Process and apparatus for converting aqueous alcohol to ethylene

Abstract

A new process and apparatus for preparing aqueous ethanol for dehydrating ethylene includes distilling aqueous ethanol from water to provide a vapor ethanol stream and charging the ethanol in the vapor phase to an ethanol dehydration reactor to produce ethylene. The process and apparatus reduce heating requirements and eliminate the need for removal of metals and heavy oxygenates present in the fermented aqueous ethanol stream.

Description

[Technical Field]

[0001] The field is the conversion of alcohols to olefins. The field may particularly relate to the dehydration of ethanol to produce ethylene and the subsequent conversion of ethylene to long-chain olefins, and the hydrogenation of the long-chain olefins to produce paraffins. [Background technology]

[0002] Oil and gas refiners worldwide are exploring methodologies and pathways to reduce their carbon footprint in more sustainable processes. The ethanol-to-jet fuel process is one promising pathway to minimize or reduce net carbon dioxide combustion. The end product of this process is jet fuel and diesel fuel produced from bioethanol. Jet fuel is a sustainable aviation fuel intended to replace jet fuel produced from traditional sources such as crude oil.

[0003] The process of converting ethanol into jet fuel involves three main steps: the first step is to dehydrate the ethanol to produce ethylene, the second step is to convert the ethylene to long-chain olefins, and the second step is to hydrogenate the long-chain olefins to produce paraffins.

[0004] Fermentation production of ethanol provides an aqueous ethanol stream containing a large proportion of water, which is largely removed from the ethanol prior to the dehydration step. Ethanol and water form an azeotrope at atmospheric pressure, making it difficult to easily separate more than 95% by weight of alcohol. Purifying the alcohol to contain less than 5% by weight of water requires two-column azeotrope distillation with the addition of an extractant or azeotrope diluent. The aqueous ethanol stream also contains metal contaminants such as sodium, zinc, phosphate, copper, and calcium, as well as heavy oxygenates, also known as fusel oil. Metal contaminants are typically removed by adsorption in a pretreatment step. Heavy oxygenates are typically removed by distillation in a heavy oxygenate removal column upstream of the reactor heater.

[0005] Improved processes for the dehydration of ethanol to ethylene and the preparation of ethanol by removing water are desirable. Summary of the Invention

[0006] A novel process and apparatus for preparing aqueous ethanol for dehydration has been discovered. The process and apparatus envision distilling aqueous ethanol from water to provide a vapor ethanol stream and charging the ethanol in the vapor phase to an ethanol dehydration reactor to produce ethylene. The process and apparatus reduce heating requirements and eliminate the need for removal of metals and heavy oxygenates present in the fermented aqueous ethanol stream. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a schematic process flow diagram of the present disclosure.

[0008] definition The term "communication" means functionally allowing the flow of materials between the listed components.

[0009] The term "downstream communication" means that in downstream communication, at least a portion of the material flowing to the subject is functionally capable of flowing from the object from which it is communicated.

[0010] The term "upstream communication" means that at least a portion of the material flowing from the component of interest in the upstream communication is functionally capable of flowing to the component from which it is communicated.

[0011] The term "direct communication" means that a stream from an upstream component enters a downstream component without passing through a fractionation or conversion unit and undergoing a change in composition by physical fractionation or chemical conversion.

[0012] The term "indirect communication" means that a stream from an upstream component passes through a fractionation or conversion unit and undergoes a change in composition by physical fractionation or chemical conversion before entering a downstream component.

[0013] The term "bypass" means that an object is out of downstream communication with a bypass subject, at least to the extent that it bypasses.

[0014] The term "column" refers to a distillation column or columns for separating one or more components of different volatility. Unless otherwise indicated, each column includes a condenser at the top of the column to condense and reflux a portion of the overhead stream returning to the top of the column, and a reboiler at the bottom of the column to vaporize a portion of the bottom stream and return it to the bottom of the column. The feed to a column may be preheated. The overhead pressure is the pressure of the overhead vapor at the vapor outlet of the column. The bottom temperature is the liquid bottom outlet temperature. The overhead and bottom lines refer to the net lines from column to column downstream of any reflux or reboil. A stripper column may omit the reboiler at the bottom of the column and instead provide the heating requirements and driving force for separation from a fluidized inert medium such as steam. A stripping column typically feeds a top tray and removes the main product from the bottom.

