is dimethyl ether. The problem of removing dimethyl ether from the olefin product stream has not been satisfactorily solved to date. Special absorbents that are believed to remove dimethyl ether from the product stream have already been considered. However, it is difficult to find an absorbent or absorbent suitable for this purpose.

In order to further process olefins, especially ethylene, propylene and butylenes, it is often necessary to reduce or eliminate the amount of undesirable hydrocarbon byproducts present in the olefin composition. This is because the derivative manufacturing process may use catalysts that are very sensitive to the presence of certain hydrocarbons. For example, an undesirable byproduct, dimethyl ether, has been found to act as a poison to certain catalysts used to convert ethylene, propylene or butylene to other products.

US Pat. No. 4,474,647 discloses, for example, that dimethyl ether may adversely affect oligomerization of certain olefins. The patent describes a process for removing dimethyl ether from a C ₄ and / or C ₅ olefins stream using distillation. The stream is distilled off and separated into top and bottom streams. The overhead stream contains dimethyl ether, water and various hydrocarbons, and the bottom stream contains purified olefins.

U.S. Patent 5,609,734 discloses a process for removing methanol and dimethyl ether from mixed hydrocarbon streams. The hydrocarbon stream containing methanol and dimethyl ether is distilled off to remove dimethyl ether and methanol from the tower stream. Additional methanol is recovered in the side stream, using a methanol permeable membrane for further separation. Purified hydrocarbons are removed from the bottoms stream.

Removing dimethyl ether from the olefin stream is particularly difficult because very small amounts of dimethyl ether can act as catalyst poisons. This is because C ₂ -C ₄ if further catalytic processing of the olefin stream is required. It is meant that olefin streams such as olefins should contain little if any dimethyl ether. Thus, it is highly desirable to find additional methods of removing dimethyl ether from olefin streams.

Summary of the Invention

The present invention provides a process for removing dimethyl ether from an olefin stream. As a result of this process of separating olefin streams, especially ethylene, propylene, and butylene streams, it was possible to substantially reduce the content of dimethyl ether.

The present invention separates dimethyl ether from the olefin product stream in a novel but economical way. In one embodiment, the present invention provides a process for removing dimethyl ether from an olefin-containing stream comprising fractionating an olefin-containing stream. The olefin-containing stream comprises a C ₃ hydrocarbon stream and dimethyl ether, and the olefin-containing stream is fractionated to separate the C ₃ hydrocarbon stream together with the dimethyl ether from the olefin-containing stream. The C ₃ hydrocarbon stream containing the dimethyl ether is sent to a rectification column. Propylene is removed from the top of the rectification column and propane is removed from the bottom of the rectification column. In addition, dimethyl ether is removed with propane from the bottom of the rectification column.

In another embodiment, the present invention provides a process for separating dimethyl ether from an olefin stream prepared from an oxygenate to olefin reaction process. The method involves contacting an oxygenate with a molecular sieve catalyst to produce an olefin stream. The olefin stream includes especially water, propylene, propane, and dimethyl ether. The olefin stream is dried and distilled to separate dimethyl ether and propane from propylene.

In the present invention, it is preferred that the dried olefin stream contains up to about 1,000 wppm water. Preferably, the dried olefins stream contains up to about 500 wppm water, and more preferably the dried olefins stream contains up to about 10 wppm water.

In one embodiment, the propylene distilled from the dried olefin stream is substantially free of dimethyl ether. Preferably, the propylene distilled from the dried olefin stream contains up to about 25 wppm dimethyl ether.

In another embodiment, the olefin stream contains at least about 0.05% by weight dimethyl ether. In another embodiment, the olefin stream further comprises butylene and high boiling point compounds, and the dried olefin stream is distilled to separate dimethyl ether and propane from propylene, butylene and high boiling point compounds. In this embodiment, the olefin stream preferably comprises about 2 to 45 weight percent propane, about 0.05 to about 5 weight percent dimethyl ether, and about 30 to about 95 weight percent butylene and high boiling point compounds.

The present invention may further comprise separating dimethyl ether from propane by contacting propane and dimethyl ether with water. Olefin can be prepared by contacting the separated dimethyl ether with a molecular sieve catalyst.

Optionally, the present invention further comprises polymerizing the separated propylene to produce polypropylene. In addition, any butylene and high boiling point compounds can be separated from propylene and further reacted. For example, isolated butylene can be converted to esters or linear alpha olefins prepared from aldehydes, acids, alcohols, C ₅ -C ₁₃ monovalent carboxylic acids and C ₅ -C ₁₃ monohydric alcohols.

In another embodiment of the invention, the olefin stream further comprises ethylene and the dried olefin stream is distilled to separate dimethyl ether and propane from ethylene and propylene. The separated ethylene can be polymerized if necessary.

The invention further provides a process for removing dimethyl ether from an olefin stream comprising water, propylene, propane and dimethyl ether. The olefin stream is dried and distilled to separate propane and dimethyl ether from propylene. In this embodiment, the propane and dimethyl ether streams preferably comprise from about 4.0 to about 99 weight percent propane and from about 1.0 to about 96 weight percent dimethyl ether, depending on the conversion of the oxygenate.

In another embodiment of the present invention, the olefin stream is contacted with a water absorbent or water adsorbent to dry the olefin stream. The water absorbent is preferably a polar hydrocarbon. The water adsorbent is preferably a molecular sieve. It is also desirable to compact the olefin stream prior to contact with the water absorbent or adsorbent.

The present invention further provides a process for the polymerization of propylene made from oxygenate. The process involves contacting an oxygenate with a molecular sieve catalyst to produce an olefin stream comprising propylene, propane and dimethyl ether. The olefin stream is distilled off to separate propylene from propane and dimethyl ether and polymerize the separated propylene. Preferably, the separated propylene stream contains up to about 25 wppm dimethyl ether. It is also desirable to dry the olefin stream before distillation.

The present invention further provides a process for polymerizing ethylene and propylene. The process involves drying the olefin stream, in particular comprising ethylene, propylene, propane and dimethyl ether. The dried olefin stream is distilled off and the ethylene stream, propylene stream, and propane and dimethyl ether streams are separated such that the ethylene stream and propylene stream each contain up to about 10 wppm of dimethyl ether. The separated ethylene and propylene streams can then be polymerized. Preferably, the dried olefin stream contains up to about 1,000 wppm water.

Examples of various embodiments of the invention are shown in the accompanying drawings.

1 is a process diagram showing the preparation of olefins from an oxygenate, drying the olefins, and separating the propane and dimethyl ether streams from the dried olefins.

2 is a process diagram of a first fractionation embodiment of the deethanizer of the present invention.

3 is a process diagram of a first fractionation embodiment of the C ₃ splitter of the present invention.

4 is a process diagram of a first fractionation embodiment from a demethanizer to a deethanizer of the present invention.

5 is a process diagram of a first fractionation embodiment of the demethanizer of the present invention.

Figure 6 is a process diagram of a first fractionation embodiment of the deethanizer of the present invention.

