Catalytic process for preparing N,N-dimethylglucamine from N methylglucamine

Abstract

The invention relates to a method for preparing aqueous solutions of N,N-dimethylglucamine, characterized by first preparing an adduct of N-methylglucamine and formaldehyde in water at temperatures of between 15 C. and 40 C., and subsequently reacting said adduct to N,N-dimethylglucamine in the presence of a metal catalyst under hydrogen pressure at 20-68 C., followed by secondary hydrogenation at 70-120 bar and 70-110 C. once hydrogen absorption at 20-68 C. is completed.

Claims

1. A process for preparing N,N-dimethylglucamine comprising the step of reacting an aqueous solution of N-methylglucamine first with an aqueous solution of formaldehyde at 15-40 C. and subsequently, at a pressure of 20-120 bar and a temperature T=30-68 C., with hydrogen under metal catalysis, wherein, after absorption of hydrogen has completed at 20-68 C., a further, after-hydrogenation is added at 70-120 bar and at 70-110 C.

2. The process as claimed in claim 1, wherein the metal catalyst is Raney nickel.

3. The process as claimed in claim 1, which is carried out at a hydrogen pressure of 70-110 bar.

4. The process as claimed in claim 1, wherein the hydrogenation is carried out at 35-65 C.

5. The process as claimed in claim 1, wherein the molar ratio of N-methylglucamine to formaldehyde is 1:1 to 1:1.5.

6. The process as claimed in claim 1, wherein the hydrogenation catalyst is reused more than 5 times.

7. The process as claimed in claim 1, wherein reaction takes place in a stirred reactor or loop reactor.

8. The process as claimed in claim 1, wherein the remaining N-methylglucamine content is <2wt %.

9. The process as claimed in claim 1, wherein the residual formaldehyde content is <0.1 wt %.

10. The process as claimed in claim 1, in which the Hazen color number of the resulting solution of N,N-dimethylglucamine is <500.

11. The process as claimed in claim 1, in which the molar ratio of N-methylglucamine to formaldehyde is 1:1 to 1:1.2.

12. The process as claimed in claim 1, in which the molar ratio of N-methylglucamine to formaldehyde is 1:1.01 to 1:1.08.

13. The process as claimed in claim 1, wherein the residual N-methylglucamine content is <1 wt %.

14. The process as claimed in claim 1, wherein the residual N-methylglucamine content is <0.25 wt %.

15. The process as claimed in claim 1, wherein the hydrogenation is carried out at 40-50 C.

Description

EXAMPLES

(1) The dimethylglucamine solutions produced in the examples were characterized by analysis as follows:

(2) Gardner Color Number and Hazen Color Number:

(3) The clear, aqueous dimethylglucamine solutions without any gas bubbles were introduced into 10 mm rectangular cuvettes. The color numbers were measured at room temperature in a LICO 690 colorimeter from Hach Lange.

(4) Total Amine Number by Acid-Base Titration:

(5) The samples, weighed out accurately on an analytical balance, were dissolved in glacial acetic acid and titrated with 0.1 molar perchloric acid in glacial acetic acid, using a titroprocessor from Metrohm.

(6) Solids Content (105 C./2 Hours):

(7) The samples, weighed out precisely, were dried to constant weight in a drying cabinet at 105 C. for two hours by evaporation of the water, and after drying were precisely weighed again.

(8) Water (Karl Fischer titration):

(9) The water content of the precisely weighed-out samples was determined by the Karl Fischer titration method using Karl Fischer solvent and Karl Fischer titrant.

(10) N-methylglucamine, N,N-dimethylglucamine and Sorbitol (GC):

(11) The samples were completely acetylated with a very large excess of acetic anhydride/pyridine at 80 C. The N-methylglucamine, N,N-dimethylglucamine and sorbitol contents were determined by gas chromatography on a 60 m Agilent HP-5 column, using decanol as internal standard and using an FID detector.

(12) Methanol (GC):

(13) The methanol content was determined by a gas-chromatographic method for volatile substances, using isobutanol as internal standard and using a TCD detector.