[0015] As used herein, the term "component-rich stream" means that the rich stream exiting the vessel has a higher concentration of the component than the feed to the vessel.

[0016] As used herein, the term "constituent lean stream" means that the lean stream exiting the vessel has a lower concentration of constituents than the feed to the vessel.

[0017] As used herein, the term "separator" means a vessel having an inlet and at least a top vapor outlet and a bottom liquid outlet, and may also have an aqueous outlet from a boot. A flash drum is a type of separator that may be in downstream communication with a separator that may be operated at a higher pressure.

[0018] As used herein, the term "predominant" or "majority" means more than 50%, suitably more than 75%, preferably more than 90%.

[0019] As used herein, "C x " should be understood to refer to a molecule having the number of carbon atoms represented by the "x" subscript. x The term "-" refers to a molecule containing less than or equal to x, preferably x and less, carbon atoms. x The term "+" refers to a molecule having more than or equal to x, preferably x and more, carbon atoms.

[0020] As used herein, the term "carbon number" refers to the number of carbon atoms per hydrocarbon molecule, and typically per paraffin molecule. DETAILED DESCRIPTION OF THE INVENTION

[0021] 1 illustrates a process and apparatus 10 for dehydrating an oxygenate feedstock according to one illustrative embodiment. The oxygenate feedstock may comprise an alcohol, preferably ethanol. The oxygenate feedstock is typically produced from a fermentation process, which also produces a large proportion of water. For example, a fermented alcohol stream may contain greater than 30% water by weight.

[0022] Because the dehydration reaction produces a large proportion of water, it is not necessary to remove water from the reactive oxygenate stream to very low concentrations in order to prepare the alcohol for the catalytic dehydration reaction. Therefore, it is proposed to distill the oxygenate stream to provide an overhead gaseous alcohol stream containing at least 5 wt.% water, and to charge the gaseous alcohol stream to the alcohol dehydration reactor. Because the energy contained in the vapor stream is much higher than that of the condensed liquid stream, it is proposed to retain heat in the gaseous alcohol stream to reduce the heater load required to vaporize the stream to the dehydration reaction temperature along the way.

[0023] Feed line 12 transports an aqueous ethanol oxygenate stream to process and apparatus 10. The aqueous ethanol stream may contain ethanol as a major component and is aqueous containing at least 30% water by weight. Preferably, the aqueous ethanol is a bio-renewable feedstock and / or is produced from an alcoholic fermentation process.

[0024] The aqueous ethanol stream in feed line 12 typically contains metals and heavy oxygenates. Heavy oxygenates, also known as fusel oils, include cyclohexanol, cyclopentanol, and heavier acids. Heavy oxygenates contain at least five carbon atoms. Metal contaminants include sodium, zinc, phosphate, copper, and calcium. Metals are conventionally removed in metal removal adsorbent beds, and heavy oxygenates are conventionally removed in heavy oxygenate removal columns.

[0025] The aqueous ethanol stream containing metals and heavy oxygenates in feed line 12 is fed to ethanol-water azeotropic distillation column 14. Distillation column 14 fractionates into a gaseous ethanol stream in top line 16 extending from the top of the column and a liquid water stream in bottoms line 18 extending from the bottom of the column. A reboil stream may be removed from the water stream in bottoms line 18, reboiled, and returned to the column providing the heating requirements for boiling ethanol from water. A net water stream is taken from the water stream in bottoms line 18 into net bottoms line 20. The net water stream contains all of the metals and heavy oxygenates from the aqueous ethanol stream in feed line 12 produced in distillation column 14. The net water stream contains at least 99% by weight of the heavy oxygenates and at least 99% by weight of the metals in the aqueous ethanol stream in feed line 12.

