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
  • C07C253/34—Separation; Purification

Definitions

• the present invention relates to an improved process for preferentially concentrating 2-methylglutaronitrile from mixtures comprising 2-methylglutaronitrile and other C 6 nitriles having very close relative volatilities ranging from 0.9 to 1.2 in the pressure range of 10 to 300 mmHg and temperature range of 170 to 210°C.
• the invention relates to an improved process for preferentially concentrating 2-methylglutaronitrile from mixtures comprising 2-methylglutaronitrile and other C 6 nitriles having very close relative volatilities, for example, 2-ethylsuccinonitrile and adiponitrile, in a particular integrated, continuous distillative refining process, advantageously utilizing a carefully staged distillation apparatus train and by operating in an optimized window for effective separation.
• adiponitrile In current commercial processes for production of adiponitrile, the starting reactants are butadiene and hydrogen cyanide.
• the adiponitrile intermediate is an important chemical for its commercial versatility and finds application in the industrial production of nylon polyamides that are used in forming films, fibers and molded parts.
• the chemical thermodynamics of such a process usually favors several other co-product species during adiponitrile synthesis. While the objective is always to minimize production of such co-products and boost the desired product yield, some of these unique co-products have highly specialized markets of their own.
• One of these co-products is a branched six-carbon dinitrile labeled 2-methylpentanedinitrile, commonly known as 2- methylglutaronitri le .
• U.S. Patent No. 5,312,959A discloses a method for purification of 2- methylglutaronitrile or adiponitrile which contain boron residues from the process of butadiene reacting with hydrogen cyanide using a nickel catalyst and a boron compound as a promoter.
• the method comprises adding an alcohol selected from the group consisting of amino alcohols and glycols, and then recovering the nitrile by distillation.
• the single distillation column would normally be run at a pressure in the range of 10 to 300 mmHg, and at a temperature in the range of 70 to 160°C.
• U.S. Patent Nos. 3,496,218; 4,330,483; and 4,339,395 disclose manufacturing nitriles by the boron-promoted catalyzed reaction between butadiene and hydrogen cyanide.
• the product mixtures thus formed contain, among desired nitrile products, varying levels of organo-boron as well as other hydrocarbon impurities. Removal of these impurities is essential to effectively process the desired nitrile products downstream.
• U.S. Patent No. 7,501,045 B2 discloses a method for the separation of a group of dinitrile compounds from a medium originating from hydrocyanation of unsaturated mononitriles.
• the separation within the group of dinitriles itself i.e., between adiponitrile, methylglutaronitrile and ethylsuccinonitrile, is not disclosed.
• the present invention involves in detail this complex separation between the dinitrile group compounds having very close relative volatilities.
• U.S. Patent No. 8,247,561 B2 discloses a chemical conversion process for the manufacture of 2-methylpentamethylenediamine (“MPMD”) and 3-methylpiperidine (“MPP”) from hydrogenation of enriched methylglutaronitrile or its mixture with other dinitriles. It is well-known that hydrogenation of an enriched but not purified stream of methylglutaronitrile would lead to a synthesis product consisting of MPMD and MPP.
• the present invention involves a selective method of purifying methylglutaronitrile to at least 99.1 wt. % with ⁇ 0.5 wt. % other dinitrile impurities. This would be a much improved hydrogenation feed material with the highest MPMD yield.
• the present invention provides an economical improved integrated continuous process for preferentially concentrating 2-methylglutaronitrile in high purity from mixtures comprising 2-methylglutaronitrile and other C 6 nitriles having very close relative volatilities, for example, ESN and adiponitrile, by way of an optimized distillation apparatus arrangement and operation.
• An embodiment of the invention process involves the steps of: a) providing a feedstock mixture comprising about 75 to about 90 wt. % 2-methylglutaronitrile, about 2 to about 25 wt. % other C 6 nitriles, and about 0 to about 8 wt.
