WO2016047960A1 - A dividing wall column and a method of purifying neopentyl glycol using the same - Google Patents

A dividing wall column and a method of purifying neopentyl glycol using the same Download PDF

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Publication number
WO2016047960A1
WO2016047960A1 PCT/KR2015/009736 KR2015009736W WO2016047960A1 WO 2016047960 A1 WO2016047960 A1 WO 2016047960A1 KR 2015009736 W KR2015009736 W KR 2015009736W WO 2016047960 A1 WO2016047960 A1 WO 2016047960A1
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WIPO (PCT)
Prior art keywords
section
neopentyl glycol
column
dividing wall
outflow
Prior art date
Application number
PCT/KR2015/009736
Other languages
French (fr)
Inventor
Nam Jin Jang
Mooyong LEE
Ji Yeon Kim
Seon Oke Lee
Jae Eock Cho
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Hanwha Chemical Corporation
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Publication of WO2016047960A1 publication Critical patent/WO2016047960A1/en

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    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C29/00—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring
    • C07C29/74—Separation; Purification; Use of additives, e.g. for stabilisation
    • C07C29/76—Separation; Purification; Use of additives, e.g. for stabilisation by physical treatment
    • C07C29/80—Separation; Purification; Use of additives, e.g. for stabilisation by physical treatment by distillation
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C29/00—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring
    • C07C29/74—Separation; Purification; Use of additives, e.g. for stabilisation
    • C07C29/88—Separation; Purification; Use of additives, e.g. for stabilisation by treatment giving rise to a chemical modification of at least one compound
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D3/00—Distillation or related exchange processes in which liquids are contacted with gaseous media, e.g. stripping
    • B01D3/14—Fractional distillation or use of a fractionation or rectification column
    • B01D3/141—Fractional distillation or use of a fractionation or rectification column where at least one distillation column contains at least one dividing wall
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C29/00—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring
    • C07C29/132—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring by reduction of an oxygen containing functional group
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C29/00—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring
    • C07C29/132—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring by reduction of an oxygen containing functional group
    • C07C29/136—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring by reduction of an oxygen containing functional group of >C=O containing groups, e.g. —COOH
    • C07C29/147—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring by reduction of an oxygen containing functional group of >C=O containing groups, e.g. —COOH of carboxylic acids or derivatives thereof
    • C07C29/149—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring by reduction of an oxygen containing functional group of >C=O containing groups, e.g. —COOH of carboxylic acids or derivatives thereof with hydrogen or hydrogen-containing gases

Definitions

  • the present invention relates to a dividing wall column and a method of purifying neopentyl glycol using the same. More specifically, it relates to a dividing wall column which can purify crude products including neopentyl glycol with high purity and a method of purifying neopentyl glycol using the same.
  • Neopentyl glycol may be formed by a hydrogenation reaction of hydroxypivaldehyde which is formed by an aldol reaction of isobutylaldehyde and formaldehyde under a basic condition.
  • monoester compounds such as NPG-isobutyrate (3-hydroxy-2,2-dimethylpropyl isobutyrate), HPNE (hydroxypivalyl hydroxypivalate), and TMPD (2,2,4-trimethyl-l,3-pentanediol) are formed as the side-reaction product in the process.
  • these compounds cause a problem in the application of the product to which neopentyl glycol is applied, and thus it is preferable to make the amount of these compounds in the final neopentyl glycol product several hundreds ppm or less.
  • Korean Patent No. 10-0231643 discloses a method of eliminating inorganic salts by applying a multi-step distillation separation column thereto and using water as an entrainment agent for the crude neopentyl glycol including metal salts after safonification, wherein a tiny amount of water is provided through the upper part of the column.
  • the process has a disadvantage in that it is complicated in the separating process and needs a great deal of energy. Therefore, simple and energy saving methods are being largely attempted recently.
  • Korean Patent No. 10-0676304 discloses the method of obtaining neopentyl glycol with high purity by using two distilling columns without safonification.
  • the Petlyuk distillation column separates low-boiling components at the top of the column, middle-boiling components at the middle of the column, and high-boiling components at the bottom of the column at the main separation column, respectively, after separating low-boiling components and high-boiling components at the preliminary separation column.
  • it has an advantage in eliminating the energy efficiency decrease problem due to remixing of the middle-boiling components which can occur when two common distillation columns are used.
  • it is difficult to operate and adjust the pressure balance.
  • Korean Patent Publication No. 10-2012-0076196 discloses a purification process of neopentyl glycol using a dividing wall column (DWC).
  • the dividing wall column is similar to the Petlyuk distillation column in view of thermodynamic aspects, but it is different from the same in view of the structure that the preliminary separation column is integrated in the main separation column by installing a dividing wall in the column.
  • it has an advantage in that it is possible to resolve the difficulty in the pressure balance between the preliminary separation column and the main separation column and the difficulty in the operation due to this and it is easy to operate the same, and the investment costs may decrease because two distillation columns are integrated into one.
  • Korean Patent Publication No. 10-2012-0076196 sets the temperature of the top section, the bottom section, and the outflow section in a specific range for high purity refinement, and, particularly, the temperature of the top section and the bottom section are defined by a mathematical formula depending on the pressure.
  • the method disclosed in said Korean Patent Publication can be applied when the mixture flowed therein includes high content, at least 55 wt% or more, of neopentyl glycol, but it has a disadvantage in that the effective purification is difficult or the energy consumption becomes large when the content of neopentyl glycol is less than 55 wt% and a large quantity, 1.5 wt% or more, of high-boiling components (heavies) is included in the mixture.
  • the purification method disclosed in said Korean Patent Publication may increase the energy consumption, or may need a pretreatment process for reducing the content of the high-boiling components in addition, before applying the purification method.
  • the present invention provides a dividing wall column, including a main column equipped with a dividing wall, a condenser, and a reboiler,
  • main column is divided into a top section, a feed section, an outflow section, and a bottom section by the dividing wall that is located at 25% to 95% ' from the top, based on the total steps of the main column, a crude product including neopentyl glycol is fed to the feed section through a feeding tray that is located at 50% or more from the top, based on the total steps of the feed section, and
  • low-boiling components in the crude product flows out at the top section
  • high-boiling components flows out at the bottom section
  • middle-boiling components flows out at the outflow section
  • the middle-components include neopentyl glycol as a main component.
  • the present invention provides a method of purifying neopentyl glycol, including the step of carrying out a fractional distillation of a crude product including neopentyl glycol by using the dividing wall column.
  • the distillation column structure suitable for the purification of neopentyl glycol is provided and it becomes possible to purify neopentyl glycol on a commercial scale with high energy efficiency.
  • the method of purifying neopentyl glycol using the dividing wall column of the present invention it is possible to purify the crude product of neopentyl glycol including low content of neopentyl glycol and large content of high-boiling components with high purity. And, it is possible to save energy, compared to a conventional process using continuous two distillation columns. Therefore, the method can contribute the productivity improvement in the total purification processes of purifying neopentyl glycol.
  • Fig. 1 illustrates a drawing of conventional continuous two distillation columns.
  • Fig. 2 illustrates a drawing of the dividing wall column according to one embodiment of the present invention.
  • Fig. 3 illustrates a drawing of the main column of the dividing wall column according to one embodiment of the present invention.
  • the terms "the first”, “the second”, and the like are used for explaining various components and said tenns are only used for distinguishing one component from the other components.
  • the word "on” or “above”, as used in the context of formation or construction of one layer or element, means pertaining to the direct formation or construction of one layer or element on another layer or element directly or the additional formation or construction of one layer or element between layers or on a subject or substrate.
