TW201514131A - Catalyst preparation and hydrogenation process - Google Patents

Abstract

Disclosed is a method for hydrogenating a dinitrile to form a diamine. Also disclosed is a method for preparing a catalyst for this hydrogenation reaction by reducing iron oxide with hydrogen. The catalyst ages during the course of making the diamine. An aged catalyst is partially reactivated by interrupting the flow of dinitrile and ammonia feed to a reactor, while maintaining a flow of hydrogen to the reactor.

Description

Catalyst preparation and hydrogenation method

This invention relates to a process for the preparation of a catalyst and to a hydrogenation process which is useful for the catalyst. More specifically, the present invention relates to catalytic hydrogenation of an organic nitrile in the presence of a heterogeneous iron catalyst. Examples of such reactions include hydrogenation of adiponitrile to hexamethylenediamine and hydrogenation of methylglutaronitrile (especially 2-methylglutaronitrile) to 2-methylpentanediamine.

A method of hydrogenating a compound containing a nitrile group to an amine is known. Hydrogenation of the dinitrile to the corresponding diamine is a method which has been used for a long period of time, in particular hydrogenation of adiponitrile to hexamethylenediamine, wherein hexamethylenediamine is the basic material for the preparation of nylon-6,6.

In recent years, the hydrogenation of aliphatic dinitriles (sometimes referred to as semi-hydrogenation) has become a growing concern for amino-acrylonitriles, especially the hydrogenation of adiponitrile to 6-aminocapronitrile, which is directly or via caprolactam. Lun-6.

U.S. Patent No. 5,151,543 to Ziemecki et al. discloses a solvent having an excess of at least 2/1 mole relative to the dinitrile at 25-150 ° C and at a pressure greater than atmospheric pressure (the solvent comprising from 1 to 4 carbons) A method for selectively hydrogenating an aliphatic dinitrile to the corresponding amino nitrile in the presence of a Raney catalyst in the presence of a liquid ammonia or an alcohol and an inorganic base soluble in the alcohol, the resulting amino nitrile Recovered as a main product.

No. 3,696,153 to Kershaw et al. discloses a method for the catalytic hydrogenation of adiponitrile in the presence of a catalyst in the form of a granule which is derived from an iron compound such as iron oxide and which has been hydrogenated at temperatures not exceeding 600 ° C. activation.

U.S. Patent No. 3,758,584, issued to U.S. Patent No. 3,758, issued to, the entire entire entire entire entire entire entire entire Activated in a mixture of hydrogen and ammonia at a temperature in the range of °C.

The catalyst used to hydrogenate the dinitrile to form the diamine ages over time. As the catalyst ages, the activity of the catalyst decreases. Aging can also cause loss of selectivity, resulting in the production of undesirable by-products. For example, when the adiponitrile is hydrogenated to form hexamethylenediamine, the undesirable by-products may include bis(hexamethylene)triamine, diaminocyclohexane, and hexamethyleneimine.

To compensate for the loss of activity due to aging, the temperature at which the dinitrile reacts with hydrogen can be increased. This increase in temperature can be achieved by increasing the inlet temperature of the reactants entering one or more reactors. The reaction is exothermic. Thus, the temperature of the effluent of one or more reactors will exceed the temperature of the feed to such reactors.

There is an upper limit to the temperature of the effluent of the reactor. In particular, the catalyst particles in the fixed bed of the catalyst tend to sinter at temperatures up to 190 °C. Sintering of the catalyst particles results in a reduction in catalyst surface area. Therefore, one or more reactors are typically shut down when it is desired to increase the reaction temperature in order to reach the upper limit of the temperature of the reactor effluent.

A problem with shutting down the reactor is that there may be less product produced during a given reaction cycle or operation. Another problem with shutting down the reactor due to aging of the catalyst is that the catalyst must be replaced. The more times the catalyst has to be replaced, the higher the cost of the entire process due to the increased catalyst cost. In addition, since the catalyst is pyrophoric, replacement of the catalyst is particularly problematic. Therefore, each time the catalyst is replaced, the cost involves handling the new catalyst and treating the aged catalyst. Disposing of the aged catalyst can include delivering the catalyst to a catalyst deactivation unit in an inert atmosphere in which the catalyst is slowly oxidized.

In view of the problems associated with catalyst aging, it is desirable to extend the life of the catalyst. According to embodiments disclosed herein, the aged catalyst is at least partially reactivated in situ. This live again The process includes temporarily interrupting the dinitrile feed stream through one or more reactors. The hydrogen flow is maintained during this interruption. Surprisingly, this temporary interruption of the dinitrile feed stream allows the catalyst to be at least partially reactivated.

The diamine is prepared by a method of converting a dinitrile to a diamine. The method may comprise the steps of: (a) continuously introducing a feed comprising dinitrile, liquid or supercritical ammonia and hydrogen into at least one converter comprising a fixed bed of catalyst; (b) causing each converter of step (a) The condition is maintained under conditions sufficient to react the dinitrile with hydrogen to form a diamine; (c) withdrawing the effluent comprising the diamine from each converter; (d) increasing the temperature of the feed of at least one converter over time to maintain sufficient Degree of conversion and compensating for catalyst aging; (e) interrupting the dinitrile and ammonia feed streams of at least one of the converters while maintaining the flow of hydrogen to the converter; (f) discharging the residual dinitrile from the converter of step (e) Feeding ammonia, a diamine product while maintaining a hydrogen stream through the converter; and (g) restoring the flow of the ammonia and dinitrile feed to the converter of step (f) and the converter of step (e) Logistics.

The level of preparation after step (g) can be comparable to the level of preparation of step (d) while maintaining the temperature of the feed to the converter below the feed temperature prior to step (e). The equivalent level of preparation in step (g) may be within 10% of the level of preparation prior to step (e), such as within 5%, such as within 2%, for example, the same as the level of preparation prior to step (e).

Each of the converters may comprise a vertically disposed cylindrical outer casing filled with a fixed bed of catalyst. The bottom of the cylindrical outer casing may further comprise at least two outlets. The top of the cylindrical outer casing may contain a void space placed on the fixed bed of the catalyst. Feeding the feed down by introducing a feed containing dinitrile, liquid or supercritical ammonia and hydrogen into the void space on the catalyst bed The catalyst is passed through the catalyst bed and the effluent is withdrawn through the outlet at the bottom of the casing to introduce the feed into each converter and the effluent can be withdrawn from each converter.

Each of the converters may further comprise a vertically disposed riser that extends upwardly through the center of the bottom of the cylindrical outer casing, through the fixed bed of catalyst and extending into a void space within the cylindrical outer casing that is above the level of the fixed bed of catalyst. The standpipe may include an inlet at the bottom of the cylindrical outer casing and at least one outlet in the region of the void space of the outer casing. The feed can be introduced into each converter by a process comprising the following steps and the effluent can be withdrawn from each converter: (i) introducing a feed comprising dinitrile, liquid or supercritical ammonia and hydrogen into the inlet of the standpipe; (ii) flowing the feed upwardly through the riser to the outlet of the riser; (iii) flowing the feed down the catalyst bed in the annular space between the riser and the vertical wall of the outer casing; and (iv) passing through the bottom of the outer casing The outlet draws out the effluent.

The dinitrile can be converted to a diamine in at least three converters connected in series. The effluent from the first converter in the series is passed to a second converter in the series, and the effluent from the second converter in the series is passed to a third converter in the series. During the conversion of the dinitrile to the diamine, the effluent from the first converter is cooled, then passed to a second converter, and the effluent from the second converter is cooled and subsequently passed to a third converter. Partial reactivation of the catalyst can be carried out by interrupting the dinitrile feed stream from all reactors connected in series.

The pressure in each of the converters in step (b) can be maintained at a level of at least 4000 psig (27,680 kPa). The catalyst can be a reduced form of iron oxide. The dinitrile can be adiponitrile (ADN) and the diamine can be hexamethylenediamine (HMD). The dinitrile can be methylglutaronitrile (MGN) and the diamine can be 2-methylpentanediamine (MPMD).

The inlet temperature of at least one of the converters can be monitored over time. Step (e) can be initiated when the inlet temperature is raised to a predetermined level during step (d).

The outlet temperature of at least one of the converters can be monitored over time. This outlet temperature is in the step (d) Step (e) may be initiated when the period is raised to a predetermined level.

The level of preparation of hexamethyleneimine (HMI) can be monitored over time. Step (e) can be initiated when the preparation level of the hexamethyleneimine (HMI) is raised to a predetermined level during step (d).

The hexamethyleneimine (HMI) preparation level after the step (e) may be lower than the hexamethyleneimine (HMI) preparation level before the start of the step (e).

2‧‧‧ pipeline

4‧‧‧ pipeline

10‧‧‧Ammonia pump

12‧‧‧ pipeline

14‧‧‧ Hydrogen compressor

16‧‧‧ pipeline

18‧‧‧ pipeline

20‧‧‧ heat exchanger

22‧‧‧ pipeline

24‧‧‧Transformer preheater/preheater

26‧‧‧ pipeline

28‧‧‧ pipeline

30‧‧‧Dinitrile pump

32‧‧‧ pipeline

34‧‧‧ pipeline

36‧‧‧tributors

38‧‧‧tributors/pipelines

40‧‧‧tributors/pipelines

42‧‧‧Transformer / First Stage Converter / Reactor / First Converter

44‧‧‧Transformer/Second Stage Converter/Second Stage Reactor/Reactor

46‧‧‧Transformer / Stage 3 Converter / Stage 3 Reactor / Reactor

48‧‧‧Transformer/Fourth Stage Converter/Reactor

50‧‧‧ pipeline

52‧‧‧ pipeline

54‧‧‧ pipeline

56‧‧‧ pipeline

58‧‧‧ pipeline

60‧‧‧ heat exchanger

62‧‧‧ pipeline

64‧‧‧Product separator

66‧‧‧ pipeline

68‧‧‧Line/heated fluid

70‧‧‧Ammonia recovery system

72‧‧‧ pipeline

74‧‧‧ pipeline

76‧‧‧ pipeline

78‧‧‧Ammonia absorber

80‧‧‧ pipeline

82‧‧‧Line/Ammonia flow

84‧‧‧ pipeline

86‧‧‧ pipeline

88‧‧‧ gas circulation compressor

100‧‧‧First hydrogen source/first source/source

102‧‧‧ pipeline

104‧‧‧Second hydrogen source/second source/source/hydrogen source

106‧‧‧ pipeline

108‧‧‧Shared hydrogen supply line/pipeline

110‧‧‧Preheater

112‧‧‧ pipeline

114‧‧‧Ammonia source/source

116‧‧‧ pipeline

118‧‧‧(hydrogen/ammonia mixer)

120‧‧‧ pipeline

122‧‧‧ pipeline

124‧‧‧ heat exchanger

126‧‧‧ pipeline

128‧‧‧Preheater

130‧‧‧ pipeline

132‧‧‧catalyst activation unit

134‧‧‧ pipeline

136‧‧‧ pipeline

138‧‧‧cooler

140‧‧‧ pipeline

142‧‧‧Separator

144‧‧‧ pipeline

146‧‧‧Compressor

148‧‧‧ pipeline

150‧‧‧ pipeline

200‧‧‧Ammonia recovery tower

202‧‧‧ top stream

204‧‧‧ pipeline

206‧‧‧Diamine product stream

210‧‧‧ storage tank

212‧‧‧ pipeline

214‧‧‧ pipeline

220‧‧‧Condenser

230‧‧ ‧ storage tank

240‧‧‧ storage tank

301‧‧‧ pipeline

302‧‧‧ pipeline

303‧‧‧ pump

304‧‧‧ pipeline

305‧‧‧ pipeline

306‧‧‧ adiponitrile pump / adiponitrile injection pump

307‧‧‧ pipeline

308‧‧‧ pipeline

309‧‧‧ pipeline

310‧‧‧ pipeline

311‧‧‧Compressed section

312‧‧‧ pipeline

313‧‧‧ pipeline

314‧‧‧Ammonia pump

315‧‧‧ pipeline

316‧‧‧Line/top flow

317‧‧‧ gas cycle compressor

318‧‧‧Conservative heat exchanger/heat exchanger

319‧‧‧ pipeline

320‧‧‧ pipeline

321‧‧‧ pipeline

322‧‧‧ pipeline

323‧‧‧Preheater/heat exchanger

324‧‧‧ pipeline

325‧‧‧ pipeline

326‧‧‧ pipeline

327‧‧‧reactor/converter/first reactor

328‧‧‧ pipeline

329‧‧‧heat recovery unit

330‧‧‧ pipeline

331‧‧‧ pipeline

332‧‧‧ pipeline

333‧‧‧ pipeline

334‧‧‧ cooler

335‧‧‧ pipeline

336‧‧‧ pipeline

337‧‧‧reactor/converter/second reactor

338‧‧‧ pipeline

339‧‧‧heat recovery unit

340‧‧‧ pipeline

341‧‧‧ pipeline

342‧‧‧ pipeline

343‧‧‧ pipeline

344‧‧‧ pipeline

344‧‧‧ pipeline

345‧‧‧cooler

346‧‧‧ pipeline

347‧‧‧ pipeline

348‧‧‧Reactor/Transformer/Third Reactor/Last Converter

349‧‧‧ pipeline

350‧‧‧heat recovery

351‧‧‧ pipeline

352‧‧‧ pipeline

353‧‧‧ pipeline

354‧‧‧ pipeline

355‧‧‧ cooler

356‧‧‧ pipeline

357‧‧‧High pressure separator

359‧‧‧Medium pressure separator

360‧‧‧ pipeline

361‧‧‧ adiponitrile absorber/absorber

362‧‧‧ pipeline

362‧‧‧ pipeline

363‧‧‧ pipeline

364‧‧‧Recycler Feed Separator/Feed Separator

365‧‧‧ pipeline

367‧‧‧Recycler tailings tank

368‧‧‧ pipeline

370‧‧‧ pipeline

371‧‧‧ pump

372‧‧‧ pipeline

373‧‧•Flasher/converter

374‧‧‧ pipeline

375‧‧‧Vapor cooler

376‧‧‧ pipeline

377‧‧‧ pump

378‧‧‧ pipeline

379‧‧‧ pipeline

380‧‧‧First flash tank

381‧‧‧ pipeline

382‧‧‧Second flash tank

383‧‧‧ pipeline

384‧‧‧ pump

385‧‧‧ pipeline

386‧‧‧ pipeline

387‧‧‧Ammonia vapor compressor

390‧‧‧ pipeline

391‧‧‧Condenser/cooler

392‧‧‧ pipeline

393‧‧‧ pipeline

394‧‧‧Finishing separator

395‧‧‧ pipeline

396‧‧‧Ammonia Receiver

397‧‧‧ pipeline

398‧‧‧Anhydrous ammonia storage tank/ammonia storage tank/anhydrous ammonia storage tank

399‧‧‧High Pressure Absorber/HPA

400‧‧‧ pipeline

401‧‧‧ pipeline

402‧‧‧purification separator

404‧‧‧ pipeline

405‧‧‧ pipeline

406‧‧‧ pump

407‧‧‧ pipeline

408‧‧‧ pipeline

409‧‧‧Ammonia water storage tank

410‧‧‧ pipeline

411‧‧‧Low pressure absorber trap

412‧‧‧ pipeline

413‧‧‧Low Pressure Absorber/LPA

414‧‧‧Process water storage tank / process water storage tank

415‧‧‧ pipeline

416‧‧‧ pump

417‧‧‧ pipeline

418‧‧‧ pipeline

419‧‧‧ pipeline

420‧‧‧Pump/Circulation Pump/Slag Pump

421‧‧‧ pipeline

422‧‧‧ pipeline

423‧‧‧ pipeline

424‧‧‧Distillation tower/tower/ammonia distillation tower

425‧‧‧ pipeline

426‧‧‧ pipeline

427‧‧‧ pipeline

428‧‧‧Condenser storage tank

429‧‧‧ pipeline

430‧‧‧ pump

431‧‧‧ pipeline

432‧‧‧ pipeline

450‧‧‧ pipeline

451‧‧‧Low boiling compound distillation section

452‧‧‧ pipeline

453A‧‧‧Line/lateral acquisition of fluid/feed stream

453B‧‧‧Line/bottom fluid/feed stream

454‧‧‧Line/Outflow Logistics/Fluid

455‧‧‧High boiling compound distillation section/high boiling compound distillation tower

