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  Method and apparatus for reducing decomposition byproducts in a methanol to olefin reactor systemUSPTO Application #: 20060129011Title: Method and apparatus for reducing decomposition byproducts in a methanol to olefin reactor system Abstract: Disclosed is a method and apparatus for reducing the amount of metal catalyzed side-reaction byproducts formed in the feed vaporization and introduction system of a methanol to olefin reactor system by monitoring and/or maintaining the temperature of at least a portion of the feed vaporization and introduction system and/or of the feedstock contained therein below about 400° C., 350° C., 300° C., 250° C., 200° C. or below about 150° C. The temperature can be maintained in the desired range by jacketing at least a portion of the feed vaporization and introduction system, such as at least a portion of the feed introduction nozzle, with a thermally insulating material or by implementing a cooling system. (end of abstract) Agent: Exxonmobil Chemical Company Law Technology - Baytown, TX, US Inventors: Kenneth Ray Clem, Stephen N. Vaughn, Teng Xu, Jeffrey L. White USPTO Applicaton #: 20060129011 - Class: 585639000 (USPTO) Related Patent Categories: Chemistry Of Hydrocarbon Compounds, Unsaturated Compound Synthesis, From Nonhydrocarbon Feed, Alcohol, Ester, Or Ether The Patent Description & Claims data below is from USPTO Patent Application 20060129011. Brief Patent Description - Full Patent Description - Patent Application Claims
FIELD OF THE INVENTION [0001] This invention is to an apparatus and method for reducing methanol decomposition byproducts in a methanol to olefin reactor system. BACKGROUND OF THE INVENTION [0002] Light olefins, defined herein as ethylene and propylene, serve as feeds for the production of numerous important chemicals and polymers. Light olefins traditionally are produced by cracking petroleum feeds. Because of the limited supply and escalating cost of petroleum feeds, the cost of producing olefins from petroleum sources has increased steadily. Efforts to develop and improve olefin production technologies, particularly light olefins production technologies, have increased. [0003] The petrochemical industry has known for some time that oxygenates, especially alcohols, are convertible into light olefin(s). There are numerous technologies available for producing oxygenates including fermentation or reaction of synthesis gas derived from natural gas, petroleum liquids, carbonaceous materials including coal, recycled plastics, municipal waste or any other organic material. Generally, the production of synthesis gas involves a combustion reaction of natural gas, mostly methane, and an oxygen source into hydrogen, carbon monoxide and/or carbon dioxide. Syngas production processes are well known, and include conventional steam reforming, autothermal reforming, or a combination thereof. [0004] Methanol, the preferred alcohol for light olefin production, is typically synthesized from the catalytic reaction of hydrogen, carbon monoxide and/or carbon dioxide in a methanol reactor in the presence of a heterogeneous catalyst. For example, in one synthesis process methanol is produced using a copper/zinc oxide catalyst in a water-cooled tubular methanol reactor. The preferred methanol conversion process is generally referred to as a methanol-to-olefin(s) process, where methanol is converted to primarily ethylene and/or propylene in the presence of a molecular sieve. [0005] In an oxygenate to olefin (OTO) reaction system, a feedstock containing an oxygenate is vaporized and introduced into a reactor. Exemplary oxygenates include alcohols such as methanol and ethanol, dimethyl ether, methyl ethyl ether, methyl formate, and dimethyl carbonate. In a methanol to olefin (MTO) reaction system, the oxygenate-containing feedstock includes methanol. In the reactor, the methanol contacts a catalyst under conditions effective to create desirable light olefins. Typically, molecular sieve catalysts have been used to convert oxygenate compounds to olefins. Silicoaluminophosphate (SAPO) molecular sieve catalysts are particularly desirable in such conversion processes because they are highly selective in the formation of ethylene and propylene. [0006] In a typical MTO reactor system, undesirable byproducts may be formed through side reactions. For example, the metals in conventional reactor walls may act as catalysts in one or more side reactions. If the methanol contacts the metal reactor wall at sufficient temperature and pressure, the methanol may be converted to undesirable methane and/or other byproducts. [0007] Byproduct formation in an MTO reactor is undesirable for several reasons. First, increased investment is required to separate and recover the byproducts from the desired light olefins. Additionally, as