(14) Formaldehyde (Free and Chemically Bonded):

(15) To release the chemically bonded formaldehyde, the samples were heated with aqueous sulfuric acid in the presence of 2,4-dinitrophenylhydrazine. Through the reaction of the formaldehyde with 2,4-dinitrophenylhydrazine, 2,4-dinitrophenylhydrazone was formed. The 2,4-dinitrophenylhydrazone content was subsequently determined by HPLC liquid chromatography. The free formaldehyde and chemically bonded formaldehyde content was captured as a sum total.

(16) Nitrosamines (Total NNO):

(17) The samples were analyzed for total nitrosamine content in a method based on the ATNC (apparent total nitrosamine content) method. With chemical denitrosation in an acidic medium, nitrogen monoxide was released from the nitrosamines and was subsequently determined quantitatively using a very sensitive detector specific for nitrogen monoxide. Calculation and indication of content were made in the form of the NNO content (>NNO with molar mass 44 g/mol).

(18) Nickel (ICP-OES):

(19) The nickel content of the samples was determined by ICP-OES (inductively coupled plasma optical emission spectrometry) in a method based on DIN EN ISO 11885.

(20) Formic Acid (Free and Chemically Bonded, IC):

(21) The samples were pretreated with heating in an aqueous-alkaline medium in order by hydrolysis to liberate the formic acid, bonded chemically in the form of ester and amide. The amount of formic acid or salts thereof already present before the alkaline hydrolysis, and of formic acid and/or salts thereof liberated only by the alkaline hydrolysis, was determined as a sum total by ion chromatography (IC).

Comparative Example 1: Example 2 From EP-0614881

(22) In a 2 liter round-bottom glass flask equipped with stirrer, thermometer and electrical heating under atmospheric pressure, 1500 g of a 43%, aqueous N-methylglucamine solution were produced by diluting a 60% N-methylglucamine solution (Gardner color number 1.7, Hazen color number 263). The 43%, aqueous N-methylglucamine solution was heated to 35 C. with stirring. From a dropping funnel, with further stirring, a total of 288.7 g of a 36.5%, aqueous formaldehyde solution were added dropwise over the course of half an hour at 35 C. The reaction to give the N-methylglucamine-formaldehyde adduct was slightly exothermic. The Gardner color number of the pale-yellow, clear, aqueous N-methylglucamine-formaldehyde adduct solution was 0.8 and the Hazen color number was 151.

(23) Immediately after the end of the dropwise addition, a portion of the aqueous N-methylglucamine-formaldehyde adduct solution amounting to 1300 g was taken from the 2 liter round-bottom glass flask and was introduced at room temperature into a 2 liter stirred autoclave.

(24) The 2 liter stirred autoclave was equipped with stirrer, heating, cooling, supply lines for hydrogen and nitrogen, temperature measurement, pressure measurement, and safety valve. 20.4 g of Raney nickel were introduced under nitrogen into the 2 liter stirred autoclave.

(25) The 2 liter stirred autoclave was closed. Three times, 10 bar of nitrogen were injected, with depressurization each time. Thereafter, three times, 10 bar of hydrogen were injected, with depressurization each time. After the leak test and depressurization, the stirring speed was set to 800 rpm. With further stirring, heating took place to 100 C. and then hydrogen was supplied. The exothermic hydrogenation took place, with renewed injection of the hydrogen consumed, at 800 rpm, 100 C. and a hydrogen pressure of 30 bar. After the end of the evident absorption of hydrogen, stirring was continued for two hours at 100 C. and a hydrogen pressure of 30 bar. This was followed by cooling to 30 C., depressurization, purging with nitrogen, and the emptying of the 2 liter stirred autoclave. The Raney nickel catalyst was separated off by a pressure filtration under nitrogen. The liquid filtrate was dark brown and had a Gardner color number of 8.

(26) This dark brown filtrate was subjected to initial distillation in a rotary evaporator at 60 C. under a pressure of 20 mbar. The distillate contained primarily water, a little methanol, and traces of other low boilers. The viscous N,N-dimethylglucamine having undergone initial distillation was adjusted to an active ingredient content of 51% and DI water content of 49% by addition of DI water with thorough mixing at 60 C. This product solution was subjected to analysis. Apart from the losses involved in emptying the autoclave and working up the solution, the yield of dissolved N,N-dimethylglucamine in the DMG 50 was virtually quantitative.

