METHOD FOR PRODUCING MONOETHYLENE GLYCOL

Abstract

Process for preparing monoethylene glycol (MEG) by metal-catalyzed reaction of a dialkyl oxalate of the formula I

##STR00001##

where R.sup.1 and R.sup.2 are each, independently of one another, methyl, ethyl, n-propyl or isopropyl, with hydrogen (H.sub.2), wherein the dialkyl oxalate (I) is used as melt or as a solution in a solvent, dialkyl oxalate (I) and H2 are used in a molar ratio of H.sub.2: dialkyl oxalate (I) in the range from 4.0 to 30 and the reaction is carried out continuously in a reactor at a cross-sectional loading of 10 m/s, a temperature in the range from 150 to 270 C., a pressure in the range from 150 to 390 bar and in the presence of a chromium-free heterogeneous catalyst comprising copper.

Claims

1.-17. (canceled)

18. A process for preparing monoethylene glycol (MEG) by metal-catalyzed reaction of a dialkyl oxalate of the formula I ##STR00004## where R.sup.1 and R.sup.2 are each, independently of one another, methyl, ethyl, n-propyl or isopropyl, with hydrogen (H.sub.2), wherein the dialkyl oxalate (I) is used as melt or as a solution in a solvent, dialkyl oxalate (I) and H.sub.2 are used in a molar ratio of H.sub.2:dialkyl oxalate (I) in the range from 4.0 to 30 and the reaction is carried out continuously in a reactor at a cross-sectional loading of 10 m/s, a temperature in the range from 150 to 270 C., a pressure in the range from 150 to 390 bar and in the presence of a chromium-free heterogeneous catalyst comprising copper.

19. The process according to claim 18, wherein the reaction is carried out continuously at a space velocity over the catalyst in the range from 0.01 to 5.0 kg of dialkyl oxalate (I).Math.liter.sub.cat..sup.1.Math.h.sup.1.

20. The process according to claim 18, wherein the space velocity over the catalyst is set so that the conversion of dialkyl oxalate (I) is 90%.

21. The process according to claim 18, wherein the reaction is carried out continuously in a reactor at a cross-sectional loading in the range from 10 to 1000 m/s.

22. The process according to claim 18, wherein the reaction is carried out continuously in a reactor at a cross-sectional loading in the range from >10 to 500 m/s.

23. The process according to claim 18, wherein dialkyl oxalate (I) and H.sub.2 are used in a molar ratio of H.sub.2:dialkyl oxalate (I) in the range from 4.2 to 20.

24. The process according to claim 18, wherein dialkyl oxalate (I) and H.sub.2 are used in a molar ratio of H.sub.2:dialkyl oxalate (I) in the range from 4.3 to 15.

25. The process according to claim 18, wherein the reaction is carried out at a temperature in the range from 170 to 260 C.

26. The process according to claim 18, wherein the reaction is carried out at a pressure in the range from 160 to 290 bar.

27. The process according to claim 18, wherein the reaction is carried out continuously in a reactor and the reactor is operated with recycle by part of the reactor output being recirculated from the reactor outlet to the reactor inlet.

28. The process according to claim 18, wherein the dialkyl oxalate (I) is dimethyl oxalate.

29. The process according to claim 18, wherein the copper-comprising heterogeneous catalyst comprises aluminum oxide.

30. The process according to claim 18, wherein the heterogeneous catalyst comprises lanthanum oxide.

31. The process according to claim 18, wherein the heterogeneous catalyst comprises from 10 to 80% by weight of copper, from 0.5 to 20% by weight of lanthanum oxide and from 19.5 to 89.5% by weight of aluminum oxide.

32. The process according to claim 18, wherein the solvent is methanol, ethanol, n-propanol, isopropanol and/or ethylene glycol.

33. The process according to claim 18, wherein the reactor is a shell-and-tube reactor or shaft reactor.

34. The process according to claim 18, wherein the catalyst is arranged as a fixed bed in the reactor.

Description

EXAMPLES

[0101] The analysis of all secondary components was carried out via GC percent by area [% by area]. The proportion of methyl glycolate and DMO was additionally measured in GC percent by weight. The gas-chromatographic separation was carried out over a solid phase (Stabil-WAX, 60 m, =320 m) using hydrogen as carrier gas (flow: 1.1 ml/min.) and an FID.

[0102] The selectivity of the catalysts under the reaction conditions was determined according to the formula

[00002]$\mathrm{Selectivity}\left[\%\right]-\frac{\mathrm{Proportion}.Math..Math.\left(\mathrm{MEG}\right)}{\begin{array}{c}\mathrm{Proportion}.Math..Math.(\mathrm{EtOH},2.Math.\text{-}.Math.\mathrm{OMeEtOH},1.Math.\text{,}.Math.2.Math.\text{-}.Math.\mathrm{propanediol},\\ 1.Math.\text{,}.Math.2.Math.\text{-}.Math.\mathrm{butanediol},\mathrm{MEG})\end{array}}.Math.100$

[0103] where the proportion is expressed in percent by area from the GC analysis. The proportions of the possible products in the denominator were summed. (EtOH=ethanol; 2-OMe-EtOH=2-methoxyethanol).

