US20150175499A1

US20150175499A1 - Conversion of Methanol to Olefins and Para-Xylene

Info

Publication number: US20150175499A1
Application number: US14/560,889
Authority: US
Inventors: John D. Ou; Nikolaos Soultanidis; Mayank Shekhar; Samia Ilias; Helge Jaensch; Stephen J. McCarthy
Original assignee: ExxonMobil Chemical Patents Inc
Current assignee: ExxonMobil Chemical Patents Inc
Priority date: 2013-12-20
Filing date: 2014-12-04
Publication date: 2015-06-25
Also published as: WO2015094697A1; WO2015094696A1; US20150175498A1; US9783460B2; US9790139B2; US20150175501A1; WO2015094698A1

Abstract

Methods are provided for conversion of methanol and/or dimethyl ether to aromatics, such as a para-xylene, and olefins, such as ethylene and propylene. The methods can be used in conjunction with molecular sieve (zeolite) catalysts that are prepared for use in conjunction with selected effective conversion conditions. The combination of a catalyst and a corresponding effective conversion condition can allow for improved yield aromatics and olefins generally; improved yield of desired aromatics and olefins, such as para-xylene, ethylene, and/or propylene; reduced production of less desirable side products, such as methane, CO, CO₂, and/or coke; or a combination thereof. The preparation of the catalyst can include modification of the catalyst with a transition metal, such as Zn or Ga. The preparation of the catalyst can also include steaming of the catalyst. In some aspects, the preparation of the catalyst can further include modifying the catalyst with phosphorous.

Description

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority to Provisional U.S. patent application Ser. No. 62/003,290 (Docket No. 2014EM128), filed May 27, 2014; Provisional U.S. Patent Application Ser. No. 61/918984 (Docket No. 2013EM376) filed Dec. 20, 2013; Provisional U.S. Patent Application Ser. No. 61/918,994 (Docket No. 2013EM377) filed Dec. 20, 2013; Provisional U.S. Patent Application Ser. No. 61/919,013 (Docket No. 2013EM378) filed Dec. 20, 2013; and EP 14176022.3 (Docket No. 2014EM128) filed Jul. 7, 2014, the disclosures of which are incorporated herein by reference in their entireties. Related applications to which priority is not claimed are U.S. Patent Application No. _____ (Docket No. 2014EM128/2US), filed Dec. 4, 2014; P.C.T. Patent Application No. _____ (Docket No. 2014EM128PCT), filed Dec. 4, 2014; P.C.T. Patent Application No. _____ (Docket No. 2014EM360PCT), filed Dec. 4, 2014; U.S. Patent Application No. _____ (Docket No. 2014EM359US) _____, filed Dec. 4, 2014; and P.C.T. Patent Application No. _____, (Docket No. 2014EM359PCT), filed Dec. 4, 2014.

FIELD OF THE INVENTION

Catalysts and methods are provided for manufacture of olefins and aromatics from oxygenate feeds.

BACKGROUND OF THE INVENTION

Conversion of methanol to olefins and other unsaturated compounds is a commonly used reaction scheme for chemical manufacture. Conventional methods can involve exposing a methanol-containing feed to a molecular sieve, such as ZSM-5. In addition to forming olefins, some desirable aromatic compounds can also be formed, such as para-xylene.
U.S. Pat. Nos. 4,049,573 and 4,088,706 disclose conversion of methanol to a hydrocarbon mixture rich in C₂-C₃olefins and mononuclear aromatics, particularly p-xylene, by contacting the methanol at a temperature of 250-700° C. and a pressure of 0.2 to 30 atmospheres with a crystalline aluminosilicate zeolite catalyst which has a Constraint Index of 1-12 and which has been modified by the addition of an oxide of boron or magnesium either alone or in combination or in further combination with oxide of phosphorus. The above-identified disclosures are incorporated herein by reference.
Methanol can be converted to gasoline employing the MTG (methanol to gasoline) process. The MTG process is disclosed in the patent art, including, for example, U.S. Pat. Nos. 3,894,103; 3,894,104; 3,894,107; 4,035,430 and 4,058,576. U.S. Pat. No. 3,894,102 discloses the conversion of synthesis gas to gasoline. MTG processes provide a simple means of converting syngas to high-quality gasoline. The ZSM-5 catalyst used is highly selective to gasoline under methanol conversion conditions, and is not known to produce distillate range fuels, because the C₁₀+ olefin precursors of the desired distillate are rapidly converted via hydrogen transfer to heavy polymethylaromatics and C₄to C₈isoparaffins under methanol conversion conditions.
Olefinic feedstocks can also be used for producing C₅+ gasoline, diesel fuel, etc. In addition to the basic work derived from ZSM-5 type zeolite catalysts, a number of discoveries contributed to the development of the industrial process known as Mobil Olefins to Gasoline/Distillate (“MOGD”). This process has significance as a safe, environmentally acceptable technique for utilizing feedstocks that contain lower olefins, especially C₂to C₅alkenes. In U.S. Pat. Nos. 3,960,978 and 4,021,502, Plank, Rosinski and Givens disclose conversion of C₂to C₅olefins alone or in admixture with paraffinic components, into higher hydrocarbons over crystalline zeolites having controlled acidity. Garwood et al have also contributed improved processing techniques to the MOGD system, as in U.S. Pat. Nos. 4,150,062, 4,211,640 and 4,227,992. The above-identified disclosures are incorporated herein by reference.
Conversion of lower olefins, especially propene and butenes, over ZSM-5 is effective at moderately elevated temperatures and pressures. The conversion products are sought as liquid fuels, especially the C₅+ aliphatic and aromatic hydrocarbons. Olefinic gasoline is produced in good yield by the MOGD process and may be recovered as a product or recycled to the reactor system for further conversion to distillate-range products. Operating details for typical MOGD units are disclosed in U.S. Pat. Nos. 4,445,031, 4,456,779, Owen et al, and U.S. Pat. No. 4,433,185, Tabak, incorporated herein by reference.
In addition to their use as shape selective oligomerization catalysts, the medium pore ZSM-5 type catalysts are useful for converting methanol and other lower aliphatic alcohols or corresponding ethers to olefins. Particular interest has been directed to a catalytic process (MTO) for converting low cost methanol to valuable hydrocarbons rich in ethene and C₃+ alkenes. Various processes are described in U.S. Pat. No. 3,894,107 (Batter et al), U.S. Pat. No. 3,928,483 (Chang et al), U.S. Pat. No. 4,025,571 (Lago), U.S. Pat. No. 4,423,274 (Daviduk et al) and U.S. Pat. No. 4,433,189 (Young), incorporated herein by reference. It is generally known that the MTO process can be optimized to produce a major fraction of C₂to C₄olefins. Prior process proposals have included a separation section to recover ethene and other gases from by-product water and C₅+ hydrocarbon liquids. The oligomerization process conditions which favor the production of C₁₀to C₂₀and higher aliphatics tend to convert only a small portion of ethene as compared to C₃+ olefins.
The methanol to olefin process (MTO) operates at high temperature and near 30 psig in order to obtain efficient conversion of the methanol to olefins. These process conditions, however, produce an undesirable amount of aromatics and C₂olefins and require a large investment in plant equipment.
The olefins to gasoline and distillate process (MOGD) operates at moderate temperatures and elevated pressures to produce olefinic gasoline and distillate products. When the conventional MTO process effluent is used as a feed to the MOGD process, the aromatic hydrocarbons produced in the MTO unit are desirably separated and a relatively large volume of MTO product effluent has to be cooled and treated to separate a C₂− light gas stream, which is unreactive, except for ethene which is reactive to only a small degree, in the MOGD reactor, and the remaining hydrocarbon stream has to be pressurized to the substantially higher pressure used in the MOGD reactor.
Chinese publications CN 101602648, CN 101602643, CN 101607864, and CN 101780417 describe use of selectivated catalysts for conversion of methanol to para-xylene. In these publications, zeolite catalysts are treated with silicate compounds, such as tetraethylorthosilicate, to provide improved selectivity for formation of olefins and para-xylene from methanol feeds. However, silicon treatment introduces several undesired effects, it reduces the per pass aromatic yield and promotes coke deposition that limits the catalyst cycle length. Especially for metal promoted zeolites, silicon treatment can promote metal migration and sintering that results to shorter catalyst lifetime.
There is an ongoing need to provide improved catalysts and methods for producing olefins and aromatics from oxygenated feeds.

