WO2009082086A1 - Process for preparing of n-methyl pyrrolidone - Google Patents

Process for preparing of n-methyl pyrrolidone Download PDF

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Publication number
WO2009082086A1
WO2009082086A1 PCT/KR2008/005790 KR2008005790W WO2009082086A1 WO 2009082086 A1 WO2009082086 A1 WO 2009082086A1 KR 2008005790 W KR2008005790 W KR 2008005790W WO 2009082086 A1 WO2009082086 A1 WO 2009082086A1
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WIPO (PCT)
Prior art keywords
butyrolactone
reaction
catalyst
methyl pyrrolidone
group
Prior art date
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PCT/KR2008/005790
Other languages
French (fr)
Inventor
In-Chul Oh
Chang-Gook Kim
Dae-Yong Rhie
Lee-Ho Kim
Jun-Soo Kim
Soo-Hyun Kim
Chan-Koo Hwang
Myung-Hun Roh
Jin-Su Jung
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Isu Chemical Co., Ltd.
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Publication date
Priority claimed from KR1020070134910A external-priority patent/KR100943528B1/en
Application filed by Isu Chemical Co., Ltd. filed Critical Isu Chemical Co., Ltd.
Priority to JP2010539279A priority Critical patent/JP5478504B2/en
Priority to CN200880121682.4A priority patent/CN101903344B/en
Publication of WO2009082086A1 publication Critical patent/WO2009082086A1/en

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    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07D—HETEROCYCLIC COMPOUNDS
    • C07D207/00—Heterocyclic compounds containing five-membered rings not condensed with other rings, with one nitrogen atom as the only ring hetero atom
    • C07D207/02—Heterocyclic compounds containing five-membered rings not condensed with other rings, with one nitrogen atom as the only ring hetero atom with only hydrogen or carbon atoms directly attached to the ring nitrogen atom
    • C07D207/18—Heterocyclic compounds containing five-membered rings not condensed with other rings, with one nitrogen atom as the only ring hetero atom with only hydrogen or carbon atoms directly attached to the ring nitrogen atom having one double bond between ring members or between a ring member and a non-ring member
    • C07D207/22—Heterocyclic compounds containing five-membered rings not condensed with other rings, with one nitrogen atom as the only ring hetero atom with only hydrogen or carbon atoms directly attached to the ring nitrogen atom having one double bond between ring members or between a ring member and a non-ring member with hetero atoms or with carbon atoms having three bonds to hetero atoms with at the most one bond to halogen, e.g. ester or nitrile radicals, directly attached to ring carbon atoms
    • C07D207/24—Oxygen or sulfur atoms
    • C07D207/26—2-Pyrrolidones
    • C07D207/263—2-Pyrrolidones with only hydrogen atoms or radicals containing only hydrogen and carbon atoms directly attached to other ring carbon atoms
    • C07D207/267—2-Pyrrolidones with only hydrogen atoms or radicals containing only hydrogen and carbon atoms directly attached to other ring carbon atoms with only hydrogen atoms or radicals containing only hydrogen and carbon atoms directly attached to the ring nitrogen atom

Definitions

  • the present invention relates to a process for preparation of N-methyl pyrrolidone, and more particularly to a process for preparation of high purity and high yield N-methyl pyrrolidone, which is a continuous two-step process using a solid catalyst comprising a metal oxide as an active component, wherein the two-step reaction can continuously progress without purification of the first step reaction product, ⁇ -butyrolactone, and can easily perform separation and purification because little of the reaction intermediate ⁇ -butyrolactone, which is difficult to separate because of a small difference in boiling point (about 2 "C) from the final product, N-methyl pyrrolidone, remains after reaction, and can produce N-methyl pyrrolidone in large quantities due to its simple process.
  • N-Methyl pyrrolidone is industrially prepared by a dehydration of monomethylamine and ⁇ -butyrolactone, and its preparation method is largely classified into a method using a catalyst and a method that does not use a catalyst.
  • a method that does not use a catalyst a method for preparing N-methyl pyrrolidone with yield of 90-93% by reacting ⁇ -butyrolactone and monomethylamine in a batch reactor at 280 "C for 4 hours has been disclosed (J. Amer. Chem. Soc, 71(1949)896). Additionally, Japanese patent publication No. Hei.
  • 1-190667 disclosed a method for preparing N-methyl pyrrolidone with a yield of 94.3% by introducing ⁇ -butyrolactone, water, and monomethylamine into an autoclave and reacting them at 240-265 0 C under a pressure of 50 atm for 3 hours.
  • Japanese patent publication No. Sho. 49-20582 disclosed a method for preparing N-methyl pyrrolidone with a yield of 63-93% by reacting ⁇ -butyrolactone and monomethylamine using a catalyst such as alumina, silica alumina, activated carbon, silica gel, silica-magnesia, etc.
  • ⁇ -butyrolactone as a starting material, which is previously prepared from 1 ,4-butandiol or maleic anhydride, and is separated and purified, to prepare N-methyl pyrrolidone.
  • ⁇ -butyrolactone the intermediate for preparing N-methyl pyrrolidone
  • 1,4-butandiol is prepared from 1,4-butandiol by dehydrogenation in the presence of a Cu/Cr catalyst or a catalyst prepared by adding Zn and Mn to a Cu/Cr catalyst, by dehydrogenation using an oxidant such as oxygen in the presence of a catalyst containing one or more kinds of Pt, Pd, Ag, etc., or by dehydrogenation in the presence of a catalyst prepared by adding an alkali metal or Al to a Cu/Zn catalyst.
  • ⁇ -butyrolactone is prepared by dehydrogenation of 1,4-butandiol using a Cu/Cr catalyst.
  • this method has defects in that the Cu/Cr catalyst may cause environmental pollution because it uses the heavy metal chromium, and a side reaction occurs to produce by-products such as tetrahydrofuran, thus decreasing selectivity and the conversion rate into ⁇ -butyrolactone.
  • Japanese patent laid-open publication No. Hei. 4-17954 added zinc or manganese to the Cu/Cr catalyst in order to overcome the above defects, but this method still has problems in that the yield is 95% and catalyst life is short at about 1 month.
  • Japanese patent publication No. Hei. 2-27349 and Japanese patent laid-open publication No. Sho. 61-212577 disclose a method for preparing ⁇ -butyrolactone by dehydrogenation of 1,4-butandiol in the presence of an oxidant such as oxygen by using a catalyst comprising palladium, silver, etc.
  • an oxidant such as oxygen
  • catalyst life is short and selectivity and conversion rate are low.
  • GB 1066979 disclosed a method for preparing ⁇ -butyrolactone by dehydrogenation of 1,4-butandiol using a catalyst prepared by adding aluminum to a Cu/Zn catalyst.
  • yield is low and catalyst life is short.
  • an environmentally harmful metal such as chromium
  • the present invention provides a process for preparation of high purity and high yield N-methyl pyrrolidone, comprising a first step of dehydrogenating 1,4-butandiol under a hydrogen atmosphere in the presence of a metal oxide solid catalyst to prepare ⁇ -butyrolactone, and a second step of directly introducing the ⁇ -butyrolactone obtained in the first step without purification to a dehydration with monomethylamine under a metal oxide solid catalyst.