[0104] The conversion of the DMO is given by the formula

[00003]$\mathrm{Conversion}.Math..Math.\mathrm{of}.Math..Math.\mathrm{DMO}.Math.\left[\%\right]=\left(1-\frac{\%.Math..Math.\mathrm{by}.Math..Math.\mathrm{weight}.Math..Math.{\left(\mathrm{DMO}\right)}_{\mathrm{output}}}{\%.Math..Math.\mathrm{by}.Math..Math.\mathrm{weight}.Math..Math.{\left(\mathrm{DMO}\right)}_{\mathrm{feed}}}\right).Math.100$

[0105] The partial reduction in the output is defined according to the formula

[00004]$\mathrm{Partial}.Math..Math.\mathrm{reduction}.Math.\left[\%\right]=\frac{\%.Math..Math.\mathrm{by}.Math..Math.\mathrm{weight}.Math..Math.\left(\mathrm{Me}.Math..Math.\mathrm{glycolate}\right)}{M.Math..Math.\left(\mathrm{Me}.Math..Math.\mathrm{glycolate}\right)}.Math.\frac{M.Math..Math.\left(\mathrm{DMO}\right)}{\%.Math..Math.\mathrm{by}.Math..Math.\mathrm{weight}.Math..Math.{\left(\mathrm{DMO}\right)}_{\mathrm{feed}}}.Math.100$

[0106] (M=molar mass; Me glycolate=methyl glycolate=methyl ester of glycolic acid=HOCH.sub.2CO(O)OCH.sub.3).

[0107] Comparative example 1 at low pressure

[0108] The apparatus used consisted of a feed section with reservoir and pump, a 77 cm long tube reactor having an internal diameter of 1.4 cm and external double-wall oil heating or cooling which was operated in the down flow mode, a separator cooled to 6 C. and also fresh gas and offgas facilities. The molar ratio of fresh hydrogen to DMO was 16:1, with the excess gas being discharged as offgas. The reactor was operated in the single pass mode.

[0109] The reactor was filled with 10 ml of a barium-doped copper chromite (3 mm pellets). The catalyst bed volume of 100 g of catalyst was 81 ml. The catalyst is a commercial product of BASF SE having the designation Cu 1155 T (69% by weight of chromium(III) oxide, 21% by weight of copper oxide, 10% by weight of barium oxide). Steatite balls were introduced as inert bed above and below the catalyst. After making inert by means of nitrogen, the catalyst was activated using a nitrogen/hydrogen mixture at atmospheric pressure. After activation of the catalyst, a solution having the composition 9% by weight of DMO, 45% by weight of methanol (MeOH) and 46% by weight of MEG was introduced as reactor feed.

[0110] At a space velocity over the catalyst of 0.23 kg of DMO.Math.liter.sub.cat..sup.1.Math.h.sup.1, 78% of the DMO was reacted (liter.sub.cat.=catalyst bed volume). At a selectivity of not more than 10%, 2-methoxyethanol, dimethyl ether, methyl formate and methyl glycolate were found as further components in addition to MEG as main product. An offgas measurement indicated that the major part of the DMO reacted (at least 85% by weight based on DMO reacted) was to be found in the form of CO and CO.sub.2 in the offgas.

COMPARATIVE EXAMPLE 2a

[0111] The apparatus used consisted of a feed section with reservoir and pump, a 1.80 m long tube reactor having an internal diameter of 3.4 cm and external double-wall oil heating or cooling which was operated in the down flow mode, a water-cooled first separator, a second separator cooled to 6 C., a circulation pump and also fresh gas and offgas facilities. The molar ratio of fresh hydrogen to DMO was 13:1, with the excess gas being discharged as offgas. The weight ratio of recycle to feed was about 11-22:1.

[0112] The reactor was filled with 50 ml of a CuO (67% by weight)/La.sub.2O.sub.3 (5% by weight)/Al.sub.2O.sub.3 catalyst (3 mm pellets). The catalyst bed volume of 100 g of catalyst was 62 ml. The catalyst was produced in a manner analogous to WO 2007/006719 A1 (BASF AG), pages 13-14, example 1. At the entrance to the reactor, 15 ml glass spheres were introduced as inert bed above the catalyst. After making inert by means of nitrogen, the catalyst was activated using a nitrogen/hydrogen mixture at atmospheric pressure. After activation of the catalyst, the circulation was taken into operation using a solution of ethylene glycol (10% by weight) in methanol and the target pressure in the reactor and also the target temperature was set. 25% by weight of DMO in MeOH were introduced as feed.

[0113] The liquid reaction outputs obtained in the separators were collected and combined and analyzed.