  • the present invention provides
  • a dividing wall column including a main column equipped with a dividing wall; a condenser; and a reboiler,
  • main column is divided into a top section, a feed section, an outflow section, and a bottom section by the dividing wall that is located at 25% to 95% from the top, based on the total steps of the main column, a crude product including neopentyl glycol is fed to the feed section through a feeding tray that is located at 50% or more from the top, based on the total steps of the feed section, and
  • low-boiling components in the crude product flows out at the top section
  • high-boiling components flows out at the bottom section
  • middle-boiling components flows out at the outflow section
  • the middle-components include neopentyl glycol as a main component.
  • crude product is the material to be purified in the present invention and means the unpurified product that is obtained by various organic synthesis reactions for preparing neopentyl glycol, the final product.
  • the dividing wall column of the present invention is used for purifying neopentyl glycol with high purity from the crude product.
  • low-boiling component means the materials of which the boiling point is less than the temperature 20 ° C lower than the boiling point (208 ° C ) of neopentyl glycol among the components included in the crude product including neopentyl glycol
  • middle-boiling component includes neopentyl glycol and the materials of which the boiling point is within the range of ⁇ 20 ° C based on the boiling point of neopentyl glycol among the components included in the crude product including neopentyl glycol
  • high-boiling component means the materials of which the boiling point is larger than the temperature 20 ° C higher than the boiling point of neopentyl glycol among the components included in the crude product including neopentyl glycol.
  • the low-boiling components may be isobutyl aldehyde, water, hydroxy pivaldehyde, isobutyl alcohol, octanol, and so on
  • the middle-boiling components may be neopentyl glycol (NPG), NPG-isobutyrate (3-hydroxy-2,2-dimethylpropyl isobutyrate), and so on
  • the high-boiling components may be hydroxypivalyl hydroxypivalate (HPNE), 2,2,4-trimethyl-l,3-pentanediol (TMPD), and so on.
  • the crude product may be a product of a hydrogenation reaction of hydro xypivaldehyde which is formed by an
  • the crude product including neopentyl glycol includes monoester compounds such as NPG-isobutyrate, HPNE, and TMPD, and primary alcohol compounds such as 2-ethyl hexanol, by-products, as impurities, it must go through purification processes for eliminating the impurities in order to obtain neopentyl glycol as the final product.
  • TMPD and HPNE have the high boiling points of 229.95 ° C and 292 ° C , respectively, and NPG-isobutyrate has the boiling point of 198.75 ° C which is similar to the boiling point of neopentyl glycol (208 ° C) among the impurities, and thus it is not easy to separate them by a simple distillation process.
  • Fig. 1 illustrates a drawing of conventional continuous two distillation columns.
  • a stream 1 of the mixture provided to a first distillation column 7 is primarily separated into low-boiling components 2 and high-boiling components 3.
  • the high-boiling components 3 flowed out through the lower part of the first distillation column 7 are continuously fed to a second distillation column 8, secondarily.
  • High-boiling components 4 provided to the second distillation column 8 are separated into low-boiling components 5 and high-boiling components 6 again and flow out finally.
  • the dividing wall column of the present invention and the method of purifying neopentyl glycol using the same can exhibit high energy efficiency because the method includes the step of carrying out a fractional distillation by using the dividing wall column that is optimally designed to purify the crude product including neopentyl glycol.
  • the crude product collected after the synthesis reaction of neopentyl glycol by an aldol reaction and a hydrogenation reaction is a mixture form including neopentyl glycol, and it includes impurities of which the boiling point is about 64 ° C to about 292 ° C .
  • neopentyl glycol corresponds to a middle-boiling component of which the boiling point is 208 ° C .
  • the target material to be purified belongs to middle-boiling components in the mixture, it is not easy to separate the same by an one-step distillation process and at least two steps of distillation processes are required.
  • the dividing wall column of the present invention for carrying out the purification process of neopentyl glycol includes
  • main column equipped with a dividing wall; a condenser; and a reboiler, wherein the main column is divided into a top section, a feed section, an outflow section, and a bottom section by the dividing wall that is located at 25% to 95% from the top, based on the total steps of the main column,
  • a crude product including neopentyl glycol is fed to the feed section through a feeding tray that is located at 50% or more from the top, based on the total steps of the feed section, and
  • low-boiling components in the crude product flows out at the top section
  • high-boiling components flows out at the bottom section
  • middle-boiling components flows out at the outflow section
  • the middle-components include neopentyl glycol as a main component.
  • the middle-boiling components flowing out from the outflow section of the dividing wall column of the present invention include neopentyl glycol as the main component, and, for example, it may include about 99 wt% or more, preferably about 99.5 wt% or more, and more preferably about 99.9 wt% or more of neopentyl glycol, based on the total weight of the middle-boiling components. Namely, it is possible to obtain neopentyl glycol having the purity of about 99 wt% or more, preferably about 99.5 wt% or more, and more preferably about 99.9 wt% or more by using the dividing wall column of the present invention.
  • Fig. 2 The structure of the dividing wall column according to one embodiment of the present invention is illustrated in Fig. 2.
  • the dividing wall column of the present invention includes a main column 100 equipped with a dividing wall 10, a condenser 200, and a reboiler 300, and the main column 100 is largely divided into a top section 20, a bottom section 30, a feed section 40, and an outflow section 50.
  • the feed section 40 may be divided into an upper feed section 40a and a lower feed section 40b and the outflow section 50 may be divided into an upper outflow section 50a and a lower outflow section 50b again.
  • the part where the upper feed section 40a and the lower feed section 40b meet is a feeding tray 40c, and the part where the upper outflow section 50a and the lower outflow section 50b meet is an outflow tray 50c.
  • the dividing wall column of the present invention includes a condenser 200 and a reboiler 300.
  • the condenser 200 is an apparatus for condensing a gas-phase mixture by taking away the heat of evaporation therefrom, and a condenser which can be used for a common chemical engineering apparatus may be used without limit.
  • the reboiler 300 is an apparatus for evaporating a liquid-phase mixture by providing the heat of evaporation thereto, and a reboiler which can be used for a common chemical engineering apparatus may be used without limit.
  • the energy consumptions of the condenser 200 and the reboiler 300 vary by various conditions including the length of the main column, the specific operation condition of the distillation column, and the ingredients of the inflow stream, and the total energy consumption may be evaluated by the sum of the energy consumptions of the condenser 200 and the reboiler 300.
  • the energy saving rate may be about 10 to about 40% in comparison to conventional continuous two distillation columns and it is possible to reduce the energy consumption apparently, in the case of purifying the same crude product.
  • the main column 100 may be largely divided into a top section 20, a feed section 40, an outflow section 50, and a bottom section 30, and the feed section 40 may be divided into an upper feed section 40a and a lower feed section 40b and the outflow section 50 may be divided into an upper outflow section 50a and a lower outflow section 50b again.
  • the top section 20 is the section above the dividing wall 10 and it means the upper part of the main column 100 where there is no dividing wall 10.
  • the feed section 40 is the section divided by the dividing wall 10 to which a stream of a crude product A including neopentyl glycol is fed.
  • the upper feed section 40a is the upper part of the feed section 40 and the subsection located above the stream of the crude product A provided to the main column 100.
  • the lower feed section 40b is the lower part of the feed section 40 and the subsection located below the stream of the crude product A provided to the main column 100.
  • the outflow section 50 is the section divided by the dividing wall 10 from which a stream of middle-boiling components B including the neopentyl glycol purified with high purity flows out.
  • the upper outflow section 50a is the upper part of the outflow section 50 and the subsection located above the stream of the middle-boiling components B flows out -from the main column 100.
  • the lower outflow section 50b is the lower part of the outflow section 50 and the subsection located below the stream of the middle-boiling components B flows out from the main column 100.