456‧‧‧ pipeline

457‧‧‧ pipeline

458‧‧‧ pipeline

458A‧‧‧ pipeline

458B‧‧‧ pipeline

460‧‧‧Medium boiling compound distillation section / medium boiling compound distillation tower / tower / distillation tower

461‧‧‧Liquid collection tray/tray

462‧‧‧Top liquid return tray/tray

463‧‧‧Fluid/pipeline

464‧‧‧ pump

465‧‧‧ pipeline

466‧‧‧Heat exchanger/conservative heat exchanger

467‧‧‧ pipeline

468‧‧‧Line/heat exchanger

469‧‧‧ pipeline

470‧‧‧ heat exchanger

471‧‧‧ pipeline

472‧‧‧ pipeline

473‧‧‧ pipeline

474‧‧‧ pipeline

475‧‧‧Atmospheric spray condenser/condenser

476‧‧‧ pipeline

477‧‧‧ pump

478‧‧‧ pipeline

479‧‧‧Fluid/pipeline

480‧‧‧ heat exchanger

481‧‧‧ pipeline

482‧‧‧ pipeline

483‧‧‧ pipeline

484‧‧‧ pipeline

485‧‧‧ Purification Concentrate Tower/Tower

486‧‧‧ top fluid

487‧‧‧ pipeline

488‧‧‧ pipeline

490‧‧‧Distillation tower/first distillation tower

491‧‧‧ pipeline

492‧‧‧Distillation tower/second distillation tower

493‧‧‧Distillation Tower/First Distillation Tower/Tower

495‧‧‧Distillation tower/second distillation tower/tower

496‧‧‧ pipeline

600‧‧‧Cylindrical shell/cylinder/reactor/catalyst cartridge

602‧‧‧Top

604‧‧‧ bottom

608‧‧‧Export

610‧‧‧ entrance

611‧‧‧Central riser/standpipe

612‧‧‧Inverted cone screen

613‧‧‧ entrance tube

614‧‧‧ hole

618‧‧‧Export distribution pipe

620‧‧‧Transformer top cover

630‧‧‧Transformer

632‧‧‧ bottom

632a‧‧‧Internal space

634‧‧‧Inlet pipe

634a‧‧‧ inlet pipe connection flange

634b‧‧‧Inlet pipe insertion section/upper end with reduced diameter

634c‧‧‧Connection flange

636‧‧‧Export

638‧‧‧Central Department

640‧‧‧Top/Transformer Top

642‧‧‧Locking teeth

644‧‧‧ holding ring

646‧‧‧Locking screw/co-acting locking teeth

648‧‧‧Locking mechanism

650‧‧ Export

652‧‧‧Central riser/standpipe

660‧‧‧Case/Shell/Chemical Reactor Closed Container

662‧‧‧ holding ring

666‧‧‧First flat end surface

670‧‧‧ cylindrical outer surface

672‧‧‧First locking thread

668‧‧‧Second locking thread

668a‧‧ teeth

668b‧‧‧ gap

672a‧‧‧ teeth / (locking thread / tooth)

672b‧‧‧ gap

1 is a diagram showing a four-stage conversion process for hydrogenating a dinitrile to produce a diamine.

2 is a diagram showing a catalyst activation system for preparing a catalyst by reducing iron oxide with hydrogen.

Figure 3 is a diagram showing details of the ammonia recovery system shown in Figure 1.

Figure 4 shows a first portion of a reaction section for reacting adiponitrile with hydrogen in the presence of liquid ammonia to form hexamethylenediamine.

Figure 5 shows a second portion of a reaction zone for reacting adiponitrile with hydrogen in the presence of liquid ammonia to form hexamethylenediamine.

Figure 6 shows a first portion of a recovery section for recovering components of the product stream produced in the reaction section of Figures 4 and 5.

Figure 7 shows a second portion of a recovery section for recovering components of the product stream produced in the reaction section of Figures 4 and 5.

Figure 8A shows a first example of a refining section for obtaining a refined dinitrile product.

Figures 8B and 8C show an example of the distillation section shown in Figure 8A.

Figure 9 shows a second example of a refining section for obtaining a refined dinitrile product.

Figure 10 is a plan view of a catalytic canister.

Figure 11 is a side view of the catalytic canister.

Figure 12 is a cross-sectional view of the catalytic canister of Figure 2 taken along line 3-3.

Figure 13A is a plan view of the converter.

Figure 13B is an exploded view of the converter.

Figure 14A is a side view of the converter.

Figure 14B is a cross-sectional view of the converter of Figure 14A taken along line 2B-2B.

Figure 15 is a plan view of the locking mechanism of the converter.

Figure 16 is a cross-sectional view of a containment vessel having a locking mechanism.

Unless otherwise expressly defined or stated herein or unless the context clearly dictates otherwise, the following terms are used in the singular grammar: "a (a)", "an" and "the" may also mean A plurality of said entities or objects are included. For example, the terms "device", "assembly", "institution", "component" and "component" as used herein may also refer to a plurality of devices, a plurality of assemblies, a plurality of mechanisms, and plural Components and multiple components.

As used herein, the following terms: "include", "including", "has", "having", "comprise" and "comprising" and Its language or grammatical variants, derivatives and/or conjugates mean "including (but not limited to)".

Numerical values of parameters, features, objects or dimensions may be stated or described in the numerical range format in the scope of the description, examples and accompanying claims. It is to be understood that the scope of the present invention is to be construed as being limited to the scope of the forms disclosed herein.

In addition, in order to state or describe a range of values, it is considered that the phrase "in the range between the first value and the second value" is equivalent to the phrase "in the range from about the first value to the second value" and It has the same meaning, so two words with equivalent meanings are used interchangeably.

It is to be understood that the various forms disclosed herein are not limited by the following description, the operation illustrated in the drawings and the examples, or the steps or procedures and sub-steps in the form of the method. Or the order or sequence of subroutines Purpose details, or types, components, construction, and configuration of peripherals, utilities, accessories, and materials in systems, system sub-units, devices, assemblies, sub-assemblies, mechanisms, structures, components, components, and configurations, and system forms Details of the order, number and number. The apparatus, systems, and methods disclosed herein may be practiced or carried out in various other alternative forms and in various other alternatives.

It is also to be understood that in the present invention, all technical and scientific terms, terms and/or phrases used herein have the same or similar meaning as commonly understood by the ordinary skill in the art. In the present invention, the idioms, terms, and notations used herein are for the purpose of description and should not be considered as limiting.

Abbreviations and definitions

The following abbreviations and definitions are used herein: ADN = adiponitrile; AMC = 6-aminocapronitrile; BHMT = bis(hexamethylene)triamine; DCH = diaminocyclohexane; ESN = ethyl succinonitrile HMI = hexamethyleneimine; MCPD = methylcyclopentanediamine; MGN = 2-methylglutaronitrile; 3-MPIP = 3-methylpiperidine; MPMD = 2-methylpentanediamine; Organic dinitrile = organic compound containing two nitrile groups, such as ADN; ppm = parts per million, by weight unless otherwise stated. When comparing two levels, the term "equal level" means that the two levels are within 10% of each other, such as within 5%, such as within 2%. When comparing two reaction temperatures, the term "lower temperature" means a difference of 5 degrees Celsius, 10 degrees Celsius, 15 degrees Celsius, 20 degrees Celsius or more than 20 degrees Celsius.

Detailed description of Figure 1

The general procedure for the reactants and products in a system for converting dinitrile to diamine can be described with reference to FIG. 1 is a diagram showing a four-stage conversion process for hydrogenating a dinitrile to produce a diamine.

In Figure 1, an ammonia source is passed via line 2 to ammonia pump 10 . A source of hydrogen gas is also delivered to the hydrogen compressor 14 via line 4 . Ammonia from ammonia pump 10 is passed via line 12 to line 18 , and hydrogen from hydrogen compressor 14 is passed via line 16 to line 18 . The ammonia and hydrogen in line 18 are partially heated in heat exchanger 20 before it is passed via line 22 to converter preheater 24 . The heated ammonia and hydrogen from preheater 24 are then passed via a series of four converters depicted in Figure 1 as converters 42 , 44 , 46 and 48 .

The dinitrile feed is fed from line 28 to the dinitrile pump 30 . The dinitrile feed from the dinitrile pump 30 is passed via line 32 to line 34 . A portion of the dinitrile feed can be passed via line 34 to ammonia feed line 2 . The dinitrile can also be introduced separately from ammonia via a dedicated pump for dinitrile feed. A portion of the dinitrile feed can also be transferred from line 34 to line 26 via side stream 36 for introduction into first stage converter 42 . Similarly, side streams 38 and 40 provide fresh dinitrile feed to second stage converter 44 and third stage converter 46 . Again, as depicted in Figure 1, the fresh dinitrile feed in line 34 is introduced into the fourth stage converter 48 .

According to one embodiment not shown in FIG. 1, a portion of the hydrogen feed may be introduced downstream of the first stage converter 42 and optionally introduced downstream of the second stage reactor 44 and the third stage reactor 46 . According to another embodiment not shown in Figure 1, it is not necessary to introduce a fresh dinitrile feed into each converter. For example, all dinitrile feeds may be introduced at locations upstream of the first stage converter 42 as appropriate.

The effluent from the first stage converter 42 is passed via line 50 to the second stage converter 44 . At a location between the exit location of the first stage converter 42 and the location at which the fresh dinitrile feed is introduced to line 50 via line 38 , it may be cooled in at least one heat exchanger or cooler not shown in FIG. The effluent of the one-stage converter.

The effluent from the second stage converter 44 is passed via line 52 to a third stage converter 46 . At a location between the exit location of the second stage converter 44 and the location at which the fresh dinitrile feed is introduced via line 40 to line 52 , it may be cooled in at least one heat exchanger or cooler not shown in FIG. The effluent of the one-stage converter.

The effluent from the third stage converter 46 is passed via line 54 to heat exchanger 20 where heat from the third stage converter effluent is passed to the coolant feed from line 18 . The cooled effluent from the third stage converter 46 is then passed via line 56 to the fourth stage converter 48 . The cooled effluent from the third stage converter 46 can optionally be passed through a cooler, not shown in Figure 1, prior to delivery to the fourth stage converter 48 .

The effluent from the fourth stage converter 48 is passed via line 58 to heat exchanger 60 . The cooled effluent is then transferred from heat exchanger 60 to product separator 64 via line 62 . Flashing occurs in product separator 64 . The liquid phase comprising the diamine from product separator 64 is passed via line 66 to heat exchanger 60 . The gas phase comprising hydrogen and ammonia from product separator 64 is passed via line 86 to gas recycle compressor 88 to facilitate the flow of hydrogen and ammonia through line 18 .

The liquid phase from product separator 64 and heated in heat exchanger 60 is passed via line 68 to ammonia recovery system 70 . The ammonia recovery system comprises an ammonia recovery column (not shown in Figure 1) and a condenser (not shown in Figure 1). However, details of the ammonia recovery system including the ammonia recovery column and the condenser are shown in Figure 3, described below. The crude product comprising the diamine is withdrawn from the bottom of the ammonia column and exits the ammonia recovery system via line 72 . The gas phase overhead product of the ammonia recovery column is passed to a condenser where a distillate phase comprising ammonia and a vapor phase comprising hydrogen are formed. A portion of the distillate phase can be returned to the ammonia recovery column as reflux. A portion of the distillate phase can be delivered to at least one storage tank for storage. A portion of the distillate phase can also be recycled as the ammonia feed to the hydrogenation reaction. In Figure 1, this ammonia recycle is indicated by the transfer of ammonia from the ammonia recovery system via line 74 to line 2 .

The vapor phase from the condenser in ammonia recovery system 70 is passed via line 76 to ammonia absorber 78 . This vapor phase contains hydrogen and residual ammonia. The vapor phase is treated in an ammonia absorber 78 by washing with water from line 80 . Ammonia water is removed from the ammonia absorber via line 82 . The vapor phase comprising hydrogen exits the ammonia absorber 78 via line 84 . Hydrogen in the fluid in line 84 can be combusted in a combustion device such as a boiler or a combustion tower. At least a portion of the vapor phase from the ammonia absorber 78 can be recycled as a hydrogen feed with the restriction that water is removed from the stream. If the water is not sufficiently removed from the stream, the water can poison the catalyst in the converter.

The vapor phase recovered from product separator 64 contains hydrogen. This vapor phase may also contain ammonia. This vapor phase can be passed from product separator 64 to gas recycle compressor 88 via line 86 for recycle to line 18 .

In an alternative embodiment, at least a portion of the vapor phase comprising hydrogen and ammonia in line 76 can be passed as a feed to a catalyst activation unit via a line not shown in FIG. 1 to reduce iron oxide by hydrogen. A catalyst was prepared.

Detailed description of the catalyst

The catalyst in this process is a hydrogenation catalyst suitable for hydrogenating a dinitrile to a diamine or a mixture of a diamine and an amino nitrile. Such catalysts may comprise Group VIII elements including iron, cobalt, nickel, ruthenium, palladium, rhodium, and combinations thereof. In addition to the Group VIII elements mentioned above, the catalyst may also contain one or more promoters, such as one or more Group VIB elements such as chromium, molybdenum and tungsten. The promoter may be present in a concentration of from 0.01 to 15% (e.g., from 0.5 to 5%) by weight of the catalyst. The catalyst may also be in the form of an alloy comprising a solid solution of two or more metals, or in the form of an individual metal or a sponge metal catalyst. "Sponge metal" is a metal having an extensible porous "skeleton" or "sponge-like" structure, preferably an alkali metal (e.g., iron, cobalt or nickel) having dissolved aluminum, optionally containing an accelerator. The amount of iron, cobalt or nickel present in the catalyst can vary. The total amount of iron, cobalt or nickel contained in the framework catalyst suitable for use in the process of the invention is from about 30 to about 97% by weight iron, cobalt and/or nickel, for example from about 85 to about 97% by weight iron, cobalt or nickel, for example 85-95% nickel. The sponge catalyst may be modified with at least one metal selected, for example, from the group consisting of chromium and molybdenum. The sponge metal catalyst may also contain surface hydrated oxides, adsorbed hydrogen radicals, and hydrogen gas bubbles in the pores. The catalyst of the present invention may also comprise aluminum, for example from about 2 to 15% by weight aluminum, for example from about 4 to 10% by weight aluminum. Commercially available catalysts of the sponge type are promoted or unpromoted Raney® Ni or Raney® Co catalysts available from Grace Chemical Co. (Columbia, Md.). Catalysts comprising a Group VIII metal are described in U.S. Patent No. 6,376,714.

The catalyst can be loaded or unloaded.

The catalyst can be prepared by reducing the oxide of the Group VIII metal with hydrogen. For example, the catalyst can be activated by: at a temperature exceeding 200 ° C but not exceeding 600 ° C, It is heated in the presence of hydrogen to reduce at least a portion of the iron oxide to metallic iron. Activation can continue until at least 80% by weight of the available oxygen in the iron has been removed and activation can continue until substantially all (eg, 95 to 98%) of the available oxygen has been removed. During activation, it is desirable to prevent the counter-diffusion of the formed water-vapor. An example of a catalyst activation technique is described in U.S. Patent No. 3,986,985.

At least a portion of the activation of the catalyst can be carried out in situ in one or more reactors for converting the dinitrile to the diamine. For example, referring to Figure 1, an iron oxide catalyst precursor can be loaded in reactors 42 , 44 , 46, and 48 . Hydrogen can then be passed over the catalyst precursor under conditions sufficient to reduce the iron oxide. When a sufficient degree of catalyst activation is achieved, the dinitrile can be included in the feed and the reactor can be maintained under conditions sufficient to convert the dinitrile to the diamine.