(27) The product obtained was characterized as follows:

(28) Appearance at 20 C.: clear, liquid, dark brown

(29) Gardner color number: 9.4

(30) Hazen color number: not measurable, since too dark

(31) Total amine number (titration): 133 mg KOH/g

(32) Solids content (105 C./2 hours): 51.4% (m/m)

(33) Water (Karl-Fischer titration): 49% (m/m)

(34) N-Methylglucamine (GC): 0.91% (m/m)

(35) N,N-Dimethylglucamine (GC): 44.5% (m/m)

(36) Sorbitol (GC): 0.6% (m/m)

(37) Methanol (GC): <0.1% (m/m)

(38) Formaldehyde (free and chemically bonded, LC): 0.026% (m/m)

(39) Nitrosamines (total NNO): <50 g/kg

(40) Nickel (ICP-OES): 35 g/g

(41) Formic acid (free and chemically bonded) 0.70% (m/m)

Comparative Example 2: As Per Example 3 From EP-0614881

(42) In a 2 liter round-bottom glass flask equipped with stirrer, thermometer and electrical heating under atmospheric pressure, 1500 g of a 43%, aqueous N-methylglucamine solution were produced by diluting a 60%, technical N-methyl-glucamine solution (Gardner color number 1.7, Hazen color number 263) with DI water.

(43) The 43%, aqueous N-methylglucamine solution was heated to 35 C. with stirring. From a dropping funnel, with further stirring, a total of 288.7 g of a 36.5%, aqueous formaldehyde solution were added dropwise over the course of half an hour at 35 C. The reaction to give the N-methylglucamine-formaldehyde adduct was slightly exothermic. Thereafter the clear, pale yellow reaction mixture was additionally stirred further for an hour at 35 C. The Gardner color number of this pale-yellow, aqueous N-methylglucamine-formaldehyde adduct solution was 0.8 and the Hazen color number was 162.

(44) Thereafter, a portion of the aqueous N-methylglucamine-formaldehyde adduct solution amounting to 1300 g was taken from the 2 liter round-bottom glass flask and was introduced at room temperature into a 2 liter stirred autoclave.

(45) The 2 liter stirred autoclave was equipped with stirrer, heating, cooling, supply lines for hydrogen and nitrogen, temperature measurement, pressure measurement, and safety valve. 20.4 g of Raney nickel were introduced under nitrogen into the 2 liter stirred autoclave.

(46) The 2 liter stirred autoclave was closed. Three times, 10 bar of nitrogen were injected, with depressurization each time. Thereafter, three times, 10 bar of hydrogen were injected, with depressurization each time. After the leak test and depressurization, the stirring speed was set to 800 rpm. With further stirring, heating took place to 125 C. and then hydrogen was supplied. The exothermic hydrogenation took place, with renewed injection of the hydrogen consumed, at 800 rpm, 130 C. and a hydrogen pressure of 100 bar. After the end of the evident absorption of hydrogen, stirring was continued for two hours at 130 C. and a hydrogen pressure of 100 bar. This was followed by cooling to 30 C., depressurization, purging with nitrogen, and the emptying of the 2 liter stirred autoclave. The Raney nickel catalyst was separated off by a pressure filtration under nitrogen. The liquid filtrate was deeply dark brown and had a Gardner color number of 13.4.

(47) This deeply dark brown filtrate was subjected to initial distillation in a rotary evaporator at 60 C. under a pressure of 20 mbar. The distillate contained primarily water, a little methanol, and traces of other low boilers. The viscous N,N-dimethylglucamine having undergone initial distillation was adjusted to an active ingredient content of 51% and DI water content of 49% by addition of DI water with thorough mixing at 60 C. The resulting product solution was subjected to analysis. Apart from the losses involved in emptying the autoclave and working up the solution, the yield of dissolved N,N-dimethylglucamine in the DMG 50 was virtually quantitative.