[0026] The gaseous ethanol stream in overhead line 16 may contain at least 5 wt. % water, suitably at least 7 wt. % water, and preferably at least 10 wt. % water. However, the gaseous ethanol stream may contain up to 21 wt. % water. The gaseous ethanol stream may have up to 1 wt. % heavy oxygenates or metals from the aqueous ethanol stream. Typically, the gaseous ethanol stream has up to 1 ppm heavy oxygenates or metals. As a result, it is not necessary to treat the gaseous ethanol stream in a feed pretreatment section to adsorb metal contaminants or fractionate it in a heavy oxygenate removal column to remove heavy oxygenates.

[0027] A net gaseous ethanol stream in net overhead line 22 can be taken from the gaseous ethanol stream in overhead line 16, while an overhead condenser stream is taken from the gaseous ethanol stream in overhead line 16 in overhead condenser line 24. The overhead condenser stream in line 24 is fully condensed and received in a receiver and then refluxed back to alcohol-water azeotrope column 14. Because higher alcohol purity is not required for the ethanol dehydration reaction, no third component is added to the receiver to break up the azeotrope between alcohol and water.

[0028] Alcohol-water azeotrope column 14 may be operated at about atmospheric pressure, with an overhead temperature of about 60°C (140°F) to about 90°C (194°F) and a bottom temperature of about 90°C (194°F) to about 110°C (230°F). Alternatively, column 14 may be operated at a higher pressure, not less than, and preferably greater than, the dehydration reaction pressure of about 420 kPa (60 psig) to about 700 kPa (100 psig). Preferably, alcohol-water azeotrope column 14 is operated at about 350 kPa (50 psid) to about 560 kPa (80 psid), above the dehydration pressure, to ensure that the gaseous ethanol stream can overcome the system pressure drop and flow through dehydration reactor 34. When operating column 14 at or above the dehydration pressure, the overhead temperature is from about 120° C. (248° F.) to about 180° C. (356° F.) and the bottoms temperature is from about 150° C. (302° F.) to about 210° C. (410° F.). If alcohol-water azeotrope column 14 is operated below atmospheric or reaction pressure, a compressor is required on the net overhead line 22 to compress the net gaseous ethanol stream to the reaction pressure.

[0029] The ethanol recycle stream in line 27 may be combined with the net gaseous alcohol stream in line 22 to provide a charge gaseous ethanol stream in line 28. The charge gaseous ethanol stream in line 28 is split into two charge gaseous ethanol streams. The first charge gaseous ethanol stream in line 30 is heat exchanged with the first dehydration exchange stream in line 32, mixed with steam in line 33, and supplied to a first charge heater 34. The first charge heater 34 may be a combustion heater and can heat the first charge gaseous ethanol stream to about 400°C to about 550°C. Because gaseous ethanol does not require vaporization enthalpy to enter the vapor phase required for the dehydration reaction, a lower heater duty is required to heat the first charge gaseous ethanol stream to the required reaction temperature. The resulting first heated charge gaseous ethanol stream in line 36 is charged to a first dehydration reactor 40. In first dehydration reactor 40, gaseous ethanol is converted to ethylene and water over a dehydration catalyst at a pressure of about 65 psig (455 kPa) (gauge) to about 90 psig (630 kPa) (gauge). A first dehydration stream exits first dehydration reactor 40 in line 42.

[0030] The second charge gaseous ethanol stream in line 44 is heat exchanged with the second dehydration exchange stream in line 46, mixed with the first dehydration stream in line 42, and supplied to a second charge heater 48. The second charge heater 48 may be a combustion heater and can heat the second charge stream to about 400°C to about 550°C. Because gaseous ethanol does not require vaporization enthalpy to enter the vapor phase required for the dehydration reaction, a lower heater duty is required to heat the second charge gaseous ethanol stream to the required reaction temperature. The resulting second heated charge stream in line 50 is supplied to a second dehydration reactor 52. In the second dehydration reactor 52, the ethanol feed is converted to ethylene and water over a dehydration catalyst at a pressure of about 420 kPa (gauge) 60 psig to about 700 kPa (gauge) (100 psig). A second dehydrated stream exits second dehydration reactor 52 in line 54 .