  • the present inventors have discovered, as a result of assiduous studies regarding a catalyst for preparing N-methyl pyrrolidone and a preparation process of
  • N-methyl pyrrolidone using the same, that if a metal oxide solid catalyst is used in the preparation of ⁇ -butyrolactone and N-methyl pyrrolidone, it shows excellent catalytic activity, and continuous performing of a reaction without purification of the synthesized ⁇ -butyrolactone does not show any difference from purifying ⁇ -butyrolactone, and thus a continuous reaction can be applied for the preparation of N-methyl pyrrolidone thus enabling its mass production, and completed the present invention.
  • a solid catalyst comprising one or more active components selected from specific metal oxide groups is used for preparing ⁇ -butyrolactone by dehydrogenation of 1,4-butandiol and preparing N-methyl pyrrolidone by dehydration of the obtained ⁇ -butyrolactone and monomethylamine.
  • the present invention is characterized in that ⁇ -butyrolactone can be directly reacted with monomethylamine without performing a purification process that is performed in the methods of the related art.
  • the process for preparation of N-methyl pyrrolidone according to the present invention comprises two continuous steps using a metal oxide solid catalyst.
  • 1,4-butandiol is dehydrogenated under hydrogen flow to prepare ⁇ -butyrolactone.
  • the reaction product of the first step, ⁇ -butyrolactone is subjected to a dehydration with monomethylamine without purification to prepare N-methyl pyrrolidone.
  • the present invention uses different kinds of solid catalysts for the first step (dehydrogenation) and for the second step (dehydration).
  • the solid catalyst used in the first step comprises one or more active components selected from oxides comprising Group 11 metal elements.
  • the catalyst used in the first step may further comprise a co-catalyst within a commonly used content-range.
  • the co-catalyst can be one or more selected from oxides comprising Group 2 metal elements.
  • the catalyst used in the first step may further comprise a support within a commonly used content-range.
  • the kinds of the support are not specifically limited, and those commonly used in the art can be used.
  • the support can be one or more selected from oxides comprising
  • the metal oxide solid catalyst used in the first step does not comprise chromium, differently from the existing catalyst, it does not cause environmental pollution by heavy metals in the process of catalyst preparation and disposal. Further, it minimizes side reactions to inhibit production of by-products such as tetrahydrofuran, thereby increasing selectivity and the conversion rate into ⁇ -butyrolactone, thus enabling high yield production of ⁇ -butyrolactone.
  • hydrogen is introduced to reduce the catalyst during the reaction to thereby increase catalytic activity and decrease catalyst coke formation speed, thus prolonging catalyst life.
  • the solid catalyst used in the second step comprises one or more active components selected from oxides comprising Group 4, Group 6, Group 8, Group 11, Group 12, Group 13, or Group 14 metal elements.
  • the metal oxide solid catalyst used in the second step may further comprise the support within a commonly used content-range.
  • the kinds of the support are not specifically limited, and those commonly used in the art can be used.
  • the support is selected one or more from oxides comprising Group 13 or Groupl4 metal elements.
  • the metal oxide solid catalyst used in the second step has beneficial effects in that using ⁇ -butyrolactone obtained in the first step without purification does not show any difference from using purified ⁇ -butyrolactone as in the existing process using a catalyst, thus making the process simple, and little of the ⁇ -butyrolactone, which is difficult to separate because of a small boiling point difference (about 2 ° C ) from the final reaction product N-methyl pyrrolidone, remains after the reaction, thus enabling production of high yield, high purity N-methyl pyrrolidone.
  • the metal oxide solid catalyst used in the first and second steps according to the present invention can be prepared by a method commonly used in the art, and its preparation method is not specifically limited.
  • the mole ratio of 1,4-butandiol to hydrogen is 1:0.1 to 1 :5, and preferably 1 :10 to 1:3.5.
  • the mole ratio of 1,4-butandiol to hydrogen is preferably 1:0.1 or more, and considering the catalyst life prolonging effect increase and selectivity improvement, and the economic efficiency in terms of the cost for recycling hydrogen, the mole ratio of 1 ,4-butandiol to hydrogen is preferably 1:5 or less.
  • reaction materials of the dehydrogenation i.e., 1 ,4-butandiol and hydrogen
  • the reaction materials of the dehydrogenation do not comprise impurities, but purity is not specifically limited because using them with impurities does not influence the effects of the present invention.
  • the mole ratio of ⁇ -butyrolactone to monomethylamine in the second step is 1 :0.5 to 1 :5, and preferably 1 :1.0 to 1 :3.5.
  • the mole ratio of ⁇ -butyrolactone to monomethylamine is preferably 1:0.5 or more, and considering conversion rate increase and economic efficiency, the mole ratio of ⁇ -butyrolactone to monomethylamine is preferably 1:5 or less.
  • the reaction intermediate ⁇ -butyrolactone can be used without purification after the first step.
  • monomethylamine in the form of an aqueous solution, and monomethylamine solution (40wt% in water) is generally used, but the concentration is not specifically limited and a lower content of monomethylamine can be used.
  • the process of the present invention consists of continuous steps, and the continuous reaction steps can be commonly used steps in the related art, and it is not specially limited.
  • Weight Hourly Space Velocity representing residence time of reactant in a reactor
  • Weight Hourly Space Velocity is preferably 0.1 to 5.0 hr "1 . Since economical production cannot be achieved with a small amount of reactant introduced in a reactor, Weight Hourly Space Velocity is preferably 0.1 hr "1 or more, and considering maximum reaction efficiency, it is preferably 5.0 hr " or less.
  • a bottom-up type or a top-down type can be used without limitation.
  • the bottom-up type is more preferably used.
  • the dehydrogenation of the first step is preferably performed at a temperature range of 150 to 350 0 C .
  • the reaction temperature is preferably 150 °C or more, and considering a yield increasing effect and economic efficiency when heating and a by-product increase and catalyst life reduction due to sintering at a high temperature, the reaction temperature is preferably 350 ° C or less.
  • Reaction pressure for the dehydrogenation is preferably atmosphere to 20 atm.
  • the reaction pressure is preferably atmosphere or more, and considering a conversion rate increase and economic efficiency such as cost for maintaining a high pressure, the reaction pressure is preferably 20 atm or less.
  • the second step of dehydration is preferably performed at a temperature range of 150 to 400 ° C .
  • the reaction temperature is preferably 150°C or more, and considering economic efficiency and yield increase when heating and a by-product increase and catalyst life reduction due to sintering at a high temperature, the reaction temperature is preferably 400 0 C or less.
  • the reaction pressure for the dehydration is preferably from atmosphere to 100 atm.
  • the reaction pressure is preferably atmosphere or more, and a considering conversion rate increase and economic efficiency such as cost for maintaining a high pressure, the reaction pressure is preferably 100 atm or less.
  • a conversion rate of ⁇ -butyrolactone of 99% or more and N-methyl pyrrolidone selectivity of 97% or more can be obtained.
  • water introduced in the aqueous monomethylamine solution during the reaction can be removed from the reaction product by a commonly used method such as distillation, and the method is not specifically limited.
  • the process for preparation of N-methyl pyrrolidone according to the present invention is a continuous two-step process using a metal oxide solid catalyst having excellent reactivity.
  • the first step of the ⁇ -butyrolactone preparation process uses a metal oxide catalyst comprising a Group 11 metal element, wherein a catalyst that does not comprise an environmentally harmful metal such as chromium is used and thus there is no concern of environmental pollution, and side reactions can be minimized to increase selectivity and the conversion rate into ⁇ -butyrolactone to thus produce high yield ⁇ -butyrolactone, and the catalyst is reduced by hydrogen flow during the reaction to thereby increase catalytic activity and decrease catalyst coke formation speed to thus prolong the catalyst life.