(48) The product obtained was characterized as follows:

(49) Appearance at 20 C.: clear, liquid, deeply dark brown

(50) Gardner color number: 16.9

(51) Hazen color number: not measurable, since too dark

(52) Total amine number (titration): 133 mg KOH/g

(53) Solids content (105 C./2 hours): 52.6% (m/m)

(54) Water (Karl-Fischer titration): 49% (m/m)

(55) N-Methylglucamine (GC): 6.0% (m/m)

(56) N,N-Dimethylglucamine (GC): 35.9% (m/m)

(57) Sorbitol (GC): 0.6% (m/m)

(58) Methanol (GC): <0.1% (m/m)

(59) Formaldehyde (free and chemically bonded, LC): 0.012% (m/m)

(60) Nitrosamines (total NNO): <50 g/kg

(61) Nickel (ICP-OES): 29 g/g

(62) Formic acid (free and chemically bonded) 0.90% (m/m)

(63) TABLE-US-00001 Hydrogenation Color 1-stage/ Hydrogenation temperature (GCN/ NMG Ni Formaldehyde Example 2-stage pressure [ C.] Hazen) [%] [ppm] [%] 1 2-stage 30 100 9.4/ 0.91 35 0.03 (comp.) 2 2-stage 100 130 16.9/ 6.0 29 0.01 (comp.) 1 2-stage 30 20-60, 1.5/246 0.16 5 0.02 then 100 2 2-stage 100 20-60, 3.5/485 0.29 2 0.01 then 130 3 2-stage 100 20-40, 1.0/158 0.12 4 0.03 then 90

Example 1

(64) In a 2 liter round-bottom glass flask equipped with stirrer, thermometer and electrical heating under atmospheric pressure, 1500 g of a 43%, aqueous

(65) N-methylglucamine solution were produced by diluting a 60%, technical N-methyl-glucamine solution (Gardner color number 1.7, Hazen color number 263) with DI water.

(66) The 43%, aqueous N-methylglucamine solution was heated to 35 C. with stirring. From a dropping funnel, with further stirring, a total of 288.7 g of a 36.5%, aqueous formaldehyde solution were added dropwise over the course of half an hour at 35 C. The reaction to give the N-methylglucamine-formaldehyde adduct was slightly exothermic. The Gardner color number of the pale-yellow, clear, aqueous N-methylglucamine-formaldehyde adduct solution was 0.8 and the Hazen color number was 154.

(67) Immediately after the end of the dropwise addition, a portion of the aqueous N-methylglucamine-formaldehyde adduct solution amounting to 1300 g was taken from the 2 liter round-bottom glass flask and was introduced at room temperature into a 2 liter stirred autoclave.

(68) The 2 liter stirred autoclave was equipped with stirrer, heating, cooling, supply lines for hydrogen and nitrogen, temperature measurement, pressure measurement, and safety valve. 20.4 g of Raney nickel were introduced under nitrogen into the 2 liter stirred autoclave.

(69) The 2 liter stirred autoclave was closed. Three times, 10 bar of nitrogen were injected, with depressurization each time. Thereafter, three times, 10 bar of hydrogen were injected, with depressurization each time. After the leak test and depressurization, the stirring speed was set to 800 rpm. At 20 C., hydrogen was injected. The exothermic hydrogenation commenced directly with supply of the consumed hydrogen at 15-25 bar hydrogen pressure and heating to 60 C., and then the recognizable hydrogen absorption was at an end. This was followed by further heating to 100 C. and then by further stirring for two hours at 800 rpm, 100 C. and 30 bar hydrogen pressure. There was cooling to 30 C., depressurization, purging with nitrogen, and the emptying of the 2 liter stirred autoclave. The Raney nickel catalyst was separated off by a pressure filtration under nitrogen. The liquid filtrate was pale yellow and had a Gardner color number of 0.7 and a Hazen color number of 130.

(70) This pale-yellow filtrate was subjected to initial distillation in a rotary evaporator at 60 C. under a pressure of 20 mbar. The distillate contained primarily water, a little methanol, and traces of other low boilers. The viscous N,N-dimethylglucamine having undergone initial distillation was adjusted to an active ingredient content of 51% and DI water content of 49% by addition of DI water with thorough mixing at 60 C. This mixture was subjected to analysis. Apart from the losses involved in emptying the autoclave and working up the solution, the yield of dissolved N,N-dimethylglucamine in the product was virtually quantitative.