[0031] The second dehydrated stream in line 54 is fed to an intermediate heater 56. The intermediate heater 56 can be a fired heater and can heat the second dehydrated stream to about 400°C to about 550°C. The resulting third heated charge stream in line 58 is fed to a third dehydration reactor 60. In the third dehydration reactor 60, the residual gaseous ethanol feed is converted to ethylene and water over a dehydration catalyst at a pressure of about 420 kPa (gauge) 60 psig to about 700 kPa (gauge) (100 psig). The third dehydrated stream exits the third dehydration reactor 60 in line 62.

[0032] The dehydration catalyst is an alumina-based catalyst.

[0033] The third dehydrated stream is split into a first dehydrated exchange stream in line 32 and a second dehydrated exchange stream in line 46. The first dehydrated exchange stream in line 32 is heat exchanged with the first charge gaseous ethanol stream in line 30, and the second dehydrated exchange stream in line 46 is heat exchanged with the second charge gaseous ethanol stream in line 44, and the cooled dehydrated streams are recombined in line 64.

[0034] The recombined, cooled, dehydrated stream in line 64 is fed to quench tower 68, where the cooled, dehydrated stream is quenched by direct contact with water from a first cooled water stream in line 70 and a second cooled water stream in line 72. A quenched ethylene stream is discharged through quench overhead line 74, and a bottoms stream is discharged in line 76 at the bottom of the tower. The bottoms stream is split into a drain stream in line 78 which can be transported to a wastewater stripper column 80 via a valve thereon, and a quench recycle stream in line 82. A first portion of the quench recycle stream is air cooled in product condenser 69 and recycled through a valve thereon as a first, cooler, cooled water stream in line 70, and a second portion of the quench recycle stream is heat exchanged in trim condenser 71 and recycled to quench tower 68 as a second, warmer, cooled water stream in line 72. Quench tower 68 may be operated at a bottom temperature of about 37°C (100°F) to about 104°C (220°F) and a pressure at the top of about 280 kPa (gauge) (40 psig) to about 490 kPa (gauge) (70 psig).

[0035] The quenched ethylene stream in line 74 is fed to first-stage suction drum 86. In the first-stage suction drum, ethylene exits top line 88 to first-stage compressor 90, while residual water exits the bottom of the drum in line 92 through a control valve thereon and is transported to wastewater stripper column 80, possibly via line 78. First-stage compressor 90 compresses the ethylene stream to a first pressure of about 350 kPa (gauge) (50 psig) to about 1225 kPa (gauge) (175 psig), and the effluent in line 91 is cooled in first-stage effluent cooler 93 and first-stage trim cooler 94.

[0036] The cooled, compressed ethylene stream from first-stage trim cooler 94 is fed to first-stage discharge drum 96. From first-stage discharge drum 96, ethylene exits top line 98 to second-stage compressor 100, while residual water exits the bottom of the drum in line 102 through a control valve thereon and is transported to wastewater stripper column 80, possibly via lines 92 and 78. The second-stage compressor compresses the ethylene stream to a second pressure of about 455 kPa (gauge) (165 psig) to about 3220 kPa (gauge) (460 psig), and the effluent in line 101 is cooled in second-stage effluent cooler 103 and second-stage trim cooler 104.

[0037] The twice-cooled, compressed ethylene stream from second-stage trim cooler 104 is fed to second-stage discharge drum 106. From second-stage discharge drum 106, ethylene exits top line 108 and is transported to water wash column 110, while a residual water stream exits the bottom of the drum in line 112 through a control valve thereon and is transported to wastewater stripper column 80, possibly via lines 102, 92, and 78.

