WO2015013427A1 - Method for making 2-methylpentamethylenediamine and adiponitrile with hot ammonia sweep - Google Patents

Method for making 2-methylpentamethylenediamine and adiponitrile with hot ammonia sweep Download PDF

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Publication number
WO2015013427A1
WO2015013427A1 PCT/US2014/047851 US2014047851W WO2015013427A1 WO 2015013427 A1 WO2015013427 A1 WO 2015013427A1 US 2014047851 W US2014047851 W US 2014047851W WO 2015013427 A1 WO2015013427 A1 WO 2015013427A1
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Prior art keywords
reaction
ammonia
mgn
hydrogen
adn
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PCT/US2014/047851
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French (fr)
Inventor
Ferdie J. TOZER
Stewart Forsyth
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INVISTA TECHNOLOGIES SÀRL
Invista Technologies SARL Switzerland
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INVISTA TECHNOLOGIES SÀRL
Invista Technologies SARL Switzerland
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    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C209/00—Preparation of compounds containing amino groups bound to a carbon skeleton
    • C07C209/44—Preparation of compounds containing amino groups bound to a carbon skeleton by reduction of carboxylic acids or esters thereof in presence of ammonia or amines, or by reduction of nitriles, carboxylic acid amides, imines or imino-ethers
    • C07C209/48—Preparation of compounds containing amino groups bound to a carbon skeleton by reduction of carboxylic acids or esters thereof in presence of ammonia or amines, or by reduction of nitriles, carboxylic acid amides, imines or imino-ethers by reduction of nitriles

Definitions

  • the invention relates to hydrogenation of nitriles to amines, including the double hydrogenation of dinitriles to diamines.
  • ADN adiponitrile
  • MGN methylglutaronitrile
  • HMD hexamethylenediamine
  • MPMD 2-methylpentamethylenediamine
  • Useful catalysts include hydrogenation metals with or without inert support.
  • hydrogenation metals examples include nickel, iron and cobalt, including Raney® Ni, with and without additional metals such as cobalt.
  • Iron oxide reduces in a hydrogen atmosphere to make iron metal catalyst with good hydrogenation activity.
  • the metal catalyst would last indefinitely, but it does not - over time under hydrogenation conversion conditions, activity gradually decreases.
  • operators compensate for the loss of catalyst activity by increasing converter inlet temperatures. But the highly exothermic nature of the reaction, coupled with the limited thermal stability of the feed means that converter inlet temperatures can rise only so much before thermal degradation, combined with the exothermic temperature increase across the converters, makes the process uneconomic and difficult to control.
  • ADN adiponitrile
  • MGN methylglutaronitrile
  • HMD hexamethylenediamine
  • MPMD 2- methylpentamethylenediamine
  • MGN methylgluteronitrile
  • MPMD 2- methylpentamethylenediamine
  • ADN adiponitrile
  • HMD hexamethylenediamine
  • the process may further comprise the steps of:
  • first and second reaction cycles of steps (a) and (d) each comprise passing hydrogen and either MGN or ADN and in the presence of ammonia over an iron-containing hydrogenation catalyst in at least three separate reaction zones under conditions sufficient to cause a hydrogenation reaction of MGN or ADN with hydrogen, wherein all of the hydrogen and all of the ammonia are fed to the first reaction zone, and wherein fresh MGN or ADN feed is fed to all three of the reaction zones;
  • step (c) comprises interrupting the flow of either MGN or ADN and hydrogen to each of the reaction zones and flowing hydrogen and ammonia to each of the reactions zones, wherein the hydrogen and ammonia is introduced to each of the reaction zones at a temperature of at least 100°C and a pressure of at least 1000 psig.
  • Step (f) may further comprise interrupting flow of either MGN or ADN when the inlet temperature of at least one of the three separate reaction zones is between 90 and 150°C, for example, between 100 and 145°C, for example between 105 and 130X.
  • the disclosed process may further comprise introducing hydrogen and ammonia to each reaction zone at temperature of between 100 and 150°C and pressure between 1000 and 6000 psig.
  • each reaction zone may operate at temperature of between 105 and 140°C and pressure between 2000 and 5000 psig, for example, temperature of between 105 and 130°C and pressure between 3000 and 4000 psig.
  • the total nitrile feed to the reaction system can suitably be at least 90 wt.% MGN in step (a), for example 95, 99 or 99.5 wt% MGN.
  • the total nitrile feed to the reaction system system can suitably be at least 90 wt.% MGN in step (a), for example 95, 99 or 99.5 wt% MGN.
  • the disclosed process can further comprise:
  • the disclosed process can still further comprise:
  • the process can include measuring outlet temperature of at least one reaction zone.
  • the process can include discontinuing one of the first or second reaction cycles when the outlet temperature a setpoint determined by the thermal stability of at least one reaction product.
  • Effluent from the last hydrogenation reactor can be refined in a single distillation train.
  • the crude effluent can be separated using a pair of parallel refining trains.
  • a first refining train is tailored for treating the hydrogenation products of an ADN-rich feed stream
  • a second refining train is tailored for treating the hydrogenation products of an MGN-rich feed stream.
  • the first and second refining trains are piped and valved so that the crude hydrogenation product stream can be selectively charged to either the first or the second refining train, depending on the nitrile feed.
  • Figure 1 is a simplified schematic process flow diagram illustrating the disclosed process for making diamines.
  • Figure 2 is a simplified schematic process flow diagram illustrating a process for activating (reducing) catalyst useful in the disclosed process.
  • Figure 1 is a diagram showing a four stage conversion process for hydrogenating dinitriles to produce diamines.
  • a source of ammonia is passed through line 2 into ammonia pump 10.
  • a source of hydrogen is also passed through line 4 into hydrogen compressor 14.
  • Ammonia from ammonia pump 10 passes through line 12 into line 18, and hydrogen from hydrogen
  • compressor passes through line 16 into line 18.
  • the ammonia and hydrogen in line 18 is partially heated in heat exchanger 20 before it passes through line 22 to converter preheater 24.
  • the heated ammonia and hydrogen from preheater 24 then passes through a series of four converters, depicted in Figure 1 as converters 42, 44, 46, and 48.
  • a source of dinitrile feed is fed from line 28 into dinitrile pump 30.
  • Dinitrile feed from dinitrile pump 30 passes through line 32 to line 34.
  • a portion of the dinitrile feed may pass through line 34 to the ammonia feed line 2.
  • a portion of the dinitrile feed may also pass from line 34 to line 26 via side stream 36 for introduction into the first stage converter 42.
  • side streams 38 and 40 provide fresh dinitrile feed to the second stage converter 44 and the third stage converter 44.
  • fresh dinitrile feed in line 34 is introduced into the fourth stage converter 48, as depicted in Figure 1.
  • the effluent from the first stage converter 42 passes through line 50 to the second stage converter 44.
  • the effluent from the first stage converter may be cooled in a cooler not shown in Figure 1.
  • the effluent from the second stage converter 44 passes through line 52 to the third stage converter 46.
  • the effluent from the first stage converter may be cooled in a cooler not shown in Figure 1.
  • the effluent from the third stage converter 46 passes through line 54 to heat exchanger 20, where heat from third stage converter effluent is transferred to the feed from line 18.
  • the cooled effluent from the third stage converter 46 then passes through line 56 to the fourth stage converter 48.
  • the effluent from the fourth stage converter 48 passes through line 58 to heat exchanger 60.
  • the cooled effluent then passes from heat exchanger 60 through line 62 to product separator 64. Flash evaporation occurs in product separator 64.
  • the liquid phase, comprising diamine, from the product separator 64 passes through line 66 to heat exchanger 60.
  • the gas phase, comprising hydrogen and ammonia, from the product separator 64 passes through line 86 to gas circulation pump 88 to promote flow of hydrogen and ammonia through line 18.
  • the ammonia recovery system comprises an ammonia recovery column (not shown in Figure 1) and condenser (not shown in Figure 1).
  • a crude product comprising diamine is taken from the bottom of the ammonia column and exits the ammonia recovery system through line 72.
  • the gas phase overhead from the ammonia recovery column passes into a condenser where a distillate phase comprising ammonia and a vapor phase comprising hydrogen is formed.
  • a portion of the distillate phase may be returned to the ammonia recovery column as reflux.
  • a portion of the distillate phase may be transported to at least one storage tank (not shown in Figure 1) for storage.
  • a portion of the distillate phase may also be recycled as ammonia feed to the hydrogenation reaction.
  • this recycle of ammonia is represented by ammonia passing from the ammonia recovery system through line 74 to line 2.
  • the vapor phase from the condenser in the ammonia recovery system 70 passes through line 76 to high pressure absorber 78.
  • This vapor phase comprises hydrogen and residual ammonia.
  • the vapor phase is treated by scrubbing with water from line 80 in the high pressure absorber 78.
  • Aqueous ammonia is removed from the high pressure absorber through line 82.
  • the vapor phase from the high pressure absorber may be recycled as a hydrogen feed by travelling through line 84 to line 4.
  • the vapor phase recovered from the product separator 64 comprises hydrogen and ammonia gas. This vapor phase may pass from the product separator 64 through line 86 to gas circulation pump 88 for recycle into line 18.