At least a portion of the catalyst activation may be carried out in a catalyst activation zone separated from a reactor for converting the dinitrile to a diamine. An example of such a separate catalyst activation zone is described herein with reference to Figure 2, discussed in more detail below. When the catalyst precursor reaches a sufficient degree of activation, it can be passed to one or more reactors for converting the dinitrile to the diamine.

Transferring the activated catalyst from the catalyst activation zone to the separate reactor can be problematic. For example, reduced iron oxide catalysts are generally flammable and must be protected from contact with atmospheric oxygen. According to one embodiment, the activated catalyst from the catalyst activation zone may be covered with an inert gas such as nitrogen and maintained in an inert atmosphere until the activated catalyst is loaded on one or more reactors for converting the dinitrile to the diamine. in. In another embodiment, the activated catalyst can be partially passivated and subsequently passed to a reaction zone for converting the dinitrile to the diamine. This passivation can be carried out by transporting an oxygen source over the activated catalyst in the activation zone prior to passing the catalyst. This passivation at least partially reoxidizes the outer surface of the catalyst particles while maintaining the catalyst inside the catalyst particles in a reduced state. After the passivated catalyst is loaded into the reactor (e.g., reactors 42 , 44 , 46, and 46 of Figure 1), hydrogen can be passed over the passivated catalyst under conditions of iron oxide on the surface of the reduced catalyst particles. An example of a catalyst passivation technique is described in U.S. Patent No. 6,815,388.

Useful precursors for the iron catalyst include iron oxide, iron hydroxide, iron (oxygen) iron or mixtures thereof. Examples include iron (III) oxide, iron (II, III) iron oxide, iron (II) oxide, iron (II) hydroxide, iron (III) hydroxide or iron (oxygen) iron (such as FeOOH). Synthetic or naturally occurring iron oxide, iron hydroxide or oxygen (hydrogen oxy) iron, such as magnetite, having the ideal chemical formula of Fe ₃ O ₄ , and brown iron ore, having Fe ₂ O _{3 , can be used} . The ideal chemical formula of H ₂ O; or red iron ore (hematite), which has the ideal chemical formula of Fe ₂ O ₃ . An example of an iron oxide source useful as a precursor to the preparation of a hydrogenation catalyst is described in U.S. Patent No. 6,815,388.

An example of an iron oxide precursor is Swedish magnetite. The composition of the magnetite can be readily determined by ICP spectroscopy analysis familiar to those skilled in the art. The iron oxide catalyst precursor may comprise one or more selected from the group consisting of a total iron content greater than 65% by weight and a Fe(II) to Fe(III) ratio of between about 0.60 and about 0.75, total The magnesium content is greater than 800 ppm by weight to less than 6000 ppm by weight, the total aluminum content is greater than about 700 ppm by weight to less than 2500 ppm by weight, the total sodium content is less than about 400 ppm by weight, the total potassium content is less than about 400 ppm by weight, and the range of 1.0 to 2.5 mm The particle size distribution within is greater than about 90%. The substantially similar iron oxide catalyst precursors are described in U.S. Patent Nos. 4,064,172 and 3,986,985 to Dewdney et al.

Reactors 42 , 44 , 46 and 48 of Figure 1 can be fixed bed reactors or other types of reactors. An example of a reactor that does not use a fixed bed is a riser and a downflow as described in U.S. Patent Application No. 6, 061, 460, to the name of U.S. Patent No. 6, 068, 760, to U.S. Pat. Tube slurry bubble column reactor. The slurry bubble column reactor is capable of easily removing the heat of reaction and providing a substantially isothermal operation.

The fixed bed reactor can have a cartridge that includes a fixed bed of catalyst. The catalytic canister can be movable. In particular, the movable cartridge can be loaded with a catalyst precursor, such as iron oxide, and placed in a catalyst activation unit. The catalyst precursor in the catalytic canister can then be activated in the catalyst activation unit. The cartridge (including the activated catalyst) can then be moved to one or more of the reactors 42 , 44 , 46, and 48 . After the reaction in reactors 42 , 44 , 46, and 48 is closed, the cartridge can then be removed from the one or more reactors and passed to the catalyst deactivation unit. The catalyst in the cartridge may be covered with an inert gas such as nitrogen when the cartridge is delivered from the catalyst activation unit to the reactor or when the cartridge is delivered from the reactor to the catalyst deactivation unit.

Deactivation of the pyrophoric catalyst in the cartridge can be carried out by transporting a gas containing oxygen through the catalytic canister in a controlled manner. This deactivation can be carried out in a catalyst deactivation unit.

Detailed description of Figure 2

The general procedure for the reactants and products in the system for preparing a reduced iron oxide catalyst can be described with reference to FIG. 2 is a diagram showing a catalyst activation system for preparing a catalyst by reducing iron oxide with hydrogen.

In Figure 2, a first hydrogen source 100 and a second hydrogen source 104 are depicted. However, it should be understood that hydrogen can be supplied from a single source or from two or more sources. Hydrogen from the first source 100 is transferred via line 102 and/or hydrogen from the second source 104 is moved via line 106 to a common hydrogen supply line 108 . In one embodiment, the first hydrogen source 100 comprises at least a portion of the vapor phase in line 76 exiting the ammonia recovery system 70 illustrated in FIG. In another embodiment, the second hydrogen source 104 comprises hydrogen from a hydrogen conduit. When a hydrogen pipe is used, the hydrogen can be purified, for example, by a pressure swing adsorption process. When two sources of hydrogen are used, they can be used simultaneously or intermittently when the second source 104 is used to stop the flow of hydrogen from the first source 100 , and vice versa.

The hydrogen feed in line 108 is fed to preheater 110 and the heated hydrogen is passed via line 112 to hydrogen/ammonia mixer 118 . The ammonia feed to the hydrogen/ammonia mixer 118 is derived from the ammonia source 114 . The ammonia feed is passed via line 116 to a hydrogen/ammonia mixer 118 . The combined hydrogen/ammonia feed is passed via line 120 and line 122 to heat exchanger 124 for heating. The heated hydrogen/ammonia feed is then passed via line 126 to preheater 128 for further heating to a temperature suitable for reducing iron oxide. This hydrogen/ammonia feed is then passed via line 130 to catalyst activation unit 132 to reduce the iron oxide. In the catalyst activating unit 132 , iron oxide is reduced, a portion of the hydrogen in the feed is converted to water (H ₂ O) and one of the ammonia (NH ₃ ) is partially decomposed to form nitrogen (N ₂ ) and hydrogen (H ₂ ).

The effluent from catalyst activating unit 132 is passed via line 134 to heat exchanger 124 where the heat of the effluent is transferred to the hydrogen/ammonia feed in line 122 and the effluent is cooled. The cooled effluent is then passed via line 136 to cooler 138 for further cooling. Cooler 138 may utilize refrigeration for all or part of the cooling to condense the maximum amount of water vapor in line 136 . The effluent from cooler 138 is passed via line 140 to separator 142 , which includes a liquid phase comprising ammonia and water and a gas phase comprising hydrogen, ammonia and nitrogen. The liquid phase is passed from separator 142 through line 148 and can be directed to a reservoir not shown in FIG.

At least a portion of the gas phase from separator 142 is passed from line 144 to compressor 146 and to line 122 for recycle to catalyst activation unit 132 . To minimize nitrogen accumulation in the recirculation loop, a portion of the gas phase may also be withdrawn from separator 142 via line 150 as a purge stream.

According to an embodiment not shown in Fig. 2, the preheater 110 and the hydrogen/ammonia mixer 118 are not used. In the embodiment selected as appropriate, ammonia from the ammonia source is fed directly from the line 120 into the system without first being mixed with hydrogen. In addition, hydrogen from source 100 or source 104 is fed directly into cooler 138 without first being mixed with ammonia.

Detailed description of Figure 3

3 is a diagram showing details of the ammonia recovery system 70 shown in FIG. In FIG. 3, a heated fluid 68 , also shown in FIG. 1 and comprising ammonia, hydrogen, and diamine, is fed to the ammonia recovery column 200 . Diamine product stream 206 is passed from bottom of ammonia recovery column 200 to storage tank 210 . The crude product in the storage tank 210 can be further refined by, for example, the steps illustrated in Figures 8A and 9. A top stream 202 comprising hydrogen and ammonia is passed to condenser 220 . A portion of the ammonia condensate is passed to the ammonia recovery column 200 via line 204 in reflux. Another portion of the ammonia condensate is transferred from condenser 220 via line 212 to storage tank 230 . A portion of the ammonia condensate in the storage tank 230 can be recycled via line 74 to line 2 as the ammonia feed to the dinitrile conversion process shown in FIG.

The vapor stream is passed from condenser 220 via line 214 to ammonia absorber 78 . A portion of this vapor stream can be withdrawn as a side stream from line 214 to enter line 76 for use as a hydrogen feed stream as described with respect to the catalyst activation system illustrated in FIG.

Water flow is introduced into ammonia absorber 78 via line 80 . The ammonia stream 82 is transferred from the ammonia absorber 78 to the reservoir 240 . The vapor stream comprising hydrogen exits the ammonia absorber 78 via line 84 . You can by distillation from the reservoir 240 and aqueous ammonia as an ammonia recovering anhydrous ammonia hydrogenation of the dinitrile of feed recycling.

Overview of Figures 4 to 7

4 to 7 show a method of reacting adiponitrile with hydrogen in the presence of liquid ammonia to form hexamethylenediamine. Figures 4 and 5 show the reaction sections used in this reaction. Figure 4 shows the portion of the reaction zone where the components of the feed are combined and heated to the reaction temperature. Figure 5 shows the portion of the reaction zone where the reaction of the feed components is carried out. Figures 6 and 7 show recovery sections for recovering components of the product streams produced in the reaction sections of Figures 4 and 5. Figure 6 shows the fraction of recovered crude hexamethylene diamine product and unreacted hydrogen in the recovery section. Figure 7 shows the portion of the recovery section where ammonia is recovered.

Overview of Figures 4 and 5

In Figures 4 and 5, fresh adiponitrile feed is introduced into the reaction zone via line 301 , fresh hydrogen feed is introduced into the reaction zone via line 309 , and fresh liquid ammonia feed is introduced into the reaction zone via line 313 . . These feeds are combined with various recycle feeds and passed via line 308 to a conservation heat exchanger 318 and preheater 323 . The heated feed is then passed via line 326 to a series of reactors 327 , 337 and 348 . The reaction is exothermic. The heat generated in reactors 327 , 337 and 348 is removed in heat recoverers 329 , 339 and 350 and coolers 334 , 345 and 355 . A recycler and a cooler are located downstream of each of reactors 327 , 337 and 348 .

The product from the reaction zone is passed via line 356 to the recovery section shown in Figures 6 and 7.

Coolant for heat recoverers 329 , 339, and 350 is transferred from the recovery section to the reaction zone via line 332 . The coolant is the liquid stream from the recovery section. The liquid stream comprises liquid ammonia and hexamethylene diamine. This coolant is passed to each of the heat recoverers 329 , 339 and 350 to form a vapor stream comprising ammonia and a liquid stream comprising ammonia and hexamethylenediamine. The vapor stream is passed back to the recovery section via line 331 and the liquid stream is passed back to the recovery section via line 333 .

4 and 5 are detailed descriptions

Adiponitrile is introduced into the reaction zone via line 301 . At least a portion of the fluid in line 301 can be passed to adiponitrile pump 306 and subsequently passed to line 307 for introduction into line 308 . The fluid in line 308 includes adiponitrile, hydrogen, and liquid ammonia. The adiponitrile pump 306 can be a reciprocating plunger pump or a multi-stage centrifugal pump. At least a portion of the adiponitrile feed can be split into line 302 . The adiponitrile in line 302 is passed to the recovery section illustrated in Figures 6 and 7. In particular, this feed is transferred to pump 303 , then through line 304 , and then to the adiponitrile absorber 361 shown in Figure 6 (but not shown in Figure 4 or Figure 5). The adiponitrile stream from the bottom of the self-dinitrile absorber 361 contains adiponitrile and ammonia. The fluid comprising adiponitrile and ammonia is returned to the reaction zone via line 305 and introduced into the adiponitrile feed stream in line 301 .

Fresh hydrogen feed is introduced into the reaction zone via line 309 . At least a portion of the hydrogen feed may be transmitted to the compression section 311 enters line 312, line 308 is then transferred to the 327, 337 and 348 is introduced to the converter. The compression section 311 can comprise, for example, two four-stage hydrogen compressors. At least one recycle hydrogen stream may also be passed from the recovery section illustrated in Figures 6 and 7 to line 309 of the reaction zone. For example, dinitrile to their hydrogen absorber 361 via the transmission line 310 to line 309. The combined fresh feed and recycle hydrogen feed is then passed via compression section 311 to line 312 and to line 308 . The hydrogen recycle stream may also be withdrawn from the high pressure separator 357 via line 316 in the form of overhead product to enter the gas recycle compressor 317 and subsequently into line 308 .

The fresh liquid ammonia feed is passed via line 313 to ammonia pump 314 into line 315 and subsequently to line 308 . The ammonia pump 314 can be a reciprocating plunger pump or a multi-stage centrifugal pump. Some adiponitrile can be directed to an ammonia pump to assist in flow control and lubrication of the pump assembly.

A feed comprising adiponitrile, hydrogen, and liquid ammonia is passed via line 308 to a conserved heat exchanger 318 . The feed in the conserved heat exchanger 318 is heated by a liquid heating stream from the reaction section or recovery section. This liquid stream is introduced into the conserved heat exchanger 318 via line 319 . An example of a liquid process stream is a liquid stream from a column for separating hexamethylenediamine from lower boiling compounds. This flow is depicted as stream 463 with reference to Figure 8A.

The conserved heat exchanger 318 can be a shell-and-tube heat exchanger. The heating fluid can enter the conserved heat exchanger 318 via line 319 and pass through the shell region of the shell-and-tube heat exchanger. The reactant fluid to be heated can enter the conserved heat exchanger 318 via line 308 and pass through the tube region of the shell-and-tube heat exchanger. The cooled heating fluid is returned to the reaction or recovery section via line 320 .

The heated reactant stream from the conserved heat exchanger 318 is then passed via line 321 to the preheater 323 . At least a portion of the stream in line 308 can be split from the conserved heat exchanger 318 and introduced into line 321 via line 322 . The amount of fluid diverted around the conserved heat exchanger 318 in line 322 can be used to control the temperature of the stream fed into line 321 in preheater 323 .

To heat the stream in line 321 , the steam is introduced into preheater 323 via line 324 . The cooled steam and/or condensate is recovered via line 325 .

The heated reactant stream is then passed via line 326 to a first reactor or converter 327 .

The effluent from reactor 327 is passed via line 328 to heat recovery unit 329 . A coolant stream comprising hexamethylenediamine and anhydrous liquid ammonia is passed via line 332 to heat recovery unit 329 . In the heat recovery unit 329 , one of the liquid ammonia in the coolant stream is partially vaporized. The stream containing vaporized ammonia is withdrawn from heat recovery unit 329 via line 331 . The stream containing hexamethylenediamine, liquid ammonia, and dissolved hydrogen is withdrawn from heat recovery unit 329 via line 333 .

The cooled effluent stream from reactor 327 is passed from heat recovery unit 329 through line 330 . At least a portion of the fluid in line 330 is transferred to cooler 334 . The cooler 334 can be an air cooler or a water cooler. Portions of the fluid in line 330 may also bypass cooler 334 by splitting into line 336 . The temperature of the fluid entering reactor 337 can be controlled by controlling the amount of fluid in line 330 bypassing cooler 334 . Any feed that passes through the cooler 334 and bypasses the cooler 334 is transferred via line 335 to the second reactor 337 .

Although not shown in FIG. 5, a portion of the fluid in line 328 can bypass recycler 329 and cooler 334 as a means of controlling the feed temperature of converter 337 via a line not shown in FIG.

Although not shown in FIG. 5, other feeds comprising hydrogen and/or adiponitrile may optionally be fed directly into reactor 337 or indirectly fed into reactor 337 by introduction into, for example, line 330 , 335 or 336 .

