Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C253/00—Preparation of carboxylic acid nitriles
  • C07C253/32—Separation; Purification; Stabilisation; Use of additives
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C253/00—Preparation of carboxylic acid nitriles
  • C07C253/32—Separation; Purification; Stabilisation; Use of additives
  • C07C253/34—Separation; Purification

Definitions

• the disclosure relates to an improved process in the manufacture of acrylonitrile and methacrylonitrile.
• the disclosure is directed to crude acrylonitrile tank operation.
• Acrylonitrile is an important commodity chemical used mainly as monomer for the manufacture of a wide variety of polymeric materials such as polymers for acrylic fibers used in textiles, and in resins such as ABS and SAN resins. Worldwide, acrylonitrile is produced in amounts exceeding four million metric tons per year.
• the most commonly used process for manufacturing acrylonitrile or other olefinically unsaturated nitrile, such as methacrylonitrile, is to react a suitable hydrocarbon, such as propylene or propane for the manufacture of acrylonitrile, or isobutylene for the manufacture of methacrylonitrile, in an ammoxidation reactor in the presence of ammonia using air or other source of molecular oxygen as an oxidant.
• Such oxidation reactions also called ammoxidation reactions, typically use a solid, particulate, heterogeneous catalyst in a fluidized catalyst bed to catalyze the ammoxidation reaction and provide the desired acrylonitrile or methacrylonitrile in acceptable conversion and yield.
• ammoxidation reactions In addition to producing an olefinically unsaturated nitrile, such ammoxidation reactions also generally produce other products such as acetonitrile, hydrogen cyanide (HCN) and other co-products.
• HCN hydrogen cyanide
• control of the water and polymerization content of acrylonitrile product is important to the stability of the acrylonitrile product.
• MEHQ hydroquinone
• acrylonitrile product typically must be maintained within specified levels or ranges.
• the MEHQ polymerization inhibitor requires a certain amount of water in order to function and inhibit undesirable polymerization of acrylonitrile product.
• Specifications, such as U.S. and international shipping specifications typically require a minimum amount of water and inhibitor in the acrylonitrile product to be shipped because the acrylonitrile product without a certain amount of water and inhibitor is highly reactive.
• Specifications typically have a maximum amount of water and inhibitor content as well because excessive water and inhibitor will make desired subsequent reaction of acrylonitrile slow and difficult, e.g., at a customer plant designed to polymerize acrylonitrile.
• Specifications for the acrylonitrile product typically have maximums on certain impurities, such as hydrogen cyanide, acetonitrile, and acetone.
• an aspect of the disclosure is to provide a safe, effective and cost
• a process for maintaining storage of a crude acrylonitrile in a crude tank.
• the process includes conveying the crude acrylonitrile to the crude tank, adding acid to the crude acrylonitrile in the crude tank in an amount effective for maintaining a pH below a target pH, and maintaining a temperature of the crude acrylonitrile in the crude tank below a target temperature.
• a process for preparing a crude tank to receive crude acrylonitrile includes adding water to a crude tank in an amount effective for absorbing organics under a floating roof, maintaining a temperature of the water in the crude tank at about 25 °C or less, and acidifying the water to a pH of 4 or less.
• a crude acrylonitrile storage tank includes multiple temperature sensors configured to detect temperatures at different temperature heights in the crude acrylonitrile storage tank and multiple removal locations configured to remove crude acrylonitrile from the crude acrylonitrile storage tank.
• the tank also includes a pH sensor configured to detect a pH of the crude acrylonitrile in the crude acrylonitrile storage tank, a chiller configured to cool a recycle stream drawn from the removal locations of the crude acrylonitrile storage tank, and a return line configured to return at least a portion of the recycle stream to the crude acrylonitrile storage tank.
• FIG. 1 is a schematic flow diagram of an embodiment in accordance with aspects of the disclosure as applied to the manufacture of acrylonitrile product.
• FIG. 2 illustrates a flow diagram of a process in accordance with aspects of the
• a process includes detecting multiple temperatures of liquid at different heights of a crude tank.
• the process includes circulating a recycle stream drawn from an effluent height of the crude tank, cooling the recycle stream, and returning at least a portion of the recycle stream to the tank when the detected temperature is outside a predetermined temperature range.
• Processes described herein are less time and fewer steps may be required before acrylonitrile product is released to final product storage than in conventional systems and methods. Both laboratory and plant labor may be reduced in carrying out analysis of samples and adjustments to operating parameters to produce acrylonitrile product that is within specifications. Other benefits provided are that the number and/or volume of the rundown tanks may be decreased over the number and/or volume of rundown tanks required in conventional systems and methods. Another benefit provided is that acrylonitrile product that is off-specification for chemical impurities may be detected sooner, allowing corrective action to be taken and reducing the amount of acrylonitrile product re-run through a portion(s) of the system to as required in conventional systems and methods.