  • At least a portion of the vapor phase comprising hydrogen and ammonia in line 76 may be passed through a line not shown in Figure 1 as a feed to a catalyst activation unit for preparing a catalyst by reducing iron oxide with hydrogen.
  • Figure 2 is a diagram showing catalyst activation unit for preparing a catalyst by reducing iron oxide with hydrogen.
  • a first hydrogen source 100 and a second hydrogen source 104 are depicted. However, it will be understood that hydrogen may be supplied from a single source or more than two sources. Hydrogen from the first source 100 passes through line 102, and hydrogen from the second source 104 travels through line 106 to common hydrogen supply line 108.
  • the first hydrogen source 100 comprises at least a portion of vapor phase in line 76 exiting form the ammonia recovery system 70 shown in Figure 1.
  • the second hydrogen source 04 comprises hydrogen from a hydrogen pipeline. When a hydrogen pipeline is used, the hydrogen may be purified, for example, by a pressure swing adsorption treatment. When two sources of hydrogen are used, they may be used simultaneously or intermittently, by stopping the flow of hydrogen from the first source 100, when the second source 104 is used, and vice versa.
  • the hydrogen feed in line 108 is fed to preheater 110, and heated hydrogen is passed through line 112 to hydrogen/ammonia mixer 118.
  • hydrogen/ammonia mixer 118 originates from ammonia source 114.
  • the ammonia feed passes into the hydrogen/ammonia mixer 118 though line 116.
  • the mixed hydrogen/ammonia feed passes through line 120 and 122 into heat exchanger 124 to be heated. The heated
  • hydrogen/ammonia feed then passes through line 126 to preheater 128 for further heating to a temperature suitable for reducing iron oxide.
  • This hydrogen/ammonia feed then passes through line 130 to catalyst activation unit 132 for reducing iron oxide.
  • catalyst activation unit 132 iron oxide is reduced, a portion of the hydrogen in the feed is converted to water and a portion of the ammonia (NH 3 ) is decomposed to form nitrogen (N 2 ) and hydrogen (H 2 ).
  • the effluent from the catalyst activation unit 132 passes through line 134 to heat exchanger, where heat from the effluent is transferred to the hydrogen/nitrogen feed and the effluent is cooled.
  • the cooled effluent is then passed through line 136 to cooler 138 for further cooling.
  • the effluent from cooler 138 passes through line 140 into separator 142, which includes a liquid phase comprising ammonia and water and a gas phase comprising hydrogen, ammonia and nitrogen.
  • the liquid phase passes from separator 142 through line 148 and may be directed to storage tanks not shown in Figure 2.
  • At least a portion of the gas phase from separator 142 is passed by line 144 to compressor 146 and into line 122 for recycle to the catalytic activation unit 132 In order to minimize buildup of nitrogen in the recycle loop, a portion of the gas phase may also be taken from the separator 142 as a purge stream via line 150.
  • This Example describes an embodiment where a catalyst is formed by reducing iron oxide using separate sources of hydrogen and ammonia.
  • hydrogen is supplied from source 104.
  • hydrogen source 104 is not used.
  • the hydrogen supplied from source 104 comes from a hydrogen pipeline, which has been purified by a pressure swing adsorption treatment.
  • the hydrogen in source 104 is pressurized to a pressure of from 200 to 400 psig, for example, from 250 to 350 psig, for example 300 psig. Hydrogen from source 104 is passed, sequentially, through line 102 and line 108 to preheater 110. Heated hydrogen is passed through line 112 to hydrogen/ammonia mixer 118. The ammonia feed to the
  • hydrogen/ammonia mixer 118 originates from ammonia source 114.
  • the ammonia in source 114 is anhydrous, liquid ammonia, pressurized to a pressure 300 to 500 psig, for example, 350 to 450 psig, for example, 400 psig.
  • the ammonia feed passes into the hydrogen/ammonia mixer 118 though line 116.
  • the liquid ammonia fed to the hydrogen/ammonia mixer 118 vaporizes in the presence of hydrogen to form a gaseous hydrogen/ammonia mixture.
  • This mixture may comprise from 96 to 98 wt %, for example, 97 wt %, hydrogen and 2 to 4 wt%, for example, 3 wt %, ammonia.
  • the liquid ammonia may be introduced into the hydrogen/ammonia mixer 118 at an ambient temperature, for example, a temperature of less than 30°C.
  • the hydrogen in preheater 110 is heated to a temperature sufficient to sustain the gaseous state of ammonia in the hydrogen/ammonia mixer 118 and in streams downstream of the hydrogen/ammonia mixer 118.
  • the temperature of hydrogen in line 112 may be at least 120°C, for example, from 120 to 140°C, for example, 130°C.
  • the temperature of the hydrogen/ammonia mixture exiting the hydrogen/ammonia mixer 118 to line 120 may be at least 30°C, for example, from 30 to 50°C, for example, 40°C.
  • the temperature of the hydrogen/ammonia mixture is ramped up to a suitable reaction temperature in two heating steps.
  • a first heating step the mixture passes from line 120 to line 122 into heat exchanger 124.
  • the temperature of the hydrogen/ammonia mixture passes from line 120 to line 122 into heat exchanger 124.
  • hydrogen/ammonia mixture exiting the heat exchanger 124 through line 126 may be, for example, at least 50°C, for example, from 60 to 120°C, for example 90 to 1 10°C, for example 100°C.
  • the temperature of the hydrogen/ammonia mixture exiting preheater 128 into line 130 and into catalyst activation unit 132 may be from 375 to 425°C, for example from 385 to 415°C, for example, from 395 to 405°C, for example 400°C.
  • the pressure of the hydrogen/ammonia mixture entering the catalyst activation unit 132 may be at least 90 psig, for example, from 100 to 130 psig, for example, from 105 to 120 psig, for example 110 psig.
  • the reaction of iron oxide with hydrogen in the catalyst activation unit 132 produces water (H 2 0) as a byproduct. Also, some decomposition of ammonia takes place to produce hydrogen (H 2 ) and nitrogen (N 2 ). Therefore the gaseous effluent, which exits the catalyst activation unit 132 and enters line 134 is a mixture of hydrogen, ammonia, water and nitrogen. The composition of this gaseous mixture depends at least in part on the purity of the hydrogen charged to the catalyst activation unit, and may vary based upon this and the selection of operating conditions.
  • the reduction reaction, which takes place in the catalyst activation unit 132 is endothermic.
  • the temperature of the effluent exiting catalyst activation unit 132 may be from 320 to 370°C, for example, from 330 to 360°C, for example, from 340 to 350°C, for example 345°C.
  • the pressure drop across the catalyst activation unit is generally not critical and in general is relatively minor under normal operating conditions.
  • the temperature of the effluent from the catalyst activation unit is reduced in two steps. In a first step, the temperature of the effluent is partially reduced by passing the effluent through line 134 and through heat exchanger 124.
  • the cooled effluent from the catalyst activation unit 132 is passed from cooler 138 through line 140 into separator 42.
  • separator 142 the effluent form the catalyst activation unit 132 separates at atmospheric pressure into a liquid phase comprising ammonia and water and a gas phase comprising hydrogen and ammonia.
  • the effluent entering separator 142 may be cooled to a temperature of the effluent to 10°C or less, for example, 5°C or less, by means of the heat exchanger 124 and cooler 138.
  • Water, in admixture with ammonia, is removed as the liquid phase from separator 142 through line 148. At least a portion of the gas phase in separator 42 is removed from the separator through line 144 for recycle to the catalytic activation unit 132.
  • the temperature of the gas in line 144 may be 10°C or less, for example, 5°C or less, for example, 2°C.
  • a portion of the gas phase in separator 142 may also be removed via line 150 as a purge stream. By taking a purge from the gas phase of separator 142, the build-up of nitrogen in the recycle loop may be minimized.
  • the gas phase used for recycle passes through line 144 and through compressor 146. In this way the pressure of the gas is increased to the pressure of the gas in lines 120 and
  • This Example describes an embodiment where a catalyst is formed by reducing iron oxide using a single source of hydrogen and ammonia.
  • feed streams comprising dinitrile and both fresh feed and recycled hydrogen and ammonia is passed into a series of four converters 42, 44, 46 and 48.
  • the feed introduced into the first converter comprises hydrogen, ammonia and at least one dinitrile selected from ADN or MGN.
  • the pressure of the feed to the first converter 42 may be at least 3500 psig, for example, at least 4000 psig, for example, at least 4500 psig, for example, at least 5000 psig.
  • the temperature of the feed to the first converter may be at least 100°C, for example at least 105°C, for example, at least 110°C.
  • the reaction of hydrogen with dinitrile in the first converter 42 is exothermic.
  • the temperature of the effluent stream exiting may be at least 5°C, for example, at least 10X, greater than the temperature of the stream entering the first converter 42.
  • the temperature of the stream exiting the first converter 42 should preferably not exceed 140°C, for example,, 135 °C, for example, 130°C.
  • the effluent stream from the first converter 42 is introduced into the second converter 44, it is preferably cooled by at least 5°C, for example, at least 10°C, for example, at least 20°C.