(71) The product obtained was characterized as follows:

(72) Appearance at 20 C. clear, liquid, pale yellow

(73) Gardner color number: 1.5

(74) Hazen color number: 246

(75) Total amine number (titration): 132 mg KOH/g

(76) Solids content (105 C./2 hours): 50.7% (m/m)

(77) Water (Karl-Fischer titration): 49% (m/m)

(78) N-Methylglucamine (GC): 0.16% (m/m)

(79) N,N-Dimethylglucamine (GC): 45.1% (m/m), depending on the NMG grade

(80) Sorbitol (GC): 0.7% (m/m)

(81) Methanol (GC): <0.1% (m/m)

(82) Formaldehyde (free and chemically bonded, LC): 0.022% (m/m)

(83) Nitrosamines (total NNO): <50 g/kg

(84) Nickel (ICP-OES): 5 g/g

(85) Formic acid (free and chemically bonded) 0.25% (m/m)

(86) (ion chromatography after alkaline hydrolysis, IC)

Example 2

(87) In a 2 liter round-bottom glass flask equipped with stirrer, thermometer and electrical heating under atmospheric pressure, 1500 g of a 43%, aqueous N-methylglucamine solution were produced by diluting a 60%, technical N-methyl-glucamine solution (Gardner color number 1.7, Hazen color number 263) with DI water.

(88) The 43%, aqueous N-methylglucamine solution was heated to 35 C. with stirring. From a dropping funnel, with further stirring, a total of 288.7 g of a 36.5%, aqueous formaldehyde solution were added dropwise over the course of half an hour at 35 C. The reaction to give the N-methylglucamine-formaldehyde adduct was slightly exothermic. Thereafter, the clear, pale-yellow reaction mixture was additionally stirred for another hour at 35 C. The Gardner color number of this pale-yellow, aqueous N-methylglucamine-formaldehyde adduct solution was 0.8 and the Hazen color number was 162.

(89) Immediately after the end of the dropwise addition, a portion of the aqueous N-methylglucamine-formaldehyde adduct solution amounting to 1300 g was taken from the 2 liter round-bottom glass flask and was introduced at room temperature into a 2 liter stirred autoclave.

(90) The 2 liter stirred autoclave was equipped with stirrer, heating, cooling, supply lines for hydrogen and nitrogen, temperature measurement, pressure measurement, and safety valve. 20.4 g of Raney nickel were introduced under nitrogen into the 2 liter stirred autoclave.

(91) The 2 liter stirred autoclave was closed. Three times, 10 bar of nitrogen were injected, with depressurization each time. Thereafter, three times, 10 bar of hydrogen were injected, with depressurization each time. After the leak test and depressurization, the stirring speed was set to 800 rpm. At 20 C., hydrogen was injected. The exothermic hydrogenation commenced directly with supply of the consumed hydrogen at 15-25 bar hydrogen pressure and heating to 60 C., and then the recognizable hydrogen absorption was at an end. This was followed by further heating to 130 C. and then by further stirring for two hours at 800 rpm, 130 C. and 100 bar hydrogen pressure. There was cooling to 30 C., depressurization, purging with nitrogen, and the emptying of the 2 liter stirred autoclave. The Raney nickel catalyst was separated off by a pressure filtration under nitrogen. The liquid filtrate was pale yellow and had a Gardner color number of 0.3 and a Hazen color number of 56.

(92) This pale-yellow filtrate was subjected to initial distillation in a rotary evaporator at 60 C. under a pressure of 20 mbar. The distillate contained primarily water, a little methanol, and traces of other low boilers. The viscous N,N-dimethylglucamine having undergone initial distillation was adjusted to an active ingredient content of 50% and DI water content of 50% by addition of DI water with thorough mixing at 60 C. This mixture was subjected to analysis. Apart from the losses involved in emptying the autoclave and working up the solution, the yield of dissolved N,N-dimethylglucamine in the DMG 50 was virtually quantitative.

