STEAMLESS PROCESS FOR CONVERTING BUTENES TO 1,3-BUTADIENE

Description

BACKGROUND Field of the Disclosure

[0001] The present disclosure generally relates to the production of butadiene. More specifically, embodiments of the disclosure relate to the catalytic conversion of butene to 1,3-butadiene.Description of the Related Art

[0002] 1,3-Butadiene (also referred to as simply "butadiene" or "1,3-BD") is an important industrial chemical used as a predecessor and a building block for many materials. 1,3-butadiene is used in various industries including construction, healthcare, consumer durables, and automotive. Major butadiene derivatives include acrylonitrile butadiene styrene (ABS), styrene butadiene rubber (SBR), nitrile butadiene rubber (NBR), and hexamethylenediamine.

[0003] A significant portion of the 1,3-butadiene produced is used in the manufacturing of synthetic rubber. The automotive industry heavily relies on butadiene for the manufacturing of tires and other parts. The recent growth of the automotive industry in locations such as China, India, and Brazil has played a pivotal role in increasing the demand for 1,3-butadiene in the market. The trends of growth in demand and decrease in supply may result in a rise in the prices of 1,3-butadiene and an increase in the price volatility. US 3915897 describes A catalyst for the olefin disproportionation of unsaturated hydrocarbons. WO 2017 / 003821 describes a metathesis process for producing propylene. WO 2008 / 153643 describes a process for producing propylene. US 2010 / 167911 describes regenerating a used catalyst mixture. CN 105749931 describes a butylene oxidative dehydrogenation. US 4225738 describes a three-step process for converting n-butene into high purity 1,3-butadiene.SUMMARY

[0004] Currently, almost all 1,3-butadiene is produced as a byproduct of ethylene steam cracking of naphtha feedstock, gasoil feedstock, or both. The switch to lighter feedstocks has reduced the amount of 1,3-butadiene available from ethylene cracking to such an extent that the reduced amount of 1,3-butadiene that is produced cannot sometimes be economically recovered. Additionally, the steam cracking processes require a significant amount of steam diluent in the feed stream to remove coke. This reduced production presents a demand for on-purpose 1,3-butadiene technologies including-but not limited to-n-butane dehydrogenation and mixed butenes oxidative dehydrogenation.

[0005] In one embodiment, a method for producing 1,3-butadiene is provided. The method includes receiving a feed stream that includes 2-butene and contacting the feed stream with a catalyst in the presence of an oxidant to convert the 2-butene to 1-3-butadiene, the catalyst including tungsten oxide impregnated on an inorganic support and magnesium oxide, wherein the catalyst comprises a first layer of the tungsten oxide impregnated on the inorganic support, a second layer of the tungsten oxide impregnated on the inorganic support, and a layer of the magnesium oxide positioned between the first layer and the second layer. In some embodiments, the feed stream does not include steam. In some embodiments, the oxidant includes air. In some embodiments, the contacting is performed at a temperature in the range of 400°C to 550°. In some embodiments, the feed stream includes 1-butene. In some embodiments, the inorganic support includes silica. In some embodiments, the magnesium oxide has a surface area in the range of 30 meters-squared / gram (m 2< / g) to 200 m 2< / g. In some embodiments, the volumetric ratio of the magnesium oxide to the tungsten oxide impregnated on the inorganic support is in the range of 1:3 to 3:1. In some embodiments, contacting the feed stream, at a temperature in the range of 400°C to 550°, with a catalyst to convert the 2-butene to 1-3-butadiene achieves a 1,3-butadiene selectivity of at least 23.

[0006] Described herein, but not presently claimed, is a system for producing 1, 3-butadiene. The system includes a reactor and a catalyst positioned in the reactor and having tungsten oxide impregnated on an inorganic support, the reactor configured to receive a feed stream that includes 2-butene and contact the feed stream at a temperature in the range of 400°C to 550°C with the catalyst in the presence of an oxidant to convert the 2-butene to 1-3-butadiene. The feed stream may not include steam. The oxidant may include air. The reactor may be a fixed bed continuous flow reactor. The feed stream may include 1-butene. The inorganic support may include silica. The catalyst may include magnesium oxide. The magnesium oxide may have a surface area in the range of 30 meters-squared / gram (m 2< / g) to 200 m 2< / g. The catalyst may include a first layer of the tungsten oxide impregnated on the inorganic support, a second layer of the tungsten oxide impregnated on the inorganic support, and a layer of the magnesium oxide positioned between the first layer and the second layer. The catalyst may include a layer of the magnesium oxide disposed on a layer of the tungsten oxide impregnated on the inorganic support. The volumetric ratio of the magnesium oxide to the tungsten oxide may be impregnated on the inorganic support in the range of 1:3 to 3:1. The system may include an impurities removal bed upstream of the reactor, the impurities removal bed configured to receive the feed stream and remove impurities from the feed stream. The system may include butadiene extraction unit downstream of the reactor, the butadiene extraction unit configured to separate 1,3-butadiene from the product stream.

[0007] Also described, but not presently claimed, is a catalyst for the production of 1,3-butadiene for the production of 1,3-butadiene. The catalyst includes tungsten oxide impregnated on an inorganic support and magnesium oxide. The catalyst may include a first layer of the tungsten oxide impregnated on the inorganic support, a second layer of the tungsten oxide impregnated on the inorganic support, and a layer of the magnesium oxide positioned between the first layer and the second layer. The catalyst may include a layer of the magnesium oxide disposed on a layer of the tungsten oxide impregnated on the inorganic support. The volumetric ratio of magnesium oxide to tungsten oxide may be impregnated on the inorganic support in the range of 1:3 to 3:1.