The effluent from reactor 337 is passed via line 338 to heat recovery unit 339 . A coolant stream comprising hexamethylenediamine and anhydrous liquid ammonia is passed via line 341 to heat recovery unit 339 . Line 341 is a side stream of line 332 . In the heat recovery unit 339 , one of the liquid ammonia in the coolant stream is partially vaporized. The stream containing vaporized ammonia is withdrawn from heat recovery unit 339 via line 342 and into line 331 . The stream comprising hexamethylenediamine and liquid ammonia is withdrawn from heat recovery 339 via line 343 to line 344 and subsequently to line 333 .

The cooled effluent stream of reactor 337 is passed from heat recovery unit 339 through line 340 . At least a portion of the fluid in line 340 is delivered to cooler 345 . The cooler 345 can be an air cooler or a water cooler. Portions of the fluid in line 340 may also bypass cooler 345 by splitting into line 347 . The temperature of the stream entering reactor 348 can be controlled by controlling the amount of flow in line 340 that bypasses cooler 345 . Any feed that passes through the cooler 345 and bypasses the cooler 345 is transferred via line 346 to the third reactor 348 .

Although not shown in FIG. 5, a portion of the fluid in line 338 can bypass recycler 339 and cooler 345 as a means of controlling the feed temperature of converter 348 via a line not shown in FIG.

Although not shown in FIG. 5, other feeds comprising hydrogen and/or adiponitrile may optionally be fed directly into reactor 348 or indirectly fed into reactor 348 by introduction into, for example, lines 340 , 346 or 347 .

The effluent from reactor 348 is passed via line 349 to heat recovery unit 350 . A coolant stream comprising hexamethylenediamine and anhydrous liquid ammonia is passed via line 352 to heat recovery unit 350 . Line 352 is a side stream of line 332 . In the heat recovery unit 350 , one of the liquid ammonia in the coolant stream is partially vaporized. The stream containing vaporized ammonia is withdrawn from heat recovery unit 350 via line 354 and into line 331 . The stream comprising hexamethylenediamine, liquid ammonia, and dissolved hydrogen is withdrawn from heat recovery unit 350 via line 353 to line 344 and subsequently into line 333 .

The cooled effluent stream of reactor 348 is passed from heat recovery unit 350 through line 351 . At least a portion of the fluid in line 351 is transferred to cooler 355 . The cooler 355 can be an air cooler or a water cooler. The cooled effluent from third reactor 348 is passed from cooler 355 via line 356 to the recovery section shown in Figures 6 and 7.

Each of the heat recoverers 329 , 339, and 350 can be a shell-and-tube type device similar to a shell-and-tube heat exchanger. The effluent from converters 327 , 337 and 348 can enter the tube side of the recycler and the cooling fluid can enter the shell side of the recycler. The vapor generated in the shell side of the heat recovery unit can exit the recycler via the first line, and the liquid from the shell side of the heat recoverer can exit the recycler via the second line.

Overview of Figures 6 and 7

In the recovery section shown in Figures 6 and 7, ammonia and hydrogen are separated from hexamethylene diamine to provide crude hexamethylene diamine product which is recovered via line 385 . This crude product also contained ammonia and other impurities which were removed in the purification step not shown in Figures 6 and 7. However, examples of such refining steps are shown in Figures 8A and 9. The recovery section shown in Figures 6 and 7 also provides recovery of hydrogen and ammonia. The recovered hydrogen and ammonia can be recycled to the reaction zone shown in Figures 4 and 5.

Most of the hydrogen entering the recycle zone via line 356 is removed in high pressure separator 357 and intermediate pressure separator 359 . The vapor stream from high pressure separator 357 can be recycled directly to the conversion section. The vapor stream from the intermediate pressure separator 359 contains hydrogen and some ammonia. The vapor stream from intermediate pressure separator 359 can be scrubbed with liquid adiponitrile in adiponitrile absorber 361 to provide a hydrogen-rich vapor stream and a liquid stream comprising adiponitrile and dissolved ammonia. These streams can all be used as feed sources in the reaction zone.

The liquid obtained from the intermediate pressure separator 359 is passed to a recycler feed separator 364 to obtain an ammonia vapor stream and a partially ammonia depleted liquid stream. The liquid stream from the recycler feed separator 364 is heated in heat recoverers 329 , 339 and 350 shown in FIG. The heated liquid and vapor from the heat recovery unit are passed to an ammonia recovery section comprising a recycler tail slag tank 367 , a vapor cooler 375 , a flasher 373 , a first flash tank 380, and a second flash tank 382 . The anhydrous ammonia product is recovered as the overhead product of vapor cooler 375 . This anhydrous ammonia product is stored in an anhydrous ammonia storage tank 398 .

The crude hexamethylene diamine product is recovered from the bottom stream from the second flash tank 382 . The overhead vapor stream from the second flash tank 382 contains ammonia vapor. In Figure 7, the ammonia vapor is recovered in the low pressure absorber 413 as an aqueous ammonia solution. In the low pressure absorber 413 , the ammonia vapor is washed with water to form ammonia water.

Figure 7 also shows a high pressure absorber 399 which also scrubs ammonia vapor with water to form a liquid solution of aqueous ammonia. In Figure 7, ammonia from high pressure absorber 399 is fed to the vapor stream of its own dinitrile absorber 361 . However, other ammonia sources not shown in Fig. 7 can be fed to the high pressure absorber 399 . Examples of such sources include steam in line 360 obtained from medium pressure separator 359 and ammonia vapor discharged from ammonia storage tank 398 .

The aqueous ammonia solution from the low pressure absorber 413 and the high pressure absorber 399 is fed to the distillation column 424 . The liquid bottoms stream is recovered from distillation column 424 and used as a water feed to low pressure absorber 413 and high pressure absorber 399 . Anhydrous ammonia is obtained as the vaporization overhead product of distillation column 424 . The condensate of this overhead product is passed to an anhydrous ammonia storage tank 398 . Although not shown in Figure 7, the anhydrous ammonia in the ammonia storage tank 398 can be used as a source of recycled ammonia feed in the conversion section shown in Figures 4 and 5.

Detailed description of Figures 6 and 7

As shown in FIG. 6, the cooled reactor effluent in line 356 is passed to high pressure separator 357 . The overhead stream comprising hydrogen and ammonia is passed through line 316 and returned to the converter section shown in Figures 4 and 5. The stream in line 316 is used as the recycle hydrogen and ammonia feed.

The bottoms stream comprising hexamethylenediamine and liquid ammonia is passed from high pressure separator 357 to intermediate pressure separator 359 via line 358 . The overhead vapor stream comprising ammonia and hydrogen is passed via line 360 from intermediate pressure separator 359 to adiponitrile absorber 361 . Adiponitrile is fed via line 304 into adiponitrile absorber 361 . The adiponitrile washes the gas in the absorber 361 . Ammonia is dissolved in adiponitrile. A liquid phase comprising adiponitrile and dissolved ammonia is passed from absorber 361 through line 305 . As shown in Figure 4, the stream in line 305 was used as a feed to adiponitrile to adiponitrile.

The gas phase stream is taken out from the absorber 361 . This stream is rich in hydrogen and consumes ammonia compared to the gas phase stream entering line 360 of absorber 361 . At least a portion of this hydrogen rich stream can be passed through line 310 and used as a recycle hydrogen feed stream in the conversion process. At least a portion of the hydrogen rich stream can be passed via line 362 to high pressure absorber 399 . In particular, the fluid in line 362 can be a purified stream of hydrogen gas from its own dinitrile absorber 361 . The amount of hydrogen purified in this manner may be sufficient to purify the hydrogen at about 1% of the total hydrogen feed rate, for example.

The adiponitrile absorber 361 can optionally be bypassed during startup, shutdown, and normal operation. The vapor from the intermediate pressure separator 359 can be directed to the high pressure absorber 399 during startup, shutdown, and normal operation.

The bottoms stream from the medium pressure absorber 359 is passed via line 363 to a recycler feed separator 364 . In the recycler feed separator 364 , the pressure of the liquid effluent from the intermediate pressure separator 359 in line 363 is reduced to provide a suitable vapor feed to the ammonia recovery section and is obtained for the heat recovery units 329 , 339 and 350 . Suitable for liquid coolant feed. The overhead vapor stream is passed from recycler feed separator 364 via line 365 to line 368 for introduction into vapor cooler 375 . The bottoms stream is passed from feed separator 364 through line 332 and into the heat recoverers (i.e., heat recoverers 329 , 339, and 350 ) shown in FIG. The vapor stream from the heat recovery unit is passed via line 331 to a vapor cooler 375 . The liquid stream from the heat recoverer is passed via line 333 to a recycler tail sump 367 .

The vapor stream is withdrawn from the recycle slag tank 367 in the form of an overhead product and passed via line 368 to a vapor cooler 375 . The bottoms stream is withdrawn from the recovery slag tank 367 and passed via line 370 to pump 371 and subsequently via line 372 to flasher 373 . The overhead vapor stream is withdrawn from flasher 373 and passed via line 374 to line 368 and subsequently to vapor cooler 375 .

The liquid condensate is withdrawn from vapor cooler 375 in bottom stream and passed via line 376 to pump 377 and to line 378 and to flasher 373 . A first bottom stream into the extraction to the flash tank 380 via line 379 from flasher 373. The bottoms stream is withdrawn from the first flash tank 380 via line 381 to enter the second flash tank 382 . The bottom stream of the second flash tank 382 flows via line 383 to pump 384 and then exits the recovery section via line 385 .

The stream in line 385 contains the crude hexamethylene diamine product which is passed to a refining section not shown in Figure 6. The crude product in line 385 can comprise, for example, 90 wt% hexamethylenediamine, 9 wt% ammonia, and 1 wt% other impurities. Other impurities (i.e., impurities other than ammonia) may include a compound having a boiling point lower than hexamethylenediamine and a compound having a boiling point higher than hexamethylenediamine. Examples of the compound having a boiling point lower than hexamethylenediamine include hydrogen, methane, diaminocyclohexane, hexamethyleneimine, and water. Examples of the compound having a boiling point higher than hexamethylenediamine include 6-aminocapronitrile, adiponitrile, and bis(hexamethylene)triamine.

The top vaporization stream is withdrawn from the first flash tank 380 via line 386 to enter the ammonia vapor compressor 387 and subsequently into the vapor cooler 375 . At least a portion of the ammonia from this first flash tank 380 can be discharged via a scrubber (not shown in Figure 6) using hexamethylenediamine (HMD) to remove any diamine entrained with ammonia. The top vaporization stream from vapor cooler 375 is passed through line 390 . This fluid in line 390 is passed to a partial or complete condenser 391 and subsequently to line 392 . The fluid in cooler 391 can be cooled by air, cooling water or chilled water/diol streams from the refrigeration unit. At least a portion of the flow in line 392 can be passed to trim separator 394 . At least a portion of the fluid in line 392 can also bypass trim separator 394 by flowing to ammonia receiver 396 via line 393 .

Phase separation is performed in the trim separator 394 . The vapor phase remains in the top of the trim separator 394 (i.e., the upper region) and the liquid phase is collected in the bottom region of the trim separator 394 . The ammonia vapor in the trim separator 394 can be discharged into the high pressure absorber 399 , the low pressure absorber 413 or the adiponitrile absorber 361 . The liquid phase is withdrawn from the bottom of the trim separator 394 via line 395 to enter the ammonia receiver 396 . The ammonia vapor in the ammonia receiver 396 may be discharged via a line not shown in FIG. 6 and transferred to the high pressure absorber 399 , the low pressure absorber 413 or the adiponitrile absorber 361, as appropriate .

The combined stream from line 393 and line 395 is collected in ammonia receiver 396 . These combined streams are then passed via line 397 to an anhydrous ammonia storage tank 398 .

Ammonia storage tank 398 contains anhydrous ammonia which is recovered underwater without contact with water to form ammonia. However, there are various ammonia containing fluids which are contacted with water to wash the vapor to remove ammonia from the vapor and produce a solution of aqueous ammonia. Ammonia water can be distilled in one or more distillation steps to produce anhydrous ammonia. Anhydrous ammonia produced from distilled ammonia water can be recovered and combined with anhydrous ammonia collected in anhydrous ammonia storage tank 398 .

In Fig. 7, ammonia water is obtained from the high pressure absorber 399 and the low pressure absorber 413 . Water is introduced into the high pressure absorber 399 via line 400 . Ammonia vapor is introduced into high pressure absorber 399 via line 362 . Ammonia vapor can also be introduced into high pressure absorber 399 from other sources via a line not shown in FIG. Examples of ammonia vapor sources include vapors discharged from trim separator 394 , vapors discharged from ammonia receivers, vapors discharged from anhydrous ammonia storage tanks 398 , and vapors discharged from ammonia water storage tanks 409 .

In the high pressure absorber 399 , water and ammonia vapor are brought into contact in a countercurrent manner. When ammonia vapor is dissolved in water, heat is generated. Vapor flows via line 401 withdrawn from the high pressure absorber 399. The vapor in line 401 is passed to purge separator 402 . A portion of the contents of the purge separator 402 is returned to the high pressure absorber 399 via line 403 and a portion of the contents of the purge separator 402 is withdrawn as a purge stream in line 404 . The purge stream contains combustible gases such as hydrogen and methane. The combustible gas can be combusted in a combustion device such as a boiler or a combustion tower.

The ammonia stream is withdrawn from the bottom of the high pressure absorber 399 via line 405 to enter pump 406 and subsequently into line 407 . A portion of the fluid in line 407 can be transferred back to high pressure absorber 399 via line 408 . At least a portion of the fluid in line 407 is also transferred via line 408 to ammonia water storage tank 409 .

As shown in FIG. 7, the top stream of second flash tank 382 is passed via line 410 to low pressure absorber trap tank 411 . The vaporized ammonia stream from the low pressure trap tank 411 is passed via line 412 to the low pressure absorber 413 . Water is also transferred via line 417 to the low pressure absorber.

At least a portion of the vapor in line 410 can be directed to ammonia vapor compressor 387 for recycle to vapor cooler 375 , in accordance with an embodiment not shown in FIGS. 6 and 7.

At least a portion of the water source introduced into the low pressure absorber 413 and the high pressure absorber 399 may be the bottom distillate of the ammonia water distillation column 424 . As shown in FIG. 7, the bottoms stream from column 424 is passed via line 432 to process water storage tank 414 . The water stream is withdrawn via line 415, a self-contained water storage tank 414 to enter pump 416 and then into line 417 . As shown in FIG. 7, a portion of the water stream in line 417 is withdrawn as a side stream in line 400 and delivered as a water feed to high pressure absorber 399 . Another portion of the water stream continues through line 417 and into the low pressure absorber 413 . Fresh or make-up water may be added to any suitable location upstream of process water sump 414 or high pressure absorber 399 or low pressure absorber 413 as desired.

Vapor from low pressure absorber 413 is passed through line 418 . These vapors may contain hydrogen or methane. Such vapors in line 418 can be passed to a combustion device, such as a boiler or a combustion tower.

Water is introduced into low pressure absorber 413 via line 417 and ammonia vapor is introduced into low pressure absorber 413 via line 412 . Water and ammonia flow through the low pressure absorber 413 in a countercurrent manner. Water collects ammonia by dissolving ammonia during the process. Ammonia dissolves in water to generate heat. The collected ammonia in the form of ammonia is passed from low pressure absorber 413 through line 419 . Ilk line 419 is transmitted to the pump 420 via line 419, then transferred to line 421. A portion of the ammonia in line 421 can be conveyed via line 422 and passed back to low pressure absorber 413 . At least a portion of the ammonia water in line 421 is also conveyed via line 422 and subsequently transferred to ammonia water storage tank 409 .