SUMMARY OF THE INVENTION

A method of converting a feed to form olefins and aromatics is provided. The method includes steaming a catalyst in the presence of at least 1 vol % water at a temperature of about 400° C. to about 850° C. for at least about 0.25 hours. The catalyst includes a molecular sieve having at least one 10-member ring channel and having no ring channels larger than a 10-member ring channel. The catalyst further includes about 0.1 wt % to about 10.0 wt % of a metal from Groups 8-14. A feed comprising at least about 50 wt % of methanol, dimethyl ether, or a combination thereof is then exposed to the steamed catalyst under effective conversion conditions to form a conversion effluent comprising ethylene, propylene, and para-xylene. The effective conversion conditions including a temperature of about 350° C. to about 600° C. Optionally, the metal from Groups 8-14 can be Zn, Ga, Ag, or a combination thereof. Optionally, the catalyst can further include about 0.1 wt % to about 10 wt % of phosphorus, lanthanum, an element from Groups 1 or 2, an element from Groups 13-16, or a combination thereof. Optionally, the method can further include one or more separations to separate a stream enriched in para-xylene from the conversion effluent.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 schematically shows an example of a reaction system for converting a feed to form olefins and aromatics.

FIG. 2 shows results from converting a feed in the presence of various catalysts to form olefins and aromatics.

FIG. 3 shows results from converting a feed in the presence of a catalyst at various temperatures to form olefins and aromatics.

FIG. 4 shows results from converting a feed in the presence of a catalyst at various temperatures to form olefins and aromatics.

FIG. 5 shows results from converting a feed in the presence of a catalyst to form olefins and aromatics.

FIG. 6 shows results from converting a feed in the presence of various catalysts to form olefins and aromatics.

FIG. 7 schematically shows an alternative example of a reaction system for converting a feed to form olefins and aromatics.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Overview

In various aspects, methods are provided for conversion of methanol and/or dimethyl ether to aromatics, such as a para-xylene, and olefins, such as ethylene and propylene. The methods can be used in conjunction with molecular sieve (zeolite) catalysts that are prepared for use in conjunction with selected effective conversion conditions. The combination of a catalyst and a corresponding effective conversion condition can allow for improved yield aromatics and olefins generally; improved yield of desired aromatics and olefins, such as para-xylene, ethylene, and/or propylene; reduced production of less desirable side products, such as methane, CO, CO₂, and/or coke; or a combination thereof. The preparation of the catalyst can include modification of the catalyst with a transition metal, such as Zn, Ga, or Ag. The preparation of the catalyst can also include steaming of the catalyst. In some aspects, the preparation of the catalyst can further include modifying the catalyst with phosphorous. Use of transition metal-modified molecular sieves can provide an improved alternative pathway for synthesis of para-xylene. Such improved alternatives are desirable in view of the increasing commercial demand for para-xylene.
It has been unexpectedly found that various types of yield improvements can be achieved during conversion of methanol and/or dimethyl ether to olefins and aromatics (including para-xylene) by using a combination of improved catalyst synthesis with corresponding conversion conditions. The improved catalyst synthesis techniques can provide a conversion catalyst that is suitable for use in a commercial production environment. For example, one improvement can be modification of a molecular sieve or zeolite catalyst with a transition metal, such as Zn, Ga, or Ag. Such a modified catalyst can then be steamed under effective steaming conditions. Steaming of a catalyst can have various impacts on the catalyst. Steaming a catalyst has an impact similar to aging of the catalyst, so that changes in catalyst activity that occur early during a processing run can be reduced or minimized This includes reducing or minimizing the initial cracking activity of a catalyst. Without being bound by any particular theory, it is also believed that steaming of metal-modified conversion catalysts can improve the dispersion of the modifying metals on the catalyst. This improved dispersion can reduce or minimize the loss of reagent to formation of side products, such as carbon oxides or coke. The reduction of loss of reagent can be valuable, for example, for allowing the conversion process to be performed at higher temperatures. Higher temperatures are believed to be beneficial for improving the yield of aromatics but higher temperatures also tend to increase the yield of undesirable side products, such as carbon oxides or coke. The improved dispersion of the modifying metal on the catalyst can reduce or minimize such formation of the undesirable side products at higher conversion temperatures.
Another type of improvement can be to further modify a steamed, metal-modified catalyst with phosphorous. In some aspects, in addition to providing an improved yield of aromatics, modifying a catalyst with phosphorous can also improve the stability of a catalyst over time during a processing run.
It is noted that various types of yield improvements can be valuable in addition to a simple increase in the yield of para-xylene. One type of yield improvement that can be valuable is an improvement in the overall yield of aromatics. In some aspects, a portion of the overall aromatics yield is due to the production of other xylene isomers. Such xylene isomers can be isomerized in a subsequent step to form para-xylene. Additionally or alternately, a portion of the overall aromatics yield is due to production of various aromatic compounds, such as benzene, toluene, or aromatics with sufficient side chains to have a total of nine or more carbon atoms. Such aromatics can be valuable as products, or such aromatics can be recycled to the methanol conversion process to enhance the overall yield.
Another type of valuable yield improvement can be an improvement in the total yield of aromatics plus olefins. The benefits of an improved yield of aromatics are noted above. Olefins are valuable as a raw material for a variety of synthesis processes, such as formation of aromatics or formation of polymers.
Still another type of valuable yield improvement can be a reduction in the yield of side products, such as carbon oxides, methane, or coke. The formation of CO or CH₄can typically represent conversion of methanol to a compound used for methanol synthesis. Formation of CO₂and/or coke can be even less favorable, as these products typically have little or no commercial value or value as reagents. Because methanol conversion processes are often run to achieve substantially complete conversion of methanol (and/or dimethyl ether), avoiding formation of lower value products can correspond to increased formation of higher value products.