[0008] Also described, but not presently claimed, is a method for preparing a catalyst for the conversion of butene to 1,3-butadiene. The method includes calcining a silica support, placing an amount of ammonium metatungstate hydrate solution on the calcined silica support, re-calcining the silica support with the ammonium metatungstate hydrate solution to yield tungsten oxide present on the support, the calcining is performed at first temperature for a first period and second temperature for a second duration. The method may include drying the silica support having the amount of the ammonium metatungstate hydrate solution. The first temperature may be at least 250°C and the second period may be at least 2 hours, and the second temperature may be at least 550°C and the second period may be at least 8 hours. Calcining the silica support may include calcining the silica support at a temperature of at least 200°C for at least 3 hours and a temperature of at least 575°C for at least 5 hours before. The amount of ammonium metatungstate hydrate solution may be sufficient to yield 10 weight % (wt%) tungsten oxide on the silica support.BRIEF DESCRIPTION OF THE DRAWINGS

[0009] FIG. 1 is a schematic diagram of a system for the conversion of 2-butene to 1,3-butadiene in accordance with an embodiment of the disclosure; FIG. 2 is a plot of x-ray diffraction (XRD) patterns of a prepared silica blank in accordance with an embodiment of the disclosure; FIG. 3 is a plot of x-ray diffraction (XRD) patterns for a prepared WO 3 / SiO 2 catalyst and WO 3 in accordance with an embodiment of the disclosure; and FIG. 4 is a plot of x-ray diffraction (XRD) patterns of an MgO catalyst prepared from commercially available MgO in accordance with an embodiment of the disclosure. DETAILED DESCRIPTION

[0010] The present disclosure will now be described more fully with reference to the accompanying drawings, which illustrate embodiments of the disclosure. This disclosure may, however, be embodied in many different forms and should not be construed as limited to the illustrated embodiments. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

[0011] Embodiments of the presently claimed invention include processes for the conversion of 2-butene to 1,3-butadiene without the use of steam or, in some embodiments, with a reduced use of steam as compared to prior art processes for the production 1,3-butadiene. The catalyst includes tungsten oxide (WO 3 ) on an inorganic support, such as silica (SiO 2 ), alumina (e.g., in the form of alumina balls), clay, carbon, or diatomaceous earth. The catalyst also includes activated magnesium oxide (MgO) and may be referred to as a "dual catalyst" or a "co-catalyst." A layer of MgO catalyst is positioned between a first layer of WO3-inorganic support catalyst and a second layer of WO 3 -inorganic support. Also described, but not forming part of the presently claimed invention, is various other arrangements of the MgO and the WO 3 -inorganic support including a layer of MgO catalyst positioned on top of a layer of WO 3 -inorganic support catalyst, and the MgO catalyst and WO 3 -inorganic support catalyst mixed in a single layer having both catalysts.

[0012] The process for the production of 1,3-butadiene includes contacting a feed stream of 2-butene with an MgO and WO 3 -inorganic support catalyst. In some embodiments, the contacting may be performed at a temperature in the range of about 150°C to about 700° and, in some embodiments, may be performed in the range of about 400°C to about 550°C. In some embodiments, the feed stream does not include steam and the 1,3-butadiene is produced without steam in the feed stream. As will be appreciated, however, steam may be produced in the oxidative dehydrogenation process, as every butene molecule will generate a molecule of steam for every molecule of 1,3-butadiene produced. In other embodiments, steam diluent may be introduced in a feed stream to aid in heat dissipation and manage temperatures in the catalyst bed. However, in such embodiments that use a steam diluent, the amount of steam may be no more than 50% of the steam used in prior processes for the production of 1,3-butadiene. In some embodiments, the feed stream may also include 1-butene.

[0013] A system for the production of 1, 3-butadiene, described herein but not presently claimed may include an impurities removal bed, a reactor, and a butadiene extraction unit. The reactor may be a fixed bed continuous flow reactor. The reactor may be operated at atmospheric pressure and at a temperature in the range of about 400°C to about 550°C. A reactor for producing 1,3-butadiene from 2-butene without the use of steam in accordance with the processes described herein may be a catalyst filled multitubular reactor with a cooling medium on the outside of the tubes.PROCESSES FOR THE PRODUCTION OF 1,3-BUTADIENE

[0014] In some embodiments, a process for the catalytic conversion of 1,3-butadiene from 2-butene includes contacting the 2-butene with a catalyst without steam or with a reduced amount of steam as compared to prior art processes. In some embodiments, steam may be used as a diluent to aid in the dissipation of heat in the catalyst bed and provide for improved management of the temperature rise in the catalyst bed.

[0015] The catalyst includes activated magnesium oxide (MgO), and tungsten oxide (WO 3 ) on an inorganic support (the MgO and WO 3 ) catalyst may be referred to as a "dual catalyst" or a "co-catalyst." In some embodiments, the volumetric ratio of MgO catalyst and WO 3 -inorganic support catalyst may be in the range of about 1:3 to about 3: 1. For example, in some embodiments, the volumetric ratio of MgO catalyst and WO 3 -inorganic support catalyst may be 2: 1, 1: 1, or 1:2.

[0016] In some embodiments, inorganic support for the WO 3 may be silica (SiO 2 ). In other embodiments, the catalyst support may be alumina (e.g., in the form of alumina balls), clay, carbon, or diatomaceous earth. In such embodiments, catalysts such as alumina, clay, carbon, or diatomaceous earth may be obtained without any silica impurities so as to reduce or eliminate potential leaching of silica into vapor produced in the reactor and that may foul downstream equipment such as compressor turbine blades.

[0017] Embodiments of the disclosure include various arrangements of the MgO and WO 3 catalyst. In some embodiments, the catalyst may be held in place in a reactor using an inert material, such as silicon carbide. In some embodiments, the inert material used to hold the catalyst may be Grade 20 silicon carbide (SiC20). In some embodiments, an arrangement may include the layering of the catalyst, the inert material, and an insulating material such as glass wool. In accordance with the presently claimed invention, the catalyst arrangement includes a layer of MgO catalyst positioned between a first layer of WO3-inorganic support catalyst and a second layer of WO 3 -inorganic support.