  • the bottom section 30 is the section below the dividing wall 10 and it means the lower part of the main column 100 where there is no dividing wall 10.
  • the space divided by the dividing wall 10 in the dividing wall column takes a role of the preliminary separator, the liquid composition almost coincides with the equilibrium distillation curve and the remixing effect is suppressed due to the elimination of the high-boiling components and the low-boiling components, and thus the thermodynamic efficiency for the separation gets better.
  • the upper feed section 40a and the lower feed section 40b take a role similar to the preliminary separator.
  • the feed section 40 including the upper feed section 40a and the lower feed section 40b may be a sort of preliminary separation section.
  • the mixture flowing into the preliminary separation section is largely separated into the low-boiling components and the high-boiling components.
  • Some of the low-boiling components and the high-boiling components flow into the top section 20 and the bottom section 30, and some of the same flow into the upper outflow section 50a and the lower outflow section 50b and are distilled again.
  • the upper outflow section 50a and the lower outflow section 50b take a role of main separator of conventional processes.
  • the outflow section 50 including the upper outflow section 50a and the lower outflow section 50b may be a main separation section.
  • the low-boiling components and the middle-boiling components are mostly separated at the upper part of the dividing wall 10 of the main separation section, and the middle-boiling components and the high-boiling components are mostly separated at the lower part.
  • the dividing wall column of the present invention may further include a condensing drum 400.
  • the condensing drum 400 is a buffer apparatus for. a stable reflux provision.
  • the dividing wall 10 is located longitudinally between about 25 and about 95% from the top, based on the total steps of the main column 100.
  • Fig. 3 illustrates a drawing for illustrating the main column of the dividing wall column of the present invention more specifically.
  • the inner column of the main column is not illustrated here for convenience, and "length” disclosed below means the length defined by the steps of the column.
  • the steps of the column are located at equal spaces in an independent section, for example, the top section 20, the bottom section 30, the upper feed section 40a, the lower feed section 40b, the upper outflow section 50a, and the lower outflow section 50b.
  • the intervals of the steps of the column in the distinguishing sections may be independently same to or different from each other.
  • the position of the dividing wall 10 may be between about 25% and about 95%, or about 25% and about 90%, or about 25% and about 85%, from the top to the bottom, based on the length of the total steps of the main column 100.
  • a starting position T of the dividing wall 10 may be 25% or more from the top, based on the length of the total steps of the main column 100
  • a ending position T' of the dividing wall 10 may be about 95% or less, or about 90% or less, or about 85% or less, from the top, based on the length of the total steps of the main column 100.
  • L' may be about 50 to about 70%, preferably about 55 to about 65%, of L.
  • the energy saving efficiency can be maximized and the high-boiling components can be effectively separated.
  • the crude product A including neopentyl glycol flows in the feed section 40 of the dividing wall column of the present invention. More specifically, the crude product A including neopentyl glycol is fed to the middle part of the feed section 40, namely, the feeding tray 40c where the upper feed section 40a and the lower feed section 40b meet.
  • the position of the feeding tray 40c is about 50% or more, for example, about 50 to about 80%, from the top, based on the steps of the column of the total feed section 40 including the upper feed section 40a and the lower feed section 40b. Namely, the position of the feeding tray 40c is determined according to the steps of each column of the upper feed section 40a and the lower feed section 40b. When the number of the steps of the column of the feed section 40 is 100, the ratio of the steps of the column of the upper feed section 40a and the lower feed section 40b may be about 50 : 50 to about 80 : 20.
  • the low-boiling components C are separated at the upper part of the dividing wall 10
  • the high-boiling components D are separated at the lower part of the dividing wall 10
  • the separated middle-boiling components B flow out at the outflow section 50.
  • the middle-boiling components B flow out from the middle part of the outflow section 50, namely, the outflow tray 50c where the upper outflow section 50a and the lower outflow section 50b meet.
  • the position of the outflow tray 50c is about 50% or less, for example, about 20 to about 50%, from the top, based on the steps of the column of the total outflow section 50 including the upper outflow section 50a and the lower outflow section 50b.
  • the position of the outflow tray 50c is determined according to the steps of each column of the upper outflow section 50a and the lower outflow section 50b.
  • the ratio of the steps of the column of the upper outflow section 50a and the lower outflow section 50b may be about 20 : 80 to about 50 : 50.
  • the middle-boiling components B include neopentyl glycol of high purity.
  • the present invention it is possible to purify neopentyl glycol with high purity of 99 wt% or more with low energy consumption, even when the crude product, the target material to be purified, includes large amount of high-boiling components, by regulating and optimizing the position of the main column, the length of the main column, the position of the feeding tray, and the position of the outflow tray as disclosed above.
  • the number of the steps of the main column, the top section, the bottom section, the upper feed section, the lower feed section, the upper outflow section, and the lower outflow section may be regulated with necessity if it satisfies said conditions.
  • the number of the total steps of the main column may be 60 to 90, preferably 70 to 80, and more preferably 73 to 77.
  • the number of the steps of the top section may be 16 to 26, preferably 18 to 24, and more preferably 19 to 22. Furthermore, the number of the steps of the bottom section may be 10 to 25, preferably , 10 to 20, and more preferably 12 to 17.
  • Each number of the steps of the upper feed section, the lower feed section, the upper outflow section, and the lower outflow section may be equally or differently 15 to 65, preferably 18 to 63, and more preferably 20 to 61, independently.
  • the present invention provides a method of purifying neopentyl glycol, including the step of carrying out a fractional distillation of a crude product including neopentyl glycol by using the dividing wall column.
  • the content of neopentyl glycol may be about 35 wt% or more, for example, about 35 to about 70 wt%, or about 35 to about 54 wt%, or about 40 to about 54 wt%, based on the total weight of the crude product including neopentyl glycol.
  • the content range of neopentyl glycol corresponds to a conventional yield in an industrial preparation process of neopentyl glycol by an aldol reaction and a hydrogenation reaction, and the present method of purifying neopentyl glycol can be directly applied to the crude product without an additional modification or pretreatment for increasing purification efficiency, and thus the method is industrially and economically very useful.
  • the content of the high-boiling components may be about 1.5 wt% or more, for example, about 1.5 to about 10 wt%, or about 1.5 to about 8 wt%, or about 2 to about 6 wt%, based on the total weight of the crude product including neopentyl glycol.
  • the purification method of neopentyl glycol using the dividing wall column of the present invention it is specifically useful when the content of the high-boiling components is high, 1.5 wt% or more, and it is possible to separate the high-boiling component effectively by using low energy.
  • neopentyl glycol In the case of purifying the crude product including neopentyl glycol by using the dividing wall column, it is possible to purify neopentyl glycol with the purity of about 99 wt% or more, preferably about 99.5 wt% or more, and more preferably about 99.9 wt% or more.
  • the temperature of the top section of the main column is preferably about 1 12 to about 134 ° C at the pressure of about -0.938 to about -0.875 kg/cm 2 g.
  • the low-boiling components may fall to the lower part of the preliminary separation section and affect the purity of the product, and when it is over 134 ° C , the high-boiling components may go up to the upper part of the preliminary separation section and affect the purity of neopentyl glycol.
  • the temperature of the bottom section of the main column is preferably about 167 to about 183 ° C at the pressure of about -0.75 to about -0.70 kg cm 2 g.
  • the middle-boiling components may come down and the product output may decrease, and when it is over 183 ° C , there is concern that the high-boiling components may flow out with the middle-boiling components as a side stream.
  • the difference in the temperature of the top section and the bottom section of the main column may be about 71 ° C or less, for example, about 33 to about 71 ° C , or about 40 to about 71 ° C , or about 50 to about 71 ° C .