The present invention provides a process for removing dimethyl ether from an olefin stream, in particular an olefin stream containing ethylene and / or propylene. Generally, the process involves distilling the olefin stream to separate propane and dimethyl ether in a common stream. Ethylene and / or propylene in the distilled olefin stream have a quality, ie polymerizable grade quality, sufficient for use as feed in the polymerization process.

The present invention provides the advantage that no additional device is required to separate the dimethyl ether from the propylene product stream. C ₃ splitters typically used to separate propane from propylene can also be used to separate unwanted dimethyl ether from propylene.

In another embodiment of the present invention, the problem of removing dimethyl ether from the olefin stream is solved according to the present invention by fractionally separating at least some of the high C ₃ hydrocarbon streams from the olefin product stream. A separated stream containing C ₃ hydrocarbons is sent to a rectification column (C ₃ splitter) for the separation of propylene and propane. A propylene product stream is taken from the top of the rectification column; Propane, and possibly other C ₃ hydrocarbons, as well as dimethyl ether, are removed from the bottom of the rectification column to yield a propylene product stream containing at most only a trace amount of dimethyl ether.

Another embodiment of the present invention is based on the fractionation of olefin streams to separate dimethyl ether after C ₃ hydrocarbons in a separation process. As such, dimethyl ether is sent to a C ₃ splitter or rectification column along with propylene, propane and possibly other C ₃ hydrocarbons in a fractionation process. Surprisingly, it has now been found that dimethyl ether almost completely goes to the bottom of the rectification column with propane. Propylene is taken from the top of the column and practically free of dimethyl ether.

In another embodiment of the present invention, it is desirable to distill a low water content olefin stream to separate propane and dimethyl ether. Low water content tends to avoid the problem of clathrate and / or free water production in distillation vessels. Cladrate and anhydrous preparation can significantly interfere with heat and mass transfer, making it very difficult to separate products with relatively close boiling points. In some cases, it may be necessary to reduce the water content in the olefin stream by drying the olefin stream to significantly reduce the effects of cladrate and anhydrous preparation.

The olefin stream which is distilled to separate dimethyl ether preferably contains up to about 1000 wppm water. Preferably, the olefin stream contains about 500 wppm, more preferably about 100 wppm, most preferably about 10 wppm or less of water.

The process of the invention is particularly useful for removing dimethyl ether from ethylene and / or propylene streams containing propane. By distilling this stream at pressures and temperatures effective to separate dimethyl ether with propane, the result of the process is a further distillation of the remaining portion of the olefin stream, resulting in a high overall efficiency of polymerizable grade ethylene and polymerizable grade propylene, respectively. Feed streams may be provided.

According to the invention, an ethylene and / or propylene stream containing propane and dimethyl ether can be obtained from any source. However, some sources will contain more of one ingredient than the other. For example, cracking various hydrocarbon materials will produce ethylene and propylene depending on the cracked material, but dimethyl ether will hardly be produced, if any. In addition, conversion of oxygenate, such as methanol, to olefins by catalytic reaction with molecular sieve catalysts can also produce ethylene and propylene, but will produce significantly more dimethyl ether than cracking hydrocarbons. However, the process of the present invention will be effective as long as the olefin stream contains propane and dimethyl ether. However, due to the relatively high content of dimethyl ether found in this stream, it is particularly effective in removing dimethyl ether from olefin streams produced by the reaction process of oxygenate to olefins.

In one embodiment of the present invention, an olefin stream containing ethylene and / or propylene, dimethyl ether and propane is provided. Optionally, the stream contains butylene and high boiling compounds as well as ethane. The olefin stream is distilled, preferably by conventional continuous distillation techniques, to separate ethylene and / or propylene, and optionally ethane, from propane and dimethyl ether. If butylene and high boiling point compounds are included in the olefin stream, it is preferred that the separated propane and dimethyl ether streams comprise butylene and high boiling point compounds.

In another embodiment of the present invention, an olefin stream is provided comprising about 2 to about 45 weight percent propane. Preferably, the olefin stream comprises about 5 to about 40 weight percent propane, more preferably about 10 to about 35 weight percent propane.

The provided olefin stream also preferably contains at least about 0.05% by weight of dimethyl ether. Preferably, the provided olefin stream contains from about 0.05 to about 5 weight percent dimethyl ether, more preferably from about 0.1 to about 3 weight percent dimethyl ether, most preferably from about 0.2 to about 2 weight percent dimethyl ether. .

Optionally, the provided stream comprises butylenes and high boiling compounds. This stream is typically present when propane and dimethyl ether are separated from an olefin stream containing various C ₂ and high boiling olefins. In this embodiment, the propylene and low boiling compounds are removed by distillation from the olefin stream comprising C ₂ and high boiling olefins.

The amount of butylene and high boiling point compounds that can be included in a provided olefin stream can vary depending on the final source of olefin. If the olefin stream comprises ethylene and propylene, butylene and high boiling point materials are present at low concentrations. When ethylene and propylene are separated from the olefin source, butylene and high boiling point compounds are present at high concentrations. Generally provided olefin streams comprise from about 30% to about 95% by weight of butylene and high boiling compounds. Preferably, in this embodiment, the provided olefin stream has already been distilled to remove ethylene and propylene, and the provided stream contains from about 40 to about 95 weight percent of butylene and high boiling point compounds, more preferably from about 50 to about 90 Wt% butylene and high boiling point compounds, most preferably from about 60 to about 80 wt% butylene and high boiling point compounds.

In another embodiment of the present invention, the dimethyl ether is separated from the propane stream by contacting propane and the dimethyl ether stream with water, preferably in the liquid phase. The contact can be performed in any conventional type of cleaning or liquid / liquid contacting vessel. The amount of water used should be sufficient to recover the propane stream containing at least about 85 weight percent propane, preferably at least about 90 weight percent propane, more preferably at least about 95 weight percent propane.

The water stream in contact with the dimethyl ether and propane stream will absorb significant amounts of dimethyl ether. The water stream will be recovered from the contacting vessel as a bottoms stream and will contain at least about 1% by weight dimethyl ether, preferably at least about 3% by weight dimethyl ether, more preferably at least about 5% by weight dimethyl ether. Dimethyl ether may be separated from water by evaporation, preferably by flash evaporation to evaporate the dimethyl ether under reduced pressure so that it can be easily separated from water. The separated dimethyl ether can be processed as needed. For example, recovered dimethyl ether can be used as feed for the reaction process from oxygenate to olefins.