[0018] In some embodiments, as noted supra, the inorganic support is silica. In such embodiments, the silica may be prepared by calcining a commercially available silica support. In some embodiments, the calcination may be performed at a temperature of about 200°C for about 3 hours and then at a temperature of about 575°C for about 5 hours, with a ramping rate of about 3°C per minute. In some embodiments, the silica support for the tungsten oxide catalyst may be prepared from a silica support having an average pore diameter of about 10 nm, a pore volume of about 1.00 ml / g, a surface area of about 300 m 2< / g and a particle size of in the range of about 1.18 mm to about 2.36 mm. In some embodiments, the commercially available silica support may be Q-10 manufactured by Fuji Silysia of Kasugai, Aichi, Japan.

[0019] The tungsten catalyst may be prepared by impregnating an inorganic support, such as a silica catalyst support prepared in the manner described in the disclosure. In such embodiments, for example, ammonium metatungstate hydrate with a 99.99 % trace metals basis may be used as the tungsten source. The ammonium metatungstate hydrate may be mixed with DI water and added dropwise to the prepare silica catalyst support and mixed, such as by using a glass rod. The silica catalyst support having the ammonium metatungstate hydrate may be dried in a drying oven and calcined to produce a WO3 / SiO2 catalyst. The silica catalyst support having the ammonium metatungstate hydrate may be dried in a drying oven at a temperature of about 80°C for a time period of about 8 hours and then calcined at a first temperature of about 250°C for about 2 hours with a ramping rate of about 1°C per minute to reach the first temperature and then at a second temperature of about 550°C for about 8 hours with a ramping rate of about 3°C per minute until the second temperature is reached.

[0020] The MgO catalyst may be prepared from a commercially available MgO. The MgO may be calcined under air to produce the MgO catalyst. Tthe MgO may be calcined under air at a rate of about 2°C / minute until a temperature of about 550°C and then held at about 550°C for about 150 minutes. The MgO catalyst may have a surface area in the range of about 30 m 2< / g to about 200 m 2< / g. The MgO catalyst may have a surface area in the range of about 60 m 2< / g to about 200 m 2< / g.

[0021] The MgO catalyst may be prepared via co-precipitation using a magnesium salt. For example, MgO catalyst may be prepared from magnesium nitrate hexahydrate [Mg(NO 3 )2 · 6H2O]. The magnesium nitrate hexahydrate may be first mixed with DI water and the magnesium nitrate hexahydrate solution added dropwise to a container of DI water. The mixture may be stirred at about 600 rpm while ammonium hydroxide is added simultaneously to the mixture, and then stirred for about an hour. The mixture may then be centrifuged and washed with DI water. The solid from the solution may be collected and dried in a drying oven at a temperature of about 80°C and calcined under air at a rate of about 2°C / minute until a temperature of about 550°C and then held at about 550°C for about 150 minutes.

[0022] The MgO catalyst may be produced by hydrating commercially available MgO by converting it to Mg(OH) 2 and then calcining it under air to convert the Mg(OH) 2 back to MgO.

[0023] A system for catalyst conversion of 1,3-butadiene from 2-butene using the catalysts described herein may include a fixed bed continuous flow reactor. The reactor may be operated at atmospheric pressure. The reactor may be operated at a temperature in the range of about 150°C to about 700° and, may be performed in the range of about 400°C to about 550°C. A reactor for producing 1,3-butadiene from 2-butene without the use of steam in accordance with the processes described herein may be a catalyst filled multitubular reactor with a cooling medium on the outside of the tubes. As will be appreciated, steam may be produced during the oxidative dehydrogenation reaction, as every 2-butene molecule will generate a molecule of steam for every molecule of 1,3-butadiene produced.

[0024] FIG. 1 depicts a system 100 for the conversion of 2-butene to 1,3-butadiene. As shown in FIG.1, the system 100 may include an impurities removal bed 102, a reactor 104, and a butadiene extraction unit 106. The system 100 may also include heat exchanger 108 and 110. The system 100 may receive a butene feed stream 112 having 2-butene. The feed stream 112 includes cis- and trans-2-butene. The feed stream 112 may include air or air may be provided in a separate stream.

[0025] The feed stream 112 may be provided to the impurities removal bed 100 to remove impurities from the feed stream 112. The purified feed stream 114 from the impurities removal bed 102 may be provided to the heat exchanger 108 to be heated using the output stream from the reactor 104. The purified feed stream 114 may be provided to a second heat exchanger 110 to produce a purified and heated feed stream 116. The purified and heated feed stream 116 may be provided to the reactor 104 for conversion of 2-butene in the feed stream 116 to 1,3-butadiene using the techniques described in the disclosure.

[0026] The output stream 118 from the reactor 104 may include 1,3-butadiene converted from the 2-butene, as well as other reaction products and unreacted feed components. The output stream 118 may be heated by the exothermic conversion reaction and may be provided to the heat exchanger 108 to provide heat to and increase the temperature of the purified feed stream 114 and cool the output stream 118. The cooled output stream may be provided to the butadiene extraction unit 106 for extraction of the 1,3-butadiene. Accordingly, the 1-3-butadiene extraction unit may provide a product stream 120 of 1,3-butadiene and a butene stream 122. The butadiene extraction unit 106 may include oil adsorption and extraction separation to purify the 1-3-butadiene from byproducts. A portion 124 of the butene stream 122 may be sent to a purge. As shown in FIG. 1, some or all of the butene stream 122 may be recycled to the feed stream 112.