Conversion Catalyst

The catalyst used herein is a composition of matter comprising a molecular sieve and a Group 8-14 element, or a molecular sieve and a combination of metals from the same group of the Periodic Table. The composition of matter can optionally further comprise phosphorus and/or lanthanum and/or other elements from Group 1-2 and/or Group 13-16 of the Periodic Table that provide structural stabilization. In this sense, the term “comprising” can also mean that the catalyst can comprise the physical or chemical reaction product of the molecular sieve and the Group 8-14 element or combination of elements from the same group (and optionally phosphorus and/or lanthanum and/or other elements from groups 1-2 and/or group 13-16). In this description, reference to a group number for an element corresponds to the current IUPAC numbering scheme for the periodic table. Optionally, the catalyst may also include a filler or binder and may be combined with a carrier to form slurry.
A catalyst comprising a molecular sieve can be modified by the Group 8-14 metal(s) in any convenient manner. Typical methods for modifying a catalyst with a metal include impregnation (such as by incipient wetness), ion exchange, deposition by precipitation, and any other convenient method for depositing a metal that is supported by a catalyst and/or a catalyst support.
In various aspects, the molecular sieve comprises ≧10.0 wt. % of the catalyst. The upper limit on the amount of molecular sieve in the catalyst may be 10.0 wt. %, 12.5 wt. %, 15.0 wt. %, 20.0 wt. %, 25.0 wt. %, 30.0 wt. %, 35.0 wt. % 40.0 wt. %, 45.0 wt. %, 50.0 wt. %, 55.0 wt. %, 60.0 wt. %, 65.0 wt. %, 70.0 wt. %, 75.0 wt. %, 80.0 wt. %, 85.0 wt. %, 90.0 wt. %, 95.0 wt. %, 99.0 wt. %, 99.5 wt. %, or 100.0 wt. %. The lower limit on the amount of molecular sieve in the catalyst may be 10.0 wt. %, 12.5 wt. %, 15.0 wt. %, 20.0 wt. %, 25.0 wt. %, 30.0 wt. %, 35.0 wt. % 40.0 wt. %, 45.0 wt. %, 50.0 wt. %, 55.0 wt. %, 60.0 wt. %, 65.0 wt. %, 70.0 wt. %, 75.0 wt. %, 80.0 wt. %, 85.0 wt. %, 90.0 wt. %, 95.0 wt. %, 99.0 wt. %, 99.5 wt. %, or 100.0 wt. %. Ranges expressly disclosed include combinations of any of the above-enumerated upper and lower limits; e.g., 10.0 to 20.0 wt. %, 12.5 to 25.0 wt. %, 20.0 to 50.0, or 40.0 to 99.0 wt. %.
As used herein the term “molecular sieve” refers to crystalline or non-crystalline materials having a porous structure. Microporous molecular sieves typically have pores having a diameter of ≦ about 2.0 nm. Mesoporous molecular sieves typically have pores with diameters of about 2 to about 50 nm. Macroporous molecular sieves have pore diameters of >50.0 nm. The upper limit on the pore diameter may be 1.00×10⁴nm, 5.00×10³nm, 2.50×10³nm, 1.00×10³nm, 5.00×10²nm, 2.50×10²nm, 1.25×10²nm, 75.0 nm, 50.0 nm, 40.0 nm, 30.0 nm, 20.0 nm, 10.0 nm, or 5.0 nm. The lower limit on the pore diameter may be 5.00×10³nm, 2.50×10³nm, 1.00×10³nm, 5.00×10²nm, 2.50×10²nm, 1.25×10²nm, 75.0 nm, 50.0 nm, 40.0 nm, 30.0 nm, 20.0 nm, 10.0 nm, 5.0 nm, 4.0 nm, 3.0 nm, 2.0 nm, 1.0 nm or less. Ranges of the pore diameters expressly disclosed include combinations of any of the above-enumerated upper and lower limits. For example, some molecular sieves may have pore diameters of about 1.0 to >5.00×10³nm, 2.0 to 5.00×10³nm, 2.0 to 1.00×10³nm, 2.0 to 5.00×10²nm, 2.0 to 2.50×10²nm, 2.0 to 1.25×10²nm, 2.0 to 75.0 nm, 5.0 to 75.0 nm, 7.5 to 75.0 nm, 10.0 to 75.0 nm, 15.0 to 75.0 nm, 20.0 to 75.0 nm, 25.0 to 75.0 nm, 2.0 to 50.0 nm, 5.0 to 50.0 nm, 7.5 to 50.0 nm, 10.0 to 50.0 nm, 15.0 to 50.0 nm, 20.0 to 50.0 nm, or 25.0 to 50.0 nm, etc.
Additionally or alternatively, some molecular sieves useful herein are described by a Constraint Index of about 1 to about 12. The upper limit on the range of the Constraint Index may be about 12.0, 11.0, 10.0, 9.0, 8.0, 7.0, 6.0, 5.0, 4.0, 3.0, or 2.0. The lower limit on the range of the Constraint Index may be about 11.0, 10.0, 9.0, 8.0, 7.0, 6.0, 5.0, 4.0, 3.0, 2.0, or 1.0. Ranges of the Constraint Indices expressly disclosed include combinations of any of the above-enumerated upper and lower limits. For example, some molecular sieves have a Constraint Index of 1.0 to about 10.0, 1.0 to about 8.0, 1 to about 6.0, 1 to about 5.0, 1 to about 3.0, 2.0 to about 11.0, 3.0 to 10.0, 4.0 to 9.0, or 6.0 to 9.0, etc. Constraint Index is determined as described in U.S. Pat. No. 4,016,218, incorporated herein by reference for details of the method.
Particular molecular sieves are zeolitic materials. Zeolitic materials are crystalline or para-crystalline materials. Some zeolites are aluminosilicates comprising [SiO₄] and [AlO₄] units. Other zeolites are aluminophosphates (AlPO) having structures comprising [AlO₄] and [PO₄] units. Still other zeolites are silicoaluminophosphates (SAPO) comprising [SiO₄], [AlO₄], and [PO₄] units.
Non-limiting examples of SAPO and AlPO molecular sieves useful herein include one or a combination of 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, AlPO-5, AlPO-11, AlPO-18, AlPO-31, AlPO-34, AlPO-36, AlPO-37, AlPO-46, and metal containing molecular sieves thereof. Of these, particularly useful molecular sieves are one or a combination of SAPO-18, SAPO-34, SAPO-35, SAPO-44, SAPO-56, AlPO-18, AlPO-34 and metal containing derivatives thereof, such as one or a combination of SAPO-18, SAPO-34, AlPO-34, AlPO-18, and metal containing derivatives thereof, and especially one or a combination of SAPO-34, AlPO-18, and metal containing derivatives thereof.
Additionally or alternatively, the molecular sieves useful herein may be characterized by a ratio of Si to Al. In particular embodiments, the molecular sieves suitable herein include those having a Si/Al ratio of about 10 to 100, preferably about 10 to 80, more preferably about 20 to 60, and most preferably about 20 to 40.
In an embodiment, the molecular sieve is an intergrowth material having two or more distinct crystalline phases within one molecular sieve composition. In particular, intergrowth molecular sieves are described in U.S. Patent Application Publication No. 2002-0165089 and International Publication No. WO 98/15496, published Apr. 16, 1998, both of which are herein fully incorporated by reference.
Particular molecular sieves useful in this invention include ZSM-5 (U.S. Pat. No. 3,702,886 and Re. 29,948); ZSM-11 (U.S. Pat. No. 3,709,979); ZSM-12 (U.S. Pat. No. 3,832,449); ZSM-22 (U.S. Pat. No. 4,556,477); ZSM-23 (U.S. Pat. No. 4,076,842); ZSM-34 (U.S. Pat. No. 4,079,095) ZSM-35 (U.S. Pat. No. 4,016,245); ZSM-48 (U.S. Pat. No. 4,397,827); ZSM-57 (U.S. Pat. No. 4,046,685); and ZSM-58 (U.S. Pat. No. 4,417,780). The entire contents of the above references are incorporated by reference herein. Other useful molecular sieves include MCM-22, PSH-3, SSZ-25, MCM-36, MCM-49 or MCM-56, with MCM-22. Still other molecular sieves include Zeolite T, ZK5, erionite, and chabazite.
Another option for characterizing a zeolite (or other molecular sieve) is based on the nature of the ring channels in the zeolite. The ring channels in a zeolite can be defined based on the number of atoms including in the ring structure that forms the channel. In some aspects, a zeolite can include at least one ring channel based on a 10-member ring. In such aspects, the zeolite preferably does not have any ring channels based on a ring larger than a 10-member ring. Examples of suitable framework structures having a 10-member ring channel but not having a larger size ring channel include EUO, FER, IMF, LAU, MEL, MFI, MFS, MTT, MWW, NES, PON, SFG, STF, STI, TON, TUN, MRE, and PON.