In one embodiment of the invention, the oxygenate is contacted with a molecular sieve catalyst to obtain an olefin stream. Oxygenates include one or more organic compounds containing one or more oxygen atoms, for example aliphatic alcohols, ethers, carbonyl compounds (aldehydes, ketones, carboxylic acids, carbonates, esters, and the like). If the oxygenate is an alcohol, the alcohol comprises aliphatic moieties having 1 to 10 carbon atoms, more preferably 1 to 4 carbon atoms. Representative alcohols include, but are not necessarily limited to, lower straight and branched chain aliphatic alcohols and their unsaturated equivalents. Examples of suitable oxygenate compounds include methanol, ethanol, n-propanol, isopropanol, C ₄ -C ₂₀ alcohol, methyl ethyl ether, dimethyl ether, diethyl ether, di-isopropyl ether, formaldehyde, dimethyl carbonate, dimethyl ketone , Acetic acid, and mixtures thereof, but are not limited to these. Preferred oxygenate compounds are methanol, dimethyl ether or mixtures thereof.

Molecular sieves capable of converting oxygenates to olefin compounds include zeolites as well as non-zeolites and have large, medium or small pore types. However, small pore molecular sieves are preferred in one embodiment of the present invention. As defined herein, small size pore molecular sieves have a pore size of less than about 5.0 mm 3. Generally suitable catalysts have a pore size in the range of about 3.5 to about 5.0 kPa, preferably about 4.0 to about 5.0 kPa, most preferably about 4.3 to about 5.0 kPa.

Natural and synthetic zeolite materials have been found to have catalytic properties in various types of hydrocarbon conversion processes. Zeolite materials have also been used as adsorbent catalyst carriers in various types of hydrocarbon conversion processes and other applications. Zeolites are complex crystalline aluminosilicates that form a network of AlO ₂ ^- and SiO ₂ tetrahedra linked to shared oxygen atoms. Negative tetrahedra are balanced by the incorporation of cations such as alkali or alkaline earth metal ions. In the preparation of some zeolites, nonmetallic cations such as tetramethylammonium (TMA) or tetrapropylammonium (TPA) are present during the synthesis. The gap spaces or channels formed by the crystalline network allow zeolites to be used as molecular sieves in separation processes, as catalysts for chemical reactions, and as catalyst carriers in a wide variety of hydrocarbon conversion processes.

Zeolites include materials containing silica and optionally alumina, and materials in which all or part of the silica and alumina moiety is replaced with other oxides. For example, germanium oxide, tin oxide and mixtures thereof may replace the silica moiety. Boron oxide, iron oxide, gallium oxide, indium oxide and mixtures thereof may replace the alumina moiety. Unless stated otherwise, the terms "zeolite" and "zeolitic material" as used herein refer to materials containing silicon atoms and optionally aluminum atoms in their crystal lattice structure, as well as suitable replacement atoms for these silicon and aluminum atoms. It means a substance containing.

One type of olefin forming catalyst capable of producing large amounts of ethylene and propylene is silicoaluminophosphate (SAPO) molecular sieves. Silicoaluminophosphate molecular sieves are generally classified as microporous materials having 8, 10 or 12 membered ring structures. These ring structures can have an average pore size in the range of about 3.5 to 15 microns. Small pore size SAPO molecular sieves having an average pore size in the range of less than about 5 GPa, preferably in the range of about 3.5 to 5 GPa, more preferably in the range of 3.5 to 4.2 GPa are preferred. This pore size is typical of molecular sieves having eight membered rings.

According to one embodiment, substituted SAPOs may also be used in the reaction process from oxygenate to olefins. These compounds are generally known as MeAPSO or metal-containing silicoaluminophosphates. Metals include alkali metal ions (Group IA), alkaline earth metal ions (Group IIA), rare earth element ions (lanthanide elements: lanthanum, cerium, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, Ytterbium and lutetium, and group IIIB including scandium or yttrium); And further transition metal cations of groups IVB, VB, VIB, VIIB, VIIIB, and IB.

Preferably, Me represents atoms such as Zn, Mg, Mn, Co, Ni, Ga, Fe, Ti, Zr, Ge, Sn and Cr. These atoms can be inserted in the tetrahedral skeleton of a [MeO ₂ ] tetrahedral unit. [MeO ₂ ] tetrahedral units carry net electric charges depending on the valence state of the metal substituents. If the metal component has a valence state of +2, +3, +4, +5 or +6, the net electric charge is -2 to +2. Introduction of the metal component typically involves adding the metal component during the synthesis of the molecular sieve. However, post-synthesis ion exchange reactions can also be used. In the post-synthesis ion exchange reaction, the metal component will introduce the cation into the ion-exchange position at the open surface of the molecular sieve rather than introducing it into the backbone itself.

Suitable silicoaluminophosphate molecular sieves are SAPO-5, SAPO-8, SAPO-11, SAPO-16, SAPO-17, SAPO-18, SAPO-20, SAPO-31, SAPO-34, SAPO-35, SAPO- 36, SAPO-37, SAPO-40, SAPO-41, SAPO-42, SAPO-44, SAPO-47, SAPO-56, metal containing forms thereof, and mixtures thereof. Preference is given to SAPO-18, SAPO-34, SAPO-35, SAPO-44 and SAPO-47, with SAPO-18 and SAPO-34 including their metal containing forms and mixtures being particularly preferred. As used herein, the term mixture is synonymous with the term combination and is considered to be a composition of matter having two or more components in varying proportions regardless of the physical state.

Aluminophosphate (ALPO) molecular sieves may also be included in the catalyst composition. Aluminophosphate molecular sieves are crystalline microporous oxides that can have an AIPO ₄ backbone. They have additional elements in the backbone, typically have a uniform pore size in the range of about 3 to about 10 microns and can selectively separate molecular species by size. More than two dozen structural types were shown, including zeolite morphological analogs. A more detailed description of the background and synthesis of aluminophosphates can be found in US Pat. No. 4,310,440, which is incorporated herein by reference in its entirety. Preferred ALPO structures are ALPO-5, ALPO-11, ALPO-18, ALPO-31, ALPO-34, ALPO-36, ALPO-37 and ALPO-46.

ALPO may also include metal substituents in the backbone. Preferably, the metal is selected from the group consisting of magnesium, manganese, zinc, cobalt and mixtures thereof. These materials preferably exhibit similar adsorption, ion-exchange and / or catalytic properties similar to aluminosilicate, aluminophosphate and silica aluminophosphate molecular sieve compositions. Species of this class and their preparation are described in US Pat. No. 4,567,029, which is incorporated herein by reference in its entirety.

Metal-containing ALPO has a three-dimensional microporous crystalline framework of MO ₂ , AlO ₂ and PO ₂ tetrahedral units. The structure thus prepared (containing the template before calcination) can be represented by the experimental chemical composition of the formula (1) based on anhydride:

Where

"R" represents at least one organic template present in the pore system in the crystal;

"m" represents the number of moles of "R" present per mole of (M _x Al _y P _z ) O ₂ , having a value from 0 to 0.3, the maximum being in each case the molecular size of the template, and including Depends on the allowable pore volume of the pore system of the particular metal aluminophosphate;

"x", "y" and "z" represent the mole fractions of the metal "M" (ie magnesium, manganese, zinc and cobalt), aluminum and phosphorus, respectively, present as tetrahedral oxides.