  • This cooling may take place at least in part by passing the effluent from converter 42 into a cooler (not shown in Figure 1) and by introducing a fresh feed of dinitrile (of a temperature less than that of the effluent from converter 42) into line 50 via line 38.
  • the pressure of the feed to the second converter 44 may be at least 3500 psig, for example, at least 4000 psig, for example, at least 4500 psig, for example, at least 5000 psig.
  • the temperature of the feed to the second converter may be at least 100°C, for example at least 105°C, for example, at least 1 10°C.
  • the reaction of hydrogen with dinitrile in the second converter 44 is exothermic. Therefore, the temperature of the effluent stream exiting may be at least 15°C, for example, at least 20°C, greater than the temperature of the stream entering the second converter 44.
  • the temperature of the stream exiting the second converter 44 should preferably not exceed 150 ⁇ 10°C.
  • the temperature delta across the converters is normally 15- 20°C and in general not more than 40°C.
  • the effluent stream from the second converter 44 is introduced into the third converter 46, it is preferably cooled by at least 5°C, for example, at least 10°C, for example, at least 20°C. This cooling may take place at least in part by passing the effluent from third converter 46 into a cooler (not shown in Figure 1 ) and by introducing a fresh feed of dinitrile (of a temperature less than that of the effluent from second converter 44 into line 52 via line 40.
  • the pressure of the feed to the third converter 46 may be at least 3500 psig, for example, at least 4000 psig, for example, at least 4500 psig, for example, at least 5000 psig.
  • the temperature of the feed to the third converter may be at least 100°C, for example at least 105°C, for example, at least 110°C.
  • the reaction of hydrogen with dinitrile in the third converter 46 is exothermic. Therefore, the temperature of the effluent stream exiting may be at least 15°C, for example, at least 20°C, greater than the temperature of the stream entering the third converter 46.
  • the temperature of the stream exiting the third converter 46 should preferably not exceed 140°C, for example, 135°C, for example, 130°C.
  • the effluent stream from the third converter 46 Before the effluent stream from the third converter 46 is introduced into the fourth converter 48, it is preferably cooled by at least 5°C, for example, at least 10°C, for example, at least 20°C. This cooling may take place at least in part by passing the effluent from third converter 48 through line 54 and heat exchanger 20 into line 56 The temperature of the stream in line 56 may be further reduced by introducing a fresh feed of dinitrile (of a temperature less than that of the effluent from third converter 46) into line 56 via line 34.
  • the pressure of the feed to the fourth converter 48 may be at least 3500 psig, for example, at least 4000 psig, for example, at least 4500 psig, for example, at least 5000 psig.
  • the temperature of the feed to the fourth converter may be at least 90°C, for example at least 95°C.
  • the reaction of hydrogen with dinitrile in the fourth converter 48 is exothermic.
  • the temperature of the effluent stream exiting the fourth converter 48 may be at least 15°C, for example, at least 20°C, greater than the temperature of the stream entering the fourth converter 48.
  • the temperature of the stream exiting the fourth converter 48 should preferably not exceed 180°C, for example, 175°C, for example, 165°C.
  • the stream exiting the fourth converter 48 may have a temperature within the range of 140 to 180°C and a pressure within the range of 4100 to 4500 psig.
  • the effluent from the fourth stage converter 48 passes through line 58 to heat exchanger 60.
  • the effluent from fourth converter may be reduced to a temperature range of 30 to 60°C at a pressure of 4100 to 4500 psig in heat exchanger 60.
  • the cooled effluent then passes from heat exchanger 60 through line 62 to product separator 64. Flash evaporation occurs in product separator 64.
  • the pressure of the effluent from the fourth converter 48 may be reduced to a range of 500 to 550 psig to cause separation of a liquid phase and a vapor phase.
  • the liquid phase, comprising diamine, from the product separator 64 passes through line 66 to heat exchanger 60.
  • the liquid phase is heated to a temperature of about 65 to 85°C in the heat exchanger 60.
  • the feed stream in line 68 entering the ammonia recovery system 70 has a temperature of 65 to 85°C and a pressure of 465 to 480 psig.
  • the stream in line 68 may comprise from 55 to 65 wt % ammonia, from 35 to 45 wt % diamine and less than 1 wt %, for example, from 0.1 to 0.5 wt %, hydrogen.
  • the ammonia recovery system 70 comprises an ammonia recovery column (not shown in Figure 1) and condenser (not shown in Figure 1 ).
  • the ammonia recovery column may have a base temperature range of 130 to 160°C but typically operates at 150°C and a head temperature range of 62 to 70°C but typically operates at 67°C.
  • the column operates under a pressure range of 420 to 480 psig.
  • a crude product comprising diamine is taken from the bottom of the ammonia column and exits the ammonia recovery system through line 72.
  • the crude product may comprise at least 90wt% diamine.
  • the crude product may be further refined to remove impurities.
  • the gas phase overhead from the ammonia recovery column passes into a condenser where a distillate phase comprising ammonia and a vapor phase comprising hydrogen is formed.
  • a portion of the distillate phase may be returned to the ammonia recovery column as reflux.
  • a portion of the distillate phase may be transported to at least one storage tank for storage.
  • a portion of the distillate phase may also be recycled as ammonia feed to the hydrogenation reaction.
  • this recycle of ammonia is represented by ammonia passing form the ammonia recovery system through line 74 to line 2.
  • the gas phase, comprising hydrogen and ammonia, from the product separator 64 passes through line 86 to gas circulation pump 88 to promote flow of hydrogen and ammonia through line 18.
  • the gas in line 86 may comprise from 92 to 96 wt % hydrogen (H 2 ) and 4 to 8 wt % ammonia (NH 3 ).
  • a source of ammonia is passed through line 2 and ammonia pump 10 via line 12 into a hydrogen/ammonia recycle stream in line 18.
  • the source of ammonia may also include recycled ammonia introduced into line 2 through line 74.
  • a source of hydrogen is also passed through line 4 into hydrogen compressor 14.
  • Ammonia from ammonia pump 10 passes through line 12 into line 18, and hydrogen from hydrogen compressor passes through line 16 into line 18.
  • the ammonia and hydrogen in line 18 is partially heated in heat exchanger 20 before it passes through line 22 to converter preheater 24.
  • the heated ammonia and hydrogen from preheater 24 then passes through a series of four converters, depicted in Figure 1 as converters 42, 44, 46, and 48.
  • a source of dinitrile feed is fed from line 28 into dinitrile pump 30.
  • Dinitrile feed from dinitrile pump 30 passes through line 32 to line 34.
  • a portion of the dinitrile feed may pass through line 34 to the ammonia feed line 2.
  • a portion of the dinitrile feed may also pass from line 34 to line 26 via side stream 36 for introduction into the first stage converter 42.
  • side streams 38 and 40 provide fresh dinitrile feed to the second stage converter 44 and the third stage converter 46.
  • fresh dinitrile feed in line 34 is introduced into the fourth stage converter 48, as depicted in Figure 1.
  • At least a portion of the vapor phase comprising hydrogen and ammonia in line 76 is passed through a line not shown in Figure 1 as a feed to a catalyst activation unit for preparing a catalyst by reducing iron oxide with hydrogen.
  • This stream may comprise 55 to 65 wt % hydrogen (H 2 ) and 35 to 45 wt % ammonia (NH 3 ).
  • Example 3 is repeated with MGN as the dinitrile feed having the following composition.
  • the pressure in the first converter is about 5000 psig.
  • the temperature of the feed to the first converter is about 10°C. Temperature rises due to the exotherm across the first converter 42. The temperature of the stream exiting the first converter 42 is maintained below about 130°C.
  • the effluent stream from the first converter 42 Before the effluent stream from the first converter 42 is introduced into the second converter 44, it is cooled by least 10 to 20°C by passing the effluent from converter 42 into a cooler and by introducing a fresh feed of dinitrile (of a temperature less than that of the effluent from converter 42) into line 50 via line 38.
  • the pressure of the feed to the second converter 44 is similarly about 5000 psig or slightly less.
  • the temperature of the feed to the second converter is about 1 10°C.
  • the reaction of hydrogen with dinitrile in the second converter 44 is exothermic, and the outlet temperature is controlled not to exceed 130°C.
  • the effluent stream from the second converter 44 is introduced into the third converter 46, it is preferably cooled by about 10 to 20°C. This cooling may take place at least in part by passing the effluent from third converter 46 into a cooler (not shown in Figure 1) and by introducing a fresh feed of dinitrile (of a temperature less than that of the effluent from second converter 44) into line 52 via line 40.
  • the pressure of the feed to the third converter 46 is about 5000 psig or slightly less.
  • the temperature of the feed to the third converter is about 1 10°C.
  • the reaction of hydrogen with dinitrile in the third converter 46 is exothermic. Therefore, the temperature of the effluent stream exiting may be at least 10°C, greater than the temperature of the stream entering the third converter 46.
  • the temperature of the stream exiting the third converter 46 is controlled below about 130°C.
  • the effluent stream from the third converter 46 Before the effluent stream from the third converter 46 is introduced into the fourth converter 48, it is cooled by at least 10 to 20°C. This cooling may take place at least in part by passing the effluent from third converter 48 through line 54 and heat exchanger 20 into line 56. The temperature of the stream in line 56 may be further reduced by introducing a fresh feed of dinitrile (of a temperature less than that of the effluent from third converter 46) into line 56 via line 34
  • the pressure of the feed to the fourth converter 48 is about 4500 psig, or slightly less.