[0038] In water wash tower 110, the twice-cooled and compressed ethylene stream is washed countercurrently with cooled, treated water in line 118 from wastewater stripper column 80, absorbing additional oxygenates to produce a washed ethylene stream discharged in top line 120 and a wash water stream discharged in bottoms line 122. The washed ethylene stream in top line 120 is transported to caustic scrubber column 116. The wash water stream in line 122 is returned to wastewater stripper column 80 through a valve thereon. Water wash tower 110 may be operated at a bottoms temperature of from about 16°C (60°F) to about 82°C (150°F) and a pressure of from about 2800 kPa (gauge) (400 psig) to about 3500 kPa (gauge) (500 psig) at the top.

[0039] Caustic scrubber column 116 has a lower caustic wash section 124 and an upper water wash section 132. In lower caustic wash section 124, the washed ethylene stream in line 120 is scrubbed with an aqueous caustic stream from line 126 to absorb acid gases, such as carbon dioxide, from the washed ethylene stream. Spent caustic is pumped from the bottom of the lower section in line 128 and replenished with fresh caustic in line 130 to provide aqueous caustic stream 126. The scrubbed vapor ethylene stream, with acid gases removed, ascends from caustic wash section 124 through a steam inlet to upper water wash section 132. In water wash section 132, the scrubbed ethylene stream is contacted with a wash water stream from line 134. The washed, scrubbed vapor ethylene stream exits the top of water wash section 132 in line 136 and is fed to product dryer section 140. A spent water stream is removed in line 142 from a liquid sump at the bottom of water wash section 132 and is supplemented with a fresh water stream from line 144 to provide a wash water stream in line 134 which is pumped to the top of water wash section 132 for contact with the scrubbed vapor ethylene stream. The caustic scrubber column may be operated at a bottom temperature of from about 38°C (100°F) to about 43°C (110°F) and a pressure of from about 2800 kPa (gauge) (400 psig) to about 2975 kPa (gauge) (425 psig) at the top.

[0040] In product dryer section 140, the washed and scrubbed ethylene stream in line 136 is fed to a first dryer inlet knockout drum 146 to remove residual water and provide a dryer inlet stream in line 148 and, possibly, a knockout water stream in a bottoms line 150 that is fed to wastewater stripper column 80 via line 122. The dryer inlet stream is fed in line 148 to a first product dryer 152. First product dryer 152 contains an adsorbent for adsorbing water from the ethylene in the dryer inlet stream in line 148 to provide a dry ethylene stream. The adsorbent may be a molecular sieve material having a pore size of 2 to 4 Å. First product dryer 152 may be operated in an upflow mode. Product dryer section 140 may include a second product dryer 156 that operates as first product dryer 142. The two product dryers may be operated in series, but are preferably arranged in lead-lag operation to facilitate regeneration during continuous operation. Second product dryer 156, like first product dryer 152, includes an adsorbent for adsorbing water from the ethylene. A dry ethylene stream exits product dryer section 140 as a dry ethylene stream in line 158. Product dryer section 140 may be operated at a temperature of from about 32°C (90°F) to about 49°C (120°F) and a pressure of from about 2.8 MPa (gauge) (400 psig) to about 3.1 MPa (gauge) (450 psig).

[0041] The dry ethylene stream in line 158 is fed to a dryer outlet knockout drum 160 to remove residual water and provide a dryer outlet stream in line 162 and possibly a second knockout water stream in a bottoms line 164 that is fed to wastewater stripper column 80 via lines 150 and 122.

[0042] The dryer effluent stream in line 162 may be fed to a heavy oxygenate removal column 170 to separate an overhead stream containing primarily ethylene, but possibly higher olefins, from heavy ketones and diethyl ether. Olefins are produced in overhead line 172 and fed to a third-stage compressor 174, and a bottom heavy oxygenate stream is produced in bottom line 176. A heavy oxygenate purge stream may be taken to heavy oxygenate processing in line 178, while the reboiled portion is reboiled and returned to column 170. The compressed ethylene stream in compressor discharge line 176 at a pressure of from about 2800 kPa (gauge) (400 psig) to about 7000 kPa (gauge) (1000 psig) may be provided to the dimerization section. Heavy oxygenate removal column 170 may be operated at a bottom temperature of about −29° C. (−20° F.) to about 121° C. (250° F.) and a top pressure of about 2.4 MPa (gauge) (350 psig) to about 3.1 MPa (gauge) (450 psig).