[0027] It should be appreciated that, the system 100 may include other components. For example, the system may include an acetylenes and aldehydes removal (AAR) bed downstream of the reactor 106. Alternatively, the system 100 may include a KLP-60 (DOW-UOP) catalyst reactor to selectively hydrogenate acetylenics and reduce oxygenates to water and alkanes. As will be appreciated, in such embodiments a promoted palladium (Pd) based catalyst may provide improved reduction of oxygenates to water but may be less selective in taking C4 acetylenics to butenes and 1-3, butadiene as compared to KLP-60.EXAMPLES

[0028] The following examples are included to demonstrate embodiments of the disclosure. It should be appreciated by those of skill in the art that the techniques and compositions disclosed in the example which follows represents techniques and compositions discovered to function well in the practice of the disclosure, and thus can be considered to constitute modes for its practice..

[0029] Examples of the preparation of various catalysts which are used separately or in combination for the catalytic conversion of 2-butene to 1,3-butadiene are described below.Example silica blank

[0030] Silica blanks were prepared by placing a desired amount of Q-10 silica catalyst support manufactured by Fuji Silysia of Kasugai, Aichi, Japan, was placed in a ceramic plate. The Q-10 sample was then calcined at 200°C for about three hours and then at 575°C for about five hours, with a ramping rate of 3°C per minute. The properties of the Q-10 silica catalyst support are shown in Table 1: Table 1: Properties of Q-10 Silica Catalyst Support Average Pore Diameter (millimeters (mm))Pore Volume (milliliters / grams (ml / g))Surface Area (meters-squared / grams) (m 2< / g))Particle Size (mm)Q-10101.003001.18 - 2.36

[0031] FIG. 2 is a plot 200 of x-ray diffraction (XRD) patterns 202 of the prepared silica blank. FIG. 2 depicts the intensity (in arbitrary units) on the y-axis 204 and 2 theta (in degrees) on the x-axis 206. As shown in FIG. 2, the broad peak in 2 theta from 15° to 30° is due to the silica support.

[0032] The Brunauer-Emmett-Teller (BET) theory was used to determine the surface area and pore volume of the silica blank and the prepare catalysts described supra. Table 2 depicts the BET results for the surface area and volume of the prepared silica blank: Table 2: BET Surface Area and Pore Volume for Silica Blank SampleBET Surface Area (m 2< / g)Pore Volume (cm 3< / g)Silica blank304.411.13 Example preparation of silica support impregnated with a tungsten precursor

[0033] 2 grams of the silica blank prepared in the manner described above were placed in an 80 ml beaker. 0.235 g of ammonium metatungstate hydrate having 99.99% trace metals was weighted out and mixed with 2 ml of deionized (DI) water. The ammonium metatungstate hydrate and DI water solution was added dropwise to the silica blank. In a typical example, 5 drops of the ammonium metatungstate hydrate and DI water solution were placed on the silica blank. A glass rod was used to thoroughly mix the support. Next, the catalyst was placed in a drying oven overnight at about 80°C. The dried catalyst was then calcined at about 250°C for about 2 hours and at about 550°C for about 8 hours, with ramping rate of about 1°C per minute until the first temperature was reached and about 3°C until the second temperature was reached. The resulting catalyst had about 10 weight (wt) % tungsten loaded on the silica blank support.

[0034] FIG. 3 is a plot 300 of x-ray diffraction (XRD) patterns for the prepared WO 3 / Si catalyst and the WO 3 . FIG. 3 depicts the intensity (in arbitrary units) on the y-axis 302 and 2 theta (in degrees) on the x-axis 304. The XRD pattern for the WO 3 / Si catalyst is depicted by line 306, and the XRD pattern for WO 3 (from the ammonium metatungstate hydrate bottle after calcination at about 550°C for about 2 hours at a ramping rate of about 1°C). Thus, the pattern shown by line 308 does not contain any silica, only calcined ammonium metatungstate.

[0035] The BET theory was used to determine the surface area and pore volume of the prepared WO 3 / Si catalyst. Table 2 depicts the BET results for the surface area and volume of the prepared WO 3 / Si catalyst: Table 3: BET Surface Area and Pore Volume for WO 3 / Si catalyst SampleBET Surface Area (m 2< / g)Pore Volume (cm 3< / g)WO 3 / Si catalyst274.350.81

[0036] As compared to the silica blank, the surface area and pore volume is slightly reduced after the tungsten is loaded onto the support.Example preparation of MgO commercial catalyst

[0037] Commercial MgO was obtained from Sigma-Aldrich. The MgO was Lot# MKBQ2256V with ≥99% trace metals basis obtained from Sigma-Aldrich Corporation of St. Louis, Missouri, USA. 4g of the commercial MgO was calcined under air at a rate of about 2°C / minute until it reached about 550°C. The temperature was held at about 550°C for about 150 minutes. Following calcination, the commercial MgO was allowed to slowly cool to room temperature inside the calcination oven.

[0038] FIG. 4 is a plot 400 of x-ray diffraction (XRD) patterns 402 of the MgO catalyst prepared from the commercially available MgO FIG. 4 depicts the intensity (in arbitrary units) on the y-axis 404 and 2 theta (in degrees) on the x-axis 406. As shown in FIG. 4, the diffraction peaks corresponding to crystalline MgO can be observed at 2 theta values of 37.0°, 43.0°, 62.4°, 74.8°, and 78.7°. At calcination temperatures greater than about 400°C, the Mg(OH) 2 is mostly or completely converted to MgO. Thus, the greater the calcination temperature, the calcination time, or both, the sharper the diffraction peaks (that is, the greater the intensity).