  • the temperature of the feed to the fourth converter may be at least 90°C, for example at least 95°C.
  • the reaction of hydrogen with dinitrile in the fourth converter 48 is exothermic. Therefore, the temperature of the effluent stream exiting the fourth converter 48 may be at least 10°C greater than the temperature of the stream entering the fourth converter 48.
  • the temperature of the stream exiting the fourth converter 48 is controlled below about 130 to 180°C but typically about 140°C, for example within the range of 108 to 125°C, for example 125 to 150°C, for example 150 to 180°C and a pressure within the range of 4100 to 4500 psig.
  • the effluent from the fourth stage converter 48 passes through line 58 to heat exchanger 60.
  • the effluent from fourth converter may be reduced to a temperature range of 30 to 60°C at a pressure of 4100 to 4500 psig in heat exchanger 60.
  • the cooled effluent then passes from heat exchanger 60 through line 62 to product separator 64. Flash evaporation occurs in product separator 64.
  • the pressure of the effluent from the fourth converter 48 may be reduced to a range of 450 to 500 psig to cause separation of a liquid phase and a vapor phase.
  • Effluent temperature of the fourth converter is monitored and recorded, as is the composition of the effluent stream. Inlet temperatures and space velocities across the converter bank are controlled within the disclosed ranges such that at least 95 weight percent of the feed MGN converts to MPMD. Inlet temperatures are gradually increased to meet this target conversion.
  • MGN feed is interrupted.
  • hydrogen and ammonia circulate through the converters at temperature of between about 102 and about 107 °C and pressure of between 3500 and 4000 psig at a flow rate of between about 15 and about 20 kpph for between about 0.5 and 2 hours. This catalyst regeneration procedure is referred to as the "hot ammonia sweep.” Following the hot ammonia sweep, MGN feed is charged again to the process and the cycle is repeated.
  • Example 3 is repeated with ADN as the dinitrile feed having the following
  • Effluent temperature of the fourth converter is monitored and recorded, as is the composition of the effluent stream. Inlet temperatures and space velocities across the converter bank are controlled within the disclosed ranges such that at least 95 weight percent of the feed ADN converts to HMD. Inlet temperatures are gradually increased to meet this target conversion.
  • ADN feed is interrupted.
  • hydrogen and ammonia circulate through the converters at temperature of between about 105 and about 110°C and pressure of between 3500 and 4000 psig at a flow rate of between about 15 and about 20 kpph for between about 0.5 and 2 hours for the hot ammonia sweep (catalyst regeneration step). Following the hot ammonia sweep, ADN feed is charged again to the process and the operation/regeneration cycle is repeated.
  • Examples 4 and 5 are repeated sequentially, with MGN first introduced as the dinitrile feed, then hot ammonia sweep, followed by a shutdown of the synthesis unit to allow a transition to the ADN dinitrile feed.
  • the synthesis unit is then operated using ADN as the dinitrile feed.
  • a catalyst regeneration step is carried out between the alternating dinitrile feeds.
  • Examples 5 and 4 are repeated sequentially, with ADN first introduced as the dinitrile feed, then hot ammonia sweep, followed by a shutdown of the synthesis unit to allow a transition to the MGN dinitrile feed.
  • the synthesis unit is then operated using the MGN as the dinitrile feed.
  • a catalyst regeneration step is carried out between the alternating dinitrile feeds.
  • Example 6 The benefit of the hot ammonia sweep operating experience we have shown in Example 6 has shown the most benefit in terms of reducing undesired side product formation from the hydrogenation of ADN.
  • MGN first dinitrile feed
  • ADN second dinitrile feed

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Abstract

Disclosed is a process for extending the useful life of a hydrogenation catalyst for making diamines in which 2-methylglutaronitrile and adiponitrile are charged separately to the catalyst in sequence with an intervening step of contacting the catalyst with hydrogen and ammonia at elevated temperature.

Description

METHOD FOR MAKING 2-METHYLPENTAMETHYLENEDIAMINE AND ADIPONITRILE WITH HOT AMMONIA SWEEP
Field of the Invention
[0001] The invention relates to hydrogenation of nitriles to amines, including the double hydrogenation of dinitriles to diamines.
Background of the Invention
[0002] Hydrogenating nitriles has long been of commercial interest. For example, adiponitrile (ADN) and methylglutaronitrile (MGN) hydrogenate to hexamethylenediamine (HMD) and 2-methylpentamethylenediamine (MPMD), respectively. These diamines find industrial applicability in a variety of end uses, including as a precursor for nylon-6,6 (in the case of HMD) and a curing agent for expoxies (in the case of MPMD, marketed by INVISTA under the tradename DYTEK® A).
[0003] Useful catalysts include hydrogenation metals with or without inert support.
Examples of such hydrogenation metals include nickel, iron and cobalt, including Raney® Ni, with and without additional metals such as cobalt.
[0004] Iron oxide reduces in a hydrogen atmosphere to make iron metal catalyst with good hydrogenation activity. Ideally, the metal catalyst would last indefinitely, but it does not - over time under hydrogenation conversion conditions, activity gradually decreases. To maintain commercially useful conversion rates across the hydrogenation converters, operators compensate for the loss of catalyst activity by increasing converter inlet temperatures. But the highly exothermic nature of the reaction, coupled with the limited thermal stability of the feed means that converter inlet temperatures can rise only so much before thermal degradation, combined with the exothermic temperature increase across the converters, makes the process uneconomic and difficult to control.
[0005] Faced with the problem of catalyst deactivation, research focused first on methods to quickly and conveniently regenerate the catalyst to maximize stream time and reduce costs. Conventional methods of regenerating the deactivated hydrogenation catalyst included substantially repeating the initial reduction treatment in flowing hydrogen at elevated
temperature. After intensive research and experimentation, we have found a novel method for extending the life of a metal catalyst in nitrile hydrogenation service. Summary of the Invention
[0006] Disclosed is a process for the double hydrogenation of adiponitrile (ADN) and methylglutaronitrile (MGN) to make hexamethylenediamine (HMD) and 2- methylpentamethylenediamine (MPMD), respectively.
[0007] We have found the extent of technical and economic benefits surprising, especially since our method can be implemented in a typical commercial process unit at relatively low cost with reasonably relatively simple retrofitting.
[000B] Disclosed is a process for converting methylgluteronitrile (MGN) to 2- methylpentamethylenediamine (MPMD) and for converting adiponitrile (ADN) to
hexamethylenediamine (HMD) over a catalyst in the same conversion system, said process comprising:
a. running at least a first reaction cycle by passing MGN into the reaction system to convert MGN to MPMD;
b. discontinuing the first reaction cycle of step (a);
c. providing an ammonia treatment step to the reaction system; and
d. running at least a second reaction cycle by passing ADN into the reaction system to convert ADN to HMD.
The process may further comprise the steps of:
e. wherein said first and second reaction cycles of steps (a) and (d) each comprise passing hydrogen and either MGN or ADN and in the presence of ammonia over an iron-containing hydrogenation catalyst in at least three separate reaction zones under conditions sufficient to cause a hydrogenation reaction of MGN or ADN with hydrogen, wherein all of the hydrogen and all of the ammonia are fed to the first reaction zone, and wherein fresh MGN or ADN feed is fed to all three of the reaction zones; and
f. wherein the ammonia treatment of step (c) comprises interrupting the flow of either MGN or ADN and hydrogen to each of the reaction zones and flowing hydrogen and ammonia to each of the reactions zones, wherein the hydrogen and ammonia is introduced to each of the reaction zones at a temperature of at least 100°C and a pressure of at least 1000 psig.
[0009] Step (f) may further comprise interrupting flow of either MGN or ADN when the inlet temperature of at least one of the three separate reaction zones is between 90 and 150°C, for example, between 100 and 145°C, for example between 105 and 130X. [00010] The disclosed process may further comprise introducing hydrogen and ammonia to each reaction zone at temperature of between 100 and 150°C and pressure between 1000 and 6000 psig. For example, each reaction zone may operate at temperature of between 105 and 140°C and pressure between 2000 and 5000 psig, for example, temperature of between 105 and 130°C and pressure between 3000 and 4000 psig.
[00011] For the first reaction cycle (when the feed is predominately methylglutaronitrile (MGN)), the total nitrile feed to the reaction system can suitably be at least 90 wt.% MGN in step (a), for example 95, 99 or 99.5 wt% MGN.
[00012] For the second reaction cycle (when the feed is predominately adiponitrile (ADN), the total nitrile feed to the reaction system system can suitably be at least 90 wt.% MGN in step (a), for example 95, 99 or 99.5 wt% MGN.
The disclosed process can further comprise:
a. discontinuing the second reaction cycle of step (d);
b. providing an ammonia treatment step to the reaction system; and
c. repeating the first reaction cycle by passing MGN into the reaction system to convert MGN to MPMD.
The disclosed process can still further comprise:
d. discontinuing the first reaction cycle;
e. providing an ammonia treatment step to the reaction system; and
f. repeating the second reaction cycle by passing ADN into the reaction system to convert ADN to HMD.