Metal containing ALPO is often referred to by the acronym as MeAPO. The acronym MAPO is also applied to the composition when the metal "Me" in the composition is magnesium. Similarly, ZAPO, MnAPO and CoAPO are applied to compositions containing zinc, manganese and cobalt, respectively. To identify the various structural species that make up the generic names classes MAPO, ZAPO, CoAPO and MnAPO, respectively, numbers are given to each species and identified as, for example, ZAPO-5, MAPO-11, CoAPO-34 and the like.

Silicoaluminophosphate molecular sieves are typically mixed (ie blended) with other materials. When blended, the resulting composition is typically referred to as an SAPO catalyst, which catalyst comprises SAPO molecular sieves.

Materials that can be blended with the molecular sieve can be various inert materials, catalytically active materials, or various binders. These materials include kaolin and other clays, various types of rare earth metals, metal oxides, other non-zeolitic catalyst components, zeolite catalyst components, alumina or alumina sol, titania, zirconia, magnesia, toria, beryllia, quartz, silica or silica Compositions such as sol, and mixtures thereof. In addition, these components are particularly effective in reducing the overall catalyst cost, acting as a heat sink to assist in the heat shielding of the catalyst during regeneration, densifying the catalyst and increasing the catalyst strength. The inert material used in the catalyst acting as a heat sink is from about 0.05 to about 1 cal / g · ° C, more preferably from about 0.1 to about 0.8 cal / g · ° C, most preferably from about 0.1 to about 0.5 cal / g · It is particularly preferable to have a heat capacity of ° C.

Additional molecular sieve materials may be included as part of the SAPO catalyst composition or may be used as individual molecular sieve catalysts in a mixture with the SAPO catalyst, if necessary. Small pore size molecular sieves suitable for use in the present invention include AEI, AFT, APC, ATN, ATT, ATV, AWW, BIK, CAS, CHA, CHI, DAC, DDR, EDI, ERI, GOO, KFI, LEV, LOV, LTA, MON, PAU, PHI, RHO, ROG, THO and substituted forms thereof. Molecular sieves of moderate type of pore size suitable for use in the present invention include MFI, MEL, MTW, EUO, MTT, HEU, FER, AFO, AEL, TON and substituted forms thereof. Such small and medium pore molecular sieves are described in more detail in Atlas of Zeolite Structural Types , WM Meier and DH Olsen, Butterworth Heineman, 3rd ed., 1997, the details of which are expressly incorporated herein by reference. Is disclosed. Preferred molecular sieves that can be mixed with the silicoaluminophosphate catalyst include ZSM-5, ZSM-34, erionite and carbazite.

The catalyst composition according to the embodiment preferably comprises about 1 to about 99% by weight, more preferably about 5 to about 90% by weight and most preferably about 10 to about 80% by weight molecular sieve. In addition, the catalyst composition preferably has a particle size of about 20 to about 3,000 mm 3, more preferably about 30 to about 200 mm 3, most preferably about 50 to about 150 mm 3.

The catalyst can be subjected to a variety of treatments to achieve the desired physical and chemical properties. Such treatments include, but are not limited to, hydrothermal treatment, calcination, acid treatment, base treatment, milling, ball milling, grinding, spray drying, and combinations thereof.

Particularly useful molecular sieve catalysts for preparing ethylene and propylene are catalysts containing a combination of SAPO-34 and SAPO-18 or ALPO-18 molecular sieves. In certain embodiments, the molecular sieve is a crystalline ductility of SAPO-34 and SAPO-18 or ALPO-18.

To convert the oxygenate to olefins, conventional reactor systems, including fixed bed, fluidized bed, or moving bed systems, can be used. Preferred reactors of one embodiment are a cocurrent riser reactor and a short contact backflow free fall reactor. Preferably the reactor oxygenate feedstock from about 1hr ^-1 or more, preferably from about 1hr ^-1 to about 1000hr ^-1, more preferably about 20hr ^-1 to about 1000hr ^-1, most preferably about 50hr ^- Contacting the molecular sieve catalyst at a weight hourly space velocity (WHSV) in the range of ¹ to about 500 hr ⁻¹ . WHSV is defined herein as the weight of reactive hydrocarbons and oxygenates that may optionally be present in the feed per weight of molecular sieve per hour in the reactor. Since the catalyst or feedstock may contain other materials that act as inactive agents or diluents, the WHSV is an oxygenate feed contained in the reactor, any reactive hydrocarbons that may be present with the oxygenate feed, and molecular sieves. It is calculated based on the weight of.

Preferably, the oxygenate feed is contacted with the catalyst in the vapor phase. Alternatively, the process may be carried out in the liquid phase or in the mixed vapor phase / liquid phase. When the process is carried out in the liquid phase or in the mixed vapor phase / liquid phase, different conversions and selectivities of the feed-to-product may depend on the catalyst and reaction conditions.

The process can generally be carried out over a wide temperature range. The effective operating temperature may be about 200 ° C to about 700 ° C, preferably about 300 ° C to about 600 ° C, more preferably about 350 ° C to about 550 ° C. At lower lower limits of the temperature range, the formation of the desired olefin product can be significantly slowed such that relatively high contents of oxygenated olefin by-products are found in the olefin product. However, at low temperatures it can increase the selectivity for ethylene and propylene. At higher upper limits of the temperature range, the process is unable to form optimal amounts of ethylene and propylene products, but the conversion of the oxygenate feed will generally be high.

The working pressure can also vary over a very wide range, including autogenous pressure. Effective pressures include, but are not necessarily limited to, a total pressure of at least about 1 psia (7 kPa), preferably at least about 5 psia (34 kPa). The process is particularly effective at higher gross pressures, including gross pressures above about 20 psia (138 kPa). The total pressure is preferably at least about 25 psia (172 kPa), more preferably at least about 30 psia (207 kPa). For practical design purposes, use methanol as the first oxygenate feed component and at a pressure of about 500 psia (3445 kPa), preferably about 400 psia (2756 kPa), most preferably about 300 psia (2067 kPa) or less. It is preferable to operate the reactor.

By operating at an appropriate gas tower velocity, undesirable by-products can be avoided. Increasing the gas tower velocity reduces the conversion to avoid undesirable byproducts. As used herein, the term "gas tower velocity" is defined as the total flow rate of the evaporated feedstock including the diluent as well as the conversion product when present in the feedstock divided by the cross-sectional area of the reaction zone. Since the oxygenate flows through the reaction zone and is converted to a product having a significant amount of ethylene and propylene, the gas column rate can vary at different locations within the reaction zone. The degree of change depends on the total moles of gas present and the cross-sectional area of the particular location in the reaction zone, the temperature, the pressure and other related reaction parameters.

In one embodiment, the gas tower velocity is maintained at a rate greater than 1 m / s at one or more points in the reaction zone. In another embodiment, it is preferred that the gas tower velocity exceeds about 2 m / s at one or more points in the reaction zone. More preferably the gas tower velocity is above about 2.5 m / s at one or more points in the reaction zone. Even more preferably the gas tower velocity exceeds about 4 m / s at one or more points in the reaction zone. Most preferably the gas tower velocity is above about 8 m / s at one or more points in the reaction zone.