  • the energy consumption of the condenser and the reboiler may further decrease while maintaining high purity of neopentyl glycol and high separation efficiency of the high-boiling components, even when the difference in the temperature of the top section and the bottom section of the main column is in a certain range as disclosed above.
  • the temperature of the crude product of neopentyl glycol flowed in the feeding tray may be about 50 to 70 ° C .
  • the energy consumption at the reboiler may be about 3.2 Mkcal/h or less, for example, about 2.5 to about 3.2 Mkcal/h, and it is possible to carry out the purification process with much less energy consumption than the case of using a conventional continuous two distillation columns or a dividing wall column of known structure.
  • the temperature of the outflow tray where the upper outflow section and the lower outflow section meet and the middle-boiling components flows out is preferably about 155 to about 158.5 ° C at the pressure of about -0.845 to about -0.835 kg/cm 2 g.
  • the temperature may largely affect the purity of the product, because it is not easy to eliminate the low-boiling components when the temperature is below 155 ° C and it is not easy to eliminate the high-boiling components when the temperature is over 158.5 ° C .
  • composition 1 A composition of the crude product (hereinafter, composition 1) fed thereto includes 50 wt% of neopentyl glycol, 44 wt% of 2-ethyl hexanol and 2 wt% of water as the low-boiling components, and 2 wt% of 2,2,4-trimethyl-l,3-pentanediol (TMPD) and 2 wt% of hydroxypivalyl hydroxypivalate (HPNE) as the high-boiling components.
  • composition 1 A composition of the crude product (hereinafter, composition 1) fed thereto includes 50 wt% of neopentyl glycol, 44 wt% of 2-ethyl hexanol and 2 wt% of water as the low-boiling components, and 2 wt% of 2,2,4-trimethyl-l,3-pentanediol (TMPD) and 2 wt% of hydroxypivalyl hydroxypivalate (HP
  • the energy consumption saving rates of the dividing wall columns of the present invention were respectively 36.6% (Example 1), 38.1 % (Example 2), and 38.1% (Example 3), compared to Comparative Example 1 carrying out two distillation column processes, and the energy efficiencies thereof were largely increased.
  • compositions 2 to 8 correspond to Examples 4 to 10 respectively and details of the compositions were listed in the following Table 5.
  • compositions 2 to 8 correspond to Comparative Examples 2 to 8 respectively and details of the compositions were listed in Table 5.
  • Example 4 8.272 Composition 3 Comparative Example 9.696 about 15%
  • Composition 6 Comparative Example . 9.541 about 32%
  • Composition 8 Comparative Example 9.145 about 19%
  • the method using the dividing wall column of the present invention can reduce 13% to 34% of energy in comparison to the method using the continuous two distillation columns when the same composition of crude product was used. Particularly, the energy saving effect was also shown even when the crude product included large amount, 2 wt% to 6 wt%, of the high-boiling components, to varying degrees.

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

Abstract

The present invention relates to a dividing wall column and a method of purifying neopentyl glycol using the same. More specifically, it relates to a dividing wall column which can purify crude products including neopentyl glycol with high purity and a method of purifying neopentyl glycol using the same. According to the dividing wall column of the present invention and the method of purifying neopentyl glycol using the same, it is possible to purify the crude product including low content of neopentyl glycol and high content of high-boiling components with high purity, and the energy consumption can be reduced, compared to conventional ways.

Description

TITLE OF THE INVENTION
A DIVIDING WALL COLUMN AND A METHOD OF PURIFYING NEOPENTYL GLYCOL USING THE SAME BACKGROUND OF THE INVENTION
(a) Field of the Invention
The present invention relates to a dividing wall column and a method of purifying neopentyl glycol using the same. More specifically, it relates to a dividing wall column which can purify crude products including neopentyl glycol with high purity and a method of purifying neopentyl glycol using the same.
(b) Description of the Related Art
Neopentyl glycol (NPG) may be formed by a hydrogenation reaction of hydroxypivaldehyde which is formed by an aldol reaction of isobutylaldehyde and formaldehyde under a basic condition. At this time, monoester compounds such as NPG-isobutyrate (3-hydroxy-2,2-dimethylpropyl isobutyrate), HPNE (hydroxypivalyl hydroxypivalate), and TMPD (2,2,4-trimethyl-l,3-pentanediol) are formed as the side-reaction product in the process. However, these compounds cause a problem in the application of the product to which neopentyl glycol is applied, and thus it is preferable to make the amount of these compounds in the final neopentyl glycol product several hundreds ppm or less.
Therefore, many methods for eliminating such high-boiling compounds have been suggested.
Korean Patent No. 10-0231643 discloses a method of eliminating inorganic salts by applying a multi-step distillation separation column thereto and using water as an entrainment agent for the crude neopentyl glycol including metal salts after safonification, wherein a tiny amount of water is provided through the upper part of the column. However, the process has a disadvantage in that it is complicated in the separating process and needs a great deal of energy. Therefore, simple and energy saving methods are being largely attempted recently. For example, Korean Patent No. 10-0676304 discloses the method of obtaining neopentyl glycol with high purity by using two distilling columns without safonification.
Conventional separation technologies using distillation columns need n-1 distillation columns for separating n components included in a multi-component mixture. Particularly, in the case of 3 components or more, remixing effect of middle-boiling components occurs generally at the bottom section of the first distillation column, and it is the main cause of the decrease of the thermodynamic efficiency at the distillation column and increasing a loss of energy.
As another alternative, there is a process using a Petlyuk distillation column having a heat integrated structure. The Petlyuk distillation column separates low-boiling components at the top of the column, middle-boiling components at the middle of the column, and high-boiling components at the bottom of the column at the main separation column, respectively, after separating low-boiling components and high-boiling components at the preliminary separation column. Basically, it has an advantage in eliminating the energy efficiency decrease problem due to remixing of the middle-boiling components which can occur when two common distillation columns are used. However, it is difficult to operate and adjust the pressure balance.
Meanwhile, Korean Patent Publication No. 10-2012-0076196 discloses a purification process of neopentyl glycol using a dividing wall column (DWC). The dividing wall column is similar to the Petlyuk distillation column in view of thermodynamic aspects, but it is different from the same in view of the structure that the preliminary separation column is integrated in the main separation column by installing a dividing wall in the column. By this, it has an advantage in that it is possible to resolve the difficulty in the pressure balance between the preliminary separation column and the main separation column and the difficulty in the operation due to this and it is easy to operate the same, and the investment costs may decrease because two distillation columns are integrated into one.
However, the dividing wall column is difficult to achieve sufficient separating efficiency and energy saving effect, unless the design of the dividing wall and the temperature and pressure condition of the top, the bottom, and the outflow section of the column are delicately controlled according to the characteristics and the content of the materials in the mixture to be purified. Korean Patent Publication No. 10-2012-0076196 sets the temperature of the top section, the bottom section, and the outflow section in a specific range for high purity refinement, and, particularly, the temperature of the top section and the bottom section are defined by a mathematical formula depending on the pressure.
The method disclosed in said Korean Patent Publication can be applied when the mixture flowed therein includes high content, at least 55 wt% or more, of neopentyl glycol, but it has a disadvantage in that the effective purification is difficult or the energy consumption becomes large when the content of neopentyl glycol is less than 55 wt% and a large quantity, 1.5 wt% or more, of high-boiling components (heavies) is included in the mixture.
However, considering that the product obtained in the preparation process of neopentyl glycol by a commercial aldol reaction and a hydrogenation reaction includes average 1.5 wt% or more of high-boiling components as by-products, the purification method disclosed in said Korean Patent Publication may increase the energy consumption, or may need a pretreatment process for reducing the content of the high-boiling components in addition, before applying the purification method.