[00013] The process can include measuring outlet temperature of at least one reaction zone. For example, the process can include discontinuing one of the first or second reaction cycles when the outlet temperature a setpoint determined by the thermal stability of at least one reaction product.
[00014] Effluent from the last hydrogenation reactor can be refined in a single distillation train. Alternatively, the crude effluent can be separated using a pair of parallel refining trains. In such an embodiment, a first refining train is tailored for treating the hydrogenation products of an ADN-rich feed stream, while a second refining train is tailored for treating the hydrogenation products of an MGN-rich feed stream. The first and second refining trains are piped and valved so that the crude hydrogenation product stream can be selectively charged to either the first or the second refining train, depending on the nitrile feed. Brief Description of the Drawings
[00015] Figure 1 is a simplified schematic process flow diagram illustrating the disclosed process for making diamines.
[00016] Figure 2 is a simplified schematic process flow diagram illustrating a process for activating (reducing) catalyst useful in the disclosed process.
Detailed Description of the Invention
[00017] Figure 1 is a diagram showing a four stage conversion process for hydrogenating dinitriles to produce diamines.
[00018] In Figure 1 , a source of ammonia is passed through line 2 into ammonia pump 10. A source of hydrogen is also passed through line 4 into hydrogen compressor 14. Ammonia from ammonia pump 10 passes through line 12 into line 18, and hydrogen from hydrogen
compressor passes through line 16 into line 18. The ammonia and hydrogen in line 18 is partially heated in heat exchanger 20 before it passes through line 22 to converter preheater 24. The heated ammonia and hydrogen from preheater 24 then passes through a series of four converters, depicted in Figure 1 as converters 42, 44, 46, and 48.
[00019] A source of dinitrile feed is fed from line 28 into dinitrile pump 30. Dinitrile feed from dinitrile pump 30 passes through line 32 to line 34. A portion of the dinitrile feed may pass through line 34 to the ammonia feed line 2. A portion of the dinitrile feed may also pass from line 34 to line 26 via side stream 36 for introduction into the first stage converter 42. Similarly, side streams 38 and 40 provide fresh dinitrile feed to the second stage converter 44 and the third stage converter 44. Also fresh dinitrile feed in line 34 is introduced into the fourth stage converter 48, as depicted in Figure 1.
[00020] The effluent from the first stage converter 42 passes through line 50 to the second stage converter 44. At a point between the exit point from the first stage converter 42 and the point of introduction of fresh dinitrile feed to line 50 via line 38, the effluent from the first stage converter may be cooled in a cooler not shown in Figure 1.
[00021] The effluent from the second stage converter 44 passes through line 52 to the third stage converter 46. At a point between the exit point from the second stage converter 44 and the point of introduction of fresh dinitrile feed to line 52 via line 40, the effluent from the first stage converter may be cooled in a cooler not shown in Figure 1.
[00022] The effluent from the third stage converter 46 passes through line 54 to heat exchanger 20, where heat from third stage converter effluent is transferred to the feed from line 18. The cooled effluent from the third stage converter 46 then passes through line 56 to the fourth stage converter 48.
[00023] The effluent from the fourth stage converter 48 passes through line 58 to heat exchanger 60. The cooled effluent then passes from heat exchanger 60 through line 62 to product separator 64. Flash evaporation occurs in product separator 64. The liquid phase, comprising diamine, from the product separator 64 passes through line 66 to heat exchanger 60. The gas phase, comprising hydrogen and ammonia, from the product separator 64 passes through line 86 to gas circulation pump 88 to promote flow of hydrogen and ammonia through line 18.
[00024] The liquid phase from the product separator 64, which is heated in heat exchanger 60, passes through line 68 to ammonia recovery system 70. The ammonia recovery system comprises an ammonia recovery column (not shown in Figure 1) and condenser (not shown in Figure 1). A crude product comprising diamine is taken from the bottom of the ammonia column and exits the ammonia recovery system through line 72. The gas phase overhead from the ammonia recovery column passes into a condenser where a distillate phase comprising ammonia and a vapor phase comprising hydrogen is formed. A portion of the distillate phase may be returned to the ammonia recovery column as reflux. A portion of the distillate phase may be transported to at least one storage tank (not shown in Figure 1) for storage. A portion of the distillate phase may also be recycled as ammonia feed to the hydrogenation reaction. In Figure 1 , this recycle of ammonia is represented by ammonia passing from the ammonia recovery system through line 74 to line 2.
[00025] The vapor phase from the condenser in the ammonia recovery system 70 passes through line 76 to high pressure absorber 78. This vapor phase comprises hydrogen and residual ammonia. The vapor phase is treated by scrubbing with water from line 80 in the high pressure absorber 78. Aqueous ammonia is removed from the high pressure absorber through line 82. The vapor phase from the high pressure absorber may be recycled as a hydrogen feed by travelling through line 84 to line 4.
[00026] The vapor phase recovered from the product separator 64 comprises hydrogen and ammonia gas. This vapor phase may pass from the product separator 64 through line 86 to gas circulation pump 88 for recycle into line 18.
[00027] In an optional embodiment, at least a portion of the vapor phase comprising hydrogen and ammonia in line 76 may be passed through a line not shown in Figure 1 as a feed to a catalyst activation unit for preparing a catalyst by reducing iron oxide with hydrogen. [00028] Figure 2 is a diagram showing catalyst activation unit for preparing a catalyst by reducing iron oxide with hydrogen.
[00029] In Figure 2, a first hydrogen source 100 and a second hydrogen source 104 are depicted. However, it will be understood that hydrogen may be supplied from a single source or more than two sources. Hydrogen from the first source 100 passes through line 102, and hydrogen from the second source 104 travels through line 106 to common hydrogen supply line 108. In one embodiment, the first hydrogen source 100 comprises at least a portion of vapor phase in line 76 exiting form the ammonia recovery system 70 shown in Figure 1. In another embodiment, the second hydrogen source 04 comprises hydrogen from a hydrogen pipeline. When a hydrogen pipeline is used, the hydrogen may be purified, for example, by a pressure swing adsorption treatment. When two sources of hydrogen are used, they may be used simultaneously or intermittently, by stopping the flow of hydrogen from the first source 100, when the second source 104 is used, and vice versa.
[00030] The hydrogen feed in line 108 is fed to preheater 110, and heated hydrogen is passed through line 112 to hydrogen/ammonia mixer 118. The ammonia feed to the
hydrogen/ammonia mixer 118 originates from ammonia source 114. The ammonia feed passes into the hydrogen/ammonia mixer 118 though line 116. The mixed hydrogen/ammonia feed passes through line 120 and 122 into heat exchanger 124 to be heated. The heated
hydrogen/ammonia feed then passes through line 126 to preheater 128 for further heating to a temperature suitable for reducing iron oxide. This hydrogen/ammonia feed then passes through line 130 to catalyst activation unit 132 for reducing iron oxide. In catalyst activation unit 132, iron oxide is reduced, a portion of the hydrogen in the feed is converted to water and a portion of the ammonia (NH3) is decomposed to form nitrogen (N2) and hydrogen (H2).
[00031] The effluent from the catalyst activation unit 132 passes through line 134 to heat exchanger, where heat from the effluent is transferred to the hydrogen/nitrogen feed and the effluent is cooled. The cooled effluent is then passed through line 136 to cooler 138 for further cooling. The effluent from cooler 138 passes through line 140 into separator 142, which includes a liquid phase comprising ammonia and water and a gas phase comprising hydrogen, ammonia and nitrogen. The liquid phase passes from separator 142 through line 148 and may be directed to storage tanks not shown in Figure 2.
[00032] At least a portion of the gas phase from separator 142 is passed by line 144 to compressor 146 and into line 122 for recycle to the catalytic activation unit 132 In order to minimize buildup of nitrogen in the recycle loop, a portion of the gas phase may also be taken from the separator 142 as a purge stream via line 150. Abbreviations and Definitions:
ADN = adiponitrile; BD = 1 ,3-butadiene; c2PN = cis-2-pentenenitrile; c3PN = cis-3- pentenenitrile; C8H13C=N = diolefinic acyclic and monoolefinic cyclic mononitrile compounds of the chemical formula C8H13C≡N; C8H14(C=N)2 = monoolefinic acyclic and aliphatic cyclic dinitrile compounds of the chemical formula C8H14(C≡N)2; dinitrile or dinitriles = ADN, MGN, and ESN unless specifically limited; ESN = ethylsuccinonitrile; 2M2BN = 2-methyl-2-butenenitrile including both (E)-2M2BN and (Z)-2M2BN isomers unless specifically limited; 2M3BN = 2- methyl-3-butenenitrile; (E)-2 2BN = (E)-2-methyl-2-butenenitrile; (Z)-2M2BN = (Z)-2-methyl-2- butenenitrile; MGN = 2-methylglutaronitrile; organic mononitrile = an organic compound comprising a single nitrile group, for example a pentenenitrile; organic dinitrile = an organic compound comprising two nitrile groups, for example ADN; pentenenitrile or pentenenitriles = 4PN, 3PN, 2PN, 2M3BN, and 2M2BN isomers unless specifically limited; 2PN = 2-pentenenitrile including both c2PN and t2PN isomers unless specifically limited; 3PN = 3-pentenenitrile including both c3PN and t3PN unless specifically limited; 4PN = 4-pentenenitrile; ppm = parts per million by weight unless stated otherwise; t2PN = trans-2-pentenenitriIe; t3PN = trans-3- pentenenitrile; VN = valeronitrile; MCPD = methylcyclopentane 2,3-diamine. HMD =
hexamethylenediamine, MPMD = methylpentamethylenediamine, 3MP = 3-methylpiperidine, HCN = Hydrogen cyanide
Examples
Example 1
[00033] This Example describes an embodiment where a catalyst is formed by reducing iron oxide using separate sources of hydrogen and ammonia.