more byproducts are formed, less light olefins are synthesized. In other words, the production of byproducts is undesirable because methanol feed is consumed to produce the byproducts. Further, although the relative concentrations of metal catalyzed side reaction byproducts are generally quite low, the total amount of byproducts produced on an industrial scale can be enormous. Thus, it is desirable to decrease or eliminate the synthesis of byproducts in an MTO reactor system. [0008] Sulfur-containing chemicals have proven effective for deactivating or passivating the metal surface of a reactor thereby reducing the formation of undesirable byproducts in the reactor. For example, Japanese Laid Open Patent Application JP 01090136 to Yoshinari et al. is directed to a method for preventing decomposition of methanol or dimethyl ether and coking by sulfiding the metal surface of a reactor. More particularly, the method includes reacting methanol and/or dimethyl ether in the presence of a catalyst at above 450.degree. C. in a tubular reactor made of Iron and/or Nickel or stainless steel. The inside wall of the reactor is sulfided with a compound such as carbon disulfide, hydrogen disulfide or dimethyl sulfide. Additionally, a sulphur compound may be added to the feed. [0009] Although passivating chemicals have proven effective in reducing metal catalyzed side reactions, the introduction of deactivating or passivating chemicals increases production costs because these chemicals or their products must be separated from the desired product. Thus, a need exists for a method and apparatus for reducing the formation of metal catalyzed side reaction byproducts in an MTO reactor system while minimizing the use of deactivating or passivating chemicals. SUMMARY OF THE INVENTION [0010] The present invention includes a method for making an olefin product from an oxygenate-containing feedstock including directing the feedstock through a feed introduction nozzle having an inner surface and being attached to an MTO reactor. The inner surface of the nozzle is maintained at a temperature below about 400.degree. C., 350.degree. C., 300.degree. C., 250.degree. C., 200.degree. C. or below about 150.degree. C. The method also includes contacting, in the reactor, the feedstock with a catalyst under conditions effective to form an effluent comprising light olefins. The present invention provides the ability to produce light olefins while reducing or eliminating the production of metal catalyzed side reaction byproducts in the feed vaporization and introduction (FVI) system. The FVI system is the region of the reactor system beginning at the point that at least a portion of the feedstock is in a vaporized state and extending to the point that the feedstock exits the feed introduction nozzle and enters the MTO reactor where the feedstock contacts the catalyst. As the resulting light olefin stream contains less metal catalyzed side reaction byproducts than is produced in conventional MTO reactor systems, olefin separation and purification costs can be reduced. The resulting purified olefin stream is particularly suitable for use as a feed in the manufacture of polyolefins. [0011] Additionally, the inventive method, optionally, includes cooling at least a portion of the inner surface of the nozzle with a cooling system. The nozzle of one embodiment is additionally or alternatively be jacketed with a thermally insulating material, which is selected from the group consisting of fire brick, alumina bricks, silica bricks, magnesite bricks, chrome bricks, silicon carbide bricks, zircon, zirconia, forsterite, high temperature calcium silicate, alumina and silica-alumina ceramics, diatomaceous silica, cements, fillers, calcium carbonate, calcium sulfate, concrete, glass, granite, marble, mineral wool, porcelain, portland cement, Pumice stone, gunnite, and other refractory materials with insulating properties. For additional insulating materials which are incorporated in one embodiment of the present invention, see Petroleum Processing Handbook, ed. W. F. Bland and R. L. Davidson, McGraw Hill Publishers, 1967, p 4-137 to 4-147, and Robert H. Perry, Perry's Chemical Engineers' Handbook, 7.sup.th Ed., 1997, p. 11-68 to 11-74, both of which are incorporated herein by reference. Optionally, he thermally insulating material covers at least a portion of an interior portion of the nozzle extending inside the MTO reactor and/or at least a portion of the exterior portion of the nozzle extending outside the MTO reactor. [0012] The invention is also directed to a method for making an olefin product from an oxygenate-containing feedstock including directing the feedstock through a feed nozzle having a nozzle temperature and being attached to a MTO reactor, wherein at least a portion of the nozzle is covered by a thermally insulating