According to another embodiment of the present invention, the gas tower velocity is kept relatively constant in the reaction zone such that the gas tower velocity is maintained at a rate in excess of 1 m / s at all points in the reaction zone. It is also preferred that the gas tower velocity exceeds about 2 m / s at all points in the reaction zone. More preferably the gas tower velocity exceeds about 2.5 m / s at all points in the reaction zone. Even more preferably the gas tower velocity exceeds about 4 m / s at all points in the reaction zone. Most preferably the gas tower velocity is above about 8 m / s at all points in the reaction zone.

The amount of ethylene and propylene produced in the reaction of oxygenate to olefins can be increased by reducing the conversion of oxygenate in the reaction of oxygenate to olefins. However, reducing the conversion of feed oxygenate in the oxygenate conversion reaction tends to increase the amount of oxygenated hydrocarbons, especially dimethyl ether, present in the olefin product. Therefore, it may be important to control the conversion reaction process to the oxygenate in the feed.

According to one embodiment, the conversion of the first oxygenate, for example methanol, is from 90 to 98% by weight. According to another embodiment, the conversion of methanol is between 92 and 98% by weight, preferably between 94 and 98% by weight.

According to another embodiment, the conversion of methanol is from 98% to less than 100% by weight. According to another embodiment, the conversion of methanol is 98.1 to less than 100% by weight, preferably 98.2 to 99.8% by weight. According to another embodiment, the conversion of methanol is from 98.2 to less than 99.5% by weight, preferably from 98.2 to 99% by weight.

In the present invention, the weight percent conversion is calculated based on the absence of water unless otherwise stated. The weight percent conversion, based on the absence of water, is calculated as:

Weight% conversion = (weight of the supplied oxygenate based on the absence of water-weight of the oxygenated hydrocarbon in the product based on the absence of water) x 100

Oxygenates based on the absence of water are calculated by subtracting the water portion of the oxygenate from the feed and product and subtracting the water formed in the product. For example, the weight flow rate of methanol based on the absence of oxygenate is calculated by multiplying the weight flow rate of methanol by 14/32 to remove the water component in the methanol. As another example, the weight flow rate of dimethyl ether based on the absence of oxygenate is calculated by multiplying the weight flow rate of dimethyl ether by 28/46 to remove the water component in the dimethyl ether. If the oxygenate mixture is in the feed or product, no traces of oxygenate are included. If methanol and / or dimethyl ether are used as feed, only methanol and dimethyl ether are used to calculate the conversion based on the absence of water.

In the present invention, the selectivity is also calculated based on the absence of water unless otherwise stated. Selectivity is calculated as Equation 2 below when methanol and / or dimethyl ether are used as feed:

Selectivity = 100 × component (wt%) / (100-water (wt%)-methanol (wt%)-dimethyl ether (wt%))

In the oxygenate to olefin reaction, the higher the amount of dimethyl ether in the olefin product, the lower the percent conversion. It is desirable to have a significant amount of dimethyl ether in the resulting olefins, since it is desirable to carry out the reaction at low conversions in order to increase the selectivity for ethylene and propylene. However, the amount of dimethyl ether present should not be high enough to make the whole process inefficient or to make the removal of dimethyl ether more difficult.

Preferably, the dimethyl ether will be present in an amount of at least about 100 ppm by weight, based on the absence of water, in the olefins produced in the reaction of oxygenate to olefins. Preferably, the dimethyl ether is present in an amount of at least about 500 ppm by weight, more preferably at least about 1000 ppm by weight. Preferably, the amount of dimethyl ether in the olefin stream obtained from the reaction of oxygenate to olefin based on the absence of water is about 10% by weight, more preferably about 5% by weight, most preferably about 2% by weight or less All.

The reaction process from oxygenate to olefin forms a significant amount of water as a byproduct. Large amounts of these water by-products can be removed by cooling the stream to a temperature below the condensation temperature of the water vapor in the stream before distillation. Preferably, the temperature of the product stream is cooled to a temperature below the condensation temperature of the oxygenate feed. In certain embodiments, it is desirable to cool the product stream below the condensation temperature of methanol.

After cooling the olefin stream obtained from the reaction of oxygenate to olefin, it is preferred to separate the cooled olefin stream into a stream containing condensed water and an olefin vapor stream. The stream containing the condensed water consists of most of the water obtained from the olefin stream and a significant portion of the oxygenated hydrocarbons obtained from the olefin stream. The olefin vapor stream consists mostly of olefins such as ethylene and propylene.

In one embodiment of the invention, the olefin stream obtained from the reaction of the oxygenate to olefins can be cooled to separate the vapor stream enriched in the olefin from the stream containing the condensed water. The vapor stream contains about 20% by weight, preferably about 15% by weight, more preferably about 12% by weight or less of water.

Quenching columns are one type of apparatus effective for cooling the olefin stream obtained from the reaction process of olefin to oxygenate. In the quench column, the quench fluid is in direct contact with the olefin stream to cool the stream to the desired condensation temperature. Condensation produces a stream containing condensed water, also referred to as a heavy bottom stream. The olefin portion in the olefin product stream remains vapor and exits the quench column as a top vapor stream. The tower vapor stream is rich in olefin products and may contain water as well as significant oxygenated hydrocarbon byproducts.

In one embodiment, the quench fluid is a regeneration stream containing condensed water, a heavy bottom stream of the quench column. The stream containing this water is preferably cooled, for example by a heat exchanger, and injected back into the quench column. In this embodiment, it may be desirable to inject the cooling medium down the stream of the quench column in another separation device, but it is preferred not to inject the cooling medium from the external source into the quench column.

In one embodiment of the invention, the olefin stream containing dimethyl ether is dried before separating the propane and dimethyl ether streams. In this embodiment, water can be removed from the olefin stream containing dimethyl ether (ie, the olefin stream can be dried) using a solid or liquid drying system prior to distillation to remove dimethyl ether more effectively.

In a solid drying system, the olefin stream is contacted with a solid adsorbent to further remove water to very low levels. Any conventional method can be used. Typically, the adsorption process is carried out in one or more fixed beds containing a suitable solid adsorbent.

Adsorption is useful to remove low concentrations of water as well as to remove certain oxygenated hydrocarbons that cannot normally be removed using other treatment systems. Preferably, the adsorbent system used as part of the present invention has multiple adsorbent layers. Multiple layers allow for continuous separation without having to stop the process to regenerate the solid adsorbate. For example, in a three layer system typically one layer is in the on-line state, one layer is in the regenerated off-line state and the third layer is in the atmospheric state.

The particular adsorbent solids or solids used in the adsorbent bed depends on the type of contaminant to be removed. Examples of solid adsorbents for removing water and various polar organic compounds such as oxygenated hydrocarbons and absorbent liquids include alumina, silica, molecular sieves and alumino-silicates. Layers containing mixtures of these molecular sieves or multiple layers with different adsorbent solids can be effectively used to remove water to very low levels.