The catalyst also includes at least one metal selected from Group 8-14 of the Periodic Table, such as at least two metals (i.e., bimetallic) or at least three metals (i.e., trimetallic). Typically, the total weight of the Group 8-14 elements is ≧0.1 wt. % based on the total weight of the catalyst. Typically, the total weight of the Group 8-14 element is ≦about 10.0 wt. %, based on the total weight of the catalyst. Thus, the upper limit on the range of the amount of the Group 8-14 elements added to the molecular sieve may be 10.0 wt. %, 9.0 wt. %, 8.0 wt. %, 7.0 wt. %, 6.0 wt. %, 5.0 wt. %, 4.0 wt. %, 3.0 wt. %, 2.0 wt. %, 1.0 wt. %, or 0.1 wt. %. The lower limit on the range of the amount of the Group 8-14 elements added to the molecular sieve may be 10.0 wt. %, 9.0 wt. %, 8.0 wt. %, 7.0 wt. %, 6.0 wt. %, 5.0 wt. %, 4.0 wt. %, 3.0 wt. %, 2.0 wt. %, 1.0 wt. %, or 0.1 wt. %. Ranges expressly disclosed include combinations of any of the above-enumerated upper and lower limits; e.g., 0.1 to 10.0 wt. %, 0.1 to 8.0 wt. %, 0.1 to 6.0 wt. %, 0.1 to 5.0 wt. %, 0.1 to 4.0 wt. %, 0.1 to 3.0 wt. %, 0.1 to 2.0 wt. %, 0.1 to 1.0 wt. %, 1.0 to 10.0 wt. %, 1.0 to 9.0 wt. %, 1.0 to 8.0 wt. %, 1.0 to 7.0 wt. %, 1.0 to 6.0 wt. %, 1.0 to 5.0 wt. %, 1.0 to 4.0 wt. %, 1.0 to 3.0 wt. %, etc. Of course, the total weight of the Group 8-14 elements shall not include amounts attributable to the molecular sieve itself.
Additionally or alternatively, in some aspects, the catalyst can also include at least one of phosphorous and/or lanthanum and/or other elements from groups 1-2 and/or group 13-16, such as at least two such elements or at least three such elements. Typically, the total weight of the phosphorous and/or lanthanum and/or other elements from groups 1-2 and/or groups 13-16 is ≧0.1 wt. % based on the total weight of the catalyst. Typically, the total weight of the phosphorous and/or lanthanum and/or other elements from groups 1-2 and/or groups 13-16 is ≦about 10.0 wt. %, based on the total weight of the catalyst. Thus, the upper limit on the range of the phosphorous and/or lanthanum and/or other elements from groups 1-2 and/or groups 13-16 added to the molecular sieve may be 10.0 wt. %, 9.0 wt. %, 8.0 wt. %, 7.0 wt. %, 6.0 wt. %, 5.0 wt. %, 4.0 wt. %, 3.0 wt. %, 2.0 wt. %, 1.0 wt. %, or 0.1 wt. %; and the lower limit on the range added to the molecular sieve may be 10.0 wt. %, 9.0 wt. %, 8.0 wt. %, 7.0 wt. %, 6.0 wt. %, 5.0 wt. %, 4.0 wt. %, 3.0 wt. %, 2.0 wt. %, 1.0 wt. %, or 0.1 wt. %. Ranges expressly disclosed include combinations of any of the above-enumerated upper and lower limits; e.g., 0.1 to 10.0 wt. %, 0.1 to 8.0 wt. %, 0.1 to 6.0 wt. %, 0.1 to 5.0 wt. %, 0.1 to 4.0 wt. %, 0.1 to 3.0 wt. %, 0.1 to 2.0 wt. %, 0.1 to 1.0 wt. %, 1.0 to 10.0 wt. %, 1.0 to 9.0 wt. %, 1.0 to 8.0 wt. %, 1.0 to 7.0 wt. %, 1.0 to 6.0 wt. %, 1.0 to 5.0 wt. %, 1.0 to 4.0 wt. %, 1.0 to 3.0 wt. %, etc. Of course, the total weight of the phosphorous and/or lanthanum and/or other elements from Groups 1-2 and/or Groups 13-16 shall not include amounts attributable to the molecular sieve itself.
For the purposes of this description and claims, the numbering scheme for the Periodic Table Groups corresponds to the current IUPAC numbering scheme. Therefore, a “Group 4 metal” is an element from Group 4 of the Periodic Table, e.g., Hf, Ti, or Zr. The more preferred molecular sieves are SAPO molecular sieves, and metal-substituted SAPO molecular sieves. In particular embodiments, one or more Group 1 elements (e.g., Li, Na, K, Rb, Cs, Fr) and/or Group 2 elements (e.g., Be, Mg, Ca, Sr, Ba, and Ra) and/or phosphorous and/or Lanthanum may be used. One or more Group 7-9 element (e.g., Mn, Tc, Re, Fe, Ru, Os, Co, Rh, and Ir) may also be used. Group 10 elements (Ni, Pd, and Pt) are less commonly used in applications for forming olefins and aromatics, as the combination of a Group 10 element in the presence of hydrogen can tend to result in saturation of aromatics and/or olefins. In some embodiments, one or more Group 11 and/or Group 12 elements (e.g., Cu, Ag, Au, Zn, and Cd) may be used. In still other embodiments, one or more Group 13 elements (B, Al, Ga, In, and Tl) and/or Group 14 elements (Si, Ge, Sn, Pb) may be used. In a preferred embodiment, the metal is selected from the group consisting of Zn, Ga, Cd, Ag, Cu, P, La, or combinations thereof. In another preferred embodiment, the metal is Zn, Ga, Ag, or a combination thereof.
Particular molecular sieves and metal-containing derivatives thereof have been described in detail in numerous publications including for example, U.S. Pat. No. 4,567,029 (MeAPO where Me is Mg, Mn, Zn, or Co), U.S. Pat. No. 4,440,871 (SAPO), European Patent Application EP-A-0 159 624 (E1APSO where El is Be, B, Cr, Co, Ga, Fe, Mg, Mn, Ti, or Zn), U.S. Pat. No. 4,554,143 (FeAPO), U.S. Pat. Nos. 4,822,478, 4,683,217, 4,744,885 (FeAPSO), EP-A-0 158 975 and U.S. Pat. No. 4,935,216 (ZnAPSO, EP-A-0 161 489 (CoAPSO), EP-A-0 158 976 (ELAPO, where EL is Co, Fe, Mg, Mn, Ti, or Zn), U.S. Pat. No. 4,310,440 (A1PO4), U.S. Pat. No. 5,057,295 (BAPSO), U.S. Pat. No. 4,738,837 (CrAPSO), U.S. Pat. Nos. 4,759,919, and 4,851,106 (CrAPO), U.S. Pat. Nos. 4,758,419, 4,882,038, 5,434,326, and 5,478,787 (MgAPSO), U.S. Pat. No. 4,554,143 (FeAPO), U.S. Pat. Nos. 4,686,092, 4,846,956, and 4,793,833 (MnAPSO), U.S. Pat. Nos. 5,345,011 and 6,156,931 (MnAPO), U.S. Pat. No. 4,737,353 (BeAPSO), U.S. Pat. No. 4,940,570 (BeAPO), U.S. Pat. Nos. 4,801,309, 4,684,617, and 4,880,520 (TiAPSO), U.S. Pat. Nos. 4,500,651, 4,551,236, and 4,605,492 (TiAPO), U.S. Pat. Nos. 4,824,554, 4,744,970 (CoAPSO), U.S. Pat. No. 4,735,806 (GaAPSO) EP-A-0 293 937 (QAPSO, where Q is framework oxide unit [QO2]), as well as U.S. Pat. Nos. 4,567,029, 4,686,093, 4,781,814, 4,793,984, 4,801,364, 4,853,197, 4,917,876, 4,952,384, 4,956,164, 4,956,165, 4,973,785, 5,241,093, 5,493,066, and 5,675,050, all of which are herein fully incorporated by reference. Other molecular sieves include those described in R. Szostak, Handbook of Molecular Sieves, Van Nostrand Reinhold, New York, N.Y. (1992), which is herein fully incorporated by reference.
In some aspects, a catalyst comprising a molecular sieve as modified by the Group 8-14 element and/or a Group 1-2, Group 13-16, lanthanum, and/or phosphorous is a ZSM-5 based molecular sieve. In some preferred aspects, the Group 8-14 element can be selected from Groups 11-13, such as Zn, Ga, Ag, or combinations thereof. In other aspects, the Group 8-14 element can be two or more elements from Groups 11-13, such as two or more elements from the same group in Groups 11-13. In still other aspects, the molecular sieve can be modified with at least one element from Groups 8-14, such as at least two elements or at least three elements from Groups 8-14, the at least two elements or at least three elements optionally being from the same group in Groups 8-14. In any of the above aspects, a catalyst comprising a molecular sieve can be further modified by an element from Groups 1-2, Groups 13-16, lanthanum, and/or phosphorus.
Various methods for synthesizing molecular sieves or modifying molecular sieves are described in U.S. Pat. No. 5,879,655 (controlling the ratio of the templating agent to phosphorus), U.S. Pat. No. 6,005,155 (use of a modifier without a salt), U.S. Pat. No. 5,475,182 (acid extraction), U.S. Pat. No. 5,962,762 (treatment with transition metal), U.S. Pat. Nos. 5,925,586 and 6,153,552 (phosphorus modified), U.S. Pat. No. 5,925,800 (monolith supported), U.S. Pat. No. 5,932,512 (fluorine treated), U.S. Pat. No. 6,046,373 (electromagnetic wave treated or modified), U.S. Pat. No. 6,051,746 (polynuclear aromatic modifier), U.S. Pat. No. 6,225,254 (heating template), International Patent Application WO 01/36329 published May 25, 2001 (surfactant synthesis), International Patent Application WO 01/25151 published Apr. 12, 2001 (staged acid addition), International Patent Application WO 01/60746 published Aug. 23, 2001 (silicon oil), U.S. Patent Application Publication No. 2002-0055433 published May 9, 2002 (cooling molecular sieve), U.S. Pat. No. 6,448,197 (metal impregnation including copper), U.S. Pat. No. 6,521,562 (conductive microfilter), and U.S. Patent Application Publication No. 2002-0115897 published Aug. 22, 2002 (freeze drying the molecular sieve), which are all herein incorporated by reference in their entirety.