  • the second step of the N-methyl pyrrolidone preparation process uses a metal oxide catalyst comprising metal elements selected from Group 4, Group 6, Group 8, Group 11, Group 12, Group 13, or Group 14, wherein the reaction product of the first step, ⁇ -butyrolactone, is used without purification thus making the process simple, little of the reaction intermediate ⁇ -butyrolactone, which is difficult to separate because of a small boiling point difference (about 2 ° C ) from N-methyl pyrrolidone, remains after the reaction thus facilitating separation and purification, and therefore enabling production of high purity, high yield N-methyl pyrrolidone and mass production.
  • a metal oxide catalyst comprising metal elements selected from Group 4, Group 6, Group 8, Group 11, Group 12, Group 13, or Group 14, wherein the reaction product of the first step, ⁇ -butyrolactone, is used without purification thus making the process simple, little of the reaction intermediate ⁇ -butyrolactone, which is difficult to separate because of a small boiling point difference (about 2 ° C ) from N-methyl pyr
  • a tubular reactor with a diameter of 1.27 cm and length of 25.4 cm was filled with 8g of catalyst A, and an electrical heating tape was adhered to the outside of the reactor to maintain reaction temperature at 240 ° C .
  • Reactant 1 ,4-butandiol was introduced into the bottom of the reactor (bottom-up) through a delivery pump at WHSV of 1.0 hr "1 .
  • the mole ratio of 1 ,4-butandiol to hydrogen was maintained at 1 :2, and reaction pressure was maintained at 5 atm.
  • selectivity for ⁇ -butyrolactone and the conversion rate of 1,4-butandiol were analyzed by gas chromatography. As results, ⁇ -butyrolactone selectivity of 99.20% was obtained, and the conversion rate of 1,4-butandiol was 99.33%.
  • Examples 2 to 5 The first step reaction ⁇ -Butyrolactone was prepared by the same procedure as Example 1 , except that reaction pressure, reaction temperature, and WHSV were changed as described in the following Table 1.
  • GBL ⁇ -Butyrolactone note 2
  • THF Tetrahydrofuran note 3
  • catalyst A CuO 64%, MgO 1.3%, SiO 2 15%
  • Comparative Example 2 Comparison of catalysts (batch reaction) ⁇ -Butyrolactone was prepared by the same procedure as Comparative Example 1, except that the amount of catalyst and the reaction pressure were changed as described in the following Table 2. [Table 2]
  • catalyst amount wt% based on the weight of 1,4-butandiol Example 6;
  • a tubular reactor with a diameter of 2.54 cm and length of 15.24 cm was filled with 9Og of catalyst B, and an electrical heating tape was adhered to the outside of the reactor to maintain reaction temperature at 220 ° C .
  • Reactant 1,4-butandiol was introduced into the bottom of the reactor (bottom-up) through a delivery pump at WHSV of 1.0 hr "1 .
  • the mole ratio of 1,4-butandiol and hydrogen was maintained at 1 :2, and reaction pressure was maintained at atmosphere.
  • selectivity for ⁇ -butyrolactone and the conversion rate of 1,4-butandiol were analyzed by gas chromatography. As results, ⁇ -butyrolactone selectivity of 99.32% was obtained, and the conversion rate of
  • 1,4-butandiol was 99.21%.
  • Examples 7 to 13 The first step reaction ⁇ -Butyrolactone was prepared by the same procedure as Example 6, except that reaction pressure, reaction temperature, WHSV, and mole ratio were changed as described in the following Table 3. [Table 3]
  • Comparative Example 3 Comparison of catalyst (batch reaction) 20 g of 1 ,4-butandiol was introduced into an autoclave (250m#), 4 g (20 wt% based on the weight of 1 ,4-butandiol) of DEH-7 (UOP Company, Pt catalyst) was added thereto, and then nitrogen gas was filled therein so that the reaction pressure reached 30 atm, and the mixture was reacted while stirring at 220 ° C for 3 hours.
  • DEH-7 UOP Company, Pt catalyst
  • Comparative Example 4 Comparison of catalyst (batch reaction) ⁇ -Butyrolactone was prepared by the same procedure as comparative example 3, except that reaction pressure and gas were changed as described in the following Table 4 [Table 4]
  • a tubular reactor with a diameter of 2.54 cm and length of 15.24 cm was filled with 98g of catalyst C, and an electrical heating tape was adhered to the outside of the reactor to maintain reaction temperature at 280 ° C .
  • Reactants ⁇ -butyrolactone prepared in Example 6 and monomethylamine solution (40wt% in water) were introduced into the bottom of the reactor (bottom-up) at WHSV of 0.2 hr "1 while maintaining the mole ratio of ⁇ -butyrolactone and monomethylamine at 1 :1.5. Reaction pressure was maintained at 50 atm. Further, ⁇ -butyrolactone that was obtained as the product of the first step was used without purification.
  • N-Methyl pyrrolidone was prepared by the same procedure as Example 14, except that reaction temperature, reaction pressure, WHSV, and mole ratio were changed as described in the following Table 5. [Table 5]
  • a tubular reactor with a diameter of 2.54 cm and length of 15.24 cm was filled with 65g of catalyst D, and an electrical heating tape was adhered to the outside of the reactor to maintain reaction temperature at 300 0 C .
  • Reactants ⁇ -butyrolactone prepared in Example 6 and monomethylamine solution (40wt% in water) were introduced into the bottom of the reactor(bottom-up) at WHSV of 1.0 hr "1 while maintaining the mole ratio of ⁇ -butyrolactone and monomethylamine at 1:1.5. Reaction pressure was maintained at 50 atm. And, ⁇ -butyrolactone which was obtained as the product of the first step was used without purification.
  • N-Methyl pyrrolidone was prepared by the same procedure as Example 27, except that reaction temperature, reaction pressure, and WHSV were changed as described in the following Table 6. [Table 6]
  • a tubular reactor with a diameter of 2.54 cm and length of 15.24 cm was filled with 40.9g of catalyst E, and an electrical heating tape was adhered to the outside of the reactor to maintain reaction temperature at 280 0 C .
  • Reactants ⁇ -butyrolactone prepared in Example 6 and monomethylamine solution (40wt% in water) were introduced into the bottom of the reactor (bottom-up) at WHSV of 1.0 hr '1 while maintaining the mole ratio of ⁇ -butyrolactone and monomethylamine at 1 :1.5. Reaction pressure was maintained at 50 atm. Further, ⁇ -butyrolactone that was obtained as the product of the first step was used without purification.
  • N-Methyl pyrrolidone was prepared by the same procedure as example 33, except that reaction temperature, reaction pressure, and WHSV were changed as described in the following Table 7. [Table 7]
  • This experiment is to show that use of GBL having low purity that has been separately prepared as well as GBL of high purity prepared in the examples regarding the first step does not present any problems in the progress of the second reaction using the metal oxide catalyst of the present invention.
  • a tubular reactor with a diameter of 2.54 cm and length of 15.24 cm was filled with 98g of catalyst C, and an electrical heating tape was adhered to the outside of the reactor to maintain reaction temperature at 280 ° C .
  • Reactants ⁇ -butyrolactone and monomethylamine solution (40wt% in water) were introduced into the bottom of the reactor (bottom-up) at WHSV of 0.2 hr "1 while maintaining the mole ratio of ⁇ -butyrolactone and monomethylamine at 1 :1.5.