[00034] Referring to Figure 2, hydrogen is supplied from source 104. In this Example, hydrogen source 104 is not used. The hydrogen supplied from source 104 comes from a hydrogen pipeline, which has been purified by a pressure swing adsorption treatment.
[00035] The hydrogen in source 104 is pressurized to a pressure of from 200 to 400 psig, for example, from 250 to 350 psig, for example 300 psig. Hydrogen from source 104 is passed, sequentially, through line 102 and line 108 to preheater 110. Heated hydrogen is passed through line 112 to hydrogen/ammonia mixer 118. The ammonia feed to the
hydrogen/ammonia mixer 118 originates from ammonia source 114. The ammonia in source 114 is anhydrous, liquid ammonia, pressurized to a pressure 300 to 500 psig, for example, 350 to 450 psig, for example, 400 psig. The ammonia feed passes into the hydrogen/ammonia mixer 118 though line 116. [00036] The liquid ammonia fed to the hydrogen/ammonia mixer 118 vaporizes in the presence of hydrogen to form a gaseous hydrogen/ammonia mixture. This mixture may comprise from 96 to 98 wt %, for example, 97 wt %, hydrogen and 2 to 4 wt%, for example, 3 wt %, ammonia. The liquid ammonia may be introduced into the hydrogen/ammonia mixer 118 at an ambient temperature, for example, a temperature of less than 30°C. The hydrogen in preheater 110 is heated to a temperature sufficient to sustain the gaseous state of ammonia in the hydrogen/ammonia mixer 118 and in streams downstream of the hydrogen/ammonia mixer 118. For example, the temperature of hydrogen in line 112 may be at least 120°C, for example, from 120 to 140°C, for example, 130°C. The temperature of the hydrogen/ammonia mixture exiting the hydrogen/ammonia mixer 118 to line 120 may be at least 30°C, for example, from 30 to 50°C, for example, 40°C.
[00037] As shown in Figure 2, the temperature of the hydrogen/ammonia mixture is ramped up to a suitable reaction temperature in two heating steps. In a first heating step, the mixture passes from line 120 to line 122 into heat exchanger 124. The temperature of the
hydrogen/ammonia mixture exiting the heat exchanger 124 through line 126 may be, for example, at least 50°C, for example, from 60 to 120°C, for example 90 to 1 10°C, for example 100°C. The temperature of the hydrogen/ammonia mixture exiting preheater 128 into line 130 and into catalyst activation unit 132 may be from 375 to 425°C, for example from 385 to 415°C, for example, from 395 to 405°C, for example 400°C. The pressure of the hydrogen/ammonia mixture entering the catalyst activation unit 132 may be at least 90 psig, for example, from 100 to 130 psig, for example, from 105 to 120 psig, for example 110 psig.
[00038] The reaction of iron oxide with hydrogen in the catalyst activation unit 132 produces water (H20) as a byproduct. Also, some decomposition of ammonia takes place to produce hydrogen (H2) and nitrogen (N2). Therefore the gaseous effluent, which exits the catalyst activation unit 132 and enters line 134 is a mixture of hydrogen, ammonia, water and nitrogen. The composition of this gaseous mixture depends at least in part on the purity of the hydrogen charged to the catalyst activation unit, and may vary based upon this and the selection of operating conditions.
[00039] The reduction reaction, which takes place in the catalyst activation unit 132 is endothermic. The temperature of the effluent exiting catalyst activation unit 132 may be from 320 to 370°C, for example, from 330 to 360°C, for example, from 340 to 350°C, for example 345°C. The pressure drop across the catalyst activation unit is generally not critical and in general is relatively minor under normal operating conditions. [00040] The temperature of the effluent from the catalyst activation unit is reduced in two steps. In a first step, the temperature of the effluent is partially reduced by passing the effluent through line 134 and through heat exchanger 124. In this way, heat is supplied to the hydrogen/ammonia mixture entering the heat exchanger 124 through line 122 and exiting the heat exchanger 124 through line 126. In a second cooling step the partially cooled effluent from the catalyst activation unit 132 is cooled in cooler 138. In this way, the temperature of the effluent is reduced to a temperature sufficient to permit the phase separation, which takes place in separator 140.
[00041] The cooled effluent from the catalyst activation unit 132 is passed from cooler 138 through line 140 into separator 42. In separator 142, the effluent form the catalyst activation unit 132 separates at atmospheric pressure into a liquid phase comprising ammonia and water and a gas phase comprising hydrogen and ammonia. In order to maximize the amount of water in the liquid phase and to minimize the amount of water which remains in the gaseous phase, the effluent entering separator 142 may be cooled to a temperature of the effluent to 10°C or less, for example, 5°C or less, by means of the heat exchanger 124 and cooler 138.
[00042] Water, in admixture with ammonia, is removed as the liquid phase from separator 142 through line 148. At least a portion of the gas phase in separator 42 is removed from the separator through line 144 for recycle to the catalytic activation unit 132. The temperature of the gas in line 144 may be 10°C or less, for example, 5°C or less, for example, 2°C. A portion of the gas phase in separator 142 may also be removed via line 150 as a purge stream. By taking a purge from the gas phase of separator 142, the build-up of nitrogen in the recycle loop may be minimized.
[00043] The gas phase used for recycle passes through line 144 and through compressor 146. In this way the pressure of the gas is increased to the pressure of the gas in lines 120 and
Example 2
[00044] This Example describes an embodiment where a catalyst is formed by reducing iron oxide using a single source of hydrogen and ammonia.
[00045] Referring to Figure 2, hydrogen and ammonia are supplied from source 100. In this Example, hydrogen source 104 and ammonia source 114 are not used. The hydrogen and ammonia supplied from source 100 comes from a portion of vapor phase in line 76 exiting form the ammonia recovery system 70 shown in Figure 1. [00046] With these exceptions, the remainder of the process is carried out in essentially the same manner as the process described in Example 1.
Example 3
[00047] Referring to Figure 1 , feed streams comprising dinitrile and both fresh feed and recycled hydrogen and ammonia is passed into a series of four converters 42, 44, 46 and 48. The feed introduced into the first converter comprises hydrogen, ammonia and at least one dinitrile selected from ADN or MGN. The pressure of the feed to the first converter 42 may be at least 3500 psig, for example, at least 4000 psig, for example, at least 4500 psig, for example, at least 5000 psig. The temperature of the feed to the first converter may be at least 100°C, for example at least 105°C, for example, at least 110°C. The reaction of hydrogen with dinitrile in the first converter 42 is exothermic. Therefore, the temperature of the effluent stream exiting may be at least 5°C, for example, at least 10X, greater than the temperature of the stream entering the first converter 42. The temperature of the stream exiting the first converter 42 should preferably not exceed 140°C, for example,, 135 °C, for example, 130°C.
[00048] Before the effluent stream from the first converter 42 is introduced into the second converter 44, it is preferably cooled by at least 5°C, for example, at least 10°C, for example, at least 20°C. This cooling may take place at least in part by passing the effluent from converter 42 into a cooler (not shown in Figure 1) and by introducing a fresh feed of dinitrile (of a temperature less than that of the effluent from converter 42) into line 50 via line 38.
[00049] The pressure of the feed to the second converter 44 may be at least 3500 psig, for example, at least 4000 psig, for example, at least 4500 psig, for example, at least 5000 psig. The temperature of the feed to the second converter may be at least 100°C, for example at least 105°C, for example, at least 1 10°C. The reaction of hydrogen with dinitrile in the second converter 44 is exothermic. Therefore, the temperature of the effluent stream exiting may be at least 15°C, for example, at least 20°C, greater than the temperature of the stream entering the second converter 44. The temperature of the stream exiting the second converter 44 should preferably not exceed 150±10°C. The temperature delta across the converters is normally 15- 20°C and in general not more than 40°C.
[00050] Before the effluent stream from the second converter 44 is introduced into the third converter 46, it is preferably cooled by at least 5°C, for example, at least 10°C, for example, at least 20°C. This cooling may take place at least in part by passing the effluent from third converter 46 into a cooler (not shown in Figure 1 ) and by introducing a fresh feed of dinitrile (of a temperature less than that of the effluent from second converter 44 into line 52 via line 40. [00051] The pressure of the feed to the third converter 46 may be at least 3500 psig, for example, at least 4000 psig, for example, at least 4500 psig, for example, at least 5000 psig. The temperature of the feed to the third converter may be at least 100°C, for example at least 105°C, for example, at least 110°C. The reaction of hydrogen with dinitrile in the third converter 46 is exothermic. Therefore, the temperature of the effluent stream exiting may be at least 15°C, for example, at least 20°C, greater than the temperature of the stream entering the third converter 46. The temperature of the stream exiting the third converter 46 should preferably not exceed 140°C, for example, 135°C, for example, 130°C.