The adsorbent bed can be operated with an upward or downward flow at ambient temperature or, if desired, elevated temperature. Regeneration of the adsorbent material may be carried out by conventional methods, including treatment with a stream of anhydrous inert gas such as nitrogen at elevated temperatures.

In liquid drying systems, water absorbents are used to remove water from the olefin stream containing dimethyl ether. The water absorbent can be any liquid effective to remove water from the olefin stream. The amount of water absorbent used is an amount effective to substantially reduce cladrate and anhydrous preparation during the distillation process.

Total feed into the water absorbent to absorbent vessel of about 1: 1 to about 1: 5,000, more preferably about 1:10 to about 1: 1,000, and most preferably about 1:25 to about 1: 500 It is preferable to add to the water absorption container in the molar ratio of water.

The water absorbent which can be used in the present invention is a liquid at 1 atmosphere. These absorbers also preferably have an average boiling point of at least 100 ° F. (38 ° C.), preferably at 120 ° F. (49 ° C.), more preferably at least 150 ° F. (66 ° C.). The mean boiling point takes into account the boiling point of each compound in the absorbent based on the weight average as defined herein. For example, an absorbent containing 90% by weight of a compound having a boiling point of 100 ° C and 10% by weight of a compound having a boiling point of 200 ° C has an average boiling point of 110 ° C.

In addition, the water absorbent is preferably a polar hydrocarbon composition. Such compositions preferably contain compounds such as monohydric alcohols, polyhydric alcohols, amines or mixtures thereof. Preferred monohydric alcohols include methanol, ethanol and propanol. Preferred polyhydric alcohols include glycols. Preferred glycols include ethylene glycol and triethylene glycol. It is preferred that the absorbent composition contains at least about 75% by weight liquid water absorbent. The remainder of the composition may be a diluent so long as the diluent does not adversely affect water absorption. Preferably, the water absorbent composition contains a compound that absorbs at least about 85% by weight, more preferably at least about 90% by weight and most preferably at least about 95% by weight of water. Methanol is most preferred as a water absorbent.

Conventional absorption systems can be used in the present invention to bring the absorbent into contact with the olefins. In one embodiment, the absorption system may use a packed column although it may use a plate absorption column. In another embodiment, the absorption column has a liquid inlet located on top of the absorption column. The absorbing liquid is evenly distributed over the top of the column. Preferably, even distribution of the absorbent liquid is achieved using a distributor plate or spray nozzle. At the bottom of the absorption column is a gas inlet through which olefins containing water and dimethyl ether enter the absorption column. The vapor component flows back up the column by countercurrent to the liquid absorbent moving down the column. This is known as countercurrent absorption.

The packing or plate in the column provides a surface for intimate contact between the vapor and liquid components in the column. The concentration of gas soluble in both liquid and vapor phases in the countercurrent absorption column is highest at the bottom of the column and lowest at the top of the column. The outlet of the vapor is typically at the bottom of the absorption column below the gas inlet. The lean gaseous outlet in the gas that is mostly soluble in the liquid absorbent is typically at the top of the absorption column above the liquid inlet.

One or more absorption columns can be used in series or in parallel to reduce the concentration of water to the desired level and to treat larger amounts of the olefin composition obtained from the reaction process of the oxygenate to olefins. After absorption, the olefin stream can be distilled to remove propane and dimethyl ether streams.

The absorbent liquid can be regenerated by conventional methods. In one embodiment, the absorbent liquid containing absorbed gas is fed to a distillation column to remove water from the tower product. The regenerated absorbent liquid is removed from the bottom product.

In another embodiment of the invention, the quenched and / or dried olefin stream can be further processed by compression, preferably by multistage compression. Two, three, four or more steps may be used, with two or three steps being preferred.

Preferably, the quenched and / or dried olefin stream is compressed to a pressure higher than the pressure at which the reaction process from oxygenate to olefin is carried out. Preferably, the olefin stream is compressed to a pressure of at least about 30 psia (207 kPa), more preferably at least about 50 psia (345 kPa), most preferably at least about 100 psia (689 kPa). The high pressure range is particularly preferred, and the upper limit is an actual value based on design cost and ease of operation. The actual high pressure limit is generally considered to be about 5,000 psia (34,450 kPa) or less, with lower limits of about 1,000 psia (6,895 kPa), about 750 psia (5171 kPa) and about 500 psia (3447 kPa) even more preferred.

Conventional distillation techniques can be used in the present invention. In one embodiment of the invention, the separation of propane and dimethyl ether streams from the olefin stream takes place in a distillation column, and the operating pressure of the column is maintained so that the bottom of the column is at a relatively low temperature to limit equipment fouling. . This bottom fraction will contain most of the C ₄ + olefin component obtained from the olefin feed. In this embodiment, it is preferred that the bottom fraction has an average temperature of about 300 ° F. (149 ° C.), more preferably about 275 ° F. (135 ° C.) and most preferably about 250 ° F. (121 ° C.) or less.

In the present invention, it is preferred to carry out distillation at a temperature at which the fractionation of the olefin feed stream is acceptable between the propylene and propane boiling points. Separation of propane in this manner will result in a stream containing dimethyl ether and propane contained in the olefin stream. The low boiling point olefin compounds such as ethylene and propylene are further distilled to obtain separate ethylene and propylene streams. This stream will be of feed quality of substantially polymerizable grades containing up to about 10 wppm dimethyl ether, preferably up to about 5 wppm dimethyl ether, more preferably up to about 1 wppm dimethyl ether.

In the present invention, the olefin stream containing dimethyl ether is distilled off to separate the stream containing propane and dimethyl ether from the olefin stream containing other components. Preferably, the stream of olefins containing dimethyl ether is distilled to provide about 4 to about 99 weight percent propane, more preferably about 10 to about 95 weight percent propane, most preferably about 15 to about 90 weight percent propane The propane and dimethyl ether streams are separated from the olefins stream containing. In addition, propane and dimethyl ether streams contain dimethyl ether in an amount of about 1 to about 96 weight percent, preferably about 15 to about 90 weight percent, more preferably about 20 to about 85 weight percent. The relative amounts of propane and dimethyl ether in the stream may vary when using olefins obtained from the process of conversion of oxygenates to olefins, due to the desired conversion of oxygenate to olefins. The conversion rate of oxygenate to olefin is preferably about 95 to about 99%.

In another embodiment of the invention, the ethylene and / or propylene stream is distilled off and then recovered. The ethylene and / or propylene stream is substantially free of dimethyl ether, and the substantial absence means that the concentration of dimethyl ether is substantially low so that there is no substantial adverse effect on downstream processing of ethylene and propylene. Preferably, the separated ethylene and / or propylene stream will contain about 25 wppm, preferably about 10 wppm, more preferably about 6, 3 or 1 wppm, most preferably about 0.5 wppm or less of dimethyl ether.