Ammonia water from the ammonia water storage tank 409 is sent to the distillation column 424 via line 423 . The top vaporization stream comprising anhydrous ammonia is withdrawn from distillation column 424 via line 425 . The vapor stream in line 425 to the condenser 426, and then transferred to line 427. The stream in line 427 is passed to condenser sump 428 . Liquid from condenser sump 428 is passed through line 429 and into pump 430 . A portion of the fluid from pump 430 can be returned to distillation column 424 in reflux. At least a portion of the fluid from pump 430 is also transferred via line 431 to anhydrous ammonia storage tank 398 .

The anhydrous ammonia in the anhydrous ammonia storage tank 398 can be recycled to the appropriate location in the reaction zone shown in Figures 4 and 5 via a line not shown in Figure 7.

Although in the above, the method depicted in Figures 4 to 7 is described with respect to the preparation of hexamethylene diamine from the self dinitrile, it will be appreciated that other diamines may also be prepared from other dinitriles in this process. For example, methylglutaronitrile can be substituted for adiponitrile to give 2-methylpentanediamine instead of hexamethylenediamine. The process conditions can be suitably adjusted in the preparation of the dinitrile other than hexamethylenediamine.

Description of the method conditions in Figures 4 to 7

The feed of a series of converters 327 , 337 and 348 is heated and pressurized to a sufficient extent. The temperature of the feed (e.g., in line 326 ) can be at least 75 °C.

Ammonia is added to the feed stream comprising hydrogen and adiponitrile to provide a heat sink to control the heat generated by the exothermic reaction of hydrogen and adiponitrile. The heat generated during the hydrogenation process can be dissipated by maintaining a sufficient amount of ammonia introduced into converters 327 , 337 and 348 . Ammonia is also used to dissolve hydrogen. The dissolved hydrogen is uniformly distributed on the catalyst particles and blended with adiponitrile to promote the hydrogenation reaction. When hydrogen is dissolved in the liquid or supercritical phase ammonia, the hydrogen can pass through a liquid film on the surface of the catalyst which may contain a nitrile or an amine.

Ammonia also inhibits the formation of various undesirable by-products in the converter. When hydrogen adiponitrile is hydrogenated to form hexamethylenediamine, the undesirable by-products may include bis(hexamethylene)triamine, diaminocyclohexane, and hexamethyleneimine. When hydrogenated 2-methylglutaronitrile to form methylpentanediamine, the undesirable by-products may include bis(methylpentamethylene)triamine, methylcyclopentanediamine, and 3-methylpiperidine. . The use of an ammonia solvent to inhibit the formation of by-products during the hydrogenation of the nitrile is described in U.S. Patent Application Publication No. 2009/0048466.

The temperatures in converters 327 , 337 and 348 are controlled to prevent the temperature in the converter from exceeding the temperature at which a large amount of catalyst degrades and impurities are formed. For example, if the temperature of the catalyst becomes too high, sintering of the catalyst particles may occur, resulting in a decrease in catalyst surface area and a decrease in activity and selectivity. This undesired catalyst degradation can be minimized by controlling the temperature of the effluent of each converter such that the temperature of the effluent does not exceed 200 °C. For example, if the temperature of the catalyst becomes too high, the formation of impurities may become excessive, resulting in a large loss of the yield of the method. Such undesired impurity reactions can be minimized by controlling the temperature of the effluent of each converter such that the temperature of the effluent does not exceed 200 °C. In one embodiment, for example, the temperature of the effluent of each converter is 190 ° C or less. In another embodiment, for example, the temperature of the effluent of each converter is 180 ° C or less.

The hydrogenation reaction in the converter of Figure 5, particularly in the first converter 327 , can be initiated by introducing a feed stream to each converter at a temperature of at least 75 °C. For example, in the early stage of the process of in line 326 to reformer feed stream temperature of 327 may be maintained at a temperature of 80 to 90 deg.] C, the temperature of the feed stream of line 335 to the converter 337 may be maintained at 80 to The temperature of 90 ° C and the temperature of the feed stream from line 346 to converter 348 can be maintained at a temperature of from 100 to 150 °C.

The catalyst ages over time. As the catalyst ages, the inlet temperature of the converter feed can be increased to compensate for the loss of catalyst activity. Eventually, the catalyst will become completely aged and the reaction must be stopped and the catalyst replaced. Catalyst replacement can be carried out when the inlet or outlet temperature of one or more converters exceeds a predetermined temperature or by the formation of by-products due to an increase in temperature such that the preparation is no longer economical. For example, the hydrogenation process can be turned off for catalyst replacement when the inlet temperature of one or more converters exceeds 150 ° C or when the outlet temperature of one or more converters exceeds 190 ° C.

During the reaction operation (initially to first introduce the feed into the converter and continue until the catalyst is replaced), the feed temperature of each converter can be in the range of 75 to 150 ° C, and the effluent temperature of each converter can be In the range of 130 to 190 °C.

The hydrogenation reaction carried out in the converter is exothermic. Thus, the effluent temperature of the converter is greater than the feed to the converter. For example, the effluent temperature of the first converter 327 can be 160 to 180 ° C, the effluent temperature of the second converter 337 can be 160 to 180 ° C, and the effluent temperature of the third converter 348 can be 150 to 170 ° C.

The pressure in each converter should be high enough to maintain the anhydrous ammonia in a liquid or supercritical state, especially at the highest temperatures reached by each converter. The hydrogen, dinitrile reactant and diamine product should be dissolved or otherwise uniformly dispersed in the ammonia phase. The pressure in each converter can be at least 2500 psig (31,128 kPa), such as 4500 psig (34,575 kPa), such as 5000 psig (34,575 kPa).

The effluent of the third converter 348 is in the form of a liquid or supercritical fluid comprising dissolved hexamethylene diamine, anhydrous ammonia, and dissolved hydrogen. The fluid can have a pressure of at least 2500 psig (31,128 kPa) and a temperature of at least 150 °C. As shown in Figures 4, 5 and 6, at least a portion of the hydrogen in the effluent of converter 348 is first passed to the effluent in heat recovery 350 and cooler 355 , and the cooled effluent is then passed to The high pressure separator 357 is removed. The effluent can be cooled to at least 80 ° C and subsequently fed into a high pressure separator 357 . The high pressure separator 357 can be operated under conditions such that the overhead stream 316 contains primarily hydrogen gas in a molar concentration range. The temperature of the feed introduced into the high pressure separator 357 can be less than 70 °C, such as 50 °C. The pressure in the high pressure separator 357 can be less than 4500 psig (31,128 kPa), such as 4200 psig (29,059 kPa).

The bottom stream of high pressure separator 357 contains some dissolved hydrogen. Most of this remaining dissolved hydrogen is removed in the intermediate pressure separator 359 . The medium pressure separator 359 can be operated at substantially the same temperature conditions as the high pressure separator 357 . For example, the temperature of the feed introduced into the intermediate pressure separator 359 can be less than 70 °C, such as 50 °C or less. The pressure in the intermediate pressure separator 359 can range from 1200 to 2500 psig (8,375 to 17,339 kPa), such as 1500 to 1800 psig (10,433 to 12,512 kPa).

In addition to hydrogen, the overhead vapor stream from line 359 in line 360 also contains ammonia. As shown in Figure 6, ammonia is recovered by scrubbing the vapor in line 360 with adiponitrile in adiponitrile absorber 361 . Another not shown in FIG. 6 of the embodiment may be the top of the intermediate pressure separator vapor stream 359 at least a portion of the guide 399 to the high pressure absorber, the absorber 399 in the high pressure vapor stream by washing with water to recover the ammonia .

The pressure of the liquid effluent of the intermediate pressure separator 359 is then further reduced in the feed separator 364 to the pressure of the ammonia flash. As shown in Figure 6, vaporized ammonia is removed as the top of feed separator 364 flows through line 365 . The temperature in the feed separator 364 can be 50 ° C or less, such as 15 to 50 ° C. The pressure in feed separator 364 can range from 450 to 600 psig (3,204 to 4,238 kPa), such as from 500 to 600 psig (3,549 to 4,238 kPa), such as 550 psig (3,893 kPa).

To facilitate further removal of ammonia from the bottom stream of feed separator 364 , the fluid in line 332 is heated to at least 50 °C, such as at least 100 °C. As shown in Figures 5 and 6, this heating is carried out by transferring the fluid in line 332 to heat recoverers 329 , 339 and 350 . When the liquid is heated in the heat recovery unit, one of the ammonia in the liquid partially vaporizes. This vaporized ammonia is passed via line 331 to vapor cooler 375 . The heated liquid fluid from the heat recoverer is passed via line 333 to a recycler tail sump 367 . The temperature of the fluid in line 333 can be from 75 to 180 °C, such as 120 °C. Similarly, the temperature of the liquid in the recycle slag bath 367 and flasher 373 can be from 130 to 180 °C, such as 170 °C. According to an embodiment not shown in Figures 5 and 6, the steam may be used as a heat source in addition to or in place of one or more heat recoverers. For example, vapor cooler 375 and flasher 373 can be replaced with a distillation column and the stream can be introduced into a heating body or reboiler of the distillation column.

The temperature in the vapor cooler can range from 40 to 80 °C, such as from 50 to 60 °C. The temperature in the first flash tank 380 may be 110 to 170 ° C, for example 140 to 150 ° C. The temperature in the second flash tank 382 can be 10 to 50 ° C lower than the temperature in the first flash tank 380 . The temperature in the second flash tank 382 can be from 100 to 150 °C, such as 140 °C. The temperature in trim separator 394 and ammonia receiver 396 can be 15 to 45 °C, such as 35 °C.

The pressure in the recycler slag bath 367 , flasher 373, and vapor cooler 375 can be 5 to 70 psig (136 to 584 kPa) lower than the pressure in the recycler feed separator 364 . The pressure in the recycle slag tank 367 , flasher 373, and vapor cooler 375 can range from 400 to 550 psig (2,859 to 3,893 kPa), such as from 475 to 500 psig (3,204 to 3,549 kPa). The pressure in the first flash tank 380 can be from 25 to 50 psig (274 to 446 kPa), such as from 30 to 42 psig (308 to 391 kPa). The pressure in the second flash tank 382 can range from 0 to 25 psig (101 to 274 kPa), such as from 0 to 10 psig (101 to 170 kPa).

The pressure in ammonia receiver 396 can range from 300 to 600 psig (2,170 to 4,238 kPa), such as from 400 to 500 psig (2,859 to 3,549 kPa).

The high pressure absorber 399 is designed to handle high pressure vapor streams, and the low pressure absorber 413 is designed to treat low pressure vapor streams. The pressure in the high pressure absorber 399 can range from 120 to 180 psig (929 to 1,342 kPa), such as 150 psig (1,136 kPa). The pressure in the low pressure absorber 413 can be from 0 to 50 psig (101 to 446 kPa), such as from 0 to 10 psig (101 to 170 kPa).

Most of the ammonia used as a diluent when adiponitrile (ADN) is converted to hexamethylenediamine (HMD) is recovered as anhydrous ammonia in the overhead stream from line 390 of vapor cooler 375 . However, some ammonia is recovered by washing the gas containing ammonia with water. The scrubbed gas may further comprise, for example, hydrogen and methane. Washing has the dual purpose of reducing air pollution and recovering ammonia.

Ammonia is recovered from the gas stream using two systems. One system uses a high pressure absorber (HPA) and the other system uses a low pressure absorber (LPA). In Figure 7, these absorbers are represented by HPA 399 and LPA 413 .

The ammonia containing gas stream can enter the high pressure absorber below the bottom tray or fill section. Purified water may be added and / or recycled water and adjusted to control the temperature of the gases leaving the high pressure absorber 399 via line 401 and leaving the high pressure absorber 399 of the ammonia concentration of ammonia in stream (NH ₃₎ through the line 405. The water stream in line 400 can enter the high pressure absorber 399 at the top of the scrubber on the distribution tray. This water flows down through the packing and absorbs ammonia (NH ₃ ). When ammonia is adsorbed by water, heat is emitted. Non-condensable gases such as hydrogen (H ₂ ) and methane (CH ₄ ) exit at the top of the scrubber. Any of entrained liquid separator in the exhaust gas can be captured or purifying a gas separator 402, and may be a gas containing H ₂ or CH ₄ of the guide may be located off-site to the combustion tower, boiler or incinerator.

The ammonia tailings of the high pressure absorber 399 can be circulated and delivered to the ammonia water storage tank 409 via an air or water cooler (not shown in Figure 7). A valve can be used to control the level in the high pressure absorber 399 . A portion of the cooled ammonia stream can be returned to the high pressure absorber 399 via lines 407 and 408 . Can flow returns high pressure absorber 399 to remove the heat absorption of the return line 408 of the high pressure absorber 399 via ammonia.

The concentration of ammonia (NH ₃ ) in the aqueous ammonia solution exiting the high pressure absorber 399 via line 405 can be controlled to a predetermined level. For example, the concentration of ammonia in this solution can range from 20 to 22 wt%. Depending on the equipment configuration used in the process, ammonia concentrations below 20 wt% can result in excessive use of steam in the ammonia distillation column 424 . In addition, an ammonia concentration above 23% by weight can cause excessive emissions in the ammonia water storage tank 409 .

The low pressure absorber 413 (LPA) can receive vapor from one or more of the first flash tank 380 and the second flash tank 382 . An ammonia filter (for removing particulates from the ammonia recycle stream) and an ammonia pump can also be depressurized as LPA 413 when not in use.

The ammonia introduced into the vapor in the low pressure absorber 413 is scrubbed in the low pressure absorber 413 . A large amount of ammonia water recycle stream can be maintained by means of a circulation pump 420 which draws liquid from the bottom of the low pressure absorber 413 through an air or water cooler (not shown in Figure 7) and then returns to the low pressure absorber 413 via the distributor. top. Liquid flows downwardly through the packing and the packing of the absorbent upwardly through the ammonia (NH ₃₎ vapor.

The liquid level at the bottom of the low pressure absorber 413 can be controlled such that a portion of the aqueous ammonia solution can flow to the ammonia water storage tank 409 .

The concentration of ammonia (NH ₃ ) in the aqueous ammonia solution exiting the low pressure absorber 413 via line 419 can be controlled to a predetermined level that is the same as the concentration in the high pressure absorber 399 . For example, the concentration of ammonia in this solution can range from 20 to 22 wt%.

The vapor can flow through an outlet scrubber located at the top of the low pressure absorber 413 . The recycled water from the self-contained water storage tank 414 can be fed to the top of the outlet scrubber and can flow downward through the packing to the bottom of the column. The liquid from the bottom of the low pressure absorber 413 can be pumped by a tailings pump 420 to a low pressure absorber cooler (not shown in Figure 7).

The unabsorbed gas exiting the top of the outlet scrubber can be directed via line 418 to a combustion tower, boiler or other combustion device.

Detailed description of Figure 8A

Figure 8A shows an example of the manner in which the purified diamine product is recovered from the crude diamine product. The features presented in FIG. 8A are intended to be illustrative and not to scale. The recovery scheme shown in Figure 8A is particularly useful for recovering hexamethylenediamine.

In Figure 8A, the crude diamine product is passed via line 450 to the low boiler distillation section 451 . Line 450 of the diamine feed stream may correspond to line 6 of FIG. 385 in the effluent stream. In the low boiler distillation section 451 , the compound in line 450 is separated into two streams, represented by lines 452 and 454 in Figure 8A. The compound in line 452 contains a compound having a boiling point lower than the boiling point of the diamine in line 450 . The compound in line 454 contains a compound having a boiling point below the boiling point of the diamine in line 450 . The boiling point of such compounds in line 454 that is less than at least a portion of the diamine may be within 50 ° C of the boiling point of the diamine.

The fluid in line 450 contains the compounds defined below as "low boiling compounds", "medium boiling compounds", diamines and "high boiling compounds". The fluid in line 450 can comprise at least 95 wt%, such as at least 97 wt%, of the diamine prepared in the hydrogenation of dinitriles. Examples of low boiling compounds include ammonia and water. Examples of the high boiling compound include an oligomer of a diamine and an amino nitrile such as a hydrogenated product prepared when only one of the two nitrile groups on the dinitrile is hydrogenated.