TABLE-US-00001 Input 1 2 3 4 5 Pressure [bar] 170 170 170 170 170 Temperature [ C.] 170 190 210 210 230 Throughput 0.20 0.20 0.20 0.10 0.10 [kg.sub.DMO .Math. liter.sub.cat..sup.1 .Math. h.sup.1] Recycle/feed [g/g] 16 15 11 21 22 Cross-sectional loading 1.9 1.7 1.3 1.2 1.3 [m/s] H.sub.2/DMO [mol/mol] 13 13 13 26 26 Conversion of DMO 34 44 65 92 100 [molar] Partial reduction 19 13 7 6 <1 (methyl glycolate) [molar] Selectivity to MEG [%] 84 88 95 97 81 Decomposition of DMO 9 16 29 32 17 [%] 1,2-BDO [% by area] <0.001 <0.001 <0.001 <0.001 0.33 1,2-PDO [% by area] <0.001 <0.001 0.003 0.01 0.8 EtOH [% by area] <0.001 0.05 0.06 0.12 1.62 2-OMeEtOH [% by 0.1 0.2 0.6 0.9 0.9 area] (BDO = Butanediol, PDO = Propanediol).

COMPARATIVE EXAMPLE 2b

[0114] Example 2a was repeated at higher pressure; in addition, a higher level of recycle was employed.

TABLE-US-00002 Input 1 2 3 4 5 Pressure [bar] 200 200 200 200 200 Temperature [ C.] 200 215 230 215 230 Throughput 0.20 0.20 0.20 0.15 0.15 [kg.sub.DMO .Math. liter.sub.cat..sup.1 .Math. h.sup.1] Recycle/feed [g/g] 38 35 28 40 33 Cross-sectional loading 4.3 4.0 3.2 3.4 2.8 [m/s] H.sub.2/DMO [mol/mol] 13 13 13 17 17 Conversion of DMO 99 99 100 100 100 [molar] Partial reduction 4 3 1 2 1 (methyl glycolate) [molar] Selectivity to MEG [%] 96 91 80 87 77 Decomposition of DMO 49 42 28 30 18 [%] 1,2-BDO [% by area] 0.002 0.006 0.03 0.01 0.04 1,2-PDO [% by area] 0.02 0.07 0.43 0.20 0.51 EtOH [% by area] 0.11 0.27 0.83 0.58 1.12 2-OMeEtOH [% by 0.14 0.30 0.51 0.36 0.55 area]

EXAMPLE 3

According to the Invention

[0115] The apparatus used consisted of a feed section with reservoir and pump, with a 4 m long coil tube reactor having an internal diameter of 0.4 cm, which was operated isothermally in the down flow mode, a separator, a circulation pump and also fresh gas and offgas facilities. The molar ratio of fresh hydrogen to DMO was 10:1, with the excess gas being discharged as offgas. The mass ratio of recycle to feed was 10:1.

[0116] The reactor was filled with 75 g of a CuO (67% by weight)/La.sub.2O.sub.3 (5% by weight)/Al.sub.2O.sub.3 catalyst (3 mm pellets), the same catalyst as in examples 2, and inert material (3 mm glass spheres), likewise as in examples 2. After making inert by means of nitrogen, the catalyst was activated using a nitrogen/hydrogen mixture at atmospheric pressure. After activation of the catalyst, the circulation was taken into operation using a solution of ethylene glycol (10% by weight) in methanol and the target pressure in the reactor and also the target temperature was set. 15% by weight of DMO in MeOH were introduced as feed.

[0117] The liquid reaction outputs obtained in the separators were collected and combined and analyzed. The offgas was examined spectroscopically by means of online analysis to determine its CO and CO.sub.2 content.

TABLE-US-00003 Input 1 2 3 4 Pressure [bar] 250 250 250 250 Temperature [ C.] 210 220 220 230 Throughput 0.32 0.31 0.64 0.74 [kg.sub.DMO .Math. liter.sub.cat..sup.1 .Math. h.sup.1] Recycle/feed [g/g] 10 10 10 10 Cross-sectional loading 109 109 219 255 [m/s] H.sub.2/DMO [mol/mol] 10 10 10 10 Conversion of DMO 92 99 98 97 [molar] Partial reduction 5 9 16 22 (methyl glycolate) [molar] Selectivity to MEG [%] 96 96 97 96 Space-time yield 0.13 0.15 0.31 0.31 [kg.sub.MEG .Math. liter.sub.cat..sup.1 .Math. h.sup.1] Decomposition of DMO 6 7 5 7 [%] 1,2-BDO [% by area] 0.005 <0.001 <0.001 <0.001 1,2-PDO [% by area] 0.012 0.015 <0.001 <0.001 EtOH [% by area] 0.12 0.19 0.12 0.09 2-OMeEtOH [% by 0.04 0.06 0.07 0.07 area]

[0118] The crude output was, at incomplete conversion, subsequently conveyed through an after-reactor in order to achieve complete conversion. The selectivities here were identical to the reaction in the main reactor.