• step b) feeding the feedstock mixture of step a) to the upper half of a first distillation column comprising at least five packed sections providing the equivalent of at least 50 theoretical distillation stages, c) passing process vapors from the top of the first distillation column of step b) overhead to a first condensing device maintained at a condensing temperature, for example about 30 to about 50°G, whereby the process vapors are cooled to become resulting liquid and purge material, d) passing a portion of the resulting liquid of step c) to the top of the first distillation column of step b) and removing a portion of the resulting purge material of step c), e) passing liquid from the bottom of the first distillation column of step b) to a first boiling device maintained at a boiling temperature, for example, about 180 to about 220°C, whereby the liquid is heated to become saturated vapors and enriched liquid, f) passing the saturated vapors of step e) to the bottom of the first distillation
• step j) passing liquid from the bottom of the second distillation column of step f) to a second boiling device maintained at a boiling temperature, for example, about 200 to about 220°C, whereby the liquid is heated to become second saturated vapors and second enriched liquid, and k) passing the second saturated vapors of step j) to the bottom of the second distillation column of step f) and removing the second enriched liquid of step j).
• the feedstock mixture of step a) above also comprises about 1 to about 12 wt. % ESN, about 1 to about 15 wt. % adiponitrile
• the product recovered in step i) above comprises ⁇ 0.4 wt. % ESN and ⁇ 0.1 wt. % adiponitrile.
• the feedstock mixture of step a) above also comprises about 0 to about 5 wt. % phenols and cresols, about 0 to about 10 wt. % water, about 0 to about 2 wt. % pentenenitrile, about 0 to about 1000 ppm boronate esters or glycols, about 0 to about 100 ppm hydrogen cyanide, and about 0 to about 100 ppm benzene.
• the first distillation column of step b) above comprises at least five packed sections providing the equivalent of about 50 to about 60, for example, about 57, theoretical distillation stages.
• the second distillation column of step f) above comprises at least three packed sections providing the equivalent of about 20 to about 30, for example, about 24, theoretical distillation stages.
• Another embodiment of the present invention comprises the optional step of passing a portion of the enriched liquid of step e) above to the first distillation column of step b) with the feedstock mixture, and/or the optional step of passing a portion of the second enriched liquid of step j) above to the second distillation column of step f) with the enriched liquid of step e).
• Another embodiment of the present invention comprises the optional step of passing a portion of the resulting liquid of step c) above along with the feedstock mixture of step a) above to the first distillation column of step b), and/or the optional step of passing a portion of the second resulting liquid of step g) above along with the enriched liquid of step e) to the second distillation column of step f).
• Fig. 1 shows a diagrammatic view of an embodiment of the present process involving first and second distillation columns configured as required in the present invention.
• Fig. 2 shows a diagrammatic view of a preliminary non-limiting embodiment of the present process.
• 2-methylglutaronitrile also known as 2- methylpentanedinitrile
• 2-methylpentanedinitrile represents the compound with a formula N ⁇ C-CH(-CH 3 )-CH 2 - CH 2 -C ⁇ N, with a normal boiling point of 273.6°C.
• 2-ethylsuccinonitrile represents the compound with a formula N ⁇ C-CH(-C 2 H 5 )-CH 2 -C ⁇ N, with a normal boiling point of 264.3°C.
• ADN adiponitrile
• 1,4- dicyanobutane represents the compound with a formula N ⁇ C-CH 2 -CH 2 -CH 2 -CH 2 -C ⁇ N, with a normal boiling point of 304.4°C. Percentages are in weight % unless otherwise indicated.
• the vessels for use as the distillation columns in the present invention must conform to the particular assemblies described herein.
• the first distillation column will comprise at least five packed sections providing the equivalent of at least 50, such as from about 50 to about 60, e.g., about 57, theoretical stages.
• the second distillation column will comprise at least three packed sections providing the equivalent of at least 20, such as from about 20 to about 30, e.g., about 24, theoretical stages.
• the packed sections of the first distillation column will be from about 8 to about 25 feet in height, and the packed sections of the second distillation column will be from about 10 to about 20 feet in height.