• an apparatus 10 comprises a tank 12.
• Tank 12 may be
• Crude acrylonitrile stream 14 may be conveyed to tank 12 from a recovery column or other vessel (not shown). Crude acrylonitrile product stream 14 may be conveyed via line 16 and into tank 12 at location 18. Temperature sensors 20, 22, 24, 26 and 28 may be configured to measure the temperature of liquid in tank 12 at corresponding vertical heights 30, 32, 34, 36, and 38 of liquid in tank 12. Crude acrylonitrile product in tank 12 may be conveyed out of tank 12 via line 40. Overhead vapor 110 may be conveyed from tank 12 via line 112 to scrubber (not shown).
• Crude acrylonitrile product may be conveyed from tank 12 via lines 82, 84, 86, and/or 88.
• Valve 92, 94, 96 and 98 may correspond to lines 82, 84, 86, and 88, respectively.
• Nozzles 102, 104, 106, and 108 may correspond to lines 82, 84, 86, and 88, respectively.
• Nozzles 102, 104, 106, and 108 may have vertical heights in tank 12 that correspond respectively to vertical heights 32, 34, 36, and 38 of liquid in tank 12. The distance a nozzle and the next nozzle in the series of nozzles may be the same.
• the distance between nozzle 102 and nozzle 104 may be the same as the distance between nozzle 104 and nozzle 106, etc.
• the distance between consecutive nozzles may be about two (2) to about twelve (12) feet, in another aspect, about five (5) to about twelve (12) feet, in another aspect, about eight (8) to about twelve (12) feet, and in another aspect, about ten (10) feet.
• nozzle 100 is shown in FIG. 1 as having a vertical height below vertical height 30, nozzle 100 may have a vertical height that is the same as or about vertical height 30.
• Line 46 may convey crude acrylonitrile product to heat exchanger or chiller 54, for example the tube side of chiller 54 at inlet 56.
• Chiller 54 may be configured to cool the crude acrylonitrile product via heat transfer with a cooling fluid 58, e.g., cooling water, introduced to the shell side of chiller 54 at inlet 60. Cooling fluid 58 may exit the chiller 54 at outlet 62.
• a cooling fluid 58 e.g., cooling water
• crude acrylonitrile product may exit at outlet 64 and be conveyed from chiller 54 via line 66 as cooled acrylonitrile product stream 78.
• Acid 68 e.g., glycolic acid or acetic acid, and combinations thereof, may be conveyed via line 70 and added at juncture 74 to crude acrylonitrile product in line 66.
• Acid 68 may be pumped by pump 72 from acid source 76 through line 70.
• acid 68 may be added to the cooled acrylonitrile product stream 78 to maintain the pH of liquid in tank 12 within a predetermined pH range. Cooled acrylonitrile product may be returned to tank 12 via line 80 through nozzle 100.
• controller 11 may be configured to process one or more signals
• Controller 11 may be configured to determine whether the measured parameter is above or below a predetermined parameter range.
• the measured parameter may be any suitable parameter useful in operation of tank 12, e.g., a temperature measured by the temperature sensors at predetermined vertical heights.
• Controller 11 may be configured to adjust operation of one or more devices via communication lines or wireless communications (not shown in FIG. 1) if the measured parameter is below or above a predetermined parameter range.
• controller 11 may be configured to adjust the amount of a crude acrylonitrile product conveyed through one or more nozzles 100, 102, 104, 106, and/or 108 by controlling the operation of chiller 54, and operation of valves, such as for example 92, 94, 96, and/or 98.
• controller 11 may be configured to control the amount of liquid withdrawn from tank 12 via line 40, the amount of crude acrylonitrile product cooled in chiller 54, and the amount crude acrylonitrile product (after cooling) conveyed back to tank 12 via line 66.
• recycle is effective to provide a temperature in the crude tank of about 25 °C or less.
• temperature is measured at 1 to about 5 locations, and in another aspect, 2 to about 4 locations.
• the process is effective for providing a turnover rate of about 50 to about 150 hours, in another aspect, about 75 to about 125 hours, in another aspect, about 75 to about 80 hours, and in another aspect, about 100 to about 105 hours.
• controller 11 may be configured to process one or more signals
• pH meter 116 may be configured measure the pH of crude acrylonitrile product in tank 12 at location 120 and convey a signal
• Controller 11 or flow controller 118 may be configured to process information from pH meter and to control the flow of acid 68 to juncture 74. In an aspect, controller 11 or flow controller 118 may be configured to adjust at least an operating parameter relating to the flow of acid 68 to juncture 74 if the measured pH at location 120 is outside a predetermined pH. In an aspect controller 11 may be configured to control the operation of flow controller 118. In an aspect, controller 11 may comprise flow controller 118. Controller 11 and/or flow controller 118 may comprise a processor. The processor of controller 11 and/or flow controller 118 may comprise a memory configured to receive and store a predetermined condition or parameter. The predetermined condition or parameter may be a value or range of desired pH of liquid at location 120.
• controller 11 or flow controller 118 may be configured to receive a signal corresponding to the pH measured by pH meter 116 at a predetermined frequency, for example, about every six (6) hours, and determine whether the measured pH is within a predetermined pH range.
• the predetermined pH range may be about 2.5-4.5, and in another aspect, about 3 to about 4.