Conversion Conditions

The feedstock for forming aromatics (such as para-xylene) and olefins can be a feed that includes methanol, dimethyl ether, or a combination thereof. The feed may also include other hydrocarbons or hydrocarbonaceous compounds (i.e., compounds similar to hydrocarbons that also contain one or more heteroatoms). Additionally or alternately, the feed can be diluted with steam at any convenient time, such as prior to entering a conversion reactor or after entering a conversion reactor. Examples of suitable feeds (excluding any optional dilution with steam) include feeds that are substantially methanol, feeds that are substantially dimethyl ether, feeds that are substantially methanol and dimethyl ether, or feeds that include at least about 50 wt % of methanol and/or dimethyl ether, such as at least about 60 wt % or at least about 70 wt %. A feed that is substantially composed of a compound (or compounds) is a feed that is at least 90% wt % of the compound (or compounds), or at least 95 wt % of the compound, or at least 98 wt % of the compound, or at least 99 wt % of the compound. For a feed that is less than 100 wt % methanol and/or dimethyl ether (excluding any optional dilution with steam), other hydrocarbon compounds (and/or hydrocarbonaceous compounds) in the feed can include paraffins, olefins, aromatics, and mixtures thereof
The feed can be exposed to the conversion catalyst in any convenient type of reactor. Suitable reactor configurations include fixed bed reactors, fluidized bed reactors (such as ebullating bed reactors), riser reactors, and other types of reactors where the feed can be exposed to the catalyst in a controlled manner.
Prior to using a catalyst for conversion of methanol and/or dimethyl ether to aromatics and olefins, the catalyst can be steamed under effective steaming conditions. General examples of effective steaming conditions including exposing a catalyst to an atmosphere comprising steam at a temperature of about 400° C. to about 850° C., or about 400° C. to about 750° C., or about 400° C. to about 650° C., or about 500° C. to about 850° C., or about 500° C. to about 750° C., or about 500° C. to about 650° C. The atmosphere can include as little as 1 vol % water and up to 100 vol % water. The catalyst can be exposed to the steam for any convenient period of time, such as about 10 minutes (0.15 hours) to about 48 hours. In some aspects, the time for exposure of the catalyst to steam is at least about 0.25 hours, such as about 0.25 hours to about 8 hours, or about 0.25 hours to about 4 hours, or about 0.25 hours to about 2 hours, or about 0.5 hours to about 8 hours, or about 0.5 hours to about 4 hours, or about 0.5 hours to about 2 hours, or about 1 hour to about 8 hours, or about 1 hour to about 4 hours, or about 1 hour to about 2 hours.
A suitable feed can be converted to aromatics (including para-xylene) and olefins by exposing the feed to a conversion catalyst under effective conversion conditions. General conversion conditions for conversion of methanol and/or dimethyl ether to aromatics and olefins include a pressure of about 100 kPaa to about 2500 kPaa, or about 100 kPaa to about 2000 kPaa, or about 100 kPaa to about 1500 kPaa, or about 100 kPaa to about 1200 kPaa. The amount of feed (weight) relative to the amount of catalyst (weight) can be expressed as a weight hourly space velocity (WHSV). Suitable weight hourly space velocities include a WHSV of about 0.1 hr⁻¹to about 20 hr⁻¹, or about 1.0 hr⁻¹to about 10 hr⁻¹.
The temperature for the conversion reaction can vary depending on the nature of the catalyst used for the conversion. Suitable reaction temperatures include a temperature of about 350° C. to about 600° C., or about 400° C. to about 600° C., or about 400° C. to about 575° C., or about 425° C. to about 600° C., or about 425° C. to about 575° C., or about 450° C. to 600° C., or about 450° C. to about 575° C., or about 475° C. to about 600° C., or about 475° C. to about 575° C., or about 500° C. to about 600° C., or about 500° C. to about 575° C., or about 525° C. to about 575° C.
In some aspects, a metal-modified and steamed catalyst can be used at any of the temperatures described above. Converting a methanol and/or dimethyl ether feed using a metal-modified and steamed catalyst can allow for an improved yield of aromatics and/or olefins; or a decreased yield of undesirable side products; or a combination thereof
In other aspects, a temperature of at least 475° C. can be used for conversion of a methanol and/or dimethyl ether feed in the presence of a metal-modified and steamed catalyst. Steaming of the catalyst can reduce or minimize the yield of undesirable side products when the conversion is performed at higher temperature while also increasing the aromatics yield.
In still other aspects, a temperature of at least 525° C. can be used for conversion of a methanol and/or dimethyl ether feed in the presence of a metal-modified and steamed catalyst. In this type of aspect, steaming of a metal-modified catalyst can provide a catalyst with an initially favorable yield profile. In a reaction system where catalyst can be exchanged and/or regenerated, such as an ebullating bed or fluidized bed reactor, the metal-modified and steamed catalyst can be used for conversion at high temperature by taking advantage of the initially favorable yield profile. The catalyst can then be withdrawn from the system to reduce or minimize the amount of conversion performed after the catalyst has been degraded to a less favorable yield profile.
During a conversion process, a feed comprising methanol, dimethyl ether, or a combination thereof can be introduced into a reactor containing a conversion catalyst. Steam can optionally also be introduced into the reactor. After performing the conversion reaction, the reactor effluent can be quenched to facilitate separation of the effluent. The quench can be sufficient to allow removal of water from the effluent as a liquid. Light organics containing 4 carbons or less are removed as a gas phase stream. Ethylene and propylene can subsequently be separated from this light ends stream. The remaining portion of the effluent can substantially correspond to hydrocarbons that are liquids at standard temperature and pressure. A series of separations can then be performed to separate out desired products. For example, a first separation on the liquid effluent can separate C₇₋(lower boiling) compounds from C₈+ (higher boiling) compounds. In the first separation, para-xylene and other C₈+molecules are included in the higher boiling fraction, while C₇₋compounds (benzene, toluene) and other lower boiling compounds such as oxygenates form the lower boiling fraction. In this discussion, a C₇₋product stream is defined as a product stream where at least 50 wt % of the hydrocarbons correspond to hydrocarbons having 7 carbons or less. Similarly, a C₈+ product stream is defined as a product stream where at least 50 wt % of the hydrocarbons correspond to hydrocarbons having at least 8 carbons. This lower boiling fraction may also contain a variety of non-aromatic compounds. The lower boiling compounds from this first separation are one suitable source, if desired, for a recycle stream to provide hydrogen-lean molecules to the conversion reaction.
The C₈+ fraction can then be further separated into a C₈fraction and a C₉+ fraction.
The C₉₊fraction will typically be primarily aromatics and is another suitable fraction for recycle, if desired. In this discussion, a C₈product stream is defined as a product stream where at least 50 wt % of the hydrocarbons correspond to hydrocarbons having 8 carbons. Similarly, a C₉₊product stream is defined as a product stream where at least 50 wt % of the hydrocarbons correspond to hydrocarbons having at least 9 carbons. In some aspects, if a distillation column is used, the first separation and second separation can be combined to form the C₇₋, C₈, and C₉₊fractions in a single distillation or fractionation process. In some aspects, the separations to form the C₇₋, C₈, and C₉₊fractions can correspond to any convenient number of distillation steps in order to improve recovery of the desired C₈fraction.
The C₈fraction of the liquid effluent from conversion will typically include at least a portion of xylene isomers other than para-xylene. The ortho- and meta-xylene isomers can be separated from the para-xylene isomers by any convenient method, such as by using crystallization to separate the isomers or by selective adsorption. Optionally, the C₈fraction can be treated in a xylene isomerization unit prior to recovery of the para-xylene. This can increase the concentration of para-xylene in the C₈fraction relative to the concentration prior to the xylene isomerization. Optionally, the separated ortho- and meta-xylenes can be recycled back to the distillation step(s) for further recovery of any remaining para-xylene and/or for further isomerization to form more para-xylene.
FIG. 1 shows an example of a reaction system for converting a methanol/dimethyl ether feed to aromatics and olefins. In FIG. 1, a methanol (and/or dimethyl ether) feed 105 is introduced into a conversion reactor 110. The reactor 110 can be a fixed bed reactor, a fluidized bed reactor, a riser reactor, or another convenient type of reactor. The total effluent 115 from the conversion reactor 110 can then be passed into a quench stage 120 for separation based on phases of the effluent. Water 124 can be separated out as one liquid phase, while a liquid hydrocarbon effluent 122 can correspond to a second liquid phase. Lower boiling hydrocarbons are removed as a gas phase or light ends stream 126. The light ends stream 126 typically includes ethylene and/or propylene, which can be recovered 160 in one or more recovery processes.
The liquid hydrocarbon effluent 122 is then separated in one or more distillation steps to recover a C₈portion of the effluent (i.e., a C₈product stream). Any convenient number of distillations may be performed. In FIG. 1, the distillation(s) are schematically represented as corresponding to two distillation steps for ease of understanding. A first distillation stage 130 can form a C₇₋stream 132 and a C₈+ stream 134. The C₈+ stream 134 is then separated in a second distillation stage 140 to form a C₉₊stream 142 and a C₈stream 144. The C₈stream 144 can then be separated 150, such as by crystallization or selective adsorption, to separate para-xylene stream 154 from the other xylene isomers 152.
In some alternative aspects, a stream of hydrogen-lean molecules can also be introduced into the conversion reactor. For example, during a conversion process, a feed comprising methanol, dimethyl ether, or a combination thereof can be introduced into a reactor containing a conversion catalyst. Steam can optionally also be introduced into the reactor. Optionally, a stream of hydrogen-lean molecules can also be introduced.
Compounds can be considered ‘hydrogen-lean’ based on the molecules containing one or more degrees of unsaturation and/or one or more heteroatoms. Examples of hydrogen-lean molecules include aromatics such as benzene, toluene and aromatics containing 9 or more carbons, olefins containing 4 or more carbons (C₄₊olefins), steam cracked naphtha or other refinery streams containing a mixture of compounds that include hydrogen-lean molecules, and oxygenates such as alcohols. Without being bound by any particular theory, it is believed that introduction of hydrogen lean molecules into the reaction environment can allow excess hydrogen in the reaction environment to be consumed while reducing or minimizing saturation of the desired para-xylene, ethylene, and propylene products. In some aspects, the stream of hydrogen-lean molecules is based at least in part on one or more recycled output streams from the conversion process.
FIG. 7 shows an example of another reaction system for converting a methanol/dimethyl ether feed to aromatics and olefins. In FIG. 7, a methanol (and/or dimethyl ether) feed 705 is introduced into a conversion reactor 710. The reactor 710 can be a fixed bed reactor, a fluidized bed reactor, a riser reactor, or another convenient type of reactor. An optional stream of hydrogen-lean molecules 707 is also shown in FIG. 7 as being introduced into the reactor. FIG. 7 shows the hydrogen-lean molecules 707 as including at least a portion 737 of a recycled C₇₋stream 732, but in other aspects a recycled portion of C₉₊stream 742 could be used instead of or in addition to the C₇₋stream. Optionally, a recycled portion 728 of the C₄₋stream can also be included in the hydrogen-lean molecules, if it is desired to include ethylene and/or propylene as part of the reactants in the conversion reactor.
The total effluent 715 from the conversion reactor 710 can then be passed into a quench stage 720 for separation based on phases of the effluent. Water 724 can be separated out as one liquid phase, while a liquid hydrocarbon effluent 722 can correspond to a second liquid phase. Lower boiling hydrocarbons are removed as a gas phase or light ends stream 726. The light ends stream 726 typically includes ethylene and/or propylene, which can be recovered 760 in one or more recovery processes.
The liquid hydrocarbon effluent 722 is then separated in one or more distillation steps to recover a C₈portion of the effluent (i.e., a C₈product stream). Any convenient number of distillations may be performed. In FIG. 7, the distillation(s) are schematically represented as corresponding to two distillation steps for ease of understanding. A first distillation stage 730 can form a C₇₋stream 732 and a C₈₊stream 734. The C₈₊stream 734 is then separated in a second distillation stage 740 to form a C₉₊stream 742 and a C₈stream 744. The C₈stream 744 can then be separated 750, such as by crystallization or selective adsorption, to separate para-xylene stream 754 from the other xylene isomers 752.