SUMMARY OF THE INVENTION
In this regard, it is an object of the present invention to provide a dividing wall column which can effectively purify a crude product containing relatively low content of neopentyl glycol and large content of impurities such as high-boiling components, and a method of purifying neopentyl glycol using the same.
According to one aspect for achieving the object, the present invention provides a dividing wall column, including a main column equipped with a dividing wall, a condenser, and a reboiler,
wherein the main column is divided into a top section, a feed section, an outflow section, and a bottom section by the dividing wall that is located at 25% to 95% ' from the top, based on the total steps of the main column, a crude product including neopentyl glycol is fed to the feed section through a feeding tray that is located at 50% or more from the top, based on the total steps of the feed section, and
low-boiling components in the crude product flows out at the top section, high-boiling components flows out at the bottom section, middle-boiling components flows out at the outflow section, and the middle-components include neopentyl glycol as a main component.
Furthermore, according to another aspect, the present invention provides a method of purifying neopentyl glycol, including the step of carrying out a fractional distillation of a crude product including neopentyl glycol by using the dividing wall column.
According to the dividing wall column of the present invention, the distillation column structure suitable for the purification of neopentyl glycol is provided and it becomes possible to purify neopentyl glycol on a commercial scale with high energy efficiency.
Furthermore, according to the, method of purifying neopentyl glycol using the dividing wall column of the present invention, it is possible to purify the crude product of neopentyl glycol including low content of neopentyl glycol and large content of high-boiling components with high purity. And, it is possible to save energy, compared to a conventional process using continuous two distillation columns. Therefore, the method can contribute the productivity improvement in the total purification processes of purifying neopentyl glycol.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 illustrates a drawing of conventional continuous two distillation columns.
Fig. 2 illustrates a drawing of the dividing wall column according to one embodiment of the present invention.
Fig. 3 illustrates a drawing of the main column of the dividing wall column according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS
In the present invention, the terms "the first", "the second", and the like are used for explaining various components and said tenns are only used for distinguishing one component from the other components.
Furthermore, the terms used in this description are just for explaining exemplary examples and it is not intended to restrict the present invention. The singular expression may include the plural expression unless it is differently expressed contextually. It must be understood that the terms such as "include", "equip", and "have" in the present description are only used for designating the existence of characteristics taken effect, numbers, steps, components, or combinations thereof, and do not exclude the existence or the possibility of addition of one or more different characteristics, numbers, steps, components of combinations thereof beforehand.
Additionally, the word "on" or "above", as used in the context of formation or construction of one layer or element, means pertaining to the direct formation or construction of one layer or element on another layer or element directly or the additional formation or construction of one layer or element between layers or on a subject or substrate.
The present invention can be variously modified and have various examples, and specific examples of the present invention are explained in this description. However, it is not intended to limit the present invention to the specific examples and it must be understood that the present invention includes every modifications, equivalents, or replacements included in the idea and technical scope of the present invention.
Hereinafter, the dividing wall column of the present invention and the method of purifying neopentyl glycol using the same are explained in more detail.
According to one embodiment, the present invention provides
a dividing wall column, including a main column equipped with a dividing wall; a condenser; and a reboiler,
wherein the main column is divided into a top section, a feed section, an outflow section, and a bottom section by the dividing wall that is located at 25% to 95% from the top, based on the total steps of the main column, a crude product including neopentyl glycol is fed to the feed section through a feeding tray that is located at 50% or more from the top, based on the total steps of the feed section, and
low-boiling components in the crude product flows out at the top section, high-boiling components flows out at the bottom section, middle-boiling components flows out at the outflow section, and the middle-components include neopentyl glycol as a main component.
In the present specification, "crude product" is the material to be purified in the present invention and means the unpurified product that is obtained by various organic synthesis reactions for preparing neopentyl glycol, the final product. The dividing wall column of the present invention is used for purifying neopentyl glycol with high purity from the crude product.
Furthermore, in the present specification, "low-boiling component" means the materials of which the boiling point is less than the temperature 20 °C lower than the boiling point (208 °C ) of neopentyl glycol among the components included in the crude product including neopentyl glycol, "middle-boiling component" includes neopentyl glycol and the materials of which the boiling point is within the range of ± 20 °C based on the boiling point of neopentyl glycol among the components included in the crude product including neopentyl glycol, and "high-boiling component" means the materials of which the boiling point is larger than the temperature 20 °C higher than the boiling point of neopentyl glycol among the components included in the crude product including neopentyl glycol.
For example, the low-boiling components may be isobutyl aldehyde, water, hydroxy pivaldehyde, isobutyl alcohol, octanol, and so on, the middle-boiling components may be neopentyl glycol (NPG), NPG-isobutyrate (3-hydroxy-2,2-dimethylpropyl isobutyrate), and so on, and the high-boiling components may be hydroxypivalyl hydroxypivalate (HPNE), 2,2,4-trimethyl-l,3-pentanediol (TMPD), and so on.
According to one embodiment of the present invention, the crude product may be a product of a hydrogenation reaction of hydro xypivaldehyde which is formed by an
Figure imgf000009_0001
Since the crude product including neopentyl glycol includes monoester compounds such as NPG-isobutyrate, HPNE, and TMPD, and primary alcohol compounds such as 2-ethyl hexanol, by-products, as impurities, it must go through purification processes for eliminating the impurities in order to obtain neopentyl glycol as the final product. However, TMPD and HPNE have the high boiling points of 229.95 °C and 292 °C , respectively, and NPG-isobutyrate has the boiling point of 198.75 °C which is similar to the boiling point of neopentyl glycol (208 °C) among the impurities, and thus it is not easy to separate them by a simple distillation process.
As the method of purifying the mixture that includes the compounds having high boiling point and the compound having the boiling point similar to the target material to be purified and is not easy to distill, there is a continuous two distillation columns process in which two or more distillation processes are continuously carried out.
Fig. 1 illustrates a drawing of conventional continuous two distillation columns.
Referring to Fig. 1 , there are two distillation columns 7, 8 including condensers 7a, 8a, reboiliers 7b, 8b, and main columns 7c, 8c, respectively, and a stream 1 of the mixture provided to a first distillation column 7 is primarily separated into low-boiling components 2 and high-boiling components 3. The high-boiling components 3 flowed out through the lower part of the first distillation column 7 are continuously fed to a second distillation column 8, secondarily. High-boiling components 4 provided to the second distillation column 8 are separated into low-boiling components 5 and high-boiling components 6 again and flow out finally.
However, since there is a problem of decreasing thermodynamic efficiency due to remixing of the middle-boiling materials in the first distillation column when the continuous two distillation columns are used, researchers are seeking various ways to improve energy efficiency. For example, many studies about new distillation structures by improvement of control system, integration of external heat, improvement of process, improvement of internal steps, and so on are ongoing. However, the continuous two distillation columns have a limitation on improvement of energy efficiency because two distillation processes are basically carried out and total four heat exchangers, two heat exchangers per each distillation column, are equipped therein.
However, the dividing wall column of the present invention and the method of purifying neopentyl glycol using the same can exhibit high energy efficiency because the method includes the step of carrying out a fractional distillation by using the dividing wall column that is optimally designed to purify the crude product including neopentyl glycol.
The crude product collected after the synthesis reaction of neopentyl glycol by an aldol reaction and a hydrogenation reaction is a mixture form including neopentyl glycol, and it includes impurities of which the boiling point is about 64 °C to about 292 °C . Among them, neopentyl glycol corresponds to a middle-boiling component of which the boiling point is 208 °C . Like this, when the target material to be purified belongs to middle-boiling components in the mixture, it is not easy to separate the same by an one-step distillation process and at least two steps of distillation processes are required.