[0039] BET theory was used to determine the surface area and pore volume of the MgO catalyst prepared from the commercially available MgO. Barrett-Joyner-Halenda (BJH) analysis was also used to estimate the surface area of the prepared MgO catalyst. Table 4 depicts the BET results for the surface area and pore volume and the BJH results for pore volume for the prepared MgO catalyst: Table 4: BET Surface Area, BJH Surface Area, and Pore Volume for MgO catalyst SampleBET Surface Area (m 2< / g)BJH Surface Area (m 2< / g)Pore Volume (cm 3< / g)MgO catalyst60.58574.670.289 Example preparation of MgO using co-precipitation

[0040] MgO was also prepared using a co-precipitation technique as an alternative to prepare the MgO catalyst. 25.64 g of magnesium nitrate hexahydrate ([MgO(NO 3 )·H 2 O]) was mixed with 100 ml of DI water in a beaker. In another beaker, 100 ml of DI water was added. The solution in the first beaker was then added dropwise using a pipette to the second beaker containing only DI water. A magnetic stirrer was placed inside the beaker and set to stir at about 600 revolutions-per-minute (600 rpm). Ammonium hydroxide was simultaneously added dropwise to the solution while the solution was being stirred to maintain the pH of the solution in the range of about 11 to about 12. After adding the magnesium nitrate hexahydrate, the solution was left to stir for an hour at about 600 rpm. The solution was then centrifuged and washed using DI water for about 4 or 5 times. A white solid was collected and dried in a drying oven overnight at 80°C. The dried solid was calcined under air at a rate of about 2°C / minute until it reached about 550°C. The temperature was held at about 550°C for about 150 minutes. Following calcination, the co-precipitated MgO was allowed to slowly cool to room temperature inside the calcination oven.Example preparation of MgO by hydrating commercial MgO

[0041] MgO was also prepared by hydrating commercially available MgO as an alternative to prepare the MgO catalyst and enhance the properties of the MgO. The hydration was performed by converting the commercially available MgO to Mg(OH) 2 and then calcining the Mg(OH) 2 under air to convert it back to MgO.

[0042] The commercially available MgO was Lot# MKBQ2256V with ≥99% trace metals basis obtained from Sigma-Aldrich Corporation of St. Louis, Missouri, USA. About 24.00g of the commercially available MgO was weighed out and added to a 500 ml round-bottom flask. About 300 ml of water was added to the MgO, and the solution was vigorously shaken for about 5 minutes. The round-bottom flask was then connected to rotary evaporator apparatus which was run at about 171 rpm in a water bath which was maintained at a temperature in the range of about 80°C to about 95°C under a vacuum of about 295 mbar, while maintaining a coolant at about -14.4°C (6°F). All the water was evaporated for a time period of up to about 4 hours. After evaporating all of the water, the round-bottom flask was placed in a drying oven overnight, which operated between about 80°C to about 100°C. A solid was collected and calcined under air at a rate of about 2°C / minute until it reached about 550°C. The temperature was held at about 550°C for about 150 minutes. Following calcination, the hydrated MgO was allowed to slowly cool to room temperature inside the calcination oven.Catalyst testing

[0043] The prepared catalysts were tested for their activity and selectivity in a fixed bed continuous flow reactor at atmospheric pressure. The fixed bed continuous flow reactor had an inner diameter of 0.25 inches (0.635 cm) and was obtained from Autoclave Engineers Ltd. A 2 ml sample of each catalyst was loaded into the reactor for each test. The bottom of the reactor was packed with 14 g of Grade 20 silicon carbide (SiC20), as shown in Table 5. The silicon carbide was used to hold the catalyst in place in the isothermal zone and does not contribute to the reaction. Different loading configurations and catalyst amounts were tested. The different loading configurations and catalyst amount combinations may be referred to as Schemes A-E and Scheme MgO and are shown in Table 5. Schemes A and E are in accordance with the presently claimed invention. Schemes B, C, D and (MgO) are provided as reference examples for the purposes of better understanding the presently claimed invention: Table 5: Loading Configurations and Catalyst Amounts Scheme A B C D E (MgO) Layering / Mixed (Top to bottom configuration)Glass WoolGlass WoolGlass WoolGlass WoolGlass WoolGlass WoolWO3 / SiO2 (1 ml)WO3 / SiO2 (2 ml)MgO (1 ml)WO3 / SiO2 (1 ml)MgO (2 ml)MgO (1 ml)Glass WoolWO3 / SiO2 (2 ml)MgO (1 ml mixedMgO (2ml)Glass WoolWO3 / SiO2 (1 ml)SiC20Glass Woolwith WO3 / SiO2WO3 / SiO2 (1ml)SiC20Glass WoolGlass WoolSiC20Glass WoolGlass WoolGlass WoolSiC20Glass WoolSiC20SiC20Glass WoolGlass WoolGlass Wool

[0044] The tested catalysts were pretreated and activated under about 25 standard cubic centimeter per minute (sccm) at about 550°C for about 60 minutes. The ramping time to 550°C was about 90 minutes. A gas hourly space velocity (GHSV) of 900 inverse hours (h -1< was maintained using a 2-butene feed at about 5 ml / min with air as an oxidant and diluent at about 25 ml / min. The 2-butene feed to the reactor includes a weight ratio of cis-2-butene to trans-2-butene of 50:50. The quantitative analysis of the reaction products was performed online using an Agilent GC-7890B gas chromatograph (GC) with an HP-Al / KCL (50m x 0.53mm x 15microns) column, manufactured by Agilent Technologies of Santa Clara, CA. The GC was equipped with a flame ionization detector (FID).

[0045] The conversion of 2-butene was determined using Equation 1: X i = n ˙ i , in − n ˙ i , out n ˙ i , in = 1 − n ˙ i , out n ˙ i , in

[0046] Where X is the conversion and n is the number of moles of 2-butene (including both cis- and trans-2-butene).