[00052] Before the effluent stream from the third converter 46 is introduced into the fourth converter 48, it is preferably cooled by at least 5°C, for example, at least 10°C, for example, at least 20°C. This cooling may take place at least in part by passing the effluent from third converter 48 through line 54 and heat exchanger 20 into line 56 The temperature of the stream in line 56 may be further reduced by introducing a fresh feed of dinitrile (of a temperature less than that of the effluent from third converter 46) into line 56 via line 34.
[00053] The pressure of the feed to the fourth converter 48 may be at least 3500 psig, for example, at least 4000 psig, for example, at least 4500 psig, for example, at least 5000 psig. The temperature of the feed to the fourth converter may be at least 90°C, for example at least 95°C. The reaction of hydrogen with dinitrile in the fourth converter 48 is exothermic.
Therefore, the temperature of the effluent stream exiting the fourth converter 48 may be at least 15°C, for example, at least 20°C, greater than the temperature of the stream entering the fourth converter 48. The temperature of the stream exiting the fourth converter 48 should preferably not exceed 180°C, for example, 175°C, for example, 165°C. For example, the stream exiting the fourth converter 48 may have a temperature within the range of 140 to 180°C and a pressure within the range of 4100 to 4500 psig.
[00054] The effluent from the fourth stage converter 48 passes through line 58 to heat exchanger 60. The effluent from fourth converter may be reduced to a temperature range of 30 to 60°C at a pressure of 4100 to 4500 psig in heat exchanger 60. The cooled effluent then passes from heat exchanger 60 through line 62 to product separator 64. Flash evaporation occurs in product separator 64. In the product separator the pressure of the effluent from the fourth converter 48 may be reduced to a range of 500 to 550 psig to cause separation of a liquid phase and a vapor phase.
[00055] The liquid phase, comprising diamine, from the product separator 64 passes through line 66 to heat exchanger 60. The liquid phase is heated to a temperature of about 65 to 85°C in the heat exchanger 60. The feed stream in line 68 entering the ammonia recovery system 70 has a temperature of 65 to 85°C and a pressure of 465 to 480 psig. The stream in line 68 may comprise from 55 to 65 wt % ammonia, from 35 to 45 wt % diamine and less than 1 wt %, for example, from 0.1 to 0.5 wt %, hydrogen.
[00056] The ammonia recovery system 70 comprises an ammonia recovery column (not shown in Figure 1) and condenser (not shown in Figure 1 ). The ammonia recovery column may have a base temperature range of 130 to 160°C but typically operates at 150°C and a head temperature range of 62 to 70°C but typically operates at 67°C. The column operates under a pressure range of 420 to 480 psig. A crude product comprising diamine is taken from the bottom of the ammonia column and exits the ammonia recovery system through line 72. The crude product may comprise at least 90wt% diamine. The crude product may be further refined to remove impurities.
[00057] The gas phase overhead from the ammonia recovery column passes into a condenser where a distillate phase comprising ammonia and a vapor phase comprising hydrogen is formed. A portion of the distillate phase may be returned to the ammonia recovery column as reflux. A portion of the distillate phase may be transported to at least one storage tank for storage. A portion of the distillate phase may also be recycled as ammonia feed to the hydrogenation reaction. In! Figure 1 , this recycle of ammonia is represented by ammonia passing form the ammonia recovery system through line 74 to line 2.
[00058] The gas phase, comprising hydrogen and ammonia, from the product separator 64 passes through line 86 to gas circulation pump 88 to promote flow of hydrogen and ammonia through line 18. The gas in line 86 may comprise from 92 to 96 wt % hydrogen (H2) and 4 to 8 wt % ammonia (NH3).
[00059] A source of ammonia is passed through line 2 and ammonia pump 10 via line 12 into a hydrogen/ammonia recycle stream in line 18. The source of ammonia may also include recycled ammonia introduced into line 2 through line 74. A source of hydrogen is also passed through line 4 into hydrogen compressor 14. Ammonia from ammonia pump 10 passes through line 12 into line 18, and hydrogen from hydrogen compressor passes through line 16 into line 18. The ammonia and hydrogen in line 18 is partially heated in heat exchanger 20 before it passes through line 22 to converter preheater 24. The heated ammonia and hydrogen from preheater 24 then passes through a series of four converters, depicted in Figure 1 as converters 42, 44, 46, and 48.
[00060] A source of dinitrile feed is fed from line 28 into dinitrile pump 30. Dinitrile feed from dinitrile pump 30 passes through line 32 to line 34. In an alternate embodiment, a portion of the dinitrile feed may pass through line 34 to the ammonia feed line 2. A portion of the dinitrile feed may also pass from line 34 to line 26 via side stream 36 for introduction into the first stage converter 42. Similarly, side streams 38 and 40 provide fresh dinitrile feed to the second stage converter 44 and the third stage converter 46. Also fresh dinitrile feed in line 34 is introduced into the fourth stage converter 48, as depicted in Figure 1.
[00061] In an optional embodiment, at least a portion of the vapor phase comprising hydrogen and ammonia in line 76 is passed through a line not shown in Figure 1 as a feed to a catalyst activation unit for preparing a catalyst by reducing iron oxide with hydrogen. This stream may comprise 55 to 65 wt % hydrogen (H2) and 35 to 45 wt % ammonia (NH3).
Examples 4-7
[00062] In each of the following Examples 4-7, catalyst was prepared according to the procedure of Example 2.
Example 4 - MGN Feed
[00063] Example 3 is repeated with MGN as the dinitrile feed having the following composition.
MGN = 99.1 wt% min
ESN = 0.4 wt% max
ADN = 1000 ppm max
HCN = 20 ppm max
Water = 0.12 wt%max
Ethylene glycol = 50 ppm max
Phosphorus = 15 ppm
PBCB = 25 ppm max
Others = 0.7 wt% max
[00064] The pressure in the first converter is about 5000 psig. The temperature of the feed to the first converter is about 10°C. Temperature rises due to the exotherm across the first converter 42. The temperature of the stream exiting the first converter 42 is maintained below about 130°C.
[00065] Before the effluent stream from the first converter 42 is introduced into the second converter 44, it is cooled by least 10 to 20°C by passing the effluent from converter 42 into a cooler and by introducing a fresh feed of dinitrile (of a temperature less than that of the effluent from converter 42) into line 50 via line 38. [00066] The pressure of the feed to the second converter 44 is similarly about 5000 psig or slightly less. The temperature of the feed to the second converter is about 1 10°C. The reaction of hydrogen with dinitrile in the second converter 44 is exothermic, and the outlet temperature is controlled not to exceed 130°C.
[00067] Before the effluent stream from the second converter 44 is introduced into the third converter 46, it is preferably cooled by about 10 to 20°C. This cooling may take place at least in part by passing the effluent from third converter 46 into a cooler (not shown in Figure 1) and by introducing a fresh feed of dinitrile (of a temperature less than that of the effluent from second converter 44) into line 52 via line 40.
[00068] The pressure of the feed to the third converter 46 is about 5000 psig or slightly less. The temperature of the feed to the third converter is about 1 10°C. The reaction of hydrogen with dinitrile in the third converter 46 is exothermic. Therefore, the temperature of the effluent stream exiting may be at least 10°C, greater than the temperature of the stream entering the third converter 46. The temperature of the stream exiting the third converter 46 is controlled below about 130°C.
[00069] Before the effluent stream from the third converter 46 is introduced into the fourth converter 48, it is cooled by at least 10 to 20°C. This cooling may take place at least in part by passing the effluent from third converter 48 through line 54 and heat exchanger 20 into line 56. The temperature of the stream in line 56 may be further reduced by introducing a fresh feed of dinitrile (of a temperature less than that of the effluent from third converter 46) into line 56 via line 34
[00070] The pressure of the feed to the fourth converter 48 is about 4500 psig, or slightly less. The temperature of the feed to the fourth converter may be at least 90°C, for example at least 95°C. The reaction of hydrogen with dinitrile in the fourth converter 48 is exothermic. Therefore, the temperature of the effluent stream exiting the fourth converter 48 may be at least 10°C greater than the temperature of the stream entering the fourth converter 48. The temperature of the stream exiting the fourth converter 48 is controlled below about 130 to 180°C but typically about 140°C, for example within the range of 108 to 125°C, for example 125 to 150°C, for example 150 to 180°C and a pressure within the range of 4100 to 4500 psig.
[00071] The effluent from the fourth stage converter 48 passes through line 58 to heat exchanger 60. The effluent from fourth converter may be reduced to a temperature range of 30 to 60°C at a pressure of 4100 to 4500 psig in heat exchanger 60. The cooled effluent then passes from heat exchanger 60 through line 62 to product separator 64. Flash evaporation occurs in product separator 64. In the product separator the pressure of the effluent from the fourth converter 48 may be reduced to a range of 450 to 500 psig to cause separation of a liquid phase and a vapor phase.