• the total packing height in the first distillation column will be from about 40 to about 125 feet, and the total packing height in the second distillation column will be from about 30 to about 60 feet.
• the packing material for use in the first and second distillation columns may be such materials commonly used for this purpose, such as, for example, industrial structured or random packing of all available types and shapes.
• Non-limiting examples of such materials include Norton #1.5T, Norton #2T, Norton IMTP, Koch FlexiPack, Koch-Glitch 352 Series, SS dumped saddle and other high efficiency packing materials.
• the conventional and improved forms of sub-cooled, heated and two-phase feed introduction, radial and axial distribution, and re-collection thereof shall apply to this application.
• the condensing device for use in each distillation column shall be of indirect heat exchanger type with sufficient heat transfer surface and minimal in-line pressure drop to effectively carry out the vapor-to-liquid condensation process with no vapor carry-over.
• the boiling device for use in each distillation column shall be of indirect heat exchanger type and sufficient circulation rate with wetted heat transfer surface so as to yield no drying of the surface due to over-temperature, thereby, causing thermal decomposition of the C6 dinitriles.
• the comingled liquid feedstock to the first distillation column will comprise about 75 to about 90 wt. % MGN and about 2 to about 25 wt. % other C 6 nitriles, and possibly other impurities, such as, for example, about 0 to about 5 wt. % phenols and cresols, about 0 to about 10 wt. % water, about 0 to about 2 wt. % pentenenitrile, about 0 to about 1000 ppm boronate esters or glycols, about 0 to about 100 ppm hydrogen cyanide, and about 0 to about 100 ppm benzene.
• the other C 6 nitriles may comprise ESN and ADN, such as, for example, about 1 to about 12 wt. % ESN and about 1 to about 15 wt. % ADN.
• Conditions in the first distillation column may include a temperature of about 125 to about 220°C and pressure of about 10 to about 200 mniHg, such as, for example, a temperature of about 150 to about 200°C and pressure of about 10 to about 120 mmHg.
• Conditions in the second distillation column may include a temperature of about 150 to about 230°C and pressure of about 10 to about 200 mmHg, such as, for example, a temperature of about 170 to about 220°C and pressure of about 50 to about 110 mmHg.
• Conditions in the first condensing device as3sociated with the first distillation column may include a condensing temperature of, for example, about 30 to about 50°C, and conditions in the first boiling device associated with the first distillation column may include a boiling temperature of, for example, about 180 to about 220°C.
• Conditions in the second condensing device associated with the second distillation column may include a temperature of, for example, about 30 to about 40°C, and conditions in the second boiling device associated with the second distillation column may include a temperature of, for example, about 200 to about 220°C.
• Fig.l shows a non-limiting example embodiment of the present invention involving first and second distillation columns conformed as required herein.
• crude stream 9 either directly from an ADN production facility or having been processed by distillation following an ADN production facility, is collected in a feed storage vessel 40.
• crude stream 9 may be pre-treated to be free of organo boron impurities as shown in, for example, U.S. Patent No. 5,312,959A, incorporated herein by reference.
• stream 17 is a crude feed collected and transported from an offsite location and added to the feed storage vessel 40.
• the co-mingled liquid of vessel 40 is fed to first distillation column 60 via stream 19 at a tray location in the upper half of column 60.
• stream 19 may undergo a pre-treatment via column 50 (Fig. 2) and the resultant treated stream 56 (Fig. 2) may comprise feed pre-treated to be free of organo boron impurities as shown in, for example, U.S. Patent No. 5,312,959A, directly therefrom.
• Column 60 comprises at least five packed sections providing the equivalent of at least 50, for example about 50 to about 60, such as about 57, theoretical distillation stages.
• the vapor-liquid traffic in first distillation column 60 is adjusted by refluxing and boil-up according to the quality and quantity of feed from stream 19.