[0047] The selectivity was determined using Equation 2: Selectivity = Yield of Product Conversion × 100

[0048] Scheme A from Table 5 was run at three temperatures of about 450°C, about 500°C, and about 550°C for about 3.5 hours at each temperature consecutively for a total of about 12 hours. Table 6A shows the reaction temperature, time on stream (TOS in hours:minutes:seconds (hr:min:s)), yields (in mole %) for each product, and Table 6B shows reaction temperature, TOS, and the conversion rate, and the 1,3-butadience selectivity for each temperature: Table 6A: Reaction Temperature, Time on stream (TOS), and product yields for Scheme A Temp (°C) TOS (hr:min:s) Trans-2-butene 1-Butene IsoButylene Cis-2-butene 1,3-BD 4500:38:2238.318125.34960.258428.09817.74854501:25:1838.058425.04040.182728.02838.45874502:12:1437.952124.66340.157928.07138.91854502:59:1237.951224.49360.146227.92359.1139477.83:46:1036.991624.46550.159927.269910.58525004:33:0733.601124.63830.265125.187515.54285005:20:0232.917624.43890.258724.897716.59925006:06:5832.885224.48440.238224.69916.97425006:53:5632.744724.30430.227524.561817.45845187:40:5332.16424.07040.222324.151118.38395508:27:4928.196822.76960.27921.537524.8095509:14:4727.702222.35650.249621.009626.141255010:01:4127.926622.16230.225321.118325.854755010:48:3928.206121.98430.209221.552725.151653311:35:3628.629521.88530.198521.810924.5762 Table 6B: Conversion Rate and 1,3-BD Selectivity for Scheme A Temp (°C) TOS (hr:min:s) Conversion 1,3-BD Selectivity 4500:38:2233.583823.072135974501:25:1833.913324.942131854502:12:1433.976626.248947814502:59:1234.125326.70716448477.83:46:1035.738529.618478675004:33:0741.211437.714807075005:20:0242.184739.348863455006:06:5842.415840.018577985006:53:5642.693540.892407515187:40:5343.684942.082962315508:27:4950.265749.355723685509:14:4751.288250.9692287955010:01:4150.955150.7401614455010:48:3950.241250.0617023553311:35:3649.559649.58918151

[0049] Table 7A shows, for each reaction temperature, the average yields for each product, and Table 7B shows, for each reaction temperature, the average conversion rate, and the average butadiene selectivity, based on the data from Tables 6A and 6B: Table 7A: Average product yields for Scheme A # of data points, n=Temp (°C)Trans-2-butene1-ButeneIsoButyleneCis-2-butene1,3-BD445038.0699524.886750.186328.03038.5599450033.0371524.466480.24737524.836516.64365455028.0079322.318180.24077521.3045325.48913 Table 7B: Average Conversion Rate and 1,3-BD Selectivity for Scheme A # of data points, n=Temp (°C)Conversion1,3-BD Selectivity445033.8997525.2426450042.1263539.49366455050.6875550.2817

[0050] Upon running the test of Scheme A, it was observed that a period of time elapses after the 2-butene feed stream is run before the 1,3-butadiene yield begins to increase, especially at the lower testing temperatures. This period of time is more pronounced with the catalyst that includes MgO. To speed up the production of 1,3-butadiene, the reaction temperature may be increased to about 550°C and then reduced.

[0051] It was also observed that running the reaction at 550°C for an extended period time deactivates the catalyst. The optimal reaction temperature was thus determined to be in the range of about 450°C to about 500°C for the catalyst system of Scheme A.

[0052] The addition of more MgO (in the ratio of about 1:1, about 2:1, and about 3:1 of MgO to WO 3 / SiO 2 ) may increase the stability and slowdown the deactivation of the catalyst.

[0053] In Scheme B from Table 5, MgO was removed from the catalyst system and the WO 3 / SiO 2 was tested individually by loading about 2 ml of WO 3 / SiO 2 in the reactor. Scheme B from Table 5 was run at a temperature of about 500°C. Table 8A shows the reaction temperature, time on stream (TOS), yields (in mole %) for each product, and Table 8B shows reaction temperature, TOS, and the conversion rate, and the 1,3-butadience selectivity: Table 8A: Reaction Temperature, Time on stream (TOS), and product yields for Scheme B Temp (°C) TOS (hr:min:s) Trans-2-butene 1-Butene IsoButylene Cis-2-butene 1,3-BD 5000:36:2534.08721.9230.21223.50916.8025001:23:2138.26122.637Less than 0.226.73412.3685002:10:1738.40722.87227.45711.2645002:57:1738.69923.02127.70410.5765003:44:1539.00523.12927.85510.0125004:31:1239.03823.11528.269.5885005:18:1139.25923.18828.3469.207 Table 8B: Average Conversion Rate and 1,3-BD Selectivity for Scheme B Temp (°C) TOS (hr:min:s) Conversion 1,3-BD Selectivity 5000:36:2542.40539.6235001:23:2135.00535.3325002:10:1734.13732.9985002:57:1733.59731.4795003:44:1533.1430.215004:31:1232.70229.3185005:18:1132.39628.421

[0054] As shown in Tables 8A and 8B, the conversion, 1,3-butadiene selectivity, and the 1,3-butadiene yield decrease at a faster rate than the catalyst system of Scheme A having the dual catalysts. The MgO catalyst appeared to stabilize the reaction and reduce catalyst deactivation.