[0043] The water stream containing oxygenates and volatiles in lines 92, 102, 112, 122, 150, 164 may be fed to wastewater stripper column 80, where the volatiles and oxygenates are boiled off to provide an overhead volatiles stream in line 182 and a stripped water stream in line 184. A portion of the stripped water stream may be reboiled and returned to the column to provide the necessary heat. The treated water stream in line 186 may be pumped to a water outlet, including another water outlet in line 188, and the cooled, treated water stream in line 118 may be sent to water wash tower 110. Wastewater stripper column 80 may be operated at a bottom temperature of from about 93°C (200°F) to about 121°C (250°F) and a pressure of from about 35 kPa (gauge) (5 psig) to about 138 kPa (gauge) (20 psig) at the top.

[0044] The overhead volatiles stream in line 182 may be cooled in air cooler 189 and fed to off-gas knockout drum 190. The overhead stream from knockout drum 190 in line 192 may be sent to a flare, while the ethanol recycle stream is pumped in line 27 to feed surge drum 26, possibly via line 24.

[0045] The disclosed process and apparatus conserves heat in the gaseous ethanol stream to avoid the need to re-vaporize the charged ethanol stream after removing most of the water from the aqueous ethanol stream in alcohol-water azeotrope column 14. Furthermore, by maintaining the overhead ethanol stream in the vapor phase, metals and heavy oxygenates are prevented from entering the gaseous overhead ethanol stream, eliminating the need for a metals pretreatment adsorption unit and heavy oxygenate removal column.

[0046] Specific Embodiments While the following will be described in conjunction with specific embodiments, it will be understood that this description is illustrative of the preceding description and appended claims, and is not intended to limit them.

[0047] A first embodiment of the present disclosure is a process for producing ethylene, comprising: feeding an aqueous ethanol stream to a distillation column to produce a gaseous ethanol stream at the top of the distillation column and a liquid water stream at the bottom of the distillation column; and charging the gaseous ethanol stream to a dehydration reactor containing a dehydration catalyst to convert the ethanol to ethylene. An embodiment of the present disclosure is one, any, or all of the preceding through first embodiments of this paragraph, wherein the aqueous ethanol stream comprises at least 30% water by weight. An embodiment of the present disclosure is one, any, or all of the preceding through first embodiments of this paragraph, wherein the gaseous ethanol stream comprises 21% or less water by weight. An embodiment of the present disclosure is one, any, or all of the preceding through first embodiments of this paragraph, wherein the liquid water stream comprises at least 99% heavy oxygenates and metals by weight. An embodiment of the present disclosure is one, any, or all of the preceding embodiments through the first embodiment of this paragraph, wherein the gaseous ethanol stream comprises at least 5 wt.% water. An embodiment of the present disclosure is one, any, or all of the preceding embodiments through the first embodiment of this paragraph, further comprising charging the gaseous ethanol stream to a dehydration reactor in the vapor phase. An embodiment of the present disclosure is one, any, or all of the preceding embodiments through the first embodiment of this paragraph, wherein the gaseous ethanol stream is compressed to a dehydration reaction pressure. An embodiment of the present disclosure is one, any, or all of the preceding embodiments through the first embodiment of this paragraph, further comprising operating the distillation column at or above the dehydration reaction pressure. An embodiment of the present disclosure is one, any, or all of the preceding embodiments through the first embodiment of this paragraph, wherein the gaseous ethanol stream comprises no more than 1 wt.% heavy oxygenates from the aqueous ethanol stream. An embodiment of the present disclosure is one, any, or all of the preceding embodiment of this paragraph through the first embodiment of this paragraph, wherein the gaseous ethanol stream contains 1% or less by weight of metals from the aqueous ethanol stream.An embodiment of the present disclosure is one, any, or all of the preceding embodiment of this paragraph through the first embodiment of this paragraph, further comprising heating the gaseous ethanol stream to a dehydration temperature.