• controller 11 or flow controller 118 may adjust the opening of the valve 119 corresponding to flow controller 118 to allow for more acid 68 to be added at juncture 74, and thus allow for more acid to be added to tank 12.
• controller 11 or flow controller 118 may adjust the opening of the valve 119 corresponding to flow controller 118 to reduce the amount of acid 68 added at juncture 74, and thus reduce the amount of acid 68 added to tank 12.
• the effluent 41 in line 40 may be drawn from the bottom of tank 12 at location 43.
• Location 43 may have a vertical height of zero or about zero in relation to the total height of tank 12.
• the crude acrylonitrile storage tank has a length to diameter ratio of about 0.5 to about 1.5, in another aspect, about 0.75 to about 1.25, and in another aspect, about 0.9 to about 1.1.
• FIG. 2 illustrates a flow diagram of a process 300 in accordance with aspects of the disclosure.
• Process 300 may be carried out using apparatus 10 shown in FIG. 1.
• Step 301 may comprise detecting a first temperature of liquid at a first height of a crude tank.
• Step 302 may comprise detecting a second temperature of liquid at a second height of the crude tank.
• Step 303 may comprise circulating a recycle stream drawn from an effluent height of the crude tank.
• Step 304 may comprise cooling the recycle stream.
• Step 305 may comprise returning at least a first portion of the recycle stream to a first return height when the detected first temperature is outside a predetermined temperature range.
• Process 300 may comprise returning at least a second portion of the recycle stream to a second return height when the detected second temperature is outside a predetermined temperature range.
• at least the first return height or the second return height is above the effluent height of the crude tank.
• a process is provided to prepare an empty crude tank for receipt of a crude acrylonitrile product stream, e.g., crude acrylonitrile product stream 14.
• the process includes adding water to the crude tank in an amount effective for absorbing organics under a floating roof of the crude tank. Absorption of organics is effective for preventing loss of organics from the crude tank.
• the startup process may include filling the empty crude tank with about 6% or more by weight water to float the roof of the tank, in another aspect, about 6 to about 15 %, in another aspect, about 6 to about 10%, and in another aspect, about 6 to about 8%.
• the process may include circulating water through a chiller, e.g., chiller 54 to obtain a target temperature of liquid in the tank, e.g., about 25°C or less, in another aspect, about 20 °C or less, in another aspect, about 18 °C or less, in another aspect, about 15 °C or less, in another aspect, about 10 °C or less, in another aspect, about 1 to about 10°C, and in another aspect, about 5 to about 10 °C .
• a chiller e.g., chiller 54 to obtain a target temperature of liquid in the tank, e.g., about 25°C or less, in another aspect, about 20 °C or less, in another aspect, about 18 °C or less, in another aspect
• the process may include adding acid to the circulating water to obtain a pH of about 4 or less of liquid in the tank, and in another aspect, a pH of about 3 to about 4.
• the acid is added to the water after the water has reached a temperature of 25 °C or less.
• the crude acrylonitrile is added to the crude tank when the crude tank is about 25 °C or less and the pH is about 4 or less.
• the process may include
• the process may include circulating crude acrylonitrile product through a chiller, e.g., chiller 54, to maintain a temperature of less than about 18 degrees Celsius.
• a chiller e.g., chiller 54
• a process may be provided to address the need to place unrefined or off specification product in a holding tank. At such time, it may be necessary to put a crude acrylonitrile tank into service to use as holding tank for unrefined or off specification product.
• tank temperature and pH is monitored to avoid or reduce chemical reaction in the tank.
• two separate tanks 12 may be operated in series or parallel. While in the foregoing specification this disclosure has been described in relation to certain preferred embodiments thereof, and many details have been set forth for purpose of illustration, it will be apparent to those skilled in the art that the disclosure is susceptible to additional embodiments and that certain of the details described herein can be varied considerably without departing from the basic principles of the disclosure. It should be understood that the features of the disclosure are susceptible to modification, alteration, changes or substitution without departing from the spirit and scope of the disclosure or from the scope of the claims. For example, the dimensions, number, size and shape of the various components may be altered to fit specific applications. Accordingly, the specific embodiments illustrated and described herein are for illustrative purposes only.

Landscapes

• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)

Priority Applications (3)

Applications Claiming Priority (2)

Publications (1)

Family

ID=51306050

Family Applications (1)

Country Status (6)

Citations (9)

Family Cites Families (5)

• 2014
  • 2014-06-09 CN CN201410250906.9A patent/CN103991653B/zh active Active
• 2015
  • 2015-06-08 EA EA201692331A patent/EA032780B1/ru not_active IP Right Cessation
  • 2015-06-08 WO PCT/US2015/034627 patent/WO2015191420A1/en active Application Filing
  • 2015-06-08 JP JP2016572274A patent/JP6718825B2/ja active Active
  • 2015-06-08 TW TW104118496A patent/TWI678356B/zh active
• 2016
  • 2016-12-06 SA SA516380445A patent/SA516380445B1/ar unknown
• 2019
  • 2019-10-02 JP JP2019182212A patent/JP6824356B2/ja active Active

Patent Citations (9)

Non-Patent Citations (2)

Also Published As

Similar Documents

Legal Events