[0055] WO 3 / SiO 2 was removed from the catalyst system and MgO was tested individually to observe the contribution of MgO to the oxidative dehydrogenation. About 2 ml of MgO was loaded in the reactor, and the individual MgO was run at three temperatures of about 450°C, about 500°C, and about 550°C. Table 9A shows the reaction temperature, time on stream (TOS), yields (in mole %) for each product, and Table 9B shows reaction temperature, TOS, and the conversion rate, and the 1,3-butadience selectivity: Table 9A: Reaction Temperature, Time on stream (TOS), and product yields for MgO individually Temp (°C) TOS (hrs:mins : sec) Methane Ethane Trans-2-butene 1-Butene IsoButylene Cis-2-butene 1,3-BD 4000:46:590050.8491.703046.5860.8624001:34:020050.7311.290047.1560.8234002:21:020050.5211.177047.4840.8174003:08:020050.6961.136047.3590.8094003:55:050050.4901.090047.6310.7904004:42:080050.4851.096047.6300.7894305:29:040049.6341.880046.6671.8194506:16:050048.9472.747045.3682.9394507:03:020048.9702.773045.3252.9334507:50:000049.4042.815044.8962.8844508:36:570050.2852.967043.8892.8594509:23:560050.1273.119043.9062.84945010:10:530049.8683.320043.9762.83650010:57:500047.7347.262039.8895.11550011:44:470.1300.14146.5067.009039.4336.78250012:31:470.1280.13547.0975.645040.0676.92950013:18:460.1260.13247.1865.219040.3077.03150014:05:420.1290.13247.4205.086040.0847.14950014:52:420.1300.13047.2655.123040.1397.21450015:39:370.1300.13547.1755.166040.1607.235 Table 9B: Average Conversion Rate and 1,3-BD Selectivity for MgO individually Temp (°C) TOS (hrs:mins : sec) Conversion 1,3-BD Selectivity 4000:46:592.56533.6084001:34:022.11338.9344002:21:021.99540.9794003:08:021.94541.5734003:55:051.88042.0364004:42:081.88541.8514305:29:043.69949.1774506:16:055.68551.6864507:03:025.70651.4024507:50:005.69950.6044508:36:575.82649.0704509:23:565.96747.73545010:10:536.15646.07150010:57:5012.37741.32950011:44:4714.06148.22850012:31:4712.83653.98050013:18:4612.50756.21450014:05:4212.49657.21250014:52:4212.59657.26850015:39:3712.66657.120

[0056] As shown in Tables 9A and 9B, the contribution of MgO does not become significant until the reaction temperature reaches about 500°C; however, MgO also deactivates at that temperature. The catalyst removed from the reactor after the testing of MgO individually was observed to be dark black and showed coke. The other catalysts removed from the other experiments of Scheme A and Scheme B were observed to be light to dark grey.

[0057] In Scheme C from Table 5, the MgO was placed on top of the WO 3 / SiO 2 (as opposed to the MgO sandwiched between two layers of WO 3 / SiO 2 as in Scheme A). As shown in Table 5, about 2 ml of WO 3 / SiO 2 and 1 ml of MgO were loaded in the reactor. The rest of the layers in Scheme C were identical to Scheme A. Scheme C from Table 5 was run at a temperature of about 500°C for about 5 hours. Table 10A shows the reaction temperature, time on stream (TOS), yields (in mole %) for each product, and Table 10B shows reaction temperature, TOS, and the conversion rate, and the 1,3-butadience selectivity: Table 10A: Reaction Temperature, Time on stream (TOS), and product yields for Scheme C Temp (°C) TOS (hrs:min:s) Trans-2-butene 1-Butene IsoButylene Cis-2-butene 1,3-BD 5000:50:0033.39218.515024.58822.9835001:36:5933.94818.152025.04622.4865002:23:5834.52317.648025.3622.0995003:10:5735.01317.335025.66121.6295003:57:5436.31420.676026.39919.368 Table 10B: Average Conversion Rate and 1,3-BD Selectivity for Scheme C Temp (°C) TOS (hrs:min:s) Conversion 1,3-BD Selectivity 5000:50:0042.0254.6955001:36:5941.00654.8365002:23:5840.11755.0865003:10:5739.32654.9985003:57:5437.2951.939

[0058] Table 11A shows the average yields for each product, and Table 11B shows the average conversion rate, and the average butadiene selectivity, based on the data points at the reaction temperature, based on the data from Tables 10A and 10B: Table 11A: Average product yields for Scheme C # of data points, n = Temp (°C) Trans-2-butene 1-Butene IsoButylene Cis-2-butene 1,3-BD 550034.63818.465025.41121.113 Table 11B: Average Conversion Rate and 1,3-BD Selectivity for Scheme C # of data points, n = Temp (°C) Conversion 1,3-BD Selectivity 550039.95252.702

[0059] As shown in Tables 10B and 11B, placing the MgO catalyst on top of the WO 3 / SiO 2 catalyst increased the 1,3-butadiene selectivity at 500°C while not significantly changing the conversion as compared to Scheme A. However, the catalyst in Scheme C deactivated faster than the catalyst used in Scheme A; however, the rate of deactivation was slower than the catalyst used in Scheme B (the catalyst without MgO).

[0060] In Scheme D from Table 5, the MgO was physically mixed with the WO 3 / SiO 2 catalyst. Scheme D from Table 5 was run at a temperature of about 450°C for about 5 hours. Table 12A shows the reaction temperature, time on stream (TOS), yields (in mole %) for each product, and Table 12B shows reaction temperature, TOS, and the conversion rate, and the 1,3-butadience selectivity: Table 12A: Reaction Temperature, Time on stream (TOS), and product yields for Scheme D Temp (°C) TOS (hrs:mins:s) Trans-2-butene 1-Butene IsoButylene Cis-2-butene 1,3-Butadiene 4500:45:0838.007425.28480.266327.80478.36054501:31:2137.864925.3230.236727.86888.4344502:17:4237.939825.24750.21327.92528.20494503:04:0038.049225.27780.197627.86818.14544503:50:1638.122625.17380.182127.96568.0944504:36:3038.113625.15280.175927.97498.1011 Table 12B: Reaction Temperature, Time on stream (TOS), and product yields for Scheme D Temp (°C) TOS (hrs:mins:s) Conversion 1,3-BD Selectivity 4500:45:0834.187924.4554501:31:2134.266326.1394502:17:4234.13524.0374503:04:0034.082723.8994503:50:1633.911823.8684504:36:3033.911523.889