[0048] A second embodiment of the present disclosure is an apparatus for producing an ethanol stream comprising an alcohol-water distillation column, the apparatus comprising a heater in direct downstream communication with the alcohol-water distillation column, and a catalytic dehydration reactor in direct downstream communication with the heater. An embodiment of the present disclosure is one, any, or all of the preceding embodiment of this paragraph through the second embodiment of this paragraph, in which the heater is in direct downstream communication with the alcohol-water distillation column.

[0049] A third embodiment of the present disclosure is a process for producing ethylene, comprising: feeding an aqueous ethanol stream to a distillation column to produce a gaseous ethanol stream at the top of the distillation column and a liquid water stream at the bottom of the distillation column; and charging the gaseous ethanol stream containing at least 30% water by weight to a dehydration reactor containing a dehydration catalyst to convert the ethanol to ethylene. An embodiment of the present disclosure is one, any, or all of the preceding through third embodiments of this paragraph, wherein the gaseous ethanol stream contains 21% or less by weight of water. An embodiment of the present disclosure is one, any, or all of the preceding through third embodiments of this paragraph, wherein the liquid water stream contains at least 99% by weight of heavy oxygenates and metals. An embodiment of the present disclosure is one, any, or all of the preceding through third embodiments of this paragraph, wherein the gaseous ethanol stream contains at least 5% by weight of water. An embodiment of the present disclosure is one, any, or all of the preceding through third embodiments of this paragraph, further comprising charging the gaseous ethanol stream to the dehydration reactor in the vapor phase. An embodiment of the present disclosure is one, any, or all of the preceding through third embodiments of this paragraph, further comprising compressing the gaseous ethanol stream to the dehydration reaction pressure. An embodiment of the present disclosure is one, any, or all of the preceding through third embodiments of this paragraph, further comprising operating the distillation column at or above the dehydration reaction pressure.

[0050] Without further elaboration, it is believed that, using the preceding description, one skilled in the art can utilize the present invention to its fullest extent and easily ascertain the essential characteristics of the present invention, and can make various changes and modifications to the present invention to adapt it to various uses and conditions, without departing from the spirit and scope of the present invention. The preceding preferred specific embodiments are, therefore, to be construed as merely illustrative, and not limitative of the remainder of the disclosure in any way, and are intended to cover various modifications and equivalent arrangements included within the scope of the appended claims.

[0051] Above, all temperatures are set forth in degrees Celsius and all parts and percentages are by weight unless otherwise indicated.

Claims

1. 1. A process for producing ethylene, comprising: feeding the aqueous ethanol stream to a distillation column to produce a gaseous ethanol stream at the top of the distillation column and a liquid water stream at the bottom of the distillation column; charging said gaseous ethanol stream to a dehydration reactor containing a dehydration catalyst to convert the ethanol to ethylene.

2. 10. The process of claim 1, wherein the aqueous ethanol stream comprises at least 30% by weight water.

3. 10. The process of claim 1, wherein the gaseous ethanol stream contains no more than 21% by weight of water.

4. 10. The process of claim 1, wherein the liquid water stream comprises at least 99% by weight of heavy oxygenates and metals.

5. 10. The process of claim 1, wherein the gaseous ethanol stream comprises at least 5% by weight of water.

6. 10. The process of claim 1, further comprising charging the gaseous ethanol stream to the dehydration reactor in the vapor phase.

7. 10. The process of claim 1, wherein the gaseous ethanol stream is compressed to a dehydration reaction pressure.

8. 10. The process of claim 1 further comprising operating the distillation column at or above the dehydration reaction pressure.

9. 10. The process of claim 1, wherein the gaseous ethanol stream contains no more than 1 wt. % heavy oxygenates from the aqueous ethanol stream.

10. 1. An apparatus for producing an ethanol stream, comprising: an alcohol-water distillation column; a heater in direct downstream communication with the alcohol-water distillation column; a catalytic dehydration reactor in direct downstream communication with said heater.

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