However, according to the dividing wall column of the present invention and the method of purifying neopentyl glycol using the same, it is possible to purify neopentyl glycol with high purity by just one distillation column process, by putting the crude product including neopentyl glycol in the dividing wall column and carrying out a fractional distillation.
The dividing wall column of the present invention for carrying out the purification process of neopentyl glycol, includes
a main column equipped with a dividing wall; a condenser; and a reboiler, wherein the main column is divided into a top section, a feed section, an outflow section, and a bottom section by the dividing wall that is located at 25% to 95% from the top, based on the total steps of the main column,
a crude product including neopentyl glycol is fed to the feed section through a feeding tray that is located at 50% or more from the top, based on the total steps of the feed section, and
low-boiling components in the crude product flows out at the top section, high-boiling components flows out at the bottom section, middle-boiling components flows out at the outflow section, and the middle-components include neopentyl glycol as a main component.
The middle-boiling components flowing out from the outflow section of the dividing wall column of the present invention include neopentyl glycol as the main component, and, for example, it may include about 99 wt% or more, preferably about 99.5 wt% or more, and more preferably about 99.9 wt% or more of neopentyl glycol, based on the total weight of the middle-boiling components. Namely, it is possible to obtain neopentyl glycol having the purity of about 99 wt% or more, preferably about 99.5 wt% or more, and more preferably about 99.9 wt% or more by using the dividing wall column of the present invention.
The structure of the dividing wall column according to one embodiment of the present invention is illustrated in Fig. 2.
Referring to Fig. 2, the dividing wall column of the present invention includes a main column 100 equipped with a dividing wall 10, a condenser 200, and a reboiler 300, and the main column 100 is largely divided into a top section 20, a bottom section 30, a feed section 40, and an outflow section 50.
The feed section 40 may be divided into an upper feed section 40a and a lower feed section 40b and the outflow section 50 may be divided into an upper outflow section 50a and a lower outflow section 50b again. The part where the upper feed section 40a and the lower feed section 40b meet is a feeding tray 40c, and the part where the upper outflow section 50a and the lower outflow section 50b meet is an outflow tray 50c.
At first, the dividing wall column of the present invention includes a condenser 200 and a reboiler 300.
The condenser 200 is an apparatus for condensing a gas-phase mixture by taking away the heat of evaporation therefrom, and a condenser which can be used for a common chemical engineering apparatus may be used without limit.
The reboiler 300 is an apparatus for evaporating a liquid-phase mixture by providing the heat of evaporation thereto, and a reboiler which can be used for a common chemical engineering apparatus may be used without limit.
The energy consumptions of the condenser 200 and the reboiler 300 vary by various conditions including the length of the main column, the specific operation condition of the distillation column, and the ingredients of the inflow stream, and the total energy consumption may be evaluated by the sum of the energy consumptions of the condenser 200 and the reboiler 300. According to the dividing wall column of the present invention and the method of purifying neopentyl glycol using the same, the energy saving rate may be about 10 to about 40% in comparison to conventional continuous two distillation columns and it is possible to reduce the energy consumption apparently, in the case of purifying the same crude product.
The main column 100 may be largely divided into a top section 20, a feed section 40, an outflow section 50, and a bottom section 30, and the feed section 40 may be divided into an upper feed section 40a and a lower feed section 40b and the outflow section 50 may be divided into an upper outflow section 50a and a lower outflow section 50b again.
The top section 20 is the section above the dividing wall 10 and it means the upper part of the main column 100 where there is no dividing wall 10.
The feed section 40 is the section divided by the dividing wall 10 to which a stream of a crude product A including neopentyl glycol is fed. The upper feed section 40a is the upper part of the feed section 40 and the subsection located above the stream of the crude product A provided to the main column 100. And the lower feed section 40b is the lower part of the feed section 40 and the subsection located below the stream of the crude product A provided to the main column 100.
The outflow section 50 is the section divided by the dividing wall 10 from which a stream of middle-boiling components B including the neopentyl glycol purified with high purity flows out. The upper outflow section 50a is the upper part of the outflow section 50 and the subsection located above the stream of the middle-boiling components B flows out -from the main column 100. And the lower outflow section 50b is the lower part of the outflow section 50 and the subsection located below the stream of the middle-boiling components B flows out from the main column 100.
The bottom section 30 is the section below the dividing wall 10 and it means the lower part of the main column 100 where there is no dividing wall 10.
Since the space divided by the dividing wall 10 in the dividing wall column takes a role of the preliminary separator, the liquid composition almost coincides with the equilibrium distillation curve and the remixing effect is suppressed due to the elimination of the high-boiling components and the low-boiling components, and thus the thermodynamic efficiency for the separation gets better.
The upper feed section 40a and the lower feed section 40b take a role similar to the preliminary separator. Namely, the feed section 40 including the upper feed section 40a and the lower feed section 40b may be a sort of preliminary separation section. The mixture flowing into the preliminary separation section is largely separated into the low-boiling components and the high-boiling components. Some of the low-boiling components and the high-boiling components flow into the top section 20 and the bottom section 30, and some of the same flow into the upper outflow section 50a and the lower outflow section 50b and are distilled again.
The upper outflow section 50a and the lower outflow section 50b take a role of main separator of conventional processes. Namely, the outflow section 50 including the upper outflow section 50a and the lower outflow section 50b may be a main separation section. The low-boiling components and the middle-boiling components are mostly separated at the upper part of the dividing wall 10 of the main separation section, and the middle-boiling components and the high-boiling components are mostly separated at the lower part.
After the low-boiling components pass through the top section 20 and the condenser 200, some of them are separated as low-boiling components C and some of them are refluxed into the top section 20 of the main column 100 again as a liquid flux LD.
After the high-boiling components pass through the bottom section 30 and the reboiler 300, some of them are separated as high-boiling components D and some of them are refluxed into the bottom section 30 of the main column 100 again as a vapor flux VB.
The dividing wall column of the present invention may further include a condensing drum 400. The condensing drum 400 is a buffer apparatus for. a stable reflux provision.
According to the dividing wall column of the present invention, the dividing wall 10 is located longitudinally between about 25 and about 95% from the top, based on the total steps of the main column 100.
Fig. 3 illustrates a drawing for illustrating the main column of the dividing wall column of the present invention more specifically. The inner column of the main column is not illustrated here for convenience, and "length" disclosed below means the length defined by the steps of the column. Furthermore, the steps of the column are located at equal spaces in an independent section, for example, the top section 20, the bottom section 30, the upper feed section 40a, the lower feed section 40b, the upper outflow section 50a, and the lower outflow section 50b. The intervals of the steps of the column in the distinguishing sections may be independently same to or different from each other.
Referring to Fig. 3, the position of the dividing wall 10 may be between about 25% and about 95%, or about 25% and about 90%, or about 25% and about 85%, from the top to the bottom, based on the length of the total steps of the main column 100. Namely, a starting position T of the dividing wall 10 may be 25% or more from the top, based on the length of the total steps of the main column 100, and a ending position T' of the dividing wall 10 may be about 95% or less, or about 90% or less, or about 85% or less, from the top, based on the length of the total steps of the main column 100.
Furthermore, when the length of the total steps of the main column 100 is L and the length of the dividing wall 10 is L', L' may be about 50 to about 70%, preferably about 55 to about 65%, of L.
According to the dividing wall column of the present invention and the purification method using the same, when the dividing wall is designed to satisfy the position and the length disclosed above, the energy saving efficiency can be maximized and the high-boiling components can be effectively separated.