• the process vapors from first distillation column 60 are collected overhead and fed via stream 31 to first condensing unit 62 and cooled to a temperature in the range of about 30 to about 50°C.
• a portion, such as about 80 to about 95 %, of the cooled liquid from unit 62 is refluxed back to column 60 via stream 38 and a small purge, such as about 5 to about 20 %, is drawn out of this stage via stream 34.
• the enriched liquid from the bottom of first distillation column 60 is fed to the bottom first boil-up apparatus 65 via stream 33.
• the liquid is heated in apparatus 65 to a temperature in the range of about 180 to about 220°C.
• the saturated vapors from apparatus 65 are fed back to the bottom of column 60 via stream 35 to maintain the vapor traffic in first distillation column 60.
• From about 5 to about 15 % of enriched liquid from apparatus 65 is fed continuously to the second distillation column 70 via stream 66.
• the remainder of the enriched liquid from apparatus 65 is drawn out of this stage via stream 37.
• Enriched liquid from apparatus 65 is fed continuously to the second distillation column 70 via stream 66 at a tray location in the middle section of column 70.
• Column 70 comprises at least three packed sections providing the equivalent of at least 20, for example about 20 to about 30, such as about 24, theoretical distillation stages.
• the vapor-liquid traffic in second distillation column 70 is adjusted via refluxing and boil-up relative to the quality and quantity of feed from stream 66.
• the process vapors from second distillation column 70 are collected overhead and fed via stream 41 to second condensing unit 72 and cooled to a temperature in the range of about 30 to about 40°C.
• a portion, such as about 50 to about 70 %, of the cooled liquid from unit 72 is refluxed back to column 70 via stream 48.
• the remaining cooled liquid from unit 72 is drawn out of this stage via stream 78 as the desired product meeting or exceeding the target purity.
• a very small purge of the cooled liquid from unit 72 can be drawn out via stream 44 to maintain the impurity control in this purification stage.
• the enriched liquid from the bottom of second distillation column 70 is fed to the bottom second boil-up apparatus 75 via stream 43.
• the liquid is heated in apparatus 75 to a temperature in the range of about 200 to about 220°C.
• the saturated vapors from apparatus 75 are fed back to the bottom of column 70 via stream 45 to maintain the vapor traffic in second distillation column 70.
• Fig. 2 shows a non-limiting preliminary embodiment of the present invention involving an optional column 50 conformed as required herein.
• crude stream 9 either directly from an ADN production facility or having been processed by distillation following an ADN production facility, is collected in a feed storage vessel 40.
• stream 17 is a crude feed collected and transported from an offsite location and added to the feed storage vessel 40.
• the co-mingled liquid of vessel 40 is fed to column 50 via stream 19 at a tray location in the lower half of column 50.
• Column 50 may be a structured packed column or a tray column and may provide a minimum of 15 theoretical stages. Feed 19 enters column 50 at a tray location about two-thirds from the top, which provides a minimum of ten equivalent theoretical stages above the feed entry point and about five equivalent theoretical stages below the feed entry point serving as stripping stages. [00035]
• the column 50 temperature profile is maintained such that the column base is in the range from about 180°C to about 215°C, preferably in the range from about 190°C to about 210°C, and more preferably in the range from about 195°C to about 205°C.
• the column head temperature is maintained to be below 100°C.
• the column pressure profile is maintained in the range from about 75 mmHg to about 150 mmHg, particularly in the range from about 85 mmHg to about 130 mmHg, and more particularly in the range from about 95 mmHg to about 125 mmHg.
• the vapor-liquid traffic in column 50 is adjusted by refluxing in the range from about 1:10 to about 5:1 (stream 28 : stream 24) and boil-up in the range from about 1:10 to about 5:1 (stream 25 : stream 56) according to the quality and quantity of feed from stream 19.
• the process vapors from column 50 are collected overhead and fed via stream 21 to condensing unit 52 and cooled to a temperature in the range of about 30 to about 50°C.