material as described above. The method also includes contacting, in the reactor, the feedstock with a catalyst under conditions effective to form an effluent comprising light olefins. Optionally, the thermally insulating material may cover at least a portion of an interior portion of the nozzle extending inside the MTO reactor and/or at least a portion of the exterior portion of the nozzle extending outside the MTO reactor. [0013] Another embodiment of the present invention is a method for making an olefin product from an oxygenate-containing feedstock including heating the feedstock in a heating device to form a heated feedstock. The heated feedstock is directed through a feed nozzle having a nozzle temperature and being attached to a MTO reactor. At least a portion of the nozzle is cooled with a cooling system. The method also includes contacting, in the reactor, the feedstock with a catalyst under conditions effective to form an effluent comprising light olefins. Optionally, a cooling medium cools the nozzle, which is directed into the MTO reactor wherein the cooling medium mixes with the feedstock. [0014] A further embodiment is a method for making an olefin product from an oxygenate-containing feedstock including directing the feedstock through a feed introduction nozzle having an inner surface and being attached to an MTO reactor. The feedstock is maintained below about 400.degree. C., 350.degree. C., 300.degree. C., 250.degree. C., 200.degree. C. or below about 150.degree. C. while the feedstock is in the nozzle. In the reactor, the feedstock contacts a catalyst under conditions effective to form an effluent comprising light olefins. This embodiment may include insulating at least a portion of the nozzle with a thermally insulating material and/or cooling at least a portion of the nozzle with a cooling medium. [0015] The invention is also directed to a method for making an olefin product from an oxygenate-containing feedstock including directing the feedstock through a feed introduction nozzle having an inner surface and being attached to an MTO reactor. The nozzle is maintained at conditions effective to produce less than 0.8 or 0.4 weight percent of metal catalyzed side reaction byproducts excluding CO, CO.sub.2 and H.sub.2. Optionally, the conditions are effective to substantially eliminate the formation of metal catalyzed side reaction byproducts. In the reactor, the feedstock contacts a catalyst under conditions effective to form an effluent comprising light olefins. [0016] The invention is also directed to a feed introduction nozzle for an MTO reactor including a generally tubular member including an exterior portion oriented externally to the MTO reactor and adapted to receive an oxygenate-containing feedstock, and an interior portion oriented within the MTO reactor and adapted to deliver the feedstock to the MTO reactor. The nozzle includes a jacket formed at least in part of a thermally insulating material, as described above, covering at least a portion of the generally tubular member. The jacket may cover at least a portion of the interior portion and/or at least a portion of the exterior portion of the generally tubular member. [0017] The invention is also directed to a feed introduction nozzle for an MTO reactor including a first generally tubular member adapted to receive a feedstock from a heating device and to deliver the feedstock to the MTO reactor. A cooling system covers at least a portion of the first generally tubular member and is adapted to cool the nozzle to a temperature effective to substantially eliminate the production of metal catalyzed side-reaction byproducts. The nozzle can include a cooling system having a second generally tubular member of larger diameter than the first generally tubular member, the first and second members being coaxially oriented about a central axis thereby defining inner and outer conduits, and wherein the inner conduit is adapted to receive the feedstock and the outer conduit is adapted to receive the cooling medium. The nozzle may include an outlet inside the MTO reactor adapted to direct the cooling medium into the MTO reactor. Also, the nozzle can include a jacket layer formed at least in part of a thermally insulating material as described above. The jacket layer may cover at least a portion of the cooling system. BRIEF DESCRIPTION OF THE DRAWINGS [0018] This invention will be better understood by reference to the Detailed Description of the Invention when taken together with-the attached drawings, wherein: [0019] FIG. 1 illustrates a flow diagram of a methanol to olefin reactor system including the FVI system and the MTO reactor; [0020] FIG. 2 illustrates a nozzle jacketing configuration in accordance with one embodiment of the present invention; and Continue reading... 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