When the diamine is hexamethylenediamine (HMD), the high boilers include bis(hexamethylene)triamine. When the diamine is hexamethylenediamine (HMD), the medium boiling compound comprises one or more diaminocyclohexane (DCH) isomers. An example of an isomer of diaminocyclohexane (DCH) is 1,2-diaminocyclohexane.

When the diamine is 2-methylpentanediamine (MPMD), the high boilers include bis(2-methylpentamethylene)triamine. When the diamine is 2-methylpentanediamine (MPMD), the medium boiling compound includes methylcyclopentanediamine (MCPD).

The effluent stream in line 385 of Figure 6 corresponds to the feed in line 450 of Figure 8A. The effluent stream in line 385 can be passed through one or more heating stages followed by introduction of low boiling compound distillation section 451 via line 450 . For example, the stream in line 385 can be passed through a first heat exchanger where it is in thermal contact with the effluent stream 454 from the low boiler distillation section 451 . This heat exchanger is used to heat the flow from line 385 and the cooling line 454 . The heated effluent of the first heat exchanger can then be passed through a second heat exchanger. Steam can be used in the second heat exchanger to further heat the feed to the low boiler distillation section 451 .

The low boiler distillation section 451 can be operated under atmospheric or vacuum conditions. The temperature distribution in the first one of the one or more columns in the low-boiling compound distillation section 451 may be such that the compound having a boiling point of boiling point of water or lower than the boiling point of water (ie, 100 ° C or less) is easily It flashes out as it enters the tower. When the column is operated under atmospheric conditions, this flashing can be promoted by heating the effluent stream in line 385 to a temperature of 110 to 150 ° C (e.g., 130 ° C). Any of the columns in the low boiler distillation section 451 can be in fluid communication with a heat exchanger, heating body or reboiler (not shown in Figure 8A) to supply at least a portion of the heat for distillation.

The distillation conditions in the low boiler distillation section 451 can be such that at least 95% of the diamine in one or more streams represented by line 450 entering the low boiler distillation section 451 is withdrawn in stream 454 . The distillation conditions may also result in at least 99 wt% (e.g., at least 99.5 wt%) of the compound having a boiling point of 100 ° C or less in one or more overhead vapor streams in line 452 . The low boiler distillation section 451 can deliver up to 5% (e.g., 0.1 to 1%) of the diamine entering the low boiler distillation section 451 to one or more of the top streams, represented as line 452 in Figure 8A. Under the conditions of operation. In this way, the loss of diamine in line 452 is minimized.

One or more streams comprising one or more high boilers are withdrawn from the low boiler distillation section 451 to the intermediate boiler distillation section 460 via one or more conduits designated by line 454 . The stream in line 454 can also contain diamines, medium boilers, and low boilers entrained with the high boilers. The stream in line 484 contains a diamine and a high boiler which is separated in a high boiler distillation section 455 . A stream comprising a compound having a high boiler is passed from a high boiler distillation section 455 through line 456 . The stream comprising the diamine is passed from the high boiler distillation section 455 through line 458 .

The stream comprising the diamine and the intermediate boiler is withdrawn from the low boiler distillation section 451 via line 454 to the intermediate boiler distillation column 460 .

The medium boiling compound distillation column 460 can be operated under vacuum conditions. The pressure difference in the medium boiling compound distillation column 460 may be 40 to 120 mm Hg (6.7 to 16 kPa), for example, 50 to 70 mm Hg (10.7 to 13.3 kPa).

The liquid phase is withdrawn from the bottom section of the intermediate boiling compound distillation column 460 via line 484 . A portion of the flow in line 484 can be passed through the pump and into the heating body (not shown in Figure 8A). Steam can be used as a heat source for the heating body. The heating body can have a forced circulation circuit design or a thermosyphon design. The pump provides a steady stream of material and sufficient back pressure (e.g., 20 to 30 psig, i.e., 239 to 308 kPa) to keep the material from boiling. The heated liquid from the heating body can be returned to the intermediate boiling compound distillation column 460 . The liquid stream from the heating body can be transferred to the medium boiling compound distillation column 460 via the orifice. The compound having the lowest boiling point will vaporize upward into the column, and the higher boiling compound will return to the bottom of the intermediate boiling compound distillation column 460 .

Two trays are installed near the top of the medium boiling compound distillation column 460 . The lower tray is a liquid collection tray 461 . This tray 461 collects liquid from the upper portion and is in contact with vapor moving upwardly along the column. The liquid from the upper portion collected in the liquid collection tray 461 includes a countercurrent from the heat exchanger 466 introduced via line 467 and a reflux introduced via 487 . The approximate temperature on the liquid collection tray 461 can be from 115 to 125 °C, such as 121 °C. The liquid is drawn from line 463 to line 465 via pump 464 and into heat exchanger 466 .

The heat exchanger 466 can be disposed in close proximity to the intermediate boiler distillation column 460 or at a location relatively remote from the intermediate boiler distillation column 460 . For example, heat exchanger 466 and medium boiling compound distillation column 460 can be located in the same or different buildings or enclosures.

The temperature of the liquid entering the heat exchanger 466 in the flux of the heat exchanger 466 may be reduced to 35 ℃ The quantity of, for example 20 to 30 ℃, and then to return the liquid in the boiler distillation column 460 via line 467. The countercurrent through line 467 can enter the intermediate boiler distillation column 460 at a location on the top liquid return tray 462 . The reflux may also enter the medium boiling compound distillation column 460 at a position on the top liquid return tray 462 . This reflux can enter the medium boiling compound distillation column 460 via line 487 .

The overhead vapor of the medium boiling compound distillation column 460 is passed through the overhead liquid return tray 462 and subsequently into a condenser (e.g., atmospheric spray condenser 475 ) where it is condensed. These vapors are delivered from the medium boiling compound distillation column 460 to the atmospheric spray condenser 475 , which is represented by line 474 in Figure 8A. Line 474 in Figure 8A enters the rectangle depicting the atmospheric spray 475 at the bottom of the rectangle. However, this depiction is only a schematic diagram. Vapor from the medium boiling compound distillation column 460 can enter the atmospheric spray condenser 475 via a plurality of locations. For example, these vapor condenser 475 may be sprayed into the atmosphere near the top condenser 475 of the condenser 475 near or at the bottom. The atmospheric spray condenser 475 can be operated in a cocurrent or countercurrent manner as described below. The atmospheric spray condenser 475 can be operated under atmospheric or vacuum conditions.

The condensed vapor exiting from the atmospheric spray condenser 475 is passed via line 476 , then via pump 477 to line 478 and into heat exchanger 480 . The liquid entering the heat exchanger 480 via line 478 can be cooled by at least 5 °C, such as 5 to 20 °C, and then exits the heat exchanger 480 via line 481 . The liquid entering the heat exchanger 480 via line 478 can have a temperature of 75 to 90 ° C (e.g., 80 to 90 ° C). The liquid exiting heat exchanger 480 via line 481 can have a temperature of 65 to 85 ° C (e.g., 70 to 80 ° C).

Cooling fluid is introduced into heat exchanger 480 via line 482 . The cooling fluid can be air or water. For example, liquid water can be introduced into heat exchanger 480 via line 482 at a temperature of 35 to 50 °C (eg, 40 to 45 °C). The temperature of the cooling water entering heat exchanger 480 via line 482 may be increased by 2 to 20 °C (e.g., 2 to 10 °C) in heat exchanger 480 , followed by exit via line 483 .

The process stream in line 481 is sprayed into an atmospheric spray condenser 475 . Line 481 in Figure 8A enters the rectangle depicting the atmospheric spray 475 at the top of the rectangle. However, this depiction is only a schematic diagram. The liquid spray can enter the atmospheric spray condenser 475 via a variety of locations. For example, these vapor condenser 475 may be sprayed into the atmosphere near the top condenser 475 of the condenser 475 near or at the bottom. The atmospheric spray condenser 475 can be operated in a cocurrent or countercurrent manner. When the atmospheric spray condenser 475 is operated in a co-current mode, the spray can be introduced into the condenser 475 at a location that is lower than or equivalent to the inlet location of the vapor introduced via line 474 . When the atmospheric spray condenser 475 is operated in a countercurrent manner, the spray can be introduced into the condenser 475 at a location above the inlet location of the vapor introduced via line 474 . An example of a co-flow atmospheric spray condenser is described in U.S. Patent No. 5,516,922. An example of a countercurrent atmospheric spray condenser is described in U.S. Patent No. 2,214,932.

As shown in Figure 8A, a distillate stream comprising a medium boiling compound, such as diaminocyclohexane (DCH), is removed in stream 479 from line 478 .

The distillate stream (before or after the air/water cooler) can be taken from the liquid and used as a column reflux. For example, this distillate stream can be withdrawn from line 476 , line 478 , line 479, or line 481 . The reflux liquid in this distillate stream can be introduced into the medium boiling compound distillation column 460 at a position higher than the overhead liquid return tray 462 . The flow of reflux to the intermediate boiling compound distillation column 460 is depicted in Figure 8A as being passed through line 487 .

The boiling point of hexamethylenediamine is 205 °C. When the adiponitrile is hydrogenated to obtain hexamethylenediamine, various isomers of diaminocyclohexane (such as 1,2-diaminocyclohexane) are formed as by-products. The boiling point of such isomers of diaminocyclohexane can be, for example, in the range of from 185 to 195 °C. These isomers of diaminocyclohexane are medium boiling compounds. In the method of hydrogenating adiponitrile to obtain hexamethylenediamine, such isomers of diaminocyclohexane are mainly separated from hexamethylenediamine in the medium boiling compound distillation column 460 .

The boiling point of methyl pentanediamine is 194 °C. When hydrogenated methylglutaronitrile is obtained to obtain methylpentanediamine, various isomers of methylcyclopentanediamine are formed as by-products. The boiling point of such isomers of methylcyclopentanediamine can be, for example, in the range of from 180 to 187 °C. These isomers of methylcyclopentanediamine are medium boiling compounds. In the method of hydrogenating methylglutaronitrile to obtain methylpentanediamine, such isomers of methylcyclopentanediamine are mainly separated from methylpentanediamine in the medium boiling compound distillation column 460 .

The stream comprising the refined diamine product is withdrawn from the high boiler distillation column 455 via line 458 as a distillate stream. Although not shown in Figure 8A, a portion of the stream in line 484 can be pumped into a heat exchanger, heating body or reboiler and heated. The heated fluid from the heat exchanger, heater or reboiler can be returned to the mid-boiling compound distillation column 460 at a location above the take-off position of line 484 . The mid-boiling compound is concentrated in a purification concentration column 485 and exits the system in the form of a top stream 486 . The bottom stream from column 485 is returned to column 460 via line 488 in reflux.

Heat exchanger 466 in Figure 8A corresponds to heat exchanger 318 in Figure 4 . The feed introduced into heat exchanger 466 via line 468 in Figure 8A corresponds to the feed introduced into heat exchanger 318 via line 308 in Figure 4 . The feed introduced into heat exchanger 466 via line 465 in Figure 8A corresponds to the feed introduced into heat exchanger 318 via line 319 in Figure 4 .

The heated feed exiting heat exchanger 466 via line 469 in Figure 8A corresponds to the heated feed exiting heat exchanger 318 via line 321 in Figure 4 . The cooled feed exiting heat exchanger 466 via line 467 in Figure 8A corresponds to the cooled feed exiting heat exchanger 318 via line 320 in Figure 4.

The temperature of the feed line 468 may be increased by 27 to 47 ℃ in the heat exchanger 466 (for example, 32 to 42 ℃) to heat away from the heat exchanger 466 of the feed via line 469.

The heat exchanger 470 in Fig. 8A corresponds to the heat exchanger 323 in Fig. 4. The feed introduced into heat exchanger 470 via line 469 in Figure 8A corresponds to the feed introduced into heat exchanger 323 via line 321 in Figure 4 . The temperature of the feed line 469 may be increased in heat exchanger 10 to 4702 deg.] C (e.g., 1 to 5 ℃) to heat exchanger 470 to leave the feed via line 473. The heated feed can then be introduced into converter 327 via line 326 , as shown in Figures 4 and 5.

The amount of thermal energy (e.g., in kilowatt hours) that is imparted by heat exchanger 466 to the feed in heating line 468 to obtain a heated feed in line 473 can be from heat exchanger 468 and heat exchanger 470. 80 to 99%, such as 90 to 99%, such as 92 to 98%, of the total heat energy imparted to the feed.

Detailed description of Figure 8B

Figure 8B shows an embodiment of the low boiling compound distillation section 451 of Figure 8A. The particular distillation section of Figure 8B contains two distillation columns 490 and 492 . However, it should be understood that the low boiling compound distillation section 451 of Figure 8A can comprise a different configuration of the distillation column, including a single distillation column or more than two distillation columns.

As shown in FIG. 8B, the crude diamine stream is passed via line 450 to first distillation column 490 . At least a portion of the low boilers from the stream of line 450 are removed from the first distillation column 490 via line 452 as a top stream.

The bottoms stream comprising the diamine, medium boiling compound, and high boilers is withdrawn from the first distillation column 490 and passed via line 491 to the second distillation column 492 . In the second distillation column 492 , the diamine and the medium boiling compound are separated from the high boiling compound. The diamine and medium boilers are withdrawn from the second distillation column 492 via line 454 as overhead vapor. As shown in Figure 8A, the stream in line 454 is fed to a medium boiling compound distillation column 460 .

The lateral withdrawal stream is withdrawn from the second distillation column 492 via line 453A . The bottom stream is withdrawn from the second distillation column 492 via line 453B . These streams are all introduced into the high boiler distillation section 455 (shown in Figure 8A). As shown in FIG. 8B, a recycle stream from the high boiler distillation section is introduced into second distillation column 492 via line 496 . The stream in line 496 can be introduced into second distillation column 492 at a location below the take-off position of lateral draw stream 453A and above the take-off position of bottom stream 453B .

Although not shown in Figure 8B, it will be appreciated that a portion of the overhead vapor stream in line 452 can be transferred to the condenser and at least a portion of the condensate can be returned to first distillation column 490 in reflux. Also shown in Fig. 8B is a heating body or a reboiler for supplying heat to the distillation. For example, a portion of the stream in line 491 can be passed through a heating body or reboiler and the heated liquid can be introduced into the first distillation column at a location below the location of the feed stream in the introduction line 450 .

Detailed description of Figure 8C

Figure 8C shows an embodiment of the high boiling compound distillation section 455 of Figure 8A. The particular distillation section in Figure 8C comprises two distillation columns 493 and 495 . However, it should be understood that the high boiler distillation section 455 of Figure 8A can comprise a different configuration of the distillation column, including a single distillation column or more than two distillation columns.

In Figure 8C, a first feed stream comprising at least one medium boiling compound, a diamine, and at least one high boiler is introduced into first distillation column 493 via line 453A . As shown in Figure 8B, the stream in line 453A is withdrawn from distillation column 492 in the form of a side draw stream. A second feed stream comprising a diamine and at least one high boiler is introduced into second distillation column 495 via line 453B . As shown in Figure 8B, the fluid in line 453B is withdrawn from distillation column 492 as a bottoms stream.

The top vaporization stream comprising at least one medium boiling compound is withdrawn from the first distillation column 493 of Figure 8C via line 457 . The liquid side draw stream containing the diamine can be withdrawn from the first distillation column 493 via line 458A .

The bottoms stream is withdrawn from the first distillation column 493 of Figure 8C via line 496 and returned to the second distillation column 492 of Figure 8B. As shown in Figure 8B, the flow in line 496 is introduced at a location above the take-off position of the bottom stream in line 453B and below the take-off position of the side stream in line 453A .

The stream in line 453B is introduced into the second distillation column 495 at a location above the take-off position of the bottom stream in line 456 and below the exit point of the overhead vapor stream in line 458B . The bottom stream in line 456 of Figure 8C corresponds to the fluid in line 456 of Figure 8A. The stream in line 456 contains at least one high boiling compound. The high boilers in the stream in line 456 can be further refined in the steps not shown in Figures 8A and 8C to separate the various components of the stream.