  • Reaction pressure was maintained at 50 atm. Further, ⁇ -butyrolactone that was obtained as the product of the first step was used without purification.
  • N-Methyl pyrrolidone was prepared by the same procedure as Example 37, except that reaction temperature and WHSV were changed as described in the following Table 8. [Table 8]
  • a tubular reactor with a diameter of 2.54 cm and length of 15.24 cm was filled with 98g of catalyst C, and an electrical heating tape was adhered to the outside of the reactor to maintain reaction temperature at 280 ° C .
  • Reactants ⁇ -butyrolactone and monomethylamine solution 35wt% in water were introduced into the bottom of the reactor (bottom-up) at WHSV of 0.15 hr "1 while maintaining the mole ratio of ⁇ -butyrolactone and monomethylamine at 1:1.3. Reaction pressure was maintained at 50 atm. Further, ⁇ -butyrolactone that was obtained as the product of the first step was used without purification.
  • N-Methyl pyrrolidone was prepared by the same procedure as Example 40, except that reaction temperature, reaction pressure, and mole ratio were changed as described in the following Table 9. [Table 9]
  • a tubular reactor with a diameter of 2.54 cm and length of 15.24 cm was filled with 98g of catalyst F, and an electrical heating tape was adhered to the outside of the reactor to maintain reaction temperature at 280 ° C .
  • Reactants ⁇ -butyrolactone and monomethylamine solution 35wt% in water were introduced into the bottom of the reactor (bottom-up) at WHSV of 0.15 hr '1 while maintaining the mole ratio of ⁇ -butyrolactone and monomethylamine at 1:1.5.
  • Reaction pressure was maintained at 50 atm. Further, ⁇ -butyrolactone that was obtained as the product of the first step was used without purification.
  • This experiment also shows that using GBL of low purity that has been separately prepared as well as GBL of high purity prepared in the examples regarding the first step does not present any problems in the progress of the second reaction using the metal oxide catalyst of the present invention. It also shows that using an aqueous monomethylamine solution with a concentration of lower than 40 wt% does not show any problems in the progress of the second step reaction.
  • a tubular reactor with a diameter of 2.54 cm and length of 15.24 cm was filled with 98g of catalyst C, and an electrical heating tape was adhered to the outside of the reactor to maintain reaction temperature at 280 "C .
  • Reactants ⁇ -butyrolactone and monomethylamine solution (30wt% in water) were introduced into the bottom of the reactor (bottom-up) at WHSV of 0.2 hr "1 while maintaining the mole ratio of ⁇ -butyrolactone and monomethylamine at 1:1.5. Reaction pressure was maintained at 50 atm. Further, ⁇ -butyrolactone that was obtained as the product of the first step was used without purification.

Abstract

The present invention relates to a process for preparation of N-methyl pyrrolidone, and more particularly to a process for preparing high purity, high yield N-methyl pyrrolidone, comprising a first step of dehydrogenating 1,4-butandiol under a hydrogen atmosphere in the presence of a metal oxide solid catalyst to prepare γ-butyrolactone, and a second step of subjecting the γ-butyrolactone obtained in the first step without purification to a dehydration with monomethylamine under a metal oxide solid catalyst. The process for preparation of N-methyl pyrrolidone according to the present invention is a continuous two-step process using a metal oxide catalyst, wherein the second step continuously progresses without purification of the reaction product of the first step, γ-butyrolactone. According to the present invention, little of a reaction intermediate γ-butyrolactone, which is difficult to separate because of a small difference in boiling point (about 2 'C) from the final product, N-methyl pyrrolidone, remains after reaction, and thus separation and purification are easy. Further, its simple process enables mass production and lowers purification equipment cost.

Description

PROCESS FOR PREPARING OF N-METHYL PYRROLIDONE
BACKGROUND OF THE INVENTION (a) Field of the Invention The present invention relates to a process for preparation of N-methyl pyrrolidone, and more particularly to a process for preparation of high purity and high yield N-methyl pyrrolidone, which is a continuous two-step process using a solid catalyst comprising a metal oxide as an active component, wherein the two-step reaction can continuously progress without purification of the first step reaction product, γ-butyrolactone, and can easily perform separation and purification because little of the reaction intermediate γ-butyrolactone, which is difficult to separate because of a small difference in boiling point (about 2 "C) from the final product, N-methyl pyrrolidone, remains after reaction, and can produce N-methyl pyrrolidone in large quantities due to its simple process. (b) Description of the Related Art
Demands for pro-environmental nontoxic N-methyl pyrrolidone are now increasing in the fields of a solvent for polymerization and processing, a solvent for paint manufacture, a metal surface detergent, a solvent for synthesis and purification of medicines, a solvent for processing semiconductors and electronic materials, a solvent for lithium battery manufacture, etc., due to increase in concern for environmental friendly process.
N-Methyl pyrrolidone is industrially prepared by a dehydration of monomethylamine and γ-butyrolactone, and its preparation method is largely classified into a method using a catalyst and a method that does not use a catalyst. As a method that does not use a catalyst, a method for preparing N-methyl pyrrolidone with yield of 90-93% by reacting γ-butyrolactone and monomethylamine in a batch reactor at 280 "C for 4 hours has been disclosed (J. Amer. Chem. Soc, 71(1949)896). Additionally, Japanese patent publication No. Hei. 1-190667 disclosed a method for preparing N-methyl pyrrolidone with a yield of 94.3% by introducing γ-butyrolactone, water, and monomethylamine into an autoclave and reacting them at 240-2650C under a pressure of 50 atm for 3 hours.
As a method using a catalyst, a method for preparing N-methyl pyrrolidone with a yield of 98% by continuous reaction of γ-butyrolactone and monomethylamine at 280 °C under atmosphere in the presence of a copper ion-exchanged Y-type zeolite catalyst has been disclosed (Bull. Chem. Soc. Japan, 50(10)(1977)2517). In addition, a method for preparing N-methyl pyrrolidone with a yield of 98.2% by a continuous reaction of γ-butyrolactone and monomethylamine at 300 °C using chromium ion-exchanged ZSM-5 zeolite catalyst has been disclosed (J. Org. Chem., 50(1994)3998). Further, Japanese patent publication No. Sho. 49-20582 disclosed a method for preparing N-methyl pyrrolidone with a yield of 63-93% by reacting γ-butyrolactone and monomethylamine using a catalyst such as alumina, silica alumina, activated carbon, silica gel, silica-magnesia, etc.
However, these methods have defects in that the yield is low, and γ-butyrolactone having a small boiling point difference (about 20C) from the product N-methyl pyrrolidone remains unreacted reactants, thus making separation and purification difficult and increasing impurities.
Most of the methods of the related art use γ-butyrolactone as a starting material, which is previously prepared from 1 ,4-butandiol or maleic anhydride, and is separated and purified, to prepare N-methyl pyrrolidone.
It is known that γ-butyrolactone, the intermediate for preparing N-methyl pyrrolidone, is prepared from 1,4-butandiol by dehydrogenation in the presence of a Cu/Cr catalyst or a catalyst prepared by adding Zn and Mn to a Cu/Cr catalyst, by dehydrogenation using an oxidant such as oxygen in the presence of a catalyst containing one or more kinds of Pt, Pd, Ag, etc., or by dehydrogenation in the presence of a catalyst prepared by adding an alkali metal or Al to a Cu/Zn catalyst.