[00072] Effluent temperature of the fourth converter is monitored and recorded, as is the composition of the effluent stream. Inlet temperatures and space velocities across the converter bank are controlled within the disclosed ranges such that at least 95 weight percent of the feed MGN converts to MPMD. Inlet temperatures are gradually increased to meet this target conversion. When the fourth converter effluent 48 reaches 125°C, MGN feed is interrupted. Next, hydrogen and ammonia circulate through the converters at temperature of between about 102 and about 107 °C and pressure of between 3500 and 4000 psig at a flow rate of between about 15 and about 20 kpph for between about 0.5 and 2 hours. This catalyst regeneration procedure is referred to as the "hot ammonia sweep." Following the hot ammonia sweep, MGN feed is charged again to the process and the cycle is repeated.
Example 5 - ADN Feed
[00073] Example 3 is repeated with ADN as the dinitrile feed having the following
composition.
ADN = 99.7 wt% min
Chlorides = 10 ppm Max
2-Cyanocyclopentylidenimine = 75 ppm Max
Cresol = 200 ppm Max
Decenedinitrile (DDN) = 500 ppm Max
Water = 500 ppm Max
2-Methylglutaronitrile (MGN) = 200 ppm
Phosphorus = 10 ppm Max
[00074] Effluent temperature of the fourth converter is monitored and recorded, as is the composition of the effluent stream. Inlet temperatures and space velocities across the converter bank are controlled within the disclosed ranges such that at least 95 weight percent of the feed ADN converts to HMD. Inlet temperatures are gradually increased to meet this target conversion. When the fourth converter effluent 48 reaches about 160°C, ADN feed is interrupted. Next, hydrogen and ammonia circulate through the converters at temperature of between about 105 and about 110°C and pressure of between 3500 and 4000 psig at a flow rate of between about 15 and about 20 kpph for between about 0.5 and 2 hours for the hot ammonia sweep (catalyst regeneration step). Following the hot ammonia sweep, ADN feed is charged again to the process and the operation/regeneration cycle is repeated.
Example 6 - MGN Feed then ADN Feed
[00075] Examples 4 and 5 are repeated sequentially, with MGN first introduced as the dinitrile feed, then hot ammonia sweep, followed by a shutdown of the synthesis unit to allow a transition to the ADN dinitrile feed. The synthesis unit is then operated using ADN as the dinitrile feed. A catalyst regeneration step is carried out between the alternating dinitrile feeds.
Example 7 - ADN Feed then MGN Feed
[00076] Examples 5 and 4 are repeated sequentially, with ADN first introduced as the dinitrile feed, then hot ammonia sweep, followed by a shutdown of the synthesis unit to allow a transition to the MGN dinitrile feed. The synthesis unit is then operated using the MGN as the dinitrile feed. A catalyst regeneration step is carried out between the alternating dinitrile feeds.
Observations and Data Collection for Example 4-7
[00077] The data of Examples 4-7 deviate from expectations. Starting with Examples 4 and 5, the intervening hot ammonia sweep steps appear substantially ineffective for improving catalyst activity and selectivity when the same dinitrile (MGN-MGN for Example 4 or ADN-ADN for Example 5) is charged to the converted before and after the hot ammonia sweep.
[00078] Turning to Examples 6 and 7, the combination of two different dinitriles (MGN-ADN for Example 6 and ADN-MGN for Example 7) separated by hot ammonia sweep are examined.
[00079] The benefit of the hot ammonia sweep operating experience we have shown in Example 6 has shown the most benefit in terms of reducing undesired side product formation from the hydrogenation of ADN. Upon completion of the first dinitrile feed (MGN), then conducting the hot ammonia sweep, followed by the second dinitrile feed (ADN), it was demonstrated that the side product formation from the hydrogenation of ADN was lower due to lower operating inlet temperatures with converters 42, 44, 46 and 48. Undesired Side Product Production - Weight Percent of Total Dinitrile Feed Converted to Products Other than the Corresponding Diamine Following
First Hot Ammonia Sweep
Example Converter No. 4
Number
- MGN/MGN 10
- ADN/AND 15
- MGN/ADN 3
- ADN/MGN 12

Claims

What is claimed is:
1. A process for converting methylglutaronitrile (MGN) to 2-methylpentamethylenediamine (MPMD) and for converting adiponitrile (ADN) to hexamethylenediamine (HMD) over a catalyst in the same conversion system, said process comprising the steps of:
a. running at least a first reaction cycle by passing MGN into the reaction system to convert MGN to MPMD;
b. discontinuing the first reaction cycle of step (a);
c. providing an ammonia treatment step to the reaction system; and
d. running at least a second reaction cycle by passing ADN into the reaction system to convert ADN to HMD.
2. The process of claim 1 :
e. wherein said first and second reaction cycles of steps (a) and (d) each comprise passing hydrogen and either MGN or ADN and in the presence of ammonia over an iron-containing hydrogenation catalyst in at least three separate reaction zones under conditions sufficient to cause a hydrogenation reaction of MGN or ADN with hydrogen, wherein all of the hydrogen and all of the ammonia are fed to the first reaction zone; and
f. wherein the ammonia treatment of step (c) comprises interrupting the flow of either MGN or ADN and hydrogen to each of the reaction zones and flowing hydrogen and ammonia to each of the reactions zones, wherein the hydrogen and ammonia is introduced to each of the reaction zones at a temperature of at least 100°C and a pressure of at least 1000 psig.
3. The process of claim 2 wherein step (f) further comprises interrupting flow of either MGN or ADN when the inlet temperature of at least one of the three separate reaction zones is between 90 and 150°C.
4. The process of claim 2 wherein step (f) further comprises interrupting flow of either MGN or ADN when the inlet temperature of at least one of the three separate reaction zones is between 100 and 145°C.
5. The process of claim 3 wherein step (f) further comprises interrupting flow of either MGN or ADN when the inlet temperature of at least one of the three separate reaction zones is between 105 and 130°C.
6. The process of claim 2 wherein step (f) further comprises introducing hydrogen and ammonia to each reaction zone at temperature of between 100 and 150°C. and pressure between 1000 and 6000 psig.
7. The process of claim 5 wherein step (f) further comprises introducing hydrogen and ammonia to each reaction zone at temperature of between 105 and 140°C and pressure between 2000 and 5000 psig.
8. The process of claim 6 wherein step (f) further comprises introducing hydrogen and ammonia to each reaction zone at temperature of between 105 and 130°C and pressure between 3000 and 4000 psig.
9. The process of claim 1 or 2 wherein the total nitrile feed to the reaction system is at least 90 wt.% MGN in step (a).
10. The process of claim 9 wherein the total nitrile feed to the reaction system is at least 95 wt.% MGN in step (a).
11. The process of claim 10 wherein the total nitrile feed to the reaction system is at least 99 wt.% MGN in step (a).
12. The process of claim 11 wherein the total nitrile feed to the reaction system is at least 99.5 wt% MGN in step (a).
13. The process of claim 1 or 2 wherein the total nitrile feed to the reaction system is at least 90 wt.% AND in step (d).
14. The process of claim 13 wherein the total nitrile feed to the reaction system is at least 95 wt.% MGN in step (d).
15. The process of claim 14 wherein the total nitrile feed to the reaction system is at least 99 wt.% MGN in step (d).
16. The process of claim 5 wherein the total nitrile feed to the reaction system is at least 99.5 wt.% MGN in step (d).
17. The process of claim 1 or 2 further comprising:
a. discontinuing the second reaction cycle of step (d);
b. providing an ammonia treatment step to the reaction system; and
c. repeating the first reaction cycle by passing MGN into the reaction system to convert MGN to MPMD.
18. The process of claim 17 further comprising:
a. discontinuing the first reaction cycle;
b. providing an ammonia treatment step to the reaction system; and
c. repeating the second reaction cycle by passing ADN into the reaction system to convert ADN to HMD.
19. The process of claim 18 further comprising measuring outlet temperature of at least one reaction zone.
20. The process of claim 19 further comprising discontinuing one of the first or second
reaction cycles when the outlet temperature a setpoint determined by the thermal stability of at least one reaction product.
21. The process of claim 1 wherein fresh MGN or ADN feed is fed to all three of the reaction zones.
PCT/US2014/047851 2013-07-25 2014-07-23 Method for making 2-methylpentamethylenediamine and adiponitrile with hot ammonia sweep Ceased WO2015013427A1 (en)

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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3773832A (en) * 1970-01-16 1973-11-20 Du Pont Hydrogenation of adiponitrile over alkali-modified cobalt catalyst
US3794602A (en) * 1972-05-03 1974-02-26 Du Pont Method for in situ reconditioning of iron catalyst bed
US5105015A (en) * 1991-06-04 1992-04-14 W. R. Grace & Co.-Conn. Synthesis of non-cyclic aliphatic polyamines

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3773832A (en) * 1970-01-16 1973-11-20 Du Pont Hydrogenation of adiponitrile over alkali-modified cobalt catalyst
US3794602A (en) * 1972-05-03 1974-02-26 Du Pont Method for in situ reconditioning of iron catalyst bed
US5105015A (en) * 1991-06-04 1992-04-14 W. R. Grace & Co.-Conn. Synthesis of non-cyclic aliphatic polyamines

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