The overhead vapor stream in line 458B can be passed to a diamine storage tank not shown in Figure 8C. Similarly, the stream in line 458A of Figure 8C can be transferred to a diamine tank not shown in Figure 8C. The stream in line 484 of Figure 8A can also be transferred to a diamine storage tank not shown in Figure 8A. The reservoirs used to store the contents of the three streams may be the same or different. For example, these three streams can be transferred to a shared tank.

A portion of any of lines 458A , 458B, and 484 can be returned to any of column 460 (shown in Figure 8A), column 493 (shown in Figure 8B), and column 495 (shown in Figure 8C). For example, all three of these streams can be stored in a common reservoir, and a portion of this coexisting diamine can be returned to distillation column 495 in Figure 8C as reflux.

The overhead vapor stream in lines 457 and 458B can be passed through a condenser (not shown in Figure 8C) and a portion of the condensate can be returned to distillation columns 493 and 458B in reflux. Portions of the bottoms stream in lines 496 and 456 can also be passed through a heat exchanger, reboiler or heating body (not shown in Figure 8C), and the portion of the heated fluid can be below the feed streams 453A and 453B . The position of the introduction position is returned to the distillation columns 493 and 458B .

Detailed description of Figure 9

Figure 9 shows a modified version of the method shown in Figure 8A. In detail, the features of FIG. 8A are omitted in FIG. Such omitted features include tray 461 , tray 462 , line 463 , pump 464 , line 465 , heat exchanger 466, and line 467 . In FIG. 9, the fluid in line 468 is delivered directly to heat exchanger 470 without first preheating in heat exchanger 466 .

Movable catalytic cylinder and converter vessel

As previously described, the mobile catalyst can contain a hydrogenation catalyst. An example of such a catalytic canister and its use in a converter vessel are described below with reference to Figures 10-16.

Detailed description of Figure 10

FIG 10 is a plan view of a catalytic cartridge, the catalytic cartridge 600 has a cylindrical housing, having a top 602, a bottom 604, the base 604 includes a chemical reactant into the central standpipe 611 (not shown in FIG. 10, FIG. 12 And the inlet 610 and one or more chemical product outlets 608 shown in FIG. The chemical reactions are all carried out in a cylinder 600 that can easily remove ambient air.

Detailed description of Figures 11 and 12

Figure 11 is a side elevational view of the structure of Figure 10, and Figure 12 is a cross-sectional view of Figure 11 taken along line 3-3 showing the internal structure of the catalytic can. The mating inlet tube 613 is inserted into the standpipe 611 via the inlet 610 . The chemical reactant flows up through the riser 611 to the top of the reaction cartridge 600 . The upper end of the reaction cylinder 600 is covered with a cover which is bolted to the top of the cylinder. Covers and bolts are not shown for clarity.

The upper end of the riser 611 extends almost to the top of the barrel and above the top of the catalyst bed (not shown for purposes of clarity) to deliver chemical reactants entering the barrel to the top of the catalyst bed, wherein the chemical reactants may It passes through the catalyst bed by gravity and is propelled by the pressure of the reactant feed. In order to evenly distribute the incoming reactant feed to the top of the catalyst bed, the upper end of the riser 611 may be provided with an inverted conical screen 612 to allow the chemical reactant to exit the top of the riser 611 and pass through the inverted cone Sieve 612 is distributed. Alternatively, an array of holes 614 drilled around the upper end of the riser 611 and around the upper end of the riser provides a fluid outlet such that the chemical reactants are evenly distributed on top of the catalyst bed. In the latter embodiment, the array of holes 614 is preferably surrounded by a screen (not shown for purposes of clarity) such that the reactants can exit the standpipe but the catalyst pellets or particles cannot enter and block it. At least a portion of the aperture 614 extends above the level of the catalyst bed. At least a portion of the aperture 614 can also be located below the top level of the catalyst bed.

After passing through the catalyst bed, the chemical reactant reacts and is converted to a chemical product which is first passed through a perforation or screen in the outlet distribution tube 618 and then down to a collection channel connected to the bottom of the bottom 604 of the barrel 600 . (not shown in Figures 11 and 12) and leave the barrel. The outlet distribution tube 618 can include a bore surrounded by a screen. The product then exits through one or more discharge tubes (not shown in Figures 11 and 12) and into the void space between the bottom of the barrel and the inner bottom cover of the converter (as shown in Figure 15B). The chemical product is then collected and further processed.

Detailed description of Figure 13A

Fig. 13A is a plan view showing a converter 630 container (hereinafter simply referred to as "converter") using a catalytic cylinder in a hydrogenation reaction. The converter is shown from the bottom.

The converter strengthens the walls of the cylinder during the hydrogenation reaction at elevated temperatures and pressures. The walls of the barrel are designed to provide a sufficiently light weight because the walls must only withstand the differential pressure across the catalyst bed. If the wall of the barrel is designed to withstand the temperature and pressure conditions of the hydrogenation reaction without reinforcement, the barrel will actually be too heavy to be inserted, transported and removed.

Converter 630 is generally cylindrical in shape and has a bottom 632 , a central portion 638, and a top portion 640 . The diameter of this top 640 can be slightly larger than the rest of the device. A centrally located inlet tube 634 and at least one outlet 636 pass through the bottom 632 .

Detailed description of Figure 13B

Figure 13B is an exploded view of the converter of Figure 13A, additionally illustrating that the inlet tube 634 includes at least three distinct portions: an inlet tube attachment flange 634a for attachment to a chemical reactant fluid inlet conduit; configured to internally catalyze The reduced diameter inlet tube insertion portion 634b of the central riser 652 of the cartridge; and the attachment flange 634c for bolting the inlet tube to the bottom of the converter 630 . The top 640 of the converter has a retaining ring 644 with a locking screw 646 on the outer circumference.

14A and 14B are detailed descriptions

14A is a side view of converter 630 , and FIG. 14B is a cross-sectional view of FIG. 14A illustrating the entire converter system in more detail. For example, in Figure 14b, fluid communication between the outlet 636 and the interior void 632a of the bottom 632 can be seen, and the entire configuration of the inlet tube 634 is also visible. The internal configuration of the top 640 can also be seen in the cross-sectional view. A converter top cover 620 is disposed on the catalytic canister 600 . A centrally placed riser 652 is placed in the converter such that the lower end of the riser 652 engages the upper end 634b of the inlet tube 634 , which provides a fluid-tight inlet for the chemical reactant to the catalyst (not shown for purposes of clarity). The converter top cover 620 is held in place by a retaining ring 644 of the locking mechanism 648 described below.

An outlet 650 that flows to a collection channel (not shown in Figure 14B) at the bottom of the catalytic canister provides an outlet for the chemical product.

The converter top 640 includes a locking mechanism 648 that includes a combination of locking teeth 642 formed on the inner circumference of the top portion 640 and a retaining ring 644 having cooperating locking teeth 646 formed on the outer circumference thereof. . The locking mechanism 648 locks the converter top cover 620 in place when engaged and rotated in the first direction. When rotated in the opposite direction, the locking mechanism 648 releases the converter top cover 620 , and the retaining ring 644 and the converter top cover 620 can be raised from the converter 630 to accommodate the catalytic cylinder 600 already in use.

Detailed description of Figure 15

15 is a plan view of a lock mechanism of a converter including a housing 660 and an internal insert configured to be inserted into the housing and partially rotated for locking, in this case a retaining ring 662 . The shell 660 has a cylindrical inner surface and has a first flat end surface 666 at one end. The cylindrical inner surface includes a first locking thread 672 that includes 2 to 20 equally spaced lock rings, each of which includes m rows of teeth 672a and m gaps 672b that are alternately arranged around the cylindrical inner surface.

The retaining ring 662 has a second locking thread 668 that includes a number m of gaps 668b and m rows of teeth 668a , wherein m is 2 to 12, alternately arranged about its cylindrical outer surface 670 . The retainer ring 662 is inserted into the void of the housing 660, the retaining ring 662 such row of teeth 668a on the surface of the gap 672b is aligned with the inner housing 660, so that the retainer ring 662 axially movable in the housing 660. To lock the locking mechanism thus formed, the retaining ring 662 is partially rotated to cause its locking thread/teeth 668a to be transferred into the locking thread/teeth 672a of the tube and between the locking threads/teeth 672a of the tube. The transfer, thereby acting together, causes the retaining ring 662 to be secured in the housing 660 in the axial direction.

Detailed description of Figure 16

In Figure 16, the locking mechanism is in fluid communication with the inlet and outlet connections of the bottom of the barrel and is disposed within the chemical reactor containment vessel 660 of the catalytic canister 600 . The converter top cover 620 is placed at the bottom of the retaining ring 662 such that rotation and locking of the locking mechanism are used to retain the retaining ring 662 within the housing 660 . The net fluid flow into and out of the cartridge is indicated by the arrows in Figure 16.

Instance

The following examples describe a method of hydrogenating a dinitrile to produce a diamine and a method of preparing a catalyst for use in the hydrogenation reaction.

Example 1

This example describes the conversion of methylglutaronitrile (MGN) to 2-methylpentanediamine (MPMD). Referring to Figure 1, a feed stream comprising MGN and fresh feed and recycle hydrogen and ammonia is passed to a series of four converters 42 , 44 , 46 and 48 . The MGN feed can have the following composition: MGN = 99.1 wt% min

ESN=0.4wt% max

HCN=20ppm max

Water = 0.12 wt% max

Ethylene glycol = 50ppm max

Phosphorus = 15ppm

Other = 0.7 wt% max.

The feed to the first converter 42 can have a pressure of at least 3500 psig (24,233 kPa), such as at least 4000 psig (27,680 kPa), such as at least 4500 psig (31,128 kPa). The temperature of the feed to the first converter can be at least 100 °C, such as at least 105 °C, such as at least 110 °C. In the first converter 42 , the reaction of hydrogen with MGN is exothermic. Thus, the temperature of the effluent stream exiting the first converter 42 can be at least 5 ° C higher than the temperature of the stream entering the first converter 42 , such as at least 10 ° C. The temperature of the stream exiting the first converter 42 should preferably not exceed 200 ° C, for example 190 ° C, for example 180 ° C.

Preferably, the effluent stream of first converter 42 is cooled to at least 5 ° C, for example at least 10 ° C, before it is introduced into second converter 44 . This cooling can be accomplished at least in part by transferring the effluent from the converter 42 to at least one heat exchanger or cooler (not shown in Figure 1) and feeding the fresh feed of MGN via line 38 (the temperature is lower than the converter 42 ) The effluent) is introduced into line 50 .

The feed to the second converter 44 can be at least 3500 psig (24,233 kPa), such as at least 4000 psig (27,680 kPa), such as at least 4500 psig (31,128 kPa). The temperature of the feed to the second converter 44 can be at least 100 °C, such as at least 105 °C, such as at least 110 °C. The reaction of hydrogen with MGN in the second converter 44 is exothermic. Thus, the temperature of the effluent stream exiting the second converter can be at least 5 ° C higher than the temperature of the stream entering the second converter 44 , such as at least 10 ° C. The temperature of the stream exiting the second converter 44 should preferably not exceed 200 ° C, such as 190 ° C, such as 180 ° C.

Preferably, prior to introducing the effluent stream of second converter 44 into third converter 46 , it is cooled to at least 5 °C, such as at least 10 °C. This cooling can be accomplished at least in part by transferring the effluent from the third converter 46 to at least one heat exchanger or cooler (not shown in Figure 1) and feeding the MGN fresh via line 40 (temperature below the second) The effluent of converter 44 is introduced into line 52 .

The feed to the third converter 46 can be at least 3,500 psig (24,233 kPa), such as at least 4000 psig (27,680 kPa), such as at least 4,500 psig (31,128 kPa). The temperature of the feed to the third converter can be at least 100 °C, such as at least 105 °C, such as at least 110 °C. The reaction of hydrogen with MGN in the third converter 46 is exothermic. Thus, the temperature of the effluent stream exiting the third converter 46 can be at least 5 ° C higher than the temperature of the stream entering the third converter 46 , such as at least 10 ° C. The temperature of the stream leaving the third converter 46 should preferably not exceed 200 ° C, for example 190 ° C, for example 180 ° C.

Preferably, prior to introducing the effluent stream of third converter 46 into fourth converter 48 , it is cooled to at least 5 °C, such as at least 10 °C. This cooling can be performed at least in part by transferring the effluent from the third converter 46 to line 56 via line 54 and heat exchanger 20 . The temperature of the stream in line 56 can be further reduced by introducing fresh feed of MGN (temperature below the effluent of third converter 46 ) into line 56 via line 34 .

The feed to the fourth converter 48 can have a pressure of at least 3500 psig (24,233 kPa), such as at least 4000 psig (27,680 kPa), such as at least 4500 psig (31,128 kPa). The temperature of the feed to the fourth converter can be at least 90 °C, such as at least 95 °C. The reaction of hydrogen with MGN in the fourth converter 48 is exothermic. Thus, the temperature of the effluent stream exiting the fourth converter 48 can be at least 5 ° C higher than the temperature of the stream entering the fourth converter 48 , such as at least 10 °C. The temperature of the stream leaving the fourth converter 48 should preferably not exceed 200 ° C, for example 190 ° C, for example 180 ° C. For example, the temperature of the stream exiting the fourth converter 48 can range from 130 to 180 °C and the pressure can range from 4100 to 4500 psig (28,370 to 31,128 kPa).

The effluent from the fourth stage converter 48 is passed via line 58 to heat exchanger 60 . The fourth converter effluent can be reduced in heat exchanger 60 at a pressure of from 4,100 to 4,500 psig (28,370 to 31,128 kPa) to a temperature range of from 30 to 60 °C. The cooled effluent is then transferred from heat exchanger 60 to product separator 64 via line 62 . Flashing occurs in product separator 64 . In product separator 64 , the pressure of the effluent of fourth converter 48 can be reduced to a range of from 450 to 500 psig (3,204 to 3,549 kPa) to separate at least one liquid phase from at least one vapor phase.

The liquid phase comprising MPMD from product separator 64 is passed via line 66 to heat exchanger 60 . The liquid phase can be heated in heat exchanger 60 to a temperature of between about 65 and 85 °C. The feed stream entering line 68 of ammonia recovery system 70 can have a temperature of 65 to 85 ° C and a pressure of 465 to 480 psig (3,307 to 3,411 kPa). The fluid in line 68 can comprise 55 to 65 wt% ammonia, 35 to 45 wt% MPMD, and less than 1 wt% (e.g., 0.1 to 0.5 wt%) hydrogen.

The ammonia recovery system 70 includes an ammonia recovery column (not shown in Figure 1) and a condenser (not shown in Figure 1). The ammonia recovery column can have a bottom temperature of 150 ° C and a top temperature of 67 ° C. The tower can be operated at super atmospheric pressure. The crude product containing MPMD is withdrawn from the bottom of the ammonia column and exits the ammonia recovery system via line 72 . This crude product may comprise at least 90% by weight MPMD. The crude product can be further refined to remove impurities.

The gas phase overhead product of the ammonia recovery column is passed to a condenser where a distillate phase comprising ammonia and a vapor phase comprising hydrogen are formed. A portion of the distillate phase can be returned to the ammonia recovery column as reflux. A portion of the distillate phase can be delivered to at least one storage tank for storage. A portion of the distillate phase can also be recycled as the ammonia feed to the hydrogenation reaction. In Figure 1, this ammonia recycle is indicated by the transfer of ammonia from the ammonia recovery system to line 2 via line 74 .

The gas phase comprising hydrogen and ammonia from product separator 64 is passed via line 86 to gas recycle pump 88 to facilitate the flow of hydrogen and ammonia through line 18 . The gas line 86 may comprise 92 to 96wt% of hydrogen (H ₂₎ and 4 to 8wt% ammonia (NH _3).