In general, γ-butyrolactone is prepared by dehydrogenation of 1,4-butandiol using a Cu/Cr catalyst. However, this method has defects in that the Cu/Cr catalyst may cause environmental pollution because it uses the heavy metal chromium, and a side reaction occurs to produce by-products such as tetrahydrofuran, thus decreasing selectivity and the conversion rate into γ-butyrolactone. Thus, Japanese patent laid-open publication No. Hei. 4-17954 added zinc or manganese to the Cu/Cr catalyst in order to overcome the above defects, but this method still has problems in that the yield is 95% and catalyst life is short at about 1 month.
Japanese patent publication No. Hei. 2-27349 and Japanese patent laid-open publication No. Sho. 61-212577 disclose a method for preparing γ-butyrolactone by dehydrogenation of 1,4-butandiol in the presence of an oxidant such as oxygen by using a catalyst comprising palladium, silver, etc. However, according to this method, catalyst life is short and selectivity and conversion rate are low.
GB 1066979 disclosed a method for preparing γ-butyrolactone by dehydrogenation of 1,4-butandiol using a catalyst prepared by adding aluminum to a Cu/Zn catalyst. However, according to this method, yield is low and catalyst life is short. SUMMARY OF THE INVENTION
In order to resolve the above problems of the prior art, it is an aspect of the present invention to provide a process for preparation of N-methyl pyrrolidone that is capable of producing high purity and high yield N-methyl pyrrolidone in a large quantity, by performing a continuous two-step process without purification of the reaction intermediate γ-butyrolactone using a metal oxide solid catalyst having excellent reactivity so that little of the reaction intermediate γ-butyrolactone, which is difficult to separate because of small boiling point difference (about 2 "C) from the final product N-methyl pyrrolidone, remains after the reaction. It is another aspect of the present invention to provide a process for preparation of γ-butyrolactone that uses a catalyst that does not comprise an environmentally harmful metal such as chromium during the process for preparing γ-butyrolactone from 1 ,4-butandiol as a first step, and thus does not cause environmental pollution, that can minimize side reactions thus increasing the yield, that can increase catalytic activity by reduction of the catalyst through hydrogen flow during the reaction and prolong catalyst life by decreasing catalyst coke formation speed, and that can produce high yield γ-butyrolactone in a large quantity through the continuous process.
In order to attain the above objects, the present invention provides a process for preparation of high purity and high yield N-methyl pyrrolidone, comprising a first step of dehydrogenating 1,4-butandiol under a hydrogen atmosphere in the presence of a metal oxide solid catalyst to prepare γ-butyrolactone, and a second step of directly introducing the γ-butyrolactone obtained in the first step without purification to a dehydration with monomethylamine under a metal oxide solid catalyst. DETAILED DESCRIPTION OF THE EMBODIMENTS
The present invention will now be explained in detail.
The present inventors have discovered, as a result of assiduous studies regarding a catalyst for preparing N-methyl pyrrolidone and a preparation process of
N-methyl pyrrolidone using the same, that if a metal oxide solid catalyst is used in the preparation of γ-butyrolactone and N-methyl pyrrolidone, it shows excellent catalytic activity, and continuous performing of a reaction without purification of the synthesized γ-butyrolactone does not show any difference from purifying γ-butyrolactone, and thus a continuous reaction can be applied for the preparation of N-methyl pyrrolidone thus enabling its mass production, and completed the present invention.
Therefore, according to the present invention, a solid catalyst comprising one or more active components selected from specific metal oxide groups is used for preparing γ-butyrolactone by dehydrogenation of 1,4-butandiol and preparing N-methyl pyrrolidone by dehydration of the obtained γ-butyrolactone and monomethylamine. Further, the present invention is characterized in that γ-butyrolactone can be directly reacted with monomethylamine without performing a purification process that is performed in the methods of the related art.
The process for preparation of N-methyl pyrrolidone according to the present invention comprises two continuous steps using a metal oxide solid catalyst.
In the first step, 1,4-butandiol is dehydrogenated under hydrogen flow to prepare γ-butyrolactone. In the second step, the reaction product of the first step, γ-butyrolactone, is subjected to a dehydration with monomethylamine without purification to prepare N-methyl pyrrolidone. The present invention uses different kinds of solid catalysts for the first step (dehydrogenation) and for the second step (dehydration).
The solid catalyst used in the first step comprises one or more active components selected from oxides comprising Group 11 metal elements. In order to further improve the catalytic activity, the catalyst used in the first step may further comprise a co-catalyst within a commonly used content-range. The co-catalyst can be one or more selected from oxides comprising Group 2 metal elements.
In order to secure the structural stability of the catalyst, the catalyst used in the first step may further comprise a support within a commonly used content-range. The kinds of the support are not specifically limited, and those commonly used in the art can be used. Preferably, the support can be one or more selected from oxides comprising
Group 13 or Group 14 metal elements.
Since the metal oxide solid catalyst used in the first step does not comprise chromium, differently from the existing catalyst, it does not cause environmental pollution by heavy metals in the process of catalyst preparation and disposal. Further, it minimizes side reactions to inhibit production of by-products such as tetrahydrofuran, thereby increasing selectivity and the conversion rate into γ-butyrolactone, thus enabling high yield production of γ-butyrolactone. In the first step, although there is a dehydrogenation, hydrogen is introduced to reduce the catalyst during the reaction to thereby increase catalytic activity and decrease catalyst coke formation speed, thus prolonging catalyst life.
The solid catalyst used in the second step comprises one or more active components selected from oxides comprising Group 4, Group 6, Group 8, Group 11, Group 12, Group 13, or Group 14 metal elements.
In order to secure the structural stability of the catalyst, the metal oxide solid catalyst used in the second step may further comprise the support within a commonly used content-range. The kinds of the support are not specifically limited, and those commonly used in the art can be used. Preferably, the support is selected one or more from oxides comprising Group 13 or Groupl4 metal elements.
The metal oxide solid catalyst used in the second step has beneficial effects in that using γ-butyrolactone obtained in the first step without purification does not show any difference from using purified γ-butyrolactone as in the existing process using a catalyst, thus making the process simple, and little of the γ-butyrolactone, which is difficult to separate because of a small boiling point difference (about 2 °C ) from the final reaction product N-methyl pyrrolidone, remains after the reaction, thus enabling production of high yield, high purity N-methyl pyrrolidone.
Meanwhile, the metal oxide solid catalyst used in the first and second steps according to the present invention can be prepared by a method commonly used in the art, and its preparation method is not specifically limited.
In the first step, the mole ratio of 1,4-butandiol to hydrogen is 1:0.1 to 1 :5, and preferably 1 :10 to 1:3.5. In order to achieve a maximum catalyst life prolonging effect and to maintain hydrogen partial pressure thus improving selectivity, the mole ratio of 1,4-butandiol to hydrogen is preferably 1:0.1 or more, and considering the catalyst life prolonging effect increase and selectivity improvement, and the economic efficiency in terms of the cost for recycling hydrogen, the mole ratio of 1 ,4-butandiol to hydrogen is preferably 1:5 or less.
Most preferably, the reaction materials of the dehydrogenation, i.e., 1 ,4-butandiol and hydrogen, do not comprise impurities, but purity is not specifically limited because using them with impurities does not influence the effects of the present invention.