[0061] Table 13A shows the average yields for each product, and Table 13B shows the average conversion rate, and the average butadiene selectivity, based on the data points at the reaction temperature, based on the data from Tables 12A and 12B: Table 13A: Average product yields for Scheme D # of data points, n = Temp (°C) Trans-2-butene 1-Butene IsoButylene Cis-2-butene 1,3-BD 645038.01625.2430.21227.9018.223 Table 13B: Average Conversion Rate and 1,3-BD Selectivity for Scheme D # of data points, n = Temp (°C) Conversio n 1,3-BD Selectivity 645034.08324.128

[0062] As shown in Tables 12A, 12B, 13A, and 13C, the performance of the catalysts in Scheme D was similar to that catalyst system in Scheme A. In both schemes, testing was performed at about 450°C and the amount of catalyst was unchanged; the only difference was the layering of the catalyst.

[0063] As shown above, of the layering schemes tested, Schemes A and D were the most stable and produced optimal amounts of 1,3-butadiene without increasing the rate of catalyst deactivation.

[0064] In Scheme E from Table 5, the same layering from Scheme A was used but the amount of the MgO catalyst was doubled. About 2 ml of the MgO catalyst and about 2 ml in the WO 3 / SiO 2 catalyst was loaded in the reactor. Scheme E was run at a temperature of about 450°C for about 5 hours. Table 14A shows the reaction temperature, time on stream (TOS), yields (in mole %) for each product, and Table 14B shows reaction temperature, TOS, and the conversion rate, and the 1,3-butadience selectivity: Table 14A: Reaction Temperature, Time on stream (TOS), and product yields for Scheme E Temp (oC) TOS (hrs:mins: s) Ethylen e Trans-2-butene s 1-Buten e IsoButylen e Cis-2-butene s 1,3-Butadien e 4500:23:430.11938.72224.9270.20628.4917.5354501:10:440.1337.99724.8190.19628.0268.5934501:57:430.12938.00524.671028.0768.8734502:44:430.12737.94324.42028.2029.054503:31:420.12537.98424.25028.2579.1194504:18:400.13138.05424.106028.329.1174505:05:390.16838.3923.929028.8668.379 Table 14B: Reaction Temperature, Time on stream (TOS), and product yields for Scheme E Temp (oC) TOS (hrs:mins:s) Conversion 1,3-BD Selectivity 4500:23:4332.78722.9814501:10:4433.97625.2914501:57:4333.91826.1614502:44:4333.85626.7324503:31:4233.75927.0124504:18:4033.62627.1124505:05:3932.74425.59

[0065] Table 15A shows the average yields for each product, and Table 15B shows the average conversion rate, and the average butadiene selectivity, based on the data points at the reaction temperature, based on the data from Tables 14A and 14B: Table 15A: Average product yields for Scheme E # of data points, n= Temp (oC) Ethylene Trans-2-butene 1-Butene IsoButylene Cis-2-butene 1,3-Butadiene 74500.132738.156424.446110.05747128.319878.666571 Table 15B: Average Conversion Rate and 1,3-BD Selectivity for Scheme E # of data points, n= Temp (oC) Conversion 1,3-BD Selectivity 745033.5237285725.83977

[0066] As shown in Tables 14A, 14B, 15A, and 15B, increasing the amount of MgO catalyst from the 1 ml in Scheme A to the 2 ml in Scheme E did not show any advantages in the 5 hour test runs. However, the increase in the MgO catalyst is expected to reduce the deactivation rate of the WO 3 / SiO 2 catalyst when the reaction is run for a longer time period.

[0067] Ranges may be expressed in the disclosure as from about one particular value, to about another particular value, or both. When such a range is expressed, it is to be understood that another embodiment is from the one particular value, to the other particular value, or both, along with all combinations within said range.

[0068] Further modifications and alternative embodiments of various aspects of the disclosure will be apparent to those skilled in the art in view of this description. Accordingly, this description is to be construed as illustrative only and is for the purpose of teaching those skilled in the art the general manner of carrying out the embodiments described in the disclosure. It is to be understood that the forms shown and described in the disclosure are to be taken as examples of embodiments.

Claims

1. A method for producing 1,3-butadiene, comprising: receiving a feed stream comprising 2-butene; contacting the feed stream with a catalyst in the presence of an oxidant to convert the 2-butene to 1,3-butadiene, the catalyst comprising tungsten oxide impregnated on an inorganic support and magnesium oxide, wherein the catalyst comprises a first layer of the tungsten oxide impregnated on the inorganic support, a second layer of the tungsten oxide impregnated on the inorganic support, and a layer of the magnesium oxide positioned between the first layer and the second layer.

2. The method of claim 1, wherein the feed stream does not include steam.

3. The method of any one of the preceding claims, wherein the oxidant comprises air.

4. The method of any one of the preceding claims, wherein the contacting is performed at a temperature in the range of 400°C to 550°C.

5. The method of any one of the preceding claims, wherein the feed stream comprises 1-butene.

6. The method of any one of the preceding claims, wherein the inorganic support comprises silica.

7. The method of claim 1, wherein the magnesium oxide has a surface area in the range of 30 meters-squared / gram (m2 / g) to 200 m2 / g.

8. The method of claim 1, wherein the volumetric ratio of the magnesium oxide to the tungsten oxide impregnated on the inorganic support is in the range of 1:3 to 3:1.

9. The method of any one of the preceding claims, wherein contacting the feed stream, at a temperature in the range of 400°C to 550°, with a catalyst to convert the 2-butene to 1,3-butadiene achieves a 1,3-butadiene selectivity of at least 23 %.