• a portion, such as about 50 to about 80 %, of the cooled liquid from unit 52 is refluxed back to column 50 via stream 28 and a small purge, such as about 0.1- about 10%, is drawn out of this stage via stream 24.
• the enriched liquid from the bottom of column 50 is fed to the boil-up apparatus 55 via stream 23.
• the liquid is heated in apparatus 55 to a temperature in the range of about 195 to about 205°C.
• the saturated vapors from apparatus 55 are fed back to the bottom of column 50 via stream 25 to maintain the vapor traffic in column 50.
• From about 50 to about 80 % of enriched liquid from apparatus 55 is fed continuously to column 60 via stream 56.
• the remainder of the enriched liquid from apparatus 55 is drawn out of this stage via stream 27.
• column 50 several low-boiling species including cresols, boron esters, phenol and other impurities from the feed stream 19 are removed from the feed via stream 24.
• Typical component splits that may be achieved in one embodiment are given below: Table 1
• compositions of various streams are shown in Table 2.
• the optional stream, if any, pre-treated to be free of organo boron impurities as shown in, for example, U.S. Patent No. 5,312,959A, directly therefrom fed with stream 19 is shown as " 56 [Fig.2]" in Table 2. Percentages are in weight percent.
• Example further demonstrates the present invention and its capability for use.
• the invention is capable of other and different embodiments, and its several details are capable of modifications in various apparent respects, without departing from the scope and spirit of the present invention. Accordingly, the Example is to be regarded as illustrative in nature and not as restrictive. All percentages are by weight unless otherwise indicated.
• the base pressure in column 60 about 120 mmHg.
• the head and bottom temperatures are maintained in the 170 tol80°C and 200 to 220°C ranges, respectively.
• the vapor-liquid traffic is set at the reflux ratio (i.e., stream 38/stream 34) in the 10 tol5 range while the boil-up rate (i.e., stream 35/stream 66) is in the 10 tol2 range.
• the overhead condenser 62 sub-cooling of about 15 MMBTU/hr is required and the balancing base boil-up apparatus 65 is about 16 MMBTU/hr.
• Stream 19 is effectively fractionated in column 60 into MGN-enriched bottoms liquid outlet stream 33 containing about 90 % MGN, less than 20 % ADN and less than 0.5 % ESN.
• the overhead condensed liquid concentrates ESN in approximately 30:70 ESN: MGN mass balance.
• the achieved split of stream 34 versus stream 66 is about l/3 r versus 2/3 r .
• about 3,345 lb/hr of overhead material is collected from about 10,000 lb/hr of feed.
• Other low-boiling impurities concentrate in the overhead and are continuously purged via stream 34.
• the MGN-enriched bottoms stream 66 is fed to second distillation column 70 which concentrates the product in the overhead by stripping MGN from the heavy impurities.
• the feed enters column 70 between the middle and bottom packed sections to allow approximately fourteen theoretical stages above the feed location and another ten theoretical trays below it.
• the head pressure in column 70 is 50 mmHg while the total pressure drop under operating conditions is about 55 mmHg. This makes the base pressure in column 70 about 105 mmHg.
• the head and bottom temperatures are maintained in the 170 tol 80°C and 200 to 220°C ranges, respectively.
• the vapor-liquid traffic is set at the reflux ratio (i.e., stream 48/stream 78) in the 1 to 5 range.
• the boil-up rate (i.e., stream 45/stream 47) is in the 50 to 60 range.
• the overhead condenser 72 sub-cooling of about 7 MMBTU/hr is required and the balancing base boil- up apparatus 75 is about 6 MMBTU/hr.
• Stream 66 is effectively fractionated in column 70 into purified Dytek ® MGN stream 78 with 99.5 % purity containing 0.4 % ESN and 0.1 % ADN as acceptable impurities.
• Stream 47 is essentially free of ESN and contains mostly ADN.
• the achieved split of stream 78 to stream 47 is about 92 to 8.
• about 6,100 lb/hr of overhead pure DYTEK ® MGN material is collected from about 6,700 lb/hr of stream 66 entering column 70.

Applications Claiming Priority (2)

Publications (1)

Family

ID=51212996

Family Applications (1)

Country Status (3)

Family Cites Families (8)

• 2014
  • 2014-06-25 WO PCT/US2014/044145 patent/WO2014210191A1/en active Application Filing
  • 2014-06-25 TW TW103121964A patent/TW201504204A/zh unknown
  • 2014-06-25 EP EP14742059.0A patent/EP3013793A1/de not_active Withdrawn

Non-Patent Citations (2)

Also Published As

Similar Documents

Legal Events