The mole ratio of γ-butyrolactone to monomethylamine in the second step is 1 :0.5 to 1 :5, and preferably 1 :1.0 to 1 :3.5. In order to prevent a decrease of the conversion rate into N-methyl pyrrolidone, the mole ratio of γ-butyrolactone to monomethylamine is preferably 1:0.5 or more, and considering conversion rate increase and economic efficiency, the mole ratio of γ-butyrolactone to monomethylamine is preferably 1:5 or less. Among the reaction materials of the dehydration, the reaction intermediate γ-butyrolactone can be used without purification after the first step. It is preferable to use monomethylamine in the form of an aqueous solution, and monomethylamine solution (40wt% in water) is generally used, but the concentration is not specifically limited and a lower content of monomethylamine can be used. The process of the present invention consists of continuous steps, and the continuous reaction steps can be commonly used steps in the related art, and it is not specially limited.
As the reaction conditions, Weight Hourly Space Velocity, WHSV, representing residence time of reactant in a reactor, is preferably 0.1 to 5.0 hr"1. Since economical production cannot be achieved with a small amount of reactant introduced in a reactor, Weight Hourly Space Velocity is preferably 0.1 hr"1 or more, and considering maximum reaction efficiency, it is preferably 5.0 hr" or less.
For the reactant flow in the continuous process, either a bottom-up type or a top-down type can be used without limitation. However, in order to prevent a channeling, the bottom-up type is more preferably used.
The dehydrogenation of the first step is preferably performed at a temperature range of 150 to 350 0C . In order to provide minimum reaction activation energy, the reaction temperature is preferably 150 °C or more, and considering a yield increasing effect and economic efficiency when heating and a by-product increase and catalyst life reduction due to sintering at a high temperature, the reaction temperature is preferably 350 °C or less.
Reaction pressure for the dehydrogenation is preferably atmosphere to 20 atm.
In order to achieve a minimum conversion rate, the reaction pressure is preferably atmosphere or more, and considering a conversion rate increase and economic efficiency such as cost for maintaining a high pressure, the reaction pressure is preferably 20 atm or less.
According to the first step of dehydrogenation of the present invention as described above, a conversion rate of 95% or more of 1,4-butandiol and γ-butyrolactone selectivity of 98% or more can be obtained.
The second step of dehydration is preferably performed at a temperature range of 150 to 400 °C . In order to provide minimum reaction activation energy, the reaction temperature is preferably 150°C or more, and considering economic efficiency and yield increase when heating and a by-product increase and catalyst life reduction due to sintering at a high temperature, the reaction temperature is preferably 4000C or less.
The reaction pressure for the dehydration is preferably from atmosphere to 100 atm. In order to achieve a minimum conversion rate, the reaction pressure is preferably atmosphere or more, and a considering conversion rate increase and economic efficiency such as cost for maintaining a high pressure, the reaction pressure is preferably 100 atm or less.
According to the second step of dehydration of the present invention as described above, a conversion rate of γ-butyrolactone of 99% or more and N-methyl pyrrolidone selectivity of 97% or more can be obtained. In the process for preparation of N-methyl pyrrolidone according to the present invention, water introduced in the aqueous monomethylamine solution during the reaction can be removed from the reaction product by a commonly used method such as distillation, and the method is not specifically limited.
The process for preparation of N-methyl pyrrolidone according to the present invention is a continuous two-step process using a metal oxide solid catalyst having excellent reactivity. The first step of the γ-butyrolactone preparation process uses a metal oxide catalyst comprising a Group 11 metal element, wherein a catalyst that does not comprise an environmentally harmful metal such as chromium is used and thus there is no concern of environmental pollution, and side reactions can be minimized to increase selectivity and the conversion rate into γ-butyrolactone to thus produce high yield γ-butyrolactone, and the catalyst is reduced by hydrogen flow during the reaction to thereby increase catalytic activity and decrease catalyst coke formation speed to thus prolong the catalyst life.
The second step of the N-methyl pyrrolidone preparation process uses a metal oxide catalyst comprising metal elements selected from Group 4, Group 6, Group 8, Group 11, Group 12, Group 13, or Group 14, wherein the reaction product of the first step, γ-butyrolactone, is used without purification thus making the process simple, little of the reaction intermediate γ-butyrolactone, which is difficult to separate because of a small boiling point difference (about 2 °C ) from N-methyl pyrrolidone, remains after the reaction thus facilitating separation and purification, and therefore enabling production of high purity, high yield N-methyl pyrrolidone and mass production.
Hereinafter, the present invention is described in further detail through examples. However, the following examples are only for the understanding of the present invention and the present invention is not limited to or by them.
Example 1; The first step reaction
A tubular reactor with a diameter of 1.27 cm and length of 25.4 cm was filled with 8g of catalyst A, and an electrical heating tape was adhered to the outside of the reactor to maintain reaction temperature at 240 °C .
Reactant 1 ,4-butandiol was introduced into the bottom of the reactor (bottom-up) through a delivery pump at WHSV of 1.0 hr"1. The mole ratio of 1 ,4-butandiol to hydrogen was maintained at 1 :2, and reaction pressure was maintained at 5 atm. After the reaction was completed, selectivity for γ-butyrolactone and the conversion rate of 1,4-butandiol were analyzed by gas chromatography. As results, γ-butyrolactone selectivity of 99.20% was obtained, and the conversion rate of 1,4-butandiol was 99.33%.
Examples 2 to 5: The first step reaction γ-Butyrolactone was prepared by the same procedure as Example 1 , except that reaction pressure, reaction temperature, and WHSV were changed as described in the following Table 1. [Table 1 ]
Figure imgf000012_0001
Figure imgf000013_0001
note 1) GBL: γ-Butyrolactone note 2) THF: Tetrahydrofuran note 3) catalyst A: CuO 64%, MgO 1.3%, SiO2 15%
Comparative Example 1: Comparison of catalyst (batch reaction)
20 g of 1 ,4-butandiol was introduced into an autoclave (250m#), 2 g (10 wt% based on the weight of 1 ,4-butandiol) of E-113TU (CALSICAT Company, copper chromite catalyst) was added thereto, and then hydrogen gas was filled therein so that the reaction pressure reached 5 atm, and the mixture was reacted while stirring at 210°C for 3 hours.
Subsequently, the catalyst was removed by a filteration, and the residue was analyzed by gas chromatography. As results, γ-butyrolactone selectivity of 96.00% was obtained, the conversion rate of 1 ,4-butandiol was 86.00%, and tetrahydrofuran was produced with selectivity of 1.43%. Comparative Example 2: Comparison of catalysts (batch reaction) γ-Butyrolactone was prepared by the same procedure as Comparative Example 1, except that the amount of catalyst and the reaction pressure were changed as described in the following Table 2. [Table 2]
Figure imgf000014_0001
note 1) catalyst amount: wt% based on the weight of 1,4-butandiol Example 6; The first step reaction
A tubular reactor with a diameter of 2.54 cm and length of 15.24 cm was filled with 9Og of catalyst B, and an electrical heating tape was adhered to the outside of the reactor to maintain reaction temperature at 220 °C .