The crude product A including neopentyl glycol flows in the feed section 40 of the dividing wall column of the present invention. More specifically, the crude product A including neopentyl glycol is fed to the middle part of the feed section 40, namely, the feeding tray 40c where the upper feed section 40a and the lower feed section 40b meet.
Referring to Fig. 3 again, the position of the feeding tray 40c is about 50% or more, for example, about 50 to about 80%, from the top, based on the steps of the column of the total feed section 40 including the upper feed section 40a and the lower feed section 40b. Namely, the position of the feeding tray 40c is determined according to the steps of each column of the upper feed section 40a and the lower feed section 40b. When the number of the steps of the column of the feed section 40 is 100, the ratio of the steps of the column of the upper feed section 40a and the lower feed section 40b may be about 50 : 50 to about 80 : 20.
The low-boiling components C are separated at the upper part of the dividing wall 10, the high-boiling components D are separated at the lower part of the dividing wall 10, and the separated middle-boiling components B flow out at the outflow section 50. More specifically, the middle-boiling components B flow out from the middle part of the outflow section 50, namely, the outflow tray 50c where the upper outflow section 50a and the lower outflow section 50b meet. In the dividing wall column of the present invention, the position of the outflow tray 50c is about 50% or less, for example, about 20 to about 50%, from the top, based on the steps of the column of the total outflow section 50 including the upper outflow section 50a and the lower outflow section 50b. Namely, the position of the outflow tray 50c is determined according to the steps of each column of the upper outflow section 50a and the lower outflow section 50b. When the number of the steps of the column of the outflow section 50 is 100, the ratio of the steps of the column of the upper outflow section 50a and the lower outflow section 50b may be about 20 : 80 to about 50 : 50.
It is the characteristic of the present invention that the middle-boiling components B include neopentyl glycol of high purity.
According to the present invention, it is possible to purify neopentyl glycol with high purity of 99 wt% or more with low energy consumption, even when the crude product, the target material to be purified, includes large amount of high-boiling components, by regulating and optimizing the position of the main column, the length of the main column, the position of the feeding tray, and the position of the outflow tray as disclosed above.
The number of the steps of the main column, the top section, the bottom section, the upper feed section, the lower feed section, the upper outflow section, and the lower outflow section may be regulated with necessity if it satisfies said conditions.
According to one embodiment of the present invention, the number of the total steps of the main column may be 60 to 90, preferably 70 to 80, and more preferably 73 to 77.
The number of the steps of the top section may be 16 to 26, preferably 18 to 24, and more preferably 19 to 22. Furthermore, the number of the steps of the bottom section may be 10 to 25, preferably , 10 to 20, and more preferably 12 to 17.
Each number of the steps of the upper feed section, the lower feed section, the upper outflow section, and the lower outflow section may be equally or differently 15 to 65, preferably 18 to 63, and more preferably 20 to 61, independently.
According to another embodiment, the present invention provides a method of purifying neopentyl glycol, including the step of carrying out a fractional distillation of a crude product including neopentyl glycol by using the dividing wall column.
Details of the dividing wall column used in the purification method of neopentyl glycol of the present invention are as disclosed above.
Meanwhile, in the purification method of neopentyl glycol using the dividing wall column, the content of neopentyl glycol may be about 35 wt% or more, for example, about 35 to about 70 wt%, or about 35 to about 54 wt%, or about 40 to about 54 wt%, based on the total weight of the crude product including neopentyl glycol. The content range of neopentyl glycol corresponds to a conventional yield in an industrial preparation process of neopentyl glycol by an aldol reaction and a hydrogenation reaction, and the present method of purifying neopentyl glycol can be directly applied to the crude product without an additional modification or pretreatment for increasing purification efficiency, and thus the method is industrially and economically very useful.
Furthermore, the content of the high-boiling components may be about 1.5 wt% or more, for example, about 1.5 to about 10 wt%, or about 1.5 to about 8 wt%, or about 2 to about 6 wt%, based on the total weight of the crude product including neopentyl glycol. According to the purification method of neopentyl glycol using the dividing wall column of the present invention, it is specifically useful when the content of the high-boiling components is high, 1.5 wt% or more, and it is possible to separate the high-boiling component effectively by using low energy.
In the case of purifying the crude product including neopentyl glycol by using the dividing wall column, it is possible to purify neopentyl glycol with the purity of about 99 wt% or more, preferably about 99.5 wt% or more, and more preferably about 99.9 wt% or more.
The temperature of the top section of the main column is preferably about 1 12 to about 134 °C at the pressure of about -0.938 to about -0.875 kg/cm2 g. When the temperature is below 1 12 °C , the low-boiling components may fall to the lower part of the preliminary separation section and affect the purity of the product, and when it is over 134 °C , the high-boiling components may go up to the upper part of the preliminary separation section and affect the purity of neopentyl glycol.
The temperature of the bottom section of the main column is preferably about 167 to about 183 °C at the pressure of about -0.75 to about -0.70 kg cm2 g. When the temperature is below 167 °C , the middle-boiling components may come down and the product output may decrease, and when it is over 183 °C , there is concern that the high-boiling components may flow out with the middle-boiling components as a side stream.
The difference in the temperature of the top section and the bottom section of the main column may be about 71 °C or less, for example, about 33 to about 71 °C , or about 40 to about 71 °C , or about 50 to about 71 °C . The energy consumption of the condenser and the reboiler may further decrease while maintaining high purity of neopentyl glycol and high separation efficiency of the high-boiling components, even when the difference in the temperature of the top section and the bottom section of the main column is in a certain range as disclosed above.
The temperature of the crude product of neopentyl glycol flowed in the feeding tray may be about 50 to 70 °C .
When the crude product is fed to the dividing wall column of the present invention with the inflow condition and the purification process of neopentyl glycol is carried out, the energy consumption at the reboiler may be about 3.2 Mkcal/h or less, for example, about 2.5 to about 3.2 Mkcal/h, and it is possible to carry out the purification process with much less energy consumption than the case of using a conventional continuous two distillation columns or a dividing wall column of known structure.
Furthermore, the temperature of the outflow tray where the upper outflow section and the lower outflow section meet and the middle-boiling components flows out is preferably about 155 to about 158.5 °C at the pressure of about -0.845 to about -0.835 kg/cm2 g. When the temperature is beyond the range, it may largely affect the purity of the product, because it is not easy to eliminate the low-boiling components when the temperature is below 155 °C and it is not easy to eliminate the high-boiling components when the temperature is over 158.5 °C .
Hereinafter, the present invention will be explained in more detail with reference to the following examples. However, these examples are only to illustrate the invention, and the scope of the invention is not limited thereto.
<Examples>
Examples 1 to 3
The dividing wall column of the present invention was designed and simulated by using ASPEN. Continuous two distillation columns without the dividing wall illustrated in Fig. 1 were used as Comparative Example, and the dividing wall column illustrated in Fig. 2 was used as Example. A composition of the crude product (hereinafter, composition 1) fed thereto includes 50 wt% of neopentyl glycol, 44 wt% of 2-ethyl hexanol and 2 wt% of water as the low-boiling components, and 2 wt% of 2,2,4-trimethyl-l,3-pentanediol (TMPD) and 2 wt% of hydroxypivalyl hydroxypivalate (HPNE) as the high-boiling components.
Details of the process conditions of Examples 1 to 3 were listed in the following
Table 1 , and details of the process conditions of Comparative Example 1 were listed in the following Table 2.