EXAMPLE 1

Selectivity of Steamed Conversion Catalyst

One benefit of steaming a conversion catalyst prior to use can be an improvement in the selectivity or yield of the desired products (aromatics, olefins) from the conversion reaction. When a conversion catalyst is newly synthesized or “fresh”, the catalyst may have a relatively high cracking activity due to the presence of additional acidic sites on the catalyst. Steaming the catalyst for a period of time prior to use in a conversion reaction can reduce the number of acidic sites, leading to increased production of desired products at the expense of side products such as carbon oxides and coke.
FIG. 2 shows results from conversion reactions performed on several catalysts with different amounts of initial steaming For the results shown in FIG. 2 (and also in FIGS. 3-5), the conversion reactions were performed to achieve 100% conversion of a methanol feed. The catalyst used for the conversion reactions in FIG. 2 was bound ZSM-5 catalyst modified to include 1 wt % Zn. Catalyst A in FIG. 2 corresponds to the as-is or “fresh” catalyst. Catalyst B was steamed for 1 hour prior to use in the conversion reaction, while
Catalyst C was steamed for 24 hours and Catalyst D was steamed for 72 hours. Steaming was used as a means to simulate catalyst aging. For instance, steaming Catalyst C for 24 hours prior to use is believed to represent the effect on the catalyst of being used in a conversion reaction for 1 year under effective conditions for converting methanol to aromatics and olefins. In FIG. 2, the results are displayed as a grouping of bar graphs for each product type, with the bars shown in the order A-B-C-D, as indicated for the first data set (paraffins) and the last data set (coke).
FIG. 2 shows the average product distribution in the conversion effluent for the fresh and steamed 1% Zn-ZSM-5 catalysts. The conversion reactions for the results in FIG. 2 were performed at 450° C., 15 psig and 2 hr⁻¹. Steaming the 1% Zn-ZSM-5 catalyst for 1 hour
(Catalyst B) caused a decrease in the unwanted side products (methane, CO, CO₂and coke) and a corresponding increase in the paraffins, olefins and olefins+aromatics selectivity compared to the fresh catalyst (Catalyst A). It is noted that the amount of coke shown in FIG. 2 represents the amount of coke measured on the catalyst after the end of the process run. As shown in FIG. 2, the aromatics selectivity was ˜55% for both Catalyst A and Catalyst B. Further steaming of the catalyst for 24 and 72 hours (Catalysts C and D) resulted in a lower aromatics selectivity of about 39% and about 32% aromatics, respectively. This decrease in aromatics selectivity, however, was accompanied by an increase in olefins and paraffins selectivity. As a result, the combined olefins+aromatics yield was found to be greater for steamed catalysts, but substantially independent of the time for which the catalyst was steamed. It is also noted that Catalyst B (1 hour of steaming) produced substantially reduced amounts of methane, CO, CO₂, and coke, while Catalyst C (24 hours steamed) and Catalyst D (72 hours steamed) produced negligible amounts of methane, CO, CO₂and coke. These results are consistent with the hypothesis that steaming reduced the acidity of the zeolite material.