Reactant 1,4-butandiol was introduced into the bottom of the reactor (bottom-up) through a delivery pump at WHSV of 1.0 hr"1. The mole ratio of 1,4-butandiol and hydrogen was maintained at 1 :2, and reaction pressure was maintained at atmosphere. After the reaction was completed, selectivity for γ-butyrolactone and the conversion rate of 1,4-butandiol were analyzed by gas chromatography. As results, γ-butyrolactone selectivity of 99.32% was obtained, and the conversion rate of
1,4-butandiol was 99.21%. Examples 7 to 13: The first step reaction γ-Butyrolactone was prepared by the same procedure as Example 6, except that reaction pressure, reaction temperature, WHSV, and mole ratio were changed as described in the following Table 3. [Table 3]
Figure imgf000015_0001
note 1) mole ratio = 1,4-butandiol : hydrogen note 2) GBL: γ-Butyrolactone note 3) THF: Tetrahydrofuran note 4) catalyst B: CuO 86-92%, CaO 2-4%, SiO2 3-9%
Comparative Example 3: Comparison of catalyst (batch reaction) 20 g of 1 ,4-butandiol was introduced into an autoclave (250m#), 4 g (20 wt% based on the weight of 1 ,4-butandiol) of DEH-7 (UOP Company, Pt catalyst) was added thereto, and then nitrogen gas was filled therein so that the reaction pressure reached 30 atm, and the mixture was reacted while stirring at 220 °C for 3 hours.
Subsequently, the catalyst was removed by a filteration, and the residue was analyzed by gas chromatography. As results, γ-butyrolactone selectivity of 16.00% was obtained, the conversion rate of 1 ,4-butandiol was 63.28%, and tetrahydrofuran was produced with selectivity of 79.00%.
Comparative Example 4: Comparison of catalyst (batch reaction) γ-Butyrolactone was prepared by the same procedure as comparative example 3, except that reaction pressure and gas were changed as described in the following Table 4 [Table 4]
Figure imgf000016_0001
Example 14; The second step reaction
A tubular reactor with a diameter of 2.54 cm and length of 15.24 cm was filled with 98g of catalyst C, and an electrical heating tape was adhered to the outside of the reactor to maintain reaction temperature at 280 °C . Reactants γ-butyrolactone prepared in Example 6 and monomethylamine solution (40wt% in water) were introduced into the bottom of the reactor (bottom-up) at WHSV of 0.2 hr"1 while maintaining the mole ratio of γ-butyrolactone and monomethylamine at 1 :1.5. Reaction pressure was maintained at 50 atm. Further, γ-butyrolactone that was obtained as the product of the first step was used without purification.
After the reaction was completed, selectivity for N-methyl pyrrolidone and the conversion rate of γ-butyrolactone were analyzed by gas chromatography. As results, N-methyl pyrrolidone selectivity of 99.73% was obtained, and the conversion rate of γ-butyrolactone was 100%. Examples 15 to 26: The second step reaction
N-Methyl pyrrolidone was prepared by the same procedure as Example 14, except that reaction temperature, reaction pressure, WHSV, and mole ratio were changed as described in the following Table 5. [Table 5]
Figure imgf000017_0001
Figure imgf000018_0001
Figure imgf000019_0001
note 1) mole ratio = γ-butyrolactone : monomethylamine note 2) NMP: N- Methyl pyrrolidone note 3) GBL: γ-Butyrolactone note 4) catalyst C: ZnO note 5) purity of GBL after the first step without purification: GBL 99.32% Example 27; The second step reaction
A tubular reactor with a diameter of 2.54 cm and length of 15.24 cm was filled with 65g of catalyst D, and an electrical heating tape was adhered to the outside of the reactor to maintain reaction temperature at 3000C . Reactants γ-butyrolactone prepared in Example 6 and monomethylamine solution (40wt% in water) were introduced into the bottom of the reactor(bottom-up) at WHSV of 1.0 hr"1 while maintaining the mole ratio of γ-butyrolactone and monomethylamine at 1:1.5. Reaction pressure was maintained at 50 atm. And, γ-butyrolactone which was obtained as the product of the first step was used without purification.
After the reaction completed, selectivity for N-methyl pyrrolidone and the conversion rate of γ-butyrolactone were analyzed by gas chromatography. As results, N-methyl pyrrolidone selectivity of 97.25% was obtained, and the conversion rate of γ-butyrolactone was 99.94%. Examples 28 to 32: The second step reaction
N-Methyl pyrrolidone was prepared by the same procedure as Example 27, except that reaction temperature, reaction pressure, and WHSV were changed as described in the following Table 6. [Table 6]
Figure imgf000020_0001
note 1) mole ratio = γ-butyrolactone : monomethylamine note 2) NMP: N-Methyl pyrrolidone note 3) GBL: γ-Butyrolactone note 4) catalyst D: ZnO 40%, Al2O3 55%, CuO 4% note 5) purity of GBL after the first step without purification: GBL 99.32%
Example 33; The second step reaction
A tubular reactor with a diameter of 2.54 cm and length of 15.24 cm was filled with 40.9g of catalyst E, and an electrical heating tape was adhered to the outside of the reactor to maintain reaction temperature at 2800C . Reactants γ-butyrolactone prepared in Example 6 and monomethylamine solution (40wt% in water) were introduced into the bottom of the reactor (bottom-up) at WHSV of 1.0 hr'1 while maintaining the mole ratio of γ-butyrolactone and monomethylamine at 1 :1.5. Reaction pressure was maintained at 50 atm. Further, γ-butyrolactone that was obtained as the product of the first step was used without purification.
After the reaction was completed, selectivity for N-methyl pyrrolidone and the conversion rate of γ-butyrolactone were analyzed by gas chromatography. As results, N-methyl pyrrolidone selectivity of 99.45% was obtained, and the conversion rate of γ-butyrolactone was 99.87%.
Examples 34 to 36; The second step reaction
N-Methyl pyrrolidone was prepared by the same procedure as example 33, except that reaction temperature, reaction pressure, and WHSV were changed as described in the following Table 7. [Table 7]
Figure imgf000021_0001
Figure imgf000022_0001
note 1) mole ratio = γ-butyrolactone : monomethylamine note 2) NMP: N-Methyl pyrrolidone note 3) GBL: γ-Butyrolactone note 4) catalyst E: TiO2 85%, SiO2 5%, WO3 10% note 5) purity of GBL after the first step reaction without purification: GBL 99.32% Example 37; The second step reaction
This experiment is to show that use of GBL having low purity that has been separately prepared as well as GBL of high purity prepared in the examples regarding the first step does not present any problems in the progress of the second reaction using the metal oxide catalyst of the present invention.
A tubular reactor with a diameter of 2.54 cm and length of 15.24 cm was filled with 98g of catalyst C, and an electrical heating tape was adhered to the outside of the reactor to maintain reaction temperature at 280 °C .
Reactants γ-butyrolactone and monomethylamine solution (40wt% in water) were introduced into the bottom of the reactor (bottom-up) at WHSV of 0.2 hr"1 while maintaining the mole ratio of γ-butyrolactone and monomethylamine at 1 :1.5.
Reaction pressure was maintained at 50 atm. Further, γ-butyrolactone that was obtained as the product of the first step was used without purification.
After the reaction was completed, selectivity for N-methyl pyrrolidone and the conversion rate of γ-butyrolactone were analyzed by gas chromatography. As results, N-methyl pyrrolidone selectivity of 98.05% was obtained, and the conversion rate of γ-butyrolactone was 100%. Examples 38 to 39: The second step reaction
N-Methyl pyrrolidone was prepared by the same procedure as Example 37, except that reaction temperature and WHSV were changed as described in the following Table 8. [Table 8]
Figure imgf000023_0001
note 1) mole ratio = γ-butyrolactone : monomethylamine note 2) NMP: N-Methyl pyrrolidone note 3) GBL: γ-Butyrolactone note 4) catalyst C: ZnO note 5) purity of GBL after the first step reaction without purification: GBL 97.54% Example 40: The second step reaction This experiment is to show that using GBL of low purity that has been separately prepared as well as GBL of high purity prepared in the examples regarding the first step does not present any problems in the progress of the second reaction using the metal oxide catalyst of the present invention. It also shows that using an aqueous monomethylamine solution with a concentration lower than 40 wt% does not show any problems in the progress of the second step reaction.