The ammonia source is passed through line 2 and ammonia pump 10 and via line 12 to the hydrogen/ammonia recycle fluid in line 18 . The ammonia source may also include recycled ammonia introduced into line 2 via line 74 . A source of hydrogen gas is also delivered to the hydrogen compressor 14 via line 4 . Ammonia from ammonia pump 10 is passed via line 12 to line 18 , and hydrogen from the hydrogen compressor is transferred via line 16 to line 18 . The stream comprising ammonia and hydrogen in line 18 is partially heated in heat exchanger 20 before it is passed via line 22 to converter preheater 24 . The heated ammonia and hydrogen from preheater 24 are then passed through a series of four converters depicted as converters 42 , 44 , 46 and 48 in FIG.

The MGN feed is fed from line 28 to the dinitrile pump 30 . The MGN feed from the dinitrile pump 30 is passed via line 32 to line 34 . A portion of the MGN feed can be conveyed via line 34 to ammonia feed line 2 . A portion of the MGN feed may also be transferred from line 34 to line 26 via side stream 36 for introduction into first stage converter 42 . Similarly, side streams 38 and 40 provide fresh MGN feed to second stage converter 44 and third stage converter 46 . Again, as depicted in Figure 1, the fresh MGN feed in line 34 is introduced into the fourth stage converter 48 .

In an embodiment selected as appropriate, at least a portion of the vapor phase comprising hydrogen and ammonia in line 76 is passed as a feed to a catalyst activating unit via a line not shown in FIG. 1 to reduce the iron oxide by hydrogen to prepare a catalyst. . This stream may comprise 55 to 65wt% of hydrogen (H ₂₎ and 35 to 45wt% ammonia (NH _3).

Example 2

This example describes an embodiment in which a catalyst is formed by reducing iron oxide with hydrogen in the presence of ammonia.

Referring to Figure 2, hydrogen is supplied from source 100 . In this example, hydrogen source 104 is not used. The hydrogen supplied from the source 100 is from a hydrogen pipe which has been purified by a pressure swing adsorption process.

The hydrogen in source 100 is pressurized to a pressure of 200 to 400 psig (1,480 to 2,859 kPa) (e.g., 250 to 350 psig (1,825 to 2,515 kPa), such as 300 psig (2,170 kPa). Hydrogen from source 100 is passed to preheater 110 via line 102 and line 108 in sequence. The heated hydrogen is passed via line 112 to a hydrogen/ammonia mixer 118 . The ammonia feed to the hydrogen/ammonia mixer 118 is derived from the ammonia source 114 . The ammonia in source 114 is anhydrous liquid ammonia pressurized to a pressure of 300 to 500 psig (2,170 to 3,549 kPa) (e.g., 350 to 450 psig (2,515 to 3,204 kPa), such as 400 psig (2,859 kPa)). The ammonia feed is passed via line 116 to a hydrogen/ammonia mixer 118 .

The liquid ammonia fed to the hydrogen/ammonia mixer 118 is vaporized in the presence of hydrogen to form a gaseous hydrogen/ammonia mixture. This mixture may contain 96 to 98 mol% (e.g., 97 mol%) of hydrogen and 2 to 4 mol% (e.g., 3 mol%) of ammonia. Liquid ammonia can be introduced into the hydrogen/ammonia mixer 118 at ambient temperature (e.g., below 30 °C). The hydrogen in the preheater 110 is heated to a temperature sufficient to maintain the gaseous state of ammonia in the hydrogen/ammonia mixer 118 and in the downstream stream of the hydrogen/ammonia mixer 118 . For example, the temperature of the hydrogen in line 112 can be at least 120 °C, such as 120 to 140 °C, such as 130 °C. The temperature of the hydrogen/ammonia mixture leaving the hydrogen/ammonia mixer 118 entering line 120 can be at least 30 °C, such as 30 to 50 °C, such as 40 °C.

As shown in Figure 2, the temperature of the hydrogen/ammonia mixture is gradually increased to the appropriate reaction temperature in both heating steps. In the first heating step, the mixture is transferred from line 120 to line 122 for delivery to heat exchanger 124 . The temperature of the hydrogen/ammonia mixture exiting heat exchanger 124 via line 126 can be, for example, at least 50 °C, such as 60 to 350 °C. The temperature of the hydrogen/ammonia mixture entering the line 130 and entering the catalyst activation unit 132 leaving the preheater 128 may be 375 to 425 °C, such as 385 to 415 °C, such as 400 °C. The pressure of the hydrogen/ammonia mixture entering the catalyst activation unit 132 can be at least 25 psig (274 kPa), such as 50 to 200 psig (446 to 1,480 kPa), such as 120 psig (929 kPa).

The reaction of iron oxide with hydrogen in the catalyst activating unit 132 produces water (H ₂ O) as a by-product. Further, ammonia (NH ₃ ) undergoes some decomposition to obtain hydrogen (H ₂ ) and nitrogen (N ₂ ). Thus, the gaseous effluent exiting catalyst activating unit 132 and entering line 134 comprises a mixture of hydrogen, ammonia, water, and nitrogen. The composition of this gas mixture depends, at least in part, on the purity of the hydrogen fed to the catalyst activation unit and can vary based on this and the choice of operating conditions.

The reduction reaction carried out in the catalyst activating unit 132 is endothermic. The temperature of the effluent exiting the catalyst activating unit 132 may be at least 10 ° C lower than the temperature of the feed to the catalyst activating unit 132 , such as 15 to 40 ° C lower, such as 25 ° C lower. The temperature of the effluent leaving catalyst activation unit 132 can range from 300 to 450 °C, such as from 350 to 425 °C, such as from 360 to 400 °C, such as 375 °C. The pressure of the effluent exiting the catalyst activating unit 132 can be at least 25 psig (274 kPa), such as 50 to 200 psig (446 to 1,480 kPa), such as 100 psig (791 kPa).

The temperature of the effluent of the catalyst activation unit is lowered in two steps. In the first step, the temperature of the effluent is partially reduced by passing the effluent through line 134 and through heat exchanger 124 . In this manner, heat is supplied to the hydrogen/ammonia mixture entering heat exchanger 124 via line 122 and exiting heat exchanger 124 via line 126 . In the second cooling step, the partially cooled effluent of the catalyst activating unit 132 is cooled in the cooler 138 . In this manner, the temperature of the effluent is reduced to a temperature sufficient to allow phase separation in separator 142 .

The cooled effluent from catalyst activation unit 132 is transferred from cooler 138 to separator 142 via line 140 . In the separator 142 , the effluent of the catalyst activating unit 132 is separated into a liquid phase containing ammonia and water and a gas phase containing hydrogen and ammonia at atmospheric pressure. In order to maximize the amount of water in the liquid phase and minimize the amount of water retained in the gas phase, the effluent entering the separator 142 can be cooled to 10 ° C or below 10 ° C by means of the heat exchanger 124 and the cooler 138 ( For example, a temperature of 5 ° C or less.

Water mixed with ammonia is removed from separator 142 via liquid line 148 in liquid phase. At least a portion of the gas phase in separator 142 is removed from the separator via line 144 for recycle to catalytic activation unit 132 . The temperature of the gas in line 144 can be 10 ° C or less, such as 5 ° C or less, such as 2 ° C. A portion of the gas phase in separator 142 may also be removed via line 150 as a purge stream. By extracting the purge stream from the gas phase of separator 142 , the accumulation of nitrogen in the recycle loop can be minimized.

The vapor phase for recycle is passed through line 144 and through compressor 146 . In this way, the pressure of the gas is increased to the pressure of the gases in lines 120 and 122 .

Example 3

This example describes the improvement of catalyst activity by temporarily interrupting the dinitrile feed stream of a converter for the conversion of adiponitrile to hexamethylenediamine (HMD).

The adiponitrile is hydrogenated by the three-stage reaction method shown in Figures 4 to 7 to form hexamethylenediamine. The catalyst was observed to age over time. In particular, to maintain a constant level of hexamethylene diamine production using a constant feed rate of each of the converters 327 , 373 , 348 , it is desirable to increase the temperature of the feed to each converter. In particular, during about two weeks, the temperature of the feed of the first converter 327 is increased from 90 ° C to 99.5 ° C, and the temperature of the feed of the second converter 337 is increased from 95 ° C to 104.1 ° C, and The temperature of the feed to the three converters 348 was increased from 141.5 ° C to 156.3 ° C.

At this point, the dinitrile feed stream from each converter was stopped. In particular, the adiponitrile pump 306 and pump 303 are turned off and the appropriate valves leading to the pumps and the lines from the pumps are closed. The gas circulation compressor 317 , the compression section 311, and the ammonia pump 314 are continuously operated. After about 0.5 hours, all of the removable dinitrile feed and diamine product were removed from the converter and the ammonia pump 314 was turned off. The gas recycle compressor 317 is continuously operated to keep the hydrogen gas circulating through the converter. The compression section 311 also continues to operate to maintain the converter at a pressure of from 2000 psig to 5500 psig (6996 kPa to 38,022 kPa). The system is heated via preheater 323 to maintain the feed temperature of the inlet of the first converter at 100 °C to 200 °C.

The hydrogen cycle lasts for 4 to 12 hours.

As the hydrogen continues to flow, the activity of the catalyst, especially the catalyst in the last converter 348 , is improved. Without being bound by theory, hydrogen can theoretically react with any iron oxide catalyst under high pressure to reactivate the catalyst.

After 4 to 12 hours of blocking, the feed of ammonia and adiponitrile was resumed. Upon returning to normal operating conditions, the inlet and outlet temperatures in the last converter 348 are reduced by 2 to 5 °C compared to the temperature before the adiponitrile feed is interrupted, even when the same degree of conversion as before the interruption is reached. This lower operating temperature of the last converter 348 also appears to reduce hexamethyleneimine (HMI) formation by up to 0.15%.

The formation of hexamethyleneimine (HMI) can be extremely temperature dependent. For example, the temperature in the last converter 348 can be high enough to cause the crude hexamethylene diamine (HMD) to contain 2.0 wt% hexamethyleneimine (HMI) before the adiponitrile feed is interrupted. After the adiponitrile feed was interrupted, the temperature in the last converter 348 was lowered such that crude hexamethylene diamine (HMD) contained 1.85 wt% hexamethyleneimine (HMI) under equivalent conversion conditions.

Renewing the aged catalyst portion by interrupting the adiponitrile feed can extend the catalyst life by at least 1 or 2 days.

The scope of the patent application and the terms used herein are to be construed as a variant of the invention described. The scope of the claims is not limited to such variations, but should be construed as covering the entire scope of the invention as implied in the invention.

2‧‧‧ pipeline

4‧‧‧ pipeline

10‧‧‧Ammonia pump

12‧‧‧ pipeline

14‧‧‧ Hydrogen compressor

16‧‧‧ pipeline

18‧‧‧ pipeline

20‧‧‧ heat exchanger

22‧‧‧ pipeline

24‧‧‧Transformer preheater/preheater

26‧‧‧ pipeline

28‧‧‧ pipeline

30‧‧‧Dinitrile pump

32‧‧‧ pipeline

34‧‧‧ pipeline

36‧‧‧tributors

38‧‧‧tributors/pipelines

40‧‧‧tributors/pipelines

42‧‧‧Transformer / First Stage Converter / Reactor / First Converter

44‧‧‧Transformer/Second Stage Converter/Second Stage Reactor/Reactor

46‧‧‧Transformer / Stage 3 Converter / Stage 3 Reactor / Reactor

48‧‧‧Transformer/Fourth Stage Converter/Reactor

50‧‧‧ pipeline

52‧‧‧ pipeline

54‧‧‧ pipeline

56‧‧‧ pipeline

58‧‧‧ pipeline

60‧‧‧ heat exchanger

62‧‧‧ pipeline

64‧‧‧Product separator

66‧‧‧ pipeline

68‧‧‧Line/heated fluid

70‧‧‧Ammonia recovery system

72‧‧‧ pipeline

74‧‧‧ pipeline

76‧‧‧ pipeline

78‧‧‧Ammonia absorber

80‧‧‧ pipeline

82‧‧‧Line/Ammonia flow

84‧‧‧ pipeline

86‧‧‧ pipeline

88‧‧‧ gas circulation compressor

Claims (14)

A method for preparing a diamine by converting a dinitrile to a diamine, the method comprising the steps of: (a) continuously introducing a feed comprising a dinitrile, a liquid or supercritical ammonia, and hydrogen into at least one fixed bed comprising a catalyst; In the converter; (b) contacting hydrogen with the diamine in each of the converters of step (a) to react the dinitrile with hydrogen to form a diamine; (c) withdrawing the effluent comprising the diamine from each converter; (d) increasing the temperature of the feed to at least one of the converters over time to compensate for catalyst aging; (e) interrupting the dinitrile and ammonia feed streams of at least one of the converters while maintaining the flow of hydrogen to the converter; f) discharging the residual dinitrile feed, ammonia and diamine product from the converter of step (e) while maintaining a hydrogen stream through the converter; and (g) restoring the flow to the converter of step (f) The ammonia and dinitrile feed stream and the effluent stream of the converter of step (e) while maintaining a comparable level of preparation prior to step (d) while maintaining the temperature of the feed to the converter below step (e) The temperature of the feed before starting. The method of claim 1, wherein after the start of step (g), maintaining a comparable level of preparation within 10% of the preparation level maintained prior to step (d), while maintaining the converter in step (g) The temperature of the feed is lower than the temperature of the feed before the start of step (e). The method of claim 1, wherein each of the converters comprises a vertically disposed cylindrical outer casing filled with a fixed bed of catalyst; wherein the bottom of the cylindrical outer casing further comprises at least two outlets; wherein a top portion of the cylindrical outer casing is disposed Void on the fixed bed of catalyst Space; and wherein the feed is introduced into the void space of the catalyst bed by introducing a feed comprising dinitrile, liquid or supercritical ammonia and hydrogen, and the feed flows downward through the catalyst bed, and via the bottom of the outer casing The outlet draws the effluent to introduce the feed into each converter and withdraw the effluent from each converter. The method of claim 3, wherein each of the converters further comprises a vertically disposed riser extending upwardly through the bottom of the cylindrical outer casing, through the fixed bed of catalyst and extending into the cylindrical outer casing above the catalyst a void space in which the bed is located; wherein the standpipe includes an inlet at the bottom of the cylindrical outer casing and at least one outlet in the region of the void space of the outer casing; and wherein steps (a), (b) and (c) is carried out by a method comprising the steps of: (i) introducing the feed comprising dinitrile, liquid ammonia and hydrogen into the inlet of the riser; (ii) passing the feed upward through the riser Flowing to the outlet of the riser; (iii) flowing the feed down the catalyst bed in the annular space between the riser and the vertical wall of the outer casing; and (iv) passing through the outer casing of the outer casing The outlets withdraw the effluent. The method of claim 1, wherein the dinitrile is converted to a diamine in at least three in series converters; wherein the effluent of the first converter in the series is passed to a second converter in the series, and the tandem The effluent of the second converter is passed to a third converter in the series; and wherein the dinitrile and ammonia feed streams of all of the converters in step (e) are interrupted. The method of claim 5, wherein the effluent of the first converter is first cooled, then transferred to the second converter, and the effluent of the second converter is first cooled However, it is then transferred to the third converter. The method of claim 1 wherein the pressure in each of the converters in step (b) is maintained at a level of at least 4000 psig (27,680 kPa). The method of claim 1, wherein the catalyst is a reduced form of iron oxide. The method of claim 1, wherein the dinitrile is adiponitrile and the diamine is hexamethylenediamine. The method of claim 1, wherein the dinitrile is methylglutaronitrile and the diamine is 2-methylpentanediamine. The method of claim 1, wherein the inlet temperature of the at least one converter is monitored over time; and wherein step (e) is initiated when the inlet temperature is raised to a predetermined level during step (d). The method of claim 1, wherein the outlet temperature of the at least one converter is monitored over time; and wherein step (e) is initiated when the outlet temperature is raised to a predetermined level during step (d). The method of claim 9, wherein the preparation level of hexamethyleneimine (HMI) is monitored over time; and wherein the preparation level of hexamethyleneimine (HMI) is raised to a predetermined level during step (d) Start step (e). The method of claim 13, wherein the hexamethyleneimine preparation level after the step (e) is lower than the hexamethyleneimine preparation level before the start of the step (e).