In another embodiment, at least about 75% of the dimethyl ether in the olefin stream containing dimethyl ether will be separated by distillation. Preferably at least about 85%, more preferably at least about 95% and most preferably at least about 99% of the dimethyl ether in the olefin stream will be separated by distillation.

Examples of distillation of an olefin stream according to the invention to separate propane and dimethyl ether streams are shown in FIGS. These examples show that there are numerous ways to distill olefin streams depending on the starting feed quality and the process route chosen. However, a common element of the present invention is the separation of dimethyl ether with propane components in the olefin stream using conventional distillation techniques.

1 is a process diagram showing the preparation of olefins from an oxygenate, drying the olefins, and separating the propane and dimethyl ether streams from the dried olefins. Methanol is used as the oxygenate, and methanol is sent to reactor 102 which converts the oxygenate to olefin via line 100, where methanol is methane, ethylene, propylene, acetaldehyde, C ₄ + olefin. Is converted to an olefin stream comprising water and other hydrocarbon components. The olefin stream is sent to the quench tower 106 via line 104 where the olefin is cooled and water and other condensable components condense.

Condensed components, including significant amounts of water, are taken from the quench tower 106 via the bottom line 108. Some of the condensed components are recycled back to the top of the quench tower 106 via line 110. Line 110 provides a cooling medium to further cool the components in the quench tower 106, including a cooling device, such as a heat exchanger (not shown), to further cool the condensed components.

Olefin vapor is left at the top of the quench tower 106 via line 112. The olefin vapor is compressed in the compressor 114 and the compressed olefin is sent to the drying unit 118 via line 116 to remove additional water from the olefin vapor. The dried olefins are sent to line distillation apparatus 122 via line 120. The distillation apparatus is operated to separate the light and heavy components from the propane and dimethyl ether (DME) streams. Ethylene and / or propylene that can be sent for further processing such as polymerization or other derivative treatment is included in the hard component. Dimethyl ether is separated from propane by water washing and the separated dimethyl ether is recycled to the olefin reactor to contact further molecular sieves in the olefin reactor to form additional olefins (not shown).

2 shows a first embodiment of a deethanized group. In FIG. 2, an olefin stream 120 comprising ethane, ethylene, propane, propylene, dimethyl ether and C ₄ + olefins and other hydrocarbons is fed to the deethanizer column 202. Deethanizer column 202 fractionates or distills olefin stream 120 to contain top stream 204 containing ethane, ethylene and low boiling components and propylene, propane, dimethyl ether and C ₄ + olefins and other hydrocarbons. The bottom stream 206 is generated. The overhead stream 204 is fed to the demethanizer column 207. The demethanizer column 207 produces a top stream 208 comprising methane and a low boiling point component and a bottom stream 210 comprising ethane and ethylene. The bottoms stream 210 is fed to the C ₂ splitter 212. C ₂ splitter 212 produces overhead stream 214 comprising ethylene and bottom stream 216 comprising ethane. The bottoms stream 206 obtained from the deethanizer 202 is fed to the C ₃ splitter 218. The C ₃ splitter fractionates or distills the bottoms stream 206 to produce a tops stream 220 comprising propylene and a bottoms stream 222 comprising propane, dimethyl ether, and C ₄ olefins and other hydrocarbons. The bottoms stream 222 is fed to the distillation column 224. Distillation column 224 fractionates or distills bottom stream 222 to produce top stream 226 comprising propane and dimethyl ether and bottom stream 228 comprising C ₄ + olefins and other hydrocarbons.

3 is a first fractionation or distillation embodiment of a C ₃ splitter. In FIG. 3, the olefin stream 120 is first fed to a C ₃ splitter 302 to provide a top stream 304 comprising propylene, ethane, ethylene and low boiling compounds and propane, dimethyl ether, and C ₄ + olefins and others. A bottoms stream 305 containing hydrocarbons is produced. A top stream 304 is fed to the deethanizer column 306 to produce a top stream 308 comprising ethane, ethylene, and low boiling compounds and a bottom stream 310 comprising propylene. The top stream 308 is fed to the demethanizer 312 to produce a top stream 314 comprising methane and low boiling components and a bottom stream 316 comprising ethane and ethylene. The bottoms stream 316 is fed to the C ₂ splitter 318 to produce a tops stream 320 comprising ethylene and a bottoms stream 322 comprising ethane. The bottoms stream obtained from the C ₃ splitter 302 is fed to the distillation column 324 to produce a top stream 326 comprising propane and dimethyl ether and a bottoms stream 328 comprising C ₄ + olefins and other hydrocarbons.

4 is a first fractionation embodiment from a demethanizer to a deethanizer. In FIG. 4, the olefin stream 120 is fed to a demethanizer column 402 to include a top stream 404 containing methane and low boiling compounds and ethane, ethylene, propane, propylene, dimethyl ether and C ₄ + hydrocarbons. The bottom stream 406 is generated. A bottom stream 406 is fed to the deethanizer column 408 to provide a top stream 410 comprising ethane and ethylene and a bottom stream 412 comprising propylene, propane, dimethyl ether and C ₄ + olefins and other hydrocarbons. Create The top stream 410 is fed to a C ₂ splitter to produce a top stream 416 comprising an ethylene feed stream and a bottoms stream 418 comprising ethane. The bottoms stream 412 is fed to a C ₃ splitter 420 to produce a bottoms stream 422 comprising propylene and a bottoms stream 424 comprising propane, dimethyl ether, and C ₄ + olefins and other hydrocarbons. The bottoms stream 428 is fed to a distillation column 426 to produce a tops stream 428 comprising propane and dimethyl ether, and a bottoms stream 430 comprising C ₄ + olefins and other hydrocarbons.

5 is a first fractionation embodiment from a demethanizer to a C ₃ splitter. In FIG. 5, olefin stream 120 is fed to demethanizer column 502 to allow top stream 504 containing methane and low boiling compounds and ethane, ethylene, propane, propylene, dimethyl ether and C ₄ + olefins and their A bottoms stream 506 is produced including the outer hydrocarbons. Ride the bottom stream 506 is obtained from the methane flame column is supplied to the C ₃ splitter 508, propylene, ethane and tapwi stream 510 and the propane, dimethyl ether, including ethylene, and C ₄ + olefins and containing other hydrocarbons The bottom stream 512 is generated. The top stream 510 is fed to the deethanizer column 514 to produce a top stream 516 comprising ethane and ethylene and a bottom stream 518 comprising propylene. The top stream 516 is fed to the C ₂ splitter 520 to produce a top stream 522 comprising ethylene and a bottom stream 524 comprising ethane. The bottoms stream 512 obtained from the C ₃ splitter is fed to the distillation column 526 to produce a tops stream 528 comprising propane and dimethyl ether, and a bottoms stream 530 including C ₄ + olefins and other hydrocarbons. .