A tubular reactor with a diameter of 2.54 cm and length of 15.24 cm was filled with 98g of catalyst C, and an electrical heating tape was adhered to the outside of the reactor to maintain reaction temperature at 280 °C .
Reactants γ-butyrolactone and monomethylamine solution (35wt% in water) were introduced into the bottom of the reactor (bottom-up) at WHSV of 0.15 hr"1 while maintaining the mole ratio of γ-butyrolactone and monomethylamine at 1:1.3. Reaction pressure was maintained at 50 atm. Further, γ-butyrolactone that was obtained as the product of the first step was used without purification.
After the reaction was completed, selectivity for N-methyl pyrrolidone and the conversion rate of γ-butyrolactone were analyzed by gas chromatography. As results, N-methyl pyrrolidone selectivity of 98.54% was obtained, and the conversion rate of γ-butyrolactone was 100.00%.
Examples 41 to 42; The second step reaction
N-Methyl pyrrolidone was prepared by the same procedure as Example 40, except that reaction temperature, reaction pressure, and mole ratio were changed as described in the following Table 9. [Table 9]
Figure imgf000024_0001
Figure imgf000025_0001
note 1) mole ratio = γ-butyrolactone : monomethylamine note 2) NMP: N-Methyl pyrrolidone note 3) GBL: γ-Butyrolactone note 4) catalyst C: ZnO note 5) purity of GBL after the first step reaction without purification: GBL 97.54%
Example 43; The second step reaction
This experiment is to show that using GBL of low purity that has been separately prepared as well we GBL of high purity prepared in the examples regarding the first step does not present any problems in the progress of the second reaction using the metal oxide catalyst of the present invention. It also shows that using an aqueous monomethylamine solution with a concentration of lower than 40 wt% does not show any problems in the progress of the second step reaction.
A tubular reactor with a diameter of 2.54 cm and length of 15.24 cm was filled with 98g of catalyst F, and an electrical heating tape was adhered to the outside of the reactor to maintain reaction temperature at 280 °C .
Reactants γ-butyrolactone and monomethylamine solution (35wt% in water) were introduced into the bottom of the reactor (bottom-up) at WHSV of 0.15 hr'1 while maintaining the mole ratio of γ-butyrolactone and monomethylamine at 1:1.5.
Reaction pressure was maintained at 50 atm. Further, γ-butyrolactone that was obtained as the product of the first step was used without purification.
After the reaction was completed, selectivity for N-methyl pyrrolidone and the conversion rate of γ-butyrolactone were analyzed by gas chromatography. As results, N-methyl pyrrolidone selectivity of 98.50% was obtained, and the conversion rate of γ-butyrolactone was 100.00%. [Table 10]
Temperature Pressure WHSV Conversion Selectivity
Mole ratio GBL i -/o
CC) (atm) (hr"1) rate (%) (NMP %)
Example
280 50 0.15 1:1.5 100.00 98.50 0.00
43 note 1) mole ratio = γ-butyrolactone : monomethylamine note 2) NMP: N-Methyl pyrrolidone note 3) GBL: γ-Butyrolactone note 4) catalyst F: SiO2 67.6%, Al2O3 28.2%, TiO2 0.41%, Fe2O3 0.57% note 5) purity of GBL after the first step reaction without purification: GBL 97.54% Example 44: The second step reaction
This experiment also shows that using GBL of low purity that has been separately prepared as well as GBL of high purity prepared in the examples regarding the first step does not present any problems in the progress of the second reaction using the metal oxide catalyst of the present invention. It also shows that using an aqueous monomethylamine solution with a concentration of lower than 40 wt% does not show any problems in the progress of the second step reaction.
A tubular reactor with a diameter of 2.54 cm and length of 15.24 cm was filled with 98g of catalyst C, and an electrical heating tape was adhered to the outside of the reactor to maintain reaction temperature at 280 "C . Reactants γ-butyrolactone and monomethylamine solution (30wt% in water) were introduced into the bottom of the reactor (bottom-up) at WHSV of 0.2 hr"1 while maintaining the mole ratio of γ-butyrolactone and monomethylamine at 1:1.5. Reaction pressure was maintained at 50 atm. Further, γ-butyrolactone that was obtained as the product of the first step was used without purification.
After the reaction was completed, selectivity for N-methyl pyrrolidone and the conversion rate of γ-butyrolactone were analyzed by gas chromatography. As results, N-methyl pyrrolidone selectivity of 98.40% was obtained, and the conversion rate of γ-butyrolactone was 99.94%. [Table 11 ]
Figure imgf000027_0001
note 1) mole ratio = γ-butyrolactone : monomethylamine note 2) NMP: N-Methyl pyrrolidone note 3) GBL: γ-Butyrolactone note 4) catalyst C: ZnO note 5) purity of GBL after the first step reaction without purification: GBL 90.15%

Claims

WHAT IS CLAIMED IS:
1. A process for preparation of high purity, high yield N-methyl pyrrolidone, comprising: a first step of dehydrogenating 1 ,4-butandiol under a hydrogen atmosphere in the presence of a metal oxide solid catalyst to prepare γ-butyrolactone; and a second step of introducing the γ-butyrolactone obtained in the first step without purification to a dehydration with monomethylamine under a metal oxide solid catalyst.
2. The process according to claim 1, wherein the solid catalyst used in the first step comprises one or more active components selected from oxides containing Group 11 metal elements.
3. The process according to claim 2, wherein the solid catalyst used in the first step further comprises a support having one or more active components selected from oxides containing Group 13 or Group 14 metal elements.
4. The process according to claim 2, wherein the solid catalyst used in the first step further comprises a co-catalyst having one or more active components selected from oxides containing Group 2 metal elements.
5. The process according to claim 1, wherein the solid catalyst used in the second step comprises one or more active components selected from oxides containing metal elements of Group 4, Group 6, Group 8, Group 11, Group 12, Group 13, or Group 14.
6. The process according to claim 5, wherein the solid catalyst used in the second step further comprises the support having one or more active components selected from oxides containing Group 13 or Group 14 metal elements.
7. The process according to claim 1, wherein in the first step, the mole ratio of 1,4-butandiol to hydrogen is 1 :0.1 to 1 :5.
8. The process according to claim 1, wherein in the second step, the mole ratio of γ-butyrolactone to monomethylamine is 1:0.5 to 1:5.
9. The process according to claim 1, wherein in the first and second steps, Weight Hourly Space Velocity (WHSV) is 0.1 to 5.0 hr"1.
10. The process according to claim 1, wherein the first step is performed at a temperature of 150 to 350 "C .
11. The process according to claim 1, wherein the second step is performed at a temperature of 150 to 400 0C .
12. The process according to claim 1, wherein the first step is performed under a reaction pressure of atmosphere to 20 atm.
13. The process according to claim 1, wherein the second step is performed under a reaction pressure of atmosphere to 100 atm.
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