[Table 1 ]
Classifications Example 1 Example 2 Example 3
Main Steps of Column 75 steps 75 steps 75 steps Column
100
Top Steps of Column 20 steps 20 steps 20 steps section
20
Temperature and Pres.: -0.9313 Pres.: -0.9313 Pres.: -0.9313 Pressure kg/cm2 g, kg/cm2 -g, kg/cm2 g,
Temp.: 1 12.5 °C Temp.: 1 12.5 °C Temp.: 112.5 °C
Main Total Steps of 40 steps 40 steps 45 steps Column Column
100
Upper feed 22 steps 27 steps 27 steps section 40a
Upper outflow 10 steps 10 steps 10 steps section 50a
Lower feed 18 steps 13 steps 18 steps section 40b
Lower outflow 30 steps 30 steps 35 steps section 50b
Crude Product Pres.: 3 kg/cm2 g, Pres.: 3 kg/cm2 g, Pres.: 3 kg/cm2 -g, Inflow Temp.: 60 °C , Temp.: 60 °C , Temp.: 60 °C , Condition Inflow: 12,500 Inflow: 12,500 Inflow: 12,500 kg/h kg/h kg/h
Bottom Steps of Column 15 steps 15 steps 10 steps section
30
Temperature and Pres.: -0.7063 Pres.: -0.7063 Pres.: 0.7063 Pressure kg/cm2 -g, kg/cm2 -g, kg/cm2 -g,
Temp.: 183 °C Temp.: 183 Γ Temp.: 183 °C
[Table 2]
Figure imgf000020_0001
The energy consumptions under the above conditions of the processes of Examples 1 to 3 and Comparative Example 1 were compared in the following Table 3.
[Table 3 ]
Figure imgf000021_0001
Referring to Table 3, the energy consumption saving rates of the dividing wall columns of the present invention were respectively 36.6% (Example 1), 38.1 % (Example 2), and 38.1% (Example 3), compared to Comparative Example 1 carrying out two distillation column processes, and the energy efficiencies thereof were largely increased.
[Table 4]
Figure imgf000021_0002
Components
High-boiling - - - - Components
outflow Low-boiling - - - - section Components
Middle-boiling 99.9 wt% 99.9 wt% 99.9 wt% 99.9 wt% Components
High-boiling 0.1 wt% 0.1 wt% 0.1 wt% 0.1 wt% Components
Bottom Low-boiling - - - - section Components
Middle-boiling 36.48 wt% 36.88 wt% 36.91 wt% 38.09 wt% Components
High-boiling 63.52 wt% 63.12 wt% 63.09 wt% 61.91 wt% Components
In Table 4, the sum of the low-boiling, middle-boiling, and high-boiling components was expressed so that the sum of them was respectively 100 wt% at the top section, the outflow section, and the bottom section.
As shown in Table 4, neopentyl glycol of high purity of 99.9 wt% was collected at the outflow section of Examples 1 to 3 and the amount of the high-boiling components at the bottom section was 63 wt% or more. Therefore, it was recognizable that most of high-boiling components were separated into the bottom section. Meanwhile, in Comparative Example 1 , the amount of the high-boiling components at the bottom section was about 61 wt% and thus the separation efficiency of the high-boiling components was inferior to Examples of the present invention.
Examples 4 to 10
The processes were carried out according to the same method as in Example 1 , except that the compositions of the fed crude products were changed. Compositions 2 to 8 correspond to Examples 4 to 10 respectively and details of the compositions were listed in the following Table 5.
Comparative Examples 2 to 8
The processes were carried out according to the same method as in Comparative Example 1, except that the compositions of the fed crude products were changed. Compositions 2 to 8 correspond to Comparative Examples 2 to 8 respectively and details of the compositions were listed in Table 5.
[Table 5]
Figure imgf000023_0001
The energy consumed under the above conditions in the processes of Examples 4 to 10 and Comparative Examples 2 to 8 and the energy saving rate of Examples compared to Comparative Examples were listed in the following Table 6.
[Table 6]
Composition No. Comparative Example Energy Energy Consumption
No./Example No. Consumption (unit: Saving Rate
Mkcal/hr)
Composition 2 Comparative Example 9.834 about 16%
2
Example 4 8.272 Composition 3 Comparative Example 9.696 about 15%
3
Example 5 8.194
Composition 4 Comparative Example 9.867 about 14%
4
Example 6 8.499
Composition 5 Comparative Example 9.244 about 36%
5
Example 7 5.925
Composition 6 Comparative Example . 9.541 about 32%
6
Example 8 6.465
Composition 7 Comparative Example 10.004 about 27%
7
Example 9 7.262
Composition 8 Comparative Example 9.145 about 19%
8
Example 10 7.414
Referring to Tables 5 and 6, it was shown that the method using the dividing wall column of the present invention can reduce 13% to 34% of energy in comparison to the method using the continuous two distillation columns when the same composition of crude product was used. Particularly, the energy saving effect was also shown even when the crude product included large amount, 2 wt% to 6 wt%, of the high-boiling components, to varying degrees.
<Description of symbols>
10: Dividing wall
20: Top section
30: Bottom section 40: Feed section
40a: Upper feed section
40b: Lower feed section
40c: Feeding tray
50: Outflow section
50a: Upper outflow section
50b: Lower outflow section
50c: Outflow tray
100: Main column
200: Condenser
300: Reboiler
400: Condensing drum

Claims

WHAT IS CLAIMED IS:
1. A dividing wall column, including a main column equipped with a dividing wall, a condenser, and a reboiler,
wherein the main column is divided into a top section, a feed section, an outflow section, and a bottom section by the dividing wall that is located at 25% to 95% from the top, based on the total steps of the main column,
a crude product including neopentyl glycol is fed to the feed section through a feeding tray that is located at 50% or more from the top, based on the total steps of the feed section, and
low-boiling components in the crude product flows out at the top section, high-boiling components flows out at the bottom section, middle-boiling components flows out at the outflow section, and the middle-components include neopentyl glycol as a main component.
2. The dividing wall column according to Claim 1, wherein the length of the dividing wall is 50 to 70% of the length of the total steps of the main column.
3. The dividing wall column according to Claim 1, wherein the feed section is divided into an upper feed section and a lower feed section, the feeding tray is the part where the upper feed section and the lower feed section meet, and the ratio of the steps of the column of the upper feed section and the lower feed section is 50 : 50 to 80 : 20.
4. The dividing wall column according to Claim 1, wherein the middle-boiling components flow out from an outflow tray at the outflow section, and the outflow tray is located at 50% or less from the top, based on the total steps of the column of the outflow section.
5. The dividing wall column according to Claim 1, wherein the outflow section is divided into an upper outflow section and a lower outflow section, the outflow tray is the part where the upper outflow section and the lower outflow section meet, and the ratio of the steps of the column of the upper outflow section and the lower outflow section is 20 : 80 to 50 : 50.
6. A method of purifying neopentyl glycol, including the step of carrying out a fractional distillation of a crude product including neopentyl glycol by using the dividing wall column according to any one of Claims 1 to 5.
7. The method of purifying neopentyl glycol according to Claim 6, wherein the content of neopentyl glycol is 35 to 54 wt%, based on the total weight of the crude product including neopentyl glycol.
8. The method of purifying neopentyl glycol according to Claim 6, wherein the content of the high-boiling components is 1.5 to 10 wt%, based on the total weight of the crude product including neopentyl glycol.
9. The method of purifying neopentyl glycol according to Claim 6, wherein the temperature of the top section of the main column is 1 12 to 134 °C at the pressure of -0.938 to -0:875 kg/cm2 g.
10. The method of purifying neopentyl glycol according to Claim 6, wherein the temperature of the bottom section of the main column is 167 to 183 °C at the pressure of -0.75 to -0.70 kg/cm2 g.
11. The method of purifying neopentyl glycol according to Claim 6, wherein the difference in the temperature of the top section and the bottom section of the main column is 71 °C or less.
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