EXAMPLE 2

Impact of Reaction Temperature with Steamed Catalysts

As shown above, steaming of a conversion catalyst can reduce or minimize the yield of side products, such as carbon oxides and coke, during a conversion reaction. The results shown in FIG. 2 corresponded to conversion reactions performed at 450° C. As the reaction temperature is increased, the benefits of using a steamed catalyst can increase.
FIG. 3 shows results from converting methanol to aromatics and olefins at reaction temperatures of 450° C., 500° C., and 550° C. using a catalyst corresponding to Catalyst A (fresh 1% Zn-ZSM-5) as described above. In FIG. 3, the results are displayed as a grouping of bar graphs for each product type, with the bars shown in the order 450° C.-500° C.-550° C., as indicated for the first data set (paraffins). The pressure during the conversion reactions was 15 psig and the WHSV was 2 hr⁻¹. Again, the conversion reaction was performed to achieve 100% conversion of the methanol feed. As the temperature is increased above 450° C., Catalyst A (fresh 1% Zn-ZSM-5) showed a significant reduction in the yields of aromatics (by ˜10% at 500° C., ˜30% at 550° C.), olefins (by ˜5% at 550° C.) and paraffins (by ˜20% at both 500° C. and 550° C.). The increase also resulted in a corresponding increase in coke formation on the catalyst, methane, CO and CO₂formation. The results in FIG. 3 show that the production of the undesired side products can be a substantial difficulty at temperatures above 450° C. when using a fresh catalyst.
FIG. 4 shows results from converting methanol to aromatics and olefins at 450° C. and 500° C. using Catalyst C (1% Zn-ZSM-5 steamed for 24 hours) as described above. In FIG. 4, the results are displayed as a grouping of bar graphs for each product type, with the bars shown in the order 450° C.-500° C., as indicated for the first data set (paraffins). The pressure during the conversion reactions was 15 psig and the WHSV was 2 hr⁻¹. As shown in
FIG. 4, performing the conversion reaction with Catalyst C at 500° C. did not result in the substantial decrease in aromatics selectivity and increases in side product yield that were observed for Catalyst A in FIG. 3. Instead, using a steamed catalyst for the conversion reaction resulted in only minimal production of CO, CO₂, CH₄, and coke on catalyst at the higher reaction temperature. For example, the combined amount of CO and CO₂produced was less than about 5 wt %, or less than about 3 wt %. In addition to reducing or minimizing the yield of side products, performing the conversion reaction with a steamed catalyst at 500° C. also increased the selectivity for aromatics formation (by about 10%) as well as the yield or selectivity for combined olefins plus aromatics (by about 7%). Without being bound by any particular theory, it appears that steaming the catalyst to reduce formation of side products allowed the conversion reaction to be performed under reaction conditions that were more favorable for production of aromatics while still maintaining high overall yields.
FIG. 5 shows results from performing the conversion reaction in the presence of Catalyst C at 550° C. The pressure during the conversion reaction was 15 psig and the WHSV was 2 hr⁻¹for the 1^stCycle. FIG. 5 shows the change in selectivity for forming various products over the course of a processing run. In FIG. 5, the diamond symbols correspond to the amount of methanol conversion (left axis); the triangles correspond to olefin selectivity (left axis); the asterisk symbols correspond to aromatics selectivity (left axis); the open squares correspond to paraffin selectivity (left axis); and the filled circles correspond to the amount of end of cycle coke formed (right axis). As shown in FIG. 5, performing the reaction at 550° C. with a steamed catalyst resulted in a yield of about 62% aromatics during the early portions of the processing run. This is substantially higher than the yield at either 450° C. (about 39%) or 500° C. (about 48%). The combined olefins plus aromatics selectivity was similarly high during the initial 4 hours (about 80%). However, this increased aromatics selectivity began to decay rapidly after 4 hours, with a corresponding increase in formation of methane, CO, CO₂and coke. Despite the rapid deactivation, the results in FIG. 5 show that processing at 550° C. could be effective for a fluidized bed reactor application. In a fluidized bed reactor or riser reactor, the nature of the reaction system can allow for withdraw and/or regeneration of the catalyst during a processing run. As a result, the catalyst in the fluidized bed or riser could be maintained in a condition of only being exposed to a few hours or less of conversion processing during the course of a longer processing run. This could allow the high initial selectivity for aromatics formation to be used in a commercial scale process.

EXAMPLE 3

Modification with Phosphorus

In addition to the benefits provided by steaming a metal-modified conversion catalyst, phosphorus can also be added to the catalyst. FIG. 6 shows the average product distributions for performing a conversion reaction using a catalyst corresponding to Catalyst C (24 hours steamed 1% Zn-ZSM-5) and a catalyst that also included phosphorous (1% P and 1% Zn-ZSM-5), which can be referred to as Catalyst E. FIG. 6 shows results from performing conversion reactions using Catalyst C and Catalyst E at temperatures of 450° C. and 500° C., a pressure of 15 psig, and a WHSV of 2 hr⁻¹for the 1^stCycle. In FIG. 6, the results are displayed as a grouping of bar graphs for each product type, with the bars shown in the order C 450° C.-E 450° C.-C 500° C.-E 500° C., as indicated for the first data set (paraffins).
In FIG. 6, for Catalyst E, the carbon selectivity towards aromatics increased by 8% and ˜6% at 450° C. and 500° C., respectively. However, the olefins selectivity decreased by ˜20% and ˜15% at 450° C. and 500° C. respectively. The addition of 1% phosphorous also lead to decreased coke and hydrogen formation. Further, the stability of the catalyst including 1% P and 1% Zn-ZSM-5 was better compared to the 1% Zn-ZSM-5 catalyst when compared at the same conditions and the same level of steaming.

ADDITIONAL EMBODIMENTS

Embodiment

1

A method of converting a feed to form olefins and aromatics, comprising: steaming a catalyst in the presence of at least 1 vol % water at a temperature of about 400° C. to about 850° C. for at least about 0.25 hours, the catalyst comprising a molecular sieve having at least one 10-member ring channel and having no ring channels larger than a 10-member ring channel, the catalyst further comprising about 0.1 wt % to about 10.0 wt % of a metal from Groups 8-14; and exposing a feed comprising at least about 50 wt % of methanol, dimethyl ether, or a combination thereof to the steamed catalyst under effective conversion conditions to form a conversion effluent comprising ethylene, propylene, and para-xylene, the effective conversion conditions including a temperature of about 350° C. to about 600° C.

Embodiment 2

A method of converting a feed to form olefins and aromatics, comprising: steaming a catalyst in the presence of at least 1 vol % water at a temperature of about 400° C. to about 850° C. for at least about 0.25 hours, the catalyst comprising a molecular sieve having at least one 10-member ring channel and having no ring channels larger than a 10-member ring channel, the catalyst further comprising about 0.1 wt % to about 10.0 wt % of Zn, Ga, Ag, or a combination thereof; and exposing a feed comprising at least about 50 wt % of methanol, dimethyl ether, or a combination thereof to the steamed catalyst under effective conversion conditions to form a conversion effluent comprising ethylene, propylene, and para-xylene, the effective conversion conditions including a temperature of about 425° C. to about 600° C.

Embodiment 3

The method of Embodiment 1 or 2, wherein the effective conversion conditions include a temperature of at least about 475° C., a combined yield in the conversion effluent of CO and CO₂being about 5 wt % or less, or about 3 wt % or less.

Embodiment 4

The method of any of the above embodiments, wherein the effective conversion conditions include a temperature of at least about 500° C.

Embodiment 5

The method of any of the above embodiments, wherein exposing a feed to the steamed catalyst comprises exposing the feed to the steamed catalyst in a fluidized bed reactor or a riser reactor.

Embodiment 6

The method of any of the above embodiments, further comprising separating at least a portion of the converted effluent to form a light ends product comprising ethylene, propylene, or a combination thereof and a liquid effluent.

Embodiment 7

The method of Embodiment 6, further comprising separating at least a portion of the liquid effluent to form a C₈product stream and one or more of a C₇₋stream and a C₉₊stream, wherein exposing a feed to the steamed catalyst optionally comprises exposing the feed to the steamed catalyst in the presence of a hydrogen-lean stream, the method optionally further comprising recycling at least a portion of the C₇₋stream, the C₉₊stream, or a combination thereof to form the hydrogen-lean stream.