Figure 6 shows a first embodiment of another type of deethanized group of the present invention. According to FIG. 6, the olefin-containing product stream (not shown in the figure) obtained from the reactor for the synthesis of olefins from methanol is sent via pipe 7 to the precooling and drying step 10. Accumulated condensate (mainly water) is removed via pipe (31). The precooled and dried product stream is sent to a C ₂ / C ₃ separation step (11). The C ₁ / C ₂ hydrocarbons are separated and sent through a pipe 32 to the C ₁ / C ₂ separation stage 12. The separated C ₁ hydrocarbons are recovered via pipes 34 and 35 as high pressure (HP) and low pressure (LF) fuel gases. The separated C ₂ hydrocarbons are sent via pipe 36 to the C ₂ splitter 13.

In a C ₂ splitter, ethylene is separated from ethane and removed through pipe 37. Ethylene, which may contain some acetylene, is sent to acetylene hydrogenation step 14 to recover as ethylene product 38 through pipe 39. C ₂ combustion gas (mainly ethane) is taken from the C ₂ splitter and sent through pipe 39.

C ₃ + hydrocarbons (ie hydrocarbons having a boiling point of at least propylene) separated from the olefins stream in the C ₂ / C ₃ separation step 11 through pipe 33, from the heavy hydrocarbons (ie C ₄ + hydrocarbons) ₃ is sent to a C ₃ / C ₄ separation step (11) where the separation of hydrocarbons takes place. Heavy C ₄ + hydrocarbons are sent via pipe 43 to the C ₄ / C ₅ separation stage 17. The C ₅ + hydrocarbons are separated from the C ₄ hydrocarbons and finally sent through line 45 for use as gasoline fractions. The C ₄ hydrocarbons are separated and sent via line 44 to the butene dimerization step 18 to form dimer hydrocarbons. Finally, dimer hydrocarbons are sent via line 45 for use as gasoline fractions.

C ₃ / C ₄ sends the C ₃ hydrocarbon separated in the separation step 15 to the C ₃ splitter 16 through the pipe 40. The dimethyl ether present in the olefin stream is also sent along with the C ₃ hydrocarbons to the C ₃ splitter, since the dimethyl ether behaves like propane in the previous fractionation step. In the C ₃ splitter 16, dimethyl ether is sent with propane to the bottom of the splitter, and both are removed through pipe 42. For example, substantially pure propylene product containing less than 3 ppm dimethyl ether is obtained from the top of the C ₃ splitter 16 via pipe 41.

The ethylene and propylene streams separated in accordance with the invention can be polymerized to produce plastic compositions, for example polyolefins, in particular polyethylene and polypropylene. Any conventional method of making polyethylene or polypropylene can be used. Catalytic method is preferred. Particular preference is given to metallocenes, Ziegler / Natta, chromium oxide and acid catalyst systems. For example, US Pat. Nos. 3,258,455, 3,305,538, 3,364,190, 5,892,079, 4,659,685, 4,076,698, 3,645,992, 4,302,565, and 4,243,691 (catalysts and processes, respectively). The disclosure is expressly incorporated herein by reference). In general, these methods include contacting an ethylene or propylene product with a catalyst for producing polyolefin at pressures and temperatures effective to produce the polyolefin product.

In one embodiment of the present invention, a polyolefin is prepared by contacting an ethylene or propylene product with a metallocene catalyst. Preferably, the polyolefin manufacturing process is performed at a temperature range of about 50 to about 320 ° C. The reaction can be carried out at any low, medium or high pressure in the range of about 1 to about 3200 bar. Inert diluents can be used in processes carried out in solution. For this type of operation a pressure range of about 10 to about 150 bar, and preferably a temperature range of about 120 to about 250 ° C is preferred. In the gas phase process, the temperature is generally in the range of about 60 to 120 ° C., and the operating pressure is preferably about 5 to about 50 bar.

In addition to polyolefins, many other olefin derivatives are prepared from ethylene, propylene and C ₄ + olefins, in particular butylene, and can be separated according to the invention. In addition, the olefin separated in accordance with the present invention an aldehyde, C ₂ -C ₁₃ acid such as a 1-carboxylic acid, C ₂ -C ₁₂ 1 are alcohols, such as alcohols, C ₂ -C ₁₂ 1-carboxylic acid and a C ₂ -C acrylonitrile-propylene rubber and acrylic, ₁₂ 1 the ester produced from an alcohol, linear alpha olefins, vinyl acetate, ethylene dichloride and vinyl chloride, ethylbenzene, ethylene oxide, cumene, acrolein, allyl chloride, propylene oxide, acrylic acid, ethylene And compounds such as trimers and dimers of ethylene and propylene. C ₄ + olefins, in particular butylene, are particularly suitable for the preparation of linear alpha olefins and esters made from aldehydes, acids, alcohols, C ₅ -C ₁₃ monovalent carboxylic acids and C ₅ -C ₁₃ monohydric alcohols.

Although the present invention has been described in detail so far, those skilled in the art will understand that the invention can be carried out within a wide range of parameters within the claimed scope without departing from the spirit and scope of the invention.

Claims (53)

Contacting the oxygenate with a molecular sieve catalyst to produce an olefin stream comprising water, propylene, propane and dimethyl ether; Drying the olefin stream; A process for separating dimethyl ether from an olefin stream prepared from an oxygenate to olefin reaction process comprising distilling a dried olefin stream to separate dimethyl ether and propane from propylene. The method of claim 1, Wherein the dried olefins stream contains up to 1,000 wpm water. The method of claim 1, Propylene distilled from the dried olefin stream contains up to 25 wppm dimethyl ether. The method of claim 1, The olefin stream further comprises butylene and the dried olefin stream is distilled to separate dimethyl ether and propane from propylene and butylene. The method of claim 4, wherein Wherein the olefin stream comprises 2 to 45 weight percent propane, 0.05 to 5 weight percent dimethyl ether, 30 to 95 weight percent butylene, and the balance comprising water and propylene. The method of claim 1, Propane and dimethyl ether streams separated from propylene comprising from 4.0 to 99% by weight of propane and from 1.0 to 96% by weight of dimethyl ether. The method of claim 1, A propylene separated from dimethyl ether and propane is used for the production of polypropylene. The method of claim 1, The olefin stream further comprises ethylene, upon distillation of the dried olefin stream, the separated propylene stream and the ethylene stream each contain up to 10 wpm dimethyl ether, the propylene stream and the ethylene stream each individually being polyethylene and polypropylene Used in the manufacture of the process. The method of claim 1, Fractionation from the olefin stream separates one or more partial streams containing C ₃ hydrocarbons and directs the partial stream to a rectification column, which is a C ₃ splitter for the separation of propylene and propane, Taking the propylene product stream from the top and removing propane as well as dimethyl ether from the bottom of the rectification column to obtain a propylene product stream containing up to 6 wppm of dimethyl ether. The method of claim 1, A method of drying an olefin stream by contacting the olefin stream with a water absorbent selected from monohydric alcohols, polyhydric alcohols, amines and mixtures thereof. delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete

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