(93) The product obtained was characterized as follows:

(94) Appearance at 20 C.: clear, liquid, deeply yellow

(95) Gardner color number: 3.5

(96) Hazen color number: 485

(97) Total amine number (titration): 129 mg KOH/g

(98) Solids content (105 C./2 hours): 49.7% (m/m)

(99) Water (Karl-Fischer titration): 50% (m/m)

(100) N-Methylglucamine (GC): 0.29% (m/m)

(101) N,N-Dimethylglucamine (GC): 43.5% (m/m)

(102) Sorbitol (GC): 0.6% (m/m)

(103) Methanol (GC): <0.1% (m/m)

(104) Formaldehyde (free and chemically bonded, LC): 0.0097% (m/m)

(105) Nitrosamines (total NNO): <50 g/kg

(106) Nickel (ICP-OES): 2 g/g

(107) Formic acid (free and chemically bonded) 0.18% (m/m)

(108) (ion chromatography after alkaline hydrolysis, IC)

Example 3

(109) In a 2 liter round-bottom glass flask equipped with stirrer, thermometer and electrical heating under atmospheric pressure, 1500 g of a 43%, aqueous

(110) N-methylglucamine solution were produced by diluting a 60%, technical N-methyl-glucamine solution (Gardner color number 1.7, Hazen color number 263) with DI water.

(111) The 43%, aqueous N-methylglucamine solution was heated to 35 C. with stirring.

(112) From a dropping funnel, with further stirring, a total of 288.7 g of a 36.5%, aqueous formaldehyde solution were added dropwise over the course of half an hour at 35 C. The reaction to give the N-methylglucamine-formaldehyde adduct was slightly exothermic. The Gardner color number of the pale-yellow, clear, aqueous N-methylglucamine-formaldehyde adduct solution was 0.8 and the Hazen color number was 154.

(113) Immediately after the end of the dropwise addition, a portion of the aqueous N-methylglucamine-formaldehyde adduct solution amounting to 1300 g was taken from the 2 liter round-bottom glass flask and was introduced at room temperature into a 2 liter stirred autoclave.

(114) The 2 liter stirred autoclave was equipped with stirrer, heating, cooling, supply lines for hydrogen and nitrogen, temperature measurement, pressure measurement, and safety valve. 20.4 g of Raney nickel were introduced under nitrogen into the 2 liter stirred autoclave.

(115) The 2 liter stirred autoclave was closed. Three times, 10 bar of nitrogen were injected, with depressurization each time. Thereafter, three times, 10 bar of hydrogen were injected, with depressurization each time. After the leak test and depressurization, the stirring speed was set to 800 rpm. At 20 C., hydrogen was injected. The exothermic hydrogenation commenced directly with supply of the consumed hydrogen at 15-25 bar hydrogen pressure. By cooling, the autoclave was maintained within a temperature range of 30-40 C. until the recognizable hydrogen absorption was at an end. This was followed by further heating to 90 C. and then by further stirring for two hours at 800 rpm, 90 C. and 30 bar hydrogen pressure. There was cooling to 30 C., depressurization, purging with nitrogen, and the emptying of the 2 liter stirred autoclave. The Raney nickel catalyst was separated off by a pressure filtration under nitrogen. The liquid filtrate was pale yellow and had a Gardner color number of 0.6 and a Hazen color number of 110.

(116) This pale-yellow filtrate was subjected to initial distillation in a rotary evaporator at 60 C. under a pressure of 20 mbar. The distillate contained primarily water, a little methanol, and traces of other low boilers. The viscous N,N-dimethylglucamine having undergone initial distillation was adjusted to an active ingredient content of 51% and DI water content of 49% by addition of DI water with thorough mixing at 60 C. This mixture was subjected to analysis. Apart from the losses involved in emptying the autoclave and working up the solution, the yield of dissolved N,N-dimethylglucamine in the product was virtually quantitative.

(117) The product obtained was characterized as follows:

(118) Appearance at 20 C.: clear, liquid, pale yellow

(119) Gardner color number: 1.0

(120) Hazen color number: 158

(121) Total amine number (titration): 131 mg KOH/g

(122) Solids content (105 C./2 hours): 50.8% (m/m)

(123) Water (Karl-Fischer titration): 49.1% (m/m)

(124) N-Methylglucamine (GC): 0.12% (m/m)

(125) N,N-Dimethylglucamine (GC): 44.6% (m/m)

(126) Sorbitol (GC): 0.6% (m/m)

(127) Methanol (GC): <0.1% (m/m)

(128) Formaldehyde (free and chemically bonded, LC): 0.025% (m/m)

(129) Nitrosamines (total NNO): <50 g/kg

(130) Nickel (ICP-OES): 4 g/g

(131) Formic acid (free and chemically bonded) 0.21% (m/m)

(132) (ion chromatography after alkaline hydrolysis, IC)