Embodiment 8

The method of Embodiment 7, further comprising separating the C₈product stream to form at least a para-xylene product stream, the para-xylene product stream having a higher concentration of para-xylene than the C₈product stream.

Embodiment 9

The method of any of the above embodiments, wherein the steamed catalyst further comprises about 0.1 wt % to about 10 wt % of phosphorus, lanthanum, an element from Groups 1 or 2, an element from Groups 13-16, or a combination thereof, or 0.1 wt % to about 10 wt % of each of two or more of the above.

Embodiment 10

The method of Embodiment 9, wherein the steamed catalyst further comprises at least about 1 wt %, or at least about 2 wt %, or at least about 3 wt %, or at least about 4 wt %, or at least about 5 wt %, or at least about 6 wt %, or at least about 7 wt %, or at least about 8 wt %, or at least about 9 wt % of phosphorus, lanthanum, an element from Groups 1 or 2, an element from Groups 13-16, or a combination thereof, or of each of two or more of the above, and/or about 10 wt % or less, or about 9 wt % or less, or about 8 wt % or less, or about 7 wt % or less, or about 6 wt % or less, or about 5 wt % or less, or about 4 wt % or less, or about 3 wt % or less, or about 2 wt % or less.

Embodiment 11

The method of any of the above embodiments, wherein the steamed catalyst comprises at least about 1 wt %, or at least about 2 wt %, or at least about 3 wt %, or at least about 4 wt %, or at least about 5 wt %, or at least about 6 wt %, or at least about 7 wt %, or at least about 8 wt %, or at least about 9 wt % of the metal from Groups 8-14 and/or about 10 wt % or less, or about 9 wt % or less, or about 8 wt % or less, or about 7 wt % or less, or about 6 wt % or less, or about 5 wt % or less, or about 4 wt % or less, or about 3 wt % or less, or about 2 wt % or less.

Embodiment 12

The method of any of the above embodiments, wherein the molecular sieve comprises ZSM-5, ZSM-11, ZSM-12, ZSM-22, ZSM-23, ZSM-34, ZSM-35, ZSM-48, ZSM-57, or ZSM-58, or wherein the molecular sieve comprises ZSM-5, ZSM-11, ZSM-23, ZSM-35 or ZSM-48, or wherein the molecular sieve comprises ZSM-5.

Embodiment 13

The method of any of the above embodiments, wherein the effective conversion conditions comprise a pressure of about 100 kPaa to about 2500 kPaa, or about 100 kPaa to about 1200 kPaa; and a WHSV of about 0.1 hr⁻¹to about 20 hr⁻¹, or about 1.0 hr⁻¹to about 10 hr⁻¹.

Embodiment 14

The method of any of the above embodiments, wherein the feed substantially comprises methanol, dimethyl ether, or a combination thereof.

Embodiment 15

The method of any of the above embodiments, wherein exposing a feed to the steamed catalyst comprises exposing the feed to the steamed catalyst in the presence of steam, a hydrogen-lean stream, or a combination thereof.

Embodiment 16

The method of any of the above embodiments, wherein the catalyst is steamed in the presence of 1 vol % to 100 vol % water for 0.25 hours to 48 hours, or for 0.25 hours to 8 hours, or for 0.5 hours to 8 hours, or for 0.5 hours to 4 hours, the steaming optionally being at a temperature of at least about 500° C., or about 750° C. or less, or about 650° C. or less.
Although the present invention has been described in terms of specific embodiments, it is not so limited. Suitable alterations/modifications for operation under specific conditions should be apparent to those skilled in the art. It is therefore intended that the following claims be interpreted as covering all such alterations/modifications as fall within the true spirit/scope of the invention.

Claims

What is claimed is:

1. A method of converting a feed to form olefins and aromatics, comprising:

steaming a catalyst in the presence of at least 1 vol % water at a temperature of about 400° C. to about 850° C. for at least about 0.25 hours, the catalyst comprising a molecular sieve having at least one 10-member ring channel and having no ring channels larger than a 10-member ring channel, the catalyst further comprising about 0.1 wt % to about 10.0 wt % of a metal from Groups 8-14; and

exposing a feed comprising at least about 50 wt % of methanol, dimethyl ether, or a combination thereof to the steamed catalyst under effective conversion conditions to form a conversion effluent comprising ethylene, propylene, and para-xylene, the effective conversion conditions including a temperature of about 350° C. to about 600° C.

2. The method of claim 1, wherein the effective conversion conditions include a temperature of at least about 475° C. and a combined yield in the conversion effluent of CO and CO₂being about 5 wt % or less.

3. The method of claim 1, wherein exposing a feed to the steamed catalyst comprises exposing the feed to the steamed catalyst in a fluidized bed reactor or a riser reactor.

4. The method of claim 1, wherein the effective conversion conditions include a temperature of at least about 500° C.

5. The method of claim 1, further comprising separating at least a portion of the converted effluent to form a light ends product comprising ethylene, propylene, or a combination thereof, and a liquid effluent.

6. The method of claim 5, further comprising separating at least a portion of the liquid effluent to form a C₈product stream and one or more of a C₇₋stream and a C₉₊stream.

7. The method of claim 6, wherein exposing a feed to the steamed catalyst comprises exposing the feed to the steamed catalyst in the presence of a hydrogen-lean stream, the method further comprising recycling at least a portion of the C₇₋stream, the C₉₊stream, or a combination thereof, to form the hydrogen-lean stream.

8. The method of claim 6, further comprising separating the C₈product stream to form at least a para-xylene product stream, the para-xylene product stream having a higher concentration of para-xylene than the C₈product stream.

9. The method of claim 1, wherein the steamed catalyst further comprises at least about 0.1 wt % of phosphorus, lanthanum, an element from Groups 1 or 2, an element from Groups 13-16, or a combination thereof.

10. The method of claim 1, wherein the steamed catalyst further comprises at least about 0.1 wt % of phosphorus.

11. The method of claim 1, wherein the molecular sieve comprises ZSM-5.

12. The method of claim 1, wherein the effective conversion conditions comprise a pressure of about 100 kPaa to about 2500 kPaa and a WHSV of about 0.1 hr⁻¹to about 20 hr⁻¹.

13. The method of claim 1, wherein the feed substantially comprises methanol, dimethyl ether, or a combination thereof.

14. The method of claim 1, wherein exposing a feed to the steamed catalyst comprises exposing the feed to the steamed catalyst in the presence of steam, a hydrogen-lean stream, or a combination thereof.

15. A method of converting a feed to form olefins and aromatics, comprising:

steaming a catalyst in the presence of at least 1 vol % water at a temperature of about 400° C. to about 850° C. for at least about 0.25 hours, the catalyst comprising a molecular sieve having at least one 10-member ring channel and having no ring channels larger than a 10-member ring channel, the catalyst further comprising about 0.1 wt % to about 10.0 wt % of Zn, Ga, Ag, or a combination thereof; and

exposing a feed comprising at least about 50 wt % of methanol, dimethyl ether, or a combination thereof to the steamed catalyst under effective conversion conditions to form a conversion effluent comprising ethylene, propylene, and para-xylene, the effective conversion conditions including a temperature of about 425° C. to about 600° C.

16. The method of claim 15, wherein the effective conversion conditions include a temperature of at least about 475° C. and a combined yield in the conversion effluent of CO and CO₂being about 5 wt % or less.

17. The method of claim 15, wherein the steamed catalyst further comprises at least about 0.1 wt % of phosphorus, lanthanum, an element from Groups 1 or 2, an element from Groups 13-16, or a combination thereof.

18. The method of claim 15, wherein the steamed catalyst further comprises at least about 0.1 wt % of phosphorus.

19. The method of claim 15, wherein the molecular sieve comprises ZSM-5.

20. The method of claim 15, wherein the effective conversion conditions comprise a pressure of about 100 kPaa to about 2500 kPaa and a WHSV of about 0.1 hr⁻¹to about 20 hr⁻¹.